ALBERT

Description: Homogenous liquid precursor for ZrC – SiC was prepared by blending of Zr ( OC 4 H 9 ) 4 and Poly[(methylsilylene)acetylene]. This precursor could be cured at 250°C and converted into binary ZrC – SiC composite ceramics upon heat treatment at 1700°C. The pyrolysis mechanism and optimal molar ratio of the precursor were investigated by XRD. The morphology and elements analyses were conducted by SEM and corresponding energy-dispersive spectrometer. The evolution of carbon during ceramization was studied by Raman spectroscopy. The results showed that the precursor samples heat treated at 900°C consisted of t- ZrO 2 (main phase) and m- ZrO 2 (minor phase). The higher temperature induced phase transformation and t- ZrO 2 converted into m- ZrO 2 . Further heating led to the formation of ZrC and SiC due to the carbothermal reduction, and the ceramic sample changed from compact to porous due to the generation of carbon oxides. With the increasing molar ratios of C / Zr , the residual oxides in 1700°C ceramic samples converted into ZrC and almost pure ZrC – SiC composite ceramics could be obtained in ZS-3 sample. The Zr , Si , and C elements were well distributed in the obtained ceramics powders and particles with a distribution of 100 ~ 300 nm consisted of well-crystallized ZrC and SiC phases.

Description: Phytochemical investigation of the seeds of Alpinia katsumadai (Zingiberaceae) led to the isolation and identification of six new diarylheptanoid derivatives, katsumains D–G ( 1 – 4 ), 3-(acetyloxy)-alpinikatin ( 5 ), and 5-(acetyloxy)alpinikatin ( 6 ). The structures of 1 – 6 were elucidated by spectroscopic data analysis including 1D- and 2D-NMR experiments.

Description: The object of this study is the interaction of the cyclic anhydride 2 of (18 α ,19 β )-19-hydroxy-2,3-secooleanane-2,3,28-trioic acid 28,19-lactone ( 1 ) with primary and secondary amines. It was shown that the products of steric control (the corresponding 2-amino-2-oxo-3-oic acids=2-amides) were formed solely upon the opening of the anhydride cycle by secondary amines ( Scheme 2 ), whereas the interaction with primary amines yielded a mixture of isomeric amides ( Scheme 10 ). In the latter case, the solvent provided a noticeable effect on the reaction selectivity, which was demonstrated in the case of 4-methoxybenzylamine. The interaction between the resulting 3-amides and oxalyl chloride yielded the corresponding cyclic imides, whereas under these conditions, 2-amides formed spiropyrrolidinetriones ( Scheme 4 ).

Description: Two novel indole alkaloids with plumeran skeleton, N -benzoyl-12-demethoxycylindrocarine and N -cinnamoyl-12-demethoxycylindrocarine ( 1 and 2 , resp.), were isolated from the MeOH extract of the stem bark of Aspidosperma cylindrocarpon Müll . Arg . These compounds were obtained by high-speed counter-current chromatography, and their structures were elucidated on the basis of their NMR (1D and 2D) data. They were tested in vitro against chloroquine-resistant strains of Plasmodium falciparum , and only 2 showed a weak activity ( IC 50 127.97 ng/ml with respect to the standard drug). Several other known compounds, comprising steroids, flavonoids, the rarely found atraric acid, as well as the previously reported alkaloid 3 , were also isolated by conventional chromatographic techniques.

Description: Two new spirostanol saponins, namely elephanosides G and H ( 1 and 2 , resp.) were isolated from the leaves of Yucca elephantipes (Agavaceae), together with the two known furostanol saponins 3 and 4 and the six known flavonoid O - and C -glycosides 5 – 10 . The new structures were elucidated as (3 β ,25 S )-spirost-5-en-3-yl O - β - D -glucopyranosyl-(1→3)- O - β - D -glucopyranosyl-(1→4)- β - D -galactopyranoside ( 1 ) and (3 β ,5 β ,25 R )-3-[(2- O - β - D -glucopyranosyl- β - D -galactopyranosyl)oxy]spirostan-12-one ( 2 ) on the basis of detailed spectroscopic analysis and acidic hydrolysis.

Description: The chemoselectivity in the reaction of 2-diazo-3-oxo-3-phenylpropanal ( 1 ) with aldehydes and ketones in the presence of Et 3 N was investigated. The results indicate that 1 reacts with aromatic aldehydes with weak electron-donating substituents and cyclic ketones under formation of 6-phenyl-4 H -1,3-dioxin-4-one derivatives. However, it reacts with aromatic aldehydes with electron-withdrawing substituents to yield 1,3-diaryl-3-hydroxypropan-1-ones, accompanied by chalcone derivatives in some cases. It did not react with linear ketones, aliphatic aldehydes, and aromatic aldehydes with strong electron-donating substituents. A mechanism for the formation of 1,3-diaryl-3-hydroxypropan-1-ones and chalcone derivatives is proposed. We also tried to react 1 with other unsaturated compounds, including various olefins and nitriles, and cumulated unsaturated compounds, such as N , N′ -dialkylcarbodiimines, phenyl isocyanate, isothiocyanate, and CS 2 . Only with N , N′ -dialkylcarbodiimines, the expected cycloaddition took place.

Description: When treated with LiN i Pr 2 (LDA) at −78°, 1-[(methylsulfanyl)methyl]-2-[(1 Z ,3 E )-4-phenylbuta-1,3-dien-1-yl]benzene easily cyclized to form benzocycloheptenyl anion, which successively underwent intramolecular nucleophilic substitution to give a cyclopropanaphthalene. Similar LDA-mediated cyclization also occurred for 4-phenyl- or 4-methyl-substituted 1-[2-(methoxymethyl)phenyl]buta-1,3-dienes to furnish the corresponding benzocycloheptenes and cyclopropanaphthalenes. A 4- tert -butyl analog also underwent LDA-mediated cyclization to give a benzocycloheptene, but not a cyclopropanaphthalene.

Description: Three new isomeric biisoflavonoids, dapholidins A–C ( 1 – 3 , resp.), have been isolated from the AcOEt-soluble fraction of the MeOH-soluble extract of the roots of Daphne oleoides , along with the known compounds daphwazirin ( 4 ), daphnetin 8- O - β - D -glucopyranoside ( 5 ), daphnin ( 6 ), daphneticin 4″- O - β - D -glucopyranoside ( 7 ), and 6,7-dihydroxy-3-methoxy-8-[2-oxo-2 H -1-benzopyran-7-( O - β - D -glucopyranosyl)-8-yl]-2 H -1-benzopyran-2-one ( 8 ). The structures of the new compounds were determined by spectroscopic analyses, including 1D- and 2D-NMR.

Description: Two spiroheterocyclic 2 H -azirin-3-amines, 1f and 1g , were shown to be useful synthons for the dipeptides N -(4-aminotetrahydro-2 H -pyran-4-yl)prolinate (Thp-Pro) and the corresponding thiopyran derivative, Tht-Pro, respectively. By coupling of 4-bromobenzoic acid with 1f or 1g and saponification, followed by repeating the coupling and saponification steps, oligopeptides of type 4-BrBz-(Thp-Pro) n -OMe and 4-BrBz-(Tht-Pro) n -OMe were prepared, and their conformations were evaluated in solution by NMR techniques and in the crystalline state by X-ray crystallography. All of these sterically highly congested oligopeptides adopt fairly rigid helical conformations. It is interesting to note that the hexapeptide with Thp forms a 3 10 -helix, whereas the Tht analog has a β -bend ribbon spiral confirmation.

Description: Two new naphthoquinones, (2 R )-6,8-dihydroxy- α -dunnione ( 1 ), 6,8-dihydroxy-2,7-dimethoxy-3-(1,1-dimethylprop-2-enyl)-1,4-naphthoquinone ( 2 ), together with three known compounds, (2 R )-6,8-dihydroxy-7-methoxy- α -dunnione ( 3 ), nevadensin ( 4 ), and lysioside C ( 5 ), were isolated from the whole plant of Lysionotus pauciflorus. Their structures were established by spectroscopic methods. Hydroxylated naphthoquinones are reported to occur in a Lysionotus species for the first time. The cytotoxic activities of compounds 1 – 3 were evaluated in vitro against a panel of tumor cell lines.

Description: The three-component reaction of aniline, benzaldehyde, and dienophiles such as 2,3-dihydrofuran, ethyl vinyl ether, 2,3-dihydropyran, and cyclopentadiene can be promoted by ionic liquids like imidazolium salts and guanidinium salts under thermal as well as microwave conditions. The chemical yield as well as the diastereoselectivity of the Povarov reaction strongly depend on the ionic liquid employed. The guanidinium salts can be recycled and reused several times without loss of reactivity.

Description: One new triterpenoid, (3 β ,11 α ,19 β )-3-(butanoyloxy)-11-hydroxytaraxast-20(30)-ene-23,28-dioic acid (clerodendrumic acid; 1 ) was isolated from the hexane extract of the leaves of Clerodendrum glabrum var. glabrum along with heptadecanoic acid ( 2 ). The structure of the new compound was elucidated by interpretation of its NMR (1D and 2D), MS, and IR data. Combined fractions C and D from the column chromatography of the hexane extract exhibited significant antifungal activities (average MIC of 0.10 mg/ml) against Candida albicans and Cryptococcus neoformans. C. albicans was relatively resistant to clerodendrumic acid ( 1 ; MIC 125 μg/ml) and was resistant to heptadecanoic acid ( 2 ; MIC 188 μg/ml). Both compounds had low antibacterial activities against two Gram -positive and two Gram -negative bacteria with average MIC values of 157 and 172 μg/ml, respectively. Compounds 1 and 2 were relatively nontoxic against monkey kidney Vero cells in vitro with IC 50 values of 202.6 and 108.4 μg/ml, respectively.

Description: Ce -doped BaTiO 3 -based ceramics were prepared and studied to satisfy ultra-broad temperature stability (from −55°C to 300°C, capacitance variation rate based on C 20°C is within ±15%). The sample with 0.6 mol% CeO 2 succeeds to achieve this performance with a remarkably high ceiling temperature of 300°C. Meanwhile, the sample has good dielectric and electrical properties at room temperature (ε r  = 1667, tanδ = 1.478%, ρ V  = 5.9 × 10 12  Ω·cm). Ce ion can substitute for Ti ion as Ce 4+ or Ba ion as Ce 3+ . The substitution decreases the spontaneous polarization of BaTiO 3 , and then weakens the ferroelectricity of BaTiO 3 . As a result, the temperature stability of samples is improved obviously. Besides, CeO 2 addition promotes the formation of exaggerated grains, which are consisting of Ba 6 Ti 17 O 40 .

Description: This study aims to optimize quantitative X-ray diffraction (XRD) mineralogical analysis of the minority phases in clinker. The proposed method consists of applying Rietveld quantitative refinement to the XRD patterns for both clinker and the insoluble residue remaining after it is attacked with methanol and salicylic acid (Takashima method). The method was tested with industrial clinker and the same material after modifying its mineralogy by refiring at 1500°C followed by slow cooling. The findings showed that the C 4 AF / C 3 A ratios for quickly and gradually cooled clinker were much higher when the clinker diffractograms were refined with the Rietveld procedure than when the proposed method was used. The proportion of C 3 A found with the proposed method was ≈2.8-fold higher than when Rietveld only was applied to the diffractograms for clinkers. Taken together, the refinement data for the two materials (clinker and Takashima residua) revealed that Rietveld quantitative XRD applied to clinker underestimates the low C 3 A content. These findings are supported by postsulfate attack durability studies conducted on cements prepared with the two clinkers.

Description: The effect of increasing poling fields on the properties of (1− x )BZT– x BCT compositions across the morphotropic phase boundary (MPB) is studied using large signal polarization and strain, small signal permittivity and piezoelectric coefficient, and XRD measurements. Successive poling causes charge carrier migration inducing an internal bias field, which becomes large with respect to the coercive field resulting in biased ferroelectric and ferroelastic switching. Improvements in piezoelectric coefficient of 9% are significantly smaller in the tetragonal 60BCT composition compared with the improvement of approximately 50% in the rhombohedral 40BCT and MPB 50BCT compositions. While the properties continue to change with increased poling fields, the remnant ferroelastic domain texture parallel to the field direction, as observed from XRD, stays approximately constant. The improvement in overall domain alignment leading to largely enhanced intrinsic piezoelectricity originates from the alignment of 180° domains and possibly non-180° domains in grains with orientations inclined to the electric field. As a result, poling is most effective in BZT–BCT materials that have low coercive fields, show low distortions and possess more polarization orientations, such as compositions in the rhombohedral phase field or near the MPB.

Description: The defect chemistry-modulated dielectric properties of dense yttria-doped zirconia ceramics prepared by conventional sintering (at 1350°C–1500°C) and electric field-assisted flash sintering (55 V/cm at 900°C) were studied by impedance spectroscopy. While the bulk dielectric properties from both sets of samples showed only small and insignificant changes in conductivity and permittivity, respectively, a huge increase of these properties was measured for the grain boundaries in the flash sintered specimens. A close analysis of these results suggests that flash sintering reduced grain-boundary thickness (by about 30%), while increasing the concentration of oxygen vacancies near these interfaces (by about 49%). The underlying mechanism proposed is electric field-assisted generation and accommodation of defects in the space-charge layers adjacent to the grain surface. The changes in measured permittivity are attributed to the boundary thickness effect on capacitance, while conductivity involved variations in its defect density-dependent intrinsic value, accounting for changes also observed in grain-boundary relaxation frequencies. Therefore, in terms of modifications to the specific dielectric properties of these materials, the overall consequence of flash sintering was to considerably lower the semi-blocking character of the grain boundaries.

Description: This article presents a detailed study on the nanoscaled interface between microelongated gold particles (GP) and biphase leucite/feldspar glass-ceramic matrix. The glass-ceramic composite with a nonuniform GP distribution was processed through hot-pressing under vacuum using a commercial dental ceramic furnace for glass-ceramic dental crown manufacturing. Heat treatments at 900°C, 1100°C, and 1300°C were conducted, and microstructural features along the interface were used to verify the chemical reactions between GP and glass-ceramic matrix. It was observed that the amorphous glass-ceramic matrix had nanoscaled biphase structures, and the distributed nanoscaled amorphous leucite phase was attracted to GP during hot-pressing, and was more reactive with GP than the feldspar phase. The thickness of the interfacial phase formed through chemical reactions between GP and glass-ceramic matrix is around 30 nm. The chemically bonded interface has contributed significantly toward the substantial improvements in both strength and toughness of the GP-reinforced glass-ceramic matrix composite. Characterization techniques, including X-ray diffraction and field-emission scanning electron Microscopy, incorporating X-ray microanalysis using energy dispersive spectrometry, have been employed in this study.

Description: Recent investigations have revealed the great potential of Raman spectroscopy for the characterization of clinker minerals and commercial Portland cements. The usefulness of this technique for the identification of anhydrous, hydrated, and carbonated phases in cement-based materials has been demonstrated. In the present work, the application of micro-Raman spectroscopy for the characterization of the main clinker phases of calcium aluminate cements and calcium sulfoaluminate cement is explored. The main stable hydrated phases as well as several important carbonated phases are investigated. Raman measurements on the following phases are reported: (i) pure, unhydrated phases: CA, C 12 A 7 , CA 2 , C 2 AS, cubic- C 3 A , C 4 AF, and C 4 A 3 ; (ii) hydrated phases: ettringite, monosulfoaluminate, and hydrogarnet ( C 3 AH 6 ); (iii) carboaluminate phases: hemicarboaluminate and monocarboaluminate. The present results, which are discussed in terms of the internal vibrational modes of the aluminate, carbonate, and sulfate molecular groups as well as stretching O–H vibrations, show the ability of Raman spectroscopy to identify the main hydrated and unhydrated phases in the aluminate and sulfoaluminate cements. The Raman spectra obtained in this work provide an extended database to the existing data published in the literature.

Description: Acmite ( NaFeSi 2 O 6 ) films were formed on steel coupons via solvothermal reaction of silica, sodium hydroxide, and 1, 4-butanediol in an autoclave under autogenous pressure. Systematic variation in processing variables led to homogenous coatings comprised of pinacoidal acmite grains with an average grain size of ~33 μm. The coatings were produced on the steel coupons from reactant conditions of 0.635 m SiO 2 , 2.546 m NaOH , and 3.087 m 1,4-butanediol for 72 h at 240°C.

Description: A 50:50 vol% MgO – Y 2 O 3 nanocomposite with ~150 nm grain size was prepared in an attempt to make 3–5 μm infrared-transmitting windows with increased durability and thermal shock resistance. Flexure strength of the composite at 21°C is 679 MPa for 0.88 cm 2 under load. Hardness is consistent with that of the constituents with similar grain size. For 3-mm-thick material at 4.85 μm, the total scatter loss is 1.5%, forward scatter is 0.2%, and absorptance is 1.8%. Optical scatter below 2 μm is 100%. Variable intensity OH absorption (~6% absorptance) is observed near 3 μm. The refractive index is ~0.4% below the volume-fraction-weighted average of those of the constituents. Thermal expansion is equal to the volume-fraction-weighted average of expansion of the constituents. Specific heat capacity is equal to the mass-fraction-weighted average of heat capacities of the constituents. Thermal conductivity lies between those of the constituents up to 1200 K. Elastic constants lie between those of the constituents. The Hasselman mild thermal shock resistance parameter for the composite is twice as great as that of common 3–5 μm window materials, but half as great as that of c -plane sapphire.

Description: Beginning early in the 19th century, developments in crystallography, optics, and chemistry in France set the stage for the discovery of molecular chirality by Louis Pasteur in 1848. He found that the crystallization of the sodium ammonium salt of ‘ paratartaric acid ’, a mysterious ‘ isomer ’ of natural (+)-tartaric acid (TA), produced two different crystal types that were non-superimposable mirror-image forms of each other. He separated the two types and found their optical rotations in solution opposite in direction and equal in absolute magnitude. This led him to conclude that paratartaric acid is a combination of two mirror-image molecule types of TA that are ‘ dissymmetric ’, an existing term he adapted to the connotation of today's ‘ chiral ’. In 1857, he found that the two enantiomers of TA were metabolized by a microorganism at drastically different rates, and thereby discovered biological enantioselectivity. In 1886, Italian chemist Arnaldo Piutti discovered D -asparagine and found that it tasted intensely sweet, in contrast to the known L -asparagine which had no taste. This was the discovery of stereoselectivity at biological receptors. As a result of advances in stereoselective synthesis and enantioselective chromatography during the last decades of the 20th century, in the 1990s the importance of molecular chirality in drug action and disposition began to receive serious attention from drug-regulatory authorities and the pharmaceutical industry, the overall result of which has been the near-complete disappearance of racemic drugs as newly introduced pharmaceuticals.

Description: In this work, novel Y 2 Si 2 O 7 / ZrO 2 composites were developed for structural and coating applications by taking advantage of their unique properties, such as good damage tolerance, tunable mechanical properties, and superior wear resistance. The γ- Y 2 Si 2 O 7 / ZrO 2 composites showed improved mechanical properties compared to the γ- Y 2 Si 2 O 7 matrix material, that is, the Young's modulus was enhanced from 155 to 188 GPa (121%) and the flexural strength from 135 to 254 MPa (181%); when the amount of ZrO 2 was increased from 0 to 50 vol%, the γ- Y 2 Si 2 O 7 / ZrO 2 composites also presented relatively high facture toughness (〉1.7 MPa·m 1/2 ), but this exhibited an inverse relationship with the ZrO 2 content. The composition–mechanical property–tribology relationships of the Y 2 Si 2 O 7 / ZrO 2 composites were elucidated. The wear resistance of the composites is not only influenced by the applied load, hardness, strength, toughness, and rigidity but also effectively depends on micromechanical stability properties of the microstructures. The easy growth of subcritical microcracks in Y 2 Si 2 O 7 grains and at grain boundaries significantly contributes to the macroscopic fracture toughness, but promotes the pull-out of individual grains, thus resulting in a lack of correlation between the wear rate and the macroscopic fracture toughness of the composites.

Description: The as-prepared BiFeO 3 ceramic shows a piezoelectric d 33 coefficient of −14 pC/N, that is, an obvious ferroelectric self-poling phenomenon. The temperature gradient between the two surfaces of BiFeO 3 ceramic was intentionally enlarged when BiFeO 3 was prepared with a rapid liquid sintering method. This temperature gradient and the corresponding thermal strain can introduce defect dipoles through separating bismuth vacancies from oxygen vacancies. A mass of these dipoles introduce a macroscopic internal electric field ( E in ) which downward poles BiFeO 3 ceramic during its cooling down process. As expected, an E in of 〉10 kV/cm is confirmed by the asymmetrical polarization/strain versus electric field curves.

Description: The effect of Ba content on the stress sensitivity of the antiferroelectric to ferroelectric phase transition in ( Pb 0.94− x La 0.04 Ba x )[( Zr 0.60 Sn 0.40 ) 0.84 Ti 0.16 ] O 3 ceramics is investigated through monitoring electric field-induced polarization and longitudinal strain under compressive prestresses. It is found that incorporation of Ba significantly suppresses the stress sensitivity of the phase transition, as manifested by slight decreases under prestresses up to 100 MPa in the maximum polarization ( P m ) and longitudinal strain ( x m ). The energy storage density is even increased under the mechanical confinement in compositions x  = 0.02 and 0.04. X-ray diffraction, transmission electron microscopy, and dielectric measurements indicate that the suppressed stress sensitivity is associated with the disruption of micrometersized antiferroelectric domains into nanodomains and the transition from antiferroelectric to relaxor behavior.

Description: Powders and nanoceramics composed of composites of CoFe 2 O 4 , CoFe 2 , and a small amount of FeO were prepared by heating CoFe 2 O 4 powder in reducing atmosphere and by sintering the product of reducing reaction at 350°C via spark plasma sintering technology. In the powders, increase in the molar ratios of CoFe 2 : CoFe 2 O 4 and a great change in magnetic parameters were observed with the change in heating temperature from 300°C to 400°C, and the dominance of dipole interaction over exchange coupling in the interparticle interactions was confirmed by the steps in magnetic hysteresis loops and the negative Henkel plots. However, in the nanoceramics, significant enhancement in exchange coupling was found when the sintering temperature was raised to 500°C and 650°C, which was confirmed by both the positivity of Henkel plot and the single-phase style of the magnetic hysteresis loop.

Description: Gas adsorption porosity measurement of geopolymers (GPs) is required for quantitative understanding of such mesoporous structures, but the complex nature of the GP system makes analysis difficult. Previous results in the literature are often ambiguous or contradictory. A systematic investigation of metakaolin GP gas adsorption results was conducted to optimize the use of this measurement technique and verify that results match known theory about GP structure. It was found that GP undergoes structural change upon degassing at 100°C or higher. If and only if this change is prevented by degassing at a lower temperature could it be shown that specific surface area and total gas adsorption increases with both increasing curing temperature and decreased Si : Al ratio. This observation is consistent with previous suggestions of increased zeolitic character under these conditions, where previous gas adsorption investigations had not observed this expected relationship. Hydrogen physisorption is proposed as a substitute technique for micropore isotherms in GPs due to the difficulty of removing trace gasses from GPs and the measurement effect of such gasses at high vacuum. A hydrogen physisorption isotherm qualitatively resembled an equivalent nitrogen micropore isotherm.

Description: In this work, the role of europium doping of glasses formulated in the ternary system ZnO – CdO – TeO 2 is described. The Eu -doped oxide glasses were prepared by the conventional melt-quenching method and by using three different compositions. Structural studies reveal that there exists a good affinity between Cd and some rare earth (RE) ions to form the crystalline phase. The X-ray diffraction (XRD) diagrams display that the structure of these glasses is amorphous and with the increase in CdO content and the compatibility of Eu 3+ , there is a tendency to form nanocrystals of CdTe 2 O 5 . The scanning electron microscopic (SEM) observation of their microstructure confirms the presence of phase separation. Differential thermal analysis (DTA) of these glasses showed small exothermic peaks noted around 450°C for the V2 glass and 480°C for V1 and V3 glasses, which could be attributed to the formation of these crystals. The infrared spectra showed a main absorption band around 800–600 cm −1 corresponding to the Te – O stretching mode in TeO 4 and TeO 3 groups. By optical absorption (OA), the band gap ( E g ) for each glass was determined; these values were 3.27, 3.14, and 3.3 eV for the V1–V3 glasses, respectively. Furthermore, the presence of Eu 3+ was detected in the 370–470 nm short-range wavelengths. The photoluminescence (PL) experiments of the glasses showed light emission due to the following transitions: 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3, and 5D0 → 7F4.

Description: The conductivity of nominal CaWO 4 , CaW 0.99 Ta 0.01 O 4–δ , 0.7( CaWO 4 )–0.3( La 0.99 Ca 0.01 NbO 4–δ ), and Ca 0.9 La 0.1 WO 4+δ has been studied by means of a.c. impedance measurements. Proton conductivity was observed for CaW 0.99 Ta 0.01 O 4–δ , which displayed exothermic hydration with enthalpy and entropy of –82 kJ/mol and –120 J/molK, respectively. The proton mobility in CaW 0.99 Ta 0.01 O 4–δ was low, with enthalpy and preexponential factor of mobility of 82 kJ/mol and 0.7 cm 2 K/Vs. The high enthalpy of mobility is interpreted to reflect association between the acceptor dopant and protonic defects, whereas the low preexponential factor of mobility may reflect a lower proton concentration than assumed. Rietveld refinement indicated low solubilities of La on Ca -site and Ta on W-site. Proton conductivity was also observed in undoped CaWO 4 , however, not in Ca 0.9 La 0.1 WO 4+δ . The conductivity of 0.7( CaWO 4 )–0.3( La 0.99 Ca 0.01 NbO 4–δ ) behaved much like that of undoped LaNbO 4 , likely due to a very low acceptor dopant concentration.

Description: A new lead-free BNT-based piezoelectric ceramics of (1 −  x ) Bi 0.5 Na 0.5 TiO 3 – x Bi ( Al 0.5 Ga 0.5 ) O 3 ( x  = 0, 0.02, 0.03, 0.04, and 0.05) were synthesized using a conventional ceramic fabrication method. Their structures and electrical properties were investigated. All the samples show a typical ferroelectric P ( E ) loops and S ( E ) curves at room temperature. The optimal properties are obtained at the composition of the x  = 0.03. The substitution of Bi ( Al 0.5 Ga 0.5 ) O 3 enhances piezoelectric constant and increases Curie temperature from 58 pC/N and 310°C of pure BNT to 93 pC/N and 325°C of the x  = 0.03. The temperature-dependent P ( E ) loops and S ( E ) curves of 0.97BNT–0.03BAG indicate that phase transition from ferroelectric to antiferroelectric takes place over a very wide temperature region from 80°C to 180°C. The results show that the introduction of BAG improves the electrical properties of BNT.

Description: We studied ancient enamels on gilded copper from a collection of archeological horse harness pendants of the Museo Instituto Valencia de Don Juan (Madrid, Spain) to test the benefits of a new, nondestructive analytical methodology based on chemometric analysis (i.e., Principal Component Analysis, PCA) on micro-ATR-FTIR spectral data and chemical quantification using SEM-EDS. The novelty of this approach was threefold: (i) PCA allowed the discrimination of the different harness pendants of known origin and attributed to the 14th and 15th centuries according to the chemical complex composition, nanostructure, glass weathering, and/or coloring mechanisms of each colored enamel, separately (i.e., red, purple, blue, and white), (ii) it is a cheap, easily available and nondestructive methodology that enables us to (iii) draw archeological conclusions about the quality of the manufacturing process, reassess the chronology of these objects and attempt to attribute them to different workshops according to the different traditional recipes identified. In particular, the enamels were made of alkali and/or alkaline earth lead-glass with a wide range of chemical compounds in the form of pigments or opacifiers. Two types of coloring mechanisms were identified, colloidal particles such as copper-ruby for red enamels, and ionic mechanisms such as Fe (II) and Co (II) to achieve a blue pigments; Mn (III) in the purple pigment; and two kind of white enamels were identified, i.e., tin oxide as an opacifier and uranium oxide. In addition, we established the reason for the poor state of conservation of some of the enamels by means of the identification of depolymerization and ion exchanges, well-known harmful effects of glass weathering, and finally a chronology was assigned for some of these pieces according to the enamel composition.

Description: Novel glass-ceramics with embedded thermoelectric Bi 2 Se 3 crystals were prepared from glass matrices in the Ge 20 Se 100− x Bi x ( x  = 5, 10, 12 mol%) system. Based on DSC results performed at different heating rates, characteristic activation energies ( E c ) and Avrami exponents ( n ) were obtained and analyzed by using Kissinger's relation, Ozawa's method, Augis–Bennett approximation and Matusita–Sakka theory. XRD results showed that pure Bi 2 Se 3 crystalline phase precipitated upon annealing at different temperatures for various time. The crystal size and crystalline fraction in the samples could be tuned by controlling the annealing time.

Description: In the present investigations nano size high alumina cements (HAC) were prepared by very effective co-melt precursor sintering technique from their metal nitrate precursors. The prime cementing phases observed were CA, CA 2 , and C 12 A 7 . The addition of nano structured cements in refractory castables has improved the thermo-chemical-mechanical properties to a significant extent. Each batch of low cement castables (LCC) was prepared from calcined Chinese bauxite, HAC, and superfine additives. The effect of HAC in bauxite castable with the additives similar to Silicon Carbide, reactive alumina, and micro-fine silica on the sinterability and properties of these castables was investigated. Physical properties such as apparent porosity and bulk density, mechanical properties such as hot modulus of rupture (HMOR), cold and hot modulus of rupture (CMOR), and cold crushing strength (CCS) of hydrated and sintered castables were studied. The sintered castables were also characterized for their solid phase compositions and microstructure using X-ray diffraction (XRD) and FE-SEM, respectively. In the castables new phases such as mullite, α-alumina were formed at the expense of bauxite and silica. Solid solution of mullite formed at high temperature acts as a bonding phase and is accounted for high HMOR, CMOR, and CCS values. These excellent properties of such castables may enable their uses in various applications such as refractory lining for fabrication of steel, aluminium, copper, glass, cement, chemicals, and ceramics.

Description: Zn 2 GeO 4 ceramic materials were synthesized by the solid-state method. Zn 2 GeO 4 powders were investigated with X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Oxygen defects in the Zn 2 GeO 4 ceramics were investigated by photoluminescence, Raman, and EDS spectra. Conductivity of Zn 2 GeO 4 was 0.18 S/cm at low temperature of 773 K, and its activation energy was 0.49 eV. The results showed that Zn 2 GeO 4 was a promising low-temperature electrolyte with high conductivity.

Description: This article details the influence of zirconium doping on the piezoelectric properties and relaxor characteristics of 94( Bi 1/2 Na 1/2 ) TiO 3 –6 Ba ( Zr x Ti 1− x ) O 3 (BNT–6BZT) bulk ceramics. Neutron diffraction measurements of BNT–6BZT doped with 0%–15% Zr revealed an electric-field-induced transition of the average crystal structure from pseudo-cubic to rhombohedral/tetragonal symmetries across the entire compositional range. The addition of Zr up to 10% stabilizes this transition, resulting in saturated polarization hysteresis loops with a maximum polarization of 40 μC/cm 2 at 5.5 kV/mm, while corresponding strain hysteresis measurements yield a maximum strain of 0.3%. With further Zr addition, the ferroelectric order is progressively destabilized and typical relaxor characteristics such as double peaks in the current density loops are observed. In the strain hysteresis, this destabilization leads to an increase of the maximum strain by 0.05%. These changes to the physical behavior caused by Zr addition are consistent with a reduction of the transition temperature T F-R , above which the field-induced transformation from the relaxor to ferroelectric state becomes reversible.

Description: Precursor glasses for the ferroelectric barium bismuth titanate ( BaBi 4 Ti 4 O 15 ) (BBiT) have been prepared by the melt-quench technique in the SiO 2 – K 2 O – BaO – Bi 2 O 3 – TiO 2 (SKBBT) glass system with and without Eu 2 O 3 doping. BBiT glass–ceramic (GC) nanocomposites have been derived from these glasses by controlled heat treatment. The structural properties of the GCs have been investigated using X-ray diffraction (XRD), electron microscopy (FE-SEM, TEM), and FT-IR reflectance spectroscopy. FE-SEM images show the formation of randomly oriented hexagonal rod-shaped crystals of 200–400 nm and TEM images show 10–20 nm crystallites. FT-IR spectra exhibit the characteristic bands of BBiT at 480, 585, and 680 cm −1 . The activation energy of crystallization ( E c ) varies from 295 to 307 kJ/mol. The dielectric constants (ε r ) of glass and GC nanocomposites increase with an increase in frequency up to 3.0 MHz and then decrease up to 5.0 MHz. Heat-treated GCs show higher ε r values, in the range 25–55, compared to the precursor glasses (20–37). Dielectric losses (tan δ) for all the samples increase from 0.005 to 1.0 with an increase in frequency from 100 Hz to 5.0 MHz. Excitation spectra were recorded by monitoring emission at 613 nm corresponding to the 5 D 0 → 7 F 2 transition. An intense 466 nm excitation band corresponding to the 7 F 0 → 5 D 2 transition was observed. Emission spectra were then recorded by exciting the glass samples at 466 nm. Longer heat-treatment times led to a 15-fold increase in the intensity of the red emission at 612 nm, attributed to the segregation of Eu 3+ ions into the low phonon energy BBiT crystallites. The hardness (3.8–5.1 GPa) and fracture toughness (1.8–3.5 MPam 0.5 ) values obtained in the GCs are high and suitable for structural applications.

Description: Carbon doping is known to be very effective for enhancing the high-field properties of magnesium diboride, MgB 2 , but not for the low-field properties. Here, we report that both the high- and the low-field properties can be improved simultaneously without doping by increasing the initial magnesium partial pressure, by simply reducing the size of the magnesium particles. It is shown that in situ processed bulk MgB 2 sintered with fine magnesium powders has superior superconducting properties compared with a bulk sample fabricated using coarse magnesium lumps. The change in the lattice parameters was almost negligible; however, a clear increase in lattice strain can be observed for the sample sintered with fine magnesium powders. The increase in the lattice strain results in an enhancement of the high-field properties. Furthermore, it has also been found that the low-field critical current density is not reduced, but rather slightly increased for the fine magnesium powder sample. This is due to a closer linkage among the grains that drastically improves grain connectivity. These findings demonstrate that the initial growth mechanism of MgB 2 is very crucial for its superior superconducting properties, and it especially indicates the importance of magnesium vapor pressure.

Description: Revisiting classic phase diagrams and chemical phase relations in the solid state of a very well-studied oxide system, such as the lithium aluminosilicate (LAS) system, can open a new window for the design of new advanced materials with improved properties. Crystal chemistry and phase equilibria are used to demonstrate the ability to design materials with particular desired properties in the alumina-rich corner of the LAS phase diagram. The experimental results demonstrate the alumina and β-eucryptite solid-state compatibility.

Description: This work reports the crystallization, microstructure, and surface composition of Cu In 0.7 Ga 0.3 Se 2 (CIGS) thin films grown by femtosecond pulsed laser deposition at different annealing temperatures. The structural and optical properties of the CIGS films were characterized by X-ray diffraction, Raman scattering, UV-visible spectroscopy, and Hall effect measurement. The results indicate that binary crystals of CuS e initially formed on the as-deposited film, but then completely turned into a quaternary chalcopyrite structure after annealing at 400°C. Phase transformation significantly affects the surface morphology, Hall properties, and band gap. Transmission electron microscopy further revealed that an interface between the Mo substrate and CIGS crystallites contains an amorphous layer even at the high temperature of 500°C. For the application of photovoltaic devices, we also report on the photoresponse of both as-deposited and annealed films as demonstrated by preliminary tests.

Description: Reactive sintering of 3 Ti : Sn :2 C and 3Ti:Sn:2C:0.6Fe powder mixtures is studied in the temperature range 510°C–1200°C under argon. It is demonstrated that the recently discovered Ti 3 SnC 2 phase is formed, provided that Fe is added to a 3 Ti : Sn :2 C reactant mixture within the synthesis conditions used. Using dilatometric and X-Ray diffraction analyses, the formation mechanism of Ti 3 SnC 2 is discussed. Results show that at low temperature (about 510°C), tin is consumed to form Fe x Sn y intermetallics. At high temperature (about 1060°C), tin is newly available to form Ti 3 SnC 2 due to the melting of Fe x Sn y . Then, the intermediate phases, TiC and Ti 2 SnC , and/or Ti 5 Sn 3 , TiC , C , and Ti are dissolved in the ( Fe  +  Sn ) liquid phase and Ti 3 SnC 2 very likely precipitate from the melt. The second part of the study deals with the optimization of the Fe content in the initial 3Ti:Sn:2C reactant powder mixture to synthesize samples with larger Ti 3 SnC 2 content by hot isostatic pressing.

Description: The effects of non-stoichiometry on the microstructure, oxygen vacancies, and piezoelectric properties of ( Na 0.5 K 0.5 ) x NbO 3 (NK x N, where x  =   0.98, 1.00, 1.01, and 1.02) ceramics doped with sintering aid CuTa 2 O 6 (CT) doping were investigated. X-ray diffraction (XRD) patterns indicated that a secondary phase formed in CT-doped NK x N (NK x NCT) ceramics with x  〈   1.00 and that a pure phase was obtained with x  ≥   1.00. The grain size of NK x NCT ceramics increased with increasing x value due to the formation of a liquid phase. The internal bias field, activation energy, and Raman analysis for NK x NCT ceramics showed that the number of induced oxygen vacancies increased with decreasing x value. The high mechanical quality factor ( Q m ) value obtained for NK x NCT ceramics did not correspond to a higher concentration of oxygen vacancies, illustrating that the suitable compensation (excess Na and K ) is more important than the concentration of oxygen vacancies to obtain the ceramics with high Q m values. The NK x NCT ceramics with x  =   1.01 exhibited excellent piezoelectric properties, with k p and Q m values of 39.9% and 2,070, respectively.

Description: Low-temperature sintering of β-spodumene ceramics with low coefficient of thermal expansion (CTE) was attained using Li 2 O – GeO 2 sintering additive. Single-phase β-spodumene ceramics could be synthesized by heat treatment at 1000°C using highly pure and fine amorphous silica, α-alumina, and lithium carbonate powders mixture via the solid-state reaction route. The mixture was calcined at 950°C, finely pulverized, compacted, and finally sintered with or without the sintering additive at 800°C–1400°C for 2 h. The relative density reached 98% for the sample sintered with 3 mass% Li 2 O – GeO 2 additive at 1000°C. Its Young's modulus was 167 GPa and flexural strength was 115 MPa. Its CTE (from R.T. to 800°C) was 0.7 × 10 −6  K −1 and dielectric constant was 6.8 with loss tangent of 0.9% at 5 MHz. These properties were excellent or comparative compared with those previously reported for the samples sintered at around 1300°C–1400°C via melt-quenching routes. As a result, β-spodumene ceramics with single phase and sufficient properties were obtained at about 300°C lower sintering temperature by adding Li 2 O – GeO 2 sintering additive via the conventional solid-state reaction route. These results suggest that β-spodumene ceramics sintered with Li 2 O – GeO 2 sintering additive has a potential use as LTCC for multichip modules.

Description: Pyrochlore-structured lanthanide stannate ceramic ( Ln 2 Sn 2 O 7 ) has been synthesized via a new complex precipitation method. A suite of characterization techniques, including FTIR, Raman, X-ray, and electron diffraction as well as nitrogen sorption were employed to investigate the structural evolution of the synthesized and calcined powder. Raman, XRD, and selected area electron diffraction results confirm the presence of the pyrochlore structure after calcination of the powder above 1200°C. TEM imaging shows fine crystallites gradually increased in size from approximately 100 nm to about 500 nm with higher calcination temperatures. Grain growth and powder densification upon increasing the calcination temperature was confirmed by nitrogen sorption results. This aqueous synthetic method provides a simple pathway for the preparation of homogeneous lanthanide stannate ceramics.

Description: Ceramics have played a crucial role in the development of fission based nuclear power, in glass & glass composite high level wasteforms, in composite cements to encapsulate intermediate level wastes (ILW) and also for oxide nuclear fuels based on UO 2 and PuO 2 /UO 2 mixed oxides. They are also used as porous filters with the ability to absorb radionuclides (RN) from air and liquids and are playing a key role in the cleanup at Fukushima. Non-oxides also find current fission applications including in graphite moderators and B 4 C control rods. Ceramics will continue to be significant in the near-term expansion of nuclear power via next-step developments of fuels with inert matrices or based on thoria and in wasteforms using alternative composite cements or single or multiphase ceramics that can host Pu & other difficult RN. Longer term advances for Generation IV reactors, which will operate at higher temperatures & with higher fuel burn-up require innovative fuel developments potentially via carbides & nitrides or composite fuel systems. Novel non-thermal (cement-like) and thermal techniques are currently being developed to treat some of the difficult legacy wastes. Non-thermally derived wasteforms developed from geopolymers, composite cements, hydroceramics, and phosphate-bonded ceramics and thermally derived wasteforms made by Hot Isostatic Pressing and fluidized bed steam reforming (FBSR) as well as vitrification techniques based on cold crucible melting (CCM), Joule-heater in-container melting and plasma melting (PM) are described. Future developments in waste treatment will be based on separation technologies for partitioning individual RN along with design & construction of RN-containing ceramic targets for inducing transmutation reactions. Near demonstration actinide-hosting ceramic wasteforms including multiphase Synroc systems are described. Opportunities also exist for ceramics in structural applications in Generation IV reactors such as composite SiC / SiC and C / C for fuel cladding and control rods and MAX phases and ultrahigh-temperature ceramics (UHTCs) may find near core fuel coating and cladding applications. Uses of ceramics in fusion reactor systems will be both functional (ceramic superconductors in magnet systems for plasma control and in Li silicate breeder blankets in tokamaks) and structural including as sapphire diagnostic windows, graphite diverters, and plasma facing C and UHTCs. In all these cases, performance is limited by poorly understood radiation damage and interface controlled processes, which demands a combined modeling/experimental approach.

Description: The promotion of zircon ( ZrSiO 4 ) crystallization by ZnO from a zirconium-based frit glaze was studied and the possible mechanism was discussed. X-ray diffraction was used to analyze the relative quantities of zircon and other transitional crystals in the samples. The results show that ZnO can significantly decrease the crystallization temperature of zirconium-based glaze, depress the formation of Ca 2 ZrSi 4 O 12 , and promote the devitrification of transitional crystals t - ZrO 2 and Ca 2 ZnSi 2 O 7 , as well as lead to the formation of more zircon than the ZnO -free glaze. It was also found that zircon not only can form from the interaction between t - ZrO 2 and SiO 2 but also can devitrify directly from the glass phase of zirconium-based glaze.

Description: Barium-substituted CsAlSi 2 O 6 pollucites, Cs x Ba (1− x )/2 AlSi 2 O 6 , and barium- and iron-substituted pollucites, Cs x Ba (1− x )/2 Al x Fe 1− x Si 2 O 6 and Cs x Ba 1− x Al x Fe 1− x Si 2 O 6 were synthesized with 1 ≥  x ≥ 0.7 using a hydrothermal synthesis procedure. Rietveld analysis of X-ray diffraction data confirmed the substitution of Ba for Cs and Fe for Al , respectively. The crystallographic analysis also describes the effects of three different types of pollucite substitutions on the pollucite unit cell: Ba 2+ for Cs 1+ cation results in little effect on cell dimensions, intermediate concentrations of Ba 2+ and Fe 3+ substitution result in net minor expansion due to Fe 3+ addition, and large Ba and Fe substitutions result in overall framework contraction. Elemental analysis combined with microscopy further supports the phase purity of these new phases. These materials can be used to study the stability of CsAlSi 2 O 6 as a durable ceramic waste form, which could accommodate with time Cs and its decay product, Ba . Furthermore, success in iron substitution for aluminum into the pollucite lattice predicts that redox charge compensation for Cs cation decay is possible.

Description: Nitrogen-doped mullite fibers were first synthesized through the nitridation of Al 2 O 3 – SiO 2 gel fibers in NH 3 . The results showed that nitrogen take-up began at 800°C, reached the maximum at 900°C, and then decreased with increasing temperature. The ceramic fibers nitridated at 900°C were essentially amorphous, but contained a small amount of nano-sized Al – Si spinel crystals. Mullite was formed after nitridation at 1200°C, accompanied by crystallization of χ- SiAlON and δ- Al 2 O 3 . The incorporation of nitrogen resulted in the formation of a variety of nitrogen-containing crystalline phases. The grain size of the mullite fibers can be adjusted by changing of the nitrogen content.

Description: The solubility limit of Ca in 99.99% pure α- Al 2 O 3 (alumina) was measured using a wavelength dispersive spectrometer mounted on a scanning electron microscope. Al 2 O 3 samples were equilibrated at a concentration which ensured saturation of the Al 2 O 3 grains with Ca , and were quenched in water from 1600°C. The results were compared with those from samples which were furnace cooled from 1600°C. For the quenched samples, the Ca solubility limit was found to be 51 ± 1 ppm, which is significantly larger than the solubility limit for samples which were furnace cooled (26 ± 1 ppm).

Description: The possibility of developing large solid oxide fuel cell (SOFC) stacks based upon 25 cm 2 ceramic oxide anode-supported cells is investigated. Planar fuel cells comprising strontium titanate-based anode support impregnated with active catalysts were prepared using a combination of deposition techniques. The fuel cell tests performed in a semisealed rig have shown power densities of 185 mW cm −2 at 850°C using humidified hydrogen as fuel and air as oxidant. The structure and evolution of the catalytically active impregnated materials-10 mol% Gd -doped CeO 2 and nickel- are analysed using electron microscopy at the end of the fuel cell test, revealing that a ceria and nickel layer surrounds the titanate backbone grains while ~50–150 nm spherical-like nickel particles uniformly decorate this top layer.

Description: Structural and dielectric properties of (1− x ) BaTiO 3 – x Bi ( Mg 1/2 Ti 1/2 ) O 3 ( x  = 0.1–0.5) were investigated to understand the binary system and utilize it for high-voltage, high energy density capacitors. The solubility limit for Bi ( Mg 1/2 Ti 1/2 ) O 3 in a BaTiO 3 perovskite was between x  = 0.4 and x  = 0.5. A phase with pseudocubic symmetry was formed for x  = 0.1–0.4; a secondary phase developed at x  = 0.5. Dielectric measurements showed highly diffusive and dispersive relaxor-like characteristics from 10 to 40 mol% of Bi ( Mg 1/2 Ti 1/2 ) O 3 . These compositions also showed high relative permittivity with low-temperature coefficients of permittivity over a wide range of temperatures −100°C–600°C. Relaxation behavior was quantitatively investigated using the Vogel–Fulcher model, which revealed the activation energy of 0.17–0.22 eV. Prototyped multilayer capacitors of 18 mm × 17 mm × 4 mm dimensions with a capacitance of 12.5 nF at 1 kHz were successfully constructed and demonstrated multiple charge–discharge characteristics up to 10 kV.

Description: K 3 Gd ( PO 4 ) 2 : RE 3+ (RE = Eu, Tb) are prepared by solid-state reaction and their photoluminescence (PL) properties are investigated under UV and VUV excitation, respectively. The obtained experimental data show that no energy transfer happens among the activator ions Tb 3+ or Eu 3+ under UV excitation. Under 147-nm excitation, the strongest emission intensity of K 3 Gd ( PO 4 ) 2 : RE 3+ (RE = Eu, Tb) is obtained when the activator ions Tb 3+ or Eu 3+ concentration is 0.8 mol, the integrate emission intensity of K 3 Gd 0.2 (PO 4 ) 2 :0.8Tb 3+ is about 204% of commercial phosphor Zn 1.96 SiO 4 :0.04 Mn 2+ with chromaticity coordinates of (0.340, 0.561) and the decay time of about 5.09 ms under 147-nm excitation. We analyze the experimental data and propose a possible energy-transfer mechanism under 147-nm excitation.

Description: The 0.72 Bi ( Fe 1− x Al x ) O 3 –0.28 BaTiO 3 ( x  = 0, 0.01, 0.03, 0.05, and 0.07, abbreviated as BFA x – BT ) lead-free high-temperature ceramics were prepared by the conventional ceramic processing. Systematic investigation on the microstructures, crystalline structures, dielectric and piezoelectric properties, and high-temperature stability of piezoelectric properties was carried out. The crystalline structures of BFA x –BT ceramics evolve from rhombohedral structure with x 〈  0.01 to the coexistence of rhombohedral structure and pseudocubic phases with x  ≈ 0.01, finally to pseudocubic phases when x 〉  0.03. Remarkably high-temperature stability with near-zero temperature coefficient of piezoelectric properties ( TCk p ), together with improved piezoelectric properties has been achieved for x  = 0.01 BFA x –BT ceramics. The BFA x –BT( x  = 0.01) ceramics simultaneously show the excellent piezoelectric properties of d 33  = 151 pC/N, k p  = 0.31 and super-high-temperature stability of T d  = 420°C, TCk p  = 1 × 10 −4 . It is considered that the observed strong piezoelectricity and remarkably high-temperature stability should be ascribed to the phase coexistence of rhombohedral and pseudocubic phases. The rhombohedral phases have a positive TCk p value and the pseudocubic phases possess a negative TCk p value. Thus, the TCk p value of BFA x –BT ceramics can be tuned by composition of x .

Description: The four new cerebrosides 1 – 4 possessing a unique C 18 9-methylsphinga-4,8-dienine-related moiety and a cyclic octapeptide, 5 , possessing alternating proline and glycine moietes were isolated from the Tuber indicum fermentation mycelium. Their structures were established on the basis of a spectroscopic analysis including NMR and HR-ESI-MS, as well as an acidic methanolysis experiment. To the best of our knowledge, the cerebrosides identified in the present study are quite different from those isolated from Tuber indicum fruiting bodies. Additionally, it was the first time that a cyclic peptide was isolated from the Tuber genus.

Description: Three fluorescent turn-on probes containing 3,6-dichloro-9 H -carbazole as carbazyl part have been designed and synthesized. Among studied anions F − , AcO − , H 2 PO , Cl − , Br − and I − , AcO − showed the strongest binding ability with all probes. The strong basic anions, such as AcO − , H 2 PO , and F − , induced a significant red-shift in absorption and a concomitant increase in fluorescent emission of the probes caused by photoinduced electron transfer (PET). The determination limit of probe 3 ( Scheme 1 ) toward AcO − is 3.0×10 −7   M . 1 H-NMR Titration experiments shed light on the nature of the interaction between the probes and the anions. Theoretical investigation further illustrated the possible binding mode in these host guest interactions and the roles of molecular frontier orbitals in molecular interplay.

Description: This Part 4 continues a general presentation of the principles of stereochemistry with special reference to medicinal compounds and their interactions with biological systems. Here, we discuss and illustrate two major aspects of conformational isomerism, namely a ) the concept of torsional isomerism about single bonds, and b ) the intertwined conformational and configurational aspects of the stereochemistry of cyclic systems. The review begins with a brief reminder of the history and thermodynamics of conformational isomerism, and goes on to explain and illustrate the conventions and graphical representations used for conformers. Examples are then examined, beginning with ethane, the simplest one, and building up to more complex cases, documenting the attractive or repulsive role of substituents. A similar approach is applied when dealing with cyclic systems, although here the presentation necessarily takes into account configurational aspects specific to cyclic systems. The pharmacological implications of the concepts discussed here will be presented in Part 6.

Description: A new eremophilane sesquiterpene, (2 β )-2-deoxo-2-methoxytessaric acid ( 1 ), and two new eudesmane sesquiterpenes, (3 β ,10 α )-3-methoxyleudesma-4,11(13)-dien-12-oic acid ( 2 ) and (3 α ,4 β ,8 α )-4-(acetyloxy)-3-(2,3-dihydroxy)-2-methyl-1-oxobutoxy-8-hydroxyeudesm-7(11)-eno-12,8-lactone ( 3 ), along with the ten known compounds 4 – 13 were isolated from the aerial parts of Laggera pterodonta. The structures of the new compounds were elucidated by spectroscopic analyses, including 2D-NMR data.

Description: Owing to the widespread presence of electromagnetic interferences, it is necessary to develop new materials with excellent high-temperature electromagnetic wave (EM) absorption properties. In the present work, ZnO is infiltrated into porous ZrSiO 4 substrates to form ZnO / ZrSiO 4 composite ceramics using sol-gel process. The doping of aluminum results in the improvement of electrical conductivity and the significant change in the morphology of ZnO . With the increase in environment temperature during measurement, the permittivity of the composite ceramics increases first and then decreases dramatically, which is attributed to the change in conductive loss. The electrical conductivity increases with increasing measurement temperature. However, the concentration of oxygen vacancies decreases under air atmosphere when the measurement temperature increases continuously, which results in the reduction in conductivity. Therefore, permittivities of the undoped and doped ceramics measured at 673 K are higher than the ones at the other temperatures. The composite ceramics maintain a relatively high EM absorption coefficient, low reflection coefficient (RC), and wide effective absorption bandwidth at environment temperatures up to 773 K. As a result, we conclude that the ZnO / ZrSiO 4 composite ceramics exhibit a promising prospect as a kind of high-temperature EM absorbing material.

Description: A simple synthesis of 2-hydrazinylidene-3-hydroxy-4 H -furo[3,2- c ]pyran-4-ones is described. A mixture of (isocyanoimino)(triphenyl)phosphorane, an aromatic aldehyde, and dehydroacetic acid (=3-acetyl-2-hydroxy-6-methyl-4 H -pyran-4-one) undergo a 1 : 1 : 1 addition reaction under mild conditions to afford the title compounds in excellent yields.

Description: A linear synthesis of the major oxepane fragment of zoapatanol, showing the induction of uterine contractions, and cervical dilation and uterine bleeding (by the concentrated zoapatle tea) in early human pregnancy, isolated from the leaves of Mexican zoapatle plant Montanoa tomentosa , is described from known intermediate involving Sharpless asymmetric epoxidation, bis-epoxide opening reaction with Corey Chaykovsky reagent, ring-closing metathesis reaction, and Horner Wadsworth Emmons olefination reaction as key steps.

Description: Total synthesis of biologically interesting natural and unnatural pyranoflavones has been accomplished starting from readily available 2,4-dihydroxyacetophenone or 2,4-dihydroxy-6-methoxyacetophenone in three steps, i.e. , benzopyran formation, condensation, and cyclization reaction.

Description: On treatment of 3-amino-5-aryl-1 H -pyrazoles 1 with dialkyl dicyanofumarates (=( E )-but-2-enedioates) 4 in boiling 1,2-dichloroethane, two competitive reactions occurred leading to 3-aryl-5-cyano-6,7-dihydro-6-oxo-1 H -pyrazolo[3,4- b ]pyridine-4-carboxylates 10 and 7-amino-2-arylpyrazolo[1,5- a ]pyrimidine-5,6-dicarboxylates 11 . In DMF at room temperature, as well as at 100°, only compounds 10 were isolated. The formation of the major products of type 10 was rationalized via Michael addition of 1 as a C ( 4 )-nucleophile onto 4 , followed by HCN elimination and lactamization. On the other hand, the minor products 11 result from a Michael addition of 1 onto 4 via the NH 2 group, and subsequent HCN elimination and cyclization. The structures of the products have been established by X-ray crystallography.

Description: A phytochemical investigation of the MeOH extract of Valeriana fauriei Briq . roots resulted in the isolation of two new sesquiterpenes, isovalerianin A (=(1 β ,4 Z ,6 β ,8 α )-8-(acetyloxy)-1,10-dihydroxy-6,11-cyclogermacr-4-en-15-al= rel -(1 R ,2 Z ,6 S ,7 R ,9 R ,10 S )-9-(acetyloxy)-6,7-dihydroxy-7,11,11-trimethylbicyclo[8.1.0]undec-2-ene-3-carboxaldehyde; 1 ) and valerianin C (=(2 α ,3 α ,6 α ,8 α )-3-(acetyloxy)-2,4,8-trihydroxyguai-1(10)-ene-12,6-lactone= rel -(3 R ,3a S ,4 R ,7 S ,8 S ,9 R ,9a R ,9b R )-8-(acetyloxy)-3a,4,5,7,8,9,9a,9b- octahydro-4,7,9-trihydroxy-3,6,9-trimethylazuleno[4,5- b ]furan-2(3 H )-one; 2 ), together with six known compounds, i.e. , camphor, methyl 4-hydroxybenzoate, 2-methoxybenzoic acid, benzoic acid, quercetin, and kaempferol. The structures of the compounds were established by detailed spectral analysis and comparison with previously reported data.

Description: [0001] textured alumina ceramics with a fine grain size were fabricated between 1400°C and 1600°C via templated grain growth (TGG) using fine alumina platelets (~0.6 and ~3 μm diameter) aligned by tape casting in either a 50 nm α- Al 2 O 3 matrix powder, or in a seeded boehmite sol. The 3 μm templates could be readily aligned by tape casting in both matrices (orientation parameters r  = 0.27 and 0.18, respectively), whereas 0.6 μm diameter templates were well aligned in the seeded boehmite sol only ( r  = 0.29). Improved alignment in boehmite sols is attributed to inorganic gelation, resulting in a strongly pseudo-plastic rheology that preserves template alignment against the influence of Brownian motion. The in situ formation of fine α- Al 2 O 3 matrix after transformation in the seeded boehmite system results in a higher driving force for TGG and improves texture development. The combination of 3 μm templates with a seeded boehmite matrix results in extremely high texture qualities (texture fraction f  = 0.97–0.99, r  = 0.17) while maintaining a relatively fine grain size (5–10 μm in diameter and 1.5–3 μm in thickness). Although undoped samples can be fully textured at 1600°C, adding as little as ~0.25 wt% CaO / SiO 2 dopant improves TGG kinetics and yields full texture at 1400°C.

Description: Yttria partially stabilized zirconia Y-PSZ/glass-ceramic composites were prepared by reaction sintering using powder mixtures of a SiO 2 – Al 2 O 3 – ZnO – CaO – ZrO 2 – TiO 2 -based glass and yttria partially stabilized zirconia (Y-PSZ). The glass crystallized during sintering at temperatures of 1173, 1273, and 1373 K to give a glass-ceramic matrix for high-temperature protecting coatings. With the increasing firing time, the added zirconia reacted with the base glass and a glass-ceramic material with dispersed zircon particles was prepared in situ . Furthermore, the added zirconia changed the crystallization behavior of the base glass, affecting the shape, amount, and distribution of zircon in the microstructure. The bipyramid-like zircon grains with imbedded residual zirconia particles turned out to have two growth mechanisms: the inward growth and the outward growth, and its rapid growth was mainly dominated by the later one. For comparison, the referenced glass-ceramic was prepared by sintering using exclusive glass granules and its crystallization behavior at 1173–1373 K was examined as well. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the crystallization behavior of the base glass and the phase evolution of the Y-PSZ/glass-ceramic composites.

Description: In this study, we present the preparation of a bulk material with a composition of 80 GeTe 2 –20 Ga 2 Te 3 by combining mechanosynthesis and sintering. This composition cannot be prepared by conventional melt/quenching technique. The progressive evolution of the powder during ball-milling is followed by X-ray Diffraction (XRD) and Differential Scanning Calorimetry analysis. The final powder obtained is highly crystalline, but a glass transition temperature ( T g ) is observed, indicating the presence of some amorphous phase remaining, allowing for its efficient sintering. By hot-pressing, a dense bulk material with a fine microstructure and a high electrical conductivity is obtained. The synthesis method described represents a simple and cost-effective way to produce tellurium-based materials of desired dimension with potential applications for optical storage or thermoelectric devices.

Description: Revealing and understanding the microscopic origins of the macroscopic properties of aluminosilicate glasses is important for the design of new glasses with optimized properties. In this work, we study the composition-structure-property relationships in 20 MgO / CaO sodium aluminosilicate glasses upon Al 2 O 3 -for- SiO 2 and MgO -for- CaO substitutions. We find that some properties (density, molar volume, Young's modulus, and shear modulus) are linear through the investigated range of Al 2 O 3 compositions, while others (refractive index, coefficient of thermal expansion, Vickers hardness, isokom temperatures, and liquid fragility index) exhibit a change in the slope around the composition with [ Al 2 O 3 ] = [ Na 2 O ], which is especially pronounced for the glasses containing MgO . We discuss these phenomena based on structural information obtained by NMR spectroscopy and topological considerations.

Description: In this article the changes on the surface of the 45S5 bioglass submitted to an enrichment with calcium ions were investigated. The method employed was the immersion of bioglass in calcium molten salt bath at 450°C. Changes in composition were probed by different techniques of chemical analysis. The use of SEM-EDS allowed estimating the thickness modified, as being about 10 μm. X-ray photoelectron spectroscopy enabled to infer over the structural changes on the surface of 45S5 bioactive glass. The entry of calcium in the vitreous network promoted the phase separation of microdomains rich in silica and phosphate on the surface of the glass. The formation of immiscibility region was attributed a depolymerization of silica network and also, to a possible migration of phosphate species from the bulk. The results of this study indicate a great change in the surface properties of this biomaterial. In addition, the method proposed in this study proved to be very promising in the possibility of designing the surface of bioactive glasses, to modulate the desired properties, keeping the bulk unchanged.

Description: Lanthanum hexaaluminate is a promising competitor to establish yttria partially stabilized zirconia as a thermal barrier coating material for Ni -based superalloy due to its relative low intrinsic thermal conductivity and low sinterability at temperatures exceeding 1100°C. Sr 2+ and Ti 4+ were selected as two dopants to partially substitute the La 3+ and Al 3+ in LaMgAl 11 O 19 , respectively. The variation in thermal conductivity with Sr 2+ and Ti 4+ fractions was analyzed based on structure information provided by X-ray diffraction and Raman spectroscopy. The average crystal size of LaMgAl 11 O 19 sintered at 1600°C for 10 min by spark plasma sintering is in nanoscale. The fully dense La 1− x Sr x MgAl 11− x Ti x O 19 solid solution showed a minimum thermal conductivity value (λ = 1.12 W/(m K) −1 , T  = 1273 K) at the composition of La 0.5 Sr 0.5 MgAl 10.5 Ti 0.5 O 19 ,which possibly reduces from the enhanced phonon scattering due to mass and strain fluctuations at the Ln 3+ and B 3+ sites.

Description: Aqueous 3Y-TZP inks with solid contents of 22 and 27 vol% were used for fabricating three-dimensional ceramic components by the direct ink-jet printing process (DIP). The DIP fabrication was realized using a thermal ink-jet (TIJ) printing system. Despite the different physical properties of the inks, both inks were successfully ejected and deposited. To define the optimum window of the ink properties required for a stable printing operation, both ceramic inks as well as a typical TIJ ink were characterized in terms of particle size distribution, zeta potential, viscosity, surface tension, and the inverse Ohnesorge number ( Oh −1 ). Moreover, single drops of all inks were deposited and analyzed by scanning electron microscopy (SEM) to examine the form and integrity of the ejected drops. Demonstration objects (a base with curved channels and a sample molar tooth) were DIP fabricated using both of the ceramic inks. These objects show the potentials of the DIP process for ceramics manufacturing particularly by using TIJ printing systems.

Description: Spherical granules of aluminum nitride (AlN) with an average particle size of about 50 μm were produced from aqueous suspensions using an AlN powder surface treated against hydrolysis with aluminum dihydrogenphosphate [Al(H 2 PO 4 ) 3 ]. Two different amounts of Al(H 2 PO 4 ) 3 were tested and the effects of surface treatment and aging time were evaluated by various techniques (XRD, TG-DTA, zeta potential and pH measurements). The treated powder exhibited antihydrolytic property and good dispersing behavior, enabling the preparation of low-viscosity and high-concentration aqueous AlN slurries for freeze granulation. The spherical AlN granules were sintered in a boron nitride (BN) powder bed followed by ultrasonic washing of the AlN granulates/BN mixture to remove BN. The sintered spherical AlN granules present excellent crystallinity and high sphericity as observed from SEM micrographs.

Description: Near-infrared (NIR) quantum cutting involving the emission of two NIR photons for each visible photon absorbed is realized from Eu 2+ /Yb 3+ codoped chalcohalide glasses. Excitation, emission and decay spectra are measured to prove the occurrence of cooperative energy transfer (ET) from Eu 2+ to Yb 3+ . The maximum ET efficiency obtained is as high as 85%. The ET from Eu 2+ to Yb 3+ is followed by dipole-dipole interaction. The possible mechanism of ET is discussed.

Description: Well-crystallized pure BiFeO 3 nanopowders were successfully synthesized at the temperature as low as 120°C by an ethanol-assisted hydrothermal process. In this synthesis, the composition of the solvent played important roles in the formation of pure BiFeO 3 . The BiFeO 3 nanopowders synthesized with 4:3 ethanol/water ratio mainly consists of cubic structures with size from 50 to 150 nm. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements indicated that pure BiFeO 3 nanopowders showed a spin-glass transition below the freezing temperature. Moreover, the BiFeO 3 nanopowders exhibited ferromagnetic order at room temperature.

Description: Nanoparticles of Co 0.6 Zn 0.4 Fe 2 O 4 , with narrow size distribution, regular morphology, and high saturation magnetization, have been synthesized. The synthesis, involved a very rapid mixing of reducible metal cations with sodium borohydride, is carried out in a colloid mill and followed by a separate hydrothermal process. The microstructure and magnetic properties of the synthesized nanoparticles are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). The effects of different synthesis conditions (synthesis temperature and reaction time) on the characteristics of the ferrite nanoparticles are discussed. The changes in cation contribution are revealed by the Raman study. The magnetic measurements explore that all the as-synthesized samples are superparamagnetic in nature. The corresponding superparamagnetic behavior is explained by paramagnetic Langevin theory. Note that, the superparamagnetic Co 0.6 Zn 0.4 Fe 2 O 4 ferrite nanoparticle, with excellent performance, can be synthesized at 160°C for a short reaction time (4 h).

Description: We show that multilayer green tapes constituted from sandwiched layers of NiO–zirconia anode and cubic zirconia electrolyte can be sintered below 1000°C in a few seconds under the influence of a DC electric field. The sintering yields a dense electrolyte layer with minor closed porosity, and an anode layer with open porosity, and, most importantly, a multilayer that is largely devoid of defects and delamination.

Description: 2,3-Dihydro-4 H -thiopyrano[2,3- b ]pyridin-4-ones 4 were prepared by a three-step sequence from commercially available 2-chloropyridine ( 1 ). Thus, successive treatment of 1 with i Pr 2 NLi (LDA) and α , β -unsaturated aldehydes gave 1-(2-chloropyridin-3-yl)alk-2-en-1-ols 2 , which were oxidized with MnO 2 to 1-(2-chloropyridin-3-yl)alk-2-en-1-ones 3 . The reactions of 3 with NaSH⋅ n H 2 O proceeded smoothly at 0° in DMF to provide the desired thiopyranopyridinones. Similarly, 2,3-dihydro-4 H -thiopyrano[2,3- c ]pyridin-4-ones 8 and 2,3-dihydro-4 H -thiopyrano[3,2- c ]pyridin-4-ones 12 were obtained starting from 3-chloropyridine ( 5 ) and 4-chloropyridine ( 9 ), respectively.

Description: Three new ent -kaurane diterpenoids, (4 α )-19-nor- ent -kaurane-4,16,17-triol ( 1 ), (4 α ,16 α )-17-(acetyloxy)-19-nor- ent -kaurane-4,16 - diol ( 2 ), and 17-hydroxy- ent -kaur-15-en-19-al ( 3 ), together with 11 known compounds, were isolated from the stem bark of Annona squamosa L. The structures of 1 – 3 were identified by analysis of their spectroscopic data. All compounds were evaluated for cytotoxic activity against human lung cancer (95-D) and ovarian cancer (A2780) cell lines, and compounds 3, 5, 7, 11 – 14 exhibited promising antiproliferative activities with IC 50 values ranging from 0.38 to 34.66 μ M .

Description: Two new triazoles, chrysotriazoles A and B ( 1 and 2 , resp.), along with two known quinazolinones, 3 and 4 , two known 2-(4-hydroxyphenyl)acetamides, 5 and 6 , and two known N -(4-hydroxystyryl)formamides, 7 and 8 , were isolated and identified from the culture extract of Penicillium chrysogenum EN-118, an endophytic fungus obtained from the marine brown alga Sargassum pallidium. The structures of the isolated compounds were elucidated by NMR-spectroscopic analysis, and that of compound 1 was confirmed by X-ray crystallographic analysis of its p -bromobenzoate derivative. Compounds 4, 5 , and 7 showed moderate cytotoxicities against Du145, A-549, and HeLa cell lines.

Description: The reaction of N , N -bis(diphenylphosphino)naphthalen-1-amine ( 1 ) with [M(CO) 6 ] (M=Cr, Mo, W; 1 : 1 molar ratio) afforded cis -[M(CO) 4 ( 1 )] 2 (M=Cr), 3 (M=Mo), and 4 (M=W). Compounds 2 – 4 were identified and characterized by elemental analysis and multinuclear NMR ( 1 H-, 13 C-, and 31 P-NMR) and IR spectroscopy. A crystal-structure determination of complex 3 was carried out.

Description: Phytochemical investigation of the whole herbs of Aconitum tanguticum ( Maxim .) Stapf var. trichocarpum Hand.-Mazz . led to the isolation of one heteratisine-hetidine-type bis-diterpenoid alkaloid, trichocarpidine ( 1 ), three hetidine-hetisine type bis-diterpenoid alkaloids, trichocarpinine A–C ( 2 – 4 , resp.), together with nine known compounds. Their structures were elucidated by spectroscopic analyses.

Description: Four metal-ion-binding nucleosides, viz. 2,6-bis(1-methylhydrazinyl)-9-( β - D -ribofuranosyl)-9 H -purine ( 2a ) and its N -acetylated derivative, 2b , 2,4-bis(3,5-dimethyl - 1 H -pyrazol-1-yl)-5-( β - D -ribofuranosyl)pyrimidine ( 3 ), and 2,4-bis(1-methylhydrazinyl)-5-( β - D -ribofuranosyl)pyrimidine ( 4 ) have been synthesized. The ability of these nucleosides and the previously prepared 2,6-bis(3,5-dimethyl - 1 H -pyrazol-1-yl)-9-( β - D -ribofuranosyl)-9 H -purine to form Pd 2+ - and Hg 2+ -mediated complexes with uridine has been studied by 1 H-NMR spectroscopy. To obtain additional support for the interpretation of the NMR data, comparative measurements on the ternary-complex formation between pyridine-2,6-dicarboxamide ( 5 ), pyrimidine nucleosides, and K 2 PdCl 4 were carried out.

Description: Organotin complexes 1 – 6 of the general formula [SnR 2 L] and [(SnR 3 ) 2 L] (L=phenanthrenequinone dioximato – a bidentate ligand, R=Me, Bu, and Ph) were synthesized by the reaction of the sodium salt of the ligand H 2 L (prepared in situ with MeONa) and SnR 2 Cl 2 /SnR 3 Cl in 1 : 1 and 1 : 2 molar ratios. The physical and spectral properties of the newly synthesized complexes 1 – 6 are described. DFT and HF Calculations were performed to confirm the proposed structures.

Description: The 3-allyl-2-methylquinazolin-4(3 H )-one ( 1 ), a model functionalized terminal olefin, was submitted to hydroformylation and reductive amination under optimized reaction conditions. The catalytic carbonylation of 1 in the presence of Rh catalysts complexed with phosphorus ligands under different reaction conditions afforded a mixture of 2-methyl-4-oxoquinazoline-3(4 H )-butanal ( 2 ) and α ,2-dimethyl-4-oxoquinazoline-3(4 H )-propanal ( 3 ) as products of ‘linear’ and ‘branched’ hydroformylation, respectively ( Scheme 2 ). The hydroaminomethylation of quinazolinone 1 with arylhydrazine derivatives gave the expected mixture of [(arylhydrazinyl)alkyl]quinazolinones 5 and 6 , besides a small amount of 2 and 3 ( Scheme 3 ). The tandem hydroformylation/reductive amination reaction of 1 with different amines gave the quinazolinone derivatives 7 – 10 . Compound 10 was used to prepare the chalcones 11a and 11b and pyrazoloquinazolinones 12a and 12b ( Scheme 4 ).

Description: Herein, we report on the crystal structures of Nb 2 AlC and TiNbAlC—actual composition (Ti 0.45 ,Nb 0.55 ) 2 AlC—compounds determined from Rietveld analysis of neutron diffraction patterns in the 300–1173 K temperature range. The average linear thermal expansion coefficients of a Nb 2 AlC sample in the a and c directions are, respectively, 7.9(5) × 10 −6 and 7.7(5) × 10 −6  K −1 on one neutron diffractometer and 7.3(3) × 10 −6 and 7.0(2) × 10 −6  K −1 on a second diffractometer. The respective values for the (Ti 0.45 ,Nb 0.55 ) 2 AlC composition—only tested on one diffractometer—are 8.5(3) × 10 −6 and 7.5(5) × 10 −6  K −1 . These values are relatively low compared to other MAX phases. Like other MAX phases, however, the atomic displacement parameters (APDs) show that the Al atoms vibrate with higher amplitudes than the Ti and C atoms, and more along the basal planes than normal to them. When the predictions of the APDs obtained from density functional theory are compared to the experimental results, good quantitative agreement is found for the Al atoms. In case of the Nb and C atoms, the agreement was more qualitative.

Description: In this study, lithium disilicate (LS 2 ) glass samples with different particle sizes ranging from less than 105 to 850 μm were prepared. These specimens were inserted in a Pt-Rh DSC crucible and heated to 850°C at different rates (ϕ = 0.5–30 K/min) to identify their crystallization peaks. The activation energies for the overall crystallization ( E ) and the Avrami coefficient ( n ) were evaluated using different nonisothermal models. Specifically, n was evaluated using the Augis–Benett model and the Ozawa method, and E was evaluated using the Kissinger and Ligero methods. As expected, the coarse particles mainly crystallized in the volume, while surface crystallization was predominant in the samples with particle sizes of less than 350 μm. This result was confirmed through SEM analysis of the double stage heat-treated samples. In contrast with previous studies, our results demonstrated that the activation energy decreased as the particle size increased. In addition, no clear correlation between the peak intensity (δ T p ) and the particle size was observed.

Description: In this letter, 2-μm Pb 0.97 La 0.02 (Zr 0.75 Sn 0.18 Ti 0.07 )O 3 antiferroelectric thick film with tetragonal structure was prepared. The effects of operating electric field, temperature, and frequency on the thermal–electrical energy harvesting capacity of the film were studied by using the Olsen cycle. The results demonstrated that giant energy harvesting effect could be realized in the antiferroelectric thick film. The maximum harvestable energy density per cycle of the film was about 7.8 J/cm 3 at 1 kHz, which was the largest reported value to date. The corresponding energy harvesting efficiency was 0.53%. Moreover, the film had a low leakage current density (about 7.3 × 10 −7 and 3.9 × 10 −5  A/cm 2 at 25 and 200°C, respectively), which was favorable for its application in the devices of the thermal–electrical energy harvesting.

Description: Discharged energy properties of PbO–SrO–Na 2 O–Nb 2 O 5 –SiO 2 glass-ceramics with crystallization time from 1 to 1000 min were investigated by measuring their hysteresis loops (described as quasi-static measuring method) and pulse-discharge current-time curves (described as dynamic measuring method). The results show the same trend for both measuring methods: With the increment of crystallization time, the discharged energy density increases gradually, while the energy efficiency decreases. The highest energy efficiencies were obtained in the sample with crystallization time of 1 min, which are 96.3% and 82.4%, corresponding quasi-static and dynamic measurement, respectively. The reduction of energy efficiency with crystallization time is attributed to combined effect of ferroelectric polarization and interfacial polarization, and part of the corresponding energy could not release in the pulse-discharge process.

Description: The dc electrical stability of ZnO varistors was effectively improved by controlling the composition proportion of Bi 2 O 3 and SiO 2 as well as annealing condition. The microstructure, current–voltage ( I – V ) property, and dc degradation characteristics are significantly affected by the molar ratio of Bi 2 O 3 to SiO 2 in composition. It is found that a phase transition from β-Bi 2 O 3 (with dissolved Si) to Bi 12 SiO 20 , with a volume contraction of 5.88%, occurred after annealing at 850°C. The formed Bi 12 SiO 20 plays an important role in improving the electrical stability by inhibiting the oxygen-desorption at the grain boundary.

Description: Dense (1- x )BaTiO 3 - x BiYbO 3 (BBTYb) ceramics were fabricated by the solid state reaction method. According to X-ray diffraction data, the average crystal symmetry of x ≤ 0.04 ceramics is described by the non-centro symmetric tetragonal P 4 mm space group, whereas the average crystal symmetry of x ≥ 0.06 ceramics is better described by the centrosymmetric cubic Pm m space group. Raman spectroscopy supports a change in the average crystal symmetry at x ≥ 0.06, but also reveals differences in the local crystal structure for x ≤ 0.04. In this compositional range, BBTYb ceramics undergo a so-called ferroelectric-to-relaxor crossover, which is a manifestation of the continuous modification of local structure. Weak-relaxor behavior was observed in x ≥ 0.06 ceramics, for which the local crystal symmetry departs from cubic, as indicated by the presence of Raman spectra.

Description: Rare earth (RE)-doped silica-based optical fibers with transparent glass ceramic (TGC) core was fabricated through the well-known modified chemical vapor deposition (MCVD) process without going through the commonly used stage of postceramming. The main characteristics of the RE-doped oxide nanoparticles namely, their density and mean diameter in the fibers are dictated by the concentration of alkaline-earth element used as phase-separating agent. Magnesium and erbium co-doped fibers were fabricated. Optical transmission in term of loss due to scattering as well as some spectroscopic characteristics of the erbium ions was studied. For low Mg content, nano-scale particles could be grown with and relatively low scattering losses were obtained, whereas large Mg-content causes the growth of larger particles resulting in much higher loss. However, in the latter case, certain interesting alteration of the spectroscopic properties of the erbium ions were observed. These initial studies should be useful in incorporating new doped materials to realize active optical fibers for constructing lasers and amplifiers.

Description: A novel two-step process has been developed for the preparation of Ba 0.9 Ca 0.1 TiO 3 plate-like grains with [110]-crystal-axis-orientation. In the first step, plate-like particles of a layered titanate H 1.07 Ti 1.73 O 4 are solvothermally treated in a Ba(OH) 2 –Ca(OH) 2 mixed solution, and then in the second step, heat-treat the solvothermally treated sample to complete the formation reaction of Ba 0.9 Ca 0.1 TiO 3 . The formation reaction and nanostructure of the Ba 0.9 Ca 0.1 TiO 3 plate-like grains were characterized using X-ray diffraction, FE-SEM, TEM, and SEAD. The Ba 0.9 Ca 0.1 TiO 3 plate-like grains are constructed from spherical nanoparticles with particle size of about 10–20 nm. The spherical nanocrystals in each plate-like grain arrange in the same crystal-axis-orientation direction, which presented a diffraction pattern similar to the single crystal. The Ba 0.9 Ca 0.1 TiO 3 plate-like grains were utilized to fabricate an oriented Ba 0.9 Ca 0.1 TiO 3 ceramic to demonstrate the potential application of the plate-like grains, and the [110]-oriented Ba 0.9 Ca 0.1 TiO 3 ceramic with a high degree orientation of F 110 = 76% and small grain size of about 1–2 μm was obtained.

Description: The surface and interface enthalpies of CeO 2 were studied by high temperature oxide melt solution calorimetry combined with water adsorption calorimetry. The surface enthalpies of the hydrated and anhydrous surfaces are 0.86 ± 0.02 and 1.16 ± 0.02 J/m 2 , respectively. The water adsorption enthalpies are similar for nano and bulk ceria; for the nano ceria the integral adsorption enthalpy for chemisorbed water relative to water vapor is −59.82 ± 0.74 kJ/mol with coverage of 8.79 ± 0.39 H 2 O/nm 2 and for the bulk it is −61.69 ± 1.26 kJ/mol with coverage of 8.15 ± 0.66 H 2 O/nm 2 . The interfacial enthalpy is 0.81 ± 0.14 J/m 2 . The obtained energies are in good agreement with reported data from atomistic simulations and less direct experimental determinations.

Description: Silicon nitride exhibits fatigue based on cyclic crack propagation which is critical for components under repeated loading. Lifetime predictions for such components are usually based on power law formulations and are most sensitive to the crack growth exponent n . Various statistical procedures exist to determine the parameters from cyclic tests of un-cracked smooth samples. In this work, an analysis is presented for silicon nitride (SL200) lifetime data with a focus on the relation between load ratio and the exponent n . It is found that n increases with the load ratio which has also been observed for macroscopic cracks in silicon nitride earlier. A high degree of uncertainty is associated with the crack growth exponent due to the sparse lifetime database. A pooling strategy is presented which increases the sample size of the underlying lifetime distribution and successfully decreases the scatter in the crack propagation curves and the uncertainty in the crack propagation exponent and, thus, in the lifetime prediction.

Description: A novel high-throughput combinatorial library preparation technique for ceramics requiring low levels of dopant is demonstrated and assessed for the case of donor-doped barium titanate (BT) materials with positive temperature coefficient of resistance (PTCR). The droplet-doping process is performed by infiltrating liquid dopant precursors into porous BT disks and viewed using a high-speed camera. The resulting dopant distribution in the body of the disk shows high uniformity as assessed by energy dispersive (EDS) and wavelength dispersive (WDS) spectroscopies. X-ray diffraction (XRD) measurements and resistivity–temperature (ρ– T ) curves show evidence of the changes in structure and PTCR profiles with change in composition and are closely matched to previously published data for samples made by conventional ceramic routes. The procedure, thus validated, has the potential to deliver dopant-doped BT-based PTCR libraries rapidly with a very wide range of dopant mixtures and concentrations for electrical property measurement and deserves to be applied to other low-level dopant ceramic systems.

Description: This article reports the target and liquid media influences on the microstructures and optical properties of ZnO nanoparticles synthesized using pulsed laser ablation (PLA) method. Zinc and ZnO target were ablated with laser in pure water and surfactant solution, respectively. The obtained nanoparticles were characterized using X-ray diffraction spectrometer, transmission electron microscopy, X-ray photoelectron spectroscopy, optical absorption spectrum, and photoluminescence spectrum. The nanoparticles synthesized in surfactant solution were of spherical shapes, but with different microstructures and optical properties. The nanoparticles synthesized in water using zinc target showed rod shapes and both UV and visible emissions. When ZnO target was ablated in water, flake-shaped nanoparticles were synthesized and strong UV, but weak violet emissions were observed. At last, the influences of PLA growth condition on the nanoparticles microstructures and the relationship between the optical properties and their stoichiometries were discussed.

Description: The (1- x )PbTiO 3 - x BiMeO 3 (Me = Fe, In, Sc) solid solutions were prepared and investigated using high-temperature X-ray diffraction for the B-site dopant effect on their thermal expansion behaviors. Compared with PbTiO 3 , the negative thermal expansion of (1- x )PbTiO 3 - x BiFeO 3 was enhanced, whereas that of (1- x )PbTiO 3 - x BiInO 3 was a little weakened and was much weakened in (1- x )PbTiO 3 - x BiScO 3 . An empirical linear correlation between the average effective radius of the B-site cations and the unit cell volumes at Curie point of the solid solutions was concluded. The relationship was also observed in other PbTiO 3 -BiMeO 3 -type solid solutions and was supposed to be widely useful in predicting the thermal expansion coefficient of compounds of this sort. Above the Curie point, the unit cell volumes of the compounds were determined by the radii of the doped B-site cations. The weaking and vanishing of the lattice distortion caused by spontaneous polarization displacements was proved by Raman scatting spectrum, which supported the relationship in the lattice dynamic aspect.

Description: A new route to synthesize SiCN(O) precursor is adopted with vinyl trichlorosilane and solid ammonia carbamate as starting materials. The reaction is controlled in autoclave. A mixture of solid oxygen-rich polysilazane and ammonia chloride is obtained for the reason of dimensional poly-condensation. It is adopted to take the byproduct apart using chemical vapor transportation. The mixture is pyrolyzed at 1100°C for 2 h in Ar, and black SiCN(O) powder is separated from the byproduct. The chemical component of the powder is Si 1.00 C 2.07 N 1.09 O 0.29 . XRD analysis indicates that the black powder keeps amorphous at a temperature up to 1450°C. At 1500°C, SiC phase is first precipitated. With the temperature further increased, Si 2 N 2 O phase appeared. It provides a way to separate other nitrides from ammonia chloride in similar system.

Description: Nano alumina powders have been synthesized by combustion method using eight new fuels. The effectiveness of key process factors on the production of nanoparticles was investigated and optimized using Taguchi L 16 array design. The products were characterized by XRD, BET, TGA, EDX, FESEM, and TEM analyses. Results demonstrated that the nano-structured aluminum oxide powders had crystal sizes between 7.2 and 13 nm and specific surface areas between 21.0 and 70.0 m 2 /g. The synthesis of γ-alumina was modified to achieve higher specific surface area (122.6 m 2 /g). A nano-network of powders which was woven by alumina nano-fibers was successfully fabricated by the modification route. The length and diameter of fibers were about 160 and 10 nm, respectively.

Description: Aqueous tape casting of yttria stabilized zirconia (YSZ) having very wide particle size range was investigated using bio-polymer, gelatin as binder and glycerol as plasticizer. Best dispersion of YSZ powder was obtained by using an anionic polyelectrolyte DARVAN 821A at pH 7.5. Gelling properties of gelatin, plasticized with water and glycerol have been studied by dynamic shear measurements. Decreasing concentration of gelatin significantly decreases the gelling temperature of it. With the addition of optimum amount of binder and plasticizer, it has been possible to prepare stable YSZ suspension of 45–50 wt% solid loading that exhibited the desired shear-thinning behavior. Green tapes with good flexibility (strain to failure: 12%–24%) and strength (2–3 MPa) with total organics content of 10–14 wt% were obtained. After removal of organics, the tapes were sintered at 1550°C for 3 h. The sintered density of the tapes thus obtained was about 99% of the theoretical density. The grain size of the sintered tape was fairly large (10–20 μm); but the surface of the sintered tape (thickness: 100 μm) did not show any visible porosity.

Description: The phase stability, electronic structure, compressibility, optical and elastic properties of two polymorphs of Ti 3 SnC 2 were investigated using first-principle calculation. α-Ti 3 SnC 2 is confirmed to be the preferred equilibrium phase under high pressure and high temperature. The electronic structure calculations reveal that the Ti and C atoms form a strong Ti1-C-Ti2-C-Ti1 covalent bond chain while the bonding between Ti1 and Sn is relatively weak. In the low frequency range from radio waves to visible light, Ti 3 SnC 2 behaves similarly with TiC. This material exhibits anisotropic compressibility under hydrostatic pressure: it is more compressible along the c -direction than along a -direction, related to the different bond stiffness and bond angle changes under high pressure. The second-order elastic coefficients were calculated. For the α-phase, the bulk, B , shear, G , and Young's moduli, E , are calculated to be 169.4, 124, and 197.4 GPa, respectively. The low G / B ratio partially explains why Ti 3 SnC 2 is relatively soft and damage tolerant.

Description: The boron carbide (B 4 C) titanium diboride (TiB 2 ) ceramic eutectic is being investigated for armor and tribological applications. Electron diffraction shows [11 0] TiB 2 //[21 1] B 4 C//growth direction, (0001) TiB 2 //( 2 0) B 4 C is parallel to the interface plane, and transmission electron microscopy (TEM) imaging reveals no interface phase. Thermal residual stress distributions are calculated via finite element modeling of an experimental eutectic microstructure. The B 4 C matrix is found to be about 400 MPa in compression, and the TiB 2 lamellae approximately 1.3 GPa in tension. Stress and strain energy concentrations are found at the tips of TiB 2 lamellae. TEM of deformed materials correlates well with the finite element calculations, showing preferential fracture in areas of stress concentration. Interfacial delamination and crack deflection are also observed in deformed materials.