ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (156)
  • 2010-2014  (156)
Collection
  • Articles  (156)
Publisher
Years
Year
Journal
  • 1
    Publication Date: 2014-12-01
    Description: Strong shock wave interactions with ceramic material ceria (CeO 2 ) in presence of O 2 and N 2 gases were investigated using free piston driven shock tube (FPST). FPST is used to heat the test gas to very high temperature of about 6800–7700 K (estimated) at pressure of about 6.8–7.2 MPa for short duration (2–4 ms) behind the reflected shock wave. Ceria is subjected to super heating and cooling at the rate of about 10 6 K/s. Characterization of CeO 2 sample was done before and after exposure to shock heated test gases (O 2 and N 2 ). The surface composition, crystal structure, electronic structure and surface morphology of CeO 2 ceramic were examined using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Results obtained from the experimental investigations show that CeO 2 can withstand high pressure accompanied by thermal shock without changing its crystal structure. Reducible CeO 2 releases lattice oxygen making it possible to shift between reduced and oxidized states upon the interaction with shock heated gas. Due to such reaction mechanism, CeO 2 ceramic undergoes nitrogen doping with decrease in lattice parameter. Investigations reveal that CeO 2 retains its crystal structure during strong shock interaction, even at elevated pressure.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2014-12-01
    Description: Titanium phosphates were prepared from titanium chloride and sodium pyrophosphate at various pH in hydrothermal process as a novel white pigment for cosmetics. Their chemical composition, powder properties, photo catalytic activity, colour phase and smoothness were studied. The obtained materials had a higher Ti/P ratio than that used in preparation conditions because of the formation of titanium oxide and hydroxide. The samples prepared at pH = 4 had particles smaller than 100 μm. Titanium phosphates had less photo catalytic activity to protect the sebum on the skin. The obtained materials in hydrothermal process and their thermal products at 100°C showed high reflectance in the range of visible light.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2014-12-01
    Description: Nickel-zinc ferrite nanoparticles are important soft magnetic materials for high and low frequency device application and good dielectric materials. Nickel-zinc ferrite nanoparticles with composition Ni 0.5 Zn 0.5 Fe 2 O 4 were prepared using mechanical alloying to analyze the effect of sintering temperature on microstructure evolution of a single sample with dielectric properties. The single sample with nanosized pellet was sintered from 600 °C to 1200 °C and analyzed by X-ray diffraction (XRD) to investigate the phases of the powders and by field emission scanning electron microscopy (FESEM) for the morphology and microstructure analyses. Dielectric properties such as dielectric constant ( ɛ ′) and dielectric loss ( ɛ ″) were studied as functions of frequency and temperature for Ni 0.5 Zn 0.5 Fe 2 O 4 . The dielectric properties of the sample were measured using HP 4192A LF impedance analyzer in the low frequency range from 40 Hz to 1 MHz and at temperature ranging from 30 °C to 250 °C. The results showed that single phase Ni 0.5 Zn 0.5 Fe 2 O 4 cannot be formed by milling alone and therefore requires sintering. The crystallization of the ferrite sample increased with increasing sintering temperature, while the porosity decreased and the density and average grain size increased. Evolution of the microstructure resulted in three activation energies of grain growth, where above 850 °C there was a rapid grain growth in the microstructure. Dielectric constant and loss factor decreased with the increase in frequency. The optimum sintering temperature of Ni 0.5 Zn 0.5 Fe 2 O 4 was found to be 900 °C which had high dielectric constant and low dielectric loss.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2014-12-01
    Description: Porcelain fused to metal (PFM) has received great attention over the last few years due to its importance in the dentistry. Kalsilite (K 2 O·Al 2 O 3 ·SiO 2 ) is a high thermal expansion porcelain, suitable for bonding to metals. However, kalsilite is a metastable phase which gets converted into crystalline leucite upon heating. In the current work feasibility of developing stable kalsilite phase, dispersion of MgF 2 in it as an additive and using mechanochemical synthesis are studied. Micro fine dental material has been formulated by mixing prepared kalsilite with low temperature frit (LTF) in different ratio. The crystalline phases evolved in fired powders are characterized by powder X-ray diffraction (XRD) technique. Kalsilite with different ratio of LTF has been cold pressed and heat treated to examine its coefficient of thermal expansion (CTE), flexural strength, apparent porosity (AP), bulk density (BD) and microstructure. Results indicate that MgF 2 addition and high milling duration help in kalsilite stabilization. Temperature also plays an important role in this stabilization, and at 1100°C single phase kalsilite formation is observed. Present outcomes demonstrate that it is easily possible to synthesize a stable single phase kalsilite with desirable properties.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2014-12-01
    Description: YBa 2 Cu 3 O y (YBCO) foam samples show an open, porous foam structure, which may have benefits for many applications of high- T c superconductors. As the basic material of these foams is a pseudo-single crystalline material with the directional growth initiated by a seed crystal similar to standard melt-textured samples, the texture of YBCO is a very important parameter. Therefore, we analysed the local texture and grain orientation of the individual struts forming the foam by means of atomic force microscopy (AFM) and electron backscatter diffraction (EBSD). Due to the processing route starting with Y 2 BaCuO 5 (211), a two-phase analysis must be performed, so a high surface quality is necessary to enable an automated EBSD scan. Good quality Kikuchi patterns were obtained from both the YBCO and 211 phases. We found an inhomogeneous distribution of the residual 211 particles, which are mainly randomly oriented and have sizes ranging between 200 nm and 15 μm. In contrast to this, the YBCO matrix shows a dominating orientation with cracks with a typical distance of 1–10 μm. Furthermore, the analysis of strut cross-sections reveals that the entire strut is converted to the YBCO phase.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2014-12-01
    Description: The effect of Mn 3 O 4 addition on microhardness, microstructure and electrical properties of vanadium oxide doped zinc oxide varistor ceramics is systematically investigated. The Vicker’s microhardness H V has decreased with increasing the amount of Mn 3 O 4 . Also, the average grain size has decreased from 27.51 μm to 19.55 μm with increasing the amount of Mn 3 O 4 up to 0.50 mol%, whereas an increase in Mn 3 O 4 up to 0.75 mol% has caused the average grain size to increase and then it decreases with increasing Mn 3 O 4 from 0.75 mol% to 1.00 mol%. The sintered density has decreased from 5.38 g/cm 3 to 5.31 g/cm 3 with increasing the amount of Mn 3 O 4 . The varistor ceramic modified with 0.50 mol% Mn 3 O 4 has exhibited excellent nonlinear properties, with 16.29 for the nonlinear coefficient and 441.9 μA/cm 2 for the leakage current density. Furthermore, the sample doped with 0.50 mol% Mn 3 O 4 has been found to possess donor density as 0.77×10 18 cm −3 and 0.916 eV barrier height.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2014-12-01
    Description: We report the glassy behavior of dysprosium doped barium zirconium titanate single phase perovskite ceramics with general formula Ba 1− x Dy 2 x /3 Zr 0.25 Ti 0.75 O 3 prepared by solid-state reaction method. Temperature and frequency dependent dielectric studies of the ceramics reveal relaxor behavior. A non-Debye relaxation, which is analogous to the magnetic relaxation in spin-glass system, is observed clearly around temperature of dielectric permittivity maximum ( T m ). Frequency dependence of T m governed by production of polar nano-regions is analyzed using Debye relation, Vogel-Fulcher (V-F) relation and power law. A clear change in dynamic behavior is observed by power parameter which is related to growth of interactions between polar nano-regions with different composition. Various parameters like activation energy for relaxation, freezing temperature, relaxation frequency, etc., are determined after non-linear curve fitting. Temperature dependence of dielectric constant at temperatures much higher and lower than T m is analyzed by two exponential functions, which gives an idea about the production of polar clusters at high temperature and distribution of freezing temperatures at lower temperature. Various other associated parameters are calculated by non-linear curve fitting and their significance has been explained.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2014-12-01
    Description: Ti doped hematite α -Fe 2− x Ti x O 3 ( x = 0.0, 0.0206 and 0.0344) samples are synthesized using solid-state ceramic route technique. Single phase and corundum (Al 2 O 3 ) type structure is revealed from the X-ray diffraction (XRD) pattern. On substitution of Ti at Fe site, all Raman active modes are shifted to higher wave numbers. An additional feature of E u (LO) mode at about 660 cm-1 is observed. The E u mode frequency is decreased and pronounced systematically as a function of Ti doping, and it reaches a value of 658 cm −1 for x = 0.0344. The coercivity H c (remanence M r ) for x = 0.0, 0.0206 and 0.0344 are determined to be 995 Oe (0.44 emu/mg), 1404 Oe (0.00019 emu/mg) and 2023 Oe (0.00016 emu/mg), respectively. The larger coercivity for Ti doped samples can be attributed to their enhanced shape and magneto-crystalline anisotropy. The observed isomer shift ( δ ) from room temperature Mössbauer data clearly shows the presence of ferric (Fe 3+ ) and Ti 4+ ions illustrating strong ferromagnetic ordering up to x = 0.0206 in α -Fe 2− x Ti x O 3 hematite and weak ferromagnetic ordering of α -Fe 2− x Ti x O 3 for x = 0.0344.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2014-12-01
    Description: Highly crystallized mullite has been achieved at temperatures of 1100 °C and 1400 °C by sol-gel technique in presence of titanium and strontium ions of different concentrations: G 0 = 0 M, G 1 = 0.002 M, G 2 = 0.01 M, G 3 = 0.02 M, G 4 = 0.1 M, G 5 = 0.2 M and G 6 = 0.5 M. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), LCR meter characterized the samples. Mullite formation was found to depend on the concentration of the ions. The dielectric properties (dielectric constant, loss tangent and AC conductivity) of the composites have been measured, and their variation with increasing frequency and concentration of the doped metals was investigated. All the experiments were performed at room temperature. The composites showed maximum dielectric constants of 24.42 and 37.6 at 1400 °C of 0.01 M concentration for titanium and strontium ions at 2 MHz, respectively. Due to the perfect nature of the doped mullite, it can be used for the fabrication of high charge storing capacitors and also as ceramic capacitors in the pico range.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2014-12-01
    Description: About 8% of the imported iron oxide pellets burdens to Egypt are wasted. In this paper, broken pellets waste (BPW) is used as raw material for the preparation of hard magnetic glass ceramics (HMGC) as well as soft magnetic glass ceramics (SMGC). About 54 wt% and 37 wt% of BPW are used to prepare SMGC and HMGC, respectively. Differential thermal analysis (DTA) reveals two broad exothermic peaks for HMGC at 591 °C and 697 °C, whereas one exothermic peak at 820 °C is detected for SMGC. X-ray diffraction (XRD) shows the crystallization of hematite as the sol phase in BPW, and meanwhile, Zn-ferrite and Ba-hexaferrite are identified in SMGC and HMGC, respectively. Transmission electron microscopy (TEM) reveals the crystallization of nanosize particles of ∼20 nm for SMGC and ∼12 nm for HMGC. Vibrating scanning magnetometer (VSM) reveals an increase in saturation magnetization from ∼1 emu/g for BPW to ∼77 emu/g for SMGC and 21 emu/g for HMGC.
    Print ISSN: 2226-4108
    Electronic ISSN: 2227-8508
    Topics: General, Interdisciplinary , Chemistry and Pharmacology , Physics
    Published by SpringerOpen
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...