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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 121-123 (Mar. 2007), p. 1157-1160 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Recent experiment showed that nano-fibers composite ceramics, fabricated through SHSprocess, can acquire high toughening and strengthening. Composite ceramics are mainly composedof fiber eutectic structures with random orientation, in which nanometer sized zirconia fibers aredispersed within the alumina matrix. First, it can be visualized that tensile force is transmitted fromthe matrix to the nano-fiber by means of shear stress that develop along the fiber- matrix interface.Then the mesomechanical strength model of the fiber eutectic structure is built. The longitudinaltensile stress of the fiber eutectic structure and shear stress on the surface of the fiber eutecticstructure are obtained. They related to the volume fraction and slenderness ratio of the nano-fibers,and external strain of the fiber eutectic structure. Then considering random orientation of the fibereutectic structure, as composite ceramics is subjected to tensile stress, external strain of the fibereutectic structure can be determined. Finally, theoretical expression for the strength prediction ofcomposite ceramics is gotten
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 326-328 (Dec. 2006), p. 273-276 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Interfacial residual stresses play an important role in the mechanicalproperties. In this paper, the interfacial residual stresses of SCI/Epoxy compositeswere determined using a novel technique-microphotoelastic method. The thermalresidual stress field was also numerically simulated using a finite element software[removed info]MSC.MARC. The difference and the similarities between the experimental results andthe simulation of FEM analysis were discussed and the availability of the method waspreliminarily certified
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  • 3
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Langasite (La3Ga5SiO14, LGS) and its isomorphs, were regarded as potential substratematerials for surface acoustic wave (SAW) and bulk acoustic wave (BAW) applications. Among thesehomologous compounds, the ordered structure crystals have attracted much attention for their low Ga2O3content, high acoustic velocity and low acoustic loss. In this work, the ordered langasite structure crystalsCa3NbGa3Si2O14 (CNGS) were grown with vertical Bridgman method for the first time. The CNGScrystals with 25mm in diameter and 40mm in length were grown successfully from its stoichiometric meltthrough LGS crystal of Ø10mm×40mm being chosen as seed. X-ray powder diffraction experimentsshowed that the CNGS single crystals had a single phase and had the same structure as the LGS crystal.The transmittance spectra with the wavelength from 200 to 800nm were recorded by means ofSpectrophotometer at room temperature
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 2432-2435 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Recent experiment showed that nano-fibers composite ceramics, fabricated through SHSprocess, could acquire high toughening and strengthening. Composite ceramics are mainly composed offiber eutectic with random orientation, in which nanometer sized zirconia fibers are dispersed within thealumina matrix. First, it can be visualized that tensile force is transmitted from the matrix to thenano-fiber by means of shear stress that develop along the fiber- matrix interface. Then the shear stress onthe surface of the fiber eutectic is obtained. It related to the volume fraction and slenderness ratio of thenano-fibers, and external strain of the fiber eutectic. The maximum shear stress is at the ends of the fibereutectic perpendicular to applied tensile stress. As maximum shear stress on the surface of the fibereutectic is equal to the critical shear stress, the composite ceramics would crack. So the applied tensilestress on composite ceramics arousing the surface crack of the fiber eutectic is gotten
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 2444-2447 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The pressure sensitive transformation criterion is used to determine the constitutive relation oftransformation toughened ceramics. By the use of the strain energy release rate criterion and the methodof weight function, the fracture enhancement of mixed-mode I-II crack in transformation toughenedceramics is predicated. The theoretical expressions of the toughening effect for both the stationary andsteady-state growing crack are given respectively. The result show there is no toughening effect for thestationary crack and the toughening effect for the steady-state growing crack is associated with themodulus of elasticity, the width of transformation and its volume fraction
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  • 6
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: To study the deformation reaction of different metallurgical phases of the micron structure ofcrack tips of zirconia ceramics in the loading state, the paper presents the micro experimental study basedon the digital correlated method of analysis by scanning electron microscope on the displacement field inthe micro areas of crack tip of the specimen of the Y2O3-ZrO2 toughened ceramic with the simple edgenotch beam method and under the action of three-point bending loads. First, SEM analyses was made onthe local area of the crack tip of a specimen’s polished surface before and after loads are applied to thespecimen, thus obtaining two SEM images, one before the application of the loads and another after theload application, which contained their displacement information. Then, digital correlation calculationswere made between the gray scales of the pixels of the two images in order to obtain the microscopicdisplacement fields of the crack tips in the microstate, thus unveiling the deformation modality anddisplacement response of different metallurgical phases of the crack tips of zirconia ceramics whensubject to loads. The results of the studies will provide foundations and basis for further research in themechanical properties of the ceramics with Y2O3-ZrO2 and their relationship with the microstructures
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 2528-2531 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The composite ceramics that contains nano-fibers and transformation particles, fabricatedthrough SHS process, is performed with high fracture toughness and high plasticity. The matrix ofcomposite ceramics was mainly composed of fiber eutectics with nano-fibers. The transformationparticles were distributed along boundaries of the fiber eutectic structures. First, Mori-Tanaka methodwas used to predict the stiffness of the fiber eutectic. The fiber eutectic is transverse isotropy and has fiveindependent elastic constants. Then considering random orientation of the fiber eutectic, the Young’smodulus and Poisson’s ratio of the matrix is determined by even strain. The matrix is isotropy. Finely,assuming the transformation particles as spheres distributed in the matrix, the effective stiffness forcomposite ceramics was computed. When the volume fraction of fibers and particles increase, theYoung’s modulus of composite ceramics decrease and are little smaller than the volume average value,the Poisson’s ratio of composite ceramics decrease and are little bigger than the volume average value
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 326-328 (Dec. 2006), p. 223-226 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Extensive research has been done on porous silicon (PS) and its applications inoptoelectronics since the discovery of its light emitting properties. Porous silicon technology is alsoused for silicon micro machining. However, porous films can be seriously strained and this oftencauses mechanical curling, fracture and device failures. In the present study an optical apparatusbased on substrate curvature method was developed for intrinsic stress measurement of thin films,which offered a lot of advantages as overall field, non-contact, high precision, nondestructive, easyoperation and quick response. Using the apparatus, the residual stress in porous silicon layersprepared by electrochemical etching was obtained. The residual stresses in the films weredetermined by measuring the curvature of the Si substrate before and after etching. It is found thatthe residual tensile stress tends to increase with the porosity increasing and the doping concentrationof the silicon wafer increasing. The results show that there is a deep connection between the microstructurePS and the residual stress distribution
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 1810-1813 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this paper, two-steps digital image correlation method is well advanced with the sub-pixelreconstruction in sub-image by utilizing the higher precision calculation of bicubic spline interpolationvalue method, and the accuracy of displacement is extended to better than 0.01 pixel, the strain resolutionis limited to less than 0.0002 in micro-region. The experimental results show that the method of two-stepsdigital image correlation is an up-to-date technique to comprehensive investigations of basemetal-coating composition at extremely small size scales. In the meantime, influence of crack in basemetal perpendicular to interface on coating is directly observed, and the measurement of the residualcompressive strain in base metal is performed according to different thickness of coatings. Lastly, thebond behavior between base metal and coating has been quantitatively analyzed, and the experimentalresults also prove the Ni-Lan coating is combined with base metal by toughened interface
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advances in science and technology Vol. 55 (Sept. 2008), p. 84-90 
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: A highly sensitive method for detecting oligonucleotide targets has been developed usingquantum dot (QD) functionalized nanotubes (NTs) that contain a cascade energy band-gaparchitecture. Their assembly with different types of QDs by the layer-by-layer (LBL) allowed forthe formation of fluorescence resonance energy transfer (FRET) structures in the NTs resulting inan enhanced fluorescence emission from dye labeled oligonucleotide targets captured by probeDNA through hybridization. This approach results in a significant enhancement of detection of dyelabeled oligonucleotide targets. The promising increase in detection sensitivity allows for lowdetection limits by tuning the QD emission, adding other types of QDs, or adjusting the distancebetween all photoactive compounds in the NTs. Hence, the strategy used here to produce newhybrid materials may pave a way for broadening application of NTs in the field of biochemicalmaterials, e.g. sensitive biosensors
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