A series of bulk polycrystalline La1-xLixMnO3 samples with x ranging from 0.1 to 0.5 was prepared by sol-gel method,X-ray diffraction patterns show that the crystal structures are single rhombohedral perorskite for th...
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A series of bulk polycrystalline La1-xLixMnO3 samples with x ranging from 0.1 to 0.5 was prepared by sol-gel method,X-ray diffraction patterns show that the crystal structures are single rhombohedral perorskite for the x≤0.3 sample and the impurity appears when x〉*** the same synthesized conditions,the higher Li content samples display a higher content of liquid phase content and larger mean grain sizes,which leads to the increases of the effect of the grain *** experimental results show that the change of the ferromagnetic transition temperature and the resistivity can attribute to the effect of the grain boundary and the connectivity of the inter grains as well as the ratio of Mn^3＋ to Mn^4＋.
Ti/Al 2O 3 composite with improved mechanical properties was synthesized by th e spark plasma sintering. The effect of Nb on the microstructure of the composit e was analyzed by TEM, SEM and so on. The experimental ...
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Ti/Al 2O 3 composite with improved mechanical properties was synthesized by th e spark plasma sintering. The effect of Nb on the microstructure of the composit e was analyzed by TEM, SEM and so on. The experimental results indicate that the bending strength, fracture toughness, micro-hardness and relative density of t he composite are 897.29MPa, 17.38MPa·m 1/2, 17.13GPa and 99.24% respec tively when adding 1.5vol%Nb. The bending strength is improved by reason of form ing dislocation ring and transfering fracture mode from intergranular to mixture fracture of intergranular and transgranular. The crack propagating is mainly th e deflection bridging. It indicates a reduction of crack driving force and an in crease in crack growth resistance,which results in toughness enhanced.
The Ti2AlC-Ti3AlC2-Ti3SiC 2 composite was fabricated in Ti-Al-Si-C quaternary system by spark plasma sintering (SPS) method from elemental powders. IN the SPS process, the gas in the chamber is discharged out at a con...
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The Ti2AlC-Ti3AlC2-Ti3SiC 2 composite was fabricated in Ti-Al-Si-C quaternary system by spark plasma sintering (SPS) method from elemental powders. IN the SPS process, the gas in the chamber is discharged out at a constant rate. It was observed that pressure peaks appeared in both samples sintered at 1200 and 1300 °C. It was found that for the sample sintered at 1300 °C, pressure peak was more pronounced than that of sample sintered at 1200 °c, which indicates the evaporation of Al or Si is more serious in sample sintered at 1300 °C, leading to the formation of TiC and the disapperance of Ti2AlC.
With the preparation of organic-inorganic layered perovskite-type compounds (C4H9NH3)2MCl4 (M = Mn, Cu) in solutions, X-ray diffraction (XRD), scanning electron microscopy (SEM),thermal gravimetry (TG) and differentia...
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Polycrystalline samples of Sr4Nd2Ti 4Ta6O30 (SNTT) and Sr4Sm 2Ti4Ta6O30 (SSTT) were prepared using high temperature solid state reaction techniques. SNTT and SSTT showed room temperature dielectric constant of around ...
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Polycrystalline samples of Sr4Nd2Ti 4Ta6O30 (SNTT) and Sr4Sm 2Ti4Ta6O30 (SSTT) were prepared using high temperature solid state reaction techniques. SNTT and SSTT showed room temperature dielectric constant of around 225 and 220 at 1 MHz. SSTT belongs to ferroelectric phase of tungsten-bronze (TB) structure and underwent diffuse type of ferroelectric-paraelectric phase transition around 30°C. Low temperature dielectric constant observed in the ceramic sample indicates that it may have attractive benefits in electrooptic and infrared pyroelectric detector applications when grown in buck single crystal or thin film form.
In order to compare the spark plasma sintedng （SPS） process plus hot isostatic press （HIP） with vacuum sintedng plus HIP, an investigation was carried out on the topography, microstructure and gain size distributi...
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In order to compare the spark plasma sintedng （SPS） process plus hot isostatic press （HIP） with vacuum sintedng plus HIP, an investigation was carried out on the topography, microstructure and gain size distribution of nanocrystalline WC-10Co composite powder and the sintered specimens prepared by SPS plus HIP and by vacuum sintering plus HIP by means of atomic force microscopy （AFM）. The mechanical properties of the sintered specimens were also investigated. It is very easy to find cobalt lakes in the specimen prepared by vacuum sintering plus HIP process. But the microstructure of the specimen prepared by SPS plus HIP is more homogeneous, and the grain size is smaller than that prepared by vacuum sintering plus HIP. The WC-10Co ultrafine cemented carbide consolidated by SPS plus HIP can reach a relative density of 99.4%, and the transverse rupture strength （TRS） is higher than 3540 MPa, the Rockwell A hardness （HRA） is higher than 92.8, the average grain size is smaller than 300 nm, and the WC-10Co ultrafine cemented carbide with excellent properties is achieved. The specimen prepared by SPS with HIP has better properties and microstructure than that prepared by vacuum sintering with HIP.
Mass production of ZnO nanobelts and hexagonal nanorods has been successfully synthesized on CuO catalyzed porous silicon （PS） using a simple vapour-solid （VS） growth method. A comparison of their morphologies is ...
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Mass production of ZnO nanobelts and hexagonal nanorods has been successfully synthesized on CuO catalyzed porous silicon （PS） using a simple vapour-solid （VS） growth method. A comparison of their morphologies is investigated by scanning electron microscopy （SEM）. The transmission electron microscopy （TEM） confirms that ZnO nanobelts and nanorods are single crystalline with the growth direction of （0110） and （0001）, respectively. Field emission tests indicate that the ZnO nanostructures on porous silicon have low turn-on field of about 3.6 V/μm （at 1.0μA/cm^2） and the threshold field of about 8.3 V/μm （at 1.0mA/cm^2）, high emission site density （ESD） of approximately 104 cm^-2.
In the present study, Fe and Si powders (3:1 in atomic proportion) were mechanical alloyed and subsequently treated under different anneal conditions. The changes of phase composition and structure during the mechanic...
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In the present study, Fe and Si powders (3:1 in atomic proportion) were mechanical alloyed and subsequently treated under different anneal conditions. The changes of phase composition and structure during the mechanical alloying and following heat treatment processes were mainly studied. The results showed that the XRD peaks of Fe were gradually broadened and weakened with the increase of the milling time associated with the shifting from low angles to high angles, and the main phase changed into α-Fe (Si) solid solution after milling for 20h. When the product was heat treated below 400°C, the main phase remained α-Fe (Si). While it was treated above 400°C, ordered Fe3Si phase was found and the XRD peaks of Fe3Si became sharper with the further increase of the temperature.
Monodispersed mesoporous silicon dioxide microspheres were prepared by polymerization-induced colloid aggregation (PICA) method and calcined at 850°C. The prepared samples were characterized with scanning electro...
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Monodispersed mesoporous silicon dioxide microspheres were prepared by polymerization-induced colloid aggregation (PICA) method and calcined at 850°C. The prepared samples were characterized with scanning electron microscopy (SEM), thermogravimetry (TG) and BET surface areas. The results showed that the obtained SiO2 microspheres had an average diameter of about 2.0 μm, a surface area of 253.3 m2g-1, an average pore volume of 0.62 mLg-1, and an average pore diameter of 7.9 nm. The formation mechanism of SiO2 spherical particles was discussed.
The functionally graded thermal barrier coating (TBC) serves in high temperature and/or high temperature gradient environment for a long time. According to the experimental and theoretical research, in the metal subst...
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ISBN:
(纸本)0878499709
The functionally graded thermal barrier coating (TBC) serves in high temperature and/or high temperature gradient environment for a long time. According to the experimental and theoretical research, in the metal substrate and the metal-rich interlayer creep deformation will appear under high temperature environment. In order to design and optimize the compositional distribution of FGM, it is necessary to analyze the stress and strain responses taking into account the creep phenomenon of the materials. In this article, the thermo-mechanical responses of ceramic/metal functionally graded TBC in work environment are analyzed by a finite element method. The creep phenomenon of the metal and the interlayers are taken into account. The numerical results indicate that the creep behavior of all interlayers, even for the ceramic-rich interlayer, cannot be neglected in analysis. It is suggested that the creep phenomenon of the material is important in the functionally graded TBC systems.
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