The temperature field during the whole process of SPS sintering TiB2 -BN sample was numerically simulated based on the simplification of the temperature rising process. The result shows that the highest temperature is...
详细信息
The temperature field during the whole process of SPS sintering TiB2 -BN sample was numerically simulated based on the simplification of the temperature rising process. The result shows that the highest temperature is found in the punch and the heat flows from punch to sample and die in SPS sintering system. In the radial direction, the center temperature of the sample is much higher than the circumference temperature of the sampie. In the axial direction, the center temperature of the sample is lower than the border temperature of the sampie. The temperature difference in the sample is growing bigger in the sintering process and reaches the maximum at the end of the heating-up process.
A series of new microwave dielectric ceramics Ba3-nLa1+nTinNb3-nO12 (n=0,1,2) were prepared in the BaO-La2O3-TiO2-Nb2O5 system by high temperature solid-state reaction route. The phase and structure of the ceramics we...
详细信息
A series of new microwave dielectric ceramics Ba3-nLa1+nTinNb3-nO12 (n=0,1,2) were prepared in the BaO-La2O3-TiO2-Nb2O5 system by high temperature solid-state reaction route. The phase and structure of the ceramics were characterized by X-ray diffraction, scanning electron microscope, and microwave dielectric properties measurements. These samples were identified as single phase and adopted A4B3O12-type cation-deficient hexagonal perovskite structure, which can be described as consisting of identical perovskite-like blocks, three corner-sharing BO6 octahedra thick, separated by layers of vacant octahedral. These ceramics have high dielectric constants in the range of 48-42, high quality factors (Q×f) up to 38 000 GHz, and low temperature coefficient of resonant frequencies (τf) in the range of (-40-+6)×10-6℃-1. With increasing content of La and Ti, the dielectric constants slightly decrease butτf gradually increases.
The nanostractures of the ball milled FeCo particles were characterized as functions of the ball milling time （ t ） using quantitative X- ray diffraction （ XRD ）, high resolution transmission electron microscopy ...
详细信息
The nanostractures of the ball milled FeCo particles were characterized as functions of the ball milling time （ t ） using quantitative X- ray diffraction （ XRD ）, high resolution transmission electron microscopy （HRTEM） analysis techniques. The results show that the nanocrystalliue bcc FeCo particles are availab.e using carbonyl iron and cobalt powders as the start materials during the high-energy ball milling. At the early stage of ball milling, Co powders are easily mashed into nanocrystalllites, by which the surface of the larger Fe particles of about 80- 150 nm is coated. With t increasing, the refinement of grain size and the incorporation of defects including dislocations, disclinations and grain boundaries happen, and then FeCo alloy with a certain layered structure is formed, finally the layered stractare disappears with the formation of isotropic grains having a steadystate grain size in the nanometer regime after a certain period of t.
A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mob...
详细信息
A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mobility degradation are investigated. Effects of interlayer (SiO2) thickness and permittivities of the high-k dielectric and interlayer on carrier mobility are also discussed. It is shown that a smooth interface between high-k dielectric and interlayer, as well as moderate permittivities of high-k dielectrics, is highly desired to improve carriers mobility while keeping a low equivalent oxide thickness. Simulated results agree reasonably with experimental data.
WC- 10Co nanocomposite powder produced by spray pyrolysis-continuoas reduction and carbonization technology was used, and the vacuum sinteriag plus sinterhip process was cdopted to prepare ultrafine WCCo cemented carb...
详细信息
WC- 10Co nanocomposite powder produced by spray pyrolysis-continuoas reduction and carbonization technology was used, and the vacuum sinteriag plus sinterhip process was cdopted to prepare ultrafine WCCo cemented carbide. The microstructure, grain size, porosity, density, Rockwell A hardness （ HRA ）, transverse rupture strength （ TRS ） , saturated magnetization and coercivity force were studied. The experimental results show that average grain size of the sample prepared by vacuum sintering plas sinterhip technology was about 420 nm, transverse rupture strength was more than 3460 MPa, and Rockwell A hardness of sintered specimen was more than 92.5. Ultrafine WC- 10Co cemented carbide with high strength and high hardness is obtained.
Yttrium-filled sku, tterudites Yy Fex Co4-x Sb12 （ Y =0- 0. 40 ） were synthesized. The effect of Y filling fraction on thermoelectric properties of Yy Fex Co4-x Sb12 was investigated. All samples showed p-type condu...
详细信息
Yttrium-filled sku, tterudites Yy Fex Co4-x Sb12
（ Y =0- 0. 40 ） were synthesized. The effect of Y filling fraction on thermoelectric properties of Yy Fex Co4-x Sb12
was investigated. All samples showed p-type conduct. The electrical conductivity decreased with increasing filling fraction y. The Seebeck coefficient inreased with increasing temperature. The lattice thermal conductivity decreased with increasing filling fraction y and showed the minimum value at a certain filling fraction y = 0.3. The effect of different filling atoms M（ M： Ba, Ce, Y） on the lattice thermal conductivity of MyFexCo4-xSb12 was discussed. The maximum ZT value of O. 7 was obtained for Y0.06 Fe0.7 Co3.3 Sb12 at 750 K.
The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 ...
详细信息
The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 （ wt% ） composite powders were prepared by the spray thermal decomposition-continuous reduction and carburization technology. In order to improve the properties of rods shaped by using powder extrusion molding, the cold isostatic pressing （CIP） technology was used before or after debinding. Specimens were siutered by vacuum siutering and hot isostatic pressing （HIP）. The density, Rockwell A hardness, magnetic coercivity , and magnetic saturation induction of siutered specimen were measured. The microstructure of the green bodies and the siutered specimens was studied by scanning electron microscopy （SEM）. Results show that the rod formed by using powder extrusion molding after debinding and followed by cold isostatic pressing can be siutered to 99.5% density of composite cemented carbide rods with an average grain size of about 200- 300 nm, magnetic coercivity of 30.4 KA / m, Rockwell A hardness of 92.6 and magnetic saturation induction of 85% . Superfine WC- 10 Co cemented carbide rods with excellent properties were obtained.
SiCp/ Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering （SPS）. and their thermophysical properties, such as thermal conductivity （TC） and *** of thermal expan...
详细信息
SiCp/ Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering （SPS）. and their thermophysical properties, such as thermal conductivity （TC） and *** of thermal expansion （CTE）, were characterized. The electric field in the vacuum column was calculated and the generation condition of the spark was analyzed. Spark can be generated by a low current if the cavity in the green body is large enough. A high relative density of the composites was successfully achieved through the optimization of sintering parameters. The measured TCs of the SiCp/ Al composites fabricated by SPS are higher than 195 W/m ·K.
Both silica and boron-silica glass materials doped with terbium organic complex were prepared by in situ sol-gel method respectively. XRD and SEM measurements were performed to verify the non-crystalline structure of ...
详细信息
Both silica and boron-silica glass materials doped with terbium organic complex were prepared by in situ sol-gel method respectively. XRD and SEM measurements were performed to verify the non-crystalline structure of the glass. The influence of the glass contents on the structure of the glass and the erwrgy level of the doped Tb （Ⅲ） ions was analyzed by the emission spectra and IR spectra. The effect of B2O3 on the photolumirwscence properties of rare earth organic complex in silica- based glass was investigated. The IR spectra indicate that the in situ sylthesized rare earth complex molecule was confined to the micropores of the bost and the vibration of the ligands was frozen. When B2O3 was added into the silica host gel, B2O3 had little influence on the noncrystallirw structure of the glass, and BO3 triangle, which had a layer structure different from the silica framework, could form. So the silica network became more inhomogenous, and the luminescence of terbium complexes was quenched with the increase of the B2O23 amount.
暂无评论