Temperature distribution in the sample and the die during the process of Spark Plasma Sintering (SPS) were studied both theoretically and experimentally. The temperature difference is inevitable in the samples in SPS....
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Temperature distribution in the sample and the die during the process of Spark Plasma Sintering (SPS) were studied both theoretically and experimentally. The temperature difference is inevitable in the samples in SPS. Under certain conditions, the difference may reach a few hundreds of degrees of centigrade. Controlling of processing parameters can decrease the temperature difference. The atom diffusion at the interfaces and necks of specimen under SPS was also investigated and compared with Hot Pressing (HP). It was found that the atom diffusion in SPS is faster than that in HP, which indicates that SPS is more efficient.
A kind of Li2O-Al2O3-SiO2 system glass-ceramics, which had a low coefficient of thermal expansion, was prepared by melting method and used as the ramp-wave generator material. On one-stage light-gas gun, the experimen...
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A kind of Li2O-Al2O3-SiO2 system glass-ceramics, which had a low coefficient of thermal expansion, was prepared by melting method and used as the ramp-wave generator material. On one-stage light-gas gun, the experimental technique for quasi-isentropic compression via the ramp-wave generator was explored. By impacting the ramp-wave generator, quasi-isentropic compression waves with an extended wave's front were produced. The quasi-isentropic loadings to LY12-A1 samples were further realized via the ramp-wave generator. The results showed that the more the thickness of the ramp-wave generator, the longer the front of the generated waves and the lower the rate of the compression. The present research offered a feasible loading means for the quasi-isentropic compression under low pressures.
Spark plasma sintering(SPS) prepared transparent AlN ceramics by using different-content CaF2 as sintering aids, preparing porous materials and welding of alloys were researched. SPS shows its merits which could prepa...
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Spark plasma sintering(SPS) prepared transparent AlN ceramics by using different-content CaF2 as sintering aids, preparing porous materials and welding of alloys were researched. SPS shows its merits which could prepare transparent ceramics with high transparency in short time, prepare porous materials with homogeneous and controllable hole under low temperature in short time, obtain quite strong welding junction under low welding temperature and in short soaking time, owing to its special characters.
Mg-W composites with 0-92% W were prepared by spark plasma sintering (SPS) technique at 600°C-30 MPa-5 min. The mechanism of densification was researched and the relation between the mechanical property and the c...
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Mg-W composites with 0-92% W were prepared by spark plasma sintering (SPS) technique at 600°C-30 MPa-5 min. The mechanism of densification was researched and the relation between the mechanical property and the content of W was discussed. The results indicated that W and Mg exit in the composites through mechanical mixtures. The samples with low content of W were spread by partly molten Mg connecting the particles of Mg, the ones with high content of W through molten Mg joining the particles of W together. Increasing the content of W, elasticity modulus and bending strength increase, the Poisson's ratio decreases.
The quasi‐isentropic loading technique allows investigation of material properties in a high‐pressure, low‐temperature regime that is inaccessible by conventional shock wave experiments. In the present paper, the l...
The quasi‐isentropic loading technique allows investigation of material properties in a high‐pressure, low‐temperature regime that is inaccessible by conventional shock wave experiments. In the present paper, the layered flier‐plate and graded density flier‐plate, which have different variations in the density gradient along the thickness direction but the same density range, were designed and fabricated. Impact experiments were then performed on a two‐stage light gas gun. VISAR‐measured results show that wave profiles with an initial jump followed by a slowly‐rising front to the peak velocity amplitude are generated by using both types of the flier‐plate, indicating that quasi‐isentropic loading to the targets have been successfully realized. The process of quasi‐isentropic loading can be seen as the successive overlap of a series of small shock waves by the transient layers in the flier‐plate. It is obvious that the graded density flier‐plate creates a more smoothly rising front, and the compression effect must be closer to isentropic loading than that of the layered flier‐plate with the same density range.
The precursor of M-type barium hexaferrite with iron excess, which the nominal composition was BaFe12.4O19.6, was prepared by a so-called co-dump coprecipitation method. The crystallization behavior of the precursor u...
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The precursor of M-type barium hexaferrite with iron excess, which the nominal composition was BaFe12.4O19.6, was prepared by a so-called co-dump coprecipitation method. The crystallization behavior of the precursor under the spark plasma sintering (SPS) conditions and the magnetic properties of the SPS samples were investigated. The results show that the samples obtained at 700-850°C were composed of single-phase M-type barium hexaferrite, and that the crystallization of intermediates such as BaFe2O4 and Y-Fe2O3 did not occur. The distribution of crystal grains obviously changed with the increase of temperature;the distribution was random at 700°C and became preferential orientation when the temperature was more than 700°C. The saturation magnetization significantly increased at 700°C and remained almost constant in the range of 750°C to 850°C. This accorded with the evolution characteristics of the phase composition of the SPS samples with the increase of temperature. The coercivity first increased and then decreased with the increase of the temperature, which was attributed to the corresponding increases in the content of M-type barium ferrite and the degree of preferential orientation of crystal grains.
Tin dioxide based ceramics doped with ZnO, Sb2O3 and ZnO-Sb2O3 were prepared by the pressureless sintering. The relative density (ρr) was measured by the Archimedes method, the resistivity (R) was measured by the van...
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Tin dioxide based ceramics doped with ZnO, Sb2O3 and ZnO-Sb2O3 were prepared by the pressureless sintering. The relative density (ρr) was measured by the Archimedes method, the resistivity (R) was measured by the van der Pauw method, and the mi-crostructure and crystal structure were measured by scanning electron microscope. Then the internal relationship between the material and structure were analyzed. The results indicate that ZnO can improve the sintering characteristics of the material;the ρr increases and then decreases with the increase of ZnO, and the optimal content of ZnO is 1.0% (mole fraction, the same below). However, the ρr decreases with the increase of Sb2O3;the R decreases at first, and then increases and decreases at last. The ρr and R of the material are good when Sb2O3 content is 0.5%. The SnO2 based ceramic doped with 1.0% ZnO-0.5% Sb2O3 and sintered at 1400°C has high performance;the ρr is 97% and the R is 0.1099 Ω·cm.
Ga dopping GaxPb1-xTe(x=0.01-0.05) compounds were prepared by melting reaction method, and the in-c fluence of Ga content on the thermoelectric properties were investigated. The results showed that temperature dopende...
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Ga dopping GaxPb1-xTe(x=0.01-0.05) compounds were prepared by melting reaction method, and the in-c fluence of Ga content on the thermoelectric properties were investigated. The results showed that temperature dopendent carrier concentration increased and the hall mobility decreased with increasing Ga content, which indicated that the carrier scattering mechanism gradually changed from an acoustical scattering to the interaction between an acoustical phone and an ionized impurity scattering as x increased. All samples show n-type conduct and the absolute Seebeck coefficient values and the electric conductivity increase significantly with increasing Ga content.
The layered perovskite-type organic-inorganic hybrids (CnH2n+1NH3)2 MnCl4 (n=2, 4, 6, 8, 10, 12) were synthesized in solution and their structures were characterized. The results showed that the structures of the prod...
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The layered perovskite-type organic-inorganic hybrids (CnH2n+1NH3)2 MnCl4 (n=2, 4, 6, 8, 10, 12) were synthesized in solution and their structures were characterized. The results showed that the structures of the products were independent on the reaction initial temperature. The X-ray diffraction (XRD) patterns and the scanning electron microscopy (SEM) images of the products demonstrated that the hybrids crystallize very well and had typical layered structures. The interlayer distance of each hybrid was obtained from the XRD patterns. It was linear dependent on the carbon atom number in the organic chain and the organic chains interdigitated between the two adjacent inorganic sheets.
The solubility of layered perovskite-type organic-inorganic hybrids (CnH2n+1 NH3)2MCl4 (where M = Mn, Co, Cu, Zn;n = 2, 4, 6, 8, 10, 12) in seven kinds of solvent are obtained by atomic absorption spectrometry and tit...
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The solubility of layered perovskite-type organic-inorganic hybrids (CnH2n+1 NH3)2MCl4 (where M = Mn, Co, Cu, Zn;n = 2, 4, 6, 8, 10, 12) in seven kinds of solvent are obtained by atomic absorption spectrometry and titration method. The solvents are sherwood oil, cyclohexane, acetone, trichloromethane, DMF, methanol and water. The results show that the hybrids are prone to dissolve in polar solvent. This is attributed to the polarity of the hybrids. The hybrids disassembly dissolve when the interaction between the ammonium and the electron-donating group of the solvent is stronger than that between the organic and the inorganic parts in the hybrids. The series of M = Zn and Co have better solubility in the polar solvent than that of M = Mn and Cu and this is presumably because there are weaker interactions between the organic and inorganic parts in hybrids of M = Zn and Co.
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