Chuan Bin Wang

Preparation and Quasi-Isentropic Characteristics of Graded Density Flier-Plates

Graded density flier-plates, including the layered density flier -plate and continuous density flier-plate, which has different variation in the densit y gradient along the thickness direction, were designed and fabricated. Impact experiments w ere then performed on a two-stage light gas gun. VISAR-measured results show that, wave profiles wi th an initial jump followed by a slowly-rising front to the peak velocity amplitude are generate d by using two types of the flierplate, indicating that quasi-isentropic loadings to the targets hav e been successfully realized. It is obvious that the continuous density flier-plate creates a more smoothl y rising front than that of the layered density flier-plate, and can achieve a better quasi-isentropic comp ression effect.

Stoichiometric Controlling of Spark Plasma Sintered Boron-Carbon Ceramics

A group of boron-carbon ceramic material was in-situ synthesized and densified simultaneously via Spark Plasma Sintering (SPS) technique from carbon and boron element powders with different molar ratio. The phase structures of samples with different B/C molar ratio were characterized by X-ray Diffraction (XRD). The B/C atomic ratio of the sintered materials was calculated from X-ray photoelectron spectroscopy (XPS) measurement data. Meanwhile, the chemical analysis (CA) method had also been taken to verify the B/C atomic ratio. Finally, the experience equation had been obtained to control the B/C atomic ratio of sintered samples.

Effect of MgTi2O5 Addition on Thermal Shock Resistance of Al2TiO5

In the present paper, magnesium dititanate (MgTi2O5, M2T) was introduced into aluminum titanate (Al2TiO5, AT) to form AT-M2T solid solution so that the thermal shock resistance of Al2TiO5 could be kept still good while without any decomposition. The effect of MgTi2O5 addition on thermal shock resistance of Al2TiO5 was investigated. The experimental results showed that the thermal shock resistance of Al2TiO5 began to decrease when a little amount of MgTi2O5 was added and then rose with the continuous addition of MgTi2O5, even overrunning that of pure Al2TiO5 when 30mol% MgTi2O5 was contained. It was found that fine solid solution was formed between Al2TiO5 and MgTi2O5, which enhanced the thermal shock resistance of Al2TiO5.

Densification of Short Carbon Fiber Reinforced Silicon Carbide by Spark Plasma Sintering

By using spark plasma sintering technique, densification of SiC reinforced with unidirectional short carbon fibers has been investigated. Graphite with Al2O3 or AlN, respectively are selected as the additives for achieving highly relative densities and thus improve their mechanical properties. The effect of these additives on the densification of short-Cf/SiC composites are mainly discussed, and the influences on the carbon fibers as well as the interfaces between fibers and SiC matrix are also studied. The results show that the (3~5)wt%Al2O3+1wt%graphite is confirmed to be an optimum additive system for the densification of short-Cf/SiC composite and the relative density approaches 95%.

Microstructure Analysis of W-Mo-Ti Functionally Graded Materials Fabricated by Co-Sedimentation

Abatract. Co-sedimentation is one of the most promising ways to fabricate large-scale functionally graded materials (FGMs) with continuous variations in composition and microstructure. A kind of W-Mo-Ti FGMs with density gradient, which can be applied in dynamic high-pressure technology, has been fabricated by co-sedimentation method. The composition and microstructures of the WMo-Ti FGMs were mainly analyzed by EPMA and X-ray Energy Dispersive Spectrometer (EDS), a series of factors affecting the microstructure and compositions were also discussed.

Control of Preferential Orientation of La1-xSrxMnO3 Thin Films by Pulsed Laser Deposition

La1-xSrxMnO3 (LSMO) thin films were grown on (100)- and (110)-oriented MgO substrates by pulsed laser deposition, so as to control the preferential orientation of the films. At the optimum deposition temperature (Td = 923K), LSMO thin films with a dense texture and a smooth surface were prepared. The XRD patterns and X-ray pole figures indicated that the LSMO thin films were epitaxially grown on MgO substrates, due to the small lattice mismatch between the films and substrates The possible orientation relationships were found to be LSMO (100) [100] // MgO (100) [100] and LSMO (110) [110] // MgO (110) [110], as for the (100) and (110) MgO substrates, respectively.

Effect of Holding Time on Microstructure and Mechanical Properties of Diffusion-Bonded Mg1/Pure Ag Foil/1060Al Joints

Mg1 and 1060 Al were diffusion-bonded by using pure silver foil under different holding times (10 min~120 min). The interface of the joint consists of Mg-Ag diffusion zone, Ag foil interlayer and Ag-Al diffusion zone. The distributions of Mg, Ag and Al show ladder-like distributions at the interface of the joints. When the holding time is below 90 min, silver foil has impeded the inter-diffusion of Mg and Al. When the holding time is beyond 90 min, the brittle eutectic Mg-Al intermetallic compounds (IMCs) cannot be avoided. Mg3Ag and MgAg intermetallic compounds formed on Mg base side. Ag2Al intermetallic compound grew on Al base side. The thicknesses of Mg3Ag, MgAg and Ag2Al increased linearly with the increasing holding time, which is contrary to that of the silver foil. The growth rate relationship of the formed IMCs is MgAg > Ag2Al > Mg3Ag according the slope values of the fitted lines. The hardness sharply increased at the interface because of the formation of IMCs. The maximum hardness values of three IMCs Mg3Ag, MgAg and Ag2Al are 287.5 HV, 196.5 HV and 175.7 HV respectively. The hardness of each IMC layer increased with the extension of holding time. The shear strength of the joints decreased from 10.5 MPa to 4.6 MPa with the rising holding time.

Structures and Properties of BiFeO3 Thin Films on Pt(111)/Ti/SiO2/Si Substrates Prepared by Pulsed-Laser Deposition under Various Oxygen Partial Pressures

Ferroelectric BiFeO3 (BFO) thin films were prepared on Pt (111)/Ti/SiO2/Si substrates by pulsed-laser deposition under various oxygen partial pressures (PO2). The effects of PO2 on the phase, orientation, surface morphology, and ferroelectric properties of the films were investigated, particularly in regard to relationships between structure and properties. It was found that the crystallographic orientation and surface morphology of the BFO thin films strongly depended on PO2. Films prepared at PO2=10 Pa had a high degree of (111) orientation and densely packed grains. A maximum of twice the remanent polarization for the BFO thin film was 68 μC/cm2.

Synthesis of Single-Phased BaTi2O5 Powders by Arc-Melting

Arc-melting was employed to synthesize BaTi2O5 powders by fast melting the reagent mixture of BaCO3 and TiO2 with different molar ratios (0.90~1.05:2). The influence of molar ratios of BaCO3 to TiO2 on the phase of the powders derived from arc-melting was investigated by X-ray diffraction and Raman spectra. When the molar ratio was larger than 0.95:2, a little amount of Ba-rich compound Ba2TiO4 was produced besides the main phase of BaTi2O5. Ti-rich compound Ba6Ti17O40, BaTi2O9 and TiO2 began to appear at the ratios ranging from 0.90:2 to 0.95:2. Single-phased BaTi2O5 powders were obtained by arc-melting the reagent mixture with the molar ratio of 0.95:2.

Reaction Process of Al2(1-x)MgxTi1+xO5 Composite Powder by Chemical Co-Precipitation and Subsequent Sintering

Al2(1-x)MgxTi1+xO5(x=0.05-0.3) composite powder was prepared by the method of chemical coprecipitation and subsequent sintering using TiCl4, MgCl2 and AlCl3 solution as the raw materials, and ammonia and ammonium carbonate as the solvent. Thermal dynamics and kinetic dynamics analysis of the precursor during the heat treatment were explored in detail, and the reaction process of Al2(1-x)MgxTi1+xO5 (x=0.3) composite powder was confirmed. Results show that, as the temperature increases MgO reacts with TiO2 of anatase phase to form MgTi2O5. At about 650°C, anatase transfers into rutile. Then MgTi2O5 reacts with Al2O3 to produce MgAl2O4 at 900°C. When the temperature is above 1100°C, the desired Al2(1-x)MgxTi1+xO5(x=0.3) composite powder is synthesized by the reaction of MgAl2O4, Al2O3 and TiO2 of rutile phase.