Advanced Materials Research Vols. 535-537

Abstract: Fused quartz granule (d50=10μm) was used as raw material, and Al₂O₃-AlN (1:1, in mass) was used as additive with dosages of 1 wt%, 2 wt% and 3 wt%. The crystallization characteristics of fused quartz ceramic fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1h has been investigated by thermal expansion ratio and XRD. The results showed that the crystallization characteristics were markedly improved by 1 wt% AI₂O₃-AIN compound additive. 1 wt% Al2O3-AIN had obvious effect on inhibiting crystallization of the samples sintered at various temperatures. The apparent porosity, bending strength and SEM of the samples were also examined. The results showed that the samples with 1 wt% AI₂O₃-AIN had the lowest apparent porosity among the samples containing Al₂O₃-AlN, the highest bending strength, and the sample AA1 sintered at 1350°C had more compact microstructure, which indicated that 1 wt% Al₂O₃-AlN was conducive to sintering of fused quartz ceramic materials. It can be deduced that the 1 wt% Al₂O₃-AIN compound additive plays the excellent role on inhibiting crystallization and promoting sintering of fused quartz ceramic materials.

Abstract: Woodceramics were prepared by using wood powder and furane resin. TG Analysis techniques were adopted to study pyrolysis behavior of wood powder and furane resin. Microstructures of woodceramics were studied by using scanning electron microscopy (SEM) and X-ray diffraction(XRD). The effect of carbonization temperature on carbon yield ratio，volume shrinkage ratio and volume electrical resistivity of woodceramics were investigated. The results show that carbonization temperature has a significant effect on the microstructure of woodceramics. When the carbonization temperature increases, the volume shrinkage ratio increases, and the carbon yield ratio and the volume electrical resistivity decrease.

Abstract: The effects of B2O3 on the sinterability and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.95Zr0.05]O3−δ−0.04TiO2 (CLNZ−0.04TiO2) ceramics were investigated . B2O3 doping can effectively reduce sintering temperatue by 150~200°C. The temperature coefficient of resonator frequency τf increased with an increase of B2O3 content and sintering temperatue. When B2O3 of 2wt% were added, the optimum microwave dielectric properties: εr =31.8,Qf =17240GHz and τf = − 5.9×10−6/°C were obtained at the sintering temperature of 950°C.

Abstract: 1.0at% Nd:YAG polycrystalline ceramics were fabricated with different sintering adds by solid-state reaction and vacuum sintering method. The optical transmittance spectra of the samples were measured using V-570 UV spectrophotometer. The microstructure and the grain size of the samples were characterized by Scanning electron microscope. It is found that the sample with 0.5wt% SiO₂ and 0.5wt% MgO had the best transmittance, the most densification and uniform grain size, and the grain size decreased with the increasing MgO. Effects of MgO on the microstructure of YAG and its action mechanism have been investigated.

Abstract: A kind of vitrified bond was selected to be sintered with diamond powders to prepare diamond abrasive. The effect of the additive of CeO2 and sintering parameters on the performance of vitrified bond diamond abrasive was investigated. The mechanical properties of diamond abrasives were tested on ZMC-Ⅱ type diamond static strength tester and the interfacial bonding states between diamond powders and vitrified bonds were studied by Scanning Electron Microscopy (SEM). The results indicated that CeO2 improved the performance of diamond abrasive by means of strengthening the bonding between diamond grits and vitrified bond. The admirable diamond abrasive was achieved when the sample was sintered at 800°C holding for 120min.

Abstract: AlN-Mo composite ceramics were prepared by spark plasma sintering (SPS) with AlN and Mo, introduction of Mo particles into the AlN matrix was through direct current magnetron sputtering, sol-gel and blending technology methods. The effect of Mo particles on densification, electrical conduction and dielectric properties of AlN ceramic was studied by XRD, SEM, dielectric frequency spectrum. The results indicate that dielectric constant of AlN-0.26vol.%Mo composite ceramics obtained by sputtering increase by 22.5% at 1MHz as compared to the pure AlN sample; AlN-18vol.%Mo composite ceramics prepared with Mo powder coated with Al2O3 show insulator character and good dielectric properties; dielectric constant and loss of the composite ceramics increase with increasing the content of the elongated shape Mo particles, the highest dielectric constant and loss will be obtained when AlN-12vol.%Mo content is 30wt.% ( =98.41, tgδ=0.018 at 1MHz), the value of electrical resistivity decreases rapidly from 1.32×104 to 3.16×101Ω•cm when AlN-12vol.%Mo weight fraction increases from 30% to 40%.

Abstract: Magnesium 2,2,2-trifluoroacetate [Mg(OOCCF3)2] has been prepared from the reaction of trifluoroacetic acid and magnesium chloride and was tested for its catalytic activity in the multi-component reaction of aldehydes, 2-naphthol and an amide (or urea). This methodology results in the synthesis of a variety of 1-amidoalkyl-2-naphthol derivatives in high yields. The catalyst can be recovered and recycled without a significant loss in the catalytic activity

Abstract: Based on the SrO-Fe2O3-FeO-SiO2-B2O3 system, the M-type strontium hexaferrites glass ceramics has been prepared through heat treating the melted glass. Using the aqueous solution solvent evaporation and melt method, we obtained the glass precursor of molecular-scale homogenously mixed compound. The precursor was completely melted in a lidded platinum crucible placed in an electric furnace at 1480°C for 1h and then annealed in a furnace at 550°C for 40min. The crystallization of the glass systems with different component has been systematically investigated by using X-ray diffraction (XRD), Transmission Electron Micrographs (TEM) as well as Vibrating Sample Magnetometer (VSM). It is found that Fe3O4 crystal precipitated during naturally cooling the melt from 1480°C to anneal temperature. Moreover, the hexaferrite glass ceramics with the main crystal phase of SrFe12O19 was obtained after heat-treated at 860°C for 2 hours. The magnetic properties of the obtained hexaferrite glass ceramics indicated that the saturation magnetization and the coercivity were 8.1A•m2/kg and 114KA/m, respectively.

Abstract: Based on the CaO-Na2O-Fe2O3-FeO-B2O3-SiO2 system, the ferrimagnetic glass-ceramic has been prepared for hyperthermia application by aqueous aolution-melt method. Using the aqueous solution solvent evaporation, we obtained the molecular-scale homogenously glass precursor. The precursor was completely melted in a lidded platinum crucible placed in an electric furnace at 1480°C for 1h and then annealed in a furnace at 550°C for 40min.The annealed glasses were heat treated at 1050°C for 2h to obtain the glass-ceramics. The crystallization of the glass systems with different component has been systematically investigated by using XRD, TG, as well as Vibrating Sample Magnetometer (VSM). The glass-ceramics with B2O3=3.0wt% show a strong magnetic, which contains highest value of specific saturation magnetization of 28.34A•m2/kg.

Abstract: The current standard is lacking of characteristic criterion and references of various copper alloys material electric components short-circuited melted-mark metallographic structure, thus it is to the disadvantage of the development of fire investigation physical evidence identification. In the thesis, by conducting fire simulated experiments of primary short circuit and secondary short circuit with pure copper and brass alloys electric components, apply metallographic analysis methods and image processing technology to discuss and analyse the melted mark metallographic structure.