Advanced Materials Research Vols. 634-638

Abstract: 1H,1H,2H,2H-1Iodide-Perfluorodecane was synthesized use perfluorooctyl iodide and ethylene as materials, then reacted with sodium methoxide /methanol to gain 1H,1H,2H-Heptadecafluorodecene. Influence factors such as kinds of solvents, raw material configuration, concentration and time in the process of dehydrogen iodide were studied mainly. Optimization was using 1,1,2-Trichloro-1,2,2-trifluoroethane as solvent, sodium methoxide /methanol (2mol/L ), 1H,1H,2H,2H-1Iodide-Perfluorodecane( M1 ): sodium methoxide( M2 ) =1:2, reacted 12 hours, the yield of 1H,1H,2H-Heptadecafluorodecene was up to 80%.

Abstract: Polyvinyl Alcohol (PVA) was blent with sodium alginate (SA) and chitosan (CS) respectively in order to enhance flexibility and compatibility of bipolar membrane(BPM). The PVA-mSA/mCS BPM was prepared by a paste method. The PVA/ SA and the PVA / CS was cross-linked by inorganic nano-materials and glutaraldehyde(GA), respectively. The SEM photographs showed the PVA-ZnO-SA/mCS BPM was consists of anion layer and cation layer. The thickness of the BPM was 121μm, the interface of BPM was 5μm. The Electronic spectrum (EDS) indicated that ZnO well-distributed in cation layer. The J-V curve and the AC impedances of PVA-ZnO-SA/mCS BPM showed lower working voltage and smaller membrane impedance. The contact Angle of PVA-ZnO-SA/mCS dropped down from the original 101.01° to 32.65°. Compared of TG curves of the BPMs modified by nano-Fe3O4, nano-TiO2 and nano-ZnO, the surface of the PVA-ZnO-SA/mCS BPM exhibited stronger hydrophilic. The dopping nano-ZnO improved the hydrophilic property, thermal stability and mechanical properties of the PVA-ZnO-SA/mCS.

Abstract: (1-X)K0.5Na0.5NbO3–xBiGaO3[(1-X)KNN-Xbg] Lead-Free Ceramics with Different Additive of Bigao3 Were Synthesized by Conventional Solid-State Sintering Technique. Dielectric, Piezoelectric and Ferroelectric Properties of (1-X)KNN-Xbg Lead-Free Ceramics Were Studied. it Is Found that the Piezoelectric Properties Was Improved due to the Additive Bigao3，The Ceramics X=0.01 near Room Temperature Exhibit Excellent Electrical Properties D33=152pC/N, TC=372 °C. these Results Indicate that Bigao3 Adjusted K0.5Na0.5NbO3-Based Ceramics Materials Are Promising Lead-Free Piezoelectric Ceramic Candidates for Practical Applications.

Abstract: Effect of different sintering additives on reaction-bonded Si3N4/SiC composite ceramics under pressureless was investigated. Si3N4/SiC composite ceramics were sintered at the temperature 1550 °C under nitrogen atmosphere with different sintering additives Y2O3, Y2O3:Al2O3=1:1, Y2O3:Mg2AlO4 :Mg3(Si4O10)(OH)2: SiO2=5:2:1:1, and ZrO2 by using SiC with different particle sizes, and Si as raw materials. The phases, microstructure and mechanical property were characterized by XRD, SEM, and compressive strength test. The results demonstrated that when the particle gradation consisted of silicon carbide of 74 μm (5 wt.%), 44 μm (10 wt.%) and 0.5 μm(30 wt.%) and silicon powder of 74 μm (42 wt.%), the more dense samples with the bulk density of 2.43 g/cm3 and the higher compressive strength of 324 MPa could be obtained when Y2O3 was used as sintering additives.

Abstract: The microstructure and phase analysis of in situ nitrides formation in MgAl2O4-C refractory were investigated with different temperature. The phase compositions and microstructure of the MgAl2O4-C refractory were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that sintering temperature has a significant influence on the microstructure and phase analysis of MgAl2O4 refractory. As the sintering temperatures are 1450°C and 1500°C, nitride that formed in samples is β-Sialon and the crystal morphology is columnar with short size. With the temperature rise to 1550°C and 1600°C, nitride formed in sample is AlON with the crystal morphology is tabular polymorph with large size.

Abstract: The effects of Si3N4 addition on the room temperature physical properties and thermal shock resistance properties of corundum based refractory castables were investigated using brown corundum, white corundum and alumina micropowder as the starting materials and pure calcium aluminate as a binder. The phase composition, microstructure, mechanical properties of corundum based castables were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that as the increase in Si3N4 addition, the bulk density decreased and apparent porosity increased, the cold strength deduced. However, the residual strength rate increased. That is, the thermal shock resistance was improved. This is because even though the introduction of Si3N4 inhibited the sintering of material and deduced the compactness, microcracks were produced in the materials due to a difference in thermal expansion coefficient. So the thermal shock resistance of corundum based castable was improved.

Abstract: To improve the hydration resistance of MgO-Al-C bricks, Na2CO3 was chosen as an additive through thermodynamic calculation. MgO-Al-C refractories were prepared by using Si, Na2CO3 or both as additives. The effects of additives on the hydration resistance of specimens were investigated. XRD was conducted to determine the phase composition. The results showed that the hydration resistance of MgO-Al-C bricks would be improved slightly with addition of only Si due to the densification of the structure. When Na2CO3 and Si were added together, the hydration resistance would be improved remarkably. The mechanism is that Na2CO3 could decompose to give off O2 during heating, which could promote the oxidation of Al metal and inhibit the formation of Al4C3 and AlN.

Abstract: High pressure is demanded in producting diamond bit by cold-pressing. Although the pressure could be reduced by hot-pressing, a certain pressure is demanded to ensure the compactness of diamond bit matrix. Four sintering parameters, sintering temperature, holding time, sintering pressure and the pressing mode, are mainly included during producting diamond bit by hot-pressing. This article mainly discusses the effect of sintering pressure on the properties of diamond bit. First, select a general formula of diamond bit, take sintering pressure as variable, other parameters remaining immovability; then load and sinter a set of samples in this parameter. Testing and analysing the samples by mechanical properties test, such as bending, tension, compression, and rigidity, and SEM fracture analysis, we obtain the optimum sintering pressure in this formula.

Abstract: The characteristics of each method for synthesis titanium carbonitride were introduced. The property of titanium carbonitride synthesized by each method is affected by raw materials, parameters and external conditions. The application of titanium carbonitride is mainly on cermets cutting tools, it also exhibits a lot of good properties on coating materials, superhard cutting tools and multi phase ceramics.

Abstract: AST-doped ZnO-MgTiO3-SrTiO₃ ceramics were prepared using a solid-state sintering process. The effects of AST (Al2O3-SiO2-TiO2) on the dielectric properties of MgTiO₃-based ceramics were investigated. The results indicate that AST-doped MgTiO3-based ceramics could be obtained after 1205~1280°C sintering for 3 h. The XRD results indicate that the obtained MgTiO₃-based ceramics contain high percentage of MgTi2O5 phase and the percentage increased with the increase of AST content. It was found that the occurred liquid-phase sintering by adding AST glass could effectively lower the sintering temperature and decrease the dielectric loss of MgTiO₃-based ceramics. A minimum tanδ of 1.5×10-4 associated with εr=19.0 was achieved for 6.0 wt% AST-doped samples sintered at 1255°C.