Advanced Materials Research Vols. 652-654

Abstract: Fused silica particles and zirconyl chloride were used as main raw material. Meanwhile, ammonia was used as precipitator and polyethylene glycol as dispersant. Firstly, the composite powders were prepared by wet chemical synthesis. Then, fused silica/zirconia ceramic composites containing zirconia with different contents (5%, 15%, 25%, 35% and 45%) were fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1 h. The thermal expansion ratios and XRD of samples were examined. The analysis of XRD indicated that the cristobalite peaks intensity of sample with more zirconia is lower at the same sintering temperature, and the intensity of cristobalite was higher while sintered at higher temperature. Zircons were found in all samples’ XRD patterns. The results of thermal expansion ratios showed the ratios of samples with more zirconia were lower, especially at higher sintering temperature. So, existence of zirconia can inhibit crystallization of fused silica/zirconia ceramic composites effectively.

Abstract: Lamination of green ceramic tapes is one of the most important technological processes in the manufacturing of multilayer ceramic devices and it has determined influence on the quality of the devices. Therefore, choosing proper lamination technique is very important to a designed structure. The development of lamination techniques of green ceramic tapes is of great significance for the electronic communication industry and it has become a hot spot in the research. In this paper, the main lamination techniques in the present research and practice are overviewed. As to the development prospect and direction of the lamination of green ceramic tapes, the own opinions are given on the basis of lamination study in recent years.

Abstract: Zimujie is the common clay which has a very important position in ceramic production. It is facing with the depletion as the non-renewable resources in recent years.It is necessary to study a substitute to solve this problem . Research shows that : When the ratio of Changbai Mountain kaolin clay, Longyan clay, Suzhou clay and the northeast black mud is respectively 65.22wt%, 8.70wt%, 4.35wt%, 21.73wt% to formate the composite clay with 0.4wt% sodium carbonate addition agent, performance of the composite clay is very similar to zimujie.Therefore, it can be applied in the ceramic casting as the substitute of the single Zimujie clay.

Abstract: Electric porcelain has a long history of being used as insulators and bushings in Power T&D. Its microstructure and composition has a large influence on the mechanical performance. In this paper, two different methods, including Artificial Neural Network (ANN) and Multi-Linear Regression (MLR), were employed for predicting mechanical properties of electric porcelain including elastic modulus, bending strength and fracture toughness. Most predicted values by ANN are in accordance with the actual values. MLR gives the best accurate results within the low average error level of ~1%. According to the statistical analysis, two methods are reliable and their predicted results are effective. Formulae obtained from MLR are recommended to be used for predicting the mechanical properties of electric porcelain as experienced formulae.

Abstract: Al2O3-TiC-ZrO2 micro-nano-composites with addition of ZrO2 nanoparticles were fabricated by vaccum hot pressing with Mo and Ni powders as sintering aids. Results showed that the mechanical properties and relative density of the micro-nano-composites increased firstly and then decreased with the increase in the content of ZrO2 nanoparticles. Al2O3-TiC-ZrO2 micro-nano-composites containing about 4vol% ZrO2 nanoparticles have the highest synthetical properties, its flexural strength, Vicker's hardness, Fracture Toughness and relative density are 920MPa, 20.4GPa, 6.3MPa•m1/2 and 98.9%, respectively. The microstructural characterization revealed that adding proper ZrO2 nanoparticles to the matrix can greatly strengthen the grain boundaries, causing more transgranular fractures and consuming more fracture energy. The excessive amount of ZrO2 nanoparticles may bring about agglomeration effect, leading to the decrease of properties of the micro-nano-composites.

Abstract: Mullite-aluminium titanate-corundum composite was prepared at 1300°C with refractory clay, aluminium titanate and high alumina grog as raw material, molded at pressure of 50MPa. Effect of raw material ratio on sintering and themal shock resistance of the mullite-aluminium titanate-corundum composite was researched by measurements of apparent porosity, bending strength and residual strength after water-cool, and analyses of XRD and SEM. The results showed that as refractory clay content, apparent porosity of samples decrease, bulk density and bending strength increase. When the weight ratio of refractory clay, aluminium titanate and high alumina grog is 60/10/30, themal shock resistance of sample is excellent, The XRD and SEM analysis results indicated that the mechanical and thermal proprieties are relative to the microstructure and crystal phases of the composite materials.

Abstract: The industrialization of gelcasting technique has been prevented because acryamide is a neurotoxin monomer. In this paper, a low-toxicity gel system based on the polymerization of low-toxicity N-hydroxymothl acrylamide was used for the gelcasting PMN-PZT piezoelectric ceramic. The effects of monomer concentration, the dosage of initiator and catalyst, pH value on polymerization were studied. The results showed that the condition suitable for gelcasting PMN-PZT piezoelectric ceramics could be obtained while monomer concentration was 10wt%～15wt%, the dosages of initiator and catalyst were respectively 0.4 vol%～0.5vol% and 0.4vol%, pH value of slurry was about 10. The highest bending strength of PMN-PZT green body prepared at the aboved conditions can reach 19.5Mpa

Abstract: The sol-gel process is a useful technique with good control over final amount of compositions which can decrease the temperature of sintering in the melting procedure. A cordierite infrared radiation ceramic with a nominal composition of Mg2(1-x)Zn2xAl4Si5O18（x=0、0.05、0.10、0.15、0.20）was prepared using the powders by sol-gel method and heat treatment at 1523K for 2 hours. The results indicate that the sol-gel method can effectively decrease the sintered temperature and the substitution of Zn2+ to Mg2+ can let structural change and improve the infrared radiation properties. The specimen of x=0.20 attained a relatively high infrared emissivity of 0.91 in the whole band.

Abstract: Nickel hollow spheres (NHSs) with different diameter have been synthesized by the autocatalytic reduction method. The morphology, size distribution and magnetic properties of NHSs were characterized. The results indicate that when the nickel hollow spheres become smaller, mechanism of magnetization reversal varies from motion of domain wall to spin coherent rotation. After the heat treatment process, the grain size of samples becomes bigger and coercivity is enhanced because domain wall is pinned by local magnetic anisotropy induced spontaneously.

Abstract: Co0.6Cu0.16Ni0.24Fe2O4/multi-walled carbon nanotubes composites were synthesized by solution filling method. Phase structure, morphology, function property of the composites were characterized. The experimental results indicate that conductivity was related to the content of MWNTs while the magnetism correlated with the volume of Co0.6Cu0.16Ni0.24Fe2O4 filled in the composites. If setting the iron concentration and sintering temperature as 0.75 mol/L and 350 oC, respectively, the composite with 2 mm of thickness exhibits the excellent absorbing performance on microwave, its minimum reflection loss reaches -22.47 dB at 9.76 GHz and the available bandwidth exceeds 2.0 GHz. Hence, the obtained products have the potential and valuable application in microwave shielding and absorption field.