Authors: Li Tong Guo, Ji Qiang Gao, Xiao Chen Liu, Tian Wen Guo, Zeng Ying He
Abstract: Low-fusing dental porcelain was fused on titanium surface. The adhesion between the titanium
and porcelain was evaluated by three-point flexure test. It was shown that the failure of the titaniumporcelain
predominantly occurred at the alloy-oxide interface. Rutile phase was present on the interface
debonding from porcelain. The influence of corrosion on bonding strength was also investigated. The
results suggested that, after being immersed in artificial saliva with pH of 2.7, 5.4 and 7.0, no decreasing
of the bonding strength of Ti-porcelain occurred.
1618
Authors: Ji Kuan Cheng, Ji Qiang Gao, Jian Feng Yang, Jun Lin Liu, Xian Jiang, Yong Gui Shi
Abstract: The research investigated the mass loss in SiC crystal growth process by analyzing the effects
of the content of Si appending in sources material, growth temperature, growth time and atmosphere
pressure. The results indicate that mass loss of total system material (source material + crucible + crystal)
and crucible augments with increasing of content of Si in sources material, growth temperature and
growth time, but crystal mass gain increases. With increasing of atmosphere pressure, mass loss of system
material decreases, crucible mass loss increases, crystal mass gain decreases. Si inclusions in crystal
multiply with the increasing of the content of Si in source material.
1558
Authors: Hong Zeng, Hong Jie Wang, Juan Li Yu, Dan Bo Lin, Guan Jun Qiao, Ji Qiang Gao
Abstract: In this paper, highly porous Si3N4 ceramics with high strength, homogeneous microstructure
were fabricated by introducing a proper amount of nanometer carbon in the Si3N4 slurry by gel-casting.
Scanning electron microscopy, X-ray diffraction, Archimedes water-displacement method and
three-point bending tests were employed to analyze the microstructures and mechanical properties of the
sintered bodies. It was shown by the XRD analysis that SiC particles were formed in the sintered bodies.
The pillar β- Si3N4 morphology, homogeneous microstructure and the SiC particles as a reinforcement
phase are the contributing factors for high porosity and good mechanical behavior.
898
Authors: Yuan Lu, Jian Feng Yang, Shao Yun Shan, Ji Qiang Gao, Zhi Hao Jin
Abstract: In this paper, porous Si3N4 ceramics were fabricated by carbothermal reduction between silicon
dioxide and carbon. The influences of four types of sintering additives on the microstructure and
mechanical properties of the porous Si3N4 ceramics were investigated. XRD analysis proved complete
formation of a single-phase β-Si3N4. SEM analysis showed that the resultant porous Si3N4 ceramics
occupied fine microstructure and a uniform pore structure. The sintered sample with Lu2O3 as sintering
additive showed finer, a higher aspect ratio β-Si3N4 grains. The addition of Eu2O3 accelerated the
densification of porous Si3N4 ceramics, decreased the porosity and increased the flexural strength.
878
Authors: Xiao Chen Liu, Li Tong Guo, Ji Qiang Gao, Tian Wen Guo, Li Liu, Shi Bao Li, Xiao Na Li
Abstract: The aim of this investigation is to study the effect of SnO coatings on the bond strength
between titanium and porcelain. The coatings were produced by sol-gel method and heat-treatment at
300°C. Once the coatings have been formed on the titanium substrates, self-made porcelain was fused.
The specimens with pre-oxidation before porcelain fused were set as control group. It was shown SnO gel
formed completely at 300°C and was composed by SnO and SnO2 in the form of a uniform film. The bond
strength between titanium and porcelain of the specimens with SnO coatings was greater than those in
control group statistically, which might prove that the coatings reduced the oxidation of titanium surface
in the porcelain fusing progress. EDS result showed almost all fractures between titanium and porcelain
occurred at the oxide layer. Si and Sn might attend the reaction at interface. It was concluded that the SnO
coatings produced in this study can improved the titanium-porcelain bond strength.
1268
Authors: Jian Feng Zhu, Ji Qiang Gao, Fen Wang, Ping Chen
Abstract: The influence of the amount of Pr6O11 additions on the microstructure and electrical properties
of varistors ceramics in the ZnO-Bi2O3 system was investigated. Samples with a low level of Pr6O11
(0.1wt %) have high microstructural homogeneity, which enhances the nonlinear coefficient greatly, and
decreases the leakage current without change of voltage ratio. When the Pr6O11 content reached 7wt%, the
ZnO grain growth was restricted and the threshold voltage was improved from 275v/mm to 440v/mm.
The additive of Pr6O11 changed the process of creating spinel phase, which came from the decomposition
of pyrochlore phase. This type of small size phase has more dragging force on the ZnO crystal, which
make the whole materials more uniform and compact.
500
Authors: Sen Liang, Ji Qiang Gao, Jian Feng Yang, Min Luo
Abstract: The electrical and structural properties of the mixture of Co3O4 and In2O3 were studied.
All the samples were added with 2% nanocrystalline SiO2 and sintered at 1000°C for 2 hours. The
sintered bodies of the samples were of high density and the average particle size was ~2μm. The
materials showed the NTC behavior in a wide temperature range (100-350°C). The resistivity of the
materials at room temperature decreased with increase the content of the In2O3 from 0% to 10%.
The thermistor constant (B) values and activation energy(E) were 7835, 6637, 5903K, and 0.675,
0.572, and 0.509 eV as the content of In2O3 were 0%, 5% and 10%, respectively.
193
Authors: Hai Yun Jin, Guan Jun Qiao, Zong Ren Peng, Ji Qiang Gao
Abstract: SiC particles coated with nano-BN were synthesized and the machinable SiC/BN ceramic
nano-composites were fabricated by Plasma Active Sintering (PAS) in N2 atmosphere. The existing
and distribution of h-BN phase were revealed by X-ray diffraction (XRD), and SEM. For the existing
of weak interface between h-BN and SiC grains, the machinability of both SiC/BN micro-composites
and nano-composites were improved obviously. Because the nano-sized h-BN crystals were
homogeneously dispersed around the SiC grains of the matrix, the fracture strength of the
nano-composites was better than the SiC/h-BN micro-composite.
45
Authors: Zhen Lin Lu, Hui Xie, Ji Qiang Gao, Zhi Hao Jin
Abstract: The oxidation behavior and electrical resistivity of reaction-bonded silicon carbide
(RB-SiC) at high temperature (900 °C) had been studied in this paper. The results showed that the
weight of RB-SiC would be increased when it was oxidized at 900. The relationship between the
weight-gain of RB-SiC and oxidation times followed the parabolic curve. The oxidation resistance of
RB-SiC at 900 could increased by the increase of SiC particles sizes. But the electrical resistivity of
RB-SiC had not affected by the oxidation at 900. The oxidation mechanism of RB-SiC and the
affecting factor on oxidation of RB-SiC were analyzed and discussed.
475
Authors: Hai Yun Jin, Guan Jun Qiao, Ji Qiang Gao
Abstract: The SiC/h-BN ceramic composites with different h-BN size were fabricated by Plasma
Active Sintering (PAS) method. For the SiC/ nano-sized h-BN ceramic composites, when the h-BN
content was increased, because the nano-sized h-BN crystals were homogeneously dispersed around
the SiC grains of the matrix, the bending strength and fracture toughness of the composites decreased
slowly, but the hardness decreased sharply, therefore the machinability and thermal shock resistance
were improved noticeable.
391