Wen WANG
,
Yu ZHOU
,
Sheng CHEN
,
Feng Y
,
Dechang JIA
材料科学技术（英）
Strontium bismuth tantalum (SBT) fine power was prepared by Sol-Gel method. Pentaethoxy tantalum, strontium acetate and bismuth subnitrate were used as raw materials, and were dissolved in proper order in ethylene glycol to form transparent sol. The mixed precursor was dried at 80℃ and annealed at 800℃ for 1 h. Crystallized nanometer sized SBT fine powder was obtained and characterized by XRD.
关键词:
Yujin WANG
,
Yu ZHOU
,
Guiming SONG
,
Tingquan LEI
材料科学技术（英）
In order to improve the high temperature strength of tungsten, 30~vol. pct ZrC particles were added to the tungsten matrix to form a 30ZrCp/W composite. The tensile properties from 20℃ to 1880℃ of the composite were examined. It was shown that with increasing testing temperature, the nonlinearity of the stress strain curve of 30ZrCp/W composite becames obvious over 1200℃ and the Young’s modulus decreases and the elongation increases. The ultimate tensile strength increases at first and then decreases with increasing testing temperature. The maximum strength of 431 MPa was obtained at 1000℃. The strengthening mechanism at high temperatures is the load transfer to ZrC particles and dislocation strengthening of the tungsten matrix with an effect of grain boundary strengthening.
关键词:
ZrCp/W composite
,
null
,
null
,
null
Junbao ZHANG
,
Tingquan LEI
,
Guangwu WEN
,
Yu ZHOU
材料科学技术（英）
Amorphous silicon oxynitride powders have been obtained by pyrolysis of polysiloxazane in a stream of anhydrous NH3 at the temperature up to 1000℃. The polysiloxazane is fabricated from ammonolysis of chloropolysiloxane that is produced by the hydrolysis of silicon tetrachloride. The conversion of polysiloxazane to silicon oxynitride and the structural features of the final powders have also been studied by infrared spectra, elemental composition and X-ray diffraction analysis and SEM observation.
关键词:
Dianran YAN
,
Jining HE
,
XiangZhi LI
,
Yangai LIU
,
Yu ZHOU
,
Dechang JIA
材料科学技术（英）
The corrosion resistance of SiO2/A12O3, TiO2/Al2O3 and (SiO2+TiO2)/Al2O3 ceramic composite coatings on Q235 substrate fabricated by means of plasma spraying was investigated. The results show that A12O3+13 wt pct TiO2 ceramic coating has the highest density, the lowest connected porosity and the best corrosion resistance. The corrosion mechanism of Q235 with ceramic coating has also been studied.
关键词:
Yujin WANG
,
Yu ZHOU
,
Guiming SONG
,
Tingquan LEI
材料科学技术（英）
The elevated temperature mechanical properties of TiCp/W composites produced using powder metallurgical technique were investigated. Results show that with increasing temperature, the strength of TiCp/W composites increases gradually and reaches its maximum value at 1000℃, which is much higher than that at room temperature. The strengthening mechanisms at high temperature are attributed to dislocation strengthening and load transfer between matrix and particles.
关键词:
Yingkui GUO
,
Yu ZHOU
,
Dongbo LI
,
Xiaoming DUAN
,
Tingquan LEI
材料科学技术（英）
2Y-PSZ/TRIP steel composites have been sintered by hot-pressing method. Their microstructure and mechanical properties were investigated by means of SEM, TEM, XRD and static tension, split Hopkinson pressure bar method. The results showed that the strength and elastic modulus of 2Y-PSZ/TRIP steel composites at room temperature decreased with the increase of 2Y-PSZ content. The main reason was that the combining strength was quite weak between the grains of ZrO2. Distortion induced martensite transformation and plasticity during the dynamic loading increased the strength and distortion capability of the composites. The transformation was carried out mainly through twins formation. The shape of martensite induced by distortion was lamellate with substructures of twins. The habit plane was near {259}γ with no mid-ridge and no explosion phenomena. The interface was straight between the austenite and martensite induced by distortion. The increase of 2Y-PSZ content, on the one hand, made the composite dynamic flow stress improved. Thereby, the fracture strength was improved. On the other hand, it depressed both the distortion capability and the martensite transformation induced by distortion. This resulted in the decrease of dynamic fracture strength.
关键词:
2Y-PSZ/TRIP steel composites
,
null
Jiancun RAO
,
Jiancheng GU
,
Yu ZHOU
,
Feng YE
,
Tingquan LEI
材料科学技术（英）
BAS glass-ceramic powders were prepared by sol-gel processing. SiC platelets reinforced BAS glass-ceramic matrix composites with high density and uniform microstructure could be made using hot-pressing method. The related processing parameters were studied in this work, including effects of additional seed on transformation from H to M of barium aluminosilicate. DTA method was used to determine exact time to press mixture powders during hot-pressing for the purpose of effective densification. Microstructure and mechanical properties of the composites were investigated by mean of SEM, XRD and TEM techniques as well as three points bending test and single edge notched beam measurement. The results showed that the flexural strength and fracture toughness value of the BAS glass-ceramic matrix composites could be effectively improved by the addition of the SiC platelets. But the relative densities of composites were slightly decreased. The main toughening mechanism is crack deflection, platelets' pull-out and bridging. The increased value of flexural strength is contributed to the load transition effect from matrix to SiC platelets.
关键词:
Congqin NING
,
Qingchang MENG
,
Yu ZHOU
,
Haitao LIU
材料科学技术（英）
Composite coatings of bioglass and hydroxyapatite (briefly named HA/BG) with different hydroxyapatite contents on titanium substrate were successfully fabricated. The fabricated coatings are characterized by rough and poriform surface.The densities of the coatings decrease with the increase of HA content. There is a transition layer with a 5 μm thickness between the BG coating and the substrate. During heat-treatment, hydroxyapatite crystals with hexastyle shape have precipitated from the BG.
关键词:
M.Naka
,
Jie ZHANG
,
Yu ZHOU
材料科学技术（英）
Si3N4 ceramic was jointed to itself using a filler alloy of Cu76.5Pd8.5Ti15, and the mechanical properties of the joint were measured and analyzed. By using a filler alloy of Cu76.5Pd8.5Ti15, the Si3N4/ Si3N4 joints were obtained by brazing at 1373～1473 K for 0.9～5.4 ks under a pressure of 2×10-3 MPa. The effect of brazing parameters on the shear strength of the joint was investigated. When the brazing temperature and holding time is 1423 K and 5.4 ks respectively, the maximum shear strength of the Si3N4/Si3N4 joint is obtained to be 198 MPa.
关键词:
Si3N4 ceramic
,
null
,
null
,
null
Jiancun RAO
,
Yu ZHOU
,
Douxing LI
材料科学技术（英）
A new type of long periodic structure has been found in ZrO2-Y2O3 ceramics in annealed states. High resolution electron microscopy (HREM), selected area electron diffraction, and computer simulation have been used to reveal the presence of the long periodic structure. The unit cell of the long periodic structure consists of a cubic ZrO2 unit cell and L10- like phase one.
关键词:
Ceramics
,
null
,
null
,
null
,
null
