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Lu Y.,Xian Special Equipment Inspection Institute | Yang J.,Xi'an Jiaotong University | Chen Z.,Xian Special Equipment Inspection Institute | Han J.,Xian Special Equipment Inspection Institute | And 2 more authors.
Materials Science Forum | Year: 2013

Porous TiN ceramics with high porosity and uniform pore structure was prepared following the carbothermal reduction reaction between TiO2 and carbon. Influences of sintering additives and particle size of TiO2 on the microstructure and mechanical properties of porous TiN ceramics were investigated. Microstructure and mechanical properties of porous TiN ceramics were studied by XRD, SEM and three-point bending measurement. XRD analysis proved that the TiN phase has completely formed after reaction. In addition, SEM analysis showed that the resultant porous TiN ceramics were composed of fine grains with uniform pore structure. The addition of La2O3 not only accelerated the densification of porous TiN ceramics, but also decreased the porosity and increased the flexural strength. With a decrease in TiO2 particle size, the linear shrinkage increased and the porosity decreased accordingly. © (2013) Trans Tech Publications, Switzerland.


Wang J.,Xian Special Equipment Inspection Institute | Liu C.-C.,Xi'an Jiaotong University | Chen Z.-L.,Xian Special Equipment Inspection Institute | Jing Q.-Z.,Xian Special Equipment Inspection Institute | Hui S.-E.,Xi'an Jiaotong University
Huaxue Gongcheng/Chemical Engineering (China) | Year: 2013

Under N2/CO2 atmosphere, non-isothermal thermo-balance experiment on different calcium-based sorbents was investigated to research the effect of the heating rate, particle size and CO2 concentration on the characteristics of calcium-based sorbent reacting with CO2. The results show that the activation energy of calcium-based sorbent prepared by calcium oxalate and calcium acetate is less than that of other five calcium-based sorbents, which are easier to react with CO2. The activation energy of calcium-based sorbent prepared by pure CaCO3 becomes higher as the number of cycles increasing, and particularly higher between the fifth and the tenth cycles. The activation energy also increases with the increasing of the particle size of pure CaCO3. When the heating rate and the volume ratio of CO2 in the reaction atmosphere increase, the activation energy of calcium-based sorbent prepared by pure CaCO3 decreases, while the frequency factor increases gradually. The activation energy of the calcium-based sorbent mixed with MgO is less than that of pure CaCO3, and the activation energy of the sorbent contained 5% MgO (mass fraction) is less than that of the sorbent contained 10% MgO (mass fraction).


Lu Y.,Northwestern Polytechnical University | Lu Y.,Xian Special Equipment Inspection Institute | Li J.-L.,Northwestern Polytechnical University | Yang J.-F.,Xi'an Jiaotong University | Li P.,Northwestern Polytechnical University
Wuji Cailiao Xuebao/Journal of Inorganic Materials | Year: 2015

The co-continuous β-Si3N4 reinforced Al matrix composites were fabricated through squeeze casting of porous β-Si3N4 preforms with porosity of 53.43% which obtained by pressureless sintering. The influences of heat-treatment temperature on the microstructures and mechanical properties of co-continuous β-Si3N4 reinforced Al matrix composites were investigated. With the heat-treatment temperature increase, the degree of interfacial reaction, dislocation density increase, and vickers hardness increases, while fracture toughness decreases, accompanied by flexural strength increasing until 850℃ and then decreasing. The fracture mode of composites changes gradually from ductile intergranular rupture to brittle intergranular rupture. When being heat-treated at 850℃, the composites obtain the optimum mechanical properties with the reaction layer of about 20-50 nm. ©, 2015, Science Press. All right reserved.


Liu R.,Xi'an Jiaotong University | Liu G.,Xi'an Jiaotong University | Yang J.,Xi'an Jiaotong University | Jin H.,Xi'an Jiaotong University | And 2 more authors.
Materials Science and Engineering A | Year: 2012

Porous α-SiC ceramics with distributed pore structure were prepared by recrystallization method using silicon as the template. The microstructure evolution of this material (sintered at 2100 °C) was investigated by varying particle size of the silicon powders (3.5 μm and 37 μm). The results demonstrated that finer silicon powder could strengthen grain growth along close-packed directions and made the material easily to form plate-like SiC crystals. Pore diameter was mainly controlled by silicon raw powder when the silicon had a greater median diameter value than the SiC powder. In this study, grain growth was determined by a mixed mechanism during silicon removing. The porosity increased with the increasing of silicon contents while the strength was in a reverse proportional relationship. High porosity ceramics with relative high strength, which were sintered at 2100 °C for 15. min, were obtained using 3.5 μm silicon powder as the template. © 2012 Elsevier B.V.


Lu Y.,Northwestern Polytechnical University | Lu Y.,Xian Special Equipment Inspection Institute | Li J.L.,Northwestern Polytechnical University | Yang J.F.,Xi'an Jiaotong University | Li P.,Northwestern Polytechnical University
Materials Science Forum | Year: 2014

A new method for preparing porous AlN ceramics with high porosity had been developed by carbothermal reduction of die-pressed green bodies composed of alumina, carbon, sintering additives and AlN seeds. The influences of sintering additives and sintering temperature on the microstructure and mechanical properties of porous AlN ceramics were investigated. XRD analysis proved that complete formation of AlN phase except for minor of glass phase. SEM analysis showed that the resultant porous AlN ceramics occupied fine microstructure and a uniform pore structure. Porous AlN ceramics with a porosity of 41~66% and a strength of 2.7~ 51.8 MPa were obtained. © (2014) Trans Tech Publications, Switzerland.


Lu Y.,Northwestern Polytechnical University | Lu Y.,Xian Special Equipment Inspection Institute | Li J.L.,Northwestern Polytechnical University | Yang J.F.,Xi'an Jiaotong University | And 3 more authors.
Materials Science Forum | Year: 2014

The co-continuous AlN composites with different Al contents were fabricated through the squeeze casting of porous AlN preform with varied porosities obtained by carbothermal reduction. The effects of volume fraction of Al phase and the heat treatment temperature on the mechanical properties of composites were investigated. The change of the mechanical properties of composites with the Al content was in line with the mixed rule. With an increase in the Al content, the fracture toughness increased, the Vickers hardness and the flexural strength decreased. The toughen mechanism of composites included ductile rupture and microcrack toughening. The avoiding of excessive interface reaction between AlN and Al was beneficial to the mechanical properties of composites. With an increase in the heat treatment temperature, the stress and the dislocation due to mismatch in the coefficients of thermal expansion increased, the fracture toughness decreased, the vickers hardness and the flexural strength increased. © (2014) Trans Tech Publications, Switzerland.


Jiang C.,Chang'an University | Jiang C.,China University of Technology | Wang J.,Chang'an University | Han J.,Xian Special Equipment Inspection Institute | And 4 more authors.
Journal Wuhan University of Technology, Materials Science Edition | Year: 2015

Fe-based amorphous and nanocrystalline coatings were fabricated by air plasma spraying. The coatings were further treated by laser remelting process to improve their microstructure and properties. The corrosion resistance of the as-sprayed and laser-remelted coatings in 3.5wt% NaCl and 1 mol/L HCl solutions was evaluated by electrochemical polarization analysis. It was found that laser-remelted coating appeared much denser than the as-sprayed coating. However, laser-remelted coating contains much more nanocrystalline grains than the as-sprayed coatings, resulting from the lower cooling rate in laser remelting process compared with plasma spraying process. Electrochemical polarization results indicated that the laser-remelted coating has great corrosion resistance than the as-sprayed coating because of its dense structure. © 2015, Wuhan University of Technology and Springer-Verlag Berlin Heidelberg.


Deng Z.,Northwestern Polytechnical University | Huang Y.,Northwestern Polytechnical University | Li X.,Xian Special Equipment Inspection Institute | Zhang T.,Northwestern Polytechnical University
Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University | Year: 2015

Fatigue driving has become an important factor in traffic accidents; warning through timely monitoring of driver fatigue may reduce the incidence of traffic accidents. Using the image processing and the driver's actual situation, we separate driver's face in the background region, use optimized equal illumination method and optimized mouthmap method respectively to extract characteristic parameters of the eyes and the mouth, firstly establish fatigue classifier to identify driver fatigue based on fuzzy neural network classifier, and then implement the driver fatigue detection system in DSP system. Experimental results and their analysis show preliminarily that the system with strong practicability can meet the requirements of dynamic recognition of general fatigue. © 2015, Northwestern Polytechnical University. All right reserved.

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