Xiu Qin Wang

Oxidation Kinetics of ZrB2 Ceramic Matrix Composite Materials

Zirconium diboride is widely applied because of some excellent performances. The oxidation kinetics of ZrB2-YAG-Al2O3 composite materials were researched, which helps to improve the performance of ultra-high-temperature composite materials. The results show the oxidation weight gain is decreased with increasing the content of YAG-Al2O3 and the molar ratio of Al2O3. The oxidation weight gain is increased with prolonging the oxidation time under 1300°Cæ, the oxidation weight gain ratio is decreased with prolonging the oxidation time. The effecting tendency of oxidation weight gain is not abvious with varying the contend of YAG-Al2O3 upon 1300°Cæ, however, the effecting tendency of oxidation weight gain is very abvious with varying the molar ratio of Al2O3.

Effect of Auxiliary on the Dispersibility of ZrB 2 Powder in the Liquid

The composite ZrB2 powder coated A12O3-Y2O3 prepared by co-precipitation method were densified via the spark plasma sintering (SPS) and then researched the oxidation resistance at high temperature. ZrB2 powder must have the better dispersibility during the coating processing for obtaining the better coating effect. Effect of dispersant on the dispersibility of ZrB2 powder in the liquid is researched in this paper, the results show ZrB2 powder have the better dispersibility as the dispersant for PMAA and the content for 2vol%, which lay foundation for synthsising the better coating effect coated A12O3-Y2O3-ZrB2 composite powder.

Effect of Molding Pressure on Densification of Al 2 O 3 /Al Cermet Materials

Cermet materials is a important new engineering materials with the advantages of ceramics and metal materials. The Al2O3/Al cermet materials is prepared via the powder metallurgy method, the effect of sintering technology on properties of Al2O3/Al cermet materials is researched in this paper, which lay the base for preparing the high performance cermet materials. The results are shown through the study, the denstity of cermet is increased with an increasing moliding pressure, the sample density is 2.084g/cm3 as the pressure for 40MPa and the sintering temperature at 600¡æ, the density is higher, that is to say it is highest performance, the distribution of aluminum and alumina is most uniform. When the sintering temperature is higher, howerver, the molding pressure is lower, the lower density of the sample is shown, the aluminum is easier to overflow the surface of the sample.

Influence of Synthesis Process on Coated Properties of Al(OH)3-Y(OH)3/ZrB2 Composite Powders

Zirconium diboride (ZrB2) ceramics with high melting point, high hardness, good electrical and thermal conductivity, good neutron control and other characteristics, can be widely used in high-temperature structural ceramics, composite materials, electrode materials. In order to improve ZrB2 difficult densification and high-temperature oxidation, the properties of coated Al (OH)3-Y(OH)3/ZrB2 composite powders prepared by co-precipitation method were investigated in this paper, The conclusions are shown that the effect of coated composite powders is getting worse with the accelerated titration rates. the coating effect will be worse with the increasing reaction time. When the concentration of mixed solution is lower, the coated effect is better. When the synthesis condition is that the titration rate of 10ml/min, and the reaction time was 1h, mixed solution ion concentration of Y3+=0.119mol/L and Al3+=0.231mol/L, the coated effect of composite powders is better.

Preparation of Superfine Alumina Powders via Hydrothermal Method

Superfine alumina has various excellent performance, superfine aluminum often used in metallurgy, aerospace, microelectronics and medicine, so the study of alumina has become a hot research at home and abroad, superfine alumina powder the body needs are also increasing. In this paper, superfine alumina powder were prepared by hydrothermal method, and to study the preparation process. The results show that the fibrous alumina particles gradually becomes granular with the increase of pH of the reaction, pH value of 9 to get a uniform particle size distribution and an average size of small powder particles. As the increasing calcination temperature, the alumina particles gradually grow, the homogeneous superfine particulate alumina powders is obtained under calcination temperature at 950¡æ. The better preferred process is that alkali molar ratio of 1:3, a concentration of 0.3mol/L, the reaction temperature at 200°C, calcination temperature of 950°C.

Mechanism of Controlled Pore Structure of Quartz Pore Gradient Materials

Pore gradient material has obvious uneven, making the material porosity, pore size and strength changes with the thickness of the material exhibits a special distribution, pore gradient material is therefore in the chemical industry, environmental protection, metallurgy, food, biotechnology and other industries widely used, it is a very promising new material. In this paper, low-grade quartz sand as the main raw material, by adding auxiliary ingredients, using foam deposition method, the pore graded material were prepared. Through experimental results and analysis, the conclusions can be obtained, quartz pore gradient material body after sintering at 1300¡æ posing obvious gradient structure. When the ratio of water to 1.4 and 1.5, the sample can be observed that there is a clear gradient structure. Considering the combination of price, quality quartz pore gradient material should be water feed ratio of 1.4, the sintering temperature is 1300 ¡æ more appropriate, the porosity of prepared quartz graded materials was 32.45%.

Densification Mechanism of Al2O3/Al Metallic Ceramics Prepared via Powder Metallurgy Method

Alumina ceramics with good mechanical and corrosion resistance, is one of the most widely used engineering ceramics. The aluminum has a high strength, high conductivity, high plasticity, etc. than aluminum ceramics used in more and more industries. In this paper, aluminum and alumina powder as raw material, mixing, forming, sintering and a series of processes for preparing the alumina/aluminum metallic ceramic materials, through performance testing and analysis can be found in the ratio of raw materials 50wt% Al, 50wt % Al2O3 relatively good moldability. After sintering, after measuring the density contrast is found better density in the pressing process pressure of 20MPa and holding pressure time for 20min. By comparing the sintering process, after the interface structure by scanning electron microscopy and found help improve density through the secondary sintering metallic ceramic materials.

Influence of Reinforcing Phase on the Oxidation Model of ZrB2 Based Multi-Phase Ceramics

ZrB2, YAG and Al2O3 are widely applied because of some excellent performances, but ZrB2 is easily oxidized in the high-temperature air. To make the ZrB2 ceramics obtain better oxidation resistance, high-density ZrB2-YAG-Al2O3 ceramics were prepared. The oxidation mechanism of ZrB2-YAG-Al2O3 ceramics is investigated. When YAG-ZrB2 ceramics are exposed to air at temperatures from 1100°C¡æ to 1600°C¡æ, the weight change rate of YAG-ZrB2 ceramics is fleetly increased, the reacted speed of ZrB2 and O to form B2O3 and ZrO2 is more faster. The quantity of melted B2O3 is increased and carried to the surface, B2O3 is reacted with Al2O3 to form Al18B4O33. Al18B4O33 is melted and coated on the surface of ceramics to form protection layer for the oxidation resistance of ceramics at high temperature, which shows the similar with the influence of reinforcing phase on the oxidation model of ZrB2 based multi-phase ceramics.

Influence of Coated Composite Powders on the Properties of ZrB2-YAG-Al2O3 Ceramics

ZrB2, YAG and Al2O3 are widely applied because of some excellent performances, but ZrB2 is easily oxidized in the high-temperature air. To make the ZrB2 ceramics obtain better oxidation resistance, high-density ZrB2-YAG-Al2O3 ceramics were prepared. The influences of coated composite powders on the densification and the oxidation resistance of ZrB2-YAG-Al2O3 ceramics were investigated. The 80wt%ZrB2-YAG-Al2O3 multiphase ceramic materials from different composite raw materials with the spark plasma sintering technique were successfully prepared. The densification of ZrB2-YAG-Al2O3 ceramics with Al2O3-Y2O3 composite powder coated is easier than that of ZrB2-YAG-Al2O3 ceramics with YAG-Al2O3 powder mixed. The reaction temperature is lower than the 1100¡æ for synthesizing YAG powders from Al2O3-Y2O3 composite powders. The weight gain are increased with increased the oxidation temperature. B2O3 is reacted with Al2O3 to form Al18B4O33, Al18B4O33 is melted and coated on the surface of ceramics to form a protective layer for the oxidation resistance of ceramics at high temperature. The oxidation weight gain of ZrB2-YAG-Al2O3 ceramic with Al2O3-Y2O3 composite powder coated is lower than that of ZrB2-YAG-Al2O3 ceramic with YAG-Al2O3 powder mixed.

Effect of Maitenance Technology on the Properties of Quartz Sand Unfired Porous Materials

The low grade quartz sands is the main raw material to prepare the unfired porous brick through adjusting the maitenance technology. The compressive strength of brick is higher with the maitenance temperature for 40¡æ. The compressive strength of brick is higher with the longer maitenance time. The high performance brick is prepared via the third technology, the pore of brick is more and uniform, it is bowl shape, that is close pore, which provide the reference for preparing the heat insulating materials. The compressive strength of brick is 1.9MPa, the density is 0.628 g/cm3.