Dali ZHOU
,
Weizhong YANG
,
Guangfu YIN
,
Changqiong ZHENG
,
Yun ZHANG
,
Huaiqing CHEN
,
Rui CHEN
材料科学技术（英文）
To develop a novel degradable poly (L-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) bioactive materials for bone tissue engineering, β-TCP powder was produced by a new wet process. Porous scaffolds were prepared by three steps, i.e. solvent casting, compression molding and leaching stage. Factors influencing the compressive strength and the degradation behavior of the porous scaffold, e.g. weight fraction of pore forming agent-sodium chloride (NaCl), weight ratio of PLLA: β-TCP, the particle size of β-TCP and the porosity, were discussed in details. Rat marrow stromal cells (RMSC) were incorporated into the composite by tissue engineering approach. Biological and osteogenesis potential of the composite scaffold were determined with MTT assay, alkaline phosphatase (ALP) activity and bone osteocalcin (OCN) content evaluation. Results show that PLLA/β-TCP bioactive porous scaffold has good mechanical and pore structure with adjustable compressive strength needed for surgery. RMSCs seeding on porous PLLA/β-TCP composite behaves good seeding efficacy, biocompatibility and osteoinductive potential. Osteoprogenitor cells could well penetrate into the material matrix and begin cell proliferation and osteogenic differentiation. Osseous matrix could be formed on the surface of the composite after culturing in vitro. It is expected that the PLLA/β-TCP porous composites are promising scaffolds for bone tissue engineering in prosthesis surgery.
关键词:
β-tricalcium phosphate (β-TCP)
,
null
Jianjun WU
,
Yun ZHANG
,
Yutian SHEN
,
Guobin LI
,
Tingquan LEI
材料科学技术（英文）
The thermodynamics and kinetics of the internal oxidation in dilute Cu-Al alloy are investigated. The internal oxidation of copper alloy containing 0.2-1.2 wt pct Al is studied in the temperature range from 1073 K to 1273 K. A related equilibrium diagram is drawn. A mathematic model of oxidation layer depth is developed on the base of the experimental results. The experiments and investigation show that the formation rate of the internal oxidation layer is mainly controlled by the diffusion of O in matrix, the O concentration on the surface and the Al concentration in the alloy.
关键词:
Weizhong YANG
,
Dali ZHOU
,
Guangfu YIN
,
Runsheng WANG
,
Yun ZHANG
材料科学技术（英文）
Nanosized ZnO powders were prepared with a two-step precipitation method. The average size of ZnO particles was about 80 nm and their size distribution was narrow. Combining with ultrafine additive powders, ZnO base varistor was produced via an oxide mixing route. ZnO varistor derived from normal reagent grade starting materials was investigated for comparison purpose. Outstanding microstructure of the ZnO varistor derived from nanosize ZnO powders and ultrafine dopants was obtained: uniform distribution of fine ZnO grains (less than 3 microns), grain boundary and the dopant position. Higher varistor voltage (U=492 V/mm) and nonlinear coefficient (α=56.2) as well as lower leakage current (I L=1.5 μA) were achieved. The better electrical properties were attributed to the uniform microstructure, which in turn led to stable and uniform potential barriers. Also this improved technique is more feasible for producing ZnO nanopowders and resulting varistor in large scales.
关键词:
Zinc oxide (ZnO)
,
null
,
null
,
null
,
null
