Study On Fabrication Of Biological Porous Ceramic With Controlled Pore Structure

Hydroxyapatite (HA) has the similar chemical composition of the natural bone resulting in good biological activity,osteoconductivity and osteoinductivity, and it plays a significant role in the area of bone repair and bone graft. However, there are some disadvantages in artificial porous HA ceramics when HA is used as bone tissue engineering scaffolds, for instance, poor mechanical properties, low porosity, and lack of pore connectivity. Consequently, preparation of porous HA ceramics met the requirements of bone tissue engineering attracted much attention of materials researchers.In order to overcome the disadvantages of poor porosity and pore connectivity, a new technique combined elastic porogen-press gelcasting method was set up to fabricate biological porous ceramic with well controlled pore structure. First of all, preparation method of elastic microsphere porogen with high strength was studied, and the influence factors on elastic microspheres'diameter and morphology were investigated. Secondly, the factors of gel-casting slurry's liquidity in acrylamide (AM) gel system were studied, and the optimized slurry was obtained. Finally, the relationship between pore structure and experimental conditions of green body forming process was investigated in detail, and porous HA ceramic with man adjustable pore structure was obtained. Some conclusions obtained were as follows.PVA elastic microsphere porogen was fabricated by a modified high-voltage electrostatic technique. The results showed that high-voltage electrostatic system modified with atmospheric steam to control temperature and humidity of PVA microsphere formation area was an effective method to overcome microfilament formation while PVA solution was in higher concentration. The PVA elastic microsphere porogen with smooth surface, good spherical shape, perfect mechanical properties, and diameter between 400~600μm was suitable in fabricating of porous ceramic scaffold.By using the method of chemical co-precipitation, HA precursor and powder were synthesized in water with the particle size of 3.308±0.924μm and 3.625±1.188μm, respectively. In addition, HA precursor and powder were harvested in blend solution of water/ethanol (V/V=3/1) with the particle size of 2.733±0.792μm and 2.828±0.599μm, respectively.Under the optimized experimental conditions, that were HA precursor as slurry powder, dispersant content 2.0wt% , pH 10 , and milling 5h, gel-casting slurry with high solid content was obtained and it was good enough for porous ceramic preparation.Biological porous HA scaffold with uniformly distributed spherical pores as well as fully interconnected and regular channels between pores was harvested by our put forward technique when the gelcasting slurry and PVA elastic microsphere porogen were mixed at the ratio of 1:1 by volume. The results revealed that aperture of biological porous scaffold could be controlled by the diameter of porogen, the diameter of the channel between pores was dependent on the compression ratio during the fabricating process, which implied that the pore structure of scaffold was man controllable, and demonstrated that the elastic porogen-press gelcasting technique would have a widely potential use in the field of bone tissue engineering.