High-Performance Ceramics III

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Authors: Fu Liu, Fu Ping Wang, Tadao Shimizu, K. Igarashi, Lian Cheng Zhao
Abstract: An oxide film containing Ca and P was obtained in an electrolyte containing calcium glycerphosphate (Ca-GP) and calcium acetate (CA) by microarc oxidation. The surfaces of the oxide films were porous and rough, and the Ca/P ratio in the oxide film was 1.71 when the oxide film was formed in the electrolyte containing 0.06 M Ca-GP and 0.25 M CA at current density 50 A/m2 and final voltage 350 V. The oxide film with Ca/P ration 1.71 was treated hydrothermally at 190°C for 10 hours in an autoclave. It was found that hydroxyapatite crystals were precipitated on the oxide film after hydrothermal treatment. The oxide films were investigated by means of electron probe micro analyzer, X-ray diffraction, scanning electron microcopy before and after hydrothermal treatment.
Authors: Jie Mo Tian, Xiao Yan Wang, Li Min Dong, Chen Wang, Wei Xu
Abstract: Porous hydroxyapatite (HA) ceramic scaffolds were prepared using three-dimensional (3-D) gel-lamination technology with sodium lauryl sulfate as foaming agent and lauryl as foaming stabilizing agent. With gelling system of sodium alginate and calcium chloride, the foamy HA slurry was gelled layer by layer on the 3-D gel-lamination machine to prepare the porous ceramic scaffolds. The viscosity of the foamy ceramic slurry was examined. After sintering, the porous HA bioceramic was characterized in terms of the porous microstructure and mechanical properties. The experimental results demonstrated that the resultant porous ceramic with appropriate pore size, porosity characters, mechanical properties and bioactivity could be obtained.
Authors: Li Min Dong, Chen Wang, Jie Mo Tian, Jian Pan, Qing Feng Zan
Abstract: Carbonated hydroxyapatite (CHA) bone cement is capable of self-setting and has the component similar to the mineral phase of natural bone. But it is compact in structure and short of cavity, which limits new bone growing into CHA bone cement. In this paper, the foaming method was adopted to prepare the porous CHA. The setting time, compressive strength, porosity and pore size of the CHA were examined. The phase composition of the CHA was tested with XRD and FT-IR. The microstructure of the CHA was observed with SEM. The results show that setting time of 7~19 minutes, compressive strength of 26~32MPa, pore size of 100~200µm, porosity of 50~60%.
Authors: Jean François Castagné, Jeanne Chamousset, Lise-Marie Minois, Alexandre Ponsinet, Jean Michel Bouler, Franck Tancret
Abstract: Macroporous biphasic calcium phosphate bioceramics, for use as bone substitutes, have been fabricated by cold isostatically pressing and conventional sintering, using naphtalen or saccharose particles to produce macropores. The resulting ceramics, composite materials made of hydroxyapatite and b-tricalcium phosphate containing ~ 45% macropores and ~ 25% micropores, have been submitted to compression and three-point bending tests, toughness tests by single-edge-notched-bending, and spherical indentation tests. A new model is established to describe mechanical properties as a function of the amount and morphology of porosity, and propositions are made to optimise the fabrication procedure. Finally, those highly porous ceramics, although very brittle, exhibit a damage-tolerant contact behaviour, due to the compaction of the porous body under the indenter.
Authors: Yu Jia, Yuji Hotta, Kimiyasu Sato, Koji Watari, Yoshinori Kanno
Abstract: Hydroxyapatite powders were prepared via mechanochemical synthesis method. The starting reagents for HAP powders were vibration ball milled for 2 h and then calcined at 800°C for 1 h. X-ray diffraction patterns and IR spectrum shown that pure crystalline apatite powder (HAP) was obtained. The as-synthesized powders were gelcasted and then sintered at 1200°C for 2 h. It was observed from SEM micrographs that the prepared green body has uniform microstructure. The bending strength of the dried green body was as high as 18 MPa that is enough to be machined into required form before sintering. The sintered ceramics has a density of 2.5 g/cm3 and a flexural strength of 72 MPa with a homogenous microstructure.
Authors: De An Yang, Zi Yang, Weijie Hu, Yuan Yuan Li, Huan Wang
Abstract: Gypsum powders and calcium phosphate/gypsum powders were synthesized by wet method. The influences of the pH and temperature on the morphology of the gypsum crystal were studied by light microscopy. The effects of the initial calcium/phosphorus molar ratio and the pH of the solution on the microstructure and phase composition of the calcium phosphate/gypsum composite powders were studied by scanning electron microscopy and X-ray diffractometry. The results show that both temperature and pH value had influence on the crystal shape of gypsum and the pH value was the predominant parameter for the particle shape and phase composition of the composite powders.
Authors: Shu Cai, Yan Wei Wang, Kang De Yao
Abstract: Macroporous biomaterials based on a-tricalcium phosphate (a-TCP) bone cement with porous structures suitable for implantation purposes were prepared in the present work. According to the reversible swelling/deswelling behavior of gelatin at a single temperature or pH, a “self-setting” method that uses gelatin granules as pore formers was developed to process the porous microstructure. By mixing gelatin powder and bone cement powder (BCP), and adding water (1% solution of NaH2PO4×HO) to form pastes which set within 15 to 30 min, this setted cement was then immerged in deionized water of temperature 25°C or 32°C for hydration. During the hydration, the pH of deionized water after cement pastes were introduced at 32°C changed from 8.6 to 7.2 which caused by the transformation of a-TCP to hydroxyapatite (HA). Meanwhile, gelatin particles will swell by water uptake to form large size spheres in cementmatrix. This swelling behavior is sensitive to the variation of pH value. After hydration for 4 day, a body containing gelatin gel spheres was obtained. Then heating the deionized water to temperature 50°C, gelatin spheres in cement matrix were solved and porous microstructure composed of larger pore sizes corresponding approximately to the average size of the swelling gelatin granules was obtained. The porous bodies by this technique were found to have tractable and interconnected porosity in the range of 60~84%, with typical pore sizes ranging from 100~300 microns. This new processing technique can be used in the manufacture of unsintered biomaterials.
Authors: Jian Pan, Jie Mo Tian, Li Min Dong, Chen Wang
Abstract: The setting behavior of fast-setting calcium phosphate cement (FSCPC) with mineral phase of bone was investigated to evaluate the possible value of the CPC for medical and dental application. Various aspects of the setting behavior such as setting time, mechanical strength and phase change of cement with time were measured by the Vicat needle method, diametral tensile strength measurement, and quantitative powder X-ray diffraction (XRD) analysis, respectively. The change of microstructure during the setting process was observed by Scanning Electron Microscope (SEM). The setting time of the CPC was 10-15min. As a result of its fast setting, set specimens of FSCPC showed high mechanical strength. Powder XRD analysis revealed faster conversion of FSCPC into HAP. SEM observation showed that the specimens are mainly formed with micropores and crystallites, and the phase composition of the set specimens is mainly low-crystallinity HAP at last.
Authors: Yin Zhang, Yoshiyuki Yokogawa, Tetsuya Kameyama
Abstract: Preparation of apatite ceramics with bimodal pore structure was studied. First fine hydroxyapatite powder was obtained through mechanochemical method. The particle size of the product was around 0.64 µm. The slurry with the fine apatite powder content of 55-62.5wt% was prepared using defloculant, and foaming reagent. The organic form was immersed into the slurry, dried under vacuum, and heated at 1100°C, 1200°C, 1300°C. Pore size distribution of the product measured by porosimeter showed that small pores of around 1 µm and large pores of 100 µm exist, and SEM observation confirmed. SEM observation showed that the large pores seemed to be interconnected through the openings of several dozens µm in size. The porosity of the products were found to be 48 – 58.5%, and the bending strength of the products obtained by heat-treatment at 1100°C for 3 hours was 5.6 MPa, and that at 1200°C was 10.5 MPa.
Authors: Bao Hui Su, Jun Guo Ran, Li Gou, Fang Hu Wang, Hai Su Guo
Abstract: BGC, HA, β-TCP and biphase calcium phosphate (β-TCP/HA) were modified by using the cold plasma technique in the present study. The study results came from the formation of bone-like apatite in SBF and results of osteoblast culture in vitro, SEM, XPS, and XRD. The results showed that the formation of bone-like apatite on bioceramics modified by cold plasma was easier than that of no modification and the growth of osteoblast could be promoted. The active mechanism was that impact on bioceramics by means of the particles with high energy and high activity led to rough and etched surface of bioceramics, as well as the distortion of bioceramics crystal, which increased solubility of materials and local concentration of Ca and P ion. It was helpful for the formation of bone-like apatite. It was showed that the modification using cold plasma technique could increase the activity of bioceramics.

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