In this work, nano-size HA was produced from bovine bone. At various heat treatment temperatures, poorly crystalline, partially crystalline and crystalline forms of HA were obtained. PLA composites were prepared by incorporating various forms and contents of HA into PLA matrix. The characteristics of the obtained HA powders affected properties of PLA composites including mechanical properties, morphologies, PLA molecular weight, in vitro bioactivity and in vitro degradation behaviors of the composites. In the case of in vitro bioactivity study, all composites illustrated the induction of bone-like calcium phosphate compounds on their surfaces, especially the PLA/a-HA composites.

Recently, calcium phosphate cements have been considered in medicine and dentistry because of their excellent biocompatibility and advantages in situ handling and shaping abilities. Nevertheless, low mechanical strength of these cements limits wider the clinical applications. The aim of this work was the synthesis of chitosan/brushite powders for preparing the calcium phosphate cements. The synthesis of brushite was carried out in the chitosan matrix from calcium chloride and sodium phosphate at moderate pH of 4 and then dried from 60 to 100°C. The obtained powders were characterized by XRD and FT-IR technique. With increasing the drying temperature, phase of dicalcium phosphate anhydrous increased. Moreover, FTIR indicate the bands attributable to chitosan and brushite. The brushite synthesized using this route was used to be a starting powder for calcium phosphate cement (CPC). To prepare CPC, the mixture of chitisan/brushite and a-tricalcium phosphate powders was mixed with various liquid phases and then cured at 100 humidity for 7 d The compressive strength of the cements was determined to evaluate the potential use for the bone cement. Cements formed with chitosan/brushite dried at 100°C had the greatest compressive strength of all cement tests. The improvement of compressive strength seemed to depend on the affinity of chitosan incorporated in the cements.

This study assesses the possible use of Korat clays, deposited at Suranaree University of Technology (SUT), for the production of lightweight aggregates. The SUT clays were collected and divided into 2 groups, i.e. white clay and reddish brown clay, to study their heat-treatment behavior. The SUT clay mixtures in various ratios were investigated to find the suitable compositions and heat-treatment (between 1000 and 1250°C) for the production of lightweight aggregates. After firing at 1250°C, the SUT clays expanded 21.05 and 5.70% for the white and reddish brown clays, respectively. Firing expansion was mainly dependent on the amount of SiO 2 , fluxing oxides and water of the raw materials. These aggregates are highly impervious to water and exhibit considerable firing expansion, low bulk density (1.29-1.76 g/cm 3 ) and fair technical properties (unit weight and bending strength) for lightweight concrete. These results encourage the use of these clays for the production of lightweight aggregates.

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Background: Calcium phosphate cements (CPC) is a promising materials for bone defect repair. Nanosized apatite or calcium orthophosphate has a better bioactivity than coarser crystals. Chitosan is produced commercially from chitin that is the structural element in the exoskeleton of crustaceans such as crabs and shrimp. The mixing of nanosized apatite and chitosan may provide the consistency cement, improving mechanical properties of the set bone cement. Objective: Develop nanosized apatite powder with chitosan for bone composite cement. Materials and method: Nanosized apatite was synthesized by chemical method at low temperature and used as the single-component for bone cement. The nanosized apatite powder was characterized using X-ray diffraction method, Fourier transform infrared spectroscopy, and transmission electron microscopy. CPCs were developed based on chitosan/nanosized apatite and calcium sulfate hemihydrate. The compressive strength of the set cement was measured after one to four weeks. The phase composition and the morphology of the set cements were investigated. Results: Calcium sulfate hemihydrate was effective in increasing the compressive strength after setting in a simulated body fluid for seven days. The compressive strength of chitosan/nanosized apatite composite was about 18 MPa after soaking. Conclusion:The workability and setting time of this composite were suitable to handling for bone cement. These composite cements had a significant clinical advantage for substitution of the regenerated bone.