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In this paper, research the hypereutectic high chromium cast iron by the methed of semi-solid method for cooling inclined plate. Influence of cooling rate on size of primary carbides and mechanical property of hypereutectic high chromium cast iron. The results showed that, speed up the cooling speed can effectively refine eutectic primary carbides in hypereutectic high chromium cast iron. The primary carbides was globularity and slug, provided with excellent mechanical properties. But when the cooling speed is too fast, the pouring temperature is too low, so that the liquid metal has high viscosity, poor mobility. there were a small amount of inclusions in the Preparation of casting. Although still generate pieces of fine carbides in the matrix, but the distribution is not uniform. disadvantage of the comprehensive performance.

Ceramic coatings were successfully fabricated on Mg-7Li alloy in Na2SiO3 electrolyte by microarc oxidation (MAO). The phase composition, formation mechanism and infrared emissivity of the coatings were investigated. Results show that the surface of MAO coating exists some micropores with a diameter of 2-6μm due to electric breakdown. The MAO coating with 13μm thickness is mainly composed of MgO, Li2O2 and Mg2SiO4. The infrared emissivity of the MAO coating is higher than that of bare Mg-7Li alloy, mainly because the coating consisting of ionic crystals has lower lattice vibration symmetry and larger dipole moment.

The excellent properties of Mg-Li alloys make them suitable light fabrication materials used extensively in many applications. The microstructure and the surface oxide film at different temperature of as-cast Mg-7Li alloy were investigated by optical microscope(OM), scanning electron microscopy(SEM), X-ray diffraction(XRD) and electronic analytical balance. Results showed that Mg-7Li alloy was composed of mainly α phase and β phase. With increasing temperature, the morphology of the alloy surface varied from the formation of a very thin oxide film, large amounts of oxide particles to the thick and coarse film with a mass of cellular protuberances in size of 40-80μm. The ratio of oxidation weight gains rose from 0.08% to 11.58%. The surface oxide film consisted of mainly magnesium oxide(MgO) phase and lithium peroxide(Li2O2) phase, resulting from the reaction of oxygen with Mg and Li. The volume of the oxides on β phase greater than that on α phase led to the formation of cellular protuberance on the surface of Mg-7Li alloy at high temperature.

The aim of this study is to describe the remineralization effect of the nano-HA on artificial caries. The artificial dental caries are made by using sour solution, and constructing an artificial mouth' plaque culture system in vitro respectively. The scanning electron microscope (SEM) and the optical microscope are used to observe the surface of enamel specimens. The effect of remineralization is assessed with the polarized light microscopy (PLM) and the confocal laser scanning microscope (CLSM) by measuring three lesion parameters (area, total and average fluorescence). The SEM analysis shows that the cavities and defects of enamel surface are decreased and many mineral salts are sedimentated, which indicate that the nano-HA could promote remineralization for the demineralized enamel. The inhibitory effect of the spherical nano-HA on dental caries is detected in the artificial mouth test. The CLSM shows that demineralization of enamel is reduced by adding the spherical nano-HA in artificial mouth. The results show that the spherical nano HA have a remineralization effect on the artificial dental caries dramatically, and can prevent and decrease caries.

Chitosan fibers(CSf) andCaSiO3 were incorporated into a poly (L-lactic acid)/hydroxyapatite (PLLA/HA) matrix as reinforcements to prepare scaffold composites with adequate strength and high porosity for bone tissue engineering combined with emulsion freeze drying technique. The structural morphology of the composites was observed by scanning electron microscope (SEM). The porosity was tested by liquid substitute method. The mechanical property was measured. The effects of addition of CSf and CaSiO3 on composites were also discussed. Simulated body fluid (SBF) experiments were conducted to assess the bioactivity of the composites. The chemical components of resultants on surfaces after the immersion in SBF were analyzed by fourier transform infrared spectroscopy (FTIR). The results show that the composites with high connectivity have pore sizes of 100~250μm, a porosity of 60%~80%, compressive strength of 3.5~8.0MPa. In the SBF tests, Chitosan fiber reinforced PLLA/HA-CaSiO3 composite degraded stably, meanwhile, the formation of a layer of bone-like apatite on the surfaces of the samples indicated a good bioactivity. Studies suggest the feasibility of using CSf reinforced PLLA /HA-CaSiO3 composite for bone tissue engineering.

The Nano-HA powder was prepared by chemical precipitation. Magnesium powders were used to make porous ultramicron HA ceramic, and the biological properties of which were investigated by hemolysis rate and cytotoxicity tests. The experimental results shows that the hemolysis rate of the nano-HA powder and porous ultramicron HA ceramic were all less than 5% and none of them showed cytotoxicity. The results indicated that nano-HA and porous ultramicron HA ceramic were provided with good biocompatibility.

The Nano-HA powder were synthesized by chemical precipitation with Ca(H2PO4)2•H2O and Ca (OH)2 and porous HA was prepared by sintering with magnesium as pore-creator. Nano-HA powder and porous HA were characterized by wide angle X-ray diffraction, transmission electron microscopy(TEM), scanning electron microscopy (SEM), SEM in combination with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy. The experimental results show that HA powder synthesized by chemical precipitation is nanometer powder. Magnesium was ideal pore-creator for preparation of porous materials. The grain size of porous HA was sub-micron and MgO which existed in the grain boundary of HA as a second phase particles that played the roles of inhibiting the HA grain growth.

Porous hydroxyapatite (HA) bioceramic matrix with interconnected ducts was obtained using a porogen burnout technique at 1200°C. The HA/silk fibroin (SF) composite scaffolds were developed with the SF sponges formed inside the pores and ducts of the bioceramics by first introducing HA/SF slurries into the pores and ducts followed by a freeze-drying process. Phase components and morphology of materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Porosity was measured by Archimedean method. Compressive strength was also measured. The simulated body fluids (SBF) experiments were conducted to evaluate bioactivity. The results show that hydroxyapatite is the main phase compositions after sintering at 1200°C. The porosity of composite scaffolds reaches 70%~80%. The sizes of pores and ducts of HA matrix range from 150μm to 400μm and the pore sizes of SF sponges formed inside the macroporous structure of bioceramics are approximately 100μm,a structure favorable for bone tissue in-growth. The compressive strength of the composite scaffolds is greatly improved in comparison with that of HA matrix. In the SBF tests, a layer of randomly oriented apatite crystals form on the scaffold surface after sample immersion in SBF. The cell culture experiments show that the osteoblast cells are attached and proliferated on the surface of the composite scaffold, which suggest good bioactivity and cellular compatibility of the composite material.

The objective of this study was to investigate the inhibitory effect of the synthetic nanohydroxyapatite (HA) on dental caries. The nano-HA was synthesized by using the depositing reaction of Ca (H2PO4)2. The artificial dental caries was made by using sour solution and inoculating Streptococcus mutans (S.mutans) to the Sprague-Dawley (SD) rat’s mouth respectively. After mineralization of solution of nano-HA for 10 days, the hardness of enamel was measured. The inhibitory effect of the synthetic nano-HA on dental caries was detected by gargling way to rinse the rat tooth with the solution of nano-HA in the animal test. Transmission electron microscopy (TEM) revealed that the dried HA particles were needle-like with ф5-20nm×60nm and the sintered HA particles were spherical with less than 100nm. The remineralized test indicated that the solution of nano-HA with different shapes enhanced the hardness of artificial caries and improved the remineralization of artificial caries. The animal test showed that the dried nano-HA had the inhibitory effect on dental caries. The good absorptive effect of the nano-HA on both the saliva protein and the glucans leads to the development of interventions that could reduce or modify bacterial colonization of tooth surfaces.

The porous scaffolds of silk fibroin-chitosan /nano-hydroxyapatite (SF-CS / n-HA) were fabricated through the freeze- drying technique. Component, structure and morphology of scaffolds were studied by infrared (IR), X-ray diffusion (XRD) and scanning electron microscope (SEM), and the mechanical properties of the scaffolds were measured. The simulated body fluid (SBF) experiments were conducted to assess the bioactivity of the scaffolds. Results indicate that chemical binding is formed between HA and organics, the macropore diameter of the scaffolds varies from 150 to 400μm. The porous scaffolds with interconnected pores possess a high porosity of 78%-91% and compressive strength of 0.26 -1.96MPa, which can be controlled by adjusting the concentration of organic phases and prefreezing temperature. In the SBF tests, a layer of randomly oriented bone-like apatite crystals formed on the scaffold surface, which suggested that the composite material had good bioactivity. Studies suggest the feasibility of using SF-CS /n-HA composite scaffolds for bone tissue engineering.

A composite of needle-like nano-Hydroxyapatite / silk fibroin (n-HA/SF) with strong interfacial bonding was successfully prepared from calcium chloride (CaCl2) and diammonium phosphate ((NH4)2HPO4) as starting materials of HA in the presence of SF powders dissolved in a ternary solvent system of CaCl2-C2H5OH-H2O (1:2:8 in molar ration) at 80 °C for 30 min prior to preparation of n-HA/SF composite. The n-HA crystals in the composite were poorly crystallized and uniformly distributed in the composite with a crystal size of 4~6 nm in diameter and 20~40 nm in length, which was smaller than that of pure nano-HA. Molecular interaction and strong chemical bonds were formed between n-HA and SF in the composite, which were revealed by Fourier transform infrared spectrometric analysis (FTIR). The synthetic n-HA/SF composite had a good homogeneity and preferential orientation along c-axis and would have a great potential for bone tissue engineering.

The aim of this study is to describe the remineralization effect of the nano-HA toothpaste on artificial caries. The artificial dental caries is made using sour solution. The demineralized teeth specimen is put into five kinds of toothpaste solution respectively for 5 days and 10 days, which are: solution of containing needle like nano-HA, solution of containing spherical nano-HA, solution of general HA, fluorine sodium solution and physiological saline. The hardness of specimen is measured and the surface morphology is characterized by SEM. The remineralized test indicates that the nano-HA toothpaste can enhance the hardness of artificial caries and improve the remineralization of artificial caries. The SEM analysis shows that the cavities and defects of enamel surface are decreased and many mineral salts are sedimentated, which indicate that the nano-HA could promote remineralization for the demineralized enamel.

The paper deals with a kind of new method of the electro-deposition on titanium by a cathode revolves. The depositing characteristic and mechanic were studied by scanning electron microscopy and X-ray diffraction. The experimental results show that the more fine uniformity and compact calcium phosphate bioactive coatings could be produced, compared with the conventional methods. The gradient Coating, which is fine inside and porous outside, could be obtained by controlling revolving velocity. The coating would transform to the hydroxyapatite after heat-treatment. After soaking in a simulated body fluid (SBF), nano-depositions were formed on the surface of the coating, then those particles would grow up needle-like, net-like, and an apatite-like layer could be observed finally. The gradient porosity coatings produced by cathode revolving electrochemical deposition would have high anti-dissolution and bioactive.

The purpose of this study is to examine the inhibitory effects of nano-HA on the caries-inducing properties of a four-organism bacterial consortium in vitro. A series of in vitro anticarious experiments have been carried out by using a continuous culture system. Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, Lactobacillus rhamnosus have been chosen as the experimental bacteria. After 48 hours, the dental plaque surface structure is observed with the scan electron microscope and the bacterial colonization was evaluated on dental plaque. The results show that Spherical nano-HA and mixed nano-HA are proved to be effective in anticarious experiments, and especially spherical nano-HA is more striking. It is able to damage the formation of biofilms (dental plaque), postpone or end the process of acid generation of bacteria metabolism. After 7 days, the demineralization of the enamel has been detected by using TEM. The spherical nano-HA might have a remineralization to early caries to prevent and decrease caries.

The hydroxyapatite (HA) particle with different morphologies were prepared by adding a certain additive into Ca(H2PO4)2·H2O and controlling the bathing and sintering temperature, and the pure needle-like HA sol were obtained when the bathing temperature was 70°C. The experimental results show that the degree of crystallization of HA increase and the particles tend to accumulate with increasing of the drying and sintering temperatures. The particles of HA were spheroid, which diameters were of less than 100nm when they were sintered at the temperature of 700°C. The effect of nano-hydroxyapatite on remineralization of early enamel caries were studied too. The hardness of dismineralized enamel was increased when dismineralized enamel was remineralized by nano-hydroxyapatite. The SEM analysis shows that the interspace of enamel surface were decreased and the many mineral salts were sedimentated, which indicated that the nano-hydroxyapatie could promote remineralization for the dismineralized enamel.

Porous composites composed of hydroxyapatite (HA), herb epimedium (EP), and chitosan (CS) were used to improve the repair of rabbit bone defects. The in vivo implantation of the HA/CS-EP showed that homogeneous bone formation occurred after 12 weeks' implantation and possessed good osteogenesis. The osteogenic process of the HA/CS-EP group was different from that of the HA/CS group. Direct bone formation of osteoblasts with HA/CS-EP as the matrix could be observed. Compared with the group filled with HA/CS, the group filled with HA/CS-EP showed significant increases in the number of osteoblasts and the bone formation area, and the areas of new bone formation in the HA/CS-EP group after 4 or 12 weeks' implantation reached 33% and 87%, respectively. The novel repair system of HA/CS-EP can induce bone formation, increase osteoblast quantity and improve osteogenesis, for EP can significantly promote the proliferation and activity of osteoblasts in the early stage and accelerate bone remodeling in the later stage. Composites containing EP could be a promising material with multifunctions of osteoinduction, osteoconduction and medication for bone repair, and herb medicine EP could be used as an osteoinduction material for bone tissue engineering.