Search

Annealed pyrolytic graphite (APG) is a material with thermal conductivity of about 1500 W/(m·K). This property may enable the usage of APG’s thermal potential to develop highly thermally conductive composites for devices requiring effective thermal management. In this paper, APG has been encapsulated in aluminum by brazing, and the thermal properties of Al-APG composite baseplates were measured. The results show that the thermal conductivity of the Al-APG composite baseplates is about 620 W/(m·K), which is four times higher than the pure aluminum plate (152 W/(m·K)).

Copper-aluminium composite heat dissipation components have both the high thermal conductivity of copper and the low density of aluminium. Copper and aluminium are dissimilar materials as they have significant differences in physical and chemical properties, and hence it is not easy to weld them together. In this paper, the joining of copper to aluminium is studied by using the ultrasonic brazing technique. The results show that the copper and aluminium can be connected by ultrasonic brazing, and it is found that the bonding of the copper side interface is the weak link of the entire joint, but the joint strength can still reach 95MPa.

In recent years, Fiber Bragg Grating (FBG) corrosion monitoring technology has gradually become a research hotspot in the field of oilfield corrosion monitoring. In previous studies, an FBG downhole rapid corrosion monitor was developed, in which the sensor was a C-shaped ring structure, and the minimum diameter after encapsulation could only reach 26 mm. In the pilot field test, it was found that due to the influence of the tubing collars in the eccentric annulus between tubing and casing, during fishing process, there often existed some problems such as tool string jamming, wear and deformation, which sometimes even led to sensor damage. Aiming at the above problems, based on the principle of FBG corrosion monitoring, the sensor structure was redesigned and optimized, and a new integrated sensor with a diameter of 22 mm and a pressure bearing capacity of 35 MPa was developed, of which the impact resistance was increased. A 120 °C high temperature resistant adhesive was also developed to encapsulate the integrated sensor successfully. In addition, a noise reduction circuit was developed to enhance the anti-interference ability of the demodulator and ensure a stable signal output. Using the improved monitor, up to now, five well field tests have been completed in the CO2-flooding production wells. The results show that the tool string fishing is smooth and safe, and the integrated sensor has high reliability and smaller size, which can work continuously for a long time in high temperature, high pressure and strong corrosion downhole environments. The improved technology has high application value for CO2-flooding injection and production wells and natural gas wells downhole and surface gathering and transportation rapid corrosion monitoring.

Compared with ordinary gas wells, injection-production wells in underground gas storage have larger throughput and longer service life. In order to protect reservoir and reservoir throughput, gas reservoir injection and production wells should have fixed completion string to reduce workover times. In this paper, the injection-production capacity, wellbore pressure loss, erosion resistance and liquid carrying capacity of the tubing are analyzed to optimize the reasonable tubing diameter for injection-production wells in gas storage. The nodal analysis method is used to optimize the tubing diameter. The results show that the size of tubing 2 inch and above can meet the requirements of gas injection and production wells in gas storage, and the size of tubing 2.5 inch and above has less pressure loss in wellbore, which can meet the requirements. When the lower limit pressure of gas storage is 2 MPa, the tubing of 2 inch and above size can avoid the tubing erosion and the bottom hole fluid accumulation. Compared with 2.5 inch tubing, the maximum reasonable gas production of 3.5 inch tubing has no obvious advantage. Under the operating pressure of gas storage 2 MPa to 8 MPa, single well gas production 2 × 104 m3/d to 10 × 104 m3/d and single well gas injection 2 × 104 m3/d to 12 × 104 m3/d, the 2.5 inch tubing is recommended as the main tubing for gas storage production.

A microchannel heat sink with microchannel cold frame was designed, fabricated and measured. It was composed of side plates, microchannel cold plates and top/bottom plate in a certain welding sequence. In order to achieve high heat transfer coefficient, a microchannel with overflow internal structure was designed in this paper. The heat transfer performance of the microchannel heat sink was simulated by ANSYS software. The key factors affecting the welding process of the microchannel heat sink were determined by experiments. The measurement results show that the appearance of the weld is well formed, and there are no obvious defects such as porosity, slag inclusions, corrosion and so on. The airtightness and heat dissipation capacity of the microchannel heat sink reach more than 15 atm for 30 min and 200 W/cm2, respectively.

The multilayer structure of Ti3C2Tx hybrid epoxy coating (Ti3C2Tx/epoxy coating) on Al alloy with micro-arc oxidation (MAO) treatment is built up toward synergistic protection. On one side is to exert the advantages on Ti3C2Tx with the physical barrier and mechanical properties, on the other is to weaken the shortcomings on poor adhesion strength of Ti3C2Tx/epoxy coating with substrate and its high conductivity. The adhesion strength of T/EP-on-MAO is increased by about two times and its wear rate lowers 4.97 × 10−5 mm3/N·m, thereby displaying excellent corrosion/wear resistance via the synergies of fostering strengths and circumventing weaknesses.

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.

In this work, ZnO particles with different morphologies were successfully prepared by a simple solution route at low temperature. The products were characterized by SEM, EDS, XRD, TEM, HRTEM, SAED, TG–DTA and UV–Vis DRS. To further understand the formation processes of these ZnO particles, XRD analyses of the intermediates and concentration measurements of Zn(II) remaining in the reaction solution were made at regular intervals throughout the reactions. A possible formation mechanism is discussed. Photocatalytic activity of the as-prepared ZnO powders, evaluated by degradation of pentachlorophenol under UV irradiation, is found to be closely related to the particle morphology.

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.

As the economy grows and the environment deteriorates, the renewable energy is urgently needed. The advanced energy storage technology in electronic equipment, electric vehicle, smart grid, etc. becomes more significant. For example, the rechargeable batteries, hydrogen storage media, supercapacitors, the new energy storage devices have received much attention today. The anodes of the lithium ion battery (LIB), as the main body of charging and discharging, should be most important. The ideal anode material for LIBs is required to possess a higher Li capacity and a lower volume expansion. Good reversibility and high Li capacity are balanced necessarily in the electrode material. The poor cycling performance of LIB is usually due to the severe volume expansion of anode in lithiation/delithiation process. In this paper, the Li storage performance of B and N doped graphyne is explored by using the density functional theory method. The Perdew-Burke-Ernzerhof functional of the generalized gradient approximation is chosen. The calculations indicate that the doping of B atoms can enhance the adsorption strength between the Li atom and the graphyne, which can greatly increase the Li storage capacity. The Li storage capacity of B doped graphyne can reach as high as 2061.62 mAh/g, which is 2.77 times that of pristine monolayer graphyne. Meanwhile, the B doping reduces the out-plane diffusion energy barrier of Li, but increases the in-plane diffusion energy barrier slightly by 0.1 eV. On the other hand, the doping of N atoms reduces the interaction between Li and graphyne, however, the Li capacity also increases to 1652.12 mAh/g because the number of the available Li adsorption sites increases. Moreover, the doping of N atoms greatly improves the diffusion performance of Li on graphyne. The in-plane diffusion energy barrier drops to 0.37 eV, and thus the charge-discharge performance of the N doping graphyne is well improved. Therefore, the doping of B and N atoms can remarkably improve the performance of graphyne as the LIB anodes. The remarkable performance of B and N doped graphdiyne shows that it will become a promising LIB anode in the future. The present research can provide a good theoretical basis and thus conduce to guiding the developing of good Li storage materials, and can also supply strong background for experimental researches.

A320 series aircraft carbon/carbon brake materials were prepared by processing a needle-punched carbon fiber preform with quasi-three-dimensional integrity. The preform was first impregnated with a resin and heated to 800℃ to convert the resin to carbon. This was followed by chemical vapor infiltration (CVD) using propylene as the source gas and a radial thermal gradient (”external heating, internal cooling” or ”internal heating, external cooling”). For the CVD process the performs were separated by graphite pads to allow free flow of propylene along the channels thus formed. The final brake discs were obtained by a further high-temperature treatment from 1600-2400℃. These carbon brake discs were compared with the advanced discs made abroad in terms of ground test and service performance. The two kinds of carbon brakes have the same friction coefficients under the designed landing energy and overload energy braking condition for A320 airplanes. Especially, under the aborted take-off condition, the friction coefficient of the domestically developed carbon brake disc was 21-48% higher and the static friction coefficient was 28% higher than that of the ones provided by the aircraft manufacturer. The average brake service life exceeds 2700 landings, 24% times larger than the original ones.

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.

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 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.

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.

Ultrafine particles PM2.5 produced during combustion is the main source of environment pollution and has raised the widespread concern around the world. There are several studies about acoustic agglomeration currently, but its removal efficiency is not high, so the scholars have proposed to join the seed particles on the basis of acoustic agglomeration, to increase the removal efficiency. In this paper, we propose to join seed particles with ultrasonic atomization and analyze the advantages of using ultrasonic atomization. This is another effective method to improve the removal efficiency.

The polishing pad plays a vital role in achieving the desired removal rate and level of surface planarity during the electrochemical mechanical planarization (ECMP) process. Material removal rate (MRR) and within wafer non-uniformity (WIWNU) are two important factors in determining the polishing performance. In this work, a theoretical model for predicting the radial distribution of tribasic ammonium citrate (TAC) concentration on the wafer is proposed. The experimentally measured MRR was found as a function of the TAC concentration in the slurry. Hence, the model could not only predict the removal rate at a given point on the wafer surface, but also reflect the WIWNU. Model predictions are in good agreement with the experimental data. The proposed model are used to perform an analysis of the effect of pad designs on the MRR and WIWNU of the wafer.

以NiCl 2 ·6H 2 O, CoCl 2 ·6H 2 O和草酸为原料, 利用氨水为配位剂和溶液pH调节剂, 通过配位共沉淀–热分解法制备了棒状多孔NiCo 2 O 4 粉末, 采用X射线衍射、扫描电镜、透射电镜以及比表面积仪对前驱体和NiCo 2 O 4 粉末的形貌和结构进行了表征, 考察了溶液pH对前驱体粉末形貌和分散性的影响; 采用循环伏安法和计时电流法研究了乙醇在棒状多孔NiCo 2 O 4 粉末修饰的玻碳电极上的电催化性能。结果表明: 前驱体的形貌与溶液的pH有关, 热分解得到的NiCo 2 O 4 粉末继承了前驱体形貌, 呈多孔棒状, 比表面积为89 m 2 /g, 平均孔径为12.56 nm。该粉末对乙醇具有良好的电催化活性, 氧化峰电流与乙醇浓度、扫速的平方根均呈直线关系, 表明棒状多孔NiCo 2 O 4 粉末对乙醇的催化反应机理为扩散控制。

A series of Y123 single phase samples with various Ba vacancy concentration was prepared by making their Ba contents deviate from the stoichiometric composition. The measurements of their structure, superconductivity and flux pinning behaviour were systematically carried out. It is found that, compared with YBa2Cu3O6.96 sample, the strength of the flux pinning in YBaxCu3O7-δ (1.8 ≤ x

In this paper it is reported that the measurement of the bulk positron lifetime as a function of substitution content x in the temperature range from 70 to 220 K was performed in two high-Tc superconducting systems, Y1-xCaxBa2Cu3-x FexO7-? and Y1-xCaxBa2Cu3O7-?. It was found that ?B of both systems decreases significantly with x and the temperature dependence of ?B is very weak in normal state. In lower temperature region (T?Tc), a dramatic x-dependent temperature variation of ?B was observed in the Ca-substituted system: from a decrease of ?B with decreasing T to an increase of ?B. With increasing x, the temperature dependence of ?B remains weak in the Ca- and Fe- substituted systems. Compared with the experimental data of positron lifetime in other substituted systems and the calculation of the positron density distribution, the authors suggest that positron bulk lifetime spectra behaviour can be interpreted by the physical model based on the transfer of electron density between the CuO2 planes and Cu-O chains. Therefore, the study of positron lifetime spectra provides a useful means to detect the local charge density and to study the correlation between the electronic structure and the high-Tc superconductivity.

In this paper, it is reported that the small size defects, which result from the introductions of Y, Ba, Cu and O ionic vacancies and the partial substitutions of Ln (Gd, Sm and Eu) for Y in YBa 2 Cu 3 O 7−δ system, may pin the flux lines. From the experimental results, authors suggest tha the flux pinning effect at lower field relates to the magnetic interaction between the vortex and the surfaces of grains in the samples; and that the flux pinning at higher field belongs to the core interaction mechanism in the samples with ionic vacancies and stems from the elastic interaction between the vortex and the lattice stress field in the partially substituted samples.

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.

The electronic band structures of SrBi2Nb2O.9 (SBN) in both the ferroelectric and paraelectric phases were calculated using firstprinciples method. The paraelectric phase is of an indirect band gap of 1.57eV ; whereas the ferroelectric phase is of a direct band gap of 2.23eV. The valence band maxima of both the paraelectric and ferroelectric phases are mainly contributed from O2p states; while the conduction band minima are from Nb4dand Bi6p states. When transforming from the paraelectric to the ferroelectric phases, the strong hybridization between Nb4d and O2pand BiO(2) hybridization enhance the distortion of NbO6poctahedra and reduce the total energy of the system,in favor of stabilizing the ferroelectric phase. The calculation shows that the low leak current in SBN is related to Bi6p state.