Daihua He

Improvement of β-TCP/PLLA biodegradable material by surface modification with stearic acid

Poly-L-lactide (PLLA) is a biodegradable polymer and used widely. Incorporation of beta tricalcium phosphate (β-TCP) into PLLA can enhance its osteoinductive properties. But the interfacial layer between β-TCP particles with PLLA matrix is easy to be destroyed due to inferior interfacial compatibility of the organic/inorganic material. In this work, a method of β-TCP surface modification with stearic acid was investigated to improve the β-TCP/PLLA biomaterial. The effects of surface modification on the β-TCP were investigated by FTIR, XPS, TGA and CA. It was found that the stearic acid reacted with β-TCP and oxhydryl was formed during the surface modification. Hydrophilicity of untreated or modified β-TCP/PLLA composite was increased by the addition of 10 wt.% β-TCP, but it decreased as the addition amount increased from 10 wt.% to 20 wt.%. Two models were suggested to describe the effect of β-TCP concentration on CA of the composites. Mechanical properties of β-TCP/PLLA composites were tested by bending and tensile tests. Fractures of the composites after mechanical test were observed by SEM. It was found that surface modification with stearic acid improved bending and tensile strengths of the β-TCP/PLLA composites obviously. The SEM results indicated that surface modification decreased the probability of interface debonding between fillers and matrix under load.

Influence of Alkali Treatment on Ti6Al4V Alloy and the HA Coating Deposited by Hydrothermal-Electrochemical Methods

Abstract The aim of this work is to investigate the influence of NaOH pretreatment time on the phases and morphologies of Ti6Al4V substrates and hydroxyapatite (HA) coatings. Ti6Al4V substrates were pretreated with a sodium hydroxide (NaOH) solution for different amounts of time (12, 24, 36, 48, and 60 h). After NaOH pretreatment, a three-dimensional porous network of sodium titanate gel was observed on the Ti6Al4V surface. Subsequently, HA deposition was achieved using the hydrothermal-electrochemical methods, while the electrolyte solution containing NaCl, K 2 HPO 4 ·3H 2 O, and CaCl 2 , was maintained at 120 °C and applied by a constant current density of 1.25 mA/cm 2 for 120 min. The results indicate that the growth pattern and micromorphology of the HA coating are all influenced by different pretreatment time. After pretreating Ti6Al4V substrates with NaOH for 12 h, needle-like structures are primarily formed on the HA coating, and some dandelion-like morphologies are presented. During 48 h NaOH solution pretreatment, the dandelion-like structures increase with the increase of time. However, the amount of the dandelion-shaped HA drops slightly, when pretreatment time is longer than 48 h. The orientation index of the (002) plane of HA reaches the minimum when Ti6Al4V substrates are pretreated for 48 h, whereas the crystallinity is the highest for this pretreatment time.

Interface Bond Mechanism of EVA-Modified Mortar and Porcelain Tile

AbstractEthylene-vinyl acetate (EVA) redispersible powder was used to modify mortar. The tensile strength of EVA-modified mortar and the interface bond strength of EVA-modified mortar and porcelain tile, cured under 20±3°C and relative humidity 50±5%, were tested. The interface bond mechanism of EVA-modified mortar and porcelain tile was discussed. Results obviously showed that EVA redispersible powder improved the tensile strength of mortar. The interface bond strength between EVA-modified mortar and porcelain tile increased with the increase of EVA content in mortar and did not always increase with the extension of curing age. Microstructure analysis illuminated that polymer film was being formed by EVA latex powder along the hydrated products and the mortar–porcelain tile interface. The EVA improved interface bond strength by penetrating the capillary and pore of porcelain tile accompanied with hydrated products.

Hydroxyapatite bioceramic coatings prepared by hydrothermal-electrochemical deposition method

The hydroxyapatite(HA) ceramic coating was successfully prepared on Ti6Al4V alloy by the hydrothermal-electrochemical deposition method with constant voltage model. The phases of deposits were analyzed by X-ray diffraction. The releationship between crystallinity and depositing temperature was discussed. The microstructures of hydroxyapatite coating were observed by scanning electron microscope. The experimental results showed that the phases, crystallinity and morphologies of deposits were influenced by depositing temperature (100 °C, 120 °C, 140 °C, 160 °C, 180 °C and 200 °C, respectively). The special hydrothermal environment can lower the crystallization temperature of HA. The crystallinity of HA increases firstly and then decreases with the increase of temperature. There is little hydroxyapatite deposited on the Ti6Al4V surface when the depositing temperature is 100 °C. The HA deposition increases with the increase of the depositing temperature. And the HA morphologies are influenced by the depositing temperature.

Preparation of hydroxyapatite-titanium dioxide coating on Ti6Al4V substrates using hydrothermal-electrochemical method

Ti6Al4V substrates were anodized in a 0.5 mol/L H2SO4 solution at applied voltages of 90-140 V. A hydroxyapatite-titanium oxide (HA-TiO2) coating was then deposited on the anodized Ti6Al4V substrates via a hydrothermal-electrochemical method at a constant current. The obtained films and coatings were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectrometry. The microstructures of the porous films on the Ti6Al4V substrates were studied to investigate the effect of the anodizing voltage on the phase and morphology of the HA-TiO2 coating. The results indicated that both the phase composition and the morphology of the coatings were significantly influenced by changes in the anodizing voltage. HA-TiO2 was directly precipitated onto the surface of the substrate when the applied voltage was between 110 and 140 V. The coatings had a gradient structure and the HA exhibited both needle-like and cotton-like structures. The amount of cotton-like HA structures decreased with an increase in voltage from 90 to 120 V, and then increased slightly when the voltage was higher than 120 V. The orientation index of the (002) plane of the coating was at a minimum when the Ti6Al4V substrate was pretreated at 120 V.

Microstructure and optical performance of In2S3 thin films grown by chemical bath deposition

ABSTRACT The In2S3 thin films were deposited by chemical bath deposition at different processing parameters. The In2S3 films were well crystallized when grown at pH values in the range of 1.6–2.0. With increase of the sulfide ion concentration and deposition temperature, the formation and growth rates of β-In2S3 crystals improve. Too high sulfide ion concentration and deposition temperature can induce decomposition of In2S3 crystals. When grown at pH value of 1.8, nIn:nS ratio of 1:4 and deposition temperature of 80°C, the In2S3 film can achieve highly crystallized structure, high transmittance of over 80% and proper energy gap value of 2.74 eV.

Surface Modification of β-TCP with Stearic Acid and Its Effects on β-TCP/PLLA Biodegradable Composite Nanofibers

In order to improve interfacial compatibility between beta-tricalcium phosphate (β-TCP) with poly-L-lactide (PLLA) to prepare bone tissue engineering (TE) scaffold material, a surface modification of β-TCP with stearic acid was investigated. Interfacial interaction between β-TCP particles with stearic acid was studied using Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analyzer (TGA) and X-ray Photoelectron Spectra (XPS). The unmodified β- TCP/PLLA and modified β-TCP/PLLA composite nanofiber membranes with different quality ratios were prepared by electrospinning. Morphology of these composite nanofiber membranes was observed by using scanning electron microscope (SEM). Mechanical properties of these composites were also tested. The results indicated that hydrogen ions of stearic acid produced protonation reaction with oxygen ions in phosphate of β-TCP and then generated hydroxyls. The β-TCP particles modified by stearic acid reduced the agglomeration of β-TCP particles in matrix and obtained continuous and uniform nanofibers. The mechanical properties of the modified β- TCP/PLLA composite nanofiber membranes were significantly improved than those of unmodified β-TCP/ PLLA composite nanofiber membranes.

Synthesis of Absorber Layer Film for CI(G)S Solar Cells by Selenization after Sputtering

The CuInSe2 and Cu(In1-xGax)Se2 absorbing layer films are prepared by selenization after magnetron sputtering. The influence of selenization parameters, including selenized temperature and time, on microstructure of CuInSe2 thin films was studied by X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). Highly crystallized CuInSe2 film could be obtained when selenized at 500°C for 40 min. By using the same selenization technique, high-quality Cu(In1-xGax)Se2 films were also successfully synthesized from two types of CuInGa precursor layers with different structure.

Surface Alloying of Nanocrystalline Fe-0.45 wt Pct C Alloy Subjected to Surface Mechanical Attrition Treatment Within Cr Powders

A Fe-0.45 wt% C alloy plate was subjected to surface mechanical attrition treatment (SMAT) in a camber filled with Cr powder and a nanocrystalline surface layer containing Cr element was produced during the treatment. Owing to the high diffusivity of nanocrystalline surface layer, Cr element can diffuse and be pressed into nanocrystalline surface layer during SMAT. Within the subsequent annealing process, Cr element can further diffuse in the surface layer, resulting in formation of new compounds, such as (Cr,Fe)23C6 and (Cr,Fe)7C3. SMAT within metallic powder, which can conveniently and effectively accomplish surface modification, should be concerned and utilized.