Xinkuan Liu

Analysis of phase in Cu–15%Cr–0.24%Zr alloy

Abstract The vacuum medium-frequency induction melting technology was employed to prepare the Cu–15%Cr–0.24%Zr alloy. The scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to analyze the phase composition, morphology and structure of the alloy. The results reveal that the as-cast structure of the alloy consists of Cu matrix, Cr dendrite, eutectic Cr and Zr-rich phase. A large number of Cr-precipitated phases occur in the Cu matrix, and Cu 5 Zr particles can be found in the grain boundary of Cu matrix. The HRTEM images prove that there is a semi-coherent relationship between Cu 5 Zr and Cu matrix.

The mechanical behavior dependence on the TiB whisker realignment during hot-working in titanium matrix composites.

Low-cost TiB whiskers reinforced titanium matrix composite (TMCs) was fabricated with enhanced mechanical performances using in situ technologies and hot working. Morphologies observation indicates that needle-like TiB whiskers with a hexagonal transverse section grow along the [010] direction due to B27 crystal structure and its growth mechanism. Mechanical properties tests show that the mechanical behavior of the TiB whiskers reinforced TMCs is dependent on the deformation amplitudes applied in hot-working. The improvement in yield strength by hot-working is attributed to the TiB whiskers realignment and the refinement of microstructure. Models are constructed to evaluate the realignment of TiB whisker during deformation and the increase in yield strength of the composite at elevated temperatures. These models clarify the alignment effect of TiB whiskers under various deformation amplitudes applied in hot-workings and reveals the yield strength dependence on TiB whiskers orientation.

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.

Influence of Anodic Oxidation on Hydroxyapatite-TiO2 Coating Deposited on Ti6Al4V Alloy

对钛合金表面进行阳极氧化预处理,然后用水热电化学方法在其上沉积羟基磷灰石-二氧化钛(HA-TiO2)复合涂层,研究了阳极电压对基体表面的物相、形貌、润湿性和粗糙度的影响,以及对HA的物相、形貌及生物活性的影响。结果表明:阳极氧化电压高于110 V时在钛基体表面出现金红石型和锐钛矿型TiO2,孔径尺寸随阳极电压的增加而增大。在120 V预处理的钛合金试样表面具有好的润湿性,粗糙度Ra达到0.56μm。HA涂层沿c轴方向择优生长,并呈现分层生长,HA的结晶度随着阳极氧化电压的提高先增大后减小,在120 V取得最大值。在120 V氧化处理的试样具有较好的生物活性。