Yinghuai Qiang

Surface modifications and Nano-composite coatings to improve the bonding strength of titanium-porcelain

Surface modifications of Ti and nano-composite coatings were employed to simultaneously improve the surface roughness, corrosion resistance and chemical bonding between porclain-Ti. The specimens were studied by field-emission scanning electron microscopy, surface roughness, differential scanning calorimetry, Fourier transform infrared spectroscopy, corrosion resistance and bonding strength tests. The SEM results showed that hybrid structures with micro-stripes, nano-pores and nano-protuberances were prepared by surface modification of Ti, which significantly enhanced the surface roughness and corrosion resistance of Ti. Porous nano-composite coatings were synthesized on Ti anodized with pre-treatment in 40% HF acid. TiO2 nanoparticles were added into the hybrid coating to increase the solid phase content of the sols and avoid the formation of microcracks. With the TiO2 content increasing from 45 wt% to 60 wt%, the quantities of the microcracks on the coating surface gradually decreased. The optimal TiO2 content for the nanocomposite coatings is 60 wt% in this research. Compared to the uncoated group, the bonding strength of the coated groups showed a bonding strength improvement of 23.96%. The cytotoxicity of the 4# coating group was ranked as zero, which corresponds to non-cytotoxicity.

Sol-gel Synthesis of Hybrid Coating to Improve Titanium–Porcelain Bonding

The hybrid coating was synthesized on titanium by sol-gel process. Three-point flexure test was used to investigate the adhesion between porcelain–Ti. The structure and micromorphology of titanium specimens were tested by X-ray diffraction and scanning electron microscopy. With decreasing the silicon content, the gel time and stability of the sol increased accordingly, indicating the increased stability of the sol. A coherent coating with SnO nanoparticles was deposited on titanium. The porcelain–Ti bonding strength and corrosion resistance were enhanced by the hybrid coating. The porcelain–Ti bonding strength maintained constant during immersion in neutral saliva and neutral saliva containing fluorine ion, respectively. However, bonding strength decreased from 49 to 35 MPa after immersion in acidic saliva containing fluorine ion of 100 ppm.

Synthesis and hydrogenation of anatase TiO2 microspheres composed of porous single crystals for significantly improved photocatalytic activity

Anatase microspheres composed of porous single crystals were successfully synthesized via a facile route without preseeding treatment and then further modified using a surface hydrogenation process. The porous materials obtained exhibit excellent photocatalytic activity and good recyclability leading to great potential in practical applications.

CNTs-Modified Nb3O7F Hybrid Nanocrystal towards Faster Carrier Migration, Lower Bandgap and Higher Photocatalytic Activity.

Novel semiconductor photocatalysts have been the research focus and received much attention in recent years. The key issues for novel semiconductor photocatalysts are to effectively harvest solar energy and enhance the separation efficiency of the electron-hole pairs. In this work, novel Nb3O7F/CNTs hybrid nanocomposites with enhanced photocatalytic activity have been successfully synthesized by a facile hydrothermal plus etching technique. The important finding is that appropriate pH values lead to the formation of Nb3O7F nanocrystal directly. A general strategy to introdue interaction between Nb3O7F and CNTs markedly enhances the photocatalytic activity of Nb3O7F. Comparatively, Nb3O7F/CNTs nanocomposites exhibit higher photodegradation efficiency and faster photodegradation rate in the solution of methylene blue (MB) under visible-light irradiation. The higher photocatalytic activity may be attributed to more exposed active sites, higher carrier migration and narrower bandgap because of good synergistic effect. The results here may inspire more engineering, new design and facile fabrication of novel photocatalysts with highly photocatalytic activity.

Effect of Anodization on Titanium-Porcelain Bonding

The effects of anodization processes on titanium-porcelain bonding were investigated. The morphologies and phase structures were evaluated by field-emission scanning electron microscopy (F-SEM) and X-ray diffraction (XRD). The bonding strength was investigated by three-point flexure test. The corrosion resistance of titanium in artificial saliva was investigated. The SEM results showed that a titanium oxide film with submicron stripes and nano-pores could be prepared by anodization and HF acid pretreatment. This titanium oxide film increased chemical bonding and mechanical interlocking between titanium and porcelain. The anodization process also enhanced the corrosion resistance of the titanium, which led to the increase of corrosion durability of the Ti-porcelain bonding strength.

Effect of composition of starting materials of Mo–Si on self-propagating high temperature SHS reaction

Abstract An experimental study of the self-propagating high temperature synthesis of Mo–Si alloys was conducted from elemental powder compacts. Test specimens with seven compositions, including Mo/Si = 1∶1·25, 1∶1·50, 1∶1·75, 1∶2·00, 1∶2·25, 1∶2·50 and 1∶2·75 respectively, were employed. Experimental evidence showed that a combustion wave featuring a spinning reaction zone can be observed. When the powder compacts are from Mo∶1·25Si to Mo∶1·75Si, the combustion temperature and the propagation velocity of combustion wave increase with increasing silicon in the sample, and the combustion products are composed of MoSi2, Mo5Si3 and Mo. However, when the powder compacts are from Mo∶2·25Si to Mo∶2·75Si, the combustion temperature and the propagation velocity decrease rapidly as the silicon in the compact increases, and the combustion products are composed of MoSi2 and Si. The sample with Mo/Si = 1∶2·00 possesses the highest combustion temperature (1628·9 K) and propagation velocity (3·13 mm s−1). A single-phase MoSi2 is synthesised by the Mo/Si = 1∶2·00 sample.

Sol–gel synthesis and laser fusion of Ti-bonding porcelain hybrid coatings on titanium

Titanium bonding porcelain was synthesized by sol–gel process and Ti-bonding porcelain hybrid coatings were fused on Ti surface by using a 400 W pulse CO2 laser. The specimens were studied by field-emission scanning electron microscopy, X-ray diffraction and bonding tests. Titanium oxide layer with hierarchical structures consisting of submicron rows of leaf-like embossments and nano-pores was obtained by combining acid etching and anodization processes, which increased the surface roughness of Ti. Pure porcelain coatings with similar hierarchical structure containing submillimeter bioglass BEADs and micropores were synthesized on Ti surface by laser fusion. When the titanium content was 80 wt%, Ti-porcelain hybrid coating with hierarchical structure composed of porcelain islands, microparticles of titanium and micropores were obtained. With the titanium content increased, wettability between Ti-coating was improved and the bond strength increased accordingly, from 28.52 ± 3.63 to 39.14 ± 4.35 MPa.Graphical Abstract

Synthesis of WSi2 powder by mechanical alloying

Abstract The mechanical alloying (MA) is a non-equilibrium powder processing technology and has been applied to many systems, including amorphous alloys, extended solid solutions, metastable crystalline phase and nanocrystalline materials. In this study, the microstructural evolution and phase transformation of W:2Si powder prepared by MA were investigated by XRD and SEM. The results showed that the supersaturated W(Si) solid solution was formed in succession as the intermediate products of MA of W/Si mixture. Then, a mixture of WSi2 microcrystallites and supersaturated W(Si) solid solution was observed. The final product was amorphous WSi2. The total energy of W:2Si powder mixture was raised by MA; thus crystalline WSi2 can be obtained by heat treatment of as milled W(Si) solid solution powder or amorphous WSi2 powder. The formation mechanism of WSi2 during MA was an atomic diffusion process. WSi2 can be synthesised more easily by filling the vial with one-third fill rather than two-third fill.

A Facile Sol-gel Synthesis of Low-fusing Titanium Opaque Porcelain Using Borate-silicate System and its Bioactivity

The titanium opaque porcelain was synthesized through sol-gel using borate-silicate system. The porcelain was characterized by DSC-TG, X-ray diffraction, N2 adsorption-desorption isotherms and scanning electron microscope tests. The results of DSC showed that the nitrates could be decomposed completely when the bioglass xerogel precursor was heat-treated at 760 ℃. The XRD results showed that the Na2Ca3Si6O16 was the major phase of the opaque porcelain. The synthesized opaque porcelain powders had an average particle size of about 5-25 µm with nanopores of around 50-70 nm on the surface. The BET average surface area of the porcelain was 12.67 m2/g, while the average pore diameters for adsorption and desorption were 9.73 and 10.16 nm, respectively. The flexure strength significantly increased from 47.4 MPa to 116.2 MPa with the sintering temperature increasing from 575 ℃ to 600 ℃. The XRD, FTIR and EDS results proved that hydroxyapatite had formed on the porcelain surface after incubation in simulated body fluid.