Jiemo Tian

Morphological behavior of osteoblast-like cells on surface-modified titanium in vitro.

In recent papers, we reported the results of a study on the graded porous titanium coatings on titanium by plasma spraying and amino-group ion implantation. The paper is to preliminarily evaluate the biocompatibility of surface-modified titanium through 2, 5 and 7 days cell culture in vitro. Cell morphology was observed by a scanning electron microscope. Cell proliferation and type I collagen synthesis were measured by 3(4.5-dimethyl-thiazole-2-yl)2,5-diphenyl tetrazolium bromide (MTT) and enzyme-linked immunosorbent assay (ELISA), respectively. Our experimental results showed that osteoblast-like cells attached and spread well on surface-modified titanium. Cells were observed to grow into the pores and form extracellular matrix. MTT and ELISA results showed no detrimental effect on the development of cell. These studies support the biocompatibility of surface-modified titanium.

Preparation of graded porous titanium coatings on titanium implant materials by plasma spraying

Graded porous titanium coatings have been deposited on titanium substrates for dental implants by plasma spraying in an argon atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness measurement, and tensile strength tests were performed on graded porous coatings. The results showed that Ti(3)O(5) was formed in the outermost surface of the porous coatings due to oxidation. The graded porous coatings consisted of three layers. The outer layer was full of macropores with a surface roughness of approximately 100 microm. The diameter of many macropores reached and even surpassed 150 microm, which could be beneficial for tissue to grow into the coating. The middle layer consisted of a mixture of micropores and macropores. The inner layer was a very dense and tight interface layer that included mechanical, physical, and metallurgical bonding. In tensile strength tests, testing bars peeled off the coatings, because the adhesive agent fractured, but the coatings remained intact.

Synthesis of SiC precursors by a two-step sol–gel process and their conversion to SiC powders

Abstract A two-step sol–gel processing was developed to synthesize phenolic resin–SiO 2 hybrid gels as SiC precursors, with tetraethoxysilane (TEOS) and novolac phenolic resin being the starting materials, and oxalic acid (OA) and hexamethylenetetramine (HMTA) being the catalysts. At the first step TEOS was prehydrolyzed under the catalysis of OA. At the second step HMTA was added to facilitate gelation. The influences of the molar ratio of OA/TEOS and prehydrolysis time on the sol–gel reaction were investigated. There existed an optimum OA/TEOS ratio where prehydrolysis time needed to form transparent gels was the shortest. The increase of temperature could accelerate sol–gel reaction. The dried hybrid gels were yellowish transparent glassy solids, with uniform microstructure composed of nanometer-sized particles. The conversion of the gels to silicon carbide powders was complete when heated at 1650°C for 30 min in vacuum. The oxygen and free carbon were 0.43 and 0.50 wt%, respectively, in the powder produced from the gel prepared with starting resin/TEOS being 0.143 g/ml.

Deposition of highly adhesive ZrO2 coating on Ti and CoCrMo implant materials using plasma spraying

ZrO(2) (4% CeO(2)) and ZrO(2) (3% Y(2)O(3)) coatings were deposited on titanium (Ti) and CoCrMo implants using plasma spraying and the adhesive, morphological and structural properties of the plasma-sprayed coatings were evaluated. Characterization of these coatings was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness, hardness, and adhesive strength. XRD patterns showed that both the coatings appeared to be primitive tetragonal phase. SEM observations showed that both the ZrO(2) coatings appeared to be rough, porous and melted. The cross-section surface morphology of the coatings, coating-substrate interfaces and substrates without acid etching was very dense and smooth. After acid etching, as compared to the dense ZrO(2) coating-CoCrMo substrate interfaces, the thin gaps appeared within the ZrO(2) coating-Ti substrate interfaces. It is suggested that plasma spraying probably formed an amorphous Ti layer in the coating-Ti substrate interface that can be removed by acid etching. The average surface roughness of ZrO(2) (3% Y(2)O(3)) and ZrO(2) (4% CeO(2)) coatings was correlated to the starting powder size and substrates. No significant difference between the hardness of all coatings and substrates was observed. The adhesive strengths of ZrO(2) (4% CeO(2)) coating to Ti and CoCrMo substrates were higher than 68MPa and significantly greater than that of ZrO(2) (3% Y(2)O(3)) coatings.

In vivo evaluation of modified titanium implant surfaces produced using a hybrid plasma spraying processing

Abstract In this study, the biological responses to surface-modified titanium (Ti) was investigated using a dog model. Titanium plasma spraying and ion implantation of amino (NH 2 + ) groups were used as means of modifying Ti surfaces. Characterization of the modified Ti surfaces was performed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning Auger electron spectroscopy. In vivo evaluations were performed using fluorescence microscope, scanning electron microscope and energy disperse spectroscopy. It was observed in this study that ion-implanted porous-graded titanium coatings had a thick surface oxide layer, containing a small amount of nitride. In vivo study indicates direct bone contact between surface-modified Ti implants and osseous tissues. In addition, osseous tissues were observed to grow into the pores inside the coatings, thereby allowing the formation of a gradual calcium phosphate interface layer. It was concluded from this study that ion implantation of Ti surfaces with amino groups, induced higher concentration of calcium and phosphorus precipitation and more mineralization as compared to non-ion-implanted Ti surfaces.

Preparation and characterization of hydroxyapatite suspensions for solid freeform fabrication

A comparative investigation on particle size, zeta potential and rheology behavior of suspensions of hydroxyapatite (HA) powders produced by a wet-chemical synthesis method is presented. Results have shown that temperature and soaking time of the calcination process significantly affects the HA particle size, and results in a reduction of the zeta potential and suspension viscosity. On the basis of the present experimental and calculated results, the reduction in the viscosity is attributed to a higher repulsion barrier in interparticle potential.

Surface modification of titanium through amino group implantation.

We modified Ti surfaces by implantation of amino (NH(2+)) groups at 10(16) and 10(17) cm(-2). The implanted surfaces were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning Auger electron spectroscopy (AES), and second ion mass spectroscopy (SIMS). The experimental results showed that the implanted Ti specimens were covered by a dominant hydrocarbon overlayer due to contamination and the surface oxide layer of implanted specimens became thicker. XPS, AES, and SIMS depth profiles showed that implanted elements had a typical ion implantation distribution and that titanium nitride (TiN) was formed.

Effect of WO3 doping on dielectric temperature characteristics of lead complex perovskite ferroelectric ceramics

Abstract The effect of WO3 doping on the dielectric temperature characteristics and the microstructure of a ternary ceramic system were investigated. Both the increase of WO3 doping level and the increase of sintering temperature led to a decrease in dielectric constant and the flatting of dielectric curves. The presence of a liquid phase and the pyrochlore phase cause this decrease. Also, microstructural and elemental analyses of the ceramics revealed the structure within one grain consists of three parts: the core, the shell and in-between one. This inhomogeneous composition distribution contributes to flat dielectric temperature dependence.

Effect of fluorine content on the crystallization of fluorsilicic mica glass

The effect of fluorine content on the crystallization of fluorsilicic mica glass was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscope (SEM). A single phase, KMg3.25Si3.625O10F2, precipitates in all the glasses. Both the crystallization activation energy (En) and the frequency factor (ν) increase with the increase of the fluorine content. This means that the fluorine content has dual effects on the crystallization of fluorsilicic mica glass, while the effect on the frequency factor is predominant.

Calculated influences of starting materials composition on carbothermal nitridation synthesis of silicon nitride/silicon carbide composite powders

Equilibrium phase composition at 1 atm total pressure is quantitatively calculated as the function of starting materials composition for carbothermal nitridation synthesis of Si3N4/SiC composite powders. N2 flow is simulated by the N2 amount in the starting materials. At low starting N2 content (molar ratio N2/SiO2 ≤ 100), Si3N4 and SiC can not exist in equilibrium at the same temperature. At higher starting N2 content, the Si3N4-SiC coexisting temperature range appears above 1760 K. The upper limit of the temperature range becomes higher with increasing starting N2 content. Starting carbon content affects the composition in the equilibrium powder products. The calculation results are compared with experiments.