Papers by Author: Jun Guo Ran

Abstract: Aiming at inadequate mechanical properties of Glass ionomer cement (GIC) commonly used in dental clinic, commercial and melt quenched GIC powders as control groups, homemade GIC powder was prepared by sol–gel route and modified by Nb₂O₅. The GIC samples were characterized by X-ray Diffraction (XRD), particle size analysis, Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FT-IR). The compressive strength, Vickers hardness, working and net setting time were tested. The data was analyzed by one-way ANOVA. The XRD results showed that commercial, melt quenched and sol gel GIC powders were similar amorphous. D90 of three GIC powders and Nb₂O₅ powder were 26 μm, 17 μm, 29 μm and 19 μm respectively. 5% Nb₂O₅-GIC exhibited the highest values of compressive strength and Vickers hardness, which were 112.93 Mpa, 139.48 MPa and 142.25 MPa respectively, increased 19.11%, 30.56% and 16.51% (P <0.05); the Vickers hardness were 35.15 MPa, 36.23 MPa and 37.62 MPa, increased 18.03%, 29.95% and 16.32% (P <0.05) compared to those of unmodified GICs as well. There was no significant change of the FT-IR characteristic peaks of modified GIC. The working time of three kinds of GIC were 4'58 ", 3'28" and 4'10 ", the net setting time were 5'16", 3'15 "and 4'38" (standard is 1.5-6 minutes). It was concluded that the dispersion stiffened effect of niobium oxide could improve the mechanical properties of the filling GIC without affecting the clinical operating performance.

Abstract: HA/ß-TCP is one kind of important bone tissue engineering scaffold materials. In order to improve the biological performance of materials, HA/ß-TCP ceramics were modified by the cold plasma technique in this paper. The biological performances of treated materials were evaluated by the results of bone-like apatite formation in SBF, the coculture of the C2C12 cell line and HA/ß-TCP, cell proliferation experiments, observations of the electron microscopy and fluorescence staining and the animal intramuscular implantation experiments. The results showed that after immersion, compared with untreated HA/ß-TCP, treated materials were more conducive to form bone-like apatite; modified HA/ß-TCP could promote the cell proliferation more; the cells grew in the course of nature on the treated scaffold and modified HA/ß-TCP had better bone-forming performance in vivo. It was concluded that modified HA/ß-TCP had better biological performance; the cold plasma technique could improve the biological performance of dental biphasic calcium phosphate ceramics.

Abstract: Hemocompatibility of a biomaterial is determined by the interactions between its surface and blood. Due to the complicated action mechanism, various effective ways and the multiple affective factors of the hemocompatibility, a comprehensive evaluation needs to be built instead of single index. Therefore, the platelet consumption ratio of 10 kinds of biomaterials including Ti6Al4V-TiC-DLC gradient coat material was studied based on image analysis method. Combined with the kinetic clotting time and the hemolysis ratio, the comprehensive hemocompatibility evaluation of the material is carried out based on the improved principal component analysis. First, linear transformation of negative index is carried out. Second, index is under a dimensionless using the logarithmic treatment, then to acquire all variants’ principal component and their characteristic vectors. Finally, comprehensive evaluation index of hemocompatibility is constructed. The improved principal component analysis avoids the effect of correlativity among indexes during anaphase evaluation, and can more correctly maintain the original information of indexes. Thus, the research provides a new idea to the comprehensive evaluation of Hemocompatibility.

Abstract: The crystalline structures of B-type carbonated hydroxyapatite (CHA) powders sintered at 700, 900 and 1100°C, respectively, were studied by Rietveld analysis of powder X-ray diffraction (XRD) data. A series of structure parameters, including lattice parameters (a and c), bond length and the distortion index of PO4 tetrahedron (Dind) were calculated by Rietveld method to characterize the fine structure of CHA. The broadening effect of XRD reflections was separated to calculate the micro-strain and crystalline size. The results showed that CHA become more stable with the increase of sintering temperature, but the CO3 2- is almost lost at temperature of 1100°C. The quantitative results about crystal structure of CHA based on crystalline structure simulated by Rietveld method are obtained.

Abstract: Two kinds of dense calcium phosphate (Ca-P) bioceramics, hydroxyapatite (HA) and β- tricalcium phoshpate/hydroxyapatite (β-TCP/HA), sintered by microwave plasma were investigated. The dense HA and β-TCP/HA bioceramics exhibited higher density, smaller grain size and higher Vickers hardness. The sintering behaviors of HA powder were also significantly different from those of calciumdeficient hydroxyapatite (d-HA) powder by the same microwave plasma sintering route. The sintering efficiency of the former was higher than that of the latter. The results indicate that dense HA and β-TCP/HA bioceramics are of better mechanical strength and might have better bioactivity.

Abstract: The surface morphology of film material directly affects its physical performance. It is of great significance for finding out its prospective physical performance to characterize the surface morphology of film material. It is hard to characterize them with some conventional methods. The surface morphology of film material was described from the fractal point of view, and the dimension was correlated with the resistivity of material. The [100]-orientated diamond film was primarily investigated. The results show that the greater the crystal grain is, the more uniform and regular the orientation is; and the more compact the arrangement is, the greater the fractal box dimension is. Moreover, when fractal box dimensions were within a certain range approximately from 2.92 to 2.97, it presents positively correlative relation with the logarithm of resistivity, Log(ρ), which resembles the Logistic curve. However, when the other dimensions are beyond the range mentioned above, resistivity doesn’t change with the increase in dimensions of fractal. This study will conduce to illustrating the relationship between the structure of crystal exemplified by arrangement and physical performance as well as material preparation.

Abstract: Resin lenses have substituted for glass lenses to be dominant productions in eyeglasses market because of lightweight, anti-impaction and easy molding. However, the problem existed that the wear resistance of resin lenses was inferior. In order to increase the wear resistance of resin lenses, we coated DLC film on PC by the method of RF-PCVD, researched the influence of depositing power, gas concentration, time on the performance of coating, chose the optimum technological parameters. The component of coating was testified by XPS. The hardness and wear resistance were tested. The results showed that DLC films deposited on PC could improve the wear resistance of material.

Abstract: Diamond film was synthesized on Co-deficient (Co content is about 0.5%) WC-Co substrate using microwave plasma chemical vapor deposition (MPCVD) equipment without special pretreatment. SEM, XRD, Rockwell-indentation test and scratch test were used to analyze the structure and morphology of the diamond film and its adhesion to the substrate. Co content was also measured by EDAX. The results show that the film synthesized is of ideal diamond structure with perfect and uniform grains, dense and continuous surface and strong adhesion. Co content on the surface of the substrate is about 0.8% after 20h deposition, which is considered as one of the main causes to get good adhesion.

Abstract: Due to some inferior performance of Chemical Vapor Deposition (CVD) diamond dosimeters, their applications are somewhat limited. The quality of diamond films was improved using Microwave Plasma CVD (MWPCVD) by the modified processes such as cyclic deposition and in-situ plasma post-treatment. The simple radiation dosimeters were fabricated in a sandwich configuration. Influence of purity and orientation of the diamond films on the sensitivity of the dosimeters was studied. The results indicate that the radiation dosimeters have high sensitivity to X-ray and the response of the devices is linear with the X-ray flux. The higher the purity of films is, the higher the resistivity and sensitivity are. The dosimeter based on [100] film has higher sensitivity than that based on [111] film. The dosimeter based on films prepared by cyclic deposition has higher sensitivity than that based on films prepared by the conventional deposition. The characterization of the response to X-ray also shows that in-situ oxygen plasma post-treatment leads to the higher sensitivity of dosimeters compared with in-situ nitrogen, hydrogen plasma post-treatments.

Abstract: In order to improve the bioactivity of calcium phosphate bioceramics, biphasic HA/β-TCP (BCP) bioceramics were prepared by the microwave sintering and the microwave plasma sintering. Bone-like apatite formation of the resulting samples was investigated in simulated body fluid (SBF). The samples were also implanted in dorsal muscles of healthy dogs for 1.5and 3 months. All samples after taking out were examined by histological observation. Bone formation in different sintering ways and temperatures was investigated in details. Better osteoinductivity was found in samples sintered by the microwave and microwave plasma instead of the conventional furnace, as well as by lower temperature (1050 oC) instead of higher temperature (1150 oC). It accounts for that the increase in degradability of materials sintered by microwave and microwave plasma or lower temperature leads to the better of bone-like apatite formation and bone formation due to fine grains and lower crystallinity.