Li Min Dong

The Color of Fe2O3 and Bi2O3 Pigmented Dental Zirconia Ceramic

The aim of this study was to explored the effects of Fe2O3 and Bi2O3 on the color properties of a 3Y-TZP zirconia ceramics for dental application. Pigmented dental ZrO2 powders were prepared by mixing different concentration of Fe2O3 and Bi2O3, also in their combinations with 3Y-TZP powders. The mixture was compacted by isostastic pressure, then densely sintered. Color parameters were measured by Minolta CM2600d spectrophotometer. XRD was used to exam the structure of colored 3Y-TZP. Experimental results showed that the hue of the materials shift from yellow-green to yellow-red with the increasing concentration of the Fe2O3 and Bi2O3. Combined use of Fe2O3 and Bi2O3 could further decrease the L* value, which color scope was suitable for dental color matching. The XRD spectra showed only tetragonal phase was detected.

Surface Functionalization of Ordered Mesoporous Carbon by Immobilization of Diamine for Cobalt-Ion Adsorption

Highly ordered mesoporous carbon (CMK-3) was fabricated for the adsorption of cobalt from aqueous solutions. With the high surface area of1112.7m2/g and pore size of 17.2 nm, its abundant mesopores were benefit for providing channels for liquid propagate. In order to improve the adsorption properties,CMK-3 was modified by hydroxylation and amination. Fourier transform infrared (FTIR) spectroscopy can be seen that the amino group was successfully grafted onto the CMK-3 with highly ordered mesoporous structure. The functionalized ordered mesoporous carbon (CMK-3-EDA) ,CMK-3 and CMK-3-OX were used as absents for the adsorption of Co (II) from aqueous solution. The results showed that CMK-3-EDA were more twice effective in adsorption of Co (II) compared to CMK-3, which indicated that CMK-3-EDA had great potential for the adsorption of Co (II).

Preparation and Characterization of Biodegradable β-TCP-Based Composite Microspheres as Bone Tissue Engineering Scaffolds

Since a small globular particle was first used as support for three-dimensional (3D) growth of anchorage-dependent cells in suspended cultures, a variety of microspheres as tissue engineering scaffolds have been developed. In this paper, β-TCP and chitosan were selected as the components of microspheres due to their biodegradability and osteogenic properties. The biodegradable β-TCP/chitosan composite microspheres were prepared by a solid-in-water-in-oil (s/w/o) emulsion cross-linking method in this paper. The size distribution, surface morphology, and microstructure of the microspheres were evaluated. Scanning electron microscopy revealed that the size of the microspheres with good spherical morphology was distributed in the range of 50~200μm. In vitro immersion experiments were carried out to evaluate the degradability of the microspheres, and the results demonstrated that the chitosan/β-TCP composite microspheres were potential materials as tissue engineering scaffolds for bone repair.

One-Step Approach for the Fabrication and Characterization of Hydroxyapatite/TiO2 Composite Ceramic Coatings by Micro-Arc Oxidation In Situ on the Surface of Pure Titanium

The hydroxyapatite (HA)/ TiO2 composite ceramic coatings were formed by micro-arc oxidation (MAO) on pure titanium in mixed electrolyte of calcium glycerophosphate and calcium acetate with DC pulse power. Microstructure, phase composition, porosity and thickness of the coatings were examined using SEM, XRD, Image-Pro Plus 6.0 Image analysis system and Eddy current thickness gauge. Results indicate that MAO coatings containing calcium and phosphorus were formed in situ on pure titanium surface. Pores formed by the discharge channels distribute uniformly on the coatings surface, and the inner layer is dense. The principal crystalline phases of the MAO coatings are anatase TiO2, rutile TiO2, HA, Ca3(PO4)2 and matrix Ti. The interface is metallurgical bonding and the bonding strength is strong. And reaction time makes a greater influence than voltage in thickness and voltage makes a greater influence than time in porosity.

Self-Setting Biphase Porous Calcium Phosphate Cement

This work has achieved a novel self-setting biphase porous calcium phosphate cement (CPC). This biphase porous CPC is mainly formed by α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP). The influence of the weight percent (wt%) of β-TCP of the powder was studied. The setting time is mainly 10-30min, and increasing with the weight percent of β-TCP. Powder ray diffraction (XRD) analysis showed that most α-TCP have turned to low-crystallinized HA after immersed in Simulated Body Fluid (SBF) of 37°C for 7 days. SEM observation showed that the resultants are mainly formed with micropores and microcrystallites, and more micropores turned out in cements with more β-TCP after immersed in SBF for 8 weeks.

Preparation of Porous Hydroxyapatite Scaffolds

Porous hydroxyapatite (HA) ceramic scaffolds were prepared using three-dimensional (3-D) gel-lamination technology with sodium lauryl sulfate as foaming agent and lauryl as foaming stabilizing agent. With gelling system of sodium alginate and calcium chloride, the foamy HA slurry was gelled layer by layer on the 3-D gel-lamination machine to prepare the porous ceramic scaffolds. The viscosity of the foamy ceramic slurry was examined. After sintering, the porous HA bioceramic was characterized in terms of the porous microstructure and mechanical properties. The experimental results demonstrated that the resultant porous ceramic with appropriate pore size, porosity characters, mechanical properties and bioactivity could be obtained.

Influence of oxidation time on microstructure and composition of micro-arc oxidation coatings formed on zirconium

Abstract Zirconia ceramic coatings on zirconium were prepared by micro-arc oxidation (MAO) method in mixed electrolyte of calcium glycerophosphate and calcium acetate. Effect of oxidation time on microstructure, element composition and phase composition of the coatings were analysised by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, respectively. The elemental composition of the coatings included Zr, O, Ca, and P. As oxidation time increased, Ca and P content of coatings correspondingly increased, and content of Zr reduced. The fabricated coatings with thickness from 20 to 30 μm were composed of c-ZrO2 and t-ZrO2, only trace amounts of m-ZrO2 phase were detected. Owing to the porous structure and components of coatings, ZrO2 coatings prepared by this method may provide available possibilities applied to biomedical materials.

Influence of Low Temperature Aging on the Flexural Strength of Y-TZP Ceramics

Low temperature aging (LTD) is an important factor of Y-TZP ceramic as artificial joint femoral head and dental restorative materials in vivo for long-term application. In this paper, the accelerated aging experiments on Y-TZP ceramics were conducted. The t-m phase transition is occurring from the surface to the inside during low temperature aging of Y-TZP ceramics. As content of phase transformation increases, thickness of phase transformation layer increases. While the content of surface monoclinic phase is less, the volume expansion and surface stress caused by phase transformation can make cracks and holes shrink or even close, then the flexural strength increase. As a large number of surface monoclinic phase was generated, due to there are a lot of microscopic defects in the phase transition layer, crystals loose, strength of grain boundary lower than that of not aging area and phase transformation layers fracture in the intergranular mode, that damages the flexural strength. Therefore, the flexural strength increase firstly and then decrease with the increase of surface monoclinic content.

Preparation and Mechanical Properties of HA/PHB Composites

This paper focuses on the influence on the mechanical properties of hydroxyapatite / poly-hydroxybutyrate (HA / PHB) composites by different HA contents, and the effect of Silane coupling agent on improving the interface of HA/PHB composite materials. The HA/PHB composites were prepared by ball milling, hot-pressing, the HA content were 0, 5, 10, 15, 20 and 30wt%, respectively. Silane coupling agent was used for HA surface treatment in HA/PHB composites to compare with not having HA surface treatment in HA/PHB composite materials. The impact strength and flexural strength of HA / PHB composites were tested, and the microstructure of the fracture surface was observed by SEM. The results showed that HA could enhance the bending strength of HA/PHB composites. With HA content increased, the bending strength increased first and then decreased, when the HA content was 10wt%, the maximum bending strength reached 32.74MPa, increased about 41% comparing with pure PHB. Silane coupling agent can improve the interface of HA / PHB, then enhance the mechanical strength. When the HA content was 15wt%, the maximum bending strength reached 46.6MPa, Increased about 56% comparing with the same proportion of untreated HA/PHB composite material, and about double comparing with pure PHB.

Tissue Engineering Scaffolds of Bioceramics and New Bone Growth

The paper describes β-TCP/DCHA and mineral phase structural bioceramics(CHA) as well as their 3-D structures, bioactivity, degradability and introducing new bone growth. FT-IR, XRD, SEM and Micro-CT were used to evaluate β-TCP/DCHA and mineral phase structural ceramics before and after implantation. Osteoblasts were immersed in the bioceramics and implanted in the rabbit femora. The experimental results showed that new bone grown in β-TCP/DCHA, and scaffolds were degraded with new bone formation and growth. The results indicated that β-TCP/DCHA was a better tissue engineering material. A kind of biomaterial (β-TCP/CHA) can be used for in situ formation or in vitro individuation formation. The experimental results indicated that β-TCP/CHA possessed better osteoblast affinity. Osteoblasts can adhere, proliferate and grow better on the material. The experiments in vivo showed the materials bonded with osseous tissue. The implants were degraded obviously after 6 months, and new bone replaced degradation materials.