Advanced Materials Research Vols. 11-12

Abstract: The Yb3+-doped silicate and phosphate laser glasses were prepared by using of traditional melt quenching technology, and the physical and spectral properties were investigated. The results show that the stimulated emission cross section and the fluorescence lifetime are 0.67×10-20cm2 and 1200μs for the silicate glass, and 0.75×10-20cm2 and 1000μs for the phosphate glass respectively. And silicate glass’s mechanical and thermal properties were better than that of phosphate glass. But Yb3+-doped phosphate glass has lower nonlinear refraction index n2. Both Yb3+-doped silicate and phosphate glasses are possible to be used as laser medium.

Abstract: CaTiO3:Pr3+ was prepared by high temperature solid state reaction and measured by SEM, XRD, excitation and emission spectra. The samples obtained possessed orthorhombic crystal structure of CaTiO3, belonging to Pbnm space group. Excitation spectra of the samples were broad band, their peaks and shoulder peaks were located at about 335nm, 379nm respectively. Emission spectra were single narrow band, emission peaks were located at about 602nm, corresponding to emission of 1D2→3H4 of Pr3+ion. The addition of Eu3+and Dy3+ as co-activator led phosphorescent intensity to greatly enhance, the addition of AgNO3 as ion compensator made the samples material pink and vibrant.

Abstract: A macroporous phosphate invert glass ceramic (PIGC) was prepared by dipping polymer sponges in the powder-slurry of the mother glass with a composition of 60CaO-30P2O-3TiO2- 7Na2O in mol%, and subsequent burning off the sponge at 850°C for 1 hr. The macroporous PIGC consists predominantly of ß-tricalcium phosphate (β-TCP) and ß-calcium pyrophosphate, and it has macropores of 500 μm in diameter and porosity of 83 %. Its compressive strength was estimated to be 160 kPa. The PIGC composite containing a large amount of β-TCP was also prepared by heating the mixture of Ca(OH)2 with the mother glass powders of the PIGC. Solubility of the composite was higher than PIGC. The macroporous PIGC and PIGC composite were expected to be applicable in high resorbable scaffolds for bone tissue engineering.

Abstract: Biphasic calcium phosphate (BCP) ceramics, a mixture of hydroxyapatite (HAp) and beta-tricalcium phosphate (β-TCP), of varying HAp/β-TCP ratios were prepared from fine powders. Porous BCP ceramic materials with HAp/β-TCP weight rations of 20/80, 40/60, and 80/20 were prepared. In this study, the bioactivity is reduced at a bigger HAp content rate, which is likely related to the high driving pore for the formation of a new phase, and the reaction rate was proportional to the β-TCP. The porous BCP ceramics having a bigger porosity rate can easily under up dissolution. The powder having a bigger β-TCP content rate can easily generate a new phase. The dissolution results confirmed that the biodegradation of calcium phosphate ceramics could be controlled by simply adjusting the amount of HAp or β-TCP in the ceramics and porosity rate.

Abstract: Sol-gel method is one of the most potential techniques for mass-production of nano hydroxyapatite. In this paper, particle size control techniques, including dripping speed control, addition of several dispersants such as ammonium citrate, castor oil and silane coupling agent, as well as usage of insoluble and water soluble starch additives, were investigated. The particle size and microstructures of as synthesized hydroxyapatite were studied by X-ray diffraction, Scanning electron microscopy and dynamic light scattering. The results indicated that all the control techniques had considerable effects on decreasing the crystallite size, and the starch additives also exhibited obvious effect on preventing the agglomeration of nano crystallites during the synthesizing process.

Abstract: Amorphous calcium silicate coating on a metallic titanium substrate for hard tissue replacement was prepared by a sol-gel method. Calcium silicate film was deposited on a titanium substrate by a spin-coating technique and subsequently heated at 500°C for 2 h in air. The deposited film, which was dense, had thickness of about 800 nm and strongly adhered to the substrate. Biomimetic apatite-forming ability of the deposited films was examined by soaking in simulated body fluid (SBF). Thin film X-ray diffractometry and scanning electron microscopy showed the formation of apatite on the surface after 10 days of soaking in SBF.

Abstract: A new type of poly(lactic acid) (PLA)/calcium carbonates hybrid membrane incorporated with silicon, which is suggested to stimulate the formation of bones, was prepared using aminopropyltriethoxysilane (APTES) for bone repair materials. Carboxyl groups in PLA made a chemical bond with amino groups in APTES, resulting in the formation of the hybrid membrane. The membrane formed hydroxycarbonate apatite (HCA) on its surface after 3 days of soaking in simulated body fluid (SBF). X-ray energy dispersive spectroscopy showed the HCA layer includes Si with Ca and P. A result of osteoblast-like cellular proliferation on the substrates that the membrane coated with silicon-containing HCA had much higher cell-proliferation ability than the membrane.

Abstract: Electrospinning has recently emerged as a potential technique for fabricating biomimetic tissue engineering scaffolds. In this study, Poly (l-lactic acid) (PLLA) /Nano-hydroxyapatite (HA) hybrid nanofibers scaffolds were prepared by electrospinning. The relationship between process parameters and fiber diameter has been investigated. The fiber diameter decreased with decreasing polymer concentration and with increasing electrospinning voltage; After 6 weeks of in vitro degradation, the mass, viscosity-average molecular weight of the nanofibers scaffolds and the pH value of the degradation solution were changed, the fibers lost their surface smoothness and a regular rough topology was generated after 32d of degradation, the degradation rates of PLLA/HA hybrid nanofibers were slower than those of pure PLLA fibers; The biocompatibility of the nanofibers scaffold has also been investigated by culturing cells on the nanofibers scaffold, elementary results showed that the cells adhered and proliferated well on the PLLA/HA hybrid nanofibers scaffolds.

Abstract: Porous calcium phosphate ceramics (apatite and TCP) with wood-like microstructures, analogous to that of silicified wood, were prepared from natural woods as templates. The production of these ceramic woods was performed by the following process: (1) infiltration with an ethanol solution containing tri-ethyl phosphate and calcium nitrate tetra-hydrate into wood specimens, (2) drying to form a calcium phosphate gel in the cell structure, (3) firing in air to form apatite and TCP. The microstructure of the obtained ceramic woods retained the same structure as that of the raw woods: with the pore sizes corresponding to those of the original wood, and the major pores being unidirectionally connected.

Abstract: The hydroxamate-based artificial siderophore that contains terminated-amine group was newly synthesized. This artificial siderophore formed stable complex with FeIII ion and high bio-activities. The FeIII-artificial siderophore complex was attached onto the glass substrate surface by stepwise self-assembling method. The obtained artificial siderophore-modified glass substrate adsorbed the Gram-positive bacterium Microbacterium. flavescens. The Gram-negative bacterium Escherichia. coli was not adsorbed. The artificial siderophore-modified glass substrates indicated the selective adsorption of microorganisms.