Key Engineering Materials Vols. 512-515

Abstract: The nano-sized ZnFe2O4 films were prepared by Sol-gel process on the conducting electricity glass, and the influence factors of the samples’ photoelectron-catalytic performances was investigated, such as the pole materials, the distance between electrodes, the voltage and the light source etc. The results indicated that, the photoelectron-catalytic effect was best when ZnFe2O4 film as the anode and the conductive glass as the cathode, which showed that the main reaction was the photo-generated holes. When the voltage was constant, there was an optimal value of plate spacing. With the plate distance increasing, the effective contact probability of the photon-generated carrier and the degradation was increased. But the plate spacing was too wider, the moving resistance of photon-generated carrier became higher, so as to the degradation rate decreased. The degradation rates of the films showed undulate increase with the voltage increasing in the different kinds light resources conditions.

Abstract: In this work, highly-ordered TiO₂ nanotube arrays were prepared by constant-voltage anodization, followed by electrodeposition of Ag to obtain Ag-loaded TiO₂ (Ag-TiO₂) nanotube arrays via alternating current (AC) process. The results of SEM and XRD show that the morphology and crystal structure of Ag-TiO₂ layer depend greatly on the electrodeposition parameters. Ag-TiO₂ nanotube arrays prepared in 2.5 mmol/L AgNO₃ solution by electrodeposition with applied voltage of 12 V for 1 minute performed the best photoelectrochemical current response and photocatalystic activity. The photocurrent density of Ag-TiO₂ is 43.32 μA/cm² under sunlight irradiation (70 mW/cm²), which is 4.2 times as that of unloaded TiO₂ nanotube arrays. Methyl orange (MO) degradation rate with the Ag-TiO₂ nanotube arrays achieves 52.13% after 90 min sunlight irradiation which is obvious higher than that of TiO₂ nanotube arrays. The mechanism of enhancing photoelectrochemical activity of decorating titania with Ag has also been discussed in the view of energy band theory.

Abstract: Applied nano-ZnFe₂O₄/TiO₂ photocatlytic films are prepared by template sol-gel method on porous haydites. The effects of ZnFe₂O₄-doping on TiO₂ crystallization, sintering temperature, light absorption and photocatalysis are mainly studied, simultaneously, effect of template, amphiphilic block copolymer P(styrene-b-acrylic acid) (PS-b-PAA) on the phtocatalytic activity of ZnFe₂O₄/TiO₂ films are also studied. The results show that right amount of ZnFe₂O₄-doping reduces TiO₂ sintering temperature and particle size, and increases TiO₂ absorbency in ultraviolet region, and a right amount of template (PS-b-PAA) forms orient arranged ZnFe₂O₄/TiO₂ films with the high photocatalytic activity and decomposes fully methyl orange in water after light irradiating 2h.

Abstract: Lithium titanate (Li₂TiO₃) ceramic pebbles are considered to be a candidate material of the tritium breeders for fusion reactor from the viewpoints of good tritium recovery, chemical stability and other excellent properties. In this study, fine grain and pure Li₂TiO₃ powders were prepared by solid-state method at 700°C using TiO₂ and Li₂CO₃ as raw materials. Li₂TiO₃ pebbles were prepared by gel-casting method using acrylamide (AM) as organic monomer, N,N’-methylenebisacrylamide (MBAM) as cross-linker, ammonium citrate as dispersant, and isooctyl alcohol as defoamer. The effect of solid content, dispersant, pH and the ball milling time on the fluidity and dispersion of ceramics slurry were investigated, and the effects of sintering temperature and holding time were also discussed in present study. The sintered ceramic pebbles with diameter of 1.0 mm show a smooth surface, uniform grain size and perfect sphericity. The Li₂TiO₃ ceramic pebbles sintered at 1250°C for 8 hours had the highest density (> 90% of theoretical density) and crush strength.

Abstract: The ZrC oxidization mechanism in air was carefully investigated by the phase composition and grain morphology through DSC, X-ray diffraction and SEM respectively at different temperature. It was found that the oxidization of ZrC start at about 400°C by oxygen atom entering the interstitial sites to substitute part of Carbon. Zr₂O and ZrO₂ can be formed at a temperature of about 600°C and 1000°Crespectively. And ZrC will completely transfer to ZrO₂ at 1000°C for 5hrs. No obvious grain morphology change was found under 600°C.

Abstract: We here report a novel biomimetic mineralization strategy for enamel remineralization by intergration of calcium phosphate loaded and thermally triggered liposomes and a self-assembly amelogenin-inspired peptide. Firstly, calcium and phosphate loaded temperature sensitive liposomes were synthesized by Interdigitation-fusion method with 1,2-bis(palmitoyl)-sn-glycero-3-phosphor- choline (DPPC) and 1,2-bis(myristoyl)-sn-glycero- 3-phosphocholine (DMPC) at mass ratio of 9:1 . The liposomes were stable at room temperature, but slowly released calcium and phosphate ions if heated to 37 °C. Secondly, a novel polyanion amelogenin-inspired oligropeptide (Gln-Pro-Ala)₄-Thr-Lys-Arg-Glu-Glu-Val-Asp ) was synthesized by standard solid-phase. Lastly, the mixture of peptide and liposomes solution was exposed to enamel surface at 37 °C. The results showed oriented enamel-like hydroxylapatite evenly deposited on enamel surface.

Abstract: Patterned octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) was fabricated on silicon substrates, utilizing short wave UV irradiation meter (λ=184.9nm) as the photolithograph apparatus under the cover of the photomask. The patterned BiFeO₃ were prepared on the functional OTS-SAMs by sol-gel method. The characterization of the samples patterns was carried out by various techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and energy disperse spectroscopy (EDS). The results indicate that the pattern BiFeO₃ thin films were successfully prepared on the functional OTS-SAMs by sol-gel method and the thin films were BiFeO₃ thin films with hexagonal perovskite distorted structure which has clear boundaries and 200µm deposited lines width.

Abstract: Fe(NO₃)₃•9H₂O and Bi(NO₃)₃•5H₂O were used as raw materials. BiFeO₃ thin films were prepared by sol-gel method. The effects of annealing temperatures on the morphology and dielectric property of the thin films were studied. XRD results show that the multi-crystal thin films with pure phase are obtained when annealed at 500°C and 550°C. But annealing at 580°C will lead to the appearance of Bi_2.46Fe₅O₁₂ phase.AFM images show that as the increase of annealing temperatures the surface toughness of the thin film is decreased, but the surface undulation of the thin films is decreased gradually. Within the frequency range of 1KHz~1MHz, the dielectric constant of BiFeO₃ thin films is kept over 125 and it does not change very much from 500°C to 580°C. Annealed at 550°C, the BiFeO₃ thin films with the lower loss are obtained. At 1MHz, the dielectric loss is 0.12.

Abstract: For successful reconstruction of skeletal defects, a range of materials including ceramics, polymers and their composites have been developed. The goal of our work is to prepare mineralized PCL/gelatin composite scaffolds in a double diffusion system as implants for bone tissue engineering application. Fibrous PCL/gelatin scaffold fabricated via electrospinning followed by immersing into disodium-β-glycerophosphate(β-GP) (10 mg/ml) for 12h were used as substrates for calcium phosphate (CaP) mineralization. The precipitation reaction was biomimetically carried out in a double diffusion system for a week. The CaP minerals precipitated on the scaffold were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and high-resolution transmission electron microscopy. The results show that apatite aggregates are combination of HAP, DCPD and ACP. β-GP can effectively promote the formation of CaP crystals. The composite scaffold fabricated in this paper hold promise for use in bone tissue engineering.

Abstract: Chitosan has found various applications in gastrointestinal stent, biomedical implants as well as an effective absorbent in waste water treatment. However, the material suffers from low strength and large shrinkage upon dehydration. The current project is aimed to develop a process to fabricate chitosan composites with the addition of functionalised montmorillonite nanoparticles and to examine the effect of ceramic content on the mechanical behavior of the composites. This paper describes the fabrication of chitosan with montmorrillonite composites and the mechanical testing of the samples and the mechanical behaviour of the composites, as well as the observations of the microstructure. The effects of composition and microstructure on the mechanical properties of the composite are investigated. The results indicate that the nanoparticles are dispersed uniformly in the matrix up to 40wt% using high speed homogeniser. The elastic modulus increases monotonically with the addition of nanoparticles, but the fracture strength drops due to the defects introduced by the nanoparticles.