Advanced Materials Research Vols. 148-149

Abstract: A series of pH/temperature sensitive hydrogel beads with semi-interpenetrating polymer network (semi-IPN), composed of sodium alginate and poly(N-acryloylglycinate) were prepared as drug delivery carrier. In pH=2.3 phosphate buffer solution (PBS), the release amount of indomethacin incorporated into the beads was about 9% within 610 min, while this value approached to 68% in pH=7.4 PBS. The release rate of indomethacin was higher at 37 than that at 20 . In addition, the release amount of indomethacin was increased with increasing poly(N-acryloylglycinate) content. These results suggest that the stimuli-sensitive beads have the potential to be used as an effective pH/temperature delivery system in bio-medical fields.

Abstract: HfC powders were synthesized by carbothermal reduction of modified hafnium alkoxide precursors using hafnium oxychloride, propanol and 2,4-pentanedione as the starting materials. The structure, composition and reaction mechanism of the solution-derived precursor were studied by FT-IR. The forming process of HfC was detected by TG-DSC-FT-IR and XRD, and the formation mechanism was also discussed. The morphology of as-derived HfC powders was observed by SEM. The research showed that the solution-derived precursors of HfC probably had structures of network or chain. Dried precursors showed a honeycomb structure. When pyrolysed, the precursors was firstly converted to HfO2 and amorphous C. HfO2 was deoxidized gradually above 1500 . It seemed that HfC powders were almost pure after heat treatment at 1800 .

Abstract: To enhance multilayer pressure vessels’ load bearing capacity, the paper presented a kind of split type compound vessel which employed split, shrink-fit and autofrettage techniques simultaneously. The vessel consists of a split layer made of sintered carbide, and an outer two-layer whole cylinder treated with autofrettage and shrink-fit. The mathematic model for the optimization design of the split type vessels was build based on stress analysis of each layer. In the model, the wall thickness of compound vessels is taken as an objective function; thickness of each layer, shrink-fit pressures, and the elastic-plastic radii of autofrettaged two layers are the design parameters; that Tresca stress of each layer equals to its design stress is constraint. An example was optimized. The results show that no additional strength was wasted in any of the layers at the optimum, and the vessels’ load capacity was far beyond the yield stress of outer whole cylinder.

Abstract: This paper is concerned about the synthesis of shape memory styrene copolymer and the investigation of the influence of cross-linking degree on its shape memory effect. The influence of cross-linking degree on shape memory effect of styrene copolymer was investigated through altering the dosage of cross-linking agent. The Tg increased from 65 to 80.7 with the gel content increase from 35% to 80% which is achieved by increasing the dosage of cross-linking agent from 1% to 4%. Moreover, the SMP experienced good SME and the largest reversible strain of the SMP reached as high as 150%. When the copolymer was heated above Tg+30 (different copolymers performed different Tg), the shape recovery speed of the copolymers increased with the gel content increase.

Abstract: Monoclinic BiVO4 photocatalysts were synthesized via facile and straightforward co-precipitation method at room temperature without high temperature treatment and characterized with X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), flourier transfer infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), and transmission electron microscopy (TEM). The results indicate that through proper selection of synthesis conditions, it is possible to obtain high efficient BiVO4 nanoparticles. The as-prepared monoclinic BiVO4 photocatalysts have an average crystallite size of about 20 nm with the particle size of about 20 to 50 nm. Their photocatalytic activities were evaluated by decolorization of rhodamine B in aqueous solution under visible light irradiation, and the relationship between the photocatalytic activity of BiVO4 and their physicochemical properties were investigated.

Abstract: The effect of Ni doping in Ni and B co-doped TiO2 composite films on photocatalytic reaction and hydrophilic property were investigated. The TiO2 composite films were prepared by sol-gel and coated on glass substrates by dipping methods. These composite thin films were calcined at the temperatures of 400°C for 1 h. Phase formation of TiO2 was characterized by XRD. Morphology of TiO2 composite films were observed by using atomic force microscopy (AFM). The chemical composition and purity of the prepared films were analyzed by EDS, FTIR and FT-Raman spectrometers. The photoactivity of synthesized films was performed by means of degradation of methylene blue dye solution under UV and visible light irradiation. The hydrophilic property was measured in terms of a contact angle of water droplet on the films with and without the activation of UV irradiation. It was found that Ni doping seems to affect on TiO2 phase, crystallinity of the anatase phase, crystallite size of the composite films and band gap energy of the catalysts, resulting in their photocatalytic reaction and hydrophilic property. The crystallinity of anatase increased with an increase in Ni content varied from 0-3 mol% but decreased with an increase in Ni content above 3 mol%. It was found that 3 mol% Ni/B/TiO2 film, having highest crystallinity and smallest crystallite size shows the highest of photocatalytic reaction while 2 mol% Ni/B/TiO2 film provides the most hydrophilic effect. Only anatase phase was found at the calcination temperature of 400°C. The smooth film surfaces exhibits a high hydrophilic property. Super-hydrophilicity (contact angle equal to zero) of all B and Ni co-doped TiO2 films was found at UV irradiation for 25 minutes.

Abstract: The(1-x)BaTi0.8Zr0.2O3-xBa0.7Ca0.3TiO3 ceramics have been prepared by sol-gel technique, where x is from 0.2 to 0.6. It reveals that the dense ceramics can be obtained when the sintered temperature is above 1250°C. It is lower than that of solid state reaction ceramics. In particular, when x=0.3, at which is near the MPB composition, the ferroelectric and piezoelectric properties are more excellent than the others. The maximum dielectric constant is above 9000, which can be observed in the butterfly shape curves of dielectric constant as a function of electric field. The maximum piezoelectric coefficient d33 can reach 400 pm/V, and it is obtained from the piezoelectric response loops.

Abstract: Self-healing by microcapsules is one of methods to stop and heal crack propagation in time. Microcapsule containing 5-ethylidene-2-norbornene (ENB) core and Melamine-Urea -Formaldehyde (MUF) shell with possibly higher healing efficiency was synthesized via three different heating histories including different heating rate and heating steps, which significantly affect microcapsule surface morphology, thermal stability, and yield, thus the reproducibility. Finally, it is demonstrated that the best quality of microcapsule was obtained from fast-slower heating method with proper outer surface and shell thickness, as well as 285 higher temperature resistance. The mean particle size is about 100m.

Abstract: The SiO2 aerogels of low density was fabricated by ion exchange and sol-gel method on the basis of sodium silicate. The effect of pH, aging，addition of DCCA and annealed temperature on the gel time, aerogel density, porosity and the micro-structure was systemly studied. The results showed that when the pH is 5, aging was 30%Vol .of TEOS/ethanol solution ,the addition of DCCA was 1.5ml, the gel system was annealed at 50 for 84 h, 60 for 72h, the best quality of silica aerogels with low density (0.14g/cm3), higher specific surface(610.643 m2/g) and pore size of 20~40 nm can be obtained.

Abstract: In this communication, Ag0.9Na0.1(Nb0.7Ta0.3)O3（ANNT） mixed oxide powder was synthesized by citrate wet chemical method. TG-DTA, XRD and TEM analyses showed that the reaction temperature was 800°C, the calcining time was three hours, and the product was pure ANNT in well-dispersed grain structure (35nm in average).