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Candidate Material (candidate + material)
Selected AbstractsA Short-Term Bioresorbable Bone Filling Material Based on Hydroxyapatite, Chitosan, and Oxidized Starch Tested in a Novel Orthotopic Metaphyseal Mouse Model,ADVANCED ENGINEERING MATERIALS, Issue 8 2009Elias Volkmer Despite significant advances in orthopedic surgery, no perfect bioresorbable bone-filling material has yet been clinically established. A new candidate material based on hydroxyapatite, chitosan and oxidised starch, which has the potential to covalently bind to bone in a watery milieu was tested in a new murine model. A special focus lies on the in vivo biocompatibility and bioresorbability of the new material. [source] Optimizing preparation of NaCS,chitosan complex to form a potential material for the colon-specific drug delivery systemJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Ming-Jun Wang Abstract A novel polyelectrolyte complex (PEC) formed by sodium cellulose sulfate (NaCS) and chitosan was prepared as a candidate material for colon-specific drug delivery system. It was found in experiments that the properties of two raw materials and the process parameters, such as the degree of substitution (DS) and concentration of NaCS, the viscosity and concentration of chitosan, were very important factors on the properties of the final product,NaCS,chitosan-PEC. The preparation of NaCS,chitosan complex was optimized by using response surface methodology to evaluate the effects of these parameters on the degradation properties of NaCS,chitosan in the simulated colonic fluid (SCF). The DS of NaCS was in the range from 0.2 to 0.6, the concentration of NaCS from 2 to 4% (w/v), the viscosity of chitosan from 50 to 550 mPa s, and the concentration of chitosan from 0.5 to 1.5% (w/v). A mathematical model was developed to describe the effect of these parameters and their interactions on the degradation of NaCS,chitosan complex. The optimum operation conditions for preparing NaCS,chitosan complex were determined to DS of NaCS of 0.2, the concentration of NaCS of 4.0% (w/v), chitosan viscosity of 327 mPa s, and the concentration of chitosan 0.5% (w/v), respectively. Validation of experiments with 5 confirmatory runs indicated the high degree of prognostic ability of response surface methodology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Enhanced Piezoelectric Properties in Mn-Doped 0.98K0.5Na0.5NbO3,0.02BiScO3 Lead-Free CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2009Xuhai Li Mn-doped 0.98K0.5Na0.5NbO3,0.02BiScO3 (0.98KNN,0.02BS) lead-free piezoelectric ceramics have been prepared by a conventional sintering technique and the effects of Mn doping on the phase structure and piezoelectric properties of the ceramics have been studied. Our results reveal that a small amount of Mn can improve the densification of the ceramics effectively. Because of the high densification, fine grain, and Mn doping effects, the piezoelectric and dielectric properties of the ceramics are improved considerably. Very good piezoelectric and dielectric properties of d33=288 pC/N, kp=0.46, ,r=1591, and TC=328°C were obtained for the 0.98KNN,0.02BS ceramics doped with 0.8 mol% Mn. Therefore, the 0.98KNN,0.02BS ceramics containing a small amount of Mn are a good candidate material for lead-free piezoelectric ceramics. [source] Microstructure and Piezoelectric Properties of 0.95(Na0.5K0.5)NbO3,0.05SrTiO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2007Kyung-Hoon Cho The 0.95(Na0.5K0.5)NbO3,0.05SrTiO3 (0.95NKN,0.05ST) ceramics formed in this study had a porous microstructure with small grains and low piezoelectric properties due to their low density. However, when a small amount of Na2O was intentionally subtracted from the 0.95NKN,0.05ST ceramics, a liquid phase was formed, which led to increased density and grain size. Piezoelectric properties were also improved for the Na2O-subtracted 0.95NKN,0.05ST ceramics. The increased density and grain size were responsible for the enhancement of the piezoelectric properties. In particular, the 0.95(Na0.49K0.5)NbO2.995,0.05ST ceramics showed high piezoelectric properties of d33=220, kp=0.4, Qm=72, and ,3T/,o=1447, thereby demonstrating their promising potential as a candidate material for application to lead-free piezoelectric ceramics. [source] Investigation on steam oxidation behaviour of TP347H FG Part 1: Exposure at 256 barMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 7 2005J. Jianmin Abstract The stainless steel TP347H FG is a candidate material for the final stage tubing of superheater and reheater sections of ultra supercritical boilers operated at steam temperatures up to 620°C in the mild corrosion environments of coal-firing. A series of field tests has been conducted with the aforementioned steel in coal-fired boilers and this paper focuses on the steam oxidation behaviour for specimens tested at various metal temperatures for exposure times of 7700, 23000 and 30000 hours as investigated by light optical and scanning electron microscopy. The oxide present on the specimens is a duplex oxide, where the outer layer consists of two sub-layers, an iron oxide layer and an iron-nickel oxide layer; the inner layer is chromium rich chromium-iron-nickel oxide. Microstructure examination showed that for all these samples the varying grain size of subsurface metal affected the oxide thickness, where the larger the metal grain size, the thicker the oxidation scale. This gave the appearance of uneven inner oxides with a varying pit thickness. Comparison of the pit thickness measurement and oxide composition reveals that the oxidation rate is fast during the initial oxidation stage, but the subsequent growth of oxide from further exposure is slower due to the formation of a healing layer consisting of chromium rich oxide near original alloy grain boundaries. At a temperature region above 600°C a thin oxide rich in chromium and manganese is sometimes formed. In addition precipitation of secondary carbides in the bulk metal also occurs at this temperature region. [source] Dielectric properties of silicon in terahertz wave regionMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2008JiuSheng Li Abstract By using backward-wave oscillator system, the terahertz dielectric properties of p-type silicon were tested in the frequency range extending from 0.68 to 0.85 THz. The refractive indices, the power absorption coefficient, and the dielectric functions of various resistivity p-type silicons were measured and compared. The variation of the refractive index of the ultra-resistivity silicon was less than 3%, ranging from 3.037 to 3.125, but the absorption coefficient of the ultra-resistivity silicon showed very different frequency-dependent behaviors, ranging from 3.25 × 10,3 cm,1 to 2.90 × 10,5 cm,1, within the investigated frequency range. The ultra-resistivity silicon will be a good candidate material for terahertz transmission waveguide with ultra-low loss. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1143,1146, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23313 [source] Synthesis and characterization of novel poly(p -phenylenevinylene) derivatives containing phenothiazine-5-oxide and phenothiazine-5, 5-dioxide moietiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2007L. Y. Yang Abstract PPV-based copolymers containing phenothiazine-5-oxide and phenothiazine-5, 5-dioxide moieties have been successfully synthesized by Wittig-Horner reaction and characterized by means of UV-vis, photoluminescence, electroluminescence spectra, and cyclic voltammetry. All of these copolymers can be dissolved in common organic solvents such as chloroform, tetrahydrofuran, and toluene. The PL maxima in the film state are located at 582, 556, and 552 nm for P1, P2, and P3, respectively. The HOMO and LUMO levels of P2 are found to be ,5.21 and ,2.68 eV, respectively; whereas those of P3 are found to be ,5.26 and ,2.71 eV, respectively. The cyclic voltammetry result indicates that the conversion of electron-donating sulfide to electron-withdrawing sulfoxide or sulfone group in polymers plays a dominating role in increasing its oxidation potential. Yellowish-green light ranging from 568 to 540 nm was observed for the single layer device with the configuration of ITO/Polymer/Ca/Al. Double layer devices with Zn (BTZ)2as a hole blocking layer exhibited enhanced EL performance compared to the single layer devices. The maximum brightness of the double layer devices of P1, P2, and P3 is 278, 400, and 796 cd/m2, respectively. The results of EL and electrochemical analyses revealed that they are promising candidate materials for organic, light-emitting diodes with hole-transporting ability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4291,4299, 2007 [source] Effect of BiScO3 and LiNbO3 on the Piezoelectric Properties of (Na0.5K0.5)NbO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Xueyi Sun Lead-free potassium sodium niobate-based piezoelectric ceramics (1,y)(Na0.5,0.5xK0.5,0.5xLix)NbO3,yBiScO3 ( y=0.01, x=0,0.06) have been prepared by an ordinary sintering process. The XRD analysis showed that the structure changes from orthorhombic to tetragonal with the increase of x (at y=0.01, abbreviated as KNNBSL100x). At room temperature, the polymorphic phase transition from the orthorhombic to the tetragonal phase was identified at approximately 0.02,x,0.04. The piezoelectric and ferroelectric properties were significantly enhanced. The temperature dependences of the relative permittivity revealed that the Curie temperature was increased with the addition of LiNbO3. These solid solution ceramics are promising as potential lead-free candidate materials. [source] Proton Conductivity Measurements in Yttrium Barium Cerate by Impedance SpectroscopyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2002W. Grover Coors Proton-conducting solid-electrolyte perovskite ceramics based on acceptor-doped barium and strontium cerates have become the focus of extensive investigations as candidate materials for fuel cells that operate at moderate temperatures. To assess the suitability of a material for this application, it is necessary that bulk electrolyte conductivity be measured at the operating temperature. However, very little reliable published conductivity data exist above 600°C. Protonic conductivity in yttrium-doped barium cerate has been observed to be less at high temperatures than would be expected, based on the activation energy and preexponential for hydrogen transport at temperatures <300°C. Conductivity data obtained from impedance spectroscopy on BaCe0.9Y0.1O3,, over the extended temperature range of 100°,900°C are presented. An Arrhenius plot of the data shows two distinct linear regions, suggesting that two different rate-limiting processes occur in series with a break-over transition at ,250°C. The decrease in conductivity is apparently not due to dehydration. An activation energy for protonic transport of 0.26 eV, about one-half of the low-temperature value, is proposed, based on curve fitting of the high-temperature data. [source] The repeatability of friction and wear results obtained from unlubricated reciprocating sliding testsLUBRICATION SCIENCE, Issue 4 2001D. Klaffke Abstract Laboratory tests can help in the analysis of tribological failures of elements, and improve tribo-systems by choosing appropriate materials. In order to characterise the friction and wear behaviour of candidate materials, various different test methods have been developed in the past and are still in use. One such method is the reciprocating sliding of a ball against a disc. In the work reported here, the repeatability of friction and wear results was evaluated with ten tests under identical conditions with a steel (100Cr6) or alumina (Al2O3) ball against a steel (100Cr6) disc under unlubricated conditions at room temperature. The influence of ambient humidity on friction and wear behaviour was determined in three additional tests in dry and in moist air, respectively. The repeatability of friction coefficient in normal air was better than 5% for alumina/100Cr6 and 12% for 100Cr6/100Cr6, while the repeatability of volumetric wear was slightly better than 10% for alumina/steel, and slightly worse than 10% for steel/steel. For both couples the coefficient of friction is lowest in moist air and about 50% higher in dry air. The coefficient of wear is also least in moist air and higher by a factor of 3(5) in dry air for tests with a 100Cr6 (alumina) ball. [source] Production of leather-like composites using short leather fibers.POLYMER COMPOSITES, Issue 6 2002Leather-like composites were prepared by addition of chemically modified short leather fibers (SLF) into a plasticized polyvinyl chloride (pPVC) matrix. The fibers were subjected to chemical modification by emulsion polymerization to achieve good interfacial adhesion between SLF and the pPVC matrix. The SLF with chemical modification were obtained from three different reaction conditions where these SLF have different percentages of grafted and deposited PMMA polymer onto the fiber surface. The incorporation of the SLF into the thermoplastic matrix was carried out using a torque-rheometer and the composites obtained were molded by compression. Tensile and tear mechanical tests were performed on composite samples, and the morphology of the fractured surfaces was analyzed using scanning electron microscopy (SEM). The results show that the incorporation by grafting of polymethyl metacrylate (PMMA) onto the fibers produced a significant improvement of their interfacial adhesion to pPVC, promoting the compatibilization between the fiber surface and matrix. The findings are discussed and interpreted in terms of enhanced adhesion at phase boundaries. Overall, the results confirm that it is possible to produce modified leather composites based on a pPVC matrix, which exhibit relatively high tensile strength, tear resistance and flexibility. These composites are very suitable candidate materials for applications in the footwear industry. [source] | |||||||||||||