A series of ferroelectric liquid crystal polymers having banana-shaped side chain mesogens were synthesized through photo-polymerization
of epoxide moiety. 2,5-disubstituted-thiophene sub-unit was used in synthesizing the banana-shaped monomers. These liquid
crystal compounds were characterized by NMR, differential scanning calorimetry (DSC) and optical polarized microscopy (POM).
Mesomorphism was investigated as a function of spacer units. All the synthesized low molar mass banana-shaped compounds exhibit
smectic blue phase, but chiral smectic C phase could be observed only on compounds having longer spacer. The clearing temperature
of low molar mass compounds fluctuated a little when spacer length varies. All polymers exhibit cholesteric mesophase and
an observable glass transition. These liquid crystalline compounds reveal strong photoluminescence at visible region (λmax = 475 nm for M9EPX) and have potential use in polarized organic light emitting diode materials. 相似文献
The stability of MoSi2 in combustion gas at 1370° and 1600°C was evaluated using SOLGASMIX-PV thermodynamic modeling, periodic weight measurements, and characterization via XRD, SEM, EDS, and image analysis. Passive oxidation occurred at both temperatures. During an initial stage of exposure, specimen surfaces oxidized to form MoO3(g) and amorphous SiO2 via reduction of CO2 and H2O. After a short time (<6.5 min at 1370°C, <1 min at 1600°C), the oxidation mechanism switched; Mo5Si3 and amorphous SiO2 formed as oxidation products. The first mechanism esulted in the formation of 46.1 vol% at 1370°C and 42.6 vol% at 1600°C of the amorphous silica surface coating. The attainment of a near-terminal weight gain implied silica formation was limited by H2O and CO2 diffusion through the silica coating. 相似文献
In this study, β-In2S3 nanowires were first synthesized by sulfurizing the pure Indium (In) nanowires in an AAO membrane. As FE-SEM results, β-In2S3 nanowires are highly ordered, arranged tightly corresponding to the high porosity of the AAO membrane used. The diameter
of the β-In2S3 nanowires is about 60 nm with the length of about 6–8 μm. Moreover, the aspect ratio of β-In2S3 nanowires is up to 117. An EDS analysis revealed the β-In2S3 nanowires with an atomic ratio of nearly S/In = 1.5. X-ray diffraction and corresponding selected area electron diffraction
patterns demonstrated that the β-In2S3 nanowire is tetragonal polycrystalline. The direct band gap energy (Eg) is 2.40 eV from the optical measurement, and it is reasonable with literature. 相似文献
The world is facing serious climate change caused in part by human consumption of fossil fuel. Therefore, developing a clean and environmentally friendly energy resource is necessary given the depletion of fossil fuels, the preservation of the earth's ecosystem and self-preservation of human life. Biological hydrogen production, using dark fermentation is being developed as a promising alternative and renewable energy source, using biomass feedstock. In this study, beverage wastewater and agricultural waste were examined as substrates for dark fermentation to produce clean biohydrogen energy. 相似文献
A bicalcium phosphate (BCP) bioceramic comprising α‐tricalcium phosphate (α‐TCP) and hydroxyapatite (HA) was prepared by a two‐step sintering. The microstructure of the BCP bioceramic was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction. The in vitro osteoinductivity was evaluated by culturing MG63 osteoblast‐like cells on the BCP bioceramic. Results showed that the BCP bioceramic comprising α‐TCP and HA in a moderate ratio possessed a hardness of 93.7 Hv. The cells spread faster on the BCP bioceramic than those on the commercial HA. It suggested that the BCP bioceramic can enhance osteoinductivity in vivo. 相似文献
Ceramic wear maps have been developed to elucidate the complex interactions of the operating parameters, environments, and wear mechanisms. This paper summarizes these interactions for four ceramics, alumina, yttria-doped zirconia, silicon carbide and silicon nitride. Wear maps of these ceramics are systematically constructed using measured data under dry sliding, water, and paraffin lubricated conditions. For each material, different wear level regions acid wear transition zones are identified as a function of operating conditions and lubrication conditions. Wear mechanism studies performed within each wear region give rise to the wear mechanism maps. These maps facilitate material comparison and selection. The knowledge of wear, wear transitions, and wear mechanisms for a material pair enables realistic wear model development. One outcome of this approach is the recognition that a single wear model for a material pair cannot cover all operating conditions and environments.
As wear maps are constructed today, they are material pair specific. Within a material pair, there are microstructural dependence and surface properties influence. These parameters can change substantially for a given chemical composition of the material. How to incorporate these factors into the wear map research remains an issue. The search for a universal parameter such as the “asperity temperature” in Ashby's wear map continues in spite of mounting evidence that this may not be practical or feasible. But the hope remains that some parameters can be identified to normalize a large number of materials, operating conditions, and environments for tribological applications. Systematic wear maps are the first steps in this direction. 相似文献
In this paper, we performed a physical mixture of PEO and PF polymers (i.e. a polymer blend) as an organic template for synthesizing PF-PEO-silica homogeneous composites in a dilute silicate solution at pH = 4.0–5.0. The PF-PEO-silica composites exhibit spherical morphology, in micrometer dimension, and the sphere size is dependent on the pH value of the solution. After undergoing calcination to remove the organic part of the PF-PEO-silica composites with and without the hydrothermal treatment, porous silica spheres of different pore sizes were obtained. Due to the existence of the carbonizing PF polymer in the PF-PEO-silica composite, porous carbon spheres can be conveniently obtained from pyrolysis of the PF-PEO-silica composites under a N2 atmosphere and HF-etching procedures. TEM images demonstrate that the mesostructures of the mesoporous silica and porous carbons are disordered. 相似文献
The cartridge filtration method and membrane filtration method based on the fluorescent antibody procedure were evaluated for their recovery efficiencies and detection limits of Giardia and Cryptosporidium. We assessed the performances of the two concentration methods for water samples collected from Taiwan water treatment plants. The membrane filtration method was characterized by higher recovery rate and detection limit comparing with the cartridge filtration method. The occurrences of both parasites, and the relationships of parasite concentrations with indicator microorganisms show inconsistency between the two methods. It was discovered that water turbidity reduced the recovery efficiencies, and raised the detection limits for both parasites regardless of the method used. 相似文献