Advanced Materials Research Vols. 560-561

Abstract: The research on microcellular polymer foam (MPF) is significant in plastic processing industry. In this study, polymethyl methacrylate (PMMA) was considered to be the foam matrix via a preliminary experiment. It is because that compared with other polymers, it is easier to swell and plasticize with supercritical CO2 (SCCO2). Moreover, its absorbability in SCCO2 is much higher. The above research provides guidance for the preparation of microcellular polymer blend foams. In order to study the foam process and the optimum experimental conditions, the average cellular sizes were measured by controlling the saturation pressure, temperature and the soak time on the basis of the orthogonal experiment. The microporous structure was observed by scanning electron microscope (SEM). Then the optimum amount of nano-fillers was achieved by solution and melt blending. In addition, the mechanical properties of MPF were measured to explore the change in foaming. The obtained results would provide better insight to planners and operators in the field of chemical engineering to handle the uncertainties effectively.

Abstract: We first modify the surfaces of BaTiO3 by hydrogen peroxide to induce hydoxyl groups that will be further reacted with a coupling agent. Then, with a silane coupling agent, we induce the amino group on the surface of particles. Modified BaTiO3 particles with the PI precursor (poly(amic acid)) are able to obtain poly(amic acid)-wrapped BaTiO3 particles. By employing this approach, higher dielectric value is obtained for the composite comprised of PI and PAA-wrapped BaTiO3 particles.

Abstract: The sintering temperature of BaTiO3 powder was reduced to 870°C due to the H3BO3-ZnO-Bi2O3 addition.Excellent densification was achieved after sintering at 870°C for 15h. The low sintering temperature of newly developed capacitor materials allows a co-firing with pure silver electrodes.The dielectric constant and the temperature stability of the dielectric constant satisfied the X7P requirements, which dielectric properties of were ε25°C≥ 2800, εr/εr25°C≤±10% (–55~125°C), tanδ≤1.5% (25°C).

Abstract: The effect of high energy electron irradiation on poly(vinlidene fluoride-trifluoroethylene) copolymer film with thickness about 180 nm has been studied. Both dielectric spectroscopy investigation and X-Ray Diffraction show that all-trans conformation of pre-irradiated films is transformed to trans-gauche conformation after irradiation. The relaxor behavior of irradiated sample obeys the modified Curie-Weiss and Vogel-Fulcher law. And the tunability is increased from 42% to 63% after irradiation.

Abstract: Modification process of carbon fiber reinforcement was investigated so as to produce aluminum matrix composite on a large scale. A series of pretreatment technologies could acquire chemical deposition silver, which became the base of copperplating on the surface of carbon fibers. The optimum conditions of electroless plating copper, including components, adding amount of carbon fibers, temperature, pH value, and mixing method, were determined to obtain a perfect copper layer on the surface of carbon fibers. The control of copper deposition and repeating utilization of many technology solutions were realized to reduce the costs. The results laid a foundation of mass production for carbon fiber reinforced aluminum matrix composite.

Abstract: Considering the crystal field parameter B, C and average covalent factor N, the energy levels of Li2GeO3: Cr3+ crystal are calculated by diagonalizing the energy matrix of 3d3. The experimental data are compared with calculated results. The results show that the calculated results are in agreement with experiments. Absorb spectra are successfully identified.

Abstract: Ammonia sulfite pulping liquor of wheat straw was treated by ultrafiltration. Experimental results indicated that the membrane with a cut-off of 10kDa was suitable for concentrating wheat straw liquor and had good anti-fouling property against pulping liquor. Permeability of ash turn higher with the increasing of volume reduction at the operating condition of 200 kPa and 25°C, and retentate was concentrated when volume reduced. Influences of ultrafiltration on physical properties of ammonia sulfite pulping liquor and its retentate after ultrafiltration were studied. Results showed that retentate had better performances as surfactant, concrete additive and dispersant. Surface tension of 1% lignin solution of retentate was 54.7 mN/m, which was lower than that of the untreated original lignosulfonate by 2.2 mN/m. Dispersing effect of retentate on cement was also investigated, it was found that flowability of neat cement paste improved from 70mm to 102mm.

Abstract: For Barium Titanate Ceramics doped with the trivalent and hexavalent chromium oxides, the influence of Cr valence state on dielectric-temperature stability was investigated with Atomic force microscopy, X-ray diffraction, Raman spectroscopy, and dielectric measurements. The application of the trivalent Cr2O3 dopant can give rise to a temperature-stable X7R specification and a lower dielectric loss (< 0.02) when the sample was prepared at 1240 °C, but the dielectric permittivity is lower (~600); Cr ions exist predominantly as Cr4+ and slightly as Cr3+. Increasing sintering temperature will destroy the core-shell structure of the samples. The application of the hexavalent CrO3 dopant can not produce a temperature-stable X7R ceramic; Cr ions exist as Cr4+ and Cr5+. Cr5+ can not enter the perovskite lattice owing to the valence mismatching.

Abstract: The thiophene plasma polymer was deposited on silicon(100) substrates by PECVD (Plasma Enhanced Chemical Vapor Deposition) with homemade stainless steel vacuum chamber. Thiophene was utilized as organic precursor with hydrogen gas as bubbling gas. Argon gas was used as a carrier gas. To analyze the electrical properties of the plasma polymerized thin films, the plasma-polymer thin films were grown under various RF power condition. The as-grown plasma-polymer thin films were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), measuring the capacitance, impedance analyzer, ellipsometry, Fourier Transform Infrared spectroscopy (FT-IR), and water contact angle measurement. AFM and SEM images showed smooth surfaces of thin films with increasing RF power. An impedance analyzer was utilized for the measurements of I-V curves (for leakage current density) and capacitance (for dielectric constant). Refractive indices were increased by increasing RF power. The IR spectra showed that the plasma polymer thin films have totally different chemical functionalities from liquid thiophene precursor, as well as the changing chemical functionalities of the thin films caused by various RF powers. The best dielectric constant is 2.52 in this study.

Abstract: The hydroentangled nonwovens have be widely used today. But the basic research of the hydroentangled nonwoven technology is relatively weak. It is not very clear so far that how the fibers are entangled with each other in the spunlaced nonwoven fabrics. In this paper, the pulling-out behavior of single fiber from hydroentangled nonwoven was first studied and analyzed the stress situation of the entanglement points in order to investigate the entanglement of the fibers in the hydroentangled nonwovens. It is found that the bigger of the pulling-out force, the more fibers are broken and the resultant hydroentangled nonwovens show better tensile property. So the pulling-out force can be used to weight the fiber entanglement effect in the hydroentangled nonwovens. Moreover, in this paper we also discover the fiber performance which can influence the fiber entanglement effect during the hydroentangled process by the cohesive of fibers, and the theory instruction will be provided to develop new fibers in the spunlaced process.