The effect of epoxy resin to reduce the compression set of polysulfide sealant

In this article, modified polysulfide sealants with lower compression set were prepared by a simple method of introducing the diglycidyl ether of bisphenol A resin (DGEBA epoxy resin) into sealants. The investigation on reactivity analysis and gel faction test verified that the incorporation of epoxy resin in sealants was just a blending process rather than copolyaddition with polysulfide resin. Stress–strain behavior during compression revealed that the epoxy resin could reduce the compression stress when the sealants were loaded to a certain strain, which effectively lessened crosslink breakages and benefited to compression resistance. Also the rigid phenyl structure in epoxy resin may retard incidental slide between polysulfide chains and prevent interchange reactions between disulfide linkages. The incorporation of 2 phr epoxy resin distinctly reduced compression set of polysulfide sealant from 28.3% to 11.2% after compressed 25% at 23°C for 1 day. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The dielectric properties of BaTiO3 based ceramics co-doped with Bi/Mn

BaTiO₃ based ceramics (with some additives such as ZrO₂, SnO₂, etc.) were prepared by solid state reaction. Mn²⁺ or Mn³⁺ as an acceptor substituting for Ti⁴⁺ in B site and Bi³⁺ as a donor substituting for Ba²⁺ in A site were co-doped in BaTiO₃ based ceramics. The dielectric properties of BaTiO₃ based ceramics co-doped with Bi/Mn were investigated. The results show that the dielectric properties of BaTiO₃ based ceramics co-doped with Bi/Mn are affected by the mole ratio of donor and acceptor (Bi/Mn). When the mole ratio of donor and acceptor is high, dielectric dispersion behavior was observed and the dielectric constant decrease and remnant polarization, coercive field and piezoelectric constant will varied. When Bi varied from 1.0% to 2.0 mol% (Mn = 0.8 mol%), remnant polarization from 10.35 to 2.25 μC/cm², coercive field from 4 to 2.75 kV/cm, and piezoelectric constant d₃₃ from 137 to 36 pC/N respectively.     

高压料床挤压对钢渣易磨性改善的应用研究

在分析了大量钢渣原料的化学成分、矿物组成和粉磨邦德功指数基础上,依据辊压机高压料床挤压粉碎原理,本文采用辊压机对钢渣进行预挤压试验,并参照相对易磨性试验方法,对比了挤压前后钢渣粉磨特性的变化,试验结果表明辊压机高压料床的挤压粉碎作用大大改善了钢渣的易磨性,有效的降低了钢渣的粉磨电耗。     

Fabrication and Characterization of Highly Oriented Composite Nanofibers with Excellent Mechanical Strength and Thermal Stability

Here, highly‐oriented poly(m‐phenylene isophthalamide)/polyacrylonitrile multi‐walled carbon nanotube (PMIA/PAN‐MWCNT) composite nanofiber membranes with excellent mechanical strength and thermal stability are successfully produced using electrospinning. It is demonstrated that the cooperation of multi‐walled carbon nanotubes (MWCNT) and high‐speed rotating collection is beneficial to the acquisition of highly oriented fibers and effectively improves the mechanical strength of the membrane along the orientation direction. Specifically, the tensile stress of poly(m‐phenylene isophthalamide)/polyacrylonitrile (PMIA/PAN) membrane is enhanced significantly from 10.6 to 20.7 MPa, benefiting from the highly oriented alignment of the fibers as well as the reinforcing effect of MWCNTs on the fibers. Furthermore, the stressing process of single fiber and fiber aggregates is carefully simulated, and the influence of MWCNTs on the mechanical properties of PMIA/PAN‐MWCNT membranes is analyzed comprehensively, providing a meaningful auxiliary means for the study of mechanical properties. In addition, the composite nanofiber membrane has the advantages of both PMIA and PAN, possessing high temperature resistance, flame‐retardancy, and chemical stability, for an ideal high‐temperature material. In short, the as‐prepared PMIA/PAN‐MWCNT composite membrane with excellent comprehensive property emerges a promising application in many fields, especially in high‐tech.     

Improving Dewaterability and Other Properties of Citric Acid Wastewater Treatment Sludge by Ozone and Peroxone

ABSTRACT

The efficacies of ozonation and peroxone (O₃/H₂O₂) pretreatments were compared for citric acid wastewater sludge conditioning with the objective of improving dewatering characteristics of the sludge. Treatment with 84 mg O₃/g dry solid (DS) and 12.5 mg/g DS H₂O₂ greatly enhanced the effectiveness of ozonation, providing sludge dewaterability similar to that obtained by ozonation at 250 mg O₃/g DS. Most importantly, treatment of citric acid wastewater sludge with 84 mg O₃/g DS and 12.5 mg/g DS H₂O₂ led to the preservation of the nutrient elements nitrogen, phosphorus, and potassium in the sludge with a minimal volatile suspended solids/total suspended solids reduction of 5.5%, which is much lower than that with ozonation at 250 mg O₃/g DS.     

Chlorine-free emission disposal of spent acid etchant in a three-compartment ceramic membrane reactor

Electrochemical technologies for the on-site treatment of spent acid etchant have received great attention due their ease of operation and economic benefits. On the other hand, a large amount of Cl₂ is generated during the electrolysis process, which leads to potential environmental risks. In the present work, a novel threecompartment ceramic membrane flow reactor, including a cathode chamber, an anode chamber, and a gas absorption chamber was developed. The three chambers were divided by an Al₂O₃ ceramic membrane and a breathable hydrophobic anode diffusion electrode (ADE). The Cl₂ evolution onset potential of the ADE was increased to 1.19 V from 1.05 V of the graphite felt, effectively inhibiting the chlorine evolution reaction (CER). The anode-generated Cl₂ diffused into the gas absorption chamber through the ADE and was eventually consumed by the H₂O₂ adsorbent. Cu could be recovered without emitting chlorine due to the special structure of reactor. The current efficiency of copper precipitation and cathode reduction from Cu²⁺ to Cu⁺ reached 97.7% at a working current of 150 mA. These results indicated that the novel membrane reactor had high potential for application in the copper recovery industry.     

往复压缩机管道的减振设计

简述往复压缩机设备特点,结合实例分析往复压缩机进出口管道振动原因,介绍简单的计算方法,提出有效的管道减振措施。     

Melanogenesis Inhibition by Homoisoflavavone Sappanone A from Caesalpinia sappan

Homoisoflavanone, sappanone A, was isolated from Caesalpinia sappan and proven to dose-dependently inhibit both melanogenesis and cellular tyrosinase activity via repressing tyrosinase gene expression in mouse B16 melanoma cells. To our knowledge, sappanone A is the first homoisoflavanone to be discovered with melanogenesis inhibitory activity. Our results give a new impetus to the future search for other homoisoflavanone melanogenesis inhibitors.     

Investigations into the impact of the substrates with ultra thin seed layers deposited by atomic layer deposition on ZnO Nanowire Arrays

ABSTRACT: The impact of various substrates and ZnO ultra thin seed layers prepared by atomic layer deposition on the geometric morphology of subsequent ZnO nanowire arrays (NWs) fabricated by the hydrothermal method was investigated. The investigated substrates included B-doped ZnO films, Indium Tin Oxide films, single crystal silicon (111), and glass sheets. Scanning electron microscopy and X-ray diffraction measurements revealed that the geometry and aligment of the NWs were controlled by surface topography of the substrates and thickness of the ZnO seed layers, respectively. According to atomic force microscopy data, we suggest that the substrate, fluctuate amplitude and fluctuate frequency of roughness on ZnO seed layers have a great impact on the alignment of the resulting NWs, wherease the influence of the seed layers' texture was negligible. Transmission Electron Microscopy and Photoluminescence spectroscopy showed that crystal defects were influenced greatly by substrates instead of seed layers.     

Microstructure observation and analysis of 3D carbon fiber reinforced SiC-based composites fabricated through filler enhanced polymer infiltration and pyrolysis

3D C/SiC-BN composites were fabricated by filler enhanced polymer infiltration and pyrolysis (FE-PIP) through in situ conversion of active filler boron into h-BN in the high temperature treatment process. The bending strengths and microstructures of composites were studied here. Interphase layers deposited on the fiber surfaces can prevent the strong bonding between fiber reinforcements and composite matrix and repair the defects on the fiber surface, which can improve the bending strength and toughness of composites. The bending stress of C/SiC-BN composites without interphase layer is about 170 MPa while those of composites with PyC or PyC/SiC interphase layers are higher than 300 MPa. Some large pores were left in the interwoven zones while intra-bundle zones were relatively dense, only a small amount of micro-pores could be observed. It could also be concluded that the length of pulled-out fibers was much longer and the pulled-out fiber surface was smoother when interphase layers were deposited. Because the matrix derived from the pyrolysis of slurries adheres to the fiber bundles, some phases with layered structures could be observed in the matrix near the reinforcements. The microstructure evolution of 3D fiber reinforced ceramic matrix composites were also analyzed in this work based on the observation of both 3D C/SiC-BN composites and 3D C/SiC composites fabricated by FE-PIP, where boron and SiC particles were applied as active fillers and inert fillers respectively.