Ablation behavior and mechanism of boron nitride - magnesium aluminum silicate ceramic composites in an oxyacetylene combustion flame

In the present study, ablation behavior and properties of BN-MAS (magnesium aluminum silicate) composites impinged with an oxyacetylene flame at temperatures up to 3100 °C were investigated. As ablation time ranged from 5 to 30 s, the mass and linear ablation rates increased from 0.0027 g/s and 0.001 mm/s to 0.0254 g/s and 0.087 mm/s, respectively. A SiO₂-rich protective oxide layer formed during the ablation process, which contributed to the oxidation resistance of the composites. Ablation products mainly consisted of magnesium-aluminum borosilicate glass, mullite, spinel and indialite. The thermal oxidation of h-BN during flame ablation and scouring of MAS by high-speed gas flow were the main ablation mechanisms.     

Coupling simulation of fluid structure interaction in the stirred vessel with a pitched blade turbine

The interaction between fluid and a down-pumping pitched blade turbine fixed with a flexible shaft in the stirred vessel,as a typical fluid structure interaction phenomenon,was simulated by coupling the Computational Fluid Dynamics and Computational Structural Dynamics.Based on the verification of the simulated impeller torque and dimensionless shaft bending moment with experimental result,the dimensionless shaft bending moment and various loads acting on impeller (including lateral force,axial force and bending moment) were discussed in detail.By separating and extracting the fluid and structural components from those loads,the results show that the shaft bending moment mainly results from the lateral force on impeller although the axial force on impeller is much larger.The impeller mass imbalance increases the shaft bending moment and the lateral force on impeller,but has little influence on the axial force and bending moment acting on impeller.The dominant frequencies of impeller forces are macro-frequency,speed frequency and blade passing frequency,and are associated with the impeller mass imbalance.     

Laccase‐catalyzed polymerization drying of Chinese lacquer sap with TiO2 nanoparticles

Nano‐TiO₂/lacquer hybrid coatings are prepared by the blend of nano‐TiO₂ and lacquer sap. Nano‐TiO₂ particles are involved in the laccase‐catalyzed polymerization process of urushiol, which improves the properties of lacquer film. With increasing nano‐TiO₂ from 0 to 5 wt %, the drying time of lacquer film to reach hardened dryness decreases from >12 h to 8 h 30 min under 30 °C and 80% relative humidity. Gel permeation chromatography analysis shows that the addition of nano‐TiO₂ accelerates the polymerization of urushiol. It is also related to the formation of Ti? O? C bonds due to the reaction between nano‐TiO₂ and the radicals produced by laccase‐catalyzed oxidation. The pencil hardness, flexibility, and adhesion of hybrid lacquer film can be improved and reach 4H, 1 mm, and grade 2, respectively. Its inhibition rate against Escherichia coli and Staphylococcus aureus increases from 22.6% and ?21.4% to 49.2% and 67.8%, respectively. Furthermore, nano‐TiO₂ hybrid lacquer films also possess higher thermo‐stability than the raw lacquer film. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45865.     

Preparation of hydrolysis of poly(acrylonitrile‐co‐methyl acrylate) membranes via thermally induced phase separation: Effects of hydrolysis conditions and additives

In this work, melt processable poly(acrylonitrile‐co‐methyl acrylate) [(P(AN‐MA)] was hydrolyzed first and then formed into microporous membrane via thermally induced phase separation. In order to optimize the hydrolysis condition and fabricate hydrophilic PAN‐based membranes, a series of hydrolysis experiments were performed to indicate the influence of hydrolysis temperature, alkaline species and time. The structure and properties of hydrolyzed P(AN‐MA) [H‐P(AN‐MA)] membranes were also investigated. It was found that with the increase of hydrolysis temperature, pure water flux (PWF) increased first and then decreased. When the hydrolysis temperature increased to 30 °C, the PWF of the H‐P(AN‐MA) membrane was up to the maximum of 6712.7 L/m² h, which increased by 1661.6 L/m² h, compared with the P(AN‐MA) membranes. When 1 wt % sodium dodecyl sulfate (SDS) was incorporated into the diluents, the PWF increased dramatically, especially in high hydrolysis temperature. When the hydrolysis temperature was up to 70 °C, the PWF of H‐P(AN‐MA) membranes containing 1 wt % SDS increased by 2.3 times compared to the sample without SDS under the same condition. With 2 wt % amino functionalized multi‐walled carbon nanotubes (MWCNTs‐NH₂) employed as the additive, the tensile strength was up to 4.55 MPa. When 1 wt % SDS and 0.5 wt % MWCNTs‐NH₂ were mixed together, the bovine serum albumin rejection increased from 31.2% to 40.9%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46380.     

Effect of ZnO/MgO ratio on the crystallization and optical properties of spinel opaque glazes

The effect of the ZnO/MgO ratio on the crystallization and optical properties of glass‐ceramic glazes from the SiO₂–Al₂O₃–ZnO–MgO–CaO–K₂O–Na₂O–B₂O₃ system was studied. The glazes with different ZnO/MgO ratios were characterized by differential scanning calorimetry, X‐ray powder diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy analysis and a spectrophotometer. The results reveal that the A glaze without ZnO content contains forsterite and sapphirine. The B and C glazes with intermediate ZnO/MgO ratio contain enstatite and spinel solid solution. The D to F glazes with higher ZnO/MgO ratio crystallize spinel solid solution as the only crystalline phase. The amount of spinel solid solution, lightness values (L*), gloss values and the reflectance of the studied glazes increase with the ZnO/MgO ratio.     

相转移催化合成11-脱氧甘草次酸-3-位酯类衍生物

以甘草次酸为原料 ,经还原制得 1 1 -脱氧甘草次酸 ,然后在聚苯乙烯固载化聚乙二醇 40 0( PS- PEG- 40 0 )的催化下。合成了七种具有潜在药理活性和应用前景的 1 1 -脱氧甘草次酸 - 3-位酯类衍生物。合成方法简单 ,产率较高 ,后处理方便     

TiO_2 与TiO_2 -SiO_2 薄膜的表面性质及生物活性研究

采用溶胶 -凝胶法在医用NiTi形状记忆合金表面制备了TiO2 与TiO2 -SiO2 薄膜 .用X射线 (XRD) ,红外光谱 (FT -IR) ,X射线光电子能谱 (XPS)和原子力显微镜 (AFM)对薄膜的表面组成、结构与形貌进行了研究 .将表面涂有薄膜的试样浸入模拟体液 (SBF) ,用XPS分析Ca ,P在薄膜表面的沉积情况 .结果表明 :TiO2 -SiO2 膜具有比TiO2 膜更高的生物活性 ,主要原因是TiO2 -SiO2 薄膜表面存在较多的羟基基团 ,在模拟体液中诱导磷灰石沉积的能力较高 ;此外 ,薄膜的表面形貌对其生物活性也有一定的影响     

Synthesis and thermal properties of poly(urethane‐imide)

The synthesis and thermal properties of thermoplastic poly(urethane‐imide) (PUI) resins were studied. Model reaction studies on the reactions of 4,4′‐diphenylcarbamatodiphenylmethane and 4,4′‐diisocyanatodiphenylmethane with phthalic anhydride were performed. We found that the reaction of anhydrides with urethane groups could take place under certain reaction conditions. According to the model reaction studies, N‐2‐methyl‐pyrrolidone was employed as a solvent, and no catalyst was used in the polymerization. To restrain the side reaction of anhydrides with urethane groups, we adopted a two‐step chain‐extending procedure in a chain‐extending reaction. The inherent viscosity of PUI was 0.83–0.99 dL/g. The prepared polymers not only exhibited improved solubility in organic solvents but also formed flexible films. Thermogravimetric analysis showed that PUI exhibited a two‐step thermal weight‐loss pattern. The first step of the thermal degradation of PUI was attributed to the thermooxidizing cleavage of weak and labile linkage, such as urethane groups, isopropylidene, and methylene, except for imide rings. The polymer inherent viscosity decreased sharply during the first step of thermal degradation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 773–781, 2001     

Preparation of modified oligochitosan and evaluation of its scale inhibition and fluorescence properties

To obtain an environmentally friendly and efficient scale inhibitor, carboxymethyl quaternary ammonium oligochitosan (CM‐QAOC) was prepared from chitosan, which was depolymerized by nitrous acid, and then reacted with chloroacetic acid and glycidyl trimethyl ammonium chloride via carboxymethylation and quaternization, respectively. The chitosan derivatives were characterized by Fourier transform infrared and NMR spectroscopy. The inhibition performance for CM‐QAOC was evaluated by a conductivity method and a static antiscaling test. The experiments demonstrated that CM‐QAOC showed an excellent scale‐inhibition performance. With a Ca²⁺ concentration of 240 mg/L, CM‐QAOC at a concentration of 50 mg/L and pH 8.0 gave an antiscaling ratio of more than 98%. So, CM‐QAOC could be applied as an excellent antiscaling agent. Furthermore, a detectable fluorescence of CM‐QAOC solution was observed. To understand this interesting fluorescence phenomenon and to explore the probability of its being a fluorescent tracer, the relations between the fluorescence intensities and CM‐QAOC concentrations and the pH influence on the fluorescence intensities were investigated. The results show the fluorescence intensities accorded well with the concentrations of CM‐QAOC with a detection limit of 0.6046 mg/L, and the fluorescence intensity was constant within pH 5–9; this indicated that it had the potential of its being a fluorescent tracer. Thus, CM‐QAOC could be applied as an antiscaling water‐treatment chemical and as a fluorescence tracer directly without any further modifications. It could be self‐traced online and in real time with its own fluorescence, although more work should be done to investigate its fluorescent mechanism and its tracing properties in detail. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42518.     

Preparation and properties of epoxy‐modified tung oil waterborne insulation varnish

This work aimed to develop a novel epoxy‐modified tung oil waterborne insulation varnish with blocked hexamethylene diisocyanate as a curing agent. The Diels–Alder reaction between tung oil and maleic anhydride, and the ring‐opening esterification reaction of epoxy resin were confirmed. The conversion rate of epoxy was explored as a function of reaction time and temperature. The effects of epoxy resin content on the thermal stability, water absorption and insulation properties (insulation strength, volume resistivity, and surface resistivity) of films were investigated, and the resistances of films to salted water were evaluated. The increase in epoxy resin contents could improve the thermal stability and insulation properties of films, and decreased the water adsorption of films, but when the epoxy resin content reached 30% and above, the water solubility of resin became poor. After being immersed in 3.5 wt % NaCl solution, the electrical insulation strength of films were lower than that in dry state, and decreased as the immersed time prolonged. In particular, the electrical insulation strength loss of films increased significantly for epoxy resin content at 15% and below. Furthermore, the increase of epoxy resin content could improve the hardness and adhesion of films, but the flexibility of films became worse. On the basis of experimental, the epoxy resin content at 25% was appropriate to prepare waterborne epoxy‐modified tung oil resin. The resulting varnish may have potential as an immersing insulation varnish for the spindle of electric motor. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42755.