A Methodology for Estimating Kinetic Parameters and Reactivity Ratios of Multi‐site Type Catalysts Using Polymerization,Fractionation, and Spectroscopic Techniques

This work describes a polymer reaction engineering framework for understanding how catalyst kinetic parameters affect the microstructure of polyolefins made with single‐ or multi‐site catalysts. Moreover, a methodology for deconvolution and kinetic parameters estimation is presented to estimate the reactivity ratios of multi‐site catalysts based on the combination of polymerization, fractionation, and spectroscopic techniques, namely, gel permeation chromatography‐IR and carbon‐13 nuclear magnetic resonance spectroscopy. The methodology capabilities are then demonstrated and validated using a case study simulated via a Monte Carlo model including random noise in order to better represent experimental result uncertainties. The methodology can reverse engineer experimental results and estimate all relevant reaction performance parameters.     

Stabilization of self‐assembled microdroplets using short chain alcohols

The condensation of water vapor on a volatile polymeric solution leads to a porous surface after evaporation of both solvent and water. However, the stabilization of the water microdroplet is of great importance, which can be achieved using specific polymer or adding a third substance to the polymer solution. Short chain alcohols (methanol, ethanol, and n‐propanol) are utilized to fabricate a self‐assembled porous honeycomb film of linear, low molecular weight polystyrene using the breath figure technique. A combination of breath figure processing and the effect of alcohol on a water droplet can stabilize the pattern and make pores on the surface of the polymer film. The quality of the porous honeycomb film is strongly dependent on the type of alcohols and the concentration of polymer. In a specific range of polymer and alcohol concentration, pores cover all the surface of the polymer film. This method offers the possibility of producing a honeycomb structure with no trace of additive residual after the fabrication process and avoiding polymer modification. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 709–718     

Fabrication and microstructural characterization of functionally graded porous acrylonitrile butadiene styrene and the effect of cellular morphology on creep behavior

The ability to control material properties in space and time for functionally graded viscoelastic materials makes them an asset where they can be adapted to different design requirements. The continuous microstructure makes them advantageous over conventional composite materials. Functionally graded porous structures have the added advantage over conventional functionally graded materials of offering a significant weight reduction compared to a minor drop in strength. Functionally graded porous structures of acrylonitrile butadiene styrene (ABS) had been fabricated with a solid‐state constrained foaming process. Correlating the microstructure to material properties requires a deterministic analysis of the cellular structure. This is accomplished by analyzing the scanning electron microscopy images with a locally adaptive image threshold technique based on variational energy minimization. This characterization technique of the cellular morphology is analyst independent and works very well for porous structures. Inferences are drawn from the effect of processing on microstructure and then correlated to creep strain and creep compliance. Creep is strongly correlated to porosity and pore sizes but more associated to the size than to porosity. The results show the potential of controlling the cellular morphology and hence tailoring creep strain/compliance of ABS to some desired values. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 795–803     

Ambiguous anti-fouling surfaces: Facile synthesis by light-mediated radical polymerization

In an attempt to create a polymer brush-based platform for the systematic study for anti-biofouling surfaces, the benefits of surface initiated, visible light-mediated radical polymerization are utilized to fabricate well-defined, chemically ambiguously patterned surfaces. A variety of analytical tools are used to illustrate the precise tuning of surface chemistry and thoroughly characterize spatially well-defined, hydrophilic/hydrophobic surfaces composed of poly(ethylene glycol methacrylate) and poly(trifluoroethyl methacrylate) with chemical definition on the micron scale. Advantages of both visible light-mediated photopolymerization and traditional copper-catalyzed atom transfer radical polymerization are combined to achieve both high spatial control and expanded monomer tolerance. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 253–262     

Emulsion Copolymerization of Vinyl Acetate and Vinyl Silanes: Kinetics and Development of Microstructure

The batch emulsion copolymerization of vinyl acetate with different vinyl silane functional monomers (vinyl trimethoxysilane [VTMS], vinyl triethoxysilane [VTES], and vinyl silanetriol [VSTO]) is studied. The nature of the silane strongly affects the development of the microstructure and crosslinking ability of the latexes. A combination of techniques (Soxhlet extraction, centrifugation, assymetric‐flow field flow fractionation AF4/MALS/RI) shows that the factor controlling the molar mass and crosslinking density is the degree of hydrolysis of the alkoxysilane, producing higher molar masses and degrees of crosslinking when the degree of hydrolysis is high. Thus, the copolymer containing VSTO produced a very crosslinked latex, the one with VTMS produced a latex with a low degree of crosslinking in the wet state that can yield high degrees of crosslinking upon drying, and the latex with VTES do not produce significant amounts of crosslinking neither before nor after drying.     

La distribution on the crater surface of W-1%La2O3 produced by a single laser pulse

The W-1%La₂O₃ alloy has been irradiated by a single laser pulse (λ = 1064 nm) to simulate transient thermal loads of high energy occurring in a tokamak under operative conditions. A zone with a diameter of ~2 mm, namely, much larger than the focal spot, results to be affected by the pulse, and a crater of about 300 μm is observed in its center. La₂O₃ particles are not present inside the crater. The change of surface morphology is accompanied by elemental redistribution. Multipoint XPS analysis evidenced that the concentration of La is very low in the crater and increases moving toward the border of the affected zone while that of W shows an opposite trend. The composition changes involve only the outmost 5 nm of the sample: through depth profiling, no differences of chemical composition were detected deeper in the alloy between the center and external border of the affected area.     

玫瑰花状氢氧化钴的结构和浸润性

在没有任何表面活性剂条件下,通过简单的方法首次合成了玫瑰花状β-Co(OH)₂微晶。玫瑰花状β-Co(OH)₂微晶宽3~5μm,厚2~3μm,是由平均厚度为15nm的纳米片所组成。玫瑰花状β-Co(OH)₂组成的薄膜的接触角为158.5°±1.2°,表面处于任意的角度,水滴都不会滴落。     

Effect of Y2O3 on microstructural characteristics and wear resistance of cobalt‐based composite coatings produced on TA15 titanium alloy surface by laser cladding

The effects of Y₂O₃ on the microstructure, phase composition of the coatings, microhardness and wear resistance of cobalt‐based composite coatings prepared by laser cladding were investigated. The TA15 titanium alloy was selected as substrate which the cobalt‐based composite powder with different content of Y₂O₃ was cladded on. The microstructure of the coatings was observed by scanning electron microscope (SEM) and metallurgical microscope. The phase structure of the coatings was determined by X‐ray diffraction (XRD), and the microhardness and wear resistance of the coatings were measured by hardness tester and wear testing machine. The results show that the rare earth oxide Y₂O₃ can refine and purify the microstructure of the coatings, reduce the porosities and cracks and improve compactness of the coatings. Moreover the addition of Y₂O₃ improves the microhardness of the coatings and reduces the friction coefficient, thus improving the wear property of the coatings. And the wear resistance of the coating with Y₂O₃ has improved about 50 times; the highest value of microhardness in the coating is HV1181.1. And 0.8 wt% content of Y₂O₃ in the coating is the best choice for improving the microhardness and wear resistance of the coating. It is feasible to improve the microstructure and tribological properties of laser cladding coatings by adding of Y₂O₃. Copyright © 2014 John Wiley & Sons, Ltd.     

氧化钙对胜利褐煤焦水蒸气气化反应性能及微结构的影响

研究了CaO对胜利褐煤焦水蒸气气化反应性能及微结构的影响。脱除矿物质的胜利褐煤混合不同含量的CaO后在1 100 ℃下进行热解得到相应的煤焦,采用BET、XRD和Raman技术对其进行表征,同时在微型固定床反应器上对所制得煤焦进行水蒸气气化实验。比较添加CaO不同含量煤焦的反应性表明,添加2%(质量分数)的CaO对煤焦水蒸气气化的催化作用很小,而CaO添加量增大到5%时,煤焦的气化反应性能明显提高。煤焦比表面积随CaO添加量的提高而增大。XRD结果表明,在热解过程中,CaO能有效地抑制煤焦向石墨化方向发展趋势。煤焦002和100峰的峰强度随CaO添加量的增加而降低,且煤焦芳香度从66.8%降至39.9%。Raman光谱结果表明,随着CaO添加量的增加,I_D/I_G由1.363增加至1.541,I_G/I_all由0.423减少到0.394。意味着由于Ca的催化作用,煤中大芳香环结构的裂解速率明显增加,且随CaO添加量的增多,煤焦的无序化程度和晶格缺陷均增大。     

水蒸气对褐煤原位气化半焦反应性能及微观结构的影响

为了揭示水蒸气对半焦反应性和微观结构的影响,在自制两段新型反应器上依次进行了褐煤干燥、热解及"热"焦的水蒸气原位气化研究。利用TGA、BET和Raman光谱仪,对原位气化半焦进行反应性和微观结构解析。结果表明,在反应温度为600 ℃时,水蒸气对半焦转化率、反应性及微观结构影响很小。温度达到700~900 ℃,在半焦与水蒸气接触的前2 min,虽然半焦转化率变化不大,但其反应性、小环(3~5个芳环)与大环(≥6个环)体系之比及含氧官能团却急剧降低;大于2 min,半焦转化率逐渐增大,反应性、小环与大环之比及含氧官能团缓慢降低;而半焦孔结构在2 min 前后却具有基本一致的变化趋势。半焦与水蒸气接触的前2 min,小环与大环之比和含氧官能团急剧降低是导致反应性显著降低的重要因素,大于2 min,芳环体系的变化是导致反应性进一步降低的原因。