Effect of single Si_(1−x)C_(x)coating and compound coatings on the thermal conductivity and corrosion resistance of Mg-3Sn alloy

A single Si_(1−x)C_(x)coating and compound coatings were deposited on Mg-3Sn matrix alloy by magnetron sputtering method.Compound coatings included Mg or Mg/AlTi intermediates between Mg-3Sn substrate and Si_(1−x)C_(x)coating.The thermal conductivity of the Mg-3Sn alloy after coating was enhanced at room temperature.The results showed that the Mg-3Sn alloy coated with Mg/AlTi/Si_(1−x)C_(x)displayed higher thermal conductivity,its thermal conductivity after corrosion was 90.1 W/(m K)and 108.4 W/(m K)at 25℃and 100℃,respectively.Meanwhile,it was revealed that the Mg/Si_(1−x)C_(x)and Mg/AlTi/Si_(1−x)C_(x)compound coatings had nobler Ecorr and much lower i_(corr),higher Rp,compared with the bare Mg-3Sn and Mg-3Sn/Si_(1−x)C_(x)system,and improved the corrosion resistance of the magnesium substrate.

Preparation Process and Characteristics Analysis of Ni-Al System Intermetallic Compound Coatings

Ni-Al system intermetallic compound coatings were acquired on the substrates of Nickel base superalloy by thermal spray accompanied with metallurgy and diffusion process. The main phases in the coatings are NiAl and Ni3Al and the microstructure oi" the coatings are dense. The coatings bond well with the substrates and show excellent characteristics of oxidation-resistance at temperature as high as 1300 °C. The coatings have been applied successfully in industry.

Superior compound coatings prepared by low-temperature vanadium-nitrocarburizing duplex treatment

Superior compound coatings were prepared on CK45 steel surface by vanadium-nitrocarburizing duplex treatment in low-temperature salt bath.In this study,the microhardness,the phase constitution and the compositional distribution in the coatings prepared under different conditions were systematically characterized.The results indicated that the reactions among activated vanadium,carbon and nitrogen atoms occurred on the steel surface,leading to the formation of compound coatings composed of outermost and compound layers.The mechanism for the formation of compound layer as well as the growth kinetics of the layer was also discussed.Upon the duplex treatment,the wear and corrosion resistances of steel surface were significantly improved.It was found that the growth kinetics of compound layer obeyed the parabolic law,with the activation energy of 122.82 kJ·moL^(-1).

In situ polymerization coating and characteristics of coated NPK compound fertilizer

Controlled release NPK compound fertilizers were prepared by means of in situ polymerization of monomers on the surface of fertilizer granules at room temperature. Methacrylate, α-methyl acrylic acid, and ethylene dimethylacrylate were used as monomers, Dibenzoyl peroxide as initiator, and cobalt naphthenate, and triethyl amine as promoters. The structures of coating materials were characterized by IR spectra. The thermogravimetric analysis result indicated that the coating materials were of good thermal stability. The mean thickness of single coating measured with screw gauge was ca. 140 μm. The morphologies of uncoated and coated fertilizer granules analyzed by using scanning electron microscopy were changed from porosities and gullies to hills and plain. The release rate of coated compound fertilizers in water could be controlled by the hydrophicity and thickness of coating. The increase in coating hydrophicity caused the increase in release rate of fertilizer. The increase in thickness of coating slowed the release rate.

The Production of Organic-Inorganic Compound Film-Coated Urea and the Characteristics of Its Nutrient Release

The effect of different concentrations of natural macromolecular compound on the characteristics of nutrient release in the membrane materials of organic-inorganic compound film-coated urea was discussed, and the optimal concentrations for better nutrient release was proposed. The characteristics of nutrient release of film-coated urea were evaluated by soil column leaching experiment. Organic-inorganic compound film-coated urea showed good characteristics of nutrient release, which could be well simulated by Logistic curve. The two parameters in this curve, a and r, can be used to present nutrient release of film-coated urea, and followed the order of B 〉 C 〉 A and C 〈 B 〈 A, respectively, indicating that the release was stronger with the increasing concentration of natural macromolecular compound in the membrane, which implied better controllability of nutrient release. The concentration of 5% of natural macromolecular compound showed better characteristic of nutrient release and can be utilized as a membrane material combined with inorganic mineral powders to develop film-coated slow-release fertilizer.

Phase and Microstructure Properties of Laser Cladding NiAl Intermetallic Compound Coating at Elevated Temperature

The phase and microstructure properties of laser cladding single phase NiAl coating at elevated temperature of 800 °C were investigated by means of XRD,SEM,and HRTEM.It was found that Ni3Al phase with a fine equiaxial microstructure precipitated along NiAl grain boundaries via the solid-state diffusion of Ni atoms during heating process.NiAl and Ni3Al phases have a common<110>zone axis.The phase and microstructure evolutions of NiAl during heating process can acquire well understand the diffusion behavior of laser cladding NiAl intermetallic compound coating and provide better guidance on its production and practical use.

Separation of Phenolic Compounds and Organic Anions Using ODS Column Coated with Meso-octamethylcalix[4]pyrrole and Water as Eluent

Octadecylsilanized silica (ODS) was coated with meso-octamethylcalix[4]pyrrole to obtain a novel calix[4]pyrrole containing stationary phase for HPLC. Compared to ODS, the new stationary phase showed a relatively large retention and an improved separation for phenolic compounds and organic anions, using pure water as mobile phase. The results can be ascribed to the interaction between analytes and calix[4]pyrrole.

Volatile Organic Compound Emissions from Surface Coating Facilities: Characterization of Facilities, Estimation of Emission Rates, and Dispersion Modeling of Off-Site Impacts

Surface coating facilities are major sources of volatile organic compounds (VOCs) in urban areas. These VOCs can contribute to ground-level ozone formation, and many are hazardous air pollutants (HAPs), including xylene, ethylbenzene, and toluene. This project was conducted in order to provide information for updating the Texas Commission on Environmental Quality (TCEQ), USA, permit by rule for Surface Coating Facilities. Project objectives were: 1) To develop a database of information regarding surface coating facilities in Texas;2) To estimate maximum emission rates for various VOC species from surface coating facilities in Texas;3) To conduct dispersion modeling to estimate off-site impacts from surface coating facilities. The database was developed using 286 TCEQ permit files authorizing surface coating facilities in Texas during 2006 and 2007. The database was designed to include information important for estimating emission rates, and for using as inputs to the dispersion model. Hourly and annual emissions of volatile organic compounds (VOCs), particulate matter (PM), and exempt solvents (ES) were calculated for each permitted entity/ company in the database, according to equations given by TCEQ. Dispersion modeling was then conducted for 3 facility configurations (worst-case stack height, good practice stack height, and fugitive emissions), for urban and rural dispersion parameters, for 8-hour and 24-hour operating scenarios, and for 1-hour, 24-hour, and annual averaging times, for a total of 36 scenarios. The highest modeled concentrations were for the worst-case stack height, rural dispersion parameters, 24-hour operation scenario, and 1-hour averaging time. 108 specific chemical species, which are components of surface coatings, were identified as candidates for further health impacts review.

In Situ Synthesis of Titanium Nickel Intermetallic Compounds Layer and TiN Coating By Laser Cladding

Laser cladding,together with laser nitriding was used to synthesize a titanium nickel intermetallic compound layer on the nickel substrate and a TiN coating on the cladding layer. During the laser cladding, Ti and Ni powders were blown into the melting pool by a six-hole coaxial nozzle powder injection system. Exothermic reactions between Ti and Ni took place in the melting pool, and a cladding layer of titanium nickel intermetallic compounds was produced. Laser nitriding in a nitrogen-rich atmosphere followed the production of the cladding layer, and formed a golden yellow TiN layer over it. An optical and a scanning electron microscope were used to investigate the microstructures and measure the thicknesses of the cladding layer and the TiN layer. Phase identification was carried out by XRD. For the nitriding sample, the microhardness profile of the clad layer was tested. The optimal process parameters of the in situ synthesis of titanium nickel intermetallic compounds were obtained.

草酸预处理AM50镁合金表面快速原位制备 蒸汽Mg−Al LDH涂层的耐蚀性

通过暴露合金表面的金属间化合物(β-Mg17Al12和AlMn),研究草酸(OA)酸洗对AM50镁合金表面原位蒸汽Mg−Al层状双氢氧化物(LDH)涂层成膜机制和耐蚀性的影响。结果表明,OA预处理使镁合金表面金属间化合物比例显著增加,Mg−Al LDH在Al−Mn相周围成核并生长。当酸洗时间为45 s时,所得LDH涂层的厚度最大、耐蚀性最佳,与基体相比,其腐蚀电流密度降低3个数量级。最后,提出了AM50镁合金表面Mg−Al LDH涂层的成膜机制。

可重复使用飞行器用低密度烧蚀防热涂层研究

通过简便、高效的方法合成了硅氮化合物,以此为固化剂,分别完成了轻量化组元和烧蚀维形组元研究,最终获得了热稳定性优异、高温下尺寸稳定性高、抗烧蚀性能好的可重复使用飞行器用低密度防热涂层。结果表明,该防热涂层经过有限次静态烧蚀,密度、质量保留率均趋于稳定,力学性能能够满足使用需求。涂层经过高达10次石英灯烧蚀考核,防隔热性能无下降;经过5次风洞烧蚀考核,防热涂层抗烧蚀、防隔热性能无下降,进一步证明该种防热涂层经过有限次重复使用,仍能够对飞行器起到良好的热防护作用。

ZSM-5分子筛对典型涂装VOCs的吸附性能及机理研究

通过水热法成功合成了一系列宽硅铝比(50、100、150、300、500、800、1500、3000)的ZSM-5分子筛,旨在研究其对涂装行业典型挥发性有机物(volatile organic compounds,VOCs)的吸附规律。同时,结合分子筛表面的酸性位点,以解析硅铝比对分子筛吸附性能的影响机制。实验结果表明,丙酮的吸附能力主要受自身极性、支链结构和分子筛表面酸位点的影响。而乙酸丁酯、苯乙烯、对二甲苯、苯、甲苯的吸附性能会同时受到自身的分子量、分子直径、极性、分子结构和官能团的影响,分子量和分子直径大、极性强且具有支链结构的VOCs更容易被ZSM-5分子筛吸附。这6种VOCs中,ZSM-5分子筛对丙酮的吸附效果最好,硅铝比对其吸附性能的影响也最大。这是因为丙酮比其他VOCs更容易吸附在Lewis酸位点上,硅铝比的改变会影响酸位点的数量。低硅铝比的分子筛由于具有较多的酸位点,更适用于丙酮的吸附。

Ni镀层对Cu/Al钎焊接头界面组织与力学性能的影响

为探究Ni-P镀层对Cu/Al异种金属钎焊界面反应的影响,采用化学镀方法对T2紫铜进行化学镀镍处理,使用BAl88Si药芯钎料通过感应钎焊方法钎焊Cu/Al接头。采用扫描电子显微镜和电子背散射衍射技术对接头进行微观组织观察与物相分析,并对接头进行力学性能测试,分析镀层对Cu/Al接头微观组织结构及力学性能的影响,探讨钎焊过程中不同钎焊接头的界面形成机理。结果表明:无镀层接头在界面处形成了Cu_(9)Al_(4)和CuAl_(2)两层金属间化合物,有镀层接头界面处形成了Al_(2)Ni和Al_(3)Ni金属间化合物。无镀层接头的抗拉强度可达56.4 MPa,优于有镀层接头。接头均发生脆性断裂,断裂位置从无镀层接头的CuAl2和α-Al固溶体的界面处转变为有镀层接头的Al3Ni金属间化合物处。

复合海藻酸钠益生菌微胶囊研究进展

海藻酸钠微胶囊制备的研究一直是微胶囊技术的重要组成部分。由海藻酸钠制成的益生菌胶囊有孔隙和裂缝,通过利用不同壁材与海藻酸钠组合形成复合海藻酸钠微胶囊,可对益生菌起到更有效的保护作用。本文概述了三类材料对海藻酸钠微胶囊复合的研究进展,包括添加益生元刺激益生菌增长,共混纳米材料来提升机械性能,利用涂层成膜材料减少外部物质进入或内部芯材渗透。总结不同包埋结构的优缺点,并对益生菌微胶囊包埋的发展趋势进行了展望,以期为复合海藻酸钠益生菌微胶囊的科学研究提供参考。

铁路客车非金属材料VOCs释放规律试验研究

为了研究温度对铁路客车典型非金属材料中挥发性有机化合物释放量的影响,基于多气固比法和数据拟合法,对典型非金属材料(重防腐涂料、地板布、玻璃纤维增强塑料)的挥发性有机化合物释放规律进行了试验研究.首先,分别测量了4种不同气固比条件下的挥发性有机化合物浓度,得到挥发性有机化合物释放关键参数(初始可散发浓度和分配系数);然后,结合车辆工艺和运用场景,研究不同温度对挥发性有机化合物释放规律的影响.研究结果表明:材质的物理化学性能和温度是影响挥发性有机化合物释放特性的重要因素;温度从16℃升高至55℃,苯系物和醛类散发浓度均呈减小的趋势,重防腐涂料的初始可散发浓度减小为1.8%,其分配系数减小,地板布和玻璃钢的初始可散发浓度减小至0.3%以下,地板布的分配系数增大,玻璃钢的分配系数减小;苯系物是挥发性有机化合物的主要成分,其中以苯乙烯占比最大,甲苯、乙苯以及二甲苯占比排序规律不明显,并且未检测出苯;在铁道车辆烘焙法环保净化处理时,建议重防腐涂料的烘焙温度不小于55℃,地板布和玻璃钢的烘焙温度不小于45℃.

不同处理方式对鲜切马铃薯条保鲜效果研究

采用鲜切马铃薯条为主要原料,分别对其进行63℃热处理、护色剂浸泡处理、复合涂膜浸泡处理、乳酸链球菌素浸泡处理,以蒸馏水浸泡为对照组,置于4℃冰箱内低温保存3 d,每12 h测定失重率、褐变度、总酚含量、还原糖含量、淀粉含量等指标。结果表明:63℃热处理会加快鲜切马铃薯条褐变并较快失去食用价值,护色剂处理可减少褐变但对失重率影响较小,复合涂膜处理和乳酸链球菌素溶液处理均可抑制鲜切马铃薯条的褐变,减少失重率,降低淀粉向还原糖转变,减少总酚的损失。

含铈纳米防腐涂层在金属防护中的研究进展

为了提高常规防腐涂层的防护效果与使用寿命,研究人员致力于开发新型纳米复合材料涂层。含铈化合物是一种高效的金属及合金缓蚀剂,将含铈化合物与常规涂层结合构建含铈纳米防腐涂层越来越受到研究人员的重视。目前,将含铈纳米防腐涂层分为含铈纳米防腐涂层、含铈纳米容器涂层和含铈自愈合纳米防腐涂层3大类,针对具体的制备方法及材料,又将其分为7个小类。介绍了每类代表性涂层的主要制备方法、结构及应用效果,阐明了铈在防护过程中的主要作用过程及机理,总结了其中的共性特点。面对当前含铈纳米涂层大规模应用存在的困难及挑战,提出相应的解决方法及思路,并对未来发展方向进行了展望。

复合结构对微纳金属粉/单质硝胺炸药复合含能材料性能影响的研究进展

为了研究微纳米金属粉对单质硝胺炸药性能的影响和机理,总结了微纳米金属粉与单质硝胺炸药不同复合方式(如机械混合、核-壳包覆、金属嵌入和其他复合方式)下不同的微纳米金属粉对不同单质硝胺炸药的作用;分析了复合含能材料中金属粉粒径和含量等变化对不同单质硝胺炸药热分解特性和感度性能的影响;讨论了微纳米金属粉与单质硝胺炸药不同复合方式和制备方法对复合含能材料性能的影响。最后建议复合含能材料今后的研究重点为:拓展新的微纳米金属粉进行研究;深化微纳米金属粉与单质硝铵炸药之间的相互作用;研究新的含能材料复合结构;综合机器学习设计筛选新型复合含能材料和开拓含能复合材料工程方面应用的研究。附参考文献103篇。

激光表面织构技术调控材料摩擦学性能的研究进展

表面织构是提高工程材料摩擦学性能有效的表面改性方法之一。近年来多种表面织构技术已被应用于提高材料表面减摩耐磨性能,而在众多表面织构化技术中,激光表面织构技术由于具有加工速度快、生产效率高、可控性好等优点而被广泛应用。综述了激光表面织构的最新进展及应用,讨论了目前激光表面织构技术存在的问题及解决方法,总结了3种不同加工原理下的激光处理方法存在的问题,包括形状参数难控制、精度较差及灵活性较低等,并介绍了液相辅助加工技术在激光表面织构技术中的应用,同时分析了不同工艺参数包括密度、形状及深度等对材料摩擦学性能的影响。综述了激光表面织构技术复合涂层技术的研究现状,其中激光表面织构与非金属或金属涂层复合,包括氧化石墨烯填充PTFE涂层复合激光表面织构、复合热丝化学气相沉积增强激光表面织构、复合电液雾化增强激光表面织构及复合激光熔覆技术增强激光表面织构。总结了激光表面织构技术结合不同润滑技术对材料摩擦学性能的影响。最后展望了激光表面织构在各个领域的未来发展方向。

铝合金与镀铜钢CMT熔钎焊技术研究

采用Al Si12药芯焊丝作为填充材料,对2 mm厚的6082铝合金与Q235B镀铜钢进行对接冷金属过渡(CMT)熔钎焊接试验,研究不同焊接速度和镀铜层厚度对接头焊缝成型、界面组织和力学性能的影响,探讨Cu元素对金属间化合物层(IMC)生长的影响。结果表明:当焊接速度为350 mm/min时,铝在钢板正反面均有良好的润湿铺展,焊缝成型美观;IMC层厚度过大或过小均会对接头性能产生不利影响,当镀铜层厚度为10μm时,IMC层厚度为2.38μm,接头抗拉强度达到峰值138.7 MPa,相较于未镀铜接头的提高了31.9%,接头断裂于铝侧热影响区。镀铜层可以抑制界面层中θ-Fe(Al,Si)_(3)相的生成,阻碍Al、Fe反应,降低IMC层厚度。适当的镀铜层厚度可以有效改善接头的力学性能。镀铜层厚度过大促使Al_(2)Cu相产生,成为接头的薄弱区域。