水滑石复合水泥基材料氯离子吸附能力的研究进展

以氯离子为诱导的钢筋锈蚀是造成混凝土耐久性问题的主要原因,其本质是氯离子通过材料基体的多孔结构在水泥基材料中扩散,并逐步迁移到钢筋表面,发生不利的物理化学反应。水滑石即层状双金属氢氧化物(LDHs)是一种新型延缓钢筋锈蚀的外掺材料,具有独特的层状结构和离子交换性质,可在特定的介质溶液中将客体阴离子与层间阳离子进行交换,达到吸附氯离子、延长混凝土结构服役寿命的目的。本文介绍了水滑石的结构性质、制备方法及氯离子吸附机理,总结了不同类型水滑石的氯离子吸附能力及相关研究成果。研究结果表明：水滑石复合水泥基材料的氯离子吸附性能受LDHs材料制备工艺、水泥基材料中孔隙液pH值及氯离子浓度影响,高温焙烧处理的水滑石对氯离子吸附效果更好;当LDHs掺量控制在1%～3%(质量分数)时,有利于改善水泥基材料的抗氯离子渗透性能。     

矿物掺合料对水泥基材料孔溶液中氯离子浓聚的影响

研究了不同矿物掺合料掺量对水泥基材料孔溶液中氯离子浓聚系数的影响。结果表明:随着矿物掺合料掺量的增加,氯离子浓聚系数降低。在NaCl溶液中浸泡91 d后,除了矿粉取代量为20%的试件,其它掺入矿物掺合料硬化浆体试件的氯离子浓聚系数均低于纯硅酸盐水泥试件。随浸泡液NaCl浓度增大,氯离子浓聚系数显著降低。氯离子吸附能力与硬化水泥浆体内水化产物的特性和数量、Ca(OH)_2含量和孔结构有关。     

硅藻土增强PVC基木塑复合材料性能研究

在聚氯乙烯(PVC)基木塑复合材料中添加功能性材料硅藻土,通过熔融共混挤出制备了功能性木塑复合材料,研究了硅藻土用量对复合材料力学性能和甲醛吸附能力的影响。结果表明:当硅藻土用量为5份时,复合材料的力学性能均有所提高,进一步增加硅藻土用量则其力学性能呈现下降趋势;硅藻土可提高复合材料的甲醛吸附能力,当硅藻土用量为25份时,吸附12 h后复合材料甲醛吸附量比未添加硅藻土时提高了88.4%,而且复合材料的甲醛吸附量随着硅藻土用量的增加而增大。     

氯离子结合及其对水泥基材料微观结构的影响

氯离子引入水泥基材料之后,部分会同某些水泥相发生化学反应,部分被吸附在水化产物或者孔壁上,前者称为氯离子化学结合,后者称为氯离子物理吸附,它们统称为氯离子结合.化学结合主要是形成Friedel's盐的过程,物理吸附主要是C-S--H凝胶对氯离子的作用.许多其它因素,包括辅助胶凝材料(粉煤灰、矿粉和硅灰)对氯离子结合也有显著影响.由于氯离子结合,水泥基材料的微观结构也发生了一些改变.熟知水泥基材料对氯离子的结合作用及氯离子引进水泥基材料之后微观结构的改变,可以为钢筋混凝土结构工程使用寿命设计和预测提供科学理论依据.     

三维孔道硅基介孔材料对Cd2+的吸附特性

采用三嵌段聚合物F127(EO106PO70EO106)为结构导向剂,正硅酸乙酯为硅源,使用无机盐(K2SO4)以增加有机物种的自组装能力,在稀酸(0.5mol/L)条件下合成了三维孔道硅基介孔材料。研究表明:介孔材料具有良好的晶体结构,属三维立方孔空穴Im3m结构;介孔排列有序,孔径分布均匀,平均孔径为3.3nm,孔容为0.51cm3/g,比表面积为611.2 m2/g。探讨了介孔材料用量、吸附液pH值、温度和初始浓度等因素对Cd2+吸附性能的影响,结果表明,介孔材料吸附Cd2+的适宜工艺条件为介孔材料用量4 g/L、吸附液pH=7、吸附温度40℃。用Langmuir和Freundlich等温吸附方程拟合了三维孔道硅基介孔材料对Cd2+的吸附过程,表明吸附过程为单层吸附,40℃时最大理论吸附量为9.253mg/g。     

电气石/硅藻土基内墙砖的制备及室内甲醛净化

以硅藻土为主要原料,添加适量电气石粉和烧结助剂,采用超细湿式研磨工艺制备釉浆,并浸渍在硅藻土基多孔陶瓷表面及孔道,通过低温煅烧,制备电气石/硅藻土基内墙砖.结合X射线衍射、扫描电子显微镜、傅里叶变换红外光谱仪等手段对材料进行了表征;以甲醛气体为目标污染物,探讨了材料对其吸附和降解能力.结果表明:所制备的电气石/硅藻土基内墙砖,硅藻土原始孔结构与颗粒堆积形成的孔隙构成了有机整体;材料釉层经870℃煅烧,电气石的结构和性能并未发生改变;电气石/硅藻土基内墙砖对甲醛气体具有很好的吸附和降解能力,1 m3的环境舱内初始浓度为0.303 mg/m3的甲醛经5h的净化,其浓度降至0.0782 mg/m3.     

影响水泥基发泡保温材料孔结构的因素研究

以普通硅酸盐水泥(P.O 42.5)为主要胶凝材料,发泡剂采用植物改性泡沫剂,以膨胀珍珠岩和聚苯颗粒作为轻质保温骨料,同时掺加适量玻璃纤维,运用物理发泡工艺制备了水泥基轻质发泡保温材料.通过电子扫描显微镜分别研究了水灰比、玻璃纤维和轻骨料(膨胀珍珠岩和聚苯颗粒)对水泥基发泡保温材料试样中孔结构及其分布的影响,同时探讨了孔结构及其分布与材料导热系数之间的相互关系.实验结果表明:水灰比、玻璃纤维、轻骨料(膨胀珍珠岩和聚苯颗粒)的加入量与水泥基发泡保温材料的孔结构及其分布状态密切相关.     

活性炭吸附甲烷和甲苯的分子模拟研究

以石墨片微元构建的多孔碳材料作为活性炭的结构模型,采用巨正则蒙特卡罗方法(GCMC)和分子动力学方法(MD),从分子层面研究甲烷和甲苯在活性炭中的吸附和扩散特性. 结果表明,石墨片微元大小对多孔碳材料吸附甲烷和甲苯有一定影响,37个碳环构成的多孔碳材料是最佳的吸附结构;甲烷气体在活性炭材料中扩散较快,甲苯在活性炭中扩散较慢,随碳环碳原子数增加,气体在多孔碳材料中的自扩散系数逐渐增大;引入基团会使最优密度向高密度方向偏移,用不同基团表面改性的吸附量顺序为羟基>氨基>羧基>未改性,基团引入会改善材料的孔结构,有利于吸附量的增加.     

热孔计法表征水泥基材料孔结构

根据提出的热孔计法表征水泥基材料孔结构方法及其热力学计算模型,研究了测试过程密封性、样品质量、升降温速率等因素对热孔计法测试水泥基材料试验结果的重现性、分辨率或精确性的影响,并比较了热孔计法与氮吸附法两种测试结果的异同。结果表明：当所取样品质量在30mg以上,测试速率控制为1℃/min时,热孔计法降温阶段的测试结果可用于表征水泥基材料孔结构,且与氮吸附测试结果相近。确定了热孔计法测定水泥基材料孔结构的基本测试参数。     

水泥多孔材料及Cr(Ⅲ)动态吸附性能研究

以预制泡沫法制备干密度为400 kg/m3的水泥多孔材料,并将其作为吸附剂,采用动态吸附法研究了吸附柱高度、初始浓度以及液体流速对模拟废水中Cr(Ⅲ)的吸附性能影响,结果表明:吸附柱高度为19 cm时,去除质量达到607 mg;初始浓度为85 mg/L时,吸附效率为81.07％;溶液的流速为7.5 mL/min时,去除Cr(Ⅲ)的量为607 mg,吸附效率为76.93％;Thomas模型拟合证明水泥多孔材料对Cr(Ⅲ)的动态吸附过程中,吸附剂外表面扩散和内扩散不是反应的速率控制步骤.可见水泥多孔材料对Cr(Ⅲ)具有较好的吸附效果.     

Properties of powder coatings in load carrying construction

The present study describes the mechanical behavior of powder coatings used under very high compressive loads in clamping force joints. Carboxyl functional polyester powder coatings cured with hydroxyl functional β-hydroxyalkylamides with variations in coating thickness and amount and type of filler, have been studied. The coatings were subjected to conventional tests for coatings and polymers and also to specially designed tests developed to study the behavior of powder coatings in clamping force joints. The specially designed tests were used to study the coatings under compressive loads, and the relation between the results from these test methods and from conventional tests is discussed. The results show the importance of coating thickness in order to achieve the desired mechanical properties of a coating when used under high compressive loads. These loads put high demands on the stability of the coating, and the defects must be kept to a minimum. Increased thickness will give rise to more defects in the coating, especially voids and blisters due to the evaporation of water formed during the curing of the polyester powder coating. The surface roughness of the coating is also affected by the coating thickness, but the main influence originates from the type and amount of filler used. A rough surface will give rise to stress concentrations and increased plastic deformations in the coating, impairing the properties of the clamping force joint.     

Model-based analysis of photoinitiated coating degradation under artificial exposure conditions

Coating degradation mechanisms of thermoset coatings exposed to ultraviolet radiation and humidity at constant temperature are investigated. The essential processes, photoinitiated oxidation reactions, intrafilm oxygen permeability, water absorption and diffusion, reduction of crosslink density, and development of a thin surface oxidation zone are quantified and a mathematical model for degrading coatings developed. Front-tracking techniques are used to determine the rate of movement of the oxidation and ablation fronts, the positions of which define the extension of the surface oxidation zone. Three previous and independent experimental investigations with two-component, densely crosslinked, epoxy?Camine model coatings were selected for verification of the mathematical model. Simulations can match and explain transient mass loss and coating thickness reduction data and are in agreement with infrared measurements of carbonyl groups formed in the surface zone. The thickness of the stable surface oxidation zone, which is established after an initial ablation lag time, is estimated by the model to 0.5?C2???m in good agreement with previous measurements. Simulated concentration profiles of active groups, oxygen, and radicals in the stable surface oxidation zone are presented and analyzed. The mathematical model can be used for obtaining a quantitative insight into the degradation of thermoset coatings and has potential, after further development, to complete commercial coatings and dynamic exposure conditions, to become a supplementing tool for predicting in-service coating behavior based on accelerated laboratory measurements.     

Effect of air oxidation of Rayon-based activated carbon fibers on the adsorption behavior for formaldehyde

The tailoring of pore surface chemistry of activated carbon fibers is shown to be an effective method for improving the adsorption efficiency of various volatile chemical compounds (VOCs). An oxidation treatment with air resulted in a significant increase in the adsorption capacities and breakthrough time for Rayon-based activated carbon fibers (ACFs) in removal of formaldehyde. The porous structure parameters of Rayon-based ACFs were determined with standard nitrogen adsorption analysis. The pore surface chemistry of samples under study was analyzed by Fourier Transform Infrared spectra (FTIR). Thus to some extent, the relationship between the adsorption properties, porous structure and pore surface chemistry was revealed.     

Investigation of the dependence of the properties of the phenoplasts of phenolaniline–formaldehyde resol resin on the degree of kaolin filling and on their physical structure

An investigation was made of the dependence of 13 types of standard physical and mechanical and electric insulation properties of phenoplasts of phenolaniline–formaldehyde resol resin on their filler content in a broad range of 14 to 47 vol-%. It is found that the respective curves have more than one maximum and periodically pass through several maximums and minimums. The periodicity is more clearly seen in the curves reflecting the dependences of the properties on the calculated mean thickness of the resin adsorption coating on the filler particles. With these curves the extremal values appear over more or less even intervals of the adsorption coating thickness. The periodicity relating to the change in this thickness is explained by the periodic formation of particles of a new type of filler in the points of a whole number of monoglobular adsorption coatings, and of a maximum amount of globules oriented toward them in the points of a whole number and a half monoglobular adsorption layer. The periodical appearance of an oriented (regarding the particles) globular layer determines the appearance of periodical positive and negative orientation effects in the properties of the phenoplasts. The diagram we propose is confirmed by the regular periodical change in the various properties as well as by the measured ratios of the mean thicknesses of the adsorption coating in the points of the extremums of the various types of curves, determined by the differential curves method.     

Experimental and computational study on sintering of ceramic coating layers with complex porous structures

This study investigated the sintering behavior of an yttria-stabilized zirconia coating for thermal barrier coatings (TBCs) with a complicated porous structure via both experiment and simulation using the finite element method for samples with only a coating (free coating) and samples with coating on a substrate (constrained coating). Sintering and grain growth proceeded from the bottom of the coating, and the coating bent convex upward in the free coating. In the constrained coating, sintering and grain growth proceeded in a manner similar to the free coating; however, the degrees of sintering and grain growth were small. Furthermore, sintering and grain growth were delayed because of substrate constraints. As a simulation result, the free coating was bent in a manner similar to the experiment. The experimental results could be reproduced in terms of time dependency and temperature dependency. The decrease in the porosity of the constrained coating was delayed compared with that in the free coating because of substrate constraints. This simulation result was able to reproduce the experimental results. Thus, the sintering behavior for the complex porous structures of TBCs can be predicted by experimental research and simulation, which could aid in the development of a prediction technology for the delamination of coatings (TBC lifetime).     

Template-directed synthesis of porous alumina particles with precise wall thickness control via atomic layer deposition

Highly porous alumina particles with precise wall thickness control were synthesized by atomic layer deposition (ALD) of alumina on highly porous poly(styrene-divinylbenzene) (PS-DVB) particle templates. Alumina ALD was carried out using alternating reactions of trimethylaluminum and water at 33 °C. The growth rate of alumina was ∼0.3 nm per coating cycle. The wall thickness can be precisely controlled by adjusting the number of ALD coating cycles. Thermo-gravimetric analysis, X-ray diffraction, nitrogen adsorption, scanning electron microscopy, and transmission electron microscopy were used to characterize the fabricated porous alumina particles. The effect of number of ALD coating cycles and calcination temperature on the mesoporous structure of the alumina particles was investigated. γ-Alumina was formed at temperature above 600 °C. Porous alumina particles with a surface area of 80-100 m²/g were obtained and thermally stable at 800 °C. The pore volume of the porous particles can be as high as 1 cm³/g after calcination at 800 °C. Such porous alumina particles may find wide application in nanotechnology and catalysis.     

污损释放型涂料的防污与减阻性能研究

制备了一种以有机硅树脂为基体树脂的污损释放型涂料,并对其防污性能与减阻性能进行了研究。结果发现,硅油能够渗出到涂层的表面,引起表面形貌和表面能的强烈变化。随着硅油渗出量的增加,涂层表现出的"结构表面能"越大,并有利于防污性能的增强。污损释放型涂层的表面粗糙度远小于通用自抛光型涂层的表面粗糙度,并且在不同雷诺数下均表现出了良好的减阻效果。所研制的污损释放型涂料同时具有良好的防污性能与减阻性能,能够为我国商品化环境友好型防污减阻涂料的研发提供借鉴。     

碳纤维增强碳复合材料表面多层复合涂层中SiC和TiC内层的比较(英文)

采用包埋法制备了碳纤维增强碳(carbon fiber reinforced carb on composites,C/C)复合材料表面多层涂层,包括SiC,TiC内层,SiC,TiC中间层以及SiC+TiC复合外层。利用场发射扫描电镜和X射线衍射对其表面和断面的结构进行研究。结果显示:和TiC内层相比较,SiC内层较厚而且致密,具多孔结构且和C/C复合材料结合紧密;TiC内层较薄且和C/C复合材料结合松散。制备的SiC+TiC复合外层由SiC,TiC和Ti3SiC2组成。     

TWO-SIDED DRYING OF COATINGS ON POROUS WEBS

A relatively simple spreadsheet-based model of the drying of coated webs has been extended to cover coatings on porous webs Two cases have been modeled. In one the coating is assumed to fully saturate the porous web, with the drying being completely symmetrical about the center plane except for differences in the air velocities and temperatures. The drying rate in the constant rate period is then increased, but because of the greater thickness that the coating now occupies, diffusion is much slower and the falling rate drying can be slower, even though it takes place on both sides. In the other case the coating is assumed to lie on top of the porous web, with solvent vapor diffusing through the web. Here the constant rate drying is only slightly faster than in the base case, but in the falling rate period the drying can be greatly accelerated Both models predict the temperatures and solvent levels throughout the length of the dryer.     

Effects of graphene content in alkaline silicate electrolyte on AA1060 pure aluminum micro-arc oxidation coating

Ceramic coatings were obtained by micro-arc oxidation (MAO) on the surface of AA1060 pure aluminum in alkaline silicate electrolyte with the addition of graphene. The effects of graphene contents in the range of 0–.30 g/L in the electrolyte on surface morphology, corrosion resistance, and wear resistance of the ceramic coatings were investigated. The outer surface structure, outer surface element content, coating cross-section structure, coating cross-section element content, coating/substrate interface structure, and coating phase were characterized by scanning electron microscope and X-ray diffraction. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior of MAO samples in a 3.5-wt% NaCl solution. In addition, the resistance to sliding and abrasive wear of the oxide coating were studied experimentally. The results show that the alkaline silicate electrolyte with the addition of graphene has a significant effect on the characteristics of MAO coating. The performance of micro-arc oxide coatings is best when the graphene content in the electrolyte is .15 g/L, the average thickness of the film is 7.24 μm, the average pore size is 6.07 μm, the impedance value is approximately 4.01 × 106 Ω, and its friction coefficient is .55.