硫酸处理对伊利石和蒙脱石结构和形貌的影响

由于伊利石和蒙脱石结构四面体中Al³⁺代Si⁴⁺的数量不一样，所以层电荷数不同，酸处理过程结构的破坏程度也不同.本文以浙江安吉膨润土和吉林安图伊利石为原料，用硫酸和过氧化氢溶液对两种原料进行酸处理对比实验研究.我们对原料和酸处理样品的物相、结构、热学属性、谱学特性及微观形貌进行了表征分析.结果表明，蒙脱石样品在酸处理浓度2 mol/L时其结构被破坏，随着酸处理浓度的升高，片层表面由光滑平整变成边缘卷曲至层间坍塌；而伊利石样品在酸处理浓度6 mol/L时其结构和形貌基本完好；蒙脱石的耐酸蚀性能不如伊利石.本文的研究结果对伊利石和蒙脱石的应用开发具有一定的意义.     

四川龙泉山地区膨润土改性研究

对四川龙泉山地区膨润土经过提纯、钠化处理,再用十六烷基三甲基澳化铵(CTMAB)进行了有机化改性试验研究.对改性土的X射线衍射分析、红外光谱分析及TG-DTA分析证明改性成功.得出有机化膨润土的最佳工艺条件为:当钠化膨润土矿浆的质量浓度为129.6g/L时,CTMAB加入量为钠化膨润土质量的45％,反应温度为65℃,反...     

湖南修梅膨润土有机改性研究

将湖南修梅膨润土钠化,对该钠化膨润土的阳离子交换容量和吸蓝量进行了测定,确定了修梅膨润土中蒙脱石的百分含量;将钠化膨润土用十六烷基三甲基溴化铵作覆盖剂对其进行有机改性,探讨了反应温度、反应时间等因素对改性反应影响,确定了较佳的工艺条件;粘度测试、红外及热重-差热分析表明,湖南修梅膨润土的有机改性是有效的.     

Zr/Al基柱撑蒙脱石的热行为

采用X线衍射分析、红外光谱分析以及氮气吸附-脱附分析等方法对Zr/Al基柱撑蒙脱石及其热处理(300～700 ℃)产物进行研究.研究结果表明:随着热处理温度升高,Zr/Al基柱撑蒙脱石的结晶程度变差;柱撑蒙脱石层间聚羟基阳离子柱撑剂发生脱水脱羟基反应,柱撑剂中的质子进入Al-O八面体层,与Si-O-Al键反应形成了Si-OH和Al-OH键;在500 ℃时,Zr/Al基柱撑蒙脱石热稳定性较强;当温度达到600 ℃以上时,柱撑蒙脱石脱水脱羟基本完全,比表面积大幅度减小,层结构遭到严重破坏,(001)面网间距从1.927 8 nm减小至 1.385 2 nm,比表面积从177.90 m2/g减小到85.19 m2/g,而平均介孔孔径则从4.172 nm增至8.592 nm.     

HTMAC和STAC对膨润土的有机改性及其结构性能表征

以新疆夏子街地区日月雷提纯膨润土为原料,考察了NaNO3含量、2种季铵盐对其改性的影响以及有机膨润土黏度的影响因素,并借助XRD和SEM表征了产物的基本结构.结果表明:当硝酸钠质量分数为2%,HTMAC为1.6mmol/g,STAC为1.4mmol/g、浆液的pH为9、反应温度60℃、反应1.5h、烘干14h时,工艺最优,制备的有机膨润土黏度较大.结构分析表明:2种有机土的d(001)值分别从提纯土的1.387 2nm增大到1.961 7nm和2.423 8nm,说明有机季铵盐阳离子已进入膨润土的蒙脱石层间.     

聚酰亚胺薄膜层叠体热处理过程中的结构演变

将双向拉伸PI薄膜,层叠后经800℃炭化所得样品在热压机中进行从2 500℃到2 800℃的高温石墨化处理制得了高定向石墨材料。借助SEM、XRD、四探针法等测试手段分析了PI薄膜层叠成型体在热处理过程中尺寸、传导性能、微观结构等的变化。结果表明石墨化处理后,样品径向增大,厚度减小;2 800℃处理后材料层间距接近单晶石墨的理论层间距,表现出了较高的石墨化程度,且具有高的取向性和传导性能,根据电阻率与热导率的相关公式推得其热导率为1 000 W/(m.K)～1600 W/(m.K).在整个热处理过程中,所生成的物质继承了原料分子的取向性。     

水环境下蒙脱石层间CH_4吸附行为的分子模拟研究

选取钠蒙脱石作为研究对象,通过分子模拟的方式来研究蒙脱石层间水对CH_4吸附的影响。首先,构建钠蒙脱石层间结构模型,采用分子力学方法对模型进行优化,然后对优化后的结构模型使用巨正则系综蒙特卡罗方法(GCMC)进行吸附模拟,将吸附模拟得到的模型结构进行分子动力学模拟。研究表明,当温度一定时,随着层间水含量的增加,CH_4的吸附量逐渐减小。钠蒙脱石层间水和CH_4存在竞争吸附。H_2O与钠蒙脱石层间结构容易形成氢键,故钠蒙脱石优先吸附H_2O。     

膨润土水化膨胀行为简化计算

在已有膨润土微观结构研究的基础上,假设其中蒙脱石的膨胀完全填充土中孔隙,得到蒙脱石膨胀体积应变sεv的表达式.根据sεv计算出水化后蒙脱石矿物层距离的一半和基于Gouy-Chapman理论的扩散双电层的厚度,并对二者进行了比较.在给定的计算参数下,当饱和含水量为80%~90%时,膨润土的孔隙完全由结合水填充.     

有机膨润土的制备及对造纸废水中酸性大红3R的吸附

对信阳上天梯钙基膨润土进行钠化后,用湿法加入溴代十六烷基三甲铵进行有机改性,研究改性后的膨润土吸附造纸废水中酸性大红3R(Acid scarlet 3R)的情况.实验表明:控制温度为65℃,pH值6,加入量6 g/L时对色素的去除率达97%.     

六钛酸钠晶须的高温热稳定性研究

以TiO(OH)_2和Na_2CO_3为原料、NaCl为助熔剂,在900℃温度下制备了六钛酸钠晶须,并对其进行不同温度条件下的热处理,借助DSC、XRD、SEM及UV-VIS-NIR对六钛酸钠的热解过程、物相组成、显微形貌及近红外反射性能进行分析测试,研究了其高温热稳定性。结果表明,经900℃热处理后,六钛酸钠晶须发生部分分解,生成金红石型TiO_2,随着热处理温度的升高,六钛酸钠晶须分解量不断增大且微观形貌随之改变;当热处理温度不高于1200℃时,样品近红外反射性能热稳定性高。     

Thermal treatment and utilization of Al-rich waste in high calcium fly ash geopolymeric materials

The Al-rich waste with aluminium and hydrocarbon as the major contaminant is generated at the wastewater treatment unit of a polymer processing plant. In this research, the heat treatment of this Al-rich waste and its use to adjust the silica/alumina ratio of the high calcium fly ash geopolymer were studied. To recycle the raw Al-rich waste, the waste was dried at 110℃ and calcined at 400 to 1000℃. Mineralogical analyses were conducted using X-ray diffraction (XRD) to study the phase change. The increase in calcination temperature to 600, 800, and 1000℃ resulted in the phase transformation. The more active alumina phase of active θ-Al₂O₃ was obtained with the increase in calcination temperature. The calcined Al-rich waste was then used as an additive to the fly ash geopolymer by mixing with high calcium fly ash, water glass, 10 M sodium hydroxide (NaOH), and sand. Test results indicated that the calcined Al-rich waste could be used as an aluminium source to adjust the silica/alumina ratio and the strength of geopolymeric materials. The fly ash geopolymer mortar with 2.5wt% of the Al-rich waste calcined at 1000℃ possessed the 7-d compressive strength of 34.2 MPa.     

Preparation, characterization and thermal behavior of silver behenate nanocrystals

TO PROVIDE A VISIBLE IMAGE, CONVENTIONAL WET PROC- ESSED PHOTOGRAPHIC IMAGING MATERIALS REQUIRE THE PROC- ESSING IN AQUEOUS BATH SUCH AS DEVELOPING AND FIXING[1].BY CONTRAST, THERMOGRAPHIC OR PHOTOTHERMOGRAPHIC MA- TERIALS PROVIDE USERS WITH A SIMPLE AND …     

High-temperature oxidation resistance of ceramic coatings on titanium alloy by micro-arc oxidation in aluminate solution

Ceramic coatings with aluminum titanuate (Al₂TiO₅) were prepared on Ti–6Al–4V alloy using pulsed bi-polar Micro-arc Oxidation (MAO). The micromorphology and phase composition of the micro-arc-oxidition ceramic coatings on the titanium alloy were characterized by X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) respectively. The results revealed that the distinct discharge channels and pores on the surface of the micro-arc-oxidition coatings appeared, and these channels were connected in the molten state. The electrolyte concentration was inversely proportional to the coating hardness; additionally, the coating prepared with sodium aluminate and sodium hypophosphite concentrations of 4 ?g/L and 0.5 ?g/L, respectively, was the most refined after high-temperature sintering, and it was demonstrated to better prevent oxidation. Increasing the electrolyte concentration coincided with fluctuating coating thermal shock resistance. The thermal shock resistance of the coating respectively prepared with sodium aluminate, and the sodium hypophosphite concentrations of 4 ?g/L and 0.5 ?g/L was the highest. Additionally, the high-concentration coatings performed significantly better than the low-concentration coatings. The oxidation resistance of the coating samples was also significantly higher than that of the TC4 titanium alloy substrate. The adhesion strength between the coatings and the substrate with and without the sealing treatment was measured by tensile tests. Then, the high-temperature oxidation performance of the coating samples with and without the sealing treatment was investigated by conducting a high-temperature oxidation experiment at a calcinating temperature of 500 ?°C. The results indicate that the adhesion strength between the coatings and substrate was high for the as-prepared and sealed micro-arc oxidation samples regardless of whether they were calcined. The high-temperature oxidation mass increase curves for the sealed and unsealed coating samples calcined at 500 ?°C for 500 ?h revealed that the high-temperature-oxidation-induced mass increase of the coating samples sealed with a sodium silicate solution was much lower than that of the titanium alloy substrate. Thus, the sealing treatment significantly improved the high-temperature oxidation resistance of the TC4 titanium alloy. Lastly, the high-temperature oxidation behavior at 500 ?°C was analyzed and discussed.     

Kinetics of thermal decomposition of hydrated minerals associated with hematite ore in a fluidized bed reactor

The kinetics of removal of loss on ignition (LOI) by thermal decomposition of hydrated minerals present in natural iron ores (i.e., kaolinite, gibbsite, and goethite) was investigated in a laboratory-scale vertical fluidized bed reactor (FBR) using isothermal methods of kinetic analysis. Experiments in the FBR in batch processes were carried out at different temperatures (300 to 1200℃) and residence time (1 to 30 min) for four different iron ore samples with various LOIs (2.34wt% to 9.83wt%). The operating velocity was maintained in the range from 1.2 to 1.4 times the minimum fluidization velocity (U_mf). We observed that, below a certain critical temperature, the FBR did not effectively reduce the LOI to a desired level even with increased residence time. The results of this study indicate that the LOI level could be reduced by 90% within 1 min of residence time at 1100℃. The kinetics for low-LOI samples (<6wt%) indicates two different reaction mechanisms in two temperature regimes. At lower temperatures (300 to 700℃), the kinetics is characterized by a lower activation energy (diffusion-controlled physical moisture removal), followed by a higher activation energy (chemically controlled removal of LOI). In the case of high-LOI samples, three different kinetics mechanisms prevail at different temperature regimes. At temperature up to 450℃, diffusion kinetics prevails (removal of physical moisture); at temperature from 450 to 650℃, chemical kinetics dominates during removal of matrix moisture. At temperatures greater than 650℃, nucleation and growth begins to influence the rate of removal of LOI.     

Effect of annealing temperature on CrN microspheres synthesized by CAP technology

CrN microspheres were synthesized by using a cathodic arc plasma source system. The obtained samples were annealed in air at temperatures of 300-800 ℃ for 60 min. The influence of annealing temperature on the microstructure and surface morphology of the CrN microspheres was investigated. The CrN microspheres were characterized by means of scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. The results show that the CrN nanoparticles arranged into leaf-like structures before annealing. With the rising of the annealing temperature, the size of CrN crystal nanoparticals became larger. When the annealing temperature exceeded the oxidation point(500 ℃), the CrN was oxidized and the leaf-like structure was broken. With further increase of the annealing temperature(700 ℃), the arrangement of CrN nanoparticles was changed from leaf-like structure to be discrete.     

寒旱地区混凝土箱形渡槽湿热耦合效应

针对冬季渡槽的湿热全耦合效应问题,避免渡槽在冬季输水过程中出现裂缝现象,以寒旱地区某渡槽为工程背景,利用湿热耦合传输理论分析,实测2023年1月5至1月20日的环境温度、环境湿度及风速,采用Fluent有限元软件建立了不同环境参数的混凝土箱形渡槽温度场、湿度场、湿热耦合场有限元模型。并分析不同工况对冬季渡槽的非耦合和全耦合状态下的温度效应的影响。分析结果表明,渡槽通水时冬季最不利温差为-14.7℃,不通水时为-6.3℃;渡槽通水时冬季最不利横向温差为-10.2℃,不通水时为-6.2℃;在湿度扩散过程中,沿板厚方向湿度由内向外逐渐减小,且吸水速度随时间的增大而减小;在湿热耦合过程中,全耦合场温度值小于非耦合场温度值,湿热全耦合作用的挠度变化值小于湿热非耦合作用下的挠度变化值,湿热耦合作用的拉应力小于湿热非耦合作用下的拉应力值,因此,湿热全耦合作用对渡槽结构变形有利。     

Effect of sintering temperature on the microstructure and properties of foamed glass-ceramics prepared from high-titanium blast furnace slag and waste glass

Foamed glass-ceramics were prepared via a single-step sintering method using high-titanium blast furnace slag and waste glass as the main raw materials The influence of sintering temperature (900-1060℃) on the microstructure and properties of foamed glass-ceramics was studied. The results show that the crystal shape changed from grainy to rod-shaped and finally turned to multiple shapes as the sintering temperature was increased from 900 to 1060℃. With increasing sintering temperature, the average pore size of the foamed glass-ceramics increased and subsequently decreased. By contrast, the compressive strength and the bulk density decreased and subsequently increased. An excessively high temperature, however, induced the coalescence of pores and decreased the compressive strength. The optimal properties, including the highest compressive strength (16.64 MPa) among the investigated samples and a relatively low bulk density (0.83 g/cm3), were attained in the case of the foamed glass-ceramics sintered at 1000℃.     

基于脑电的温度阶跃变化环境下的人体热舒适研究

热环境作为评价建筑物理环境的重要部分,影响着人的工作效率和情绪变化。不同环境温度下的脑电信号与人体主观投票相结合是一种评价热舒适的新方法。选取14名身体健康的成年人在人工气候室经历由低温15℃分别突变到18、24和30℃3个过程,通过快速傅里叶变换,将温度阶跃变化环境下测得的脑电信号转化为脑电频谱功率,与主观投票和额头温度相结合,进一步探究脑电各分区和各波段与热舒适的相关性。研究表明,额叶区频谱功率变化可作为人体热舒适的评价指标,频谱功率与热舒适显著相关,且随着舒适程度的增加而降低,当温度突变到接近人体中性温度24℃时,功率最低。同时发现与热愉悦情绪和注意力有关的额叶区θ波段功率随着舒适程度的增加而增加,当温度突变到24℃时,θ波相对脑电功率变化最明显,增加了约20%。     

二氧化硅气凝胶的性能受热过程的影响

成功地以水玻璃为硅源,经乙醇溶剂替换及六甲基二硅醚和盐酸的混合液对SiO₂湿凝胶表面基团改性后,常压干燥制备出低密度、高比表面积、超疏水、低热导率的高性能SiO₂气凝胶块体.SiO₂气凝胶在室温至400℃附近具有稳定的疏水性能,460℃附近气凝胶由疏水型完全转变成亲水型.重点研究了室温至400℃之间,SiO₂气凝胶的微观结构和物理性能受热处理过程的影响.SiO₂气凝胶即使经过400℃高温热处理后,仍能保持优异的疏水性能、较高的比表面积和较低的热导率等.