前驱体对炭泡沫孔结构的影响

分别以煤沥青、石油中间相沥青和AR沥青为前驱体制备炭泡沫材料。采用GPC测定前驱体分子量,SEM观察所制炭泡沫的孔结构,光学显微镜测量所制炭泡沫的孔径及其分布。结果发现,由于煤焦油沥青不含中间相,且QI含量较高,导致在实验条件下不能直接制备出合格的炭泡沫。以石油中间相沥青和AR沥青为原料均能制备出具有分布均匀开孔结构,且微观各向异性的炭泡沫。由AR沥青制备的炭泡沫呈现平均孔径较小(212μm)、孔壁较薄、孔径分布较窄(180μm~300μm)、开孔率较高、以及韧带排列较规整等特点,表明低QI含量、低分子量且分布较窄的前驱体有利于发泡。     

炭材料用基体前驱体沥青的改性研究

首次以二乙烯基苯为交联剂,在酸性催化剂的作用下对煤沥青进行了改性研究,同时对改性后的煤沥青进行显微结构和耐热性分析。研究结果表明：改性后的煤沥青不仅出现大量的中间相小球,而且耐热性优良,可作为炭材料优质的基体前驱体。     

作为炭材料前驱体的离子液聚合物的简易合成(英文)

采用一步法合成新型离子液聚合物,并以聚合物作为炭材料的前驱体。这种新型离子液聚合物的特征包括:聚合无需添加引发剂,聚合引入的阴离子能够控制材料的微孔大小。以含Cl-的离子液聚合物为前驱体合成的炭材料具有较小的比表面积(47m2/g),而以含较大(三氟甲基磺酰基)亚胺基阴离子的离子液聚合物为前驱体合成的炭材料具有较大的比表面积(595m2/g)。含二氰胺阴离子的离子液聚合物为前驱体合成的炭材料的比表面积为30m2/g。     

冷冻干燥法制备的前驱体研究

利用XRD、SEM研究了冷冻干燥法制备的前驱体。结果表明：冷冻干燥法制备的前驱体为表面光滑的无定性态。盐相沿晶界分布形成了片状形态，沿大单晶冰粒边界分布则形成了六边形态。当溶液浓度较高时，主要是片状前驱体；当溶液浓度较低时，则出现六边形态的前驱体。     

HfC前驱体的合成及其裂解行为研究

以HfCl₄、乙酰丙酮、无水甲醇、对苯二酚为原料, 采用一锅法合成了HfC陶瓷前驱体, 通过前驱体裂解制备得到了HfC陶瓷粉体。采用XRD、FTIR、SEM/EDS、TEM、SAED等分析手段对裂解产物的组成、形貌和微观结构进行了分析和表征, 利用TG-DSC和TG-MS对前驱体的裂解行为进行了研究。结果表明: HfC前驱体在600℃左右开始陶瓷化, 在1300℃左右开始形成HfC陶瓷相, 在1500℃及以上完全转化为HfC陶瓷及自由碳。HfC陶瓷相具有单晶结构, 颗粒粒径在50~100 nm之间。HfC陶瓷相的形成基于前驱体在低温段裂解形成的HfO₂的碳热还原反应, 裂解过程中形成的自由碳抑制了HfC晶体的生长。     

新型碳产品的前驱体设计

一、引言如进藤开发PAN基炭纤维和吉村开发石墨膜所表示的那样,前驱体的选择是开发新型炭产品的最基本因素。然而他们的选择从没超出过现存的产品,本身没有制造新的前驱体。     

MOCVD法制备HfO2薄膜前驱体的研究现状

HfO2薄膜是一种新兴的薄膜材料,在耐高温保护涂层、微电子、催化等领域有着非常重要的应用.HfO2薄膜优异的性能及广阔的应用前景已经引起人们极大的关注.介绍了MOCVD法制备HfO2薄膜前驱体的研究进展和现状,着重讨论了MOCVD工艺中各类前驱体的优缺点,概述了目前研究的热点和进一步研究的方向.最后得出结论:目前使用较多的β二酮类铪配合物自身存在许多不利于MOCVD工艺的缺点,因此混合配体的铪配合物成为进一步研究的焦点.     

催化剂前驱体对碳纳米管生长影响的研究

采用柠檬酸络合法, 通过改变La和Ni的摩尔比例获得了一系列的La-Ni-O催化剂前驱体, 以H₂作为还原气体, N₂为保护气体, C₂H₂为碳源, 采用化学气相沉积法制备碳纳米管(CNT). 用XRD研究所得催化剂前驱体还原前后的结构, TEM观察所得CNT的形貌. 结果发现: 在所制备的一系列La-Ni-O催化剂前驱体中, 具有催化活性的物质只有: LaNiO₃和La₂NiO₄. 但由LaNiO₃所制备的CNT的产率却大大高于由La₂NiO₄所制备的CNT的产率. 经分析认为, 这主要是与两者被还原后的产物中的纳米级金属Ni的(111)晶面含量有关, 纳米级金属Ni的(111)晶面含量和晶粒度越大, 其CNT的产率和内径也就越大.     

炭前驱体对活性炭孔结构和电化学性能的影响

分别以毛竹和石油焦为炭前驱体,采用KOH活化法制备超级电容器用高比表面积活性炭材料,考察了碱/炭比对不同炭前驱体所制得的活性炭的孔结构、吸附性能和电容性能的影响。结果表明,在相同的碱/炭比下,竹基活性炭孔径2nm的微孔较发达,而石油焦基活性炭孔径在2～50nm的中孔率较高。在适宜的工艺条件下,以毛竹为炭前驱体可制得比表面积为2610.7m2/g,比电容为206F/g的活性炭材料;以石油焦为炭前驱体可制得比表面积为2597.9m2/g,比电容为213F/g的活性炭材料。     

高氢选择性分子筛炭膜的制备

以聚酰胺酸为涂膜液,以自制的最可几孔径0.39 μm的粉煤灰膜为支撑体,采用浸渍一提拉法涂膜,经过亚胺化-炭化,制备了支撑分子筛炭膜.通过时间一延迟(time-lag)法表征了膜的气体渗透性能.和聚酰亚胺膜相比分子筛炭膜同时具有高的渗透性和选择性,所得到的分子筛炭膜具有高氢选择性,H2/CH4分离因子达到951,H2/N2分离因子为380,氢气渗透速率达到1.64×10-8 mol/(m2·s·Pa).     

纳米分子筛MCM-41颗粒大小的控制

采用为硅源,表面活性剂十六烷基三甲基溴化氨为结构导向剂,用室温合成方法在碱性介质中合成MCM-41中孔分子筛,基于硅酸盐的水解-缩聚机理讨论了用调节PH值、控制搅拌速率的方法来控制分子筛颗粒的大小.     

新型杂化炭分子筛膜研究进展

杂化炭分子筛膜是炭膜杂化改性的产物,是炭和其他物质之间的杂化,改变了单一炭膜的结构和性质。详细介绍了炭膜杂化改性技术及研究进展,综述了影响杂化炭膜性能的制备条件,并对杂化炭膜的发展方向进行了展望。     

定向聚合制备硅分子筛复合膜

研制出一种高强度、高选择透过性的硅分子筛复合膜 .这种膜的最大特点 ,是其表面分离层是由定向聚合制得的硅树脂膜裂解制成 .由于这种硅树脂的大分子呈规则排列 ,因而导致最终裂解膜的孔径分布极窄 ,膜选择透过性能较大幅度提高 .这种膜对气体的渗透系数约为1 0 3Barrer(1Barrer =7.6× 1 0 - 8cm3·cm/cm2 ·s·MPa) ,H2 /N2 分离因子可达 90 ,其选择透过性能远优于常规的有机膜和无机膜 ,也优于常规碳分子筛膜和硅分子筛膜 .这种膜以多孔陶瓷为支撑体制成复合膜 ,因而具有较高的强度 .     

The role of organic molecules in molecular sieve synthesis

During the last 15 years, organic quaternary species, ions and amines, have been extensively employed as ‘templating’ additives in both aluminosilicate and aluminophosphate molecular sieve syntheses. A ‘template theory’ was evolved to explain the structure-directing effect of these organic species. The charge distribution and the size and geometric shape of a template are believed to be the causes for structure-directing. Meanwhile, data available in the literature also strongly suggest that gel chemistry, i.e. hydroxyl ion concentration, Si0₂/Al₂O₃ ratio, temperature, etc., is extremely important. The basic questions to be answered by the ‘template theory’ are: (1) How can one template give rise to so many different structures? (2) How can so many templates, differing in size and shape, all direct the same structure? (3) On the other hand, why do certain structures not form in the absence of a specific template molecule?In this article we intend to carefully review much of the synthesis data available in the literature and to examine the importance of the basic gel chemistry as well as of the templating effect. Also, we want to explore the close relationship of these two effects in molecular sieve synthesis.Based on the data reviewed, we propose that during the hydrothermal synthesis of molecular sieves, both gel chemistry and template species can play important roles in the formation of a specific structure, but that templating becomes operative only in the environment of the right ‘gel chemistry’.     

A conceptual model for hydrothermal molecular sieve zeolite synthesis

The effort in this study has been to develop a mathematical model for hydrothermal molecular sieve synthesis which accounts for the dependence of nucleation and growth rates on the concentration of pseudocell equivalents in the slurry, in order to predict the relevant statistical parameters of the crystal product size distribution.The development is shown for both well mixed batch and continuous flow stirred tank zeolite crystallizers. It is shown that by treating the product as an inorganic polymer having a uniform morphology, the crystal product size distribution, all important statistical parameters, and other key quantities of interest in zeolite synthesis can be predicted by this type of model.     

Phase-selective synthesis of a silicoaluminophosphate molecular sieve from dry gels

Silicoaluminophosphate (SAPO) molecular sieves with AFI and CHA structures have been synthesized from a reaction mixture containing triethylamine (TEA) as a template or structure-directing agent. The syntheses were carried out at 180-200 °C for several days both from dry gels (dry gel conversion) and homogeneous gels (conventional electric heating). From similar reaction mixtures, SAPO-5 (AFI structure) and SAPO-34 (CHA structure) molecular sieves are phase-selectively obtained from dry gel conversion and conventional electric heating, respectively. The phase-selectivity may be explained by the slow crystallization of the dry gel conversion due to low water or TEA concentration under the reaction conditions and the difference of the relative stability of SAPOs (AFI < CHA) under hydrothermal conditions. This phase-selective synthesis with dry gel conversion may lead to a new method for the synthesis of relatively unstable molecular sieves (having large pores) such as VFI or VPI-5.     

Surface structure modification on the gas separation performance of carbon molecular sieve membranes

Carbon molecular sieve (CMS) membranes for separating gases were deposited on porous Al₂O₃ disks using CH₃COCH₃+CH₄, by a remote inductively coupled-plasma (ICP) chemical vapor deposition (CVD). The new method for preparing membranes with a high H₂/N₂ selectivity without any reduction of the permeance was introduced by combining the surface treatment with high-energy ion bombardment and subsequent high-temperature pyrolysis study. The H₂/N₂ selectivity reached 50 with an extremely high permeance of approximately 1.6×10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ at 423 K. The O₂/N₂ selectivity reached 2.5 and the O₂ permeance was approximately 2×10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at 398 K.Short and optimized surface treatment periods were required to ensure high efficiency. Without pyrolysis, surface treatments alone markedly reduced the H₂ and N₂ permeances but did not affect selectivity. Besides, without any surface treatment, pyrolysis alone markedly increased the H₂ and N₂ permeances, but did not improve selectivity, because the desorption of carbon left large pores. Surface treatment must be combined with pyrolysis to enhance simultaneously the permeance and selectivity of CMS membranes, in a manner very different from that associated with conventional pore-plugging mechanism in typical CVD.     

13X分子筛为载体制备单壁碳纳米管研究

采用流化床法,以Fe/13X分子筛作为催化剂载体,催化裂解正己烷制备出定向排列的、较纯的单壁碳纳米管.利用TEM、HRTEM、TG和Raman对产物进行了表征,对不同浸泡时间Fe/13X分子筛制成的单壁碳管的含量和分子筛的负载量进行了分析,研究了催化剂铁负载量对单壁碳纳米管的产量和直径的影响.结果表明,单壁碳纳米管产量受催化剂含量和活性的共同影响,且在一个特定催化剂负载量下碳管产量可以达到最高,而其直径变化不大,且不受催化剂负载量的影响.     

炭分子筛膜的制备及应用研究进展

炭分子筛膜(CMSM)是用于气体分离的一种高效节能新型材料,在气体分离中具有极大的工业化应用潜力.综述了炭分子筛膜的前躯体选择、制备工艺及气体分离应用方面的研究进展,并对炭分子筛膜的发展方向进行了展望.