共查询到19条相似文献,搜索用时 734 毫秒
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本文用氰尿酰氯为后交联剂,通过Friedel-Crafts反应使低交联聚苯乙烯发生后交联,形成大孔树脂。详细研究了反应条件对树脂孔结构的影响,所得树脂的比表面积可达500m2/g以上,孔容在0.3-0.5ml/g之间,骨架密度可达到1.3g/ml以上。树脂在不同的溶剂中有几乎相同的溶胀度。 相似文献
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《高等学校化学学报》1987,8(10),946本文用氰尿酰氯为后交联剂,通过Friedel-Crafts反应使低交联聚苯乙烯发生后交联,形成大孔树脂。详细研究了反应条件对树脂孔结构的影响,所得树脂的比表面积可达500m~3/g以上,孔容在0.3-0.5ml/g之间,骨架密度可达到1.3g 相似文献
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煤焦外表面分形维数在燃烧过程中的变化 总被引:6,自引:2,他引:6
煤燃烧的化学反应及其物质输运过程均具有非线性动力特征,燃烧过程是孔洞分形体的变化过程,其外表面结构的变化部分的反映出颗粒内部孔结构的变化过程,本文利用分形理论及其相关的图像处理方法对不同煤种,不同燃烧阶段煤焦外表面结构的SEM图像进行研究,研究结果表明,XIE法较适合计算煤焦表面分形维数,在燃烧过程中煤焦的外表面分形数呈现两种变化趋势,通过最小二乘法多项式拟合确定煤焦外表面分形维数与燃尽率之间的关系式,并得到不同煤种的方程参数。 相似文献
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交联聚苯乙烯型多孔吸附剂的中孔性质研究 总被引:12,自引:0,他引:12
采用77K温度下的氮气吸附方法,测定了经悬浮聚合制备的不同交联度的交联聚苯乙烯多孔吸附剂的吸附/脱附等温线.根据BET吸附模型计算了比表面,由吸附量计算了总的孔体积,由孔体积和比表面计算出平均孔径,并依据脱附等温线采用BJH方法计算孔径分布.结果表明,交联度对交联聚苯乙烯多孔吸附剂的孔结构均具有显著影响.随着交联聚苯乙烯多孔吸附剂的交联度升高,其孔径变小,比表面增大,而且低交联度吸附剂的中孔接近圆柱形,高交联吸附剂的中孔形状接近“墨水瓶”形.显然,交联度对孔性质的影响与孔结构在交联聚苯乙烯多孔吸附剂制备和后处理过程中的稳定性密切相关.交联度低时,初期形成的小孔不能保持稳定,在后续聚合及后处理过程中合并为大孔,结果造成低交联吸附剂大孔径、低比表面的现象.通过对孔径分布的研究,揭示了不同吸附剂在中孔范围内的孔特征,并对其形成机制进行了分析. 相似文献
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由大孔氯甲基化聚苯乙烯合成了含有悬挂醚键的甲氧基修饰的大孔交联树脂.通过化学分析(氯含量的测定)、红外光谱和元素分析等手段,确证甲氧基负载在聚苯乙烯骨架上,负载量为4.10mmol/g.测定了这种树脂对正己烷中苯酚的吸附等温线,表明其对正己烷中苯酚的吸附是放热的,随着温度的升高,吸附量逐渐降低,且吸附等温线可拟合成直线.通过吸附焓的计算、不同条件下吸附等温线的比较以及理论计算等方法,确证氢键是甲氧基修饰的大孔交联树脂吸附正己烷中苯酚的主要驱动力,树脂骨架上负载的醚氧原子与苯酚的酚羟基氢原子形成了强烈氢键. 相似文献
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互贯型螯合树脂的研究(Ⅰ)─交联聚苯乙烯-聚丙烯腈互贯树脂的合成 总被引:1,自引:0,他引:1
研究了交联聚苯乙烯-聚丙烯腈新型互贯树脂(PS-PAN)的合成,考察了交联度、重量比、孔结构和溶剂对互贯量的影响。结果表明,以凝胶型树脂为第一网时,交联度的影响比较显着,两网交联度相同时互贯量最大;以大孔型树脂做第一网时,孔结构的作用较突出。此外,溶剂对互贯量的影响非常大。 相似文献
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非晶态半导体硅(α-Si:H)薄膜作为新型的光电子材料,近年来备受关注,发展迅速。但其晶化机理有待深入探索。用分形理论所作的分析表明,在一定条件下,a-Si:H薄膜中形成的微结构具有分形性质。本文计算了分维值,讨论了a-Si:H薄膜结构弛豫(相变)与分形结构形成的关联,和非晶硅薄膜可能的晶化机理。并研究了在高真空中用透射电子显微镜(TEM)及动态方法跟踪观测a-Si:H薄膜原位(in situ)退火过程中发生的晶化现象,获得晶化形貌的显微图像。利用图像处理技术对显微像进行光电转换,A/D转换和数字计算,得到a-Si:H薄膜样品在不同退火条件下,显微象的Sandbox关系曲线。从而获得薄膜中形成不同分形结构的分维。文中给出应用分形理论对非晶态半导体薄膜进行分析的技术细节。 相似文献
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高磺化度聚苯胺体系中的分形结构研究 总被引:6,自引:0,他引:6
通过透射电镜的观察研究发现磺化聚苯胺的胶体聚集体和胶粒内部结构都具有分形体的特征 ,从而将分形的概念及其数学模型引入共轭导电聚合物体系之中 .磺化聚苯胺胶体的聚集体为很不均匀的分支状开放结构 ,其形成过程可用扩散控制集团聚集模型 (DLCA)进行模拟 ,计算机模拟生成的图形及其分形维数都与实验观测结果相当吻合 .胶粒由于是在分散介质所形成的平均化场中生成 ,屏蔽效应减弱 ,是比由它组成的聚集体要致密的球形结构 ,该结构的生成可用随机雨点模型模拟且结果相近 . 相似文献
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聚甲基丙烯酸甲酯/聚醋酸乙烯酯共混相分离过程的标度行为与逾渗结构 总被引:2,自引:0,他引:2
本文用激光光散射和光学显微镜方法研究了聚甲基丙烯酸甲酯/聚醋酸乙烯酯共混体系不稳相分离过程最大散射强度I_m(t,T)和相应波矢q_m(t,T)随时间变化规律及相区的逾渗结构.实验结果表明:I_m(T,t)和q_m(t,T)与时间t满足简单的标度关系I_m(t,T)~t~β,q_m(t,T)~t~(-α),且标度关系β=3α成立.揭示了相态结构的分维特征.给出了计算相态结构分维数的简便方法,其分维数D值约为1.64±0.03.与逾渗模型给出的D值接近. 相似文献
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Prediction of three-dimensional fractal dimensions using the two-dimensional properties of fractal aggregates 总被引:1,自引:0,他引:1
Fractal dimension analysis using an optical imaging analysis technique is a powerful tool in obtaining morphological information of particulate aggregates formed in coagulation processes. However, as image analysis uses two-dimensional projected images of the aggregates, it is only applicable to one and two-dimensional fractal analyses. In this study, three-dimensional fractal dimensions are estimated from image analysis by characterizing relationships between three-dimensional fractal dimensions (D(3)) and one (D(1)) and two-dimensional fractal dimensions (D(2) and D(pf)). The characterization of these fractal dimensions were achieved by creating populations of aggregates based on the pre-defined radius of gyration while varying the number of primary particles in an aggregate and three-dimensional fractal dimensions. Approximately 2000 simulated aggregates were grouped into 33 populations based on the radius of gyration of each aggregate class. Each population included from 15 to 115 aggregates and the number of primary particles in an aggregate varied from 10 to 1000. Characterization of the fractal dimensions demonstrated that the one-dimensional fractal dimensions could not be used to estimate two- and three-dimensional fractal dimensions. However, two-dimensional fractal dimensions obtained statistically, well-characterized relationships with aggregates of a three-dimensional fractal characterization. Three-dimensional fractal dimensions obtained in this study were compared with previously published experimental values where both two-dimensional fractal and three-dimensional fractal data were given. In the case of inorganic aggregates, when experimentally obtained three-dimensional fractal dimensions were 1.75, 1.86, 1.83+/-0.07, 2.24+/-0.22, and 1.72+/-0.13, computed three-dimensional fractal dimensions using two-dimensional fractal dimensions were 1.75, 1.76, 1.77+/-0.04, 2.11+/-0.09, and 1.76+/-0.03, respectively. However, when primary particles were biological colloids, experimentally obtained three-dimensional fractal dimensions were 1.99+/-0.08 and 2.14+/-0.04, and computed values were both 1.79+/-0.08. Analysis of the three-dimensional fractal dimensions with the imaging analysis technique was comparable to the conventional methods of both light scattering and electrical sensing when primary particles are inorganic colloids. 相似文献
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聚丙烯酰胺/醋酸铬与聚丙烯酰胺/酚醛胶态分散凝胶的纳米颗粒自组织分形结构 总被引:5,自引:0,他引:5
采用原子力显微镜 ,分别对无机交联体系聚丙烯酰胺 Cr3+ 和有机交联体系聚丙烯酰胺 酚醛胶态分散凝胶的微观结构进行了显微图像分析 .发现无论是在有机还是无机交联体系中 ,也无论聚丙烯酰胺和交联剂浓度如何变化 ,在微米尺度上最终形成的都是具有自相似性的树枝状分形图像 ,在更小尺度上则发现单个小树杈分形体都是由纳米级的颗粒紧密堆积而成 .在所研究的胶态分散凝胶体系中 ,树枝状分形结构的形成及其具体的形态取决于聚丙烯酰胺的浓度 ,而交联剂的有无及其多少只对树枝状凝胶分形的几何形态产生一定影响 .实验结果还表明纳米级 (≤ 10 0nm)的胶体颗粒构成的分形结构的凝胶其弹性模量G′比微米级的高出一个数量级 .且粒子尺度越小 ,则凝胶的力学稳定性越强 相似文献
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The fractal nature of latex particles and their aggregates was characterised by image analysis in terms of fractal dimensions.
The one- and two-dimensional fractal dimensions, D
1 and D
2, were estimated for polystyrene latex aggregates formed by flocculation in citric acid/phosphate buffer solutions. The dimensional
analysis method was used, which is based on power law correlations between aggregate perimeter, projected area and maximum
length. These aggregate characteristics were measured by image analysis. A two-slopes method using cumulative size distributions
of aggregate length and solid volume has been developed to determine the three-dimensional fractal dimension (D
3) for the latex aggregates. The fractal dimensions D
1, D
2 and D
3 measured for single latex particles in distilled water agreed well with D
1 = 1, D
2 = 2 and D
3 = 3 expected for Euclidean spherical objects. For the aggregates, the fractal dimension D
2 of about 1.67 ± 0.04 (±standard deviation) was comparable to the fractal dimension D
3 of approximately 1.72 ± 0.13 (±standard deviation), taking the standard deviations into account. The measured three-dimensional
fractal dimension for latex aggregates is within the fractal dimension range 1.6–2.2 expected for aggregates formed through
a cluster-cluster mechanism, and is close to the D
3 value of about 1.8 indicated for cluster formation via diffusion-limited colloidal aggregation.
Received: 28 September 1998 Accepted: 29 October 1998 相似文献
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Motivated by the characteristics of highly clustered single nucleotide polymorphism (SNP) across the human genome, we propose a set of chromosome-wise fractal dimensions as a measure for identifying an individual for human polymorphism. The fractal dimension quantifies the degree of clustered distribution of SNPs and represents parsimoniously the genetic variation in a chromosome. In this sense, the proposed scheme projects the SNP genotype data into a new space which is simpler and lower in dimension. As an illustrative example, we estimate the chromosome-wise fractal dimensions of SNPs that are extracted from the HapMap of Phase III data set. To determine the validity of the proposed measure, we apply principal component analysis (PCA) to the set of estimated fractal dimensions and demonstrate that the set more or less described the population structure of 11 global populations. We also use multidimensional scaling to relate the genetic distances based on PCA to the geographical distances between global populations. This shows that, similar to the SNP genotype data, the fractal dimensions also has a role in genetic distance in the population structure. In addition, we apply the proposed measure to a signature for the classification of global populations by developing a support vector machine model. The selected feature model predicts the global population with a balanced accuracy of about 77%. These results support that the fractal dimension is an efficient way to describe the genetic variation of global populations. 相似文献
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