Effect of montmorillonite on the swelling behavior and drug‐release behavior of nanocomposite hydrogels

A series of nanocomposite hydrogels were prepared from various ratios of N‐isopropylacrylamide (NIPAAm) and organic montmorillonite (MMT). The influence of the extent of MMT in the NIPAAm/MMT nanocomposite hydrogels on the physical properties and drug‐release behavior was the main purpose of this study. The microstructure and morphology were identified by X‐ray diffraction (XRD) and scanning electronic microscopy (SEM). The results showed that the swelling ratios for these nanocomposite hydrogels decreased with increase in the content of MMT. The gel strength and Young's modulus of the gels also increased with increase in the content of MMT. XRD results indicated that the exfoliation of MMT was achieved in the swollen state. Finally, the drug‐release behavior for the gels was also assessed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3652–3660, 2003     

凹凸棒石粘土悬浮液的悬浮性研究

研究了凹凸棒石粘土尺寸、悬浮液浓度、分散时间等因素对凹凸棒石粘土水和乙醇悬浮液悬浮性的影响,试验结果表明:凹凸棒石粘土水悬浮液的悬浮性显著高于乙醇悬浮液的悬浮性;水悬浮液中凹凸棒石粘土长度在38μm和71μm之间对悬浮性影响不大;使用50 W功率的超声波发生器分别分散10 min和15 min可以使凹凸棒石粘土分别在水和乙醇介质中充分分散;悬浮剂浓度为5 g/150 mL时水悬浮液的悬浮性最好。     

Chlorophyll adsorption on acid-activated clay

An acid-activated clay (Çanakkale montmorillonite from Turkey) was used to adsorb chlorophyll from hexane solutions. The phenomenon seems to be mainly driven by the interaction of chlorophyll with acid sites. The adsorption of chlorophyll on Brönsted acid sites was indicated by a characteristic infrared band for the -OH group at 3671 cm^?1. The variations in the structure of clay mineral and chlorophyll during adsorption have been examined by differential thermal analysis, thermogravimetry and infrared spectroscopy of the activated clay before and after adsorption of chlorophyll. Oxidation of adsorbed chlorophyll was completed at quite a high temperature.     

Synthesis and dielectric properties of polystyrene‐clay nanocomposite materials

Polystyrene‐clay nanocomposite (PsCN) materials were synthesized and their properties of crystallinity, thermal behavior, and dielectric characteristics were investigated. A polymerizable cationic surfactant, [2‐(dimethylamino)ethyl]triphenylphonium bromide, was used for the intercalation of montmorillonite (MMT). The organophilic MMT was prepared by Na⁺‐exchanged MMT and ammonium cations of a cationic surfactant in an aqueous medium. Organophilic styrene monomers were intercalated into the interlayer regions of organophilic clay hosts followed by a free‐radical polymerization. Exfoliation to 2 wt % MMT in the polystyrene (PS) matrix was achieved as revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also studied. The dielectric properties of PsCNs in the form of film with clay loading from 1.0 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 25–70°C. A decreased dielectric constant and low dielectric loss were observed for PsCN materials. The dielectric response at low frequency that originated from dipole orientation was suppressed due to the intercalation of clay materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1368–1373, 2004     

深厚覆盖层上高心墙坝地震惯性力动态分布系数研究

对于强震区坐落在深厚覆盖层(深度超过50 m)上的高土石坝,通过拟静力稳定分析结果初步判定其抗震稳定性是抗震设计的主要内容,其中水平向地震惯性力沿坝基覆盖层至坝顶的动态分布系数是关键。然而,现行《水工建筑物抗震设计标准》(GB 51247—2018)中地震惯性力动态分布系数多基于坐落在基岩上的高土石坝的动力响应规律确定,现有动态分布系数忽略了深厚覆盖层和地震动强度对地震动传播规律的影响。因此,以坐落在深厚砂砾石覆盖层上150 m级高黏土心墙堆石坝为研究对象,结合现行土石坝设计规范和国内已建高土石坝实例,基于统计平均的方法确定了坝顶宽度、坝料分区、坝坡坡比、覆盖层材料的静、动力特性等关键参数,深入探讨了150 m级高黏土心墙堆石坝在小震(0.1 g)、中震(0.2 g)和大震(0.4 g)规范谱地震动作用下不同深度砂砾石料覆盖层的动力响应分布规律,进而总结归纳出不同深度覆盖层下150 m级高黏土心墙堆石坝的水平向地震惯性力的动态分布系数,将其引入到拟静力法稳定分析中,最后基于最危险滑动面和最小安全系数与现行规范所得结果进行对比分析。研究结果表明,小震(0.1 g)和中震(0.2 g)下采用文中推荐的考虑深厚覆盖层和地震动输入强度影响的水平向地震惯性力动态分布系数时将得到更符合工程实际的评价结果。研究成果可为深厚覆盖层上的高土石坝抗震设计提供参考依据。     

存在高渗透区的黏土心墙土石坝渗流稳定性分析

黏土心墙土石坝是重要的挡水建筑物,心墙的低渗透性可以大幅降低坝体水力梯度,减少坝体发生渗透破坏的风险。然而心墙的质量问题（如局部高渗透区）会影响坝体的渗透稳定性,甚至酿成管涌溃坝等严重后果。以瀑布沟心墙土石坝为原型开展坝体渗流大型水槽模型试验,并结合有限元数值模拟方法研究高渗透区对坝体内部渗流场和渗流稳定性的影响。试验表明高渗透区域将改变心墙的渗流场,成为优势渗流通道,导致高渗透区域附近孔压值大幅上升,同时高渗透区域的存在将显著提升坝体渗漏速率。试验与模拟结果一致表明,随着高渗透区域逐步上移,高渗透区所在位置处的孔隙水压力增大,坝体渗漏量减小。高渗透区和心墙的渗透系数增加都会使心墙孔压值和渗漏量增加;随着高渗透区的渗透系数的增大,心墙坝渗流稳定性系数降低,导致坝体稳定性下降;随着心墙渗透系数的增大,高渗透区水力梯度略微减小,但心墙整体临界水力梯度下降,坝体稳定性降低。所得结论可为基于监测数据反演分析心墙的质量问题和评估坝体的安全性能提供依据。     

细菌对红黏土抗剪强度的影响

为了探究土壤原生细菌对红黏土强度的影响,通过对红黏土中天然赋存的原生细菌进行富集培养,并在红黏土重塑试样中添加培养后的细菌菌液,通过土工试验和电镜试验分析红黏土物理力学性质和微观结构的变化。结果表明:随着细菌的掺入,三轴试样的破坏峰值和压缩模量都有所提高,并且随时间的增长,呈现先增大后减小的趋势;同时从电镜图像上来看,细菌的掺入使得红黏土中粉粒含量有所增加,相应的黏粒含量下降。研究结果可为进一步研究单一的细菌种类对红黏土物理力学性质和微观结构的影响提供参考。     

NH3·H2O对桂林地区红黏土工程特性的影响试验研究

为研究氮肥污染对桂林红黏土物理力学性质的影响,使用氨水(NH₃·H₂O)溶液对具有代表性的桂林雁山红黏土进行浸泡,考虑氨水质量分数(0,4.5%,9.0%,13.5%,18.0%)和养护时间(1,7,14 d)双因子因素,通过室内试验,分析氨水污染对桂林雁山红黏土物理力学性质的影响规律。试验结果表明:随着氨水质量分数及养护时间的增加,桂林雁山红黏土的质量、含水率、相对密度和液塑限均增大,压缩模量减小,土体压缩性增强;碱-土作用是引起红黏土物理力学性质发生变化的主要原因,其相互作用导致红黏土颗粒间的胶结物被溶解后又重新生成絮状物,使其原本稳定的结构状态发生改变。     

脱湿过程中红黏土热导率的变化试验研究

自然状态下岩土体中的三相组成处于动态变化之中,对土体热传导性能的准确测试造成困难,通过热导率脱湿曲线(TCDC)可间接获取土体的传热性能。为此,以桂林红黏土为研究对象,采用压力板仪和KD2 Pro土壤热特性分析仪,研究了红黏土在脱湿过程中热导率的变化规律。试验结果表明:在进气值之前,土体饱和度不变,3种干密度的土体热导率都有小幅度增加,此阶段主要与吸力变化引起的土体密实度变化有关;当吸力超过进气值后,热导率随饱和度减小逐渐减小,此阶段含水率为影响热导率的主要因素。基于热导率试验结果,采用Lu模型和William模型对红黏土脱湿过程中热导率变化曲线进行拟合,整体上2模型对试验结果拟合较好,可以用于红黏土脱湿过程中热导率变化的模拟。     

利用废旧胶粉改善红黏土工程性质试验研究

随着废旧轮胎的日益剧增,回收利用率较低带来了严重的环保问题。利用废旧轮胎胶粉对红黏土进行改良,形成混合土。通过标准轻型击实试验、等效击实试验、直剪试验以及渗透试验,研究了不同胶粉掺量(0%,3%,8%,15%,25%)和不同含水量对混合土的击实特性、抗剪强度特性以及渗透性的影响。研究结果表明:①混合土的最大干密度比原状红黏土低,且胶粉的掺量越大,最大干密度越小;②胶粉掺量增大,标准击实试验的最优含水率增大,等效击实试验的最优含水率有减小趋势;③胶粉掺量不超过15%时,随着胶粉掺量增大,混合土的抗剪强度增大,内摩擦角增大,且出现应变硬化现象:④标准击实下,胶粉掺量为8%时,混合土的渗透速率变化不明显;但胶粉掺量增加到15%时,混合土的渗透速率显著提高,提升幅度达到97.3%。研究成果可为贵州地区今后废旧胶粉的循环利用和胶粉改良红黏土的工程运用提供参考。