不同工艺有机插层蛭石的制备及表征

以2倍蛭石阳离子交换容量的十六烷基三甲基溴化铵为插层剂,利用热液搅拌法、球磨法、煮沸法、熔融搅拌法等4种不同工艺对蛭石进行插层处理.对有机插层后的蛭石进行了粉晶X射线衍射、Fourier变换红外光谱和热重分析表征.结果表明:不同插层工艺会导致有机插层蛭石的层间距及微结构的变化.随着层间距的增大,蛭石层间的有机相含量逐渐增大.     

溶液法制备有机蛭石

为了获得层间距较大的有机蛭石,将蛭石在酸介质中,用十六烷基三甲基溴化铵(CTAB)作阳离子交换剂,以1.5倍阳离子交换容量与蛭石进行阳离子交换反应。通过X衍射实验,将有机化蛭石前后情况进行对比分析。结果表明:蛭石通过有机化之后,层间距由1.76 nm增大至4.01 nm。通过分析之后得出,蛭石有机化的影响因素主要是有机化环境的和蛭石原料形态。     

不同超临界压力下有机超细蒙脱土的结构性质演变

为了促进层间阳离子交换,将原始蒙脱土进行超细化和接枝处理后以超临界二氧化碳(sc SO2)为介质、以十四烷基三己基氯化鏻(TTPC)为插层剂对其进行插层改性。结果表明:经sc CO2处理后蒙脱土的亲水性减弱,颗粒变得蓬松,且随着压力从10 MPa提高到20 MPa再至30 MPa,TTPC在sc CO2中的溶解度先增加后降低,20 MPa时达到饱和,在该压力下制备的有机超细蒙脱土FTIR曲线中2 927 cm-1和2 855 cm-1的-CH2不对称和对称伸缩振动峰峰强最强,TG曲线中200~550℃的热失重率最高,(001)衍射面对应的衍射角最小,蒙脱土片层间距最大,制备的改性蒙脱土颗粒最蓬松。     

季铵盐插层剂对高密度聚乙烯性能的影响

采用季铵盐阳离子作为插层剂与钠基蒙脱土层间的无机阳离子进行离子交换,制备系列有机化蒙脱土,利用红外光谱对蒙脱土的结构进行表征,结果表明,插层剂已进入蒙脱土的层间.同时将有机化蒙脱土与HDPE进行熔融插层,制备了纳米聚乙烯复合材料,研究了插层剂对其部分力学性能的影响.     

不同表面活性剂制备有机蒙脱土

分别利用阳离子表面活性剂十六烷基三甲基溴化铵、十六烷基三甲基氯化铵和阴离子表面活性剂十二烷基磺酸钠制备了有机蒙脱土,并通过红外光谱分析和X-射线衍射分析对其进行了表征。结果表明,有机插层剂已进入蒙脱土的层间,蒙脱土的层间距由1.24 nm分别增加到2.14,2.20和2.51 nm。沉降实验结果表明,这种有机蒙脱土在有机介质中表现出很好的分散性。     

复合插层有机蒙脱土的制备及表征

以钠基蒙脱土、十六烷基三甲基溴化铵(CTAB)和己内酰胺为原料,制备了复合插层有机蒙脱土。红外光谱分析(IR)、热重分析(TGA)和X-射线衍射分析(XRD)表明,有机插层剂已进入蒙脱土的层间,CTAB/己内酰胺复合插层有机蒙脱土的层间距大于单阳离子CTAB插层有机蒙脱土的层间距。Molau实验结果表明,这种有机蒙脱土在有机介质中表现出很好的分散性。     

季膦盐插层蒙脱土的制备及表征

利用丁基三苯基溴化膦（BTPB）、十二烷基三苯基溴化膦（DTPB）湿法改性天然钠基蒙脱土。x射线衍射、红外光谱测试表明膦阳离子已插层到蒙脱土片层间并成功打开层间距；热重分析结果表明DTPB和BTPB改性的蒙脱土比十六烷基三甲基溴化铵改性蒙脱土的热分解温度分别提高102℃和57℃；沉降实验研究表明改性后蒙脱土在甲苯、苯乙烯中表现出很好的分散性和溶胀性。     

封口膜的红外光谱研究

采用变温红外光谱技术,分别研究了封口膜(Parafilm)的一维变温红外光谱和二阶导数变温红外光谱。研究发现:Parafilm主要存在着甲基的不对称伸缩振动峰、亚甲基的不对称伸缩振动峰、亚甲基的对称伸缩振动峰、亚甲基的变角振动峰(δ_(CH_2))、甲基的不对称变角振动峰(δ_(asCH_3))、甲基的对称变角振动峰、C—C骨架伸缩振动峰和亚甲基的面内摇摆振动峰,最终确定Parafilm的主要结构是聚异丁烯,其临界温度(由结晶转变为无规的温度)为40℃;以Parafilm的δ_(CH_2)和δ_(asCH_3)为对象,进一步研究了相关二维红外光谱;拓展了变温红外光谱技术及二维红外光谱技术在高分子包装材料结构方面的研究范围。     

Cu-,Mg-蒙脱石层间吸附水的研究

通过现场红外分析研究了Mg-、Cu-蒙脱石在真空加热体系中脱水过程的红外光谱。发现荥脱石层间有三种吸附水,即“牢固键合水”、“松散键合水”和“自由水”。前两种键合水具有相同的取向结构,但吸附能上有差别。层间吸附水的稳定性与层间阳离子属性有关。Mg-蒙脱石层问水比Cu-蒙脱石层间水稳定,在吸附能上,Mg-蒙脱石层间“自由水”高于或接近Cu-蒙脱石层间的“松散键合水”。     

聚苯硫醚/有机蒙脱土复合材料热氧化研究

以十六烷基三甲基溴化铵作为插层剂,采用阳离子交换法对钠基蒙脱土粉体进行有机改性制备有机蒙脱土(OMMT);采用熔融插层法制得聚苯硫醚(PPS)/OMMT复合材料并将复合材料进行热处理;利用红外光谱技术研究热处理前后PPS树脂及其复合材料的结构变化,对PPS的热氧化机理进行探讨;利用电脑测色配色仪对热处理前后的PPS树脂及其复合材料颜色的变化值进行测试。结果表明:与纯PPS树脂相比,OMMT的添加可以在一定程度上提高PPS树脂的抗氧化性;经过热处理后PPS树脂及PPS/OMMT复合材料均发生不同程度的氧化,苯环上发生交联,C—S键上发生氧化;C—H的面外弯曲振动峰及苯环C—O伸缩振动峰均发生蓝移;PPS/OMMT复合材料的色度变化程度明显降低,其中添加质量分数为5%的OMMT的复合材料的抗氧化效果较好。     

X-ray diffraction studies of the thermal behaviour of commercial vermiculites

For the purpose of knowing the vermiculites which would have larger capability to retain contaminating substances heating commercial samples from different places have been identified and their thermal behaviour at several temperatures has been investigated by X-ray diffraction (XRD), electron microprobe, thermal analysis (TG and DTA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).The commercial vermiculites can be divided into two types: type 1 (Sta. Olalla, Piauí and Goiás) with Mg²⁺ and K⁺ (< 1) as the principal cations in the interlayer space, and type 2 (China E, China W, China G and Palabora) with K⁺ (approximately = or > 1) and/or Na⁺ and/or Ca²⁺ with or without Mg²⁺ as the principal interlayer cations.The process of dehydration in situ with the temperature seems restricted to interlamellar water monolayers of 1-WLHS type-1 of vermiculites, without dehydration to a zero-water-layer-hydration state (0-WLHS) and the dehydroxylation starts at lower temperatures than in vermiculites of type 2. The maximum hydration state exhibited by the type-2 samples at ambient temperature was equal or lower than the monolayer hydrate, the dehydration process in situ with the temperature was slower and the dehydrated vermiculite coexists with a mica-like structure.The behaviour of vermiculites at elevated temperature examined in situ can be understood considering that the vermiculites constitute a complex system not necessarily in equilibrium and where kinetics plays an important role.Commercial vermiculites heated abruptly at 1000 °C during 1 min transform to mica-like or mica-like coexisting with enstatite, in contrast to the purest Sta. Olalla vermiculite, with only magnesium interlayer cations, which changes to enstatite.     

Synthesis of nano-layered vermiculite of low density by thermal treatment

The present work consists in the study of the modification of a nano-layered vermiculite by thermal treatment up to 900 °C. Changes in the structure and texture after thermal treatment were used for evaluation of dehydration properties of the studied material. The dehydration properties of the clay are strongly affected by the crystal structure.The Differential Thermal Analysis (DTA) allows the determination of the specific temperatures at which phase modifications take place, principally the ones attributed to the removal of the interlayer water molecules and the formation of a series of less hydrated phases. Structural and textural studies were carried out using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analysis. The SEM micrographs reveal structural changes of the sample, such as exfoliation phenomena and contraction of the vermiculite, related to the heating temperature. These observations are confirmed by the XRD patterns, which demonstrate that the d-spacing of the first basal diffraction varies depending on the applied heating temperature, this showing several states of dehydration. As a complementary characterization, porosity analysis by Hg-porosimetry has also been carried out.     

FTIR analyses of water in MX-80 bentonite compacted from high salinary salt solution systems

The effect of the exchangeable cations on the infrared (IR) spectra of water in MX-80 bentonite compacted from high salinary salt solution systems was studied using self-supporting film and attenuated total reflection (ATR) techniques. Na-bentonite MX-80 was saturated with homo-cationic (NaCl, KCl, CaCl₂ or MgCl₂) or hetero-cationic (mixtures of Na–, K–, Ca– and Mg–chlorides) solutions. The specimens for IR spectroscopy were prepared as self-supporting films (ssf) or compacted pastes. Differences in the wavenumbers and intensities of the structural OH group vibrations in relation to the type of the interlayer cation were found in the spectra of heated ssf. The most pronounced changes were observed for Mg-ssf, while only negligible changes occurred for K-ssf. The absorptions of water in heated Na- and K-ssf showed displacement of the stretching and bending bands to higher and lower wavenumbers, respectively, which indicates decreasing strength of H-bonding between water molecules. In contrast, for Mg-ssf the position of the stretching band of water substantially decreased on heating up to 90 °C followed by an increase upon further heating above 100 °C. The origin of these differences was discussed in terms of variations in the polarising ability of the interlayer cations influencing their hydration number. The ATR spectra of homo-cationic clay-pastes showed that the interlayer cations modify both the position and the intensity of the complex water band near 3400 cm⁻¹. The position decrease and the intensity increase followed the same order: K⁺, Na⁺, Ca²⁺, Mg²⁺. Good correlation between water band position and polarising power of the cations confirmed their influence on the strength of hydrogen bonds between water molecules. Similarly, a systematic shift of the H₂O-stretching band to lower frequencies with the increasing Mg²⁺ content in the samples was observed in the spectra of clay-pastes saturated with hetero-cationic chloride solutions. The intensity of the stretching band of water of both homo- and hetero-cationic pastes correlated very well with the water content obtained gravimetrically.     

Temperature effects on iodine adsorption on organo-clay minerals: I. Influence of pretreatment and adsorption temperature

The sorptive capability of clay minerals for anionic radionuclides can be improved substantially by exchanging the natural inorganic interlayer cations with certain organic cations. After screening a variety of possible candidates, four organic cations were selected and combined with three clay minerals, providing 12 organo-cation/clay mineral combinations. The samples were tested for anion adsorption in batch experiments with radioiodide in a concentration range of 10⁻² to 10⁻⁹ mol l⁻¹ and exhibited high adsorption in bidistilled water as well as in synthetic groundwater. Results for two clay minerals—a smectite and a vermiculite—and four organic cations are given in this paper.Tests were also performed with temperature pretreated material. An increase of the pretreatment temperature from 20 to 40, 60, 80 and 100 °C did not result in a remarkable effect on iodide adsorption, except for the 1,12-dipyridiniododecan/vermiculite combination.In batch experiments with equilibrium temperatures of 20–60 °C, iodide adsorption decreased slightly with increasing temperature. Only 1,12-dipyridiniododecan in combination with smectite and vermiculite showed a somewhat lower iodide adsorption at higher temperatures.     

Sorption of Cyclohexylamine by Montmorillonites

Infrared spectra indicate that protonation of cyclohexylamine sorbed by montmorillonite depends upon the interlayer cations and the origin of the lattice charge. No protonation occurs with Cs and very little with Na, but with all the other interlayer cations studied cyclohexylammonium ions are formed. Protonation occurs more readily if the lattice charge originates in the octahedral layer. Various associations are inferred between interlayer hydroxides, hydrated cations, ionic and molecular cyclohexylamine and water. The sorption of cyclohexylamine is compared with that of aniline and the validity of the concept “surface acidity” is questioned.     

Isotope Effects in the High-Overtone Spectrum of C-H Stretches in HCN

The same Morse potential predicts the vibrational overtone spectra for the various isotopomers of HCl. However, the C-H stretching overtones of HCN require different Morse parameters for different isotopomers. This paper considers how the other vibrational coordinates change the frequency of the C-H overtones. A simple model is used that considers the C-H to be a Morse oscillator and the other motions to be harmonic oscillators. The change in bending frequency with overtone level and kinetic coupling between the two stretching motions accounts for the observed C-H overtone spectrum. The simple Morse potential that accounts for a single isotopomer is only an effective potential.     

Kaolinite Clay Mineral Reactivity Improvement through Ionic Liquid Functionalization

Since the intercalation of 1‐ethylpyridinium chloride in the interlayer space of kaolinite in 2005, several other ionic liquids (ILs) have been successfully intercalated. Unlike other clay minerals that display charged structural units, kaolinite is almost neutral. ILs intercalation in kaolinite results in both the cation and the anion in the interlayer space. The confinement of ILs in this two‐dimensional polarized space is of numerous interests, with certainly the most important to be discovered. Moreover, kaolinite interlayer space is decorated by a dense network of hydroxyl functions that can be easily functionalized. Recent study demonstrates that it is possible to synthesize ILs from simple organic molecules whose cations can be permanently grafted into the interlayer space of kaolinite. This review presents the results obtained in kaolinite functionalization by ILs, by focusing on the synthesis, applications and potential perspectives offered by these new nanohybrid materials.     

Synthesis and characterization of CdWO4 nanocrystals

The CdWO₄ nanocrystals were successfully synthesized by simple co-precipitation method. The X-ray diffraction pattern confirms the phase purity and the single phase formation of monoclinic Wolframite structure of CdWO₄. The average crystallite size of 22 nm was calculated from X-ray line broadening method. The FT-IR spectra confirm the presence of stretching and bending vibrations of metal cations like Cd-O, W-O and Cd-O-W bands in the CdWO₄ structure. The morphological features were analyzed by TEM and HRTEM techniques. The electrical conductivity of the materials is found to increase with increasing temperature as well as frequency which enumerates the semiconducting behavior of the material.     

Effects of exchanged ammonium cations on structure characteristics and CO2 adsorption capacities of bentonite clay

Different alkali and alkaline earth cation forms of bentonite clay were exchanged with protonated mono-, di- and triethanolamine compounds, to study the effect of the exchanged ammonium cations on the structure characteristics, thermal behavior, surface properties and CO₂ adsorption capacities of bentonite clay. The revolution of the interlayer structure characteristics, thermal properties, the specific surface area and elemental analysis were characterized by XRD, FTIR, TGA, BET and CHNS techniques respectively, while the CO₂ adsorption capacities were gravimetrically measured by using magnetic suspension balance (MSB) equipment. It was found that the intercalation of ammonium cations into the interlayer space of bentonite clay induced a step change in its basal spacing, depending on their molar mass and the interlayer molecular arrangement. The presence of the characteristic IR peaks of amine compounds in the spectra of bentonite clay adsorbents modified by amines was qualitatively supported by the incorporation of ammonium cations in the interlayer space of bentonite, while the presence of C, H and N elements using CHNS technique was quantitatively confirmed by the intercalation process of amine compounds. It was also found that the molar mass of amines has an inverse effect on the amount of the adsorbed water (intensity), its desorption temperature (position) and the specific surface area of the synthesized materials. The CO₂ adsorption capacities on all the studied bentonite clay adsorbents modified by amines were found to increase between 2.68 and 3.15 mmol/g, compared to 0.93 mmol/g for untreated bentonite at the studied temperature and pressure. As expected, bentonite clay modified with di- and triethanolammonium cations showed lower CO₂ adsorption capacities than that treated with monoethanolammonium cations, due to their low specific surface area.     

Apparatus for the Oscillating-Heating Method of X-Ray Powder Diffraction

An apparatus for obtaining the X-ray powder diffraction pattern of a sample while its temperature is increasing at a constant controlled rate has been developed. This equipment is described in enough detail to permit duplicate construction. The program controller is continuously sensitive to the sample temperature and controls the amount of power supplied to the sample heater. Complete schematic details of the electronic circuitry are included, and mechanical details of the program generator are illustrated photographically. The dehydration of clays and related minerals is discussed to illustrate the use of this versatile apparatus. The first order diffraction maxima of water-wet vermiculite and monoionic sodium, calcium, and magnesium montmorillonites are recorded while the sample temperature is increased at the rate of 5°C. per minute. This is then repeated with ethylene glycol substituting for the water. The temperatures of dehydration and of deglycolation depend on the nature of the exchange cation and are shown to increase in the order sodium < calcium < magnesium.