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.     

XRD, EDX and IR analysis of solid solutions between thaumasite and ettringite

Solid solutions between thaumasite and ettringite were prepared by methods analogous to those well established for the preparation of thaumasite and ettringite. The extent of immiscibility in this system is investigated by varying the Al:Si and SO₄²⁻:CO₃²⁻ ratios in reactant mixtures. The solids produced were analysed by quantitative X-ray diffraction, with Rietveld refinement also providing accurate unit cell dimensions, energy-dispersive X-ray analysis and infrared spectroscopy. The compositional and unit cell variations in the solid solution are discussed. A wide variety of solid solution compositions were produced with both the thaumasite and ettringite structures, but all preparations were considerably diluted by secondary amorphous products.     

Characterization and adsorption properties of polymer-based microporous carbons with different surface chemistry

Polymers are promising activated carbon precursors due to their high percentage of carbon and also due to their abundance in a relatively pure state from waste recovery. Microporous activated carbons were prepared from poly(ethyleneterephthalate) (APETW, APETOX) and polyacrylonitrile (APAN). Their surface behaviour was characterized under dry and wet conditions by X-ray photoelectron spectroscopy (XPS), pH, pH_PZC and Boehm titration. The oxygen content of the nitrogen-free APETW and APETOX (S_BET = 1440 and 1509 m²/g) is 4.3 and 10.0 at.%, respectively. APAN (356 m²/g) contains 5.4 at.% oxygen and 5.3 at.% nitrogen. The ratios of the surface density of the titrated groups are approximately 20:28:65 in APETW, APETOX and APAN, respectively. The last has the most basic character. The larger oxygen content of APETOX yields greater affinity towards water, as does the presence of nitrogen functionalities in APAN. The higher the concentration of the functional groups, the higher is the water uptake at low relative humidity.

The greatest formaldehyde uptake per unit surface area was found in APAN, which is decorated with both nitrogen and oxygen functional surface groups. Due to the competitive adsorption of formaldehyde and water, increasing oxygen concentration in the APETW sample changed the kinetics of sorption but did not affect the formaldehyde uptake at saturation.     

Chemical Synthesis of PEDOT–Au Nanocomposite

In this work, gold-incorporated polyethylenedioxythiophene nanocomposite material has been synthesized chemically, employing reverse emulsion polymerization method. Infrared and Raman spectroscopic studies revealed that the polymerization of ethylenedioxythiophene leads to the formation of polymer polyethylenedioxythiophene incorporating gold nanoparticles. Scanning electron microscope studies showed the formation of polymer nanorods of 50–100 nm diameter and the X-ray diffraction analysis clearly indicates the presence of gold nanoparticles of 50 nm in size.     

The influence of demineralisation and ammoxidation on the adsorption properties of an activated carbon prepared from a Polish lignite

The preparation of cheap nitrogen-enriched materials with large adsorptive capacities and selectivity towards volatile organic compounds remains a challenge. Ammoxidation has been used to prepare nitrogen-enriched activated carbons using a demineralised Polish lignite. The lignite samples were demineralised by two different methods before nitrogen-enrichment by ammoxidation and physical activation in steam. The surface chemistry was investigated by elemental analysis, Boehm titration, infrared and XPS spectroscopies and adsorptive properties by a linear solvation energy relationship approach. Results show a quasi-total demineralisation and a higher reactivity towards nitrogen for the demineralised samples. The BET surface is also higher than for the non-demineralised lignite. Active carbons previously ammoxidated and demineralised are more interesting in terms of selective removal of gaseous pollutants.     

Photoluminescence of zinc oxide nanopowder synthesized by a combustion method

Zinc oxide (ZnO) nanopowder was synthesized by a simple and quick combustion method using zinc nitrate as a precursor and glycine as a fuel material. The starting materials were mixed at room temperature and spontaneous ignition of which resulted into the ZnO nanopowder. The synthesized nanopowder was characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), Infrared (IR) spectrophotometer and spectroflurometer in order to study the structural, morphological, compositional and photoluminescence (PL) properties. The ZnO powder shows polycrystalline nature with preferential peak (101) having crystallite size 25 nm. A significant band at 532 cm⁻¹ in the IR spectrum corroborates the presence of characteristic band of ZnO. Room temperature photoluminescence spectrum of the synthesized nanopowder exhibits a dominant, sharp and strong ultraviolet (UV) emission with a suppressed deep-level emission indicating good crystal quality and optical properties.     

Comparative Evaluation of Physical Properties of Edible Chitosan Films Prepared by Different Drying Methods

Edible films are alternative packaging, which have recently received much attention due mainly to environmental reasons. Edible films may be formed from edible biomaterials such as polysaccharides, proteins, or lipids. Among these biopolymers, chitosan is of interest because it has a good film-forming property and is biodegradable, biocompatible, and nontoxic. Several techniques have been used to prepare edible chitosan films with various degrees of success. However, it is always interesting to find an alternative technique to produce films of superior quality at shorter processing (drying) time. In this study, the influences of different drying methods and conditions on the drying kinetics and various properties of chitosan films were investigated. Drying at control conditions (ambient air drying and hot air drying at 40°C) as well as vacuum drying and low-pressure superheated steam drying (LPSSD) at an absolute pressure of 10 kPa were carried out at different drying temperatures (70, 80, and 90°C). The properties of chitosan films, in terms of color, tensile strength, percent elongation, water vapor permeability (WVP), glass transition temperature (T_g), and crystallinity, were also determined. Based on the results of both the drying behavior and film properties, LPSSD at 70°C was proposed as the most favorable conditions for drying chitosan films.     

Comparative Evaluation of Physical Properties of Edible Chitosan Films Prepared by Different Drying Methods

Edible films are alternative packaging, which have recently received much attention due mainly to environmental reasons. Edible films may be formed from edible biomaterials such as polysaccharides, proteins, or lipids. Among these biopolymers, chitosan is of interest because it has a good film-forming property and is biodegradable, biocompatible, and nontoxic. Several techniques have been used to prepare edible chitosan films with various degrees of success. However, it is always interesting to find an alternative technique to produce films of superior quality at shorter processing (drying) time. In this study, the influences of different drying methods and conditions on the drying kinetics and various properties of chitosan films were investigated. Drying at control conditions (ambient air drying and hot air drying at 40°C) as well as vacuum drying and low-pressure superheated steam drying (LPSSD) at an absolute pressure of 10 kPa were carried out at different drying temperatures (70, 80, and 90°C). The properties of chitosan films, in terms of color, tensile strength, percent elongation, water vapor permeability (WVP), glass transition temperature (T _g ), and crystallinity, were also determined. Based on the results of both the drying behavior and film properties, LPSSD at 70°C was proposed as the most favorable conditions for drying chitosan films.     

Giant dielectric constant,dielectric relaxations,and tunable properties of Sm2/3Cu3Ti4O12 ceramics

The polycrystalline Sm_2/3Cu₃Ti₄O₁₂ (SCTO) ceramics have been prepared by solid-state reaction. The crystallinity of the compound has been investigated by Rietveld refinement which has revealed a cubic structure with space group Im3. It is observed that at low frequencies, SCTO ceramic exhibits tremendously high values of dielectric permittivity ε′, larger than 32,000, at room temperature. Two distinct, thermally triggered, dielectric relaxations have been noted. This mechanism has been confirmed through impedance analysis of the ceramics. The complex impedance plane shows three semicircles, which confirm the existence of two dielectric relaxations in SCTO ceramics. In general, the electrical as well as dielectric behavior of SCTO ceramics are seen to be reasonably analogous to those of CaCu₃Ti₄O₁₂ (CCTO) ceramics. The emergence of the enormous dielectric constant in SCTO ceramic is accredited to the combined effect of polarization both at the sample-electrode interface as well as at the insulating grain boundary interface. The SCTO ceramics are identical to the CCTO ceramics in their structure and composition and hence, as the above results indicate, the IBLC effect mechanism, originally put forward for CCTO ceramics, is furthermore plausible to account for the mammoth values of dielectric constant in SCTO ceramics.     

Effect of La and Ni substitution on structure,dielectric and ferroelectric properties of BiFeO3 ceramics

In this communication, we present the results on Bi_1−xLa_xFe_1−yNi_yO₃ (x=0.0, 0.1; y=0.0, 0.05) samples processed by solid-state reaction route in order to study crystalline and electronic structure, dielectric and ferroelectric properties. The best refinement was achieved by choosing rhombohedral structure (R3c) for BiFeO₃ and Bi_0.9La_0.1FeO₃ samples. Whereas, the XRD pattern of BiFe_0.95Ni_0.05O₃ and Bi_0.9La_0.1Fe_0.95Ni_0.05O₃ samples were refined by choosing rhombohedral (R3c) and cubic (I23) structure. Raman scattering measurement infers nine Raman active phonon modes for all the as prepared samples. The substitution of Ni ion at Fe-site in BiFeO₃ essentially changes the modes position i.e. all the modes are observed to shift to lower wave number. Dielectric constant (ε′) and dielectric loss (tan δ) as a function of frequency have been investigated and they decreases with increasing frequency of the applied alternating field and become constant at high frequencies. This feature is a characteristic of Maxwell Wagner type of interfacial polarization. The remnant polarization (P_r) for Bi_0.9La_0.1FeO_3, BiFe_0.95Ni_0.05O₃, and Bi_0.9La_0.1Fe_0.95Ni_0.05O₃ are 0.08, 0.11, 0.69 μC/cm², respectively and the value of coercive field for Bi_0.9La_0.1FeO_3, BiFe_0.95Ni_0.05O₃, and Bi_0.9La_0.1Fe_0.95Ni_0.05O₃ are 0.53, 0.67, 0.68 kV/cm, respectively. X-ray absorption spectroscopy (XAS) experiments at Fe L₂,₃ and O K-edges are performed to investigate the electronic structure of well-characterized Bi_1−xLa_xFe_1−yNi_yO₃ (x=0.0, 0.1; y=0.0, 0.05) samples. The presence of reasonable ferroelectric polarization at room temperature in Bi_0.9La_0.1Fe_0.95Ni_0.05O₃ ceramics makes it suitable for technological applications.     

Solvated structure of C60 nanowhiskers

This work characterizes the structure of C₆₀ nanowhiskers prepared by the liquid-liquid interfacial precipitation method in the C₆₀-saturated m-xylene and isopropyl alcohol system. Transmission electron microscopy and X-ray diffraction measurement show that the C₆₀ nanowhiskers had a hexagonal structure with cell dimensions a = 2.407 nm and c = 1.018 nm which is different from pristine C₆₀. The structure of the C₆₀ nanowhiskers in solution is different from that of the solvated structure reported for the C₆₀ nanotubes but similar to that reported for the C₆₀ bulk crystal solvated with m-xylene. X-ray diffraction analysis also showed a shift to fcc structure after solvent evaporation. The C₆₀ nanowhiskers prepared using toluene as solvent also showed a similar solvated structure, and a more rapid structural change into fcc upon drying was again observed.     

磺基甜菜碱型氟碳表面活性剂在蒙脱土上的吸附性能

针对黏土吸附表面活性剂造成的损耗使得二元复合驱不能具有很好的协同效用,采用比色法研究了磺基甜菜碱型氟碳表面活性剂（FS）在钠基蒙脱土上的吸附性能,并考察了醇、部分水解的聚丙烯酰胺（HPAM）、pH值、温度对FS在钠基蒙脱土上吸附量的影响。结果表明：加入10%(体积)的不同种类的醇时,甲醇、乙醇、异丙醇、正丁醇降低FS在蒙脱土上的吸附,而辛醇、癸醇、乙二醇、丙三醇则增加FS在蒙脱土上的吸附,其中乙醇使FS吸附量降低67.25%,辛醇使FS吸附量增加86.76%;所以分子量相对较小的醇能降低FS相似文献   

生物质阴离子树脂的合成、表征及吸附性能

采用环氧氯丙烷、二乙烯三胺和三乙胺等对麦草秸秆进行化学改性,制备改性麦草秸秆阴离子交换树脂（改性麦秸树脂）,研究改性麦秸树脂的性能指标并重点考察其对水体中NO^-₃的吸附性能及效果。 研究结果表明,改性麦秸树脂引入了带正电荷的胺基基团,可以显著提高对NO^-₃的吸附性能;拉曼、红外光谱及zeta电位分析证明改性麦秸树脂对NO^-₃的吸附机理为离子交换;吸附过程符合Langmuir等温吸附模式;竞争吸附实验结果表明,改性麦秸树脂对不同阴离子的竞争吸附顺序为SO^2-₄>H₂PO^-₄>NO^-₃>NO^-₂,改性麦秸树脂对NO^-₃的最大吸附量为52.1 mg·g^-1,与商业树脂相当;柱吸附实验表明,改性麦秸树脂对NO^-₃的柱饱和吸附量为45.2 mg·g^-1,0.1 mol·L^-1的NaCl及HCl溶液均可有效再生改性麦秸树脂。     

Influence of Li doping on the morphological evolution and optical & electrical properties of SnO2 nanomaterials and SnO2/Li2SnO3 composite nanomaterials

SnO₂ nanomaterials and SnO₂/Li₂SnO₃ composite nanomaterials doped with different Li contents were synthesized via a simple one-step thermal evaporation method. X-ray diffraction patterns showed that with the increase of Li doping, the intensity of Li₂SnO₃ diffraction peaks gradually increased, while that of SnO₂ diffraction peaks gradually decreased. With the increase of Li doping, the width of nanobelts gradually increased, with the morphology changing from banded structure to standard hexagonal sheet structure. The Raman scattering spectra indicated that with the increase of Li doping, the peak of Li₂SnO₃ at 588.8 cm^?1 kept increasing, and the strongest vibration mode A_1g in SnO₂ gradually weakened. X-ray photoelectron spectroscopy revealed that with the increase of Li doping, the surface electrophilic oxygen species in SnO₂/Li₂SnO₃ composite nanomaterials greatly increased. Under the condition of light irradiation with a wavelength of 505 nm, the bright current of the Li-doped SnO₂ samples was higher than the dark current, while that of the SnO₂/Li₂SnO₃ composite nanomaterials was higher than the dark current, which was mainly due to more oxygen vacancies in SnO₂/Li₂SnO₃ composite nanomaterials than electrons excited by light. Consequently, positive photoconductivity gradually weakened, and even the negative photoconductivity emerged.     

Study of the distribution of the molecular orientation in thick polyethylene samples by X-ray diffraction, infra-red dichroism and Raman spectroscopy

The molecular orientation in thick polyethylene samples has been studied by wide-angle X-ray diffraction, i.r. dichroism and Raman spectroscopy. The original specimens, with dimensions of the order of a centimetre, were cut to obtain 1 mm thick platelets on which the measurements were made. The mean coefficient of the second-order Legendre polynomial, P₂, was calculated from X-ray diffraction and from the 1894 cm⁻¹ i.r. band for the crystalline phase, from the 909 cm⁻¹ i.r. band for the vinyl end groups and from the 1130 and 1060 cm⁻¹ Raman bands for the all-trans C-C conformers. The fourth-order coefficient, P₄, was also determined from X-ray diffraction and Raman spectroscopy for a series of cylindrical rods of draw ratios (λ) ranging from 6 to 20. An excellent correlation is observed between the P₂ coefficients measured from different X-ray reflections and from the 1894 cm⁻¹ i.r. band. The Raman spectroscopy results show that the all-trans bonds located in the amorphous phase are aligned perpendicular to the extrusion direction for the λ = 6 rod, and gradually reorient towards the fibre axis for λ values up to 20, while the P₂ and P₄ coefficients calculated for the crystalline phase remain constant at λ ≥ 12. The variation of the orientation through the thickness of the samples was investigated for the cylindrical rods and for an H-shaped moulding produced by extrusion and rolling. Minor differences in the degree of molecular orientation were detected between the centre and the surface of the rods, whereas important variations were measured for the H-shaped sample.     

Preparation and dielectric properties of CaTaO2N and SrNbO2N ceramics

A new approach for the synthesis of perovskite oxynitride ceramics via ammonolysis of thin pellets of their corresponding oxide precursors is reported. Phase-pure CaTaO₂N- and SrNbO₂N-ceramics with relative densities up to 78% were obtained by ammonolysis of Ca₂Ta₂O₇- and Sr₂Nb₂O₇-pellets with ≈10% porosities at 950 °C (SrNbO₂N) and 1100 °C (CaTaO₂N). The oxynitride samples were investigated with respect to their optical, thermal and dielectric properties. Temperature- and frequency-dependent impedance measurements revealed that CaTaO₂N is an insulator at room temperature with a relative permittivity in the order of 100. In contrast, SrNbO₂N exhibits a high relative bulk permittivity of ε′ = 25000 and a comparatively high bulk conductivity of 1.6 × 10⁻⁴ S cm⁻¹ at room temperature. At elevated temperatures, the evolving small electrical conductivity of CaTaO₂N can be assigned to the formation of thermally activated electron-hole pairs. For SrNbO₂N two defect-dominated conduction paths can be distinguished and related to grain boundary and bulk conductivity, respectively.     

Influence of soapstone waste on the mechanical and rheological properties of high-density polyethylene

Soapstone is an abundant mineral in Ouro Preto - Minas Gerais, Brazil and its main destination is in the production of craftsmanship. Rock recovery in those activities is low and the waste disposal is done with little control, which can be hazardous to the environment. This work proposes an alternative use of such potentially harmful waste as reinforcement in a novel polymer matrix composite, which can be particularly attractive to the automotive industry and of which very little information is available elsewhere in the literature. Firstly, the characterization of the waste was performed. Particle size and shape parameters were determined by automated image analysis and the mineralogical composition was determined by X-ray diffraction, infrared, and Raman spectroscopy. High-density polyethylene was used as matrix and the composites were made in three matrix/filler ratios: 90/10, 80/20, and 70/30 by weight. Tensile and rheological properties were measured in order to determine the influence of the particles on the polymer mechanical behavior and processing conditions. The materials showed a pseudoplastic behavior and the filler's influence was more pronounced in the 70/30 composites, which showed higher viscosities than the neat polymer. The addition of particles resulted in more brittle and rigid composites, with higher values of tensile strength.     

The influence of starting materials on the structure of ultrafine carbon powders

The primary ultrafine carbon powders were prepared by sol–gel supercritical fluid drying method using different starting materials. After heat-treatment at 1100 and 2600°C, respectively, the ultrafine carbon powders were obtained. The properties of primary ultrafine carbon powders and their annealed products were characterized by TEM, XRD, Raman spectra and nitrogen adsorption. The results reveal that starting materials have influence on the structure of ultrafine carbon powders.