Application of Methyl Cinnamate/Montmorillonite as Ultraviolet Radiation Shelters

The interaction of methyl cinnamate/montmorillonite samples prepared by melting the former onto the second or by joint grinding, has been studied by x-ray diffraction. differential thermal analysis, thermogravimetric analysis and Fourier-transform infrared spectroscopy. Formation of an interlayer compound has been observed, leading to an increase of 4.15 or 3.42 A (samples obtained by melting or grinding, respectively) in the basal spacing of the clay. Formation of such a complex leads to a displacement of molecular water from the interlayer space, as concluded from the thermal studies. No chemical change is observed in the methyl cinnamate molecule, as confirmed by infrared spectroscopy. The system prepared improve the shelter properties of the clay and the drug separately, mainly in the C zone of the ultraviolet spectrum (290-190 nm).     

Formation of aluminosilicate geopolymers from 1:1 layer-lattice minerals pre-treated by various methods: a comparative study

Materials resembling aluminosilicate geopolymers have been prepared from the kaolinitic 1:1 layer lattice aluminosilicate clay mineral halloysite by reaction with sodium silicate solution under alkaline conditions. The effect on geopolymer formation of pretreating the clay mineral reactant by heating, high-energy grinding or exposure to acid or alkali was monitored by the ability of the samples to cure and harden, and by XRD, ²⁷Al and ²⁹Si solid-state MAS NMR spectroscopy. Only samples prepared from the fully thermally dehydroxylated clay showed the typical XRD and NMR geopolymer characteristics. Less complete reaction was found in samples pretreated by highly energetic grinding, whereas samples exposed to chemical pretreatment with dilute acid did not react to form viable geopolymers. Pretreatment with dilute alkali produced a zeolite which reacted with sodium silicate, but the hardened sample was not X-ray amorphous and showed subtle differences in its NMR spectra. These results are discussed in terms of the vital role played in the early stages of the reaction sequence by the presence of labile aluminium. The efficacy of the various pretreatment methods is related to their ability to render the aluminium source (the solid aluminosilicate clay) sufficiently soluble in alkali.     

Preparation of polystyrene–clay nanocomposite by solution intercalation technique

Polymer–clay nanocomposites of commercial polystyrene (PS) and clay laponite were prepared via solution intercalation technique. Laponite was modified suitably with the well known cationic surfactant cetyltrimethyl ammonium bromide by ion-exchange reaction to render laponite miscible with hydrophobic PS. X-ray diffraction analysis in combination with scanning electron microscopy gives an idea of structural and morphological information of PS–laponite nanocomposite for different varying organo-laponite contents. Intercalation of PS chain occurs into the interlayer spacings of laponite for low organo-laponite concentration in the PS–O-laponite mixture. However, aggregation and agglomeration occur at higher clay concentration. The molecular bond vibrational profile of laponite as well as PS–laponite nanocomposite have been explored by Fourier transform infrared spectroscopy. Thermogravimetric analysis along with differential scanning calorimetry results reveal the enhancement of both thermal stability and glass transition temperature of PS due to the incorporation of clay platelets.     

Studies on spironolactone polymorphic forms

Abstract

The phenomenon of polymorphism of spironolactone was studied using melting point and aqueous solubility determinations, infrared spectroscopy, differential thermal analysis, X-ray powder diffraction and powder dissolution. The results showed that spironolactone crystals obtained from ethyl acetate had the lowest melting range, while those obtained from acetonitrile had the highest range. The aqueous solubility data indicated the presence of different forms of spironolactone, each with a specific solubility, although practically all of these forms could be considered to be water-insoluble. The infrared spectra were not useful in clearly distinguishing between the different forms. Differential thermal analysis curves indicated that some of the forms obtained by treating spironolactone with different solvents were somewhat similar, others were variable, but all of them were different from the original form of the drug. Moreover, the thermal study proved the absence of any solvates. X-ray patterns were different in spacing (d) values and intensities of radiation absorption, confirming the presence of four different forms of spironolactone. The form obtained from ethyl acetate had the highest dissolution rate, while that obtained from acetonitrile had the lowest rate.

Spironolactone is known to crystallize out from different solvents in different polymorphic forms and to undergo structural rearrangements on heating.^{1, 2} The study was mainly concerned with the infrared identification of steroids, and the results showed that sample preparation techniques have a profound effect on the spectra of these steroids.

Florence and Salole³ undertook a brief investigation into the effects of grinding on the crystalline properties of spironolactone. The results showed no major changes in infrared spectrum after grinding, apart from a decrease in resolution of the absorption peaks. The premelting behavior of the drug was altered, which would indicate that grinding significantly affected the spironolactone crystallinity.

El-dalsh et al.⁴ showed that spironolactone co-precipitate with povidone using different solvents such as absolute ethyl alcohol, acetonitrile and chloroform had a different X-ray diffraction pattern which may be explained on the basis of various polymorphic forms.

The purpose of the present work is to carry out studies to specify the number of polymorphs of spironolactone under the crystallization conditions.     

Effects of modified Clay on the morphology and thermal stability of PMMA/clay nanocomposites

The potential to improve the mechanical, thermal, and optical properties of poly(methyl methacrylate) (PMMA)/clay nanocomposites prepared with clay containing an organic modifier was investigated. Pristine sodium montmorillonite clay was modified using cocoamphodipropionate, which absorbs UVB in the 280–320 nm range, via ion exchange to enhance the compatibility between the clay platelets and the methyl methacrylate polymer matrix. PMMA/clay nanocomposites were synthesized via in situ free-radical polymerization. Three types of clay with various cation-exchange capacities (CEC) were used as inorganic layered materials in these organic–inorganic hybrid nanocomposites: CL42, CL120, and CL88 with CEC values of 116, 168, and 200 meq/100 g of clay, respectively. We characterized the effects of the organoclay dispersion on UV resistance, effectiveness as an O₂ gas barrier, thermal stability, and mechanical properties of PMMA/clay nanocomposites. Gas permeability analysis demonstrated the excellent gas barrier properties of the nanocomposites, consistent with the intercalated or exfoliated morphologies observed. The optical properties were assessed using UV–Visible spectroscopy, which revealed that these materials have good optical clarity, UV resistance, and scratch resistance. The effect of the dispersion capability of organoclay on the thermal properties of PMMA/clay nanocomposites was investigated by thermogravimetric analysis and differential scanning calorimetry; these analyses revealed excellent thermal stability of some of the modified clay nanocomposites.     

Characterization and study of Na2O-B2O3-SiO2 glasses prepared by the sol-gel method

The sol-gel procedure has been used to prepare vitreous materials whose compositions are situated in the liquid-liquid immiscibility area of the Na₂O-B₂O₃ SiO₂ phase equilibrium diagram. Gels were prepared from different precursors and under different experimental conditions. After determining optimum conditions for gelling and heat-treatment, the gels were characterized with the aid of thermal analysis, X-ray diffraction, density and specific surface area measurements, as well as infrared and near-infrared spectroscopy. The textures of the samples and their microstructures were studied by means of scanning electron microscopy and transmission electron microscopy, respectively. The phase separation in the gels was compared to the same phenomenon in one of the glasses of identical composition, but prepared by conventional melting.     

Physicochemical Study of the Adsorption of Oxprenolol Hydrochloride by Montmorillonite

Abstract

The interaction between oxprenolol hydrochloride and montmorillonite was studied by adsorption isotherms, x-ray diffraction and i.r. spectroscopy.

The adsorption isotherm fits Langmuir's equation and the maximum amount of oxprenolol adsorbed by the clay is 70 mEq/100 g of clay.

The results of x-ray diffraction studies and i.r. spectroscopy reveal that the oxprenolol molecule is adsorbed into the interlayer space of the clay and that the mechanism of adsorption is cation exchange.     

One-step synthesis and characterization of carbon nanospheres via natural gas condensate pyrolysis

Abstract

In the current work, carbon nanospheres (CNSs) were prepared via pyrolysis of gas condensate in N₂ at 1273?K and atmospheric pressure for 2?h using ferric chloride as a catalyst precursor. X-ray diffraction, energy dispersive X-ray spectrometry (EDX) in scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectrometry (Raman), Fourier transform infrared spectroscopy, and thermal gravimetric analysis (TGA) are employed for the structural and morphological characterization of the nanomaterials formed. The conductivity of these films was measured using the four probe method. As results, SEM-EDX and TEM analysis reveal spherical shaped particles, with diameter varying between 100 and 200 nm and graphene interlayer distance of 0.339 nm. The very low I_D/I_G ratio obtained reveals a relatively low amount of disorder in the nanostructures and TGA analysis implies that thermal stability was achieved after 470?°C. Our work provides a simple synthetic strategy in one-step sample preparation of CNSs, which can be used for furfur applications such as high-performance supercapacitors or adsorbents.     

Preparation and characterization of organo-montmorillonites. Application in adsorption of the 2,4,5-trichlorophenol from aqueous solution

X-ray diffraction has been used to study the changes in the surface properties of montmorillonitic clay through the changes in the basal spacings of sodium-montmorillonite (NaMt), acid-activated montmorillonite (AMt), pillared-montmorillonite (AlMt) and surfactant-intercalated organoclays. The basal spacing value of the NaMt increased from 12.01 to 18.1 Å by pillaring with Keggin ions ((hydroxyaluminum polycation) and until 21 Å by intercalation of the cationic surfactant in the interlayer space of the clay. Confirmations of the intercalated cationic surfactant have been characterized using Fourier transform infrared spectroscopy (FTIR). Thermogravimetric analysis shows that the thermal decomposition of montmorillonites modified with the cationic surfactant hexadecyltrimethylammonium (HDTMA) takes place in four steps. The surface areas of organo-montmorillonites were found to be much lower than that of raw montmorillonite. Surface areas of pillared and acid-activated montmorillonite are very high. This was explained by the emergence of the micropores and mesopores in the structure of the sample resulting from treatment. Adsorption of the 2,4,5-trichlorophenol (2,4,5-TCP) onto samples was studied. The greatest value of adsorption capacity of samples is attributed to the organo-montmorillonite (MtC16).     

Solid State Characterization of Stanozolol

Abstract

A study was undertaken to illustrate the ability to characterize various crystal forms of Stanozolol by by thermal analysis (differential scanning calorimetry-DSC), X-ray powder diffraction (XRPD), and Fourier transform infrared spectroscopy (FTIR). Mixtures of forms I and II were prepared and analyzed by each technique to investigate the strengths and weaknesses of the three methods. The detection of a contaminant polymorph in mixtures of forms I and II was possible by both FTIR and XRPD but not possible by DSC.

Various solvated forms were prepared by recrystallization from methanol, ethanol, 2-propanol, and were shown by thermal gravimetric analysis to exist in a 1:1 stoichiometry with Stanozolol. XRPD analysis of solvates indicated that each solvated form (monohydrate, ethanol solvate, methanol solvate, 2-propanol solvate) exists in a crystal unique with respect to forms I and II.

The concentration of drug in solution for the different crystal forms was determined at room temperature in 2% SLS at 5 and 24 hours. A significantly higher concentration was observed for the form II sample at 5 hours versus the form I and the monohydrate samples. It is likely that the form I sample had converted to the monohydrate form after 5 hours and a maximum concentration would be observed at an earlier time. At 24 hours, both the form I and II samples had converted to the monohydrate form and concentrations of 0.5–0.6 mg/mL were observed for each form. Due to the transformations to the hydrate during solubility studies, meaningful comparisons were difficult.     

Characterisation of K, Na, and Li birnessites prepared by oxidation with H2O2 in a basic medium. Ion exchange properties and study of the calcined products

Birnessites containing Na, K or Li in the interlayer have been prepared by oxidation of Mn(II) cations with H₂O₂ in a basic medium with different alkaline cation/Mn molar ratios. The solids prepared have been characterised by elemental chemical analysis, powder X-ray diffraction, thermal analyses (differential thermal analysis and thermogravimetric analysis), FT-IR spectroscopy and surface texture assessment by adsorption of N₂ at –196°C. Crystalline birnessites are obtained for A/Mn ratios (A = K, Li) larger than 3.4, but MnO(OH) has been also identificed when such a ratio is smaller than 3.4. Ion exchange is topotactic, but is not complete for exchanging Na, K, or Mg for pre-existing Li. The solids are stable up to 400°C, and formation of spinels and solids with tunnel structures is observed at this temperature. Li-containing birnessites are transformed to LiMn₂O₄ spinel at 400°C, and co-crystallization of bixbyte (Mn₂O₃) is observed at higher temperatures. Bixbyte and cryptomelane are formed at 500°C for the K-containing birnessites.     

Study of interlayer spacing collapse during polymer/clay nanocomposite melt intercalation

The influence of the chemical structure of alkylammonium organo-modifying montmorillonite clays on the ability to form nanocomposites by melt blending, depending on the processing temperature and the organoclay thermal treatment, has been investigated. On one side chlorinated polyethylene/Cloisite 30B (nano)composite has been prepared by melt intercalation at 175 degrees C and its wide angle X-ray diffraction pattern revealed that the peak characteristic of the interlayer spacing of the organoclay was shifted to lower d-spacing, indicating a collapse of the organoclay structure. On the other side, (nano)composites based on ethylene-vinyl acetate copolymer/Cloisite 30B have been prepared by melt intercalation at 140 degrees C. At this temperature, exfoliation was observed with the as-received organoclay while the same organo-modified clay, simply dried at 180 degrees C for 2 hours, induced again the formation of a composite with a collapsed structure. The effect of the Cloisite 30B thermal treatment on the morphology and mechanical properties of ethylene-vinyl acetate-based (nano)composites was investigated using wide angle X-ray diffraction and tensile tests. In order to shed some light on the origin of this clay interlayer collapse, organoclay modified with various ammonium cations bearing long alkyl chains with different amounts of unsaturations were studied using wide angle X-ray diffraction and X-ray photoelectron spectroscopy before and after thermal treatment at 180 degrees C for 2 hours. Isothermal thermogravimetric analysis of all organoclays was also investigated. The layers collapse effect is discussed depending upon the level of unsatured hydrocarbon present in the organic surfactant.     

Effect of solvents on the dynamic viscoelastic behavior of poly(methyl methacrylate) film prepared by solvent casting

Poly(methyl methacrylate) films were prepared by dissolving the polymer in chloroform, toluene and tetrahydrofuran, with identical concentrations of 200 mg/mL, and drop casting the solutions on Teflon surface at room temperature. The thermal, thermomechanical and structural properties have been investigated by differential scanning calorimetry, dynamic mechanical analyzer, and Fourier transform infrared spectroscopy, respectively. The dynamic mechanical behavior of the films has been measured over a temperature range of 30–150 °C, using sinusoidal stress with a frequency of 2 Hz. The samples prepared from tetrahydrofuran showed the highest storage modulus, indicating a higher polymer chain entanglement in that solvent, whereas the samples prepared from chloroform showed the lowest storage modulus. The samples prepared from chloroform, which showed the weakest mechanical properties, also showed the lowest glass transition temperature, which is evidence of the plasticization and solvent retention mechanism of chloroform. The spectroscopic analysis confirmed the solvent-polymer interactions giving rise to the above mentioned effects.     

Solvothermal synthesis and characterization of acicular α-Fe2O3 nanoparticles

Nanometer-sized α-Fe₂O₃ particles have been prepared by a simple solvothermal method using ferric acetylacetonate as a precursor. The products were characterized by X-ray diffraction (XRD), energy dispersive X-ray microanalysis (EDAX), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transition electron microscopy (TEM), infrared spectroscopy (IR) and thermal analysis (TG-DTA). XRD indicates that the product is single-phase α-Fe₂O₃ with rhombohedral structure. Bundles of acicular shaped nanoparticles are seen in TEM images with an aspect ratio ～ 12; typically 8–12 nm wide and over 150 nm long. The α-Fe₂O₃ nanoparticles posses a high thermal stability, as observed on thermal analysis traces.     

Mechanochemical synthesis of zinc-apatitic calcium phosphate and the controlled zinc release for bone tissue engineering

Abstract

In this study, in order to control zinc (Zn)-release from calcium phosphate (CaP), the crystalline forms of CaP-containing Zn were modified by wet ball milling and/or heat treatment. The CaP (CaO:CaHPO₄:ZnO?=?7:20:3, molar ratio) was ground in a ball mill with the addition of purified water, and the ground products were heated to 400?°C and 800?°C. The physicochemical properties of these ground products were measured by powder X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy and energy-dispersive X-ray spectroscopy. Zn release characteristics from the samples were evaluated using a dissolution tester. The results of XRD and IR suggested that the structures of the starting materials were destroyed after 2.5?h of grinding, and new apatite-like amorphous solid containing Zn was generated. The Zn-release from the ground products was markedly suppressed after 2.5?h of grinding.     

Synthesis,characterization and properties of polyaniline/expanded vermiculite intercalated nanocomposite

Abstract

The synthesis characterization and conductivities of polyaniline/expanded vermiculite intercalated nanocomposite are presented in this paper. The conductive emeraldine salt form of polyaniline is inserted into the interlayer of expanded vermiculite to produce the nanocomposite with high conductivity. The structures and properties are characterized by transmission electron microscopy x-ray diffraction spectroscopy fourier transform infrared spectroscopy thermogravimetry analysis and by the measurements of conductivity and stability. The results show that an intercalated nanocomposite with high conductivity and stability is obtained. The synthesis conditions are optimized to obtain the highest conductivity which is 6.80 S cm^?1.     

Properties of Solid Dispersions of Naproxen in Various Polyethylene Glycols

Abstract

Solid dispersions of naproxen in polyethylene glycol 4000, 6000, and 20000, aimed at improving the drug dissolution characteristics, were prepared by both the solvent and melting methods. The drug-polymer interaction in the solid state was investigated using differential scanning calorimetry, hot-stage microscopy, Fourier-transform infrared spectroscopy, and x-ray diffraction analysis. Interaction in solution was studied by phase solubility analysis and dissolution experiments. Computer-aided molecular modeling was used to supplement the results from phase solubility studies. No important chemical interaction was found between naproxen and polyethylene glycol, either in solution or in the solid state, apart from the formation of weak drug-polymer hydrogen bonds. The increase of naproxen dissolution rate from its binary systems with polyethylene glycol could be attributed to several factors such as improved wettability, local solubilization, and drug particle size reduction. No influence of polymer molecular weight or of the solid dispersion preparation method on drug dissolution properties was found.     

Synthesis and characterization of polyaniline nanorods/Ce(OH)3-Pr2O3/montmorillonite composites through reverse micelle template

Polyaniline (PANI) nanorods/Ce(OH)₃-Pr₂O₃/montmorillonite (MMT) nanocomposites were synthesized via in situ polymerization of aniline monomer through reverse micelle template (RMT) in the presence of montmorillonite and Ce(OH)₃, Pr₂O₃. In the experiment, sulphosalicylic acid was used as dopant, aniline was designated as oil phase and the aqueous solution comprising Ce³⁺ and Pr³⁺ as water phase. The nanocomposites were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopy and thermogravimetry-differential thermal analysis (TG-DTA). The results showed that PANI nanorods were synthesized in the interlayer spaces of MMT with uniform spherical rare earth nanoparticles. The thermal stability of the nanocomposites prepared was enhanced drastically compared with pure polyaniline.     

Effects of Ti transition layer on stability of silver/titanium dioxide multilayered structure

Thermal stability is critically important for silver-based multilayered structures such as Ag/TiO₂. Al and NiCr are reported to be applied as interlayers between Ag and TiO₂ to improve the thermal stability but both decrease the transparency in visible region. In this work, a Ti interlayer can effectively improve the thermal stability of the Ag film but does not adversely affect the optical transmission through the multilayer from the near ultraviolet to near infrared spectral region. Atomic force microscopy indicates that the titanium interlayer improves the surface quality and agglomeration resistance of the Ag film. Depth profiles obtained by Auger electron spectroscopy show that the L₃M₂₃V line of titanium shifts to a higher binding energy after annealing, indicating that the titanium layer is oxidized during annealing at 573 K in air for 30 min. X-ray diffraction results indicate that the transition layer is oxidized to Ti₂O₃ during deposition and the Ag (111) orientation preferentially emerges after the thermal treatment. The Ag layer remains chemically stable but some diffusion is observed through the top dielectric layer after annealing. About 10% degradation in the visible light transmission and 20% in near IR reflection are observed from the samples without the interlayers after annealing. In comparison, less than 10% decrease in the near IR reflectivity is observed from the samples with the interlayers. The transition layer is found to stabilize the silver film by improving the wettability, agglomeration resistance, and diffusion resistance.     

On the investigation of acid and surfactant modification of natural clay for photocatalytic water remediation

In this study, a series of mineral and organic acids are introduced to natural clay modification. Several analytical techniques are employed to identify the physical and chemical changes in clay. The effect of surfactants on these properties is also investigated. The samples are prepared using simple acid treatment without filtration. The alteration in surface morphology is proportional to the acid strength as evident from SEM and XRD analyses. Therefore, the treatment with mineral acid and organic acid/HNO₃ results in the formation of new layers by surface modification as depicted in SEM images, and a higher degree of suppression in characteristic XRD reflections of clay is noticed. However, the treatment with organic acids modifies the existing interlayer spacing of clay, and therefore, the XRD characteristic reflections of clay are less affected. These observations are also supported by FT-IR analysis. The surface area of modified clay is dependent on the acid strength, composition and size of counter-anion of acid. An increase in surface area and porosity is noticed after surfactant modification of HNO₃-treated clay, where the change is more prominent at the concentration higher than their respective critical micelle concentration. Thermal stability is dependent on the chemical composition and surface area of clay materials. A relatively higher absorbance is observed for modified clay materials compared with untreated clay during DRS analysis. The catalytic efficiency of modified clay materials in Eriochrome Black T degradation has been demonstrated.