Natural silicates in glass fibre production

The article analyzes the research devoted to the study of the structure and morphology of composite materials based on polyaniline (PAn) and natural minerals (NM) such as montmorillonite, kaolinite, zeolite, glauconite, etc.,. It focuses on the experimental results received by the most important and widely used methods applied to study the structure and morphology of composite materials based on polyaniline and natural minerals (PAn/NM), namely X-ray diffraction, ultraviolet-visible and Fourier transformation infrared spectroscopy, scanning electron and transmission electron microscopy. X-ray analysis is the basis for determination of the phase state and structure, the presence of the effect of intercalation and separation (exfoliation) of layered silicates in nanocomposites of PAn. The type of PAn/NM composite determines the position of the peak of the basal reflex, which is within the range of 2θ = 5–8o. The displacement of this reflex in the direction of the smaller diffraction angles (in comparison to diffraction angles of the initial NM) confirms the presence of a regular multilayer structure inherent to the intercalated composite. The disappearance of this reflex occurs under an increase of the interlayer distance in the NM or due to disordering of silicate plates, which is inherent in fully separated (exfoliated) composites. The presence of two main peaks at 2θ = ~20.0o or 2θ = ~25.0o on the diffractograms of the PAn samples indicates the form of produced PAn, namely the emeraldine base (EMB) or the emeraldine salt (EMS), respectively. The presence of NM in the reaction mixture usually does not affect the crystallinity of PAn, deposited on their surfaces. To study the chemical structure, interphase interaction between PAn and NM, the characteristics of intercalation and separation states, the FTIR spectroscopy are used. A shift or change of intensity of the main adsorption bands (~1 640, ~1 470 cm –1 , etc.) characteristic of the PAn, an expansion, decrease of intensity or complete disappearance of the O–H band (~3 420 cm –1 ) in the spectra of PAn nanocomposites in comparison with same band in the FTIR spectrum of pure PAn are connected with the formation of hydrogen bonds between the surface O–H groups of NM and N–H groups in PAn macromolecules.These effects confirms the presence of interphase interactions and, respectively, the composite nature of the produced materials. Besides, an important element of the chemical structure of polyaniline is the consequtive mainly 1,4-addition of aniline molecules with the formation of macromolecular chains of PAn. Electron spectroscopy in the ultraviolet and visible spectral region allows us to quickly determine the form of PAn formed during the synthesis of composites with NM. The blue shift of the main peaks of the PAn can correspond to the interphase interaction between the PAn and the surface of NM. The characteristics of UV-vis spectra also are determined by the amount of encapsulated An in the interlayer expanses of NM. The morphology of the particles of polyaniline on the surface of the NM is usually heterogeneous. The polymer particles have basically quasispherical or semispherical forms, they are of varying sizes and are unevenly layed on particles of NM. An exception isthevirtually uniform layers of polyaniline on nanotubes of halloysite modified by hematite. Keywords: natural minerals, polyaniline, composites, structure, morphologies.

Controllable synthesis of hierarchical zeolites from natural aluminosilicate minerals is considered an efficient and eco-friendly approach for the production of high-performance zeolites, but its synthesis mechanism is still obscure. Herein, we take the synthesis of a single-crystalline hierarchical NaA zeolite using submolten salt depolymerized kaolin (SMS-K) as the sole source of silicon and aluminum via a mesoscale reorganization strategy as an example to elucidate the reorganization process. Comprehensive morphological and structural analyses reveal that sodium-rich voids in SMS-K facilitate concurrent assembly both within the interior and at the interface of the amorphous gel, leading to the formation of numerous nanoparticles with short-range order which assemble into single-crystal nanocube NaA zeolites with intracrystalline mesopores. By harnessing confinement effects, SMS-K modulates the growth of nanoparticle sizes and enhances the intimate interconnection of nanocubes, thereby yielding NaA zeolite aggregates that exhibit hierarchical porosity, encompassing micro-, meso-, and macropores. This study offers the potential for designing and precisely controlling the fabrication of hierarchical zeolites derived from natural minerals.

Mechanical properties, durability and environmental assessment of low-carbon cementitious composite with natural fibrous wollastonite

Differential redox and sorption of Cr (III/VI) on natural silicate and oxide minerals: EXAFS and XANES results

Locally available wastes were found to provide a good alternative source of highly active silica for the synthesis of zeolites. In the present investigation a collection of barely husk (from Erbil/north of Iraq), colourless glass (fruity glass) and white ceramic glass wastes were used usefully as a renewable sources of silica and alumina for synthesis of four types of zeolites; a suitable procedure was employed to extract silica and alumina from the selected wastes. The detections showed that the barley husk had the largest amount of silica. While the white ceramic glass wastes (laboratory waste) had the largest amount of alumina. Each zeolite sample was prepared starting from a mixture constituted by a source of silica and/or a source of alumina under hydrothermal condition at atmospheric pressure. The studied wastes were converted to zeolite Y, zeolite SOD, zeolite A and zeolite AFX. Raw materials and synthesized zeolites were characterized by x-ray fluorescence spectroscopy (XRF), X-ray diffraction spectroscopy (XRD) and Infrared spectroscopy (IR).

The effect of land plants on weathering rates of silicate minerals

5 - Glass fibers

Several factors affecting Al-MCM-41 synthesis

Several terrestrial minerals, most of them amphiboles, were analyzed by means of the secondary ion mass spectrometry (SIMS) technique for the rare-earth elements (REE). The present measurements were made with a Cameca IMS 4F ion microprobe, using a moderate energy filtering (80 V offset from the maximum of the energy distribution, with an energy window of ~50 V), in order to eliminate complex ion interferences. The analyzed spectra were essentially free from molecular ions over the measured mass range. A peak deconvolution method was required, however, to separate the Eu signal from the BaO contribution, being still active at this offset. Quantitative determinations were carried out using relative sensitivity factors (RSF) calculated from natural mineral standards (RSFsnat.) and the same minerals reduced to glass pellets (RSFsglass). Such factors were successively compared with those calculated from synthetic geostandard glasses (NBS 612, NBS 610, NBS 614) and an ensemble of international silicate (mafic-ultramafic) rock standards fused in glasses. Differences in RSFs were shown, depending on crystalline structure and local inhomogeneities. It is demonstrated that, even if the use of mineral standards for natural minerals and glassy standards for natural silicate melts is recommended in order to obtain a more accurate analysis, nevertheless a wide set of RSFsglass could be tentatively applied in the analysis of silicates when suitable mineral standards are not available.

Transformation of coal mineral matter in relation to coal metamorphism in the Rajhara sub-basin, Daltonganj Coalfield, India

Synthetic investigation of CIT-5 catalyst

Experimental investigations on geopolymer stabilised compressed earth products

Isomerization of 1-butene over SAPO-11 catalysts synthesized by varying synthesis time and silica sources

In this paper the formation of a gelatinous hydrate phase from the natural dicalcium silicate minerals larnite and bredigite is described. Detailed study of the gel so formed indicates that the process of hydration is a solid reaction which is effeeted by diffusion. The preferred orientation of the hydrate phase suggests that the hydration is facilitated by a relationship between the structure of the anhydrous silicate and that of the hydrate phase produced.In this investigation the variations in density, mean refractive index, and chemical composition of the natural gels have been determined and the characteristics of the adsorbed water studied by isothermal dehydration and rehydration. In discussing the mechanism of hydration it has been assumed that this obtains at constant volume. This assumption is based on the study of gel pseudomorphs after single crystals of larnite and bredigite in thin section.

Occupational exposure to asbestos fibers has been associated with the development of pulmonary fibrosis (i.e., asbestosis), bronchogenic carcinoma and mesothelioma. Therefore, the commercial use of asbestos is likely to be curtailed or limited in the near future and mineral fiber substitutes are currently being promoted to fill the void. Wollastonite fibers are natural acicular calcium silicate minerals which have been proposed as alternatives for asbestos in applications such as brake linings, wallboard and insulation materials. Wollastonite fiber diameters are generally in the 1–10 µm range with an average diameter of 3.5 µm (Vu, 1988).