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The aim of this work was to develop and optimize the method for geopolymeric materials preparation, which can be potentially used as membranes in gas or liquids separation processes. The used method involved hydrothermal growth of zeolite layers on geopolymeric support – the compatibility of spatial structure of supports with zeolite should encourage the formation of layers consistent with the supports (partial recrystallization of the support is also observed). Geopolymeric support was obtained by alkali-activation of metakaolinite and zeolite membranes were synthesized by crystallization of a zeolite layer during the hydrothermal treatment. It is possible to obtain hybrid material with phase composition and microstructure promising for potential use in gas or liquid separation processes. Image 1 • Hydrothermal treatment of metakaolin geopolymeric support was carried out. • The effect of activator type on the phase composition of resulting materials was investigated. • We used the Raman spectra to describe the geopolymerization progress. • Microscopic characteristics of zeolite layer were carried out. [ABSTRACT FROM AUTHOR]

We present a direct and geometric construction for an invariant measure in Poncelet's porism. [ABSTRACT FROM AUTHOR]

This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA+) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO42-, AsO43- and PO43- ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. [ABSTRACT FROM AUTHOR]

The results of FT-IR spectroscopic studies of coal fly ashes, originated from various polish power plants are reported. The results of MIR investigations were compared to the X-ray diffraction (XRD) measurements and chemical analyses. They are mainly composed of silica, alumina and lime. The infrared spectrum in the middle range can be used to describe both the structure of phases present in the fly ash and to identify the characteristic elements of the individual components of ash. The results indicate that the amount of aluminosilicate and its Si/Al ratio induce a shift in the T-O stretching band appearing at 950-1100 cm-1. Moreover, FWHM of these bands indicates the participation of the crystalline phase relative to amorphous. The presence of carbonate phases generates substantial changes in the 1450-1400 cm-1 area of the spectra. The presence of such phases as anhydrite, mullite or illite has also been established on the basis of IR spectra. [ABSTRACT FROM AUTHOR]

The results of vibrational spectroscopy studies of zeolites synthesized from expanded perlite using hydrothermal method were presented. The starting material used was a waste obtained during the production of expanded perlite. The effects of synthesis temperature and time, as well as NaOH concentration and solid to liquid ratio on the obtained products were determined. The resulting materials were analyzed regarding phase composition. In particular, the structures of materials were examined using FT-IR spectroscopy in the middle and far infrared ranges as well as Raman spectroscopy. The results were compared to the XRD and XRF measurements, as well as SEM observations. It has been found that by using a sufficiently high concentration of NaOH, it is possible to efficiently synthesize zeolite at temperatures above 50 °C. The presence of zeolite phase was confirmed by the measurement of spectra. Pseudolattice range, i.e. 800-400 cm -1 , was analyzed in detail. In this range, bands associated with the ring vibrations occur. They are characteristic for secondary building units (SBU) existing in zeolite structure. Depending on time, temperature and NaOH concentration, zeolite X, A, Na-P1 and hydroxysodalite have been identified as synthesis products in autogenous pressure. [ABSTRACT FROM AUTHOR]

Highlights: [•] The paper presents the study of silicate sols with the addition of calcium. [•] The series of sols after heat treatment in air and in argon were compared. [•] The nature of samples depends on the composition and conditions of heat treatment. [•] Analysis of IR spectra revealed pseudowollastonite, tobermorite and quartz. [ABSTRACT FROM AUTHOR]

Highlights: [•] We examine the synthesis of zeolites from expanded perlite and fly ash microspheres. [•] It is possible to obtain a coating of sodium zeolites on the light microfillers. [•] We optimized the synthesis temperature, time and NaOH concentration. [•] It is possible to obtain the product in relatively low temperature. [•] We used the infrared spectra to describe the zeolitization progress. [ABSTRACT FROM AUTHOR]

This work presents the results of spectroscopic (MIR and Raman) studies of zeolite structures after immobilization of heavy metal cations from aqueous solutions. The sorption of Ag +, Cu 2+, Cd 2+, Pb 2+, Zn 2+, and Cr 3+ ions has been conducted on zeolites belonging to different structural groups, i.e., sodium forms of natural chabazite, mordenite, ferrierite, and clinoptilolite, as well as on synthetic zeolite Y. Systematic changes in intensities and positions of the bands corresponding to the characteristic ring vibrations have been observed in the measured spectra. The most visible changes are observed in the FT-IR spectra of the samples in the range of 850–450 cm –1, and in the Raman spectra in the range of 600–250 cm –1. Depending on the zeolite structure, the bands, which can be regarded as a kind of indicator of ion exchange, were indentifi ed. For example, in the case of IR spectra, these bands are at 766, 703, 648, 578, and 506 cm –1 for zeolite Y, at 733 and 560 cm –1 for mordenite, at 675 cm –1 for clinoptilolite, etc. The degree of changes depends on both the type of cation and its concentration in the initial solution. This is connected with the way of binding of metal ions to the zeolite aluminosilicate framework, i.e., a proportion of the ion exchange and chemisorption in the process. Cations mainly undergoing ion exchange, such as Cd 2+ or Pb 2+, have the greatest impact on the character of the spectra. On the other hand, Cr 3+ ions practically do not modify the spectra of zeolites. Results of IR and Raman spectroscopic studies have been compared with those obtained by atomic absorption spectroscopy (AAS), from which the proportion of ion exchange to chemisorption in the process and the effective cation exchange capacity of the individual samples have been estimated. [ABSTRACT FROM AUTHOR]

Abstract: This work presents results of FT-IR spectroscopic studies (MIR and FIR range) of zeolites (belonging to D4R and D6R structural groups) after heavy metal cations (Ag+, Cu2+, Cd2+, Pb2+, Zn2+, Ni2+ and Cr3+) immobilization. Sorption has been conducted on monoionic forms of synthetic zeolite A (LTA) and Y (FAU) as well as on natural chabazite (CHA). It was proven that those cations’ sorption causes changes in the spectra of the zeolites. Changes in intensities and positions of the bands corresponding to the characteristic ring and Meons have been observed. These rings occur in pseudomolecular complexes (built of alumino- and silicooxygen tetrahedra) which constitute the secondary building units (SBU) and form spatial framework of the zeolite. Based on the results of DFT method (B98 HF 6–31G(d)) calculations, normal vibrations of the SBU terminated by different cations (Na+, K+) have been visualized. Obtained results have been applied for interpretation of experimental spectra of selected zeolites. The most significant changes have been determined in the region of pseudolattice vibrations (800–550cm−1). On the other hand, an introduction of heavy metal cations into the structure of zeolites has caused the considerable modification of bands due to Meons in FIR spectra (below 400cm−1). In both cases systematic changes connected with the type of cation (its chemical character) have been revealed. Based on changes in the spectra due to immobilization of heavy metal ions, a scale of sorption can be established. [Copyright &y& Elsevier]

Abstract: A number of compounds of the mimetite Pb5(AsO4)3Cl–pyromorphite Pb5(PO4)3Cl solid solution series were synthesized at room temperature and analyzed with Raman and infrared spectroscopy. The fundamental antisymmetric stretching (ν 3) and bending (ν 4) vibrations of the mimetite–pyromorphite solid solutions occur in the regions 720–1040cm−1 and 400–580cm−1. The band originating from the ν 3 and ν 4 modes shifts to higher wavenumbers between mimetite and pyromorphite because the atomic mass of As is higher than P and As–O bonds are longer than P–O bonds. The position, shape and relative intensity of the bands vary primarily as a function of As/(As+P) in the analyzed solid. The strong correlations between the positions of the vibrational modes and the As/(As+P) ratio can be used to determine the composition of the investigated natural and synthetic samples of the minerals from the mimetite–pyromorphite series. [Copyright &y& Elsevier]

Abstract: This work presents the results of FT-IR spectroscopic studies of heavy metal cations (Ag+, Pb2+, Zn2+, Cd2+ and Cr3+) immobilization from aqueous solutions on natural sorbents. The sorption has been conducted on sodium forms of zeolite (clinoptilolite) and clay minerals (mixtures containing mainly montmorillonite and kaolinite) which have been separated from natural Polish deposit. In the next part of the work both sorbents were used to obtain new building composites. It was proven those heavy metal cations’ sorption causes changes in IR spectra of the zeolite and clay minerals. These alterations are dependent on the way the cations were sorbed. In the case of zeolite, variations of the bands corresponding to the characteristic ring vibrations have been observed. These rings occur in pseudomolecular complexes 4–4–1 (built of alumino- and silicooxygen tetrahedra) which constitute the secondary building units (SBU) and form spatial framework of the zeolite. The most significant changes have been determined in the region of pseudolattice vibrations (650–700cm−1). In the instance of clay minerals, changes in the spectra occur at two ranges: 1200–800cm−1 – the range of the bands assigned to asymmetric Si–O(Si,Al) and bending Al–OH vibrations and 3800–3000cm−1 – the range of the bands originating from OH− groups stretching vibrations. Next results indicate possibilities of applying the used natural sorbents for the obtainment of new building materials having favourable composition and valuable properties. The zeolite was used for obtaining autoclaved materials with an addition of CaO, and the clay minerals for ceramic sintered materials with an addition of quartz and clinoptilolite were produced. FT-IR studies were also conducted on the obtained materials. [Copyright &y& Elsevier]

Abstract: This work presents the results of FT-IR spectroscopic studies of anions – chromates, phosphates, arsenates, sulfates and nitrates – sorbed from aqueous solutions (different concentrations of anions) on natural sorbents. The sorption has been conducted on zeolite (clinoptilolite) and smectite (mixtures of clay minerals containing mainly montmorillonite and kaolinite) which have been separated from natural Polish deposit. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA+). Cation exchange capacities (CEC) of clinoptilolite and smectite were measured. Their values are 23mmol/100g and 41mmol/100g respectively. The used initial inputs of HDTMA correspond to 100% (1.0) and 200% (2.0) CEC of the minerals. Organo-modified sorbents were subsequently used to immobilization mentioned anions. It was proven that those anions’ sorption causes changes in IR spectra of the HDTMA-zeolite and smectite. These alterations are dependent on the kind of anions that were sorbed. In both cases, variations are due to bands corresponding to the characteristic Si–O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolite or layer structure of smectite), OH group vibrations and alkylammonium surfactant vibrations have been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed , , , , and ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of chromates were determined by colorimetry using the biphenylocarbazide method. For phosphates and arsenates molybdenum blue method, turbidimetric method for sulfates and hydrazine reduction method for nitrates was used. [Copyright &y& Elsevier]

Abstract: The work presents the results of application of natural clinoptilolite for immobilization of heavy metal cations (Ag+, Pb2+, Cd2+ and Cr3+) from aqueous solutions and uses zeolite to prepare autoclaved building composites. Sorption has been conducted on sodium form of natural clinoptilolite originated from Poland. Clinoptilolite (sodium form containing heavy metal cations) has been applied to obtain new building materials which have good physical properties. Samples produced by autoclaving process showed relatively low bulk density (about 1.35g/cm3). The compressive strength depended on the amount of CaO in the initial mixture. Its maximum value was about 40MPa. The influence of heavy metal cations on the compressive strength values was insignificant (except for the Cr3+ ions). However, all the cations modified the microstructure and the ordered state of C–S–H phase. Efficiency of Ag+, Cd2+ and Pb2+ ions immobilization on the mineral matrix was shown. In the work, results of IR spectroscopy, atomic absorption spectroscopy (AAS) studies, X-ray diffraction analysis, SEM observations and technological investigations are presented. [Copyright &y& Elsevier]

Abstract: In the work, results of structural studies of different geopolymers, obtained using a granulated blast furnace slag, are presented. The slag was subjected to an alkaline activation process. As activators, NaOH, Na2CO3 and liquid glass were applied. IR and NMR spectroscopy were the main experimental methods used, the results obtained were compared with XRD phase analysis and SEM observations. In the IR spectra of raw slag as well as in the spectra of products of paste hydration, the bands due to the characteristic vibrations of bonds observed in both types of oxygen bridges: Si–O–Si and Si–O–Al, were assigned. These bridges constitute basic structural units, forming tetrahedral geopolymer chains. It was found that the slag composition, mainly SiO2/Al2O3 ratio and modification in oxides concentration, influences the presence of the bands connected with the phases (mainly C–S–H) formed during the hydration in the IR spectra. Additionally, significant effect of amorphous phases share on the spectra shape was established. 29Si and 27Al MAS-NMR spectra of initial slag geopolymers and pastes provided information concerning coordination of both atoms in the structures. It was revealed that the kind of slag geopolymers and the conditions of paste hydration influence connectedness of silicooxygen tetrahedra and coordination number of aluminium atoms. Based on IR spectra, it was also possible to determine the influence of the activator type, activation time and hydration conditions on the products formed. Significant changes were observed for the bands assigned to vibrations of carbonate and hydroxide groups. The changes were also noticed in the case of bands due to vibrations of silicate and aluminosilicate bonds. [Copyright &y& Elsevier]

Abstract: This work presents the results of FTIR spectroscopic studies (MIR) of heavy metal cations (Pb2+, Cd2+, Ag+ and Cr3+) immobilization from aqueous solutions on various forms of natural sorbents. Sorption has been conducted on natural clinoptilolite–montmorillonite mudstone and on its major components which have been separated from this deposit, i.e. on zeolite and smectite (their sodium forms). Based on changes in the spectra due to the immobilization of heavy metal ions, a scale of the sorption and the type of mechanism involved in the process (ion-exchange and/or chemisorption) can be established. Changes in intensities and positions of the bands corresponding to the characteristic ring vibrations have been observed. These rings occur in pseudomolecular 4-4-1 complexes (built of alumino- and silicooxygen tetrahedra) which constitute the secondary building units (SBU) and form spatial framework of the zeolite. The most significant changes have been determined in the region of pseudolattice vibrations. On the other hand, introduction of heavy metal cations into the structure of montmorillonite has caused the modification of band intensities due to stretching vibrations of OH− groups. In both cases, systematic changes connected with the type of cation (its chemical nature) and its concentration in the initial solution have been revealed. Results of IR spectroscopic studies have been compared with those obtained by atomic absorption spectroscopy (AAS), from which the proportion of ion-exchange to chemisorption in the process and the effective cation exchange capacity of the individual samples have been estimated. [Copyright &y& Elsevier]

Abstract: The work describes results of spectroscopic studies (MIR, FIR and Raman) of zeolites on which sorption of various metal cations, namely Pb2+, Cd2+, Cr3+, Zn2+, Cu2+ and Ag+ has been carried out. Sorption has been performed on sodium forms of natural zeolites (clinoptilolites from various sources) using aqueous solutions of the metals studied. Changes in intensities and positions of the pseudolattice bands corresponding to ring vibrations have been observed in the measured spectra. Pseudolattice bands are located in the range of ca. 400–700cm−1. The degree of changes depends on both, the type of the cation sorbed and the extent of deformation of zeolite ring units. This, in turn, is connected with the way of metal ions binding to aluminosilicate framework of the zeolite, i.e. the proportion of ion exchange and chemisorption in the process. Results of spectroscopic studies have been compared with those obtained by atomic absorption spectrometry (AAS). [Copyright &y& Elsevier]

Abstract: Vibrational spectra have been applied to study the spatial framework of the zeolites containing double 4- and 6-membered rings as characteristic structural units. Using ab initio methods, theoretical vibrational spectra of isolated D4R and D6R units have been calculated. All the units have been terminated by different cations, i.e. K+, Na+ and Zn2+ to balance their negative charge. Based on the results of calculations, normal vibrations of the units have been visualized and the characteristic ring- or pore-opening vibrations, occurring in these units, have been identified. The effect of cation substitution in terminal positions and Al→Si substitution in tetrahedral positions on the obtained spectra shape has been analyzed. The studied D4R and D6R units constitute the model of secondary building units (SBU) of two important structural zeolite groups. Therefore, the obtained theoretical results have been applied to interpret experimental MIR, FIR and Raman spectra of selected zeolites. In particular, vibrational spectra of zeolite A (LTA), whose structure is composed exclusively of spatially connected D4R units have been analyzed. Spectra of LTA, which was subjected to ion exchange process, have been compared to complete the interpretation procedure. [Copyright &y& Elsevier]

Abstract: E. Ghys in [E. Ghys, Appendix E: Riemannian foliations: Examples and problems, in: P. Molino (Ed.), Riemannian Foliations, Birkhäuser, Boston, 1988, pp. 297–314. ] has posed a question (still unsolved) if any Finslerian foliation is a Riemannian one? In this paper we prove that the natural lift of a Finslerian foliation to its normal bundle is a Riemannian foliation for some Riemannian transversal metric. The methods we used here are closely related to those used by M. Abate and G. Patrizio in [M. Abate, G. Patrizio, Finsler Metrics—A Global Approach, Springer-Verlag, Berlin, 1994]. [Copyright &y& Elsevier]

Abstract: Calculated vibrational spectra of aluminosilicate D4R and D6R structural units have been derived using ab initio methods. These units constitute the models of secondary building units (SBU) of two important structural zeolite groups. In the calculations, the model of isolated double four- and six-membered rings containing both AlO4 and SiO4 tetrahedra has been used. Based on the results of calculations, normal vibrations of the units have been visualized. This has enabled us to identify the bands in the spectra obtained. In particular, distinguishment of the characteristic ring or pore-opening vibrations occurring in these units has been possible. The effect of Al→Si substitution in tetrahedral positions on the spectra shape has been also analysed. The calculated results obtained have been applied to interpret experimental spectra of selected zeolites. Their frameworks are formed by spatial connection of structural units in three directions. For the interpretation, the spectra of zeolites whose structure is exclusively composed by the connection of the structural units studied have been chosen. [Copyright &y& Elsevier]

In the work vibrational spectra have been used to describe the framework aluminosilicate structures. Results of spectra calculations carried out for isolated, overtetrahedral structural units which occur in silicates and aluminosilicates are presented. Clusters composed of single and double silico- and alumino-oxygen rings with various numbers of members (4 and 6) containing terminal hydrogen atoms have been chosen for calculations. These clusters have constituted the model analogues of secondary building units (SBU) existing in real zeolite structures. The units selected for calculations have differed in the degree of substitution of silicon atoms with aluminum ones in tetrahedral positions. Visualization of individual vibrations performed has facilitated the band assignments. The results obtained have been used in the interpretation of experimental framework silicates (zeolites) spectra containing the same types of SBU in their structures. The spectra have been analyzed mainly in the ring vibrations region with the aim to determine the influence of aluminum on the spectrum. [Copyright &y& Elsevier]

Calculations which made it possible to determine the pseudo-lattice vibrations characteristic of isolated rings of alumino- and silico-oxygen terahedra were conducted. The calculations for the rings with different number of members and different ratios of Si and Al substitution in tetrahedral positions (Al/Si ratio range from 1:1 to 1:5) using PM3 method were carried out. The increase in the number of [AlO4]5− tetrahedra in the ring caused changes in ring deformation and, consequently, changes in the band positions in the spectra.Theoretical results obtained were compared with the experimental vibrational spectra of the ring aluminosilicates and with the spectra of the framework aluminosilicates belonging to different structural groups. In the framework of aluminosilicates, rings built up of tetrahedra are linked to each other, creating three-dimensional networks. This fact causes distinct differences in their spectra in comparison with the spectra of isolated ring structures. [Copyright &y& Elsevier]

In the work, the results of 27Al MAS NMR studies carried out for structures of different framework aluminosilicates are presented. The spectra of natural clinoptilolite and its sodium and hydrogen forms were measured. The zeolite spectra were obtained before and after incorporation of heavy metal cations (Pb2+, Cd2+, Ni2+ and Cr3+) into the zeolite structure. After decomposition of the spectra into component peaks differences caused by ion exchange were observed.Additionally, NMR spectra of kalsilite (framework aluminosilicate, not belonging to zeolite group) and other zeolites (chabazite, heulandite and analcime) were measured.27Al MAS NMR spectra of all the samples studied were compared with the FTIR spectra measured in the middle infrared region.Based on the results obtained it has been proved that the interpretation of spectra obtained using these two different techniques can give some information concerning changes occurring in various framework aluminosilicate structures. [Copyright &y& Elsevier]

This contribution presents the results of structural investigations on the cured and high temperatures of three series of geopolymers. The specimens were synthesized at 80 °C from coal fly ash and three activators of variable composition based on sodium hydroxide and sodium silicate solutions. Structural and microstructural analysis was performed, especially using in-situ measurements of XRD patterns and IR spectra as a function of temperature. The cured compounds' phase content and compressive strength changed slightly depending on the starting chemical composition. All analyzed materials experience a mass loss due to water removal at 300 °C, followed by increased porosity from disintegrating compounds above 300 °C. Higher alkali content improves strength (400–600 °C) possibly due to nepheline formation. The amorphous phase gradually softens during heating, influenced by alkali content. Structural analyses were supported by model calculations of a number of aluminosilicate structures. The cluster analysis using the k-means algorithm was used to divide the PCA space into regions that represent structural similarities, and analyzing specific point positions in the space allowed for several conclusions to be drawn about the studied materials, including that changes in chemical composition and thermal treatment can promote the transformation from sodalite to nepheline and that the glass network has elements that are nepheline-like and may promote its crystallization. [ABSTRACT FROM AUTHOR]

This study investigated the effect of alkali activation process conditions on the IR spectra, on which amount and types of zeolites in the resultant geopolymers influence significantly. Kaolinite was used as starting materials. The kaolinitic clay was first calcined to transform into the amorphous aluminosilicate phases (metakaolinite) and then activated with sodium silicate (as water glass) and sodium hydroxide. The effects of reaction systems composition (expressed as SiO 2 /Al 2 O 3 and Al 2 O 3 /Na 2 O molar ratios) as well as synthesis temperature on the phase composition of obtained products have been determined. In particular, the structures of materials were examined using FT-IR spectroscopy in the middle infrared range. The results were compared to the XRD measurements, as well as SEM observations. Alkali-activation treatment of the metakaolin yielded bulk materials with different amounts and types of zeolite, which reveal the IR spectra of received materials. With proper selection of the initial conditions (temperature and composition), it is possible to obtain a solid material containing zeolite phase such as zeolite X, zeolite A or sodalite. The presence of zeolite phase was confirmed by the measurement of spectra in the middle infrared. In particular in pseudolattice range of the spectra, i.e. 800–400 cm −1 , there are bands associated with the ring vibrations, which are characteristic for secondary building units (SBU) occurred in zeolite structure. IR spectroscopy is also useful in the studies of resulting amorphous phase structure. [ABSTRACT FROM AUTHOR]

We present some new results on the relations between the rotation index of bar billiards of two nested circles CR and Cr, of radii R and r and with distance d between their centers, satisfying Poncelet's porism property. The rational indices correspond to closed Poncelet transverses, without or with self-intersections. We derive an interesting series arising from the theory of special functions. This relates the rotation number ⅓, of a triangle of Poncelet transverses, to a double series involving R, r, and d. We also provide a Steiner-type formula which gives a necessary condition for a bar billiard to be a pentagon with self-intersections and rotation index ⅖. Finally we show that, close to a pair of circles having Poncelet's porism property for index ⅓, there exist always circle pairs having indices ... they and ⅙; in the case ... they are even unique. [ABSTRACT FROM AUTHOR]

Abstract: In the present work the behaviour of HAp extracted from pig bones at elevated temperatures up to 1000°C in O2 and CO2 atmospheres has been studied. It has been found that CO2 atmosphere arrests HAp decomposition. Chemical analysis and infrared spectroscopy reveal that no free CaO appears and no decrease of CO3 −2 group concentration occurs in the material calcined in CO2 atmosphere. In the O2 atmosphere at elevated temperatures, CaO and CO2 are emitted from the samples, although the remaining material retains the HAp structure as indicated by the X-ray diffraction. [Copyright &y& Elsevier]

Abstract: Hydrolytic polycondensation process, also called sol–gel process, leads to formation of xerogels from simple molecules e.g. most widely used tetraethoxysilane (TEOS). In the presented work 2,4,6,8-tetraethoxy-2,4,6,8-tetramethylcyclotetrasiloxane – D4(OEt)4 was applied as the molecular precursor. Polycondensation reactions were performed in the presence of Bu4NF or HCl/NH4OH as the catalysts. The obtained xerogels were studied by FT-IR, MAS-NMR and XRD methods. Depending on the condensation process conditions, structure of the resulting materials varied from octahedral cage unit (T8) through a ladder chain to random structure. Dried xerogels were heated at the temperature of 800 and 1000°C in argon or air atmosphere (pyrolysis or ceramization). In the atmosphere of argon SiC x O y glass materials were obtained, while in air silica glass was formed. Their properties depended on the pyrolysis conditions as well as on the xerogel structure. IR spectroscopy results allowed to conclude about the short range order in amorphous xerogel and glass materials. [Copyright &y& Elsevier]

Abstract: It is known that the chemical activity phenomenon is characteristic for some inorganic glasses and they are able to participate in biological processes of living organisms (plants, animals and human bodies). An example here is the selective removal of silicate–phosphate glass components under the influence of biological solutions, which has been applied in designing glasses acting as ecological fertilizers of controlled release rate of the nutrients for plants. The structure of model silicate–phosphate glasses containing the different amounts of the glass network formers, i.e. Ca2+ and Mg2+, as a binding components were studied. These elements besides other are indispensable of the normal growth of plants. In order to establish the function and position occupied by the particular components in the glass structure, the glasses were examined by FTIR spectroscopy (with spectra decomposition) and XRD methods. It has been found that the increasing amount of MgO in the structure of silicate–phosphate glasses causes the formation of domains the structure of which changes systematically from a structure of the cristobalite type to a structure corresponding to forsterite type. Whilst the increasing content of CaO in the structure of silicate–phosphate glasses causes the formation of domains the structure of which changes from a structure typical for cristobalite through one similar to the structure of calcium orthophosphate, to a structure corresponding to calcium silicates. The changing character of domains structure is the reason of different chemical activity of glasses. [Copyright &y& Elsevier]

In this work the influence of the activator concentration on the inorganic polymer structure based on metakaolin was investigated. Changes in the aluminosilicate structure of the metakaolin during alkali-activation have been analyzed in detail on the basis of XRD, SEM and FT-IR analysis and ATR/FT-IR spectra as well. Based on the change of attenuated total reflectance FT-IR spectra over time at 80 °C, the zeolitization/geopolymerization process can be analyzed. Image 1 • The study investigated the effect of alkali activation on the ATR-FTIR spectra. • Treatment of metakaolin with the use NaOH solutions was carried out. • We used the infrared spectra to describe the zeolite formation progress. [ABSTRACT FROM AUTHOR]

[Display omitted] • We synthesized amorphous aluminosilicate gel in the presence of heavy metal ions. • The effect of heavy metal ions on structure of aluminosilicate gel has been investigated. • We used the vibrational spectra to describe the structure of C-(A)-S-H phase. • We have attempted to evaluate the mechanism of immobilization of individual ions. Calcium aluminosilicate hydrates (C-(A)-S-H) with two different C/S molar ratios of 1.0 and 1.7 were synthesized by precipitation with the use of the alkali-activation method. The samples were synthesized with solutions of heavy metals nitrates such as nickel (Ni), chromium (Cr), cobalt (Co), lead (Pb), and zinc (Zn). Metal cations were added in the amount of Ca:Me equal to 9:1, while Al/Si was 0.05. The influence of the addition of heavy metal cations on the structure of the C-(A-)S-H phase was investigated. For this purpose, XRD was used to examine the phase composition of the samples, FT-IR and Raman spectroscopy were used to determine the effect of heavy metal cations on the structure of the obtained C-(A)-S-H phase and their degree of polymerization. Using SEM and TEM, changes in the morphology of the obtained materials were determined. Possible mechanisms of immobilization of heavy metal cations have been determined. It was found that some heavy metals (Ni, Zn, and Cr) could be immobilized by precipitation of insoluble compounds. On the other hand, they could remove Ca2+ ions from the structure of aluminosilicate and take their place, as evidenced by the crystallization of Ca(OH) 2 in samples with the addition of Cd, but also Ni and Zn in small amounts. A third possibility is the incorporation of heavy metal cations at the silicon and/or aluminum tetrahedral sites, as is the case with Zn. [ABSTRACT FROM AUTHOR]

Coal fly ash as a secondary aluminosiliceous raw material that is commonly used in the so-called geopolymerization process has been activated with different alkali hydroxides solutions: LiOH, NaOH and KOH. Changes in the aluminosilicate structure of the material during alkali-activation have been analyzed in detail on the basis of ATR/FT-IR spectra. These changes mainly affect both the integral intensity and FWHM of bands in the range of 1200–950 cm −1 , however dehydration and carbonation process can be also analyzed based on obtaining results. [ABSTRACT FROM AUTHOR]

Hydroxyapatite of natural origin differs from the synthetic one. It is non-stoichiometric, contains carbonate groups and some other trace elements. The organic matter was removed from the animal bones by their treatment in sodium or potassium hydroxide. In the present study the effect of NaOH and KOH treatment of different concentrations and for different times was observed. It has been found that the process of dissolution–precipitation occurs. It leads to the decreased specific surface area of the resulting powder and the increased crystallites sizes. The de-convoluted infrared spectra allowed us to state that the newly crystallized matter contains fewer carbonate groups and higher concentration of hydroxyl groups as compared to the starting material. So the material shifts towards the A-type HAp. Nevertheless, it can still be defined as the AB-type hydroxyapatite. The phenomena become more advanced with time of treatment and concentration of the treating reagent. [ABSTRACT FROM AUTHOR]

• Recent advances in research of clinker phases by the use vibrational spectroscopy were discussed. • The experimental spectra of pure cement phases were compared with the computational ones. • Comprehensive band assignment was done. This paper summarized the recent advances in research of clinker phases by the use vibrational spectroscopy. Synthetic clinker minerals and commercial Portland clinker have been analyzed by FT-IR and Raman spectroscopy. The spectra of synthetic C 2 S, C 3 S, C 3 A and C 4 AF have been compared to calculated ones and on this basis, detailed assignments of individual bands have been made. Comprehensive band assignment, both in the mid and far infrared ranges, is presented for the first time. We also present results of Raman microscopic imaging of commercial Portland clinker as example of technique yielded phase distribution in mineral sample. [ABSTRACT FROM AUTHOR]

Abstract: Sol–gel method, which is based on hydrolytic polycondensation reaction, leads to formation of xerogels from simple molecules, e.g., most widely used tetraethoxysilane (TEOS). In the presented work alkoxy derivatives of cyclosiloxane molecules of general formula: Si n O n (CH3) n (OEt) n where n =4, 5 and 6 were applied as the molecular precursors. Polycondensation reactions were performed in the presence of tetrabutylammonium fluoride (TBAF) or HCl/NH4OH as catalysts, without using any template or surfactant whatsoever. The composition and structure of obtained xerogels were studied by FT-IR and XRD as a main method, the MAS NMR and SEM measurements were also performed. The surface of the studied samples was measured by nitrogen adsorption methods. We have found that the obtained materials were mesoporous. [Copyright &y& Elsevier]

Inorganic–organic hybrid materials produced by the sol–gel method from Si(OR)4 and R′x−ySi(OR)y (R,R′—CnHm groups) compounds are very interesting materials for new optical techniques. Recognition of the structure of these materials is very important for controlling their production process as well as their properties.Five different hybrid gels were obtained using tetraethoxysilane (TEOS) with addition of the following modifiers: methyltrimethoxysilane (MTMS) (CH3)Si(CH3O)3, vinyltriethoxysilane (VTES) (CH=CH2)Si(CH3CH2O)3, phenyltriethoxysilane (PhTES) Ph–Si(CH3CH2O)3 (Ph—phenyle group C6H5), diethoxydimethylsilane (DEDMS) (CH3)2Si(C2H5O)2, diethoxymethylvinylsilane (DEMVS) (CH3)(CH=CH2)Si(C2H5O)2.Copolymerisation of tetraethoxysilane (TEOS) and of the organic modifiers was studied by means of both the 29Si MAS NMR and the FTIR spectroscopy. It has been found that according to the organic modifier used different 29Si MAS NMR chemical shifts were observed. An attempt has been made to assign the signals to the corresponding structure units of gels. The FTIR spectra confirmed the formation of copolymers between TEOS and organic modifiers. Moreover, using 29Si MAS NMR and FTIR spectroscopy the stability of the hybrid structure at the temperatures 100–500 °C was determined. [Copyright &y& Elsevier]