Thermochemistry of Biologically Active Glasses

Mutual relation between thermal activity and biochemical activity of the phospho-silicate glasses which are used as controlled rate release fertilisers and bioglasses for medical applications, has been observed. Analysis of the local atomic interactions in the structure of glass is used to explain this relation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectroscopic and thermal studies of silicate-phosphate glass

The structure of silicate-phosphate glass containing the different amounts of phosphorus, magnesium and calcium cations, acting as macroelements was examined by FTIR, XRD and thermal (DTA/DSC) methods. It has been found that in the structure of silicate-phosphate glass modified by an addition of Mg²⁺ and Ca²⁺ there are formed domains characterized by certain degree of ordering of the units present in their composition, while the structure of the newly formed domains is similar to the structure of the crystal compounds formed during crystallization of these glasses. The changing character of domains structure may be the reason of different chemical activity of glass acting as glassy fertilizers.     

Thermal analysis and thermochemistry of vitreous into crystalline state transition

Thermochemistry and structural mechanism of crystallization of MgO-Al₂O₃-SiO₂ glasses with TiO₂ as crystallization activator were studied. Thermal and HREM investigation proved that near the T _g temperature crystallization is going by rearrangement of glass structure elements and part of its components redistribution like at disorder — order phase transition in solid bodies. Nanocrystals of Mg-titanate and high quartz structure solid solution are formed then. Next enstatite and cordierite are crystallizing. Thermochemical and chemical bonds strength analysis indicate that during multistage crystallization of glasses, kind and order of crystal phase formation, is determined by the glass structure decomposition progress and its particular components release accompanying increase of temperature. It has been proved that molar heat capacity change (ΔC _p) accompanying the glass transition is the significant measure of degree of changes in the structure of glass preceding crystallization. This revised version was published online in July 2006 with corrections to the Cover Date.     

固体NMR在玻璃微结构研究中的应用

核磁共振(NMR)是探测物质微结构的有力手段,本文简要介绍了固体NMR技术在玻璃微结构研究中的应用,尤其是近年来的新进展,包括硅酸盐玻璃、硼酸盐玻璃、磷酸盐玻璃以及含铝的氧化物玻璃等玻璃体系。     

Thermal Behaviour of Silicate-Phosphate Glasses in Relation to Their Biochemical Activity

Glasses of theK₂O–MgO–CaO–SiO₂ and K₂O–MgO–CaO–P₂O₅–SiO₂ systems with microelements (Fe, Mo, Zn, B, Mn, Cu) were obtained by melting of apatite and serpentinite rocks, K₂CO³ and oxides of appropriately metals mixtures. The amorphous state of glasses and the structural changes during their heating were determined by RDF and DTA/DSC methods. The solubility of the glasses in 2 mass% citric acid solution was studied by chemical analysis (ICP-AES, EDS) and SEM observations.It has been found that the biochemical activity of silicate-phosphate glasses depends on the content of P₂O₅ and K₂O in their framework and is related to crystallisation ability of these glasses.This revised version was published online in November 2005 with corrections to the Cover Date.     

Cobalt absorption bands for the differentiation of historical Na and Ca/K rich glass

The main purpose of this publication is to define sensing parameters by means of optical spectroscopy to study and characterize ancient glass. Because during different times different flux agents were used, a chemical individuation of these elements provides a first dating classification. Normally, X‐ray‐based chemical methods are applied to this kind of investigation. On the basis of the Ligand‐field theory, the absorption band positions of a transition metal ion undergo a change when the ion is placed in different chemical environments. A total of 25 cobalt coloured Roman, post‐medieval and industrial glasses were analyzed by means of SEM–energy dispersive X‐ray spectroscopy to group them according to their chemical composition. Optical spectroscopy was applied to build a method to study glass with this low‐cost and non‐destructive technique. It is proved that the cobalt absorption band situated around 535.5 nm for sodium‐rich glasses (Roman and industrial material) is shifted towards 526.5 nm for calcium–potassium‐rich glasses (post‐medieval window glass). This feature was employed as a marker in the case study of the Renaissance window of the Church Wardens from the Church of Our Lady in Bruges, Belgium to distinguish the post‐medieval material from the 19th and 20th century restoration material. Copyright © 2011 John Wiley & Sons, Ltd.     

Microanalysis of Glass Containing Alkali Ions

 The common problems connected with alkali ion migration during EPMA were studied on glasses containing nearly all possible alkali ions (Na, K, Rb, Cs). Binary silica glasses were prepared by melting from a very pure batch in Pt crucible. The glasses were carefully polished using alcohol to prevent surface corrosion by water and they were stored in vacuum. The specimens were coated with carbon layers approximately 30-nm thick and exposed to a 50- keV electron beam of 100 μm diameter. It was found that all alkali ions migrate under the electron beam, but the rate of the migration depends on the current density. The decay curves (characteristic X-ray intensity versus time) are similar in shape in all cases. The decay curve shows two transport regimes, the first being linear-like, the second being the exponential-like. The first transport regime busts into the rapid alkali migration after a time known as the incubation period. The period is in general longer for the larger-alkali ions size. It was found that even large rubidium and caesium ions migrate inside the glass with the same mechanism as sodium and potassium ions. While for K, Rb, and Cs ions the incubation periods were observed under the suitable experimental conditions, binary glass containing Na exhibits no observable incubation period. Except for the binary Na₂O + SiO₂ glass, the suitable experimental conditions for reliable quantitative EPMA can be found.     

Changes of the affinity between fungal proteins and vanillin bonded to thermally modified porous glass support

Summary The affinity of peroxidase and the fungal proteins to vanillin attached to controlled porous glasses depends on the porosity of the glass and additional thermal treatment of the support. The additional thermal treatment of controlled porous glasses leads to an enrichment in boron atoms of their surface.The results presented in this paper show a better resolution of the analyzed substances when glass with a surface enriched in boron was used as the support for vanillin.     

Smart gel–glass based on the responsive properties of polymer gels

Polymer gels are unique smart materials in the sense that they can respond to many different stimuli. In this paper we report how poly(N‐isopropylacrylamide) (abbreviated as PNIPA) and other polymer hydrogels can be used to construct an intelligent gel‐glass which can moderate the amount of light and radiated heat. This environmental sensitive glass, which is a smart hydrogel layer placed between two glass or plastic sheets, becomes opaque when the temperature exceeds a critical value. It becomes transparent again if it is cooled down. The adaptive properties of gel‐glasses make them a promising materials to protect from strong sunlight and heat radiation. Copyright © 2001 John Wiley & Sons, Ltd.     

Quantitation of Metal Ions in Archaeological Glass by Abrasive Stripping Square‐Wave Voltammetry Using Graphite/Polyester Composite Electrodes

A method for identifying Co, Cu, Sb, Sn, Fe, Zn, and Zr pigments in glasses using square‐wave voltammetry as the detection mode is described. It is based on the abrasive attachment of glass microsamples to graphite/polyester composite electrodes. Sample amounts less than 1 μg are used allowing for the study of archaeological samples. In all cases well‐defined anodic stripping peaks corresponding to the oxidation of metal deposits generated at potentials ranging from ?0.6 to ?1.6 V (vs. SCE) are obtained. This response is in agreement with that displayed by the corresponding metal oxides. Quantitative estimates of the relative population of metal ions in glasses are obtained from peak area measurements with an accuracy comparable to that obtained with SEM/EDX.     

An investigation of glasses for capillary chromatography

An investigation was conducted of various glasses, other than soda lime or borosilicate, for use in glass capillary gas chromatography. The work has uncovered some unique chromatographic qualities in the use of potash soda lead and fused silica glasses as materials for making glass capillary columns. The fused silica proved to be an ideal material for capillary column construction, being inherently more inert than glass containing metal oxides. It has been shown that through the use of thin wall capillary tubing of high flexibility many of the mechanical problems associated with glass capillary columns, such as fragility and column straightening, can be avoided.     

Glass Transition Behavior in Se-Rich Ge-Se Alloys

Differential scanning calorimetry (DSC) was utilized to study the behavior of six Ge-Se glasses containing 0, 5, 10, 15, 17.5 and 20 at.% Ge during the glass transition. These alloys readily form glasses and can be prepared by quenching in air. Moreover, their behavior depends greatly on the composition. This work reveals that two additional properties must be considered: the variation in the glass transition temperature and different structural relaxation. The quantity used to quantify the relaxation was the enthalpy relaxation as this measures the heat lost by the glass during annealing. Given the complexity of the relaxation process, the experimental results were analysed by means of the empirical Kohlrausch-Williams-Watts relaxation model. This revised version was published online in July 2006 with corrections to the Cover Date.     

Etching and annealing studies of nuclear tracks in glasses

A series of etching and annealing experiments are designed to evaluate the characteristics of fission tracks in a number of glasses of varying silica content. A comparative study has been made by comparing the calculated value of bulk etch rate, optimum etch time and annealing rate for each glass. The present investigation suggests that both bulk etch rate (V_G) and annealing rate (V_a) increases with the decrease in silica content of glasses. A minimum value of these parameters is observed for pure silica glass.     

From gel to glass

Oxide gels are amorphous and porous materials. The main recent challenge in the investigations of these materials is to reduce and even eliminate their porosity while keeping their starting amorphous nature. In this paper, we describe how, during the last few years, the understanding of both their structural and textural evolutions with temperature allowed to fully densify gels at temperatures as low as the glass-transition temperature corresponding to the parent glass. Regarding their structure, glasses are very peculiar materials. And regarding their technological applications, glasses are conventionally produced in a variety of shapes. Working of glasses may also be achieved using gels as starting materials. And for several applications, scientists use gels to synthesise specific compositions, materials having peculiar functions or shapes that are difficult to obtain using traditional melting processes.     

PACKING OF IONS IN SILICATE GLASSES

Any silicate glass can be regarded as the relaxation of SiO_2 glass and the volumeis composed of two parts. One is the topological volume of O~(2-), which is equal to thevolume per oxygen of SiO_2 glass, the other is the topological volumes of cations. Thetopological volume of a monovalent cation equals the volume shared by each sphere indense haphazard packing of equal spheres of the cation's size. The charges of bivalentcations cause a decrease of volume, the decrement being the packing volume of Ca~(2+). Anequation is reached for the calculation of the volume per oxygen of silicate glasses. Alot of calculations show that the equation is accurate, so accurate that the densities canbe calculated. The study reveals some characters of the glass structure and clearly ex-presses the contributions of various cations to the volumes of glasses.     

氧化钆对铁磷酸盐玻璃结构的影响

为探究Gd2O3含量对40Fe2O3-60P2O5(mol%)基础玻璃结构的影响,采用传统熔融-冷却法制备xGd2O3-(100-x)(40Fe2O3-60P2O5)(0≤x≤12mol%)系列玻璃。利用XRD、SEM、FTIR和Raman等手段对玻璃结构进行表征,并测试了玻璃密度和维氏硬度。结果表明,在Gd2O3含量小于等于4mol%时,易形成均质玻璃,在此范围内,玻璃密度和硬度都随Gd2O3含量的增加而增加,玻璃结构以焦磷酸盐结构为主,并伴随少量的正磷酸盐和偏磷酸盐结构。在磷酸盐玻璃结构中,Gd3+作为网络修饰离子,位于玻璃网络结构间隙。     

Study of glassy microporous filters in the sodium borosilicate glasses with appropriate carriers

Summary DúThe aim of this work is to prepare a porous filter composed of two porous layers: macro-porous carrier and micro-porous sodium borosilicate (NBS) glass with TiO₂ additive (NBST glass), a Vycor-type glass. In the present work we prepared the macroporous support from the same material (NBST glass) as the upper microporous layer and then by sintering both parts to produce the required composite. This work introduces the results of experiments in the preparation of micro-porous filter on NBST glass base, laid on macro-porous carrier. After sintering of scrap NBST glass, porous samples were prepared to be used as carriers for micro-porous samples of phase-separated NBST glass. In other cases, the following carrier materials were used: a) frita SIMAX, b) Al₂O₃. The properties of the NBST glass and the changes in the glass structure with temperature were studied in order to determine the optimal sintering temperature of the prepared glasses. For the development of the sintered glasses, valuable information was obtained from heating microscopy (HM) and scanning electron microscopy (SEM) studies. The combination of the HM and SEM results with the measurements of the micro-hardness and density directed to the further study of the phase separated NBST glasses.     

Thermal and structural studies of nanocrystallization of oxyfluoride glasses

The influence of fluorine content on the structure and crystallization of oxyfluoride glasses from the Na₂O–Al₂O₃–SiO₂–LaF₃ system was studied by DTA/DSC, XRD, FTIR and SEM methods. It has been found that the increase in the fluorine content in the structure of oxyfluoride glasses causes the increase of the flexibility of their structure, which inhibits the process of crystallization of the silicate- aluminium matrix. Simultaneously the ability of the glass for LaF₃ crystallization, which shows a multistage character, is increasing. Analysis of the local atomic interactions in the structure of glasses has been used to explain the course of the crystallization.     

Oxidation of methyl phenyl sulfide with molecular oxygen in the presence of isobutyraldehyde and transition metal monosubstituted heteropolytungstates

The capture of oxygen molecules by deep traps during oxygen diffusion in butanol glasses has been studied at 77 K as the kinetics of thetert-butyl radical oxidation. Slow glass formation in the samples increases the concentration of deep traps in the matrix. The total value of nonrelaxed free volume has no effect on the concentration of deep traps. It is assumed that trap formation is due to the formation of certain molecular structures below room temperature, most probably, with dissolved gas molecules.     

Synthesis and Characterization of Indium-borate Glass-ceramics Containing Ho0.01Ce0.74Zr0.25O1.995 Nanorods via Incorporation Method

Glasses in the system 5In₂O₃·94Na₂B₄O₇ were fabricated via melt quenching technique. The amorphous nature of the quenched glasses was confirmed by X‐ray powder diffraction studies, and the infrared spectra of the glasses show no boroxol ring formation in the structure of these glasses. Differential thermal analysis is shown glass transition temperature 696°C and crystallization temperature 1151°C. A cerium‐zirconium mixed oxide Ce_0.75Zr_0.25O₂ and Ho‐doped cerium‐zirconium mixed oxide were obtained by solid‐state method. Then glass powder and Ho‐doped cerium‐zirconium mixed oxide were mixed. The mixture was heated in a crucible. The glass‐ceramic sample was obtained by pouring the melts on stainless steel. Obtained samples were annealed at 450°C for 1 h to remove thermal strain. Differential thermal analysis for glass‐ceramic sample is shown glass transition temperature 668°C and crystallization temperature 1159°C. The scanning electron microscopy study for glass‐ceramic indicates that the crystallized glass consists of rod‐like crystals with average diameter of about 38 nm dispersed in the glassy regions.