FTIR spectral characterization of thin film coatings of oleic acid on glasses: I. Coatings on glasses from ethyl alcohol

Oleic acid was coated on soda lime–silicate, soda-silicate, and silica glasses from ethyl alcohol. The coating properties of oleic acid were related to the structure, composition, and dissolution properties of the glasses. The bonding mechanism between the organic coating and the glass surface for each different composition of the glass was revealed by analysis of the diffuse reflectance infrared Fourier transform (DRIFT) spectra. The metal ions on the soda lime–silicate glass surface produced metal-(Na-, Ca-, and Al-) oleates through the formation of metal–carboxylate complexes. Two different structural types were present for calcium-oleate. Some of the oleic acid coated undissociatively on the glass surface through hydrogen bonding. Oleic acid reacted with the surface of the soda-silicate glass, which possessed less Na2O content than the soda lime–silicate glass did, completely dissociating, producing only sodium-oleate species because of the high diffusion and dissolution rates of Na+ ions. Oleic acid formed only hydrogen bonds with silanol groups on silica glass. The coated organic layer on soda lime–silicate glass possessed a more ordered and compact structure than either on silica glass or in pure oleic acid. The metal ions on the soda lime–silicate glass surface strongly coordinated to COO– ions from the oleic acid and made the alkyl chains of the oleates more rigid and oriented, consequently causing the coated layer to be more ordered and compact. This structural result caused the dimeric pairs of COOH groups of undissociatively adsorbed oleic acid molecules to be closer, possessing stronger hydrogen bonds than occurring on the silica glass surface. These results suggest that the composition of the glass is one of the most important factors for determining the coating mechanism involving oleic acid.     

Alkali oxide containing mesoporous bioactive glasses: Synthesis,characterization and in vitro bioactivity

We report, for the first time, the synthesis of sodium oxide containing mesoporous bioactive quaternary glasses and compared with two different mesoporous ternary silicate systems by modified sol–gel process. With the aid of three different glass systems, a systematic analysis has been made on phosphorous-bearing (P-bearing) and phosphorous-free (P-free) mesoporous bioactive glasses to investigate the role of phosphorus on in vitro bioactivity of various silicate glasses with constant alkali oxide content. The combined use of multiple analytical techniques XRD, FTIR, SEM, nitrogen adsorption/desorption analysis before and after soaking in the SBF solution allowed us to establish strong correlation between composition, pore structure and bioactivity. We find that the P-bearing mesoporous glasses show the rapid hydroxycarbonate apatite (HCA) crystallization than P-free mesoporous glasses independent of calcium content. The present study reveals that the presence of phosphorous jointly with calcium in the bioactive glass system significantly enhances the rate of apatite formation as well as crystallization of apatite phase. Additionally, we find that a glass with sodium orthophosphate rich phase enhances the solubility when immersed in SBF and further accelerate the kinetics of apatite formation. The influences of the chemical composition and their superior textural properties on bioactivity are explained in terms of the unique structure of mesoporous bioactive glasses.     

Interaction of water vapor with silicate glass surfaces: Mass-spectrometric investigations

The secondary ion mass-spectroscopy technique was used to study the results of hydration of borosilicate, aluminosilicate, and soda-lime silicate glasses in ¹H₂ ¹⁸O water vapor containing 97% of the isotope ¹⁸O. It is shown that hydration of the surface of the soda-lime silicate glass occurs as a result of the ion-exchange reaction with alkali metals. In the case of borosilicate and aluminosilicate glasses, water molecules decompose on the glass surface, with the observed formation of hydrogenated layer in the glass being the result of a solid-state chemical reaction—presumably, with the formation of hydroxides from aluminum and boron oxides.     

Structural study of sodium silicate glasses and melts

We report an X-ray diffraction study and modeling of the structure of sodium silicate glasses and melts that are used as binders in the production of the latest generation of ceramic welding fluxes. Experimental data and reverse Monte Carlo (RMC) simulations results are analyzed in comparison with results for a sodium silicate monolith and the water glass prepared from it. The RMC results agree well with structure factor and radial distribution function analysis data. The sodium silicate glasses and melts are shown to have a number of structural features, which have much in common with their crystalline counterparts. The high capacity of the silicate glasses and melts for water is due to the presence of nanopores formed (largely) by six-membered rings of silicon-oxygen tetrahedra and partially by sodium-oxygen octahedra.     

Characterization of gas components and deposits in bubbles in silicate glasses prepared with sodium sulphate

The gas contents and surface deposits in bubbles that were formed at various temperatures in sodium calcium silicate glasses using sodium sulphate as a starting material were investigated by means of Raman microprobe and scanning microscopic techniques. Either elemental sulphur or sodium sulphate could be readily detected in the deposits, depending on treatment conditions for the glass. Higher amounts of elemental sulphur were found as deposits on bubble surfaces for glasses prepared using both carbon and sodium sulphate. SO₂ or CO₂ could be detected as gas components in various bubbles.     

Ein modell zur auflösung von silicatgläsern

The reaction of water with silicate glasses is modeled as a sequence of chemical reactions. The model can explain the rate of attack of acid, neutral, and alkaline solutions on the glass surface. The calculated rate constants depend on the glass composition and the pH and constituents of the attacking solutions. The calculations suggest that the glass surface is not static under given reaction conditions, so that there is a continuous composition change in the hydrated layer, and only certain surface sites take part in the reaction.     

The effect of ionic dissolution products of Ca–Sr–Na–Zn–Si bioactive glass on in vitro cytocompatibility

Many commercial bone grafts cannot regenerate healthy bone in place of diseased bone. Bioactive glasses have received much attention in this regard due to the ability of their ionic dissolution products to promote cell proliferation, cell differentiation and activate gene expression. Through the incorporation of certain ions, bioactive glasses can become therapeutic for specific pathological situations. Calcium–strontium–sodium–zinc–silicate glass bone grafts have been shown to release therapeutic levels of zinc and strontium, however the in vitro compatibility of these materials is yet to be reported. In this study, the in vitro cytocompatibility of three different calcium–strontium–sodium–zinc–silicate glasses was examined as a function of their ion release profiles, using Novabone® bioglass as a commercial comparison. Experimental compositions were shown to release Si⁴⁺ ranging from 1 to 81 ppm over 30 days; comparable or enhanced release in comparison to Novabone. The maximum Ca²⁺ release detected for experimental compositions was 9.1 ppm, below that reported to stimulate osteoblasts. Sr²⁺ release was within known therapeutic ranges, and Zn²⁺ release ranged from 0.5 to 1.4 ppm, below reported cytotoxic levels. All examined glass compositions show equivalent or enhanced in vitro compatibility in comparison to Novabone. Cells exposed to BT112 ionic products showed enhanced cell viabilities indicating cell proliferation was induced. The ion release profiles suggest this effect was due to a synergistic interaction between certain combinations and concentrations of ions. Overall, results indicate that the calcium–strontium–sodium–zinc–silicate glass compositions show equivalent or even enhanced in vitro compatibility compared to Novabone®.     

电解液对PAN-基碳纤维电化学改性效果的影响

分别采用磷酸、氢氧化钠和碳酸氢铵3种电解液对PAN-基碳纤维进行电化学改性处理,研究电解液种类对碳纤维电化学改性效果的影响规律.通过酸碱滴定法、原子力显微镜表征和复合材料界面剪切强度(IFSS)测试,分析纤维表面酸性官能团含量、表面形貌及其复合材料界面强度的变化规律.研究结果表明:采用磷酸和氢氧化钠电解液处理时,纤维表面酸性官能团含量随着电流强度的增加先迅速增大而后逐渐减少,电流强度为0.4 A/g时达到最大值;采用碳酸氢铵电解质时,纤维表面酸性官能团含量随着电流强度的增大先缓慢增大而后迅速减少,电流强度为1.4 A/g时达到最大值.针对纤维表面形貌的AFM分析表明,在磷酸和氢氧化钠电解液中处理时,复合材料的IFSS主要受纤维表面刻蚀作用的影响,而采用碳酸氢铵电解液处理时,复合材料的IFSS主要受纤维表面酸性官能团含量的影响.     

Co-operative study on the release of lead from crystalware

The Istituto Superiore di Sanità promoted a study on lead availability from crystalware. The study was conducted in collaboration with a glass research Institute, on glass articles provided by two of the major Italian lead crystal producers. The whole spectrum of lead-bearing glasses from 7 up to 32% PbO was investigated. Short-term extraction tests carried out with 4% acetic acid on three sets of 24% PbO stemware of different composition, show that lead release is closely related to the hydrolytic resistance of the glass. A linear correlation was found between sodium released from the bulk glass and lead released from the surface at any time after the first leach. Experiments of repeated leaching with wine and brandy showed that lead release decreases with increasing number of extractions, similarly to the decrease observed with 4% acetic acid. Long-term experiments carried out with brandy on a set of six decanters for three months at room temperature confirmed the well-known square root dependence of lead release with time. On the basis of these results an estimation of the risk associated with the conditions of consumer use is attempted. © 1998 John Wiley & Sons, Ltd.     

Raman spectroscopic investigation of sodium borosilicate glass structure

Raman spectra of sodium borosilicate glasses with a wide range of Na₂O/B₂O₃ ratios were systematically measured. Variations of the spectra with glass composition were studied to interpret the implied distribution of Na⁺ ions between silicate and borate units. When Na₂O/B₂O₃ is less than 1, all Na⁺ ions are associated with borate units as indicated by the absence of the 1100 cm⁻¹ band of Si-O⁻ non-bridging bond stretching. For the (1−x)Na₂O · SiO₂ ·xB₂O₃ glass withx≦0.4 the peak-height ratio of the 950 cm⁻¹ band to the 1080 cm⁻¹ band was used to analyse semiquantitatively the distribution of the Na⁺ ions between silicate and borate units. Sodium ions are divided between silicate and borate units approximately in proportion to the amount of SiO₂ and B₂O₃ present in these glasses. Some of the high sodium content glasses were crystallized and their spectra were compared with the bulk glass spectra. The distribution of Na⁺ ions in the glass was quite different from their distribution after crystallization. Spectra of high silica glasses that had been heat-treated for phase separation indicated exclusion of borate units from the silica network and the formation of borate groups. For high boron content glasses, no change was observed on heat treatment. Raman bands due to borate groups seem to be little affected by their environments. Also affiliated with the Department of Geosciences.     

Microinhomogeneity of high-alkali aluminosilicate glasses studied by nuclear magnetic resonance spectroscopy

The structure of quenched aluminosilicate glasses with Na₂O/Al₂O₃ > 1 has been studied by high-resolution nuclear magnetic resonance spectroscopy. The aluminum in the structure of the glasses is shown to be in fourfold coordination. Increasing the sodium oxide content of the glasses reduces the degree of polymerization in their structure and leads to a nonuniform nonbridging oxygen distribution over the aluminosilicate glass network. The glasses have a locally microinhomogeneous structure due to the presence of both highly polymerized aluminosilicate anion groups and relatively depolymerized silicate anions.     

Chemical modification of jute fibers for the production of green-composites

Natural fiber reinforced composites is an emerging area in polymer science. Fibers derived from annual plants are considered a potential substitute for non-renewable synthetic fibers like glass and carbon fibers. The hydrophilic nature of natural fibers affects negatively its adhesion to hydrophobic polymeric matrices. To improve the compatibility between both components a surface modification has been proposed. The aim of the study is the chemical modification of jute fibers using a fatty acid derivate (oleoyl chloride) to confer hydrophobicity and resistance to biofibers. This reaction was applied in swelling and non-swelling solvents, pyridine and dichloromethane, respectively. The formation of ester groups, resulting from the reaction of oleoyl chloride with hydroxyl group of cellulose were studied by elemental analysis (EA) and Fourier Transform infrared spectroscopy (FTIR). The characterization methods applied has proved the chemical interaction between the cellulosic material and the coupling agent. The extent of the reactions evaluated by elemental analysis was calculated using two ratios. Finally electron microscopy was applied to evaluate the surface changes of cellulose fibers after modification process.     

The role of Sr<Superscript>2+</Superscript> on the structure and reactivity of SrO–CaO–ZnO–SiO<Subscript>2</Subscript> ionomer glasses

The suitability of Glass Polyalkenoate Cements (GPCs) for use in orthopaedics is retarded by the presence in the glass phase of aluminium, a neurotoxin. Unfortunately, the aluminium ion plays an integral role in the setting process of GPCs and its absence is likely to hinder cement formation. However, the authors have previously shown that aluminium free GPCs may be formulated based on calcium zinc silicate glasses and these novel materials exhibit significant potential as hard tissue biomaterials. To further improve their potential, and given that Strontium (Sr) based drugs have had success in the treatment of osteoporosis, the authors have substituted Calcium (Ca) with Sr in the glass phase of a series of aluminium free GPCs. However to date little data exists on the effect SrO has on the structure and reactivity of SrO–CaO–ZnO–SiO₂ glasses. The objective of this work was to characterise the effect of the Ca/Sr substitution on the structure of such glasses, and evaluate the subsequent reactivity of these glasses with an aqueous solution of Polyacrylic acid (PAA). To this end ²⁹Si MAS-NMR, differential scanning calorimetry (DSC), X-ray diffraction, and network connectivity calculations, were used to characterize the structure of four strontium calcium zinc silicate glasses. Following glass characterization, GPCs were produced from each glass using a 40 wt% solution of PAA (powder:liquid = 2:1.5). The working times and setting times of the GPCs were recorded as per International standard ISO9917. The results acquired as part of this research indicate that the substitution of Ca for Sr in the glasses examined did not appear to significantly affect the structure of the glasses investigated. However it was noted that increasing the amount of Ca substituted for Sr did result in a concomitant increase in setting times, a feature that may be attributable to the higher basicity of SrO over CaO.     

Raman microprobe investigation of oxygen and carbon dioxide dissolution from bubbles in silicate glasses containing antimony oxide

The effect of addition of antimony oxide and/or sodium nitrate to silicate glass compositions upon the changes in the relative concentrations of oxygen and carbon dioxide in their bubbles from heat treatment was investigated using the Raman microprobe technique. The addition of antimony oxide to these glasses increased the relative rates of oxygen dissolution from their bubbles with respect to glasses containing no refining agents. These increases were closely related to the absolute amounts of Sb³⁺ ions that were present in the glasses. The relative rates were faster for glasses containing antimony oxide than for glasses containing the same molar amounts of arsenic oxide. The higher Sb³⁺/Sb⁵⁺ ratios for glasses containing antimony oxide with respect to the As³⁺/As⁵⁺ ratios for glasses containing arsenic oxide caused the relative rates of oxygen dissolution to be dramatically greater for the former glasses. In contrast to an earlier investigation with silicate glasses containing arsenic oxide, the addition of sodium nitrate to glasses containing antimony oxide using a similar glass preparation did not significantly change their relative rates of oxygen dissolution.     

光谱学研究银纳米颗粒在玻璃中的生成规律

通过离子交换法将银离子引入白硅酸盐玻璃和绿硅酸盐玻璃,利用光致发光(photoluminescence-PL)和光吸收(optical absorption-OA)谱研究银离子的团簇化、成核和生长.由于白硅酸盐玻璃不含二价铁离子,因此,银纳米颗粒形成困难,颗粒体积分数非常低,以致样品中银纳米颗粒的共振吸收峰不明显.在这种条件下,样品中存在大量银离子和银的小原子团簇.在绿玻璃中,氧化铁含量较高,引入到玻璃中的银离子大部分被二价铁离子还原成中性银原子,通过热处理,银离子在玻璃中成核和生长.在相近的热处理条件下,绿玻璃有利于银纳米颗粒的生成.银纳米颗粒在形成过程中,消耗大量银离子,造成样品的发光强度逐渐降低.     

The role of aluminium and silicon in the setting chemistry of glass ionomer cements

A model of the setting chemistry of glass-ionomer cements (GICs) is proposed based on ²⁷Al and ²⁹Si solid state nuclear magnetic resonance spectroscopy data on three GICs. All the precursor glasses are found to contain three aluminium species viz.: four, five and six-coordinate aluminium environments as well as four-bridging silicate tetrahedra. Upon cement formation, Al³⁺ ions in the glass are leached out from the surface layer of the glass. On entering the cement matrix, these ions adopt six-coordination and crosslink the polymer chains as part of the setting reaction. The remaining four-coordinate aluminium is distributed between two species: one in the inert core of the glass particles; and a second, less concentrated, in the surface layer of the glass particles, modified by the curing reactions. There is some evidence for residual five and six coordinate aluminium species in the final cement in some of the systems. In the case of the silicate tetrahedra, the curing reactions result in a decrease in the number of aluminium atoms in the second coordination sphere, with a subsequent recondensation of silicate network of the glass.     

Bivalent cationic ions doped bioactive glasses: the influence of magnesium,zinc, strontium and copper on the physical and biological properties

Bioactive glass and glass ceramic materials are widely used as substitutes for bone augmentation and restoration, in orthopaedic, dental and maxillofacial surgery and in the tissue engineering field. Indeed, these materials are bioactive, biocompatible, mechanically stable, biodegradable and favour osteointegration, being able to promote bone tissue formation at their surface and to bond to surrounding living tissues when implanted in the human body. It has been demonstrated that bioglass (BG) ionic dissolution products (e.g. Si, Ca, P and Na) are able to induce and stimulate the expressions of genes related to the osteoblastic differentiation and bone formation, to stimulate angiogenesis in vitro and in vivo, as well as to play possible antibacterial and anti-inflammatory actions. Thus, it is possible to tailor BGs properties properly formulating their chemical composition and adding selected ions with specific functional and biological role. In this perspective, Hench proposed a new generation of genetically designed glasses, on the basis of their ability to activate specific genes involved in in situ tissue regeneration, by doping silicate and phosphate glasses with several active ions, particularly metallic ions with therapeutic effects. In this framework, the present review is aimed to provide an overview about the effect of selected cationic substitutions (i.e. magnesium, zinc, strontium and copper), incorporated within the bioglasses structure, on the physical and biological properties of these materials, since the comprehension of the influence of the most employed metallic ions has to be considered pivotal to address the formulation of more promising and performing glasses.     

紫铜表面吸附膜的制备及性能研究

为解决紫铜表面抗氧化变色问题,以甲基硅酸钠、环氧烷衍生物、多聚磷酸酯为原料,采用浸泡方法在紫铜片表面制备防腐蚀吸附膜。采用硝酸点滴法、Tafel曲线、电化学阻抗谱表征膜层耐蚀性,利用原子力显微镜观察膜层微观结构形貌。通过单因素试验筛选出最佳成膜工艺条件为7.0%甲基硅酸钠溶液,7.0%环氧烷衍生物,2.0%多聚磷酸酯,以最佳新工艺制备的膜层均匀致密,具有很好的耐蚀性。     

Wet chemical etching of silicate glasses in hydrofluoric acid based solutions

The etching of silicate glasses in aqueous hydrofluoric acid solutions is applied in many technological fields. In this review most of the aspects of the wet chemical etching process of silicate glasses are discussed. The mechanism of the dissolution reaction is governed by the adsorption of the two reactive species: HF and HF ₂ ^- and the catalytic action of H⁺ ions, resulting in the breakage of the siloxane bonds in the silicate network. The etch rate is determined by the composition of the etchant as well as by the glass, although the mechanism of dissolution is not influenced. In the second part of this review, diverse applications of etching glass objects in technology are described. Etching of SiO₂ and doped SiO₂ thin films, studied extensively for integrated circuit technology, is discussed separately.     

An investigation into the structure and reactivity of calcium-zinc-silicate ionomer glasses using MAS-NMR spectroscopy

The suitability of Glass Polyalkenoate Cements (GPCs) for orthopaedic applications is retarded by the presence in the glass phase of aluminium, a neurotoxin. Unfortunately, the aluminium ion plays an integral role in the setting process of GPCs and its absence is likely to hinder cement formation. However, the authors have previously shown that aluminium-free GPCs may be formulated based on calcium zinc silicate glasses and these novel materials exhibit significant potential as hard tissue biomaterials. However there is no data available on the structure of these glasses. ²⁹Si MAS-NMR, differential thermal analysis (DTA), X-ray diffraction (XRD), and network crosslink density (CLD) calculations were used to characterize the structure of five calcium zinc silicate glasses and relate glass structure to reactivity. The results indicate that glasses capable of forming Zn-GPCs are predominantly Q₂/Q₃ in structure with corresponding network crosslink densities greater than 2. The correlation of CLD and MAS-NMR results indicate the primary role of zinc in these simple glass networks is as a network modifier and not an intermediate oxide; this fact will allow for more refined glass compositions, with less reactive structures, to be formulated in the future.