Conditions for Transformation and Equilibrium of Iron Oxides in Glass Melting

It is demonstrated that transformations of iron oxides in glass melting occur mainly in the solid phase. The ratio between the two forms of iron oxides in a glass melt is determined by the melt temperature. Achieving an equilibrium with the gaseous medium requires a long time due to high melt viscosity and low diffusion coefficients. To ensure high service parameters in products, one needs stability of raw material compositions and melting process parameters, including diathermancy of the melt.     

Use of the Anion Structure Coefficient in Developing Glass Ceramic Materials

Anion structure coefficients (ASC) are given for solid solutions synthesized on the basis of stoichiometric compositions with a ratio of Li₂O : Al₂O₃ : SiO₂ equal to 1 : 1 : 4 – 1 : 1 : 12. A fundamental possibility of selecting the residual vitreous phase and predicting the process of sintering of glass powders by calculating the ASC of the initial compositions and the residual vitreous phase in developing glass ceramic materials with preset properties is demonstrated.     

Assessment of thermal,morphological, and mechanical properties of poly(methyl methacrylate)/glass flake composites

In this work, poly(methyl methacrylate)/(glass flake) (GF) composites were prepared with different compositions via melt mixing. The effect of the filler ingredient on thermal behavior, morphology, and mechanical and optical properties was investigated by using various techniques, namely differential scanning calorimetry, ultraviolet‐visible spectra, mechanical testing, and scanning electron microscopy. For evaluating the level of dispersion of particles, energy dispersive X‐ray analysis was performed. Differential scanning calorimetry analysis showed that the glass transition temperature of the samples slightly increased by increasing GF content. Scanning electron microscopy images showed that sized flakes were uniformly dispersed within poly(methyl methacrylate). Energy dispersive X‐ray analysis images of samples with different inclusions of GFs showed that the appearance of white dense spots represents the GF particles. It was found that the presence of 0.5 wt% of GF in composites gave more transparency than the other compositions. Furthermore, this composition indicated maximum tensile strength and elongation‐at‐break values in comparison with the other compositions. J. VINYL ADDIT. TECHNOL., 23:62–69, 2017. © 2015 Society of Plastics Engineers     

Styrene-Butadiene Polytelomers for Pressure-Sensitive Applications

Novel styrene-butadiene polymer latex compositions and their utility for pressure-sensitive and other adhesive applications are described. These compositions, termed polytelomers, are based on the concept of synthesising sequentially a low glass transition temperature, high molecular weight (polymeric) fraction, followed by a high glass transition, low molecular weight (telomeric) fraction, in an attempt to simulate the compounding of elastomeric adhesives. Some of the described compositions can exhibit multiphase morphology, having discrete styrene-rich domains surrounded by butadiene rich phase, both of these phases being embedded in a “honeycomb” carboxyl-rich phase. The compositions were characterized by dynamic mechanical spectroscopy and by electron transmission microscopy, as well as by molecular weight distribution and glass transition temperature range data. Examples of adhesive applications are also given.     

水-丙酸二元体系汽液平衡的热力学性质

用新型泵式沸点仪测定了在101.325kPa下水-丙酸二元系在不同液相组成时的沸点,用过量自由焓函数Q,采用间接法由Tpx推算了水-丙酸二元系的汽相平衡组成y。汽相的非理想性用截至第二项的维里系数的状态方程求出汽相混合物中组分逸度系数。二元体系活度系数的关联分别用Wilson模型、NRTL模型、Margules模型和vanLaar模型进行关联,用最小二乘法求出了它们的液相活度系数模型参数。用所得的液相活度系数来计算三个二元体系的过量吉布斯自由焓函数GE/RT。计算的泡点温度与实验测得的沸点温度吻合良好,由面积积分法检验这些模型参数计算的二元体系相平衡数据,得到很好的热力学一致性。     

甲醇-乙酸-丙酸多元体系汽液平衡

用新型泵式沸点仪测定了在100kPa下甲醇-乙酸、甲醇-丙酸、乙酸-丙酸3个二元体系以及甲醇-乙酸-丙酸三元系在不同液相组成时的沸点,并用间接法T-p-x(温度、压力和液相摩尔分数)推算了3个二元体系的汽相平衡组成。3个二元体系活度系数分别用Wilson模型、NRTL模型、Margules模型和van Laar模型进行关联,用最小二乘法求出了它们的液相活度系数模型参数,同时,用这些模型参数来计算它们的汽相摩尔分数。所得的液相活度系数来计算3个二元体系的过量吉布斯自由能函数,且所研究的所有体系中各组分之间不存在共沸点。用3个二元体系Wilson模型参数对所测的三元体系数据进行关联,建立该系统汽液平衡的热力学模型并计算平衡时的汽相摩尔分数和泡点温度。由面积积分法检验这些模型参数计算的3个二元体系相平衡数据,得到很好的热力学一致性。     

Free volume properties of thermoplastic polyurethane/polymethylmethacrylate blends: Evidence of interchain interaction

A polymer blend based on thermoplastic elastomeric polyurethane and polymethylmethacrylate (TPU/PMMA) has been studied by positron annihilation lifetime spectroscopy (PALS) and thermomechanical analysis. Thermomechanical analysis allowed the determination of two glass transitions for the blends in the overall range of compositions. The first one (T_g¹) showed a constant value of ?45°C for all blends, the same value of the pure TPU. The second glass transition (T_g²), which is associated with a PMMA rich phase, presented variations with composition. T_g² showed minimum values for the blends in the 20–40 wt % TPU range, which indicates increase of interaction in this composition region. PALS systematic investigation allowed the determination of relative mean free volume fractions, f_v/C, and binary interchain interaction parameters, β. These parameters exhibited a noticeable negative deviation from additivity in all range of composition and minima for the 20 wt % TPU blend. PALS results were interpreted as associated to a strong attractive interchain interaction between TPU and PMMA in the PMMA rich phase which contracts the free volume fraction of the blends. Moreover, the miscibility achieved in the PMMA rich phase would allow a good adhesion between this phase and the TPU phase, which was corroborated by scanning electron microscopy images. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Influence of Fe3+/Fe2+ Ratio on the Crystallization of Iron-Rich Glasses Made with Industrial Wastes

The influence of the Fe³⁺/Fe²⁺ ratio on the crystallization of iron-rich glasses was investigated in this study. The glass batches were made from two hazardous industrial wastes: mud (goethite and jarosite) originating from the zinc hydrometallurgical process and electric arc furnace dust (EAFD). Glass compositions were prepared by adding different percentages of carbon powder. The crystallization process was investigated by a combined thermogravimetry/differential thermal analysis technique, in air or nitrogen atmospheres, using powder and bulk glass samples. The crystalline phases formed, i.e., pyroxene and spinels, and their relative ratio were determined by X-ray diffractometry. The experimental results indicated that melting temperature and crystallization behavior were influenced by the initial Fe³⁺/Fe²⁺ ratio and by the amount of carbon added to the glass batch. For goethite and jarosite glass compositions, decreasing the Fe³⁺/Fe²⁺ ratio increased the crystallization rate by favoring magnetite formation. For EAFD glass compositions, the addition of carbon to the batch inhibited chromite–magnetite spinel formation and favored the attainment of an amorphous glassy phase.     

The influence of MgO on the crystallization behaviour and properties of SrO-rich phosphosilicate glasses

A series of glass was produced to investigate the effect of MgO/SrO replacement on the crystallization characteristics and properties of phosphosilicate glasses containing high SrO content. The glass samples were synthesized by conventional melting technique based on 5CaO-(40-X)SrO-X MgO– 43SiO₂–7P₂O₅–5CaF₂ (where; X = 10, 20, 30 and 40 mol%). The influence of MgO/SrO replacement on phase assemblages, microcrystalline structures, thermal expansion, and mechanical properties was examined as a function of basic chemical compositions and crystallization parameters. Predominant strontium meta-silicates together with strontium fluoroapatite phases are crystallized from the base glass free of magnesium. The substitution of strontium by magnesium up to 50% led to formation strontium akermanite phase Sr₂MgSi₂O₇ at the expense of SrSiO₃ phase. Whereas the increase of the MgO/SrO of more than 50%, which led to the crystallization of the clino-enstatite MgSiO₃ as a predominant phase. The results show that the α-values of the glass-ceramics are ranged in 94–125 × 10⁻⁶ K⁻¹ over the temperature range (25–500 °C). On the other hand, MgO/SrO replacements led to enhancing the microhardness of the resultant crystalline materials from 4713 Mpa to 6744 Mpa. As a result of the designed glass compositions, promising crystalline phases were obtained as well as good thermal and mechanical properties for the resultant glass-ceramics. Therefore, the designed glass-ceramics can be strongly used as biomaterials especially for bone reconstruction applications.     

Styrene-Butadiene Polytelomers for Pressure-Sensitive Applications

Novel styrene-butadiene polymer latex compositions and their utility for pressure-sensitive and other adhesive applications are described. These compositions, termed polytelomers, are based on the concept of synthesising sequentially a low glass transition temperature, high molecular weight (polymeric) fraction, followed by a high glass transition, low molecular weight (telomeric) fraction, in an attempt to simulate the compounding of elastomeric adhesives. Some of the described compositions can exhibit multiphase morphology, having discrete styrene-rich domains surrounded by butadiene rich phase, both of these phases being embedded in a “honeycomb” carboxyl-rich phase. The compositions were characterized by dynamic mechanical spectroscopy and by electron transmission microscopy, as well as by molecular weight distribution and glass transition temperature range data. Examples of adhesive applications are also given.     

Characterization of coal fly ash for possible utilization in glass production

The recycling of three different fly ashes obtained from the coal fired thermal power plants has been studied. Coal fly ashes were vitrified by melting them at 1773 K for 5 h without any additives. After the glass production, glass samples were subjected to a heat treatment process to be able to see whether or not the glasses could be transformed into a microcrystalline structured materials. Produced glass samples were heated to 1423 K and held at this temperature for 2 h to determine the effect of heat treatment process on the properties of glasses. The properties of glass and the heat treated glass samples produced from coal fly ash were investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. DTA study indicated that there were only inflection points of the endothermic peaks in the DTA curves of the glass samples. XRD analysis showed the amorphous state of the glass samples and also the presence of only the diopside phase in the heat-treated glass samples. SEM investigations revealed that small amount of crystallites occurred in the microstructure of the heat treated glass samples in contrast to the amorphous structure of the glass samples. The mechanical, physical and chemical properties of the heat-treated glass samples are found better than those of the glass samples. Toxicity characteristic leaching procedure (TCLP) results showed that the heavy metals of fly ashes were successfully immobilized into both glass and heat treated glass samples. It can be said that glass and heat treated glass samples obtained by the recycling of coal fly ash can be taken as a non-hazardous material. Overall, results indicated that the vitrification technique is an effective way for the stabilization and recycling of coal fly ash.     

P2O5‐Fe2O3‐CaO‐SiO2 ferromagnetic glass‐ceramics for hyperthermia

Ferromagnetic glass‐ceramics are an important kind of thermoseed material for hyperthermia treatments. In order to investigate the applications of glass‐ceramics in magnetic hyperthermia, P₂O₅‐Fe₂O₃‐CaO‐SiO₂ (PFCS) glass‐ceramics with different compositions were prepared by the sol‐gel method. The crystal phase, magnetic properties, induction heating ability, and cytotoxicity of the as‐prepared glass‐ceramics were investigated. The results show that all the samples exhibit low cytotoxicity and good induction heating ability. Moreover, it was found that the phosphorus content affected the crystal phase component of the sample, and thus influenced the induction heating ability. Results of the magnetic hyperthermia experiments showed that the PFCS glass‐ceramic samples induced significant cell death of the LoVo cancer cells. The highest cell death rate for sample B2P7 was more than 95%, which suggests good application prospects in the field of hyperthermia therapy.     

Thermal analysis of poly(acrylic acid)/poly(oxyethylene) blends

Blends between poly(acrylic acid) and two different poly(oxyethylenes), (1) polyethylene glycol (PEG-1000) and (2) poly(oxyethylene) (20) sorbitan monooleate (Tween-80), were studied by differential scanning calorimetry. The glass transition temperatures, T_g, of the various compositions of these blends were found to follow Fox's equation. At room temperature, blends containing no more than 60% PEG-1000 were amorphous and exhibited only a single glass transition. For these blends with PEG-1000, the glass transition temperatures for the annealed samples were higher than for the quenched samples due to the formation of a PEG crystalline phase. It was also found that addition of an amorphous polymer such as poly(acrylic acid) significantly reduced the degree of crystallinity of a semicrystalline polymer such as poly(oxyethylene). The Tween-80 systems did not show phase separation at room temperature. The compatibility between this poly(acrylic acid) and this poly(oxyethylene) was attributed to hydrogen bonding and to the lower crystalline lattice energy of this poly(oxyethylene) through its effect on its ideal solution solubility. © 1993 John Wiley & Sons, Inc.     

Lead-Ion Stability in Soda–Lime Lead Silicate Glasses

Sodium-calcium-lead silicate glass compositions were prepared over a wide compositional range by conventional glass-melting methods. The acid chemical stability of the glass structure was studied by corroding samples of glass in 4% acetic acid solution at 22°C for periods up to 24 h. Lead corrosion stability was evaluated by measuring lead concentrations in the corrosion solution. At short times, parabolic time dependence was observed and the parabolic time coefficients were regressed against composition, yielding a simple additive relationship. A similar model was fitted to 24-h release data, which showed compositional effects similar to the 2-h data. Of the oxides studied, sodium was the most detrimental to durability, and the coefficients of the oxides decreased in the series: Na₂O, PbO, CaO, SiO₂. The effects of the oxides could be partially explained by the number of nonbridging oxygens expected in the glass structure, and the residual effect was attributed to cation characteristics. Small phosphate additions to the glass greatly increased the lead-ion stability under nearly all experimental conditions examined.     

Effects of composition and phase relations on mechanical properties and crystallization of silicate glasses

Crystallization, mechanical properties, and workability are all important for the commercialization and optimization of silicate glass compositions. However, the inter-relations of these properties as a function of glass composition have received little investigation. Soda-lime-silica glasses with Na₂O-MgO-CaO-Al₂O₃-SiO₂ compositions relevant to commercial glass manufacture were experimentally studied and multiple liquidus temperature and viscosity models were used to complement the experimental results. Liquidus temperatures of the fabricated glasses were measured by the temperature gradient technique, and Rietveld refinements were applied to X-Ray powder diffraction (XRD) data for devitrified glasses, enabling quantitative determination of the crystalline and amorphous fractions and the nature of the crystals. Structural properties were investigated by Raman spectroscopy. Acoustic echography, micro-Vicker's indentation, and single-edge-notched bend testing methods were used to measure Young's moduli, hardness, and fracture toughness, respectively. It is shown that it is possible to design lower-melting soda-lime-silica glass compositions without compromising their mechanical and crystallization properties. Unlike Young's modulus, brittleness is highly responsive to the composition in soda-lime-silica glasses, and notably low brittleness values can be obtained in glasses with compositions in the wollastonite primary phase field: an effect that is more pronounced in the silica primary phase field. The measured bulk crystal fractions of the glasses subjected to devitrification at the lowest possible industrial conditioning temperatures indicate that soda-lime-silica glass melts can be conditioned close to their liquidus temperatures within the compositional ranges of the primary phase fields of cristobalite, wollastonite, or their combinations.     

醋酸-水二元系25——75℃恒温汽液平衡的研究

建立了利用静态法测定溶液蒸气压的装置,它包括平衡器、零压计、水银压差计、脱气室以及高真空设备。在此装置中测定了醋酸-水二元系在25—75℃范围内的蒸气压。为了得到完整的恒温汽液数据,利用我们先前发展的一个直接热力学方法来计算平衡汽相组成,计算时考虑了汽相缔合。本文中用表格形式发表了所得的计算结果。 为了拟合实验数据,用了一个由热力学推导得到的关联活度系数与温度的多项式,多项式参数由最小二乘法求得。利用这些参数,并外推至常压,预测所得泡点和汽相组成与文献报导的恒压实验数据,具有良好地一致。这些参数,可在低压至常压的广阔范围内的实际汽液平衡计算中使用。     

Thermal Expansion and High-Temperature Phase Transition of Ba6−3xLn8+2xTi18O54 (Ln=La, Nd, and Sm) Ceramics

Thermal expansion behaviors of Ba_{6−3 x} Ln_{8+2 x} Ti₁₈O₅₄ (Ln=La, Nd, and Sm, x =0.5, 0.67, and 0.75) ceramics were determined by dilatometric measurement. The samples of all investigated compositions expanded nearly linearly with increasing temperature in the range of 20°–1200°C. Their thermal expansion coefficients were determined to be 10.7–11.4 ppm/°C. A discontinuous change in sample size was observed at about 1350°C for each composition, indicating the existence of a phase transition. As determined by the high-resolution X-ray diffraction analysis, the phase constitution and the lattice parameters of Ba_{6−3 x} Sm_{8+2 x} Ti₁₈O₅₄ ceramics were maintained in the quenched samples. The origin of the phase transition was discussed thoroughly. Phase equilibrium in the BaTiO₃–Ln_2/3TiO₃ system was reviewed by considering the phase transition.     

Characterization and in vitro-bioactivity of natural hydroxyapatite based bio-glass–ceramics synthesized by thermal plasma processing

Natural bovine hydroxyapatite/SiO₂–CaO–MgO glass–ceramics were produced using the transferred arc plasma (TAP) processing method. Homogeneous mixtures of HA/25 wt% SiO₂–CaO–MgO and HA/50 wt% SiO₂–CaO–MgO batches obtained by dry mixing the respective compositions in a ball mill were processed in argon plasma using the TAP torch at 5 kW for 1, 2 and 3 min, respectively. The synthesized glass–ceramic samples were studied for phase composition, microstructure and bioactivity. The phase study of the synthesized glass–ceramics revealed the formation of calcium phosphate silicate with traces of calcium silicate. The structural study by SEM revealed that the prepared samples possessed smooth glassy surface morphology. The in vitro-bioactivity of the TAP synthesized glass–ceramics was examined in simulated body fluid (SBF). The SBF test results confirmed the development of crystalline carbonated apatite phase after 12 days of immersion. The cytocompatibility was evaluated through human fibroblast cell proliferation. The fibroblasts culture results showed that the sample was non-toxic and promoted cell growth.     

An environmentally friendly process for preparing commercial ceramic foam composites based on frit/glass wastes

Considering the size of the amount of energy consumption in ovens during the production of gas ceramic foam materials in the ceramic industry, it can be stated that natural gas is one of the highest energy resources. Natural gas consumption during the production has been evaluated and financial analyses were made for saving consumption amounts. Raw materials and glass/frit wastes obtained from different regions were investigated and their chemical compositions were determined by X-Rays fluorescence spectrometry (XRF) analysis. Compared to their current alternatives, glass foams with homogenous structure and low density were developed by adding frit/glass wastes in the amount of 80%-90%. X-Ray diffraction (XRD) analysis has been conducted for mineralogical investigation of the samples. Also, to analyze the pore sizes and examine the surface morphology of foams, SEM images were obtained. With the addition of glass/frit wastes, natural gas consumption decreased (ca. 20%-25%) in firing process.     

Temperature dependent elastic-plastic behaviour of polystyrene studied using AFM force-distance curves

Force-displacement curves have been obtained on two polystyrene samples, having different molecular weight, at various temperatures and probe rates using an atomic force microscope. The force-displacement curves have been analysed using a novel method, which extends continuum elastic contact theories also to the plastic deformations. The Young's modulus and the yielding force of the two polystyrene samples have been determined as a function of temperature and frequency. It was also possible to calculate the Williams-Landel-Ferry coefficients for measurements above the glass transition temperature, and the viscoelastic activation energy for measurements below the glass transition temperature using the Arrhenius equation. All the calculated coefficients were in very good agreement with the literature values. The measured quantities span a wide range of temperature (85 °C) and frequency (eight decades) and the shifts of all the quantities calculated from force-displacement curves obey the Williams-Landel-Ferry and Arrhenius equation with the same parameters. Quantitative and qualitative comparison of the Young's modulus, of the stiffness in the plastic region and of the yielding force of the two polystyrene samples revealed different viscoelastic behaviour because of the variation in glass transition temperature of the two samples, due to their difference in the molecular weight.