Influence of additives on the crystallization and thermal conductivity of container glass cullet for foamed glass preparation

Foamed glass preparation is a complex combination of reactions, greatly influenced by the composition of the used glass and often hindered by simultaneous crystallization. The crystallization phenomenon is undesirable in foamed glass production since it decreases the quality of the final product. In this work the influence of different types of additives (foaming agents, flux agents, crystallization inhibitors and nucleating agent) on the crystallization of waste container glass and properties of the sintered samples (density and thermal conductivity) was studied. Results of our study confirmed partial crystallization during sintering stage. We found that waste container glass manifests complex crystallization with the formation of four main crystalline phases, which can be inhibited with the addition of fluxing agents (B₂O₃ and borax). Moreover, here we show that prevention of the crystallization can lead to a significant decrease of the thermal conductivity.     

Effect of P2O5 on the Nonisothermal Sinter‐Crystallization Process of a Lithium Aluminum Silicate Glass

Dense (~98.5%), lithium aluminum silicate glass‐ceramics were obtained via the sinter‐crystallization of glass particle compacts at relatively low temperatures, that is, 790–875°C. The effect of P₂O₅ on the glass‐ceramics' sinter‐crystallization behavior was evaluated. We found that P₂O₅ does not modify the surface crystallization mechanism but instead delays the crystallization kinetics, which facilitates viscous flow sintering. Our glass‐ceramics had virgilite (Li_xAl_xSi_3‐xO₆; 0.5 < x < 1), a crystal size <1 μm, and a linear thermal expansion coefficient of 2.1 × 10^?6°C^?1 in the temperature range 40–500°C. The overall heat treatment to obtain these GCs was quite short, at ~25 min.     

Suppressing the effect of cullet composition on the formation and properties of foamed glass

The process of foaming glass is very dependent on the chemical composition of the glass. In this study we used a foaming-agent/oxidizing-agent couple and a crystallization inhibitor to foam cullets of flat, container and CRT-panel glass. Foamed glass with a density of 110–120?kg?m^–3, a thermal conductivity of 50–52?mW?m^–1 K^–1 and a homogeneous pore structure was obtained from a mixture of panel glass, 0.33?wt% carbon and 4.45?wt% Fe₂O₃. We also showed that it is possible to fabricate foamed glass with the same density or pore structure as mentioned above by adding up to 50?wt% container cullet or 70?wt% flat glass to the mixture. In the foamed samples with a low content of panel glass, crystals form, resulting in an increased open porosity, density and inhomogeneous pore structure. The crystallization can, however, be inhibited by adding calcium phosphate, so enabling the preparation of high-quality foamed glass from flat glass or flat/container-glass mixture. The pore gas is predominantly CO₂ and the pressure inside the pores is 0.36–0.47?bar. The reduced effect of the composition on the foaming process suggests that there is a great potential for stabilizing the production of foamed glass and ensuring the product's quality.     

反应烧结ZTM陶瓷显微结构分析及热处理对晶界玻璃相析晶的影响

本实验利用电子扫描电镜重点研究了以锆英石与氧化铝、A级铝矾土为原料反应烧结ZTM陶瓷的显策结构。分析表明：在不同的液相条件下,莫来石的晶粒发育产生了三种完全不同的晶形;液相量越高,莫来石的针状发育越好,过量氧化铝的存在严重阻碍了残余晶界玻璃相的析晶,金属铝粉的添加容易引入热处理难以消除的贯通笥气孔,这些气孔是影响反应烧结材料性能提高的重要因素。     

Analysis of the density and the enthalpy of poly(ϵ-caprolactone)-polycarbonate blends: Amorphous phase compatibility and the effect of secondary crystallization

The dependency of the density of poly(ϵ-caprolactone)-polycarbonate (PCL-PC) blends on composition has been studied. PCL/PC blends are typical of miscible blends containing crystallizable components, and miscibility is therefore considered with respect to the amorphous phase. In literature, a single glass transition temperature is reported for the PCL-PC system; however, the exact dependency on amorphous phase composition is not clear. For quenched amorphous blends, we found the Fox equation to be appropriate in order to describe the glass transition temperature as a function of composition. For amorphous samples containing low amounts of PCL (≤40 wt %), an increase in the density of the blend over that of a linear average of the densities of amorphous PC and PCL was observed experimentally. This is indicative of significant interactions in the blend. For samples containing ≥ 50 wt % PCL, crystallization of PCL has to be accounted for in the analysis of the density. It is shown that the experimental density data can only be described satisfactorily by assuming that secondary crystallization of PCL does not lead to an increase of the overall blend density. This is attributed to the rigid and volume filling primary crystalline structure at room temperature, i.e., below the melting point of PCL. Excess density is present in the amorphous phase of the PCL/PC blend over the whole range of composition; therefore, specific interactions exist in the amorphous phase of the blend over the whole range of composition. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 921–927, 1997     

Obtention of high-density quartz glass-ceramics in gas-flame furnaces

Conclusions It is shown to be possible to sinter quartz glass-ceramics in furnaces heated with natural gas to zero apparent porosity at 1350–1560°C, which is very important for the mass production of products.The region of the optium sintering cycles were determined, and we obtained quartz glass-ceramics with properties close to those of quartz glass.It is established that zero apparent porosity can be achieved in a material with a wide range of original density and grain-size composition. The closed porosity depends on the original density of the material, and for specimens having a porosity of 12.7 and 21.7% it equals respectively about 1.0 and 3.6%.Translated from Ogneupory, No.5, pp.36–39, May, 1972.     

反应析晶烧结法制备硅灰石玻璃陶瓷

本文提出了一种直接利用废玻璃制备硅灰石玻璃陶瓷的新工艺:反应析晶烧结法。将高岭土和碳酸钙为主要原料合成的析晶促进剂加入到废玻璃粉末中烧结,通过两者间的反应析出硅灰石。研究了析晶促进剂含量和烧结温度对硅灰石玻璃陶瓷的组织、烧结和性能的影响,结果表明:随着析晶促进剂含量的增加,玻璃陶瓷的体密度和开孔隙率增加,强度先增后降。提高烧结温度促进反应析晶,并导致玻璃陶瓷的体密度、开孔隙率和强度降低。析晶促进剂含量为15%,烧结温度为850℃时,制得的硅灰石玻璃陶瓷的力学性能最佳。     

Studies of sintering of coal ash relevant to pulverized coal utility boilers: 1. Examination of the Raask shrinkage—electrical resistance method

The Raask shrinkage and electrical resistance method for determining the onset of sintering of fly ash has been tested on a soda lime glass, coal ASTM ashes, fly ashes and pulverized synthetic mineral mixtures. Results with the glass confirmed those of Raask and showed that particle size distribution and bulk density affected the resistance values: the sinter point was indicated by a change in the characteristic temperature coefficient of resistance. The shrinkage and electrical sinter points were usually the same, but a high Na content lignite gave 850°C for shrinkage but 600°C for characteristic resistance change. Sinter points were 200°C less for fly ash than for ASTM ash. The fly ashes had a slight enrichment of alkalies and a decrease in Fe content compared to the total ash. Holding a compact at a temperature above the sinter point gave increased strength and shrinkage, but no decrease in electrical resistance, indicating that the decrease in resistance as temperature increased was due to the establishment of contact points between particles, with little effect of the continued growth of a contact neck. Addition of pulverized sodium silicate or iron silicate glasses to a synthetic ash also reduced the sinter points, as did alkali additions, whereas addition of pyrite did not. It was concluded that the method was a valuable tool, but sources of variability had to be determined and controlled.     

钛渣微晶玻璃晶化工艺的研究

１前言我国攀西地区蕴藏着极其丰富的钒钛矿资源,经过冶金科技工作者多年的努力,创造出高炉治炼磁铁矿新技术,使得高钛型钒钛矿冶炼成为可能。然而由此产生了大量含ＴｉＯ２的高炉钛渣。目前,还没有找到较好的途径来处理这些钛渣,其直接堆放在露天中,占据了大量的土...     

Submicrometer Transparent Alumina by Sinter Forging Seeded γ-Al2O3 Powders

Seeding boehmite with α-Al₂O₂, followed by calcination at 600°C, results in an agglomerated alumina powder (<53 μm) that can be sinter forged to full density at 1250°C. Compressive strains as high as ɛ_x=−0.9, and radial flow (ɛ_x= 1.0) during sinter forging remove large, interagglomerate pores. The fully dense alumina has a grain size of 0.4 pm and is visually transparent. It is proposed that deformation of dense agglomerates is the primary mecha- nism responsible for large pore elimination and compact densification. The sinter forging of sol-gel-derived alumina powders offers a new technology to prepare highly transparent, optical ceramics at lower temperatures than conventional routes.     

Implementing statistical modeling approach towards development of ultrafine grained bioceramics: Case of ZrO2‐toughened Al2O3

The application of statistical modeling approach with the predictive capability of sinter density and grain size is perceived as a central theme in the development of next generation ceramics. Such computationally intensive method can be equally significant, if the predicted process conditions can be adapted experimentally to develop complex shaped ceramics with variable sizes. In the first ever attempt to address such issues for the ceramics, we have, in the present work, considered a range of factors and levels from relevant process variables (sintering temperature, sintering time) and material variables (sinter‐aid addition and reinforcement content) as input parameters to formulate data‐driven, high throughput analytical assays by response surface method (RSM). Using ZrO₂ toughened Al₂O₃ (ZTA) as a model system, the adopted RSM approach has been used to quantitatively predict independent and interactive role of process and material variables on sinter density and grain size.     

铁对R_2O-CaO-gO-Al_2O_3-SiO_2系玻璃微晶化的影响

就石材锯切粉在微晶玻璃中应用的主要问题—铁对析晶的影响展开研究。结果表明,少量铁(＜2mol%)的引入,可能引起析晶参数的升高,但外加铁含量超过2mol%时均可降低析晶参数,并使起始析晶至析晶峰的温度区间(Tp-Tg)变窄；外加铁量＜2mol%时,不同含铁量配方的(Tp-Tg)区间重叠显著,可以采用同一温度晶化处理；配方含铁与否对主晶相没有明显影响,但影响玻璃的析晶能力,铁含量＜2mol%时,使玻璃体析晶能力增加,接近或大于3mol%时,玻璃析晶能力降低；微粉制备微晶玻璃可以大幅度缩短晶化时间。     

铁对R2O-CaO-MgO-Al2O3-SiO2系玻璃微晶化的影响

就石材锯切粉在微晶玻璃中应用的主要问题-铁对析晶的影响展开研究。结果表明，少量铁（〈2mol％）的引入，可能引起析晶参数的升高，但外加铁含量超过2mol％时均可降低析晶参数，并使起始析晶至析晶峰的温度区间（Tp-Tg）变窄；外加铁量〈2mol％时，不同含铁量配方的（Tp—Tg）区间重叠显著，可以采用同一温度晶化处理；配方含铁与否对主晶相没有明显影响，但影响玻璃的析晶能力，铁含量〈2mol％时，使玻璃体析晶能力增加，接近或大于3mol％时，玻璃析晶能力降低；微粉制备微晶玻璃可以大幅度缩短晶化时间。     

Periodic Accumulation of Voids Observed in Calcium Phosphate Glass-Ceramics

After the crystallization of calcium phosphate glass, a pattern of stripes like the rings of a tree is observed in the glass-ceramic. The pattern of stripes, formed only from a particular glass composition and under specific crystallization conditions, is made up of voids resulting from a difference in density between the original glass and the resulting glass-ceramic. The size and distribution pattern of these voids must be controlled to achieve maximum mechanical properties.     

Al2O3含量对PbO-CaO-B2O3-SiO2系玻璃析晶行为与烧结性能的影响

PbO-CaO-B₂O₃-SiO₂系玻璃粉体是耐高过载低温共烧陶瓷(LTCC)生瓷带的主要组成部分。玻璃粉体的析晶行为影响烧结性能,进而决定基板的使用性能。本文研究了Al₂O₃含量对PbO-CaO-B₂O₃-SiO₂系玻璃析晶行为与烧结性能的影响。结果表明:向PbO-CaO-B₂O₃-SiO₂系玻璃中引入Al₂O₃可抑制玻璃析晶,防止高膨胀晶相的析出,并提高玻璃烧结密度;不含Al₂O₃的PbO-CaO-B₂O₃-SiO₂玻璃粉体析晶峰温度为862 ℃,烧结过程中析出方石英晶相,20~200 ℃的平均线膨胀系数高达260.8×10^-7 ℃^-1;引入2.1%(质量分数)Al₂O₃可显著抑制玻璃析晶,700 ℃烧结后膨胀系数降低至72.9×10^-7 ℃^-1,介电常数显著增大,由6.30提高至7.02。     

Immobilization of hospital waste incineration ashes in glass-ceramic composites

In the paper process of sintering of hospital incineration ash as a counterpart of low-level active waste with borosilicate glass frit is presented. It is shown that low porosity glass-ceramic waste-form can be obtained at a temperature range of 850–900 °C. In the sinter, the main crystal phases are wollastonite and aegirine-augite pyroxenes which have a large isomorphous capacity of binding hazardous elements. The crystal phases are fully encapsulated by the glass that provides additional protection against environmental influence. Thus, multibarrier material can be obtained at a temperature considerably lower than vitrification. This, in turn, can improve the economics of immobilization process.     

光致变色烧结膜玻璃的开发及性能测试

引入卤化银作为玻璃光敏剂涂刷在普通平板玻璃表面,烧结后在玻璃表面形成一层光致变色烧结膜。对引入各类卤化银感光成分的烧结膜玻璃及其在500 ℃热处理1 h前后的透光率进行检测,结合光致变色机理及测试数据分析,研究了光致变色烧结膜玻璃的开发前景和发展方向。光致变色烧结膜玻璃能够彻底弥补现有光致变色玻璃昂贵、贴膜不牢、容易刮伤剥落、易疲劳、寿命短的缺陷,在建筑、车用等光致变色玻璃领域有着广泛的应用前景。     

Disordering of crystalline PEEK upon mechanical treatment

It has been established that crystalline PEEK can become completely amorphous upon rolling at room temperature. This effect was verified by data of differential scanning calorimetry. X-ray diffraction and density measurements. In contrast to quenched amorphous PEEK samples, cold crystallization in rolled amorphous samples is shifted to lower temperatures and starts just with the onset of the glass transition. This shift, along with the decrease in the heat of cold crystallization from 21 J/g (for quenched amorphous sample) to 11 J/g, suggest some retention of paracrystalline structure in rolled amorphous samples.