Preparation of glass-ceramics with low density and high strength using blast furnace slag,glass fiber and water glass

To reduce the production costs of glass-ceramics and broaden the application field of solid waste in steel industry, low-density and high-strength glass-ceramics were produced by using blast furnace slag as the basic material, choosing glass fiber and water glass as the strengthening agents. The effects of glass fiber and water glass on the phase composition, microstructure, apparent density, water absorption and compressive strength of glass–ceramics were investigated. The results show that the rod structure of glass fiber can be retained in the sintered samples and high content of diopside and augite significantly improve the compressive strength of glass-ceramics. Tiny spherical crystalline phases can be obtained for the glass-ceramics soaked in the moderate concentration of water glass. The BGW-2 samples fabricated with 70% blast furnace slag, 30% glass fiber and 4% water glass, exhibit excellent comprehensive properties. The bulk density, water absorption and compressive strength of BGW-2 are 1.76 g/cm³, 2.26% and 68 MPa, respectively. Consequently, using blast furnace slag to prepare glass-ceramics can be another applicable way to utilize blast furnace slag efficiently.     

热处理温度对磷渣-煤矸石微晶玻璃结构和性能的影响

以磷渣和煤矸石为原料,采用一步烧结法制备了性能优良的CaO?Al2O3?SiO2(CAS)系微晶玻璃,用差示扫描量热法(DSC),X射线衍射(XRD)和扫描电子显微镜(SEM)等对其进行分析和表征,研究了热处理温度对微晶玻璃晶相组成、微观结构和宏观性能的影响规律。结果表明,固废利用率达100%,微晶玻璃性能良好;以磷渣和煤矸石为原料在1250℃下熔融2 h、于850℃热处理保温2 h可制备主晶相为假硅灰石Ca3(Si3O9)的微晶玻璃,其抗折强度、显微硬度和体积密度分别为74.4 MPa,566.9 HV和2.75 g/cm3。随热处理温度升高,微晶玻璃主晶相由Ca3(Si3O9)相转变为硅灰石CaSiO3相,晶体形态由球状向针状、短柱状改变,对提高微晶玻璃抗折性能有利,而显微硬度和体积密度均先增加后降低。     

Preparation of glass-ceramics with diopside as the main crystalline phase from low and medium titanium-bearing blast furnace slag

Because of the low content of TiO₂, the utilization of low and medium Ti-bearing blast furnace slag is a difficult problem. In this study, glass-ceramics with diopside as the main crystalline phase was made by using TiO₂ in the blast furnace slag as the nucleating agent and adding additional elements of TiO₂, Fe₂O₃ and Cr₂O_3. The effects of these three nucleating agents on the phase composition and structural properties of the prepared glass-ceramics were evaluated by DSC, XRD, and SEM to determine their optimal dosage. Research results show that the suitable mass percentages of the TiO₂, Fe₂O₃ and Cr₂O₃ crystal nucleation agents of the glass-ceramics are 7.69%, 0.96%, and 2.88%, respectively. The prepared glass-ceramics have excellent physical and chemical properties, e.g., a bending strength of 114.74 MPa, a bulk density of 2.77 g/cm³, a water absorption rate of 0, and a mass-loss rate of only 0.085%.     

Cr2 O3、TiO2对高炉渣制备微晶玻璃晶化方式的影响

以包钢高炉渣为主要原料,采用熔融法制备CaO-SiO2-MgO-Al2O3系微晶玻璃,主要通过差热分析方法,并借助于Augis-Bennett方程和Ozawa方程研究了分别添加2%Cr2O3和8%TiO2作晶核剂时基础玻璃的晶化方式.研究结果表明:添加2%Cr2O3作晶核剂时,晶体生长指数均可实现大于3,晶化方式为整体晶化;而添加8%TiO2作晶核剂时,晶体生长指数均不可能大于3,晶化方式为表面晶化.因此,Cr2O3是高炉渣制备透辉石类微晶玻璃适宜的晶核剂成分,可单独用作晶核剂,而TiO2无法使基础玻璃整体晶化,不能单独用作晶核剂.研究结果为利用高炉渣成功研制开发透辉石类微晶玻璃在晶核剂种类选择确定方面提供了理论指导.     

Sinterability,microstructure and compressive strength of porous glass-ceramics from metallurgical silicon slag and waste glass

Porous glass-ceramics have been prepared by the direct sintering of powder mixtures of metallurgical silicon slag and waste glass. The thermal behavior of silicon slag was examined by differential thermal analysis and thermogravimetry to clarify the foaming mechanism of porous glass-ceramics. The mass loss of silicon slag below 700 °C was attributed to the oxidation of amorphous carbon from residual metallurgical coke in the silicon slag, and the mass gain above 800 °C to the passive oxidation of silicon carbide. The porosity of sintered glass-ceramics was characterized in terms of the apparent density and pore size. By simply adjusting the content of waste glass and sintering parameters (i.e. temperature, time and heating rate), the apparent density changed from 0.4 g/cm³ to 0.5 g/cm³, and the pore size from 0.7 mm to 1.4 mm. In addition to the existing crystalline phases in the silicon slag, the gehlenite phase appeared in the sintered glass-ceramics. The compressive strength of porous glass-ceramics firstly increased and then decreased with the sintering temperature, reaching a maximal value of 1.8 MPa at 750 °C. The mechanical strength was primarily influenced by the crystallinity of glass-ceramics and the interfaces between the crystalline phases and the glassy matrix. These sintered porous glass-ceramics exhibit superior properties such as light-weight, heat-insulation and sound-absorption, and could found their potential applications in the construction decoration.     

以高炉渣废玻璃为原料一次烧结法制备微晶玻璃

研究了以高炉渣、废玻璃粉为主要原料,以TiO2为成核剂,采用一次烧结法制备微晶玻璃。该材料以透辉石为主晶相,配料中高炉渣质量分数可达55%。这为高炉渣的综合利用开辟了一个新的途径,具有明显的环境效益、经济效益和社会效益。     

利用工业固体废弃物制备微晶泡沫玻璃的研究现状及展望

工业固体废弃物在一定程度上属于可以重新利用的资源,其综合利用问题一直备受国内外学者关注.分析了利用工业固体废弃物制备微晶泡沫玻璃的可行性.综述了以粉煤灰、煤矸石、废玻璃、高炉渣、尾矿和油页岩渣等工业固体废弃物为原料制备微晶泡沫玻璃的国内外研究进展,以期为相关科学研究工作和工业化生产提供参考和借鉴.总结了目前利用工业固体废弃物制备微晶泡沫玻璃亟待解决的问题.     

SiO2含量对钛矿渣微晶玻璃晶化行为的影响

以钛矿渣为主要原料,采用熔融法制备CaO-MgO-Al₂O₃-SiO₂系微晶玻璃,通过综合热分析仪、X射线衍射仪和扫描电子显微镜分析了SiO₂含量对钛矿渣微晶玻璃的基础玻璃稳定性及晶化行为的影响。结果显示:以原渣制备微晶玻璃时,其基础玻璃结构不稳定,易析出钙钛矿晶体,随着SiO₂含量的增加,基础玻璃趋于稳定,析晶温度上升,热处理后析晶程度更高,显微结构更加致密,因而强度更高。通过加入辅助原料石英粉来调节SiO₂含量,当SiO₂含量为40%(质量分数)时,可以制备出具有稳定玻璃体、晶相仅为透辉石、抗弯强度为82.1 MPa的微晶玻璃,其钛矿渣掺量在80%(质量分数)以上,具有重要的经济与社会效应。     

Synergistic effect of glass fibre and Al powder on the mechanical properties of glass-ceramics

To explore the synergistic effect of glass fibre and Al powder on the mechanical properties of glass-ceramics, blast furnace slag was chosen as the main material, and glass fibre and Al powder as reinforcement materials. The phase compositions, microstructures, compressive properties, and apparent density of the glass-ceramics with varying quantities of glass fibre and Al powder were investigated. The experimental results indicated that Al powder could exist as a simple substance in glass-ceramics and form a dense net coating on the surface of blast furnace slag to improve the plasticity of the glass-ceramic. The glass fibre had better reinforcement effect than Al powder because of its extremely high mechanical strength. The plasticity of glass-ceramics, however, severely decreased; the glass-ceramics exhibited brittle failure during compression. A slight increase in the content of CaSi₂ and SiO₂ in the glass-ceramics was closely related to the addition of glass fibre. Considering safety and economy, glass-ceramics with 6% Al and 14% glass fibre (S4) have the best mechanical properties. The compressive strength, strain at maximum force, and apparent density were 40?MPa, 19% and 1.974?g/cm³, respectively.     

Glass-ceramics produced from thin-film transistor liquid-crystal display waste glass and blast oxygen furnace slag

This study employed waste glass from thin-film transistor liquid-crystal displays (TFT-LCD) and slag from a basic oxygen furnace (BOF) to produce CaO–MgO–Al₂O₃–SiO₂ (CMAS) glass-ceramics through vitrification and further heat treatment of compacts of the obtained glass powders for densification and crystallization. CMAS glass-ceramics are known for their excellent mechanical and dielectric properties. MgO and Al₂O₃ were selected as modifying agents to ensure that the composition of the wastes featured these important characteristics.     

Preparation of TiC ceramics from hot Ti-bearing blast furnace slag: Carbothermal reduction,supergravity separation and spark plasma sintering

TiC ceramics, a kind of ultra-high temperature ceramics, are primarily prepared by the synthesized TiC powders from high purity metallic titanium or titania. In this work, a novel method for sustainable utilization of hot Ti-bearing blast furnace slag to prepare TiC ceramics was developed. Firstly, the Ti was efficiently transformed into the TiC in hot Ti-bearing blast furnace slag through carbothermal reduction. The high-purity TiC powders were fully recovered from molten carbonized Ti-bearing slag through supergravity separation, where the mass fraction and recovery ratio of Ti in TiC powders were up to 77.89 wt.% and 95.58 %. The TiC ceramics with a relative density of 98.23 % were prepared from the recovered TiC powders via spark plasma sintering method, which possess the favourable mechanical properties including Vickers hardness (Hv) of 23.3 ± 0.4 GPa, fracture toughness (K_IC) of 3.96 ± 0.24 MPa m^1/2 and flexural strength of 371.9 ± 15.4 MPa.     

Potential utilization of oil sludge incineration bottom ash for glass-ceramics: Crystallization kinetics,properties and toxicological evaluation

The bottom ash (OIBA) generated from the incineration of hazardous oil sludge is classified as a hazardous waste. In this work, the OIBA was applied as raw material to prepare SiO₂-Al₂O₃-CaO system glass-ceramics by melt-sintering with the addition of waste glass wool (GW). The effects of basicity (CaO/SiO₂ ratio, 0.52-1.05) and sintering temperature (900–1050 °C) on the crystallization kinetics, properties, microstructure, leaching concentrations of heavy metals and potential toxicity of glass-ceramics were investigated. The results showed that the crystallization pattern was two-dimensional crystallization, and with the decrease of basicity, the main crystalline phase evolved from gehlenite to diopside. And the glass-ceramics with basicity of 0.88 and sintering temperature of 950 °C exhibited the best comprehensive properties, including density (2.72 g/cm³), water absorption (0.06%), compressive strength (452.45 MPa) and chemical corrosion resistance. In addition, the reduction of heavy metal leaching concentration indicates that produced glass-ceramics showed excellent solidification effect on heavy metals, the low toxicity of glass-ceramics leaching solution to the wheat seeds and Artemia suggests the environmental protection characteristics of OIBA-based glass-ceramics. These findings proved that the glass-ceramics produced by OIBA and GW could be a promising method to dispose hazardous waste with preparing high value-added construction materials.     

熔融态黄磷炉渣的综合利用现状

电炉法制备黄磷产生的工业固体废物——黄磷炉渣,属于化工废渣。黄磷熔融炉渣,根据冷却方式的不同,可分为水淬渣和自然冷却黄磷炉渣,我国主要是水淬渣。本文综述了黄磷炉渣用于微晶玻璃、水泥工业、硅钙肥、路基材料、陶瓷材料、白炭黑、玻璃材料、砖、稀土元素等领域,同时对熔融态黄磷炉渣出炉时温度高达1200～1300 ℃的热量充分利用进行了探讨,直接用来制造建筑装饰用微晶玻璃,达到保护环境和黄磷行业清洁生产的目的。     

Effect of ZnO content on the physical,mechanical and chemical properties of glass-ceramics in the CaO–SiO2–Al2O3 system

The objective of this study was to evaluate the effect of ZnO content on the physical, mechanical and chemical properties of CaO–Al₂O₃–SiO₂ (CAS) glass-ceramics produced from Colombian wastes, such as fly ash, granulated blast furnace slag and glass cullet. The CaO/SiO₂ molar ratio of the mixtures was held constant (0.36). ZnO was added to the mixtures in proportions of 4, 7 and 10 wt%. The glass-ceramics were produced by the controlled crystallization of a parent glass. The values of crystallization temperature (T_p) show a fall up to 7 wt% and then shoots up with 10 wt% concentration of ZnO, but in general, ZnO addition lowers the temperature required for the formation of crystalline phases. In general, anorthite (CaAl₂Si₂O₈) is the main phase observed in all heat treated samples, in addition to albite (Na(AlSi₃O₈)) and labradorite (Na_0.45 Ca_0.55 Al_1.55 Si_2.45 O₈). The crystalline phases hardystonite (Ca₂ZnSi₂O₇) and willemite (Zn₂SiO₄) were also identified in the samples with 7 and 10 wt% ZnO. The densities of the glass-ceramics were between 2658 and 2848 kg/m³, and it was found that ZnO helps to increase the density of glass-ceramics. The elastic modulus was in the 100–105 GPa range, the fracture toughness was between 0.45 and 0.64 MPa m^1/2, and the Vickers microhardness was between 632 and 653 MPa. With regards to the durability, the weight loss of the glass-ceramics immersed in alkaline solution (NaOH) did not exceed 1.5 wt% after immersion for 6 h at 80 °C. The results of this study confirm that the vitrification process is a favorable option to utilize these industrial wastes.     

核化及晶化温度对微晶玻璃性能的影响

本文以95％炼铁高炉渣和5％钾长石为原料,采用简易的烧结法制备出炉渣微晶玻璃。利用DSC、XRD等分析手段研究了不同核化晶化温度对矿渣微晶玻璃性能的影响。研究表明：不同的核化晶化温度对高炉渣微晶玻璃的性能有较大的影响;最后得出最佳核化温度为760℃、最佳晶化温度为960℃。     

Influence of heat treatment temperature on the properties of the lithium disilicate-fluorcanasite glass-ceramics

This study aims to investigate the influence of heat treatment temperatures on the mechanical properties and chemical solubility (CS) of lithium disilicate-fluorcanasite glass-ceramics and to develop new dental materials. The glasses and glass-ceramics were prepared using CaF₂-SiO₂-CaO-K₂O-Na₂O-Li₂O-Al₂O₃-P₂O₅-based glass system using a conventional melt quenching method followed by a two-stage crystallization process. This two-stage method involves two heating temperature steps: first at a constant temperature (T_S1) of 600°C and second step at varying temperatures (T_S2) of 650, 700, 750, and 800°C. The crystallization behavior, phase formation, microstructure, translucency characteristic, density, hardness, fracture strength, and CS were investigated. It was found that the lithium disilicate crystal acted as the main crystalline phase, and the crystalline phase of fluorcanasite occurred at the heat treatment temperatures of 750 and 800°C. In addition, it was found that density, hardness, fracture strength, and CS increased while the translucency values decreased with increasing heat treatment temperatures. Furthermore, the CS increased dramatically when the fluorcanasite phases occurred in the glass-ceramic samples. The maximum density values, Vickers hardness, fracture toughness, and flexural strength are 2.56 g/cm³, 6.73 GPa, 3.38 MPa.m^1/2, and 259 MPa, respectively. These results may offer a possibility to design a new material for dental applications based on lithium disilicate-fluorcanasite glass-ceramics.     

Controlling the microstructure and properties of lithium disilicate glass-ceramics by adjusting the content of MgO

In order to obtain lithium disilicate glass-ceramics for dental restoration with both high strength and high translucency, lithium disilicate glass-ceramics with different MgO contents were prepared by melt-casting and heat treatment method. The effects of MgO content on the crystallization temperature, microstructure and flexural strength of lithium disilicate glass-ceramics were investigated. The results indicate that Mg²⁺ exists in the form of [MgO₄] in the network of lithium disilicate glass-ceramics when the MgO content is 0.56 mol% (M0.56), which is beneficial to increasing the homogeneity and thermal stability of the glass system, and short rod-like lithium disilicate crystals can be formed after heat treatment at 840°C. Thus, the obtained lithium disilicate glass-ceramics exhibit excellent comprehensive performance, with the flexural strength being 312 ± 23 MPa, and the average transmittance of visible light being 37.3% (d = 1.62 mm). Especially, the glass-ceramic sample shows better translucency than the commercially available products. The research results are of great significance for developing high performance lithium disilicate glass ceramics and promoting its broad application in the field of dental restoration.     

超低膨胀微晶玻璃热处理工艺优化研究

采用熔融法制备了Li₂O-Al₂O₃-SiO₂系透明玻璃,以TiO₂、ZrO₂和P₂O₅为复合晶核剂对该玻璃进行热处理,获得了超低膨胀微晶玻璃。采用正交试验研究了热处理工艺参数对微晶玻璃热膨胀系数的影响,并通过计算分析获得了最优的热处理工艺参数,即核化温度为600 ℃,核化时间为3 h,晶化温度为820 ℃,晶化时间为5 h。在此热处理工艺制度下获得的微晶玻璃主晶相为β-石英固溶体,热膨胀系数为1.6×10^-8 ℃^-1。采用差热分析、X射线衍射分析、扫描电子显微镜分析、透射电子显微镜分析等手段研究了微晶玻璃的析晶情况和微观结构,并进一步分析了热处理工艺与微晶玻璃热膨胀性能和微观结构之间的对应关系。结果表明,微晶玻璃的热膨胀系数由晶相种类和含量决定,微晶玻璃内部晶相的尺寸和含量与热处理工艺密切相关。     

Use of glass waste as an activator in the preparation of alkali-activated slag. Mechanical strength and paste characterisation

The alkaline activation of aluminosilicates yields alkaline cements, eco-efficient alternatives to ordinary Portland cements. Alkaline cements and concretes exhibit highest strength and longest durability when activated with a solution of alkaline silicate hydrates (waterglass). To obtain these alkaline silicates, however, an aqueous solution of the proper proportion of carbonate and silica salts must be heated to temperatures of around 1300 °C. The present paper explores the feasibility of using urban and industrial glass waste as a potential alkaline activator for blast furnace slag (AAS).AAS pastes were prepared with three activators: waterglass, a NaOH/Na₂CO₃ mix and the solutions resulting from dissolving glass waste in NaOH/Na₂CO₃. Mechanical, mineralogical (XRD, FTIR) and microstructural (porosimetry, NMR and SEM/EDX) trials were conducted to characterise the pastes obtained.The findings proved the feasibility of using glass waste to alkali activate slag. Treating glass waste with NaOH/Na₂CO₃ (pH = 13.6) favours the partial dissolution of the Si in the glass into its most reactive monomeric form.The solutions resulting from the treatment of glass waste act as alkaline activators, partially dissolving vitreous blast furnace slag. The composition and microstructure of the reaction products identified in the two types of paste were similar. Strength and microstructural development in the pastes activated with glass waste were also comparable to the parameters observed in AAS pastes prepared with conventional activators.     

ZnO对黄磷炉渣微晶玻璃析晶影响

以黄磷炉渣为主要原料,通过添加不同比例ZnO,采用熔融法制备了CaO-Al2O3-SiO2系微晶玻璃.借助Kissinger方程分析黄磷炉渣基础玻璃的析晶能力,借助化学热力学软件FactSage 6.4模拟计算黄磷炉渣微晶玻璃晶相类型,借助X射线衍射仪(XRD)和扫描电子显微镜(SEM)进行验证.结果表明:随着ZnO添加量的增加,黄磷炉渣基础玻璃的析晶峰温度Tp和析晶活化能E逐渐减小;当ZnO添加量为7wt％时,黄磷炉渣基础玻璃的析晶活化能E最小,析晶能力最强;随着ZnO的加入量的增大,黄磷炉渣微晶玻璃晶相类型并不发生改变,主晶相为硅灰石(CaSiO3),次晶相为铝透辉石(Ca(Mg,Al)(Si,Al)2O6),这与FactSage 6.4模拟计算结果一致.