Effects of sintering atmosphere on the physical and mechanical properties of modified BOF slag glass

This study proposes an efficient way to utilize all the chemical components of the basic oxygen fttrnace （BOF） slag to prepare high value-added glass-ceramics. A molten modified BOF slag was converted from the melting BOF slag by reducing it and separating out iron component in it, and the modified BOF slag was then quenched in water to form glasses with different basicities. The glasses were subsequently sintered in the temperature range of 600-1000℃ in air or nitrogen atmosphere for 1 h. The effects of different atmospheres on the physical and mechanical properties of sintered samples were studied by using differential scanning calorimetry （DSC）, X-ray diffraction （XRD） and scanning electron microscopy （SEM） and by conducting experiment on evaluating the sintering shrinkage, water absorption and bulk density. It is found that the kinetics of the sintering process is significantly affected by sintering atmosphere. In particular, compared with sintering in air atmosphere, sintering in N2 atmosphere promotes the synergistic growth of pyroxene and melilite crystalline phases, which can contribute to better mechanical properties and denser microstructure.

Effect of sintering temperature on the microstructure and properties of foamed glass-ceramics prepared from high-titanium blast furnace slag and waste glass

Foamed glass-ceramics were prepared via a single-step sintering method using high-titanium blast furnace slag and waste glass as the main raw materials The influence of sintering temperature(900–1060℃) on the microstructure and properties of foamed glass-ceramics was studied. The results show that the crystal shape changed from grainy to rod-shaped and finally turned to multiple shapes as the sintering temperature was increased from 900 to 1060℃. With increasing sintering temperature, the average pore size of the foamed glass-ceramics increased and subsequently decreased. By contrast, the compressive strength and the bulk density decreased and subsequently increased. An excessively high temperature, however, induced the coalescence of pores and decreased the compressive strength. The optimal properties, including the highest compressive strength(16.64 MPa) among the investigated samples and a relatively low bulk density(0.83 g/cm^3), were attained in the case of the foamed glass-ceramics sintered at 1000℃.

Preparation of CaO-Al_2O_3-SiO_2 system glass from molten blast furnace slag

To use the potential heat of molten blast furnace slag completely, a CaO-Al2O3-SiO2 system glass （MSG） was prepared from the molten industrial slag. The corresponding method proposed in this study utilized both slag and its potential heat, improving the production rate and avoiding the environmental pollution. Using appropriate techniques, an MSG with uniform color and superior performances was produced. Based on the experimental results and phase diagram, the chemical composition of MSG by mass is obtained as follows：CaO 27%-33%, SiO2 42%-51%, Al2O3 11%-14%, MgO 6%-8%, and Na2O＋K2O 1%-4%. Thermodynamic processes of MSG preparation were analyzed, and the phases and microstructures of MSG were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that alkali metal oxides serve as the fluxes, calcium oxide serves as the stabilizer, and alumina reinforces the Si-O network. XRD and SEM analyses show that, the prepared MSG displays the glass-feature patterns, the melting process is more complete, and the melt viscosity is lowered with an increase in calcium oxide content;however, a continuous increase in slag content induces the crystalli-zation of glass, leading to the formation of glass subphase. The optimum content of molten slag in MSG is 67.37wt%. With respect to bend-ing strength and acid/alkali resistance, the performance of MSG is better than that of ordinary marble.

Development of Glass Ceramics Made From Ferrous Tailings and Slag in China

A great amount of ferrous tailings and slag cause severe damage to the ecological environment, which must be reclaimed and utilized. The composition, type, and characteristics of ferrous tailings and slag in China were introduced. The research status and the application outlook of glass ceramics made from ferrous tailings and slag were discussed. Glass ceramics made from ferrous tailings and slag can be applied to various fields, and it will be environmentally conscious materials in the 21st century.

A novel process of preparing glass-ceramics directly from molten steel slag

A novel process technology to prepare glass-ceramics directly from molten steel slag （MSS） is proposed in the study. The liquid-solid mixing method was used to adjust the components of the MSS and glass-ceramics was obtained. The effects of heat-treatment conditions on the microstructure ,physical and mechanical properties of samples were studied. Economical benefits of the novel process were analyzed. The results show that heat-treatment is a very effective approach to achieving crystallization. The dominant crystal phase in products is diopside [ （ Mg6Al2Fe2 ） Ca （ Si1.5 Al5 ） O2 ]. The shape of the crystallization is like a granule. The glass-ceramic samples exhibited good mechanical properties and presented chemical stability. The economic benefits of the process are remarkable due to less energy consumption compared with conventional glass-ceramics production methods.

Crystallization characteristics of iron-rich glass ceramics prepared from nickel slag and blast furnace slag

The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag（NS） and blast furnace slag（BFS） with a small amount of quartz sand was investigated.A modified melting method which was more energy-saving than the traditional methods was used to control the crystallization process.The results show that the iron-rich system has much lower melting temperature,glass transition temperature（Tg）,and glass crystallization temperature（Tc）,which can result in a further energy-saving process.The results also show that the system has a quick but controllable crystallization process with its peak crystallization temperature at 918°C.The crystallization of augite crystals begins from the edge of the sample and invades into the whole sample.The crystallization process can be completed in a few minutes.A distinct boundary between the crystallized part and the non-crystallized part exists during the process.In the non-crystallized part showing a black colour,some sphere-shaped augite crystals already exist in the glass matrix before samples are heated to Tc.In the crystallized part showing a khaki colour,a compact structure is formed by augite crystals.

Influence of aluminium nitride as a foaming agent on the preparation of foam glass-ceramics from high-titanium blast furnace slag

To effectively reuse high-titanium blast furnace slag （TS）, foam glass-ceramics were successfully prepared by powder sintering at 1000℃. TS and waste glass were used as the main raw materials, aluminium nitride （AIN） as the foaming agent, and borax as the fluxing agent. The influence of the amount of A1N added （lwt%-5wt%） on the crystalline phases, microstructure, and properties of the produced foam glass-ceramics was studied. The results showed that the main crystal phases were perovskite, diopside, and augite. With increasing A1N content, a transformation from diopside to augite occurred and the crystallinity of the pyroxene phases slightly decreased. Initially, the aver- age pore size and porosity of the foam glass-ceramics increased and subsequently decreased; similarly, their bulk density and compressive strength decreased and subsequently increased. The optimal properties were obtained when the foam glass-ceramics were prepared by adding 4wt% AIN.

Corrosion mechanism of magnesia-chromite refractories by ZnO-containing fayalite slags: Effect of funnel glass addition

An efficient approach for lead extraction from waste funnel glass through the lead smelting process has been proposed. To clarify the effect of funnel glass addition on the degradation of magnesia-chromite refractories by ZnO-containing fayalite slag, the corrosion behavior of magnesia-chromite refractories in lead smelting slags with different funnel glass additions from 0wt% to 40wt% was tested. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) was used to acquire the microstructural information of the worn refractory samples. Experimental results showed that the corrosion of magnesia-chromite refractory consisted predominantly of the dissolution of MgO into slag. ZnO and FeO reacted with periclase and chromite to form (Zn,Fe,Mg)O solid solution and (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel, respectively. With the addition of funnel glass, the solubility of MgO increased whereas ZnO levels remained stable, thereby resulting in a reduced Mg content and an elevated Zn and Fe content in the (Zn,Fe,Mg)O solid solution and the (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel. Considering the stability of the (Zn,Fe,Mg)O solid solution layer and the penetration depth of the slag, the optimal funnel glass addition for lead smelting was found to be 20wt%.

Experimental study on glass-ceramics preparation from hot steel slag

When liquid steel slag produced from steelmaking process was treated into the post-cold slag by conventional methods,the great deal of slag heat was dissipated into the environment,causing a lot of energy waste and environmental pollution.In this study,a novel approach of direct utilization of hot steel slag as a raw material and slag heat for the production of glass-ceramics was proposed and experimentally tested.In order to simulate liquid slag from steelmaking electric furnace,40%water-quenched slag was remelted at 1 450℃and then mixed with 60%melting additives(silica powder,alumina powder and sodium oxide, etc.)and subsequently melted together at 1 500℃for 1 h into modified liquid slag which was cast,heat-treated, annealed and transformed into glass-ceramics.The heat-treated glass samples were investigated using differential thermal analysis(DTA),X-ray diffraction(XRD),and scanning electron microscopy(SEM). The results show that dominant crystalline phase is diopside[CaFe(SiO_3)_2]and the shape of the crystal is like the granule,diameter is about 0.2 -0.6μm.A glass-ceramic with nucleation temperature of 695℃for two hours and crystallization temperature of 893℃for one hour and 1 163℃for half-hour exhibited the best combination of properties.This method of slag mixed with melting additives to adjust the composition of the parent glass is important for the industrial production of glass-ceramics by direct utilization of hot steel slag.

Influence of CeO_2 addition on the preparation of foamed glass-ceramics from high-titanium blast furnace slag

Foamed glass-ceramics doped with cerium oxide（CeO_2）were successfully prepared from high-titanium blast furnace slag by one-step sintering.The influence of CeO_2 addition（1.5wt%–3.5wt%）on the crystalline phases,microstructure,and properties of foamed glass-ceramics was studied.Results show that CeO_2 improves the stability of the glass phase and changes the two-dimensional crystallization mechanism into three-dimensional one.XRD analysis indicates the presence of Ca（Mg,Fe）Si_2O_6 and Ca（Ti,Mg,Al）（Si,Al）_2O_（6 ）in all sintered samples.Added with CeO_2,Ti CeO_4 precipitates,and crystallinity increases,leading to increased thickness of pore walls and uniform pores.The comprehensive properties of foamed glass-ceramics are better than that of samples without CeO_2.In particular,the sample added with a suitable amount of CeO_2（2.5wt%）exhibits bulk density that is similar to and compressive strength（14.9 MPa）that is more than twice of foamed glass-ceramics without CeO_2.

Volume and Surface Nucleation of Crystals in Glass Based on Blast-Furnace Slag

Using differential thermal analysis, X-ray phase analysis, electron microscopy, and optical microscopy, the nucleation of crystals in glass obtained by blending metallurgical slag with silicon dioxide has been studied. The type of crystallization (homogeneous or heterogeneous, volume or surface) is revealed for each of nine compositions of synthesized glass. It is shown that the first crystalline phase in a volume crystallizing glass is perovskite (CaO·TiO2);in this phase a nucleation of the main phase occurs: melilite (solid solution of gehlenite 2CaO·Al2O3·SiO2 in akermanite 2CaO·MgO·2SiO2). The fundamental characteristics of homogeneous (for a catalizing phase, perovskite) and heterogeneous (for a catalyzed phase, melilite) of crystallization are determined: the steady state nucleation rate Ist, time of unsteady state nucleation τ, crystal growth rate U, and activation energy of frictional flow. The temperature dependences of Ist, τ, and U are obtained. The kinetics of the crystallization of glass is studied and the rates of the surface crystal growth are determined in the glass of nine compositions. The influence of grinding the particles of the original glass on the sequence of deposition of the crystalline phases was studied. Practical recommendations are presented for the use of blast-furnace slag as a raw material for the synthesis of glass and their further utilization.

响应曲面法优化二次镍渣微晶玻璃热处理制度

镍渣作为有色冶炼过程产生的冶金废渣,以堆存形式处理,环境影响突出,但含铁量高,是一种极具开发前景的二次利用资源。以二次镍渣为原料制备微晶玻璃,采用响应曲面法并结合Box-Behnke原理设计探讨了核化温度、核化时间、晶化温度、晶化时间及其交互作用对微晶玻璃抗折性能的影响,建立了抗折强度与各因子间的模型。通过模拟优化,确定了最佳热处理工艺参数:核化温度和晶化温度分别为845℃和955℃、核化时间和晶化时间均为80 min。采用最优工艺参数试验验证发现,微晶玻璃主晶相为铁硅灰石和钙长石,抗折强度均值达到126.78 MPa,与模型预测值偏差较小,表明该预测模型可靠有效及工艺优化合理可行。

利用不锈钢渣制备微晶玻璃的研究进展

工业的快速发展导致固体废弃物逐年增加,由其带来的环境与资源问题不容忽视。利用工业固体废弃物制备微晶玻璃材料是固废资源化利用的重要途径之一,同时,该方法还可实现有害重金属元素的固化,减少环境危害。本文基于不锈钢渣的来源与特性,对比分析了不锈钢渣无害化处理的常见方法。针对不锈钢渣的无害化处理和资源化利用问题,重点综述了利用不锈钢渣制备微晶玻璃过程中主要成分对材料结构与性能的影响;另外,基于微晶玻璃对重金属元素的固化研究现状,重点讨论了微晶玻璃对不锈钢渣中Cr、Ni、Mn重金属元素的固化;最后对不锈钢渣无害化处理与资源化利用的未来研究方向进行了展望。

煤气化细灰熔渣制备泡沫微晶玻璃

由于缺乏成熟的大规模工业化处置技术,大量堆存的煤气化细灰造成严重的环境污染和资源浪费。流化熔融处置煤气化细灰可实现碳灰分离和灰分的改性提质,使灰分转变为富硅铝元素的玻璃相熔渣;泡沫微晶玻璃由于其特殊的玻晶交织结构使其具有良好的机械性能和保温隔热性能,确立了熔渣制备泡沫微晶玻璃的高值化利用思路。以煤气化细灰熔渣为原料,采用无机凝胶铸造工艺制备泡沫微晶玻璃,研究了主要工艺参数预固化时间和烧结温度对泡沫微晶玻璃析晶特性、孔结构和抗压强度的影响。结果表明:泡沫微晶玻璃析晶特性和孔结构与烧结温度、预固化时间均呈现相关性。较高的烧结温度可促进烧结过程中晶相析出进而强化泡沫微晶玻璃的抗压强度。预固化时间影响泡沫玻璃胚体的网络结构,导致晶相析出时克服的阻力不同,从而影响晶相种类。预固化时间30 min时,泡沫玻璃胚体在烧结析晶过程中易发生大孔径孔隙坍塌。抗压强度随孔隙率的增大而减小,随孔径增加呈非线性减小。预固化时间为90 min时,可获得良好的孔隙结构。抗压强度受到析晶特性和孔隙结构特性的共同作用。烧结温度900℃时可强化抗压强度,尤其是预固化时间90 min时,泡沫微晶玻璃的抗压强度为3.77 MPa;而700和800℃时,抗压强度是否增大与预固化时间相关。预固化时间60 min、烧结温度900℃时,析出大量晶体,孔隙率为66.20%且孔径均匀分布,抗压强度为1.40 MPa。

废玻璃粉和矿渣对混凝土力学及抗硫酸盐侵蚀性能的影响

固定废玻璃粉和矿渣的总掺量为30%,研究了废玻璃粉和矿渣的复掺比例对混凝土力学及抗硫酸盐侵蚀性能的影响,其中,废玻璃粉掺量分别为0、5%、10%、15%、20%、25%、30%。结果表明:随着废玻璃粉掺量的增加,试件的抗压强度先增大后减小,总孔隙率先减小后增大,最佳废玻璃粉掺量为10%;随着干湿循环次数的增加或侵蚀溶液浓度的增大,试件表面出现了不同程度的粉化、起砂等现象,质量变化率和抗压强度耐蚀系数均呈先增大后减小的趋势,且随着废玻璃粉掺量的增加,质量变化率的峰值先减小后增大,抗压强度耐蚀系数的峰值先增大后减小;适量废玻璃粉与矿渣在混凝土中有效发挥了颗粒效应、水化效应、交互活性效应等,从而在一定程度上改善了混凝土的力学及抗硫酸盐侵蚀性能。

水玻璃种类对聚合物改性碱激发矿渣性能的影响

从水化过程、力学性能、收缩性能等方面系统研究了2种水玻璃对苯丙乳液(SA乳液)改性碱激发矿渣(AAS)性能的影响及其作用机理,以期指导SA乳液在AAS中的应用.结果表明:钾水玻璃(PWG)加速矿渣水化进程的能力强于钠水玻璃(SWG);SA乳液不影响AAS的水化进程,不会阻碍水化硅酸钙/水化硅铝酸钙的生成,但会抑制水滑石的生成;SA乳液显著降低了AAS的抗压强度,并且对PWG激发AAS的影响强于SWG激发AAS;AAS的抗折强度随着SA乳液掺量的增加呈先增大后减小的趋势,在SWG与PWG激发AAS中,SA乳液的最佳掺量分别为2.5%与5.0%;PWG激发AAS在14d内的总变形量高于SWG激发AAS,SA乳液可显著降低硬化浆体的总收缩量.

一种再生复合相变材料泡沫玻璃的制备与性能测试

为减少建筑材料能耗,试验通过固废物水淬渣和陶瓷废料,结合氧化铝和硼砂,制备一种泡沫玻璃材料,并研究其强度和保温性能。结果表明,该泡沫玻璃材料的最佳配方为:在900℃发泡温度条件下,水淬渣、陶瓷废料和纯碱份数比例固定为40∶60∶10,氧化铝和硼砂添加量分别是4%、8%。此时,制备的泡沫玻璃材料抗压强度为9.38 MPa,导热系数为0.411 W/(m·K),均符合建筑保温材料要求。综上,试验中的泡沫玻璃材料有着良好的强度和保温性能,是一种绿色环保的建筑节能材料,可以适用于建筑外墙等。

海水环境下GFRP筋与低碱混凝土界面黏结性能研究

针对GFRP筋在低碱耐腐蚀水泥基体环境下界面黏结性能的时变规律进行研究,采用中心拉拔试验方法测定了GFRP筋-矿渣硫铝酸盐水泥(G·SAC)混凝土、GFRP筋-硅酸盐水泥(OPC)混凝土在淡水和人工海水环境下养护30 d、90 d和180 d的界面黏结强度,并利用扫描电子显微镜(SEM)及pH计分析了孔溶液浸泡后GFRP筋微观结构的劣化过程及水泥基体孔溶液pH值的变化规律。结果表明:在淡水环境下,GFRP筋-G·SAC混凝土界面黏结强度随养护时间的增加而提高,但GFRP筋-OPC混凝土的黏结强度逐渐降低;在海水环境下,G·SAC基体碱度进一步降低,且海水对其强度发展有促进作用,GFRP筋-G·SAC混凝土在海水中的黏结强度较淡水增长较快。

Influence of Crucible Material on the Microstructure and Properties of Iron Rich Glass-Ceramics

Slag glass melting is usually performed on a laboratory scale in crucibles, which are economically viable tools for the production of slag glass-ceramics. In this work, quaternary CaO-Al2O3-MgO-SiO2（CAMS） glass-ceramics were prepared by melting the tailing of Bayan Obo mine tailing, blast furnace slag, and fly ash in alumina and graphite crucibles. The effect of the crucible material on the microstructure and properties of the glass-ceramics was investigated using differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and inductively coupled plasma atomic emission spectroscopy. Results indicated that the contents of Al2O3 and Fe2O3 in the initial glass were significantly changed by the corrosion of the alumina crucibles during the glass melting process and by the reducing action of the graphite crucibles. The main crystal phases of glass-ceramics melted in alumina crucibles and graphite crucibles were Ca（Mg, Fe, Al）（Si, Al）2O6, coesite and Ca（Mg, Al）（Si, Al）2O6, respectively. According to these findings, we conclude that the microstructure and properties of the glass-ceramics are affected by the crucibles.

碱激发铜渣-粉煤灰复合胶凝材料的力学性能及水化机理研究

旨在探讨利用碱激发剂制备铜渣-粉煤灰复合胶凝材料的可行性及其性能表现。选择铜渣和粉煤灰作为主要原料,通过实验确定其最佳配比和激发剂种类及浓度,发现以7.5%的水玻璃为激发剂时,材料的力学性能最佳。过量的碱激发剂会导致返碱现象、增加与模具的粘合度及拆模困难,甚至降低成品强度,因此在生产过程中需严格控制激发剂的掺量。通过实验分析不同变量对材料性能的影响,包括原材料细度、激发剂浓度、养护条件等,确定了优化的制备工艺。实验结果表明,优化后的复合材料在28 d内的强度可达71 MPa,显著优于普通硅酸盐水泥。在早期强度发展迅速的同时,后期强度虽然增长缓慢,但整体性能依然优越。这种表现为其在实际工程应用中提供了理论依据和实践支持。结合微观结构分析和实际应用研究,揭示了硅铝酸盐凝胶的形成机制,进一步优化了配方和工艺。研究结果证明,该材料具有显著的环保效益和经济潜力。其广泛的应用前景不仅可以部分替代传统水泥,还能实现工业废弃物的高效资源化利用,推动建筑行业的可持续发展。通过不断优化技术和降低成本,碱激发铜渣-粉煤灰复合胶凝材料将在绿色建筑和环保材料领域发挥更大的作用。