Reuse of mineral wool waste and recycled glass in ceramic foams

Novel ceramic foams have been prepared by high temperature sintering of waste mineral wool and waste glass using SiC as a foaming agent. The aim of the research was to understand the effects of composition and sintering conditions on the properties and microstructure and produce commercially exploitable ceramic foams. Optimum ceramic foams were formed from 40 wt% mineral wool waste and 2 wt% SiC, sintered at 1170 °C using a heating rate of 20 °C/min with a 20 min hold at peak temperature. The ceramic foams produced had a bulk density of 0.71 g/cm³ and a uniform pore size distribution. The research shows that ceramic foams can be formed from waste mineral wool and these can be used for thermal insulation with associated economic and environmental benefits.     

Performance study of foam ceramics prepared by direct foaming method using red mud and K-feldspar washed waste

In this study, foam ceramics were prepared via a direct foaming method at high temperatures (1080–1120 °C), using red mud (RM) and K-feldspar washed waste (KFW) as the raw materials and SiC as the foaming agent, respectively. The chemical compositions and crystalline phases of the raw materials as well as the structural and mechanical properties of the foam ceramics were investigated. By adjusting the formulation and sintering process parameters, the porous structure of the foam ceramics could be effectively modulated. In addition to some residual crystalline phases in the raw materials, new phases, including rutile (TiO₂) and anorthite (CaAl₂Si₂O₈), were generated in foam ceramics. The compressive strength of the foam ceramics decreased with an increase in the KFW/RM ratio and sintering temperature, which was mainly related to the low density of the foam ceramics and the poor support of the pore walls to the structure. Among all the foam ceramics investigated, the foam ceramic with the KFW/RM ratio of 1:1, SiC content of 1 wt%, sintering temperature of 1100 °C and sintering time of 60 min showed the best overall performance with a bulk density, an apparent porosity, an average pore size and a compressive strength of 0.77 g/cm³, 61.89%, 0.52 mm, and 3.64 MPa, respectively. Its excellent porous structure and mechanical properties rendered it suitable for application as insulation materials or decorative materials for building partition walls.     

Preparation of high–strength closed–pore foamed ceramics from desalted sea sand at temperatures below 1000 °C

Based on high–temperature sintering with SiC as the foaming agent, the technical potential of preparing foamed ceramics (FCs) from desalted sea sand at temperatures below 1000 °C was studied. Rapid melting of the ceramic bodies at elevated temperatures helped to seal more foaming gas, resulting in a large foaming volume for the FCs. If the interior of the ceramic bodies melted quickly during sintering, the foaming gas was trapped in situ, resulting in a homogenous FC pore structure. By coordinating the borax content and sintering temperature of the green bodies, the melting characteristics of the ceramic bodies could be optimised during sintering, usually producing a large foaming volume and a homogeneous FC pore structure. The FCs sintered from the green bodies with 25–35 wt% of borax at 900–1000 °C obtained high total/closed porosities of (68–75)%/(65–72)%, a relatively dense surface, a homogenous pore structure, and a relatively high compressive strength of 8.1–11.2 MPa.     

利用赤泥制备轻质高强保温装饰一体化建筑材料

利用赤泥为主要原料,添加建筑垃圾、抛光砖废料和粘土制备轻质高强保温装饰一体化建筑材料.通过改变赤泥用量、烧结温度、发泡剂添加量等条件,对样品体积密度、孔隙率、抗压强度进行了研究.利用X射线衍射仪(XRD)、扫描电镜(SEM)对样品物相组成和形貌进行表征.研究结果表明:赤泥用量为35%,发泡剂添加量为5%,烧结温度为1100℃时,制备样品的气孔分布均匀,孔径大小较一致,体积密度为0.26 g/cm3,孔隙率为73.28%,闭气孔率达到90.52%,抗压强度为7.83 MPa.     

Preparation and characterization of porous ceramics from nickel smelting slag and metakaolin

Porous ceramics with high porosity and low bulk density were prepared by using nickel slag and metakaolin as the primary raw materials, glass powder as flux, and SiC as the foaming agent. The content of nickel slag and foaming agent had a significant effect on the bulk density, porosity, and flexural strength of the porous ceramics. The porous ceramics with the best properties were obtained at 1100 °C for 30 min with 50 wt% nickel slag, 40 wt% metakaolin, 10 wt% waste glass, and 0.8 wt% SiC. It had a low bulk density (as low as 245 kg/m³), high flexural strength and compressive strength (0.6 MPa and 1.17 MPa, respectively), and high porosity (about 89.8%). The nickel slag was magnetically separated as well. The density of nickel slag powder could be reduced via magnetic separation, and there was no significant change in the crystal structure of the raw material. Compared with porous ceramics prepared using nickel slag without magnetic separation, ceramics subjected to magnetic separation had lower bulk density, higher porosity, and the same phase composition. This study can be used as an indicator for the application of nickel slag in porous ceramics, which is of great significance in providing a great substitute nickel slag towards recovery and utilization.     

黄姜废渣发泡陶瓷的制备及其性能研究

发泡陶瓷作为一种新型建筑墙体材料,具有轻质保温的优良特性,有利于实现建筑节能.以黄姜废渣为主要坯料,掺加适量麻城石粉优化坯料组分,并以SiC为发泡剂,通过混料、压片、烧结等工艺实现了一种新型闭孔发泡陶瓷的制备.主要研究了烧成制度、成型压力、发泡剂掺量、石粉掺量对黄姜废渣发泡陶瓷宏观性能及其微观特征的影响.试验结果表明,...     

Fine grained Al2O3/SiC composite ceramic tool material prepared by two-step microwave sintering

Fine-grained Al₂O₃/SiC composite ceramic tool materials were synthesized by two-step microwave sintering. The effects of first-step sintering temperature (T1), content and particle size of SiC on the microstructure and mechanical properties were studied. It was found that the sample with higher content of SiC was achieved with finer grains, and the incorporation of SiC particles could bridge, branch and deflect the cracks, thus improving the fracture toughness. Higher T1 was required for the densification of the samples with higher content of SiC (>5?wt%). The sample containing 3?wt% SiC particles with the mean particle size of 100?nm, which was sintered at 1600?°C (T1) and 1100?°C (T2) for 5?min had the fine microstructure and optimal properties. Its relative density, grain size, Vickers hardness and fracture toughness obtained were 98.37%, 0.78?±?0.31?μm, 18.40?±?0.24?GPa and 4.97?±?0.30?MPa?m^1/2, respectively. Compared to the sample prepared by single-step microwave sintering, although near full densification can be achieved in both two methods, the grain size was reduced by 36% and the fracture toughness was improved by 28% in two-step microwave sintering.     

工艺参数对石英质多孔材料孔性能的影响

以长江沿岸低品位石英砂为主要原料,采用真空烧结制备了石英质多孔材料。通过实验分析发现:随烧结温度的升高、水料比的增大或发泡剂含量的增加,多孔材料的气孔率增大,抗压强度降低;而随着保温时间的延长,多孔材料的气孔率降低,抗压强度升高。通过优化得出最佳配比为:石英砂60 wt%、高岭土30 wt%、助烧剂9.6 wt%、发泡剂0.4 wt%。按这一最佳配比配料,在水料比为0.9的条件下球磨2 h制浆发泡,而后在1175°C烧结1 h,可以制备得到性能较佳的石英质多孔材料。     

利用黄金尾矿制备发泡陶瓷的研究

中国黄金尾矿资源量大,作为二次资源在建筑材料领域的综合利用有着重要的经济价值和环境意义。以黄金尾矿为主要原料,SiC为发泡剂,通过高温制备发泡陶瓷,用激光共聚焦显微镜、XRD等手段,研究了烧结温度、黄金尾矿掺入量、原料粒度对材料的容重、真气孔率和孔径等性能的影响。研究表明:随着烧结温度的升高,发泡陶瓷材料的真气孔率和孔径增大,容重减小;材料的真气孔率和容重随着黄金尾矿掺入量的增大分别降低和提高,随着原料粒度的减小分别提高和降低,气孔孔径随着黄金尾矿掺量的增大和原料粒度的减小均呈下降趋势。优化后,在烧成温度1 050 ℃,黄金尾矿掺入量50%(质量分数),黄金尾矿平均粒度D(50)=5.6 μm,SiC平均粒度D(50)=3.0 μm的条件下可制备出性能良好的发泡陶瓷。     

Preparation of foamed ceramics from steel slag with high calcium and iron content

In this paper, steel slag foamed ceramics were fabricated by using steel slag, kaolin, feldspar, and quartz as main raw materials, and adding SiC as high-temperature foaming agent. The effects of steel slag content and SiC particle size on porosity and mechanical properties of foamed ceramics were researched. Results indicate that when content of steel slag is 40 wt%, and particle size of SiC is 20 µm, foamed ceramics exhibited optimized properties: water absorption rate of 2.59%, total porosity of 55.91%, bulk density of 1.33 g·cm⁻³, and compressive strength of 1.21 MPa. The results show that with the increase of steel slag content, the phase composition of foamed ceramics changes, and foam process is hindered. The increase of steel slag content contributes to the formation of diopside. Fe³⁺, Fe²⁺ in liquid phase enter into diopside by solid solution, the amount of liquid phase decreases. Liquid phase mass transfer slows down, and content of SiC in liquid phase decreases, so that the porosity decreases. At the same steel slag content, different SiC particle size affects the difference between pressure inside the closed pore and surface pressure, thereby the porosity changes.     

Preparation and characterisation of diopside-based glass–ceramic foams

Foaming and crystallisation behaviours of compacted glass powders based on a diopside glass–ceramic composition were investigated using the sintering route. The foaming agent was 2 wt.% SiC particles. The effect of PbO on the foaming ability of glasses was investigated. The results showed that the addition of PbO not only improved the foaming ability, by improving the wettability of the glass–SiC particles but also increased the crystallisation temperature and widened the temperature interval between the dilatometric softening point and the onset of crystallisation. The glass–SiC wetting angle was decreased from 85° for the lead-free glass, to 55° for the glass that contains 15 wt.% PbO.     

Novel glass ceramic foams materials based on red mud

Glass ceramic foams were prepared using red mud and fly ash with added CaCO₃ as foaming agents. The aim of the present work was to investigate the possibility of adding red mud, an alkaline leaching waste, in the raw material for the preparation of glass ceramic foams. The results of mineralogical analyses as well as the microscopic examination showed that the use of the red mud affect the mineralogical characteristics and structures of the as produced foams. The influence of amount of red mud on the bulk density and compressive strength of samples was further evaluated. The experimental results showed that relatively low bulk density foams (0.33–0.41 g/cm³) could be obtained by using low sintering temperature (760–840 °C) when the red mud/fly ash ratio does not exceed 40:60. The reduction of sintering temperature or, above all, the reduction of the holding time, was found to limit the coalescence and significantly improve the compressive strength of the foams (0.33–2.74 MPa).     

Recycling of extracted titanium slag and gold tailings for preparation of self-glazed ceramic foams

Self-glazed ceramic foams were successfully synthesized via powder sintering method, using extracted titanium slag (ETS) and gold tailings (GT) as raw materials without adding any sintering aids and foaming agents. Influence of ETS addition and sintering temperature on crystal phase evolution, physical–mechanical properties, and micro-morphology of ceramic foams was systematically studied. Results indicated that products sintered at 1180 °C with 30 wt% ETS and 70 wt% GT showed the best performance, i.e., bulk density of 1.66 g cm^?3, flexural strength of 20.4 MPa, water absorption of 0.14%, open porosity of 0.23%, and glaze Vickers hardness of 6.5 GPa. Moreover, it was observed that there existed strong correlation between bulk density and bending strength. Self-glazed ceramic foams developed in this study are expected to be used as building envelope materials and provide new ideas for effective reuse of other similar solid wastes.     

Preparation of castable foam with regular micro-spherical pore structure as a substitute for diatomite brick

To replace the existing diatomite brick used in the field of medium and low temperature (below 1000 °C) thermal insulation and realize the comprehensive utilization of waste resources, a novel foamed insulation material was prepared with waste granite via a direct foaming method. In particular, the proportion of waste granite reached 88 wt%. The optimum parameter for the specimens were obtained at 1050 °C with 8 wt% foam and milling time of waste granite was 7 h. Meanwhile, the experimental results showed that the bulk density was 0.7 g/cm³, the linear shrinkage was 3.71%, the total porosity was 73.59%, the compressive strength was 8.0 MPa, the linear shrinkage of resintering at 900 °C for 8 h was 0.2%, and the thermal conductivity was 0.108 W/(m·K) at 300 °C. The effects of particle size of waste granite, content of foam on the macro and micro properties were systematically investigated, then the MIAPS software was used to obtain the pore structure parameters. Finally, the relationship between the pore structure and properties of specimens under different variables was analyzed based on image method and fractal geometry. The results show the potential use of waste granite as the main raw material to replace the use of natural diatomite brick.     

Foaming performance of the closed–pore foamed ceramics using silicon nitride as a foaming agent and sodium tetraborate as a modifier of foaming

Using silicon nitride as a foaming agent and sodium tetraborate as a modifier of foaming, foamed ceramics (FCs) with porous internal structure and dense surface were prepared by a high temperature foaming method based on the foaming mechanism which is simultaneous occurrence of oxygen diffusion from the air into the molten matrix balanced with the generation of the oxidation–derived nitrogen from silicon nitride at a specific molten matrix viscosity. The foaming performance of the FCs was improved significantly by establishing the conditions for the best synergy between the generation rate of the oxidation–derived nitrogen and the viscosity of the molten matrix during sintering. By synergistically changing the proportion of raw materials and the sintering time at 1150–1250 °C, the FCs demonstrated excellent overall properties with a high closed porosity of 89 %, a low bulk density of 0.32 g/cm³ and a relatively high compressive strength of 6.2 MPa.     

Microstructure and properties of a graphene platelets toughened boron carbide composite ceramic by spark plasma sintering

A kind of B₄C/SiC composite ceramic toughened by graphene platelets and Al was fabricated by spark plasma sintering. The effects of graphene platelets and Al on densification, microstructure and mechanical properties were studied. The sintering temperature was decreased about 125–300?°C with the addition of 3–10?wt% Al. Al can also improve fracture toughness but decrease hardness. The B₄C/SiC composite ceramic with 3?wt%Al and 1.5?wt% graphene platelets sintered at 1825?°C for 5?min had the optimal performances. It was fully densified, and the Vickers hardness and fracture toughness were 30.09?±?0.39?GPa and 5.88?±?0.49?MPa?m^1/2, respectively. The fracture toughness was 25.6% higher than that of the composite without graphene platelets. The toughening mechanism of graphene platelets was also studied. Pulling-out of graphene platelets, crack deflection, bridging and branching contributed to the toughness enhancement of the B₄C-based ceramic.     

以铜尾矿制备发泡陶瓷墙板的研究

以山西某地铜尾矿作为主要原料制备轻质、高强度发泡陶瓷墙板,并采用抗压强度测试仪、XRD测试仪作为主要检测手段,研究铜尾矿加入量、烧成制度以及发泡剂对发泡陶瓷墙板物理性能的影响。研究结果表明:铜尾矿加入量控制在85%左右,SiC微粉0.25%,烧成温度1170℃保温40min,可以试制出适合发泡陶瓷隔墙板性能的产品。通过规模化生产中试,产品密度437.52kg/m^3,抗压强度9.77MPa,产品外观孔径0.5-1.5mm,满足实际应用要求。     

Integrated utilization of high alumina fly ash for synthesis of foam glass ceramic

Due to the numerous increase of the building energy consumption and huge volume of industrial wastes produced in China, the development of thermal insulation materials is quite needed. Herein, foam glass ceramic, a kind of thermal insulation materials, was fabricated by using solid wastes high alumina fly ash and waste glass as the main raw materials. First, in this study the proportion scheme of this research was designed by using Factsage 7.1 and the foaming agent was CaSO₄. Secondly, the decomposition of calcium sulfate and the influence of process parameters, namely the sintering temperature and the foaming agent additive amount, on the microstructure and mechanical properties of foam glass ceramic were investigated. The experimental results showed that when the proposed foam glass ceramic was sintered at between 1180 and 1220?°C, it exerted excellent macro and micro properties. The optimum parameters were 2% CaSO₄ addition and sintering temperature of 1200?°C, and the corresponding bulk density and compress strength values were 0.98?g/cm³ and 9.84?MPa, respectively. Overall these results indicated that the preparation of foam glass ceramic made up a promising strategy for recycling industrial waste into new kind of building insulation materials.     

Low‐Density Open Cellular Silicon Carbide Foams from Sucrose and Silicon Powder

Open cellular SiC foams with low densities were prepared by thermo‐foaming and setting (130°C–150°C) of silicon powder dispersions in molten sucrose followed by pyrolysis and reaction sintering at 1500°C. The bubbles generated in the dispersion by water vapor produced by the –OH condensation was stabilized by the adsorption of silicon particles on the air‐molten sucrose interface. The composition of a sucrose‐silicon powder mixture for producing SiC foam without considerable unreacted carbon was optimized. The sucrose in the thermo‐foamed silicon powder dispersion leaves 24 wt% carbon during the pyrolysis. The sintering additives such as alumina and yttria promoted the silicon‐carbon reaction. SiC nanowires with diameters in the range of 35–55 nm and length >10 μm observed on the cell walls as well as in the fractured strut region were grown by both vapor–liquid–solid and vapor–solid mechanisms. Large SiC foam bodies without crack could be prepared as the total shrinkage during pyrolysis and reaction sintering was only ~30 vol%. The relatively low compressive strength (0.06–0.41 MPa) and Young's modulus (14.9–24.2 MPa) observed was due to the large cell size (1.1–1.6 mm) and high porosity (93%–96%).     

Preparation of spherical foamed body with function of media for waste water treatment by using waste LCD glass

Using waste LCD glass as a base material helped developed the manufacturing process of the spherical foamed body and its varied functionality. Also, the manufactured spherical foamed body showed great performance as a water treatment media. By mixing 90 wt% of waste LCD glass, 100 parts by weight of glass mixture that has 10 wt% kaolinite as a shaping agent, 1.0 part by weight of carbon foaming agent, and mixture of each 1.5 parts by weight of Na₂CO₃, CaCO₃ and Na₂SO₄ as foaming agents and the MgO as a parting agent for 10 min of foaming calcination in the rotary kiln at 970–1000 °C, the spherical foamed body can be manufactured effectively. The manufactured spherical foamed body performed as a great water treatment media by showing 70.5% of SS removal efficiency, 56.1% of BOD removal efficiency, 57.5% of COD removal efficiency, 28.6% of denitrification and 49.8% of phosphorous removal.