Preparation and characterization of high compressive strength foams from sheet glass

High compressive strength glass foams were produced using sheet glass cullet with the aid of 1 wt.% SiC powder, as gassing agent, and the incorporation of small amounts of an alkali earth aluminosilicate glass powder (AD), which is intrinsically prone to be crystallised to anorthite and diopside. The amount of SiC used as well as the mean particle sizes of the powders of both glasses and SiC were lower than those used in earlier studies. The experimental results showed that homogenous microstructures of large pores could be obtained by adding 1 wt.% SiC. The compressive strength of the glass foams was considerably increased when the incorporated AD-glass was higher than 1 wt.%. It is concluded that the presence of the AD glass is beneficial for the produced glass foams because of the formation of a well packed honeycomb structure which features an optimal distribution of pentagonal- and hexagonal-like shaped pores surrounded by dense struts. The crystallization of wollastonite and diopside inside the struts should also have a positive impact on the mechanical behaviour of the produced porous glass foams.     

Preparation of ultra-light ceramic foams from waste glass and fly ash

Ultra-light ceramic foams were successfully prepared by a green spheres technique, which used waste glass powder and fly ash as the main material. Besides, borax and SiC were introduced as fluxing agent and foaming agent, respectively. The effects of fly ash content, borax content and sintering temperature on the microstructures and properties of ceramic foams were systematically investigated. The optimum composition is 30?wt-% fly ash, 70?wt-% waste glass, 15?wt-% borax and 0.5?wt-% SiC. Ultra-light ceramic foams sintered at 680–780°C possess bulk density of 0.14–0.41?g?cm^?3, porosity of 82.9–94.1%, compressive strength of 0.91–6.37?MPa and thermal conductivity of 0.070–0.121?W?m^?1?K^?1, respectively. This method is convenient, low-cost and environment friendly, which makes it a promising way for recycling solid wastes.     

Recycling of waste glasses into partially crystallized glass foams

Waste soda-lime glass, alone or mixed with wastes from the manufacturing of glass fibers, was successfully converted into partially crystallized glass foams by a particularly simple and economic processing, consisting of a direct heating of glass powders at temperatures from 900 to 1050 °C. The foaming operated by the oxidation of SiC, inserted as powder additive, was found to depend on a complex combination of processing temperature, soaking time, tendency of the investigated glasses toward devitrification, and amount of MnO₂, acting as oxidation promoter. Selected combinations led to foams with a good microstructural homogeneity and mechanical strength, suitable for application as aggregates in lightweight concrete.     

Alkali-bonded SiC based foams

Silicon carbide (SiC) foams were developed by using a low temperature process such as chemical consolidation that is suitable to replace the sintering step. An alkali aluminosilicates binder, also known as geopolymer, was used. It was prepared from metakaolin, as aluminosilicatic raw powder, and KOH/K₂SiO₃ aqueous solution. The foaming agent was the metallic silicon present as impurity in SiC powders. Different grades of SiC were used as the main component (90 wt%) of the foams and the micro and macrostructures varied with the morphologies of the SiC raw powders. The surface of SiC grains participates to the geopolymeric process because of the dissolution of the silica layer into the alkaline solution. SiC foams were tested and characterized under oxidative atmospheres up to 1200 °C.     

The use of egg shells to produce Cathode Ray Tube (CRT) glass foams

Cleaned Cathode Ray Tube (CRT) (panel and funnel) waste glasses produced from dismantling TV and PC colour kinescopes were used to prepare glass foams by a simple and economic processing route, consisting of a direct heating of glass powders at relatively low temperatures (600–800 °C). This study reports on the feasibility of producing glass foams using waste egg shells as an alternative calcium carbonate-based (95 wt%) foaming agent derived from food industry. The foaming process was found to depend on a combination of composition, processing temperature and mixture of raw materials (glass wastes). Hot stage microscopy (HSM), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize foams and evaluate the foaming ability and the sintering process. The experimental compositions allowed producing well sintered glass foams with suitable properties for some functional applications with environmental benefits such as: (1) reduced energy consumption because of the low heat treatment temperatures used; and (2) materials produced exclusively from residues.     

Reutilization and stabilization of wastes by the production of glass foams

Glass foams are known to represent highly valuable products for thermal and acoustic insulation, often produced by employing wastes. Although the usage of recycled glass is widely reported for developing the glass matrix, little research has been due to the usage of wastes for the foaming reaction. In this work the cellular structure is achieved after oxidation of SiC-based wastes coming from the polishing of glass articles. The foamed recycled soda-lime glass incorporated the residues from oxidation and provided a reasonably good chemical stability. The addition of MnO₂ to the starting mixtures of wastes led to a certain improvement of the oxidation of SiC, and a complex effect on the correlation between density and mechanical strength. For selected additions, a more homogeneous foaming was found to provide a stronger cellular structure.     

粉煤灰泡沫玻璃工艺性能的研究

以粉煤灰和废玻璃为主要原料，添加适量发泡剂、助熔剂等制备粉煤灰泡沫玻璃。讨论分析了成型压力和退火制度等工艺过程对泡沫玻璃性能的影响。     

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.     

硼硅酸盐微晶泡沫玻璃耐酸性研究

以废玻璃粉为主要原料,掺入适量的脱镁硼泥,以C和MnO2为复合发泡剂,以ZrO2、TiO2为晶核剂,引入适量的添加剂,采用粉末烧成法工艺制备硼硅酸盐微晶泡沫玻璃。运用DSC-TG、XRD、SEM等微观测试方法,确定试样的核化和晶化温度、晶相种类以及在酸中浸泡前后的微观形貌,研究试样的耐酸腐蚀性。研究结果表明:当废玻璃粉和脱镁硼泥的质量比为8∶2,添加3%TiO2晶核剂,在1150℃保温30min,制备出硼硅酸盐微晶泡沫玻璃试样。把试样浸泡在0.1mol/L的稀硫酸中,浸泡14d后质量仅增加了0.02%,而浸泡35d-42d试样质量基本不变,说明硼硅酸盐微晶泡沫玻璃具有较强的耐酸性。     

发泡剂对空心石英玻璃微球结构的影响

空心玻璃微球因具有低密度、高强度、耐高温等优点而被广泛研究。采用喷雾造粒法与粉末法相结合,掺入发泡剂,以射频等离子体作为热源制备空心石英玻璃微球,研究了SiC、CaSO₄、CaCO₃三种发泡剂对制备空心石英玻璃微球的影响。结果表明,通过喷雾造粒法将发泡剂与SiO₂充分混合形成粗坯颗粒,再利用射频等离子设备对粗坯粉末进行高温烧结,得到空心石英玻璃微球。其中CaSO₄、CaCO₃发泡剂效果较差,所产生的气体难以留在玻璃微球内部形成中空气泡;而SiC发泡剂效果最好,在射频等离子烧结过程中产生气体,被玻璃液包裹形成空心结构,得到的玻璃微球平均真密度为1.799 5 g/cm³。选用菲利华石英块状疏松体作为SiO₂原料,当m(SiO₂)∶m(SiC)∶m(H₂O)为100∶3∶300时,可制备出平均真密度为0.72 g/cm³的空心多孔石英玻璃微球。     

Preparation and characterization of foams from sheet glass and fly ash using carbonates as foaming agents

Glass foams were produced using sheet glass cullet and fly ashes from thermal power plant with added carbonates (commercial dolomite- and calcite-based sludges) as foaming agents. The influence of type and amount of carbonates as well as of the sintering temperature on the apparent density, compressive strength, microstructure and crystalline phases was evaluated. The experimental results showed that homogenous microstructures of large pores could be obtained by adding just 1–2 wt.% carbonates and using low sintering temperature (850 °C), leading to foams presenting apparent density and compressive strength values of about 0.36–0.41 g/cm³ and 2.40–2.80 MPa, respectively. Good correlations between compressive strength, apparent density and microstructure (pore size, struts’ thickness and internal porosity) were observed.     

高密度聚氨酯硬泡塑料／玻纤粉复合材料的研究

以聚醚多元醇、PAPI、催化剂、发泡剂和玻璃纤维等为原料,制备高密度聚氨酯硬泡及它与磨碎玻纤粉的复合材料。研究了不同密度硬泡的强度及磨碎玻纤粉粒径、预处理及其含量对复合材料强度的影响,不同复合材料的热稳定性。结果表明,随着密度的增加,硬泡的各种强度值总体上均呈逐渐增加趋势,其中500kg/m^3的聚氨酯的拉伸强度比200kg/m^3的提高了104．74％,冲击强度提高了194．84％;400目粒径的玻纤粉可使复合材料具有更高的拉伸强度、弯曲强度及压缩强度;玻纤的加入将降低材料的强度值,但偶联剂预处理可使它们有所改善;加入磨碎玻纤粉后,材料的热稳定性增加,且采用偶联剂KH550对玻纤粉进行预处理可进一步改善复合材料的耐热性能。     

The influence of process parameters on in situ inorganic foaming of alkali-bonded SiC based foams

Silicon carbide (SiC) foams were developed with a low temperature process by using an inorganic alkali aluminosilicates binder, also known as geopolymer. The foaming agent was the metallic silicon present as impurity in the SiC powder. Si⁰ in the alkaline solution led to gas evolution that induced the foaming of the slurries. The binder was a geopolymeric resin with atomic ratio Si/Al = 2 and potassium as alkaline cation, classified as (K)poly(silalate-siloxo). The geopolymeric resin was prepared using metakaolin as aluminosilicatic raw powder, while the alkali aqueous solution was KOH/K₂SiO₃. Metakaolin in alkaline conditions dissolved and re-precipitated to form geopolymeric nano-particulates that acted as a glue to stick together SiC particles (90 wt.%). Process parameters such as water addition, mixing time and curing temperature were correlated to the foam structure. The formation of prolate pores induced anisotropy in the compressive strength. The foams were studied by dilatometric analysis in inert and oxidative atmospheres up to 1200 °C.     

Glass foams produced by glass waste,sodium hydroxide,and borax with several pore structures using factorial designs

Glass foams have great potential for several technological applications, for example, filters and thermal or acoustic insulators. Sodium hydroxide is an efficient foaming agent to obtain glass foams with high level of porosity. However, the control of variables that influences on structure, type, and size of pores of glass foams is necessary. This study evaluates the influence of composition and process parameters on glass foams based on soda-lime glass waste, sodium hydroxide, and borax. Experiments were conducted using factorial designs. According to the experimental conditions, bulk density varied from 0.16 to 0.79 g cm⁻³ and maximum porosity of 92%. Amounts of NaOH and borax in addition to sintering temperature are the main variables of the foaming process. The role of NaOH content is to reduce the density and closed porosity of glass foams associated with an increase in their open porosity. The addition of borax with low NaOH amount promoted densification and pore closure in glass foams. NaOH and borax content allows controlling the type of predominant porosity on foams (open or closed porosity). Glass foams were resistant to sulfuric acid, hydrochloric acid, and nitric acid in diluted solutions. These results allow controlling the pore structure of glass foams for different applications.     

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.     

Preparation of high open porosity ceramic foams via direct foaming molded and dried at room temperature

Herein an alternative approach was considered for addressing one difficulty of ceramic foams that the foam slurry with a high content of bubbles which were obtained via direct foaming, cannot maintain well for a long time at room temperature. It is fascinating that the foam slurry mentioned above could stably mold and dry at room temperature, based on an animal protein as foaming agent, kaolin, talc powder and alumina as raw materials, alpha-tricalcium phosphate prepared via co-precipitation as curing agent, and hydrophobic activated carbon powders as stabilizing agent. Effects of the calcination temperatures, the contents of alpha-tricalcium phosphate and activated carbon powder on microstructures, crystal phases, compressive strength and open porosities of ceramic foams were studied systematically. The results indicated that ceramic foams with a high open porosity and uniform pore distribution and sizes sought for application in catalysts supports, could be produced by adjusting these parameters.     

高阻尼聚氨酯结构泡沫材料的研究

探讨了高阻尼ＰＵ结构泡沫的配方、工艺和性能。结果表明：以六官能团的聚醚多元醇和有机多异氰酸酯（ＰＡＰＩ）制得的ＰＵ结构泡沫力学性能最优;反应对胺类催化剂和有机锡类催化剂的比例及用量非常敏感;硅酮类泡沫稳定剂对泡沫体的性能起重要作用;发泡剂Ｆ１１可用符合环保要求的戊烷完全替代;一种粉状填料和短切玻纤的加入可显著提高ＰＵ结构泡沫的损耗因子和冲击强度值。     

Foaming of flat glass cullet using Si3N4 and MnO2 powders

The introduction of a compound capable of releasing oxygen, such as MnO₂, greatly improves the foaming ability of Si₃N₄ used as foaming agent in soda-lime glass powder, leading to expansion at a relatively low temperature (800–850 °C) and short processing time (7–30 min). The effect is based on the supply of oxygen, in addition to that in the furnace atmosphere. At the highest level of porosity, however, the strength of foams is negatively affected by a coarse microstructure, determined by cell coalescence. The reduction of firing temperature or, above all, the reduction of the processing time, was found to limit the coalescence and significantly improve the strength of the foams.     

粉煤灰泡沫玻璃的试验研究

以粉煤灰和玻璃粉为主要原料,添加适量的发泡剂、稳泡剂等助剂,可制得粉煤灰泡沫玻璃。通过对制品体积密度、表观密度、开口孔孔隙率、吸水率等性能的测定,分析了发泡剂、粉煤灰掺量对泡沫玻璃性能的影响。实验表明,适量添加粉煤灰和玻璃粉,可制得性能较好的粉煤灰泡沫玻璃。     

木粉／低密度聚乙烯复合材料的发泡研究

用模压法制备木粉／低密度聚乙烯发泡材料。通过差示量热扫描分析,考察了纯偶氮二甲酰胺(AC)及与 ZnO共混物、纯NaHCO3及与柠檬酸(L)共混物的热分解特性,探讨了发泡剂AC、NaHCO3、柠檬酸、交联剂过氧化二异丙苯等对材料力学性能的影响,并在扫描电镜下观察了材料断面的微观形态。结果表明:采用放热发泡剂和复合发泡剂都能使复合材料密度下降20％左右,发泡后材料的冲击性能为发泡前体系的1．5倍左右;复合发泡剂的发泡效果优于单放热发泡剂的效果。