熔铸耐火材料抗盖板玻璃熔体侵蚀行为研究

本文以熔铸耐火材料为研究对象进行抗盖板玻璃熔体侵蚀试验,采用化学分析、岩相分析和电子显微镜能谱分析等测试分析方法,对比研究钠钙玻璃熔体、高铝玻璃熔体和锂铝玻璃熔体对熔铸耐火材料的侵蚀行为。结果表明,玻璃熔体中的碱金属离子向耐火材料中的玻璃相扩散,导致玻璃相黏度降低,同时耐火材料中刚玉相溶解,斜锆石分散,主体结构遭到破坏,并形成界面层。界面层内存在富铝含锆的玻璃相,由于高铝玻璃和锂铝玻璃氧化铝含量高,表面张力大,界面层内的玻璃相聚集在试样周围且扩散慢,从而阻止了侵蚀的发展。玻璃熔体的侵蚀速率为钠钙玻璃熔体＞高铝玻璃熔体＞锂铝玻璃熔体。     

红柱石原料高温结构演变及抗钾蒸气侵蚀行为研究

红柱石是铝硅系耐火材料重要的原料之一，因完全莫来石化后具有莫来石-高硅氧玻璃相相间的结构而表现出优异的抗碱侵蚀性能。然而，其莫来石化程度与抗碱侵蚀性能之间的关系尚未厘清。为此，本工作以粒度为3～5 mm的红柱石为研究对象，在1 450～1 600℃下热处理红柱石3 h,研究了红柱石的莫来石化过程与结构演变，并采用碱蒸气法研究了抗碱侵蚀行为。结果表明，随着热处理温度的提高，红柱石表面及裂纹附近先转变形成莫来石-高硅氧玻璃相结构，随后莫来石化转变不断向内部发展，直至完全莫来石化。红柱石莫来石化程度不同决定了其不同的抗碱侵蚀行为。1 450℃热处理后的红柱石表面及大裂纹附近形成的莫来石-高硅氧玻璃相复合层较薄，侵蚀以红柱石与钾蒸气直接反应为主，抗碱侵蚀性能较差；1 500℃及以上温度热处理的红柱石表面及大裂纹附近形成了一定厚度的莫来石-高硅氧玻璃相复合层，钾蒸气首先与高硅氧玻璃相反应形成含钾硅酸盐液相，随后该液相对莫来石相产生侵蚀溶解，阻止了碱蒸气对莫来石的直接反应侵蚀，从而使红柱石表现出优良的抗碱侵蚀性能。     

铝硅系耐火原料与碱蒸气反应侵蚀行为

近年来,污泥、生活垃圾作为水泥生产的部分燃料应用于水泥生产,造成水泥窑炉衬材料硅莫砖的严重碱侵蚀破坏和剥落,影响水泥窑的稳定运行。采用碱蒸气法系统研究了水泥窑硅莫砖用高铝矾土、莫来石(M60)及莫来凯特3种铝硅系耐火原料抗碱蒸气侵蚀行为。结果表明：3种铝硅系耐火原料的碱蒸气侵蚀行为,与原料中的化学成分、玻璃相含量和成分及其显微结构等密切相关。对于以刚玉、莫来石为主的高铝矾土,碱与刚玉、莫来石晶相发生反应形成钾霞石,产生体积膨胀,使得高铝矾土表面先发生疏松和开裂,后碱蒸气渗入颗粒内部,造成严重碱侵蚀破坏;而对于以莫来石为主的莫来石(M60)原料,碱与莫来石和玻璃相发生反应,形成瞬间液相并析出白榴石相,形成的液相阻止了碱的渗透,使碱侵蚀仅发生在表面层而表现出优良的抗碱侵蚀性能。而莫来凯特原料中晶相莫来石与玻璃相含量相当,玻璃相含量高达46%,其与碱蒸气发生化学反应形成更多的液相,同时析出白榴石相,因氧化钾反应溶解在该原料玻璃相中,造成原料整体性侵蚀破坏。     

高铅玻璃耐水性的研究

高铅玻璃是我国先民独创的。史美光、何欧里等对中国古铅玻璃进行过大量的研究,他们对我国出土的20多种古代铅玻璃样品进行了实物考察和性能测定。 随着科学的发展,一些学者对铅在硅酸盐玻璃中的结构,光学性质进行了研究。干福熹等用电导法测定了各类火石玻璃、重火石玻璃在水中侵蚀深度达30毫微米时,所需时间与PbO含量的关系.Shamy研究了二元PbO-SiO_2玻璃在不同的酸性介质中的稳     

CaF_2与硅酸铝耐火材料的化学反应及化学侵蚀

根据AlF_3-H_2O、CaF_2-H_2O系统的热力学计算及已有资料讨论了SiF_4、AlF_3、CaF_2高温水解作用的可能性。 采用化学反应法和砖面熔化法实验研究了CaF_2-硅酸铝耐火材料的化学、侵蚀反应。结果表明,在高温下CaF_2具有极强的破坏铝硅酸质玻璃成晶体的骨架結构的能力,首先与耐火材料中玻璃、SiO_2矿物发生化学作用,进而促使莫来石熔融、分解,其次是对刚玉组份的溶解作用。生成氟铝硅酸钙熔体和揮发态氟化物;揮发物中主要是SiF_4、AlF_3,部分地包含SiF_xO_y、AlF_xO_y等氟化物。氟化鈣对于硅酸铝耐火材料的侵蝕作用十分剧烈,虽然刚玉矿物的稳定性较高,但是由于caF_2首先与磚中玻璃貭、莫来石起作用,出現低粘度为熔体,造成熔融孔道,因此加剧了对高鋁氧砖的渗透作用。 文中列出了化学反应生成物中的六方鈣长石及合成六方钙长石的結晶光学常数及X-射线粉末衍射数据,并且对于自熔体中生成这种介稳定物相的原因进行了分析、討论。 有人认为CaF_2-Al_2O_3,将形成固熔体,在实驗条件下未被証实。     

玻璃生产关键工艺性能的测量方法综述

综述玻璃生产制备过程中的关键工艺性能的测量表征方法和适用仪器设备,关键工艺性能主要包括熔解特性、熔体特性、侵蚀特性和温黏特性等.熔解特性包括原料选择、原料间互溶反应、玻璃液澄清等;熔体特性包括表面张力、高温电阻率、羟基含量等;侵蚀特性包括玻璃液对耐火材料的侵蚀和耐火材料对玻璃液的污染两个方面;温黏特性主要包括高温黏度(熔融温度Tm、工作点Tw、液相线TL)、中温黏度(软化点Ts)、低温黏度(膨胀软化点Td、退火点Ta、转变点Tg和应变点Tst等).上述工艺性能精确测量和表征,对制备高质量玻璃制品具有重要意义.     

黑白显像管玻璃的组成评述

一、黑白显像管玻璃的主要物理、化学性质显像管是电视机的核心部件。其作用是将天线接收的电信号转变成光学图像在屏幕上显示。显像管玻壳处在高电压和强大气压差的条件下进行工作,在显像管制造过程中,玻屏与玻锥,玻锥与金属阳极帽之间必须牢固封接;而使用时,屏面尚需显示清晰的光     

玄武岩纤维生产炉窑耐火材料侵蚀研究

以玄武岩纤维生产炉窑顶部加料口上部的刚玉莫来石砖和侧壁内衬高铬砖作为研究对象,采用XRD、XRF、SEM和EDX等分析方法,研究了玄武岩熔体对炉窑耐火材料的侵蚀行为,结果表明炉窑顶部的刚玉莫来石砖以50 mm/a侵蚀速率被侵蚀,刚玉莫来石砖内部的刚玉和莫来石晶粒与玄武岩反应生成低熔点的钙长石、橄榄石、铁尖晶石等物质,同时受到挥发分气流的物理性冲刷,导致刚玉莫来石砖耐侵蚀性能差;而炉窑内侧壁高铬砖耐侵蚀性较好,腐蚀速率为2. 5 mm/a,高铬砖与熔体接触区以化学反应结合物理磨损侵蚀方式为主,同时,Fe元素在高铬砖侵蚀过程中起着固溶-传质的作用,加速炉衬材料侵蚀。     

黑白显象管玻璃池窑蓄热室硅质格子砖的使用

作者通过对黑白显像管玻璃池窑的蓄热室采用硅质格子砖替代电熔十字型格子砖的使用情况分析,探讨了PbO及其比合物与碱尘和碱蒸汽对硅砖的共同作用,使侵蚀速度加剧,且熔融物冷凝可随格子体堵塞,寿命只能维持3年左右.如采用烧渣的办法疏通,其寿命可延至5年.采用电熔十字型格子砖,其寿命以达6～8年,甚至更长.指出熔制高铅玻璃,蓄热室格子体不宜采用硅砖.     

添加锂对显像管玻璃性能的影响

研究了添加锂对显像管玻璃物理性能和熔制性能的影响。显像管玻璃中加入少量的碳酸锂可降低玻璃的高温黏度 ,加快其熔制过程 ,降低其泡沫层厚度 ,从而提高显像管玻璃的澄清效果 ,减少玻璃气泡缺陷     

Effect of some properties of aluminosilicate refractories on their glass resistance

Conclusions The glass resistance of aluminosilicate blocks with similar porosity values depends mainly on the quantitative ratios of crystalline and glassy phases, their chemical composition, and the grain size of the mullite. The higher the crystalline phase concentration in the refractory (mullite and mullite+ corundum) the fewer the impurities (oxides of iron, titanium, calcium, sodium, potassium, etc.), and the coarser the grains of mullite, then the lower their corrosion by molten glass.An increase in the glass resistance of aluminosilicate blocks can be achieved by using pure clays and kaolins, and also by using high temperatures for firing, longer soaking periods, and also mineralizing additives.Translated from Ogneupory, No.6, pp. 40–44, June, 1970.     

Mullite‐glass and mullite‐mullite interfaces: Analysis by molecular dynamics (MD) simulation and high‐resolution TEM

The properties of mullite‐glass and mullite‐mullite interfaces have been investigated at 1800 K by molecular dynamics (MD) simulation and high‐resolution TEM. The simulation showed that mullite‐glass interfaces typically have much lower interfacial energies than mullite‐mullite interfaces, which results from the structural flexibility of the glass and associated accommodation of interfacial mismatch. The (110)‐glass interface has the lowest energy of all interfaces studied, which is consistent with the observed dominance of this interface in experimental mullite‐glass samples examined by TEM. The simulation shows that the interfacial energies of the (100)‐glass and (010)‐glass interfaces are higher than that those of the (001)‐glass interface, so [100] and [010] would be expected to be the dominant growth directions. However, the growth of mullite in glass occurs predominantly in the [001] direction. This apparent discrepancy can be explained by the fact that growth in the [100] and [010] directions is limited by the slow growth of (110) plane (i.e., [110] direction), which facilitates [001] growth, which is confirmed by the TEM data.     

Fabrication of homogeneous mullite-based fiber porous ceramics with high strength and porosity

Silica sol is widely used in the preparation of mullite-based fiber porous ceramics (MFPCs), but it aggregates at the top surface of MFPCs during the drying process. This leads to the decrease in mechanical strength and porosity. To overcome the problem and fabricate homogeneous MFPCs, the sodium silicate solution and glass fibers were applied in the fabrication process of MFPCs. The effects of concentrations of sodium silicate solution and silica sol, amounts of glass fibers and sintering temperatures on the properties of prepared MFPCs were studied. The sodium silicate solution consolidated the silica sol and mullite fibers, forming a homogeneous structure and ensuring the even distribution of silica sol. Compared with other reported MFPCs, this process required low sintering temperature while maintaining high compressive strength (2.14 MPa) and porosity (75.93%). This study provides an effective method for preparing MFPCs with high strength, uniformity and porosity.     

FIRE CLAYS. SOME FUNDAMENTAL PROPERTIES AT SEVERAL TEMPERATURES1

This report gives the results obtained in the second phase of an extensive investigation of fireclay refractories. It is limited to the twenty-six representative clays included in that investigation. The geologic formation, chemical analyses, and pyrometric cone equivalents are given together with such properties of the clays fired at two widely different temperatures, as porosity, shrinkage, thermal expansion, moduli of elasticity and rupture, and plastic flow. Data are given to show the conversion of aluminous fire clays into mullite and cristobalite by firing at certain temperatures. At higher temperatures the cristobalite is converted to glass.     

高密度泡沫玻璃的研制及应用

以废阴极射线管颈玻璃和氧化铅为主要原料,加入一定量的碳化硅、氟化铅、三氧化二铁、氧化铋,采用烧结法制备高密度泡沫玻璃。通过XRD,SEM等分析手段对泡沫玻璃的性能进行了研究。结果表明,随PhO加入量的增加,发泡温度逐渐降低,密度和强度逐渐增大。试样在发泡温度810℃下保温30min,产生了PhFe02F、Pb、PhO等3种针状晶体,试样力学性能提高.     

NATURE OF THE GLASS PHASE IN HEATED CLAY MATERIALS: II*

The glass phase in the bodies studied was more sensitive to variations in heat treatment than were the physical properties. Increased rates of heating caused less glass and mullite formation, less quartz corrosion, more pores and blebs, and increased heterogeneity of the glassy matrix. Microstructure and physical properties indicated an optimum heating rate between 50° and 90° per hour. Soaking increased the amount of glass, more so after slow than after rapid heating. Soaking after rapid heating did not reduce the number of blebs. Soaking too long and at too high temperatures made blebs more numerous. A minimum soaking time of one hour seemed desirable. The optimum heating rate and minimum soaking time governed the shortest heating schedule productive of the best microstructure and physical properties.     

Influence of heat treatment of fused mullite materials on their properties

Conclusion It is shown that the temperature of initial crystallization of glass spheres of mullite composition with diameters of less than 0.1 mm, in the metastable state, equals 935°C. The phase composition of the spheres of diameters from 0.1 to 0.5 mm varies. With an increase in the diameter of the spheres from 0.5 to 1–1.7 mm their properties vary slightly.Thermal processing of the spheres of mullite composition with different starting contents of mullite and glass in the mullite component influences the crystallization of the mullite and causes increases in the density at temperatures from 900–1300°C. The most rapid change in properties takes place in the spheres containing the maximum amount of glass phase (100%). In the 1300–1500°C range in all spheres, with different contents of glass phase in the starting condition, there is a variation in the density and in the mass proportion of mullite.An increase in soaking from 0.5 to 1.5 h at 1300 and 1500°C leads to an increase in the mullite content and a rise in the density of the glass spheres.During the firing of finely milled powders made of granules and spheres with different contents of glass phase and mullite, and also specimens prepared from these powders, with temperature rise the material's density and the amount of mullite are both increased, and the changes in these factors are identical. It is established that with increase in the mullite concentration in specimens of finely milled powders there are marked reductions in shrinkage, and apparent density; and an increase in the porosity of the specimens fired at 1750°c. There is much less change in the properties at 1700°c.Translated from Ogneupory, No. 4, pp. 7–10, April, 1990.     

Coal Slag Protection of Silicon Carbide with Chemically Vapor Deposited Mullite Coatings

The corrosion characteristics of bulk alumina, SiC, mullite, and CVD mullite coatings on SiC in contact with coal slag were investigated. Uncoated SiC corroded in the presence of coal slag, forming mixed FeSi phases and carbon. Bulk Al₂O₃ and slag formed a diffusional phase believed to be the spinel hercynite (Fe,Mg)O·(Al,Fe)₂O₃. After exposure to coal slag, a compositional difference was observed at bulk mullite/coal slag interfaces, yet this diffusional phase did not appreciably degrade the mullite samples and no cracking was observed. CVD mullite coatings offered protection to SiC in a simulated coal gasification atmosphere with corrosion protection dependent on the uniformity of the coating. Microprobe analysis of the CVD mullite coating/slag interface showed the formation of a Fe(Mg)Al.     

Wet-oxygen corrosion resistance and mechanism of bi-layer Mullite/SiC coating for Cf/SiC composites

A bi-layer oxidation-resistant coating consisting of a mullite outer coating, and a SiC inner coating on the surface of C_f/SiC composites was prepared by the chemical vapour deposition and an air spray sol-gel process, and its corrosion behavior was evaluated in a wet-oxygen coupling environment. Results show that the formation of SiO₂ glass layer and its reaction with mullite particles to form aluminosilicate glass layer, leading to an increase in the density of the mullite outer coating, so that the weight loss of bi-layer Mullite/SiC coating coated C/SiC sample was only 1.11 × 10^?3 g·cm^?2 in the first 100 h of oxidation. However, the weight loss of the coated sample reached 26.82 × 10^?3 g·cm^?2 after 200 h of oxidation due to a part of the mullite outer coating was detached. The SiO₂ glass phase reacted with water vapour to generate gaseous Si(OH)_x, which created distinct holes on the surface of the SiO₂ glass layer or inside the molten aluminosilicate glass layer. Eventually, the mullite outer coating was blistered and detached from the surface of the sample due to the combination and growth of holes.     

Hot corrosion studies of nanostructured gadolinium zirconate thermal barrier coatings

Improvement of hot corrosion resistance is one of the important parameters governing the lifetime and efficiency of the thermal barrier coatings (TBCs). In this study, the Gadolinium Zirconate (GZ) was synthesized by ball milling method and deposited by Electron Beam-Physical Vapour Deposition (EB-PVD) on Ni-based superalloy substrate with NiCrAlY as an intermediate bond coat. The effect of nanostructured GZ TBCs on hot corrosion resistance were studied under three different salt mixture environments viz; SM1, SM2 and SM3 in isothermal condition at 900 °C for 12 h. The results indicated that EB-PVD coated nanostructured GZ TBCs have improved the hot corrosion resistance and performed well under SM1 and SM3 conditions with minimal weight gain and without any spallation, whereas, the TBC suffered severe spallation under of SM2 salt condition with higher weight gain among the other two conditions. The formation of microcracks along the columnar gaps of the topcoat were found in the SM2 condition, have allowed the molten salts infiltration up to the coating interface. The formation of dense corrosive products GdVO₄ and m-ZrO₂ phases were identified after hot corrosion in SM1 and SM3 condition, which were absent in SM2 condition.