Pressure-molded high-alumina ceramic castables. 2. Compaction and properties of materials based on plasticized bauxite HCBS,reactive alumina,and their binary mixtures

The effect of compacting pressure (20–100 MPa) on the densification of refractory clay plasticized molding mixes based on bauxite HCBS containing 10% highly dispersed quartz glass, reactive STS-30 alumina, and their binary compositions has been studied. The properties of these materials subjected to heat treatment are discussed. Optimum compositions for binary systems are formulated that show promise as matrices for refractory materials and for preparation of engineering ceramics. __________ Translated from Novye Ogneupory, No. 11, pp. 25–31, November, 2005.     

Fabrication and properties of binders for high-alumina suspensions. 1. HCBS based on bauxite

The method of wet milling with step loading of the material has been used to prepare HCBS with a moisture content of 12–13% (the volume concentration of the solid phase ≤ 0.7) on the base of an available natural raw material, i.e., Chinese bauxite. The suspension is characterized by thixotropic-dilatant flow. The time of stabilization of the suspension by the method of gravitational mixing is shown to affect its rheological and technological properties more than those of HCBS of other compositions. The reduction of the viscosity of the suspension (by a factor of 4) decreases the porosity of the castings by 50–70 rel.% and increases their strength characteristics to 130–150 MPa after heat treatment at 1000‡C. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 6, pp. 21–26, June, 2000     

Materials based on highly concentrated ceramic binding suspensions (HCBS). Corundum and corundum-mullite ceramic castables based on plasticized hcbs of bauxite

HCBS of roasted Chinese bauxite, plasticized with additives of refractory clay, and corundum or bauxite filler are used for the production of pressed ceramic castables of corundum and mullite-corundum compositions with 93–95% and 80–85% A1₂,O₃, respectively. The optimum clay additive does not exceed 1–2%. The ceramic castables have a porosity of 15–18% and an ultimate compressive strength of 100–200 MPa after treatment at 1200–1300°C. As compared to traditional corundum refractories they are characterized by a finer capillary structure and a higher mechanical strength attained at a diminished (by a factor of 2–3) pressing pressure and a lower (by 400- 500°C) firing temperature.     

Cast (self-flow) ceramic castables. 2. Effect of structurizing additives of high-alumina cement on the properties of silica ceramic castables

HCBS of quartz sand modified by additives of high-alumina cement (HAC) and polydisperse silica fillers are used to obtain self-flow cast ceramic castables with a porosity of 16–18% and an ultimate compressive strength of 20–50 MPa after a heat treatment at 1000?C and 60–110 MPa after a heat treatment at 1300°C. A low additive of HAC (0.35–0.45%) accelerates the process of hardening and causes a certain (by 1–2%) increase in the porosity as compared with ceramic castables without such an additive. An increase in the HAC content to 1–3% causes a marked increase in the porosity and a decrease in the strength of the castable.     

Production of high-alumina articles from chinese bauxite chamotte

Conclusions We established that the properties and chemical-mineral composition of Chinese bauxite chamotte are inconsistent; this leads to high shrinkage and difficulties in making high-grade goods. The use of this bauxite in the manufacture of mullite and mullite-corundum refractories is possible only after a second calcination of the material in a rotary kiln.Translated from Ogneupory, No. 4, pp. 15–17, April, 1992.     

Materials based on highly concentrated ceramic binding suspensions (HCBS). Evaluation of methods for molding bauxite ceramic concretes

The processes of molding and vibromolding of laboratory samples and large-sized nested blocks for intermediate ladles are studied using bauxite mixtures of the same composition. The ceramic concretes obtained exhibit comparable porosity and strength characteristics, namely, substantial starting strength, significant strengthening upon low-temperature heat treatment, and insignificant shrinkage in service. An effect of substantial grinding of the bauxite filler in the structure of the mold is found even under conditions of a relatively low (25 MPa) molding pressure for nested-block molding on a friction press. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 5, pp. 11–14, May, 1997.     

Materials based on highly concentrated ceramic binding suspensions (HCBS). On preparation and some properties of silica refractory mixtures based on quartzite HCBS

Quartzite-based HCBS plasticized with additives of refractory clay are described. These HCBS and quartzite are used to produce refractory ramming mixtures. As compared with the known quartzite-clay ramming mixture on orthophosphoric acid, the obtained siliceous mixture has a much lower porosity and higher mechanical strength     

Production and properties of high-alumina ceramic concrete

Conclusions A high-alumina ceramic concrete containing ACBS based on the waste products of the high-alumina products industry and on a filler with D _s ^gr =2.5–15.0 mm of an analogous chemical composition has been obtained. The combination of studied properties suggests that new ceramic concrete shows promise for use in heat assemblies of various designs.Translated from Ogneupory, No. 2, pp. 54–56, February, 1982.     

硅线石对矾土基浇注料性能的影响

以矾土为主要原料,加入硅线石粉、SiO2微粉、活性A l2O3微粉、水泥等制备矾土基浇注料,研究了硅线石加入量(质量分数分别为0、4%、8%和12%)对浇注料常温性能和抗渣侵蚀性能的影响。结果表明:随着硅线石加入量的增加,浇注料的常温强度和体积密度下降,显气孔率增大;在浇注料中加入硅线石有助于提高试样的抗渣侵蚀性能,但加入质量分数大于8%时,试样抗渣侵蚀性能下降,渣渗透深度和侵蚀深度增加;硅线石加入质量分数为4%~8%时,浇注料的综合性能较好。     

Cast (self-flow) ceramic castables. 1. Fabrication and some properties of cast silica ceramic castables

A classification of methods for manufacturing cast (without the use of vibration) ceramic castables is suggested and the mechanism of their structure formation is formulated. Cast (self-flow) castable mixtures with a moisture content of 4.8–5.5% are developed based on HCBS of quartz sand and a polydisperse silica filler (d_max = 1–7 mm). The mixtures are used to cast ceramic castables with an open porosity of 11–16%. After drying and heat treatment at 1200 and 1300°C their ultimate compressive strength is 6–14, 20–35, and 60–120 MPa, respectively. As compared with similar pressed and rammed ceramic castables; cast ones are characterized by a lower porosity and a substantially higher strength.     

Materials based on highly concentrated ceramic binding suspensions (HCBS). The effect of heat treatment temperature on the strength properties of siliceous ceramic castables

Mechanical properties of siliceous ceramic castables shaped by vibration and static pressing with binders of quartz sand HCBS (pure and with a 5% additive of refractory clay) are studied. Other conditions being equal the porosity and the strength of the materials is affected by the content of the binder (varied from 10 to 33%). Ceramic castables heat treated at 1200 — 300°C exhibit a compressive strength of 50 –60 MPa at a porosity of 12–16%. The effect of the porosity on the strength of the materials is analyzed.     

Pressure-molded high-alumina ceramic castables. 3. Effect of processing additives on pressure-induced compaction and properties of bauxite-quartz glass matrix systems

The effect of lignosulfonate (LST) and surface-active substances (SAS) on compaction and properties of bauxite-quartz glass matrix systems is studied. LST added at an optimum concentration to bauxite-based highly concentrated ceramic binding suspensions (HCBS) causes a 2–3% decrease in preform porosity. In materials sintered at high temperature the effect of decreased porosity is more pronounced. In preforms molded at 500–700 MPa no defect due to overpress is observed. The SAS, judged from their efficiency for decreasing porosity, are arranged in ascending order: sodium silicate water glass, sodium tripolyphosphate, complex organomineral thinner, and FS-20 castament. __________ Translated from Novye Ogneupory, No. 4, pp. 126–133, April, 2006.     

复合外加剂对矾土基低水泥浇注料性能的影响

研究了单独外加0.1%的三聚磷酸钠(STP),以及0.1%的三聚磷酸钠(STP)分别与0.01%~0.06%的聚丙烯酸钠(PAANa)或氨基磺酸盐系高效减水剂(AS)复合外加时对矾土基低水泥浇注料性能的影响。结果表明与单独加入STP的浇注料相比,STP与PAANa或AS复合外加的流动值均显著增加,热处理后的物理性能也均略有提高;STP与PAANa复合相对于STP与AS复合的效果来说,在基本配方和加水量相同的情况下,前者的流动性比后者好,而烘干和热处理后,后者的强度略高于前者。     

不同二氧化硅微粉对矾土基低水泥浇注料性能的影响

研究了4种理化性能不同的二氧化硅微粉对矾土基低水泥浇注料流动性、抗热震性和高温抗折强度的影响。结果表明:加入纯度高,杂质含量少,颗粒分布均匀、集中,表面光滑,自身流动性好的二氧化硅微粉,则浇注料的流动性好,抗热震性好,高温抗折强度高;加入碳和碱金属含量高,颗粒粒度偏粗,表面粗糙,自身分散性差的二氧化硅微粉,则浇注料流动性差,抗热震性差,高温抗折强度低。     

林州天然硅线石-红柱石复合矿粉对高铝质浇注料性能的影响

以山西特级矾土熟料为主要原料制备高铝质低水泥浇注料,研究了分别用质量分数为0、3%、5%、7%的林州天然硅线石-红柱石复合矿粉等量替代矾土熟料粉对浇注料基质物相和浇注料性能的影响.结果表明:将硅线石-红柱石复合矿粉加入到高铝质低水泥浇注料中,明显改善了浇注料的物理性能,提高了材料的烧后冷态强度和高温强度,改善了浇注料的抗热震性能,而且适量加入还明显提高了材料的荷重软化温度.综合各项性能认为,加入硅线石-红柱石复合矿粉的质量分数以5%为佳.     

Refractory plastic mixtures based on highly concentrated ceramic binding suspensions (HCBS). 1. Structural and mechanical properties of suspensions (Pastes) of refractory clays

In contrast to the known refractory plastic mixtures that possess certain drawbacks the authors pose the problem of preparing similar mixtures with HCBS under the assumption that by using HCBS of an acid or acid-amphoteric composition plasticized by a refractory clay it is possible to improve the characteristics of this group of unshaped refractories (to reduce the shrinkage due to drying and heat treatment and the porosity and increase the strength). The properties of mixtures based on Nizhne-Uvelskoe clay as a plasticizer of plastic refractory mixtures arc described. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 14–19, April, 2000.     

Development of high-alumina ceramic concrete based on a composite binder

Information is provided for preparing high-alumina ceramic concretes based on a combined silicate-phosphate binder. Features are revealed for structure formation of the ceramic concrete developed during hardening, drying and firing; probable chemical reactions that occur are indicated.     

Materials based on highly concentrated ceramic binding suspensions (HCBS). Molding processes and strength of silica mixtures based on plasticized hcbs of quartz sand

A composition of a ramming silica mixture based on quartzite filler and HCBS of quartz sand plasticized by an additive of refractory clay and having a total clay content of at most 2% is presented. Three methods of molding (compaction) are considered, namely, pneumo(vibro)ramming, vibropressing, and static pressing. The first is shown to give maximum compaction. The effects of some process factors on the properties of the new refractory material are described. The suggested mixture promises to serve well in rammed monolithic linings of heating units     

添加Si粉对超低水泥结合高铝浇注料性能的影响

以高铝矾土为主要原料,在超低水泥结合的高铝浇注料中加入3％ ～9％(w)的Si粉,振动浇注成型试样,经烘干后,分别在空气和氮气气氛下于1450℃热处理,研究了Si粉加入量对试样性能,尤其是1300C0.5h(埋炭)高温抗折强度和荷重软化温度的影响.结果表明,在两种气氛下处理后,由Si粉反应生成的氧化物和非氧化物相均可显著提高试样的高温抗折强度和荷重软化温度,尤以氮气气氛下处理的显著,Si粉加入量为7％(w)时,氮化处理后试样的高温抗折强度可达23 MPa,是未加Si粉试样的3倍.SEM和EDAX分析表明,氮气气氛热处理后,引入的Si粉反应生成了纤维状Si3N4等非氧化物增强相,是材料高温性能得到显著提高的主要原因.综合考虑各项性能,Si粉的最佳加入量为5％ ～7％(w).