MgO加入量对刚玉尖晶石浇注料性能的影响

以致密电熔白刚玉、刚玉微粉、电熔白刚玉细粉、电熔镁砂细粉为原料,研究了5种不同加入量的镁砂对同配比刚玉尖晶石浇注料性能和理化指标的影响。实验结果表明:1.7%的MgO加入量的刚玉尖晶石浇注综合性能最佳,加入量超过7%后,材料的性能降低;2.MgO加入量的增加有利于提高110℃×24h烘干后刚玉尖晶石浇注料的致密度,体积密度逐渐增大,气孔率逐渐减小,并提高常温强度;3.随着MgO加入量的增加,1500℃×3h处理后刚玉尖晶石浇注料尖晶石化剧烈,材料体积膨胀大,结构疏松,材料的气孔率逐渐增大,体积密度和强度降低。     

电熔镁砂加入量对刚玉-尖晶石轻质隔热材料性能的影响

以α-Al2O3细粉(≤74μm)、α-Al2O3微粉(d50=2μm)为主要原料,加入5%(w)的ρ-Al2O3微粉(d50=5μm)为结合剂,外加0.3%(w)的发泡剂和2%(w)的六偏磷酸钠减水剂,在1 550℃3 h煅烧后原位制备了刚玉-尖晶石轻质隔热材料,研究了电熔镁砂加入质量分数(0、5%、10%和15%)对刚玉-尖晶石轻质隔热材料物理性能、热导率及显微结构的影响。结果表明:随着电熔镁砂加入量的增加,试样的体积密度逐渐减小,强度先减小后增大,烧后线变化和重烧线变化(1 550℃3 h)由收缩逐渐表现为膨胀,试样在300～900℃下的热导率均降低;通过发泡法制得的刚玉-尖晶石轻质隔热材料气孔分布均匀,呈球形,且随着电熔镁砂加入量的增加,试样的结构疏松,微孔数量增加,但其对大孔的影响较小。综合考虑试样的各项性能,认为电熔镁砂适合的加入质量分数为15%。     

方镁石、刚玉、尖晶石、莫来石等晶体特异形貌的表征

借助于高分辨力仪器研究了方镁石、刚玉、尖晶石和莫来石在不同条件下晶体生长现象,表征了晶体的特异形貌.立方晶系的方镁石和尖晶石自形晶为典型的立方体和正八面体,亦可构成任何其他形状,如连晶化和台阶生长,皆由析晶环境限定.莫来石属斜方晶系,具有长柱状结晶习性,但自形发展常受到环境限制,只有当存在一定液相时析晶(或刚玉与液相发...     

RH炉浸渍管外衬刚玉-尖晶石浇注料的研制

通过选择合适的超细粉加入量、镁砂粒度组成及加入量,优化基质的组成,利用A1     

刚玉-尖晶石-炭不烧上水口的研制和使用

以电熔刚玉砂、高纯电熔尖晶石为主要原料,以热固性树脂为结合剂,添加复合抗氧化剂而制成的刚玉-尖晶石-炭不烧上水口,具有热态强度好、耐渣蚀性强、工艺简单等优点。该水口在某钢厂90t连铸钢包上批量使用,较刚玉上水口寿命提高50％～60％。     

氢氧化镁粒度对刚玉-尖晶石材料结构与性能的影响

以氢氧化镁和α-Al2 O3微粉为原料,经过干混、成型和1750℃反应烧结制备了刚玉-尖晶石骨料,研究了氢氧化镁粒度(平均粒径分别为55、36.4和10.6μm)对刚玉-尖晶石材料体积密度、气孔率及显微结构等的影响.结果表明:随着氢氧化镁粒度的减小,试样的体积密度增加,显气孔率下降,封闭气孔增加,总气孔率和孔径逐渐下降...     

镁砂细粉加入量对轻骨料刚玉-尖晶石浇注料性能的影响

以轻质刚玉-尖晶石陶瓷颗粒为骨料,以白刚玉细粉、90尖晶石细粉、镁砂细粉、α-Al2O3微粉、SiO2微粉为基质料,在固定镁砂细粉和白刚玉细粉的总质量分数为17.5%的情况下,改变镁砂细粉的质量分数(分别为0、3.5%、6.5%、9.5%和12.5%),制备成5种轻骨料刚玉-尖晶石浇注料试样,经110、1100和1600℃热处理后,检测试样的常温物理性能,并分析试样的相组成和显微结构。结果表明:1)随着镁砂细粉加入量的增加,不同温度热处理后试样的显气孔率和体积密度的变化均不大;110℃热处理后试样的强度有增大的趋势,而1100和1600℃热处理后试样的强度则有减小的趋势;1100℃烧后试样的线膨胀率有增大的趋势,而1600℃烧后线膨胀率显著增大;试样基质的显微结构变疏松,平均孔径和孔隙率增大。2)当镁砂细粉加入量(w)为3.5%和6.5%时,试样的抗渣渗透性相对较强,而抗渣侵蚀性相对较差;当镁砂细粉加入量(w)增加到9.5%和12.5%时,试样的抗渣侵蚀性显著提高,而抗渣渗透性显著下降。     

镁砂与电熔合成铁铝尖晶石-刚玉复合材料的反应

以电熔合成铁铝尖晶石-刚玉复合材料和电熔镁砂为原料制备了铁铝尖晶石-镁铝尖晶石复合材料。检测了各烧后试样的线变化率、体积密度和显气孔率,并用XRD、SEM等研究了镁砂与电熔铁铝尖晶石-刚玉复合材料之间的反应,结果未发现有单一的镁铝尖晶石相生成,在高温下,MgO与铁铝尖晶石-刚玉之间存在互扩散,形成镁铝尖晶石和铁铝尖晶石固溶体;随着镁砂细粉加入量的提高,镁铝尖晶石向铁铝尖晶石中的固溶量加大;当电熔铁铝尖晶石-刚玉复合材料以颗粒加入时,发现在某些铁铝尖晶石颗粒周围存在环形裂纹;随着镁砂加入量的提高,试样的显气孔率下降,体积密度增大。     

微孔镁尖晶石碳耐火材料的抗渣性能研究

以方镁石-尖晶石微孔陶瓷、电熔镁砂为骨料,以电熔镁砂细粉、鳞片石墨、金属铝粉为基质材料,以酚醛树脂为结合剂制备了含微孔陶瓷骨料的镁尖晶石碳试样.采用感应炉浸渍法对试样进行了抗渣试验,并对渣蚀后的试样进行了SEM和EDAX分析.结果发现:熔渣和熔钢冲刷是损毁的主要原因,熔损并不显著.显微结构分析表明,在侵蚀层和原质层之间可以发现MgO致密层的形成,MgO致密层的形成可抑制渣对试样进一步的侵蚀和渗透.渣对MSO颗粒的侵蚀主要是FeO和MnO等在方镁石中的固溶,导致MgO颗粒出现结构剥落;方镁石-尖晶石微孔陶瓷骨料的蚀损主要是尖晶石被渣中的CaO和SiO2所侵蚀,而渣对微孔骨料渗透并不严重.     

纳米添加剂对低碳MgO-C材料高温力学性能的影响

德国研究人员在低碳MgO-C砖中分别加入不同种类的纳米添加剂,以期改善低碳MgO-C砖的高温力学性能。试验用主原料为:≤4.0 mm的电熔镁砂颗粒,其w(MgO)>97.0%;≤0.045 mm的烧结镁砂粉,其w(MgO)>95.0%;d50=0.14 mm     

尖晶石质浇注料显微结构的研究

对尖晶石质浇注料及高纯铝镁浇注料的基质进行了显微结构分析,分析了不同结合系统和硅灰纯度对显微结构的影响,结果表明：结合系统中主要由尖晶石、橄榄石和硅酸盐玻璃相构成,有水泥结合的系统中还有长石析出。     

尖晶石加入量对铬刚玉浇注料性能的影响

研究了尖晶石加入量对铬刚玉浇注料的烧结性能、抗折强度、抗热震性以及抗渣渗透和侵蚀能力的影响。尖晶石的加入使铬刚玉浇注料线变化率增大 ,显气孔率升高 ,常温强度略有降低。加入 2a %～ 3a %的尖晶石能明显改善铬刚玉浇注料的抗热震性。加入尖晶石后 ,铬刚玉浇注料的抗高钙、高铁渣的渗透、侵蚀能力有所下降     

基体种类对CTBN改性环氧树脂结构和性能的影响

研究了ＣＴＢＮ对不同种类的环氧树脂（Ｅ－５１、Ｆ－５１）力学性能的影响,通过扫描电镜观察了２种增韧体系的微观结构形态,并探讨了２种增韧体系的微观结构形态与力学性能间的关系。     

加入纳米碳酸钙对铬刚玉浇注料力学性能的影响

以板状刚玉、氧化铝微粉、氧化铬微粉(平均粒径<5μm)、铝酸钙水泥(Secar 71)、商品纳米碳酸钙(平均粒径<100 nm)为主要原料,FS10为减水剂,制备了不同纳米碳酸钙加入量(0、0.2%、0.4%、0.6%、0.8%、1%)的铬刚玉浇注料试样,测定了其经1 000及1 600℃热处理后的显气孔率、体积密度和强度,并用扫描电子显微镜(SEM)观察了材料的微观结构。结果表明,在减水剂加入量一定时,随纳米碳酸钙加入量的增大,浇注料的流动性显著下降,显气孔率逐渐升高,冷态和热态强度逐渐降低;在浇注料流动值基本一致的情况下,随纳米碳酸钙加入量的增大,浇注料的显气孔率明显增大,但其冷态和热态强度皆逐渐提高,这主要是由于纳米碳酸钙在高温下分解产生的CaO和结构中的A l2O3原位反应形成铝酸钙物相的缘故。     

Effect of microporous magnesia aggregates on microstructure and properties of periclase-magnesium aluminate spinel castables

The present study investigated three lightweight periclase-magnesium aluminate spinel castables containing microporous magnesia aggregates with a varying apparent porosity (12.8%, 30.8% and 39.3%). The effect of the apparent porosity of the aggregates on the phase composition, microstructure, fracture behavior and strength of the lightweight castables was investigated by XRD, SEM and three-point bending tests. Large cracks between the aggregates with an apparent porosity of 12.8% and the matrix reduced the strength of the castable. For the aggregates with an apparent porosity of 30.8%, an excellent interlocking interface with the matrix increased the strength considerably, but also reduced the fracture toughness. At the highest level of the apparent porosity of the aggregates of 39.3%, the formation of a small number of microcracks between the aggregates and matrix reduced the strength, while the fracture toughness was only slightly affected. The lightweight castables with the best combination of properties were achieved at an apparent porosity of the aggregates of 30.8% since they had a low bulk density of 2.63 g/cm³ as well as a high compressive and flexural strength of 70.2 MPa and 20.9 MPa, respectively.     

Preparation of tabular corundum aggregate from different sources alumina raw powder: Sintering kinetics and establishment of kinetics model

In this paper, we report the use of four types of commercial alumina raw powders as raw materials for the preparation of tabular corundum aggregates under the same conditions. The influence of the transition phases of alumina raw powder on the sintering kinetics of tabular corundum is discussed, the sintering model of materials with pseudomorphic structure is established, and the mechanisms underlying the different performances of various commercial tabular corundum samples are evaluated. The following conclusions were drawn based on the results of the study. (1) A double tetrakaidecahedron model was established and was shown to satisfactorily describes the sintering mechanism of alumina raw powder with pseudomorphic structure, which accords with the porosity change trend of sintered body and provides a basis for perfecting the sintering theory. (2) Compared with the other transition phases, γ-Al₂O₃ shows the largest phase transformation volume contraction, which provides the driving force for the sintering process via an increase in surface energy and mainly acts in the densification and grain growth stages. Thus, high-quality refractory raw materials are prepared with optimized physical properties and Intracrystalline pores or pore clusters in the crystal structure. The preparation of these high-quality refractory products is of importance for prolonging the life of these materials and also meeting rising energy demands.     

Some Influencing Factors on Rheological Properties of Bauxite-based Castable Matrix

The effects of corundum, magnesia and spinel additions on rheological properties of matrix of bauxite-based castables were studied using bauxite, fused white corundum, magnesia, spinel, microsilica, ultra-fine α-Al2O3 and cement as starting materials and trimeric sodium phosphate as dispersant. The results show: (1) the matrix slurry of bauxite-based castables belongs to Bingham fluid and shows thixotropy behavior; (2) appropriate corundum addition improves rheological properties of the matrix; (3) magnesia addition is detrimental to matrix rheological properties; (4) spinel addition has slightly negative effects on matrix rheological properties.     

Microstructure and properties of bilayered B4C-based ceramics

Bilayered B₄C-based ceramics were obtained by hot-pressing. Microstructure, mechanical and ballistic properties of the bilayered ceramics were investigated. One layer was obtained upon addition of Ti and C to the hard B₄C matrix, the newly formed TiB₂ phase uniformly distributed in the matrix. The other layer included variable amounts of Ti₃SiC₂, equal to 10, 20, 30, 40 wt%, and the B₄C-SiC matrix in a fixed weight ratio of 7:3. The amount of TiB₂ and SiC phases, deriving from Ti₃SiC₂ decomposition upon sintering, increased with increasing the Ti₃SiC₂ content. The flexural strength and fracture toughness of bilayered ceramics both increased with increasing the Ti₃SiC₂ content from 10 to 40 wt%. Ballistic testing showed that the B₄C-based ceramic target containing 30 wt% Ti₃SiC₂ broken into pieces upon being impacted by a 12.7 mm armor-piercing incendiary (API) projectile, and effectively consumed the bullet energy and protected the backing plate from serious damage.     

Degradation behavior of SiO2f/Al2O3-SiO2 composites: Anti-oxidation behavior and high-temperature flexural strength

2.5-Dimensional SiO₂ fiber-reinforced Al₂O₃-SiO₂ (SiO_2f/Al₂O₃-SiO₂) composites were prepared by the sol-gel method, using diphasic SiO₂ sol as the precursor into which Al₂O₃ powders were added. Their antioxidative behaviors and flexural strengths at high temperature were tested and compared. In an oxidation atmosphere, the composites showed high oxidation resistance, with a flexural strength retention ratio of over 90.00% at 1200?°C. After oxidation at 1500?°C, the mass retention ratio and flexural strength were 97.49% and 65.0?MPa respectively. The oxidation resistance of SiO_2f/Al₂O₃-SiO₂ composites was higher than that of SiO_2f/SiO₂ composites. After high-temperature test, the flexural strength retention ratios of SiO_2f/SiO₂ and SiO_2f/Al₂O₃-SiO₂ composites were 86.18% and 94.80% respectively, and the latter had a flexural strength of 134.9?MPa. SiO_2?f/Al₂O₃-SiO₂ composites worked better than SiO_2f/SiO₂ composites did in the flexural strength test at 1200?°C. The mechanical performance degradation and mass variations of the composites during tests were closely associated with their microstructural evolutions.     

Low temperature sintering of Hf0.95Nb0.05B2-based ceramics with submicron-scaled grains and enhanced mechanical properties

Hf_0.95Nb_0.05B₂ ceramics and their composites containing 20 vol% SiC were prepared via high-pressure spark plasma sintering in the study. The densification, microstructures, and mechanical properties of the prepared materials were then investigated. It is challenging to achieve full densification of HfB₂ ceramics, even with markedly refined Hf_0.95Nb_0.05B₂ solid solution powder under the sintering conditions of 2000 °C/30 MPa. However, under the sintering conditions of 1700 °C/200 MPa, a dense microstructure of Hf_0.95Nb_0.05B₂ ceramics was achieved. Moreover, the Hf_0.95Nb_0.05B₂-20 vol% SiC composite was densified at a lower temperature (1500 °C) and exhibited ultrafine grains (300 nm) and high-density defects, including stacking faults, Lomer-Cottrell locks, and twins, thus resulting in exceptional comprehensive mechanical properties, such as ultra-high hardness (32 GPa) and significantly improved fracture toughness (5.2 MPa.m^1/2).