二氧化硅对二次铝灰烧结制备镁铝尖晶石材料性能的影响

国内二次铝灰产量大,且总铝含量不低,堆放过程中受到雨水淋溶,导致自然水体被污染和土壤盐碱化等危害。在前期研究的基础上,以再生铝行业产生的二次铝灰为主要原料,采用固相烧结法开展二氧化硅含量对二次铝灰烧结制备镁铝尖晶石材料性能影响的研究,并采用XRD、SEM及红外谱图等手段分析烧结产物。研究结果表明,二次铝灰和氧化镁质量分数比为1∶0.2时,在1 400℃条件下烧结,保温3 h,二次铝灰可以烧结制备镁铝尖晶石材料;二氧化硅对二次铝灰烧结制备镁铝尖晶石材料性能有影响,添加5%二氧化硅时,所得镁铝尖晶石材料性能最佳,体积密度为2.03 g/cm³,线变化率为0.42,抗压强度为91.1 MPa;含5%～20%二氧化硅的原料样品在1 400℃烧结,烧结材料主要物相为MgAl₂O₄,随二氧化硅含量增加,MgAl₂O₄衍射峰强度减弱,烧结体中出现较厚纤维状组织,材料致密性提高,适量二氧化硅的存在对二次铝灰烧结制备镁铝尖晶石材料起到促进作用;在烧结过程中,产物的晶胞常数和晶胞体积都经历先变大后...     

预处理铝灰制备镁铝尖晶石研究

采用铝灰制备耐火材料是其高附加值资源化利用的一个方向,以预处理后的无害化铝灰为主要原料,利用烧结法合成镁铝尖晶石材料。借助XRD、SEM及EDS等对烧结试样的晶型组成及微观形貌进行了分析。结果表明:利用预处理后铝灰添加部分氧化镁可制备出物理性能优良的耐火材料,烧结后的主要物相为镁铝尖晶石,烧结温度对产品性能影响较大,适宜的烧结温度为1 650℃。     

氧化铝、氧化铬对方镁石-尖晶石材料抗钢水侵蚀性的影响

以电熔镁砂和高纯尖晶石作为主体原料,研究氧化铝、氧化铬两种添加剂对方镁石-尖晶石材料抗钢水侵蚀性的影响。首先针对原料性质对试样进行高压成形、高温烧成处理,烧后试样利用感应炉炼钢机理进行抗钢水侵蚀性试验。利用反光显微镜对侵蚀后试样进行显微观察,结果发现：加入Al2O3与Cr2O3有利于方镁石-尖晶石材料基质中镁铝尖晶石和...     

添加氧化铈对反应烧结制备镁铝尖晶石材料性能的影响

为了进一步提高高品质钢冶炼用镁铝尖晶石耐火材料的关键性能,以电熔镁铝尖晶石、轻烧氧化镁和白刚玉为原料,镁铝溶胶为结合剂,氧化铈为添加剂,采用反应烧结工艺成功制备了镁铝尖晶石材料.系统研究了氧化铈添加量(质量分数,0、3％,6％、9％和12％)对合成镁铝尖晶石材料显气孔率、体积密度、线收缩率、体积收缩率、常温耐压强度和抗...     

稀土氟化镧对多孔铝的性能影响研究北大核心

采用添加造孔剂的方法制备多孔铝试样。研究烧结温度和稀土氟化镧含量对多孔铝材料的性能影响。结果表明,烧结温度为600℃时多孔铝材料的烧结性能最佳;稀土氟化镧的适量加入可以提高多孔铝的力学性能;稀土氟化镧添加量为0.5%时,多孔铝材料的抗压强度和弹性模量最佳,分别为52.4 MPa和1.56 GPa。     

CeO_2对水泥窑用方镁石-复合尖晶石砖结构与性能的影响

以高纯镁砂、铁铝尖晶石、高铁镁砂为原料制备出了方镁石-复合尖晶石砖,研究了CeO_2对复合尖晶石砖结构与性能的影响。通过XRD及SEM检测试样的矿物相和显微结构,利用X’Pert Plus软件计算各试样中主晶相方镁石相的晶格常数,得出如下结论,随着CeO_2含量增加,试样的各项指标均增加;CeO_2与MgO生成固溶体,使MgO晶格常数增加,缺陷浓度增加,烧结趋动力增加,促进了试样的烧结,用半定量法计算有2%CeO_2剩余,剩余CeO_2存在于方镁石晶间,促进了材料的直接结合。     

镁铝尖晶石质耐火材料的合成

以MgAl2O4为骨料,MgO和Al2O3为基质料,通过固相烧结法合成了镁铝尖晶石质耐火材料,考察了原料组成、骨料粒度和成型压力对一步烧结法合成镁铝尖晶石烧结性能的影响.结果表明,随着基质料含量的增加和骨料粒度的增大,试样的线变化率和显气孔率逐渐增大;随着成型压力的增加,试样的显气孔率明显减小,线变化率增加.以镁铝尖晶石(粒度＜177μm)为骨料,按镁铝尖晶石,氧化镁,氧化铝的摩尔比为20:40:40配料,在200MPa压力下成型,可以获得显气孔率较低、线变化率适宜的镁铝尖晶石质耐火材料.     

普通镁质浇注料原料优化配置的试验研究

采用棕刚玉、中档镁砂、电熔镁砂等为主要原料,设计5组配方,按照浇注料制备工艺制成试样并分别进行性能表征.以中档镁砂为骨料,通过加入棕刚玉优化配置制备镁质耐火浇注料试样.通过检测试样的高温抗折强度、常温性能、1 550℃烧后性能、热膨胀和抗渣渗透性等性能优选最佳试验方案.结果表明:随着棕刚玉加入量增加,镁铝尖晶石的生成量...     

稀土氟化镧对多孔铝的性能影响研究

采用添加造孔剂的方法制备多孔铝试样。研究烧结温度和稀土氟化镧含量对多孔铝材料的性能影响。结果表明,烧结温度为600℃时多孔铝材料的烧结性能最佳;稀土氟化镧的适量加入可以提高多孔铝的力学性能;稀土氟化镧添加量为0.5%时,多孔铝材料的抗压强度和弹性模量最佳,分别为52.4 MPa和1.56 GPa。     

二次铝灰烧制镁铝尖晶石固相反应动力学及材料耐水蚀性能

以再生铝行业二次铝灰为主要原料,开展二次铝灰烧结制备镁铝尖晶石材料的研究。材料物相分析表明:二次铝灰可以烧结制备镁铝尖晶石材料。根据适宜的原料配比,在不同温度条件下烧结制备材料,进一步探讨烧结温度对材料耐水蚀性能的影响。二次铝灰烧结制备镁铝尖晶石材料的晶化反应表观活化能E_a=104.54 kJ/mol。在1 200~1 500 ℃烧结3 h,材料水化反应动力学方程依次为:（1-（1-5.76η）1/2）2=kt,（1-（1-6.15η）1/2）2=kt,（1-（1-6.43η）1/2）2=kt和（1-（1-6.34η）1/2）2=kt;1 400 ℃烧结3 h,材料水化率为8.83%,达不到高耐水性材料标准（0.2%）要求。      

Effects of Sm2O3 addition on sintering behavior of pre-synthesized magnesia-rich magnesium aluminate spinel

The effects of Sm₂O₃ as an additive on the densification of a pre-synthesized magnesia-rich spinel were investigated. The sintering behavior of the material was characterized by analyzing its dilatometric characteristics, linear shrinkage, bulk density, apparent porosity, phase structure, and microstructure. Moreover, the cold modulus of rupture (CMOR) and microhardness of the spinel were measured. The results show that samarium oxide reacts with the spinel to form SmAlO₃ (a rare-earth aluminate) to improve the sintering performance and mechanical properties of the spinel. The formation of magnesite phases decreases the rupture strength of the spinel. However, this MgO phase is inlaid in spinel grains boundary, has a pinning effect which can improve the sinterability of the spinel.     

钢中镁铝尖晶石夹杂物热力学分析

本文利用一阶和二阶相互作用系数以及对Mg-Al尖晶石固溶体采用内插法的活度取值,并基于吉布斯自由能最小原理利用C++编写热力学程序,计算得到Mg-Al-O的热力学优势区域图。特别分析了Mg-Al尖晶石的稳定区域与氧含量和温度之间的关系,为进一步深入研究Mg-Al-O系脱氧方式下MgO·Al_2O_3夹杂物行为特征提供理论依据。     

Effect of Rare Earths on Hot Cracking Resistant Property of Mg-Al Alloys

The effect of rare earths （RE） ranging from 0.1% to 1.2%（mass fraction） on hot cracking resistant property of Mg-Al alloys was investigated. The results show that hot cracking resistant property of Mg-Al alloys remarkably declines with an increase of RE addition. The causes of the decline are as follows： First, grain coarsening of Mg-Al alloys caused by RE addition reduces the fracture strain required for hot crack initiation. Second, RE reduces the eutectic microstructure of Mg- Al alloys, and as a result, shortens the time that the feeding channel remains open, making it difficult to feed the alloy. Furthermore, RE elevates the eutectic reaction temperature, which leads to the decrease in the strength of the interdendritic liquid film at the late stage of solidification. Third, when a-Mg dendrites form continuous skeletons, the interdendritic Al11 RE3 phase tends to block the feeding channels and increases the difficulty of feeding. Last, the shrinkage ratio discrepancy between Al11RE3 phases and α-Mg matrix is prone to cause shrinkage stress and promote hot crack initiation.     

Characteristic Analysis of Solidified Crust for Basic Tundish Flux With Al-Killed Steel Casting

The solidified crust was harmful to Al-killed steel casting using a basic tundish flux. After sampling from an actual tundish, XRD, SEM and EDX examinations were carried out to analyze the microstructure of solidified crusts. The conclusions were obtained as follows: main crystallization phases existing in tundish crust were Ca12A14 O33, Ca2SiO4 and a little spinel; spinel and Ca2SiO4 distributed between the grain boundaries of Ca12A14O33,which increased the connection strength of crystallization phases by pinning grain boundary, density or hardness of solidified crust maybe also significantly increases; when initial composition of tundish flux was located in spinel region of CaO-SiO2-Al2O3-10%MgO phase diagram, it was easier to precipitate spinel from molten slag; three approaches of spinel formation in flux were summarized. When flux was saturated with magnesia on the metal/flux interface, MgO in flux was reduced by dissolved aluminum and then formed spinel. On the interface of steel/refractory,with feasible aluminum content, it was also easy to form spinel, and spinel inclusions will be floated and captured bytundish flux.     

Selective Separation of Fe-Concentrates in EAF Slags Using Mechanical Dissimilarity of Solid Phases

We sought to develop an optimized particle size-dependent separation method to lower the Fe content of pulverized glass-ceramic electric arc furnace (EAF) slag for its improved reclamation as construction materials by considering the structures and the mechanical behavior of the discrete solid phases. After an isothermal crystallization process to enhance the spinel growth, the Vickers hardness and fracture toughness were measured on the spinel and amorphous phases separately from the solidified slag using indentation methods. The characteristic differences in the hardness of the phases were magnified when this glass-ceramic composite was isothermally crystallized. The hardness of the spinel was observed to be lower in slags with higher Fe_tO/Al₂O₃ mass ratios due to the triclinic unit cell expansion of the spinel, whereas the hardness of the amorphous phase decreased with increasing isothermal period because of the structural transformation into a silicate-dominant network. Fracture toughness could be calculated based on the hardness and crack length, where the Young’s modulus was determined using nanoindentation. The amorphous phase with a lower Fe content and lower fracture toughness resulted in finer powder distribution after pulverization, allowing better separation of the primary crystalline spinel containing higher Fe content from the Fe-deficient amorphous phase according to the particle size.     

Microscopic and Spectroscopic Characterization of Aluminosilicate Waste Form with Cs/Sr/Ba Loading Using Scanning Electron Microscopy,Transmission Electron Microscopy,and X-Ray Diffraction

An aluminosilicate waste form has been proposed for the storage and disposal of cesium and strontium isolated from recycled nuclear fuel. To examine the impact of sintering temperature on the waste form product, thermal analysis (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)) was used to identify key transition temperature ranges. Samples were produced in each temperature range to examine the impact on phase formation and microstructure. Examination of the synthesized materials by X-ray diffraction (XRD) confirmed the formation of the expected Cs- and Sr-aluminosilicate crystalline phases. However, microscopic characterization by scanning electron microscopy (SEM) revealed a spongelike, glassy morphology with high porosity and no observed crystallinity. This discrepancy was investigated by transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), which identified the presence of discrete, submicron, crystalline phases within the bulk amorphous matrix. Elemental analysis by energy-dispersive X-ray (EDX) indicated that the strontium and barium were incorporated into the crystalline phase, while the cesium was incorporated into the amorphous matrix. Further analysis of samples synthesized without barium or strontium allowed for the identification of submicron crystalline phases within the amorphous matrix, identifying the source of the cesium aluminosilicate crystal peaks in the XRD patterns, with elemental analysis showing that the cesium was present in both the crystalline inclusions and the amorphous bulk phase.     

炉渣组分对CaO-MgO-Al2O3-Si2O-Cr2O3-FeO-TiO2渣系中铬尖晶石相析出影响的热力学

根据熔体的非平衡凝固理论,采用热力学数据库Factsage7.1模拟计算研究了不同碱度、MgO以及FeO的质量百分数对不锈钢渣微晶玻璃的基础玻璃成分CaO-MgO-Al₂O₃-SiO₂-Cr₂O₃-FeO-TiO₂体系中尖晶石矿相开始析出温度、种类及其析出量的影响规律。计算结果表明,碱度为0.47时,析出矿物相主要包括透辉石、钙长石以及尖晶石等相,其中透辉石为主要物相。尖晶石相为高温析出相,主要由MgCr₂O₄和FeCr₂O₄组成。在不同碱度条件下,总尖晶石开始析晶温度随着MgO质量百分数的增加而增加。当w（C）/w（S）为0.47,氧化镁的质量百分数小于10.52%时,镁铬尖晶石和铁铬尖晶石的析出量随着氧化镁质量百分数的增加而增加。氧化镁的质量百分数大于10.52%时,随着氧化镁质量百分数的增加,镁铬尖晶石析出量增加,而铁铬尖晶石的析出则逐渐减少。FeO的质量百分数小于7.57%时,镁铬尖晶石和铁铬尖晶石的析出量随着氧化铁含量的增加而增加,FeO的质量百分数大于7.57%以后,随着氧化铁含量的增加,镁铬尖晶石析出量减少,铁铬尖晶石析出量增加。     

轻烧菱镁石粉对低硅含镁球团矿孔隙和强度的影响

本文研究了向两种铁精粉和膨润土中添加不同质量分数的轻烧菱镁石粉对球团矿孔隙、强度和物相的影响.研究结果表明:轻烧菱镁石粉平均粒径较小,结晶水和MgCO₃质量分数高(分别为3.94%和8.59%),对球团矿性能影响较大.轻烧菱镁石添加量由1.5%增加到3.5%时,焙烧球孔隙率由11.12%升高到15.95%,大气孔(孔径大于5μm)的体积分数由8.94%升高到36.61%,且分布均匀化程度降低;同时,球团矿变得“疏松”,固结指数由60.45%降低到43.00%,预热球和焙烧球强度分别降低79.3N和247.6N;球团矿中的铁酸镁和磁铁矿相质量分数增加,赤铁矿相再结晶减弱.适量增加球团矿中轻烧菱镁石粉的配比,可使球团矿孔隙率、大气孔和高熔点物相增多,进而提高球团矿的还原和软熔滴落等性能.     

钒渣焙烧过程中物相的矿物学特征探讨

为了探讨钒渣焙烧过程中物相的矿物学特征,试验采用偏光显微镜、扫描电镜及能谱仪对不同温度下钒渣钙化焙烧过程中产生的6组钙盐进行分析。偏光显微镜下初步鉴定结果表明,焙烧过的6组钒渣中主要含有钒尖晶石、氧化铁、钒酸钙、铁板钛矿等主要物相;扫描电镜图像表明:随着温度的升高,主要含钒物相钒尖晶石逐渐分解为氧化铁、铁板钛矿和钒酸钙;而通过能谱的成分分析表明:低价钒和铁的含量在减少,而高价钒和铁的含量在增加。因此通过考察钒渣焙烧过程中形貌和晶型的变化规律,可得出钒酸钙含量最高的焙烧温度,这可以作为浸出钒酸钙工艺中钒转浸率高低的一个重要指标,为其工艺流程参数的制定提供理论依据。     

Effect of microstructure on mechanical properties of as-cast Mg-Al alloys

The mechanical properties of Mg-Al alloys are mainly determined by the microstructure, i.e., the amount and morphology of the phases, but also by the presence of defects arising from the melt handling and casting process. In order to obtain information about the isolated effect of the microstructure, it is, therefore, necessary to minimize the amounts of defects. In this study, this has been achieved by remelting and solidifying the alloys in a gradient furnace. The drawing rate was varied from 0.3 to 6 mm/s, which yielded a wide variety of microstructures. Three samples were produced for each parameter set, in order to have a statistical basis for the evaluation. The results showed that homogeneous and reproducible samples could be produced, and that the tensile properties obtained showed a very small scatter. The effects of microstructural parameters such as grain size, secondary dendrite arm spacing (SDAS), eutectic fraction, and eutectic morphology on the yield strength, ultimate tensile strength (UTS), fracture elongation, and hardness has been investigated.