CaO-SiO2-MgO-Al2O3四元渣系Al2O3活度预测模型

高炉渣系各组元活度对高炉冶炼和产品质量具有重要的影响作用. 基于分子-离子共存理论,建立CaO-SiO₂-MgO-Al₂O₃四元渣系Al₂O₃活度预测模型;结合试验测定值对其进行验证与修正,最终建立了修正的CaO-SiO₂-MgO-Al₂O₃四元渣系Al₂O₃活度预测模型;同时,依据模型计算结果探究R(w(CaO)/w(SiO₂)),w(MgO)/w(Al₂O₃)和w(Al₂O₃)对Al₂O₃活度的影响. 研究结果表明:修正后的CaO-SiO₂-MgO-Al₂O₃四元渣系Al₂O₃活度预测模型具有较高的预测精度,能够很好地预测熔渣Al₂O₃活度;当w(MgO)/w(Al₂O₃)=0.40,w(Al₂O₃)=20%时,随着R增加,Al₂O₃活度逐渐减小;当R=1.25,w(Al₂O₃)=20%时,随着w(MgO)/w(Al₂O₃)增加,Al₂O₃活度逐渐减小;当w(MgO)/w(Al₂O₃)=0.40,R=1.25时,随着w(Al₂O₃)增加,Al₂O₃活度逐渐增大.     

用于45#钢丝拉拔加工的叠层陶瓷拉拔模具磨损分析

为研究45#钢丝拉拔加工过程中受力和Al₂O₃-TiC/Al₂O₃-TiC-CaF₂叠层陶瓷拉拔模具磨损情况,采用真空热压烧结方式制备Al₂O₃-TiC/Al₂O₃-TiC-CaF₂叠层陶瓷拉拔模具,并将其固定在万能拉伸试验机上进行钢丝拉拔实验。 采用三维造型软件SolidWorks建立钢丝坯料和拉拔模具的有限元模型,通过有限元模拟软件对钢丝拉拔成形过程进行仿真分析,得到45#钢丝在变形过程中的轴向应力、应变以及拉拔力的变化情况。 扫描电镜（SEM）及能量弥散X射线谱（EDS）观察拉拔模具磨损后的微观形貌。 结果表明:叠层陶瓷拉拔模具工作区的Al₂O₃-TiC-CaF₂材料层比Al₂O₃-TiC材料层磨损严重,Al₂O₃-TiC-CaF₂材料层的固体润滑膜被拖覆到Al₂O₃-TiC材料层,模具整体具有自润滑性能。 实际测量拉拔力与公式计算所得拉拔力相吻合,模拟所得拉拔力比实际测量拉拔力小。      

Effect of aluminum oxide on the compressive strength of pellets

Analytical-reagent-grade Al₂O₃ was added to magnetite ore during the process of pelletizing, and the methods of mercury intrusion, scanning electron microscopy, and image processing were used to investigate the effect of Al₂O₃ on the compressive strength of the pellets. The results showed that, as the Al₂O₃ content increased, the compressive strength of the pellets increased slightly and then decreased gradually. When a small amount of Al₂O₃ was added to the pellets, the Al₂O₃ combined with fayalite (2FeO·SiO₂) and the aluminosilicate (2FeO·2Al₂O₃·5SiO₂) was generated, which releases some iron oxide and reduces the inhibition of fayalite to the solid phase of consolidation. When Al₂O₃ increased sequentially, high melting point of Al₂O₃ particles hinder the oxidation of Fe₃O₄ and the recrystallization of Fe2O3, making the internal porosity of the pellets increase, which leads to the decrease in compressive strength of the pellets.     

w(CaO)/w(Al2O3)对钙铝基保护渣结晶性能的影响

利用热丝法测试技术,结合扫描电镜和能谱分析,研究了不同w(CaO)/w(Al₂O₃)条件下钙铝基保护渣的结晶性能.结果表明,较低w(CaO)/w(Al₂O₃)下,保护渣结晶物相为LiAlO₂和CaO·Al₂O₃.其析出由渣中的Li⁺离子和Ca²⁺离子分别对高聚合度铝氧四面体结构的电荷补偿所致.而且,Li⁺离子优先参与,LiAlO₂优先析出.较高w(CaO)/w(Al₂O₃)下,结晶物相转变为LiAlO₂和3CaO·Al₂O₃.其变化原因为,CaO相对质量分数提高,保护渣聚合度降低,Ca²⁺离子和低聚合度铝氧四面体结构单元Q²结合而形成3CaO·Al₂O₃并析出.随着w(CaO)/w(Al₂O₃)由1.13提高至1.82,钙铝基保护渣析晶能力先减弱然后增强.在w(CaO)/w(Al₂O₃)为1.50和1.82时分别具有最弱和最强的析晶能力.     

Formation mechanism of calcium hexaluminate

To investigate the formation mechanism of calcium hexaluminate (CaAl₁₂O₁₉, CA₆), the analytically pure alumina and calcia used as raw materials were mixed in CaO/Al₂O₃ ratio of 12.57:137.43 by mass. The raw materials were ball-milled and shaped into green specimens, and fired at 1300–1600°C. Then, the phase composition and microstructure evolution of the fired specimen were studied, and a first principle calculation was performed. The results show that in the reaction system of CaO and Al₂O₃, a small amount of CA₆ forms at 1300°C, and greater amounts are formed at 1400°C and higher temperatures. The reaction is as follows: CaO·2Al₂O₃ (CA₂) + 4Al₂O₃ → CA₆. The diffusions of Ca2+ in CA₂ towards Al₂O₃ and Al3+ in Al₂O₃ towards CA₂ change the structures in different degrees of difficulty. Compared with the difficulty of structural change and the corresponding lattice energy change, it is deduced that the main formation mechanism is the diffusion of Ca2+ in CA₂ towards Al₂O₃.     

Electrical conductivity optimization of the Na3AlF6-Al2O3-Sm2O3 molten salts system for Al-Sm intermediate binary alloy production

Metal Sm has been widely used in making Al-Sm magnet alloy materials. Conventional distillation technology to produce Sm has the disadvantages of low productivity, high costs, and pollution generation. The objective of this study was to develop a molten salt electrolyte system to produce Al-Sm alloy directly, with focus on the electrical conductivity and optimal operating conditions to minimize the energy consumption. The continuously varying cell constant (CVCC) technique was used to measure the conductivity for the Na₃AlF₆-AlF₃-LiF-MgF₂-Al₂O₃-Sm₂O₃ electrolysis medium in the temperature range from 905 to 1055℃. The temperature (t) and the addition of Al₂O₃ (W(Al₂O₃)), Sm₂O₃ (W(Sm₂O₃)), and a combination of Al₂O₃ and Sm₂O₃ into the basic fluoride system were examined with respect to their effects on the conductivity (κ) and activation energy. The experimental results showed that the molten electrolyte conductivity increases with increasing temperature (t) and decreases with the addition of Al₂O₃ or Sm₂O₃ or both. We concluded that the optimal operation conditions for Al-Sm intermediate alloy production in the Na₃AlF₆-AlF₃-LiF-MgF₂-Al₂O₃-Sm₂O₃ system are W(Al₂O₃) + W(Sm₂O₃)=3wt%, W(Al₂O₃):W(Sm₂O₃)=7:3, and a temperature of 965 to 995℃, which results in satisfactory conductivity, low fluoride evaporation losses, and low energy consumption.     

纳米Al2O3/膨胀石墨的制备及吸附性能

针对Al₂O₃和膨胀石墨（EG）单独作为吸附剂时存在不易分离和吸附性能较差等问题, 以EG为骨料、  Al(NO₃)₃9H₂O为铝源、  NH₃H₂O为沉淀剂、  无水乙醇为分散剂制备纳米Al₂O₃/EG, 并用Fourier变换红外光谱(FT-IR)、  X射线衍射（XRD）和扫描电子显微镜（SEM）等方法对吸附剂进行表征; 以Al₂O₃/EG为吸附剂, 对刚果红溶液进行吸附, 并考察加氨水方式、  活化温度、  活化时间、  Al₂O₃与EG质量比和浸渍时间对吸附性能的影响. 结果表明：  纳米级Al₂O₃成功负载在EG上; 逐滴加入氨水、  活化温度170 ℃、  活化时间3 h、  Al₂O₃与EG质量比为0.06∶1、  浸渍时间为20 min时, 吸附效果最好, 脱色率约为86%;  Al₂O₃/EG明显优于EG的吸附效果, 其脱色率是EG的2倍以上; 与Al₂O₃相比, 在吸附后的分离操作中, Al₂O₃/EG更易分离.     

Al2O3含量变化对CaO–SiO2–Cr2O3–Al2O3熔渣粘度及结构的影响

熔渣粘度对冶炼过程中渣金反应的传质有着至关重要的作用，适当的熔渣粘度能够有效促进渣金反应，提升传质效率。为了促进含铬熔渣中铬的回收利用，本文使用柱体旋转法研究了Al₂O₃含量变化对CaO-SiO₂-Cr₂O₃-Al₂O₃渣粘度和结构的影响规律。熔渣在高温下表现出良好的牛顿流体行为。当Al₂O₃含量从0%增加到10wt%时，酸性渣的粘度首先从0.825增加到1.141 Pa·s，然后当Al₂O₃含量进一步增加到15wt%时，粘度降低到1.071 Pa·s。当Al₂O₃含量从0增加到15wt%时，碱性炉渣的粘度首先从0.084增加到0.158Pa·s，然后当Al₂O₃含量进一步增加到20wt%时，粘度降低到0.135 Pa·s。此外，含Cr₂O₃的炉渣比无Cr₂O₃的炉渣需要更少的Al₂O₃才能达到最大粘度；对于酸性和碱性炉渣，熔渣粘度达到最大值所需的Al₂O₃含量分别为10%和15%。熔渣的活化能变化规律与粘度结果一致。拉曼光谱表明，熔渣中仅有少量Al₂O₃时，Al以[AlO₄]四面体形式出现，随着Al₂O₃含量的逐渐增加，[AlO₄]四面体被[AlO₆]八面体所取代，对硅酸盐结构的分峰解谱结果也与粘度结果一致。     

Sintering Behavior and Microstructure of diphasic β-Sialon/Al2O3 Composites

Six compositions with different ratio of β-Sialon/Al₂O₃ were synthesized from Al₂O₃, Si₃N₄ and SiO₂ by sintering with 3%Y₂O₃(mass fraction) as addition under the cover with powders of SiC+C and at nitrogen atmosphere. Theeffects of atmosphere, sintering temperature and composition on the sintering behavior were studied. The results showedthat the composites reached the best sintering behavior with the highest density about 92% at 1 650℃ under the weakreduction atmosphere. Finally the relative density of diphasic β-Sialon and β-Sialon/Al₂O₃ composites were studied andpredicted using ANN (Artificial Neural Networks) method and the results were experimental examined by fore randomsamples.     

In situ reaction mechanism of MgAlON in Al-Al2O3-MgO composites at 1700℃ under flowing N2

The Al-Al₂O₃-MgO composites with added aluminum contents of approximately 0wt%, 5wt%, and 10wt%, named as M₁, M₂, and M₃, respectively, were prepared at 1700℃ for 5 h under a flowing N₂ atmosphere using the reaction sintering method. After sintering, the Al-Al₂O₃-MgO composites were characterized and analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that specimen M₁ was composed of MgO and MgAl₂O₄. Compared with specimen M₁, specimens M₂ and M₃ possessed MgAlON, and its production increased with increasing aluminum addition. Under an N₂ atmosphere, MgO, Al₂O₃, and Al in the matrix of specimens M₂ and M₃ reacted to form MgAlON and AlN-polytypoids, which combined the particles and the matrix together and imparted the Al-Al₂O₃-MgO composites with a dense structure. The mechanism of MgAlON synthesis is described as follows. Under an N₂ atmosphere, the partial pressure of oxygen is quite low; thus, when the Al-Al₂O₃-MgO composites were soaked at 580℃ for an extended period, aluminum metal was transformed into AlN. With increasing temperature, Al₂O₃ diffused into AlN crystal lattices and formed AlN-polytypoids; however, MgO reacted with Al₂O₃ to form MgAl₂O₄. When the temperature was greater than (1640 ±10)℃, AlN diffused into Al₂O₃ and formed spinel-structured AlON. In situ MgAlON was acquired through a solid-solution reaction between AlON and MgAl₂O₄ at high temperatures because of their similar spinel structures.     

镁铝比对高炉渣脱硫能力的影响

利用双层石墨坩埚,模拟铁液滴下穿过炉渣的过程,主要研究渣中Mg O,Al2O3质量分数对炉渣硫质量分数的影响,探索镁铝比与高炉渣硫质量分数的关系.结果表明渣中Mg O质量分数由6%提高到12%时,炉渣脱硫能力逐渐提高,由12%提高到14%,脱硫能力逐渐降低;渣中Al2O3质量分数由9%提高到15%时,炉渣脱硫能力逐渐降低,但降低幅度较小,当Al2O3质量分数由15%提高到17%时,炉渣脱硫能力大大降低;Mg O质量分数小于12%,Al2O3质量分数小于15%,提高炉渣镁铝比可以显著提高炉渣脱硫能力.     

V2O5/ZrO2-Al2O3催化甲醇选择性氧化合成二甲氧基甲烷

采用浸渍法制备了V₂O₅质量分数不同的V₂O₅/Al₂O₃催化剂,采用Zr对Al₂O₃载体进行改性并应用于催化甲醇选择性氧化制备二甲氧基甲烷(DMM)的反应中。经X-射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见分光光谱(UV-Vis)、傅里叶变换红外光谱(FTIR)、拉曼光谱(Raman)、N₂吸附-脱附(BET)、H₂程序升温还原(H₂-TPR)和NH₃程序升温脱附(NH₃-TPD)表征分析,结果表明:与单一Al₂O₃负载的钒基催化剂相比,Zr改性提高了钒氧化物的分散性与稳定性,加强了催化剂中各组分间的相互作用,有效调变了催化剂的酸性和氧化性,进而提高了DMM的选择性。考察了反应条件对甲醇选择性氧化制备DMM的影响,最佳反应温度为175 ℃,经20%V₂O₅/12%ZrO₂-Al₂O₃催化氧化,甲醇转化率为27.9%,DMM选择性为99.9%。     

表面活性剂对Al2O3基泡沫陶瓷性能的影响

采用三维网状的聚氨酯有机泡沫体作为载体制备Al₂O₃基泡沫陶瓷。选用了不同质量分数的木质素磺酸钙溶液作为表面活性剂对泡沫进行了表面活化,研究表面活性剂加入量对氧化铝基小孔泡沫陶瓷过滤器性能的影响。研究表明:随着活化剂质量分数的增大,试样的抗压强度和热震稳定性先升后降,当活化剂木质素质量分数为1.0%时,泡沫陶瓷性能最好,此时强度达到1.147 MPa,热震循环次数达到11次。     

Ti对Sn-xTi/Al2O3润湿性的影响

针对添加活性元素Ti有利于改善金属/Al₂O₃体系的润湿性、但润湿机制仍不明确问题,研究采用改良座滴法,研究了熔融Sn-(原子分数为0%、2%、5%)Ti合金在973~1 273 K高真空中在Al₂O₃表面的润湿性.研究结果表明:Ti原子分数的增加会显著改善Sn-xTi/Al₂O₃体系的润湿性,润湿性改善的原因在于Ti在界面处的吸附降低了固/液界面自由能,而并非界面析出的反应产物.对此结论,应用吸附的统计热力学模型验证了实验结果,并证明Sn-xTi/Al₂O₃体系的铺展动力学在很大程度上受控于吸附动力学.     

MgCl_2-KCl-AlF_3-(La_2O_3)熔盐体系电解制备Al-Mg-La中间合金

在质量比为41.5∶48.5∶10的MgCl_2-KCl-AlF3熔盐体系中加入质量分数为0.6%La_2O_3,利用电解法制备了Al-Mg-La合金.用ICP-OES(电感耦合等离子体光谱仪)和XRD进行了合金的组成和物相分析.研究结果表明,在电解温度800℃,阴极电流密度6.92A/cm2,槽电压5.3~5.4V,电解时间为1h的条件下,电流效率为86.2%,得到的合金主相为α-Mg基体、β-Al12Mg17相与Al11La3相.高的阴极电流密度有利于合金中镁含量的增加.     

IF钢生产过程非金属夹杂物行为研究

对首钢京唐生产IF钢的同一浇次前2炉的RH精炼、镇静和中间包浇铸过程进行了系统取样,并利用Aspex自动扫描电子显微镜分析统计了钢中夹杂物的成分、尺寸等信息.研究发现,Al2O3-TixO复合夹杂物在Ti合金化和二次氧化的情况下都会生成,并随着精炼的进行逐渐转变为Al2O3,这与热力学计算的结果一致;而Al2O3可以作为Al2O3-TixO的形核核心,形成Al2O3-TixO包裹Al2O3的夹杂物,并且在Al2O3-TixO转变为Al2O3的过程中会导致钢滴进入夹杂物内部,从而形成Al2O3包裹钢滴的夹杂物.     

Co_2O_3添加量对高频低功耗MnZn功率铁氧体性能的影响

采用氧化物陶瓷工艺制备高频低功耗MnZn功率铁氧体,研究不同Co2O3添加量对高频低功耗MnZn功率铁氧体微观结构及磁性能的影响。结果表明:适当的Co2O3添加可以提高样品的起始磁导率,并在宽温范围内具有低功耗特性;同时,适当的Co2O3添加降低了材料的剩磁,可改善材料的叠加特性。     

掺杂氧化物对ZrO_2相结构稳定性及烧结性能的影响

采用共沉淀-凝胶方法,通过低温煅烧和中温烧结,分别制备了Y2O3、Al2O3掺杂的ZrO2粉体和陶瓷;利用X射线衍射分析、扫描电镜和透射电镜等手段,对掺杂不同氧化物ZrO2相结构的稳定性及烧结性能进行了研究.结果表明:在ZrO2中掺杂摩尔分数5%的Y2O3或者Al2O3,870℃焙烧15min的粉体前者为立方相,后者为四方相;它们的粉体成型后经1400℃烧结4h,前者在室温下仍能保持立方相,后者却得到的是单斜相;在焙烧粉末中,Al3+固溶到ZrO2的晶格中,对ZrO2四方相晶格起到稳定作用,而在其陶瓷中,Al3+从ZrO2的晶格中扩散到晶界,对ZrO2不起稳定作用,只起促进烧结和细化晶粒的作用.