MgAl2O4透明陶瓷粉体的研究进展

透明镁铝尖晶石陶瓷的制备,对粉体有特殊的要求.高纯、超细、分散性好、高活性的粉体是制备镁铝尖晶石透明陶瓷的首要条件.本文以制备镁铝尖晶石透明陶瓷为目标,从粉体的纯度和粉体颗粒特征两方面分析了粉体的性能对制备透明镁铝尖晶石陶瓷的影响,介绍了几种可用于制备镁铝尖晶石透明陶瓷粉体的方法,分析比较了每种方法的优缺点.     

金属元素掺杂尖晶石型镓酸镁的研究进展

镓酸镁（MgGa₂O₄）是一种尖晶石结构的镓酸盐,由氧化镁（MgO）和氧化镓（Ga₂O₃）复合而成,具有良好的介电性能、光学性能、耐辐射性能和高温稳定性等特点。由于其在蓝色可见光区存在自激活的发射带,在发光研究中受到了广泛的重视。稀土、过渡金属元素掺入后可改变其能量传递过程,提高发光效率,拓宽发光范围,应用于显示、照明、医学诊断及激光器等众多领域,是一种具有良好应用前景的材料。综述了近年来铬（Cr）、钴（Co）、锰（Mn）、镝（Dy）、铕（Eu）等金属元素单掺杂、共掺杂镓酸镁在结构与光学性能等方面的研究进展,分析了当前研究中所存在的主要问题,并对今后金属元素掺杂镓酸镁发光材料的研究与开发应用进行了展望。     

过渡金属离子掺杂石榴石基荧光材料的晶格调控、光谱特性及应用

石榴石基荧光材料具有多格位掺杂、离子掺杂选择范围宽、能量传递效率高等突出优势，是无机发光材料研究的热点；过渡金属离子在光谱可调谐性、原料来源广泛性等方面显著优于稀土离子；然而，其在发光效率、价态调控特别是在复杂晶格结构中的发光机理尚存在挑战，吸引了众多研究者关注。本文综述了过渡金属离子特别是Cr³⁺、Mn^2+/4+在石榴石结构荧光材料中的光谱特性和发光行为，介绍了该类材料在固态照明与显示、生物医学成像、植物照明等前沿领域的研究与应用现状。     

固溶反应对MA-Al2O3材料结构和性能的影响

以电熔镁铝尖晶石为主要原料并加入少量烧结刚玉细粉部分替代尖晶石细粉,或以白刚玉为主要原料并加入少量电熔镁铝尖晶石细粉替代白刚玉细粉,制备了两组MA-Al₂O₃材料。研究刚玉与镁铝尖晶石之间的固溶反应对材料性能及显微结构的影响。结果表明：1)在两组材料中均发生了固溶反应,使得镁铝尖晶石的富铝程度增大,镁铝尖晶石中的氧化铝含量(w)由约76%增加到80%以上,从而加强了试样骨料与基质的结合,减少结构缺陷,改善了材料的高温性能;2)在以镁铝尖晶石为主要原料的MA-Al₂O₃材料中,加入烧结刚玉可使其常温耐压强度增大,改善其高温抗蠕变性和抗热震性;3)在以白刚玉为主要原料的MA-Al₂O₃材料中,加入镁铝尖晶石细粉,其常温耐压强度、高温抗蠕变性和高温抗折强度均有大幅度提高。     

La2O3对镁铝尖晶石透明陶瓷致密化及其性能的影响

镁铝尖晶石透明陶瓷兼具了良好的光学和力学性能,在军、民两用领域有着广泛的实际和潜在应用前景。由于其致密化速率低,在烧结过程中往往需要引入烧结助剂。稀土倍半氧化物熔点高,高温不易挥发,近些年被证实可以促进镁铝尖晶石陶瓷的致密化,但其促烧机理尚不明确。本文以高纯商业化镁铝尖晶石粉体为原料,La₂O₃为烧结助剂,采用无压预烧结合热等静压烧结,制备镁铝尖晶石透明陶瓷,通过XRD、SEM、紫外-可见分光光度计、万能试验机等测试手段对其致密化过程及其力学和光学性能进行表征和分析,研究了La₂O₃对镁铝尖晶石透明陶瓷致密化过程的影响规律和作用机制。结果表明,La₂O₃通过与尖晶石反应或固溶产生晶格畸变,增加缺陷浓度,从而起到促进致密化的作用,一定程度上降低了预烧温度和热等静压温度。对于190 MPa、1 500 ℃热等静压烧结3 h的样品,La₂O₃掺杂可以显著提高紫外区域的透过率;同时,La偏析到晶粒表面,抑制了尖晶石晶粒的生长,从而提高了样品的力学强度。掺杂0.05%(质量分数)La₂O₃样品较未掺的样品,400 nm处透过率从63%提高到81%,弯曲强度从263.7 MPa提高至319.0 MPa,断裂韧性从1.69 MPa·m^1/2提高至1.82 MPa·m^1/2。     

不球磨无机粉体发光材料制备技术进展

综述了不球磨无机粉体发光材料制备技术进展,着重总结了稀土掺杂型无机粉体发光材料的制备方法。介绍了溶胶-凝胶法,燃烧合成法,微波合成法,共沉淀法,喷雾热解法,水热合成法,气相反应合成法和微乳液法等制备方法。对比总结了每种合成方法的优缺点,并对其未来发展趋势作了展望。综述国内外研究报告和论文82篇。     

熔铸锆铬刚玉耐火材料抗硼硅酸盐熔体的侵蚀行为

Al₂O₃–ZrO₂–Cr₂O₃–SiO₂(AZCS)材料是一种新型熔铸耐火材料，该材料在高温、高侵蚀性条件下的抗侵蚀性能优于其他类型的电熔耐火材料。为了研究该材料对硼硅酸盐玻璃熔体的抗侵蚀行为，利用含B₂O₃质量分数约12%的硼硅酸盐玻璃固化体对AZCS材料在1 500℃条件下进行侵蚀试验。结果表明：AZCS材料在侵蚀后，按照侵蚀程度可划分为变质层、过渡层、中心层。中心层变化很小，该层仍存在大量的铝–铬固溶体和斜锆石相，只有少量新形成的镁铝尖晶石相；渗入材料的MgO与固溶体反应，在原位形成镁铝尖晶石，并部分取代原有位置上的铝–铬固溶体。在过渡层中镁铝尖晶石形成的量达到最大，铝–铬固溶体溶解消失，该层存在的相为镁铝尖晶石相与斜锆石相；在变质层中基本只存在未被溶解的Cr₂O₃相，Cr₂O₃结构松散，呈蠕虫状形貌，铝–铬固溶体、斜...     

LiCoO2合成过程对镁铝尖晶石陶瓷侵蚀的研究

研究了LiCoO2合成粉体过程对镁铝尖晶石陶瓷的侵蚀,并探讨了相关侵蚀机制.研究结果显示,经历10次的LiCoO2粉体合成过程后,镁铝尖晶石陶瓷的平均被侵蚀深度仅约100μm;其侵蚀机制为:含锂化合物先于含钴化合物对镁铝尖晶石陶瓷进行侵蚀并形成LixMyOz(M=Al/Mg)化合物,含钴化合物进一步侵蚀渗透形成LixMyOx(M'=Al/Mg/Co)化合物并从LixMyOz(M=Al/Mg)化合物中析出.研究认为,用镁铝尖晶石陶瓷制备合成钴酸锂粉体用匣钵具有良好的抗侵蚀性能.     

掺杂对CeO2基电解质材料性能的影响研究进展

掺杂CeO₂基电解质是中低温固体氧化物燃料电池（SOFC）理想的电解质材料。首先阐述了掺杂CeO₂基电解质结构与性能的关系,接着介绍了金属离子掺杂对CeO₂基电解质晶体结构和电子结构的影响,重点综述了单元素掺杂和双元素掺杂对CeO₂基电解质性能的影响。通过分析得出：稀土金属元素单掺杂比碱土金属元素单掺杂更能显著提高CeO₂基电解质的导电性和可烧结性,但稀土氧化物的原料成本要远高于碱土氧化物;双元素掺杂比单元素掺杂具有更多的氧空位无序度和更小的氧离子迁移激活能,因此在提高CeO₂基电解质的离子电导率方面更有优势。总结了CeO₂基电解质材料的掺杂规律及构效关系,以期对制备出性能更加优异的CeO₂基电解质起到一定的指导作用。     

钛酸盐体系长余辉发光材料研究进展

钛酸盐基质长余辉发光材料具有稳定的物化性能,是一类新型的储能和环保型材料。综述了近年来钛酸盐体系长余辉发光材料的最新研究进展,总结了掺杂离子、基质种类、电荷补偿以及制备方法等对钛酸盐长余辉发光材料发光特性的影响,并提出了今后可能的研究和应用发展方向。     

Synthesis and densification of magnesium aluminate spinel: effect of MgO reactivity

Stoichiometric magnesium aluminate spinel was synthesized by reaction sintering of alumina with caustic and sintered magnesia. The volume expansion of 5–7% during MgAl₂O₄ formation was utilized to identify the starting temperature of spinel formation and densification by high temperature dilatometry. The magnesia reactivity was determined by measurement of crystallite size and specific surface area. Caustic magnesia and sintered magnesia behave differently vis-à-vis phase formation and densification of spinel. Densification of stoichiometric Mag-Al spinel was carried out between 1650 and 1750 °C. Attempts were made to correlate the MgO reactivity with microstructure and densification of spinel.     

MgO源对纳米η-Al2O3制备镁铝尖晶石的影响

分别以轻烧氧化镁粉、碳酸镁、分析纯氢氧化镁为MgO源,纳米η-Al₂O₃为原料(其摩尔比为1∶1),采用固相反应法制备镁铝尖晶石。研究不同MgO源对纳米η-Al₂O₃制备镁铝尖晶石的显气孔率、体积密度、物相组成、晶胞参数以及微观结构的影响。结果表明,随着烧结温度升高,三种MgO源与纳米η-Al₂O₃制得镁铝尖晶石试样的致密性逐渐升高。在1 600 ℃下,以氢氧化镁为MgO源与纳米η-Al₂O₃制得尖晶石试样的体积密度最大为3.296 g/cm³,显气孔率最低为1.9%,晶粒发育最好,晶粒尺寸约为3~5 μm。1 300 ℃时,三种MgO源与纳米η-Al₂O₃全部生成镁铝尖晶石,与以α-Al₂O₃为Al₂O₃源制备镁铝尖晶石的传统固相法相比,镁铝尖晶石的合成温度降低了100 ℃,可以降低镁铝尖晶石的成本,对镁铝尖晶石的应用具有实际意义。     

氮气气氛下Al对SiC-MgAl2O4复合材料物相和结构演变的影响

以SiC、MgAl₂O₄细粉为主要原料,分别添加质量分数为1%、3%、5%、7%、9%和12%的金属Al,置于流动氮气中,在1 500 ℃下保温5 h烧成得到SiC-MgAl₂O₄复合材料,对烧后试样进行XRD、SEM及EDS分析。结果表明,1 500 ℃高温烧结后,材料体系发生一系列复杂反应,试样中物相均以β-SiC、MgAl₂O₄、氮化物和sialon相为主。部分金属Al在高温下氮化形成氮化铝,并参与sialon相和MgAlON形成的反应。尖晶石则转变为富铝尖晶石和MgAlON两相共存。随着Al含量的增加,尖晶石中固溶铝含量达到极限时,析出α-Al₂O₃。Al含量的增加使得结合相Si-Al-O-N的形貌发生变化,由板带状向板柱状过渡,最终发育成形貌较为清晰的板层状。经SEM-EDS分析,sialon相中固溶一定量的Mg元素,为sialon多型体Mg-sialon相。     

镁铝双金属醇盐合成工艺的研究

介绍了镁铝双金属醇盐的合成方法,详细介绍和评述了乙醇镁铝、异丙醇镁铝、正丁醇镁铝、异丁醇镬铝等双金属醇盐的合成工艺。正丁醇镁铝、异丁醇镁铝可用来制备高纯镁铝尖晶石,也可以直接用作催化剂,有着广阔的开发前景。     

化学组成对轻烧镁铝尖晶石结构与性能的影响

相比传统电熔镁铝尖晶石和烧结镁铝尖晶石,轻烧镁铝尖晶石晶格畸变大,反应活性高,所制备的铝镁浇注料抗渣渗透性更好。本文以工业氧化铝和轻烧镁砂细粉为原料,在1 600 ℃下烧结合成Al₂O₃质量分数在68%~76%的富镁尖晶石(68%和70%)、正尖晶石(72%)和富铝尖晶石(76%)试样,研究Al₂O₃含量对尖晶石试样常温物理性能、物相组成、晶体结构参数和显微结构的影响。结果表明:Al₂O₃含量的增加提高了试样的显气孔率;富镁尖晶石试样的物相为尖晶石和少量方镁石,其余试样只有尖晶石相;富铝尖晶石的晶格畸变大于富镁尖晶石和正尖晶石,晶粒尺寸和平均孔径小于富镁尖晶石和正尖晶石。     

Effect of Impurities on the Strength of Polycrystalline Magnesia and Alumina

The bending strength of pure and alloyed magnesium oxide and aluminum oxide was studied. The magnesium oxide was doped with nickel oxide and cobalt oxide, both of which form a complete series of solid solutions with magnesia. The aluminum oxide was doped with ferric oxide which has limited solid solubility in aluminum oxide, with titanium dioxide which also has limited solid solubility in alumina, and with chromic oxide which forms a complete series of solid solutions with alumina. The modulus of rupture was corrected to a standard grain size and porosity to determine the intrinsic effects of the impurities on the modulus of rupture. The results indicate that the formation of NiO-MgO and Coo-MgO solid solutions increases the strength of MgO. The formation of Cr₂O₃-Al₂O₃, Fe₂O₃-Al₂O₃, and TiO₂-Al₂O₃ solid solutions, however, has no intrinsic effect on the strength of sintered alumina.     

Effect of compositional variation and fineness on the densification of MgO–Al2O3 compacts

Single stage densification of magnesia—alumina compacts were studied with MgO to Al₂O₃ molar ratios 1:1 (stoichiometric spinel), 2:1 (magnesia rich spinel) and 1:2 (alumina rich spinel). Attritor milling has been adopted to produce variation in fineness. Milling greatly improved the densification. Densification was found to be easier for the magnesia rich composition and difficult for the alumina rich one. X-ray diffraction patterns showed the expected phases in stoichiometric and magnesia rich spinel. Alumina rich composition showed no free corundum phase on sintering at 1650°C and only spinel phase marks the complete solid solution of excess alumina in spinel at this composition. EDAX analysis also supports the event and also reflects that the impurities are mainly present at the grain boundaries.     

Effects of high concentrations of liquid phase and magnesia on the grain growth of alumina

Grain growth phenomenon of alumina in the presence of various quantities of liquid phase and magnesia was investigated at 1600°C, and the data were regressed by a statistical approach. The statistical result indicated that liquid phase, compared with magnesia, was a major factor in determining the grain growth mechanism of alumina. The alumina phase developed into faceted grains when the liquid phase was so abundant as to penetrate all the grain boundaries and junctions of alumina, whether with the doping of magnesia or not. This observation implied that magnesia, when co-existing with a large quantity of liquid phase, did not effectively reduce the degree of anisotropy in interfacial energy of alumina. Nevertheless, when its concentration was high enough to result in the precipitation of MgAl₂O₄, it avoided the evolution of elongated alumina grains by pinning the fast moving boundaries.     

Effect of spinel content on slag attack resistance of high alumina refractory castables

High alumina refractory castables based on the Al₂O₃-MgO-CaO diagram ternary system were prepared using tabular alumina, white electrofused corundum, calcined alumina, synthetic spinel, dead-burned magnesia, dolomite, and calcium aluminate cement as starting raw materials. Two kinds of slags with 9.02 and 4.14 CaO/SiO₂ ratios were studied for slag resistance by means of crucible tests. The corrosion thickness increases with increase in magnesia content in all the designed compositions. The slag penetration decreases with increases in spinel content. Taking into account these results a refractory castable composition for its positioning into a steelmaking ladle was chosen.

Microstructural studies by SEM of samples taken from the slag line and wall in a steelmaking ladle were carried out. The correct amount of spinel required for practical applications was determined by the Al₂O₃-MgO-CaO-SiO₂ diagram quaternary system. A detailed model of the attack mechanisms is proposed.