锆英石对Al_2O_3 MgO系浇注料性能的影响

在Ａｌ２Ｏ３ＭｇＯ 系浇注料中,添加的锆英石在１３００ ℃时完全分解生成单斜ＺｒＯ２ 和无定形ＳｉＯ２ ,促进了试样的烧结,使试样在较低温度下可以获得较高的强度。锆英石在高温下分解时,产生的无定形ＳｉＯ２ 流出而在锆英石颗粒中留下空洞。产生的单斜ＺｒＯ２ 与尖晶石的热膨胀系数几乎相同,二者可形成高度的直接结合;而方镁石的热膨胀系数是它们的２ 倍,因此,在单斜ＺｒＯ２ 和方镁石之间、尖晶石和方镁石之间产生显微裂纹,提高了试样的热震稳定性。     

骨料对Al_2O_3-尖晶石钢包浇注料性能的影响

研究了三种不同骨料对Al2O3-尖晶石钢包浇注料性能的影响。结果表明：用电冶矾土刚玉骨科制得的浇注料具有较好的流动性、高温烧结性和抗渣性,但热震稳定性比电熔白刚玉有所降低。这主要与电冶矾土刚玉的组成和显微结构有关。     

MgO、Y2O3添加剂对原位反应制备ZTM/A12O3材料性能的影响

本文主要探讨了MgO、Y2 O3 添加剂对原位反应制备ZTM/Al2 O3 材料常温力学性能的影响。实验表明 :MgO可明显提高材料的烧结致密度 ;Al2 O3 的含量越高 ,MgO的添加越有利于材料常温抗弯强度的提高 ;MgO对材料韧性的贡献小于Y2 O3 ;Y2 O3 可明显改善材料的韧性 ,但对常温抗弯强度的提高作用不大 ;对烧结致密化的作用小于MgO。Y2 O3 改善材料韧性的原因是与ZrO2 形成固溶体。     

钢包渣线浇注料基质组成及其抗渣性

采用特级高铝矾土熟料和电熔镁砂为主要原料,研究了Al2O3-MgO系浇注料中MgO/Al2O3质量比对浇注料基本性能的影响,并分析对比了基质中添加适量工业氧化格、镁锆合成料及矾土尖晶石对浇注料抗渣性的影响及其规律。结果表明：恰当控制基质中MgO/Al2O3质量比及在基质中添加适量的工业氧化铬等组分,可明显提高浇注料的抗渣性。     

Sol-Gel法制备Al2O3-SiO2-TiO2-ZrO2复合陶瓷膜的研究

将Sol-Gel法应用于无机膜的制备,成功的研制出一种新型的膜面平整、膜厚均匀且无宏观缺陷的Al2O3-SiO2-TiO2-ZrO2复合陶瓷膜,复合膜含有γ-Al2O3、SiO2、TiO2、ZrO2和Al2SiO5等晶相,改变体系组成含量,晶相组成和含量随之变化,从而引起膜的显微结构的变化。利用XRD、SEM、AFM、EPMA等测试手段重点研究了膜的表面形貌和显微结构,并分析了添加剂、热处理方式等对膜的表面形貌和显微结构影响。     

ZnO对MgO-Al2O3-SiO2体系的结构和红外辐射性能的影响

采用固相反应法制备名义组成为Mg2 ( 1x) Zn2xAl4Si5O1 8(x =0～ 0 .6)的红外辐射材料 ,测试了样品的红外辐射性能 ,并用XRD ,IR ,2 9SiMASNMR等方法研究了体系的结构。研究结果表明 :x≤ 0 .2时样品主要为Zn2 固溶α堇青石结构 ,Zn2 的固溶使T1 (与 [MgO6 ]八面体一起在六元环之间起连接作用的四面体 )和T2 (组成六元环结构的四面体 )四面体上Al,Si分布的有序度提高 ,引起α堇青石晶格产生畸变 ,增强了晶格振动的非简谐效应和样品的红外辐射性能。x =0 .2时样品的红外辐射性能达到最佳 ,其法向全波段比辐射率达到 0 .89,在 8～ 2 5 μm内各波段的辐射率达到 0 .90～ 0 .93。x >0 .2时样品的红外辐射性能随x的增大而降低 ,x≥ 0 .4时样品中主要形成 (Mg1xZnx)Al2 O4尖晶石固溶体和方石英     

Al2O3和MgO对低水泥尖晶石耐火浇注料性能的影响

研究了预先合成的尖晶石对水泥含量低的高铝耐火浇注料性能的影响。     

MgO-Al2O3-SiO2-TiO2-CeO2微晶玻璃的相转变

通过DTA，XRD，TEM，SEM和EDS等测试手段，研究了MgO—Al2O3一SiO2一TiP2-CeO2微晶玻璃的相转变过程。研究结果表明：退火后的原始玻璃已存在液相分离结构。在热处理过程中硅钛铈矿(Ce2Ti2Si2O11)首先在840℃从富含Ti^4 ，Ce^4 的孤立液滴相中析出。金红石(TiO2)晶核于950℃开始形成。α堇青石相在1140℃左右从富含Si^4 ，Al^3 的玻璃相中大量生成。当温度升高到1205℃时，部分硅钛铈矿分解并与残余玻璃相反应生成金红石和新相氧化铈。通过控制晶化得到的MgO—Al2O3-SiO2-TiO2—CeO2微晶玻璃，其晶相由硅钛铈矿、金红石、α堇青石及少量氧化铈构成。     

铝酸钙水泥结合莫来石-碳化硅浇注料的组成及性能

采用烧结莫来石、Secar71水泥及SiC为原料,制备了不同水泥和SiC含量的莫来石质浇注料,研究了浇注料的常温物理性能、热导率及热震稳定性,并借助XRD和EDS研究了材料的物相组成和显微结构.结果表明:随着水泥的加入,浇注料110℃ 24h显气孔率降低、抗折强度逐渐提高;1100℃ 3h和1400℃ 3h抗折强度呈现出先增大后逐渐减小的趋势,当水泥量为25%(质量分数,下同)时,浇注料的显气孔率最高,同时抗折强度达到最大值.随着水泥加入量的增多,浇注料的热震稳定性稍有降低,当水泥量超过25%后,浇注料的热震稳定性逐渐恢复;通过加入5%～10%的SiC,浇注料的热震稳定性明显改善.浇注料的性能同其物相组成及显微结构相关.     

AlON加入量对MgO-Al2O3浇注料性能的影响

研究了还原气氛下在MgO -Al2 O3 浇注料中加入AlON对其性能的影响。结果表明 :(1)在 16 0 0℃热处理后 ,随着AlON加入量的增加 ,浇注体强度变化不大 ,体积密度略有下降 ;(2 )在16 0 0℃进行抗渣试验 ,材料的抗侵蚀性和抗渗透性都随着AlON加入量的增加而有明显的提高 ,这可能是由于形成的MgAlON固溶体对熔渣润湿性较差 ,有利于阻碍熔渣的侵蚀和渗透。     

纯铝酸钙水泥对镁铝钛系浇注料性能的影响

以镁铝钛电熔合成料颗粒和细粉(w(MgO)76.09%,w(Al2O3)15.67%,w(TiO2)5.05%)、镁砂细粉(w(MgO)>97.1%)、纯铝酸钙水泥(Secar71)、SiO2微粉、SiC细粉(≤0.074mm)及活性氧化铝微粉为原料制成镁铝钛系浇注料,研究了纯铝酸钙水泥含量(分别为2%、4%、6%)对镁铝钛系浇注料性能的影响,结果表明(1)水泥结合的镁铝钛浇注料具有较好的常温物理性能和抗水泥熟料侵蚀的性能,本试验条件下水泥加入量以<4%为宜;(2)高温下镁铝钛电熔合成料存在TiO2的脱溶现象,而脱溶可能对浇注料的理化性能产生影响;(3)在水泥结合镁铝钛系浇注料中加入SiC,对于抑制浇注料收缩是有益的。     

Thermodynamic Modeling of MgO-Al2O3-TiO2 System

This scientific paper gives consideration to the information on the structure of the triple component system,in particular MgO-Al2O3-TiO2 that serves as a basis...     

MgO—Al2O3系浇注料的设计

以相关知识和实践经验为依据,探讨了ＭｇＯ－Ａｌ２Ｏ３系中铝镁质（含刚玉－尖晶石质和矾土熟料－尖晶石质）浇注料的基质料的设计和结合剂的合理选择问题。     

Phase-microstructure-property relationship in high quality factor MgO-Al2O3-SiO2-TiO2-La2O3 glass-ceramics

MgO-Al₂O₃-SiO₂-TiO₂-La₂O₃ glass-ceramics were investigated with respect to the phase compositions and the microstructure as well as the microwave dielectric properties. Indialite, magnesium aluminum titanate (MAT, Mg₄Al₂Ti₉O₂₅), perrierite, and spinel were the main crystal phases in the studied 1.8MgO-1.2Al₂O₃-2.8SiO₂-1.4TiO₂-xLa₂O₃ (x=0.4, 0.3, 0.2) glass-ceramics. Mg₄Al₂Ti₉O₂₅ was detected inside the indialite domain as well as at the boundary while no decomposition product (rutile) is found, proving that Mg₄Al₂Ti₉O₂₅ is fully stabilized. After heat-treatment at 1200 °C, the quality factor (Q×f) of the glass-ceramics increases from 27,500 to 40,000 GHz with decreasing La₂O₃ concentrations. This is caused by the formation of more indialite and MAT. Meanwhile, the temperature coefficient (τ_f) shifts positively from −95 to −65 ppm/°C because of the smaller perrierite concentration. However, τ_f is still too negative due to the absence of rutile that possesses a high positive τ_f. For the 1.3MgO-1.2Al₂O₃-2.8SiO₂-1.4TiO₂-0.2La₂O₃ glass-ceramic with lower MgO molar composition, the peaks assigned to rutile is found and the chemical formula of MAT changes to MgAl₂Ti₃O₁₀ while spinel disappears. MgAl₂Ti₃O₁₀, which distributes mainly at the boundary, decomposes partially, leading to the precipitation of rutile inside the indialite domain. Thus, the τ_f of the glass-ceramic could be adjusted to near 0 ppm/°C with ε_r=9.9 and Q×f=28,600 GHz, which are favorable properties for microwave dielectric applications.     

Effects of MgO on Crystallization and Microwave Dielectric Properties of MgO-Al2O3-SiO2-TiO2-La2O3 Glass-Ceramics

A new glass-ceramic material with dielectric constant ε_r~9–12 and optimum quality factor Q × f~29000 GHz was fabricated from xMgO-1.2Al₂O₃-2.8SiO₂-1.2TiO₂-0.4La₂O₃ (x = 1.0, 1.4, 1.8 and 2.2) system. The effects of MgO on crystallization, microstructure, and dielectric properties of the material were investigated by differential scanning calorimeter(DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and network analyzer. The results show that the glass-ceramic consists of multicrystalline phases, including perrierite, cordierite, magnesium aluminotitanate (MAT), rutile, and spinel (MgAl₂O₄). Rising MgO content promotes the formation of MAT with compositions richer in magnesia, stabilizes spinel at high temperature, and at the same time suppresses the existence of rutile in the material. Quality factor Q × f value of the material is significantly improved with increasing MgO, which is mainly attributed to the existence of more MAT and spinel, while the drop of dielectric constant is related to the decrease in rutile.     

Understanding the structure,thermal, and optical properties in Al2O3-incorporated La2O3-TiO2-Nb2O5 glasses

Glasses in the 30La₂O₃-40TiO₂-30Nb₂O₅ system are known to have excellent optical properties such as refractive indices over 2.25 and wide transmittance within the visible to mid-infrared (MIR) region. However, titanoniobate glasses also tend to crystallize easily, significantly limiting their applications in optical glasses due to processing challenges. Therefore, the 30La₂O₃-40TiO₂-(30−x) Nb₂O₅-xAl₂O₃ (LTNA) glass system was successfully synthesized using a aerodynamic containerless technique, which improves glass thermal stability and expands the glass-forming region. The effects of Al₂O₃ on the structure, thermal, and optical properties of base composition glasses were investigated by XRD, DSC, NMR, Raman spectroscopy, and optical measurements. DSC results indicated that as the content of Al₂O₃ increased, the thermal stability of the glasses and glass-forming ability increased, as the 30La₂O₃-40TiO₂-25Nb₂O₅-5Al₂O₃ (Nb-Al-5) glass obtained the highest ΔT value (103.5°C). Structural analysis indicates that the proportion of [AlO₄] units increases gradually and participates in the glass network structure to increase connectivity, promoting more oxygen to become bridging oxygen and form [AlO₄] tetrahedral linkages to [TiO₅] and [NbO₆] groups. The refractive index values of amorphous glasses remained above 2.1 upon Al₂O₃ substitution, and a transmittance exceeding 65% in the visible and mid-infrared range. The crystallization activation energies of 30La₂O₃-40TiO₂-30Nb₂O₅ (Nb-Al-0) and Nb-Al-5 glasses were calculated to be 611.7 and 561.4 kJ/mol, and the Avrami parameters are 5.28 and 4.96, respectively. These results are useful to design new optical glass with good thermal stability, high refractive index and low wavelength dispersion for optical applications such as lenses, endoscopes, mini size lasers, and optical couplers.     

TiO_2对MgO-Al_2O_3-SiO_2-TiO_2-La_2O_3系微晶玻璃相变和微波介电性能的影响

采用高温熔融法和-步法微晶化热处理制备了MgO-Al_2O_3-SiO_2-TiO_2-La_2O_3(MASTL)微晶玻璃。利用差热分析、X射线衍射、扫描电子显微镜和网络分析仪等手段研究了TiO_2含量对MASTL玻璃析晶相变过程、显微结构和微波介电性能的影响。结果表明,在玻璃热处理过程中先后有硅钛铈矿、金红石(TiO_2)、镁铝钛酸盐、尖晶石(MgAl_2O_4)和堇青石(Mg_2Al_4Si_5O_(18)))5种晶相析出。其中,镁铝钛酸盐含量相对较低,尖晶石是一个亚稳过渡相。随着TiO_2含量的增多,原始玻璃的析晶倾向增大,初晶相硅钛铈矿和主晶相金红石的析晶温度显著降低,而尖晶石的析晶温度升高;材料的介电常数和谐振频率温度系数均显著增大,这主要由样品中具有高介电常数(100.0)和较大正温度系数(400×10~(-6)/℃)的金红石相含量增多引起。同时,由于高品质因数相堇青石(40000GHz)的析出量略有减少,品质因数有所降低。     

Thermomechanical properties of ceramics in the systems Al2O3-TiO2 and Al2O3-TiO2-mullite

Conclusions We studied certain properties of ceramics in the systems Al₂O₃-TiO₂ and Al₂O₃-TiO₂-mullite, obtained by the use of the double-stage synthesis of aluminum titanate.We established the nature of the change in the high-temperature strength in relation to the ratio of Al₂O₃ and aluminum titanate. The maximum high-temperature strength (bending) at 1200°C is possessed by ceramic with a corundum matrix and a volume proportion of aluminum titanate equal to 40–45%.It is established that the addition of CaO + SiO₂ made in amounts of up to 1.0–1.5% contributes to the partial breakdown of the aluminum titanate in the compositions Al₂O₃-TiO₂ and the production of a ceramic with a bending strength of 160–190 N/mm² at 20–200°C, thermal-shock resistance 650–800°C, and thermal conductivity of 1.9–2.1 W/(m·K).We studied the effect of the mullite concentration on the properties of the ceramic in the system Al₂O₃-TiO₂-mullite. The introduction of mullite in amounts of not more than 50%, containing up to 3% of impurities, contributes to an increase in the ceramic's strength in the range 20–1300°C and in the thermal shock resistance.Translated from Ogneupory No. 2, pp. 22–26, February, 1988.     

Crystallization,structure and properties of MgO-Al2O3-SiO2 highly crystalline transparent glass-ceramics nucleated by multiple nucleating agents

Generally, highly crystalline transparent glass-ceramics possess excellent physical and chemical properties compared to organic and other inorganic optical materials. We have successfully prepared highly crystalline transparent glass-ceramics in the MgO-Al₂O₃-SiO₂ system by "extreme-time" nucleation & "finite-time" crystallization processes using P₂O₅, ZrO₂ and TiO₂ as multiple nucleating agents. The results revealed that the crystallization of glass is controlled by a three-dimensional interfacial crystal growth process. These glass-ceramics mainly consisted of cordierite crystals with a residual glassy phase, and crystallinity increased with crystallization time, but light transmittance decreased with crystallization time due to enlarged grain sizes. EDS mapping revealed a uniform distribution of elements within the glass-ceramic. In the optimal preparation condition (825?°C/96?h?+?990?°C/3?h), these glass-ceramics exhibited a high crystallinity (87.3?vol. %), high transmittance (78%), and excellent mechanical properties. This work provides a roadmap for preparing highly crystalline transparent glass-ceramics for applications in optical engineering.