AlON加入物对碱性浇注料抗渣性的影响

氧化镁氧化铝碱性浇注料一个弱点为抗渗透性差, 为改善钢包浇注料抗渣性能, 提高其使用效果和寿命, 运用静态坩埚法研究含AlON的MgO-Al2O3浇注料抗渣性.实验温度为1 600 ℃, 渣侵蚀时间为3 h.研究结果表明: 在还原气氛下, AlON取代浇注料基质中Al2O3能显著提高试样的抗渣侵蚀和抗渗透性. 在氧化气氛下, AlON对基质中Al2O3取代质量比不超过50%时, 抗氧化剂的加入有助于保持AlON优良的抗渣性, 产生这种结果的原因可归结于形成在高温下与氧化物渣难以润湿的含N尖晶石MgAlON, 从而延缓渣对浇注料的侵蚀和渗透.     

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。     

BN对Al2O3-MgO系浇注料性能的影响

研究了分别添加0,1%,1.5%,3%的氮化硼的Al2O3-MgO浇注料分别在空气和埋炭气氛下于1600℃保温3 h烧成后的物理性能和抗渣性能,借助X射线衍射仪、扫描电子显微镜对材料的物相变化和显微结构进行了分析和观察.研究结果表明(1)在空气中1600℃烧成时,BN氧化生成B2O3并放出N2,B2O3与Al2O3反应生成一定量的过渡液相,促进了浇注料烧结,使浇注料线收缩增大,体积密度升高,显气孔率下降,抗折强度明显提高;而当BN加入量超过1%时,其氧化后形成大量的气孔,阻碍了浇注料的致密化过程,影响了浇注料的上述物理性能.(2)在埋炭条件下烧成时,浇注料中BN不易被氧化,它的存在使浇注料难于烧结,同时,浇注料中引入的镁砂和铝酸钙水泥与氧化铝反应伴随着一定体积膨胀,使浇注料体积密度下降,显气孔率增加,抗折强度下降.(3)在空气和埋炭条件下的抗渣试验发现,当在浇注料中加入1%BN时,其抗转炉终渣侵蚀性能均有较大的提高.但两种试验条件下浇注料抗渣作用机理不同在空气中,BN氧化后形成的过渡液相吸收了生成镁铝尖晶石等反应所伴随的体积膨胀,促进了浇注料烧结,抑制了渣的渗透和侵蚀;而埋炭条件下,浇注料基质中的氮化硼难以被氧化物熔渣润湿,阻碍了渣的渗透和侵蚀,因而使浇注料具有优良的抗渣侵蚀性和渗透性.     

熔铝炉用抗渗透浇注料的抗渗透性能研究

为了提高熔铝炉用抗渗透浇注料的抗渗透性能,对以铝矾土均化料和电熔棕刚玉为骨料,以Al2O3微粉和Si O2微粉为基质的熔铝炉用抗渗透浇注料,研究了抗渗透剂硫酸钡的添加与否、铝合金种类和侵蚀温度对抗渗透浇注料抗渗透性能的影响。结果表明:加入抗渗透剂硫酸钡能明显改善抗渗透浇注料的抗渗透性能;在865℃时,7075铝合金对浇注料的渗透比3003铝合金的严重。     

研究动态

垃圾熔融炉用含Cr2O3浇注料抗侵蚀性能的提高含Cr2O3浇注料以其优良的抗侵蚀性和抗渣渗透性而广泛用于垃圾熔融炉使用条件最苛刻的部位。通过添加SiO2微粉或Cr2O3微粉有可能提高其抗侵蚀性以减少剥落。传统的纯Al2O3-Cr2O3材料(其中w(Al2O3)=77%,w(Cr2O3)=20%,w(SiO2)=2%)渗透严重,所以,因结构剥落而造成严重的损毁。为此,从两个方面来抑制渣的渗透:1)在热面形成液相;2)增加材料中Cr2O3的含量,可以大大降低对渣的润湿。现场试验结果表明:随着材料中Cr2O3含量的增加,材料的抗侵蚀性提高,但材料的残余膨胀增大;当材料中Cr2O3(质量分…     

水泥和水合氧化铝对铝镁浇注料性能的影响

固定电熔白刚玉、电熔镁砂粉、αAl2O3微粉、SiO2微粉等原料的含量不变,分别加入不同量的水合氧化铝和纯铝酸钙水泥作结合剂(ρAl2O3加入量为2%、3%和4%,水泥加入量为3%、5%和7%),对比研究了水泥结合和水合氧化铝结合铝镁浇注料的显气孔率、体积密度、耐压强度、抗折强度、抗热震性和抗渣性能。结果表明:与水泥结合铝镁浇注料相比较,水合氧化铝结合浇注料具有更好的抗热震性、抗渣侵蚀和渗透性能;水合氧化铝在浇注料中的合适加入量为3%;水泥结合铝镁浇注料具有较高的常温强度,但其抗渣侵蚀和渗透性能随着水泥含量的增加而逐渐降低。     

基质组成对MgO-尖晶石浇注料抗渣性能的影响

采用静态坩埚法研究了添加不同组成尖晶石的ＭｇＯ－ 尖晶石浇注料基质组成与抗渣性能的关系。实验结果表明：随着基质中Ａｌ２Ｏ３ 含量增加,浇注料抗渣侵蚀能力减弱,而抗渣渗透能力增强。在基质中ＳｉＯ２ 含量固定在１０ ％ 的情况下,基质中Ａｌ２Ｏ３ 含量在３０ ％ ～５０ ％ 时浇注料抗渣侵蚀性能较好;Ａｌ２Ｏ３ 含量超过５０ ％ 时,侵蚀速率急剧增加两倍以上。不同组成尖晶石对浇注料抗渣侵蚀性能没有明显影响,但含富铝尖晶石的浇注料具有较好的抗渣渗透性能。     

AlON对Al2O3-MgO钢包浇注料抗渣性的影响

在Al2O3-MgO钢包浇注料中引入6%的AlON后,用静态坩埚法考察了添加AlON的浇注料在不同气氛条件下1600℃3 h的抗渣性,采用SEM分析了试样的显微结构.结果表明在埋炭保护条件下,添加AlON后浇注料的抗渣性得到改善;在大气气氛中,未加抗氧化剂的试样的抗渣性恶化;分别加入SiC、Si和B4C作抗氧化剂后,抗渣性虽有所改善,但仍比空白试样和含AlON试样在埋炭保护条件下的抗渣性稍差.抗渣性与加入到浇注料中的AlON是否氧化和材料内部能否形成和保持由尖晶石、六铝酸钙和刚玉构成的相组合有关.     

铝镁浇注料的抗渣侵蚀机理

采用静态坩埚法进行了铝镁浇注料的抗渣侵蚀试验 ,从动力学和热力学角度分析了铝镁浇注料的抗渣侵蚀机理。结果表明 :浇注料的熔渣侵蚀过程受化学反应和扩散的混合控制 ;熔渣侵蚀的表观活化能约为 4 2 4 .8kJ·mol- 1;渣中CaO与Al2 O3反应生成高熔点的CA6 ,抑制了熔渣的进一步侵蚀 ;渣中CaO含量的不断降低 ,使熔渣的粘度增大 ,渗透能力降低。     

氧化铁粉对MgO-Al2O3质浇注料性能的影响

以电熔镁砂、二氧化硅微粉、MA尖晶石粉、α-Al2O3微粉、氧化铁粉为原料制备MgO-Al2O3质浇注料,研究氧化铁粉加入量(0、2%、4%、6%)对MgO-Al2O3质浇注料常温物理性能、抗热震性和抗渣性的影响.按照国家相关标准进行各项物理性能检测,并用X射线衍射仪对1550℃3 h烧后试样进行物相分析,采用风冷法进行抗热震性试验,静态坩埚法进行抗渣试验.结果表明加入氧化铁粉对MgO-Al2O3质浇注料的抗渣渗透性能和常温力学性能有利.随着基质中氧化铁粉加入量的增加,试样抗渣侵蚀能力有所减弱,抗渣渗透能力明显增强,试样经1100℃3 h和1550℃3 h热处理后的常温力学性能得以提高,但抗热震性降低.氧化铁粉加入量≤2%时,试样的抗热震性较好.     

氧化铝载体的水热改性研究

采用低温水热处理技术对γ-Al₂O₃载体进行改性,通过XRD、SEM、BET及NH_3、TPD等测试表征技术对改性后的氧化铝进行表征。研究结果表明,低温水热处理γ-Al₂O₃时,γ-Al₂O₃部分再水合生成湃铝石,焙烧后形成γ-η-Al₂O₃,此双结构氧化铝表面形态为均匀分散的球形细小颗粒,双结构氧化铝载体制备的催化剂表面酸性能与常规γ-Al₂O₃制备的催化剂相比,强酸中心的酸强度减弱,弱酸中心的酸强度增强。     

原位合成纳米氧化铝烧结助剂制备轻质氧化铝陶瓷

采用氧化铝空心球和α-Al2O3细粉为原料，以硫酸铝和硫酸铝铵水溶液及PVA水溶液为结合剂，并以硫酸铝和硫酸铝铵受热分解而原位合成的纳米γ-Al2O3作为烧结助剂制备轻质高强氧化铝陶瓷。研究结果；引入的氧化铝空心球助烧剂能促进轻质高强氧化铝陶瓷的烧结，烧结温度为1700℃，对应密谋为1.21-1.60g/cm^3，常温抗压强度为22－42MPa。荷重软化温度超过1700℃(0.1MPa），是高温窑炉理想的轻质高强内衬结构材料。     

溶胶-凝胶法在氧化铝板晶和微粉表面包裹玻璃涂层

以硅酸乙酯和硝酸钙为原料，制备了CaO-SiO2溶胶。采用液相包裹技术在氧化铝板晶和粉末表面上包裹了一层Ca0-SiO2玻璃。用DTA／TGA研究了凝胶热分解过程。用SEM观察表明，玻璃涂层在氧化铝板晶或氧化铝微粉团聚体表面上的分布是均匀的。     

Aluminium-Based Surfactant Mesophases Structurally and Morphologically Controlled by Anions

Aluminium-based dodecyl sulfate mesophases were synthesized by the homogeneous precipitation from a mixture of aluminium nitrate, sodium dodecyl sulfate, urea and water with or without five kinds of additional anions. The addition of monovalent Cl^-, CH₃COO^- and HCOO^- anions yielded a hexagonal mesophase, whereas F^- anions induced a different mesophase. The crystallinities of these mesophases increased in the following order: NO₃ ^- and Cl^->CH₃ COO^->HCOO^->F^-, corresponding to the reverse order of affinity for Al³⁺. The resulting mesophases were also largely affected in morphology by the anion species added to form worm-like shaped particles for NO₃ ^- and/or Cl^- anions, and widely varying shapes of particles for the others. On calcination, these mesophases were transformed into -alumina particles with macro pores having the specific surface area of ca. 20 m²g^-1. On the other hand, the addition of divalent SO₄ ^2- anions or the single use of aluminium sulfate led to a mesophase with a structural period as long as 6 nm, which was deorganized into a layered phase with an interlayer spacing of 1.4 nm.     

Pore bifurcation, growth and pore termination in nanoporous alumina with concave and convex surfaces

The growth of nanoporous alumina on concave or convex aluminium surfaces has been investigated. The number of pores during anodic oxidation increases or decreases almost linearly with the thickness of the oxide which is due to bifurcation or termination of single pores during alumina growth. The anodic oxidation has been constantly conducted in oxalic acid at 40 V. Therefore the average interpore distance has not changed during alumina growth. In earlier papers it has been shown that a bifurcation of pores is the result of the change of voltage and the electrolyte. In this work we have demonstrated that a termination or a bifurcation of pores is also possible by structuring the aluminium to a curved surface with concave or convex properties before oxidation. Those results do not depend on the substrate characteristics or on the alumina preparation techniques.     

Al2O3微粉及Alphabond加入量对无水泥刚玉质浇注料性能的影响

为了改善刚玉质浇注料的热态强度和抗侵蚀性,采用水合氧化铝Alphabond作为结合剂,分别调整Al2O3微粉及Alphabond加入量,研究了Al2O3微粉及Alphabond加入量对无水泥刚玉质浇注料性能的影响。结果表明:Al2O3微粉加入量对浇注料的成型性能和烧后强度影响较大,其最佳加入量在Alphabond含量(质量分数,下同)为3%时为11%左右;增加Alphabond加入量(在0~4%范围内)可大幅度提高浇注料的烘干强度,但1400℃及1600℃烧后常温抗折强度和1400℃高温抗折强度明显降低。     

Freeze Casting of Aqueous Alumina Slurries with Glycerol

Freeze-drying concepts were utilized in the shape forming of alumina parts by pressureless slip molding using aqueous slurries. A water solidification modifier, glycerol, was utilized to eliminate the defects associated with the expansion and ceramic particle rejection of water during freezing. Castable alumina slurries with solids loading up to 60 vol% were prepared and characterized using viscosity and zeta-potential measurements with and without glycerol additions. Frozen parts were dried under vacuum by sublimation of ice to obtain net-shape green bodies. The combined effects of high-solids-loading slurries, >57.5 vol%, and glycerol additions were essential for freeze casting to achieve highly dense alumina bodies with a uniform microstructure.     

Al2O3陶瓷材料的增韧

氧化铝陶瓷因脆性而限制了其广泛应用。本文对目前氧化铝瓷的增韧方法及主要机理进行了评述，主要有层状复合增韧、纳米复合增韧、纤维（晶须）增韧、自增韧等。其中复合增韧是主要手段。而且纳米技术和微观结构设计将是今后氧化铝提高韧性的发展方向。     

Processing of High-Density Submicrometer Al2O3 for New Applications

Sintered corundum components with submicrometer grain sizes exhibit properties which enable numerous new applications. Wet powder processing is developed to associate minimum grain sizes at highest densities with the lowest population of macrodefects. A closest ratio of powder particle size and sintered grain size is important for obtaining most fine-grained microstructures. This target was approached best by using powders with particle sizes in the range of 100–200 nm rather than with smaller nanoparticles.     

Ultrarapid Phase Conversion in β"-Alumina Tubes

β"-Alumina, the electrolyte of choice of sodium/sulfur and sodium/metal chloride batteries and alkali-metal thermal-electric converters, was sintered from precursor phases to high β"-phase purity in less than 15 s from the onset of densification by rapid pass-through rf induction coupled plasma sintering. The maximum instantaneous shrinkage rate was 1.8%/s. The resistivity was measured to be 13.8 ± 1.4 Ω·cm. The rapid conversion found is a significant improvement over conventional processing of β"-alumina, which requires extended postsintering annealing times to obtain high β"-phase purity.