铝纤维对Al2O3-Al-C材料高温机械性能和显微结构的影响

分别以板状刚玉、α-Al2O3微粉、金属铝(铝纤维和铝粉)、石墨为原料,以酚醛树脂为结合剂,制得Al2 O3-Al-C材料.借助XRD和SEM分析了试样的物相组成和显微结构,研究了铝纤维加入量对材料抗热震性、高温抗折强度的影响,结果表明:用铝纤维代替铝粉可提高材料的高温抗折强度和抗热震稳定性.保持金属铝的总加入量为6;,当铝纤维加量由0;增加到1;时,1400℃的高温抗折强度由26.5 MPa提高到34.7 MPa,热震后的残余强度保持率由62;增加到69;.高温时铝纤维转变为非氧化物晶须编织体或纤维束,与基质紧密结合,起桥接和强化作用,可改善材料的抗热震性并显著提高其高温抗折强度.     

Al2O3膜层制备参数对SiO2/Al2O3/PET复合膜透湿性能的影响

采用磁控溅射工艺在PET衬底上依次沉积了Al2 O3和SiO2薄膜,制备出SiO2/Al2 O3/PET复合膜.利用扫描电镜和透湿仪对复合膜的表面形貌和透湿性能进行表征.研究了制备Al2 O3膜层的射频功率、氩气流量、本底真空度和溅射时间4个参数对复合膜透湿率的影响.结果表明:复合膜的透湿率随着本底真空度的升高而减小,随着射频功率、氩气流量和溅射时间的增加均呈现先减小后增大的变化趋势;4个制备参数对复合膜透湿率的影响程度由大到小依次是本底真空度、氩气流量、射频功率、溅射时间;4个制备参数的较优组合为本地真空度0.5×10-3 Pa,射频功率300 W,溅射时间6 min,氩气流量70 mL·min-1.     

Ti-Al-Nb2O5系原位合成Al2O3晶须的形成机理分析

本文研究了以粉埋法原位合成的Al2O3晶须的形态和反应过程以及晶须的生长机理.通过物相测试表明产物由Al2O3、TiAl3、NbAl3和少量的AlN相组成,SEM结合EDS分析表明原位合成了直径小于100nm的Al2O3晶须,晶须呈棉絮状分布于基体交界处.基于铝的过剩,TiAl3相是Ti-Al界面的唯一产物.Ti与O2以反应时间短的动力学势优先形成的TinOm中间产物是Al2O3晶须生成的控制步骤.Nb2O5与铝液的双效复合催化作用,提高了晶须的生成速率;同时Al的用量因AlN的生成而减小,导致生成晶须的催化活性点减小,而扩散到每个活性点周围的TinOm及Nb2O5浓度增加,导致晶须分布密而均匀.Al2O3晶核在催化剂的作用下以螺旋位错生长形成长径比较为理想的Al2O3晶须.     

Fe3Al/Al2O3纳微米复合材料的界面电子结构研究

利用EET理论计算了Al2O3与Fe3Al的价电子结构及其部分晶面的电子密度.结果表明,两相界面的电子密度差Δρ＞10;,界面有较大的应力.两相以一定方式取向时,可增强结构的稳定性.     

温度对Al2O3-C材料中β-Sialon晶须形成的影响研究

本文研究了温度对Al3O3-C耐火材料中β-Si3Al3O3N5晶须形成的影响规律.研究发现:在弱还原性气氛下,Al2O3-Si-Al-C稳定存在的非氧化物物相为Al4C3 、AlN、SiC和p-Sialon相.其中,催化作用下,Al2O3-C耐火材料中的金属Al在1000℃时转化为AlN,金属Si在1200℃时转化成SiC,在1400℃时有β-Sialon相生成;而无催化剂存在时,生成的物相仅为SiC和AlN相.催化作用下,AlN形貌呈短柱状;SiC呈晶须状,直径为亚微米级,且晶须有液点存在;β-Sialon相呈纳米晶须状.SiC和β-Sialon晶须的生长都符合气-液-固机理.     

Fe2O3含量对SiO2-Al2O3-MgO-F系微晶玻璃析晶特征的影响

为研究Fe2O3含量对SiO2-Al2O3-MgO-F系微晶玻璃析晶特征的影响,采用高温熔融法制备不同Fe2O3含量的基础玻璃,利用差示扫描量热仪(DSC)、x射线衍射(XRD)及扫描电子显微镜(SEM)分别研究此基础玻璃的热效应、相组成及组织形貌.结果表明:在不同Fe2O3含量的样品中析出的晶相主要有云母、ZrO2莫来石及柱晶石,Fe2O3含量超过0.5;时莫来石相消失.随着Fe2O3含量的增加,云母的析出量逐渐提高,且晶体尺寸逐渐变大.但是当样品中Fe2O3含量超过0.8;时,云母晶体析出量反而减少且晶体尺寸变小.     

Al2O3陶瓷非等温烧结研究

以高纯α-Al2O3粉体为原料,采用非等温烧结法制备了纯Al2O3陶瓷(AL)及掺杂MgO-Y2O3复合助剂的AJ2O3陶瓷(ALMY).研究了AL和ALMY在不同烧结温度下的相对密度、显微结构及硬度.结果表明,在非等温烧结中,纯Al2O3致密化的烧结温度范围较窄,烧结温度为1500℃时,其相对密度及硬度分别为98.1;和18.1GPa,当烧结温度为1600℃时,AL由于晶粒显著粗化,且产生了晶内气孔,相对密度及硬度分别显著下降到94.6;和12.5 GPa.MgO-Y2O3复合助剂的引入拓宽了Al2O3致密化的烧结温度范围,细化了显微结构,烧结温度在1500℃和1600℃时,ALMY的相对密度均在98;以上,硬度分别为19.2 GPa和17.6 GPa.     

共沉淀法制备Al2O3-ZrO2复合纳米粉体

以ZrOCl2·8H2O、Al(NO3)3·9H2O、Y(NO3)3为原料,NH4HCO3 (AHC)为络合剂,采用共沉淀法制备Al2 O3-ZrO2复合纳米粉体.利用X射线衍射分析(XRD)、扫描电镜(SEM)、透射电子显微镜(TEM)、激光粒度分析仪等对Al2 O3-ZrO2复合粉体进行测试表征,详细研究了pH和AHC/Zr摩尔比对复合粉体的影响.结果表明,当前驱体的煅烧温度低于1200℃时,只形成t-ZrO2相,当煅烧温度达到1300℃时,α-Al2O3相开始形成;沉淀反应的pH和AHC/Zr摩尔比对Al2O3-ZrO2复合粉体的产率有很大的影响.在pH7、AHC/Zr =4.5:1的条件下制备前驱体,经过1300℃煅烧2h得到两相纯度高,分散性能好,粒度分布窄,平均粒径为0.75 μm的Al2O3-ZrO2复合粉体.     

Al2TiO5/Al2O3陶瓷复合材料的晶粒异向生长

通过机械激活法制备了Al2TiO5/Al2O3(nAl2TiO5: nAl2O3=1: 4)的陶瓷复合材料.利用X射线衍射(XRD)、扫描电镜(SEM)以及能谱(EDS)分析了不同的温度制度下Al2TiO5/Al2O3陶瓷复合材料的晶粒生长特性.X射线衍射谱图(XRD)显示烧结样品的主晶相为α-Al2O3和Al2TiO5.SEM和EDS分析显示,较低温度下烧结(1350 ℃)时Al2TiO5晶粒为等轴状.当温度升高到1450 ℃时,Al2TiO5开始异向长大,形成棒状晶粒.随着温度的升高(1500 ℃),棒状Al2TiO5的长径比继续增加.而Al2O3则始终为片状和等轴晶粒,且异向生长的Al2TiO5晶粒填充于Al2O3三角晶界处.研究表明,烧结温度的升高会促进晶体异向生长并增加其体积分数.Al2TiO5会阻碍Al2O3基体颗粒进一步生长,所以当Al2TiO5颗粒平均尺寸随着烧结温度增加而增大,Al2O3基体晶粒生长几乎停滞.     

用BP神经网络模型预测Ni-Al2O3复合涂层Al2O3粒子复合量研究

运用人工神经网络技术建立一个结构为4×9×1型的BP神经网络模型,用该模型对Ni-Al2O3复合涂层中Al2O3复合量进行预测研究,并用XRD衍射仪和原子力显微镜(AFM)对Ni-Al2O3复合涂层的Al2O3复合量和立体形貌进行分析.结果表明,当隐含层数为9个时,BP神经网络的均方根误差最小(1.13;),BP神经网络的拟合相似度R=0.99937,这表明BP神经网络模型能够较好的预测涂层Al2O3复合量.当占空比60;、阴极电流密度4 A/dm2、pH值4、镀液温度55 ℃时,Ni-Al2O3复合涂层结构密实,结晶细致.     

TOPCon太阳电池发射极Al2O3/SiNx与SiO2/Al2O3/SiNx叠层膜钝化性能的比较

本文对TOPCon电池发射结的叠层钝化膜进行了研究,对比了3种不同叠层钝化膜(SiO₂/SiN_x、Al₂O₃(1.5 nm)/SiN_x、SiO₂/Al₂O₃(1.5 nm)/SiN_x)的钝化性能。结果表明:Al₂O₃(1.5 nm)/SiN_x的钝化性能优于SiO₂/SiN_x,SiO₂/Al₂O₃(1.5 nm)/SiN_x的钝化水平最佳,隐开路电压均值可达到705 mV。基于Al₂O₃/SiN_x叠层膜研究了Al₂O₃厚度(1.5 nm、3 nm和5 nm)对钝化性能和电池转换效率的影响。当Al₂O₃厚度由1.5 nm增加到3 nm时,钝化性能得到明显提升,隐开路电压均值提高了20 mV,达到707 mV,对应电池的光电转换效率升高了0.23个百分点,与SiO₂/Al₂O₃(1.5 nm)/SiN_x叠层膜电池的转换效率持平。然而,当Al₂O₃厚度继续增加至5 nm时,隐开路电压均值保持不变。因此可以使用Al₂O₃(3 nm)/SiN_x叠层膜代替SiO₂/Al₂O₃(1.5 nm)/SiN_x叠层膜,不仅简化了电池的工艺步骤,而且降低了生产成本。     

Infrared reflection spectra of selected modifications of SiO2 and Al2O3

Infrared reflection spectra were measured within the wave number range of 1400 – −400 cm⁻¹ for following SiO₂ and Al₂O₃ modifications: quartz, opal, quartz glass, cristobalite, tridymite, corundum, sapphire, ruby, gibbsite, boehmite, and diaspore. The spectral bands were attributed, according to literature quotations, to individual vibrations of bonds Si O, O Si O, Si O Si, Al O, O Al O, and Al O Al. The evaluation of infrared reflection spectra has shown that they are very sensitive to internal vibrations of Si O, Al O, which are affected by the symmetry of the surrounding crystal field. They are therefore selective for individual minerals and thus suitable for quick identifying purposes.     

Crystallization of amorphous Al2O3–SiO2 precursors doped with nickel

The crystallization of amorphous diphasic Al₂O₃–SiO₂ precursors doped with nickel has been studied by differential scanning calorimetry (DSC), XRD diffraction (XRD) and scanning and transmission electron microscopy (SEM, TEM) equipped with energy dispersive X-ray spectroscopy (EDS). Diphasic gels with constant atomic ratio (Al + Ni)/Si = 3:1, where 0, 1, 2 and 3 at.% of aluminum were replaced by nickel, have been prepared by hydrolyzing of TEOS in aqueous solution of aluminum nitrate. Crystallization of Ni-containing γ-Al₂O₃ preceded the crystallization of Al–Si spinel. Activation energy of 603 ± 16 kJ mol⁻¹ for crystallization of Ni-containing γ-Al₂O₃ was obtained in non-isothermal conditions. Ni-incorporated γ-Al₂O₃ transforms gradually with the temperature increase into Ni aluminate spinel, while Al–Si spinel reacts with amorphous silica forming mullite at about 1200 °C. Rietveld structure refinement of phases present in the samples annealed at 1600 °C and SEM-EDS and TEM-EDS analyses of related phases have shown that nickel predominantly crystallizes as NiAl₂O₄, but small amount of nickel is incorporated in mullite structure, as well as, dissolved in the glassy phase of the system.     

Non-isothermal crystallization kinetic studies on MgO–Al2O3–SiO2–TiO2 glass

Thermal stability and crystallization kinetics of the glass 21% MgO, 21.36% Al₂O₃, 53.32% SiO₂ and 4.11% TiO₂ (mol%) has been studied using differential thermal analysis (DTA), dilatometry and X-ray diffraction (XRD). Glass in both bulk and frit forms were produced by melting in platinum crucible at 1600 °C for 1–2 h. From variation of DTA peak maximum temperature with heating rate, the activation energies of crystallization were calculated to be 340 kJ mol⁻¹ and 498 kJ mol⁻¹ for first and second crystallization exotherms, respectively. Crystallization of bulk glass was carried out at various temperatures and for different time durations in the range of 850–1000 °C. The influence of the addition of TiO₂ on the crystallization sequence of the glass was experimentally determined and discussed.     

Annealing effect on photoluminescence properties of Er doped Al2O3–SiO2 sol–gel films

Annealing effect on photoluminescence intensity of Er doped Al₂O₃–SiO₂ prepared from Er doped boehmite (AlOOH) and GPS (3-glycidoxypropyltrimethoxysilane) hybrid was investigated. The emission intensities peaked at 1.54 μm, which correspond to the ⁴I_13/2 → ⁴I_15/2 transition of the Er³⁺ ion, are greatly increased by about 8 times between 900 and 1000 °C, than that expected from TGA associated with the elimination of hydroxyl groups which is responsible for the fluorescence quenching. The residual hydroxyl groups for Er doped Al₂O₃–SiO₂ after annealing at high temperature was further analyzed by FT-IR. Finally, fluorescence intensities were compared with the variation of BET surface areas against the annealing temperature. It was found that photoluminescence intensity below 1000 °C was more dependent on surface hydroxyl groups re-adsorbed by a high specific surface area rather than internal hydroxyl groups remained in gel film.     

Square-wave voltammetry and impedance spectroscopy in iron-doped melts of the system Li2O/Al2O3/SiO2

Glass melts with the basic compositions xLi₂O · 15Al₂O₃ · (85 − x)SiO₂ (x = 8.5, 11, 13.5, 16 and 18.5) doped with 0.25 mol% Fe₂O₃ were studied by square-wave voltammetry and impedance spectroscopy at temperatures in the range from 1100 to 1600 °C. The square-wave voltammograms show a pronounced peak attributed to the reduction of Fe³⁺ to Fe²⁺. The attributed peak potentials which are equal to the standard potentials of the redox pair decrease linearly with the temperature. Impedance spectra measured could be simulated using an equivalent circuit attributed to a simple electron transfer reaction controlled by diffusion.