Al_2O_3-B_2O_3-Ce_2O_3体系中Ce~(3+)的光谱特性与基质的相关性

在Al2 O3_B2 O3_Ce2 O3体系中 ,于 12 0 0～ 140 0℃的温度范围内 ,合成了一系列不同配比 (Al/B比从 4 5～ 2变化 )磷光体 .研究了它们的结构和光谱特性之间的相关性 .发现随着基质配比Al/B从 4 5～ 2的变化 ,基质结构发生明显的变化 .这种变化导致光谱特性的巨大变化 ,表明铈离子晶场环境的变化 ,随着配比的变化 ,激发与发射峰向短波方向移动 .在合适的配比下 ,可以获得新型的稀土发光材料

Al_2O_3-B_2O_3-Ce_2O_3体系相关系的研究

Ａｌ２Ｏ３Ｂ２Ｏ３Ｃｅ２Ｏ３体系相关系的研究尤洪鹏洪广言（中国科学院长春应用化学研究所，长春１３００２２）ＩｎｖｅｓｔｉｇａｔｉｏｎｏｎＰｈａｓｅＲｅｌａｔｉｏｎｓｉｎｔｈｅＳｙｓｔｅｍＡｌ２Ｏ３Ｂ２Ｏ３Ｃｅ２Ｏ３ＹｏｕＨｏｎｇｐｅｎｇＨｏｎ...

Al_2O_3-B_2O_3-Eu_2O_3体系的振动光谱和发光特性

采用高温固相反应法，合成了一系列不同组份的磷光体，测定了它们的振动光谱．结果表明，随着Al／B比的减小，在1100～1000cm－1的区域内的振动光谱没有明显变化，铕离子不可能进入Al18B4O33的晶格中；振动光谱的背底升高，非晶相逐渐增加．研究了Al2O3－B2O3-Eu2O3中Eu3＋离子的光谱特性，发现随着Al／B比的减少，Eu3＋离子的存在相由晶相逐渐向非晶相转化。在非晶相中，Eu3＋离子的声子伴带表明电子与声子的耦合强度随着Al／B比的减少而减小，Eu3＋离子的发射强度相应的增加，这与多声子弛豫的理论一致.

掺Eu~(2+)的B_2O_3-Al_2O_3-SrO长余辉玻璃陶瓷

传统的长余辉材料存在着余辉时间短,余辉亮度弱等缺点,为了克服这些缺点,往往在材料中加入放射性元素,但这样对人的身体及环境都产生危害。近年来,一种新型的稀土铝酸盐长余辉材料:SrAl_2O_4:Eu~~(2+),Dy~(3+)引起了人们的极大兴趣。这种材料具有余辉时间长,余辉亮度强的优点。与多

含微裂纹的95%Al_2O_3陶瓷的力学性能

本文采用三种不同加载方式(单轴拉伸,三点弯曲以及圆盘压缩)研究含微裂纹Al_2O_3的陶瓷的弹性性能及其抗拉强度.微裂纹是通过对材料瞬时突变加热和冷却(简称热冲击)形成的.试验结果表明:1)三点弯曲试验得到的力学性能参数较其它两种加载方式所得到的结果要稳定和集中.单轴拉伸试验结果分散性最大.2)热冲击温度越高,材料的等效弹性模量?和等效泊松比?以及各种加载方式下试件的抗拉强度??都有不同程度的下降.电镜观察证实了力学性能参数下降主要与材料内部微裂纹密度增加有关.3)Budiansky-O'Connell方法被用来估计不同热冲击处理后的圆盘试件在断裂过程中的微裂纹密度变化,结果表明实际材料的微裂纹密度较理想材料的微裂纹密度都有一定的偏差.

中频对靶反应磁控溅射Al_2O_3、TiO_2、ZrO_2功能薄膜的特性研究

利用中频对靶磁控溅射技术,分别制备出厚度低于5μm、表面光滑的TiO2、ZrO2、Al2O33种功能薄膜。研究了不同工艺条件下薄膜的成膜速率和表面形貌,用四探针法测量了材料的薄膜电阻,并表征了膜层材料在大气压热等离子射流急速加热条件下的抗热冲击特性。

Al_2O_3/SiC_p复合材料中热失配残余应力的测量

采用纳米压痕仪测量了Al2O3/SiCp复合材料中的热失配残余应力。根据研究材料的微结构和非均匀热残余应力分布特点,建立一压痕实验模型。在该模型中,实验材料被视为由若干含有单一SiC颗粒的Al2O3胞元构成,而热失配残余压应力均匀分布于胞元基体中。在考虑到浅压痕时材料表面粗糙和压头针尖曲率半径的影响的基础上测得的Al2O3/SiCp复合材料基体中热失配残余压应力与理论计算结果非常接近。

Oxidative chemisorption of SO_2 on γ - Al_2O_3 and deposition of H_2-permselective SiO_2 films

The interaction of SO_2 with γ - Al_2O_3 and the deposition of H_2 permselective SiO_2 films have been investigated. The adsorption and oxidative adsorption of SO_2 on γ - Al_2O_3 have been examined at temperatures 500-700°C by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). At temperatures above 500°C most of SO_2 adsorbed on the strong sites on alumina. The adsorbed SO_2 species was characterized by an IR band at 1065 cm^(-1). The equilibrium coverage and initial rate of adsorption decreased with temperature suggesting a two-step adsorption. When γ - Al_2O_3 was contacted with a mixture of SO_2 and O_2, adsorption of SO_2 and oxidation of the adsorbed SO_2 to a surface sulfate characterized by broad IR bands at 1070 cm^(-1), 1390 cm^(-1) took place. The results of a series of TGA experiments under different atmospheres strongly suggest that surface SO_2 and surface sulfate involve the same active sites such that SO_2 adsorption is inhibited by already formed sulfate. The results also indicate a broad range of site strengths.

The desorption of adsorbed SO_2 and the reductive desorption of oxidatively adsorbed SO_2 have been investigated by microreactor experiments and thermogravimetric analysis (TGA). Temperature programmed reduction (TPR) of adsorbed SO_2 showed that SO_2 was desorbed without significant reaction with H_2 when H_2 concentration was low while considerable reaction occurred when 100% H_2 was used. SO_2 adsorbed on the strong sites on alumina was reduced to sulfur and H_2S. The isothermal reduction experiments of oxidatively adsorbed SO_2 reveal that the rate of reduction is very slow below 550°C even with 100% H_2. The reduction product is mainly composed of SO_2. TPR experiments of oxidatively adsorbed SO_2 showed that H_2S arose from a sulfate strongly chemisorbed on the surface.

Films of amorphous SiO_2 were deposited within the walls of porous Vycor tubes by SiH_4 oxidation in an opposing reactants geometry : SiH_4 was passed inside the tube while O_2 was passed outside the tube. The two reactants diffused opposite to each other and reacted within a narrow front inside the tube wall to form a thin SiO_2 film. Once the pores were plugged the reactants could not reach each other and the reaction stopped. At 450°C and 0.1 and 0.33 atm of SiH_4 and O_2, the reaction was complete within 15 minutes. The thickness of the SiO_2 film was estimated to be about 0.1 µm. Measurements of H_2 and N_2 permeation rates showed that the SiO_2 film was highly selective to H_2 permeation. The H_2:N_2 flux at 450°C varied between 2000-3000.

Thin SiO_2 films were heat treated in different gas mixtures to determine their stability in functioning as high-temperature hydrogen-permselective membranes. The films were heat-treated at 450-700°C in dry N_2, dry O_2, N_2-H_2O, and O_2-H_2O mixtures. The permeation rates of H_2 and N_2 changed depending on the original conditions of film formation as well as on the heat treatment. Heating in dry N_2 slowly reduced the permeation rates of both H_2 and N_2. Heating in a N_2-H_2O atmosphere led to a steeper decline of H_2 permeability. But the permeation rate of N_2 increased or decreased according to whether the film deposition had been carried out in the absence or presence of H_2O vapor, respectively. Thermal treatment in O_2 caused rapid decline of the permeation rates of H_2 and N_2 in films that were deposited under dry conditions. The decline was moderate in films deposited under wet conditions.

Chemical and mineralogical characterization of micro-inclusions in diamonds

Secondary-ion mass spectrometry (SIMS), electron probe analysis (EPMA), analytical scanning electron microscopy (SEM) and infrared (IR) spectroscopy were used to determine the chemical composition and the mineralogy of sub-micrometer inclusions in cubic diamonds and in overgrowths (coats) on octahedral diamonds from Zaire, Botswana, and some unknown localities.

The inclusions are sub-micrometer in size. The typical diameter encountered during transmission electron microscope (TEM) examination was 0.1-0.5 µm. The micro-inclusions are sub-rounded and their shape is crystallographically controlled by the diamond. Normally they are not associated with cracks or dislocations and appear to be well isolated within the diamond matrix. The number density of inclusions is highly variable on any scale and may reach 10^(11) inclusions/cm^3 in the most densely populated zones. The total concentration of metal oxides in the diamonds varies between 20 and 1270 ppm (by weight).

SIMS analysis yields the average composition of about 100 inclusions contained in the sputtered volume. Comparison of analyses of different volumes of an individual diamond show roughly uniform composition (typically ±10% relative). The variation among the average compositions of different diamonds is somewhat greater (typically ±30%). Nevertheless, all diamonds exhibit similar characteristics, being rich in water, carbonate, SiO_2, and K_2O, and depleted in MgO. The composition of micro-inclusions in most diamonds vary within the following ranges: SiO_2, 30-53%; K_2O, 12-30%; CaO, 8-19%; FeO, 6-11%; Al_2O_3, 3-6%; MgO, 2-6%; TiO_2, 2-4%; Na_2O, 1-5%; P_2O_5, 1-4%; and Cl, 1-3%. In addition, BaO, 1-4%; SrO, 0.7-1.5%; La_2O_3, 0.1-0.3%; Ce_2O_3, 0.3-0.5%; smaller amounts of other rare-earth elements (REE), as well as Mn, Th, and U were also detected by instrumental neutron activation analysis (INAA). Mg/(Fe+Mg), 0.40-0.62 is low compared with other mantle derived phases; K/ AI ratios of 2-7 are very high, and the chondrite-normalized Ce/Eu ratios of 10-21 are also high, indicating extremely fractionated REE patterns.

SEM analyses indicate that individual inclusions within a single diamond are roughly of similar composition. The average composition of individual inclusions as measured with the SEM is similar to that measured by SIMS. Compositional variations revealed by the SEM are larger than those detected by SIMS and indicate a small variability in the composition of individual inclusions. No compositions of individual inclusions were determined that might correspond to mono-mineralic inclusions.

IR spectra of inclusion- bearing zones exhibit characteristic absorption due to: (1) pure diamonds, (2) nitrogen and hydrogen in the diamond matrix; and (3) mineral phases in the micro-inclusions. Nitrogen concentrations of 500-1100 ppm, typical of the micro-inclusion-bearing zones, are higher than the average nitrogen content of diamonds. Only type IaA centers were detected by IR. A yellow coloration may indicate small concentration of type IB centers.

The absorption due to the micro-inclusions in all diamonds produces similar spectra and indicates the presence of hydrated sheet silicates (most likely, Fe-rich clay minerals), carbonates (most likely calcite), and apatite. Small quantities of molecular CO_2 are also present in most diamonds. Water is probably associated with the silicates but the possibility of its presence as a fluid phase cannot be excluded. Characteristic lines of olivine, pyroxene and garnet were not detected and these phases cannot be significant components of the inclusions. Preliminary quantification of the IR data suggests that water and carbonate account for, on average, 20-40 wt% of the micro-inclusions.

The composition and mineralogy of the micro-inclusions are completely different from those of the more common, larger inclusions of the peridotitic or eclogitic assemblages. Their bulk composition resembles that of potassic magmas, such as kimberlites and lamproites, but is enriched in H_2O, CO_3, K_2O, and incompatible elements, and depleted in MgO.

It is suggested that the composition of the micro-inclusions represents a volatile-rich fluid or a melt trapped by the diamond during its growth. The high content of K, Na, P, and incompatible elements suggests that the trapped material found in the micro-inclusions may represent an effective metasomatizing agent. It may also be possible that fluids of similar composition are responsible for the extreme enrichment of incompatible elements documented in garnet and pyroxene inclusions in diamonds.

The origin of the fluid trapped in the micro-inclusions is still uncertain. It may have been formed by incipient melting of a highly metasomatized mantle rocks. More likely, it is the result of fractional crystallization of a potassic parental magma at depth. In either case, the micro-inclusions document the presence of highly potassic fluids or melts at depths corresponding to the diamond stability field in the upper mantle. The phases presently identified in the inclusions are believed to be the result of closed system reactions at lower pressures.

α-Al_2O_3:C晶体的热释光和光释光特性

以高纯α-Al2O3和石墨为原料,采用温梯法生长了α-Al2O3:C晶体,使用RisΦTL/OSL-DA-15型热释光和光释光仪研究了其热释光和光释光特性.α-Al2O3:C晶体在462K附近有单一热释光峰,发射波长位于410nm.随着辐照剂量的增加,热释光强度逐渐增强,462K的热释光特征峰位置保持不变.α-Al2O3:C晶体的光释光衰减曲线由快衰减和慢衰减两个部分组成,随着辐照剂量的增加,快衰减部分衰减速率变化不大,而慢衰减部分衰减速率加快.在5×10-6—10Gy剂量范围内,α-Al2O3:C晶体的热释光剂量响应呈现良好的线性关系,30Gy时达到饱和;光释光剂量响应在5×10-6—60Gy剂量范围内呈现良好的线性关系,100Gy时达到饱和.与热释光相比,光释光剂量响应具有更高的灵敏度和更宽的线性剂量响应范围.

4H-SiC基底Al_2O_3/SiO_2双层减反射膜的设计和制备

在4H-SiC基底上设计并制备了Al2O3/SiO2紫外双层减反射膜,通过扫描电镜(SEM)和实测反射率谱来验证理论设计的正确性。利用编程计算得到Al2O3和SiO2的最优物理膜厚分别为42.0nm和96.1nm以及参考波长λ=280nm处最小反射率为0.09%。由误差分析可知,实际镀膜时保持双层膜厚度之和与理论值一致有利于降低膜系反射率。实验中应当准确控制SiO2折射率并使Al2O3折射率接近1.715。用电子束蒸发法在4H-SiC基底上淀积Al2O3/SiO2双层膜,厚度分别为42nm和96nm。SEM截面图表明淀积的薄膜和基底间具有较强的附着力。实测反射率极小值为0.33%,对应λ=276nm,与理论结果吻合较好。与传统SiO2单层膜相比,Al2O3/SiO2双层膜具有反射率小,波长选择性好等优点,从而论证了其在4H-SiC基紫外光电器件减反射膜上具有较好的应用前景。

2.7NaF·AlF_3(7wt%CaF_2)-Al_2O_3-Y_(mm_2)O_3体系物理化学性质的研究

为了充分利用我国丰富的钇族稀土资源，以适应钇族稀土金属在铝及铝合金方面应用日益增长的趋势，寻找制取钇族稀土铝合金的新方法，本文系统研究了冰晶石熔体中添加钇族稀土碳酸盐即2.7NaF·AlF_3(7wt%CaF_2)-Al_2O_3-Y_(mm_2)O_3体系的一系列物理化学性质。应用最优化设计原理，研究了该本系的初晶温度，表面张力、密度、粘度和电导率，分别得到了表征该体系初晶温度、粘度与Al_2O_3、Y_(mm_2)O_3浓度关系的回归方程以及该本系表面张力、密度电导率与Al_2O_3、Y_(mm_2)O_3浓度和温度关系的回归方程。根据这五个回归方程，分别讨论了Al_2O_3、Y_(mm_2)O_3浓度及温度对熔体表面张力、密度和电导率的影响；Al_2O_3、Y_(mm_2)O_3浓度对初晶温度和粘度的影响；还讨论了Al_2O_3和Y_(mm_2)O_3对上述五个性质的交互作用。通过综合分析，比较了Al_2O_3和Y_(mm_2)O_3对上述五个物化性质的影响程度，以及对电解过程和电流效率可能发生的影响，得出用该体系作为电解制备钇族稀土铝合金的电解质是可行的，为选择合适的电解质组成提供了基础依据；同时填补了该体系一些物化性质的资料空白。

耐硫水煤气变换反应NiO-MoO_3-K_2CO_3/r-Al_2O_3催化剂研究

在本工作中，制备了一系列催化剂样品，其中有K、Ni、Mo单组份催化剂，K-Ni、K-Mo、Ni-Mo双组份催化剂及不同活性组份含量的K-Ni-Mo三组份催化剂。针对水煤气变换反应，对上述催化剂进行反应活性考察，得出如下结果：①催化剂各活性组份的最佳含量大致是NiO(3%), MoO_3(13%), K_2CO_3(6%)；②催化剂制备中的最佳焙烧温度在400 ℃左右；③催化剂使用前用H_2S/H_2的混和气进行预处理其效果最佳；④催化剂的催化活性与催化剂表面硫的含量有关，当催化剂表面处于严重缺硫状态时其活性下降；⑤反应的最佳汽:气 = 0.5-1.5；⑥加压有利于催化剂活性的提高，在加压情况下催化剂的活性随着反应温度的增加通过一极大值（在约200 ℃左右），不加压的反应催化剂活性随着反应温度的提高而增加。在催化剂的表征部分，利用XPS、XRD、紫外可见温反射光谱、SEM、ESR、比表面、TPR、酸度测定、TPD、TPS、TPS-TPR等实验对我们所制备的催化剂进行了研究。最后，我们用ESR和XRD实验技术研究了MoO_3、M_2CO_3 (M = Li、Na、K、Cs)-MoO_3加热过程中的固相反应，知道MoO_3在空气中焙烧时可以失去晶格氧，使晶体中的一些Mo~(6+)变成Mo~(5+)。在焙烧过程中，Li、Cs~+的加入将阻止MoO_3晶格氧向气相氧的转变，对Mo~(5+)的生成有抑制作用。加入一定量Na~+、K~+的MoO_3在焙烧过程中，其晶格氧被活化更易失去它们对Mo~(5+)的生成有促进作用，这种作用的大小是Na~+ > K~+。

CoMoK/γ-Al_2O_3类催化剂的研究

钴离子在γ-Al_2O_3上的吸附等温线符合Langmuir等温式，而钼的吸附等温线符合Freundlich等温式。在等孔体积法制备催化剂时，低PH下由于Al_2O_3吸附钼较多而对钴的吸附较少导致钴、钼在颗粒中分布不均；在高PH值下，由于钼的吸附量锐减，可用共浸法得到钴、钼分布均匀的催化剂。K_2CO_3在均匀型CoMo/Al_2O_3催化剂上的吸附等温线符合Langmuir等温式，虽然吸附量较大，但在浸渍液中今是足够时，等孔体积法也能得到均匀分布的结果。Co/Al_2O_3氧化态催化剂中存在和Al_2O_3表面作用的Co_3O_4及表面Co~(2+)离子；Co~(2+)/Al_2O_3中，K~+的存在减弱了Al_2O_3表面上的Co~(2+)和表面的作用，有是于Co~(2+)的还原和硫化。Mo/Al_2O_3催化剂中Mo以+6价的形式存在于Al_2O_3表面上，Al~(3+)对表面上Mo的极化作用Mo~(6+)在低温易于被部分还原，Mo-o-Al键作用较强，使Mo的完全还原又比MoO_3困难；K~+的存在减弱了MoK/Al_2O_3氧化态催化剂中的Mo-o-Al键强度，有助于Mo的深度还原和硫化。Co, Mo水溶液等孔体积共浸制备的氧化态CoMo/Al_2O_3催化剂中，存在CoMoO_4，并有利于Co, Mo硫化为Co_9S_8和MoS_2；CoMoK/Al_2O_3氧化态催化剂中，K~+的存在破坏了催化剂中CoMoO_4结构，被置换出的Co~(2+)和Al_2O_3表面发生一定作用使Co的硫化程度降低；当K_2CO_3在催化剂中含量小于15wt%时，Mo的硫化随K~+含量增加而增大，但当K_2CO_3在催化剂中含量高于15wt%，Mo的硫化程度随K~+含量增加而微有减少。CoMoK/Al_2O_3, CoMo/Al_2O_3, MoK/Al_2O_3, Mo/Al_2O_3, CoK/Al_2O_3, Co/Al_2O_3催化剂在H_2S/H_2的TPS过程中，H_2S 对活性组份起硫化和还原作用，H_2仅仅是还原了反应中生成的单质S。

水煤气变换反应催化剂CoMoK/Al_2O_3的结构和催化性能的研究

本论文运用程序升温还原（TPR）、漫反射光谱（DRS）、X-射线衍射（XRD）、顺磁（ESR）、质谱（MS）、能谱（XPS）、原子发射光谱（AES）和化学分析法等手段研究了Co/Al_2O_3、Mo/Al_2O_3、CoMo/Al_2O_3的结构和不同K_2CO_3含量对上述样品结构的影响，并与相应CoMoK/Al_2O_3催化剂的反应活性相关联，进而判断不同组份在催化反应中的作用。另外，还研究了Mg~(2+)、Zn~(2+)、Cu~(2+)、Cr~(3+)等具有不同八面体配位倾向能的过渡金属离子对Al_2O_3载体的改性从而对Co分布和催化剂反应活性的影响。