氧化铒涂层制备技术的研究进展

核聚变环境中材料的防氚渗透问题是聚变堆材料研究的重要课题之一.近年来,Er2O3涂层凭借着优良的热稳定性和防氚渗透性能引起了人们极大的关注.影响Er2O3涂层大规模应用在于其制备工艺及性能.综述了Er2O3涂层的制备技术及相关发展现状,展望了今后的发展趋势.     

溶液浸渍法制备Al2O3陶瓷布的研究

以棉布和粘胶纤维布作为前驱体布,采用溶液浸渍法制备了Al2O3陶瓷布。采用扫描电子显微镜、X射线衍射研究了不同工艺对Al2O3陶瓷布显微结构和成分的影响。结果表明:采用棉布及粘胶纤维布均能制得Al2O3陶瓷布,其纤维纹理与前驱体布织物结构保持一致;随着烧结温度升高,显微组织越愈加致密,纤维断裂程度减小,烧结应在900～1000℃进行。     

热障涂层用La2O3、Y2O3共掺杂ZrO2陶瓷粉末的制备及其相稳定性

采用反向化学共沉淀法制备了热障涂层用La₂O₃-Y₂O₃-ZrO₂（LaYSZ）原始复合粉末, 将原始粉末团聚造粒和热处理后得到适于等离子喷涂的团聚粉末. 采用电感耦合等离子体原子发射光谱（ICP-AES）、扫描电子显微镜（SEM）、霍尔流速计、X射线衍射（XRD）等方法分别对LaYSZ的化学组成、微观形貌、流动性和松装密度、高温相稳定性进行了研究. 结果表明: LaYSZ团聚粉末室温呈四方ZrO₂结构, 在1150℃热处理2h后为致密的球形或近球形颗粒, 粉末流动性较好, 适于等离子喷涂. LaYSZ团聚粉末在1300℃热处理100h后仍保持单一的四方ZrO₂晶型, 而8YSZ中有12mol%的四方相转变为单斜相; LaYSZ在1400℃热处理100h后, 单斜相含量为2mol%, 而8YSZ中单斜相含量达到47mol%, 表明La₂O₃、 Y₂O₃共掺杂稳定ZrO₂较单一Y₂O₃ 稳定ZrO₂具有更好的高温相稳定性.     

溶胶-凝胶法制备致密α-Al2O3涂层的研究

以异丙醇铝为前驱物,水为溶剂,硝酸为胶溶剂,用分散法制得了稳定透明的氧化铝溶胶,并用降液法制得了氧化铝凝胶涂层,经热处理后最终获得Al2O3涂层.利用TG-DTA分析了氧化铝凝胶向Al2O3的转变过程.XRD分析表明所获得的涂层为α-Al2O3晶型结构.SEM分析表明所制得的涂层致密均匀,无开裂,并且涂层与基底结合良好.因而该法是一种简单易行的制备致密α-Al2O3涂层的好方法.     

溶液燃烧法制备Ni-Al2O3催化剂用于CO2-CH4重整研究

采用溶液燃烧法制备了Ni含量为2wt%、4wt%、6wt%、8wt%和10wt%系列催化剂, 并对反应前后催化剂进行N₂吸附-脱附、XRD、H₂-TPR、TPH、Raman、TEM和TG-DTG等表征。与等体积浸渍法(以溶液燃烧法制备的Al₂O₃为载体)制备的催化剂相比, 溶液燃烧法制备的催化剂具有较大的比表面积, 孔径分布可分为2~4.5 nm和4.5~10 nm两段, 属典型的多级孔结构; NiO高度分散在载体上, 与载体具有较强的相互作用, 这种相互作用有利于提高催化剂的稳定性。催化剂210 h稳定性试验表明, 溶液燃烧法制备的Ni含量为8wt%试样的CH₄转化率维持在90%左右, 失活速率仅为0.035%/h, 优于浸渍法制备的相同Ni含量催化剂。     

Sol-Gel法制备低阻In2 O3薄膜

采用sol-gel法制备In2O3薄膜材料,研究了不同制备条件对薄膜电阻的影响;分别用XPS、XRD方法对材料进行了分析,确定了其结构和组成,并用此薄膜材料制作了直热式气敏元件,发现它对乙醇、丁烷气体具有较高的灵敏度。     

化学溶液沉积法制备Y2O3过渡层

为了满足YBa2Cu3O7(YBCO)超导带材生产实际的需要,在金属基带和YBCO超导薄膜之间制备一层合适的氧化物过渡层显得尤为重要。以乙酸钇为原料配制前驱体溶液,采用金属盐化学溶液沉积法在织构的Ni-5%W(质量分数)(Ni-5W)带上成功制备了Y_2O_3过渡层。结果显示,氮气氛下1050℃热处理1h后,所获得的Y_2O_3过渡层具有良好的晶体织构,晶体生长取向为(100),完全复制了Ni-5W带模板的结构,为YBCO生长提供了良好的模板。在Y_2O_3过渡层上制备的YBCO薄膜表现出良好的超导性能。     

化学溶液电沉积法制备Li2SiO3薄膜研究

利用化学溶液电沉积方法，在阴极和阳极衬底材料上都成功制备出了单相的含氧酸盐硅酸锂（Li2SiO3）薄膜。探讨了该工艺下的实验反应机理。通过X射线衍射技术（XRD）、扫描电子显微镜（SEM）分别表征研究了不同实验条件下薄膜的晶体结构和表面形貌。研究结果表明，采用化学溶液电沉积法制备的Li2SiO3薄膜具有物相结构单一，表面形貌平整致密的特点。与制备Li2SiO3的传统方法相比，这一技术具有廉价、简单、低温等特点。     

微波法制备γ-Al2O3蜂窝陶瓷涂层的实验研究

采用微波加热法制得了γ-Al₂O₃蜂窝陶瓷涂层及相应的三效催化剂.比较并详细分析了微波涂层（TC-B）与传统涂层（TC-A）在晶型、比表面积及三效催化剂活性上的差别.结论是.微波涂层的主要特性参数均达到或超过了传统涂层.以微波法制备γ-Al₂O₃涂层的工艺过程能耗少、周期短、生产成本低.     

溶胶-凝胶法在PMMA上制备SiO2-Al2O3涂层过程的研究

采用溶胶－凝胶法,以无机盐ＡｌＣｌ３．６Ｈ２Ｏ、醇盐ＴＥＯＳ及自制偶联剂为原料,在ＰＭＭＡ上制备抗磨涂层,选择出得到高质量涂膜的合适组分及工艺。研究了膜形成的基本规律。     

Refractories based on 3Er2O3-Ta2O5

Refractory Er₂O₃-Ta₂O₅ compositions in the high Er₂O₃ region were prepared by coprecipitation as hydroxides, followed by calcination. Based on x-ray diffraction and wet chemical and electron microanalysis, the fluorite phase was found at 17.3–34.2 (±0.5) mole percent Ta₂O₅. This fluorite phase was stable to at least 2140 C in reducing atmospheres; although measurable vaporization occurred above 1975 C. Above 2100 C minor Ta reduction with preferential vaporization of Er and O was observed.     

Metalorganic chemical vapor deposition of Er2O3 thin films: Correlation between growth process and film properties

Er₂O₃ thin films have been grown by metalorganic chemical vapor deposition (MOCVD) at 600 °C on different substrates, including glass, Si (100) and sapphire (0001) using tris(isopropylcyclopentadienyl)erbium and O₂. The effects of growth parameters such as the substrate, the O₂ plasma activation and the temperature of organometallic precursor injection, on the nucleation/growth kinetics and, consequently, on film properties have been investigated. Specifically, very smooth (111)-oriented Er₂O₃ thin films (the root mean square roughness is 0.3 nm) are achieved on Si (100), α-Al₂O₃ (0001) and amorphous glass by MOCVD. Growth under O₂ remote plasma activation results in an increase in growth rate and in (100)-oriented Er₂O₃ films with high refractive index and transparency in the visible photon energy range.     

Preparation and characterization of Bi2Ti2O7 thin films by chemical solution deposition technique

Transparent and crack-free Bi₂Ti₂O₇ thin films with strong (111) orientation were successfully prepared on n-Si(100) by chemical solution deposition (CSD) using bismuth nitrate and titanium butoxide as starting materials. The structural properties were studied by X-ray diffraction. The dielectric constant at 100 kHz at room temperature was 118 and loss factor was 0.074, for a 0.4-μm-thick film annealed at 500°C for 30 min. The leakage current density was 4.06×10⁻⁷ A/cm² at an applied voltage of 15 V.     

Preparation of LiMn2O4 thin films by aqueous solution deposition

Cathode material LiMn₂O₄ thin films were prepared by aqueous solution deposition using lithium acetate and manganese acetate as starting materials. The structures, morphologies, and the first discharge specific capacity of the thin films were investigated as a function of annealing temperature and time. The cycling properties of the thin films were also examined. The results show that LiMn₂O₄ thin films prepared by this method are homogenous and crack-free. The thin film annealed at 750°C for 30 min has good rechargeability. The capacity loss per cycle is about 0.05% after being cycled 100 times.     

Studies on the high-pressure reaction of Er2O3 and VO2

The reaction of erbium sesquioxide (Er₂O₃) and vanadium dioxide (VO₂) at 50 kbar and 30 kbar pressures and 1400°C were studied. In the course of the reaction, tetravalent vanadium ions were reduced to the trivalent state and erbium vanadites (ErVO₃) were obtained. The crystal structures of the products were examined by an x-ray diffraction analysis. At 50 kbar, a vaterite-type (μ-CaCO₃) compound isostructural with ErBO₃, which belonged to a hexagonal system, and at 30 kbar, a calcite-type vanadite belonging to a rhombohedral (pseudo-hexagonal) system were obtained. In the case of the reaction of erbium sesquioxide and vanadium trioxide (V₂O₃) at high pressure, a perovskite-type erbium vanadite was obtained. The magnetic properties of the compounds were studied.     

Fabrication of heavily Er2O3 doped aluminophosphosilicate glass fibers

This work examines vapor-phase doping of aluminophosphosilicate (APS) glasses with erbium oxide using Er(dpm)₃ (erbium dipivaloylmethanate) as a metalorganic precursor. We describe two vapor-phase processes for Er₂O₃ doping of APS glasses for fiber cores. In one of them, a standard MCVD procedure, all the oxides of the glass core are deposited simultaneously. With this procedure, the erbium content of the APS glasses does not exceed 1 wt % because of the reaction of AlCl₃ with POCl₃ and Er(dpm)₃. In the other procedure, a porous Al₂O₃-P₂O₅-SiO₂ layer is infiltrated with Er₂O₃ from the vapor phase. Owing to the separation of the reactant flows, this procedure ensures considerably higher rare-earth doping levels in the APS glasses, up to several weight percent.     

La-substitution Bi2Ti2O7 thin films grown by chemical solution deposition

(La_0.05Bi_0.95)₂Ti₂O₇ (LBTO) thin films had been successfully prepared on P-type Si substrate by chemical solution deposition method. The structural properties of the films were studied by X-ray diffraction. The phase of (La_0.05Bi_0.95)₂Ti₂O₇ is more stable than the phase of Bi₂Ti₂O₇ without La substitution. The films exhibited good insulating properties with room temperature resistivities in the range of 10¹²-10¹³ Ω cm. The dielectric constant of the film annealed at 550 °C at 100 kHz was 157 and the dissipation factor was 0.076. The LBTO thin films can be used as storage capacitors in DRAM.     

Preparation of nanocrystalline SnO2 thin film coated Al2O3 ultrafine particles by fluidized chemical vapor deposition

Fluidized chemical vapor deposition (FCVD) technology was developed for coating SnO₂ thin film on Al₂O₃ ultrafine particles. TEM and HREM analysis found that SnO₂ films with different structures were deposited by controlling the coating temperature, reactant concentration, etc. Nanocrystalline SnO₂ film was coated at 573.15 K by gas phase reaction of SnCl₄ with H₂O. EPMA and EDS studies indicated that the distribution of SnO₂ inner and outer of the agglomerates was uniform. Nucleation and film deposition were coexisted mechanism during the FCVD coating process. The fraction of SnO₂ in the composite particles increased with increasing coating temperature, SnCl₄ concentration, and coating time. The mass fraction of SnO₂ in the composite particles increased strongly with the ratio of P_H2O and P_SnCl4 at low mole ratio of H₂O with SnCl₄, but increased little under the conditions of excess H₂O with respect to SnCl₄.     

Pulsed plasma-enhanced chemical vapor deposition of Al2O3-TiO2 nanolaminates

Self-limiting synthesis of alumina-titania nanolaminates (ATO, Al₂O₃/TiO₂) was accomplished via pulsed plasma-enhanced chemical vapor deposition. At the synthesis temperature of 150 °C the alumina layers were amorphous, while TiO₂ layers displayed a polycrystalline anatase structure. Digital control over nanolaminate structure was demonstrated through elemental analysis and transmission electron microscopy imaging. The dielectric performance of the ATO structures was examined as a function of composition and bilayer thickness. Capacitance-voltage measurements showed that the effective dielectric constant was consistent with treating the nanolaminates as individual capacitors in series. Current-voltage measurements showed that leakage current deteriorated with TiO₂ content, though low leakage was restored through interfacial engineering.     

Al2O3 formation on Si by catalytic chemical vapor deposition

Catalytic chemical vapor deposition (Cat-CVD) has been developed to deposit alumina (Al₂O₃) thin films on silicon (Si) crystals using N₂ bubbled tri-methyl aluminum [Al(CH₃)₃, TMA] and molecular oxygen (O₂) as source species and tungsten wires as a catalyzer. The catalyzer dissociated TMA at approximately 600 °C. The maximum deposition rate was 18 nm min⁻¹ at a catalyzer temperature of 1000 °C and substrate temperature of 800 °C. Metal oxide semiconductor (MOS) diodes were fabricated using gates composed of 32.5-nm-thick alumina film deposited at a substrate temperature of 400 °C. The capacitance measurements resulted in a relative dielectric constant of 7.4, fixed charge density of 1.74×10¹² cm⁻², small hysteresis voltage of 0.12 V, and very few interface trapping charges. The leakage current was 5.01×10⁻⁷ A cm⁻² at a gate bias of 1 V.