SHS等离子喷涂制备FeAl2O4-Al2O3-Fe纳米复合涂层的研究

利用SHS等离子喷涂技术，将经过机械团聚法制备的Fe₂O₃-Al复合粉体送入等离子焰流，沉积出厚度约为400 μm的复合涂层.利用XRD，SEM 和TEM等检测手段对涂层的成分和组织进行了分析，测定了涂层的显微硬度、断裂韧性以及耐磨性.结果表明涂层为具有纳米结构的FeAl₂O₄-Al₂O₃-Fe纳米复合组织；涂层的显微硬度为HV_100g870；断裂韧性是普通Al₂O₃涂层的2倍；无润滑磨损的耐磨性是普通Al₂O₃涂层的2.5倍. 关键词： SHS等离子喷涂 纳米涂层 断裂韧性     

激光熔覆Al2O3/Fe901复合涂层的强化机制及耐磨性

为提高金属材料表面涂层的耐磨性,采用激光熔覆工艺制备了Al_2O_3增强Fe901金属陶瓷复合涂层,研究了Al_2O_3陶瓷增强相对Fe基熔覆层组织与性能的影响。利用扫描电镜和X射线衍射仪检测了复合涂层的微观组织和物相;采用显微硬度仪和摩擦磨损试验机分析了复合涂层的显微硬度与耐磨性。结果表明:Fe901涂层的组织以柱状枝晶和等轴枝晶为主,添加的Al_2O_3可促使涂层组织转变为均匀的白色网状晶间组织及其包裹的细小黑色晶粒;复合涂层中的Al_2O_3陶瓷颗粒表面发生微熔,与Fe、Cr结合生成Fe3Al及(Al,Fe)4Cr金属间化合物,起到增加Al_2O_3陶瓷颗粒与金属黏结相结合强度的作用;当Al_2O_3陶瓷颗粒的质量分数为10%时,复合涂层的显微硬度较Fe901涂层增加了16.4%,复合涂层的摩擦磨损质量损失较Fe901涂层降低了50%;添加适量的Al_2O_3陶瓷有助于提高涂层的显微硬度及耐磨性。     

稀土CeO_2对镍基纳米Al_2O_3激光熔覆复合涂层组织和性能的影响

采用激光熔覆技术在45钢基体上制备了不同CeO2含量的镍基纳米Al2O3复合涂层,对熔覆层进行了微观组织分析和显微硬度测试。结果表明,随着CeO2含量的增加,熔覆层组织由亚共晶向共晶组织转变;加入1.0%CeO2对镍基纳米Al2O3熔覆层的组织起到明显的细化和净化作用,枝晶生长的方向性减弱,组织趋向均匀,熔覆涂层的显微硬度值比未加稀土的涂层提高了60-95HV0.2。     

电解等离子体法制备Al2O3陶瓷层及其特性研究

利用电弧喷铝并重熔后进行电解等离子体处理(EPP)的方法在Q235钢基体上制备出呈冶金结合的Al2O3陶瓷层.利用XRD,SEM和EDS等手段对陶瓷层的成分和显微组织进行了分析,测定了陶瓷层的耐蚀性能和耐磨性能.实验结果表明,陶瓷层主要由α-Al2O3,γ-Al2O3,θ-Al2O3以及一些非晶相组成,组织致密,耐蚀性能和耐磨性能良好.     

负载型纳米TiO2-Al2O3载体的液相合成及表征

采用沉淀法、共沉淀法、溶胶-凝胶法和改进的溶胶-凝胶法制备出TiO2-Al2O3复合载体,并用XRD、TEM、FT-IR等手段对其进行了表征。XRD结果表明,复合载体经550℃焙烧后,TiO2和Al2O3分别以锐钛矿和γ-Al2O3晶型存在,其中沉淀法和改进的溶胶-凝胶法制得载体的锐钛矿特征峰宽而尖锐;共沉淀法和溶胶-凝胶法制得的载体的锐钛矿特征峰表现不明显。TEM结果表明,TiO2为纳米粒子且均匀分布在Al2O3表面上,共沉淀法制备出的复合载体的粒子形貌表现为锐钛型TiO2粒子在γ-Al2O3上以单层或亚单层分散形式存在,而改进的溶胶-凝胶法制备出的复合载体中锐钛型TiO2和γ-Al2O3粒子形貌以更为清晰的橄榄状和絮状形式存在。FT-IR结果表明,4种方法制备出的复合载体酸性均主要表现为以L酸形式存在,仅含微量B酸。     

快冷熔覆法原位合成大厚度铁基非晶复合涂层的研究

通过水冷提高凝固速率及降低基体金属对熔覆层的稀释,采用改进的钨极惰性气体氩弧熔覆的方法,原位制备了大厚度(1—5 mm)Fe基非晶/纳米晶复合涂层.利用X射线衍射,光学显微镜和透射电子显微镜对涂层成分和组织进行分析,并测试了涂层的显微硬度.结果表明,采用快冷熔覆的方法可以制备出含有50%以上非晶含量的非晶/纳米晶复合涂层,涂层内纳米晶颗粒表面被非晶过渡层包覆.较厚涂层的显微硬度达到1600HV_0.3,与基体为冶金连接,有良好的结合强度及耐磨性.非晶/纳米晶复合结构使得涂层与基体之间的过渡区具备较强的弹塑性,提高了涂层的抗冲击性. 最后重点讨论了微观结构和性能之间的内在联系,涂层内非晶相与纳米晶相的协同作用是造成涂层高硬度的主要原因. 关键词： 非晶 涂层 熔覆 显微硬度     

Er3+掺杂SiO2复合的Al2O3粉末结构及光致发光特性

采用溶胶-凝胶(sol-gel)工艺制备0.1 mol% Er3+掺杂Al2O3体系和SiO2-Al2O3复合体系粉末. 实验结果表明:5 mol%的SiO2复合加入Al2O3抑制γ→θ和θ→α相转变. 掺0.1 mol%Er3+:Al2O3体系粉末,900℃烧结,在1.47-1.63 μm波段内光致发光(PL)谱为中心波长1.53 μm、半高宽56 nm的单一宽峰,1000-1200℃烧结,劈裂为多峰PL谱. 掺0.1 mol%Er3+:SiO2-Al2O3复合体系粉末,在高达1200℃烧结,仍保持中心波长1.53 μm的单一宽峰PL谱,由于-OH更完全的脱除,PL强度较900℃烧结Al2O3体系,SiO2-Al2O3复合体系均提高1个数量级.     

TiN/Al2O3纳米多层膜的共格外延生长及超硬效应

采用多靶磁控溅射法制备了一系列具有不同Al2O3调制层厚度的TiN/Al2O3纳米多层膜.利用X射线能量色散谱、X射线衍射、扫描电子显微镜、高分辨透射电子显微镜和微力学探针表征了多层膜的成分、微结构和力学性能.研究结果表明,在TiN/Al2O3纳米多层膜中,单层膜时以非晶态存在的Al2O3层在厚度小于1.5 nm时因TiN晶体层的模板效应而晶化,并与TiN层形成共格外延生长,相应地,多层膜产生硬度明显升高的超硬效应,最高硬度可达37.9 GPa.进一步增加多层膜中Al2O3调制层的层厚度,Al2O3层逐渐形成非晶结构并破坏了多层膜的共格外延生长,使得多层膜的硬度逐步降低.     

Al2O3-H2O纳米流体的相变蓄冷实验研究

通过在水介质中添加纳米氧化铝粒子,研制了一种新型传热冷却工质一氧化铝-水纳米流体,粒径分布显示了加入分散剂的悬浮液具有很好的分散性,同时对Al2O3-H2O纳米流体和水溶液的结冰过程进行了实时观察.结果表明,加入Al2O3纳米粒子后,流体的结冰速率得到了很大提高,结冰时间大大缩短,DSC测试结果得到0.1%Al2O3-H2O纳米流体的相变潜热值为313.1 J/g.     

Al2O3添加量对超高压烧结SiC的影响

碳化硅陶瓷具有高温强度大、抗氧化性强、耐磨损性好、热膨胀系数小、硬度高以及抗热震和耐化学腐蚀等优良特性，已经在很多领域获得应用。文中探索采用超高压烧结工艺烧结低Al2O3助剂添加量（质量分数O%-7％）的纳米SiC粉末，研究了烧结体的物相组成、化学成分、显微结构及显微硬度等。     

Polarisation resistance of the O2, Au/O2− and H2-H2O, Au/O2− electrode systems

Gold electrodes with known contact geometries were studied using impedance spectroscopy. From these data it was possible to determine the specific polarisation conductivity per unit length of three-phase boundary (TPB). The values were found to be (3÷22)×10⁻⁴ S·cm⁻¹ dependent on the electrode history in pure oxygen at 977 °C and 2×10⁻⁶ S·cm⁻¹ at 977 °C in “pure” hydrogen (P_O2=10⁻²⁰ atm at 1001 °C). The results are compared with previous data obtained for platinum electrodes.     

对含Y_2O_3和Gd_2O_3的La_2O_3-B_2O_3-BaO玻璃化学稳定性研究

本文研究了含Ｙ２Ｏ３和Ｇｄ２Ｏ３的Ｌａ２Ｏ３－Ｂ２Ｏ３－ＢａＯ玻璃的耐水性和耐酸性。结果表明，比硅酸盐玻璃化学稳定性差的Ｌａ２Ｏ３－Ｂ２Ｏ３－ＢａＯ玻璃，可以适量的用Ｙ２Ｏ３和Ｇｄ２Ｏ３取代Ｌａ２Ｏ３，可得以改善     

Mixed conductivity of glasses in the P2O5-V2O5-Na2O system

The conductivity of glasses in the P₂O₅−[(1−x) V₂O₅−x Na₂O] system is studied as a function of temperature and composition. For all compositions, the conductivity variations as a function of temperature follow an Arrhenius type relationship: . The activation energies and pre-exponential factors corresponding to the V₂O₅ richest compositions are lower than that corresponding to the ionic ones. Isothermal variations of the conductivity as a function of composition show a deep minimum for a molar ratio x near 0.65. On either side of this minimum, the conductivity is mainly electronic (x<0.7) or ionic (x>0.8). The variations are interpreted assuming a prevailing diluting effect of the non predominantly present oxide without any interactions between the electronic and ionic charge carriers. Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998.     

Surface complexes between O2, H2O and lithium

The He(I) photoelectron spectra of lithium and its surfaces as a function of exposure to O₂ or to H₂O are reported in this paper. The spectra provide evidence for the formation of a stable complex between H₂O and lithium rather than for formation of a product such as LiOH. The spectral evidence for the H₂O/Li complex is supported by calculations using several ten atom models of binding sites on unreconstructed lithium surfaces bearing H₂O in various conformations.     

Raman Scattering of H2O/D2O Solutions

The stretching vibrations of water are perfect characteristics of the hydrogen bond. Studying their frequency shift, changes of intensities, broadening of the bands and appearence of submaxima we can receive very important structural information about the groups involved in H-bonding and about the bond itself. The observed Raman spectra, however, are rather complicated because the OH and OD stretching bands are always superpositions of several bands due to intra- and intermolecular coupling, effect of Fermi resonance etc. The     

Spectroscopic studies on Li2O–MgO–Bi2O3–B2O3 glasses

MgO-Li₂O-Bi₂O₃-B₂O₃ glasses were prepared by melt quench technique and analyzed with the help of refractive index, optical, IR, and Raman spectroscopy studies. The present glasses exhibited the mixed modifier effect (MME) through refractive index change non-linearly. The variation in the indirect optical band gap and band tailing in MgO content have been discussed with the glass structure. Based on the obtained values of α_o2-, optical basicity, and interaction parameters, the present glasses were termed as very semi covalent acidic oxide glasses. Raman and Infrared spectra reveal that these glasses are built up of BO₃, BO₄ units of B₂O₃ and octahedral [BiO₆], pyramidal [BiO₃] units of Bi₂O₃ were observed.