制钛过程中阴极钙钛矿的形成与阳极溢出气体间的关系

采用FFC剑桥工艺在熔融CaCl₂中电解二氧化钛时,钙钛矿是阴极上不可避免形成的相。本文研究了在制备钛的过程中,阴极钙钛矿的形成与阳极释放气体的关系。结果表明,阴极上相的形成主要有三个阶段,包括钙钛矿的形成、钙钛矿的脱氧及钛的低价氧化物脱氧为TiO、和TiO到Ti的脱氧。尽管分解电压低于CaCl₂,但阴极形成的钙钛矿与从阳极释放的气体密切相关。由于短时间内钙钛矿的形成造成过电压,因而阳极释放出氯气,氯气的量取决于TiO₂和电解过程中产生的不同低价钛的量。当钛的低价氧化物介于Ti₃O₅和TiO₂之间时,在第一脱氧阶段TiO₂和氯的质量比为9：2到46：2。在氯气释放的过程中阳极没有明显的消耗。钙钛矿的形成和Ti₂O的脱氧是在熔融CaCl₂中电解制备钛的主要限制性环节。从TiO₂到Ti的总电流效率是24.07％。目前第一阶段的电流效率在22.37％~44.74％之间,第二阶段在30.18％~37.72％之间。     

CaWO4-NaCl-CaCl2体系熔盐电解制备钨粉的表征与电化学分析

通过熔盐电解法从CaWO4-NaCl-CaCl2体系制备出金属钨粉,采用X射线衍射仪(XRD)、电子扫描显微镜(SEM)和能谱分析仪(EDS)对钨粉的形貌和相组成进行表征。在试验数据的基础上计算电流效率,通过分析电解过程中形成的中间产物,讨论电解过程中的电极反应,采用循环伏安法和方波伏安法分析体系的基本热力学性质。结果表明:在750℃、槽电压2.5 V下经5 h以上电解可制备出纯度达到99%、平均粒度低于2μm的金属钨粉,实验中的电流效率可达到80%;电解过程的电极反应不可逆,浓差极化是体系电解速率的主要阻力。     

CaCl2-NaCl-CaO熔盐中电解精炼Si的研究

以冶金级Si和电解Cu为原料,制备了Cu-31Si（摩尔分数,%）合金.以Cu 31Si合金为阳极、Mo为阴极和参比电极,采用循环伏安和计时电位方法研究了1173 K下熔盐81CaCl₂ 8.0NaCl 8.5CaO-2.5Si（摩尔分数,%）的阴极行为,讨论了熔盐中Si电解精炼过程的还原步骤.用SEM,EDS和电感耦合等离子原子发射光谱仪（ICPAES）分析和表征了Si晶体的形貌和组成.电解精炼后得到了多晶Si,与冶金Si原料相比,主要杂质含量都显著降低,特别是对太阳能级Si危害较大的杂质B和P去除效果明显,分别从42×10^-6和25×10^-6降至4.5×10^-6和8.2×10^-6.电解精炼过程的电流效率为84.4%.     

炭阳极与CO2气体反应机理初探

通过对炭阳极与CO2气体的反应机理研究，指出炭阳极CO2反应性的各项指标与炭阳极消耗的关系。     

熔盐电解法制备单一Sm2Fe17合金相的机理研究

选择在LiF-CaF₂-SmF₃熔盐体系中,采用熔盐电解法在1160℃下通过恒电流在Fe阴极表面获得了不同厚度(17.22～40.34μm)的Sm₂Fe₁₇合金层,同时通过循环伏安法与方波伏安法研究了Sm³⁺在W与Fe阴极上的电化学行为。结果表明,Sm³⁺无法单独沉积于W电极上,Sm³⁺在铁阴极上的还原为Sm⁰分为2步,首先在-0.33V(vs.Cr/Cr₂O₃)发生Sm³⁺还原为Sm²⁺的可溶-可溶型反应,然后当电极电势超过-0.78V(vs.Cr/Cr₂O₃)时Sm²⁺开始在阴极界面处上发生欠电势还原,在Fe电极表面生成Sm₂Fe₁₇合金,这是由于在Sm₂Fe₁₇合金中降...     

TiO2/Bi2S3光阳极的制备及其光电性能

TiO₂光学带隙较宽,对可见光的响应较弱。为拓宽TiO₂光吸收范围和降低载流子复合概率,采用窄带隙的Bi₂S₃与TiO₂复合,构建异质结光阳极复合材料。首先对复合材料的物相和微观形貌进行表征,其次分析了复合材料的光电性能,结合复合材料的光电特性优化了制备工艺。改变水热生长Bi₂S₃的沉积次数,重点分析Bi₂S₃对异质结光电性能的影响。结果表明：当Bi₂S₃水热沉积次数为2时,复合材料的光电性能最佳,光电流密度达到0.22 mA/cm²,电子寿命为61 ms。与纯TiO₂相比,复合材料可显著提升对光吸收范围和强度,并提高了载流子的分离效率。     

电流密度对Na2B4O7-CaCl2熔盐电解法制备TiB2/TiB渗层的影响

采用熔盐电解法在纯钛表面渗硼,以硼砂作硼源、无水氯化钙为支持电解质,在电解温度920℃,电解时间1h的条件下,研究不同电流密度对渗层物相、微观结构及渗层厚度的影响,并用循环伏安法对阴极反应机理进行了研究。利用XRD对渗硼试样表面进行物相分析,利用扫描电镜(SEM)观察渗硼试样的断面形貌并采用能谱(EDS)进行元素分析。结果表明:在不同的电流密度下电解渗硼,得到的渗层均由TiB_2和TiB组成,且TiB_2渗层厚度可达到4.5μm,渗层厚度随电流密度非线性变化。循环伏安法结果显示阴极的反应主要是钠离子的还原,随后钠原子将硼砂生成的B_2O_3中的B置换出来,高温下B原子向钛基体扩散而形成硼化物渗层。     

Lu2O3/TiO2/Nb2O5共稳定ZrO2热障涂层材料研究

采用Lu2O3/TiO2/Nb2O5作为ZrO2热障涂层材料的稳定剂,研究Lu2O3/TiO2/Nb2O5共稳定ZrO2(15%LTNSZ)热障涂层材料在900℃、40 mol%V2O5+60 mol%Na2SO4熔盐中的热腐蚀行为。结果表明:8%YSZ热障涂层材料热腐蚀2 h后,t相ZrO2全部相变为m相ZrO2,热腐蚀产物为尺寸较大的YVO4晶体;15%LTNSZ热障涂层材料热腐蚀20 h后,m相ZrO2的比例仅为5.5%,热腐蚀产物为尺寸较小的LuVO4晶体。与Y2O3稳定剂相比,Lu2O3/TiO2/Nb2O5稳定剂使ZrO2在40 mol%V2O5+60 mol%Na2SO4熔盐中的抗热腐蚀性能提高1个量级以上。     

WO3修饰TiO2纳米管阵列制备、表征及光催化活性

利用化学浴沉积 (CBD) 结合热解工艺制备了WO₃修饰TiO₂纳米管 (WTN) 阵列, 且WTN阵列分布均匀。通过改变沉积时间可调整WTN的钨含量。利用SEM、EDX、XRD对WTN进行了表征。结果表明,阴极氧化后,TiO₂纳米管生长于钛体基体上,纳米管的内径为90~120 nm, 外径为120~160 nm,壁厚在30~60 nm范围,长约39 μm。经C. I.硫化红14的有效去除证实, 修饰TiO₂纳米管的WO₃增强了WTN光催化活性, 在可见光照射下,所制备复合膜光催化活性优于未修饰纳米管阵列 (TN)。     

氯化物熔体中电解制备Dy－Cu中间合金的研究

用循环伏安法、恒电位电解断电后的电极电位－时间曲线、电位阶跃法和Ｘ射线衍射法研究了Ｃｕ电极在ＮａＣｌ－ＫＣｌ－ＤｙＣｌ３熔体中的电化学行为，获知Ｄｙ在Ｃｕ电极上的还原过程是首先生成Ｄｙ－Ｃｕ合金，然后才析出纯金属Ｄｙ．测得Ｄｙ－Ｃｕ合金在１０７３Ｋ的标准生成自由能；在１０２３－１１４３Ｋ范围内，Ｄｙ原子在Ｄｙ－Ｃｕ合金相中的扩散系数与温度的关系式为ｌｎＤ＝－６７．１×１０３／ＲＴ－１５．８，其扩散活化能为６７．１ｋＪ·ｍｏｌ－１．用自耗阴极法制取了Ｄｙ－Ｃｕ中间合金并对其工艺条件进行了探讨。电解制取了含Ｄｙ高达９２％（质量分数）的Ｄｙ－Ｃｕ中间合金，其组成为ＤｙＣｕ和Ｄｙ，电流效率可达８０％．     

钕电解阳极产物的研究

用Orsat气体分析器和色谱－质谱联用仪研究了正常电解和发生阳极效应时钕电解的阳极气体成分,探讨了温度,阳极电流密度等对阳极气体组成的影响,计算了钕电解的总反应方程式,结果表明,正常电解时钕电解的阳极气体主要成分为CO,另有少量CO2,气体组成与铝电解有所不同,电解温度升高,CO的相对含量增多,电流密度增加,CO的相对含量减少,发生阳极效应时,利用色谱－质谱联用仪首次检测出阳极气体中所含氟碳化合物为CF4。     

Structure differences between TiO2 and phosphorus implanted TiO2 films caused by thermal treatment

The titanium oxide film has been deposited on Si wafers (110) by unbalance reactive magnetron sputtering and modified by phosphorus ion implantation and succeeding vacuum annealing. The structural, states of surface chemistry and surface morphology of the films have been investigated by X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS), atomic force microscope (AFM) and Scanning Electron Microscope (SEM), respectively. The results of XRD show rutile structure of as-deposited film, which is not changed by phosphorus implantation and vacuum annealing. However, a slightly shift of the peaks position to higher degree and the half width increases after ion implanted and vacuum annealing represent that the variety of the structure film caused by these treatments. The surface roughness is inclined to increase with the rising of annealing temperature for both undoped and P doped titanium oxide films. The surface chemistry presents significant difference between undoped and phosphorus doped films after a vacuum annealing, it may be attributed to the different evolvement of the surface defects existing in the film, which may be considered as an important influencing factor in the blood compatibility of the titanium oxide film.     

Composition, surface structure, and thermal behavior of ZrO2 + TiO2/Ti and ZrO2 + CeOx + TiO2 composites formed by plasma-electrolytic oxidation

Specific surface structures of ZrO₂ + TiO₂ (I) and ZrO₂ +CeO_x + TiO₂ (II) coatings on titanium before and after annealing at 850°C for 24 h in air are studied. Whiskers are found on the surface of type-I coatings before annealing, and perfectly edged crystals composed of TiO₂ and ZrO₂ oxides are found upon annealing. Pores in both coatings have a multilevel structure. In the case of type-I coatings, orifices of pores are covered with titanium. In type-II coatings, pore orifices contain titanium, zirconium, and oxygen. Oxygen deficiency implies that titanium and zirconium are present in pore orifices in metallic state. In type-II coatings, the surface distribution of cerium is heterogeneous. Mechanical treatment of the annealed coatings causes their exfoliation from the substrate metal. In the case of both coatings, the exfoliating surfaces are composed of TiO₂ blocks containing excess oxygen.     

Self-organized porous TiO2 and ZrO2 produced by anodization

The present work investigates the electrochemical formation of self-organized high aspect ratio TiO₂ and ZrO₂ nanotube layers. The formation and growth of a self-organized porous layer can be achieved directly by anodization without any templates in fluoride containing electrolytes. The morphology of the porous layers is affected by the electrochemical conditions such as the electrolyte composition, the pH and the exact polarization treatment (such as the potential sweep rate from the open-circuit potential to the anodizing potential). For Ti, nanotube layers are formed with diameters varying from approx. 20 nm to 100 nm and lengths from approx. 0.25 μm to 2.5 μm depending on the electrolytes and pH. On the other hand, for Zr, tubes of 50 nm in diameter and up to approx. 17 μm in length can be grown—a key parameter in this case is the potential sweep rate. The large difference between Ti and Zr in the achievable thickness of nanotube layers indicates a difference in the growth mechanism which may be based on the different chemical dissolution rates of electrochemically formed oxides.     

Properties of TiO2 support and the performance of Au/TiO2 Catalyst for CO oxidation reaction

Gold catalysts were prepared on TiO₂ supports of different phase structures (i.e., anatase, rutile and biphasic), TiO₂ crystal size (i.e., 9–23 nm), surface and textural properties (i.e., hydration and surface area). The CO oxidation on the gold catalysts was carried out in an operando-DRIFTS set-up equipped with DRIFTS reactor cell connected on-line to CO gas analyser and gas chromatograph enabling real time monitoring of surface reaction and simultaneous reaction rate measurements. Gold catalysts supported on pure anatase TiO₂ were more resistant to sintering compared to catalysts supported on rutile and bi-phasic TiO₂. Besides catalyst sintering, deposition of surface carbonates is an important cause of catalyst deactivation. The best gold catalyst was prepared on 13 nm anatase TiO₂. It displays both increased activity and stability for CO oxidation reaction at room temperature. Surface and textural properties of TiO₂ also play a role on the performance of the Au/TiO₂ catalyst.     

Glass fibers templated preparation of TiO2 microtubes assembled from nano/micro hierarchical TiO2 crystals

The unique rutile TiO₂ microtubes with the larger specific surface area and the distinct external/internal surface morphology have been fabricated in large-scale by a sol-gel-hydrothermal method via the readily available glass fibers as templates. The crystal phase, morphology and surface area of as-obtained samples were measured by XRD, SEM, TEM and BET. The results indicate that these microtubes with the inner diameter of ca. 8 μm and the wall thickness of 2-3 μm have a novel double-layer structure, which is built from closely associated TiO₂ rod arrays and TiO₂ gel film. Detailed electric microscopy investigations on such TiO₂ rod arrays exhibit that they are mainly constructed by flower-like rod clusters, and each TiO₂ rod derives from the assembly of the parallel-growth TiO₂ nanowires with the diameter of ca. 10 nm. Such unique hierarchical nano/micro TiO₂ structure enhances the specific surface area of these microtubes effectively, which makes them have more potential applications in the fields of catalysis, sensors, and drug delivery.     

保护渣对铝钛系夹杂物溶解的吸收规律

以CaO-SiO₂-Al₂O₃-Na₂O-CaF₂-MgO为基础渣系,采用旋转动力学方法研究了不同碱度、BaO质量分数(0~15%)、B₂O₃质量分数(0~15%)对连铸保护渣吸收Al₂O₃或TiO₂速率的影响以及吸收前后矿相变化。结果表明,保护渣吸收TiO₂的速率要远大于吸收Al₂O₃的速率;添加BaO或B₂O₃后均能提高保护渣吸收Al₂O₃和TiO₂的能力;保护渣主要物相为钙镁黄长石(2CaO·MgO·2SiO₂)、钙铝黄长石(2CaO·Al₂O₃·2SiO₂)、枪晶石(3CaO·2SiO₂·CaF₂)及玻璃相(Na₂O·Al₂O₃·SiO₂);添加BaO后,钙镁黄长石转变为重硅酸钡钙镁(2CaO·MgO·2SiO₂·BaO),并抑制黄长石和枪晶石晶体长大;当添加B₂O₃的质量分数不低于10%,保护渣形成的物相为玻璃相。试验条件下,不同碱度的保护渣和添加B₂O₃的保护渣中TiO₂仍以TiO₂形式存在,而在添加BaO的保护渣中,TiO₂形成钙钛矿。     

Performance Enhancement in Dye-Sensitized Solar Cells with Composite Mixtures of TiO2 Nanoparticles and TiO2 Nanotubes

In the present investigation,a new composite nanostructured photoanodes were prepared using TiO₂ nanotubes（TNTs） with TiO₂ nanoparticles（TNPs）.TNPs were synthesized by sol-gel method,and TNTs were prepared through alkali hydrothermal method.Dye-sensitized solar cells（DSSCs） were fabricated with different photoanodes comprising of various ratios of TNTs + TNPs,synthetic indigo dye as photosensitizer,PMII（l-propyl-3-methylimidazolium iodide） as ionic liquid electrolyte and cobalt sulfide as counter electrode.The structures and morphologies of TNPs and TNTs were analyzed through X-ray diffractometer,transmission electron microscope and scanning electron microscopes.The results of the investigation showed that the DSSC-4 made with composite photoanode structure（TNTs/TNPs）（90% of TNPs + 10% of TNTs） had improved photocurrent efficiency（2.11%） than pure TNPs（1.00%） and TNT film（0.78%）.Electrochemical impedance spectra revealed that the composite TNTs/TNPs film-based DSSCs possessed the lowest charge-transfer resistances and longest electron lifetime.Hence,it could be concluded that the composite TNTs/TNPs photoanode facilitates the charge transport rate and enhances the efficiencies of DSSCs.     

CO oxidation: Deactivation of Au/TiO2 catalysts during storage

In a study of the phenomenon of catalyst deactivation during storage, Au/TiO₂ catalyst was stored under various conditions, viz. vacuum, nitrogen, air, refrigeration, dark, and light, and tested for CO oxidation activity at regular intervals. The data shows that the catalyst deactivates under all the storage conditions over 12 months and that storage in vacuum significantly enhances the rate and extent of deactivation. Storage in light accelerates the deactivation. The catalyst appears to deactivate through a combination of Au(III) reduction, Au nanoparticle agglomeration, loss of surface hydroxyl groups, loss of surface moisture, and accumulation of surface carbonates and formates. The rate and extent of catalyst deactivation can be limited by storing the catalyst in the dark at sub ambient temperature (refrigerator) and under inert atmosphere.