Phase formation of nano-TiO<Subscript>2</Subscript> particles during flame spraying with liquid feedstock

The nanostructured TiO₂ photocatalytic coatings were synthesized through flame spraying with liquid feedstock under different conditions. The nanostructured TiO₂ deposit of substantial anatase phase was annealed at different temperatures. X-ray diffraction analysis showed that significant transformation from anatase to rutile occurred at a temperature above 600 °C. However, thermal analysis suggested that the phase transformation from anatase to rutile started at a temperature from 400 to 500°C. It was found that the grain size of rutile phase was larger than that of anatase. The deposits annealed at temperatures lower than 450°C were photocatalytically active. However, the deposit annealed at 500°C, which contained 95% anatase crystalline, became photocatalytically inactive. Based on the experimental findings, a model is proposed to explain the phase transformation of the nano-TiO₂ particles and the phase formation in flame-spraying of nanostructured TiO₂ deposit with liquid feedstock. The original version of this paper was published as part of the DVS Proceedings: “Thermal Spray Solutions: Advances in Technology and Application,” International Thermal Spray Conference, Osaka, Japan, 10–12 May 2004, CD-Rom, DVS-Verlag GmbH, Düsseldorf, Germany.     

有机电解液中TiO2纳米管阵列的制备及其光电性能

在氟化铵/丙三醇电解液中,采用恒压直流阳极氧化法制备TiO2纳米管阵列,并研究其在空气热处理过程中的结晶行为,最后将管阵列作为光阳极组装成染料敏化太阳能电池(DSSC),研究氧化时间和热处理温度对其光电性能的影响。结果表明:TiO2纳米管阵列的形成是一个随时间渐进演变的过程;随着氧化时间的延长,纳米管长度逐渐增大,当时间为70 h时,长度达到5μm左右;管阵列在空气中于400℃以下热处理后,由锐钛矿相构成,450和500℃热处理时,由锐钛矿相和金红石相构成,同时管阵列结构具有良好的高温稳定性。光电性能测试显示,20 V、70 h制备的TiO2纳米管阵列经450℃热处理后,组装成的染料敏化太阳能电池的(有效面积1 cm2)光电转换效率可达到0.989%。     

Synthesis of iron(Ⅲ)-doped nanostructure TiO2/SiO2 and their photocatalytic activity

Iron(Ⅲ)-doped nanostructure TiO2-coated SiO2 (TiO2/SiO2) particles were prepared using the layer-by-layer assembly technique and their photocatalytic property was studied. TiO2 colloids were synthesized employing the sol-gel method with TiCl4 as a precursor. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), SEM, EDS, XPS, and XRD. The experimental results show that TiO2 nanopowders on the surface of SiO2 particles are well distributed, the amount of TiO2 is increased with the adding of coating layers, the pure anatase-TiO2 coating layers are synthesized at 500℃, and the photocatalytic activity of Fe3+-doped TiO/SiO2 is higher than tnat of undoped TiO2/SiO2.     

聚乙二醇对TiO2-SiO2粒子的生成及光催化性能影响

以TiCl4为原料,采用自组装技术制备TiO2-SiO2复合粒子,加入聚乙二醇2000（PEG 2000）,探讨聚乙二醇对TiO2-SiO2粒子生成及光催化降解甲基橙的影响。研究发现：随组装次数的增多,复合粒子表面TiO2 的含量增多;随PEG2000的加入,TiO2颗粒间呈现一定的孔隙,使TiO2层粒子的表面积增加;样品经550 ℃煅烧,得到均为锐钛矿与金红石的混合相,且随着PEG2000含量的增加,锐钛矿的相对含量随之增加;光催化实验表明,PEG2000的掺杂使TiO2-SiO2的光催化性能得以提高。     

纳米TiO2/玻璃微珠复合颗粒的制备和光催化性能

用钛酸丁酯为原料,通过胶溶-沉淀的方法在低温下制备了纳米TiO2/玻璃微珠复合颗粒,利用SEM、DRS、XRD等表征了复合颗粒的结构和形貌。结果表明,玻璃微珠表面被20nm左右的TiO2包覆形成核-壳型结构,XRD结果显示表面的TiO2为锐钛矿型,复合颗在紫外光区有强烈吸收,呈现出纳米TiO2半导体光吸收特征。以含甲基橙废水为降解对象研究了所制备复合颗粒的光催化活性。     

Ti/nano-TiO2-Pt复合电极催化甲醇氧化的研究

采用溶胶-凝胶法(sol-gel)制备纳米TiO2(Ti/nano-TiO2)膜电极,再用电沉积法在纳米TiO2膜上修饰Pt微粒,制成Ti/nano-TiO2-Pt复合电极.用循环伏安法研究了纯Pt丝电极和Ti/nano-TiO2-Pt电极对甲醇氧化的电催化活性以及稳定性.结果表明:对甲醇氧化,复合电极比Pt丝电极具有更高的催化活性,且对甲醇氧化中间产物CO的吸附量少,因而不易中毒;复合电极载铂量达到一定值时,电极具有最强的催化活性.     

退火工艺对二氧化钛薄膜光催化性能的影响

利用磁控溅射法制备得到二氧化钛薄膜,将薄膜在高温管式炉中分别进行退火,利用XRD、AFM和紫外-可见光谱仪研究了不同温度下退火前后薄膜的晶相结构、光学性能和光催化性能。结果表明,随着退火温度的升高二氧化钛的晶相由锐钛矿向金红石转变,600℃时为两相共存,表面颗粒大小也会有相应变化,锐钛矿相表现出了更好的光催化性能。     

纳米复合材料CdS/TiO2NTs的制备及光催化产氢活性

通过离子交换和沉淀反应制备纳米复合材料CdS/TiO2NTs.采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、漫反射紫外-可见吸收光谱(DRUVAS)、荧光光谱(FES)、X射线荧光分析(XRF)等手段对该复合材料的结构进行表征.SEM结果表明:钛酸盐纳米管的形成经由TiO2颗粒-片状的钛酸盐-卷曲的钛酸盐纳米管的自组装过程.XRD、DRUVAS、FES和FES结果表明:平均粒度大约 8 nm 的六方相CdS均匀的负载于锐钛矿型TiO2纳米管表面,其吸收边扩展到可见区.与TiO2纳米管及TiO2粉末相比,CdS/TiO2NTs 纳米复合材料展示了较高的可见光催化分解水产氢活性.     

磁性纳米光催化剂的制备及其光催化性能

以Fe3O4为载体,制备了易于固液分离回收的磁性复合纳米光催化剂,采用SEM,元素分析,XRD等方法表征催化剂的表面形貌,晶体结构,结果表明,二氧化钛包裹在Fe3O4的表面,其包裹量越大,粒径越大,锐钛矿峰越强,利用光催化降解甲基橙的效果来考察磁性复合光催化剂的活性,直接包裹在Fe2O4表面的TiO2活性低于纯TiO2的,而在Fe3O4与TiO2之间包裹SiO2,可以有效地提高其光催化活性,其活性与纯TiO2接近。     

钕铁硼磁体表面电沉积纳米氧化硅复合镀锌层的研究

目的增强钕铁硼材料的耐腐蚀性能。方法在钕铁硼磁体材料表面电沉积含有氧化硅、氧化钛纳米粒子的复合锌层。结果在氯化物镀锌溶液中加入10 g/L的氧化硅纳米粒子,可以获得氧化硅质量分数在3%以上的氧化硅纳米粒子复合镀锌层,而加入10 g/L的氧化钛纳米粒子的镀液所获得的复合镀层中,氧化钛的质量分数只有0.3%。结论中性盐雾腐蚀和盐水浸泡腐蚀试验结果表明,含有氧化硅纳米颗粒的复合镀锌层的耐腐蚀性能得到了提高,而含有氧化钛纳米颗粒的复合镀锌层的耐腐蚀性能则没有提高。含有纳米粒子的复合镀液经过1年的放置和间断使用,仍然保持着纳米颗粒均匀分散的稳定性和在镀层中稳定析出氧化硅纳米粒子的特征。     

Hydrogen Storage Property of Porous/Hollow TiO2 Using Yeast as Template

研究表明：在620 ℃煅烧后,模板除去,TiO2形成。产物主要由TiO2 和少量的H2Ti3O7组成。得到的产物的比表面积为252.6 m2/g。P-C-I测试结果表明,30 ℃时TiO2显示可逆的吸/放氢过程。在吸/放氢过程中,化学键发生微小的偏移,表明氢可能和OH基团发生反应。随着吸/放氢循环的增加以及比表面积的明显的降低,多孔/中空TiO2坍塌。同时,随着温度的升高,化学吸附量增加,吸氢量升高     

La、Nd、Bi共掺杂制备TiO2电致变色薄膜及其性能研究

为了提高TiO2薄膜的光学属性和着色效率,采用溶胶-凝胶工艺,以钛酸丁酯为前驱体在ITO导电玻璃基片表面制备了La、Nd、Bi共掺杂TiO2薄膜。采用XRD、UV-vis和化学工作站等手段研究了TiO2薄膜的结构和表面的光学和电致变色性能。结果表明:在400、500和600℃热处理的二氧化钛干凝胶中形成锐钛矿型二氧化钛,且热处理温度越高,晶体发育越完整。La、Nd、Bi掺杂TiO2增加了TiO2八面体的排列无序性,导致非晶化程度提高。体积分数为12%的钛酸丁酯相应制备的薄膜具有优良的电致变色性能。500℃热处理的TiO2薄膜电致变色性能最为优异。实验进行了La、Nd、Bi单独掺杂TiO2薄膜的性能分析,单独掺杂摩尔分数为8%La、18%Nd、6%Bi的TiO2薄膜具有较优异的变色性能,单独掺杂变色效果的顺序是6%Bi<8%La<18%Nd。La、Nd、Bi共掺杂锐钛矿型TiO2仍然具有很高的非晶化程度,且当掺杂摩尔比La:Nd:Bi=4:10:2时,取得薄膜最佳循环伏安特性,掺杂TiO2非晶化程度最高。     

Synthesis and Optical Absorpition Properies of Anatase TiO2 Nanoparticles via a Hydrothermal Hydrolysis Method

以硫酸钛为钛源,浓氨水为沉淀剂,通过水热水解法在240 ℃,48 h,pH=9时合成了粒径约为20 nm的锐钛矿TiO2纳米颗粒。利用X射线衍射仪（XRD）、热场发射扫描电子显微镜（SEM）、热场发射透射电子显微镜（TEM）和紫外可见分光光度计（UV-VIS）对试样进行分析。结果表明：硫酸钛溶液水热水解法不加入浓氨水时,随着水解时间的延长,虽然获得的锐钛矿型TiO2颗粒的粒径已达到了纳米级,但是其粒径的变化不明显;硫酸钛溶液水热水解法时加入浓氨水,合成锐钛矿型TiO2颗粒的粒径明显变小,但是,随着pH值的增加,合成锐钛矿型TiO2颗粒的粒径变化不明显。对不同条件下水热水解法合成的TiO2进行UV-VIS分析可得,TiO2颗粒粒径的变小有利于TiO2吸收峰的蓝移。     

添加纳米TiO2的Ni-P化学复合镀层显微结构与性能

采用化学复合镀法制备了Ni-P-纳米TiO2复合镀层,研究了纳米TiO2添加对Ni-P复合镀层的显微结构、硬度、耐磨性、孔隙率及耐蚀性的影响,并讨论了其影响机理。结果表明:纳米TiO2粒子较为均匀地分布在Ni基镀层,未发生明显团聚;纳米TiO2粒子的弥散强化作用,使复合镀层具有较高的表面硬度和良好的耐摩擦性能,晶化热处理后的复合镀层表面硬度达到了10 925 MPa,耐摩擦性能也显著提高。添加纳米TiO2粒子后,镀层的孔隙率增加,耐碱和耐盐腐蚀的能力稍有降低,耐HCl溶液腐蚀的能力较差。     

纳米二氧化钛硅烷接枝密度对水性环氧涂层耐蚀性能的影响

目的研究水性环氧/硅烷化纳米TiO2复合防护涂层在3.5%NaCl溶液中的失效规律和防腐性能。方法采用3-氨丙基三乙氧基硅烷(APTES)化学接枝改性纳米TiO2颗粒,将硅烷改性纳米TiO2均匀分散在水性环氧涂料中,并把混合涂料涂覆在Q235钢试样上。采用傅里叶红外光谱仪(FTIR)和热重分析仪(TGA)测试纳米TiO2表面化学接枝改性情况,采用电化学工作站测试复合涂层的电化学性能,采用激光共聚焦显微镜观察复合膜层的表面形貌。结果使用质量分数10%APTES改性纳米TiO2,单齿螺旋结构占有的比例更高;使用质量分数20%APTES改性纳米TiO2,具有最高的接枝密度,为11.78 APTES/nm^2。电化学测试结果显示,环氧/TiO2复合涂层比纯环氧涂层具有更好的耐蚀性能,其中加入质量分数20%APTES改性纳米TiO2的环氧/TiO2复合涂层对基体的保护性能最好,其涂层电阻是纯环氧涂层的12倍,电荷转移电阻是纯环氧涂层的18倍。在相同的腐蚀条件下,单齿螺旋结构更容易被破坏。加入硅烷纳米TiO2颗粒后,可以显著减少涂层表面尖峰状突起和孔洞。结论纳米TiO2的APTES接枝分子密度,是水性环氧/硅烷化纳米TiO2复合防护涂层耐腐蚀性能提高的直接原因。     

具有循环净化性能的纳米TiO2/活性炭复合表面的构筑

目的构筑净化性能优异的纳米TiO_2/活性炭复合表面。方法采用溶凝胶模板法构筑球形表面,将乳化法制备的石蜡球和复合活性炭的纳米TiO_2溶胶挤压成形,温和处理后形成规则稳定的球形表面。使用SEM、XRD和FTIR进行表面微观结构、形貌和物相检测,采用X射线断层扫描对球形表面结构进行重构和球面特征分析。分析测定了不同当量直径球形表面的样品对亚甲基蓝的净化效果。结果温和处理工艺维持了原始P25粉末的晶型和晶粒尺寸,溶凝胶模板法可以形成贯通、多面、多孔径的结构和簇状均匀表面。3DCT结果显示,活性炭的复合使样品形成了碳增强的TiO_2球形表面。构筑成功的纳米TiO_2复合活性炭样品,在8个周期的循环吸附-净化中可以完全将亚甲基蓝净化降解。平均当量直径为0.67mm的样品,在9个周期的净化反应中,净化率可以保持100%。结论溶凝胶模板法成功构筑了纳米TiO_2复合活性炭的球形连续表面,球形表面之间大的孔道连接和活性炭在纳米TiO_2颗粒之间的复合,可以提高传质效率,从而提高循环净化性能。     

Enhanced tribological behaviors of sintered polycrystalline diamond by annealing treatment under humid condition

The tribological behaviors of the 700 °C annealed sintered polycrystalline diamond (PCD) at various relative humidity (RH) levels were systematically investigated. The comparison of tribological behaviors between the 700 °C annealed PCD and the pristine PCD was made to further understand the tribological mechanisms. The results reveal that the friction inducing carbonaceous transfer film and oxidation and hydrolysis induced tribochemistry reaction dominant the tribological behaviors of the annealed PCD at various RH levels. The low coefficient of friction (COF) obtained in dry environments is attributed to carbonaceous transfer film on the worn Si₃N₄ surface, which was formed by the layers shearing action of massive tiny diamond grains exfoliated from the annealed PCD surface. The graphitization, oxidation and stress relaxation of the PCD induced by the 700 °C annealing treatment make the tiny diamond grains more easily to exfoliate and be grinded on the Si₃N₄ interface. It facilitates the formation of friction reducing carbonaceous transfer film, and finally results in the 30% lower COFs than those of pristine PCD at low RH levels (5%–50% RH). Meanwhile, an enhanced wear resistance of PCD can be achieved after 700 °C annealing treatment. The tribochemistry reaction induced by the oxidation and hydrolysis of Si₃N₄ governs the tribological behaviors of the annealed PCD at high RH levels (60%–99.9% RH). It reveals higher COFs accompanied with serious wear of Si₃N₄ ball and nearly no wear loss of annealed PCD. The produced SiO₂ and silicic acid embeds into massive spalling pits on the annealed PCD surface, resulting in slighter wear of the PCD and Si₃N₄ than that of the pristine PCD/Si₃N₄. These results propose that the tribological behaviors of PCD under humid environment can be significantly improved by the 700 °C annealing treatment.     

碳纤维负载Pd-TiO2光催化材料的制备及表征

以PAN基碳纤维为载体,采用溶胶-凝胶法制备碳纤维负载TiO2的光催化材料(TiO2/CF),用常温氧化-还原法在其表面沉积贵金属Pd粒子对其改性,制备碳纤维负载Pd-TiO2的光催化材料(Pd-TiO2/CF).XRD分析表明:采用溶胶-凝胶法在碳纤维表面形成了锐钛矿型TiO2.选择偶氮类染料酸性橙Ⅱ作为光催化降解目标物,用紫外吸收光谱分析等TiO2负载量的TiO2/CF,Pd-TiO2/CF和粉末型TiO2的光催化活性.结果表明:TiO2在负载条件下光催化活性有所下降;Pd粒子沉积可有效提高光催化活性;对于酸性橙Ⅱ溶液,Pd-TiO2/CF光催化活性较TiO2/CF、粉末型TiO2均有显著提高.     

WO3-TiO2复合空心球的制备及其光催化性能

以钛酸四正丁酯和偏钨酸铵为原料,采用水热-模板法制备复合WO3-TiO2光催化剂。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、比表面积(BET)和紫外-可见漫反射(UV-Vis DRS)等手段对催化剂的结构和光学性能进行表征。结果表明:WO3-TiO2复合半导体中的TiO2为锐钛矿晶型,焙烧后的WO3-TiO2呈中空球形结构,粒径在320 nm左右,且粒径分布均匀,其比表面积和平均孔径分别为40.95 m2/g和16.91 nm,WO3-TiO2复合半导体的紫外-可见吸收边带较TiO2的红移约50 nm,并在400~500 nm处有吸收。光降解甲基橙(MO)实验显示:经过80 min光照后,WO3-TiO2复合半导体在紫外和可见光下对甲基橙的降解率分别为99.2%和81%,而TiO2的仅为64%和25%,且在紫外和可见光下WO3-TiO2复合半导体的表观速率常数分别是TiO2的3.2和4.9倍左右。     

Elaboration and characterization of nanocrystalline TiO2 thin films prepared by sol–gel dip-coating

Nanocrystalline TiO₂ thin films were deposited on a ITO coated glass substrate by sol–gel dip coating technique, the layers undergo a heat treatment at temperatures varying from 300 to 450 °C. The structural, morphological and optical characterizations of the as deposited and annealed films were carried out using X-ray diffraction (XRD), Raman spectroscopy, Atomic Force Microscopy (AFM), visible, (Fourier-Transform) infrared and ultraviolet spectroscopy, Fluorescence and spectroscopic ellipsometry. The results indicate that an anatase phase structure TiO₂ thin film with nanocrystallite size of about 15 nm can be obtained at the heat treatment temperature of 350 °C or above, that is to say, at the heat treatment temperature below 300 °C, the thin films grow in amorphous phase; while the heat treatment temperature is increased up to 400 °C or above, the thin film develops a crystalline phase corresponding to the titanium oxide anatase phase. We have accurately determined the layer thickness, refractive index and extinction coefficient of the TiO₂ thin films by the ellipsometric analysis. The optical gap decreases from 3.9 to 3.5 eV when the annealing temperature increases. Photocatalytic activity of the TiO₂ films was studied by monitoring the degradation of aqueous methylene blue under UV light irradiation and was observed that films annealed above 350 °C had good photocatalytic activity which is explained as due to the structural and morphological properties of the films.