Effect of sintering on TiO2-impregnated alumina foams

The effect of sintering on the bulk properties, morphology and phase composition of ultralight Al₂O₃ foams impregnated with TiO₂ was investigated in comparison with pure alumina foam in the temperature range of 900–1600°C in air. Impregnation was carried out by immersion of pre-sintered alumina foam in a sol of titanium isopropoxide-acetylacetone complex. The changes of the foam linear shrinkage, effective density and porosity were studied along with morphological evolution and relationship between these properties was demonstrated. Titania impregnation increased the linear shrinkage (LS) during sintering by a maximum of 5% relative to pure alumina foams. The change of LS and weight loss of TiO₂/Al₂O₃ foams lead to a final density of 0.19 g/cm³ and porosity of 95%. The initial coating was found to develop a mosaic structure due to early shrinkage of the coating. After sintering at 1600°C the coating reacted with the underlying Al₂O₃ surface and became uniformly distributed. Finally, it was shown that the reacting TiO₂ layer formed the tialite (Al₂TiO₅) phase below 1400°C. This Tialite coating remained intact under 1200°C without stabilizers.     

以TiO2纤维制备微滤膜过程中烧结温度的影响

采用Al2O3多孔陶瓷为载体,使用浸浆法以TiO2陶瓷纤维制备微米级膜厚的微滤膜,借助气体泡压、渗透性能、环境扫描电镜、失重差热分析和X射线粉末衍射等手段对膜的微结构性能进行表征,讨论了影响膜层性能的因素--烧结温度对成膜的影响.实验结果表明:以TiO2陶瓷纤维制备的微滤膜适宜于低温烧结,晶型转变温度区间为800～1 000℃.500℃下制得的微滤膜平均孔径为1.5 μm,孔径分布较窄.与相对应的以陶瓷粒子烧结成的微滤膜相比,具有更大的气体通量.     

TiO2负载工艺对膨胀石墨吸附原油性能的影响

将异丙醇钛盐与水洗后的可膨胀石墨，或者与水洗并干燥后的可膨胀石墨混合并加热，分别制备了负载TiO2的两种膨胀石墨吸附材料-膨胀石墨／TiO2-1（记为EG／TiO2-1）和膨胀石墨／TiO2-2（记为EG／TiO2-2）。结果表明：异丙醇钛盐与水洗后的可膨胀石墨混合后，部分TiO2溶胶存在于石墨层间；而与水洗并干燥后的可膨胀石墨混合后，绝大部分TiO2溶胶分布在石墨层表面及边缘。EG／TiO2-1和EG／TiO2-2对原油的最大吸附量分别为57g／g和55g／g。     

钽掺杂金红石TiO2电子结构的第一性原理研究

采用第一性原理中的CASTEP模块计算了金红石相TiO2掺杂过渡金属钽元素的能带结构以及态密度。计算结果表明，Ta原子替换Ti原子后，Ta的5d轨道对TiO2的导带影响较明显，且使TiO2的带隙宽度减小，这样有可能使金红石TiO2吸收带出现红移现象或产生在可见光区的吸收，其中Ta原子的t2g态起了重要作用。     

Effect of collector speed and flow rate on morphology of Er doped TiO2 nanofibers

The 0.5 mol% Er3+ doped TiO2 (Er(3+)-TiO2) nanofibers were synthesized by a sol-gel derived electrospinning and subsequent calcination for 3 h at 500 degrees C in air. The calcined fibers were examined to evaluate the effect of collector speed and flow rate on morphology of the fibers. The dynamic viscosity and surface tension of precursor solution were 34 cP and 22.7 mN/m, respectively. The Er(3+)-TiO2 nanofibers were electrospun horizontally on the drum rotated at 100-500 rpm and flow rate of 0.2-0.5 mL/h under a DC voltage of 10 kV. The grounded collector is a stainless mandrel placed 12 cm away from the tip of the needle. Beads were observed for the nanofibers prepared at flow rates from 0.2 mL/h to 0.5 mL/h when the collector speed was 100 rpm. The nanofibers increased in diameter slightly from 150 nm to 190 nm as the flow rate was raised from 0.2 mLh to 0.5 mL/h. No beads were found at the collector speed of above 300 rpm when the flow rate was 0.2 mL/h. The optimized flow rate and collector speed of the nanofibers were determined to be in the range of 0.2-0.3 mL/h and 300-400 rpm, respectively. Uniform, smooth and continuous fibers with diameters of 150 to 170 nm were detected. Crystallite size determined by the Scherrer formula was about 6 nm. It can be concluded that the collector speed and the flow rate are influential on the morphology of the Er(3+)-TiO2 nanofibers. The Er(3+)-TiO2 nanofibers, prepared at 0.2 mL/h and 300 rpm, had typical absorption peaks located at 490, 523 and 654 nm, corresponding to the transitions from 4I15/2 to 4F7/2, 2H11/2 and 4F9/2, respectively. The Er(3+)-TiO2 nanofibers showed enhanced photoresponses under visible light.     

硫掺杂TiO_2光催化剂的研究

采用溶胶-凝胶法制备了硫掺杂二氧化钛粉体(S-TiO2),采用XRD、Nano-series Sizer、FT-IR、UV-Vis、PL等方法对其进行表征和分析。结果表明,S掺杂抑制了TiO2从锐钛矿相向金红石相的转变,减小了粒子间的团聚,拓展了TiO2对可见光的吸收范围,有效地抑制了光生电子-空穴对的复合。光催化降解亚甲基蓝(MB)的实验表明,n(S)∶n(Ti)=0.14,450℃烧结的S-TiO2粉体具有最佳光催化性能,在普通日光灯下对亚甲基蓝的降解率3h达74.12%,明显优于德国Degussa公司生产的P25纯TiO2光催化剂对亚甲基蓝的降解率31.89%。     

Effect of ZrSiO2 and MgO additions on reaction sintering and properties of Al2TiO5-based materials

Two sets of Al₂TiO₅-based composites were prepared by reaction sintering of (a) Al₂O₃/TiO₂/ZrSiO₄ and (b)Al₂O₃/TiO₂/ZrSiO₄/MgO powder mixtures. The influence of the variation of ZrSiO₄ content (0 to 10wt%) and the addition of 2 wt% MgO on the reaction-sintering process, microstructure, mechanical and thermal properties, were evaluated. ZrSiO₄ addition shifted the Al₂TiO₅ formation to higher temperatures, whereas MgO accelerated both Al₂TiO₅ formation and ZrSiO₄ decomposition. The presence of ZrSiO₄ and an excess of Al₂O₃ generated a dispersion of ZrO₂ and mullite particles in the grain boundaries and enhanced simultaneously the densification process. After sintering in the temperature range 1350 to 1500 ° C, the obtained composites exhibited significantly higher bending strength than the monophasic aluminium titanate (up to 80 M Pa). Al₂TiO₅ (80wt%)-mullite-ZrO₂ composites which combined good mechanical strength (55MPa), low thermal expansion (_20–1000C < 1 × 10^–6 K^–1) and excellent thermal stability were obtained by reaction and sintering of powder mixtures containing both ZrSiO₄ and MgO.     

Slip casting and sintering of monodispersed TiO2 particles

Monodispersed TiO₂ particles were used to prepare a uniformly packed green compact with a high relative density by slip casting. A suspension consisting of monodispersed TiO₂ particles, solvent and binder was cast in the mould. The sintering behaviour of the green compact was investigated. The green compact could be sintered to a relative density of > 99% by treatment at 1050 °C for 120 min. The average grain size of the sintered body was 1.26 m without abnormal grain growth. The green sheet cast on a glass board could be densified with no grain growth. The experimentally obtained relation between densification rate and grain size indicated a volume diffusion mechanism according to Coble's equation.     

稀土元素掺杂纳米TiO2Zeta电位的研穷

采用溶胶-凝胶法制备纳米TiO2以及稀土元素（Ce、Nd、Pr、Sm）掺杂纳米TiO2粉体．采用透射电镜（TEM）表征粉体形貌，MARVEN NANO ZS-90仪器测试粉体Zeta电位。结果表明：制备粉体属于纳米级别；在pH值2～11范围内，Pr、Sm、Nd掺杂与纯纳米TiO2 Zeta电位-pH曲线形状大致相同，相对于纳米TiO2的Zeta电位-pH曲线，Pr、Sm掺杂曲线右移，等电点增大；Nd掺杂曲线左移，等电点减小。Ce掺杂未出现等电点，在pH值2～11范围内，其Zeta电位始终为负值，在pH值相同时，5％Ce-TiO2 Zeta电位绝对值〉1％Ce-TiO2、2．5％Ce-TiO2．     

Chemical vapor deposition of doped TiO2 thin films

Niobium-, tantalum- and fluorine-doped TiO₂ films were made by atmospheric pressure chemical vapor deposition from titanium alkoxides mixed with niobium ethoxide, tantalum ethoxide and t-butyl fluoride respectively. 4% H₂ in N₂ was used as the carrier gas and the deposition temperatures were in the range 400–600°C. The resistivities of the films increased dramatically with film thickness. For highly doped films 1 μm thick resistivities as low as 0.01 Ω cm were achieved.     

掺银TiO2薄膜的亲水特性

采用溶胶—凝胶法及浸渍提拉法在普通的载玻片上制得含不同掺银量的TiO2薄膜，通过对薄膜及相应粉体的XRD、XPS及薄膜致密度的测量，分析了银的掺杂量对TiO2薄膜亲水特性的影响。结果表明：TiO2薄膜中银的掺杂量≤0．635mol％时有利于TiO2薄膜亲水性能的改善；表面羟基和表面桥氧的含量对TiO2薄膜的亲水性能均有直接影响。     

Effect of sintering temperature on the microstructure and electrical properties of zirconium doped barium titanate ceramics

Lead-free Ba(Zr_0.15Ti_0.85)O₃ (BZT15) ceramics were synthesized by adopting the solid-state synthesis method. The effect of increasing sintering temperature (T_s) in the range of 1,350–1,450 °C on the microstructure, dielectric, polarization, and electric field induced strain of the ceramics was studied. Fine grained (~260 nm) BZT15 ceramics displayed single phase perovskite structure with relative densities >94 % of the theoretical density. Both grain size and shape were influenced by the sintering parameters. With increase in T_s, not only the maximum dielectric constant decreased from 11,412 to 8,734 along with an increase in the degree of diffuseness, but also interestingly the Curie temperatures were found to vary within an interval of 61–73 °C. Optimum sintering temperature has been found resulting in high remnant polarisation and strain in these ceramics. The properties observed are attributed to a contribution from all polar vectors present in coexistent phases.     

TiO2掺杂的NiO-NiFe2O4电导率及合成动力学研究

采用固相合成法,在1173～1213K温度范围内合成了NiO-NiFe2O4和0.5%TiO2掺杂的NiO-NiFe2O4。用X射线衍射表征了合成产物。在合成过程中将试样置于两个铂片之间,通过连续测量加热过程中试样的电阻,获得了试样电导率随时间的变化规律,建立了稳态扩散控制的NiFe2O4合成动力学方程,并讨论了掺杂0.5%TiO2对NiFe2O4合成反应速率的影响,获得了0.5%TiO2掺杂的NiFe2O4合成反应的速率系数、活化能、Ni 2＋和Fe3＋离子的平均扩散系数。     

阴离子掺杂型TiO2可见光活性研究进展

阴离子掺杂改性TiO2光催化材料是目前光催化材料界的一个研究热点.综述了阴离子掺杂改性TiO2可见光活性的研究进展,重点探讨了N、C和S等元素掺杂TiO2材料的原理,实验工艺,效果以及优缺点.并对TiO2光催化材料可见光活性未来发展趋势进行了展望.     

TiO2 doped with nitrogen: synthesis and characterization

In this study, nitrogen-doped titanium dioxide (TiO2) powders were synthesized in two ways: by heating of titanium hydroxide with urea and by direct hydrolysis of titanium tetraisopropoxide (TTIP) with ammonium hydroxide. The samples were characterized by structural (XRD), analytical (XPS), optical (UV/Vis absorption/reflection and Raman spectroscopy) and morphological (SEM, TEM) techniques. The characterization suggested that the doped materials have anatase crystalline form without any detectable peaks that correspond to dopants. The absorption threshold of titanium dioxide was moved in the visible range of optical spectrum from 3.2 eV to 2.20 eV. Particle sizes of synthesized powders were obtained from XRD measurements and from TEM data ranging from 6-20 nm. XPS and Raman spectroscopy were used for detection of nitrogen in doped samples.     

TiO2对CaO陶瓷烧结和抗水化性能的影响

研究了TiO2添加剂对CaO陶瓷抗水化性能的影响.结果表明:TiO2与CaO反应生成的Ca3(TiO7)连结CaO晶粒,促进固相烧结,增大了陶瓷的烧结密度,同时TiO2能促进CaO晶粒长大,提高了CaO陶瓷的抗水化性能.提高烧结温度,能提高陶瓷密度,从而提高CaO陶瓷的抗水化性能,实验中TiO2最佳添加量为3%.