Study on Ferroelectric and Dielectric Properties of La-Doped CaBi_4Ti_4O_(15)-Based Ceramics

Lanthanum doped bismuth layer structured ferroelectrics （BLSFs） Ca1 - x LaxBi4 （Ti0.9W0. 1 ）4O15 （ x = 0, 0.2, 0.3, 0.4, 0.6） ceramics were prepared by solid-state reaction method. X-ray diffraction （XRD） patterns showed that single phase was formed when x = 0 - 0.6. The effects of La^3＋ doping on dielectric, piezoelectric and ferroelectric properties of Ca1-xLaxBi4（Ti0.9W0.1）4O15 ceramics were studied. Ca0.7La0.3Bi4（Ti0.9W0.1）4O15 ceramic had optimal properties, its dielectric constant was 166.85, dielectric loss was 0.0063, piezoelectric strain constant was 11 pc·N^-1, remanent polarization was 18.1μC·cm^-2 and coercive field was 118 kV·cm^-1. SEM micrographs showed that the grains of CaBi4Ti4O15-based ceramics were plate-like. The results of energy spectrum analysis （EDS） showed that La^3＋ incorporation could increase Bi/Ca ratio.

Characterization of La-doped xBiInO_3(1-x)PbTiO_3 Piezoelectric Films Deposited by the Radio-Frequency Magnetron Sputtering Method

La-doped and undoped xBiIn03-（1 - x）PbTi03 （BI-PT） thin films are deposited on （101）SrRuO3/（lOO）Pt/（lO0） MgO substrates by the rf-magnetron sputtering method. The structures of the films are characterized by XRD and SEM, and the results indicate that the thin films are grown with mainly （100） oriented and columnar structures. The ferroelectricity and piezoelectricity of the BI-PT films are also measured, and the measured results illustrate that both performances are effectively improved by the La-doping with suitable concentrations. These results will open up wide potential applications of the films in electronic devices.

Structural and Magnetic Properties of La-Doped Li-Ni Ferrite

A series of polycrystalline La-doped Li-Ni ferrites LiNi_ 0.5La_xFe_ 2-xO_4 (where x=0.0～0.08 in steps of 0.02) were prepared by thermolysising of oxalate precursors which were obtained by rheological phase reaction. Results were observed by powder X-ray diffractometer (XRD) on samples indicate that all doped ferrites have the major spinel phase, and the single spinel phase is obtained in La content x≤0.04. The lattice parameter increases in the range of x=0～0.04, then decreases up to x=0.08. The hysteresis loops show that the value of saturation magnetization is less than that of the pure Li-Ni ferrite except for x=0.04, while the coercivity increases with the La content.

H_2 generation kinetics/thermodynamics and hydrolysis mechanism of high-performance La-doped Mg-Ni alloys in Na Cl solution——A large-scale and quick strategy to get hydrogen

In this work,La-doped Mg-Ni multiphase alloys were prepared by resistance melting furnace(RMF)and then modified by high-energy ball milling(HEBM).The hydrolysis H_(2) generation kinetics/thermodynamics of prepared alloys in Na Cl solutions have been investigated with the help of nonlinear and linear fitting by Avrami-Erofeev and Arrhenius equations.Combining the microstructure information before and after hydrolysis and thermodynamics fitting results,the hydrolysis H_(2) generation mechanism based on nucleation&growth has been elaborated.The final H_(2) generation capacities of 0La,5La,10La and 15 La alloys are 677,653,641 and 770 m L·g^(-1)H_(2) in 240 min at291 K,respectively.While,the final H_(2) generation capacities of HEBM 0La,5La,10La and 15 La alloys are 632,824,611 and 653 m L·g^(-1)H_(2) in 20 min at 291 K,respectively.The as-cast 15La alloy and HEMB 5La alloy present the best H_(2) production rates and final H_(2) production capacities,especially the HEBM 5La can rapidly achieve high H_(2) generation capacity(670 and 824 m L·g^(-1)H_(2) )at low temperature(291 K)within short time(5 and 20 min).The difference between the H_(2) generation capacities is mainly originated from the initial nucleation rate of Mg(OH)_(2) and the subsequent processes affected by the microstructures and phase compositions of the hydrolysis alloys.Relative low initial nucleation rate and fully growth of Mg(OH)_(2) nucleus are the premise of high H_(2) generation capacity due to the hydrolysis H_(2) generation process consisted by the nucleation,growth and contacting of Mg(OH)_(2) nucleus.To utilization H_(2) by designing solid state H_(2) generators using optimized Mg-based alloys is expected to be a feasible H_(2) generation strategy at the moment.

La-doped Copper Nitride Films Prepared by Reactive Magnetron Sputtering

Copper nitride film （Cu3N） and La-doped copper nitride films （LaxCu3N） were prepared on glass substrates by reactive magnetron sputtering of a pure Cu and a pure La targets under N2 atmosphere. The results show that La-free film was composed of Cu3N crystallites with anti-ReO3 structure with （111） texture. The formation of the LaxCu3N films is affected strongly by La, and the peak intensity of the preferred crystalline [111]-orientation decreases with increasing the concentration of La. High concentration of La may prevent the formation of the Cu3N from crystallization. Compared with the Cu3N films, the resistivity of the LaxCu3N films have been decreased.

纳米二氧化钛/玻璃鳞片协同增强环氧树脂的耐磨性研究

[目的]环氧树脂(EP)复合材料虽有良好的力学性能和化学稳定性,但脆性大、摩擦因数高、耐磨性差,使其难以满足运动摩擦部件的性能要求。[方法]通过向EP基体中添加改性纳米TiO_(2)和玻璃鳞片(GF)制备了TiO_(2)/GF/EP复合材料,研究了纳米TiO_(2)添加量对复合涂层性能的影响。采用扫描电子显微镜(SEM)和傅里叶变换红外光谱仪(FT-IR)对涂层的断面形貌和分子结构进行了表征。[结果]利用KH-550硅烷偶联剂对纳米TiO_(2)进行改性处理消耗了其表面大量的羟基,有效减少了纳米TiO_(2)的团聚。GF和改性纳米TiO_(2)与EP基体的界面相容性良好,TiO_(2)/GF/EP复合涂层的致密性与纯EP涂层相比明显提高。对于添加了相对于EP质量4%的纳米TiO_(2)和30%的GF的复合涂层,其显微硬度比纯EP提高了46.8%,摩擦因数和磨损后的质量损失分别比纯EP减小了46.1%和52.0%。[结论]改性纳米TiO_(2)和GF共同作为填料加入,可使EP的显微硬度和耐磨性得到明显提高,摩擦因数明显减小,综合性能得到提升。

TiO_(2)包覆高镍NCM811的电化学性能研究

高镍材料具有较好的电化学性能,但其存在着表面稳定性较差的问题,通过钛酸四丁酯在NCM811材料表面水解生成TiO_(2),改善了高镍材料的表面稳定性。利用SEM和TEM对改性后的材料进行表面分析,结果表明,实验成功将TiO_(2)层均匀地包覆在高镍NCM811表面,并且发现,在表面包覆过程中,还发生了体相掺杂。利用表面包覆和体相掺杂的共同作用,在1C放电的条件下,循环200圈后,材料的容量保持率从81.40%提升至92.39%,改善了材料的电化学性能。

适用于地面装备的特种降温涂层研究与应用

[目的]为了有效降低太阳辐射引起的导弹温升,考察了一种针对地面装备的特种涂层的降温性能。[方法]通过基料与颜填料的筛选,确定以环氧树脂搭配固化剂作为基料,金红石型二氧化钛作为主要颜填料。对涂层方案及其作用机理进行分析后,确定了特种降温涂层的设计原则。对涂层建立了热传导模型,分析辐射来源,对地面装备进行了仿真分析。[结果]通过试样级试验验证了特种涂层的环境适应性与降温性能。[结论]该特种降温涂层解决了太阳辐射下地面装备内部升温较高的问题,为地面装备的应用打下了基础。

光催化二氧化钛超亲水无机涂层的制备及性能

[目的]超亲水涂层具有自清洁、防雾、防污等特性,但在玻璃上应用时透光性往往不够理想。[方法]以钛酸丁酯为前驱体,乙酰丙酮为抑制剂,无水乙醇和去离子水为溶剂,加入硝酸进行催化,合成了TiO2溶胶,并将其涂覆在玻片上,经煅烧处理后获得超亲水性透明涂层。分别考察了溶胶的粒径及涂层的表面形貌、水接触角、透明度和热稳定性。[结果]TiO2亲水涂层的水接触角为8.0°,400~700 nm波长范围内的透光率仅比空白玻璃低4个百分点,加热至800℃的过程中质量损失仅为8%。[结论]该涂层具有良好的亲水性和防雾性能。

低膨胀石英玻璃的制备技术与发展趋势

低膨胀石英玻璃(Low-expansion quartz glass)是指掺有低膨胀氧化物的石英玻璃,其热膨胀系数比一般的石英玻璃低一个或两个数量级,基于这种特质,低膨胀石英玻璃受到了许多人的关注。然而,随着高新技术的快速发展,低膨胀石英玻璃的性能已不能满足新技术领域的需求,直到1968年研制出SiO_(2)-TiO_(2)石英玻璃。相较于其他低膨胀石英玻璃,SiO_(2)-TiO_(2)石英玻璃的热膨胀系数更低,在一定温度范围内甚至可以做到零膨胀或负膨胀,因此掺钛石英玻璃又被称为超低膨胀(Ultra low expansion,ULE)石英玻璃。SiO_(2)-TiO_(2)石英玻璃凭借优秀的性能被广泛应用于半导体、航空航天、电子、光学等领域。SiO_(2)-TiO_(2)石英玻璃通常有以下几种制备方法——溶胶-凝胶法、化学气相沉积法、气相轴向沉积法和等离子体化学气相沉积法等,其中,火焰水解沉积法使用较为广泛,具有成熟的工业应用。

Chemical equilibrium controlled synthesis of polyoxymethylene dimethyl ethers over sulfated titania

The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers （DMMn） were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn.

Enhancement of formaldehyde degradation by amine functionalized silica/titania films

Doping amine functional groups into SiO2/TiO2 films for enhancing the decomposition of formaldehyde has been investigated using the modified sol-gel method to prepare organic-inorganic hybrid photocatalysts via the co-condensation reaction of methyltrimethoxysilane （MTMOS） and amine functional groups, n-（2-Aminoethyl）-3-aminopropyl-trimethoxysilane （AEAPTMS） and 3-aminopropyl-trimethoxysilane （APTMS） were selected to study the effect of amine functional groups on the enhancement of formaldehyde adsorption and degradation under a UV irradiation process. Physicocbemical properties of prepared photocatalysts were characterized with nitrogen adsorption-desorption isotherms measurement, X-ray diffraction （XRD） and Fourier transform infrared （FT-IR） spectroscopy. The results indicated that the APTMS/SiO2/TiO2 film demonstrated a degradation efficiency of 79% superior to those of SiO2/TrO2 and AEAPTMS/SiO2/TiO2 films due to the synergetic effect of adsorption and photocatalytic properties. The APTMS/SiO2/TiO2 film can be recycled with about 7% decreasing of degradation efficiency after seven cycles.

Preparation of nitrogen-doped titania and its photocatalytic activity

Yellowish nitrogen-doped titania was produced through sol-gel method in mild condition, with the elemental nitrogen derived from aqua ammonia. The titania catalysts were characterized using XRD, BET, TEM, XPS, and UV-Vis diffuse reflectance spectrophotometer, and their photocatalytic activities were evaluated under UV and visible light, respec tively. The XRD results showed that all titania catalysts were anatase. More significantly, the crystallite size of nitrogen-doped titania increased with an increase in N/Ti proportion, and the doping of nitrogen could extend the absorption shoulder into the visible-light region, thus it possessed a higher visible-light activity illustrated by decolorization of methyl orange （65.3%） under the irradiation of visible light, whereas pure titania showed little of such kind of visible light activity. The UV-light activity of nitrogen-doped titania catalysts was worse than that of pure titania and Degussa P25. In the range of N/Ti proportion of 4-10 mol%, the activity of nitrogen-doped titania weakened appreciably in the visible-light region as the N/Ti proportion increased, whereas a reverse relationship existed under the irradiation of UV light.

Molybdosphoric Acid Mixed with Titania Used as a Catalyst to Synthesize Diphenyl Carbonate via Transesterification of Dimethyl Carbonate and Phenol

The 12-molybdosphoric acid mixed with titania （MPA-TiO2） was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate （DPC） via transesterification of dimethyl carbonate （DMC） and phenol. The X-ray diffraction （XRD） and infrared （IR） techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate （MPC） were obtained over MPA-TiO2 with the weight ratio of MPA to TiO2 as 5：1.

Synthesis and Characterization of Co-Doped Brookite Titania Photocatalysts with High Photocatalytic Activity

Transition metal-doping could effectively extend the light response range of TiO _2 photocatalysts from the ultraviolet(UV)to the visible region.Co-doped brookite titanium dioxide(Co–TiO_2)photocatalysts were synthesized via the hydrothermal method with titanium tetrachloride as the raw material and cobalt chloride hexahydrate as the dopant.The prepared Co–TiO_2 photocatalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and UV–Vis diffuse reflectance spectroscopy(UV–Vis DRS).The photocatalytic activities of Co–TiO _2 photocatalysts were evaluated by photocatalytic degradation of isopropanol alcohol(IPA),a typical volatile organic compound(VOC),under visible light.The influences ofdifferent Co doping rates,initial concentrations of IPA gas and the amounts of photocatalyst addition were also studied.At the same time,the enhancement mechanism ofcobalt ions as a trap for photogenerated holes was discussed.Thus,we found the optimum doping rate,initial concentration of IPA gas and amount of photocatalyst to add.The results show that the mesoporous Co–TiO _2 photocatalysts possess smaller size particles,larger specific surface area,lower forbidden bandgap energy(Eg)and better photocatalytic activity than pure brookite TiO _2.When the doping of Co was 7% by mass,the initial concentration ofIPA gas was 1.0×10^(-6 )mol/L and the addition of Co–TiO_2 photocatalysts was 50 mg,the best photocatalytic activity was achieved.Furthermore,the degradation rate ofIPA was up to 91%,which shows great potential for waste water treatment.

Synthesis of Nanoscale Shell-core Titania Coated Silica Particles in the Presence of Polyether Polyamine and the Phase Transition

The nanoscale titania coated silica was prepared via a two-step precipitating approach, where the nanoscale silica nuclei were first prepared by passing an aqueous solution of sodium silicate through an ion-exchange resin bed, then coated with the precipitation from hydrolyzed butyl titanate in an ethanol-hexane mixture at a low pH value in the presence of poly(ethylene oxide) polyamine salt(PPA) at a high temperature of 90 ℃. In the second-step precipitating process, the spontaneously precipitated titania shell on the silica nuclei was stabilized in the suspension solution with the help of the adsorption of PPA on the particles. A possible precipitating mechanism was suggested. Furthermore, the amorphous titania shell could undergo crystallization from the amorphous to the anatase structure at a high temperature of 650 ℃, and a further phase transition from the anatase to the rutile structure in the different sintering processes at a rising temperature of 750 ℃.

Synthesis of Nanostructured Copper-doped Titania and Its Properties

Nanostructured pure-Ti O_2 and Cu3%-Ti O_2 were successfully synthesized via co-precipitation method. The X-ray diffraction(XRD) result proves that the synthesized sample were predominantly in anatase phase with size in the range of 8～16 nm, which are in good agreement with the transmission electron microscopy data. Owing to doping of copper, not only did the thermal stability of the Ti O_2 decrease, but also a significant decrease in its particle size and a shift of the adsorption edge to a higher wavelength region appear. The activity of both pure-Ti O_2 and Cu3%-doped Ti O_2 was tested to study their ability to decolorize congo red(CR) dye in aqueous solution. We observed that the CR dye was decolorized faster by Cu3%-Ti O_2 than pure-Ti O_2. Results of this study demonstrate a potential application of the synthesized sample for decolorizing dye pollutants from aqueous waste.

Heterogeneous Photocatalytic Mineralization of Chlorobenzene by Paratungstate-loaded Titania Catalysts in an Aqueous Medium

Paratungstate-loaded titania catalysts were prepared %via% the addition of a series of aqueous solutions of paratungstate(denoted as W_ 7) into an isopropanol solution of Ti[OCH(CH_ 3)_ 2]_ 4 by means of the sol-gel method. The catalysts were characterized by EDX, BET, FTIR, UV-Vis DRS, XRD and the results indicate that such paratungstate-loaded catalysts maintained their heptatungstate structure in the anatase titania matrix up to 400 ℃. The catalysts were tested for the heterogeneous photodegradation of chlorobenzene in aqueous media and showed a better catalytic activity than P-25 TiO_ 2 because paratungstate can prevent the recombination of the holes and electrons produced during irradiation. Moreover, the paratungstate-loaded titania catalysts can resist the disaggregation during the photoirradiation and can be easily recycled from the aqueous suspensions after reactions.

Synthesis and Characterization of Mesoporous Titania Particles and Thin Films

Well-organized mesoporous titania particles and thin films were successfully synthesized by using tetrabutyl titanate as the inorganic precursor and triblock copolymer （Pluronic P123） as the template via evaporationinduced self-assembly process. The resulting materials were characterized by high resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）. Fourier-transform infrared spectroscopy （FT-IR）,Brunauer-Emmett-Teller （BET） and atomic force microscopy （AFM）. Macro shape of mesoporous titania would greatly influence the mesostructure of materials, and the probable reasons were also discussed.

INVERSE OPALINE STRUCTURE TITANIA PHOTONIC CRYSTALS BY FUNCTIONALLY MODIFIED COLLOIDAL CRYSTALS TEMPLATING

Ordered macroporous titania photonic crystals （PCs） and photonic balls were fabricated by functional modified polymer colloidal crystals. The TiO2 PCs and balls formed through this method exhibit no cracks and lacunae in large areas on their surface and their inner structures.