Influence of interface point defect on the dielectric properties of Y doped CaCu3Ti4O12 ceramics

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Jianming Deng

2016-03-01

Full Text Available CaCu3Ti4−xYxO12 (0≤x≤0.12 ceramics were fabricated with conventional solid-state reaction method. Phase structure and microstructure of prepared ceramics were characterized by X-ray diffraction (XRD and scanning electron microscopy (SEM, respectively. The impedance and modulus tests both suggested the existence of two different relaxation behavior, which were attributed to bulk and grain boundary response. In addition, the conductivity and dielectric permittivity showed a step-like behavior under 405K. Meanwhile, frequency independence of dc conduction became dominant when above 405K. In CCTO ceramic, rare earth element Y3+ ions as an acceptor were used to substitute Ti sites, decreasing the concentration of oxygen vacancy around grain-electrode and grain boundary. The reason to the reduction of dielectric behavior in low frequencies range was associated with the Y doping in CCTO ceramic.

Application of CaCu3Ti4O12 based quadruple perovskites as a promising candidate for optoelectronic devices

Science.gov (United States)

Pal, Kamalesh; Jana, Rajkumar; Dey, Arka; Ray, Partha P.; Seikh, Md Motin; Gayen, Arup

2018-05-01

We report the synthesis of nanosized (40-50 nm) CaCu3-xMnxTi4-xMnxO12 (x = 0, 0.5 and 1) quadruple perovskite (QP) semiconductor via a modified combustion method for use as Schottky barrier diode (SBD) at the Al/QP junction. The fabricated SBD is analysed on the basis of thermionic emission theory to observe its quality and some important diode parameters. For insight analysis of charge transport mechanism through metal-semiconductor junction, theory of space charge limited currents is applied and discussed in the light of parameters like carrier concentration, mobility-lifetime product and diffusion length. The Mn-doped exhibit better device performance compared to parent material.

Phase-pure Nanocrystalline Li4Ti5O12 for Lithium ion Battery

Czech Academy of Sciences Publication Activity Database

Kalbáč, Martin; Zukalová, Markéta; Kavan, Ladislav

2003-01-01

Roč. 8, č. 1 (2003), s. 2-6 ISSN 1432-8488 R&D Projects: GA MŠk OC D14.10 Institutional research plan: CEZ:AV0Z4040901 Keywords : phase purity * Li4Ti5O12 * nanocrystalline materials Subject RIV: CG - Electrochemistry Impact factor: 1.195, year: 2003

Giant dielectric response in (Sr, Sb) codoped CaCu3Ti4O12 ceramics: A novel approach

Science.gov (United States)

Pradhan, M. K.; Rao, T. Lakshmana; Karna, Lipsarani; Dash, S.

2018-04-01

The CaCu3Ti4O12 (CCTO) remains as the best material for practical applications due to its high dielectric constant. To improve further the dielectric properties of CCTO to several orders in magnitude, a novel approach is adopted by codoping of Sr, Sb ions. The ceramic samples were fabricated by the conventional solid state route. The structure, morphology and detail dielectric properties were investigated systematically. All the samples crystalizes in a cubic symmetry with Im-3 space group. Sr substituted in Ca site can effectively suppress the grain growth, achieving a fine grained ceramic structure; however the grain size decreased slightly as Sb concentration increased further; whereas the dielectric permittivity of the ceramics increased drastically. The giant dielectric response was considered to be closely related with a reduction in the potential barrier height at grain boundaries (GBs) supported by the reduction in the activation energy for the conduction process.

High-rate nano-crystalline Li{sub 4}Ti{sub 5}O{sub 12} attached on carbon nano-fibers for hybrid supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Naoi, Katsuhiko; Isobe, Yusaku; Aoyagi, Shintaro [Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8558 (Japan); Ishimoto, Shuichi [Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8558 (Japan); Nippon Chemi-Con Corporation, 363 Arakawa, Takahagi-shi, Ibaraki 318-8505 (Japan)

2010-09-15

A lithium titanate (Li{sub 4}Ti{sub 5}O{sub 12})-based electrode which can operate at unusually high current density (300 C) was developed as negative electrode for hybrid capacitors. The high-rate Li{sub 4}Ti{sub 5}O{sub 12} electrode has a unique nano-structure consisting of unusually small nano-crystalline Li{sub 4}Ti{sub 5}O{sub 12} (ca. 5-20 nm) grafted onto carbon nano-fiber anchors (nc-Li{sub 4}Ti{sub 5}O{sub 12}/CNF). This nano-structured nc-Li{sub 4}Ti{sub 5}O{sub 12}/CNF composite are prepared by simple sol-gel method under ultra-centrifugal force (65,000 N) followed by instantaneous annealing at 900 C for 3 min. A model hybrid capacitor cell consisting of a negative nc-Li{sub 4}Ti{sub 5}O{sub 12}/CNF composite electrode and a positive activated carbon electrode showed high energy density of 40 Wh L{sup -1} and high power density of 7.5 kW L{sup -1} comparable to conventional EDLCs. (author)

Strong red-emission of Eu{sup 3+}:Li{sub 4}Ti{sub 5}O{sub 12} powders for phosphor applications

Energy Technology Data Exchange (ETDEWEB)

Yang, Yan [Kazuo Inamori School of Engineering, New York State College of Ceramics, Alfred University, Alfred, NY 14802 (United States); Jiménez, José A. [Department of Chemistry, University of North Florida, Jacksonville, FL 32224 (United States); Wu, Yiquan, E-mail: wuy@alfred.edu [Kazuo Inamori School of Engineering, New York State College of Ceramics, Alfred University, Alfred, NY 14802 (United States)

2016-08-15

The synthesis and photoluminescence properties of trivalent europium doped lithium titanate (Eu{sup 3+}:Li{sub 4}Ti{sub 5}O{sub 12}) with different Eu{sup 3+} concentrations (0.1 mol%, 0.3 mol%, 1.0 mol%, 3.0 mol%) are reported and analyzed as a phosphor. Europium (III) nitrate (Eu(NO{sub 3}){sub 3}) was employed as Eu{sup 3+} source, while lithium acetate dihydrate (CH{sub 3}COOLi·2H{sub 2}O) and titanium n-butoxide (Ti(OC{sub 4}H{sub 9}){sub 4}) were adopted as raw materials to synthesize the host lithium titanate with a Li:Ti stoichiometry of 4.5:1. Phase identification was performed using X-ray diffraction (XRD), and morphology was examined using scanning electron microscopy (SEM). Eu{sup 3+}:Li{sub 4}Ti{sub 5}O{sub 12} powders showed strong red emission at 612 nm, corresponding to the {sup 5}D{sub 0}–{sup 7}F{sub 2} transition, with the strongest excitation peak observed in the blue light region at 464 nm. Decay time analyses revealed relatively short lifetimes accompanying typical exponential decay rates. The effect of Eu{sup 3+} concentration (0.1 mol%, 0.3 mol%, 1.0 mol%, 3.0 mol%) on photoluminescence intensity and decay time was explored, and is reported here. It was determined that the CIE color coordinates (0.66, 0.34) of the doped Li{sub 4}Ti{sub 5}O{sub 12} powders were independent of Eu{sup 3+} concentration, and that the coordinates are very similar to the ideal red chromaticity (0.67, 0.33) designated by the National Television Standard Committee (NTSC) system.

Mechanochemical preparation of nanocrystalline TiO2 powders and their behavior at high temperatures

International Nuclear Information System (INIS)

Gajovic, A.; Furic, K.; Tomasic, N.; Popovic, S.; Skoko, Z.; Music, S.

2005-01-01

Nanocrystalline TiO 2 powders were prepared by high-energy ball-milling using zirconia vial and balls. The changes of microstructure caused by material processing were studied using Raman spectroscopy, X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The milling of the starting TiO 2 powder (anatase + rutile in traces) induced phase transitions to high-pressure polymorph, TiO 2 II, and rutile. We found that the phase transition to TiO 2 II was initiated at the surface of the small particles, while transition to rutile started in their center. Changes in crystallite size during milling process were obtained by the Scherrer method, while the particle size changes were monitored by TEM. The kinetics of phase changes, a decrease in crystallite/particle size, as well as zirconia contamination depended on the powder-to-ball weight ratio. The starting powder and some selected ball-milled samples were investigated in situ by Raman spectroscopy and XRD at high temperatures (up to 1300 deg. C) to examine their behavior during the sintering process. A difference in the results obtained by these two techniques was explained in frame of basic physical properties characterizing both methods. The morphology of the final sinters was monitored by scanning electron microscopy (SEM)

Na insertion into nanocrystalline Li4Ti5O12 spinel: An electrochemical study

Czech Academy of Sciences Publication Activity Database

Zukalová, Markéta; Pitňa Lásková, Barbora; Klementová, Mariana; Kavan, Ladislav

2017-01-01

Roč. 245, AUG 2017 (2017), s. 505-511 ISSN 0013-4686 R&D Projects: GA ČR GA15-06511S; GA MŠk LM2015087 Institutional support: RVO:61388955 ; RVO:68378271 Keywords : Na insertion * Li4Ti5O12 * nanocrystalline Subject RIV: CG - Electrochemistry; BM - Solid Matter Physics ; Magnetism (FZU-D) OBOR OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis); Condensed matter physics (including formerly solid state physics, supercond.) (FZU-D) Impact factor: 4.798, year: 2016

Assessment of the synthesis conditions for nano-Bi_4Ti_3O_1_2 production by the combustion route

International Nuclear Information System (INIS)

Dias, Jeferson A.; Nascimento, Cassia C.; Oliveira, Jessica A.; Morelli, Marcio R.

2016-01-01

The bismuth titanate has interesting optoelectronic properties. Its production in nanometric scale is important due to the demand of miniaturized electronic devices and greater synthesization facility. This study aims at the evaluation of synthesis parameters for nano-Bi_4Ti_3O_1_2 production by the combustion route. For that, the materials were synthesized and calcined at 600°C, 700°C and 800°C. The materials were posteriorly characterized by X-Ray diffraction, SEM, DSC-TGA, FTIR; DRS and impedance spectroscopy. The results have demonstrated that the combustion method was effective for nanocrystalline powders production, which also showed high levels of purity. Particles size growth was observed for high treatment temperatures. Low level of residual organic matter was determined and the high electrical resistivity was observed. The temperature of 600°C was enough to produce particles with optimal properties. Therefore, the results have confirmed the efficacy of combustion route to produce nanometric Bi_4Ti_3O_1_2. (author)

Photocatalytic characteristics for the nanocrystalline TiO{sub 2} on the Ag-doped CaAl{sub 2}O{sub 4}:(Eu,Nd) phosphor

Energy Technology Data Exchange (ETDEWEB)

Kim, Jung-Sik, E-mail: jskim@uos.ac.kr; Sung, Hyun-Je; Kim, Bum-Joon

2015-04-15

Highlights: • The photocatalytic reactivity of the TiO{sub 2}-coated on the Ag-doped long-lasting phosphor (CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+}). • The photodecomposition of benzene gas under visible light irradiation. • The TiO{sub 2}-coated on the Ag-doped long-lasting phosphor showed much higher photocatalytic reactivity. • The light emitted from the long-lasting phosphors contributed to the photo generation of TiO{sub 2}. - Abstract: This study investigated the photocatalytic behavior of nanocrystalline TiO{sub 2} deposited on Ag-doped long-lasting phosphor (CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+}). The CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+} phosphor powders were prepared via conventional sintering using CaCO{sub 3}, Al{sub 2}O{sub 3}, Eu{sub 2}O{sub 3}, and Nd{sub 2}O{sub 3} as raw materials according to the appropriate molar ratios. Silver nanoparticles were loaded on the phosphor by mixing with an aqueous Ag-dispersion solution. Nanocrystalline TiO{sub 2} was deposited on Ag-doped CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+} powders via low-pressure chemical vapor deposition (LPCVD). The TiO{sub 2} coated on the phosphor was actively photo-reactive under irradiation with visible light and showed much faster benzene degradation than pure TiO{sub 2}, which is almost non-reactive. The coupling of TiO{sub 2} with phosphor may result in an energy band bending in the junction region, which then induces the TiO{sub 2} crystal at the interface to be photo-reactive under irradiation with visible light. In addition, the intermetallic compound of CaTiO{sub 3} that formed at the interface between TiO{sub 2} and the CaAl{sub 2}O{sub 4}:(Eu{sup 2+},Nd{sup 3+}) phosphor results in the formation of oxygen vacancies and additional electrons that promote the photodecomposition of benzene gas. The addition of Ag nanoparticles enhanced the photocatalytic reactivity of the TiO{sub 2}/CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+} phosphor. TiO{sub 2} on the Ag

Investigation of phases developed in Bi/sub 4/Ti/sub 3/O/sub 12/ system by thermal and analytical techniques

International Nuclear Information System (INIS)

Naz, S.; Shazad, S.; Qureshi, A.H.; Waqas, H.; Hussain, N.; Ahmed, N.; Saeed, K.; Ali, L.

2012-01-01

Bismuth titanate (Bi/sub 4/Ti/sub 3/O/sub 12/) powders were prepared by conventional mixed oxide method using oxide mixture i.e. bismuth oxide (Bi/sub 2/O/sub 3/) and titanium oxide (TiO/sub 3). The mixed powders were ball milled for different times (8, 16, and 24 hours). The phase formation was investigated by X-ray diffraction (XRD) and the results revealed that milled powder mainly consisted of Bi/sub 2/O/sub 3/ and TiO/sub 2 /phases and a small amount corresponded to Bi/sub 4/Ti/sub 3/O/sub 12/. However, after calcination at 700 deg. C, Bi/sub 4/Ti/sub 3/O/sub 12/ phase was mainly observed. Thermal decomposition (Differential Scanning Calorimetry (DSC)-Thermal Gravimetric Analysis (TGA)-Differential Thermometric Analysis (DTA)) and XRD results showed that the formation of desired phase Bi/sub 4/Ti/sub 3/O/sub 12/ was only possible above 600 deg. C. Single phase Bi/sub 4/Ti/sub 3/O/sub 12/ ceramic was obtained with the orthorhombic structure in three pellets by sintering at 800 deg. C. XRD patterns of sintered pellets are shown. Maximum density (8.61 g/cm/sup 3/) was achieved in the sample milled for 24 hours due to reduction in particle size which ultimately enhanced the diffusion process during sintering. (Orig./A.B.)

Assessment of the synthesis conditions for nano-Bi{sub 4}Ti{sub 3}O{sub 12} production by the combustion route; Avaliacao das condicoes de sintese para producao de nano-Bi{sub 4}Ti{sub 3}O{sub 12} pelo metodo de combustao

Energy Technology Data Exchange (ETDEWEB)

Dias, Jeferson A.; Nascimento, Cassia C.; Oliveira, Jessica A.; Morelli, Marcio R., E-mail: jeferson.unifal@gmail.com [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

2016-07-01

The bismuth titanate has interesting optoelectronic properties. Its production in nanometric scale is important due to the demand of miniaturized electronic devices and greater synthesization facility. This study aims at the evaluation of synthesis parameters for nano-Bi{sub 4}Ti{sub 3}O{sub 12} production by the combustion route. For that, the materials were synthesized and calcined at 600°C, 700°C and 800°C. The materials were posteriorly characterized by X-Ray diffraction, SEM, DSC-TGA, FTIR; DRS and impedance spectroscopy. The results have demonstrated that the combustion method was effective for nanocrystalline powders production, which also showed high levels of purity. Particles size growth was observed for high treatment temperatures. Low level of residual organic matter was determined and the high electrical resistivity was observed. The temperature of 600°C was enough to produce particles with optimal properties. Therefore, the results have confirmed the efficacy of combustion route to produce nanometric Bi{sub 4}Ti{sub 3}O{sub 12}. (author)

Mechanosynthesis of nanocrystalline CaTi1-xMnxO3-δ

Directory of Open Access Journals (Sweden)

Figueiredo, F. M.

2008-08-01

Full Text Available The mechanosynthesis of nanocrystalline CaTi1-xMnxO3-δ is reported for the first time. Powdered CaO, TiO2 anatase and Mn2O3 (Aldrich were weighed in the appropriate stoichiometric quantities in order to obtain CaTi1-xMnxO3-δ (x=0.05, 0.10, 0.15, 0.20, 0.30, 0.50 and 0.80 and dry milled in a planetary high-energy ball mill, using zirconia containers and balls, with a 10:1 ball/mass ratio. The planetary rotation was kept constant at 650 rpm and the container at 1300 rpm, in the opposite direction. Powder XRD patterns revealed a perovskite forming from the early milling stages and a completed reaction after 180 min, with no apparent crystalline or amorphous intermediates, indicating significant Mn solubility in CaTiO3. Patterns show a decrease in lattice volume upon Mn substitution, as expected from the lower Mn3+ or Mn4+ ionic radii when compared to Ti4+. The average crystallite size is in the range 5-30 nm, as determined from Williamson-Hall plots and confirmed by high resolution transmission electron microscopy.La mecanosíntesis de CaTi1-xMnxO3-δ nanocristalino es presentada por primera vez. Polvos reactivos de CaO, TiO2 anatasa y Mn2O3 (Aldrich fueron pesados en las cantidades estequiométricas adecuadas para obtener CaTi1-xMnxO3-δ (x=0.05, 0.10, 0.15, 0.20, 0.30, 0.50 y 0.80 por molienda en seco en un molino planetario de alta energía utilizando contenedores y bolas de circona, en una relación masa de bolas : masa de polvo de 10:1. La rotación del planetario se mantuvo constante a 650 revoluciones por minuto (rpm y la del contenedor a 1300 rpm, en el sentido inverso. La formación de una fase con estructura de perovskita fue identificada a través del análisis de los polvos por difracción de rayos X, siendo esta fase claramente mayoritaria en los polvo molidos durante 180 min y sin observarse la formación de compuestos intermediarios. Los patrones de difracción de rayos X también indicaron una disminución de los parámetro de red

Monoclinic β-Li{sub 2}TiO{sub 3} nanocrystalline particles employing novel urea assisted solid state route: Synthesis, characterization and sintering behavior

Energy Technology Data Exchange (ETDEWEB)

Tripathi, Biranchi M., E-mail: biranchi.barc@gmail.com [Powder Metallurgy Division, Bhabha Atomic Research Centre, Vashi Complex, Navi Mumbai 400705 (India); Mohanty, Trupti; Prakash, Deep [Powder Metallurgy Division, Bhabha Atomic Research Centre, Vashi Complex, Navi Mumbai 400705 (India); Tyagi, A.K. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sinha, P.K. [Powder Metallurgy Division, Bhabha Atomic Research Centre, Vashi Complex, Navi Mumbai 400705 (India)

2017-07-15

Pure phase monoclinic nano-crystalline Li{sub 2}TiO{sub 3} powder was synthesized by a novel urea assisted solid state synthesis method using readily available and economical precursors. A single phase and well crystalline Li{sub 2}TiO{sub 3} powder has been obtained at slightly lower temperature (600–700 °C) and shorter duration (2 h) as compared to the conventional solid state method. The proposed method has significant advantages in comparison to other viable methods mainly in terms of phase purity, powder properties and sinterability. Analysis of chemical composition using inductively coupled plasma atomic emission spectroscopy (ICP-AES) shows no loss of lithium from Li{sub 2}TiO{sub 3} in the proposed method. The emergence of monoclinic Li{sub 2}TiO{sub 3} phase was confirmed by X-ray diffraction (XRD) pattern of as-synthesized powder. The crystallite size of Li{sub 2}TiO{sub 3} powder was calculated to be in the range of 15–80 nm, which varied as a function of urea composition and temperature. The morphology of as-prepared Li{sub 2}TiO{sub 3} powders was examined by scanning electron microscope (SEM). The effect of urea composition on phase and morphology was investigated so as to delineate the role of urea. Upon sintering at < 1000 °C temperature, the Li{sub 2}TiO{sub 3} powder compact attained about 98% of the theoretical density with fine grained (grain size: 2–3 μm) microstructure. It indicates excellent sinter-ability of Li{sub 2}TiO{sub 3} powder synthesized by the proposed method. The fine grained structure is desirable for better tritium breeding performance of Li{sub 2}TiO{sub 3}. Electrochemical impedance spectroscopy at variable temperature showed good electrical properties of Li{sub 2}TiO{sub 3}. The proposed method is simple, anticipated to be cost effective and convenient to realise for large scale production of phase pure nanocrystalline and having significantly enhanced sinter-ability Li{sub 2}TiO{sub 3} powder.

Syntheses of nanocrystalline BaTiO3 and their optical properties

Science.gov (United States)

Yu, J.; Chu, J.; Zhang, M.

Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

Spherical Li{sub 4}Ti{sub 5}O{sub 12} synthesized by spray drying from a different kind of solution

Energy Technology Data Exchange (ETDEWEB)

He Zhenjiang [School of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China); Wang Zhixing, E-mail: zhixingwang163@163.com [School of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China); Wu Feixiang; Guo Huajun; Li Xinhai; Xiong Xunhui [School of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China)

2012-11-05

Highlights: Black-Right-Pointing-Pointer The precursor powders comprise hollow particles. Black-Right-Pointing-Pointer H{sub 2}O{sub 2} acts as coordination agent that reacts with the Ti to form a large anion. Black-Right-Pointing-Pointer Li{sub 4}Ti{sub 5}O{sub 12} powders can be synthesized at a low temperature of 700 Degree-Sign C. Black-Right-Pointing-Pointer The spherical Li{sub 4}Ti{sub 5}O{sub 12} powders show excellent electrochemical performance. Black-Right-Pointing-Pointer We hope our work will be helpful for other research groups. - Abstract: High energy density Li{sub 4}Ti{sub 5}O{sub 12} powders comprising of spherical nanocrystalline are synthesized by spray drying followed by solid-state calcination. The influences of Li/Ti atomic ratios (0.784, 0.800, 0.816, and 0.832) on the performance of Li{sub 4}Ti{sub 5}O{sub 12} are investigated by means of Thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscope (TEM), Galvanostatic cell cycling, as well as Ac impedance spectroscopy. The results indicate that, when the spray-drying precursors at the Li/Ti molar ratio of 0.816 are calcined at 700 Degree-Sign C for 16 h in air, a pure LTO phase with a lithium-excess composition is obtained, which shows the best properties. Between 1.0 and 2.5 V (vs. Li/Li{sup +}), the initial discharge capacities of the powder are 174, 168, 163, 153, and 136 mAhg{sup -1} at a constant current density of 0.1, 0.5, 1, 2, and 5 C, respectively. After 100 cycles, the discharge capacities of the LTO powders remain 97, 95, and 99% of initial discharge capacities at current densities of 1, 2, and 5 C, respectively.

Preparation and characterization of nanocrystalline porous TiO2/WO3 composite thin films

International Nuclear Information System (INIS)

Hsu, C.-S.; Lin, C.-K.; Chan, C.-C.; Chang, C.-C.; Tsay, C.-Y.

2006-01-01

TiO 2 materials possessing not only photocatalytic but also electrochromic properties have attracted many research and development interests. Though WO 3 exhibits excellent electrochromic properties, the much higher cost and water-sensitivity of WO 3 as compared with the TiO 2 may restrict the practical application of WO 3 materials. In the present study, the feasibility of preparing nanocrystalline porous TiO 2 /WO 3 composite thin films was investigated. Precursors of sols TiO 2 and/or WO 3 and polystyrene microspheres were used to prepare nanocrystalline pure TiO 2 , WO 3 , and composite TiO 2 /WO 3 thin films by spin coating. The spin-coated thin films were amorphous and, after heat treating at a temperature of 500 o C, nanocrystalline TiO 2 , TiO 2 /WO 3 , and WO 3 thin films with or without pores were prepared successfully. The heat-treated thin films were colorless and coloration-bleaching phenomena can be observed during cyclic voltammetry tests. The heat-treated thin films exhibited good reversible electrochromic behavior while the porous TiO 2 /WO 3 composite film exhibited improved electrochromic properties

Electrochemically active nanocomposites of Li4Ti5O12 2D nanosheets and SnO2 0D nanocrystals with improved electrode performance

International Nuclear Information System (INIS)

Han, Song Yi; Kim, In Young; Lee, Sang-Hyup; Hwang, Seong-Ju

2012-01-01

Electrochemically active nanocomposites consisting of Li 4 Ti 5 O 12 2D nanosheets and SnO 2 0D nanocrystals are synthesized by the crystal growth of tin dioxide on the surface of 2D nanostructured lithium titanate. According to powder X-ray diffraction and electron microscopic analyses, the rutile-structured SnO 2 nanocrystals are stabilized on the surface of spinel-structured Li 4 Ti 5 O 12 2D nanosheets. The homogeneous hybridization of tin dioxide with lithium titanate is confirmed by elemental mapping analysis. Ti K-edge X-ray absorption near-edge structure and Sn 3d X-ray photoelectron spectroscopy indicate the stabilization of tetravalent titanium ions in the spinel lattice of Li 4 Ti 5 O 12 and the formation of SnO 2 phase with tetravalent Sn oxidation state. The electrochemical measurements clearly demonstrate the promising functionality of the present nanocomposites as anode for lithium secondary batteries. The Li 4 Ti 5 O 12 –SnO 2 nanocomposites show larger discharge capacity and better cyclability than do the uncomposited Li 4 Ti 5 O 12 and SnO 2 phases, indicating the synergistic effect of nanocomposite formation on the electrode performance of Li 4 Ti 5 O 12 and SnO 2 . The present experimental findings underscore the validity of 2D nanostructured lithium titanate as a useful platform for the stabilization of nanocrystalline electrode materials and also for the improvement of their functionality.

HRTEM analysis on nanocrystalline BaTiO3 and PbTiO3: size effects on ferroelectric phase transition temperature

International Nuclear Information System (INIS)

Bursill, L.A.; Jiang, B.; Peng, J.L.; Zhong, W.L.; Zhang, P.L.

1997-01-01

High-Resolution Transmission Electron Microscopic studies of nanocrystaline particles of BaTiO 3 and PbTiO 3 are reported. There are characteristic differences observed for BaTiO 3 prepared using sol gel (SG) and steric acid gel (SAG) methods. The former exhibit a critical size below which there is no paraelectric/ferroelectric phase transition, whereas BaTiO 3 prepared via the SAG route remained cubic for all conditions. The SAG preparations always showed chemical intergrowth defects whereas the SG preparations were single phase. Atomic resolution images of both varieties showed interesting surface steps and surface relaxations/reconstructions of some facets. Nanocrystalline PbTiO 3 prepared by the SG route remains tetragonal, albeit with decreasing c/a ratio, down to 25nm diameter. HRTEM observations of nanocrystalline PbTiO 3 are also presented. X-ray diffraction, dielectric and Raman scattering measurements also demonstrate pronounced size effects. The relationship between the observed nanostructures and size effects on the physical properties is discussed. 6 refs., 1 tab., 6 figs

Electrochemical behaviors of wax-coated Li powder/Li 4Ti 5O 12 cells

Science.gov (United States)

Park, Han Eol; Seong, Il Won; Yoon, Woo Young

The wax-coated Li powder specimen was effectively synthesized using the drop emulsion technique (DET). The wax layer on the powder was verified by SEM, Focused Ion Beam (FIB), EDX and XPS. The porosity of a sintered wax-coated Li electrode was measured by linear sweep voltammetry (LSV) and compared with that of a bare, i.e., un-coated Li electrode. The electrochemical behavior of the wax-coated Li powder anode cell was examined by the impedance analysis and cyclic testing methods. The cyclic behavior of the wax-coated Li powder anode with the Li 4Ti 5O 12 (LTO) cathode cell was examined at a constant current density of 0.35 mA cm -2 with the cut-off voltages of 1.2-2.0 V at 25 °C. Over 90% of the initial capacity of the cell remained even after the 300th cycle. The wax-coated Li powder was confirmed to be a stable anode material.

The influence of mechanical activation on the morphological changes of Fe/BaTiO_3 powder

International Nuclear Information System (INIS)

Kosanović, D.; Obradović, N.; Pavlović, V.P.; Marković, S.; Maričić, A.; Rasić, G.; Vlahović, B.; Pavlović, V.B.; Ristić, M.M.

2016-01-01

Highlights: • Fe/BaTiO_3 ceramic was prepared using a solid-state reaction. • Powder mixture of 60% Fe and 40% BaTiO_3 was mechanically activated up to 240 min. • Microstructure was characterized using Powder XRD and SEM. • Thermal stability of the activated samples was investigated using DSC. • Raman spectrum changes with activation, along with atypical resonant scattering. - Abstract: Crystal structure and morphology of mechanically activated nanocrystalline Fe/BaTiO_3 was investigated using a combination of spectroscopic and microscopic methods. These show that mechanical activation led to the creation of new surfaces and the comminution of the initial powder particles. Prolonged milling resulted in formation of larger agglomerates of BaTiO_3 and bimodal particle size distribution, where BaTiO_3 particles were significantly larger than those of iron-containing phases. Milling times of 210 min and above lead to a significant decrease in temperature of the oxidation of iron in the sample, indicating abrupt change in reactivity. Raman spectroscopy analysis has revealed that activation had a pronounced influence on Fe/BaTiO_3 lattice, thereby affecting both the stability of the crystal structure and the phase transition phenomena.

Dielectric behavior of CaCu3Ti4O12: Poly Vinyl Chloride ceramic polymer composites at different temperature and frequencies

Directory of Open Access Journals (Sweden)

Ajay Pratap Singh

2016-12-01

Full Text Available In this study, the efforts have been made to obtain relatively high dielectric constant polymer-ceramic composite by incorporating the giant dielectric constant material, calcium copper titanate (CCTO in a PVC polymer matrix. We have prepared composites of CaCu3Ti4O12 (CCTO ceramic and Poly Vinyl Chloride (PVC polymer in various ratios (by volume in addition to pure CCTO. For this, CCTO was prepared by the conventional oxide route (solid-state reaction method. The structural, the microstructural and the dielectric properties of the composites were studied using X-ray diffraction, Scanning Electron Microscope, and impedance analyzer respectively. The study of dielectric constant and dielectric loss of the pure CCTO and the composites reveal that there is good range of dielectric constants and dielectric losses for the studied composites. The pure sample of CCTO exhibits giant dielectric constant at low frequency within the studied temperature range. As frequency increases, dielectric constant drastically decreases and approaching a constant value at 1 MHz. Above the intermediate temperature, the dielectric constant and dielectric loss for pure CCTO is more frequency dependent than its composites.

Low-Temperature Preparation of Amorphous-Shell/Nanocrystalline-Core Nanostructured TiO2 Electrodes for Flexible Dye-Sensitized Solar Cells

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Dongshe Zhang

2008-01-01

Full Text Available An amorphous shell/nanocrystalline core nanostructured TiO2 electrode was prepared at low temperature, in which the mixture of TiO2 powder and TiCl4 aqueous solution was used as the paste for coating a film and in this film amorphous TiO2 resulted from direct hydrolysis of TiCl4 at 100∘C sintering was produced to connect the particles forming a thick crack-free uniform nanostructured TiO2 film (12 μm, and on which a photoelectrochemical solar cell-based was fabricated, generating a short-circuit photocurrent density of 13.58 mA/cm2, an open-circuit voltage of 0.647 V, and an overall 4.48% light-to-electricity conversion efficiency under 1 sun illumination.

Ferroelectric properties of sandwich structured (Bi, La)4T3O12/Pb(Zr, Ti)O3/ (Bi, La)4Ti3O12 thin films on Pt/Ti/SiO2/Si substrates

International Nuclear Information System (INIS)

Bao Dinghua; Wakiya, Naoki; Shinozaki, Kazuo; Mizutani, Nobuyasu

2002-01-01

Sandwich structured (Bi, La) 4 Ti 3 O 12 /Pb(Zr, Ti)O 3 /(Bi, La) 4 Ti 3 O 12 thin films were fabricated on Pt/Ti/SiO 2 /Si substrates, with the intention of simultaneously utilizing the advantages of both (Bi, La) 4 Ti 3 O 12 (BLT) and Pb(Zr, Ti)O 3 (PZT) thin films such as non-fatigue behaviours of BLT and good ferroelectric properties of PZT. Both BLT and PZT layers were prepared by a chemical solution deposition technique. The experiments demonstrated that the sandwich structure showed fatigue-free characteristics at least up to 10 10 switching bipolar pulse cycles under 8 V and excellent retention properties. The sandwich structured thin films also exhibited well-defined hysteresis loops with a remanent polarization (2P r ) of 8.8 μC cm -2 and a coercive field (E c ) of 47 kV cm -1 . The room-temperature dielectric constant and dissipation factor were 210 and 0.031, respectively, at a frequency of 100 kHz. These results suggest that this sandwich structure is a promising material combination for ferroelectric memory applications. (author)

Microwave dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12}-Al{sub 2}O{sub 3} composite

Energy Technology Data Exchange (ETDEWEB)

Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Zaman, Rosyaini Afindi; Ahmad, Zainal Arifin [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Karim, Saniah Ab; Mohamed, Julie Juliewatty, E-mail: juliewatty.m@umk.edu.my [Advance Materials Research Cluster, Faculty of Earth Sciences, Universiti Malaysia Kelantan, Jeli Campus, 17600 Jeli, Kelantan (Malaysia); Ain, Mohd Fadzil [School of Electrical and Electronic Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)

2016-07-19

(1-x)CaCu{sub 3}Ti{sub 4}O{sub 12} + (x)Al{sub 2}O{sub 3} composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO{sub 3}, CuO and TiO{sub 2} powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al{sub 2}O{sub 3} were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl{sub 2}O{sub 4} and Corundum (Al{sub 2}O{sub 3}) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al{sub 2}O{sub 3} (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al{sub 2}O{sub 3} (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al{sub 2}O{sub 3} was reduced both dielectric loss and permittivity at least for an order of magnitude.

Synthesis and characterization of FeTiO3 ceramics

OpenAIRE

Anil B. Gambhire; Machhindra K. Lande; Sandip B. Rathod; Balasaheb R. Arbad; Kaluram N. Vidhate; Ramakrishna S. Gholap; Kashinath R. Patil

2016-01-01

Nanocrystalline FeTiO3 ceramic powders were prepared by the sol–gel process combined with a surfactant-assisted template method. The resulting powders were calcined at different temperatures ranging from 150 °C to 600 °C for 2 h in air. The results revealed that a pure hexagonal phase of FeTiO3 could be obtained at a low temperature, 600 °C. The phase evolution of FeTiO3 was investigated by X-ray diffraction patterns (XRD), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelect...

EFFECT OF CUP AND BALL TYPES ON MECHANO-CHEMICAL SYNTHES IS OF Al2O3–TiC NANOCOMPOSITE POWDER

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M. Zakeri

2012-07-01

Full Text Available Al2O3–TiC nanocomposite powder was successfully synthesized by ball milling TiO2, Al and graphite powders. Effects of cup and ball type, milling time and annealing were investigated. XRD was used to characterize milled and annealed powders. The morphological and microstructural evolutions were studied by SEM and TEM. Results showed that the formation of this composite begins after 20 h and completes after 35 h of milling with stainless steel cup and balls. In contrast, there is no reaction during milling (up to 80 h with ZrO2 cup and balls. Fe and ZrO2 were the major impurities introduced during milling with stainless steel and ZrO2 cups, respectively. The Fe impurity was removed by leaching in 3HCl·HNO3 solution for 4 days. Mean grain size less than 7 nm was achieved at the end of milling. In spite of grain growth, this composite maintained its nanocrystalline nature after annealing at 1000°C.

Thermal analysis of formation of nano-crystalline BaTiO3 using Ba(NO32 and TiO2

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Md. Jawed Ansaree

2015-12-01

Full Text Available The reaction of Ba(NO32 with TiO2 was studied by thermogravimetric (TG and differential scanning calorimetric (DSC techniques up to 1000 °C and in nitrogen atmosphere. It was found that the formation of BaTiO3 takes place above 600 °C and that precursor mixing time and heating rate have no effect on the reaction temperature. BaTiO3 powder was prepared by calcination of Ba(NO32 and TiO2 precursor mixture at 800 °C for 8 h. X-ray diffraction analysis of the synthesized BaTiO3 confirmed the formation of tetragonal phase with lattice parameters a = 3.9950±0.0003 Å and c = 4.0318±0.0004 Å. Thermal analysis of the synthesized BaTiO3 powder showed weight loss within temperature range 40–1000 °C of only 0.40%. This small amount of weight loss was connected with some impurity phase, and identified as BaCO3 using Fourier transform infrared (FTIR technique.

Electric Properties of Pb(Sb1/2Nb1/2)O3 PbTiO3 PbZrO3 Ceramics

Science.gov (United States)

Kawamura, Yasushi; Ohuchi, Hiromu

1994-09-01

Solid-solution ceramics of ternary system xPb(Sb1/2Nb1/2)O3 yPbTiO3 zPbZrO3 were prepared by the solid-state reaction of powder materials. Ceramic, electric, dielectric and piezoelectric properties and crystal structures of the system were studied. Sintering of the system xPb(Sb1/2Nb1/2)O3 yPbTiO3 zPbZrO3 is much easier than that of each end composition, and well-sintered high-density ceramics were obtained for the compositions near the morphotropic transformation. Piezoelectric ceramics with high relative dielectric constants, high radial coupling coefficient and low resonant resistance were obtained for the composition near the morphotropic transformation. The composition Pb(Sb1/2Nb1/2)0.075Ti0.45Zr0.475O3 showed the highest dielectric constant (ɛr=1690), and the composition Pb(Sb1/2Nb1/2)0.05Ti0.45Zr0.5O3 showed the highest radial coupling coefficient (kp=64%).

Dye-Sensitized Solar Cells Based on Bi4Ti3O12

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Zeng Chen

2011-01-01

Full Text Available Bismuth titanate (Bi4Ti3O12 particles were synthesized by hydrothermal treatment and nanoporous thin films were prepared on conducting glass substrates. The structures and morphologies of the samples were examined with X-ray diffraction and scanning electron microscope (SEM. Significant absorbance spectra emerged in visible region which indicated the efficient sensitization of Bi4Ti3O12 with N3 dye. Surface photovoltaic properties of the samples were investigated by surface photovoltage. The results further indicate that N3 can extend the photovoltaic response range of Bi4Ti3O12 nanoparticles to the visible region, which shows potential application in dye-sensitized solar cell. As a working electrode in dye-sensitized solar cells (DSSCs, the overall efficiency reached 0.48% after TiO2 modification.

The Formation of Lithiated Ti-Doped α-Fe2O3 Nanocrystalline Particles by Mechanical Milling of Ti-Doped Lithium Spinel Ferrite

International Nuclear Information System (INIS)

Widatallah, H. M.; Gismelseed, A. M.; Bouziane, K.; Berry, F. J.; Al Rawas, A. D.; Al-Omari, I. A.; Yousif, A. A.; Elzain, M. E.

2004-01-01

The milling of spinel-related Ti-doped Li 0.5 Fe 2.5 O 4 for different times is studied with XRD, Moessbauer spectroscopy and magnetic measurements. Milling converts the material to Li-Ti-doped α-Fe 2 O 3 nanocrystalline particles via an intermediate γ-LiFeO 2 -related phase. The role played by the dopant Ti-ion in the process is emphasized.

Silver film on nanocrystalline TiO{sub 2} support: Photocatalytic and antimicrobial ability

Energy Technology Data Exchange (ETDEWEB)

Vukoje, Ivana D., E-mail: ivanav@vinca.rs [Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11000 Belgrade (Serbia); Tomašević-Ilić, Tijana D., E-mail: tommashev@gmail.com [Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11000 Belgrade (Serbia); Zarubica, Aleksandra R., E-mail: zarubica2000@yahoo.com [Department of Chemistry, Faculty of Science and Mathematics, University of Niš, Višegradska 33, 18000 Niš (Serbia); Dimitrijević, Suzana, E-mail: suzana@tmf.bg.ac.rs [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade (Serbia); Budimir, Milica D., E-mail: mickbudimir@gmail.com [Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11000 Belgrade (Serbia); Vranješ, Mila R., E-mail: mila@vinca.rs [Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11000 Belgrade (Serbia); Šaponjić, Zoran V., E-mail: saponjic@vinca.rs [Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11000 Belgrade (Serbia); Nedeljković, Jovan M., E-mail: jovned@vinca.rs [Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11000 Belgrade (Serbia)

2014-12-15

Highlights: • Simple photocatalytic rout for deposition of Ag on nanocrystalline TiO{sub 2} films. • High antibactericidal efficiency of deposited Ag on TiO{sub 2} support. • Improved photocatalytic performance of TiO{sub 2} films in the presence of deposited Ag. - Abstract: Nanocrystalline TiO{sub 2} films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO{sub 2} film modified with alanine that covalently binds to the surface of TiO{sub 2} and at the same time chelate silver ions induced formation of metallic silver film. Optical and morphological properties of thin silver films on nanocrystalline TiO{sub 2} support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO{sub 2} films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO{sub 2} support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact.

Synthesis and characterization of FeTiO3 ceramics

Directory of Open Access Journals (Sweden)

Anil B. Gambhire

2016-09-01

Full Text Available Nanocrystalline FeTiO3 ceramic powders were prepared by the sol–gel process combined with a surfactant-assisted template method. The resulting powders were calcined at different temperatures ranging from 150 °C to 600 °C for 2 h in air. The results revealed that a pure hexagonal phase of FeTiO3 could be obtained at a low temperature, 600 °C. The phase evolution of FeTiO3 was investigated by X-ray diffraction patterns (XRD, Fourier-transform infrared spectroscopy (FT-IR, and X-ray photoelectron spectroscopy (XPS. Particle size and morphology were studied by transmission electron microscopy (TEM.

In situ preparation of (TiB + TiC + Nd2O3)/Ti composites by powder metallurgy

International Nuclear Information System (INIS)

Lu Junqiang; Qin Jining; Lu Weijie; Liu Yang; Gu Jiajun; Zhang Di

2009-01-01

Titanium matrix composites reinforced with multiple ceramic particulates TiB, TiC and Nd 2 O 3 were prepared by powder metallurgy utilizing the chemical reactions among Ti, B 4 C, NdB 6 and oxygen in Ti powder. The thermodynamic feasibility of the in situ reaction has been calculated. The phases were identified by X-ray diffraction (XRD). The result shows that multiple ceramic phases TiB, TiC and Nd 2 O 3 particulates have been synthesized. The microstructures were examined by means of optical microscopy (OM), scanning electron microscopy (SEM), backscattered electron microscopy and transmission electron microscope (TEM). The results show that the reinforcements are distributed uniformly in the matrix alloy and grow in different shapes. TiB grows in needle shape; TiC and Nd 2 O 3 grow in equiaxed or near-equiaxed shapes. The addition of NdB 6 is beneficial to grain refinement, grain-boundary purification and porosity reduction

Directed laser processing of compacted powder mixtures Al2O3-TiO2-Y2O3

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Vlasova M.

2013-01-01

Full Text Available The phase formation, microstructure and surface texture of laser treated ternary powder mixtures of Al2O3-TiO2-Y2O3 had been studied. Rapid high temperature heating and subsequent rapid cooling due to the directed movement of the laser beam forms concave ceramic tracks. Phase composition and microstructure of the tracks depends on the Al2O3 content and the TiO2/Y2O3 ratio of the initial mixtures. The main phases observed are Y3Al5O12, Y2Ti2O7, Al2O3 and Al2TiO5. Due to the temperature gradient in the heating zone, complex layered structures are formed. The tracks consist of three main layers: a thin surface layer, a layer of crystallization products of eutectic alloys, and a lower sintered layer. The thickness of the crystallization layer and the shrinkage of the irradiation zone depend on the amount of Y3Al5O12 and Al2O3 crystallized from the melt.

Dielectric and electrical characteristics of Sr modified Ca1Cu3Ti4O12

Science.gov (United States)

Sahu, M.; Choudhary, R. N. P.; Roul, B. K.

2018-05-01

This paper mainly reports on the effect of Sr substitution on dielectric and electrical properties of CaCu3Ti4O12 at different temperature and frequency. Preliminary analysis of X-ray diffraction data of sintered samples confirms the reported cubic structure. Study of surface morphology shows that the surface of the samples contains well-defined and uniformly distributed grains. Some electrical parameters (permittivity, tangent loss and impedance) of the materials were measured and analyzed over a wide range of temperature (25 to 315 °C) and frequency (50 to 2x106 Hz). The ultra high dielectric constant and low energy dissipation have been observed in the said experimental conditions of phase-pure prepared compounds. It is expected that the addition of nano-size compounds or oxide will help to enhance the above properties useful for fabrication of super-capacitor.

Characterization of Bi2/3Cu3Ti4O12 ceramics synthesized by semi-wet route

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Pooja Gautam

2016-12-01

Full Text Available Bi2/3Cu3Ti4O12 (BCTO ceramic was synthesized by the semi-wet route using metal nitrate solutions and solid TiO2 powder in a stoichiometric ratio. Fourier transform infrared (FTIR study of BCTO precursor powder and calcined ceramic showed the presence of alcoholic functional groups and the stretching band of Ti-O and Cu-O respectively. X-ray diffraction (XRD, scanning electron microscope (SEM and energy dispersive x-ray spectroscopy (EDX were employed to characterize the structure, surface morphology and purity of the sintered BCTO ceramic respectively. X-ray diffraction study confirmed the single phase formation of BCTO ceramic at 1073 K. The average dimension of grains calculated by SEM and AFM was found to be in the range of 0.73±0.2 µm with clear grain boundaries. Magnetic property was investigated over a wide temperature range 2–300 K at a magnetic field of 7 tesla. The Curie temperature was calculated by zero field cooled (MZFC and field cooled (MFC magnetization at 100 Oe applied field which was found to be 125 K. The sintered BCTO ceramic shows high dielectric constant (ε'=2.9×104 at 323 K and 100 Hz.

Preparation of cauliflower-like shaped Ba0.6Sr0.4TiO3 powders by modified oxalate co-precipitation method

International Nuclear Information System (INIS)

Li Mingli; Xu Mingxia

2009-01-01

The quantitative barium-strontium titanyl oxalate (Ba 0.6 Sr 0.4 TiO(C 2 O 4 ) 2 .4H 2 O, BSTO) precursor powders were prepared by the modified oxalate co-preparation method. It was based on the cation-exchange reaction between the stoichiometric solutions of oxalotitanic acid (H 2 TiO(C 2 O 4 ) 2 , HTO) and barium + strontium nitrate solution containing stoichiometric quantities of Ba and Sr ions. The pyrolysis of BSTO at 800 deg. C/4 h in air produced the homogeneous cauliflower-like shaped barium-strontium titanate (Ba 0.6 Sr 0.4 TiO 3 , BST) powders. The effect of polyethylene glycol (PEG) on morphology of BSTO and BST powders was also investigated. The characterization studies were carried on the as-dried BSTO and calcined BST powders by various physicochemical techniques, IR, X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The BSTO and BST powders obtained by aforementioned technique without PEG were homogeneous with spherical shape. The particles grew into spindle shape with the effect of PEG

Magnetic properties of Aurivillius lanthanide-bismuth (LnFeO3nBi4Ti3O12 (n = 1,2 layered titanates

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Tartaj, J.

2008-06-01

Full Text Available Bismuth titanates of Aurivillius layer-structure (BiFeO3nBi4Ti3O12, are of great technological interest because of their applications as non-volatile ferroelectric memories and high-temperature piezoelectric materials. The synthesis and crystallographic characterization of a new family of compounds (LnFeO3nBi4Ti3O12 was recently reported, in which the layers consist of LnFeO3 perovskites with a lanthanide Ln3+ substituting diamagnetic Bi3+. We report herein the magnetic properties of bulk samples, with Ln = Nd, Eu, Gd and Tb, and n = 1 and 2. Single-layer materials are paramagnetic, similar to non-substituted bismuth titanate Bi5FeTi3O15, and show crystal field effects due to the crystallographic environment of Eu3+ and Tb3+. Several anomalies are detected in the magnetization M(T of double-layer (LnFeO32Bi4Ti3O12 compounds, related to the strong magnetism of Tb and Gd, since they weakly appear for Nd and they are absent in the VanVleck Eu3+ ion and in the parent Bi6Fe2Ti3O18 compound.Los titanatos de hierro y bismuto con estructura laminar tipo Aurivillius, (BiFeO3nBi4Ti3O12, tienen un gran interés tecnológico debido a sus aplicaciones como memorias ferroeléctricas no volátiles y como piezoeléctrico cerámico de alta temperatura. La síntesis y la caracterización cristalina de una nueva familia de compuestos (LnFeO3nBi4Ti3O12 han sido recientemente reportadas, en la que el catión diamagnético Bi3+ ha sido sustituido por los paramagnéticos Ln3+ en los bloques de perovskita. Se estudian las propiedades magnéticas de muestras cerámicas en volumen con Ln = Nd, Eu, Gd y Tb, y n = 1 y 2. Los materiales con n=1 son paramagnéticos y similares al no sustituido Bi5FeTi3O15, y muestran efectos de campo cristalino debido al entorno cristalino de Eu3+ y Tb3+. Se han detectado algunas anomalías en la magnetización M(T de los compuestos n=2 (LnFeO32Bi4Ti3O12 que están relacionadas con el fuerte magnetismo de Tb y Gd, que aparecen d

The Formation of Lithiated Ti-Doped {alpha}-Fe{sub 2}O{sub 3} Nanocrystalline Particles by Mechanical Milling of Ti-Doped Lithium Spinel Ferrite

Energy Technology Data Exchange (ETDEWEB)

Widatallah, H. M., E-mail: hisham@ictp.trieste.it [Khartoum University, Department of Physics (Sudan); Gismelseed, A. M.; Bouziane, K. [Sultan Qaboos University, Department of Physics (Oman); Berry, F. J. [Open University, Department of Chemistry (United Kingdom); Al Rawas, A. D.; Al-Omari, I. A.; Yousif, A. A.; Elzain, M. E. [Sultan Qaboos University, Department of Physics (Oman)

2004-12-15

The milling of spinel-related Ti-doped Li{sub 0.5}Fe{sub 2.5}O{sub 4} for different times is studied with XRD, Moessbauer spectroscopy and magnetic measurements. Milling converts the material to Li-Ti-doped {alpha}-Fe{sub 2}O{sub 3} nanocrystalline particles via an intermediate {gamma}-LiFeO{sub 2}-related phase. The role played by the dopant Ti-ion in the process is emphasized.

Electrochemical Characteristics and Li+ Ion Intercalation Kinetics of Dual-phase Li4Ti5O12/Li2TiO3 Composite in Voltage Range of 0−3 V

KAUST Repository

Bhatti, Humaira S

2016-04-20

Li4Ti5O12, Li2TiO3 and dual-phase Li4Ti5O12/Li2TiO3 composite were prepared by sol-gel method with average particle size of 1 µm, 0.3 µm and 0.4 µm, respectively. Though Li2TiO3 is electrochemically inactive, the rate capability of Li4Ti5O12/Li2TiO3 is comparable to Li4Ti5O12 at different current rates. Li4Ti5O12/Li2TiO3 also shows good rate performance of 90 mA h g-1 at high rate of 10 C in voltage range of 1−3 V, attributable to increased interfaces in the composite. While Li4Ti5O12 delivers capacity retention of 88.6 % at 0.2 C over 50 cycles, Li4Ti5O12/Li2TiO3 exhibits no capacity fading at 0.2 C (40 cycles) and capacity retention of 98.45 % at 0.5 C (50 cycles). This highly stable cycling performance is attributed to the contribution of Li2TiO3 in preventing undesirable reaction of Li4Ti5O12 with the electrolyte during cycling. CV curves of Li4Ti5O12/Li2TiO3 in 0−3 V range exhibit two anodic peaks at 1.51 V and 0.7−0.0 V, indicating two modes of lithium intercalation into the lattice sites of active material. Owing to enhanced intercalation/de-intercalation kinetics in 0−3 V, composite electrode delivers superior rate performance of 203 mAh/g at 2.85 C and 140 mAh/g at 5.7 C with good reversible capacity retention over 100 cycles.

Electrochemical Characteristics and Li+ Ion Intercalation Kinetics of Dual-phase Li4Ti5O12/Li2TiO3 Composite in Voltage Range of 0−3 V

KAUST Repository

Bhatti, Humaira S; Anjum, Dalaver H.; Ullah, Shafiq; Ahmed, Bilal; Habib, Amir; Karim, Altaf; Hasanain, Syed Khurshid

2016-01-01

Li4Ti5O12, Li2TiO3 and dual-phase Li4Ti5O12/Li2TiO3 composite were prepared by sol-gel method with average particle size of 1 µm, 0.3 µm and 0.4 µm, respectively. Though Li2TiO3 is electrochemically inactive, the rate capability of Li4Ti5O12/Li2TiO3 is comparable to Li4Ti5O12 at different current rates. Li4Ti5O12/Li2TiO3 also shows good rate performance of 90 mA h g-1 at high rate of 10 C in voltage range of 1−3 V, attributable to increased interfaces in the composite. While Li4Ti5O12 delivers capacity retention of 88.6 % at 0.2 C over 50 cycles, Li4Ti5O12/Li2TiO3 exhibits no capacity fading at 0.2 C (40 cycles) and capacity retention of 98.45 % at 0.5 C (50 cycles). This highly stable cycling performance is attributed to the contribution of Li2TiO3 in preventing undesirable reaction of Li4Ti5O12 with the electrolyte during cycling. CV curves of Li4Ti5O12/Li2TiO3 in 0−3 V range exhibit two anodic peaks at 1.51 V and 0.7−0.0 V, indicating two modes of lithium intercalation into the lattice sites of active material. Owing to enhanced intercalation/de-intercalation kinetics in 0−3 V, composite electrode delivers superior rate performance of 203 mAh/g at 2.85 C and 140 mAh/g at 5.7 C with good reversible capacity retention over 100 cycles.

Crystal and magnetic structures of CaCu3Fe4O12 and LaCu3Fe4O12: distinct charge transitions of unusual high valence Fe

International Nuclear Information System (INIS)

Shimakawa, Yuichi

2015-01-01

New 134-type perovskites, CaCu 3 Fe 4 O 12 (CCFO) and LaCu 3 Fe 4 O 12 (LCFO), were prepared by means of high-pressure synthesis. The compounds contain unusual high valence Fe 4+ in CCFO and Fe 3.75+ in LCFO at high temperatures. With decreasing temperature, the instabilities of the high valence states of Fe are relieved by distinct charge transitions, which are charge disproportionation (4Fe 4+   →  2Fe 3+   +  2Fe 5+ ) in CCFO and intermetallic charge transfer (3Cu 2+   +  4Fe 3.75+   →  3Cu 3+   +  4Fe 3+ ) in LCFO. Crystal structure analysis with synchrotron x-ray diffraction and magnetic structure analysis with neutron diffraction revealed the nature of the transitions. Although the two behaviors look completely different from each other in simple ionic models, they can both be explained by the localization of ligand holes, which are produced by the strong hybridization of low-lying Fe-d and oxygen p orbitals in the oxides. The ligand holes in the charge disproportionated CCFO are localized at the Fe–O sites alternately (4d 5 L  →  2d 5   +  2d 5 L 2 ) and the ligand holes in the charge transferred LCFO are localized at the Cu–O sites (3d 9   +  4d 5 L 0.75   →  3d 9 L  +  4d 5 ). (review)

Zr doping effect with low-cost solid-state reaction method to synthesize submicron Li4Ti5O12 anode material

Science.gov (United States)

Seo, Inseok; Lee, Cheul-Ro; Kim, Jae-Kwang

2017-09-01

To improve the electrochemical properties, fine Zr-doping Li4Ti5O12 anode materials for rechargeable lithium batteries with a uniform particle size distribution were synthesized by a modified solid-state reaction using fine Li2CO3 and TiO2 (anatase) powders as precursors with a Li:Ti molar ratio of 4:5. The use of fine Li2CO3 and TiO2 (anatase) powders as precursors prevented the formation of ZrO2 at 0.1 mol Zr-doping. XRD analysis revealed that the substitution of Zr for Ti leads to the increase of lattice parameters, allowing improved Li diffusion. The discharge capacity retention increased slightly with Zr-doping and the 0.1 mol Zr-doped Li4Ti5O12 electrode achieved 99% retention of discharge capacity.

Comparison of LiVPO4F to Li4Ti5O12 as anode materials for lithium-ion batteries.

Science.gov (United States)

Ma, Rui; Shao, Lianyi; Wu, Kaiqiang; Shui, Miao; Wang, Dongjie; Pan, Jianguo; Long, Nengbing; Ren, Yuanlong; Shu, Jie

2013-09-11

In this paper, we reported on a comparison of LiVPO4F to Li4Ti5O12 as anode materials for lithium-ion batteries. Combined with powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, galvanostatic discharge/charge tests and in situ X-ray diffraction technologies, we explore and compare the insertion/extraction mechanisms of LiVPO4F based on the V3+/V2+/V+ redox couples and Li4Ti5O12 based on the Ti4+/Ti3+ redox couple cycled in 1.0-3.0 V and 0.0-3.0 V. The electrochemical results indicate that both LiVPO4F and Li4Ti5O12 are solid electrolyte interphase free materials in 1.0-3.0 V. The insertion/extraction mechanisms of LiVPO4F and Li4Ti5O12 are similar with each other in 1.0-3.0 V as proved by in situ X-ray diffraction. It also demonstrates that both samples possess stable structure in 0.0-3.0 V. Additionally, the electrochemical performance tests of LiVPO4F and Li4Ti5O12 indicate that both samples cycled in 0.0-3.0 V exhibit much higher capacities than those cycled in 1.0-3.0 V but display worse cycle performance. The rate performance of Li4Ti5O12 far exceeds that of LiVPO4F in the same electrochemical potential window. In particular, the capacity retention of Li4Ti5O12 cycled in 1.0-3.0 V is as high as 98.2% after 20 cycles. By contrast, Li4Ti5O12 is expected to be a candidate anode material considering its high working potential, structural zero-strain property, and excellent cycle stability and rate performance.

Dielectric properties of Zr doped CaCu{sub 3}Ti{sub 4}O{sub 12} synthesized by sol-gel route

Energy Technology Data Exchange (ETDEWEB)

Jesurani, S. [Department of Physics, Jeyaraj Annapackium College for Women, Periyakulam 625 601, Tamil Nadu (India); Center for Material Science and Nano Devices, Department of Physics, SRM University, Kattankulathur 603 203, Tamil Nadu (India); Kanagesan, S., E-mail: kanagu1980@gmail.com [Materials Synthesis and Characterization Laboratory (MSCL), Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hashim, M. [Materials Synthesis and Characterization Laboratory (MSCL), Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Physics Department, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Ismail, I. [Materials Synthesis and Characterization Laboratory (MSCL), Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)

2013-02-25

Highlights: Black-Right-Pointing-Pointer Zr doped CaCu{sub 3}Ti{sub 4}O{sub 12} samples have been synthesized using sol-gel process. Black-Right-Pointing-Pointer The particle size of the powder ranges from 47 to 85 nm. Black-Right-Pointing-Pointer Less sintering at 1040 Degree-Sign C results in high density and high dielectric constant. - Abstract: Zr substituted CaCu{sub 3}Ti{sub 4-x}Zr{sub x}O{sub 12} (CCTZO) with x = 0.00, 0.02, 0.10, 0.20 and 0.50 mol% were prepared by sol-gel route from the metal nitrate solutions, Titanium isoproxide, and zirconium oxy chloride. XRD analysis confirmed the formation of a single phase material in the samples calcinated at 800 Degree-Sign C for 3 h. The crystal structure did not change on doping with zirconium and it remained cubic in all the four studied compositions. The permittivity and dielectric loss of 0.1 mol% Zr doped CaCu{sub 3}Ti{sub 4}O{sub 12} were improved for K Almost-Equal-To 6020 and tan {delta} Almost-Equal-To 0.52 at 1 kHz after the sample had been sintered at 1040 Degree-Sign C for 4 h. AFM studies showed that the particle size of the CCTZO powder ranged from 47 to 85 nm. FE-SEM micrographs of the CaCu{sub 3}Ti{sub 4-x}Zr{sub x}O{sub 12} samples showed that the grain size was in the range of 250 nm to 5 {mu}m for these samples. EDX studies showed the presence of calcium, copper, titanium, oxygen and zirconium. Remarkably, the dielectric constant increased and dielectric loss had lower values compared to the undoped CCTO.

Green synthesis of nanocrystalline α-Al2O3 powders by both wet-chemical and mechanochemical methods

Science.gov (United States)

Gao, Huiying; Li, Zhiyong; Zhao, Peng

2018-03-01

Nanosized α-Al2O3 powders were prepared with AlCl3ṡ6H2O and NH4HCO3 as raw materials by both wet-chemical and mechanochemical methods, through the synthesis of the ammonium aluminum carbonate hydroxide (AACH) precursor followed by calcination. The environmentally benign starch was used as an effective dispersant during the preparation of nanocrystalline α-Al2O3 powders. X-ray diffraction (XRD), thermogravimetric differential thermal analysis (TG-DTA), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to characterize the precursor AACH and products. The results show that nanosized spherical α-Al2O3 powders without hard agglomeration and with particle size in the range of 20-40 nm can be obtained by the two methods. Comparing the two “green” processes, the mechanochemical method has better prospects for commercial production.

Structural evolution of Ba8Ti3Nb4O24 from BaTiO3 using a series of Ba(Ti1−5xNb4x)O3 solid solutions

International Nuclear Information System (INIS)

Barrientos Hernández, F.R.; Lira Hernández, I.A.; Gómez Yáñez, C.; Arenas Flores, A.; Cabrera Sierra, R.; Pérez Labra, M.

2014-01-01

Highlights: • The evolution phase Ba 8 Ti 3 Nb 4 O 24 was obtained through the mechanism Ba(Ti 1-5x Nb 4x )O 3 . • Addition of niobium can accelerate grain growth of BaTiO 3 ceramics. • Ba 8 Ti 3 Nb 4 O 24 presents a dielectric loss of 0.0035 and permittivity value of 54.6. • Electrical measurements showed that Nb 5+ content drops Curie temperature. • Samples with x ⩾ 0.0625 shows an insulating behavior. -- Abstract: In this work, the structural evolution of hexagonal phase Ba 8 Ti 3 Nb 4 O 24 by adding Nb 2 O 5 to perovskite structure of BaTiO 3 was investigated. The compositions Ba(Ti 1-5x Nb 4x )O 3 ceramics, with 0.00025 ⩽ x ⩽ 0.125 were prepared by the conventional solid state route in air atmosphere, the powders precursors, BaTiO 3 , BaCO 3 and Nb 2 O 5 , were mixed in stoichiometric proportions and ground in a ball mill using alumina balls and acetone. The mixed powders were calcined at temperatures up to 1500 °C. The phase transformation of Ba 8 Ti 3 Nb 4 O 24 from BaTiO 3 was studied by DRX, Raman spectroscopy, SEM, electrical measurements (relative permittivity and P–E hysteresis loops); Rietveld’s refinement was used to structurally characterize the samples. For the devices obtained capacitance was measured at 1 kHz; with these values we calculated the relative permittivity. The samples show typical P–E hysteresis loops at room temperature accompanied by saturation polarization (Ps) and remnant polarization (Pr). The DRX and Rietveld’s refinement results show x ⩽ 0.01 has a ferroelectric behavior. When the doped level is increased x ⩾ 0.02, a peak displacement is observed, this is due to the phase transformation of tetragonal to cubic into the unit cell. Finally, with x = 0.125 the crystal structure transforms to the characteristic hexagonal phase Ba 8 Ti 3 Nb 4 O 24 which resonates at microwave frequencies

Solid State Formation Mechanism of Li₄Ti₅O₁₂ from an Anatase TiO₂ Source

DEFF Research Database (Denmark)

Shen, Yanbin; Søndergaard, Martin; Christensen, Mogens

2014-01-01

Solid state synthesis of Li4Ti5O12 anode material for Li ion batteries typically results in products containing rutile TiO2 and Li2TiO3 impurities, and subsequent high calcination temperatures lead to particle growth that reduces capacity and rate ability. Here, the formation and growth of Li4Ti5O......12 particles by a solid-state reaction using anatase TiO2 with various crystallite sizes and Li2CO3 is investigated by in situ high temperature powder X-ray diffraction (HT-PXRD) and thermal gravimetry-differential thermal analysis (TG-DTA). The combined data provide insight into the origin...... crystallite sizes (∼50 nm, ∼30 nm, ∼20 nm, and amorphous) were explored, and decreasing crystallite sizes causes a reduced initial reaction temperature. Using anatase with a crystallite size of ∼20 nm resulted in phase pure Li4Ti5O12 at the lowest temperature (800 °C). PXRD and TG-DTA results also revealed...

Photocatalytic properties of nanocrystalline TiO2 thin film with Ag additions

International Nuclear Information System (INIS)

Chang, C.-C.; Lin, C.-K.; Chan, C.-C.; Hsu, C.-S.; Chen, C.-Y.

2006-01-01

In the present study, nanocrystalline TiO 2 /Ag composite thin films were prepared by a sol-gel spin coating technique. While, by introducing polystyrene (PS) microspheres, porous TiO 2 /Ag films were obtained after calcining at a temperature of 500 o C. The as-prepared TiO 2 and TiO 2 /Ag thin films were characterized by X-ray diffractometry, and scanning electron microscopy to reveal the structural and morphological differences. In addition, the photocatalytic properties of these films were investigated by degrading methylene blue under UV irradiation. After 500 o C calcination, the microstructure of PS-TiO 2 film without Ag addition exhibited a sponge-like microstructure while significant sintering effect was noticed with Ag additions and the films exhibited a porous microstructure. Meanwhile, coalescence of nanocrystalline anatase-phase TiO 2 can be observed with respect to the sharpening of XRD diffraction peaks. The photodegradation of porous TiO 2 doped with 1 mol% Ag exhibited the best photocatalytic efficiency where 72% methylene blue can be decomposed after UV exposure for 12 h

Rapid rate sintering of nanocrystalline ZrO2-3 mol% Y2O3

International Nuclear Information System (INIS)

Chen, D.J.; Mayo, M.J.

1996-01-01

Conventional ramp-and-hold sintering with a wide range of heating rates was conducted on submicrometer and nanocrystalline ZrO 2 -3 mol% Y 2 O 3 powder compacts. Although rapid heating rates have been reported to produce high density/fine grain size products for many submicrometer and smaller starting powders, the application of this technique to ZrO 2 -3 mol% Y 2 O 3 produced mixed results. In the case of submicrometer ZrO 2 -3 mol% Y 2 O 3 , neither densification nor grain growth was affected by the heating rate used. In the case of nanocrystalline ZrO 2 -3 mol% Y 2 O 3 , fast heating rates severely retarded densification and had a minimal effect on grain growth. The large adverse effect of fast heating rates on the densification of the nanocrystalline powder was traced to a thermal gradient/differential densification effect. Microstructural evidence suggests that the rate of densification greatly exceeded the rate of heat transfer in this material; consequently, the sample interior was not able to densify before being geometrically constrained by a fully dense shell which formed at the sample exterior. This finding implies that rapid rate sintering will meet severe practical constraints in the manufacture of bulk nanocrystalline ZrO 2 -3 mol% Y 2 O 3 specimens

Nanocrystalline spinel ferrite (MFe2O4, M = Ni, Co, Mn, Mg, Zn) powders prepared by a simple aloe vera plant-extracted solution hydrothermal route

International Nuclear Information System (INIS)

Phumying, Santi; Labuayai, Sarawuth; Swatsitang, Ekaphan; Amornkitbamrung, Vittaya; Maensiri, Santi

2013-01-01

Graphical abstract: This figure shows the specific magnetization curves of the as-prepared MFe 2 O 4 (M = Ni, Co, Mn, Mg, Zn) powders obtained from room temperature VSM measurement. These curves are typical for a soft magnetic material and indicate hysteresis ferromagnetism in the field ranges of ±500 Oe, ±1000 Oe, and ±2000 Oe for the CoFe 2 O 4 , MgFe 2 O 4 and MnFe 2 O 4 respectively, whereas the samples of NiFe 2 O 4 and ZnFe 2 O 4 show a superparamagnetic behavior. Highlights: ► Nanocrystalline MFe 2 O 4 powders were synthesized by a novel hydrothermal method. ► Metal acetylacetonates and aloe vera plant-extracted solution are used. ► This biosynthetic route is very simple and provides high-yield oxide nanomaterials. ► XRD and TEM results indicate that the prepared samples have only spinel structure. ► The maximum M s of 68.9 emu/g at 10 kOe were observed for the samples of MnFe 2 O 4 . - Abstract: Nanocrystalline spinel ferrite MFe 2 O 4 (M = Ni, Co, Mn, Mg, Zn) powders were synthesized by a novel hydrothermal method using Fe(acac) 3 , M(acac) 3 (M = Ni, Co, Mn, Mg, Zn) and aloe vera plant extracted solution. The X-ray diffraction and selected-area electron diffraction results indicate that the synthesized nanocrystalline have only spinel structure without the presence of other phase impurities. The crystal structure and morphology of the spinel ferrite powders, as revealed by TEM, show that the NiFe 2 O 4 and CoFe 2 O 4 samples contain nanoparticles, whereas the MnFe 2 O 4 and MgFe 2 O 4 samples consist of many nanoplatelets and nanoparticles. Interestingly, the ZnFe 2 O 4 sample contains plate-like structure of networked nanocrystalline particles. Room temperature magnetization results show a ferromagnetic behavior of the CoFe 2 O 4 , MnFe 2 O 4 and MgFe 2 O 4 samples, whereas the samples of NiFe 2 O 4 and ZnFe 2 O 4 exhibit a superparamagnetic behavior

Synthesis, Characterization and Sonocatalytic Activity of Co/N/Er3+ : Y3Al5O12 /TiO2 Film for the Degradation of Organic Dyes

Directory of Open Access Journals (Sweden)

Wang L.

2015-07-01

Full Text Available The sonocatalytic degradation of organic dyes (C.I. 50040, C.I. Reactive Red 1, C.I. Acid Orange 7 catalysed by Co/N/Er3+ : Y3Al5O12/TiO2 films was studied. For the preparation of Co/N/Er3+ : Y3Al5O12/TiO2 films, the sol-gel coating process was used. The phase composition, morphology, precursor at different temperatures and emitting light properties of the calcined powders were analysed by X-ray diffraction (XRD, absorption spectra and upconversion emission spectra. The X-ray diffraction of powder samples of Co/N/Er3+ : Y3Al5O12/TiO2 took on anatase mine peaks and upconversion luminous agent, respectively. Analysis of absorption spectra of amorphous Co/N/Er3+ : Y3Al5O12/TiO2 showed that doping N stretching vibration peak of water or hydroxyl adsorption, Co2+ ion had very strong absorption in 1.0–1.7 μm wavelength range, the transition luminescence of Er3+ ions was just on Co2+ ions absorption band. The emission spectrum indicated that Co/N/Er3+ : Y3Al5O12/TiO2 could launch green 500–560 nm and red 650–700 nm, 525, 550 and 660 nm peaks corresponding to 2H11/2, 4S3/2 → 4I15/2 and 4H9/2 → 4I15/2 transition of Er3+. Doping Co and N enhanced the upconversion luminescence and absorption effect. Sonocatalytic degradation effect of organic dyes loading Co/N/Er3+ : Y3Al5O12/TiO2 was better when ultrasonic intensity was equal to 15 W cm–2. The degradation ratios of aqueous solutions of these three kinds of organic dyes by ultrasonic irradiation were obviously lower than by ultrasonic irradiation together with Co/N/Er3+ : Y3Al5O12/TiO2 films in the same conditions. Degradation kinetics of organic dyes by ultrasonic irradiation and by ultrasonic irradiation cooperating with Co/N/Er3+ : Y3Al5O12/TiO2 films followed the first-order reaction.

A simple dissolved metals mixing method to produce high-purity MgTiO3 nanocrystals

International Nuclear Information System (INIS)

Pratapa, Suminar; Baqiya, Malik A.; Istianah,; Lestari, Rina; Angela, Riyan

2014-01-01

A simple dissolved metals mixing method has been effectively used to produce high-purity MgTiO 3 (MT) nanocrystals. The method involves the mixing of independently dissolved magnesium and titanium metal powders in hydrochloric acid followed by calcination. The phase purity and nanocrystallinity were determined by making use of laboratory x-ray diffraction data, to which Rietveld-based analyses were performed. Results showed that the method yielded only one type magnesium titanate powders, i.e. MgTiO 3 , with no Mg 2 TiO 4 or MgTi 2 O 5 phases. The presence of residual rutile or periclase was controlled by adding excessive Mg up to 5% (mol) in the stoichiometric mixing. The method also resulted in MT nanocrystals with estimated average crystallite size of 76±2 nm after calcination at 600°C and 150±4 nm (at 800°C). A transmission electron micrograph confirmed the formation of the nanocrystallites

NiTiO3 powders obtained by polymeric precursor method: Synthesis and characterization

International Nuclear Information System (INIS)

Lopes, K.P.; Cavalcante, L.S.; Simoes, A.Z.; Varela, J.A.; Longo, E.; Leite, E.R.

2009-01-01

Nickel titanate (NiTiO 3 ) powders were synthesized by the polymeric precursor method after thermal treatment at different temperatures for 2 h in air atmosphere. The decomposition of the precursors was monitored by differential scanning calorimetry and thermogravimetric analysis. The NiTiO 3 powders presented a reduction in the specific surface area and increase of the average particle size with the evolution of the temperature. The structural evolution of NiTiO 3 phase was accompanied by X-ray diffraction and Fourier transform Raman spectroscopy. By scanning electron microscopy was revealed the agglomerated nature of very fine particles of NiTiO 3 powders annealed from 600 to 1000 deg. C

Ag doped (Bi1.6Pb0.4Sr2CaCu2O8+δ textured rods

Directory of Open Access Journals (Sweden)

Díez, J. C.

2008-06-01

Full Text Available In this work, superconducting samples of (Bi1.6Pb0.4Sr2CaCu2O8+δ with Ag additions have been studied. (Bi1.6Pb0.4Sr2CaCu2O8+δ + x wt.% Ag (with x = 0, 1 and 3 powders were synthesized using a sol-gel method. The obtained powders were used as precursors to fabricate long textured cylindrical bars through a floating zone melting method. A drastic change on the microstructure has been found when comparing with undoped Bi2Sr2CaCu2O8+δ samples. The results showed that electrical resistivity at room temperature, critical current as well as flexural strength are improved when Ag is added to these Pb doped samples, while critical temperature does not change. On the other hand, it has been found that samples with composition (Bi1.6Pb0.4Sr2CaCu2O8+δ + Ag shown E-I curves with very high sharpness values on the zone of the superconducting to normal transition, reaching n-values (E∼In as high as 45 at 65K.Se han preparado polvos cerámicos de composición (Bi1.6Pb0.4Sr2CaCu2O8+δ + x % Ag en peso (con x = 0, 1 y 3 mediante un proceso sol-gel. Estos polvos se han utilizado para fabricar precursores que se texturaron por medio del método de fusión zonal flotante. Se ha encontrado un gran cambio en la microestructura cuando se compara con muestras de composición pura Bi2Sr2CaCu2O8+δ. Tanto la resistividad eléctrica a temperatura ambiente, como la corriente crítica, así como la resistencia a flexión se mejoran cuando la Ag se adiciona a estas muestras dopadas con Pb, mientras que no se observa cambio en la temperatura crítica. Por otra parte, se ha encontrado que las muestras de composición (Bi1.6Pb0.4Sr2CaCu2O8+δ + Ag presentan una gran pendiente de la curva E-I en la zona de transición entre el estado superconductor y el estado normal. Con estas composiciones, se han encontrado valores de n (E∼In de hasta 45 a 65K.

Nanocrystalline AL2 O2 powders produced by laser induced gas phase reactions

International Nuclear Information System (INIS)

Borsella, E.; Botti, S.; Martelli, S.; Zappa, G.; Giorgi, R.; Turt, S.

1993-01-01

Nanocrystalline Al 2 O 3 powders were successfully synthesized by a CO 2 laser-driven gas-phase reaction involving trimethylaluminium (Al(CH 3 ) 3 ) and nitrous-oxide (N 2 O). Ethylene (C 2 H 4 ) was added as gas sensitizer. The as-synthesized powder particles showed a considerable carbon contamination and an amorphous-like structure. After thermal treatment at 1200-1400 degrees C, the powder was transformed to hexagonal a-Al 2 O 3 with very low carbon contamination as confirmed by X-ray diffraction, X-ray photo-electron spectroscopy and chemical analysis. The calcinated powders resulted to be spherical single crystal nanoparticles with a mean size of 15-20 nm, as determined by X-ray diffraction, electron microscopy and B.E.T. specific surface measurements. The laser synthesized Al 2 O 3 particles are well suited dispersoids for intermetallic alloy technology

Photocatalytic removal of NO and HCHO over nanocrystalline Zn2SnO4 microcubes for indoor air purification

International Nuclear Information System (INIS)

Ai Zhihui; Lee Shuncheng; Huang Yu; Ho Wingkei; Zhang Lizhi

2010-01-01

Nanocrystalline Zn 2 SnO 4 microcubes were hydrothermally synthesized and systematically characterized by XRD, SEM, TEM, XPS, N 2 adsorption-desorption, and UV-vis DRS analysis. The resulting Zn 2 SnO 4 microcubes with the edge size ranging from 0.8 to 1.2 μm were composed of numerous nanoparticles with size of 10-20 nm, and their optical band gap energy was estimated to be 3.25 eV from the UV-vis diffuse reflectance spectra. On degradation of nitrogen monoxide (NO) and formaldehyde (HCHO) at typical concentrations for indoor air quality, these nanocrystalline Zn 2 SnO 4 microcubes exhibited superior photocatalytic activity to the hydrothermally synthesized ZnO, SnO 2 , and Degussa TiO 2 P25, as well as C doped TiO 2 under UV-vis light irradiation. This enhanced photocatalytic activity of the nanocrystalline Zn 2 SnO 4 microcubes was attributed to their bigger surface areas, smaller particle size, special porous structures, and special electronic configuration. The nanocrystalline Zn 2 SnO 4 microcubes were chemically stable as there was no obvious deactivation during the multiple photocatalytic reactions. This work presents a promising approach for scaling-up industrial production of Zn 2 SnO 4 nanostructures and suggests that the synthesized nanocrystalline Zn 2 SnO 4 microcubes are promising photocatalysts for indoor air purification.

Apparent vanishing of ferroelectricity in nanostructured BiScO3PbTiO3

OpenAIRE

Amorín , H; Jiménez , R; Ricote , J; Hungría , T; Castro , A; Algueró , M

2010-01-01

Abstract Nanostructured ceramics of high-temperature piezoelectric 0.375BiScO 3 -0.625PbTiO 3 were prepared by spark plasma sintering of nanocrystalline powders obtained by mechanosynthesis. The macroscopic electrical properties were characterized on dense ceramics with decreasing average grain size down to 28 nm. Results indicate that the electric field is screened by the electrically insulating grain boundaries at the nanoscale, which needs to be considered when discussing size effects i...

Enhanced ferro-and piezoelectric properties of Bi4Ti3O12-CaBi4Ti4O15 thin film on Pt(111)/Ti/SiO2/Si substrate

Science.gov (United States)

Yan, J.; Hu, G. D.

2018-05-01

Bi4Ti3O12-CaBi4Ti4O15 (BT-CBTi) film was fabricated on Pt(111)/Ti/SiO2/Si substrate by the sol-gel method. The intergrowth structure was demonstrated to be obtained both in the film and corresponding powder sample according to x-ray diffraction (XRD) patterns. The good fatigue resistance as well as a strong charge-retaining ability can be obtained in the intergrowth BT-CBTi film. The remanent polarization (P r ) and coercive field (E c ) for BT-CBTi film was about 28 μC cm‑2 and 150 kV cm‑1 under an electric field of 540 kV cm‑1, respectively. The P r value of purely (100)-oriented BT-CBTi film can be roughly estimated to be higher than 50 μC cm‑2 based on both the volume fraction of (100)-oriented grains and the piezoelectric properties. The P r value of BT-CBTi film is about 50 μC cm‑2 under an electric field of 1100 kV cm‑1 in predominently (100)-oriented BT-CBTi film. It means that it is reasonable to predict the performance of (100)-oriented BT-CBTi films based on the ferroelectric and piezoelectric properties of the polycrystalline BT-CBTi film. The spontaneous polarization is larger than 80 μC cm‑2 under an electric field of 1100 kV cm‑1.

Photocatalytic behaviors and structural characterization of nanocrystalline Fe-doped TiO2 synthesized by mechanical alloying

International Nuclear Information System (INIS)

Kim, Dong Hyun; Hong, Hyun Seon; Kim, Sun Jae; Song, Jae Sung; Lee, Kyung Sub

2004-01-01

Nanocrystalline Fe-doped TiO 2 powders were synthesized by mechanical alloying (MA) with varying Fe contents from 0 up to 4.8 wt.% to shift the absorption threshold into the visible light region. The photocatalytic feasibility of the Fe-doped TiO 2 powder was evaluated by quantifying the visible light absorption capacity using ultraviolet and visible (UV-Vis) spectroscopy and photoluminescence spectroscopy. Effects of Fe additions on the crystal structures and the morphologies of the Fe-doped powders were also investigated as a function of the doping content using transmission electron microscopy-electron diffraction pattern (TEM-EDP), X-ray diffraction (XRD) and energy dispersive X-ray (EDAX) and X-ray photoelectron spectroscopy (XPS). The UV-Vis study showed that the UV absorption for the Fe-doped powder moved to a longer wavelength (red shift) and the photoefficiency was enhanced. Based on the analysis of the photoluminescence spectra, the red shift was believed to be induced by localizing the dopant level near the valence band of TiO 2 . The UV-Vis absorption depended on the Fe concentration. TEM-EDP and XRD investigations showed that the Fe-doped powder had a rutile phase in which the added Fe atoms were dissolved. The rutile phase was composed of spherical particles and chestnut bur shaped particles, resulting in a larger surface area than the spherical P-25 powder

Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

Science.gov (United States)

Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

2017-02-01

TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.

Amorphous and nanocrystalline titanium nitride and carbonitride materials obtained by solution phase ammonolysis of Ti(NMe2)4

International Nuclear Information System (INIS)

Jackson, Andrew W.; Shebanova, Olga; Hector, Andrew L.; McMillan, Paul F.

2006-01-01

Solution phase reactions between tetrakisdimethylamidotitanium (Ti(NMe 2 ) 4 ) and ammonia yield precipitates with composition TiC 0.5 N 1.1 H 2.3 . Thermogravimetric analysis (TGA) indicates that decomposition of these precursor materials proceeds in two steps to yield rocksalt-structured TiN or Ti(C,N), depending upon the gas atmosphere. Heating to above 700 deg. C in NH 3 yields nearly stoichiometric TiN. However, heating in N 2 atmosphere leads to isostructural carbonitrides, approximately TiC 0.2 N 0.8 in composition. The particle sizes of these materials range between 4-12 nm. Heating to a temperature that corresponds to the intermediate plateau in the TGA curve (450 deg. C) results in a black powder that is X-ray amorphous and is electrically conducting. The bulk chemical composition of this material is found to be TiC 0.22 N 1.01 H 0.07 , or Ti 3 (C 0.17 N 0.78 H 0.05 ) 3.96 , close to Ti 3 (C,N) 4 . Previous workers have suggested that the intermediate compound was an amorphous form of Ti 3 N 4 . TEM investigation of the material indicates the presence of nanocrystalline regions x (C,N) y crystalline phases

Crystal structures of lazulite-type oxidephosphates TiIIITiIV3O3(PO4)3 and MIII4TiIV27O24(PO4)24 (MIII=Ti, Cr, Fe)

International Nuclear Information System (INIS)

Schoeneborn, M.; Glaum, R.; Reinauer, F.

2008-01-01

Single crystals of the oxidephosphates Ti III Ti IV 3 O 3 (PO 4 ) 3 (black), Cr III 4 Ti IV 27 O 24 (PO 4 ) 24 (red-brown, transparent), and Fe III 4 Ti IV 27 O 24 (PO 4 ) 24 (brown) with edge-lengths up to 0.3 mm were grown by chemical vapour transport. The crystal structures of these orthorhombic members (space group F2dd ) of the lazulite/lipscombite structure family were refined from single-crystal data [Ti III Ti IV 3 O 3 (PO 4 ) 3 : Z=24, a=7.3261(9) A, b=22.166(5) A, c=39.239(8) A, R 1 =0.029, wR 2 =0.084, 6055 independent reflections, 301 variables; Cr III 4 Ti IV 27 O 24 (PO 4 ) 24 : Z=1, a=7.419(3) A, b=21.640(5) A, c=13.057(4) A, R 1 =0.037, wR 2 =0.097, 1524 independent reflections, 111 variables; Fe III 4 Ti IV 27 O 24 (PO 4 ) 24 : Z=1, a=7.4001(9) A, b=21.7503(2) A, c=12.775(3) A, R 1 =0.049, wR 2 =0.140, 1240 independent reflections, 112 variables). For Ti III Ti IV O 3 (PO 4 ) 3 a well-ordered structure built from dimers [Ti III,IV 2 O 9 ] and [Ti IV,IV 2 O 9 ] and phosphate tetrahedra is found. The metal sites in the crystal structures of Cr 4 Ti 27 O 24 (PO 4 ) 24 and Fe 4 Ti 27 O 24 (PO 4 ) 24 , consisting of dimers [M III Ti IV O 9 ] and [Ti IV,IV 2 O 9 ], monomeric [Ti IV O 6 ] octahedra, and phosphate tetrahedra, are heavily disordered. Site disorder, leading to partial occupancy of all octahedral voids of the parent lipscombite/lazulite structure, as well as splitting of the metal positions is observed. According to Guinier photographs Ti III 4 Ti IV 27 O 24 (PO 4 ) 24 (a=7.418(2) A, b=21.933(6) A, c=12.948(7) A) is isotypic to the oxidephosphates M III 4 Ti IV 27 O 24 (PO 4 ) 24 (M III : Cr, Fe). The UV/vis spectrum of Cr 4 Ti 27 O 24 (PO 4 ) 24 reveals a rather small ligand-field splitting Δ o =14,370 cm -1 and a very low nephelauxetic ratio β=0.72 for the chromophores [Cr III O 6 ] within the dimers [Cr III Ti IV O 9 ]. - Graphical abstract: Single crystals of the oxidephosphates Ti III Ti IV 3 O 3 (PO 4 ) 3 (black), Cr III 4 Ti IV 27 O

In-Flight Formation of Nano-Crystalline Titanium Dioxide Powder in a Plasma Jet and Its Characterization

International Nuclear Information System (INIS)

Ananthapadmanabhan, P. V.; Thiyagarajan, T. K.; Sreekumar, K. P.; Vijay, M.; Selvarajan, V.; Yu, Jiaguo; Liu, Shengwei

2010-01-01

Nanocrystalline titanium dioxide powder was synthesized by in-flight oxidation of titanium dihydride (TiH 2 ) powder in a thermal plasma jet. TiH 2 powder was injected into the thermal plasma jet and allowed to react with oxygen injected downstream the jet. Characterization of the powder by various analytical tools indicated that the powder consisted of nano-sized titanium dioxide particles consisting predominantly of the anatase phase. It is suggested that the thermo-chemistry of the oxidation process contributes significantly to the formation of nano-sized titania. The large energy released during the oxidation process dissociates the TiO 2 particles into TiO (g) and titanium vapour, which recombine downstream with oxygen and form nano particles of TiO 2 .

Preparation of cauliflower-like shaped Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} powders by modified oxalate co-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Li Mingli [School of Materials Science and Engineering, Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072 (China)], E-mail: lml@tju.edu.cn; Xu Mingxia [School of Materials Science and Engineering, Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072 (China)

2009-04-17

The quantitative barium-strontium titanyl oxalate (Ba{sub 0.6}Sr{sub 0.4}TiO(C{sub 2}O{sub 4}){sub 2}.4H{sub 2}O, BSTO) precursor powders were prepared by the modified oxalate co-preparation method. It was based on the cation-exchange reaction between the stoichiometric solutions of oxalotitanic acid (H{sub 2}TiO(C{sub 2}O{sub 4}){sub 2}, HTO) and barium + strontium nitrate solution containing stoichiometric quantities of Ba and Sr ions. The pyrolysis of BSTO at 800 deg. C/4 h in air produced the homogeneous cauliflower-like shaped barium-strontium titanate (Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}, BST) powders. The effect of polyethylene glycol (PEG) on morphology of BSTO and BST powders was also investigated. The characterization studies were carried on the as-dried BSTO and calcined BST powders by various physicochemical techniques, IR, X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The BSTO and BST powders obtained by aforementioned technique without PEG were homogeneous with spherical shape. The particles grew into spindle shape with the effect of PEG.

Structure determinations for Ca3Ti2O7, Ca4Ti3O10, Ca3.6Sr0.4Ti3O10 and a refinement of Sr3Ti2O7

International Nuclear Information System (INIS)

Elcombe, M.M.; Kisi, E.H.; Hawkins, K.D.; White, T.J.; Goodman, P.; Matheson, S.

1991-01-01

The structures of the orthorhombic Ruddlesden-Popper (A n+1 B n X 3n+1 ) phases Ca 3 Ti 2 O 7 (n=2) refined from neutron powder diffraction data at λ=1.893 A. They consist of coherent intergrowths of perovskite (CaTiO 3 ) blocks, n TiO 6 octahedra thick, with single layers of CaO having a distorted NaCl configuration. TiO 6 octahedra are tilted and distorted in a very similar fashion to those in CaTiO 3 (n=∞). This fact was used to determine the space groups of the layered structures. Convergent-beam electron diffraction patterns are best matched by calculations in the above space groups which are thus confirmed. Octahedral tilt angles increase slightly in the sequence n=2, 3, ∞. Strontium addition reduces the octahedral tilt angles because of preferential substitution of Sr on the Ca sites within the perovskite blocks of Ca 4 Ti 3 O 10 . The algorithm used to produce starting models for structure refinements is thought to be generally applicable to Ruddlesden-Popper and possibly other layered perovskite structures. It furnishes the predictions: (a) all n-even compounds in the Ca n+1 Ti n O 3n+1 series will have space group Ccm2 1 , (b) all n-odd compounds in this series will have space group Pcab, (c) all A n+1 B n X 3n+1 series for which the n=∞ end member (ABX 3 ) is isostructural with CaTiO 3 will be isostructural with the compounds reported above (e.g. Ca n+1 Zr n O 3n+1 ). (orig./WL)

Deposition of Li{sub 4}Ti{sub 5}O{sub 12} and LiMn{sub 2}O{sub 4} films on the lithium-ion conductor of Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet

Energy Technology Data Exchange (ETDEWEB)

Wu, Xian Ming, E-mail: xianmingwu@163.com [College of Chemistry and Chemical Engineering, Jishou University, Jishou Hunan 416000 (China); Xiangxi Minerals and New Materials Research and Service Center, Jishou Hunan 416000 (China); Chen, Shang [College of Chemistry and Chemical Engineering, Jishou University, Jishou Hunan 416000 (China); Xiangxi Minerals and New Materials Research and Service Center, Jishou Hunan 416000 (China); He, Ze Qiang; Chen, Shou Bin; Li, Run Xiu [College of Chemistry and Chemical Engineering, Jishou University, Jishou Hunan 416000 (China)

2015-08-31

LiMn{sub 2}O{sub 4} and Li{sub 4}Ti{sub 5}O{sub 12} films were deposited on the lithium-ion conductor of Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet by spray technique. The effect of annealing temperature, annealing time, Li:Ti and Li:Mn molar ratio on the phase and crystallization of the films were investigated with X-ray diffraction. The LiMn{sub 2}O{sub 4}/Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3}/Li{sub 4}Ti{sub 5}O{sub 12} thin-film lithium-ion battery using Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet as both electrolyte and substrate was also studied. The results show that the effect of annealing temperature, annealing time, Li:Ti and Li:Mn molar ratio has great effect on the phase and crystallization of Li{sub 4}Ti{sub 5}O{sub 12} and LiMn{sub 2}O{sub 4} films deposited on the Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet. The optimal Li:Ti and Li:Mn molar ratio for the deposition of Li{sub 4}Ti{sub 5}O{sub 12} and LiMn{sub 2}O{sub 4} films on Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet are 7.2:5 and 1.05:2, respectively. The optimal annealing temperature and time for the deposition of LiMn{sub 2}O{sub 4} film on Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet are 650 °C and 10 min. While those for Li{sub 4}Ti{sub 5}O{sub 12} film are 700 °C and 10 min. The LiMn{sub 2}O{sub 4}/Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3}/Li{sub 4}Ti{sub 5}O{sub 12} thin-film battery offers a working voltage about 2.25 V and can be easily cycled. - Highlights: • LiMn{sub 2}O{sub 4} and Li{sub 4}Ti{sub 5}O{sub 12} films spray deposited on Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet • Film crystal phase depends on the spray solution composition and annealing conditions. • Prepared thin-film lithium-ion battery employs sintered pellet as electrolyte and substrate. • LiMn{sub 2}O{sub 4}/Li{sub 1.3}Al{sub 0.3}Ti{sub 1

Adsorption-controlled growth of ferroelectric PbTiO{sub 3} and Bi{sub 4}Ti{sub 3}O{sub 12} films for nonvolatile memory applications by MBE

Energy Technology Data Exchange (ETDEWEB)

Theis, C.D.; Yeh, J.; Schlom, D.G. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering; Hawley, M.E.; Brown, G.W. [Los Alamos National Lab., NM (United States). Center for Materials Science

1997-09-01

Epitaxial PbTiO{sub 3} and Bi{sub 4}Ti{sub 3}O{sub 12} thin films have been grown on (100) SrTiO{sub 3} and (100) LaAlO{sub 3} substrates by reactive molecular beam epitaxy (MBE). Titanium is supplied to the film in the form of shuttered bursts each containing a one monolayer dose of titanium atoms for the growth of PbTiO{sub 3} and three monolayers for the growth of Bi{sub 4}Ti{sub 3}O{sub 12}. Lead, bismuth, and ozone are continuously supplied to the surface of the depositing film. Growth of phase pure, c-axis oriented epitaxial films with bulk lattice constants is achieved using an overpressure of these volatile species. With the proper choice of substrate temperature (600--650 C) and ozone background pressure (P{sub O{sub 3}} = 2 {times} 10{sup {minus}5} Torr), the excess of the volatile metals and ozone desorb from the surface of the depositing film leaving a phase-pure stoichiometric crystal. The smooth PbTiO{sub 3} surface morphology revealed by atomic force microscopy (AFM) suggests that the PbTiO{sub 3} films grow in a layer-by-layer fashion. In contrast the Bi{sub 4}Ti{sub 3}O{sub 12} films contain islands which evolve either continuously or around screw dislocations via a spiral-type growth mechanism.

Effect of freeze-drying and self-ignition process on the microstructural and electrochemical properties of Li{sub 4}Ti{sub 5}O{sub 12}

Energy Technology Data Exchange (ETDEWEB)

Jamin, Claire [GREEnMat/LCIS, Department of Chemistry, B6a, University of Liège, Sart-Tilman, 4000 Liège (Belgium); Traina, Karl [GREEnMat/LCIS, Department of Chemistry, B6a, University of Liège, Sart-Tilman, 4000 Liège (Belgium); APTIS, Department of Physics, B5a, University of Liège, Sart-Tilman, 4000 Liège (Belgium); Eskenazi, David [Chemical Engineering Laboratory, Department of Applied Chemistry, B6a, University of Liège, Sart-Tilman, 4000 Liège (Belgium); Krins, Natacha; Cloots, Rudi; Vertruyen, Bénédicte [GREEnMat/LCIS, Department of Chemistry, B6a, University of Liège, Sart-Tilman, 4000 Liège (Belgium); Boschini, Frédéric, E-mail: frederic.boschini@ulg.ac.be [GREEnMat/LCIS, Department of Chemistry, B6a, University of Liège, Sart-Tilman, 4000 Liège (Belgium); APTIS, Department of Physics, B5a, University of Liège, Sart-Tilman, 4000 Liège (Belgium)

2013-11-15

Graphical abstract: - Highlights: • Li{sub 4}Ti{sub 5}O{sub 12} is prepared by a method involving self-ignition of a freeze-dried gel. • Addition of NH{sub 4}NO{sub 3} modifies the self-ignition propagation mode. • Well-crystallized Li{sub 4}Ti{sub 5}O{sub 12} phase is obtained after only 2 h at 800 °C. • Li{sub 4}Ti{sub 5}O{sub 12} powder has 161 mAh g{sup −1} capacity and good retention at C/4 rate. - Abstract: Crystalline Li{sub 4}Ti{sub 5}O{sub 12} is synthesized by a method involving the freeze-drying and self-ignition of a gel prepared from titanium isopropoxide, lithium nitrate and hydroxypropylmethylcellulose (HPMC). This synthesis route yields crystalline Li{sub 4}Ti{sub 5}O{sub 12} particles after calcination at 800 °C for 2 h. In an alternative route, addition of ammonium nitrate shifts the self-ignition mode from wave-like propagation to simultaneous. Powders with different microstructures are thereby obtained. Electrochemical characterization shows that the best results for Li{sup +} intercalation/desintercalation are obtained for the powder prepared without ammonium nitrate addition. These results highlight the necessity for a control of the self-ignition mode to obtain adequate properties.

Microstructural, Raman and XPS properties of single-crystalline Bi3.15Nd0.85Ti3O12 nanorods

International Nuclear Information System (INIS)

Hu Zhenglong; Gu Haoshuang; Hu Yongming; Zou Yanan; Zhou Di

2009-01-01

Bi 3.15 Nd 0.85 Ti 3 O 12 (BNT) nanorods were successfully synthesized first time by hydrothermal method. The nanorods are uniform along their length, and are composed of single-crystalline BNT with orthorhombic structure. The diameters of BNT nanorods are about 30-120 nm and growth along the [1 0 4] direction, which are promising candidate for nanoscale ferroelectric sensors. Ten Raman active modes were observed for orthorhombic phase BNT nanorods, which are overdamped and highly shifted compare to that of Bi 4 Ti 3 O 12 (BIT) powders. The chemical composition of the samples and the valence states of elements were determined by X-ray photoelectron spectroscopy

Nanocrystalline spinel ferrite (MFe{sub 2}O{sub 4}, M = Ni, Co, Mn, Mg, Zn) powders prepared by a simple aloe vera plant-extracted solution hydrothermal route

Energy Technology Data Exchange (ETDEWEB)

Phumying, Santi; Labuayai, Sarawuth; Swatsitang, Ekaphan; Amornkitbamrung, Vittaya [Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Integrated Nanotechnology Research Center (INRC), Khon Kaen University, Khon Kaen 40002 (Thailand); Maensiri, Santi, E-mail: santimaensiri@gmail.com [School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand)

2013-06-01

Graphical abstract: This figure shows the specific magnetization curves of the as-prepared MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders obtained from room temperature VSM measurement. These curves are typical for a soft magnetic material and indicate hysteresis ferromagnetism in the field ranges of ±500 Oe, ±1000 Oe, and ±2000 Oe for the CoFe{sub 2}O{sub 4}, MgFe{sub 2}O{sub 4} and MnFe{sub 2}O{sub 4} respectively, whereas the samples of NiFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} show a superparamagnetic behavior. Highlights: ► Nanocrystalline MFe{sub 2}O{sub 4} powders were synthesized by a novel hydrothermal method. ► Metal acetylacetonates and aloe vera plant-extracted solution are used. ► This biosynthetic route is very simple and provides high-yield oxide nanomaterials. ► XRD and TEM results indicate that the prepared samples have only spinel structure. ► The maximum M{sub s} of 68.9 emu/g at 10 kOe were observed for the samples of MnFe{sub 2}O{sub 4}. - Abstract: Nanocrystalline spinel ferrite MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders were synthesized by a novel hydrothermal method using Fe(acac){sub 3}, M(acac){sub 3} (M = Ni, Co, Mn, Mg, Zn) and aloe vera plant extracted solution. The X-ray diffraction and selected-area electron diffraction results indicate that the synthesized nanocrystalline have only spinel structure without the presence of other phase impurities. The crystal structure and morphology of the spinel ferrite powders, as revealed by TEM, show that the NiFe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} samples contain nanoparticles, whereas the MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples consist of many nanoplatelets and nanoparticles. Interestingly, the ZnFe{sub 2}O{sub 4} sample contains plate-like structure of networked nanocrystalline particles. Room temperature magnetization results show a ferromagnetic behavior of the CoFe{sub 2}O{sub 4}, MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples, whereas the

Chrystal structure properties of Al-doped Li{sub 4}Ti{sub 5}O{sub 12} synthesized by solid state reaction method

Energy Technology Data Exchange (ETDEWEB)

Sandi, Dianisa Khoirum, E-mail: dianisa875@gmail.com; Suryana, Risa, E-mail: rsuryana@staff.uns.ac.id [Department of Physics, Faculty of Mathematics and Natural Sciences, Sebelas Maret University (Indonesia); Priyono, Slamet, E-mail: slam013@lipi.go.id [Physics Research Center (P2F)-LIPI, Puspiptek Area, Serpong, Tangerang (Indonesia)

2016-02-08

This research aim is to analyze the effect of Aluminum (Al) doping in the structural properties of Al-doped Li{sub 4}Ti{sub 5}O{sub 12} as anode in lithium ion battery. Al-doped Li{sub 4}Ti{sub 5}O{sub 12} powders were synthesized by solid state reaction method. LiOH.H{sub 2}O, TiO{sub 2}, and Al{sub 2}O{sub 3} were raw materials. These materials were milled for 15 h, calcined at temperature of 750{sup o}C and sintered at temperature of 800{sup o}C. Mole percentage of doping Al (x) was varied at x=0; x=0.025; and x =0.05. Al-doped Li{sub 4}Ti{sub 5}O{sub 12} powders were synthesized by solid state reaction method. X-ray diffraction was employed to determine the structure of Li{sub 4}Ti{sub 5}O{sub 12}. The PDXL software was performed on the x-ray diffraction data to estimate the phase percentage, the lattice parameter, the unit cell volume, and the crystal density. Al-doped Li{sub 4}Ti{sub 5}O{sub 12} has cubic crystal structure. Al-doping at x=0 and x=0.025 does not change the phase as Li{sub 4}Ti{sub 5}O{sub 12} while at x=0.050 the phase changes to the LiTiAlO{sub 4}. The diffraction patterns show that the angle shifted to the right as the increase of x which indicated that Al substitute Ti site. Percentage of Li{sub 4}Ti{sub 5}O{sub 12} phase at x=0 and x=0.025 was 97.8% and 96.8%, respectively. However, the lattice parameters, the unit cell volume, and the crystal density does not change significantly at x=0; x=0.025; and x=0.050. Based on the percentage of Li{sub 4}Ti{sub 5}O{sub 12} phase, the Al-doped Li at x=0 and x=0.025 is promising as a lithium battery anode.

Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

Directory of Open Access Journals (Sweden)

Yang Yang

2013-11-01

Full Text Available This work reports the excellent dielectric properties of polyimide (PI embedded with CaCu3Ti4O12 (CCTO nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz–1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67 is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

Investigation of structural and optical properties of CaTiO3 powders doped with Mg2+ and Eu3+ ions

International Nuclear Information System (INIS)

Oliveira, Larissa H.; Savioli, Julia; Moura, Ana P. de; Nogueira, Içamira C.; Li, Maximo S.; Longo, Elson; Varela, José A.; Rosa, Ieda L.V.

2015-01-01

In this work, CaTiO 3 powders doped with Mg 2+ ions and CaTiO 3 powders co-doped with Mg 2+ and Eu 3+ ions were prepared by the polymeric precursor method (PPM). These powders were characterized by different characterization techniques to study the influence of Mg 2+ doping as well as Mg 2+ and Eu 3+ co-doping in structural and optical properties of CaTiO 3 perovskite-type structure. The Rietveld refinement and Micro-Raman analyses suggested the substitution Mg 2+ and Eu 3+ ions in the A-site of CaTiO 3 perovskite. The influence of Mg 2+ doping can be detected by the displacement of calcium and oxygen atomic positions when compared to the non-doped CaTiO 3 powder. When Eu 3+ ions are added to the A-site of this perovskite the excess of positive charge can be compensated by the formation of calcium vacancies. Luminescence data showed that Ca 1-x Mg x TiO 3 and Ca 1x Mg x/2 Eu 2y/3 TiO 3 powders are potential materials for fabrication of lighting devices based on near-UV and blue LED using an excitation wavelength of 397 and/or 450 nm. - Highlights: • CaTiO 3 co-doped with Mg 2+ and Eu 3+ were obtained by the Polymeric Precursor Method. • Incorporation of Mg 2+ and Eu 3+ ions in the CaTiO 3 lattice. • Enhancement of the Eu 3+ photoluminescence

Electrophoretic deposition of nanocrystalline TiO2 films on Ti substrates for use in flexible dye-sensitized solar cells

International Nuclear Information System (INIS)

Tan Weiwei; Yin Xiong; Zhou Xiaowen; Zhang Jingbo; Xiao Xurui; Lin Yuan

2009-01-01

Nanocrystalline TiO 2 films were prepared on flexible Ti-metal sheets by electrophoretic deposition followed by chemical treatment with tetra-n-butyl titanate (TBT) and sintering at 450 deg. C. X-ray diffraction (XRD) analysis indicates that TBT treatment led to the formation of additional anatase TiO 2 , which plays an important role in improving the interconnection between TiO 2 particles, as well as the adherence of the film to the substrate, and in modifying the surface properties of the nanocrystalline particles. The effect of TBT treatment on the electron transport in the nanocrystalline films was studied by intensity-modulated photocurrent spectroscopy (IMPS). An increase in the conversion efficiency was obtained for the dye-sensitized solar cells with TBT-treated nanocrystalline TiO 2 films. The cell performance was further optimized by designing nanocrystalline TiO 2 films with a double-layer structure composed of a light-scattering layer and a transparent layer. The light-scattering effect of the double-layer nanocrystalline films was evaluated by diffuse reflectance spectra. Employing the double-layer nanocrystalline films as the photoelectrodes resulted in a significant improvement in the incident photo-to-current conversion efficiency of the corresponding cells due to enhanced solar absorption by light scattering. A high conversion efficiency of 6.33% was measured under illumination with 100 mW cm -2 (AM 1.5) simulated sunlight.

Preparation and characterization of phase-pure anatase and rutile TiO2 powder by new chemistry route

International Nuclear Information System (INIS)

Pereira, E. A.; Montanhera, M.A.; Paula, F.R.; Spada, E.R.

2014-01-01

Titanium dioxide (TiO 2 ) is used in a wire range applications such as photocatalysis and sensor device. In this work is shown a new and effective method for the preparation of TiO 2 nanocrystalline in the crystallographic forms, anatase and rutile. The method involves dissolving the TiOSO 4 powder in H 2 O 2 solution and thermal treatment of amorphous precipitate. The technique of X-ray diffraction was used to follow the structure evolution of amorphous precipitate. Pure anatase structure and rutile are obtained at 600 deg C and 1000 deg C with a grain size estimated 24 and 55 nm respectively. TiO 2 nanoparticles is a promising alternative of the low cost whose potential for solar cells deserve a careful evaluation, especially in hybrid solar cells that employs TiO 2 as electron acceptor and as transport channels. (author)

Synthesis of nanocrystalline TiB2 powder from TiO2, B2O3 and Mg ...

Indian Academy of Sciences (India)

gered by using: (i) a furnace or (ii) an electrical element touching the surface ... plicity, low energy consumption and good purity of the products. [12,13]. SHS method .... Similar to the TiO2–Mg system, by increasing the ini- tial temperature, the ...

Carbon coated Li4Ti5O12 nanorods as superior anode material for high rate lithium ion batteries

International Nuclear Information System (INIS)

Luo, Hongjun; Shen, Laifa; Rui, Kun; Li, Hongsen; Zhang, Xiaogang

2013-01-01

Highlights: •A novel approach has been developed to fabricate 1D Li 4 Ti 5 O 12 /C nanorods by a wet-chemical route. •Carbon coating layer effectively restrict the particle growth and enhance electronic conductivity. •The Li 4 Ti 5 O 12 /C nanorods exhibit remarkable rate capability and long cycle life. -- Abstract: We describe a novel approach for the synthesis of carbon coated Li 4 Ti 5 O 12 (Li 4 Ti 5 O 12 /C) nanorods for high rate lithium ion batteries. The carbon coated TiO 2 nanotubes using the glucose as carbon source are first synthesized by hydrothermal treatment. The commercial anatase TiO 2 powder is immersed in KOH sulotion and subsequently transforms into Li 4 Ti 5 O 12 /C in LiOH solution under hydrothermal condition. Field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption/desorption and Raman spectra are performed to characterize their morphologies and structures. Compared with the pristine Li 4 Ti 5 O 12 , one-dimensional (1D) Li 4 Ti 5 O 12 /C nanostructures show much better rate capability and cycling stability. The 1D Li 4 Ti 5 O 12 /C architectures effectively restrict the particle growth and enhance their electronic conductivity, enabling fast ion and electron transport

Structural evolution of Ba{sub 8}Ti{sub 3}Nb{sub 4}O{sub 24} from BaTiO{sub 3} using a series of Ba(Ti{sub 1−5x}Nb{sub 4x})O{sub 3} solid solutions

Energy Technology Data Exchange (ETDEWEB)

Barrientos Hernández, F.R., E-mail: frbh68@hotmail.com [Academic Area of Earth Sciences and Materials, Autonomous University of Hidalgo State, Road Pachuca-Tulancingo km 4.5, Mineral de la Reforma zip code 42184, Hidalgo (Mexico); Department of Metallurgical and Materials Engineering, ESIQIE, National Polytechnic Institute, UPALM, Zacatenco, Mexico City, zip code 07738 (Mexico); Lira Hernández, I.A. [Department of Metallurgical and Materials Engineering, ESIQIE, National Polytechnic Institute, UPALM, Zacatenco, Mexico City, zip code 07738 (Mexico); Industrial Engineering Department, Technological Institute of Pachuca, Road México-Pachuca km. 87.5, Pachuca de Soto zip code 42080, Hidalgo (Mexico); Gómez Yáñez, C. [Department of Metallurgical and Materials Engineering, ESIQIE, National Polytechnic Institute, UPALM, Zacatenco, Mexico City, zip code 07738 (Mexico); Arenas Flores, A. [Academic Area of Earth Sciences and Materials, Autonomous University of Hidalgo State, Road Pachuca-Tulancingo km 4.5, Mineral de la Reforma zip code 42184, Hidalgo (Mexico); Cabrera Sierra, R. [Department of Metallurgical and Materials Engineering, ESIQIE, National Polytechnic Institute, UPALM, Zacatenco, Mexico City, zip code 07738 (Mexico); Pérez Labra, M. [Academic Area of Earth Sciences and Materials, Autonomous University of Hidalgo State, Road Pachuca-Tulancingo km 4.5, Mineral de la Reforma zip code 42184, Hidalgo (Mexico)

2014-01-15

Highlights: • The evolution phase Ba{sub 8}Ti{sub 3}Nb{sub 4}O{sub 24} was obtained through the mechanism Ba(Ti{sub 1-5x}Nb{sub 4x})O{sub 3}. • Addition of niobium can accelerate grain growth of BaTiO{sub 3} ceramics. • Ba{sub 8}Ti{sub 3}Nb{sub 4}O{sub 24} presents a dielectric loss of 0.0035 and permittivity value of 54.6. • Electrical measurements showed that Nb{sup 5+} content drops Curie temperature. • Samples with x ⩾ 0.0625 shows an insulating behavior. -- Abstract: In this work, the structural evolution of hexagonal phase Ba{sub 8}Ti{sub 3}Nb{sub 4}O{sub 24} by adding Nb{sub 2}O{sub 5} to perovskite structure of BaTiO{sub 3} was investigated. The compositions Ba(Ti{sub 1-5x}Nb{sub 4x})O{sub 3} ceramics, with 0.00025 ⩽ x ⩽ 0.125 were prepared by the conventional solid state route in air atmosphere, the powders precursors, BaTiO{sub 3}, BaCO{sub 3} and Nb{sub 2}O{sub 5}, were mixed in stoichiometric proportions and ground in a ball mill using alumina balls and acetone. The mixed powders were calcined at temperatures up to 1500 °C. The phase transformation of Ba{sub 8}Ti{sub 3}Nb{sub 4}O{sub 24} from BaTiO{sub 3} was studied by DRX, Raman spectroscopy, SEM, electrical measurements (relative permittivity and P–E hysteresis loops); Rietveld’s refinement was used to structurally characterize the samples. For the devices obtained capacitance was measured at 1 kHz; with these values we calculated the relative permittivity. The samples show typical P–E hysteresis loops at room temperature accompanied by saturation polarization (Ps) and remnant polarization (Pr). The DRX and Rietveld’s refinement results show x ⩽ 0.01 has a ferroelectric behavior. When the doped level is increased x ⩾ 0.02, a peak displacement is observed, this is due to the phase transformation of tetragonal to cubic into the unit cell. Finally, with x = 0.125 the crystal structure transforms to the characteristic hexagonal phase Ba{sub 8}Ti{sub 3}Nb{sub 4}O{sub 24} which

Density variation and piezoelectric properties of Ba (Ti1− xSnx) O3 ...

Indian Academy of Sciences (India)

Home; Journals; Bulletin of Materials Science; Volume 35; Issue 5. Density variation and piezoelectric properties of Ba(Ti1−Sn)O3 ceramics prepared from nanocrystalline powders ... The density variation of the ceramics with sintering temperature has been studied by sintering the samples at different temperatures.

Fabrication and tritium release property of Li2TiO3-Li4SiO4 biphasic ceramics

Science.gov (United States)

Yang, Mao; Ran, Guangming; Wang, Hailiang; Dang, Chen; Huang, Zhangyi; Chen, Xiaojun; Lu, Tiecheng; Xiao, Chengjian

2018-05-01

Li2TiO3-Li4SiO4 biphasic ceramic pebbles have been developed as an advanced tritium breeder due to the potential to combine the advantages of both Li2TiO3 and Li4SiO4. Wet method was developed for the pebble fabrication and Li2TiO3-Li4SiO4 biphasic ceramic pebbles were successfully prepared by wet method using the powders synthesized by hydrothermal method. The tritium release properties of the Li2TiO3-Li4SiO4 biphasic ceramic pebbles were evaluated. The biphasic pebbles exhibited good tritium release property at low temperatures and the tritium release temperature was around 470 °C. Because of the isotope exchange reaction between H2 and tritium, the addition of 0.1%H2 to purge gas He could significantly enhance the tritium gas release and the fraction of molecular form of tritium increased from 28% to 55%. The results indicate that the Li2TiO3-Li4SiO4 biphasic ceramic pebbles fabricated by wet method exhibit good tritium release property and hold promising potential as advanced breeder pebbles.

A chemical route to room-temperature synthesis of nanocrystalline TiO2 thin films

International Nuclear Information System (INIS)

Pathan, Habib M.; Kim, Woo Young; Jung, Kwang-Deog; Joo, Oh-Shim

2005-01-01

A lot of methods are developed for the deposition of TiO 2 thin films; however, in each of these methods as-deposited films are amorphous and need further heat treatment at high temperature. In the present article, a chemical bath deposition (CBD) method was used for the preparation of TiO 2 thin films. We investigated nanocrystalline TiO 2 thin films using CBD at room temperature onto glass and ITO coated glass substrate. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The chemically synthesized films were nanocrystalline and composed of crystal grains of 2-3 nm

Magnetic properties of nanocrystalline CoFe{sub 2}O{sub 4} powders prepared at room temperature: variation with crystallite size

Energy Technology Data Exchange (ETDEWEB)

Rajendran, M.; Pullar, R.C.; Bhattacharya, A.K. E-mail: ashokbhattacharya@warwick.ac.uk; Das, D.; Chintalapudi, S.N.; Majumdar, C.K

2001-06-01

The magnetic properties of nanocrystalline CoFe{sub 2}O{sub 4} powders prepared by a redox process at room temperature have been studied by vibrating sample magnetometer (VSM). The average crystallite size of the powders varied from 6 to 20 nm by changing the synthesis conditions and the corresponding saturation magnetisation (M{sub s}) value ranged from 9 to 38 emu g{sup -1}. On heating, the crystallite size increased with corresponding increase in M{sub s} values. At 1073 K all samples achieved M{sub s} values close to 73 emu g{sup -1}. On increasing the crystallite size, the coercivity (H{sub c}) increased passed through a maximum and dropped. Cobalt ferrite powder with an average crystallite size of 6 nm prepared at room temperature achieved desirable values of M{sub s}=60 emu g{sup -1} and H{sub c}=1.42 kOe after thermal annealing at 973 K. The Moessbauer spectra were recorded for CoFe{sub 2}O{sub 4} having a range of crystallite sizes at room temperature and at low temperatures down to 40 K. The magnetic and Moessbauer results are provided for nanocrystalline CoFe{sub 2}O{sub 4} as a function of crystallite size and measurement temperature.

Synthesis, characterization, and analysis of enhanced photocatalytic activity of Zr-doped TiO2 nanostructured powders under UV light

Science.gov (United States)

Sekhar, M. Chandra; Purusottam Reddy, B.; Mallikarjuna, K.; Shanmugam, Gnanendra; Ahn, Chang-Hoi; Park, Si-Hyun

2018-01-01

Zr-doped and pure TiO2 nanoparticles (NPs) were synthesized using a simple inexpensive sol-gel method. X-ray powder diffractometry and Fourier transform infrared spectrometry revealed the presence of anatase-phase TiO2 NPs. Scanning electron microscopy and transmission electron microscopy revealed that the average nanocrystalline size of approximately 15 nm. The photocatalytic activities of these materials were evaluated using Rhodamine B (Rh B) as an organic contaminant. The photocatalytic activity of pure and Zr-doped TiO2 NPs (with at% 4, 8, 12 and 16) was measured in terms of the degradation of Rh B under UV light. The antibacterial activities of pure and Zr-doped (with 8 at%) TiO2 NPs were evaluated against Bacillus subtillis, Escherichia coli, and Pseudomonas aeruginosa. A maximum inhibition zone (19 mm) was observed for pure TiO2 NPs, against Bacillus subtillis and Pseudomonas aeruginosa, while Zr-doped TiO2 (8 at%) exhibited a lesser inhibition zone (18 mm) against the same Bacillus subtillis and Pseudomonas aeruginosa (18 mm). However, Zr-doped TiO2 (8 at%) NPs exhibited a greater inhibition zone against Escherichia coli (17 mm), while the activity of pure TiO2 NPs against Escherichia coli (15 mm) was retarded. Thus, pure TiO2 NPs and Zr-doped TiO2 (8 at%) NPs have competent activities and can be used as antibacterial agents against different bacteria.

Solid-state synthesis of Li{sub 4}Ti{sub 5}O{sub 12} for high power lithium ion battery applications

Energy Technology Data Exchange (ETDEWEB)

Han, Seung-Woo [School of Materials Science and Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Ryu, Ji Heon [Graduate School of Knowledge-Based Technology and Energy, Korea Polytechnic University, Siheung 429-793 (Korea, Republic of); Jeong, Joayoung [Cell Precedence Development Group, Samsung SDI, Yongin 446-577 (Korea, Republic of); Yoon, Dang-Hyok, E-mail: dhyoon@ynu.ac.kr [School of Materials Science and Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of)

2013-09-05

Highlights: •High energy milling using 0.30 and 0.45 mm beads for Li{sub 4}Ti{sub 5}O{sub 12} synthesis. •Synthesis of 162 nm-sized pure Li{sub 4}Ti{sub 5}O{sub 12} by solid-state reaction. •Spray drying using fine starting materials to confer paste tackiness. •High capacity of 174 mAh/g and adequate rate properties for high power LIBs applications. -- Abstract: Li{sub 4}Ti{sub 5}O{sub 12} was synthesized by a solid-state reaction between Li{sub 2}CO{sub 3} and anatase TiO{sub 2} for applications to high power lithium ion batteries. The starting materials underwent 6 h of high energy milling using ZrO{sub 2} beads with two different sizes, 0.30 and 0.45 mm. The smaller ZrO{sub 2} beads resulted in finer starting materials. Spray drying was also performed on the 0.30 mm beads-treated particles to enhance the screen printability of a paste containing this powder. The finer starting materials showed a pure 162 nm-sized Li{sub 4}Ti{sub 5}O{sub 12} due to the decreased diffusion length for a solid-state reaction, whereas the 0.45 mm beads-treated starting materials resulted in a 242 nm-sized Li{sub 4}Ti{sub 5}O{sub 12} phase containing 2 wt.% of rutile TiO{sub 2} that had transformed from the anatase phase during heat treatment at 800 °C for 3 h. The finer Li{sub 4}Ti{sub 5}O{sub 12} showed higher charge capacity and better charge/discharge rates than the coarser particles, which highlights the importance of the primary particle size on the electrochemical properties of Li{sub 4}Ti{sub 5}O{sub 12} for high power applications. The fine Li{sub 4}Ti{sub 5}O{sub 12} particles had a discharge capacity of 174 mAh/g at 0.1 C and capacity retention of 80% at 10.0 C.

Effect of incorporating nonlanthanoidal indium on the ferroelectric performance of Bi4Ti3O12 thin films

Science.gov (United States)

Chang, Y. C.; Kuo, D. H.

2006-08-01

Nonlanthanoid-substituted In-x-Bi4Ti3O12 films with different indium contents at x =0, 0.2, 0.4, and 0.5, based upon the chemical formula of (Bi4-xInx)Ti3O12, were prepared at 600°C by chemical solution deposition. In-0.4-Bi4Ti3O12 films displayed a large remanent polarization of 57μC /cm2, coercive field of 100KV/cm, high nonvolatile polarization ⩾30μC/cm2 after 1010 switching cycles, and low annealing temperature of 600°C. Good ferroelectric properties are mainly attributed to the partial substitution of the smaller-sized Ti4+ site by the larger-sized In3+ to enhance electrical polarization by a dimensional change of unit cell and to provide fatigue resistance by lattice distortion and chemical stabilization.

Photochemical solar cells based on dye-sensitization of nanocrystalline TiO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Deb, S.K.; Ellingson, R.; Ferrere, S.; Frank, A.J.; Gregg, B.A.; Nozik, A.J.; Park, N.; Schlichthoerl, G. [National Renewable Energy Lab., Golden, CO (United States)

1998-09-01

A photoelectrochemical solar cell that is based on the dye-sensitization of thin nanocrystalline films of TiO{sub 2} (anatase) nanoparticles in contact with a non-aqueous liquid electrolyte is described. The cell, fabricated at NREL, shows a conversion efficiency of {approximately} 9.2% at AM1.5, which approaches the best reported value of 10--11% by Graetzel at EPFL in Lausanne, Switzerland. The femtosecond (fs) pump-probe spectroscopy has been used to time resolve the injection of electrons into the conduction band of nanocrystalline TiO{sub 2} films under ambient conditions following photoexcitation of the adsorbed Ru(II)-complex dye. The measurement indicates an instrument-limited {minus}50 fs upper limit on the electron injection time. The authors also report the sensitization of nanocrystalline TiO{sub 2} by a novel iron-based dye, CIS-[Fe{sup II}(2,2{prime}-bipyridine-4,4,{prime}-dicarboxylic acid){sub 2}(CN){sub 2}], a chromophore with an extremely short-lived, nonemissive excited state. The dye also exhibits a unique band selective sensitization through one of its two absorption bands. The operational principle of the device has been studied through the measurement of electric field distribution within the device structure and studies on the pH dependence of dye-redox potential. The incorporation of WO{sub 3}-based electrochromic layer into this device has led to a novel photoelectrochromic device structure for smart window application.

Large-scale synthesis of Pb1-xLa xTiO3 ceramic powders by molten salt method

International Nuclear Information System (INIS)

Cai Zongying; Xing Xianran; Yu Ranbo; Liu Guirong; Xing Qifeng

2006-01-01

The ferroelectric perovskite type lanthanum doped lead titanate (PLT) ceramic powders were synthesized in one step with the starting materials of PbC 2 O 4 , La 2 O 3 and TiO 2 in NaCl-KCl molten salts in the temperature range of 700-950 deg. C. It was found that molten salt method was a large scale and easy preparation way to produce PLT powders with high dispersity. Tetragonal phase Pb 1-x La x TiO 3 ceramic powders were identified by XRD in the composition range 0 ≤ x ≤ 0.3 and mono-dispersed particles with spheric shape and less than 100 nm size were observed by SEM. The grain sizes of Pb 1-x La x TiO 3 ceramic powders increased with the increase of La content and decreased with calcination temperature. The grain growth progress and the possible reaction mechanism in molten salts and its influencing factors were discussed in this work. The grain growth process was the main influencing factor of the grain size, which depended on the solubility in the flux

Photocatalytic decomposition of N{sub 2}O over TiO{sub 2}/g-C{sub 3}N{sub 4} photocatalysts heterojunction

Energy Technology Data Exchange (ETDEWEB)

Kočí, K., E-mail: kamila.koci@vsb.cz [Institute of Environmental technologies, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic); Reli, M.; Troppová, I.; Šihor, M. [Institute of Environmental technologies, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic); Kupková, J. [Nanotechnology center, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic); Kustrowski, P. [Faculty of Chemistry, Jagiellonian University in Kraków, ul. Ingardena 3, 30-060 Kraków (Poland); Praus, P. [Institute of Environmental technologies, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic); Department of Chemistry, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic)

2017-02-28

Highlights: • TiO{sub 2}/g-C{sub 3}N{sub 4} photocatalysts with the various TiO{sub 2}/g-C{sub 3}N{sub 4} weight ratios. • N{sub 2}O photocatalytic decomposition under UVC and UVA irradiation. • Heterojunction on the TiO{sub 2}/g-C{sub 3}N{sub 4} interface play an important role. • Optimal ratio of TiO{sub 2}:g-C{sub 3}N{sub 4} was 1:2 for the highest activity at UVA irradiation. - Abstract: TiO{sub 2}/g-C{sub 3}N{sub 4} photocatalysts with the various TiO{sub 2}/g-C{sub 3}N{sub 4} weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO{sub 2} was prepared by thermal hydrolysis and pure g-C{sub 3}N{sub 4} was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV–vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO{sub 2} and g-C{sub 3}N{sub 4} were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO{sub 2}/g-C{sub 3}N{sub 4} nanocomposites showed moderate improvement compared to pure g-C{sub 3}N{sub 4} but pure TiO{sub 2} proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO{sub 2}/g-C{sub 3}N{sub 4} (1:2) nanocomposite exhibited an increase compared to pure TiO{sub 2}. Nevertheless, further increase of g-C{sub 3}N{sub 4} amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO{sub 2} and g-C{sub 3}N{sub 4} have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C{sub 3}N{sub 4}. This is

Anti-fish bacterial pathogen effect of visible light responsive Fe3O4@TiO2 nanoparticles immobilized on glass using TiO2 sol–gel

International Nuclear Information System (INIS)

Yeh, N.; Lee, Y.C.; Chang, C.Y.; Cheng, T.C.

2013-01-01

This paper demonstrates a fish pathogen reduction procedure that uses TiO 2 sol–gel coating Fe 3 O 4 @TiO 2 powder on glass substrate. Such procedure can effectively relieve two constraints that haunt TiO 2 sterilization applications: 1) the need for UV for overcoming the wide band gap of pure TiO 2 and 2) the difficulty of its recovering from water for reuse. In the process, visible light responsive Fe 3 O 4 /TiO 2 nanoparticles are synthesized and immobilized on glass using TiO 2 sol–gel as the binder for fish bacterial pathogen disinfection test. After 3 h of visible light irradiation, the immobilized Fe 3 O 4 @TiO 2 's inhibition efficiencies for fish bacterial pathogen are, respectively, 50% for Edwardsiella tarda (BCRC 10670) and 23% for Aeromonas hydrophila (BCRC 13018)

Low temperature synthesis of nanocrystalline lanthanum monoaluminate powders by chemical coprecipitation

Energy Technology Data Exchange (ETDEWEB)

Kuo, C.-L. [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Wang, C.-L. [Department of Materials Science and Engineering, I-Shou University, 1 Section 1, Hsueh-Cheng Road, Ta-Hsu Hsiang, Kaohsiung 840, Taiwan (China); Chen, T.-Y. [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Chen, G.-J. [Department of Materials Science and Engineering, I-Shou University, 1 Section 1, Hsueh-Cheng Road, Ta-Hsu Hsiang, Kaohsiung 840, Taiwan (China); Hung, I-M. [Department of Chemical Engineering and Materials Science, Yuan Ze University, 135 Yuan-Tung Road, Chungli, Taoyuan 320, Taiwan (China); Shih, C.-J. [Faculty of Fragrance and Cosmetics, Kaohsiung Medical University, 100 Shi-Chuan 1st Road, Kaohsiung 807, Taiwan (China)]. E-mail: CJShih@kmu.edu.tw; Fung, K.-Z. [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China)

2007-08-16

Nanocrystalline lanthanum monoaluminate (LaAlO{sub 3}) powders were prepared by chemical coprecipitation using 25 vol.% of NH{sub 4}OH, 0.05 M La(NO{sub 3}){sub 3}.6H{sub 2}O and 0.05 M Al(NO{sub 3}){sub 3}.9H{sub 2}O aqueous solutions as the starting materials. Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analyses (TGA/DTA), X-ray diffraction (XRD), Raman spectrometry, specific surface area (BET) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED) were utilized to characterize the LaAlO{sub 3} powders prepared by chemical coprecipitation. The crystallization temperature of the LaAlO{sub 3} precursor gels precipitated at pH 9 is estimated as 810 deg. C by TG/DTA. The XRD pattern of the LaAlO{sub 3} precursor gels precipitated at pH 8-12 and calcined at 700 deg. C for 6 h shows a broad arciform continuum exist between 24{sup o} and 32{sup o} and sharp peaks of LaAlO{sub 3} except the precursor gels precipitated at pH 9. For the LaAlO{sub 3} precursor gels precipitated at pH 9 and calcined at 700 deg. C for 6 h, the formation of the perovskite LaAlO{sub 3} phase occurs and the presence of crystalline impurities is not found. The crystallite size of LaAlO{sub 3} slightly increases from 37.8 to 41.5 nm with calcination temperature increasing from 700 to 900 deg. C for 6 h. The LaAlO{sub 3} powders prepared by chemical coprecipitation have a considerably large specific surface of 30 m{sup 2}/g. The relative density greater than 97% is obtained when these nanocrystalline LaAlO{sub 3} powders are sintered at 1550 deg. C for 2 h.

Nanocrystalline CdSnO3 Based Room Temperature Methanol Sensor

Directory of Open Access Journals (Sweden)

Shanabhau BAGUL

2017-04-01

Full Text Available Synthesis of nanocrystalline CdSnO3 powder by ultrasonic atomizer assisted wet chemical method is reported in this paper. Synthesized CdSnO3 powder was characterized by X-Ray Diffraction (XRD, Field Emission Scanning Electron Microscopy (FESEM and Transmission Electron Microscopy (TEM to examine phase and microstructure. FESEM and TEM analysis reveals that the CdSnO3 powder prepared here is porous monodisperse nanocrystalline in nature, with average particle size of approximately 17 nm or smaller. The material is also characterized by UV-Visible and Photoluminescence (PL spectroscopy. Thick films of synthesized CdSnO3 powder fired at 850 0C are made by using screen printing method. The films surface is modified by using dipping method. CuCl2 (0.005 M dipped (for 2 min thick film shows high response (R= 477 to 100 ppm methanol at room temperature (35 0C. The sensor shows good selectivity and fast response recovery time to methanol. The excellent methanol sensing performance, particularly high response values is observed to be mainly due to porous CdSnO3 surface.

Formation of nanocrystalline TiC from titanium and different carbon sources by mechanical alloying

Energy Technology Data Exchange (ETDEWEB)

Jia Haoling [Key Lab of Liquid Structure and Heredity of Materials, Jingshi Road 73, Jinan 250061, Shandong (China); Zhang Zhonghua [Key Lab of Liquid Structure and Heredity of Materials, Jingshi Road 73, Jinan 250061, Shandong (China)], E-mail: zh_zhang@sdu.edu.cn; Qi Zhen [Key Lab of Liquid Structure and Heredity of Materials, Jingshi Road 73, Jinan 250061, Shandong (China); Liu Guodong [School of Materials Science and Engineering, Shandong University, Jingshi Road 73, Jinan 250061 (China); Bian Xiufang [Key Lab of Liquid Structure and Heredity of Materials, Jingshi Road 73, Jinan 250061, Shandong (China)

2009-03-20

In this paper, the formation of nanocrystalline TiC from titanium powders and different carbon resources by mechanical alloying (MA) has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental results show that nanocrystalline TiC can be synthesized from Ti powders and different carbon resources (activated carbon, carbon fibres or carbon nanotubes) by MA at room temperature. Titanium and different carbon resources have a significant effect on the Ti-C reaction and the formation of TiC during MA. Moreover, the formation of nanocrystalline TiC is governed by a gradual diffusion reaction mechanism during MA, regardless of different carbon resources.

Hydrothermal synthesis of Li4-xNaxTi5O12 and Li4-xNaxTi5O12/graphene composites as anode materials for lithium-ion batteries

Directory of Open Access Journals (Sweden)

Zhu Jiping

2016-01-01

Full Text Available A potential Lithium-ion battery anode material Li4-xNaxTi5O12 (0≤x≤0.15 has been synthesized via a facile hydrothermal method with short processing time and low temperature. The XRD and FE-SEM results indicate that samples with Na-doped are well-crystallized and have more homogeneous particle distributions with smaller overall particle size in the range of 300-600nm. Electrochemical tests reveal that Na-doped samples exhibit impressive specific capacity and cycle stability compared to pristine Li4Ti5O12 at high rate. The Li3.9Na0.1Ti5O12 electrode deliver an initial specific discharge capacity of 169mAh/g at 0.5C and maintained at 150.4mAh/g even after 40 cycles with the reversible retention of 88.99%. Finally, a simple solvothermal reduction method was used to fabricate Li3.9Na0.1Ti5O12/graphene(Li3.9Na0.1Ti5O12/G composite. Galvanostatic charge-discharge tests demonstrate that this sample has remarkable capacities of 197.4mAh/g and 175.5mAh/g at 0.2C and 0.5C rate, respectively. This indicates that the Li3.9Na0.1Ti5O12/G composite is a promising anode material for using in lithium-ion batteries.

Doped nanocrystalline ZnO powders for non-linear resistor applications by spray pyrolysis method.

Science.gov (United States)

Hembram, Kaliyan; Vijay, R; Rao, Y S; Rao, T N

2009-07-01

Homogeneous and doped nanocrystalline ZnO powders (30-200 nm) were synthesized by spray pyrolysis technique. The spray pyrolysed powders were calcined in the temperature range of 500-750 degrees C. Formation of insulating pyrochlore phase started from 700 degrees C during the calcination itself. The calcined powders were compacted and sintered at different temperatures ranging from 900-1200 degrees C for 0.5-4 h. The densification behavior was found to be dependent on calcination temperature of the nanopowder. The resulting discs were found to have density (5.34-5.62 g/cc) in the range of 96-99% of theoretical density. The breakdown voltage value obtained for the nanopowder based non-linear resistor is 10.3 kV/cm with low leakage current density of 0.7 microA/cm2 and coefficient of nonlinearity as high as 193. The activation energy for grain growth of the doped ZnO nanopowder powders is 449.4 +/- 15 kJ/mol.

Kinetic analysis of the thermal decomposition of Li4Ti5O12 pellets

Directory of Open Access Journals (Sweden)

Hugo A. Mosqueda

2011-12-01

Full Text Available A single dynamic kinetic analysis, describing the surface decomposition of Li4Ti5O12 pellets, has been performed. Samples were analyzed by X-ray diffraction and scanning electron microscopy. The analyses were performed between 1000 and 1100°C and different times, perceiving the Li4Ti5O12 decomposition to Li2Ti3O7, with a loss of lithium. As expected, more rapid decomposition behaviour was found at higher temperatures. Finally, the activation energy for this decomposition of Li4Ti5O12 to Li2Ti3O7 was estimated to be equal to 383 kJ/mol.

Influence of Feedstock Powder Modification by Heat Treatments on the Properties of APS-Sprayed Al2O3-40% TiO2 Coatings

Science.gov (United States)

Berger, Lutz-Michael; Sempf, Kerstin; Sohn, Yoo Jung; Vaßen, Robert

2018-04-01

The formation and decomposition of aluminum titanate (Al2TiO5, tialite) in feedstock powders and coatings of the binary Al2O3-TiO2 system are so far poorly understood. A commercial fused and crushed Al2O3-40%TiO2 powder was selected as the feedstock for the experimental series presented in this paper, as the composition is close to that of Al2TiO5. Part of that powder was heat-treated in air at 1150 and 1500 °C in order to modify the phase composition, while not influencing the particle size distribution and processability. The powders were analyzed by thermal analysis, XRD and FESEM including EDS of metallographically prepared cross sections. Only a maximum content of about 45 wt.% Al2TiO5 was possible to obtain with the heat treatment at 1500 °C due to inhomogeneous distribution of Al and Ti in the original powder. Coatings were prepared by plasma spraying using a TriplexPro-210 (Oerlikon Metco) with Ar-H2 and Ar-He plasma gas mixtures at plasma power levels of 41 and 48 kW. Coatings were studied by XRD, SEM including EDS linescans of metallographically prepared cross sections, and microhardness HV1. With the exception of the powder heat-treated at 1500 °C an Al2TiO5-Ti3O5 (tialite-anosovite) solid solution Al2- x Ti1+ x O5 instead of Al2TiO5 existed in the initial powder and the coatings.

Preparation of TiO2 Nanocrystallite Powders Coated with 9 mol% ZnO for Cosmetic Applications in Sunscreens

Directory of Open Access Journals (Sweden)

Moo-Chin Wang

2012-02-01

Full Text Available The preparation of TiO2 nanocrystallite powders coated with and without 9 mol% ZnO has been studied for cosmetic applications in sunscreens by a co-precipitation process using TiCl4 and Zn(NO32·6H2O as starting materials. XRD results show that the phases of anatase TiO2 and rutile TiO2 coexist for precursor powders without added ZnO (T-0Z and calcined at 523 to 973 K for 2 h. When the T-0Z precursor powders are calcined at 1273 K for 2 h, only the rutile TiO2 appears. In addition, when the TiO2 precursor powders contain 9 mol% ZnO (T-9Z are calcined at 873 to 973 K for 2 h, the crystallized samples are composed of the major phase of rutile TiO2 and the minor phases of anatase TiO2 and Zn2Ti3O8. The analyses of UV/VIS/NIR spectra reveal that the absorption of the T-9Z precursor powders after being calcined has a red-shift effect in the UV range with increasing calcination temperature. Therefore, the TiO2 nanocrystallite powders coated with 9 mol% ZnO can be used as the attenuate agent in the UV-A region for cosmetic applications in sunscreens.

Studies on the sensing behaviour of nanocrystalline CuGa(2)O(4) towards hydrogen, liquefied petroleum gas and ammonia.

Science.gov (United States)

Biswas, Soumya Kanti; Sarkar, Arpita; Pathak, Amita; Pramanik, Panchanan

2010-06-15

In the present article, the gas sensing behaviour of nanocrystalline CuGa(2)O(4) towards H(2), liquefied petroleum gas (LPG) and NH(3) has been reported for the first time. Nanocrystalline powders of CuGa(2)O(4) having average particle sizes in the range of 30-60nm have been prepared through thermal decomposition of an aqueous precursor solution comprising copper nitrate, gallium nitrate and triethanol amine (TEA), followed by calcination at 750 degrees C for 2h. The synthesized nanocrystalline CuGa(2)O(4) powders have been characterised through X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM) study, energy dispersive X-ray (EDX) analysis and BET (Brunauer-Emmett-Teller) surface area measurement. The synthesized CuGa(2)O(4) having spinel structure with specific surface area of 40m(2)/g exhibits maximum sensitivity towards H(2), LPG, and NH(3) at 350 degrees C.

Effect of calcination temperature on the photocatalytic activity of TiO2 powders prepared by co-precipitation of TiCl3

International Nuclear Information System (INIS)

Yudoyono, Gatut; Ichzan, Nur; Zharvan, Vicran; Daniyati, Rizqa; Santoso, Hadi; Indarto, Bachtera; Pramono, Yono Hadi; Zainuri, Mochamad; Darminto

2016-01-01

The adsorption of basic dye methylene blue (MB) onto titanium dioxide (titania) powder that were prepared by coprecipitation method of TiCl 3 and NH 4 OH as iniatial material with different calcination temperature was studied to examine the photocatalytic activity. Synthesis process carried out by the solution pH was adjusted to be 8. Effect of calcination temperature on the titania powder were characterized with Differential Scanning Calorimetry/Thermogravimetry (DSC/TG), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM). The result of TG and XRD showed that the NH 4 Cl decomposed between 235-372°C. The XRD result showed that the anatase TiO 2 only contained a single phase when the calcination temperature of the precursor at 800°C, and over which it began to grow rutile phase. The influence of synthesis condition on the photocatalytic activity of TiO 2 powder was determined by the photodegradation of MB dye under UV light.

Preparation and characterization of rare earth modified nanocrystalline Al2O3/13 wt%TiO2 feedstock for plasma spraying.

Science.gov (United States)

Wang, Y; Tian, W; Yang, Y

2009-02-01

The preparation and characterization of RE modified nanocrystalline Al2O3/13 wt%TiO2 feedstock for plasma spraying are described in this paper. Taking individual nano particles as starting materials, by wet ball milling, spray drying, sintering and plasma treating, nanocrystalline plasma sprayable feedstock is prepared. The as-prepared feedstocks were analyzed by XRD, SEM, EDS, TEM and HRTEM methods. As shown from analyses results, the reconstituted agglomerate feedstock possesses spherical geometry, proper particle size, homogeneous composition distribution and nano scaled grains. There are three dimensional net structures in the prepared feedstock, which could be retained in coatings if the feedstock does not melt or partially melts during the plasma spray process. The three dimensional net structures could play an important role in improving crack propagation resistance and wear resistance of coatings. The reconstitution process and characterization methods discussed in this paper can also be applied to prepare intraclass nanocrystalline feedstock such as ZrO2/Y2O3 and Cr2O3 et al.

Magnetic and Mössbauer studies of pure and Ti-doped YFeO _3 nanocrystalline particles prepared by mechanical milling and subsequent sintering

International Nuclear Information System (INIS)

Khalifa, N. O.; Widatallah, H. M.; Gismelseed, A. M.; Al-Mabsali, F. N.; Sofin, R. G. S.; Pekala, M.

2016-01-01

Single-phased nanocrystalline particles of pure and 10 % Ti "4"+-doped perovskite-related YFeO _3were prepared via mechanosynthesis at 450"∘C. This temperature is ∼150–350 "∘C lower than those at which the materials, in bulk form, are normally prepared. Rietveld refinements of the X-ray diffraction patterns reveal that the dopant Ti "4"+ ions prefer interstitial octahedral sites in the orthorhombic crystal lattice rather than those originally occupied by the expelled Fe "3"+ ions. Magnetic measurements show canted antiferromagnetism in both types of nanoparticles. Doping with Ti "4"+ lowers the Néel temperature of the YFeO _3 nanoparticles from ∼ 586 K to ∼ 521 K. The Ti "4"+-doped YFeO _3 nanoparticles exhibit enhanced magnetization and coercivity but less magnetic hyperfine fields relative to the un-doped nanoparticles. The "5"7Fe Mössbauer spectra show ∼ 15 % of the YFeO _3 nanoparticles and ∼22 of Ti "4"+-doped YFeO _3 ones to be superparamagnetic with blocking temperatures < 78 K. The broadened magnetic components in the "5"7Fe Mössbauer spectra suggest size-dependent hyperfine magnetic fields at the "5"7Fe nuclear sites and were associated with collective magnetic excitations. The "5"7Fe Mössbauer spectra show the local environments of the Fe "3"+ ions in the superparamagnetic nanoparticles to be more sensitive to the presence of the Ti "4"+ ions relative to those in the larger magnetic nanoparticles.

Improved electrochemical properties of Li{sub 4}Ti{sub 5}O{sub 12}–Li{sub 0.33}La{sub 0.56}TiO{sub 3} composite anodes prepared by a solid-state synthesis

Energy Technology Data Exchange (ETDEWEB)

Zhu, Yan-Rong; Yuan, Jing; Zhu, Min [School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan, Anhui 243002 (China); Hao, Guodong [College of Chemistry and Chemical Engineering, Mudanjiang Normal University, Mudanjiang, Heilongjiang 157012 (China); Yi, Ting-Feng, E-mail: tfyihit@163.com [School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan, Anhui 243002 (China); Xie, Ying, E-mail: xieying@hlju.edu.cn [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin, Heilongjiang 150080 (China)

2015-10-15

Li{sub 4}Ti{sub 5}O{sub 12}–Li{sub 0.33}La{sub 0.56}TiO{sub 3} composite anodes are successfully prepared by a facile solid state route. The structure, morphology and electrochemical performance of all samples are characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge–discharge tests, respectively. XRD reveals that the little La{sup 3+} ions enter into the lattice, and then make the crystal lattice of Li{sub 4}Ti{sub 5}O{sub 12} expand. SEM shows that all samples are composed of 1–2 μm primary particles with irregular shapes. CV and EIS imply that Li{sub 4}Ti{sub 5}O{sub 12}–Li{sub 0.33}La{sub 0.56}TiO{sub 3} composites have lower polarization, larger lithium-ion diffusion coefficient and smaller charge transfer resistance corresponding to a much higher conductivity than those of Li{sub 4}Ti{sub 5}O{sub 12} corresponding to the extraction of Li{sup +} ions. The improved electrochemical performance of Li{sub 4}Ti{sub 5}O{sub 12}–Li{sub 0.33}La{sub 0.56}TiO{sub 3} composites can be attributed to the enhanced transfer kinetics of both the lithium ions and electrons. Particularly, Li{sub 4}Ti{sub 5}O{sub 12}–Li{sub 0.33}La{sub 0.56}TiO{sub 3} (5 wt.%) composite shows a excellent high-rate capability and cycling stability. Therefore, the present Li{sub 4}Ti{sub 5}O{sub 12}–Li{sub 0.33}La{sub 0.56}TiO{sub 3} (5 wt.%) composite anode is capable of large-scale applications, such as electric vehicles and hybrid electric vehicles, requiring high energy, long life and excellent safety. - Highlights: • The electrochemical property of Li{sub 4}Ti{sub 5}O{sub 12}–Li{sub 0.33}La{sub 0.56}TiO{sub 3} down to 0 V is first reported. • Li{sub 0.33}La{sub 0.56}TiO{sub 3} modifying results in fast lithium insertion/extraction kinetics. • Li{sub 4}Ti{sub 5}O{sub 12}–Li{sub 0.33}La{sub 0.56}TiO{sub 3} (5 wt.%) exhibits a good fast charge

Enhanced photovoltaic performance of dye-sensitized solar cells based on NaYF4:Yb(3+), Er(3+)-incorporated nanocrystalline TiO2 electrodes.

Science.gov (United States)

Zhu, Guang; Wang, Hongyan; Zhang, Quanxin; Zhang, Li

2015-08-01

Near infrared to visible up-conversion of light by rare earth ion-doped phosphors (NaYF4:Yb(3+), Er(3+)) that convert multiple photons of lower energy to higher energy photons offer new possibilities for improved performance of photovoltaic devices. Here, up-conversion phosphor NaYF4:Yb(3+), Er(3+) doped nanocrystalline TiO2 films are designed and used as a electrode for dye-sensitized solar cells, and the photovoltaic performance of DSSCs based on composite electrodes are investigated. The results show the cell with NaYF4:Yb(3+), Er(3+) achieves a power conversion efficiency of 7.65% under one sun illumination (AM 1.5G, 100mWcm(-2)), which is an increase of 14% compared to the cell without NaYF4:Yb(3+), Er(3+) (6.71%). The performance improvement is attributed to the dual effects of enhanced light harvesting from extended light absorption range and increased light scattering, and lower electron transfer resistance. Copyright © 2015 Elsevier Inc. All rights reserved.

Effects of sintering and paste-baking conditions on PTCR characteristic of (Ba,Sr)TiO{sub 3} vacuum-sintered compact added with TiO{sub 2}(Ti) powder; TiO{sub 2}(ti) fun tenka (Ba,Sr)TiO{sub 3} shinku shoketsutai no PTCR tokusei ni oyobosu shoketsu oyobi paste yakitsuke joken no eikyo

Energy Technology Data Exchange (ETDEWEB)

Kim, J.; Hayashi, K. [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science

1999-04-15

The effects of sintering temperature (T{sub s}; 1,573 {approx} 1,748K) and time (t{sub s}; 0.6 {approx} 14.4ks) and paste-baking-temperature or heating temperature (T{sub b} or T{sub h}; 673 {approx} 1,273K; t{sub b} is 0.3ks) on PTCR characteristic were investigated for (Ba, Sr)TiO{sub 3} vacuum-sintered compact added with 3.9mass% TiO{sub 2}(Ti) powder of 12.5mass% TiO{sub 2}. The results obtained were as follows; (1) PTCR characteristic developed at all T{sub s} (t{sub s}=3.6ks, T{sub b}=853K). The electrical resistivity at room temperature ({rho}{sub rt}) showed a minimum value of 1.8 times 10{sup 2}ohmcenter dotcm and the {rho}{sub max}/{rho}{sub rt} showed a maximum value of about 10{sup 6} at 1,723K. (2)For all t{sub s} (T{sub s}=1,623K, T{sub b}=853K), PTCR characteristic developed. The {rho}{sub rt} showed a minimum value of 2.6 times 10{sup 3}ohmcenter dotcm at 7.2ks. (3) At T{sub b} above 823K (T{sub s}=1,623K, t{sub s}=3.6ks), PTCR characteristic developed. The {rho}{sub rt} showed a minimum value of 1.0 times 10{sup 3}ohmcenter dotcm. (4)The {rho}-T curve of (Ba, Sr)TiO{sub 3}+TiO{sub 2}(Ti) vacuum-sintered compact was affected more largely by T{sub s}, t{sub s} and T{sub b} than that of (Ba, Sr)TiO{sub 3} air-sintered compact. This was considered to be mainly due to the porous and fine gained microstructure in the former compact. (author)

Host-Sensitized and Tunable Luminescence of GdNbO4:Ln3+ (Ln3+ = Eu3+/Tb3+/Tm3+) Nanocrystalline Phosphors with Abundant Color.

Science.gov (United States)

Liu, Xiaoming; Chen, Chen; Li, Shuailong; Dai, Yuhua; Guo, Huiqin; Tang, Xinghua; Xie, Yu; Yan, Liushui

2016-10-17

Up to now, GdNbO 4 has always been regarded as an essentially inert material in the visible region with excitation of UV light and electron beams. Nevertheless, here we demonstrate a new recreating blue emission of GdNbO 4 nanocrystalline phosphors with a quantum efficiency of 41.6% and host sensitized luminescence in GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors with abundant color in response to UV light and electron beams. The GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors were synthesized by a Pechini-type sol-gel process. With excitation of UV light and low-voltage electron beams, the obtained GdNbO 4 nanocrystalline phosphor presents a strong blue luminescence from 280 to 650 nm centered around 440 nm, and the GdNbO 4 :Ln 3+ nanocrystalline phosphors show both host emission and respective emission lines derived from the characterize f-f transitions of the doping Eu 3+ , Tb 3+ , and Tm 3+ ions. The luminescence color of GdNbO 4 :Ln 3+ nanocrystalline phosphors can be tuned from blue to green, red, blue-green, orange, pinkish, white, etc. by varying the doping species, concentration, and relative ratio of the codoping rare earth ions in GdNbO 4 host lattice. A single-phase white-light-emission has been realized in Eu 3+ /Tb 3+ /Tm 3+ triply doped GdNbO 4 nanocrystalline phosphors. The luminescence properties and mechanisms of GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) are updated.

An investigation of the photosubstitution reaction between N719-dyed nanocrystalline TiO2 particles and 4-tert-butylpyridine

DEFF Research Database (Denmark)

Nour-Mohammadi, Farahnaz; Nguyen, Thai Hoang; Boschloo, Gerrit

2007-01-01

concentration. Based on this observation, a degradation mechanism was proposed, in which the reaction proceeds through the rate-determining formation of a common intermediate complex, I=[RuII(H2dcbpy)2(NCS)(NCS)]+. An average degradation rate of kdeg=6×10-3s-1 was obtained from the value of Φdeg and the back...... electron-transfer rate, kback of the reaction TiO2+e-|N719+→TiO2|N719, obtained by means of photo-induced absorption (PIA) measurements. The lifetime of the solar cell sensitizer N719 was estimated to be between 34 years, based on kdeg and an average literature value of the regeneration rate, kreg=2×106M-1...... simple model experiments. In these experiments, colloidal solutions of N719-dyed nanocrystalline TiO2 particles in acetonitrile were irradiated with 532-nm laser light in the presence of 0-1mol/l of 4-TBP. Five degradation products were identified using LC-ESI-MS: the 4-tert-butylpyridine substitution...

Rapid charge-discharge property of Li4Ti5O12-TiO2 nanosheet and nanotube composites as anode material for power lithium-ion batteries.

Science.gov (United States)

Yi, Ting-Feng; Fang, Zi-Kui; Xie, Ying; Zhu, Yan-Rong; Yang, Shuang-Yuan

2014-11-26

Well-defined Li4Ti5O12-TiO2 nanosheet and nanotube composites have been synthesized by a solvothermal process. The combination of in situ generated rutile-TiO2 in Li4Ti5O12 nanosheets or nanotubes is favorable for reducing the electrode polarization, and Li4Ti5O12-TiO2 nanocomposites show faster lithium insertion/extraction kinetics than that of pristine Li4Ti5O12 during cycling. Li4Ti5O12-TiO2 electrodes also display lower charge-transfer resistance and higher lithium diffusion coefficients than pristine Li4Ti5O12. Therefore, Li4Ti5O12-TiO2 electrodes display lower charge-transfer resistance and higher lithium diffusion coefficients. This reveals that the in situ TiO2 modification improves the electronic conductivity and electrochemical activity of the electrode in the local environment, resulting in its relatively higher capacity at high charge-discharge rate. Li4Ti5O12-TiO2 nanocomposite with a Li/Ti ratio of 3.8:5 exhibits the lowest charge-transfer resistance and the highest lithium diffusion coefficient among all samples, and it shows a much improved rate capability and specific capacity in comparison with pristine Li4Ti5O12 when charging and discharging at a 10 C rate. The improved high-rate capability, cycling stability, and fast charge-discharge performance of Li4Ti5O12-TiO2 nanocomposites can be ascribed to the improvement of electrochemical reversibility, lithium ion diffusion, and conductivity by in situ TiO2 modification.

In situ synthesis of Ti{sub 2}AlC–Al{sub 2}O{sub 3}/TiAl composite by vacuum sintering mechanically alloyed TiAl powder coated with CNTs

Energy Technology Data Exchange (ETDEWEB)

Wang, Jian [Department of Materials Science and Engineering of Tianjin University, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China); Zhao, Naiqin, E-mail: nqzhao@tju.edu.cn [State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin (China); Department of Materials Science and Engineering of Tianjin University, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China); Nash, Philip [Thermal Processing Technology Center, Illinois Institute of Technology, IL (United States); Liu, Enzuo; He, Chunnian; Shi, Chunsheng; Li, Jiajun [Department of Materials Science and Engineering of Tianjin University, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China)

2013-11-25

Highlights: •Using zwitterionic surfactant to enhance the dispersion of the CNTs on the powder surface. •CNTs as carbon source decreased the formation temperature of Ti{sub 2}AlC. •Al{sub 2}O{sub 3} was generated in situ from the oxygen atoms introduced in the drying procedure. •Nanosized Ti{sub 3}Al was precipitated at 1250 °C and distribute in the TiAl matrix homogeneously. •Ti{sub 2}AlC–Al{sub 2}O{sub 3}/TiAl composite was synthesized in situ by sintering pre-alloy Ti–Al coated with CNTs. -- Abstract: Bulk Ti{sub 2}AlC–Al{sub 2}O{sub 3}/TiAl composites were in situ synthesized by vacuum sintering mechanically alloyed Ti–50 at.% Al powders coated with carbon nanotubes (CNTs). The pre-alloyed Ti–50 at.% Al powder was obtained by ball milling Ti and Al powders. The multi-walled carbon nanotubes as the carbon resource were covered on the surface of the pre-alloyed powders by immersing them into a water solution containing the CNTs. A zwitterionic surfactant was used to enhance the dispersion of the CNTs on the powder surface. The samples were cold pressed and sintered in vacuum at temperatures from 950 to 1250 °C, respectively. The results show that the reaction of forming Ti{sub 2}AlC can be achieved below 950 °C, which is 150 °C lower than in the Ti–Al–TiC system and 250 °C lower than for the Ti–Al–C system due to the addition of CNTs. Additionally, the reinforcement of Al{sub 2}O{sub 3} particles was introduced in situ in Ti{sub 2}AlC/TiAl by the drying process and subsequent sintering of the composite powders. Dense Ti{sub 2}AlC–Al{sub 2}O{sub 3}/TiAl composites were obtained by sintering at 1250 °C and exhibited a homogeneous distribution of Ti{sub 2}AlC, Al{sub 2}O{sub 3} and precipitated Ti{sub 3}Al particles and a resulting high hardness.

Carbon coated Li{sub 4}Ti{sub 5}O{sub 12} nanorods as superior anode material for high rate lithium ion batteries

Energy Technology Data Exchange (ETDEWEB)

Luo, Hongjun; Shen, Laifa; Rui, Kun; Li, Hongsen; Zhang, Xiaogang, E-mail: azhangxg@nuaa.edu.cn

2013-09-25

Highlights: •A novel approach has been developed to fabricate 1D Li{sub 4}Ti{sub 5}O{sub 12}/C nanorods by a wet-chemical route. •Carbon coating layer effectively restrict the particle growth and enhance electronic conductivity. •The Li{sub 4}Ti{sub 5}O{sub 12}/C nanorods exhibit remarkable rate capability and long cycle life. -- Abstract: We describe a novel approach for the synthesis of carbon coated Li{sub 4}Ti{sub 5}O{sub 12} (Li{sub 4}Ti{sub 5}O{sub 12}/C) nanorods for high rate lithium ion batteries. The carbon coated TiO{sub 2} nanotubes using the glucose as carbon source are first synthesized by hydrothermal treatment. The commercial anatase TiO{sub 2} powder is immersed in KOH sulotion and subsequently transforms into Li{sub 4}Ti{sub 5}O{sub 12}/C in LiOH solution under hydrothermal condition. Field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption/desorption and Raman spectra are performed to characterize their morphologies and structures. Compared with the pristine Li{sub 4}Ti{sub 5}O{sub 12}, one-dimensional (1D) Li{sub 4}Ti{sub 5}O{sub 12}/C nanostructures show much better rate capability and cycling stability. The 1D Li{sub 4}Ti{sub 5}O{sub 12}/C architectures effectively restrict the particle growth and enhance their electronic conductivity, enabling fast ion and electron transport.

Theoretical Verification of Photoelectrochemical Water Oxidation Using Nanocrystalline TiO2 Electrodes

Directory of Open Access Journals (Sweden)

Shozo Yanagida

2015-05-01

Full Text Available Mesoscopic anatase nanocrystalline TiO2 (nc-TiO2 electrodes play effective and efficient catalytic roles in photoelectrochemical (PEC H2O oxidation under short circuit energy gap excitation conditions. Interfacial molecular orbital structures of (H2O3 &OH(TiO29H as a stationary model under neutral conditions and the radical-cation model of [(H2O3&OH(TiO29H]+ as a working nc-TiO2 model are simulated employing a cluster model OH(TiO29H (Yamashita/Jono’s model and a H2O cluster model of (H2O3 to examine excellent H2O oxidation on nc-TiO2 electrodes in PEC cells. The stationary model, (H2O3&OH(TiO29H reveals that the model surface provides catalytic H2O binding sites through hydrogen bonding, van der Waals and Coulombic interactions. The working model, [(H2O3&OH(TiO29H]+ discloses to have a very narrow energy gap (0.3 eV between HOMO and LUMO potentials, proving that PEC nc-TiO2 electrodes become conductive at photo-irradiated working conditions. DFT-simulation of stepwise oxidation of a hydroxide ion cluster model of OH−(H2O3, proves that successive two-electron oxidation leads to hydroxyl radical clusters, which should give hydrogen peroxide as a precursor of oxygen molecules. Under working bias conditions of PEC cells, nc-TiO2 electrodes are now verified to become conductive by energy gap photo-excitation and the electrode surface provides powerful oxidizing sites for successive H2O oxidation to oxygen via hydrogen peroxide.

Residual tensile stresses and piezoelectric properties in BiFeO3-Bi(Zn1/2Ti1/2O3-PbTiO3 ternary solid solution perovskite ceramics

Directory of Open Access Journals (Sweden)

Weilin Zheng

2016-08-01

Full Text Available For low dielectric loss perovskite-structured (1-x-yBiFeO3-xBi(Zn1/2Ti1/2O3-yPbTiO3 (BF-BZT-PT (x = 0.04-0.15 and y = 0.15-0.26 ceramics in rhombohedral/tetragonal coexistent phase, structural phase transitions were studied using differential thermal analyzer combined with temperature-dependent dielectric measurement. Two lattice structural phase transitions are disclosed in various BF-BZT-PT perovskites, which is different from its membership of BiFeO3 exhibiting just one lattice structural phase transition at Curie temperature TC= 830oC. Consequently, residual internal tensile stresses were revealed experimentally through XRD measurements on ceramic pellets and counterpart powders, which are reasonably attributed to special structural phase transition sequence of BF-BZT-PT solid solution perovskites. Low piezoresponse was observed and argued extrinsically resulting from residual tensile stresses pinning ferroelectric polarization switching. Post-annealing and subsequent quenching was found effective for eliminating residual internal stresses in those BZT-less ceramics, and good piezoelectric property of d33 ≥ 28 pC/N obtained for 0.70BF-0.08BZT-0.22PT and 0.05 wt% MnO2-doped 0.70BF-0.04BZT-0.26PT ceramics with TC ≥ 640oC, while it seemed no effective for those BZT-rich BF-BZT-PT ceramics with x = 0.14 and 0.15 studied here.

Electrochemical Behavior of TiO2 Nanoparticle Doped WO3 Thin Films

Directory of Open Access Journals (Sweden)

Suvarna R. Bathe

2014-01-01

Full Text Available Nanoparticle TiO2 doped WO3 thin films by pulsed spray pyrolysis technique have been studied on fluorine tin doped (FTO and glass substrate. XRD shows amorphous nature for undoped and anatase phase of TiO2 having (101 plane for nanoparticle TiO2 doped WO3 thin film. SEM shows microfibrous reticulated porous network for WO3 with 600 nm fiber diameter and nanocrystalline having size 40 nm for TiO2 nanoparticle doped WO3 thin film. TiO2 nanoparticle doped WO3 thin film shows ~95% reversibility due to may be attributed to nanocrystalline nature of the film, which helpful for charge insertion and deinsertion process. The diffusion coefficient for TiO2 nanoparticle doped WO3 film is less than undoped WO3.

Facile preparation of Ti{sup 3+} self-doped TiO{sub 2} nanosheets with dominant {0 0 1} facets using zinc powder as reductant

Energy Technology Data Exchange (ETDEWEB)

Si, Lingling; Huang, Ze’ai; Lv, Kangle, E-mail: lvkangle@mail.scuec.edu.cn; Tang, Dingguo; Yang, Changjun

2014-07-15

Highlights: • Ti{sup 3+}-doped high-energy TiO{sub 2} nanosheets was prepared using zinc powder as reductant. • Effects of Zn on morphology and BET surface areas of TiO{sub 2} nanosheets is negligible. • Zn powder resulted in the formation of Ti{sup 3+} self-doped anatase TiO{sub 2} nanosheets. • Ti{sup 3+} self-doped TiO{sub 2} nanosheets showed enhanced visible-light photoactivity. - Abstract: Ti{sup 3+} self-doped TiO{sub 2} nanosheets with dominant {0 0 1} facets for excellent visible-light photocatalytic activity were prepared by a facile one-pot hydrothermal reaction strategy using tetrabutyl titanate (TBT) as titanium source, hydrofluoric acid (HF) as structure-directing agent and zinc powder (Zn) as reductant. The synthesized catalysts were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectra (XPS), diffuse reflectance spectrum (DRS) and nitrogen adsorption–desorption isotherms. The photocatalytic activity of the photocatalyst was evaluated by measure the formation rate of photo-induced hydroxyl radicals (·OH) under visible-light irradiation (λ = 420 ± 10 nm) using coumarin as a probe. It was found that the presence of zinc shows little effect on the morphology, phase structure, BET surface areas and pore structure. However, the addition of Zn powder resulted in the formation of Ti{sup 3+} self-doped anatase TiO{sub 2} nanosheets with dominant {0 0 1} facets, which is responsible for the enhanced visible-light photocatalytic activity. The sample prepared with zinc/TBT molar ratio of 0.3 showed the highest visible-light photocatalytic activity, which is 1.9 times higher than that of commercial P25 TiO{sub 2}.

A promising tritium breeding material: Nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles

Science.gov (United States)

Dang, Chen; Yang, Mao; Gong, Yichao; Feng, Lan; Wang, Hailiang; Shi, Yanli; Shi, Qiwu; Qi, Jianqi; Lu, Tiecheng

2018-03-01

As an advanced tritium breeder material for the fusion reactor blanket of the International Thermonuclear Experimental Reactor (ITER), Li2TiO3-Li4SiO4 biphasic ceramic has attracted widely attention due to its merits. In this paper, the uniform precursor powders were prepared by hydrothermal method, and nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles were fabricated by an indirect wet method at the first time. In addition, the composition dependence (x/y) of their microstructure characteristics and mechanical properties were investigated. The results indicated that the crush load of biphasic ceramic pebbles was better than that of single phase ceramic pebbles under identical conditions. The 2Li2TiO3-Li4SiO4 ceramic pebbles have good morphology, small grain size (90 nm), satisfactory crush load (37.8 N) and relative density (81.8 %T.D.), which could be a promising breeding material in the future fusion reactor.

Synthesis and electrochemical properties of Li4Ti5O12

CSIR Research Space (South Africa)

Liu, GQ

2011-06-01

Full Text Available The spinel compound Li4Ti5O12 was synthesized by a solid state method. In this synthesizing process, anatase TiO2 and Li2CO3 were used as reactants. The influences of reaction temperature and calcination time on the properties of products were...

Magnetic and Mössbauer studies of pure and Ti-doped YFeO {sub 3} nanocrystalline particles prepared by mechanical milling and subsequent sintering

Energy Technology Data Exchange (ETDEWEB)

Khalifa, N. O. [University of Khartoum, Physics Department, Faculty of Science (Sudan); Widatallah, H. M., E-mail: hishammw@squ.edu.om; Gismelseed, A. M.; Al-Mabsali, F. N.; Sofin, R. G. S. [Sultan Qaboos University, Physics Department, College of Science (Oman); Pekala, M. [University of Warsaw, Chemistry Department (Poland)

2016-12-15

Single-phased nanocrystalline particles of pure and 10 % Ti {sup 4+}-doped perovskite-related YFeO {sub 3}were prepared via mechanosynthesis at 450{sup ∘}C. This temperature is ∼150–350 {sup ∘}C lower than those at which the materials, in bulk form, are normally prepared. Rietveld refinements of the X-ray diffraction patterns reveal that the dopant Ti {sup 4+} ions prefer interstitial octahedral sites in the orthorhombic crystal lattice rather than those originally occupied by the expelled Fe {sup 3+} ions. Magnetic measurements show canted antiferromagnetism in both types of nanoparticles. Doping with Ti {sup 4+} lowers the Néel temperature of the YFeO {sub 3} nanoparticles from ∼ 586 K to ∼ 521 K. The Ti {sup 4+}-doped YFeO {sub 3} nanoparticles exhibit enhanced magnetization and coercivity but less magnetic hyperfine fields relative to the un-doped nanoparticles. The {sup 57}Fe Mössbauer spectra show ∼ 15 % of the YFeO {sub 3} nanoparticles and ∼22 of Ti {sup 4+}-doped YFeO {sub 3} ones to be superparamagnetic with blocking temperatures < 78 K. The broadened magnetic components in the {sup 57}Fe Mössbauer spectra suggest size-dependent hyperfine magnetic fields at the {sup 57}Fe nuclear sites and were associated with collective magnetic excitations. The {sup 57}Fe Mössbauer spectra show the local environments of the Fe {sup 3+} ions in the superparamagnetic nanoparticles to be more sensitive to the presence of the Ti {sup 4+} ions relative to those in the larger magnetic nanoparticles.

Sintered powder cores of high Bs and low coreloss Fe84.3Si4B8P3Cu0.7 nano-crystalline alloy

Directory of Open Access Journals (Sweden)

Yan Zhang

2013-06-01

Full Text Available Nano-crystalline Fe-rich Fe84.3Si4B8P3Cu0.7 alloy ribbon with saturation magnetic flux density (Bs close to Si-steel exhibits much lower core loss (Wt than Si-Steels. Low glass forming ability of this alloy limits fabrication of magnetic cores only to stack/wound types. Here, we report on fabrication, structural, thermal and magnetic properties of bulk Fe84.3Si4B8P3Cu0.7 cores. Partially crystallized ribbons (obtained after salt-bath annealing treatment were crushed into powdered form (by ball milling, and were compacted to high-density (∼88% bulk cores by spark plasma sintering (SPS. Nano-crystalline structure (consisting of α-Fe grain in remaining amorphous matrix similar to wound ribbon cores is preserved in the compacted cores. At 50 Hz, cores sintered at Ts = 680 K show Wt 1 kHz. A trade-off between porosity and electrical resistivity is necessary to get low Wt at higher f. In the f range of ∼1 to 100 kHz, we have shown that the cores mixed with SiO2 exhibit much lower Wt than Fe-powder cores, non-oriented Si-steel sheets and commercially available sintered cores. We believe our core material is very promising to make power electronics/electrical devices much more energy-efficient.

Preparation and characterization of phase-pure anatase and rutile TiO{sub 2} powder by new chemistry route; Preparacao e caracterizacao de nanoparticulas de TiO{sub 2} nas fases anatase e rutila por uma nova rota quimica

Energy Technology Data Exchange (ETDEWEB)

Pereira, E. A.; Montanhera, M.A.; Paula, F.R., E-mail: sevlarede2@yahoo.com.br [Universidade Estadual Paulista Julio de Mesquista Filho (UNESP), Ilha Soltiera, SP (Brazil). Faculdade de Engenharia. Departameinto de Fisica e Quimica; Spada, E.R. [Universidade de Sao Paulo (USP), Sao Carlos, SP (Brazil). Institutlo de Fisica

2014-07-01

Titanium dioxide (TiO{sub 2}) is used in a wire range applications such as photocatalysis and sensor device. In this work is shown a new and effective method for the preparation of TiO{sub 2} nanocrystalline in the crystallographic forms, anatase and rutile. The method involves dissolving the TiOSO{sub 4} powder in H{sub 2}O{sub 2} solution and thermal treatment of amorphous precipitate. The technique of X-ray diffraction was used to follow the structure evolution of amorphous precipitate. Pure anatase structure and rutile are obtained at 600 deg C and 1000 deg C with a grain size estimated 24 and 55 nm respectively. TiO{sub 2} nanoparticles is a promising alternative of the low cost whose potential for solar cells deserve a careful evaluation, especially in hybrid solar cells that employs TiO{sub 2} as electron acceptor and as transport channels. (author)

Microstructure characterization of nanocrystalline TiC synthesized by mechanical alloying

International Nuclear Information System (INIS)

Ghosh, B.; Pradhan, S.K.

2010-01-01

Nanocrystalline TiC is produced by mechanical milling the stoichiometric mixture of α-Ti and graphite powders at room temperature under argon atmosphere within 35 min of milling through a self-propagating combustion reaction. Microstructure characterization of the unmilled and ball-milled samples was done by both X-ray diffraction and electron microscopy. It reveals the fact that initially graphite layers were oriented along and in the course of milling, thin graphite layers were distributed evenly among the grain boundaries of α-Ti particles. Both α-Ti and TiC lattices contain stacking faults of different kinds. The grain size distribution obtained from the Rietveld's method and electron microscopy studies ensure that nanocrystalline TiC particles with almost uniform size (∼13 nm) can be prepared by mechanical alloying technique. The result obtained from X-ray analysis corroborates well with the microstructure characterization of nanocrystalline TiC by electron microscopy.

Li_2ZrO_3-coated Li_4Ti_5O_1_2 with nanoscale interface for high performance lithium-ion batteries

International Nuclear Information System (INIS)

Zhang, Han; Liu, Yang; Wang, Ting; Yang, Yang; Shi, Shaojun; Yang, Gang

2016-01-01

Graphical abstract: - Highlights: • Zr doped and Li_2ZrO_3 coated Li_4Ti_5O_1_2 are prepared by a solid-state method. • Zr-doping and LZO coating are positive in improving lithium diffusion ability. • Li_2ZrO_3 coated Li_4Ti_5O_1_2 deliver 168.1 mAh g"−"1 higher than 150.2 mAh g"−"1 of Li_4Ti_5O_1_2. • Li_2ZrO_3 coated Li_4Ti_5O_1_2 remains 162 mAh g"−"1 after 100 cycles. • The lowest D_L_i"+ is 5.97 × 10"−"1"7 and 1.85 × 10"−"1"5 cm"2 s"−"1 of Li_4Ti_5O_1_2 before and after coating. - Abstract: Zr doped sample of Li_4Ti_4_._9_9Zr_0_._0_1O_1_2 (LZTO) and Li_2ZrO_3 (LZO) coated Li_4Ti_5O_1_2 (LTO) are prepared by a solid-state method. The lattice structure of LTO is remained after doping element of Zr and coating layer of LZO. The crystal structure and electrochemical performance of the material are investigated by X-ray diffractometry (XRD), high-resolution transmission electron microscopy (HRTEM), cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) and charge-discharge tests, respectively. Zr-doping and LZO coating play the positive role in improving the diffusion ability of lithium cations. LZTO and LZO-LTO show much improved specific capacity and rate capability compared with pristine sample of LTO. LZO-LTO has the smallest voltage differential (ΔV) of the redox peaks because the coating of Li_2ZrO_3 is helpful for the diffusion ability of lithium ions during charge/discharge processes. LZTO and LZO-LTO as electrode deliver the initial capacities of 164.8, 168.1 mAh g"−"1, respectively, which are much higher than 150.2 mAh g"−"1 of intrinsic sample of LTO. Even at the current density of 2 A g"−"1, LTZO and LZO-LTO offer capacity of 96 and 106 mAh g"−"1, which are much higher than 33 mAh g"−"1 of LTO. The improved electrochemical performance is attributed to the improved diffusion ability of lithium. During the whole discharge process, the lowest value of LTO is 5.97 × 10"−"1"7 cm"2 s"−"1 that is

Anti-fish bacterial pathogen effect of visible light responsive Fe{sub 3}O{sub 4}@TiO{sub 2} nanoparticles immobilized on glass using TiO{sub 2} sol–gel

Energy Technology Data Exchange (ETDEWEB)

Yeh, N. [Center of General Education, MingDao University, Taiwan (China); Lee, Y.C. [Graduate Institute of Materials Engineering, National Pingtung University of Science and Technology, Taiwan (China); Chang, C.Y. [Center of General Education, National Taitung Junior College, Taiwan (China); Cheng, T.C., E-mail: cheng.tachih@gmail.com [Department of Tropical Agriculture and International Cooperation, National Pingtung University of Science and Technology, Taiwan (China)

2013-12-31

This paper demonstrates a fish pathogen reduction procedure that uses TiO{sub 2} sol–gel coating Fe{sub 3}O{sub 4}@TiO{sub 2} powder on glass substrate. Such procedure can effectively relieve two constraints that haunt TiO{sub 2} sterilization applications: 1) the need for UV for overcoming the wide band gap of pure TiO{sub 2} and 2) the difficulty of its recovering from water for reuse. In the process, visible light responsive Fe{sub 3}O{sub 4}/TiO{sub 2} nanoparticles are synthesized and immobilized on glass using TiO{sub 2} sol–gel as the binder for fish bacterial pathogen disinfection test. After 3 h of visible light irradiation, the immobilized Fe{sub 3}O{sub 4}@TiO{sub 2}'s inhibition efficiencies for fish bacterial pathogen are, respectively, 50% for Edwardsiella tarda (BCRC 10670) and 23% for Aeromonas hydrophila (BCRC 13018)

Charge retention characteristics of (Bi,La)4Ti3O12 capacitors : comparison with Pb(Zr,Ti)O3 capacitors

International Nuclear Information System (INIS)

Yoon, J. G.; Kim, D. J.; So, Y. W.

2005-01-01

We investigated the retention characteristics of (Bi,La) 4 Ti 3 O 12 (BLT) capacitors with Pt electrodes and compared them with Pb(Zr,Ti)O 3 (PZT) capacitors in the same- and opposite-state retentions. Polarization relaxations in short-time regime (t < 100 s) were well described by a power-law decay function, but the polarization relaxation of BLT was more significant than that of PZT. We discuss the difference in the relaxation process of polarization in conjunction with film microstructures and magnitudes of polarization for BLT and PZT. In long-time opposite-state retention, BLT capacitors showed much better characteristics than PZT. For both BLT and PZT, the opposite-state retention loss was governed by the development of an internal field during retention. For BLT capacitors, internal field development was much weaker than for PZT after retention, resulting in a good opposite-state retention. Structural and electrical properties are discussed in conjunction with the retention characteristics of the materials.

Zn2+ in-situ substitution behavior during the formation of BaTiO3 coatings from plasma-sprayed powders collected in liquid nitrogen

Science.gov (United States)

Liu, Zhe; Xing, Zhiguo; Wang, Haidou; Xue, Zifan; Chen, Shuying; Cui, Xiufang; Jin, Guo

2018-04-01

The dielectric performance of BaTiO3 ceramic coatings is enhanced significantly by the addition of ZnO. In this study, the maximum relative permittivity value (εr ≈ 923) was measured in BaTiO3 coatings with ZnO added at 6 wt%. The Curie temperature (Tc) was in the range of 111 °C-121 °C for all of the ZnO-modified BaTiO3 coatings. Tc shifted to low temperatures as the ZnO content increased. Detailed analyses were performed to determine the phase composition and optical band gaps of powders collected in liquid nitrogen, which showed that the Zn2+ ions were incorporated into the BaTiO3 lattice where they substituted into the Ti4+ sites, and the composite powders (BaTiO3 + 6 wt% ZnO) tolerated high temperatures in the plasma beam. In addition, some residual Zn accumulated in the grain boundary in the form of ZnO. X-ray diffraction and Raman spectroscopy showed that the substitution led to changes in the compositional and structural properties. The red shift in the optical band gap of BaTiO3 indicated that the ZnTi'' defects caused by the dopants acted as carriers in the doped BaTiO3 coatings.

Presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution: A Rietveld study

Energy Technology Data Exchange (ETDEWEB)

Pandey, Rishikesh, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in; Singh, Akhilesh Kumar, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

2014-07-28

We present here the results of structural studies on multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution using Rietveld analysis on powder x-ray diffraction data in the composition range 0.35 ≤ x ≤ 0.55. The stability region of various crystallographic phases at room temperature for (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} is determined precisely. Structural transformation from pseudo-cubic (x ≤ 0.40) to tetragonal (x ≥ 0.50) phase is observed via phase coexistence region demarcating the morphotropic phase boundary. The morphotropic phase boundary region consists of coexisting tetragonal and monoclinic structures with space group P4mm and Pm, respectively, stable in composition range 0.41 ≤ x ≤ 0.49 as confirmed by Rietveld analysis. The results of Rietveld analysis completely rule out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier workers. A comparison between the bond lengths for “B-site cations-oxygen anions” obtained after Rietveld refinement, with the bond length calculated using Shannon-Prewitt ionic radii, reveals the ionic nature of B-O (Ni/Ti-O) bonds for the cubic phase and partial covalent character for the other crystallographic phases.

CoFe2O4 nanocrystalline powders prepared by citrate-gel methods: Synthesis, structure and magnetic properties

International Nuclear Information System (INIS)

Cannas, C.; Falqui, A.; Musinu, A.; Peddis, D.; Piccaluga, G.

2006-01-01

Nanocrystalline CoFe 2 O 4 powders were prepared by decomposition of metal ion citrate precursors. Four samples were synthesized from precursor solutions having different pH values in the range 2 physisorption and Transmission Electron Microscopy. Magnetic properties were explored by a SQUID magnetometer. Three out of the four samples, coming from solutions of pH 2, 4 and 7, were produced by an autocombustion reaction and are very similar as regards average size of the nanoparticles (about 20 nm), their morphology and the magnetic properties, while the fourth sample was produced by a slower thermal decomposition and is composed of smaller nanoparticles (about 10 nm)

Physical characteristics and magnetic properties of BaFe12O19/SrTiO3 based composites derived from mechanical alloying

International Nuclear Information System (INIS)

Widodo, Rahmat Doni; Manaf, Azwar

2016-01-01

A composite system BaFe 12 O 19 /SrTiO 3 with ferrimagnetic BaFe 12 O 19 phase (BHF) and ferroelectric SrTiO 3 phase (STO) have been prepared by mechanical alloying and subsequent heat treatment. The composite powders were studied by Particle Size Analyze, X-ray diffraction and magnetic measurement. It was found that the particle size of composite powders initially increased due to laminated layers formation of a composite and then decreased to an asymptotic value of ∼8 µm as the milling time extended even to a relatively longer time. However, based on results of line broadening analysis the mean grain size of the particles was found in the nanometer scale. We thus believed that mechanical blending and milling of mixture components for the composite materials has promoted heterogeneous nucleation and only after successive sintering at 1100°C the milled powder transformed into particles of nanograin. In this report, microstructure as well as magnetic properties for the composite is also briefly discussed.

Studies on the synthesis of nanocrystalline Y{sub 2}O{sub 3} and ThO{sub 2} through volume combustion and their sintering

Energy Technology Data Exchange (ETDEWEB)

Sanjay Kumar, D. [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Ananthasivan, K., E-mail: asivan@igcar.gov.in [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Venkata Krishnan, R. [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Amirthapandian, S. [Material Physics Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Dasgupta, Arup [Microscopy and Thermo-Physical Property Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India)

2016-10-15

Volume combustion was observed in the auto-ignition of the citrate gels containing the nitrates of yttrium/thorium for the first time in mixture with a fuel (citric acid) to oxidant (Y{sup 3+} or Th{sup 4+} nitrate) ratio close to that demanded by the stoichiometry. These nanocrystalline powders were characterized for their bulk density, specific surface area, particle size distribution, carbon residue and X-ray crystallite size and were sintered by both the conventional and the two-step method. The maximum relative sintered density of Y{sub 2}O{sub 3} was 98.9% TD. The sintered density of thoria (97.8% TD) is the highest among the values reported so far, for nanocrystalline ThO{sub 2}. Characterization of the pellets and powders by using scanning electron microscopy and transmission electron microscopy reaffirmed nanocrystallinity and that the sintered pellets comprised faceted sintered grains. The two-step sintering was found to restrict “runaway” sintering. - Highlights: • Scaled-up synthesis of nanocrystalline Y{sub 2}O{sub 3} and ThO{sub 2} using citrate gel-combustion method. • VCR was observed at a fuel to nitrate ratio (R) of 0.125 and 0.17 in mixtures containing Th(NO{sub 3}){sub 4} and Y(NO{sub 3}){sub 3} respectively. • The calcined powders were compacted and sintered by using a novel two-step sintering method. • Sintered densities as high as 97.8% T.D. (ThO{sub 2}, T{sub H} = 0.48) and 98.9% T.D. (Y{sub 2}O{sub 3}, T{sub H} = 0.61) were obtained.

Photocatalytic Activity in CH3CN Related to the Surface Properties of TiO2 Powders Prepared by Sol-Gel Method

Directory of Open Access Journals (Sweden)

Marta Bettoni

2009-01-01

Full Text Available Some TiO2 powders, prepared from titanium(IVtetraisopropoxide by the sol-gel method and thermally treated between 100 and 1000∘C, have been characterized by X-ray powder diffraction and by nitrogen adsorption and desorption at 77 K to calculate the BET-specific surface area, from which the micropore volume and the external surface area can be derived. The photocatalytic activity (ka of the above powders has been evaluated considering the TiO2-sensitized photo-oxidation of 4-methoxybenzyl alcohol in CH3CN as the test reaction. The decrease of ka have been related to the decrease of the BET surface area, the micropore volume, and the external surface area of the TiO2 powders, but a satisfactory linear correlation is observed only for the last superficial parameter.

Investigating the local structure of B-site cations in (1-x)BaTiO3-xBiScO3 and (1-x)PbTiO3-xBiScO3 using X-ray absorption spectroscopy

Science.gov (United States)

Blanchard, Peter E. R.; Grosvenor, Andrew P.

2018-05-01

The structural properties of (1-x)BaTiO3-xBiScO3 and (1-x)PbTiO3-xBiScO3 were investigated using powder X-ray diffraction and X-ray absorption spectroscopy. Diffraction measurements confirmed that substituting small amounts of BiScO3 into BaTiO3 initially stabilizes a cubic phase at x = 0.2 before impurity phases begin to form at x = 0.5. BiScO3 substitution also resulted in noticeable changes in the local coordination environment of Ti4+. X-ray absorption near-edge spectroscopy (XANES) analysis showed that replacing Ti4+ with Sc3+ results in an increase in the off-centre displacement of Ti4+ cations. Surprisingly, BiScO3 substitution has no effect on the displacement of the Ti4+ cation in the (1-x)PbTiO3-xBiScO3 solid solution.

Preparation, characterization and luminescence of nanocrystalline Y2O3:Ho

International Nuclear Information System (INIS)

Biljan, Tomislav; Gajovic, Andreja; Meic, Zlatko; Mestrovic, Ernest

2007-01-01

Nanocrystalline Y 2 O 3 :Ho was synthesized by solution combustion method with ethylene glycol as fuel. Material was characterized using powder X-ray diffraction and transmission electron microscopy (TEM). X-ray diffraction and TEM showed that the material is nanostructured. Luminescence properties were studied using Raman spectrometers with excitation in near infrared (NIR) and visible regions. The visible and NIR luminescence spectra of nanocrystalline Y 2 O 3 :Ho show some important differences from those of bulk material. The convenience of using Raman instruments for studying luminescence of lanthanide ions is demonstrated

Anatase-TiO{sub 2} nanocoating of Li{sub 4}Ti{sub 5}O{sub 12} nanorod anode for lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Chen, Ming-ming, E-mail: chmm@tju.edu.cn; Sun, Xin; Qiao, Zhi-jun; Ma, Qian-qian; Wang, Cheng-yang

2014-07-15

Highlights: • TiO{sub 2}-coated LTO was in-situ prepared via a microemulsion-assisted hydrothermal route. • Anatase-TiO{sub 2} coating layer enhances the electrochemical performance of Li{sub 4}Ti{sub 5}O{sub 12}. • The as-prepared sample presents high-rate capability and cyclic stability. - Abstract: Li{sub 4}Ti{sub 5}O{sub 12} nanorod coated by anatase-TiO{sub 2} is in situ synthesized via a microemulsion-assisted hydrothermal method followed by heat treatment at 550 °C in air. Compared with pure Li{sub 4}Ti{sub 5}O{sub 12}, Li{sub 4}Ti{sub 5}O{sub 12} nanorod coated by anatase-TiO{sub 2} presents much improved electrochemical characteristics in terms of high specific capacity, excellent rate capability and cyclic stability (96.0% of initial capacity at a current density of 1.75 A g{sup −1} up to 100 cycles). Acting as a perfect nanocoating layer, anatase-TiO{sub 2} contributes some capacity and gives an enhanced performance to the Li{sub 4}Ti{sub 5}O{sub 12} electrode. All the results suggest that Li{sub 4}Ti{sub 5}O{sub 12} nanorod coated by anatase-TiO{sub 2} could be suitable for use as a high-rate anode material for lithium-ion batteries.

Synthesis, structural characterization of nano ZnTiO3 ceramic: An effective azo dye adsorbent and antibacterial agent

Directory of Open Access Journals (Sweden)

R.S. Raveendra

2014-12-01

Full Text Available Nanocrystalline meta-zinc titanate (ZnTiO3 ceramic was prepared using a self-propagating solution combustion synthesis (SCS for the first time using urea as fuel. The product was calcined at 800 °C for 2 h to improve the crystallinity. Powder X-ray diffraction (PXRD, Fourier transform infrared spectroscopy (FTIR, scanning electron microscopy (SEM, energy-dispersive X-ray spectroscopy (EDAX, high resolution transmission electron microscopy (HR-TEM and UV–vis absorption spectroscopy were used to characterize the final product. PXRD results show that the ilmenite type rhombohedral structure was formed when the sample was calcined at 800 °C for 2 h. Adsorption experiments were performed with cationic malachite green (MG dye. ∼96% dye was adsorbed onto nanocrystalline ZnTiO3 ceramic at pH 9 for 30 min of the contact time. The optimum adsorbent dose was found to be 0.45 g/L of dye. Langmuir–Hinshelwood model was used to study adsorption kinetics and first order kinetic model best describes the MG adsorption on ZnTiO3. Antibacterial activity was investigated against gram negative Klebsiella aerogenes, Pseudomonas desmolyticum, Escherichia coli, and gram positive Staphylococcus aureus bacteria by agar well diffusion method. Nanocrystalline ZnTiO3 ceramic showed significant effect on all the four bacterial strains at the concentration of 1000 and 1500 μg per well.

Preparation of Fluorine-Doped TiO2 Photocatalysts with Controlled Crystalline Structure

Directory of Open Access Journals (Sweden)

N. Todorova

2008-01-01

Full Text Available Nanocrystalline F-doped TiO2 powders were prepared by sol-gel route. The thermal behavior of the powders was recorded by DTA/TG technique. The crystalline phase of the fluorinated TiO2 powders was determined by X-ray diffraction technique. It was demonstrated that F-doping using CF3COOH favors the formation of rutile along with anatase phase even at low temperature. Moreover, the rutile's phase content increases with the increase of the quantity of the fluorine precursor in the starting solution. The surface area of the powders and the pore size distribution were studied by N2 adsorption-desorption using BET and BJH methods. X-ray photoelectron spectroscopy (XPS revealed that the fluorine is presented in the TiO2 powders mainly as metal fluoride in quantities ∼16 at %. The F-doped TiO2 showed a red-shift absorption in UV-vis region which was attributed to the increased content of rutile phase in the powders. The powders exhibited enhanced photocatalytic activity in decomposition of acetone.

Electrical analysis of inter-growth structured Bi4Ti3O12-Na0.5Bi4.5Ti4O15 ceramics

Science.gov (United States)

Jiang, Xiangping; Jiang, Yalin; Jiang, Xingan; Chen, Chao; Tu, Na; Chen, Yunjing

2017-06-01

Inter-growth bismuth layer-structured ferroelectrics (BLSFs), Bi4Ti3O12-Na0.5Bi4.5Ti4O15 (BIT-NBT), were successfully synthesized using the traditional solid-state reaction method. X-ray diffraction (XRD) Rietveld refinements were conducted using GSAS software. Good agreement and low residual are obtained. The XRD diffraction peaks can be well indexed into I2cm space group. The inter-growth structure was further observed in the high-resolution TEM image. Dielectric and impedance properties were measured and systematically analyzed. At the temperature range 763-923 K (below {T}{{c}}), doubly ionized oxygen vacancies (OVs) are localized and the short-range hopping leads to the relaxation processes with an activation energy of 0.79-1.01 eV. Above {T}{{c}}, the doubly charged OVs are delocalized and become free ones, which contribute to the long-range dc conduction. The reduction in relaxation species gives rise to a higher relaxation activation energy ˜1.6  eV. Project supported by the National Natural Science Foundation of China (Grant Nos. 51562014, 51262009, and 51602135).

Solid-state synthesis of Li_4Ti_5O_1_2 whiskers from TiO_2-B

International Nuclear Information System (INIS)

Yao, Wenjun; Zhuang, Wei; Ji, Xiaoyan; Chen, Jingjing; Lu, Xiaohua; Wang, Changsong

2016-01-01

Highlights: • The Li_4Ti_5O_1_2 whiskers were synthesized from TiO_2-B whiskers via a solid state reaction. • The TiO_2-B crystal structure for lithium diffusion is easier than anatase. • The separated diffusion and reaction process is crucial for the solid-state syntheses of Li_4Ti_5O_1_2 whiskers. - Abstract: In this work, Li_4Ti_5O_1_2 (LTO) was synthesized from the precursors of TiO_2-B and anatase whiskers, respectively. The synthesized LTO whiskers from TiO_2-B whiskers via a solid state reaction at 650 °C have a high degree of crystallinity with an average diameter of 300 nm. However, when anatase whiskers were used as the precursor, only particle morphology LTO was produced at 750 °C. The further analysis of the precursors, the intermediate products and the final products reveal that the crystal structure of the anatase hinders the diffusion of lithium, leading to a typical reaction–diffusion process. Under this condition, only particle morphology LTO can be produced. However, the crystal structure of the TiO_2-B is easy for lithium diffusion and the process is performed in two separated steps (i.e., diffusion and reaction), which makes it possible to decrease the solid-state reaction temperature down to 650 °C and then maintain the morphologies of whiskers.

Grain size dependent phase stabilities and presence of a monoclinic (Pm) phase in the MPB region of (1-x)Bi(Mg_1_/_2Ti_1_/_2)O_3_-_xPbTiO_3

International Nuclear Information System (INIS)

Upadhyay, A.; Singh, A.K.

2016-01-01

The results of the room temperature structural studies on (1-x)Bi(Mg_1_/_2Ti_1_/_2)O_3_-_xPbTiO_3 ceramics using Rietveld analysis of the powder X-ray diffraction data in the composition range 0.28≤x≤0.45 are presented. The morphotropic phase boundary region exhibits coexistence of monoclinic (space group Pm) and tetragonal (space group P4mm) phases in the composition range 0.33≤x≤0.40. The structure is nearly single phase monoclinic (space group Pm) in the composition range 0.28≤x≤0.32. The structure for the compositions with x≥0.45 is found to be predominantly tetragonal with space group P4mm. Rietveld refinement of the structure rules out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier authors. The Rietveld structure analysis for the sample x=0.35 calcined at various temperatures reveals that phase fraction of the coexisting phases in the morphotropic phase boundary region varies with grain size. The structural parameters of the two coexisting phases also change slightly with changing grain size. (author)

In situ XANES studies of TiO{sub 2}/Fe{sub 3}O{sub 4}-C during photocatalytic degradation of trichloroethylene

Energy Technology Data Exchange (ETDEWEB)

Hsu, T.-F.; Hsiung, T.-L. [Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Wang, James [Department of Biomedical Engineering, University of Southern California, Los Angeles 90007 (United States); Huang, C.-H. [Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Paul Wang, H., E-mail: wanghp@mail.ncku.edu.t [Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Sustainable Environmental Research Center, National Cheng Kung University, Tainan 70101, Taiwan (China)

2010-07-21

Mainly anatase and Fe{sub 3}O{sub 4} in the magnetic photocatalysts (TiO{sub 2} on Fe{sub 3}O{sub 4}-C core-shell nanoparticles (TiO{sub 2}/Fe{sub 3}O{sub 4}-C)) are observed by X-ray powder diffraction (XRD) spectroscopy. The Ti K-edge least-square fitted XANES spectra of the TiO{sub 2}/Fe{sub 3}O{sub 4}-C photocatalyst indicate that the main titanium species are nanosize TiO{sub 2} (9 nm) (77%) and bulky TiO{sub 2} (23%). Speciation of titanium in the TiO{sub 2}/Fe{sub 3}O{sub 4}-C during photocatalytic degradation of 100 ppm of trichloroethylene (TCE) has also been studied by in situ X-ray absorption near-edge structural (XANES) spectroscopy. TiO{sub 2} is not perturbed during the course of photocatalysis. However, it is worth to note that during photocatalytic degradation of TCE, about 33% of FeO and 67% of Fe{sub 3}O{sub 4} are observed in the photocatalyst. It seems that the carbon layer on the TiO{sub 2}/Fe{sub 3}O{sub 4}-C photocatalysts can reduce the possibility for photoexcited electron-hole recombination as usually found on the relatively narrow bandgap of ferric oxide during photocatalysis.

Synthesis, optical, and photocatalytic properties of a new visible-light-active ZnFe{sub 2}O{sub 4}-TiO{sub 2} nanocomposite material

Energy Technology Data Exchange (ETDEWEB)

Moreira, E. [University of Lisbon, Department of Chemistry and Biochemistry, Faculty of Sciences (Portugal); Fraga, L. A. [Universidade da Coruna, Facultade de Ciencias (Spain); Mendonca, M. H.; Monteiro, O. C., E-mail: ocmonteiro@fc.ul.pt [University of Lisbon, Department of Chemistry and Biochemistry, Faculty of Sciences (Portugal)

2012-06-15

The synthesis of new ZnFe{sub 2}O{sub 4}-TiO{sub 2} crystalline nanocomposites with enhanced visible-light catalytic performance is reported. Zinc ferrite powders were prepared by a wet method through oxalate precursor at 400 Masculine-Ordinal-Indicator C during 12 h and the nanocomposite materials were obtained through TiO{sub 2} incorporation before (ZnFe{sub 2}O{sub 4}/TiO{sub 2}) and after (TiO{sub 2}/ZnFe{sub 2}O{sub 4}) the ZnFe{sub 2}O{sub 4} synthesis. The influence of the nanocomposite design in the structural, morphological, and optical properties of the composite oxide materials was studied, by XRD, SEM/TEM, BET measurements, and DRS. New and improved optical features were observed in the ZnFe{sub 2}O{sub 4}-TiO{sub 2} absorption spectra comparatively with the TiO{sub 2} and ZnFe{sub 2}O{sub 4} ones. These results are discussed based on the interface effect and a proposal for the photogenerated electron transitions in the ZnFe{sub 2}O{sub 4}-TiO{sub 2} is presented. The photocatalytic performance of the prepared samples was evaluated for the methyl orange (MO) degradation process. From all the tested materials, the TiO{sub 2}/ZnFe{sub 2}O{sub 4} was the one with the best photocatalytic activity, even superior to the nanocrystalline TiO{sub 2} one. 100 % reduction of the MO concentration was achieved after 10 min of UV-Vis irradiation on a 10 ppm dye aqueous solution with 0.43 g L{sup -1} of TiO{sub 2}/ZnFe{sub 2}O{sub 4} catalyst. By performing visible-light experiments, it was possible to discuss the influence of the visible-light absorption, charge separation, and photogenerated charge-carrier recombination in the TiO{sub 2}/ZnFe{sub 2}O{sub 4} photocatalytic performance.

Integration of High-Performance Nanocrystalline TiO2 Photoelectrodes for N719-Sensitized Solar Cells

Directory of Open Access Journals (Sweden)

Ke-Jian Jiang

2013-01-01

Full Text Available We report on enhanced performance of N719-sensitized TiO2 solar cells (DSCs incorporating size and photoelectron diffusion-controlled TiO2 as sensitizer-matched light-scatter layers on conventional nanocrystalline TiO2 electrodes. The double-layered N719/TiO2 composite electrode with a high dye-loading capacity exhibits the diffused reflectance of more than 50% in the range of λ = 650–800 nm, even when the films are coupled with the titania nanocrystalline underlayer in the device. As a result, the increased near-infrared light-harvesting produces a high light-to-electricity conversion efficiency of over 9% mainly due to the significant increase of Jsc. Such an optical effect of the NIR-light scattering TiO2 electrodes will be beneficial when the sensitizers with low molar extinction coefficients, such as N719, are introduced in the device.

The influence of Bi content on dielectric properties of Bi4–xTi3O12–1.5x ceramics

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Hui Gong

2017-06-01

Full Text Available A kind of lead-free dielectric materials, such as the bismuth layered perovskite-type structure of Bi4–xTi3O12–1.5x (x=0.04,0.02,0,–0.02,–0.04, was prepared by the conventional solid-state method at 800∘C and sintered at 1100∘C. The variation of structure and electrical properties with different Bi concentration was studied. All the Bi4–xTi3O12–1.5x (x=0.04,0.02,0,–0.02,–0.04 samples exhibited a single structured phase. SEM could be a better approach to present the microstructure of Bi4–xTi3O12–1.5x (x=0.04,0.02,0,–0.02,–0.04 ceramics. It could be found that the grain size of Bi4.02Ti3O12.03 sintered at 1100∘C was smaller than that of others among the five samples through grain size mechanics. Through impedance spectra analysis, we knew, when the Bi content was fixed, that the dielectric constant and the loss values increased with the decrease of frequency. The Curie temperature of the five samples was about 670∘C. In particular, while at the frequency of 100kHz, the lowest loss was 0.001 when Bi content was 3.98. The Bi4.02Ti3O12.03 ceramics with the minimum grain size had highest dielectric constant and the relatively low loss. Due to its high Curie temperature, high permittivity and low loss, the Bi4Ti3O12 (BIT ceramics have a broad application prospect in high density memory, generator, sensor, ferroelectric tunnel junctions and so on.

A Highly Selective Room Temperature NH3 Gas Sensor based on Nanocrystalline a-Fe2O3

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Priyanka A. PATIL

2017-05-01

Full Text Available Nanocrystalline a-Fe2O3 powder was synthesized by simple, inexpensive sol-gel method. The obtained powder was calcined at 700 0C in air atmosphere for 2 hours. The structural and morphological properties of calcined powder were studied by X-ray diffraction (XRD and Field Emission Scanning Electron Microscopy (FESEM respectively. Thermal properties of dried gel were studied by Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC. The XRD pattern of the powder confirmed the a-Fe2O3 (hematite phase of iron oxide with average crystalline size of 30.87 nm calculated from Scherrer equation. The FESEM images showed uniform wormlike morphology of a-Fe2O3 powder. TGA result indicated that a-Fe2O3 is thermodynamically stable. Room temperature NH3 sensing characteristics of a-Fe2O3 were studied for various concentration levels (250-2500 ppm of NH3 at various humid conditions. The sensor based on a-Fe2O3 exhibited good selectivity and excellent sensitivity (S=92 towards 1000 ppm of NH3 with quick response of 4 sec and fast recovery of 9 sec. Room temperature sensing mechanism is also discussed.

Structural and light up-conversion luminescence properties of Er3+-Yb3+-W6+ substituted Bi4Ti3O12

Science.gov (United States)

Bokolia, Renuka; Rai, Vineet K.; Chauhan, Lalita; Sreenivas, K.

2016-05-01

The structural and light up-conversion (UC) luminescence properties of W6+ substituted Bi3.79Er0.03Yb0.18Ti3-xWxO12 (0 ≤ x ≤ 0.10) ceramics prepared by solid state reaction method have been investigated. X-ray diffraction (XRD) confirms the formation of single phase material with orthorhombic structure. A decrease in the lattice parameters and unit cell volume is observed with increasing W content. Strong UC luminescence at 527, 548 and 662 nm is seen under an excitation of 980 nm for an optimum W content (x = 0.06) and is attributed to the transitions 2H11/2 →4I15/2, 4S3/2 →4I15/2 and 4F9/2 →4I15/2 respectively. The improved UC luminescence is ascribed to the reduced defects such as oxygen vacancies and change in the crystal field around Er3+ ions due to B-site (Ti4+) substitution with W6+ ions. Enhanced UC emission is observed for an optimum content of w6+ in the prepared composition Bi3.79Er0.03Yb0.18Ti3-xWxO12 for x = 0.06.

Effects of Homogenization Scheme of TiO2 Screen-Printing Paste for Dye-Sensitized Solar Cells

Directory of Open Access Journals (Sweden)

Seigo Ito

2012-01-01

Full Text Available TiO2 porous electrodes have been fabricated for photoelectrodes in dye-sensitized solar cells (DSCs using TiO2 screen-printing paste from nanocrystalline TiO2 powder dried from the synthesized sol. We prepared the TiO2 screen-printing paste by two different methods to disperse the nanocrystalline TiO2 powder: a “ball-milling route” and a “mortal-grinding route.” The TiO2 ball-milling (TiO2-BM route gave monodisperse TiO2 nanoparticles, resulting in high photocurrent density (14.2 mA cm−2 and high photoconversion efficiency (8.27%. On the other hand, the TiO2 mortal-grinding (TiO2-MG route gave large aggregate of TiO2 nanoparticles, resulting in low photocurrent density (11.5 mA cm−2 and low photoconversion efficiency (6.43%. To analyze the photovoltaic characteristics, we measured the incident photon-to-current efficiency, light absorption spectroscopy, and electrical impedance spectroscopy of DSCs.

A Facile Method for the Preparation of Colored Bi4Ti3O12−x Nanosheets with Enhanced Visible-Light Photocatalytic Hydrogen Evolution Activity

Directory of Open Access Journals (Sweden)

Yizeng Zhang

2018-04-01

Full Text Available Bi4Ti3O12−x nanosheet photocatalysts with abundant oxygen vacancies are fabricated by a facile solid-state chemical reduction method for the first time. This method is simple in operation, has short reaction time, and can be conducted at mild temperatures (300~400 °C. The electron paramagnetic resonance, thermogravimetric analysis, X-ray photoelectron spectrometer, and positron annihilation lifetime spectra results indicate that oxygen vacancies are produced in Bi4Ti3O12−x, and they can be adjusted by tuning the reduction reaction conditions. Control experiments show that the reduction time and temperature have great influences on the photocatalytic activities of Bi4Ti3O12−x. The optimal Bi4Ti3O12−x is the sample undergoing the reduction treatment at 350 °C for 60 min and it affords a hydrogen evolution rate of 129 μmol·g−1·h−1 under visible-light irradiation, which is about 3.4 times that of the pristine Bi4Ti3O12. The Bi4Ti3O12−x photocatalysts have good reusability and storage stability and can be used to decompose formaldehyde and formic acid for hydrogen production. The surface oxygen vacancies states result in the broadening of the valence band and the narrowing of the band gap. Such energy level structure variation helps promote the separation of photo-generated electron-hole pairs thus leading to enhancement in the visible-light photocatalytic hydrogen evolution. Meanwhile, the narrowing of the band gap leads to a broader visible light absorption of Bi4Ti3O12−x.

Fabrication and thermal characterization of amorphous and nanocrystalline Al{sub 9}FeNi/Al{sub 3}Ti compound

Energy Technology Data Exchange (ETDEWEB)

Tavoosi, Majid, E-mail: ma.tavoosi@gmail.com

2017-01-15

In this study, the fabrication and structural characterization of amorphous/nanocrystalline Al{sub 9}FeNi/Al{sub 3}Ti phase has been performed. In this regards, milling and annealing processes were applied on Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} (at. %) powder mixture for different periods of time. The prepared samples were characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM) and differential scanning calorimetery (DSC). According to the results, supersaturated solid solution, nanocrystalline Al{sub 9}FeNi/Al{sub 3}Ti (with average crystallite size of about 7 nm) and amorphous phases indicated three different microstructures which can be formed in Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} system during milling process. The formed supersaturated solid solution and amorphous phases were unstable and transformed to Al{sub 9}FeNi/Al{sub 3}Ti intermetallic compound during annealing process. It is shown that, Al{sub 9}FeNi phase in Al{sub 9}FeNi/Al{sub 3}Ti intermetallic compound can decompose into Al{sub 3}Ni, Al{sub 13}Fe{sub 4} and liquid phases during a reversible peritectic reaction at 809 °C. - Highlights: • We study the effect of milling process on Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} alloy. • We study the effect of annealing on Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} supersaturated solid solution phase. • We study the effect of annealing on Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} amorphous phase. • We study the thermal behaviour of Al{sub 9}FeNi/Al{sub 3}Ti compound.

Tailoring the piezoelectric and relaxor properties of (Bi1/2 Na1/2) TiO3- BaTiO3 via zirconium doping

DEFF Research Database (Denmark)

Glaum, Julia; Simons, Hugh; Acosta, Matias

2013-01-01

This article details the influence of zirconium doping on the piezoelectric properties and relaxor characteristics of 94(Bi1/2Na1/2)TiO3-6Ba(ZrxTi1-x)O3 (BNT-6BZT) bulk ceramics. Neutron diffraction measurements of BNT-6BZT doped with 0%-15% Zr revealed an electric-field-induced transition...

Evolving morphotropic phase boundary in lead-free (Bi1/2Na1/2)TiO3-BaTiO3 piezoceramics

Science.gov (United States)

Jo, Wook; Daniels, John E.; Jones, Jacob L.; Tan, Xiaoli; Thomas, Pamela A.; Damjanovic, Dragan; Rödel, Jürgen

2011-01-01

The correlation between structure and electrical properties of lead-free (1-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-100xBT) polycrystalline piezoceramics was investigated systematically by in situ synchrotron diffraction technique, combined with electrical property characterization. It was found that the morphotropic phase boundary (MPB) between a rhombohedral and a tetragonal phase evolved into a morphotropic phase region with electric field. In the unpoled material, the MPB was positioned at the transition from space group R3m to P4mm (BNT-11BT) with optimized permittivity throughout a broad single-phase R3m composition regime. Upon poling, a range of compositions from BNT-6BT to BNT-11BT became two-phase mixture, and maximum piezoelectric coefficient was observed in BNT-7BT. It was shown that optimized electrical properties are related primarily to the capacity for domain texturing and not to phase coexistence.

Evolving morphotropic phase boundary in lead-free (Bi1/2Na1/2)TiO3-BaTiO3 piezoceramics

International Nuclear Information System (INIS)

Jo, Wook; Roedel, Juergen; Daniels, John E.; Jones, Jacob L.; Tan Xiaoli; Thomas, Pamela A.; Damjanovic, Dragan

2011-01-01

The correlation between structure and electrical properties of lead-free (1-x)(Bi 1/2 Na 1/2 )TiO 3 -xBaTiO 3 (BNT-100xBT) polycrystalline piezoceramics was investigated systematically by in situ synchrotron diffraction technique, combined with electrical property characterization. It was found that the morphotropic phase boundary (MPB) between a rhombohedral and a tetragonal phase evolved into a morphotropic phase region with electric field. In the unpoled material, the MPB was positioned at the transition from space group R3m to P4mm (BNT-11BT) with optimized permittivity throughout a broad single-phase R3m composition regime. Upon poling, a range of compositions from BNT-6BT to BNT-11BT became two-phase mixture, and maximum piezoelectric coefficient was observed in BNT-7BT. It was shown that optimized electrical properties are related primarily to the capacity for domain texturing and not to phase coexistence.

Synthesis of a TiBw/Ti6Al4V composite by powder compact extrusion using a blended powder mixture

Energy Technology Data Exchange (ETDEWEB)

Lu, Huiyang, E-mail: hl209@waikato.ac.nz [Waikato Center for Advanced Materials, School of Engineering, University of Waikato, Hamilton (New Zealand); Zhang, Deliang, E-mail: zhangdeliang@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai (China); Gabbitas, Brian, E-mail: briang@waikato.ac.nz [Waikato Center for Advanced Materials, School of Engineering, University of Waikato, Hamilton (New Zealand); Yang, Fei, E-mail: fyang@waikato.ac.nz [Waikato Center for Advanced Materials, School of Engineering, University of Waikato, Hamilton (New Zealand); Matthews, Steven, E-mail: S.Matthews@massey.ac.nz [School of Engineering and Advanced Technology, Massey University, Auckland (New Zealand)

2014-09-01

Highlights: • TiB/Ti6Al4V composites were prepared from extruded BE powders. • Different starting powders affected the morphologies of TiB whiskers formed in-situ. • A TiB/Ti6Al4V composite with TiB whiskers had good strength and ductility. • The strength and ductility achieved were superior to those obtained by other methods. - Abstract: A Ti–6 wt%Al–4 wt%V alloy (Ti6Al4V) matrix composite, reinforced by in situ synthesized TiB whiskers (TiBw) has been successfully fabricated by powder compact extrusion using a blended powder mixture. The microstructural characterization of the various extruded samples showed that the different starting powders, pre-alloyed powder plus boron powder or titanium plus Al–40V master alloy powder plus boron powder, had a significant effect on the morphology of the in situ synthesized TiB whiskers. It is also evident that the TiB whiskers affect the microstructural evolution of the Ti6Al4V matrix. The tensile test results indicated that the composite with a dispersion of fine TiB whiskers with high aspect ratios exhibited a high ultimate tensile stress (UTS) and yield stress (YS) of 1436 MPa and 1361 MPa, respectively, a reasonably good tensile ductility reflected by an elongation to fracture of 5.6% was also achieved. This is a significant improvement compared with as-extruded monolithic Ti6Al4V alloy produced in this study.

Synthesis of a TiBw/Ti6Al4V composite by powder compact extrusion using a blended powder mixture

International Nuclear Information System (INIS)

Lu, Huiyang; Zhang, Deliang; Gabbitas, Brian; Yang, Fei; Matthews, Steven

2014-01-01

Highlights: • TiB/Ti6Al4V composites were prepared from extruded BE powders. • Different starting powders affected the morphologies of TiB whiskers formed in-situ. • A TiB/Ti6Al4V composite with TiB whiskers had good strength and ductility. • The strength and ductility achieved were superior to those obtained by other methods. - Abstract: A Ti–6 wt%Al–4 wt%V alloy (Ti6Al4V) matrix composite, reinforced by in situ synthesized TiB whiskers (TiBw) has been successfully fabricated by powder compact extrusion using a blended powder mixture. The microstructural characterization of the various extruded samples showed that the different starting powders, pre-alloyed powder plus boron powder or titanium plus Al–40V master alloy powder plus boron powder, had a significant effect on the morphology of the in situ synthesized TiB whiskers. It is also evident that the TiB whiskers affect the microstructural evolution of the Ti6Al4V matrix. The tensile test results indicated that the composite with a dispersion of fine TiB whiskers with high aspect ratios exhibited a high ultimate tensile stress (UTS) and yield stress (YS) of 1436 MPa and 1361 MPa, respectively, a reasonably good tensile ductility reflected by an elongation to fracture of 5.6% was also achieved. This is a significant improvement compared with as-extruded monolithic Ti6Al4V alloy produced in this study

Minimum ignition energy of nano and micro Ti powder in the presence of inert nano TiO₂ powder.

Science.gov (United States)

Chunmiao, Yuan; Amyotte, Paul R; Hossain, Md Nur; Li, Chang

2014-06-15

The inerting effect of nano-sized TiO2 powder on ignition sensitivity of nano and micro Ti powders was investigated with a Mike 3 apparatus. "A little is not good enough" is also suitable for micro Ti powders mixed with nano-sized solid inertants. MIE of the mixtures did not significantly increase until the TiO2 percentage exceeded 50%. Nano-sized TiO2 powders were ineffective as an inertant when mixed with nano Ti powders, especially at higher dust loadings. Even with 90% nano TiO2 powder, mixtures still showed high ignition sensitivity because the statistic energy was as low as 2.1 mJ. Layer fires induced by ignited but unburned metal particles may occur for micro Ti powders mixed with nano TiO2 powders following a low level dust explosion. Such layer fires could lead to a violent dust explosion after a second dispersion. Thus, additional attention is needed to prevent metallic layer fires even where electric spark potential is low. In the case of nano Ti powder, no layer fires were observed because of less flammable material involved in the mixtures investigated, and faster flame propagation in nanoparticle clouds. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of structure on nonlinear optical properties in CaCu{sub 3}Ti{sub 4}O{sub 12} films

Energy Technology Data Exchange (ETDEWEB)

Ning, Tingyin [School of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Zhou, Yueliang, E-mail: ylzhou@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2015-12-21

We report the third-order nonlinear optical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} films with different preferred growth orientations on MgO and fused silica substrates. The films have (310)- and (220)-orientation on MgO and fused silica, respectively, due to the lattice-mismatch. Raman spectra further indicate different atom-bonding states in the films. The nonlinear optical measurements show the films possess the same self-defocusing behavior but with different values of nonlinear refraction, and changed signs of nonlinear absorption. The difference of optical nonlinearity in CaCu{sub 3}Ti{sub 4}O{sub 12} films is ascribed to different lattice parameters and intermediate levels induced by structure.

Neutron Diffraction Study of the High-Tc Superconductor HgBa2CaCu2O6.3 under High Pressure

International Nuclear Information System (INIS)

Aksenov, V.L.; Balagurov, A.M.; Savenko, B.N.; Capponi, J.J.; Glazkov, V.P.; Goncharenko, I.N.; Somenkov, V.A.

1994-01-01

The pressure dependence of the crystal structure of a powder sample of HgBa 2 CaCu 2 O 6.3 (T c =123 K) was studied in the pressure range of 0 to 3.6 GPa, using the DN-12 time-of-flight diffractometer at the IBR-2 pulsed reactor and a sapphire anvil cell chamber. At P=0 the results are in a good accordance with the published data. At P=3.0 and 3.6 GPa the best fit of the experimental data was achieved using the structural model with apical oxygen disordered in the (a,b) plane. The compressibility values of the lattice constants and selected bonds were calculated from the structural data. The highest absolute value of compressibility was found for the distance between the O atom layers. 12 refs., 6 figs., 3 tabs

Determination of the electronic, dielectric, and optical properties of sillenite Bi12TiO20 and perovskite-like Bi4Ti3O12 materials from hybrid first-principle calculations

KAUST Repository

Lardhi, Sheikha F.; Noureldine, Dalal; Harb, Moussab; Ziani, Ahmed; Cavallo, Luigi; Takanabe, Kazuhiro

2016-01-01

Density functional theory calculation was conducted to determine the optoelectronic properties of bismuthtitanate sillenite (Bi12TiO20) and perovskite-like (Bi4Ti3O12) structures. The lattice parameters were experimentally obtained from Rietveld analysis. The density functional perturbation theory approach was used with the standard Perdew–Burke–Ernzerhof functional and screened Coulomb hybrid Heyd–Scuseria–Ernzerhof functional to investigate the electronic structure and absorption coefficient. Both compounds have good carrier transport properties, low effective hole and electron masses, high dielectric constant, and low exciton binding energy.

Determination of the electronic, dielectric, and optical properties of sillenite Bi12TiO20 and perovskite-like Bi4Ti3O12 materials from hybrid first-principle calculations

KAUST Repository

Lardhi, Sheikha F.

2016-04-05

Density functional theory calculation was conducted to determine the optoelectronic properties of bismuthtitanate sillenite (Bi12TiO20) and perovskite-like (Bi4Ti3O12) structures. The lattice parameters were experimentally obtained from Rietveld analysis. The density functional perturbation theory approach was used with the standard Perdew–Burke–Ernzerhof functional and screened Coulomb hybrid Heyd–Scuseria–Ernzerhof functional to investigate the electronic structure and absorption coefficient. Both compounds have good carrier transport properties, low effective hole and electron masses, high dielectric constant, and low exciton binding energy.

TiO{sub 2} and TiO{sub 2}-SiO{sub 2} thin films and powders by one-step soft-solution method: Synthesis and characterizations

Energy Technology Data Exchange (ETDEWEB)

Ennaoui, A.; Sankapal, B.R.; Skryshevsky, V.; Lux-Steiner, M.Ch. [Division Solar Energy Research, Department Heterogeneous Material Systems, Hahn-Meitner-Institut, Glienicker Strasse 100, 14109 Berlin (Germany)

2006-06-15

Simple soft-solution method has been developed to synthesize films and powders of TiO{sub 2} and mixed TiO{sub 2}-SiO{sub 2} at relatively low temperatures. This method is simple and inexpensive. Furthermore, reactor can be designed for large-scale applications as well as to produce large quantities of composite powders in a single step. For the preparation of TiO{sub 2}, we used aqueous acidic medium containing TiOSO{sub 4} and H{sub 2}O{sub 2}, which results in a peroxo-titanium precursor while colloidal SiO{sub 2} has been added to the precursor for the formation of TiO{sub 2}-SiO{sub 2}. Post annealing at 500{sup o}C is necessary to have anatase structure. Resulting films and powders were characterized by different techniques. TiO{sub 2} (anatase) phase with (101) preferred orientation has been obtained. Also in TiO{sub 2}-SiO{sub 2} mixed films and powders, TiO{sub 2} (anatase) phase was found. Fourier transform infrared spectroscopy (FTIR) results for TiO{sub 2} and mixed TiO{sub 2}-SiO{sub 2} films have been presented and discussed. The method developed in this paper allowed obtaining compact and homogeneous TiO{sub 2} films. These compact films are highly photoactive when TiO{sub 2} is used as photo anode in an photoelectrochemical cell. Nanoporous morphology is obtained when SiO{sub 2} colloids are added into the solution. (author)

Effect Of Ti Powder Addition On The Fabrication Of TiO2 Nanopowders

Directory of Open Access Journals (Sweden)

Raihanuzzaman R.M.

2015-06-01

Full Text Available Sintered samples of Ti added TiO2 nanopowders were fabricated by combined application of magnetic pulsed compaction (MPC and sintering. The effect of Ti nano powder on density, shrinkage and hardness of the samples were investigated as part of the study. The optimum processing conditions were found to be around 0.5 GPa MPC pressure and 1450°C sintering temperature, illustrating maximum density, hardness and minimum shrinkage. High pressure compaction using MPC was found to enhance density with increasing MPC pressure up to 0.9 GPa, and significantly reduce the total shrinkage (about 16% in this case in the sintered bulks compared to other general processes (about 18%. While sintered samples blended with micro Ti showed presence of microstructural cracks, the samples with 1-2% nano Ti had less or no cracks on them. Overall, the inclusion of nano Ti indicated improvement in mechanical properties of TiO2 nanopowders sintered preforms as opposed to micro Ti-added TiO2.

Electron paramagnetic resonance investigation of polycrystalline CaCu{sub 3}Ti{sub 4}O{sub 12}

Energy Technology Data Exchange (ETDEWEB)

Mozzati, Maria Cristina [INFM-Dipartimento di Fisica ' Alessandro Volta' , Universita di Pavia, via Bassi 6, I-27100 Pavia (Italy); Azzoni, Carlo Bruno [INFM-Dipartimento di Fisica ' Alessandro Volta' , Universita di Pavia, via Bassi 6, I-27100 Pavia (Italy); Capsoni, Doretta [Dipartimento di Chimica Fisica ' Mario Rolla' , Universita di Pavia and IENI-CNR, Sezione di Pavia, viale Taramelli 16, I-27100 Pavia (Italy); Bini, Marcella [Dipartimento di Chimica Fisica ' Mario Rolla' , Universita di Pavia and IENI-CNR, Sezione di Pavia, viale Taramelli 16, I-27100 Pavia (Italy); Massarotti, Vincenzo [Dipartimento di Chimica Fisica ' Mario Rolla' , Universita di Pavia and IENI-CNR, Sezione di Pavia, viale Taramelli 16, I-27100 Pavia (Italy)

2003-11-05

Electron paramagnetic resonance (EPR) measurements on pure polycrystalline CaCu{sub 3}Ti{sub 4}O{sub 12} have been performed and are discussed within a crystal-field approach. A symmetric signal centred at g = 2.15 is observed for T>25 K, with no evidence of hyperfine structure. At this temperature an antiferromagnetic transition is observed as confirmed by static magnetization data. Cu defective and 2% doped (V, Cr, Mn, La) samples were also prepared and considered, mainly to understand the nature of the observed paramagnetic centre. Substitutions in the octahedral sites, causing variations of the configuration in CuO{sub 4}-TiO{sub 6}-CuO{sub 4} complexes, change the magnetic and EPR features. To justify the EPR response a strong copper-hole delocalization is suggested.

Characteristics of nano Ti-doped SnO2 powders prepared by sol-gel method

International Nuclear Information System (INIS)

Liu, X.M.; Wu, S.L.; Chu, Paul K.; Zheng, J.; Li, S.L.

2006-01-01

Ti 4+ -doped SnO 2 nano-powders were prepared by the sol-gel process using tin tetrachloride and titanium tetrachloride as the starting materials. The crystallinity and purity of the powders were analyzed by X-ray diffraction (XRD) and the size and distribution of Ti 4+ -doped SnO 2 grains were studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that Ti 4+ has been successfully incorporated into the SnO 2 crystal lattice and the electrical conductivity of the doped materials improves significantly

Rietveld refinement of KLaTiO4 from X-ray powder data

Directory of Open Access Journals (Sweden)

Bai-Chuan Zhu

2011-04-01

Full Text Available Potassium lanthanum titanate(IV, KLaTiO4, has been synthesized by conventional solid-state reaction. It crystallizes isotypically with the NaLnTiO4 (Ln = La, Pr, Nd, Sm, Eu, Gd, Y and Lu family. Five of the six atoms in the asymmetric unit (one K, one La, one Ti and two O atoms are situated on sites with 4mm symmetry, whereas one O atom has 2mm. site symmetry. The crystal structure can be described as being composed of single layers of distorted corner-sharing TiO6 octahedra extending parallel to (001. The layers are alternately separated by K+ and La3+ cations along [001]. The coordination number of both K+ and La3+ cations is nine, resulting in distorted KO9 and LaO9 polyhedra.

The effect of TiO2 on nucleation and crystallization of a Li2O-Al2O3-SiO2 glass investigated by XANES and STEM.

Science.gov (United States)

Kleebusch, Enrico; Patzig, Christian; Krause, Michael; Hu, Yongfeng; Höche, Thomas; Rüssel, Christian

2018-02-13

Glass ceramics based on Li 2 O/Al 2 O 3 /SiO 2 are of high economic importance, as they often show very low coefficients of thermal expansion. This enables a number of challenging applications, such as cooktop panels, furnace windows or telescope mirror blanks. Usually, the crystallization of the desired LAS crystal phases within the glasses must be tailored by a careful choice of crystallization schedule and type of nucleation agents to be used. The present work describes the formation of nanocrystalline TiO 2 within an LAS base composition that contains solely TiO 2 as nucleating agent. Using a combination of scanning transmission electron microscopy as well as X-ray absorption spectroscopy, it is found that a mixture of four- and six-fold coordinated Ti 4+ ions exists already within the glass. Heating of the glass to 740 °C immediately changes this ratio towards a high content of six-fold coordinated Ti, which accumulates in liquid-liquid phase-separation droplets. During the course of thermal treatment, these droplets eventually evolve into nanocrystalline TiO 2 precipitations, in which Ti 4+ is six-fold coordinated. Thus, it is shown that the nucleation of nanocrystalline TiO 2 is initiated by a gradual re-arrangement of the Ti ions in the amorphous, glassy matrix, from a four-fold towards a six-fold coordination.

Single step synthesis of GdAlO3 powder

International Nuclear Information System (INIS)

Sinha, Amit; Nair, S.R.; Sinha, P.K.

2011-01-01

Research highlights: → First report on direct formation of GdAlO 3 powder using a novel combustion process. → Study of combustion characteristics of Gd(NO 3 ) 3 and Al(NO 3 ) 3 towards three fuels. → Preparation of highly sinterable GdAlO 3 powders through fuel-mixture approach. → Significant reduction in energy consumption for production of GdAlO 3 sintered body. - Abstract: A novel method for preparation of nano-crystalline gadolinium aluminate (GdAlO 3 ) powder, based on combustion synthesis, is reported. It was observed that aluminium nitrate and gadolinium nitrate exhibit different combustion characteristics with respect to urea, glycine and β-alanine. While urea was proven to be a suitable fuel for direct formation of crystalline α-Al 2 O 3 from its nitrate, glycine and β-alanine are suitable fuels for gadolinium nitrate for preparation of its oxide after combustion reaction. Based on the observed chemical characteristics of gadolinium and aluminium nitrates with respect to above mentioned fuels for the combustion reaction, the fuel mixture composition could be predicted that could lead to phase pure perovskite GdAlO 3 directly after the combustion reaction without any subsequent calcination step. The use of single fuel, on the other hand, leads to formation of amorphous precursor powders that call for subsequent calcination for the formation of crystalline GdAlO 3 . The powders produced directly after combustion reactions using fuel mixtures were found to be highly sinterable. The sintering of the powders at 1550 o C for 4 h resulted in GdAlO 3 with sintered density of more than 95%. T.D.

Efficient solar light-driven degradation of Congo red with novel Cu-loaded Fe3O4@TiO2 nanoparticles.

Science.gov (United States)

Arora, Priya; Fermah, Alisha; Rajput, Jaspreet Kaur; Singh, Harminder; Badhan, Jigyasa

2017-08-01

In this work, Cu-loaded Fe 3 O 4 @TiO 2 core shell nanoparticles were prepared in a single pot by coating of TiO 2 on Fe 3 O 4 nanoparticles followed by Cu loading. X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), thermogravimetric analysis (TGA), Brunauer-Emmett- Teller (BET), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), and valence band X-ray photoelectron spectroscopy (VB XPS) techniques were used for characterization of as prepared nanoparticles. Synergism between copper and titania was evaluated by studying the solar light-driven photodegradation of Congo red dye solution in the presence of Fe 3 O 4 @TiO 2 nanoparticles on one side and Cu-loaded Fe 3 O 4 @TiO 2 nanoparticles on the other side. The latter performed better than the former catalyst, indicating the enhanced activity of copper-loaded catalyst. Further photodegradation was studied by three means, i.e., under ultraviolet (UV), refluxing, and solar radiations. Cu-loaded Fe 3 O 4 @TiO 2 enhanced the degradation efficiency of Congo red dye. Thus, Cu act possibly by reducing the band gap of TiO 2 and widening the optical response of semiconductor, as a result of which solar light could be used to carry out photocatalysis. Graphical abstract Photodegradation of congo red over Cu-loaded Fe 3 O 4 @TiO 2 nanoparticles.

The Synthesis of Eu3+ Doped with TiO2 Nano-Powder and Application as a Pesticide Sensor

International Nuclear Information System (INIS)

Yao, Fei; Sun, Yang; Tan, Chunlei; Wei, Song; Zhang, Xiaojuan; Hu, Xiaoyun; Fan, Jun

2011-01-01

Using tetrabutyl titanate as precursor, Eu 3+ doped TiO 2 nano-powder was prepared by sol-gel method, the nature of luminescence of nano-powder was studied. The interaction of chlorpyrifos with Eu 3+ doped TiO 2 was studied by absorption and fluorescence spectroscopy. The results indicated the fluorescence intensity of Eu 3+ doped TiO 2 was quenched by chlorpyrifos and the quenching rate constant (kq) was 1.24Χ10 11 L/mol·s according to the Stern-Volmer equation. The dynamics of photoinduced electron transfer from chlorpyrifos to conduction band of TiO 2 nanoparticle was observed and the mechanism of electron transfer had been confirmed by the calculation of free energy change (ΔG et ) by applying Rehm-Weller equation as well as energy level diagram. A new rapid method for detection of chlorpyrifos was established according to the fluorescence intensity of Eu 3+ doped TiO 2 was proportional to chlorpyrifos concentration. The range of detection was 5.0Χ10 -10 -2.5Χ10 -7 mol/L and the detection limit (3σ) was 3.2Χ10 -11 mol/L

Extreme biomimetic approach for synthesis of nanocrystalline chitin-(Ti,Zr)O2 multiphase composites

International Nuclear Information System (INIS)

Wysokowski, Marcin; Motylenko, Mykhaylo; Rafaja, David; Koltsov, Iwona; Stöcker, Hartmut; Szalaty, Tadeusz J.; Bazhenov, Vasilii V.; Stelling, Allison L.; Beyer, Jan; Heitmann, Johannes; Jesionowski, Teofil; Petovic, Slavica; Đurović, Mirko; Ehrlich, Hermann

2017-01-01

This work presents an extreme biomimetics route for the modification of the surface of fibre-based scaffolds of poriferan origin by the creation of novel nanostructured multiphase biocomposites. The exceptional thermal stability of the nanostructured sponge chitin allowed for the formation of a novel nanocrystalline chitin-(Ti,Zr)O 2 composite with a well-defined nanoscale structure under hydrothermal conditions (160 °C). Using a combination of experimental techniques, including X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, EDX mapping and near-edge electron loss spectroscopy (ELNES) in TEM and thermogravimetry/differential scanning calorimetry coupled with mass spectrometry; we showed that this bioorganic scaffold facilitates selective crystallization of TiO 2 , predominantly in form of anatase, over the monoclinic zirconium dioxide (baddeleyite). The control of the crystal morphology through the chitin templates is also demonstrated. Obtained samples were characterized in terms of their photoluminescent properties and photocatalytic performance. These data confirm the high potential of the extreme biomimetics approach for developing a new generation of multiphase biopolymer-based nanostructured materials. - Highlights: • Extreme biomimetically prepared chitin-(Ti,Zr)O 2 and (Ti,Zr)O 2 composites. • Chitin-(Ti,Zr)O 2 composite contains anatase as the most inorganic component. • The mean crystallite size is (31.7 ± 0.3) nm for chitin-(Ti,Zr)O 2 composite. • The mean crystallite size is (2.4 ± 0.5) nm for (Ti,Zr)O 2 composite. • (Ti,Zr)O 2 composite is 2 times more effective photocatalyst than chitin-(Ti,Zr)O 2 .

Neutron diffraction study of the inverse spinels Co2TiO4 and Co2SnO4

Science.gov (United States)

Thota, S.; Reehuis, M.; Maljuk, A.; Hoser, A.; Hoffmann, J.-U.; Weise, B.; Waske, A.; Krautz, M.; Joshi, D. C.; Nayak, S.; Ghosh, S.; Suresh, P.; Dasari, K.; Wurmehl, S.; Prokhnenko, O.; Büchner, B.

2017-10-01

We report a detailed single-crystal and powder neutron diffraction study of Co2TiO4 and Co2SnO4 between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)M reflection due to ferrimagnetic ordering, which sets in below TN=48.6 and 41 K for Co2TiO4 and Co2SnO4 , respectively. An additional low intensity magnetic reflection (200)M was noticed in Co2TiO4 due to the presence of an additional weak antiferromagnetic component. Interestingly, from both the powder and single-crystal neutron data of Co2TiO4 , we noticed a significant broadening of the magnetic (111)M reflection, which possibly results from the disordered character of the Ti and Co atoms on the B site. Practically, the same peak broadening was found for the neutron powder data of Co2SnO4 . On the other hand, from our single-crystal neutron diffraction data of Co2TiO4 , we found a spontaneous increase of particular nuclear Bragg reflections below the magnetic ordering temperature. Our data analysis showed that this unusual effect can be ascribed to the presence of anisotropic extinction, which is associated to a change of the mosaicity of the crystal. In this case, it can be expected that competing Jahn-Teller effects acting along different crystallographic axes can induce anisotropic local strain. In fact, for both ions Ti3 + and Co3 +, the 2 tg levels split into a lower dx y level yielding a higher twofold degenerate dx z/dy z level. As a consequence, one can expect a tetragonal distortion in Co2TiO4 with c /a <1 , which we could not significantly detect in the present work.

Properties of TiO2 prepared by acid treatment of BaTiO3

International Nuclear Information System (INIS)

Okada, Kiyoshi; Yanagisawa, Tomoki; Kameshima, Yoshikazu; Nakajima, Akira

2007-01-01

TiO 3 powders were prepared by acid treatment of BaTiO 3 and their properties were investigated. The BaTiO 3 powder was subjected to HNO 3 in concentrations ranging from 10 -3 to 8 M at 90 deg. C for 0.5-6 h. Dissolution of BaTiO 3 and precipitation of TiO 2 occurred at acid concentrations of 2-5 M. BaTiO 3 dissolves completely to form a clear solution at reaction times of 0.5-1 h, but a rutile precipitate is formed after 2 h of acid treatment. By contrast, anatase is precipitated by adjusting the pH of the clear solution to 2-3 using NaOH or NH 4 OH solution. The rutile crystals were small and rod-shaped, consisting of many small coherent domains connected by grain boundaries with small inclination angles and edge dislocations, giving them a high specific surface area (S BET ). With increasing HNO 3 concentration, the S BET value increased from 100 to 170 m 2 /g while the crystallite size decreased from 25 to 11 nm. The anatase crystals obtained here were very small equi-axial particles with a smaller crystallite size than the rutile and S BET values of about 270 m 2 /g (higher than the rutile samples). The photocatalytic activity of these TiO 2 was determined from the decomposition rate of Methylene Blue under ultraviolet irradiation. Higher decomposition rates were obtained with larger crystallite sizes resulting from heat treatment. The maximum decomposition rates were obtained in samples heated at 500-600 deg. C. The photocatalytic activity of the TiO 2 was found to depend more strongly on the sample crystallite size than on S BET

Effect of nanocrystalline phase on the electrochemical behavior of the alloy Ti{sub 60}Ni{sub 40}

Energy Technology Data Exchange (ETDEWEB)

Mathur, Shubhra, E-mail: shubhramathur3@gmail.com [Department of Physics, Jagannath Gupta Institute of Engineering and Technology, Jaipur 303905 (India); Jain, Rohit [Department of Physics, Jagannath Gupta Institute of Engineering and Technology, Jaipur 303905 (India); Kumar, Praveen [Surface Physics and Nanostructure Group, National Physical Laboratory, New Delhi 110012 (India); Sachdev, K.; Sharma, S.K. [Department of Physics, Malaviya National Institute of Technology, JLN-Marg, Jaipur 302017 (India)

2012-10-15

Highlights: Black-Right-Pointing-Pointer Polarization studies carried out on different structural states of the alloy Ti{sub 60}Ni{sub 40}. Black-Right-Pointing-Pointer Nanocrystalline state exhibits superior corrosion resistance as compared to other states of the alloy Ti{sub 60}Ni{sub 40}. Black-Right-Pointing-Pointer XPS results show that nanocrystalline specimen contains only TiO{sub 2} species. Black-Right-Pointing-Pointer It leads to the formation of adherent and stable film and improves the corrosion resistance. - Abstract: Polarization studies were carried out on crystalline, amorphous and nanocrystalline states of the alloy Ti{sub 60}Ni{sub 40} in 1 M NaCl aqueous medium at room temperature. It was observed that nanocrystalline state exhibits superior corrosion resistance as compared to other states of the alloy Ti{sub 60}Ni{sub 40}. Cyclic voltammetry studies and weight loss data corroborates the polarization studies. X-ray photoelectron spectroscopy (XPS) technique was used in order to decipher the nature of the oxide film formed after corrosion test on the specimens of the alloy Ti{sub 60}Ni{sub 40}. The crystalline specimen of the alloy Ti{sub 60}Ni{sub 40} shows the presence of Ti{sup 2+}, Ti{sup 3+} and Ti{sup 4+} species along with some unoxidized Ti in metallic form (Ti{sup 0}) whereas the amorphous specimen consists of Ti{sup 3+} and Ti{sup 4+} species. On the other hand nanocrystalline specimen contains only Ti{sup 4+} species. Thus it is likely that the presence of fewer species and the absence of Ti{sup 3+} in the oxide film formed on nanocrystalline specimen of Ti{sub 60}Ni{sub 40} lead to the formation of a film with greater homogeneity and protective quality in comparison to the films formed on crystalline and amorphous states of the alloy Ti{sub 60}Ni{sub 40} in 1 M NaCl aqueous medium.

Mechanochemically synthesized Al2O3-TiC nanocomposite

International Nuclear Information System (INIS)

Mohammad Sharifi, E.; Karimzadeh, F.; Enayati, M.H.

2010-01-01

Al 2 O 3 -TiC nanocomposite was synthesized by ball milling of aluminum, titanium oxide and graphite powder mixtures. Effect of the milling time and heat treatment temperatures were investigated. The structural evolution of powder particles after different milling times was studied by X-ray diffractometry and scanning electron microscopy. The results showed that after 40 h of ball milling the Al/TiO 2 /C reacted with a self-propagating combustion mode producing Al 2 O 3 -TiC nanocomposite. In final stage of milling, alumina and titanium carbide crystallite sizes were less than 10 nm. After annealing at 900 o C for 1 h, Al 2 O 3 and TiC crystallite sizes remained constant, however increasing annealing temperature to 1200 o C increased Al 2 O 3 and TiC crystallite size to 65 and 30 nm, respectively. No phase change was observed after annealing of the synthesized Al 2 O 3 -TiC powder.

Laser Cladding of Ti-6Al-4V Alloy with Ti-Al2O3 Coating for Biomedical Applications

Science.gov (United States)

Mthisi, A.; Popoola, A. P. I.; Adebiyi, D. I.; Popoola, O. M.

2018-05-01

The indispensable properties of Ti-6Al-4V alloy coupled with poor tribological properties and delayed bioactivity make it a subject of interest to explore in biomedical application. A quite number of numerous coatings have been employed on titanium alloys, with aim to overcome the poor properties exhibited by this alloy. In this work, the possibility of laser cladding different ad-mixed powders (Ti - 5 wt.% Al2O3 and Ti - 8wt.% Al2O3) on Ti-6Al-4V at various laser scan speed (0.6 and 0.8 m/min) were investigated. The microstructure, phase constituents and corrosion of the resultant coatings were characterized by scanning electron microscope (SEM), Optical microscope, X-Ray diffractometer (XRD) and potentiostat respectively. The electrochemical behaviour of the produced coatings was studied in a simulated body fluid (Hanks solution). The microstructural results show that a defect free coating is achieved at low scan speed and ad-mixed of Ti-5 wt. % Al2O3. Cladding of Ti - Al2O3 improved the corrosion resistance of Ti-6Al-4V alloy regardless of varying neither scan speed nor ad-mixed percentage. However, Ti-5 wt.% Al2O3 coating produced at low scan speed revealed the highest corrosion resistance among the coatings due to better quality coating layer. Henceforth, this coating may be suitable for biomedical applications.

Nano ZrO{sub 2} particles in nanocrystalline Fe–14Cr–1.5Zr alloy powders

Energy Technology Data Exchange (ETDEWEB)

Xu, W.Z.; Li, L.L.; Saber, M.; Koch, C.C.; Zhu, Y.T., E-mail: ytzhu@ncsu.edu; Scattergood, R.O.

2014-09-15

Here we report on the formation of nano ZrO{sub 2} particles in Fe–14Cr–1.5Zr alloy powders synthesized by mechanical alloying. The nano ZrO{sub 2} particles were found uniformly dispersed in the ferritic matrix powders with an average size of about 3.7 nm, which rendered the alloy powders so stable that it retained nanocrystalline structure after annealing at 900 °C for 1 h. The ZrO{sub 2} nanoparticles have a tetragonal crystal structure and the following orientation relationship with the matrix: (0 0 2){sub ZrO2}//(0 0 2){sub Matrix} and [0 1 0]{sub ZrO2}//[1 2 0]{sub Matrix}. The size and dispersion of the ZrO{sub 2} particles are comparable to those of Y–Ti–O enriched oxides reported in irradiation-resistant ODS alloys. This suggests a potential application of the new alloy powders for nuclear energy applications.

Preparation of Ce- and La-Doped Li4Ti5O12 Nanosheets and Their Electrochemical Performance in Li Half Cell and Li4Ti5O12/LiFePO4 Full Cell Batteries

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Meng Qin

2017-06-01

Full Text Available This work reports on the synthesis of rare earth-doped Li4Ti5O12 nanosheets with high electrochemical performance as anode material both in Li half and Li4Ti5O12/LiFePO4 full cell batteries. Through the combination of decreasing the particle size and doping by rare earth atoms (Ce and La, Ce and La doped Li4Ti5O12 nanosheets show the excellent electrochemical performance in terms of high specific capacity, good cycling stability and excellent rate performance in half cells. Notably, the Ce-doped Li4Ti5O12 shows good electrochemical performance as anode in a full cell which LiFePO4 was used as cathode. The superior electrochemical performance can be attributed to doping as well as the nanosized particle, which facilitates transportation of the lithium ion and electron transportation. This research shows that the rare earth doped Li4Ti5O12 nanosheets can be suitable as a high rate performance anode material in lithium-ion batteries.

Preparation of Ce- and La-Doped Li4Ti5O12 Nanosheets and Their Electrochemical Performance in Li Half Cell and Li4Ti5O12/LiFePO4 Full Cell Batteries

Science.gov (United States)

Qin, Meng; Li, Yueming; Lv, Xiao-Jun

2017-01-01

This work reports on the synthesis of rare earth-doped Li4Ti5O12 nanosheets with high electrochemical performance as anode material both in Li half and Li4Ti5O12/LiFePO4 full cell batteries. Through the combination of decreasing the particle size and doping by rare earth atoms (Ce and La), Ce and La doped Li4Ti5O12 nanosheets show the excellent electrochemical performance in terms of high specific capacity, good cycling stability and excellent rate performance in half cells. Notably, the Ce-doped Li4Ti5O12 shows good electrochemical performance as anode in a full cell which LiFePO4 was used as cathode. The superior electrochemical performance can be attributed to doping as well as the nanosized particle, which facilitates transportation of the lithium ion and electron transportation. This research shows that the rare earth doped Li4Ti5O12 nanosheets can be suitable as a high rate performance anode material in lithium-ion batteries. PMID:28632167

Shell model for BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions

Science.gov (United States)

Vielma, J.; Jackson, D.; Roundy, D.; Schneider, G.

2010-03-01

Even though the composition of BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions is similar to other ferroelectric compounds, the dielectric response is unusual. Results of permittivity measurements as a function of temperature show a diffuse phase transition indicative of a weakly coupled relaxor behavior.footnotetextC. C. Huang and D. P. Cann, J. Appl. Phys. 104, 024117 (2008) To investigate the weakly coupled relaxor behavior in these materials at intermediate length scales we are developing a newly calibrated shell model based on first-principles supercell calculations of both the solid solution and its compositional endpoints. Initial results for its phase diagram will presented.

Dry etching of ferroelectric Bi4-xEuxTi3O12 (BET) thin films

International Nuclear Information System (INIS)

Lim, Kyu-Tae; Kim, Kyoung-Tae; Kim, Dong-Pyo; Kim, Chang-Il

2004-01-01

Bi 4-x Eu x Ti 3 O 12 (BET) thin films were etched by using a inductively coupled Cl 2 /Ar plasma. We obtained a maximum etch rate of 69 nm/min at a gas mixing ratio of Cl 2 (20 %)/Ar (80 %). This result suggests that an effective method for BET etching is chemically assisted physical etching. With increasing coil RF power, the plasma density increases so that the increased reactive free radicals and ions enhance the etch rates of BET, Pt, and SiO 2 . As the dc-bias voltage is increased, the increased ion energy leads to an increased etch rate of BET films. From X-ray photoelectron spectroscopy, the intensities of the Bi-O, the Eu-O, and the Ti-O peaks change with increasing Cl 2 concentration. For a pure Ar plasma, the peak associated with the oxygen-metal (O-M: TiO 2 , Bi 2 O 3 , Eu 2 O 3 ) bond seems to disappear while the pure oxygen peak does not appear. After the BET thin films is etched by using a Cl 2 /Ar plasma, the peak associated with the O-M bond increases slowly, but more quickly than the peak associated with pure oxygen atoms, due to a decrease in the Ar-ion bombardment. These results seem to indicate that Bi and Eu react little with Cl atoms and are removed predominantly by argon-ion bombardment. Also, Ti reacts little with Cl radicals and is mainly removed by chemically assisted physical etching.

Enhanced cycling stability of microsized LiCoO2 cathode by Li4Ti5O12 coating for lithium ion battery

International Nuclear Information System (INIS)

Yi, Ting-Feng; Shu, J.; Yue, Cai-Bo; Zhu, Xiao-Dong; Zhou, An-Na; Zhu, Yan-Rong; Zhu, Rong-Sun

2010-01-01

The effect of Li 4 Ti 5 O 12 (LTO) coating amount on the electrochemical cycling behavior of the LiCoO 2 cathode was investigated at the high upper voltage limit of 4.5 V. Li 4 Ti 5 O 12 (≤5 wt.%) is not incorporated into the host structure and leads to formation of uniform coating. The cycling performance of LiCoO 2 cathode is related with the amount of Li 4 Ti 5 O 12 coating. The initial capacity of the LTO-coated LiCoO 2 decreased with increasing Li 4 Ti 5 O 12 coating amount but showed enhanced cycling properties, compared to those of pristine material. The 3 wt.% LTO-coated LiCoO 2 has the best electrochemical performance, showing capacity retention of 97.3% between 2.5 V and 4.3 V and 85.1% between 2.5 V and 4.5 V after 40 cycles. The coulomb efficiency shows that the surface coating of Li 4 Ti 5 O 12 is beneficial to the reversible intercalation/de-intercalation of Li + . LTO-coated LiCoO 2 provides good prospects for practical application of lithium secondary batteries free from safety issues.

Ti-Mg alloy powder synthesis via mechanochemical reduction of TiO 2 by elemental magnesium

CSIR Research Space (South Africa)

Mushove, T

2009-04-01

Full Text Available This paper reports the preliminary results of an investigation on the synthesis of a Ti-Mg alloy powder through mechanochemical processing of TiO 2 and Mg powders. TiO 2 was mixed with elemental Mg according to a nominal stoichiometric composition...

C, N co-doped TiO_2/TiC_0_._7N_0_._3 composite coatings prepared from TiC_0_._7N_0_._3 powder using ball milling followed by oxidation

International Nuclear Information System (INIS)

Hao, Liang; Wang, Zhenwei; Zheng, Yaoqing; Li, Qianqian; Guan, Sujun; Zhao, Qian; Cheng, Lijun; Lu, Yun; Liu, Jizi

2017-01-01

Highlights: • TiO_2/TiC_0_._7N_0_._3 coatings were prepared by ball milling followed by oxidation. • In situ co-doping of C and N with simultaneous TiO_2 formation was observed. • Improved photocatalytic activity under UV/visible light was noticed. • Synergism in co-doping and heterojunction formation promoted carrier separation. - Abstract: Ball milling followed by heat oxidation was used to prepared C, N co-doped TiO_2 coatings on the surfaces of Al_2O_3 balls from TiC_0_._7N_0_._3 powder. The as-prepared coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectrophotometer (UV–vis). The results show that continuous TiC_0_._7N_0_._3 coatings were formed after ball milling. C, N co-doped TiO_2/TiC_0_._7N_0_._3 composite coatings were prepared after the direct oxidization of TiC_0_._7N_0_._3 coatings in the atmosphere. However, TiO_2 was hardly formed in the surface layer of TiC_0_._7N_0_._3 coatings within a depth less than 10 nm during the heat oxidation of TiC_0_._7N_0_._3 coatings in carbon powder. Meanwhile, the photocatalytic activity evaluation of these coatings was conducted under the irradiation of UV and visible light. All the coatings showed photocatalytic activity in the degradation of MB no matter under the irradiation of UV or visible light. The C, N co-doped TiO_2/TiC_0_._7N_0_._3 composite coatings showed the most excellent performance. The enhancement under visible light irradiation should attribute to the co-doping of carbon and nitrogen, which enhances the absorption of visible light. The improvement of photocatalytic activity under UV irradiation should attribute to the synergistic effect of C, N co-doping, the formation of rutile-anatase mixed phases and the TiO_2/TiC_0_._7N_0_._3 composite microstructure.

Microstructure and physical properties of laser Zn modified amorphous-nanocrystalline coating on a titanium alloy

Science.gov (United States)

Li, Jia-Ning; Gong, Shui-Li; Shi, Yi-Ning; Suo, Hong-Bo; Wang, Xi-Chang; Deng, Yun-Hua; Shan, Fei-Hu; Li, Jian-Quan

2014-02-01

A Zn modified amorphous-nanocrystalline coating was fabricated on a Ti-6Al-4V alloy by laser cladding of the Co-Ti-B4C-Zn-Y2O3 mixed powders. Such coating was researched by means of a scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM), etc. Experimental results indicated that the Co5Zn21 and TiB2 nanocrystalline phases were produced through in situ metallurgical reactions, which blocked the motion of dislocation, and TiB2 grew along (010), (111) and (024). The Co5Zn21 nanocrystals were produced attached to the ceramics, which mainly consisted of the Co nanoparticles embedded in a heterogeneous zinc, and had varied crystalline orientations.

Synthesis of Li4Ti5O12 and its electrochemical properties

CSIR Research Space (South Africa)

Liu, G

2011-12-01

Full Text Available Lithium-ion batteries are now well established in the market as the rechargeable power source. The spinel Li4Ti5O12 has many advantages over the graphite, although, which has been used as anode since lithium ion batteries was invented. Li4Ti5O12...

Wear-triggered self-healing behavior on the surface of nanocrystalline nickel aluminum bronze/Ti3SiC2 composites

Science.gov (United States)

Zhai, Wenzheng; Lu, Wenlong; Zhang, Po; Wang, Jian; Liu, Xiaojun; Zhou, Liping

2018-04-01

Self-healing can protect materials from diverse damages, but is intrinsically difficult in metals. This paper demonstrates a potential method through a simultaneous decomposition and oxidation of Ti3SiC2 to achieve healing of stress cracking on the surface of nickel aluminum bronze (NAB)/Ti3SiC2 nanocrystalline composites during fretting wear. At the finest nanocrystalline materials, a crack recovery would be attained at 76.5%. The repetitive fretting wear leads to a modest amount of 'flowability' of Ti3SiC2 toward the crack, facilitating crack recovery. Along with the wear-triggered self-healing, the NAB/Ti3SiC2 shows an improved tribological performance with the stable decreased friction torque due to the formation of lubrication TiO2 oxide.

Synthesis and characterization of BaTiO3 ferroelectric material

International Nuclear Information System (INIS)

Osman, K.I.

2011-01-01

BaTiO 3 powder was prepared at low temperatures using the solid-state reaction, starting with two different precursors; the BaCO 3 /TiO 2 and the Ba(NO 3 ) 2 /TiO 2 powder mixtures. It was found that, a single phase BaTiO 3 was formed after calcination at 750 degree C for 10 h and at 600 degree C for 6 h for the first and second mixtures, respectively. Thermal and XRD analyses were used to study the formation kinetics of BaTiO 3 . Contracting volume reaction model was found to control both reactions. The SEM of the as milled powder, TMA, TG and thermodynamics analysis have been used to propose a realistic approach describing the reaction mechanism of BaTiO 3 . Characterization and the dielectric properties of the sintered BaTiO 3 were investigated. The relative permittivity and the dielectric loss measured at room temperature and at 1 khz were 2028.5 and 0.043 for BaTiO 3 prepared from BaCO 3 /TiO 2 , while they were 1805.33 and 0.41 for BaTiO 3 prepared from Ba(NO 3 ) 2 /TiO 2 .

Electrochemical performance of La2O3/Li2O/TiO2 nano-particle coated cathode material LiFePO4.

Science.gov (United States)

Wang, Hong; Yang, Chi; Liu, Shu-Xin

2014-09-01

Cathode material, LiFePO4 was modified by coating with a thin layer of La2O3/Li2O/TiO2 nano-particles for improving its performance for lithium ion batteries. The morphology and structure of the modified cathode material were characterized by powder X-ray diffraction, scanning electron microcopy and AES. The performance of the battery with the modified cathode material, including cycling stability, C-rate discharge was examined. The results show that the battery composed of the coated cathode materials can discharge at a large current density and show stable cycling performance in the range from 2.5 to 4.0 V. The rate of Li ion diffusion increases in the battery with the La2O3/Li2O/TiO2-coated LiFePO4 as a cathode and the coating layer may acts as a faster ion conductor (La(2/3-x)Li(3x)TiO3).

Comparative analysis of Dye-Sensitized Solar Cells (DSSC) having different nanocrystalline TiO2 layer structures

International Nuclear Information System (INIS)

Forcade, Fresnel; Gonzalez, Bernardo; Vigil, Elena; Jennings, James R.; Duna, Halina; Wang, Hongxia; Peter, Laurence M.

2009-01-01

Full text: Dye-sensitized solar cells (DSSC) are very prospective because of their low cost and comparatively not so low efficiency. This represents an advantage together with the innocuous character of the constituent materials. We study different types of DSSC. The procedure for making them has been the same except for the TiO 2 layer structure. This layer must be porous and nanocrystalline in order to increase light absorption by the sensitizer. On the other hand, this condition causes that the electrolyte contacts the transparent conducting oxide (TCO) underneath the TiO 2 originating undesired recombinations. Also the electrical contact of the Tio to the TCO depends on the technology used to deposit the TiO 2 . In order to avoid possible leakage currents caused by recombinations from the TCO to the electrolyte and improve TiO 2 -TCO electrical contact, a thin TiO 2 film is placed in between the porous TiO 2 layer and the TCO. Different structures are obtained using different technologies to obtain the thin TiO 2 film. These structures are analyzed from their volt-amperic characteristic, external quantum efficiency spectra and voltage decay observed when light is suppressed. Results obtained allow making recommendations regarding nanocrystalline TiO 2 structure to be used in DSSC. (author)

Preparation of CaTiO3 Asymmetric Membranes Using Polyetherimide as Binder Polymer

Directory of Open Access Journals (Sweden)

Endang Purwanti Setyaningsih

2016-03-01

Full Text Available Asymmetric dense and thin membranes have been prepared from powders of perovskite oxide-type CaTiO3 without cracking by phase inversion method. Polyetherimide was used as a polymeric binder in the method. The resulting green membranes, composed of CaTiO3 powder and polyetherimide binder, were sintered at 890, 1100 or 1200 °C. The crystal phase of CaTiO3 was analyzed using X-Ray Diffraction (XRD. The XRD pattern of the synthesized CaTiO3 powder was matched with the reference indicating the formation of CaTiO3 structure. Sintering at 890 °C fails to form a strong membrane. Scanning Electron Microscope (SEM images of the membranes showed that the membrane had the asymmetric structure with dense layer on one side and porous layer on the other side. The pores in the porous layer were both finger-like and sponge-like structure. The mechanical strength of the membranes, which were determined by Vickers micro hardness method, varied from 3.5 to 25.8 Hv. The strongest membrane without any crack was resulted from sintering at 1200°C with hardness values between 19.4 and 25.8 Hv. Thermal expansion coefficients of the asymmetric membranes sintered at 1100 and 1200 °C, measured with Thermomechanical Analyzer (TMA, were 10.82 × 10-6 and 12.78 × 10-6.C-1 respectively.

Combustion synthesis of nanocrystalline ceria (CeO2) powders by a dry route

International Nuclear Information System (INIS)

Hwang, C.-C.; Huang, T.-H.; Tsai, J.-S.; Lin, C.-S.; Peng, C.-H.

2006-01-01

In this study, ceria (CeO 2 ) powders were synthesized with 50 g per batch via a combustion technique using two kinds of starting materials-urea [(NH 2 ) 2 CO] (as a fuel) and ceric ammonium nitrate [Ce(NH 4 ) 2 (NO 3 ) 6 ] (acting as both the source of cerium ion and an oxidizer). The starting materials were mixed thoroughly without adding water, and then ignited in the air at room temperature. It underwent a self-combustion process with a large amount of smoke, a voluminous loose product. The as-synthesized powders were characterized by X-ray diffraction (XRD) analysis, transmission electron microscope (TEM), scanning electron microscope (SEM), CHN elemental analyzer, surface area measurements, and sinterability. Experimental results revealed that the nanocrystalline CeO 2 powders with low impurity content ( 2 /g and ∼25 nm, respectively, through the stoichiometric fuel/oxidizer ratio reaction. The powder, when cold pressed and sintered in the air at 1250 deg. C for 1 h, was measured to attain the sintered density ∼92% of theoretical density having submicron grain size. In addition, the thermal decomposition and combustion process of the reactant mixture were investigated using thermogravimetry (TG), differential scanning calorimetry (DSC), and mass spectrometry (MS) techniques simultaneously. Based on the results of thermal analysis, a possible mechanism concerning the combustion reaction is proposed

High Tap Density Li4Ti5O12 Microspheres: Synthetic Conditions and Advanced Electrochemical Performance

KAUST Repository

Ming, Jun; Zheng, Junwei; Zhou, Qun; Ren, Jianxin; Ming, Hai; Jia, Zhenyong; Zhang, Yanqing

2017-01-01

Preparation of uniform spherical Li4Ti5O12 with high tap density is significant to achieve a high volumetric energy density in lithium-ion batteries. Herein, Li4Ti5O12 micro-spheres with variable tap-density and tunable size distribution were synthesized by a newly designed industrial spray drying approach. The slurry concentration, sintering time and sintering conditions after spray, the effect of Li/Ti molar ratio on the lithium ion (Li+) storage capability were investigated. A narrow particle size distribution around 10 μm and high tap-density close to 1.4 g cm-3 of the Li4Ti5O12 spheres can be obtained under the optimized conditions. The Li4Ti5O12 spheres can deliver much higher capacity of 168 mAh g-1 at 1 C-rate and show high capacity retention of 97.7% over 400 cycles. The synthetic conditions are confirmed to be critical for improving the electron conductivity and Li+ diffusivity by adjusting the crystal and spatial structures. As-prepared high performance Li4Ti5O12 is an ideal electrode for Li-ion batteries or capacitors; meanwhile the presented approach is also applicable for preparing other kind of spherical materials.

High Tap Density Li4Ti5O12 Microspheres: Synthetic Conditions and Advanced Electrochemical Performance

KAUST Repository

Ming, Jun

2017-03-17

Preparation of uniform spherical Li4Ti5O12 with high tap density is significant to achieve a high volumetric energy density in lithium-ion batteries. Herein, Li4Ti5O12 micro-spheres with variable tap-density and tunable size distribution were synthesized by a newly designed industrial spray drying approach. The slurry concentration, sintering time and sintering conditions after spray, the effect of Li/Ti molar ratio on the lithium ion (Li+) storage capability were investigated. A narrow particle size distribution around 10 μm and high tap-density close to 1.4 g cm-3 of the Li4Ti5O12 spheres can be obtained under the optimized conditions. The Li4Ti5O12 spheres can deliver much higher capacity of 168 mAh g-1 at 1 C-rate and show high capacity retention of 97.7% over 400 cycles. The synthetic conditions are confirmed to be critical for improving the electron conductivity and Li+ diffusivity by adjusting the crystal and spatial structures. As-prepared high performance Li4Ti5O12 is an ideal electrode for Li-ion batteries or capacitors; meanwhile the presented approach is also applicable for preparing other kind of spherical materials.

Synthesis of Nanocrystalline SnO2 Modified TiO2:a Material for Carbon Monoxide Gas Sensor

Directory of Open Access Journals (Sweden)

A. B. BODADE

2008-11-01

Full Text Available Nanocrystalline SnO2 doped TiO2 having average crystallite size of 45-50 nm were synthesized by the sol-gel method and studied for gas sensing behavior to reducing gases like CO, liquefied petroleum gas (LPG, NH3 and H2. The material characterization was done by using X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR and scanning electron microscope (SEM. The sensitivity measurements were carried out as a function of different operating temperature in SnO2 doped TiO2. The 15 wt.% SnO2 doped TiO2 based CO sensor shows better sensitivity at an operating temperature 240°C Incorporation of 0.5 wt% Pd improved the sensitivity, selectivity, response time and reduced the operating temperature from 240°C to 200°C for CO sensor.

Dye Sensitized Solar Cell with Conventionally Annealed and Post-Hydrothermally Treated Nanocrystalline Semiconductor Oxide TiO2 Derived from Sol-Gel Process

Directory of Open Access Journals (Sweden)

Akhmad Yuwono

2011-05-01

Full Text Available Dye-sensitized solar cell (DSSC is one of the very promising alternative renewable energy sources to anticipate the declination in the fossil fuel reserves in the next few decades and to make use of the abundance of intensive sunlight energy in tropical countries like Indonesia. In the present study, TiO2 nanoparticles of different nanocrystallinity was synthesized via sol−gel process with various water to inorganic precursor ratio (Rw of 0.85, 2.00 and 3.50 upon sol preparation, followed with subsequent drying, conventional annealing and post-hydrothermal treatments. The resulting nanoparticles were integrated into the DSSC prototype and sensitized with an organic dye made of the extract of red onion. The basic performance of the fabricated DSSC has been examined and correlated to the crystallite size and band gap energy of TiO2 nanoparticles. It was found that post-hydrothermally treated TiO2 nanoparticles derived from sol of 2.00 Rw, with the most enhanced nanocrystalline size of 12.46 nm and the lowest band gap energy of 3.48 eV, showed the highest open circuit voltage (Voc of 69.33 mV.

Improved dielectric properties and grain boundary response in neodymium-doped Y_2_/_3Cu_3Ti_4O_1_2 ceramics

International Nuclear Information System (INIS)

Liang, Pengfei; Yang, Zupei; Chao, Xiaolian

2016-01-01

Rare earth element neodymium was adopted to refine grain and in turn increase the volume of grain boundary of Y_2_/_3Cu_3Ti_4O_1_2 ceramics, which could strongly increase the resistance of grain boundary. Proper amount of Nd substitution in Y_2_/_3_−_xNd_xCu_3Ti_4O_1_2 ceramics could significantly depress the low-frequency dielectric loss. When the doping level is 0.06 and 0.09, the samples exhibited a relatively low dielectric loss (below 0.050 between 0.3 and 50 kHz) and high dielectric constant above 11000 over a wide frequency range from 40 Hz to 100 kHz. Based on the ε′-T plots, dielectric relaxation intensity was substantially weakened by Nd doping so that the temperature stability of dielectric constant was improved obviously. The correlations between low-frequency dielectric loss and the resistance of grain boundary were revealed. After Nd doping, the activation energies for the conduction behavior in grain boundaries were significantly enhanced, and the activation energies for the dielectric relaxation process in grain boundaries were slightly influenced. - Highlights: • Significant decrease in dielectric loss of Y_2_/_3_−_xNd_xCu_3Ti_4O_1_2 ceramics was realized. • The enhanced grain boundary density is responsible for the lowered dielectric loss. • Nd doping could improve the temperature stability of dielectric constant. • Oxygen vacancies contribute to conduction and relaxation process of grain boundaries.

Superconductivity at 108 K in the simplest non-toxic double-layer cuprate of Ba2CaCu2O4(O,F)2

International Nuclear Information System (INIS)

Shirage, P M; Shivagan, D D; Crisan, A; Tanaka, Y; Kodama, Y; Kito, H; Iyo, A

2008-01-01

We report the superconductivity in apical fluorine system of Ba 2 CaCu 2 O 6-y F y : the second member of Ba 2 Ca n-1 Cu n O 2n (O,F) 2 homologous series. The polycrystalline samples of Ba 2 CaCu 2 O 6-y F y (F-0212) were synthesized under high pressure as a parameter of nominal fluorine content (y). Samples with y = 2.0 ∼ 1.2 elucidating the very sharp superconducting transitions in temperature dependence of susceptibility from under doping state to slightly over doping state via optimal doping state. A remarkable highest T c of 108 K has been achieved for the sample synthesized from a nominal composition of Ba 2 CaCu 2 O 4.4 F 1.6 . This T c is highest among the double CuO 2 layered system except for that including toxic elements such as Hg and T1. The T c has been systematically controlled from 57 K to 108 K by controlling the doping state, by designing the starting composition of fluorine and oxygen. The strong dependence of the 'a' and 'c' lattice constants were found on the nominal F content. We propose the Ba 2 CaCu 2 O 4 (O,F) 2 as a promising material for practical use due to its high T c and non-toxicity with a simple crystal structure

Electrical properties of niobium doped Bi4Ti3O12-SrBi4Ti4O15 intergrowth ferroelectrics

International Nuclear Information System (INIS)

Parida, Geetanjali; Bera, J.

2013-01-01

Bismuth layer structured ferroelectrics (BLSFs) have attracted much attention because of their potential applications in non-volatile ferroelectric random access memories and high temperature piezoelectric. They are very attractive for these applications due to their fatigue free nature and environment friendly lead-free composition. BLSF crystal structure has layers of bismuth oxide and pseudo perovskite block stacked alternately along their c-direction, For commercial application, numerous efforts have been made to improve the electrical properties of BLSFs. Some effective approaches are: (i) doping at A-site, (ii) high valentcation doping at B-site and (iii) formation of intergrowth between different BLSFs. The intergrowth BLSFs are consist of regular stacking of one half the unit cell of m-member structure and one half the unit cell of (m+1) member BLSF structure along their c-axis. In this report, Nb-doped Bi 4 Ti 3 O 12 -SrBi 4 Ti 4 O 15 intergrowth ceramics have been prepared by modified oxalate route. XRD phase analysis confirmed the formation of single phase compound. Nb-doping does not affect the basic crystal structure of the intergrowth. SEM micrographs showed that the grain size of the ceramics decreases with Nb-doping. The temperature dependence of dielectric constant and losses was investigated in the temperature range 30 to 800℃ and frequency range 1 kHz to 1 MHz. With Nb-doping, the T c of the ferroelectrics reduces and peak permittivity increases. Doping also introduces small relaxor behaviour in the ferroelectrics. The dc conductivity of the ceramics decreases with doping. The remnant polarization (Pr) of the intergrowth ferroelectrics is increased with Nb doping. (author)

Spray drying of spherical Li{sub 4}Ti{sub 5}O{sub 12}/C powders using polyvinyl pyrrolidone as binder and carbon source

Energy Technology Data Exchange (ETDEWEB)

Liu, Wei [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 110049 (China); Shanghai Nanotechnology Promotion Center, Shanghai 200237 (China); Wang, Qian; Cao, Chunhui [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 110049 (China); Han, Xuewu [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Zhang, Jian, E-mail: zjskycn@163.com [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Xie, Xiaohua, E-mail: xiaohuaxie@126.com [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Xia, Baojia [Research Center for New Energy Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 110049 (China)

2015-02-05

Highlights: • The spherical Li{sub 4}Ti{sub 5}O{sub 12}/C granules were prepared by spray drying. • Polyvinyl pyrrolidone (PVP) was used as binder and carbon source. • Tap density and spherical structure increase with the increase of PVP content. • Li{sub 4}Ti{sub 5}O{sub 12}/C granules exhibits better rate capability and excellent cyclability. - Abstract: Polyvinyl pyrrolidone (PVP) was used as binder and carbon source to synthesize stable and spherical Li{sub 4}Ti{sub 5}O{sub 12}/C granules by spray drying. The effects of PVP content and atmospheres on the properties of Li{sub 4}Ti{sub 5}O{sub 12} were investigated. The obtained samples were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and electrochemical tests, respectively. The results indicate that the average particle size, tap density and degree of spherical structure increase accordingly to the increase of PVP content. However, the large secondary particle would deteriorate the rate capacity at high current density. The carbon coating could significantly improve the rate capacity, which is attributed to the smaller primary particle and higher electrical conductivity.

Microstructure and enhanced dielectric properties of yttrium and zirconium co-doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

Energy Technology Data Exchange (ETDEWEB)

Xu, Zunping, E-mail: xzp16213@163.com [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China); Qiang, Hua [College of Electromechanical Engineering, Chongqing College of Humanities, Science and Technology, Chongqing 401524 (China); Chen, Yi; Chen, Zhiqian [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China)

2017-04-15

CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics doped with Y{sub 2}O{sub 3}, ZrO{sub 2}, and (Y{sub 2}O{sub 3}+ZrO{sub 2}) were prepared by the citrate-nitrate combustion derived powders in order to investigate the effect of dopants on the microstructure and electrical properties. The results showed that giant dielectric response was enhanced by co-doping of Y{sup 3+} and Zr{sup 4+} ions at the Ti site. Y{sub 2}O{sub 3} and ZrO{sub 2} additive can inhibit the grain growth. Compared with other samples, (Y{sub 2}O{sub 3}+ZrO{sub 2}) co-doped ceramics exhibit a dense and homogenous fine-grained microstructure. A much better temperature and frequency stability of dielectric properties were realized in these ceramics. The dielectric loss (tan δ) < 0.05 in the frequency range of 200 Hz–60 kHz at room temperature, and in the temperature range of 15–72 °C at 10 kHz was successfully accomplished in (Y{sub 2}O{sub 3}+ZrO{sub 2}) co-doped CCTO ceramics. Low tan δ ∼0.039 and high dielectric constant (ε{sub r} ∼10196) were observed at room temperature and 10 kHz for the above ceramic samples, and the characteristic frequency shifts to higher frequency with increasing measuring temperature. The present results indicate that (Y{sub 2}O{sub 3}+ZrO{sub 2}) co-doping may improve the dielectric properties and increase the grain boundary resistance of CCTO. - Highlights: • Y and Zr co-doped CCTO exhibits a dense and homogenous fine-grained microstructure. • Y and Zr co-doped CCTO performs a lower dielectric loss in wide-range of frequency. • Temperature and frequency stability of dielectric properties were greatly enhanced.

Solution based synthesis of mixed-phase materials in the Li{sub 2}TiO{sub 3}–Li{sub 4}SiO{sub 4} system

Energy Technology Data Exchange (ETDEWEB)

Hanaor, Dorian A.H., E-mail: dorian.hanaor@sydney.edu.au [School of Civil Engineering, University of Sydney, NSW 2006 (Australia); Kolb, Matthias H.H. [Institute for Applied Materials, Karlsruhe Institute of Technology, 76021 (Germany); Gan, Yixiang [School of Civil Engineering, University of Sydney, NSW 2006 (Australia); Kamlah, Marc; Knitter, Regina [Institute for Applied Materials, Karlsruhe Institute of Technology, 76021 (Germany)

2015-01-15

Highlights: • Investigation of phase stability in the quasi-binary Li{sub 2}TiO{sub 3}–Li{sub 4}SiO{sub 4} system. • Sol-based syntheses of mixed phase materials from organometallic precursors. • LiCl based synthesis results in greater lithium deficiency than LiOH synthesis. • The Li{sub 2}TiO{sub 3}–Li{sub 4}SiO{sub 4} quasi binary system appears to exhibit monotectic behaviour. • Mixed phase materials show liquid formation from melting of silicate material at 1100 °C. - Abstract: As candidate tritium breeder materials for use in the ITER helium cooled pebble bed, ceramic multiphasic compounds lying in the region of the quasi-binary lithium metatitanate–lithium orthosilicate system may exhibit mechanical and physical advantages relative to single phase materials. Here we present an organometallic solution-based synthesis procedure for the low-temperature fabrication of compounds in the Li{sub 2}TiO{sub 3}–Li{sub 4}SiO{sub 4} region and investigate phase stability and transformations through temperature varied X-ray diffraction and scanning calorimetry. Results demonstrate that the metatitanate and metasilicate phases Li{sub 2}TiO{sub 3} and Li{sub 2}SiO{sub 3} readily crystallise in nanocrystalline form at temperatures below 180 °C. Lithium deficiency in the region of 5% results from Li sublimation from Li{sub 4}SiO{sub 4} and/or from excess Li incorporation in the metatitanate phase and brings about a stoichiometry shift, with product compounds exhibiting mixed lithium orthosilicate/metasilicate content towards the Si rich region and predominantly Li{sub 2}TiO{sub 3} content towards the Ti rich region. Above 1150 °C the transformation of monoclinic to cubic γ-Li{sub 2}TiO{sub 3} disordered solid-solution occurs while the melting of silicate phases indicates a likely monotectic type system with a solidus line in the region 1050–1100 °C. Synthesis procedures involving a lithium chloride precursor are not likely to be a viable option for

Lithium ion diffusion in Li4+xTi5O12: From ab initio studies

International Nuclear Information System (INIS)

Chen, Y.C.; Ouyang, C.Y.; Song, L.J.; Sun, Z.L.

2011-01-01

Highlights: → Li diffusion pathways in Li 4 Ti 5 O 12 and Li 7 Ti 5 O 12 are obtained from ab initio calculations. → Cooperative Li migration in Li 7+δ Ti 5 O 12 with very low energy barrier is proposed. → Li diffusion is faster in lithiated state than in delithiated state is confirmed theoretically. - Abstract: Lithium ion dynamics in Li 4+x Ti 5 O 12 spinel are investigated from first principles calculations. The diffusion pathways are optimized and the energy barriers of lithium migration under four types of dilute defect extremes: Li 4+δ Ti 5 O 12 , Li 4-δ Ti 5 O 12 , Li 7+δ Ti 5 O 12 and Li 7-δ Ti 5 O 12 (δ << 1) are calculated with the nudged elastic band method. Results show that lithium diffusion in the charged state (energy barriers are 1.0 and 0.7 eV for interstitial Li and Li vacancy diffusion, respectively) is much slower than in the discharged state (energy barriers are 0.13 and 0.35 eV for interstitial Li and Li vacancy diffusion, respectively). The diffusion coefficients are evaluated based on lattice gas model and hopping mechanism. The obtained results are compared with available experimental data within a two-phase co-existence framework.

Investigations of the physical and chemical properties of solid solutions Pb/Mnsub(1/2), Nbsub(1/2)/O3 - PbTiO3 - PbZrO3

International Nuclear Information System (INIS)

Szadkowska, A.; Majewska-Pilchowska, K.

1981-01-01

The preparation of the PMTZ materials on the basis of solid solutions Pb/Mnsub(1/2)/O 3 - PbTiO 3 - PbZrO 3 has been described. The X-ray analysis of the examined materials has been made, and porosity and grain size have been determined. Dielectric constant and mechanical quality factor as a function of PbZrO 3 content have been determined. The obtained results indicate that solid solutions Pb/Mnsub(1/2), Nbsub(1/2)/O 3 - PbTiO 3 - PbZrO 3 are useful piezoelectric materials. (author)

Solid-state synthesis of Li{sub 4}Ti{sub 5}O{sub 12} whiskers from TiO{sub 2}-B

Energy Technology Data Exchange (ETDEWEB)

Yao, Wenjun [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, No. 5 Xin Mofan Road, Nanjing 210009 (China); Zhuang, Wei [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, No. 5 Xin Mofan Road, Nanjing 210009 (China); College of Biotechnology and Pharmaceutical Engineering, National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, No. 30, Puzhu South Road, Nanjing 211816 (China); Ji, Xiaoyan [Division of Energy Science/Energy Engineering, Luleå University of Technology, Luleå 97187 Sweden (Sweden); Chen, Jingjing; Lu, Xiaohua [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, No. 5 Xin Mofan Road, Nanjing 210009 (China); Wang, Changsong, E-mail: wcs@njtech.edu.cn [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, No. 5 Xin Mofan Road, Nanjing 210009 (China)

2016-03-15

Highlights: • The Li{sub 4}Ti{sub 5}O{sub 12} whiskers were synthesized from TiO{sub 2}-B whiskers via a solid state reaction. • The TiO{sub 2}-B crystal structure for lithium diffusion is easier than anatase. • The separated diffusion and reaction process is crucial for the solid-state syntheses of Li{sub 4}Ti{sub 5}O{sub 12} whiskers. - Abstract: In this work, Li{sub 4}Ti{sub 5}O{sub 12} (LTO) was synthesized from the precursors of TiO{sub 2}-B and anatase whiskers, respectively. The synthesized LTO whiskers from TiO{sub 2}-B whiskers via a solid state reaction at 650 °C have a high degree of crystallinity with an average diameter of 300 nm. However, when anatase whiskers were used as the precursor, only particle morphology LTO was produced at 750 °C. The further analysis of the precursors, the intermediate products and the final products reveal that the crystal structure of the anatase hinders the diffusion of lithium, leading to a typical reaction–diffusion process. Under this condition, only particle morphology LTO can be produced. However, the crystal structure of the TiO{sub 2}-B is easy for lithium diffusion and the process is performed in two separated steps (i.e., diffusion and reaction), which makes it possible to decrease the solid-state reaction temperature down to 650 °C and then maintain the morphologies of whiskers.

Preparation and characterization of Yttrium-Aluminium garnet (Y3Al5O12)

International Nuclear Information System (INIS)

Ruzicka, J.; Niznansky, D.; Houzvicka, J.; Nikl, M.; Cerny, R.

2009-01-01

This work deals with the preparation of powders and transparent yttrium aluminium garnet (Y 3 Al 5 O 12 - YAG) from nanopowders. Stoichiometric amounts of nanocrystalline Al 2 O 3 and Y 2 O 3 were mixed and chemically pretreated using different basic agents and using ultrasonic bath. Resulting mixture was dried, pressed and heated up to 1750°C. Final material was characterized by X-ray diffraction, DTA and optical and electron microscopy

Photocatalytic Activity in CH3CN Related to the Surface Properties of TiO2 Powders Prepared by Sol-Gel Method

OpenAIRE

Bettoni, Marta; Candori, Pietro; Marmottini, Fabio; Perenze, Nicoletta; Rol, Cesare; Sebastiani, Giovanni V.; Vecchiocattivi, Franco

2009-01-01

Some TiO2 powders, prepared from titanium(IV)tetraisopropoxide by the sol-gel method and thermally treated between 100 and 1000∘C, have been characterized by X-ray powder diffraction and by nitrogen adsorption and desorption at 77 K to calculate the BET-specific surface area, from which the micropore volume and the external surface area can be derived. The photocatalytic activity (ka) of the above powders has been evaluated considering the TiO2-sensitized photo-oxidation of 4-methoxybenzyl al...

Gas swelling behaviour at different stages in Li4Ti5O12/LiNi1/3Co1/3Mn1/3O2 pouch cells

Science.gov (United States)

Liu, Wei; Liu, Haohan; Wang, Qian; Zhang, Jian; Xia, Baojia; Min, Guoquan

2017-11-01

Gas swelling behaviour is a major drawback of batteries that are based on Li4Ti5O12 anode materials and hinders their application. In this article, the morphology and electronic structure changes of Li4Ti5O12 electrodes at ageing and cycling stages are investigated using scanning electron microscopy, X-ray absorption near-edge structure and X-ray photoelectron spectroscopy. A simple method that uses an air bag to collect the generated gases was conducted and the gases were then characterised by gas chromatography/mass spectrometry. The results indicate that the charge transformation of Ti ions would aggravate the gas swelling behaviour. The solid electrolyte interphase (SEI) films form on the surface of the Li4Ti5O12 particles and become thicker with increasing charge state. The gas components change significantly during the ageing and cycling, indicating the complexity of the gas swelling mechanism.