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Title: The role of NH{sub 3} atmosphere in preparing nitrogen-doped TiO{sub 2} by mechanochemical reaction

Abstract

NH{sub 3} atmosphere in ball milling plays an important role in preparing TiO{sub 2-} {sub X} N {sub X} by a simple mechanochemical reaction. The results show that the structure transformation of titania milled in NH{sub 3} is greatly delayed compared with that in air. The specific surface area of titania milled in NH{sub 3} for 2 h is two times larger than that in air. It was also found that titania prepared in NH{sub 3} has obvious absorbance for visible light. Mechanochemical milling in NH{sub 3} atmosphere offers a new route to prepare TiO{sub 2-} {sub X} N {sub X} with high surface area. -- Graphical Abstract: The specific surface area (BET) of titania varies with the increase of milling time in air and gaseous ammonia.

Authors:
 [1];  [1];  [1];  [2];  [3]
  1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)
  2. Australian Research Council Centre for Functional Nanomaterials, School of Engineering, University of Queensland, Qld. 4072 (Australia). E-mail: maxlu@uq.edu.au
  3. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China). E-mail: cheng@imr.ac.cn
Publication Date:
OSTI Identifier:
20784866
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 179; Journal Issue: 1; Other Information: DOI: 10.1016/j.jssc.2005.10.030; PII: S0022-4596(05)00502-5; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AIR; AMMONIA; DOPED MATERIALS; NITROGEN; SPECIFIC SURFACE AREA; TITANIUM OXIDES

Citation Formats

Liu Gang, Li Feng, Chen Zhigang, Lu Gaoqing, and Cheng Huiming. The role of NH{sub 3} atmosphere in preparing nitrogen-doped TiO{sub 2} by mechanochemical reaction. United States: N. p., 2006. Web.
Liu Gang, Li Feng, Chen Zhigang, Lu Gaoqing, & Cheng Huiming. The role of NH{sub 3} atmosphere in preparing nitrogen-doped TiO{sub 2} by mechanochemical reaction. United States.
Liu Gang, Li Feng, Chen Zhigang, Lu Gaoqing, and Cheng Huiming. Sun . "The role of NH{sub 3} atmosphere in preparing nitrogen-doped TiO{sub 2} by mechanochemical reaction". United States. doi:.
@article{osti_20784866,
title = {The role of NH{sub 3} atmosphere in preparing nitrogen-doped TiO{sub 2} by mechanochemical reaction},
author = {Liu Gang and Li Feng and Chen Zhigang and Lu Gaoqing and Cheng Huiming},
abstractNote = {NH{sub 3} atmosphere in ball milling plays an important role in preparing TiO{sub 2-} {sub X} N {sub X} by a simple mechanochemical reaction. The results show that the structure transformation of titania milled in NH{sub 3} is greatly delayed compared with that in air. The specific surface area of titania milled in NH{sub 3} for 2 h is two times larger than that in air. It was also found that titania prepared in NH{sub 3} has obvious absorbance for visible light. Mechanochemical milling in NH{sub 3} atmosphere offers a new route to prepare TiO{sub 2-} {sub X} N {sub X} with high surface area. -- Graphical Abstract: The specific surface area (BET) of titania varies with the increase of milling time in air and gaseous ammonia.},
doi = {},
journal = {Journal of Solid State Chemistry},
number = 1,
volume = 179,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}
  • In situ Raman spectroscopy has been used at temperatures up to 400{sup o}C under O{sub 2}, NH{sub 3}/N{sub 2}, H{sub 2}/N{sub 2}, NH{sub 3}/NO/O{sub 2}/N{sub 2}, O{sub 2}/H{sub 2}O/N{sub 2}, and SO{sub 2}/O{sub 2}/N{sub 2} for studying the influence of these gases on the molecular structure of V{sub 2}O{sub 5}/TiO{sub 2} catalysts with V surface density, n{sub s}, in the range 2.5-18.7 VO{sub x}/nm{sup 2}. The catalyst activities for the SCR of NO by NH{sub 3} have been determined to derive structure-activity relationships in combination with the Raman data. Isolated monovanadates and polyvanadates are formed at various proportions (depending onmore » the loading) on the catalyst surface under dehydrated conditions. The band positions and characteristics are discussed in terms of possible configurations for the dispersed VO{sub x} species. The bands observed, the surface composition, and the bond conservation rule allow to propose a small size for the chains of polyvanadates (i.e., 2, 3). The reducing action of NH{sub 3} is favored in the presence of adjacent V sites; at low loadings, the presence of NH{sub 3} has no effect on the structural properties of surface VO{sub x}. The reducibility in H{sub 2} follows an opposite trend and is favored at low n{sub s}, as indicated by both in situ Raman and H{sub 2}-TPR. The SO{sub 2} presence affects only the molecular structure of catalysts with low n{sub s}, for which a significant part of surface TiO{sub 2} sites are vacant; the effect (judged from the in situ Raman data) is merely one of driving the dispersed vanadia species in a state of 'virtually' high surface density by crowding them together, thereby providing more adjacent V sites for activation of NH{sub 3} in SCR reaction conditions.« less
  • N-doped TiO{sub 2} photocatalysts were prepared by annealing two different precursors, P25 and a TiO{sub 2} xerogel powder under NH{sub 3}/Ar flow at 500, 550, and 600 deg. C. The xerogel powder prepared by peptizing Ti(OH){sub 4} with HNO{sub 3} was composed of nanoparticles and had large specific surface area. During the annealing process, the xerogel powder underwent increase in crystallinity, grain growth and phase transformation, whereas P25 did not show obvious changes. Compared with the N-doped TiO{sub 2} photocatalysts from P25, the N-doped TiO{sub 2} photocatalysts from the xerogel powder possessed higher concentrations of the substitutional nitrogen and exhibitedmore » more obvious absorption in the visible light region. The N-doped TiO{sub 2} photocatalysts from the xerogel powder exhibited obvious visible-light activities for photodegrading methylene blue and the sample prepared at 500 deg. C achieved the best performance with a rate constant (k) about 0.44 h{sup -1}, whereas those from P25 did not exhibit improved visible-light activities. - Graphical abstract: The N-doped TiO{sub 2} powders prepared by annealing the TiO{sub 2} xerogel (named FT) under NH{sub 3}/Ar flow exhibited obvious visible-light activities, whereas annealing P25 under the same conditions did not produce the photocatalysts with improved visible-light activities.« less
  • Hydrogenated diamond-like Carbon (DLC) films have been deposited on Si substrates using CH{sub 4}-based radio-frequency plasmas. The films have been doped with nitrogen by addition of either N{sub 2} or NH{sub 3} into the source gas mixture, producing films with up to 16% and 25% N content, respectively. The effect of additions of Ne to these gas mixtures has been investigated as a possible method to increase the growth rate and the N-content of the films. The authors find that addition of Ne increases the film growth rate until the Ne flow rate equals that of the CH{sub 4}, givingmore » maximum growth rate increases of 70% and 200% for NH{sub 3} and N{sub 2} containing gas mixtures, respectively. At the same time the field emission threshold voltage decreases by a factor of {approximately} 0.5 and 2, respectively. With further increases in Ne flow rate, the film growth rates decrease in both cases, whilst the threshold voltage increases. Micro-combustion measurements show that the N content within the films is proportional to the percentage of the N-containing precursor in the gas phase, but is independent of Ne concentration.« less
  • Lead-free (Bi{sub 0.5}Na{sub 0.5}){sub 0.93}Ba{sub 0.07}TiO{sub 3}-x wt %In{sub 2}O{sub 3} ceramics synthesized by direct reaction sintering have been studied. X-ray diffraction reveals that all (Bi{sub 0.5}Na{sub 0.5}){sub 0.93}Ba{sub 0.07}TiO{sub 3}-x wt %In{sub 2}O{sub 3} ceramics are of a perovskite structure with coexistence of rhombohedral and tetragonal phases. It is found that the direct reaction sintering promotes growing of ceramic grains while doping of In{sub 2}O{sub 3} contributes to inhibit and homogenize the grain growth, as shown by scanning electron microscopy. The ceramics show excellent piezoelectric and dielectric properties with thickness electromechanical coupling factor k{sub t}=0.503, piezoelectric constant d{sub 33}=205more » pC/N, dielectric constant {epsilon}{sub 33}{sup T}/{epsilon}{sub 0}=1046, and loss tangent tan {delta}=0.036.« less
  • Trace amounts of H/sub 2/O and limited exposure to air of reaction mixtures of UCl/sub 4/ and 12-crown-4, 15-crown-5, benzo-15-crown-5, 18-crown-6, or dibenzo-18-crown-6 in 1:3 mixtures of CH/sub 3/OH and CH/sub 3/CN resulted in the hydrolysis and oxidation of UCl/sub 4/ to (UO/sub 2/Cl/sub 4/)/sup 2/minus//. In the presence of these crown ethers, it has been possible to isolate intermediate products via crystallization of crown complexes of the (UO/sub 2/Cl/sub 4/)/sup 2/minus// ion, the (UCl/sub 6/)/sup 2/minus// ion, and (UO/sub 2/Cl/sub 2/(OH/sub 2/)/sub 3/). The neutral moiety crystallizes as a hydrogen-bonded crown ether complex; however, crown ether complexation of amore » counterion, either an ammonium ion formed during the oxidation of U(IV) or a Na/sup +/ ion leached from glass reaction vessels, resulted in novel crystalline complexes of the ionic species. ((NH/sub 4/)(15-crown-5)/sub 2/)/sub 2/(UO/sub 2/Cl/sub 4/) /times/ 2CH/sub 3/CN, ((NH/sub 4/)(benzo-15-crown-5)/sub 2/)/sub 2/(UCl/sub 6/) /times/ 4CH/sub 3/CN, and ((NH/sub 4/)(dibenzo-18-crown-6))/sub 2/(UO/sub 2/Cl/sub 4/) /times/ 2CH/sub 3/CN have been structurally characterized by single-crystal X-ray diffraction techniques. The results of all the crystal studies are presented in detail. The ammonium ions interact with the crown ethers via hydrogen-bonding and electrostatic interactions. 15-Crown-5 and benzo-15-crown-5 form 2:1 sandwich cations, allowing no H/sub 4/N/sup +//hor ellipsis/(UO/sub 2/Cl/sub 4/)/sup 2/minus// interaction. The dibenzo-18-crown-6 complexed ammonium ions are 1:1 and form bifurcated hydrogen bonds with the chlorine atoms in the (UO/sub 2/Cl/sub 4/)/sup /minus// anion. The formation of (Na(12-crown-4)/sub 2//sub 2/(UO/sub 2/Cl/sub 4/) /times/ 2OHMe and (UO/sub 2/Cl/sub 2/(OH)/sub 2/)/sub 3/) /times/ 18-crown-6 /times/ H/sub 2/O /times/ OHMe has been confirmed by preliminary single-crystal X-ray diffraction studies.« less