Microstructures and Properties of WC/Natural Zeolite Composites

doi:10.3724/SP.J.1077.2012.00129

Abstract

Abstract:

WC/zeolite nanocomposites were prepared by ball-milling a mixture of ammonia metatungsten (AMT) and zeolite and then reducing the ball-milled precursor under mixed CH₄/H₂ atmosphere at 900℃. The effects of carbonization time on the microstructure, phase composition, and WC distribution of as-prepared nanocomposites were investigated by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), and scanning transmission electron microscope (STEM). The electrocatalytic activities in alkaline solutions of these nanocomposites were evaluated in a three-electrode system by a powder microelectrode method. Due to the porous structure and high surface area of zeolite, the ball-milled AMT/zeolite precursor could be rapidly reduced in a mixed CH₄/H₂ atmosphere and then formed WC/zeolite nanocomposites. It was found that the active formed phase mainly composed of W₂C and WC which were highly dispersed and extremely small-sized. The results also showed that the WC/zeolite nanocomposite obtained by carbonizing the ball-milled precursor for 4 h exhibited the best electrocatalytic activity, because this sample had smallest-sized and highest relative concents of tungsten carbide.

Key words: WC, natural zeolite, nanocomposites, microstructures, electrocatalytic activity

CLC Number:

TQ131

ZHENG Yi-Fan, ZHAO Na, ZHANG Jie, YU Xiao-Ye, MO Wei-Min. Microstructures and Properties of WC/Natural Zeolite Composites[J]. Journal of Inorganic Materials, 2012, 27(2): 129-133.

Figures/Tables 6

Fig. 1 XRD patterns of natural zeolite(a), AMT/zeolite precursor (b) and products from carbonized at 900℃ (c, d, e) different reaction time performed (c) 2 h, (d) 4 h and (e) 6 h at 900℃

Table 1 Phase composition and crystal size D (nm) of the samples carbonized for different time

Reaction time /h		2	4	6
Phase/wt%	Heulandite	69.9	70.3	74.7
	Mordenite	1.9	1.7	1.6
	Quartz	18.7	15.4	16.0
	W₂C	8.8	10.7	8.4
	WC	0.7	2.1	0.9
Crystal size, D/nm	W₂C	13.5	13.0	14.7
Crystal size, D/nm	WC	15.6	9.9	18.6

Fig. 2 TEM images of natural zeolite (a) and the samples carbonized for 2 h (b), 4 h (c) and 6 h (d)

Fig. 3 HRTEM images of the samples carbonized for 4 h (a) and 6 h (b)

Fig. 4 STEM images of the samples carbonized for 4 h (a) and 6 h (b)

Fig. 5 Cyclic voltammograms of the samples in 0.1 mol/L PNP +0.5 mol/L NaCl solution

References 24

[1]	Wang Y, Lim S. Tribological.Behavior of nanostructured WC particles/polymer coatings. Wear, 2007, 262(9/10): 1097-1101.
[2]	Wu J H, Karthikeyan S, Falk M L, et al. Tribological characteristics of diamond-like carbon (DLC) based nanocomposite coatings. Wear, 2005, 259(1-6): 744-751.
[3]	Sangaraju S, David S J, Aharon G. Solide state synthesis of tungsten carbide nanorods and nanoplatelets by a single-step pyrolysis. J. Phys. Chem. B, 2005, 109(41): 19056-19059.
[4]	Voevodin A A, Zabinski J S. Nanocomposite and nanostructured tribologicalmaterials for space applications. Composites Science and Technology, 2005, 65(5):741-748.
[5]	Shi X L, Shao G Q, Duan X L, et al.The effect of tungsten buffer layer on the stability of diamond with tungsten carbide-cobalt nanocomposite powder during spark plasma sintering. Diamond & Related Materials, 2006(15): 1643-1649.
[6]	Pallone E M J A, Martin D R, Tomasi R, et al. Al2O3-WC synthesis by high-energy reactive milling. Materials Science and Engineering A, 2007, 464(1/2): 47-51.
[7]	El-Eskandarany M S. Fabrication and characterizations of new nanocomposite. WC/Al2O3 materials by room temperature ball milling and subsequent consolidation. Journal of Alloys and Compounds, 2005, 391(1/2): 228-235.
[8]	Keller V, Wehrer P, Garin F, et al. Catalytic activity of tungsten carbides modified by oxygen. J. Catal., 1997, 166(2): 125-135.
[9]	Garin F, Keller V, Ducros R, et al. Catalytic activity of bulk tungsten carbides for alkane reforming III. reaction mechanisms and the kinetic model. J. Catal., 1997, 166(2): 136-147.
[10]	Houston J E, Laramore G E, Park, R L. Surface electronic properties of tungsten, tungsten carbide, and platinum. Science, 1974, 185(4147): 258-260.
[11]	McIntyre D R, Burstein G T, Vossen A D. Effect of carbon monoxide on the electrooxidation of hydrogen by tungsten carbide. J. Power Sources, 2002, 107(1): 67-73.
[12]	Papazov G, Nikolov I, Pavlov D, et al. Sealed lead/acid battery with auxiliary tungsten carbide electrodes. J. Power Sources, 1990, 31(1-4): 79-88.
[13]	Zellner M B, Chen J G G. Surface science and electrochemical studies of WC and W2C PVD films as potential electrocatalysts. Catal. Today, 2005, 99(3/4): 299-307.
[14]	Mayya K S, Gittins D I, Caruso F. Gold-titania core-shell nanoparticles by polyelectrolyte complexation with a titania precursor. Chem. Mater., 2001, 13(11): 3833-3836.
[15]	Teng F, Tian Z J, Xiong G X, et al. Preparation of CdS/SiO2 core-shell particles and hollow SiO2 spheres ranging from nanometers to microns in the nonionic reverse microemulsions. Catal. Today, 2004, 93(5): 651-657.
[16]	Ocana M, Hsu W P, Matijevic E. Preparation and properties of uniform-coated colloidal particles. 6. titania on zinc oxide. Langmuir, 1991, 7(12): 2911-2916.
[17]	Yang X L, Dai W L, Gao R H, et al. Characterization and catalytic behavior of highly active tungsten-doped SBA-15 catalyst in the synthesis of glutaraldehyde using an anhydrous approach. J. Catal., 2007, 249(2): 278-288.
[18]	Garau J M, Seoane X L, Arcoya A. Heptane dehydrocyclization over Pt/KL catalysts doped with barium or lanthanum. Catal. Lett., 2002, 83(3/4): 247-255.
[19]	Jongpatiwut S, Sackamduang P, Rirksomboon T, et al. n-octane aromatization Pt/KL catalystprepared by vapor-phase impregnation. J. Catal, 2003, 218(1): 1-11.
[20]	Jongpatiwut S, Trakarnroek S, Rirksomboon T, et al. n-octane aromatization on Pt-containing non-acidic large pore zeolite catalysts. Catal. Lett., 2005, 100(1/2): 7-15.
[21]	Nagamatsu S, Inomata M, Imura K, et al. Conversion of light naphtha to aromatic hydrocarbons. Part 4. Kinetic study of hexane conversion catalyzed by platinum supported on zeolite L. J. Jpn. Petrol. Inst., 2001, 44(6): 351-359.
[22]	Ren N, Yang YH, Zhang YH, et al. Heck coupling in zeolitic microcapsular reactor: A test for encaged quasi-homogeneous catalysis. J. Catal., 2007, 246(1): 215-222.
[23]	孙军, 王兴棠, 王晓东, 等(SUN Jun.et al). 不同晶相碳化钨的肼分解性能及其CO微量吸附量热研究. 催化学报(Chinese J. Catal.), 2008, 29(8): 710-714.
[24]	蔡玉曼, 姬辰. 天然沸石改性应用研究进展. 地质学刊, 2008, 32(3): 244-248.