Malaysian Journal of Analytical Sciences Vol 20 No 6 (2016): 1510 - 1514

DOI: http://dx.doi.org/10.17576/mjas-2016-2006-32

 

 

 

REDUCTION BEHAVIOUR OF TUNGSTEN DIOXIDE BY VARIOUS CONCENTRATION OF CARBON MONOXIDE

 

(Kelakuan Penurunan Tungsten Dioksida oleh Kepekatan Karbon Monoksida yang Berbeza)

 

Fairous Salleh¹*, Alinda Samsuri^1,2, Tengku Shafazila Tengku Saharuddin¹,

Mohamed Wahab Mohamed Hisham¹, Rizafizah Othaman¹, Mohd. Ambar Yarmo¹

 

¹Catalyst Research Group, School of Chemical Sciences and Food Technology,

Faculty of Science and Technology,

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

²Centre for Defense Foundation Studies,

Universiti Pertahanan Nasional Malaysia, Kem Sungai Besi, 57000 Kuala Lumpur, Malaysia

 

*Corresponding author: fairoussalleh@gmail.com

 

 

Received: 24 February 2015; Accepted: 27 October 2015

 

 

Abstract

The reduction behaviour of tungsten dioxide (WO₂) under both non-isothermal and isothermal conditions in various concentrations of carbon monoxide (CO) were investigated by using temperature-programmed reduction (TPR) and X-ray diffractometry (XRD) techniques. The influences of carbon monoxide concentration (20 and 40% v/v CO in N₂) on the reducibility of WO₂ to tungsten metal W have been investigated in the temperature range 40 – 900 ºC. The TPR profile shows that reduction using 40% CO produce higher thermal conductivity detector (TCD) signal in comparison by using 20 % CO. XRD results show that, by increasing the concentration of CO, the intensity of WO₂ decreases and tungsten carbide (WC) peak appeared. Moreover, holding the reduction time for 30 min in 20 and 40% of CO resulted in the formation of new peak of tungsten hemi carbide (W₂C) and WC, respectively. It can be concluded that by using CO, reduction steps comprise of WO₂ → W → W₂C → WC.  The reduction behaviour of WO₂ is strongly dependent on the concentration of CO and hold time of reaction. Furthermore, excess of CO by isothermal reduction results in the formation of WC.

 

Keywords:  tungsten dioxide, tungsten, tungsten carbide, carbon monoxide

 

Abstrak

Kelakuan penurunan tungsten dioksida (WO₂) melalui penurunan bukan isotermal dan isotermal menggunakan kepekatan karbon monoksida (CO) berbeza telah dikaji dengan menggunakan suhu penurunan berprogram (TPR) dan pembelauan sinar-X (XRD). Kesan kepekatan karbon monoksida (20 dan 40% v/v CO dalam N₂) terhadap kadar penurunan WO₂ kepada W telah dikaji dalam suhu 40 – 900 °C. Profil TPR menunjukkan bahawa penurunan dengan menggunakan 40% CO menghasilkan isyarat TCD lebih tinggi berbanding dengan menggunakan 20% CO. Keputusan XRD menunjukkan bahawa, dengan meningkatkan kepekatan CO, keamatan WO₂ menurun dan puncak tungsten karbida (WC) muncul. Selain itu, dengan penambahan masa tindak balas selama 30 minit menggunakan 20 dan 40% CO menghasilkan puncak baru masing-masing tungsten hemi karbida (W₂C) dan WC. Dapat disimpulkan bahawa dengan menggunakan CO, langkah penurunan terdiri daripada WO₂ → W → W₂C → WC.  Tingkahlaku penurunan WO₂ amat bergantung kepada kepekatan CO dan penambahan masa tindak balas. Tambahan pula, pendedahan kepada CO berlebihan daripada penurunan isotermal menyebabkan pembentukan WC.

 

Kata kunci:  tungsten dioksida, tungsten, tungsten karbida, karbon monoksida

 

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