Preparation of aqueous sols of tungsten oxide dihydrate from sodium tungstate by an ion-exchange method

Yong Gyu Choi, Go Sakai, Kengo Shimanoe, Norio Miura, Noboru Yamazoe

Research output: Contribution to journalArticle

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Abstract

Aqueous sols of tungsten oxide dihydrate (WO3·2H2O) were prepared from Na2WO4 by an ion-exchange method. An aqueous solution of Na2WO4 was let to flow through a glass column packed with protonated cation-exchange resin. The effluent, initially transparent, turned into an opaque viscous fluid (pale yellow) in a few hours, before yellow precipitate deposited to completion in three days. The precipitate was a mixture of a crystalline phase of WO3·2H2O and an amorphous phase, and the crystalline part could be separated from another by washing with deionized water and centrifuging. The gel of WO3·2H2O thus obtained consisted of platelike crystallite 25nm thick and 42nm wide as evaluated from the X-ray diffractometer (XRD) peaks, and could be dispersed well into deionized water to form a stable suspension of colloidal particles with a mean diameter of about 30nm. The mean particle size as well as the crystallite size tended to increase gradually with the repetition of dispersion in water under ultrasonic wave agitation and gelling by centrifuging. On heating, the gel (WO3·2H2O) changed to the monohydrate (WO3·H2O) at 100°C, which in turn changed to the anhydride (WO3) at 240°C. Remarkably XRD patterns showed conspicuous preferred orientation of WO3·2H2O crystallites in (010) plane after the sol was centrifuged for a long time (10h) and, upon dehydration, it was inherited by the dehydrated phases, resulting in the conspicuous orientation of WO3 crystallites in (001).

Original languageEnglish
Pages (from-to)63-72
Number of pages10
JournalSensors and Actuators, B: Chemical
Volume87
Issue number1
DOIs
Publication statusPublished - Nov 15 2002

Fingerprint

tungsten oxides
tungstates
Deionized water
Diffractometers
Polymethyl Methacrylate
centrifuging
Sols
Crystallites
Crystal orientation
Tungsten
Precipitates
Ion exchange
Gels
Sodium
sodium
Cation Exchange Resins
Crystalline materials
diffractometers
X rays
preparation

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Electrochemistry
  • Electrical and Electronic Engineering

Cite this

Preparation of aqueous sols of tungsten oxide dihydrate from sodium tungstate by an ion-exchange method. / Choi, Yong Gyu; Sakai, Go; Shimanoe, Kengo; Miura, Norio; Yamazoe, Noboru.

In: Sensors and Actuators, B: Chemical, Vol. 87, No. 1, 15.11.2002, p. 63-72.

Research output: Contribution to journalArticle

Choi, Yong Gyu ; Sakai, Go ; Shimanoe, Kengo ; Miura, Norio ; Yamazoe, Noboru. / Preparation of aqueous sols of tungsten oxide dihydrate from sodium tungstate by an ion-exchange method. In: Sensors and Actuators, B: Chemical. 2002 ; Vol. 87, No. 1. pp. 63-72.
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