Tungsten

About: Tungsten is a research topic. Over the lifetime, 35225 publications have been published within this topic receiving 456213 citations. The topic is also known as: W & element 74.

Infrared and X-ray studies of hydrogen intercalation in different tungsten trioxides and tungsten trioxide hydrates

Abstract: Hydrogen intercalation via spillover reaction in various tungsten trioxides leads to the formation of blue hydrogen bronzes. These reversible reactions induce changes in the W-O bond system while maintaining the W-O skeleton. The effect of the intercalation process on the host crystalline structure has been studied with respect to the ν(O-W-O) stretching vibration changes and lattice parameter variations by means of infrared and X-ray diffraction measurements. Among the main results, the intercalation process is shown to be strongly influenced by the structural type of the host compound as well as its amorphous versus crystalline nature. For instance, for the ReO3 type oxides (monoclinic and cubic WO3) and hexagonal WO3, ν(O-W-O) shifts to higher frequency are assigned to a shortening effect of W-O bonds. A W-O bond system arrangement is also measured for the crystallized and amorphous hydrates WO3 · H2O, but no detectable changes could be found in the pyrochlore WO3 and in the hydrate WO3·1/3 H2O.

An investigation of the intracellular pH of crab muscle fibres by means of micro-glass and micro-tungsten electrodes

Abstract: The intracellular pH of tissues, especially of muscle, is of interest for various reasons. In particular, changes in intracellular pH may be related to the way in which variations of external potassium concentration or of membrane potential influence metabolic activity (Eddy & Hinshelwood, 1950, 1951; Caldwell & Harris, 1952) and in muscle they may also be associated with the processes of contraction and relaxation (Dubuisson, 1950; Goodall & SzentGyorgyi, 1953; Hajdu, 1953). There are three main methods for measuring intracellular pH. The first, used by Rous (1925), Margaria (1934), and Arvanitaki & Chalazonitis (1951) involves the use of pH indicator dyes but is open to the objection that they may become adsorbed on to the cell protein, the pH range over which they change colour being altered as a result. The second method, used by Fenn (1928), Stella (1929), Cowan (1933) and Conway & Fearon (1944), consists of the measurement of the amounts of carbonic acid and bicarbonate inside the cells, the pH being calculated from the Henderson-Hasselbalch equation. This method involves the destruction of the tissue and cannot be used for following rapid changes of pH, although alterations in CO2 content have been used by Lipmann & Meyerhof (1930) and by Hill (1940) for following slow changes in frog muscle after activity. In the third method various electrodes which respond to pH are used and with these changes can be followed continuously. Micro-antimony (Buytendyk & Woerdeman, 1927) and micro-platinum/hydrogen (Dorfman, 1936) electrodes have been used to study pH changes during the development of amphibian eggs, but these are not always specific for pH. The glass electrode which is specific for pH in the range 0-9 (Dole, 1941) has been used by Dubuisson (1950) for following pH changes at the surface of frog muscle during

Morphology-controlled synthesis of highly adsorptive tungsten oxide nanostructures and their application to water treatment

Abstract: A facile route to control the morphology of tungsten oxide hierarchical hollow structures was demonstrated. The morphology of the tungsten oxide nanostructures could be tuned from size-controlled hollow urchins to nanowires by adjusting the concentration of the tungsten precursor, with no need for catalysts, surfactants, or templates. The tungsten oxide nanostructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and nitrogen adsorption–desorption measurements. The as-prepared tungsten oxide hierarchical hollow nanostructures showed a very high specific surface area and demonstrated an excellent ability to remove organic pollutants. The adsorption capability of our tungsten oxide hierarchical hollow nanostructure was much higher than those of previously reported transition metal oxide nanostructures including Mn3O4, Fe2O3, and MnO2 as well as other alternative adsorbents such as MCM-22, fly ash, and red mud. This study provides a simple strategy for template/surfactant-free synthesis of hierarchical hollow nanostructures. Also, the as-prepared products are expected to be new promising materials for environmental remediation.