Oxygen deficiency measurements

HRTEM results showed that SiNW were made of amorphous materials. EDX of the nanowires showed both Si and O peaks, with the ratio ranged from SiOi s to Si02. The observation that SiNW were amorphous materials was further supported by the Raman measurements, in which very small amounts of crystalline Si was detected. Even the amorphous Si peak at 480 cm was undetectable due to the presence of high PL signal. On the basis of the information presented here, we concluded that the majority of the SiNW are made of amorphous silicon dioxide, with a certain amount of oxygen deficiencies. 

In an oxygen-rich atmosphere, carbon burns to produce carbon dioxide, CO2. Both carbon monoxide, CO, and carbon dioxide are produced when carbon is burned in an oxygen-deficient atmosphere. This makes the direct measurement of the enthalpy of formation of CO difficult. CO, however, also burns in oxygen, O2, to produce pure carbon dioxide. Explain how you would experimentally determine the enthalpy of formation of carbon monoxide. 

J. Raleigh, A. Franko, D. Kelly, L. Trimble, P. Allen, Development of an in vivo 19F MR method for measuring oxygen deficiency in tumors, Magn. Reson. Med 22 (1991) 451 66. 

The earliest design of the glucose electrode (which is generally applicable to any oxidase and uses oxygen as the ultimate electron acceptor) is based on the differential measurement of oxygen deficiency at the oxygen electrode, caused by the... 

The lanthanide higher oxides have not only peculiar thermodynamic properties, but also unique physical and chemical properties. The physical and chemical properties are presented as a macroscopic parameter, such as the electrical conductivity, the coefficient of expansion, and the conversion rate of a catalysis process. Due to the lack of knowledge of the wide range of non-stoichiometry of the oxygen-deficient fluorite-related homologous series of the lanthanide higher oxides, the macroscopically measured data of the physical and chemical properties are scattered, and therefore, based on the structural principle of the module ideas a deep understanding the relationship between the properties and structures is needed. 

In general, it is accepted that recombination of electrons and holes, trapping of electrons by oxygen deficiency sites and a low mobility of the holes, cause a low conductivity and accordingly a low photoresponse for hematite. Electron mobility in the range 0.01 [60] to 0.1 cm2/V-s [17] has been reported. In the latter case, it was found that the electron mobility was independent of donor concentration. More recently, an electron mobility of about 0.1 cm2/V-s has been measured with doped single crystals and the mobility was also here independent of donor concentration [5]. A diffusion length of holes has been determined to be only of 2-4 nm [6], which is about 100 times lower than many other (III-V) oxides. 

Figure 8.9 Variation with quenching temperature of, (a) positron lifetime, (b) Doppler broadened lineshape parameter, I, and (c) oxygen deficiency, as obtained from weight loss (+) and Tc (o) measurements. From Bharathi et al. [54].

The effect of various stoichiometry VO2 powders on temperature and heat of phase transition has not been reported so far. In this paper, the heats and the temperatures of transition from VO196 to VO207 in the crystalline state were measured from DSC scans. The results are listed in Table 1, indicating that the heats of the oxygen-deficient VO2 are less than those of the oxygen-rich VO2, and the VO2 02 has the maximum transition heat. The transition temperature is increased about 10°C from VOi 95 to VO2.07- Those results are not consistent with the results observed by determination of electrical resistivity of monocrystals reported in the literature, and the results in the literature are also contradictory [16,17]. The IR spectra of various size, crystalline state and stoichiometry VO2 are observed, showing the effects of size, crystalline state and stoichiometry [18]. 

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