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Humidity Sensors Based on Metal-Oxide Mesoporous-Macroporous and Hierarchical Structures
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2020
It should be noted that the manufacturing technology of the mesoporous-macroporous metal-oxide-based humidity sensors is no different from the technology used in the manufacture of gas sensors. Schematically, this process is shown in Figure 23.11 for TiO2:Co-based sensors developed by Li et al. (2017). Using F127 as the soft template for the self-assembly synthesis, 2 g F127 was dispersed into 12 ml of anhydrous ethanol with the condition of stirring at 40°C. Then, 2.5 g soluble resol was added to the solution and the stirring continued at the same temperature for 30 min. After that, a certain amount of cobalt acetate was added into the solution. This solution was named Solution-A. Next, 1.5 ml HCl and 3.4 g tetrabutyl titanate were added into 8 ml anhydrous ethanol, orderly. After stirring for 30 min, we obtained Solution-B. Then, it was slowly dropped into Solution-A with the condition of stirring for 2 h at 40°C to obtain a homogeneous brick-red solution. Afterward, a dark red film was received by evaporating the solvents at room temperature and thermo-polymerizing at 100°C for 24 h. Then it was pyrolyzed in a tubular furnace at the temperature of 350°C for 4 h under the atmosphere of N2 and heating rate of 1°C/min to convert tetrabutyl titanate to titanium oxide within the pores of the F127 template and obtained a puce polymer–TiO2:Co composite. Finally, the polymer was removed at 400°C for 5 h in the air atmosphere and filtered the white pure ordered mesoporous TiO2:Co.
Chemical Synthesis of Hybrid Nanoparticles Based on Metal–Metal Oxide Systems
Published in Inamuddin, Rajender Boddula, Mohammad Faraz Ahmer, Abdullah M. Asiri, Morphology Design Paradigms for Supercapacitors, 2019
Vivek Ramakrishnan, Neena S. John
V. Gandhi et al. reported the effect of Co doping on structural, optical, and magnetic properties of ZnO nanoparticles prepared via co-precipitation method (2014). ZnO nanoparticles were prepared initially by alkaline hydrolysis of zinc acetate (Figure 8.10a). For the preparation of Co-doped ZnO, the precipitation was done from a mixture of cobalt acetate and aqueous Zn precursor. A series of Co-doped ZnO nanoparticles were synthesized with different Co loading levels (Zn1−xCox O, where x = 0.05, 0.10, and 0.15) (Figure 8.10b–d). Diamagnetic behavior of pure ZnO was changed to ferromagnetic nature in Co-doped ZnO nanoparticles with significant changes in M−H loop, which was attributed to the oxygen vacancies and zinc interstitials.
Generation of Particles by Reactions
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
Kakeru Fujiwara, Sotiris E. Pratsinis, Hisao Suzuki
In the redox reaction technique,46 fine metal particles, such as noble metals and sulfur, are produced by reducing or oxidizing the metal salt or the metal chelate complex solutions. Many kinds of complex or protective colloid agents are frequently employed to moderate the reaction speed and to stabilize the generated particles, so that highly monodispersed particles are obtained. Matijevic also reported that preparation of fine powders of some noble metals and copper, using this technique, was combined with the following technique, called decomposition of the compound.47 Some organic compounds such as EDTA, triethanol amine, thioacetamide and urea can be used in the technique of decomposition of compound. Haruta et al. obtained molybdenum and cobalt sulfide particles by hydrolysis of thioacetamide promoted with hydrazine in ammonium orthomolybdate and cobalt acetate, respectively.48
Solvent-free oxidation of ethylbenzene over LDH-hosted Co(II) Schiff base of 2-hydroxy-1-naphthaldehyde and 4-amino benzoic acid
Published in Inorganic and Nano-Metal Chemistry, 2019
Savita Khare, Jagat Singh Kirar, Swati Parashar
Conversion of hydrocarbons to their oxygenated derivatives is one of the most important reactions in the context of industrial biology. The conversion of ethylbenzene to acetophenone through oxidation is a great industrially significant process because acetophenone acts as an intermediate in the production of many pharmaceuticals, fragrances, chewing gum, resins, alcohols, esters, aldehydes, etc.[1,2] Earlier reports demonstrate that acetophenone is conventionally synthesized by oxidation of ethylbenzene using stoichiometric amounts of inorganic oxidants (permanganate or dichromate).[3,4] The main drawback of this process is that it generates a large amount of hazardous and corrosive wastes.[5] The present industrial process of acetophenone production utilizes cobalt acetate as a homogeneous catalyst in acetic acid in the presence of oxygen. However, in this process, homogeneous transition metal catalyst is used; hence, the major disadvantage is the recovery of the catalyst for its reuse, which affects the overall economics of the process.[6] Overcoming from this problem, concepts of heterogenization of homogeneous metal complex have aroused attention. Various methods have been developed to synthesize heterogeneous catalysts for the oxidation of ethylbenzene.[7–13]