Different grades of magnetic cobalt ferrite (Co_xFe_{3-x}O₄) nanoparticles were synthesized with various molar ratios of Fe²⁺ to Co²⁺ ions in the initial salt solutions method with using contact non-equilibrium plasma. The crystal structure and morphology of the nanoparticles are obtained from X-ray diffraction and transmission electron microscopy studies. With an increase in the value of x, the saturation magnetization for the samples of CoFe₂O₄ has decreased from 150.9 emu/g to 1.2 emu/g. The dependence of the coercive force on x is extremal with a plateau maximum corresponding to the x=0.5-1.25.
For two series of catalysts based on praseodymium ferrite, their structural and redox properties as well as performance in ethanol steam reforming have been studied. The first series was PrFe1-xNi(Co)xO3 (x=0.3-0.4) perovskites prepared by modified Pechini route, and the second one was 5%wt.Ni(Co)/PrFeO3 of different dispersion prepared by impregnation of PrFeO3, including samples modified by 5%wt. Mo. At temperatures above 700°C, for all catalysts, the main products were hydrogen and CO. At temperatures below 700°C, initial ethanol conversion and hydrogen yield were higher for supported catalysts as compared with ones derived from Ni(Co)-containing perovskites. While Ni-based catalysts derived from perovskite were more active as compared with Co-based samples, Co-supported PrFeO3 perovskite has shown a higher initial activity as compared with Ni-supported one. The long-term tests in the realistic feed and TEM studies of spent catalysts revealed that perovskite-derived catalysts have a higher coking stability than perovskite-supported ones due to formation of highly dispersed Ni-Fe alloy particles strongly interacting with disordered perovskite–like matrix. The method of Mo supporting only slightly affects the initial activity of Ni/PrFeO3–based catalysts but noticeably modifies their coking stability: 5%Mo/5%Ni/PrFeO3 catalyst prepared by successive impregnation possesses the highest stability among perovskite-supported catalysts.
Continuing miniaturization of electronic devices necessarily requires assembly of several different objects or devices in a small space. Therefore, besides thin films growth, the possibility of fabricating wires and dots [1, 2] at the nanometre scale composed of metal silicides is of the top interest. This report is about the STM/STS investigation of cobalt silicides’ nanostructures created on Si(111)-(√19 Ã- √19) substrates via Co evaporation and post deposition annealing. This (√19 Ã- √19) reconstruction was induced by Ni doping. Less than 1ML of Co on surface was obtained. Surface reconstruction induced growth of agglomerates of clusters rather than an uniform layer. The post deposition annealing of a crystal sample (up to 670 K, 770 K, 870 K, 970 K, 1070 K and 1170 K) led to creation of silicides’ nanostructures. Measurements showed that coalescence of Co nanoislands begun around 970 K. Annealing above 1070 K led to alloying of a Co, Ni and Si. As a consequence the Si(111)-(7Ã-7) reconstruction occurred at the cost of Si(111)-(√19 Ã- √19).
This work reports on focused electron beam induced deposition (FEBID) using a custom built gas injection system (GIS) equipped with nitrogen as a gas carrier. We have deposited cobalt from Co2(CO)8, which is usually achieved by a heated GIS. In contrast to a heated GIS, our strategy allows avoiding problems caused by eventual temperature gradients along the GIS. Moreover, the use of the gas carrier enables a high control over process conditions and consequently the properties of the synthesized nanostructures. Chemical composition and growth rate are investigated by energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM), respectively. We demonstrate that the N2 flux is strongly affecting the deposit growth rate without the need of heating the precursor in order to increase its vapour pressure. Particularly, AFM volume estimation of the deposited structures showed that increasing the nitrogen resulted in an enhanced deposition rate. The wide range of achievable precursor fluxes allowed to clearly distinguish between precursor- and electron-limited regime. With the carrier-based GIS an optimized deposition procedure with regards to the desired deposition regime has been enabled
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