In this research, nanocrystalline lithium ferrite (Li 0.5 Fe 2.5 O 4 ) was synthesized using the solution combustion approach with using glycine as fuel and a chelating agent at various Red / Ox ratios ("glycine to nitrate" ratio G / N = 0.4, 0.6, 0.8, 1.0). According to the data of energy-dispersive X-ray spectroscopy (EDX) and atomic absorption spectroscopy (AAS), the prepared samples correspond in their composition to stoichiometric ferrite Li 0.5 Fe 2.5 O 4 within the error of the determination methods used. The results of powder X-ray diffractometry (PXRD) confirmed the formation of α-Li 0.5 Fe 2.5 O 4 at G / N ratio of 0.8 and 1.0 and the presence of β-Li 0.5 Fe 2.5 O 4 modification in case of deficiency (G / N = 0.4) and stoichiometry (G / N = 0.6) of the chelating agent. It is shown that a change in the Red / Ox composition of reacting solutions affects not only the phase composition of the synthesized lithium ferrite samples, but also the crystallite size, which lies in the range from 22 to 35 nm. Based on the scanning electron microscopy (SEM) data, it was found that Li 0.5 Fe 2.5 O 4 powders had a developed porous microstructure consisting of micron agglomerates. According to the vibration magnetometry data of nanocrystalline lithium ferrite powders, it follows that all synthesized compositions have a pronounced ferrimagnetic behavior, despite the presence of β-modification in some of them. It is shown that by varying the Red / Ox environment and, as a consequence, the phase composition and crystallite size, it is possible to obtain Li 0.5 Fe 2.5 O 4 nanocrystals with magnetic parameters in the following ranges: saturation magnetization (M s ) = 51.6 -61.9 emu / g, residual magnetization (M r ) =14.3 -17.8 emu / g, coercive force (H c ) =109 -135 Oe.

No abstract

Soft magnetic LiZnMn ferrite with low coercivity obtained via glycine-nitrate combustion was estimated in this work. According to SEM, the synthesized ceramics have a grain size ranging from 1.5 to 8 µm and the EDX, AAS and XRD data show that the obtained samples correspond to Li 0.45 Zn 0.05 Mn 0.06 Fe 2.43 O 4 structure. The hysteresis loops of LiZnMn ferrite ceramics provide evidence for the magnetically soft nature of the obtained materials. Basic magnetic characteristics, including remanent magnetization, saturation magnetization, and coercive force was also described. For a sample sintered at 1000 • C, the values of saturation magnetization (4πMs), residual magnetization (Br) and coercive force (Hc) were 2644 G, 2139 G and 6.4 Oe, respectively, whereas the sample obtained at 1070 • C shows large values of saturation magnetization (3240 G) and residual magnetization (2459 G) and the coercive force is approximately half (3.4 Oe). Analysis of the influence of thermal treatment provided the possibility to determine necessary conditions for obtaining microwave ceramics based on LiZnMn ferrite via solution combustion method. Grain size distribution was examined to determine their influence on the properties of obtained ceramics.

No abstract

Authors have studied the interaction between high-melting compounds from various classes, such as transition-metal carbides, borides, nitrides, and silicides, and covalent-bonded B4C, SiC, Si3N4, AlN etc. (over 160 phase diagrams), ternary B4C-SiC-MedB2, SiC-TiC-TiB2and other eutectics, which is important for optimizing the sintering temperature, material design and prediction of properties of many materials for high temperature applications including wear, aggressive, impact and radiation conditions. A vast identified group of eutectics with number of components n ≥ 2 has reduced eutectic temperature Тeut.(in some sistems reducing reaches 1200 °C). Noted, that increasing of n suppresses grain growth, which is particularly important for developing nanostructured ceramics via pressureless sintering and for controlling the ceramic's performance. Multiphase ceramics (SiC-TiC-TiB2, B4C-SiC-MedB2, B4C-W2B5-MedB2, B4C-LnB6-MedB2, etc.) feature improved mechanical parameters and high wear and impact resistance.