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Use of the Retarded Solution-Reprecipitation Process to Attain a Higher Initial Permeability in MnZn Ferrites 总被引:1,自引:0,他引:1
Miha Drofenik rej nidari Darko Makovec 《Journal of the American Ceramic Society》2003,86(9):1601-1604
We investigated the effect of various amounts of liquid phase on microstructure development during sintering and the resulting magnetic permeability of MnZn ferrite (MZF) samples. Our results revealed that the microstructure and the final magnetic permeability depend on the thickness of the liquid-phase film during sintering. The solution-reprecipitation (S-R) process, which is associated with an intensive microstructure development in MZF, starts when a continuous liquid-phase film of critical thickness δo , which wets the MZF grains, is formed. The solid-state sintering that takes place before the formation of the continuous liquid-phase film is essential for the final microstructure of MZF. 相似文献
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Hydrothermal Synthesis of Ba-Hexaferrite Nanoparticles 总被引:1,自引:0,他引:1
Miha Drofenik Matja Kristl rej nidari Darko Hanel Darja Lisjak 《Journal of the American Ceramic Society》2007,90(7):2057-2061
Barium hexaferrite BaFe12 O19 nanoparticles with a single-domain size were synthesized using a controlled hydrothermal process involving the LaMer–Dinger principle and the Ostwald ripening mechanism. Nanocrystalline particles of BaFe12 O19 were obtained when the molar ratio of the precursor composition Ba(OH)2 ·8H2 O/γ-Fe2 O3 was 0.3 and the concentration of the suspension was about 1 wt%. The as-synthesized crystalline BaFe12 O19 platelets approximately 50 nm in length and 5 nm in thickness exhibited a saturation magnetization of 40 Am2 /kg. 相似文献
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Darko Makovec Miha Drofenik rej nidari 《Journal of the American Ceramic Society》1999,82(5):1113-1120
Manganese zinc (MnZn) ferrite powders were prepared via the hydrothermal treatment of a homogeneous mixture of the raw oxides (i.e., Fe2 O3 , ZnO, and Mn3 O4 or MnO) at temperatures of 220°-320°C in air or an inert atmosphere. The final results of the hydrothermal reactions between the raw oxides were fine powders with a heterogeneous phase composition. In addition to lower concentrations of the residual reactants (Fe2 O3 , Mn3 O4 ), two types of spinel-structure-based reaction products-ferrite ((Mn2+ ,Zn)Fe2 O4 ) and manganate ((Zn,Mn2+ )Mn2 3+ O4 )-were detected after the synthesis. The composition of the ferrite products, as well as the ratio of ferrite products to manganate products, were mainly functions of the oxidation state of the manganese that was present during treatment. The oxidation state of manganese during reaction was dependent on the valence of the manganese in the starting manganese oxide and on the atmosphere in the autoclave during reaction. When the hydrothermal reaction was conducted in air, almost-pure zinc ferrite was identified, whereas during reaction in an inert atmosphere, MnZn ferrite was formed. The kinetics of the hydrothermal reactions also were dependent on the oxidation state of manganese, as well as the temperature and specific surface area of the starting Fe2 O3 . 相似文献
4.
It is shown that a steepening of the radial plasma pressure profile leads to a decrease in the critical value of beta, above which, small-scale balloon-type perturbations in a mirror trap become unstable. This may mean that small-scale ballooning instability leads to a smoothing of the radial plasma profile. The critical beta values for the real magnetic field of the gas-dynamic trap and various plasma pressure radial profiles was also calculated. For a plasma with a parabolic profile critical beta is evaluated at the level of 0.72. A previous theoretical prediction for this trap was almost two times lower than maximal beta 0.6 achieved experimentally. 相似文献
5.
Alexandre E. Chmel rej N. Smirnov Victor S. Shashkin 《Journal of the American Ceramic Society》2001,84(1):29-32
We present a Raman spectroscopy study of silica glasses prepared by hot-pressing of gels. Our particular interest is the structure at the interfaces formed during hot-pressing of small parts to obtain large pieces, such as silica tubes for optical-fiber preforms. A specific feature of the interface that distinguishes this layer from the bulk is its fractal structure. The parameters of the fractal units, including their maximum dimensions in real space, are determined by the pre-hot-pressing mechanical processing. We attribute this structure to residual microcracks inherent in the surface layer of polished plates. There are no fractals at the interfaces sintered at temperatures higher than the glass transition temperature. 相似文献
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Miha Drofenik rej Znidarsic Darko Makovec 《Journal of the American Ceramic Society》1998,81(11):2841-2848
Additions of Bi2 O3 were used to promote grain growth and to increase magnetic permeability during sintering of MnZn ferrites. The results showed that small additions of Bi2 O3 of <0.05 wt% remarkably increase the permeability of MnZn ferrites. On the other hand, addition of 0.05 wt% Bi2 O3 induced the formation of a microstructure composed of giant grains with trapped pores embedded in a normal microstructure. The permeability of these samples showed a pronounced secondary maximum in permeability. At still higher Bi2 O3 concentrations, above 0.2 wt%, the grain growth was retarded and a normal microstructure appeared; however, the magnetic permeability was strongly reduced. 相似文献
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Ming-Chun Zhao Ying-Chao Zhao Deng-Feng Yin Shuo Wang Yong-Ming Shangguan Chao Liu Li-Li Tan Ci-Jun Shuai Ke Yang rej Atrens 《金属学报(英文版)》2019,32(10):1195-1206
As-extruded Mg–Sr alloy, a kind of promising biodegradable biomedical material, was coated using micro-arc oxidation and also using a phosphate conversion coating. The corrosion behaviors were investigated using Hanks' solution. The corrosion of the as-extruded Mg–Sr alloy became more serious with increasing immersion time; that is, the corrosion pits became more numerous, larger and deeper. The micro-arc oxidation coating and the phosphate conversion coating were effective in improving the corrosion resistance of the as-extruded Mg–Sr alloy. The micro-arc oxidation coating was much more effective. Moreover, the as-extruded Mg–Sr alloy and the coated as-extruded Mg–Sr alloy exhibited lower corrosion rates than the as-cast Mg–Sr alloy and the corresponding coated as-cast Mg–Sr alloy, indicating that the corrosion properties of the coated samples are dependent on their substrates. The finer microstructure of the substrate of the as-extruded condition corroded much slower. The corrosion resistance of the coated Mg–Sr alloy depended on the coating itself and on the microstructure of the substrate. 相似文献
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Chao-Yue Zhao Xian-Hua Chen Peng Peng Teng Tu rej Atrens Fu-Sheng Pan 《金属学报(英文版)》2020,33(9):1217-1225
The influence of Al alloying on the microstructures and the mechanical properties of Mg–x Al–1 Sn–0.3 Mn alloy sheets was investigated. The microstructure of Mg– x Al–1 Sn–0.3 Mn consisted of α-Mg and Mg 17 Al 12 precipitates. Alloying with Al increased the amount of Mg_(17)Al_(12) and the average grain size. Uniaxial tensile tests were carried out along the extrusion direction(ED), the transverse direction(TD) and 45° toward the ED. Mg–5 Al–1 Sn–0.3 Mn alloy sheet exhibited the best combination of mechanical properties along the ED: a yield strength of 142 MPa, an ultimate tensile strength of 282 MPa and an elongation of 23%. The good performance of Mg–5 Al–1 Sn–0.3 Mn sheet was mainly attributed to the large quantity of Mg_(17)Al_(12) precipitates and a weak basal texture. Annealing caused static dynamic recrystallization, refined the grain size and enhanced the mechanical properties: yield strength of 186 MPa, ultimate tensile strength of 304 MPa, elongation of 21% along ED. Both strength and ductility were enhanced by Al alloying. 相似文献
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