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1.
Sachin Tyagi Himanshu B. Baskey R. C. Agarwala Vijaya Agarwala T. C. Shami 《Transactions of the Indian Institute of Metals》2011,64(3):271-277
Mixture of cobalt ferrite and strontium hexaferrite nanocrystals i.e. SrFe12O19/CoFe2O4 exhibiting super paramagnetic nature were synthesized by modified flux method. The resulting precursors were heat treated
(HT) at 900 and 1200°C for 4 h in nitrogen atmosphere. During heat treatment, transformation proceeds as instantaneous rate
of nucleation and three dimensional growth with activation energy of 135.835 kJ/mole. The hysteresis loops showed a hike in
saturation magnetization from 1.045 to 84.362 emu/g with an increase in HT temperature. The ‘as synthesized’ particles have
size in the range of 10–20 nm with spherical shape. Further, these spherical shape particles tend to change their morphology
to hexagonal plates with increase in HT temperatures. The relative complex permittivity and permeability of the composite
powder are investigated. The minimum reflection loss of the composite powder reaches to −27.6 dB at 10.8 GHz which suits its
application in RADAR absorbing materials. 相似文献
2.
The glass series with general formula 15 Li2O–(85 − x) B2O3–x La2O3 was prepared. Electrical and optical properties of these glasses were studied. It is observed that the conductivity of these
glasses decreases while density, glass transition temperature and refractive index increases with the addition of La2O3. Ion concentration of La3+ in glasses, polaron radius, field strength, molar refractivity and molar electronic polarizability were calculated. The absorption
coefficient and direct optical band gaps are evaluated using the absorption edge calculations. The different factors that
play a role for controlling the refractive indices such as electronic polarizability, field strength of cations and rigidity
of glass structure are discussed in accordance with the obtained index data. 相似文献
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Density measurements of a low-silica CaO-SiO2-Al2O3 system were carried out using the Archimedes principle. A Pt 30 pct Rh bob and wire arrangement was used for this purpose.
The results obtained were in good agreement with those obtained from the model developed in the current group as well as with
other results reported earlier. The density for the CaO-SiO2 and the CaO-Al2O3 binary slag systems also was estimated from the ternary values. The extrapolation of density values for high-silica systems
also showed good agreement with previous works. An estimation for the density value of CaO was made from the current experimental
data. The density decrease at high temperatures was interpreted based on the silicate structure. As the mole percent of SiO2 was below the 33 pct required for the orthosilicate composition, discrete
\textSiO44 - {\text{SiO}}_{4}^{4 - } tetrahedral units in the silicate melt would exist along with O2– ions. The change in melt expansivity may be attributed to the ionic expansions in the order of
\textAl 3+ - \textO 2- < \textCa 2+ - \textO 2- < \textCa 2+ - \textO - {\text{Al}}^{ 3+ } - {\text{O}}^{ 2- } < {\text{Ca}}^{ 2+ } - {\text{O}}^{ 2- } < {\text{Ca}}^{ 2+ } - {\text{O}}^{ - } 相似文献
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Ghasem Roghani Evgueni Jak Peter Hayes 《Metallurgical and Materials Transactions B》2003,34(2):173-182
Phase-equilibrium data and liquidus isotherms for the system “MnO”-CaO-(Al2O3+SiO2) at silicomanganese alloy saturation have been determined in the temperature range of 1373 to 1723 K. The results are presented
in the form of the pseudoternary sections “MnO”-CaO-(Al2O3+SiO2) with Al2O3/SiO2 weight ratios of 0.55 and 0.65. The primary-phase fields have been identified in this range of conditions. 相似文献
9.
Moo-Chin Wang You-Cheng Lai Wei-Jen Shih Ping-Yu Shih Guo-Ju Chen Wang-Long Li 《Metallurgical and Materials Transactions A》2010,41(2):297-307
The crystallization behavior and microstructure of silica-free 5K2O-45CaO-50P2O5 (KCP) bioglass have been studied using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning election microscopy
(SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The activation energy for the
KCP bioglass crystallization is found to be 337.4 kJ/mol using a nonisothermal method. The crystalline phases of the glass
surface determined by XRD are KCa(PO3)3, 4CaO·3P2O5, and β-Ca(PO3)2 when the KCP bioglass is crystallized at 903 K for 4 hours. The crystalline phase of the powder samples determined by XRD
is β-Ca(PO3)2 when silica-free KCP glasses crystallized at 873 to 1073 K for 8 hours. Crystallization starts at the surface of the KCP
bioglass and then proceeds toward the interior of the glass matrix. The morphology of β-Ca(PO3)2 is a fibrillar shape 20 to 180 nm in length and 17 to 20 nm in diameter, with an aspect ratio ranging from 1.0 to 10.6. 相似文献
10.
Cu-10Cr-3Ag (wt pct) alloy with nanocrystalline Al2O3 dispersion was prepared by mechanical alloying and consolidated by high pressure sintering at different temperatures. Characterization
by X-ray diffraction and scanning electron microscopy or transmission electron microscopy shows the formation of nanocrystalline
matrix grains of about 40 nm after 25 hours of milling with nanometric (<20 nm) Al2O3 particles dispersed in it. After consolidation by high pressure sintering (8 GPa at 400 °C to 800 °C), the dispersoids retain
their ultrafine size and uniform distribution, while the alloyed matrix undergoes significant grain growth. The hardness and
wear resistance of the pellets increase significantly with the addition of nano-Al2O3 particles. The electrical conductivity of the pellets without and with nano-Al2O3 dispersion is about 30 pct IACS (international annealing copper standard) and 25 pct IACS, respectively. Thus, mechanical
alloying followed by high pressure sintering seems a potential route for developing nano-Al2O3 dispersed Cu-Cr-Ag alloy for heavy duty electrical contact. 相似文献
11.
Luckman Muhmood Nurni Neelakandan Viswanathan Masanori Iwase Seshadri Seetharaman 《Metallurgical and Materials Transactions B》2011,42(2):274-280
The chemical diffusion coefficient of sulfur in the ternary slag of composition 51.5 pct CaO-9.6 pct SiO2-38.9 pct Al2O3 slag was measured at 1680 K, 1700 K, and 1723 K (1403 °C, 1427 °C, and 1450 °C) using the experimental method proposed earlier
by the authors. The
P\textS2 P_{{{\text{S}}_{2} }} and
P\textO2 P_{{{\text{O}}_{2} }} pressures were calculated from the Gibbs energy of the equilibrium reaction between CaO in the slag and solid CaS. The density
of the slag was obtained from earlier experiments. Initially, the order of magnitude for the diffusion coefficient was taken
from the works of Saito and Kawai but later was modified so that the concentration curve for sulfur obtained from the program
was in good fit with the experimental results. The diffusion coefficient of sulfur in 51.5 pct CaO-9.6 pct SiO2-38.9 pct Al2O3 slag was estimated to be in the range 3.98 to 4.14 × 10−6 cm2/s for the temperature range 1680 K to 1723 K (1403 °C to 1450 °C), which is in good agreement with the results available
in literature 相似文献
12.
R. Vinaykumar Swayam Majhi J. Bera 《Transactions of the Indian Institute of Metals》2015,68(2):217-220
Strontium hexagonal ferrite SrFe11.6Zn0.2Ti0.2O19 was prepared by citrate sol gel combustion process. Phase formation behavior and crystal structure analysis were performed using XRD pattern. The sintering behavior of ferrite was investigated with and without the addition of CuO using dilatometry. The on-set temperature of sintering was found to decrease significantly by the addition of CuO. The sintered density of CuO-added ferrite was about 95 % of the theoretical density after sintering at 1000 °C. The effects of CuO addition on microstructural development, permeability and permittivity have been studied using scanning electron microscope and LCR meter respectively. The ferrite with CuO addition showed greater permeability, lower loss and lower permittivity due to higher densification. 相似文献
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V. Selvamurugan A. Marikani G. Mangamma D. Madhavan M. Kamruddin Sitaram Dash A. K. Tyagi 《Transactions of the Indian Institute of Metals》2017,70(4):903-908
Samarium (Sm) substituted bismuth titanate (Bi4Ti3O12, BT) nanoparticles with compositions of Bi4?xSmxTi3O12 (BSmT) (where x = 0.0, 0.25, 0.50, 0.75, 1.0) were prepared by using the gel combustion method. X-ray diffraction pattern of prepared nanoparticles confirmed that all the BSmT compositions were of the single phase orthorhombic structure with the space group of B2ab. The dielectric loss at 100 Hz varied from 0.0925 to 0.056 with an increase in Samarium content. Dielectric loss confirmed the lower leakage current of BSmT nanoparticles. The ferroelectric behavior of BSmT nanoparticles showed that the Bi3.50Sm0.50Ti3O12 had good ferroelectric property and also had minimum leakage current. The increase of coercive field (Ec) and the increase of remnant polarizations (Pr) were pronounced with the increase in Sm content confirming to the fact that the substitution of Sm3+ had improved the ferroelectric properties of BT. 相似文献
15.
The Cu solubility was measured in the CaO-B2O3 and BaO-B2O3 slag systems to understand the dissolution mechanism of Cu in the slags. The Cu solubility had a linear relationship with
oxygen partial pressure in the CaO-B2O3 slag system, which corresponds with previous studies. Also, the Cu solubilities in slag decreased with increasing the slag
basicity, which value of slope was close to –0.5 in logarithmic form. From the results of experiment, the Cu dissolution mechanism
established as follows:
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