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1.
Refractive indexes for the Al2O3-Na2O-SiO2 system have been measured using an ellipsometer for a wavelength of 632.8 nm over a wide temperature range (1100 to 1800
K). Two kinds of sample were used: xAl2O3-(40-x)Na2O-60SiO2 and yAl2O3-yNa2O-(100-2y)SiO2, where x ranged between 6 and 20 mol pct and y between 12.5 and 25 mol pct. In the former samples, the temperature coefficient of refractive indexes changed from negative
to positive on increasing the concentration of Al2O3. In the latter samples, the refractive indexes increased monotonically with decreasing concentration of SiO2, and the temperature coefficient was always positive. It has been found that the temperature dependence of refractive indexes
in these melts is determined by the coefficient of thermal expansion, which would be relevant to the degree of polymerization
of the melts. In addition, the electronic polarizability of oxygen derived from the refractive indexes increased with increasing
temperature in each melt. This suggests that the basicity of the alumino-silicate melts increases as temperature increases.
The positive temperature coefficient of the electronic polarizability of oxygen can be attributed to an increase in the distance
between cation and oxygen ion due to thermal expansion. The dependence of the electronic polarizability of oxygen on the concentration
of Al2O3 has also been discussed in terms of the electronic polarizabilities of three types of oxygen contained in the melts.
This article is based on a presentation given in the Mills Symposium entitled “Metals, Slags, Glasses: High Temperature Properties
& Phenomena,” which took place at The Institute of Materials in London, England, on August 22–23, 2002. 相似文献
2.
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
3.
M. Stoica R. Li S. Roth J. Eckert G. Vaughan A. R. Yavari 《Metallurgical and Materials Transactions A》2011,42(6):1476-1480
Recently, (Fe-Co)-B-Si-Nb bulk metallic glasses (BMGs) were produced. Such BMGs exhibit high glass-forming ability (GFA) as
well as good mechanical and magnetic properties. These alloys combine the advantages of functional and structural materials.
The soft magnetic properties can be enhanced by nanocrystallization. To force the nanocrystallization, small content of Cu
was added to the starting composition. In this article, {[(Fe0.5Co0.5)0.75Si0.05B0.20]0.96Nb0.04}100–x
Cu
x
glassy alloys (x = 1, 2, and 3) were chosen for investigation. The GFA and the thermal stability of these alloys were evaluated. The effects
of crystallization during heat-treatment processes on the phase evolution and the magnetic properties, including M
s
, H
c
, and T
c
, in these alloys were investigated. The phase analyses were done with the help of the X-ray diffraction patterns recorded
in situ by using the synchrotron radiation in transmission configuration. 相似文献
4.
Sachin Tyagi Himanshu B. Baskey Ramesh Chandra Agarwala Vijaya Agarwala Trilok Chand Shami 《Transactions of the Indian Institute of Metals》2011,64(6):607-614
Zinc ferrite and strontium hexaferrite; SrFe12O19/ZnFe2O4 (SrFe11.6Zn0.4O19) nanoparticles having super paramagnetic nature were synthesized by simultaneous co-precipitation of iron, zinc and strontium
chloride salts using 5 M sodium hydroxide solution. The resulting precursors were heat treated (HT) at 850, 950 and 1150°C
for 4 h in nitrogen atmosphere. The hysteresis loops showed an increase in saturation magnetization from 1.040 to 58.938 emu/g
with increasing HT temperatures. The ‘as-synthesized’ particles have size in the range of 20–25 nm with spherical and needle
shapes. Further, these spherical and needle shaped nanoparticles tend to change their morphology to hexagonal plate shape
with increase in HT temperatures. The effect of such a systematic morphological transformation of nanoparticles on dielectric
(complex permittivity and permeability) and microwave absorption properties were estimated in X band (8.2–12.2 GHz). The maximum
reflection loss of the composite reaches −26.51 dB (more than 99% power attenuation) at 10.636 GHz which suits its application
in RADAR absorbing materials. 相似文献
5.
Ye-Jin Kim Dae-Hee Woo Henri Gaye Hae-Geon Lee Youn-Bae Kang 《Metallurgical and Materials Transactions B》2011,42(3):535-545
The activities of MnO and MnS in a MnO-SiO2-Al2O3(or AlO1.5)-MnS liquid oxysulfide solution were investigated by employing the gas/liquid/Pt-Mn alloy chemical equilibration technique
under a controlled atmosphere at 1773 K (1500 °C). Also, the sulfide capacity, defined as C
S = (wt pct S)(pO2/pS2)1/2, in MnO-SiO2-Al2O3 slag with a dilute MnS concentration was obtained from the measured experimental data. As X
SiO2/(X
MnO + X
SiO2) in liquid oxysulfide increases, the activity coefficient of MnO decreases, while that of MnS first increases and then decreases.
As X(AlO1.5) in liquid oxysulfide increases, the activity coefficient of MnS increases, while no remarkable change is observed for the
activity coefficient of MnO. The behavior of the activity coefficient of MnS was qualitatively analyzed by considering MnO + A
x
S
y
(SiS2 or Al2S3) = MnS + A
x
O
y
(SiO2 or Al2O3) reciprocal exchange reactions in the oxysulfide solution. The behavior was shown to be consistent with phase diagram data,
namely, the MnS saturation boundary. Quantitative analysis of the activity coefficient of the oxysulfide solution was also
carried out by employing the modified quasichemical model in the quadruplet approximation. 相似文献
6.
K. B. Bakin O. N. Simakova P. V. Polyakov Yu. G. Mikhalev D. A. Simakov A. O. Gusev 《Russian Metallurgy (Metally)》2010,(8):707-711
The electrical conductivity of NaF-AlF3-Al2O3 melts with a CaF2 concentration of 5 wt % is measured at a continuously varying cell constant when the molar cryolitic ratio CR = [NaF]/[AlF3] changes from 1.2 to 2.0 [1, 2]. The experimental data are used to obtain a regression equation to describe the dependence
of the electrical conductivity of the melts under study on CR, the alumina content, and temperature {χ] = f(CR, [Al2O3], T)}. 相似文献
7.
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
8.
9.
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
10.
W. Kai I.F. Ren B. Barnard P.K. Liaw M.D. Demetriou W.L. Johnson 《Metallurgical and Materials Transactions A》2010,41(7):1720-1725
The oxidation behavior of both Pd43Cu27Ni10P20 bulk metallic glass (Pd4-BMG) and its amorphous foam containing 45 pct porosity (Pd4-AF) was investigated over the temperature
range of 343 K (70 °C) to 623 K (350 °C) in dry air. The results showed that virtually no oxidation occurred in the Pd4-BMG
at T < 523 K (250 °C), revealing the alloy’s favorable oxidation resistance in this temperature range. In addition, the oxidation
kinetics at T ≥ 523 K (250 °C) followed a parabolic-rate law, and the parabolic-rate constants (k
p
values) generally increased with temperature. It was found that the oxidation k
p
values of the Pd4-AF are slightly lower than those of the Pd4-BMG, indicating that the porous structure contributes to improving
the overall oxidation resistance. The scale formed on the alloys was composed exclusively of CuO at T ≥ 548 K (275 °C), whose thickness gradually increased with increasing temperature. In addition, the amorphous structure remained
unchanged at T ≤ 548 K (275 °C), while a triplex-phase structure developed after the oxidation at higher temperatures, consisting of Pd2Ni2P, Cu3P, and Pd3P. 相似文献
11.
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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