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1.
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
2.
3.
D. M. Liu Z. H. Nie Y. Ren Y. D. Wang J. Pearson P. K. Liaw D. E. Brown 《Metallurgical and Materials Transactions A》2011,42(10):3062-3070
The high-energy ball-milling method was used for fabricating Ni50Mn36.7In13.3 fine-sized particles. The as-melt polycrystalline Ni50Mn36.7In13.3 alloy exhibits a 14 M modulated martensite structure at room temperature (RT). The atomic pair distribution function analysis
together with the differential scanning calorimetry technique proved that the 14 M modulated martensite transformed to a metastable
amorphous-like structure after ball milling for 8 hours. Annealing of the ball-milled particles with the amorphous-like phase
first led to the crystallization to form a B2 structure at 523 K (250 °C), and then an ordered Heusler L21 structure (with a small tetragonal distortion) at 684 K (411 °C). The annealed particles undergo different structural transitions
during cooling, tailored by the atomic arrangements of the high-temperature phase. Low-field thermomagnetization measurements
show that the ball-milled particles with the amorphous-like structure or the atomically disordered crystalline structure exhibit
a magnetic transition from the paramagnetic-like to the spin-glass state with decreasing temperature, whereas the crystalline
particles with the ordered Heusler L21 structure present a ferromagnetic behavior with the Curie temperature T
c
≈ 310 K (37 °C). 相似文献
4.
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
5.
D. Roy R. Mitra O. A. Ojo W. Lojkowski I. Manna 《Metallurgical and Materials Transactions A》2011,42(8):2498-2508
The structure and mechanical properties of nanocrystalline intermetallic phase dispersed amorphous matrix composite prepared
by hot isostatic pressing (HIP) of mechanically alloyed Al65Cu20Ti15 amorphous powder in the temperature range 573 K to 873 K (300 °C to 600 °C) with 1.2 GPa pressure were studied. Phase identification
by X-ray diffraction (XRD) and microstructural investigation by transmission electron microscopy confirmed that sintering
in this temperature range led to partial crystallization of the amorphous powder. The microstructures of the consolidated
composites were found to have nanocrystalline intermetallic precipitates of Al5CuTi2, Al3Ti, AlCu, Al2Cu, and Al4Cu9 dispersed in amorphous matrix. An optimum combination of density (3.73 Mg/m3), hardness (8.96 GPa), compressive strength (1650 MPa), shear strength (850 MPa), and Young’s modulus (182 GPa) were obtained
in the composite hot isostatically pressed (“hipped”) at 773 K (500 °C). Furthermore, these results were compared with those
from earlier studies based on conventional sintering (CCS), high pressure sintering (HPS), and pulse plasma sintering (PPS).
HIP appears to be the most preferred process for achieving an optimum combination of density and mechanical properties in
amorphous-nanocrystalline intermetallic composites at temperatures ≤773 K (500 °C), while HPS is most suited for bulk amorphous
alloys. Both density and volume fraction of intermetallic dispersoids were found to influence the mechanical properties of
the composites. 相似文献
6.
7.
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
8.
M. Sherif El-Eskandarany Satoru Ishihara Wei Zhang A. Inoue 《Metallurgical and Materials Transactions A》2005,36(1):141-147
A single glassy phase of Co71Ti24B5 alloy has been synthesized by high-energy ball milling the elemental powders at room temperature, using the mechanical alloying
method. The synthetic glassy powder obtained after 130 ks of ball milling exhibits good soft magnetic properties with a polarization
magnetization and coercivity values of 1.01 T and 2.86 kA/m, respectively. This ternary glassy alloy in which its glass transition
temperature (T
g
) lies at a rather high temperature (805 K) crystallizes at 868 K through a single sharp exothermic peak with an enthalpy
change of crystallization (ΔH
x
) of −3.28 kJ/mol. The supercooled liquid region before crystallization, ΔT
x of the synthesized glassy powders shows a large value (63 K) for a ternary system. The reduced glass transition temperature
(ratio between T
g and liquidus temperatures, T
l
(T
g
/T
l
)) was found to be 0.55. The end product of the glassy powder (130 ks) was compacted in an argon gas atmosphere at 835 K with
a pressure of 780 MPa, using the hot-pressing technique. The consolidated sample is fully dense (∼99.5 pct) and maintains
its chemically homogeneous glassy structure. The measured polarization magnetization and coercivity values of as-consolidated
powders are measured and found to be 0.96 T and 2.92 kA/m, respectively. The Vickers microhardness of the bulk glassy Co71Ti24B5 sample is measured and found to be in the range between 7.32 and 7.46 GPa. 相似文献
9.
10.
Qiong-Zhu Huang Gui-Min Lu Jin Wang Jian-Guo Yu 《Metallurgical and Materials Transactions B》2010,41(5):1059-1066
The reaction mechanism and kinetic behavior of thermal decomposition of MgCl2 × 6H2O were studied by thermal gravimetric analysis. The results showed that the thermal decomposition process of MgCl2 × 6H2O could be divided into six stages. In the first two stages, four crystalline waters were lost. The dehydration and hydrolysis
coexisted during the third and fourth stages. The fifth stage corresponded to the evaporation of 0.3 crystalline waters, and
one molecular hydrogen chloride was eliminated in the last stage. The kinetic analysis of the thermal decomposition process
was performed using the Doyle, Coats–Redfern, and Malek methods. The results suggested that the mechanisms of six stages were
two-dimensional phase boundary mechanism, three-dimensional phase boundary mechanism, nucleation and nuclei growth mechanism
(Avrami–Erofeev equation n = 3), two-dimensional phase boundary mechanism, three-dimensional diffusion mechanism (cylinder
and G-B equation), and nucleation and nuclei growth mechanism (Avrami–Erofeev equation n = 1), respectively. The apparent
active energies of six stages were 66.8 kJ × mol−1, 138.0 kJ × mol−1, 77.2 kJ × mol−1, 135.6 kJ × mol−1, 77.4 kJ × mol−1, and 92.2 kJ × mol−1, respectively. The frequency factors were 3.6 × 109 s−1, 8.8 × 1017 s−1, 4.6 × 109 s−1, 3.0 × 1014 s−1, 78.6 s−1, and 1.2 × 103 s−1, respectively. 相似文献
11.
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
12.
H.M. Lin C.K. Lin R.R. Jeng H.Y. Bor P.Y. Lee 《Metallurgical and Materials Transactions A》2008,39(8):1857-1861
Amorphous Ti50Cu28Ni15Sn7 alloy powders were synthesized by a mechanical alloying (MA) technique. Differential scanning calorimetry (DSC) results showed
that, after 7 hours of exposure to the milling process, amorphous Ti50Cu28Ni15Sn7 alloy powders exhibit a wide supercooled liquid region of 61 K. Consolidation of amorphous powders were performed at a temperature
slightly higher than the glass transition temperature under a pressure of ∼1.2 GPa, and bulk metallic glass (BMG) discs can
be prepared successfully. However, we noticed partial crystallization during the hot pressing process and were not able to
achieve full densification of BMG. The Vickers microhardness of Ti50Cu28Ni15Sn7 BMG was 634 kg/mm2, and the trace of the indentation revealed that pre-existing particle boundaries or interfaces between nanocrystals and amorphous
matrix may serve as the crack initiation sites. Thus, typical brittle failure of Ti50Cu28Ni15Sn7 BMG was observed and resulted in relatively low fracture stress compared to that estimated by the microhardness.
This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February
25–March 1, 2007 during the TMS Annual Meeting in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of
Materials Committee. 相似文献
13.
CH.F. Xu Z.F. Gu G. Cheng J. Ren H.Y. Zhou Y.Y. Lin X.M. Liu 《Metallurgical and Materials Transactions A》2010,41(1):57-60
Alloys of the rare earths R (including La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Y, Ho, Er) with platinum, having the composition R3Pt4, have been synthesized and investigated by X-ray diffraction (XRD) and differential thermal analysis (DTA). At temperatures
above about 900 °C and below 250 °C, all the single phases R3Pt4 are formed, which crystallize with the same structure of the rhombohedral Pu3Pd4 type. Over the temperature range of about 250 °C to 900 °C, they occur at an eutectoid decomposition into RPt and RPt2 compounds neighboring in the corresponding phase diagram, R3Pt4 → RPt + RPt2. The stability of these phases R3Pt4 may be restricted to a radius ratio r
R/r
Pt range of 1.27 to 1.35. 相似文献
14.
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
15.
The crystallization kinetics of CaO-SiO2-Al2O3-MgO (CSAM) slags was studied with the aid of single hot thermocouple technique (SHTT). Kinetic parameters such as the Avrami exponent (n), rate coefficient (K), and effective activation energy of crystallization (E A ) were obtained by kinetic analysis of data obtained from in situ observation of glassy to crystalline transformation and image analysis. Also, the dependence of nucleation and growth rates of crystalline phases were quantified as a function of time, temperature, and slag basicity. Together with the observations of crystallization front, they facilitated establishing the dominant mechanisms of crystallization. In an attempt to predict crystallization rate under non-isothermal conditions, a mathematical model was developed that employs the rate data of isothermal transformation. The model was validated by reproducing an experimental continuous cooling transformation diagram purely from isothermal data. 相似文献
16.
17.
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
18.
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
19.