scholarly journals Ceramic materials of the quasi-binary LaB6-MoB2 system

2007 ◽  
Vol 1 (1-2) ◽  
pp. 19-22 ◽  
Author(s):  
Galyna Kysla ◽  
Petro Loboda
Keyword(s):  
Phase Diagram ◽  
Melting Point ◽  
Diffusion Process ◽  
High Temperatures ◽  
Boron Content ◽  
Ceramic Materials ◽  
Decomposition Temperature ◽  
Zone Melting ◽  
Cubic Structure ◽  
Eutectic Colony

Alloys of the quasi-binary LaB6-MoB2 system synthesized by melting in an atmosphere of helium have been studied. It has been established that the phase diagram of the system is eutectic and the phases do not interact. The eutectic colony crystallizes in form of the platelike eutectic on the basis of the LaB6 crystal of a cubic structure. It has been also shown that the crystallization from melt under conditions of crusibleless zone melting is accompanied by the MoB2 phase decomposes during cooling with precipitation of the submicron Mo2B5 and ?-MoB crystallites. This results in an increase of hardness. According to the Mo - B phase diagram, the decomposition temperature of the MoB2 increases with increasing the boron content. In addition, the degree of the decomposition is higher if the melting point of alloy is higher, since the intensity of diffusion process increases at high temperatures.

scholarly journals The phase diagram of Ti-6Al-4V at high-pressures and high-temperatures

2021 ◽  
Author(s):  
Simon MacLeod ◽  
Daniel Errandonea ◽  
Geoffrey Adam Cox ◽  
Hyunchae Cynn ◽  
Dominik Daisenberger ◽  
...  
Keyword(s):  
Phase Diagram ◽  
High Temperatures ◽  
High Pressures

C60 UNDER PRESSURE

1992 ◽  
Vol 06 (19) ◽  
pp. 1153-1158 ◽  
Author(s):  
MANUEL NÚÑEZ-REGUEIRO
Keyword(s):  
Phase Diagram ◽  
High Pressure ◽  
High Temperatures ◽  
Room Temperature ◽  
Fullerene Cage ◽  
Temperature Phase ◽  
Bonded Phase ◽  
Temperature Phase Diagram

The high pressure experiments done on fullerenes are reviewed. C 60 has found to be stable up to about 20 GPa at room temperature and hydrostatic conditions. Application of stronger, or non-hydrostatic, pressures at room temperature can induce the formation of a partially sp3 bonded phase, that apparently conserves the fullerene cage. Extreme non-hydrostatic compressions above about 15 GPa can, though, break down the cage and produce amorphous or cubic diamond. Destruction of the cage at high temperatures has also been observed, but the resulting product is amorphous sp2 material. A preliminary pressure-temperature phase diagram for C 60 is proposed.

Experimental Studies and Thermodynamic Modeling of the Interaction of O2 with SiC

2002 ◽  
Vol 742 ◽  
Author(s):  
Y. Song ◽  
F. W. Smith
Keyword(s):  
Phase Diagram ◽  
Thermal Decomposition ◽  
High Temperatures ◽  
Thermodynamic Modeling ◽  
Surface Segregation ◽  
Experimental Studies ◽  
Temperature Phase ◽  
Temperature Phase Diagram

ABSTRACTWe report on experimental studies and thermodynamic modeling of the reaction of O2 with the 4H- and 6H-SiC surfaces at high temperatures. This reaction leads to the growth of passivating SiO2 layers at high O2 pressures, etching of the surfaces at lower pressures, and enhancements of the surface segregation of carbon at still lower pressures. A pressure-temperature phase diagram for the oxidation of SiC is presented. Evidence for the thermal decomposition of the SiO2 layer on SiC is also presented.

Thermal Analysis of Nomex® and Kevlar® Fibers

1977 ◽  
Vol 47 (1) ◽  
pp. 62-66 ◽  
Author(s):  
J. R. Brown ◽  
B. C. Ennis
Keyword(s):  
Thermal Analysis ◽  
Thermal Decomposition ◽  
Glass Transition ◽  
Melting Point ◽  
Transition Region ◽  
High Temperatures ◽  
High Performance ◽  
Polymer Melt ◽  
Glass Transition Region ◽  
Dta Curves

DTA, TG, and TMA curves of commercial Kevlar® 49 and Nomex® fibers have been used to assess their behavior at high temperatures. The fibers lost absorbed water around 100°C, and a glass transition was reflected in the DTA and TMA curves in the region of 300°C. Difficulties in the interpretation of DTA and TMA curves in the glass-transition region and in the assignments of Tv‘s for these high-performance fibers are discussed. Whereas Kevlar 49 showed both a crystalline melting point (560°C) and a sharp endothermal thermal decomposition (590°C), Nomex showed only the latter (440°C) and no evidence of melting from the DTA curves. The endothermal decomposition peaks apparently correspond to “polymer melt temperatures” reported for related materials, and correlate well with the TG and TMA features. During thermal analysis of Kevlar 49, oxidation occurs more readily than thermal decomposition, but the latter predominates for Nomex. Differences between dyed and undyed Nomex were due to differences in yarn constitution.

J-INTEGRAL MEASUREMENTS WITH CERAMIC MATERIALS AT HIGH TEMPERATURES

1980 ◽  
pp. 257-264 ◽  
Author(s):  
K. Kromp ◽  
R.F. Pabst
Keyword(s):  
High Temperatures ◽  
Ceramic Materials ◽  
J Integral

Conductivities of Binary Molten Alkalihalide/Silverhalide Mixtures

1991 ◽  
Vol 46 (1-2) ◽  
pp. 206-210
Author(s):  
H.-P. Boßmann ◽  
J. Richter ◽  
N. Struck
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Melting Point ◽  
Temperature Coefficients ◽  
The Common ◽  
Common Anion

AbstractThe electric conductivities of molten (Na, Ag)Cl, (Rb.Ag)Cl, (Na,Ag)Br, (Rb. Ag)Br, and (Cs, Ag)Br are determined as functions of composition and temperature from the melting point to 1100 K. The relation of the temperature coefficients to the phase diagram of the systems (K.Ag)Cl, (Rb. Ag)Cl, (Cs, Ag)Cl, and (Cs, Ag)I near and at the phase transition (liquid-solid) is studied. The molar conductivities and mobilities of the cations with reference to the common anion are evaluated.

The “Solidification” of Grain Boundaries with Increasing Temperature

1994 ◽  
Vol 357 ◽  
Author(s):  
Witold Lojkowski ◽  
Bogdan Palosz
Keyword(s):  
Solid State ◽  
Melting Point ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
High Temperatures ◽  
Low Temperatures ◽  
Melting Behavior ◽  
Wetting Transitions ◽  
Increasing Temperature ◽  
Segregation Of Impurities

AbstractThe aim of the paper is to explain the recently observed de-wetting grain boundary transition with increasing temperature. On the example of a bicrystal from the Fe-6at.%Si alloy, it was found recently that as temperature is increased, the following GB transitions take place: “solid” (or regular) GB-→“premelted” GB →“solid” GB. At the same time the wetting/de-wetting transitions have taken place. Another example of such GB behavior was discovered during sintering of alumina. The inverse melting behavior is explained as follows: low melting point impurities cause GB premelting at low temperatures, However de-segregation of impurities at high temperatures causes return of the GB structure to its regular “solid” state.

scholarly journals Research Progress on Ni-Based Antiperovskite Compounds

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
P. Tong ◽  
Y. P. Sun
Keyword(s):  
Phase Diagram ◽  
Transition Temperature ◽  
Single Crystals ◽  
Superconducting Transition Temperature ◽  
Spin Fluctuations ◽  
Research Progress ◽  
Future Research ◽  
Magnetic Element ◽  
Superconducting Transition ◽  
Cubic Structure

The superconductivity in antiperovskite compound MgCNi3was discovered in 2001 following the discovery of the superconducting MgB2. In spite of its lower superconducting transition temperature (8 K) than MgB2(39 K), MgCNi3has attracted considerable attention due to its high content of magnetic element Ni and the cubic structure analogous to the perovskite cuprates. After years of extensive investigations both theoretically and experimentally, however, it is still not clear whether the mechanism for superconductivity is conventional or not. The central issue is if and how the ferromagnetic spin fluctuations contribute to the cooper paring. Recently, the experimental results on the single crystals firstly reported in 2007 trend to indicate a conventionals-wave mechanism. Meanwhile many compounds neighboring to MgCNi3were synthesized and the physical properties were investigated, which enriches the physics of the Ni-based antiperovskite compounds and help understand the superconductivity in MgCNi3. In this paper, we summarize the research progress in these two aspects. Moreover, a universal phase diagram of these compounds is presented, which suggests a phonon-mediated mechanism for the superconductivity, as well as a clue for searching new superconductors with the antiperovskite structure. Finally, a few possible scopes for future research are proposed.

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