اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThermoelastic Equation of State of Boron Suboxide B6O up to 6 GPa and 2700 K: Simplified Anderson-Gruneisen Model and Thermodynamic Consistency
68
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
p-V-T equation of state of superhard boron suboxide B6O has been measured up to 6 GPa and 2700 K using multianvil technique and synchrotron X-ray diffraction. To fit the experimental data, the theoretical p-V-T equation of state has been derived in approximation of the constant value of the Anderson-Gruneisen parameter {delta}T. The model includes bulk modulus B0 =181 GPa and its first pressure derivative B0 = 6 at 300 K; two parameters describing thermal expansion at 0.1 MPa, i.e. a = 1.4x10-5 K-1 and b = 5x10-9 K-2, as well as {delta}T = 6. The good agreement between fitted and experimental isobars has been achieved to the absolute volume changes up to 5% as compared to volume at standard conditions, V0. The fitted thermal expansion at 0.1 MPa is well consistent with the experimental data, as well as with ambient-pressure heat capacity cp, bulk modulus B0 and {delta}T describing its evolution with volume and temperature. The fitted value of Gruneisen parameter {gamma} = 0.85 is in agreement with previous empiric estimations for B6O and experimental values for other boron-rich solids.
قيم البحث
اقرأ أيضاً
In the present paper we performed the analysis of available data on structural, thermodynamic and mechanical properties of B6O. Although the compound is known for half a century and has been extensively studied, many properties of this boron-rich sol
id remain unknown or doubtful. Semi-empirical analysis of our experimental and literature data allowed us to choose the best values of main thermodynamic and mechanical characteristics among previously reported data, to predict the thermoelastic equation of state of B6O, and dependence of its hardness on non-stoichiometry and temperature.
Ultrafast acoustics measurements on liquid mercury have been performed at high pressure and temperature in diamond anvils cell using picosecond acoustic interferometry. We extract the density of mercury from adiabatic sound velocities using a numeric
al iterative procedure. The pressure and temperature dependence of the thermal expansion, the isothermal compressibilty, the isothermal bulk modulus and its pressure derivative are derived up to 7 GPa and 520 K. In the high pressure regime, the sound velocity values, at a given density, are shown to be only slightly dependent on the specific temperature and pressure conditions. The density dependence of sound velocity at low density is consistent with that observed with our data at high density in the metallic liquid state.
Boron carbide is a ceramic material with unique properties widely used in numerous, including armor, applications. Its mechanical properties, mechanism of compression, and limits of stability are of both scientific and practical value. Here, we repor
t the behavior of the stoichiometric boron carbide B13C2 studied on single crystals up to 68 GPa. As revealed by synchrotron X-ray diffraction, B13C2 maintains its crystal structure and does not undergo phase transitions. Accurate measurements of the unit cell and B12 icosahedra volumes as a function of pressure led to conclusion that they reduce similarly upon compression that is typical for covalently bonded solids. A comparison of the compressional behavior of B13C2 with that of alpha-B, gamma-B, and B4C showed that it is determined by the types of bonding involved in the course of compression. Neither molecular-like nor inversed-molecular-like solid behavior upon compression was detected that closes a long-standing scientific dispute.
The 300 K equation of state of cubic (zinc-blende) boron phosphide BP has been studied by in situ single-crystal X-ray diffraction with synchrotron radiation up to 55 GPa. The measurements have been performed under quasi-hydrostatic conditions using
a Ne pressure medium in a diamond anvil cell. A fit of the experimental p-V data to the Vinet equation of state yields the bulk modulus B0 of 179(1) GPa with its pressure derivative of 3.3(1). These values are in a good agreement with previous elastic measurements, as well as with semiempirical estimations.
We report ab initio calculations of the melting curve and Hugoniot of molybdenum for the pressure range 0-400 GPa, using density functional theory (DFT) in the projector augmented wave (PAW) implementation. We use the ``reference coexistence techniqu
e to overcome uncertainties inherent in earlier DFT calculations of the melting curve of Mo. Our calculated melting curve agrees well with experiment at ambient pressure and is consistent with shock data at high pressure, but does not agree with the high pressure melting curve from static compression experiments. Our calculated P(V) and T(P) Hugoniot relations agree well with shock measurements. We use calculations of phonon dispersion relations as a function of pressure to eliminate some possible interpretations of the solid-solid phase transition observed in shock experiments on Mo.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
