scholarly journals The estimation of the parameter Gruneisen metal hexaborides

2018 ◽  
Vol 20 (90) ◽  
pp. 36-39
Author(s):  
Y. Fedyshyn ◽  
D. Vadets ◽  
O. Garashchenko ◽  
O. Romanov ◽  
T. Fedyshyn
Keyword(s):  
High Temperature ◽  
Molar Volume ◽  
Characteristic Temperature ◽  
Mathematical Expression ◽  
Crystalline Lattice ◽  
Grüneisen Parameter ◽  
X Ray ◽  
Volumetric Expansion ◽  
Different Temperatures ◽  
Implicit And Explicit

The basis for the estimation of the Gruneisen parameter γ is laid  (θД – Debye’s characteristic temperature, V– molar volume) from which the mathematical expression follows . In previous publications in order to determine θД the Lindemann formula was used. However, due to the ambiguity of the dimensional coefficient C in the Lindemann formula, the authors used the method of high-temperature roentgenography within the limits of 293–973 K. On the basis of analisys of the intensity of one maximum interference (hkl) at different temperatures, was determined by Chipman’s method X-ray characteristic temperature  θр(Т) groups of hexaboard type CaB6, namely CaB6, YB6, LaB6, CeB6, PrB6 , NdB6, ErB6, ThB6, YbB6. Considering, that neither the structure nor the interatomic connections within the temperature search of hexaborides does not change, the value of the parameter γ is determined. Its value was obtained within 2.5–4.7 for CeB6, NdB6, ErB6, YbB6, ThB6 and order 5.5–6.6 for CaB6, YB6, LaB6, PrB6. The parameters of Gruneisen proved to be practically independent of temperature. The presence of the meanings of γ made it possible to divide the implicit and explicit parts of the anagrammonism into a calming measure. The generalizing measure of anharmonism is mainly exhausted by the product γβ (β – the coefficient of the volumetric expansion of the crystalline lattice.

scholarly journals Estimation of the Gruneisen parameter and an explicit measure of anharmonicity of dodecaborides

2018 ◽  
Vol 20 (90) ◽  
pp. 3-6
Author(s):  
Y. Fedyshyn ◽  
D. Vadets ◽  
O. Garashchenko ◽  
O. Romanov ◽  
T. Fedyshyn
Keyword(s):  
Characteristic Temperature ◽  
Real Coefficient ◽  
Crystalline Lattice ◽  
Grüneisen Parameter ◽  
Ray Method ◽  
Gruneisen Parameter ◽  
Average Value ◽  
Volumetric Expansion ◽  
Explicit Measure ◽  
Universal Measure

In previous works on the ratio   (θД – the characteristic temperature of Debye, was calculated according to the Lindemann formula; V – molar volume of hypothetical lattice atoms; γ is the Gruneisen parameter) for the group of dodecaborides (TbB12, DyB12, HoB12, ErB12, TuB12, LaB12, UB12) the average value of γ = 1.3 was determined. However, due to the ambiguity of the coefficient of proportionality in the Lindemann formula by definition θD, the authors selected an independent high-temperature X-ray method for determining the dependence θr (T). Taking into account the immutability of the structure and type of interatomic connection in the temperature interval of the search (293–973 K), the authors evaluated the value and temperature dependence of γ (T) of each dodecaboride separately. The results of the search showed that the value of γ for each given dodecaboride is different, but practically independent from temperature. For some dodecaborides, the parameter γ is about 2–3 units, and for others it is overestimated. The values of γ made it possible to estimate the magnitude of the implicit γβ and the explicit  parts of the universal measure of anharmonicity of dodecaborides , where β – real coefficient of volumetric expansion of the crystalline lattice. Because    (n – dimensionless coefficient of proportionality), then the temperature change n(T) is also determined.

scholarly journals Study on High-Temperature Interaction Mechanism of Nd–Fe–As System

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3060
Author(s):  
Chenghui Fu ◽  
Run Huang ◽  
Wenhao Xie ◽  
Jinxiao Luo ◽  
Yulian Li ◽  
...  
Keyword(s):  
High Temperature ◽  
Heat Insulation ◽  
Interaction Mechanism ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
The Common ◽  
Atomic Vacancy ◽  
Temperature Interaction ◽  
Scanning Electron

In this study, Nd and As are mainly sealed into industrial pure Fe cylinders. The effect of different temperatures on the high-temperature interaction of an Nd–Fe–As ternary system is studied via X-ray diffraction, optical microscopy, and scanning electron microscopy after heat insulation for 30 h at 1173, 1223, and 1273 K. The results show that the common products under high-temperature interaction are NdAs, Fe17Nd2, and Fe. Fe12As5 is present at 1173 K, whereas Fe2As is produced at 1223 and 1273 K. The diffusion ability of Nd is weaker than that of As. Nd mainly diffuses through the Fe atomic vacancy mechanism. As mainly binds to Fe to form Fe and As compounds.

scholarly journals The effect of temperature on the intensity of X-ray reflexion

1947 ◽  
Vol 188 (1015) ◽  
pp. 509-521 ◽  
Keyword(s):  
Coefficient Of Thermal Expansion ◽  
Characteristic Temperature ◽  
Lattice Parameter ◽  
Effect Of Temperature ◽  
Special Method ◽  
Foreign Material ◽  
Powder Specimen ◽  
X Ray ◽  
Characteristic Temperatures ◽  
Different Temperatures

The effect of temperature on the intensity of X-ray reflexion by gold, copper and aluminium has been studied by making microphotometric measurements on lines in X-ray structure spectra obtained with powder specimens in a Debye-Scherrer camera. A special method was employed to make cylindrical powder specimens, 0.8 mm. in diameter, which held together without adhesive and were free from a core of foreign material. The primary beam was standardized by means of a flat-plate X-ray camera, furnished with a plate of powdered gold which provided a spectrum whose lines could be accurately measured. The powder specimen under investigation was maintained in vacuo at temperatures ranging up to about 900° K, and its temperature estimated from lattice parameter measurements. The observed fall in intensity of X-ray reflexion by gold and copper as the temperature is raised up to about 900° K can be accounted for if the characteristic temperature varies with temperature in accordance with the relation θ T = θ 1 [1 ─ αγ( T ─ T 1 )], where θ T and θ 1 are the characteristic temperatures at temperatures T and T 1 , α is the cubical coefficient of thermal expansion and γ is the Grȕneisen constant. This relation is found to hold also for aluminium up to about 600° K. Beyond 600° K the fall of intensity exceeds that to be expected from the above relation, and it is suggested that another factor becomes prominent in the case of aluminium at the higher temperatures. The characteristic temperatures of gold, copper and aluminium now found by X-ray measurement at different temperatures, agree with the values obtained at those temperatures by specific heat and electrical conductivity methods.

Research on the Si-Ti High Temperature Oxidation-Resistant Coatings for Tantalum Alloys

2013 ◽  
Vol 785-786 ◽  
pp. 45-51
Author(s):  
Pei Pei Song ◽  
Jun Le ◽  
Feng Ye ◽  
Xiao Cheng Sheng ◽  
Xiao Wei Zhang
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Isothermal Oxidation ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Temperature Oxidation ◽  
X Ray ◽  
Different Temperatures ◽  
Slurry Method ◽  
Sectional Structure

Si-Ti coatings were prepared on the surface of T-222 alloy by fused slurry method at different temperatures (1425-1500°C). Microstructure and composition of the coatings were characterized and analysed through scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), energy dispersive X-ray spectrometry (EDS) respectively. The coating fabricated at 1450°C exhibited excellent structure compatible with high temperature oxidation resistance. Its surface is relatively smooth with few holes and cracks and the main phase on the surface is (Ti, Ta)Si that possesses outstanding corrosion resistance. Moreover, the cross-sectional structure of the coating is smooth and compact which can effectively prevent O2 from permeation. The isothermal oxidation behaviors in pure O2 atmosphere at 1500°C for 2h finally demonstrate that the optimum coating temperature is 1450°C.

scholarly journals Fabrication of TiO2Nanofilm Photoelectrodes on Ti Foil by Ti Ion Implantation and Subsequent Annealing

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Yichao Liu ◽  
Feng Ren ◽  
Guangxu Cai ◽  
Mengqing Hong ◽  
Wenqing Li ◽  
...  
Keyword(s):  
High Temperature ◽  
Photoelectron Spectroscopy ◽  
Subsequent Annealing ◽  
Xps Spectra ◽  
X Ray ◽  
Annealing Temperatures ◽  
Ions Implantation ◽  
Different Temperatures ◽  
Type Property ◽  
P Type

The TiO2photoelectrodes fabricated on the substrate of Ti foils by Ti ions implantation and subsequent annealing at different temperatures were applied for water splitting. The size of TiO2nanoparticles increased with annealing temperatures, and the GIXRD patterns and Raman spectra demonstrate that the phase of TiO2turns to rutile at high temperature. The photoelectrochemical (PEC) and X-ray photoelectron spectroscopy (XPS) spectra of the valence band demonstrate that the samples annealed at 400 and 500°C show the n-type property. The sample annealed at 600°C shows the weak p-type TiO2property. For the sample annealed at 700°C, the negative photocurrent is main, which mainly performs the p-type property of TiO2. The IPCE values indicate that the absorption edges are red shifted with the increase of annealing temperatures.

Formation of the high temperature phase in vacuum deposited SnSe thin films

1986 ◽  
Vol 175 (1-2) ◽  
Author(s):  
T. Subba Rao ◽  
B. K. Samantaray ◽  
A. K. Chaudhuri
Keyword(s):  
Thin Films ◽  
High Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Glass Substrates ◽  
Different Temperatures ◽  
Substrate Temperatures ◽  
Low Temperature Phase

AbstractThin films of SnSe vacuum deposited on glass substrates kept at different temperatures have been studied by X-ray diffraction. It is observed that the high temperature phase of SnSe, usually found above 807 K is frozen in along with the low temperature phase when deposited at substrate temperatures of 473 K and above.

scholarly journals Core growth of detonation nanodiamonds under high-pressure annealing

RSC Advances ◽  
2021 ◽  
Vol 11 (21) ◽  
pp. 12961-12970
Author(s):  
Denis Bogdanov ◽  
Alexander Bogdanov ◽  
Vladimir Plotnikov ◽  
Sergey Makarov ◽  
Alexander Yelisseyev ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Raman Spectra ◽  
Detonation Nanodiamonds ◽  
X Ray ◽  
High Pressure High Temperature ◽  
Different Temperatures

The present paper reports the results of a study of the X-ray and Raman spectra of detonation nanodiamonds after high-pressure high-temperature (HPHT) annealing at different temperatures.

scholarly journals In-Situ Isothermal Crystallization of Poly(l-lactide)

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3377
Author(s):  
Zirui Huang ◽  
Meiling Zhong ◽  
Haibo Yang ◽  
Enqin Xu ◽  
Dehui Ji ◽  
...  
Keyword(s):  
High Temperature ◽  
Nucleation Rate ◽  
Low Temperatures ◽  
Isothermal Crystallization ◽  
The Other ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures

The isothermal crystallization of poly(l-lactide) (PLLA) has been investigated by in-situ wide angle X-ray diffraction (WAXD) and polarized optical microscopes (POM) equipped with a hot-stage accessory. Results showed that the spherulites of PLLA were formed at high temperature, whereas irregular morphology was observed under a low temperature. This can be attributed to the varying rates of crystallization of PLLA at different temperatures. At low temperatures, the nucleation rate is fast and hence the chains diffuse very slow, resulting in the formation of imperfect crystals. On the other hand, at high temperatures, the nucleation rate is slow and the chains diffuse fast, leading to the formation of perfect crystals. The change in the value of the Avrami exponent with temperature further verifies the varying trend in the morphological feature of the crystals.

Investigation of tetragonal distortion in the PbTiO3–BiFeO3 system by high-temperature x-ray diffraction

1995 ◽  
Vol 10 (5) ◽  
pp. 1301-1306 ◽  
Author(s):  
V.V.S.S. Sai Sunder ◽  
A. Halliyal ◽  
A.M. Umarji
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Room Temperature ◽  
Tetragonal Distortion ◽  
X Ray Diffraction ◽  
Solution System ◽  
X Ray ◽  
Lattice Constants ◽  
Solid Solution System ◽  
Different Temperatures

Compositions in the (Pb1−xBix (Ti1−xFex)O3 solid solution system for x ⋚ 0.7 show unusually large tetragonal distortion. High-temperature x-ray diffraction was used to study the tetragonal distortion as a function of temperature (25–700 °C) for compositions (x = 0–0.7) using powders prepared by solid-state reaction in the above system. Large changes in the lattice parameters were observed over a narrow temperature range near Curie temperature (TC) for compositions near the morphotropic phase boundary (MPB) (x ≃ 0.7). Compositions near MPB showed a c/a ratio of 1.18 at room temperature. Polar plots of lattice constants at different temperatures indicated strong anisotropic thermal expansion with zero thermal expansion along the [201] direction.

High-precision parallel-beam X-ray system for high-temperature diffraction studies

2002 ◽  
Vol 17 (3) ◽  
pp. 173-177 ◽  
Author(s):  
Toru Mitsunaga ◽  
Mari Saigo ◽  
Go Fujinawa
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Characteristic Temperature ◽  
Structural Phase ◽  
Incident Beam ◽  
X Ray Diffraction ◽  
Parallel Beam ◽  
X Ray ◽  
Multilayer Mirror ◽  
Thermal Expansion Coefficients

A recently developed Rigaku parallel-beam X-ray diffraction system equipped with a parabolic graded-multilayer mirror in the incident beam and a parallel-slits analyzer in the diffracted beam was used for precision high-temperature diffraction studies. The lattice parameters a and c of α-Al2O3 at room temperature and up to 1473 K were determined with precision in the range of 0.6–7.3×10−5. The thermal expansion coefficients for a and c agreed with literature values to better than 3%. The system was used successfully also to determine the Debye characteristic temperature of Si and to study structural phase transition of LaCoO3 from rhombohedral at room temperature to cubic at 1700 K.

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