scholarly journals Anisotropic Thermal Expansion of Zirconium Diboride: An Energy-Dispersive X-Ray Diffraction Study

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
William A. Paxton ◽  
Tevfik E. Özdemir ◽  
İlyas Şavklıyıldız ◽  
Terence Whalen ◽  
Hülya Biçer ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Nonlinear Least Squares ◽  
Zirconium Diboride ◽  
Hexagonal Structure ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
Temperature Anisotropy ◽  
X Ray ◽  
Anisotropic Expansion ◽  
Expansion Coefficients

Zirconium diboride (ZrB2) is an attractive material due to its thermal and electrical properties. In recent years, ZrB2 has been investigated as a superior replacement for sapphire when used as a substrate for gallium nitride devices. Like sapphire, ZrB2 has an anisotropic hexagonal structure which defines its directionally dependent properties. However, the anisotropic behavior of ZrB2 is not well understood. In this paper, we use energy-dispersive synchrotron X-ray diffraction to measure the thermal expansion of polycrystalline ZrB2 powder from 300 to 1150 K. Nine Bragg reflections are fit using Pseudo-Voigt peak profiles and used to compute the a and c lattice parameters using a nonlinear least-squares approximation. The temperature-dependent instantaneous thermal expansion coefficients are determined for each a-axis and c-axis direction and are described by the following equations: αa = (4.1507×10-6 + 5.1086 × 10-9(T-293.15))/(1+4.1507 × 10-6(T-293.15) + 2.5543×10-9(T-293.15)2) and αc = (4.5374×10-6 + 4.3004×10-9(T-293.15))/(1+4.5374×10-6(T-293.15) + 2.1502×10-9(T-293.15)2). Our results are within range of previously reported values but describe the temperature anisotropy in more detail. We show that anisotropic expansion coefficients converge to the same value at about 780 K and diverge at higher temperatures. Results are compared with other reported values.

The crystal structure and thermal expansion of the CCl4 adduct of Dianin's compound

1990 ◽  
Vol 68 (8) ◽  
pp. 1352-1356 ◽  
Author(s):  
Walter Abriel ◽  
André Du Bois ◽  
Marek Zakrzewski ◽  
Mary Anne White
Keyword(s):  
Crystal Structure ◽  
Thermal Expansion ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Dianin's Compound

The crystal structure of the title compound has been determined by single crystal X-ray diffraction data collected at 293 K, and refined to a final Rw of 0.057. The crystals are rhombohedral, space group [Formula: see text], with a = 27.134(8) Å, c = 10.933(2) Å, and Z = 18. The mole ratio of Dianin's compound (4-p-hydroxyphenyl-2,2,4-trimethylchroman) to CCl4 is 6:1. The guest molecules are disordered. X-ray powder diffraction was carried out in the temperature range from 10 to 300 K. From this, the thermal expansion coefficients for the a- and c-axes and the volume have been determined. Keywords: thermal expansion, crystal structure, clathrate.

Structure and Thermal Expansion Behavior of Dy2-xGdxMo4O15 Solid Solution

2008 ◽  
Vol 368-372 ◽  
pp. 1665-1667
Author(s):  
M.M. Wu ◽  
X.L. Xiao ◽  
Y.Z. Cheng ◽  
J. Peng ◽  
D.F. Chen ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Thermal Expansion ◽  
Monoclinic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Cell Volumes

A new series of solid solutions Dy2-xGdxMo4O15 (x = 0.0-0.9) were prepared. These compounds all crystallize in monoclinic structure with space group P21/c. The lattice parameters a, b, c and unit cell volumes V increase almost linearly with increasing gadolinium content. The intrinsic thermal expansion coefficients of Dy2-xGdxMo4O15 (x = 0.0 and 0.25) were obtained in the temperature range of 25 to 500°C with high-temperature X-ray diffraction. The correlation between thermal expansion and crystal structure was discussed.

Relationship Between Thermal Expansion and Crystal Chemical Parameters in Diborides

1986 ◽  
Vol 30 ◽  
pp. 503-510
Author(s):  
H.A. McKinstry ◽  
Lai Daik Chai ◽  
R.V. Sara ◽  
K.E. Spear
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Zirconium Phosphate ◽  
Hexagonal Structure ◽  
Crystal Chemical ◽  
X Ray Diffraction ◽  
Chemical Parameters ◽  
X Ray ◽  
Sodium Zirconium ◽  
Sodium Zirconium Phosphate

Thermal expansion is an interesting, ubiquitous and neglected property of materials. Recently, Lenain et al. (1985) and Limaye (1986) have been investigating anisotropy in the low-expansion structures of the sodium zirconium phosphate family. In the hexagonal structure one axis expands while another contracts. In going from the calcium to the strontium analog the anisotropy actually changes sign. A change in anisotropy between CrB2 and TiB2 had been observed by R.V. Sara (1960). The results in Fig. 1 obtained by high temperature x-ray diffraction measurements indicate that for TiB2 the thermal expansion of the c-axis is greater than the expansion of the a-axis, whereas for CrB2 the reverse is true.

scholarly journals An examination of the thermal expansion of urea using high-resolution variable-temperature X-ray powder diffraction

2005 ◽  
Vol 38 (6) ◽  
pp. 1038-1039 ◽  
Author(s):  
Robert Hammond ◽  
Klimentina Pencheva ◽  
Kevin J. Roberts ◽  
Patricia Mougin ◽  
Derek Wilkinson
Keyword(s):  
Thermal Expansion ◽  
High Resolution ◽  
Variable Temperature ◽  
X Ray Diffraction ◽  
Polymorphic Transformations ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Cell Dimensions ◽  
Expansion Coefficients ◽  
Unit Cell Dimensions

Variable-temperature high-resolution capillary-mode powder X-ray diffraction is used to assess changes in unit-cell dimensions as a function of temperature over the range 188–328 K. No evidence was found for any polymorphic transformations over this temperature range and thermal expansion coefficients for urea were found to be αa= (5.27 ± 0.26) × 10−5 K−1and αc= (1.14 ± 0.057) × 10−5 K−1.

Crystal structure and thermal expansion of hexakis(phenylthio)benzene and its CBr4 clathrate

1995 ◽  
Vol 73 (4) ◽  
pp. 513-521 ◽  
Author(s):  
Darek Michalski ◽  
Mary Anne White ◽  
Pradip K. Bakshi ◽  
T. Stanley Cameron ◽  
Ian Swainson
Keyword(s):  
Crystal Structure ◽  
Thermal Expansion ◽  
Neutron Powder Diffraction ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

The crystal structures of hexakis(phenylthio)benzene (HPTB) and its CBr4 clathrate have been determined by single crystal X-ray diffraction data collected at T = 18 °C and refined to final Rw of 0.036 and 0.047, respectively. Pure HPTB is triclinic, space group [Formula: see text] (No. 2), with a = 9.589(2) Å, b = 10.256(1) Å, c = 10.645(2) Å, α = 68.42(1)°, β = 76.92(2)°, γ = 65.52(1)°, and Z = 1. The CBr4 clathrate of HPTB is rhombohedral, space group [Formula: see text] (No. 148), with a = 14.327(4) Å, b = 20.666(8) Å, and Z = 3. The host–guest mole ratio of HPTB–CBr4 is 1:2. Neutron powder diffraction was carried out on powders of both compounds in the temperature range 25 K < T < 295 K. Thermal expansion coefficients were determined for HPTB and HPTB–CBr4 over this temperature range. Keywords: thermal expansion, crystal structure, clathrate.

The thermal expansion of staurolite, Fe4Al18Si8O44(OH)4

1981 ◽  
Vol 44 (333) ◽  
pp. 69-72 ◽  
Author(s):  
K. Gibbons ◽  
M. J. Dempsey ◽  
C. M. B. Henderson
Keyword(s):  
Thermal Expansion ◽  
Computer Modelling ◽  
Complex Structures ◽  
X Ray Diffraction ◽  
Ray Method ◽  
X Ray ◽  
Temperature Ranges ◽  
Expansion Coefficients ◽  
Expansion Behaviour ◽  
Good Agreement

AbstractThe thermal expansion of iron end-member staurolite has been studied by high-temperature powder X-ray diffraction methods and by modelling with the Distance Least Squares (DLS) computer program. The X-ray approach was complicated by dehydroxylation of the staurolite. Mean linear expansion coefficients for the a, b, and c cell edges of dehydroxylated staurolite determined by the X-ray method are (× 10−6 °C−1); 20–500 °C, 8.93, 8.23, and 7.95, respectively, and 20–800 °C, 7.85, 9.43, and 9.13, respectively. Expansion coefficients of a, b, and c calculated for hydroxylated staurolite using the DLS program over the same temperature ranges are (7.86, 7.18, and 7.55 × 10−6 °C−1) and (7.87, 7.17, and 7.57 × 10−6 °C−1). The good agreement between the results from the two methods supports the use of computer modelling in estimating the thermal expansion behaviour of complex structures. The latter approach could be preferable for studying hydrated minerals.

Behaviors of the Zr–1.0Sn–0.39Nb–0.31Fe–0.05Cr Alloy at High Temperature

2011 ◽  
Vol 399-401 ◽  
pp. 80-84
Author(s):  
Yi Yuan Tang ◽  
Jie Li Meng ◽  
Kai Lian Huang ◽  
Jian Lie Liang
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
High Temperature ◽  
Oxide Film ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thin Oxide Film ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

Phase transformation of the Zr-1.0Sn-0.39Nb-0.31Fe-0.05Cr alloy was investigated by high temperature X-ray diffraction (XRD). The XRD results revealed that the alloy contained two precipitates at room temperature, namely β-Nb and hexagonal Zr(Nb,Fe,Cr,)2. β-Nb was suggested to dissolve into the α-Zr matrix at the 580oC. Thin oxide film formed at the alloy’s surface was identified as mixture of the monoclinic Zr0.93O2and tetragonal ZrO2, when the temperature reached to 750oC and 850 oC. The thermal expansion coefficients of αZr in this alloy was of αa = 8.39×10-6/°C, αc = 2.48×10-6/°C.

Structural Disorder and Thermal Dilatation Behavior in Cr-Doped Mullite

1994 ◽  
Vol 346 ◽  
Author(s):  
M.P. Villar ◽  
J.M. Geraldia ◽  
L. Gago-Duport
Keyword(s):  
Thermal Expansion ◽  
Diffraction Data ◽  
Chromium Content ◽  
Sol Gel ◽  
Structural Disorder ◽  
Lattice Parameters ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anisotropic Expansion ◽  
Thermal Dilatation

ABSTRACTLattice parameters of some different chromium-doped mullites obtained by a sol-gel route and sintered at 1650° C have been determined from X-Ray Diffraction data as a function of both temperature and Cr contents. Profile refinements on the X-ray diffraction diagrams have been carried out, showing that, at temperatures between 800° and 1535° C, an anisotropic thermal expansion takes place for the a and b lattice parameters of the Cr-doped mullite. We show that this anisotropic expansion is dependent on the temperature increase and the chromium content for the different compositions of the mullite crystals.

A time-resolved x-ray diffraction study of Ti5Si3 product formation during combustion synthesis

1997 ◽  
Vol 12 (12) ◽  
pp. 3230-3240 ◽  
Author(s):  
C. R. Kachelmyer ◽  
I. O. Khomenko ◽  
A. S. Rogachev ◽  
A. Varma
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Product Formation ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
Time Resolved ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
High Temperature Synthesis ◽  
Expansion Coefficients

Time-resolved x-ray diffraction (TRXRD) was performed during Ti5Si3 synthesis by the self-propagating high-temperature synthesis mode for different Ti size fractions. It was determined that the time for product formation (ca. 15 s) was independent of Ti particle size. However, the formation of Ti5Si4 phase occurred when relatively large titanium particles were used. A simultaneous measurement of the temperature and TRXRD allowed us to attribute the shifting of XRD peaks at high temperature to thermal expansion of the Ti5Si3 product. The thermal expansion coefficients differ for different crystal planes, and their numerical values compare well with those reported previously in the literature.

Residual Stress in Two Dental Alloys During Porcelain Application

1987 ◽  
Vol 31 ◽  
pp. 255-260
Author(s):  
M. Bagby ◽  
SJ Marshall ◽  
GW Marshall
Keyword(s):  
Residual Stress ◽  
Thermal Expansion ◽  
Residual Stresses ◽  
Casting Process ◽  
Dental Alloys ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Dental Restorations ◽  
Expansion Coefficients

Residual stresses in dental castings are widely held to be the cause of distortion and change of fit in ceramic bonded to metal dental restorations. Residual stresses are thought to result from the casting process and from ceramic/metal mismatch of thermal expansion coefficients. Such stresses have not been confirmed experimentally. The purpose of this study was to measure residual stress with x-ray diffraction at the various porcelain application steps for two noble dental alloys with two dental opaque porcelains.

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