Influence of Nitride on Sinterability of the Composite of Lithium Aluminum Silicate and Silicon Carbide

2006 ◽  
Vol 317-318 ◽  
pp. 177-180 ◽  
Author(s):  
Mabito Iguchi ◽  
Motohiro Umezu ◽  
Masako Kataoka ◽  
Hiroaki Nakamura ◽  
Mamoru Ishii
Keyword(s):  
Silicon Carbide ◽  
Thermal Expansion ◽  
Melting Point ◽  
Liquid Phase ◽  
Room Temperature ◽  
Aluminum Silicate ◽  
Lithium Aluminum ◽  
Sintering Process ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

Ceramics with zero thermal expansion coefficients at room temperature (293K) were investigated. We found the thermal expansion coefficient was controlled by a compounding ratio of lithium aluminum silicate (LAS) and silicon carbide (SiC), which have negative and positive thermal expansion coefficients respectively. Although it was difficult to densify the composite of the LAS and SiC (LAS/SiC) in the sintering process, an addition of nitride improved the sinterability of the LAS/SiC. In order to examine the effect of the nitride additive, at first, the melting point of the LAS with silicon nitride (Si3N4) or aluminum nitride was measured by TG-DTA. The melting point of the LAS decreased with existence of nitride. It is believed that the densification of the LAS/SiC was promoted by the nitride, because the nitride causes the LAS/SiC to form a liquid phase, thereby decreasing the melting point. Next, the lattice constant of the LAS with Si3N4 was measured by XRD and it was verified that the a-axis was longer and the c-axis was shorter than those of the LAS without additive. It is supposed that this phenomenon is due to the substitution of nitrogen for oxygen in the LAS lattice, and the decrease of the melting point of the LAS with nitride seems to be influenced by this substitution of nitrogen.

Crystal Distortion Associated with Magnetic Ordering in Alpha Iron Oxide and Manganese Carbonate

1972 ◽  
Vol 16 ◽  
pp. 390-395 ◽  
Author(s):  
W. S. McCain ◽  
D. L. Albright
Keyword(s):  
Thermal Expansion ◽  
Lattice Constant ◽  
Room Temperature ◽  
Axial Ratio ◽  
Manganese Carbonate ◽  
Lattice Constants ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Position Parameter ◽  
Oxygen Distance

AbstractThe magnetic crystal disrortion of weakly ferromagnetic α-Fe2O3 was investigated by x-ray diffraction techniques. Here crystal distortion is taken as the temperature dependent changes of lattice constants and thermal expansion coefficients. Moreover, the oxygen position parameter and the carbon-oxygen distance of MnCO3 were determined.The lattice constants and thermal expansion coefficients of α-Fe2O3 were measured from room temperature down to 243°K. The crystal distortion, as measured by the changes in lattice constants, thermal expansion coefficients and axial ratio, was found to be highly anisotropic. The co hexagonal lattice constant was influenced very slightly by magnetic distortion; it changed only by 0.01 percent between room temperature and the Morin temperature of 254°K. On the other hand, the ao lattice constant changes by 0.11 percent between room temperature and the Morin temperature. The thermal expansion coefficients of the lattice constants showed a similar contrast. The co coefficient was found to be independent of temperature from room temperature down to the Morin temperature. However, in the same temperature range, the ao coefficient showed an anomalous increase with decreasing temperature. In addition, the ao coefficient showed an infinite discontinuity at the Morin temperature.The change in the axial ratio with temperature suggests that the net weak ferromagnetic moment of α-Fe2O3 reaches a maximum at 275°K.The oxygen position parameter, x, in MnCO3 as determined from two reflections has a value of 0.2702 ± 0.001. The carbon-oxygen distance as calculated from the lattice constants and the oxygen position parameter is 1.29 ±0.002 Å. This value is another confirmation of the Pauling theory of the resonating carbonate structure.

scholarly journals Extraordinary anisotropic thermal expansion in photosalient crystals

IUCrJ ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Khushboo Yadava ◽  
Gianpiero Gallo ◽  
Sebastian Bette ◽  
Caroline Evania Mulijanto ◽  
Durga Prasad Karothu ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Solid State ◽  
Metal Complexes ◽  
Single Crystals ◽  
Room Temperature ◽  
Volumetric Thermal Expansion ◽  
Anisotropic Thermal Expansion ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Multifunctional Properties

Although a plethora of metal complexes have been characterized, those having multifunctional properties are very rare. This article reports three isotypical complexes, namely [Cu(benzoate)L 2], where L = 4-styrylpyridine (4spy) (1), 2′-fluoro-4-styrylpyridine (2F-4spy) (2) and 3′-fluoro-4-styrylpyridine (3F-4spy) (3), which show photosalient behavior (photoinduced crystal mobility) while they undergo [2+2] cycloaddition. These crystals also exhibit anisotropic thermal expansion when heated from room temperature to 200°C. The overall thermal expansion of the crystals is impressive, with the largest volumetric thermal expansion coefficients for 1, 2 and 3 of 241.8, 233.1 and 285.7 × 10−6 K−1, respectively, values that are comparable to only a handful of other reported materials known to undergo colossal thermal expansion. As a result of the expansion, their single crystals occasionally move by rolling. Altogether, these materials exhibit unusual and hitherto untapped solid-state properties.

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.

Thermal Expansion Coefficients of 6H Silicon Carbide

2008 ◽  
Vol 600-603 ◽  
pp. 517-520 ◽  
Author(s):  
Matthias Stockmeier ◽  
Sakwe Aloysius Sakwe ◽  
Philip Hens ◽  
Peter J. Wellmann ◽  
Rainer Hock ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Thermal Expansion ◽  
Photon Energy ◽  
High Energy ◽  
Lattice Parameter ◽  
X Rays ◽  
Bulk Properties ◽  
Nitrogen Doped ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

The thermal expansion of 6H Silicon Carbide with different dopant concentrations of aluminum and nitrogen was determined by lattice parameter measurements at temperatures from 300 K to 1575 K. All samples have a volume of at least 6 x 6 x 6 mm3 to ensure that bulk properties are measured. The measurements were performed with a triple axis diffractometer with high energy x-rays with a photon energy of 60 keV. The values for the thermal expansion coefficients along the a- and c-direction, α11 and α33, are in the range of 3·10-6 K-1 for 300 K and 6·10-6 K-1 for 1550 K. At high temperatures the coefficients for aluminum doped samples are approximately 0.5·10-6 K-1 lower than for the nitrogen doped crystal. α11 and α33 appear to be isotropic.

Intrinsic and Thermal Stress in Gallium Nitride Epitaxial Films

1996 ◽  
Vol 449 ◽  
Author(s):  
J. W. Ager ◽  
T. Suski ◽  
S. Ruvimov ◽  
J. Krueger ◽  
G. Conti ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Thermal Expansion ◽  
Thermal Stress ◽  
Growth Temperature ◽  
Room Temperature ◽  
Intrinsic Stress ◽  
Experimental Methodology ◽  
Thermal Expansion Coefficients ◽  
Si Doped ◽  
Expansion Coefficients

ABSTRACTStrain in GaN epitaxial layers at room temperature is measured with three complementary methods: Raman spectroscopy (via shifts of phonon frequencies), low temperature photoluminescence (via shifts of band-edge luminescence), and X-ray diffraction (via shifts in lattice spacings). GaN films grown on the c-plane of sapphire tend to be in compression. Increasing the Si-dopant concentration (up to 1019 cm−3) is observed to add compressive strain to the layer. Axially resolved measurements obtained by micro-Raman in 4 μm thick Si-doped films reveal strain relaxation toward the sample surface at Si concentrations above 1018 cm−3. Mg- and Si-doped GaN films on SiC substrates are found to be in tension. An experimental methodology is presented that separates two contributions to the room temperature residual stress in GaN epilayers: (1) the thermal stress due to differences in the thermal expansion coefficients of the epilayer and substrate and (2) the intrinsic stress, which is influenced by the growth conditions. We measure stress as a function of temperature up to 325 C, about one-third of the growth temperature, by monitoring the frequency of the E2 phonon mode by Raman spectroscopy. A high-quality bulk single crystal of GaN is used as a strain-free standard. Over this temperature range, most layers behave elastically; the observed stress trends are well-fit by a thermal expansion model using previous reported values of the thermal expansion coefficients of GaN and the substrates. The intrinsic stress states at the growth temperature for films grown on sapphire and SiC are predicted to be tensile and compressive, respectively, in agreement with the a-plane lattice coefficient mismatch.

Thermal Expansion Behavior of ZnSe and ZnS0.03Se0.97 Epilayers on GaAs at Temperatures in the Range, 25°C - 250°C

1994 ◽  
Vol 340 ◽  
Author(s):  
J. R. Kim ◽  
R. M. Park ◽  
K. S. Jones
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Lattice Mismatch ◽  
X Ray Diffraction ◽  
Thermal Expansion Behavior ◽  
Lattice Constants ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Lattice Matched

ABSTRACTThe thermal expansion behavior of ZnSe and ZnS0.03Se0.97 epilayers grown on GaAs has been investigated using high resolution X-ray diffraction at temperatures between room temperature and the growth temperature. The lattice parameters perpendicular and parallel to the surface were measured with the Bond's method. The lattice mismatch for a partially relaxed ZnSe layer was Δa(⊥)/a =2300 ppm and Δa(‖)/a = 2600 ppm at room temperature(R.T.) and Δa (⊥)/a =3600 ppm and Δa(‖)/a =2400 ppm at 250°C. For ZnS0.03Se0.97 which is almost lattice matched at R.T. to GaAs, Δa(⊥)/a =200 ppm, Δa(⊥)/a =20ppmatR.T. and Δa(⊥)/a =1400ppm, Δa(⊥)/a =50ppm at 250°C. The relaxed lattice constants were evaluated and the thermal expansion coefficients of relaxed ZnSe layers were found to vary from 7.8*10−6/°C at room temperature to 12.2*10−6/°C at 250°C and for ZnS0.03Se0.97 layers the variation was from 7.5*10−6/°C at R.T. to 11.7*10−6/°C at 250°C.

Effect of Water Sorption on Carbonate Rock Expansivity

1975 ◽  
Vol 12 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Peter P. Hudec ◽  
Nicholas Sitar
Keyword(s):  
Thermal Expansion ◽  
Water Sorption ◽  
Carbonate Rock ◽  
Room Temperature ◽  
Length Change ◽  
Thermal Coefficient ◽  
Saturated Rock ◽  
Thermal Expansion Coefficients ◽  
Isothermal Expansion ◽  
Expansion Coefficients

Length change experiments on carbonate rock samples indicate that the thermal coefficient of expansion (contraction) from normal room temperature to below freezing is a function of the sorptive characteristic of the rock. The highly adsorptive rocks, i.e. those adsorbing more than 40% of their water from near 100% humidity atmosphere, show an increased thermal contraction coefficient in the saturated state over their dry state. The low adsorptive rocks have the same thermal expansion coefficients either in a dry or saturated state.The highly adsorptive rocks expand isothermally upon saturation. The average isothermal expansion of a group of nine rocks was equivalent to the dry thermal expansion of a 78 °C temperature change. The low adsorptive rocks showed a small net isothermal contraction upon wetting.The results indicate that the thermal coefficients of expansion obtained below the 100 °C range must specify the saturation conditions of the rock, and may differ for dry and saturated rock. A mechanism of weathering of highly adsorptive rocks is suggested, based on isothermal expansion and contraction of these rocks in dry and saturated states respectively. If confined, as in concrete, such rocks may generate destructive expansive forces upon wetting.

Thermal expansion of cancrinite

1996 ◽  
Vol 60 (403) ◽  
pp. 949-956 ◽  
Author(s):  
Ishmael Hassan
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Expansion Mechanism ◽  
Expansion Coefficients ◽  
Cell Volumes

AbstractThermal expansion coefficients were measured for a cancrinite from Bancroft, Ontario, Canada. Measurements of cell parameters and unit-cell volumes were obtained at room temperature and at heating intervals of 50°C over the temperature range from 50 to 1400°C. The unit-cell parameters for cancrinite increase non-linearly with temperature up to 1200°C and shortly thereafter, the mineral melted. The c parameter increases more rapidly than the a parameter, and the c/a ratio increases linearly with temperature. A plausible thermal expansion mechanism for cancrinite, which is based on the framework expansion that occurs as a function of cavity content, is presented. In the thermal expansion of cancrinite, the short Na-H2O in the H2O-Na—H2O chain expands to form equal distances to the two H2O molecules in the chain. This causes the Na atoms to move towards the plane of the six-membered rings and forces the tetrahedra to rotate and the rings become more planar. The Na atoms then form bonds to all six (O1 and O2) oxygen atoms in a ring; the Na-O1 bonds become shorter and the Na-O2 bonds become longer. These effects cause an increase in both a and c, and thus an increase in the c/a ratio. A similar thermal expansion mechanism operates in the sodalite-group minerals where the six-membered rings and Na-Cl bond are involved.

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