scholarly journals Mineralogical Transformations in Granitoids during Heating at Fire-Related Temperatures

2021 ◽  
Vol 12 (1) ◽  
pp. 188
Author(s):  
Patricia Vazquez ◽  
David Benavente ◽  
David Montiel ◽  
Miguel Gomez-Heras
Keyword(s):  
Thermal Expansion ◽  
High Temperatures ◽  
Temperature Increase ◽  
Structural Changes ◽  
Mechanical Damage ◽  
Structural Behaviour ◽  
Weathering Processes ◽  
Thermal Expansion Coefficients ◽  
Xrd Techniques ◽  
Mineral Transformations

Fire is a major decay agent of rocks and can generate immediate catastrophic effects as well as directional and anisotropic damage that affect long-term weathering processes. Temperature increase is the most relevant factor, among other components in a fire, generating mineral transformations and bulk mechanical damage. Mineralogical changes at high temperatures are key to understanding the overall mechanical behaviour. However, most studies to date were carried out after rock specimens were heated to a target temperature and cooled down to room temperature. Therefore, these studies are missing the observation of the actual mineral processes during heating. This paper aims to compare mineralogical changes in crystalline rocks during heating by means of XPS and different XRD techniques. Samples of four different granitoids were heated to several temperatures up to 1000 °C to evaluate their chemical and structural changes. Results show how standardised thermal expansion coefficients are not a suitable indicator of the bulk effect of high temperatures on rocks. Results also show how thermal expansion estimations from XRD lattice measurements may be an alternative to bulk dilatometric tests, as they can be performed with limited sampling, which may be necessary in some studies. Nevertheless, XRD and XPS results need to be interpreted carefully in relation to the bulk effects of temperature increase in the rocks, as the structural behaviour may seemingly contradict the macroscopic effect.

scholarly journals Temperature-dependent structural behaviour of samarium cobalt oxide

2017 ◽  
Vol 32 (S2) ◽  
pp. S38-S42
Author(s):  
Matthew R. Rowles ◽  
Cheng-Cheng Wang ◽  
Kongfa Chen ◽  
Na Li ◽  
Shuai He ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Cobalt Oxide ◽  
Sol Gel ◽  
Linear Thermal Expansion ◽  
Rietveld Analysis ◽  
Structural Behaviour ◽  
Temperature Dependent ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Sol Gel Synthesis

The crystal structure and thermal expansion of the perovskite samarium cobalt oxide (SmCoO3) have been determined over the temperature range 295–1245 K by Rietveld analysis of X-ray powder diffraction data. Polycrystalline samples were prepared by a sol–gel synthesis route followed by high-temperature calcination in air. SmCoO3 is orthorhombic (Pnma) at all temperatures and is isostructural with GdFeO3. The structure was refined as a distortion mode of a parent $ Pm{\bar 3}m $ structure. The thermal expansion was found to be non-linear and anisotropic, with maximum average linear thermal expansion coefficients of 34.0(3) × 10−6, 24.05(17) × 10−6, and 24.10(18) × 10−6 K−1 along the a-, b-, and c-axes, respectively, between 814 and 875 K.

The structural behaviour of tetrahedral framework compounds — a review Part II. Framework structures

1984 ◽  
Vol 48 (346) ◽  
pp. 65-79 ◽  
Author(s):  
D. Taylor
Keyword(s):  
Thermal Expansion ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Structural Changes ◽  
Structural Data ◽  
Structural Behaviour ◽  
Tetrahedral Framework ◽  
Cell Parameters ◽  
Silicon And Germanium ◽  
Framework Compounds

AbstractTetrahedral framework compounds, as defined in this paper, generally exist as tilted and distorted versions of ideal fully expanded structures at room temperature and atmospheric pressure. How pressure, temperature, and composition (P, T, and X) affect the tilting and distortion is critically reviewed. It is shown that although the effects of P, T, and X on the cell parameters are broadly analogous, the underlying structural changes are generally different. An important, and frequently neglected thermal effect is the apparent shortening of the framework bonds by the anisotropic thermal motion of the framework oxygens. Tilting models of framework compounds are critically examined and their failure to match the observed structural behaviour is attributed to changes in tetrahedral distortion. For quartz it appears that during compression the change in tetrahedral distortion is virtually all angular (O-Si-O angles), whereas during thermal expansion the change in distortion is in the Si-O distances. Such behaviour may typify the behaviour of many other framework compounds but the structural data needed to establish this are lacking. The review is illustrated by reference to the quartz and cristobalite analogues; to the sodalite, leucite, nepheline, scapolite, and feldspar families; and to the nitrides and oxynitrides of silicon and germanium. It is concluded that our understanding of the structural behaviour of framework compounds is still superficial and that much theoretical and experimental work remains to be done.

Thermal expansivities of water + tetrahydrofuran mixtures at 298.15 K

1978 ◽  
Vol 56 (22) ◽  
pp. 2803-2807 ◽  
Author(s):  
Osamu Kiyohara ◽  
Patrick J. D'Arcy ◽  
George C. Benson
Keyword(s):  
Thermal Expansion ◽  
Mole Fraction ◽  
Structural Changes ◽  
Molar Excess ◽  
Thermal Expansion Coefficients ◽  
Thermal Expansivities ◽  
Expansion Coefficients ◽  
Mole Fraction Range

Densities of water + tetrahydrofuran mixtures were measured at 5 K intervals of temperature from 288.15 to 308.15 K. Excess thermal expansion coefficients and partial molar excess thermal expansivities at 298.15 K over the whole mole fraction range were derived from the results. The significance of the expansivities is discussed in terms of the structural changes accompanying the formation of the mixture.

Exfoliated Graphite Formed by Intercalation

2003 ◽  
Author(s):  
Toshiaki Enoki ◽  
Morinobu Endo ◽  
Masatsugu Suzuki
Keyword(s):  
Thermal Expansion ◽  
Surface Area ◽  
High Temperatures ◽  
Structural Integrity ◽  
Liquid Metals ◽  
High Surface ◽  
High Surface Area ◽  
Intercalation Compound ◽  
Exfoliated Graphite ◽  
Thermal Expansion Coefficients

When a graphite intercalation compound (GIC) is heated, a thermal expansion, large (~3.5 × 10−5/K) compared with most materials, occurs along the c-axis, while the in-plane lattice constant remains almost unchanged. This anisotropic thermal expansion behavior is reversible and can be modeled in terms of a superposition of the c-axis thermal expansion coefficients of the constituent layers (Salamanca-Riba and Dresselhaus, 1986). However, when a GIC is heated above a specific critical temperature, a gigantic c-axis expansion can occur, with sample elongations (ΔLS/LS) of a factor of 300 (Inagaki et al., 1983). This extremely large elongation, also called “exfoliation,” is generally irreversible, and leads to a spongy, foamy, low-density, high-surface-area carbon material of about 85 m2/g (Thomy and Duval, 1969). This exfoliation effect alters the structural integrity of the GIC material and therefore is undesirable for structural applications of GICs. However, this spongy, foam-like material is advantageous for some applications, such as gas adsorption. The commercial version of the exfoliated wormy-like material is called vermicular graphite from its appearance, and is used for high-surface-area applications. Furthermore, when pressed into sheets, it is called grafoil and is widely used as a high-temperature gasket or packing material because of its flexibility, chemical inertness, low transverse thermal conductivity, and ability to withstand high temperatures. Grafoil-type products can also be used to contain molten corrosive liquid metals at high temperatures and to extinguish metal fires (Anderson and Chung, 1984). These products have been expected to be useful for oil adsorption (Toyoda et al., 1998a, 1998b, 1999). In this chapter, the preparation and conventional as well as advanced applications of exfoliated graphite with unique properties, obtained from QIC-based materials, is demonstrated.

scholarly journals Высокотемпературная теплоемкость и термическое расширение FeTa-=SUB=-2-=/SUB=-O-=SUB=-6-=/SUB=-

2019 ◽  
Vol 61 (10) ◽  
pp. 1985
Author(s):  
Р.И. Гуляева ◽  
С.А. Петрова ◽  
В.М. Чумарев ◽  
А.Н. Мансурова
Keyword(s):  
Thermal Expansion ◽  
Structural Changes ◽  
Ratio Method ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Cell Parameters ◽  
Thermal Expansion Coefficients ◽  
Thermal Analyzer ◽  
Phase Transition Temperatures ◽  
Temperature Dependences

The heat capacity of the synthesized FeTa2O6 iron tantalate was measured in the temperature range of 323-1103 K by the ratio method using a thermal analyzer with combined thermogravimetry and scanning calorimetry. The phase transition temperatures were determined. Structural changes and thermal expansion of the oxide in the range of 300-1173 K were studied by high-temperature X-ray diffraction. The temperature dependences of the unit cell parameters were approximated by third-degree polynomials. From the data obtained, the values of thermal expansion coefficients and anisotropy factors were calculated.

Thermal expansion anomalies at high temperatures near stoichiometric Zn4Sb3 composition

2007 ◽  
Vol 436 (1-2) ◽  
pp. 65-68 ◽  
Author(s):  
Go Nakamoto ◽  
Keisuke Kinoshita ◽  
Makio Kurisu
Keyword(s):  
Thermal Expansion ◽  
High Temperatures

Influence of Cr deficiency on sintering, thermal expansion and electrical properties of La0.75Sr0.25Cr1−xO3−δ as a SOFC interconnect material

2016 ◽  
Vol 30 (11) ◽  
pp. 1650127 ◽  
Author(s):  
Yi Ren ◽  
Wen Ma ◽  
Xiaoying Li ◽  
Jun Wang ◽  
Yu Bai ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Electrical Properties ◽  
Perovskite Phase ◽  
Ignition Process ◽  
Thermal Expansion Coefficients ◽  
Auto Ignition ◽  
Pure Perovskite Phase ◽  
Maximum Conductivity ◽  
Expansion Coefficients ◽  
Interconnect Material

The SOFC interconnect materials La[Formula: see text]Sr[Formula: see text]Cr[Formula: see text]O[Formula: see text] [Formula: see text]–[Formula: see text] were prepared using an auto-ignition process. The influences of Cr deficiency on their sintering, thermal expansion and electrical properties were investigated. All the samples were pure perovskite phase after sintering at 1400[Formula: see text]C for 4 h. The cell volume of La[Formula: see text]Sr[Formula: see text]Cr[Formula: see text]O[Formula: see text] decreased with increasing Cr deficient content. The relative density of the sintered bulk samples increased from 93.2% [Formula: see text] to a maximum value of 94.7% [Formula: see text] and then decreased to 87.7% [Formula: see text]. The thermal expansion coefficients of the sintered bulk samples were in the range of [Formula: see text]–[Formula: see text] (30–1000[Formula: see text]C), which are compatible with that of YSZ. Among the investigated samples, the sample with 0.02 Cr deficiency had a maximum conductivity of 40.4 Scm[Formula: see text] and the lowest Seebeck coefficient of 154.8 [Formula: see text]VK[Formula: see text] at 850[Formula: see text]C in pure He. The experimental results indicate that La[Formula: see text]Sr[Formula: see text]Cr[Formula: see text]O[Formula: see text] has the best properties and is much suitable for SOFC interconnect material application.

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