Graphite thermal expansion relationship for different temperature ranges

Tsang, D.K.L.; Marsden, Barry; Fok, S L; Hall, Graham

doi:10.1016/j.carbon.2005.06.009

Cited by 177 publications

(98 citation statements)

References 6 publications

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“…Averaging techniques have also been used to devise methodologies which are used to predict the change in CTE as a function of temperature. 53,54 It has also been observed that under load the CTE of graphite changes significantly, from ∼4 × 10…”

Section: Averaging Methodsmentioning

confidence: 97%

Dimensional change, irradiation creep and thermal/mechanical property changes in nuclear graphite

Marsden

Haverty

Bodel

et al. 2016

International Materials Reviews

106

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Since the start of the 'nuclear age' graphite has been employed as a moderator in around 100 nuclear reactors, and today there are still some 30 graphite-moderated reactors operating and there are plans for new Generation IV high-temperature reactors. Many of the graphite moderator reactors now producing power are operating beyond their original design life. Therefore in some cases, to aid the reactor operators and designers, the existing graphite irradiation databases need to be extended either to a higher temperature or higher neutron fluence. Furthermore, data are needed for the different grades of graphite that are available at present. This can either be achieved by expensive, time consuming irradiation programmes or by improving the understanding of the mechanisms and processes which lead to irradiationinduced dimensional and property changes in the graphite core components. This review looks at three of the most important graphite properties which change with exposure to irradiation, namely dimensional change, irradiation creep and thermal expansion. The behaviour of UK AGR, Magnox and an experimental grade of German reactor graphite are explored in some detail. First graphite reactor core design is briefly discussed, giving examples of typical graphite components and core arrangements. Issues related to aging graphite component and core behaviour are illustrated through examples of component internal and thermal stress generation, and issues related to whole core behaviour are also outlined. Second the manufacture and microstructure of different nuclear graphite grades are discussed, highlighting how the choice of raw materials and manufacturing technique influences the graphite properties. Third the coefficient of thermal expansion, dimensional change and irradiation creep are analysed using microstructural and averaging methods which are used to relate crystal to bulk properties by accounting for graphite crystal orientation and porosity. These techniques, which were first applied to nuclear graphite in the 1960s, are extended and discussed with the aim of trying to lend some understanding to the role the microstructural crystallite and porosity distributions play in defining the dimensional stability and properties of virgin graphite, irradiated graphite and stressed graphite.

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Section: Averaging Methodsmentioning

confidence: 97%

Dimensional change, irradiation creep and thermal/mechanical property changes in nuclear graphite

Marsden

Haverty

Bodel

et al. 2016

International Materials Reviews

106

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“…15 It is well known that the origin of thermal expansion is anharmonic atomic lattice interactions, where the average interatomic distances increase as higher vibrational energy levels become available and are occupied. Therefore, crystal structure can greatly affect the TEC, for example, diamond is a positive TEC material, 16 graphite exhibits negative in-plane but positive out-of-plane TECs, 17 and from experiment and theoretical predictions, graphene is recognized as having a negative TEC over a wide range of temperatures. [18][19][20][21][22][23] Other 2D materials such as monolayer hexagonal boron nitride are also predicted to exhibit a negative TEC.…”

mentioning

confidence: 99%

Probing thermal expansion coefficients of monolayers using surface enhanced Raman scattering

Zhang

Yang

et al. 2016

RSC Adv.

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Monolayer transition metal dichalcogenides exhibit remarkable electronic and optical properties, making them candidates for application within flexible nano-optoelectronics, however direct experimental determination of their thermal expansion coefficients (TECs) is difficult. Here, we propose a non-destructive method to probe the TECs of monolayer materials using surface-enhanced Raman spectroscopy (SERS). A strongly coupled Ag nanoparticle over-layer is used to controllably introduce temperature dependent strain in monolayers.Changes in the first-order temperature coefficient of the Raman shift, produced by TEC mismatch, can be used to estimate relative expansion coefficient of the monolayer. As a demonstration, the linear TEC of monolayer WS 2 is probed and is found to be 10.3 Â 10 À6 K À1, which would appear support theoretical predictions of a small TEC. This method opens a route to probe and control the TECs of monolayer materials.Two dimensional (2D) materials, such as transition metal dichalcogenides (TMDs), have attracted much attention due to their outstanding electronic and optical attributes. 1-10 For integration with existing semiconductor technology 2D TMDs have a natural advantage over graphene, in that they typically possess an energy bandgap, and yet can display high carrier mobilities. The bandgaps of TMDs are thickness dependent, typically displaying a transition from an indirect to directbandgap when the thickness is reduced to a monolayer. 2,3,11,12 However, a key physical consideration for the application of 2D materials is their thermal expansion coefficient (TEC), which relates changes in dimension to temperature. While many of the optical and electronic properties of TMDs have been well characterized, the thermal properties of many 2D materials remain less explored due to the difficulties associated with experimental measurements. Most materials exhibit positive thermal expansion, expanding when heated and contracting when cooled. However some materials do exhibit negative thermal expansion, and an interesting few exhibit very low (less than 2 Â 10 À6 K À1 ) or zero thermal expansion within specic temperature ranges. 13 A small TEC is highly desirable for applications where there is little tolerance for dimensional change or for systems that experience rapid temperature variations but require consistency, such as for nano-electromechanical devices 14 or nanosensors.15 It is well known that the origin of thermal expansion is anharmonic atomic lattice interactions, where the average interatomic distances increase as higher vibrational energy levels become available and are occupied. Therefore, crystal structure can greatly affect the TEC, for example, diamond is a positive TEC material, 16 graphite exhibits negative in-plane but positive out-of-plane TECs, 17 and from experiment and theoretical predictions, graphene is recognized as having a negative TEC over a wide range of temperatures.18-23 Other 2D materials such as monolayer hexagonal boron nitride are also predicted to exhibit a nega...

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“…In order to estimate the influence of strain we assume that graphene is free of stress at the formation temperature. With the thermal expansion coefficient of SiC [30] we calculate a relative reduction of the lattice constant of over the same temperature range [31]. Since the SiC substrate is much thicker than the graphene monolayer the ensuing strain will be taken up entirely by the graphene overlayer if no relaxation takes place during cool down.…”

Section: Discussionmentioning

confidence: 99%

Characterization of defects in silicon carbide by Raman spectroscopy

Hundhausen

Püsche

Röhrl

et al. 2008

Physica Status Solidi (b)

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1 Introduction In this contribution we review the application of Raman spectroscopy for the material characterization of SiC. Raman spectroscopy as an optical method is well suited as a non-contact analysis tool that requires little or no sample preparation. When employed in the form of micro Raman spectroscopy with a spatial resolution of 1-2 µm mapping of structural and electronic properties of SiC wafers by Raman spectroscopy is feasible.Here we present three exemplary case studies. (i) The detection and quantification of polytype inclusions during the growth of cubic 3C-SiC; (ii) the assessment of the electronic levels of N and P co-doped 6H-, 4H-, and 15R-SiC; and (iii) the analysis of layer thicknesses and strain in few layer graphene grown on the Si-face of 6H-SiC. Whereas (i) and (iii) rely on the ability of Raman spectroscopy to measure phonon frequencies with high precision, case (ii) utilizes Raman scattering by electronic excitations, a mode of Raman scattering that is not as widely used as scattering by phonons but equally useful as we shall show.

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Graphite thermal expansion relationship for different temperature ranges

Cited by 177 publications

References 6 publications

Dimensional change, irradiation creep and thermal/mechanical property changes in nuclear graphite

Dimensional change, irradiation creep and thermal/mechanical property changes in nuclear graphite

Probing thermal expansion coefficients of monolayers using surface enhanced Raman scattering

Characterization of defects in silicon carbide by Raman spectroscopy

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