X-Ray diffraction, thermal expansion, electrical conductivity, and optical microscopy studies of coal-based graphites

Graphene aerogels derived from graphene-oxide (GO) starting materials recently have been shown to exhibit a combination of high electrical conductivity, chemical stability, and low cost that has enabled a range of electrochemical applications. Standard synthesis protocols for manufacturing graphene aerogels require the use of sol-gel chemical reactions that are maintained at high temperatures for long periods of time ranging from 12 hours to several days. Here we report an ultrafast, acid-catalyzed sol-gel formation process in acetonitrile in which wet GO-loaded gels are realized within 2 hours at temperatures below 45°C. Spectroscopic and electrochemical analysis following supercritical drying and pyrolysis confirms the reduction of the GO in the aerogels to sp 2 carbon crystallites with no residual carbon-nitrogen bonds from the acetonitrile or its derivatives. This rapid synthesis M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 enhances the prospects for large-scale manufacturing of graphene aerogels for use in numerous applications including sorbents for environmental toxins, support materials for electrocatalysis, and high-performance electrodes for electrochemical capacitors and solar cells.

Section: Microstructural Analysis Of Pyrolyzed Aerogelsmentioning

confidence: 99%

Ultrafast sol–gel synthesis of graphene aerogel materials

Lim

Manandhar

et al. 2015

“…The conventional XRD patterns are the convolution of instrumental and microstructural effects that contribute to the line profile broadening. In order to analyse the diffraction line profile that is a direct result of the microstructural effects, a standard single crystal silicon sample was used to correct for instrumental broadening [29]. The microstructural effects responsible for the shape profile of the diffraction peaks (line broadening and shift) are the crystallite size distribution and the micro-strain within the crystallites introduced due to lattice defects.…”

Section: X-ray Diffractionmentioning

confidence: 99%

An understanding of lattice strain, defects and disorder in nuclear graphite

Krishna¹,

Wade²,

Jones³

et al. 2017

In this study, microstructural parameters, such as lattice dimension, micro-strain and dislocation density, of different neutron-irradiated graphite grades have been evaluated using the diffraction profiles of X-ray diffraction (XRD) and the scattering profiles of Raman spectroscopy. Using Gen-IV candidate graphite samples (grade PCEA, GrafTech), subjected to neutron irradiation at 900°C to 6.6 and 10.2 dpa, and graphite samples of similar grain size and microstructure taken from the core of the British Experimental Pile Zero reactor, which have been irradiated at 100-120 °C to 1.60 dpa, an investigation on the effect of irradiation dose and temperature on the aforementioned microstructural parameters is

“…This approach originated from an empirical line profile fitting procedure developed for non-graphitic, or disordered lamellar carbons [72][73][74]. As such it significantly underestimates domain sizes at high FWHM ratios as shown in Fig.…”

mentioning

confidence: 99%

Microstructure of natural graphite flakes revealed by oxidation: Limitations of XRD and Raman techniques for crystallinity estimates

Badenhorst

2014

The estimation of the active surface area (ASA) of various macrocrystalline graphitic materials is industrially valuable but the microstructures of these materials are still contestable. This in turn has led to difficulties in the unambiguous interpretation of crystallographic measurements with powder X-ray diffraction (pXRD) and Raman spectroscopy as well as their relationship to the ASA. To resolve this issue a systematic approach is required. As a starting point two widely accepted pXRD and Raman methodologies were utilized. Purified, oxidized, natural graphite flakes were extensively examined to elucidate the essential microstructural features. Based on this an illustrative model was formulated as grounds for interpreting the measured crystallite domain sizes. Only one of the crystallographic parameters could be linked to the observed microstructure. For macrocrystalline graphite both techniques are subject to instrumental limitations and should not be used. Due to the non-linearity of the correlations they are prone to measurement uncertainty and should not be used above acceptable limits. In addition, the current inability to distinguish between different defect types leads to ambiguous results. Despite being a single, interrelated 2 crystal the composite nature of the flakes will make it difficult to relate even an ideal, accurate domain size measurement to the ASA.