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Instruments / Technical Area	Publication Details	Published
I13-2-Diamond Manchester Imaging	Tracking the shape of nutshells during biochar production Meredith Rose Barr , Roberto Volpe Diamond Proposal Number(s): [21587] Show Abstract ▼ Abstract: A charcoal-like product known as ‘biochar’ can be produced from agricultural waste biomass such as nutshells. One conversion method is pyrolysis, a process that involves heating the waste in the absence of oxygen. During pyrolysis, changes in the size and shape (morphology) of particles increase the surface area of the biomass. This surface area controls how biochar binds to (adsorbs) pollutants, speeds up chemical reactions, and stores energy. A lack of understanding of how biomass morphology changes during biochar production makes it difficult to tailor biochar properties for specific applications. Facilities at the Diamond Manchester Imaging Branchline (I13-2) enabled a team of researchers to conduct rapid high-resolution X-ray imaging of biomass. This allowed real-time tracking of particle morphology and porosity during pyrolysis. The results showed that the morphology and porosity of different nutshells evolved differently during pyrolysis. However, these differences were less pronounced in biomass pre-soaked with an alkaline solution. Almond shells shrank more but gained less porosity than walnut shells, which have thicker- walled cells on average. The results suggest that the difference is related to how heat penetrates particles of biomass during pyrolysis. Porosity was found to accumulate towards the centre of particles during pyrolysis for the same reason. The ability to customise biochar morphology would benefit its many environmental applications. These include removing pollutants from air, water, and soil; speeding up chemical reactions; and even storing energy. Tracking the morphology of biomass during biochar production is the first step towards achieving this.	Jul 2021
B16-Test Beamline	In-situ synchrotron x-ray topography study on the stress relaxation process in 4h-sic homoepitaxial layers Jianqiu Guo , Tuerxun Ailihumaer , Hongyu Peng , Balaji Raghothamachar , Michael Dudley Ecs Transactions 86, 75 - 82 DOI: 10.1149/08612.0075ecst Diamond Proposal Number(s): [13464] Show Abstract ▼ Abstract: During 4H silicon carbide (4H-SiC) homoepitaxy and post-growth processes, the development of stress relaxation has been observed, in which interfacial dislocations (IDs) are formed at the epilayer/substrate interface, relaxing the misfit strain induced by the nitrogen doping concentration difference between the epilayer and substrate. It is widely believed that an interfacial dislocation is created by the glide of a mobile segment of a basal plane dislocation (BPD) in the substrate or epilayer towards the interface, leaving a trailing edge component right at the interface. However, direct observation of such mechanisms has not been made in SiC before. In this work, we present an in situ study of the stress relaxation process, in which a specimen cut from a commercial 4H-SiC homoepitaxial wafer undergoes the stress relaxation process during a high-temperature heat treatment while sequential synchrotron white beam X-ray topographs were recorded simultaneously. Based on the dynamic observation of this process, it can be concluded that thermal stress plays a role in the relaxation process while the increased misfit strain at elevated temperature most likely drives the formation of an interfacial dislocation.	Sep 2018
B16-Test Beamline	Direct observation of stress relaxation process in 4H-SiC homoepitaxial layers via in situ synchrotron x-ray topography Jian Qiu Guo , Yu Yang , Balaji Raghothamachar , Michael Dudley , Swetlana Weit , Andreas N. Danilewsky , Patrick J. Mcnally , Brian K. Tanner Materials Science Forum 924, 176 - 179 DOI: 10.4028/www.scientific.net/MSF.924.176 Diamond Proposal Number(s): [13464] Show Abstract ▼ Abstract: During 4H silicon carbide (4H-SiC) homoepitaxy and post-growth processes, the development of stress relaxation has been observed, in which interfacial dislocations (IDs) are formed at the epilayer/substrate interface, relaxing the misfit strain induced by the nitrogen doping concentration difference between the epilayer and substrate. It is widely believed that an interfacial dislocation is created by the glide of a mobile segment of a basal plane dislocation (BPD) in the substrate or epilayer towards the interface, leaving a trailing edge component right at the interface. However, direct observation of such mechanisms has not been made in SiC before. In this work, we present an in situ study of the stress relaxation process, in which a specimen cut from a commercial 4H-SiC homoepitaxial wafer undergoes the stress relaxation process during a high-temperature heat treatment while sequential synchrotron white beam X-ray topographs were recorded simultaneously. Based on the dynamic observation of this process, it can be concluded that thermal stress plays a role in the relaxation process while the increased misfit strain at elevated temperature most likely drives the formation of an interfacial dislocation.	Jun 2018
B16-Test Beamline	In situ synchrotron x-ray topography observation of double-ended Yu Yang , Jian Qiu Guo , Balaji Raghothamachar , Michael Dudley , Swetlana Weit , Andreas N. Danilewsky , Patrick J. Mcnally , Brian K. Tanner Materials Science Forum 924, 172 - 175 DOI: 10.4028/www.scientific.net/MSF.924.172 Diamond Proposal Number(s): [13464] Show Abstract ▼ Abstract: We present in-situ observations of the dynamical operation of multiple double-ended Frank-Read dislocation sources in a PVT-grown 4H-SiC wafer under thermal gradient stresses. The nucleation of these sources is facilitated by a specific configuration consisting of one basal plane dislocation (BPD) segment pinned by two threading edge dislocations (TEDs). This configuration is formed during PVT crystal growth by deflection of TEDs on to the basal planes by macrosteps and re-deflection of resulting BPDs back into TEDs. Under the influence of thermal gradient stresses induced by heating inside a double ellipsoidal mirror furnace, the pinned BPD segment glides and activates dislocation multiplication by the double Frank-Read source mechanism. A more intricate mechanism of swapping of TED pinning points between Frank-Read sources lying on the same basal plane is identified, enabling one dislocation loop to effectively “pass through” the other dislocations on the same basal plane.	Jun 2018
I12-JEEP: Joint Engineering, Environmental and Processing	Characterisation of vapour grown CdZnTe crystals using synchrotron X-ray topography Christopher K. Egan , Ashutosh Choubey , Moreton Moore , Robert J. Cernik Journal Of Crystal Growth 343 (1), 1-6 DOI: 10.1016/j.jcrysgro.2012.01.003 Diamond Proposal Number(s): [2933] Show Abstract ▼ Abstract: Synchrotron white beam X-ray topography has been used to characterise bulk crystal defects of thick vapour grown CdZnTe crystals. Whole 50 mm diameter wafers with thicknesses in the range of 2–3 mm were sliced from boules grown by the multi-tube physical vapour transport method and analysed by diffraction topography in a transmission geometry. A variety of defects were observed including cracks, voids and grain boundaries. The largest quantity of defects observed were sub-grains appearing as localised increased intensity in the topographs. The periphery of the wafers showed the highest number of defects, whereas central regions where largely defect-free. We failed to observe any inclusions or precipitates within these crystals. Surface damage from wire-saw cutting was also observed on poorly processed wafers; these defects were otherwise invisible to standard characterisation methods. X-ray topography has proven to be a useful tool for non-destructively investigating bulk extended defects in CdZnTe crystals for radiation detector applications.	Jan 2012

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