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Vohler, O.; Sturm, Ferdinand von; Wege, Erhard; Frohs, Wilhelm

doi:10.1002/9783527674046.ch5

Cited by 6 publications

(6 citation statements)

References 16 publications

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“…The morphology is quite different to that of the more rounded EG produced by Tian et al, characterized by V-type open or semi-open interconnected pores on the surface, whose pore sizes range from dozens of microns to hundreds of microns, even if the granular dimension is comparable [52]. The skeleton density evaluated with helium pycnometer was 2.268 ± 0.004 g/cm 3 , in accordance with graphite theoretical density (2.26 g/cm 3 ) [43].…”

Section: Sem Observations Of Eg Before Impregnationsupporting

confidence: 74%

“…For each sample, 30 measurements were performed using a testing chamber of 1 cm 3 . The theoretical density (ρth) was evaluated by considering the weight fractions of the phases as well as the phase density, the PA-SA measured density and a reference value of 2.26 g/cm 3 for graphite [43].…”

Section: Sample Preparationmentioning

confidence: 99%

“…The apparent density (ρ app ) measurements of the neat PA-SA and impregnated powdery mixtures were conducted using an AccuPycII 1330 helium pycnometer (Micrometrics Instrument Corporation, Norcross, GA, USA) operating at a temperature of 23 • C. For each sample, 30 measurements were performed using a testing chamber of 1 cm 3 . The theoretical density (ρ th ) was evaluated by considering the weight fractions of the phases as well as the phase density, the PA-SA measured density and a reference value of 2.26 g/cm 3 for graphite [43].…”

Section: Sample Preparationmentioning

confidence: 99%

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Expanded Graphite (EG) Stabilization of Stearic and Palmitic Acid Mixture for Thermal Management of Photovoltaic Cells

Sacchet,

Valentini,

Benin

et al. 2024

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In this work, passive cooling systems for the revamping of existent silicon photovoltaic (PV) cells were developed and analysed in order to mitigate the efficiency loss caused by temperature rise in the hot season. For this purpose, expanded graphite (EG) was used to stabilize a phase change material (PCM) with a melting temperature close to 53 °C in order to realize thermal management systems (TMSs) able to store heat at constant temperature during melting and releasing it in crystallization. In particular, stearic and palmitic acid mixture (PA-SA) was shape-stabilized in EG at different concentrations (10, 12 and 14 part per hundred ratio) under vacuum into a rotary evaporation apparatus followed by cold compaction; PA-SA leakage was reduced due to its intercalation between the graphite lamellae, and the thermal conductivity necessary to maximize the heat transfer to a bulk TMS was improved via powder cold compaction, which minimizes voids and creates preferential thermal conductive patterns. The composite materials, stable till 150 °C, were tested by differential scanning calorimetry (DSC) at 1 °C/min to precisely determine the phase transition temperatures and the enthalpic content, which was only slightly reduced from 196 J/g of the neat PCM to 169 J/g due to the very low EG fraction necessary for the stabilization. Despite only the 14:100 EG-to-PA-SA ratio, the system’s thermal conductivity was enhanced 40 times with respect to the neat PCM (from 0.2 to 8.3 W/(m K), value never reached in works present in the literature), with a good convergence of the values evaluated through hot disk tests and laser flash analysis (LFA), finding correlation with both graphitic content and density. In order to completely avoid leaking with the consequent dispersion of PCM in the environment during the final application, all the samples were encapsulated in a PE-made film. The mechanical properties were evaluated with compression tests at 30 °C and 80 °C simulating a possible compressive stress deriving from the contact needed to maintain the TMS position on the rear of the PV cells. Finally, the material response was simulated by imposing thermal cycles into a climatic chamber and reproducing the three hottest and coldest days of summer 2022 of two Italian locations, Verona (Veneto, 45° N, 11° E) and Gela (Sicily, 37° N, 14° E), thus highlighting the thermal management effects with delays in temperature increase and daily peak temperature smoothing. The role of EG is strategic for the processing and the properties of the resulting composites in order to realize a proper compromise between the melting enthalpy of PCM and the thermal conductivity enhancement given by EG.

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Section: Sem Observations Of Eg Before Impregnationsupporting

confidence: 74%

Section: Sample Preparationmentioning

confidence: 99%

Section: Sample Preparationmentioning

confidence: 99%

See 1 more Smart Citation

Expanded Graphite (EG) Stabilization of Stearic and Palmitic Acid Mixture for Thermal Management of Photovoltaic Cells

Sacchet,

Valentini,

Benin

et al. 2024

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“…Varieties of NGC differ significantly in such aggregate and nanoglobule sizes. 30,49 For instance, furnace NGCs consist of tens to hundreds of small nanoglobules (10–80 nm) arranged in branched aggregates, possessing a somewhat developed interglobular space teeming with “dead zones”. Supported metal NPs could be obscured from larger adsorbate or reactant molecules.…”

Section: Origins Of “Dead” Metal In M/c Catalysts and Methods Of Its ...mentioning

confidence: 99%

“…For NGC, thermal types (thermal blacks) composed of large, weakly aggregated, or completely nonaggregated nanoglobules are a better choice. 30,49 Palladium catalysts supported on thermal NGC (0.5–2 wt% Pd) display a higher fraction of accessible palladium ( i.e. , Pd dispersion) and exhibit increased activity (in terms of TOF and substrate conversion) in the liquid-phase hydrogenation of furfural and ethyl 4-nitrobenzoate compared to similar palladium catalysts prepared with furnace-type NGC.…”

Section: Origins Of “Dead” Metal In M/c Catalysts and Methods Of Its ...mentioning

confidence: 99%

The phenomenon of “dead” metal in heterogeneous catalysis: opportunities for increasing the efficiency of carbon-supported metal catalysts

Mironenko,

Eremin,

Ananikov

2023

Chem. Sci.

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Insights into the influence of functional groups on the properties of graphene from first‐principles calculations

Liang

Gao

Wang

et al. 2022

J of Physical Organic Chem

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Carbon dots (CDs) are a kind of popular carbon nanomaterials with many functional groups that can be used in catalysis. However, in terms of calculation and simulation, most researchers choose to simplify CDs to pure graphene (GR) or graphene doped with nitrogen, boron, oxygen, and other elements due to the complexity of the calculation. In this study, the effects of adsorption of some functional groups (carboxyl, amino, and hydroxyl) on the properties of graphene have been investigated through first-principles calculations. The calculated results suggest that the adsorbed carboxyl group on graphene is relatively unstable, while the amino and hydroxyl groups can form covalent bonds with carbon atoms on the graphene and capture some electrons. When the bifunctional groups are adsorbed on the para or ortho position, it is beneficial for enhancing their stability on the graphene. However, when the bi-functional groups are adsorbed on the meta position, it will reduce the stability of the functionalized graphene. This research is beneficial for evaluating the specific functional groups on the surface of CDs, and it has particular significance for the simulation and modeling of CDs.

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Graphite*

Cited by 6 publications

References 16 publications

Expanded Graphite (EG) Stabilization of Stearic and Palmitic Acid Mixture for Thermal Management of Photovoltaic Cells

Expanded Graphite (EG) Stabilization of Stearic and Palmitic Acid Mixture for Thermal Management of Photovoltaic Cells

The phenomenon of “dead” metal in heterogeneous catalysis: opportunities for increasing the efficiency of carbon-supported metal catalysts

Insights into the influence of functional groups on the properties of graphene from first‐principles calculations

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