Thermal transport properties of graphene aerogel as an advanced carrier for enhanced energy storage.

Leveraging graphene aerogels as carriers offers innovative avenues for achieving enhanced energy density, thermal conductivity, and stability in energy storage materials due to their unique attributes. This study investigates the thermal transport properties of composite sulfur cathode materials and phase change materials based on graphene aerogels using molecular dynamics simulation. A graphene aerogel model is established, and the effects of sulfur and octadecane content on the thermal transport properties of graphene aerogels and graphene aerogel-based composites are examined. A theoretical model of heat transport is developed to analyze the contribution of fillers and graphene aerogels to the thermal conductivity of the composites. The results show that the theoretical analytical model shows strong agreement with the molecular dynamics results, especially at high filler content. This research provides valuable theoretical guidance for understanding the thermal transport properties of graphene aerogel-based composite sulfur cathode materials and phase change materials.

Modulation of the thermal conductivity, interlayer thermal resistance, and interfacial thermal conductance of C2N.

C2N, a novel 2D semiconductor with orderly distributed holes and nitrogen atoms, has attracted significant attention due to its possible practical applications. This paper investigates the in-plane thermal conductivity and interlayer thermal resistance of C2N and the interfacial thermal conductance of in-plane heterostructures assembled by C2N and carbonized C2N(C-C2N) using molecular dynamics simulations. The in-plane thermal conductivities of C2N monolayers along zigzag and armchair directions are 73.2 and 77.3 W m-1 K-1, respectively, and can be effectively manipulated by point defects, chemical doping, and strain engineering. Remarkably, nitrogen vacancies have a more substantial impact on reducing the thermal conductivity than carbon vacancies because of the more pronounced suppression of the high-frequency peaks. The difference in doping sites leads to a change in phonon mode localization. When the C2N size is small, as the tensile strain increases, ki is affected by dimensional lengthening due to stretching in addition to tensile strain. The interlayer thermal resistance decreases with increasing layer number and interlayer coupling strength. The AA stacking gives rise to a lower thermal resistance than the AB stacking when the heat flow passes through the multilayer due to the weaker in-plane bonding strength. Moreover, various possible atomic structures of C2N/C-C2N in-plane heterojunctions and the effect of carbon and nitrogen vacancies on interfacial thermal conductance are explored. The results provide valuable insights into the thermal transport properties in the application of C2N-based electronic devices.

Advanced oxidation of hypophosphite and phosphite using a UV/H2O2 process.

The oxidation of hypophosphite and phosphite in an aqueous solution by an ultraviolet (UV)/H2O2 process was studied in this work. The reactions were performed in a lab-scale batch photoreactor. The effect of different parameters such as H2O2 dosage, H2O2 feeding mode and the initial pH of the solution on the oxidation efficiency of the process was investigated. The results indicated that the UV/H2O2 process could effectively oxidize hypophosphite and phosphite in both synthesized and real wastewater. However, neither H2O2 nor UV alone was able to appreciably oxidize the hypophosphite or phosphite. The best way of feeding H2O2 was found to be 'continuous feeding', which maximized the reaction rate. It was also found that the process presented a wide range of applicable initial pH (5-11). When treating real rinse-wastewater, which was obtained from the electroless nickel plating industry, both hypophosphite and phosphite were completely oxidized within 60 min, and by extending by another 30 min, over 90% of the chemical oxygen demand removal was obtained. Without any additional catalyst, the UV/H2O2 process can oxidize hypophosphite and phosphite to easily removable phosphate. It is really a powerful and environmentally friendly treatment method for the wastewater containing hypophosphite and phosphite.

Thermal Transport Properties of Sulfur-Loaded Carbon-Based Nanotubes and Composite Sulfur Cathodes in Lithium-Sulfur Batteries.

The thermal management of lithium-sulfur batteries with high specific energy has become one of the critical issues for their applications. Carbon-based nanotubes are widely used to construct composite sulfur cathodes. This paper focuses on the thermal transport properties of sulfur-coated and sulfur-embedded boron carbide nanotubes (BCNTs) and carbon nanotubes (CNTs) and their composites using molecular dynamics. It is found that phonon softening and localization play a role in making BCNT exhibit a lower thermal conductivity (TC) than CNT. Furthermore, it is discovered that the sulfur embedded inside the carbon-based nanotube has a greater negative impact on carbon-based nanotube phonon transport. Moreover, the effective medium theory model is not suitable for predicting the effective thermal conductivity of coated sulfur composites, in contrast to its good applicability to embedded sulfur composites. These findings provide an in-depth understanding of the thermal transport properties of composite sulfur cathodes in lithium-sulfur batteries.

State functions/quantities in thermodynamics and heat transfer.

In thermodynamics, it is essential to distinguish between state functions and process functions. The reason is that the simple compressible thermodynamic system is a bivariate-process system, and the change of internal energy, a state function, corresponds to two process functions, heat and work. Among the state functions in thermodynamics, entropy is a special one because it has to be defined through a process function, exchanged heat δ Q , and a unique factor of integration, 1/T. In heat transfer, it is shown that Fourier's law and the differential equation of heat conduction are both relations of state quantities alone, and process quantities appear when an integration with respect to time is applied. Moreover, an incompressible heat conduction medium element without conversion between heat and work is a univariate-process system governed by a single variable, temperature. In this case, the change of the thermal energy ("heat content") stored in the system, a state quantity as a function of T alone, corresponds to only one process quantity, the transferred heat. Therefore, on the one hand, it is unnecessary to strictly distinguish between state quantities and process quantities in heat transfer, and on the other hand, there is no need to use a factor of integration to prove entransy a state quantity in heat transfer. Thermodynamics and heat transfer are two parallel sub-disciplines in thermal science. It is incorrect to deny entransy as a state quantity in heat transfer by the uniqueness of the factor of integration for entropy in thermodynamics, and entransy has significant physical meaning in the analysis and optimization of heat transfer processes.

[Experimental studies on biocompatibility of heterogeneous demineralized bone matrix particles].

OBJECTIVE: To evaluate the biocompatibility of manufactured heterogeneous demineralized bone matrix (DBM) particles and to provide basis for further experimental study and clinical application. METHODS: Heterogeneous DBM particles A (decreased and demineralized) and B (decreased, demineralized and acellular), particle size from 250 to 810 microm, and leaching liquor were made with a series of physical and chemical methods from pig limbs cortical bone. The residual calcium and phosphorus contents of bone particles were measured after decreased and demineralized. The acute toxicity test, skin stimulating test, pyrogeneous test, hemolysis test, cellular toxicity test and muscular embedded test were carried out according standard toxicological method. RESULTS: The contents of calcium and phosphorus in cortical bone were (189.09 +/- 3.12) mg/g and (124.73 +/- 2.87) mg/g, and in demineralized bone matrix particles were (3.48 +/- 0.09) mg/g and (3.46 +/- 0.07) mg/g. The residual calcium content was 1.87%, of phosphorus was 2.69%. The activity of mice was normal in the acute toxicity test. No animal died and no toxicity symptom or adverse effects were shown within 7 days. The mean weight daily increased showed no statistically significant difference (P > 0.05) between two groups after 7 days. Skin stimulating reactions were not found in the two experimental groups and negative control group by intradermal stimulation test. The maximal increase of body temperature in two experimental groups were 0.4 degree C, which meet the national standard (< 0.6 degree C). The rate of haemolysis to the leaching liquor was 1.14% (A) and 0.93% (B), which was lower than the national standard (< 5%). The cell proliferation rates of two experimental groups when compared with control group showed no statistically significant difference (P > 0.05). The toxicity of DBM particles leaching liquor was graded from 0 to 1, which means the material has no cytotoxicity. All the animals survived well. There was no tissue necrosis, effusion or inflammation at all implantation sites. For the index of HE and Masson staining, there were no effusion around the material and inflammatory cell infiltrate obviously in two experimental groups. Inflammatory cell infiltrate is slight in control group 2 weeks postoperatively. The inflammatory cell infiltration was mitigate gradually over time in two experimental groups after 4, 8 and 12 weeks. New bone and collagen fibers formation were observed when the material was degraded and absorbed. Score evaluation of local cellular immune response at different time after operation of two experimental groups showed no statistically significant difference (P > 0.05). CONCLUSION: Heterogeneous DBM has no obvious toxicity, skin irritation, pyrogenicity, and no cytotoxicity with a rate of haemolysis < 5%, so it has good biocompatibility and partial osteoinductive.

[An experimental study on SIS in reconstruction of tracheal defect in rabbits].

OBJECTIVE: To investigate the feasibility of polypropylene mesh (PPM) coated with SIS to reconstruct tracheal defect and the efficiency of SIS in improving epithelialization of the reconstructed trachea and reducing the postoperative complications. METHODS: Twelve New Zealand white rabbits were chosen and divided randomly into 2 groups: PPM reconstruction group (n=6) and SIS-PPM reconstruction group (n=6). A tracheal full defect with a size of 1.2 cm x 0.6 cm was created. A PPM coated with SIS of 1.4 cm x 0.8 cm was inserted to the defect in SIS-PPM reconstruction group, pure PPM of 1.4 cm x 0.8 cm in PPM reconstruction group. Complications such as death, local inflammation, tracheal stenosis and subcutaneous emphysema were documented. After 4, 8 and 12 weeks, tracheal histological examination and SEM examination were performed. RESULTS: In SIS-PPM reconstruction group, all animals survived at the end of the experiment, no infection, subcutaneous emphysema and breathing difficulties occurred. In PPM reconstruction group, there was 2 deaths because of infection of lumina and suffocation after 6 and 18 days of implantation; all rabbits had local subcutaneous emphysema. The histological examination showed that there was no obvious granulation tissue and scar in two groups and that the mucous membrane and cilia grew more normally in SIS-PPM reconstruction group than in PPM reconstruction group. SEM observation: At 8 weeks after implantation, most of the reconstructed area of the trachea in SIS-PPM reconstruction group was covered by relatively mature cilia; the corresponding area in PPM reconstruction group was covered by the naive cilia. At 12 weeks after implantation, the cilia in SIS-PPM reconstruction group grew orderly without obvious secretion adherence; while the cilia in PPM reconstruction group grew in a disorderly manner and were attached by an abundance of secretion. CONCLUSION: Good epithelial regeneration can be achieved after repair of tracheal defect using PPM coated with SIS. SIS can promote regeneration of ciliated epithelium, decrease postoperative complications, such as subcutaneous emphysema. It may be a prospective biomaterial for circumferential tracheal defect reconstruction clinically.