Effects of Current Annealing on Thermal Conductivity of Carbon Nanotubes

This work documents the annealing effect on the thermal conductivity of nanotube film (CNTB) and carbon nanotube fiber (CNTF). The thermal properties of carbon nanotube samples are measured by using the transient electro-thermal (TET) technique, and the experimental phenomena are analyzed based on numerical simulation. During the current annealing treatment, CNTB1 always maintains the negative temperature coefficient of resistance (TCR), and its thermal diffusivity increases gradually. When the annealing current is 200 mA, it increases by 33.62%. However, with the increase of annealing current, the TCR of CNTB2 changes from positive to negative. The disparity between CNTB2 and CNTB1 suggests that they have different physical properties and even structures along their lengths. The high-level thermal diffusivity of CNTB2 and CNTF are 2.28–2.46 times and 1.65–3.85 times higher than the lower one. The results show that the decrease of the thermal diffusivity for CNTB2 and CNTF is mainly caused by enhanced Umklapp scattering, the high thermal resistance and torsional sliding during high temperature heating.

A Study of the Key Factors on Production of Graphene Materials from Fe-Lignin Nanocomposites through a Molecular Cracking and Welding (MCW) Method

In this work, few-layer graphene materials were produced from Fe-lignin nanocomposites through a molecular cracking and welding (MCW) method. MCW process is a low-cost, scalable technique to fabricate few-layer graphene materials. It involves preparing metal (M)-lignin nanocomposites from kraft lignin and a transition metal catalyst, pretreating the M-lignin composites, and forming of the graphene-encapsulated metal structures by catalytic graphitization the M-lignin composites. Then, these graphene-encapsulated metal structures are opened by the molecule cracking reagents. The graphene shells are peeled off the metal core and simultaneously welded and reconstructed to graphene materials under a selected welding reagent. The critical parameters, including heating temperature, heating time, and particle sizes of the Fe-lignin composites, have been explored to understand the graphene formation mechanism and to obtain the optimized process parameters to improve the yield and selectivity of graphene materials.

Capture of Pollutants from Exhaust Gases by Low-Temperature Heating Surfaces

One of the most effective methods towards improving the environmental safety of combustion engines is the application of specially prepared water-fuel emulsions (WFE). The application of WFE makes it possible to reduce primary sulfur fuel consumption and reveals the possibility of capturing the pollutants from exhaust gases by applying condensing low-temperature heating surfaces (LTHS). In order to realize such a double effect, it is necessary to investigate the pollution processes on condensing LTHS of exhaust gas boilers (EGB), especially the process of low-temperature condensing a sulfuric acid vapor from exhaust gases to investigate the influence of condensing LTHS on the intensity of pollutants captured from the exhaust gases. The aim of this research is to assess the influence of the intensity of pollutants captured from exhaust gases by condensing LTHS in dependence of water content in WFE combustion. Investigations were carried out at a special experimental setup. The processing of the results of the experimental studies was carried out using the computer universal statistical graphic system Statgraphics. Results have shown that in the presence of a condensing heating surface, the degree of capture (purification) of pollutants from the exhaust gas flow is up to 0.5–0.6.

Chili and Sweet Pepper Seed Oil Used as a Natural Antioxidant to Improve the Thermo-Oxidative Stability of Sunflower Oil

The main purpose of this work was to assess the potential of chili pepper seed oil (CPSO) and sweet pepper seed oil (SPSO) to inhibit or retard the thermo-oxidative processes undergoing in sunflower oil (SFO) when subjected to high-temperature heating for 4 and 8 h in simulated frying conditions. The effects of high-temperature treatment for 4 and 8 h on the fatty acid composition and the lipid oxidation degree of the investigated oil samples were evaluated using the peroxide value (PV), the p-anisidine value (p-AV) and the thiobarbituric acid test (TBA). All determinations were performed before and after sample heating in order to evaluate the changes in lipid oxidation as well as in the chemical composition. In all studied samples, both after 4 h and 8 h of high-temperature heating, there was an increase of the saturated fatty acid content. This increase is lower in the case of SFO samples supplemented with CPSO and SPSO when compared with SFO. A 41.67% increase was recorded for the SFO sample supplemented with 300 ppm CPSO, and a 36.76% increase was recorded for the SFO supplemented with 300 ppm SPSO, compared to the 44.97% increase recorded for the SFO. Heating the samples supplemented with CPSO and SPSO with a concentration of 300 ppm for 8 h led to the much lower values of the investigated parameters in relation to the control sample, as follows: PV (12.95 ± 0.17 meq/kg oil for SFO + 300 ppm CPSO and 13.45 ± 0.32 meq/kg oil for SFO + 300 ppm SPSO, compared with 16.4 + 0.17 meq/kg oil for SFO), p-AV (63.445 ± 1.259 ppm oil for SFO + 300 ppm CPSO and 64.122 ± 1.208 ppm oil for SFO + 300 ppm SPSO, compared with 72.493 + 1.340 ppm oil for SFO), CD (45%; 30%), TOTOX (88.374 for SFO + 300 ppm CPSO and 101.366 for SFO + 300 ppm SPSO compared with 105.347 ppm for SFO) and TBA (98.92 ± 2.49 µg MDA/g oil for SFO + 300 ppm CPSO and 114.24 ± 3.51 µg MDA/g oil for SFO + 300 ppm SPSO, compared with 180.08 + 5.82 µg MDA/g oil for SFO). Regarding the lipid oxidation process occurring during the heat treatment, we observed the reduction of lipid oxidation by the addition of CPSO and SPSO and recommend these seed oils as potential natural antioxidants in order to improve the oxidative stability of SFO during heat treatment.

Class 2 Heating Cycles: A New Class of Thermodynamic Cycles

Considering the significance of thermodynamic cycles in the global energy system, it is necessary to develop new general classes of thermodynamic cycles to relieve current energy and environmental problems. Inspired by the relationship between power cycles and refrigeration cycles, we realize that general classes of thermodynamic cycles should occur in pairs with opposite functions. Here we reverse class 1 heating cycles to obtain another new general class of thermodynamic cycles named class 2 heating cycles (HC-2s). HC-2s have two basic forms, and each contains six thermodynamic processes. HC-2s present the simplest and most general approach to utilizing the temperature difference between a medium-temperature heat source and a low-temperature heat sink to achieve efficient high-temperature heating. HC-2s fill the gaps that have existed since the origin of thermal science, and they will play significant roles in the global sustainable energy system.