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Silver nanowire (AgNW) has excellent thermal conductivity, which is an ideal material for fabricating flexible electrical heating materials. However, the poor stability of AgNWs is far from meeting the requirements for the practical application of electrical heating materials. Herein, by imitating the layered structure of nacre, the reduced graphene oxide (rGO)/AgNWs paper with a nacre-like structure was successfully prepared using a simple gravity-induced deposition approach. The obtained rGO/AgNWs paper showed excellent electrical conductivity (19.61 Ω/sq) and good pattern adjustability at the rGO to AgNWs ratio of 1:1. More importantly, the rGO/AgNWs paper exhibited high resistance to oxygen and water vapor, thus realizing long-term stability and reliability. Moreover, the design of a nacre-like structure could improve the thermal management performances of rGO/AgNWs paper, making it achieve a high Joule heating temperature (∼215.83°C) at low supplied voltages (3 V), the rapid response time (∼12 s) and long-term heating stability. These results indicate that the prepared rGO/AgNWs paper promises to be an electrical heating component with high chemical stability for thermal management electric materials.

In this study, numerical simulation of flow and heat transfer of S-CO2 (supercritical CO2) in the inclined upward and downward smooth tubes with an inner diameter of 10 mm and a heating length of 2000 mm at an inclination angle of 45° were conducted. The SST k - ω low Reynolds number turbulence model was used, and the accuracy of the calculation model was verified by the experimental data of S-CO2 flowing upward in the vertical smooth tube. The variation characteristics of the axial and circumferential inner wall temperature T w,i and the convective heat transfer coefficient h were analyzed. The S-CO2 would undergo the phase change from a liquid-like to the vapor-like at the pseudocritical temperature T pc by assuming supercritical pseudo-boiling. Based on this assumption, the reasons for a difference in the wall temperature distribution at the top generatrix during S-CO2 flowing in different directions were studied. By the detailed analysis of the velocity distribution, thermophysical properties distribution, including specific heat capacity at constant pressure cp and thermal conductivity λ , and the turbulent kinetic energy k distribution in the cross-sections of the inclined circular tube, the heat transfer mechanism related to the wall temperature difference at upward and downward was studied. The results showed that the thickness of vapor-like film, axial velocity u , turbulent kinetic energy k , and the thickness of viscosity sub-layer δ y +=5 were the main factors affecting the difference in the wall temperature distribution at the top generatrix in different flow directions.

Biodegradable copolymer-based composites produced from straw fiber (SF) with hydrolyzed soybean protein isolate/urea/formaldehyde (HSPI/U/F) copolymer-based adhesive for biocomposite flowerpots (BFP) application was presented in this work, and molecular structure, morphology, biodegradability and microbial population of the resulting materials were also investigated. FTIR and SEM results indicated that the copolymer resin have been successfully prepared. The prepared BFP showed good biodegradation, and the introduction of HSPI increased the degradation rate of BFP, which was nearly 50% at 24 months. After 30 days of controlled composting, the CO2 release accumulation of BFP could reach 24 g. During the process of BFP degradation, the number of bacteria and fungi on the surface was higher than that of actinomyces, indicating the bacteria and fungi selectively accumulated on the BFP composites surface to accelerate its degradation. At the same time, nitrate ion could also be formed by nitrobacteria, which promoted plant growth. There is no doubt that the obtained biodegradable copolymer possessed great potential for BFP application.

As a kind of fossil energy, coal plays an important role in global energy structure. In China, coal fired power plants provide more than 60% of the total electricity supply. Compared to the water-steam Rankine cycle, the supercritical carbon dioxide (S-CO2) Brayton cycle exhibits advantages in simpler cycle layout and higher efficiencies. The objective of this paper is to explore the possibility that the S-CO2 Brayton cycle can be used for large scale coal fired power plant. Such application presents challenges in the thermodynamic cycle construction, arrangement of heat transfer components and residual heat utilization of flue gas. Here, the S-CO2 recompression cycle, incorporating reheating/double-reheating technique, is integrated with the coal fired power plant. The performance of the power plant is analyzed by coupling the thermodynamics cycle, boiler pressure drops in heat transfer components, and thermal energy distribution of flue gas in the boiler tail flue. The residual heat of flue gas is absorbed by the S-CO2 cycle, an additional flue gas cooler (FGC) and two air preheaters to satisfy the energy cascade utilization principle. The results show that, if the S-CO2 recompression cycle is used alone without reheating, the low-temperature flue gas energy is difficult to be absorbed to cause non-acceptable outlet flue gas temperature such as higher than 120°C. By neglecting pressured drops in heat transfer components, the S-CO2 recompression cycle incorporating reheating increases the system thermal efficiency, but makes it difficult to recover the residual heat of flue gas. When pressure drops are considered, we show that, for the first time, the curves of thermal efficiencies versus reheater pressure drops are crossed between the S-CO2 recompression-reheating cycle and the S-CO2 recompression-double-reheating cycle. Based on this finding, the criterion is proposed to judge at what condition a single-reheating cycle is needed, and at what condition a double-reheating cycle is necessary. It is demonstrated that the CO2 temperature entering the boiler can be decreased by elevating the main vapor pressure. Thus, the adjusting main vapor pressure method is proposed to absorb the residual heat of flue gas. The system efficiency is sharply increased with increase of main vapor pressures. Because the main vapor temperature T 5 and pressure P 5 are strongly coupled, for example, P 5 reaches 43.6 MPa at T 5=615°C and the secondary air temperature of 500°C, the adjusting main vapor pressure method challenges the material pressure tolerance limit. Adding a flue gas cooler (FGC) not only recovers the residual heat of flue gas, but also ensures that the pressure is within the material pressure tolerance limit. The optimal scheme of the FGC integrated with the thermal cycle is investigated, among which, a smaller CO2 flow rate stream consecutively extracted from the main compressor outlet, being heated by the low temperature flue gas, and entering the outlet of the low temperature recuperator heat exchanger, is the best. By using the S-CO2 recompression-reheating cycle together with a FGC, the system thermal efficiency and boiler efficiency attain 50.82% and 94.43%, respectively. This paper gives a clue to design and operate high efficiency, simple layout and compact S-CO2 coal fired power plant.

Rice straw (RS) was utilized to produce biogas, and its biogas residues (BR) were studied on different degradation time. When rice straw was digested, much biogas was produced with average 50% methane. In anaerobic condition, non-fiber contents were mainly digested in the initial 10 days. Meanwhile, the surface of rice straw fibers became rough and its onset decomposition temperature also rose from 170 °C to 210 °C. Cellulose and hemicellulose were digested from 10 days to 30 days, and it determined that the cellulose crystallinity declined from 44.9% to 40.1% and hydroxyl groups was also seen to decrease, which conduces to the reduction of polarity and hydroscopicity. However, lignin was hardly digested in the whole anaerobic process. Inevitably, lignin was accumulated to contribute to the thermal stability and mechanical properties of rice straw fibers. Furthermore, rice straw/low-density polyethylene (RS/LDPE) and biogas residues/low-density polyethylene (BR/LDPE) composites were prepared. Compared with RS/LDPE composites, BR/LDPE composites showed obviously better tensile and flexural properties. Consequently, biogas residues of rice straw have better chemical and physical properties than the undigested rice straw.

Hyperthermophilic pretreatment composting (HPC) is superior to traditional composting (CK) with shortened maturity period and enhanced humification degree. However, the chemical and structural evolution of humic substances (HS) at the molecular level is not known. In this study, the impact of hyperthermophilic pretreatment (90 °C, 4 h) on the content and chemical composition of HS during composting were investigated. The HS content of the final compost was 87.8 g/kg and 76.7 g/kg in HPC and CK, respectively. Significantly higher humic acid/fulvic acid ratio (1.27 in HPC v.s. 0.77 in CK) was observed in HPC. 13C NMR spectroscopic data showed a higher aromatics percentage and earlier enrichment of aromatic structures in HS extracted from HPC than CK. Intensified humification of HPC was related to the increased levels of HS precursors and degradation of lignocellulose. Redundancy analysis demonstrated that aromatic C, phenolic C and O-alkyl C can be used for evaluation of the humification degree.

In order to reduce the negative ecological effects and environmental pollution caused by large-scale herbicide application in rice cultivation, a straw fiber mulch film (FMF) was developed. This study applied high-temperature enzymatic solution technology as a pretreatment process for rice straw (RS) fibers, causing beneficial physicochemical structural changes. Chemical composition, crystallinity index (CrI), degree of polymerization (DP), thermal stability, and other parameters of deconstructed RS fibers were analyzed. The change in CrI showed that appropriate pretreatment times can improve crystallinity, while excessively long pretreatment times caused crystallinity to sharply decrease from 44.65 wt% to 41.34 wt%. The C O bonds between lignin and hemicellulose were almost completely destroyed, confirming the deconstruction of linkages within RS fibers, making the material significantly softer and looser. Compared with untreated straw fibers, the mechanical pulping beating time decreased significantly, reducing energy consumption by 43.75%. The FMFs prepared with appropriate fermenting times exhibited improved mechanical properties. The tensile strength of FMF prepared using biological pretreatment fermentation (BPF) as a raw material increased from 11.26 N m g−1 to 15.68 N m g−1, exhibiting an increase of 39.25% compared to traditional fermentation (TF). This work provides a novel method, which has the potential to effectively control herbicides and support the development of sustainable agricultural systems.

Hyperthermophilic pretreatment composting (HPC) is superior to traditional composting (TC) with shortened maturity period and increased nitrogen (N) retention. However, the mechanism associated with N retention in HPC remains unclear. In this study, we compared the impact of HPC and TC on N retention, and found the proportion of N retained in the final compost was 83.3% and 67.2% for HPC and TC, respectively. Decreased ammonification rate, urease and protease activities together with an elevated temperature were found in HPC. Illumina amplicon sequencing showed that HPC caused a major decline in microbial community richness and diversity in the thermophilic phase. Notably, bacterial (Pseudomonas and Bacillus) and fungal ammonifiers (Acremonium, Alternaria and Penicillium) decreased remarkably in HPC during this phase. Changes in the microbial community could be related to unfavorable modifications of environment from HPC, and which resulted in decreased ammonification and enzyme activities and improved N retention.

The effects of soil burial on the biodegradation of biocomposite flower pots (BFP) made from straw fiber (SF) and hydrolyzed soy protein isolate/urea/formaldehyde (HSPI/U/F) copolymer resin were studied in detail. The microstructure, crystallinity, functional groups, mechanical, degradation and thermal property of the prepared SF with HSPI/U/F copolymer resin have been studied, and the degradation mechanism was also elucidated. XRD results showed that the bond breakage between SF and HSPI/U/F copolymer resin induced a decrease in relative degradation-resistant crystal structures. FTIR spectra showed that the methylolated HSPI units could form a cross-linking network with U/F and SF. The BFP degradation after soil burial was mainly attributed to the effects of microorganisms. The degradation products were environmentally friendly, because they were degradable and could fertilize the soil. In addition, the U/F adhesives were slightly degraded by the microorganisms due to the HSPI in the pots. The TG and DSC results showed that the molecular motion of the BFP matrix could be restricted by the degradation action and the content of HSPI, resulting in decreased crystallization enthalpy and showing good thermal property. The tensile strength of different reinforced samples was not significantly reduced in comparison to U/F resin, and still kept good mechanical performance. Thus, the prepared SF reinforced HSPI/U/F copolymer resins could have good potential for use in the field of biodegradable flower pots because of their good thermal property, mechanical property, biodegradability, and relatively low cost.

Rice straw fibers are potential raw materials that can be used to produce biogas and reinforcing fibers for composites. In order to ascertain the effects of anaerobic digestion on the structural properties of the fibers, the structure of fibrous residuals with different digestion time, including 0, 10, 20, and 30 days, were investigated. The normalized biogas production volume was 224 mL/g volatile solid of substrate, of which the methane content was about 50%. Fiber detergent analyses of the straw before and after 10 days digestion indicated that the cellulose levels increased from 34.3% to 41.3%, and cellulose crystallinity index ranged from 44.9% to 49.9%, respectively. After the rice straw had been digested for 30 days, the cellulose and hemicelluloses of the rice straw were partially degraded; the crystallinity index of the cellulose decreased from 44.9% to 40.1% based on XRD analyses, and the amount of hydroxyl groups were observed to decrease based on FT-IR analyses. Consequently, the polarity and hygroscopicity of the rice straw fibers were speculated to be lowered based on these observed changes. Furthermore, the relative amount of lignin in the straw residuals increased as digestion time increased, which increased the thermal stability of the resulting fibers. As a result of anaerobic digestion, the properties of the rice straw fibers for their use in plastic composites were enhanced.

The hydrolytes soy protein isolates (HSPI)-modified urea–formaldehyde (UF) resins were synthesized via copolymerization process. The best bonding strength is 1.50 MPa and improves 51.5% compared with pure UF. In addition, the formaldehyde emission decreased. The effect of (HSPI) on the biodegradable (UF) resins was investigated. Biodegradation was evaluated by composting under controlled conditions in accordance with ISO 14855. The faster degradation rate was obtained when lower hydrolysis degree of HSPI was added into the system. Characterization of the resulting samples was performed by attenuated total reflection Fourier transform infrared spectroscopy, thermo-gravimetric analysis, XRD, scanning electron microscopy, and AFM. The results showed that no evidence of biodegradation was found for UF resins. The UF modified with lower hydrolysis degree of hydrolytes soy protein isolates (HSPI) resulted in a faster degradation rate. The HSPI in the network of modified UF degraded first, which resulted in the ...

The hydrolyzed soy protein isolate (HSPI) was used to partially substitute urea to synthesis modified urea–formaldehyde (UF) adhesives via copolymerization process, in order to reduce the dependency on petroleum-based chemicals and mitigate possible environmental pollution. The soy protein isolate (SPI), HSPI, and modified UF adhesives were characterized by attenuated total reflection Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (1H NMR), and thermo-gravimetric analysis (TGA). The bonding strength, adhesive properties, biodegradability, and micrographs of the UF and HSPI-modified UF after degradation were also measured. The results show that the SPI native structure is unfolded during the treatment with sodium hydroxide. The thermal stability of HSPI is better than SPI. HSPI can incorporate into the structure of cured UF adhesives with three different feeding methods. And the best bonding strength of modified UF adhesives is 1.31 MPa when HSPI is added at the first step. The form...

Hydrothermal carbonization (HTC) is an efficient conversion process that treats solid digestates from anaerobic digestion plants and converts it into valuable solid products. In this study, digestates of swine manure (DS_M) and rice straw (DS_S) were HTC-treated at 190 °C with biomass-to-water ratios of 1:4 and 1:9. The hydrochars were characterized physically and chemically to elucidate their potential as a valuable resource. The hydrochars from the solid digestates were acidic, and the dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and Brunauer-Emmett-Teller surface area (SBET) were significantly (P < 0.05) higher compared with that of the feedstocks and pyrochars. Mesopores were dominant in the hydrochars, where the pores had slit-type holes and a stratified structure. The hydrochars possessed more O functional groups and aromatic C=C and C-H band than the feedstocks and pyrochars. The hydrochars derived from solid digestates were better as a solid fuel because of their combustion property. The increase in the crystallinity of the hydrochars enhanced their stability. The hydrochars produced from the DS_M were more acidic than those from the DS_S. The HTCDS_S had a better adsorptive effect on pollutants than the HTCDS_M because of the higher SBET and optimal functional groups.

To improve the compatibility between rice straw and reinforcing polymers, rice straw (RS) was pretreated by an anaerobic process, and its biogas residues (BR) were acetylated with acetic anhydride (AA) to prepare acetylated biogas residues (ABR). The optimum conditions of acetylation were determined by orthogonal experiments. When acetylation was performed at 140 °C with 10 mL AA/g BR and 0.08 g catalyst/g BR, the maximum weight gain rate (WGR) obtained was 23.7%. Fourier transform infrared (FTIR) analysis showed that many hydroxyl groups were displaced by acetoxy groups. Scanning electron microscopy (SEM) showed that many defects of BR were filled by the acetylation, and an ester layer was formed over the BR surface. However, the lower crystallinity of ABR than the BR and RS affected the mechanical properties of acetylated biogas residue/low density polyethylene (ABR/LDEP) composite. Interestingly, the BR and ABR showed higher onset decomposition temperature, but they exhibited faster decomposition rates because of the lower crystallinity of BR and ABR. Furthermore, the mechanical properties of the RS/LDEP, BR/LDEP, and ABR/LDEP composites were analyzed. Compared with RS/LDEP composites, the BR/LDEP and ABR/LDEP composites showed obviously better tensile and flexural properties. Consequently, rice straw fibers attained excellent compatibility with non-polar polymers.

A composting treatment was employed in an effort to improve the processability of rice husks. Changes in the chemical composition, physical structure, and rheological properties of modified rice husks were analyzed. The results indicated that the average diameter of compost-treated samples was significantly higher than that of the untreated samples because they were able to adhere to each other by the bacterial protein. Scanning electron microscopy images showed that the epidermis became rugged and lumpy because the composition of rice husks (cellulose, hemicellulose, lignin, and pectin) was partially decomposed, an effect confirmed by the chemical composition and FTIR analysis. Thermogravimetric analysis showed that the composted samples had better thermal stability than the untreated ones. Stress-strain curves showed that the treated samples displayed a moderately significant change of slope at about 0 to 10% strain, and they had better mechanical properties than untreated samples. Juxtaposing the rheological properties of both untreated and treated samples determined that the latter had higher apparent viscosity as a result of degradation and bacterial protein effects. All results indicated that the composting treatment changed the physical, chemical, and rheological properties of the rice husks, which are beneficial for its utilization and processability.

The degradation behavior was investigated for eco-composite nursery containers (NCs) prepared with rice husk and cornstarch adhesive modified with urea formaldehyde (UF) as a wet strength agent. The wet shear strength, water absorption capacities, and biological degradation of NCs within soil were also investigated. Quantitative analysis of the thermal degradation behavior of different NC versions was performed by thermo-gravimetric analysis (TGA). The results demonstrated that the introduction of the UF agent accelerated the soil degradation of the NCs matrix to a certain extent. The maximum cumulative mass loss was 51.1% when the UF content of NCs was 8 wt.%. Moreover, the dry strength of the mixed urea formaldehyde-cornstarch adhesive (UCA) was increased by 108.9% compared with cornstarch adhesive (CA). The results of this work indicate the improved biodegradability of the NC eco-composites, which could make them potential sustainable alternatives for conventional plastic pots.

The hydrolyzed soy protein isolate (HSPI) with different hydrolysis degree was applied to modify urea-formaldehyde resins (UF) via copolymerization process. The properties of HSPI were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and TGA. The results show that HSPI with different hydrolysis degree is obtained. 1H NMR and ATR-FTIR spectra indicate that HSPI with different hydrolysis degree can incorporate into the structure of cured and uncured UF. The UF modified with higher hydrolysis degree of HSPI possess more stable units and contribute to the lower exothermic peak temperature in DSC curves. The bonding strength of HSPI modified UF increases as the hydrolysis degree of HSPI increases at the hot-press temperature of 120°C and decreases at the hot-press temperature of 150°C. The best bonding strength is 1.53 MPa at the hot-press temperature of 135°C and improved 56.12% compared with UF. In addition, the formaldehyde emission is dramatically reduced. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41469.

A biodegradable planting container made with rice straw and starch adhesives modified by polyvinyl alcohol was studied in this paper. The effect of heat treatment and polyamide resin on the properties of planting containers was investigated. The physical property and biodegradability were characterized by means of hygroscopicity, FTIR, degradability, and the thermogravimetric analysis. The results showed that the dry strength of planting containers increased as a result of both treatments. The wet strength of planting containers increased as a result of heat treatment, while the wet strength of planting containers decreased as a result of polyamide resin. The hygroscopicity of planting containers decreased with heat treatment and polyamide resin. The effect of heat treatment was more obvious than the effect of polyamide resin. It was observed that the peak intensity and position were changed for the 3400 cm-1, 2900 cm-1, 1640 cm -1, 1500 cm-1, 1400 cm-1, and 1050 cm-1 under the treatment of polyamide resin. The weight loss of specimens treated with polyamide resin was larger because of the presence of nitrogen in the resin. The appearance of planting containers showed the heat treatment containers were not easily prone to mildew when used for planting. The thermogravimetric analysis (TGA) showed that heat treatment can improve the thermal stability, while the polyamide resin was shown to promote the degradation of planting containers.