Heating Temperature Range Research Articles

Research on heating temperature control method of VOC gas sensor and development of new sensor module

Abstract Sensors made of various new materials exhibit high sensitivity and accuracy in detecting volatile organic compounds (VOCs). However, they also demand higher working temperatures to unleash their outstanding performance within a certain temperature range. Furthermore, the fluctuation of ambient temperature throughout the year significantly impacts the heating temperature of the sensors. Conventional commercial sensor modules utilizing constant voltage heating are no longer able to meet the precise temperature control requirements. Therefore, our research team conducted a heat transfer analysis to establish the mathematical relationship between heating temperature and voltage. This was subsequently validated through finite element analysis, leading to the development of a multivariate linear regression model for predicting voltage based on the desired target temperature and ambient temperature. To address this, we proposed an approach to automatically adjust the heating temperature by controlling the heating voltage duty cycle using a microcontroller based on the ambient temperature. As a result, a novel adaptive temperature-controlled sensor module was developed. Experimental tests demonstrated that within the heating temperature range of 263-464°C, the substrate temperature could be controlled with an average error of 4.36%, meeting the precision requirements for sensor heating temperature control. In comparison with the commercial module, the temperature-controlled module exhibited a notable improvement in sensitivity when responding to different ambient temperatures. At 0°C, the average sensitivity enhancement for the MQ3 and MQ7 sensors compared to the commercial module was 12.77% and 31.5%, respectively, and at 40°C, the average enhancements were 5.94% and 19.8%. This sensor module and temperature control method provide theoretical and technical references for the accurate measurement of VOC parameters.

Enhanced mechanical and damping properties of Cu-Modified Al-Ni eutectic alloys: Solid-solution and precipitation hardening effects

The study aimed to analyze the mechanical properties, precipitation strengthening, and microstructure of Al-Ni-Cu alloys to understand their enhanced characteristics. Additionally, the damping behavior was examined using a dynamic mechanical analyzer across a continuous heating temperature range with frequencies from 0.5 to 15 Hz. The experimental results indicate that the Al-Ni eutectic alloy, which exhibits an ultrafine Al3Ni intermetallic fiber-reinforced Al matrix, transitions to a dendritic-ultrafine eutectic composite structure. The Cu-containing alloys exhibit two distinct primary phases: α-Al and Al-Ni-Cu ternary intermetallic compounds. The eutectic matrix transforms from Al-Al3Ni to Al-Al7Cu4Ni, and subsequently to Al-Al2Cu. These microstructural evolutions result in an enhancement of the tensile yield strength from 170 MPa to 440 MPa, with additional hardening achieved through aging-induced precipitation. Moreover, the damping capacity improves with the addition of Cu at elevated temperatures, and there is an increase in frequency dependence. This paper will discuss the microstructural features, mechanical properties, deformation behaviors, and damping properties in detail.

Experimental investigation of an off-grid CPC system integrated with a radiator for the application of space heating

Compound parabolic collectors (CPC) are non-tracking concentrators capable of producing lower to medium-range heating (temperature range of 50–80 °C), making them suitable for space heating applications. CPCs raise the heat transfer fluid temperature to a specific value depending upon the solar irradiation received at the location. In this study, CPC is used to harness the solar energy, and an insulated tank is used to store thermal energy. To facilitate space heating, the hot fluid from the thermal storage tank is passed through a radiator, transferring the thermal energy from the tank to the target heating load. The overall setup consists of two loops with water as heat transfer fluid. Both loops consist of a pump that uses solar PV power. An experimental test setup was installed to measure the ambient heat transfer fluid, radiator fin, and room temperature. The combined system was tested for its performance under actual weather conditions prevailing in the area. Experiments were performed to investigate space heating potential at night, evening, and full day. The energy stored and collector efficiency were calculated for each day. The total thermal energy stored in the tank on a typical day was 67.79 MJ, and the collector efficiency was evaluated to be around 43.7 %. As per the experiment results, the combined CPC and radiator system have a significant potential to be explored in space heating.

Preparation of CeO2 particles via ionothermal synthesis and its application to chemical mechanical polishing

CeO2 is a widely used abrasive for the chemical mechanical polishing of silicon during chip manufacturing. CeO2 can be synthesized via traditional coprecipitation, hydrothermal, and solvothermal methods; however, these methods have some issues, including high vapor pressure, flammability, toxicity, volatile solvents, and narrow heating temperature range. To overcome these issues, we developed a new ionothermal synthesis approach for high-quality CeO2 particles using 1-ethyl-3-methylimidazolium tetrafluoroborate as an imidazole ionic liquid without a template. Based on the scanning electron microscopy and particle size distribution, CeO2 particles synthesized at a reaction temperature of 210 °C for 16 h displayed sizes ranging between 0.1 and 0.3 μm. Additionally, the spherical shapes exhibited good crystallinity, regular morphology, and uniform dispersion. The results of CMP experiments indicated that the abrasives could reduce the surface roughness from 1.63 to 0.29 nm (scanning area is 5 μm × 5 μm). The obtained synthesized CeO2 particles demonstrated promising performance in Si polishing, achieving removal rates of up to 255.5 nm/min. It found that the removal rate of the abrasive prepared by ionic thermal synthesis in Si polishing was twice as much as other abrasives. Further, a possible mechanism was put forward to explain the formation of CeO2 structures with various morphologies. The proposed method presents a new approach for synthesizing CeO2 particles with uniform morphology and excellent polishing properties.

Studying the influence of heat treatment modes on the properties of medium-carbon steel

Problem. Parts of modern machines and structures operate under high dynamic loads, stress concentrations, and low or high temperatures. All of this contributes to brittle fracture and reduces the reliability of machines. Therefore, structural steels must, in addition to high mechanical properties, have high structural strength, which is manifested in the conditions of its actual use in the form of parts, structures, etc. [1] A properly selected heat treatment mode allows to obtain an optimal combination of properties in a part, thereby ensuring its reliability and operational durability.
 Goal. The aim of the study is to determine the effect of heat treatment parameters on the hardness, impact strength, and structure of 40 and 40X medium-carbon steels. Method. In the course of the work, a set of mechanical studies was carried out on samples of 40 and 40X steels in the initial state and after various heat treatment modes. Results. Based on the analysis of mechanical studies, the influence of heat treatment parameters on the mechanical properties and structure of medium-carbon steels 40 and 40X was studied. On the basis of mechanical and microstructural studies, the relationship between the effect of economical alloying of medium-carbon steel and the main indicators of mechanical properties in the range of heating temperatures was established. The experiments conducted in this work allowed us to obtain a comparative characterization of the effect of various technological parameters of heat treatment on the structure and properties of medium-carbon steels 40 and 40X, which are being improved. The factors that may affect the quality of parts made from these steel grades were also identified. Summarizing the results of metallographic studies and mechanical properties, the following conclusions can be drawn: 1. Steel 40, which has low supercooled austenite stability, must be cooled sharply (cold water, 8-12% aqueous solutions of NaOH or NaCl, etc.) to obtain continuous hardenability of parts. 2. The addition of 1 % chromium increases the stability of supercooled austenite, i.e. increases the hardenability of steel, so parts made of economical 40X alloy steel can be cooled in oil. However, if the part is large, a higher cooling rate should be used – in water. 3. Normalizing can be recommended for 40 and 40X steels as a work hardening heat treatment that increases ductility and impact strength. However, if the hardness level of the normalized alloy steel is high, then full or isothermal annealing should be used. 4. To prevent decarburization of steel at high temperatures and long holding times, protective atmospheres must be used. In the case of processing parts in furnaces with an oxidizing atmosphere, the parts must be filled with graphite, because cast iron chips do not provide reliable protection against oxidation. 5. In the range of tempering temperatures of improving steels recommended by the reference literature (400-600 °C), a monotonic decrease in hardness of both steels occurs, but in carbon steels, the hardening is more intense than in alloy steels. 6. To prevent the development of tempering brittleness of the second kind, to which 40X steel is prone, cooling during tempering should be accelerated (in oil, water), especially if the tempering temperature exceeds 550 °C.

Characterizing the Cathode Degradation Process from Thermal Abuse in Solid State Batteries

With an ever-increasing reliance on batteries for all aspects of life, safety of energy storage is a growing concern as reported instances of lithium-ion battery (LIB) fires and even a solid-state battery (SSB) fire arise. However, the understanding of battery safety from a fundamental materials level is not well understood. As the push for higher energy density batteries in the electrification of transportation continues, it is imperative to understand how underlying material degradation and failure affects the safety of current and next-generation lithium battery technology.In this study, heat release and corresponding degradation due to external heating are explored for the following battery configurations: All solid-state batteries (ASSBs), SSBs containing a low amount of liquid electrolyte, and LIBs. NMC532 cathode was used in all battery configurations, Ta-doped LLZO was used for the solid electrolyte, and LiPF6 in EC/EMC was used as the liquid electrolyte in the SSB and LIB configurations. Differential scanning calorimetry (DSC) was used to raise microcells to definitive temperatures of interest depending upon their respective exotherm profile. LIB sample heat release was significantly higher than the heat release of the ASSB and SSB, even though the heating temperature range and final temperature were lower for the LIB samples. The disassembled microcell components were then analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis revealed the LIB samples did not show the presence of the fully degraded rock salt crystalline phase after peak heat release, whereas ASSB and SSB configurations revealed the presence of the rock salt phase. Additionally, SEM image analysis shows no degradation of the LIB particles, while ASSB and SSB samples show surface degradation of the high temperature samples. Decomposition of NMC to the rock salt phase involves the release of oxygen, which may undergo an exothermic reaction inside the SSB. These investigations shed light into the expected extent of NMC decomposition at key temperatures and exothermic heat flow peaks for each battery composition. Future work combining these results with further elemental characterization experiments will pave the way for a materials-level understanding that can be incorporated into the initial design and development stages of next generation lithium batteries, impacting the creation of energy storage devices by ensuring commitment to safety from the ground up.

Impregnation of Activated Carbon with Organic Phase-Change Material.

In this study, we developed a thermal storage medium comprising porous activated carbon filled with organic phase-change materials (PCMs) that utilizes the latent heat of phase-change to absorb heat during heating and release heat during cooling. For the activated carbon, we used both charcoal-based powdered activated carbon (250-350 mesh) and granular activated carbon. The organic phase-change materials used in the experiments were dodecane, tridecane, tetradecane, and pentadecane. Material properties such as thermal conductivity, latent heat, and melting temperature range were evaluated experimentally and theoretically, with the results observed to be consistent. The cyclic thermal performance of the proposed medium was also evaluated. Notably, filling the activated carbon with a mixture of organic PCMs resulted in the highest temperature-moderating effect. The procedure and results presented in this study are expected to aid in further improvement in the performance of thermal storage media containing PCM where stable temperatures are required, including building heating and cooling.

Fabrication and capillary performance of multi-scale microgroove ceramic wicks via nanosecond laser irradiation for ultrathin ceramic heat pipes

Ultrathin ceramic heat pipes have great potential in solving the heat dissipation problems for power semiconductor devices with ever-increasing power density. Ceramic wick structures with superior capillary performance plays a decisive role in the heat transfer performance of the ceramic heat pipe. In the study, a multi-scale microgroove wick (MSMGW) prepared by laser irradiation is developed. The effects of laser scan pitch, laser fabrication parameters and ceramic material on the surface morphology, wettability and capillary performance of the MSMGW were investigated. The 66 μm thick ceramic wick proposed that consists of micron-sized microgrooves, nanoscale voids and material surface reconsolidation layers demonstrates remarkable capillary performance. The laser scan pitch, laser power, repetition frequency, and scanning speed have significant impacts on the surface morphology and capillary performance of MSMGW. The MSMGW with optimal parameters could reach capillary wicking height of 114 mm within 28 s and yield a capillary parameter (K/reff) of 1.49 μm. Moreover, MSMGW on the material of alumina with advantages of excellent machining property and technology maturity, and working fluid of DI water with high vaporization latent heat and wide operating temperature range, exhibits the maximum capillary performance, indicating its highly promising prospects for high-performance ultrathin ceramic heat pipes.

Influence of cooling manners on microstructure and mechanical properties of AISI 430 ferritic stainless steel

This paper investigated the microstructure and mechanical properties of AISI 430 ferritic stainless steel (FSS) after annealing in either the single-phase or two-phase region, followed by different cooling manners: water cooling, air cooling and furnace cooling. After annealing at 840 °C in the single-phase region, the sample consisted primarily of ferrite, with M23C6 and M2(C, N) precipitates aligned mainly along the rolling direction (RD). For the water-cooled and air-cooled samples annealed at 950 °C in the double-phase region, they formed a dual-phase structure comprising ferrite and martensite, with precipitations primarily located within the martensite lath. Conversely, the sample subjected to annealing at 950 °C followed by furnace cooling displayed a single ferrite structure, owing to the decomposition of austenite. In this case, the precipitations were mainly found along the grain boundaries, with some also forming within the ferrite grain. The paper delved into the analysis of mechanical properties and strengthening mechanism through tensile experiments and fracture morphology examination. The influence of heating range and cooling manner on the yield characteristics of FSS was discussed. The results indicated that the air-cooled and furnace-cooled samples annealed at 840 °C displayed a clear yield platform in their tensile curves. Conversely, the samples treated with other heat treatments exhibited continuous yielding or no obvious yield platform. This difference may be attributed to the influence of heating temperature range and cooling manner on the distribution of dislocations and interstitial atoms within the ferrite grains.

Thermo-kinetic behaviour of green synthesized nanomaterial enhanced organic phase change material: Model fitting approach

Metal, carbon and conducting polymer nanoparticles are blended with organic phase change materials (PCMs) to enhance the thermal conductivity, heat storage ability, thermal stability and optical property. However, the existing nanoparticle are expensive and need to be handle with high caution during operation as well during disposal owing to its toxicity. Subsequently handling of solid waste and the disposal of organic PCM after longevity usage are of utmost concern and are less exposed. Henceforth, the current research presents a new dimension of exploration by green synthesized nanoparticles from a thorny shrub of an invasive weed named Prosopis Juliflora (PJ) which is a agro based solid waste. Subsequently, the research is indented to decide the concentration of green synthesized nanoparticle for effective heat transfer rate of organic PCM (Tm = 35–40 °C & Hm = 145 J/g). Furthermore, an in-depth understanding on the kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM after usage via Coats and Redfern technique is exhibited. Engaging a two-step method, we fuse the green synthesized nanomaterial with PCM to obtain nanocomposite PCM. On experimental evaluation, thermal conductivity of the developed nanocomposite (PCM + PJ) increases by 63.8% (0.282 W/m⋅K to 0.462 W/m⋅K) with 0.8 wt% green synthesized nanomaterial owing to the uniform distribution of nanoparticle within PCM matrix thereby contributing to bridging thermal networks. Subsequently, PCM and PCM + PJ nanocomposites are tested using thermogravimetric analyzer at different heating rates (05 °C/min; 10 °C/min; 15 °C/min & 20 °C/min) to analyze the decomposition kinetic reaction. The kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM and its nanocomposite of PCM + PJ provides insight on thermal parameters to be considered on large scale operation and to understand the complex nature of the chemical reactions. Adopting thirteen different chemical mechanism model under Coats and Redfern method we determine the reaction mechanism; kinetic parameter like activation energy (Ea) & pre-exponential factor (A) and thermodynamic parameter like change in enthalpy (ΔH), change in Gibbs free energy (ΔG) and change in entropy (ΔS). Dispersion of PJ nanomaterial with PCM reduces Ea from 370.82 kJ/mol−1 to 342.54 kJ/mol−1 (7.7% reduction), as the developed nanomaterial is enriched in carbon element and exhibits a catalytic effect for breakdown reaction. Corresponding, value of ΔG for PCM and PCM + PJ sample within heating rates of 05–20 °C/min varies between 168.95 and 41.611 kJ/mol−1. The current research will unbolt new works with focus on exploring the pyrolysis behaviour of phase change materials and its nanocomposite used for energy storage applications. This work also provides insights on the disposal of PCM which is an organic solid waste. The thermo-kinetic profile will help to investigate and predict the optimum heating rate and temperature range for conversion of micro-scale pyrolysis to commercial scale process.

Study on the working medium of high temperature heat pump suitable for industrial waste heat recovery

In order to find a high-temperature heat pump (HTHP) working medium suitable for industrial waste heat recovery, this paper theoretically analyzes the thermodynamic properties of six refrigerants, including the coefficient of performance (COP), condensation pressure, compression ratio, heating capacity, exhaust temperature, and compressor power consumption. Based on the theoretical analysis results, environmental effects and the temperature range of industrial waste heat, MC-1 can be considered as a suitable working medium for high-temperature water source heat pump. The thermodynamic performance of MC-1 was experimentally studied and compared with that of HFC245fa and F-1 refrigerants. The results show that when the outlet water temperature of the condenser changes from 65 to 110 ℃ and the temperature lift is 35 ℃, the coefficient of performance of MC-1 varies from 4.24 to 5.05, which is much higher than that of both HCFC245fa and F-1. When the outlet water temperature of the condenser varies from 95 to 100 ℃, the average coefficient of performance of MC-1 is 16.2% higher than F-1 and 18.0% higher than HCFC245fa. The relative deviation between the theoretical calculation results and the experimental results of the main thermodynamic performance parameters does not exceed 10%, indicating that the theoretical results are reliable. Therefore, MC-1 can be recommended as the working medium for high-temperature heat pump with a single-stage cycle.

Evolution Behavior and Fracture Criterion of Carbides in D2 Cold‐Work Die Steel During Hot Working Process

Investigating the fracture mechanisms of carbides is of paramount importance for optimizing hot working processes in die steels. This work establishes a comprehensive criterion equation to predict the behavior of carbide fracture in D2 cold‐work die steel during hot working process. High‐temperature laser confocal microscope is employed to prepare samples with varying solidification rates. Subsequently, these samples are subjected to a range of heating temperatures spanning from 1000 °C and 1100 °C. The samples are analyzed utilizing scanning electron microscopy energy spectrum analysis and X‐ray diffraction. The activation energy of M7C3 carbides is calculated through the utilization of kinetic equations and the Arrhenius law. Additionally, a criterion model for the fracture behavior of M7C3 carbides in D2 cold‐work die steel is established. The results reveal that thin hollow rod‐shaped carbide is easy to fracture. Moreover, the activation energy for phase transition of M7C3 carbides in D2 cold‐work die steels is determined to be 226.974 KJ mol−1. Furthermore, the fracture behavior of carbides in D2 cold‐work steel is found to be influenced by various factors such as heating temperature, deformation rate, and peak stress. Finally, the criterion model demonstrates substantial agreement with the experimental observations gathered, affirming its reliability and accuracy.

Formation mechanism of copper-gilded coronet ornaments excavated from a Sui or early Tang tomb situated in Xi’an, Shaanxi

The formation of the gold layer in mercury gilding occurs through the heating a gold amalgam. As a result, the formation mechanism and technical characteristics of gilded products are closely related to the temperature at which they are heated. In this study, XRD and XPS analysis of a copper-gilded coronet from the Sui or Tang dynasties revealed that Au3Cu was one of the main phases of the gold layer. Therefore, base on the thermodynamic stability of ordered phases like Au3Cu, the estimated heating temperature for this copper-gilded coronet ranged from 240 to 285 ℃. Furthermore, SEM–EDS analysis of the cross-sectional concentration distribution of Cu indicated that the diffusion distance of Cu during heating did not exceed 2 μm. At 240–285 ℃, Cu diffused along the defects of the gold layer, and the diffusion process followed Fick’s second law. Previous research has indicated that the defect path diffusion coefficient of Cu is on the order of 10–12 cm2/s, and the heating time of the gilding process is typically considered to be 15 min. Using the diffusion equation, the calculated diffusion distance of Cu aligned with the diffusion behavior of Cu at 240–285 ℃, confirming the inferred heating temperature range. Additionally, at these temperatures, the gold layer was formed through the solid-state reaction of the gold amalgam and was bonded to the substrate through the diffusion of Cu.

Information theory-based dynamic feature capture and global multi-objective optimization approach for organic Rankine cycle (ORC) considering road environment

Efficient capture and global optimization of organic Rankine cycle (ORC) operating features in road environment is the key to obtain actual waste heat recovery potential. The complexity of time-varying characteristics intensifies the nonlinear coupling relationship between ORC performance and parameters. This paper first designs and builds an ORC experimental system for recovering waste heat from internal combustion engine (ICE). The experimental system includes ICE and its measurement subsystem, ORC subsystem, expander lubrication subsystem, cooling subsystem, and ORC measurement subsystem. R245fa is used as working fluid; The expander adopts a specially designed single screw expander. The performance of ORC waste heat recovery is tested by adjusting the operating conditions of the ICE, expander, pump, and valve opening. The temperature range of waste heat is 627–686 K. Subsequently, a dynamic feature capture and global multi-objective optimization approach for ORC is proposed. The results show that the precision of dynamic feature capture can be improved at least 41.78% with the introduction of information theory in complex environment. Frequent fluctuation of vehicle speed is not conducive to the improvement of evaporator inlet temperature at working fluid side. As the speed of the vehicle is greatly reduced, the evaporator inlet temperature drops sharply. The frequent fluctuation of speed will intensify the nonlinear correlation between operating parameters and system performance and make the system performance more dependent on the coupling correlation between operating parameters. The approach proposed in this paper can provide a new idea for efficient capture of dynamic characteristics and global multi-objective optimization of ORC in road environment.

Fluoride removal in batch and column systems using bonechar produced in a top-lit updraft drum gasifier and furnace

Hundreds of millions of people are exposed to excessive levels of fluoride in drinking water, predominately in low-resource communities. Activated alumina is recognized as the best available technology for fluoride removal from drinking water by the United States Environmental Protection Agency, but it has substantial economic and environmental costs. Bonechar is a more environmentally friendly and potentially lower cost alternative adsorbent. Here, fluoride adsorption from groundwater (pH 8.1 ± 0.2) by activated alumina was compared with bonechar primarily produced from bovine bones at peak heating temperatures between 400 and 1100 °C in a modular top-lit updraft drum (TLUD) stove (using a bone-wood mixture) and furnace. TLUD and furnace bonechar produced at peak heating temperatures 650–1000 °C and 400–800 °C, respectively, outperformed activated alumina in batch tests (i.e., required smaller doses to achieve 90% fluoride removal). The impact of using bovine versus swine bones to produce bonechar had a negligible impact on fluoride adsorption. A wide range of peak heating temperatures in the TLUD achieved by varying primary air flow rates and fuel selection (e.g., bone-to-wood mass ratios) produced efficient fluoride adsorbents. This finding demonstrates that a TLUD can be a robust, operationally flexible production system. Fluoride removal by TLUD and furnace bonechars showed strong, negative correlations (R2 ≥0.88) with organic matter content. Bonechar pilot column tests indicated that the mass transfer zone was captured (i.e., immediate fluoride breakthrough was not observed) at an empty bed contact time (EBCT) of 5 min, increasing EBCT to 30 min had a minimal impact on adsorption efficiency, and intermittent operation (3–10 d shut-off periods) decreased effluent fluoride concentrations. Furnace bonechars produced at peak heating temperatures 400–700 °C outperformed activated alumina in pilot columns. Differences in adsorption efficiencies in batch and column tests were associated with the linearity of fluoride adsorption. A theoretical model quantifying adsorption linearity with Freundlich 1/n values was able to predict adsorber performance solely based on batch test data.

A study on vermiculite-based salt mixture composite materials for low-grade thermochemical adsorption heat storage

High-performance renewable energy technologies are desired to meet the enormous demand during the clean energy transition. Thermal energy storage can help balance the mismatch between renewable energy supplies and end-user's demands. Thermochemical adsorption heat storage (TAHS) has attracted widespread attention for its ability to efficiently utilise low-grade renewables and waste heat. Composite adsorbent materials have been gaining increased research interest, which combine hygroscopic salts and host matrix via impregnating salts in the matrix. This paper reviews recent progress in composite materials for TAHS and provides material characterisation analysis on different vermiculite-based composites. The composites use vermiculite as the host matrix with impregnation of different binary and ternary salt mixtures (i.e., MgSO4–CaCl2, MgCl2–LiNO3, MgSO4–LiCl and MgSO4–LiNO3–MgCl2). Vermiculite impregnated with a binary mixture of MgSO4–CaCl2 demonstrated a high energy storage density of 1213 kJ/kg, with fast desorption kinetics in the temperature range of low-grade heat. It shows good suitability for domestic TAHS applications, particularly for space heating, with stable cyclic performance over 20 charging-discharging cycles, maintaining approximately 91.3% of its initial energy storage density. The findings of this study contribute to the growing body of research on composite materials and demonstrate the potential of vermiculite-based composites impregnated with binary salt mixtures for low-grade TAHS.

Effects of wood fiber loading, silane modification and crosslinking on the thermomechanical properties and thermal conductivity of EPDM biocomposite foams

Ethylene propylene diene monomer (EPDM) rubber based bio-composites filled with silane-modified wood fiber (SiWF) were foamed by using chemical foaming method. The SiWF and the incorporation of dicumyl peroxide (DCP) generated crosslinking in the developed EPDM bio-composite foams, which showed much lower water absorption and improved thermomechanical properties. With SiWF and in situ cross-linking, the tensile strength and modulus of EPDM bio-composite foams exhibited up to 90% and 600% enhancement compared to the unfilled foam, respectively. The compressive strength and modulus individually showed up to 170% and 600% increase. The developed bio-composite foams also displayed lower apparent thermal conductivity than the unfilled EPDM foam over the heating temperature range, showing possible applications as insulation materials.

Organic Matter Transfer Caused by Concentration Difference Creates TC4 Surfaces with Switchable Wettability.

In this paper, low-cost electrochemical processing and heat treatment were adopted to fabricate titanium alloy surfaces with switchable wettability. Meanwhile, surface structure, roughness, and oxide content were regulated by electrochemical processing voltage. The effects of surface structure, roughness, oxide content, temperature, and time of heat treatment on switchable wettability were investigated. In addition to suitable structural conditions, surface chemistry is also crucial to preparing metal surfaces with switchable wettability. The surface chemistry of electrochemical processed surfaces was changed by organic matter transfer during heat treatment. In a certain voltage range, suitable surface structure, high roughness, and surface oxide content by high voltage contribute to the organic matter transfer. In a certain range of heating temperature and time, the concentration difference of organic matter is the premise of organic matter transfer. Concurrently, the higher the temperature, the faster the speed of organic matter transfer. Different from other relevant studies, the hypothesis that the concentration difference promotes organic matter transfer is proposed and verified by interesting experiments. The difference concentration of organic matter between the environment and the samples, as well as between the two samples, was created to promote organic matter transfer. Therefore, the electrochemical processed surfaces with switchable wettability were obtained by organic matter transfer in two ways.

Density-Induced Joule-Heating Characteristics of Nanocarbon Aerogels: Implications for Tunable Electrothermal Behaviors

An in-depth understanding of the electrothermal characteristics and behaviors of nanocarbon aerogels is crucial for optimizing their Joule-heating performance and expanding their applications. Modifying a single parameter of nanocarbon aerogels can reveal potential variations in Joule heating, which makes it a valuable area for investigation. This study explores reduced graphene oxide aerogels and reduced graphitized nanofiber aerogels with varying densities (14.9–31.7 mg·cm–3), fabricated using the hydrothermal method and polymer-assisted cross-linking method, to elucidate density-induced Joule-heating discrepancies. The critical step in aerogel preparation is the freeze-drying process, which yields structurally intact nanocarbon aerogels for Joule-heating experiments. Aerogels with higher densities displayed enhanced electrical and thermal conductivities (up to 24.9 S·m–1 and 0.882 W·m–1·K–1, respectively) compared to their lower-density counterparts, owing to the increased number of pathways available for electron/phonon transportation. The low-density aerogels exhibited more pronounced features in the heating temperature range (up to 117 °C) and efficiency (up to 46.5 °C·W–1), making them more suitable for energy-efficient applications. Despite variations in the density, all of the fabricated aerogels showed efficient electron hopping between the interconnected nanocarbons, which enabled uniform resistive heating throughout the aerogel entity. This work highlighted the importance of density control in altering the Joule-heating performance of nanocarbon aerogels for specific applications, which has far-reaching implications for optimizing the properties of other electrically conducting aerogel materials.

The dynamic stability of silicone oil-based MWCNT nanofluids under high-temperature, high-flux irradiation, and shear-flow conditions

Nanofluid-based volumetric-type solar collectors have emerged as a promising technique for solar thermal applications. However, achieving the long-term stability of nanofluids under high-temperature, high-flux irradiation, and shear-flow conditions is still challenging. Herein, we propose a facile method to stabilize silicon oil-based multi-walled carbon nanotube (MWCNT) nanofluids via shear flow. The effects of shear flow on the stability of nanofluids are experimentally evaluated. Results indicate that the shearing force can break up the clusters. Once achieving a dynamic equilibrium between cluster formation and cluster breakage, the instability of nanofluids can be controlled within 7.3% for the heating temperature range 140 °C–180 °C. Besides, the shear-flow stabilized nanofluids can keep dynamic stability and maintain high solar thermal conversion performance with an efficiency reduction of within 7% after cyclic tests under irradiation of 19 Sun for 24 h. The proposed method offers a practical path for stabilizing nanofluids under harsh conditions.