Thermal Resistance Research Articles

Evaluating Recycled Concrete Aggregate and Sand for Sustainable Construction Performance and Environmental Benefits

This research investigates the potential of utilizing recycled concrete aggregate (RCA) and recycled sand (RS), derived from crushed concrete cubes, as sustainable alternatives in construction materials. The study comprehensively evaluates the properties of RCA and RS, focusing on workability, impact resistance, abrasion resistance, and compressive strength to determine their viability as substitute construction materials. A notable finding is RS’s enhanced fire and heat resistance when used as a fine aggregate in mortar blends, mixed with cement and Sinicon PP in a 3:1 ratio. The experimental analysis included thorough assessments of uniformity, durability, and curing time, alongside Scanning Electron Microscopy (SEM) for structural examination. Results show that RCA has an Aggregate Impact Value (AIV) of 5.76% and a Los Angeles Abrasion Value (LAA) of 21.78%, demonstrating excellent strength of the recycled aggregates. The mortar mix was also prepared using recycled sand, cement, and Sinicon PP, and its stability was confirmed through soundness tests, which resulted in a 0.53 mm expansion and a satisfactory consistency level of 44%. Ultrasonic pulse velocity (UPV) tests also indicated high-quality concrete formation using RCA and RS. SEM imaging corroborated this by revealing a bond between the cement paste and the aggregates. Incorporating RS and RCA in concrete mixtures impressively yielded a compressive strength of 26.22 N/mm2 in M20-grade concrete. The study concludes that using RCA and RS waste materials in the construction sector underlines that sustainable practices can be integrated without compromising material quality. This approach aligns with sustainable development goals and fosters a more environmentally friendly construction industry.

Ceramic Fiber-Reinforced Polyimide Aerogel Composites with Improved Shape Stability against Shrinkage.

Polyimide (PI) aerogels, renowned for their nano-porous structure and exceptional performance across a spectrum of applications, often encounter significant challenges during fabrication, primarily due to severe shrinkage. In this study, we innovatively incorporated ceramic fibers of varying diameters into the PI aerogel matrix to enhance the shape stability against shrinkage. The structure of the resulting ceramic fiber-reinforced PI (CF-PI) aerogel composites as well as their performance in thermal decomposition, thermal insulation, and compression resistance were characterized. The results revealed that the CF-PI aerogel composites dried by supercritical ethanol achieved greatly reduced shrinkage as low as 5.0 vol.% and low thermal conductivity ranging from 31.2 mW·m-1·K-1 to 35.3 mW·m-1·K-1, showcasing their excellent performance in shape stability and thermal insulation. These composites also inherited the superior residue-forming ability of ceramic fibers and the robust mechanical attributes of PI, thereby exhibiting enhanced thermal stability and compression resistance. Besides, the effects of different drying conditions on the structure and properties of CF-PI aerogels were also discussed. The coupling use of supercritical ethanol drying with the addition of ceramic fibers is preferred. This preferred condition gives birth to low-shrinkage CF-PI aerogel composites, which also stand out for their integrated advantages include high thermal stability, low thermal conductivity, and high mechanical strength. These advantages attribute to CF-PI aerogel composites substantial potential for a wide range of applications, particularly as high-performance thermal insulation materials for extreme conditions.

Cost-effective enhancement of high viscosity modified bitumen anti-aging properties using organic layered double hydroxide/fume silica nanoparticles composite nanomaterials

High-viscosity modified bitumen (HVMB) is prone to thermal-oxidative and photooxidative aging, resulting in pavement diseases. The use of conventional Nano-modifiers to enhance the aging resistance of bitumen is often hindered by high costs, limiting their adoption in widespread applications. This study aims to evaluate the impact of a cost-effective Multi-Dimensional Nano-Composite (MDNC) modifier on the durability of HVMB, which includes organically modified Layered Double Hydroxides (OLDHs) and Fumed Silica Nanoparticles (FSNPs). Additionally, Zero-Dimensional Nanomaterials (ZDNs) such as FSNPs, Nano-SiO2, or Nano-TiO2, in combination with various MDNC modifiers consisting of OLDHs and ZDNs, were also utilized as comparative anti-aging modifiers for HVMB binders. FTIR, XRD, and contact angle tests indicate that LDHs modified with KH560 (OLDHs) exhibit improved hydrophobicity and increased interlayer distance. The temperature sweep test of the unaged binders and the FESEM test of the Nano-modifier indicate that the branched network structure of the FSNPs significantly enhances the high-temperature elasticity of the HVMB binders. Rheological test results have shown that both ZDNs and MDNC modifiers can delay the changes in rheological parameters after aging. Combining FTIR and SARA (Saturates, Aromatics, Resins, Asphaltenes) results, it was found that the combination of OLDHs/FSNPs synergistically inhibited the increase in the content of heavy components in bitumen during thermal oxygen and ultraviolet aging. The enhancement of the HVMB's thermal oxidation aging resistance by OLDHs/FSNPs composite modifiers is primarily due to the multidimensional structure of the composite nanomaterial, which effectively prevents the penetration of oxygen molecules. Meanwhile, the improvement in resistance to ultraviolet aging is mainly due to the absorption and scattering characteristics of FSNPs. Therefore, OLDHs/FSNPs are demonstrated to be a cost-effective multidimensional nano-modifier.

An analysis of the impact of nanofluids on the cooling effectiveness of pin and perforated heat sinks

In the presented numerical study, the effect of the use of mono and hybrid (CuO/Water at 2% volume concentration and CuO + Fe/Water (1% CuO + 1% Fe)) type nanofluid in heat sinks designed in new geometric structures used to increase the processor cooling performance was investigated. The geometries used are circular, triangular, square, hexagonal, square, and hexagonal, and their perforated structures and their effects on a total of eight geometries were analyzed. In addition to these, the rate of improving the temperature distribution and heat transfer in the heat sink, i.e., the Performance Evaluation Criterion (PEC), was also examined. According to the results obtained, the lowest thermal resistance value is seen in the circular cross-section with Rth = 0.289 K/W, while the highest thermal, i.e., cooling performance is seen in the triangular perforated structure with Rth = 0.63 K/W and at the lowest pressure inlet condition. In terms of temperature distribution, the most uniform distribution was obtained between 311.82 and 308.98 K in the circular section. The most interesting result in terms of the results was the PEC = 1.4 for the triangular hole structure in the heat transfer improvement performance. The main reason for this is that the range of the temperature distribution shown is very high (319–311.5K).

Biomimetic porous wick with efficient fluid transport and excellent heat transfer for loop heat pipes

The porous wick, as a core component of the loop heat pipe (LHP), serves as a source of circulation power. Inspired by the transport system of plant vessels, a radially stacked polyethersulfone (PES) porous wick was designed using PES membranes with an anisotropic porous structure. The PES membranes exhibited excellent capillary force and high permeability. However, the supply capacity of the axially stacked wick was far inferior to that of sintered wick due to the problem of contact gaps and pore misalignment between layers. From the bionic point of view, a laminar winding special transport structure, which is perpendicular to the direction of liquid transport was proposed. The method effectively avoids the adverse effects of gap and pore misalignment on liquid transport. Combining experimental and simulation methods, the heat transfer characteristics and liquid transport characteristics of the radial stacking polyethersulfone wick (RPES) were studied and compared with those of traditional axial stacking polyethersulfone wick (APES) and sintered nickel wick. The results showed that the heat transfer performance of RPES-LHP was significantly improved, with the heating surface temperature maintained at 54.1 °C and thermal resistance of 0.095 °C/W under a heat load of 400 W, which was respectively 26.6 °C and 0.066 °C/W lower than that of the APES-LHP. The evaporator thermal resistance of RPES-LHP also ranked among the top in existing research on wicks. Simulation results indicated that the radial stacking method avoided capillary force weakening and flow resistance increase caused by gap and pore misalignment, thereby enhancing the supply capacity of RPES. The concept of regulating the stacking orientation of the wick to be perpendicular to the direction of liquid transport can strengthen the supply capacity and provide light on the design of porous wicks in the future.

Topological and multi-objective optimization of single-phase heat transfer and energy efficiency using manifold micro-channels for high-power electrics cooling

To achieve energy-efficient cooling of high-power electrics, present work demonstrates combined methods using topological design and multi-objective optimization to reconstruct manifold micro-channels (MMC). The micro-channel domain is first topologized by density-based method under pressure drop and energy dissipation constraints. The multi-objective optimization is subsequently applied to optimize structure and operating parameters of reconstructed MMC using kriging model and genetic algorithm. The simulation results show that favorable thermal performance is obtained in the topological MMC with branch-channels, pin fins and root-channels, increasing average heat transfer coefficient by 19.4 % compared to conventional MMC. For the optimal flow rate, the lowest total thermal resistance (Rtotal) of 0.17 KW−1 is obtained for the optimized-topological MMC at a pumping power (Pp) of 9.53 mW, meanwhile the maximum temperature-rise is decreased by 15.2K. Furthermore, an extensive benchmark of different single-phase micro-fluidic cooling technologies is performed. For an extremely low Rtotal of 0.2 KW−1, present optimized-topological MMC only requires Pp of 3 mW, which is 11.7 times, 26.7 times and 70 times lower than that of conventional MMC, pin-fin and strip-fin micro-fluidic systems. This superior hydro-thermal performance successfully manages the heat flux of 100 W/cm2 to 400 W/cm2 with cooling coefficient of 104 to 107, significantly outperforming other micro-fluidic cooling technologies.

Hydrothermal analysis of parallel and symmetric microchannels with phase change slurry and porous fin designs

The dynamic information of microchannel systems with parallel and symmetric configurations is insufficient, which limits our ability to compare and optimize these systems in all directions. In this study, thermal and hydraulic characteristics in parallel and symmetric microchannel heat sinks (MCHSs) with porous fins cooled by phase change slurry are investigated. A 3-D steady state conjugate model is adopted to compare the effects of fin configuration, coolant type and structural parameters on hydrothermal properties of wavy MCHS. The variations of dimensionless parameters involving Nu, f, η (temperature control effectiveness) and PEF (performance evaluation factor) are considered to demonstrate the effectiveness of combined design on overall performance enhancement of wavy MCHS. Results indicate that lower temperature increment and higher pressure loss appear in wavy configuration with porous fins than in straight mode, and lowest thermal resistance arises in parallel porous fin design. At the narrow position of symmetric channel, the fluid changes from the low-speed drop-shaped micelle to high-speed bullet-shaped one with increasing A, which leads to higher Nu with larger pressure drop penalty. Due to the extended flow route and improved fluid mixing, η increases with decreasing wavelength in all cases, and η of porous microchannels with both phase change slurry and parallel fins is much larger than that of symmetric one and the one with only base fluid. Compared with wavy fin configurations with small and large ε, lower temperature and its more uniform distribution happen in the mode with medium porosity. In comparison with basic configuration, the parallel configuration with slurry as cooling medium has the maximum PEF value when the pore size is 0.14 mm, up to 1.64. Larger f increase occurs in wavy channel with increasing N, and the space shortening between adjacent channel cavities in symmetric mode makes the adjoining Dean vortices easier to contact and repel, thus making it appear larger rise of f than parallel mode. Compared with other channel parameters, it is not effective to improve the overall performance of wavy MCHS with porous fins by adjusting α. Overall, the throat effect of symmetric MCHS significantly occurs in channel configuration with larger A, bigger λ, lower ε, smaller dp, more N, and lesser α, leading to higher f rise than the parallel mode.

Monofilaments of isosorbide-based tetrapolyesters with enhanced (bio)degradability prepared by a solid-state drawing process: Synthesis and struture-property relations

To enhance the degradation rate of poly (butylene adipate-co-terephthalate) (PBAT) in the natural environment and to investigate the effect of modified monomers on the molding and structure of copolyester fibers, a series of isosorbide modified PBAT (PBIAT) tetrapolyesters were synthesized and monofilaments were prepared by solid-state drawing in this work. The experimental results revealed that the introduction of isosorbide formed a partial block structure in the molecular chain, and that a significant improvement in the properties of heat resistance and degradability of the copolyester was observed with the introduction of isosorbide. In the research of fiber forming and structure-property relationship by isosorbide, it was found that although the monofilament orientation process was affected by the V-shape structure of isosorbide, the change of the crystal structure under stress was similar to that of polybutylene terephthalate (PBT). The PBIAT monofilaments showed a decrease in the strength at break affected by the introduction of isosorbide but they still met the requirements for textile applications.

Mechanical properties and thermal shock resistance of TiB2‒B4C composite ceramic tool materials at microscopic scale

AbstractA finite model incorporating microstructure was developed to investigate the thermal shock resistance of TiB2‒B4C composite ceramic cutting tool materials. Numerical simulations were conducted to analyze changes in the transient temperature field and thermal stress field during the thermal shock process. TiB2‒B4C composite ceramic tool materials were fabricated using discharge plasma sintering technology. With different B4C contents, different sintering temperatures and holding times as study variables, optimization of the sintering process parameters and ceramic material components was achieved through testing the mechanical and microscopic morphology of the ceramics. Thermal shock water quenching experiments were performed, and the strength‐decay method was employed to assess the thermal shock resistance of TiB2‒B4C ceramics. The findings indicate that the optimal sintering conditions are temperature of 1700°C and holding time of 5 min. The TiB2‒B4C ceramic material containing 20 vol% B4C exhibits superior comprehensive mechanical properties and thermal shock resistance, and its relative density, fracture toughness, hardness, and flexural strength were 99.3%, 6.8 MPa m1/2, 22.8 GPa, and 598 MPa, respectively. The critical thermal shock temperature difference falls within the range of 400°C‒500°C.

Comparative Study between Multiwall Carbon Nano Tube and Carbon Waste from Aluminium Production in the Preparation of Thermally Stable Cementitious Mortar

Objective: The objective of this study is to conduct a comparative investigation into the performance of multiwall carbon nanotube (MWCNT) and carbon wastes (C-waste) derived from the aluminum industry in the creation of thermally stable cementitious mortar. Specifically, the research aims to assess their impact on compressive strength and thermal stability, with a focus on identifying the superior additive for enhancing the properties of cement mortar. Methods: Cement mortar is produced using a blend of CEMIII cement and sand passing through a 1 mm sieve. Various ratios of MWCNT and C-waste, ranging from 0.1% to 0.7%, are incorporated into the mixture. Compressive strength tests are conducted at different intervals, up to 90 days, to evaluate the effects of additives on strength enhancement. Additionally, the resistance to high temperatures is examined by subjecting the mortar samples to firing temperatures up to 700 degrees Celsius. Results: The inclusion of both MWCNT and C-waste leads to improvements in compressive strength values, with the most significant enhancement observed at 0.1% concentration, resulting in approximately 70MPa and 75MPa at 90 days, respectively. Notably, C-waste demonstrates superior physical and mechanical properties compared to MWCNT, along with a lower production cost. Moreover, both additives exceed the specified limits for thermal resistance in mortar, achieving measurements of about 60MPa for MWCNT and 63MPa for C-waste when exposed to firing temperatures of 700 degrees Celsius. These results highlight the higher thermal stability of C-waste relative to MWCNT. Conclusion: In conclusion, this study confirms the efficacy of utilizing C-waste as an additive in cementitious mortar production, showcasing its superior performance over MWCNT in terms of compressive strength enhancement and thermal stability. The findings underscore the potential of repurposing industrial by-products such as C-waste to improve material properties while also addressing environmental concerns and reducing production costs in construction applications.

Effect of contact thermal resistance and skeleton thermodynamic properties on solid-liquid phase change heat transfer in porous media: A simulation study

Phase change materials (PCMs) have the potential for heat storage and release, but low thermal conductivity limits their wide application in thermal systems. This work proposes a mathematical model to simulate the freezing process of water in porous media. Unlike traditional methods that solve for two temperatures in different materials, the hybrid finite element method computes a single temperature satisfying the jump on the interface. The effect of contact thermal resistance and skeleton parameters on solid-liquid phase change heat transfer was investigated. This model was validated by experiments in reference. Results show that increased contact thermal resistance decreases temperature gradient, phase interface deflection and freezing rate. Specifically, with contact thermal resistance of 0.0001 K/W, 0.0005 K/W, and 0.001 K/W, freezing rates decrease by 36.4 %, 52.35 %, and 54.14 %, respectively, compared to the case without resistance. Although the contact thermal resistance reduced the temperature gradient, it stabilized the phase change process. Moreover, higher thermal conductivity of the skeleton enhances the freezing rate. However, after a certain value is reached, the rate increases only marginally. Skeletons with lower density and specific heat capacity are favorable to enhancing phase change heat transfer.

Enhancement in thermo-hydraulic performance of ceramic-based disk heat sink with fractal micro-channels via double layering, hybrid nanofluids, and cross-sectional convergence

The focus of this paper is to further improve the thermo-hydraulic performance of a disk heat sink with fractal-like microchannels by introducing four distinct modifications: incorporating convergent cross-sections in microchannels, implementing double layering, utilizing a high-conductivity material (AlN ceramic) for the heat sink, and integrating hybrid nanofluids. Hybrid nanofluids, encompassing Aluminum Oxide-Graphene, Aluminum Oxide-Copper, and Copper-Graphene, each with varying volume fractions and an overall volume fraction of 2 % and 4 %, were systematically evaluated. The cumulative impact of these modifications on the four levels fractal-like microchannel heat sink's thermo-hydraulic performance was rigorously assessed through numerical simulations. The flow rate ranges from 300 to 600 ml/min, corresponding to an inlet Reynolds number in the range of 3014 to 6018.The findings reveal that the increase around 10 % in Nusselt number can be achieved through implementing converging cross-sections at levels 3 and 4. Substituting silicon with AlN ceramic leads to a reduction in maximum temperature from 1.85 to 2.58 ℃, depending on the flow rate. Under a heat flux of 40 W/cm2, double layering can reduce thermal resistance by 0.2. Most effective configuration involves a double-layered fractal microchannel with convergent cross-sections at levels 3 and 4, employing AlN ceramic as the material, and utilizing a hybrid water-based nanofluid with a volume fraction of Cu 3 %-Al2O3 1 %. This configuration achieves a notable reduction in maximum temperature by 11.1 °C and 17.97 °C under heat fluxes of 40 and 80 W/cm2, respectively, at a volumetric flow rate of 300 ml/min.

Effects of compound compatibilizer and CaTiO3 filler on the properties of polypropylene/polyphenylene ether/glass fiber composites

AbstractThe present study used polyphenylene ether/Polypropylene/glass fiber (PPO/PP/GF) composites as the matrix material to obtain the dielectric plate material to be used in the dielectric phase shifters for 5G base stations. First, the reinforcement effect of the compound compatibilizers comprising PP‐g‐MAH and SEBS‐g‐MAH on the PPO/PP/GF composites was investigated. The experimental results revealed that the compound compatibilizers could dramatically improve the compatibility and performance of the PP/PPO/GF composites through synergistic compatibility. Next, the crystallization effect of CaTiO3 fillers on the PPO/PP/GF composites was investigated. The DSC analysis revealed that using a small amount of CaTiO3 promoted the crystallization of PP, while using a large amount of CaTiO3 inhibited the crystallization effect. At a compatibilizer content of 6 wt% and CaTiO3 in the range of 10–85 wt%, the CaTiO3/PP/PPO/GF composite presented a continuously adjustable dielectric constant (εr = 2.32–20.9), low dielectric loss (tanδ < 0.0019), and high heat resistance (VST = 169.5–177°C), and could, therefore, be used as a dielectric plate material in the dielectric phase shifters for 5G base stations.Highlights The compound compatibilizers comprising PP‐g‐MAH and SEBS‐g‐MAH could dramatically improve the compatibility and performance of the PP/PPO/GF composites through synergistic compatibility. A small amount of CaTiO3 promoted the crystallization of PP and a large amount of CaTiO3 inhibited the crystallization effect. The CaTiO3/PP/PPO/GF composites could serve as ideal dielectric plate materials in the development of dielectric phase shifters for 5G base stations.

Fabrication of sodium lignosulfonate/waterborne polyurethane composites with high biological content to enhance mechanical properties and UV resistance

The conversion of sodium lignosulfonate (SL) into high-value functional materials remains challenging. Hereon, a bio-based waterborne polyurethane (WPU) was synthesized using castor oil and isophorone diisocyanate as the raw materials. SL was used as a functional filler to prepare transparent or translucent composites of sodium lignosulfonate/waterborne polyurethane with good properties through physical blending method. The influence of varying SL contents on the performance of composite emulsions and films were studied. The results indicated that the composite derived from bio-based materials had an occupancy rate of 89.5 %, and all composite emulsions exhibited outstanding storage stability. Interestingly, the addition of sodium lignosulfonate greatly improved the mechanical properties and heat resistance due to the strong interfacial interaction between WPUs and SL molecular chains. Furthermore, the composite film could achieve complete UV shielding performance when the sodium lignosulfonate content reached 9 wt %. This work had significantly expanded the range of high-value-added applications for lignin and potential prospects for its use in the field of sunscreen coatings.

Insights into optoelectronic, thermodynamic, and thermoelectric properties of novel GePtCh (Ch = S, Se, Te) semiconductors: first-principles perspective

Ternary chalcogenides are often studied for their remarkable heat resistance and flexible optical properties. We used density functional theory and examine complicated connections between the various physical features of the exclusive GePtCh (Ch = S, Se, and Te) ternary chalcogenides. The valence band is formed by the hybridization of the Ge-s/p/d, Pt-s/p/d, S-p, Se-p, and Te-p orbitals in the energy range of −6.0 eV to 0 eV. The materials under consideration are confirmed as indirect bandgap materials with estimated energy gaps of 1.29 eV, 0.86 eV, and 0.48 eV, respectively. By substituting Se and Te for S reduced the bandgap in these materials. The complex dielectric function’s components, absorption coefficients, real optical conductivity, energy loss functions, refractive index, reflectivity, and extinction coefficient, are studied and examined to identify their potential use in optoelectronic applications. The thermodynamic parameters of these ternary systems are calculated by employing the quasi-harmonic Debye model. The materials are suitable for thermoelectric devices, as evidenced by their considerable and outstanding thermoelectric features. The GePtTe possessed the highest absorption, indicating that it is a suitable material for the use in optoelectronic applications.

The performance promotion of polyphenylene sulfide fibers based on the electron beam irradiation

To give full play to the good performance of polyphenylene sulfide (PPS) fiber, electron beam irradiation was used to promote the property of the PPS fiber. The fibers were irradiated at different doses, and changes in structure and property of PPS fibers were analyzed by X-ray diffraction, moisture regain, heat resistance and thermo-gravimetric analysis. The strength of the specimen increased from 3.75 cN dtex−1 to 3.88 cN dtex−1 at 10 kGy and then decreased. And the elongation of the irradiated fibers decreased after irradiation. The crystalline shape of the fibers did not change and the crystallinity increased from 57.3% to 59.4% and then decreased. Irradiation had the good effect on moisture regain and heat resistance. The moisture regain of PPS fibers increased from 0.28% to 0.74% after 60 kGy irradiation which was 2.6 times of the initial fibers. After heating at 150 °C for 2 h in an oven, the mass loss ratio of the fibers decreased from the original 9.96%–4.97% at 10 kGy dose which was helpful to the application of PPS fiber in high-temperature fields. At the same time, it could be seen from TG data that the maximum loss rate temperature of fibers rose from the initial 526.6 °C–532.7 °C.

Unveiling the temperature-dependent mechanisms of viscoelasticity of sand-enhanced epoxy

The viscoelastic behavior of epoxy is critical for its engineering performance and applications. This work focuses on the improvement of its viscoelastic performance by using natural sand particles as fillers. Experiments are carried out to investigate the static and dynamic viscoelastic properties of epoxy with various sand particles content. Static mechanical tests demonstrated an increase in the elastic modulus, albeit at the cost of reduced strength at higher sand content due to stress concentrations. Dynamic tests indicated substantially improved storage modulus and damping of epoxy after being filled with the sand particles. Moreover, the glass transition temperature of the epoxy shows a substantial rise upon the addition of sand particles, signifying an augmentation in its heat resistance. Static viscoelastic characterization revealed an elevation in both room and high-temperature relaxation moduli upon incorporating sand. By applying time-temperature superposition principles, long-term relaxation curves are obtained, which can provide a reference for engineering design. These viscoelastic investigations offer insights into the underpinning mechanisms governing the performance of sand-reinforced epoxy. This enables the rational design of sand particle reinforced epoxy for customized durability, heat resistance, and vibration damping.

Heat flow topology-driven thermo-mass decoupling strategy: Cross-scale regularization modeling and optimization analysis

The liquid desiccant dehumidification (LDD) is both eco-friendly and highly effective in humidity control, widely investigated across diverse angles. This study expands the application of the newly devised heat current method to examine the liquid desiccant dehumidification process. It introduces a new regularized temperature, which includes using a heat flow topology driven thermo-mass decoupling strategy, and constructing the heat current model by defining both the thermal resistance and moisture resistance. It significantly extends the application of the heat current method, clarifying the thermo-mass coupling energy transfer mechanism. The findings indicate that key factors influencing system performance indicators include total thermal conductivity (αA), solution mass flow rate (ms), air-solution mass flow rate ratio (RA/S,D), and heat source temperature (tH). Furthermore, under the influence of distinct thermal conductivities, the optimal output values for performance indicators, including moisture removal rate, exergy efficiency and entransy efficiency, are determined as 8.4 g/s, 71.2%, and 12.3%, respectively. The results of synergistic influence analysis reveal that, for the performance indicator entransy efficiency, msand RA/S,D display a significant degree of synergistic influence, resulting in a strong positive effect and benefiting 68.53% of the total area. Multi-objective optimization indicates a trade-off relationship among the system performance evaluation indicators moisture removal rate, exergy efficiency and entransy efficiency, with optimal solution values of 3.25 g/s, 65.92%, and 12.01%, respectively.

Cloning and functional verification of the CmHSP17.9 gene from chrysanthemum.

Small molecular heat shock proteins (sHSPs) belong to the HSP family of molecular chaperones. Under high-temperature stress, they can prevent the aggregation of irreversible proteins and maintain the folding of denatured proteins to enhance heat resistance. In this study, the CmHSP17.9-1 and CmHSP17.9-2 genes, which were cloned from chrysanthemum (Chrysanthemum×morifolium 'Jinba') by homologous cloning, had a complete open reading frame of 480 bp each, encoding 159 amino acids. The protein subcellular localization analysis showed that CmHSP17.9-1 and CmHSP17.9-2 were located in the cytoplasm and mostly aggregated in granules, especially around the nucleus. Real-time quantitative PCR (qRT-PCR) analysis showed that the relative expression level of the CmHSP17.9-1 and CmHSP17.9-2 genes was highest in the terminal buds of the chrysanthemum, followed by the leaves. CmHSP17.9-1 and CmHSP17.9-2 overex-pression vectors were constructed and used to transform the chrysanthemum; overexpression of these genes led to the chrysanthemum phenotypes being less affected by high-temperature, and the antioxidant capacity was enhanced. The results showed that chrysanthemum with overex-pression of the CmHSP17.9-1 and CmHSP17.9-2 genes had stronger tolerance than the wild type chrysanthemum after high-temperature treatment or some degree of heat exercise, and overex-pression of the CmHSP17.9-1 gene led to stronger heat resistance than that of the CmHSP17.9-2 gene, providing an important theoretical basis for the subsequent molecular breeding and pro-duction applications of chrysanthemum.

Thermoplastic polyimide with good comprehensive performance based on carbazole groups and short flexible linkages

AbstractThermoplastic polyimides (TPIs) can meet the requirements of advanced electronic packaging such as flexible copper clad laminate (FCCL) applied under extreme conditions, attributed to their excellent thermal stability, mechanical properties, electrical insulation and chemical resistance. With the increasing demands for electronic devices, such as applications in high‐frequency communication, it is highly desirable to develop high‐performance TPI with good thermoplasticity, thermal stability, mechanical properties and dielectric properties. However, there is a trade‐off between thermoplasticity and other properties. Herein, we introduce an effective strategy to afford TPIs with good performance by copolymerization of a diamine monomer consisted of a coplanar aromatic carbazole group and a short flexible linkage methylene group. On the one hand, short flexible linkages help improve the flexibility of polymer chains and are not too much to enable small‐scale molecular motions below Tg. On the other hand, coplanar aromatic donor groups benefit to strong charge transfer complex (CTC) interaction and π‐π stacking interaction. Based on this strategy, the resultant TPI possesses good thermoplasticity with a proper Tg of 348 °C. Meanwhile, it preserves a low coefficient thermal expansion of 48 ppm K−1, low dielectric constant/dielectric loss factor of 3.27/0.0073 at 10 GHz, and tensile strength of ca. 78 MPa.