Thermal Analysis Research Articles

Electrospun hybrid microfibers for desiccant cooling/air dehumidification

The aim of this work was to assess the efficiency and suitability of hybrid adsorbent microfibers, produced by the electrospinning technique, in open-cycle adsorption applications, such as desiccant cooling, air dehumidification/humidification and heat storage, requiring high water adsorption capacity and high stability at high relative humidity, up to 80 %. Specifically, silica gel (SG) and magnesium sulfate (MS) as adsorbents and polyacrylonitrile (PAN) as polymer carrier, were used to prepare the hybrid microfibers at different concentrations of adsorbents and tested under isothermal conditions (50 °C) with relative humidity increasing from 0 % to 90 %. Characterization included morphological, structural, and thermal analyses, as well as measurement of ad/desorption isotherms and cyclic hydrothermal stability. The adsorption performances of the SG microfibers were comparable to that of the pure adsorbent: the microfibers with 50 w% silica gel showed a water absorption of 26.1 w% at 80 % relative humidity and T = 50 °C, which was in agreement with the content of SG. Under the same conditions, PAN microfibers with 50 w% MS achieved a water absorption of 42.7 w%. The dispersion of MS crystals in the microfibers improved the stability of the salt to hydration, allowing for a significant enhancement in the adsorption performance of magnesium sulfate.

Co-Amorphous Solid Dispersion System for Improvement in Dissolution Profile of N-(((1r,4r)-4-((6-fluorobenzo[d]oxazol-2-yl)amino)cyclohexyl)methyl)-2-methylpropane-2-sulfonamide as a Neuropeptide Y5 Receptor Antagonist.

Background/Objectives: Brick dust molecules exhibit high melting points and ultralow solubility. Overcoming this solubility issue is challenging. Previously, we formulated a co-amorphous system for a neuropeptide Y5 receptor antagonist (NP) as a brick dust drug using sodium taurocholate (ST) to improve its dissolution profile. In this study, we have designed a ternary amorphous system involving polymer addition to further improve a co-amorphous system. Methods: The amorphous samples were prepared by the ball milling. The thermal and spectroscopic analyses were performed, and the isothermal crystallization and dissolution profiles were evaluated. Results: The ball milling of NPs, ST, and each of the three types of polymers successfully converted crystalline NPs to amorphous NPs. Thermal analysis confirmed the formation of a single amorphous phase. The infrared spectra revealed a specific interaction between an NP and ST in the co-amorphous system. Moreover, the intermolecular interactions of NP-ST were maintained in the ternary amorphous systems, suggesting the miscible dispersion of the co-amorphous system into the polymer via weak interactions as co-amorphous solid dispersions. The dissolution profile of co-amorphous NP-ST was 4.1- and 6.7-fold higher than that of crystalline NPs in pH 1.2 and 6.8 buffers, respectively. The drug concentration in the ternary amorphous system in pH 1.2 and 6.8 buffers became 1.1-1.2- and 1.4-2.7-fold higher than that seen in the co-amorphous system, respectively. Conclusions: Co-amorphous solid dispersion is a promising method for enhancing the solubility of brick dust molecules.

Adaptability analysis of flow and heat transfer multi-scale numerical method for printed circuit heat exchanger

The printed circuit heat exchanger (PCHE) is a high-efficiency and compact mini-channel heat exchanger. Due to the large number of fine channels, it is difficult to conduct the flow and heat transfer numerical simulation of the entire heat exchanger based on the actual channels, which requires a lot of computational resource and time. In this paper, a simplified multi-scale numerical method with a non-equilibrium porous media model (NOPM) is proposed to study the flow and heat transfer performance of PCHE at high temperature and pressure. The pressure field, velocity field and temperature field of NOPM and actual multi-channel model (MC) under different working conditions are compared to study the adaptability of NOPM for the PCHE. The results indicate that the NOPM can accurately predict the flow and heat transfer performance under PCHE configurations with a large number of channels. However, as the channel number decreases, the relative errors in the temperature and pressure prediction significantly increase due to the increased flow maldistribution. Similarly, the NOPM can well predict the overall temperature distribution of the PCHE solid when the channel number is numerous. This work could support accurate thermal design, and provide accurate temperature field for the thermal stress analysis of PCHE.

Thermal Cycle Reliability of Copper Pillar Bumps in Advanced Fan-Out Packages

Thermal Cycle Reliability of Copper Pillar Bumps in Advanced Fan-Out Packages

Evaluation of heat transfer enhancement effect at the hot/cold end of a Stirling engine using performance improvement factor

The driving force of a Stirling engine comes from the heating expansion and cooling compression of working medium. The enhancement of heat transfer capacity of the hot/cold end is the key to improve the Stirling engine performance, while how to objectively evaluate the heat transfer enhancement effect is a precondition. Herein, a polytropic model of a Stirling engine thermal cycle process was firstly established. A method for evaluating the heat transfer enhancement performance under oscillating flow was proposed based on the efficiency and power improvement of a Stirling engine. This method was further used to evaluate the heat transfer enhancement effect of a novel four-leaf helical heating tube under oscillating flow, the efficiency and power improvement factor of which was reached 13.5 % and 6.1 %, respectively. The results show that the efficiency and power improvement evaluation criterion was more comprehensive and intuitive in evaluating the heat transfer enhancement performance under oscillating flow compared with the conventional evaluation indictor like performance evaluation criterion and equivalent tube length and tube number criterion.

B-195 Accelerating Molecular Diagnostics: Development of a novel Rapid, Integrated PCR System for Acute Respiratory Infections Detection

Abstract Background The COVID-19 pandemic and acute respiratory infections have underscored the necessity for high-throughput and timely molecular diagnostics. Existing molecular diagnostic methods are labor-intensive, a challenge particularly evident in large-scale testing. This study aims to streamline the nucleic acid testing process by integrating extraction and detection in PCR testing, thereby optimizing efficiency. Methods We developed 'EXP-160R', an integrated PCR system capable of rapid thermal cycling. This innovation employs advanced temperature control technology to markedly reduce heating, cooling, and annealing-extension times. The PCR reagent-kit (Zybio Inc.) was optimized to complement the instrument's capabilities, aiming for pathogen nucleic acid detection in acute respiratory infections within 25 minutes. The precision of in-tube temperature during rapid amplification was validated by using temperature-sensitive molecular probes in system development stage. Performance evaluation used the WHO International Standard for SARS-CoV-2 RNA to assess sensitivity and detection limits. We also analyzed 500 clinical samples from multiple Chinese hospitals, including 295 COVID-19 positives and 205 negatives, comparing the EXP-160R system's performance with an NMPA-approved PCR kit. Results The innovative system significantly improved PCR cycle times, enabling detection of 16 samples in 22 minutes and a throughput of 2400 tests per day, without compromising sensitivity or specificity. Validation confirmed a detection limit of 200 copies/mL, and the system achieved a 100% detection rate for medium and high viral load samples, with a coefficient of variation (CV) for Ct values ≤ 5%. Clinical trial comparisons with clinical standard diagnostics revealed a sensitivity of 98.05%, specificity of 100%, accuracy of 99.2%, and a Kappa coefficient of 0.984. When compared to the established PCR kit, our system showed comparable efficacy, with a sensitivity of 98.50%, specificity of 98.67%, accuracy of 98.6%, and a Kappa of 0.971. Conclusions The rapid PCR system represents a significant advancement in molecular diagnostics, offering rapid, high-throughput, and accurate detection of SARS-CoV-2. This system is particularly beneficial in urgent testing scenarios, such as airports and fever clinics. It addresses current pandemic needs and sets a new benchmark for future respiratory and infectious disease diagnostics, enhancing both efficiency and user experience.

Highly active and stable oxygen electrode PrBaCo2O5+δ-Ba2CoWO6 enabled by In Situ formed misfit dislocation interface for reversible solid oxide cell

The energy conversion efficiency and durability of the reversible solid oxide cell (RSOC) is restricted by the development of highly active and stable oxygen electrode. Herein, an in-situ formed composite PrBaCo2O5+δ-Ba2CoWO6 oxygen electrode is proposed, which consists of a highly active A-site double perovskite (A-DP) phase and a stable B-site double perovskite (B-DP) phase. Misfit dislocation interface is formed between these two phases, exerting lattice tensile stress on the A-DP phase, which enhances catalytic activity and inhibits Ba segregation. Additionally, the B-DP phase suppresses lattice expansion of A-DP phase through the dislocation interface, thereby improving thermo-mechanical stability. Consequently, the composite electrode demonstrates a low polarization resistance of 0.056 Ω cm2 at 650 °C, impressive stability at 650 °C for 500 h in symmetrical cell tests, and excellent thermal-mechanical stability under 29 thermal cycles. A maximum power density of 0.75 W cm−2 and an electrolysis current density of 0.84 A cm−2 at 1.3 V were achieved at 650 °C by the composite electrode on a 260 μm-electrolyte supported cell configuration, which surpass most of the reported oxygen electrode materials. Furthermore, the cell exhibits excellent operational stability, with low degradation rates of 0.49 × 10−1 mV h−1 and 1.5 × 10−1 mV h−1 in fuel cell and electrolysis cell modes, respectively. This work offers an effective method for designing highly active and stable oxygen electrodes for RSOCs.

Thermal Analysis of Infrared Heater as an Alternative Heat Source for Flexitank Application Using CFD

The heating pad was a mechanism for heating elements using steam as a heat source and heating the liquid inside a flexitank to liquidise for easy discharge completely. Alternative heat sources such as infrared, electric, and exothermic reactions may improve thermal performance for the heating process. Infrared heating is chosen for this study due to its efficient radiation heat transfer compared to conduction and convection. This study aims to determine the optimal infrared heater configuration to improve the time to liquidify fluid on the flexitank for easier discharge. Nine flexitank and infrared heater geometries were made using SolidWorks with different heater positions and heating element thicknesses. Each geometry was simulated using Ansys Mechanical to study the thermal performance of radiation heat transfer with three different heating element materials. The heat output and energy input obtained from the simulation were used to calculate heating time and energy efficiency, respectively. The effects of each parameter were studied to determine the best configuration of the infrared heater in terms of heating time, energy consumption and both. The results showed that the position of the heater plays the most crucial role in determining the heating time and energy consumption, as a heater position that produces a larger heated surface area on the flexitank can reduce heating time. The thickness of the heating element and its material contributes a minor impact on heating time and energy consumption. Increasing thickness would lower the heating time and increase energy efficiency if the thickness improves heat retention capabilities. Increasing material emissivity will increase the heating time. Higher conductive materials would use more energy compared to lower conductive materials. The heating time was improved by about 30% compared to a steam heating pad. Energy consumption was reduced by about 85% compared to a small steam generator. In conclusion, the infrared heater was a promising alternative as a heat source for flexitank applications.

Sustainable lignocellulosic mediterranean biocomposites: Thermogravimetric analysis, mechanical performance, morphological and comparative study

Utilizing accessible agricultural waste to create sustainable materials is a potentially beneficial attempt toward developing better bio-products and a more sustainable socioeconomic environment. Accordingly, this work aims to investigate the mechanical performance enhancement and/or deteriorations as well as morphological and thermal characteristics of certain Mediterranean lignocellulosic fiber composites considering various reinforcement conditions. Several composites of polypropylene pomegranate peel powder (PG) and short corn leaves (CL) were designed and fabricated with various reinforcement conditions to demonstrate their potential characteristics. Moreover, the experimental results of this work were compared with commonly used fiber/PP composites worldwide to demonstrate their appropriateness for producing bio-based composites suitable for various applications. The investigations included determining the tensile strength, tensile modulus, elongations at break properties under various reinforcement conditions, as well as revealing the thermal properties of the fibers to expose their suitability for such bio-based composites to improve utilizing such available waste of fibers into useful materials for various mechanical components. Thermal gravimetric analysis (TGA) and derivative thermal gravimetric analysis (DTG) were also carried out to examine thermal stability and to distinguish the maximum degradation temperature (Tmax) of the cellulosic fiber compositions. The outcomes revealed that both types of fibers, pomegranate peel powder and short corn leaves, had positive impacts on the tensile strength and modulus of PP regardless of the weight percentage. The 40 wt% of corn leaves displayed the best improvement in the strength (+29 %) and modulus (+17 %). The 40 wt%, CL-PP reached tensile modulus of 1589.5 MPa, whereas the best modulus for the PG-PP was 1399.4 MPa at 30 wt%. When comparing the tensile strength and modulus of PG/PP and CL/PP composites with those reported in the literature, these composites demonstrated superior tensile properties relative to thirteen other types documented. Regarding the thermal analysis, PG and CL fibers could withstand the processing temperature without degradation, which enables them to be feasibly utilized in bio-based composites to enhance the development of green bio-products. When it comes to the morphological analysis, it was observed that there was a good adhesion between PP and CL, which interprets the enhancement tensile properties.

Exploring barium-titanium-peroxo-hydroxide as an excellent single-source precursor for crystallographically diverse barium titanate ceramics – parametric study

Barium-titanium-peroxo type amorphous materials gained importance with the advent of wet-chemical methods for the production of crystalline perovskite barium titanate (BaTiO3) electroceramics. In this paper, the chemical nature of the barium-titanium-peroxo precursor was determined by means of elemental (EPMA), spectroscopic (FT-IR and FT-Raman), XRD and thermal (DSC and TGA/DTA) analyses. Several synthesis parameters such as the barium source, the peroxide treatment time, the reaction temperature and the reaction time were investigated. The precursor was also thermally treated at varying temperatures between 30 °C and 1000 °C. Relatively high reaction temperatures are detrimental to the Ba∙O∙Ti structure, resulting in plain TiO2 formation. Though relatively low temperatures (ice bath) are needed to suppress unwanted TiOCl2, ambient synthesis conditions and short reaction time (2 h) resulted in the desired single-source properties, i.e. amorphous Ba∙O∙Ti-peroxo structure with Ba/Ti ratio of unity (1.04 ± 0.04). The addition of an extra stirring step during H2O2 addition lowered the chance of carbonate incorporation in the precursor. Thermal analysis under air and nitrogen atmosphere was performed and a stoichiometric formula of Ba2,08Ti2O(O2)1,9(OH)5,3∙3,1H2O was calculated, which was in very good agreement with literature data. The barium-titanium-peroxo-hydroxide material proved to be an excellent single-source precursor. Phase-pure, highly crystalline and facetted, stoichiometric BaTiO3 particles with differently crystallographically oriented facets were obtained via the molten-salt solid-state method ({100} or {111} oriented facets) as well as the hydrothermal route ({100} oriented facets).

Application of indoor thermal energy cycle and visual communication simulation scene based on Machine vision and optical image enhancement

Traditional thermal analysis methods have limitations in complex environments, and innovative technologies are urgently needed to improve the accuracy of indoor thermal monitoring and optimization. In this paper, machine vision and optical image enhancement technology are combined to simulate the indoor heat energy cycle process to achieve more efficient heat management and visual communication, so as to improve the energy utilization efficiency and residential comfort of buildings. In this paper, a high-resolution camera is used to capture real-time images of indoor environment, image quality is enhanced by image processing algorithm, and heat distribution characteristics are extracted. The machine learning model is used to analyze the dynamic changes of the thermal energy cycle, and the visual model of the indoor thermal energy cycle is constructed by combining the fluid dynamics theory. The experimental results show that the proposed method can effectively identify and display the key areas of indoor heat circulation and their changing trends. The simulation results show that the optical enhanced images can show different temperature regions more clearly, directly reflect the heat flow situation, and have a high agreement with the actual measurement data. Therefore, the indoor thermal energy cycle simulation method based on machine vision and optical image enhancement not only improves the accuracy and real-time performance of thermal energy analysis, but also provides visual support for indoor environmental management.

Full-scale in-situ tests on a displacement cast in situ energy pile: Effects of cyclic thermal loads under different mechanical load levels on pile stress and strain

Numerous full-scale in situ tests have been conducted to assess the effect of thermal cycles on the pile response. However, those studies investigated the response of only precast and cast in-situ energy piles, with limited focus on the impact of the applied mechanical load on the pile response. This study presents the results of a field test conducted on a new type of energy pile, i.e. a displacement cast in-situ energy pile in multilayered soft soils, subjected to different fixed mechanical loads while undergoing simultaneous thermal cycles. Four tests were carried out, each corresponding to various axial loads ranging from 0 to 60% of the pile’s estimated bearing capacity. After applying the axial load on the pile head (0%, 30%, 40%, or 60% of the bearing capacity), the pile was subjected to up to ten thermal cycles. The highest magnitudes of thermal axial strains were observed near the pile top due to the lowest restraint provided by the made ground layer in all tests. Under zero (0%) mechanical load, the thermal axial strains near the pile head were elastic and recoverable, while residual strain was observed near the toe. Under reasonable working mechanical loads (30%, 40%, or 60%) residual strains were observed near both the pile head and the toe, with higher residual strains observed under higher mechanical loads. The results indicate that the cyclic thermal loadings could induce an increase in the compressive stress in the energy pile, attributed to the drag-down effects of the surrounding soil. The compressive stress induced by drag-down effects counteracts thermally induced tensile stress and thus leads to an insignificant effect on the energy pile during cooling. A limited impact of the shaft capacity was observed and was mainly attributed to the drag-down of the surrounding soil and thermal creep along the pile-soil interface.

Synergetic effect of diamond particle size on thermal expansion of Cu-B/diamond composite

Diamond particles reinforced Cu matrix (Cu/diamond) composites have promising applications for heat dissipation of high-power electronic devices because of their high thermal conductivity and suitable coefficient of thermal expansion. The effect of diamond particle size on thermal conductivity has been addressed; however, the effect of diamond particle size on thermal expansion still needs to be clarified. In this study, Cu-B/diamond composites with various diamond particle sizes ranging from 66 μm to 701 μm were fabricated to assess the impact of diamond particle size on the thermal expansion behavior. The composites exhibit low and adjustable coefficient of thermal expansion (CTE) values of 4.58–6.63 × 10−6 K−1, which align with 4–8 × 10−6 K−1 of widely employed semiconductors. The CTE of the Cu-B/diamond composites first decreases and then increases with increasing diamond particle size, which arises from a synergetic effect of interfacial bonding strength and matrix strengthening effect. As the diamond particle size is smaller than 272 μm, the interfacial bonding strength rises with increasing particle size, enabling the diamond particles to restrain the expansion of the Cu matrix more effectively and to reduce the CTE. As the diamond particle size exceeds 272 μm, the dislocation density in the Cu matrix continually decreases with increasing particle size, reducing the strength increment in the Cu matrix and increasing the CTE. The effect of thermal cycling on the thermal expansion of the Cu-B/diamond composites was also investigated, and all the composites show an increase in the CTE after 100 thermal cycles. Notably, the composite with 272 μm diamond particle size exhibits the lowest CTE increment. It shows a CTE value of 5.29 × 10−6 K−1 after thermal cycling, still compatible with the semiconductors for electronic packaging applications.

Effect of dimensional stabilization treatment on mechanical properties of 45% SiCp/Al composites

Abstract With 14μm SiC particles and 2024Al alloy as raw materials, 45% SiCp/Al composites were prepared by hot isostatic pressing method to study the effect of dimensional stabilization treatments on the mechanical properties of composites. The dimensional stabilization treatments used were divided into annealing heat treatment and cold and thermal cycle treatments, and the research method found that the primary annealing treatment decreased the bending strength from 694MPa to 639MPa, and the secondary annealing treatment decreased the bending strength from 863.69MPa to 605MPa. The bending strength decreased from 694 MPa to 639 MPa after the second annealing treatment, and further to 605 MPa after the second annealing treatment. The bending strength of the composites also decreased from 863.69 MPa to 836.16 MPa, and then to 855.54 MPa after solution aging due to the cold and thermal cycle treatments of 120°C to −20°C and 190°C to −196°C, respectively. The micro yield strength increased from 356.57 MPa to 402.66 MPa, and then to 476.03 MPa. The dimensional stabilization treatments included heat treatment, as well as cold and thermal cycle treatments. The cold and thermal cycle treatments further increased the brittleness of the composites after solution aging. Both annealing and cold and thermal cycling reduce the density of the composite, with the annealing resulting in a smaller reduction than the cold and thermal cycling.

Silicon nitride shadowed selective area growth of low defect density vertical GaN mesas via plasma-assisted molecular beam epitaxy

Ion bombardment during inductively coupled plasma reactive-ion etching and ion-implantation introduces irreparable crystalline damage to gallium nitride (GaN) power devices, leading to early breakdown and high leakage current. To circumvent this, a bi-layer selective area growth mask was engineered to grow up to 3.0 µm thick epitaxy of GaN using plasma-assisted molecular beam epitaxy as an ion-damage-free alternative to standard epitaxial processing routes. The masks and regrown architectures are characterized via SEM, conductive-atomic force microscopy (AFM), x-ray photo electron spectroscopy, Raman, and cathodoluminescence. Mask deposition conditions were varied to modulate and minimize the stress induced during thermal cycling. The resulting mesas exhibit low leakage, attributed to naturally terminated sidewalls as measured by an innovative perpendicular AFM measurement of the regrown sidewall. The regrown sidewall exhibited RMS (root mean square) roughness of 1.50 (±0.34) nm and defect density of 1.36 × 106 (±1.11 × 106) cm−2. This work provides a method to eliminate defect-inducing steps from GaN vertical epitaxial processing and stands to enhance GaN as a material platform for high-efficiency power devices.

Impact of atmospheric plasma spraying parameters on microstructure, mechanical properties and thermal cycling performance of YSZ coatings

Yttria-stabilized zirconia (YSZ) coatings are widely utilized thermal protective layers for metal and superalloy surfaces. These coatings are employed as thermal barrier coating (TBCs) to insulate metallic parts from higher thermal energy, thereby minimizing the cooling need for the topcoat ceramic layer. The choice of material is 7 wt% YSZ due to its exceptional capability to withstand challenging conditions characterized by extremely high temperatures and pressures, typically employed by the atmospheric plasma spraying (APS) in gas turbines, effectively extending their lifespan and improving performance. The deposition process of TBCs is significantly influenced by various spraying parameters, including gas flow rate and current (amp). These key parameters mutually play a significant role in controlling thermal stability, phase composition, and improved mechanical and microstructure properties. The aim of this research is to evaluate and contrast the impact of various spraying parameters on YSZ TBC performance. Accordingly, the influence of Hydrogen (H2), Argon (Ar) flow rate, and Current (amp) was investigated. Microstructure and elemental mapping studying was conducted using Field Emission Scanning Electron Microscopy FESEM/EDS and phase studying was examined with X-ray diffraction (XRD). Porosity was measured by IMAGE J software while hardness measurement was calculated by Vickers hardness tester. Additionally, thermal cycling tests were conducted between 700 °C and 1200 °C. The porous coatings exhibited poor performance, delaminating early during the tests. In contrast, dense coatings performed significantly better, enduring up to 140 cycles before failure.

Relationship between grain structure evolution and tensile anisotropy in Al-Zn-Mg-Cu cylindrical part formed by additive friction stir deposition

The thick-walled Al-Zn-Mg-Cu cylindrical part was obtained by additive friction stir deposition, and the relationship between grain structure evolution and tensile anisotropy was investigated in detail. The intra-layer grains are significantly refined due to continuous dynamic recrystallization (CDRX), and the grains at the interface are further refined by 30%-45% due to geometric dynamic recrystallization (GDRX). The early cracking and ductility deterioration under Z direction loading are caused by strain localization due to coarse and fine grain distribution and pre-existing strain at the interface. The grain growth rates for specific orientations (Cube, P, Q, and Rotated Goss) are higher than average, and the mismatch in elastic modulus between these grown grains and the matrix results in ductility differences in the X and Y directions. Texture components and residual stresses affect yield strength in the X and Y directions. Meanwhile, dissolution of η/η' and the coarsening of the particles due to the thermal cycling effect leads to a decrease in the yield strength in the building direction. The average ultimate tensile strength (UTS) and elongation (El) of the part could reach 370 MPa and 20%, respectively. The tensile properties of the as-deposited Al-Zn-Mg-Cu cylindrical part are generally higher than those of melt-based additive manufacturing, but lower than those of the extruded and forged states due to the dissolution and coarsening of the strengthening precipitates during thermal cycling.

Effects of electron beam and atomic oxygen irradiation on hypervelocity - Impact tested / polyimide coated carbon fiber-reinforced plates

In a low-Earth orbit, space debris orbit at approximately the first cosmic velocity. When space debris strike a spacecraft, ejecta (fragments) from the spacecraft are widely scattered. The reduction in the number of ejecta (fragments caused by impact) must also be considered when selecting spacecraft materials. The authors’ group has previously examined the size of ejecta (fragments) and reduction in the number of ejecta. In general, the mechanical properties of polymer materials and CFRP plates may be damaged by space environments, such as radiation (gamma rays and electron beams (EBs)), atomic oxygen (AO), ultraviolet rays, temperature, and thermal cycling. The authors suggested an anti-AO coating/polyimide CFRP as a material resistant to space environments. The effects of EB and AO irradiation on the fracture behavior and ejecta of anti-AO coating/polyimide CFRP were examined for hypervelocity impacts. The results of static three-point flexural tests were compared with the fracture behavior and ejecta. A two-stage light-gas gun was used for the impact tests. Spherical projectiles formed of aluminum alloy 2017-T4 with a diameter of 1.6 mm were used. Photographs of the ejecta scattered in front of each polyimide CFRP plate were captured from the side using a high-speed video camera. The number and weight of the ejecta on the front side and perforation holes were examined.

Insight into the effect of Gd-doping on conductance and thermal matching of CeO2 for solid oxide fuel cell

GDC (Gd-doped CeO2) play a dual role in solid oxide fuel cell (SOFC), effectively blocking the reaction between YSZ (Y2O3-doped ZrO2) electrolyte and high-performance cathode materials such as La0.6Sr0.4Co0.2Fe0.8O3-δ, and improving the low-temperature oxygen ion transport in composite cathodes. It is crucial to systematically investigate the influencing mechanism of Gd-doping on conductance and thermal matching of CeO2 for high-efficiency and stable SOFC. In this paper, the physical phase, morphology and electrochemical performance of Ce1-xGdxO2-δ (x=0.1, 0.15, 0.2, 0.25) were characterized, and the thermal matching between GDC and other cell components was investigated by finite-element thermal stress calculations and cold-heat-cycling tests. The results indicate that Ce0.8Gd0.2O2-δ obtains the optimum conductivity, whether in the low temperature segment affected by the grain boundary with the space charge layer, or in the activation energy controlled medium temperature segment. Moreover, the finite-element calculation shows that the thermal stresses of the electrolyte facing the barrier layer and the barrier layer facing the cathode decrease gradually with the increase of Gd-doping. Consequently, the cell with Ce0.8Gd0.2O2-δ applied to the composite cathode and the barrier layer presents the optimal output performance of 0.87 W⋅cm-2 at 750 °C, and the cell performance decreased by only 1.15% after 50 thermal cycles between 25-800 °C. This is significant for improving the long-term operational stability of SOFC under thermal cycling conditions.

The integrated performance of adaptive temperature control and temperature measurement of PTC materials with high thermal cycle repeatability

Abstract As the temperature increases, the resistance of the positive temperature coefficient (PTC) material becomes larger. Using this material can reduce the complexity of the temperature control system. In this paper, a new PTC material is developed by means of melt blending, which still has operable PTC characteristics after 60 high and low temperature cycles. The data points collected in multiple thermal cycles were fitted to obtain the relationship between the sample’s temperature and resistance. In addition, the integrated performance of adaptive temperature control and temperature measurement of PTC materials is proposed for the first time. Based on the prepared samples, the temperature control characteristics of PTC materials on the controlled object under different environmental conditions are studied experimentally, and the temperature value converted from the resistance value is compared with the temperature value measured by the platinum resistance. The results show that the prepared sample has good temperature control performance, and the material has an operable temperature measurement function in the PTC effect range.