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991.
《Ceramics International》2023,49(20):32470-32477
The increasing miniaturization and densification of electronic components have increased the demands for efficient heat sinks to dissipate the dense heat generated by these small components. However, owing to the limitations of the substrate material of heat sinks, optimizing the fin structure and its arrangement to enhance heat conduction and convection remains a challenge. In this study, the temperature change of hot water in a 304 steel barrel with and without a La0.9Ca0.1Al0.9Fe0.1O3 (LAF) coating was studied. The results demonstrated that the cooling rate of hot water in the barrel coated with LAF coating increased by 28%. Furthermore, a high-emissivity LAF ceramic coating (0.91) was applied to an aluminum heat sink, and the heat transfer performance of the heat sink with and without the LAF coating was studied. The experimental results showed that the equilibrium temperature of the LAF-coated heat sink was reduced by ∼8 °C. Additionally, the LAF coating increased the total heat transfer coefficient by 20% and reduced the thermal resistance by 18%. The proportion of radiation heat transfer on the surface of the heat sink increased with the LAF coating, which accounted for 44% of the total heat transfer coefficient. Thus, LAF coatings have the potential to effectively improve the heat-transfer performance of thermal devices with different metals. 相似文献
992.
《International Journal of Hydrogen Energy》2023,48(46):17677-17688
As the only carbon-free energy carrier without CO2 emission upon decomposition, ammonia is an ideal storage medium for H2. However, the current low efficiency of ammonia synthesis is a main challenge on intermediate-temperature proton-conducting electrochemical cells. Herein, we develop a novel non-precious cathode catalyst consisting of Fe nanoparticles loaded on two-dimensional MXene nanosheets (Fe@MXene) that can achieve a high Faradaic efficiency of 8.4% and an NH3 yield of 8.24 × 10−9 mol. s−1·cm−2 on an anode-supported Ba0·95Ce0·6Tb0·1Y0·2Zr0·1O3-δ-based electrolyte. The resultant catalyst with high specific surface area and catalytic active sites is beneficial to N2 reduction, resulting from the effective activation of N2 molecules imposed by the transported protons. The mechanism of catalytic NRR reveals that Fe@MXene catalyst can increase the electrocatalytic efficiency because of the improvement in the reaction rate constant. These show a promising catalyst of Fe@MXene for N2 reduction reaction using intermediate-temperature proton-conducting solid oxide cell. 相似文献
993.
《International Journal of Hydrogen Energy》2022,47(2):1092-1102
Multiple energy sources are combined to solve the shortage due to more and more energy consumption. Hydrogen as an ideal clean and renewable energy was injected to the porous media burner to realize the utilization with methane simultaneously. The numerical model of double-layer structure imported with multi-step kinetics mechanisms was built to study the effects of hydrogen injecting position and width on the combustion characteristics of methane after the experimental validation. Results indicate that the axial temperatures during the hydrogen injection at the upstream and interface positions were obviously higher than that at the downstream position. With the increasing of hydrogen injection width, the overall temperature gradually decreased, which was corresponding to the decreasing trend of CO and NOx emissions. However, the temperature and pollutant emissions increased as the equivalence ratio of methane and hydrogen increased. In addition, the increasing of methane and hydrogen velocity increased the CO emission and decreased the NOx emission. 相似文献
994.
《International Journal of Hydrogen Energy》2021,46(57):29216-29229
The objective of this study is to develop ceramic supports employed in the preparation of catalytic membrane reactor using less catalyst and lower temperature and enabling H2 production and separation together through the dry reforming of methane. For this reason, nine different ceramic supports are fabricated by using three different types of activated alumina (acidic, basic and neutral) and three different Si/Al molar ratios at two different calcination temperatures in order to investigate the surface acidity and basicity effect of supports to be used with impregnated Rh catalyst for rising the activity to CH4, CO2 and sensitivity to coke formation encountered with Ni-based catalysts. Subsequently, the effect of those variations on supports is determined by using XRD, SEM and BET instruments, in addition to this, H2 permeability test of five supports having high BET surface areas is also performed with using constant volume-variable pressure technique at the temperatures of between 25 and 250 °C. Acidic alumina sintered at 600 °C and containing Si/Al ratio of 0.648 represented the highest hydrogen permeability with higher activity, whereas, neutral alumina calcined at the temperature of 600 °C having Si/Al ratio of 0.555 gave the highest activity with the lower hydrogen permeability, while basic alumina sintered at the temperature of 600 °C and including Si/Al ratio of 0.648 imparted lower activity with higher hydrogen permeability. 相似文献
995.
《International Journal of Hydrogen Energy》2021,46(67):33594-33600
The aim of the present study is to enhance the performance of a microbial fuel cell (MFC) design by making simple interventions. Specifically, terracotta “t” and mullite “m” ceramics are tested as membranes while carbon veil and carbon cloth are used as electrodes. In the case of “m” cylinders different dimensions are examined (m: ID 30 mm x height 11.5 mm; sm: ID 18 mm x height 18 mm). The units operated continuously with urine as the feedstock. The best performing is the sm type (60–100 μW), followed by the t type (40–80 μW) and the m type (20–40 μW). Polarisation experiments indicated that activated carbon on the anode enhances the power output (t: 423 μW, sm: 288 μW). Similarly, the increase of the surface area and the addition of stainless steel mesh on the cathode improves the power performance for the “sm” and the “t” units. Furthermore, it is shown that the design with the smaller internal diameter, performs better and is more stable through time. 相似文献
996.
《International Journal of Hydrogen Energy》2021,46(75):37429-37439
An effective strategy for generating combined heat and power (CHP) systems is to use the combustion of hydrocarbons to provide fuel reforming and heat production for solid oxide fuel cell (SOFC) operation. Though tubular SOFCs (tSOFCs) are well suited to the thermal cycling associated with combustion systems, they have a geometric limitation which requires significant alteration to the combustion chamber. These alterations can be eliminated by producing an anode supported internal cathode-tSOFC (IC-tSOFC) which can be directly integrated into the chamber with minimal alterations. Novel methods used to produce IC-tSOFCs are discussed in this work. Scanning electron microscopy (SEM) and performance characterization are used to analyze fabricated cells. With a peak power density of 369 mW∙cm−2, and an open circuit voltage (OCV) of 0.98 V, it is confirmed that novel production methods for IC-tSOFCs have been successful. 相似文献
997.
Ablation behavior and mechanism of 3D C/ZrC composite in oxyacetylene torch environment 总被引：1，自引：0，他引：1
Dan Zhao Changrui Zhang Haifeng Hu Yudi Zhang 《Composites Science and Technology》2011,71(11):1392-1396
Ablation property of three dimensional carbon fiber reinforced zirconium carbide composite (3D C/ZrC composite) was determined using oxyacetylene torch test with a heat flux of 4187 kW/m2 and flame temperature of over 3000 °C. C/ZrC composite exhibited an excellent configurational stability with a surface temperature of over 2000 °C during 60-300 s period, while 3D C/SiC composite was perforated at 55 s. After ablation for 300 s, the composite showed a mass loss rate of 0.006 g/s and a linear recession rate of 0.004 mm/s. The formation of zirconia melt on the surface of the C/ZrC composite contributed mainly the ablation property improvement. The C/ZrC composite after ablation showed four different layers due to the temperature and pressure gradients: the melting layer, the loose tree-coral-like ZrO2 layer, the undersurface oxidation layer, and the composite layer. 相似文献
998.
Perovskite structure based ceramic precursors have a characteristic property of substitution in the “A” site of the ABO3 structure. This makes them a potential material for nuclear waste management in synthetic rock (SYNROC) technology. In order
to simulate the mechanism of rare earth fixation in perovskite, Lax Ca1−xTiO3 (wherex = 0.05) has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and La as starting
materials. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture
in a muffle furnace at 1050°C. The ceramic phase has been characterized by its powder diffraction pattern. Step analysis data
has been used to determine the structure of solid solution of lanthanum substituted calcium titanate. The SEM and EDAX analyses
also confirm that the CaTiO3 can act as a host for lanthanum. X-ray data has been interpreted using CRYSFIRE and POWDERCELL softwares. Theh, k, l values for different lattice planes have been generated from the experimental data. The lanthanum substituted perovskite
crystallizes in orthorhombic symmetry with space groupP n m a (#62). Following unit cell parameters have been calculated:a = 5.410,b = 7.631,c = 5.382. The calculated and observed values of corresponding intensities, 2θ, and density show good agreement. GSAS based
calculation for bond distances Ti-O, Ca-O, La-O and bond angles Ti-O-Ca, Ca-O-Ca, La-O-Ti have been reported. 相似文献
999.
1000.
Reciprocating sliding friction experiments were conducted with various two-phase, directionally solidified Al2O3/ZrO2 (Y2O3) pins sliding on B4C flats in air at temperatures of 296, 873, and 1073 K under dry sliding conditions. Results indicate that all the Al2O3/ZrO2 (Y2O3) ceramics, from highly Al2O3-rich to ZrO2-rich, exceed the main wear criterion requirement of 10−6 mm3 N−1 m−1 or lower for effective wear-resistant applications. Particularly, the eutectics and Al2O3-rich ceramics showed superior wear properties. The composition and microstructure of Al2O3/ZrO2 (Y2O3) ceramics played a dominant role in controlling the wear and friction properties. The controlling mechanism of the ceramic wear, friction, and hardness was an intrinsic effect involving the resistance to shear fracture of heterophase bonding and cohesive bonding and the interlocking microstructures at different scales in the ceramics. 相似文献