Amongst thermoelectrics, Bi2Te3 is special owing to its peak performance near room temperature, which enables it to be used for both energy harvesting and cooling. Despite extensive studies on this ...compound, Bi2Te3-based bulk materials are usually prepared by field-assisted sintering and hot pressing. This necessitates sophisticated equipment and tedious compositional control, both of which are undesirable for large scale applications. In this work, a low-temperature liquid phase sintering (LPS) method was employed to prepare p-type Bi0.5Sb1.5Te3/SiC composites with enhanced thermoelectric properties. In addition, a nearly two-fold increase in the power factor was observed post heat treatment at 350 °C. This can be ascribed to carrier concentration modulation due to porosity induced by heat treatment. Further addition of 0.6 vol% SiC results in a low lattice thermal conductivity of 0.33 W m−1 K−1, which can be ascribed to phonon scattering due to various defects induced by the SiC inclusion. Ultimately, a figure of merit ZT of 1.05 at 340 K was achieved for Bi0.5Sb1.5Te3/0.6 vol% SiC, 20% higher than that of the pristine sample. Moreover, an average ZT of 0.87 at 300–500 K was attained, comparable to state-of-the-art values via high-temperature processing. This work showcases the promising application of the low-temperature LPS technique for energy-efficient processing of thermoelectrics.
Bismuth telluride-based compounds have been extensively utilized for commercial application. However, thermoelectric materials must suffer numerous mechanical vibrations and thermal stresses while in ...service, making it equally important to discuss the mechanical properties, especially at high temperature. In this study, the compressive and bending strengths of Bi
0.5
Sb
1.5
Te
3
commercial zone melting (ZM) ingots were investigated at 25, 100, and 200 °C, respectively. Due to the obvious anisotropy of materials prepared by ZM method, the effect of anisotropy on the strengths was also explored. Two-parameter Weibull distribution was employed to fit a series of values acquired by a universal testing machine. And digital speckle photography was applied to record the strain field evolution, providing visual observation of surface strain. The compressive and bending strengths along ZM direction were approximately three times as large as those perpendicular to the ZM direction independent of the temperature, indicating a weak van der Waals bond along the
c
axis.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Owing to the unfavorable wetting and density difference between graphene and copper, it remains challenging to achieve homogeneous dispersion of graphene for utilizing the unique nature of graphene ...in copper matrix composites. Here, we design an in-situ process to fabricate graphene-like carbon (GLC) reinforcing copper matrix composites: GLC can be directly fabricated on commercial copper particles using modified PECVD method followed by vacuum hot pressing, which is high-efficiency and can be massively produced for graphene reinforced metal matrix composites in industrial level. After hot pressing, the GLC with ultralow content (170 to 350 ppm) can be uniformly dispersed and tightly embedded within the copper matrix. A remarkable thermal conductivity enhancement efficiency of 85% and enhanced thermal conductivity (439 W m−1 K−1), accompanied by the higher wear resistance, can be obtained in our GLC reinforced copper matrix composites. In actual arc ablation performance measurement, the breakdown strength and relative arc ablation resistance of GLC/Cu composites can be significantly improved by 106.5% and 33.3% than pure copper, respectively, demonstrating GLC/Cu composites a promising candidate for application as high voltage electrical contacts.
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•A facile method for in-situ synthesis of graphene-like carbon reinforced copper matrix composites is developed.•A remarkable thermal conductivity enhancement efficiency and enhanced thermal conductivity can be achieved.•The graphene-like carbon reinforced composites demonstrate a promising candidate for application as electrical contacts.•This work provides an efficient synthesis method for mass production of graphene reinforced metal matrix composites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Thermally conductive and electrically insulating polymer composites are ideal for applying in electrical or electronic fields as thermal management materials. Diamond nanomaterials have been used as ...an ideal thermal conductive filler due to their excellent intrinsic thermal conductivity. In this work, utilizing single-crystal nanodiamond (SCND) flakes as the thermally conductive filler, flexible cellulose nanofiber/single-crystal nanodiamond (CNF/SCND) flake composite films with high thermal conductivity were prepared by vacuum-assisted filtration. The strong hydrogen bonding interaction between CNF and SCND and the highly ordered stacking structure of SCND flake layers endowed the composite films with satisfactory flexibility and excellent heat dissipation performance. Compared with pure CNF film, a remarkable thermal conductivity enhancement of approximately 145.6 times and enhanced thermal conductivity (76.23 W m
−1
K
−1
) was achieved in our CNF/SCND composite films. In addition, the enhanced thermal conductivity and excellent mechanical strength, accompanied with excellent flexibility, can be attributed to the CNF/SCND films with low and medium filling content of SCND. This demonstrates that the CNF/SCND composite films are a promising candidate as a heat spreader to rapidly cool LED lamps or electronic devices.
A simple method was proposed to produce a flexible heat spreader with efficient thermal transportation performance.
The nitrogen-vacancy (NV) color center in chemical vapor deposition (CVD) diamond has been widely investigated in quantum information and quantum biosensors due to its excellent photon emission ...stability and long spin coherence time. However, the temperature dependence of the energy level of NV color centers in diamond is different from other semiconductors with the same diamond cubic structure for the high Debye temperature and very small thermal expansion coefficient of diamond. In this work, a diamond sensor for temperature measurement with high precision was fabricated based on the investigation of the energy level shifts of NV centers by Raman and photoluminescence (PL) spectra. The results show that the intensity and linewidth of the zero-phonon line of NV centers highly depend on the environmental temperature, and the energy level shifts of NV centers in diamond follow the modified Varshni model very well, a model which is better than the traditional version. Accordingly, the NV color center shows the ability in temperature measurement with a high accuracy of up to 98%. The high dependence of NV centers on environmental temperature shows the possibility of temperature monitoring of NV center-based quantum sensors in biosystems.
Copper powder has broad applications in the powder metallurgy, heat exchanger, and electronic industries due to its intrinsically high electrical and thermal conductivities. However, the ease of ...formation of surface oxide or patina layer raises difficulty of storage and handling of copper powder, particularly in the case of Cu microparticles. Here, we developed a thermal chemical vapor deposition chemical vapor deposition (CVD) process for large-scale synthesis of graphene coatings on Cu microparticles, which importantly can remain monodisperse without aggregation after graphene growth at high temperature by using removal spacers. Compared to other protective coating methods, the intrinsic electrical and thermal properties of Cu powder would not be degraded by uniform growth of low defect few-layer graphene on each particle surface. As a result, when the anticorrosion performance test was carried out by immersing the samples in Cu etchant, the corrosion rate of graphene/Cu microparticles was significantly improved (ca three times slower) compared to that of pristine Cu powder, also showing a comparable anticorrosion ability to commercial CuZn30 alloy.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Copper-based materials are common industrial products which have been broadly applied to the fields of powder metallurgy, electrical contact, and heat exchangers, etc. However, the ease of surface ...oxidation limits the durability and effectiveness of copper-based components. Here, we have developed a powder metallurgy process to fabricate graphene/copper composites using copper powders which were first deposited with graphene layers by thermal chemical vapor deposition (CVD). The graphene/copper composites embedded with an interconnected graphene network was then able to be obtained by vacuum hot-pressing. After thermal oxidation (up to 220 °C) in humid air for several hours, we found that the degree of surface oxidation of our samples was much less than that of their pure Cu counterpart and our samples produced a much smaller increase of interfacial contact resistance when used as electrical contact materials. As a result, our graphene/copper composites showed a significant enhancement of oxidation resistance ability (≈5.6 times) compared to their pure Cu counterpart, thus offering potential applications as novel electrical contact materials.
Bismuth telluride based thermoelectric materials have been commercialized for a wide range of applications in power generation and refrigeration. However, the poor machinability and susceptibility to ...brittle fracturing of commercial ingots often impose significant limitations on the manufacturing process and durability of thermoelectric devices. In this study, melt spinning combined with a plasma‐activated sintering (MS‐PAS) method is employed for commercial p‐type zone‐melted (ZM) ingots of Bi0.5Sb1.5Te3. This fast synthesis approach achieves hierarchical structures and in‐situ nanoscale precipitates, resulting in the simultaneous improvement of the thermoelectric performance and the mechanical properties. Benefitting from a strong suppression of the lattice thermal conductivity, a peak ZT of 1.22 is achieved at 340 K in MS‐PAS synthesized structures, representing about a 40% enhancement over that of ZM ingots. Moreover, MS‐PAS specimens with hierarchical structures exhibit superior machinability and mechanical properties with an almost 30% enhancement in their fracture toughness, combined with an eightfold and a factor of six increase in the compressive and flexural strength, respectively. Accompanied by an excellent thermal stability up to 200 °C for the MS‐PAS synthesized samples, the MS‐PAS technique demonstrates great potential for mass production and large‐scale applications of Bi2Te3 related thermoelectrics.
Melt‐spinning combined with plasma activated sintering is adopted to design hierarchical nanostructured BiSbTe alloys. Because of the hierarchical configuration and nanodispersion, the lattice thermal conductivity is reduced significantly, leading to superior thermoelectric performance and robust mechanical properties. Accompanied by an excellent thermal stability, the melt‐spinning‐based synthesis approach offers great potential for commercial applications.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Selective oxidation is a common strategy for enhancing protective oxide layers on an alloy. In this work, oxide films were obtained on Al2Au under a series of temperatures, and the structure, ...chemical state, and corrosion resistance were investigated. The oxidation behavior was confirmed to be temperature-dependent, exhibiting two distinct kinds of oxide films. Uniform oxidation occurred below the critical temperature T s (700 < T s < 800 °C), resulting in ultrathin oxide layers (<10 nm) with corrosion resistance enhanced by Au solute atoms. Phase-separate oxidation, occurring at temperatures above T s, resulted in a much thicker oxide-affected region (250–300 nm) composed of Al2O3 and AlAu phases. Above 625 °C, bulk recrystallization led to Al diffusion through grain boundaries, disrupting the continuity of the oxide layer on the surface. These findings help further improve the existing alloy oxidation theory and develop potential surface modification methods on precious-metal-based alloys.
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IJS, KILJ, NUK, PNG, UL, UM
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