Reduced graphene oxide has excellent mechanical properties, environmental friendliness, excellent electrical and thermal conductivity, but its self-agglomeration phenomenon limits its application in ...energy storage. Combining it with transition metal oxides is an effective way to adjust the growth structure, prevent agglomeration, and improve capacity. In this work, manganese ferrite/reduced graphene oxide (MnFe
2
O
4
/rGO) nanocomposite electrode materials were prepared by a one-step hydrothermal method. MnFe
2
O
4
nanorods are uniformly dispersed on rGO sheets, and embedding between adjacent rGO layers can ensure good interfacial interaction and prevent rGO agglomeration. This unique arrangement resulted in enhanced charge transfer properties within the composites. The samples underwent characterization using X-ray diffraction (XRD), Transmission electron microscopy (TEM), scanning electron microscopy (SEM), Brunauer–Emmett–Teller analyzer (BET), and X-ray photoelectron spectroscopy (XPS). Subsequently, the physical properties of MnFe
2
O
4
/rGO were thoroughly investigated. The MnFe
2
O
4
/rGO nanocomposite exhibited a specific capacity of 195 F g
−1
under a current density of 1 A g
−1
. Moreover, it demonstrated exceptional cycle stability, retaining 75.22% of its initial capacitance after 4000 charge–discharge cycles at 2 A g
−1
. Notably, the asymmetric supercapacitor (ASC) device achieved an energy density of 16 W h kg
−1
at a power density of 1280 W kg
−1
. Additionally, the ASC device displayed remarkable cycling stability, preserving 73.78% of its capacitance after 5000 cycles. The results highlight the enhanced performance of MnFe
2
O
4
/rGO nanocomposites compared to individual MnFe
2
O
4
(77 F g
−1
) and rGO (67 F g
−1
).
In this paper, a near-ultraviolet LED structure was fabricated on a sapphire substrate by using metal–organic chemical vapor deposition with an undoped AlGaN insertion layer introduced between ...multiple quantum wells and electron blocking layers, and the effect of layer thickness on light-electric performance was investigated. Results of epitaxial structure characterization show that the introduction of an undoped AlGaN insertion layer almost does not affect the crystal quality and surface morphology of the LED epitaxial structure. Electroluminescence testing results indicate that as the insertion layer thickness increases, the device performance initially increases and then decreases. Furthermore, simulation analysis suggests that increasing the insertion layer thickness reduces the injection efficiency of carriers, lowers the radiative recombination rate and light emission performance of the active region's carriers. Additionally, the AlGaN insertion layer can effectively suppress the diffusion of Mg impurities, reduce the non-radiative recombination rate in the multiple quantum well active region, and thus improve the LED's light emission performance. Overall, under the competing effects of these two mechanisms, the optimal light emission performance for the near-ultraviolet LED is achieved when the insertion layer thickness is 1 nm.
“Red/blue spot” is a common undesirable phenomenon in small and medium-sized TFT-LCD products, which directly affects the display quality of the product. It has always been a difficult problem in the ...display industry, which greatly reduces the market competitiveness of corresponding products. In this work, pressure tests are carried out on liquid crystal panels with different sizes and resolutions. The effects of different factors such as the flatness of the photo space, the distribution density of the spacers, and the glass thickness on the “red/blue spot” are compared. By increasing the flatness of the PS station, the septum distribution density, and the thickness of the glass, the sample’s anti-extrusion ability can be increased by 46.1%, 30%, and 23.1%, respectively. The experimental results can provide the basis for industry to further improve quality of products.
Betavoltaic batteries are promising sustainable energy sources for the application of autonomous wireless sensor microsystems. The bottleneck is their relatively low energy efficiency and ...sustainability. In this work, we report a novel betavoltaic device with significant conversion efficiency using electrochemically reduced graphene oxide (ERGO) on TiO 2 nanotube arrays (TNTAs) for capturing beta-energy as well as energy conversion. A 10 mCi of 63 Ni source with area of 10 × 20 mm 2 was assembled to graphene on TNTAs (G-TNTAs) to form the sandwich type betavoltaic devices. By I-V measurements, the optimum betavoltaic device exhibits a significant effective energy conversion efficiency of 26.55% with open-circuit voltage of 2.38 V and short-circuits current of 27.18 nA. The experimental results indicate that G-TNTAs are high-potential nanocomposite for developing betavoltaic batteries.
This paper reports on the fabrication and electrochemical properties of porous carbon nanospheres, which have been prepared by the hydrothermal carbonization of natural glucose and subsequent ...activation of potassium hydroxide (KOH). Porous nanospheres with high bulk porosity and partial graphitization are obtained by the optimization of mass ratio (KOH: hydrochar). The optimal of specific surface area reaches 1563 m2/g with an average diameter of 3.64 nm. The maximum of specific capacitance of the activated carbon nanospheres is 207 F/g at a current density of 0.5 A/g, high rate capability (181 F/g at a current density of 10 A/g) and cycling stability (capacitance retention of nearly 96.7% over 1000 cycles). The high-conductive porous carbon nanosphere material with low microporosity and blind porosity might be a potential material for electrochemical double-layer capacitors (EDLCs).
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•A facile and scalable HTC method was used to synthesize high-conductive carbon nanoshperes from natural glucose.•Hollow carbon nanoshpere structures were achieved subsequently by KOH activating agent.•Graphitization of the HTC processed glucose was tuned through the process of adjusting mass ratio of KOH/hydrochar.•Optimized hollow nanospheres exhibit high specific surface area (1563 m2/g) and narrow particle size distribution.
The porous fiber structure is advantageous for supercapacitor electrode material owning to flexibility, tunable porosity and large specific surface area. Nickel oxide (NiO) is a promising ...supercapacitor electrode material because of its low cost, friendly environment as well as high specific capacitance, but its poor electronic conductivity limits its application in practice. Doping appropriate transition metal ions is an excellent means of adjusting the structure of the electrons and improving conductivity, also is an effective way to improve the capacity. In this work, the nickel copper oxide/carbon (NCO/C) fiber nanocomposites were prepared via electrospinning and calcination treatment. NCO nanoparticles are decorated on the carbon nanofiber skeleton, which not only guides the growth of NCO nanoparticles and prevents agglomeration, but also acts as a conductive network to facilitate electron transfer. The electrochemical properties of NCO/C fiber nanocomposites affected by the copper dosage in the precursor solution and the calcination temperature were investigated. The optimized NCO/C fiber nanocomposites electrode achieves excellent electrochemical properties (277 C g–1 at 0.5 A g–1) because of generous specific surface area and excellent electrical conductivity. The asymmetric supercapacitor (ASC) device exhibits an energy density of 48.1 Wh kg–1 at 560.6 W kg–1. Excellent cycling performance with 95% capacitance retention was achieved after 5000 cycling tests at 1 A g–1. The results show that copper introduction is an effective way and that the porous NCO/C fiber nanocomposites are promising electrode materials for supercapacitors.
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•The nickel copper oxide/carbon porous fiber nanocomposites were synthesized via electrospinning and calcination method.•The porous fiber structured nanocomposite accelerates ion diffusion and electron transfer.•The optimized nickel copper oxide/carbon fiber nanocomposite electrode exhibits excellent electrochemical performance.•The ASC device exhibits an energy density of 48.1 Wh kg−1 at 560.6 W kg−1 and excellent cycling performance.
Developing electrode materials with hierarchically porous structure and high electrochemical stability is crucial for improving the energy density of supercapacitors (SCs). Herein, the NiCoAl layered ...trimetallic hydroxides supported on hollow carbon shells (NCA@HCs LTHs) with various Al doping amounts is synthesized by a simple hydrothermal method. The electrode material with the optimal NCA doping ratio (mass ratio 3:2:0.3) displays a stable layered hydroxides structure and low crystallinity. Additionally, the unique 3D hollow structure not only increases the specific surface area (SSA) but also effectively prevents the agglomeration of LTHs. The synergistic interaction of these two aspects is responsible for the exceptional specific capacity and cycling performance. The optimal N3C2A0.3 @HCs LTHs exhibits a high specific capacitance of 792 C g−1 at 1 A g−1. Moreover, the constructed asymmetric supercapacitor (ASC) achieves a coulombic efficiency of 98% and retains 80% of its capacitance after 12,000 cycles at 5 A g−1. The above results show that the synergistic strategy of Al doping and hollow structure design provides new insights into improving the electrochemical performance of SCs.
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•The construction of NiCoAl-LTHs@mesoporous carbon core-shell hollow nanospheres.•The synergistic strategy of atomic doping and structure design facilitates performance.•The electrode exhibits a high specific capacitance of 792 C g−1 at 1 A g−1.
Abstract
The interfacial thermal resistance of the nanocontact system of carbon nanotubes and nickel crystals was investigated using molecular dynamics. It was found that with the increase in ...temperature, the interface thermal resistance gradually increased. In addition, the interfacial thermal resistance also increases gradually with the increase of the contact distance. The ballistic transport of phonons is proposed to be the main reason for the interfacial thermal resistance in this case.
Abstract
To facilitate the simulation of heat dissipation of high-power LED lamps, a set of simplified models for tubular heat pipes and carbon nanotube arrays were first established to estimate ...their thermal conductivity. Then several kinds of radiators were designed. The application of nanomaterials and heat pipes in the heat dissipation of lamps was studied by the finite element method. It is found that the radiator with vertical suspended fins strengthened by a heat pipe and heat dissipation coating has a better heat dissipation effect than other radiators. Finally, the simulation study of thermal interface materials and heat dissipation coatings for lamps and lanterns heat dissipation is carried out. The results show that the thermal interface materials of carbon nanotubes and carbon nano coatings can enhance the heat dissipation performance of lamps.
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