Graphene Heat Research Articles

Improved Longevity and Reliability for Hundreds of Amps, Repetition Frequency Avalanche GaAs PCSS by High Thermal Conductivity Graphene Heat Sink

Improved Longevity and Reliability for Hundreds of Amps, Repetition Frequency Avalanche GaAs PCSS by High Thermal Conductivity Graphene Heat Sink

Enhanced Free-Electron-Photon Interactions at the Topological Transition in van der Waals Heterostructures.

Heterostructures composed of graphene and molybdenum trioxide (MoO3) can support in-plane hybrid polaritons in the infrared. The isofrequency contour for these subwavelength polaritons can exhibit a quasi-flat region when the topological transition occurs as the doping level of graphene is tuned. Such a topological transition can be useful for optical sensing and imaging at nanoscale. Here, by analyzing electron energy-loss spectroscopy (EELS), we theoretically demonstrate that free-electron-photon interactions in the heterostructure can be enhanced due to this quasi-flat region. Moreover, the free-electron-photon interaction is sensitive to the electron trajectory and is robust against certain types of defects in the structure. Furthermore, we show that the free-electron-photon interaction can undergo an ultrafast subpicosecond modulation by optical pumping and heating of graphene. Our findings may pave the way toward dynamical electron beam shaping, free-electron-based quantum light sources, and quantum sensing.

Entropy and Negative Specific Heat of Doped Graphene: Topological Phase Transitions and Nernst's Theorem Revisited.

This study explores the thermodynamic properties of doped graphene using an adapted electronic spectrum. We employed the one-electron tight-binding model to describe the hexagonal lattice structure. The dispersion relation for graphene is expressed in terms of the hopping energies using a compositional parameter that characterizes the different dopant atoms in the lattice. The focus of the investigation is on the impact of the compositions, specifically the presence of dopant atoms, on the energy spectrum, entropy, temperature, and specific heat of graphene. The numerical and analytical results reveal distinct thermodynamic behaviors influenced by the dopant composition, including topological transitions, inflection points in entropy, and specific heat divergences. In addition, the use of Boltzmann entropy and the revision of Nernst's theorem for doped graphene are introduced as novel aspects.

Universal, minute-scale synthesis of transition metal compound nanocatalysts via graphene-microwave system for enhancing sulfur kinetics in lithium-sulfur batteries

The application of Li-S batteries on large scale is held back by the sluggish sulfur kinetics and low synthesis efficiency of sulfur host. In addition, the preparation of catalysts that promote polysulfide redox kinetics is complex and time-consuming, reducing the cost of raw materials in Li-S. Here, a universal synthetic strategy for rapid fabrication of sulfur cathode and metal compounds nanocatalysts is reported based on microwave heating of graphene. Heat-sensitive materials can achieve rapid heating due to graphene reaching 500 ℃ within 4 s via microwave irradiation. The MoP-MoS2/rGO catalyst demonstrated in this work was synthesized within 60 s. When used for catalysts for Li-S batteries whose graphene/sulfur cathodes were also synthesized by microwave heating, enhanced catalytic effect for sulfur redox reaction was verified via experimental and DFT theoretical results. Benefiting from fast redox reaction (MoP), smooth Li+ diffusion pathways (MoS2), and large conductive network (rGO), the assembled Li-S battery with MoP-MoS2/rGO-Add@CS displays a remarkable initial specific capacity, stable lithium anode and good cycle stability (in pouch cells) using this two-pronged strategy. The work provides a practical strategy for advanced Li-S batteries toward a wide range of applications.

Thermal design of focal plane assembly of wavefront camera for exoplanet imaging corona module

The focal plane assembly of wavefront camera is the key imaging device of wavefront detection camera and the key load of the exoplanet imaging coronagraph module. In order to ensure the imaging quality and reduce the dark current and thermal noise, it is necessary to effectively dissipate the heat of the focal plane CCD and other high-power electronic devices to ensure the working performance and reliability of the focal plane assembly. Based on the limited space and cooling resources, this paper adopts the flexible graphene heat conducting cable and grooved heat pipes, and carries out detailed thermal design and thermal analysis of its cooling path. The finite element model is established by thermal analysis software and thermal simulation is carried out. in that steady state, the work temperature range of the CCD chip is -12.8∼-10.9°C, which meets the temperature control index, and the work temperatures of other components are also within the design requirements, which indicate that the thermal design scheme is reasonable and feasible, and meets the task requirements.

Experimental study of icing and deicing situations of different wettability surfaces composite electric heating

Aircraft icing affects the safety of life and property, and traditional anti-icing methods have faced problems such as high weight and energy consumption. The superhydrophobic surfaces are used as a new material for passive anti-icing method. In view of the limited performance of superhydrophobic surface in extreme environment, a new anti-icing method combining superhydrophobic surface with electric heating technology is proposed. Test samples that covered different wettability coating on the leading edge of the wing and cooperating with the graphene heating film for electric heating composite are used for icing and deicing tests in the ice wind tunnel. The icing and deicing characteristics of four different wettability surfaces under different airflow speed and heating power are investigated. The results show that with the increase of surface hydrophobic property, the icing area ratio on the surface is gradually reduced. Under the same external environment, the ice area and minimum heating power of no ice accumulation of the superhydrophobic surface are reduced by 40.5 %–78.8 % and 29.1 %–38.6 %, respectively, compared with the hydrophilic surface. Moreover, the icing area is mainly concentrated in the area near the stagnation line. The morphology and freezing time of droplet impinging on the surface is different under different initial heating power and different ice accumulation shapes is exhibited. Combination of the superhydrophobic surface and electric heating significantly reduces the heating energy consumption compared with single superhydrophobic surface heating and single electric heating method, providing reference data for the development of new anti-icing technology.

Design and analysis of nonvolatile GSST-based modulator utilizing engineered Mach-Zehnder structure with graphene heaters

Photonic integrated circuits (PICs) are the foundation of on-chip optical technologies. In these circuits, Mach-Zehnder modulators (MZMs) are versatile building blocks which mostly rely on weak and volatile optical effects in materials. In contrast, phase change materials (PCMs) such as Ge2Sb2Se4Te1 (GSST) are promising candidates to realize efficient and nonvolatile reconfigurable photonic devices. However, the phase transitions of PCMs are also accompanied by large changes in the imaginary parts of their refractive indices which make the design of MZMs challenging. In this paper, two interesting design methods named as “loss-balancing” and “pre-equalization” are introduced to propose high-performance GSST-based MZMs. In this regard, a GSST-based waveguide with graphene as a microheater is proposed which plays the role of configurable active switch in both the introduced methods. In order to improve the speed and efficiency of the device, a suspended graphene sheet is applied as the heater to excite GSST. According to the presented analysis, a nonvolatile MZM with active length of 4.725 µm and insertion loss of less than 2 dB at the wavelength of 1550 nm is realizable. Finally, thermal simulation of the proposed GSST-based waveguide is performed to show that the required voltages for amorphization (erasing) and crystallization (writing) processes are 12 V and 4.3 V, respectively.

Electrically controllable optical switch metasurface based on vanadium dioxide.

We report a voltage-tunable reflective gold wire grid metasurface on vanadium dioxide thin film, which consists of a metal-insulator-metal (MIM) structure. We excite surface plasmon polariton (SPP) modes on the gold surface by fabricating a one-dimensional structured gold wire grid. Joule heating of laser-induced graphene (LIG) can be controlled by the voltage at the bottom, allowing vanadium dioxide in the structure to complete the transition from the insulating state to the metallic state. The phase transition of vanadium dioxide strongly disrupts the plasmon modes excited by the gold wire grid above, thereby realizing a huge change in the reflection spectrum. This acts as a tunable metasurface optical switch with a maximum modulation depth (MD) of over 20 dB. We provide a more effective and simple method for creating tunable metasurfaces in the near-infrared band, which can allow metasurfaces to have wider applications in optical signal processing, optical storage, and holography.

Freestanding graphene heat engine analyzed using stochastic thermodynamics

We present an Ito-Langevin model for freestanding graphene connected to an electrical circuit. The graphene is treated as a Brownian particle in a double-well potential and is adjacent to a fixed electrode to form a variable capacitor. The capacitor is connected in series with a battery and a load resistor. The capacitor and resistor are given separate thermal reservoirs. We have solved the coupled Ito-Langevin equations for a broad range of temperature differences between the two reservoirs. Using ensemble averages, we report the rate of change in energy, heat, and work using stochastic thermodynamics. When the resistor is held at higher temperatures, the efficiency of the heat engine rises linearly with temperature. However, when the graphene is held at higher temperatures, the efficiency instantly rises and then plateaus. Also, twice as much entropy is produced when the resistor is hotter compared to when the graphene is hotter. Unexpectedly, the temperature of the capacitor is found to alter the dissipated power of the resistor.

Effects of a Graphene Heating Device on Fatigue Recovery of Biceps Brachii.

Far-infrared (FIR) is considered to be an ideal method to promote fatigue recovery due to its high permeability and strong radiation. In this paper, we report a flexible and wearable graphene heating device to help fatigue recovery of human exercise by using its high FIR divergence property. This study compares two different fatigue recovery methods, graphene far-infrared heating device hot application and natural recovery, over a 20 min recovery time among the male colleges' exhaustion exercise. Experimental results show that the achieved graphene device holds excellent electro-thermal radiation conversion efficiency of 70% and normal total emissivity of 89%. Moreover, the graphene FIR therapy in our work is more energy-efficient, easy to use, and wearable than traditional fatigue recovery methods. Such an anti-fatigue strategy offers new opportunities for enlarging potential applications of graphene film in body science, athletic training recovery, and wearable devices.

Hybrid photothermal structure based on Cr-MgF2 solar absorber/PMMA-graphene heat reservoir for enhanced thermoelectric power generation

In this paper, a facile strategy for a hybrid photothermal structure that can efficiently manage solar heat is reported. The hybrid photothermal structure consists of a Cr/MgF2 multilayer structure absorber and a poly(methyl methacrylate) (PMMA)-graphene heat reservoir that prevents the absorbed heat from being lost through radiation or convection. It exhibits a quite high light absorption of approximately 80% over a wavelength range of 0.5–2.5 µm. The thermal conductivity and thermal diffusivity are improved by about 47% according to the addition of graphene to PMMA, effectively transferring the stored heat to a place where it can be used efficiently. When the hybrid photothermal structure was applied to the hot zone of a thermoelectric generator, the output voltage is improved by 2.74 times compared to the device with only the light absorber. In addition, the difference between the high and low temperatures reached up to approximately 27 K.

Research on PVT Module Operating at High Temperature

At present, the research and development of PVT modules by researchers and engineers worldwide is still in the stage of small-scale production and research and development. Most PVT modules use ordinary photovoltaic cells. In order to ensure their best operating efficiency, the output hot water temperature is generally not more than 30°C. To obtain high temperature hot water, secondary heating is required, such as using heat pump, so the overall system cost is high. Based on the above problems, this paper studies and develops a new PV-thermal integrated module, re-optimizes the overall structure, selects the characteristic high-temperature resistant crystalline silicon photovoltaic cell (black silicon) and solar special heat-absorbing coating to improve the operating temperature of the PVT module, and uses graphene heat conductive material to increase the contact area of heat conduction and heat transfer, which is packaged and processed. After a series of experimental tests, the operating temperature of the PVT module reaches 60°C, and it can stably obtain high-quality hot water above 50°C. The PVT module can work under high temperature conditions for a long time, effectively improving the overall energy conversion efficiency of the system, and the generated hot water can directly meet the needs of daily life and space heating without secondary heating, has a good market development prospect.

Electrically tunable mode-locked fiber laser using laser induced graphene assisted long-period fiber grating

We demonstrate an electrically tunable all-fiber mode-locked erbium-doped fiber laser using a long-period fiber grating (LPFG) assisted by laser induced graphene heaters (LIG-H). Wavelength tunability is achieved by the temperature-dependent transmission spectrum of the LPFG. The central wavelength can be continuously tuned from 1549.00 nm to 1563.63 nm with a spectral tuning range of 14.63 nm. The graphene on polyimide (PI) paper is fabricated using a 10.6 μm CO2 laser, which has a maximum operating temperature of around 500 °C. The proposed LPFG-based electrical tunability of mode-locked fiber laser provides a novel, repeatable, simple, and cost-effective laser tuning technique.

Free-standing laser-induced graphene heaters for efficient curing and repairing of composites

Free-standing laser-induced graphene heaters for efficient curing and repairing of composites

The establishment and numerical calculation of a heat transfer model of a graphene heating energy storage floor

A new type of graphene electric heating solid wood composite floor and its heat transfer model were designed to enable users to have a higher-quality and safe living experience. A heat transfer mathematical model was developed. The structural entity of the composite graphene heating floor was drawn using Solidworks software. The floor structure was abstracted as a two-dimensional model using MATLAB software to obtain the temperature rise curves and corresponding time of each group. Then, six groups of the best data were selected from the experimental data to simulate the heat storage capacity of graphene floors. The optimal group of the model was verified via experiments. According to the simulation, the comprehensive performance was optimal when the overall thickness of the floor was 18 mm, the thickness of the floor surface was 4 mm, and the thickness of the heat-accumulating layer was 2 mm. The experimental results showed a maximum difference between the measured and calculated data of only 3.2%, which shows the scientific validity, accuracy, and advancement of the model. The composite graphene electric heating energy storage floor designed in this study can be regarded as safe, reliable, environmentally friendly, and healthy.

Enhanced in-plane thermal conductivity of polyimide-based composites via in situ interfacial modification of graphene.

Interfacial thermal resistance is the main barrier restricting the heat dissipation of thermal management materials in electronic equipment. The interface structure formed by covalent bonding is an effective way to promote interfacial heat transfer. Herein, an integrated composite with multi-aspect covalent bonding beneficial for heat transmission is constructed by polyimide (PI) polymerization with maleimide modified graphene nanosheets (M@GNS). The interfacial structure with low thermal resistance built by covalent bonding and oriented graphene arrangement initiated by the coating process makes the in-plane thermal conductivity of the composite as high as 16.10 W m-1 K-1. Finite element simulation and 1000 bending tests are carried out to further verify the performance advantages of the integrated structure in the internal thermal diffusion and long-term use of the composite. M@GNS/PI with integrated structure provides extra heat transfer channels for heat dissipation, possibly providing an effective way to address the traditional thermal accumulation issue of electronic devices.

Superhydrophobic coating induced anti-icing and deicing characteristics of an airfoil

Aircraft icing seriously threatens flight safety. The widely used electrothermal anti/de-icing technology has high energy consumption and poor performance. The bionic superhydrophobic surface has anti-icing potential, which can be combined with electric heater technology to achieve energy savings and efficiency improvement. In the previous research, we developed a superhydrophobic coating with mechanochemical robustness for aircraft anti-icing and proved its excellent anti-icing performance. This research combines this coating with the graphene electric heater to obtain a coupling system and explores its anti-icing effect under aviation conditions through the ice wind tunnel test. The results showed that the coating significantly improves the anti-icing properties, delaying the icing process for 10 s, saving the anti-icing energy consumption by 21% compared with graphene heating alone, and increasing the deicing efficiency by 250%. When the coating protection area reaches 30% chord, it can achieve a 'dry' anti-icing state, and this coupling system saves energy by 60% compared with wire heating. Furthermore, The ‘honeycomb structure’ coating is better in anti-icing effect, and the ‘island structure’ coating has stronger anti-icing stability. The hydrophobicity of the coating is less affected by the high-speed droplet impact, so it has a long life expectancy in the active anti-icing mode. This study can provide new ideas for solving the problem of aircraft icing.

Structural and electrochemical properties of N-doped graphene–graphite composites

This work studied the impact of graphene content and heat treatment on the structural changes and electrical parameters of graphite/N-doped graphene mixtures. Using photoelectron spectroscopy the appearance of two types of carbon-containing phases was detected in the visible range of the N-doped graphene samples synthesized from liquid nitrogen. The following features of the samples were shown: one typical structure of graphene (sp2C–sp2C), two atypical structures (sp3C–N and the C–O bond), and graphene components modified with nitrogen (pyridine–N, pyrrole–N, graphite–N and oxidized N–O). The dependence between the ratio of components in graphite–graphene mixtures and their electrochemical properties was found. The effect of graphite content and heat treatment on the change in the type of conductivity in a graphite–graphene mixture was determined by comparison of resistance and capacitance distribution in the frequency range of 100–900 Hz. The change of the graphite concentration in the graphene–graphite mixture allows governing the type of doping and electrical parameters of the mixtures.

Research on the snow melting and defogging performance of graphene heating film coupled concrete road

Snow and sudden heavy fog on the road are significant factors that contribute to traffic congestion and frequent accidents. In light of a number of environmental, economic, and road corrosion problems caused by road snow melting and fog elimination, this work studies a graphene heating film coupled concrete road snow melting and defogging system, which is critical to the transportation safety and economic and social benefits. The graphene heating film is embedded in the road and electrified as a heat source to analyze its function and effect in the process of melting snow and defogging. Furthermore, the heating performance of the various heating elements is compared and analyzed, and the working temperature, spacing, and buried depth of the graphene heating film is investigated. The rationality and efficiency of the graphene heating film coupling concrete road snow melting and defogging system are verified through experimental and simulation analyses.

A lab-on-chip platform for simultaneous culture and electrochemical detection of bacteria

A simple, cost-effective and miniaturized lab-on-a-chip platform has been developed amenable to perform simultaneous cultivation and detection of bacteria. A microfluidic chamber was integrated to screen-printed electrodes for electrochemical detection of bacteria. The temperature required for the bacterial culture was provided through the optimized laser-induced graphene heaters. The concentration of bacteria was quantified accurately with the three-electrode system in the range of 2×104 to 1.1×109 CFU/mL without any need of biological modifications to the electrodes. The viability of cultured bacteria in the microfluidic device was also confirmed through fluorescent imaging. Furthermore, the metabolic activity of the cultured bacteria was validated through a miniaturized microbial fuel cell. Furthermore, the specificity of electrodes was also performed through electrochemical technique. Finally, a handheld and portable lab-on-a-chip platform was realized by 3D packaging, integrated with a portable potentiostat for real-time and on-field applications.