Joule Heating Process Research Articles

Sintering Nano-Silver Paste by Resistive Joule Heating Process for 2G HTS Tape Joints.

Developing a joining technology for 2G HTS tapes without significantly reducing their superconducting property is crucial for numerous applications (MRI, motor/generator, power transmission, etc.). In this study, low sintering temperature (~230 °C) nano-silver paste was used as solder to join two 2G HTS tapes. In addition, two heating methods, i.e., furnace heating (heat flux outside-in) and resistive Joule heating (heat flux inside-out), were studied. This study indicates that the heat flux from internal by resistive Joule heating method shows less deteriorating impact to the 2G RE-Ba-Cu-O tape (RE: rare earth element) during the sintering process with the best specific resistance of 0.074 μΩ∙cm2 and Ic retention percentage of 99% (i.e., Ic reduced from 100 A before joining to 99 A after joining). This study indicates that nano-silver paste together with resistive Joule heating can possibly be used as soldering materials to join 2G HTS tapes.

Machine Learning Guided Synthesis of Flash Graphene.

Advances in nanoscience have enabled the synthesis of nanomaterials, such as graphene, from low-value or waste materials through flash Joule heating. Though this capability is promising, the complex and entangled variables that govern nanocrystal formation in the Joule heating process remain poorly understood. In this work, machine learning (ML) models are constructed to explore the factors that drive the transformation of amorphous carbon into graphene nanocrystals during flash Joule heating. An XGBoost regression model of crystallinity achieves an r2 score of 0.8051 ± 0.054. Feature importance assays and decision trees extracted from these models reveal key considerations in the selection of starting materials and the role of stochastic current fluctuations in flash Joule heating synthesis. Furthermore, partial dependence analyses demonstrate the importance of charge and current density as predictors of crystallinity, implying a progression from reaction-limited to diffusion-limited kinetics as flash Joule heating parameters change. Finally, a practical application of the ML models is shown by using Bayesian meta-learning algorithms to automatically improve bulk crystallinity over many Joule heating reactions. These results illustrate the power of ML as a tool to analyze complex nanomanufacturing processes and enable the synthesis of 2D crystals with desirable properties by flash Joule heating.

Phase controlled synthesis of transition metal carbide nanocrystals by ultrafast flash Joule heating

Nanoscale carbides enhance ultra-strong ceramics and show activity as high-performance catalysts. Traditional lengthy carburization methods for carbide syntheses usually result in coked surface, large particle size, and uncontrolled phase. Here, a flash Joule heating process is developed for ultrafast synthesis of carbide nanocrystals within 1 s. Various interstitial transition metal carbides (TiC, ZrC, HfC, VC, NbC, TaC, Cr2C3, MoC, and W2C) and covalent carbides (B4C and SiC) are produced using low-cost precursors. By controlling pulse voltages, phase-pure molybdenum carbides including β-Mo2C and metastable α-MoC1-x and η-MoC1-x are selectively synthesized, demonstrating the excellent phase engineering ability of the flash Joule heating by broadly tunable energy input that can exceed 3000 K coupled with kinetically controlled ultrafast cooling (>104 K s−1). Theoretical calculation reveals carbon vacancies as the driving factor for topotactic transition of carbide phases. The phase-dependent hydrogen evolution capability of molybdenum carbides is investigated with β-Mo2C showing the best performance.

Carbonized Polymer for Joule Heating Processing Towards Biosensor Development.

This paper presents the experimental findings towards developing carbonized microelectrodes using a Joule heating process within a temperature window that is compatible with CMOS. Bridge-on-pillars polymer structures have been 3D-printed using two-photon polymerization (2PP). They have been annealed in various processing conditions to increase the fraction of carbon in the precursor material and to achieve appreciable electric conductivity so that they can be used to drive current to enable Joule heating. To evaluate the outcome of the processing sequences, Raman spectroscopy has been performed to assess the degree of carbonization. Such CMOS-compatible carbon electrodes are important for monolithic, low-cost biosensor development.Clinical relevance- This establishes the potential of carbonized polymer electrode for low-cost, CMOS-compatible monolithic biosensor platform for implementation in medical diagnosis and treatment.

Catalytic flower-shaped α-MoO3 lamellar structure for solid-state fiber-dye-sensitized solar cells

Herein, we report a novel micro-flower lamellar structured α-MoO 3 counter electrode for solid-state fiber-shaped dye–sensitized solar cells. The α-MoO 3 sol-gel precursor, which is Tricarbonyltris (propionitrile) molybdenum, fabricates the α-MoO 3 microstructures by applying Joule heating. Cyclic voltammetry and Tafel polarization results indicate that the α-MoO 3 counter electrode with micro-flower lamellar has higher catalytic activity than pristine Pt. Therefore, based on the efficient reduction reaction of triiodide ions, the novel α-MoO 3 counter electrode with flower-structure could enhance short-circuit current with high power conversion efficiency (PCE). Furthermore, the device with the α-MoO 3 counter electrode provides better device stability and flexibility. Under 500 bending cycles, the PCE of the novel α-MoO 3 counter electrode device maintains more than 90% characteristics, while the bare Pt device reduces to 70%. • Micro-flower lamellar structured α-MoO 3 was synthesized by Joule heating process. • Micro structured α-MoO 3 shows efficient catalytic characteristics than Pt. • Structured α-MoO 3 counter electrode significantly improved PCE of fiber DSSCs. • Fabricated fiber DSSC was used for healthcare clothes operation.

Numerical study of heat transfer and friction drag in MHD viscous flow of a nanofluid subject to the curved surface

The basic objective of this article is to highlight the impact of Joule heating, thermal radiation, and viscous dissipation on heat transfer rate and friction drag in the flow of viscous nanofluid subject to the curved stretching sheet. Moreover, the effects of magnetic field and two-heating process termed as prescribed surface temperature and prescribed heat flux is considered on the surface. The nanofluid is addressed as a mixture of alumina ( A l 2 O 3 ) nanoparticle and ethylene glycol ( C 2 H 6 O 2 ) base fluid. Initially, certain dimensionless variables have been addressed to modify the governing partial differential equation (PDEs) and the associated boundary condition into non-dimensional ordinary differential equations (ODEs) coupled with boundary conditions. Subsequently, the resulting equations are solved numerically by implementing bvp4c package in MATLAB. Multiple graphical results for heat transfer rate, friction drag, velocity, and temperature are obtained under the influence of several flow parameters like radiation parameter, Eckert number, curvature parameter, stretching parameter, Hartmann number, and volume fraction of nanoparticles. Moreover, several interesting results for the flat surface ( K → ∞ ), with prescribed heat flux and surface temperature have been determined. The current radiative and dissipative flow coupled with the Joule heating process have countless applications in various industrial and engineering techniques.

Fabrication of Semi-transparent W film Heaters via Phase Transformation

In this study, we prepared highly thermostable semi-transparent heaters composed of W layers with thicknesses of 1-20 nm, on which a 30 nm-thick ZnO layer was deposited to serve as an anti-oxidation barrier. The optical transmittance and sheet resistance of the heaters could be greatly modulated by varying the W layer thickness. For layer thicknesses up to 10 nm, the initial Joule heating above 100 oC significantly reduced the sheet resistance, by 300% for a 6 nm-thick W layer at a fixed voltage for a duration of 400 s. During the test period, heater current and heating capability continuously increased. In subsequent heater operations, the heaters exhibited highly reproducible heating capability. In contrast, for films thicker than 10 nm, the Joule heating process resulted in only a marginal reduction in sheet resistance, i.e., by 4% for a 20 nm-thick W layer. In order to investigate the sharp dependence of heater characteristics on thickness, we performed x-ray diffraction analyses, which revealed that the films thinner than 10 nm were composed of both the equilibrium low-resistivity <i>α</i>-phase and metastable high-resistivity <i><i>β</i></i>-phase, and films thicker than 10 nm contained mostly <i>α</i>-phase. The Joule heating process for the thinner films was found to transform the <i><i>β</i></i>-phase into <i>α</i>-phase at temperatures above 100 oC, which resulted in significant improvement in the heating capability of the 6 nm-thick W layer. For films thicker than 10 nm, the W layers contained mostly <i>α</i>-phase and no such transformation-induced effects were observed. Finally, W heaters composed of <i>α</i>-phase exhibited highly thermostable and reproducible heater properties, which make the heaters suitable for applications with semi-transparent heaters.

Generalized split monopole magnetospheres: The effects of current sheets

We show that energy should be dissipated or extracted in the current sheet (CS) of a split magnetosphere deviating from the Michel split monopole, with the CS heating up or cooling down. But the electromagnetic energy remains unchanged everywhere. Based on the de-centered monopole solution generated by symmetry in flat spacetime, we construct two generalized split monopole configurations, in which the field lines intersect with the CS at arbitrary angles. One configuration resembles the outer geometry of the so-called ``new pulsar magnetosphere model", for which up to $47\%$ of the spin down energy is transferred to the Joule heating process in the CS. In the other configuration, we observe that negative energy is dissipated in the CS, which is usually observed in magnetospheres on rotating black holes. This means that energy is extracted simultaneously from the central star and the CS to power the output Poynting flux at infinity. We interpret the extraction of energy from the CS as that thermal energy of charged particles in the CS is transferred to the ordered kinetic energy of these particles drifting in the force-free (FF) electromagnetic fields. Hence, the CS is like an ``air conditioner" in the sky, which can heat up or cool down, depending on the configurations.

Numerical investigations of heat transfer and skin effect characteristics within rods located in a 48-rod Siemens reactor heated by AC

Abstract In the polysilicon reduction furnace, all the energy is supplied by the heat generation on silicon rods which are heated up by the passage of electric current. The alternating current (AC) produces the alternating magnetic field, and the oscillating magnetic field induces the corresponding eddy current in the conductor, which causes the phenomenon of skin effect. In the present paper, the coupling model of thermal and electromagnetic field for the silicon rods has been developed by coupling Joule heating equation controlled by frequency and heat dissipation (radiation, convection and reaction energy). Comparing the calculated results with the industrial data, it is found that the average relative errors of the current intensities of the inner, middle and outer ring silicon rods are 7.55%, 5.55% and 7.43%, respectively, indicating that the model calculation results are accurate and can be used to accurately analyze the thermoelectric behavior of the silicon rods. Based on the Joule heating process of silicon rods in a 48-rod polysilicon reduction furnace, the influences of AC frequency on temperature and current density profile within rod arranged in different rings have been studied. The interesting results show that the high frequency current sources can generate an even temperature profile and an isothermal region inside the rod can be obtained when the RF increases to 10. Therefore, utilizing the high frequency current sources can decrease the temperature gradient within silicon rod effectively, which provides a method for producing larger diameter silicon rod. Furthermore, the voltage-current curves of low frequency (50 Hz) and high frequency (10 kHz and 50 kHz) can be predicted by the present Joule heating model, at the same time, a hybrid heating process of low frequency and high frequency is proposed.

Phosphor-in-glass (PIG) converter sintered by a fast Joule heating process for high-power laser-driven white lighting.

Currently, laser-driven lighting based on phosphor-in-glass (PIG) has drawn much interest in solid state lighting due to its high electro-optical efficiency and high-power density. However, the fabrication of PIG requires expensive equipment, long sintering time, and high cost. In this work, we utilized a simple, fast, and high temperature Joule heating process to make phosphor-in-glass bulk sintered in less than 20 s, which greatly improved the production efficiency. The PIG converters sintered under different sintering temperatures were investigated experimentally. The optimized PIG converter exhibited high and robust luminous efficacy (164.24 lm/W), a high radiant flux, and a small CCT deviation at 3.00 W. Moreover, the optimized sample also showed high temperature resistance at 3.00 W, robust temperature management during normal working. These results indicated that the optimized PIG converter sintered by the Joule heating process could offer great potential for the application in high-power laser-driven white lighting.

Continuous stabilization of polyacrylonitrile (PAN) - carbon nanotube (CNT) fibers by Joule heating

Stabilization is one of the important processes used to convert polyacrylonitrile (PAN) fibers into carbon fiber and is usually driven by energy-intensive and time-consuming convective heating. A continuous and energy-efficient alternative is desirable. Here, a continuous Joule heating process has been used for the first time to stabilize PAN fibers containing carbon nanotubes (CNT). Single-component PAN/CNT fibers and bi-component fibers with core-sheath geometry were fabricated through the gel spinning method. Joule heating was conducted continuously on a 200 filament bundle for single-component fibers and on bundles with up to 6000 filaments for the bi-component fibers. A model of heat transfer and thermodynamics occurring during Joule heating is developed and utilized to understand the reductions in stabilization time and energy consumed when compared to convective heating. The minimum energy needed for stabilization through Joule heating is estimated to be less than 1% of the energy used through convective heating.

Effects of Gyro-Tactic Organisms in Bio-convective Nano-material with Heat Immersion, Stratification, and Viscous Dissipation

Analysis has been conducted to investigate the nonuniform heat immersion phenomenon in bio-convective rheology of nanoparticles combined with gyro-tactic microorganisms. Inclined magnetic field effects are incorporated to predict magneto-nano properties. Simultaneous properties of motile microorganisms along with heat and mass transfer effects are investigated. Bio-convective phenomenon (addition of gyro-tactic microorganisms in the system to stabilize the nanoparticles) has been analyzed along with thermal stratification, viscous dissipation, and Joule heating processes. Mathematical modeling has been presented to obtain the solution numerically and analytically. Error analysis and comparison with published data have been presented to show the validity of the obtained results. Bar charts and velocity plots have been prepared for the emerging physical quantities. Numerically computed magnitudes of skin friction, local Sherwood number, motile microorganism density function, and local Nusselt number for various physical quantities have been presented in tabular form.

Thermo-mechanical modeling and experimental validation for multilayered metallic microstructures

This paper presents thermo-mechanical modeling on multilayered metallic microstructures consisting of two bilayers that enable 3D deployment once being Joule heated. A representative design of such microstructures, as well as their working principle is introduced. A mathematical model is derived using Euler–Bernoulli beam theory, and analytical solutions describing out-of-plane displacement of the multilayered microstructures when uniformly heated, which is validated by finite element analysis. Parametric analysis on thermal load and dimensional change of beam shows a good agreement between the analytical solutions and results given by finite element analysis. The phases of the near-equiatomic NiTi layer are analyzed by EDS and XRD, which prove to be austenite during the Joule heating process. The mechanical properties of austenite NiTi are incorporated into the analytical solutions that provides a good estimation of 3D deployment of microstructures made of NiTi and aluminum. The experimental results provide an approximately 7 µm out-of-plane deployment by applying a uniform temperature increase of 132 K, and parametric analysis on the dimension of top aluminum beam offers another promising approach to larger 3D deployment. The proposed mathematical model provides an efficient tool for predicting the out-of-plane deployment of such multilayered microstructures.

Strategies for Scalable Gas-Phase Preparation of Free-Standing Graphene

The preparation of graphene with high quality serves as a prerequisite for its usage. Traditional methods of graphene production, represented by liquid-phase exfoliation and chemical vapor depositi...

Enhanced Electrical and Mechanical Properties of Chemically Cross-Linked Carbon-Nanotube-Based Fibers and Their Application in High-Performance Supercapacitors

The electrical conductivity and mechanical strength of fibers constructed from single walled carbon nanotubes (CNTs) are usually limited by the weak interactions between individual CNTs. In this work, we report a significant enhancement of both of these properties through chemical cross-linking of individual CNTs. The CNT fibers are made by wet-spinning a CNT solution that contains 1,3,5-tris(2'-bromophenyl)benzene (2TBB) molecules as the cross-linking agent and the cross-linking is subsequently driven by Joule heating. Cross-linking with 2TBB increases the conductivity of the CNT fibers by a factor of ~100 and increases the tensile strength on average by 47%; in contrast, the tensile strength of CNT fibers fabricated without 2TBB decreases after the same Joule heating process. Symmetrical supercapacitors made from the 2TBB-treated CNT fibers exhibit a remarkably high volumetric energy density of ~4.5 mWh cm-3 and a power density of ~1.3 W cm-3.

Possibility of obtaining hot plasma during the breakdown of high-pressure gases in strong magnetic fields

The hot plasma production during the high-pressure gas breakdown in the strong magnetic fields with a magnetic strength H of up 16·106 A/m was considered experimentally. The breakdown occured in a short gap as a result of interaction of the monoenergetic electron beam (ne ∼ 1018 m−3, energy is about several keVs) with dense plasma (n ∼ 6 · 1022 m−3). The breakdown leads to the formation of the magnetic trap (magnetic mirror), and the discharge plasma becomes heated due to the electron beam, electron cyclotron resonance, and Joule heating processes. The studies have shown that the use of the strong longitudinal magnetic fields results in an increase in the specific power, conductivity, and plasma temperature.

In Situ Transmission Electron Microscope: Joule Heating Effect on Graphitization of Copper Incorporated Carbon Nanofiber

The joule heating process on copper (Cu) incorporated carbon nanofiber was observed carefully under the in-situ transmission electron microscope (TEM) facilities. Significant structural formation was occurred after the joule heating process showing a single crystalline encapsulated graphitic structure with dramatic improvement on graphitic structure of carbon nanofiber from amorphous to crystalline. The latter structure knowingly similar to multi-layered graphene structure. This Cu incorporated carbon nanofiber initially was shaped by the mixture of amorphous carbon and very fine crystalline Cu structure significantly changed by the effect of applied bias voltage. The change of Cu particles crystallinity also showing that the important of crystalline structure for the graphene formation. The in situ TEM results might provide very useful information on the formation of graphene and the solid phase reaction which is very interesting and vital in the graphene synthesis mechanism.

Coupled photothermal and joule-heating process for stable and efficient interfacial evaporation

Access to water and clean energy is a major concern in modern society. Although there have been huge improvements in the efficiency of solar interfacial evaporation as a technique to obtain clean water, it remains challenging for solar-driven interfacial evaporation systems to maintain stable steam generation and water production without an energy storage system. To overcome these issues, we propose a coupled tunable photothermal and joule-heating process for interfacial evaporation using a low-cost commercial carbon fiber (CF) material. The CF material had a high porosity, good water absorption, salt-rejection ability, and high total absorption (93%) and electrical conductivity (1666 S/m), which make it suitable for photothermal and joule-heating conversion. By coupling photothermal and joule-heating processes through the same CF material as the evaporation medium, a stable and efficient interfacial evaporation performance could be achieved, in which the input power of the electrical energy could be adjusted to match the loss of solar energy. Through coupled evaporation experiments, it was found that the evaporation rate reached 1.36 kg m−2 h−1, with sun irradiation power of 1 kW m−2. For photothermal conversion or joule-heating conversion, the efficiency first decreased and then increased. “Cold Vapor’’, with a lower input power, resulted in a higher efficiency, whereas heat localization led to a significant decrease in the relative ratio of the thermal losses and improved the efficiency at a higher input power. This work has further improved the multi-process coupling and multi-energy complementary process and will promote its actual application.

Highly elastic conductive sponges by joule heat-driven selective polymer reinforcement at reduced graphene oxide junctions

Polymer reinforcement of reduced graphene oxide (rGO) sponges is widely employed to enhance mechanical strength and elasticity. However, the surplus polymer decreases electrical conductivity by passivating the conductive surface of rGO flakes. Here we firstly report the selective polydimethylsiloxane (PDMS) reinforcement at the flake junction of rGO sponge by the Joule heating process utilizing the high electrical contact resistance. The preferential Joule heating of the junction is theoretically simulated by finite element modeling and experimentally confirmed by micro-thermal infrared imaging. The local temperature increase results in the further reduction of rGO and preferential PDMS curing at the flake junction only. The PDMS/rGO mass ratio was carefully optimized at 3.96. The electrical conductivity (0.087 S m−1 at 0% strain) is more than an order of magnitude higher than that (0.00251 S m−1) of the conventional oven-heated sponge with a similar PDMS/rGO mass ratio. The mechanical strength is equivalent (210.3 kPa at 70% strain), in spite of the preferential polymer coating at the rGO flake junction only, with excellent elasticity. The Joule heating method is an excellent curing strategy to selectively reinforce flake junctions for conductive elastic rGO-polymer sponges.

3D characterization of hard breakdown in RRAM device

Resistive Random Access Memory (RRAM) device is considered as a promising NVM device to replace flash memory device due to its simple design, small size and low operating conditions. The reliability of RRAM devices has been studied with respect to endurance, retention and variability for many years. However, the increasing demand of high performance and drastic down scaling trend make the reliability issues more challenging than before. In this work, a comprehensive study of hard breakdown (HBD) process in crossbar RRAM device was carried out via electrical, compositional and structural characterization methods. The results confirm that the HBD process was caused by Ta2O5 dielectric breakdown with intensive joule heating and melting process. The 3D structures of defects are well reconstructed. The percolation path was confirmed to be located at the edges of crossbar structure due to the low quality of peripheral materials and process variation. The presented work can offer a critical insight on preventing the HBD process in crossbar RRAM structure.