Low Thermal Resistance Research Articles

4D Printing of Multifunctional and Biodegradable PLA-PBAT-Fe3O4 Nanocomposites with Supreme Mechanical and Shape Memory Properties.

4D printing magneto-responsive shape memory polymers (SMPs) using biodegradable nanocomposites can overcome their low toughness and thermal resistance, and produce smart materials that can be controlled remotely without contact. This study presented the development of 3D/4D printable nanocomposites based on poly (lactic acid) (PLA)-poly (butylene adipate-co-terephthalate) (PBAT) blends and magnetite (Fe3O4) nanoparticles. The nanocomposites are prepared by melt mixing PLA-PBAT blends with different Fe3O4 contents (10, 15, and 20 wt%) and extruded into granules for material extrusion 3D printing. The morphology, dynamic mechanical thermal analysis (DMTA), mechanical properties, and shape memory behavior of the nanocomposites are investigated. The results indicated that the Fe3O4 nanoparticles are preferentially distributed in the PBAT phases, enhancing the storage modulus, thermal stability, strength, elongation, toughness, shape fixity, and recovery of the nanocomposites. The optimal Fe3O4 loading is found to be 10 wt%, as higher loadings led to nanoparticle agglomeration and reduced performance. The nanocomposites also exhibited fast shape memory response under thermal and magnetic activation due to the presence of Fe3O4 nanoparticles. The 3D/4D printable nanocomposites demonstrated multifunctional multi-trigger shape-memory capabilities and potential applications in contactless and safe actuation.

Extremely Low Thermal Resistance of β-Ga2O3 MOSFETs by Co-integrated Design of Substrate Engineering and Device Packaging.

Gallium oxide (Ga2O3) emerges as a promising ultrawide bandgap semiconductor, which is expected to surpass the performance of current wide bandgap materials, like GaN and SiC, in electronic devices. However, widespread application of Ga2O3 is hindered by its extremely low thermal conductivity and lack of effective device-level thermal management strategies. In this work, Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) are fabricated by conducting co-integrated design of substrate engineering with layer transferring and device packaging. 3D Raman thermography is introduced as a novel method to analyze the temperature distribution within the device, which provides valuable insights into their thermal performances. A high-quality Ga2O3-SiC heterogeneous integrated material is successfully fabricated with an extremely low interface thermal resistance of 6.67 ± 2 m2·K/GW. Compared to the homoepitaxial Ga2O3 MOSFETs, the degradation of Ion/Ioff in Ga2O3-SiC MOSFETs is decreased by 1.5 orders of magnitude, and that of Ron is decreased by 31%, showing the great thermal stability of Ga2O3-SiC MOSFETs. With the additional device packaging, a significant one order-of-magnitude reduction in the thermal resistance of the Ga2O3-SiC MOSFET is achieved, reaching a record-low value of 4.45 K·mm/W in the reported Ga2O3 MOSFETs. This work demonstrates an efficient strategy for device-level thermal management in next-generation Ga2O3 power and RF applications.

Preparation and thermal conductivity properties of CF/SR composites with high orientation and low interfacial thermal resistance based on the synergistic effect of magnetic field, torsional vibration and Diels-Alder reaction

Preparation and thermal conductivity properties of CF/SR composites with high orientation and low interfacial thermal resistance based on the synergistic effect of magnetic field, torsional vibration and Diels-Alder reaction

Integrated Technologies for Anti-Deicing Functions and Structures of Aircraft: Current Status and Development Trends

With the increasing adoption of composite materials in aircraft construction, traditional anti-icing technologies face significant challenges due to the low thermal conductivity and heat resistance of composite resins. These limitations have spurred the development of lightweight, efficient, durable, and cost-effective integrated anti-icing technologies as a critical area of research. This paper begins with an overview of advancements in electrothermal anti-icing and de-icing technologies for aircraft. It then explores the configurations and applications of functional-structural integration technology for anti-icing and de-icing, emphasizing pivotal technologies and current challenges in this field. Finally, the study forecasts the development trends in the multifunctional integration of thermal conductivity/insulation, anti-icing, and electromagnetic wave transparency/wave-absorbing properties. These advancements are driven by the evolution of composite materialization in aircraft and the progression of multi-electrical/all-electrical technologies. The objective is to provide a comprehensive guide for technological development in anti-icing, aiding researchers and relevant departments to further enhance the application of anti-icing technology in composite material aircraft.

Heat transfer performance and startup characteristics of separated gravity heat pipe

Separated gravity heat pipes, with distinct arrangements of evaporating and condensing sections, offer low thermal resistance, high heat transfer efficiency, and a simple structure, making them suitable for passive cooling of spent fuel pools through gravity-driven processes. In this study, a steady-state, one-dimensional, two-phase flow model is developed to analyze phase change heat transfer in a separated gravity heat pipe. The research investigates the impact of liquid filling rate and vacuum level on heat pipe operation. The findings reveal a notable increase in pressure drop inside the tube with higher liquid filling rates, which diminishes the adaptability of the heat pipe as pressure rises, resulting in a narrower range of effective liquid filling rates. Specifically, the liquid filling rate of the heat pipe ranges from 38 % to 72 % at P = 13.75 kPa and from 44 % to 68 % at P = 15.75 kPa. Additionally, a startup prediction model is formulated based on a thermal resistance network model using the ideal gas assumption. Two startup states—namely, the initial startup state and the subsequent startup state—are proposed for large-scale separated gravity heat pipe arrays. The heat pipe achieves the large-temperature-difference initial startup state at a 50 % liquid filling rate within 7 min before transitioning to the subsequent startup state. The vapor mass, heat transfer coefficient, and working fluid temperature initially increase and then decrease over time, with varying peak times. As the liquid filling rate increases, the maximum vapor mass also increases. The heat transfer coefficient peaks at a 60 % liquid filling rate before subsequently declining. The optimal liquid filling rate of 60 % is identified based on startup time, heat transfer coefficient, and overall heat transfer efficiency.

Experimental study on the thermal performance of a novel vapor chamber manufactured by 3D-printing technology

Vapor chamber holds great application potential in the field of heat dissipation for high-power electronic devices. This study developed a novel vapor chamber using 3D-printing technology to enhance heat dissipation for compact electronic devices. The vapor chamber was constructed from aluminum alloy with a structural dimension of 60×60×30mm3. In this work, the extended condensation structure of the vapor chamber was combined with an external cooling structure, resulting in a 729 % increase in the external heat dissipation area compared to the evaporation area in a limited space. Extensive experiments were conducted using deionized water as the working fluid under various cooling conditions and heat loads. The results showed that the vapor chamber was capable of maintaining a low thermal resistance at high power and high heat flux conditions, with a minimum thermal resistance of 0.087 °C/W when the heat load was 1000 W. At a cooling water flow rate of 0.1 L/s, the vapor chamber demonstrated the capacity to withstand a critical heat load of up to 1600 W, with the heat flux of 326 W/cm2. Compared to conventional vapor chambers, this novel vapor chamber is better able to achieve stable and efficient heat dissipation under high power and high heat flux conditions, especially in a limited space.

DETERMINATION THERMAL AND MECHANICAL PROPERTIES OF NANO CARBON, GRAPHITE AND GRAPHENE REINFORCED RECYCLING POLYPROPYLENE COMPOSITE SAMPLES

Polymer-based plastic materials occupy a major place in daily life. However, due to the nature of polymer materials, low thermal resistance and mechanical properties of these products, the need for new and sustainable materials in the industry has increased. With the rapid technological developments in advanced manufacturing industries such as aviation, marine, motor sports and defence industry, lightweight and high-strength composite products have become even more important. In this context, in this study, 1% carbon, graphene and graphite particle reinforced Polypropylene (PP) composite material mixed in a twin-screw extruder and MA/G series injection moulding machine standard tensile test sample produced. Melt Flow Index (MFI), Heat Deformation Test (HDT), tensile test, Shore-D hardness measurement and density tests performed on these test samples. According to the results obtained from these tests, the mechanical and thermal properties of the test samples produced from different composite materials were determined. The best mechanical and thermal properties occurred in the graphene particle. It formed in graphite and carbon, respectively.

MXene-based semi-circle with a thin wire-shaped resonator wideband polarization-insensitive solar absorber

Fossil fuels’ supply peaks, decreases, and shortages are determined by their proven reserves, research, and consumption rates. With a large upfront cost, renewable and alternative energy sources are essential to solving the twin issues of energy and climate change. Solar absorbers are an excellent way to use renewable energy from the environment. This paper suggested an MXene-based semi-circle with a thin wire-shaped resonator (MSCWTWSR) solar absorber where the resonator layer consists of MXene material and Fe is used as substrate layer and the resonator has semi-circle and thin wire geometry which effectively absorbs the sun radiation with wideband. This proposed MSCWTWSR solar absorber works at 200–3000 (nm) wavelength and has more than 93% average absorption. The first band bandwidth of this MSCWTWSR solar absorber is 400 (nm), the second band is 530 (nm), and the third band is 470 (nm). This structure got more than 93% absorption in the AM 1.5 solar irradiation configuration. The structure gives in the Transverse electric (TE) field and Transverse magnetic (TM) field and the structure has polarization for insensitive. Furthermore, there is also investigated different incidence angles. A suggested article includes sections on testing for electric and magnetic intensities with a comparison table. The suggested solar absorber is employed in a distinct thermal heating application since MXene has a low thermal resistance and good thermal stability.

The Development of Poly(lactic acid) (PLA)-Based Blends and Modification Strategies: Methods of Improving Key Properties towards Technical Applications-Review.

The widespread use of poly(lactic acid) (PLA) from packaging to engineering applications seems to follow the current global trend. The development of high-performance PLA-based blends has led to the commercial introduction of various PLA-based resins with excellent thermomechanical properties. The reason for this is the progress in the field of major PLA limitations such as low thermal resistance and poor impact strength. The main purpose of using biobased polymers in polymer blends is to increase the share of renewable raw materials in the final product rather than its possible biodegradation. However, in the case of engineering applications, the focus is on achieving the required properties rather than maximizing the percentage of biopolymer. The presented review article discusses the current strategies to optimize the balance of the key features such as stiffness, toughness, and heat resistance of PLA-based blends. Improving of these properties requires molecular structural changes, which together with morphology, crystallinity, and the influence of the processing conditions are the main subjects of this article. The latest research in this field clearly indicates the high potential of using PLA-based materials in highly demanding applications. In the case of impact strength modification, it is possible to obtain values close to 800 J/m, which is a value comparable to polycarbonate. Significant improvement can also be confirmed for thermal resistance results, where heat deflection temperatures for selected types of PLA blends can reach even 130 °C after modification. The modification strategies discussed in this article confirm that a properly conducted process of selecting the blend components and the conditions of the processing technique allows for revealing the potential of PLA as an engineering plastic.

Effect of thermal resistance and infrared transparency on radiative cooling efficiency

Radiative cooling materials that reflect sunlight and emit infrared light to the cold sky can lower the surface temperatures of building envelopes, reducing cooling energy usage by buildings. Over the last decade, various structures, such as thin films/coatings and thick infrared-transparent/opaque foams, have been developed for these applications. Understanding the influence of thermal resistance and infrared transparency of radiative cooling materials, along with the thermal resistance of the substrate to which they are applied, is vital for optimizing their energy savings potential. Herein, we employed a heat transfer model that integrates conduction, convection, and radiation to investigate the energy savings of radiative cooling materials with varying roof and material thermal resistances. Our results suggest that radiative cooling materials are most effective on roofs with low thermal resistance, like metal roofs, and increasing roof thermal resistance reduces their energy-saving effect. Thermally insulating infrared-transparent radiative cooling foams can significantly boost energy savings by minimizing convection and radiation losses. Conversely, compared to thin film, thermally insulating infrared-opaque foams can enhance or reduce energy savings depending on whether their surface temperatures are above or below room temperature. Throughout summer, infrared-transparent foam consistently achieves the highest energy savings, whereas infrared-opaque foam shows the least. This work provides guidance for the practical application and structural design of radiative cooling materials.

Numerical investigation of the impact of inlet and outlet ports of water jet impingement cooling modules

AbstractThe ever‐growing applications of high‐power chips have driven research efforts to enhance the performance of their active cooling modules. This study proposes a simple tweak of the cooling module's ports for lower thermal resistance. A dual‐inlet single‐outlet (CP2) jet impingement cold plate (JICP), a dual‐inlet dual‐outlet (CP3) JICP, and a single‐inlet dual‐outlet (CP4) JICP were assessed computationally and benchmarked against a single‐inlet single‐outlet JICP (CP1) at the same area ratio (AR) and average diameter (Davg) of inlet and outlet ports. The results show that the pressure losses inflate by up to 4.67 folds when using CP3 with AR = 5/3 and Davg = 3.0 mm. Yet, this design also shows the largest Nusselt number and the lowest outlet water temperature, module body temperature, average temperature of the target surface, and thermal resistance (0.07415 K/W). The thermal resistance is reduced by 34.13% using CP3 at AR = 3/5 and Davg = 6.0 mm. The temperature uniformity index was boosted to 97.5%. These enhancements are attributed to the shorter and symmetric flow path, the shorter residence time of water within the JICP, and the direct heat diffusion by the walls of the lower chamber.

A practical method for the in-situ estimation of the effective thermal resistance of gas diffusion layers in PEMFC

The membrane electrode assembly of a PEM fuel cell is hotter than the gas feeding plates because heat is generated within it, and the diffusion layers are thermally resistive. The temperature gradient created, which increases as a function of the current density, is useful for evacuating the water produced in vapor form. This water transport mechanism is known as the “heat pipe effect”. The temperature gradient produces a saturation vapour pressure gradient, which in turn produces a diffusive vapor flow. Mastering water management, coupled with heat management, requires knowledge of the temperature of the MEA and therefore the effective thermal resistance of the diffusion layers. In this paper, we present an original method for estimating this thermal resistance in situ, without using heat flux sensors or directly measuring the temperature of the MEA. The method requires the ability to impose a temperature gradient between the anode and cathode plates, and to perform a hot-side water balance. Thermal resistance is deduced from the coupling between heat and water transfer. Two diffusion layers widely used by the community are tested. The GDL Sigracet 22 BB (from SGL Carbon) has a lower effective thermal resistance than the GDL Freudenberg H15C14. Variations in these thermal resistances are measured as a function of the temperature gradient imposed and of the compression ratio.

Adsorption performance with field emission scanning electron microscopy of fruit peel induced Silver Nanoparticles in C16H18ClN3S for waste water treatment

There is a growing demand for cost-effective and sustainable technologies for treating wastewater as water consumption increases and conventional technologies become more expensive. Nanoparticles have a great deal of potential for use in the treatment of waste water. Their unique surface area allows them to effectively remove toxic metal ions, pathogenic microorganisms, organic and inorganic solutes from water. This study investigated the potential of orange and banana peels as renewable nano adsorbents for removing dyes and dissolved organic compounds from textile wastewater. Orange and banana peels are an optimal selection due to their favourable chemical characteristics, namely the presence of cellulose, pectic, hemicellulose, and lignin. Their capacity to adsorb diverse anionic and cationic compounds on their surface-active sites is attributed to their unique functional group compositions. Silver nanoparticles are able to adsorb heavy metals due to their exceptionally low electrical and thermal resistance and surface plasmon resonance. The samples were thoroughly characterised using field emission scanning electron microscopy (FESEM), UV–Visible spectrometry, Fourier transform infrared spectroscopy (FTIR) and XRD. The nanoparticles were prepared (10 gm,50 gm,100 gm) and subsequently introduced to the wastewater sample. The optical density values were recorded at various time points. The optical density values demonstrate a decline over the course of the experiment, with a notable decrease observed over time. The results of this study provide valuable insights into the efficacy of these natural adsorbents and their potential for sustainable water purification technologies. For the purpose of this research, high performance instrumentation methods were performed as follows:•Field emission scanning electron microscopy for surface morphology studies.•Gas chromatography-mass spectrometry (GC–MS) for analytical technique that combines gas chromatography (GC) and mass spectrometry (MS) to identify unknown substances or contaminants.•Optical density values were measured for different timings of degradation.

Wafer-scale N-polar GaN heterogeneous structure fabricated by surface active bonding and laser lift-off

N-polar Gallium nitride (GaN) technology is one of the most important technical routes for millimeter-wave devices. This paper introduces a new approach based on reverse epitaxial layer transfer technology to fabricate N-polar GaN materials. By combining low-damage surface-activated bonding and laser lift-off techniques, a wafer-scale N-polar GaN heterogeneous structure with low O impurities, high two-dimensional electron gas density, and high carrier mobility was obtained. The thin (∼2 nm) crystal bonding interlayer, coupled with the low thermal boundary resistance of only 6.8 m2K/G·W, provides evidence for the low interfacial damage caused by this approach. These results demonstrate its superiority as an attractive method for fabricating high-performance N-polar GaN millimeter-wave devices.

Ti3C2Tx MXene/Graphene hybrid frameworks for constructing thermally conductive phase change composites with solar-thermal conversion ability

Application of three-dimensional (3D) carbon framework in phase change material (PCM) has aroused a tremendous interest. However, implementing a high alignment carbon framework with low interfacial thermal resistance (ITR) remain challenging. Herein, we demonstrated a synergetic effect strategy by Ti3C2Tx MXene and graphene nanoplate (GNP) to achieve a 3D thermally conductive framework with high alignment skeleton and low filler-to-filler ITR. Typically, the 3D anisotropic carbon framework is fabricated by unidirectional ice template freezing cellulose nanofibers (CNF)/GNP solution with the assistance of MXene. The abundant functional groups of MXene and the similar layered structure promote the dispersion stability of GNP in CNF aqueous solution, resulting in the significant improvement in GNP alignment and the filler-to-filler ITR. Therefore, the final phase change composites obtained by impregnating polyethylene glycol (PEG) into the framework achieves a satisfactory thermal conductivity (TC) of up to 3.49 W/m K at only 6.25 vol% filler loading. Combining the solar-thermal conversion ability of graphene and MXene, the PCM reveals a rapid energy conversion, transfer and storage capability. More importantly, the phase change enthalpy of the PCM can be as high as 164.3 J/g, with little change even after 50 heating-cooling cycles, and the existence of carbon framework can effectively prevent the leakage phenomenon in solid-liquid conversion process, ensuring its shape stability.

Construction of tree-ring mimetic 3D networks in polyvinyl alcohol/boron nitride composites for enhanced thermal management and mechanical properties

Constructing a three-dimensional (3D) filler network in polymer thermal interface materials (TIMs) is crucial for enhancing thermal conductivity and mechanical properties. However, the discontinuous and loose network of fillers are one of the main reasons hindering the joint improvement of thermal conductivity and mechanical properties. The construction of a regular and dense 3D continuous filler network remains a significant challenge. In this study, an innovative bidirectional freezing technique was designed to create a polyvinyl alcohol (PVA)/boron nitride (BN) composite with a tree-ring-like 3D network. This technique promotes the formation of 3D network consisting of long-range lamellar BN layers with a tree-ring-like structure by controlling the nucleation and growth of ice crystals along the bidirectional temperature gradient induced by a polytetrafluoroethylene (PTFE) cone. The resulting PVA/BN composite exhibits high thermal conductivity (6.25 W/m·K) due to the lower interfacial thermal resistance between fillers (1.271 × 10−7 K m2/W), and an enhanced tensile strength of 41.71 MPa, which is attributed to the regular and dense BN network. This study presents a feasible strategy for constructing a 3D continuous network structure in polymer-based TIMs, paving the way for advancements in thermal management solutions.

Theoretical study of solidification phase change heat and mass transfer with thermal resistance and convection subjected to a time-dependent boundary condition

The solidification of phase-change materials (PCMs) is a key process that occurs commonly in materials science and metallurgy, such as in the casting of alloys and energy management systems. There is a lot of literature in this area that assumes the PCMs are in close contact with the heat source or sink. However, a non-freezing wall frequently encloses them in practical situations. This work presents a phase change problem that describes the solidification of a semi-infinite PCM with thermal resistance. We assume that time-dependent heat flux drives the solidification process. The PCM first convert into mush and then into solid, which leads to a three-region problem. The current study accounts for both conduction as well as convection heat transfer mechanisms. Unfortunately, the exact solution to such problems with time-dependent flux-type boundary conditions may not be possible. Thus, there is considerable interest in deriving the analytical solution. The space–time transformation yields the analytical solution to the problem. A numerical example of Al−Cu alloy with 5%Cu is presented to demonstrate the current study. Thermal resistance shows a pronounced impact on the temperature field. Lower thermal resistance offers faster solidification rate. It is found that as the heat transfer constant increases, the rate of propagation of solid–mush and mush–solid interfaces gets enhanced. In addition, the growth of thermal resistance is of linear nature, with variation in the value of Q. The solidified region has higher concentration than the mush region. The current study is applicable to both eutectic systems and solid solution alloys.

Advancing cryogenic electronic cooling: A case study on embedded manifold microchannels in micromachined Joule-Thomson coolers

Thermal management plays a crucial role in the performance of electronic devices. For devices operating at room temperatures, manifold microchannels (MMCs) are essential for heat dissipation in heat sinks due to their low thermal resistance and pressure drop. However, their application in cryogenic electronic devices to enhance thermal performance has been largely unexplored. Herein, we integrated manifold microchannels into the evaporator of a micromachined Joule-Thomson (MJT) cooler to improve its cooling performance. The results show a notable reduction in the minimum cooling temperature from 105.0 K to 95.3 K, accompanied by an approximate 20 % increase in maximum cooling power. Furthermore, the coefficient of performance (COP) exhibits a rise of over 20 %. These findings underscore the feasibility and effectiveness of using MMCs in cryogenic electronic devices.

3D printable phase change based thermal interface material with lower total thermal resistance at operating temperature

Thermal interface materials (TIMs) play a crucial role in addressing the heat dissipation challenges of electronic components, which needing high thermal conductivity and low thermal resistance to effectively improve heat transfer between chip and heat sink. This work focuses on the design of a 3D printable phase change based TIMs, which can be integrated with 3D printing technology to provide shapes suitable for quickly filling the gap between the chip and the heat sink in actual automated production. The optimized sample exhibits a total thermal resistance of 0.0012 m2K/W at operating temperature, with a through-plane thermal conductivity of 0.48 W/mK and an in-plane thermal conductivity of 1.24 W/mK. In practical thermal management, the resulting samples demonstrated a temperature reduction of 22 °C comparison with commercial TIM, highlighting its superior heat dissipation capability.

Printable thermal interface materials with excellent heat dissipation capability

The rapid progression of electronic devices underscores the need for thermal interface materials (TIMs) with superior heat dissipation capabilities to address the overheating issues of high-power density electronic devices. However, the importance of excellent printability in practical automated production for TIMs has often been overlooked. This study introduces poly(2-[[(butylamino)carbonyl]oxy]ethyl acrylate)/liquid metal (Poly (BCOE)/LM) composites, which exhibit excellent printability and heat dissipation properties. The resulting materials, containing 80 wt% LM, display a low total thermal resistance of 0.69 cm2 kW−1, a low contact thermal resistance of 0.25 cm2 kW−1, a high thermal conductivity of 3.49 W m−1K−1, and effective printing capabilities through material jetting 3D printing onto chip surfaces. In thermal management applications, the composite material prepared in this work was able to reduce the temperature of the chip by a further 17 °C compared to a commercial product (Laird TFlex 300), thus highlighting its practical utility in automated production processes. This novel TIM offers a viable solution for addressing the thermal management needs of modern electronic devices.