High Thermal Conductivity Of Copper Research Articles

Dynamic phase change materials with extended surfaces

Phase change materials (PCMs) present opportunities for efficient thermal management due to their high latent heat of melting. However, a fundamental challenge for PCM cooling is the presence of a growing liquid layer of relatively low thermal conductivity melted PCM that limits heat transfer. Dynamic phase change material (dynPCM) uses an applied pressure to pump away the melt layer and achieve a thin liquid layer, ensuring high heat transfer for extended periods. This paper investigates heat transfer during dynPCM cooling when the heated surface has extended features made from high thermal conductivity copper (Cu). Using experiments and finite element simulations, we investigate the heat transfer performance of dynPCM paraffin wax on finned Cu surfaces. A total of 102 transient temperature measurements characterize the performance of dynPCM with extended surfaces and compare the performance with other cooling methods including hybrid PCM and air cooling. The study examines the effects of fin geometry, applied power (20–65 W), and pressure (0.97–12.5 kPa). For dynPCM on a finned surface and a heating power of 65 W, the thermal conductance is 0.45 W/cm2-K, compared to 0.22 W/cm2-K for dynPCM on a flat surface and 0.10 W/cm2-K for hybrid PCM. The heat transfer is highest at the fin tips where the melt layer is thinnest, providing valuable design guidelines for future high performance dynPCM cooling technologies.

Optimization Of Photophoretic Forces In Coated-Hollow Microspheres

Photophoresis, a thermal phenomenon, generates non-contact forces on microparticles in a fluid when exposed to a light beam, such as a laser. These forces depend on the geometrical, thermal, and optical properties of the particles, and aligning these properties in inhomogeneous particles can enhance photophoretic forces. The use of coated-hollow microspheres offers a promising approach to this challenge. This work presents a photophoresis model for a threelayered microsphere in the slip-flow regime, applying Navier-Stokes equations with corrected boundary conditions. We used numerical approaches to compute the heat source function using Lorenz-Mie theory and validated the results against previous works. Applied to a copper-coated glass bubble, the model analyzed the photophoretic force as a function of coating thickness, considering several shell thicknesses. Results show that nanometric scale coatings enhance the force up to a maximum, after which the high thermal conductivity of copper reduces it. For coatings above 100 nm, the force becomes insensitive to shell thickness, demonstrating copper’s dominance in optical and thermal phenomena. The study suggests depositing excess coating for higher photophoretic forces, providing a framework for optimizing microparticle design for photophoretic applications. Future work includes further validation through numerical models and experiments and finding analytical solutions for integrals associated with terms in the boundary coefficients using Lorenz-Mie Theory, which holds great promise for advancing our understanding of photophoresis.

Advancements in Additive Manufacturing for Copper-Based Alloys and Composites: A Comprehensive Review

Copper-based materials have long been used for their outstanding thermal and electrical conductivities in various applications, such as heat exchangers, induction heat coils, cooling channels, radiators, and electronic connectors. The development of advanced copper alloys has broadened their utilization to include structural applications in harsh service conditions found in industries like oil and gas, marine, power plants, and water treatment, where good corrosion resistance and a combination of high strength, wear, and fatigue tolerance are critical. These advanced multi-component structures often have complex designs and intricate geometries, requiring extensive metallurgical processing routes and the joining of the individual components into a final structure. Additive manufacturing (AM) has revolutionized the way complex structures are designed and manufactured. It has reduced the processing steps, assemblies, and tooling while also eliminating the need for joining processes. However, the high thermal conductivity of copper and its high reflectivity to near-infrared radiation present challenges in the production of copper alloys using fusion-based AM processes, especially with Yb-fiber laser-based techniques. To overcome these difficulties, various solutions have been proposed, such as the use of high-power, low-wavelength laser sources, preheating the build chamber, employing low thermal conductivity building platforms, and adding alloying elements or composite particles to the feedstock material. This article systematically reviews different aspects of AM processing of common industrial copper alloys and composites, including copper-chrome, copper-nickel, tin-bronze, nickel-aluminum bronze, copper-carbon composites, copper-ceramic composites, and copper-metal composites. It focuses on the state-of-the-art AM techniques employed for processing different copper-based materials and the associated technological and metallurgical challenges, optimized processing variables, the impact of post-printing heat treatments, the resulting microstructural features, physical properties, mechanical performance, and corrosion response of the AM-fabricated parts. Where applicable, a comprehensive comparison of the results with those of their conventionally fabricated counterparts is provided.

Microwave joining of copper pipes using selective microwave hybrid heating process: Simulation and experimental study

High thermal conductivity of copper poses serious challenges in its joining in conventional welding techniques leading to development of alternate welding techniques. Microwave welding is one such newly developed joining technique that use selective microwave hybrid heating (SMHH). The joining of the copper pipes using SMHH has not been explored in existing literature. The present paper attempts the microwave joining of copper pipes using SMHH. The exposure time required for joining copper pipes using SMHH was predicted by COMSOL Multiphysics software. The joining was attempted at the predicted exposure time using a novel cavity design inside a conventional microwave oven. The copper pipes have been successfully joined at temperature and exposure period of 1080ºC and 720 s respectively and was in good agreement with the predicted values i.e., 708 s. Scanning electron microscopy (SEM) revealed good metallurgical bonding between the base metal and joint interface. The presence of columnar grains has been observed at heat affected zone (HAZ) using electron back scattered diffraction (EBSD). EBSD analysis revealed randomly arranged grains with mixed modes of planes inside the base metal. The occurrence of high angle grains (HAGs) along with high dislocation density in base metal resulted in the improvement in the mechanical properties as revealed in grain average misorientation (GAM) maps. The maximum value of microhardness has been observed at the joint region (105 ± 7 Hv) followed by base metal and HAZ i.e. (97 ± 5 Hv) and (89 ± 8 Hv) respectively owing to the existence of fine grain of copper (µm) and carbide formation.

Study on wear properties of high hardness and high thermal conductivity copper alloy for crystallization roller

The crystallization roller in thin strip continuous casting combines the cooling function of the plate crystallizer with the rolling function of the roll, thereby significantly enhancing process efficiency. This also imposes higher demands on the thermal conductivity and hardness of the crystallization roller. During the utilization of the crystallization roller, as it comes into contact with the billet, the base material must exhibit exceptional wear resistance. The thermal conductivity and mechanical properties of high-strength beryllium copper alloy C17200 and traditional crystallization material CrZrCu alloy C18150 were assessed at various temperatures using a laser thermal conductivity meter (LFA-427) and microhardness meter (ZD-HVZHT-10), respectively. Detailed analysis confirms the potential suitability of C17200 as an alternative material for crystallization rollers. The hardness of C17200 was twice that of C18150 while maintaining the original thermal conductivity. The wear characteristics of C17200 were investigated at room temperature (25 °C) and simulated operating conditions (300 °C) using a reciprocating wear tester (MZF-1). Additionally, the wear mechanism of C17200 at different temperatures was studied using scanning electron microscopy (SEM). The findings demonstrated that C17200 exhibited favorable wear resistance even at a temperature of 300 °C, thereby satisfying the performance criteria for the crystallization roller during operational usage.

Towards an Understanding of the Challenges in Laser Beam Welding of Copper – Observation of the Laser-Matter Interaction Zone in Laser Beam Welding of Copper and Steel Using in Situ Synchrotron X-Ray Imaging

The increasing demand for contacting applications in electric components such as batteries, power electronics and electric drives is boosting the use of laser-based copper processing. Laser beam welding is a key for an efficient and high-quality electric vehicle production due to its local, non-contact energy input and high automation capability enabling reproducible weld quality. Nevertheless, a major challenge in process design is the combination of energy-efficiency and precise process guidance with regard to weld seam depth and defect prevention (i.e. spatter, melt ejections), partly caused by the high thermal conductivity of copper. High power lasers in the near infrared range and emerging visible laser beam sources with excellent beam quality can provide a suitable joining solution for this purpose. However, the underlying physical phenomena are currently only partly understood and a reflection on the challenges of laser beam welding of copper compared to well researched steel processing has not yet been carried out. In order to improve the understanding of the effect of the different material properties and the influence of process parameters on the vapor capillary and melt pool geometry in laser beam welding, in situ synchrotron investigations on Cu-ETP and S235 using 515 and 1030 nm laser sources were conducted. The material phase contrast analysis was successfully used to distinguish vapor capillary and melt pool phase boundaries during the welding process with high spatial and temporal resolution up to 5 kHz. A significantly different vapor capillary geometry and sensitivity to parameter variation were found between the steel and copper material. In addition, the visualization of characteristic melt flows revealed different melt pool dynamics and a pronounced eddy close to the melt pool surface for copper, which is assumed to be causal for the observation of pronounced spatter formation during copper welding in a certain process window.

Thermal performance comparison of flat plate pulsating heat pipes of different material thermal conductivity using ethanol-water mixtures

A flat plate pulsating heat pipe (FPPHP) consists of mini/micro capillary channels machined on a flat plate in a serpentine manner. The working fluid oscillates in the form of liquid slugs and vapor plugs transferring heat. The slug-plug oscillations, internal flow regimes, startup heat requirement, thermal resistance, and evaporator dry-out depend on the thermal conductivity of the flat plate. High thermal conductivity material has larger heat spreading through it with a possibility of pressure homogenizing in the system, low working fluid oscillations, and early dry-out of the working fluid. No study has compared the thermal conductivity of the different plate materials suitable with various working fluids in an FPPHP, and the present work fills this gap in the literature. In this work, the thermal characteristics of a high thermal conductivity copper and a comparatively low thermal conductivity steel FPPHPs are experimentally investigated and compared using different ethanol–water mixtures as the working fluid. Results are reported for pure water and ethanol and mixtures of ethanol:water in the ratio 1:1, 3:1, 5:1, 9:1, and 30:1 as the working fluids, filled at 60%. The power inputs are given from 40 to 200 W. The ethanol–water mixed in an ideal ratio compared to pure water or ethanol as the working fluid gives smaller thermal resistances, larger slug-plug oscillations, and lesser evaporator drying-out occurrences. The working fluid oscillations mainly influence the total thermal resistance in the steel FPPHP, and the fluid resistance is the minimum at all power inputs. In copper FPPHP, the spreading (dry) resistance through the plate primarily influences the total thermal resistance. At the optimum ethanol–water mixture ratio of 9:1, steel FPPHP has lower thermal resistance and larger slug velocities than copper FPPHP in the wide range of power inputs of 60 to 140 W. The present work on the effect of thermal conductivity and binary mixtures on the thermal performance of the FPPHP will help to design suitable FPPHP for different applications.

Performance of micro-beam X-ray absorption spectroscopy at beamline 7.2W of Synchrotron Light Research Institute

The existing BL7.2W beamline at SLRI, initially developed for Macromolecular Crystallography, was upgraded with a Si-drift X-ray detector, sample micro-stage, and polycapillary X-ray lens to provide possibilities for experiments using X-ray fluorescence (XRF) imaging and micro-beam X-ray absorption spectroscopy (μXAS) techniques. The micro X-ray beam was characterized. The beam diameter of approximately 25 μm was determined from the knife-edge scan method. The measured photon flux was 3.8 × 109, 1.8 × 109, and 6.4 × 108 photons/s for 8.0, 10.0, and 12.0 keV X-rays, respectively. Imaging XRF and μXAS measurements were successfully performed on a welding joint of oxygen-free high thermal conductivity copper and AISI304 stainless steel. This opens opportunities for SLRI users to utilize this new measurement setup for elemental and chemical characterizations of small areas on various samples.

Experimental Analysis of Two Different Heating Systems Using Copper Pipe and Carbon Steel Pipe in Shell and Tube Heat Exchanger

In this thesis, the experimental analysis of two different systems was carried out by using copper tube and steel tube in shell and tube heat exchangers. The experimental systems were designed and manufactured to have the same physical properties in two types of heat exchangers. Manufacturing costs were noted to enable comparison. 
 
 In the system where the experiments were carried out, only the heat exchanger bodies were replaced and the analyses were carried out and the other systems were kept constant. In order to perform an efficient analysis of the efficiency, the inlet temperature of the heater water was kept constant and it was not exposed to any recirculation or heat loss. Although it was observed that the efficiency of the copper tube heat exchanger increased significantly when the inlet water temperature was high during the experiments, there was no significant difference in efficiency between the two heat exchangers at low temperatures.
 
 As a result of these analyses, it has been concluded that if the heat transfer is to be carried out for low temperatures, considering the cost, the carbon steel tube heat exchanger can be used despite of the high thermal conductivity of copper.

Outgassing rate testbed for in-operation analysis of powered and heated assemblies

We introduce a new apparatus for measuring the outgassing rate of assemblies and functional units. Outgassing rates given in the literature, if available, are mostly insufficient to plan and set up a vacuum system, more so if commercial parts, preassembled items, or complex electronics with unknown components are deployed. Outgassing rates have a severe impact on the required pumping speed in ultrahigh vacuum systems and they change if the samples are powered or heated. The newly built apparatus uses the throughput method to measure outgassing rates. It can house probes with a size of 0.10×0.10×0.13m3 and supplies electrical currents of up to 5 A. In addition, a heater can establish temperatures of up to 200 °C directly. A procedure is given to identify the main gas inputs and to retrieve data with a lower limit of 1.5×10−8Pam3s−1 after 100 h in vacuum. In this paper, we present the experimental setup and first results for samples of polytetrafluorethylene, polyamide (PA6), Viton (1A), and oxygen-free high thermal conductivity copper at room temperature.

420 stainless steel-Cu parts fabricated using 3D Multi-Material Laser Powder Bed Fusion: a new solution for plastic injection moulds

A novel multi-material design concept to be applied in plastic injection moulds is proposed combining the mechanical resistance of the 420 stainless steel alloy and the high thermal conductivity of copper, in a single component, fabricated in just one event by means of homemade 3D Multi-Material Laser Powder Bed Fusion equipment. The processing strategy and the interface region between both materials are analysed and discussed both from a metallurgical and mechanical point of view. The results show a good metallurgical bonding between the two materials, with a diffusion zone of about 10 µm, capable of providing mechanical interlocking, i.e. entrapment of one material in the other, creating a physical link between them. Both materials have low porosity and the pores detected present a sub-micrometre size distribution. A few pores and cracks on both the top and cross-section surfaces were detected with some tens of micrometres in size, at the interface zone. The hardness of the 420 stainless steel and copper varied from 482 to 532 HV and 99 and 116 HV, respectively.

A copper pyramidal fractal antenna fabricated with green-laser powder bed fusion

Recent advances in additive manufacturing have enabled a new generation of electromagnetic applications to flourish. Complex geometries for dielectrics and conductors can now be simulated and rapidly fabricated from digital data. Powder bed fusion of metals is arguably the most widely adopted additive process by industry and can provide intricately-detailed structures in a wide range of high performance alloys. Copper and copper alloys have remained a challenge in this additive process, as the typical laser wavelength (approximately 1070 nm) used fails to provide sufficient absorption. Moreover, the high thermal conductivity of copper does not allow for the required heat generation for a stable melt pool. However, the recent commercial introduction of the green laser (515 nm wavelength) is enabling the printing of copper, which is particularly interesting for electrical and electromagnetic applications due to the high electrical conductivity and solderability. This paper describes the use of a green laser powder bed fusion system used to fabricate a complex fractal Sierpinski gasket ground structure with an isolated internal pyramid antenna built simultaneously—within and dielectrically isolated from the external ground element: a ship-in-the-bottle design paradigm. The electromagnetic performance, surface finish, dimensional compliance, and conductivity were measured and reported to inform the design of freestanding, geometrically-complex antennas.

A Study on the Joining Technology of Copper-Aluminium Composite Heat-Dissipating Components

Copper-aluminium composite heat dissipation components have both the high thermal conductivity of copper and the low density of aluminium. Copper and aluminium are dissimilar materials as they have significant differences in physical and chemical properties, and hence it is not easy to weld them together. In this paper, the joining of copper to aluminium is studied by using the ultrasonic brazing technique. The results show that the copper and aluminium can be connected by ultrasonic brazing, and it is found that the bonding of the copper side interface is the weak link of the entire joint, but the joint strength can still reach 95MPa.

Effect of Particle Size Distribution on Laser Powder Bed Fusion Manufacturability of Copper

One of the major benefits of the Laser Powder Bed Fusion (LPBF) technology is the possibility of fabrication of complex geometries and features in only one-step of production. In the case of heat exchangers in particular, this is very convenient for the fabrication of conformal cooling channels which can improve the performance of the heat transfer capability. Yet, obtaining dense copper parts printed via LPBF presents two major problems: the high reflectivity of 1 μm (the wavelength of commonly used laser sources) and the high thermal conductivity of copper that limits the maximum local temperature that can be attained. This leads to the formation of porous parts.In this contribution, the influence of the particle size distribution of the powder on the physical and mechanical properties of parts produced via LPBF is studied. Three copper powders lots with different particle size distributions are used in this study. The effect on densification from two laser scan parameters (scan speed and hatching distance) and the influence of contours scans on the lateral surface roughness is reported. Subsequently, samples manufactured with the optimal process parameters are tested for thermal and mechanical properties evaluation.

Simulation of the Heat Transfer Process of Superconducting Films in the Resistive State

The heat transfer in a contact–film–substrate system was analyzed under conditions in which the heat removal from a sample to the substrate is insufficient to avoid overheating of the sample. A method for increasing the heat removal from thin-film samples is proposed for low temperatures, when a high-density electric current passes through them. The property of an anomalously high thermal conductivity of copper at temperatures from 5 to 50 K is used as the main factor of the heat-sink intensification. The heat-conduction equation for the film–substrate system is solved numerically under the condition of an additional heat transfer to the potential contacts. It is shown that beryllium bronze contacts can provide an effective heat removal from samples of superconducting films in the resistive state under the conditions of a strong Joule heat release.

Additive manufacturing of copper-stainless steel hybrid components using laser-aided directed energy deposition

Combining dissimilar materials in a single component is an effective solution to integrate diverse material properties into a single part. Copper-stainless steel hybrid components are attracting more and more attention since the high thermal conductivity of copper can greatly enhance the thermal performance of stainless steel, which benefits its applications in many industries. However, direct joining of copper and stainless steel such as SS316 L is challenging since they preserve significant dissimilarities in physical, chemical, and thermo-mechanical properties. This paper aims to fabricate well-bonded copper-SS316 L hybrid parts using a laser-aided directed energy deposition (DED) process. A nickel-based alloy Deloro 22 (D22) is introduced between copper and SS316 L to address the detrimental issues in copper-SS316 L direct joints. Using this technique, defect-free interfaces are achieved at both the D22-SS316 L and copper-D22 transition zones. Tensile testing of Cu-D22-SS316 L and D22-SS316 L hybrid parts shows the fracture occurs at pure copper and SS316 L region, respectively, indicating an excellent bonding at the interfaces. Ascending in the building direction, a transition of grain structure is observed. A significant diffusion zone is obtained at both the D22-SS316 L and the Cu-D22 interfaces. The large diffusion distance results in a smooth variation in microhardness over the dissimilar materials. The microhardness increases from SS316 L to D22 with the highest value of 240 HV and then decreases from D22 to Cu with the lowest value of 63 ± 4 HV. Testing of thermophysical properties of the Cu-D22-SS316 L system indicates there is a ∼300 % increase in thermal diffusivity and a ∼200 % increase in thermal conductivity when compared to pure SS316 L. The significant increase in thermal diffusivity and conductivity validates the enhanced thermal performance of SS316 L when it is joined with pure copper.

Моделирование процесса теплоотдачи сверхпроводящих пленок в резистивном состоянии

The analysis of heat transfer in the contact-film-substrate system under conditions when the heat removal from the sample to the substrate is insufficient to ensure that the sample is not overheated. For low temperatures, a method is proposed for increasing the heat removal from thin-film samples by passing a high-density electric current through them. The property of an anomalously high thermal conductivity of copper at temperatures from 5 to 50 K was used as the main factor in enhancing heat removal. The heat equation for the film-substrate system was numerically solved under the condition of additional heat transfer to potential contacts. It has been shown that beryllium bronze contacts can provide efficient heat removal from samples of superconducting films in a resistive state under conditions of strong Joule heat release.

High speed laser cladded Ti-Cu-NiCoCrAlTaY burn resistant coating and its oxidation behavior

To improve the high temperature oxidation resistance and burn resistance performance of titanium alloy, Ti-Cu-NiCoCrAlTaY composite coating was designed and deposited on TC4 alloy using a novel high speed laser cladding technology. The chemical composition, constituent phases, microstructure and morphology of the coating were characterized by EDS, XRD, SEM and 3D laser microscope respectively. The oxidation behavior of laser-cladded Ti-Cu-NiCoCrAlTaY coating and TC4 titanium alloy was analyzed at 800 °C. It was found that the functional coating has good oxidation performance attributed to the formation of dense double layered composite oxide scales. The flame-retardant functions of TC4 substrate and Ti-Cu-NiCoCrAlTaY coating were evaluated through laser spot melting test. The high thermal conductivity of copper and high anti-oxidation of NiCoCrAlTaY promote the flame retardant performance. The formation of TiCu eutectic transition zone in front of the substrate also helps to delay the combustion process.

Measurement of Thermophysical Properties of Loose Coal Based on Multi-dimensional Constant Temperature Boundary Unsteady Heat Transfer Model

Based on the unsteady state heat transfer model, production solution method is proposed to calculate the thermal diffusivity and thermal conductivity of loose coal. By constructing the heat transfer model of the infinite large plate and the infinitely long cylinder, the temperature rise formula of the production solution method is established. The measured temperature rise is then used by the MATLAB programming software to inversely calculate the thermophysical parameters of the loose coal. During the experiment, a constant temperature boundary was constructed using an incubator and a high thermal conductivity copper cylindrical case. The experiment selected anthracite, bituminous coal in Panyi Mine, and bituminous coal in Lizuo Mine for thermophysical property measurement. The results show that the relative deviation between each measurement result and related literature is within 5 %, and each sample is tested three times. The deviations are less than 5 %, which verify the stability of the test method. Finally, the experimental model was established in the ANSYS FLUENT simulation software, and the thermophysical parameters of the measured coal samples were substituted into the model for simulation calculation. It was found that the simulation temperature rise was consistent with the measured temperature rise.

Fabrication of Mesh Patterns Using a Selective Laser-Melting Process

The selective laser-melting (SLM) process can be applied to the additive building of complex metal parts using melting metal powder with laser scanning. A metal mesh is a common type of metal screen consisting of parallel rows and intersecting columns. It is widely used in the agricultural, industrial, transportation, and machine protection sectors. This study investigated the fabrication of parts containing a mesh pattern from the SLM of AISI 304 stainless steel powder. The formation of a mesh pattern has a strong potential to increase the functionality and cost-effectiveness of the SLM process. To fabricate a single-layered thin mesh pattern, laser layering has been conducted on a copper base plate. The high thermal conductivity of copper allows heat to pass through it quickly, and prevents the adhesion of a thin laser-melted layer. The effects of the process conditions such as the laser scan speed and scanning path on the size and dimensional accuracy of the fabricated mesh patterns were characterized. As the analysis results indicate, a part with a mesh pattern was successfully obtained, and the application of the proposed method was shown to be feasible with a high degree of reliability.