Contact Resistance Values Research Articles

Use of Ni/CNT Particles as Additive Fillers in Ebonite Bipolar Plates for Proton-Exchange Membrane Fuel Cells.

Composite-based bipolar plates are a chance to substitute graphite and metal bipolar plates because of their corrosion resistance and better chemical and mechanical properties, but they still have various electrical conductivity properties. One of the problems is the loading of filler that depends on matrix types which will affect the electrical conductivity of bipolar plates; ebonite has potential as a matrix in composite bipolar plates because it is obtained from elastomer or rubber. In this work, nickel and carbon nanotubes (CNT) that have a high electrical conductivity will be investigated as additive fillers on graphite particles to enhance the electrical conductivity of ebonite bipolar plates. The formulation and characterization of ebonite bipolar plates with graphite and graphite Ni/CNT and their various contents are the main objectives of this research. Characterization by scanning electron microscopy (SEM) for identification and morphology of compounds and ebonite bipolar plates and Raman spectroscopy for identification of the type carbon in Ni/CNT was performed. Some tests such as bending/flexural tests, corrosion tests, and resistance testing for interfacial contact resistance were conducted to study the properties and optimum of the composite materials. In this research, Ni/CNT particles were added as additive fillers with graphite to enhance the electrical conductivity of fillers in ebonite bipolar plates of proton-exchange membrane fuel cells and their impacts were studied. By through-plane testing, graphite fillers were added in ebonite bipolar plates with 65-75% w/w content, achieving electrical conductivity values from 22.3 to 34 S/cm. This is still below the technical target set by the US DOE for composite bipolar plates. But by adding 30% Ni/CNT filler contents in ebonite bipolar plates at various filler contents from 65% to 75% w/w, one can achieve electrical conductivities from 104.35 to 165.52 S/cm. Only 65% w/w filler with 30% Ni/CNT can meet the technical targets such as a bending/flexural test value of 25.58 N/mm2, a corrosion test value of 0.894 μA/cm2 (I corr), and an interfacial contact resistance value of 3.09 mΩ cm2. Further improvements are needed based on fuel cell applications, as indicated by some additional data that did not meet technical targets.

Preparation and Properties of Mo/Ti/Sn Conductivity Conversion Coatings on 6063 Aluminum Alloy

ABSTRACTConductivity chromium‐free conversion coatings on aluminum substrates were achieved by utilizing Na2SnO3 and Mo/Ti solutions. The composition and morphology of the coatings were characterized using XPS, SEM, EDS, AFM, and Raman spectroscopies. The corrosion behavior of the coatings in 3.5‐wt% NaCl solution was investigated through a dynamic potential polarization method and EIS analysis. Mott–Schottky and UV–Vis analyses were used to determine the semiconductor properties of the coatings, including carrier concentration and band gap. The results revealed that the main components of the coating were Al2O3, SnO2, MoO3, and MoO2 and the coating presented a double‐layer structure, including a transition layer close to the substrate and a compact layer on the surface. The coating also exhibited the properties of a p‐type semiconductor. The electrical contact resistance value of adding Na2SnO3 decreased from 0.4331 to 0.1343 Ω/in2 (in 200 psi), while the band gap decreased from 2.281 to 2.232 eV.

Hot probe technique for thin films Seebeck coefficient measurement

A new experimental method using a 50 μm diameter hand fabricated hot probe of Pt90/10Rh alloy is proposed as a tool to measure the Seebeck coefficient of thin films deposited onto electrically insulated substrates. A thermal model for heat transfer inside the probe and to the sample was developed to simulate the corresponding temperature distributions. Simulations showed that the ratio of the temperature rise in the contact point to the average temperature of the probe evolves basically independent on electrical current and film-substrate properties. Moreover, the values of contact radius and thermal contact resistance should not be necessary known, but only the pairs which are best fitting the probe thermal resistance in contact with the film-substrate. This brings a great simplification in respect with certain AFM based hot probe methods for which is necessary to determine these two parameters by calibration of the two substrates with known thermal conductivity. The values can be further used to evaluate the Seebeck coefficient of the sample with a macroscopic probe, within 1 % precision. By variance to the classical measuring methods, which resort to a heater-heat sink ensemble instrumented with thermocouples, heated metallic rods with built-in thermocouples or microfabricated structures, the proposed method is fast, reliable and of higher spatial resolution. The method was validated by measuring the Seebeck coefficient on CdS, Bi and Cr thin films reference samples, respectively.

Ohmic contacts to n-type SiC: Influence of Au and Ta intermediate layers

In this study, the optimization of metal-semiconductor contacts to reduce the contact resistance of ohmic contacts on n-type 4H-SiC. The commonly used Ni/Au metal scheme served as a reference. We introduced two novel metal schemes: (i) incorporating a thin interfacial Au layer (2 nm) into Ni/Au, resulting in Au/Ni/Au, and (ii) introducing a thin intermediate barrier layer of Ta (20 nm) into Ni/Au, resulting in Ni/Ta/Au. Rapid thermal annealing (RTA) is performed at different temperatures and durations and the electrical characteristics of the contacts are measured. X-ray diffraction analysis was employed to investigate the intermediate phases formed during annealing. In the Au/Ni/Au metal scheme, the presence of Au at the interface promoted the formation of additional phases of nickel-silicide (Ni3Si and Ni3Si2). Compared to the traditional Ni/Au scheme, the modified metal schemes led to lower surface roughness and reduced contact resistance. Specific contact resistivity values are calculated, 2.2 × 10−5 Ω-cm2 for Ni/Au, 1.37 × 10−5 Ω-cm2 for Au/Ni/Au, and 4.84 × 10−5 Ω-cm2 for Ni/Ta/Au. This research offers valuable insights for the selection of metal schemes in designing ohmic contacts on n-type SiC, with potential applications in various semiconductor device technologies.

Hyaluronic acid mediated ZnO-NPs: In relation to electrical and photocatalytic activity for dye degradation

Various processes have been implemented to purify water; however, photocatalysis is comprehensively utilized in wastewater treatment and plays a significant role in water remediation. A photocatalyst is a nanostructured metal oxide ZnO nanoparticles, which boosts the reaction rate by its existence. ZnO nanoparticles show great performance in the absorption of various organic pollutants from wastewater. The objective of this research was to enhance the photocatalytic degradation performance of HA-added ZnO NPs using methylene blue as a model wastewater. Adjusting the main physical properties and photocatalytic efficiency of ZnO-NPs was performed using hyaluronic acid (HA), a natural bioactive stabilizer. The characterization of the fabricated ZnO-NPs samples with and without HA involved the utilization of FE-SEM, AFM, XRD, FTIR, PL, and I-V. As demonstrated by the FE-SEM analysis, ZnO formed rod-like structures, 3.0 % HA:ZnO exhibited cauliflower-like structures, and 5.0 % HA:ZnO displayed honeycomb-like structures. The X-ray diffraction (XRD) analysis demonstrated that the HA:ZnO nanoparticles exhibited hexagonal wurtzite structures. The average crystallite sizes of the ZnO, 3.0 % HA:ZnO, and 5.0 % HA:ZnO NPs were determined to be 25.20, 27.30, and 20.20 nm, respectively, using the XRD patterns. The surface area was 4.439, 2.987, and 5.204 m²/g of bare ZnO, 3.0 % HA:ZnO, and 5.0 % HA:ZnO-NPs were 4.439, 2.987, and 5.204 m2/g, respectively. It is very likely that there are two different decay and/or capture mechanisms in the emission spectra because the TRPL decay profile behaves in a double-exponential way. The fast decay time constant (τ1) was 212 ps for bare ZnO and 3.0 % HA:ZnO NPs and 231 ps for 5.0 % HA:ZnO NPs. The slow decay time constant (τ2) has a similar pattern, with values of 3.716, 2.836, and 2.984 ns. The specific contact resistance values of the ZnO NPs increased from 0.113 to 45.624 ( × 105 Ω cm2) as a function of the HA concentration, as evidenced by the results of the electrical studies. The outcomes of this research present comprehensive information on noble-modified ZnO-NP materials containing HA for direct applications in electronic materials and photocatalytic degradation of organic waste in water.

Analisis Tahanan Kontak pada Pemisah (PMS) 150 kV Berdasarkan Hasil Pemeliharaan di PT. PLN (Persero) Gardu Induk Sutami

The substation is a part of the electricity distribution system from consumer generators. To maintain the operation of the substation in optimal condition, maintenance or upkeep needs to be carried out in accordance with applicable maintenance standards. One of the equipment that requires routine maintenance at the main substation is the Separator (PMS). The disconnector (PMS) functions as protective equipment installed at the main substation and functions to disconnect and connect electrical power in a no-load condition. For this reason, maintenance needs to be carried out which aims to maintain the performance of the Separator. In this practical work report, tests were carried out on the knives or contacts on the Separator (PMS) to determine the contact resistance value. Next, this value is processed to determine the value of Power Loss, Electrical Energy Loss, and Electricity Costs and to determine whether or not it is necessary to repair the Separator (PMS). The results of the 150 kV Separator contact resistance (PMS) test in the Tarahan 1 Conductor bay of the Sutami Main Substation in the R, S and Contact Resistance phases are in the normal category because they meet the permitted standards, namely R <100 µΩ. This means that the Contact Resistance tested is still in good condition and the PMS does not require further repairs and the calculation results show that the largest electricity costs occur in Phase S when the injection current is 300A, amounting to Rp. 1,098,938 and the lowest electricity costs occur in Phase R when the injection current is 100A, amounting to Rp. 89,397.

Regulating the structure and performance of amorphous carbon-based films by introducing different interlayers for applications in PEMFC bipolar plates

In this work, the effects of inserting an interlayer on the anti-corrosion performance of amorphous carbon (a-C) films in a simulated Proton Exchange Membrane Fuel Cell (PEMFC) environment have been systematically studied. Four a-C films with different interlayers, namely CCr, C-Cr-N, CrN and Cr, were prepared on 316L stainless steel substrates using unbalanced magnetron sputtering. The surface/fractural morphologies, carbon bonding structure and the anti-corrosion performance of the 4 films were observed/characterized in detail. The nanostructure and composition evolution from the film surface down to the film-substrate interface before and after electrochemical tests were also analysed via high resolution transmission electron microscopy (HRTEM). Results indicate that a-C films with CCr and C-Cr-N interlayers display superior corrosion resistance compared to undoped samples and those lacking an interlayer, with the lowest self-corrosion current density (i.e. 2.1 × 10−7 A/cm2, C-Cr-N interlayer) being nearly two orders of magnitude lower than that of the substrate (i.e. 1.1 × 10−5 A/cm2). The doped C-Cr-N interlayer plays a vital role in the corrosion resistance of the samples by accelerating oxidation of surface defect locations, inhibiting the continuous penetration of electrolyte, and improving corrosion resistance. Additionally, a-C films with a C-Cr-N interlayer exhibited an outstanding interface contact resistance (ICR) value (~3.5 mΩ/cm2) than that with a CrN interlayer (~30 mΩ/cm2) or the 316L substrate (~100 mΩ/cm2) at a typical contact pressure of 1.5 MPa. All 4 films demonstrate obviously improved hydrophobicity (contact angles against distilled water under room temperature up to 94.2°) compared to the substrate (75.8° under identical condition). In a word, this study proves that the strategy of inserting an appropriately designed interlayer (with the ternary C-Cr-N being most promising) to a-C films could alter and enhance the anti-corrosion, ICR and hydrophobic properties of 316L, proposing valuable solutions for high-performance bipolar plates (BPs) in the PEMFC industry.

Construction of unary and ternary ZnO–CuO–CdO composite thin films and comprehensive analysis of their optical, electrical, and photocatalytic performance

In this study, unary ZnO, CuO, CdO, and ternary ZnO–CuO–CdO metal oxide thin film materials were fabricated using the SILAR procedure. The XRD spectra of the synthesized films show sharp and dominant diffraction lines, indicating the high crystallinity of both the unary and ternary composite films. The crystallite size values of unary ZnO, CuO, CdO, and ZnO–CuO–CdO ternary films were found to be 18.71 nm, 12.86 nm, 15.88 nm, and 21.96 nm, respectively. FESEM pictures exhibited that nanocomposites have spherical and nanorod-like hybrid morphology, and EDX showed that Cd has a higher content than Zn and Cu. The prepared samples’ FT-IR spectra in the wavenumber range of 500–4000 cm−1 revealed the existence of numerous vibrational modes. The optical bandgap values were found to be 1.47, 3.20, 2.21, and 2.51 eV for the CuO, ZnO, CdO, and ternary ZnO-CuO-CdO films, respectively. The photocatalytic efficiency of the ternary composites is higher than that of the unary metal oxides. The specific contact resistivity values were 780.83 kΩcm2, 213.33 kΩcm2 347.33 Ωcm2, and 1.97 kΩcm2 for ZnO, CuO, CdO, and ternary ZnO–CuO–CdO thin films, respectively. Our inventions provide advanced prompting for constructing new types of catalysts. The characterization results imply that the ternary nanocomposite can be used as a cost-effective alternative material for optoelectronic and photocatalytic implementations.

Current carrying tribological properties of multi arc ion plated titanium nitride doped silver coating

Sliding electrical contact materials play a crucial role in the transmission and conversion of electrical energy, but due to various factors such as force, electricity, and heat, the interface exhibits complex wear behavior. A single solid or liquid lubrication system can no longer meet the growing performance requirements of current carrying tribology. In this study, a TiN-Ag coating was prepared using multi arc ion plating technology, and a solid–liquid composite lubrication system was formed with ionic liquid and polyurea grease, respectively. Through current carrying friction and wear tests, their tribological properties, electrical contact resistance(ECR) values, and stability were tested, and compared with the results obtained during dry friction. The coating and worn surfaces were analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results indicated that compared with dry friction, TiN-Ag coatings lubricated with ionic liquids and polyurea grease showed higher friction reduction, wear resistance, and conductivity, especially the synergistic effect between ionic liquids and coatings is prominent. The behavior of ionic liquids under voltage was analyzed, and it was found that ionic liquids formed a physical adsorption film composed of a mixture of anions and cations on the worn surface. The ordered layered structure improved the tribological performance of the system.

Influence of boron doping profile on emitter and metal contact recombination for n-PERT silicon solar cells

Increasing interest in n-type silicon (Si) solar cells due to the high-quality material properties of the n-Si wafers, their relatively low sensitivity to donor-like impurities like iron and their resistance to light-induced degradation brings more recent attention to the studies on the p+ emitter and its metal contact. In this work, we investigate the effect of the Boron doping profile on the quality of p+ emitter and their contacts with screen-printed Ag/Al metal fingers. The emitters within the scope of this study are created with BBr3 diffusion in an atmospheric diffusion furnace on n-type Si wafers and also applied to n-PERT Si cells to analyze their effects on device performance. Our results highlight the significance of the doping profile for solar cell performance, as it considerably affects the contact resistivity at the emitter-metal interface and the saturation current densities for emitter (J0, emitter) and Ag/Al metal contacts (J0, AgAl). Reducing the Boron concentration within the emitter leads to a decrease in carrier recombination in the non-contacted region of the emitter, which in turn decreases J0, emitter. However, this reduction increases the recombination in the contacted areas of the emitter, consequently elevating the J0, AgAl, and increasing the contact resistance values. Besides, the power loss analysis and simulation results based on experimental values obtained for our best solar cells group show how much J0, emitter and J0, AgAl values contribute to and would improve solar cell efficiency. The manuscript presents a case study of experimental emitter doping profile optimization applicable to similar n-type PERT or TOPCon cells with varying design parameters.

Improved Test Fixture for Collecting Microcontact Performance and Reliability Data.

Microelectromechanical systems (MEMS) ohmic contact switches are considered to be a promising candidate for wireless communication applications. The longevity of MEMS switches is directly related to the reliability and performance of microcontacts. In this work, an improved microcontact test fixture with high actuation rates (KHz) and highly precise position control (nm) and force (nN) control was developed. Here, we collected microcontact performance data from initial contact tests (ICT) and microcontact reliability data from cold switched tests (CST). To perform these tests with our test fixture, we fabricated MEMS microcontact test structures with relatively high Young's modulus electroplated Nickel (Ni)-based, fixed-fixed beam structure with Au/RuO2 bimetallic microcontacts. These structures were characterized for forces ranging from 200-1000 µN in ICT tests. In a CST test, the tested microcontact survived more than 200 million cycles at a 1 KHz cycle rate, with a stable contact resistance value ranging between 3.8-5.2 Ω. These experiments validate the potentiality of our microcontact test fixture, and will facilitate further investigation on advanced microcontacts to enhance the MEMS switch's reliability.

Inverse Estimation of Thermal Contact Resistance Between Two Layers of Cylindrical Wall

This study presents a method for estimating the space-dependent thermal contact resistance between the two-layer walls of a furnace using the boundary element method (BEM) and conjugate gradient method (CGM) for the heat conduction problem. The global solution equation in matrix form is derived using the interface conditions, and the BEM is used to solve the direct problem. The CGM minimizes the objective function and calculates the sensitivity coefficients with the complex variable derivation method (CVDM). Comparative results show that the present approach is more accurate, stable, and efficient than the conventional CGM, which is attributed to the calculation of the sensitivity coefficients by CVDM. The effects of the value of thermal contact resistance, thermal conductivity ratio, Biot number, initial guess, measurement error, and the number and position of measurement points on the inversion results are also analyzed. Finally, the effectiveness of this approach is demonstrated through numerical examples, and the inversion results show its stability, efficiency, and accuracy in identifying different and complex distributions of thermal contact resistance. Furthermore, this approach is feasible for nonintrusive measurement, which is very meaningful in practical applications.

The Impact of AI on Contact Resistance and Its Suitability in Fine Pitch Interconnects

Integration issues for a three-dimensional (3D) interconnect in a Face-to-Face (F2F) configuration are discussed. In particular, the effect of AI and organic dielectrics under the bump and their effect in chip-package-interaction (CPI) stresses as well as AI contact resistance issues that arise as the interconnection pitch is decreased. This paper will present a finite-element model created to study the stresses in advanced 3D microelectronic package. To assess the reliability of the 3D packages a submodeling approach is used to capture the CPI stresses. The modeling study presented indicates that it is beneficial to continue using AI pads as it has significatly lower stresses compared to copper pads/vias. In the second portion of the paper, the effect of PBO developer on AI corrosion is presented. Reactive ion etching (RIE) chemistries and wet chemistries were optimized using contact resistance as the success metric. Process robustness was achieved by decoupling the hard dielectric opening from the PBO via opening. Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) analysis were used to add clarity to the bump contact resistance values.

Role of Phonon Scattering on the Transport and Performance of an N-Channel Monolayer Black Phosphorus Transistor

We investigate the influence of phonon scattering on the transport properties and performance metrics of a monolayer n-channel black phosphorus transistor within a four-band tight binding Hamiltonian, employing a recursive Green's function algorithm and Buttiker probe scattering model. Our analysis reveals that electron-phonon scattering significantly degrades the on-state current, while its effects in the subthreshold region are found to be negligible. Further examination identifies optical phonons as the primary contributors to the degradation of on-state current, with acoustic phonons playing a less prominent role. The ballisticity of the device declines from 42% to 24% when transitioning from solely acoustic phonon scattering to the combined influence of acoustic and optical phonons. Expanding the placement of Buttiker probes from beneath the gate region to cover the entire path from source to drain results in a further 48% reduction in on-state current. The on-state current exhibits a parabolic relationship with the inverse Kelvin temperature. To quantify the effects of phonon scattering on device performance, we assess the key parameters, transconductance and unity current gain frequency. Phonon scattering is observed to severely impact both the parameters. The on-state transconductance declines from its ballistic value of 24.9 mS/µm to 3.99 mS/µm when both acoustic and optical phonons are concurrently active. Similarly, the unity current gain frequency decreases from 1.18 to 0.2 THz due to phonon scattering. Additionally, our analysis reveals that approximately 7–9% of the total power dissipated within the device is attributed to phonon scattering effects, while the remainder is released through thermalization in the device's contacts. Phonon scattering is shown to induce both lattice cooling and heating, depending on the presence or absence of potential barriers. When a potential barrier exists in the channel, electrons injected from the source experience lattice cooling before the barrier region and lattice heating after crossing the barrier. Including the source and drain contact resistances in our model unveils that achieving a contact resistance value of approximately 100 Ω-µm is crucial for the effective functioning of black phosphorus devices.

How to Accurately Determine the Ohmic Contact Properties on n-Type 4H-SiC

The electrical properties of ohmic contacts are classically investigated by using the transfer length method (TLM). In the literature, the TLM patterns are fabricated onto different substrate configurations, especially directly onto the 4H-SiC wafers. But, due to the high doping level of commercial substrates, the current is not confined close to the contact and, in this case, the specific contact resistance (SCR) value is overestimated. In this article, we propose, by the means of simulations, to investigate the influence of the layer under the contact towards the estimation of the SCR. The simulation results highlight that, for an accurate determination of the SCR values, an isolation layer between the contact and the silicon carbide substrate is mandatory. Thus, we have determined the characteristics (doping level and thickness) of a suitable isolation layer compatible with SCR values ranging from 10−3 to 10−6 Ω·cm2.

Characterization of the performance of Ti doped α-C/α-C multilayer coating on SS316L as bipolar plates for PEMFC

In order to improve the corrosion resistance and conductivity of 316L stainless steel (SS316L) in the PEMFC (proton exchange membrane fuel cells) environment, DC-balanced magnetron sputtering was used to deposit Ti doped α-C/α-C multilayer coating on SS316L. The influence of coating structure on its micromorphology and phase composition is characterized, and the coating corrosion and conductivity were further explored. Notably, the investigation reveals that multi-layer structure can inhibit the growth of columnar crystal structure and refine the coating surface, which gradually decreased the coating porosity of from 4.54 % (1 layer) to 0.21 % (4 layers), and the passivation current density decreases to 0.22 μA/cm2 at 0.6 V, remarkably better than the targets. In addition, the introduction of Ti-doped α-C layer further promoted the sp2 hybridization of the coating, its interfacial contact resistance (ICR) value gradually decreased from 5.28 mΩ·cm2 (1 layer) to 2.28 mΩ·cm2 (4 layers) under 1.4 MPa. Therefore, the multilayer composite structure coating significantly enhances the conductivity and corrosion resistance of the SS316L bipolar plate, are more practically applied for commercialization of PEMFC technology.

Investigation of the effect of the TaC/α-C coating process on the properties of stainless steel bipolar plates

In this study, we present a series of innovative single-layer TaC/α-C coatings designed for integration into proton exchange membrane fuel cells (PEMFC). These coatings are fabricated on stainless steel (SS316L) substrates employing the magnetron sputtering technique. We systematically explore the influence of varying TaC content and the current applied to the tantalum target on the composition, morphology, and properties of these coatings. Notably, the investigation reveals that the coatings exhibit remarkably low values for interfacial contact resistance (ICR), amounting to 0.56 mΩ cm2, and corrosion current density, measuring at 10.7 nA cm−2. Subsequently, Single-cell performance of PEMFC test shows that the highest peak power density of TaC/α-C coated SS316L bipolar plates is 1003 mW cm−2 slightly higher than that of graphite bipolar plates, which is 948 mW cm−2. All the results show that the novel TaC/α-C coating is a prospective coating for PEMFC metal bipolar plates.

A numerical framework for three-dimensional optimization of cooling channels in thermoplastic printed molds

The rapid progress of additive manufacturing (AM) technology in the last few decades has unlocked new potentials for the injection molding industry by enabling the quick and cost-efficient manufacture of molds with complex geometries Despite the wide literature regarding experimental investigations on AM polymer-based soft tools specifically produced to cope with low-volume production of small-sized injected parts, their lifespan remains uncertain, and premature failures are often related to poor thermal performance. This paper is devoted to the numerical study and enhancement of the heat transfer within a thermoplastic 3D printed insert with cooling channels (CCs). Experimental thermal characterization is performed on printed composite samples made of polycarbonate reinforced with carbon fibers, considered as tool material. The simulations are performed on an industrial case, thereby facilitating a comprehensive validation of the proposed framework. Parametric studies show a marked cycle time sensitivity to insert thermal conductivity within the 0.1–1.0 W/(mK) range while demonstrating negligible influence on cycle times for polymer–polymer thermal contact resistance values below 10−3m2K/W. Furthermore, to find a suitable arrangement of the CCs’ layout, we propose here an accurate optimization methodology based on 3D overset meshes in the finite element method context coupled to the augmented Lagrangian particle swarm optimizer. The optimized bent CCs’ configuration enhances part surface temperature uniformity by 42% and reduces its temperature delta by over 6∘C, all while employing 67% of the reference cycle time. The thermal shortcomings of the thermoplastic AM mold, compared to its steel counterpart, are also addressed in this work.

Thermal Contact Resistance of the Copper–Copper Pair with Graphene Thermal Interface in Magnetic Fields up to 10 T

Abstract—
 The thermal contact resistance of a detachable connection in copper-copper contact pair with a thermal interface from layers of graphene synthesized by the method of a low pressure chemical vapor deposi-tion on the contact surface was studied. Obtaining the value of the thermal contact resistance of a detachable contact pair copper–graphene–copper by the method of transient heat flow, at a temperature of 15–150 K under the influence of an external magnetic field up to 10 T.

Bias Voltage Dependency of Structural and Bipolar Plate-Related Properties of Cathodic Arc-Deposited Carbon-Based Coatings.

Carbon-based coatings composed of a chromium interlayer and a carbon top layer were deposited on stainless steel substrates via cathodic arc evaporation. During the carbon deposition, the bias voltage was varied between 900 and 1 V to investigate the influence on the structural, electrical, and electrochemical properties. Raman spectroscopy indicated a dependency of the intensity ratio and G peak position on the bias voltage, which can be attributed to an alteration of the structure. Transmission electron microscopy (TEM) cross-section investigations revealed a graphite-like structure for most carbon top layers but with an increasing amount of disordered fractions, eventually resulting in an amorphous structure at 1 V. To further examine the structure, electron energy loss spectroscopy (EELS) was used. In the high-loss region, distinct π* and σ* peaks could be observed, which agree well with the TEM results. Additionally, analysis of the low-loss region showed that the 1 V carbon top layer exhibits a shifted σ plasmon peak at 20 eV corresponding to an amorphous structure. The carbon-based coatings are highly conductive with low interfacial contact resistance values between 4 and 1.5 mΩ cm2 at 150 N cm-2. From a bias voltage of 200 V, the resistance increases. To evaluate the corrosion resistance, we conducted potentiodynamic polarization tests. At first, with decreasing bias voltage, the corrosion resistance increases and then decreases for both the 100 and 1 V samples. Considering the low thickness, the coating with a carbon top layer deposited at 600 V had the best corrosion resistance. In combination with the excellent contact resistance, the 600 V sample is a highly suitable coating for metallic bipolar plates.