Excellent Thermal Conductivity Research Articles

Achieving enhanced thermal conductivity and mechanical properties in Mg-Zn-Gd-Zr alloys via regulation microstructure characteristics

It is well known that the microstructure of metallic materials determines the mechanical properties. However, the effect of microstructure on thermal conductivity lacks an accurate quantitative description of this relationship. In this work, the mechanism of variation in mechanical and thermal conductivities with microstructure was revealed by the characterization of cast, heat-treated, and extruded Mg-xZn-yGd-0.6Zr (wt%) alloys: ZV66, ZV62, and ZV26. The contributions of solution atoms, second phases, grain size, and dislocations to the yield strength and thermal conductivity were quantitatively calculated, and their effects on the plasticity and work-hardening behavior were qualitatively analyzed. The results show that hot extrusion promotes the precipitation of nanoprecipitates, such as MgZn2, Mg4Zn7, and Mg5Gd, resulting in the reduction of Zn and Gd solute atoms and the introduction of high-density dislocations and grain boundaries. The extruded ZV66 alloy exhibits excellent mechanical properties and thermal conductivity (a tensile yield strength of 232 MPa, an elongation of 22 %, and a thermal conductivity of 127.6 W/(m·k)); these values are better than those reported for similar products. The achievement of high strength and thermal conductivity is attributed to the precipitation of solute atoms to improve thermal conductivity in addition to grain boundary strengthening and work-hardening strengthening to improve strength. These findings provide new insights into achieving excellent strength–thermal conductivity property amalgamations in magnesium alloys by tailoring their microstructure.

Enhancing heat transfer performance of aluminum-based vapor chamber with a novel bionic wick structure fabricated using additive manufacturing

Given the lightweight nature and excellent thermal conductivity of aluminum, it offers significant potential for light-weighting of phase-change cooling components. To further enhance the thermal performance of aluminum-based vapor chambers, this study utilized selective laser melting (SLM) to design and integrally manufacture the slightly oleophilic wick for the condenser of the aluminum-based vapor chamber, along with three different superoleophilic wick structures for the evaporator: the gyroid bionic composite porous wick vapor chamber (GBCPVC), the groove composite porous wick vapor chamber (GCPVC), and the uniform porous wick vapor chamber (UPVC). A water-cooling experimental setup was established, and the effects of wick structure, cooling water flow rate, and cooling water temperature on the maximum heat load, temperature uniformity, and thermal resistance of vapor chambers were systematically investigated. The results indicated that the gyroid bionic porous wick structure significantly enhanced the thermal performance of the vapor chamber. Under the same conditions, GBCPVC exhibited lower thermal resistance and superior temperature uniformity, achieving a higher heat load than GCPVC and UPVC. When the cooling water temperature was decreased, its maximum heat load significantly increased. Specifically, at 15 °C, the maximum heat load for GBCPVC reached 300 W, an increase of 33.33 % and 53.33 % compared to 25 °C and 35 °C, respectively. Conversely, a rise in cooling water temperature enhanced the temperature uniformity and reduced thermal resistance of CBCPVC. At 35 °C and a heat load of 120 W, GBCPVC achieved a minimum thermal resistance of 0.034 K/W and a maximum temperature difference of 1.46 °C. Additionally, an increased flow rate enhanced the maximum heat load of GBCPVC, and under high heat loads, it could also reduce the thermal resistance and improve temperature uniformity. This study provides new insights and solutions for the thermal management of phase-change cooling components in aerospace electronic devices.

Controllable defects in monolayer graphene induced by hydrogen and argon plasma

Graphene has attracted wide attentions since its successfully exfoliation. Honeycomb sp 2 carbon lattice and Dirac semi-metal band structure make graphene a promising material with excellent mechanical strength, thermal conductivity, and carrier mobility. However, the absence of intrinsic bandgap limits its application in semiconductor. Defects in graphene is supposed to modify its band structure and lead to an opened bandgap. Many methods have been demonstrated to introduce defects into graphene, such as chemical reaction, plasma, electron beam, and laser. However, the species of defects are mostly uncontrollable in most treatment processes. In this study, we report three kinds of defects can be controllably induced in graphene via hydrogen (H2) and argon (Ar) plasma. With different parameter and feeding gas, hydrogenated graphene, graphene nanomesh and graphene with vacancies can be well obtained. The defect density can be precisely controlled by tuning plasma power and irradiation time. Morphological, spectroscopic, and electrical characterizations are performed to systematically investigate the defect evolution. Graphene nanomesh and graphene with vacancies show obvious difference for roughness and coverage, whereas the morphology of hydrogenated graphene remains similar with that of as-prepared graphene. For hydrogenated graphene, an opened bandgap of ∼20 meV is detected. For graphene nanomesh and graphene with vacancies, the semiconductive on/off behaviors are observed. We believe this work can provide more details of plasma-induced defects and assist the application of graphene in semiconductor industry.

Application of carbon fiber composite materials in aircraft

Carbon fiber composite is a material with excellent mechanical properties. Compared with other high-performance fiber materials, carbon fiber composites have the advantages of high strength and high modulus even at ultra-high temperatures. In addition, the carbon fiber composite material also has excellent electrical and thermal conductivity and electromagnetic shielding performance. Carbon fiber composites are widely used in the aircraft manufacturing industry due to their incomparable performance with other composite materials. In recent years, the amount of carbon fiber composite materials in newly developed aircraft products has reached more than 50%. This paper aims to explore the application of carbon fiber in aircraft, and to reflect the importance of carbon fiber composite materials by comparing models that use composite materials and models that do not use composite materials. The study explores the application of carbon fiber composite materials in aircraft through a comprehensive literature analysis and review. Key findings indicate significant advantages of these materials in enhancing aircraft performance, including reduced weight and increased strength. The paper also discusses the challenges in manufacturing and environmental impacts, offering insights into future research directions for sustainable aviation technologies.

Experimental Investigation on Ultra-Thin Vapor Chamber with Composite Wick for Electronics Thermal Management.

Ultra-thin vapor chambers (UTVCs) are widely used to cool high-power electronics due to their excellent thermal conductivity. In this study, a UTVC of 82 mm × 58 mm × 0.39 mm with composite wick was prepared. The composite wick is composed of two layers of copper mesh and multiple spiral-woven meshes (SWMs), and the composite wick was applied in UTVC to improve liquid replenishment performance and temperature uniformity. Furthermore, the thermal performance of UTVCs with different support column diameters, filling ratios (FRs), and SWM structures was experimentally studied. The results found that the equivalent thermal conductivity (ETC) decreases as the diameter of the support column increases; the UTVC with 0.5 mm support column diameter has the highest ETC, at 3473 W/(m·K). Then, the effect of FR on the heat transfer performance of UTVCs with SWM numbers of 0, 1, 2, and 3 (0 SWMs, 1 SWM, 2 SWMs, 3 SWMs) is consistent, the 30% FR UTVC with 3 SWMs having the highest ETC, at 3837 W/(m·K). Finally, the increased number of SWMs can significantly improve the ultimate power of the UTVCs, the UTVC with 3 SWMs having the highest ultimate power, at 26 W. The above experimental studies indicate that the designed and manufactured UTVCs have great potential advantages in thermal dissipation for electronics.

Liquid phase synthesis of AgNWs composites modified with Ag2O nanoparticles

Silver nanowire transparent electrodes (TCEs) are promising candidates for various applications. This is because of their excellent optoelectronic properties and thermal conductivity. However, the mechanical characteristics of silver nanowires (AgNWs) are not very prominent. In recent years, metal oxide surface modifications have been used to enhance the properties of AgNWs. Meanwhile, most of them have aimed at improving the macroscopic parameters, making little mention of theoretical guidance concerning the modification mechanism and bonding mode. To address this issue, composites of Ag2O nanoparticles grown on the surface of PVP@AgNWs were prepared in the present work through a straightforward liquid-phase synthesis approach, while guaranteeing the initial dispersion. The mechanism of the sodium borohydride (NaBH4) modifier on the surface of PVP@AgNWs and the growth mode between Ag2O and the PVP@AgNWs surface were analyzed using XPS, TEM, and other characterization techniques. This supports the subsequent introduction of metal oxide nanoparticles to modify AgNWs.

Vertically aligned and conformal BN-coated carbon fiber to achieve enhanced thermal conductivity and electrical insulation of a thermal interface material

Due to excellent thermal conductivity, high aspect ratio, and low density, mesophase pitch-based carbon fibers (MPCFs) are highly desired in electronic packaging. However, their thermal conductivity is hard to present in the polymer matrix because of the disordered stacking and low filling. Moreover, few researches are focused on the enhancement of the electrical insulation performance for MPCFs. Herein, we report vertically aligned and insulating boron nitride (BN) coated carbon fiber (CF) powders as significant fillers for polymer composites, endowing markedly improved thermal conductivity and electrical insulation. The high-quality BN coating layer on the surface of the CF is produced by a cooling precipitation method and high-temperature treatment with ingenious use of solubility properties, exhibiting a conformal, dense, and highly crystalline structure. This preparation method overcomes the limitations of coating thickness and particle agglomeration, resulting in a 31-fold enhancement of the electrical resistivity of the CF powders. After orientation treatment in a silicone rubber matrix, such CF@BN-filled pads exhibit good thermal conductivity, significantly improved insulation performance, and excellent mechanical properties. Among them, the optimized pad achieves a thermal conductivity of 12.06 W m−1 K−1, a volume resistivity of 50 × 108 Ω cm and a breakdown voltage of 3100 V mm−1, exceptional flexibility, and a favorable compression ratio (@45 psi) of 41.7 %. This work provides unique insights into constructing carbon fiber fillers as well as the preparation of high thermal conductivity composites, thereby expanding the application scenarios of carbon fiber powder in electronic packaging.

Simultaneously improving thermal conductivity, mechanical properties and metal fluidity through Cu alloying in Mg-Zn-based alloys

Mg-Zn-based alloys have been widely used in computer, communication, and consumer (3C) products due to excellent thermal conductivity. However, it is still a challenge to balance their mechanical performance and thermal conductivity. Here, we investigate microstructure, mechanical performance, thermal conductivity and metal fluidity of Mg-5Zn (wt.%) alloy after Cu alloying by experimental and simulation methods. First, Mg-5Zn alloy consist of α-Mg matrix and interdendritic MgZn phases. As the Cu content increases, however, MgZn phases disappear but intragranular Mg2Cu and interdendritic MgZnCu phases appear in Mg-5Zn-Cu alloys. Besides, the grain size of α-Mg phase is refined and the volume fraction of MgZnCu phase increases as the Cu content increases. Second, Cu addition is found to improve thermal conductivity of Mg-5Zn alloy remarkably. Especially, Mg-5Zn-4Cu alloy exhibits the best thermal conductivity of 124 W/(m·K), which is mainly due to the significant reduction in both solid solubility of Zn in the α-Mg matrix and lattice distortion of α-Mg matrix. Moreover, a stable crystal structure of MgZnCu phase also contributes to an increased thermal conductivity based on first principles and molecular dynamics simulations. Third, Cu addition simultaneously enhances strength and ductility of Mg-5Zn alloy. Tensile yield strength and elongation of Mg-5Zn-6Cu alloy reach 117 MPa and 18.0 %, respectively, which is a combined result of refinement, solution, second phase, and dislocation strengthening. Finally, combined with a phase field simulation, we found that Cu addition enhances metal fluidity of Mg-5Zn alloy. On the one hand, Cu alloying not only delays dendrite growth but also prolongs solidification time. On the other hand, MgZnCu phase stabilizes the dendrite growth of the α-Mg phases by reducing energy consumption during solidification of liquid metal. This work demonstrates that Cu alloying is an ideal strategy for synergistically improving the thermal conductivity, mechanical performance and metal fluidity of Mg-based alloys.

Investigation of liquid crystal epoxy resin composites for application in cryogenic environments

AbstractIt is well accepted that the intrinsic thermal conductivity is extremely important in achieving excellent thermal conductivity composite and can be improved via incorporation of mesogens. In this work, an azomethine type liquid crystal epoxy (LCE) with aliphatic ether was designed and synthesized with expected structure, and the liquid crystal epoxy resin (LCER), together with KH‐550‐modified boron nitride (K‐BN)/LCER composites, has been obtained. Results show an increase of 31.6% in the thermal conductivity of the matrix, which could result in an enhancement of 57.7% for the composites when compared with E‐51. Additionally, the coefficient of thermal expansion (CTE), dielectric properties, and shear strength of LCER and K‐BN/LCER composites were assessed across a broad temperature range. Remarkably, the 30 wt% K‐BN/LCER composites showed a maximum decrease of 37.8% in CTE, while maintaining adequate shear strength to fulfill the bonding requirement and high thermal conductivity at both RT and −196°C.

Eco-friendly preparation of polyimide/boron nitride composite films with excellent thermal conductivity and mechanical properties

Polyimide/hexagonal boron nitride (PI/BN) composite films have attracted interest as heat dissipation materials for advanced microelectronic devices. However, conventional preparations of PI/BN composite films employ harmful and expensive high-boiling organic solvents. In this work, thermally conductive PI/BN composite films were, for the first time, prepared using a nontoxic, eco-friendly, and inexpensive aqueous solvent. BN was ultrasonically exfoliated in a mixed solvent of water and tert-butanol to obtain aqueous BN suspensions, in which a poly(amic acid) salt (PAAS) was synthesized. The PAAS/BN suspensions were then drop-casted, and thermally imidized into PI/BN composite films. The PI/BN films exhibited excellent in-plane and out-of-plane thermal conductivities (up to 15.043 W/mK and 1.142 W/mK, respectively), which is attributed to the effective exfoliation and dispersion of BN in the aqueous solvent. Furthermore, these films exhibited high tensile strength, flexibility, and thermal stability.

Multifunctional flexible composite membrane based on nanocellulose-modified expanded graphite/electrostatically spun fiber network structure for solar thermal energy conversion

To enhance the application range of flexible films, it is crucial to rationally design composite films with high stretchability, excellent thermal conductivity, and water resistance. Flexible composite films with nanocellulose (CNF)-modified expanded graphite and spun fibers loaded with phase change materials as the backbone were obtained by electrospinning method. The prepared materials were characterized by good tensile properties (328.32%), high latent heat (107.0 J/g), good thermal stability, high photo-thermal conversion efficiency, good reusability, flame retardant properties, UV resistance and visible light absorption properties. What's more, the performance of the flexible composite membrane is adjustable. The prepared flexible composite membranes are promising in the fields of solar thermal energy conversion, wearable flexible materials and renewable energy utilization.

Rational design of diamond through microstructure engineering: From synthesis to applications

AbstractDiamond possesses excellent thermal conductivity and tunable bandgap. Currently, the high‐pressure, high‐temperature, and chemical vapor deposition methods are the most promising strategies for the commercial‐scale production of synthetic diamond. Although diamond has been extensively employed in jewelry and cutting/grinding tasks, the realization of its high‐end applications through microstructure engineering has long been sought. Herein, we discuss the microstructures encountered in diamond and further concentrate on cutting‐edge investigations utilizing electron microscopy techniques to illuminate the transition mechanism between graphite and diamond during the synthesis and device constructions. The impacts of distinct microstructures on the electrical applications of diamond, especially the photoelectrical, electrical, and thermal properties, are elaborated. The recently reported elastic and plastic deformations revealed through in situ microscopy techniques are also summarized. Finally, the limitations, perspectives, and corresponding solutions are proposed.

Vertically aligned carbon fiber/polydimethylsiloxane composites prepared by lyophilization with exceptional thermal conductivity and electromagnetic interference shielding performance

Composites with high thermal conductivity and exceptional electromagnetic interference (EMI) shielding properties are crucial for ensuring the long-term stability of electronic devices. One-dimensional carbon fibers (CFs) stand out as promising materials due to their excellent thermal and electrical conductivity. However, the anisotropic nature of CFs limits the overall electrical and thermal conductivity of the composite, thus impeding its practical application. To address this limitation, we investigated the effect of different freezing methods on CF orientation using the ice template method. Subsequently, CF-150/PDMS and CF-250/PDMS composites with varying average lengths of CFs were prepared using the unidirectional freezing technique. We studied the influence of CF content and average length on the anisotropic thermal conductivity and EMI shielding properties of the composites. The CF-250/PDMS composite, with a CF content of 15.71 vol%, exhibits a remarkable thermal conductivity of 9.07 W·m−1·K−1 and a low thermal resistance of 2.61 °C·cm2‧W−1. The thermal conductive mechanism of CF/PDMS composites was simulated by thermal conduction model and finite element analysis. Furthermore, it demonstrates longitudinal electromagnetic interference shielding effectiveness (EMI SE) reaches up to 39.66 dB, while the transverse EMI SE reaches up to 52.55 dB. The vertically aligned CF/PDMS composites exhibit significant potential for a range of applications in thermal management and EMI shielding.

Artificial neural network analysis of the flow of nanofluids in a variable porous gap between two inclined cylinders for solar applications

Copper (Cu) nanoparticles (NPs) and polyvinyl alcohol (PVA) are utilized to enhance heat transfer (HT) which is used in the efficiency of solar energy systems. Copper nanoparticles have excellent thermal conductivity (TC) properties that enable them to conduct heat efficiently. In this arrangement, the gap between the two cylindrical channels is settled for the hybrid nanofluids (HNFs) flow in an inclined position that is favourable to sunlight. The nanomaterials consist of a mixture of PVA and Cu nanoparticles (NPs), to execute HNFs. Solar radiation is present on the hot side of the system. The porous gap between the two channels is considered variable which plays a crucial role in enhancing heat transfer and energy conversion. The varying permeability of the gap is adjusted to control the flow resistance and improve the stability of the system. It is observed that higher porosity allows for better convective heat transfer and reduced pressure drop. The transformed equations are solved through an artificial neural network (ANN) while the control volume finite element method (CVFEM) is also used to handle the governing equations. The Cu and PVA (HNF) improves solar radiation absorption and protects components, ultimately increasing the performance and efficiency of the systems.

Enhancement effects of hydrolysable/soluble Al-type dopants on the efficiency of CaO/CaCO3 thermochemical energy storage

Modification of CaO-based materials using Al-type dopants has been considered a promising method to enhance energy storage performance. The synergistic multi-doping effects of different Al-type dopants (soluble, hydrolysable and insoluble) on the energy storage performances, thermophysical and mechanical properties of CaO-based materials have never been reported. The hydrolysable/soluble Al-type supports co-doped CaO-based pellets were prepared, which exhibited superior energy storage density, multi-cycle stability, reaction rate, thermal conductivity and crushing strength compared to undoped CaO pellets. The regulation mechanisms of hydrolysable/soluble Al-type dopants (AlN/Al(NO3)3) on the reaction kinetics, multi-cycle stability, thermophysical properties and mechanical properties of CaO-based pellets were revealed. The addition of different Al-type dopants results in different dispersions of the formed Ca12Al14O33, which leads to different micro-morphologies and pore structures of CaO-based pellets. Hydrolysable Al-type dopants exhibit a more concentrated distribution in CaO-based pellets and the pellets have smaller crystallite sizes of CaO and predominantly microporous pores, which results in the high CO2 reactivity. Soluble Al-type dopants exhibit a more uniform dispersion in CaO-based pellets and the pellets have larger crystallite sizes of CaO and obvious pore channels, which results in the improved cyclic stability and decomposition kinetics. The optimized CaO-based pellets combine the advantages of the two Al-type dopants and present an increasing trend of energy storage density during the cyclic process. Its energy storage density remains 1571 kJ/kg after 50 cycles, and the value for CaO is only 569 kJ/kg. In addition, the optimal synthesized material has excellent thermal conductivity and crushing strength, which are 1.36 and 9.75 times those of CaO, respectively.

Preparation and characterization of eicosane-paraffin/expanded graphite/polyurethane as form-stable composite phase change materials with wide phase change temperature range

Phase change materials (PCMs) with wide phase change temperature range, high latent heat, good thermal conductivity, and shape stability are essential for applications such as solar energy conservation and thermal management of electronic devices. Form-stable composite PCMs (FSCPCMs) with a broad phase change temperature range of 18–65 °C were successfully developed by using a mixture of eicosane and paraffin mixture along with cross-linking polyurethane as PCM, expanded graphite as thermally conductive filler and supporting material. The prepared FSCPCMs demonstrated excellent thermal stability and thermal conductivity with a latent heat up to 142.5 J/g. In conclusion, the synthesized FSCPCMs exhibit promising potential for practical applications in thermal energy storage.

Cell membrane-inspired self-assembly corrosion resistant liquid metal composite coating with photothermal/electrothermal anti-icing/de-icing performance

Liquid metals have been expected to be promising photothermal/electrothermal anti-icing materials for their excellent electrical and thermal conductivity. However, inescapable oxidation and corrosion limit the life and efficiency of liquid metal materials. Inspired by the self-assembly of phospholipid molecules in cell membranes, self-assembly corrosion resistant liquid metal composite coating is designed to protect liquid metal from icing and corrosion hazards. Based on self-assembly of fluor‑silicon molecules mimicking phospholipid molecules and micro-nano surface morphology, the coating has water contact angle of 150.8°and icing delay time of 497 s, which is 4.21 times that of unmodified liquid metal. Under the combined action of 80.5 °C photothermal effect and superhydrophobicity, the de-icing efficiency of the coating is 2.04 times that of the unmodified liquid metal. The photothermal de-icing efficiency remains 99.3 % after two months of acid corrosion and 94.4 % after two months of alkali corrosion. In addition, the thermal network of the coating leads to thermal conductivity of 3.66 W/mK and flame retardancy with UL94 at V0 rating. The coating is made into an electrothermal device with 52.5 °C heating temperature and rapidly de-icing property. The cell membrane-inspired self-assembly liquid metal composite coating provides a secure solution for long-term photothermal/electrothermal anti-icing/de-icing in exposed environment.

Thermoelectric Limitations of Graphene Nanodevices at Ultrahigh Current Densities.

Graphene is atomically thin, possesses excellent thermal conductivity, and is able to withstand high current densities, making it attractive for many nanoscale applications such as field-effect transistors, interconnects, and thermal management layers. Enabling integration of graphene into such devices requires nanostructuring, which can have a drastic impact on the self-heating properties, in particular at high current densities. Here, we use a combination of scanning thermal microscopy, finite element thermal analysis, and operando scanning transmission electron microscopy techniques to observe prototype graphene devices in operation and gain a deeper understanding of the role of geometry and interfaces during high current density operation. We find that Peltier effects significantly influence the operational limit due to local electrical and thermal interfacial effects, causing asymmetric temperature distribution in the device. Thus, our results indicate that a proper understanding and design of graphene devices must include consideration of the surrounding materials, interfaces, and geometry. Leveraging these aspects provides opportunities for engineered extreme operation devices.

Infrared Radiation-Assisted Non-Pressure Sintering of Micron-Sized Silver for Power Electronic Packaging

In recent years, silver sintering has gained increasing attention in high-power density electronic packaging due to its characteristics such as a high melting point and excellent thermal and electrical conductivity. Micron-sized silver sintering offers a lower cost, but requires a longer processing time and additional pressure, which constrains its application. This paper presents a low-cost sintering process using infrared radiation (IR) as a heat source. By leveraging the unique properties of IR, the process achieves selective heating. The thermal energy can be mainly absorbed by the specific areas requiring sintering. This innovative approach eliminates the need for external pressure during the sintering process. This feature not only simplifies the overall process but also reduces the processing time required for sintering. The silver joints obtained from IR sintering process for 45 min achieved an average chip shear strength of 38 MPa at a temperature of 225 °C, which is higher than the strength of silver joints obtained from a traditional sintering process for 2 h. Additionally, the IR-sintered silver joints have a resistivity of 9.83 × 10−5 Ω·cm and scanning electron microscope (SEM) images of the joints reveal that the sintered joints obtained through the IR sintering process exhibit less porosity compared to joints obtained through a traditional sintering process. The porosity of the IR silver joints at 225 °C is 6.4% and does not change even after 3000 cycles of thermal shock testing, showing outstanding reliability. A GaN power device using IR silver joint also performed better in thermal and electrical performance testing, showing promising potential for the application of micro-silver paste in power electronic devices.

Improving the Wear Resistance Properties of 7A04 Aluminum Alloy with Three Surface Modification Coatings

Multiple advantages, such as good formability, high specific strength, excellent thermal conductivity, and high corrosion resistance, enable aluminum alloy wide application in various fields; however, low surface hardness and poor wear resistance limit its further development. In this study, three surface modification coatings were successfully prepared on the surface of 7A04 aluminum alloy by microarc oxidation (MAO) and a combination of hard anodizing treatment (HA) and physical vapor deposition (PVD), named MAO, HA+W+DLC, and HA+Ti+ta-C, respectively. The microstructure, hardness, and tribological properties of the three coatings and the 7A04 aluminum alloy substrate were studied. The results show that the surface quality and hardness of the coated samples were higher than those of the 7A04 aluminum alloy and that the HA+Ti+ta-C coating possessed the highest hardness of 34.23 GPa. Moreover, the wear resistance of the two multilayer coatings was significantly improved during the ring-block wear tests under oil lubrication, exhibiting a wear rate of 1.51 × 10−7 mm3/N·m for HA+W+DLC and 1.36 × 10−7 mm3/N·m for HA+Ti+ta-C.