ObjectivesWith the rapid development of the semiconductor and related industries, the power density and heat generation per unit area of electronic devices have increased dramatically. To solve the increasingly serious thermal problems of electronic components, researchers have focused on advanced thermal management materials. Diamond/Al composites have become a research hotspot for the new generation of thermal management materials due to their advantages of high thermal conductivity, low thermal expansion coefficient, and light weight. How to effectively reduce the interfacial thermal resistance is the key to fully leveraging the thermal conductivity enhancement provided by the diamond reinforcement.MethodsIn this paper, diamond particles are modified with Ti nanolayers (40, 80, and 160 nm) and Ti-Al double-nanolayers (Ti80 nm-Al60 nm) with controllable thicknesses by single-target and dual-target magnetron sputtering strategies, respectively. The rotating vibration platform used in the magnetron sputtering process controls the thickness of the layers at the nanoscale while ensuring uniform thickness. The diamond/Al composites are then fabricated by gas pressure infiltration technology, and the theoretical thermal conductivities of the composites are predicted using a combined differential effective medium and acoustic mismatch model. The influences of Ti nanolayers and Ti-Al double-nanolayers on the microstructures and thermo-physical properties of the composites are investigated.ResultsThe results show that the Ti nanolayers react with diamond to form TiC interfacial layers during the fabrication process of diamond-Ti/Al composites, which significantly enhances the interfacial bonding of the composites. By optimizong the thickness of the Ti nanolayers, a TC of 598.6 W/(m·K) is achieved at a justified TiC nanolayer thickness of 80 nm, which is about 81.08% of the theoretical value. Based on this optimized thickness of the Ti nanolayers, diamond particles with Ti-Al double-nanolayers (Ti80 nm-Al60 nm) are prepared using a dual-target sputtering strategy. After introducing the Al layer, the composites form a Diamond/TiC/TiAl3/Al gradient interface, and the thermal conductivity increases to 640.1 W/(m·K), which is 89.13 % of the theoretical value. Infrared thermography test is used to visually verify the thermal response of the composites over 0～10 s. The heating rate VDia-(Ti80 nm-Al60 nm)/Al＝2.46 ℃/s, VUncoated dia/Al＝1.53 ℃/s, and Vpure Al＝0.91 ℃/s. The heating rate of diamond-(Ti80 nm-Al60 nm)/Al is 1.6 times higher than that of uncoated diamond/Al and 2.7 times higher than that of pure Al, and the results of the infrared thermography tests correspond well with the thermal conductivity of the composites. The diamond/Al composite with Ti-Al double-nanolayers is subjected to a thermal cycling test from －50 ℃ to 150 ℃ for 100 thermal cycles, and the thermal conductivity declines by just 3.06%, indicating the excellent thermal cycling stability.ConclusionsThe formation of the Diamond/TiC/TiAl3/Al gradient interface not only benefits the improvement of the interfacial bonding, but also effectively reduces the difference in Debye temperature between the diamond reinforcement and the Al matrix. Therefore, the acoustic velocity mismatch between the diamond and the Al matrix is reduced, and the thermal conductivity of the composite is effectively improved. Compared with the single Ti nanolayer strategy, the Ti-Al double-nanolayers strategy provides new insights into the preparation of high thermal conductivity diamond/Al composites.

Interface design and optimization is critical to enhance the thermal properties of diamond/Al composites. Herein, Ti-Al hybrid coatings with the thickness range of 50-200 nm on diamond particles were deposited by a dual-target co-sputtering strategy. The coatings were dense and uniform and the interfacial structure of the diamond/Al composite was characterized as TiC/TiAl3 nano-interlayer. This structure not only enhanced the interfacial bonding, but also promoted the thermal conductivity (TC) enhancement of the composites. A maximum TC of 668 W/mK was achieved at a justified nano-interlayer thickness of similar to 100 nm. This work offers a new insight for designing of multi-phases interface modification for diamond/Al composites.

Interface design and optimization is critical to enhance the interfacial bonding and thermal properties of the diamond/Cu composites. Herein, Cr and CuCr30 dual coatings with the different thickness on diamond particles were deposited by magnetron sputtering. The Cr element on diamond particles transformed to Cr3C2 during sintering, with coexisting interfacial phases of Cr3C2 and Cu to strengthen the interface bonding. Relatively thicker interlayers (-200 nm and -270 nm) act as an effective bridge between diamond and Cu, improving wettability and reducing thermal stress, where no obvious debonding was found and the compact diamond/Cu composites were achieved. The results suggest that the interface structure evolution plays a critical role in determining the thermal conductivity, CTE and thermal cycling behavior of diamond/Cu composites. By measuring the thermal conductivity before and after thermal cycling, we found that the composites with an intermediate thickness of the interlayer possessed the maximum thermal conductivity (686 W/mK), while that with a thicker interlayer presented a better comprehensive performance with a relatively high initial thermal conductivity (646 W/mK), compatible CTE (7.49 & times; 10- 6/K from room temperature to 200 degrees C) and stable thermal cycling performance (4% attenuation of thermal conductivity for 300 cycles from -50 degrees C to 150 degrees C). This work demonstrates that a trade-off exists between maximizing initial thermal conductivity and ensuring long-term thermal stability for diamond/Cu composites.

Electrochemical detection of uric acid (UA) is critical for diagnostics and clinical risk assessment, but commercial enzymatic sensors suffer from accuracy limitations and high cost. Here we report a non-enzymatic UA sensor based on a nanocrystalline boron-doped diamond (BNCD) electrode. Compared to conventional microcrystalline boron-doped diamond sensors, the BNCD sensor with optimal boron doping (0.8%) exhibits stronger signal response and lower detection limit due to the synergistic effect of appropriate doping and abundant grain boundary conductive network. This nanocrystalline surface features low surface roughness of 91.8 nm, providing superior anti-fouling properties. The optimized sensor achieves a sensitivity of 0.170 & micro;A & micro;M-1 cm-2 and a detection limit of 0.12 & micro;M, along with good selectivity, repeatability and long-term stability. The proposed BNCD electrode exhibits promising potentials as the next-generation commercially viable devices for non-enzymatic UA detection.

Interface design is critical for enhancement of interfacial bonding and thermal properties of diamond/Al composites as promising thermal management materials. Herein, we propose a new strategy combining in-situ formation of WC (W2C)-W coatings and gas pressure infiltration (GPI) process to construct diamond-WC (W2C)-W-Al5W interlayers to improve the interfacial bonding and thermal properties of diamond/Al composite. The microstructure of the modified coatings and their effect on interfacial bonding and thermal properties of diamond/Al composites were examined. By altering deposition time in only several minutes, the thickness of the coatings ranged from ∼100 nm to ∼400 nm was tailored. Results showed the interfacial bonding of the composites was greatly improved, while the thermal conductivity was initially increased with the thickness and decreased with a maximum thermal conductivity of 677 W/mK achieved. Besides the moderate thickness of W interlayers, the high thermal conductivity was also attributed to the interface configuration with the following characteristics: small amount of W carbides on diamond side, uniform and dense W metal interlayer in middle, as well as W-Al intermetallic sublayer on Al side. The successful configuration of diamond-WC (W2C)-W-Al5W-Al interface greatly promoted the balance of the interfacial thermal resistance and interfacial bonding to maximize the thermal conductivity of the composites, which was among the first-class team reported for diamond/metal composites modified by W-related coatings. This study offers a feasible method to prepare effective W coatings for modifying interfacial bonding and enhancing the thermal properties of diamond/Al composites.

Diamond reinforced Al matrix (Diamond/Al) composites have garnered significant attention owing to their excellent heat dissipation and low density. However, preventing the interfacial Al4C3 while optimizing interface thermal conductance and thermal expansion mismatch remains a challenge. Herein, nano-scale Si-Al coatings were introduced on the diamond surface via a low-temperature synthesis strategy, which developed a multilayer structure comprising SiC, Al4SiC4, and Si when annealed at 900 degrees C. The phase transition of SiC from 3C- to 4H- type is crucial for forming Al4SiC4. During the infiltration, the crystalline Si within the coatings effectively inhibits the interaction between molten Al and elemental C. First-principles calculations confirmed superior interfacial bonding and phonon matching with the introduction of SiC and Al4SiC4. By regulating the coating thickness, an excellent thermal conductivity (TC) of 723.18 W center dot m- 1 center dot K- 1 and a suitable coefficient of thermal expansion of 5.96 x 10-6 K- 1 at 373 K are achieved. The 50 nm Si-Al coated diamond/Al composites exhibit remarkable service stability, with a 6.1 % reduction in TC after 200 cycles of temperature shock tests, and a 0.2 % decrease after 200 h of soaking water treatments. These findings highlight the Si-Al coatings to address interfacial challenges in diamond/Al composites, laying the groundwork for their practical application.

Boron-doped diamond (BDD) electrode is widely recognized as an ideal anode electrode material for electrochemical wastewater treatment. However, constructing a BDD electrode capable of achieving high electrochemical active surface area (ECSA) and mass transfer efficiency remains challenging. Herein, a novel three-dimensional (3D) BDD electrode with a staggered network structure built by 3D printing technology was constructed via hot-filament chemical vapor deposition. Experimental results demonstrated that 3D BDD electrodes exhibited a higher degradation efficiency and lower energy consumption under various experimental conditions compared to the flat BDD electrode. The superior degradation performance of 3D BDD electrodes resulted from the increased ECSA, spatiotemporal yield of reactive active radicals and charge transfer rate as well as the significantly improved mass transfer rate confirmed by the computational fluid dynamics simulations. This work could offer a potential solution to the structural design of high-performance electrodes for wastewater treatment.

Although diamond-reinforced Cu matrix (diamond/Cu) composites can achieve high thermal conductivity (TC) via interface modification, the significant mismatch in the coefficient of thermal expansion (CTE) between these composites and semiconductors, along with the degradation of heat transfer performance during long-term service, severely impedes their engineering applications. In this work, inspired by the concept of elemental interdiffusion, a novel interface design strategy combined with the control of the interface layer thickness was put forward to achieve the goal of simultaneously enhancing the heat transfer ability, thermal expansion matching, and thermal stability of the diamond/Cu composites. The results reveal that, when adjusting the sputtering time to 45 min, the designed diamond/Cu composites exhibit an excellent TC of 743 W center dot m- 1 center dot K- 1, a low CTE of 4.5 x 10-6 K- 1 at 323K and a faster thermal response. After undergoing 100 thermal cycles in an atmospheric environment, the composites maintain a high thermal diffusion coefficient up to 244.9 mm2 center dot s- 1, with only a 20.7 % decrease. It has been confirmed that introducing the WC-(Zr,W)C multi-level interface layer is conducive to improving the interfacial bonding strength and phonon matching between diamond and matrix. In addition, there are uniformly distributed diamond particles, a high relative density, and isolated pores in the diamond/Cu composites post-thermal shock, ensuring the distinguished heat transfer ability. This work not only tackles the engineering application challenges of diamond/Cu composites and elucidates in-depth understanding of the enhancement mechanisms, but also offers a fresh perspective for interface layer design in thermal management composites.

The weak interfacial bonding strength between diamond and copper intrinsically restricts the enhancement of the thermal conductivity of diamond particles/copper composites (abbreviated as DP/Cu). This work first proposed the diamond skeleton (DS) as the reinforcement element rather than dispersed diamond particles. The tungsten (W) transition layer (c.a. similar to 300 nm thick) having adequate thermal expansion coefficient was sputtered onto the surface of DS via vacuum evaporation technology, aiming to improve the wettability between diamond and copper and accordingly increase the thermal conductivity of DS/copper composites extruded by gas pressure infiltration technique. The experimental results show that the coated W layer can effectively improve the wettability of the diamond surface and reduce the wettability angle from 108.6 degrees to 13.2 degrees. Raman and XRD spectra show that the W layer can, to a great extent, prevent the graphitization of the diamond surface. SEM and EDX evidence a continuous heat transfer path of DS inside the composites. The thermal conductivity of the DS/Cu composite with low diamond loading of 18.4 vol% reaches 575 W/mK, 43.3% higher than that of pure Cu. Finite element simulations show that DS exhibits excellent heat transfer characteristics, agreeing well with the thermal conductivity simulation results.

Real-time sensing of dopamine is essential for understanding its physiological function and clarifying the pathophysiological mechanism of diseases caused by impaired dopamine systems. However, severe fouling from nonspecific protein adsorption, for a long time, limited conventional neural recording electrodes concerning recording stability. This study reported a high-antifouling nanocrystalline boron-doped diamond microsensor grown on a carbon fiber substrate. The antifouling properties of this diamond sensor were strongly related to the grain size (i.e., nanocrystalline and microcrystalline) and surface terminations (i.e., oxygen and hydrogen terminals). Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond microsensor exhibited enhanced antifouling characteristics against protein adsorption, which was attributed to the formation of a strong hydration layer as a physical and energetic barrier that prevents protein adsorption on the surface. This finally allowed for in vivo monitoring of dopamine in rat brains upon potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors. Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond (O-NCBDD) microsensor exhibited ultrahydrophilic properties with a contact angle of 4.9 degrees, which was prone to forming a strong hydration layer as a physical and energetic barrier to withstand the adsorption of proteins. The proposed O-NCBDD microsensor exhibited a high detection sensitivity of 5.14 mu A mu M-1 cm-2 and a low detection limit of 25.7 nM. This finally allowed for in vivo monitoring of dopamine with an average concentration of 1.3 mu M in rat brains upon 2 mu L of potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors.

Using copper-boron alloy as the metal matrix and different-sized diamond particles through 110 μm, 230 μm to 550 μm as reinforcement, the diamond/copper-boron alloy composites were prepared via gas pressure infiltration technology under 1100 ℃ and 10 MPa gas pressure. The influences of the size of diamond particles on the configuration, interlayer phase distribution, and thermophysical properties of the composites were investigated. The results show that with the increase of particle size, there is a benefit of better interface bonding, and the thermal conductivity of the diamond/copper-boron composite is enhanced while the thermal expansion coefficient decreases. When the diamond particle size is 500 μm, the best performance of the composite is obtained. The thermal conductivity is 680.3 W/(m·K), and the thermal expansion coefficient increases from 4.095×10−6 K−1 to 7.139×10−6 K−1.

Electrode fouling is an inevitable phenomenon when encountering biological agents (e.g., dopamine, peptides, proteins), particularly working under continuous oxidation of fouling agents. Diamond is emerging as an ideal fouling-resistant sensing material due to favorable antifouling properties and biocompatibility, but the detection sensitivity and specificity narrow its biomedical applications. In this work, we engineered a Au-NPs/Nafion modified nanoporous diamond sensing interface (termed as NanoDiaSens) in which the target's voltammetric response (i.e., dopamine) is dominant while interference agents (i.e., human serum, ascorbic acid) are eliminated, rendering reliable target quantification in human serum. The resulting nanopores and electrodeposited Au NPs have close size distribution of 43.1 +/- 9.2 nm and 43.9 +/- 12.7 nm respectively. The unique nanoporous diamond sensing surface provides anchored sites to stabilize electroactive gold nanoparticles preserving their long lifespan and high sensitivity, while surface-modified Nafion membrane effectively eliminates the voltammetric response of the interference agents and shifts the target's potential window away from the interferent's ones, achieving specific voltammetric quantification of the target. The NanoDiaSens also holds the highest heterogeneous kinetic constant of 6.7 x 10-3 cm s- 1, indicating the significantly enhanced electrocatalytic properties. Leveraging NanoDiaSens, we realized high accuracy of > 90% recovery rate for dopamine's voltammetric response currents over wide levels (from 3 to 100 mu M) in human serum. NanoDiaSens preserves the reliable voltammetric signals within 2.1% signal attenuation up to one month and maintains 95% of the initial response current after six-month storage in the ambient environment. We expect NanoDiaSens holds the potentials for personalized dopamine monitoring for many months.

A continuous diamond film layer was initially deposited on the surface of the foam skeleton by chemical vapor deposition (CVD), followed by the vertical growth of carbon nanotubes (CNTs) on diamond film using nickel particles as a catalyst. The CNTs extended into the interior of the pores inside the foam skeleton as a secondary heat transfer pathway. The effect of different pore densities on the thermal conductivity and latent heat of phase change composites (PCMs) was explored. The obtained diamond foam/carbon nanotube/paraffin composites (DF-CNT/PWs) was demonstrated to achieve an ultra-high conductivity of 5.3 W/m.K, which is 19.6 times that of the paraffin matrix. The latent heat of the DF-CNT/PWs is 83.37 J.g(-1). In addition, finite element simulation confirmed that the thermal conductivity enhancer system could significantly improve the uniformity of heat transfer inside the foam skeleton.

The Cu–B alloy with boron mass fraction of 0.5% was used as the metal matrix, and the diamond with an average particle size of 500 μm was used as reinforcement, the diamond/Cu–B alloy composites were prepared by gas pressure infiltration method. The effects of gas pressure parameters on the microstructures and the thermophysical properties of the composites were studied. The results show that the interfacial bonding effect and the thermal conductivity between diamond and Cu–B alloy are enhanced and the thermal expansion coefficient is reduced with the increase of gas pressure. When the gas pressure is 10 MPa, the interfacial bonding effect is the best. The carbide layer formed at the interface completely covers the diamond, the thermal conductivity of the sample at 100 ℃ is 680.3 W/(m·K), and the thermal expansion coefficient is 5.038×10−6 K−1, which meets the thermal expansion coefficient requirements of electronic packaging materials.

Diamond/aluminum composite material has the advantages of high thermal conductivity, low expansion, and lightweight, which has a wide range of application prospects in the field of electronic packaging thermal management. However, the serious interface problems between diamond and aluminum limit the full play of the thermal conductivity of composite materials. A reasonable interface design can maximize the thermal conductivity of composite materials. This article focuses on the interface modification of diamond/aluminum composites, briefly describing the theoretical basis of interface design, the research status of interface modification, interface reaction and composite stability, and prospects for diamond/aluminum composites material development.

The preforms were prepared with SiC and W-coated diamond reinforcements, and the diamond-SiC/Al composites were prepared by gas pressure infiltration technology at 800 ℃ and 5 MPa. The properties of composite materials were analyzed by scanning electron microscope, infrared thermal imager and laser thermal conductivity meter. The influences of the content and the particle size ratio R of SiC and diamond on the configuration of composites were investigated to optimize the thermal conductivity of the composites. The results show that with the same SiC particle size, the thermal conductivity of the composites will be significantly improved with the increase of diamond volume fraction. When the volume fraction of diamond is 30%, the thermal conductivity of the composites containing F100 SiC is the best, which reaches 344 W/(m∙K). When the volume fraction of diamond is the same and the particle size ratio R increases from 0.07 to 0.65, the thermal conductivity of the composite increases in turn. Moreover, the thermal conductivity of composites with diamond volume fraction of 15% increases from 174 W/(m∙K) to 274 W/(m∙K), which achieves the largest increase of 57%.Therefore, by improving the content and the particle size ratio of reinforcements in the diamond-SiC/Al composites, the configuration of composites can be regulated to realize full potential of thermal conductivity.

Diamond/aluminum composite material has the advantages of high thermal conductivity, low expansion, and lightweight, which has a wide range of application prospects in the field of electronic packaging thermal management. However, the serious interface problems between diamond and aluminum limit the full play of the thermal conductivity of composite materials. A reasonable interface design can maximize the thermal conductivity of composite materials. This article focuses on the interface modification of diamond/aluminum composites, briefly describing the theoretical basis of interface design, the research status of interface modification, interface reaction and composite stability, and prospects for diamond/aluminum composites material development.

A Co-doped Ni-P-O film supported on nickel foam is successfully prepared. It exhibits high activity toward urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Regarding UOR, the onset potential of Ni-P-O is reduced by the introduction of Co and gradually decreases with the incremental of Co content in the film ascribed to the reduction of conversion potential of Ni2+/Ni3+. Concerning HER, the incorporated Co in Ni-P-O film not only increases the amounts of active sites, but also boost the synergetic effect on water dissociation and hydrogen desorption. Particularly, the optimum activity of Ni-P-O is achieved by the introduction of an 8% cobalt source (8% Co:Ni-P-O/NF), which offers the highest activity with the lowest overpotential of 94 mV and Tafel slope of 46.2 mV.dec(-1). Furthermore, the efficiency of hydrogen generation is further improved by urea-assistance over the electrolyzer coupled with 8% Co:Ni-P-O/NF electrode. Only 1.481 V is needed to afford 20 mA.cm(-2) in urea-mediated electrolysis cell, much lower than that for ureafree electrolyte with 1.689 V. (C) 2022 Published by Elsevier B.V.

Copper foams with different pore densities were chosen as the substrate to deposit the continuous diamond film on the surface by chemical vapor deposition (CVD) technology. The influence of the pore density of the foam skeleton on the overall heat transfer effect of the diamond film was explained by finite element simulation. The scanning electron microscope, the Raman spectrum and the infrared thermal imager were used to compare and analyze the micro morphology, the film composition and the thermal diffusivity of diamond foam with different pore densities. The results show that high pore density foam substrate is more conducive to heat transfer, but its tiny pore size limits the flow of free radicals in the pores, and the size of diamond grains deposited by CVD is significantly reduced, with only 2~3 μm. The grain quality is also slightly inferior to that of medium and low pore density samples. In the infrared thermal imaging with the same heating time, the surface heating rate of the medium pore density diamond foam is higher than that of the high and low void density samples, which increases by 43.4% and 12.7%, respectively. In summary, the diamond foam with excellent three-dimensional connectivity and excellent diamond quality has excellent thermal conductivity, and is a better choice of heat conduction reinforcement.

选择不同孔隙密度的泡沫铜为沉积衬底,通过化学气相沉积(chemical vapor deposition,CVD)技术在其表面沉积连续金刚石膜,借助有限元模拟阐释泡沫骨架的孔隙密度对金刚石膜整体传热效果的影响,并通过扫描电镜、拉曼光谱及红外热成像仪等对不同孔隙密度的泡沫金刚石微观形貌、膜层成分以及热扩散性能进行对比与分析.结果表明:高孔隙密度泡沫衬底更有利于热量传递,但其极小的泡沫孔径会限制自由基在孔隙内部流动,CVD沉积的金刚石晶粒尺寸明显减小,仅有2～3μm,晶粒质量也略逊于中、低孔隙密度样品的.在相同加热时间内的红外热成像中,中孔隙密度泡沫金刚石的表面升温速率相比低、高孔隙密度样品的升温速率分别提升43.4％与12.7％.综上所述,兼具良好三维连通特性与优异金刚石质量的中孔隙密度泡沫金刚石表现出更为优异的导热性能,是更理想的导热增强体选择.