Highly Thermally Conductive and Structurally Ultra‑Stable Graphitic Films with Seamless Heterointerfaces for Extreme Thermal Management

Highly thermally conductive graphitic film(GF)materials have become a competitive solution for the thermal management of high-power electronic devices.However,their catastrophic structural failure under extreme alternating thermal/cold shock poses a significant challenge to reliability and safety.Here,we present the first investigation into the structural failure mechanism of GF during cyclic liquid nitrogen shocks(LNS),which reveals a bubbling process characterized by“permeation-diffusion-deformation”phenomenon.To overcome this long-standing structural weakness,a novel metal-nanoarmor strategy is proposed to construct a Cu-modified graphitic film(GF@Cu)with seamless heterointerface.This well-designed interface ensures superior structural stability for GF@Cu after hundreds of LNS cycles from 77 to 300 K.Moreover,GF@Cu maintains high thermal conductivity up to 1088 W m^(−1)K^(−1)with degradation of less than 5%even after 150 LNS cycles,superior to that of pure GF(50%degradation).Our work not only offers an opportunity to improve the robustness of graphitic films by the rational structural design but also facilitates the applications of thermally conductive carbon-based materials for future extreme thermal management in complex aerospace electronics.

Highly Thermally Conductive Polymer/Graphene Composites with Rapid Room‑Temperature Self‑Healing Capacity

Composites that can rapidly self-healing their structure and function at room temperature have broad application prospects.However,in view of the complexity of composite structure and composition,its self-heal is facing challenges.In this article,supramolecular effect is proposed to repair the multistage structure,mechanical and thermal properties of composite materials.A stiff and tough supramolecular frameworks of 2-[[(butylamino)carbonyl]oxy]ethyl ester(PBA)–polydimethylsiloxane(PDMS)were established using a chain extender with double amide bonds in a side chain to extend prepolymers through copolymerization.Then,by introducing the copolymer into a folded graphene film(FGf),a highly thermally conductive composite of PBA–PDMS/FGf with self-healing capacity was fabricated.The ratio of crosslinking and hydrogen bonding was optimized to ensure that PBA–PDMS could completely self-heal at room temperature in 10 min.Additionally,PBA–PDMS/FGf exhibits a high tensile strength of 2.23±0.15 MPa at break and high thermal conductivity of 13±0.2 W m^(−1)K^(−1);of which the self-healing efficiencies were 100%and 98.65%at room temperature for tensile strength and thermal conductivity,respectively.The excellent self-healing performance comes from the efficient supramolecular interaction between polymer molecules,as well as polymer molecule and graphene.This kind of thermal conductive self-healing composite has important application prospects in the heat dissipation field of next generation electronic devices in the future.

New Activated Carbon with High Thermal Conductivity and Its Microwave Regeneration Performance

Using a walnut shellas a carbon source and ZnCl_2 as an activating agent,we resolved the temperature gradient problems of activated carbon in the microwave desorption process.An appropriate amount of silicon carbide was added to prepare the composite activated carbon with high thermalconductivity while developing VOC adsorption-microwave regeneration technology.The experimentalresults show that the coefficient of thermalconductivity of SiC-AC is three times as much as those of AC and SY-6.When microwave power was 480 W in its microwave desorption,the temperature of the bed thermaldesorption was 10 ℃ to 30 ℃ below that of normalactivated carbon prepared in our laboratory.The toluene desorption activation energy was 16.05 k J·mol^（-1）,which was 15% less than the desorption activation energy of commercialactivated carbon.This study testified that the process could maintain its high adsorption and regeneration desorption performances.

Performance of High Thermal Conductivity Dense Silica Bricks and Their High Thermal Conductivity Mechanism

High thermal conductivity dense silica bricks have the higher thermal conductivity than ordinary silica bricks,which is conducive to the realization of energy saving and emission reduction in the iron and steel industry.The performance of ordinary silica bricks and high thermal conductivity dense silica bricks was compared,and the high thermal conductivity mechanism was analyzed.The results show that(1)compared with ordinary silica bricks,high thermal conductivity dense silica bricks have the characteristics of higher thermal conductivity,lower apparent porosity,higher tridymite content,higher compressive strength,and higher thermal expansion;(2)by increasing the tridymite content and reducing the porosity,the close packing of honeycombα-tridymite improves the density and continuity of the SiO_(2)frame structure of the silica bricks,and the larger area perpendicular to the heat transfer direction improves the thermal conductivity of the bricks;(3)the densification of the silica bricks also increases the thermal expansion of the bricks,but they still meet the standard requirements.

New Type of Nitrides with High Electrical and Thermal Conductivities

The nitrogen dimer as both a fundamental building unit in designing a new type of nitrides, and a material gene associated with high electrical and thermal conductivities is investigated by first principles calculations.The results indicate that the predicted Si N4 is structurally stable and reasonably energy-favored with a striking feature in its band structure that exhibits free electron-like energy dispersions. It possesses a high electrical conductivity（5.07 × 10^5 S/cm） and a high thermal conductivity（371 W/m·K） comparable to copper. The validity is tested by isostructural Al N4 and Si C4. It is demonstrated that the nitrogen dimers can supply a high density of delocalized electrons in this new type of nitrides.

Liquid metal compartmented by polyphenol-mediated nanointerfaces enables high-performance thermal management on electronic devices

The exponentially increasing heat generation in electronic devices,induced by high power density and miniaturization,has become a dominant issue that affects carbon footprint,cost,performance,reliability,and lifespan.Liquid metals(LMs)with high thermal conductivity are promising candidates for effective thermal management yet are facing pump-out and surface-spreading issues.Confinement in the form of metallic particles can address these problems,but apparent alloying processes elevate the LM melting point,leading to severely deteriorated stability.Here,we propose a facile and sustainable approach to address these challenges by using a biogenic supramolecular network as an effective diffusion barrier at copper particle-LM(EGaIn/Cu@TA)interfaces to achieve superior thermal conduction.The supramolecular network promotes LM stability by reducing unfavorable alloying and fluidity transition.The EGaIn/Cu@TA exhibits a record-high metallic-mediated thermal conductivity(66.1 W m^(-1) K^(-1))and fluidic stability.Moreover,mechanistic studies suggest the enhanced heat flow path after the incorporation of copper particles,generating heat dissipation suitable for computer central processing units,exceeding that of commercial silicone.Our results highlight the prospects of renewable macromolecules isolated from biomass for the rational design of nanointerfaces based on metallic particles and LM,paving a new and sustainable avenue for high-performance thermal management.

Microstructure and properties of electronic packaging shell with high silicon carbide aluminum-base composites by semi-solid thixoforming

The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of different parts of the shell were observed by scanning electron microscopy and optical microscopy, and the thermophysical and mechanical properties of the shell were tested. The results show that there exists the segregation phenomenon between the Si C particulate and the liquid phase during thixoforming, the liquid phase flows from the shell, and the Si C particles accumulate at the bottom of the shell. The volume fraction of Si C decreases gradually from the bottom to the walls. Accordingly, the thermal conductivities of bottom center and walls are 178 and 164 W·m-1·K-1, the coefficients of thermal expansion(CTE) are 8.2×10-6 and 12.6×10-6 K-1, respectively. The flexural strength decreases slightly from 437 to 347 MPa. The microstructures and properties of the shell show gradient distribution.

Low dielectric constant and highly intrinsic thermal conductivity fluorine-containing epoxy resins with ordered liquid crystal structures

Epoxy resins with a high dielectric constant and low intrinsic thermal conductivity coefficient cannot meet the current application requirements of advanced electronic and electrical equipment.Therefore,novel fluorine-containing liquid crystal epoxy compounds(TFSAEy)with fluorinated groups,biphenyl units,and flexible alkyl chains are first synthesized via amidation and esterification reactions.Then,4,4′-diaminodiphenylmethane(DDM)is used as a curing agent to prepare the corresponding fluorine-containing liquid crystal epoxy resins.The obtained dielectric constant(ε)and dielectric loss(tanδ)values of TFSAEy/DDM at 1 MHz are 2.54 and 0.025,respectively,which are significantly lower than those of conventional epoxy resins(E-51/DDM,3.52 and 0.038).Additionally,the intrinsic thermal conductivity coefficient(λ)of TFSAEy/DDM is 0.36 W/(m⋅K),71.4%higher than that of E-51/DDM(0.21 W/(m⋅K)).Meanwhile,the corresponding elastic modulus,hardness,glass transition temperature,and heat resistance index of TFSAEy/DDM are 5.73 GPa,0.35 GPa,213.5◦C,and 188.7℃,respectively,all superior to those of E-51/DDM(3.68 GPa,0.27 GPa,107.2℃,and 174.8℃),presenting potential application in high-heating electronic component packaging and printed circuit boards.

Promising high-thermal-conductivity substrate material for high-power electronic device:silicon nitride ceramics

High-thermal-conductivity silicon nitride ceramic substrates are indispensable components for nextgeneration high-power electronic devices because of their excellent mechanical properties and high thermal conductivities, which make them suitable for applications in complex and extreme environments. Here, we present an overview of the recent developments in the preparation of high-thermal-conductivity silicon nitride ceramics. First,the factors affecting the thermal conductivity of silicon nitride ceramics are described. These include lattice oxygen and grain boundary phases, as well the oxygen content of the crystal lattice, which is the main influencing factor.Then, the methods to prepare high-thermal-conductivity silicon nitride ceramics are presented. Recent work on the preparation of high-thermal-conductivity silicon nitride is described in detail, including the raw materials used and the forming and sintering processes. Although great progress has been made, the development of a high-quality,low-cost fabrication process remains a challenge. Nevertheless, we believe that high-thermal-conductivity silicon nitride substrates are promising for massive practical applications in the next generation of high-power electronic devices.

Liquid crystalline texture and hydrogen bond on the thermal conductivities of intrinsic thermal conductive polymer films

Polymer-dispersed liquid crystal(PDLC)films comprising polyvinyl alcohol(PVA)and liquid crystal monomer(LCM)were successfully obtained by the method of solution casting&thermal compressing.LCM was distributed orderly in PVA matrix by hydrogen bond interaction,to form PVA-LCM interpe net rating-layered networks.When the mass fraction of LCM was up to 35 wt%,the corresponding in-plane thermal conductivity coefficient(λ//)of PDLC film was significantly increased to 1.41 W m^(-1)K^(-1),about 10.8 times that of neat PVA(0.13 W m^(-1)K^(-1)).High intrinsicλ//values of PDLC films were mainly attributed to the formed microscopic-ordered structures from ordered stacking of LCM,ordered arrangement of PVA chains,and their hydrogen bond interaction.This work would offer a new way to design and prepare novel intrinsic high thermal conductive polymers.

Highly anisotropic thermal conductivity of few-layer CrOCl for efficient heat dissipation in graphene device

With the packing density growing continuously in integrated electronic devices,sufficient heat dissipation becomes a serious challenge.Recently,dielectric materials with high thermal conductivity have brought insight into effective dissipation of waste heat in electronic devices to prevent them from overheating and guarantee the performance stability.Layered CrOCl,an antiferromagnetic insulator with low-symmetry crystal structure and atomic level flatness,might be a promising solution to the thermal challenge.Herein,we have systematically studied the thermal transport of suspended few-layer CrOCl flakes by microRaman thermometry.The CrOCl flakes exhibit high thermal conductivities along zigzag direction,from~392±33 to~1,017±46 W·m^(−1)·K^(−1) with flake thickness from 2 to 50 nm.Besides,pronounced thickness-dependent thermal conductivity ratio(/from~2.8±0.24 to~4.3±0.25)has been observed in the CrOCl flakes,attributed to the discrepancy of phonon dispersion and phonon surface scattering.As a demonstration to the heat sink application of layered CrOCl,we then investigate the energy dissipation in graphene devices on CrOCl,SiO_(2) and hexagonal boron nitride(h-BN)substrates,respectively.The graphene device temperature rise on CrOCl is only 15.4%of that on SiO_(2) and 30%on h-BN upon the same electric power density,indicating the efficient heat dissipation of graphene device on CrOCl.Our study provides new insights into two-dimentional(2D)dielectric material with high thermal conductivity and strong anisotropy for the application of thermal management in electronic devices.

Enhanced thermal performance from liquid metal in copper/graphite filled elastomer

With the increasing integration level of modern electronics,thermal management becomes an urgent issue for guaranteeing the work efficiency and lifespan of electronics.On the basis of intrinsic high thermal conductivity nature,highly ordered graphite and copper stripes are densely aligned in the silicone gel pads in vertical(VCuGr)and oblique(@15°CuGr)directions to couple the high thermal conductivity and mechanical softness.The wetting nature of liquid metal(LM)on the chemically treated Cu surface is utilized to form a LM layer on the two surfaces of thermal pads.The obtained LM-pad TIMs possessed ultrahigh through-plane thermal conductivity(VCuGr:71.4 W/(m K),@15°CuGr:62.5 W/(m K))under the normal packaging pressure.The thermal resistance decreased from 0.69 cm^(2) K/W to 0.25 cm^(2) K/W with the surface modification with LM.Theoretical simulation and practical thermal dissipation test results further demonstrate the excellent thermal management capability of these composites in high-power electronics.