Ultralow Interfacial Thermal Resistance of Graphene Thermal Interface Materials with Surface Metal Liquefaction

Developing advanced thermal interface materials(TIMs)to bridge heat-generating chip and heat sink for constructing an efficient heat transfer interface is the key technology to solve the thermal management issue of high-power semiconductor devices.Based on the ultra-high basal-plane thermal conductivity,graphene is an ideal candidate for preparing high-performance TIMs,preferably to form a vertically aligned structure so that the basal-plane of graphene is consistent with the heat transfer direction of TIM.However,the actual interfacial heat transfer efficiency of currently reported vertically aligned graphene TIMs is far from satisfactory.In addition to the fact that the thermal conductivity of the vertically aligned TIMs can be further improved,another critical factor is the limited actual contact area leading to relatively high contact thermal resistance(20-30 K mm^(2) W^(−1))of the“solid-solid”mating interface formed by the vertical graphene and the rough chip/heat sink.To solve this common problem faced by vertically aligned graphene,in this work,we combined mechanical orientation and surface modification strategy to construct a three-tiered TIM composed of mainly vertically aligned graphene in the middle and micrometer-thick liquid metal as a cap layer on upper and lower surfaces.Based on rational graphene orientation regulation in the middle tier,the resultant graphene-based TIM exhibited an ultra-high thermal conductivity of 176 W m^(−1) K^(−1).Additionally,we demonstrated that the liquid metal cap layer in contact with the chip/heat sink forms a“liquid-solid”mating interface,significantly increasing the effective heat transfer area and giving a low contact thermal con-ductivity of 4-6 K mm^(2) W^(−1) under packaging conditions.This finding provides valuable guidance for the design of high-performance TIMs based on two-dimensional materials and improves the possibility of their practical application in electronic thermal management.

Adhesion strength of tetrahydrofuran hydrates is dictated by substrate stiffness

Understanding the hydrate adhesion is important to tackling hydrate accretion in petro-pipelines.Herein,the relationship between the Tetrahydrofuran(THF)hydrate adhesion strength(AS)and surface stiffness on elastic coatings is systemically examined by experimental shear force measurements and theoretical methods.The mechanical factor-elastic modulus of the coatings greatly dictates the hydrate AS,which is explained by the adhesion mechanics theory,beyond the usual factors such as wettability and structural roughness.Moreover,the hydrate AS increases with reducing the thickness of the elastic coatings,resulted from the decrease of the apparent surface elastic modulus.The effect of critical thickness for the elastic materials with variable elastic modulus on the hydrate AS is also revealed.This study provides deep perspectives on the regulation of the hydrate AS by the elastic modulus of elastic materials,which is of significance to design anti-hydrate surfaces for mitigation of hydrate accretion in petro-pipelines.

Infl uence of nitrate concentrations on EH40 steel corrosion aff ected by coexistence of Desulfovibrio desulfuricans and Pseudomonas aeruginosa bacteria

Nitrate addition is a common bio-competitive exclusion(BCE)method to mitigate corrosion in produced water reinjection systems,which can aff ect microbial community compositions,especially nitrate and sulfate reducing bacteria,but its eff ectiveness is in controversy.We investigated the infl uence of nitrate concentrations on EH40 steel corrosion aff ected by coexistence of Desulfovibrio vulgaris and Pseudomonas aeruginosa bacteria.Results demonstrate that only mixed bacteria or nitrate had little eff ect on EH40 steel corrosion,and nitrate could accelerate the corrosion of EH40 steel through the action of microorganisms.The corrosion promotion of nitrate was dependent on its concentrations,which increased from 0 to 5 g/L and decreased from 5 to 50 g/L.These diff erences were believed to be related to the regulation of nitrate in the growth of bacteria and biofi lms.Therefore,care must be taken to BCE method with nitrate when nitrate reducing bacteria with high corrosive activity are present in the environments.

Corrosion Performance of Stainless Steel Reinforcement in the Concrete Prepared with Seawater and Coral Waste and Its Ecological Effects

Durability and ecological effects of the stainless steel reinforced coral waste concrete were compared with those of the carbon steel reinforced ordinary concrete.The results showed that the corrosion current densities of the stainless steel in the coral waste concrete were less than one-tenth of those of the carbon steel in the same grade ordinary concrete.The stainless steel in the seawater coral waste concrete maintained passivation even after more than two years of immersion in 3.5%NaCl solution,while the carbon steel counterparts in the ordinary concrete were seriously corroded under the same condition.Simultaneously,the corrosion current density of the stainless steel reinforcement decreased slightly with the strength grade of the coral waste concrete.The ecological evaluation indicated that the non-renewable energy consumption and CO_(2)emission of per cubic meter of the newly constructed stainless steel reinforced coral waste concrete were 23.72%and 1.419%less than those of the carbon steel reinforced ordinary concrete with the same grade,while the aforementioned two parameters of the former material were reduced by 44.81%and 32.0%in comparison to the latter one in 50 years duration.

The Role of Renewable Protocatechol Acid in Epoxy Coating Modification: Significantly Improved Antibacterial and Adhesive Properties

It is of great significance to design epoxy coatings with superior antibacterial properties and high adhesive properties, as well as excellent processing, superior durability, and high transparency. However, it is still a challenge because of the common complex design and synthesis. Herein, the bio-based monomer protocatechuic acid(PCA) was used as raw material, the catechol structure with high bonding and antibacterial properties was introduced into the flexible alkane segment of ethylene glycol diglycidyl ether(EGDE) through an efficient, and green method, and it was cured with isophorone diamine(IPDA) to prepare corresponding thermosets. The cured resins exhibited excellent allaround qualities, particularly in bonding and antibacterial. When 30% PCA was added to pure epoxy resin, the adhesion between substrate and coating increased from 4.40 MPa to 13.60 MPa and the antibacterial rate of coating against E. coli and S. aureus could approach 100%. All of this is due to the fact that the catechol structure present in PCA has the ability to interact with various substrates and alter the permeability of bacterial cell membranes. The architecture of this method offers a fresh approach to dealing with the issues of challenging raw material selection and complex synthesis techniques.

Design of the rare-earth-containing materials based on the micro-alloying phase equilibria, phase diagrams and phase transformations

Rare-earth(RE)elements,known as“industrial vitamins”,have permeated modern lives,especially in high-tech applications.Although the RE elements possess close chemical similarities and have been treated as“one element”in the periodic table,their characteristics differ from each other.The RE microalloying effect is the crux to ameliorate the physicomechanical and thermochemical properties of materials,thereby the study of RE-related phase diagrams becomes indispensable to the design and optimization of RE-containing materials.However,in reality,the knowledge base in this area is considerably scarce compared with that of other commonly-used elements.In this work,the phase equilibria,phase diagrams,phase transformations,and some recent examples of RE-containing materials design are summarized,with which one can predict the RE solubilities,the RE precipitates,as well as the corresponding service behaviors.The attainment of enhanced materials’properties suggests that the thermodynamic rules extracted from the phase diagrams could serve as fundamental criteria for the successful development of novel RE-containing materials.

Effect of Aluminum Tri-polyphosphate on Corrosion Behavior of Reinforcing Steel in Seawater Prepared Coral Concrete

Atri-polyphosphate was used as a corrosion inhibitor in the seawater prepared coral concrete, and its influence on the corrosion behavior of carbon steel, 304 austenitic stainless steel, and 2205 duplex stainless steel was studied by the open-circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization, respectively. The results reveal that the corrosion potential and impedance of the reinforcing steel increase, while the corrosion current density decreases with the content of aluminum tripolyphosphate in the coral concrete. A low content of the corrosion inhibitor significantly retards the corrosion of the two stainless steels, but it cannot effectively inhibit the corrosion of the carbon steel in the coral concrete.In general, the carbon steel is unsuitable for the coral concrete for its poor corrosion resistance. In contrast,the stainless steels, especially the 2205 duplex stainless steel, shows an excellent anti-corrosion property in the seawater prepared coral concrete containing a certain amount of inhibitor, which is one of the satisfactory candidate methods to build the long-life coral concrete constructions.

Touch-Responsive Hydrogel for Biomimetic Flytrap-Like Soft Actuator

Stimuli-responsive hydrogel is regarded as one of the most promising smart soft materials for the next-generation advanced technologies and intelligence robots,but the limited variety of stimulus has become a non-negligible issue restricting its further development.Herein,we develop a new stimulus of“touch”(i.e.,spatial contact with foreign object)for smart materials and propose a flytrap-inspired touch-responsive polymeric hydrogel based on supersaturated salt solution,exhibiting multiple responsive behaviors in crystallization,heat releasing,and electric signal under touch stimulation.Furthermore,utilizing flytrap-like cascade response strategy,a soft actuator with touch-responsive actuation is fabricated by employing the touch-responsive hydrogel and the thermo-responsive hydrogel.This investigation provides a facile and versatile strategy to design touch-responsive smart materials,enabling a profound potential application in intelligence areas.

Bioinspired Adaptive,Elastic,and Conductive Graphene Structured Thin-Films Achieving High-Efficiency Underwater Detection and Vibration Perception

Underwater exploration has been an attractive topic for understanding the very nature of the lakes and even deep oceans.In recent years,extensive efforts have been devoted to developing functional materials and their integrated devices for underwater information capturing.However,there still remains a great challenge for water depth detection and vibration monitoring in a high-efficient,controllable,and scalable way.Inspired by the lateral line of fish that can sensitively sense the water depth and environmental stimuli,an ultrathin,elastic,and adaptive underwater sensor based on Ecoflex matrix with embedded assembled graphene sheets is fabricated.The graphene structured thin film is endowed with favourable adaptive and morphable features,which can conformally adhere to the structural surface and transform to a bulged state driven by water pressure.Owing to the introduction of the graphene-based layer,the integrated sensing system can actively detect the water depth with a wide range of 0.3-1.8 m.Furthermore,similar to the fish,the mechanical stimuli from land(e.g.knocking,stomping)and water(e.g.wind blowing,raining,fishing)can also be sensitively captured in real time.This graphene structured thin-film system is expected to demonstrate significant potentials in underwater monitoring,communication,and risk avoidance.

A novel approach of deposition for uniform diamond films on circular saw blades

Uniform diamond films are highly desirable for cutting industries, due to their high performance and long lifetime used on cutting tools. Nevertheless, they are difficult to obtain on cutting tools with complicated shapes, greatly limiting the applications of diamond films. In this study, a novel approach of deposition for uniform diamond films is proposed, on circular saw blades made of cemented carbide using reflectors of brass sheets. Diamond films are deposited using hot filament chemical vapor deposition（HFCVD）. A novel concave structure of brass sheets is designed and fabricated, improving the distribution of temperature field, and overcoming the disadvantages of the conventional HFCVD systems. This increases the energy efficiency of use without changing the structure and increasing the cost of HFCVD. The grains are refined and the intensities of diamond peaks are strengthened obviously, which is confirmed by scanning electron microscopy and Raman spectra respectively.

Bioinspired Nanostructured Superwetting Thin-Films in a Self-supported form Enabled“Miniature Umbrella”for Weather Monitoring and Water Rescue

Two-dimensional(2D)soft materials,especially in their self-supported forms,demonstrate attractive properties to realize biomimetic morphing and ultrasensitive sensing.Although extensive efforts on design of self-supported functional membranes and integrated systems have been devoted,there still remains an unexplored regime of the combination of mechanical,electrical and surface wetting properties for specific functions.Here,we report a self-supported film featured with elastic,thin,conductive and superhydrophobic characteristics.Through a well-defined surface modification strategy,the surface wettability and mechanical sensing can be effectively balanced.The resulted film can function as a smart umbrella to achieve real-time simulated raining with diverse frequencies and intensity.In addition,the integrated umbrella can even response sensitively to the sunlight and demonstrate a positively correlation of current signals with the intensity of sun illumination.Moreover,the superhydrophobic umbrella can be further employed to realize water rescue,which can take the underwater object onto water surface,load and rapidly transport the considerable weight.More importantly,the whole process of loaded objects and water flow velocity can be precisely detected.The self-supported smart umbrella can effectively monitor the weather and realize a smart water rescue,demonstrating significant potentials in multifunctional sensing and directional actuation in the presence of water.

Corrosion performance of zinc coated steel in seawater environment

Considering the continuous exploitation of marine resources, it is very important to study the anticorrosion performance and durability of zinc coated streel （ZCS） because its increasing use as reinforcements in seawater. Tafel polarization curves and linear polarization curves combined with electrochemical impedance spectroscopy （EIS） were employed to evaluate the corrosion performance of ZCS at Qingdao test station during long-term immersion in seawater. The results indicated that the corrosion rate of the ZCS increased obviously with immersion time in seawater. The corrosion products that formed on the zinc coated steel were loose and porous, and were mainly composed of Zn5（OH）8C12, Zn5（OH）6（CO3）2, and ZnO. Pitting corrosion occurred on the steel surface in neutral seawater, and the rate of ZCS corrosion decreased with increasing pH.

In situ Nanomechanical Research on Large-Scale Plastic Deformation of Individual Ultrathin Multi-walled Carbon Nanotube

Carbon nanotubes are a promising candidate for the application of flexible electronics due to the ultrahigh intrinsic conductivity and excellent mechanical flexibility. In the present work, the morphology of the ultrathin (diameter<20 nm) multi-walled carbon nanotubes (MWCNTs) under an axial compression was investigated by using in-situ transmission electron microscopy. Moreover, the overall dynamic deformation processes and the force-displacement (F-D) curves of the MWCNTs were also examined. Interestingly, the MWCNTs almost restored their original morphology after 15 loading-unloading cycles. The deformation and recovery process indicate that the MWCNTs are flexible and exhibit excellent durability against compression. The Young’s modulus of the MWCNTs is estimated with the value of ∽0.655 TPa derived from the F-D curves fitting. Our results suggest that the ultrathin carbon nanotube structures may have great application potentials in flexible devices.

Synthesis of Diamond Nanoplatelets/Carbon Nanowalls on Graphite Substrate by MPCVD

The films composed of carbon nanowalls and diamond nanoplatelets,respectively,can be simultaneously formed on graphite substrate by controlling the hydrogen etching rate during microwave plasma chemical vapor deposition.To modulate the etching rate,two kinds of substrate design were used：a bare graphite plate and a graphite groove covered with a single crystal diamond sheet.After deposition at 1200℃ for 3 hours,we find that dense diamond nanoplatelets were grown on the bare graphite,whereas carbon nanowalls were formed on the grooved surface,indicating that not only reaction temperature but also etching behavior is a key factor for nanostructure formation.

Growth of mirror-like ultra-nanocrystalline diamond(UNCD)films by a facile hybrid CVD approach

In this study, growth of mirror-like ultra-nanocrystalline diamond（UNCD） films by a facile hybrid CVD approach was presented. The nucleation and deposition of UNCD films were conducted in microwave plasma CVD（MPCVD） and direct current glow discharge CVD（DC GD CVD） on silicon substrates, respectively. A very high nucleation density（about 1×10^11 nuclei cm^-2） was obtained after plasma pretreatment. Furthermore, large area mirrorlike UNCD films of Φ 50 mm were synthesized by DC GD CVD. The thickness and grain size of the UNCD films are 24 μm and 7.1 nm, respectively. In addition, the deposition mechanism of the UNCD films was discussed.

Achieving anti-corrosion and anti-biofouling dual-function self-healing coating by natural carrier attapulgite loading with 2-Undecylimidazoline

In the marine environment,the protective coatings face serious corrosion and biofouling problem,lim-itations,and challenges that made self-healing coatings unable to perform both anti-corrosion and anti-biofouling dual-function at the same time.Here we constructed the corrosion resistance and anti-biofouling self-healing coating by integrating nano-containers into the coating matrix,the 2-Undecylimidazoline(ULM)acted as a corrosion inhibitor and anti-biofouling dual-functional agent which was loaded on the natural container attapulgite(ATP).To obtain high healing efficiency,a fluidity-driven self-healing silicone oil coating was thickened by fibrous ATP to enhance its stability,which played a key role in the self-healing and long-term corrosion resistance.The self-healing time of ULM@ATP rein-forced oil coating was 4 s at least in the air and up to 30 s in the 1 M HCl solution.Meanwhile,the ULM@ATP can significantly enhance the corrosion resistance of the self-healing coating,with the best effect achieved when the content of ULM@ATP was 5 wt.%.The impedance modulus of ULM@ATP-2 still reached 1.62×10^(8)Ωcm^(2) after 480 immersion in 3.5 wt.%NaCl solution,which is 3 orders of magnitude high than pure Oil coating(2.17×10^(5)Ωcm^(2)).The restructure of the ATP network and the release of ULM could largely inhibit the corrosion of metal.The continuous open circuit potential of the compos-ite coating performed the potentially infinite self-healing capacity.The self-healing performances of the composite coating in strong acid and base solutions exhibited high environmental suitability.This anti-corrosion and anti-biofouling(the surface coverage of adhered chlorella decreased 96.88%)dual-function strategy of self-healing coatings could be also realized by many other porous nano-materials or function modifications.The self-healing performances of the composite coating in strong acid and base solutions exhibited high environmental suitability.This anti-corrosion and anti-biofouling dual-function strategy of self-healing coatings could be also realized by many other porous nano-materials or function modifica-tions.The rapid response self-healing coating possessed anti-biofouling and active self-healing functions and showed wide application under more service environments.

MAX phase forming mechanism of M-Al-C(M=Ti,V,Cr)coatings:In-situ X-ray diffraction and first-principle calculations

The interesting hybrid properties of ceramics and metals induced by unique nano-laminated structures make the M_(n+1)AX n(MAX)phase attractive as a potential protective coating for vital structural compo-nents in harsh systems.However,an extremely narrow phase-forming region makes it difficult to prepare MAX phase coatings with high purity,which is required to obtain coatings with high-temperature anti-oxidation capabilities.This work describes the dependence of the phase evolution in deposited M-Al-C(M=Ti,V,Cr)coatings as a function on temperature using in-situ X-ray diffraction analysis.Compared to V_(2)AlC and Cr_(2)AlC MAX phase coatings,the Ti_(2)AlC coating displayed a higher phase-forming tempera-ture accompanied by a lack of any intermediate phases before the appearance of the Ti_(2)AlC MAX phase.The results of the first-principle calculations correlated with the experience in which Ti_(2)AlC exhibited the largest formation energy and density of states.The effect of the phase compositions of these three MAX phase coatings on mechanical properties were also investigated using ex-situ Vickers and nano-indenter tests,demonstrating the improved mechanical properties with good stability at high temperatures.These findings provide a deeper understanding of the phase-forming mechanism of MAX phase coatings to guide the preparation of high-purity MAX phase coatings and the optimization of MAX phase coatings with expected intermediate phases such as Cr_(2)C,V_(2)C etc.,as well as their application as protective coat-ings in temperature-related harsh environments.

Prussian Blue/Cellulose Acetate Thin Film Composite Nanofiltration Membrane for Molecular Sieving and Catalytic Fouling Resistance

Nanofiltration(NF)membranes as high selective separators are appealing for molecular sieving,which still remains a great challenge for the mixed dyes with same charge.In this study,cellulose acetate(CA)membranes were firstly aminated by ethylene imine polymer(PEI),and then the thin film of metal organic frameworks(MOFs)were constructed onto aminated CA membrane through forward-diffusion,slow crystallization and in situ growth of Fe Co-Prussian blue(FeCo-PB)crystallization layers.The designed PB@CA composite NF membrane shows an ideal rejection for Congo red(CR)/methyl orange(MO)mixture solution,with 99.7%±0.2%for CR and 33.5%±2%for MO.In addition,the composite NF membrane demonstrated good efficiency for photocatalytic degradation of organic fouling(permeability recovery ratio was up to 92%)due to the active FeCo-PB micro-cubes.Thus,this work provides a practical strategy to prepare MOFs mediated thin film composite nanofiltration membrane for precise molecular sieving and catalytic antifouling performances.

Carbon-Based Janus Films toward Flexible Sensors, Soft Actuators, and Beyond

Janus films have attracted widespread interest due to their asymmetric structure and unique physical and/or chemical properties,demonstrating broad and blooming potentials in mechanical sensing,soft actuation,energy management,advanced separation,energy conversion and storage,etc.Among them,based on the unique features of carbon nanomaterials,extensive efforts have been dedicated to exploiting carbonbased Janus films for high-performance electronic skins,soft actuators,and their integration for smart robotics.Drawing inspiration from nature,biological skins can actively perceive external physical/chemical stimuli and further perform specific motion behaviors.However,there still remain challenges of guided structural design principles,an alternative combination of multifunctions,and advanced synergetic applications.Specifically,their intrinsic properties and related device performances are strongly determined by the functional components’coupling,surface wettability,and controllability of the interface structures.The asymmetric combination of carbon nanomaterials and functional polymers in controllable manners can facilitate the design of high-performance sensing,actuation,and integrated devices,enabling the development of smart soft robotics.Therefore,it is highly desired to summarize this research area of carbon-based Janus functional films for sensing,actuating,and integration as well as to have a deep understanding of the relationship between interfacial structures and their performance for directing future development.In this Account,we will summarize the significant advances in carbon-based Janus films mainly conducted by our group and also discuss the relevant important reported works.We start by introducing the basic properties of commonly used carbon nanomaterials and then discuss the general fabrication strategies for high-performance carbon-based Janus films,including solid-supported physical/chemical approaches and interfacial strategies based on liquid support.Among them,we carefully present the typical combination of two functional components for advanced and synergetic properties.Based on the combined designable functionality,the bioinspired artificial skins that target sensors,actuators,self-sensing actuators,and beyond will be discussed in detail.Finally,challenges and the prospect of structural design,structural interfaces,and integrated functionality will be proposed.We expect that this Account would provide a better understanding of the design,fabrication,applications,and challenges of carbon-based Janus functional films and their significant potential for the development of smart robotics.

Cu合金在电弧熔丝增材制造过程中的组织与力学性能演化

本文研究了Cu-8Al合金在电弧熔丝增材制造过程中的微观组织、物相、显微硬度和拉伸性能的演化行为。结果表明,刚沉积的CuAl合金晶粒为尺寸较大的枝晶,在后道次的热影响作用下转变成较细小的柱状晶,而后柱状晶长大,直到晶粒尺寸在距样品端部几毫米的位置趋于稳定。刚沉积的CuAl合金发生Al的枝晶偏析,但在后道次热影响的作用下偏析可消除,使合金组织和成分均匀化。板状样品端部即最后沉积未受后续热影响的位置显微硬度高达HV 160,但随着Al偏析的消除以及枝晶转变成柱状晶,硬度降低到HV 80。原位拉伸结果显示CuAl合金板的抗拉强度高达400 MPa,伸长率可达50%,其屈服强度还有一定的提升空间。拉伸过程中原位观察到了位错滑移和晶粒转动,断裂机制总体为韧窝断裂,端部屈服强度更高、塑性略低、晶粒转动更普遍。总体上电弧熔丝增材制造的CuAl合金板除端部之外组织均匀,具备良好的力学性能。如需其组织性能均匀,或要求高耐蚀性,有必要在沉积后对端部进行局部热处理;如需更好的耐磨性能则不需处理。可进一步添加少量析出强化元素提高CuAl合金的强度与耐磨性能。