Research status and prospects of the fractal analysis of metal material surfaces and interfaces

As a mathematical analysis method,fractal analysis can be used to quantitatively describe irregular shapes with self-similar or self-affine properties.Fractal analysis has been used to characterize the shapes of metal materials at various scales and dimensions.Conventional methods make it difficult to quantitatively describe the relationship between the regular characteristics and properties of metal material surfaces and interfaces.However,fractal analysis can be used to quantitatively describe the shape characteristics of metal materials and to establish the quantitative relationships between the shape characteristics and various properties of metal materials.From the perspective of two-dimensional planes and three-dimensional curved surfaces,this paper reviews the current research status of the fractal analysis of metal precipitate interfaces,metal grain boundary interfaces,metal-deposited film surfaces,metal fracture surfaces,metal machined surfaces,and metal wear surfaces.The relationship between the fractal dimensions and properties of metal material surfaces and interfaces is summarized.Starting from three perspectives of fractal analysis,namely,research scope,image acquisition methods,and calculation methods,this paper identifies the direction of research on fractal analysis of metal material surfaces and interfaces that need to be developed.It is believed that revealing the deep influence mechanism between the fractal dimensions and properties of metal material surfaces and interfaces will be the key research direction of the fractal analysis of metal materials in the future.

Friction Characteristics Between Marine Clay and Construction Materials

Structure-soil interface friction characteristics is of importance to investigate the interaction between engineering structures and soils,especially for offshore structures.The interface friction behavior between marine clay and structural materials with different roughness was studied in this paper by using 3D optical scanning tests,a modified direct shear device and numerical simulation.Relationships between the surface roughness of structures,water content and interface friction angle were presented by model tests.The increase of water contents decreased the interface friction angles.For interfaces with different roughness,the interface friction angles will be smaller than that of the soil when the water content exceeds a certain value.The roughness of the interface and the water content of the soil are mutually coupled to influence the coefficient of friction(COF).This paper proposed a Finite Element Method(FEM)to simulate the interface direct shear tests of structures with different roughness.The surface models with different roughness are established based on the structure data obtained by 3D scanning.The Coupled Eulerian-Lagrangian(CEL)approach was employed to analyse soils sheared by irregular surfaces.The interface behavior for interfaces with different roughness under cyclic shear stresses was analyzed by FEM.

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.

A review of ultrafast laser micro/nano fabrication:Material processing,surface/interface controlling,and devices fabrication

Ultrafast laser processing technology has offered a wide range of opportunities in micro/nano fabrication and other fields such as nanotechnology,biotechnology,energy science,and photonics due to its controllable processing precision,diverse processing capabilities,and broad material adaptability.The processing abilities and applications of the ultrafast laser still need more exploration.In the field of material processing,controlling the atomic scale structure in nanomaterials is challenging.Complex effects exist in ultrafast laser surface/interface processing,making it difficult to modulate the nanostructure and properties of the surface/interface as required.In the ultrafast laser fabrication of micro functional devices,the processing ability needs to be improved.Here,we review the research progress of ultrafast laser micro/nano fabrication in the areas of material processing,surface/interface controlling,and micro functional devices fabrication.Several useful ultrafast laser processing methods and applications in these areas are introduced.With various processing effects and abilities,the ultrafast laser processing technology has demonstrated application values in multiple fields from science to industry.

Exploring Trade-offs in Thermal Interface Materials:The Impact of Polymer-Filler Interfaces on Thermal Conductivity and Thixotropy

Effective thermal transport across solid-solid interfaces which is essential in thermal interface materials(TIMs),necessitates both optimal thixotropy and high thermal conductivity.The role of filler surface modification,a fundamental aspect of TIM fabrication,in the influence of these properties is not fully understood.This study employs the use of a silane coupling agent(SCA)to modify alumina,integrating experimental approaches with molecular dynamics simulations,to elucidate the interface effects on thixotropy and thermal conductivity in polydimethylsiloxane(PDMS)-based TIMs.Our findings reveal that the variations of SCAs modify both interface binding energy and transition layer thickness.The interface binding energy restricts macromolecular segmental relaxation near the interface,hindering desirable thixotropy and bond line thickness.On the contrary,the thickness of the transition layer at the interface positively influences thermal conductivity,facilitating the transport of phonons between the polymer and filler.Consequently,selecting an optimal SCA allows a balance between traditionally conflicting goals of high thermal conductivity and minimal bond line thickness,achieving an impressively low interface thermal resistance of just 2.45-4.29 K·mm^(2)·W^(-1)at275.8 kPa.

Understanding the Thermal Impedance of Silicone Rubber/Hexagonal Boron Nitride Composites as Thermal Interface Materials

Silicone rubber(SR) composites are most widely used as thermal interface materials(TIMs) for electronics heat dissipation. Thermal impedance as the main bottleneck limiting the performance of TIMs is usually neglected. Herein, the thermal impedance of SR composites loaded with different levels of hexagonal boron nitride(h-BN) as TIMs was elaborated for the first time by the ASTM D 5470 standard test and finite element analysis. It was found that elastic modulus and surface roughness of SR composites increased with the increase of h-BN content, indicating that the conformity was reduced. When the assembly pressure was 0.69 MPa, there existed an optimal h-BN content at which the contact resistance was minimum(0.39 K·cm^(2)·W^(-1)). Although the decreased bond line thickness(BLT) by increasing the assembly pressure was beneficial to reduce the thermal impedance, the proper assembly pressure should be selected to prevent the warpage of the contact surfaces and the increase in contact resistance, according to the compression properties of the SR composites. This study provides valuable insights into fabrication of high-performance TIMs for modern electronic device applications.

Optimizing the electronic spin state and delocalized electron of NiCo_(2)(OH)_(x)/MXene composite by interface engineering and plasma boosting oxygen evolution reaction

The electrocatalytic activity of transition-metal-based compounds is closely related to the electronic configuration.However,optimizing the surface electron spin state of catalysts remains a challenge.Here,we developed a spin-state and delocalized electron regulation method to optimize oxygen evolution reaction(OER)performance by in-situ growth of NiCo_(2)(OH)_(x) using Oswald ripening and coordinating etching process on MXene and plasma treatment.X-ray absorption spectroscopy,magnetic tests and electron paramagnetic resonance reveal that the coupling of NiCo_(2)(OH)_(x) and MXene can induce remarkable spin-state transition of Co^(3+)and transition metal ions electron delocalization,plasma treatment further optimizes the 3 d orbital structure and delocalized electron density.The unique Jahn-Teller phenomenon can be brought by the intermediate spin state(t2 _(g)^(5) e_(g)^(1))of Co^(3+),which benefits from the partial electron occupied egorbitals.This distinct electron configuration(t2_(g)^(5) e_(g)^(1))with unpaired electrons leads to orbital degeneracy,that the adsorption free energy of intermediate species and conductivity were further optimized.The optimized electrocatalyst exhibits excellent OER activity with an overpotential of 268 m V at 10 m A cm^(-2).DFT calculations show that plasma treatment can effectively regulate the d-band center of TMs to optimize the adsorption and improve the OER activity.This approach could guide the rational design and discovery of electrocatalysts with ideal electron configurations in the future.

Surface chemistry of electrode materials toward improving electrolyte-wettability:A method review

The electrolyte-wettability at electrode material/electrolyte interface is a criticalfactor that governs the fundamental mechanisms of electrochemical reactionefficiency and kinetics of electrode materials in practical electrochemicalenergy storage. Therefore, the design and construction of electrode materialsurfaces with improved electrolyte-wettability has been demonstrated to beimportant to optimize electrochemical energy storage performance of electrodematerial. Here, we comprehensively summarize advanced strategies and keyprogresses in surface chemical modification for enhancing electrolytewettabilityof electrode materials, including polar atom doping by post treatment,introducing functional groups, grafting molecular brushes, and surfacecoating by in situ reaction. Specifically, the basic principles, characteristics,and challenges of these surface chemical strategies for improving electrolytewettabilityof electrode materials are discussed in detail. Finally, the potentialresearch directions regarding the surface chemical strategies and advancedcharacterization techniques for electrolyte-wettability in the future are provided.This review not only insights into the surface chemical strategies forimproving electrolyte-wettability of electrode materials, but also provides strategicguidance for the electrolyte-wettability modification and optimization ofelectrode materials in pursuing high-performance electrochemical energy storagedevices.

MAGNETIC PERFORMANCE TRANSITION IN Fe/Tb MULTILAYERS INDUCED BY INTERFACE ROUGHNESS

Fe/Tb multilayers with various Fe layer thickness and fixed Tb layer thickness were prepared by e-beam alternate vapor deposition. Analyses of the microstructure of these films show that the magnetic performance is strongly affected by the interface structure. Fe in the films evolved to amorphous phase and the Fe/Tb interface became indiscernible with decreasing Fe thickness. At the same time, the film was observed to perform superparamagnetically, which is quite different from the ferromagnetic behavior of Fe/Tb multilayers that have sharp Fe/Tb interface. Our work shows that the interface roughness has strong influence to the properties of magnetic multilayers.

Microstructure and mechanical properties of hot isostatically pressed cermets with TiN coatings

To increase the adhesion strength between the coating and the substrate, sintered Ti（C,N）-based cermets were selected and deposited with monolayer TiN using a multiarc ion-plating technique; subsequently, hot isostatic pressing （HIPhag） treatment was performed at 1000℃ using nitrogen pressure up to 110 MPa. The mechanical properties of cermets after a coating process and subsequent HIPing treatment have been evaluated with respect to the hardness, the residual stress, and the coating adhesion. The results show that atter the HIPing process, there was a higher increase ha critical load ha the TiN-coated cermets with lower surface roughness compared with those with higher surface roughness. In all cases, the residual stress was found to be compressive. The effects of substrate surface roughness and posttreatment on the adhesion strength of the coatings were thus investigated. It was also fotmd that the HIPing posttreatment process is well suited for hacreasing the adhesion strength between the coating and the substrate.

Evaluation of Stress Intensity Factors Subjected to Arbitrarily Distributed Tractions on Crack Surfaces

The stress intensity factors （SIF） considering arbitrarily distributed surface tractions are evaluated based on the sealed boundary finite element method （SBFEM）. The semi-analytical solving process for the stress intensity factors including the effects of surface tractions is presented. Provided are the numerical examples for the evaluation of mode I and Ⅱ stress intensity factors with linear and non-linear distributing forces loaded on the crack surfaces. The crack problems of anisotropy and bimaterial interface are also studied and the stress intensity factors of single-edge-cracked orthotropic material and bi-material interface problems with surface tractions are calculated. Comparisons with the analytical solutions show that the proposed approach is effective and possesses high accuracy.

Research on Effect of Adding Nanomaterial to Propellant on Gun Barrel

The barrel lifes of three small caliber rifles were tested by using the propellant with nanomaterial and the standard propellant respectively. The test results show that the service life increases observably due to adding nanomaterial to the propellant. Then, the influence of the nanomaterial on the tube was researched by splitting the two barrels tested and detecting their inner surfaces. It was found that the erosion of the barrel bore is reduced observably by using the propellant with nanomaterial. And it makes the volume and the size of the gun chamber change less. Therefore, the barrel life can be prolonged by adding the nanomaterial in the propellant.

Corrosion behavior of tantalum and its nitride in alkali solution

The corrosion behavior of tantalum and its nitrides in stirring NaOHsolutions was researched by potentiostatic method, cyclic voltammetry and XPS. The results showedthat the corrosion products were composed of Ta_2O_5 and NaTaO_3. The corrosion reaction formula oftantalum and its nitrides was written according to cyclic volt-ampere curves. The electric chargetransfer coefficient and the electric charge transfer number were calculated

Detection and formation mechanism of micro-defects in ultrafine pitch Cu-Cu direct bonding

In this paper, Cu-Cu interconnects with ultrafine pad pitches of 6 p.m, 8 p.m, and 15 p.m are implemented on the 12 inch wafers by a direct bonding process. Defects are not found by traditional non-destructive （NDT） c-mode scanning acoustic microscopy （c-SAM）. However, cross sectional observation of bonding interfaces reveals that micro-defects such as micro seams are located at SiO2 bonding interfaces. In order to examine the micro-defects in the ultra-fine pitch direct bonding process by the NDT technology, a novel ＂defect-enlarged approach＂ is proposed. The bonded dies are first annealed in an N2 oven at 300 ℃ for a few hours and then cooled quickly in air. The c-SAM scanning images show large defects at the place where nothing can be detected by c-SAM before this treatment. Cross sectional observation of the bonding interfaces indicates that these defects consist of large size micro seams at the SiO2 bonding interface, especially near Cu pads with an ultrafine pitch of 6μm. However, these large defects disappear after several hours at room temperature, observed by c-SAM. It is inferred that the disappearance of these defects inspected by the ＂defect-enlarged approach＂ results from the combination of intrinsic micro seams and ＂weak＂ bonds in the silicon oxide layer. Then the underlying physical mechanism of these micro-defects is proposed, which is influenced by Cu pad surface topology and bonding models.

增强体表面改性在高导热金属基复合材料中的应用

随着电子技术的高速发展和电子器件的更新换代,电子封装材料的性能需求越来越高。金属基复合材料,尤其是铝基和铜基复合材料具有高导热、低膨胀、高稳定性等特点,是具有广阔应用前景的电子封装材料。然而,金刚石、石墨烯、硅等增强体与基体的润湿性差,或者在高温下与基体发生有害的界面反应,限制了此类高导热金属基复合材料的开发和应用。本文简述了金属基复合材料的界面研究进展,结合影响金属基复合材料界面结合的因素,提出了几种改善界面结合的方法。增强体表面改性是改善金属基复合材料界面的重要途径之一,常用工艺有磁控溅射法、化学气相沉积法、溶胶凝胶法、化学镀法等;最后,对增强体表面改性在高热导金属基复合材料中的应用进行分析和展望。

纳米材料增强植物纤维复合材料研究进展

对近4年来纳米材料增强植物纤维复合材料制备方法进行了综述。纳米材料增强植物纤维复合材料的制备方法主要包括硅烷偶联剂处理、溶胶-凝胶法、化学接枝法、横穿结晶技术和机械混杂法,总结了各种方法的优缺点,讨论了纳米纤维增强植物纤维复合材料制备过程中存在的问题,最后展望了纳米材料增强植物纤维复合材料未来的发展方向。

金属表面微结构对CFRP/TC4界面黏结强度的影响分析

CFRP/TC4异质材料黏结界面主要由金属表面、黏结剂以及复合材料表面组成,该界面是异质材料融合构件的核心部位,其界面黏结强度的优劣,对该类异质材料融合构件的长寿命和高可靠性会产生显著影响。本文主要针对TC4金属表面微结构对界面黏结强度的影响进行研究,基于Abaqus建立剪切力作用下的重叠黏结有限元模型,确定优选后的三角形结构主要参数为宽度、高度以及开槽方向与剪切受力方向之间的夹角,进而采用响应面Box-behnken法设计仿真试验并建立金属表面微结构与界面切应力之间的映射模型,并基于方差分析验证了该模型的有效性。通过该研究,揭示了金属表面微结构参数对界面切应力的影响规律。

组织工程治疗股骨头坏死软骨下分离的适用技术

背景:股骨头坏死出现新月征是病情进程的“分水岭”,修复和稳定骨-软骨界面对阻止病情继续进展和预防股骨头塌陷尤为重要。利用组织工程学同步修复、整合骨-软骨界面具有潜在优势。目的:综述探讨解决股骨头坏死软骨下分离的潜在适宜技术。方法:检索1970年1月至2023年4月PubMed、Web of Science及中国知网、万方数据库中发表的相关文献,英文检索词:“Femoral head necrosis,Avascular necrosis of femoral head,Osteonecrosis of femoral head”等,中文检索词:“股骨头坏死,软骨下骨,软骨,软骨与软骨下骨整合”等,最终纳入114篇文献进行综述分析。结果与结论:①结构缺陷、缺血缺氧环境、炎症因素和应力集中可能造成股骨头坏死软骨下分离现象,软骨下骨分离会造成塌陷进展,并且可能与保髋手术失败相关,利用组织工程支架实现支架与骨-软骨界面的整合是治疗股骨头坏死软骨下分离的潜在方法之一。②目前的文献研究表明,多相、梯度支架和复合材料在促进骨、软骨细胞黏附与增殖,骨软骨基质的沉积方面均有提升,有助于支架与骨-软骨界面的整合,对治疗股骨头坏死软骨下分离有参考价值。③通过对支架表面进行修饰可以提高与界面整合的效率,但有各自不同的优缺点,提供不同环境的支架能够诱导同种间充质干细胞差异分化,有助于不同界面之间的整合。④未来有望应用于股骨头坏死软骨下分离的支架应为复合材料,具有梯度化和差异化的仿生结构,通过表面修饰和干细胞加载促进骨-软骨界面与支架的整合以实现治疗目的,但仍需进一步研究验证,而支架的降解速率与修复进度同步和不同界面之间的稳定性是未来需要解决的主要问题。

PBO纤维表面改性处理的研究进展

聚对苯撑苯并二噁唑(PBO)纤维因其比强度高、比模量高、耐热性好、阻燃性好以及优异的介电性能,现已在安全防护、建筑汽车等领域得到广泛应用。由于PBO纤维表面光滑、化学惰性,导致其与基体树脂界面结合差,进一步影响复合材料的整体性能,这大大限制了PBO纤维优异综合性能的发挥,所以对PBO纤维表面进行改性处理显得尤为重要。介绍了近年来国内外针对PBO纤维不同表面改性方法及对应复合材料性能改善程度的研究进展,从PBO纤维改性方法的分类入手,阐述了各种方法的基本原理。通过对这些处理方法的比较,阐述了国内PBO纤维表面改性的研究进展,指出了国内外在PBO纤维表面改性处理上的差距,为未来的发展方向提供了参考。PBO纤维表面改性方法包括化学刻蚀法、等离子体处理、表面涂层法、化学接枝法、紫外刻蚀法、上浆剂处理等。各种改性技术各有利弊,在选择改性方法时,理应考虑达到工艺快捷有效、经济环保和无损纤维性能等指标。未来,在PBO纤维表面改性的处理方法领域,将逐步向绿色环保的上浆剂处理方向发展。