Research on Silicon Carbide Dispersion-Reinforced Hypereutectic Aluminum-Silicon Electronic Packaging Materials

The objective of this study is to improve the mechanical properties and machining performance of high thermal conductivity and low expansion silicon carbide dispersion-strengthened hypereutectic aluminum-silicon electronic packaging materials to meet the needs of aviation,aerospace,and electronic packaging fields.We used the powder metallurgy method and high-temperature hot pressing technology to prepare SiC/Al-Si composite materials with different SiC contents(5vol%,10vol%,15vol%,and 20vol%).The results showed that as the SiC content increased,the tensile strength of the composite material first increased and then decreased.The tensile strength was the highest when the SiC content was 15%;the sintering temperature significantly affected the composite material’s structural density and mechanical properties.Findings indicated 700℃was the optimal sintering and the optimal SiC content of SiC/Al-Si composite materials was between 10%and 15%.Besides,the sintering temperature should be strictly controlled to improve the material’s structural density and mechanical properties.

A Simple Way to Prepare Silicon Carbide Reinforced Graphite Composite Lubricating Materials

SiC reinforced graphite composites were prepared via introducing carbide silicon into the natural graphite flakes（NGF） by hot-pressing process. Their physical and mechanical properties, including density, open porosity, flexural strength, and friction behavior were investigated. The addition of 30vol% Si C increased the bending strength of composites materials to 127 MPa, 2 times higher than 60 MPa of commercial pure graphite block. What was particularly interesting was that the as-obtained graphite composite with 30vol% Si C kept the same low friction coefficient of about 0.1 as pure graphite, and the wear resistance of composites increased.

Finite element simulation of the micromachining of nanosized-silicon-carbide-particle reinforced composite materials based on the cohesive zone model

A finite element method based on the cohesive zone model was used to study the micromachining process of nanosized silicon-carbide-particle(SiCp) reinforced aluminum matrix composites. As a hierarchical multiscale simulation method, the parameters for the cohesive zone model were obtained from the stress-displacement curves of the molecular dynamics simulation. The model considers the random properties of the siliconcarbide-particle distribution and the interface of bonding between the silicon carbide particles and the matrix.The machining mechanics was analyzed according to the chip morphology, stress distribution, cutting temperature, and cutting force. The simulation results revealed that the random distribution of nanosized SiCp causes non-uniform interaction between the tool and the reinforcement particles. This deformation mechanics leads to inhomogeneous stress distribution and irregular cutting force variation.

Drain-induced barrier lowering effect for short channel dual material gate 4H silicon carbide metal-semiconductor field-effect transistor

Sub-threshold characteristics of the dual material gate 4H-SiC MESFET （DMGFET） are investigated and the analytical models to describe the drain-induced barrier lowering （DIBL） effect are derived by solving one- and two- dimensional Poisson＇s equations. Using these models, we calculate the bottom potential of the channel and the threshold voltage shift, which characterize the drain-induced barrier lowering （DIBL） effect. The calculated results reveal that the dual material gate （DMG） structure alleviates the deterioration of the threshold voltage and thus suppresses the DIBL effect due to the introduced step function, which originates from the work function difference of the two gate materials when compared with the conventional single material gate metal-semiconductor field-effect transistor （SMGFET）.

STUDY ON PREPARATION OF REACTION BURNING SILICON CARBIDE BY CARBON POWDER

The technology of preparing reaction burning silicon carbide (RBSC) by replacing SiC/C with entirely carbonaceous raw materials is investigated. Experimental results show the predominant factors of successfully preparing RBSC are as following:strictly controlling the porosity and pore diameter of biscuit, obtaining ideal carbon network permeating of Si and completely reaction between Si and beta-SiC.

Effects of Three Silicon-based Raw Materials on Properties and Microstructure of MgO-Al-C Materials

To improve the thermal shock resistance(TSR)of MgO-Al-C materials,three silicon-based raw materials with low expansion coefficients(Si,fused quartz,and SiC)were introduced to the materials,and their effects on the properties of the materials were studied by XRD and SEM.The results show that:(1)the conversion of Si to SiC,SiO2 and forsterite at high temperatures improves the hot modulus of rupture(HMOR),TSR and oxidation resistance of the materials,and the optimal Si addition is 6 mass%;(2)fused quartz improves the TSR of the materials,but its high temperature softening and crystal transformation are not conducive to the HMOR and oxidation resistance of the materials,and the optimal addition is 2 mass%;(3)the SiC addition improves the TSR,HMOR and oxidation resistance of the materials;however,when the SiC addition exceeds 10 mass%,there are more micro-cracks in the materials,decreasing the TSR and oxidation resistance.

Body armour-New materials, new systems

This is a very timely review of body armour materials and systems since new test standards are currently being written, or reviewed, and new, innovative products released. Of greatest importance, however, is the recent evolution, and maturity, of the Ultra High Molecular Weight Polyethylene fibres enabling a completely new style of system to evolve e a stackable system of Hard Armour Plates. The science of body armour materials is quickly reviewed with emphasis upon current understanding of relevant energy-absorbing mechanisms in fibres, fabrics, polymeric laminates and ceramics. The trend in ongoing developments in ballistic fibres is then reviewed, analysed and future projections offered. Weaknesses in some of the ceramic grades are highlighted as is the value of using cladding materials to improve the robustness, and multi-strike performance, of Hard Armour Plates. Finally, with the drive for lighter, and therefore smaller, soft armour systems for military personnel the challenges for armour designers are reported, and the importance of the relative size of the Hard Armour Plate to the Soft Armour Insert is strongly emphasised.

Material Removal Characteristics of Single-Crystal 4H-SiC Based on Varied-Load Nanoscratch Tests

Single-crystal silicon carbide(SiC)has been widely applied in the military and civil fields because of its excellent physical and chemical properties.However,as is typical in hard-to-machine materials,the good mechanical properties result in surface defects and subsurface damage during precision or ultraprecision machining.In this study,single-and double-varied-load nanoscratch tests were systematically performed on single-crystal 4H-SiC using a nanoindenter system with a Berkovich indenter.The material removal characteristics and cracks under different planes,indenter directions,normal loading rates,and scratch intervals were analyzed using SEM,FIB,and a 3D profilometer,and the mechanisms of material removal and crack propagation were studied.The results showed that the Si-plane of the single-crystal 4H-SiC and edge forward indenter direction are most suitable for material removal and machining.The normal loading rate had little effect on the scratch depth,but a lower loading rate increased the ductile region and critical depth of transition.Additionally,the crack interaction and fluctuation of the depth-distance curves of the second scratch weakened with an increase in the scratch interval,the status of scratches and chips changed,and the comprehensive effects of the propagation and interaction of the three cracks resulted in material fractures and chip accumulation.The calculated and experimental values of the median crack depth also showed good consistency and relativity.Therefore,this study provides an important reference for the high-efficiency and precision machining of single-crystal SiC to ensure high accuracy and a long service life.

Progress on Space Materials Science in China:Debris Shielding Fibrous Materials and High Specific Energy Lithium Sulfur Batteries

The development of China’s space industry puts forward urgent requirements for high-performance debris shielding materials and high energy density rechargeable battery.In this review,the recent progress on debris shielding fibrous materials and high energy density Li-S battery are particularly summarized.According to the experimental results,basalt fibers and silicon carbide fibers were chosen as the effective filling shielding materials.The geometric structure of fabrics was also investigated.For the novel shielding materials,high-strength and flexible silicon carbide micro-nano fibrous membranes were designed and fabricated.The obtained membranes with excellent mechanical properties portend the potential applications in debris protection structure.Furthermore,the high specific energy lithium sulfur batteries have made remarkable progress in fundamental research and application research in recent years.In order to solve the key problems of polysulfides shuttle and slow redox kinetics in lithium sulfur battery,a series of transition metal compound@hollow carbon-based material as sulfur host with dual functions of catalysis and adsorption towards polysulfides were designed and constructed.The obtained Li-S pouch cells with high areal sulfur loading of 6.9 mg·cm^(-2)yield exceptional high practical energy density of 382 W·h·kg^(-1)under lean electrolyte of 3.5μL·mg^(-1),demonstrating the great potential of realistic high-energy Li-S batteries.

半导体碳化硅衬底的湿法氧化

半导体碳化硅(4H-SiC)材料具有硬度高、脆性大、化学性质稳定等特点,一般使用化学机械抛光工艺来加工4H-SiC以获得超光滑平坦表面。湿法氧化作为单晶4H-SiC化学机械抛光的重要过程,直接影响着化学机械抛光的速率和表面质量。本文综述了目前单晶4H-SiC湿法氧化的研究现状,讨论了4H-SiC湿法氧化工艺所选用的氧化剂,如KMnO_(4)、H_(2)O_(2)、K_(2)S_(2)O_(8)等。在此基础上,进一步总结了常用的氧化增效方法,如光催化辅助氧化、电化学氧化、芬顿反应等,并从理论计算的角度分析了单晶4H-SiC湿法氧化的机理,最后展望了4H-SiC湿法氧化未来的研究方向。

SiC复合陶瓷增韧研究现状

SiC陶瓷具有优良的性能,被广泛应用于各领域,但因韧性不足而制约其作为结构材料的应用,故提升其韧性已成为研究热点和焦点。因此,综述了颗粒、晶须、纤维和低维纳米材料(碳纳米管和石墨烯)等不同增强相增韧SiC复合陶瓷的研究现状,期望为今后SiC陶瓷的增韧研究提供参考。

碳化硅化学机械抛光中材料去除非均匀性研究进展

化学机械抛光已经成为半导体制造中关键的工艺步骤之一,该技术是目前实现碳化硅晶片超精密加工的一种常用且有效的方法,可用于加工晶片表面,以获得高材料去除率、高表面质量和高表面平整性的晶片。然而,在碳化硅晶片化学机械抛光中,晶片表面材料去除非均匀性一直是一个具有挑战性的问题,减小晶片表面材料去除非均匀性对确保半导体器件的高性能和稳定性至关重要。本文介绍了碳化硅材料的性质及应用与化学机械抛光工艺,研究了不同碳化硅化学机械抛光技术的材料去除机理、不同化学机械抛光技术的发展状况和性能及优缺点,综述了碳化硅晶片化学机械抛光中材料去除非均匀性影响因素,如:抛光压力、抛光液(磨粒)和转速等因素,最后对未来碳化硅化学机械抛光中材料去除非均匀性研究做出了展望。

碳化硅复合陶瓷密封材料的烧结性能、显微结构与力学性能

以纳米TiN、SiC晶须为增强相,采用液相烧结法制备了碳化硅复合陶瓷密封材料,研究了不同烧结温度(1800,1850,1900,1950℃),不同增强相添加质量分数(0,2.5%,5.0%,10.0%,纳米TiN与SiC晶须质量比为1∶1)下复合陶瓷的烧结性能、显微组织和力学性能。结果表明:随烧结温度升高,陶瓷硬度和抗弯强度均先增大后减小,断裂韧度先减小后增大,当烧结温度为1900℃时,碳化硅复合陶瓷烧结完全,相对密度较高,晶粒平均尺寸较小;在1900℃下烧结,与未添加增强相相比,添加增强相碳化硅复合陶瓷的晶粒尺寸减小,晶粒结构排列紧密;随着增强相添加量增加,陶瓷硬度下降,抗弯强度先增大后减小,断裂韧度明显增大;当烧结温度为1900℃,增强相质量分数为5.0%时,碳化硅复合陶瓷具有最佳综合性能,相对密度为94.68%,抗弯强度为429.51 MPa,硬度为17.14 GPa,断裂韧度为4.32 MPa·m^(1/2)。

Formation of Laser-Induced Periodic Surface Structures on Reaction-Bonded Silicon Carbide by Femtosecond Pulsed Laser Irradiation

Reaction-bonded silicon carbide(RB-SiC)is an excellent engineering material with high hardness,stiffness,and resistance to chemical wear.However,its widespread use is hindered due to the properties mentioned above,making it difficult to machine functional surface structures through mechanical and chemical methods.This study investigated the fundamental characteristics of laser-induced periodic surface structures(LIPSSs)on RB-SiC via femtosecond pulsed laser irradiation at a wavelength of 1028 nm.Low-spatial-frequency LIPSS(LSFL)and high-spatial-frequency LIPSS(HSFL)formed on the surface along directions perpendicular to the laser polarization.SiC grains surrounded by a large amount of Si show a reduced threshold for LIPSS formation.By varying laser fluence and scanning speed,HSFL-LSFL hybrid structures were generated on the SiC grains.Transmission electron microscopy observations and Raman spectroscopy were carried out to understand the formation mechanism of the hybrid LIPSS.A possible mechanism based on the generation of multiple surface electromagnetic waves due to the nonlinear response of SiC was proposed to explain the hybrid structure formation.Furthermore,the direction of laser scanning with respect to laser polarization affects the uniformity of the generated LIPSS.

SiC界面热化学反应演化响应机理研究

超高温陶瓷是保障飞行器在极端热环境下安全服役的理想热防护材料之一,其中SiC组分由于其优异的力热性能已成为陶瓷基体或抗氧化涂层领域的研究热点。但由于目前尚未能清晰认知其在高温边界层内界面热响应演化的复杂机理,限制了其热防护性能设计的进一步提升。为在微观尺度上研究SiC复杂界面演化及热响应机制提供新的可能,采用基于反应力场的反应分子动力学模拟方法,模拟了SiC界面的高温演化过程,并探究了界面在温度和压强变化下的热响应机理,包括热氧化反应及升华等;计算了典型工况下SiC界面的氧化反应速率、升华速率及烧蚀速率,并将计算获得的烧蚀后退速率结果与文献实验结果进行了对比,发现误差在10%以内,进一步验证了该方法在材料界面热化学反应定量计算方面应用的可行性。

SiC聚合物前驱体和Zn粉复合对Al_(2)O_(3)-C不烧滑板材料性能的影响

为提高Al_(2)O_(3)-C不烧滑板材料的中低温强度,首先将质量比为1∶0.15∶2.7∶0.03的蔗糖、六水合硝酸镍、正硅酸乙酯、草酸水溶液依次添加至乙醇水溶液中,经110℃干燥18 h后得到SiC聚合物前驱体,然后以板状刚玉、α-Al_(2)O_(3)微粉、鳞片石墨为主要原料,复合添加SiC聚合物前驱体和Zn粉,在150 MPa下压制成150 mm×25 mm×25 mm的坯体试样,经180℃固化24 h后,在埋碳条件下经600、800、1000、1200和1400℃热处理3 h。研究了SiC聚合物前驱体和Zn粉复合添加对Al_(2)O_(3)-C材料性能的影响。结果表明:SiC聚合物前驱体和Zn粉的最佳添加量(w)分别为4.5%和1.5%,此时Al_(2)O_(3)-C材料综合性能最优。低温时Zn粉熔融,在材料体系中形成金属结合相;中温时SiC聚合物前驱体发生热解反应及Zn粉气化的催化作用,使体系形成SiC纤维结合相;二者共同作用,赋予Al_(2)O_(3)-C不烧滑板材料较高的中低温强度,克服了现有材料使用过程中因强度过低导致的失效问题。

添加改性纳米碳和碳化硅颗粒对芒硝相变材料吸光、透光性能的影响

【目的】研究改性纳米碳颗粒和碳化硅颗粒对芒硝相变复合材料吸光性能和透光性能的影响。【方法】改性纳米碳粉和改性纳米碳化硅粉与芒硝相变材料结合,制备纳米颗粒芒硝复合相变材料,讨论不同波长对复合相变材料吸光、透光性和分散稳定性的影响;分散稳定性利用鞘流法图像仪对纳米颗粒进行分析,稳定性通过在50℃和室温下进行7 d静置后观察确定;采用积分反射仪分析相变材料吸光、透光性。【结果】鞘流法图像分析发现,改性纳米碳粉和改性纳米碳化硅粉形貌结构基本无变化且没有团聚现象,静置观察发现没有出现纳米颗粒分层和团聚现象;添加质量分数分别为0.1%、 0.5%、 1.0%的改性碳粉后,相变材料对紫外光的平均吸光度提高20%-35%,可见光的平均透过率下降26%-35%,红外光(波长为800-1 500 nm)的透光率下降10%-42%;分别添加相同质量分数的改性碳化硅后,相变材料对紫外光的平均吸光度提高22%-26.6%,可见光的平均透过率下降20%-29%,红外光(波长为1 500-2 700 nm)的透光率提高8%-29%。【结论】改性纳米颗粒在芒硝基相变材料中具有良好的分散性和稳定性;通过在传统芒硝基相变材料基础上添加不同含量的改性纳米颗粒,获得的纳米颗粒芒硝基相变材料对不同波长光的吸光率和透光率的基础性数据,为高性能纳米颗粒芒硝相变材料快速光热响应的研究打下基础。

单晶SiC超精密加工研究进展

单晶碳化硅(SiC)的高脆性、高硬性和强化学惰性是制约第三代半导体超精密抛光发展的关键,实现衬底高效率、超光滑表面的加工具有挑战性。对于单晶SiC的化学机械抛光(CMP),分别从材料去除和工艺优化两个维度出发,阐述了CMP SiC的影响因素和规律,指出了该方法的不足。介绍了光催化、超声振动、电场、等离子体、磁流变、表面预处理等辅助CMP抛光方法,分析了复合增效抛光的去除机理和优势。通过对比发现,辅助能场的介入有助于改善SiC表面质量,并能获得较好的加工效果,然而,复合抛光技术涉及的能场复杂,多能场作用下的材料去除机制和工艺参数匹配仍需进行深入研究。最后,对未来单晶SiC超精密加工的研究给出了建议,并进行了展望。

碳化硅材料在5G通信中的应用展望

阐述碳化硅材料在5G技术中的应用状况,包括在无线通信系统、射频器件、光通信系统、电源管理、能量传输、5G封装与散热中的应用。探讨碳化硅材料的发展,将推动无线通信、物联网和高速数据传输等领域的发展。

成型工艺对黏土结合碳化硅制品性能的影响

以碳化硅、硅微粉为主要原料,以粘土为结合剂,制备出粘土结合的碳化硅制品。探究了不同成型压力(100 MPa、150 MPa、180 MPa、200 MPa和230 MPa)和颗粒级配对碳化硅制品显微结构及其性能的影响。结果表明:当添加质量分数17%的碳化硅细粉时,体积密度值为2.42 g/cm^(3);常温耐压强度和常温抗折强度分别为83.46 MPa和17.4 MPa;同时抗氧化性得到进一步改善。当成型压力为230 MPa时,压制的试样的机械性能和抗氧化性均达到最大值。