基于搅拌摩擦加工制备石墨烯增强铝基复合材料

为减少增强相团聚现象,利用搅拌摩擦加工方法,分别将多层石墨烯和无电镀铜石墨烯添加进6061-T651铝合金,制备铝基复合材料。通过光学显微镜、拉曼光谱仪、XRD衍射仪和硬度计,分析复合材料中增强相的分布质量、复合材料成分及硬度。结果表明:与多层石墨烯相比,无电镀铜石墨烯更容易在搅拌区中分散均匀,但出现石墨化现象;多层石墨烯和无电镀铜石墨烯均未与铝母材结合生成金属间化合物;无电镀铜石墨烯添加到铝合金中,可有效提高其硬度,硬度最大可达搅拌摩擦母材的85%,硬度波动最大仅为13 HV。     

粉末冶金法制备镀铜石墨烯/铝复合材料的组织与性能研究

采用真空热压烧结法制备了分别添加体积分数为5%和10%镀铜石墨烯的铝基复合材料。通过金相显微镜、扫描电镜、X射线衍射仪、布氏硬度计、导热系数测试仪和四探针电阻率测试仪,检测了复合材料的组织、硬度、导热和导电性能。试验结果表明:采用简化的化学镀铜方法在石墨烯表面成功化学镀铜,镀铜后增重2倍左右,镀铜后仍然存在石墨烯团聚现象。利用镀铜石墨烯制备铝基复合材料,避免了石墨烯与铝发生界面反应生成Al4C3。复合材料主要由铝相组成,加体积分数为5%的石墨烯时生成少量Cu Al2,在加体积分数为10%的石墨烯时,铝晶粒细化。随着镀铜石墨烯加入量增加,复合材料致密度下降,导电性能有一定改善,导热性能显著提高,硬度显著增大,添加体积分数为5%和10%石墨烯时其硬度较纯铝的分别提高了12%和75%。     

石墨烯/SnO2/Cu复合材料微观组织及性能研究

采用微波水热合成法对石墨烯进行表面改性,形成石墨烯/SnO2纳米复合物;将其用于粉末冶金法制备石墨烯/SnO2/Cu复合材料。采用多种分析测试手段对复合材料的微观组织及性能进行研究。结果表明,石墨烯表面吸附的SnO2纳米颗粒不会在复合材料制备过程中脱落,并可有效抑制石墨烯团聚,提高复合材料的致密度、硬度和热导率等性能。本文制备的石墨烯/SnO2/Cu复合材料致密度为91.0%,硬度为166HBW,热导率139W/(m℃),远高于Graphene/Cu复合材料。Graphene/SnO2/Cu复合材料中,界面结合良好,无开裂和界面反应;基体Cu中的刃型位错、形变孪晶以及石墨烯表面的SnO2纳米颗粒,是导致复合材料电导率下降的主要原因。     

石墨烯增强铝基复合材料的微观结构及力学性能研究

采用无水乙醇中超声波震荡和高能球磨实现石墨烯与铝粉的均匀混合,然后采用冷压和真空烧结制备了石墨烯增强铝基复合材料。研究了该复合材料的微观结构及力学性能研究。结果表明:所制备的复合材料基体致密,石墨烯结构完整,以片状物形式均匀的分布在基体内,石墨烯与铝基体界面结合良好。当石墨烯含量为0.6%(wt%)时,复合材料抗弯强度最好,达到114 MPa,比纯铝增加了24%;当石墨烯含量为0.4%时,复合材料的硬度最好,达44 HV,比纯铝增加了22%     

石墨烯增强钛基复合材料的压缩变形行为研究

通过粉末冶金方法利用等离子电火花烧结在850℃制备了石墨烯增强钛基复合材料,并利用Gleeble-1500D研究了复合材料在室温和800℃时的压缩变形行为。研究发现:石墨烯均匀地分散在钛基体中,细化了钛基体的微观组织,提高了基体室温和高温的压缩强度和硬度。其中室温和高温屈服强度分别提高了22.87%和23.07%,抗压强度分别提高了13.91%和28.57%,室温和高温的硬度分别提高了16.4%和10%。同时发现石墨烯和钛基体反应生成了少量的碳化钛颗粒,能对基体产生强化效应。研究结果表明石墨烯/钛复合材料可成为一种高性能的特种材料,具有潜在的工程应用价值。     

石墨烯含量对多层石墨烯/银复合材料组织和性能的影响

采用粉末冶金法制备了多层石墨烯/银电接触复合材料,并系统研究了多层石墨烯含量对多层石墨烯/银复合材料微观组织、导电率、硬度及电弧侵蚀的影响。结果表明,复合材料密度随多层石墨烯含量的增加而减小。多层石墨烯含量为0.5%的石墨烯/银复合材料具有最佳的导电率,为84.5% IACS。当多层石墨烯含量高于2.0%以后,复合材料硬度降低幅度明显增大。多层石墨烯含量为1.5%的多层石墨烯/银电接触复合材料表现出最优异的抗电弧侵蚀性能。     

石墨烯含量对多层石墨烯/银复合材料组织和性能的影响（英文）

采用粉末冶金法制备了多层石墨烯/银电接触复合材料,并系统研究了多层石墨烯含量对多层石墨烯/银复合材料微观组织、导电率、硬度及电弧侵蚀的影响。结果表明,复合材料密度随多层石墨烯含量的增加而减小。多层石墨烯含量为0.5%的石墨烯/银复合材料具有最佳的导电率,为84.5%IACS。当多层石墨烯含量高于2.0%以后,复合材料硬度降低幅度明显增大。多层石墨烯含量为1.5%的多层石墨烯/银电接触复合材料表现出最优异的抗电弧侵蚀性能。     

石墨烯对搅拌摩擦加工铝基复合材料性能的影响

采用结合粉末工艺的两步法搅拌摩擦加工制备石墨烯增强铝基复合材料,研究了石墨烯添加量对复合材料力学性能和导电性能的影响。结果表明,石墨烯的添加对铝基复合材料性能有明显的影响,随石墨烯添加量增加,复合材料的硬度逐渐提高、塑性持续下降,而抗拉强度和电导率均呈先增后减的趋势。石墨烯体积分数为3.7%时,复合材料的抗拉强度最高,达到146.5 MPa,与同等加工条件下的纯铝相比,提高了78.7%,而石墨烯体积分数为1.3%时,复合材料的电导率最高,达到30.62 MS/m,较同等加工条件下的纯铝基体提高了53.4%。     

微纳石墨烯片增强铝合金的力学性能及其机理

采用电化学加超声剥离制取微纳石墨烯片,通过粉末冶金制备石墨烯增强铝合金。使用纳米压痕和摩擦磨损试验机对样品的纳米硬度、弹性模量、室温蠕变以及摩擦性能进行研究。结果表明:铝合金的纳米硬度和弹性模量随着微纳石墨烯片含量的增加呈线性提高;当微纳石墨烯片含量为0.20%(质量分数)时,石墨烯增强铝合金的纳米硬度和弹性模量比纯铝合金的分别提高66%和52%,室温平均蠕变度在保载阶段为纯铝合金的54.56%,在稳定阶段平均蠕变速率仅为纯铝合金的1/10,摩擦因数随微纳石墨烯片含量的增加而逐渐降低。微纳石墨烯片的加入使得晶粒细化、产生高位错密度和晶格畸变,提高了石墨烯铝合金复合材料的纳米硬度以及弹性模量,微纳石墨烯片对部分可动位错钉扎提高了铝合金抗蠕变性能,微纳石墨烯片存在自润滑性提高了铝合金摩擦性能。     

热处理对半固态注射成形石墨烯/镁基复合材料组织及性能的影响

研究了不同固溶温度和时效时间对半固态注射成形石墨烯增强镁基复合材料组织及性能的影响。结果表明,随着固溶温度升高,复合材料硬度(HV)逐渐减小,在200℃时复合材料硬度最高;β-Mg17Al12相含量先增大后减少,在400℃时几乎全部消失。随着时效时间增加,复合材料硬度(HV)先增加后减少,在时效12h时达到最大,为93.17。经过固溶处理和时效处理后石墨烯在复合材料基体中稳定存在,且对复合材料的硬度产生影响。     

Mechanical and tribological behaviors of graphene/Inconel 718 composites

Graphene/Inconel 718 composites were innovatively synthesized through selective laser melting, and the mechanical and tribological performances of the grapheme-reinforced Inconel 718 matrix composites were evaluated. The composite microstructures were characterized by XRD, SEM and Raman spectroscopy. The results show that selective laser melting is a viable method to fabricate Inconel 718 matrix composite and the addition of graphene nanoplatelets leads to a significant strengthening of Inconel 718 alloy, as well as the improvement of tribological performance. The yield strength and ultimate tensile strength of 1.0% graphene/Inconel 718 composites (mass fraction) are 42% and 53% higher than those of pure material, and the friction coefficient and wear rate are 22.4% and 66.8% lower than those of pure material. The decrease of fraction coefficient and wear rate is attributed to the improved hardness of composites and the formation of graphene nanoplatelet protective layer on the worn surfaces.     

An Investigation on the Sinterability and the Compaction Behavior of Aluminum/Graphene Nanoplatelets (GNPs) Prepared by Powder Metallurgy

In the present study, the densification response of Al matrix reinforced with different weight percentages (0, 0.5, 1.0, 1.5 and 2.0 wt.%) of graphene nanoplatelets (GNPs) was studied. These composites were produced by a wet method followed by a conventional powder metallurgy. The Raman spectrum of graphene indicates that preparation of the composites through the wet mixing method did not affect the disordering and defect density in the GNPs structure. The nanocomposite powder mixture was consolidated via a cold uniaxial compaction. The samples were sintered at different temperatures (540, 580 and 620 °C) under nitrogen flow so as to assess the sinterability of the nanocomposites. X-ray diffraction (XRD) has been carried out to check the possible reaction between GNPs and aluminum. According to the XRD patterns, it seems that Al₄C₃ did not form during the fabrication process. The relative density, compressibility, sinterability and Vickers hardness of the nanocomposites were also evaluated. The effects of GNPs on the consolidation behavior of the matrix were studied using the Heckel, Panelli and Ambrosio Filho, and Ge equations. The outcomes show that at early stage of consolidation the rearrangement of particles is dominant, while by increasing the compaction pressure, due to the load partitioning effect of GNPs, the densification rate of the powder mixture decreases. Moreover, the fabricated nanocomposites exhibited high Vickers hardness of 67 HV₅, which is approximately 50% higher than monolithic aluminum. The effect of graphene addition on the thermal conductivity of Al/GNPs nanocomposites was evaluated by means of thermal diffusivity measurement, and the results showed that the higher thermal conductivity can be only achieved at lower graphene content.     

Optimization to develop multiple response hardness and compressive strength of zirconia reinforced alumina by using RSM and GRA

In this work the effect of powder forming process parameters of zirconia reinforced alumina composites on micro hardness and compressive strength was studied. The weight percentages of zirconia added to alumina, compaction pressure and sintering temperature are the process parameters selected for this analysis. Using Box–Behnken technique in Response Surface Methodology (RSM), seventeen experimental runs are developed. The sintering temperature and weight percentage of zirconia added to alumina are found to influence the responses. The influencing parameters were identified by using analysis of variance and Grey Relational Analysis (GRA). The regression model for both micro hardness and compressive strength are developed. The increasing amount of zirconia added to alumina matrix is found to enhance the compressive strength of the composite and reduces the hardness of composite. Also, multi response optimization to obtain higher hardness and compressive strength are done using both RSM and GRA.     

A Novel Cu–GNPs Nanocomposite with Improved Thermal and Mechanical Properties

Classical powder metallurgy followed by either hot isostatic pressing(HIPing) or repressing–annealing process was used to produce Cu–graphene nanoplatelets(GNPs) nanocomposites in this work. A wet mixing method was used to disperse the graphene within the matrix. The results show that a uniform dispersion of GNPs at low graphene contents could be achieved, whereas agglomeration of graphene was revealed at higher graphene contents. Density evaluations showed that the relative density of pure copper and copper composites increased by using the post-processing techniques.However, it should be noticed that the efficiency of HIPing was remarkably higher than repressing–annealing process, and through the HIPing, fully dense samples were achieved. The Vickers hardness results showed that the reconsolidation steps can improve the mechanical strength of the specimens up to 50% owing to the progressive porosity elimination after reconsolidation. The thermal conductivity results of pure copper and composites at high temperatures showed that the postprocessing techniques could enhance the conductivity of materials significantly.     

含石墨烯胞室结构的铜复合材料及其耐腐蚀性能

目的 开发一种石墨烯在铜基复合材料中的均匀分散结构,制备出兼具高导电和强抗刻蚀性能的石墨烯/铜复合材料。方法 采用化学气相沉积原位生长法结合分散剂工艺,制备分散均匀石墨烯/铜基粉体复合材料。利用制备的石墨烯/铜粉体材料,采用真空热压工艺,制备了石墨烯/铜块体材料,然后用拉曼光谱、X射线粉末衍射仪和金相显微镜,考察石墨烯/铜试样的质量和形貌,最后用数字便携式涡流电导仪测量其电导率。利用自主设计的石墨烯/铜在过硫酸铵中刻蚀的实验装置,测试石墨烯/铜的抗刻蚀性能。结果 利用石墨烯/铜粉体制备的石墨烯/铜块体和铜具有相同的(111)、(200)和(220)晶面,多层石墨烯以立体胞室结构均匀分布在铜晶粒的晶界处。石墨烯/铜块体的导电率为96%IACS,明显优于文献报道的以其他方法制备的石墨烯/铜块体,并且在过硫酸铵溶液中浸泡90 min后,石墨烯/铜块的质量损失为126.6 mg, 石墨烯/铜比纯铜的抗刻蚀能力提高了37.6%,具有比铜更强的抗刻蚀性能。结论 以CVD原位生长法和真空热压法制 备的石墨烯/铜复合材料,石墨烯以立体胞室结构均匀分散在铜界面处,并且兼具高的导电性和强的抗刻蚀性能。     

具有梯度特性的齿科修复复合材料制备及表征

本工作的目的是研究原生牙齿的梯度力学性能,制备聚合物渗透陶瓷网络(PICN)复合材料,模拟天然牙的力学行为。采用纳米压痕法测定了牙釉质和牙本质的弹性模量和维氏硬度。结果表明,原生牙齿的力学性能具有梯度特性。树脂填充部分烧结硅铝酸钠、氧化铝和氧化锆的力学性能有很大差异。通过逐步改变陶瓷组分,实现了力学性能的梯度变化。一种是纳米玻璃相硅铝酸钠/微米α氧化铝层合复合材料。陶瓷坯体的烧结温度为700℃,保温时间分别为2、4和6 h。对复合材料的抗弯强度、断裂韧性、弹性模量和硬度进行了测试,结果表明:硅铝酸钠/微米α氧化铝复合材料的弹性模量和硬度呈现梯度特性。另一种是3Y-TZP/微米α氧化铝层合复合材料。坯体烧结温度分别为1150和1200℃,保温时间为2h。其弹性模量和硬度均呈现梯度特性。SEM观察表明,过渡区形成了相互咬合的网络结构。与普通均质材料不同,本研究制备的复合材料具有各向异性。因此,复合材料的力学性能更接近于原生牙齿。     

Thermal and Mechanical Properties of Graphene-Titanium Composites Synthesized by Microwave Sintering

The x wt%graphene-Ti composites(x = 0,0.2,0.3 and 0.4) were obtained using the powder metallurgy method.The X-ray diffraction results demonstrated that the peak intensity of graphene increased monotonically with increasing graphene content.Furthermore,the number of grain boundary and interface between graphene and matrix increased as graphene increased,which led to a sharp rise of thermal resistances.The thermal conductivity and specific heat capacity of composites initially decreased drastically with addition of graphene,but then increased with increasing graphene content from 0.2 to 0.4 wt%.This phenomenon was connected with the graphene content and the characteristics of Ti matrix(pores,grain boundary and interface between graphene and matrix).The variation of the compressive strength of composites was attributed to the interaction effects of the average grain size of the Ti matrix(d_m) and the volume fraction(V_f) and aspect ratio(A) of graphene.