Multifunctional A356 alloy/ PKSAnp composites: Microstructure and mechanical properties

Mechanical properties and microstructure of multifunctional composites produced with palm kernel shell ash nanoparticle (PKSAnp)-A356 alloy composites was studied. The composites were produced using Double layer feeding stir casting method (DLF-SCM) by adding 1 wt%‒4 wt.% PKSAnp. The microstructure, density, electrical and mechanical properties were determined. The results shows that there was a uniform distribution of the PKSAnp in A356 alloy. The mismatch at the interface between the PKSAnp and A356 alloy was 4.26%. Improvement of 30.47%, 41.91%, 49.52%, 40.90% and 65.09% were obtained for hardness values, tensile, yield strength, %elongation and impact energy at 4 wt% PKASnp. The work has established that the developed composites can be used for multifunctional applications where combination of toughness and strength is vital.     

室内装饰织物燃烧特性研究

室内装饰织物因其容易点燃、燃烧速度快、蔓延迅速等燃烧特性,对室内火灾的发展蔓延及火灾危害都有重要影响。运用锥形量热仪对棉麻、涤纶、帆布、泡纱、条绒等5种室内装饰织物的燃烧性能进行了实验研究,测量了室内装饰织物在不同热辐射条件下的燃烧特性,并对实验数据进行图像拟合,通过具体的实验数据和图像分析比较了5种室内装饰织物在不同热辐射条件下的点燃时间、热释放速率、质量损失速率、比消光面积及CO生成量。最后得出了各种织物的火灾危险性相对大小。     

Synergistic effect of hybrid Himalayan Nettle/Bauhinia-vahlii fibers on physico-mechanical and sliding wear properties of epoxy composites

The cellulosic bast fibers are recognized as a justifiable and biodegradable substitute for producing moderate strength polymer composite materials because of their characteristics of renewability, eco-friendliness, and higher specific strength. Hence the aim of this research work is to fabricate Himalayan bast fibers (Nettle fiber (NF)/bauhinia vahlii fiber (BF)) based mono/hybrid epoxy composites at varying weight percentage of 2–6 wt% and evaluate the physical (void fraction and water absorption), mechanical (tensile strength, flexural strength, hardness) and sliding wear properties of as-fabricated composites. The 6 wt% NBF reinforced composites exhibited higher mechanical properties as compared to NF and BF composites with tensile strength of 34.04 MPa, flexural strength of 42.45 MPa, and hardness of 37.01 H_v respectively. The influence of various control factors (sliding velocity, NF/BF/NBF contents, normal load and sliding distance) on specific sliding wear rate of composites was evaluated by Taguchi (three factors at three levels) experimental design and the percentage contribution of these selected parameters on sliding wear performance was examined by Analysis of variance (ANOVA). The sliding wear property of as-developed composites was found to be greatly influenced by sliding velocity and the wear resistance was observed to be improved with the NF/BF/NBF contents. The wear mechanism of the as-fabricated composites has been elucidated by scanning electron microscopy analysis. The research outcomes demonstrated that the hybridization of Bauhinia vahlii fiber with Nettle fiber led to improve the mechanical and wear properties of epoxy composites.     

Liquid phase in-situ synthesis of LiF coated boron powder composite and performance study

Among practical metal additives, boron (B) has a high volumetric heating value, making it a promising choice as a fuel additive. Although B can theoretically yield a large amount of energy upon complete combustion, its combustion is retarded by the initial presence of B oxide, which coats the surfaces of B particle. To improve the ignition and combustion properties of B powder, LiOH and NH₄F were used as precursors to synthesize uniformly LiF-coated B composites (LiF-B) in situ. The LiF-B mixture was also prepared for comparison using a physical method. X-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the morphologies and compositions of the products. The thermal and combustion properties of the samples were characterized by thermal gravity-differential thermal gravity (TG-DTG), differential scanning calorimetry (DSC) and closed bomb experiment. The XRD, FTIR, SEM and EDS results demonstrated the successful preparation of the coated LiF-B sample. The TG-DTG and closed bomb experiment results indicated that the addition of LiF decreased the ignition temperature of B powder, and increasing its reaction efficiency. DSC results show that when LiF-B was added, the released heat of underwater explosive increased by 6727.2, 7280.4 and 3109.6 J/g at heating rates of 5, 10, and 15 °C/min, respectively. Moreover, LiF-B decreased the activation energy of secondary combustion reaction of explosive system as calculated through Kissinger's method by 28.9%, which indicated an excellent catalytic effect for the thermal decomposition of underwater explosive. The results reveal that LiF can improve the combustion efficiency of B powder, thereby increasing the total energy of explosives. The mechanical sensitivity increased slightly after adding LiF-B to the underwater explosive. Compared to the underwater explosive with added B, the mechanical sensitivity of the explosive with added LiF-B was significantly lower.     

Ni-Co-P／导电聚苯胺复合材料电磁和红外性能

采用化学镀对高氯酸掺杂聚苯胺（PANI/HClO4）粉体进行Ni-Co-P合金化改性,改性材料磁损耗因子得到提高。进行红外光谱分析,PANI/HClO4在3-5μm和8-14μm 2个大气窗口没有强吸收峰,具有雷达红外隐身兼容特性。     

材料力学性能纳米压入测试仪器发展综述

综述了材料力学性能纳米压入测试仪器的发展现状。阐述了纳米压入测试技术的发展历程;从驱动、载荷测量和位移测量3方面对目前材料力学性能纳米压入测试仪器的基本结构进行了比较分析;介绍了材料力学性能纳米压入测试仪器集成技术,包括影响压入深度测量精度的集成技术、观测技术、大载荷模块和高温试验模块等;最后,对未来材料力学性能纳米压力测试仪器的发展趋势作了展望。     

Effects of jute fibre content on the mechanical and dynamic mechanical properties of the composites in structural applications

Due to notable characteristics, sustainability concept and environmental issues, hybridisation natural with synthetic fibres to fabricate composites have been rapidly gaining market share in different applications (structural, military, aerospace and automotive vehicles). Compression, tension and fatigue tests of various stacking sequences of plain jute/carbon reinforced (PVB) polyvinyl butyral by hot hydraulic press technique were experimentally conducted. Six types of fabricated composites with various constituents (jute, carbon and their hybrids) were fabricated and tested. Notably, fatigue lifetime of hybrids increases with increasing the carbon content relative to the jute fibre content. On the other hand, Jute composites possess high strain compared to pure carbon composite, which gives an overall improvement in mechanical behaviours. Interestingly, H1 hybrid with Carbon/Jute/Carbon sequences offers similar fatigue stiffness behaviour of H3 hybrid with Carbon/Jute/Carbon/Jute sequences when subjected to cyclic loading. Carbon composite (C) exhibited the highest fatigue resistance, whiles jute composite (J) possessed the highest strain and semi brittle trends in both mechanical and fatigue performance. Results concluded that plain jute fibres could partially replace high-cost synthetic carbon fibres to produce more eco-friendly hybrids to be utilised in different composites industries.     

FeAlCrNbB金属间化合物复合涂层的制备与表征

研究开发了一种FeAlCrNbB新型喷涂粉芯丝材,并结合自动化高速电弧喷涂工艺制备了该材料的复合涂层,分析了涂层的常规力学性能、组织结构和油润滑条件下的滑动摩擦磨损性能,并和常规FeAl涂层进行了对比。结果显示:FeAlCrNbB涂层具有相对较高的显微硬度和拉伸结合强度、低的孔隙率,组织致密,形成了由Fe-Al金属间化合物相、氧化物以及少量非晶和纳米晶组成的复合结构,由于这种复合结构的材料特征,使涂层具备较好的耐磨损性能。