Materials Science Forum Vol. 975

Abstract: Nickel cobaltite has become a popular energy storage material in recent years for high performance energy storage devices because of its low lost, high electronic conductivity, high electrochemical activity and environmental benignity. Nickel cobaltite (NCO)/porous graphene nanosheets network (PG) composites were synthesized via the two-steps hydrothermal method to enhance electrochemical properties in this study. The NCO/PG composite electrode demonstrated high specific capacitance of 3965 F g^-1 at the current density of 1 A g^-1 compared with the value of NCO that capacitance is 644 F g^-1, and it maintained the 72% of the original capacitance after 3,000 charge-discharge cycles. It showed the maximum energy density of 46.3 Wh kg^-1 and maximum power density of 1450 W kg^-1. The NCO/GO composite has high potential as a psudocapacitance material for energy storage devices.

Abstract: Porous Co/C composite nanofibers were fabricated by combination of electrospinning method and polymer blend. The phase composition, microstructure and electromagnetic characteristics of them were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and vector network analyzer (VNA), and their microwave absorption performances were studied. The results indicate that nanofibers were composited by amorphous carbon and face-centered cubic structured Co nanoparticle after sintering. The addition of PMMA is a key factor of nanofibers morphology and the aperture was improved with the increase of PMMA. When the thickness is 2.0 mm, the samples exhibit the best microwave absorption performance. Their effective absorpt ion bandwidths (RL < 10 dB) are 6.3 GHz, 6.2 GHz and 6.1 GHz, and it’s obviously superior to ordinary morphology nanofibers.

Abstract: Although there are currently different applications for gallium in microelectronics, literature is sparse about its applications in the area of conductive inks. The important characteristics to consider from the ink are viscosity, corrosion and surface tension. The importance of viscosity is a critical parameter in the printing ink mixture, which requires a metal to fulfill the function of conductor, such as gold, copper, and silver. Gallium as a conductor replacement is proposed due to the high cost of such metals currently used. The valence electrons are discussed in this paper due to the direct relation that has with metal conductivity, to provide a justified analysis about gallium application in conductive ink. The application of gallium could mean a significant change in conductive ink elaboration process. Thus, the aim of this research is to analyze the application of gallium as conductive ink, which is done by a literature review on gallium as a semi-conductor because of his valence electrons. Results about gallium as a potential conductive ink show that there is evidence that gallium shares similar properties as the current of materials conductive inks being adopted. This first literature review has some implications on the potential use of gallium as a conductive ink, requiring further experimental research to better test for conducting efficiency.

Abstract: The paper presents the impact of doses of an air-entraining additive on the mechanical properties of a composite based on aluminous cement. The presented data have been selected from the authors’ most recent research, which supports an economic development of a lightweight composite with the ability to withstand elevated temperatures of up to 1000 °C. The interest in the behaviour of concrete at high temperatures mainly results from the many cases of fires taking place in buildings, high-rises, tunnels, and drilling platform structures. Operation at high temperatures is also of fundamental importance to many major sectors of industry, including material production and processing, chemical engineering, power generation and more. Concrete has a great intrinsic behaviour when exposed to fire, especially when compared to other building materials. However, its fire resistance should not be taken for granted and proper structural fire protection is certainly necessary, e.g. in the form of high-temperature barriers. For the purposes of this experiment, the specimens were composed of cement paste and an air-entraining additive dosage between 2 – 10 % by weight of the cement dose. The properties of investigated specimens, dried at a temperature of 105 °C, were compared with each other. Values of compressive strength, flexural strength, and bulk density are measured in this work. The purpose was to evaluate the effects of the air-entraining agent on the workability of a fresh mixture, its bulk density, and mechanical properties after drying. In the case of a mixture with added short basalt fibres, the effects after high thermal loading were also evaluated. The proposed composites with air-entraining additive over 8 % shown the values of bulk density below 1800 kg/m³, along with the satisfactory strength results.

Abstract: Carbon fiber epoxy resin composite and polyimide material are likely to be applied to pulley-guideway system of the new satellite antenna. Their tribological properties have effects on the motion characteristics of the pulley-guideway system. To master the tribological properties of carbon fiber epoxy resin composite and polyimide material, this paper carries out tests of tribological properties and wear behavior of carbon fiber epoxy resin composite and polyimide material at 130°C and 30°C. Carbon fiber epoxy resin composite is used as the grinding specimen and polyimide material is used as the counter-grinding specimen. Tribological properties of this material pairs is studied under diverse linear velocity and external loads. The results show that friction coefficient of this material pairs is stable under different conditions, especially at 30°C. Meanwhile, wear behavior of this material pairs is mainly affected by ploughing of surface roughness at low temperature, while by surface micro-spalling at high temperature.

Abstract: Filling the thin-walled tubes with a foam core is a typical method to enhance the energy absorption performance and stabilize their crushing responses under impact loading. Recently, auxetic foam material with negative Poisson’s ratio has gained remarkable popularity as an effective candidate to enhance the energy absorption capability of structures. In this paper, polyurethane auxetic foam is suggested as a foam core with the negative Poisson’s ratio of-0.31. Numerical simulation was performed to quantify the crush characteristics of auxetic foam-filled square aluminum tubes for variations in initial width of tube under quasi-static axial loading using the nonlinear finite element (FE) code LS-Dyna. Based on the numerical results, the influence of tube width was quantified in terms of energy absorption (EA), specific energy absorption (SEA), initial peak force (P_max) and crush force efficiency (CFE). It is found that the progressive collapse and deformation modes of auxetic foam-filled tube (AFFT) is pronouncedly affected by varying the tube width. Furthermore, the SEA of AFFT is remarkably sensitive to the tube width variations, yet show low sensitivity to the EA of AFFT. The present study provides new design information on the crush response and energy absorption performance of auxetic foam-filled square tube with varying tube width.

Abstract: Direct hot extrusion is a sustainable technique for recycling aluminium chips into aluminium matrix composite. Reinforcement particles are used to improve the mechanical properties. In this paper, the reinforcing medium of alumina layer that forms on the chip surface were enriched in situ via thermal treatment. Three types of chips were prepared namely; non-treated, treatment of 300 °C for 60 minutes and treatment of 500 °C for 10 minutes. The chips were compacted into chip-based feedstock having a density of 75 %, 85 % and 95 %. The chip-based feedstocks were preheated at 500 °C for 3 hours before extrude. Tensile test performed on the extrudate found that variation in the types of chip and feedstock relative density has affected the ultimate tensile strength. The highest ultimate tensile strength of 256 MPa is obtained from the condition of chip treated at 300 °C for 60 minutes and a feedstock density of 85 %. Elemental analysis on the extrudates reveals that the oxygen content is increased when the extrudates made from heat treated chip. Apart from heat treatment, the oxygen content also affected by the feedstock density.

Abstract: The present research focuses on the synergetic effect of ZrB₂-Si₃N₄ on the properties of AA8011 for service life improvement in automobile components. The hybrid composites were developed by liquid metallurgy route with varying particulates composition of 0% - 20% in a step of 5. The developed composites were subjected to SEM microstructural characterization and mechanical analysis to evaluate their microstructural evolution, microhardness, and tensile strength mechanism. The results show better improvement in the hardness and ultimate tensile strength of the composite when compared with the unreinforced AA8011. The microstructure clearly revealed an even dispersion of hybrid particulates with no clear trace of voids.

Abstract: This research is aimed to study effect of holding time and temperature in solution treatment and ageing on the hardness of the Aluminum A356 reinforced with silicon carbide particles. Alumimium matrix coposite was particulated with 15 microns-SiC with the content of 15 percent by weight. A356/SiC composites was prepared by the stirr casting. The stirrer was continuously stired at a speed of 300 rpm during acooling temperature to semi-solid state of 610 °C. During stirring the SiC powder was slowly added into the melt and continuously stirred for another 10 min. Then poured into the mold at the pouring temperature of 680°C. A356/SiC composites then subjected to a solid solution treatment with temperature of 540 °C for 1 hr. quenched with water and age hardening temperature of 120 and 135 °C for 3, 6, 12 and 18 hr. The result showed that, in as cast conditions, the composite with 15 microns silicon carbide, the 15 wt%SiC specimen exhibited the average hardness of 64.33 HB. After solution treated, the hardness of samples decreased. the specimen exhibited the average hardness of 53.83 HB. After ageing, the hardness of samples increased. the specimen ageing 120 °C 6 hr. exhibited the lowest average hardness of 51.45 HB while the specimen ageing 135 °C 18 hr. exhibited the highest average hardness of 73.54 HB.

Abstract: By using the material of reinforced polyurethane (RPU) foam, the common bulkhead is devised for cryogenic tanks in this paper. Properties of RPU foam are obtained through experiments. Based on the properties, the structure is designed with the integration of special features including lightweight, easy to manufacture, load bearing and thermal insulation. Based on numerical simulation, thermal analysis, stability and thermal mechanical coupling behavior of the structure are analysed. The results show that the common bulkhead not only satisfies the heat insulation requirements of cryogenic tanks for liquid hydrogen and oxygen, but also keeps stability.