Materials Science Forum Vol. 1083

Abstract: Aluminum-supported iron and cobalt (Fe-Co/Al₂O₃) bimetallic nano-sized catalyst has been synthesized by the sol-gel method. The average diameter of the Fe-Co/Al₂O­₃ catalyst was measured to be around 7 nm from SEM images. EDX measurements revealed that Fe-Co/Al₂O­₃ consists of 59.98% of Al, 20.00% of Fe, and 20.02% of Co by atomic weight. Multi-walled carbon nanotubes (MWCNT) were prepared with as-synthesized nanocatalyst from a commercial butane gas by the CCVD method at different reaction temperatures. TEM and XRD measurements revealed that Fe-Co/Al₂O₃ bimetallic nano-sized catalyst is beneficial to fabricating MWCNTs by the CCVD method. The highest yield of MWCNTs was obtained at 690°C.

Abstract: Rotational rheology was used to analyze the performance of polypropylene (PP) composites reinforced with date palm nanofiber (DNF) in the molten state in this study. In the first stage, mechanical ball milling was used to obtain date nanofillers with average filler sizes ranging from 30–110 nm in width and 1–10 mm in length. Dry blending technique was used to reinforce this filler to the polypropylene in the 1-5wt. % loading. The resulting PP/DNF biocomposites were subsequently tested using a rotating rheometer with a 25 mm parallel plate geometry. The broad range of angular frequency from 0.1 rad·s⁻¹ to 100 rad·s⁻¹ was applied to study their complex viscosity (η*) at a fix strain (1%). The decrease in complex viscosity with angular frequency in all the samples was observed compared to the neat PP. The complex viscosity of the neat PP and the 5 wt.% of filler samples at 0.1 rad·s⁻¹ frequency was found to have 18170 Pa. s and 5335 Pa. s, respectively. Therefore, this analysis revealed that this biocomposites exhibits typical viscoelastic behavior of entangled polymeric liquid.

Abstract: Reinforced natural fibre composite materials are attracting greater attention in the area of material engineering due to their low density, low cost and higher mechanical strength. In the present study, the Areca Husk Fiber (AHF) was extracted through the retting process. The surface modification of AHF was done by chemical treatments such as mercerization, potassium permanganate treatment, benzoylation, acrylation and acetylation. The surface modification was studied through FE-SEM imaging. The composites of surface modified AHF reinforced polyester resin composites were prepared as per ASTM standards using polyester resin as matrix material and methyl ethyl ketone peroxide (MEKPO) as hardener. The Izod-Charpy impact strength, Hardness (Shore-) hardness analysis was carried out to study the mechanical behaviour of the composites. The results showed that surface modification of AHF can enhance the impact strength of the composite materials but not the hardness of the composites.

Abstract: Ceramic-metal functionally graded materials (FGMs) are advantageous to two dissimilar materials joined directly together, which includes smoothing of thermal stress distributions, minimization or elimination of stress concentrations and singularities at the interface corners and increase in bonding strength. In this study, ZrO₂/ 304 stainless steel (SUS304) FGMs with continuous gradient manners, not stepwise manners, were fabricated by a combination of centrifugal slurry methods and spark plasma sintering (SPS). The size and surface smoothness of the powders of SUS304 highly affected formation of compositional gradient patterns in the FGMs. Effects of ball milling time and ball sizes on such conditions of the powders as well as compositional gradients in the FGMs were investigated by microstructure observations with element analysis and hardness probing on the cross sections of the FGMs.

Abstract: Honeycomb structures are frequently used as energy absorption devices in the automotive and aerospace industry. Many studies have been conducted to optimise these structures and improve crashworthiness behaviour. This paper attempts to improve the crashworthiness behaviour of a honeycomb crash box by filling the cells with open-cell aluminium foams. Experimental tests were conducted to develop the honeycomb and aluminium foam material model and, also, to validate the finite element model by experimental data. Foam-filling the crash box allows the control of the densification zone for different impact energies using open-cell aluminium foam, which shows the main novelty of this research. In the end, the optimised structure is presented concerning the optimum number of foam-filled cells and, also, to the aluminium foam’s density that best fits this application.

Abstract: It had been reported that repeated induction heating process decreased the prior austenite grain size and refined the martensitic structure of JIS SUJ2 samples. In the present work, we compared hardness values and structures of hard surface and soft core of three-times repeated induction heated and once tempered (IH Q3T1) JIS S45C steel bar specimen and once induction heated and once tempered (IH Q1T1) bar. Structures consist of three areas: Hard; Transition; and Soft Core Areas. Martensite, ferrite and martensite, and ferrite and pearlite were observed at the Hard, Transition, and Soft Core Areas. From these observations, it was found that ferrite ratio increased with depth from the surface, and repeated induction heating had little effect on the hardness distribution and internal structure.

Abstract: To research effects of cyclic loadings and the loading magnitude on the crack opening-closing behavior, crack opening displacement evaluations for fatigue cracks on a silicon nitride ball were carried out. The compressive loading magnitude, which was less than 2.7 kN, did not affect crack opening-closing behavior. The crack opened at the early cycles of fatigue during 0 to 10³ cycles.

Abstract: In this study, fatigue property of green composite using unidirectional jute fiber sliver and poly (lactic acid) resin was investigated for a long term safety of sustainable structural materials. The fiber volume fraction of green composite was about10%. The green composite plate was fabricated by using jute fiber sliver/poly (lactic acid) resin prepreg. The molding method was vacuum compression molding method. The quasi-static tensile and fatigue tests of green composites were conducted under room temperature. The maximum number of cycle to failure was 10⁶ cycles. Fracture surfaces of green composites were observed after fatigue and static tensile tests. Following conclusions were obtained. The fatigue strength of green composite decreased with an increase of number of cycle. The fatigue strength at 10⁵ cycles of green composite was 50% of the tensile strength. From surface observation, the fiber pull-out in fracture surface of green composite were not found after quasi-static tensile and fatigue tests. Therefore, fatigue property of green composite using low addition amount of jute fiber sliver might be dominated by fatigue property of poly (lactic acid) resin.

Abstract: At the present time, the electrodeposition of chromium metal coatings of sufficient thickness and quality is possible only from chromium plating electrolytes containing chromic acid. The authors investigated the effect of the composition of chromium plating electrolyte on the quality of the resulting metal coating. It has been demonstrated that the introduction of organic additives, of gallic acid in particular, leads to significant changes in the surface of the metal deposit and to a decrease in its hardness. Assumptions have been made about the influence of organic additives on the metal deposition process. The experimental data on the content of gases in the chromium deposits obtained from electrolytes with gallic acid additive and without it have been presented.

Abstract: In-situ evaluation of crack generation using acoustic emission (AE) technique as a non-destructive testing method was applied during laser cladding of WC-Co cemented carbide via a multi-beam laser metal deposition (LMD) system. Especially, this study aims to investigate relationships between the laser output and the number of cracks generated in beads of WC-12mass%Co cemented carbide cladded by the LMD system. The number of cracks was evaluated using an AE sensor attached to a substrate. The number of cracks was also evaluated from SEM images of beads. By comparing these results, problems in the both evaluation methods for crack generation in laser cladding were discussed.