Advanced Materials Research Vol. 686

Abstract: Magnesium-ion conducting gel polymer electrolytes (GPEs) based on PMMA with ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizing solvent were prepared via the solution casting technique. Mg(CF3SO3)2 salt was used as source of magnesium ions, Mg2+. The variation of conductivity with salt concentrations, from 5 wt.% to 30 wt.% was studied. The gel polymer electrolyte with composition 20 wt.% of Mg(CF3SO3)2 exhibited the highest conductivity of 1.27 x 10-3 S cm-1 at room temperature. The conductivity-temperature dependence of gel polymer electrolyte films obeys Arrhenius behaviour with activation energy in the range of 0.18 eV to 0.26 eV. Ionic transport number was evaluated using DC polarization technique and it reveals the conducting species are predominantly ions. It is found that the ionic conductivity and transport properties of the prepared GPEs are consistent with the X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) studies.

Abstract: This study was carried out to develop renewable and degradable plastics film with good mechanical properties. The mechanical properties between compatibilized montmorillonite (MMT)/chitosan filled tapioca starch (TPS), uncompatibilized MMT/TPS, and chitosan/TPS nanocomposite films were investigated. Experimental works were started with the extraction of local chitosan from chitin derived from prawn shells which involving deprotenization, demineralization and deacetylation treatments. Degree of deacetylation of chitosan was determined using infrared spectroscopy method. Chitosan was acted as compatibilizer between MMT and starch in order to improve the dispersion of MMT in nanocomposite systems. Nanocomposite films were prepared using a solution casting method with addition of glycerol as the plasticizer. The starch solution was cast onto PTFE mold with cavity thickness of 0.5mm. Characterizations of the nanocomposite films were done using Fourier Transform Infrared Analysis (FTIR). Tensile properties of nanocomposites were investigated. The compatibilized nanocomposite films, chitosan/MMT/TPS give significant effects to tensile properties. Chitosan has played its role as the compatibilizer and also as flexibility improvers to nanocomposite films because elongation at break improved after addition of chitosan.

Abstract: Abstract. Sintered powder metallurgy Fe based composites with advanced mechanical properties have been proposed as substitutes for more expensive cemented carbide and wrought alloys in many applications, especially as inexpensive wear resistance parts. The aim of this work was to fabricate and characterize a composite made of Fe-Cr as the matrix and Al2O3 particles as reinforcement. The composite was made by powder metallurgy method. The effect of different amount of binder, mixing duration, compaction pressure and sintering temperature has been investigated. Densification, micro hardness, wear resistance and compressive strength were used to characterize the composite. Powder metallurgy parameters that satisfy the composites quality have been optimized and result showed that higher sintering temperatures promote good sintering in the composites which produced better densification, higher reading of micro hardness, better wear resistance and compressive strength.

Abstract: Metal Injection Moulding (MIM) is an efficient method for high volume production of complex shape components from powders. The purpose of this study is to determine the sintering condition of titanium alloy (Ti6Al4V) tensile shape sample. In high temperature, Ti6Al4V will react with oxygen to form of titanium oxide (TiO₂) which present a problem during sintering thus affected the mechanical properties and microstructure. This reaction can be avoided either by introducing argon gases or in vacuum condition. Ti6Al4V with binder formulation consist of polyethylene (PE), paraffin wax (PW), stearic acid (SA) and palm oil derivatives; palm stearin (PS) were mixed homogenously and injected to produce green compact. The binders then are removed and sintered at 1100 °C for 8 h. During sintering, the debound part is heated, thus allowing densification of the powder into a dense solid with the elimination of pores. It was expected that the impurity gas in argon had strong effects on aspects of the densification and properties. Samples of PE/PS formulation with argon added to the sintering atmosphere, experience density of 4.375g/cm₃ and tensile strength stated at 1000.100MPa compared to samples in vacuum condition which do not show any significant increment with density of 3.943g/cm₃ and tensile strength at 325.976MPa. PE/PW/SA samples of vacuum condition also show no improvement in sintered properties. However with additional argon flow the density can reach until 4.359g /cm₃ and 940.823MPa of tensile strength. Ti-alloy sintered in argon exhibited better densification rate than in vacuum with high strength, better elongation and lower porosity. In argon, the powder particles became interconnected signifying densification was achieved due of non-reactive properties of inert gases that prevent undesirable chemical reactions from taking place.

Abstract: Creep damage investigation was carried out in Fe-Ni-Cr alloy at 800°C, 900°C, and 983°C using rectangular section form of specimen. In all the tests conducted on this material, some creep curves showed primary stage, secondary stage and tertiary stage. The creep fracture shows ductile transgranular fracture where separation occurred at the dendrites carbide interface suggesting that the detrimental effect of creep was compounded by precipitation of carbides at matrix. The presence of cavities may be due to the difference in thermal expansion characteristics of the austenite and carbide during high temperature test. Coarsening of carbides lead to cavities formation within the dendrite and carbide interface and form cavities linkage due to formation of crack and finally cause creep fracture. Increase in creep temperature it will lead to increase in creep rate. The fracture modes of creep samples were investigated to predict the failure mode.

Abstract: In this study, a commercial Ti-50.7at.%Ni was subjected to solution treatment at 800oC and 900oC for one hour followed by ageing at 300oC, 400oC, 500oC and 600oC for 1 hour, 2 hours and 4 hours respectively. Characterization of the material using optical microscope, XRD, FESEM and EDX has shown that the presence of Ti2Ni and Ti-rich precipitates in the as-received material remained unchanged even after heat treatment. The presence of oxygen in the air condition heat treatment has stabilized Ti2Ni since this condition causing the formation of Ti4Ni2O which is also determined as Ti2Ni due to their same crystal structure. The formation of Ti3Ni4 precipitates during ageing encouraged the establishment of R phase instead of martensite due to the depletion of Ni content in the matrix. Ageing treatment at 300oC generates two steps of R phase transformation due to the differences in Ni composition in the matrix at the grain boundary and grain interior region. However, for samples subjected to ageing at higher temperature, 400-500oC, only one step of R phase transformation occurred because Ni atomic diffusion was not forbidden in the high temperature. Hardness test performed on the samples revealed that increasing the ageing time will increase the hardness of material; however for the sample aged at 600oC, increasing the ageing time would reduce the hardness due to dissolution of Ti3Ni4 precipitaes into the matrix.

Abstract: In the present study, NiTi alloy coatings were deposited onto AISI 316L stainless steel substrates using the Closed Field Unbalanced Magnetron Sputtering (CFUBMS) system. The as-deposited NiTi alloy coating was Ni rich NiTi alloy with a composition of 44.1 at. % of Ti and 55.9 at. % of Ni and demonstrated an amorphous structure. The post-annealing treatment of the as-deposited Ni rich NiTi alloy coating was successfully produced a crystalline structure. The as-deposited and the annealed Ni rich NiTi alloy coatings were characterized to determine the effect of the annealing process on their wear properties. The Ni rich NiTi phases and structure were determined by XRD. Wear morphology was investigated using the pin-on-disk wear test. The existence of a TiO2 rutile layer with a combination of the Ni3Ti and NiTi B2 parent phases, that formed during the annealing process produced a significant improvement over the wear performance compared to the as-deposited Ni rich NiTi SMA coating. The post-sputtered annealing process at the annealing temperatures of 550°C for a period of 60 minutes and 600°C for a period of 30 minutes succeeded in increasing the adhesion and wear resistance of the Ni rich NiTi coating. The findings show the potential the post-sputtering annealing process in creating an excellent structure of NiTi coating which demonstrates significant wear resistance properties for tribological applications.

Abstract: Since the ban of lead containing solders, eutectic SAC solders has been claimed to posses better properties compared to other series of lead free solders. As the technology trend for portable devices change over time, solder joints are continuously miniaturized. The VLSI in modern devices will subject the solder joints to repeated temperature cycling during both assembling and use due to higher I/O. These lead free solders are prone to excessive intermetallic compound (IMC) growth at the interface between the solder and the substrate due to the reasons cited earlier. The most common substrate used in electronic packaging is Cu while Au or its alloys are often used as metallization layer. In this study PCBs coated with both Cu and Au to study the interfacial morphology of Sn-3.8Ag-0.7Cu (SAC387) alloy with these metals. SEM imaging and EDX analysis were used to observe the interfacial layers and to confirm formation of IMCs. IMCs formed between Au-solder are more blocky-like compared to those formed between Cu-solder. Thus further studies must be conducted to resolve this issue as Au is a commonly used metallization materials.

Abstract: This work has been undertaken in order to determine the effect of alloying with Ni, Mo and B additions on physical and mechanical properties of FeAl alloys. The structural evolutions and morphological changes alloys were characterized by X. ray diffractometry (XRD), Scanning Electron Microscope (SEM) and an Optical Microscope. Antiphase domain sizes and morphologies are reported and correlations between such ordening phenomena, phase precipitations and mechanical properties (micro hardness at low temperature) are discussed.

Abstract: The protection of carbon steel in freshwater media has been examined via two techniques (Impressed current cathodic and coating). This paper shows the reduction of corrosion rates under different conditions. Experimental tests were carried out for two types of steel (bared, coated) and with ICCP/without ICCP in stagnant and flowing freshwater. The results showed there was a variation in the values of potential according to the formation of the protection layer on the surface of steel plates. Furthermore, this layer showed such an excellent protection for both steels with ICCP in stagnant and flowing freshwater, where the values of potential had decreased from -840mV to -875 mV. However, the values of potential had increased from -702 mV to -630 mV for the coated steel without ICCP. On the other hand, the values of potential slightly fluctuated up to -10 mV for the bare steel without ICCP. The reason behind this increase is attributed to the formation of an oxide layer on the surface of the steel plate.