Solid State Phenomena Vol. 185

Abstract: The growth process and corrosion resistance of the phosphate coating on 25Cr2Ni4WA alloy steel fabricated by a high temperature manganese phosphating were investigated by XRD, SEM, EDS and electrochemical polarization method, respectively. It is found that the phosphate coating consists of lots of close packed lump crystallites and mainly composed of (Mn,Fe)₅H₂(PO₄)₄·4H₂O. The coating weight increased rapidly, and then the increase rate slowed down when phosphating process was carried for about 5 min. The corrosion potentials of the phosphated steel shifted positively about 250 mV than the bare steel, indicating that the phosphating can improve the corrosion resistance of the 25Cr2Ni4WA alloy steel.

Abstract: Recently, thermoelectric thin films have been gaining attention as potential thermoelectric generators that can be used to power external devices. Such films can recover electrical energy from waste heat and are environmentally friendly. Micro fabrication of thin films is achieved by sputtering on silicon films. In this study, the sputtering of Bismuth Telluride (N-type, P-type) films was investigated. Research has verified the efficiency of Bismuth Telluride films, but little is known about how the sputtering process affects the film's quality. Thus, the focus of this study explores how sputtering parameters of discontinuous sputtering intervals, exposure to normal atmospheric conditions and in situ annealing affect the thickness, thermoelectric properties, and microstructure of films. This will bring about a better understanding of the relationship between the sputtering process and the properties of the produced film for both N and P type materials. Recommendations based on this study can contribute to the production of more efficient thin films suitable for energy harvest application.

Abstract: The aim of this work is to fabricate and develop the innovative ceramic coatings for protection applications with both high hardness and coating adhesion particularly performing in extremely environmental conditions. In this study, nanocomposite AlCrTiSiN coatings were developed and deposited on Carbide coupons (WC with Co binder) substrate using Cathodic Arc Deposition techniques. The resultant coatings were evaluated with respect to fundamental mechanical properties such as hardness, modulus and coating adhesion. It was found that the nanomposite AlCrTiSiN coatings has a good adhesion to the substrate and retained extremely high hardness as superhard coatings with hardness values above 50 GPa.

Abstract: In this work, an attempt was made to examine the microstructure changes on the gas tungsten arc welded AISI 304 subjected to hot corrosion in Na₂SO₄ + V₂O₅ (60%) at 700°C under cyclic conditions. It was found that welding of AISI 304 using E308L showed better corrosion resistance and tensile strength as compared to ENiCu-7 filler wire. The corrosion products were analyzed using SEM/EDAX and XRD.

Abstract: Oxidation and hot corrosion are serious problems in marine and power plants. Hence understanding the corrosion behavior of weldment at elevated temperatures has become the vital scientific investigation nowadays. Monel 400 is one of the widely used high temperature material that can obviate the problems. The objective of the present investigation is to study the mechanical properties and corrosion behaviour of gas tungsten arc welded Monel 400 plates subjected to air oxidation. It was observed from the tensile tests that fracture occurred at the weld region. In addition, cyclic air oxidation tests were performed on the different regions of welded Monel 400 at 700°C. It was found that corrosion was found to be extremely severe on the weld zone after exposed to 50 cycles. The corrosion products were characterized using the combined techniques of optical microscopy, XRD, SEM/EDAX analysis.

Abstract: In the intumescent fire retardant (IFR) coating char thickness and its strength play a vital role to protect the base steel structure from the fire. The IFR coating contains expandable graphite (EG), ammonium polyphosphate (APP), melamine, boric acid, bisphenol, epoxy resin BE-188 (BPA) which is used as a binder with ACR hardener H-2310 polyamide amine and multi wall carbon nanotubes (MWCNTs). A range of different formations were prepared to study the heat shielding effect and char expansion after fire test. The intumescent coating was tested at 800°C for one hour in the furnace and found to be very stable and well bonded with the steel substrate. The characterization was done by using Thermo gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and Field emission scanning electron microscopy (FESEM) after fire test. The results confirmed that MWCNTs enhanced the char resistant of IFR coating on steel substrate after fire test. Keywords: Intumescent fire retardant coating, Expandable Graphite, Multiwall Carbonnano tubes, FESEM and TGA.

Abstract: Thermoelectric is an ever evolving field that serves many critical needs (cooling and power generation) in the industry. The key objective of this work is to fabricate Bismuth Telluride (Bi₂Te₃) thin-films by varying the various process parameters using a radio-frequency (RF) magnetron sputtering disposition technique. Characterization methods such as four point probe resistivity, surface profiler, atomic force microscopy (AFM), X-ray diffraction (XRD), Seebeck coefficient and thermal diffusivity are performed on the N and P-type Bi₂Te₃ films. The samples are analysed for their electrical properties in relation to the evolved microstructures, for how the process parameters of sputtering and annealing affect these changes. The results demonstrate that N-Type film (S2) processed using sputtering parameters of 7mT, 100W, 50sccm of argon flow under room temperature for 30mins with no annealing and the P-Type film processed using sputtering parameters of 7mT, 100W, 60sccm under room temperature for 30mins with institute annealing at 200°C for 2h exhibit desirable thermoelectric properties suitable for cooling application in microelectronic and optoelectronic devices, optimizing their performance and reliability.

Abstract: This paper describes a technique, quantifying the differences in waveforms between damaged and undamaged states to measure damage severity. The technique has been verified experimentally and demonstrated promise in detecting and quantifying subsurface defects. Finite element analysis (FEA) has been performed alongside as a valid model may avoid time consuming and expensive experiments. Testing is first performed on a simple flat plate and a realistic wing skin structure with geometry such as stiffening ribs. This revealed geometry will alter the regions of scatter which leads queries over optimal sensor location. It was also discovered actuator location may not necessarily be intuitive. The comparisons made here show that implementation of an ISHM system on real world subjects is feasible despite added complexity.

Abstract: This research presents the effects of temperature and cooling rate on mechanical properties of powder injection molded 316L Stainless steel. Steel powder and binder were mixed together to produce the feedstock. The green samples were produced by injection molding and debinded. Brown test samples were sintered in vacuum at 1325°C, 1360°C and 1380°C for 2h with two heating and cooling rates 5°C/min and 10°C/ min. The test samples sintered at 1325°C achieved maximum sintered density. The higher cooling rate improved the strength of the sintered test samples. The maximum sintered density of 96% and tensile strength of 503MPa was achieved and these results are comparable to the wrought 316L stainless steel (according to ASTM standard).

Abstract: Over the years, Sol-gel has been widely used in aerospace industry for surface treatment process in preparation of adhesive bonded repair to aircraft. It plays a crucial role in the process of bonded repair of aircraft as a chemical linkage between adhesive bonded repair and damaged metallic structure of aircraft. As a chemical linkage, it produces strong and durable bond between metal and organic adhesive (Thermoplastics) which improves the overall strength in adhesive bonded repair to aircraft. In this paper, both conventional and newly formulated sol-gel will be subjected under Wedge Test (ASTM D 3762-03) to examine its durability. This would be a crucial milestone if the durability of the newly formulated sol-gel is higher than conventional sol-gel. Cost of repair would be able to reduce as serviceability of the aircraft increase. Keywords: Sol Gel, Chemical linkage, Bonding Strength, Shear strength