Nor Hayati Saad

Characterization of coupled micro/nanoresonators using inverse eigenvalue analysis

This paper reports a method of determining the system matrix of a nearest neighbor coupled array of micro/nanomechanical resonators. The simple method requires contacts to only one element of the array to determine two sets of eigenvalues related to the system matrix. The elements of the system matrix are then determined from these eigenvalues. This system matrix can then be used to determine the characteristics of the individual resonators or as the starting point for a perturbation analysis to determine the changes observed when a functionalized array of resonators is used as a sensor.

Critical process and performance parameters of thermal arc spray coating

Usage of thermal spray coating for corrosion protection was started since early 1900. Even though it was successful, the application was limited. In recent years, most industries especially oil and gas companies have selected the thermal spray wire arc coating as a corrosion protection for steel structure. Advancement in coating research causes major developments in coating processes, equipments, and raw materials for coating. It leads to further expansion in functional coatings and applications scope from conventional coating to specialised industries. The selection of the thermal arc spray coating is due to its ability to act as an effective corrosion protection, able to withstand high process temperature, and cost saving. Previous research revealed that thermal arc spray coating provides better coating characteristics compared to other method of sprays. This paper reviews some critical part of thermal arc spray coating by discussing the process parameter of thermal arc spray technology and quality control of coating. Comparison between coating material usage was reviewed to determine the best applied material coating in certain critical environment. Coating performance against corrosion, wear and special characteristic of coating are discussed. The field application of arc spray technology is presented.

Modeling and Multi-Response Optimization on WEDM Ti6Al4V

Wire electrical discharge machining (WEDM) is a material removal process of electrically conductive materials by the thermo-electric source of energy which is extensively used in machining of materials for a highly precision productivity. This work presents the machining of titanium alloy (TI-6AL-4V) using WEDM with a brass wire diameter of 0.25mm.The objective of this work is to study the influence of three machining parameters, namely peak current (IP), feed rate (FC) and wire tension (WT) to cutting speed and surface roughness. Response Surface Methodology was used to develop second order model in order to predict cutting rate and surface roughness responses. The results showed that the average percentage error between the predicted and experimental value for both models was less than 2%.Furthermore, the developed models were used for multiple-response optimization by desirability function approach to determine the optimum machining parameters. These optimized machining parameters are validated experimentally, and it is observed that the response values are in good agreement with the predicted values.

Thermal Arc Spray Overview

Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

The Effects on Microstructure and Hardness of 0.28% Vanadium and 0.87% Nickel Alloyed Ductile Iron after Boronizing Process

Boronizing/boriding is a thermo mechanical process which produced protective surface layers to enhance the performance of engineering components utilized in mechanical, wear and corrosion. The present study investigate the microstructure and the hardness of boride layers formed on 0.28% Vanadium and 0.87% Nickel alloyed ductile iron after boronizing process. Specimens were boronized at 950° C for 6, 8 and 10 hours holding time before being cooled in the furnace. The microstructure and boride layer formed on the surface of substrates were observed under Olympus BX60 Optical Microscope. Vickers Micro Hardness Tester was also performed to determine the hardness of boride layers. Boride layer was formed by diffusion of the boron into the metal lattice at the surface which composed double phase of FeB and Fe2B with saw-tooth morphology. The results of this study indicated that the thickness of boride layers increased from 109.8μm at 6 hours to 195.4μm at 8 hours holding time before they crack at 10 hours. The hardness of the material surface also increased from 1535 HV to 1623 HV at 6 and 8 hours respectively. In conclusion, the microstructure, borides thickness and hardness of borides layer were depending on boronizing time while temperature kept constant.

Modeling and Influence of Machining Parameters on Titanium Aloy

Wire electrical discharge machining (WEDM) is a material removal process of electrically conductive materials by the thermo-electric source of energy which is extensively used in machining of materials for a highly precision productivity. This work presents the machining of titanium alloy (TI-6AL-4V) using WEDM with a brass wire diameter of 0.25mm.The objective of this work is to study the influence of three machining parameters, namely peak current (IP), feed rate (FC) and wire tension (WT) to cutting speed and surface roughness as a responses. Response Surface Methodology was used to develop second order model in order to predict cutting speed and surface roughness responses. The results showed that the average percentage error between the predicted and experimental value for both models was less than 2%. Effects of each parameter and their interaction with percentage contribution ratios (PCR) are included for each response.

Study on Hydrothermal Process Variables Correlation to WO3 Nanostructure through Design of Experiments (DOE) Approach

There are few known parameters which govern tungsten trioxide (WO3) hydrothermal synthesis process which includes material source concentration, synthesis temperature, duration, pH value and additive level. Using design of experiments (DOE) approach, a systematic experimental procedure was conducted to investigate the effect of each parameter to the final morphology of the synthesized nanostructure. Despite the response obtained from this study is in qulitative form, the analysis still can be done to identify the combination of variables that most likely can produce either 1-D, 2-D or 3-D nanostructure. This insight is essential before further optimization of the process can be done in order to predict the behavior of the WO3 hydrothermal synthesis process.

Plasma Enhanced Chemical Vapor Deposition Time Effect on Multi-Wall Carbon Nanotube Growth Using C2H2 and H2 as Precursors

Multi-wall carbon nanotube (MWCNT) structures were grown on cobalt catalyst layer through Plasma Enhanced Chemical Vapor Deposition (PECVD) process. Acetylene (C2H2) and hydrogen (H2) are used as precursors during the PECVD process. The morphology structures of the MWCNTs grown under different PECVD time were investigated and characterized using Scanning Electron Microscope (SEM). The effect of the PECVD time on the MWCNT growth is studied by varying the PECVD time at 45 sec and 600 sec. The morphology structures suggest that the growth rate is proportional to the PECVD time under the similar setting condition of pressure, acetylene flow-rate and temperature.

PH Tester Gauge Repeatability and Reproducibility Study for WO3 Nanostructure Hydrothermal Growth Process

PH value is one of the important variables for tungsten trioxide (WO3) nanostructure hydrothermal synthesis process. The morphology of the synthesized nanostructure can be properly controlled by measuring and controlling the pH value of the solution used in this facile synthesis route. Therefore, it is very crucial to ensure the gauge used for pH measurement is reliable in order to achieve the expected result. In this study, gauge repeatability and reproducibility (GR&R) method was used to assess the repeatability and reproducibility of the pH tester. Based on ANOVA method, the design of experimental metrics as well as the result of the experiment was analyzed using Minitab software. It was found that the initial GR&R value for the tester was at 17.55 % which considered as acceptable. To further improve the GR&R level, a new pH measuring procedure was introduced. With the new procedure, the GR&R value was able to be reduced to 2.05%, which means the tester is statistically very ideal to measure the pH of the solution prepared for WO3 hydrothermal synthesis process.

Effect of Double Sided Process Parameters in Lapping Silicon Wafer

Silicon wafer is widely used in semiconductor industries for development of sensors and integrated circuit in computer, cell phones and wide variety of other devices. Demand on the device performance requires flatter wafer surface, and less dimensional wafer variation. Prime silicon wafer is hard and brittle material. Due to its properties, double sided lapping machine with ceramic grinding agent were introduced for machining high quality standard silicon wafers. The main focus is the silicon wafer with high accuracy of flatness; to reduce total thickness variation, waviness and roughness. In this paper the lapping experiment and analysis showed that the double sided lapping machine is able to produce total thickness variation less than 10 um at controlled process parameters within short processing time. Machining using low mode method reduced the total thickness variation (TTV) value. The lapping load and speed directly reflected the performance and condition of final silicon wafer quality.