[Show abstract][Hide abstract] ABSTRACT: Photocatalytic degradation of methyl orange (MO) in water was examined using TiO 2 nanopowders under solar irradiation. These photocatalysts were successfully synthesized by hydrolysis of titanium tetra chlo-ride (TiCl 4) in the temperature range of 70-95 °C and calcined at higher temperatures of between 400 and 900 °C. The samples prepared were characterized using x-ray powder diffraction, scanning electron microscope (SEM) and Fourier transform infrared spectrophotometer (FTIR). UV-Vis spectrometer was used for analyzing the concentration of MO in solution at different time intervals during the photodeg-radation experiment. Parameters affecting the photodegradation rate such as catalyst crystallinity, con-centration of the catalyst, MO concentration, and pH of the solution have been investigated. The results indicate that TiO 2 nanopowder was antase at low calcination temperatures in the range of 400-500 °C. The sample calcined at 600 °C is composed of both anatase and rutile phase. Further increase in the temper-ature enhanced the intensities of diffraction peaks of the rutile phase. The size of the crystallites for all the samples prepared were found to be in the 6-13 nm range and from SEM micrographs it was in the range of 19-43 nm. The mixture of both phases exhibited a higher photoactivity in comparison with pure anatase or rutile catalysts.
[Show abstract][Hide abstract] ABSTRACT: In the present study, the main objective is to predict the physical thermomechanical behavior when high-speed machining an aluminium alloy (7075-O) using a polycrystalline diamond (PCD) cutting tool with a variable depth of cut (DOC). An advance commercial machining finite element software was used to aid the study and to help to predict physical parameters of cutting process such as cutting forces, temperature, maximum shear stress, and plastic strain.From the simulations made, it can be concluded that the DOC mainly influences the cutting and feed forces. On the contrary, an increase of DOC does not significantly influence cutting temperature, shear stress, or plastic strain.
Materials and Manufacturing Processes - MATER MANUF PROCESS. 01/2011; 26(8):1034-1040.
[Show abstract][Hide abstract] ABSTRACT: The current paper presents a Finite Element Model (FEM) simulation and experimental analysis of orthogonal cutting on aluminium alloy using Polycrystalline Diamond (PCD) tools. FEM machining simulations used a Lagrangian finite element‐based machining model, AdvantedgeTM, applied to predict cutting forces, temperature distribution, plastic strain, von Mises and maximum shear stresses. The orthogonal cutting model was validated by comparing cutting forces obtained experimentally with a thermo‐mechanical FEM analysis under orthogonal cutting conditions. Finally, FEM analysis prediction of the evolution of plastic strain, von Mises stress and maximum shear stresses during the machining of a commonly used aluminium alloy using PCD tools was conducted.
International Journal of Materials and Product Technology 01/2010; 37. · 0.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper, a prediction of the thermo mechanical behaviour of the machining of an aluminium alloy is made, using a Polycrystalline Diamond (PCD) cutting tool with a variable rake angle. To aid the study, a commercial machining finite element software was used and several parameters In conclusion, from the simulations made, it was possible to predict a positive influence of the inclusion of rake angle in PCD cutting tools. A reduction of cutting forces and temperature was shown with the increase of the rake angle, allowing this way an additional extension of the tool life.
International Journal of Materials and Product Technology 01/2010; 37. · 0.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The initial stages of intimate contact between an inclined wedge and low carbon steel creates significant opportunities for manufacturers of machined products to understand how dry machining and minimum quantity lubrication affect the economics of manufacturing, especially when one considers how important frictional interactions between chip and tool are on the final structure of the workpiece materials in terms of structural phase transformations. The present work not only compares various computational approaches to the solution of shear plane and tool face temperatures, but also explains why there is a large discrepancy when calculating temperature generated during machining when using Loewen and Shaw's method for calculating shear plane and tool face temperatures.
International Journal of Materials and Product Technology 11/2009; · 0.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: NiAl and Ni-Al-N thin films with a thickness of approximately 1 μm have been deposited onto glass and stainless steel 316 substrates using closed field unbalanced magnetron sputter ion platting process. A CSM scratch tester was used to determine the critical load, the coefficient of friction and wear rate of the films. XRD analysis confirmed the presence of β-NiAl phase. EDAX revealed nearly equal atomic composition of Ni and Al at 300 W for Ni and 400 W for Al targets, respectively with the Ni-Al-N thin films showing a nickel rich NiAl phase. AFM indicated a smooth surface finish with surface roughness ≤ 100 nm. Nanoindentation for coatings on glass substrates displayed hardness and elastic modulus of 7.7 GPa and 100 GPa respectively. Hardest coatings obtained were at 10% of N content. Scratch test of coated samples gave critical load, friction of coefficient and wear rate of 24 N, 0.24 and 1×10<sup align="right">−6</sup> mm<sup align="right">3</sup>/m respectively on steel.
International Journal of Nano and Biomaterials 01/2009; 2.
[Show abstract][Hide abstract] ABSTRACT: The analysis of the micro milling process is described in this paper. The present work not only compares various computational approaches to the solution of shear plane and tool face temperatures, but also explains why there is a discrepancy when calculating temperatures generated during the micromachining process. The paper shows that the temperature of the shear plane never exceeds 35°C when micro milling at spindle speeds in excess of 250,000 revolutions per minute. The paper also explains how machining AISI 1015 steel presents significant challenges to tool wear especially at high cutting speeds.
International Journal of Nanomanufacturing 01/2009; 3.
[Show abstract][Hide abstract] ABSTRACT: The interaction between a newly formed metal chip and the rake face of a cutting tool reveal the complicated nature of initial chip formation and plastic shear strains during the first few seconds of intimate contact. The loading placed on the metal chip during the first encounter with the cutting tool manifest themselves as an unpredictable curl that forces the chip to move away from the surface of the rake face and produce uneven plastic shear strains throughout the chip. The variation of the load causes instabilities on the shear plane that is directly observed using a high speed camera. As the variation of load progresses, the chip tends to curl away from the tool with varying radii until the apparently curved shear plane becomes linear. The results of initial chip formation demonstrate a very complex interaction between metal chip and rake face of the tool and the resulting development of the shear plane and its effect on plastic shear strains within the metal chip.
Materials Science and Technology 11/2008; 24(12):1452-1461. · 0.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this paper is to study the thermal and mechanical behaviour in machining of aluminium alloys (Al 7075-0) using
PCD (polycrystalline diamond) and K10 (cemented carbide) tools and to make a comparison between the performances of both tools.
The study was made using a commercial finite element software. This software has a user friendly interface and can output
several results including cutting forces, temperature, pressure, von Mises stress, maximum shear stress, plastic strain, and
plastic strain rate which were the objectives of this study. By analysing the simulations, it was concluded that the polycrystalline
tool has a superior performance in terms of cutting and feed forces and temperature when compared to the cemented carbide
International Journal of Advanced Manufacturing Technology 01/2008; 39(11):1093-1100. · 1.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The analysis of the high‐speed mechanical micro milling process is described in this paper. The present work not only compares various computational approaches to the solution of shear plane and tool face temperatures, but also explains why there is a difference when calculating temperatures generated during the micromachining process. The analysis shows that the computed temperature of the shear plane never exceeds 35°C when micro milling at spindle speeds in excess of 250,000 revolutions per minute. Machining AISI 1020 steel at significantly high speeds presents significant challenges to prevent the accelerated wear of the cutting tool that is caused by the frictional interactions between chip and tool and the nature of the intermittent contact. The analysis also shows the effect of coating at reducing the interface temperatures between chip and tool and concludes that each coating has very little effect at reducing temperature at the tool face and at the primary shear zone.
International Journal of Nano and Biomaterials 01/2008; 1(4).
[Show abstract][Hide abstract] ABSTRACT: Chip formation is of fundamental importance during the formation of nanostructured pure metals. Poor chip control leads to chip build-up and an uncontrollable surface roughness. The use of chip breaking is arbitrary because of the mechanics of chip curl is not well understood. The causes of chip curl and chip flow are still the subject of intense discussion and research among plasticity researchers. The subject originally focused on cutting forces and on the conditions at the chip-tool interface using soft plastic metals. The increasing speed of cutting has focused researchers to look at chip breaking after the chip has been cut. In the first instance, chips were considered to be continuous, discontinuous and continuous with a built-up edge. The theories of metal cutting allow one to predict the forces and stresses in the chip during formation but do not tell us anything about the strain within the chip, unless a computational approach is used. This paper describes the mechanics of chip formation using the grinding process at the microscale and explains how the deformation of the grinding grains affects shear strain rates and the average grain size in the cut chip.
International Journal of Nanoparticles 01/2008; 1(4).
[Show abstract][Hide abstract] ABSTRACT: Improvements associated with the life of cutting tools used to machine M42 tool steel are discussed in this paper. To achieve this, experiments using a variety of tool coatings are conducted on quenched and tempered M42. The limitations of the study include the employment of a short-time tool wear method. The paper presents original information on the characteristics of dry machining M42 tool steels under finish machining conditions.
Int. J. of Nanomanufacturing. 01/2008; 2(1/2):174 - 180.
[Show abstract][Hide abstract] ABSTRACT: The machining of M42 tool steel is discussed in this paper. Traditionally, these materials have been machined using uncoated cutting tools with limited success. New developments in titanium-based coatings such as cation-substituted Ti<sub align="right"> l-x-y-z </sub>Al<sub align="right"> x </sub>Cry<sub align="right"> y </sub>Y<sub align="right"> 2 </sub>N alloys, with y = 0.03 and z = 0.02, have been shown to offer enhanced high-temperature oxidation resistance compared to presently used TiN and Ti<sub align="right"> l-x </sub>Al<sub align="right"> x </sub>N films that are deposited to cutting tool surfaces. Machining experiments indicated that cutting tool life is improved significantly using yttrium-doped titanium based coatings, when machining M42 tool steels.
Int. J. of Nanomanufacturing. 01/2008; 2(1/2):163 - 173.
[Show abstract][Hide abstract] ABSTRACT: A chemical vapor deposition (CVD) system has been used to produce polycrystalline and nanocrystalline diamond (NCD) films.
For biomedical and electronic engineering applications, it is highly desirable to deposit smooth films with decreased crystal
size. In general, diamond coatings with a crystal size of 10-100nm range are known as NCD. There are several ways in which
NCD may be deposited including growth from fullerene precursors with argon dilution. Several workers have proposed various
mechanisms for the growth process using inert gas dilution to conventional hot filament (HF) or microwave chemical vapor deposition
(MWCVD) systems, or NCD growth through the deployment of CO2/CO or O2-rich gas environments. However, the use of inert gas dilution, with carbon containing species is the least complex approach
to growing nanocrystalline, and more recently, ultrananocrystaline diamond (UNCD). Mechanical properties of UNCD have been
determined by nanoindentation, and their nanotribological properties have been measured by nano-scratch and nano-impact testing.
The relative importance of toughness (∼E/H ratio) and elastic strain-to-break (∼H/E ratio) of these systems on their behavior
in nano-scratch and nano-impact tests is considered, and strategies for optimizing the deposition conditions for enhanced
durability under different contact conditions are suggested in this short communication.
Journal of Materials Engineering and Performance 01/2007; 16(1):131-134. · 0.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The application of diamond coatings on cemented tungsten carbide (WC-Co) tools has been the subject of much attention in recent years in order to improve cutting performance and tool life in orthodontic applications. WC-Co tools containing 6% Co metal and 94% WC substrate with an average grain size of 1 - 3 microm were used in this study. In order to improve the adhesion between diamond and WC substrates it is necessary to etch cobalt from the surface and prepare it for subsequent diamond growth. Alternatively, a titanium nitride (TiN) interlayer can be used prior to diamond deposition. Hot filament chemical vapour deposition (HFCVD) with a modified vertical filament arrangement has been employed for the deposition of diamond films to TiN and etched WC substrates. Diamond film quality and purity has been characterized using scanning electron microscopy (SEM) and micro Raman spectroscopy. The performances of diamond-coated WC-Co tools, uncoated WC-Co tools, and diamond embedded (sintered) tools have been compared by drilling a series of holes into various materials such as human tooth, borosilicate glass, and acrylic tooth materials. Flank wear has been used to assess the wear rates of the tools when machining biomedical materials such as those described above. It is shown that using an interlayer such as TiN prior to diamond deposition provides the best surface preparation for producing dental tools.
Journal of Medical Engineering & Technology 01/2007; 31(2):81-93.