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Iqbal S.,Pakistan Institute of Industrial Control Systems | Gualini M.M.S.,Polytechnico di Turin
Journal of Physics: Conference Series | Year: 2013

In view of the fast advancement in ophthalmic technology and corneal surgery, there is a strong need for the comprehensive mapping and characterization techniques for corneal surface. Optical methods with precision non-contact approaches have been found to be very useful for such bio measurements. Along with the normal mapping approaches, elasticity of corneal surface has an important role in its characterization and needs to be appropriately measured or estimated for broader diagnostics and better prospective surgical results, as it has important role in the post-op corneal surface reconstruction process. Use of normal corneal topographic devices is insufficient for any intricate analysis since these devices operate at relatively moderate resolution. In the given experiment, Pulsed Electronic Speckle Pattern Interferometry has been utilized along with an excitation mechanism to measure the dynamic response of the sample cornea. A Pulsed ESPI device has been chosen for the study because of its micron-level resolution and other advantages in real-time deformation analysis. A bovine cornea has been used as a sample in the subject experiment. The dynamic response has been taken on a chart recorder and it is observed that it does show a marked deformation at a specific excitation frequency, which may be taken as a characteristic elasticity parameter for the surface of that corneal sample. It was seen that outside resonance conditions the bovine cornea was not that much deformed. Through this study, the resonance frequency and the corresponding corneal deformations are mapped and plotted in real time. In these experiments, data was acquired and processed by FRAMES plus computer analysis system. With some analysis of the results, this technique can help us to refine a more detailed corneal surface mathematical model and some preliminary work was done on this. Such modelling enhancements may be useful for finer ablative surgery planning. After further experimentation, this technique can possibly be developed for in-vivo experiments on animals and humans and then may prospectively be matured for future clinical usage. © Published under licence by IOP Publishing Ltd.

Khalid M.,National University of Sciences and Technology | Mujahid M.,National University of Sciences and Technology | Amin S.,Pakistan Institute of Nuclear Science and Technology | Rawat R.S.,Nanyang Technological University | And 2 more authors.
Ceramics International | Year: 2013

Hydroxyapatite (HA) powders were synthesized by the wet precipitation method, with and without surfactant, under identical processing parameters. These powders were then heat treated at 900 °C for 3 h in air. The detailed characterization of the powders was done by using SEM, dynamic light scattering, nitrogen adsorption, XRD, Raman spectroscopy, and FTIR techniques. The HA phase, identified by well defined PO 4 3- and OH - ion peaks in Raman and FTIR spectra, was observed in all the powder samples. The addition of surfactant changed the morphology of the particles from spherical to needle/rod-like structure and increased the surface area up to three times (from 33 to 96 m 2/g). Also, suppression in the evolution of β-TCP phase was observed along with decrease in the crystal size and crystallinity of the powder due to the addition of surfactant. Synthesized nano-HA crystals were found to have diameters and lengths in the range 10-25 nm and 75-150 nm, respectively. The heat treatment changed the architecture of the particles, increased the crystallinity and reduced the surface area to ≈7 m 2/g. However, the relative increase in crystallinity was much higher for the powder synthesized with surfactant. The ratio of the average crystallite size to the crystallinity degree was about 0.53±0.07 for all the powders. The particle size distribution was bimodal and coarser for the powder synthesized without surfactant. The pore size analysis showed transformation of a predominantly mesoporous structure into a meso- plus macroporous one on heat treatment. The intensity of OH - group peak in Raman spectra was found to be highly sensitive to the crystalline state of the HA powder and may be used to assess crystallinity. © 2012 Elsevier Ltd and Techna Group S.r.l.

Akbar S.,Pakistan Institute of Industrial Control Systems | Ahmad Z.,Pakistan Institute of Industrial Control Systems | Farooque M.,Pakistan Institute of Industrial Control Systems
Key Engineering Materials | Year: 2010

The present work describes the development of Fe-Co-Ni-Al-Ti-Cu permanent magnets. Magnetic and microstructural studies were carried out using microscopy, magnetometery and X-ray diffraction techniques. The results indicate that both microstructural and magnetic properties are sensitive to the heat treatment conditions. Magnetic properties in the studied alloys could be improved by controlling the annealed state microstructure and by efficiently aligning and elongating the nano-structured ferromagnetic α1 particles in <001> crystallographic directions. The best magnetic properties in the alloy Fe-34.7Co-15.3Ni-8.3Al-5.4Ti-3.9Cu is obtained as coercive force (Hc) of 1528Oe, residual magnetic induction (Bs) of 7105G, saturation magnetization (Bs) of 19060G and maximum energy product ((BH)max) of 3.3MGOe.

Mansoor M.,Pakistan Institute of Industrial Control Systems
Key Engineering Materials | Year: 2012

A step-by-step, hierarchical approach is explored in the present work to purify and functionalize carbon nanotubes synthesized by chemical vapor deposition. Attempts are made to purify and functionalize CNTs without extinguishing their aspect ratios. The carbon impurities are removed by thermal oxidation, whilst the unprotected metallic catalyst particles are eliminated by wet oxidation, subsequently; CNT bundles are de-roped by surfactant assisted sonication. Finally, protected metallic catalyst particles are removed and functional groups (hydroxyl and carboxyl) are attached by acid treatment and wet oxidation, respectively. The derivate CNTs are characterized using zeta potential measurements, TGA, XRD, FTIR and SEM. The characterization showed that in optimum experimental conditions the catalytic particles are removed upto 80%, the carbon impurities are eliminated upto 95% and chemical functionalities of hydroxyl and carboxyl is occurred with noticeable de-roping of the CNT bundles. © (2012) Trans Tech Publications.

Ejaz N.,Pakistan Institute of Industrial Control Systems | Muhammad W.,Pakistan Institute of Industrial Control Systems | Salam I.,Pakistan Institute of Industrial Control Systems
Key Engineering Materials | Year: 2010

Aluminum alloys generally contain constituent particles. The population density and size these particles are important while considering fatigue performance. In present study, the crack growth process in stage II in the rolled plate of a high strength aluminum alloy AA 2219 was studied on samples prepared along the rolling direction. A three fold approach was adopted to understand the fatigue crack growth process: i) microstructural analysis ii) fatigue testing iii) postfracture analysis. Microstructural analysis revealed a high density of constituent particles in the material. EDS analysis showed that the particles were mainly of CuAl2 type. However, particles with high concentration of Fe and Mn were also present in the material. Fatigue crack propagation tests were performed by using middle tension (MT) specimens prepared in rolling direction under constant amplitude loads. The da/dN vs ΔK plot on log-log scale showed a sigmoidal shape with a sharp increase of crack growth rate in the steady state regime. Topographical features were studied to understand the interaction of fatigue crack with the microstructural features. Post fracture analysis revealed that the macro fracture appearance changed with the change of stress level. However, the general mechanism of crack growth, in all the stress levels studied, was by formation of striations. At lower stress levels almost flat region with striations is present upto the final fracture. The crack growth surface showed crystallographic features with crack propagation almost perpendicular to the loading direction. However, a comparatively tortuous fatigue region was evident in the sample tested at high level of stress. The observation of crack path surface at high magnification did not reveal any influence of particles on the crack growth process. However, in sections taken from the fractured samples cracking and debonding of the constituent particles was observed near the fatigue crack path.

Mansoor M.,Pakistan Institute of Industrial Control Systems | Salam I.,Pakistan Institute of Industrial Control Systems | Tauqir A.,Pakistan Institute of Industrial Control Systems
IOP Conference Series: Materials Science and Engineering | Year: 2016

Eutectic Al-Si alloys find their applications in moderate to severe tribological conditions, for example: pistons, casings of high speed pumps and slide sleeves. The higher hardness, so the better tribological properties, are originated by the formation of a silicon rich secondary phase, however, the morphology of the secondary phase drastically influence the toughness of the alloy. Microstructural modifiers are used to control the toughness which modifies the Si rich secondary phase into dispersed spherical structure instead of needle-like network. In the present study, a mixture of chemical fluxes was used to modify the Si phase. The alloy was cast into a sand mold and characterized by scanning electron microscopy, energy dispersive spectroscopy, hardness testing and tensile testing. It was found that the morphology of the Si phase was altered to acicular structure due to the modification process. In comparison, the un-modified alloy contained Si phase in needle-like structure. The effect of modifier was also pronounced on the mechanical properties, where increase of 50% in yield strength, 56% in tensile strength and 200% in elongation occurred. A discernable raise in strain hardening component indicated the improved strain harden ability and formability of the modified alloy. © Published under licence by IOP Publishing Ltd.

Salam I.,Pakistan Institute of Industrial Control Systems | Muhammad W.,Pakistan Institute of Industrial Control Systems | Ejaz N.,Pakistan Institute of Industrial Control Systems
IOP Conference Series: Materials Science and Engineering | Year: 2016

A two-fold approach was adopted to understand the fatigue crack growth process in an Aluminum alloy; fatigue crack growth test of samples and analysis of fractured surfaces. Fatigue crack growth tests were conducted on middle tension M(T) samples prepared from an Aluminum alloy cylinder. The tests were conducted under constant amplitude loading at R ratio 0.1. The stress applied was from 20,30 and 40 per cent of the yield stress of the material. The fatigue crack growth data was recorded. After fatigue testing, the samples were subjected to detailed scanning electron microscopic (SEM) analysis. The resulting fracture surfaces were subjected to qualitative and quantitative fractographic examinations. Quantitative fracture analysis included an estimation of crack growth rate (CGR) in different regions. The effect of the microstructural features on fatigue crack growth was examined. It was observed that in stage II (crack growth region), the failure mode changes from intergranular to transgranular as the stress level increases. In the region of intergranular failure the localized brittle failure was observed and fatigue striations are difficult to reveal. However, in the region of transgranular failure the crack path is independent of the microstructural features. In this region, localized ductile failure mode was observed and well defined fatigue striations were present in the wake of fatigue crack. The effect of interaction of growing fatigue crack with microstructural features was not substantial. The final fracture (stage III) was ductile in all the cases. © Published under licence by IOP Publishing Ltd.

Siddique S.,University of Management and Technology | Shah Z.H.,University of Management and Technology | Shahid S.,University of Management and Technology | Yasmin F.,Pakistan Institute of Industrial Control Systems
Acta Chimica Slovenica | Year: 2013

Nano particles have received increased attention regarding their potential utility in biomedicine. In this study, we have investigated the antibacterial activity of ZnO nano particles with various particle sizes. ZnO nano particles were synthesized by conventional precipitation method using zinc sulphate and sodium hydroxide as precursors followed by the calcinations of precipitates at 350 °C for 6 h (sample A) and 550 °C for 2 h (sample B). The products were characterized by X-ray diffraction (XRD) analysis and morphology of the particles was evaluated by Scanning Electron Microscopy (SEM). Antibacterial activities against four different microorganisms were evaluated by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and zones of inhibitions using different concentrations of ZnO nanoparticles. The antibacterial activity was directly proportional to the concentration and inversely proportional to the particle size in all the microorganisms; moreover Gram positive bacteria were generally more affected than Gram negative bacteria. The stability of ZnO nanoparticles combined with potent antibacterial properties favours their application as antibacterials against broad spectrum of microorganisms.

Bhatty M.B.,Ghulam Ishaq Khan Institute of Engineering Sciences and Technology | Khalid F.A.,Ghulam Ishaq Khan Institute of Engineering Sciences and Technology | Khan A.N.,Pakistan Institute of Industrial Control Systems
Journal of Thermal Spray Technology | Year: 2012

Thermal barrier coatings (TBCs) are employed to protect metallic components from heat, oxidation, and corrosion in hostile environments. In this paper Ni-20Cr bond coat followed by CaZrO 3 top coat was deposited on 316 stainless steel substrates by air plasma spray coating technique. Isothermal treatment of coated samples was carried out to investigate the effect of heat exposure on the microstructure and metallurgical phase changes of TBCs system. The fractured surface of as-sprayed and delaminated CaZrO 3 coatings was also studied to observe the splats morphology, structural defects, and lamellas internal microstructure. CaZrO 3 coating was found to be stable for 100 h at 700 °C but accelerated degradation was observed at 900 °C even at 20 h and lead to delamination after 60 h of exposure time. Chromium rich oxide formation was found to be responsible for the complete delamination of the top coat. Further, the formation of meta-stable monoclinic phase was also observed on the top surface of the top coat. © 2011 ASM International.

Muhammad W.,Pakistan Institute of Industrial Control Systems
IOP Conference Series: Materials Science and Engineering | Year: 2014

High-carbon high-chromium cold work tool steels are widely used for blanking and cold forming of punches and dies. It is always advantageous to obtain an increased wear resistant surface to improve life and performance of these steels. In this connection boriding of a high-carbon high-chromium cold work die steel, D3, was conducted in a mixture of 30% B4C, 70% borax at 950 °C for two, four and six hours. Case depth of the borided layer obtained was between 40 to 80 μm. After boriding, the surface hardness achieved was between 1430 to 1544 HV depending upon the process time. X-ray diffraction studies confirmed the formation of a duplex compound layer consisting of FeB and Fe2B. It is generally considered that FeB is undesirable because of its inherent brittleness. Post boriding treatment (homogenization) transformed the compound layer into single-phase layer of Fe2B, while surface hardness decreased to 1345-1430 HV. Pin-on-disc wer test showed that wear resistance of the borided samples was superior as compared to non-borided material and increased with boriding time. © Published under licence by IOP Publishing Ltd.

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