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.
Mirza M.S.,Pakistan Institute of Engineering and Applied Sciences |
Yasin T.,Pakistan Institute of Engineering and Applied Sciences |
Ikram M.,Pakistan Institute of Engineering and Applied Sciences |
Khan M.N.,Pakistan Institute of Nuclear Science and Technology |
Shuaib M.,Pakistan Institute of Industrial Control Systems
Ceramics International | Year: 2014
This paper presents a novel die-pressing technique for the fabrication of 1-3 piezoceramic/polymer composites. Piezoceramic (Ba0.95Pb 0.05)(Ti0.99Co0.01)O3 (BT) powder having particle size ∼0.4 μm was synthesized by a solid state reaction method. Key properties of sintered and poled BT samples were εr=1100, d33=136 pC/N, g33= 14×10-3 V m/N and tan δ=0.005. The 1-3 connectivity BT/monothane-A70 samples with variable BT contents (11-31 vol%) were fabricated by a die-pressing technique. The dielectric, elastic and resonant characteristics were investigated by using standard equipments. Results revealed that the composites possess moderate dielectric constant εr (140-349), higher thickness mode electromechanical coupling coefficient k t (44%) and higher figure of merit FOM (1896-7169 fm2/N) compared to monolithic BT ceramic. The fabricated composites also possess favorable properties such as lower acoustic impedance Z (8-13 Mrayl) and lower elastic stiffness C33 D (36-65 GPa) compared to single phase BT ceramic. These results indicate that BT/monothane-A70 composites have the potential to be used as transducer in various applications. © 2014 Elsevier Ltd and Techna Group S.r.l.
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.
Khalid M.,National University of Sciences and Technology |
Mujahid M.,National University of Sciences and Technology |
Khan A.N.,Pakistan Institute of Industrial Control Systems |
Rawat R.S.,Nanyang Technological University
Journal of Materials Science and Technology | Year: 2013
This paper reported a novel coating approach to deposit a thin, crack free and nano-structured hydroxyapatite (HA) film on Ti6Al4V alloy with Al2O3 buffer layer for biomedical implants. The Al2O3 buffer layer was deposited by plasma spraying while the HA top layer was applied by dip coating technique. The X-ray diffraction (XRD) and Raman reflections of alumina buffer layer showed α- to γ-Al2O3 phase transformation; and the fractographic analysis of the sample revealed the formation of columnar grains in well melted splats. The bonding strength between Al2O3 coating and Ti6Al4V substrate was estimated to be about 40 MPa. The presence of dip coated HA layer was confirmed using XRD, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis. The SEM images exhibited that HA top layer enveloped homogenously the troughs and crests of the underneath rough (Ra = 2.91 μm) Al2O3 surface. It is believed that the novel coating approach adopted might render the implant suitable for rapid cement-less fixation as well as biocompatible for longer periods. © 2013 .
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.