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TGA-DSC: A Screening Tool for the Evaluation of Hydrocracking Catalyst Performance

American Journal of Analytical Chemistry 2015年第4期6卷 364-375页

作者： Muhammad Salman shazia nisar Zahid Hussain Hina Salman Mohib R. Kazimi Department of Chemistry University of Karachi Karachi Pakistan Institute of Chemistry International Center for Chemical and Biological Sciences University of Karachi Karachi Pakistan Department of Applied Chemistry and Chemical Technology University of Karachi Karachi Pakistan

DSC-TGA was used for screening of commercially available and synthesized catalyst for the degradation of polypropylene (PP). In this study, all the runs were performed with 50% load of the catalyst and the results were compared with those of PP + 50% pure silica having no catalytic activity. The degradation behavior of PP using catalyst Zeolyst-713 exhibited much higher degradation activity among the other catalysts used in this study. Moreover, it contributed to lowering of initial stage temperature showing a shape-selective effect. DSC-TGA tools such as Ton, Tmax, T99%, activation energy, enthalpy change in the process and coke content were used for screening. It was concluded that the pore construction and unique acid properties of the Zeolyst-713 as well as proper reaction temperatures were significant influential factors to fully exert this effect. In this work, kinetics of catalytic thermogravimetric degradation of PP used for domestic purposes was investigated using Alumino-silicate catalyst. Zeolyst-713 was observed to lower activation energy and enhances degradation activity in comparison with thermal degradation without a catalyst.

关键词： Thermogravimetric Analysis (TGA) DSC Pyrolysis Catalytic Degradation Polypropylene Waste Plastic Catalysis

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Ethnopharmacological evaluation and antioxidant activity of some important herbs used in traditional medicines

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Journal of Traditional Chinese Medicine 2016年第5期36卷 689-694页

作者： Sofia Rashid Mushtaq Ahmad Muhammad Zafar Asad Anwar shazia Sultana Shahzadi Tabassum Sidra nisar Ahmed Department of Plant Sciences Quaid-i-Azam University Institute of Biochemistry and Biotechnology Pir Mehr Ali Shah (PMAS) University of Arid Agriculture

OBJECTIVE: To document the indigenous knowledge and evaluate the antioxidant activity of medicinal herbs used for treatment of various ***: The ethnomedicinal data were collected through semi-structured interviews of local informants along with collection of herbarium specimens. The antioxidant activity was evaluated by using 1-diphenyl-2-picryl-hydrazyl radical scavenging ***: A total of 12 important medicinal herbs were evaluated for ethnomedicinal uses and antioxidant activity. Medicinal plant diversity showed that Solanaceae was the dominating family(3 spp.),followed by Asteraceae and Lamiaceae(both 2spp.). Leaves(31%) were most frequently used in preparation of traditional medicines, and the most recommended mode of preparation was powder(28%). The antioxidant results revealed that thehighest activity was found in Atropa acuminata and Crocus ***: The results of this study proved that A. accuminata and C. sativus can be the excellent sources of antioxidant compounds. A sustainable use and conservation of the valuable natural resource greatly promote the development of functional food additives and cosmetics.

关键词： Plants medicinal Medicine Traditional Antioxidants Ethnopharmacology

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Effect of fluence and ambient environment on the surface and structural modification of femtosecond laser irradiated Ti

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Chinese Physics B 2016年第1期25卷 789-795页

作者： Umm-i-Kalsoom shazia Bashir nisar Ali M Shahid Rafique Wolfgang Husinsky Chandra S R Nathala Sergey V Makarov Narjis Begum Institute for Applied Physics Vienna University of TechnologyViennaAustria Centre for Advanced Studies in Physics GC University LahorePakistan Department of Physics The University of LahorePala'stan Department of Basic Sciences and Humanities University of Engineering and Technology FasalabadPakistan Department of Physics University of Engineering and Technology LahorePakistan P.N.Lebedev Physics Institute RAS MoscowRussia Department of Physics COMSATS Institute of Information and TechnologyIslamabadPakistan

Under certain conditions, ultrafast pulsed laser interaction with matter leads to the formation of self-organized conical as well as periodic surface structures （commonly reffered to as, laser induced periodic surface structures, LIPSS）. The purpose of the present investigations is to explore the effect of fsec laser fluence and ambient environments （Vacuum ＆ 02） on the formation of LIPSS and conical structures on the Ti surface. The surface morphology was investigated by scanning electron microscope （SEM）. The ablation threshold with single and multiple （N = 100） shots and the existence of an incubation effect was demonstrated by SEM investigations for both the vacuum and the 02 environment. The phase analysis and chemical composition of the exposed targets were performed by x-ray diffraction （XRD） and energy dispersive x-ray spectroscopy （EDS）, respectively. SEM investigations reveal the formation of LIPSS （nano ＆ micro）. FFT d-spacing calculations illustrate the dependence of periodicity on the fluence and ambient environment. The periodicity of nano-scale LIPSS is higher in the case of irradiation under vacuum conditions as compared to 02. Furthermore, the 02 environment reduces the ablation threshold. XRD data reveal that for the 02 environment, new phases （oxides of Ti） are formed. EDS analysis exhibits that after irradiation under vacuum conditions, the percentage of impurity element （A1） is reduced. The irradiation in the 02 environment results in 15% atomic diffusion of oxygen.

关键词： LIPSS ablation threshold incubation coefficient structural modification

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Femtosecond laser induced nanostructuring of zirconium in liquid confined environment

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Chinese Physics B 2017年第1期26卷 310-319页

作者： nisar Ali shazia Bashir Umm-i-Kalsoom M.Shahid Rafique Narjis Begum Wolfgang Husinsky Ali Ajami Chandra S.R.Natahala Laser Laboratories Institute for Applied Physics Vienna University of Technology 1040 Vienna Austria Department of Basic Sciences and Humanities University of Engineering and Technology Lahore Faisalabad Campus Faisalabad Pakistan Laser Laboratories Centre for Advanced Studies m Physics GC University 1-Church Road Lahore Pakistan Department of Physics GC University Kachehri Road Lahore Pakistan Department of Physics Riphah International University Islamahad (Lahore Campus) Lahore Pakistan Department of Physics University of Engineering and Technology Lahore Pakistan Department of Physics COMSATS Institute of Information Technology Islamabad Pakistan

The surface, structural, and mechanical properties of zirconium after irradiation with Ti： sapphire laser（800 nm, 30 fs,1 k Hz） have been investigated. The zirconium targets were exposed for a varying number of laser pulses ranging from 500 to 2000 at a fixed fluence of 3.6 J/cm^2 corresponding to an intensity of 1.2×10^14W/cm^2 in ambient environments of deionized water and propanol. A scanning electron microscope（SEM） was employed to investigate the surface morphology of the irradiated zirconium. The SEM analysis shows the formation of various kinds of features including nanoscale laser induced periodic surface structures（LIPSS）, sponge like surface structure, flakes, conical structures, droplets, pores, and cavities. The energy dispersive x-ray spectroscopy（EDS） analysis exhibits the variation in chemical composition along with an enhanced diffusion of oxygen under both ambient conditions. The crystal structure and phase analyses of the exposed targets were explored by x-ray diffraction（XRD） and Raman spectroscopy techniques, respectively. The XRD analysis confirms the presence of various phases of zirconium hydride and zirconia after ablation in both de-ionized water and propanol. However, excessive hydrides are formed in the case of propanol. The Raman analysis supports the EDS and XRD results. It also reveals the presence of oxides（zirconia） after irradiation in both de-ionized water and propanol *** chemical reactivity of zirconium was significantly improved in the presence of liquids which were accountable for the growth of novel phases and modification in the chemical composition of the irradiated Zr. A nanohardness tester was employed to measure the nanohardness of the laser treated targets. The initial increase and then decrease in nanohardness was observed with an increase in the number of laser pulses in the de-ionized water environment. In the case of propanol,a continuous decrease in hardness was observed.

关键词： ambient environments periodic structure crystallinity synthesis

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Surface Analysis Correlated with Structural and Mechanical Properties of Laser Irradiated Brass

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Materials Sciences and Applications 2015年第1期6卷 23-32页

作者： Shahbaz Ahmad shazia Bashir Daniel Yousaf nisar Ali Tousif Hussain Center for Advanced Studies in Physics Government College University Lahore Pakistan

Brass targets were irradiated with various laser pulses of Excimer laser ranging from 1200 to 3000 for constant fluence of 3.4 J/cm2 in oxygen atmosphere (100 Torr). The surface morphology and crystallographic analyses were performed by using Scanning Electron Microscope (SEM) and X-Ray Diffractometer (XRD). SEM analysis reveals the formation of laser-induced micro-sized cavities, bumps, cones and wave-like ridges with non-uniform shape and density distribution. These features are formed for all number of pulses;however with increasing number of pulses from 1200 to 2400, the density of cavities decreases whereas, the wave-like ridges become more pronounced and bump-formation is vanished. For maximum number of 3000 shots, the appearance of cones and wave-like ridges becomes diffusive, whereas the density and size of cavities increase again. XRD analysis demonstrates that no new phases are formed in irradiated brass. However, the change in peak intensity along with lower and higher angle shifting is observed which is attributed to generation of laser induced stresses. The Yield Stress (YS), Ultimate Tensile Strength (UTS) as well as Microhardness increase monotonically with increasing number of laser pulses.

关键词： Laser Pulses Surface Morphology Mechanical Properties Crystallographic Alteration

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