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41.
Analysis of Solvent Effect on Mechanical Properties of Poly(ether ether ketone) Using Nano-indentation 下载免费PDF全文
Tanveer Iqbal Saima Yasin Ahmad Shakeel Hamayoun Mahmood Fahad Nazir Paul F. Luckham 《化学物理学报(中文版)》2018,31(2):211-215
Poly (ether ether ketone)(PEEK) is a high-performance semi-crystalline thermoplastic polymer.Exposure of the polymeric surface to solvents can have a strong effect like softening/swelling of polymeric network or dissolution.In this study, nano-indentation analysis was performed to study the effect of acetone on the surface mechanical properties of PEEK using different exposure time.The experiments were performed with a constant loading rate (10 nm/s) to a maximum indentation displacement (1000 nm).A 30-second hold segment was included at the maximum load to account for any creep effects followed by an unloading segment to 80% unloading.The indentation hardness and the elastic modulus were computed as a continuous function of the penetration displacement in the continuous stiffness mode (CSM) indentation.The experimental data showed that the peak load decreased from ~5.2 mN to ~1.7 mN as exposure time in solvent environment increased from 0 to 18 days.The elastic modulus and the hardness of PEEK samples also displayed a decreasing trend as a function of exposure time in the solvent environment.Two empirical models were used to fit the experimental data of hardness as a function of exposure time which showed a good agreement with the experimental values. 相似文献
42.
M. A. Chaudhri Q. Jabbar Q. Nadeem 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(1):211-213
Production yields of all the isotopes, with Z = 20 to >92, under bombardment with protons, deuterons and alphas of up to 36 MeV, have been estimated using empirically constructed excitation functions and our simplified method. Results are presented in graphical form, from which the production yield of any isotope in the aforementioned range can be directly obtained for an infinitely thick (stopping the incoming beam completely), moderately thick or even a thin target under given irradiation conditions. These yields would not only help to select the best reaction to produce a particular isotope and help in minimizing the losses due to further processing of the isotopes but would also provide an indication of the unwanted activities which are also being produced simultaneously. 相似文献
43.
M. A. Chaudhri M. N. Chaudhri Q. Nadeem Q. Jabbar 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(3):701-703
A new method for non-destructive depth profiling of fluorine has been developed which extends the profiling range to much
larger depths than hitherto possible. In this method the thick-target yield of 6–7 MeV gammas from the reaction of 19F(p,αγ) 16O in the tooth sample, was measured as a function of the incident energy from threshold to up to 2.7 MeV and the yield curve
plotted. This curve was compared to the calculated yield curve of 6–7 MeV gammas from the same reaction but on an enamel matrix
containing uniformly distributed fluorine. The difference in the shape of the two curves was only due to the non-uniform distribution
of fluorine in the tooth sample, which could then be calculated. By making use of this method F-depth profiles in teeth of
monkeys were determined non-destructively to a depth of 14 μm. This method is also applicable for profiling other elements
through appropriate resonant or non-resonant nuclear reactions. 相似文献
44.
Ali N. Siyal Saima Q. Memon Aydan Elçi Abdullah Akdogan Aysen Hol Aslihan A. Kartal 《International journal of environmental analytical chemistry》2013,93(14-15):1463-1477
Polystyrene (PS) was extracted from styrofoam waste and functionalised with schiff base, N,N-bis(salicylidene)cyclohexanediamine (SCHD) through an azo spacer. The resin was characterised and used for preconcentration of Pb(II), Ni(II) and Cd(II) ions prior to their trace determinations by microsample injection system–coupled flame atomic absorption spectrometry (MIS-FAAS). The recoveries of studied metal ions were achieved ≥96.0% with relative standard deviation (RSD) ≤4.5 at optimum parameters: pH 8; resin amount 300 mg; flow rates 3.0 mL min?1 of sample solution; and 2.0 mL min?1 of eluent (2.0 mol L?1 HNO3). The limits of detection (LODs) and limits of quantification (LOQs) were found to be 0.32, 0.23 and 0.21 and 1.10, 0.78 and 0.69 μg L?1, respectively, with preconcentration factors (PFs) of 500, 800 and 1000, respectively. The linear ranges of the method were 1–40, 1–25 and 1–20 μg L?1 for Pb(II), Ni(II) and Cd(II) ions, respectively. The accuracy and validation of the method were evaluated by analysis of certified reference materials (CRMs). The method was successfully applied for preconcentration of studied metal ions in wastewater and wastewater-irrigated vegetable samples. 相似文献
45.
Transport in Porous Media - The object of this study is to investigate the question of convective movement of a reacting solute in a viscous incompressible occupying a plane layer in a saturated... 相似文献
46.
Hydralazine hydrochloride itself is a reducing agent and its redox properties like other reducing agents vary as the oxidizing agent and applied conditions vary. The redox properties of hydralazine were studied by spectrophotometric method. Formal redox potential of hydralazine was calculated and effect of pH was observed on redox properties of hydralazine. 相似文献
47.
48.
Assessment of Primordial Radionuclides in Pakistani Red Bricks and Associated Radiation Doses 下载免费PDF全文
Specific activity of primordial radionuclides and associated radiation hazards due to 40K, 226Ra, and 232Th have been measured in backed red brick samples, collected from five highly populated areas of the North West Frontier Province of Pakistan. For the detection, analysis and data acquisition, a high purity germanium detector was used. Associated external doses were calculated using a Monte Carlo neutron photon transport code. A theoretical model to determine the gamma dose rate at 1 m height from the floor, made of bricks, was employed for the calculation of mass attenuation coefficient and self-absorption in the floor for the gamma energies of these radionuclides and their progeny. Monte Carlo simulation shows that in this study the floor, having more than an effective thickness of 15 cm, contributes very little to the external gamma dose rate. The values of the external dose rate and annual effective dose are found to be much lower than the world average as well as from other countries of the world. 相似文献
49.
Thermally stable hyperbranched polyamide-ethers (HBPAEs) containing pyrimidine moieties were synthesized using new AB2 type monomer, 6-hydroxy-2,4-bis(4′-nitrobenzamide)pyrimidine (NAL), which was prepared through amidation and its structural characterization was made by FTIR, 1H, 13C NMR spectrometry and elemental analysis. Polymerization of NAL proceeded homogeneously to yield a gel-free polymer (HBPAE 1). End group derivatization of nitro-terminated HBPAE 1 yielded HBPAE 2 and 3. FTIR confirmed the structure and complete modification of ensuing polymers. DB and inherent viscosity (ηinh) of HBPAE 1 was found to be 0.41 and 0.23 dL/g, respectively. Modified HBPAE 2 and 3 were soluble in various organic solvents including NMP, DMAc and DMSO but amorphous HBPAE 1 was partially soluble in DMF. Glass transition temperature (Tg) of thermally stable HBPAEs was affected by nature of end groups as well as introduction of pyrimidine rings. 相似文献
50.
A new trifunctional monomer, 1,3,5-tris(3′,4′-carboxyphenyl)benzene trianhydride (TAn), was synthesized and characterized by elemental analysis, FTIR, 1H and 13C NMR spectroscopy. Subsequently, one-step high-temperature polymerization of TAn and a series of commercially available diamine monomers such as p-phenylenediamine (PDA, 1), 4,4′-oxydianiline (ODA, 2), and 1,5-diaminonaphthalene (DAN, 3) successfully yielded wholly aromatic anhydride-terminated hyperbranched poly(ester-imide)s HBPEI 1, 2, and 3, respectively. Gelation was effectively avoided by controlling 1:1 M ratio of A2 and B3 monomers and maintaining total solid content 10 mmol, thereby, producing a novel family of aromatic HBPEIs with inherent viscosities (ηinh) of 0.17-0.28 dL/g. As-prepared HBPEIs were fully characterized by FTIR spectroscopy and were soluble in DMAc, DMSO and NMP. Degree of branching (DB) by 1H NMR analysis of the HBPEIs was estimated to be 0.52-0.56. Differential scanning calorimetry (DSC) showed glass transition temperatures (Tg) between 198 and 208 °C and the synthesized polymers were thermally stable. Furthermore, crystallinity of the polymers was evaluated by means of X-ray diffraction patterns. 相似文献