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101.
102.
Investigations on the Behavior of HVOF and Cold Sprayed Ni-20Cr Coating on T22 Boiler Steel in Actual Boiler Environment 总被引:1,自引:0,他引:1
Niraj Bala Harpreet Singh Satya Prakash J. Karthikeyan 《Journal of Thermal Spray Technology》2012,21(1):144-158
High temperature corrosion accompanied by erosion is a severe problem, which may result in premature failure of the boiler
tubes. One countermeasure to overcome this problem is the use of thermal spray protective coatings. In the current investigation
high velocity oxy-fuel (HVOF) and cold spray processes have been used to deposit commercial Ni-20Cr powder on T22 boiler steel.
To evaluate the performance of the coatings in actual conditions the bare as well as the coated steels were subjected to cyclic
exposures, in the superheater zone of a coal fired boiler for 15 cycles. The weight change and thickness loss data were used
to establish kinetics of the erosion-corrosion. X-ray diffraction, surface and cross-sectional field emission scanning electron
microscope/energy dispersive spectroscopy (FE-SEM/EDS) and x-ray mapping techniques were used to analyse the as-sprayed and
corroded specimens. The HVOF sprayed coating performed better than its cold sprayed counterpart in actual boiler environment. 相似文献
103.
G.C. Obasi S. Birosca D.G. Leo Prakash J. Quinta da Fonseca M. Preuss 《Acta Materialia》2012,60(17):6013-6024
The role of starting texture in variant selection has been studied during α → β → α transformation in Ti–6Al–4V. By hot rolling at different temperatures followed by recrystallization, material with either a strong basal texture or a strong transverse texture was generated. Subsequently, both conditions were heat-treated above the β transus followed by slow cooling. The degree of variant selection was assessed by comparing the strength of the measured and predicted α texture from high temperature β texture, assuming equal occurrence of all possible variants during β → α transformation. It was found that, even though the material rolled originally at 800 °C displayed a stronger α texture after β heat treatment, it was the material rolled originally at 950 °C that showed greater variant selection. The variant selection mechanism is discussed in terms of the generated β texture and common 〈1 1 0〉 poles in neighbouring β grains selecting a similar α variant on both sides of the prior β grain boundary. Predictions of possible 〈1 1 0〉 pole misorientation distributions for the two investigated β textures showed that the combination of texture components generated during rolling Ti–6Al–4V at 950 °C increases the likelihood of having β grain pairs with closely aligned (1 1 0) planes compared to rolling at 800 °C. Therefore, it can be proposed that avoiding the generation of certain combinations of β texture components during thermomechanical processing has the potential for reducing variant selection during subsequent β heat treatment. 相似文献
104.
105.
Gangadhara Parigi Ramesh Kumar Vishweshwaraiah Prakash 《Journal of the American Oil Chemists' Society》2009,86(8):773-781
Porcine pancreatic lipase (PPL) has been used as a biocatalyst for many years and is one of the most widely used enzymes for
biotechnological applications; however, it is a rather complex mixture with various active enzymes. The present study has
been undertaken to determine the effects of polyols and sugars (cosolvents) on the thermal stability of PPL preparation. The
thermal stability of PPL exposed to 60°C for 10 min was enhanced in the presence of cosolvents in terms of both residual specific
activity and conformational stability. Thermal denaturation, changes in circular dichroism, fluorescence spectra, apparent
kinetic parameters, activity, and preferential interaction parameter of PPL preparation are discussed in terms of contributions
to the mechanism of thermal stability and the activity enhancement. Partial specific volume measurement of PPL in the presence
of cosolvents is presented for the first time. The preferential interaction parameter (ξ
3) was negative in all cosolvents used, and maximum hydration was observed in the presence of trehalose, where the preferential
interaction parameter was −0.076 g/g. The observed increase in the thermal stability of PPL preparation in the presence of
cosolvents is due to the preferential hydration of the enzyme. 相似文献
106.
Prita Pant Sarangi Sampat Raj Vadera Manoj Kumar Patra Chandra Prakash Narendra Nath Ghosh 《Journal of the American Ceramic Society》2009,92(10):2425-2428
Nanocrystalline pure α-Fe2 O3 powder, with an average particle size of 35 nm, has been synthesized by using an aqueous solution-based synthetic route. DC electrical resistivity of the synthesized material was measured with respect to temperature by the two-probe method from 28° to 225°C. Room temperature resistivity of the nanopowder was ∼108 Ω·cm. Magnetic hysteresis measurement revealed that the synthesized α-Fe2 O3 nanopowder exhibited ferromagnetic behavior at room temperature. The hysteretic features are high saturation magnetization of 5.1 emu/g, high remanence of 2.2 emu/g, and coercivity of 200.5 Oe. 相似文献
107.
To investigate the flocculation characteristics of polyacrylamide (PAM)‐grafted chitosan, a series of PAM‐grafted chitosan copolymer (Chito‐g‐PAM1 to Chito‐g‐PAM4) have been synthesized by ceric ammonium nitrate‐induced solution polymerization technique in nitrogen atmosphere. The flocculation characteristics of the polymer samples (PAM, grafted and ungrafted chitosan) were studied by settling test and jar test methods in the colloidal suspensions of kaolin, iron ore, silica, and bentonite powder. It was found that the settling performance of Chito‐g‐PAM3 is best among the polymer samples. The jar test results indicate that the ungrafted chitosan has better water clarifying performance than both the PAM and grafted chitosan. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
108.
Racemic heavy isotope analogs of 1-O-alkyl-sn-glycero-3-phosphocholine (lysoPAF) and 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine (PAF) were prepared for use as internal standards to facilitate quantitative studies based on mass
spectrometry. Starting from pentadencane-1,15-diol andrac-glycerol-1,2-acetonide, a convergent synthesis of 1-O-[16′-2H3]hexadecyl and 1-O-[18′-2H3]octadecylrac-glycero-3-phosphocholine and their acetyl derivatives is described. Three deuterium atoms were introduced at the terminal
position of the 1-O-alkyl group by displacement of thep-toluensulfonyl group from 1-O-alkyl-15′-p-toluensulfonate and 1-O-alkyl-17′-p-toluensulfonate with [2H3]-methylmagnesium iodide. The 1-O-alkyl-17′-p-toluensulfonate was obtained by reaction of the 1-O-alkyl-15′-p-toluensulfonate with allylmagnesium bromide, followed by reductive ozonolysis and treatment withp-toluenesulfonyl chloride. The hydroxyl group at C-2 was protected by a benzyl group and removed at a late stage in the synthesis.
This provided the corresponding lysoderivatives or allowed preparation of racemic PAF by subsequent acetylation of the free
hydroxy group. The phosphocholine moiety was introduced at glycerol C-3 by reaction with bromoethyldichlorophosphate and trimethylamine.
The synthetic compounds were analyzed by FAB/MS and GC/NICIMS. They were shown to contain less than 0.6% protium impurity. 相似文献
109.
Ajaya Kumar Singh Bhawana Jain Reena Negi Yokraj Katre Surya Prakash Singh Virender K. Sharma 《Catalysis Letters》2009,131(1-2):98-104
Kinetics of Ruthenium(III) [Ru(III)] chloride catalyzed oxidation of valine (Val) has been studied by N-bromophthalimide (NBP) in the acidic medium at 35 °C. The reaction rate follows first-order and zero-order dependence with respect to [NBP] and [Val]. First-order kinetics was observed for Ru(III) chloride at low range of concentrations and tending towards zero-order at higher concentrations. A negative effect was observed for [H+] and [phthalimide], while a positive effect was observed for [Cl?] on the reaction rate. Hg(OAc)2, ionic strength (I), and dielectric constant (D) of the medium did not change significantly the reaction rate. The rate constants as a function of temperature (298–318 K) were used to calculate activation parameters of the oxidation of Val by NBP. A plausible mechanism was proposed to explain the results of kinetic studies, reaction stoichiometry and product analysis. 相似文献
110.
Prashant Singh Pradeep Kumar Anju Katyal Rashmi Kalra Sujata K. Dass Satya Prakash Ramesh Chandra 《Catalysis Letters》2010,134(3-4):303-308
In this present work, we report that phosphotungstic acid provides a simple, efficient and environmentally benign route is a two-component one-pot domino Knoevenagel-type condensation/Michael reaction between 4-coumarin derivative and an aldehyde in water as a solvent in shorter duration with high yields. 相似文献