The influence of cementite spheroidization on the impact toughness and electrochemical properties of a high-carbon steel has been thoroughly investigated in this study. Heavy warm rolling, followed by 2 h of annealing, has resulted in near-complete spheroidization, leading to a microstructure consisting of nano-cementite globules dispersed in the ultrafine-grained ferritic matrix. The Charpy impact test exhibited superior impact toughness with increased spheroidization. It is validated by the presence of abundant dimples in the fractographs of spheroidized specimens, in contrast to the as-received one that experienced a brittle failure due to its lamellar pearlitic structure. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) carried out in a 3.5% NaCl solution revealed that the corrosion resistance of the alloy gets improved with the increase in the degree of spheroidization. This is attributed to the lower susceptibility of the spheroidized specimen to microgalvanic corrosion owing to the minimum area of contact between nano-spheroidized cementite and ferrite, as elucidated with the help of EIS results aided by equivalent electrical circuit model. 相似文献
Layers of naturally occurring clay minerals are rearranged to prepare highly sensitive multiresponsive clay–clay bilayer membrane (CCBM). The CCBM introduced here responds to the minuscule changes in the surrounding environments including temperature, humidity, and presence of solvent vapors by morphing in specific manners. Strips cut from CCBM exhibit up to 588 N kg?1 force output when exposed to temperature fluctuations. Inheriting the natural stability of clay minerals, CCBM demonstrates extreme robustness, heating up to 500 °C, cooling with liquid N2 and exposure to corrosive chemical vapors did not deteriorate its bending performance. Mechanistic studies suggest that shape transformations of CCBM are driven by the unequal response of its components to external stimuli. 相似文献
Aliphatic hyperbranched poly(urethane-urea)s with different weight percentages of branch generating moiety were synthesized by a one pot A2 + BC2 approach. Isophorone diisocyanate was used as the A2 type monomer, while a tri-functional dihydroxyamine compound synthesized from ?-caprolactam and diethanol amine acted as the BC2 monomer. Evidence supporting the hyperbranched structure of the synthesized poly(urethane-urea) was obtained from 1H NMR spectra. FTIR study confirmed the nature and extent of hydrogen bonding present in this novel macromolecule. A Gaussian band fitting procedure of the IR band at amide-I region showed that the extent of hydrogen bonding increases with the increase of weight percentage of the tri-functional compound. The tensile strength, elongation at break, impact resistance, scratch hardness and gloss followed an increasing trend with the same. The thermal degradation of the hyperbranched poly(urethane-urea) was found to be dependent on the weight percentage of the BC2 type moiety. The kinetics of thermal degradation studied by the Ozawa method showed that the activation energy required for thermal degradation of hyperbranched polymer is higher than its linear polyurethane analog. The synthesized polymer was found to be biodegradable by Pseudomonas aeruginosa bacteria. The study showed superiority of the hyperbranched structure over the linear one. Thus the results indicated the potential usage of the studied hyperbranched poly(urethane-urea) as an advanced surface coating material. 相似文献
A study was conducted to evaluate the nutritional potential of four commonly available, unexplored aquatic weeds namely, Salvinia cuculata, Trapa natans, Lemna minor and Ipomoea reptans from northeast India for ascertaining their suitability for utilization as supplementary fish feed with the aim to reduce the cost of commercial feeds. Results of proximate analysis showed that the crude protein content of the aquatic weeds ranged between 11.0% and 32.2% (w/w), whereas crude fibre and ash contents varied between 4.2% and 20% (w/w), and 13.3% and 31.2% (w/w), respectively. Protein to energy ratio (P/E) of these weeds ranged between 30.7 mg/kcal and 95.3 mg/kcal and the highest value was displayed by I. reptans. All these aquatic weeds contained high amounts of vitamins E and C and mineral elements required for the normal growth and development of fish. 相似文献
The copper(II)‐catalyzed decarboxylative coupling reactions of arylglyoxylic acids with isatins afford 4H‐benzo[d][1,3]oxazin‐4‐ones via decarbonylation and concurrent C–N, C–O bond formation.
The anodic dissolution of U and Zr metal was studied in LiCl–KCl–UCl3 and LiCl–KCl–ZrCl4, respectively, at 773 K by cyclic voltammetry and compared with their respective dissolution behaviour in blank LiCl–KCl eutectic. The anodic dissolution of U–Zr alloy in LiCl–KCl–UCl3 was also studied at 773 K to compare with the dissolution of U and Zr. The transfer coefficients evaluated by Tafel analysis and the method of Allen–Hickling for U and Zr dissolution were found to be in fair agreement with each other. U dissolution in LiCl–KCl–UCl3 and Zr dissolution LiCl–KCl–ZrCl4 were also studied by chronoamperometry and the diffusion coefficient value of U3+ was calculated to be in the range of 2.9 × 10−5 to 3.3 × 10−5 cm2 s−1 which is in agreement with those reported in literature. Convolution voltammetric analysis of Zr4+/Zr2+ redox couple in LiCl–KCl–ZrCl4 was carried out for the first time to have a comprehensive understanding of the electrode kinetics. 相似文献
A transdermal drug delivery system of diclofenac was developed for prolonged and controlled release of diclofenac. The designed system essentially based on polymeric pseudolatex dispersion. The formulation variables that could effect the formulation stability vis a vis drug release were studied. To achieve the desired release rate, different combination of hydrophilic and hydrophobic polymer were used for the preparation of pseudolatex system. The designed system exhibited linear relationship between drug release (Q) V/s square root of time (t0.5). The product having skin permeability rate 0.188 mg/h/cm was selected for the in vitro anti-inflammatory activity and in vivo evaluation. The system could maintained a constant and effective plasma level for 24 hours. The effective drug plasma concentration was monitored periodically. The study revealed that designed pseudolatex transdermal drug delivery system of diclofenac could be used successfully with improved performance and hold promise for further studies. 相似文献