Protection of Metals and Physical Chemistry of Surfaces最新文献

The emission released by diesel engines NO_x, CO, CO₂, and HC leads to human discomfort and environmental changes. Coating on the piston is an efficient method and innovative approach to decrease emissions in diesel engines. In this work, coating is carried out on the piston crown in a single-cylinder diesel engine and is compared with the uncoated piston. The percentage composition was coated on the piston crown namely, 95% ZrO₂ + 5% TaC, 97% ZrO₂ + 3% TaC, 98% ZrO₂ + 2% TaC, and 100% ZrO₂ using plasma spray coating. The brake thermal efficiency of the piston coated with a mixture of 95% ZrO₂ and 5% TaC is 8.1% more than that of the uncoated piston. Similarly, the mechanical efficiency of the coated piston is 11.6% greater than that of the unprotected piston.

The adsorption potential of Vigna mungo husk was evaluated for phosphate uptake from aqueous solutions. The vanadate–molybdate and liquid batch methods were used to investigate the effect of various physico-chemical factors such as adsorbent dose, initial phosphate concentration, temperature, pH, and contact time on the adsorption efficiency of Vigna mungo husk particle sizes 1, 2, and 3. Results on Temkin, Freundlich equilibrium, and Langmuir adsorption isotherms confirmed that the data fitted well to the Langmuir isotherm but was unfit to the Freundlich isotherm and the Temkin isotherm. The adsorption capacities (q_max) on monolayer coverage were found to be 10.4263, 10.3854, and 10.3608 mg/g for particle sizes 1, 2, and 3 at 301 K temperature. At 311 K temperature, the monolayer adsorption capacities were found to be 10.4345, 10.3936, and 10.3854 mg/g. At 321 K temperature, the monolayer adsorption capacities were found to be 10.1524, 10.410, and 10.4018 mg/g. At 331 K temperature the monolayer adsorption capacities were found to be 10.4837, 10.4182, and 10.410 mg/g. Similarly, at 341 K temperature, the monolayer adsorption capacities were found to be 10.5493, 10.4345, and 10.4263 mg/g. Pseudo-first-order and pseudo-second-order kinetics were analyzed at different time intervals and concentrations of phosphate. The kinetic data fitted well with the pseudo-second-order kinetics, as the calculated value of q_e in this model was observed very close to the experimental value of q_e. Outcomes on the thermodynamic factors (ΔG°, ΔH°, ΔS°) showed the spontaneous, feasible, and endothermic nature of adsorption.

The review is devoted to generalizing the results of studies of the relaxation behavior of latex acrylate polymers used as a binder in composite coatings on surfaces of various chemical nature, and structure in order to clarify the temperature ranges of their elastic and inelastic (dissipative) properties at temperatures from –150 to +200°C. Part 1.1 analyzes experimental data on the spectrum of internal friction and temperature–frequency dependences of the oscillatory process in statistical latex polyacrylates in comparison with polyacrylates of the free radical type obtained using the method of dynamic relaxation spectroscopy, which demonstrates the prospect of using the method to describe the physicomechanical properties of acrylate copolymers of various monomeric composition.

The charge carrier mobility of doped tris(8-hydroxyquinolinato)aluminum (AlQ₃) have been investigated in detail. Substituted lithium quinolate complexes are used as molecular n-type dopant in AlQ₃. Dopant concentration dependent charge carrier mobility have been investigated in detail and compared. Effect of substituent (electron donating or withdrawing) on the dopant molecules have also been analysed. In this study, bilayer device structure was fabricated on the patterned ITO coated glass substrate. Applied field dependent mobility of the fabricated devices were investigated and analysed. The highest electron mobility of 1.63 × 10^–4 and 6.92 × 10^–5 cm²/V s for 20% LiMeQ and LiClQ doped AlQ₃, respectively at the applied electric field of 1050 (V/cm)^1/2.

Polystyrene/halloysite composite film materials were prepared by the mechanical dispersion method. Differential scanning calorimetry and thermogravimetric analysis were used to examine thermal destruction and relaxation transitions in the prepared composites. It was established that modification of polystyrene with halloysite raised the glass-transition temperature. The characteristic thermal destruction temperatures of the composite were found to exceed those of the unmodified polymer. The kinetic parameters of the thermal decomposition were determined using the Freeman–Carroll method.

Ni–W thin films are fabricated on an ITO coated glass substrate by varying the current density. Cyclic voltammetry is carried out to know the required range of deposition potential for the synthesis of thin films. The influence of electrodeposition parameters on composition, crystal structure, micro-strain and corrosion properties of the film is studied. The presence of diffraction peaks at 2θ values of 43.9°, 50.7°, and 74° corresponding to (111), (200), and (220) planes have confirmed the face centered cubic structure of Ni–W films. Additionally, the (110) and (101) diffraction peaks recorded at 2θ values of 21.3° and 30.4° are attributed to the formation of Ni₄W phase. The formation of homogeneous, compact and cauliflower like morphology is confirmed by high resolution FESEM. The corrosion behavior of the films is investigated using Tafel Polarization technique in a 3.5 wt % NaCl solution. Ni–W film deposited at a current density of ‒50 mA/cm² has shown corrosion potential of –276 mV and highest corrosion resistance of 1917 Ω-cm². The enhanced corrosion resistance of Ni–W alloy is caused by the preferential dissolution of Ni and the formation of a W-rich film on the surface, which prevented additional corrosion.

The present study aimed to investigate the effects of heating rates and solid solution time on the microstructure and properties of hot-pressed 7085 aluminum alloy This was achieved through various tests, including metallographic analysis, hardness and conductivity tests, X-ray diffraction (XRD) analysis, electron backscatter diffraction (EBSD) scanning test, and corrosion test. The results revealed that the tensile strength of the alloy was enhanced by a slow heating rate (3.6°C/h) and a short holding time (470°C × 2 h) during the solution treatment, up to the maximum tensile strength of 585.74 MPa. On the other hand, rapid heating rate (180°C/h) and short holding time (470°C × 2 h) increased the elongation of the alloy, with a maximum value of 16.94%. This increase in elongation can be attributed to the occurrence of recovery during the slow heating rate, which transformed numerous dislocations into low-angle grain boundaries, thereby strengthening the effect of dislocations and low-angle grain boundaries. Besides, an increase in holding time resulted in increased recrystallization of the alloy, which weakened the dislocation and low-angle grain boundary strengthening. Furthermore, the study found that the heating rate and solution time did not have a significant impact on the hardness and electrical conductivity of the alloy. The maximum intergranular corrosion depth recorded was 86.72 mm, and the corrosion resistance of the alloy was improved through a solution treatment involving the rapid heating rate and long-time holding. Finally, the study observed that the exfoliation corrosion resistance of the alloys after different solution treatments was similar, with all being rated as P grade.

Effects of cerium (Ce) on the microstructure and corrosion resistance of high manganese steel (HMS) in 3.5 wt % NaCl were investigated. It was found that the carbides in the grain boundaries in HMS were refined with the addition of Ce. The corrosion current density was reduced to about one-fifth of the original with the addition of Ce, and the resistance of the oxide film (R_f) with the addition of Ce was 2.549 × 10³ Ω cm^–2, which was increased by nearly an order of magnitude compared with that of without Ce addition. When Ce was added, the degree of segregation of carbides in the HMS substrate was weakened, and the entire corrosion process was dominated by uniform corrosion. The corrosion product film of HMS with the addition of Ce was relatively dense and uniform. The corrosion resistance of HMS with the addition of Ce was improved significantly. The influence mechanisms of Ce on the microstructure and corrosion resistance of HMS are also discussed.

Upon interaction of free-base 12-crown-4-substituted porphyrin with rhodium chloride trihydrate RhCl₃·3H₂O in benzonitrile, corresponding rhodium(III) crown-porphyrinate is obtained in a high yield. The structure of the obtained complex of rhodium(III) is determined based on the data of mass spectrometry, chemical analysis, electron absorption spectroscopy, and luminescence spectroscopy. An analysis of the luminescence properties of this compound in a DMSO–water solution and a polystyrene film is carried out. An analysis of the interaction of obtained rhodium(III) 12-crown-4-porphyrinate with sodium, potassium, and calcium cations in a solution is performed based on the data of electron absorption spectroscopy. The complex is not prone to self-association of the molecules in a DMSO–water solution and may be of interest as a photosensitizer for generation of singlet molecular oxygen. It is found that novel rhodium(III) crown-porphyrinate possesses fluorescence and phosphorescence properties in a polystyrene film and may be of interest as a luminescence temperature sensor by the ratio of the intensity of transitions of phosphorescence to fluorescence.

To improve the hardness of AlCoCrFeNi high-entropy alloy coatings, Ti and WC are added to the high-entropy alloys in this paper. Composite coatings of AlCoCrFeNi, Ti, and x-WC (x = 3, 6, 9 wt %) on the surface of H13 hot work die steel are prepared by laser cladding. Coatings are characterized by hardness test, electrochemical test, friction and wear experiment, X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and EBSD (electron backscatter diffraction). The results reveal that the crystal structure of the coatings does not alter after the addition of Ti and WC. Coatings consisting of BCC/B2 and precipitated phases. BCC/B2 phases are mainly Al–Ni, and Fe–Cr phases. The precipitated phases are the WC and TiC phases. The results indicate that the hardness is improved after the addition of Ti and WC. Besides, the wear mechanism becomes different, and the grain size is refined. Coating hardness is increased from 528.9HV_0.5 to 625.3HV_0.5. Wear mechanisms change to oxidative, adhesive, and abrasive wear with the addition of Ti and WC. The precipitation of the second phase deteriorates the corrosion resistance of the coatings.