Volume 114, Issue 12

In this study, nanocrystalline PbS film coating on a glass slide was done using the chemical bath deposition method. PbS film was deposited in an alkaline solution using Pb(NO 3 ) 2 , CS(NH 2 ) 2 , and the inhibitor (Na 2 S 2 O 3 ) for 30–120 min at room temperature (25 °C) and 40 °C, and inhibitor levels were investigated in the range of 3.2 mM–12.7 mM. The physicochemical properties of the obtained thin films were investigated by scanning electron microscopy, MAPPING, atomic force microscopy, fourier-transform infrared spectroscopy, water contact angle and X-ray diffraction analyses. The relationship between nanocrystallite size, distribution, pin-hole development, and synthesis conditions were examined using image processing and surface response methodology. The band gap of the produced PbS thin film was calculated using FT-IR analysis results (0.41 eV).

NiCr coatings were prepared on H13 steel by laser cladding with different laser power. The microstructure and phases of the obtained coatings were analyzed using a super depth of field microscope and X-ray diffraction, respectively, and the effect of laser power on the friction–wear performance at high-temperature was investigated using a friction tester. The results show that the laser clad NiCr coatings fabricated at the different laser powers are composed of Cr 2 Ni 3 and FeNi 3 phases, and the porosity is decreased from 1.28 % to 0.48 % with the increase of laser power. The average coefficients of friction of NiCr coatings are decreased with the increase of laser power, and the wear rate of NiCr coating fabricated at the laser power of 1400 W power is the lowest among the three kinds of coatings, showing that the suitable laser power can improve the surface quality and wear resistance of NiCr coating.

The mechanical properties and corrosion resistance of annealed superferritic stainless steel model alloy 25Cr–6Mo–5Ni were investigated in 0.6 M NaCl solution. The microstructure consisted of a ferrite matrix and eutectoid phase with a lamellar structure distributed at grain boundaries and within the ferrite grains with a spherical morphology. Tensile and impact results suggested brittle behavior of the model alloy. Fractography analysis revealed typical cleavage facets, river patterns and micro-cracks at grain boundaries and across the ferrite grains. Pitting corrosion began within the eutectoid phase, which contains in chrome depletion zones. Electrochemical impedance spectroscopy measurements suggest that the breakdown of passive films was more susceptible in the eutectoid phase.

The elongation of two low temperature bainitic steels with different sulfur contents was compared under the same heat treatment. Elongations of 1.0 ± 0.5 % and 11.4 ± 1.5 % were achieved for the high- and low-S steels, respectively. A high carbon concentration and fine grain size leading to over stability of the retained austenite in the high-S steel is the main reason for the poor elongation. The differences in carbon concentration and grain size between the two steels can be attributed to pinning by MnS, where the existence of a large number of long slivers of MnS in the high-S steel was responsible for the pinning. The stability of retained austenite was also analyzed by the local tensile elongation and hardness, and the volume fraction of retained austenite that transformed to martensite during the tensile process.

Fiber-reinforced composites have changed additive manufacturing into a sustainable manufacturing paradigm with the capacity to produce items with outstanding mechanical performance. The fused filament fabrication (FFF) process is the latest in advanced digital fabrication techniques used for fabricating polymer material using additive layer deposition. In this study, the results of mechanical and vibration tests were used to examine the impact of process variables such as layer thickness (0.08 mm, 0.25 mm, and 0.64 mm), infill density (20 %, 40 %, 60 %, and 80 %), and infill pattern (rectilinear, triangular, and hexagonal). The novelty of this work is to correlate the contact angle measurement with the mechanical properties of the 3D-printed specimens. The adhesion behaviour of the 3D printed parts is examined by measuring the contact angle from the wettability test. From the findings, it was observed that the infill density and layer pattern play a significant role in the interlayer adhesion, as evident from the contact angle measurement.

The CALPHAD (CAlculation of PHAse Diagrams) technique is used in the critical remodeling of the Cd–Ce system. On the basis of new experimental data in the literature, the excess Gibbs energies of the solution phase expression (liquid, bcc, fcc, and hcp_A3) are described using the Redlich–Kister equation. Four compounds (Cd 3 Ce, Cd 6 Ce, Cd 11 Ce, and Cd 17 Ce 2 ) are treated as stochiometric compounds. Two intermetallic compounds (Cd 2 Ce and Cd 58 Ce 13 ), which exhibit a little homogeneity range, are treated as a two-sublattice model. Two thermodynamic models are used for the CdCe and bcc. Model I is to model the compound CdCe and bcc-Ce separately. Model II is to use the formula (Cd, Ce) 0.5 (Cd, Ce) 0.5 (Va) 3 to describe the compound CdCe with a CsCl-type structure (B2) and cope with the disorder–order transition from bcc-A2 to bcc-B2. The present work shows that four eutectic reactions, three peritectic reactions, two eutectoid reactions, one peritectoid transformation and three congruent reactions are observed, and the stoichiometric compound Cd 17 Ce 2 is only stable from 804 to 882 °C in the Cd–Ce system.

The phase relations of the Fe–Pt–Ho ternary system at 500 °C have been studied by using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. The Ho 3 Pt 4 phase is stable at 500 °C, and the introduction of Fe does not cause the Ho 3 Pt 4 phase to be decomposed into the two neighbouring phases HoPt and HoPt 2 . The single phase ranges of α-Fe, Fe 3 Pt, FePt, FePt 3 and Pt in Fe–Pt binary system are from 0 to 10 at.% Pt, 14 to 32 at.% Pt, 33 to 63 at.% Pt, 66 to 78 at.% Pt, and 82 to 100 at.% Pt, respectively. The highest solid solubility of Ho in the α-Fe, Fe 3 Pt, FePt, FePt 3 and (Pt, Fe) phases is less than 1.5 at.% Ho, 2 at.% Ho, 2 at.% Ho, 1.5 at.% Ho and 1.5 at.% Ho, respectively. The isothermal section at 500 °C of the Fe–Pt–Ho ternary alloy phase diagram has been constructed, which consists of 19 single-phase regions, 35 two-phase regions and 17 three-phase regions. No new ternary compounds were found.

Trivalent gadolinium (Gd 3+ )-doped calcium zinc silicate (Ca 2 ZnSi 2 O 7 /hardystonite) with a molar composition of Ca 2− x ZnSi 2 O 7 : x Gd 3+ ( x = 0.09 mol) was produced using a sol–gel system. The hardystonite was characterized using X-ray diffraction and Fourier transform infrared spectroscopy. The X-ray diffraction study revealed that the prepared sample contained a tetragonal phase of Ca 2 ZnSi 2 O 7 . The vibrational structures of the sample were studied using Fourier transform infrared spectroscopy measurements. The photoluminescence emission spectrum of the Ca 1.91 ZnSi 2 O 7 :0.09Gd 3+ phosphor narrow band was optimized at 312 nm in the Ultraviolet-B region under excitation at 273 nm wavelength. Electron paramagnetic resonance study authenticates the presence of gadolinium (Gd) ions within the trivalent state in the Ca 1.91 ZnSi 2 O 7 :0.09Gd 3+ host.

This study examines the optical properties of Ca 2 La 8− x (SiO 4 ) 6 O 2 : x Ho 3+ phosphors derived using the sol–gel method. X-ray diffraction data and Rietveld analysis confirmed that the phosphors formed in hexagonal phase with an average estimated crystalline size of 27 nm. The prominent excitation peak observed at wavelength 463 nm corresponding to excitation energy 2.68 eV was due to the 5 I 8 → 5 G 6 + 5 F 1 transition. The photoluminescence emission spectra revealed that the synthesized phosphors emitted in the green color region with the 5 S 2 + 5 F 4 → 5 I 8 transition, releasing 2.27 eV energy. The emission and excitation analyses revealed the presence of concentration quenching as the Ho 3+ concentration exceeded 0.03 mol in the Ca 2 La 8− x (SiO 4 ) 6 O 2 : x Ho 3+ series. Further, photometry analysis demonstrated a color purity exceeding 94 %, which supports the candidacy of these phosphors for solid-state lighting applications.

The thermal stability of Al 3 BC 3 powders under nitrogen was studied. AlN–BN composites were generated during the nitridation of Al 3 BC 3 . Possible reaction mechanisms responsible for the thermal decomposition of Al 3 BC 3 powders were discussed. The relatively weaker Al–C bonds in Al 3 BC 3 promoted the fast diffusion of Al and the generation of AlN–BN layers inhibited the deeper nitridation, thus the thermal decomposition was governed by surface reaction. The formed nitrides resulted in a volume change and cracked the resulting layers as the reactions progressed, facilitating the diffusion of N 2 and enhanced the decomposition of Al 3 BC 3 . The intensive reaction involving Al 3 BC 3 and N 2 could be attributed to the prolonged reaction time at high temperature and continued escape of vaporized Al and B. This result contributes to a theoretical basis of high-temperature application of Al 3 BC 3 under nitrogen.