Properties of Mechanochemically Synthesized Famatinite Cu3SbS4 Nanocrystals

In this study, we report the optoelectric and thermoelectric properties of famatinite Cu3SbS4 that was mechanochemically synthesized in a planetary mill from powder elements for 120 min in an inert atmosphere. The tetragonal famatinite Cu3SbS4 was nanocrystalline with a crystallite size of 14 nm, as endorsed by Rietveld refinement. High-resolution transmission electron microscopy showed several crystallites in the range of 20–50 nm. Raman spectroscopy proved the purity of the synthesized famatinite Cu3SbS4 and chemical-state characterization performed by X-ray photoelectron spectroscopy confirmed that the prepared sample was pure. The Cu1+, Sb5+, and S2− oxidation states in Cu3SbS4 sample were approved. The morphology characterization showed homogeneity of the prepared sample. The photoresponse of Cu3SbS4 was confirmed from I–V measurements in the dark and under illumination. The photocurrent increase reached 20% compared to the current in the dark at a voltage of 5 V. The achieved results confirm that synthesized famatinite Cu3SbS4 can be applied as a suitable absorbent material in solar cells. The performed thermoelectric measurements revealed a figure of merit ZT of 0.05 at 600 K

Magnetic losses reduction in grain oriented silicon steel by pulse and continuous fiber laser processing

The present paper shows the impact of different laser scribing conditions on possible reduction of magnetic losses in grain oriented electrical steel sheets. The experimental Fe-3%Si steel was taken from industrial line after final box annealing. The surface of investigated steel was subjected to fiber laser processing using both pulse and continuous scribing regimes in order to generate residual thermal stresses inducing the magnetic domains structure refinement. The magnetic losses of experimental samples before and after individual laser scribing regimes were tested in AC magnetic field with 50Hz frequency and induction of 1.5T. The most significant magnetic losses reduction of 38% was obtained at optimized conditions of continuous laser scribing regime. A semi quantitative relationship has been found between the domain patterns and the used fiber laser processing

ODS EUROFER Steel Strengthened by Y-(Ce, Hf, La, Sc, and Zr) Complex Oxides

Oxide dispersion-strengthened (ODS) materials contain homogeneous dispersions of temperature-stable nano-oxides serving as obstacles for dislocations and further pinning of grain boundaries. The strategy for dispersion strengthening based on complex oxides (Y-Hf, -Zr, -Ce, -La) was developed in order to refine oxide dispersion to enhance the dispersion strengthening effect. In this work, the strengthening of EUROFER steel by complex oxides based on Y and elements of the IIIB group (lanthanum, scandium) and IVB group (cerium, hafnium, zirconium) was explored. Interparticle spacing as a dispersoid characteristic appeared to be an important factor in controlling the dispersion strengthening contribution to the yield strength of ODS EUROFER steels. The dispersoid size and average grain size of ODS EUROFER steel were altered in the ranges of 5–13 nm and 0.6–1.7 µm, respectively. Using this strategy, the yield strength of the prepared alloys varied between 550 MPa and 950 MPa depending on the doping element

The Effects of Electrochemical Hydrogen Charging on Charpy Impact Toughness and Dry Sliding Tribological Behavior of AISI 316H Stainless Steel

In this work, solution-annealed AISI 316H grade austenitic stainless steel was studied in terms of investigating the electrolytic hydrogen charging effects on the resulting Charpy impact toughness and dry sliding tribological behavior. Conventional Charpy impact bending tests were employed to study the mechanical response of the investigated material to dynamic loading conditions, whereas dry linear sliding tribological tests were used to study material friction and wear behavior. The obtained mechanical and tribological properties were correlated with corresponding fracture and tribological mechanisms, which were determined from morphological observations of fracture surfaces and tribological tracks. The applied testing procedures were individually carried out for the non-hydrogenated, hydrogen-charged, and dehydrogenated material conditions. The observed changes in individual properties due to applied hydrogen charging were rather small, which indicated the good resistance of solution-annealed AISI 316H steel against material degradation in currently used electrolytic hydrogenation conditions

Possibilities of Repairing Functional Surfaces of Molds for Injecting Al Alloys Using Manual GTAW Cladding

The paper presents the results of research that is focused on the renovation of molds for high-pressure aluminum casting. An analysis of the worn molds was carried out after they were removed from the operator. The extent and mechanism of the wear were determined. GTAW (Gas tungsten arc welding) technology was chosen for the renovation of the shaped parts of the molds. The renovation layers were realized with four types of additional materials Cronitex RC 44, UTP A 73 G 3, UTP A 673 and Dievar® TIG. The quality of the coatings was assessed by destructive as well as non-destructive tests. The mixing of the build-up layers with the base material was determined on the basis of structural analyses. The hardness of the cladding was determined by a metallographic analysis of the cross crowns with the Vickers method. The resistance of the cladding was tested by a complete immersion in a melt of AlSi8Cu3 aluminum alloy which was maintained at a temperature of 680 ± 20 °C in a laboratory resistance furnace for 120 and 300 min. The tribological properties of the produced deposits were determined using the ball-on-disc dry method. Based on the experiments that were carried out, it is possible to recommend the additive material UTP A 73 G 3 for the restoration of the functional surfaces of molds for the injection of Al alloys as the patterns that were created by it have shown the best results in terms of their resistance to Al melt, which is the dominant degradation factor limiting the life of the molds

The Influence of Laser Surface Remelting on the Tribological Behavior of the ECAP-Processed AZ61 Mg Alloy and AZ61–Al2O3 Metal Matrix Composite

This paper deals with the tribological study of the laser remelted surfaces of the ECAP-processed AZ61 magnesium alloy and AZ61–Al2O3 metal matrix composite with 10 wt.% addition of Al2O3 nanoparticles. The study included the experimental optimization of the laser surface remelting conditions for the investigated materials by employing a 400 W continual wave fiber laser source. Tribological tests were performed in a conventional “ball-on-disc” configuration with a ceramic ZrO2 ball under a 5 N normal load and a sliding speed of 100 mm/s. The results showed that both the incorporation of Al2O3 nanoparticles and the applied laser treatments led to recognizable improvements in the tribological properties of the studied AZ61–Al2O3 composites in comparison with the reference AZ61 alloy. Thus, the best improvement has been obtained for the laser modified AZ61–10 wt.% Al2O3 nanocomposite showing about a 48% decrease in the specific wear rate compared to the laser untreated AZ61 base material

Structural and Tribological Studies of “(TiC + WC)/Hardened Steel” PMMC Coating Deposited by Air Pulsed Plasma

The deposition of a thin (several tens of microns) protective coating in atmospheric conditions is a challenging task for surface engineering. The structural features and tribological properties of a particle-reinforced metal matrix composite coating synthesized on middle-carbon steel by air pulse-plasma treatments were studied in the present work. The 24–31 µm thick coating of “24 vol.% (TiC + WC)/Hardened steel matrix” was produced by 10 plasma pulses generated by an electro-thermal axial plasma accelerator equipped with a consumable cathode of novel design (low-carbon steel tube filled with “TiC/WC + Epoxy resin” mixture). The study included optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD, microhardness measurements, and dry “Ball-on-Plate” testing. The carbides were directly plasma-transferred to the substrate (steel of AISI 4145H grade) from the cathode without substantial melting. The hard (500–1044 HV) coating matrix consisted of 57 vol.% austenite (1.43 wt.% C) and 43 vol.% plate martensite was formed via carbon enrichment of steel from plasma flow. Additionally, a minor amount of oxide phases (TiO2, WO2, WO3) were dispersed in the matrix. As compared to substrate, the coating had a lower coefficient of friction; its volumetric wear was decreased by 4.4 times when sliding against hardened steel ball and by 16 times when sliding against SiC ball

YAG Ceramic Nanocrystals Implementation into MCVD Technology of Active Optical Fibers

Nanoparticle doping is an alternative approach the conventional solution doping method allowing the preparation of active optical fibers with improved optical and structural properties. The combination of the nanoparticle doping with MCVD process has brought new technological challenges. We present the preparation of fiber lasers doped with Er-doped yttrium aluminum garnet (Er:YAG) nanocrystals. These nanocrystals, prepared by a hydrothermal reaction, were analyzed by several structural methods to determine the mean nanocrystal size and an effective hydrodynamic radius. The nanocrystals were incorporated into silica frits with various porosity made by the conventional MCVD process. The Er:YAG-doped silica frits were processed into preforms, which were drawn into optical fibers. We studied the effect of the nanocrystal size and frit’s porosity on the final structural and optical properties of prepared preforms and optical fibers. Selected optical fibers were tested as an active medium in a fiber ring laser setup and the characteristics of the laser were determined. Optimal laser properties were achieved for the fiber length of 7 m. The slope efficiency of the fiber laser was about 42%. Presented method can be simply extended to the deposition of other ceramic nanomaterials

Selected Properties of Hardfacing Layers Created by PTA Technology

The paper presents research results on the quality of hardfacing layers made during the renovation of unheated mold surfaces designed for injection of aluminum alloys using the plasma transferred arc (PTA) technology. As mold material, the medium alloy steel X38CrMoV5-1 (H11) was used. For the formation of functional layers, three types of additives in the form of powder were applied: two types on an iron basis with the designation HSS 23 and HSS 30 and one type on a nickel basis with the designation DEW Nibasit 625-P. The hardfacing layers were made on a 120 × 350 × 50 mm plate in two layers on the plasma hardfacing machine PPC 250 R6. The quality of the layers was evaluated by means of nondestructive and destructive tests. The surface integrity of the layers was assessed using visual and capillary tests. The samples passed these tests. The impact of the parameters used and the mixing of the hardfacing metal with base material, as well as the structure analysis, were assessed by means of light and electron microscopy (SEM). The chemical composition of the elements was determined by energy-dispersive X-ray spectroscopy (EDX) analysis using a SEM microscope. The hardness of the individual layers was evaluated. Since, during operation, molds are subjected to significant wear due to friction, the friction coefficients for selected temperatures were determined by the equipment for the evaluation of tribology properties. Based on the experiments conducted, all three types of additives can be used for renovation. However, from a tribology perspective, the additive DEW Nibasit 625-P on a nickel alloy basis is recommended for renovation