Publikační činnost Katedry neželezných kovů, rafinace a recyklace / Publications of Department of Non-ferrous Metals (637)

Permanent URI for this collectionhttp://hdl.handle.net/10084/64790

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Katedry neželezných kovů, rafinace a recyklace (637) v časopisech registrovaných ve Web of Science od roku 2003 do roku 2022.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

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Study of bond formation in ceramic and composite materials ultrasonically soldered with Bi–Ag–Mg-type solder
(MDPI, 2023) Koleňák, Roman; Meluš, Tomáš; Drápala, Jaromír; Gogola, Peter; Pašák, Matej
This research aimed to study a Bi–Ag–Mg soldering alloy and the direct soldering of Al2O3 ceramics and Ni–SiC composites. Bi11Ag1Mg solder has a broad melting interval, which mainly depends on the silver and magnesium content. The solder starts to melt at a temperature of 264 ◦C. Full fusion terminates at a temperature of 380 ◦C. The microstructure of the solder is formed by a bismuth matrix. The matrix contains segregated silver crystals and an Ag (Mg, Bi) phase. The average tensile strength of solder is 26.7 MPa. The boundary of the Al2O3/Bi11Ag1Mg joint is formed by the reaction of magnesium, which segregates in the vicinity of a boundary with a ceramic substrate. The thickness of the high-Mg reaction layer at the interface with the ceramic material was approximately 2 µm. The bond at the boundary of the Bi11Ag1Mg/Ni–SiC joint was formed due to the high silver content. At the boundary, there were also high contents of Bi and Ni, which suggests that there is a NiBi3 phase. The average shear strength of the combined Al2O3/Ni–SiC joint with Bi11Ag1Mg solder is 27 MPa.
Phase transformation after heat treatment of Cr-Ni stainless steel powder for 3D printing
(MDPI, 2022) Čech Barabaszová, Karla; Slíva, Aleš; Kratošová, Gabriela; Holešová, Sylva; Volodarskaja, Anastasia; Cetinkaya, Tugrul; Brožová, Silvie; Kozubek, Libor; Simha Martynková, Gražyna
Today, Ni-Cr steel is used for advanced applications in the high-temperature and electrical industries, medical equipment, food industry, agriculture and is applied in food and beverage packaging and kitchenware, automotive or mesh. A study of input steel powder from various stages of the recycling process intended for 3D printing was conducted. In addition to the precise evaluation of the morphology, particle size and composition of the powders used for laser 3D printing, special testing and evaluation of the heat-treated powders were carried out. Heat treatment up to 950 degrees C in an air atmosphere revealed the properties of powders that can appear during laser sintering. The powders in the oxidizing atmosphere change the phase composition and the original FeNiCr stainless steel changes to a two-phase system of Fe3Ni and Cr2O3, as evaluated by X-ray diffraction analysis. Observation of the morphology showed the separation of the oxidic phase in the sense of a brittle shell. The inner part of the powder particle is a porous compact core. The particle size is generally reduced due to the peeling of the oxide shell. This effect can be critical to 3D printing processing, causing defects on the printed parts, as well as reducing the usability of the precursor powder and can also change the properties of the printed part.
Mechanical characterization of graphene nanoplatelets-reinforced Mg-3Sn alloy synthesized by powder metallurgy
(MDPI, 2021) Kumar, Pravir; Skotnicová, Kateřina; Mallick, Ashis; Gupta, Manoj; Čegan, Tomáš; Juřica, Jan
The present study investigated the effects of alloying and nano-reinforcement on the mechanical properties (microhardness, tensile strength, and compressive strength) of Mg-based alloys and composites. Pure Mg, Mg-3Sn alloy, and Mg-3Sn + 0.2 GNP alloy-nanocomposite were synthesized by powder metallurgy followed by hot extrusion. The microstructural characteristics of the bulk extruded samples were explored using X-ray diffraction, field-emission scanning electron microscopy, and optical microscopy and their mechanical properties were compared. The microhardness, tensile strength, and compressive strength of the Mg-3Sn alloy improved when compared to those of monolithic Mg sample and further improvements were displayed by Mg-3Sn + 0.2 GNP alloy-nanocomposite. No significant change in the compressive strain to failure was observed in both the alloy and the alloy-nanocomposite with respect to that of the pure Mg sample. However, an enhanced tensile strain to failure was displayed by both the alloy and the alloy-nanocomposite.
Structure and properties of cast Ti-Al-Si alloys
(MDPI, 2021) Knaislová, Anna; Novák, Pavel; Linhart, Jiří; Szurman, Ivo; Skotnicová, Kateřina; Juřica, Jan; Čegan, Tomáš
Intermetallic compounds based on Ti-Al- (Si) are attractive materials with good thermal stability and low density. However, the production of these materials is quite complicated. Partially modified conventional methods of melting metallurgy are most often used due to availability, possible high productivity, and relatively low production costs. Therefore, some technologies for the production of intermetallics based on Ti-Al are currently available, but with certain disadvantages, which are caused by poor casting properties or extreme reactivity of the melt with crucibles. Some shortcomings can be eliminated by modifying the melting technology, which contributes to increasing the cost of the process. The work deals with the preparation of Ti-Al-Si intermetallic compounds with different contents of aluminum and silicon, which were produced by centrifugal casting in an induction vacuum furnace Linn Supercast-Titan. This process could contribute to the commercial use of these alloys in the future. For this research, the TiAl15Si15(in wt.%) alloy was selected, which represents a balanced ratio of aluminides and silicides in its structure, and the TiAl35Si5 alloy, which due to the lower silicon content allows better melting conditions, especially with regard to the melting temperature. This alloy was also investigated after HIP ("Hot Isostatic Pressing") treatment.
Characterization of waste sludge pigment from production of ZnCl2
(MDPI, 2021) Ovčačíková, Hana; Velička, Marek; Maierová, Petra; Vlček, Jozef; Tokarský, Jonáš; Čegan, Tomáš
This study is focused on the treatment of waste sludge from a zinc chloride production in order to prepare iron-rich pigments usable for a production of glazes. In galvanizing plants, yellow waste sludge containing significant amount of ZnO, Cl, and Fe2O3, is formed. This raw waste sludge cannot be used as a pigment in glaze. Therefore, three methods of treating this material were proposed: (a) washing with H2O, (b) calcination at 180 degrees C and washing by H2O, and (c) calcination at 900 degrees C and washing by H2O. These methods helped to reduce Zn and Cl content up to 97%. According to X-ray fluorescence analysis percentage of Fe2O3 increased from similar to 41% to similar to 98%. X-ray power diffraction analysis confirmed the formation of alpha-Fe2O3 (hematite) in the pigment prepared. Scanning electron microscopy with Energy dispersive X-ray analysis showed clusters of rounded particles, and also the change in size of particles after calcination was observed. Particle size, specific surface area, and density measurements together with thermogravimetric and differential thermal analyses were performed. Pigments prepared from the waste sludge were added to transparent glaze in amounts of 1, 5, 10, and 15 wt.%. Pigment-containing glazes were applied by spraying on fired ceramic tiles and then fired at 1060 degrees C. Color of glazes was determined by (Commission Internationale de l'Eclairage) CIE L*a*b* coordinates as colorless, light brown shades, brown-red, brown-yellow, and deep red-brown. Comparison with colors of glazes prepared using commercial pigments was also performed. Waste sludge can be used to prepare pigments and glazes containing pigments as an alternative to commercial products.
Characterization of Sn-Sb-Ti solder alloy and the study of its use for the ultrasonic soldering process of SiC ceramics with a Cu-SiC metal-ceramic composite
(MDPI, 2021) Koleňák, Roman; Kostolný, Igor; Drápala, Jaromír; Babincová, Paulína; Pašák, Matej
The aim of this research was to characterize soldering alloys of the type Sn-Sb-Ti and to study the ultrasonic soldering of SiC ceramics with a metal-ceramic composite of the type Cu-SiC. The Sn5Sb3Ti solder exerts a thermal transformation of a peritectic character with an approximate melting point of 234 & DEG;C and a narrow melting interval. The solder microstructure consists of a tin matrix, where the acicular constituents of the Ti-6(Sb,Sn)(5) phase and the sharp-edged constituents of the TiSbSn phase are precipitated. The tensile strength of the soldering alloy depends on the Ti content and reaches values from 34 to 51 MPa. The average strength of the solder increases with increasing Ti content. The bond with SiC ceramics is formed owing to the interaction of titanium, activated by ultrasound, with SiC ceramics, forming the (Ti,Si)(6)(Sb,Sn)(5) reaction product. The bond with the metal-ceramic composite Cu-SiC is formed owing to the solubility of Cu in a tin solder forming two phases: the wettable eta-Cu6Sn5 phase, formed in contact with the solder, and the non-wettable epsilon-Cu3Sn phase, formed in contact with the copper composite. The average shear strength of the combined joint of SiC/Cu-SiC fabricated using the Sn5Sb3Ti solder was 42.5 MPa. The Sn-Sb-Ti solder is a direct competitor of the S-Bond active solder. The production of solders is cheaper, and the presence of antimony increases their strength. In addition, the application temperature range is wider.
The effect of rare earth metals alloying on the internal quality of industrially produced heavy steel forgings
(MDPI, 2021) Jonšta, Petr; Jonšta, Zdeněk; Brožová, Silvie; Ingaldi, Manuela; Pietraszek, Jacek; Klimecka-Tatar, Dorota
The paper presented the findings obtained by industrial research and experimental development on the use of rare earth metals (REMs) in the production of heavy steel ingots and their impact on the internal quality of the 42CrMo4 grade steel forging. REMs alloying was carried out after vacuuming the steel. A relatively large melting loss of cerium (about 50%) and its further decrease in casting due to reoxidation were observed. Refinement of structure and better mechanical properties of forged bar containing about 0.02 wt.% of Ce compared to that of the standard production were not achieved. The wind power shaft with content of about 0.06 wt.% of Ce showed high amount of REM inclusions, which were locally chained, and in some cases, initiated cracks. Four stoichiometrically different types of REM inclusions were detected in forgings, namely (La-Ce)(2)O2S + (La-Ce)O-2 + SiO2 (minority); oxygen, phosphorus, arsenic, and antimony bound to lanthanum and cerium probably bonded with iron oxides La + Ce, MgO, Al2O3 a SiO2; (La-Ce)(2)O2S, FeO, SiO2, and CaO or CaS.
Hydrometallurgical recycling process for mobile phone printed circuit boards using ozone
(MDPI, 2021) Brožová, Silvie; Lisińska, Magdalena; Saternus, Mariola; Gajda, Bernadeta; Simha Martynková, Gražyna; Slíva, Aleš
Printed circuit boards (PCBs) can be an important source of non-ferrous metals (Al, Sn, Zn, and Ni) and precious metals (Au, Ag, Cu, and Pd). With the continuous increase in demand for metals due to the depletion of ores, recycling of this waste is becoming an attractive alternative. The printed circuits also contain hazardous metals, such as Pb, Hg, As, and Cd. Due to the huge increase in the amount of e-waste, the processing of printed circuit boards for metal recovery and proper handling of hazardous substances has a positive effect on the environment. Pyrometallurgical and hydrometallurgical methods are used for the treatment of this waste. Various oxidizing agents are used in the hydrometallurgical processes, including ozone. PCBs from mobile phones were assessed for the recovery of Cu, Sn, and precious metals. The ground and sieved materials were leached in nitric acid, hydrochloric acid, and sulfuric acid at various process parameters, such as leaching time, leaching agent, and temperature. It was found that the best result was obtained using hydrochloric acid with the addition of ozone at 353 K for a period of 4 h to obtain 68.45 g/dm(3) of copper. Preliminary results of electrolysis and cementation are also presented.
Characterization of soldering alloy type Bi-Ag-Ti and the study of ultrasonic soldering of silicon and copper
(MDPI, 2021) Koleňák, Roman; Kostolný, Igor; Drápala, Jaromír; Babincová, Paulína; Gogola, Peter
The aim of the research work was to characterize the soldering alloy type Bi-Ag-Ti and to study the direct soldering of silicon and copper. Bi11Ag1.5Ti solder has a broad melting interval. Its scope depends mainly on the content of silver and titanium. The solder begins to melt at the temperature of 262.5 degrees C and full melting is completed at 405 degrees C. The solder microstructure consists of a bismuth matrix with local eutectics. The silver crystals and titanium phases as BiTi2 and Bi9Ti8 are segregated in the matrix. The average tensile strength of the solder varies around 42 MPa. The bond with silicon is formed due to interaction of active titanium with the silicon surface at the formation of a reaction layer, composed of a new product, TiSi2. In the boundary of the Cu/solder an interaction between the liquid bismuth solder and the copper substrate occurs, supported by the eutectic reaction. The mutual solubility between the liquid bismuth solder is very limited, on both the Bi and the Cu side. The average shear strength in the case of a combined joint of Si/Cu fabricated with Bi11Ag1.5Ti solder is 43 MPa.
Characterization of waste sludge pigment from production of ZnCl2
(MDPI, 2021) Ovčačíková, Hana; Velička, Marek; Maierová, Petra; Vlček, Jozef; Tokarský, Jonáš; Čegan, Tomáš
This study is focused on the treatment of waste sludge from a zinc chloride production in order to prepare iron-rich pigments usable for a production of glazes. In galvanizing plants, yellow waste sludge containing significant amount of ZnO, Cl, and Fe2O3, is formed. This raw waste sludge cannot be used as a pigment in glaze. Therefore, three methods of treating this material were proposed: (a) washing with H2O, (b) calcination at 180 degrees C and washing by H2O, and (c) calcination at 900 degrees C and washing by H2O. These methods helped to reduce Zn and Cl content up to 97%. According to X-ray fluorescence analysis percentage of Fe2O3 increased from similar to 41% to similar to 98%. X-ray power diffraction analysis confirmed the formation of alpha-Fe2O3 (hematite) in the pigment prepared. Scanning electron microscopy with Energy dispersive X-ray analysis showed clusters of rounded particles, and also the change in size of particles after calcination was observed. Particle size, specific surface area, and density measurements together with thermogravimetric and differential thermal analyses were performed. Pigments prepared from the waste sludge were added to transparent glaze in amounts of 1, 5, 10, and 15 wt.%. Pigment-containing glazes were applied by spraying on fired ceramic tiles and then fired at 1060 degrees C. Color of glazes was determined by (Commission Internationale de l'Eclairage) CIE L*a*b* coordinates as colorless, light brown shades, brown-red, brown-yellow, and deep red-brown. Comparison with colors of glazes prepared using commercial pigments was also performed. Waste sludge can be used to prepare pigments and glazes containing pigments as an alternative to commercial products.
Polyamide 12 materials study of morpho-structural changes during laser sintering of 3D printing
(MDPI, 2021) Simha Martynková, Gražyna; Slíva, Aleš; Kratošová, Gabriela; Čech Barabaszová, Karla; Študentová, Soňa; Klusák, Jan; Brožová, Silvie; Dokoupil, Tomáš; Holešová, Sylva
The polyamide (PA)-12 material used for additive manufacturing was studied in aspects of morphology and their structural properties for basic stages received during 3D laser printing. Samples were real, big-scale production powders. The structure of polymer was evaluated from the crystallinity point of view using XRD, FTIR, and DSC methods and from the surface properties using specific surface evaluation and porosity. Scanning electron microscopy was used to observe morphology of the surface and evaluate the particle size and shape via image analysis. Results were confronted with laser diffraction particles size measurement along with an evaluation of the specific surface area. Fresh PA12 powder was found as inhomogeneous in particle size of material with defective particles, relatively high specific surface, high lamellar crystallite size, and low crystallinity. The scrap PA12 crystallinity was about 2% higher than values for fresh PA12 powder. Particles had a very low, below 1 m(2)/g, specific surface area; particles sintered as twin particles and often in polyhedral shapes.
Structure and properties of cast Ti-Al-Si alloys
(MDPI, 2021) Knaislová, Anna; Novák, Pavel; Linhart, Jiří; Szurman, Ivo; Skotnicová, Kateřina; Juřica, Jan; Čegan, Tomáš
Intermetallic compounds based on Ti-Al- (Si) are attractive materials with good thermal stability and low density. However, the production of these materials is quite complicated. Partially modified conventional methods of melting metallurgy are most often used due to availability, possible high productivity, and relatively low production costs. Therefore, some technologies for the production of intermetallics based on Ti-Al are currently available, but with certain disadvantages, which are caused by poor casting properties or extreme reactivity of the melt with crucibles. Some shortcomings can be eliminated by modifying the melting technology, which contributes to increasing the cost of the process. The work deals with the preparation of Ti-Al-Si intermetallic compounds with different contents of aluminum and silicon, which were produced by centrifugal casting in an induction vacuum furnace Linn Supercast-Titan. This process could contribute to the commercial use of these alloys in the future. For this research, the TiAl15Si15(in wt.%) alloy was selected, which represents a balanced ratio of aluminides and silicides in its structure, and the TiAl35Si5 alloy, which due to the lower silicon content allows better melting conditions, especially with regard to the melting temperature. This alloy was also investigated after HIP ("Hot Isostatic Pressing") treatment.
Mechanical characterization of graphene nanoplatelets-reinforced Mg-3Sn alloy synthesized by powder metallurgy
(MDPI, 2021) Kumar, Pravir; Skotnicová, Kateřina; Mallick, Ashis; Gupta, Manoj; Čegan, Tomáš; Juřica, Jan
The present study investigated the effects of alloying and nano-reinforcement on the mechanical properties (microhardness, tensile strength, and compressive strength) of Mg-based alloys and composites. Pure Mg, Mg-3Sn alloy, and Mg-3Sn + 0.2 GNP alloy-nanocomposite were synthesized by powder metallurgy followed by hot extrusion. The microstructural characteristics of the bulk extruded samples were explored using X-ray diffraction, field-emission scanning electron microscopy, and optical microscopy and their mechanical properties were compared. The microhardness, tensile strength, and compressive strength of the Mg-3Sn alloy improved when compared to those of monolithic Mg sample and further improvements were displayed by Mg-3Sn + 0.2 GNP alloy-nanocomposite. No significant change in the compressive strain to failure was observed in both the alloy and the alloy-nanocomposite with respect to that of the pure Mg sample. However, an enhanced tensile strain to failure was displayed by both the alloy and the alloy-nanocomposite.
Characterizing the soldering alloy type Zn-Al-Cu and study of ultrasonic soldering of Al7075/Cu combination
(MDPI, 2021) Koleňák, Roman; Kostolný, Igor; Drápala, Jaromír; Babincová, Paulína; Sahul, Martin
The aim of the research was to characterize the soldering alloy type Zn-Al-Cu and study the fluxless ultrasonic soldering of the combination of aluminum alloy type Al7075 with copper substrate. The Zn-Al-Cu solder is of the close-to-eutectic type with two phase transformations: the eutectic transformation at 378 degrees C and the eutectoid transformation at 285 degrees C. The solder microstructure is formed of a matrix composed of the solid solutions of aluminum (Al) and zinc (Zn) in which the copper phases CuZn4 and CuAl2 are precipitated. The shear strength of the soldering alloy type Zn5Al with copper addition reaches values from 167 to 187 MPa and it depends on the copper content in the solder. The bond with aluminum alloy type Al7075 is formed due to the solubility of Al in zinc solder at the formation of solid solution Al. Contrary to this observation, the bond with the copper substrate is in this case formed due to the interaction of zinc and aluminum with the copper substrate. Two new intermetallic phases, namely Al(Cu,Zn)(2) and Cu3.2Zn0.7Al4.2, were formed. The average shear strength of Al7075/Zn5Al3Cu/Cu joints attained was 134.5 MPa. For comparison, the Cu/Zn5Al3Cu/Cu joint attained an average shear strength of 136.5 MPa.
Effect of hot isostatic pressing on porosity and mechanical properties of 316 L stainless steel prepared by the selective laser melting method
(MDPI, 2020) Čegan, Tomáš; Pagáš, Marek; Juřica, Jan; Skotnicová, Kateřina; Hajnyš, Jiří; Horsák, Lukáš; Souček, Kamil; Krpec, Pavel
The manufacturing route primarily determines the properties of materials prepared by additive manufacturing methods. In this work, the microstructural features and mechanical properties of 316 L stainless steel prepared by the selective laser method have been determined. Three types of samples, (i) selective laser melted (SLM), (ii) selective laser melted and hot isostatic pressed (HIP) and (iii) selective laser melted and heat treated (HT), were characterized. Microstructural analysis revealed that SLM samples were formed by melt pool boundaries with fine cellular-dendritic-type microstructure. This type of microstructure disappeared after HT or HIP and material were formed by larger grains and sharply defined grain boundaries. The SLM-prepared samples contained different levels of porosity depending on the preparation conditions. The open interconnected LOF (lack of fusion) pores were observed in the samples, which were prepared with using of scanning speed 1200 mm/s. The blowhole and keyhole type of porosity were observed in the samples prepared by lower scanning speeds. The HIP caused a significant decrease in internal closed porosity to 0.1%, and a higher pressure of 190 MPa was more effective than the usually used pressure of 140 MPa, but for samples with open porosity, HIP was not effective. The relatively high yield strength of 570 MPa, tensile strength of 650 MPa and low ductility of 30-34% were determined for SLM samples with the lower porosity content than 1.3%. The samples after HIP showed lower yield strengths than after SLM (from 290 to 325 MPa) and relatively high ductility of 47.8-48.5%, regardless of the used SLM conditions.
Morphological peculiarities of R–Fe–B (R = Nd, Pr) alloys formed upon solidification by strip-casting
(Springer Nature, 2020) Kolchugina, Natalia B.; Lukin, Alexander A.; Kaminskaya, Tatiana P.; Burkhanov, Gennadij Sergeevich; Skotnicová, Kateřina; Kursa, Miroslav; Dormidontov, Nikolay A.; Prokofev, Pavel A.; Zelezhnyi, M. V.; Čegan, Tomáš; Ginzburg, Boris A.; Bakulina, Anna S.
X-ray diffraction analysis, scanning electron microscopy, and atomic force microscopy are used to study the phase composition, texture, and peculiarities of the morphology of R-Fe-B (R = Nd, Pr, Dy) alloys prepared by strip-casting technology. Along with the traditional structural components of the alloys, namely, areas characterized by randomly oriented fine grains of the main magnetic phase with the Nd2Fe14B-type structure (which are formed near the contact surface of flakes) and coarse extended textured grains of the phase (in the volume of flakes), wide areas characterized by uniform distribution of rare-earth metal-rich phase with a period of 2-4 mu m were also found. The formation of these areas takes place in the absence of coarse dendritic crystallites and, according to the suggested mechanism, is related to the solidification of the melt under conditions of its motion upon quenching on a cooled cylindrical surface. Data indicating the melt twisting upon solidification, which favors the formation of the structure with the aforementioned distribution of intergranular phase, are reported. The data obtained are discussed from the viewpoint of their practical utility for the improvement of the structure of alloys prepared by strip-casting and powders for manufacturing Nd-Fe-B permanent magnets.
Blending powder process for recycling sintered Nd-Fe-B magnets
(MDPI, 2020) Prokofev, Pavel A.; Kolchugina, Natalia B.; Skotnicová, Kateřina; Burkhanov, Gennadij Sergeevich; Kursa, Miroslav; Zheleznyi, Mark V.; Dormidontov, Nikolay A.; Čegan, Tomáš; Bakulina, Anna S.; Koshkid'ko, Yury S.; Smetana, Bedřich
The wide application of Nd-Fe-B permanent magnets, in addition to rare-earth metal resource constraints, creates the necessity of the development of efficient technologies for recycling sintered Nd-Fe-B permanent magnets. In the present study, a magnet-to-magnet recycling process is considered. As starting materials, magnets of different grades were used, which were processed by hydrogen decrepitation and blending the powder with NdHx. Composition inhomogeneity in the Nd2Fe14B-based magnetic phase grains in the recycled magnets and the existence of a core-shell structure consisting of a Nd-rich (Dy-depleted) core and Nd-depleted (Dy-enriched) shell are demonstrated. The formation of this structure results from the grain boundary diffusion process of Dy that occurs during the sintering of magnets prepared from a mixture of Dy-free (N42) and Dy-containing magnets. The increase in the coercive force of the N42 magnet was shown to be 52%. The simultaneous retention of the remanence, and even its increase, were observed and explained by the improved isolation of the main magnetic phase grains as well as their alignment.
Simulating the hysteretic characteristics of hard magnetic materials based on Nd2Fe14B and Ce2Fe14B intermetallics
(MDPI, 2020) Kolchugina, Natalia B.; Zheleznyi, Mark V.; Savchenko, Aleksandr G.; Menushenkov, Vladimir P.; Burkhanov, Gennadij Sergeevich; Koshkid'ko, Yurii S.; Ćwik, Jacek; Dormidontov, Nikolai A.; Skotnicová, Kateřina; Kursa, Miroslav; Prokofev, Pavel A.
The Ce2Fe14B intermetallic, like Nd2Fe14B, has the tetragonal Nd2Fe14B-type structure (space groupP4(2)/mnm), in which Ce ions have a mixed-valence state characterized by the coexistence of trivalent 4f(1)and tetravalent 4f(0)electron states. Despite the fact that the saturation magnetization, magnetic anisotropy field, and Curie temperature of the Ce2Fe14B intermetallic are substantially lower than those of Nd2Fe14B and Pr2Fe14B, Ce2Fe14B retains the capacity of being able to be used in the manufacturing of rare-earth permanent magnets. Moreover, at low temperatures, the anisotropy field of Ce2Fe14B is higher than that of Nd2Fe14B, and Ce2Fe14B does not undergo the spin-reorientation transition. In this respect, studies of (Nd, Ce)-Fe-B alloys, which are intended for the improvement of the service characteristics-to-cost ratio, are very relevant. A model and algorithm for calculating the hysteresis loops of uniaxial hard magnetic materials with allowance for the K(1)and K-2(K-2> 0 and K-1> 0 and K-1< 0) magnetic anisotropy constants were developed and allowed us to obtain data on their effect on the parameters of hysteresis loops for a wide temperature range (0-300 K). The simulation and analysis of hysteresis loops of the quasi-ternary intermetallics (Nd1-xCex)(2)Fe14B (x = 0-1) was performed. Results of the simulation indicate that the alloying of the Nd2Fe14B intermetallic with Ce tox= 0.94 (1) does not completely eliminate the negative effect of spin-reorientation phase transition on the residual magnetization of the (Nd1-xCex)(2)Fe14B intermetallic and (2) slightly decreases the slope of magnetization reversal curve.
Metallurgical preparation of Nb-Al and W-Al intermetallic compounds and characterization of their microstructure and phase transformations by DTA technique
(MDPI, 2020) Čegan, Tomáš; Petlák, Daniel; Skotnicová, Kateřina; Juřica, Jan; Smetana, Bedřich; Zlá, Simona
The possibilities of metallurgical preparation of 40Nb-60Al and 15W-85Al intermetallic compounds (in at.%) by plasma arc melting (PAM) and vacuum induction melting (VIM) were studied. Both methods allow easy preparation of Nb-Al alloys; however, significant evaporation of Al was observed during the melting, which affected the resulting chemical composition. The preparation of W-Al alloys was more problematic because there was no complete re-melting of W during PAM and VIM. However, the combination of PAM and VIM allowed the preparation of W-Al alloy without any non-melted parts. The microstructure of Nb-Al alloys consisted of Nb2Al and NbAl3 intermetallic phases, and W-Al alloys consisted mainly of needle-like WAl4 intermetallic phase and Al matrix. The effects of melting conditions on chemical composition, homogeneity, and microstructure were determined. Differential thermal analysis was used to determine melting and phase transformation temperatures of the prepared alloys.
Microstructure and properties of nanostructured coating on Ti6Al4V
(MDPI, 2020) Jordanovová, Veronika; Losertová, Monika; Štencek, Michal; Lukášová, Tereza; Simha Martynková, Gražyna; Peikertová, Pavlína
Implant surface properties of Ti6Al4V alloy that is currently used as a biocompatible material because of a variety of unique properties can be improved by a self-organized TiO2 layer. The TiO2 nanotubes forming on the titanium-based materials is a relatively recent technology for the surface properties modification and represents pronounced potential in promoting cell adhesion, proliferation, and differentiation that facilitate an implant osseointegration. This work focuses on the influence of surface treatment quality and anodic oxidation parameters on the structure features and properties of TiO2 nanotube coatings. The nanotubes were formed on Ti6Al4V alloy substrates by simultaneous surface oxidation and controlled dissolving of an oxide film in the presence of fluorine ions. The anodization process on ground or polished samples was performed at experimental condition of 30 V for 1 h. The selected anodized samples were heat treated for 2 h at 500 degrees C under flowing argon. All samples were characterized by scanning electron microscopy, X-ray diffraction analysis, and Raman spectroscopy. The corrosion rate in physiological solution reached 0.0043, 0.0182, and 0.0998 mm per year for the samples in polished and not-anodized, as-anodized, and anodized-heat treated conditions, respectively.

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