X-ray Diffraction Phase Analysis Research Articles

Влияние технологических параметров на микроструктуру и свойства сплава AlSiMg, полученного методом селективного лазерного плавления

Introduction. The development of additive technologies is aimed at the synthesis of new powder compositions for selective laser melting plants, the study of the effect of mode parameters on the stable quality of products. The purpose of this work is to study the effect of the scanning strategy on the microstructure, elemental composition, porosity and density of specimens obtained by selective laser melting from non-spherical powders (Al — 91 wt. %, Si — 8 wt. %, Mg — 1 wt. %), subjected to special preparation to determine the optimal conditions for selective laser melting. The research methods are methods of X-ray diffraction and X-ray phase analysis, transmission electron microscopy. The paper examines specimens formed using four different scanning strategies. Results and discussions. A promising aluminum alloy AlSi8Mg is developed for selective laser melting. The material has good manufacturability and low powder cost. The technological parameters of melting make it possible to form a thin structure with a low level of porosity. The mechanism of influence of the scanning strategy on porosity, surface morphology, relative density and microstructure is investigated. A specimen from the AlSi8Mg powder composition with a high relative density of 99.97 % is produced by selective laser melting with an energy density of 200 J/mm3, a specimen scanning circuit when the direction of laser movement changes by an angle of 90° each odd layer. It is proved that the density of the AlSiMg alloy depends on the scanning strategy used. The calculated density of the specimen was 2.5 g/cm3, which corresponds to the density of silumin. Analysis of SEM images and maps of the distribution of elements (Al, Mg, Si) of the specimens showed that different specimen formation strategies do not affect the nature of silicon distribution. A unique grain structure is observed in the resulting AlSi8Mg alloy. The melt pool consists of small grains along the border and large grains in the center. The formation of fine grains is explained by the addition of Si and the high cooling rate during selective laser melting.

Quaternary Zinc Alloys with Magnesium, Calcium and Strontium after Hydrostatic Extrusion-Microstructure and Its Impact on Mechanical and Corrosion Properties.

The development of bioabsorbable implants from Zn alloys is one of the main interests in the new generation of biomaterials. The main drawbacks of Zn-based materials are their insufficient mechanical properties. In the presented studies, a quaternary alloy composed of zinc with magnesium (0.2-1 wt. %), calcium (0.1-0.5 wt. %) and strontium (0.05-0.5 wt. %) was prepared by gravity casting followed by hot extrusion and then by hydrostatic extrusion. Microstructural characterization using scanning electron microscopy (SEM) and X-ray diffraction (XRD) phase analysis was performed. The mechanical properties were examined, using static tensile tests. Corrosion properties were analyzed using immersion tests. Samples were immersed in Hanks' solution (temperature = 37 °C, pH = 7.4) for 14 days. All alloys were subjected after corrosion to SEM observations on the surface and cross-section. The corrosion rate was also calculated. The microstructure of the investigated quaternary alloy consists of the α-Zn grains and intermetallic phases Mg2Zn11, CaZn13 and SrZn13 with different grain sizes and distribution, which impacted both mechanical and corrosion properties. Thanks to the alloying by the addition of Mg, Ca, and Sr and plastic deformation using hydrostatic extrusion, outstanding mechanical properties were obtained along with improvement in uniformity of corrosion rate.

Synthesis of biocompatible Ti-6Al-4V composite reinforced with ZrO2 and bioceramic produced by powder metallurgy: Morphological, structural, and biocompatibility analysis.

In this experimental study, the initial phase involved preparing composite structures with various mix ratios using the Ti-6Al-4V alloy, widely used in clinical applications, in conjunction with ZrO2 and hydroxyapatite (HA) synthesized via the precipitation method, employing powder metallurgy techniques. Subsequently, the microstructures of the resultant hybrid composite materials were imaged, and x-ray diffraction (XRD) phase analyses were conducted. In the final phase of the experimental work, tests were performed to determine the biocompatibility properties of the hybrid composites. For this purpose, cytotoxicity and genotoxicity assays were carried out. The tests and examinations revealed that structures compatible both morphologically and elementally were obtained with no phase transformations that could disrupt the structure. The incorporation of ZrO2 into the Ti-6Al-4V alloy was observed to enhance cell viability values. The value of 98.25 ± 0.42 obtained by adding 20% ZrO2 gave the highest cell viability result. The addition of HA into the hybrid structures further increased the cell viability values by approximately 10%. All viability values for both HA-added and HA-free groups were obtained above the 70% viability level defined in the standard. According to the genotoxicity test results, the highest cytokinesis-block proliferation index values were obtained as 1.666 and 0.620 in structures containing 20% ZrO2 and 10% ZrO2 + 10% HA, respectively. Remarkably, all fabricated composite and hybrid composite materials surpassed established biocompatibility standards and exhibited nontoxic and nongenotoxic properties. This comprehensive study contributes vital insights for future biomechanical and other in vitro and in vivo experiments, as it meticulously addresses fundamental characterization parameters crucial for medical device development. RESEARCH HIGHLIGHTS: Support of optimum doping rates ions on hybrid composites and concentrations. Development of uniform surface appearance and distributions/orientations of microcrystals on ceramic compounds Improvement of cell viability and desired increase in biocompatibility with the doping of HA.

Selection of heat treatment and its impact on the structure and properties of AK10M2N–10%TiC composite material obtained via SHS method in the melt

The composite materials based on the Al–Si system alloys, strengthened with a highly dispersed titanium carbide phase, possess improved characteristics and belong to the group of promising structural materials. Currently, self-propagating high-temperature synthesis (SHS) based on the exothermic interaction, wherein titanium and carbon precursors directly involve in the melt, is the most accessible and effective method to obtain them. This paper proves the feasibility and demonstrates the successful synthesis of a 10 wt.% titanium carbide phase in the melt of the AK10M2N alloy, resulting in the AK10M2H-10% TiC composite material. Samples of the matrix alloy and the composite material were subjected to heat treatment according to the T6 mode, with various temperature-time parameters for hardening and aging operations. Based on the results, optimal heat treatment modes were selected to ensure maximum hardness. We studied the macroand microstructure of the obtained samples and performed micro X-ray spectral and X-ray diffraction phase analyses. Different groups of properties underwent comparative tests. It was established that the density of AK10M2N–10%TiC samples before and after heat treatment, according to optimal modes, is close to the calculated value. We showed that the combination of reinforcement and heat treatment significantly increases hardness, microhardness, and compressive strength, with a slight decrease in ductility. Additionally, it maintains the values of the coefficient of thermal linear expansion, high-temperature strength, and resistance to carbon dioxide and hydrogen sulfide corrosion at the level of the original alloy. The greatest effect was observed during the investigation of tribological characteristics: heat treatment of the composite material according to the recommended mode significantly reduces the wear rate and friction coefficient, eliminates seizure and tearing, and prevents temperature rise due to friction heating.

Thermal-induced evolution of microstructure as a plasma arc coating Direction-Dependent phenomenon

This study elucidates the effects of different directed energy deposition trajectories on the microstructure and properties of powder plasma transferred arc welding (PPTAW) fabricated coatings. Two trajectories, straight (STT) and complex (CXT), were explored to deposit NiCrBSi powders onto a low alloy steel substrate. Finite element thermal analysis revealed distinct heat distribution zones, the middle zone (MZ) and transition zone (TZ), showing temperature variations between the STT and CXT coatings. Microstructural examination indicated lower dendrite arm spacing (DAS) in the STT coating (11 μm) than in the CXT coating (16 μm). Electron backscatter diffraction (EBSD) analysis demonstrated significant grain refinement in the STT coating (17.4 μm) versus the CXT coating (68.7 μm). X-ray diffraction phase analysis identified three reinforcing phases − γ-Ni, Cr23C6, and Cr3C2 – enhancing corrosion resistance and tribological properties. The STT coating exhibited superior corrosion resistance with a corrosion current density (icorr) of 12.8 µA/cm2, while the CXT coating showed icorr of 34.3 µA/cm2. Additionally, the STT coating exhibited higher hardness (832 ± 33 HV1.0) and better wear resistance with a wear rate of 10.46 ± 0.29 × 10-3 m3/m, over the CXT coating (hardness: 450 ± 36 HV1.0; wear rate: 12.67 ± 0.54 × 10-3 m3/m).

Оптимизация режимов селективного лазерного плавления порошковой композиции системы AlSiMg

Introduction. New aluminum-based powder systems are currently being developed for additive manufacturing. The scientists' work is aimed at comprehensive studies of powder production, optimization of conditions for alloy production and formation of three-dimensional specimens with minimal porosity and absence of cracking during selective laser melting. The purpose of this work is the synthesis of an almost spherical Al-Si-Mg composite powder (91 wt. % Al, 8 wt. % Si, 1 wt. % Mg) from aluminum powder PA-4 (GOST 6058-22), silicon powder (GOST 2169-69) and magnesium powder MPF-4 (GOST 6001-79), which were not originally intended for selective laser melting technology. The work also provides for the optimization of selective laser melting modes to obtain an alloy and form three-dimensional specimens with minimal porosity and no cracking. To create a powder composition, powders ranging in size from 20 to 64 μm were selected by sieve analysis and subjected to mechanical mixing in a ball mill in a protective argon medium for one hour. The research methods are methods of X-ray diffraction and X-ray phase analysis, transmission electron microscopy, mechanical tests of microhardness. Studies of the powder composition after mechanical mixing showed that the mixed powder of aluminum, silicon and magnesium is a conglomerate of particles of spherical, oval and irregular shape. Results and discussions. The optimal modes for obtaining a specimen with a minimum porosity of 0.03 % and a microhardness of 1,291 MPa are selective laser melting modes: P = 90 W, V = 225 mm/s, S = 0.08 mm, h = 0.025 mm. The conducted research shows the possibility of synthesizing products from metal powders that are not adapted to processing by selective laser melting and obtaining an alloy with new mechanical properties during laser action.

Comparative Evaluation of Titanium Feedstock Powder Derived from Recycled Battlefield Scrap vs. Virgin Powder for Cold Spray Processing.

Gas-atomization is extensively used to produce metallic feedstock powders for additive manufacturing processes, including gas dynamic cold spray processing. This work explores the potential utility of on-demand recycled titanium scrap feedstock powder as a viable substitute for virgin powder sources. Three recycled titanium powders were atomized from different battlefield scrap sources using a mobile foundry developed by MolyWorks Materials Corporation. Recycled titanium alloy powders were compared against virgin Ti-6Al-4V powder to verify there were no significant variations between the recycled and virgin materials. Powder characterization methods included chemical analysis, particle size distribution analysis, scanning electron microscopy (SEM), Karl Fischer (KF) titration moisture content analysis, X-ray diffraction (XRD) phase analysis, microparticle compression testing (MCT), and nanoindentation. Results indicate that recycled titanium powder provides a viable alternative to virgin titanium alloy powders without compromising mechanical capabilities, microstructural features, or ASTM-specified composition and impurity standards. The results of this work will be used to aid future research efforts that will focus on optimizing cold spray parameters to maximize coating density, mechanical strength, and hardness of recycled titanium feedstock powders. "Cold spray" presents opportunities to enhance the sustainability of titanium component production through the utilization of recycled feedstock powder, mitigating issues of long lead times and high waste associated with the use of conventional virgin feedstock.

Spontaneous room temperature reaction of titanium and its alloys with hydrogen during self-shearing reactive milling

Surface wear-activated spontaneous reactions of titanium and its alloys with hydrogen at room temperature are shown in this work. Titanium powder, intensively mixed under hydrogen pressure in a planetary mill, without any grinding media, reacts readily with hydrogen gas with the formation of stoichiometric titanium dihydride. The reaction, once initiated, proceeds spontaneously even without movement of the milling vial with a similar reaction rate. The moment of initiation of the reaction seems to be related to the removal of oxide impurities from the surface of the titanium particles and is strongly correlated with milling velocity. According to thermogravimetric measurements and X-ray diffraction (XRD) phase analysis, titanium is fully converted to TiH2. Titanium alloys were found to react in the same manner. Ti-5553 (β) reacts more easily than grade 5 Ti (Ti-Gd5) (α’), which is more reactive than grade 2 Ti (Ti-Gd2). The titanium alloy particles maintain their shape and coherency after hydrogenation. The method seems to be extremely cost-effective in the synthesis of titanium hydride and also allows the production of hydrogenated alloyed powders in spherical form, which can potentially be applied in the additive manufacturing of titanium foams. The results also show a significant risk of using titanium alloys in a hydrogen atmosphere at room temperature. It seems that after losing the protective oxide layer, parts made of pure titanium or its alloys may undergo catastrophic destruction after losing strength and ductility upon full conversion to hydride.

Исследование превращений переохлажденного аустенита при ступенчатой закалке стали 20Cr2Mn2SiNiMo

Currently, step quenching of steels in the temperature range of martensitic transformation, including quenching – partitioning, has found wide application in the automotive industry. Step quenching technology is successfully used to increase a set of properties, which most often include temporary tensile strength and relative elongation. The authors carried out a dilatometric study of the supercooled austenite transformations occurring in the 20Cr2Mn2SiNiMo steel, when implementing various options of step quenching with holding in the martensitic region. It was found that after single-stage quenching, single-stage quenching followed by tempering, and two-stage quenching, primary martensite, isothermal bainite, and secondary martensite are formed in various quantitative ratios. Using X-ray diffraction phase analysis, the amount of residual austenite was determined during step quenching. It has been shown that two-stage quenching makes it possible to stabilise up to 14 % of residual austenite, in the structure of the studied steel, at room temperature. Research has revealed that 20Cr2Mn2SiNiMo steel is characterised by a decrease in the crystal lattice parameter of the residual austenite, with an increase in its content in the steel structure. Uniaxial tensile and impact bending tests were carried out, and the values of the mechanical properties were determined. It has been found that during two-stage quenching, higher strength and elongation values, with lower values of relative contraction and impact strength are achieved compared to oil quenching and low-temperature tempering. The study showed that, with regard to the structural reliability of machine-building parts, step quenching is not the optimal heat treatment mode for the steel under study. The best combination of strength, ductility and impact hardness is achieved after quenching and low-temperature tempering.

Теплопроводность керамических композитов YAG:Nd + Mo, полученных методом электроимпульсного плазменного спекания

The microstructure and thermophysical properties (specific heat capacity, thermal conductivity coefficient, heat conductivity coefficient) of fine-grained ceramic composites based on yttrium-aluminum garnet Y2.5Nd0.5Al5O12 (YAG:Nd) with different molybdenum content (10, 20, 40 vol. %) are investigated. Submicron Y2.5Nd0.5Al5O12 powders are obtained by co-precipitation method. Powder compositions of YAG:Nd + Mo with the structure “YAG:Nd core – Mo shell” were obtained using wet chemistry techniques and precipitation of the metal phase from salt solutions. Ceramic composite samples were obtained by the Spark Plasma Sintering (SPS) method. The microstructure and phase composition of ceramics were investigated by electron microscopy and X-ray diffraction phase analysis. YAG:Nd + Mo composites have a high relative density (98.1 – 99 %) and a homogeneous fine-grained microstructure with a grain size of 2 – 3 μm. Increased thermal conductivity and heat conductivity of composites is provided with a content of at least 20 vol.% Mo. For composites with 20% and 40% Mo, the heat conductivity coefficient at 1100 °C reaches 7.0 and 8.8 W⋅m–1⋅K–1, respectively. Sintered composites YAG: Nd + Mo at room temperature and elevated temperatures (up to 1100 °C) have a high heat conductivity coefficient, exceeding the heat conductivity coefficient of uranium dioxide UO2. This makes it possible to use ceramics YAG:Nd+Mo as heat-resistant inert fuel matrices.

Электроискровое модифицирование поверхности аддитивного сплава ВТ6 высокоэнтропийным и аморфным электродами

Unsatisfactory quality of the surface layer of additive products, in particular increased surface roughness, prevents the widespread use of electron beam powder bed fusion (EBPBF). Electrospark treatment (EST) is one of the methods for smoothing and hardening the surface layer. The work shows the possibility of modifying the surface of additive VT6 alloy samples by reactive EST with multicomponent electrodes. For this purpose, the authors used electrodes made of the Fe48Cr15Mo14Y2C15B6 bulk metallic glass forming alloy and the FeCoCrNi2 high-entropy alloy. Based on the results of scanning electron microscopy, it was identified that after EST, both modified layers have a thickness of about 16 μm. X-ray diffraction phase analysis showed that in the case of treatment with an amorphous electrode they contain carboborides of the Ti(B,C) type, and in the case of treatment with a high-entropy electrode – intermetallic of the Ti2(Fe,Ni) type. The modified layers have average hardness values of 19 and 10 GPa and elastic modulus of 234 and 157 GPa, respectively, which significantly exceeds the values of these parameters for the EBPBF-grown VT6 alloy. Electric discharge modification of the surface with multicomponent electrodes led to a decrease in roughness by 8...11 times due to the melting of the protrusions and filling of the dimples with the melt to a depth of more than 50 μm. A comparative analysis of the results of tribological tests showed a change in the wear mechanism as a result of EST of the additive VT6 alloy. Wear resistance increased by 4 and 3 orders of magnitude when using electrodes made of a bulk metallic glass and high-entropy alloy, respectively.

Results of experimental simulation of interaction between corium of a nuclear reactor and sacrificial material (Al<sub>2</sub>O<sub>3</sub>) with a lead layer

<abstract> <p>This paper presents the results of an experimental study of the interaction of a candidate sacrificial material (SM) for a light water reactor melt trap with corium at the Lava-B test-bench. The candidate sacrificial material is a combination of aluminum oxide and a lead layer. The idea of using such a combination of SM is based on the fact that when the lead layer interacts with corium, there will be an increase in the intensity of heat removal from the corium, as well as the chemical interaction between the corium and SM due to the high heat-conducting properties of lead. This approach will improve the efficiency of corium localization in the melt trap compared to the current set of sacrificial material. Experiments have shown active melting and boiling of lead during its interaction with corium. This is confirmed both by the readings of thermocouples and by the X-ray diffraction phase analysis of the deposit material formed on the walls of the melt receiver (MR) of the Lava-B bench, sampled after the experiment. The experiment results show that the lead layer reduces the rate of increase in the temperature of the corium and increases the rate of erosion of the ceramic part of the SM. With these circumstances, it is possible to conclude that the use of aluminum oxide with a lead layer is promising in practice.</p> </abstract>

Investigation of High-Temperature Oxidation of Homogeneous and Gradient Ni-Cr-Al Coatings Obtained by Detonation Spraying

The high-temperature oxidation of homogeneous and gradient coatings based on Ni-Cr-Al obtained by detonation spraying is investigated. To assess the resistance to high-temperature oxidation of Ni-Cr-Al coatings, cyclic tests were carried out at a temperature of 1000 °C for 50 cycles. The assessment of high-temperature oxidizing ability was carried out by measuring the weight gain of samples after each cycle. After high-temperature oxidation tests, the morphology and chemical composition of the coating structure in the cross-section were investigated using SEM/EDS. The phase composition of the samples was studied by X-ray diffraction (XRD) phase analysis. Visual analysis of the sample surface under study after high-temperature oxidation showed that the surface of homogeneous or gradient Ni-Cr-Al coatings remained undamaged. The results of X-ray phase analysis showed the peaks of Al2O3 in Ni-Cr-Al gradient coatings are more expressed and intense compared to homogeneous coatings of Ni-Cr-Al. Gradient coatings also retain an increased chromium content compared to homogeneous Ni-Cr-Al coatings. This increased chromium content can slow down mixing or diffusion between different phases of the material at their boundary, which, in turn, contributes to increasing the resistance of the gradient coating to oxidation.

Revealing corrosion behavior of B4C/pure Al composite at different interfaces between B4C particles and Al matrix in NaCl electrolyte

In the present work, the corrosion behavior of the B4C/pure Al composite in a Cl− containing environment is investigated. Thereby, the B4C/pure Al composites have been subjected to the different heat treatments to highlight the impact of the corrosion behavior at the different interfaces. The results of current sensing atomic force microscope (CSAFM) and scanning Kelvin probe microscopy (SKPFM) show that the dissolution of the Al matrix is relevant to the micro-galvanic corrosion between anodic Al matrix and cathodic B4C particles. The as quenched (AQ) composites with a higher volta potential difference (VPD) show inferior anticorrosion property than that of the as produced (AP) composites and the as annealed (AA) composites. By combining X-Ray diffraction (XRD) and geometric phase analysis (GPA), the higher residual stress and obvious interfacial strain between the B4C particles and the Al matrix of the AP samples is detected, which result in increasing the driving force of micro-galvanic corrosion.

Study on the performance of micro-arc oxidation coatings on TA10 titanium alloy with graphite additions

To improve the corrosion resistance of the Ti–0.3Mo–0.8Ni (TA10) titanium alloy, a micro-arc oxidation coating was prepared on its surface, and the effect of different amounts of graphite addition on the structure and corrosion resistance of the coatings was studied. Through methods such as X-ray diffraction phase analysis, microscopic morphology analysis, roughness analysis, coating thickness analysis and hardness testing, it was found that the added graphite particles can react with silicon (Si) in the electrolyte to promote the formation of the silicon carbide (SiC) phase, thereby improving the surface morphology of the coatings, increasing the thickness of the coatings and improving the microhardness of the coatings. At the same time, dynamic potential polarization curve and scanning electrochemical test results show that the formation of the silicon carbide phase can increase self-corrosion potential and reduce self-corrosion current density. When the amount of graphite added is 1.0 g/l, the self-corrosion potential and self-corrosion current density are −0.129 V and 2.9 × 10−8 A/cm2, respectively. This indicates that adding graphite particles can enhance the corrosion resistance of the TA10 titanium alloy.

Correlation of the chemical composition, phase content, structural characteristics and magnetic properties of the Bi-substituted M-type hexaferrites

Bi-substituted M-type hexaferrites, BaFe12-xBixO19 (0.1 ≤ x ≤ 1.2), or Bi-BaM, were produced by the solid-state reactions. The correlation between the phase content, chemical composition, crystal structure features, and peculiarities of the magnetic properties of Bi-BaM was established using XRD (X-ray diffraction), SEM (scanning electron microscopy), and VSM (vibrational sample magnetometry). XRD phase analysis made it possible to establish the limit of substitution of Fe3+ ions by Bi3+ ions. It was shown that at a low substitution level (x ≤ 0.3), no impurity phases were detected, and the samples are characterized by a single-phase state with the space group (SG) P63/mmc. As the degree of substitution (x ≥ 0.6) increases, the formation of impurity phases was observed, which can be explained by the difficulties of ion diffusion in the process of solid-phase synthesis as well as the formation of defects in the magnetoplumbite structure due to the large ionic radius of Bi3+. As impurity phases in the studied compositions (x ≥ 0.6) the following were noted: BiFeO3 (SG: Pnma); BiO2 (SG: Fm-3m); BaBi2O6 (SG: R-3); and Ba0.5Bi1.5O2.16 (SG: Im-3m). The content of the main phase (SG: P63/mmc) decreases from 95.11 to 88.27 vol% with an increase in x from 0.6 to 1.2, respectively. Analysis of SEM images showed the growth of particles up to 10 μm, depending on the concentration of bismuth oxide during hexaferrite synthase. The Bi-BaM magnetic characteristics were examined using VSM in the range of 3 T at 300 K. Due to the magnetic structure's frustration, with increased x a decrease in saturation magnetization (Ms) was found. There were two concentration diapasons with different speeds of Ms decrease. In the first diapason, the main contribution belong to the magnetic structure frustration in the frame of the main phase (P63/mmc) due to the long-range Fe-O-Fe exchange interaction weakening (under Bi substitution). In the second diapason, the main contribution belong to the impurity phase formation and decrease of the main magnetic phase concentration in samples.

Effect of Nano Ni Particles on the Microstructure and Thermophysical Properties of Sn-Bi-Zn Heat Transfer and Heat Storage Alloys.

The specific heat capacity plays a crucial role in influencing the heat transfer efficiency of materials. Considering the relatively low specific heat capacity of metals, this study focuses on investigating the impact of second-phase nano Ni particles on the microstructure and thermophysical properties of the alloy matrix. The alloys' phase compositions and microstructures were examined using X-ray diffraction phase analysis (XRD), electron probe micromorphology analysis (EPMA), and X-ray fluorescence spectroscopy (XRF). Furthermore, the thermophysical properties of the alloys were comprehensively analyzed through the employment of a differential scanning calorimeter (DSC) and the laser flash method (LFA). The addition of second-phase nanoparticles significantly increased the specific heat capacity of the alloy in the liquid state; however, the phenomenon of nanoparticle agglomeration diminishes this improvement. The analysis of the specific heat enhancement mechanism indicates that ordered states are formed between the second-phase solid nanoparticles and the melted metal in the liquid state. With the increase in temperature, the destruction of these ordered states requires additional heat, resulting in the increase of specific heat capacity.

A combined study on microstructure, microchemistry and magnetic behavior of (Sm0.12Co0.88)95Hf1B4 nano-composite ribbons by electron microscopy and atom probe tomography

In this work, Hf and B modified ribbon produced by RSP (rapid solidification process) method have been studied to investigate the microstructure, phase formation and magnetic properties of the Sm-Co-based alloy. (Sm0.12Co0.88)95Hf1B4 ribbon has been synthesized and annealed at various temperatures (700 °C, 800 °C & 900 °C) to analyze the effect of temperature on magnetic properties and structure. X-ray diffraction (XRD) phase analysis has confirmed the 1:7 H phase as a significant phase in the as-spun ribbon. A combination of 1:5 H and 2:17 R phases were found in the ribbon annealed at 900 °C due to disorder-order transformation upon heat treatment. The development of ordered structure and grain growth upon annealing at 800 °C and 900 °C have deteriorated the magnetic properties. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) analysis also revealed the grain growth and the development of the ordered 2:17 R structure upon annealing. The ribbon annealed at 700 °C showed better magnetic properties, Hc≈ 8.6 kOe, Mr ≈ 49 emu/g and (BH)max≈ 5.63 MGOe with an average grain size of ∼149 ± 5 nm. TC of the as-spun ribbon was found to be ⁓750 °C, and the temperature co-efficient of magnetization (α) and coercivity (β) were about − 0.008 and − 0.161%/°C, respectively. The APT analysis confirmed the fine borides in both as-spun and annealed (700 °C & 900 °C) ribbons.

Nanostructured coatings based on titanium for electrodes of electrochemical devices with proton exchange membrane

During the operation of electrochemical devices with a proton-exchange membrane under the action of oxygen, the electrode is gradually destroyed and degraded from the anode side. It is possible to increase the performance and service life of electrodes of electrochemical devices by applying Ti-based protective coatings to the surface of current collectors. In this work, nanostructured films of the compositions Ti, TiO𝑥, TiN𝑦, TiO𝑥N𝑦 were obtained by magnetron sputtering of a titanium target under various conditions. The structure and composition of the samples were studied by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction phase analysis. The effect of various modes and conditions of magnetron sputtering on the composition and structure of titanium coatings has been established. The service life of an electrode coated with the TiN𝑦 composition in the electrolyzer mode is 2 times higher than the service life of an anode without a coating under similar conditions with comparable efficiency

Influence of nano hexagonal boron nitride on the wear properties of aluminium alloy

ABSTRACT Spark plasma sintered, AA7050 reinforced with nano hexagonal boron nitride (n-h-BN) particles followed by characterisation research was carried out to determine the impact of h-BN in the aluminium matrix. With the aid of field-emission scanning electron microscopy , the uniform dispersion of hexagonal boron nitride was examined, and the impact of altering h-BN concentration on the mechanical and tribological properties was studied. In order to achieve individual dispersion of h-BN particles at low milling time without causing any structural damage, pre-mixing of powders prior to high-energy ball milling proved beneficial. Using the X-ray diffraction method, structural and phase analysis was performed on the powders as well as sintered samples. Pin-on disc apparatus is used for testing the weight loss of the composites. SEM was used to examine the worn surfaces of the substrate. According to the wear analysis, adding reinforcement with 0.5 wt% h-BN resulted in a 65% reduction in wear rate and a 33% increase in hardness. It has been found that h-BN tends to aggregate in composite powder above 0.5 wt%, reducing its physical and mechanical qualities.