Phase Composition Of Powders Research Articles

Phase composition and luminescent properties of cesium lead bromide perovskite nanopowders

Halide perovskite nanopowders were synthesized by ligand-assisted re-precipitation technique with different volume ratios of mixture solution to antisolvent (toluene). It was found that with an increase in the proportion of toluene, the phase formed as a result of recrystallization changes predominantly from Cs4PbBr6 to the CsPbBr3, while less stable CsPb2Br5 phase was also discovered. The change in the phase composition of powders obtained with different volume ratios of mixture solution to toluene is explained by the salting out effect of slightly soluble compounds. The phase composition had a correlation with the crystal size distribution, as well as with the photoluminescence quantum yield. Optical properties, including absorption spectra, photoluminescence excitation and luminescence spectra were investigated. Nanopowders obtained with a ratio of the mixture of solution to toluene of about 1:0.9 had the maximum quantum efficiency. The following was associated with the formation of low-dimensional CsPbBr3 “slabbed” crystals sticked on rhombohedral Cs4PbBr6 crystals. The composite film based on nanocrystals and thermoplastic polyurethane was made by hot pressing, the potential of its use as a phosphor coating for an ultraviolet LED was shown.

Design and Characterization of Innovative Gas-Atomized Al-Si-Cu-Mg Alloys for Additive Manufacturing

Metallic powders are widely utilized as feedstock materials in metal additive manufacturing (MAM). However, only a limited number of alloys can currently be processed using these technologies, with most of them being casting alloys. The objective of this study is to investigate novel aluminum alloys produced via a close-coupled gas atomizer (CCGA) by adding an increasing amount of copper (4, 8, and 20 wt%) to an AlSi10Mg alloy. The obtained powders were fully characterized to evaluate the effect of copper, a well-established strengthener for aluminum alloys, in order to correlate the obtained hardness to the powder phase composition and microstructure. In particular, a dendritic microstructure was observed in all alloys, and, as the copper content was increased, the size of the secondary dendrite arm spacing (SDAS) decreased progressively. Consequently, the hardness measured on the powder cross-section linearly increased with the copper content, and the hardness value of 185 ± 13 HV of the AlCu20Si10Mg composition was found to be twice that of the AlSi10Mg alloy (88 ± 5 HV).

Wet Ball Milling Applied to Production of Composites and Coatings Based on Ti, W, and Nb Carbides

The paper demonstrates the potential of wet ball milling of metals for the synthesis of various carbides and carbohydrides. The work reports on multicomponent carbides formed in Ti-(Cu/Fe/Si)-C, W-Fe-C, and Nb-(Cu/Fe/Si/Al)-C systems, as well as metastable or high-temperature intermetallics formed in Ti-Si, Nb-Si, Nb-Al, and Nb-Cu-Fe systems, which are stabilized with interstitial carbon. The formation of phase composition of powders fabricated under mechanochemical synthesis and subsequent thermal treatment has been studied. The as-fabricated powders have been used to produce bulk compacts and to apply wear-resistant coatings on steel (iron).

Ball milling assisted preparation of nano La–Y/ZrO2 powder ternary oxide system: Influence of doping amounts

Zirconia powder with good dispersion, fine particle size, and stability is used as high-quality raw material in many fields, such as ceramic materials and refractories. In this paper, the influence of lanthanum oxide (La2O3) and yttrium oxide (Y2O3) co-doped zirconia (ZrO2) on its phase transformation behavior, phase stability, and microstructure were investigated. The ball milling method is applied to fabricate different amounts of La2O3-doped yttrium oxide stabilized zirconia oxide. Then, the powder obtained from ball milling was roasted using the microwave sintering method. The samples were characterized using XRD, FT-IR, Raman, SEM and BET to determine the optimal conditions for La2O3–Y2O3 co-doped ZrO2 powder. The results showed that replacing part of Y2O3 with La2O3 increases zirconia powder's tetragonal and cubic phase, enhancing the fracture strength of the subsequent synthesized materials. At the same time, the stability of zirconia stabilized with La2O3 doping is significantly improved compared to that of Y2O3 alone. According to all analysis methods, when the doping amount is 2.8Y0.2La, the powder's phase composition, stability, particle size distribution, and dispersion degree are the best compared with other doping amounts in our study. The obtained powder has a smaller specific surface area, a lower surface energy, a smaller porosity, and a higher density. The samples under this condition can be better used in subsequent materials. The enhancement of various properties of zirconia can significantly prolong the service life of materials in practical applications.

Preparation and Investigation of Spherical Powder Made from Corrosion-Resistant 316L Steel with the Addition of 0.2% and 0.5% Ag.

The paper describes the production and study of spherical powder made from corrosion-resistant 316L steel with the addition of 0.2% and 0.5% Ag. The study of granulometric composition, morphology, fluidity and bulk density, phase composition, microhardness and impurity composition of the spherical powders was carried out. The study showed compliance of the spherical powders with the requirements for powders used for additive manufacturing. The fluidity of the powders was 17.9 s, and the bulk density was 3.76 g/cm3. The particles have a spherical shape with a minimum number of defects and an austenitic-ferritic structure. The study of the phase composition of ingots, wires and powders showed that the ingot structure of all samples consists of austenite. According to the results of studies of the phase composition of the wire, there is a decrease in γ-Fe and an increase in α-Fe and σ-NiCr in going from wire No. 1 to wire No. 3. According to the results of studies of the phase composition of the powder particles, there are three phases, γ-Fe, α-Fe, and Fe3O4. The study of microhardness showed a decrease in HV depending on the increase in silver. The hardness of the powder is lower than that of the ingot by 16-24% due to the presence of a ferritic phase in the powder. As a result of plasma spraying, an increase in residual oxygen is observed, which is associated with the oxidation of the melt during plasma dispersion. The amount of nitrogen and sulfur does not change, while the amount of carbon and hydrogen decreases, and the impurities content corresponds to the standards for corrosion-resistant steel. Qualitative and quantitative analysis of the silver content in the samples indicates that it was not affected by the stages involved in obtaining the spherical powder.

Powders Based on Ca2P2O7-CaCO3-H2O System as Model Objects for the Development of Bioceramics

Nanoscale powders of hydrated Ca2P2O7, CaCO3, and a product of mixed-anionic composition containing P2O74− and CO32− anions were synthesized from aqueous solutions of Ca(CH3COO)2, pyrophosphoric acid (H4P2O7), and/or (NH4)2CO3. Pyrophosphoric acid was previously obtained on the basis of the ion exchange process from Na4P2O7 solution and H+-cationite resin for further introduction into the reactions as an anionic precursor. The phase composition of powders after the syntheses was represented by bioresorbable phases of X-ray amorphous hydrated Ca2P2O7 phase, calcite and vaterite polymorphs of CaCO3. Based on synthesized powders, simple cylindrical constructions were prepared via mechanical pressing and fired in the temperature range of 600–800 °C. Surface morphology observation showed the presence of bimodal porosity with pore sizes up to 200 nm and 2 μm, which is likely to ensure tight particle packing and roughness of the sample surface required for the differentiation of osteogenic cells. Thus, the prepared ceramic samples can be further examined as model objects for bone tissue repair.

Preparation of nano/micro-bimodal Ti/Al/(Mo, W, Cu) powders by simultaneous electrical explosion of dissimilar metal wires

Novel mixtures of micro- and nanoparticles have been obtained by simultaneous electrical explosion of three intertwisted wires (EEW). The possibility of obtaining of titanium‑aluminum micro- and nanoparticles alloyed with molybdenum, tungsten and copper by the electrical explosion of Ti/Al/(Mo, W, Cu – up to 6 at. %) wires has been shown. Spherical particle with sizes from 20 nm to 7 μm are formed under condition of introducing the electric energy at the level of 0.57–0.77 of the total sublimation energy. The mass content of particles with sizes less than 100 nm does not exceed 10%. The phase composition of powders includes double and triple intermetallic phases, titanium oxide (TiO) as well as phases of the initial metals. The study of the phase composition of bulk materials obtained by sintering powders Ti-Al-Mo, Ti-Al-W and Ti-Al-Cu for 2 h at 1000 °C showed the increase in the content of intermetallic phases, providing enhanced physical and mechanical properties of the titanium‑aluminum alloys. The results of the studies show that the obtained powders alloys can be used to produce feedstocks of TiAl alloys.

Influences of Precursors Phase Composition on the Phase Evolution Dynamics of Bi-2223 Superconducting Tapes

Bi2Sr2Ca2Cu3O10+ (Bi-2223) precursors for the fabrication of high temperature superconducting tapes were prepared by spray pyrolysis technique followed by a calcination process. The influences of precursor powder phase composition on the phase evolution dynamics and final current capacity of Bi-2223 superconducting tapes were systematically studied. It was interesting to notice that slight increase of Cu content in chemical composition could cause obvious variations of both the phase composition and the morphology of CuO particles in precursors. Therefore, the Bi-2223 phase formation process during the sintering process of tapes could be affected, and the current capacity changed accordingly. On the other hand, during the calcination temperature optimization process, the Bi-2223 phase content in precursors changed accordingly, thus the Bi-2223 phase formation dynamics were also studied. More Bi-2223 nuclei were formed due to the pre-existed Bi-2223 grains, which worked as inhomogeneous nuclei centers. Thus, although the final Bi-2223 phase contents were similar in all the tapes, the particle size and texture structure of Bi-2223 varied greatly, which caused a dramatic decrease of critical current in Bi-2223 tapes with the formation of Bi-2223 in precursors. Therefore, it could be concluded that both the morphology of CuO particles and the Bi-2223 phase content in precursors were the factors controlling the phase evolution dynamics during Bi-2223 tape sintering process.

Fine Biocompatible Powders Synthesized from Calcium Lactate and Ammonium Sulfate

Fine biocompatible powders with different phase compositions were obtained from a 0.5 M solution of ammonium sulfate (NH4)2SO4 and calcium lactate Ca(C3H5O3)2. The powder after synthesis and drying at 40 °C included calcium sulfate dehydrate CaSO4·2H2O and calcite CaCO3. The powder after heat treatment at 350 °C included β-hemihydrate calcium sulfate β-CaSO4·0.5H2O, γ-anhydrite calcium sulfate γ-CaSO4 and calcite CaCO3. The phase composition of powder heat-treated at 600 °C was presented as β-anhydrate calcium sulfate β-CaSO4 and calcite CaCO3. Increasing the temperature up to 800 °C leads to the sintering of a calcium sulfate powder consisting of β-anhydrite calcium sulfate β-CaSO4 main phase and a tiny amount of calcium oxide CaO. The obtained fine biocompatible powders of calcium sulfate both after synthesis and after heat treatment at temperature not above 600 °C can be recommended as a filler for producing unique composites with inorganic (glass, ceramic, cement) or polymer matrices.

Corrosion Behavior of FeB-30 wt.% Al0.25FeNiCoCr Cermet Coating in Liquid Zinc

The corrosion of galvanizing equipment parts by liquid zinc is an urgent problem that needs solving. In this work, FeB-30 wt.% Al0.25FeNiCoCr cermet coating was deposited on the surface of 316L stainless steel by AC-HVAF to protect galvanizing equipment parts from corrosion by liquid zinc. The microstructures and phase compositions of powders and the coating were determined by SEM, EDS, and XRD in detail. Additionally, the microhardness, fracture toughness, abrasion wear resistance, and corrosion resistance of the coating to liquid zinc were also studied. The results indicate that the abrasion wear resistance and corrosion resistance of the coating are much better than that of the 316L stainless steel substrate. The failure of the coating in liquid zinc is mainly due to the penetration of liquid zinc into macro-cracks, which causes the coating to peel off.

Structure formation and properties of corundum ceramics based on metastable aluminium oxide doped with stabilized zirconium dioxide

The work presents a successful example of the use of YSZ binary systems for production of composite ceramic materials based on θ-Al2O3 with improved physical and mechanical characteristics which was previously considered an unpromising material. It was first obtained result of extreme nature of dependence of physical and mechanical properties of Al2O3+YSZ on the concentration of YSZ (ZrO2–3mol% of Y2O3) additive. The sintering temperature was decreased on 250 °C (from 1800 to 1550 °C). The phase composition of powders and the structure of ceramics of the Al2O3 + YSZ system were investigated depending on the amount of YSZ dopant, the structure-properties relationship was established. It is shown that maximum of physical and mechanical characteristics achieved at YSZ concentration equal to 10% wt.

Fabrication of spherical WC-Co powders by radio frequency inductively coupled plasma and a consequent heat treatment

To obtain spherical cemented carbide powders suitable for the additive manufacturing process, granulated WC-Co powders made by spray drying were spheroidized by radio frequency inductively coupled plasma. The influence of powder feed rate on the sphericity of the obtained powders was investigated. Results show that spheroidization efficiency of near 100% was achieved at different applied feed rates. Applying plasma processing decreased the particle size, compacted the microstructure and caused obvious improvements in the apparent density and flowability. However, complete decomposition of WC and certain evaporation loss of Co were noted in these powders. The spheroidized powders consisted of W2C, C, Co3W3C, and contained higher Co at a higher applied feed rate. After conducting heat treatment at 950 °C for 3 h, the powder phase composition was regenerated as WC and Co. The heat-treated powders, due to their good sphericity, improved apparent density and flowability are suitable for the printing processes.

Nanostructured Strain-Hardened Aluminum–Magnesium Alloys Modified by C60 Fullerene Obtained by Powder Metallurgy: Part 1. The Effect of the Magnesium Concentration on the Structure and Phase Composition of Powders

This paper provides the first part of a study on the effect of magnesium on the structural phase composition and physical and mechanical properties of nanostructured aluminum–magnesium composite materials with the composition AlxMgy + 0.3 wt % C60 fullerene. Composite powders are obtained by the simultaneous mechanical activation of the initial materials in a planetary ball mill in an argon atmosphere. It is found that the powders have a complex hierarchical structure made up of 50–200 μm aggregates consisting of 5–10 μm strong high-density agglomerates, which in turn are a combination of nanoscale (30–60 nm) crystallites. It is found that the increase in magnesium concentration in the composite up to 18 wt % makes it possible to obtain crystallites with an average size of less than 30 nm during mechanical activation, while the size of aggregates is less than 50 μm. The maximum solubility of magnesium in aluminum with a crystallite size of 30–70 nm during mechanical activation is 15 wt % (17 at %). Using the differential scanning calorimetry method, it is found that nanostructured composites undergo irreversible structural phase transformations during heat treatment in a temperature range of 250–400°C: recrystallization, decomposition of the α-solid solution of magnesium in aluminum, and the formation of intermetallic β-(Al3Mg2), γ-(Al12Mg17) and carbide (Al4C3) phases. In addition, the Raman spectra contain peaks that, according to some sources, correspond to covalent compounds of aluminum with C60 fullerene—aluminum–fullerene complexes. The data that have been obtained will be used in further research to determine the parameters for the thermobaric treatment of nanocomposite powder mixtures in order to obtain and test bulk samples.

Laser modification of the microstructure and mechanical properties of (Cr3C2-25(Ni20Cr))-5(Ni25C) cermet coatings containing a solid lubricant

This paper presents a study on the effect of laser surface treatment on the microstructure and mechanical characteristics of cold sprayed Cr3C2-25(Ni20Cr)-(Ni-graphite) cermet coatings. The as-sprayed deposits retained the initial powder phase composition. The Cr3C2 particles were homogeneously distributed within the deformed nickel-chromium matrix phase. Moreover, the carbide particles were heavily fragmented due to a high-velocity impact on the substrate or particles already embedded. The solid lubricant (graphite) was mostly distributed between crushed Cr3C2 particles or deformed nickel-chromium matrix. The surface of the as-deposited coatings was laser-treated using a CO2 laser. With the higher applied power of the laser beam, the changes in the coating microstructure and surface topography were more significant. The refinement of the deposit structure and formation of new phases such as Cr7C3 and Cr2O3 were observed. All coatings, both those cold sprayed and those laser-treated, revealed compressive residual stresses, which increased with higher laser power. The post-deposition laser modification of the coating surfaces improved their mechanical properties by almost half.

Синтез порошков в системе Li2O—ZnO—TiO2для получения низкотемпературной сообжиговой керамики .

The change in the phase composition of powders in the Li2O —ZnO —TiO2system at different temperatures and holding times was studied. It was determined thatthe synthesis of Li2ZnTi3O8and Li2Zn3Ti4O12compounds is possible at temperatures of 850–900 °C. At the same time, the synthesized phases are extremely sensitive to the ratio of the initial components.

Nanostructured strain hardened aluminum-magnesium alloys modified by C<sub>60</sub> fullerene obtained by powder metallurgy. Part 1. Effect of magnesium concentration on the structure and phase composition of powders

This paper provides the first part of the study on the magnesium effect on the structural phase composition, physical and mechanical properties of nanostructured aluminum-magnesium composite materials with the composition AlxMgy + 0.3 wt.% C60 fullerene. Composite powders were obtained by the simultaneous mechanical activation of initial materials in a planetary ball mill in an argon atmosphere. It was found that the obtained powders have a complex hierarchical structure made up of 50–200 μm aggregates consisting of 5–10 μm strong high-density agglomerates, which in turn are a combination of nanoscale (30–60 nm) crystallites. It was found that the increase in magnesium concentration in the composite up to 18 wt.% makes it possible to obtain crystallites with an average size of less than 30 nm during mechanical activation, while the size of aggregates is less than 50 μm. The maximum solubility of magnesium in aluminum with a crystallite size of 30–70 nm during mechanical activation was 15 wt.% (17 at.%). Using the differential scanning calorimetry method, it was found that nanostructured composites undergo irreversible structural phase transformations during heat treatment in a temperature range of 250–400 °C: recrystallization, decomposition of the α-solid solution of magnesium in aluminum and formation of intermetallic β-(Al3Mg2), γ-(Al12Mg17) and carbide (Al4C3) phases. In addition, the Raman spectra contain peaks that, according to some sources, correspond to covalent compounds of aluminum with C60 fullerene – aluminum-fullerene complexes. The data obtained will be used in further research to determine parameters for the thermobaric treatment of nanocmposite powder mixtures in order to obtain and test bulk samples.

Microstructure and Phase Composition of Electroerosion Materials Based on Bronze Used for the Application of Metallization and Galvanic Coatings

A study of the phase composition of powder materials obtained by the electroerosion dispersion of BrC30 lead-bronze metal waste in distilled water is carried out. The preparation of metal materials of microfractions and nanofractions is carried out using an electroerosion-dispersion unit. The filings are placed in the reactor of the installation, which is filled with distilled water (an oxygen-containing medium). The following operating modes of the installation are set: pulse repetition rate of 95−105 Hz, voltage applied to the electrodes of 190−200 V, capacitor capacitance of 65.5 μF. At the places where the discharges occur, the temperature increases, and the materials melt and evaporate, which leads to the formation of fine particles. The phase composition of the powders is studied by X-ray diffraction on a Rigaku Ultima IV diffractometer. It is established that the main phases in the resulting electroerosion materials are Cu, Pb(Cu2O2), Pb5O8, Pb. The resulting powder materials can be used for metallization and galvanic coatings.

Nucleation and growth of YAG: Yb crystallites: A step towards the dispersity control

In this work, the dynamics of changing the ceramic powder phase composition and the size of garnet crystallites during calcination of the precursor at various temperature and time conditions were studied on the example of YAG: Yb oxide composition. The precursor powder was synthesized by the chemical precipitation of a salts solution by ammonia. Based on the obtained data, a model of the garnet crystallite nucleation and growth has been proposed. The crystallite growth process, in this case, includes 3 stages: the crystallite nucleation, the stage of growth due to the conversion of the amorphous phase to crystalline, and the stage of agglomeration and crystallite growth due to their mutual absorption. The dependence of the YAG: Yb crystallite size on the calcination time in the temperature range of 830 °C–1200 °C has been approximated using the regression equation. The approximation error of the obtained equation was 4%. The approach proposed in the framework of this work can be used to describe the change of crystallite size during calcination both for systems with a garnet structure and for other oxide compositions. A description of the dependence of crystallite size on temperature and time of heat treatment opens up the possibility of controlling the particle size, their agglomeration degree, and the specific surface area of the ceramic powder, which is an important step towards obtaining materials with desired properties.

α-Tricalcium phosphate/fluorapatite based composite cements: Synthesis, mechanical properties, and biocompatibility

Composite cements based on α-tricalcium phosphate (α-TCP) and nanostructured fluorapatite (FAp), α-TCP/FAp, appropriate for dental usage as root canal filling material, have been prepared with the improved mechanical properties and biocompatibility. The influence of FAp concentration on the composite cement properties was investigated. The processing conditions for FAp powders synthesis were optimized and the powder with optimal properties was chosen to obtain α-TCP/FAp composite types of cement. α-TCP powder was prepared by calcination of hydrothermally synthesized hydroxyapatite (HAp) at 1500 °C for 2 h. Morphology and phase composition of powders were investigated by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDS). Soaking of α-TCP/FAp specimens in simulated body fluid (SBF) affected the successful transformation of α-TCP into HAp, while the compressive test revealed the influence of this transformation and FAp content on the mechanical properties of the composites. Specimen containing 5% of FAp after 10 days in SBF showed the highest compressive strength. In vitro MTT and DET biocompatibility tests, performed in the culture of MRC-5 human fibroblast cells, revealed that α-TCP/FAp had no cytotoxic effect. These initial findings showed that α-TCP/FAp composite cements could yield favorable mechanical properties with no adverse effect on biocompatibility.

Synthesis and Electron Beam Facing of Titanium Monoboride–Titanium Matrix Composite Powders

Titanium monoboride–titanium composite powders with the titanium matrix content from 20 to 60% are obtained by self-propagating high temperature synthesis (SHS) in titanium and boron powder mixtures. The SHS powders are used for cladding of coatings with a thickness of up to 3 mm on a VT1-0 titanium sheet by electron beam facing. The phase composition and microstructure of the initial powders and cladded coatings are investigated via X-ray diffraction analysis and optical and scanning electron microscopy. On the basis of the microstructure investigation and microhardness profiles in the coating/base plate transition zone, a conclusion about effective adhesion of the coating to the base plate is made. The dependence of the hardness and abrasive wear resistance of the cladded coatings on the phase composition of the powders used for cladding is studied. It is found that the hardness of the coatings strengthened by needle-like titanium monoboride inclusions in the titanium matrix is 2.2-fold higher and abrasive wear is 3.7-fold higher when compared to the properties of VT1-0 titanium. Here, the effect of strengthening and increase in the wear resistance of the titanium matrix by titanium monoboride particles is much smaller than similar effects in the case of the use of disperse titanium carbide particles as the strengthening phase in cladded coatings.