Nanostructured Powders Research Articles

Mn2+ doped Zn2SiO4 phosphors: A threefold-mode sensing approach for optical thermometry in the visible region at 525 nm

Optical functional materials such as nanostructured silicates have been studied for photonics applications involving energy conversion. In this scenario, we studied Zn2SiO4:Mn2+ nanostructured powders prepared by combustion synthesis for optical thermometry based on photon downshifting. The structural analysis showed that Zn2SiO4 particles were found embedded in clustered silica nanoparticles. The photoluminescence analysis showed that the samples exhibit intense green emission (centered around 525 nm), corresponding to the electronic transition 4T1 → 6A1 of Mn2+, when exposed to a low power ultraviolet lamp (centered around 255 nm). The temperature sensing performance of this material was evaluated using three different methodologies, i.e. the luminescence decay time constant, the spectral full width at half maximum, and the luminescence peak intensity from the 4T1 → 6A1 radiative transition. The thermometric analysis based on luminescence peak intensity provided a maximum relative sensitivity of ∼4.9x10−3 K−1 at 498 K, while the decay lifetime and the spectral width at half maximum provided maximum relative temperature sensitivities of ∼2.9x10−3 K−1 at 523 K and ∼1.7x10−3 K−1 at 298 K, respectively.

Enhanced properties of hard metal WC-Ni processed from nanostructured powders

In this study, we investigated the effects of nanostructured composite powders (WC-Ni), nickel binder content, and sintering techniques on the morphology and mechanical properties of tungsten carbide. An alternative low-temperature gas-solid reaction route with a short reaction time was employed to produce nanostructured composite powders with 5 and 15 wt% Ni. The powders were consolidated using spark plasma sintering (SPS) and conventional vacuum furnace sintering at temperatures of 1350 °C and 1450 °C. The composite powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and particle size measurements. The expansion/contraction of the compacted nanocomposite powders was studied through dilatometric analysis. The composite powders exhibited a uniform distribution of Ni, in both compositions. For the WC-5 wt% Ni nanocomposite powders, the average crystallite sizes for WC and Ni were 41.6 nm and 46.2 nm, respectively. While, for the WC-15 wt% Ni nanocomposite, the crystallite sizes for WC and Ni were 45.6 and 38.4 nm. The sintered composites were evaluated through XRD, SEM, measurements of density and Vickers hardness. The enhanced sinterability of the nanostructured powders enabled their consolidation into (WC-Ni) hard metal with densities approaching the theoretical relative density of 96.07 %, even with low binder content (5 wt% Ni). This is attributed to the uniform distribution of Ni and an extensive Ni-WC interface present prior to sintering. The SPS process at 1350 °C produced sintered bodies (WC-5 wt% Ni and WC-15 wt% Ni) with higher Vickers hardness (2322 HV and 1512 HV, respectively) and superior microstructural quality compared to samples produced by conventional vacuum furnace techniques. These results demonstrated that the mechanical properties of the system WC-Ni processed by SPS are superior to those obtained by vacuum furnace. Therefore, WC-Ni hard metals processed by this approach is a promising alternative to conventional hard metals (WC-Co) for a wide range of applications.

Fabrication of aqueous asymmetric supercapacitor device by using spinel type (FeCoNiCuZn)3O4 high entropy oxide and green carbon derived from plastic wastes

As the world shifts towards renewable energy and more efficient energy storage systems, the demand for advanced materials that can support these technologies has increased. One such promising material class is High Entropy Alloys (HEAs). Unlike conventional alloys, which are typically composed of one or two principal elements, HEAs consist of multiple principal elements in near-equiatomic proportions. Their unique atomic structure, characterized by high configurational entropy, endows them with enhanced stability, tunability, and a high specific surface area—qualities that are highly desirable in supercapacitor applications. HEAs offer significant advantages as supercapacitor electrodes, including increased energy storage capacity, superior electrochemical stability, and the potential for synergistic effects that improve overall performance such as higher energy density, longer cycle life, and greater reliability. FeCoNiCuZn)3O4 has been synthesized by utilizing multiple induction melting process in a quartz tube at 1100 °C, followed by ball milling in order to transform the small pieces into nanostructured powder. The highest specific capacitance obtained is 245.7 F g−1 at 1.5 A g−1 in three electrode measurement system. In addition, plastic biochar was prepared using pyrolysis techniques from plastic wastage. Moreover, it is utilized for supercapacitor application, which shows a maximum specific capacitance of 180 F g−1 at 1 A g−1 for three electrode system. The combing above two electrode materials, the fabricated asymmetric device shows a maximum specific capacitance of 58 F g−1 at 1 A g−1 for 3M KOH electrolyte with maximum specific energy of 23.44 Wh kg−1 at specific power of 1700 W kg−1.

Redispersible dry powders containing nanoencapsulated curcumin increase its antioxidant activity

The present study aimed to develop redispersible spray-dried powders containing curcumin-loaded Eudragit® L100 nanocapsules and evaluate their physicochemical properties and antioxidant potential. The spray drying process showed a yield of over 85%, low residual moisture content (<2%), and all the physicochemical characteristics of the nanocapsules were recovered after the aqueous redispersion of the dry powders. In addition to the dry powders, the following samples were also analyzed: pure curcumin, pure lactose, and curcumin-lactose mix. In TGA and DSC analysis, all samples were thermostable and exhibited no chemical interactions with each other. In FTIR analysis, the nanostructured powder system showed functional groups of the precursors (curcumin and lactose), confirming the effectiveness in the preparation of the nanostructured material. In the evaluation of the free radical scavenging activity of DPPH•, the dry powder containing nanoencapsulated curcumin showed antioxidant activity approximately six times higher than free curcumin. Therefore, spray drying of nanoencapsulated curcumin made it possible to obtain a dry powder with homogeneous aqueous redispersion, as well as promoting the potentiation of the antioxidant activity of curcumin.

Photocatalytic performance of (Zn,Me)–SnO2 nanoparticles (Me= Nb5+ or W6+) under UV light for efficiently degradation of organic dye pollutants

In this study (Zn,Nb)-doped SnO2 and (Zn,W)-doped SnO2 were synthetized using chemical route by calcination at 600 °C/2 h and milling at 500 rpm/1 h to verify its behavior as a photocatalyst. The powders showed high surface area: 57.1 m2/g for (Zn,Nb)-doped SnO2 and 74.3 m2/g for (Zn,W)-doped SnO2, both showed 10–25 nm of average diameter and rutile crystalline phase after morphological and structural characterizations. UV–vis spectroscopy indicated a band gap of 3.53 eV for (Zn,Nb)–SnO2 and 3.35 for (Zn,W)–SnO2. The photocatalytic activity was verified through the decomposition of Rodhamine B (RhB) aqueous solution under ultraviolet light radiation of 9W. After 120 min the efficiency of (Zn,Nb)–SnO2 was 68.5 % and for (Zn,W)–SnO2 was 71.1 %. Using a UV-lamp of 11W the efficiency in photodiscoloration of RhB aqueous solution increased to 83.2 % with (Zn,W)-doped SnO2 powder in a shorter irradiation time (90 min), indicating its potential use as nanostructured photocatalyst ceramic powder.

Magnetic and microstructural properties of thin film Fe-Sb obtained by thermal evaporation of nanostructured milled powder

Magnetic and microstructural properties of thin film Fe-Sb obtained by thermal evaporation of nanostructured milled powder

Synthesis and characterization of multi-walled carbon nanotube-reinforced Ti–Mg alloy prepared by mechanical alloying and microwave sintering

Titanium-magnesium (Ti–Mg) alloy is a widely accepted bimetallic material suitable for biomedical applications. However, reduced wear and corrosion resistance, low strength and hardness, and stress shielding effect limit their widespread applications. Reinforcing multi-walled carbon nanotubes (MWCNTs) possessing low density, high modulus, and improved mechanical properties overcome the shortcomings of Ti–Mg alloy. In the present work, nanostructured Ti–Mg alloy was synthesized at room temperature and simultaneously reinforced with MWCNTs. The high energetic ball milling process (HEBM) has been successfully utilized to mechanically alloy Ti with Mg at room temperature by decreasing the grain size to the nanoscale and reinforcing the alloy with MWCNTs. The synthesized nanostructured powder size was 25 nm. Characterization results have shown the emergence of new phases like Ti4C4 and Mg2C3 as a result of mechanical alloying (MA). The reinforced alloy powder was consolidated by cold compaction and followed by microwave sintering. The consolidated sample crystallite size attained was 72 nm and then characterized by Nanoindentation, XRD, and SEM. XRD results show intermetallic compounds Mg2C3 and TiC in bulk samples. SADP TEM confirmed the retention of Nano and partial amorphous structures in the consolidated samples. The nanoindentation test revealed the hardness and elastic modulus values 0.93 GPa and 28.12 GPa, respectively, equivalent to CpTi and its associated alloys. The results are prevalent in those alloys used in biomedical applications produced by conventional melting and casting techniques and can be a potential biomaterial.

Temperature-dependent structural and magnetic properties of mechanically alloyed Ni80Co17Mo3 powder mixture

Nanostructured materials containing nickel improve the effectiveness of several applications. This study examines the preparation and characterization of nanostructured Ni80Co17Mo3 alloy powders using high-energy mechanical alloying and subsequent annealing. A 72 h milling process used pure elemental powders to synthesise nanocrystalline FCC-NiCo(Mo) solid solution. The milled powders were then subjected to annealing at different temperatures:300°C, 500°C, and 750°C. X-ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy, and vibrating sample magnetometry indicated significant changes in the powdered alloy properties. The particles growth occurred as the annealing temperature increased, while the microstrain decreased significantly; 14.30±0.07 nm up to 56.30±0.28 nm and 0.680±0.003% up to 0.180±0.001%, at 25°C and 750°C respectively. SEM analysis revealed differences in particle size and shape as milling progressed. Surprisingly, the milled powdered alloy displayed improved magnetic properties, manifesting significant magnetic susceptibility and enhanced saturation magnetisation, remanent magnetisation, and coercivity within the temperature range of 300°C to 750°C. These findings indicate the development of a consistent and structured state, accompanied by significant crystal growth due to the annealing temperature. This study highlights the great importance of high-energy mechanical milling and subsequent annealing to tune / tailor the characteristics and subsequently investigate the potential utilization of nanostructured Ni-based alloys.

Production of High-Coercive nanostructured Nd-Fe-B alloy by chemical method

For the first time, a nanostructured alloy powder with high coercive force was obtained by a chemical method without the addition of Dy, which can compete with physical methods of production. The work carried out a study of the influence of stoichiometric composition on the magnetic properties of nanostructured Nd-Fe-B alloys. Alloys with different contents of Nd, Fe, and B were synthesized: Nd12Fe84B6, Nd14Fe80B6, Nd16Fe76B8, and Nd16Fe72B8. With a decrease in the iron content in the first two compositions, a decrease in the iron content in the soft magnetic phase α-Fe was observed, which led to an increase in the coercive force Hc and a decrease in the values of Ms and Mr. Experiments have shown that an increase in the content of Nd and B promotes the formation of the hard magnetic phase Nd2Fe14B and an increase in the coercive force. For example, the nanostructured Nd16Fe76B8 alloy demonstrated a maximum coercive force of Hc = 8439 Oe, while compensating for the values of Ms (109 emu*g−1) and Mr (78 emu*g−1). A comprehensive study of the nanostructured Nd16Fe76B8 alloy was carried out, including structural analysis. XRD using FullProff and Vesta software revealed the tetragonal crystal structure of the Nd2Fe14B phase, providing details of the atomic arrangement. The unit cell contains four layers with Nd and Fe atoms, and boron atoms are embedded in the center of the octahedron of Nd and Fe atoms, playing an important role in the magnetic exchange interaction. The results of Mössbauer spectroscopy confirmed the presence of the Nd2Fe14B phase and revealed details of the state of Fe atoms in the structure of six sextets.

Structural, magnetic, and electronic structure of the nanostructured (CoMn)50Ni50 powders used in dye discoloration via a heterogeneous Fenton-like process

Structural, magnetic, and electronic structure of the nanostructured (CoMn)50Ni50 powders used in dye discoloration via a heterogeneous Fenton-like process

A green approach for synthesizing high pure gadolinium zirconate nano-particles using microwave energy

Nano crystalline high purity gadolinium zirconate powder has been prepared by wet chemical synthesis method using microwave energy. Co-precipitation of zirconium oxychloride and gadolinium nitrate under the influence of microwave energy is studied. The powder has been characterized using thermal TG-DTA/DSC, XRD, EDS and FESEM. The average crystallite size (ACS) of the ZrO2 (600 °C) nano-particles is found to be 26 nm. The characterization studies have shown the existence of non agglomerated nano-crystalline particles with regular and uniform spherical morphology. Microwave energy is found to assist in achieving the desired properties of gadolinium zirconate. The microwave assisted synthesis is faster, better and green chemistry approach which not only provides the enhanced reaction rates and high yields but also, it provides short reaction time, higher selectivity and reduction of pollutant solvents. The key features of obtaining the pure non agglomerated nano-structured gadolinium zirconate powder are the notable attractions of the present study.

Characterization of Pure and Doped ZnO Nanostructured Powders elaborated in Solar Reactor

The synthesis of nano-oxides is an important field of nanotechnology, as these materials possess unique properties and applications. Several methods have been developed for synthesizing nano-oxides, each offering advantages and disadvantages depending on the desired material characteristics. Solar energy focused on solar reactors can be utilized for nano-oxide elaboration, offering a sustainable and environmentally friendly approach. The current article presents the research carried out for the elaboration of pure and doped nanostructured zinc oxides using solar energy. The morphostructural characteristics were determined by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and the Brunauer-Emmett-Teller method. The attenuated total reflectance Fourier transform infrared spectroscopy confirmed the synthesis of pure and doped nanostructured ZnO. The optical properties were highlighted by UV-VIS Spectroscopy. The research points out that crystallite sizes vary between 37 and 51 nm due to the influence of doping metal. The morphology associated with these particles is predominantly whiskers with elongated parts between 0.18 and 1.4 um. Doping with Fe, Si, Yb, and Ce causes a wider band gap compared to pure ZnO nanoparticles. As solar energy becomes more accessible and efficient, solar-driven synthesis of pure and doped ZnO is poised to be a crucial factor in shaping the future of material science and technology.

Effect of H2S gas flow rate on the stoichiometric ratio of S:Zn and transparency of ZnS nanostructure ceramic in IR region

In this research, zinc sulfide (ZnS) nanostructure powder was successfully synthesized via two-stage annealing (Ar + H2S). The annealing under argon medium was responsible for eliminating impurities such as SO4, SO3 and SO2. The annealing under hydrogen sulfide (H2S) medium also led to compensation of sulfur and establishment of Zn to S stoichiometric ratio following sintering. Investigation of different flow rates of H2S gas indicated that 30 mL/min would contribute to optimal Zn to S stoichiometric ratio. The Zn to S stoichiometric ratio before sintering under H2S medium was 1.28, which increased to 1.55 after annealing under H2S medium. The ceramic obtained from ZnS powder annealed under H2S medium at 30 mL/min had density of 99.98% and IR transmission of 62% within 8–12 μm range (wavenumbers of 1250–850 cm−1).

Quantum confinement effects on the structural and optical properties of nanostructured tin oxide powder

Nanostructured Tin oxide powders, prepared by chemical precipitation method, exhibit interesting structural and optical properties at nanoscale dimensions. Structural characterization confirmed the formation of pure nanostructured SnO2 powders with average crystalline grain size of 54.4[Formula: see text]nm calculated with relative uncertainty of 1.62%. The optical properties of nanoSnO2 powder performed by using transmittance and photoluminescence measurements reveal high transparency and multi-photon emissions in visible and ultraviolet regions. The different photon emissions are attributed to radiative transitions via oxygen vacancies, Sn interstitials, Sn substitutional and dangling bonds. The lower wavelength value corresponded to the absorption edge peak indicating the good quantum confinement of nanostructured SnO2 powder. The larger optical band gap, calculated through transmittance measurements, confirms the quantum confinement effects. The presence of quantum confinement and native point defects in nanostructured SnO2 powders can contribute to enhancing photon emissions process. This result may offer inherent advantages over conventional materials for photonic quantum information technology. The sustained photon emission at room temperature, indicates that SnO2 nanoparticles could be useful in room temperature quantum computing and can maintain the delicate quantum states required for computation at higher temperatures.

Сферические субмикронные порошки с нано-поликристаллической субструктурой — перспективное сырье для получения мелкозернистой высокоплотной керамики (обзор)

The review reflects the unique properties and possible areas of application of submicron non-agglomerating powders from refractory oxides obtained by aerosol-spray pyrolysis. An analysis of the experimental results obtained by researchers at different times convincingly proves the promise of using aerosol nanostructured submicron spherical powders to obtain ceramic materials with a high-density, uniform fine-grained structure without pores. The uniqueness of aerosol powders is due to the presence in the particles of the nano-polycrystalline substructure of a developed network of inter-grain boundaries, which during sintering has a significant impact on the efficiency of diffusion mass transfer and contributes to an increase in the speed and completeness of pores overgrowth. Aerosol powders acquire these properties through the use of ultrasonic spray pyrolysis, where equilibrium physicochemical processes occur in ultra-small local volumes of aerosol droplets, ensuring a high degree of uniformity of the resulting powder. The formed ultrathin substructure of aerosol powders ensures their full sintering at low temperatures, making it possible to obtain high-density ceramic materials with extreme physical and mechanical characteristics. The practical use of nanostructured aerosol powders does not require the use of preliminary preparation operations (grinding-grinding, classification, purification from impurities, etc.) and, unlike ultrafine powders, they are easily molded using traditional methods of powder technology (uniaxial pressing, hot casting, etc.).

Is synthesizing a Cu35Co35Ni20Ti5Al5 high-entropy alloy beyond the rules of solid-solution formation?

In this research, an attempt was made to produce multi-component nanocrystalline Cu­35Co35Ni20Ti5Al5 alloy by mechanical alloying. To produce this high-entropy alloy, the primary powders were milled for 40 h and characterized by XRD, SEM, EDS, and DSC analyses. The milling process has reduced the size of the crystallites to the nanometer scale and a nanostructured multicomponent powder with a crystallite size of 29 nm was obtained. According to the XRD patterns and EDS maps of the milled powder for the longest time, aluminum and copper were homogeneously distributed, cobalt had a less homogeneous distribution than these two elements, but nickel and titanium remained in concentrated spots. Finally, thermodynamic calculations were done to clarify the reason for the impossibility of forming a solid solution for the synthesis of the Cu­35Co35Ni20Ti5Al5 high-entropy alloy.

Developing of Lead/Polyurethane Micro/Nano Composite for Nuclear Shielding Novel Supplies: γ-Spectroscopy and FLUKA Simulation Techniques.

In this work, the effect of adding Pb nano/microparticles in polyurethane foams to improve thermo-physical and mechanical properties were investigated. Moreover, an attempt has been made to modify the micron-sized lead metal powder into nanostructured Pb powder using a high-energy ball mill. Two types of fillers were used, the first is Pb in micro scale and the second is Pb in nano scale. A lead/polyurethane nanocomposite is made using the in-situ polymerization process. The different characterization techniques describe the state of the dispersion of fillers in foam. The effects of these additions in the foam were evaluated, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) have all been used to analyze the morphology and dispersion of lead in polyurethane. The findings demonstrate that lead is uniformly distributed throughout the polyurethane matrix. The compression test demonstrates that the inclusion of lead weakens the compression strength of the nanocomposites in comparison to that of pure polyurethane. The TGA study shows that the enhanced thermal stability is a result of the inclusion of fillers, especially nanofillers. The shielding efficiency has been studied, MAC, LAC, HVL, MFP and Zeff were determined either experimentally or by Monte Carlo calculations. The nuclear radiation shielding properties were simulated by the FLUKA code for the photon energy range of 0.0001-100 MeV.

Cold spray coating: A review of material systems and future perspectives

Spraying solid powders onto a substrate at high velocity with a de Laval nozzle characterizes cold spray, also known as a cold gas dynamic spray (CS). Particles will stick to a surface if the impact velocity is high enough to create a plastic deformation. Metals, ceramics, composites, and polymers are just some materials that may be deposited utilizing CS, opening up a world of interesting possibilities for specialized harvesting applications. CS has some technological advantages compared to thermal spray due to using kinetic energy for deposition. There has been a proliferation of material combinations that can be sprayed utilizing cold spray technology due to the emergence of new material systems with superior properties in disciplines as disparate as internal combustion engines and biotechnology. The need to provide a concise summary of the state of the art increases as the amount of research into a topic grows in line with the breadth of its potential applications. This overview will discuss the various material systems studied for potentially revolutionary uses. Polymer is considered in two contexts: as a substrate and a layer, allowing us to discuss metal incorporation. CS has shown promise in depositing nanostructured materials, unlike many traditional consolidation processes, without significantly altering their microstructure. Relevant material systems, which may include nanostructured powders, are also considered. It examines microstructural bonding techniques for those relatively new material systems and discusses their potential future uses. Examples of suitable materials include ceramics, polymers, MMCs, and nanostructured powders. More study is required, particularly to quantify the relationship between process parameters and the effective behaviour of the targeted material systems.

Fabrication and Characterization of Dielectric ZnCr2O4 Nanopowders and Thin Films for Parallel-Plate Capacitor Applications.

We report here the successful shape-controlled synthesis of dielectric spinel-type ZnCr2O4 nanoparticles by using a simple sol-gel auto-combustion method followed by successive heat treatment steps of the resulting powders at temperatures from 500 to 900 °C and from 5 to 11 h, in air. A systematic study of the dependence of the morphology of the nanoparticles on the annealing time and temperature was performed by using field effect scanning electron microscopy (FE-SEM), powder X-ray diffraction (PXRD) and structure refinement by the Rietveld method, dynamic lattice analysis and broadband dielectric spectrometry, respectively. It was observed for the first time that when the aerobic post-synthesis heat treatment temperature increases progressively from 500 to 900 °C, the ZnCr2O4 nanoparticles: (i) increase in size from 10 to 350 nm and (ii) develop well-defined facets, changing their shape from shapeless to truncated octahedrons and eventually pseudo-octahedra. The samples were found to exhibit high dielectric constant values and low dielectric losses with the best dielectric performance characteristics displayed by the 350 nm pseudo-octahedral nanoparticles whose permittivity reaches a value of ε = 1500 and a dielectric loss tan δ = 5 × 10-4 at a frequency of 1 Hz. Nanoparticulate ZnCr2O4-based thin films with a thickness varying from 0.5 to 2 μm were fabricated by the drop-casting method and subsequently incorporated into planar capacitors whose dielectric performance was characterized. This study undoubtedly shows that the dielectric properties of nanostructured zinc chromite powders can be engineered by the rational control of their morphology upon the variation of the post-synthesis heat treatment process.

Electrochemical Determination of Ascorbic Acid by Mechanically Alloyed Super Duplex Stainless Steel Powders

SAF-2507 super duplex stainless steel powders (SDSS) were prepared using a high-energy planetary ball milling process. The X-ray diffraction (XRD) shows peak broadening after 20 h of ball milling and revealed a phase transformation resulting in a two-phase alloy mixture containing nearly equal amounts of ferrite (α) and austenite (γ). After 20 h of ball milling the particle size was reduced to ~201 nm. Scanning electron microscope (SEM) micrographs showed small-size irregular grains with an average particle size ranging from 5–7 µm. The high-resolution transmission microscope (HRTEM) analysis confirmed the presence of nanocrystalline particles with sizes ranging from 10 to 50 nm. The presence of ferrite phase is visible in the corresponding diffraction pattern as well. In this paper, we have discussed the electrochemical sensor application of mechanically alloyed nano-structured duplex stainless steel powders. The fabricated 4 mg duplex stainless steel modified carbon paste electrode (SDSS-MCPE) has shown excellent current sensitivity in comparison with 2, 6, 8, and 10 mg SDSS-MCPEs during the detection of ascorbic acid (AA) in a phosphate buffer solution with a pH of 6.8. The calculated electrode active surface area of SDSS-MCPE was found to be almost two times larger than the surface area of the bare carbon paste electrode (BCPE). The limit of detection (LD) and limit of quantification (LQ) were found to be 0.206 × 10−8 M and 0.688 × 10−8 M, respectively, for the fabricated 4 mg SDSS-MCPE.