Search

Incorporation of functional water-soluble technological lubricants (FWTL) of zinc nanopowder into fractal clusters improves their greasy properties, and increases the stamping efficiency and iron plate draw-forming under the transport body parts fabrication.

Severe effects of the mercury use on health as an amalgam material have required an alternative material in order to eliminate it from amalgam composition. This research was conducted to analyze the physical properties and compressibility of ZnO nanopowder as an alternative amalgam material. The physical properties including morphology, dimensions, and the atomic ratio were analyzed by SEM, XRD-XRF and EDX. Further, the compressibility was conducted by using hydraulic press machine. The results showed that ZnO has particle size of 14.34 nm with morphology classified as nanorods. In the compressibility test, both the variation of compression loadings and holding time have brought an effect on the significant increase of ZnO nanopowder density.

Free carbon appears in β -SiC nanopowders as two-dimensional and ultrathin structures exposed predominantly on particle surfaces. These structures range from graphitic to lamella and amorphous, with more than one type being present at once. Their relative proportions and total percentage are quantified based on CO 2 evolution traces resulting from temperature-programmed oxidation (TPO). The TPO peak parameters are representative of the carbon nanostructure. The temperature of the peak maximum relates to the degree of graphitic order, whereas an apparent activation energy to structure homogeneity. Among the Raman parameters (for a 514-nm excitation wavelength), the area ratio of the D and G + D′ lines closely correlates with the relative proportion and structural perfection of the graphitic form. Furthermore, the area ratio of the β -SiC and carbon Raman lines is a strong function of the free carbon content in the range 0.1 to 5 wt%. The established correlations provide a guide to the consistent implementation of both techniques to characterize mixed carbon forms in β -SiC nanopowders. [ABSTRACT FROM AUTHOR]

In the present research, SiC–B 4 C nano powders were synthesized through sol–gel process in water–solvent–catalyst–dispersant system. In order to evaluate the formation mechanism of the product during sol-gel process, TEM, SEM, DTA/TG, BET, XRD, FTIR and DLS analysis methods were employed. The nanometric size of precursor was controlled by dispersing agents and controlling pH inside the sol. DLS analysis revealed that the particles of the precursor inside the sol were below 10 nm. FTIR results indicated that the (Si–O–B) bonds were formed in the dried gel powder, due to hydrolysis and condensation reactions. DTA analysis confirmed that the synthesis temperature was lower than 1400 °C. XRD results implied the presence of cubic β-SiC and the rhombohedral B 4 C phases, which were formed simultaneously in the SiC–B 4 C nanopowder. BET analysis indicated a high surface area for the particles of about 171.42 m2/g, and that the surfaces of these particles were meso porous. SEM analysis exhibited that SiC– B 4 C particle size was in the range of 20–40 nm with homogenous morphology. Ultimately, the TEM/EDS microstructural analysis showed that B 4 C and SiC particles were formed simultaneously and uniformly in the final product. [ABSTRACT FROM AUTHOR]

In this paper, we study compact samples of pyrophoric nickel powders with the average particle size of 85 nm, obtained by the chemical-metallurgical method. For the first time, it is experimentally shown that it is possible to passivate compact samples with a diameter of 3 mm from pyrophoric nickel powders with nanosized particles in air. For a relative density of 0.4 to 0.5, the passivation time is only 3–5 s. According to the X-ray phase analysis data, only the Ni phase is observed in passivated samples. It is found that passivated samples retain their thermal stability in air upon slow (<10 deg/s) heating to ~200°C, which is an important parameter for fire safety when handling nanopowders. The electron microscopic analysis of the passivated samples did not reveal traces of sintering of nickel nanoparticles, including after checking for thermal stability. The uniform distribution of oxygen over the passivated samples according to the data of energy dispersive analysis (the standard deviation is 0.9 at %) indicates the volumetric nature of the interaction of the samples with air during passivation. For the obtained passivated samples, the critical heating conditions were determined, under which self-ignition occurs, which is in agreement with N.N. Semyonov's classical theory of thermal explosion. [ABSTRACT FROM AUTHOR]

Pure and doped SnO2 with V2O5 nanopowders were synthesized via sol–gel method using different V2O5 ratios. Novel thin films of SnO2:V2O5 were thermally vacuum deposited from the nanopowders and utilized for gas sensor devices to detect volatile organic compounds hazardous gases. The morphological and crystalline structure, textural properties, functional groups, optical properties and thermal behavior were investigated by FESEM, XRD, HRTEM, surface area BET, FTIR and UV–Visible spectroscopy, respectively, for both the nanopowders, and thin films. From XRD patterns, the average calculated crystallite sizes decreased from 7.8 nm to 4.5 nm as the V2O5 concentration was varied from 0 to 10%. FESEM and HRTEM show that all the synthesized nanomaterials composed of mesoporous networks of aggregated nanoparticles that almost spherical. Thus, V2O5 doped SnO2 nanopowders synthesized by sol–gel method exhibited the structural and textural features required to be used as an active area for gas sensor devices. The effect of various doping weight amounts (1, 5 and 10 wt%) of V2O5 as the dopant element enhanced the gas response time and sensitivity. The electrical behavior of the sensors was determined by measuring the resistance of two deposited platinum electrodes for sensor's devices for different kinds of gases (LPG, H2, NH3 and acetone) at different temperatures. [ABSTRACT FROM AUTHOR]

In this study, the conversion of Celestite to SrCO3 was studied by wet mechanochemical synthesis in a high‐energy ball mill and treatment with Na2CO3. For this purpose, solid strontium carbonate and soluble Na2SO4 were obtained after wet milling of Celestite powder and sodium carbonate. The solid phase was washed with water at room temperature by filter pressing. X‐Ray diffraction patterns showed that the SrCO3 nanopowder was synthesized and conversion boosted with increasing the milling time up to 8 hours Also, Rietveld refinement analysis was used to calculate the fraction of SrCO3 as well as structural properties of synthesized samples. It was found that initial Celestite could be converted to strontium carbonate with a purity more than 98% using high‐energy milling without simultaneous heating. The optimum milling time was determined as 4 hours resulting in formation of nanopowders with an average particle size around 90 nm. Field Emission Scanning Electron Microscopy (FE‐SEM), clearly showed the nanoscale structure of the synthesized powders. [ABSTRACT FROM AUTHOR]

The paper presents the experiments on irradiation of the yttrium oxide powder target with a relativistic electron beam and evaporative production of yttrium oxide nanopowder. The phase and chemical consistence, specific surface and particles geometry of nanopowder was studied. A model of mass productivity of nanopowder vs. input e-beam power was tested qualitatively. The effect of continuous operation of setup on the filter catching capacity was studied. A phenomenon of a tubular-shaped structure growing from the hot targeting point toward the electron beam direction was described. [ABSTRACT FROM AUTHOR]

In the present study, Cu 2 ZnSnS 4 (CZTS) powder was synthesized by the mechano-chemical method from its elemental constituents. X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and diffusion reflectance spectroscopy (DRS) were used for characterization of structural, morphological and optical properties. XRD result confirmed that a highly crystalline CZTS phase corresponding to the kesterite structure was formed after 50 h ball milling. Raman analysis confirmed the existence of single phase CZTS without any other phases. FESEM and TEM images reveal the irregular CZTS nanoparticles with an average size of 90 nm. The elemental mapping of the CZTS nanopowder showed the uniform distribution in agreement with the stoichiometry. DRS result showed a band gap value of 1.53 eV. XPS result revealed the oxidation states as Cu+, Zn2+, Sn4+ and S2−. The photocatalytic activity of CZTS has been investigated through photodegradation of methylene blue (MB) and methyl orange (MO) dyes solution with different concentrations under visible light irradiation. Although the CZTS decomposed MO only 81% until 210 min, the MB solution was completely photodegraded after 100 min. A kinetic study by Langmuir-Hinshelwood (L-H) model indicated about 3.7 times faster degradation of MB than MO and also higher adsorption capacity for MB by CZTS. Furthermore, the prepared CZTS was reusable and can be repeatedly used for the removal of dyes from aqueous solutions. • Cu 2 ZnSnS 4 nanophotocatalyst was mechano-chemically synthesized. • Improved visible light photocatalytic efficiency for MB and MO dyes was obtained. • The degradation kinetics of MB and MO dyes was discussed. • The photocatalyst exhibited significant recycle efficiency. [ABSTRACT FROM AUTHOR]

Demand for high‐density press and sinter components is increasing day by day. Of the different ways to improve the sinter density, the addition of nanopowder to the conventional micrometer‐sized metal powder is an effective solution. The present investigation is aimed at studying the surface chemistry of iron nanopowder coated with graphitic carbon, which is intended to be mixed with the conventional iron powder. For this purpose, iron nanopowder in the size range of 30 nm to submicron (less than 1 micron) was investigated using thermogravimetry at different temperatures: 400°C, 600°C, 800°C, 1000°C, and 1350°C. The X‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and high‐resolution scanning electron microscopy (HR‐SEM) were used for characterizing the powder as well as samples sintered at different temperatures. The presence of iron, oxygen, carbon, chromium, and zinc were observed on the surface of the nanopowder. Iron was present in oxide state, although a small metallic iron peak at 707 eV was also observed in the XPS spectra obtained from the surface indicating the oxide scale to be maximum of about 5 nm in thickness. For the sample treated at 600°C, presence of manganese was observed on the surface. Thermogravimetry results showed a two‐step mass loss with a total mass loss of 4 wt.% when heated to 1350°C where the first step corresponds to the surface oxide reduction. [ABSTRACT FROM AUTHOR]

Investigation of the peculiarities of photoluminescence in different gas ambients of Si- and Ge-doped ZnO nanopowders was carried out. Nanopowders were obtained and doped by means of pulsed laser reactive technology. X-ray diffractometry, scanning, and transmission electron microscopy were conducted to determine the structure, shape, and size of the nanoparticles. Changing the gas environment leads to a significant change in the intensity of the photoluminescence spectra and its deformation; this is a result of the redistribution of existing luminescence centers and the emergence of additional luminescence centers caused by the adsorption on the nanopowders surface. The decomposition of luminescence spectra into elementary bands shows the presence of four elementary peaks at 430, 480, 515, and 555 nm. The influence of the impurity and the gas medium on the redistribution of elementary luminescence band intensities was investigated. The investigated nanopowders can be effectively used as sensitive materials for the construction of gas sensor systems. [ABSTRACT FROM AUTHOR]

NiO nanopowder is produced through plasma-chemical synthesis in a low-pressure arc reactor in an atmosphere of 80% Ar + 20% O 2 at a pressure of 40 (sample 1) and 180 Pa (sample 2). The crystalline, morphological, and impedance properties are studied by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and impedance spectroscopy. It is shown that an increase in pressure leads to the synthesis of nanomaterials with fundamentally different crystalline and electrical properties. Sample 1 shows a non-stoichiometric composition (Ni 42 O 58), a face-centered cubic lattice, and a size of coherent scattering regions (CSR) of 16 nm. The impedance studies shows that the frequency dependences are well described by the Debye relaxation model, at low frequencies the real part of the dielectric constant is equal to 35, and thermal studies show a negative temperature coefficient of resistance (NTCR). Sample 2 has an amorphous structure, almost stoichiometric composition (Ni 48 O 52). At low frequencies, the real and imaginary parts of the dielectric constant reaches 105. The anomaly is explained by the formation of a double electric layer near the electrodes due to proton-ion conductivity. [ABSTRACT FROM AUTHOR]

This paper reports the analytical and experimental studies aimed at designing and modeling fluoropolymer anti-friction materials. The optimal ratios of the total surface of polymer particles to the total surface of filler particles for different brands of fluoropolymer-4 have been determined, as well as the critical concentrations of the modifiers of fluoropolymer anti-friction materials. The calculations of antifriction carboplastics' elasticity modules indicate the existence of adhesion between carbon fiber and polytetrafluoroethylene. When constructing composites that combine high durable and tribotechnical characteristics, it is advisable to combine modifiers with different dispersion and polymer-oligomeric matrices, which enables the implementation of the principle of multilevel modifying. It has been established that the adhesion between carbon fiber and polytetrafluoroethylene can be improved by applying a fluoropolymer coating onto the surface of carbon fibers or by modifying with zirconium oxide nanopowders. The binary fluoropolymer matrix applied to the surface of carbon fiber can be used as an effective base for composite materials. This study has demonstrated that filling polytetrafluoroethylene (PTFE) with coke, carbon fibers (18‒19.5 % by weight), and zirconium oxide nanopowders in the amount of up to 2 % by weight produces materials with high mechanical characteristics and durability. It has been shown that the existence of an oligomer component improves the thermodynamic compatibility at the interface and promotes the plasticization of the PTFE boundary layers. Molecular structure with a certain orientation of coke and carbon fiber in the interphase areas is inherent in the materials with improved physical and mechanical properties. [ABSTRACT FROM AUTHOR]

Visible-light photocatalytically active titanium oxide (TiO2) nano-powder was synthesized by a flat-flame chemical vapor condensation method. The formation of TiO2 consisting of different ratios of anatase and rutile phases was controlled by two parameters: the acetylene flow rate (C2H2, 600 sccm and 800 sccm) and the acetylene/oxygen flow ratio (C2H2/O2, 1:3, 1:4, 1:5, and 1:6). The location of the photonic center was identified for visible-light absorption, which is in the anatase grains. The photonic center on the surface of anatase grains happens to be the nucleation site for rutile in an oxygen-deficient environment. The visible-light absorption could be attributed to the formation of defect levels related to the photonic center within the band gap of anatase. The major role of the mixed-phase structure of TiO2 in the enhancement of visible-light photocatalytic activity is in the enhancement of carrier separation and not of light harvest, for the powder produced in this study. [ABSTRACT FROM AUTHOR]

We have studied the influence of the glycine : nitrate (G/N) ratio and heat treatment temperature on characteristics of nanocrystalline Li4Ti5O12 powders synthesized from titanium tetrabutylate and lithium carbonate via combustion of an aqueous–organic precursor, followed by heat treatment. At the optimum reactant ratio G/N = 0.7, the content of the Li4Ti5O12 phase after heat treatment of the powders for 2 h at 700°C is 97% and the crystallite size is 100 nm. It has been shown that modifying the glycine–nitrate process by adding citric acid to solution (CitH3/ΣM = 0.37–0.56) allows one to improve the homogeneity of the components in the precursor, thus ensuring the preparation of single-phase powders. [ABSTRACT FROM AUTHOR]

Nanopowders with different average particle sizes of 20 to 40 nm are obtained by milling TaC microcrystalline powder. Analytical chemistry, X-ray diffraction, scanning electron microscopy, and the Brunauer–Emmett–Teller approach are used to study the effect the average particle size of TaC nanopowder and the temperature of its vacuum annealing (400–1400°С) had on the chemical and phase composition, morphology, and average particle size of the powder after annealing. It is found that the vacuum annealing of TaC nanopowders over the considered range of temperatures is accompanied by their decarbonization as a result of the interaction between carbon and impurity oxygen. It is shown that a rise in the temperature of annealing of TaC nanopowder is accompanied by an increase in both its size of particles and its decarbonization. As a result not only does the composition y of TaCy carbide change, but the phase composition of the entire powder changes as well. TaC nanopowder becomes microcrystalline after vacuum annealing at temperatures of 1200°C and above. [ABSTRACT FROM AUTHOR]

This study presents a low-cost method for obtaining nanometric zinc oxide (ZnO) using a cassava starch (Tapioca)-assisted by sol-gel route. In this procedure, ZnO nanopowders (~20 nm and 59 nm according to XRD) were obtained after 2 h of calcination at 500oC. The cassava starch played a fundamental role during the sol-gel synthesis allowing the obtention of ZnO nanopowders (ZnO T) with crystallite size three times smaller than the ones without cassava starch (ZnO). SEM and TEM images corroborate the idea that Tapioca inhibited crystal growth in ZnO T when compared to the ZnO obtained from the same methodology. The synthesis of the obtained ZnO T was studied by FTIR and the results point to a possible interaction between zinc cations and C–O groups of glucose molecule that arises from the starch hydrolysis; thus, showing that Tapioca works as a good chelating agent, as well as presenting a very low cost. [ABSTRACT FROM AUTHOR]

This study focused on the comparison of the Pechini and sugar-based combustion synthesis methods to produce nano-zirconia. Zirconium hydroxide was utilized as metal precursor and citric acid, sucrose, and fructose were used as chelating agents, followed by calcination at 500, 600, and 700°C in air, respectively. Characterization was conducted by thermal analysis, specific surface area measurement, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning and transmission electron microscopy. When sucrose and citric acid were used as chelating agents during synthesis, mixtures of monoclinic and tetragonal phases were formed after calcination at 600 and 700°C. In the fructose samples, the tetragonal structure was the unique characterized phase. The tetragonal parameters in the fructose samples were determined using the diffraction data and the lattice parameter ratio was proven to increase with the temperature increase. Compared with the citrate and sucrose samples, the largest specific surface area (27 m2·g−1) and smallest particle size (39.1 nm) were obtained for the fructose sample after calcination at 700°C. The study revealed the formation of single-phase stabilized tetragonal zirconia using fructose as chelating agent after calcination at 500°C, and the presence and formation mechanism of stabilized tetragonal phase were also discussed on the basis of the X-ray and electron diffraction studies. [ABSTRACT FROM AUTHOR]

Aluminum powders were comprehensively described as the prospective ingredients of the modern propellants. The paper also studied the influence of micro‐ and nanopowders of metals (μ‐Me and n‐Me) and metal oxides (μ‐MeO and n‐MeO) on the burning process of modern aluminized propellant with HMX, CL‐20, AP, and active binder. The following metal additives were used: Al, B, Zn, Ni, Co, and Mo. The effect of the following oxides CoO, V2O5, MnO2, and Fe2O3 was studied together with LiF. The combustion tests of modified propellant compositions were carried out in the Vielle bomb in a pressure range 2–10 MPa. n‐Me addition resulted in an increase in the burning rate by 10 % for n‐B, by 30–40 % for n‐Ni and n‐Mo in the studied pressure range. The introduction of n‐Cu caused a burning rate to increase fivefold. n‐Zn additive resulted in increasing of the propellant burning rate by 130 % and 260 % at 4 and 10 MPa, respectively. It was probably caused by the catalytic activity of those metals in the gaseous phase. The effect of complex additive was observed to be insignificant for additives with μ‐Co3O4, μ‐V2O5, μ‐Fe2O3 and n‐Fe2O3. The burning rate of propellant with n‐CuO additive value was higher by a factor of 4 in comparison with the basic formulation in the studied pressure range. [ABSTRACT FROM AUTHOR]

This article presents descriptions of theoretical models and numerical methods for simulating turbulent thermal plasma flow with nanopowder growth. Turbulence models must express turbulent and laminar states because both states co-exist with thermal plasmas showing large density variation and transport properties. Time-dependent 3D simulations are conducted based on Large Eddy Simulation using a dynamic Smagorinsky model. Results show significant difference depending on temporal and spatial discretization schemes and velocity–pressure coupling algorithms. Simulation results demonstrate that advanced numerical methods with high-order accuracy should be used for long and robust computations capturing steep gradients of nanopowder concentration and plasma temperature and 3D dynamic motions of multiscale vortices, which are turbulent features of thermal plasma flows with low Mach numbers. A thermal plasma jet generates a double-layer structure of inner high-temperature thick vortex rings and outer low-temperature thin vortex rings near the nozzle exit. Flowing downstream, these vortices interact, deform, and break up. Consequently, plasma transits to a complex thermal flow. The widely spreading distribution of multiscale vortices agrees with experimental observations, which are not simulated using conventional methods. Nanopowder is generated from material vapour by nucleation and condensation at interfacial regions between plasma and cold gas. Those regions include numerous vortices. Therefore, the vortices convey the nanopowder, producing a complex distribution of nanopowder. Simultaneously, the nanopowder diffuses and increases in size, decreasing in number by interparticle coagulation. Cross-correlation analysis suggests that a nanopowder distribution distant from a plasma jet can be controlled through temperature fluctuation control at the upstream plasma fringe. [ABSTRACT FROM AUTHOR]

A technology that allows one to create new diamond–metal compositions for stone-cutting diamond tools is proposed, which is based on selecting new metallic binders with the use of powders of tailings (crushed samples of tungsten carbide and cobalt) of Tyrnyauz Tungsten–Molybdenum Plant and black tailings of Pobedit plant with almost the same composition. The proposed technology substantially increases the efficiency of diamond–metal compositions. The addition of powders of Tyrnyauz Tungsten–Molybdenum Plant or their mixtures with powders of black tailings of Pobedit plant to the blend provides finer porosity and increases the durability of diamond tools. [ABSTRACT FROM AUTHOR]

ZrB 2 –ZrC–SiC nanopowders with uniform phase distribution were prepared from cost-effective ZrOCl 2 ·8H 2 O by a simple sol-gel method. The synthesis route, ceramization mechanism and morphology evolution of the nanopowders were investigated. ZrB 2 –ZrC–SiC ceramic precursor can be successfully obtained through hydrolysis and condensation reactions between the raw materials. Pyrolysis of the precursor was completed at 650 °C, and it produced ZrO 2 , SiO 2 , B 2 O 3 and amorphous carbon with a yield of 39% at 1300 °C. By heat-treated at 1500 °C for 2 h, highly crystallized ZrB 2 –ZrC–SiC ceramics with narrow size distribution were obtained. With the holding time of 2 h, both the crystal size and the particle size can be refined. Further prolonging the holding time can lead to serious particles coarsening. Studies on the microstructure evolution of the generated carbon during the ceramic conversion demonstrates the negative effect of the ceramic formation on the structure order improvement of the carbon, due to the large amount of defects generated in it by the boro/carbothermal reduction reactions. [ABSTRACT FROM AUTHOR]

In this study, high purity gamma-alumina nanopowders with crystalline structures have been prepared via a sol–gel process by waste metal aluminum, HCl, NaOH, Polyethylene glycol (PEG) and polyvinyl alcohol (PVA). Polyethylene glycol and polyvinyl alcohol have been used as stabilizing agents. The characterization of the samples has been performed utilizing XRD, FTIR, SEM, N2 adsorption/desorption techniques. Prepared samples of gamma-alumina at 800∘C with PEG has an average crystallite size of 2.58 nm, average particle size of 21 nm, specific surface area (SSA) of 65.55 m2/g, and pore volume of ∼ 0.06 cm3/g. The average crystallite size of 3.07 nm, average particle size of 31 nm, specific surface area of 131.25 m2/g, and pore volume of ∼ 0.14 cm3/g, were obtained using PVA surfactant. [ABSTRACT FROM AUTHOR]

Magnesium Zinc Phosphate (MgZn 2 (PO 4) 2 = MZP) nanopowder, both undoped and doped with Eu3+ ions, were synthesized using the Solid State Reaction Method (SSR). Structural and optical characterization of synthesized samples using various analytical and spectroscopic techniques such as X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), and Energy dispersive spectroscopy (EDS), High-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), Diffuse reflectance spectroscopy (DRS), and Photoluminescence spectroscopy (PL) was evaluated. The XRD analysis shows both in monoclinic phase and high degree of crystallinity with an average size of crystallites approximately 26 nm and 30 nm for the undoped and Eu3+ doped host samples, respectively. From the DRS study, the sample exhibits broad optical direct band gap values of 3.01 eV for MZP and 2.88 eV for MZP doped with Eu3+ ions. The surface morphology of the prepared samples reveals that they are arranged in stone like shapes. The PL results of the MZP doped with Eu3+ ions exhibited the luminescence. The excitation at 394 nm and emission observed at 612 nm in the red region of the electromagnetic spectrum is attributed to an electric dipole transition whereas the emission detected at 591 nm in the orange region is commonly associated with a magnetic dipole transition. [Display omitted] • The Magnesium Zinc Phosphate (MgZn 2 (PO 4) 2 = MZP) nanopowder doped with 0.01 mol % of Eu3+ were prepared by SSR method. • The most intense emission peak is found at 591 nm, which is attributed to the transition 5D 0.→7F 1 (MD). • The ratio of intensities of MD to ED transitions is found to be 2.5, which suggest that the dopant occupies local identical symmetry site. • The CCT (2825 K), value calculated from the emission spectrum suggests that the material is suitable for warm-emitting LEDs and other solid-state lighting systems. [ABSTRACT FROM AUTHOR]

This study used substituted barium hexaferrites, which were previously prepared and reported by the authors, to detect acetaminophen by the modification of a conventional glassy carbon electrode (GCE), which led to promising results. The synthesis of this electrode-modifying material was conducted using a citrate sol gel process. A test synthesis using glycerin and propylene glycol revealed that glycerin produced a better result, while less positive anodic potential values were associated with the electrooxidation of N-acetyl-p-aminophenol (NAP). Excellent electroactivity was exhibited by the cobalt-substituted barium-hexaferrite-nanomaterial-modified electrode. A good linear relationship between the concentration and the current response of acetaminophen (paracetamol) was obtained with a detection limit of (0.255 ± 0.005) µM for the Ba1.0Co1.22Fe11.41O18.11 GCE, (0.577 ± 0.007) µM for the Ba1.14Cu0.82Fe11.65O18.02 GCE, and (0.595 ± 0.008) µM for the bare GCE. The levels of NAP in a real sample of urine were quantitatively analyzed using the proposed method, with recovery ranges from 96.6% to 101.0% and 93.9% to 98.4% for the modified electrode with Cobalt-substituted barium hexaferrites (CoFM) and Copper-substituted barium hexaferrites (CuFM), respectively. These results confirm the high electrochemical activity of Ba1.0Co1.22Fe11.41O18.11 nanoparticles and thus their potential for use in the development of sensing devices for substances of pharmaceutical interest, such as acetaminophen (NAP).

Fluorapatite nanopowders with different amounts of fluoride ions were prepared using the surfactant-assisted microwave method under isothermal conditions. Microwave irradiation was applied for the rapid formation of crystals. A micellar solution of polyoxyethylene (23) lauryl ether was used as a regulator of nucleation and crystal growth. Characterization studies from X-ray diffraction, field-emission scaning electron microscopy and Fourier-transform infrared spectra showed that crystals have an apatite structure and particles of all samples are nano size, with an average length of 50 nm and about 15-25 nm in diameter. Antimicrobial studies have demonstrated that synthesized fluorapatite nanopowders exhibit activity against tested pathogens: Escherichia coli, Staphylococcus aureus and Candida albicans. Activity increased with the amount of fluoride ions. The synthesized fluorapatite nanomaterials are promising as materials in environmental protection and medicine for orthopedics and dental restorations. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 43009]

Over a decade ago, it was confirmed that detonation nanodiamond (DND) powders reflect very cold neutrons (VCNs) diffusively at any incidence angle and that they reflect cold neutrons quasi-specularly at small incidence angles. In the present publication, we report the results of a study on the effect of particle sizes on the overall efficiency of neutron reflectors made of DNDs. To perform this study, we separated, by centrifugation, the fraction of finer DND nanoparticles (which are referred to as S-DNDs here) from a broad initial size distribution and experimentally and theoretically compared the performance of such a neutron reflector with that from deagglomerated fluorinated DNDs (DF-DNDs). Typical commercially available DNDs with the size of ~4.3 nm are close to the optimum for VCNs with a typical velocity of ~50 m/s, while smaller and larger DNDs are more efficient for faster and slower VCN velocities, respectively. Simulations show that, for a realistic reflector geometry, the replacement of DF-DNDs (a reflector with the best achieved performance) by S-DNDs (with smaller size DNDs) increases the neutron albedo in the velocity range above ~60 m/s. This increase in the albedo results in an increase in the density of faster VCNs in such a reflector cavity of up to ~25% as well as an increase in the upper boundary of the velocities of efficient VCN reflection.

This study aimed to produce electrospun nanofibers from a polyvinyl butyral polymer (PVB) solution enriched with red and grey selenium nanoparticles. Scanning electron microscopic analysis was used to observe the samples, evaluate the fiber diameters, and reveal eventual artifacts in the nanofibrous structure. Average fiber diameter is determined by manually measuring the diameters of randomly selected fibers on scanning electron microscopic (SEM) images. The obtained nanofibers are amorphous with a diameter of approximately 500 nm, a specific surface area of approx. 8 m2 g−1, and 5093 km cm−3 length. If the red and grey selenium nanoparticles were produced in powder form and suspended to the ethanolic solution of PVB then they were located inside and outside the fiber. When selenium nanoparticles were synthesized in the PVB solution, then they were located only inside the fiber. These nanofiber sheets enriched with selenium nanoparticles could be a good candidate for high-efficiency filter materials and medical applications.

Background: Orthodontic tooth movement is a continual and balanced process between bone deposition and bone resorption in pressure and tension sites. Stichopus hermanii is one of the best fishery commodities in Indonesia. It is natural and contains various active ingredients such as hyaluronic acid, chondroitin sulphate, cell growth factor, eicosa pentaenoic acid (EPA) docosa hexaenoic acid (DHA) and flavonoid that potentially play a role in orthodontic tooth movement. Purpose: The aim of this study was to investigate the active ingredients of nanopowder Stichopus hermanii promoting bone resorption in tension area orthodontic tooth movement. Methods: A quantitative test for active ingredients of stichopus hermanii was conducted. Thirty two male Cavia cobaya were divisibled became four groups. K (–) groups as a negative control group (without treatment), K (+) groups as a positive control group which were provided with a separator rubber for orthodontic tooth movement, and P1, P2 groups, which were treated with 3% and 3.5% stichopus hermanii for orthodontic tooth movement. After treatment the cavia cobaya were sacrificed. TRAP-6 expression as a osteoclast marker was examined by means of an immunohistochemistry method. Results: A one-way Anova test confirmed that TRAP-6 expression was significantly increased with p = 0.00 (p≤0,05) in P2 compared to K (+). P2 to K (–), P2 to P1 and P1 to K (+) had no significant differences Conclusion: Nanopowder Stichopus hermanii 3.5% has an active ingredient that could increase osteoclast activity to resorb periodontal ligament and alveolar bone in tension areas of orthodontic tooth movement.

Mechanochemically prepared nanopowder of selenium-free kesterite Cu2ZnSnS4 (CZTS) in combination with n-type semiconductors, i.e., CdS, ZnO and TiO2, was tested in planar and bulk-heterojunction solar cells. The samples have been studied by macroscopic current-voltage (I-V) measurements and Kelvin-probe atomic-force microscopy (KPFM). KPFM images taken under light illumination showed the distribution of the potential across the surface, with negative potential on the n-type semiconductor domains and positive potential on the CZTS domains, which indicated charge separation at the interface of the counterparts. The best result was found for the CdS-CZTS composition, which showed a potential difference between the domains up to 250 mV. These results were compared with the planar heterojunctions of CdS/CZTS and TiO2/CZTS, where CZTS nanopowder was pressed/deposited directly onto the surface of films of the corresponding n-type semiconductors. Again, I-V characteristics showed that cells based on CdS/CZTS heterojunctions have the best performance, with a photovoltage up to 200 mV and photocurrent densities up to 0.1 mA/cm2. However, the carrier generation was found to occur mainly in the CdS semiconductor, while CZTS showed no photo-response and served as the hole-transporting layer only. It is concluded that sensitization of the kesterite powder obtained by mechanochemical method is necessary to improve the performance of the corresponding solar cells.

In this research a high purity copper powder was fabricated via wires explosion technique using copper wire with (99%) purity by the following dimensions (300 mm length, 0.2 mm diameter) on glass substrate inside vacuum chamber and under ambient argon gas, with the utilization of 2.2 KV of explosion voltage and 100 J of storage energy. The used wire purity and structural and morphology properties of the powder surface were diagnosed via X-Ray Fluorescence (XRF), X-RayqDiffraction (XRD), ScanningqElectron Microscopy (SEM) and AtomicqForce Microscope (AFM). Experimental results showed that the average particle.size of the prepared copper powder was in the rangeqof (20-40 nm) and the samples have high purity and no impurities were observed which makes this nanopowder suitable for many applications especially as additives in lubricating oil for tribological characteristics improvement and suitable catalyst in the heat exchanger systems in the industrial installations.

In this study, the effects of dopant concentrations on the structural and morphological characteristics of Zn1-xMnxO powders (x= 0.025, 0.05, 0.075, and 0.1 mole) synthesized by the Pechini method has been investigated. The powder was characterized by X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET) specific surface, energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and Spectroscopy with Fourier transform (FTIR). An XRD analysis of the powder showed the formation of ZnO phase with a typical single phase wurtzite structure. The EDX analysis revealed Mn incorporated in the ZnO structure. The particle size calculated by BET ranged from 24 to 63 nm, confirming the nanometric size of the powder particles. The SEM analysis revealed irregular shaped particle agglomerates and the presence of nanosheets. From FTIR it was confirmed the wurtzite structure in ZnO and ZnO nanoparticles doped with Mn.

The relevance. The preparation of refractory nitrides in the air under the conditions of thermal explosion of aluminum nanopowder mixtures with metal oxides presents practical interest both for materials science and for the theory of the reactivity of air at high temperatures. This synthesis is the least energy-intensive, and it does not require complicated equipment. Only the heating of the initial charge is necessary for synthesis, then the process proceeds spontaneously. The main aim of the research is to determine experimentally the composition of combustion products of aluminum nanopowder mixtures with niobium pentaoxide in the air, to substantiate theoretically the stabilization of niobium nitride Nb2N in the air. Object: powder containing niobium nitride obtained by burning a mixture of aluminum nanopowder with niobium pentoxide in the air. Methods: x-ray analysis (diffractometer Difrey-401), differential thermal analysis SDT Q600 Instrument company. On the basis of the results of the differential thermal analysis the authors have calculated four parameters of the mixtures activity: temperature of oxidation beginning (tst.ox., °C), oxidation degree (α, %), maximal oxidation speed (vmax, mg/min), specific thermal effect (ΔН, J/g). X-ray analysis was used for investigating crystal structure of oxidation ending products. Results. Combustion of mixtures of aluminum nanopowder with niobium pentaoxide in the air proceeded in two stages with formation of niobium nitride Nb2N. According to the x-ray analysis in the combustion products, the mixture of NP Al:Nb2O5=3:1 reached maximum of 47 rel. %. The calculation of the isobaric-isothermal potential showed that niobium nitride should be oxidized by air oxygen. The reason of stabilization of Nb2N crystalline phase is the air oxygen deactivation by emission of burning aluminum nanopowder.

Large emissions of nitrogen dioxide (NO 2 ) pose a significant threat to human health, Monitoring its content and implementing timely measures are crucial. Utilizing oxide semiconductors, such as tin dioxide (SnO 2 ), has proven to be an effective way to detect and analyze NO 2 . The design and preparation of sensing materials with high sensitivity and excellent selectivity is the key to improve the detection efficiency. SnO 2 nanopowders with small and uniform particle size, large specific surface area, adjustable defect content, and no impurities were prepared by a new plasma spraying method. The SnO 2 nanopowders exhibit outstanding performance in detecting NO 2 at a low temperature of 100 °C, the response to 5 ppm of NO 2 reaches 48, and the material demonstrates rapid response and recovery times, coupled with excellent selectivity. The exceptional gas-sensitive properties can be attributed to the superior morphology and structure of SnO 2 . It provides more reaction sites for gas sensitive reactions, fast electron transport, a large number of charge carriers, and improved adsorption of the material to the target gas. This study provides valuable insights into nanomaterial preparation and the enhancement of gas-sensitive properties for SnO 2 .

A simple technique was utilized to fabricate pure hexagonal La 2 O 3 nanorods by utilizing lanthanum(III) nitrate hexahydrate (La(NO 3 ) 3 ·6H 2 O) and ammonia (NH 4 OH). The La 2 O 3 nanoparticles were analyzed using XRD, TGA, Raman, SEM, FTIR, TEM, PL spectroscopy, and Mott-Schottky techniques. The XRD analysis confirmed the production of La(OH) 3 nanorods under appropriate conditions, which were then successfully converted into La 2 O 2 CO 3 and finally into La 2 O 3 nanorods through annealing. The TGA analysis showed that the total weight loss was due to water evaporation and the dissolution of minimal moisture present in the environment. The FTIR analysis confirmed the presence of functional groups. The SEM analysis revealed changes in morphology. The TEM analysis to determine the particle size. The PL findings showed three emission peaks at 390, 520, and 698 nm due to interband transitions and defects in the samples. The Mott-Schottky analysis demonstrated that the flatband potential and acceptor density varied with annealing temperature, ranging from 1 to 1.2 V and 2 × 10 18 to 1.4 × 10 19  cm -3 , respectively. Annealing at 1000 °C resulted in the lowest resistance to charge transfer (Rct)., (© 2024. The Author(s).)

Neutrons can be an instrument or an object in many fields of research. Major efforts all over the world are devoted to improving the intensity of neutron sources and the efficiency of neutron delivery for experimental installations. In this context, neutron reflectors play a key role because they allow significant improvement of both economy and efficiency. For slow neutrons, Detonation NanoDiamond (DND) powders provide exceptionally good reflecting performance due to the combination of enhanced coherent scattering and low neutron absorption. The enhancement is at maximum when the nanoparticle diameter is close to the neutron wavelength. Therefore, the mean nanoparticle diameter and the diameter distribution are important. In addition, DNDs show clustering, which increases their effective diameters. Here, we report on how breaking agglomerates affects clustering of DNDs and the overall reflector performance. We characterize DNDs using small-angle neutron scattering, X-ray diffraction, scanning and transmission electron microscopy, neutron activation analysis, dynamical light scattering, infra-red light spectroscopy, and others. Based on the results of these tests, we discuss the calculated size distribution of DNDs, the absolute cross-section of neutron scattering, the neutron albedo, and the neutron intensity gain for neutron traps with DND walls.

Crystalline lead sulfide (PbS) nanowires doped with terbium (Tb3+) ions were synthesized by the chemical bath deposition method at room temperature. The powder was obtained from an aqueous solutions using lead acetate dehydrate, terbium nitrate, thiourea, potassium hydroxide and ammonia. The terbium molar concentrations were varied in the deposition process to investigate the effect on the structural, optical, morphological and luminescent properties of PbS nanowires. The crystalline size was found to be dependent on the concentration of the Tb3+ ions used. The estimated average crystalline sizes were calculated from the X-ray diffraction and found to be 34, 33 and 37 nm for PbS: 0% Tb3+, PbS: 0.2% Tb3+ and PbS: 0.5% Tb3+, respectively. The scanning electron microscopy micrographs depict nanowire shape for the undoped as well as Tb-doped samples. The energy-dispersive X-ray and Auger electron spectroscopy analyses confirmed the presence of all the expected elements. The solid powder nanowires exhibited high absorptions in the UV–Vis regions. The band gap energies were estimated in the range of 1.99–2.46 eV. The absorption edge and the band gap energies of these PbS nanowires have shifted depending on the concentration of the dopant. The maximum luminescence intensity was obtained for PbS: 0.2% Tb3+ ions and luminescent quenching was observed for higher terbium concentrations. [ABSTRACT FROM AUTHOR]

The in situ measurement of Sr isotopes in carbonates by MC‐ICP‐MS is limited by the availability of suitable microanalytical reference materials (RMs), which match the samples of interest. Whereas several well‐characterised carbonate reference materials for Sr mass fractions > 1000 µg g−1 are available, there is a lack of well‐characterised carbonate microanalytical RMs with lower Sr mass fractions. Here, we present a new synthetic carbonate nanopowder RM with a Sr mass fraction of ca. 500 µg g−1 suitable for microanalytical Sr isotope research ('NanoSr'). NanoSr was analysed by both solution‐based and in situ techniques. Element mass fractions were determined using EPMA (Ca mass fraction), as well as laser ablation and solution ICP‐MS in different laboratories. The 87Sr/86Sr ratio was determined by well‐established bulk methods for Sr isotope measurements and is 0.70756 ± 0.00003 (2s). The Sr isotope microhomogeneity of the material was determined by LA‐MC‐ICP‐MS, which resulted in 87Sr/86Sr ratios of 0.70753 ± 0.00007 (2s) and 0.70757 ± 0.00006 (2s), respectively, in agreement with the solution data within uncertainties. Thus, this new reference material is well suited to monitor and correct microanalytical Sr isotope measurements of low‐Sr, low‐REE carbonate samples. NanoSr is available from the corresponding author. [ABSTRACT FROM AUTHOR]

The influence of compaction pressure during semidry compaction in a steel mold of zirconia powder partially stabilized by yttria on the phase composition and microstructure of formed compacts, as well as samples sintered at 1400°C for 2 h, is investigated. An aqueous solution of polyvinyl alcohol is selected as a temporary manufacturing binder. The yttria content in the powder synthesized according to the sol–gel technology (the deposition by an aqueous-ammonia solution from aqueous ethanol solutions of corresponding reagents with the agar-agar additive) is 3.2 mol % according to the X-ray fluorescent analysis data. The results of studying the compacts and sintered samples by Raman spectroscopy, optical microscopy, and atomic force microscopy are presented. It is established that an increase in their density is not monotonic. There is the critical range of compaction pressures P = 400–450 MPa, in which the porosity, pore shape and sizes, microstructure, and phase composition of the material vary abruptly. A monoclinic phase, the content of which varies upon varying P, is fixed in compacted samples along with tetragonal zirconia. Material grain grinding is associated with the destruction of agglomerates and actively occurs in range P = 350–550 MPa. A similar effect when studying the compaction process of nanopowders of zirconia is also noted by other researchers, who assumed that the response of the nanopowder system on the pressure effect is associated with the influence on the aqueous component (the temporary manufacturing binder in this case) and is caused by the transition of one form of water into another one at 10–25°C and a pressure of 400–700 MPa. [ABSTRACT FROM AUTHOR]

We describe an aerosol spray pyrolysis system for the synthesis of yttria-stabilized zirconia (YSZ) nanoparticles with precisely tunable composition. Extensive structural and compositional characterization confirm that this technique gives access to particles with combined size and composition that are not commercially available. We have densified these particles via spark plasma sintering to investigate the mechanical and optical properties of the resulting bulk samples. Direct transmittance of the densified samples was measured to determine the role of grain size, porosity, oxygen vacancies, and crystal structure on the transparency of the samples. Small grain sizes and low porosity are commonly suggested as the essential property to obtain transparency. We have found that the transparency strongly correlates with crystal structure, with isotropic crystal structure having the highest transparency. Finally, to determine the mechanical properties of the densified samples, we used Vickers hardness testing confirming that YSZ in a tetragonal crystal structure is both harder and tougher than in a cubic crystal structure. This study suggests that aerosol spray pyrolysis is a promising synthetic approach for the synthesis of small YSZ nanocrystals with controllable composition. This could enable the optimization of both the optical and mechanical properties of bulk YSZ. [ABSTRACT FROM AUTHOR]

• Laminar burning velocity of nanocellulose-air mixtures was determined experimentally. • A value of 20 cm s−1 is proposed for the laminar burning velocity of nanocellulose. • Tests performed in a semi-open tube a modified 20 L sphere give consistent results. • Linear and nonlinear correlations between flame stretching and velocity were compared. • These results are useful as inputs to CFD models of dust explosion on a larger scale. Due to their low sedimentation rate, nano-objects offer the opportunity to study flame propagation at low turbulence. The burning velocity was then estimated by flame visualization in two apparatuses: a vertical 1 m long tube with a square cross-section and a 20 L sphere equipped with visualization windows and a vent. This works aims to study the laminar burning velocity of nanocellulose by a direct visualization of the flame propagation within these devices. A high-speed video camera was used to record the flame propagation, and an estimation of the unstretched burning velocity was obtained through linear and nonlinear relationships relating the flame stretching and the flame velocities. Although these methods were initially established for gases, the organic nature of nanocellulose implies a fast devolatilization, which makes the application of the methods possible in this work. Similar results were obtained in both apparatuses in different turbulence conditions, proving the laminar burning velocity was approached. The laminar burning velocity for the nanocellulose was determined to be 21 cm s−1. This value, estimated through flame propagation visualization, was then compared to the value calculated by applying a semi-empiric correlation to the pressure-time evolution recorded during standard explosion tests in the 20 L vessel. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metal Materials & Engineering is the property of Northwest Institute for Nonferrous Metal Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)