Average Particle Size Of Powders Research Articles

Low-temperature fabrication of high-entropy rare earth hexaboride powders

Herein, we report a low-temperature method for synthesizing high-entropy rare earth hexaboride powders by reaction among rare earth oxides, B4C, and Al powders. Al was used as a reducing and decarburization agent in this process, which further reduced the Gibbs free energy change for the reaction of RexOy with B4C to form REB6. By investigating the influence of reacting temperature and amount of Al added on preparation of LaB6, the optimum experimental conditions of this method were determined to be 1300 °C and 2 times the stoichiometric ratio of Al. Theoretical supports were proposed to verify the feasibility for formation of high-entropy borides. Then, multicomponent hexaborides La0.5Ce0.5B6, La0.33Ce0.33Nd0.33B6, and La0.25Ce0.25Nd0.25Sm0.25B6 as well as high-entropy hexaboride La0.2Ce0.2Nd0.2Sm0.2Eu0.2B6 powders were successfully prepared by doping with Ce, Nd, Sm, and Eu on LaB6. RE elements with different radius were uniformly distributed in the multicomponent boride powders without obvious segregation. More importantly, the lattice distortion and stress induced by the element substitution contribute to the reduction of the average powder particle size. Finally, the DTA-TG curves show that rare earth hexaborides have good oxidation resistances when the temperature is below about 1000 °C.

Enhancement of nutrient bioaccessibility and functional property of chicken bone powder through steam explosion

There are technological and nutritional challenges to efficient use of chicken bone in foods, due to its low bioaccessibility and techno-functionality. The impacts of steam explosion (SE), autoclave, steam treatment on the powder characteristics and the effect of SE on the physicochemical properties and bioaccessibility of chicken bone powders were investigated. X-ray diffraction and Fourier transform infrared spectroscopy indicated that SE treatment might increase crystallinity, partial loss of organic substance, but not completely destroyed its crystal type. SE had a smaller particle size of chicken bone powder with time and energy saving compared with other treatments, and it was conducive to improving the color acceptability. Compared with native chicken bone powder, SE significantly decreased the average particle size of powder by 79.23 %, whereas its specific surface of unit volume increased by 119.98 %. And SE improved the techno-functionality which evaluated by water holding capacity (4.19 %), oil holding capacity (10.53 %), water solubility index (117.64 %) and ABTS radical scavenging activity (14.05 %). The higher protein digestibility, calcium and major amino acids contents in chicken bone powder during digestion showed SE upgraded the bioaccessibility. The results were suggestive that steam explosion was an efficient process for preparing bone powder with improved techno-functionality and noticeable bioaccessibility.

Effect of polystyrene addition on properties of porous Si3N4 ceramics fabricated by digital light processing

Porous Si3N4 ceramics with high strength and high transmittance have been widely used in the field of defense and military. Additive manufacturing (AM) technology is one of the effective means to fabricate porous Si3N4 ceramics. Nevertheless, it is difficult to prepare porous Si3N4 ceramics by using digital light processing (DLP) because of the large refractive index difference between Si3N4 powders and photosensitive resin. In this study, the effects of the amount of polystyrene (PS) powders on the properties of Si3N4 ceramic slurries and sintered ceramics were systematically discussed. The addition of PS reduced the overall refractive index of powders and increased the average particle size of powders, thus improving the cure depth of Si3N4 ceramic slurries from 11.0 ± 2.0 μm to 55.7 ± 1.8 μm. With the increase of PS content, the shrinkage and porosity of Si3N4 ceramics gradually increased, and the bulk density and flexural strength showed the opposite trend. The slurry with low viscosity (2.38 Pa٠s at a shear rate of 30 s−1) and high cure depth (51.2 ± 4.6 μm) was obtained when the content of PS was 15 wt%, which met the thickness requirements for printing. The total porosity of Si3N4 ceramics reached the maximum values at 28.21 ± 2.58%. The addition of PS solved the problem of low cure depth of slurries, and PS as a pore-forming agent could help Si3N4 ceramics form porous structure. This research provides valuable insights into the fabrication of non-oxide ceramics with high refractive index using DLP technology.

The Effect of Powder Granulometric Composition on the Structure and Size of the Porous Ceramics Channels

The paper studies the structure of the end-toend channel network of porous ceramic specimens. Electro corundum powders with different granulometric compositions were used to manufacture ceramics, which was achieved by grinding electro corundum in a ball mill for various time periods. The characteristic dimensions of end-to-end channels of porous ceramics were determined. A relationship was established between the granulometric composition of powders and the properties of theend-to-end channel network in porous ceramics. It is shown that the largest pores, whose size monotonically depends on the powder average particle size, comprise most of the pore space of a permeable ceramic manufactured, using narrow-fraction powders. On the other hand, if a powder with polydisperse particle size is used for ceramics manufacturing, a wide range of pore channel sizes is observed. The smaller the pores, the greater their contribution to the ceramic pore space. It should be noted that such information makes it possible to purposefully design materials with the required structure, which is most optimal for a particular product (filter elements, heat-insulating materials, etc.). Keywords — electrocorundum, permeable ceramics, end-toend channels, liquid extrusion porosimeter, granulometric powder composition, filter elements.

Mathematical optimization of the average particle size of powders obtained by electroerosive dispersion of heat-resistant nickel alloy ZHS6U

Mathematical optimization of the average particle size of powders obtained by electroerosive dispersion of heat-resistant nickel alloy ZHS6U

Effect of Mechanical Alloying on Structural and Electrical Properties of (P<sub>2</sub>O<sub>5</sub>)<sub>(x)</sub>-(Y<sub>2</sub>O<sub>3</sub>)<sub>(0.03)</sub>-(ZrO<sub>2</sub>)<sub>(0.97)</sub> Electrolyte

Pentavalent phosphorous oxide doped yttria-stabilized zirconia (P2O5)X-(Y2O3)0.03-(ZrO2)0.97 with x=0.06 mol.% was achieved via an economical technique using mechanical alloying (MA) technique. Three types of nanocomposite powders of electrolyte were produced by high-energy ball milling with different milling times. The phases of synthesized electrolyte powders and sintered electrolytes were illustrated by X-ray diffraction (XRD). The average particle sizes of powders indicated around (360, 245, and 48) nm at milling duration (1, 10, and 45) hrs, respectively. The XRD analysis results of 1 h MA electrolyte powder obtained tetragonal ZrO2, while the 45 h MA electrolyte manifested a minority phase of monoclinic ZrO2. Then, the XRD of the sintered electrolyte with the optimum electrical properties appeared two phases. The major phase of the tetragonal zirconium yttrium oxide and a minor phase was a monoclinic zirconium oxide. The average grain sizes of the three types of the sintered manufacturing electrolytes were (7.638, 2.642, and 1.245 µm) after the mechanical alloying duration of (1, 10, and 45) hrs, respectively and sintered at 1873 °K. The DC conductivity (σ) studied corresponded to the influence of milling times on the microstructure for each sintered electrolyte. From the results, the synthesized sintered electrolyte with a long MA duration gave a maximum DC (σ) 1.03E-1S.m. And, the DC conductivity (σ) was 1.11E-02 of electrolyte produced with 10 hr mechanical alloying. Otherwise, the lower DC conductivity got with the electrolyte prepared in the lowest milling duration was 8.9 E-2 S.m.

Spattering and oxidation phenomena during recycling of low alloy steel powder in Laser Powder Bed Fusion

This study reports on the impact of repeated powder recycling on the degradation of low alloy steel powder in Laser Powder Bed Fusion. The average powder particle size increased slightly upon recycling due to powder agglomeration and the presence of spatters and other ejecta from the process zone. The oxygen content showed a continuous growth after each recycle, while the other chemical elements of the recycled powder remained largely unchanged. A map of ejecta classification is presented, featuring various ejecta types formed during laser processing. Ejecta of increased diameter and different shapes were observed in the recycled powder, using high-speed imaging and Scanning Electron Microscopy. The ejecta were collected after each powder recycle to enable the calculation of the ejecta mass generated during the process. The result showed a direct correlation between oxygen content in the powder and spatter/ejecta formation with the number of recycling events. It is likely that the increase in oxygen contributes to powder spattering.

Study on the kinetics of process for obtaining cobalt nanopowder by hydrogen reduction under isothermal conditions

The kinetics of metallic cobalt nanopowder synthesizing by hydrogen reduction from Co(OH)2 nanopowder under isothermal conditions were studied. Co(OH)2 nanopowder was prepared in advance by chemical deposition from aqueous solutions of Co(NO3)2 cobalt nitrate (10 wt.%) and NaOH alkali (10 wt.%) at room temperature, pH = 9 under continuous stirring. The hydrogen reduction of Co(OH)2 nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 270 to 310 °C. The crystal structure and composition of powders was studied by X-ray phase analysis. The specific surface area of samples was measured using the BET method by low-temperature nitrogen adsorption. The average particle size of powders was determined by the measured specific surface area. Particles size characteristics and morphology were investigated by transmission and scanning electron microscopes. Kinetic parameters of Co(OH)2 hydrogen reduction under isothermal conditions were calculated using the Gray–Weddington model and Arrhenius equation. It was found that the rate constant of reduction at t = 310 °C is approximately 1.93 times higher than at 270 °C, so the process accelerates by 1.58 times for 40 min of reduction. The activation energy of cobalt nanopowder synthesizing from Co(OH)2 by hydrogen reduction is ~40 kJ/mol, which indicates a mixed reaction mode. It was shown that cobalt nanoparticles obtained by the hydrogen reduction of its hydroxide at 280 °C are aggregates of equiaxed particles up to 100 nm in size where individual particles are connected to several neighboring particles by contact isthmuses.

Effects of moisture and particle size distribution on flame propagation of L-lysine sulfate powder

Lysine is an essential amino acid for human body, and lysine sulfates are at risk of fire and explosion during the production and processing. However, there is no public report on the lysine sulfate powder explosion hazard research. In this paper, the effects of moisture, mass concentration and particle size on the flame propagation behaviors of L-lysine sulfate powder were studied in a vertical pipe. The results showed that the flame propagation could be divided into 3 stages: free propagation, acceleration and attenuation, in which the acceleration was owed to the positive feedback of combustion reaction, gas expansion and turbulence. Moisture content could promote the flame propagation of L-lysine sulfate powder to a certain extent, but it had a strong inhibitory effect on the explosion when the moisture content was too large. The flame propagation velocity increased with the decrease of the average particle size of powder,.With the increase of the particle concentration, the flame propagation velocity of powder explosion increased first and then decreased, that was, there was an optimal concentration of powder explosion, and the powder was more sensitive to the change of concentration in the range of low concentration.

Development and Research of Flux-Cored Electrodes For Welding And Surfacing Of Parts From Aluminum And Titanium Alloys

Perpose of research was to study the properties of powder materials obtained from aluminum and titanium waste by the method of electroerosion dispersion for the development of electrodes suitable for welding and surfacing of parts from aluminum and titanium alloys. Methods . To obtain an aluminum powder material by electroerosion dispersion method, an aluminum wire GOST 14838-78 was used, pre-cut to 5-7 cm. the Wire was loaded into a reactor filled with a working liquid – distilled. The process was carried out at the following electrical parameters: discharge capacitor capacity 65 UF, voltage 100 V, pulse frequency 100 Hz. To obtain a titanium powder material by electroerosion dispersion method, shavings of VT6 grade were used. The chips were loaded into a reactor filled with a working liquid – distilled water. The process is carried out at the following electrical parameters: capacity of the bit capacitors 65 µf, a voltage of 150 V, pulse frequency of 250 Hz. The result of the local effects of intermittent electrical discharges between the electrodes was the destruction of the material with the formation of dispersed particles of powder. In order to study the shape and morphology of powder material particles obtained by electroerosion dispersion from aluminum waste, images were taken on a raster (scanning) electron microscope QUANTA 600 FEG. The study of granulometric composition of powder materials obtained by the method of electroerosion dispersion of aluminum and titanium waste was carried out on a laser analyzer particle size Analysette 22 NanoTec. Results. It is established that the most promising and not industrially used materials for the production of electrodes used in welding and surfacing of parts are powder materials obtained by electroerosion dispersion. It is experimentally established that the powder materials obtained by electroerosive dispersion of aluminum and titanium wastes consist of spherical and elliptical particles. The results of the study of the elemental composition of powder materials obtained by electroerosive dispersion of aluminum and titanium waste, it is shown that the main elements of the powders produced and aluminum waste are aluminum and oxygen, and the main elements of the powders produced and shavings of the VT6 BRAND are Ti, Al, O, V, Fe, W and K. Studies of the particle size distribution of powder materials obtained by electroerosion dispersion showed that the average particle size of powders obtained from aluminum waste is 19.08 microns, and the average particle size of powders obtained from titanium waste is 33.12 microns. It is established that the most promising method for the production of electrodes used for welding and surfacing of parts from aluminum and titanium alloys is the method of spark plasma sintering. Conclusion . The obtained results can be used to create resource-saving processes for processing metal alloys and composite materials.

Synthesis of Fe:ZnSe nanopowders via the co‐precipitation method for processing transparent ceramics

AbstractFe:ZnSe nanopowders were synthesized via the co‐precipitation method for fabricating transparent ceramics. FexZn1−xSe (0.00 ≤ x ≤ 0.06) powders that were calcined at 400°C yielded a single‐phased cubic ZnSe, but when the calcination temperature was raised to 500‐600°C, ZnO phase was created. Introduction of pressure could avoid appearance of ZnO. XRD Scherrer analysis revealed a monotonic increase in lattice parameter with increasing Fe2+ content. The average powder particle size increased with calcination temperature from several nanometers at 80°C to hundreds of nanometers at 600°C. Attempts to pressurelessly sinter ZnSe powders resulted in the partial decomposition of ZnSe, thus spark plasma sintering was employed to sinter Fe0.01Zn0.99Se transparent ceramics with pure ZnSe phase composition, which could be well sintered at 950°C for 30 minutes under an applied pressure of 60 MPa. SEM observations of the polished and thermally etched microstructure of the ceramic revealed a dense microstructure with average grain size of approximately 35 μm, and a few micropores were observed at the grain boundaries. The transparent ceramic exhibited good transmittance in the mid‐far infrared range, with the highest transmittance 57% at 12 μm. This paper confirmed the scheme of synthesis of Fe:ZnSe nanopowders by liquid‐phase co‐precipitation method for sintering transparent ceramics.

Planetary ball‐milling of AlON powder for highly transparent ceramics

AbstractA detailed investigation of planetary ball‐milling for coarsened AlON powder was carried out. Our results showed that the weight ratios of milling ball‐to‐powder, the revolution rate and the planetary ball‐milling time have significant impacts on the microscopic morphology, particle size distribution and average particle size of powder. The process and mechanism were analyzed, and the outcome of our study can be used to optimize the complicated planetary ball‐milling method by controlling the planetary ball‐milling time or adjusting the revolution rate at the final stage of planetary ball‐milling. Sequentially, using fine and uniform AlON powder by optimized planetary ball‐milling with an average particle size below 300 nm and excellent sintering properties, highly transparent AlON ceramic with an in‐line transmittance of 84% at 2000 nm was successfully prepared through pressureless sintering at 1880°C for 6 hours using the elaborative treated powder synthesized from carbothermal nitridation method.

Formulation of levodopa containing dry powder for nasal delivery applying the quality-by-design approach

The aim of this work was to carry out preliminary experiments for preparation of levodopa (LEVO)-containing intranasal powder. The experiments were designed according to the Quality by Design (QbD) concept. Based on prior risk assessment, LEVO and chitosan (CH) or sodium hyaluronate (HA) as mucoadhesive matrix formers were co-milled using planetary ball mill to prepare microparticles as drug delivery systems. The rotation speed, the milling time and the drug-additive ratio were evaluated to be the most relevant milling factors - as a result of the initial risk assessment; which were set according to a factorial design. The effects of critical process parameters and excipients were investigated on the particle size and surface characteristics of products, and on the crystallinity, in vitro dissolution and permeability of LEVO. Milling in the presence of higher amount of HA resulted in smaller average particle size of powders (D50 = 13.068 μm) and higher initial dissolution and permeation of LEVO compared to CH-containing formulations (D50 = 21.667 μm).

Particle and Crystallite Size Characterisation of Lead Titanate Derived from Solid-state Reaction Method

Lead titanate (PbTiO3) ceramic was produced by solid state reaction via a vibratory ball milling machine and subsequent heat treatment. The effect of milling time on the particle and crystallite size of PbTiO3 powder was investigated. Powder samples were studied using particle size analyser (PSA). The annealing process was up to 1,000°C and the products were examined by X-ray diffractometer (XRD) to determine phase formation and crystallite size. It was found that the average particle size of powder initially increased due to laminated layers formation and then decreased to an asymptotic value of ~0.8 μm as the milling time extended even to a relatively longer time. Single-phase PbTiO3 were achieved at 600°C for 1 h holding time of annealing temperature. Annealing the sample of the particles at 1,000°C resulted in a dense compact and promoted the formation of particles containing nanocrystallites. The crystallite size of PbTiO3 increased as the function of temperature of annealing process.

Characterization of β-tricalcium phosphate powders synthesized by sol–gel and mechanosynthesis

β-Tricalcium phosphate (β-TCP) is one of the most investigated calcium phosphates to be used in bone tissue regeneration. Nowadays, β-TCP has been synthetized by different methods that allow obtaining different morphologies with chemical compositions similar to the bone tissue, broadening the possibilities of use. In this work, β-TCP powders were obtained using two different routes: mechanosynthesis and sol–gel. Results shown that both methods had significant effects on morphology and size particle of the obtained powders. The average size particles obtained using mechanosynthesis at 24 and 12h of milling time were 1000 and 170nm, respectively. The average size particles of the powders fabricated using sol–gel was 350nm, and the average powder particle size of the sigma reagent was 1450nm. Besides, sol–gel and sigma reagent powders were observed residual phases, instead mechanosynthesis shown only tricalcium phosphate beta phase. The formation of agglomerates with different sizes was observed in both methods by sol–gel and mechanosynthesis.

Effect of Mechanical Activation on the Structural Parameters of Ceramic Powders cBN-Co, hBN-Co

The paper describes the study of mechanical activation of multi-component ceramic powder materials based on boron nitride. The mechanical activation of the powders was carried out according to the best optimal parameters in a ball mill AGO-2U. Increasing the time of mechanical activation leads to more fine-grained powders. We described the technique of mechanical activation of ceramic powder materials. We introduced the results of X-ray diffraction analysis of the ceramic powder cBN, cBN-Co, hBN-Co before and after mechanical activation. We generated mathematical equations of dependence of an average powder particle size on the average mechanical activation time. We described how the crystal lattice "a" parameters and unit cell volume "V" of cBN and hBN powders depend on mechanical activation time. We studied the chemical composition of powder materials. We also studied the structural parameters of ceramic powders.

Self-propagating high-temperature synthesis of an aluminum nitride nanopowder from a Na3AlF6 + 3NaN3 + nAl powder mixture

Methods for producing aluminum nitride nanopowder were reviewed. It was shown that an azide technology of self-propagating high-temperature synthesis using sodium azide as a solid nitriding agent produces quite a cheap nano- and ultradispersed AlN powder by the combustion of a Na3AlF6–3NaN3–nAl powder mixture. This AlN powder is of interest for electronics, light-emitting diode technology, and reinforcement of modification of aluminum alloy. A nanostructured aluminum nitride powder forms by the combustion of a Na3AlF6–3NaN3. With increasing the aluminum content of the initial mixture, the aluminum nitride yield increases, but so does the average powder particle size.

Electrophoretic deposition of spherical carbonyl iron particles on carbon fibers as a microwave absorbent composite

Carbonyl iron (CIPs) micron size spherical particles were deposited on carbon fibers by electrophoretic deposition method (EPD). A well stabilized suspension of CIPs was prepared in acetone-ethanol media and two different stabilizer of Iodine and Trietanolamine (TEA) were used to investigate stability of suspension. X-ray Diffractometer (XRD) was employed to study structure of CIPs, CFs and CFs/CIPs composite. Field Emission Scanning Electron Microscopy (FE-SEM) images were taken to see the morphology of CFs and deposited particles. Dynamic Light Scattering (DLS) and zeta potential test were carried out to study the stability of particles and also to see the average particle size of powder. To investigate magnetic and reflection loss properties, Vibrating Sample Magnetometer (VSM) and Vector Network Analyzer (VNA) were used, respectively. Uniformly coated fibers were selected to make composites and results revealed that the best Reflection Loss (RL) was related to CFs coated for 20 minutes in a bath containing iodine with a layer thickness of 2mm. Maximum recorded RL was found to be -13.8dB at frequency of 9.22GHz.

Nanoparticulate titanium dioxide synthesized by sol–gel and solution combustion techniques

Nano-sized titanium dioxide is renowned for its prominent photocatalytic properties. Various synthesis techniques have been successfully employed in production of nano-titanium dioxide. Some of the techniques require expensive initial reagents as well as extensive preparation time. A rapid, simple and cost-effective technique capable of producing high quality nano-particles is highly desirable. This study, therefore, aims at examining effects of synthesis techniques and initial reagents on chemical compositions and particle sizes of titanium dioxide. A solution combustion technique as well as a sol–gel method using Titanium (IV) isopropoxide (TTIP) and submicrometer-sized titanium dioxide as initial reagents were employed as synthesis techniques. Experimental results indicated that all synthesized powders contained pure anatase titanium dioxide. Average particle sizes of powders prepared by the solution combustion technique from TTIP and submicrometer-sized titanium dioxide were 44 and 77nm whereas, powder sizes prepared by the sol–gel method averaged at 48 and 85nm respectively.

The effect of milling energy input during mechano-chemical activation synthesis (MCAS) of the nanocrystalline manganese borohydride (Mn(BH4)2) on its thermal dehydrogenation properties

Abstract A manganese borohydride, Mn(BH4)2, co-existing with a nanocrystalline LiCl salt, which is a reaction “dead-weight” byproduct, was successfully synthesized by the mechano-chemical activation synthesis (MCAS) during ball milling the (nLiBH4 + MnCl2) mixtures having the molar ratios n = 2 and 3, using the total milling energy input, QTR, from 36.4 to 364 kJ/g. The crystallite (grain) size of the synthesized nanocrystalline Mn(BH4)2 hydride attains 21 ± 5.0 nm for the energy input QTR = 36.4 kJ/g and then it is further reduced to 18 ± 1.0 nm for QTR = 145.6 kJ/g and finally to 14 ± 0.5 nm for QTR = 364 kJ/g. The crystallite (grain) size of LiCl is very close to 30 nm regardless of the milling energy input, QTR. During continuous heating in a Differential Scanning Calorimeter (DSC), Mn(BH4)2 decomposes in endothermic reaction releasing H2 and forming amorphous Mn and B in the process. The synthesized nanocrystalline Mn(BH4)2 hydride, co-existing with a nanocrystalline LiCl salt, is capable of desorbing up to ∼ 4.5 wt.% at 100 °C. The values of the apparent activation energy for dehydrogenation obtained in the present work are very low. The apparent activation energy for the n = 3 nanocomposite decreases monotonically from ∼70 to ∼59 kJ/mol with increasing milling energy input whereas the apparent activation energy for the n = 2 nanocomposite decreases from about 65 kJ/mol for QTR = 36.4 kJ/g to about 53 kJ/mol for QTR = 145.6 kJ/g and then again increases to ∼59 kJ/mol for the QTR = 364 kJ/g. These changes closely follow the variations in the average powder particle size obtained with the varying milling energy input. For the milling energy input QTR = 36.4 and 145.6 kJ/g the average powder particle size decreases to 14.9 ± 6.6 and 7.5 ± 2.6 μm, respectively, and subsequently increases reaching the average size of 16.1 ± 6.3 μm for the milling energy input QTR = 364 kJ/g. On the other hand, the apparent activation energy for dehydrogenation doesn't depend on the average crystallite (grain) size. The amorphous Mn and B elements are also formed after isothermal dehydrogenation. The synthesized Mn(BH4)2 hydride is very stable and doesn't excessively release H2 during a long-term storage at room temperature for over 120 days under a slight overpressure of argon.