Powders Of Different Particle Sizes Research Articles

Hydrogen production from aluminum-water reactions at low Temperatures: based on an in-situ two powders of different particle sizes

To investigate the granule reaction of two-micron aluminum powders with water at low temperatures, differential scanning calorimetry was used to analyze the initial exothermic temperature. Additionally, adiabatic accelerated calorimetry was employed to study the exothermic reaction under adiabatic conditions. The hydrogen production and particle size variation were investigated in order to gain insights into the Al-water reaction in a reactor with no induction time. Through focused beam reflectance measurement analysis, it was observed that during the reaction process of Al-water, particle sizes initially increased and then decreased. Specifically, the particle size of 3 µm aluminum powder experienced a 189% increase after the reaction while 25 µm aluminum powder decreased by 29%. Ultimately, both types of particles reached similar final sizes around 13.89 µm. The process of Al-water reaction was explained and hydrogen production was analyzed, and the kinetic model was obtained.

Effect of Starting Powder Particle Size on the Thermoelectric Properties of Hot-Pressed Bi0.3Sb1.7Te3 Alloys.

P-type Bi0.3Sb1.7Te3 polycrystalline pellets were fabricated using different methods: melting and mechanical alloying, followed by hot-press sintering. The effect of starting powder particle size on the thermoelectric properties was investigated in samples prepared using powders of different particle sizes (with micro- and/or nano-scale dimensions). A peak ZT (350 K) of ~1.13 was recorded for hot-pressed samples prepared from mechanical alloyed powder. Moreover, hot-pressed samples prepared from ≤45 μm powder exhibited similar ZT (~1.1). These high ZT values are attributed both to the presence of high-density grain boundaries, which reduced the lattice thermal conductivity, as well as the formation of antisite defects during milling and grinding, which resulted in lower carrier concentrations and higher Seebeck coefficient values. In addition, Bi0.3Sb1.7Te3 bulk nanocomposites were fabricated in an attempt to further reduce the lattice thermal conductivity. Surprisingly, however, the lattice thermal conductivity showed an unexpected increasing trend in nanocomposite samples. This surprising observation can be attributed to a possible overestimation of the lattice thermal conductivity component by using the conventional Wiedemann-Franz law to estimate the electronic thermal conductivity component, which is known to occur in nanocomposite materials with significant grain boundary electrical resistance.

Material Properties of Nickel Based Cold Spray by Means of Small Specimens

The article is aimed on material properties evaluation of Ni and NiCr Cold Spray layers by means of proportional small specimens. For the purpose of testing, various cold spray layers were prepared. Spraying with nozzle for inner tube application from two NiCr powders of different particle sizes and from Ni powder of one particle size was applied. In addition, spraying with nozzle type for outer tube applications from same Ni powder was applied too. The evaluation is aimed on mechanical properties and metallographic analysis of cold spray layers as received and after defined heat treatment, comparing small and standard testing specimens. It provide overview of the tensile properties at room temperature and the microstructure of used powders and final cold sprays. Ultimate tensile strength, yield strength, hardness and plastic elongation are evaluated from the mechanical point of view. Metallographic analysis is focused on particle size in powders and splat size in manufactured layers. Porosity of sprayed layers is evaluated on tested specimens and the influence of specimen dimensions is discussed.

Tabletability and compactibility of α-lactose monohydrate powders of different particle size. II: predicted relationships

This study aimed to evaluate a material sparing method to predict tabletability and compactibility relationships. Seven α-lactose monohydrate powders with varying particle size were used as test materials. The compressibility of the powders was determined experimentally, whereas tabletability and compactibility profiles were derived both experimentally and predicted. In the prediction method, two experimental compression parameters (Kawakita and Heckel plastic stiffness) and a single tensile strength reference value were used, all necessary data obtained from a single compression experiment. For both predicted and experimental relationships, compaction and tableting parameters (performance indicators) were calculated. The correction for viscoelastic recovery was successful in generating compressibility profiles that corresponded to the series of experimental out-of-die tablet porosities. For both the tabletability and compactibility, the experimental and predicted profiles showed a high degree of similarity. Good correlations were obtained between the predicted and experimental compaction and tableting parameters. It is concluded that the hybrid prediction method is a material sparing method, which can give good approximations of tabletability and compactibility relationships. The prediction method has the potential to be included as a part of a protocol for the characterisation of the tableting performance of particulate solids.

Morphological Characterization of Nicotiana tabacum Inflorescences and Chemical-Functional Analysis of Extracts Obtained from Its Powder by Using Green Solvents (NaDESs)

The production of smokeable tobacco for use in cigarettes is characterized by the production of pre-harvest and post-harvest waste, with ensuing undesirable effects on the environment. The inflorescences of tobacco after blunting, deflowering, or topping are considered pre-harvest waste and left in the field. Using green and ecofriendly solvents such as Natural deep eutectic solvents (NaDESs), these wastes could be used to obtain antioxidant molecules of interest in cosmetics. Taking into account its potential as plant matrix to obtain metabolites of commercial interest, tobacco inflorescences and inflorescence powders of different particle sizes were characterized by optic and electronic microscopy. Thus, the powdered inflorescences were extracted with four conventional solvents, i.e., distilled water (DW), acetone: distilled water (AW), ethanol 70° (EW), methanol (Me), and five NaDESs, i.e., lactic acid: sucrose (LAS), lactic acid: sucrose: distilled water (SALA), fructose: glucose: sucrose: distilled water (FGS), choline chloride: urea: distilled water (CU), and citric acid: propylene glycol (CAP). Among the tested NADESs, SALA was the most promising solvent; higher extraction yields of total phenolic compound (3420.0 ± 9.4 µg GAE/mL) than conventional solvents were attained and it was the only selective solvent to phenolics. CU was the best solvent for flavonoids and alkaloids extraction (215.3 ± 3.2 µg QE/mL and 392.3 ± 8.0 µg ACE/mL, respectively). All extracts showed antioxidant activity. A heatmap with dendrogram and main component analysis showed that acid-based NaDESs are grouped together, this group being the one with the best performance in H2O2 scavenging. The extracts obtained with green solvents could be used directly in cosmetic formulations as antioxidant ingredients because both tobacco flower oil and flower extracts are listed in the cosmetic ingredients database as non-toxic products. Additionally, the demand for sustainable ecological cosmetics is growing. In this sense, NaDESs represent an opportunity to develop innovative extracts with unique phytochemical fingerprints and biological activities.

Effect of initial powder particle size on densification behavior and mechanical properties of laser additive manufacturing of AlCoCrFeNi2.1 eutectic high-entropy alloy

The AlCoCrFeNi2.1 eutectic high-entropy alloys (EHEAs) were prepared by selective laser melting (SLM) with powders of different particle sizes as variables. The spreading process of powders with different particle sizes and the effect of particle size on densification behavior, phase and mechanical properties were studied. The maximum densification of the D5016 sample is 99.58%, while that of D5035.8 is 99.1%. For the D5016 system, the BCC/B2 phase of the powder is transformed into the FCC phase of the SLM product, while the reverse is true for the D5035.8. The microhardness of SLM-printed coarse powder samples is higher than that of fine powder by more than 100 HV, and the microhardness of X-Y plane is about 20–40 HV higher than that of X-Z plane. The compressive strength and plasticity of the D5016 sample are 300 MPa, 8% (⊥BD) and 60 MPa, 9% (∥BD) higher than that of D5035.8.

Dense and strong ceramic composites via binder jetting and spontaneous infiltration

The objective of this study is to test the feasibility to produce fully ceramic composites (i.e., without containing any metal phases) by binder jetting of alumina preforms and spontaneous infiltration by copper in air. Alumina powders of different particle sizes (submicron and micron) were used as the feedstock for binder jetting. Afterward, standard post-processing steps were first applied, including curing, depowdering, debinding, and sintering. The sintered specimens were then spontaneously infiltrated with copper in air. The sintered specimens made with both powders had high porosity and poor mechanical properties. The infiltrated specimens made with both powders approached full density, and their mechanical properties were significantly improved. The compressive strength of 826.0 MPa and the flexural strength of 317.5 MPa achieved in this study are greater than those of any alumina-based specimens made via binder jetting followed by sintering and/or infiltration in the literature.

Preparation of water-quenched manganese slag and fly ash ultrafine mineral admixture and its application in UHPC

Abstract In this paper, S95 grade ultrafine mineral admixture (UMA) was prepared by water quenched manganese slag and fly ash 1:1 compound mechanical ball milling to a specific surface area of 714 m2/kg. Its activity index was 86.8% at 7d and 96.3% at 28d. The S95 UMA prepared by ball milling has the characteristics of small particle size, high specific surface and high activity. Mixing with powders of different particle sizes, such as cement and silica fume (SF), is helpful to improve particle gradation, reduce its pore structure and increase its compacting property for ultra-high performance concrete (UHPC) whose raw materials are fine aggregate. UHPC was prepared by using the obtained UMA based on orthogonal test. The effects of different factors on the workability, mechanical properties, hydration heat and microstructure of UHPC were studied. The results show that when the SF content is 10%, the mineral admixture content is 10%, the binder–sand ratio is 1.1, and the water–binder ratio is 0.17, the fluidity of UHPC slurry can reach 261 mm, the compressive strength of 7d and 28d age can reach 128 MPa and 154.6 MPa, respectively. The hydration heat release of cementitious materials in 3d was 139.8 J/g. In terms of solid waste resource utilization, S95 grade UMA prepared by water-quench manganese slag and fly ash can replace 10% SF for the preparation of UHPC. It can not only solve the utilization problem of high added value of water quench manganese slag but also reduce the preparation cost of UHPC to a certain extent.

Effect of superfine-grinding on the physicochemical and antioxidant properties of Dendrobium nobile powders

In herbal markets, an overwhelming majority the Dendrobium nobile are sold in dried strips form, and this product type would lead to the incomplete release of the active ingredient. To increase the bioaccessibility of Dendrobium nobile, we obtained powders of different particle sizes by shear-breaking and superfine-grinding to further compare its sensory properties, physical properties, the leaching rate of active ingredients and antioxidant activity in vitro. The results showed that the superfine-grinding changed the sensory properties and physical properties of Dendrobium nobile, with an increase in bulk density, a decrease in swelling capacity and water-holding capacity and an increase in water solubility index. The method also contributed to the release of total polysaccharides, dendrobine, total polyphenols and total flavonoids components, thereby increasing ABTS, DPPH and nitrite ion scavenging activity. In addition, scanning electron microscopy and infrared spectroscopy analyses showed that superfine-grinding had no effect on the primary structure of the fractions as with decreasing particle size. This study suggested that superfine-grinding could be a promising method for producing Dendrobium nobile powders with higher contents of bioactive compounds and bioactivity.

Binder Jetting Additive Manufacturing: Powder Packing in Shell Printing

Shell printing is an advantageous binder jetting technique that prints only a thin shell of the intended object to enclose the loose powder in the core. In this study, powder packing in the shell and core was investigated for the first time. By examining the density and microstructure of the printed samples, powder packing was found to be different between the shell and core. In addition, the powder particle size and layer thickness were found to affect the powder packing in the shell and core differently. At a 200 µm layer thickness, for the 10 µm and 20 µm powders, the core was less dense than the shell and had a layered microstructure. At a 200 µm layer thickness, for the 70 µm powder, the core was denser and had a homogeneous microstructure. For the 20 µm powder, by reducing the layer thickness from 200 µm to 70 µm, the core became denser than the shell, and the microstructure of the core became homogeneous. The different results could be attributed to the different scenarios of particle rearrangement between the shell and core for powders of different particle sizes and at different layer thicknesses. Considering that the core was denser and more homogeneous than the shell when the proper layer thickness and powder particle size were selected, shell printing could be a promising method to tailor density and reduce anisotropy.

Fabrication of a Magnetic Field Shielding Resin Sheet Using YBa2Cu3O7-δ Powders

YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-δ</sub> (YBCO) superconductors exhibit the perfect diamagnetism effect at a critical temperature (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of 93 K or lower. This effect can be exploited by creating materials that shield the magnetic field. In this study, light and flexible magnetic field shielding sheets were prepared by mixing a polyethylene terephthalate (PET) resin with YBCO powders of different particle sizes. The investigation of the effect of the YBCO particle size on the structure of the sheets formed resulted in the preparation of sheets in which YBCO powders were uniformly dispersed in the resin. By contrast, sheets that were prepared with using larger particle sizes showed more cracks and vacancies. The ease of occurrence of cracks and pores was determined to be dependent on the particle size, and it was shown that powders with small particle sizes are suitable for sheets.

Valorization of asparagus-leaf by-product through nutritionally enriched chips to evaluate the effect of powder particle size on functional properties and rutin contents

This study first observed that the nutritional and phytochemical contents in asparagus leafy by-product were comparable or higher than those in edible portion. The extractable rutin in leaf was found to increase with a decrease in powder particle size (400–120 μm), as indicated by ultra-performance liquid chromatographic analysis. Then, such leaf powders of different particle sizes were incorporated into freeze-dried chips formulation to evaluate the effect on chips properties. There was an apparent higher retention of total chlorophylls (161%), total phenolic (46%), and total flavonoid (79%) due to the decrease in particle size, ultimately showing an increase in the antioxidant activities. Also, the color (L*, a*, and b* values) was significantly difference (p < 0.05). LF-NMR study indicated the status of water and safer level of drying (a w = 0.6). Conclusively, samples containing finer asparagus powder showed higher nutritional and phytochemical contents than those made with coarser powder.

Effect of magnetic flux density of bar magnet on removal rate of magnetic material in powder

In this study, in order to improve the iron removal rate of iron remover, the effects of magnetic flux density, number of magnetic poles and powder fluidity on the removal rate of filed SUS304 particles mixed with high-purity spherical silica powders of different particle sizes were investigated. The iron removal tests were performed using an iron removal testing device equipped with a single bar magnet. The silica powders mixed with filed SUS304 particles were sifted, and the weight of the filed SUS304 particles captured by the bar magnet was measured. Three types of bar magnets were prepared in order to investigate the effect of the maximum magnetic flux density and the number of magnetic poles. As a result, the number of magnetic poles was more effective in improving iron removal performance than the maximum magnetic flux density. In addition, the iron removal rate decreased with decreasing the nominal particle size of the silica powder. As a result of the constant load direct shear test, the shear cohesion of silica powders increased with decreasing the average particle size [Formula: see text]. Therefore, it was found that the iron removal performance deteriorates when the powder cohesion increases.

Tabletability and compactibility of α-lactose monohydrate powders of different particle size. I. Experimental comparison

In this paper, two types of parameters representing tabletability and compactibility profiles of a series of α-lactose monohydrate powders, ranging in particle size from approximately 3.5 to 203 µm, are derived and compared. By approximating the tabletability profiles using a three-stage model and the compactibility profiles using the Ryshkewitch–Duckworth equation, two compaction rate parameters and two compaction endpoint parameters were derived. The original median particle diameter had generally a strong effect on the tablet tensile strength and hence the tabletability and compactibility profiles. The experimental profiles were well approximated by the models used, and the compaction parameters were regarded as representative of the experimental profiles. The compaction endpoint parameters increased with decreased particle size and were controlled by the same structural feature as the compacts. The tabletability rate parameter also increased with decreased particle size and correlated well with the tabletability endpoint parameter. The compactibility rate parameter tended to increase with decreased particle size, but the effect was limited; moreover, no general correlation was obtained with the compactibility endpoint parameter. It is concluded that compactibility and tabletability parameters collectively provide a concentrated description of the compaction properties of a powder.

Studying the Influence of Mica Particle Size on the Properties of Epoxy Acrylate/Mica Composite Coatings through Reducing Mica Particle Size by the Ball-Milled Method

In this work, a series of epoxy acrylate (EA)/mica composite coatings were synthesized through introducing mica powders of different particle size into epoxy acrylate coatings and using an ultraviolet (UV) curing technique to investigate the influence of mica particle size on the coatings. Mica powders of different particle sizes were obtained by ball-milling for 4, 8, 12, 16, and 20 h with a planetary high-energy ball mill. The particle size and morphologies of ball-milled mica powders were characterized by laser particle size analyzer and scanning electron microscopy (SEM). The results indicated that planetary ball-milling reduced the particle size of mica powders effectively. Mica powders that were un-ball-milled and ball-milled were added into the epoxy acrylate matrix by a blending method to synthesize the organic-inorganic UV curable coatings. The optical photographs of the coatings showed greater stability of liquid mixtures with smaller particle size fillers. The chemical structures of EA/mica composite coatings were investigated by Fourier transform infrared spectroscopy (FTIR), and the conversion rate of C=C bonds was calculated. The results indicated that the C=C conversion of coatings with mica powders of smaller particle sizes was higher. Tests of mechanical properties and tests using electrochemical impedance spectroscopy (EIS) showed that pencil hardness, impact resistance, and coating resistance were improved due to the reduction of mica powders particle size.

Characterization of pre-alloyed NiTi powders produced by electrode induction-melting inert gas atomization for additive manufacturing

In this research, the characteristics of nickel-titanium (NiTi) powders produced by electrode induction melting inert gas atomization (EIGA) technique for additive manufacturing (AM) technology are investigated using various powder characterization technologies. The results show that the particle size distribution (PSD) of pre-alloyed NiTi powders prepared by EIGA has the range of 10 ?m to 180 ?m. The mean particle size distribution (D50) of the powder is 75 ?m. The oxygen increase of the powder is only 0.005% compared to the raw rod. According to the requirements of the characteristics of the metal powder material used for AM, the powders are sieved into three categories, P1 (15-63 ?m), P2 (63-150 ?m), and P3 (&gt;150 ?m), respectively. The flow rates of P1 and P2 are 19.3 and 17.5 s?(50 g)-1, respectively. The surface, crosssectional microstructure, phase structure, and martensitic transformation temperature of the pre-alloyed NiTi powders with different particle sizes are investigated. The results show that powders of different particle sizes are primarily spherical or nearly spherical. The grain size of powders reduces with the decreasing of particle size. Both the bar stock and the powders of P1, P2, and P3 mainly exhibit the B2 phase. Comparing the powders P1, P2, and P3, the transformation temperature reduces with the decrease of particle size. A high density (99.55%) pre-alloyed NiTi specimen is successfully produced by selective laser melting (SLM) technology using P1 powders. The results indicate that the pre-alloyed NiTi alloy powder is appropriate for AM, which also has a good reference value for researchers producing AM powders.

Heat Treatment Influence on Mechanical Properties of Nickel Based Cold Spray

The article deals with evaluation of Ni and NiCr Cold Spray layers as a potential method for repairing components in energy industry by replacing or refilling flawed material. Cold spray layers from two NiCr powders of different particle sizes sprayed with nozzle for inner tube application and from Ni powder of one particle size sprayed with different nozzle types – for inner and outer tube applications – were tested. The evaluation is aimed on mechanical properties and metallographic analysis of cold spray layers as received and after defined heat treatments. It summarizes tensile properties at room temperature and microstructure of used powders and final cold spray layers. Ultimate tensile strength, hardness and plastic elongation are evaluated from the mechanical point of view. Metallographic analysis is focused on ovality and size of particles in powders and of splats in final cold sprays. Porosity of sprayed layers is evaluated on tested specimens.

Size- and Surface-Dependent Solubility of Cadmium Telluride in Aqueous Solutions

Due to the toxicity of cadmium (Cd) and the scarcity of telluride (Te), CdTe-based photovoltaic modules have been under discussion during the last few years. In particular, the stability of CdTe in aqueous solutions is under debate. Here we show that the stability of CdTe depends not only on the pH of water-based solutions but also on size and surface treatment of CdTe particles. We compare milled module pieces with CdTe powders of different particle size. The leaching of CdTe is conditioned by the outdiffusion of Cd and Te at the interface between CdTe particles and the aqueous solution. The smaller the particle size, the faster the leaching. Therefore, milled module pieces decompose faster than CdTe powders with relatively large grains. We observe a dependence on time t according to t0.43. The room temperature diffusion coefficients are calculated as DCd ≈ 3 × 10−17 cm2/s for Cd, and DTe ≈ 1.5 × 10−17 cm2/s for Te in pH4. The chemical instability in aqueous solutions follows thermodynamic considerations. The solution behavior of Cd and Te depends on the pH value and the redox potential of the aqueous solutions. Chemical treatments such as those used in solar cell production modify the surface of the CdTe particles and their leaching behavior.

To what extent does friction-stir welding deteriorate the properties of powder metallurgy Al?

Powder metallurgy (PM) fabricated HITEMAL is a near- and sub-micrometer aluminum (Al) material that is stabilized by a small fraction of a nano alumina (Al2O3) secondary phase. This phase forms in situ from surface Al2O3 films present on as-atomized Al powders during compaction. HITEMAL showed unique mechanical properties and creep performance at high homologous temperatures owing to its ultra-fine Al grain structure effectively stabilized by Al2O3. However, conventional fusion welding is generally not applicable to PM Al. This study reports on friction stir welding (FSW) that was applied to join bars extruded from Al powders of different particle size. As PM Al performance crucially depends on the Al2O3 phase, we focused on changes to this phase that were, induced by FSW. Thermal stability, mechanical properties, and deformation behavior of the weld materials were studied versus changes in the morphology and distribution of the Al2O3 phase during FSW. The study confirmed that FSW can be successfully used to join PM Al, although some detrimental transformation of the Al2O3 phase occurred upon FSW. This transformed Al2O3 phase did not provide sufficient stabilization under severe plastic deformation induced by a rotating tool action. The transformation involved dynamic recrystallization and minor Al grain growth in weld zones. This led to a decrease in the mechanical strength of the weld compared with that of the respective base materials. While this negative effect was pronounced for HITEMAL with the finest Al grain size, it was negligible in the coarse-grained material produced from the coarsest Al powder.

Size Effect of Nanoscale Powders on the Polarization of the BCZT Piezoceramic: A Pyroelectric and Fatigue Perspective

Solid state synthesis route was employed to form Ba0.85Ca0.15Zr0.1Ti0.9O3 powder. The calcined powder was high energy ball milled at different milling speeds to get powders of different particle sizes. XRD pattern of the ceramics made from these powders show the presence of pure perovskite. This paper deals with a systematic study of the pyroelectric and the fatigue properties of the ceramics. The room temperature pyroelectric coefficient (p) attains the minimum value p = 0.119X10−8 C cm−2 K−1 for the ceramic made from the powder milled at 250 rpm. The fatigue was also found to be minimum for the same ceramic samples.