Powder Diameter Research Articles

ANALISIS KADAR KAFEIN DALAM MINUMAN KOPI KHOP ACEH DENGAN METODE SPEKTROSKOPIK

In addition of being dubbed as the city of "Serambi Mekah", Aceh is also famous as the city of "Thousand Coffee Shops". One of coffee dish that attracts consumers' is khop coffee (read: kopi khop) because it is served with a glass dish upside down. The khop coffee, a typical coffee drink from Meulaboh, West Aceh Regency, is served by reversing the glass that has been filled with coarse coffee powder on top of the pan. Therefore, it is deemed necessary to conduct a special study on the analysis of unique taste-determining compounds in khop coffee to elevate the local wisdom of the Acehnese to the scientific region. The aim of this study was to determine the concentration of caffeine compounds of khop coffee due to the modification of coffee powder diameter by using the thin layer chromatography (TLC) method and UV-Vis spectrophotometry. This study used four types of samples with diameter variations coffee, namely original, fine, medium, and coarse. The four samples were extracted with boiling hot water according to the same conditions when the bartender served it (90 °C) followed by liquid-liquid extraction using chloroform solvent. Dry extract was analyzed by using TLC followed by a UV-Vis spectrometer. The results showed that the concentrations of original, fine, medium, and coarse coffee were respectively 57.85%; 17.61%; 1.29%; and 0.83%.

THE SINTERING PROCESS LIMITS GRINDING QUARTZ POWDER IN A PLANETARY MILL AGO-2 WITH OPTIMAL ENERGO TENSION

The study of the agglomeration limit of quartz powder grinding at the AGO-2 planetary mill was carried out. For operation, several modes were selected, 3 basic modes with a coefficient of filling grinding media φ=0,5; 0,6; 07, as well as one additional mode with a filling factor φ=0,4 and a smaller proportion of quartz powder. The agglomeration limit for quartz during mechanical activation on AGO-2 is the average powder diameter of 1.5 µm, and the maximum value of the specific surface is 15,000 cm2/g. The paper proposes a method for calculating the energy intensity of the AGO-2 activator, by which it was possible to estimate the optimal mode of treatment of quartz to obtain ultrafine particles with a load factor φ=0,4 and a time of mechanical activation up to 60 seconds. Determination of the average size and specific surface area of the particles after mechanical activation was carried out by the method of gas permeability Of the pocket - Goat using the device PSH-11. Measuring the temperature of the mixture of grinding media and powder in the drum was made contact thermometer TK-5.09, equipped with a thermocouple 3V9-500.

On the role of powder flow behavior in fluid thermodynamics and laser processability of Ni-based composites by selective laser melting

Abstract A deep understanding of the underlying relation of powder paving and subsequent melting/solidification behavior is critical in predicting and tailoring the processing quality of components fabricated by selective laser melting (SLM) additive manufacturing technology based on the mesoscopic scale. Combining discrete element method (DEM) and finite volume method (FVM), the present work proposed a newly developed three-dimensional DEM physical model coupling with mesoscopic FVM model to give a unique insight into the influence of powder particle size on the flow behavior of powder and resultant melting/solidification characteristics of SLM-processed WC/Inconel 718 composites. The contacting force among powder particles, transition of solid/liquid, and surface tension of melt were considered in the model. By characterizing the packing profiles, velocity vectors and packed state of particles, the simulation results and corresponding experimental validations generally revealed that the powder possessed an elevated flow-ability as increasing the average diameter of powder below 25 μm, due to the alleviation of the domination of adhesive force among neighboring particles. The considerably high-quality SLM-processed surface without apparent laser-induced defects was obtained with a significantly low surface roughness of 2.2 μm, attributing to the formation of a denser and more homogeneous powder-bed during SLM. However, when the average diameter of powder particles was elevated over 25 μm, the combined influence of the elevated gravity of large-scaled powder and the considerable space between neighboring powder particles worsened the flow-ability of powder. The discontinuous and loose powder-bed with a low packing density of particles had a high tendency to produce the top surface with a higher surface roughness, resulting in the formation of a number of defects in SLM-processed parts such as cave-like porosities, balling and discontinuous laser-melted tracks.

Burning Rates of Nanoaluminum–Water Solid Propellants at Various Pressures

The burning rates of solid propellants comprising different nanoaluminum powders and distilled water were examined at pressurized conditions up to . Several aluminum powders were tested using a strand burner technique: uncoated nanopowder (ALEX), stearic-acid coated nanopowder (L-ALEX), Viton-coated nanopowder (V-ALEX) with two different particle sizes, and bimodal mixture of V-ALEX and micrometer-size powders. Propellants containing ALEX, L-ALEX, and bimodal compositions followed the power law relation throughout the pressure range, with pressure exponents of , 0.5, and 0.28, respectively. Propellants containing V-ALEX powder demonstrated two different regimes: at pressures lower than 1.8 MPa, the burning rates were constant with respect to pressure; whereas for higher pressures, the burning rates followed the power law relation with and for powder diameters of 60 and 100 nm, respectively. The combustion efficiency, defined as the fraction of aluminum that oxidized during combustion, showed high values (90–95%) for all tested compositions.

Microstructure and mechanical properties of Ti-6Al-4V-5% hydroxyapatite composite fabricated using electron beam powder bed fusion

A novel, Ti-6Al-4V (Ti64)/Hydroxyapatite (HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion (EPBF) additive manufacturing (AM): specifically, the commercial electron beam melting (EBM®) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell (model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm3, and corresponding Young’s moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ∼3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. Both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, EPBF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography (OM) and scanning electron microscopy (SEM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha (hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ∼5 μm in the EPBF-fabricated Ti64 to ∼1.1 μm for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 μm. This work highlights the use of EPBF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors’ knowledge has not been reported before. The results also illustrate the prospects not only for fabricating specialized, novel composite bone replacement scaffolds and implants, through the combination of Ti64 and HA, but also prospects for producing a variety of related metal/ceramic composites using EPBF AM.

Study on the Obtaining of MnSi1.75 Intermetallic Compound by Mechanical Alloying

Thermoelectric higher manganese silicide (HMS) having the composition MnSi1.75 material was obtained by mechanical alloying after 18 hours of milling. As starting materials, manganese and silicon elemental powders were used. After 18 hours of milling beside the HMS in the powders, MnSi phase was obtained as well. After only 4 hours of milling, both binary MnSi phases are found in material besides a significant amount of non-reacted elements. Milling up to 10 hours leads to the silicon characteristic peaks disappearance and the HMS and MnSi phases amount increase. Subsequent annealing of the milled powders was performed in order to promote internal stresses removal. The 4 hours annealing of the powder at the temperature of 350 °C under high vacuum (10−6 Torr) leads to stress release and an increase in the MnSi phase quantity. The particle size analysis shows that the powder diameter is in 0.1-125 μm range. A large amount of powder is in the range of 15-125 μm, but there is also a small amount that is in the 0.1-15μm range. Scanning electron microscopy (SEM) was used to characterize the powders morphology.

Tubes with coated and sintered porous surface for highly efficient heat exchangers

Surface modification is a direct and effective way to enhance the efficiency of heat exchangers. Surface modification by forming a microporous coated layer can greatly enhance the boiling heat transfer and thus achieve a high performance. In this paper, we systematically investigate the boiling behavior on a plain surface with/without sintered microporous coatings of copper powder. The results demonstrated that the sintered surface has a better performance in nucleate boiling due to the increased nucleation sites. The superheat degree is lower and the bubble departure diameter is larger for the sintered surface than for the plain surface, so the heat can be carried away more efficiently on the sintered surface. In addition, the heat transfer capacity on the sintered surface depends on both the powder size and the coating thickness for a high flux tube. The optimum heat transfer capacity can be obtained when the thickness of the microporous coating layer is 3–5 times of the sintered powder diameter. As a result, the heat transfer coefficient tube can be up to 3 times higher for the tube with a sintered surface than that with a plain surface, showing a pronounced enhancement in heat transfer and a high potential in chemical engineering industry application.

Effect of carrier agents on the physical properties and morphology of spray-dried Monascus pigment powder

Spray drying is an economic technique used in preservation and production of Monascus pigment powder. This study was performed to encapsulate the Monascus pigment with maltodextrin using spray drying technique with three types of carrier agents: propylene glycol, mannitol and polyglycerol ester at different concentrations (0.5%, 1% and 1.5%). Analyses of particle size, the spattering behavior, microstructure, color value, and thermal profile were performed on the obtained powder. The addition of propanediol, mannitol and polyglycerol ester in combination with maltodextrin led to an increase of 17.5%, 45.8%, and 23.5% in the volume mean diameter of Monascus pigment powder, respectively. The decrease of spattering of Monascus pigment with maltodextrin was clearly evident in the case of formulations containing 1.5% polyglycerol ester. Scanning electronic microscopy analyses showed that Monascus pigment particle treated with maltodextrin exhibited microstructures that were smooth and dented, while the particles treated with carriers exhibited rough, irregular surface and adherence of smaller particles on their surfaces. UV–visible spectroscopy proved that the addition of carriers did not influence the molecular structure of Monascus pigment compared to the powder without carrier treatment. Differential scanning calorimeter analysis revealed that mannitol enhanced water vaporization during spray drying process as lower enthalpy change was observed in thermogram. The addition of an appropriate carrier (0.5%, 1.5% propanediol or 1% mannitol) improved the color values of Monascus pigment.

Low-temperature synthesis of micro/nano Lithium Fluoride added magnesium aluminate spinel

In this study, a significant decrease in temperature for the phase formation of magnesium aluminate spinel in presence of nano-Lithium Fluoride additive during the solid-state process has been evaluated. Adding 1 wt% of micron LiF to the Stoichiometric content of alpha alumina and magnesia nanopowders resulted in the decrease of temperature for spinel phase formation from 1650 °C to 1450 °C. Furthermore, decreased size of LiF additive from micron to nano lowered the spinel phase formation temperature from 1450 °C to 1200 °C. Average particle diameter (D50) of spinel powder has been decreased from 475 nm to 275 nm in a normal procedure (using micron LiF) and by using nano LiF additive this particle size has been decreased further up to 110 nm. The synthesized spinel powder at 1200 °C kept for 2 h was calculated 99.8% pure, and the particles were finer and homogeneously distributed with an average size of 110 nm, and a specific surface area of 17 m2/g.

Parametric Thermal FE Analysis on the Laser Power Input and Powder Effective Thermal Conductivity during Selective Laser Melting of SS304L

A low-cost parametric finite element thermal model is proposed to study the impact of the initial powder condition, such as diameter and packing density, on effective thermal conductivity as well as the impact of the laser power input on the final temperature distributions during selective laser melting (SLM). Stainless steel 304L is the material used, since it is not yet commercially available in SLM equipment and our main goal was to show the capabilities of the finite element method in the evaluation of power input in the process. The results from our sensitivity analysis showed that packing density has a greater impact on the final temperature distributions compared with powder diameter variance. However, overall the thermal conductivity of the powder only showed significant effects below the melting point, otherwise the thermal conductivity no longer affected the temperature distributions. Among the three different power inputs analyzed, the temperature profile demonstrated that power inputs of 100 and 200 W are recommended when printing SS-304L rather than 400 W, which generates too high temperature in the powder bed, a non-favorable behavior that can induce high residual stresses and material evaporation.

Microstructural characterisation of CuAgZr powder particles produced by argon gas atomisation

ABSTRACTCuAgZr alloy is known for its high strength and high conductivity, which are reasons for its wide application. In this work, CuAgZr powder alloys were produced by high-pressure argon gas atomisation. The results indicate that the surface morphology of the powder is a cellular crystal structure with a pentagonal crystal structure, with a ‘rose-like’ lattice and cross-shaped dendrites. A three-dimensional model of the primary dendritic changes in the CuAgZr alloy powder with different powder diameters was established by studying the surface morphology and internal microstructure of the powder. The relationship between the powder diameter and the powder cooling rate was established as the function of the primary dendritic length (PDL), the primary dendritic volume fraction (PDVF), the secondary dendrite arm spacing (SDAS) and the secondary dendritic volume fraction (SDVF). A confidence validation was performed, and the function fitting error is within 10%. The results establish that the function is meaningful.

Microstructure evolution of Al0.6CoCrFeNi high entropy alloy powder prepared by high pressure gas atomization

The influence of cooling rate on the microstructure of Al0.6CoCrFeNi high entropy alloy (HEA) powders was investigated. The spherical HEA powders (D50≈78.65 μm) were prepared by high pressure gas atomization. The different cooling rates were achieved by adjusting the powder diameter. Based on the solidification model, the relationship between the cooling rate and the powder diameter was developed. The FCC phase gradually disappears as particle size decreases. Further analysis reveals that the phase structure gradually changes from FCC+BCC dual-phase to a single BCC phase with the increase of the cooling rate. The microstructure evolves from planar crystal to equiaxed grain with the cooling rate increasing from 3.19×104 to 1.11×106 K/s.

Prostate Cancer Cell-Specific Cytotoxicity of Sub-Micron Potassium Niobate Powder.

Oxide nanoparticles have numerous potential applications in medicine such as carriers for therapeutic drugs, contrast agents for bio-imaging and targeting agents for tumors. Oxide nanoparticles may also have an inherent cytotoxicity towards cancer cells, as recently found for cerium oxide. KNbO3 nanoparticles have a combination of low toxicity and nonlinear optical properties which make them attractive for use as a bio-imaging material. However, little is known yet about the cytotoxicity of KNbO3 particles towards cancerous cells. In the present work, the cytotoxicity of KNbO3 particles to normal and prostate cancer cell lines is studied. The mixed oxide method is used to prepare KNbO3 powder. Using dynamic light scattering the mean particle diameter of the KNbO3 powder is found to be ∼500 nm. X-ray diffraction, Fourier transform infra-red spectroscopy and Raman scattering spectroscopy are used to examine the structure of the KNbO3 powder. Powder morphology is examined using scanning electron microscopy. MTT assays of EA.hy926, PC-3 and DU-145 cell lines are carried out to study cell-specific cytotoxicity. KNbO3 sub-micron particles are found to have low toxicity to PC-3 cells, moderate toxicity to EA.hy926 cells and high toxicity to DU-145 cells. A new avenue towards the treatment of prostate cancer may be opened by the cell-specific cytotoxicity of KNbO3.

Dropwise Condensation on Superhydrophobic Microporous Wick Structures

Previous research in dropwise condensation (DWC) on rough microtextured superhydrophobic surfaces has demonstrated evidence of high heat transfer enhancement compared to smooth hydrophobic surfaces. In this study, we experimentally investigate the use of microporous sintered copper powder on copper substrates coated with a thiol-based self-assembled monolayer to attain enhanced DWC for steam in a custom condensation chamber. Although microtextured superhydrophobic surfaces have shown advantageous droplet growth dynamics, precise heat transfer measurements are underdeveloped at high heat flux. Sintered copper powder diameters from 4 μm to 119 μm were used to investigate particle size effects on heat transfer. As powder diameter decreased, competing physical factors led to improved thermal performance. At consistent operating conditions, we experimentally demonstrated a 23% improvement in the local condensation heat transfer coefficient for a superhydrophobic 4 μm diameter microporous copper powder surface compared to a smooth hydrophobic copper surface. For the smallest powders observed, this improvement is primarily attributed to the reduction in contact angle hysteresis as evidenced by the decrease in departing droplet size. Interestingly, the contact angle hysteresis of sessile water droplets measured in air is in contradiction with the departing droplet size observations made during condensation of saturated steam. It is evident that the specific design of textured superhydrophobic surfaces has profound implications for enhanced condensation in high heat flux applications.

Synthesis of Silica Powder from Sugar Cane Bagasse Ash and Its Application as Adsorbent in Adsorptive-distillation of Ethanol-water Solution

In this study, sugarcane bagasse ash (SCBA) as waste from sugarcane factory was extracted into silica powder. This powder was then used as adsorbent for ethanol purification. Prior to used, the SCBA was washed using HCl solution. The silica extraction was conducted using various NaOH concentrations (0.5; 1; 1.5 and 2 mol/L) as well as extraction times (30, 60 and 90 minutes). After that the mixture was precipitated using HCl solution. The solution was filtrated through a paper filter and its solid particle was dried until its weight was constant. The particle was grounded and sieved using 18 mesh sieves. The silica powder obtained was analysed using FTIR and its result showed that the powder has silica functional groups. The silica yield increases with increasing of concentration of NaOH solution as well as extraction time. The highest silica yield (45.5% w/w) was achieved at 2 mol/L NaOH solution at 90 min. The surface area, pore diameter, and pore volume of silica powder were measured to be 407 m2/g, 3.81Å, and 2.76 dm3/g, respectively. From application of silica powder as adsorbent in adsorptive-distillation, ethanol concentration can reach 99.3% w/w which indicates azeotropic point can be passed.

Preparation of gas-atomized Fe-based alloy powders and HVOF sprayed coatings

High-pressure gas atomization was employed to prepare the Fe-based Fe50Cr24Mo21Si2B3 alloy powder. The effect of flow rate of atomizing gas on the median powder diameter was studied. The results show that the powder size decreased with increasing the flow rate of atomizing gas. Fe-based alloy coatings with amorphous phase fraction was then prepared by high velocity oxygen fuel spraying (HVOF) of gas atomized Fe50Cr24Mo21Si2B3 powder. Microstructural studies show that the coatings present dense layered structure and low porosity of 0.17% in about 200 μm thickness. The Fe-based alloy coating exhibits an average hardness of about 1230 HV. Our results show that the HVOF process results in dense and well-bonded coatings, making it attractive for protective coatings applications.

Alumina supported zinc oxide catalyst for production of biodiesel from kesambi oil and optimization to achieve highest yields of biodiesel

Biodiesel is one of the promising alternative energy substitutes for fossil fuel. In this work kesambi (Schleichera Oleosa L.) oil (SOO) is converted into biodiesel with clean technology using alumina supported zinc oxide solid catalysts. The alumina supported zinc oxide (AZO) catalyst was prepared by the precipitation and gel method and calcined at a temperature of 500 °C. The synthesized catalyst was characterized by Breneuer-Emmet-Teller (BET) and X-ray fluorescence (XRF) methods. The surface area, total pore volume and mean pore diameter of the catalyst powder obtained were 71.561 m2 g−1, 0.137 cm3 g−1, and 8.149 nm, respectively. The effects of catalyst amount, the molar ratio of oil to methanol and time of reaction on the yield of biodiesel were investigated. The results showed that those three variables significantly influenced the yield of biodiesel. The highest biodiesel yield of 92.29% was obtained at a catalyst loading of 4% (wt% to oil), a molar ratio of oil to methanol of 1:12, a reaction time of 6 h and a reaction temperature of 65 °C.

Molecular dynamics study of thermodynamic properties of nanoclusters for additive manufacturing

4D printing is a new process that involves the use of 3D-printed objects and materials able to change shape over time. Therefore, a comprehensive understanding of 3D-printed objects is needed prior to developing 4D-printed ones. Selective laser melting (SLM) is a very promising 3D printing technique; however, because of the intense heat input, problems such as balling phenomena, deteriorated surface finish, tensile residual stress, and part distortion are still frequently observed in the SLM process. For such cases, micro-/nano-scale heat management becomes a key problem. Indeed, heat conduction during the SLM process is significantly affected by powder diameter and compactness. The thermodynamic behaviors of powder due to laser heating are considerably different from that of a solid bulk body. In this paper, molecular dynamics (MD) and empirical embedded atom computational methods are applied to study the thermodynamic properties of Ag nanoclusters, which are 2.1-6.9 nm in diameter during the heating and cooling process. We find that the melting point, heat of fusion, entropy of fusion, and surface energy are highly dependent on nanocluster size. Remarkably, we define the mesoscale regime where the properties of nanoclusters can be described in terms of macroscopic concepts with well-defined bulk and surface thermodynamic properties.

The effect of silicon nitride powder characteristics on SiAlON microstructures, densification and phase assemblage

The surface characteristics, particle size distribution and impurities of starting Si3N4 powders exert a very significant influence on the microstructure of sintered silicon nitride based ceramics. Even a change of the processing conditions such as milling liquid media (water or isopropyl alcohol) and milling time can have a substantial effect on particle surface groups, and hence on the microstructure of sintered samples. In this study, SEM, XRD, FTIR, BET, elemental analysis and laser diffraction techniques were used for the comprehensive characterization of Si3N4 powders which were produced by diimide, direct nitridation and combustion synthesis, in as received state, and after milling in different liquid media (aqueous or alcohol), for various milling durations. The correlation of the surface characteristics and properties of the Si3N4 powders with sintering behavior, and microstructural evolution, densification and phase assemblages of the resulting SiAlON ceramics were reported. The milling conditions affected the surface chemistry of Si3N4 powders and the subsequent microstructural evolution. The microstructures evolved from the coarser β-Si3N4 powders were coarser, but the fine β-Si3N4 powders yielded a bimodal microstructure. The critical particle diameter of the β-Si3N4 powder for the formation of needle like SiAlON grains was determined to be less than 0.5 µm.

Al-Limestone and Al-Granite Composites Prepared by Cold Spraying

Two types of aluminium metal matrix composites (Al-MMCs) were prepared by cold spray process. The first Al-MMC was reinforced with granite rock and the second was reinforced with limestone rock particles. Al powder and rock powders (granite or limestone) were mixed to homogeneous mixtures and sprayed onto the Al substrate. The microstructure of as-sprayed composites was compared with microstructure of MMCs reinforced with commercially available Al2O3. The microstructures of Al-MMCs reinforced with granite and limestone were affected by hardness of rocks, particle sizes and compositions of the mixture. The coating is formed through high velocity impact of solid powders. The diameter of Al powder was about 30 μm and diameters of rock powders were from 5 to100 μm. Rock particles are distributed uniformly through the coating, maintaining their irregular morphologies. However, some large sized particles cracked and fragmented. The powder porosity was approximately 2.3 % for both types of Al-MMCs. Porous microstructure leads to lower critical velocity. The results indicate that, introducing irregular morphologies and/or pores into the feedstock. High quality metallic coatings can be more easily deposited by cold spray.