Papers by Keyword: Particle Size

Abstract: Hydrothermal water treatments of silver acetate (CH₃COOAg) were investigated to reveal the factors controlling the formation of silver nanoparticles (AgNPs) with uniform size distribution. The effects of reaction time and concentration of silver acetate solution on the synthesis of Ag nanoparticles were studied, and the fabricated products were characterized. The hydrothermal water treatments of CH₃COOAg were carried out between the temperatures of 250 - 450 °C in a batch reactor. In supercritical water regions, at 400 °C and a pressure of 31.5 MPa, silver particles are rapidly synthesized due to reaction rate increases at a low dielectric constant of supercritical water. The preparation of the silver particles with 30-80 nm in size showed a highly crystalline structure identified by XRD and TEM observations.

Abstract: The effect of particle size and shape on flowability of FGH96 superalloy powder was investigated by field emission scanning electron microscopy (FE-SEM), laser particle size analyzer (LPSA) and X-ray photoelectron spectroscopy (XPS). The results showed that the powder flowability basically presented a decreasing trend as the median diameter decreased. The Hall velocity of the five median diameter powders (𝑑₅₀=203.9 μm, 106.3 μm, 83.2 μm, 73.8 μm, 19.9 μm) was 27.18 s/50g, 23.25 s/50g, 23.86 s/50g, 23.42 s/50g and none, respectively. The surface oxides/ hydroxide/nitride of the five median diameter powders were mostly the same, mainly including Al₂O₃, Cr₂O₃, MoO₃, Nb₂O₅, Ni (OH)₂, TiO₂ and TiN. The median diameter 𝑑₅₀, shape factors (circularity, aspect ratio, roundness, solidity) and fractal dimension were selected to quantitatively characterize particle size and shape. For the same fluctuation value of powder flowability, the roundness and solidity showed lower sensitivity. Compared with the two shape factors, the sensitivity of circularity and aspect ratio was at an intermediate level, while the median diameter and fractal dimension displayed higher sensitivity. The median diameter and fractal dimension can be used to characterize the principal variation of flowability. The circularity and aspect ratio can be utilized to characterize the variation of flowability supplementally.

Abstract: RHA has been the subject of investigation for its pozzolanic activity that heavily linked to the controlled temperature burning process in order to achieve amorphous form of silica. This paper present the characterization of RHA that was taken directly from the boiler of rice mill with uncontrolled burning temperature. Particle size analysis revealed grinding process of RHA could significantly curb the diameter size and increased specific surface area. Microstructure analysis suggest that RHA is very porous and EDX test showed the chemical content of RHA. The prospect of using uncontrolled burnt RHA as part of construction material is feasible.

Abstract: The objective of this research is to study the effect of water content on particle characterization and agglomeration of bamboo charcoal resulted from ball milling process. The characterization is determined by the particle size and the morphology of the particle. The milling was performed in cylinder vial of stainless steel. The element of milling is steel balls. The dimension of the cylinder vial was 120 mm length and 1-inch diameter, while the ball diameter was 5/32 inch. The charcoal resulted from pyrolysis was milled manually then strained with a filter size of 200 meshes. The particles passing the strainer were washed in water and then dried to obtain 25%, 28%, 32% and 35% water content. Then they were put together with the milling balls into cylinder vial. There were four vials with a water content of 25%, 28%, 32% and 35% respectively for milling process. Every vial contained 11 grams of bamboo charcoal and approximately 299 grams of steel balls. It represents 1/3 of vial volume for charcoal, 1/3 of vial volume for ball and 1/3 of vial volume for empty space. Two type tests were conducted. The first test was to run the milling machine at 700 rpm for 2 million cycles and the second test was to run the milling machine at 1000 rpm for 3 million cycles. Particulate characterization was done by a particle size analyzer (PSA), a scanning electron microscope (SEM) with energy dispersive X-Ray (EDX). The results showed that the water content does not have any influenced to the particle size. For the both test the particle sizes are in the range of 100 nm or less to more than 1 μm. However, the second test produces smaller particles and a higher number of smaller particles due to higher impact energy and longer milling time. The two tests inform that agglomeration does not happen by having wet milling. The dominant element of the bamboo charcoal is carbon with more than 90% in number.

Abstract: Utilization of palm oil waste in palm kernel shells as activated carbon, the activated carbon manufacturing goes through several processes, including dehydration, carbonization, and activation. Palm shell particle size was controlled during the activated carbon synthesis process through the temperature of the milling time and carbonization processes. The carbonization process was carried out using an electric furnace at carbonization temperatures 400, 600, and 800 °C, respectively. A carbonization time was 1 hour under vacuum condition to produce initial values of particle and grain sizes that had a neat structure and had absorption capacity. The particle size of formed activated carbon was measured by PSA (particle size analyzer) type Coulter LS 100Q micron scale. The particle size of active carbon was dependent on the carbonization temperature at 400, 600, and 800 °C was obtained particle size 19,90, 9,507, and 6,264 μm, respectively. Several characterizations are required to determine the properties of activated carbon was obtained. FTIR Spectrophotometer was used to observe activated carbon’s molecule structure before and after dehydration and carbonization process. It was found that the specific fingerprint at 2913,91 cm^-1 and 2923,56 cm^-1 for the carbon chain of activated carbon. Other physical and chemical properties were conducted to investigate moisture content, thermal property, yield enhancement, and formed product appearance.

Abstract: This study aims to investigate the effects of powder particle size on the densification and microhardness properties of spark plasma sintered superalloy. Three particles size ranges of nickel were used in this study, namely, (3-44, 45-106 and 106-150 μm), and this is the matrix in the IN738LC superalloy composition (powder), used in the study. The effects of the particle size were examined at a specific applied temperature and pressure. The transitioning stages during the sintering process of the green powders to the formation of the sintered alloy were analyzed and given as the particle rearrangement stage, the localized deformation stage and the neck formation/grain growth stage. There was the formation of γ, γ' and a solid solution within the microstructure of the sintered alloys. The effect of particle size was more pronounced on the grain sizes obtained, while the phases formed is the same for the three alloys. The results indicate that the nickel particle size (>60% of the total composition) has a significant influence on the densification, porosity, grain size and hardness properties of the IN738LC sintered alloy. Finer nickel particle size resulted in a sintered product with smaller grain size (9 µm), reduced percentage porosity (3.9%), increased relative density (96.1%) and increased hardness properties (371 Hv).

Abstract: Particle size analysis of synthesized Al₂O₃ by dissolution and alkali fusion-coprecipitation methods has been conducted. The formation of nano- or microparticles can be synthesized by the top-down (physically) and bottom-up (chemically) methods. In this study, the commercial alumina (Merck) with the particle size of 63 µm was synthesized through the bottom-up method. The dissolution method was done by reacting to alumina with ammonium hydroxide (NH₄OH). The alkali fusion method was carried out by reacting alumina with sodium hydroxide (NaOH) and it obtained by coprecipitation of the alkali fusion product with HCl and NH₄OH. The result from both methods were calcined at 600°C. The phase of synthesized Al₂O₃ was identified by using X-ray diffraction (XRD), whereas the morphology observed using a transmission electron microscope (TEM), and the particle sizes measured by particle sizes analyzer (PSA). The XRD pattern shows the γ-Al₂O₃ phases with particle sizes of ~33 nm and ~25 nm from TEM observations, while the PSA results revealed agglomerated particles with particle sizes of 1263 nm and 477 nm for the dissolution and alkali fusion-coprecipitation method, respectively. Therefore, both methods can be used to reduce the particle size of γ-Al₂O₃.

Abstract: Gypsum is one of the important construction materials in Iraq in plastering surfaces and gypsum board , the ability of gypsum to give a comfortable an aesthetic ambiance as a construction material increase the need of gypsum , The particle size , total surface area and particle size distribution were factors affecting plaster properties used for construction properties . In this study gypsum paste was used with different mixing ratios of particle size and studied the physical properties of these types of pastes named (standard consistency ,setting time ,density) and compressive strength . The results showed that the water to gypsum ratio increased with increasing the fineness of the gypsum to (0.75%) and the setting time to the maximum allowed according to the Iraqi standard (25 minute) when the distribution of particle size between (600-75) microns . Thus ,superplasticizer was used in more fine paste types .There is a direct relationship between setting time and the water to gypsum ratio ,but the setting time decreasing with increasing the fineness of the gypsum when the distribution of particle size between (300-75) microns. There is also a direct relationship between density and gypsum fineness . In terms of compressive resistance , it increases slightly when the particle size distribution is between (900-75) μm and increases significantly (40-42)% relatively to the reference paste with particle size distribution (300-75) μm and superplasticizer additive .Compression strength is also affected by the water to gypsum ratio ,there is an inverse relationship between them.

Abstract: A bonded permanent magnet of Barium hexa Ferrite has been made using powder BaFe₁₂O₁₉ (commercial ferrite) and a polymer of bakelite powder as binder. The composition of bakelite was varried 5% wt. The preparation of sample was begun with mass weighing for each material, then mixed together using ball mill for 1, 6 and 12 hours and using aquades as milling media. The mixed powder is dried in an oven at 110 °C for 4 hours, then the particle size distribution was measured. After that, the dried sample powder was pressed to form a pellet at pressure 40 MPa and temperature about 160 °C for 20 minutes. The characterization of sample pellet was done such as measurement of bulk density, hardness , magnetic properties using VSM and anylisis of microstructure using SEM. The results of the characterization show that the density and magnetic properties tend to increase with increasing of milling time, where the highest density, hardness and highest magnetic properties are achieved at sample with milling time for 12 hours. The value of magnetic properties at this condition are flux magnetic of 530 Gauss, remenance of 3100 Gauss, coercivity of 1,10 kOe.

Abstract: This study aims to investigate the effect of the electrophoretic deposition process (EPD) of natural HA (extracted from bovine bones) with various particle size on Ti-29Nb-13Ta-4.6Zr (TNTZ) coating surfaces. HA particles were refined from bovine bone powders using planetary ball mill and then sieving to separate the particle based on its size. The maximum size according to sieving mesh size is #25 µm, #63 µm and #125 µm. The coating process was conducted by using EPD apparatus with voltage and time process 10V and 5 minutes, respectively, for each sample. The coating layer morphology was observed with Stereo Microscopy, Scanning Electron Microscopy (SEM) and the thickness was measured with Thickness Gauge. The result shows that the size of the particle determines the coating layer characteristics. The best of HA coating quality according to the implant coating standard is obtained for the 25 µm particle size with the surface coverage is 99%. The thickness is 121 µm and the ratio of chemical composition Calcium and Phosphor Ca/P) is 1,49%. These may be concluded that, on the point of view physical characteristics, natural HA from bovine bone has potential enough as a coating layer to improve the bioactivity implant for biomedical application. However, the mechanical characteristic of the layer is still needed to determine the strength of coating layer for avoiding delamination during application.