Abstract: Taking into account the concept of the quasi-chemical model of the liquid micro-non-uniform composition and the research made on the physical properties of the Fe-and Co-based melts being crystallized, the unique technology of the melt time-temperature treatment has been developed. Amorphous ribbons produced using this technology require optimal annealing temperatures to be specifically selected. The results of studying nanocrystalline magnetic core’ properties and their structure in the course of annealing at temperatures below and above the optimal ones are presented.
Abstract: The structure and physical properties of the Fe72.5Cu1Nb2Mo1.5Si14B9 nanocrystalline alloy have been studied both in terms of dynamics, using thermomagnetic analysis and statics, using specimens subjected to a complete course of heat treatment at the specified annealing temperature. In the course of nanocrystallization, there was a peak detected on the curve of permeability, that peak appeared several minutes later than the heat production peak. The permeability peak occurrence can be related to the formation of a sufficiently large amount of the crystalline ferromagnetic phase α-FeSi followed by saturating it with silicon due to diffusion.
Abstract: Hybrid bonded magnet Ba-Ferrite/NdFeB with 5% wt Epoxy Resin (ER) as polymer binder hsa been developed with variations in BaFe12O19 to NdFeB weight ratio. The variation of the BaO6Fe2O3 : Nd-Fe-B weight ratio are 90%:10%; 80%:20%; 70%:30% and 60%:40%. The magnetic particle consist of Ba-Ferrite and NdFeB were mixed until homogenize and compacted by using hydraulic press machine with 8 Tonf force to form a disc shape sample. The disc sample was dried using vacuum dryer with 10 mm bar pressure at 80°C for one hour before being magnetized using impulse magnetizer. The best %wt composition ratio of Ba-Ferrite/NdFeB is 70%/30% and 60%/40%. The hybrid bonded magnetic properties at the best %wt composition ratio are: bulk density = 4.28-4.43 g/cm3, FM = 1057-1121 Gauss, Br = 3.46-3.70 kG, Hc = 3.25-3.70 kOe, and BHmax = 1.60-1.70 MGOe.
Abstract: The Nyodimium-Iron-Boron (Nd-Fe-B) based materials are known as the best type of magnetic materials and it contains a magnetic phase Nd2Fe14B. The Nd-Fe-B alloy Flakes is one of the main raw material for producing of NdFeB-based permanent magnets and the size of Nd-Fe-B flakes are still coarse. Synthesis of Nd2Fe14B powder has been done by a wet mechanical milling method using the High Energy Milling (HEM) for 10 hrs and continued by heating at 600°C in vacuum condition (10-4 Pa). This process is used to produce a fine powder Nd2Fe14B for making of permanent magnets. The milling medium was used a toluene (pa-Emerck)) to protect of particle from oxidation during the milling process. After milling processes, the samples were measured distribution particle size by using Particle Size Analyzer (PSA). Microstructure analysis has been conducted by using X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM/EDX) for samples before milling and sample after heating. The characterization results show that after milling 10 hours, it was obtained fine powder with average size about 1.35 μm. According to SEM/EDX and XRD analysis show that the crystal structure of the sample before milling was different compared to the sample after heating. It is found new magnetic phase with formula Nd2Fe14B.
Abstract: This Lauric acid is the most abundant fat in coconut oil, which can undergo an esterification and trans-esterification reactions to form methyl laurate. The aim of this study was to characterize the results obtained from lauric acid esterification and tran-esterification VCO enzymatic produce methyl esters with a distinctive odor ester. VCO enzymatic_methanol esterification (9: 1) with phosphoric acid catalyst and tran-esterification results esterification_methanol (1: 3) with KOH catalyst with varies time were 0.5; 1; 1.5; and 2 hours with the percentage obtained FAME row is 73.97; 78.09; 91.75; and 89.83%. Characterizations of methyl laurate were (1) density: 857.97; 857.97; 859.90; and 860.00 kg/m3, (2) % FFA: 0.16; 0.12; 0.09; 0.07% and acid value: 0.44; 0.32; 0.24; 0.14 mg-KOH/g sample. (3) Functional groups showed similarities value with the methyl laurate standard by the FT-IR spectrophotometer, the presence of ester compounds such as C = O; C-O; C-H; CH3; and RCOOR.
Abstract: Supercritical CO2 is commonly used in the processing of natural products due to several advantageous factors such as inexpensiveness, moderate operating parameters and simple purification step. In the processing of phyto-pharmaceuticals, CO2 has been used mostly for extraction, purification and particle formation. This article is a review of supercritical particle formation processes applied to phenolic compounds, specifically curcumin. In summary, supercritical technologies constitute a process platform for the modification of curcumin physicochemical properties. The use of supercritical CO2 as a solute, solvent or anti-solvent in curcumin processing enabled the production of material with particle size as small as 15 nm and improved antioxidant activity.
Abstract: Titanium-based alloys are among the most common materials implanted into the human body to permanently support or replace injured or disease-damaged bones due to their high flexural strength and tolerable elastic modulus. However, titanium is considered a bio-inert material and surface modification is needed to improve its bioactivity. Studies have shown that hydroxyapatite coatings are typically bioactive but have poor adhesion strength to titanium. On the other hand, TiO2 coatings strongly adhere to titanium but their bioactivity is limited. This study aims to improve the surface properties of titanium by anodic oxidation and coated with porcine bone-derived hydroxyapatite (HAp). The influence of different anodization voltage on the surface morphology of the titanium substrate and the coating was investigated. The average roughness and wetting angle of the HAp/TiO2 coating increased along with the increasing applied voltage. The increase in roughness and wetting angle is attributed to the change in pore size of TiO2 layer when subjected to varying voltage. With the influence of surface roughness and morphology on the biological performance of titanium implants, the correlation of improved roughness in the coating to the bioactivity can be considered.
Abstract: Pin-on-disk wear test using Co-Cr-Mo-C-N-Si-Mn cast alloy pins and alumina disks was conducted in Kokubo and 1mass% lactic acid solutions. The precipitates in the as-cast alloys were M23X6 type, π-phase and M2X type. After wear test, it was found that the ratio of the amount of eluted ions in 1mass% lactic acid solution corresponded to the chemical composition of alloys. The detached of M2X type precipitate was observed in as-cast alloy after wear test in 1mass% lactic acid solution. Meanwhile, the elution of metallic ions in Kokubo solution was much less that in 1mass% lactic acid solution. Concentration of Cr was extremely low in Kokubo solution. The formation of CrOOH during test in Kokubo solution might suppress the concentration of Cr.
Abstract: The applicability of LaMnO3 perovskite as nanocatalyst was investigated for removing of methylene blue as a model compound of organic pollutant under visible light and ultrasonic irradiation simultaneously. The LaMnO3 perovskite was synthesized by co-precipitation method and it was characterized in terms of morphological, structural, compositional, optical and magnetic properties. The detailed characterization confirmed that LaMnO3 perovskite had a single-phase orthorhombic structure with estimated crystallite size of 44 nm. UV-vis diffuse reflectance spectra showed a weak reflection with small band gap energy. The weak ferromagnetic behavior with a saturation magnetization of 3 emu/g was obtained at 1 Tesla. The photosonocatalytic showed significantly higher catalytic activity in decomposing methylene blue compared to that of sonocatalytic or photocatalytic alone. Radical scavenger experiments revealed that holes were the predominant oxidative species involved in the process.
Abstract: The magnetic Fe3O4-nanographene platelets (Fe3O4–NGP) platelets composites with various concentrations of nanographene platelets were used as a catalyst for the removal of methylene blue in aqueous solution. The adsorption and sonocatalytic performances were evaluated using methylene blue in aqueous solution. The effect of NGP content in the Fe3O4–NGP, pH and initial concentrations of methylene blue were investigated. Compared in the dark Fe3O4–NGP shows faster and higher removal efficiency by the adsorption and sonodegradation. It could be concluded that synergy of adsorption and sonodegradation have a significant progress for removal of methylene blue compared with adsorption alone. The removal of methylene blue follows the order adsorption-sonocatalysis > sonocatalysis > adsorption. The predominant oxidative species for degradation of methylene blue was identified to be hydroxyl radicals and holes.