ABSTRACT
The magnetic nano-structured Ba-Al ferrite powders were prepared by high energy ball milling under the conditions of various rotation rates and milling times. The micro structure was characterized by SEM, XRD and TEM, and the magnetic properties were obtained by VSM. As the rotation rate and milling time increased, the size of nano-sized particles gradually decreased. The high energy ball milling for 5 h without relation to the rotation rate drastically reduced the coercivity as a consequence of the formation of nano-sized particle with the amorphous structure. However, the coercivity gradually decreased with increasing the milling time, resulting from the decrease of particle size with maintaining the crystal structure.
ABSTRACT
The Fe-based self-fluxing alloy powders and SiC particles were mixed and milled by high energy ball-milling, and their microstructure and micro-hardness were investigated after subsequent compaction and sintering. The initial alloy powders with a mean size of approximately 80 microm were fined to 2.1 microm after milling at 800 rpm for 5 h. However, the powder mixture of alloy powder and SiC particle showed much larger powder size compared to the initial alloy powders. The bulk composites were obtained from the powder mixture by compaction under a pressure of 800 MPa for 10 min and sintering at 1073 K for 3 h. The composites had much higher micro-hardness of more than 700 Hv compared to alloy powder. The micro-hardness of composites slightly increased with the content of SiC particles.
ABSTRACT
Mg-1.0wt%Zn-2.0wt%Y alloy powders were produced by gas atomization, and subsequently sintered by spark plasma sintering (SPS). The SPSed Mg-1.0wt%Zn-2.0wt%Y alloy, which showed a microstructure of well-bonded grains containing nano-sized powders of approximately 100 nm in diameter, was coated by a plasma electrolytic oxidation (PEO) method. Microstructure, mechanical properties and corrosion properties of PEO coatings were investigated and compared to those of normally sintered Mg-1.0wt%Zn-2.0wt%Y and cast Mg-1.0wt%Zn alloys. All coatings consisted of MgO and Mg2SiO4. The micro-hardness and friction coefficient of coatings on the SPSed Mg-1.0wt%Zn-2.0wt%Y alloy were higher than those on normally sintered Mg-1.0wt%Zn-2.0wt%Y and cast Mg-l.0wt%Zn alloys. However, the corrosion resistance in 3.5% NaCl solution for the SPSed Mg-1.0wt%Zn-2.0wt%Y alloy was between that for normally sintered Mg-1.0wt%Zn-2.0wt%Y alloy and cast Mg-1.0wt%Zn alloy.
ABSTRACT
The aims of this study were to develop a transdermal gel formulation for ibuprofen using experimental design techniques and to evaluate its pharmacokinetic properties. The three factors chosen for factorial design were the concentrations of drug, polyoxyethylene(5)cetyl/oleyl ether and ethanol and the levels of each factor were low, medium and high. Skin permeation rates and lag times of ibuprofen were evaluated using the Franz-type diffusion cell in order to optimize the gel formulation. The permeation rate of ibuprofen significantly increased in proportion to the drug concentration, but significantly decreased in proportion to POE(5)cetyl/oleyl ether concentration. Ethanol concentration was inversely proportional to the lag time. The pharmacokinetic properties of the optimized formulation were compared with those of two marketed products in rats. The relative bioavailability of ibuprofen gel compared to the two marketed products was 228.8% and 181.0%. In conclusion, a transdermal ibuprofen gel was formulated successfully using the technique of experimental design and these results helped in finding the optimum formulation for transdermal drug release.
Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/administration & dosage , Anti-Inflammatory Agents, Non-Steroidal/chemistry , Ibuprofen/administration & dosage , Ibuprofen/chemistry , Administration, Cutaneous , Animals , Anti-Inflammatory Agents, Non-Steroidal/pharmacokinetics , Area Under Curve , Chemistry, Pharmaceutical , Chromatography, High Pressure Liquid , Gels , Ibuprofen/pharmacokinetics , In Vitro Techniques , Mice , Mice, Hairless , Pharmaceutical Vehicles , Rats , Reproducibility of Results , Skin AbsorptionABSTRACT
Personal neutron dosimetry is quite a difficult area because a neutron is always accompanied with gamma radiation, which is required of a capability for mixed field dosimetry. CaSO4:Dy phosphor is known to have a very high sensitivity to gamma radiation, but the neutron capture cross section of the constituents of CaSO4:Dy are so small that the interactions between the thermal neutron and the phosphor are rare. One method to improve the neutron interaction is by introducing an impurity ion with a large thermal neutron captures cross section into the phosphor to act as a neutron target centre such as 6Li. In neutron-gamma mixed radiation fields, if two detectors for the 6Li-7Li compounds embedded CaSO4:Dy thermoluminescent (TL) pellets are used, a 6Li-compound embedded pellet can detect the neutron and gamma radiations together, and the other pellet can only detect the gamma radiation. Recently, the Korea Atomic Energy Research Institute (KAERI) has developed a new type of CaSO4:Dy TL materials embedded with phosphorous (KCT-300) to detect beta and gamma radiation with a very high sensitivity. This paper presents the development of CaSO4:Dy TL pellets embedded with 6Li compound for a thermal neutron measurement, and the detection method of the neutron and gamma dose in mixed fields with CaSO4:Dy TL pellets embedded with a 6Li compound (KCT-306) and CaSO4:Dy TL pellets embedded with a 7Li compound (KCT-307) is introduced. The net neutron sensitivity of CaSO4:Dy TL pellets embedded with 6Li compound developed in this study is about two times higher than that of the TLD-600 (Harshaw Chemical) dosemeter which is available commercially.
