Study of Stainless Steel Solid Phase Microextraction Fiber for Selective Absorption of Impurities in Gutter Oil / 分析化学

A special solid phase micro extraction ( SPME ) fibre was successfully attained by coating with a special adsorptive material on a porous stainless steel support. And the porous stainless steel support was prepared by electrochemical corrosion for the first time. The optimized erosion condition in this research was as follows: the current intensity of 30 mA, the stainless steel was etched in 2 mol/L hydrochloride solution for 1 min, then sonicated for 3 min; these procedures repeated 5 times. Meanwhile, the treated fiber coated 35 times in the sorbent solution with concentration of 5% ( m/V) in dichloromethane. The SPME fibre was applied to the analysis of gutter oil samples, and the performance of the SPME fibre for the headspace solid phase micro extraction of the exogenous impurities in gutter oil was specific, durable, stable and low-cost. The four detected trace level characteristic impurities in certain gutter oil were given as follows:42 . 7 mg/kg for acetic acid, 21. 6 mg/kg 3-butenenitrile, 71. 8 mg/kg carbon disulfide and 2. 8 mg/kg allylisothiocyanate.

Improvement effects of electrochemical stability of magnetic materials for prosthetic dentistry / 대한치과보철학회지

STATEMENT OF PROBLEM: Dental magnetic materials have been applied to removable prosthetic appliances, maxillofacial prostheses, obturator and dental implant but they still have some problems such as low corrosion resistance in oral environments. PURPOSE: To increase the corrosion resistance of dental magnetic materials, surfaces of Sm-Co and Nd-Fe-B based magnetic materials were plated with TiN and sealed with stainless steels. MATERIALS AND METHODS: Surfaces of Sm-Co and Nd-Fe-B based magnetic materials were plated with TiN and sealed with stainless steels, and then three kinds of electrochemical corrosion test were performed in 0.9% NaCl solution; potentiodynamic, potentiostatic, and electrochemical impedance test. From this study, corrosion behavior, amount of elements released, mean average surface roughness values, the changing of retention force, and magnetic force values were measured comparing with control group of non-coated magnetic materials. RESULTS: The values of surface roughness of TiN coated Sm-Co and TiN coated Nd-Fe-B based magnetic materials were lower than those of non coated Sm-Co and Nd-Fe-B alloy. From results of potentiodynamic test, the passive current density of TiN coated Sm-Co alloy were smaller than those of TiN coated Nd-Fe-B alloy and non coated alloys in 0.9% NaCl solution. From results of potentiostatic and electrochemical impedance test, the surface stability of the TiN coated Sm-Co alloy was more drastically increased than that of the TiN coated Nd-Fe-B alloy and non-coated alloy. The retention and magnetic force after and before corrosion test did not change in the case of TiN coated magnetic alloy sealed with stainless steel. CONCLUSION: It is considered that the corrosion problem and improvement for surface stability of dental magnetic materials could be solved by ion plating with TiN on the surface of dental magnetic materials and by sealing with stainless steels.

A STUDY ON THE PHYSICAL PROPERTIES AND BIOLOGICAL CHARACTERISTICS OF DENTAL MAGNETIC ATTACHMENTS / 대한치과보철학회지

In order to investigate various physical and biological properties of dental magnetic attachments studies on retentive characteristics, corrosion properties, cytotoxicity of different magnetic systems for dental applications were done. For the study of retentive characteristics changes of retentive force by increasing air gap, wear properties of various attachment systems and loss of magnetic force by heat treatment were measured. For the study of corrosion property of magnet covering metal electrochemical corrosion was done in artificial saliva and 0.9% NaCl solution between -1,000 mVSCE and +1,000 mVSCE. Anodic polarization curves are obtained about 6 types of samples and 2 types of solution. Corroded surfaces were examined with metallurgical microscope, scanning electron microscope and surface profilometer. For the study of cytotoxicity of magnetic attachment and its field cell growth and agar overlay test were done. The results of this study were as follows. 1.In Magnetic attachments using closed circuit retentive force at zero air gap was greater than magnets using open circuit, but decrease of retentive force by increasing air gap was also greater than open systems. 2.After 40,000 cycles of wear test all mechanical attachment resulted in varing degree of retention loss but in magnetic attachments no loss of retentive force was observed. 3.The magnetic attachment using Neodymium magnet showed early loss of retentive force about 200degrees C but attachment using Samarium magnet showed some resistance to heat treatment and complete retention loss was observed about 500degrees C. The keeper was not influenced by heat treatment in retention. 4.In electrochemical corrosion test Dyna magnetic attachment covering metal showed the highiest corrosion resistance and Shiner magnet covering metal showed the least corrosion resistance and examination of corroded surface with metallurgical microscope, scanning electron microscope and surface profilometer also showed same results with anodic polarization curves. 5.The result of cell culture tests on the magnet covered with metal showed least recognizable cytotoxicity.