A new method for determination of tert-butylhydroquinone (TBHQ) in RBD palm olein with FTIR spectroscopy

Fourier transform infrared (FTIR) spectra of refined bleached and deodorized (RBD) palm olein samples between 3600 and 2800 cm-1 were used for quantitative determination of the content of tert-butylhydroquinone (TBHQ). The method was based on sodium chloride (NaCl) windows with transmission path fixed at 50 μm at room temperature. Fifty stripped oil samples spiked with known amounts of TBHQ concentrations up to 300 mg/ kg (ppm) were separated into two sets for calibration and validation models based on partial least squares (PLS) analyses. The accuracy of the method was comparable to that of the method established by the International Union of Pure and Applied Chemistry (IUPAC) with a coefficient of determination (R2) of 0.9961 and standard error of calibration of (SEC) 5.06. The model was validated, and the R2 of validation and standard error of prediction were 0.9951 and 6.49, respectively. The standard deviation of difference for repeatability for the method was comparable to that for the IUPAC method. The new FTIR method developed for determining TBHQ in palm olein was demonstrated to be efficient, accurate, rapid and required minimum solvent as only acetone was used for cleaning NaCl windows. The method is suitable for routine quality control analysis. © Copyright 2004, Blackwell Publishing

Isothermal and Cyclic Aging of 310S Austenitic Stainless Steel

Unusual damage and high creep strain rates have been observed on components made of 310S stainless steel subjected to thermal cycles between room temperature and 1143 K (870 °C). Microstructural characterization of such components after service evidenced high contents in sigma phase which formed first from δ-ferrite and then from γ-austenite. To get some insight into this microstructural evolution, isothermal and cyclic aging of 310S stainless steel has been studied experimentally and discussed on the basis of numerical simulations. The higher contents of sigma phase observed after cyclic agings than after isothermal treatments are clearly associated with nucleation triggered by thermal cycling

Effect of Austenite Deformation on the Microstructure Evolution and Grain Refinement Under Accelerated Cooling Conditions

Although there has been much research regarding the effect of austenite deformation on accelerated cooled microstructures in microalloyed steels, there is still a lack of accurate data on boundary densities and effective grain sizes. Previous results observed from optical micrographs are not accurate enough, because, for displacive transformation products, a substantial part of the boundaries have disorientation angles below 15 deg. Therefore, in this research, a niobium microalloyed steel was used and electron backscattering diffraction mappings were performed on all of the transformed microstructures to obtain accurate results on boundary densities and grain refinement. It was found that with strain rising from 0 to 0.5, a transition from bainitic ferrite to acicular ferrite occurs and the effective grain size reduces from 5.7 to 3.1 μm. When further increasing strain from 0.5 to 0.7, dynamic recrystallization was triggered and postdynamic softening occurred during the accelerated cooling, leading to an inhomogeneous and coarse transformed microstructure. In the entire strain range, the density changes of boundaries with different disorientation angles are distinct, due to different boundary formation mechanisms. Finally, the controversial influence of austenite deformation on effective grain size of low-temperature transformation products was argued to be related to the differences in transformation conditions and final microstructures