Method of Ga removal from a specimen on a microelectromechanical system-based chip for in-situ transmission electron microscopy

In-situ transmission electron microscopy (TEM) holders that employ a chip-type specimen stage have been widely utilized in recent years. The specimen on the microelectromechanical system (MEMS)-based chip is commonly prepared by focused ion beam (FIB) milling and ex-situ lift-out (EXLO). However, the FIB-milled thin-foil specimens are inevitably contaminated with Ga+ ions. When these specimens are heated for real time observation, the Ga+ ions influence the reaction or aggregate in the protection layer. An effective method of removing the Ga residue by Ar+ ion milling within FIB system was explored in this study. However, the Ga residue remained in the thin-foil specimen that was extracted by EXLO from the trench after the conduct of Ar+ ion milling. To address this drawback, the thin-foil specimen was attached to an FIB lift-out grid, subjected to Ar+ ion milling, and subsequently transferred to an MEMS-based chip by EXLO. The removal of the Ga residue was confirmed by energy dispersive spectroscopy.

A method of Ga removal from a specimen fabricated on MEMS-based chip for in-situ transmission electron microscopy

In-situ transmission electron microscopy (TEM) holders, which are widely used in recent years, employ a chip-type specimen stage. To prepare the specimen on the microelectromechanical system (MEMS)-based chip, focused ion beam (FIB) and ex-situ lift-out (EXLO) techniques has been widely used. However, thin foil specimens prepared using the FIB inevitably contain the contamination induced by Ga+ ions. In particular, when the specimen is heated for real time observation, it is observed that Ga+ ions influence the reaction or aggregate in the protection layer. An effective method of removing the Ga residue is demonstrated using Ar+ ion milling within FIB. In the case of lifting the thin foil specimen from the trench by the EXLO technique, Ga still remained even if Ar+ ion milling was conducted. To avoid this problem, the thin foil specimen was attached to FIB lift-out grid, performing Ar+ ion milling, and then transferred to a MEMS chip using EXLO technique. The removal of the Ga residue was confirmed using energy dispersive spectroscopy (EDS).

Uniaxial Tensile Behaviour of 75μm Thick Stainless-Steel Foils

Accurate knowledge about tensile behavior of thin stainless-steel foils at micro/meso scale is of great importance for potential industrial applications. In this work, two 75μm thick AISI 304L and 439 stainless-steel foils were tested under uniaxial tension. Digital image correlation (DIC) based strain measurement method was applied to characterize the plastic deformation of foil specimen. The stress-strain relations of foil specimens were identified from DIC-based strain measurement and compared with the results derived from crosshead displacement. It is found that the applied DIC method can more precisely characterize the mechanical behaviors of foil materials at small size scale. Fracture surface of foil specimens were also characterized. The material microstructures are found have predominant effect on tensile behaviors of foil materials.

Double-Direction Pressure Distributions Generated by Vaporizing Metal Foils

In this work, a research on double-direction pressure distributions (DDPD) induced by vaporizing a single metal foil was conducted. The shock pressure in the up direction revealed the same amplitude as that in the down direction. Based on a comparison of pressure amplitudes between double-direction pressure distributions (DDPD) and single-direction pressure distributions (SDPD), the pressure upward in DDPD was found to be smaller than that in SDPD. In addition, an approach to vary the pressure amplitudes in the up and down directions in DDPD was introduced. Using polyurethane plates in different thicknesses leads to various pressure amplitudes on both sides of the foil specimen. Finally, the application of DDPD in metal forming process was examined. A profile forming part with two bulging zones was successfully manufactured.

Creep Deformation Characteristics of Austenitic Stainless Steel Foils

Creep deformation process of austenitic stainless steel foil with thickness 0.25 mm was investigated. The foil specimen was creep tested at 750oC, 54 MPa to establish baseline behavior for its extended use as primary surface recuperator in advanced microturbine. The creep curve of the foil shows that the primary creep stage is brief and creep life is dominated by tertiary creep deformation. The curve is well represented by the modified theta-projection concept model with hardening and softening terms. Morphology of fractured foil surface reveals intergranular fracture with shallow network of faceted voids. The formation of w-type creep cavities is significant, as revealed by microstructure of ruptured specimen. Composition analysis indicates the formation of carbides, namely, Cr23C6, NbC and Fe3Nb3C.

Slide-Bend Forming of Very Thin Metal Sheet Using Slide-Ironing Tool

Characteristics of slide-bend forming were investigated. In this process, foil specimens can be bent to various shaped products by indenting and sliding a tool. The effects of the tool indentation load, the foil thickness and the number of slide repetition on the bending angle were examined experimentally for three kinds of foil materials. In addition, the deformation of bent region was examined using a rigid-plastic finite element analysis. Bending angle increased with increasing the indentation load or decreasing the foil thickness. When the number of slide repetition increased, the bending angle increased slightly. The slide repetition can be effective for adjusting bending angle slightly. By sliding a thin edge-shaped tool relative to the foil specimen, bending angle and radius of curvature of specimens can be controlled freely.

The Stereoscopic Morphology of Martensite in Ferrous Alloys

The space morphology of martensite in 15, 45 and T9 steels quenched from high temperatures had been observed under a scanning electron microscope using a thin-foil specimen which were deeply etched. The results show that the space appearance of packet martensite is not lath-like in shape, but sheet-like in low carbon steel, and thin plate-like in medium and high carbon steels. The stereoscopic models of two kinds of packet martensite, named sheet-like and thin plate-like martensite by authors, were proposed.

Quantitative X-Ray Microanalysis for the Study of Nanometer-Scale Phases in the Aem

ABSTRACTSecondary excitation can be a large source of inaccuracy in quantitative X-ray microanalysis of inhomogeneous specimens in the AEM. The size of the secondary excitation component in the measured X-ray spectrum is sensitive to the geometry of the thin foil specimen. Secondary excitation has been examined in a self-supporting disc specimen of composition NiO-20 wt.% TiO2 which has been partially masked by a gold slot washer. The ratio of the intensities of the characteristic Kα peaks of Ti and Ni in X-ray spectra from a periclase-structured phase, of nominal composition NiO, has been measured to be NTi / NNi ≈ 0.005. There is no apparent Ti L2,3 signal in the corresponding electron energy-loss spectrum. The secondary excitation contribution to the characteristic Ti K≈a-peak from all sources can therefore be no larger than 0.5%. It should be possible to reduce this modest level of secondary excitation still further with a better masking arrangement.