Site-specific specimen preparation by focused ion beam milling for transmission electron microscopy of metal matrix composites.

This work describes the application and usefulness of the focused ion beam (FIB) technique for the preparation of transmission electron microscopy (TEM) samples from metal matrix composite materials. Results on an Aldiamond composite, manufactured by the squeeze casting infiltration process, were chosen for demonstration. It is almost impossible to prepare TEM specimens of this material by any other conventional method owing to the presence of highly inhomogeneous phases and reinforcement diamond particles. The present article gives a detailed account of the salient features of the FIB technique and its operation. One of the big advantages is the possibility to prepare site-specific TEM specimens with high spatial resolution. The artifacts occurring during the specimen preparation, for example, Ga-ion implantation, curtain effects, amorphous layers, bending of the lamella, or different milling behaviors of the materials have been discussed. Furthermore, TEM examination of the specimens prepared revealed an ultrafine amorphous layer of graphite formed at the interface between the Al and diamond particles that may affect the interfacial properties of the composite materials. This may not have been feasible without the successful application of the FIB technique for production of good quality site-specific TEM specimens.     

Improved method of obtaining piperitone

A new convenient variant of the reduction of thymol methyl ether by lithium and isopropanol in the presence of ethylenediamine at 80–85°C and a molar equivalent ratio of ether to alcohol to amine to metal of 1:(8–12):(2.5–3):(4–6) has been developed. The proposed method permits the yield of piperitone to be doubled in comparison with known methods.I. N. Ul'yanov Chuvash State University, Cheboksary. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 335–338, May–August, 1992.     

Application of focused ion beam to atom probe tomography specimen preparation from mechanically alloyed powders.

Focused ion-beam milling has been applied to prepare needle-shaped atom probe tomography specimens from mechanically alloyed powders without the use of embedding media. The lift-out technique known from transmission electron microscopy specimen preparation was modified to cut micron-sized square cross-sectional blanks out of single powder particles. A sequence of rectangular cuts and annular milling showed the highest efficiency for sharpening the blanks to tips. First atom probe results on a Fe95Cu5 powder mechanically alloyed in a high-energy planetary ball mill for 20 h have been obtained. Concentration profiles taken from this powder sample showed that the Cu distribution is inhomogeneous on a nanoscale and that the mechanical alloying process has not been completed yet. In addition, small clusters of oxygen, stemming from the ball milling process, have been detected. Annular milling with 30 keV Ga ions and beam currents >or=50 pA was found to cause the formation of an amorphous surface layer, whereas no structural changes could be observed for beam currents 相似文献   

Efficient method for the preparation of (S)-5-hydroxynorvaline

(S)-5-Hydroxynorvaline 4 has been prepared from l-glutamic acid 1 by simultaneous protection of the α-amino and α-carboxyl groups, and selective reduction of the resulting boroxazolidone 2. This method is rapid and highly reproducible, and gives very pure (S)-5-hydroxynorvaline after simple anion-exchange purification. It improves existing methods by providing a purer product in higher yields.     

Improved method for the iodine(III)-mediated preparation of aryl sulfonimidates

[reaction: see text] One-pot hypervalent iodine-mediated oxidations of arylsulfinamides to arylsulfonimidates is reported. Contrary to the case of alkylsulfinamides, use of iodosobenzene was not satisfactory. The reaction worked best with diacetoxyiodosobenzene (DIB) and a mild base (MgO). The influence of substituents on the iodine(III) reagent arene has been examined.     

Electrospinning: a fascinating method for the preparation of ultrathin fibers

Electrospinning is a highly versatile method to process solutions or melts, mainly of polymers, into continuous fibers with diameters ranging from a few micrometers to a few nanometers. This technique is applicable to virtually every soluble or fusible polymer. The polymers can be chemically modified and can also be tailored with additives ranging from simple carbon-black particles to complex species such as enzymes, viruses, and bacteria. Electrospinning appears to be straightforward, but is a rather intricate process that depends on a multitude of molecular, process, and technical parameters. The method provides access to entirely new materials, which may have complex chemical structures. Electrospinning is not only a focus of intense academic investigation; the technique is already being applied in many technological areas.     

A nuclear geochemical analysis system for boron quantification using a focused ion beam

Journal of Radioanalytical and Nuclear Chemistry - Ion beam analysis has for decades been used as a tool for geochemical analysis of trace elements using both X-rays (particle induced X-ray...     

Improved method for the preparation of diethylaluminum hydride

Summary A convenient method is proposed for the preparation of diethylaluminum hydride from diethylaluminum bromide and lithium hydride.     

ESR study for ion beam induced phenomena in poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP)

Trapped radicals induced in poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP) were observed by X-band electron spin resonance (ESR) spectroscopy at room temperature (RT) under atmospheric field after an irradiation with various kinds of high energy ion beams (6 MeV/u). The irradiation was carried out to a stacked FEP films under vacuum (<4E?4 Pa) at RT with various fluences from 1.0×10⁹ to 1.0×10¹¹ ions/cm². All ESR spectra indicated an existence of peroxy radicals in each of the FEP films without any relation to a kind of ion and a penetration depth. Obtained depth profiles of radical concentrations induced with each ion beam almost correspond to those of stopping power. The trapped radical concentrations were strongly dependent on stopping power. It was found that G-value of trapped radicals by ion beam irradiation was decreased with increasing a stopping power, and was less than the case of gamma-rays irradiation.     

An organometallic approach for ultrathin SnO(x)Fe(y)S(z) plates and their graphene composites as stable anode materials for high performance lithium ion batteries

Through an organometallic approach, ultrathin SnO(x)Fe(y)S(z) plates with ~2 nm single layer-thicknesses were obtained and their graphene composites showed very promising discharge capacities of up to 736 mA h g(-1) and excellent stabilities as anode materials in lithium ion batteries.     

Methods of obtaining ultrathin sections of highly disperse materials for electron microscopy

Conclusions Comparative data on the suitability of methacrylates, epoxide resins ÉD-5 and ÉD-6 and compound K-156 for casting polycrystalline materials into blocks for electron-microscopic investigation have been obtained. K-156 gave the best results.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1350–1351, June, 1967.     

Improved method for the preparation of a ruthenium carbonylcarbide cluster,Ru6C(CO)17

An improved method has been developed for the synthesis of the ruthenium carbonylcarbide cluster Ru₆C(CO)₁₇ by heating Ru₃(CO)₁₂ in octane at reflux.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1893–1894, August, 1990.     

New insight into the solid electrolyte interphase with use of a focused ion beam

The formation and evolution of the solid electrolyte interphase (SEI) film on the surface of natural graphite spheres in the electrolyte of 1 M LiPF6 in ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio 1:1) were investigated with use of focused ion beam (FIB) technology. Secondary electron FIB images clearly show the surface and cross-section morphology of the SEI film. The composition variation along the surface and cross section of the SEI film was also explored by the elemental line scan analysis (ELSA). The initial SEI film with an apparent thickness range of approximately 450 to approximately 980 nm is rough in morphology and nonuniform in composition, and contains small splits. After certain electrochemical cycles, the thickened SEI film displays microscale holes and obvious cracks on the surface, and the content of organic compounds increases. In addition, the concept of "internal SEI film" is first proposed based on the characterization of the cross section of the natural graphite spheres with the aid of FIB. Finally, the capacity fading mechanisms of the natural graphite spheres corresponding to different electrochemical stages are discussed.     

An investigation on focused electron/ion beam induced degradation mechanisms of conjugated polymers

Irradiation damage, caused by the use of beams in the electron microscopes, leads to undesired physical/chemical material property changes or uncontrollable modification of structures that are being processed. Particularly, soft matter such as polymers or biological materials is highly susceptible and very much prone to react on irradiation by electron and ion beams. The effect is even higher when materials are subjected to energetic species such as ions that possess high momentum and relatively low mean path due to their mass. Especially when Ga(+) ions (used as the ion source in Focused Ion Beam (FIB) instruments) are considered, the end-effect might even be the total loss of the material's properties. This paper will discuss the possible types of degradation mechanisms and defect formations that can take place during ion and electron beam irradiation of the conjugated polymers: e.g. polyfluorene (PF) and poly-3-hexylthiophene (P3HT) thin films. For the investigation of the irradiation induced degradation mechanisms in this study, complementary analytical techniques such as Raman Spectroscopy (RS), Infrared Spectroscopy (IR), Electron Energy Loss Spectroscopy (EELS), Atomic Force Microscopy (AFM), and Fluorescence Microscopy including Photoluminescence (PL) and Electroluminescence (EL) Microscopy were applied.     

Off-axis electron holography of unbiased and reverse-biased focused ion beam milled Si p-n junctions.

Off-axis electron holography is used to measure electrostatic potential profiles across a silicon p-n junction, which has been prepared for examination in the transmission electron microscope (TEM) in two different specimen geometries using focused ion beam (FIB) milling. Results are obtained both from a conventional unbiased FIB-milled sample and using a novel sample geometry that allows a reverse bias to be applied to an FIB-milled sample in situ in the TEM. Computer simulations are fitted to the results to assess the effect of TEM specimen preparation on the charge density and the electrostatic potential in the thin sample.