bluuebunny/crossref_metadata_2025_split huggingface dataset:
TEM investigation of lattice-matched In0.53Ga0.47 as layers grown on InP by low-pressure metalorganic vapor-phase epitaxy
Authors: Sung C.M. , Ostreicher KJ. , Abdalla M. , Kenneson D.G. , Powazinik W. , Hefter J. 
Published: June 2020

High-quality defect-free In0.53Ga0.47 As thin film layers lattice matched to InP are important materials for the efficient operation of many optoelectronic devices used in long wavelength communication systems. The presence of defects in these devices is known to have a marked effect on their performance and long-term reliability. The In0.53Ga0.47 As layers reported here were grown by a low-pressure metalorganic vapor phase epitaxy method using tertiarybutylarsine as the As precursor; the layers were found to have high mobility and low background carrier concentrations. The aim of the present work is to investigate the microstructure, ordering, and degree of lattice misfit between the epitaxial In0.53Ga0.47 As layer and the InP using cross-sectional TEM (XTEM) and convergent beam electron diffraction (CBED) methods.A bright-field TEM image (Philips EM400T, 120 keV) taken in the cross-sectional view shows the In0.53Ga0.47As layer, a thin InP buffer layer (≈0.05μm), and the InP (Fe-doped) substrate (Figure 1). The dark cluster-like regions in the InP substrate are Fe-rich (confirmed by EDX).
TEM studies of fine low dimensional modulated fringes (FLDMF) in GaAs/Ga1-xAlx As multilayer heterojunction structure grown by MBE
Authors: Fan Rongtuan 
Published: June 2020

The characteristics of GaAs/Ga1-x Alx As superstructure grown by MBE are always noticed. Recently, as well known, cross-sectional trasmission electron microscopy (XTEM) has been used and many workers have observed the superstructure(multilayer heterojunction structure) of GaAs/Ga1-x Alx, As hetero-multilayer. They usually observed a wide fringes with several nanometers or even more in GaAs/GaAlAs multilayer structure.In this work, we have studied a phenomenon which was named"Fine Low Dimensional Modulated Fringes" of GaAs/GaAlAs heteromutilayer structure grown by MBE, using XTEM technique. It is found that the FLDMFs are an equal width and very narrow, the order of Å’s.The GaAs/GaAls layers that are examined were grown on (001) GaAs substrate by MBE. Cross-section TEM specimens with a wafer cleaved along (110) plane were prepared, and thinned by argon ion.A typical structure is given in Fig.l, the image is of superlattice(SL) and Fine Low Dimensional Modulated Fringes area of MBE grown GaAs/GaAlAs heteromutilayer.
Formation of high temperature phase in flash-evaporated SnSe films
Authors: Hanjra J.P.S. 
Published: June 2020

Tin mono selenide (SnSe) with an energy gap of about 1 eV is a potential material for photovoltaic applications. Various authors have studied the structure, electronic and photoelectronic properties of thin films of SnSe grown by various deposition techniques. However, for practical photovoltaic junctions the electrical properties of SnSe films need improvement. We have carried out investigations into the properties of flash evaporated SnSe films. In this paper we report our results on the structure, which plays a dominant role on the electrical properties of thin films by TEM, SEM, and electron diffraction (ED).Thin films of SnSe were deposited by flash evaporation of SnSe fine powder prepared from high purity Sn and Se, onto glass, mica and KCl substrates in a vacuum of 2Ø micro Torr. A 15% HF + 2Ø% HNO3 solution was used to detach SnSe film from the glass and mica substrates whereas the film deposited on KCl substrate was floated over an ethanol water mixture by dissolution of KCl. The floating films were picked up on the grids for their EM analysis.
Study of the interphases in SiC/LAS composites by HREM and SIMS
Authors: Ponthieu C. , Lancin M. 
Published: June 2020

The strength and toughness of the SiC Nicalon 202 fibers/LAS-matrix composites originates from the carbon richlayer which develops at the interfaces fibers/matrix during the process, To reach a better understanding of the formation of this carbon interphase in the SiC Nicalon/LAS, we have studied the interfacial region in several SiC/LAS composites which differ by i) the composition of the matrix, ii) the time of the hot pressing and iii) the composition of the reinforcement. As the interfacial region (IR) is about 100 nm thick, its characterization needs localised analyses. They have been performed by TEM, HREM and SIMS. In the composites SiC Nicalon fibers/LAS glass matrix and SiC Nicalon fibers/LAS + Nb2O5 glass matrix hot pressed during 10 minutes,the reaction between the fibers and the matrix results in:- a carbon layer whose thickness is increased by addition of Nb205 as previously found. We have shown that the microstructure of the carbon depends on the oxydant character of the matrix : it is mainly turbostratic in Nicalon/LAS (fig.l), whereas it is mainly amorphous in Nicalon/LAS + Nb205(fig.2).
Using an iron overlayer to enhance contrast in SEMPA
Authors: Browning R. , VanZandt T. , Landolt M. 
Published: June 2020

Secondary electron microscopy with polarization analysis (SEMPA), uses the spin polarization of the low energy secondary electrons to image the surface magnetization of a magnetic sample. However, many systems of interest to the magnetic recording industry have a low secondary electron spin polarization. This is because, either the material’s magnetization is low, or because surface treatments have reduced the spin polarization. The low spin polarized contrast from these samples means that detailed study of the characteristics of a recorded field is very time consuming. Typically tens of minutes are needed to collect a single image that may cover a very small part of a sample. As a result, it is difficult to provide sufficient information over the range of length scales needed to characterize the magnetic distribution.One method by which the problem of low spin polarized contrast may be overcome, is to use an overlayer with a high spin polarization. This film must be thin, and magnetically soft to minimize any change in the sample’s magnetization. Pure Fe films appear suitable, and high spin polarized contrast can be observed in nanometer thick fims of Fe.
Analytical Electron Microscopy of cast (Nd1-xRx)13Fe80C7 [R=Tb,Dy] permanent magnet materials
Authors: Fidler Josef , Groiss Claudia , Eisses J. , Buschow K.H.J. 
Published: June 2020

High performance permanent magnets are based on compounds of the type SmCo5, Sm2Co17 and Nd2Fe14B exhibiting high magnetization and high magnetocrystalline anisotropy. The primary preparation technique for such magnets is the powdermetallurgical sintering process. The search for new materials and processing techniques led to the ternary system R-Fe-C.Compounds of the type R2Fe14C are isotypic with the crystal structure of Nd2Fe14B. Cast magnets based on R2Fe14C exhibit already a high coercive field, but decompose at higher temperatures into compounds of the type R2F17Cx. The transformation temperature Tt depends on the rare earth element and is about 850°C for the Nd-system and is larger than 1100°C for the Tb- and the Dy-system.The specimens investigated were cast in an arc furnace and annealed for 31 days at 850°C. Various magnets with different composition (Nd/Dy- and Nd/Tb-ratios) and coercivities were studied. The coercive field increases with decreasing Nd-content (see Table 1).
Initial stages of electron beam-induced transformations in potassium β‴-Ferrite, KFe17O25
Authors: Hutchison J.L. , Matsui Y. , Lincoln F.J. 
Published: June 2020

Potassium β’’’-ferrite, nominal composition KFe17O25 and isostructural with sodium β’’’- alumina, has a hexagonal structure consisting of spinel blocks (SB) separated by loosely packed conduction planes (CP) containing relatively mobile K+ cations. Various structural changes which occur during electron irradiation have been characterised by high resolution electron microscopy and may be summarised as follows:1Migration of K+ and O2−from the conduction planes, followed by2Frequent collapse of CP.3Topotactic transformation of the resulting multiply-twinned spinel layers to form broad laths of magnetite, Fe304.4Gradual growth of wüstite, Fe1-xO on exposed surfaces.We have examined KFe17O25 at 400 kV, using a JEOL 4000EX, the resolution (1.65 Å)being sufficient to resolve all cation rows along two main crystallographic directions, and We could thus monitor the earliest stages of structural transformation at the atomic level.
Re-examining mechanisms of radiation damage in organic specimens
Authors: Armstrong David A. , Luo Suichu , Joy David C. 
Published: June 2020

Radiation damage to organic specimens is the major limiting factor in high resolution electron microscopy studies of biological systems. Electron beam irradiation compromises resolution by altering chemical microstructure, resulting in local mass loss and volume shrinkage in a specimen. All significant mass loss is thought to occur prior to a total incident dose of 50 electrons/ square angstrom If this is the case it is hard to reconcile the observation that images must be recorded at doses of less than 100 el/Å in order to avoid excessive mass loss and shrinkage while microanalytical (EDS and EELS) studies of the same tissue are routinely carried out at doses of 104 - 105el/Å2. Also, since most workers typically use either low dose (for imaging) or high dose (for microapalysis) there are apparently no studies in the literature which attempt to follow the process of radiation damage between these two extremes.We have chosen to investigate mass loss in polymer embedding resins such as are routinely used for TEM imaging as well as for X ray microanalytical applications.
In Situ SEM study of iodine-induced stress corrosion cracking (ISCC) in Zircaloy-4
Authors: Fick Marthinus P 
Published: June 2020

Stress corrosion cracking (SCC) of Zirconium alloys by an abundant fission product, iodine, has been extensively studied in order to understand the mechanism of failure of fuel cladding in nuclear reactors. This study was an attempt to observe the fracture mechanics of ISCC in Zircaloy-4 during in situ scanning electron microscope (SEM) tensile tests.A 200mm long section of a Zircaloy-4 cladding tube with an outer diameter of 9’55mm and a wall thickness of 0,55mm, was bisected and then cold rolled into flat strips 14mm wide and 0,5mm thick. The material was annealed at 680°C for 1 h at a time in an Argon atmosphere between successive cold working steps. Following the final cold roll the material was annealed at 1080°C for 4 h in an Argon atmosphere and air-quenched.Tensile test specimens with a gauge length of 12’5mm and a width of 3’12mm were cut from the sheet metal by spark erosion accordinq to scaled down ANSI/ASTM E8-79a specifications. The specimens had to be lapped and polished to a thickness of 0’16mm in order to obtain a maximum stress of 500MPa without exceeding the 250N limit of the apparatus.
Indexing and simulation of electron diffraction patterns using the microcomputer
Authors: Feldewerth Gerald B. 
Published: June 2020

Microscopists in the material science field must work with electron diffraction patterns. The ability to quickly index unknown patterns and simulate patterns of known phases would make this task much easier. Computers present the perfect solution for doing the tedious calculations involved in indexing and simulation. The following paper describes the program SIMDEX, developed by the author for these applications.SIMDEX is a set of computer programs and data base files. All of the programs are self-contained, executable files designed to run on IBM or compatible computer systems. All data files, while by no means comprehensive, are easily updated using any word processor.The files in simdex and their function are:1.Main program - index and simulate diffraction patterns.2.Plot program - produce screen image of simulated patterns.3.Menu program - change control between two working programs.4.Material data - hold lattice parameters of materials.5.Position data - hold atom positions for each space group.6.Pattern data - hold data for experimental patterns.
An improved dimpling technique for the preparation of TEM specimens
Authors: Fischione P.E. , Howe J.M. , Garg A. 
Published: June 2020

Traditional techniques for the preparation of TEM specimens have been electrolytic thinning or a combination of mechanical prethinning (dimpling) and ion-beam milling. The focus of discussion for this paper is an advanced technique for the mechanical dimpling procedure.A new device has been designed so that TEM specimens are consistently produced, thus minimizing the need for intensive operator intervention, trial and error methods, and ion-milling time. This instrument incorporates many of the features utilized in standard dimpling techniques. In addition, it provides the ability to simultaneously rotate and oscillate the specimen, resulting in an increased electron beam transparent area. Actual grinding rates are programmed with a resolution of 0.1 μ.m/min, thus eliminating the reliance on adjustable counterweight systems to control the grinding rate/force. A 40X microscope and movable magnetic specimen mount permit precise positioning that enables the dimple to be located at any point on the specimen. This is illustrated in Fig. 3, where the dimple is positioned on the interface of interest. An integral lamp back lights the specimen so that transparency can be detected without removing the specimen from the instrument. During the preparation process, the actual specimen thickness is continuously indicated on an alphanumeric display.
Effects of high pressure on the crystallization of carbon fiber reinforced polyetheretherketone (CF/PEEK) laminate composites
Authors: Lin Hong-Ming , Liu C. H. , Lee R. F. 
Published: June 2020

Polyetheretherketone (PEEK) is a crystallizable thermoplastic used as composite matrix materials in application which requires high yield stress, high toughness, long term high temperature service, and resistance to solvent and radiation. There have been several reports on the crystallization behavior of neat PEEK and of CF/PEEK composite. Other reports discussed the effects of crystallization on the mechanical properties of PEEK and CF/PEEK composites. However, these reports were all concerned with the crystallization or melting processes at or close to atmospheric pressure. Thus, the effects of high pressure on the crystallization of CF/PEEK will be examined in this study.The continuous carbon fiber reinforced PEEK (CF/PEEK) laminate composite with 68 wt.% of fibers was obtained from Imperial Chemical Industry (ICI). For the high pressure experiments, HIP was used to keep these samples under 1000, 1500 or 2000 atm. Then the samples were slowly cooled from 420 °C to 60 °C in the cooling rate about 1 - 2 degree per minute to induce high pressure crystallization. After the high pressure treatment, the samples were scanned in regular DSC to study the crystallinity and the melting temperature. Following the regular polishing, etching, and gold coating of the sample surface, the scanning electron microscope (SEM) was used to image the microstructure of the crystals. Also the samples about 25mmx5mmx3mm were prepared for the 3-point bending tests.
Fracture of ceramics in the SEM
Authors: Frei H. , Grathwohl G. 
Published: June 2020

The progress in the development of advanced structural ceramics is characterized by a remarkable increase in their strength and fracture toughness. Further improvement of these essential mechanical properties is still desirable and requires a fundamental understanding of the crack propagation process. In the new types of ceramic microstructures, e. g. in whisker-, particle-, or platelet-reinforced ceramics the relevant crack growth processes are not adequately understood. These processes are responsible, for example, for the R-curve behaviour which may be due to the formation of a process zone around the crack tip, or by a wake effect of interacting forces between the crack surfaces. Furthermore, fatigue in ceramics is a problem in toughened ceramics in particular and relies directly on the various mechanisms of increased crack resistance.In order to understand the formation and extension of the relevant micro- and macrocracks, SEM is a
powerful tool because of its ample range of magnification and large depth of focus.A complete description of the bending device used is given elsewhere, so that only the main features will be mentioned here.Using a very stiff frame and a position controlled piezo translator it was possible to obtain controlled fracture of brittle ceramic materials. This means that a crack is not spontaneously propagated through the specimen, but slowly advances micrometer for micrometer. The fracture experiments are recorded by a video recorder directly connected to the SEM.
The butterfly martensite nucleation in an iron and nickel alloy
Authors: Chen Q.Z. , Wu X.F. , Ko T. 
Published: June 2020

Some butterfly martensite nuclei were observed in an Fe-27.6Ni-0.89V-0.05C alloy. The alloy was austenitized at 1200°C for 1 hour. Some samples were aged at 850° C for 40 minutes and quenched in 10% brine at room temperature. All the samples were cooled in ethyl alcohol for martensite transformation.A nucleus in an unaged specimen is shown in Fig.1. The nucleus has certain contrast different from the matrix and is shaped like one wing of a butter fly martensite. The SADP of the circled region is measured to be: da=dh, and approximate to dγ(111) and dm(110) with ∠AOB = 55° . It is similar to [011]f.c.c and b patterns in the anglez ∠AOB and the ratio ra/rb, respectively. The SADP shows that the structure of the nucleus is between f.c.c and b.c.c. The dislocation structure within the nucleus is shown in Fig.2. Their Burgers vectors and line directions are also given in it. There are many long dislocations near it without dislocations piled up as shown in Fig.3.Long dislocations are closed at one end as an envelope.
Effect of hydrogen on irradiated defects in iron
Authors: Wan Farong , Xiao Jimei , Yuan Yi 
Published: June 2020

With the development of the study about fusion reactor, it has been becoming a serious problem to investigate the interaction between defects and gaseous elements, such as hydrogen and helium. Many data about helium have been reported, but few experiments about hydrogen were done. The aim of this study was to clarify the behavior of hydrogen under irradiation.Hydrogen was implanted into iron by ion accelerator at an energy of 100 KeV at room temperature. After implantation, the specimens were analyzed at various temperatures using a 1 MeV high voltage electron microscope ( HVEM ).The damage structure in the as-implanted condition was shown in Figure 1. Such defects would develop into dislocation loops by annealing. With increasing annealing temperature, the size of the loops increases and the number density of the loops decreases. It is very interesting that the nature of the loops depends on the annealing temperature. In general, interstitial-type loops were observed at annealing temperature below 720 K. These loops would grow continuously under followed electron irradiation.
Precipitation of copper in proeutectoid cementite in steel
Authors: Khalid F. A. , Farooque M. , Edmonds D. V. 
Published: June 2020

The morphology and mechanism of Cu precipitation in grain boundary allotriomorphs of proeutectoid cementite forming isothermally inaustenite in two Fe-10Mn-3Cu-0.8C and Fe-lOMn- lCu-0.8C (nominal wt%) alloys are being studied. These particular alloys can be partially decomposed to the proeutectoid and eutectoid phases recognisable in ferritic steels, but possess the advantage that unlike ferritic steels the parent austenite phase is retained after cooling to room temperature thus facilitating studies of the decomposition reactions.A 50 g ingot of each experimental alloy was argon arc melted using high purity materials and homogenised. Samples were rolled, swaged and machined to 3mm diameter rod, solution treated at 1200 °C for 1 hr and quenched in water. Specimens were then solutionised at 1200°C for 10 min and isothermally transformed at 615 °C for 4 hrs. Methods for the preparation of thin foils for TEM are given elsewhere.The heat treatment resulted in the formation of grain boundary allotriomorphs of cementite in austenite (Fig 1). TEM confirmed that the cementite allotriomorphs formed with the Pitsch orientation relationship to one of the austenite grains at the grain boundary (Fig 2c ) consistent with a previous analysis.
Observations on acicular structures in a Fe-10Cr-0.4C steel
Authors: Kaya A. A. , Edmonds D.V. 
Published: June 2020

High concentrations of alloying elements can cause significant variations from the classical forms of the decomposition products of austenite in steels, for example, of proeutectoid ferrite, pearlite and bainite . In the case of high Cr additions to steels Schrader, using replica TEM, discovered a product which had an acicular macroscopic shape, but contained a fine lamellar aggregate of alloy carbide; it was described as resulting from the oriented growth of pearlite.The form of this structure described above was more recently confirmed by thin foil TEM in a higher Cr steel, although no attempt was made to classify the reaction mechanism, other than noting its morphological similarity to microstructural characteristics of both pearlite and bainite. However, in a related paper the term “bainitic pearlite” was used.The present paper reports the results of further thin foil TEM, currently in progress, that is aimed at identifying the reaction mechanism.
Crystal structures, defects and transformations in the Al-(Fe,Mn)-Si alloy system
Authors: Hansen V. , Skjerpe P. , Gjønnes J. 
Published: June 2020

The alloy system Al-Fe,Mn-Si is attracting interest because of its tendency to produce quasicrystals. It is also of considerable importance in alloy technology Recent studies have in fact shown that precipitation of icosahedral particles may be the first step in the formation of secondary particles during treatment of Mn-containing alloys produced by strip-casting (Hansen, Gjønnes and Andersson 1989).Our studies of the system have been governed partly by the industrial interest They include several stable and metastable phases which appear in commercial alloys produced by direct chill- (DC-) or strip-casting. Both primary and secondary particles are studied. Especially for the metastable particles electron diffraction and microscopy is essential for determination of crystal structure as well as of defect arrangement.Previous studies included twins and stacking faults in primary particles of AL3Fe and derivation of a structure proposal for the tetragonal metastable phase AlmFe by diffraction and imaging.
TEM study of Nd-Fe-B melt-spun permanent magnets with Fe3B as main phase
Authors: Coene W. , Hakkens F. , Coehorn R. , de Waard C. 
Published: June 2020

Permanent magnet materials with isotropic hard magnetic properties have been obtained by annealing amorphous melt spun flakes with Nd4Fe78B18 composition. This yields a two-phase permanent magnet consisting of the metastable Fe3B in tetragonal modification, and of the hard magnetic Nd2Fe14B for 15% of the alloy.The microstructure of the flakes is dependent on the annealing treatment. The amorphous as-spun flakes were first heated to 730°C with a rate of 200 K/min . Fig. 1 shows that further isothermal annealing during 0, 15 and 60 min yields crystallite diameters of approximately 10, 30 and 50 nm, respectively.Optimal coercivity (μoHc = 0.4 T ) is obtained for 15 min of annealing, in which case the grain size is of the order of the domain wall widthAnalytical TEM with EDX and parallel EELS confirms the two-phase nature of these magnets . For the sample with an annealing time of 60 min ( fig. lc ), parallel EELS is carried out on a CM12 at 120 kV in nanoprobe mode so that a local area of ∼ 10 nm can be analysed.