bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Early stages of the growth of BaTiO3 thin films studied by Transmission Electron Microscopy
Authors: Grant Norton M. , English Gerald R. , Scarfone Christopher , Barry Carter C.
Published: June 2020

Barium titanate (BaTiO3) may be used in a number of thin-film applications in electronic and optoelectronic devices. For these devices the formation of epitactic films of the correct stoichiometry and phase is essential. In particular, the tetragonal form of BaTiO3, which is stable at room temperature, exhibits ferro-, pyro- and piezoelectric properties. It is desirable to form films of the tetragonal phase directly and thus to avoid formation of either amorphous or polycrystalline material or to form material of the non-ferroelectric cubic phase. Recently two techniques, pulsed-laser ablation and reactive evaporation, have been used to form BaTiO3 thin-films. In the present study BaTiO3 thin-films have been formed using the pulsed-laser ablation technique. Pulsed-laser ablation is now widely used to produce thin-films of the high temperature superconductors and has many advantages over other techniques, in particular the formation of films which maintain the stoichiometry of the target material and by controlling the processing conditions the formation of films having defined crystalline phases.
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).
Electron beam induced modifications of SnO2 and SrTiO3
Authors: McCartney M. R. , Smith David J.
Published: June 2020

In addition to providing information about the interaction of ionizing radiation with solids, a knowledge of the changes induced in the specimen by the electron beam is important when interpreting high-resolution electron micrographs of surfaces. Beam-induced modifications to the surfaces of several maximally-valent transition-metal oxides (TMO) have been previously reported. It was found that irradiation at 400keV within a high-resolution electron microscope (HREM) caused TiO2, V2O5, Nb2O5, and WO3 to reduce epitaxially to their respective monoxide phases. Because of their ionicity and relatively deep core levels, these materials should be susceptible to electron-stimulated desorption (ESD) of oxygen due to a radiolytic damage mechanism proposed by Knotek and Feibelman (K-F) involving inter-atomic Auger decay of core holes on the metal ions. Reduction of these oxides to the (metallic) monoxide phases within the HREM is consistent with this mechanism. When these oxides were exposed to the extreme current densities available in a 100keV electron microscope equipped with a field emission gun (FEG) they developed pits at the probe position . Electron energy loss spectroscopy (EELS) studies established that they had suffered mass loss and a reduction in the oxygen/metal ratio. HREM imaging occasionally revealed lattice fringes corresponding to the bare metal in the amorphous contrast of these pits.
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:

1

Migration of K+ and O2−from the conduction planes, followed by

2

Frequent collapse of CP.

3

Topotactic transformation of the resulting multiply-twinned spinel layers to form broad laths of magnetite, Fe304.

4

Gradual 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.
The influence of supporting grid bars on the temperatore increase of a thin fiim subjected to electron irradiation
Authors: Curzon A.E.
Published: June 2020

The heating effect of an incident electron beam may cause a material to be radiation-sensitive. For example, the adsorption behaviour of inert gases on graphite observed in a transmission electron microscope depends critically on the temperature of the substrate. Early consideration of beam heating dealt with a circular film illuminated at the centre by an electron beam of circular cross-section. In practice, however, the film is often supported across a square aperture and is not centrally illuminated. It has recently been shown that the method of images may be used to solve the problem of the heating of a square film of thermal conductivity k by a beam whose cross-section is entirely within the film. This solution has the advantage that it applies regardless of where the incident electron beam strikes the film. The general solution involves an infinite sum over a two dimensional lattice of heat sources and sinks. Though the sum is readily evaluated by means of a computer, it is helpful to consider a particular limiting case which is readily understood in terms of three images and the main beam. This case is illustrated in Figure 1.
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.
Ground surface finishes in carbonized resorcinol/formaldehyde foam
Authors: Price C. W. , Lindsey E. F.
Published: June 2020

Low-density resorcinol/formaldehyde foams developed by Pekala are stabilized by carbonizing (CRF). These delicate foams require machining for critical applications in the Inertial Confinement Fusion program at LLNL. The machining was preformed by first diamond-point turning and then grinding to final dimension. The first several grinding passes removed about 10 (μm per pass, several more passes were made at about 5 (μm per pass, and as the part approached final dimensions, the grinding depth was decreased to about 2 μ.m, and several passes were made at each setting. The final surface finish could be controlled to some extent by adjusting a scraper nozzle that removed grinding debris from the grinding wheel to leave a slight amount of debris on the wheel. During preliminary studies, inconsistencies were observed in the visual appearances of machined surfaces. Some specimens had moderately reflective surfaces, but others had a dull, flat appearance. Therefore, ground CRF surface microstructures were examined to determine the cause of the differences in reflectivity. Secondary-electron images of the specimens were obtained with a Hitachi S-800 FESEM at 25 kV; the specimens were uncoated. Specimens chosen for this study had dull, partially reflective, and reflective surfaces.
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.
Microstructure of borides in titanium and titanium aluminides
Authors: Schwartz Daniel S. , Sastry S. M. L.
Published: June 2020

The high strength-to-weight ratios and high elevated-temperature strength of dispersion strengthened titanium and titanium aluminides make them attractive materials for aerospace applications. A fine dispersion of hard particles is introduced into these alloys to increase their strength through an Orowan hardening mechanism. In addition to strengthening the material, dispersoids with whisker morphologies can produce toughening. Titanium alloys containing boride dispersions are currently being investigated at McDonnell Douglas Research Laboratories, and the microstructure of the dispersoids will be reported in this paper. Fine boride dispersions were produced in alloys with the compositions Ti-6B, Ti-25A1-4B and Ti-48A1-5B (at.%) using rapid solidification processing. The alloys were then annealed at ∼800°C/1 h, TEM specimens produced by electropolishing, and the structure of the borides examined in detail with a JEOL 2000FX TEM.
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 width

Analytical 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.
The evolution of the microstructure of 600 Mev proton irradiated materials
Authors: Gotthardt R. , Horsewell A. , Paschoud F. , Proennecke S. , Victoria M.
Published: June 2020

Fusion reactor materials will be damaged by an intense field of energetic neutrons. There is no neutron source of sufficient intensity at these energies available at present, so the material properties are being correlated with those obtained in irradiation with other irradiation sorces. Irradiation with 600 MeV protons produces both displacement damage and impurities due to nuclear reactions. Helium and hydrogen are produced as gaseous impurities. Other metallic impurities are also created . The main elements of the microstructure observed after irradiation in the PIREX facility, are described in the following paragraphs.

A. Defect clusters at low irradiation doses: In specimens irradiated to very low doses (1021-1024 protons.m-2), so that there is no superimposition of contrast, small defect clusters have been observed by the weak beam technique. Detailed analysis of the visible contrast (>0.5 nm diameter) revealed the presence of stacking fault tetrahedra, dislocation loops and a certain number of unidentified clusters . Typical results in Cu and Au are shown in Fig. 1.
SEM study of diffusion bonded interfaces in Cu-Al(11,46)-Mn(6,62) and Cu-Al(6,94)- Zn(18,86) copper-based shape memory alloys
Authors: Calvo F.A. , Gómez de Salazar J.M. , Ureña A. , Méndez F.J. , Guilemany J.M.
Published: June 2020

The copper-based alloys studied belong to the group of those materials showing Shape Memory Effect (SME). Diffusion Bonding (DB) procedure is an alternative joining method of welding copper-based Shape Memory Alloys, traditionally welded by techniques like electron bean welding (EBW). However EBW provides embrittlement to the joint. This situation has been corrected by DB as confirm the SEM-EDS study presented here.

A material shows SME when once has been thermomechanically deformed, it is able to recover its original (as fabricated) shape by means of a simple heat-up. This pheno menom is possible only for those materials which have β phase prone to undergo martensitic transformation. DB technique estimulates diffusion processes betwen materials by the combination of pressure, temperature, time, surface materials roughness and atmosphere condition in the experimental unit with the aid, sometimes, of a third material, in foil or plated form, which is known by the name of interlayer. The parameter set and details of attaing diffusion bonding joints procedure are under a patent developed recently by the authors .
Microstructural studies of matrix and interface in ceramic fibre-reinforced aluminium alloys
Authors: Yang Ming , Scott V.D.
Published: June 2020

This study is a part of an ongoing research programme aimed at optimising the properties of ceramic fibre reinforced aluminium alloys. It involves a detailed study of matrix and interface and an understanding of the overall mechanical behaviour of the composite. Here, we report an investigation of an Al-7wt%Si alloy reinforced with alumina fibres. A range of techniques including analytical electron microscopy are used to characterise the structure of the fibre matrix interface, the crystallography and morphology of matrix precipitates, and dislocation substructures.

It is shown that the eutectic structure of the Al-Si alloy is markedly changed in the presence of fibres, with silicon showing a tendency to segregate on the fibres. Coarse silicon particles are characterised by twins having the twin the {111} silicon habit plane and related by a rotation of 180° about the [110] direction.The particles have a lamellar morphology with the longitudinal axis lying in the {111} habit plane, but show no evidence of any epitaxial relationship with the aluminium lattice.
Nucleating transformation in ZrO2
Authors: Ma L.T.
Published: June 2020

To understand the michanism of transformation in ZrO2, the Al2O3/ZrO2 composite and Y-TZP have been studied. For the Y-TZP the nucleating transformation has been confirmed.

For the Al2O3/ZrO2 composite the intragranular ZrO2, which is in tetragonal phase , has been studied. Fig. 1-2 show the interface between Al2O3 and ZrO2 Fig. 3 shows the nucleating transformation in the t-ZrO2 grain. Before nucleation it appears the stressing stripes. When the nucleation occurs the stripes are reduced. Then the nucleating transformation is formed. It means that for nucleation some stress was absorbed. So, in the t-ZrO2 whether in Y-TZP or in composite the nucleating transformation generally exists.

At the early time, the untransformed t-ZrO2 phase has been found. From the viewpoint of nucleation the untransformed t-ZrO2 grain unexists, if the nucleating condition is satisfied.

We also examine the nucleating necessary in Y-TZP. Under restraint of the neighbour grains the t-ZrO2 phase can be maintained in Y-TZP. If the nucleating condition is not satisfied, the t-ZrO2 can not be transformed to monoclinic phase, even though the restraint of the t-ZrO2 grain is reduced and the grain has enough size.
Effect of furnace atmosphere and silica content on the consolidation behaviour of magnesia partially stabilised zirconia
Authors: Drennan J. , Hannink R.H.J. , Clarke D.R. , Shaw T.M.
Published: June 2020

Magnesia partially stabilised zirconia (Mg-PSZ) ceramics are renowned for their excellent nechanical properties. These are effected by processing conditions and purity of starting materials. It has been previously shown that small additions of strontia (SrO) have the effect of removing the major contaminant, silica (SiO2).

The mechanism by which this occurs is not fully understood but the strontia appears to form a very mobile liquid phase at the grain boundaries. As the sintering reaches the final stages the liquid phase is expelled to the surface of the ceramic. A series of experiments, to examine the behaviour of the liquid grain boundary phase, were designed to produce compositional gradients across the ceramic bodies. To achieve this, changes in both silica content and furnace atmosphere were implemented. Analytical electron microscope techniques were used to monitor the form and composition of the phases developed. This paper describes the results of our investigation and the presentation will discuss the work with reference to liquid phase sintering of ceramics in general.
Microstructural observations of the “Wustite-Spinel” coexistence following quenching of cation-excess spinels, Ni2(1+x)Ti1-xO4
Authors: Anderson Ian M. , Muan Arnulf , Barry Carter C.
Published: June 2020

Oxide mixtures which feature a coexistence of phases with the wüstite and spinel structures are considered model systems for the study of solid-state reaction kinetics, phase boundaries, and thin-film growth, and such systems are especially suited to TEM studies. (In this paper, the terms “wüstite” and “spinel” will refer to phases of those structure types.) The study of wüstite-spinel coexistence has been limited mostly to systems near their equilibrium condition, where the assumptions of local thermodynamic equilibrium are valid. The cation-excess spinels of the type Ni2(1+x)Ti1-xO4, which reportedly exist only above 1375°C4, provide an excellent system for the study of wüstite-spinel coexistence under highly nonequilibrium conditions. The nature of these compounds has been debated in the literature. X-ray and neutron powder diffraction patterns have been used to advocate the existence of a single-phase, non- stoichiometric spinel. TEM studies of the microstructure have been used to suggest equilibrium coexistence of a stoichiometric spinel, Ni2TiO4, and a wüstite phase; this latter study has shown a coexistence of wüstite and spinel phases in specimens thought to have been composed of a single, non- stoichiometric spinel phase. The microstructure and nature of this phase coexistence is the focus of this study. Specimens were prepared by ball-milling a mixture of NiO and TiO2 powders with 10 wt.% TiO2. The mixture was fired in air at 1483°C for 5 days, and then quenched to room temperature. The aggregate thus produced was highly porous, and needed to be infiltrated prior to TEM sample preparation, which was performed using the standard techniques of lapping, dimpling, and ion milling.
Unusually large magnetite (Fe3O4) crystals inside a magnetotatic bacterium
Authors: Farina Marcos , Lins Henrique G.P. , Esquivel Darci M.S.
Published: June 2020

Magnetite crystals inside magnetotactic microorganisms have been shown to cover a wide range of dimensions and shapes. However in almost all cases reported until now, crystals width and length remain under the magnetic monodomai dimensions when using Butler and Banerjee theoretical curves. We report here one type of magnetotactic bacterium which produces very large magnetite crystals as compared with those described in the literature. In previous communication we had notified this fact, but without detail. Samples were collected from brakish water from ITAIPU lagoon near Rio de Janeiro (24º Southern hemisphere). In the same sample it was possible to find different magnetotactic microorganisms.

After standard isolation treatments we obtained different groups of crystals identifyed as magnetite (Fe3O4) by electron diffraction. It was observed that larger crystals(> 1000 Aº in length) stayed always closely attached in linear chains differently from smaller ones appearing as rolled chains under the electron microscope (Fig.l).
Electron microscopy of diamond films grown by bias-controlled chemical vapor deposition
Authors: Ma G.-H. M. , Lee Y. H. , Glass J. T.
Published: June 2020

The synthesis of diamond films by various low pressure methods has attracted much attention recently. The primary reasons for the great interest are diamond’s substantial potential as a high temperature semiconductor, heat sink, wear resistant coating, etc. Most recently reported research has been directed towards achieving better films quality and higher growth rates. In the present study, a biased hot filament chemical vapor deposition system (or Bias Controlled CVD, BCCVD) has been utilized to examine the role of charged species in the deposition of diamond. Utilizing this system, high quality diamond films which have the characteristics similar to the natural diamond have been achieved.Transmission Electron Microscopy (TEM) is employed to study the microstructure- processing relationships of diamond films deposited by BCCVD under different biasing conditions.

Diamond films were deposited on Si (001) substrates under forward bias (more positive substrate potential relative to filament), zero bias (no potential difference between substrate and filament), and reverse bias (more negative substrate potential) conditions.
Morphological identification of ethylene-propylene block copolymer and polypropylene/polyethylene blend
Authors: Shaokun Lin , Peng Xia
Published: June 2020

Surface etching technique and scanning electron microscopy were used to identify the morphology of ethylene-propylene block copolymer (EPC, ethylene content 30%) and iso-polypropylene/low density polyethylene blend (iPP/LDPE, 70/30). Fractured surfaces of EPC and iPP/LDPE, obtained from notch wedge impact at room temperature were examined with SEM also. A Hitachi S-520 SEM was employed in these experiments.

Samples of EPC and iPP/LDPE for surface etching were prepared by melt crystallization at 230°C for 15 minutes and then were kept at 180°C for 20 minutes in nitrogen atmosphere. The etching procedure was carried out by immersing the samples into an aqueous solution of H2SO4-CrO3 mixture (H2SO4: CrO3 : H2O = 22:30:48), with a little amount of emulsifying agent at 80°C for 10-12 minutes. Prior to this process, the samples were treated with a 10% emulsion of diamylene at 80°C for 3-5 minutes. All of the samples for SEM examination were coated with gold in an Eiko IB-3 ion coater.
Application of low-voltage Scanning Electron Microscopy to studies of polymer near-surface diffusion and hydrophobicity
Authors: Chang J. , Krause s. , Gorur R.
Published: June 2020

The study of the surface characteristics of a polymeric insulator - such as silicone rubber (SR) and ethylene propylene diene monomer (EPDM) -- is necessary to understand the hydrophobicity recovery mechanism that governs the ability of insulators to withstand electrical stresses during high voltage service. It has been shown that hydrophobicity of a polymeric insulator surface could be reduced by electrical discharges during outdoor service, causing the surface to become wettable, and thus allow water films to form, and ultimately leading to power outages. It was also reported that the recovery process could be due to the diffusion of low molecular weight (LMW) polymer chains from the bulk of the material to the surface. Because the LMW chains are in fluidic form (oil), they are able to diffuse through the material due to the concentration gradient of these species between the bulk and the surface. The exact mechanism of hydrophobicity recovery in polymeric insulators is still not well understood. In this study, an investigation was conducted to examine the effects of near surface molecular diffusion in the hydrophobicity recovery process of SR and EPDM insulators. Different analytical techniques were used to examine the surface morphology and surface charging effects of these elastomeric materials. Low voltage scanning electron microscopy (LVSEM) was used to measure the second cross-over point (E2) of the material surfaces, and electron spectroscopy for chemical analysis (ESCA) was also used to identify the surface chemical composition.
A SEM study of the macro-crystalline structure of 2-(2 ,4-dinitrobenzyl) pyridine
Authors: Ware Jacqueline , Hammond Ernest C.
Published: June 2020

The compound, 2-(2,4-dinitrobenzyl) pyridine, was synthesized in the laboratory; an introductory level electron microscopy study of the macro-crystalline structure was conducted using the Scanning Electron Microscope (SEM). The structure of these crystals was compared with the macro-structure of the crystals of 2-(2,4- dinitrobenzyl) pyridinium bromide, a salt of the compound which was also synthesized in the laboratory. A Scanning Electron Microscopy crystal study was combined with a study of the principle of the electron microscope.

Sandy colored crystals of 2-(2,4-dinitrobenzyl) pyridine have the interesting property of turning a deep blue color in sunlight, which then, reverts again to the sandy color in the dark. The phenomenon is explained by the formation of a tautomeric form by the action of light. Study of the macro-structure of these unique and tiny crystals, as well as a comparison study of the macro-structure of a salt derivative is possible because of the excellent resolving power of the electron microscope, as opposed to the optical microscope.
Molecular images of crystal domain structure and new phase in [M(Pc)O]n polymer
Authors: Bensan Zou , Junhua Wu , Ziang Pan , Xiao Zhou , Xueli Du
Published: June 2020

The samples, thin crystalline films of metallophthalocyanines polymer, have been prepared epetaxially by condensation polymerization of the monomer sublimed onto a newly-cleaved and degassed face of NaCl single crystal,at a constant temperature 440°C and in a dynamic vacuum about several Pa. The polymerization reaction equation is as follow;

nM(Pc)(OH)2—[M(Pc)O]n+ nH2O where M=Si ,Ge.

[M(Pc)O]n are a row-dimensional electronic conductive polymer. Its electrical conductivity can he as high as several (Ωcm)-1 after iodine-doping. This make it possibly become a hopeful functional polymer material which meet some special need. The crystal data were determined X-Ray diffraction; The investigation indicate that phthalocyanine rings tend to stack themselves up in the way in which they are parallel to each other and form molecular columns of rigid chains in [001] direction during the process of crystal growth.
Instrumentation and Computation
Authors: Hirsch P.B.
Published: June 2020

The benefit to society arising from developments in instrumentation and computation can be judged primarily by the advances in knowledge and understanding generated by their application in different branches of science, covered in the other papers in this symposium. Without advances in instrumentation none of these advances is possible; developments in instrumentation and in image interpretation are therefore fundamental to and precede scientific advances in fields in which knowledge of structure is important. There is little doubt that the revolutionary first step was the development of the transmission electron microscope (TEM) in 1931 by Ernst Ruska; a second was the development of the scanning electron microscope (SEM); and the third the introduction of the scanning tunnelling microscope (STM) for high resolution surface imaging, by Binnig and Rohrer.

The TEM and SEM have undergone continuous developments over the last 50 years or so, and have had a far-reaching impact in a wide range of disciplines; the STM is a relative newcomer but no doubt it too will have an increasing impact in furthering our understanding of solids and surfaces in particular. Once the basic instruments became available subsequent developments have been driven by the demands of the scientific disciplines in which these instruments have been applied. Many of the new developments in instrumentation and interpretation have been pioneered by the users themselves, and these in turn have led to modifications in commercial instruments to make such advances in technique available to the user community as a whole. Other developments have been initiated directly by the manufacturers as a result of a perceived need. There has been and continues to be a close interaction between the developers of hardware (not only of electron microscopes but also of ancillary equipment, e.g. microanalysis attachments, image processing equipment, specialist specimen stages, and specimen preparation facilities) and the users, leading to extensions in the range of applications and the types of information which can be obtained by electron microscopy. The following examples from the developments of electron microscopy in Materials Science illustrate these interactions and the particular advances arising from specific developments:
Contribution of Electron Microscopy to Structural Materials
Authors: Hornbogen Erhard
Published: June 2020

Structural materials are expected to fulfil mechanical functions, for example in bridges, crank shafts, turbine blades, or medical implants. In use, high strength is aspired at low materials weight. The structure should be safe and the costs of the material, semi—finished products, or parts should be low. The term strength implies the resistance of a material against plastic deformation, as well as against propagation of cracks (i. e. toughness). Safety is connected with the control of various mechanisms of crack growth such as rupture, fatigue, and stress corrosion cracking. Finally, interaction of surfaces will induce a frictional shear stress, which may cause wear. The life of structures is usually limited by mechanical failure, which may become catastrophic, if it is unexpected due to lack of understanding of structural materials.

The specific weight of materials predominantly stems from the kind of atoms from which the material is built. The properties implied in strength are mainly related to microstructure. There are only two types of phases of which materials are built: crystals and glasses (if the quasicrystals are neglected, for which applications have not yet been found). Metals are usually crystalline. Their strength is closely related to the properties of crystal dislocations. Transmission electron microscopy (TEM) is the major tool for their investigation. Resistance against plastic deformation (i. e. yield stress) is controlled by elements of the microstructure, which act as obstacles against their motion. These microstructural features and their interaction with dislocations can also be analysed by TEM. It is reasonable to classify microstructural objects according to their geometrical dimensions 0 ≤ d ≤ 3. They become hardening mechanisms which are the ways by which the yield strength (i. e. load carrying ability of a material canb be raised).