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Misfit-layered compounds (MLCs) are formed by the combination of different lattices and exhibit intriguing structural and morphological characteristics. MLC SrxLa1-xS-TaS2 nanotubes with varying Sr composition (10, 20, 40, and 60 Sr atom %, corresponding to x = 0.1, 0.2, 0.4 and 0.6, respectively) were prepared in the present study and systematically investigated using a combination of high-resolution electron microscopy and spectroscopy. These studies enable detailed insight into the structural aspects of these phases to be gained at the atomic scale. The addition of Sr had a significant impact on the formation of the nanotubes with higher Sr content, leading to a decrease in the yield of the nanotubes. This trend can be attributed to the reduced charge transfer between the rare earth/S unit (LaxSr1-xS) and the TaS2 layer in the MLC which destabilizes the MLC lattice. The influence of varying the Sr content in the nanotubes was systematically studied using Raman spectroscopy. Density functional theory calculations were carried out to support the experimental observations. © 2019 Serra et al. Center for Nanoscale Science and Technology, CNST: 43535000350000, 720821 Government Council on Grants, Russian Federation: NORTE-45-2015-02 Israel Science Foundation, ISF: 7130970101 We acknowledge the support of the Israel Science Foundation (grant No. 7130970101). We also wish to acknowledge the Perlman Family Foundation, the Kimmel Center for Nanoscale Science Grant No. 43535000350000, and the Irving and Azelle Waltcher Foundations in honor of Prof. M. Levy Grant No. 720821. The activity of A.E. was supported by Act 211 Government of the Russian Federation, contract No.02.A03.21.0006. E.A.A and F.L.D acknowledge the financial support by the N2020: Nanotechnology based functional solutions (NORTE-45-2015-02).

This work presents our recent findings that a small addition (0.5 at. %) of Cr to FeCo–2V alloy leads to a great improvement in creep resistance. High resolution electron microscopy was applied to study microstructural evolution of the Cr added alloy during the creep process performed at 600 °C under 200 MPa. At an initial step of the creep, there appear plate-like precipitates with bcc/fcc structure as well as some rod-like ones with hcp structure. A coherent relationship is identified between the precipitates and bcc FeCo matrix. With prolonging the creep, the rod-like hcp precipitates are revealed to remain in the bcc matrix, showing a good stability under the creep condition and in turn resulting in piling-up of dislocations to a great extent around the precipitates. In addition, the Cr added alloy is shown to have a large stress exponent of 8.4, indicating a strong interaction between dislocations and the hcp precipitates.

Carbon extracted from a cathodic graphite rod following arc-discharge in helium is examined using high-resolution electron microscopy. It is found that, in addition to the well known extended graphitic tubules ('buckytubes'), carbon produced in this way contains many other novel graphitic structures. Of particular interest are small hollow particles which, although essentially tubular, appear to differ in significant ways from the extended tubules. Evidence for tetrahedral bonding in some of the graphitic particles is also presented.

High-resolution electron microscopy is used to study the structure of two typical non-graphitizing carbons before and after heat treatment at temperatures in the range 2100–2600°C. It is found that these heat treatments can result in the formation of closed carbon nanoparticles, which are apparently fullerene-like in structure. This suggests that fullerene-like elements were present in the original carbons and leads us to propose a new model for the structure of non-graphitizing carbons.

In the present work, transmission electron microscopy (TEM) techniques were used in order to study the morphology and investigate the structural properties of a (BixSb1-x)2Te3(BST) thin film. The sample was fabricated on silicon substrate by pulsed laser deposition (PLD) method. Towards this aim, cross sectional and planar view samples were prepared, suitable for High Resolution Electron Microscopy. Results revealed a polycrystalline, c-axis oriented film with coherent boundaries between neighboring columnar grains. © Springer International Publishing Switzerland 2015. 164 3 7 3-7

Correlative microscopy combines the advantages of both light and electron microscopy to enable imaging of rare and transient events at high resolution. Performing correlative microscopy in complex and bulky samples such as an entire living organism is a time-consuming and error-prone task. Here, we investigate correlative methods that rely on the use of artificial and endogenous structural features of the sample as reference points for correlating intravital fluorescence microscopy and electron microscopy. To investigate tumor cell behavior in vivo with ultrastructural accuracy, a reliable approach is needed to retrieve single tumor cells imaged deep within the tissue. For this purpose, fluorescently labeled tumor cells were subcutaneously injected into a mouse ear and imaged using two-photon-excitation microscopy. Using near-infrared branding, the position of the imaged area within the sample was labeled at the skin level, allowing for its precise recollection. Following sample preparation for electron microscopy, concerted usage of the artificial branding and anatomical landmarks enables targeting and approaching the cells of interest while serial sectioning through the specimen. We describe here three procedures showing how three-dimensional (3D) mapping of structural features in the tissue can be exploited to accurately correlate between the two imaging modalities, without having to rely on the use of artificially introduced markers of the region of interest. The methods employed here facilitate the link between intravital and nanoscale imaging of invasive tumor cells, enabling correlating function to structure in the study of tumor invasion and metastasis.

The infinite layer compound Ca0.85Sr0.15CuO 2 has been synthesized by the sol-gel technique using the acetate gel route. The compound is found to be single-phasic as evidenced from the powder X-ray and electron diffraction measurements. EDAX analysis confirms the presence of homogenous stoichiometric phase pertaining to the composition Ca 0.85Sr0.15CuO2. High-resolution electron microscopy (HREM) studies reveal interesting defects in the infinite layer frame work of the system. Apart from the usual strain and shear induced defects observed in the lattice, which is common among the perovskite compounds, the main finding is the defect along [0 1 0], occurring due to the intercalation of extra AO layer in the CuO2 plane. Such a defect is accommodated in the lattice by the increase in the interplanar distance (which is basically the c-axis parameter) from 3.2 to 3.4 � in the defective layer. This implies the formation of square pyramidal oxygen co-ordination of copper at the defect site. ? 2005 Elsevier Ltd. All rights reserved.

Boron nitride (BN) nanohorns with various tip angles were synthesized by an arc-melting method, and atomic structure models for BN nanohorns were proposed from high-resolution electron microscopy. Stability and electronic structures of the BN nanohorns were investigated by molecular orbital/mechanics calculations, which indicated that multi-walled BN nanohorns would be stabilized by stacking of BN nanohorns. The energy gaps of the BN nanohorns were calculated to be 0.20∼0.85 eV, which are lower compared to those of BN clusters and nanotubes.

Crystal structures of a homologous series of Co-based layered cuprates, CoSr2(Y,Ce)sCu2O5+2s (s=1–3), have been investigated by high-resolution electron microscopy (HREM) and electron diffraction (ED) techniques. For all the three phases ED patterns showed double periodicity along a direction parallel to the CoO layers, indicating a regular alternation of two types of CoO4-tetrahedra chains within the layers. Also seen was ordering of the chains along the layer-stacking direction for the s=1 phase (Co-1212); ED patterns simulated based on the proposed superstructure model well reproduced the observed patterns. For the s=2 (Co-1222) and s=3 (Co-1232) phases in which an additional fluorite-type layer-block is inserted between two CuO2 planes, HREM and ED analysis revealed complete disorder of the CoO4 chains along the layer-stacking direction. This implies that the interlayer ordering is mainly controlled by the distance between the neighboring CoO layers.

High-resolution electron microscopy is discussed as a measuring, rather than an imaging, technique. It is shown that the interpretation or the images could greatly benefit from a quantitative instead of a qualitative approach accompanied by quantitative statistical experimental design.

Twinning plays an important role in phase transformations and can have significant effects on microstructural evolution. Different roles of twinning in the development of microstructures during precipitation and phase transformations are reviewed and illustrated with examples from investigations by high-resolution electron microscopy, including the effect of multiple twinning on the development of Ge precipitates in Al-Ge and Ag-Ge alloys, the twin dissociation of grain boundaries in Au, the formation of hexagonal Si at twin intersections and the effect of twin boundaries on the equilibrium shape of Pb inclusions in Al.

Pd 80 Pt 20 and Pd 85 Pt 15 alloys were exposed at 673 K to a hydrogen pressure of 100 MPa for 4 h, which is called hydrogen heat treatment (HHT). After HHT the pressure composition isotherms at 273 K change remarkably and H-diffusion is enhanced. The change can be interpreted by a decomposition into a continuous Pd-rich and an embedded Pt-rich alloy. Direct evidence for this hypothesis is provided for the first time from high resolution electron microscopy. It will be shown that coherent platelets are formed after HHT which are two atomic layers thick and have an average diameter of ∼10 nm. Simulating the contrast observed in the electron microscope shows that the plates are Pt-rich.

The structure of grain boundaries in rocks, which are composed mainly of fine-grained quartz and feldspar, was studied by high-resolution electron microscopy (HREM) . At most of the boundaries, not only between the same minerals but also between different minerals, lattice fringes in connected grains meet each other at interfaces with no other appreciable phases. In these boundaries, it has been found that some of the straight segments of the boundaries correspond to a low-index plane of one of the connected grains. Boundaries containing voids, with a spheroidal shape elongated along the boundaries, were observed. It is suggested that these boundaries were formed by healing of microcracks.

The n integer members of the A n +2 B n B ′O 3 n +3 homologous series keeping B = B ′=Co the same have been characterized by selected area electron diffraction and high resolution electron microscopy. Its commensurate modulated structure is made up of chains, separated by A atoms, running along the c direction containing a succession of one Co atom ( B ′) in prismatic trigonal sites and n Co atoms octahedrally coordinated sharing faces. All of them can be described as ordered intergrowths of two structures of the end members of the family, 2H–BaCoO 3 ( n =∞) and Ca 3 Co 2 O 6 ( n =1). The modulation observed in all terms can be described as a function of the difference between the c -axis of the Co sublattice with respect to the 2H structure. Members of the series can be obtained by modifying the distance between layers keeping B =Co the same, as shown in (Sr 1− x Ba x ) 6 Co 5 O 15 ( n =4), Sr 5 Co 4 O 12 ( n =3), and (Sr 0.5 Ca 0.5 ) 4 Co 3 O 9 ( n =2).

As one of our systematic studies of the modulated structures of a series of new homologous compounds RM O 3 (ZnO) m ( R =Sc, In, Y, and La; M =In, Fe Ga, and Al; m =integer), this paper reports the modulated structure of Fe 2 O 3 (ZnO) 15 ( R =Fe; M =Fe) studied by high-resolution electron microscopy. It is found that the main and satellite spots in the diffraction patterns can be indexed as h a * + k b * + l c * + m q by considering a monoclinic unit cell of a =0.57 nm, b =0.33 nm, c =4.5 nm, and β =92° and a modulation wave vector of q=b * /34.8+c * /2. The possible space groups for the basic structure are C 2, Cm , and C 2/ m , and the possible four-dimensional superspace groups for the modulated structure are C C 2 1 , C Cm 1 , and C C 2/ m 1 1 . The crystal structure of Fe 2 O 3 (ZnO) 15 consists of Fe–O layers interleaved with 16 Fe/Zn–O layers. In the high-resolution image, the modulated structure appeared as zigzag-shaped contrasts among the Fe/Zn–O layers, where Fe is in high concentration. Compared with those of In M O 3 (ZnO) m ( R =In; M =In, Fe and Ga) reported in our earlier paper, the special features of the present modulated structure are the half-periodicity relative shift of the neighboring zigzag-shaped contrasts and the appearance of modulation within the Fe–O layers.

Zeolites are one of the most important materials currently used in the petroleum industry for a wide variety of catalytic transformations. However, they are increasingly being considered for other applications such as for designing quantum-confined materials in their spaces. With such applications in mind, precise characterisation of zeolites and related porous materials has never been more necessary. Here we show how electron diffraction coupled with high-resolution imaging can reveal the detailed fine structure in both the bulk and at the surface of these materials. A variety of case studies are considered which include ETS-10, FAU, LTL and FSM-16.

First, constitution of a simulation program for high-resolution electron microscopy is outlined. In order to record high-resolution images accurately, (S/N) and DQE (detective quantum efficiency) characteristics for new recording materials like the imaging plate are presented. It is shown that digital data of high-resolution microscope images appropriately recorded on the imaging plate can quantitatively be analyzed through image simulation with a residual index. Finally, quantitative high-resolution microscopy with a residual index is briefly discussed by comparing with the X-ray and neutron diffraction analysis with the so-called R-factor.

A method is described to prepare a high-resolution electron micrograph for quantitative comparison with a simulated high-resolution image. The experimental data are converted from the darkening of film used to acquire the image to units of electrons per incident electron, the same units used in the simulation. Also, distortions in the image arising from distortions in the image-forming lenses of the electron microscope are removed to improve the quality of the data. Finally, an alignment procedure is described which gives precise, pixel-by-pixel alignment of the experimental image with the simulated image. Examples of the procedure are shown to illustrate how actual data are prepared for quantitative analysis.

Basic theory of high-resolution electron microscopy is described in view point of lattice images and structure images of crystalline samples. Image formation process, factors determining the resolution, contrast transfer functions, dynamical diffraction effect and relativistic effect are explained in detail.

The structures of martensites in a Cu–11.2 wt% Al–3 wt% Ni specimen, which was quenched from 1173 K, have been studied by high resolution electron microscopy (HREM) and diffraction techniques. Two kinds of martensites, i.e. β′1 and γ′1, coexisting adjacent to each other in the specimen were observed. The γ′1 matensite consists of microtwins with monoclinic structure. Three variants of the twin structure, i.e. {1 2 1}, {2 1 0} and {1 0 1} twins, are arranged within a single plate. The β′1 martensite possesses basically ordered N9R structure, but mixed with thin 2H domains. Some diffraction spots of this martensite shift along the [0 0 1] direction. In addition, extra weak reflections appear in the diffraction pattern due to heterogeneous atomic displacements. The microstructural features of the martensites are examined and discussed.

The internal structure of monodisperse CdS particles was investigated by high-resolution electron microscopy of thin sections prepared with an ultramicrotome. High-resolution images of the thin sections clearly revealed the arrangements and the crystallographic orientations of subcrystals as components of the particles. It was found that the central part of a particle was composed of randomly oriented small subcrystals about 10 nm in diameter, while near the surface of the particle, relatively large subcrystals about 50 nm in maximum width were observed. Furthermore, stacking faults and twins on the {1 1 1} planes were observed in the sections.

A new type of ordered structure in a Ti-48at%Al alloy quenched from the disordered α-Ti phase field has been determined by high-resolution electron microscopy and image simulation. The structure is based on an h.c.p. structure having an orthorhombic unit cell with the lattice parameters a = 0.45 nm, b = 0.28 nm and c = 0.49 nm, and belongs to a B19 type. The B19 TiAl can be described as the AB… stacking of close-packed /(111/) planes in γ-TiAl with an L1 0 structure, and the ordered arrangement of Ti and Al for the B19 structure is interpreted as a local arrangement in the sample.

On utilise la microscopie electronique en haute resolution pour mettre en evidence des boucles de dislocations partielles provenant de l'amincissement par bombardement ionique d'un echantillon de ZnO. Les defauts d'empilement crees par insertion d'une double couche de Zn-O dans le plan basal sont du type 1Δ

Core structures of edge and screw dislocations in CoTi were studied by high-resolution electron microscopy (HREM). An HREM image of an edge dislocation showed that the spreading of the dislocation core was limited within a distance of about 1.2 nm. From an HREM image of screw dislocations in CoTi, it was shown that the core was spreading on the (010) plane and the spreading of the core was limited within a distance of about 1.8 nm. It was suggested that the core spreading on the {010} plane, which was different from the slip plane of {110}, affected the abnormal temperature dependence of yield stress of CoTi.

The decomposition process of the model precipitation-hardening Al + 4 wt. % Cu supersaturated solid solution induced by Ar+ ions irradiation. Using X-ray diffraction, high- resolution electron microscopy methods and microhardness measurements, it was established, that, already at low temperatures (T < 60 °C), ion irradiation causes accelerated decomposition of solid solution, with precipitation of 9' and 9-phase particles at a depth greatly exceeding the Ar+ ions projected range. This work was performed in the framework of the State Task, no. 0389-2414-0002, supported in part by RFBR (project No. 15-08-06744-A). We thank E. Wieser for the idea and participation in discussing the results.

The direct confirmation of the existence of Cd-stabilized β″″-ferrite prepared as a stable phase in a K2O-Fe2O3-CdO system was done by high-resolution electron microscopy. It was confirmed that the Cd-stabilized β″″-ferrite had a rhombohedral symmetry with lattice constants a = 0.600 and c = 5.026 nm. The structure is composed of an alternate stacking of ion-conductive layers and spinel-like blocks which have six cubic close-packed oxygen layers expressed as · · · A1(BCABCA)B1(CABCAB)C1(ABCABC)A1 · · ·. In addition, twins which had reversed stacking sequences were observed in the spinel-like blocks.

Local atomic arrangements and wide tilings for two types of decagonal quasicrystals, which are formed in alloys with compositions near Al 70 Ni 15 Co 15 , were studied by high-resolution electron microscopy. The decagonal quasicrystals can be interpreted as structures formed with different tilings, so-called rhombic and pentagonal ones, which are constructed with definite linkages of similar atom clusters

In a previous paper, we have shown that high resolution electron microscopy (HREM) is able to reveal nanometric domains in ferroelectric oxides, the existence of which cannot be proven by other means. However, this method cannot reveal all the domains. In this paper we calculate the limits of the HREM possibilities and expound a method to obtain some statistical information on the observed sample.

The structure and the microstructure of the new high Tc superconductor Tl0.5Pb0.5Sr4 Cu2CO3O7 have been studied by high resolution electron microscopy. The experimental images fit well with the calculated ones based on a structure built up from the intergrowth of a 1201-type slice [Tl0.5Pb0.5Sr2CuCO5]1201~ with a [Sr2CuCO3O2]~ unit. The comparison of the calculated and experimental images with those of a 1223 structure, which exhibits similar cell parameters to those of Tl0.5Pb0.5Sr4Cu2CO3O7, shows that the oxycarbonate exhibits a characteristic contrast for some focus values which allows to differentiate the two structures. The investigation of numerous crystals attests of the high regularity of the stacking of the layers along c. One single type of defect was observed which suggests the possible existence of a new member [Tl0.5Pb0.5Sr2CuO5] [Sr2CuCO3O2]2 .

Weak-beam and high-resolution electron microscopy of dislocations in CoSi2 with the Cl structure, introduced at room temperature by pulverization, has shown that dislocations with the 〈100〉 Burgers vector and those with 1/2〈110〉 are dissociated into partial dislocations by the following reactions: 〈100〉 1/2〈100〉 + 1/2〈100〉 on {001} 1/2〈110〉 1/4〈111〉 + 1/4〈111〉 on {110} 1/2〈110〉 1/6〈211〉 + 1/6〈121〉 on {111} Stacking faults and micro-twins have also been observed by high resolution electron microscopy. Evidence that vacancies are mobile at room temperature has been obtained by observations of helical dislocations.

In the field of high-resolution transmission electron microscopy (HRTEM), the term “resolution” has come to hold a number of different meanings [M.A. O'Keefe and J.C.H. Spence, in: Proc. 49th Annual EMSA Meeting, p. 498]. The present work reviews the various definitions of HRTEM resolution, derives theoretical expressions for resolution, and suggests how high resolutions may be attained in practice.

Using high resolution electron microscopy, the stage formation of the icosahedral phase during the process of mechanochemical treatment of the cubic Mg 3Z (Zn, Al) 49 crystals has been studied. It has been shown that in the initial stages the icosahedral phase forms locally owing to the formation of rotation defects and disorder of the crystal planes due to the action of plastic deformation. The size of the disordered regions in the icosahedral phase increases with increase in the time of mechanical treatment. An orientation correspondence has also been revealed between the initial cubic and icosahedral phases; this is apparently due to the similarity in the structural designs of the cubic and icosahedral phases.

Various types of G. P. zones and θ'-phase are formed by aging in Al-1.6 at%Cu crystals. Formation processes of these structures have been investigated by high resolution electron microscopy with the following results: (a) Three-dimensional Cu-atom clusters are formed at the beginning of aging at both 373 and 423 K, respectively. (b) In 373 K aging, these clusters change to G.P.-1 zones and/or G.P.-2(3) zones whose Cu-rich planes are separated with three Al-rich planes. Multi-layered G.P.-2(3) zones and sometimes multi-layered G.P.-2(2) zones whose Cu-rich planes are separated with two Al-rich planes are formed by further aging at 373 K

The structure of 3:2 mullites is investigated by high-resolution electron microscopy. Attention is paid to the identification of isolated defects, i.e., oxygen vacancies in pure 3:2 mullite and chromium interstitials in chromium-doped mullite. Models for such defects, including lattice reconstruction effects, are analyzed with the help of image simulations.

The fine structure of unhydrated cement clinker Ca4Al6SO16 (C4A3S) and its four superstructures have been studied by means of electron diffraction and high resolution electron microscopy (HREM). The match between experimental images and simulated ones verifies the result of X-ray structural analysis: C4A3S having a cubic lattice with space group l43m,Z = 2. The frequent apperance of forbidden reflections such as 1/2, −1/2, 0 along the 〈110〉* directions of C4A3S imply the presence of superstructures which may be due to an orderly inverse occupation of Ca2+ ions. Various structure models based upon the observed structural images have been proposed for these four superstructures. A new cubic phase witha′ = 1.5 nm is also found by selected area electron diffraction (SAED).

Superstructure phenomena in the barium diphosphate tungsten bronzes with hexagonal tunnels, Ba (P2O4)2 (WO3)2m , are characterized by electron diffraction and high resolution electron microscopy. A model of superstructure is deduced from the observations and used to perform image calculations. The comparison of experimental and calculated images allows to associate the superstructure phenomena to orderings of the barium cations in the hexagonal tunnels.

By using immersion calorimetry with liquids of various molecular dimensions, the distributions of the micropore sizes have been obtained for a number of active carbons, for the range 0.3 to 0.75 nm. These carbons have also been examined by high-resolution electron microscopy, the results from both techniques being displayed in the form of histograms. The agreement between the two methods appears to be good and provides possible evidence of the reduced interaction radius of adsorbed molecules and of exfoliation.

We introduce a simple preparation method for ultrathin carbon support films that is especially useful for high-resolution electron microscopy (HREM) of nanoparticles. Oxidized iron nanoparticles were used as a test sample in a demonstration of this method. The film qualities are discussed on the basis of electron-energy-loss spectroscopy (EELS) and image analysis techniques such as thickness maps and histograms. We carried out a comparison between the homemade and commercial film qualities. The relative thickness of the homemade support films was 0.6 times less than that of the commercial films, which was calculated from the EELS analysis, whereas the thicknesses of both carbon support films varied within about 3%. The percentage of the observable area was about 67 ± 7.6% of the support film. This was about twice as large as the commercial film (32 ± 9.3%). The HREM image of the sample prepared with our support film improved 9% in brightness and 15% in contrast compared with images obtained with the commercial support.

In order to investigate internal structures of monodispersed hematite (α-Fe 2 O 3 ) particles of pseudocubic and peanut-type shapes prepared by the gel-sol method, their thin sections were prepared by an ultra-microtome and studied by transmission electron microscopy. The surfaces and arrangements of the individual small subcrystals as components of the monodispersed particles were clearly observed on the atomic scale by high-voltage high-resolution electron microscopy. This is direct evidence of the polycrystallinity of these particles

Transmission electron microscopy and high-resolution electron microscopy investigations of the structure of Cu precipitates in the size range 4–30 nm were carried out as part of a wider investigation into Cu precipitation from thermally aged Fe-Cu and Fe-Cu-Ni ferritic model alloys. A twinned 9R structure was found to be present in precipitates slightly larger than 4nm in diameter, following transformation from b.c.c. Two twin-related 9R variants were observed in all the smallest 9R particles studied. The 9R precipitates were observed to grow subsequently as spherical, multiply twinned particles up to approximately 17 nm, indicating that further twinning must occur during growth in the 9R phase. At sizes larger than 17 nm, a second transformation to the more stable 3R structure takes place. Observations on these 3R particles indicate that, following transformation from 9R, the precipitates are untwinned and have a distorted f.c.c. structure. The particle-matrix orientation is close to, but not ex...

Crack tips in thin SiO2 glass films were observed directly by high-resolution/high-voltage electron microscopy. An elliptical crack with radius of curvature ∼ 1.5 nm was observed. When the glass film with the crack was soaked in water at 90°C for 7 d, the crack tip became blunt by a process of dissolution and precipitation.

A complex bismuth oxide crystal, prepared by heating powders with a nominal composition Bi 2 CaNb 2 O 9 ·4NaNbO 3 , is composed of several phases, Bi 2 CaNa n −2 Nb n O 3 n +3 , mainly with n = 5–8. One-megavolt high-resolution electron microscopy reveals that the structure of each phase is constructed by perovskite-like layers interleaved with Bi 2 O 2 sheets. Any one of these phases grows only in limited regions, in which other phases with different values of n intergrow very finely. This causes a characteristic intensity profile on the diffraction pattern. Experimental evidence on the reaction of the crystal with water is presented.

The silica lorica of Stephanoeca diplocostata Ellis has been studied by ultra-high and high resolution electron microscopy. Ultra-high resolution electron microscopy reveals an extremely amorphous silica structure within costal strips. T-junctions between strips in intact loricae have been examined and in several cases strips of viscid connective material containing in part amorphous silica have been observed running between the two strips. Silica demineralization initiates from the central axis of the costal strips leaving tubular brittle rods. The surface of costal strips is shown to be active in binding low concentrations of cations (Co 2+ , Fe 3+ ) from external solutions.

A superstructure of TiS1.62 is determined by 100 kV high-resolution electron microscopy, in which the arrangement of metal vacancies is obtained from structure images. The crystal has monoclinic symmetry (pseudo-hexagonal) with lattice parameters a = 11.9, b = 6.85, c = 11.5A, β = 90°. The space group is considered as F2m. Metal vacancies are confined to every second metal layer and ordered within the partly filled metal layer, resulting in formation of a (2H)22C type of superstructure. The ordered metal vacancy layers are arranged in 2C-type stacking sequence along the c axis, while sulfur atoms are arranged in 2H-type stacking sequence along the c axis.

Although facilities for high resolution electron microscopy (HREM) are available, interpretation of micrographs at high magnifications is far from unambiguous. The interpretation of the micrographs using a computed structure analysis program is therefore necessary. The paper presents the theory behind HREM, together with a computer method for image interpretation. Special reference is made to the JEOL JEM 200CX transmission electron microscope used in the study of sodium beta-alumina.

High-resolution electron microscopy has revealed a difference in morphology of the crystallites of samples of LaPO 4 which are good and poor catalysts for the hydrolysis of aromatic chlorides. In the good catalysts an acicular habit is such as to expose chains of La and PO 4 ions which run parallel to the c axis of the crystal. Observations of lattice fringes include those of forbidden reflections, suggesting some modification of the structure, as well as revealing structural imperfections.

Electron microscopists are on the threshold of achieving their ultimate goal: atomic resolution and identification. Success depends on a little more technology and a lot more dollars.