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The cell structure and interface between cultured cells and a multiwalled carbon nanotube (MWCNT)-coated sponge (MWCNT-coated sponge) were observed by transmission electron microscopy (TEM). Moreover, the atomic structure of MWCNTs that entered the cells was also examined by means of high-resolution TEM (HRTEM). MWCNTs were observed in the cytoplasm, and a few MWCNTs were recognized in the cell nuclei. Those MWCNTs maintained their structure there. Subcellular organelles did not appear to be different from those on the collagen sponge despite the cellular uptake of MWCNTs.

In this paper, microstructures and properties of die casting components with various thicknesses made of AZ91D alloy have been investigated by means of scanning electron microscope (SEM), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), etc. It is concluded that mechanical properties of the die casting components mainly depend on grain size of α-Mg phase. At the same time, however, the voids formed by entrapping air during die casting process have a remarkable detrimental effect on the mechanical properties. To what extent the effect is caused is determined by quantity, size and shape of the voids, which are related to the thicknesses and position of the component in die. Nanometer particles found on the wall of the voids are magnesium oxide compounds, which are formed when oxygen from the entrapped air reacts with magnesium during die casting process. The compounds have no obvious effect on the mechanical properties even though there is possibly volume change present to form other compounds in the course of the components’ being used.

Atomic and electronic structures of interfaces in an internally oxidized Pd/ZnO system were studied by high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS). {0001}ZnO polar planes tend to be parallel to the interface. A ZnO precipitate was terminated by an oxygen surface at one end of the precipitate and by a zinc (0001) surface at the other end of the precipitate. A pre-edge peak was detected only in O-K energy-loss near-edge spectra (ELNES) acquired from the oxygen-terminated interface. Ab initio calculations indicated that the origin of the pre-edge peak could be attributed to the strong chemical bonding and hybridization of Pd-d and O-p orbitals at the oxygen-terminated polar interface.

Growth mechanisms and material quality of the laterally overgrown cubic-phase gallium nitride (c-GaN) and hexagonal-phase gallium nitride (h-GaN) on stripe-patterned GaAs (001) substrates were investigated using transmission electron microscopy (TEM). Investigational results show that h-GaN is only laterally overgrown along the (111)B facets of the c-GaN stripes with the growth direction of (0001)h-GaN//(111)B c-GaN for all the mask stripe orientations. Dislocation density in the laterally overgrown h-GaN regions for the [110]-stripe pattern is reduced to be lower than 104 cm–2, which is six orders of magnitude smaller than that in the conventionally grown h-GaN films. On the other hand, the laterally overgrown c-GaN with lower planar defect (stacking faults and twins) density presents in the region just above the stripe windows for the [10]-stripe pattern. In addition, a large reduction of planar defect density was found in the laterally overgrown c-GaN regions for the [100] stripe direction. Also, a model is used to describe the cubic-to-hexagonal structural transition in lateral-overgrown GaN on patterned GaAs (001) substrates for the purpose of lower dislocation and lower planar defect densities in the laterally overgrown h-GaN and c-GaN, respectively. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

{112} Σ3 CSL grain boundary in silicon was investigated by high-resolution transmission electron microscopy (HRTEM) and ab-initio calculation. A {112} Σ3 CSL boundary consisted of two segments which differed in atomic structure. The segment near the connected corner to {111} Σ3 CSL boundary showed symmetric structure and the other long segment, being distant region from the corner, showed asymmetric structure. It was shown that the asymmetric structure is more stable than the symmetric one. In the symmetric segment a 5-fold coordinated atom presented, which elevated the structure energy of the boundary and produced a new state in the band gap.

A simple, inexpensive and one-step synthesis method of metal-containing carbon nanocapsules using an arc discharge in aqueous solution is reported. It was found that Ni, Co and Fe nanoparticles could be in situ encapsulated in carbon shells when the arc was performed respectively in aqueous solutions of NiSO 4 , CoSO 4 and FeSO 4 . Transmission electron microscopy, energy dispersive X-ray spectroscopy and electron diffraction patterns of selected areas were used to determine the crystalline phase of the metal cores. To explain the formation mechanism of metal-containing carbon nanocapsules, a model of discharge in solution is proposed. This result presents a simply controllable way to synthesize metal-containing carbon nanocapsules.

A notebook personal computer casing, made of AZ91D alloy, is manufactured by precision die casting. When the computer casing was kept for some time, it was found that there were some small pits on the surface of the casing. The formation mechanism of the pits was investigated by means of scanning electron microscope and fourier transform infrared spectrophotometry. It is concluded that MgO inclusions in the Mg–Al alloy are an important factor, which leads to the formation of small pits. MgO turns into Mg(OH)2 by absorbing water or steam. Because of density difference between MgO and Mg(OH)2, volume expansion takes place. A basic way of reducing pits is to cut down the content of MgO inclusions.

The ultrastructures of Fe-encapsulating onion-like fullerenes (OLFs) synthesized at different temperatures were analyzed by scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction. The results indicate that the structure of OLFs is strongly affected by the growth temperature. In a reaction temperature range of 900-1000°C, the morphology of produces was changed from clew-, shaped, tree-shaped to metal encapsulating OLFs. The metal particles encapsulated into OLFs were found to be pure Fe. In some degree, the transformation of ultrastructures shows the formation of Fe-encapsulating OLFs. In the meantime, TEM observation indicated that OLFs grown at higher temperature possess higher degree of graphitization.

Fe-included Onion-Like Fullerenes (OLFs) have been synthesized by Chemical Vapor Deposition(CVD) at 1100 °C in all zones. The samples with diameter from 15 to 40 nm have been characterised by XRD, FESEM, HRTEM, and Raman methods. The results show that Fe-included OLFs are of high degree graphitization. It is the strain of graphene shells and the uniform size of Fe-included OLFs that caused the Raman spectra shifted upward slightly from 1582 cm − 1 .

Theoretical calculations via a transfer matrix method were performed to investigate the possibility of fullerene films acting as two-dimensional (2D) photonic band gap crystals. The response within and out of the periodic structure of 2D photonic crystals consisting of air rods drilled into C60 or (C59N)2 films was studied. PBG was found around 0.85–1.24 eV in the near infrared region. We find that fullerene-based networks could be good candidates for absolute inhibition of transmission in the near infrared range for given orientations.

Theoretical calculations via a transfer matrix method (TMM) were performed to investigate the possibility of fullerene/AlN multilayer films acting as one-dimensional (1D) photonic band gap (PBG) crystals. The response within and out of the periodic plane of (C60, C70)/AlN multilayers was studied. (C60, C70)/AlN multilayer films presented incomplete PBG behavior in UV region. C60/AlN multilayers with two pairs of 49 nm-C60 and 21 nm-AlN layers exhibited a high reflectivity of 90.4% at a wavelength of about 200 nm. As a consequence, this photonic crystal may be important for achieving materials with an incomplete band gap in the UV region.

The influence of undersized solute additions on radiation-induced segregation (RIS) at grain boundaries was examined for austenitic model alloys. High-purity Fe-15Cr-20Ni alloys, doped with either 0.5 mass% silicon or 0.025 mass% phosphorus, were exposed to electron irradiation at several temperatures in a high-voltage electron microscope. The grain boundary depletion of chromium and segregation of nickel were significantly suppressed by the addition of silicon and phosphorus, and the addition of phosphorus significantly reduced the RIS at a grain boundary. It was shown by numerical simulation that the present results stem from the strong interaction between the additives and interstitial atoms produced by the electron irradiation.

Atomic resolution high voltage transmission electron microscopy (ARHVTEM) was applied to a fivefold twin center in diamond film. The atomic structure of the fivefold twin center was the same as that suggested by Matsumoto and Matsui. The structure had no dangling bond. The fivefold-membered ring was observed to be at the center. The location of the fivefold twin center, observed in this study, indicated that it was produced by the meeting of two {111} Σ3 grain boundaries.

Atomic resolution high voltage transmission electron microscopy was applied to the Σ3 and Σ9 boundaries in CVD diamond film. The atomic structure of the {1 1 1}Σ3, {1 1 2}Σ3, {2 2 1}Σ9, and {1 1 4}Σ9 boundaries was revealed. The simulated image coincided well with the experimental images.

We studied the structural and optical properties of InxGa1−xAs1−yNy (x = 0.116, ∼0.3 and y = 0–0.031) alloy films grown by low-pressure metalorganic vapour epitaxy (LP-MOVPE), performing high-resolution transmission electron microscopy (HRTEM) and photoluminescece (PL) measurements. The effects of rapid thermal annealing (RTA) at 700 °C under N2 ambient were also examined. The TEM images showed that with increasing In content, not only misfit dislocations near the InGaAsN/GaAs interface due to the large lattice mismatch with the GaAs subatrate, but also many defects in the InGaAsN layer due to the relaxation of local strain increased. From energy dispersive X-ray (EDX) analysis of the high In-content layers (x = 0.3–0.355), we found a significant In fluctuation in the InGaAsN layer. The PL peaks of In0.116Ga0.884As1−yNy (y = 0–0.031) measured at 7 K shifted to the high-energy side after RTA, while those of InxGa1−xAs1−yNy (x = ∼0.3, y = 0–0.015) shifted unusually to the low-energy side. This unsual behavior of the high In-content layer after RTA may be attributed to the enlargement of quantum-dot-like regions, which are formed by the compositional fluctuation in microscopic scale. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have proposed the use of cubic-GaN (c-GaN) as an intermediate layer for the metalorganic vapor phase epitaxy (MOVPE) growth of hexagonal-GaN (h-GaN) on GaAs (111)B substrates. Insertion of the c-GaN layer at the h-GaN (0001)/GaAs (111) interface significantly improves the crystallinity of the h-GaN layer. Although, we have used [111]-oriented c-GaN layer so far, the lattice-mismatch between h-GaN (0001) and c-GaN (111) is expected to be less than 0.1%, which is much smaller than that for the other commonly used substrate materials. Furthermore, the c-GaN layer was grown at a relatively low growth temperature (Tg = 600°C) to prevent the GaAs substrate from thermal decomposition and to provide a strain relief template layer. This technique enables us to succeed in obtaining nearly strain free h-GaN layers on GaAs (111)B substrates. In this report, the relationship between the nature of the c-GaN intermediate layer and the cubic-to-hexagonal structural transition machanisms are discussed.

Atomic-resolution high-voltage transmission electron microscopy was applied to the atomic structure analysis of a well-defined Pd/ZnO polar interface, which was produced by internal oxidation. Viewing the ZnO along axis, each atomic column consists of either oxygen or zinc, so that an individual column was directly identified from the image contrast of the picture taken at the Scherzer defocus condition. The terminating chemical element at the Pd/ZnO interface, which is parallel to {111} P d and to (0001) Z n O , was shown to be zinc but not oxygen on both sides of the precipitate.

The metalorganic vapor phase epitaxy (MOVPE) growth of cubic-GaN (c-GaN) layers has been performed on the [110]-stripe patterned GaAs (001) substrates. The surface morphology of the laterally overgrown layer was much improved with the formation of the flat (311)A surfaces as the growth proceeded. It is shown that the c-GaN layer thicker than 20 μm was grown on GaAs(001) substrates with the stripe direction in [110] for 90 min. Microstructure and extended defect distribution in the laterally overgrown c-GaN films have been analysed by transmission electron microscopy (TEM). It is found that the planar defect (stacking faults and twins) density drastically decreases at the region away from the substrate toward the top of the c-GaN stripe. On the other hand, the dislocations become dominant. The density of the dislocations was found to be lower than 10 8 cm -2 . These results suggest that the lateral overgrowth on [110]-stripe-patterned GaAs (001) substrates via MOVPE is an efficient method for obtaining a low planar defect density c-GaN layer.

The characteristics of single-crystal GaN regions obtained by selective-area and subsequent lateral overgrowth on stripe-patterned GaAs (001) substrates by MOVPE were studied. Under certain growth conditions, the surface kinetics of the MOVPE process result in lateral-growth of both hexagonal-GaN (h-GaN) and cubic-GaN (c-GaN) stripes with the appropriate mask stripe orientation, namely [110] and [110], respectively. The facet structure comprises the c-GaN stripes surrounded with (111) B facets and mixture facets of (311) A, (111) A, and an inversed (111) B for the stripe window opening along the [110] and [110] directions, respectively. The cross-sectional TEM micrographs showed that the h-GaN is laterally overgrown along the (111) B facets of the c-GaN stripes. For the [110]-stripes, the laterally overgrown h-GaN regions contained a very low density of dislocations (< 10 8 cm -2 ). On the other hand, for the [110]-stripes, a large reduction of stacking fault density was found in the overgrown c-GaN regions. We demonstrated that both high quality h-GaN and c-GaN films were successfully grown on the stripe-patterned GaAs (001) substrates by MOVPE.

The grain-boundary atomic structure of a high-purity α-SiC bicrystal was investigated by atomic-resolution high-voltage transmission electron microscopy (ARHVTEM). The angular relation of the boundary corresponded to a 70.5° rotation around the (1120) axis. The boundary plane was parallel to the (0001) plane of one of the crystals and the (1102) plane of the other. The structural unit of this boundary consisted of five-seven-six-six-six-six-membered rings. The atomic site and atomic species of both the slicon and the carbon in the grain boundary were successfully distinguished in the ARHVTEM image. All the atomic pairs, except for only one pair in the unit period of the boundary, consisted of unlike atoms. The pair of like atoms consisted of silicon atoms and was located in between the five- and seven-membered rings. The atomic species of the threefold-coordinated atom was directly shown from the contrast of the ARHVTEM image to be carbon.

A sample-polishing technique was developed to provide a well-defined thin foil of Si with a clean surface down to atomic dimensions. The resulting samples permit high-resolution transmission electron microscope (HRTEM) imaging unobstructed by artifacts originating from a damaged sample. Samples were not polished by dynamic momentum transfer via accelerated ions like in ion milling; instead, valence electron excitation by photon absorption was used. HRTEM inspection showed that the foils prepared by this method were free from extrinsic lattice defects and had smooth surfaces down to atomic dimensions.

We investigated the structure of unepitaxial crystallites (UC; non-epitaxial crystallites) in homoepitaxial diamond films on Ib (001) diamond substrate grown by the chemical vapor deposition (CVD), employing field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM). The UC was classified into two types depending on the orientation relationship to the homoepitaxial film; one rotates by 70.5° around the common 〈110〉 axis, corresponding to Σ3 coincidence site lattice (CSL) relation. The other type does not have any particular angular relationship. It was found that the growth of the former type is closely related to a lattice dislocation on the substrate surface as well as the homoepitaxial film. On the other hand, there was hardly any lattice dislocation observed at the bottom of the latter type. A nanometer-sized crystalline diamond particle was observed at the nucleation site of the latter one.

Origin of the band-A emission of diamond was investigated to use homoepitaxial diamond films by means of scanning cathodoluminescence (CL) using field emission scanning electron microscopy and high-resolution transmission electron microscopy (HRTEM). It was revealed that the band-A emission localized only inside of the non-epitaxial crystallites (unepitaxial crystallites or UCs), and grain boundaries and dislocations around the emission site of the band-A were also localized in the UC sites; cross-sectional CL revealed in sub-micron scale that some parts in an UC showed the band-A emission, and HRTEM revealed that there were the same structures of grain boundaries as those had π* states determined by electron energy loss spectroscopy (EELS), where π* states correspond to sp2 states of defects in diamond. These experimental results indicate that one of the origins of the band-A emission is attributed to sp2 states of defects in diamond located in grain boundaries and/or dislocations.

Sublattice-reversed GaAs crystals grown by the lattice-matched GaAs/Ge/GaAs (100) and (111) sublattice reversal epitaxy have been characterized by reflection high-energy electron diffraction and cross-sectional transmission electron microscopy. The sublattice reversal in the GaAs/Ge/GaAs (100) system has been verified to be assisted by self-annihilation of the antiphase domains generated at the GaAs/Ge interface. The sublattice reversal in the GaAs/Ge/GaAs (111) system seems to result from the unique structure of the As-terminated Ge (111) surfaces. Unusual (111) Σ3 grain boundaries have been observed in the sublattice-reversed GaAs (111) crystal.

This paper is concerned with the development of a haptic sensor system that monitors the human skin conditions. The base of the sensor is an aluminum shell, around which a sponge rubber layer, a PVDF film, a protective acetate film and a gauze are stacked in sequence. The sensor is attached onto the tip of an elastic cantilevered beam and pressed against the human skin. It is then moved by hand over the skin to collect the surface morphological features through the sensor. The characteristics of data are extracted by calculating the variance and the distribution of power intensity over several segmented frequency ranges. Each set of data obtained is used as a training set of data for a neural network that distinguishes the skin with atopic dermatitis from the normal healthy skins. Experimental results show that 100% of recognition is achieved by using the constructed network system.

An electron emitter which is made of carbon nanotubes and C60 crystals has been produced by wire drawing process. The nanotubes were aligned along the longitudinal direction of the wire. The emission current against the applied voltage of the emitters indicated different behavior at the first emission and the second hereafter . After the second run the emission begun at rather lower voltage. TEM observations have revealed that a protrusion arose at the tip of the nanotube after field emission. The result suggests that the I-V characteristic of the emitter is affected by the tip structure of the nanotube. The experiments lead us to a new concept of a high efficiency carbon-based electron emitter.

Structures of alloys prepared by an inert-gas condensation and compaction method and subsequently rolled were examined with interest in the deformation mechanism. The initial grain size is found to be smaller in the alloy than in the single component material, but XRD measurements indicate that a normal preferred orientation of rolling is developed in the Ag/Fe alloy slightly but not in the Ag at all. The grain growth occurs more or less but hardness is not increased by deformation in both materials. Strain contrasts along grain boundaries are observed by TEM, but tangled dislocations are found in grain interior of neither of the deformed materials. The observation has indicated that the dominant mechanism of deformation in the examined nanocrystalline materials, especially in the single component material, is considered to be grain boundary sliding accomplished by a diffusional process.

Homoepitaxial diamond films grown in the condition of CH 4 /H 2 ratio lower than 0.15% in a microwave-assisted plasma chemical vapor deposition system had excellent electrical and optical properties without any unepitaxial crystallites (UCs). Under such a low CH 4 concentration condition, however, the growth rate becomes too slow to obtain a useful thickness. In order to overcome this problem, we attempted a two-step growth method. In the first step the substrate surface was treated by homoepitaxial growth of diamond in the presence of 0.05% CH 4 in H 2 ; in the second step the CH 4 concentration was increased. By considering the origin of UCs with cross-sectional transmission electron microscope studies, it was found that this method is based on surface improvement of the initial substrate by means of ultra-low CH 4 concentration growth. This method was quite useful for obtaining high quality films, with high growth rate and reproducibility.

An ECR-C'VD system was newly designed and applied on the growth of a fine-grained polycrystalline diamond film. The film was grown on the polished surface of a heated silicon substrate in H 2 -CO-O 2 mixing gas. Grain sized of the grown polycrystalline film was nanometer in average. Atomic structure of CSL boundaries of the diamond film was different from that of silicon and germanium; The (112) Σ 3 boundary was symmetry in atomic arrangement and the Σ 9 boundary was parallel to (114) plane in which dangling bonds were supposed to present. A new EELS line corresponding to π * state was detected in addition to major σ * line in the boundary, which contained three coordinated atoms. Observed π * line suggests rebonding of a dangling bond into π-bonding which is much softer than the o -bonding.

Reactive wetting of a Ag-Cu-Ti molten alloy on a SiC substrate was observed in situ using a high-resolution transmission electron microscope. SiC dissolution and TiC nucleation and growth were repeated at the spreading front. The formation process of the interface between SiC and TiC was classified into two types depending on the nucleation site of the TiC. When the TiC nucleated on SiC. the interface between SiC and TiC was coherent and two crystallographic orientational relationships were observed. The stability of these relationships is discussed using a geometrical model. In contrast, when the TiC nucleated on preformed TiC, the TiC grew continuously with SiC dissolution.

The microstructure of the C60/carbon nanotube composite produced at a pressure of 5.5GPa at 1073K wasexamined by X-ray diffraction (XRD) and high resolution electron microscopy (HRTEM). The XRD profile froma compaction surface indicated that C60 matrix changed into a polymerized phase which can be indexed as fcc structure (a =1.31 nm). On a cross-sectional area of the specimen and the crushed specimen, however, the XRD profiles andthe HRTEM observation suggested that the polymerized structure was approximated as the rhombohedral structure. The structural orientation of the bulk specimen and handling of the specimen (bulk or powder) should be taken intoaccount in structural characterization of high pressure polymerized C60. In the nanotubes, no obvious change in the structureis observed even after high-pressure compaction except for a partial collapse.

Carbon nanotube reinforced aluminum (Al) composites were produced by hot-press and hot-extrusion methods. The interfacial structure between the carbon nanotube and Al was examined using a transmission electron microscope (TEM), and the mechanical properties were measured by a tensile test. TEM observations have shown that the nanotubes in the composites are not damaged during the composite preparation and that no reaction products at the nanotube/Al interface are visible after annealing for 24 h at 983 K. The strength of the composites is only slightly affected by the annealing time at 873 K, while that of the pure Al produced in a similar powder metallurgy process significantly decreases with time. These studies are considered to yield experimental information valuable for producing high performance composites.

Carbon nanotubes have a whisker-like structure so an extremely high strength and lack of plasticity are generally predicted. In-situ observations made by transmission electron microscopy, however, prove that carbon nanotubes bend plastically at room temperature. The bending process at the atomic level is suggested by a molecular mechanics calculation: a nanotube deforms elastically until certain critical curvature is attained; then the atomic bonding in the stressed side changes from a graphite-like bonding state to a diamond-like state.

A new carbon/carbon (C/C) composite was successfully produced at room temperature by drawing a silver tube containing carbon nanotubes as the fiber material and nanocrystalline carbon 60 (C60) as the matrix. Fine structures of the composite were examined by transmission electron microscopy (TEM) and the mechanical properties by conventional tensile tests. TEM observations have shown that the carbon nanotubes in the composite are not damaged and well aligned along the longitudinal direction of the composite wire. The stress-strain curve of the composite wire de-sheathed by the evaporation of silver through a heat treatment exhibited an approximately 20-fold increase in fracture stress over that of polycrystalline C60, and the higher fracture strain (more than 10%). The fractured surface of the wire showed that nanotubes have been pulled out but not fractured. The experiments lead us to a new concept of a ductile C/C composite.

Non-equilibrium Pr 100-x Fe x alloys (x= 4, 10, 20, 30, 40) prepared by melt-quenching were investigated by X-ray diffraction, VSM, Mossbauer spectroscopy and TEM observation. The experimental results indicated that, in the Pr-1 at%Fe alloy, iron atoms have little magnetic moment and may be dissolved in a dhcp-Pr matrix. In other compositions, iron atoms, having a magnetic hyperfine field of about 29 T (290 kOe) at 77K, are mainly in an amorphous phase. We analyze the magnetic data for Pr-10, 20, 30 at%Fe with the model based on super-ferromagnetism-magnetically connecting Fe-rich clusters dispersed in a non-magnetic matrix-, in which the inter-cluster interactions are treated as molecular field. The results show that the Curie temperature within clusters, T intra c , is nearly constant for all compositions, and that for inter-cluster coupling, T inter c , becomes higher toward T intra c as the iron concentration increases. The analysis also shows that the average size of clusters increases with the iron concentration. It is suggested that the patches in an amorphous region observed in the TEM image of Pr-10at%Fe, each of which estimates to contain a few hundreds of atoms, behave as the super-ferromagnetic clusters.

The effects of the interfacial fine structure (interfacial bonding interaction) on the mechanical properties of nanotube/C60 composite were examined by high resolution transmission electron microscope (HRTEM) observations of nanotube/vapor-deposited C60 crystal interfaces and pull-out tests of high modulus carbon fiber with a vapordeposited C60 single crystal. Interfaces between nanotube and {111}-faceted C60 crystal were observed to possess a parallel orientation relationship between the tube axis and of the C60 crystal. The shear strength of the carbon fiber/C60 composite was estimated to be 4.4 x 10 -2 MPa. Interfacial sliding was observed in the carbon fiber/C60 single crystal interface without deformation of the C60 matrix nor the fracture of fiber. It has been inferred that the pull-out of the carbon fiber from the C60 matrix is due to the shear sliding, which is caused by the weak bonding between graphitic basal plane and C60. The experiments have indicated that the ductility of the nanotube/C60 composite originates probably from sliding at the interface between the nanotube and the C60 matrix.

Nanocrystalline silver (Ag) was prepared by in situ compacting of ultra-fine silver particles. The structures of as-compacted and annealed specimens were analysed by high-resolution transmission electron microscopy and scanning electron microscopy. Vickers microhardness was measured on the specimens. The ultra-fine particles aggregate before compaction. It is found that the nanocrystalline specimens are obtained by the compaction of the aggregates. Microstructure inside the aggregates does not change as the compacting pressure increases from 0.25 to 2.00 GPa. The compacting pressure affects on the structure and density of the boundaries between the aggregates, i.e. the formation of the crack-type defects of about 1 μm at the boundaries. Thermal stability of nanocrystalline Ag is significantly low; grain coarsening starts below 200 °C. However, a nanometre-sized layered structure forms in local regions upon annealing and is stable up to 800 °C. Vickers microhardness of as-compacted specimens increases with increasing compacting pressure. The increase is attributed to the decrease of the number of crack-type defects. Vickers microhardness of nanocrystalline Ag begins to decrease due to grain coarsening upon annealing around 200 °C. The microhardness of nanocrystalline Ag deviates from the HalI–Petch relation.