Nitration Sulphonation and Hydroxylation

Nitration of C60 is carried out reacting nitronium ion generated from a mixture of H2SO4 and KNO3 at 95 C or with nitronium tetrafluoroborate in the presence of alkyl or aryl carboxylic acid in methylene chloride at ambient temperature under atmospheric pressure of N2 93 . In the latter reaction instantaneous formation of nitronium alkyl or aryl carboxylate salt is observed. Electrophilic attack of nitron-ium ion from RCOO-NO+ (R C6H5, p-C6H4-Br) to C60 forms an intermediate C60(NO+)x and...

Fe and their Alloys on Other Fluorides

Several studies have demonstrated that crystalline thin films of ferromagnetic metals and alloys can be grown on LiF crystal substrates. At the beginning of the 1970s, different groups in the former Soviet Union worked on the structural, magnetic, and magnetooptical properties of Fe Co and Fe Ni alloy thin films, as well as on double-layer ferromagnetic films, deposited on LiF crystal substrates, but many of these references are difficult to access 81-83 . According to these reports, the...

Fluorides on Semiconductors

The epitaxial growth of alkali metal fluorides, such as KF and RbF, is a very difficult task since they are dissociatively adsorbed due to the reaction of halogen atoms with Si dangling bonds 43 . Concomitant with this fact, the fluorination of the Si surface exposed to fluorine leads to spontaneous surface etching at room temperature 44, 45 . LiF on Si is another interesting system because LiF is the material with the most extreme ultraviolet (UV) transmission of all, and therefore it is...

Stability of Fivefold Twins

Frequently, MTPs and fivefold twinned structures do not exist separately, but in coexistence or even competition with structures that exhibit regular crystal lattice without twins. Their stability is an intriguing issue mainly because of the discrepancy between noncrystallographic packing of atoms and its extension in three-dimensional space. Experimental and theoretical investigations of clusters, a few atoms up to several hundreds or even a few thousands of atoms in size, aimed at determining...

Dgeba Dgeba

TGAP (trifunctional triglycidyl p-amino phenol tetraglycidyldiamino diphenylmethane (TGDDM) NH2CHCH3CH2(OCH2CHCH3)xNH2, x 2.6 Commercial name JEFFAMINE 230 JEFFAMINE 230 (3DCM) Amicure bisparaaminocyclohexylmethane (PACM) 4,4'-diaminodiphenyl methane (DDM) m-phenylene diamine (mPDA) 4,4'-diaminodiphenylsulfone (DDS) JEFFAMINE D400 (N 5.6) Boron trifluoride monoethylamine (BTFA) Bis(2-hydroxy-ethyl)methyl tallow ammonium MMT Dimethyl benzyl hydrogenated tallow ammonium chloride Intercalated...

Chemistry of Carbon Nanotubes

The chemistry of carbon nanotubes, which encompasses the aspects of purification and functionalization, is a very important field for tailoring their structural and electronic properties and thus for the development of future applications. (see Rakov 77 and references therein). Purification aims at removing the nontubular material in raw nanotube samples. Several techniques, more or less complex, have been proposed, including solvent treatment followed by ultrafiltration 78 , flocculation using...

Measurement of Mean Inner Potential

Experimental measurements of K0 reported in the literature are sparse in number, and the scatter in the quoted values is wide. Values obtained using both refraction and phase-shifting techniques have been compiled by Gajdardziska-Josifovska and Carim 90 and are reproduced in Table 3. A similar table has been published by Spence 83 . Electron holography permits much greater accuracy to be obtained. One approach to measure K0 has used electron holograms of 20-40 nm diameter Si nanospheres coated...

References

Trans. 12A, 695-708 (1981). 2. H. Gleiter, in Deformation of Polycrystals Mechanisms and Microstructures (N. Hansen, A. Horsewell, T. Leffers, and H. Lil-holt, Eds.), p. 15. Riso National Laboratory, Roskilde, 1981. 3. C. Suryanarayana, Internat. Mater. Rev. 40, 41 (1995). 4. D. G. Morris, Mechanical Behavior of Nanostructured Materials, in Materials Science Foundations, Series 2 (M. Magini and F. H. Wohlbier, Eds.). Trans. Tech. Publications, Uetikon-Zurich, 1998. 5. J. R....

Info

Multiple additions of free radicals to C60 leading to formation of persistent radical species (20, 22, 24). Adapted from 62 . electron in R-C60 is mostly confined to the two fused, six-membered rings without delocalization of the unpaired electron over the C60 sphere. The ESR spectrum of the (CH3)3C-C60 is obtained by several photochemical and thermal methods including the UV irradiation of a saturated solution of C60 in benzene containing tert-butyl bromide. The spectrum is...

Fine Particles

Figure 14 shows representative results obtained by applying off-axis electron holography and optical reconstruction to particles of Co and permalloy. The Co fine particles shown in Figure 14a-d were prepared by gas evaporation of Co in an inert gas atmosphere 177 . Figure 14a shows a bright-field image of a 55-nm-thick plate-shaped Co particle, which has 111 surfaces and (110) edges and is uniform in thickness. In this image, only the outline of the particle can be Figure 14. (a) Bright-field...

PbTiO3

Lead titanate is a typical displacive ferroelectric with very good dielectric, pyroelectric, and piezoelectric properties. It has a cubic perovskite structure above TC 490 C and transforms to a tetragonal ferroelectric phase below it. The room temperature tetragonal distortion, (c a) a, is as large as 6 , as compared to only 1 for BaTiO3. Due to its obvious application potential, detailed size effect studies have been carried out in this system during the past decade. Ishikawa et al. 21...

Mym

Where Vi and V are the molar volumes of an i element and alloy, respectively, and k is the isothermal compressibility coefficient. dx dx and d2x dx2 can be calculated from If we consider the phase equilibrium of the bcc and fcc phases in the Cu-Fe binary system, the equilibrium equation bcc x vbcc pbcc _ fcc x vfcc pfcc bcc vbcc pbcc _ xCu (T0,x ,P ) xCu(T0, x ,P )> xFe (T0,x ,P ) xFe(T0, xfcc, Pfcc) should hold, and the equation may be bcc bcc pbcc fcc T -i-fcc pfcc _ _ J ii bcc vbcc xi...

FIB Implantation

FIB implantation takes place in conditions of much higher local ion currents than conventional implantation. Compared to the fundamental meaning of the damage production by ion irradiation, however, there exist only a few systematic investigations concerning high current density irradiations with a focused ion beam. For nanoscale patterning the appropriate level of interaction between ions and solids is translated toward low dose effects. In this case local defect injection now plays a major...

Artifacts

The effects of Fresnel diffraction at the biprism wire can cause phase and amplitude modulations of both the image and the reference wave 80 . These disturbances can be removed to some extent by using a reference hologram, although the positions of the Fresnel fringes in the sample and reference holograms are not always identical. They can also be minimized by using the undisturbed part of a broader hologram for recording and reconstruction. Residual effects can be removed by Fourier filtering...

Spectroscopic Characterization

Mass spectroscopy plays an important role in the characterization of fullerene dimers because this technique requires substantially fewer samples (and machine time) than other analysis methods such as NMR, X-ray diffraction, and so on. However, the fragmentation of fullerene dimers into monomers and the low solubility of fullerene dimers made most of the ionization methods inaccessible for these samples. Typically, only MALDI-TOF-MS gives sufficient mass accuracy and intensity for most of the...

Escape Time of Electrons from Localized States

As we have seen in most approaches of the tunnelling time problem, only the scattering configuration in which the free electron (or wavepacket) is coming from the left (right) on a 1D arbitrary potential barrier has been considered. More than one tunnelling time is involved in this time problem, no matter whether we deal with the Buttiker-Landauer tbl or complex t t1 it2 characteristic times (see Eqs. (12) and (24)). Furthermore, this seems not to be a peculiarity of a quantum-mechanical wave,...

Formation of Fullerene Complexes

Braun and co-workers studied the mechanochemical synthesis of the supramolecular host-guest complex of C60 and gamma-cyclodextrin (y-CD) 83 . The equipment used in the mechanochemical investigation was a 50 ml agate ball mill (diameter 70 mm, height 15 mm) (Pulverisette, Type 701, Fritsch, Germany). A homogenized mixture of 10 mg of C60 and 100 mg of y-CD was ball-milled for about 20 h at room temperature. A 1 2 C60-y-CD complex 41 with a bicapped structure was supposed to be formed (Fig. 19)....

Electromagnetic Transport in Heterostructures

Theoreticians pointed out that the theoretical framework used in many instances to explain the electromagnetic transport in granular materials is a modelization in terms of a continuum media. As previously observed elsewhere 44 , the basic assumption used is that there exist length scales above which fluctuations at the microscopic level may be ignored. In this way, useful predictions of a granular material's bulk properties can be made with no references to its discrete nature. At issue is the...

Evanescent Wave Spectroscopy Of Atomic Vapors

This section deals with applications of evanescent waves to the detailed spectroscopy of atomic vapors near dielectric surfaces. Boissel and Kerherve reported in 1981 the absorption of the sodium D2 line when the sodium vapor was excited by an EW at a sapphire prism surface 14 . This can be thought of as the first experiment on linear EWS of atomic vapors. The authors calculated based on the theory of optical response of atoms in the vicinity of a bounding surface the absorption of the EW in...

Fullerene metal complexes

In the exohedral fullerene-transition metal complexes, the fullerenes act as an olefinic ligand and bind the metal center in -2-fashion 109 . There are several examples of -5-fullerene metal complexes 110 . For this purpose a cyclopentadiene moiety is generated on the fullerene surface from a pentaadduct, such as C60Ph5H. A number of cyclopentadienyl (Cp) metal complexes (-5-C60Ph5)MLn (43) (MLn Li, K, Tl, Cu PEt3) are synthesized (Fig. 17) using the cyclopentadienyl ring generated through...

BaTiO3

Barium titanate has a cubic perovskite structure in its high-symmetry, paraelectric phase (above TC 125 C). With a decrease in the temperature, it transforms successively to three structurally distinct ferroelectric phases a tetragonal phase (TC < T < 5 C), an orthorhombic phase (5 C < T < -90 C), and a rhombohedral phase (T < -90 C). All three transitions are of the first order. Early measurements involved sintered samples with grain size in the submicrometer to few micrometer range...

Polyfullerenes And Fulleropolymers

In view of the interesting properties of fullerenes, there have been a number of studies exploring the behavior of fullerenes under the routine polymerization conditions. Extensive literature is available on the subject, with a number of review articles 397 . Polyfullerene ideally should be a linear chain of the fullerene molecules joined by one or more covalent bonds. Fullerenes are known to undergo photopolymerization in the solid state 398 . In this reaction a 2 + 2 cycloaddition between two...

Growth Mediated Formation

If not nucleated from the beginning, MTPs also may form during growth by repeated cyclic twinning. The main source of growth twinning is misstacking of atoms at faces of low growth rate so as to produce reentrant edge configurations, which enable accelerated growth along a twin boundary 43, 117, 120, 186, 253 . In the particle stage of growth, twinning may proceed by the formation of primary, secondary, and tertiary twins on pre-existing tetrahedra as shown schematically in Figure 12. This...

The Unitedatom Model

The works of Hautman and Klein 22, 23 are among the earliest MD studies concerned with the structure and dynamics of long-chain molecules on metallic substrates. Although these are not tribological studies, they are particularly relevant because they employ a basic molecular model that has been subsequently adopted by most groups undertaking computational studies of alkanethiol SAMs. More recently, the structure 22-39 , compression 74, 75 , and the friction 76, 77, 79-92 of alkanethiol...

Ac Conductivity

For the frequency and temperature dependent dielectric constants (e) and ac conductivity (o-ac(w)) measurements, the two polished faces of each of the samples (thickness 0.25-0.30 mm) were gold plated by sputtering and then annealed at about 150 C for half an hour before conductivity measurement. This was done for better electrical contact with the sample surface. Conductivity measurements were made in the ohmic region as determined from the study of current-voltage (I-V) method. It is well...

Glossary

AC conductivity Frequency dependent conductivity. The conductivity of the material changes both with temperature and frequency. From the study of electric conductivity of solid materials (composites etc.), mechanism of electron or ion transport, responsible for the electrical conductivity, can be explained. Correlated barrier hopping (CBH) Mechanism of electrical conductivity. The charge carrier is assumed to hop between site pairs over the potential barrier (W) separating them. For the...

Field Emission Stability

A stable field emission is imperative for practical devices. The residual gases in vacuum influence the field-emission stability dramatically. It has been found that metal and silicon emitters are very sensitive to residual gases. Various residual gases originate from the components that constitute a device, such as a cathode, anode, sealing frit, spacer, and so on. Although pumped out in outgassing process and absorbed by getters after sealing, the residual gases are difficult to remove...

Extrinsic Effects

Changes in ferroelectric properties usually occur when the film thickness is below 200 nm, but the actual value of this critical thickness often depends sensitively on the nature of the microstructure (and hence on the synthesis conditions), interfacial stresses, crystallographic orientation, and epitaxy. As mentioned earlier, it may be difficult to distinguish between particle size effects and thickness effects since the microstructure often changes continuously with f thinner films being...

Introduction

During the last two decades, semiconducting properties of many multicomponent and transition metal oxide TMO and other metal oxide glasses have been studied because of their probable technological applications 1-4 in optical and electrical memory switches, oxygen sensors, etc. The high temperature T gt 6D 2,6D being the Debye temperature conductivity data in many of these glasses, for example, V2O5-RO2 5 , V2O5-K2O3 6 , V2O5-P2O5 7 , V2O5-MnO-TeO2 8 , V2O5-SnO-TeO2 9 , V2O5-P2O5-TiO2 10 ,...

Reference Hologram

In most standard microscope applications, image distortions are small enough to be ignored. Off-axis electron holography, however, stores information in the lateral displacement of interference fringes, and distortions can cause similar Figure 4. Simulations of phase lines around a small magnetic bar, calculated a assuming a perfect reference wave and b using a reference wave that has been perturbed by the long-range magnetic field extending into vacuum around the object. Reprinted with...

Rapid Solidification

One of the popular techniques to synthesize nanoembedded metallic particles is by rapid solidification. This processing technique involves the achievement of a high cooling rate in the range 104-107 K s, and significant undercooling of the melt that leads to a large departure from equilibrium conditions. This process involves the ejection of a stream of molten metal alloy into a thin layer or fine droplets, which is brought in intimate contact with a cooling medium solid substrate . The heat...

Ferroelectric Domain Imaging In Scanning Force Microscopy

Scanning force microscopy can be considered as a combination of a surface force apparatus and a surface profilometer, as it is based on local monitoring of the interaction forces between a probing tip and a sample 4 . The forces acting on the tip after it has approached the sample surface cause a deflection of the cantilever according to Hooke's law. This deflection can be detected optically or electrically with sub-angstrom accuracy and is controlled by a feedback device, which regulates the...

Epitaxial CaF2 ON Si111

In 1989, Schowalter and Fathauer 3 published a complete review of the growth of CaF2 on Si 111 where various aspects of the epitaxial growth of films were analyzed, such as the crystalline quality of epitaxial layers of CaF2, the surface energy, the cracking of epitaxial layers, and the CaF2 Si interface. With the democratization of surface study techniques and spectroscopic and structural techniques based on synchrotron radiation in the 1990s, it was rapidly possible to obtain a deeper...

C6h5cn

Angle of 42 relative to the symmetry axis of the molecule. The methyl and Cp hydrogen atoms are in van der Waals contact with each other. The Cp group and cyclopentadi-enide in the fullerene moiety are arranged in a staggered manner. All C-C bond lengths in each pentagon are equal to each other and hence both rings are aromatic. The distances between the pentagon carbon atoms and the iron are comparable to those in known ferrocene derivatives. JH and 13 C NMR spectra indicate that 60 has C5v...

Etching of FIB Exposed Surface

It is well known that a high concentration of p doping in Si drastically reduces its etch rate in certain chemical etchants such as KOH and hydrazine. The FIB irradiation of selected regions on Si substrate leads to the same result. The exposure to Ga FIB with ion doses gt 1015 cm-2 of selected Figure 16. Ion beam tail effect on the deposited pattern. Top as-deposited tungsten meander microheater Bottom the same structure after GAE cleaning. Figure 15. FIB induced deposition of SiO2 dielectric...

Defects in the Embedded Particles and the Matrix

There exist a limited number of studies to unravel defects at the interfaces and inside the nanoembedded particles. The possible defects that can arise from the geometrical effect of a constraining cavity have been discussed by Pond and Vlachavas 55 . In case the particles have the same intersection symmetry as that of the matrix, one does not expect any geometrical defect to occur. However, if they are different, defects can exist either at the interface as steps or in the interior as...

Fieldemission Materials

Field emission also called Fowler-Nordheim tunneling 1 is a process where electrons tunnel through the surface potential barrier of a metal-vacuum interface and float in the vacuum region during the presence of an extremely high electric field Fig. 1 . This quantum-mechanical tunneling of electrons is an important mechanism for thin surface potential barriers, just like those in heavily doped semiconductor-metal junctions. Different from thermionic emission, electron field emission occurs...

Diels Alder Reaction of Phthalazine to C60

When the reaction of C60 with one equivalent of phthalazine was carried out in a solution of 1-chloronaphthalene at 255 C for 1 h, the open-cage fullerene derivative 24 was obtained in 44 yield together with 23 of recovered C60 by a one-pot reaction. In contrast, the HSVM reaction of

FeCu Binary Phase Diagram With Nanometersized Particles

It is mentioned in Section 4 that the solid solubilities of Fe in the fcc phase and Cu in the bcc phase are enhanced by mechanical alloying, as shown in Figure 6. The enhancement of solid solubility could be linked with small grain sizes induced by milling. Although some attempts 21, 26-31, 91 tried to explain the extension of the solid solubility during the mechanical milling process, the subject is still not well understood. Recently, a method to calculate phase diagram with nanometer-sized...

Melt Quenching Technique

The melt quenching technique is widely used to prepare glasses and glass-ceramics. It needs higher temperature compared to that required for the sol-gel technique, but it takes less time. The TiO2, BaTiO3, SrTiO3, doped vanadate glasses or the VP glasses or other low melting TMO glasses VP type base glasses , in general, can be prepared by a fast quenching method 48, 50 . For example, VP glass can be used to prepare a typical 80V205-20P205 xTiO2 type FGNC with different concentrations of TiO2 x...

Fullerene Cyclodextrins

The synthesis of water-soluble, covalently bound fullerene cyclodextrin conjugates 520, 521 reacting cyclodextrin monoamine derivatives and fullerenes has been reported Fig. 233 487 . Depending upon the macrocycle, the aqueous solubility of the corresponding conjugate varied. Even though a-CD has a very small cavity, which does not facilitate complex formation easily, covalent binding to the fullerenes leads to a material which is even more soluble than the ones from 8-CD. Considering the fact...

Otq

Deformation of c-domains as a result of the converse piezoelectric effect. where AL is the sample deformation and L is the sample thickness. Equation 4 can be rewritten as where V is an applied voltage. The sign reflects the opposite piezoelectric coefficients for antiparallel domains. Therefore, opposite domains can be visualized by monitoring their voltage-induced surface displacement. Because of its extremely high vertical sensitivity, nanoscale topography variations can be...

Melting

Melting of small particles has received considerable attention over the last few decades 95 . Results show that the melting points of fine particles have a strong dependence on their sizes. Ubbellohde 96 has reported the importance of Lindemann's criterion of melting. Lindemann 97 proposed melting as a vibrational instability released when the root mean square amplitude of vibration reaches a critical fraction of atomic distances. According to Lindemann, the melting temperature is given by Tm r...

Measurement Of Mean Inner Potential And Sample Thickness

Electron holography has been widely used to obtain medium-resolution information about sample morphology and composition. In this section, we consider phase changes that are associated solely with local variations in mean inner potential and sample thickness. The characterization of magnetic and electrostatic fields is considered in the following Sections 3 and 4. The mean inner potential, V0, is defined as the volume average, or the zero-order Fourier coefficient, of the electrostatic...

Passivated Nanoparticles

Passivated nanoparticles are nanometer sized colloidal particles chemically terminated by organic monolayers, typically alkanethiol molecules. They can be produced from many materials and show a diversity of functional behavior beyond that of the corresponding bulk materials, with many of their electronic 9 , optical 10, 11 , and catalytic 12-14 properties originating from their quantum-scale dimensions. The organic layer, typically bound to the nanoparticle core by a metal-sulphur thiolate...

Powder Metallurgy Composites and Magnetic Properties

Although extensive literature exists on the properties of nanophase materials, only a limited number of systematic studies have been reported on the electromagnetic and magnetic properties of granular systems. It is useful to succintly summarize existing studies. Shaikh and co-workers 22 were among the first to report on the dielectric properties of ultrafine grained BaTiO3 the permittivity was observed to increase with decreasing grain size, reaching a peak value at 1 m and decreasing...