Optical near fields exist close to any illuminated object They account for interesting effects such as enhanced pinhole transmission or enhanced Raman scattering enabling single-molecule spectroscopy Also, they enable high-resolution (below 10 nm) optical microscopy The plasmon-enhanced near-field coupling between metallic nanostructures opens new ways of designing optical properties and of controlling light on the nanometre scale Here we study the strong enhancement of optical near-field coupling in the infrared by lattice vibrations (phonons) of polar dielectrics We combine infrared spectroscopy with a near-field microscope that provides a confined field to probe the local interaction with a SiC sample The phonon resonance occurs at 920 cm(-1) Within 20 cm(-1) of the resonance, the near-field signal increases 200-fold; on resonance, the signal exceeds by 20 times the value obtained with a gold sample We find that phonon-enhanced near-field coupling is extremely sensitive to chemical and structural composition of polar samples, permitting nanometre-scale analysis of semiconductors and minerals The excellent physical and chemical stability of SiC in particular may allow the design of nanometre-scale optical circuits for high-temperature and high-power operation

Phonon-enhanced light–matter interaction at the nanometre scale

A substrate-free gas-phase synthesis apparatus and method that is capable of rapidly and continuously producing graphene in ambient conditions without the use of graphite or substrates is provided. Graphene sheets are continuously synthesized in fractions of a second by sending an aerosol consisting of argon gas and liquid ethanol droplets into an atmospheric-pressure microwave-generated argon plasma field. The ethanol droplets are evaporated and dissociated in the plasma, forming graphene sheets that are collected. The apparatus can be scaled for the large-scale production of clean and highly ordered graphene and its many applications. The graphene that is produced is clean and highly ordered with few lattice imperfections and oxygen functionalities and therefore has improved characteristics over graphene produced by current methods in the art. The graphene that is produced by the apparatus and methods was shown to be particularly useful as a support substrate that enabled direct atomic resolution imaging of organic molecules and interfaces with nanoparticles at a level previously unachievable.

Substrate-free gas-phase synthesis of graphene sheets

Current issues and problems in the chemical vapor deposition (CVD) of diamond are those which relate to its characterization, its nucleation on foreign surfaces, the question of its formation in preference to the other phases of solid carbon (for example, graphite, chaoite, or lonsdaleite), why different morphologies and crystallographic orientations (textures) are seen in different experiments or with different parameters in the same experiment, and finally whether well-crystallized metastable phases can be obtained by CVD in other material systems or are only a peculiarity of carbon chemistry. Whether a given carbon coating is justly described as diamond has been such an issue, and coatings should clearly show evidence for diamond by x-ray diffraction and Raman spectroscopy before the claim of diamond is made. Experimental results have not been consistent in many cases, and much work remains to be done before an accurate assessment can be made of the technological impact of the development.

https://science.sciencemag.org/content/sci/247/4943/688.full.pdf

Current Issues and Problems in the Chemical Vapor Deposition of Diamond

Recent advances in aerosol generation of materials are reviewed Gas-to-particle and spray processes (spray pyrolysis) for powder generation and various routes for film generation are discussed from the experimental and theoretical perspectives The range of materials generated by these routes has increased in recent years to include fullerenes and ceramic superconductors Many metals and various oxide and nonoxide ceramics have also been added to the list of materials generated by gas-phase routes Established aerosol routes such as vapor condensation have found widespread applications for generation of nanophase materials The formation of quantum dots via aerosol approaches has also been demonstrated The theoretical understanding of gas-to-particle conversion routes has advanced to include the finite rate of particle fusion or sintering occurring after collisions of particles The modeling of spray pyrolysis systems has provided insight into the control of particle morphology and reactor design In th

https://www.tandfonline.com/doi/pdf/10.1080/02786829308959650

Aerosol Processing of Materials

Supertough wear-resistant coatings with ‘chameleon’ surface adaptation

Friction induced phase transformation of pulsed laser deposited diamond-like carbon

Homogeneous nucleation of diamond powder is reported. The experiments were performed in a low‐pressure microwave‐plasma reactor. The deposits were collected downstream of the reaction zone and subjected to wet oxidation to remove nondiamond carbons. The residues were analyzed by optical and electron microscopy, electron diffraction, and Raman spectroscopy. A variety of hydrocarbons diluted in argon, hydrogen, or oxygen gas mixtures were tested. In most cases only nondiamond materials, like graphite and carbyne, were obtained. Homogeneous nucleation of diamond was clearly observed in dichloromethane‐ and trichloroethylene‐oxygen mixtures. The particles formed had crystalline shapes, mostly hexagonal. The largest particles were about 0.2 μm, although most of the particles were on the order of 50 nm in diameter. The powder was identified to be a mixture of polytypes of diamond.

Homogeneous nucleation of diamond powder in the gas phase

A series of diamond polytype structures are described and their IR and Raman vibrational modes predicted. The diamond polytypes are analogous to the well-known silicon carbide polytypes. The intermediate 6H diamond polytype was recently identified by single crystal electron diffraction of vapor precipitated diamond powder. In addition, end member polytypes of 3C (cubic diamond) and 2H diamond (hexagonal lonsdaleite) have been previously established, and polytypes such as 4H, 8H, 15R, and 21R diamond are predicted, but may be difficult to isolate and identify. The various diamond polytype structures differ only in the stacking sequences of identical puckered hexagonal carbon layers. These identical carbon layers lie parallel to the cubic 3C {111} and the hexagonal 2H {001} planes. A new method for uniquely labeling the structural layers in the polytype stacking sequences is presented. Factor group analysis was used to determine the IR and Raman selection rules for five diamond polytypes with structures intermediate between those of end members diamond and lonsdaleite. Brillouin zone folding techniques were used to determine band positions, in analogy with analyses of SiC polytypes discussed in the literature. The results predict that (i) all diamond polytypes are Raman active, (ii) limiting polytypes 3C and 2H are not IR active, and (iii) polytypes 4H, 6H, 8H, 15R, and 21R have IR active modes.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400037134

Diamond polytypes and their vibrational spectra

A corrosion-inhibiting pigment comprising a rare earth element and a valence stabilizer combinded to form a rare earth/valence stabilizer complex. The rare earth element is selected from cerium, terbium, praseodymium, or a combination thereof, and at least one rare earth element is in the tetravalent oxidation state. An inorganic or organic material is used to stabilize the tetravalent rare earth ion to form a compound that is sparingly soluble in water. Specific stabilizers are chosen to control the release rate of tetravalent cerium, terbium, or praseodymium during exposure to water and to tailor the compatibility of the powder when used as a pigment in a chosen binder system. Stabilizers may also modify the processing and handling characteristics of the formed powders. Many rare earth-valence stabilizer combinations are presented that can equal the performance of conventional hexavalent chromium systems.

Non-toxic corrosion-protection pigments based on rare earth elements

A corrosion-inhibiting coating, process, and system that provides a tight, adherent zinc- or zinc-alloy coating that is directly deposited onto steel or cast iron surfaces for enhanced corrosion protection. A process for applying the coating is also provided. The process includes the application of two sequential aqueous baths. The first bath contains a precursor zinc compound while the second bath contains a reducing agent to deposit the zinc directly upon the steel or cast iron.

Andrew Wells Phelps

Papers

Friction induced phase transformation of pulsed laser deposited diamond-like carbon

Homogeneous nucleation of diamond powder in the gas phase

Diamond polytypes and their vibrational spectra

Non-toxic corrosion-protection pigments based on rare earth elements

Corrosion-inhibiting coating