Structural transformations, reactions, and electronic properties of fullerenes, onions, and buckytubes

We describe the results of extensive quantum molecular dynamics calculations of the properties of fullerenes and microtubules. The topics to be discussed include: (i) stability of C₆₀ isomers and barriers to isomerization; (ii) reactivity of C₆₀ and C₅₈ with C₂ and C₃, and its implications on the formation and growth of fullerenes; and (iii) atomic and electronic structure and doping of semiconducting microtubules. We also discuss the structures, stabilities and atomic transformations of large multishell fullerenes and offer an explanation for the formation of spheroidal “onions” under high fluence electron irradiation conditions. The last results, which involved calculations for up to 15 000 atoms, were obtained using classical three-body potentials.     

Preparation and Properties of Sodium, Potassium, Magnesium, Calcium, and Aluminum Terephthalates

Group I–III terephthalates were prepared: KOOCC₆H₄COOH, NaOOCC₆H₄COOH, NaOOCC₆H₄COONa, Mg(OOCC₆H₄COO) · 2H₂O, Ca(OOCC₆H₄COO) · 3H₂O, and Al₂(OOCC₆H₄COO)₃ · 8H₂O. The salts were characterized by differential thermal analysis and IR spectroscopy. The results demonstrate that the thermal decomposition of the terephthalates yields metal carbonates or oxides. On heating to 1000°C, aluminum terephthalate converts into submicron-sized -alumina particles.     

Synthesis and structure of dodecamolybdates of tetravalent cerium,thorium, uranium,neptunium, and plutonium

A series of isostructural compounds of the composition Na₇H[EMo₁₂O₄₂]·12H₂O, where E(IV) = Ce, Th, U, Np, or Pu, were synthesized and structurally characterized. In the [EMo₁₂O₄₂]^8– heteropolyanion (HPA), the central E(IV) atom is surrounded by six Mo₂O₉ groups, each constituted by two octahedra sharing a common face. The coordination polyhedron (CP) of the central atom is a weakly distorted icosahedron with the mean E(IV)–О bond lengths of 2.498, 2.529, 2.500, 2.490, and 2.488 Å for Ce, Th, U, Np, and Pu, respectively. In the structure of the compounds Na₇H[EMo₁₂O₄₂]·12H₂O, there are two crystallographically independent sodium atoms: Na(1) and Na(2). The oxygen surrounding of the Na(1) atom is formed by the terminal oxygen atoms of two heteropolyanions adjacent along [001], and its coordination polyhedron is an octahedron. The surrounding of the Na(2) atom (a six-vertex polyhedron) is formed by three terminal oxygen atoms of three Mo₂O₉ groups belonging to the same HPA and by three water molecules. The coordination polyhedra of the Na(2) atoms are linked with each other via common oxygen atoms of O_w(2) water molecules to form a chain “winding” around the 3₁ screw axis. The heteropolyanions and Na⁺ cations in the crystal form a framework constructed in a fashion characteristic of Dexter–Silverton type anions, with the coordination via three terminal oxygen atoms of three Mo₂O₉ groups. Excess negative charge of HPA is compensated by the proton localized on one of the six bridging O atoms. In the Mo₂O₉ doubled octahedra, the Mo–O bonds with the О atoms bonded to E(IV) and forming the edge of the common face are sensitive to the kind of the central atom.     

Elastic, structural, bonding, and defect properties of zinc-blende BN, AlN, GaN, InN and their alloys

Simple tight-binding simulations, incorporating only the Herman–Skillman atomic term values, are shown to provide valuable information about the bonding, elastic and structural properties of zinc-blende group III-nitrides. Our calculated values of the elastic parameters (viz., bulk modulus, elastic stiffness constants, Kleinman's internal displacement parameter, Keating force constants, etc.) for BN, AlN, GaN, and InN are shown to exist well within the range of values derived from more sophisticated methods. Despite the crude approximations used, the tight-binding method has clearly provided the meaningful trends to the local distortions around isoelectronic impurities and has described reasonably well the bond length variations as a function of composition in ternary alloys.     

Autonomy, security, and inequality: China, India, the United States, and the globalization of science and technology

Perhaps no three countries have benefited from the globalization of science and technology (S&T) more than India, China, and the United States. All three have leveraged the growing internationalization of innovation to offset weaknesses in their own national innovation systems. Still, globalization raises critical questions of autonomy, security, and equality, and in turn the political struggle over these three issues shapes the pace and scope of the globalization of S&T. Significant deterioration on any one of these criterion could lead to substantially less support among policy makers and the public for the globally networked system of innovation that appears to be emerging.     

Modeling the release, spreading, and burning of LNG, LPG, and gasoline on water

Current interest in the shipment of liquefied natural gas (LNG) has renewed the debate about the safety of shipping large volumes of flammable fuels. The size of a spreading pool following a release of LNG from an LNG tank ship has been the subject of numerous papers and studies dating back to the mid-1970s. Several papers have presented idealized views of how the LNG would be released and spread across a quiescent water surface. There is a considerable amount of publicly available material describing these idealized releases, but little discussion of how other flammable fuels would behave if released from similar sized ships. The purpose of this paper is to determine whether the models currently available from the United States Federal Energy Regulatory Commission (FERC) can be used to simulate the release, spreading, vaporization, and pool fire impacts for materials other than LNG, and if so, identify which material-specific parameters are required.

The review of the basic equations and principles in FERC's LNG release, spreading, and burning models did not reveal a critical fault that would prevent their use in evaluating the consequences of other flammable fluid releases. With the correct physical data, the models can be used with the same level of confidence for materials such as LPG and gasoline as they are for LNG.     

Densities,Viscosities, and Refractive Indices of Mixtures of Hexane with Cyclohexane,Decane, Hexadecane,and Squalane at 298.15 K

Densities, ρ, viscosities, η, and refractive indices, n_D, have been measured as a function of composition for binary mixtures of cyclohexane, decane, hexadecane, and squalane with hexane at 298.15 K and atmospheric pressure. From these measurements the excess molar volumes, V_m^E, viscosity deviations, δη, and the change in refractive indices on mixing, Δn_D, were calculated. These results were fitted to Redlick–Kister polynomial equations to estimate the binary coefficients and standard errors. The effects of size and shape of the components on excess properties have been discussed.     

The vapor pressure of indium,silver, gallium,copper, tin,and gold between 0.1 and 3.0 bar

The vapor pressure of several liquid metals was measured using a method based on the gas-controlled heat pipe. Small samples of the test material were placed in a tungsten tube and heated to temperatures above 2900 K. The vapor pressure was measured using a gas-buffered pressure transducer and the vapor temperature was inferred from the tube surface temperature, which was measured with an optical pyrometer. Most of the tests were terminated by the failure of the containment tube. The measured pressures agree well with those calculated by thermodynamic methods from data at lower temperatures.     

Optical properties of the metals Al, Co, Cu, Au, Fe, Pb, Ni, Pd, Pt, Ag, Ti, and W in the infrared and far infrared

Infrared optical constants collected from the literature are tabulated. The data for the noble metals and Al, Pb, and W can be reasonably fit using the Drude model. It is shown that -epsilon1(omega) = epsilon2(omega) approximately omega(2)(p)/(2omega(2)(tau)) at the damping frequency omega = omega(tau). Also -epsilon1(omega(tau)) approximately - (1/2) epsilon1(0), where the plasma frequency is omega(p).     

Properties, synthesis, and characterization of graphene

Graphene is a wonder material that attracts great interests in materials science and condensed matter physics. It is the thinnest material and also the strongest material ever measured. Its distinctive band structure and physical properties determine its bright application prospects. This review introduces briefly the properties and applications of graphene. Recent synthesis and characterization methods are summarized in detail, and the future research direction is also pointed out in this paper.     

制冷剂的过去、现状和未来

回顾了制冷剂发展的三个历史阶段,综述了适应环保需要的国外制冷剂现状和使用中的主要技术问题,探讨了制冷剂未来发展趋势以及所应面对的几个问题,最后提出了相应的对策建议。     

Solubilities of ethylene,ethane, and carbon dioxide in mixed solvents consisting of methanol,acetone, and water

The amount of gas absorbed in a liquid solvent or solvent mixture is measured with a high-precision gas burette. Solubility coefficients (Henry and Ostwald coefficients) of C₂H₄ and C₂H₆ are determined at ambient temperature and atmospheric pressure (1) in the pure solvents C₃H₆O, CH₃OH, and H₂O; (2) in the three binary mixtures of the solvents as a function of the composition of the solvent mixture; and (3) in several ternary mixtures of arbitrary composition. The experimental data are presented in diagrams and tables.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Degradability and Clearance of Silicon,Organosilica, Silsesquioxane,Silica Mixed Oxide,and Mesoporous Silica Nanoparticles

The biorelated degradability and clearance of siliceous nanomaterials have been questioned worldwide, since they are crucial prerequisites for the successful translation in clinics. Typically, the degradability and biocompatibility of mesoporous silica nanoparticles (MSNs) have been an ongoing discussion in research circles. The reason for such a concern is that approved pharmaceutical products must not accumulate in the human body, to prevent severe and unpredictable side‐effects. Here, the biorelated degradability and clearance of silicon and silica nanoparticles (NPs) are comprehensively summarized. The influence of the size, morphology, surface area, pore size, and surface functional groups, to name a few, on the degradability of silicon and silica NPs is described. The noncovalent organic doping of silica and the covalent incorporation of either hydrolytically stable or redox‐ and enzymatically cleavable silsesquioxanes is then described for organosilica, bridged silsesquioxane (BS), and periodic mesoporous organosilica (PMO) NPs. Inorganically doped silica particles such as calcium‐, iron‐, manganese‐, and zirconium‐doped NPs, also have radically different hydrolytic stabilities. To conclude, the degradability and clearance timelines of various siliceous nanomaterials are compared and it is highlighted that researchers can select a specific nanomaterial in this large family according to the targeted applications and the required clearance kinetics.     

Growth, characterization, and properties of nanographene

A systematic study on nanographene grown directly on silicon dioxide substrates is reported. The growth is carried out in a remote plasma-enhanced chemical vapor deposition system at a low temperature of around 550 °C with methane gas as the carbon source. Atomic force microscopy is used to characterize the nanographene morphology, and Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning tunneling microscopy are exploited to identify the in-plane sp(2) bonding structures of nanographene samples. Electrical transport properties are measured at various temperatures down to 4 K. Tunneling effects, minimal conductance at the charge-neutral point, sheet resistances, and Dirac point position at different channel lengths are investigated. In addition, nanographene film possesses high transmittance properties, as indicated by transmittance spectra. Nanographene devices are fabricated from rippled structures, and show great promise for strain-gauge sensor applications.     

Properties,synthesis, and characterization of graphene

Graphene is a wonder material that attracts great interests in materials science and condensed matter physics. It is the thinnest material and also the strongest material ever measured. Its distinctive band structure and physical properties determine its bright application prospects. This review introduces briefly the properties and applications of graphene. Recent synthesis and characteri-zation methods are summarized in detail, and the future research direction is also pointed out in this paper.