The physical–chemical study of detonation nanodiamond application in adsorption and chromatography

In the present work, the study on detonation nanodiamond (DND) powders modifications in gaseous media was carried out. The surface properties of DND were studied by TGA, IR-spectroscopy, pH-potentiometry and chromatography methods. It was determined that modifying the DND surface reduces specific retention volumes and retention times of adsorbates. At the same time, specific and dispersion interactions have decreased. Such phenomena are significant for gas chromatographic separation of complex mixtures. The study of DND in contact with water and water solutions showed that chemical modification of DND produces on its surface oxygen-containing groups with acidic character. The latter stipulates its ion-exchange properties and applicability to liquid chromatography. In summary, the performed research provides significant perspective toward new-generation adsorbent creation with controlled surface identification for gaseous and liquid chromatography purposes.     

Diamond-like carbon deposited by plasma technique as a function of methane flow rate

Diamond-like carbon (a-C:H) prepared by plasma enhanced chemical vapor deposition (PECVD) as a function of methane gas flow rate is reported. Films deposited at zero flow rate, i.e., without the use of vacuum pumps during the deposition, are also investigated. For that purpose, the reactor chamber was baked and pumped down to about 10^?8 Torr to reduce contamination released from the reactor walls. The films were analyzed by visible, infrared and Raman spectroscopes. It was observed that the deposition rate, hydrogen concentration and optical gap depend on the methane gas flow rate. A maximum for deposition rate found at methane flow was much smaller than the flow usually adopted in conventional procedures.     

Surface analysis of CVD diamond exposed to fusion plasma

Microcrystalline undoped and heavily boron-doped polycrystalline diamond layers have been deposited on various substrates by hot filament CVD and exposed to hydrogen plasma in a linear plasma reactor (Pilot-PSI, The Netherlands) that simulates the high flux and high density plasma conditions of tokamak divertors, as well as in the DIII-D tokamak (US). Pre- and post-exposure analysis by SEM and Raman spectroscopy characterised the surface appearance and the sp³ and sp² components of the diamond films respectively. Surface roughness variation was measured by AFM. Hardness and Young's modulus were assessed by nanoindentation in order to characterise the effect of the plasma on the mechanical properties. HRTEM and EELS have been used to evaluate the nature of the modification induced at the diamond surface by the plasma exposure. The measurements have shown that, despite some surface amorphisation of the exposed layers, further long-term exposure studies are warranted as neither delamination, dramatic film failure nor entire erosion of the film were observed.     

Boron and nitrogen functionalized diamondoids: A first principles investigation

Chemically functionalized adamantane molecules have been investigated by first principles total energy calculations. Boron and nitrogen functionalized molecules were found to be very stable, consistent with available experimental data. Two hypothetical molecular crystals, involving functionalized adamantane, were investigated. These molecular crystals presented direct electronic bandgaps and large bulk moduli, which suggested a possible road for molecular self-assembly using functionalized diamondoids.     

Relating Complex Fluid Composition and Thermophysical Properties with the Advanced Distillation Curve Approach

Complex fluids have long posed a significant challenge in our ability to characterize and model fluid properties. Here, we consider complex fluids to be mixtures with many components that can differ significantly in polarity and polarizability. The penultimate complex fluid is crude oil, although many other fluids such as finished fuels are also highly complex. We have recently introduced a measurement strategy that can simplify these efforts and provides the added potential of linking chemical composition (i.e. analytical) information with physical property information. In addition to chemical characterization, the approach provides the ability to calculate thermodynamic and transport properties for such complex heterogeneous streams. The technique is based on the advanced distillation curve (ADC) metrology, which separates a complex fluid by distillation into fractions that are sampled, and for which thermodynamically consistent temperatures are measured at atmospheric pressure. The collected sample fractions can be analyzed by any method that is appropriate. Analytical methods we have applied include gas chromatography (with flame ionization, mass spectrometric and sulfur chemiluminescence detection), thin‐layer chromatography, FTIR, Karl Fischer coulombic titrimetry, refractometry, corrosivity analysis, neutron activation analysis and cold neutron prompt gamma activation analysis. We have applied this method on product streams such as finished fuels (gasoline, diesel fuels, aviation fuels, rocket propellants), crude oils (including a crude oil made from swine manure) and waste oil streams (used automotive and transformer oils). In this review, we describe the essential features of the ADC metrology with illustrative examples.     

Selective Adsorption of Adenosine and Guanosine by a β‐Cyclodextrin/Layered Double Hydroxide Intercalation Compound

A film of carboxymethyl‐β‐cyclodextrin‐intercalated Zn–Al layered double hydroxide (CMCD–LDH) was investigated for selective adsorption of the nucleosides adenosine (A) and guanosine (G). The effects of pH value and adsorption time on the adsorption behavior were studied. The CMCD–LDH film shows a higher selectivity for G than A under identical conditions of G and A, which results from the ability of selective recognition of the interlayer CMCD. The kinetic studies show that adsorption of A and G by the CMCD–LDH film can be described satisfactorily by the slab diffusion model. Both the values of diffusion coefficient (D) and adsorption capability (q_e) of G by the CMCD–LDH film are larger than those of A, demonstrating the selective adsorption of the CMCD–LDH film for nucleosides. Due to its easy preparation and manipulation, this film is expected to be successfully applied in the field of selective adsorption and separation.     

Partial hydrogenation of propyne over copper-based catalysts and comparison with nickel-based analogues

The partial hydrogenation of propyne was studied over copper-based catalysts derived from Cu–Al hydrotalcite and malachite precursors and compared with supported systems (Cu/Al₂O₃ and Cu/SiO₂). The as-synthesized samples and the materials derived from calcination and reduction were characterized by XRF, XRD, TGA, TEM, N₂ adsorption, H₂-TPR, XPS, and N₂O pulse chemisorption. Catalytic tests were carried out in a continuous flow-reactor at ambient pressure and 423–523 K using H₂:C₃H₄ ratios of 1–12 and were complemented by operando DRIFTS experiments. The propyne conversion and propene selectivity correlated with the copper dispersion, which varied with the type of precursor or support and the calcination and reduction temperatures. The highest exposed copper surface was attained on hydrotalcite-derived catalysts, which displayed C₃H₆ selectivity up to 80% at full C₃H₄ conversion and stable performance in long-run tests at T ? 473 K. Both activated Cu–Al hydrotalcites (this work) and Ni–Al hydrotalcites [S. Abelló, D. Verboekend, B. Bridier, J. Pérez-Ramírez, J. Catal. 259 (2008) 85] exhibited a relatively high alkene selectivity under optimal operation conditions, but they present a markedly distinctive catalytic behavior with respect to temperature and hydrogen-to-alkyne ratio. The product distribution was assigned through Density Functional Theory (DFT) simulations to the different stability of subsurface phases (carbides, hydrides) and the energies and barriers for the competing reaction mechanisms. The behavior of Cu in partial alkyne hydrogenation resembles that of Au nanoparticles, while Ni is closer to Pd.     

Nanostructured alumina particles synthesized by the Spray Pyrolysis method: microstructural and morphological analyses

Ultrafine particles or nanoparticles (ranging from a few nanometers to 100 nm) are of considerable interest for a wide variety of applications, ranking from catalyst to luminescence ceramics, due to their unique and improved properties primarily determined by size, composition and structure. This study presents the preparation and characterization of nanostructured spherical alumina particles by the Spray Pyrolysis method for the application in reinforcements of metal-matrix composites (MMCs). Synthesis procedure includes aerosol formation ultrasonically from alumina nitrate water solution and its decomposition into a tubular flow reactor at 700 °C. The obtained particles are spherical, smooth, amorphous and in non-agglomerated state. Microstructural and morphological analyses were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM/EDS) and analytical and high resolution transmission electron microscopy (TEM/HRTEM).     

Surfactant-free hydrothermal synthesis and characterization of single-crystal K2V8O21 nanobelts

Single-crystal K₂V₈O₂₁ nanobelts were prepared from the reaction between V₂O₅ and KHSO₄ under hydrothermal condition using no surfactant or template. The synthesized nanobelts were characterized by X-ray diffraction, X-ray photon-electron spectrometry, scanning electron microscopy, and transmission electron microscopy. The nanobelts are single-crystalline in nature, and have typical width of 100–500 nm, thickness of less than 100 nm and length up to a few tens of microns. The effects of solution concentration, reaction temperature and molar ratio of K and V on the morphology and phase component of the obtained products have been investigated. The possible formation mechanism was also discussed.