Influence of additional UV-light illumination on preparation of TiN by ion beam assisted deposition

Titanium nitride films were prepared by a newly developed photon and ion beam assisted deposition system at room temperature. Titanium was deposited on Si(111) in a controlled nitrogen environment and simultaneously bombarded with low-energy N ions or illuminated with UV-light. The influence of UV-light illumination during deposition is compared with the influence of ion bombardment on film properties like structure, topography and composition, measured by XRD, AFM and ERD, respectively. The results demonstrate that photon assisted deposition (PHAD) is also a good method to modify film characteristics like ion beam assisted deposition (IBAD).     

Oxygen-free precursor for chemical vapor deposition of gold films: thermal properties and decomposition mechanism

Thermal properties of oxygen-, phosphorus-, and halogen-free dimethylgold(III) diethyldithiocarbamate complex (CH₃)₂AuS₂CN(C₂H₅)₂ (gold, dimethyl(diethylcarbamodithioato -S,S′)-) having excellent storage stability and the mechanism of its decomposition to elemental gold were studied. Saturated vapor pressure was found to be ~10⁻³–10⁻¹ Torr at 50–90°C. Decomposition of the vapor on the surface starts at T = 210°C. The temperature dependence of gas phase composition was studied using the original mass spectrometric technique, it was established that the decomposition of the compound on the surface in vacuum follows three main pathways. Two of them result in the formation of elemental gold, saturated C2–C4 alkanes and (1) protonated ligand or (2) methylated ligand. The third one results in elemental gold and gaseous products: C2–C3 alkylmercaptanes and CH₃SCN(C₂H₅)₂. The formation of gold as a sole solid product within the temperature range 210–240°C was confirmed by X-ray photoelectron spectroscopy analysis. It was shown that the compound exhibits the best combination of volatility, thermal, and storage stability among volatile organogold complexes and thus it may be a promising precursor for obtaining gold films by chemical vapor deposition.     

Tensile behavior of polyolefin composites: the effect of matrix parameters

Polyolefin composites were prepared from 14 PE matrices and three different mineral fillers (montmorillonite, palygorskite and glass microspheres) via melt compounding in an extruder. Mechanical properties of the obtained systems were analyzed with emphasis on elongation at break and conditions for ductile/brittle failure were determined. When filler content is raised beyond a certain “critical” value, tensile properties are dramatically altered and transition occurs from ductile behavior to brittle fracture. This transition is displayed by a well‐defined “step” on the plot of strain at break versus concentration of particles. The value of “critical filler content” was found to depend mainly on level of crystallinity of a matrix while other parameters (chemical nature of filler particles, their size, shape and surface treatment) are less significant. “Critical filler content” will decrease with growth of crystallinity of a polymer and with highly crystalline HDPEs it is as low as 2–8 vol %. Otherwise, with noncrystallizing and low‐crystalline polymers elongation at break decreases gradually with concentration of mineral particles and ductile type deformation is maintained at fairly large filler fractions. The results presented here will be useful for a proper selection of a matrix polymer in composites with mineral fillers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43819.     

Acyl Poly(Glycerol-Succinic Acid) Oligoesters: Synthesis,Physicochemical and Functional Properties,and Biodegradability

Biobased surfactants were synthesized using poly(glycerol-succinate) as the polar head group and variable acyl groups as hydrophobic tails. Acyl chain lengths ranged from 8 to 14 carbon atoms. The resulting oligomeric surfactants were characterized by quantitative ¹³C nuclear magnetic resonance (NMR), acid values and size exclusion chromatography. Investigation of the physicochemical properties of the acyl poly(glycerol-succinate) surfactants revealed their potential for use in a wide array of applications. The acyl poly(glycerol-succinate) functional properties appeared to be particularly concentration-dependent. This study highlights the relative impact of acyl chain length on the polymeric structure, physicochemical and functional behaviors, and biodegradability of the acyl poly(glycerol-succinate) surfactants.     

Illuminant metamerism potentiality of metameric pairs

Indices for describing the degree of metamerism are based on either the deviation of the spectra of a metameric pair or the colour difference of the pair under test conditions. The magnitude of illuminant metamerism is commonly evaluated by measuring the colour difference under the test illuminant. The calculated colour differences absolutely vary with the selected test illuminants, so the measured (special) index of metamerism could be considered as a test‐illuminant‐dependent value. The spectral‐based indices of metamerism act as a single‐number value, but most of them are criticised for their poor correlation with visual assessment. In this paper, a general metric is developed for evaluating the upper limit of the degree of illuminant metamerism. The suggested approach combines the advantages of general and special indices, avoiding their drawbacks at the same time. The performance of the formula is analysed in a number of numerical experiments, as well as by practical testing.     

MICROWAVE INDUCED CONVERSION OF HYDROGEN SULFIDE

Abstract

The reaction of hydrogen sulfide with trona and calcium oxide in the presence of char started as soon as microwave energy was applied. However, with conventional heating, the reaction started only when the bed temperature reached approximately 540^°c. char absorbing microwave energy is rapidly heated to very high temperatures, enhancing the H₂S reaction with oxides contained in char or oxides added to char in the reaction. A 100% conversion of trona was achieved but the maximum conversion of calcium oxide was only 79%. The minimum content of char required to induce the reaction of H₂S with trona using microwave energy was 20% of char-trona mixture. When the trona content in the mixture of char-trona mixture was greater than 50%, an additional conversion of H₂S occurred to produce some amount of elemental sulfur that was deposited in the bed. This clearly demonstrates that char combined with microwave induces H₂S reaction with mineral oxides.     

Determination of Mass Transfer Coefficients During the Vacuum Cooling of Pre-Cooked Meat Cuts

The influence of meat sample dimensions on the mass transfer coefficient (kS) of precooked cuts of pork, beef, and chicken during vacuum cooling, as well the behavior of this coefficient during the vacuum cooling process, were investigated. It was evidenced that the kS parameter presented statistical correlations with sample volume. The strongest dependence was found for precooked breast chicken, showing that this product can be cooled by vacuum impregnation. Knowledge of this dependence is important in order to evaluate the dimensions and geometric formats of meat cuts to be treated by vacuum cooling. Experiments with cylinders filled with moist sand showed that for porous materials kS can be considered proportional to the sample volume, and that the initial moisture content influences the internal temperatures during the cooling process. Knowledge of the kS behavior, with respect to sample volume, aids an understanding of the water evaporation and temperature decrease during the vacuum cooling of porous foods.     

Metal-assisted hydrogen storage on Pt-decorated single-walled carbon nanohorns

The catalytic dissociation of hydrogen molecules by metal nanoparticles and spillover of atomic hydrogen onto various supports is a well-established phenomenon in catalysis. However, the mechanisms by which metal catalyst nanoparticles can assist in enhanced hydrogen storage on high-surface area supports are still under debate. Experimental measurements of metal-assisted hydrogen storage have been hampered by inaccurate estimation of atomically stored hydrogen deduced from comparative measurements between metal-decorated and undecorated samples. Here we report a temperature cycling technique combined with inelastic neutron scattering (INS) measurements of quantum rotational transitions of molecular H₂ to more accurately quantify adsorbed hydrogen aided by catalytic particles using single samples. Temperature cycling measurements on single-wall carbon nanohorns (SWCNHs) decorated with 2–3 nm Pt nanoparticles showed 0.17% mass fraction of metal-assisted hydrogen storage (at ≈0.5 MPa) at room temperature. Temperature cycling of Pt-decorated SWCNHs using a Sievert’s apparatus also indicated metal-assisted hydrogen adsorption of ≈0.08% mass fraction at 5 MPa at room temperature. No additional metal-assisted hydrogen storage was observed in SWCNH samples without Pt nanoparticles cycled to room temperature. The possible formation of C–H bonds due to spilled-over atomic hydrogen was also investigated using both INS and density functional theory calculations.     

Molecular characteristics of native sago starch and isolated fractions determined using asymmetrical flow field‐flow fractionation

The apparent average molar masses (M_w,app), apparent average radii of gyration (R_g,app), of native sago starch and fractions were determined using asymmetrical flow field‐flow fractionation coupled with multi‐angle light scattering and refractive index detectors (AF4/MALS/RI). Amylose‐type (Fraction A) and amylopectin‐type (Fraction B) were chemically separated from native sago starch. Native sago starch and Fractions (A–B) were dissolved in 1M KSCN using a high pressure microwave vessel. The effect of varying cross flow rates at a fixed channel flow rate upon the M_w,app and R_g,app distributions of native sago starch and Fractions (A–B) were investigated. The average M_w,app values of native sago starch, Fraction (A) and Fraction (B) were 60 × 10⁶, 1.5 × 10⁶ and 60 × 10⁶ g/mol, respectively, with average R_g,app values of 142, 75 and 127 nm, respectively. The sphere‐equivalent hydrodynamic radii (R_h) values for native sago starch and fractions were determined from AF4 experimental parameters.