Surface Chemical Composition Of Particles Research Articles

The influence of surface chemical composition of particles of boron carbide powders on their biological properties

The aim of this study was to explain differences in the biological behaviour of two boron carbide powders prepared by different synthesis methods. The commercial powder HD had a lower boron content in comparison to the synthesized powder SP. The analysis both powders surface confirmed the higher content of B-C bonds but the presence of heteroatomic B-C-O bonds indicating the oxide passivation of the surface of particles of only HD powder. On the other hand, the SP powder contains more boron in the volume as well as on the surface of particles. These differences facilitated the interaction between the carbide particles with the proteins in the culture medium. Proteins from the culture medium and active collagen peptides were more easily adsorbed to the surface of the synthesized powder particles, which was evidenced by new bands appearing in the spectrum. This translated into an increasing hydrophilicity of the synthesized boron carbide powder. The presence of proteins on the surface of the powder facilitated the cells adhesion of macrophages and fibroblasts. The synthesized boron carbide powder improved the macrophage functional status; the cells were characterized by high viability and low cytotoxicity as well as the correct morphology.

Wettability of micron/submicron-sized particles in oilsands bitumen characterized by suspension turbidity

Determination of the wettability of micron/sub-micron sized particles remains a great challenge. The present work proposes a new approach to evaluate the particle wettability by measuring the turbidity of particle suspension. The fine solid samples with varying wettability were prepared by hydrothermal treatment of oilsands bitumen at different temperatures. The turbidity of particle-in-toluene suspension was determined and correlated to the particle surface chemical composition, i.e., C/(Al + Si). A good linear relationship was observed between particle wettability and suspension turbidity. The results suggest suspension turbidity can be used to characterize the wettability of organically-modified fine solids in oilsands bitumen.

The improved thermal oxidative stability of silicone rubber by incorporating reduced graphene oxide: Impact factors and action mechanism

To investigate the impact factors and action mechanism for the improved thermal oxidative stability of silicone rubber (SR) by incorporating reduced graphene oxide (rGO), graphene oxide (GO), and rGO were prepared, and subsequently graphite, GO and different amounts of rGO were introduced into SR. Transmission electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction were performed to characterize morphology and surface chemical composition of particles (graphite, GO, and rGO). Scanning electron microscope and X‐ray diffraction were employed to investigate the dispersion of particles in the SR matrix. Moreover, the effect of morphology and surface chemical composition of particles on the thermal oxidative degradation of SR and the action mechanism were studied via measuring the mechanical properties and the average molecular weight between crosslinking points of the SR before and after aging, as well as utilizing thermogravimetric/infrared spectrometry. The results showed that rGO exhibited the largest exfoliation extent, few oxygen‐containing functional groups and better dispersion among these particles, causing the best thermal oxidative stability of rGO/SR nanocomposites, especially when its amount is 1 phr; incorporating rGO could increase the initial formation temperatures of pyrolysis products and decrease the concentrations of products from the oxidation and fracture of side groups of SR. POLYM. COMPOS., 39:1105–1115, 2018. © 2016 Society of Plastics Engineers

XPS surface chemical characterization of atmospheric particles of different sizes

Surface chemical composition of particles has a key role in determining the reactivity and optical properties of atmospheric aerosol. This composition depend on the particles sources and formation processes and it influences human health and climate. In this work, the X-ray photoelectron spectroscopy (XPS) has been used for the systematic surface characterization of atmospheric particles of different sizes, collected using a 10-stage MOUDI-II rotating cascade impactor in an urban background site. The high resolution XPS spectra allowed to distinguish different organic functional groups (C–C/CC, –C–O, –CO/-C(O)N, –C(O)O, C¯O3=) and to speciate the detectable hetero-elements, sulphur (S¯O42−, sulphone and sulphide compounds), nitrogen (N¯H4+, N¯O3−, N¯O2− and organic-nitrogen compounds), sodium (Na+) and chlorine (Cl−) species. Significant differences in particles belonging to accumulation (small particles) and coarse (large particles) modes were observed being due to the formation processes and sources from which particles originated. The oxygen concentrations is inversely correlated with carbon concentrations, however, the content of oxidized organic carbon is not correlated with oxygen content confirming that the oxygen increment observed in large particles can likely be attributed to the contribution of inorganic species (crustal origin). The speciation of nitrogen showed ammonium only in the accumulation mode and nitrate only in coarse mode excluding the presence of ammonium nitrate of secondary origin in the area studied. A correlation of Na and Cl was attributed to the marine contribution with an excess of Cl on the surface correlated with the depletion of Cl observed in the bulk of particles.