Nanofibrous carbon with herringbone structure as an effective catalyst of the H2S selective oxidation

Granular nanofibrous carbons (NFCs) with herringbone structure were synthesised by the decomposition of natural gas over Ni/Al2O3 catalysts, and their performance in the selective oxidation of hydrogen sulphide was studied. Samples obtained over pure Ni catalysts are the strongest mechanically and easiest to produce. However, they show low selectivity for sulphur and are unstable during operation. Boiling in nitric acid followed by annealing led to improvements in catalytic stability and a significant increase in the selectivity for sulphur in the direct oxidation of hydrogen sulphide. The addition of large amounts of water vapour to the reaction mixture dramatically improved the selectivity and stability of the NFCs. © 2010 Elsevier Ltd. All rights reserved

Synthesis of Black Phosphorene Quantum Dots from Red Phosphorus

Phosphorene quantum dots (PQDs) are most commonly derived from high-cost black phosphorus, while previous syntheses from the low-cost red phosphorus (Pred) allotrope are highly oxidised. Herein, we present an intrinsically scalable method to producing high quality PQDs, by first ball-milling Pred to create nanocrystalline Pblack and subsequent reductive etching using lithium electride solvated in liquid ammonia. The resultant ~25 nm PQDs are crystalline with low oxygen content, and spontaneously soluble as individualized monolayers in tertiary amide solvents, as directly imaged by liquid-phase transmission electron microscopy. This new method presents a scalable route to producing quantities of high quality PQDs for academic and industrial applications

Reactive ball milling to produce nanocrystalline ZnO

Ball milling of zinc powders in oxygen atmosphere leads to nanocrystalline ZnO. The average grain size has a value of 9 nm. The zinc oxidation proceeds gradually. It is compared with the combustion oxidation reactions of metals (Zr, Ti, Fe and Sn) reported previously. We propose a new parameter &Delta;H/Cp(metal) instead of simplified adiabatic temperature to judge if the mechanochemical oxidation of a particular metal happens via gradual or combustion reaction.<br /

Anomalous evaporation behavior of ZnO powder milled mechanically under high-energy conditions

ZnO powder showed anomalous evaporation behavior after its mechanical milling treatment under high-energy conditions. The amount of generated vapor is about 10 times higher in the first 15 min of annealing at 1300 &deg;C than that of unmilled ZnO powders. The strong ball impacts are responsible for the greatly enhanced evaporation ability. Low-energy ball milling involving shearing actions and rare weak impacts leads only to a small evaporation rate enhancement. The possible explanation of the high evaporation rate of the heavily milled material is the existence of large fraction of weakly bonded atoms in grain boundaries, surface defects and strained areas.<br /

The influence of inert impurities on the catalyst lifetime and properties of nanofibrous carbon produced by utilization of diluted hydrocarbon gases

Experimental studies were focused on the feasibility of utilization of hydrocarbons diluted with inert gases (such as associated oil gases) during the synthesis of nanofibrous carbon. The carbon yield and catalyst lifetime were studied regarding the initial reaction mixture parameters. Varying the composition of the initial gas mixture, it is possible to control textural characteristics of the resulting carbon product. <br /

Titanium dioxide nanotube films for electrochemical supercapacitors: biocompatibility and operation in an electrolyte based on a physiological fluid

Growing interest in developing devices that can be implantable or wearable requires the identification of suitable materials for the components of these devices. Electrochemical supercapacitors are not the exception in this trend, and identifying electrode materials that can be not only suitable for the capacitive device but also biocompatible at the same time is important. In addition, it would be advantageous if physiological fluids could be used instead of more conventional (and often corrosive) electrolytes for implantable or wearable supercapacitors. In this study, we assess the biocompatibility of films of anodized TiO2 nanotubes subjected to the subsequent annealing in Ar atmosphere and evaluate their capacitive performance in a physiological liquid. A biocompatibility test tracking cell proliferation on TiO2 nanotube electrodes and electrochemical tests in 0.01 M phosphate-buffered saline solution are discussed. It is expected that the study will stimulate further developments in this area

Methane to ethylene by pulsed compression

Pulsed compression is introduced for the conversion of methane, by pyrolysis, into ethylene. At the point of maximal compression temperatures of 900 to 1620 K were reached, while the initial and final temperature of the gas did not exceed 523 K. By the use of a free piston reactor concept pressures of up to 460 bar were measured with nitrogen as a diluting gas. From 1100 K onwards methane conversion was measured. By increasing the temperature, the mechanism of pyrolytic methane conversion, being subsequent production of ethane, ethylene, acetylene, …, benzene, and ultimately tar/soot, was clearly observed. Without hydrogen in the feed, the attainable operating window (C2-selectivity vs. methane conversion) observed was similar to other catalytic oxidative and non-oxidative coupling processes. With hydrogen, in a first attempt to optimize the product yield, 24% C2-yield (62% ethylene selectivity, 93% C2-selectivity) at 26% conversion was reached without producing observable soot. It is worthwhile to explore pulsed compression further because it does not require a catalyst and therefore, does not deactivate over time and it operates at low reactor temperature

In situ doping and synthesis of two-dimensional nanomaterials using mechano-chemistry

Doping foreign atoms into materials can modify their electronic configuration and tune their chemical and physical properties. Developing an efficient doping strategy is thus critically important for many new applications of two-dimensional (2D) nanomaterials. Here, we report an in situ process to produce and simultaneously dope carbon and nitrogen in a number of 2D materials including graphene, BN, MoS 2 and WS 2 using mechanochemistry. This new process produces large quantities of 2D materials with controlled doping contents and new properties

Efficient production of ZnO nanowires by a ball milling and annealing method

ZnO powder was mechanically milled in a ball mill. This procedure was found to greatly increase its evaporation ability. The anomalous evaporation behaviour was caused by the disordered structure of the milled material and was not related to the increase in its surface area after milling. ZnO nanowires were synthesized by evaporation of this milled precursor. Nanowires with smooth and rough surfaces were present in the sample; the latter morphology was dominant. A green emission band centred at 510 nm was dominant in the cathodoluminescence spectrum of the nanowires.<br /