Several Aspects of Application of Nanodiamonds as Reinforcements for Metal Matrix Composites

After detonation synthesis, primary nanodiamond particles are around 4–6 nm in size. However, they join into agglomerates with larger parameters and weak bonds between particles. The introduction of agglomerates into a metal matrix can lead to the weakness of composites. This paper demonstrates the possibility of obtaining a non-agglomerated distribution of nanodiamonds inside a metal matrix. The fabrication method was based on mechanical alloying to create additional stresses and deformations by phase transformations during treatment in a planetary mill. According to the findings, the starting temperature of the reaction between the non-agglomerated nanodiamonds and aluminium matrix reduces to 450 °C. Furthermore, the paper shows that existing methods (annealing for the transformation of a diamond structure into graphitic material and cleaning from this graphitic material) cannot reduce the sizes of nanodiamonds in the agglomerated state. Agglomerated nanodiamonds transform into carbon onions (graphitic material) during annealing in a vacuum in the following way: the nanodiamonds located in the surface layers of the agglomerate are the first to undergo the complete transformation followed by the transformation of nanoparticles in its deeper layers. In the intermediate state, the agglomerate has a graphitic surface layer and a core from nanodiamonds: cleaning from graphite cannot reduce nanodiamond particle size.

Removal of diclofenac from aqueous solutions by adsorption on thermo-plasma expanded graphite

The adsorption of diclofenac on thermo-plasma expanded graphite (a commercial product) from water solutions was investigated. The adsorbent material was characterized by SEM, TEM, BET, Raman and X-ray diffraction analyses. Typical diffractogram and Raman spectrum of graphitic material, dimension of 24.02 nm as crystallite dimension and a surface area of 47 m2 g−1 were obtained. The effect of pH on the adsorption capacity was evaluated in the range 1–7 and the adsorption mechanism was described by kinetic and isothermal studies. Pseudo-second order and Dubinin–Radushkevich models agreed with theoretical values of adsorption capacity (i.e. 400 and 433 mg g−1, respectively) and resulted to be the best fit for kinetics and isothermal experimental data. The thermodynamics of the process was evaluated by plotting the adsorption capacity/concentration ratio at the equilibrium as a function of different values of the multiplicative inverse of temperature. Moreover, the adsorbent regeneration was also investigated, comparing two different remediation techniques. Solvent washing performed with NaOH 0.2 M and thermo-treatment carried out by heating in an oven at 105 °C for 2 h and then at 200 °C for 4 h. The thermo-treatment was the best technique to regenerate the adsorbent, ensuring same performance after 4 cycles of use and regeneration.

Examining Slit Pore Widths within Plasma-Exfoliated Graphitic Material Utilising Barret-Joyner-Halenda Analysis

Plasma-exfoliated multilayer graphitic material (MLG) consists of orderly aligned stacks which contain many partially oxidised graphitic layers. Slit pores are present between successive stacks and their presence allows for improved...

Graphene Layers Functionalized with A Janus Pyrrole-Based Compound in Natural Rubber Nanocomposites with Improved Ultimate and Fracture Properties

The ultimate properties and resistance to fracture of nanocomposites based on poly(1,4-cis-isoprene) from Hevea Brasiliensis (natural rubber, NR) and a high surface area nanosized graphite (HSAG) were improved by using HSAG functionalized with 2-(2,5-dimethyl-1H-pyrrol-1-yl)propane-1,3-diol (serinol pyrrole) (HSAG-SP). The functionalization reaction occurred through a domino process, by simply mixing HSAG and serinol pyrrole and heating at 180 °C. The polarity of HSAG-SP allowed its dispersion in NR latex and the isolation of NR/HSAG-SP masterbatches via coagulation. Nanocomposites, based either on pristine HSAG or on HSAG-SP, were prepared through traditional melt blending and cured with a sulphur-based system. The samples containing HSAG-SP revealed ultimate dispersion of the graphitic filler with smaller aggregates and higher amounts of few layers stacks and isolated layers, as revealed by transmission electron microscopy. With HSAG-SP, better stress and elongation at break and higher fracture resistance were obtained. Indeed, in the case of HSAG-SP-based composites, fracture occurred at larger deformation and with higher values of load and, at the highest filler content (24 phr), deviation of fracture propagation was observed. These results have been obtained with a moderate functionalization of the graphene layers (about 5%) and normal lab facilities. This work reveals a simple and scalable way to prepare tougher NR-based nanocomposites and indicates that the dispersion of a graphitic material in a rubber matrix can be improved without using an extra-amount of mechanical energy, just by modifying the chemical nature of the graphitic material through a sustainable process, avoiding the traditional complex approach, which implies oxidation to graphite oxide and subsequent partial reduction.

Extraterrestrial, shock-formed, cage-like nanostructured carbonaceous materials

Shock caused by impacts can convert carbonaceous material to diamond. During this transition, new materials can form that depend on the structure of the starting carbonaceous materials and the shock conditions. Here we report the discovery of cage-like nanostructured carbonaceous materials, including carbon nano-onions and bucky-diamonds, formed through extraterrestrial impacts in the Gujba (CBa) meteorite. The nano-onions are fullerene-type materials and range from 5 to 20 nm; the majority shows a graphitic core-shell structure, and some are characterized by fully curved, onion-like graphitic shells. The core is either filled with carbonaceous material or empty. We show the first, natural, 4 nm sized bucky-diamond, which is a type of carbon nano-onion consisting of multilayer graphitic shells surrounding a diamond core. We propose that the nano-onions formed during shock metamorphism, either the shock or the release wave, of the pre-existing primitive carbonaceous material that included nanodiamonds, poorly ordered graphitic material, and amorphous carbonaceous nanospheres. Bucky-diamonds could have formed either through the high-pressure transformation of nano-onions, or as an intermediate material in the high-temperature transformation of nanodiamond to nano-onion. Impact processing of planetary materials was and is a common process in our solar system, and by extension, throughout extrasolar planetary bodies. Together with our previous discovery of interstratified graphite-diamond in Gujba, our new findings extend the range of nano-structured carbonaceous materials formed in nature. Shock-formed nano-onions and bucky-diamonds are fullerene-type structures, and as such they could contribute to the astronomical 217.5 nm absorption feature.