Renaud Metz

Life cycle assessment of nanocomposites made of thermally conductive graphite nanoplatelets

PurposePolymers typically have intrinsic thermal conductivity much lower than other materials. Enhancement of this property may be obtained by the addition of conductive fillers. Nanofillers are preferred to traditional ones, due to their low percolation threshold resulting from their high aspect ratio. Beyond these considerations, it is imperative that the development of such new fillers takes place in a safe and sustainable manner. A conventional life cycle assessment (LCA) has been conducted on epoxy-based composites, filled with graphite nanoplatelets (GnP). In particular, this study focuses on energy requirements for the production of such composites, in order to stress environmental hot spots and primary energy of GnP production process (nano-wastes and nanoparticles emissions are not included).MethodsA cradle-to-grave approach has been employed for this assessment, in an attributional modeling perspective. The data for the LCA have been gathered from both laboratory data and bibliographic references. A technical LCA software package, SimaPro (SimaPro 7.3), which contains Ecoinvent (2010) life cycle inventory (LCI) database, has been used for the life cycle impact assessment (LCIA), studying 13 mid-point indicators. Sensitivity and uncertainty analyses have also been performed.Results and discussionOne kilogram of GnP filler requires 1,879xa0MJ of primary energy while the preparation of 1xa0kg of epoxy composite loaded with 0.058xa0kg of GnP 303xa0MJ. Besides energy consumption in the filler preparation, it is shown that the thermoset matrix material has also a non-negligible impact on the life cycle despite the use of GnP: the primary energy required to make epoxy resin is 187xa0MJ, i.e., 62xa0% of the total energy to make 1xa0kg of composite.ConclusionsRaw material extraction and filler and resin preparation phase exhibit the highest environmental impact while the composite production is negligible. Thermosetting resin remains the highest primary energy demand when used as matrix for GnP fillers. The result of the sensitivity analysis carried out on the electricity mix used during the GnP and the composite production processes does not affect the conclusions.

MAX phase ternary carbide derived 2-D ceramic nanostructures [CDCN] as chemically interactive functional fillers for damage tolerant epoxy polymer nanocomposites

A 2-dimensional ceramic nanostructure was successfully processed out of nanolamellar 312 MAX phase ternary carbide, titanium silicon carbide, Ti3SiC2 (TSC), via a simple shear-induced delamination technique. It has been explored as a functional nanofiller for obtaining chemically homogeneous, low-friction, self-lubricating epoxy nanocomposites. The structural characterization of the MAX phase Carbide Derived Ceramic Nanostructure (CDCN) was carried out using Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analysis. Subsequently, CDCN was mixed with Araldite CY 225 (DGEBA) at different percentages and thermally cured using Aradur HY 925 hardener at 130 °C to make epoxy–Ti3SiC2 nanocomposites. The effect of CDCN-nanofiller was studied on epoxy rheology, glass transition temperature (Tg), thermal stability, flexural and compressive strengths, microhardness, dry sliding wear and friction properties. It was found that, unlike other ceramic fillers, CDCN chemically interacts with epoxy and readily dispersed in a polymer matrix without any deleterious structural defects. It resulted in the formation of physico-chemically homogeneous microstructures. Epoxy composites prepared with CDCN filler attained 50% more mechanical strength and hardness. Wear analysis trends indicate Ti3SiC2 nano reinforcement possibly formed a lubricating tribo-chemical film that decreases the wear rate and coefficient of friction. This work is significant in such a way that a novel nanofiller has been identified from MAX phase carbide family which offers a self-lubricating interface and produces mechanically reliable, damage tolerant epoxy composite for state-of-the-art engineering applications.

Kinetics Model of the Thermal Oxidation of Indium Powder

The complete oxidation kinetics of indium powder in air has been studied from thermogravimetric studies under isothermal conditions in the range 858–1173xa0K. The influence of particle size was analyzed in the 25–375xa0μm range. We succeeded in carrying out the full oxidation of the powders far above the indium-metal melting point (429.75xa0K) without apparent coalescence of the particles through the presence of a thin In2O3 layer which confines the liquid metal during the oxidation process. The apparent activation energy obtained from the Arrhenius law was 62.2xa0kJxa0mol−1.

Recycling zinc oxide varistor blocks for electro-active silicone composites

Recycling route toward electro-active silicone composites has been explored. In this paper, a non-linear composite based on silicone and non-linear fillers has been studied. The dependence of the electric field and current density characteristics on the aggregate content in the polymer matrix has been analyzed. The non-linear composite has been optimized to get a percolation way by determination of rate and shape of filler. The waste of metal oxide varistor during processing could be used as non-linear filler. This opens a way to valorize varistor wastes to make a non-linear synthetic material to manage electrical field in a given area in insulator parts.

Life Cycle Assessment of Medium Surge Arresters in the Context of Size‐Reduction Design

Zinc oxide (ZnO) polycrystalline ceramics are the focal point of lightning arrester technology. These semiconductor materials are able to switch rapidly from high to low impedance while handling large amounts of electrical energy. Since the early 1970s, considerable efforts have been made to improve the specific energy absorption capacity and device reliability of such components. This document describes a case study carried out on the life cycle impacts of three different designs of electroceramics made of ZnO. Results show that the best design involves decreasing the diameter while maintaining the thickness of the compound. Of the production, transport, use, and end�?of�?life phases, the use phase is found to contribute by far the most to environmental impacts, with leakage currents in the 10−6 ampere range. The next�?largest impacts come in the transport and production stages. Sensitivity analysis shows that impacts associated with the production stage originate from ZnO production and are related to the by�?products (heavy metals) of zinc metallurgy.

First study of oxygen diffusion in a ZnO - based commercial varistor

Oxygen diffusion coefficients were determined in a commercial ZnO-based varistor by means of the gas-solid exchange method using the isotope 18O as the oxygen tracer. The diffusion annealings were performed at 892, 942, 992 and 1092oC, in an Ar + 18O2 atmosphere under an oxygen partial pressure of 0.2 atm. After the diffusion annealings, the 18O diffusion profiles were established by secondary ion mass spectrometry (SIMS). The results show an increase of the oxygen diffusion in the varistor, both in bulk and in grain boundaries, when compared to the oxygen diffusion in undoped ZnO. The increase of the oxygen bulk diffusion in the varistor agrees with an interstitial mechanism for the oxygen diffusion. The results also show that the grain boundary is a fast path for the oxygen diffusion in the varistor. However, the oxygen diffusion in the grain boundaries of the varistor seems to depend on several chemical and microstructural parameters and does not allow a simple explanation.