J.B. Correia

Oxidative stress and histological changes following exposure to diamond nanoparticles in the freshwater Asian clam Corbicula fluminea (Müller, 1774).

Recently, the scientific community became aware of the potential ability of nanoparticles to cause toxicity in living organisms. Therefore, many of the implications for aquatic ecosystems and its effects on living organisms are still to be evaluated and fully understood. In this study, the toxicity of nanodiamonds (NDs) was assessed in the freshwater bivalve (Corbicula fluminea) following exposure to different nominal concentrations of NDs (0.01, 0.1, 1, and 10 mg l(-1)) throughout 14 days. The NDs were characterized (gravimetry, pH, zeta potential, electron microscopy, and atomic force microscopy) confirming manufacturer information and showing NDs with a size of 4-6 nm. Oxidative stress enzymes activities (glutathione-S-transferase, catalase) and lipid peroxidation were determined. The results show a trend to increase in GST activities after seven days of exposure in bivalves exposed to NDs concentrations (>0.1 mg l(-1)), while for catalase a significant increase was found in bivalves exposed from 0.01 to 1.0 mg l(-1) following an exposure of 14 days. The histological analysis revealed alterations in digestive gland cells, such as vacuolization and thickening. The lipid peroxidation showed a trend to increase for the different tested NDs concentrations which is compatible with the observed cellular damage.

Effects of diamond nanoparticle exposure on the internal structure and reproduction of Daphnia magna

Nanomaterials have significant technological advantages but their release into the environment also carry potential ecotoxicological risks. Carbon-based nanoparticles and particularly diamond nanoparticles have numerous industrial and medical applications. The aim of the present study was to evaluate the toxic effects of diamond nanoparticles with an average particle size of 20 nm on the survival, reproduction and tissue structure of the freshwater crustacean Daphnia magna. The chronic toxicity test results showed 100% mortality at concentrations higher than 12.5 mg l(-1) and that reproduction inhibition occurred in concentrations higher than 1.3 mg l(-1). Light microscopy showed that diamond nanoparticles adhere to the exoskeleton surface and accumulate within the gastrointestinal tract, suggesting that food absorption by the gut cells may be blocked. The results support the use of chronic approaches in environmental protection as part of an integrated environmental monitoring and assessment strategy.

A multi-integrated approach on toxicity effects of engineered TiO2 nanoparticles

The new properties of engineered nanoparticles drive the need for new knowledge on the safety, fate, behavior and biologic effects of these particles on organisms and ecosystems. Titanium dioxide nanoparticles have been used extensively for a wide range of applications, e.g, self-cleaning surface coatings, solar cells, water treatment agents, topical sunscreens. Within this scenario increased environmental exposure can be expected but data on the ecotoxicological evaluation of nanoparticles are still scarce. The main purpose of this work was the evaluation of effects of TiO2 nanoparticles in several organisms, covering different trophic levels, using a battery of aquatic assays. Using fish as a vertebrate model organism tissue histological and ultrastructural observations and the stress enzyme activity were also studied. TiO2 nanoparticles (Aeroxide® P25), two phase composition of anatase (65%) and rutile (35%) with an average particle size value of 27.6±11 nm were used. Results on the EC50 for the tested aquatic organisms showed toxicity for the bacteria, the algae and the crustacean, being the algae the most sensitive tested organism. The aquatic plant Lemna minor showed no effect on growth. The fish Carassius auratus showed no effect on a 21 day survival test, though at a biochemical level the cytosolic Glutathione-S-Transferase total activity, in intestines, showed a general significant decrease (p<0.05) after 14 days of exposure for all tested concentrations. The presence of TiO2 nanoparticles aggregates were observed in the intestine lumen but their internalization by intestine cells could not be confirmed.

Novel Approach to Plasma Facing Materials in Nuclear Fusion Reactors

A novel material design in nuclear fusion reactors is proposed based on W-nDiamond nanostructured composites. Generally, a microstructure refined to the nanometer scale improves the mechanical strength due to modification of plasticity mechanisms. Moreover, highly specific grain- boundary area raises the number of sites for annihilation of radiation induced defects. However, the low thermal stability of fine-grained and nanostructured materials demands the presence of particles at the grain boundaries that can delay coarsening by a pinning effect. As a result, the concept of a composite is promising in the field of nanostructure d materials. The hardness of diamond renders nanodiamond dispersions excellent reinforcing and stabilization candidates and, in addition, diamond has extremely high thermal conductivity. Consequently, W-nDiamond nanocomposites are promising candidates for thermally stable first-wall materials. The proposed design involves the production of WAV-nDiamondAV-Cu/Cu layered castellations. The W, W-nDiamond and W-Cu layers are produced by mechanical alloying followed by a consolidation route that combines hot rolling with spark plasma sintering (SPS). Layer welding is achieved by spark plasma sintering. The present work describes the mechanical alloying processsing and consolidation route used to produce W-nDiamond composites, as well as microstructur al features and mechanical properties of the material produced Long term plasma exposure experiments are planned at ISTTOK and at FTU (Frascati).

Nanodiamond dispersions in metallic matrices with different carbon affinity

Dispersing nanodiamond (nD) particles in metallic matrices can be achieved by ball milling resulting in metaldiamond composite powders [1-7]. The matrices have been selected considering the whole range of carbon affinity: copper that shows extremely reduced affinity towards carbon phases, potentially compromising the composite interfaces, and nickel and tungsten that are mild and strong carbide formers, respectively, displaying thus intermediate and strong carbon affinities. For the latter matrices, dispersing carbon phases represent a challenge due to carbide conversion.

Studies on deuterium retention in W-Ta based materials

** *IST/ITN, Instituto Superior Tecnico, Instituto Tecnologico e Nuclear, Universidade Tecnica de Lisboa, Estrada Nacional 10, P-2686-953 Sacavem, Portugal **Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal ***LNEG, Laboratorio Nacional de Energia e Geologia, Estrada do Paco do Lumiar, 1649-038 Lisboa, Portugal ****ICEMS, Instituto Superior Tecnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal *****National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564, Japan ******CENIMAT-I3N, Departamento de Ciencia dos Materiais, Faculdade de Ciencias e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal The high melting point, high sputtering threshold and low tritium inventory rendered W as a potentially suitable material in fusion devices [1-4]. The major problem associated with presently available tungsten grades as structural materials is its brittleness at lower temperatures. This is further worsened by irradiation embrittlement. A strategy for ductility improvement is producing a composite, with the brittle W matrix being reinforced by short fibres of tantalum [5]. As Ta is more ductile than W it can therefore divert or stop cracks propagating in the W matrix. In the present research Ta short fibres and powder were used as reinforcement component for W [6] by alloying Ta short fibres or powder in a W powder matrix. The composites were subsequently irradiated with deuterium to assess the retention of this hydrogenic species in the materials. The irradiated composites, with Ta contents of 10 or 20 at%, were produced from pure elemental powders (W-Ta powder composites), and pure W powder and Ta fibre (W-Ta fibre composites) with 100 μm in diameter by low energy ball milling in argon atmosphere. These materials were consolidated via spark plasma sintering (SPS) in the temperature 1200 to 1600 oC range. Pure W and Ta plates (controls) and W-Ta composites were irradiated with He