Analysis of Microstructure and Mechanical Properties of Bi-Modal Nanoparticle-Reinforced Cu-Matrix

Bi-modal particles are used as reinforcements for Cu-matrix. Nano TiC and/or Al2O3 were mechanically mixed with Cu particles for 24 h. The Cu-TiC/Al2O3 composites were successfully produced using spark plasma sintering (SPS). To investigate the effect of TiC and Al2O3 nanoparticles on the microstructure and mechanical properties of Cu-TiC/Al2O3 nanocomposites, they were added, whether individually or combined, to the copper (Cu) matrix at 3, 6, and 9 wt.%. The results showed that titanium carbide was homogeneously distributed in the copper matrix, whereas alumina nanoparticles showed some agglomeration at Cu grain boundaries. The crystallite size exhibited a clear reduction as a reaction to the increase of the reinforcement ratio. Furthermore, increasing the TiC and Al2O3 nanoparticle content in the Cu-TiC/Al2O3 composites reduced the relative density from 95% for Cu-1.5 wt.% TiC and 1.5 wt.% Al2O3 to 89% for Cu-4.5 wt.% TiC and 4.5 wt.% Al2O3. Cu-9 wt.% TiC achieved a maximum compressive strength of 851.99 N/mm2. Hardness values increased with increasing ceramic content.

Isobaric Specific Heat Capacity for Al2O3/ Water Ethylene Glycol Mixture Nanofluid

Specific heat is a vital characteristic of nanofluids. The present work is an experimental assessment for the isobaric specific heat measurements for the Al2O3 nanoparticle dispersed in a base fluid of different mixture ratio of ethylene glycol and water at 30, 40, 50, and 60 vol%. The experiments were conducted over temperature range from 35 to 105 °C with nanoparticle concentrations of 0.5 to 2.5 vol%. The results indicated that the specific heat of nanofluid decreases as the nanoparticle volume increases and EG ratio increases but increases as the temperature increases. This characteristic demonstrates that the use of nanofluids should be at as high temperature as possible to fulfill a good beneficial effect. A new correlation from the measurements with maximum deviation of 2.2% was found to estimate the specific heat for these nanofluids.

The role of exogenous silicon to mitigate Al2O3 nanoparticle-induced toxicity in barley (Hordeum vulgare L.)

<p>In this study, we used silicon (Si, in the form of K₂SiO₃, 2 mM) to alleviate the toxicity of aluminum oxide (Al₂O₃) nanoparticles (NPs) in barley (<em>Hordeum vulgare</em> L.). Using Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) analyses, we showed that the Al₂O₃ NPs were taken up by barley plants. Barley growth was negatively affected by the addition of 3 g l^-1 nano-Al₂O₃, whereas the diminishing effect of NPs on barley growth was not obvious when 1 g l^-1 nano-Al₂O₃ was applied, indicating that the nano-Al₂O₃ action is dependent on nano-Al₂O₃ dose. Si pretreatment ameliorated toxic effects of high nano-Al₂O₃ on root growth. Si pretreatment did not decrease nano-Al₂O₃ entry into roots but reduced nano-Al₂O₃ accumulation in the shoot. The restriction of the root-to-shoot translocation of nano-Al₂O₃was one of the important mechanisms for Si to mitigate high nano-Al₂O₃ toxicity. The occurrence of oxidative stress was found under 3 g l¹ nano-Al₂O₃treatment, as evaluated by the accumulation of malondialdehyde (MDA). Exogenous addition of Si could alleviate toxicity symptoms induced by Al₂O₃ nanoparticles by reducing lipid peroxidation via enhancing antioxidant activity of catalase as well as by limiting the root-to-shoot translocation of nano-Al₂O₃. These data provide the first direct evidence that the Si pretreatment ameliorates nano Al₂O₃ phytotoxicity in plants.</p>