Nanoscale elastic-plastic deformation and mechanical properties of 3C-SiC thin film using nanoindentation

The elastic-plastic deformation of 3C-SiC thin film was investigated by a nanoindenter equipped with the Berkovich tip. Transition from pure elastic to elastic-plastic deformation was evidenced at an approximate load of 0.35 mN, when loading the sample at several peak loads ranging from 0.5 to 5 mN. The indentation size effect observed in 3C-SiC and was analyzed by Nix-Gao model. In purely elastic region, the Oliver- Pharr hardness values were 44 ± 2 GPa. In contrast, indentation size effects were evidenced in 3C-SiC specimen and the average value of Oliver-Pharr hardness in the indentation size effect region was 36 ± 2 GPa. Furthermore, depth independent or intrinsic hardness extracted from Nix-Gao was estimated as H_o = 26 ± 1 GPa which was also validated by proportional specimen resistance model, ie, H₁ = 28 ± 1 and H₂ = 28.5 ± 0.1 GPa. Besides, energy principle was utilized to extract Sakai Hardness as 104 GPa, which is combined elastic and elastic-plastic response. Moreover, based on energy principle, another property, ie, work of indentation was also determined to be 20 nJ/μm³. Similarly, elastic modulus had almost depicted stabilized value of 325 ± 8 GPa in pure elastic and elastic-plastic regions. In addition, plastic zone size was also estimated in elastic-plastic region using Johnson cavity model at pop-in and higher loads. Based on the first pop-in load at 0.35 mN, the distributions of shear and principal stresses were evaluated on various slip planes to elaborate the deformation behavior. Increase in loading rate from 100 to 400 μN/s increased critical pop-in load from 0.35 to 0.64 mN. This increase in critical pop-in load with increasing loading rate and values of maximum contact pressure indicates that no phase assisted transformation will occur at pop-in load. Based on theoretically calculated maximum tensile and cleavage strengths, it was affirmed that the elastic-plastic deformation occurred due to pop-in formation rather than tensile stresses. Moreover, it was also concluded on basis of Hertzian contact theory and Schmidt law that the highest possibility of slippage in 3C-SiC was along the {111} glide plane.     

Superconductivity and Electron–Phonon Interaction in?Cu0.5Tl0.5Ba2Ca2Cu3?yMyO10?δ (M=0, Si, Ge, Sn, and?y=0,?1)

Superconducting properties of Cu_0.5Tl_0.5Ba₂Ca₂Cu_3−y M _y O_10−δ (M=0, Si, Ge, Sn and y=0, 1) samples have been studied by using x-ray diffraction (XRD), resistivity, ac-susceptibility and Fourier Transform Infrared (FTIR) absorption measurements. We have tried to explore the role of the electron-phonon interaction in bringing about superconductivity in the Cu_0.5Tl_0.5Ba₂Ca₂Cu_3−y M _y O_10−δ material. A change in the cell parameters from XRD and the change in the shape of FTIR absorption spectra have shown the incorporation of doped elements (M=Si, Ge, Sn) in the unit cell of the final compound. It is most likely that the change in oxygen phonon modes is associated with the oscillations of heavier and lighter atoms in MO₂/CuO₂ planes. These oscillations of heavier and lighter atoms suppress the density of the phonon population from the desired level for optimum superconductivity in the final compound.     

Correcting and extending the Boomsma–Poulikakos effective thermal conductivity model for three-dimensional,fluid-saturated metal foams

Metal foams have emerged as promising materials for use in heat sink and heat exchanger applications. Boomsma and Poulikakos put forward an important and widely adopted model for the effective thermal conductivity of metal foams; however, the model contains errors in its development and presentation. Whether partially or fully corrected, the model does not provide accurate predictions of the effective thermal conductivity of metal foams. Because the model fails even when corrected, its mechanistic basis is reviewed, and an extension to the approach is put forward to account for ligament orientation in calculating effective thermal conductivity. This modification provides predictions of k_eff that are much more accurate than the original Boomsma–Poulikakos model.     

Synthesis and characterization of waterborne polyurethane acrylate copolymers

Polyurethane acrylate copolymers were synthesized by emulsion polymerization process. To reduce the environmental hazards, organic solvents were replaced by eco-friendly aqueous system. Concentration of polyurethane and acrylate monomer was varied to investigate the effect of chemical composition on performance properties of copolymers. FTIR spectroscopy was used as a key tool to record the chemical synthesis route. The synthesized copolymer emulsions were characterized by evaluating their particle size, viscosity, dry weight content, chemical and water resistance. Thermal decomposition was studied by thermogravimetric analysis. Scanning electron microscope was used to visualize the morphological structure of copolymers. The experimental results indicate better polyurethane acrylate compatibility till the ratio of 30/70. However, these copolymers exhibited synergistic effects between the two polymers and revealed a remarkable improvement in numerous coating properties.     

Quest for high performance carbon capture membranes: Fabrication of SAPO-34 and CNTs-doped polyethersulfone-based mixed-matrix membranes

Gas separation process is an effective method for capturing and removing CO₂ from post-combustion flue gases. Due to their various essential properties such as ability to improve process efficiency, polymeric membranes are known to dominate the market. Trade-off between gas permeability and selectivity through membranes limits their separation performance. In this study, solution casting cum phase separation method was utilized to create polyethersulfone-based composite membranes doped with carbon nanotubes (CNTs) and silico aluminophosphate (SAPO-34) as nanofiller materials. Membrane properties were then examined by performing gas permeation test, chemical structural analysis and optical microscopy. While enhancing membranes CO₂ permeance, SAPO-34 and CNTs mixture improved their CO₂/N₂ selectivity. By carefully adjusting membrane casting factors such as filler loadings. Using Taguchi statistical analysis, their carbon capture efficiency was improved. The improved mixed-matrix membrane with loading of 5 wt% CNTs and 10 wt% SAPO-34 in PES showed highly promising separation performance with a CO₂ permeability of 319 Barrer and an ideal CO₂/N₂ selectivity of 12, both of which are within the 2008 Robeson upper bound. A better mixed-matrix membrane with outstanding CO₂/N₂ selectivity and CO₂ permeability was produced as a result of the synergistic effect of adding two types of fillers in optimized loading.     

Formation of furan in baby food products: Identification and technical challenges

Furan is generally produced during thermal processing of various foods including baked, fried, and roasted food items such as cereal products, coffee, canned, and jarred prepared foods as well as in baby foods. Furan is a toxic and carcinogenic compound to humans and may be a vital hazard to infants and babies. Furan could be formed in foods through thermal degradation of carbohydrates, dissociation of amino acids, and oxidation of polyunsaturated fatty acids. The detection of furan in food products is difficult due to its high volatility and low molecular weight. Headspace solid-phase microextraction coupled with gas chromatography/mass spectrometer (GC/MS) is generally used for analysis of furan in food samples. The risk assessment of furan can be characterized using margin of exposure approach (MOE). Conventional strategies including cooking in open vessels, reheating of commercially processed foods with stirring, and physical removal using vacuum treatment have remained unsuccessful for the removal of furan due to the complex production mechanisms and possible precursors of furan. The innovative food-processing technologies such as high-pressure processing (HPP), high-pressure thermal sterilization (HPTS), and Ohmic heating have been adapted for the reduction of furan levels in baby foods. But in recent years, only HPP has gained interest due to successful reduction of furan because of its nonthermal mechanism. HPP-treated baby food products are commercially available from different food companies. This review summarizes the mechanism involved in the formation of furan in foods, its toxicity, and identification in infant foods and presents a solution for limiting its formation, occurrence, and retention using novel strategies.     

Nano SIMS characterization of boron- and aluminum-coated LiNi1/3Co1/3Mn1/3O2 cathode materials for lithium secondary ion batteries

The LiNi_1/3Co_1/3Mn_1/3O₂ powders required for the present study, obtained by coprecipitation method has been surface coated with boron and aluminum. The morphology and crystal structure of powders have been characterized using scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy techniques. The elemental distribution of the coated samples analyzed by transmission electron microscopy images and nano secondary ion mass spectrometry indicates a thin uniform layer of [B, Al]₂O₃ on the surface of spherical LiNi_1/3Co_1/3Mn_1/3O₂. The surface-modified LiNi_1/3Co_1/3Mn_1/3O₂ has been explored as a cathode material for lithium secondary ion battery applications. The electrochemical charge–discharge results reveal that the capacity retention rate of coated LiNi_1/3Co_1/3Mn_1/3O₂ after 40 cycles at 1 C rate maintains 93% of the initial discharge capacity while the rate of bare LiNi_1/3Co_1/3Mn_1/3O₂ maintains only 88%. It is noticed that the small amounts of boron and aluminum coatings on the surface of LiNi_1/3Co_1/3Mn_1/3O₂ can significantly improve the electrochemical properties of electrode materials because of the suppression of reaction between the cathode and the electrolytes.     

Ni@Fe₂O₃ heterodimers: controlled synthesis and magnetically recyclable catalytic application for dehalogenation reactions

Ni@Fe(2)O(3) heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe(2)O(3) heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), M?ssbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants.