Abstract: Geothermal mining from brines becomes increasingly important with the increasing demand for rare earth elements in various engineering applications. Geothermal fluids contain valuable minerals and metals such as silica, zinc, lithium, and other materials that can be processed to recover these products. Solution mining by nature is challenging because of variable composition as well as the concentration of the interfering ions, particularly calcium and magnesium, and the presence of interfering ions increases the recovery costs requiring additional steps. The aim of this study is the fabrication of single-walled carbon nanotube functionalized electrospun chitosan, poly (methyl methacrylate) (PMMA), and polyacrylonitrile (PAN) fiber mats. Effect of polymer type, dilution factor, and surface modification on the sorption of lithium ( QUOTE ) ions was investigated. The maximum sorption performance was obtained with SWCNT functionalized PAN (15 wt%) fiber mats and they have sorption percentage as 55% at diluted (1/100) brine samples.
Abstract: This study proposes a systematic quantification of effectiveness of the Degussa P-25 titania particles used as a benchmark in photocatalytic applications to standardize ability of self-cleaning textile applications and to compare activity of developing new self-cleaning textiles. To quantify photocatalytic efficiency of P-25, textile production was performed in a harmony with textile manufacturing by combining finishing process and coating procedure. The results of the study suggest that the textiles treated with P-25 particles produced without a secondary treatment were effectively coated and their stain discoloration ability was also validated with solid color spectrometer.
Abstract: Graphene-Tin Oxide (G-SnO2) nanocomposites in different morphology were synthesized using tin (II) chloride (SnCl2) and graphene Oxide (GO) via hydrothermal process in the presence of hydrazine and ammonia by adding surfactant for 12 hours in a teflon autoclave at 100oC reaction temperature. Poly (vinyl prolidon) (PVP) and poly (ethylene glycol) (PEG) were used as nonionic surfactants while hexadecyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulfonate (SDS) were utilized as cationic and anionic surfactants, respectively. The synthesized nanocomposites were characterized by XRD, FESEM, C-TEM and FT-IR. The gas sensing properties of the obtained samples to the vapors of various Volatile Organic Compounds (VOC), such as Ethanol, Methanol, Chloroform, Toluene and Acetone were also investigated at room temperature. The prepared G-SnO2 nanocomposites exhibited high detection performances for ethanol, chloroform and methanol. The nanocomposites could be used as sensor material for VOC gases.
Abstract: The effects of the Achnanthes taeniata and the diatomaceous earth (diatomite) frustules addition on the compressive strength of an epoxy matrix were investigated experimentally. The Achnanthes taeniata frustules having relatively high length/diameter aspect ratio (2-4) were isolated and cultured in laboratory. While the as-received commercial natural diatomite frustules were non-homogenous in shape and size. The filling epoxy matrix with ~6 wt% of commercial natural diatomite increased the compressive strength from 60 MPa to 67 MPa, while the Achnanthes taeniata frustules addition increased to 79 MPa. The increased compressive strength and modulus of the the Achnanthes taeniata frustules filled epoxy was attributed to the higher aspect ratio and relatively strong bonding with the epoxy matrix. The more effective load transfer from the matrix to the Achnanthes taeniata frustules associated with the enhanced interface bonding was also proved microscopically. The frustules were observed to pull-out on the fracture surface of the Achnanthes taeniata frustules filled epoxy.
Abstract: Actuation response of NiTiHf high temperature SMAs can be enhanced by means of suitable heat treatment on the material through precipitation hardening. Heat treatments can be chosen carefully to improve the performance of the NiTiHf SMAs in order to meet the requirements of targeted applications to design more robust and efficient high temperature solid-state actuator systems. The present work aims to develop a novel approach to model and predict the behavior of heat-treated NiTiHf SMAs. The predictions of the thermomechanical response of NiTiHf SMAs are based on Representative Volume Elements (RVEs). The precipitated NiTiHf SMA is modeled as a composite consist of of thermo-elastic non-transforming precipitates and a polycrystalline SMA matrix. The structural effect of precipitates and the effect of Hf-concentration gradient resulted from Hf depletion during precipitation are included. The composition distribution resulting from the elemental depletion and the transformation temperature distributions in the SMA matrix are related. In the present work, these relations are developed from experimental measurements on several NiTiHf compositions. Thermo-mechanical responses of Ni50.3Ti29.7Hf20 heat-treated at 500°C for 48h at different loading conditions are predicted and the correlations with experimental results demonstrate the validity of the proposed framework.
Abstract: In the work reported here the magnetic properties of nanocomposite system composed of polystyrene (PS) latex polymer and superparamagnetic nanoparticles (MNPs), is presented. A series of mixtures were prepared by mixing of PS latex dispersion with different amount of MNPs and drop casting on glass substrates at room temperature. After drying, film samples were annealed at 250 °C for 10 min. Morphological changes of the films were examined by scanning electron microscopy (SEM) and magnetic properties studied using vibrating sample magnetometer (VSM) as a function of MNPs content. The saturation magnetization (Ms) of composites increased as MNPs content increased. Ms showed two maxima at 50 wt% and 85 wt% MNPs contents with Ms values of 0.014 emu and 0.020 emu, respectively. The morphological changes of PS/MNPs composite films were also found consistent with these results indicating that magnetic properties these composites can be readily tuned by varying MNPs content.
Abstract: I-III-VI QDs (CuInS2/ZnS or AgInS2/ZnS core/shell structures) possess low toxicity, and are a logical replacement for cadmium-based QDs for biomedical applications. Our synthesis of I-III-VI QDs is based on thermal decomposition of less toxic precursors and can be easily scaled up for mass production for sustainable and reliable imaging and sensing experiments. Through nonstoichiometric composition adjustment, we synthesized I-III-VI QDs with reliable and controllable optical properties, including high QYs and tunable photoluminescence. We also developed new zwitterionic amphiphiles and applied them to encapsulate I-III-VI QDs to achieve colloidal stability in proteinaceous solutions with wide pH/ionic ranges, low non-specific binding, and easily bio-conjugation. On the basis of these developments, we applied our I-III-VI QDs in cellular imaging to to specifically target human brain tumor cells.
Abstract: This research reports a theoretical investigation on the role of filtered optical feedback (FOF) in the quantum dot light emitting diode (QD-LED). The underlying dynamics is affected by a sidle node, which returns to an elliptical shape when the wetting layer (WL) is neglected. Both filter width and time delay change the appearance of different dynamics (chaotic and mixed mode oscillations ,MMOs). The results agrees with the experimental observations. Here, the fixed point analysis for QDs was done for the first time. For QD-LED with FOF, the system transits from the coherence collapse (CC) case in conventional optical feedback (COF) to a coherent case with a filtered mode in FOF. It was found that the WL washes out the modes which is an unexpected result. This may attributed to the longer capture time of WL compared with that between QD states. Thus, WL reduces the chaotic behavior.
Abstract: Nanostructured ceramic materials and compositions based on them find an increasing application in all branches of science and technology. At the same time, the performance properties of new ceramic nanomaterials (strength, adhesion, optical and others) are significantly different from properties of traditional ceramics, which were used before. The qualitative characteristics of nanoceramics are largely determined by the initial structure and methods of nanopowder synthesis, as well as by the characteristics of conditions and methods for their consolidation. This work is devoted to the synthesis of nanopowders and effective method of its sintering for the production of nanoceramic materials which have special mechanical properties, e.g. components with increased modulus of elasticity ("ceramic steel"), etc. It makes it possible to effectively use them in aerospace industry.
Abstract: Interfacial behavior of Al and α-Al2O3 are investigated via molecular dynamic simulation (MD) employing reactive force fields parameterized for Al and Al2O3. The main result of this work is elucidating the wetting behavior and interface chemistry of molten aluminum on the α-Alumina (0001) surface through MD simulations. Wetting and interface chemistry are studied at 8 different temperatures from 700 to 1400 K for four different droplet sizes: with 16, 24, 32 and 40 Å diameters. Chemical reactions are observed at all temperatures and sizes in addition to diffusion between droplet and substrate atoms into each other during the wetting process. To define the level of wetting, we characterized contact angles of aluminum droplets on alumina substrates for all temperatures and sizes by using a method developed by Hautman and Klein. Chemical reactions are more extensive for the small droplets (16 and 24 Å) due to their larger surface to volume ratio in comparison to the larger droplets (32, and 40 Å) of droplets.