Local environment of fluorescent dyes could strongly affects emission dynamics of the latter. In particular, both signal intensities and emission lifetimes are highly sensitive to solvent temperatures. Here, temperature-dependent behavior Rhodamine B fluorescence in water and ethanol solutions was experimentally investigated. Phase transition point between liquid water and ice was shown to have a dramatic impact on both in intensity (30-fold drop) and in lifetime (from 2.68 ns down to 0.13 ns) of the dye luminescence along with the shift of spectral maxima from 590 to 625 nm. At the same time, use of ethanol as solvent does not lead to any similar behavior. The reported results and approaches enable further investigations of dye-solvent interactions and studies of physical properties at phase transition points.

Cryptomelane type manganese dioxides (α-MnO2, OMS-2) are interesting potential cathode materials due to the ability of their one dimensional (1D) tunnels to reversibly host various cations including Li+ and an accessible stable 3+/4+ redox couple. Here, we synthesized metal cation free OMS-2 materials where the tunnels were occupied by only water and hydronium ions. Water was subsequently removed from the tunnels. Cation free OMS-2 and Dry-OMS-2 were used as cathodes in Li based batteries to investigate the role of tunnel water on their electrochemistry. The initial discharge capacity was higher for Dry-OMS-2 (252 mAh/g) compared to OMS-2 (194 mAh/g), however, after 100 cycles Dry-OMS-2 and OMS-2 delivered 137 mAh/g and 134 mAh/g, respectively. Li+ ion diffusion was more facile for Dry-OMS as evidenced by rate capability, at 400 mA/g. Dry-OMS-2 delivered 135mAh/g whereas OMS-2 delivered ∼115 mAh/g. This first report of the impact of tunnel water on the electrochemistry of OMS-2 type materials demonstrates that the presence of tunnel water in OMS-2 type materials negatively impacts the electrochemistry.

There are growing interests on magnetic nanowires, due to their potential applications in magnetic sensors and recording devices. In this work, we report a comparative ab-initio study based on the Density Functional Theory (DFT) of Ni x Fe1-x nanowire periodic arrays by using atomic-orbital and plane-wave basis respectively through DMol3 and CASTEP codes. After performing the geometry optimization, we calculate the spin-polarized electronic density of states, average interatomic distance, and magnetic moments. For pure Ni nanowires (x = 1, the dependence of the magnetic moment obtained from CASTEP calculations on the cutoff energy, as well as that from DMol3 on the thermal smearing parameter is analyzed in detail. Both ab-initio calculations predict close magnetic moments for each x, being slightly larger those of DMol3 obtained with significantly less computing cost. Finally, these DFT results are compared with experimental data and a good agreement is observed.

Aluminum-Graphite composites were prepared from pure aluminum and natural graphite the mixture was processed by the mechanical milling (MM) technique. The microstructural characteristics of prepared composites were investigated by X-rays diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). The mechanical response of samples was evaluated by compression and hardness tests. To obtain solid samples from milled powders we used an alternative sintering process based on induction heating. Although this method is frequently used for refractory ceramics fabrication (>1500°C), it has not been properly evaluated for materials processing at low temperature (<500°C). This work presents a comparative study of Al-Gr composites sintered by using two routes: conventional pressure-less and high frequency induction heating. After the inductive sintering, is noticeable a pronounced reduction of porosity and increase on the mechanical response of induction sintered specimens, compared with the processed by conventional route. Also, yield strength and hardness increases with graphite addition and induction sintering reaching an increase of 50 and 90%, respectively (compared with an Alp-2h blank).

We demonstrate that Additive Manufacturing (3D printing) is a viable approach to rapidly prototype personalised fins for surfboards. Surfing is an iconic sport that is extremely popular in coastal regions around the world. We use computer aided design and 3D printing of a wide range of composite materials to print fins for surfboards, e.g. ABS, carbon fibre, fibre glass and amorphous thermoplastic poly(etherimide) resins. The mechanical characteristics of our 3D printed fins were found to be comparable to commercial fins. Computational fluid dynamics was employed to calculate longitudinal (drag) and tangential (turning) forces, which are important for surfboard maneuverability, stability and speed. A commercial tracking system was used to evaluate the performance of 3D printed fins under real-world conditions (i.e. surfing waves). These data showed that the surfing performance of surfboards with 3D printed fins is similar to that of surfboards with commercial fins.

Since the discovery of graphene in 2004, graphene has already been one of the researching hotspots in the material science. As a promising method, electrochemical exfoliation has drawn great attention for producing graphene on industrial scale with high efficiency, low cost, and non-pollution. However, like other wet-chemical methods, the induced oxidation and chemical functionalization are unavoidable during the exfoliation process. Several solutions have been reported to overcome this issue and improve the graphene quality. In this review, we summarize the recent progress in preparation and potential applications of high-quality graphene via electrochemical exfoliation in acidic electrolytes, focusing on the technological innovation and related properties of obtained high-quality graphene.

Microstructural, chemical, and electrochemical property measurements results, for (111) crystallographically oriented Pt100-xMx (M = V, Zr; 3 < xv < 14; and 4 < xZr < 35, At.%) sputtered thin films are presented, with electronic structure calculations. These Pt-based alloys were prepared to investigate early transition metal (ETM), late-transition-metal (LTM) alloys as potential electrode materials in hydrogen-air polymer-electrolyte-membrane fuel cells (PEMFCs). The Pt100-xMx oxygen-reduction-reaction (ORR) currents peak for 8 < x < 10 atomic percent, so local chemical-short-range-order, may exist; as the peak in ORR activity is commensurate with the strong ordering in Pt8M (M = Ti, V, Zr). The hydrogen under potential deposition (Hupd) at Pt active area, and ORR reaction kinetics, on the alloyed surfaces are composition dependent, suggesting three possible effects: 1) charge transfer from V-(3d)3 [or Zr- (4d)2] states, to the hole in the top of the Pt-(5d)9 band alters the electronic structure at the Fermi energy; 2) alloying Pt with the ETM elements introduces a bi-functional character to the electrode surface, and 3) or the presence of short range chemical order induces a Fermi energy shift. To confirm the 1st and 3rd hypotheses, the electronic structure of Pt8Ti, Pt8V, and Pt8Zr, were calculated using the WIEN2k program package. The electronic structure calculations for ordered Pt8M give strong confirmation of the hypotheses, as they reveal that the Pt8M Fermi energy lies within the Pt-5d anti-bonding band, and also falls into a pseudogap in between the Md bonding and anti-bonding bands. In addition, the Pt8M DOS calculations confirm the presence of a deep pseudogap formed across the Fermi energy for both the Pt-sp and M-sp electrons. These experimental and theoretical results motivate additional studies of the novel Pt8M phases.

For the first time, we are reporting the growth of high quality single crystalline 3C-SiC epitaxially on hexagonal silicon carbide substrates using Hot Filament Chemical Vapor Deposition (HF-CVD) on full 4” wafers. Rocking curve X-Ray diffraction (XRD) measurements resulted in a full width at half maximum (FWHM) as low as 88 arcsec for a 40 µm thick layer. We achieved this quality using a carefully optimized process making use of the additional degrees of freedom the hot filaments create. The filaments allow for precursor pre-cracking and a tuning of the vertical thermal gradient, which creates an improved thermal field compared to conventional Chemical Vapor Deposition. Growth rates of up to 8 µm/h were achieved with standard silane and propane chemistry, and further increased to 20 µm/h with chlorinated chemistry. The use of silicon carbide substrates promises superior layer quality compared to silicon substrates due to their better match in lattice parameters and thermal expansion coefficients. High resolution scanning electron microscopy, X-Ray rocking measurements, and micro-Raman allow us to assess the crystalline quality of our material and to compare it to layers grown on low-cost silicon substrates. Hall measurements reveal a linear increase of the charge carrier density in the material with the flow of nitrogen gas as a dopant. Electron densities above 10-18 cm-3 have been reached.

Metal Organic Decomposition (MOD)-made BaTiO3 (BT) thin films were prepared for Resistive Random Access Memory (ReRAM) under various annealing conditions and investigated for improving the properties of bipolar-type resistive switching, focusing on the relation between oxygen vacancies and the behavior of resistive hysteresis. BT thin films with both pre- and final- annealing in nitrogen showed the resistive hysteresis of bipolar-type switching with current ON/OFF ratios of 2 orders of magnitude for both bias polarities. Finally they showed the endurance property with the 106 switching cycles. It was suggested that oxygen vacancies near the oxide surface (both interfaces at metal electrode/oxide and between layer-by-layered oxide layers) are increased by N2 annealing and enhanced the interface-type resistive switching. Pre-annealing in N2 was also found to be very effective to improve endurance properties, implying that not only the electrode/oxide interface but also the middle part of the film would contribute the interface-type mechanism.

Halloysite nanotubes (HNTs) have attracted attention for their potential use in a variety of applications owing to their mechanical robustness, thermal stability, natural abundance and low cost. The inclusion of HNTs into epoxy matrix at low concentrations was found to be effective in stiffening and hardening. At 1 vol% loading, composites showed improvements up to 50% in modulus and 100% in hardness compared to pure epoxy, based on nanoindentation measurements. In addition, tribology studies using TriboIndenter and AFM showed an increase of wear resistance; depending on their orientation in the composite, HNTs can decrease the scratch volume by 50% at fixed loading levels. Adding HNTs into epoxy had almost no effect on the transmittance over the range of wavelength from 400 to 700 nm. Transmittance values of 91% were observed for HNT concentrations as high as 10 vol%.

Typically, composites are lightweight, and high strength and hence are attractive for use in aerospace, automotive applications. For most of the aerospace applications, laminated composites serve as a primary load carrying structure and are subjected to a variety of loadings including transverse impact and fatigue loadings. The typical laminated composites are weak in the transverse direction. Since laminated composites are weak in the transverse direction, when these laminates are subjected to transverse loading, most of the time interlaminar failure occurs in the form of delaminations. Conventional methods of preventing delaminations include improving the design and improving the matrix properties. Although, improving the composite design suppress delaminations to some extent, a substantial amount of compromise with other properties like increase of resin volume fraction, degradation of inplane properties, voids, distortion in fibers and laminate, an increase of cost or process complexities are common. The present day researchers are more focused on improving matrix by nanomaterials such as Carbon Nano Tube(CNT), though the cost is hampering its potential for an industrial prospect. Electrospun nanofibers are being considered as a cheap alternative for vapor grown CNTs and other nanomaterials which involve complex fabrication and application methods in the field of interlaminar reinforcement for polymer matrix composites. Most of the aerospace quality composites are manufactured using prepreg due to the higher percentage of fiber volume fraction and hence higher mechanical properties. Although, nanomaterials have been recognized as a major advancement for improvement of composite material properties, there has been very little effort to fabricate prepregs using nanofibers. The current research focuses on the challenges involved in the fabrication of nanofiber enhanced prepregs and process difficulties and possible solutions for fabricating electrospun nanofiber overlaid prepregs. The effects of heat treatment on electrospun nanofiber overlaid woven fabric on the mechanical properties of both glass and carbon are investigated. A novel technique is proposed for manufacturing of nanofiber engineered prepregs.

An adhesive that can withstand elevated temperatures is necessary for the conservation of artifacts in hot climates. The use of Butvar B-98 as a modifier to raise the glass transition temperature of Paraloid B-72 was investigated. The characteristics of B-48N and B-72 blends, currently in use in the field of conservation, were used as a comparison for analysis of the B-98 and B-72 blends. Differential Scanning Calorimetry (DSC) was used to determine the glass transition temperatures (Tg) of the blends and shear testing was used to investigate the shear strength of the blends. While the B-98 and B-72 blends attained elevated glass transition temperatures and performed well during shear testing, issues regarding miscibility and phase separation of the blends were investigated using transmission FTIR, DSC, and optical microscopy.

Over the last 30 years organic carbon nanotube-yarn (CNTY) based dye-sensitized solar cells (DSSCs) have received considerable interest. CNTY based DSSCs have become a main focus of alternative energy source research. CNTY based PV cells have an advantage over cells based on non-flexible substrates, such as fluorine doped tin oxide glass; as a foundation for dye-sensitized solar cells, CNTYs are superior due to their low-cost, environmental sustainability, high mechanical integrity, and numerous beneficial practical applications. CNTY based DSSCs also have additional advantages because of their low electrical resistance, excellent electrocatalytic activity, and ultra-high mechanical integrity. Additionally, quantum dots and polymers have shown great promise for photovoltalic application due to their tunable bandgap and wide photon absorption range. This research explores the barrier characteristics associated with new absorbing photovoltaic materials that promote electron/hole pair separation and transportation. Utilizing the hybrid bandgap structures of quantum dots and polymers as well as the flexibility of CNTY, we reported a 3D flexible DSSC with an efficiency of 2.9%.

Polyaniline (PAni)/B-doped diamond/carbon fiber (CF) ternary composites were produced and characterized, aiming their application as electrodes for supercapacitor device. In order to optimize the composite properties, structurally different CF substrates, heat treated at 1000 and 2000°C, were used to grown diamond films. Moreover, the diamond films were grown on CF in two different morphologies, boron doped micro and nanocrystalline diamond (BDD/BDND), by Hot Filament Chemical Vapor Deposition (HFCVD) technique. FEG-SEM images showed that PAni covered and enwrapped the diamond/CF surfaces, producing tridimensional electrodes. Raman spectra confirmed the PAni formation for all composites. Electrochemical characterizations indicated that the PAni/BDD/CF2000 composite has the highest current density and capacitance response among the studied composites combinations. In addition, it showed the most reversible oxidation and reduction processes, the greatest charge storage capacity as well as the lowest charge transfer resistance.

Poly (lactic acid) (PLA) bioplastics are recyclable and biodegradable thermoplastics. They are derived from environmentally friendly sources such as potatoes, cornstarch and sugarcane. However, PLA is inherently brittle with low impact strength. The goal of this study is to improve mechanical properties of PLA by the addition of calcium carbonate (CaCO3) fillers. PLA composites were prepared by injection molding conventional limestone (LS) and white chicken eggshell (WES) powders with particle sizes of 63 μm and 32 μm in amounts of 5 wt. %, 10 wt. % and 20 wt. %. Mechanical properties such as, tensile strength, tensile modulus, and Charpy impact strengths were investigated. These three properties were evaluated and the results statistically analyzed using ANOVA F-test. For both particle sizes, the tensile strength decreased as the filler content increased, but was highest for a filler loading of 5 wt. %. In general, the 32 μm powder fillers had better tensile strengths than 63 μm sized fillers. The tensile modulus increased with filler content and was highest at 20 wt. % for both particle sizes. The LS/PLA composites had better toughness than the WES/PLA composites. The particle filler morphology and fractured surfaces were observed by scanning electron microscopy (SEM) and determined to have well dispersed particles with smooth fractured surfaces. Water absorption behavior of PLA/CaCO3 composites were studied by immersion in distilled water at room temperature for 56 days. Virgin PLA absorbed the least amount of water while the water absorption of CaCO3 composites were a function of powder type and content.

In this study, a novel technique has been developed for the fabrication of uniform, stable, and strongly bonded graphene layers on microporous ceramic membranes. A composite ceramic-LIG membrane was obtained following one step scalable methodology. First, the ceramic support was spin-coated with poly (pyromellitic dianhydrideco-4,4´-oxidianiline, amic acid) (PMDA-ODA) and transformed to polyimide (PI) by thermal imidization. The PI was then irradiated with a CO2 laser to photothermally convert the sp3-carbon atoms to sp2-carbon atoms. Different PMDA-ODA layers were applied to achieve uniform coating by LIG on the membrane surface. The LIG was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and contact angle (CA) measurements. FTIR results showed a complete conversion of PMDA-ODA to PI following the thermal imidization reaction. The XRD results revealed the crystalline structure of graphene layer, which had a surface area of 130 ± 5.6 m2/g, determined by BET nitrogen adsorption. However, the permeability of uncoated ceramic membranes decreased with increasing number of PMDA-ODA layers, as evidenced by the clean water filtration experiments. The new composite membrane is a promising new material for membrane distillation or electro osmosis, where the hydrophobicity of the graphene layer may provide important advantages over current membrane materials.

Extrusion-based bioprinting (EBP) is limited by loss of pattern fidelity when printing on wet substrates. This can be overcome using aqueous two-phase systems (ATPSs) as novel ink formulations for EBP. In this study, optimal concentrations of ATPS “inks” were determined and used to pattern human epidermal keratinocyte (HEK001) colonies on a wet substrate for promoting epidermal growth. Four equilibrated and non-equilibrated ATPS formulations were tested for stable ATPS formation and uniform cell patterning. We identified an optimal formulation that produced stable droplets on a standard tissue culture plate coated with PEG. This process was also tested on an acellular dermal matrix (DermGENTM ) to evaluate biopattern fidelity on a tissue matrix. Cell proliferation and formation of adherens junctions between cells were analyzed by immunocytochemistry. Non-equilibrated 5.0% PEG and 5.0% DEX solutions formed tighter colonies than equilibrated solutions containing identical total polymer concentrations. Cells patterned in colonies displayed higher cell viability and increased formation of E-cadherin junctions compared to non-patterned cells. Finally, when the cells were patterned on DermGENTM , discrete cell colonies were observed. This suggests that ATPS EBP holds promise for biopatterning epidermal keratinocyte cells to improve skin tissue engineering.

We report the capacitance of entangled carbon nanotubes (CNTs) synthesized on flexible carbon fabric via water-assisted chemical vapor deposition. The CNTs were grown at atmospheric pressure with iron (Fe) as the catalyst, ethylene (C2H4) and 5%/95% H2/Ar as precursor gasses, and aluminum oxide as a buffer/barrier layer. The effect of the catalyst thickness (5 and 10 nm) on the specific capacitance was studied. The capacitance behavior of CNTs was evaluated by cyclic voltammetry measurements via a three-electrode system. The highest specific capacitance, approximately 56 F/g, was obtained for electrodes with 5nm Fe thickness. A nearly rectangular shaped cyclic voltammogram was exhibited for the CNTs grown on the carbon fabric. A specific power density of 0.012 KW/Kg and specific energy density 0.15 Wh/Kg were calculated from the galvanic charge/discharge (CD) curves. In addition, electrochemical impedance spectroscopy (EIS) revealed a characteristic supercapacitive behavior with a low equivalent series resistance of 7 Ωcm2.

By laser metal deposition (LMD) samples from Fe–28Al (at.%) have been built on iron and various steels. Chemically graded iron aluminium and Fe–28Al/steel samples were fabricated with intended concentration gradients by controlling the feed rates of the powders. All samples were subsequently heat treated at 700 °C for 1000 h to study possible reactions between Fe–28Al and the steels and the long-term stability of the composition gradients. Microstructures were characterized by scanning electron microscopy (SEM) and concentration profiles along the building direction were analysed by energy- and wavelength-dispersive spectrometry (EDS, WDS).

Cerium dioxide (CeO2) thin films were deposited by atomic layer deposition (ALD) on both Si and TiN substrates. The ALD growth produces CeO2 cubic polycrystalline films on both substrates. However, the films show a preferential orientation along <200> crystallographic direction for CeO2/Si or <111> for CeO2/TiN. In correspondence, we measure a relative concentration of Ce3+ equals to 22.0% in CeO2/Si and around 18% in CeO2/TiN, by X-ray photoelectron spectroscopy. Such values indicate the presence of oxygen vacancies in the films. Our results underline the films differences and similarities between ALD-deposited CeO2 either on Si or TiN substrates, thus extending the knowledge on the CeO2 structural and chemical properties.