An electrophoretic process is proposed to deposit electrochemically-preformed Au or Pd NPs, with controlled size, directly on MWCNTs-based chemiresistors to improve the detection of aromatic pollutants, compared to pristine ones.

The sensing properties of pristine and functionalized MWCNTs were evaluated at an operating temperature of 40°C towards various concentrations of one aromatic pollutant, belonging to the dangerous BTEX class of compounds, m-Xylene. The sensing performance was related to the metal used in the functionalization process. Metal-doped MWCNTs sensors exhibited a very high gas sensitivity to m-Xylene even at low (80 ppb) concentration at low operating temperature (40°C), good reversibility and repeatability, with the sensing properties controlled by the type of deposited metal catalyst.

The results indicate that Metal-modified MWCNT-based chemiresistive gas sensors has good potential in practical applications, due to its remarkable performance, low power consumption, and facile synthesized methods.

In this work, the integration of ZnO-CuO core-shell nanostructures shows improvement in the conversion efficiency of ZnO-based dye-sensitized solar cells (DSSCs). This is due to CuO acting as a secondary absorption layer that allows the absorption of near-infrared (NIR) light increasing the generated photocurrent in the device, and as a blocking layer that reduces electron-hole recombination. The ZnO core and encapsulating CuO shell are synthesized through chemical vapor deposition (CVD), and thermal oxidation of a Cu seed layer, respectively. The crystallinity of the synthesized ZnO and CuO is analyzed by X-ray diffraction (XRD). Scanning electron microscope (SEM) images show the change in morphology through the steps of Cu seed layer deposition and thermal oxidation of this layer. To determine optical properties of CuO on ZnO nanorods, UV-Vis-NIR photospectrocopy is used. The comparison of conversion efficiency of DSSCs using two different photoelectrodes (i.e. ZnO nanorods versus ZnO-CuO core-shell nanostructure) is performed by I-V measurements.

TiO2 film with the anatase structure was grown on the substrate by electrochemical parameters (high stability of NH2OH groups). In this investigation, TiO2 film with the anatase structure and the smooth surface would be electrochemically grown on the FTO conductive substrate by adding N-Methylhydroxyl amine into titanium potassium oxalate dehydrate aqueous solution.

We have found that several nitrogen-related luminescence centers appear at 389 nm, 503 nm (H3 center), 575 nm (NV0 center), 637 nm (NV- center) in single-crystalline Ib diamond cut by means of a YAG laser irradiation process, followed by a suitable hydrogen microwave-plasma treatment, and that cathodoluminescence peaks related to these centers substantially change in intensity by irradiating the sample with 15-keV electron beam (EB). The relative number of 389-nm centers originating from a pair of a substitutional nitrogen atom and an adjacent interstitial carbon atom increased while the concentrations of the vacancy-related centers were reduced with increasing 15-keV EB doses. These facts indicate that both the process-induced self-interstitials and the vacancies in the diamond rather easily moved to more preferential positions to form their stabler defect states, being suggestive of possibility to control densities of NV and NV-related centers.

The corrosion of unirradiated and unsensitized Advanced Gas-cooled Reactor cladding material, 20/25/Nb stainless steel, was studied as a function of temperature and [Cl-] typical of those found in interim spent fuel storage pond waters. With respect to preventing corrosion, it found to be advantageous to dose the ponds to pH≈11.4. At pH lower than 7, the initiation of pitting is observed at ∼0.4V vs Ag/AgCl, an undesirable condition as pits are considered to be initiators of stress corrosion cracking (SCC) which may contribute to loss of cladding integrity during storage. Such pits are not seen at a pH 11.4 for the expected and projected pond operating temperatures of 24-60°C. There generally appears to be no localised corrosion threat to cladding as the temperature is increased in this range, although substantial pit formation is observed at the extreme maloperation temperature of 90°C at pH 11.4 indicating a loss of protection.

Ferromagnetic/Ferroelectric/Ferromagnetic (Ni/PZT/Ni) tri-layer artificial multiferroelectric structures in spin capacitor configuration were fabricated by sputtering ferromagnetic electrodes on PZT. Magnetocapacitance, magnetoimpedance, and phase angle measurements were carried out by a wide range of frequencies and magnetic fields at room temperature. We also compared the magnetodielectric measurements with Ni/PZT/Ag and Ag/PZT/Ag tri-layers structures. Ni/PZT/Ni spin capacitor shows a significantly different behavior compared to conventional PZT capacitor with Ag electrode and mixed electrode capacitor with one ferromagnetic and one conventional electrode.

Traditional solar power applications largely avoid using the infrared spectrum. Nevertheless, this region makes up about 45% of the solar power spectrum and therefore represents an untapped resource. Temperature control of buildings represents a significant cost for both businesses and private consumers. We are interested in developing thermochromic materials for building coatings to help moderate solar infrared absorption and thereby offset temperature control costs for buildings. Our initial effort in this study has been to characterize materials which might represent starting points for our research. We previously designed and 3D-printed an optical test platform to perform reflectance measurements with an ultraviolet-visible-near infrared spectrometer over a spectral range from 200-1000nm. The test platform temperature can be adjusted in real time using Peltier modules. In this study, a sample of microencapsulated 7-anilino-3-diethylamino-6-methyl fluoran was studied by diffuse reflectance spectroscopy from 15-40 degrees Celsius. Scanning electron microscopy was used to characterize the dye particles. Temperature and spectral data were monitored while the sample temperature was adjusted. The visible diffuse reflectance from the sample increased from around 15% below the transition to more than 40% above the transition. A modification of this fluoran which extends the switching behavior into the infrared may be viable for passive thermo-optical switching in building coatings.

Applications such as batteries, fuel cells, solar cells, and sensors, can benefit from high surface-to-volume ratio core/shell arrays of nanorods. The fabrication of the conformal shell layers on nanorod arrays has been a formidable task. In order to assess the deposition conditions for the production of conformal shell coatings by physical vapor deposition (PVD) techniques, we employed Monte Carlo (MC) simulations that involved shell depositions under different flux distributions and angles on arrays of rods. We investigated the conformality of PVD shell layers on nanorod arrays of different aspect ratios, which is defined to be the ratio of rod height to the gaps between nearest-neighbor rods. MC simulated core/shell structures were analyzed for the thickness uniformity of the shell layer across the sidewalls of rods. Our results show that a small angle deposition approach involving a uniform oblique flux (U-SAD) with a small incidence angle ≤ 30o can generate a fairly conformal shell coating around small aspect-ratio rods. However, normal angle deposition with an angular flux distribution (A-NAD) achieves superior conformality both on small and high-aspect-ratio structures compared to U-SAD, conventional uniform normal angle deposition (U-NAD), and SAD with an angular flux distribution (A-SAD). A-NAD can be realized in a PVD system such as by high pressure sputter deposition; while U-SAD can be achieved in thermal evaporation system with a small angle incident flux. In addition, U-NAD and A-SAD can correspond to film growth by normal incidence thermal evaporation and SAD-high pressure sputter deposition, respectively.

Bulk metallic glass and their composites are unique new materials which have superior mechanical and structural properties as compared to existing conventional materials. Owing to this, they are potential candidates for tomorrow’s structural applications. However, they suffer from disadvantages of poor ductility and little or no toughness which render them brittle and they manifest catastrophic failure on the application of force. Their behavior is dubious and requires extensive experimentation to draw conclusive results. In present study, an effort has been made to overcome this pitfall by simulation. A quantitative mathematical model based on KGT theory has been developed to describe nucleation and growth of second phase dendrites from melt in glassy matrix during solidification. It yields information about numerical parameters necessary to understand the behaviour of each individual element in multicomponent sluggish slurry and their effect on final microstructural evolution. Model is programmed and simulated in MATLAB®. Its validation is done by comparison with identical curves reported in literature previously for similar alloys. Results indicate that the effect of incorporating all heat transfer coefficients at macroscopic level and diffusion coefficients at microscopic level play a vital role in refining the model and bringing it closer to actual experimental observations. Two types of hypo and eutectic systems namely Zr65Cu15Al10Ni10 and Zr47.5Cu45.5Al5Co2 respectively were studied. Simulation results were found to be in good agreement with prior simulated and experimental values.

The parameter optimizations of square-wave anodic stripping voltammetry using boron doped diamond (BDD) electrodes with different doping levels for cadmium detection were studied. The optimized relation among the peak current with the pulse frequency, the amplitude, and the potential increment for highly (1019 cm-3) and heavily BDD (1021 cm-3) electrodes was considered. The peak currents were measured around -0.75 V vs. Ag/AgCl for Cd2+ concentration ranged from 1 to 20 ppb. Both BDD films provided detection limits lower than 5 ppb showing that these electrodes are suitable to use in a mercury-free method to determine cadmium trace levels in water.

Two metal fillers with TiC nanoparticles (TiC NPs) of less than 100 nm for the overlay process is an alternative to hardfacing for treating surfaces subjected to severe wear. In this work, the effect of tribological behavior for TiC NPs addition on two Co-based filler materials, as well as the dilutions, was studied. Mixtures of Co-based filler metals without and with 0.5% and 2% TiC NPs were deposited onto D2 steel plates using PTA (Plasma Transferred Arc). The BET surface area was 0.17 m2 g-1 and 0.31 m2 g-1, respectively, for Stellite 6 and 12. The distribution of ca 23% macroporous for Stellite 6 was sufficient to get inside the TiC NPs, as well as in the case of Stellite 12, with a pore distribution of ca 13%. Stellite 12 has an increase in the dilutions (70%) and enthalpies showed endothermic reactions. Stellite 6 with NPs was determined to be most effective in increasing the wear resistance.

Most research of texturization of solar cells has been devoted to Si based cells. For perovskites, it was assumed that texturization would not have much of an impact because of the relatively low refractive indexes lead to relatively low reflection as compared to the Si based cells. However, our optical modeling shows that a significant gain in perovskite (1.55 Ev) absorption from 84.6% to 93.5% for the wavelength range of 400 nm up to 800 nm. The largest gain in absorption is achieved between wavelengths of 700 nm and 800 nm. Because this is a range with a high photon density, the current density increases up to 10rel.%.

We have modeled different sine texture sizes and show generic trends in performance with texture. Moreover, by introducing a texture, the light is locally concentrated, depending on the texture configuration. This offers new cell architectures with optimized front and back contacts.

Glassy materials for HLW immobilization were produced from HLW surrogate, quartz sand, datolite (CaBSiO4OH), and bentonite clay at a temperature of up to 1200 °C. Waste loading (WL) ranged between 20 and 40 wt.%. The glasses were characterized by X-ray diffraction, scanning electron microscopy and Fourier-Transform infrared spectroscopy. Glasses with waste loading of up to 35 wt.% obtained by melt pouring onto a metal plate were found to be rather homogeneous but contained minor noble metal oxides and britholite (at high waste loadings) while those annealed in turned-off furnace were partly devitrified. Average chemical composition of britholite corresponded to formula Na1.00Ca4.02Y0.33Ce0.05Nd3.64Gd0.17Si6.79O24.39. The glass network is built from SiO4 units with one or two bridging oxygens and complex borate groups with primarily ternary coordinated boron. Increase of waste loading resulted in shift of band’s maxima to lower wavenumbers exhibiting increasing the fraction of SiO4 unit with lower number of bridging oxygen ions and thus reduction of glass network connectedness. Glasses with up to 30 wt.% waste loading kept their high hydrolytic durability making them suitable for HLW immobilization.

Light-weight alloys based on intermetallic titanium aluminides (TiAl) are structural materials considered for high-temperature applications, e.g. in aero engines or automotive engines. TiAl alloys of engineering interest consist of two phases, the γ-TiAl and the α2-Ti3Al-phase. Recent developments have led to the so-called TNM alloys (T = TiAl; N = Nb; M = Mo) with an Al-content of 43.5 at.%. These alloys also possess the disordered body centered cubic β-Ti(Al)-phase at elevated temperatures, which ensures a better hot-workability compared to conventional two-phase alloys. However, the relatively low Al content (< 45 at.%) limits the high-temperature capability due to reduced oxidation resistance. This impedes their application in a temperature range above 800°C. The present work shows how the fluorine effect counteracts this disadvantage due to the formation of a protective alumina layer. The performance of the TNM alloy with the nominal composition of Ti-43.5Al-4Nb-1Mo-0.1B (at.%) is compared with another TNM alloy variant containing additional elements, such as Si and C, and the so-called GE alloy (Ti-48Al-2Cr-2Nb; at.%), which is already in use for turbine blades. The results of isothermal and thermocyclic high-temperature exposure tests of untreated and fluorine treated specimens will be compared. The effect of composition and microstructure of the alloys on the oxidation behavior with and without fluorine treatment are discussed.

Adoption of Materials Science and Engineering (MSE) into the pre-college classroom is an ideal strategy for addressing Next Generation Science Standards (NGSS), specifically the Science and Engineering Practices. MSE offers core science and engineering topics that can be incorporated into existing Science, Technology, Engineering, and Mathematic (STEM) curricula through teaching modules. Using MSE as a teaching vehicle, the Center for Research on Interface Structures and Phenomena (CRISP) conducted a series of small-scale studies of its teacher professional development workshops and a student summer program, along with related teaching modules, in an effort to measure the contribution MSE has on students and K-12 STEM educators. Based on participant survey feedback, CRISP found improvement in students’ MSE knowledge, interests, and career goals. For teachers, in addition to improving their MSE knowledge, they also increased their comfort and confidence in teaching MSE concepts in their classroom. These results provide evidence for the use of MSE modules as productive teaching tools for NGSS Science and Engineering Practices, as well as producing workforce-competitive STEM students.

This paper discusses the use of solvent-gel systems for the cleaning of poly (methyl methacrylate) (PMMA) surfaces. Aqueous polymer gel systems have been introduced to the conservation field with a particular focus on paintings, painted surfaces of wooden artefacts and stone. However, their application on plastics is very recent. Statistically designed experiments aimed to assess the efficiency and damage potential of materials constituting selected solvent-gel cleaning systems. The effect of the free solvents (deionized water, ethanol, isopropanol and petroleum ether), the hydrogel carriers (Agar, Pemulen™ TR-2, Carbopol® EZ 2-Ethomeen® C-25 and 80% hydrolysed PVAc-borax) and their combinations after 5 and 60 minutes of application time on PMMA surfaces, were evaluated through qualitative visual microscopic observation and SEM imaging, and quantitative weight change measurements. Visual observations revealed that the action of solvents (i.e. ethanol and isopropanol) was moderated by gellation (i.e. Agar), while other gel systems (i.e. Pemulen) were unsatisfactory. Results of gravimetric studies showed that most solvent-gels resulted in inconsistencies and large weight changes.

This paper presents a parametric study to investigate the effect of relevant design variables on mechanochemical reaction and mechanical properties of a mechanophore-embedded thermoset polymer matrix. Mechanophores emit fluorescence when a specific covalent bond breaks due to external stress, and thus have attracted immense research interest as a damage sensor. Recently, a mechanophore named dimeric 9-anthracene carboxylic acid (Di-AC) was synthesized successfully and incorporated into epoxy-based thermoset polymer matrix to detect damage precursor. However, there is significant potential in modeling the complex mechanochemistry associated with the Di-AC to obtain a better understanding of this mechanophore and its interaction with the host thermoset material. In this study, a hybrid MD simulation methodology is employed to explore this complex mechanochemistry along with the investigation of the effect of design parameters on the mechanophore performance. The hybrid MD simulation method enables the simulation of Di-AC synthesis, epoxy curing, and mechanical loading test; therefore, the experimental process performed can be emulated accurately. Previously, the hybrid MD method showed the capability of capturing experimentally observed phenomena such as early signal detection and yield strength variation between neat epoxy system and epoxy with 5 wt% Di-AC thermoset polymer. In this paper, the effect of curing temperature on mechanophore activation and mechanical properties is investigated. A series of temperatures are used in the curing simulation, which are experimentally achievable. Results show that curing temperature below glass transition temperature maintains early signal detection and yield strength decreases when the curing temperature increases above the glass transition temperature. Good correlation is observed with experimental results.

This study reports the development of a one-step method for the production of antimicrobial protective coatings for aluminum surfaces with titania nanoparticles. An aerosol flame synthesis system was used to produce monodisperse, ultra-fine TiO2 nanoparticles, which were directly deposited by thermophoresis onto plates of aluminum alloy by means of a rotating disc. Fuel-lean reactor conditions were used to synthesize pure anatase nanoparticles of 3.5 nm in diameter. Substrates were mounted onto the rotating disc that repetitively passes through the flame. Convection due to the rotational motion cooled the substrates, on which particles were deposited as films by thermophoresis. Such a system allowed to obtain submicron coatings of different thickness, by varying the total time of deposition. The antimicrobial activity of TiO2 coatings was tested against the Gram positive bacterium Staphylococcus aureus. To determine the inhibition of biofilms formation, microbes were plated on TiO2 coatings and a semi-quantitative colorimetric assay was performed using crystal violet. The tests showed that the TiO2 coating obtained with tdes=10 s inhibits up to 70-80% Staphylococcus aureus biofilm formation, and the inhibition of biofilms formation was confirmed by means of Scanning Electron Microscopy observation. Also, the antimicrobial properties of the coatings was enhanced by irradiating the samples in the UV region. The results of the present work are promising for using titania films as protective coatings for applications where an antimicrobial activity is required.

Two-dimensional layered materials, materials with weak out-of-plane van der Waals bonding and strong in-plane covalent bonding, have attracted special attention in recent years since the isolation and characterization of monolayer graphite, the graphene. The electrical bandgap in Transition Metal Di-Chalcogenides (TMDCs), non-existent in graphene, make them a good alternative family of materials for novel electronic and optoelectronic applications. 2H- MoS2, one of the most stable TMDCs, has been extensively studied, including the synthesis methods, and its potential applications in photodetection. The chemical vapor deposition (CVD) synthesis method has increased its potential over the years. The advantages of this method are scalability compared to micromechanical exfoliation, common process used in research laboratories, and the maintenance of the quality and intrinsic properties of the material compared to the liquid exfoliation methods. In this work, we synthesized high quality pristine 2H-MoS2 via atmospheric pressure chemical vapor deposition (APCVD) by vapor phase reaction of MoO3 and S powder precursors. The samples were characterized via Raman and photoluminescence (PL) spectroscopy and compared to mechanically exfoliated MoS2 crystal by measuring the full-width half maxima (FWHM) of monolayer and few-layer mesoscopic flakes. In addition, the CVD synthesized single and few-layered MoS2 domains were transferred to different substrates using a high yield process, including a flexible substrate, preserving the quality of the material. Finally, and mechanically exfoliated MoS2 two-terminal photodetector was designed, fabricated, and measured. Demonstrating thus the capability of heterostructure fabrication and the quality of our synthesis and device fabrication process.