A laboratory-scale hot-rolled Ti-Mo-V-Nb steel with 1 GPa tensile strength is produced, and its microstructure and tensile properties are characterized using advanced analysis techniques and uniaxial tensile testing. A Gleeble 3800 thermomechanical simulator is used to determine a process window for the thermomechanical controlled processing (TMCP) procedure. Although the simulated TMCP specimens are fully ferritic at coiling temperatures (CT) of 590 and 630 degrees C, the bainitic and mixed (bainitic + ferritic) microstructure is formed in the hot-rolled steels. The variation in the microstructure causes variations in the dislocation density through the sheet thickness, which significantly reduces the steel's ductility properties, whereas a 16% elongation is achieved with the fully bainitic microstructure. Another significant difference between the simulated TMCP and hot-rolled specimens is the precipitation behavior. No nanosized interphase-precipitated (IP) carbides are formed in the hot-rolled steel during the austenite-to-ferrite phase transformation, although the formation of the nanosized spherical IPs is observed within the polygonal ferrite grains of the simulated TMCP specimens at the CT of 630 degrees C. Relatively coarse (5-20 nm) spherical (V,Mo,Ti,Nb)C carbides do not strongly affect the tensile properties of the hot-rolled Ti-Mo-V-Nb steel. The results show that the dislocation and grain boundary strengthening mainly contribute to the strength properties of this steel.

The precipitation of nanosized carbides in the hot-deformed low-alloy Ti-Mo-V-Nb and Ti-Mo-V- steels during the isothermal dwell at three different temperatures (590 degrees C, 630 degrees C, and 680 degrees C) was investigated. Scanning transmission electron microscopy (STEM) revealed that the formation of regularly and irregularly distributed interphase precipitates (IP) and their orientation relationship with the polygonal ferrite matrix depended strongly on steel chemistry, dwelling time, and temperature. Results also showed that precipitation occurred not only at the austenite/ferrite phase boundary during the phase transformation, but nanosized precipitates also formed within the supersaturated polygonal ferrite grains after the phase transformation. Interpretation of the results suggested that finely dispersed interphase precipitated V(Mo)C carbides, formed rows in which the spacing and the size of the precipitates grew slightly during the isothermal dwell time in the Ti-Mo-V-Nb steel at the temperatures of 680 degrees C and 630 degrees C, whereas spherical V(Mo)C carbides formed within the supersaturated ferrite matrix at all temperatures. In the case of the Ti-Mo-V steel, the formation of the interphase precipitated Ti (Mo,V)C carbides occurred only at the highest dwell temperature of 680 degrees C. No IPs was detected at the other dwell temperatures in this steel, but an irregular carbide distribution consisting mostly of spherical Ti(Mo,V)C carbides was formed within the supersaturated polygonal ferrite matrix.

New steel alloying concepts are designed in order to produce a fully ferritic, low‐alloy steel with high (1 GPa) ultimate tensile strength (TS). A simulated hot‐deformation process of the Ti–Mo–V–Nb and Ti–Mo–V steels is designed for that purpose, and the strengthening mechanisms of the steels are evaluated after the isothermal dwell at three different temperatures (590, 630, and 680 °C). The TS and the yield strength (YS) of the test alloys are estimated via hardness measurements. Results show that the estimated TS of over 1000 MPa and YS of over 900 MPa can be achieved in both steels, although the contribution of different strengthening mechanisms to the YS varies between the steels. The effect of the dislocation strengthening can especially compensate the reduced effect of the precipitation strengthening at all tested coiling temperatures (CTs). Based on the results, a CT range of 590–630 °C with the 1800 s dwell time seems to be a potential process window for the studied steels after the present thermomechanically controlled processing (TMCP) route.

Despite extensive investigations conducted on magnetic Fe-Co-V alloys, some aspects of microstructural evolution during annealing of cold rolled sheets have not yet been clarified yet. Various techniques such as dilatometry, X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM, SEM) as well as ThermoCalc predictions were employed to study ordering, precipitation and austenite transformation in an 86% cold-rolled 40Fe-50Co-10 V alloy. Dilatometric results revealed atomic ordering initiated from disordered martensite at 350 degrees C, while XRD patterns ascertained the completion of the process at 600 degrees C and its disappearance close to 750 degrees C. X-ray and electron diffraction patterns exhibited the B2 type ordered structure in this temperature range. Rod-shaped precipitates with HCP crystalline structure and the constant composition of (Co,Fe)(3) V were detected by SEM within the deformed ferrite grains after annealing in the temperature range of 500-700 degrees C. The percentage of the precipitates decreased by raising the annealing temperature and they vanished above 700 degrees C, in accordance with ThermoCalc prediction. Austenite grains formed below 750 degrees C had an ordered L1(2)-type structure as revealed by TEM and XRD patterns. A combination of different techniques demonstrated that the two-phase ferrite-austenite region exists in the temperature range of 495-840 degrees C. Vanadium partitioning into austenite during isothermal holding in addition to austenite grain size were evaluated as the main parameters affecting austenite stability during quenching from temperatures between 500 and 800 degrees C. As a final result, most of the existing disagreements and ambiguities in previous works could be explained.

Shi, Xinying, Posysaev, Sergei, Huttula, Marko, Pankratov, Vladimir, Hoszowska, Joanna, Dousse, Jean-Claude, Zeeshan, Faisal, Niu, Yuran, Zakharov, Alexei, Li, Taohai, Miroshnichenko, Olga, Zhang, Meng, Wang, Xiao, Huang, Zhongjia, Saukko, Sami, González, Diego López, van Dijken, Sebastiaan, Alatalo, Matti and Cao, Wei 2018. Metallic contact between MoS2 and Ni via Au Nanoglue. Small 14 (22) , 1704526. 10.1002/smll.201704526 file

Dimethyl disulfide (DMDS, CH3SSCH3) is an odorous and harmful air pollutant (volatile organic compound (VOC)) causing nuisance in urban areas. The abatement of DMDS emissions from industrial sources can be realized through catalytic oxidation. However, the development of active and selective catalysts having good resistance toward sulfur poisoning is required. This paper describes an investigation related to improving the performance of Pt and Cu catalysts through the addition of Au to monometallic “parent” catalysts via surface redox reactions. The catalysts were characterized using ICP-OES, N2 physisorption, XRD, XPS, HR-TEM, H2-TPR, NH3-TPD, CO2-TPD, and temperature-programmed 18O2 isotopic exchange. The performance of the catalysts was evaluated in DMDS total oxidation. In addition, the stability of a Pt–Au/Ce–Al catalyst was investigated through 40 h time onstream. Cu–Au catalysts were observed to be more active than corresponding Pt–Au catalysts based on DMDS light-off experiments. However, the reaction led to a higher amount of oxygen-containing byproduct formation, and thus the Pt–Au catalysts were more selective. H2-TPR showed that the higher redox capacity of the Cu-containing catalysts may have been the reason for better DMDS conversion and lower selectivity. The lower amount of reactive oxygen on the surface of Pt-containing catalysts was beneficial for total oxidation. The improved selectivity of ceria-containing catalysts after the Au addition may have resulted from the lowered amount of reactive oxygen as well. The Au addition improved the activity of Al2O3-supported Cu and Pt. The Au addition also had a positive effect on SO2 production in a higher temperature region. A stability test of 40 h showed that the Pt–Au/Ce–Al catalyst, while otherwise promising, was not stable enough, and further development is still needed.

A critical factor for electronics based on inorganic layered crystals stems from the electrical contact mode between the semiconducting crystals and the metal counterparts in the electric circuit. Here, a materials tailoring strategy via nanocomposite decoration is carried out to reach metallic contact between MoS2 matrix and transition metal nanoparticles. Nickel nanoparticles (NiNPs) are successfully joined to the sides of a layered MoS2 crystal through gold nanobuffers, forming semiconducting and magnetic NiNPs@MoS2 complexes. The intrinsic semiconducting property of MoS2 remains unchanged, and it can be lowered to only few layers. Chemical bonding of the Ni to the MoS2 host is verified by synchrotron radiation based photoemission electron microscopy, and further proved by first-principles calculations. Following the system's band alignment, new electron migration channels between metal and the semiconducting side contribute to the metallic contact mechanism, while semiconductor-metal heterojunctions enhance the photocatalytic ability.

In article number 1704526, Wei Cao and co-workers realize a metallic contact between the Ni and layered MoS2 semiconductor by introducing gold nanobuffers, leading to a substantial decrease of electric resistivity at the M/S interface. Simultaneous microscopic and spectroscopic determinations prove the formation of Ni–Au–MoS2 ternary alloy subjected to a facile wet method synthesis. The metallic M/S contact and band alignment provide a potential for layered semiconductors in future electronics.

Inorganic layered crystal MoS2 is considered as one of the most promising and efficient semiconductor materials for future transistors, photoelectronics, and electrocatalysis. To boost MoS2-based material applications, one direction is to grow physically and chemically reactive nanoparticles onto MoS2. Here we report on a simple route to synthesis crystalized MoS2-Au complexes. The gold nanoparticles were grown on MoS2 flakes through a wet method in the oxygen free environment at room temperature. Nanoparticles with diameters varying from 9 nm to 429 nm were controlled by the molar ratios of MoS2 and HAuCl4 precursors. MoS2 host flakes keep intrinsic honeycomb layered structures and the Au nanoparticles cubic-center crystal microstructures. From product chemical states analysis, the synthesis was found driven by redox reactions between the sulphide and the chloroauric acid. Photoluminescence measurement showed that introducing Au nanoparticles onto MoS2 stacks substantially prompted excitonic transitions of stacks, as an analogy for doping Si wafers with dopants. Such composites may have potential applications in wide ranges similar as the doped Si. (C) 2015 Elsevier B.V. All rights reserved.

Hexagonal and monoclinic tungsten oxide (h- and m-WO3) samples were produced by annealing hexagonal ammonium tungsten bronze, (NH4)0.07(NH3)0.04(H2O)0.09WO2.95 at 470 and at 600°C, respectively. Their structure, composition and morphology were analyzed by XRD, Raman, XPS, 1H-MAS NMR and SEM. In order to study the effect of crystal structure on the gas sensitivity of tungsten oxides, h- and m-WO3 were tested as gas sensors to CH4, CO, H2, NO and H2S (1000 and 10ppm) at 200°C. Monoclinic WO3 responded to all gases, but its gas sensing signal was two magnitudes greater to 10ppm H2S than to other gases, and it also detected H2S even at 25°C. Hexagonal WO3 responded only to 10ppm H2S. Its sensitivity was smaller compared to m-WO3, however, the response time of h-WO3 was significantly faster. The gas sensing tests showed that while m-WO3 had relative selectivity to H2S in the presence CH4, CO, H2, NO; h-WO3 had absolute selectivity to H2S in the presence these gases.

This paper discusses the formation of nanosized hexagonal tungsten oxide (h-WO3) during the annealing of hexagonal ammonium tungsten bronze (HATB), (NH4)0.33−xWO3−y. This process was investigated by TG/DTA-MS, XRD, SEM, Raman, XPS, and 1H-MAS NMR analyses. Through adjusting the temperature and atmosphere of annealing HATB, the composition (W oxidation state, residual NH4+ and NH3 content) of h-WO3 could be controlled. The effect of composition on the conductivity and gas sensitivity of h-WO3 was studied. New structural information was obtained about both HATB and h-WO3. It was found that NH4+ and NH3 could be situated at three different positions in HATB. Residual NH4+ and NH3 in the hexagonal channels seemed to be vital for stabilizing h-WO3: when they were completely released, the hexagonal framework collapsed. We propose that the structure of h-WO3 cannot be maintained without some stabilizing ions or molecules in the hexagonal channels.

Hexagonal (h-) WO3 was prepared through heating hexagonal ammonium tungsten bronze (HATB), (NH4)(0.07)(NH3)(0.04)(H2O)(0.09)WO2.95. By adjusting the heating temperature and atmosphere of HATB, we could control the oxidation state of tungsten atoms and the residual NH3/NH4+ content in h-WO3. The as-produced h-WO3 nanoparticles with different composition were tested as gas sensors and the effect of composition on gas sensing properties was studied. Our results showed that oxidized h-WO3 had the best sensitivity to H2S.

We present the fabrication and characterization of logic elements (transistors and interconnects) built using our recently developed inkjet-printer-controlled deposition of single-wall carbon nanotube network films. The method requires no preselection of ``metallic'' or ``semiconducting'' nanotubes. By selecting the number of prints on a specified region, it is possible to have low-density, nonlinear, gate-voltage controllable transistors or high-density, linear, high-current-throughput metallic interconnects without any gate-voltage response. Intermediate steps drive the films between the nonlinear and linear regimes with precise controllability. The transport mechanism in these films as a function of bias, gate voltage, and temperature dependence have been investigated and analyzed using junction properties of metal-semiconductors in the context of networks of carbon nanotubes.

Quartz exhibits a structural phase transition known as alpha -beta phase transition at 846K, accompanied by an incommensurate (IC) phase between alpha and beta phases.Although there are many structural studies about the alpha -beta phase transition of bulk quartz, fewer reports on surface structure have been found.In the present study, temperature variation in surface structure and morphology of quartz was observed with X-ray diffraction ranging from room temperature to 1000K.A polished (001) surface of synthetic quartz with an area of 20 mm x 20mm was placed in an ultrahigh vacuum chamber installed on BL13XU of SPring-8.Surface-sensitive X-ray diffractions we exploited for characterizing the surface are the crystal truncation rod (CTR) scattering emanated from 003 Bragg point and X-ray reflectivity (XR).Rocking curves (qx scan) and longitudinal curves (qz scan) between 2theta = 0 to 5-8 deg. of XR were collected at each temperature.In beta phase (>846K), a noticeable increase in width of specular XR (qx scan), obeying (T -846K), is reproducibly observed.Longitudinal scans measured in beta phase also revealed an anomalous broadening in total reflection regime.

Vanadium dioxide (VO2) thin films with different microstructure and orientations were deposited on sapphire and MgO substrates using pulsed laser deposition technique (PLD). X-ray diffraction (XRD), scanning probe microscopy (SPM), resistivity, and spectrophotometry measurements were used to analyze the effect of microstructure and orientation on the metal–insulator transition (MIT) characteristics of the films in order to optimize film properties for IR wavelength optical shutters. Films with five different epitaxial in plane orientations including (100), (001), (020), (011), and (111), and polycrystalline films were deposited by varying substrate orientation and partial oxygen pressure. Depending on the crystal orientation, microstructure, and thickness, films performed 3–4 decades MIT in resistivity with varying transition temperatures and hysteresis loop widths. Metal state transmittance at the wavelength of 1.5μm as low as 0.1% was measured leading to optical density of ODλ≈105. Steepest transitions and narrow hysteresis loops were found in the films with lowest lattice misfit strain and in the polycrystalline structures, where residual macroscopic stress was relaxed due to cracking.

Nitric oxide (NO) gas sensing with carboxyl functionalized single‐ and multi‐walled carbon nanotubes (SWCNTs and MWCNTs) is demonstrated in this work. Stable solutions of the carboxylated nanotubes were made and then drop‐cast on alumina substrates equipped with gold electrodes and also with platinum heater elements. The obtained resistive nanotube sensors were tested in a 2‐point setup at different temperatures and NO gas concentrations up to 100 ppm in synthetic air and also in argon buffer. When exposed to NO, the conductivity of the sensors changed up to ∼40% for SWCNTs and ∼12% for MWCNTs; however, in the investigated regime, the response was found to be fairly independent on NO concentration. Though all sensors showed practically instantaneous gas response, the time needed for saturation (few tens of minutes) was found to be concentration dependent. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Transparent and conductive patterns of carboxyl functionalized single-walled carbon nanotubes (SWCNT-COOHs) and the composites of those with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) were deposited on various substrates by inkjet printing. For low print repetitions, the PEDOT-PSS/SWCNT-COOH composite patterns show enhanced conductance as compared to the corresponding PEDOT-PSS conductors. The results suggest a decreased percolation threshold for the printed composite since the nanotubes establish electrical interconnections between the separate PEDOT-PSS (conductive phase) islands being dispersed in the insulating PSS-phase. However, the interaction between PEDOT-PSS and SWCNTs becomes insignificant and the conductivity is not enhanced by the nanotubes, when the amount of PEDOT-PSS is sufficient to form a continuous conducting phase. Up to now, patterns having sheet resistivities as low as similar to 1 k Omega/square could be achieved. Though there is a trade-off between transparency and conductivity - we achieved highly transparent patterns (similar to 90%) with a reasonably low resistivity of similar to 10 k Omega/square. The ink and printing method proposed here offer new alternatives of conventional transparent conductive materials based on either polymers or indium oxides; and pose scaleable production of cost-effective transparent electronics. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New Nanoparticle-based Materials and Devices Produced by Advanced Gas Evaporation, Reactive Sputtering and Microorganisms