Pt/MoO3 nano-flower/SiC Schottky diode based hydrogen gas sensor

In this paper, we report the development of a novel Pt/MoO3 nano-flower/SiC Schottky diode based device for hydrogen gas sensing applications. The MoO3 nanostructured thin films were deposited on SiC substrates via thermal evaporation. Morphological characterization of the nanostructured MoO3 by scanning electron microscopy revealed randomly orientated thin nanoplatelets in a densely packed formation of nano-flowers with dimensions ranging from 250 nm to 1 μm. Current-voltage characteristics of the sensor were measured at temperatures from 25°C to 250°C. The sensor showed greater sensitivity in a reverse bias condition than in forward bias. Dynamic response of the sensor was investigated towards different concentrations of hydrogen gas in a synthetic air mixture at 250°C and a large voltage shift of 5.7 V was recorded upon exposure to 1% hydrogen.

Pt/Graphene Nano-sheet Based Hydrogen Gas Sensor

In this paper, we present gas sensing properties of Pt/graphene-like nano-sheets towards hydrogen gas. The graphene-like nano-sheets were produced via the reduction of spray-coated graphite oxide deposited on SiC substrates by hydrazine vapor. Structural and morphological characterizations of the graphene sheets were analyzed by scanning electron and atomic force microscopy. Current-voltage and dynamic responses of the sensors were investigated towards different concentrations of hydrogen gas in a synthetic air mixture at 100°C. A voltage shift of 100 mV was recorded at 1 mA reverse bias current.

Pt/ZnO/SiC thin film for hydrogen gas sensing

Zinc oxide (ZnO) is one of the most promising electronic and photonic materials to date. In this work, we present an enhanced ZnO Schottky gas sensor deposited on SiC substrates in comparison to those reported previously in literature. The performance of ZnO/SiC based Schottky thin film gas sensors produced a forward lateral voltage shift of 12.99mV and 111.87mV in response to concentrations of hydrogen gas at 0.06% and 1% in air at optimum temperature of 330 ºC. The maximum change in barrier height was calculated as 37.9 meV for 1% H2 sensing operation at the optimum temperature.

Pt/anodized TiO2/SiC-based MOS device for hydrocarbon sensing

Pt/anodized TiO2/SiC based metal-oxide-semiconductor (MOS) devices were fabricated and characterized for their sensitivity towards propene (C3H6). Titanium (Ti) thin films were deposited onto the SiC substrates using a filtered cathodic vacuum arc (FCVA) method. Fluoride ions containing neutral electrolyte (0.5 wt% NH4F in ethylene glycol)were used to anodize the Ti films. The anodized films were subsequently annealed at 600 °C for 4 hrs in an oxygen rich environment to obtain TiO2. The current-voltage(I-V) characteristics of the Pt/TiO2/SiC devices were measured in different concentrations of propene. Exposure to the analyte gas caused a change in the Schottky barrier height and hence a lateral shift in the I-V characteristics. The effective change in the barrier height for 1% propene was calculated as 32.8 meV at 620°C. The dynamic response of the sensors was also investigated and a voltage shift of 157 mV was measured at 620°C during exposure to 1% propene.

Graphene-like nano-sheets/36° LiTaO3 surface acoustic wave hydrogen gas sensor

Presented is the material and gas sensing properties of graphene-like nano-sheets deposited on 36° YX lithium tantalate (LiTaO3) surface acoustic wave (SAW) transducers. The graphene-like nano-sheets were characterized via scanning electron microscopy (SEM), atomic force microscopy(AFM)and X-ray photoelectron spectroscopy (XPS). The graphenelike nano-sheet/SAW sensors were exposed to different concentrations of hydrogen (H2) gas in a synthetic air at room temperature. The developed sensors exhibit good sensitivity towards low concentrations of H2 in ambient conditions, as well as excellent dynamic performance towards H2 at room temperature.

Graphene-like nano-sheets based LiTaO3 surface acoustic wave NO2 gas sensor

Thin films consisting of graphene-like nano-sheets were deposited onto LiTaO3 surface acoustic wave transducers. A thickness of less than 10 nm and the existence of C-C bond were observed during the characterization of graphene-like nano-sheets. Frequency shift of 18.7 kHz and 14.9 kHz towards 8.5 ppm NO2 at two different operating temperature, 40°C and 25°C, respectively, was observed.

Pt/SnO2 nanowires/SiC based hydrogen gas sensor

Pt/SnO2 nanowires/SiC based metal-oxidesemiconductor (MOS) devices were fabricated and tested for their gas sensitivity towards hydrogen. Tin oxide (SnO2) nanowires were grown on SiC substrates by the vapour liquid solid growth process. The material properties of the SnO2 nanowires such as its formation and dimensions were analyzed using scanning electron microscopy (SEM). The currentvoltage (I-V) characteristics at different hydrogen concentrations are presented. The effective change in the barrier height for 0.06 and 1% hydrogen were found to be 20.78 and 131.59 meV, respectively. A voltage shift of 310 mV at 530°C for 1% hydrogen was measured.

Preparation and characterization of tin oxide nanowires on SiC

Interest in nanowires of metal oxide oxides has been exponentially growing in the last years, due to the attracting potential of application in electronic, optical and sensor field. We have focused our attention on the sensing properties of semiconducting nanowires as conductometric and optical gas sensors. Single crystal tin dioxide nanostructures were synthesized to explore and study their capability in form of multi-nanowires sensors. The nanowires of SnO2 have been used to produce a novel gas sensor based on Pt/oxide/SiC structure and operating as Schottky diode. For the first time, a reactive oxide layer in this device has been replaced by SnO2 nanowires. Proposed sensor has maintained the advantageous properties of known SiC- based MOS devices, that can be employed for the monitoring of gases (hydrogen and hydrocarbons) emitted by industrial combustion processes.

Hydrogen gas sensing properties of Pt/Ta2O5 Schottky diodes based on Si and SiC substrates

We developed Pt/tantalum oxide (Ta2O5) Schottky diodes for hydrogen sensing applications. Thin layer (4 nm) of Ta2O5 was deposited on silicon (Si) and silicon carbide (SiC) substrates using the radio frequency sputtering technique. We compared the performance of these sensors at different temperatures of 100 °C and 150 °C. At these operating temperatures, the sensor based on SiC exhibited a larger sensitivity, whilst the sensor based on Si exhibited a faster response toward hydrogen gas. We discussed herein, the experimental results obtained for these Pt/Ta2O5 based Schottky diodes exhibited that they are promising candidates for hydrogen sensing applications.

Deformation with coupled chemical diffusion

The deformation of rocks is commonly intimately associated with metamorphic reactions. This paper is a step towards understanding the behaviour of fully coupled, deforming, chemically reacting systems by considering a simple example of the problem comprising a single layer system with elastic-power law viscous constitutive behaviour where the deformation is controlled by the diffusion of a single chemical component that is produced during a metamorphic reaction. Analysis of the problem using the principles of non-equilibrium thermodynamics allows the energy dissipated by the chemical reaction-diffusion processes to be coupled with the energy dissipated during deformation of the layers. This leads to strain-rate softening behaviour and the resultant development of localised deformation which in turn nucleates buckles in the layer. All such diffusion processes, in leading to Herring-Nabarro, Coble or “pressure solution” behaviour, are capable of producing mechanical weakening through the development of a “chemical viscosity”, with the potential for instability in the deformation. For geologically realistic strain rates these chemical feed-back instabilities occur at the centimetre to micron scales, and so produce structures at these scales, as opposed to thermal feed-back instabilities that become important at the 100–1000 m scales.

Ethanol sensitivity of thermally evaporated nanostructured WO3 thin films doped and implanted with Fe

Ethanol sensing performance of gas sensors made of Fe doped and Fe implanted nanostructured WO3 thin films prepared by a thermal evaporation technique was investigated. Three different types of nanostructured thin films, namely, pure WO3 thin films, iron-doped WO3 thin films by co-evaporation and Fe-implanted WO3 thin films have been synthesized. All the thin films have a film thickness of 300 nm. The physical, chemical and electronic properties of these films have been optimized by annealing heat treatment at 300ºC and 400ºC for 2 hours in air. Various analytical techniques were employed to characterize these films. Atomic Force Microscopy and Transmission Electron Microscopy revealed a very small grain size of the order 5-10 nm in as-deposited WO3 films, and annealing at 300ºC or 400ºC did not result in any significant change in grain size. This study has demonstrated enhanced sensing properties of WO3 thin film sensors towards ethanol at lower operating temperature, which was achieved by optimizing the physical, chemical and electronic properties of the WO3 film through Fe doping and annealing.

Sensors for missions

An onboard payload may be seen in most instances as the “Raison d’Etre” for a UAV. It will define its capabilities, usability and hence market value. Large and medium UAV payloads exhibit significant differences in size and computing capability when compared with small UAVs. The latter have stringent size, weight, and power requirements, typically referred as SWaP, while the former still exhibit endless appetite for compute capability. The tendency for this type of UAVs (Global Hawk, Hunter, Fire Scout, etc.) is to increase payload density and hence processing capability. An example of this approach is the Northrop Grumman MQ-8 Fire Scout helicopter, which has a modular payload architecture that incorporates off-the-shelf components. Regardless of the UAV size and capabilities, advances in miniaturization of electronics are enabling the replacement of multiprocessing, power-hungry general-purpose processors for more integrated and compact electronics (e.g., FPGAs). Payloads play a significant role in the quality of ISR (intelligent, surveillance, and reconnaissance) data, and also in how quick that information can be delivered to the end user. At a high level, payloads are important enablers of greater mission autonomy, which is the ultimate aim in every UAV. This section describes common payload sensors and introduces two examples cases in which onboard payloads were used to solve real-world problems. A collision avoidance payload based on electro optical (EO) sensors is first introduced, followed by a remote sensing application for power line inspection and vegetation management.

Process monitoring using sensors in YAWL

This article describes the architecture of a monitoring component for the YAWL system. The architecture proposed is based on sensors and it is realized as a YAWL service to have perfect integration with the YAWL systems. The architecture proposed is generic and applicable in different contexts of business process monitoring. Finally, it was tested and evaluated in the context of risk monitoring for business processes.

Physico-chemical/biological properties of tripolyphosphate cross-linked chitosan based

In this study, chitosan-PEO blend, prepared in a 15 M acetic acid, was electrospun into nanofibers (~ 78 nm diameter) with bead free morphology. While investigating physico-chemical parameters of blend solutions, effect of yield stress on chitosan based nanofiber fabrication was clearly evidenced. Architectural stability of nanofiber mat in aqueous medium was achieved by ionotropic cross-linking of chitosan by tripolyphosphate (TPP) ions. The TPP cross-linked nanofiber mat showed swelling up to ~ 300 % in 1h and ~ 40 % degradation during 30 d study period. 3T3 fibroblast cells showed good attachment, proliferation and viability on TPP treated chitosan based nanofiber mats. The results indicate non-toxic nature of TPP cross-linked chitosan based nanofibers and their potential to be explored as a tissue engineering matrix.