1,721,024 research outputs found
The Influence of Nb on the Synthesis of WO<sub>3</sub> Nanowires and the Effects on Hydrogen Sensing Performance
No full textHydrogen sensing is becoming one of the hottest topics in the chemical sensing field, due to its wide number of applications and the dangerousness of hydrogen leakages. For this reason, research activities are focusing on the development of high-performance materials that can be easily integrated in sensing devices. In this work, we investigated the influence of Nb on the sensing performances of WO3 nanowires (NWs) synthetized by a low-cost thermal oxidation method. The morphology and the structure of these Nb-WO3 nanowires were investigated by field emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD), Raman and X-ray photoelectron (XPS) spectroscopies, confirming that the addition of Nb does not modify significantly the monoclinic crystal structure of WO3. Moreover, we integrated these NWs into chemical sensors, and we assessed their performances toward hydrogen and some common interfering compounds. Although the hydrogen sensing performances of WO3 nanowires were already excellent, thanks to the presence of Nb they have been further enhanced, reaching the outstanding value of more than 80,000 towards 500 ppm @ 200 °C. This opens the possibility of their integration in commercial equipment, like electronic noses and portable devices
Low-power detection of food preservatives by a novel nanowire-based sensor array
No full textFood preservatives are compounds that are used for the treatment of food to improve the shelf life. In the food industry, it is necessary to monitor all processes for both safety and quality of the product. An electronic nose (or e-nose) is a biomimetic olfactory system that could find numerous industrial applications, including food quality control. Commercial electronic noses are based on sensor arrays composed by a combination of different sensors, which include conductometric metal oxide devices. Metal oxide nanowires are considered among the most promising materials for the fabrication of novel sensing devices, which can enhance the overall performances of e-noses in food applications. The present work reports the fabrication of a novel sensor array based on SnO2, CuO, and WO3 nanowires deposited on top of μHPs provided by ams Sensor Solutions Germany GmbH. The array was tested for the discrimination of four typical compounds added to food products or used for their treatment to increase the shelf life: ethanol, acetone, nitrogen dioxide, and ozone. Results are very promising; the sensors array was able to operate for a long time, consuming less than 50 mW for each single sensor, and principal component analysis (PCA) confirmed that the device was able to discriminate between different compounds
Solid oxide fuel cell: Decade of progress, future perspectives and challenges
No full textIn an increasing demand of renewable energy resources, fuel cell represents the highly efficient, clean and sustainable energy conversion source. Broadly speaking, fuel cell can be divided into six different categories according to the types of electrolyte and fuels used. Each type of fuel cells has their own advantages and disadvantages. Among them, solid oxide fuel cell (SOFC) gains significant attentions due to their high efficiency, cost-effectiveness and the possibility to utilize variety of fuels other than hydrogen such as hydrocarbons, coal gas etc. As name implies, SOFC uses solid electrolyte for their operation. Indeed, in medium and large power requirement sectors, SOFC are highly suitable. In the present review article, recent advances and future perspectives of SOFC have been discussed via reviewing the literature over last five years. Most of the available review articles discussed the literature in terms of specific SOFC component such as anode, cathode, electrolytes and so on. In contrast, herein the literatures have been reviewed in the context of two types of SOFC stack designs i.e. planar and tubular that have been immensely used to fabricate efficient SOFC devices. Furthermore, fundamental of SOFC operation and its typical I–V characteristics and SOFC designs are also discussed in detail. Furthermore, preparation techniques for planar and tubular SOFC are briefly described. Finally, some of the recent trends in SOFC technology along with challenges and future perspectives are presented in this review article
NiO-GDC nanowire anodes for SOFCs: novel growth, characterization and cell performance
No full textA solid-oxide fuel cell (SOFC) is a sustainable energy resource that has been efficiently used for large-scale applications such as gas-turbines. However, its miniaturization for small-scale applications requires novel electrode materials especially anodes (other than Ni-YSZ) in different configurations and designs such as in the nanostructure form. Herein, we are proposing the growth of a novel nickel oxide-gadolinium doped ceria (NiO-GDC) nanowire-based anode using a vapor-liquid-solid (VLS) mechanism. To the best of our knowledge, NiO-GDC has never been grown before in the form of nanowires using the VLS mechanism. The nanowires are prepared at different evaporation temperatures and exhibit dense morphology. Detailed Raman spectroscopy reveals that during the growth, reorganization of NiO-GDC particles results in the formation of a more complex structure that diverges from pristine NiO-GDC powder. Furthermore, the temperature-dependence of the electrical conductivity reveals that the nanowires prepared at 1400 degrees C (evaporation temperature) possess high conductivity due to better charge-carrier transport, confirmed by their low activation energies. The electrolyte-supported button cell synthesized using a NiO-GDC nanowire anode exhibits a maximum power density of similar to 178 mW cm(-2) at 800 degrees C and concentration polarization is found to be the major loss, as revealed by electrochemical impedance spectroscopy (EIS) data. Based on our preliminary investigations, these nanowires have great potential to be used as an anode for SOFCs
Materials Engineering for Chemical Sensing Enhancement
No full textMetal oxides nanowires and novel heterostructures are synthesized using different techniques and finally integrated into gas sensing platform. In particular, nanowires were synthesized using thermal oxidation and VLS mechanism. While, heterostructures i.e. NiO/ZnO (p-n) and NiO/NiWO4/WO3 (p-p-n) were synthesized using VLS and VS mechanisms. Detailed investigations reveal the dependence of sensors selectivity and sensitivity on nanowires synthesis techniques. While, the superior performance of heterostructures as compared to bare nanowires presents the novel pathway to further enhance the performance of nanostructured gas sensors
Shelf Life Study of NiO Nanowire Sensors for NO2 Detection
No full textAbstract: In this letter, conductometric sensing devices based on VLS grown NiO nanowires were presented for the detection of low concentrations of NO2. Moreover, the shelf life of sensing devices stored in ambient environmental conditions was tested over a period of 6 months. The VLS grown NiO nanowires were uniform in nature, covering completely the substrate surface area, with diameters ranging from 10 to 50 nm. The sensing devices show excellent performances, such as good stability, high response, outstanding selectivity toward NO2 and low detection limit. The devices were tested toward different analytes such as H2, acetone, NO2, etc. Indeed, at optimal working temperature, they show highly selective behavior towards NO2. Finally, the shelf life study reports that, due the exposure to the atmosphere, NiO nanowires exhibit a decrease in their conductivity, which enhances the response of the sensor. Graphic Abstract: [Figure not available: see fulltext.
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
One dimensional ZnO nanostructures: Growth and chemical sensing performances
No full textRecently, one-dimensional (1D) nanostructures have attracted the scientific community attention as sensitive materials for conductometric chemical sensors. However, finding facile and low-cost techniques for their production, controlling the morphology and the aspect ratio of these nanostructures is still challenging. In this study, we report the vapor-liquid-solid (VLS) synthesis of one dimensional (1D) zinc oxide (ZnO) nanorods (NRs) and nanowires (NWs) by using different metal catalysts and their impact on the performances of conductometric chemical sensors. In VLS mechanism, catalysts are of great interest due to their role in the nucleation and the crystallization of 1D nanostructures. Here, Au, Pt, Ag and Cu nanoparticles (NPs) were used to grow 1D ZnO. Depending on catalyst nature, different morphology, geometry, size and nanowires/nanorods abundance were established. The mechanism leading to the VLS growth of 1D ZnO nanostructures and the transition from nanorods to nanowires have been interpreted. The formation of ZnO crystals exhibiting a hexagonal crystal structure was confirmed by X-ray diffraction (XRD) and ZnO composition was identified using transmission electron microscopy (TEM) mapping. The chemical sensing characteristics showed that 1D ZnO has good and fast response, good stability and selectivity. ZnO (Au) showed the best performances towards hydrogen (H2). At the optimal working temperature of 350◦ C, the measured response towards 500 ppm of H2 was 300 for ZnO NWs and 50 for ZnO NRs. Moreover, a good selectivity to hydrogen was demonstrated over CO, acetone and ethanol
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