Triggering the catalytic activity of SrTiO3-based ceramics by flash sintering

Confinement of charge carriers in nanoscopic systems has revealed to be an effective strategy to confer ceramic materials unconventional conductive properties by exploiting particle size effects and interfaces characteristics[1]. Strontium titanate (SrTiO3) is a piezoelectric oxide that requires to be doped by acceptor species (e.g. Fe substitution of Ti centers) in order to acquire fair chemical reactivity[2]. Please click Additional Files below to see the full abstract

SiO2/Ladder-Like Polysilsesquioxanes Nanocomposite Coatings: Playing with the Hybrid Interface for Tuning Thermal Properties and Wettability

The present study explores the exploitation of ladder-like polysilsesquioxanes (PSQs) bearing reactive functional groups in conjunction with SiO2 nanoparticles (NPs) to produce UV-curable nanocomposite coatings with increased hydrophobicity and good thermal resistance. In detail, a medium degree regular ladder-like structured poly (methacryloxypropyl) silsesquioxane (LPMASQ) and silica NPs, either naked or functionalized with a methacrylsilane (SiO2@TMMS), were blended and then irradiated in the form of a film. Material characterization evidenced significant modifications of the structural organization of the LPMASQ backbone and, in particular, a rearrangement of the silsesquioxane chains at the interface upon introduction of the functionalized silica NPs. This leads to remarkable thermal resistance and enhanced hydrophobic features in the final nanocomposite. The results suggest that the adopted strategy, in comparison with mostly difficult and expensive surface modification and structuring protocols, may provide tailored functional properties without modifying the surface roughness or the functionalities of silsesquioxanes, but simply tuning their interactions at the hybrid interface with silica fillers

Sol-gel derived mesoporous Pt and Cr-doped WO(3) thin films: the role played by mesoporosity and metal doping in enhancing the gas sensing properties

Mesoporous Cr or Pt-doped WO(3) thin films to be employed as ammonia gas sensors were prepared by a fast one-step sol-gel procedure, based on the use of triblock copolymer as templating agent. The obtained films were constituted by aggregates of interconnected WO(3) nanocrystals (20-50 nm) separated by mesopores with dimensions ranging between 2 and 15 nm. The doping metals, Pt and Cr, resulted differently hosted in the WO(3) mesoporous matrix. Chromium is homogeneously dispersed in the oxide matrix, mainly as Cr(III) and Cr(V) centers, as revealed by EPR spectroscopy; instead platinum segregated as Pt (0) nanoparticles (4 nm) mainly included inside the WO(3) nanocrystals. The semiconductor layers containing Pt nanoclusters revealed, upon exposure to NH(3), remarkable electrical responses, much higher than Cr-doped and undoped layers, particularly at low ammonia concentration (6.2 ppm). This behavior was attributed to the presence of Pt nanoparticles segregated inside the semiconductor matrix, which act as catalysts of the N-H bond cleavage, decreasing the activation barrier in the ammonia dissociation. The role of the mesoporous structure in influencing the chemisorption and the gas diffusion in the WO(3) matrix appeared less decisive than the electronic differences between the two examined doping metals. The overall results suggest that a careful combination between mesoporous architecture and metal doping can really promote the electrical response of WO(3) toward ammonia

SiO2/Ladder-Like Polysilsesquioxanes Nanocomposite Coatings: Playing with the Hybrid Interface for Tuning Thermal Properties and Wettability

The present study explores the exploitation of ladder-like polysilsesquioxanes (PSQs) bearing reactive functional groups in conjunction with SiO2 nanoparticles (NPs) to produce UV-curable nanocomposite coatings with increased hydrophobicity and good thermal resistance. In detail, a medium degree regular ladder-like structured poly (methacryloxypropyl) silsesquioxane (LPMASQ) and silica NPs, either naked or functionalized with a methacrylsilane (SiO2@TMMS), were blended and then irradiated in the form of a film. Material characterization evidenced significant modifications of the structural organization of the LPMASQ backbone and, in particular, a rearrangement of the silsesquioxane chains at the interface upon introduction of the functionalized silica NPs. This leads to remarkable thermal resistance and enhanced hydrophobic features in the final nanocomposite. The results suggest that the adopted strategy, in comparison with mostly difficult and expensive surface modification and structuring protocols, may provide tailored functional properties without modifying the surface roughness or the functionalities of silsesquioxanes, but simply tuning their interactions at the hybrid interface with silica fillers

The Role of Inorganic Fillers in Electrostatic Discharge Composites

The occurrence of uncontrolled electrostatic discharge (ESD) is among the major causes of damage in unprotected electronic components during industrial processes. To counteract this undesired phenomenon, ESD composites showing static-dissipative and antistatic responses are developed. In particular, static-dissipative materials are able to slow down the flow of electric charges, whereas antistatic materials directly suppress the initial charges induced by undesired charging by properly dispersing conductive fillers within an insulant matrix and thus forming a conductive filler network. In this context, the purpose of this review is to provide a useful resume of the main fundamentals of the technology necessary for facing electrostatic charging. The formation mechanisms of electrostatic charges at the material surface were described, providing a classification of ESD composites and useful characterization methods. Furthermore, we reported a deep analysis of the role of conductive fillers in the formation of filler networks to allow electric charge movements, along with an overview of the different classes of inorganic conductive fillers exploitable in ESD composites, evidencing pros/cons and criticalities of each category of inorganic fillers

New Insights into the SnO₂ Sensing Mechanism Based on the Properties of Shape Controlled Tin Oxide Nanoparticles

We report on the sensing behavior of SnO₂ shape controlled nanocrystals in order to evaluate the role of their exposed crystal surfaces in the sensing mechanism. Octahedral (OCT), elongated dodecahedral (DOD), and nanobar shaped (NBA) nanocrystals were synthesized by previously reported procedures and their performances were evaluated in the sensing toward CO. Singly ionized oxygen vacancies (V_O^•) were detected by electron spin resonance (ESR), and their abundance and reactivity were associated to the exposed crystal faces and, in turn, to the sensing responses of the nanocrystals. Results indicated that the electrical properties and the formation/reactivity of the V_O^• centers are interconnected and are relatable to the nanoparticle specific surfaces. Two different temperature-dependent sensing mechanisms were proposed, depending on the prevalence of the surface structure or of the specific surface area on the sensing ability of shape controlled SnO₂ nanoparticles

Hydrothermal N-doped TiO2: Explaining photocatalytic properties by electronic and magnetic identification of N active sites

N-doped TiO2 nanocrystals with high photoactivity in the visible range, were successfully synthesized by hydrothermal method, followed by thermal annealing at different temperatures (350–600 8C), in order to allow differential nitrogen diffusion into the TiO2 lattice. Optical and magnetic properties, studied by diffuse reflectance spectroscopy, electron paramagnetic resonance and X-ray photoelectron spectroscopy analysis, revealed that TiO2 was effectively doped. The thermal treatment induces insertion of nitrogen into TiO2 lattice in the form of nitride anion NÀ, detected as N by EPR, whose ionic character varies with the temperature of annealing. The amount of N increases till 450 8C, then it decreases. Similar trend was observed for the photomineralization of phenol under visible light irradiation (l > 385 nm): the photoactivity of N-doped samples becomes maximum for N–TiO2 annealed at 450 8C. The overall results suggest that the efficacy of the catalyst depends on the ability of NÀ centers to trap photogenerated holes. This effect lowers the rate of electron–hole recombination and allows the N (NÀ + h+) center acts as strong oxidizing agent

Hydrothermal N-doped TiO2: Explaining photocatalytic properties by electronic and magnetic identification of N active sites

N-doped TiO2 nanocrystals with high photoactivity in the visible range, were successfully synthesized by hydrothermal method, followed by thermal annealing at different temperatures (350–600 8C), in order to allow differential nitrogen diffusion into the TiO2 lattice. Optical and magnetic properties, studied by diffuse reflectance spectroscopy, electron paramagnetic resonance and X-ray photoelectron spectroscopy analysis, revealed that TiO2 was effectively doped. The thermal treatment induces insertion of nitrogen into TiO2 lattice in the form of nitride anion NÀ, detected as N by EPR, whose ionic character varies with the temperature of annealing. The amount of N increases till 450 8C, then it decreases. Similar trend was observed for the photomineralization of phenol under visible light irradiation (l > 385 nm): the photoactivity of N-doped samples becomes maximum for N–TiO2 annealed at 450 8C. The overall results suggest that the efficacy of the catalyst depends on the ability of NÀ centers to trap photogenerated holes. This effect lowers the rate of electron–hole recombination and allows the N (NÀ + h+) center acts as strong oxidizing agent

Tailoring the Thermal Conductivity of Rubber Nanocomposites by Inorganic Systems: Opportunities and Challenges for Their Application in Tires Formulation

The development of effective thermally conductive rubber nanocomposites for heat management represents a tricky point for several modern technologies, ranging from electronic devices to the tire industry. Since rubber materials generally exhibit poor thermal transfer, the addition of high loadings of different carbon-based or inorganic thermally conductive fillers is mandatory to achieve satisfactory heat dissipation performance. However, this dramatically alters the mechanical behavior of the final materials, representing a real limitation to their application. Moreover, upon fillers’ incorporation into the polymer matrix, interfacial thermal resistance arises due to differences between the phonon spectra and scattering at the hybrid interface between the phases. Thus, a suitable filler functionalization is required to avoid discontinuities in the thermal transfer. In this challenging scenario, the present review aims at summarizing the most recent efforts to improve the thermal conductivity of rubber nanocomposites by exploiting, in particular, inorganic and hybrid filler systems, focusing on those that may guarantee a viable transfer of lab-scale formulations to technological applicable solutions. The intrinsic relationship among the filler’s loading, structure, morphology, and interfacial features and the heat transfer in the rubber matrix will be explored in depth, with the ambition of providing some methodological tools for a more profitable design of thermally conductive rubber nanocomposites, especially those for the formulation of tires