A Summary of Methods for Fire Tests of Roof Coverings

AbstractThe testing method about the fire performance of roof covering and materials has not been put into operation in China. This article focuses on two main international testing about fire performance of roof covering and materials, comparing the difference between the two test methods

Controlling the Quality Factor of a Single Acoustic Nanoresonator by Tuning its Morphology

The mechanical vibrations of individual gold nanodisks nanopatterned on a sapphire substrate are investigated using ultrafast time-resolved optical spectroscopy. The number and characteristics of the detected acoustic modes are found to vary with nanodisk geometry. In particular, their quality factors strongly depend on nanodisk aspect ratio (i.e., diameter over height ratio), reaching a maximal value of ≈70, higher than those previously measured for substrate-supported nano-objects. The peculiarities of the detected acoustic vibrations are confirmed by finite-element simulations, and interpreted as the result of substrate-induced hybridization between the vibrational modes of a nanodisk. The present findings demonstrate novel possibilities for engineering the vibrational modes of nano-objects

Ultrafast Thermo-Optical Dynamics of Plasmonic Nanoparticles

Time-resolved thermoplasmonics is emerging as the go-to technique for nanoscale thermal metrology. In this context, connecting the ultrafast optical response of nanoobjects to the correct thermal pathways is of paramount importance. We developed full thermo-optical models relating transient spectroscopy measurements, performed on metal nanoobjects in dielectric environments, to the overall system thermal dynamics. The models are applicable to small spherical nanoparticles embedded in a homogeneous matrix, following an analytical approach, and are expanded to include the cases of arbitrarily complex geometries and sizes relying on the finite-element method. These approaches are then exploited to rationalize several observations made in the context of previous time-resolved thermo-optical studies at the nanoscale. The present tools open the path for accurate retrieval of thermal parameters, notably the Kapitza resistance and the local environment thermal conductivity, from experiments. They also allow identifying the optimal parameters for selectively probing thermal dynamics of either a nanoobject or its nanoscale environment

Bottom-Up Mechanical Nanometrology of Granular Ag Nanoparticles Thin Films

Ultrathin metal nanoparticles coatings, synthesized by gas-phase deposition, are emerging as go-to materials in a variety of fields ranging from pathogens control and sensing to energy storage. Predicting their morphology and mechanical properties beyond a trial-and-error approach is a crucial issue limiting their exploitation in real-life applications. The morphology and mechanical properties of Ag nanoparticle ultrathin films, synthesized by supersonic cluster beam deposition, are here assessed adopting a bottom-up, multitechnique approach. A virtual film model is proposed merging high resolution scanning transmission electron microscopy, supersonic cluster beam dynamics, and molecular dynamics simulations. The model is validated against mechanical nanometrology measurements and is readily extendable to metals other than Ag. The virtual film is shown to be a flexible and reliable predictive tool to access morphology-dependent properties such as mesoscale gas-dynamics and elasticity of ultrathin films synthesized by gas-phase deposition

Bottom-Up Mechanical Nanometrology of Granular Ag Nanoparticles Thin Films

Ultrathin metal nanoparticles coatings, synthesized by gas-phase deposition, are emerging as go-to materials in a variety of fields ranging from pathogens control and sensing to energy storage. Predicting their morphology and mechanical properties beyond a trial-and-error approach is a crucial issue limiting their exploitation in real-life applications. The morphology and mechanical properties of Ag nanoparticle ultrathin films, synthesized by supersonic cluster beam deposition, are here assessed adopting a bottom-up, multitechnique approach. A virtual film model is proposed merging high resolution scanning transmission electron microscopy, supersonic cluster beam dynamics, and molecular dynamics simulations. The model is validated against mechanical nanometrology measurements and is readily extendable to metals other than Ag. The virtual film is shown to be a flexible and reliable predictive tool to access morphology-dependent properties such as mesoscale gas-dynamics and elasticity of ultrathin films synthesized by gas-phase deposition