Search results for "engineering.material"
showing 10 items of 2352 documents
Out-of-plane transport of 1T-TaS2/graphene-based van der Waals heterostructures
2021
Due to their anisotropy, layered materials are excellent candidates for studying the interplay between the in-plane and out-of-plane entanglement in strongly correlated systems. A relevant example is provided by 1T-TaS2, which exhibits a multifaceted electronic and magnetic scenario due to the existence of several charge density wave (CDW) configurations. It includes quantum hidden phases, superconductivity and exotic quantum spin liquid (QSL) states, which are highly dependent on the out-of-plane stacking of the CDW. In this system, the interlayer stacking of the CDW is crucial for the interpretation of the underlying electronic and magnetic phase diagram. Here, thin-layers of 1T-TaS2 are …
Microhardness and adhesion measurements of reactively sputtered TiN/AlN multilayer coatings deposited as function of mass-flow of nitrogen
1998
Abstract Multilayer coatings of (Ti, Al)N x have been deposited by reactive sputtering from Ti and Al targets in a side-by-side configuration on WC and stainless steel substrates. The rotation of the substrate holder varied from 2 to 14 r.p.m. corresponding to a bilayer thickness of 0.8–8 nm. The acoustic emission scratch technique for adhesion measurements was used for studying coating performance, and critical load values for the coatings on WC substrate up to 150 N were obtained. The Vickers microhardness in the load range 0.003–2 N was measured, and in order to obtain true hardness values, an optimal range of indentation depth and coating thickness was determined. Depending on the nitro…
The role of atomic static displacements in binary-alloy formation
2003
Abstract A microscopic approach to considering the influence of local atomic static displacements (LASD) on binary alloy thermodynamic properties has been developed. The explicit expression for the free energy of a disordered alloy is derived within the collective variables method. The LASD are shown to promote formation of a disordered alloy. The theory is illustrated by numerical calculations performed for alloys of the Ca–Ba system. Dependence of the alloy formation heat on temperature and concentration obtained numerically agrees perfectly with the experimental data.
Chitosan-Coating Deposition via Galvanic Coupling
2019
A galvanic method to deposit chitosan coatings on stainless steel substrate is reported. Deposition of suitable coatings is desired to improve biocompatibility and corrosion resistance of metallic medical devices to be implanted in human body. In the present work, a thin hydrogel layer of chitosan was deposited on 304SS by a galvanic displacement reaction, which is advantageous first as it does not require external power supply. 304SS was immersed into an aqueous solution of chitosan/lactic acid and electrochemically coupled with magnesium acting as a sacrificial anode. SEM images showed the formation of a uniform layer of chitosan with a thickness controlled by deposition time. Corrosion t…
Halloysite nanotubes as support for metal-based catalysts
2017
Halloysite nanotubes (HNTs) are clay minerals with a hollow nanotubular structure. There is growing interest in these nanomaterials, due to their biocompatibility, potential applications and availability. The surface chemistry of HNTs is versatile for the targeted chemical modification of the inner lumen and outer surface. Functionalized halloysite constitutes a valuable support for metal nanoparticles, promoting catalytic applications with tunable properties. The peculiar tubular shape of HNTs favors the dispersion and surface availability of the supported metal nanoparticles that are active in the catalytic path. Moreover, the presence of an empty lumen opens new perspectives for the prod…
Halloysite Nanotubes: Interfacial Properties and Applications in Cultural Heritage
2020
The peculiar surfaces of halloysite nanotubes and their biocompatibility are attracting the interest of researchers based on the wide range of attainable applications. The large aspect ratio of this nanotubular material ensures promising properties as a reinforcing agent in polymeric matrixes, such as cellulose and its derivatives, that entail strengthening due to, for instance, aging-induced degradation. The halloysite cavity has a suitable size for hosting a large variety of active species such as deacidifying (calcium hydroxide) and flame retardant agents (fluorinated surfactants) for a controlled and sustained release relevant to the conservation of cultural heritage. Additionally, anio…
Boosting the properties of a fluorescent dye by encapsulation into halloysite nanotubes
2021
Abstract The synthesis of a new biocompatible bichromophoric system (CURBO) was developed, by connecting the skeleton of the naturally occurring curcumin to a BODIPY derivative. The system exhibited an intense fluorescence band with maximum at about 510 nm in organic solvent, while its emission spectra in aqueous solution were more complicated and slightly red-shifted, due to the effect of aggregation for the poor solubility of the dyad. To overcome these problems, the bichomophoric system has been loaded into the halloysite nanotubes (HNT). The HNT/CURBO nanocomposite, suspended in aqueous solution, showed an intensity of emission in the red region of the spectrum higher than the one exhib…
Water-dispersed semiconductor nanoplatelets with high fluorescence brightness, chemical and colloidal stability
2019
Quasi-two dimensional semiconductor nanoplatelets (NPLs) exhibit high spectral brightness and large absorption cross sections, making them promising for various applications including bioimaging. However, the synthesis of NPLs takes place in organic solvents, therefore they require phase transfer in order to use them in aqueous environments. The phase transfer of NPLs has so far been challenging with few examples in literature. This is likely due to the facile agglomeration of materials with plate-like geometries during the coating procedure. Here we demonstrate how to overcome agglomeration and transfer NPLs, individually coated with amphiphilic polymer chains, to aqueous phase. Upon one a…
Multicavity halloysite-amphiphilic cyclodextrin hybrids for co-delivery of natural drugs into thyroid cancer cells
2015
Multicavity halloysite nanotube materials were employed as simultaneous carriers for two different natural drugs, silibinin and quercetin, at 6.1% and 2.2% drug loadings, respectively. The materials were obtained by grafting functionalized amphiphilic cyclodextrin onto the HNT external surface. The new materials were characterized by FT-IR spectroscopy, SEM, thermogravimetry, turbidimetry, dynamic light scattering and ζ-potential techniques. The interaction of the two molecules with the carrier was studied by HPLC measurements and fluorescence spectroscopy, respectively. The release of the drugs from HNT-amphiphilic cyclodextrin, at two different pH values, was also investigated by means of…
Biopolymer-Targeted Adsorption onto Halloysite Nanotubes in Aqueous Media.
2017
Studies on the adsorption of biopolymers onto halloysite nanotubes (HNTs) in water were conducted. Three polymers with different charges-anionic (pectin), neutral (hydroxypropyl cellulose), and cationic (chitosan)-were chosen. The thermodynamic parameters for the adsorption of polymers onto the HNT surface were determined by isothermal titration calorimetry (ITC). The experimental data were interpreted based on a Langmuir adsorption model. The standard variations in free energy, enthalpy, and entropy of the process were obtained and discussed. Turbidimetry was used to evaluate the stability of functionalized nanoparticles in water. The ζ-potential clarified the surface charge properties of …