Search results for "Thermal Stability"

Epoxy composites filled with high surface area-carbon fillers

2013

Citation: J. Appl. Phys. 114, 164304 (2013); doi: 10.1063/1.4826529 (Received 24 July 2013; accepted 6 October 2013; published online 22 October 2013) A comprehensive analysis of electrical, electromagnetic (EM), mechanical, and thermal properties of epoxy resin composites filled with 0.25–2.0 wt. % of carbon additives characterized by high surface area, both nano-sized, like carbon nanotubes (CNTs) and carbon black (CBH), and micro-sized exfoliated graphite (EG), was performed. We found that the physical properties of both CNTs- and CBH-based epoxy resin composites increased all together with filler content and even more clearly for CBH than for CNTs. In the case of EG-based composites, go…

Highly Robust but Surface-Active: N-Heterocyclic Carbene-Stabilized Au25 Nanocluster as a Homogeneous Catalyst

2019

<div> <div> <div> <p>Surface organic ligands play a critical role in stabilizing atomically precise metal nanoclusters in solutions. However, it is still challenging to prepare highly robust ligated metal nanoclusters that are surface-active for liquid-phase catalysis without any pre-treatment. Herein, we report a novel N-heterocyclic carbine-stabilized Au25 nanocluster with high thermal and air stabilities as a homogenous catalyst for cycloisomerization of alkynyl amines to indoles. The nanocluster, characterized as [Au25(iPr2-bimy)10Br7]2+ (iPr2-bimy=diisopropyl-benzilidazolium) (1), was synthesized by direct reduction of AuSMe2Cl and iPr2- bimyAuBr with NaBH4 in o…

Effect of the preparation method and grinding time of some mixed valency ferrite spinels on their cationic distribution and thermal stability toward …

1996

Abstract The reactivity in oxygen of several mixed valency ferrite spinels, namely Fe3O4, FeCr2O4, Fe3 − xTixO4 and Fe3 − xMoxO4 was investigated by derivative thermogravimetry (DTG) analysis as a function of the conditions of preparation and grinding. For all these compounds, low temperature preparation or prolonged grinding time enables small particles ( 0.5 μm), it was observed that oxidation was starting at higher temperature and that the defect spinel phases could not be retained during oxidation. This behaviour was attributed to the presence of stresses induced by the lattice parameter gradient and promoting the formation of nuclei of the α-rhombohedral phase from the superficial γ-de…

The Annealing Behavior of the Subsurface Zone Induced by Friction in Bismuth Detected by Positron Lifetime Technique

2013

The annealing behavior of the subsurface zone (SZ) in pure bismuth induced by dry sliding was studied using the positron lifetime measurement. This measurement allows us to detect the SZ and its recovery, and recrystallization processes. The comparative measurements of the sample exposed to compression revealed the thermal stability of the SZ. The compressed sample rebuilt its structure due to the recovery and recrystallization processes at the temperature of 60 °C, whereas the sample exposed to dry sliding does it at higher temperature of 260 °C, which is close to the melting point. The isothermal annealing at the temperature of 100 °C confirmed these results. The defect depth profile indu…

Thermostability of polymeric langmuir-blodgett films

1991

Surfactant-Assisted Synthesis of Mesoporous Alumina Showing Continuously Adjustable Pore Sizes

1999

Porous materials displaying tailor-made pore sizes and shapes are particularly interesting in a great variety of real and potential applications where molecular recognition is needed, such as shape-selective catalysis, molecular sieving, and selective adsorption. Classically, apart from silica, materials most commonly used for catalysis and catalyst supports have been those based on high surface aluminas, owing to their thermal, chemical, and mechanical stability and their low cost. Earlier aluminas with high surface areas (~500 m/g) had been prepared using structure-directing agents. However, they were X-ray amorphous materials and their porosity was purely textural, characterized by wide …

Methoxycarbazolyl-disubstituted dibenzofuranes as holes- and electrons-transporting hosts for phosphorescent and TADF-based OLEDs

2020

This research was funded by European Social Fund (Project No 09.3.3-LMT-K-712-02-0105). DG acknowledges to the ERDF PostDoc grant No. 1.1.1.2/VIAA/1/16/177.

Dispersions of Nanoclays of Different Shapes into Aqueous and Solid Biopolymeric Matrices. Extended Physicochemical Study

2010

Dispersions of nanofillers into aqueous and solid biopolymeric matrices were studied from the physicochemical viewpoint. This work was carried out based on the idea that the combination of biopolymers, derived from renewable resources, and nanofiller, environmentally friendly, may form a new generation of nanomaterials with excellent and unique properties at low cost. To this purpose, two pectins with different degrees of methyl esterification and nanoclays like halloysite and laponite RD were selected. The thermodynamic and structural studies on the aqueous mixtures of pectin and nanoclay were able to discriminate the interactions, which control the adsorption of pectin onto the filler and…

Enhanced surface area in thermally stable pure mesoporous TiO2

2000

Abstract We describe here for the first time the surfactant-assisted synthesis of thermally stable mesoporous pure TiO 2 having a high surface area. Our synthetic approach to the chemistry of this system is based on the equilibrium between the hydrolysis and condensation reactions of the inorganic species and the organic–inorganic self-assembling processes. The use of titanatrane complexes helps to retard the hydrolysis and condensation reactions, thus allowing us to overcome the difficulties in preparing titanium dioxide mesoporous materials starting from highly reactive Ti-alkoxides. The mesoporous material has been characterized by TEM, XRD and N 2 adsorption–desorption isotherms and dis…

Stable anchoring of dispersed gold nanoparticles on hierarchic porous silica-based materials

2010

The nanometric organization of MOx (M = Co, Zn, Ni) domains partially embedded inside the mesoporous silica walls but accessible to the pore voids, which is achieved through a simple one-pot surfactant-assisted procedure, define optimal anchors for the nucleation and growth of gold nanoparticles, which in turn favours an exceptional thermal stability for the final Au-supported materials. As silica support we have selected a UVM-7 silica having a highly accessible architecture defined by two hierarchic pore systems. The combination of nanometric pore length, tortuous mesopores and MOx inorganic anchors favours the stability of the final Au/CoOx-UVM-7 nanocomposites.