Search results for "ALLOYS"

Halloysite Nanotubes: Smart Nanomaterials in Catalysis

2022

The use of clay minerals as catalyst is renowned since ancient times. Among the different clays used for catalytic purposes, halloysite nanotubes (HNTs) represent valuable resources for industrial applications. This special tubular clay possesses high stability and biocompatibility, resistance against organic solvents, and most importantly be available in large amounts at a low cost. Therefore, HNTs can be efficiently used as catalysts themselves or supports for metal nanoparticles in several catalytic processes. This review reports a comprehensive overview of the relevant advances in the use of halloysite in catalysis, focusing the attention on the last five years.

Orientation of charged clay nanotubes in evaporating droplet meniscus.

2015

© 2014 Elsevier Inc. During drying, an aqueous suspension of strongly charged halloysite clay nanotubes concentrates at the edge of the droplet ("coffee-ring" effect) which provides alignment of the tubes along the liquid-substrate contact line. First, the surface charge of the nanotubes was enhanced by polyanion adsorption inside of the lumen to compensate for the internal positive charges. This increased the magnitude of the ξ-potential of the tubes from -36 to -81mV and stabilized the colloids. Then, colloidal halloysite was dropped onto the substrate, dried at 65°C and after a concentration of ~0.05mgmL-1 was reached, the alignment of nanotubes occurred starting from the droplet edges. …

MODELING OF SPIRAL HALLOYSITE NANOTUBES

2013

Functionalized halloysite nanotubes for enhanced removal of lead(II) ions from aqueous solutions

2018

In this study, environmental friendly halloysite nanotubes and their amino derivatives were used as adsorbent materials for lead(II) ions. The adsorption ability of both nanomaterials towards Pb2+ ions has been studied in NaClaq, at I = 0.1 mol L−1, in the pH range 3–6. Moreover, the effect of ionic strength on the adsorption process was evaluated at the pH of maximum efficiency of the adsorbent materials. Kinetic and equilibrium experiments were carried out by using the Differential Pulse Anodic Stripping Voltammetry (DP-ASV) technique to check the metal ion concentration in solution after contact with the two adsorbents. Different isotherm and kinetic equations were used to fit the experi…

Co-loaded cardanol/triazole-halloysite system: characterization of the supramolecular complex and evaluation of its antiproliferative activity

2014

Halloysite nanotubes modified with triazolium salts (f-HNT) were found to be promising drug carriers for biological molecules [1 ]. In this work we report data about f-HNT as carrier for cardanol, a molecule with interesting biological activity [2]. The interactio n between cardanol and f- HNT was highlighted by HPLC, FTIR spectroscopy, TGA , water contact angle measurements and SEM investigations. Release of cardanol from the system and cytotoxic e ffect of the complex f- HNT/Card on hepatocarcinoma cell lines were, also, evaluated. The obtained results put forward the use of halloysite as drug c arrier

HALLOYSITE NANOTUBES AS SUPPORT FOR METAL NANOPARTICLES FOR CATALYTIC APPLICATION

2017

Halloysite (HNT) is a natural clay that, in the last years, has shown an important increasing on various applications in different field of interesting. Chemically similar to kaolin, it shows the predominately rolled shape, to form multilayers tubes of nanometric dimensions. The different chemical composition of the inside lumen (Al-OH) surface and outside (Si-O) give to the tubes a partial negative charge outside and positive inside. In this way, it is possible to get different interactions of different molecules or systems selectivity on one or another surface. The selective functionalization, covalent or not, of the HNT lumen or outer surface, gives the possibility to the nanotubes to fu…

Protonation Constants of Halloysite Clay Nanotubes

2015

Halloysite is one of the most interesting nano-structured clay materials. It is similar to kaolin but has a hollow tubular structure that can be attributable to particular crystallization conditions. Typically, halloysite nanotubes (HNTs) are formed by 15 – 20 aluminosilicate layers, has a length of 1 ± 0.5 μm and inner and outer diameters of 1 - 30 and 30 - 50 nm, respectively [1,2]. In each layer the SiOH and the AlOH groups are disposed on the external and the internal surfaces, respectively. The particular structure of HNTs makes this kind of material very useful for different purposes in several fields. Among the various applications, worth of mention are: i) their use as additive for …

WOOD TREATMENT BASED ON HALLOYSITE/HYDROXYPROPYL CELLULOSE COMPOSITE. THERMOMECHANICAL AND POROSITY CHARACTERIZATION

2014

Materiali argillosi ibridi con potenziale attività biologica

2021

CHEMICAL MODIFICATIONS OF HALLOYSITE NANOTUBES FOR THE DEVELOPMENT OF SMART NANOMATERIALS

2015

Halloysite nanoclays (HNTs) are promising nanomaterials because of their versatile properties, such as hollow tubular morphology and tunable surface chemistry. HNTs are biocompatible, no toxic and abundantly available at low cost. Due to these characteristics HNTs are suitable for development of hybrid sustainable materials, which are perspective for wastewater remediation, green packaging and drug delivery. HNTs are quite polydisperse in size with a length of ca. 1 m, while the external diameter and the lumen range between 50-80 nm and 10-15 nm, respectively. Chemically, halloysite is composed of gibbsite octahedral sheet (Al-OH) groups on the inner surface and siloxane (Si−O−Si) groups o…