Review of thermal conductivity in composites: Mechanisms, parameters and theory

The light-harvesting and recycle of powder photocatalyst in suspended system are bottlenecks for high-efficient solar photocatalysis. Floating photocatalyst are highly sought-after and good candidates for practical environmental application due to the satisfaction with above requirements simultaneously. Over the past decades, floating TiO2-based photocatalysts have attracted much attention, which makes great progress and it is significant to review the recent advances. This review highlights the rational design and fabrication strategy for floating photocatalyst immobilized on various lightweight substrates (e.g. perlite, vermiculite, glass microbead, polymer, cork, expanded graphite) or self-floating photocatalyst. The special characteristics and deep understanding of photocatalytic mechanism for floating photocatalyst are summarized and discussed thoroughly. Moreover, the future research and challenge will focus on designing and optimizing the high-efficient broadband response floating photocatalyst to improve solar energy utilization. From an application viewpoint, floating photocatalyst have real practical applications in natural environment and are worthy of great attention.

Recent advances in floating TiO2-based photocatalysts for environmental application

Adsorption of organic pollutants by natural and modified clays: A comprehensive review

Surfactant-free mixed-metal hydroxide water oxidation nanocatalysts were synthesized by pulsed-laser ablation in liquids. In a series of [Ni-Fe]-layered double hydroxides with intercalated nitrate and water, [Ni1–xFex(OH)2](NO3)y(OH)x−y·nH2O, higher activity was observed as the amount of Fe decreased to 22%. Addition of Ti4+ and La3+ ions further enhanced electrocatalysis, with a lowest overpotential of 260 mV at 10 mA cm–2. Electrocatalytic water oxidation activity increased with the relative proportion of a 405.1 eV N 1s (XPS binding energy) species in the nanosheets.

Highly active mixed-metal nanosheet water oxidation catalysts made by pulsed-laser ablation in liquids.

Polyurethane (PU)-based composite films containing highly aligned graphene sheets are produced through an environmentally benign process. An aqueous liquid crystalline dispersion of graphene oxide (GO) is in situ reduced in PU, resulting in a fine dispersion and a high degree of orientation of graphene sheets. The PU particles are adsorbed onto the surface of the reduced graphene oxide (rGO), and the rGO sheets with a large aspect ratio of over 10 000 tend to self-align during the film formation when the graphene content is high enough, say more than 2 wt%. The resulting composites show excellent electrical conductivity with an extremely low percolation threshold of 0.078 vol%, which is considered one of the lowest values ever reported for polymer composites containing graphene. The electrical conductivity of the composites with high graphene contents presents significant anisotropy due to the preferential formation of conductive networks along the in-plane direction, another proof of the existence of the self-aligned, layered structure.

Self-alignment and high electrical conductivity of ultralarge graphene oxide–polyurethane nanocomposites

This review summarizes recent work on manufacturing of different types of composites. There is a great need to engineer multi-phase (i.e., composite) materials that combine the advantages exhibited by each component of the material. The discussion concentrates on preparation of composites contain different types of nanoparticles (3D fillers, nanofibers, nanotubes, and plate-like filler) with polymer matrices. Special attention is paid to the preparation of nanocomposites with individual (non-aggregated) nanoparticles because dispersion of nanofillers is a key problem in nanotechnology industrialization. Several approaches that may be applied to overcome this problem will be described in this review.

Effect of Nanofillers Dispersion in Polymer Matrices: A Review

Clay Minerals in Nature - Their Characterization, Modification and Application

Effects of silicon carbide particle sizes on friction-wear properties of friction composites designed for car brake lining applications

The effort to clarify the meanings of the terms ‘clay’, ‘clays’, and ‘clay minerals‘ was the subject of the joint nomenclature committees (JNCs) of the Association Internationale pour l’Etude des Argiles (AIPEA) and the Clay Minerals Society (CMS). The JNCs have proposed the term a class of hydrated phyllosilicates forming the fine-grained fraction of rocks, sediments, and soils and have defined ‘clay’ as ‘‘a naturally occurring material composed primarily of fine-grained minerals, which is generally plastic at appropriate water contents and will harden when dried or fired’’ [1]. According to this definition synthetic clays and clay-like materials are not regarded as clay even though they may be fine grained, and display the attributes of plasticity and hardening on drying and firing.

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Vermiculite: Structural Properties and Examples of the Use

The ordering of three different sizes of quaternary ammonium salts (QUATs) has been studied with respect to concentration of guests in the host's interlayer gallery. From the modeling, we could verify that small molecules of n-butylammonium salt build a monolayer structure in the vermiculite gallery without reference to concentration. On the other hand, the larger molecules of dodecyltrimethylammonium and dioctadecyldimethylammonium salts are responsive to the numbers of their molecules in the interlayer space of the host, building mono- or bilayered structures. Supersaturated structure of both QUATs keep an arrangement of alkyl chains nearly perpendicular to silicate layers, while only saturated samples exhibit tilted alkyl chains in the gallery. The ordering changes bring out the calculation of mean crystallite size. Low values of the nonbond energy of supersaturated forms predict that those organovermiculites will readily exfoliate, e.g., in polymer/clay nanocomposite.

Gražyna Simha Martynková

Papers

Effect of Nanofillers Dispersion in Polymer Matrices: A Review

Clay Minerals in Nature - Their Characterization, Modification and Application

Effects of silicon carbide particle sizes on friction-wear properties of friction composites designed for car brake lining applications

Vermiculite: Structural Properties and Examples of the Use

Structural ordering of organovermiculite: Experiments and modeling