With increasing environmental and ecological concerns due to the use of petroleum-based chemicals and products, the synthesis of fine chemicals and functional materials from natural resources is of great public value. Nanocellulose may prove to be one of the most promising green materials of modern times due to its intrinsic properties, renewability, and abundance. In this review, we present nanocellulose-based materials from sourcing, synthesis, and surface modification of nanocellulose, to materials formation and applications. Nanocellulose can be sourced from biomass, plants, or bacteria, relying on fairly simple, scalable, and efficient isolation techniques. Mechanical, chemical, and enzymatic treatments, or a combination of these, can be used to extract nanocellulose from natural sources. The properties of nanocellulose are dependent on the source, the isolation technique, and potential subsequent surface transformations. Nanocellulose surface modification techniques are typically used to introduce e...

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Nanocellulose, a Versatile Green Platform: From Biosources to Materials and Their Applications

Thanks to their remarkable mechanical, electrical, thermal, and barrier properties, graphene-based nanocomposites have been a hot area of research in the past decade. Because of their simple top-down synthesis, graphene oxide (GO) and reduced graphene oxide (rGO) have opened new possibilities for gas barrier, membrane separation, and stimuli-response characteristics in nanocomposites. Herein, we review the synthesis techniques most commonly used to produce these graphene derivatives, discuss how synthesis affects their key material properties, and highlight some examples of nanocomposites with unique and impressive properties. We specifically highlight their performances in separation applications, stimuli-responsive materials, anti-corrosion coatings, and energy storage. Finally, we discuss the outlook and remaining challenges in the field of practical industrial-scale production and use of graphene-derivative-based polymer nanocomposites.

Synthesis, properties, and applications of graphene oxide/reduced graphene oxide and their nanocomposites

Graphene oxide-based aerogels with carefully tailored properties are developed to enable efficient solar steam generation. Aerogels, with inherent porous structures, are excellent thermal insulators and provide channels for water supply and vapor escape. With enhanced absorption and hydrophilicity by incorporation of carbon nanotubes and sodium alginate, the resulting aerogels can enable efficient (≈83%) solar steam generation under one-sun illumination.

Tailoring Graphene Oxide-Based Aerogels for Efficient Solar Steam Generation under One Sun.

A review on the current progress of metal hydrides material for solid-state hydrogen storage applications

DOI: 10.1002/aenm.201702884 during desalination process and block the channels for vapor escape, resulting in the reduction of energy transfer efficiency, pure water yield, and unstable performance. Therefore, long-term stability becomes critical issues that need to be addressed. Recently, Janus membrane is emerging as a novel class of materials comprised of a two-layer structure with opposing properties and different functions.[26,27] Since the first study of Janus particle by Cho and Lee in 1985,[28] various Janus such as micelles,[29] rods,[30] and sheets[31] have been fabricated, with wide applications in oil/water separation,[32] switchable ion transport,[33] interfacial mass transfer,[34] and fog collection.[35] Here we demonstrate that a flexible Janus absorber fabricated by convenient electrospinning process can enable stable and efficient solar desalination. Taking advantage of the unique structures of Janus absorbers, two functions of solar steam generation, solar absorption and water pumping, are decoupled into different layers, with upper hydrophobic carbon black nanoparticles (CB) coating polymethylmethacrylate (PMMA) layer for light absorption and water evaporation, and bottom hydrophilic polyacrylonitrile (PAN) layer for pumping water. Therefore, salt may only be deposited in the hydrophilic PAN layer and quickly be dissolved because of continuous water pumping. Under 1-sun illumination, the Janus absorber demonstrates efficient solar steam generation (72%) and stable water output (1.3 kg m−2 h−1, over 16 d, with 45 min each day), not achieved in most of previous absorbers. With unique structure design achieved by scalable process, our flexible Janus absorber provides an efficient, stable, and portable solar steam generator for direct solar desalination. Figure 1 presents the illustration of solar steam generation (Figure 1a), and structures of Janus absorber (Figure 1b) in sea water. Porous absorbers naturally float on the water surface, absorbing solar energy to generate steam, without heating the bulk water. CB coating PMMA (CB/PMMA) layer stays above the water surface due to its hydrophobic property while PAN layer is immersed in water for efficient water supply. During the solar steam generation process, the CB/PMMA layer harvests solar energy and converts light to heat, generating vapor from the interfacial region of CB/PMMA and PAN. Thus, the With recent progress in interfacial solar steam generation, direct solar desalination is considered a promising technology for providing a clean water solution through a cost effective and environmental-friendly pathway. As a high and stable water production rate is the key to enable widespread applications, salt deposition becomes a critical issue that needs to be addressed. Herein, the authors demonstrate that a flexible Janus absorber fabricated by sequential electrospinning can enable stable and efficient solar desalination. Taking advantage of the unique structure of Janus, two functions of steam generation, solar absorption and water pumping, are decoupled into different layers, with an upper hydrophobic carbon black nanoparticles (CB) coating poly methylmethacrylate (PMMA) layer for light absorption, and a lower hydrophilic polyacrylonitrile (PAN) layer for pumping water. Therefore, salt can only be deposited in the hydrophilic PAN layer and quickly be dissolved because of continuous water pumping. Janus absorber demonstrates high efficiency (72%) and stable water output (1.3 kg m–2 h–1, over 16 days) under 1-sun, not achieved in most previous absorbers. With a unique structure design achieved by scalable process, this flexible Janus absorber provides an efficient, stable and portable solar steam generator for direct solar desalination.

Flexible and Salt Resistant Janus Absorbers by Electrospinning for Stable and Efficient Solar Desalination

High-performance thermally insulating materials from renewable resources are needed to improve the energy efficiency of buildings. Traditional fossil-fuel-derived insulation materials such as expan ...

Thermally insulating and fire-retardant lightweight anisotropic foams based on nanocellulose and graphene oxide

The effect of nano-structured alumina coating on resin-bond strength to zirconia ceramics.

The combined effect of alumina and silica co-doping on the ageing resistance of 3Y-TZP bioceramics.

Conventional sintering is a time- and energy-consuming process used for the densification of consolidated particles facilitated by atomic diffusion at high temperatures. Nanoparticles, with their increased surface free energy, can promote sintering; however, size reduction also promotes agglomeration, so hampering particle packing and complete densification. Here we show how the ordered agglomeration of zirconia primary crystallites into secondary particle assemblies ensures their homogeneous packing, while also preserving the high surface energy to higher temperatures, increasing the sintering activity. When exposed to intense electromagnetic radiation, providing rapid heating, the assembled crystallites are subjected to further agglomeration, coalescence and sliding, leading to rapid densification in the absence of extensive diffusional processes, cancelling out the grain growth during the initial sintering stages and providing a zirconia nanoceramic in only 2 minutes at 1300 °C.

The agglomeration, coalescence and sliding of nanoparticles, leading to the rapid sintering of zirconia nanoceramics.

The purpose of this study was to evaluate the influence of contamination and subsequent cleaning on the bond strength and durability of an adhesive resin to nano-structured alumina-coated zirconia ceramic. Zirconia ceramic disks were coated with nano-structured alumina, utilizing the hydrolysis of aluminum nitride powder. After immersion in saliva or the use of a silicone disclosing agent, specimens were cleaned with phosphoric acid etching or with tap water rinsing only. Uncontaminated specimens served as controls. Plexiglas tubes filled with composite resin were bonded with a phosphate monomer [10-methacryloxydecyl-dihydrogenphosphate (MDP)]-containing resin (Panavia 21). Subgroups of eight specimens each were stored in distilled water at 37 degrees C, either for 3 d without thermal cycling (TC) or for 150 d with 37,500 thermal cycles from 5 to 55 degrees C. The tensile bond strength (TBS) was determined using a universal testing machine at a crosshead speed of 2 mm min(-1). The topography of the debonded surface was scrutinized for fractographic features, utilizing both optical and scanning electron microscopy. The TBS to uncontaminated nano-structured alumina-coated zirconia ceramic was durable, while contamination significantly reduced the TBS. Phosphoric acid cleaning was effective in removal of saliva contamination from the coated bonding surface but was not effective in removal of the silicone disclosing agent. Nano-structured alumina coating improves resin bonding to zirconia ceramic and eliminates the need for air-abrasion before bonding.

Andraž Kocjan

Papers

Thermally insulating and fire-retardant lightweight anisotropic foams based on nanocellulose and graphene oxide

The effect of nano-structured alumina coating on resin-bond strength to zirconia ceramics.

The combined effect of alumina and silica co-doping on the ageing resistance of 3Y-TZP bioceramics.

The agglomeration, coalescence and sliding of nanoparticles, leading to the rapid sintering of zirconia nanoceramics.

Influence of contamination on resin bond strength to nano‐structured alumina‐coated zirconia ceramic