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Porous materials with wrinkled surfaces could have broad applications in catalysis and adsorption. However, designing cellular ceramics with similar structures is challenging. Herein, we demonstrated the binary colloidal self-assembly of γ-Al 2 O 3 nanoparticle/silica gelation network for constructing such materials. The competitive effect between volume shrinkage and surface bend during water evaporation of silica gel contributed to wrinkled aperture surface. During calcination, silica nanoparticles were highly active to react with alumina to form mullite nanocrystals, bringing about high compressive strength at low relative densities. After calcining at 1350 °C, resultant products with hierarchical structure exhibited an outstanding compressive strength of 4.2 MPa, a relatively high surface area of 7.23 m2/g at a porosity level of 83.3%. The current strategy provides a feasible and affordable approach for producing high performance ceramic foams towards practical application fields in catalysis and adsorption. [ABSTRACT FROM AUTHOR]

Gas-in-liquid foam templating is considered as a promising method for commercial-scale production of porous materials. However, Ostwald ripening occurs frequently during the preparation, which could bring about inhomogeneous bubbles with large sizes and deteriorate the performance of resultant products. To tackle this challenging task, we report a gelation network-triggered morphology-regulation strategy during the foaming process. As an exemplar, boehmite sol was incorporated into the andalusite suspension to stabilize the foam framework. After casting, the wet foam was able to maintain its overall shape, since andalusite particles were anchored onto the gas-liquid interface by the gelation network during mechanical frothing. The samples calcined at 1400°C feature homogeneous bubble with hierarchical porous architecture, smaller pore size with a mean value of 5.32 μm and robust compressive strength of 11.97MPa at a porosity level of 84 %. Our approach substantially broadens the design philosophy of high performance porous ceramics. [ABSTRACT FROM AUTHOR]

Hydrogels have been extensively used in many fields. Current synthesis of functional hydrogels requires incorporation of functional molecules either before or during gelation via the pre-organized reactive site along the polymer chains within hydrogels, which is tedious for polymer synthesis and not flexible for different types of hydrogels. Inspired by sandcastle worm, we develop a simple one-step strategy to functionalize wet hydrogels using molecules bearing an adhesive dibutylamine-DOPA-lysine-DOPA tripeptide. This tripeptide can be easily modified with various functional groups to initiate diverse types of polymerizations and provide functional polymers with a terminal adhesive tripeptide. Such functional molecules enable direct modification of wet hydrogels to acquire biological functions such as antimicrobial, cell adhesion and wound repair. The strategy has a tunable functionalization degree and a stable attachment of functional molecules, which provides a tool for direct and convenient modification of wet hydrogels to provide them with diverse functions and applications. Functionalisation of hydrogels can be difficult to achieve and often requires modification of polymers before gelation. Here, the authors report on a sandcastle worm inspired adhesive tripeptide for the post gelation functionalisation of wet hydrogels, demonstrating the addition of different functionality. [ABSTRACT FROM AUTHOR]

Though the use of conventional self‐assembled architectures in functional applications involving advanced energy chemistries is an important research area, it remains largely unexplored. The self‐assembly of the threefold and sixfold‐symmetric terpyridines (tpy) with Co(II) salts results in a novel morphological and structural characteristics, regardless of the nature of the self‐assembled fragments. Herein, such metallopolymers are achieved by one‐pot synthesis in CH3OH/CHCl3 (v/v = 5:1) mixture ambient. It is found, for the first time, that Co‐containing polymers can be well dispersed in deionized water to form gel‐like self‐assemblies that consist of a highly interconnected 3D network and exhibit enhanced electrical conductivity and thus are attractive as electrocatalysts. As expected, the optimized Co‐based polymeric structures exhibit a low overpotential of 320 mV at 10 mA cm−2 and high stability over 2000 cycles toward oxygen evolution reaction (OER), surpassing commercial RuO2/C, single‐site Co catalysts, polymer, and metal–organic framework‐based OER catalysts reported to date. X‐ray absorption spectroscopy and density functional theory calculations reveal that the tpy‐Co2+ (3N‐Co or tpy‐Co2+) configurations act as highly active sites. Importantly, this work demonstrates the functional application of the self‐assembled metallopolymers as electrocatalysts for energy conversion. [ABSTRACT FROM AUTHOR]

Engineering high performance cellular ceramics with both ultralow density and satisfactory compressive strength for practical applications still represents a grand challenge. Herein, alumina-based cellular ceramics bonded by in-situ formed mullite phase were constructed by Al 2 O 3 –Si-boehmite particle-stabilized foams. The gelation of boehmite sol improved the stability and harnessed the deformation of dried Al 2 O 3 –Si composite foam. The oxidation of silicon and further generation of in-situ mullite phase enhanced the chemical bond between alumina particles on cell walls, resulting in the superior mechanical properties. As an exemplar, the resulting cellular ceramic possessed the robust compressive strength of 2.26 MPa at a high porosity of 87.8%. The gelation-assisted Al 2 O 3 –Si particle-stabilized foams provide a facile and convenient strategy for construction of composite ceramic foams with high porosity and robust strength. [ABSTRACT FROM AUTHOR]

A gelcasting system of alumina utilizing tartaric acid as the dispersant and glutaraldehyde as the crosslinker is reported, in which glutaraldehyde can polymerize itself and react with tartaric acid, thus forming a three-dimensional network. Measurement of zeta potential and viscosity shows good dispersion ability of tartaric acid. Shear modulus during gelation demonstrates its good gelation strength and fast gelation speed at room temperature. Moreover, an effective way to control the gelation speed is provided to improve the feasibility of this method. Results indicate that this gelcasting method has the advantages of low viscosity, small amounts of additives and short forming time and is a promising method to fabricate green bodies with large sizes and complex shapes. [ABSTRACT FROM AUTHOR]

Ceramic foams with significant porosity and robust mechanical properties have received extensive attentions. However, it is still difficult to achieve excellent compressive strength at high porosity levels. In this work, a gelation of foamed boehmite sol method is proposed to settle this issue. The technological parameters during preparation process are systematically investigated. As‐prepared alumina ceramic foams possess unprecedentedly high compressive strength of 34.1‐89.1 MPa at high porosity levels of 66.0%‐87.2%, which is attributed to the present of hierarchical pore structure, small grain size and pore size. This work demonstrates a facile and novel method for the fabrication of high‐performance alumina ceramic foams toward practical applications. [ABSTRACT FROM AUTHOR]

Motivated by the extensive application of agar, this work developed a wet-spinning process to fabricate micro-scale fibers using the gelation process of agar. The effect of three vital spinning parameters, namely dope concentration, coagulation bath composition, and fiber post-processing on morphological properties, tensile properties and chemical structure of the fiber have been discussed. The concentration of agar was determined by the results of rheological measurement. The addition of barium chloride in the coagulation process improved the mechanical properties of fibers as compared to deionized water as coagulation. The agar fibers immersed in amino silicone demonstrated significantly showed better mechanical properties compared to the agar fibers only immersed in ethanol. The physical and chemical properties of agar fibers were characterized by X-ray diffraction, FTIR, tensile testing, and SEM. The results showed that excellent agar fibers with several potential applications can be produced with amino silicone modification in optimum coagulation bath. [ABSTRACT FROM AUTHOR]

A new gelcasting approach of alumina inspired by Isobam was designed utilizing a polyelectrolyte dispersant named BTT, which is able to form cross-links via thiol-ene reaction with pentaerythritol tetrakis(2-mercaptoacetate). Measurement of zeta potential and viscosity shows good dispersion ability of BTT in 52 vol% alumina suspensions. The flow curves and shear modulus of wet green bodies during gelation demonstrate its high gelation strength in comparison with Isobam. The analysis of effects of addition of ammonium citrate tribasic into the system indicates that a polymer-particle double network is supposed to form during gelation. Elastic part and viscous part of gelation strength of the system are mainly dominated by interaction between polyelectrolyte and particles and cross-linking respectively, which accounts for the existence of both high gelation strength and flexibility of wet green bodies fabricated in this approach. [ABSTRACT FROM AUTHOR]

Traditionally, the carrageenan fibers were prepared by process of extracting, drying, dissolving of carrageenan power and wet spinning process of fibers. However, in this study, carrageenan fibers were prepared by carrageenan solution directly from the extraction of Chondrus , without the steps of precipitation, and drying. The properties of carrageenan powder, spinning solution and carrageenan fibers were characterized with zeta potential, NMR, FTIR, dynamic light scattering (DLS), SEM, tensile testing and energy dispersive spectrometer (EDS). The results showed that the Chondrus contained mainly iota-carrageenan. The extraction of Chondrus was a uniform liquid with good properties of a solution, which was suitable as a spinning solution. The so prepared carrageenan fibers possessed good morphology and tensile properties. The excellent tensile properties of the carrageenan fibers were attributed to the combination of sulfate ester in the carrageenan and barium ions in the coagulation and then form a three-dimensional network structure. [ABSTRACT FROM AUTHOR]

Isobam, a copolymer of isobutylene and maleic anhydride, is a newly developed gelling agent for ceramic colloidal forming. However, the Isobam system exposes a weakness of high viscosity when solids loading exceeds 54 vol%. Suitable additives to effectively decrease viscosity and have minimal impact on gelation strength were discovered from various dicarboxylic acids through investigation on zeta potential, viscosity of suspensions, shear modulus during gelation and yield stress and modulus of elasticity of wet green bodies. Alumina ceramics with flexural strength of 442 ± 49 MPa and a Weibull modulus of 10.8 were produced from 54 vol% suspensions with 0.5 wt% Isobam assisted by 0.04 wt% phthalic acid and 0.03 wt% oxalic acid after pressureless sintering. [ABSTRACT FROM AUTHOR]

As a copolymer of isobutylene and maleic anhydride, Isobam, a newly-developed gelling agent, plays a significant role in ceramic forming process. However, dispersion and gelation behavior of Isobam has not been discussed in detail yet. To investigate the influence of other dispersants, pH and electrolytes on dispersion and gelation behavior of Isobam, zeta potential, viscosity and modulus curves during gelation were measured from 50 vol% alumina suspensions with 0.1–0.7 wt% Isobam. A two-step bridging mechanism is proposed to explain the gelation behavior of Isobam, providing guidance on usage of Isobam in combination of other additives to achieve suspensions with high solids loading and adjustable gelation characteristic. [ABSTRACT FROM AUTHOR]

A new thermoreversible and tunable hydrogel CS-M with high water content prepared by metal cation (M = Cu2+, Zn2+, Cd2+ and Ni2+) and chitosan (CS) was reported. The influence of metal cations on the thermosensitive gelation of CS-M systems were studied. All prepared CS-M systems were in the transparent and stable sol state and could become the gel state at gelation temperature (T g). These systems after gelation could recover to its original sol state at low temperature. CS-Cu hydrogel was mainly investigated and characterized due to its large T g scale (32–80 °C), appropriate pH range (4.0–4.6) and low Cu2+ concentration. The result showed that the T g range was influenced and could be tuned by adjusting Cu2+ concentration and system pH within an appropriate range. The influence of anions (Cl−, NO3− and Ac−) in cupric salts in the CS-Cu system was also investigated. Scale application as heat insulation window was investigated outdoors. The different supramolecular interactions of the -NH 2 group in chitosan at different temperatures were proposed to dominate the thermoreversible process of CS-Cu hydrogel. [Display omitted] [ABSTRACT FROM AUTHOR]