▪ Abstract Solution phase syntheses and size-selective separation methods to prepare semiconductor and metal nanocrystals, tunable in size from ∼1 to 20 nm and monodisperse to ≤5%, are presented. Preparation of monodisperse samples enables systematic characterization of the structural, electronic, and optical properties of materials as they evolve from molecular to bulk in the nanometer size range. Sample uniformity makes it possible to manipulate nanocrystals into close-packed, glassy, and ordered nanocrystal assemblies (superlattices, colloidal crystals, supercrystals). Rigorous structural characterization is critical to understanding the electronic and optical properties of both nanocrystals and their assemblies. At inter-particle separations 5–100 A, dipole-dipole interactions lead to energy transfer between neighboring nanocrystals, and electronic tunneling between proximal nanocrystals gives rise to dark and photoconductivity. At separations <5 A, exchange interactions cause otherwise insulating ass...

Synthesis and Characterization of Monodisperse Nanocrystals and Close-Packed Nanocrystal Assemblies

Temperature-sensitive aqueous microgels.

The ability to pattern materials in three dimensions is critical for several technological applications, including composites, microfluidics, photonics, and tissue engineering. Direct-write assembly allows one to design and rapidly fabricate materials in complex 3D shapes without the need for expensive tooling, dies, or lithographic masks. Here, recent advances in direct ink writing are reviewed with an emphasis on the push towards finer feature sizes. Opportunities and challenges associated with direct ink writing are also highlighted.

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Direct ink writing of 3D functional materials

Colloidal processing of ceramics is reviewed with an emphasis on interparticle forces, suspension rheology, consolidation techniques, and drying behavior. Particular attention is given to the scientific concepts that underpin the fabrication of particulate-derived ceramic components. The complex interplay between suspension stability and its structural evolution during colloidal processing is highlighted.

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Colloidal Processing of Ceramics

Design and Production of Nanoparticles Formulated From Nano-Emulsion Templates-A Review

Concentrated polystyrene latices form strongly interacting systems, and under appropriate conditions of particle radii, volume fraction and ionic strength the repulsive forces can be strong enough to give rise to measurable viscoelastic behaviour. In this paper an experimental investigation of the viscoelastic behaviour of concentrated latices is described. The methods used included creep compliance and shear-wave propagation. The former was used to determine the low stress viscosities and the latter to determine the shear modulus. The particle radii were varied from 26 to 98 nm and the volume fraction range was 0.2–0.4.

Viscoelastic properties of concentrated latices. Part 1.—Methods of examination

The equations governing consolidation in a continuous-flow gravity thickener are developed based on the assumption that a flocculated suspension possesses a compressive yield stress Py(ϕ) that is a function of local volume fraction only. These equations are used to model the steady state operation of a thickener. The bed height required to achieve a given underflow concentration is found to be a relatively sensitive function of the details of the Py(ϕ) function, particle flux through the thickener, and variations in the cross-sectional area of the thickener. The limiting values of the underflow concentration ϕu for a given flux or the limiting values of flux for a desired ϕu are studied and shown to exist only for cylindrical and converging thickeners.

The continuous‐flow gravity thickener: Steady state behavior

Whereas our understanding of the role and mechanism of wall slip has improved substantially over the last decade or two, it is still common to see papers on disperse systems appear wherein scant details of the measurement methods are given and wherein no mention of the possibility (probability?) of slip is made. It is argued that there is a need to raise awareness. It takes experience, judgement and skill to make meaningful measurements on disperse systems and it is suspected that the nature of the experimental challenge is under-estimated grossly by too many workers even now.

Letter to the Editor: Wall slip in dispersion rheometry

Network formation and its consequences for the physical behaviour of associating polymers in solution

Even though our appreciation of the importance and ubiquity of wall slip has grown substantially over the last decade or two, it is still common to find papers on disperse systems wherein scant details of the measurement methods are given and where no mention of the possibility of slip is made. It seems then that there is a need still to raise awareness and to promote the idea that the rheometry of disperse systems is not so straightfoward as it might seem. It takes experience, judgment, and skill to make meaningful measurements on disperse systems and it is suspected that the nature of the experimental challenge is under-estimated grossly by too many workers even now. Slip is not merely a rheometric complication; of course, it an intrinsic feature of the response of disperse systems and one deserving of more attention in its own right.

Richard Buscall

Papers

Viscoelastic properties of concentrated latices. Part 1.—Methods of examination

The continuous‐flow gravity thickener: Steady state behavior

Letter to the Editor: Wall slip in dispersion rheometry

Network formation and its consequences for the physical behaviour of associating polymers in solution

Letter to the Editor: Wall slip in dispersion rheometry