The rare earth metals have been identified by the European Union and the United States as being at greatest supply risk of all the materials for clean energy technologies. Of particular concern are neodymium and dysprosium, both of which are employed in neodymium-iron-boron based magnets. Recycling of magnets based on these materials and contained within obsolete electronic equipment, could provide an additional and secure supply. In the present work, hydrogen has been employed as a processing agent to decrepitate sintered neodymium-iron-boron based magnets contained within hard disk drives into a demagnetised, hydrogenated powder. This powder was then extracted mechanically from the devices with an extraction efficiency of 90 ±5 % and processed further using a combination of sieves and ball bearings, to produce a powder containing <330 parts per million of nickel contamination. It is then possible for the extracted powder to be re-processed in a number of ways, namely, directly by blending and re-sintering to form fully dense magnets, by Hydrogenation, Disproportionation, Desorption, Recombination processing to produce an anisotropic coercive powder suitable for bonded magnets, by re-melting; or by chemical extraction of the rare earth elements from the alloy. For example, it was shown that, by the re-sintering route, it was possible to recover >90% of the magnetic properties of the starting material with significantly less energy than that employed in primary magnet production. The particular route used will depend upon the magnetic properties required, the level of contamination of the extracted material and the compositional variation of the feedstock. The various possibilities have been summarised in a flow diagram. INTRODUCTION:Rare earth magnets based upon neodymium-iron-boron (NdFeB) are employed in many clean energy and high tech applications, including hard disk drives (HDDs), motors in electric vehicles and electric generators in wind turbines. In recent years, the supply of rare earth metals has come under considerable strain. China currently provides over 85% of rare earth metals to the world market but, in recent years, began to impose export quotas. This resulted in dramatic price fluctuations for the rare earth metals, in particular, neodymium, praseodymium and dysprosium, the rare earth constituents of NdFeB magnets. According to the EU Critical Materials list (2010, 2014) and the US Department of Energy's energy critical element list (2010), the rare earth metals are classified as at greatest risk of supply shortages compared to those of all other materials used for clean energy technologies. There are several ways in which these material shortages could be addressed including: (a) opening rare earth mines in countries outside of China, (b) using alternative technologies which do not contain rare earths (c) reducing the amount of rare earth metal used in particular

Contrasting mesoscale aggregate features of a promising conjugated polymer, poly­(2,5-bis­(3-tetradecyl­thiophene-2-yl)­thieno­[3,2-b]­thiophenes) (pBTTT-C14), that result from the use of two slightly different aromatic solvents, i.e., toluene and chlorobenzene, for a range of dilute solutions (0.5–1.2 mg/mL) are systematically explored using depolarized dynamic light scattering (DDLS), dynamic/static light scattering (DLS/SLS), small-angle X-ray scattering (SAXS), and scanning transmission electron/scanning electron/transmission electron microscopy (STEM/SEM/TEM) analysis schemes. The central findings are as follows: (1) DDLS and all EM features reveal that whereas pBTTT-C14 aggregate clusters fostered in toluene (a poorer solvent) are moderately anisotropic (cylindrical; aspect ratio ∼3) in shape, they are nearly isotropic (spherical) in chlorobenzene (a better solvent), with mean sizes in the range of a few hundred nanometers. (2) Combined DDLS/DLS/SLS/SAXS analyses indicate that the aggregate clusters in both solvent media are coexistent with a certain fraction of small rod-like species (∼10 nm in length; aspect ratio ∼2), similar or even identical to the packing units which build up the fractal network of an aggregate cluster. (3) Accurate atomistic molecular dynamics (AMD) simulations of one- and five-chain aggregate systems reveal that the solvent-induced, contrasting nanoscale/mesoscale aggregate features bear a dynamic origin, through the backbone torsional relaxation that substantially impacts the bolstering interaction force (van der Waals vs π–π) and, hence, the “anisotropic persistence” of the fundamental packing units. (4) The overall features suggest that different organic solvents may be utilized to engineer the (mesoscale) size and shape as well as the (nanoscale) packing units of the aggregate species incubated in solution and shed light on the morphological developments during thin-film fabrication that have been the focus of recent research on the pBTTT-C n series.

We report on anomalous structure and relaxation features of the aggregate clusters fostered in a representative series of dilute poly­(3-hexylthiophene)/chlorobenzene (P3HT/CB) solutions (3, 5, 8, and 10 mg/mL), as resolved by multiscale dynamic/static analysis schemes including depolarized/polarized dynamic light scattering (DDLS/DLS), static light/X-ray scattering (SALS/SLS/SAXS), and scanning transmission electron/transmission electron microscopy (STEM/TEM). DLS/DDLS analyses reveal the coexistence and dynamic equilibrium of diffusive isolated-chain species (fast mode) and nondiffusive, microsized cluster species (slow mode), largely unaffected by the polymer concentration, system temperature, sonication, laser exposure time, and, in particular, repeated filtrations during the sample preparation and measurements. The SALS/SLS/SAXS analyses further reveal that while the fast mode corresponds to isolated chains (R g ∼ 1.5 nm), the slow mode represents microsized clusters comprising a condensed core (R g ∼ 4 μm) and loose corona (∼700 nm in shell thickness). These combined features and detailed analyses performed herein suggest that the core–shell clusterwhich is rarely observed for homopolymer solutionsis formed during a dynamic equilibrium process wherein the isolated chains undergo condensation/decomposition on the (stabilized) core material, leading to an apparent “elastic” slow-mode relaxation whose apparent rate is set by the core-material diffusion. Only at a low temperature (15 °C) and high concentration (c > 5 mg/mL) does the shell material become indistinguishable from the core material, when one has a homogeneous and fairly condensed cluster that exhibits the normal diffusional behavior. The present findings provide new insight into the mechanistic aspects and precise controls of the morphological properties of P3HT solutions for future applications with polymer-based electronic devices.

A versatile conjugated polymer, poly(2,5-bis(3-hexadecyllthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT-C, with M = 61 309 g mol), in a relatively good solvent (chlorobenzene, CB) medium is shown to produce gels through hierarchical colloidal bridging. Multiscale static/dynamic light and X-ray scattering analysis schemes along with complementary microscopy imaging techniques clearly reveal that upon cooling from the solution state at 80 °C to various gelation temperatures (5, 10, and 15 °C), rod-like colloidal pBTTT-C aggregates morph into spherical ones, triggering hierarchical colloid formation and bridging that eventually turn the solution into a gel after about one-day aging. A certain fraction of primal packing units-spherical gelators (∼1 nm in mean radius)-constitute the spherical building particles (∼10 nm) noted above, which in turn constitute loose-packing aggregate clusters (∼300 nm) in the sol state. As gelation proceeds, the aggregate cluster interiors tighten substantially, and micrometer-sized clusters (∼3 μm) formed by them begin to take shape and further interconnect to form the gel network (mean porosity size ∼240 nm and spatial inhomogeneity length ∼20 μm). Rheological measurements and kinetic analysis reveal that the gelation temperature can also have a notable impact on gel microstructure, gelation rate, and mechanical strength, resulting in, for instance, a prominently nonergodic and porous structure for the soft gel incubated at a higher temperature T = 15 °C. The ac conductivity exhibits a notable upturn near pBTTT-C/CB gelation, well above those achieved by the counterpart pBTTT-C solutions, which, in interesting contrast, cannot be brought to the gel phase under similar experimental conditions.

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The present report reveals an unconventional way by which the molecular weight of a conjugated polymer can impact its solution, sol, gel and thin film properties.

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Mixed solvents that are selectively attractive to different parts of an amphiphilic polyelectrolyte lead to exceptional and promoted solution properties.