Electroresistance in multipolar antiferroelectric Cu2Se semiconductor

Electric field-induced changes in the electrical resistance of a material are considered essential and enabling processes for future efficient large-scale computations. However, the underlying physical mechanisms of electroresistance are currently remain largely unknown. Herein, an electrically reversible resistance change has been observed in the thermoelectric α-Cu2Se. The spontaneous electric dipoles formed by Cu+ ions displaced from their positions at the centers of Se-tetrahedrons in the ordered α-Cu2Se phase are examined, and α-Cu2Se phase is identified to be a multipolar antiferroelectric semiconductor. When exposed to the applied voltage, a reversible switching of crystalline domains aligned parallel to the polar axis results in an observed reversible resistance change. The study expands on opportunities for semiconductors with localized polar symmetry as the hardware basis for future computational architectures.

Sodium-Ion Battery Anode Construction with SnPx Crystal Domain in Amorphous Phosphorus Matrix

The high-capacity phosphorus- (P-) based anode materials for sodium-ion batteries (NIBs) often face poor performance retentions owing to the low conductivity and large volume expansion. It is thus essential to buffer these problems by appropriately alloying with other elements such as tin (Sn) and constructing well-designed microstructures. Herein, a series of P-/Sn-based composites have been synthesized by the facile and low-cost one-step ball milling. Pair distribution function (PDF) has been employed as a hardcore quantitative technique to elucidate their structures combined with other techniques, suggesting the formation and ratios of Sn4P3 and Sn crystalline domains embedded inside an amorphous P/carbon matrix. The composite with the largest amount of Sn4P3 in the P/C matrix can deliver the most balanced electrochemical performance, with a capacity of 422.3 mA-h g−1 for 300 cycles at a current density of 1000 mA g−1. The reaction mechanism has been elucidated by 23Na and 31P solid-state nuclear magnetic resonance (NMR) investigations. The study sheds light on the rational design and concrete identification of P-/Sn-based amorphous-dominant composite materials for NIBs.

Comparison of Silks from Pseudoips prasinana and Bombyx mori Shows Molecular Convergence in Fibroin Heavy Chains but Large Differences in Other Silk Components

Many lepidopteran larvae produce silk feeding shelters and cocoons to protect themselves and the developing pupa. As caterpillars evolved, the quality of the silk, shape of the cocoon, and techniques in forming and leaving the cocoon underwent a number of changes. The silk of Pseudoips prasinana has previously been studied using X-ray analysis and classified in the same category as that of Bombyx mori, suggesting that silks of both species have similar properties despite their considerable phylogenetic distance. In the present study, we examined P. prasinana silk using ‘omics’ technology, including silk gland RNA sequencing (RNA-seq) and a mass spectrometry-based proteomic analysis of cocoon proteins. We found that although the central repetitive amino acid sequences encoding crystalline domains of fibroin heavy chain molecules are almost identical in both species, the resulting fibers exhibit quite different mechanical properties. Our results suggest that these differences are most probably due to the higher content of fibrohexamerin and fibrohexamerin-like molecules in P. prasinana silk. Furthermore, we show that whilst P. prasinana cocoons are predominantly made of silk similar to that of other Lepidoptera, they also contain a second, minor silk type, which is present only at the escape valve.

Joining host/guest with contrary affinity at the nanoscale by chemical bonds or non-covalent interactions with organic media under diffusion: control of embedded versus exposed magnetite dispersions.

Emulating natural dynamism distributing earth minerals using diffusion and gravity, herein it is reported a strategy to unite nanostructured materials of similar size but intrinsic physical repellence, magnetite guest bestowed with C18 alkyl chain ligands and highly hydrophilic ammonium dawsonite NH4Al(OH)2CO3 host, based in electromagnetic and chemical forces. Notwithstanding augmented polarity of nanostructured surface’s carrier, has been used as fine-tuning tool in conjunction with continuum, for triggering a disseminated array of specific interactions covering entire carrier NH4+-RDW-NP periphery. Strong interactions heighten enthalpic contributions balancing unfavourable entropic penalty. Shelter adsorbs diffused guest like conventional Fe3O4-NP dispersions but additionally, whether restricts void’s access or, sinters carrier enabling isolation of a second morphology where magnetite is quantitatively embedded into cavities left between agglomerates. Reported deposition protocol extends sort of practical interactions beyond the known dipole-dipole derived ones, to ion-p and truly chemical coordination bonds, strengthening wetting interfaces that define noticeable g-Al2O3 crystalline domains at minor temperatures. Manuscript illustrates how certain organic media may assist to reliable guest depositions in, hydrotalcite to alumina carriers within controlled morphology, at the same weight level than common procedures reported for more akin host/guest. Interestingly, protocol enables practical SBET measurements for solids with significative contributions of interparticle porosity. Detrimental effects are also addressed.

Distribution of Cracks in a Chain of Atoms at Low Temperature

We consider a one-dimensional classical many-body system with interaction potential of Lennard–Jones type in the thermodynamic limit at low temperature $$1/\beta \in (0,\infty )$$ 1 / β ∈ ( 0 , ∞ ) . The ground state is a periodic lattice. We show that when the density is strictly smaller than the density of the ground state lattice, the system with N particles fills space by alternating approximately crystalline domains (clusters) with empty domains (voids) due to cracked bonds. The number of domains is of the order of $$N\exp (- \beta e_\mathrm {surf}/2)$$ N exp ( - β e surf / 2 ) with $$e_\mathrm {surf}>0$$ e surf > 0 a surface energy. For the proof, the system is mapped to an effective model, which is a low-density lattice gas of defects. The results require conditions on the interactions between defects. We succeed in verifying these conditions for next-nearest neighbor interactions, applying recently derived uniform estimates of correlations.

Analysis of Performance Losses and Degradation Mechanism in Porous La2−X NiTiO6−δ:YSZ Electrodes

The electrode performance and degradation of 1:1 La2−xNiTiO6−δ:YSZ composites (x = 0, 0.2) has been investigated to evaluate their potential use as SOFC cathode materials by combining electrochemical impedance spectroscopy in symmetrical cell configuration under ambient air at 1173 K, XRD, electron microscopy and image processing studies. The polarisation resistance values increase notably, i.e., 0.035 and 0.058 Ωcm2 h−1 for x = 0 and 0.2 samples, respectively, after 300 h under these demanding conditions. Comparing the XRD patterns of the initial samples and after long-term exposure to high temperature, the perovskite structure is retained, although La2Zr2O7 and NiO appear as secondary phases accompanied by peak broadening, suggesting amorphization or reduction of the crystalline domains. SEM and TEM studies confirm the ex-solution of NiO with time in both phases and also prove these phases are prone to disorder. From these results, degradation in La2−xNiTiO6−δ:YSZ electrodes is due to the formation of La2Zr2O7 at the electrode–electrolyte interface and the ex-solution of NiO, which in turn results in the progressive structural amorphization of La18NiTiO6−δ phases. Both secondary phases constitute a non-conductive physical barrier that would hinder the ionic diffusion at the La2−xNiTiO6−δ:YSZ interface and oxygen access to surface active area.

Cellulose Nanocrystals from Native and Mercerized Cotton

Nanocelluloses occur under various crystalline forms that are being selectively used for a wide variety of high performance materials. In the present work, cellulose fibers (CF-I) were mercerized by alkaline treatment (CF-II) without molar mass variation (560 000 g/mol) and both were acid hydrolyzed, forming cellulose nanocrystals in native (CNC-I) and mercerized (CNC-II) forms. This work establishes detailed characterization of these two nanoparticles morphology (light and neutron scattering, TEM, AFM), surface chemistry (zetametry and surface charge), crystallinity (XRD, 13C NMR), and average molar mass coupled to chromatographic technics (SEC-MALLS-RI, A4F-MALLS-RI), evidencing variations in packing of the crystalline domains. The crystal size of CNC-II is reduced by half compared to CNC-I, with molar masses of individual chains of 41 000 g/mol and 22 000 g/mol for CNC-I and CNC-II respectively, whereas the same charged surface chemistry is measured. This fundamental analysis may give insight to new applicative development.