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We have investigated the effects of crystal structure and size of Li[Ni1/3Co1/3Mn1/3]O2 (L333) cathodes on the performance of lithium-ion batteries. Cation ordering and particle sizes were determined as a function of annealing temperature with subsequent electrochemical performance monitored by cyclic voltammetry (CV) and charge–discharge testing. With increasing annealing temperature, L333 exhibits a greater cation ordering, which subsequently benefitted cell performance. However, higher annealing temperatures yielded larger crystal sizes, which resulted in a decrease in high rate discharge capacity and a significant capacity fade. This is attributed to an increase in lattice parameter and volume expansion during cycling, with the largest crystal sizes displaying the most significant structural changes due to the lower strain accommodation.
In the present work, for the first time, the inorganic Si-based materials lacking preexisting mixed bonds (O–Si–C, silicon in tetrahedral coordination bonded to both carbon and oxygen) have been successfully used as starting materials in a laser evaporation/condensation system for making hydrogenated silicon oxycarbide (Si–O–C–H) nanoparticles containing mixed bonds. The obtained materials are characterized by spectroscopic, microscopic, and calorimetric measurements. Thermodynamically stable 5–10 nm amorphous Si–O–C–H particles with a complex structure containing a combination of pure and mixed Si-based tetrahedral units (SiOiC4−i; i = 0–4), and a considerable amount of Si–OH and C–H bonds have been synthesized. The nanoparticles possess high surface areas (428–467 m2/g), suggesting potential use in functionalities requiring high surface to volume ratios. In addition, making thermodynamically stable Si–O–C–H ceramics using a pathway different from the polymer route raises the likelihood of formation of similar carbon containing compounds in the planetary accretion and the Earth's interior.
The magnetization behavior under temperature and magnetic field variation was investigated for La0.7Pb0.3MnO3 ceramics and ferromagnetic–ferroelectric 0.85(La0.7Pb0.3MnO3)–0.15(PbTiO3) composite. The second-order ferromagnetic phase transition in manganite is shifted to the tricritical point in composite material. Comparison of the intensive caloric effect and the difference between relative cooling powers (RCP) in both materials proves a significant role of intrinsic pressure in elevating caloric efficiency in composite induced by elastic coupling between the grains of LPM and PT components. No temperature change in composite under an electric field of 2 kV/cm associated with electrocaloric effect or indirect magnetoelectric coupling was observed. The effect of magnetic field on some peculiar temperatures is considered. A contribution from pressure generated by magnetic field to baric coefficient dT/dp of ferromagnetic transformation temperature in composite was suggested. The results obtained were analyzed in the framework of the magnetic equation of state and compared with the experimentally measured heat capacity.
We presented the investigation on the cooling rate dependent undercooling of the microsized and nanosized Bi droplets in the Zn matrix via differential fast scanning calorimetry at scanning rates ranging from 300 to 6000 K/s. The experimental results demonstrated that the embedded nanosized Bi droplets gave more reproducible undercooling measurements than that of microsized Bi droplets at the grain boundaries. In addition, different cooling rate dependences of undercooling of microsized and nanosized Bi droplets were found. When the cooling rate is increased from 300 to 6000 K/s, the undercooling of the embedded nanosized Bi droplets increased gradually from 125 to 130 K. However, for microsized Bi droplets at the grain boundaries, there was an obvious increase of undercooling when the cooling rate was higher than 2000 K/s. In other words, the undercooling evolution displayed a sigmoidal relationship with the increase in cooling rate, indicating the change of the heterogeneous nucleation mechanism from a surface-induced mode to a volume-induced one.
One of the defining properties of biological structural materials is self-healing, i.e., the ability to undergo long-term reparation after instantaneous damaging events, but also after microdamage due to repeated load cycling. To correctly model the fatigue life of such materials, self-healing must be included in fracture and fatigue laws, and related codes. Here, we adopt a numerical modelization of fatigue cycling of self-healing biological materials based on the hierarchical fiber bundle model and propose modifications in Griffith's and Paris' laws to account for the presence of self-healing. Simulations allow us to numerically verify these modified expressions and highlight the effect of the self-healing rate, in particular, for collagen-based materials such as human tendons and ligaments. The study highlights the effectiveness of the self healing process even for small healing rates and provides the possibility of improving the reliability of predictions of fatigue life in biomechanics, e.g., in sports medicine.
The 18th International Symposium on the Reactivity of Solids (June 9–13, 2014 in Saint-Petersburg, Russia) brought together 137 researches from 18 countries, from crystallographers to electrochemists, to discuss the new materials design, advanced methods of preparation and characterization, mechanisms of reactions involving solids, structure–property relations, and new horizons of the materials application. What emerged from the meeting was an understanding that even if up-to-date solid state chemistry cannot be limited to organic, inorganic, or physical one, different groups of researches can understand each other and find a way for collaboration. More than half of the talks were devoted to energy production and storage problems, where the researcher should take into account not only just the chemistry of solid material, but also its crystalline structure, surface morphology, and even the bath liquid phase and interface properties. It means that only the interdisciplinary partnership can lead to outstanding results.
X-ray diffraction (XRD) has been routinely employed in the Earth sciences to characterize the crystallography of rocks and minerals. Routine characterization of samples too small for analysis by classic automated powder diffraction methods becomes challenging without access to single crystal or micro-diffraction equipment. Here, we show that a traditional Gandolfi camera lined with an image-plate (IP) as the detection medium can return a fully quantitative diffraction pattern from a sub-milligram single grain specimen in a simple and straightforward manner. Data pertaining to peak positions (d-spacings) were assessed using SRM640c Si powder, while intensity data were compared to the certified values for intensity standard SRM676a alumina powder. The refined unit-cell dimension of Si powder differed from the certified value of 5.4312 Å by no more than 0.0003 Å with a standard deviation (σ) of 0.0002 Å among the three experiments. For intensity, the σ and disparity from the certified values of three diffraction experiments on SRM676a were both <2%. The results of a comparative study of the crystallographic parameters determined for a naturally occurring garnet and clinopyroxene given through the refinement of their crystal structure by single-crystal XRD method are presented. These show through Rietveld refinement of X-ray data obtained by the Gandolfi–IP method outlined here that both accurate and precise XRD data can be produced in a timely and cost-effective manner using only an IP, Gandolfi camera, and software freely available on the internet.
The effect of high-energy electropulsing treatment (EPT) on the microstructure evolution, mechanical properties, and fracture behavior of as-treated Ti–6Al–4V alloy strips was investigated. EPT was found to accelerate phase transition and microstructure evolution of quasi-single-phase titanium alloy strips at a relatively low temperature, and obtain characteristic duplex microstructure and Widmanstatten microstructure. The EPT-induced microstructural changes increased elongation-to-failure remarkably with a slight decrease in tensile strength. Fracture surface observation and three-dimensional analysis showed that transition from small-shallow dimple colony to big-deep colony fracture took place with an increase in frequency of EPT. The rapid phase change of the Ti–6Al–4V alloy strip under EPT was attributed to the enhancement of nucleation rate and atomic diffusion resulting from the coupling of the thermal and athermal effects. It is supposed that EPT can provide a highly efficient method for the intermediate-softening annealing of titanium alloy sheet/strips.
The creep behavior of advanced 9%Cr-1 (BM1) and advanced 9%Cr-2 (BM2) dissimilar welded joints was investigated in this paper, and also the microstructures were elaborately characterized. Based on the fitting with MATLAB, a 3-D curved surface describing the primary and steady-state creep stage was achieved. The comparison of the microstructures of the precreep and aftercreep welded joints shows that δ-ferrite distribution in the heat affected zone (HAZ) of BM2 side plays an important role in determining creep rupture strength. Fracture occurred at the overtempered heat affected zone (OT-HAZ) adjacent to BM2 after creep tests at 538 °C under different stress loads. Microhardness tests revealed that the OT-HAZ adjacent to BM2 has the lowest hardness value compared with the whole welded joint. Numerous creep voids occurring around δ-ferrite, carbides, and grain boundaries were observed on the specimen after creep test. They concentrated and grew up to microcracks, and then induced the fracture at OT-HAZ. Many second phases were also observed in the grain boundary after creep, and the tempered martensite boundaries in the HAZ gradually become obscure as the creep time increases.