The oxidation of copper single crystals is known to proceed at different rates on different crystal faces. To determine whether this behavior extends to subsequent atmospheric sulfidation as well, we have exposed polycrystalline copper and (100), (110), and (111) single crystals of copper to low concentrations of hydrogen sulfide in high humidity air. For short exposures, all of the single crystals sulfidize much more slowly than does polycrystalline copper. In each case, 
is the predominant sulfur species formed. As with oxide formation on copper single crystals, there is a slight tendency for the (111) face to be the most inert. For long exposures, the sulfide film on the single‐crystal samples increases to become essentially equal to that on polycrystalline copper. We envision a corrosion process initially controlled by grain boundary diffusion (and thus the degree of crystallinity of the underlying oxide), followed by a transition to a regime in which the diffusion of copper ions through 
limits the growth of the corrosion film.
Source:IOPscience
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Triglycine sulfate (TGS) single crystals modified with phosphoric acid (TGS1−xPx) have been grown by slow evaporation technique at room temperature. Lattice parameters were identified by using single crystal x-ray diffractometer. The dielectric, pyroelectric, ferroelectric properties and electrocaloric effect have been investigated. Curie temperature of grown crystals was determined from dielectric constant measurements at various temperatures at a frequency of 1 kHz. The Curie temperature is found decreased for the TGS single crystals with the addition of phosphoric acid. Room temperature P-E hysteresis loops of TGS1−xPx single crystals are presented. The values of coercive field Ec, spontaneous polarization Ps and internal bias field Eb were obtained from the hysteresis loops. Discussion on pyroelectric properties as a function of temperature and applied electric field is presented. Figure of merits (FOMs) were determined to study the pyroelectric performance of the grown crystals. Among all compositions of x, x = 0.2 (i.e., TGS0.8P0.2) single crystals exhibited the largest pyroelectric coefficient and pyroelectric figure of merit at room temperature. From the above investigations the electrocaloric temperature change, ΔT of TGS1−xPxsingle crystals at selected applied fields and temperatures are obtained by indirect method and discussed.
Source:IOPscience
Single crystal positive electrode materials for lithium-ion batteries have superior properties compared to their polycrystalline counterparts as has been demonstrated by industry and academia. Single crystal LiNi0.5Mn0.3Co0.2O2 (NMC532), NMC622 and now NMC811 have been successfully commercialized. However, single crystal LiNi1-x-yCoxAlyO2(NCA) materials have not been reported yet. One simple method for producing single crystal NMC material requiring high temperature and excess lithium during synthesis creates Li5AlO4 impurities if applied directly in attempts to synthesize single crystal NCA materials. This work introduces a two-step lithiation method for single crystal LiNi0.88Co0.09Al0.03O2 synthesis, which can prevent the formation of Li5AlO4 impurities. Powder X-ray diffraction, electron backscatter diffraction, and electrochemical measurements show the viability of the two-step lithiation method. Full coin cell cycling shows that the capacity retention of the single crystal NCA samples is at least as good as their polycrystalline counterparts. It is believed that this two-step lithiation method can be used for the synthesis of single crystal NCA and other single crystal Al-containing positive electrode materials. We believe this can lead to longer lived Li-ion cells with Ni-rich positive electrode materials.
Source:IOPscience
