Lamellar Clusters Research Articles

1T-VS2@V2O3 Synergistic Nanoarchitecture-Based Lamellar Clusters as the High Conductivity Cathodes of Thermal Batteries.

Thermal batteries are solid-state, thermally activated batteries with long storage times and high reliability. FeS2 is used as a cathode material commonly, but the high internal resistance and low voltage platform limit the improvement of battery performance. Herein, the 1T-phase vanadium disulfide (VS2) is prepared via the scalable hydrothermal method and applied to thermal battery cathode materials for the first time. 1T-VS2 lamellar flower clusters have high electronic conductivity (1.583 S cm-1) at room temperature, which is 75 times higher than FeS2 (0.021 S cm-1). Mechanism analysis shows that 1T-VS2@V2O3 can be formed based on the part of 1T-VS2 being oxidized to V2O3 at the discharge temperature. Benefiting from the synergistic effect of vanadium sulfide and vanadium oxide as a cathode for thermal batteries enhanced specific capacity (292.4 mA h g-1) and mass energy density (572.5 W h kg-1) when cutoff voltage is 1 V. Additionally, the discharge results indicate that the cells utilizing 1T-VS2 cathodes provided a higher voltage platform of 2.11 V than 1.84 V for FeS2. This impressive work can offer a good strategy for boosting cathode materials for a high-performance thermal battery.

Effect of roll temperature on the structure and properties of oriented polypropylene cast film and stretched microporous membrane

AbstractThe effect of roll temperature from 60 to 120°C on the crystalline structure and properties of oriented polypropylene (PP) cast films and the stretched microporous membrane was studied. It was found that the long period, the thickness of the crystalline and amorphous phase increase with the increasing roll temperature. And the regularity of the lamellar structure also improves with the increasing roll temperature. In comparison, the lamellae lateral dimension is nearly unchanged at 50 nm. The orientation of the lamellar structure slightly decreases from 0.81 to 0.76 with increasing roll temperature. The increase of the long period and the improvement of the regularity of the lamellar structure lead to the increase of the elastic recovery value of PP cast film. The corresponding microporous membrane also shows a smaller thickness of lamellar clusters, larger pores, better air permeability and better thermal shrinkage resistance. The higher roll temperature is beneficial to the perfection of the lamellar structure, obtaining the higher‐performance microporous membrane.

Effect of cyclic DHT on microstructural evolution and mechanical properties of Ti44Al6Nb1Cr2V alloy

To clarify effects of microstructure on tensile properties of high Nb-TiAl alloys after cyclic directional heat treatment (DHT), Ti44Al6Nb1Cr2V alloys are conducted DHT for 1, 2 and 3 cycles (DHT-1, DHT-2 and DHT-3) at 1730 K, respectively. The pulling rate is set as 4.17 µm/s. Results show the phase component mainly consists of γ, α2 and B2 phases for Ti44Al6Nb1Cr2V alloy after cyclic DHT. Directional microstructure is obtained. Lamellar clusters are columnar and B2 phases present banded morphology. They are distributed alternately. As DHT cycles increase, the radial size of lamellar clusters enlarges as well. Blocky γ phases grow up and coarsen. At room temperature, good tensile properties are obtained in Ti44Al6Nb1Cr2V alloys after cyclic DHT. Tensile strength is about 609 MPa for DHT-1 alloy. Their fractures show that cleavage microstructure is mainly formed for cracks propagation during tensile test. Both DHT-1 and DHT-3 alloys present good tensile properties stability at 900 °C. Their yield strength, ultimate tensile strength and elongation are about 355–487 MPa-3.3% and 355–421 MPa-1.5%, respectively. Combining their microstructures with fractures, it concludes for their tensile properties difference that many blocky γ phases precipitate and coarsen during cyclic DHT, which decreases deformation coordination between lamellar clusters and banded B2 phases. Some microcracks form easily near B2 phases. Consequently, tensile properties of DHT-3 alloy decrease. This study will provide basic experimental data and theoretical support for high Nb-TiAl alloys to further optimize DHT parameters and improve their mechanical properties.

Effect of annealing treatment on microstructure and tensile properties of Ti-48Al-2Cr-5Nb alloy fabricated by laser additive manufacturing

Using laser additive manufacturing (LAM), a Ti-48Al-2Cr-5Nb alloy was fabricated and studied systematically for its microstructure, phase composition, texture, and tensile properties. The results indicate that both the microstructure of as-deposited and annealed alloys consists of phases Ti3Al (α2) and TiAl (γ). When the annealing temperature was increased, the microstructure changed significantly and a greater amount of lamellar α2 phase precipitated between the lamellae. Meanwhile, the thickness of γ lamellar at the edges of lamellar clusters increased. In comparison with the annealed alloy, the secondary annealed alloy demonstrated a significant coarsening of the lamellar γ phase. Increasing the annealing temperature gradually increased the texture strength of the γ (111) orientation. At room temperature and high temperature, the as-deposited alloy had a higher tensile strength than the annealed alloy. Ti-48Al-2Cr-5Nb alloy samples secondary annealed at 1260 °C/1h/FC exhibited the highest elongations at room temperature, 750 °C, and 850 °C, with values of 1.6%, 3.8%, and 4.8%, respectively. As compared to the as-deposited alloy, the elongation increased by 1.15, 1.36, and 1.07 times, respectively.

Dynamical origin for winner-take-all competition in a biological network of the hippocampal dentate gyrus.

We consider a biological network of the hippocampal dentate gyrus (DG). Computational models suggest that the DG would be a preprocessor for pattern separation (i.e., a process transforming a set of similar input patterns into distinct nonoverlapping output patterns) which could facilitate pattern storage and retrieval in the CA3 area of the hippocampus. The main encoding cells in the DG are the granule cells (GCs) which receive the input from the entorhinal cortex (EC) and send their output to the CA3. We note that the activation degree of GCs is very low (∼5%). This sparsity has been thought to enhance the pattern separation. We investigate the dynamical origin for winner-take-all (WTA) competition which leads to sparse activation of the GCs. The whole GCs are grouped into lamellar clusters. In each cluster, there is one inhibitory (I) basket cell (BC) along with excitatory (E) GCs. There are three kinds of external inputs into the GCs: the direct excitatory EC input; the indirect feedforward inhibitory EC input, mediated by the HIPP (hilar perforant path-associated) cells; and the excitatory input from the hilar mossy cells (MCs). The firing activities of the GCs are determined via competition between the external E and I inputs. The E-I conductance ratio R_{E-I}^{(con)}^{*} (given by the time average of the ratio of the external E to I conductances) may represent well the degree of such external E-I input competition. It is thus found that GCs become active when their R_{E-I}^{(con)}^{*} is larger than a threshold R_{th}^{*}, and then the mean firing rates of the active GCs are strongly correlated with R_{E-I}^{(con)}^{*}. In each cluster, the feedback inhibition from the BC may select the winner GCs. GCs with larger R_{E-I}^{(con)}^{*} than the threshold R_{th}^{*} survive, and they become winners; all the other GCs with smaller R_{E-I}^{(con)}^{*} become silent. In this way, WTA competition occurs via competition between the firing activity of the GCs and the feedback inhibition from the BC in each cluster. Finally, we also study the effects of MC death and adult-born immature GCs on the WTA competition.

Effect of SiC Nanoparticles on AZ31 Magnesium Alloy.

Magnesium alloys are attractive for the production of lightweight parts in modern automobile and aerospace industries due to their advanced properties. Their mechanical properties are usually enhanced by the incorporation with reinforcement particles. In the current study, reinforced AZ31 magnesium alloy was fabricated through the addition of bulk Al and the incorporation of SiC nanoparticles using a stir casting process to obtain AZ31-SiC nanocomposites. Scanning electron microscope (SEM) investigations revealed the formation of Mg17Al12 lamellar intermetallic structures and SiC clusters in the nanocomposites. Energy dispersive spectroscopy (EDS) detected the uniform distribution of SiC nanoparticles in the AZ31-SiC nanocomposites. Enhancements in hardness and yield strength (YS) were detected in the fabricated nanocomposites. This behavior was referred to a joint strengthening mechanisms which showed matrix-reinforcement coefficient of thermal expansion (CTE) and elastic modulus mismatches, Orowan strengthening, and load transfer mechanism. The mechanical properties and wear resistance were gradually increased with an increase in SiC content in the nanocomposite. The maximum values were obtained from nanocomposites containing 1 wt% of SiC (AZ31-1SiC). AZ31-1SiC nanocomposite YS and hardness were improved by 27% and 30%, respectively, compared to AZ31 alloy. This nanocomposite also exhibited the highest wear resistance; its wear mass loss and depth of the worn surface decreased by 26% and 15%, respectively, compared to AZ31 alloy.

Structural Explanation on Uniaxial Tensile Behavior of Crystalline Polymer Solids

We proposed a novel deformation process in the tensile stress-strain behavior of semicrystalline polymer solids. At the yield point, the stacked lamellar clusters are fragmented into cubic cluster blocks of single chain size; the rearrangement of these blocks under uniaxial tension produces the texture of necking. The initiation of necking is explained by a first-order catastrophic phase transition analogous to the model of a van der Waals gas. Thus, the catastrophic arrangement of the cluster blocks results in a sudden emergence of a locally close-packed layer structure. The negative molecular dependence of the natural draw ratio at the necked portion can be explained by the catastrophic rearrangement of the cluster blocks, the size of which is proportional to the square root of the molecular weight.

Population and individual firing behaviors in sparsely synchronized rhythms in the hippocampal dentate gyrus.

We investigate population and individual firing behaviors in sparsely synchronized rhythms (SSRs) in a spiking neural network of the hippocampal dentate gyrus (DG). The main encoding granule cells (GCs) are grouped into lamellar clusters. In each GC cluster, there is one inhibitory (I) basket cell (BC) along with excitatory (E) GCs, and they form the E-I loop. Winner-take-all competition, leading to sparse activation of the GCs, occurs in each GC cluster. Such sparsity has been thought to enhance pattern separation performed in the DG. During the winner-take-all competition, SSRs are found to appear in each population of the GCs and the BCs through interaction of excitation of the GCs with inhibition of the BCs. Sparsely synchronized spiking stripes appear successively with the population frequency Hz) in the raster plots of spikes. We also note that excitatory hilar mossy cells (MCs) control the firing activity of the GC-BC loop by providing excitation to both the GCs and the BCs. SSR also appears in the population of MCs via interaction with the GCs (i.e., GC-MC loop). Population behaviors in the SSRs are quantitatively characterized in terms of the synchronization measures. In addition, we investigate individual firing activity of GCs, BCs, and MCs in the SSRs. Individual GCs exhibit random spike skipping, leading to a multi-peaked inter-spike-interval histogram, which is well characterized in terms of the random phase-locking degree. In this case, population-averaged mean-firing-rate (MFR) is less than the population frequency . On the other hand, both BCs and MCs show "intrastripe" burstings within stripes, together with random spike skipping. Thus, the population-averaged MFR ( MC and BC) is larger than , in contrast to the case of the GCs. MC loss may occur during epileptogenesis. With decreasing the fraction of the MCs, changes in the population and individual firings in the SSRs are also studied. Finally, quantitative association between the population/individual firing behaviors in the SSRs and the winner-take-all competition is discussed.

Optimizing microstructure and mechanical properties of directionally solidified Ti44Al6Nb1Cr2V alloy by directional heat treatment

To optimize microstructure and improve mechanical properties of directionally solidified (DS) TiAl alloys containing high alloying elements, DS Ti44Al6Nb1Cr2V alloy was conducted directional heat treatment (DHT) at 1730 K. Results indicate that columnar grains grow up straightly after DHT. It decreases from 17.55° to 10.67° for the angle in the axial direction between columnar grains and ingot. Morphology of B2 phases changes obviously, from reticular to banded microstructure. Lamellar clusters grow up greatly and are parallel to the growth direction of columnar grains. These changes are mainly caused by sufficient atoms diffusion during DHT. α grains grow up adequately and residual B2 phases reduce. Compared with that of DS Ti44Al6Nb1Cr2V alloy (505 MPa and 1.40%), ultimate tensile strength and total strain are 609 MPa and 1.86% for DHT alloy, respectively. They are increased by 21% and 33%, respectively. Fracture shows that many tearing edges and some similar dimples morphology are also found in DHT alloy, besides cleavage planes and cleavage steps. TEM image shows that many dislocations are produced in lamellar γ phases of DS alloy. They wind and intercross each other. Dislocation interaction is lower and the stress concentration is less for DHT alloy, due to thin lamellar γ phases. Furthermore, some stacking faults are also produced in lamellar γ phases, which benefits to improving mechanical properties. Therefore, mechanical properties are improved greatly for DS alloy after DHT. • The angle between growth direction of columnar grains and axial direction of ingot decreases from 17.55° to 10.67°. • Lamellar clusters grow up obviously and distribute along the growth direction of columnar grains after DHT. • Morphology of B2 phases changes from reticular to banded structure and its content reduces after DHT. • The ultimate tensile strength and total strain are 609 MPa and 1.86% for DHT alloy, respectively.

Effects of delayed repair of peripheral nerve injury on the spatial distribution of motor endplates in target muscle.

Motor endplates (MEPs) are important sites of information exchange between motor neurons and skeletal muscle, and are distributed in an organized pattern of lamellae in the muscle. Delayed repair of peripheral nerve injury typically results in unsatisfactory functional recovery because of MEP degeneration. In this study, the mouse tibial nerve was transected and repaired with a biodegradable chitin conduit, immediately following or 1 or 3 months after the injury. Fluorescent α-bungarotoxin was injected to label MEPs. Tissue optical clearing combined with light-sheet microscopy revealed that MEPs were distributed in an organized pattern of lamellae in skeletal muscle after delayed repair for 1 and 3 months. However, the total number of MEPs, the number of MEPs per lamellar cluster, and the maturation of single MEPs in gastrocnemius muscle gradually decreased with increasing denervation time. These findings suggest that delayed repair can restore the spatial distribution of MEPs, but it has an adverse effect on the homogeneity of MEPs in the lamellar clusters and the total number of MEPs in the target muscle. The study procedures were approved by the Animal Ethics Committee of the Peking University People's Hospital (approval No. 2019PHC015) on April 8, 2019.

Solvent-Free UV Polymerization of n-Octadecyl Acrylate in Butyl Rubber: A Simple Way to Produce Tough and Smart Polymeric Materials at Ambient Temperature.

One of the most fascinating challenges in recent years has been to produce mechanically robust and tough polymers with smart functions such as self-healing and shape-memory behavior. Here, we report a simple and versatile strategy for the preparation of a highly tough and highly stretchable interconnected interpenetrating polymer network (c-IPN) based on butyl rubber (IIR) and poly(n-octadecyl acrylate) (PC18A) with thermally induced healing and shape-memory functions. Solvent-free UV polymerization of n-octadecyl acrylate (C18A) at 30 ± 2 °C in the presence of IIR leads to IIR/PC18A c-IPNs with sea-island or co-continuous morphologies depending on their IIR contents. The lamellar crystals with a melting temperature Tm of 51-52 °C formed by side-by-side packed octadecyl (C18) side chains are responsible for more than 99% of effective cross-links in c-IPNs, the rest being hydrophobic associations and chemical cross-links. The c-IPNs exhibit varying stiffness (9-34 MPa), stretchability (72-740%), and a significantly higher toughness (1.9-12 MJ·m-3) than their components, which can be tuned by changing the IIR/PC18A weight ratio. The properties of c-IPNs could also be tuned by incorporating a second, noncrystallizable hydrophobic monomer, namely, lauryl methacrylate (C12M), in the melt mixture. We show that the lamellar clusters acting as sacrificial bonds break at the yield point by dissipation of energy, while the ductile amorphous continuous phase keeps the structure together, leading to the toughness improvement of c-IPNs. They exhibit a two-step healing process with >90% healing efficiency with respect to the modulus and a complete shape-recovery ratio induced by heating above Tm of alkyl crystals. The temperature-induced healing occurs via a quick step where C18 bridges form between the damaged surfaces followed by a slow step controlled by the interdiffusion of C18A segments in the bulk. We also show that the strategy developed here is suitable for a variety of rubbers and n-alkyl (meth)acrylates of various side-chain lengths.

Study on improving microstructure and mechanical properties of directionally solidified Ti44Al6Nb1Cr alloy by cyclic DHT

Abstract To improve microstructure of high-Nb TiAl alloys after directional solidification (DS) further, DS Ti44Al6Nb1Cr alloy was conducted cyclic directional heat treatment (DHT) for 1 and 4 times under pulling rate of 4.17 μm/s at 1750 K, respectively. Results indicate that columnar grains grow up obviously after DHT. Compared with DS alloy (2.56 mm), the maximum width of columnar grains is up to about 9.07 mm for DHT alloy after 4 times (DHT-4). The SEM images and EDS results indicate that phase component of DS alloy has not changed after cyclic DHT for different times. It is still composed of α2, γ and B2 phases. As cyclic DHT times increase, thickness of lamellar phases increases gradually. More massive γ phases precipitate from B2 phases and grow up. The content of B2 phases reduces due to atoms diffusing sufficiently during cyclic DHT. Tensile curves show optimal mechanical properties are obtained in DHT alloy for 1 time (DHT-1). The ultimate tensile strength is 636 MPa and total strain is 2.28%. Compared with that of DS alloy (523 MPa and 3.03%), tensile strength is improved greatly. As cyclic times increase, mechanical properties decrease for DHT alloy, due to massive γ phases coarsening and B2 phases distributing discontinuously. This microstructure could not hinder cracks propagation effectively, which may be the main reasons to result in premature fracture for DHT-4 alloy. At 973 K, the better mechanical properties are still achieved in DHT-1 alloy. The ultimate tensile strength is up to 695 MPa and total strain is 6.21%. The mechanical properties improvement is mainly resulted from directional microstructure, especially the directional lamellar clusters and B2 phases. In addition, dislocations, stacking fault bands and deformation twins are observed in lamellar γ phases of DHT-1 alloy. These microstructure changes play an important role in improving compressive mechanical properties of DHT alloy.

Study on improving directional microstructure of Ti44Al6Nb1Cr alloy by continuous regional phase transformation

To improve the directionally solidified (DS) microstructure and mechanical properties of high-Nb containing TiAl alloys, DS Ti44Al6Nb1Cr alloy was directionally heat treated (DHT) with pulling velocity of 4.17 µm/s at 1750 K. Microstructure and grains orientation were characterized by the OM, SEM, TEM and EBSD. Chemical composition and phase component were detected by the EDS and XRD. Results indicate that wide columnar grains are formed along the axial direction after DHT. Microstructure is still fully lamellar and composed of α2, γ and B2 phases. Crystallographic orientation relationship among phases (α2, γ and B2) is not changed. Lamellar clusters in columnar grains change from blocky to columnar, and the reticular B2 phases become banded structure after DHT. During DHT, the β phase transforms into α phase continuously and α grains grow into columnar clusters. Nb and Cr atoms can diffuse more adequately under the influence of directional heat flow and segregate at boundaries of columnar clusters. Therefore, lamellar clusters and B2 phases are distributed almost in parallel along the axial direction of columnar grains at room temperature. Tensile testing shows that the yield strength, ultimate strength and total strain of the DHT alloy are increased to 574 MPa, 636 MPa and 2.28% from 422 MPa, 523 MPa and 3.03% of as DS alloy, respectively. The tensile strength increases about 36% and this improvement is mainly caused by the directionally aligned B2 phases. In addition, a large number of dislocations and stacking fault bands are formed in lamellar γ phases of DHT alloy after testing, which also plays an important role in improving mechanical properties of DS alloy.

Microstructure formation and elevated temperature mechanical properties of directionally solidified Ti44Al6Nb1Cr alloy

To improve room and elevated temperature mechanical properties of high-Nb TiAl alloys, Ti44Al6Nb1Cr alloy has been prepared by cold crucible directional solidification (CCDS) technique under loaded power of 40 kW and pulling rate of 8.3 μm/s. Macro/micro-structure and phase composition have been characterized. Tensile properties have been tested at room and elevated temperature and the related mechanisms have been revealed. Results show that equiaxed grains change to columnar grains growing up along the axial direction of ingot after CCDS. Phase component is still composed of α2, γ and B2 phases. Microstructure consists of lamellar clusters and network structure. The lamellar clusters in a grain possess the same orientation. The content and size of B2 phases decrease and some casting defects with small size decrease as well due to sufficient diffusion of Nb and Cr atoms under action of electromagnetic force during CCDS. Tensile results indicate that comprehensive mechanical properties of Ti44Al6Nb1Cr alloy are improved significantly after CCDS. At room temperature, ultimate tensile strength and total strain are 523 MPa and 3.03%, respectively, which are improved by 18.1% and 64.7% compared with that of as-cast Ti44Al6Nb1Cr alloy (443 MPa and 1.84%). Moreover, fracture morphology also indicates that there are many deep ravines between cleavage steps and some similar dimples microstructure on cleavage steps. They are beneficial to improving comprehensive mechanical properties. At 973 K, ultimate tensile strength of Ti44Al6Nb1Cr alloy does not decrease at all, still reaching 530 MPa after CCDS. When service temperature rises to 1173 K, the strain is less than 4.28% showing excellent mechanical stability under tensile stress less than 436 MPa. The excellent stability for mechanical properties is due to thin lamellar phases, directional microstructure and large plastic deformation region.

Uniaxial stretching induced pore nucleation and growth in row-nucleated crystalline hard-elastic polypropylene film: The effect of activation volume and stretching work

In this paper, the pore nucleation and growth during uniaxial stretching of polypropylene hard-elastic film at different temperatures were followed. The stretching-induced microstructure including lamellar clusters, fibrillar crystals and pores were tracked by in-situ x-ray scattering. The correlation between activation volume and lamellar clusters thickness and the relationship between stretching work and the new formed fibrillar crystals/pore surface area were built. It was found that compared with that obtained at 105 °C, the hard-elastic film stretched at 145 °C induced larger lamellar cluster thickness, longer fibrillar crystals and fewer pores with larger size. With the stretching temperature increasing, the chain segment activation volume increases, whereas the activation energy and stretching work decreases. During uniaxial stretching, the stretching work was mainly dissipated by forming new surfaces. Higher activation volume lead to larger lamellar cluster thickness and less pore number in unit area, whereas lower activation energy induced longer fibrillar crystals and lower stretching work resulted in less new surface. This paper clarifies how the stretching temperature affect pore formation and growth during the uniaxial tensile deformation of hard elastic film and the obtained results are beneficial for the pore control during the industrial fabrication of polypropylene microporous membrane.

Janus particle rotator-to-lamellar nucleation and growth kinetics

We determine the free energy barrier, critical nucleus size, and kinetics of a Janus particle solid-solid transition by nucleation and growth of lamellar clusters within a metastable rotator phase. The transition involves negligible change in particle position and phase volume and entails only particle orientational ordering. Fast kinetics enable the analysis of unbiased crystal growth and shrinkage trajectories from Brownian dynamic simulations. By fitting simulation trajectories to a diffusion-migration equation, the nucleus free energy and growth coefficient as a function of nucleus size are extracted. Observed transition times are on the order of hundreds of characteristic particle rotation times. Lamellar crystal nuclei are oblate rather than spherical, but otherwise classical nucleation theory applies, with the bulk free energy contribution following closely the Maier-Saupe theory for purely orientational transitions and the interfacial energy contribution following trends from 3-dimensional Ising spin kinetics.

Structural Interpretation of Eyring Activation Parameters for Tensile Yielding Behavior of Isotactic Polypropylene Solids

The temperature and strain rate dependence of the stress-strain curves of isotactic polypropylene were analyzed on the basis of Eyring kinetic theory. The molecular and structural basis underlying the parameters, such as activation volume and activation energy, used by the Eyring analysis were studied using the lamellar cluster theory, where a stacked lamella acts as a basic structural unit under yielding and necking deformation. It was suggested that, at lower temperatures, the activation volume corresponds to chain slippage within crystalline lamellae in the lamellar clusters whereas at higher temperature the increase in activation volume results in intralamellar slip corresponding to the α2 relaxation.

Deformation mechanism of high-density polyethylene probed by in situ Raman spectroscopy

The microscopic mechanism of high-density polyethylene under uniaxial drawing is investigated using in situ Raman spectroscopy. From the peak shifts of the symmetric and anti-symmetric C–C stretching modes, it is found that the load sharing on the polymer chain in the yielding region is anisotropic with stretching along the chain and compression perpendicular to the chain. The orientation functions (〈P2〉 and 〈P4〉) as well as the orientation distribution function (N(θ)) are determined from the polarized Raman spectra. The molecular orientation with cold drawing is found to proceed more effectively for lower crystallinity specimens. In the yielding region, it is also found that N(θ) has a maximum at the polar angle θ = 30–70°. This peculiar behavior in the microscopic scale is explained by the preferential collapse of spherulites and the existence of lamellar clusters as the bulky mobile units.

The electrodeposition of Ga-doped CuInSe2 thin film in the presence of Triton 100-X

The codeposition of Cu, In, Ga and Se from pH 1.5 at Na2SO4/H2SO4 solution onto fluorine doped tin oxide (FTO) was studied. The effects of Triton 100-X as a noncomplexing and nonionic additive in the electrodeposition process was evaluated. At optimised experimental conditions was possible to obtain of Ga-doped CuInSe2 films (CIGSe). The films presented two different morphologies, one layer formed by globular structures and another layer constituted of lamellar clusters. The major phase in the films was CIGSe, but binary phases as InSe and CuSe were also identified. The value of the band gap was at about 1.35eV for all the films. It was observed that the additive presence in electrolytic bath reduces the number of surface defects and increases the crystallinity and purity of the electrodeposited CIGSe.

Fabrication and atomic structure of size-selected, layered MoS2 clusters for catalysis.

Well defined MoS2 nanoparticles having a layered structure and abundant edges would be of considerable interest for applications including photocatalysis. We report the atomic structure of MoS2 size-selected clusters with mass in a range all the way from 50 to ∼2000 MoS2 units. The clusters were prepared by magnetron sputtering and gas condensation prior to size selection and soft landing on carbon supports. Aberration-corrected scanning transmission electron microscopy (STEM) in high-angle annular dark-field (HAADF) mode reveals a layered structure and Mo-Mo spacing similar to the bulk material. The mean number of layers in these lamellar clusters increases from one to three with increasing mass, consistent with density functional theory calculations of the balance between edge energies and interlayer binding.