Typical Layered Structure Research Articles

Study on shield configuration stuffed with the integrated fabric layer and its bracing structure

Two alternative techniques to brace the fabric layers stuffed in high-performance shield configurations are evaluated by hypervelocity impact tests respectively. Al honeycomb core and Al mesh are proposed to brace the fabric layers separately. There are four types of stuffed layer structures. The first structure consists of two kinds of fabrics, one layer of basalt fabric followed with one layer of Aramid-III fabric repeatedly. The second type is the first one plus Al honeycomb core. The third type contains several layers of basalt fabric and one layer of Al mesh. The fourth type is similar to the third one, while the stuffed layer is sewed with the aramid thread. For the target configurations, the bumper and the rear plate are 1mm-thick Al plate and the stuffed layer is 100 mm from the bumper. The targets are impacted by Al projectile with the diameters about 5 mm, and the velocities range from 4 km/s to 5 km/s. According to the test results, the fixing and support structure weight of the fabric layer is lightened by using the Al honeycomb core. The Al honeycomb core absorbs and dissipates the kinetic energy of debris cloud effectively, however, its channel effect aggravates the perforation damage on the rear plate. For the fourth structure, the Al mesh plays the role of fixing and supporting basalt fabric, but the performance of stuffed layer intercepting debris cloud is reduced.

Synthesis of vanadium oxides nanosheets as anode material for asymmetric supercapacitor

Vanadium oxides (V2O5) have been intensely investigated for advanced supercapacitors due to its extensive multifunctional properties of typical layered structure and multiple stable oxide states of vanadium in its oxides. In this study, V2O5 nanosheets are synthesized via V2O5 xerogel solvothermal reaction in ethanol solvent at 200 °C for 12 h. The V2O5 nanosheets facilitate the easy accessibility of ions and can provide more area available for electrochemical reactions. We have achieved the highest specific capacitance of 298 F/g and good rate discharge for V2O5 electrodes. Notably, the capacitance still retains a high retention rate of 85% after 10,000 cycles at 200 mV/s. Furthermore, asymmetric supercapacitors is assembled based on V2O5 nanosheets and active carbon electrode, and a specific capacitance of 13.2 F/g is obtained at 1 A/g, with a energy density of 4.7 Wh/kg at a power density of 0.798 kW/kg and remains 2.28 Wh/kg at 7.992 kW/kg. Based on these results, the asymmetric supercapacitor exhibits a good cycle life with 77.3% capacitance retention after 3000 cycles. It suggests that the V2O5 nanosheets are promising electrode material for electrochemical supercapacitors.

Textured Na x CoO2 Ceramics Sintered from Hydrothermal Platelet Nanocrystals: Growth Mechanism and Transport Properties

Nanostructuring is an effective approach to improve thermoelectric (TE) performance, which is caused by the interface and quantum effects on electron and phonon transport. For a typical layered structure such as sodium cobalt (NCO), a highly textured ceramic with nanostructure is beneficial for the carrier transport properties due to the strong anisotropy. In this paper, we established a textured NCO ceramic with highly oriented single crystals in nanoscale. The Na0.6CoO2 platelet crystals were prepared by a one-step hydrothermal method. The growth mechanism was revealed to involve dissolution–recrystallization and exchange reactions. NCO TE ceramics fabricated by a press-aided spark plasma sintering method showed a high degree of texturing, with the platelet crystals basically lying along the in-plane direction perpendicular to the press direction. TE properties of the textured NCO ceramics showed a strong anisotropic behavior. The in-plane electrical conductivity was considerably larger than the out-of-plane data because of fewer grain boundaries and interfaces that existed in the in-plane direction. Moreover, the in-plane Seebeck coefficient was higher because of the anisotropic electronic nature of NCO. Although the in-plane thermal conductivity was high, a prior ZT value was enabled for these NCO ceramics along this direction because of the dominant electrical transport. This finding provides a new approach to prepare highly oriented ceramics.

NMR study on the demineralization mechanism of the enamel and dentin surfaces in MDP-based all-in-one adhesive.

The acidic monomers utilized in all-in-one adhesives play a key role in the enamel and dentin bonding performance. The purpose of this study is to investigate the mechanism by which 10-methacryloyloxydecyl dihydrogen phosphate (MDP) demineralizes the enamel and dentin surfaces prepared by a diamond bur in three types of experimental MDP-based all-in-one (EX) adhesives containing different amounts of water (46.6, 93.2 and 208.1 mg/g). The enamel and dentin reactants of EX adhesives were analyzed using solidstate phosphorous-31 nuclear magnetic resonance and X-ray diffraction. Increased amount of water led to increases in the efficacy by which MDP demineralizes the enamel and dentin surfaces. However, the rate of calcium salts of MDP produced slowed down at the water concentrations above 93.2 mg/g. The dentin yielded greater amounts of di-calcium salts of the MDP monomer and dimer than the enamel, which develops a different type of layered structure of MDP from the enamel.

Growth and characterization of Bi3.15Nd0.85Ti2.95Hf0.05O12/La0.67Sr0.33MnO3 composite film with strong magnetoelectric effect by chemical solution deposition under moderate crystallization temperature

Using chemical solution deposition method, La0.67Sr0.33MnO3 (LSMO) and Bi3.15Nd0.85Ti2.95Hf0.05O12 (BNTH) layers were successively fabricated onto (001) LaAlO3 (LAO) substrates, and then BNTH/LSMO ferromagnetic-ferroelectric composite films with a 2-2 layered type structure were obtained. The LSMO ferromagnetic layer was epitaxially grown on the LAO substrate and showed the low resistivity of 5.0 × 10−3 Ω cm. It was not only used as a seed layer to induce the oriented growth of BNTH ferroelectric layers, but also as a bottom electrode to measure ferroelectric/magnetoelectric (ME) properties. The effects of crystallization temperature on the orientation degree, the surface morphology, and the dielectric and ferroelectric performances of the composite films were investigated. The composite film crystallized at 730 °C has the largest remnant polarization (Pr) of 35.0 μC/cm2, the lowest leakage current density of 1.35 × 10−7 A/cm2 and the high saturated magnetization (Ms) of 370 emu/cm3. The composite film also exhibits a strong ME response in the absence of DC bias magnetic field. Its ME voltage coefficient, αE, gradually increases from zero with the increasing of the AC magnetic field frequency, and eventually reaches 35.8 V/cm·Oe at 100 kHz.

Development of the layered structure in a double-gated glass fiber-reinforced polypropylene injection molding: Experimental and simulated results

The present study aims to experimentally validate numerical simulation of fiber orientation distribution performed by molding simulation software Moldex3D in a double-gated injection-molded glass fiber-filled (40 wt%) polypropylene box, by making a detailed comparison of predicted and experimentally measured fiber orientation distribution data. The modeling approach evaluated in this work consists in the implementation of the Folgar–Tucker rotary diffusion model with the invariant-based optimal fitting closure approximation for the fourth-order orientation tensor. The specimen used has a weld line in the center and sharp corners. This investigation characterizes in detail the development of the through-thickness layered structure at distinctive locations of the specimen. The sensitivity of fiber orientation distribution and the layered structure to changes upon injection time and melt temperature is also evaluated. The boxes display the typical layered laminate structure, with fibers aligned in the main flow direction near the walls (shell layer) and less oriented in the middle plane (core layer). The boxes injected at the lowest melt temperature display an additional skin layer. Unfortunately, simulation fails in predicting the five layers structure developed under these latter conditions. The grade of fiber orientation is deemed to be independent of process parameters but not the layered structure.

Improvement of ORR Catalyst Layer with Highly Graphitized CNF in PEMFC

Polymer electrolyte membrane fuel cell (PEMFC) is regarded as a promising power source with the advantages of high power density and low operating temperature. However, there still remains water management problem. Water flooding is a phenomenon that the pores of the catalyst on gas diffusion layer are filled up with the excessive water produced near cathode side. And the pathway of oxygen (or air) could be blocked leading to the acceleration of the mass transfer limitation and degradation of durability because of the carbon corrosion reaction between carbon and water at cathode. Therefore, it is important to remain the right amount of water in membrane electrode assembly to keep the reaction working smoothly. In recent investigations,1,2 various types of catalyst layer structure have been studied in order to keep a proper humidity level in membrane electrode assembly (MEA) and reduce the oxygen transport resistance. In this study, we incorporate a highly graphitized carbon nanofiber (CNF) into cathode catalyst layer for improvement mass transfer in PEMFC, and found out that graphitic CNF might serve as a pathway of water drainage and also diminish the ohmic losses due to the improved electrical conductivity of the electrode. References J. Joo, M. Choun, K. Kim, S. Uhm, Y. D. Kim and J. Lee, Curr. Appl. Phys., 14, 1374 (2014).M. Choun, D. Nauryzbayev, D. Shin and J. Lee, Catal. Today, 262, 155 (2016).

Effect of substrate preheating treatment on the microstructure and ultrasonic cavitation erosion behavior of plasma-sprayed YSZ coatings

Inconel 718 was used as the substrate and preheated at different temperatures to deposit yttrium stabilized zirconia (denoted as YSZ) coatings by atmospheric plasma spraying. The microstructure of the as-deposited YSZ coatings and those after cavitation-erosion tests were characterized by field emission scanning electron microscopy, Raman spectroscopy, and their hardness and toughness as well as cavitation-erosion resistance were evaluated in relation to the effect of substrate preheating temperature. Results indicate that the as-deposited YSZ coatings exhibit typical layered structure and consist of columnar crystals. With the increase of the substrate preheating temperature, the compactness and cohesion strength of coatings are obviously enhanced, which result in the increases in the hardness, elastic modulus and toughness as well as cavitation-erosion resistance of the ceramic coatings therewith. Particularly, the YSZ coating deposited at a substrate preheating temperature of 800 °C exhibits the highest hardness and toughness as well as the strongest lamellar interfacial bonding and cavitation-erosion resistance (its cavitation-erosion life is as much as 8 times than that of deposited at room temperature).

Lanthanum magnesium hexaluminate thermal barrier coatings with pre-implanted vertical microcracks: Thermal cycling lifetime and CMAS corrosion behaviour

Atmospheric plasma-sprayed (APS) coatings have a layered structure as well as lower strain tolerance and a shorter lifetime than EB-PVD coatings. In this study, TBCs composed of a LaMgAl11O19 (LMA) top coat and a NiCrAlY bond coat were prepared by APS coupled with dry-ice blasting to implant vertical microcracks in the top coat. The thermal cycling lifetime and CMAS corrosion behaviour of LMA-TBCs with pre-implanted vertical microcracks were investigated in detail. The results show that the LMA top coat possesses an improved proportion of vertical microcracks and that the corresponding TBC has an improved thermal cycling lifetime. The vertical microcracks in the top coats, which not only reduce the thermal stress but also improve the strain tolerance of TBCs, dramatically contribute to the improvement in the thermal cycling lifetime. Surprisingly, the CMAS corrosion resistance of LMA-type TBCs with implanted vertical microcracks is better than that of conventional TBCs with a typical layered structure.

Study on the properties of FeCrNi/CBN composite coating with high velocity arc spraying

FeCrNi/CBN cored wire is prepared by use of the pull-type flux cored wire machine (FCWM50 type), FeCrNi/CBN composite coating is made by high velocity arc spraying. The special properties of the composite coating can be improved by adding Cr, Ni and small amounts of rare earth elements to adjust the coating composition. The Tribological properties of FeCrNi/CBN composite coating with high velocity arc spraying is studied. Images and components and cross-section microstructure of coatings are analyzed by means of SEM, and EDS, etc. This research indicated that FeCrNi/CBN composite coatings have typical layered structure feature and high bond strength and hardness. Friction of coatings at near room temperature or higher has “Run-up” period. With the increase of temperature, friction coefficient of coatings becomes low and wearing capacity of coatings high. The adding of CBN powder highly improved the wearing capacity of coatings.

Investigation of α-MnO2 Tunneled Structures as Model Cation Hosts for Energy Storage.

Future advances in energy storage systems rely on identification of appropriate target materials and deliberate synthesis of the target materials with control of their physiochemical properties in order to disentangle the contributions of distinct properties to the functional electrochemistry. This goal demands systematic inquiry using model materials that provide the opportunity for significant synthetic versatility and control. Ideally, a material family that enables direct manipulation of characteristics including composition, defects, and crystallite size while remaining within the defined structural framework would be necessary. Accomplishing this through direct synthetic methods is desirable to minimize the complicating effects of secondary processing. The structural motif most frequently used for insertion type electrodes is based on layered type structures where ion diffusion in two dimensions can be envisioned. However, lattice expansion and contraction associated with the ion movement and electron transfer as a result of repeated charge and discharge cycling can result in structural degradation and amorphization with accompanying loss of capacity. In contrast, tunnel type structures embody a more rigid framework where the inherent structural design can accommodate the presence of cations and often multiple cations. Of specific interest are manganese oxides as they can exhibit a tunneled structure, termed α-MnO2, and are an important class of nanomaterial in the fields of catalysis, adsorption-separation, and ion-exchange. The α-MnO2 structure has one-dimensional 2 × 2 tunnels formed by corner and edge sharing manganese octahedral [MnO6] units and can be readily substituted in the central tunnel by a variety of cations of varying size. Importantly, α-MnO2 materials possess a rich chemistry with significant synthetic versatility allowing deliberate synthetic control of structure, composition, crystallite size, and defect content. This Account considers the investigation of α-MnO2 tunnel type structures and their electrochemistry. Examination of the reported findings on this material family demonstrates that multiple physiochemical properties influence the electrochemistry. The retention of the parent structure during charge and discharge cycling, the material composition including the identity and content of the central cation, the surface condition including oxygen vacancies, and crystallite size have all been demonstrated to impact electrochemical function. The selection of the α-MnO2 family of materials as a model system and the ability to control the variables associated with the structural family affirm that full investigation of the mechanisms related to active materials in an electrochemical system demands concerted efforts in synthetic material property control and multimodal characterization, combined with theory and modeling. This then enables more complete understanding of the factors that must be controlled to achieve consistent and desirable outcomes.

Preparation of rare earth oxides from Synchysite oxidized ore by acid leaching

Mixed rare earth oxides have been prepared from synchysite ore from the Lugiin gol rare earth deposit (Mongolia) which contains about 6% of cerium light rare earth elements. Ore powders were leached for up to 60 min using 80-120 g/l sulfuric acids at an acid to powder ratio of 20, agitation was performed by magnetic stirring followed by precipitation and calcination at 700°C for 1h. The highest leaching of REEs equal to 85% of the total REE was observed in the acid solution of 80 g/l. Obtained mixed rare earth oxides represent a layered type structure.

Accurate identification of layer number for few-layer WS2 and WSe2 via spectroscopic study

Transition metal dichalcogenides (TMDs) with a typical layered structure are highly sensitive to their layer number in optical and electronic properties. Seeking a simple and effective method for layer number identification is very important to low-dimensional TMD samples. Herein, a rapid and accurate layer number identification of few-layer WS2 and WSe2 is proposed via locking their photoluminescence (PL) peak-positions. As the layer number of WS2/WSe2 increases, it is found that indirect transition emission is more thickness-sensitive than direct transition emission, and the PL peak-position differences between the indirect and direct transitions can be regarded as fingerprints to identify their layer number. Theoretical calculation confirms that the notable thickness-sensitivity of indirect transition derives from the variations of electron density of states of W atom d-orbitals and chalcogen atom p-orbitals. Besides, the PL peak-position differences between the indirect and direct transitions are almost independent of different insulating substrates. This work not only proposes a new method for layer number identification via PL studies, but also provides a valuable insight into the thickness-dependent optical and electronic properties of W-based TMDs.

Wear Resistance of a Large Thick Fe Based Amorphous Composite Coating Deposited by Laser Cladding

A large thick Fe based amorphous composite coating was deposited on the carbon steel substrate by laser cladding method. The phase composition and microstructure are characterized using X-ray diffraction and scanning electron microscope, respectively. The results demonstrate that the large thick laser cladding coating has a typical layered structure mainly consisting of amorphous and nanocrystal phases. The wear resistance and microhardness property are tested by the Vickers hardness tester and MLS-225 type wet sand rubber wheel abrasion tester. The results show that the large thick laser cladding coating has excellent wear resistance and hardness.

Effects of 316SS addition on the properties of the coatings based on Al2O3 applied by plasma spraying

Ceramic plasma-sprayed coatings are successfully used for prolonging the service life of industrial components where high wear and corrosion resistance are required. In this work, various types of coatings based on alumina were deposited by atmospheric plasma spraying on 304 L austenitic stainless steel substrate. These coatings were used in further tribological studies. For the atmospheric plasma spraying applications, spraying parameter choices such as carrier gases, plasma enthalpy, current intensity, spraying distance, and particles granulometry are the key issues. Two kinds of Al2O3 particle sizes 2–12 µm (Amperit) and 15–45 µm (Norton) were used to prepare pure and composite coatings. The spraying distance was varied from 90 mm to 120 mm. Microstructure characterization performed by scanning electron microscopy showed that the Amperit powders projected at a distance of 90 mm provided better cohesion and a more dense microstructure. However, the choice of the spraying distance of 120 mm was defined to manufacture composite structures, which allowed more stability in the plasma jet and enabled large metal particles to be mixed with ceramics. To develop hard and wear-resistant coatings, alumina and 316SS were mixed with different addition rates by volume (Al2O3–5 vol.%316SS and Al2O3–25 vol.%316SS) and fed through a single injection port. Composite coatings include porosity and unmolten particles in a lamellar microstructure. The addition of 316SS powder led to the formation of typical layered structure due to the effect of viscosity and different densities of the two particles. These coatings were investigated by different tests to evaluate microhardness, cohesion, and fracture values of such materials. Despite the significant decrease in the microhardness values, the 316SS particle addition demonstrates an improvement in the toughness and crack resistance.

Lanthanide oxalatophosphonates with two types of layered structures: syntheses, structures, luminescence and magnetic properties

Five novel lanthanide(iii) oxalatophosphonates with two types of 2D layered structures have been hydrothermally obtained and structurally characterized. The luminescence and magnetic properties of the title compounds have been studied.

Effect of lithium content on electrochemical property of Li 1+x (Mn 0.6 Ni 0.2 Co 0.2 ) 1-x O 2 (0≤ x ≤0.3) composite cathode materials for rechargeable lithium-ion batteries

Abstract In order to confirm the optimal Li content of Li-rich Mn-based cathode materials (a fixed mole ratio of Mn to Ni to Co is 0.6:0.2:0.2), Li1+x(Mn0.6Ni0.2Co0.2)1-xO2 (x=0, 0.1, 0.2, 0.3) composites were obtained, which had a typical layered structure with and C2/m space group observed from X-ray powder diffraction (XRD). Electron microscopy micrograph (SEM) reveals that the particle sizes in the range of 0.4-1.1 μm increase with an increase of x value. Li1.2(Mn0.6Ni0.2Co0.2)0.8O2 sample delivers a larger initial discharge capacity of 275.7 mA·h/g at the current density of 20 mA/g in the potential range of 2.0–4.8 V, while Li1.1(Mn0.6Ni0.2Co0.2)0.9O2 shows a better cycle performance with a capacity retention of 93.8% at 0.2C after 50 cycles, showing better reaction kinetics of lithium ion insertion and extraction.

Theoretical Investigation of the Mechanical and Thermodynamic Properties of the Layered Yttrium Diborocarbides

The mechanical, electronic, and thermodynamic properties of typical layered structure yttrium diborocarbides (YB2 C 2) were investigated by the density functional theory. The calculated lattice constants were slightly higher than the available experimental data. The elastic constants revealed that YB2 C 2 was mechanically stable. The bulk modulus (190.8 GPa), shear modulus (127.4 GPa), Young’s modulus (312.7 GPa), Poisson’s ratio (0.227), and Vickers hardness (18–19 GPa) were obtained, and the ductility, plasticity, and elastic anisotropy were further analyzed. The total and partial density of states were also calculated, indicating that the metallic character was mainly attributed to the contribution from Y-4d states and weakly hybridized with the 2p states from the B and C atoms. Finally, we obtained the Debye, melting, and the superconducting transition temperatures of YB2 C 2 as 824, 2239 and 2.38 K, respectively. Our study showed that YB2 C 2 offers potential in superconductivity or ultrahigh temperature applications.

CeO2 coating to improve the performance of Li[Li0.2Mn0.54Ni0.13Co0.13]O2

The Li[Li0.2Mn0.54Ni0.13Co0.13]O2 coated with CeO2 has been fabricated by an ionic interfusion method. Both the bare and the CeO2-coated samples have a typical layered structure with R-3m and C2/m space group. The results of XRD and TEM images display that the CeO2 coating layer on the precursor could enhance the growth of electrochemically active surface planes ((010), (110), and (100) planes) in the following ionic interfusion process. The results of galvanostatic cycling tests demonstrate that the CeO2-coated sample has a discharge capacity of 261.81 mAh g−1 with an increased initial Coulombic efficiency from 62.4 to 69.1% at 0.05 °C compared with that of bare sample and delivers an improved capacity retention from 71.7 to 83.4% after 100 cycles at 1 °C (1 °C = 250 mA g−1). The results of electrochemical performances confirm that the surface modification sample exhibits less capacity fading, lower voltage decay, and less polarization.

Preparation of layered K/Mg-Fe-Al catalysts and its catalytic performances in CO hydrogenation

A series of K promoted K/MgFeAl-HTLcs catalysts with different Mg/Fe/Al molar ratios were prepared by means of coprecipitation and impregnation method for direct synthesis of light olefins from CO hydrogenation. The samples were characterized by XRD, N2 adsorption-desorption, SEM, TG, H2-TPR and XPS measurements. The results show that MgFeAl-HTLcs catalyst precursors have typical layered structure. MgO, Fe2O3 and small amount of MgFeAlO4 are formed after calcination. MgCO3 and Fe3O4 could be observed after reaction, and a little Fe5C2 iron carbide with broad and weak peaks appears simultaneously. Thermal stability of K/MgFeAl-HTLcs is improved due to recovery of hydrotalcite-like structure after K promotion. With increase of Al content, specific surface area of the precursors decreases monotonically after structure reconstruction. Reduction of Fe2O3 to Fe3O4 is inhibited with addition of Al, compared with K/Mg-Fe sample. Fe enrichment before reaction and K enrichment after reaction are observed on secondary calcination samples. During CO hydrogenation, the prepared samples show high activity and C2=-C4= selectivity with low C5+ weight fraction. C5+ hydrocarbons decrease and olefin selectivity increases with increasing Fe/Al molar ratio. The C5+ decreases from 22.17% to 10.90%, and C2=-C4= weight content increases from 40.98% to 47.28% on K/1.5Mg-0.67Fe-0.33Al sample compared with that of K/1.5Mg-0.67Fe sample.