Layered Morphology Research Articles

Electrosynthesis of Ti3AlC2-Derived Porous Carbon in Molten Salt

Carbide-derived carbon (CDC) as an unconventional porous carbon material has been widely used for various applications. In this work, Ti3AlC2-derived porous carbon (Ti3AlC2-CDC) was electrochemically synthesized at 900°C and 3.0 V in molten CaCl2-NaCl. The obtained Ti3AlC2-CDC with abundant slit-like mesopores showed a high specific surface area of 425 m2/g. The variation of the morphology from the Ti3AlC2 precursor to Ti3AlC2-CDC was investigated, with the Ti3AlC2-CDC demonstrating a typical loose layered morphology and amorphous carbon structure. The intermediate products were also systematically analyzed to investigate the molten salt electrochemical etching process. It was found that Ti3AlC2 can be oxidized by residual O2− in the molten salt to form tiny Al2O3 particles on the anodic Ti3AlC2 surface during the etching process, then Ti3AlC2-CDC can be obtained by successively removing these Al2O3, Al, and Ti from the Ti3AlC2 precursor.

Simultaneous and selective determination of dopamine and tyrosine in the presence of uric acid with 2D-MoS2 nanosheets modified screen-printed carbon electrodes

Two-dimensional molybdenum disulphide nanosheets (2D-MoS2) were prepared by liquid-phase exfoliation and used to modify screen-printed carbon electrodes (SPCE), in order to develop an electrochemical sensor for the simultaneous determination of dopamine (DA) and tyrosine (Tyr) in presence of uric acid (UA). To demonstrate the layered morphology, the synthesized molybdenum disulphide nanostructures, have been characterized by Raman and SEM in both liquid dispersion and after deposition on SPCE. The performances of the 2D-MoS2-SPCE electrode have been tested and optimized in terms of sensitivity, reaching high sensitivity values of 1044 μA mM−1 cm−2 for DA and 321 μA mM−1 cm−2 for Tyr, selectivity against UA and high stability. The simultaneous detection of these biomolecules is the first study so far reported with the use of 2D-MoS2-based sensors. The promising characteristics of the developed electrodes suggest 2D-MoS2 as a versatile, low cost and easy to produce material for the next generation of electrochemical sensors of a variety of important biomolecules.

Cracks, porosity and microstructure of Ti modified polymer-derived SiOC revealed by absorption-, XRD- and XRF-contrast 2D and 3D imaging

Morphology, phase composition, cracks and porosity are investigated in monolithic Ti modified SiOC polymer-derived ceramics pyrolyzed at 1000 °C and 1400 °C using synchrotron X-ray full field absorption-contrast tomographic microscopy and scanning XRF- and XRD-contrast microscopy. Samples pyrolyzed at 1000 °C show a crack-free structure, but pyrolysis at 1400 °C results in formation of cracks and at higher Ti content also shows porosity. Tomography revealed the formation of a layered morphology that varies in terms of crystallographic structure and/or Ti stoichiometric concentration. The microstructural observations and electrical conductivity are discussed in terms of pyrolysis temperature and Ti content.

An In Situ Cross-Linked Nonaqueous Polymer Electrolyte for Zinc-Metal Polymer Batteries and Hybrid Supercapacitors.

This work reports the facile synthesis of nonaqueous zinc-ion conducting polymer electrolyte (ZIP) membranes using an ultraviolet (UV)-light-induced photopolymerization technique, with room temperature (RT) ionic conductivity values in the order of 10-3 S cm-1 . The ZIP membranes demonstrate excellent physicochemical and electrochemical properties, including an electrochemical stability window of >2.4V versus Zn|Zn2+ and dendrite-free plating/stripping processes in symmetric Zn||Zn cells. Besides, a UV-polymerization-assisted in situ process is developed to produce ZIP (abbreviated i-ZIP), which is adopted for the first time to fabricate a nonaqueous zinc-metal polymer battery (ZMPB; VOPO4 |i-ZIP|Zn) and zinc-metal hybrid polymer supercapacitor (ZMPS; activated carbon|i-ZIP|Zn) cells. The VOPO4 cathode employed in ZMPB possesses a layered morphology, exhibiting a high average operating voltage of ≈1.2V. As compared to the conventional polymer cell assembling approach using the ex situ process, the in situ process is simple and it enhances the overall electrochemical performance, which enables the widespread intrusion of ZMPBs and ZMPSs into the application domain. Indeed, considering the promising aspects of the proposed ZIP and its easy processability, this work opens up a new direction for the emergence of the zinc-based energy storage technologies.

Change in Orientation of Polyacrylic Acid and Chitosan Networks by Imprintment of Gold Nanoparticles

ABSTRACT Herein, gold nanoparticles (Au Nps) imprinted polyacrylic acid/chitosan (PAA/CS) nanocomposite hydrogels are designed by in situ polymerization technique. The change in crystallite size and d-spacing is established from X-ray diffraction study. It is interesting to notice that the layered morphology of PAA/CS/Au nanocomposite hydrogel is achieved from field emission scanning electron microscopy due to entanglement of polymeric chains by imprintment of Au Nps. The orientations of polymeric chains reveal the enhancement in pH-responsive swelling percentage and prolong water holding capacity of PAA/CS/Au nanocomposites. Biodegradation of the as-synthesized material is studied from which the antimicrobial activity of Au Nps is predicted.

An electrochemical sensor for ifosfamide, acetaminophen, domperidone, and sumatriptan based on self-assembled MXene/MWCNT/chitosan nanocomposite thin film.

New multi-walled carbon nanotubes supported on Ti3C2-MXene and chitosan (chit) composite film-based electrochemical sensor for ifosfamide (IFO), acetaminophen (ACOP), domperidone (DOM), and sumatriptan (SUM)have been developed. Ti3C2-MXene was synthesized by a fluoride method. Structural and chemical characterizations suggested the successful preparation of Ti3C2-MXene with clearly seen layered morphology, defined 0 0 2 diffraction peak at 7.5° and complete absence of 1 0 4 plane at 39°. The electrochemical performance of the sensor was investigated by cyclic voltammetry and adsorptive stripping differential pulse voltammetry. The Ti3C2/MWCNT/Chit modified glassy carbon electrode exhibits enhanced electrocatalytic activities toward the oxidation of target analytes. Excellent conductivity, large surface area, and high catalytic properties of the Ti3C2-MXene showed synergistic effects with MWCNTs and helped in achieving low detection limits of targets with high selectivity and reproducibility. The assay allows determination of IFO, ACOP, DOM, and SUM in the concentration ranges 0.0011-1.0, 0.0042-7.1, 0.0046-7.3, and 0.0033-61μM with low detection limits of 0.00031, 0.00028, 0.00034, and 0.00042μM, respectively. The sensor was successfully applied for voltammetric screening of target analytes in urine and blood serum samples with recoveries > 95.21%. Schematic illustration of the synthesis of self-assembled MXene/MWCNT/chitosan nanocomposite is givenand its application to the voltammetric determination of ifosfamide, acetaminophen, domperidone, and sumatriptandescribed. Graphical abstract.

Toward the application of electromagnetic wave absorption by two-dimension materials

Searching for the superior electromagnetic wave absorption materials (EMWAMs) has sparked giant interest owing to the increasingly serious electromagnetic wave (EMW) pollution and the boosting development of stealth fighters. Among numerous EMW absorbing materials, the two-dimension (2D) materials with unique layered morphology, low mass density, excellent processability and controllable electromagnetic parameters stand out for the lightweight, high-efficiency EMW absorbing materials. Here, we will summary the state-of-art progress on the 2D materials for EMWAMs, including graphene, MoS2, h-BN, g-C3N4, LDH (layered double hydroxides) and others. Meanwhile, the relevant preparation synthesis, absorption mechanisms and performance comparisons are presented. Specially, with the aim to obtain the superior absorption ability in term of broad effective absorption bandwidth (EAB), strong absorption intensity and thin thickness, the two key factors that significantly influence the ultimate performance, namely, good impedance matching and strong attenuation capacity, have been considered all the time. Finally, the bottlenecks and outlooks are further put forward on the basis of its current development.

Chemistry of Germanene: Surface Modification of Germanane Using Alkyl Halides.

Two-dimensional materials attract enormous attention across several scientific fields. The current demands in nano- and optoelectronics, semiconductors, or in catalysis have been accelerating the research process in the field of 2D materials. Among the 14th group 2D materials besides graphene and silicene, layered germanium represents a promising candidate for another class of materials, and its functionalization represents a way to tune either its electronic or optical properties. Here, the exfoliation and functionalization of germanane surface is achieved via abstraction of hydrogen from Ge-H bond and its subsequent alkylation utilizing n-alkyl halides or trifluoromethyl (CF3) group containing benzyl halides. Composition of materials is confirmed by several methods including FT-IR, Raman, X-ray photoelectron, and energy-dispersive X-ray spectroscopy as well as X-ray powder diffraction. Scanning and transmission electron spectroscopy is used to reveal the layered morphology of functionalized germananes.

Layer-by-Layer Motif Heteroarchitecturing of N,S-Codoped Reduced Graphene Oxide-Wrapped Ni/NiS Nanoparticles for the Electrochemical Oxidation of Water.

A new heterostructured material is synthesized with lamellar arrangements in nanoscale precision through an innovative synthetic approach. The self-assembled Ni-based cyano-bridged coordination polymer flakes (Ni-CP) and graphene oxide (GO) nanosheets with a layered morphology (Ni-CP/GO) are used as precursors for the synthesis of multicomponent hybrid materials. Annealing of Ni-CP/GO in nitrogen at 450 °C allows the formation of Ni3 C/rGO nanocomposites. Grinding Ni-CP/GO and thiourea and annealing under the same conditions produces N,S-codoped reduced GO-wrapped NiS2 flakes (NiS2 /NS-rGO). Interestingly, further heating up to 550 °C allows the phase transformation of NiS2 into NiS accompanied by the formation of a face-centered cubic (FCC-Ni) metal phase between NS-rGO layers (FCC-Ni-NiS/NS-rGO). Among all the materials, the resulting FCC-Ni-NiS/NS-rGO exhibits good electrocatalytic activity and stability toward the oxygen evolution reaction (OER) owing to the synergistic effect of multiphases, the well-designed alternating layered structures on the nanoscale with abundant active sites.

On Constituents of the Periodic Layered Microstructure Developed in the Solid-State Reaction Between Zinc and Co2Si

The composition and crystal structure of the constituents of the periodic layered microstructure developed during the solid-state reaction between Co2Si intermetallic and zinc at 390 °C were investigated using scanning electron microscopy, transmission electron microscopy, and electron-probe microanalysis. It was demonstrated that the periodic layered morphology generated in the reaction zone of the Co2Si/Zn diffusion couples consists of bands of in situ-formed precipitates of cubic CoSi intermetallic, embedded in a continuous matrix of Co-Zn-based hexagonal phase containing a small amount of silicon. It was suggested that the formation of the hexagonal intermetallic of the same crystal structure as the binary δ phase of the Co-Zn system can be attributed to the possible stabilizing effect of silicon: the δ-phase structure becomes stable in the ternary Co-Si-Zn system at 390 °C.

Room-temperature ferromagnetism in nanostructured submicron Cd/CdO particles

Cd/CdO submicron particle sets (Ps) with average particle sizes of about 1 μm were prepared by using the modified levitation-jet method through condensation of metallic cadmium vapor in helium gas flow with an appropriated in situ oxidation. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and vibrating sample magnetometry were used for the Ps characterization. Room-temperature ferromagnetism with maximum saturation magnetization up to 37 memu/g was discovered in the Ps with nanostructured polymorphic layered (terraced) morphology. This magnetization has achieved its maximum when CdO content was about 1.2 at.%. Ps with maximum magnetization possessed a certain unit cell volume of the Cd component. It is suggested that the observed ferromagnetic ordering may be related to intrinsic Cd defects in the Cd side of Cd/CdO interface areas.

Synthesis of Ge-based nanosheet bundles using calcium germanides as templates in IP6 aqueous solution

Ge-based nanosheet bundles were synthesized by de-intercalating Ca atoms from the lattice of CaGe2 and Ca-Germanide (synthesized and commercially available) using inositol hexakisphosphate (IP6) acid, with and without ultrasonication assistance. Ca-Germanides were synthesized via the thermal annealing and the mechanical alloying (MA) processes. Multiple binary phases of Ca–Ge system with low X-ray diffraction (XRD) intensities were obtained after the MA operation along with high XRD intensity elemental Ge phases, whereas with the thermal annealing process yielded phase transformation from elemental Ge to mixed binary mixture of Ca–Ge system. The obtained Ge-based nanosheet bundles were subjected phase and morphological characterization. It revealed that CaGe2 underwent phase transformation after IP6 treatment and a layered morphology was obtained. This paper describes a simplistic approach to synthesize Ge-based nanosheets using Ca-Germanide crystals as templates. A detailed morphological and phase evolution of the template Ca-Germanide and exfoliated Ge-based nanosheet bundles have been presented in this work.

Thermo-Mechanical Behavior and Hydrolytic Degradation of Linear Low Density Polyethylene/Poly(3-hydroxybutyrate) Blends

In this work, a commercial linear low density polyethylene (LLDPE) utilized for packaging applications was melt compounded with different amounts (from 10 wt% up to 50 wt%) of poly(3-hydroxybutyrate) (P(3HB)), with the aim to evaluate the possibility to partially replace LLDPE with a biodegradable matrix obtained from renewable resources. The processability, microstructural and thermo-mechanical behaviour of the resulting blends was investigated. Melt flow index (MFI) values of the LLDPE matrix were not much affected until a P(3HB) content of 20 wt%, while for higher P(3HB) concentrations an evident decrease of the viscosity was detected. Scanning electron microscope (SEM) observations on the blends highlighted that at limited P(3HB) concentrations the secondary phase was homogeneously dispersed in form of isolated domains, while at a P(3HB) content of 50 wt% a continuous layered morphology could be detected. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) did not evidence any chemical or physical interaction between the two polymer phases. Quasi-static tensile tests and dynamical mechanical analysis showed that the introduction of P(3HB) led to a pronounced stiffening effect, while the progressive drop of the yield and ultimate mechanical properties could be attributed to the weak interfacial adhesion and poor compatibility between the two matrices. The resistance to hydrolytic degradation of the LLDPE/P(3HB) blends was evaluated over a period of 100 days of immersion in water at 50 °C. It was observed that the weight variation and the decrease of the tensile properties due to the hydrolytic process on the biodegradable phase were evident only for a P3HB content of 50 wt%. In conclusion, this work showed that the partial replacement of LLDPE with a biobased P(3HB) could lead to the development of an innovative blend with good processability and mechanical properties, until a P(3HB) amount of 20 wt%.

Cracks, Porosity and Microstructure of Ti Modified Polymer-Derived Sioc Revealed by Absorption-, XRD- and XRF-Contrast 2D and 3D Imaging

Morphology, phase composition, cracks and porosity are investigated in monolithic Ti modified SiOC polymer-derived ceramics pyrolyzed at 1000°C and 1400°C using synchrotron X-ray full field absorption-contrast tomographic microscopy and scanning XRF- and XRD-contrast microscopy. Samples pyrolyzed at 1000°C show a crack-free structure, but pyrolysis at 1400°C results in formation of cracks and for the higher Ti doping also porosity. Tomography revealed formation of a layered morphology that varies in terms of crystallographic structure and/or Ti stoichiometric concentration. The microstructural observations and electrical conductivity are discussed in terms of pyrolysis temperature and Ti content.

Ternary thermoelectric composites of polypyrrole/PEDOT:PSS/carbon nanotube with unique layered structure prepared by one-dimensional polymer nanostructure as template

Recently, organic polymer-based thermoelectric (TE) hybrids or composites have received significant attention. Here, a unique layered morphology of polypyrrole/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotube (PPy/PEDOT:PSS/SWCNT) ternary TE composites are designed using 1D nanostruture of PPy as template. The nanowires of PPy/PEDOT:PSS binary composites are obtained via coating PEDOT:PSS on the surfaces of 1D PPy nanowires. Interestingly, the PPy/PEDOT:PSS/SWCNT ternary composites reveal unexpected layered morphology and dramatically-enhanced TE function with an optimal power factor of 45.3 ± 1.4 μW m−1 K−2 at room temperature. This study will enrich the structure design and preparation strategy of novel TE composites by judicious combing 1D polymer nanostructure with 3D layered networks of composites.

Effect of Atomized Delivery of Nutrients on the Growth Characteristics and Microstructure Morphology of Bacterial Cellulose.

This work demonstrates a general strategy for introducing remarkable changes in matrix organization and, consequently, functional properties of bacterial cellulose (BC). BC-producing cells were induced, using a well-defined atomized droplet nutrient delivery (ADND) system, to form pellicles with a regular layered morphology that persists throughout the mat depth. In contrast, the morphology of mats formed by conventional static medium nutrient delivery (SMND) is irregular with no distinguishable pattern. ADND also resulted in larger meso-scale average pore sizes but did not alter the fibril diameter (∼70 nm) and crystallinity index (92-95%). The specific modulus and specific tensile strength of ADND mats are higher than those of SMND mats. This is due to the regularity of dense layers that are present in ADND mats that are able to sustain tensile loads, when applied parallel to these layers. The density of BC films prepared by ADND is 1.63-fold lower than that of the SMND BC film. Consequently, the water contents (g/g) of ADND- and SMND-prepared BC mats are 263 ± 8.85 and 99.6 ± 2.04, respectively. A model that rationalizes differences in mat morphology resulting from these nutrient delivery methods based on nutrient and oxygen concentration gradients is proposed. This work raises questions as to the extent that ADND can be used to fine-tune the matrix morphology and how the resulting lower density mats will alter the diffusion of actives from the films to wound sites and increase the ability of cells to infiltrate the matrix during tissue engineering.

Enhanced stability of retained austenites in quenched 25SiMn2MoV steel by electro-pulsing current

In this contribution, an electro-pulsing current is applied to 25SiMn2MoV steel to obtain substantial retained austenite contents. Interestingly, after only 440 m s, retained austenite with a volume fraction higher than 10% is obtained via electro-pulsing. In addition, the Ms temperatures of the samples in the different electro-pulsing treated states are all much lower than room temperature, which implies the sufficient stability of this retained austenite. By choosing different initial states, the morphology and content of retained austenite can also be adjusted. It is found that when the initial state is eutectoid, the morphology of the retained austenite formed during electro-pulsing is globular, and the volume fraction is also higher. While the initial state is quenched, the retained austenite exhibits a layered morphology, and the content is relatively low. The mechanical properties indicate that compared with traditionally treated samples, the electro-pulse-treated samples possess a better strength and ductility. In addition, due to the TRIP effect induced by retained austenite, the ability of the resulting materials to prevent crack propagation and work-hardening is also improved. This work proposes a novel method to efficiently obtain adequate contents of retained austenite in low alloy steels and paves a new way for developing new low alloy steels with good properties.

Investigation of the stable and the metastable liquidus miscibility gaps in Fe–Sn and Fe–Cu binary systems

Two kinds of experimental methods were tried in the present work: (i) the powder metallurgy method combined with differential thermal analysis (DTA) to determine the metastable liquidus miscibility gap for a Fe–Cu binary system and (ii) the high-temperature melting method combined with isothermal treatment to determine the stable liquidus miscibility gap for a Fe–Sn binary system. The experimental method was adopted according to the characteristics of the liquidus miscibility gap of the specific system. Using the powder metallurgy method, a uniform microstructure morphology and chemical composition was obtained in the DTA specimen, and the phase-separation temperature of the supercooled metastable liquid was measured. The isothermal treatment was applied for the samples inside the stable liquidus miscibility gap; here, equilibrated compositions were reached, and a layered morphology was formed after rapid cooling. The liquid miscibility gaps of the Fe–Cu and Fe–Sn binary systems were measured, and the peak temperatures of the corresponding miscibility gaps were determined to be about 1417°C at x(Cu) = 0.465at% and 1350°C at x(Sn) = 0.487at%, respectively. On the basis of the experimental results, both the Fe–Cu and the Fe–Sn binary systems were thermodynamically assessed.

Fabrication and properties of TiB2-TiC reinforced NiAl coatings by reactive plasma spraying on AZ91D magnesium alloy

TiB2-TiC ceramic reinforced in situ NiAl matrix composite coatings were fabricated on AZ91D magnesium alloy by reactive plasma spraying (RPS) from the mixtures of Ni-Al and self-propagating high-temperature synthesis product in a 10 wt%Ni-3Ti-B4C system. Microstructure and properties including bonding strength, microhardness and electrochemical corrosion and wear resistances for the RPS coatings were investigated. The results showed that the coatings were mainly composed of the desired phases of TiB2, TiC and NiAl, and exhibited the compacted and layered morphology. The RPS coatings bound tightly to the magnesium alloy due to the prior preparation of a thin electroless plating Ni-P layer on the substrate, with bonding strength as high as 24.2–34.6 MPa. The produced Ni-P/TiB2-TiC reinforced in situ NiAl matrix coatings provided good protection against both wear and corrosion for substrate. Wear resistance of the coatings increased with an increase in the content of TiB2-TiC in the in situ NiAl matrix, while the corrosion resistance displayed a decreasing trend.

Microwave-Assisted Synthesis of an Alternant Poly(fluorene-oxadiazole). Synthesis, Properties, and White Light-Emitting Devices.

An alternant poly(dihexyl fluorene-co diphenyl oxadiazole) has been synthetized by microwave-assisted oxidative polymerization. The structure has been confirmed by 1H-NMR and FTIR spectroscopies. Gel permeation chromatography indicated high molecular weight and low polydispersity index. DFT calculations suggested a complete separation of HOMO and LUMO orbitals, which were located on fluorene and oxadiazole moiety, respectively. X-ray diffraction, polarized light microscopy, and atomic force microscopy indicated the polymer tendency to stack into a layered morphology with a more compact structure for the films prepared by spin coating. Furthermore, UV-vis and photoluminescence spectroscopies indicated the formation of H-aggregates which played a key role in photoluminescence quenching in solid state. Nevertheless, the good charge mobility gained due to the orbital overlapping in H-aggregates led to excellent electroluminescence, which enabled the development of white OLED devices with outstanding stability.