One-dimensional Growth Research Articles

Thermodynamic and kinetic parameters of the chemical order–disorder transformation in L10 FeNi (tetrataenite)

The thermodynamic and kinetic parameters describing the chemical disordering process of L10 FeNi (tetrataenite) are quantified through analysis of calorimetric data obtained from material (Fe57Ni43) extracted from the NWA 6259 meteorite. The material presents an endotherm with peak temperatures of 800–860 K depending on heating rate and a transformation enthalpy of 4.0 ± 0.2 kJ/mol of atoms that corresponds to the L10 → A1 chemical order–disorder phase transformation. Using reported values of the enthalpy of mixing of the A1 phase and the enthalpy difference between the A1(γ) and the A2(α) phases of Fe, the enthalpy of formation of the L10 phase at the composition 43 at.% Ni constituted from Fe and Ni in their standard state is calculated as −4.4 ± 0.6 kJ/mol of atoms. These results indicate that the L10 FeNi phase is at the edge of enthalpic stability relative to a mixture of α-Fe and L12 FeNi3. The measured kinetic chemical-disordering transformation temperature is well above the reported order–disorder temperature of 593 K (320 °C) confirming that the disordering process is highly kinetically limited. The activation energy of chemical disordering of L10 FeNi (43 at% Ni) is 3.08 ± 0.07 eV/atom. Results obtained in this study are consistent with a model of one-dimensional growth of the disordered phase wherein the transformation rate is limited by the creation and migration of vacancies. Establishment of the enthalpy difference between the chemically-ordered and -disordered phases as well as determination of the activation energy for transformation provide guidance for laboratory synthesis of the L10 FeNi phase, which is of significant applied interest as a new advanced permanent magnet material.

Conformational States of Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide in Bulk and Confined Silica Nanopores Probed by Crystallization Kinetics Study

The nonaqueous sol–gel process has been used to synthesize the “ionogels” by confining ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; [EMIM][TFSI]) into silica gel matrices. The present study is concerned mainly with probing the conformational states of the IL ([EMIM][TFSI]) through crystallization kinetics study of the bulk and confined ionic liquid (IL) in nanopores of silica matrix. The crystallization kinetics has been studied by the isothermal method using differential scanning calorimetry (DSC). For bulk IL, DSC result shows three crystallization peaks due to different conformations of IL molecules. DSC results show that one of these crystallization peaks disappears upon confinement due to interaction of IL molecules with the silica pore wall surfaces. The crystallization kinetics of bulk and confined IL is quantified using the Avarami analysis. Confinement of IL results in a decrease of the Avarami exponent, indicating one-dimensional crystal growth. To support the res...

Synergistic effect of bimetallic Ag@Cu nanorods modified electrode for enhanced electrochemical sensing of thiocyanate ions

The thiocyanate (SCN−) level in human saliva, serum, and blood has been considered as a biomarker for analyzing the practice of cigarette smokers. Here, we have developed a highly sensitive and selective electrochemical sensor for SCN− in phosphate buffer using an Ag@Cu bimetallic nanorods (NRDs) modified glassy carbon electrode (GCE). The bimetallic Ag@Cu NRDs were grown on the GCE surface by a simple seed-mediated growth method. Initially, Ag seeds were deposited on the Nafion coated GCE. The deposited Agseeds in turn accelerate the growth of bimetallic Ag@Cu NRDs in the presence of cetyltrimethyl ammonium bromide, which acts as a soft template for the one-dimensional growth of NRDs. The synthesised NRDs were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy measurements. The Ag@Cu NRDs modified electrode shows an excellent response towards the electrochemical oxidation of SCN−. Cyclic voltammetry was used to study the linear correlation of SCN− oxidation between 1 and 10 mM, and, subsequently, 10 nM was achieved as the detection limit with a signal to noise ratio (S/N = 3) for Ag@Cu bimetallic NRDs modified GCE. This unique sensor shows a high selectivity towards trace amounts of SCN− in the presence of various interfering cations and anions. It satisfactorily recognized the generated SCN− in a real-time application such as in human saliva. Finally, the fingerprint of SCN− existence in the saliva samples of cigarette smokers and non-smokers were differentiated in a short span of time with ease.

Controlling the Microstructure of Reverse Micelles and Their Templating Effect on Shaping Nanostructures.

Reverse micelles as nanoreactors have been most successful in designing nanostructures of different sizes and shapes. Nevertheless, important questions regarding the explicit roles of intrinsic parameters in modifying soft colloid templates which eventually give rise to variety of nanostructures are still unresolved. In this paper, we have focused on this challenging aspect of microemulsion based synthesis of nanostructures, i.e., how the tunable parameters like water to surfactant molar ratio, solvent properties, and surfactant structure modify the microstructure (size/shape) of reverse micelles (surfactant/cosurfactant/oil/water). Further, we have elucidated the correlation between these nanoreactors with the size and morphology of the evolving nanostructures within the aqueous core (using in situ studies) as well as the finally obtained nanostructures. We have employed fluorescence correlation spectroscopy (FCS), small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and transmission electron microscopy (TEM) to obtain details on the microstructural transformation of reverse micelles and their templating behavior on designing nanostructures, at (near) single droplet level and in an ensemble. The structure (size/shape) of nanoreactors, i.e., reverse micelles, finally guides the size and shape of nanostructures. As the water content increases, it induces the micellar growth and subsequently the growth of nanostructures develops linearly up to a critical value beyond which the finite bending modulus of surfactant film triggers the structural rearrangement of microemulsion droplets (MEDs) and the linear plot shows deviation. Bulkiness of the solvent molecules modulates the ME droplets, and MEDs encapsulates nanostructures by influencing the curvature and rigidity of the surfactant film and results in smaller dimensions of the micellar core, which leads to nanostructures with large aspect ratio. The origin of this structural evolution may be explained in terms of solvent molecular structure, which affects the penetrability of solvent molecules into the surfactant tail region. Interestingly, MEDs with cationic surfactants feature the onset of one-dimensional micellar growth and the shape evolves into a nearly prolate spheriod. Consequently, the growth of the micellar core and dynamical exchange in an anisotropic manner leads to the formation of nanorods. The implication of such studies could be far reaching due to the geometry-dependent novel properties and potential applications of anisotropic nanostructures.

Growth of Aragonite CaCO3 Whiskers in a Microreactor with Calcium Dodecyl Benzenesulfonate as a Control Agent

This study presents a novel technique for the controllable preparation of aragonite CaCO3 whiskers using a microdispersion process. Calcium dodecyl benzenesulfonate [Ca(Ar–SO3)2] was first used as an additive for controlling the crystalline form. A homogeneous concentration distribution in the system was achieved due to the efficient micromixing. The effects of various operation parameters on the whiskers were determined, and the reaction conditions were optimized. The mechanism of the additive was discussed. The dynamic adsorption of Ca(Ar–SO3)2 on the surface of whiskers was experimentally demonstrated to be in charge of maintaining the one-dimensional growth and the high purity of the crystals. Aragonite CaCO3 with a crystalline purity of 98–99.5% was controllably synthesized at room temperature. The whiskers were approximately 27 μm in length and had an aspect ratio of about 58.

Effect of Fe2O3 on non-isothermal crystallization of CaO–MgO–Al2O3–SiO2 glass

The crystallization behavior and kinetics of CaO–MgO–Al2O3–SiO2 (CMAS) glass with the Fe2O3 content ranging from zero to 5% were investigated by differential scanning calorimetry (DSC). The structure and phase analyses were made by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The experiment results show that the endothermic peak temperature about 760 °C is associated with transition and the exothermic peak temperature about 1000 °C is associated with crystallization. The crystallization peak temperature decreases with increasing the Fe2O3 content. The crystallization mechanism is changed from two-dimensional crystallization to one-dimensional growth, and the intensity of diopside peaks becomes stronger gradually. There is a saltation for the crystallization temperature with the addition of 0.5% Fe2O3 due to the decomposition of Fe2O3. Si—O—Si, O—Si—O and T—O—T (T=Si, Fe, Al) linkages are observed in Fe2O3–CaO–MgO–Al2O3–SiO2 glass.

Mask-Like Symmetrical Microclusters through a Diffusion-Limited Assembly Approach.

A diffusion-limited assembly approach was explored to fabricate symmetrical [Cu(Succinate)]n microclusters with a different shape and size for the first time. The molecular structure of succinate and its coordination reaction capability towards copper(II) ions governed the one-dimensional growth of the nanofibers and the concomitant formation of the microclusters. In detail, a symmetrical concentration gradient was formed around the endpoints of the nanofibers caused by the diffusion-limited process at high reactant concentrations. The concentration gradient forced the nanofibers to grow divergently and further aggregate into open microcluster structure. The shape and size of the microclusters could be tuned by altering the concentration of the reactants. Particularly, mask-like double-hole symmetrical microclusters (MDHSMs) were obtained when the concentration of both reactants was as high as 140 mM. The resultant MDHSMs showed high selectivity in adsorption of dyes and proteins, and may find potential applications in water treatment, bioseparation, and immobilization of biomacromolecules.

Kinetic approach of multi-step thermal decomposition processes of iron(III) phosphate dihydrate FePO4∙2H2O

In this study, we have reinvestigated the thermal decomposition kinetics of iron(III) phosphate dihydrate FePO4∙2H2O in air atmosphere by TG/DTG and DTA techniques using non-isothermal experiments. The apparent activation energy Eα was determined by the differential and integral isoconversional methods and suggested that the decomposition reaction is complex and follows multi-step processes. A mathematical deconvolution technique using Fraser–Suzuki equation was applied to the DTG curves and allowed the separation of two distinct processes. The apparent activation energies determined by the isoconversional Friedman’s method were 93.05±3.80kJmol−1 and 73.41±3.14kJmol−1 for the first and second process respectively. Using Malek’s procedure for each process, the characteristics of y(α) and z(α) functions showed that the kinetic reaction follows the Johnson–Mehl–Avrami model (JMA(n)). One-dimensional nucleation and growth mechanism occurred firstly with f(α1)=1.272(1−α1)[−ln(1−α1)](1−1/1.272) and pre-exponential factor A1=9.11×1010min−1. After 27% of total conversion, a two-dimensional nucleation and growth mechanism becomes predominant with f(α2)=2.306(1−α2)[−ln(1−α2)](1−1/2.306) and A2=1.28×108min−1. It was concluded that the two decomposition processes of FePO4∙2H2O are closely interrelated and thus neglected the first process leads to incoherent results.

Crystallization mechanisms and properties of α-cordierite glass–ceramics from K2O–MgO–Al2O3–SiO2 glasses

Low temperature co-fired cordierite glass–ceramics were fabricated with K2O–MgO–Al2O3–SiO2 glasses. It was confirmed that α-cordierite crystals were precipitated from the glasses directly below 950°C and at the higher temperature additional leucite crystals were formed. The calculation of crystallization activation energy (Eα) for a onefold α-cordierite was 230.77–279.81kJ/mol; and the Eα of the concurrent precipitation of α-cordierite and leucite was 348.85–374.33kJ/mol, by Kissinger and Ozawa methods. Moreover, the Avrami constant (n) was calculated to be about 2 for onefold α-cordierite and to be 2.27–2.91 for the concomitant α-cordierite and leucite by the Augis–Bennett equation. Therefore, a bulk nucleation with one-dimensional crystal growth mechanism for α-cordierite was determined, which was verified by the results of Scanning Electron Microscope (SEM). The mechanisms for the concomitant α-cordierite and leucite changed from one-dimensional crystal growth to two-dimensional crystal growth with the variation of chemical composition. Furthermore, the α-cordierite glass–ceramics from the low-cost natural material exhibited good sintering capability below 950°C, low dielectric constant (6.0–8.0) and loss (below 0.01), matchable thermal expansion (4.40–5.63×10−6K−1) and applicable flexural strength, which were essential for the application as low temperature co-fired ceramic (LTCC) substrates.

Microstructural evolution and crystallization mechanism of zircon from frit glaze

Zircon (ZrSiO4) is widely used as a glaze opacifier in the ceramic industry. The crystallization mechanism of ZrSiO4 from a CaO-riched zirconium-based frit glaze was studied by XRD, SEM, and DSC in this work. Isothermal and non-isothermal heat treatments were used to study the phase development and microstructural evolution during the firing process. It was found that t-ZrO2 and Ca2ZrSi4O12 were first crystallized at a relative low temperature and then converted to ZrSiO4 with the increasing of temperature. ZrSiO4 originating from t-ZrO2 has an inward growth and an outward growth, while ZrSiO4 transformed from Ca2ZrSi4O12 only has an outward growth. SEM showed that ZrSiO4 appeared to be a rod shape in fired samples. The calculated activation energy for ZrSiO4 is 311.2kJ/mol, and the Avrami index (n) is 0.35–0.39. This indicates the one-dimensional diffusion-controlled growth of ZrSiO4, which explains the formation of rod-shape ZrSiO4 crystal.

Improved Photoresponse of Hybrid ZnO/P3HT Bilayered Photodetector Obtained Through Oriented Growth of ZnO Nanorod Arrays and the Use of Hole Injection Layer

We report highly oriented one-dimensional (1-D) growth of zinc oxide (ZnO) nanorod arrays (NRA) which were later utilized to fabricate hybrid photodiodes having the typical photodiode configuration of indium tin oxide (ITO)/ZnO/poly(3-hexylthiophene) (P3HT)/Ag. These functional hybrid bilayered photodiodes were found to have high rectification ratio under dark conditions and demonstrated enhanced responsivity under light illumination. Further, we studied the effect of an intermediate electron blocking layer of poly(ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) on the photodiode characteristics and demonstrated ITO/ZnO/P3HT/PEDOT:PSS/Ag photodiodes, reporting very high rectification ratio and responsivity in this bilayered configuration. The observed results are explained on the basis of the increased surface area of contact between the ZnO nanorods and the P3HT, and also the efficient hole injection into the P3HT layer from the top Ag electrode.

Interactive effect of agitation rate and oxidative etching on growth mechanisms of silver nanowires during polyol process

In this work, the interaction between agitation rate and oxidative etching on the growth mechanisms of silver nanowires during polyol process, the most conventional applied method for metallic nanoparticles synthesis, is evaluated. It was found that the main reason for the formation of multidiameter nanowires (MDNWs) is the local accumulation of silver ions in the system, i.e. even at a low concentration of silver ions (94 mM) under the mild agitation conditions, MDNWs were producible. Moreover, it was inferred that the more stress (stemming from the high agitation) applied on the initially formed decahedron Ag particles affects the ‘re-entrant grooves opening’ process which results in the formation and growth of irregular nanostructures. A polynomial equation for tuning aspect ratio of silver nanowires using different concentration of CuCl2 solution was also proposed. Finally, based on the obtained experimental data together with the thermodynamic considerations, a growth mechanism was proposed which can promisingly be employed for describing the one-dimensional growth of silver nanowires in both surfactant-modified and surfactant-free procedures.

Morphological transition of a conductive molecular organization with non-covalent from nanonetwork to nanofiber

The formation of nanofiber morphology at a mesoscopic scale, and molecular level stacking of a tetrathiafulvalene (TTF) derivative with a chiral group were investigated by the one-dimensional growth method in interfacial molecular films. Monomolecular films of a TTF derivative with a chiral borneol group display a two-dimensional phase transition at the air/water interface. At high surface pressures, nanonetwork domains are formed, where the TTF molecular planes are densely packed with an interlayer distance of 4.1Å. The formation of this network is attributed to the organized aggregation of the TTF derivatives, which is a result of strong intermolecular interactions. Subsequently, the growth of morphology is encouraged by the application of the one-dimensional growth method at low surface pressure conditions, varying compression speeds, and subphase temperatures. At low surface pressure and a subphase temperature of 15°C, the TTF derivatives aggregated as nanofibers with close packing of molecules. Upon raising the subphase temperature, the thickness of the nanofibers was found to increase and hence, spontaneous morphogenesis at the air/water interface was achieved.

Enhancement of corrosion protection effect in poly(2,3-dimethylaniline) via the formation of nanofiber materials by introducing p-phenylenediamine

Abstract Poly(2,3-dimethylaniline) (P(2,3-DMA)) nanofiber was prepared by introducing p-phenylenediamine as an initiator into the reaction mixture solution. The P(2,3-DMA) nanofiber was characterized by X-ray diffraction, Fourier transformation infrared spectroscopy and scanning electron microscopy. The results showed that the introduction of p-phenylenediamine favors one-dimensional growth of P(2,3-DMA). In order to compare the anticorrosion performance of P(2,3-DMA) nanofiber with that of poly(2,3-dimethylaniline) prepared without adding p-phenylenediamine (C-P(2,3-DMA)), epoxy resin coating containing P(2,3-DMA) nanofiber and C-P(2,3-DMA) was painted on mild steel, respectively. The anticorrosion property of the as-prepared nanofiber coating was evaluated by open circuit potential, tafel polarization curves and impedance spectroscopy in 3.5 wt% NaCl aqueous solution. Experimental results indicated that P(2,3-DMA) nanofiber had higher anticorrosion property compared with C-P(2,3-DMA). Hence, the morphology could be responsible for better anti-corrosion performances.

Application of extremely non-equilibrium plasmas in the processing of nano and biomedical materials

Some applications of extremely non-equilibrium oxygen plasma for tailoring the surface properties of organic as well as inorganic materials are presented. Plasma of low or moderate ionization fraction and very high dissociation fraction is created by high frequency electrodeless discharges created in chambers made from a material of low recombination coefficient. The O atom density often exceeds 1021 m−3 which allows for rapid functionalization of carbon-containing materials. Surface saturation with polar oxygen-rich groups is achieved in a fraction of a second and further exposure leads to etching. The etching is often non-uniform and results in nano-structuring of surface morphology. A combination of rich morphology and saturation with polar functional groups allows for a super-hydrophilic character of originally hydrophobic materials. Polymer composites are etched selectively so the polymer component is removed from the sample surface, leading to modified surface properties. Furthermore, such a treatment allows for distinguishing the distribution and orientation of fillers inside the polymer matrix. The exposure of inorganic materials to non-equilibrium oxygen plasma causes one-dimensional growth of metal oxide nanoparticles, thus representing a unique technique for the rapid catalyser-free growth of nanowires.

Ultrafine Au Nanowires Synthesized via One-Step Wet Chemical Method

UltrafineAu nanowires (AuNWs) were synthesized in high yields by a one-step wet chemical method using oleylamine as the solvent, surfactant, and reductant. The obtained AuNWs were of high purity and had a high aspect ratio, with diameters of ~2 nm and lengths of tens of micrometers.AuNWs of diameter ~9 nm were also obtained in the presence of oleic acid, at an oleic acid:oleylamine volume ratio of 1:1. The formation of AuNWs was studied by changing the reaction temperature and the volume of oleylamine. It is proposed that the growth mechanism of the Au nanostructures involves strong aurophilic interactions from oleylamine-AuCl complexes; the reducedAu atoms agglomerate and attach to preformed particles, and the oleylamine molecular layer acts as a soft template, leading to one-dimensional growth of Au atoms into AuNWs.

A general strategy to construct uniform carbon-coated spinel LiMn2O4 nanowires for ultrafast rechargeable lithium-ion batteries with a long cycle life.

Control over one-dimensional growth of spinel-type LiMn2O4 nanowires is challenging in the area of materials science due to their cubic crystal structure. The current strategy is to use a self-support template to fabricate LiMn2O4 nanowires, which is time-consuming and limits their large-scale commercial production. In this paper, we propose a general strategy to construct well-defined LiMn2O4 nanowires terminated with amorphous carbon at the edges by an ingenious method without using any template. Benefited from its unique carbon-coated nanowire structure, the electrode exhibits a capacitor-like rate performance and battery-like high capacity for long-time cycling. Even after 1500 cycles at an extremely high current density of 30 C, approximately 82% of its initial capacity can still be retained. Significantly, the strategy reported here will be beneficial and revelatory to manufacture other extensive one-dimensional robust carbon-decorated nanowires, paving new ways for future developments of ultrafast rechargeable lithium-ion batteries.

Aqueous chemical synthesis of tellurium nanowires using a polymeric template for thermoelectric materials

We report the simple synthesis of tellurium nanowires (TeNWs) by a one-pot scale-up hydrothermal process. A clean wet-chemical method, employing telluric acid (Te(OH)6) as a source of tellurium, ascorbic acid as a weak reducing agent, and a linear polymer as a template, has been developed for the synthesis of TeNWs with a diameter of 30–140 nm and a length of several micrometers at 105 °C. A possible explanation for the one-dimensional growth of TeNWs is the linear polymer template. The effects of the concentration of the polymeric template on the nanowire morphology were investigated. Evaluation of the thermoelectric properties indicated a high Seebeck coefficient and a power factor of about 568 μV K−1 and 8.44 μW mK−2, respectively, of the optimized TeNW films, and these values were about 80 times larger than those of the TeNW films formed without a polymeric template. We expect this simple process to be widely applicable for large-scale production of one-dimensional inorganic nanomaterials for energy harvesting and electronic devices.

Crystallization Kinetics of CaO-SiO<sub>2</sub>(CaO/SiO<sub>2</sub>=1)-TiO<sub>2</sub>-10 mass%B<sub>2</sub>O<sub>3</sub> Glassy Slag by Differential Thermal Analysis

Crystallization characteristics of the CaO-SiO2-TiO2-10%B2O3 glassy slag at w(CaO)/w(SiO2)=1 have been studied by Differential Thermal Analysis (DTA) and Matusita-Sakka method. Crystallization products have been distinguished by employing X-ray diffraction (XRD) and Scanning Electron Microscopy equipped with Energy Dispersive Spectroscopy (SEM-EDS). As the TiO2 content is within 10-18%, the crystal phase precipitated is mainly CaSiO3, and the effective activation energies for crystal growth increase with the increase of TiO2 content. Crystallization mechanism for CaSiO3 shifted from surface crystallization to one-dimensional growth with increase of TiO2. As the TiO2 content in slag further increases to 22% and 26%, CaTiSiO5 becomes the predominant crystal phase precipitated, and the effective activation energies for crystal growth decrease with the increase of TiO2 content. Crystallization mechanism for CaTiSiO5 is mainly surface crystallization. Therefore, with the increase of TiO2 content, the crystallization ability of the CaO-SiO2-TiO2-10%B2O3 glass system decreases initially and then increases.

First stage of CoSi2 formation during a solid-state reaction

The kinetics of CoSi2 formation via a solid-state reaction between CoSi and single crystal Si has been the object of many studies in the past. Because of the importance of nucleation, complex kinetics has been reported. In this work, we investigate CoSi2 formation kinetics with in-situ diffraction during isothermal annealing of CoSi films on Si (100). In-situ measurements allow capturing the initial stage of CoSi2 formation. An initial t3/2 time-dependent evolution is observed and attributed to 3D growth of individual nuclei. This first regime is followed after the coalescence of the nuclei by a classical parabolic t1/2 one-dimensional film growth. We evidence a marked influence of the initial Co thickness (50 nm vs 10 nm) on the growth kinetics. A significant slowdown of the CoSi2 formation kinetics is observed for the thinnest film, whereas the activation energy remains the same. These results shine a new light on the complex formation kinetics of CoSi2 during solid-state reaction between CoSi and single crystal silicon and bring new knowledge about what occurs in the ultra-thin film regime, which is important for nanotechnologies.