Formation Of Nanophases Research Articles

Unraveling the Formation of Ternary AgCuSe Crystalline Nanophases and Their Potential as Antibacterial Agents.

AgCuSe nanoparticles could contribute to the growth of strongly light-absorbing thin films and solids with fast ion mobility, among other potential properties. Nevertheless, few methods have been developed so far for the synthesis of AgCuSe nanoparticles, and those reported deliver nanostructures with relatively large sizes and broad size and shape distributions. In this work, a colloidal cation exchange method is established for the easy synthesis of AgCuSe NPs with ca. 8 nm diameters and narrow size dispersion. Notably, in this lower size range the conucleation and growth of two stoichiometric ternary compounds are generally observed, namely the well-known eucairite AgCuSe compound and the novel fischesserite-like Ag3CuSe2 phase, the latter being less thermodynamically stable as predicted computationally and assessed experimentally. An optimal range of Cu/Ag precursor molar ratio has been identified to ensure the growth of ternary nanoparticles and, more specifically, that of the metastable Ag3CuSe2 nanophase isolated for the first occasion. The attained size range for the material paves the way for utilizing AgCuSe nanoparticles in new ways within the field of biomedicine: the results obtained here confirm the antibacterial activity of the new Ag x Cu y Se z nanoparticles against Gram-positive bacteria, with significantly low values of the minimal inhibitory concentration.

Kinetically controlled metal-elastomer nanophases for environmentally resilient stretchable electronics

Nanophase mixtures, leveraging the complementary strengths of each component, are vital for composites to overcome limitations posed by single elemental materials. Among these, metal-elastomer nanophases are particularly important, holding various practical applications for stretchable electronics. However, the methodology and understanding of nanophase mixing metals and elastomers are limited due to difficulties in blending caused by thermodynamic incompatibility. Here, we present a controlled method using kinetics to mix metal atoms with elastomeric chains on the nanoscale. We find that the chain migration flux and metal deposition rate are key factors, allowing the formation of reticular nanophases when kinetically in-phase. Moreover, we observe spontaneous structural evolution, resulting in gyrified structures akin to the human brain. The hybridized gyrified reticular nanophases exhibit strain-invariant metallic electrical conductivity up to 156% areal strain, unparalleled durability in organic solvents and aqueous environments with pH 2–13, and high mechanical robustness, a prerequisite for environmentally resilient devices.

Correlating the Photovoltaic Performance and Stability of the All-Small-Molecule Organic Solar Cells to Their Intermixed Phases Determined by Concentration-Dependent Ultraviolet-Visible Absorption Spectroscopy.

In addition to the donor-acceptor nano phases, the intermixed phase within the organic blends is crucial for the photovoltaic performance and stability of the bulk-heterojunction organic solar cells (OSCs). Here, the intermixed phase of a representative M-PhS:BTP-eC9 all-small-molecule organic solar cell was investigated by a concentration-dependent ultraviolet-visible (UV-vis) absorption spectroscopy method, where a shift of the absorption maximum wavelength was measured for the acceptor component with the increase of the acceptor concentration. The blend ratios of the acceptor to the donor in the intermixed phase, corresponding to the critical concentration for the formation of the acceptor nanophase (CAP), were determined to be 0.35, 0.20, and 0.15 for the as-cast, thermal annealing (TA), and the combined TA and solvent vapor annealing films. These results indicated that M-PhS and BTP-eC9 are kinetically well intermixed during spin coating, whereas TA and the following solvent annealing promote the crystallization of BTP-eC9 molecules out of the intermixed phase. The photovoltaic performance of the M-PhS:BTP-eC9 cells with different blend ratios was investigated. The formation of the BTP-eC9 nano phase in the blend film leads to stable VOC and fast increased JSC, which can be understood by the reduction of bimolecular charge recombination and the formation of electron transporting pathways within the photoactive layer. Similarly, the critical concentration for the formation of the donor phase was estimated to be 0.15 by measuring the stabilized VOC and increased JSC values of the cells with different donor blending ratios. More importantly, after a fast "burn-in" thermal degradation, the M-PhS:BTP-eC9 cell showed excellent thermal stability aging at 85 °C for over 1128 h, which is in good accordance with the unchanged intermixed phases measured by the UV-vis spectra of the annealed films. The current work demonstrates the feasibility of the spectroscopy method to investigate the intermixed phases for organic bulk-heterojunction solar cells and proves that all-small-molecule solar cells can be intrinsically very stable.

Phase Engineering of Nanostructural Metallic Materials: Classification, Structures, and Applications.

Metallic materials are usually composed of single phase or multiple phases, which refers to homogeneous regions with distinct types of the atom arrangement. The recent studies on nanostructured metallic materials provide a variety of promising approaches to engineer the phases at the nanoscale. Tailoring phase size, phase distribution, and introducing new structures via phase transformation contribute to the precise modification in deformation behaviors and electronic structures of nanostructural metallic materials. Therefore, phase engineering of nanostructured metallic materials is expected to pave an innovative way to develop materials with advanced mechanical and functional properties. In this review, we present a comprehensive overview of the engineering of heterogeneous nanophases and the fundamental understanding of nanophase formation for nanostructured metallic materials, including supra-nano-dual-phase materials, nanoprecipitation- and nanotwin-strengthened materials. We first review the thermodynamics and kinetics principles for the formation of the supra-nano-dual-phase structure, followed by a discussion on the deformation mechanism for structural metallic materials as well as the optimization in the electronic structure for electrocatalysis. Then, we demonstrate the origin, classification, and mechanical and functional properties of the metallic materials with the structural characteristics of dense nanoprecipitations or nanotwins. Finally, we summarize some potential research challenges in this field and provide a short perspective on the scientific implications of phase engineering for the design of next-generation advanced metallic materials.

Towards controlling the morphology of cobalt loaded nanocomposites in polyol process with polyethylene glycol

The polyol process is one of the simple, efficient and productive methods for the synthesis of metal loaded polymer composites. Functional properties of metal-polymer nanocomposites are determined by chemical composition, size and morphology of their particles. Finding effective ways to control the nanoparticle's properties during the polyol process is a crucial task. The effect of molar ratio Mn+/OHPEG on the formation of cobalt loaded metal-polymer nanocomposites during a one-pot two-component polyol process by polyethylene glycol with Mr = 4000 g·mol–1 (PEG) was studied. The PEG-based polyol process and the formation of cobalt nanophase were studied at molar ratios νCo2+/νOH(PEG) = 1:1, 1:10, 1:100 and 1:500 using UV-Vis, diffuse reflectance IR and ATR FT-IR spectroscopy, nanoparticle tracking analysis (NTA), dynamic light scattering (DLS). It was found that PEG can act as a reducing agent and stabilizing matrix for the cobalt nanophase at a ratio higher than Mn+/OHPEG= 1:10. The composition and morphology of Co/PEG nanocomposites were determined by XRD and TEM methods. Two types of spheroid particles with average diameters of 88±55 nm / 8±4 nm and 12±3 nm / 3±1 nm, respectively, represent Co/PEG nanocomposites 1:500 and 1:100. Scaly structures with a diameter of 15±5 nm are formed at a molar ratio of νCo2+/νOH(PEG) = 1:10. An increase in the Co2+ content in the PEG-based polyol process leads to the immobilized cobalt nanophase Co3O4 (1:500), Co0/CoO (1:100), CoO (1:10) in PEG. Co/PEG nanocomposites are hemocompatible. The HC50value depends on the composition and morphology of the nanoparticles.

PPG-PEG-PPG/Epoxy systems cured at 100 °C: relationship between miscibility, microstructure, thermal and mechanical properties

This article evaluated the thermal, mechanical, morphological and fracture properties of systems with poly (ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) (PPG-PEG-PPG) triblock copolymer, with molecular weight 2000 g•mol−1 and 50% PEG in its composition, in DGEBA/DDM epoxy matrix. Systems with 10, 20 and 30 wt.% copolymer were prepared by in-situ polymerization and curing at 100 °C. In the differential scanning calorimetry (DSC) analysis, the characteristic temperatures of both the copolymer and the matrix in the binary systems were verified, indicating that phase separation had occurred. However, the glass transition temperature referring to the epoxy phase (Tg-E) occurred at lower temperatures than in neat matrix, which indicates partial miscibility in binary systems. The epoxy/copolymer systems presented a Young's modulus higher than the neat matrix, and without loss of mechanical resistance, reinforcing the miscibility of the PEG block in the blends and a microstructure with nanophase separation. When evaluating the fracture surface of the blends by scanning electron microscopy, the presence of deflection and crack immobilization mechanisms was observed, but no phase separation of the copolymer was observed. In this way, the systems studied showed partial miscibility with the formation of nanophases at the curing temperature of 100 °C, influencing Tg-E and improving the stiffness of the matrix.

Interfacial structure-property relationship in a carbon nanotube-reinforced aluminum alloy matrix composite fabricated by an advanced method

In our previous study, a bulk carbon nanotube (CNT)-reinforced aluminum alloy matrix composite with enhanced comprehensive mechanical properties was fabricated via an advanced powder processing, denoted as Mixed Ball-Milling (MBM) technique. Here, we attempted to explore the relationship between the composite microstructure and the elevated mechanical behavior with a special focus on CNT/Al interfacial features. To this end, high-resolution scanning transmission electron microscopy (HRSTEM) imaging combined with Raman spectroscopy were conducted to take a panoramic view of the subject. It was shown that in addition to the matrix heterogeneous grain structure and maintaining the structural integrity of CNTs, the interfacial bonding structure can be tailored using MBM methodology. Indeed, the formation of aluminum oxide nanophases in and around acid treatment-induced oxygen defects not only contributed to CNT structural conservation but also facilitated the load-transfer capability of the composite. A semi-quantitative analysis, performed on Raman spectroscopy data, authenticated that the aluminum carbide (Al4C3) formation was significantly restricted in the MBM processing, probably due to the presence of oxide species. The findings may also grant insight into the seldom-studied role of surficial oxygen defects in carbon-containing metal matrix composites.

Synthesis and DC Electrical Conductivity of Nanocomposites Based on Poly(1-vinyl-1,2,4-triazole) and Thermoelectric Tellurium Nanoparticles.

In this work, the structural characteristics and DC electrical conductivity of firstly synthesized organic-inorganic nanocomposites of thermoelectric Te0 nanoparticles (1.4, 2.8, 4.3 wt%) and poly(1-vinyl-1,2,4-triazole) (PVT) were analyzed. The composites were characterized by high-resolution transmission electron microscopy, X-ray diffractometry, UV-Vis spectroscopy, and dynamic light scattering analysis. The study results showed that the nanocomposite nanoparticles distributed in the polymer matrix had a shape close to spherical and an average size of 4-18 nm. The average size of the nanoparticles was determined using the Brus model relation. The optical band gap applied in the model was determined on the basis of UV-Vis data by the Tauc method and the 10% absorption method. The values obtained varied between 2.9 and 5.1 nm. These values are in good agreement with the values of the nanoparticle size, which are typical for their fractions presented in the nanocomposite. The characteristic sizes of the nanoparticles in the fractions obtained from the Pesika size distribution data were 4.6, 4.9, and 5.0 nm for the nanocomposites with percentages of 1.4, 2.8, and 4.3%, respectively. The DC electrical conductivity of the nanocomposites was measured by a two-probe method in the temperature range of 25-80 °C. It was found that the formation of an inorganic nanophase in the PVT polymer as well as an increase in the average size of nanoparticles led to an increase in the DC conductivity over the entire temperature range. The results revealed that the DC electrical conductivity of nanocomposites with a Tellurium content of 2.8, 4.3 wt% at 80 °C becomes higher than the conventional boundary of 10-10 S/cm separating dielectrics and semiconductors.

NaF assisted preparation and the improved corrosion resistance of high content ZnO doped plasma electrolytic oxidation coating on AZ31B alloy

In the present research, the NaF assisted plasma electrolytic oxidation (PEO) is designed to fabricate the high-content ZnO nanoparticles doped coating on AZ31B alloy. The microstructure, phase constituents and corrosion behavior of the PEO coatings are investigated systematically. The results reveal that the introduction of NaF promotes the formation of MgF2 nanophases in the passivation layer on Mg alloy, decreasing the breakdown voltage and discharge voltage. As a result, the continuous arcing caused by high discharge voltage is alleviated. With the increasing of NaF content, the Zn content in the PEO coating is enhanced and the pore size in the coating is decreased correspondingly. Due to the high-content ZnO doping, the PEO coating protected AZ31B alloy demonstrates the better corrosion resistance. Compared with the bare AZ31B alloy, the high-content ZnO doped PEO coated sample shows an increased corrosion potential from -1.465 V to -1.008 V, a decreased corrosion current density from 3.043×10-5 A·cm-2 to 3.960×10-8 A·cm-2 and an increased charge transfer resistance from 1.213×102 ohm·cm2 to 2.598×105 ohm·cm2. Besides, the high-content ZnO doped PEO coated sample also has the excellent corrosion resistance in salt solution, exhibiting no obvious corrosion after more than 2000 h neutral salt spraying and 28 days’ immersion testing. The improved corrosion resistance can be ascribed to the relative uniform distribution of ZnO in PEO coating which can transform to Zn(OH)2 and form a continuous protective layer along the corrosion interface.

Enhanced Titania Photocatalyst on Magnesium Oxide Support Doped with Molybdenum

Titania photocatalysts supported on mesoporous MgO carriers doped with Mo(VI) ions were prepared and characterized by XRD, BET nitrogen adsorption, FT-IR, and EPR methods. The photocatalytic activity was evaluated by bleaching an aqueous dye solution in the presence of a dispersed photocatalyst and by bleaching the dry surface of a solid tablet of photocatalyst using rhodamine B and nigrosin as model organic pollutants. It was established that TiO2 photocatalyst based on MgO carrier doped with 1 wt.% Mo(VI) ions, with the ratio of MgO:TiO2 = 1:0.5, possessed the highest activity under UV radiation. The increase in the content of molybdenum up to 10 wt.% leads to the formation of a MoO3 nanophase on the MgO surface, the formation of an isotype n–n heterojunction at the MoO3/TiO2 interface, and photocatalytic activity under the action of visible light.

Regularities of the Formation of SiO2 Nanophases and Nanofilms on a Si Surface during $${\text{O}}_{2}^{ + }$$-Ion Implantation

Regularities of the Formation of SiO2 Nanophases and Nanofilms on a Si Surface during $${\text{O}}_{2}^{ + }$$-Ion Implantation

Effect of the Synthetic Approach on the Formation and Magnetic Properties of Iron-Based Nanophase in Branched Polyester Polyol Matrix

This article shows the success of using the chemical reduction method, the polyol thermolytic process, the sonochemistry method, and the hybrid sonochemistry/polyol process method to design iron-based magnetically active composite nanomaterials in a hyperbranched polyester polyol matrix. Four samples were obtained and characterized by transmission and scanning electron microscopy, infrared spectroscopy and thermogravimetry. In all cases, the hyperbranched polymer is an excellent stabilizer of the iron and iron oxides nanophase. In addition, during the thermolytic process and hybrid method, the branched polyol exhibits the properties of a good reducing agent. The use of various approaches to the synthesis of iron nanoparticles in a branched polyester polyol matrix makes it possible to control the composition, geometry, dispersity, and size of the iron-based nanophase and to create new promising materials with colloidal stability, low hemolytic activity, and good magnetic properties. The NMR relaxation method proved the possibility of using the obtained composites as tomographic probes.

Formation of Li10Zn4O9, Li2MoO3, and ZnSeO3 Nanophases: Roles in Electrical Conductivity and Electrochemical Stability in Lithium Ion Conductors and their Crystalline Counterparts

Li2O doped glass-nanocomposites and their crystalline counterparts have been developed and analyzed on the light of DC conductivity and cyclic-voltammetic (CV) studies. Micro-structural study reveals the distribution of Li10Zn4O9, Li2Zn2(MoO4)3, ZnMoO4, Zn(MoO2)2, Li2Mo6O7 and Li2MoO3 nanophases in the glassy matrices. Crystalline counterparts exhibit an enhancement in crystallites’ sizes. As the crystalline counterpart is formed by controlled cooling, ZnSeO3 chain structure is expected to break by increasing dimensions of molybdate rod-like structures. In the present study, crystalline counterpart shows better electrochemical stability. Interconnected ZnSeO3 nanophases have to initiate structural stability as they play pivotal role in the formation of structure. Formation of Li10Zn4O9 and Li2MoO3 nanophases are supposed to be responsible for higher conductivity in the glassy system.

Copper-Content Dependent Structural and Electrical Properties of CZTS Films Formed by “Green” Colloidal Nanocrystals

Thin films of colloidal CZTS nanocrystals (NCs) synthesized using a “green” approach in water with a variation of the copper-to-tin ratio are investigated by Raman scattering, mid-infrared (molecular vibrations) and near-infrared (free carrier) absorption, X-ray photoemission spectroscopy (XPS), electrical conductivity, and conductive atomic force microscopy (cAFM). We determined the effect of the actual Cu content on the phonon spectra, electrical conductivity, and spectral parameters of the plasmon band. An increase in the electrical conductivity of the NC films upon annealing at 220 °C is explained by three factors: formation of a CuxS nanophase at the CZTS NC surface, partial removal of ligands, and improved structural perfection. The presence of the CuxS phase is concluded to be the determinant factor for the CZTS NC film conductivity. CuxS can be reliably detected based on the analysis of the modified Auger parameter of copper, derived from XPS data and corroborated by Raman spectroscopy data. Partial removal of the ligand is concluded from the agreement of the core-level XPS and vibrational IR spectra. The degree of lattice perfection can be conveniently assessed from the Raman data as well. Further important information derived from a combination of photoelectron and optical data is the work function, ionization potential, and electron affinity of the NC films.

Nanostructure formation and thermal stability of nanophase materials prepared by mechanical means

Abstract Mechanical attrition, mechanical alloying and other methods of extreme plastic deformation (high pressure torsion, equal channel angular pressing) have been developed as versatile alternatives to other physical and chemical processing routes in preparing nanophase materials. Here several examples are discussed including the deformation-induced nanophase formation in powder particles, in thin-foil sandwich structures and at the surface of alloys exposed to friction-induced wear, leading to the formation of nanocrystals and, in some cases, amorphous nanostructures. This opens exciting perspectives in preparing nanostructured materials with a number of different interface types in terms of structure (crystalline/crystalline, crystalline/amorphous) as well as atomic bond (metal/metal, metal/semiconductor, metal/ ceramic etc.). It is expected that the study of nanostructure formation by mechanical means in the future not only opens new processing routes for a variety of advanced nanophase materials but also improves the understanding of technologically relevant deformation processes on a nanoscopic level.

Влияние предварительной ионной бомбардировки на формирование нанопленок Co и CoSi-=SUB=-2-=/SUB=- на поверхности Si при твердофазном осаждении

In work to obtain ordered nanophases of Co and CoSi2, nuclei are preliminarily created on the Si surface by bombardment with Ar+ ions with E0 = 0.5 keV and D = 8 × 1013 cm-2. It was found that a narrow band gap (Еg = 0.3 eV) appears in the band structure at a Co layer thickness of less than 3 ML. The metallic properties of the Co film are manifested at a thickness of more than 4-5 ML. Heating the Co/Si(111) system at T = 900 K leads to the formation of nanophases and CoSi2 nanofilms. Еg of CoSi2 nanophases with Ɵ  3 ML is ~0.8 eV, and of CoSi2 films - 0.6 eV.

Influence of preliminary ion bombardment on the formation of Co and CoSi-=SUB=-2-=/SUB=- nanofilms on Si surface during solid-phase deposition

In this work, to obtain ordered nanophases of Co and CoSi2, nuclei are preliminarily created on the Si surface by bombardment with Ar+ ions with E0=0.5 keV and D=8· 1013 cm-2. It was found that a narrow band gap (Eg~ 0.3 eV) appears in the band structure at the Co layer thickness of less than 3 ML. The metallic properties of the Co film manifest themselves at a thickness of more than 4-5 ML. Heating the Co/Si(111) system at T=900 K leads to the formation of nanophases and CoSi2 nanofilms. The Eg value is 0.8 eV for the CoSi2 nanophases with theta~ 3 ML and 0.6 eV for the CoSi2 film. Keywords: nanophase, epitaxy, low-energy bombardment, surface, single crystal, island growth, ion dose, degree of coverage.

Effect of the alkyl chain length on the non-ideality and the microstructure of alcohol binary mixtures

In this study the microstructure of alcohol binary mixtures (toluene and cyclohexane) is investigated from molecular dynamics simulations. In case of cyclohexane mixtures, we show that the strong deviation from the ideality is the result of the formation of nanophases of alcohol molecules gathered in aggregates from hydrogen bonds leading to the spatial heterogeneity. Nanophases disappear as the alkyl chain size increases because the hydrophobic interactions counteracts the hydrogen bonds ones. The aggregates of short alcohol are found uncorrelated at the long range correlations which is related to an absence of the prepeak at low Q in the total structure factor. From toluene similar trends are observed with a lesser extend given the favorable π-OH interactions.

Nanocrystalline CoCrFeNiMn high-entropy alloy with tunable ferromagnetic properties

A nanocrystalline CoCrFeNiMn high-entropy alloy (nc-HEA) with nano-multiphase structure was prepared by inert gas condensation (IGC) using a laser evaporation source. Encouragingly, the laser-IGC nc-HEA exhibits unexpected ferromagnetic behavior and the Curie temperature (Tc) increased nearly 10 times compared to any CoCrFeNiMn HEAs prepared by various other methods. In addition, the saturation magnetization (Ms) and Tc of the laser-IGC nc-HEA can be controlled via heat treatment, which is resulting from the formation and structural evolution of magnetic nanophases during annealing. This work widens the design toolbox for high-performance nc-HEAs based upon laser-IGC technique.

Crystal Structure and Band Gap of Nanoscale Phases of Si Formed at Various Depths of the Near-Surface Region of SiO2

Si nanophases and nanolayers were obtained by bombardment with Ar+ ions followed by annealing at various depths of silicon oxide. As ion energy E0 varies from 10 to 25 keV, the average depth of Si nanophase formation varies from 15 to 25 nm. It is shown that, as the sizes of Si nanophases vary from ~10 to 25 nm, band gap Eg decreases from 1.9 to 1.5 eV. For Si nanolayers, Eg is ~1.1–1.2 eV.