Nanocrystalline Composite Materials Research Articles

Molecular dynamics study of the interface fine structure and mechanical properties of Ni@SWCNT/Cu nanocrystalline composite materials

The use of carbon nanotubes (CNTs) as reinforcing phase in copper-based composites has been extensively studied. However, controlling the synthesis interface structure and explaining the nanoscale interface bonding mechanism through experimental methods still poses challenges. In this study, a model of single-walled carbon nanotube nanocrystalline copper composite was established based on molecular dynamics (MD) simulations to investigate the effects of grain boundaries and dislocations on the composite material. It was found that the addition of nickel atoms improved the interface bonding between carbon nanotubes and the copper matrix, reducing vacancies at the interface. Ni@SWCNT/Cu exhibited better mechanical properties. Structural changes and defect evolution during deformation were studied. The ultimate tensile strength of SWCNT/Cu and Ni@SWCNT/Cu composites increased by 62.29 % and 68.78 % respectively compared to nanocrystalline copper, while the Young's modulus increased by 25.91 % and 32.48 % respectively; moreover, the Young's modulus of these two composites increased by 45.24 % and 49.42 % respectively. Ni@SWCNT/Cu had the lowest wear rate and friction coefficient, with a minimum wear rate of 0.0055 and a minimum friction coefficient of 0.67, demonstrating better wear resistance. The effects of different friction speeds and depths of indentation on the friction performance of the composite materials were also investigated.

Retracted: Application of Polypyrrole Cellulose Nanocrystalline Composite Conductive Material in Garment Design

Retracted: Application of Polypyrrole Cellulose Nanocrystalline Composite Conductive Material in Garment Design

Nanocomposite Based on HA/PVTMS/Cl2FeH8O4 as a Gas and Temperature Sensor.

In this paper, a novel nanocrystalline composite material of hydroxyapatite (HA)/polyvinyltrimethoxysilane (PVTMS)/iron(II)chloride tetrahydrate (Cl2FeH8-O4) with hexagonal structure is proposed for the fabrication of a gas/temperature sensor. Taking into account the sensitivity of HA to high temperatures, to prevent the collapse and breakdown of bonds and the leakage of volatiles without damaging the composite structure, a freeze-drying machine is designed and fabricated. X-ray diffraction, FTIR, SEM, EDAX, TEM, absorption and photoluminescence analyses of composite are studied. XRD is used to confirm the material structure and the crystallite size of the composite is calculated by the Monshi-Scherrer method, and a value of 81.60 ± 0.06 nm is obtained. The influence of the oxygen environment on the absorption and photoluminescence measurements of the composite and the influence of vaporized ethanol, N2 and CO on the SiO2/composite/Ag sensor device are investigated. The sensor with a 30 nm-thick layer of composite shows the highest response to vaporized ethanol, N2 and ambient CO. Overall, the composite and sensor exhibit a good selectivity to oxygen, vaporized ethanol, N2 and CO environments.

A review on wear characterization of electrodeposited nickel matrix composites

Corrosion resistance across a wide temperature range, increased physical, mechanical, and tribological capabilities, variable surface hydrophobicity, and an attractive appearance are all advantages of electrodeposited metal matrix composite coatings (MMCs). As a result, several studies have been conducted to evaluate the various physical, mechanical, biochemical, electrochemistry, and thermodynamics characteristics of nanocrystalline composite material, generated on a variety of substrates with numerous electrodeposition settings. In this review paper, the current literatures on wear rate of electrode-posited Ni-based coatings made of composite materials are being reviewed. More specifically, the research papers on weight management, wear resistance, coefficient of friction, surface roughness, hardness and associated deterioration methods has been identified and reviewed. The observations showed that nano-composite films offer substantially superior wear resistance than magnesium alloys and pure nickel coatings due to the diffraction stiffening and grain refining effects. Also, abrasion is the main wear process for nano-composite coatings, whereas adhesion wear is the primary wear arrangement for magnesium alloys and major wear mechanism for pure nickel coatings is exfoliation wear.

Application of Polypyrrole Cellulose Nanocrystalline Composite Conductive Material in Garment Design

The Chinese nation has a long cultural history and has deep attainments in food, clothing, art, and other cultural fields. With the development of science, technology, economy, and culture, new materials continue to appear, providing new ideas for clothing design. Polypyrrole is a common conductive polymer. The pure pyrrole monomer presents a colorless oily liquid at room temperature, slightly soluble in water and nontoxic. Nanocrystals, also called nanoscale crystals, use high-energy polymer spheres to pack calcium, magnesium ions, and bicarbonate in water to produce a water-insoluble crystal structure. Conductive composite materials mainly refer to composite conductive polymer materials, which are composed of polymers and various conductive substances through a certain composite method. This article aims to study the application of polypyrrole cellulose nanocrystalline composite conductive material in clothing design. Starting from the structural characteristics of the polypyrrole cellulose nanocrystalline composite conductive material, this article uses case analysis to study deeply the suitable polypyrrole cellulose nanocrystalline composite conductive material. This article can effectively use the innovative application method of its appearance style, so as to realize its application in clothing design. Starting from the functional properties of the polypyrrole cellulose nanocrystalline composite conductive material, the specific application of the polypyrrole cellulose nanocrystalline composite conductive material in different clothing designs is analyzed. Combining the postmodernist clothing style characteristics, aesthetic habits, and the characteristics of polypyrrole cellulose nanocrystalline composite conductive materials, this paper studies the innovative style design of polypyrrole cellulose nanocrystalline composite conductive materials. The experimental results in this paper show that when the reaction time is 2 min, the reaction rate at this time is zero, indicating that this time is in the initial stage of the reaction. After 4 minutes, as the reaction time increases, the reaction rate shows an increasing trend; when the reaction time is longer than 10 minutes, the reaction rate increases slowly and has a downward trend, which indicates the end of the reaction. The highest average reaction rate is about 7.5 mg/min.

High performance of amorphous nanocrystalline composite structure materials

During last two decades, grain refinement and amorphization are the main way of high-performance material research and development, which already show enormously successful in material science, especially super steel engineering. However, the further improvement of material performance by the traditional methods seem to reach its limitation. A novel method is urgent for scientists to break through the limitation. At present, it is difficult to prepare different nanoscale microstructures in the same material system for performance comparison. In this paper, coatings with different microstructure (nanocrystalline, amorphous-nanocrystalline composite and amorphous) have been successfully prepared by electrodeposition method in the same material system (Ni–P alloy). The results show that the amorphous-nanocrystalline Ni–P alloy had higher hardness and better wear resistance. The wear resistance of the amorphous-nanocrystalline Ni–P alloy was 7.4 times of that of the amorphous Ni–P alloy and 3.1 times of that of the nanocrystalline Ni–P alloy. Therefore, the composite of different microphase structures at nanoscale is a new method to obtain high-performance materials.

Extraction–Pyrolytic Method for TiO2 Polymorphs Production

The unique properties and numerous applications of nanocrystalline titanium dioxide (TiO2) are stimulating research on improving the existing and developing new titanium dioxide synthesis methods. In this work, we demonstrate for the first time the possibilities of the extraction–pyrolytic method (EPM) for the production of nanocrystalline TiO2 powders. A titanium-containing precursor (extract) was prepared by liquid–liquid extraction using valeric acid C4H9COOH without diluent as an extractant. Simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA–DSC), as well as the Fourier-transform infrared (FTIR) spectroscopy were used to determine the temperature conditions to fabricate TiO2 powders free of organic impurities. The produced materials were also characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The results showed the possibility of the fabrication of storage-stable liquid titanium (IV)-containing precursor, which provided nanocrystalline TiO2 powders. It was established that the EPM permits the production of both monophase (anatase polymorph or rutile polymorph) and biphase (mixed anatase–rutile polymorphs), impurity-free nanocrystalline TiO2 powders. For comparison, TiO2 powders were also produced by the precipitation method. The results presented in this study could serve as a solid basis for further developing the EPM for the cheap and simple production of nanocrystalline TiO2-based materials in the form of doped nanocrystalline powders, thin films, and composite materials.

Rapid Sintering and Synthesis of Nanocrystalline Ta-ZrO<sub>2</sub> Composite

ZrO<sub>2</sub> is a promising candidate for knee and hip joint replacements due to its excellent combination of low density, corrosion resistance and biocompatibility. Nevertheless, a low fracture toughness of pure ZrO<sub>2</sub> at room temperature limits its wider application in the industry. One of the most obvious ways to solve the problem is to add a reinforcing phase, to produce a nanocrystalline composite material. Nanomaterials have been widely studied in recent years because they can improve hardness and fracture toughness. To produce nanocrystalline materials, the pulsed current activated sintering method has the advantage of simultaneously applying mechanical pressure and pulsed current during sintering. As a result, nanocrystalline materials can be produced within a very short time. Ta and ZrO<sub>2</sub> nanopowders were mechanically synthesized from Ta<sub>2</sub>O<sub>5</sub> and 2.5Zr powders according to the reaction (Ta<sub>2</sub>O<sub>5</sub> + 5/2Zr → 2Ta + 5/2ZrO<sub>2</sub>). The synthesized powders were then sintered using pulsed current activated heating under 80 MPa uniaxial pressure within two minutes. Hardness and fracture toughness were measured using a Vickers hardness tester. The average hardness and fracture toughness of the nanocrystalline 2Ta-5/2ZrO<sub>2</sub> composite sintered at 1350 <sup>o</sup>C were 1008 kg/mm<sup>2</sup> and 10 MPa·m<sup>1/2</sup>, respectively. Both the hardness and fracture toughness of the composite were higher than monolithic ZrO<sub>2</sub>. The microstructure and phase of the composite was also investigated by FE-SEM and XRD.

Synthesis and Study of Composite Materials in the ZrO2(Y2O3)–MgAl2O4 System

Powders–precursors of a tetragonal solid solution based on partially stabilized zirconium dioxide (t-ZrO2) and aluminum-magnesium spinel (MgAl2O4) are synthesized using the method of the cocrystallization of solutions of nitrate salts from which nanocrystalline (<100 nm) composite materials are fabricated at 1400°C in the ZrO2(Y2O3)–MgAl2O4 system with an open porosity of 3%. The structure, physical–mechanical properties, and thermal stability of the nanocomposites are investigated. It is established that the introduction of MgAl2O4 into the matrix of the solid t-ZrO2 solution increases the thermal resistance of the ceramics under the thermal cycling conditions (20–1000°С). The effect of thermal cycling on the phase composition, hardness, and bending strength of the ceramics in the ZrO2(Y2O3)–MgAl2O4 system is investigated.

Structure and Properties of Nanosized Composites Based on Fe3O4 and Humic Acids

Nanocrystalline composite materials based on magnetite Fe3O4 and humic acids (HA) were synthesized and characterized. Investigation of these materials by EPR, fluorescence spectroscopy, electron microscopy, and XRD analysis showed that the surface of magnetite nanoparticles was densely covered with HA molecules, the size of the Fe3O4 nucleus decreasing when the HA : Fe3O4 ratio increased. An EPR study showed that the structure of the ferromagnetic magnetite nanoparticles changed at increased HA contents. The IR and fluorescence spectroscopy data suggest active participation of carboxyl and hydroxyl groups of HA in the adsorption of HAs on the Fe3O4 surface. The main types of interaction of Fe3O4 with HA were considered, and a scheme of possible chemical reactions was proposed.

Growth behaviour of silica/carbonate nanocrystalline composites of calcite and aragonite.

The precipitation of barium and strontium carbonate in alkaline silica gels or silica solutions produces nanocrystalline self-assembled composite materials displaying biomimetic shapes and textures. We have crystallized concomitantly in time and space two anhydrous polymorphs of calcium carbonate, under similar conditions at different temperatures. The orthorhombic phase aragonite produces nanocrystalline aggregates exhibiting non-crystallographic morphologies and complex textures characteristic of silica biomorphs. Conversely, the simultaneously forming trigonal phase, calcite, yields rhombohedral crystals that experience fibrous growth and that maintain memory of the point symmetry group of the crystalline structure. Experiments performed at different temperatures (room temperature, 45, 60 and 80 °C) revealed that the higher the temperature the higher the aragonite/calcite precipitation ratio, but the crystallization of calcite was never fully inhibited. We have studied the growth mechanism, the growth texture and the morphogenesis for both cases. We have found that the dramatic difference between the crystallization behaviours of the two mineral phases is due to the difference in the growth mechanism at the nanoscale.

Effect of nanocrystalline composite fullerene-doped MoO3-TiO2 material on photoassisted degradation of Alizarin red S dye

ABSTRACTA fullerene-doped MoO3-TiO2 nanocrystalline composite material was prepared by sol-gel method. The catalyst prepared was characterized by means of some modern sophisticated techniques such as XRD, SEM-EDS, FT-IR, TEM, BET, and TGA analysis. It shows successful synthesis of porous, nanocrystalline material with higher surface area. The photodegradation of Alizarin red S was used as a model reaction to study the activity of the synthesized catalyst. The high photodegradation activity obtained using the fullerene-doped MoO3-TiO2 mainly due to the more adsorption of the dye (Alizarin red S) on the large surface area of catalytic material.

Improved electrochemical properties of solvothermally synthesized Li2FeSiO4/C nanocomposites: A comparison between solvothermal and sol-gel methods

We have synthesized porous Li2FeSiO4/C nanocomposites by two different routes such as sol-gel (Li2FeSiO4/C-SG) and solvothermal (Li2FeSiO4/C-ST) using block copolymer pluronic (P123) as both in-situ carbon source and structure directing agent. Various techniques, like, powder x-ray diffraction, BET nitrogen adsorption–desorption measurement, scanning electron microscopy, transmission electron microscopy, galvanostatic cycling, cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the nanocomposites. A comparative study of their structural, electronic and electrochemical properties show that the solvothermally synthesized nanocomposite sample Li2FeSiO4/C-ST-600 (annealed at 600°C) shows better electrochemical performance compared to the corresponding sol-gel synthesized (Li2FeSiO4/C-SG-600) sample. At a rate of C/30, Li2FeSiO4/C-ST-600 nanocomposite delivered a discharge capacity of ~276mAhg−1 (84% of theoretical capacity) and also exhibited excellent stability at high rates. It retained 95% of its initial discharge capacity (140mAhg−1) after 100cycles at 1C, comparable to the recently published data on Mg-doped Li2FeSiO4/C composites. We attribute this enhanced electrochemical behavior of Li2FeSiO4/C-ST-600 due to the formation of porous nanocrystalline (~15nm) composite material with a large BET surface area (~100m2g−1) resulting in a lower charge transfer resistance (~30Ω) and a higher Li-ion diffusion coefficient (~5×10−14cm2s−1). The present study demonstrates that solvothermal synthesis of Li2FeSiO4/C nanocomposites using P123 as a carbon source is an effective method for improving its electrochemical properties.

Synthesis and Characterizations of Carbon Doped MoO3-TiO2 Nanocrystalline Composite Materials

The series of carbon doped MoO3-TiO2 nanocrystalline composite material was prepared by using simple sol-gel method. The carbon material used was obtained from natural sources as Acacia Arabica plant. The synthesized materials were characterized by various sophisticated techniques. The crystalline nature of composite material was increased with addition of carbon. The 3 wt% carbon doped MoO3-TiO2 material has particle size in around 9–12 nm. This material absorbed light in more visible region at 457 nm and has band gap 2.71 eV. Thus material may be use as catalyst for photodegradation of pollutant.

Photodegradation of Molasses by a MoO3-TiO2 Nanocrystalline Composite Material

A MoO 3 -TiO 2 nanocrystalline composite material was prepared by a simple sol-gel method. The synthesized material was characterized by X-ray diffraction, scanning electron microscopy with an electron dispersion spectroscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. Melanoidin is a dark brown pigment found in wastewater from the sugar industry and it pollutes water. This polluted water is generally referred to as molasses and it undergoes fermentation and is solely responsible for water, soil, and air pollution. The synthesized catalytic material was found to be effective in degrading molasses under UV-visible radiation. Analysis of treated and untreated molasses was carried out by measuring its color, chemical oxygen demand, biological oxygen demand, pH, and total dissolved solid. Results from these analyses indicate the effective photodegradation of the molasses. This methodology has several advantages such as high photocatalytic activity, non-toxicity, cleanliness, and reusability of the catalytic material. A MoO 3 -TiO 2 nanocrystalline composite material was prepared by the sol-gel method and characterized using various sofisticated techniques. The synthesised catalytic material effectively degrades molasses from the sugar industry under UV-visible radiation.

Formation of nanodispersoids in Fe–Cr–Al/30%TiB 2 composite system during mechanical alloying

Mechanical alloying is an effective processing technology which allows the synthesis of nanocrystalline composite materials. In this study, a nanocrystalline Fe–Cr–Al/30%TiB 2 composite material is synthesized without process control agents by the mechanical alloying process using a planetary high-energy ball mill. Crystalline (or grain) size reduction and dispersion behavior of brittle TiB 2 powder during ball milling are investigated together with mechanical alloying behavior of ductile metallic matrix powder for synthesis of the composite. Mechanical alloying between metallic elements is almost completed after approximately 8 h milling. The crystalline size of TiB 2 decreases to 36 nm after 48 h of ball milling, while the average particle size of the composite powder increases in comparison with the initial size. Transmission electron microscopy reveals formation of TiB 2 nanodispersoids of size around 50 nm after 48 h milling.

Enhanced Seebeck coefficient through energy-barrier scattering in PbTe nanocomposites

Resistivity, Seebeck coefficient, and Hall measurements were performed on densified nanocrystalline composite materials of undoped and Ag-doped PbTe nanocrystals to investigate the physical mechanisms responsible for Seebeck coefficient enhancement in nanocrystalline systems. The unique temperature dependence of the resistivity and mobility for these PbTe nanocomposites suggests that grain-boundary potential barrier scattering is the dominant scattering mechanism. We propose that carrier trapping in the grain boundaries forms energy barriers that impede the conduction of carriers between grains, essentially filtering charge carriers with energy less than the barrier height. These nanocomposites therefore demonstrate an enhanced Seebeck coefficient as compared to single crystal or polycrystalline PbTe at similar carrier concentrations.

Mechanochemical synthesis and electrochemical properties of nanostructured electrode materials for Li ion batteries

We focus on the synthesis by ball milling and on the electrochemical characterization of nanocrystalline bimetallic and composite materials to be employed as anodes in Li ion batteries. Ni3Sn4 and Ni3Sn2 based compounds were obtained by ball milling of three different Ni–Sn mixtures. The properties of the resulting anodes for Li ion batteries were evaluated as a function of composition. Moreover, a biphasic system is presented, with CoSn2 and CoSn type structures, arising from the synthesis of the Sn31Co28C41 composition. When cycled in a Li cell, this material showed a high reversible specific capacity, about 450 mA h g−1, and a very good electrochemical and structural stability, making it of interest for application purposes.

Collaborative Sintering of the Amorphous Alloy and Ceramic Powders for Nanocrystalline Composite Materials

This article reports some process controls to optimize the collaborative sintering of the amorphous powder mixture as blended by mechanical alloying for the synthesis of nanocrystalline composite materials. The pulse electric current pressure sintering combined with high pressure and high heating rate techniques can be used to obtain the fully dense nanocrystalline Ti 50 Al 50 alloy having a spatial dispersion of finely divided (Zr02-3mol%Y203)55(Al 2 O 3 ) 45 particle with the crystallite size of 21 nm at the relatively low temperature of 1423 K. The sub-μm sized ceramic particle dispersed Ti 50 Al 50 composite shows the yielding event in compression; its proof stress increases up to approximately 3 GPa with an increase up to 0.2 in particle volume fraction of nanocrystalline (Zr02-3mol%Y203)55(Al 2 O 3 )4s. The instrumented spark pressure sintering with temperature slope control using specially designed graphite dies makes it possible to provide an overall powder densification and superplastic compressive forming along the gradient composition consisting of amorphous and/or nanocrystalline Ti 52 Al 48 and (Zr02-3mol%Y 2 O 3 ) 80 (Al 2 O 3 ) 20 phases.

Nanocrystalline Metal Oxides Dispersed Multiwalled Carbon Nanotubes as Supercapacitor Electrodes

RuO2/MWNT, TiO2/MWNT, and SnO2/MWNT nanocrystalline composites for supercapacitor electrodes have been synthesized by chemical reduction method using functionalized MWNT and respective salts. MWNT have been synthesized by thermal catalytic chemical vapor deposition (CCVD) over hydrogen decrepitated Mischmetal (Mm)-based AB3 alloy hydride catalysts. Structural and morphological characterizations of metal oxide dispersed MWNT have been carried out using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM and HRTEM), energy dispersive X-ray analysis (EDAX), and Raman spectroscopy. Electrochemical performance of these electrodes has been investigated using cyclic voltammetry, galvanostatic charge−discharge, and electrochemical impedance spectroscopy. Specific capacitance of RuO2, TiO2, and SnO2 dispersed MWNT electrodes increases compared to that pure MWNT electrode due to the pseudo capacitance of the nanocrystalline metal oxides dispersed on the functionalized MWNT. The present study shows the potential of cost-effective TiO2/MWNT novel nanocrystalline composite material for electrochemical double layer capacitor.