Hard Nanoparticles Research Articles

Impact of grinding media on high-energy ball milling-driven amorphization in multiparticulate As4S4/ZnS/Fe3O4 nanocomposites

Amorphization scenarios in multiparticulate grinding media composed of As4S4/ZnS/Fe3O4 nanocomposites driven by high-energy ball mechanical milling are identified employing the X-ray powder diffraction analysis on intermediate-range ordering in the generated amorphous phase. This amorphous phase is supposed to be nucleated heterogeneously from grain boundaries of β-As4S4 crystallites followed by penetration deeply into grain interior, stabilizing the crystalline-amorphous core-shell structure of the fine-grained nanoparticles. Coexistence of nanocrystalline nc-β-As4S4 and amorphous arsenic monosulphide a-AsS phases is crucial feature of these nanocomposites, the amorphous substance being generated continuously due to re-amorphization of disordered phase initially existed in arsenic sulphide prepared by synthesis from elements and direct milling-driven vitrification of nc-β-As4S4. In monoparticulate β-As4S4-based and biparticulate As4S4/Fe3O4 nanocomposites, the amorphizing configurations are composed of single- and triple-broken chain-like network clusters. Under stronger conditions realized in the grinding medium composed by hard nanoparticles biased by their sizes in respect to 20:1 rule, as in triparticulate 1⋅As4S4-4⋅ZnS-1⋅Fe3O4 nanocomposite, the amorphization scenario differs being activated by double-breaking of intramolecular covalent bonds within As4S4 cage-like molecules. This effect is identified as nanocrystalline nc-ZnS-assisted milling-driven arsenic monosulphide amorphization in triparticulate 1⋅β-As4S4-4⋅ZnS-1⋅Fe3O4 nanocomposite solution.

Analysis of soft and hard nanoparticle alternating multilayers for the development of theory for long-period stacking order structure prepared by Langmuir-Blodgett method

Two types of hard and soft nanoparticles with a size of 5 nm were alternately layered to adjust the multi-particle structure with high regularity, and structural analysis was performed. Specifically, we alternately transferred two kinds of single-particle layers composed of surfactant-modified organo-magnetite and a hydrophobic polymer to a solid substrate using the Langmuir-Blodget (LB) method. The morphology of two-dimensional particle integration in each single particle layer was confirmed by atomic force microscopy observations. The obtained LB multilayers exhibited almost the same periodicity, crystallite size, and lattice distortion, based on X-ray diffraction (XRD) analysis. The alternating multilayers composed of hard and soft particle monolayers were not inferior to single component multilayers in terms of periodicity and regularity. The utilization of this preparation method facilitates effective control of the period of hard and soft layers. It is asserted that the high degree of regularity was attained due to the affinity and miscibility between the organic polymer particle layer and the modified organic chains on the inorganic nanoparticle surface. The most notable result is that in the XRD data, the spacing between inorganic nanoparticles was not enhanced, and the period of the hard-soft particle correlation was confirmed. Therefore, it seems that both layers have the same high degree of regularity.

Effect of Hard Magnetic CoFe<sub>2</sub>O<sub>4</sub> Nanoparticles Additives on Improving Rheological Properties and Dispersion Stability of Magnetorheological Fluids

Increasing dispersion stability is the main issue in recent research at magnetorheological (MR) fluids. The presentation of nanoparticle addictive in MR fluids is an effective method not only to increase dispersion stability but also increasing performance in MR fluids. In this study, the effect of hard magnetic CoFe2O4 nanoparticles addition on rheological properties and dispersion stabilization had been studied. Rheological properties were investigated using a rheometer at room temperature. The result showed that the addition of CoFe2O4 nanoparticles 1wt% in particles of MR fluids were improving the shear stress and viscosity of MR fluids. Both MR fluids with and without nanoadditives behaving like a Newtonian fluid at the off-state condition and act like Bingham fluid at the on-state condition. Moreover, MR fluid with CoFe2O4 additives had a higher sedimentation ratio than MR fluids without additives.

Bridging chains mediate nonlinear mechanics of polymer nanocomposites under cyclic deformation

Elastomer-based nanocomposites, mixtures of elastomeric rubber with hard nanoparticles, generally exhibit strain stiffening under large strains while also showing strain softening at low strain during large cyclic deformations due to the Mullins Effect. Numerous studies have documented the Mullins effect over the last 50 years, and many models have been developed to explain (and predict) the Mullins effect as it is closely related to material failure. Even with this rich history, relatively few studies have connected experimentally measured changes in nanocomposite chain structure with nonlinear strain hardening and nanofiller dispersion. In this work, we quantify the strain hardening mechanics, and chain anisotropy in situ in silica-filled acrylonitrile butadiene rubber (NBR) nanocomposites under cyclic tensile loading. Macroscopic strain hardening and molecular chain anisotropy increased after the first loading cycle, as a strong Mullins effect appeared, for nanocomposites with sufficient filler volume fraction. In composites with low filler content, we observed little increase in strain hardening or chain anisotropy and a barely-visible Mullins effect. Our results provide strong experimental support that chain delamination from the filler surface is related to the Mullins effect in nanocomposite materials.

Stabilizing Hard Magnetic SmCo5 Nanoparticles by N-Doped Graphitic Carbon Layer.

We report a chemical method to synthesize size-controllable SmCo5 nanoparticles (NPs) and to stabilize the NPs against air oxidation by coating a layer of N-doped graphitic carbon (NGC). First 10 nm CoO and 5 nm Sm2O3 NPs were synthesized and aggregated in reverse micelles of oleylamine to form SmCo-oxide NPs with a controlled size (110, 150, or 200 nm). The SmCo-O NPs were then coated with polydopamine and thermally annealed to form SmCo-O/NGC NPs, which were further embedded in CaO matrix and reduced with Ca at 850 °C to give SmCo5/NGC NPs of 80, 120, or 180 nm, respectively. The 10 nm NGC coating efficiently stabilized the SmCo5 NPs against air oxidation at room temperature or at 100 °C. The magnetization value of the 180 nm SmCo5/NGC NPs was stabilized at 86.1 emu/g 5 days after air exposure at room temperature and dropped only 1.7% 48 h after air exposure at 100 °C. The stable SmCo5/NGC NPs were aligned magnetically in an epoxy resin, showing a square-like hysteresis behavior with their Hc reaching 51.1 kOe at 150 K and 21.9 kOe at 330 K and their Mr stabilized at around 84.8 emu/g. Our study demonstrates a new strategy for synthesizing and stabilizing SmCo5 NPs for high-performance nanomagnet applications in a broad temperature range.

Micro-Alloying and Surface Texturing of Ti-6Al-4V Alloy by Embedding Nanoparticles Using Gas Tungsten Arc Welding

Titanium alloy Ti-6Al-4V is known for both its excellent mechanical properties and its low surface hardness. This study explores a two-step process for depositing a hard nanocrystalline coating onto the surface of the Ti-alloy, followed by surface melting, which embeds hard nanoparticles into a thin surface layer of the alloy. The treated surface layer was studied using X-ray diffraction, scanning electron microscopy, and Vicker’s micro-hardness testing. The results of the study show that the surface of the Ti-6Al-4V alloy can be successfully hardened by embedding nanosized Al2O3 particles into the surface using gas tungsten arc welding to melt the surface of the material. Surface melting the Ti-6Al-4V alloy with a 50A welding current produced the maximum microhardness of 701 HV0.2kg. The micro-hardness of the treated surface layer decreased with the increasing size of the nanoparticles, while the roughness of the surface increased with the increasing welding current. The heat input into the surface during the surface melting process resulted in the formation of various intermetallic compounds capable of further increasing the hardness of the Ti-6Al-4V surface.

Recent advances in stimuli-responsive core-shell microgel particles: synthesis, characterisation, and applications

Inspired by the path followed by Matthias Ballauff over the past 20 years, the development of thermosensitive core-shell microgel structures is reviewed. Different chemical structures, from hard nanoparticle cores to double stimuli-responsive microgels have been devised and successfully implemented by many different groups. Some of the rich variety of these systems is presented, as well as some recent progress in structural analysis of such microstructures by small-angle scattering of neutrons or X-rays, including modelling approaches. In the last part, again following early work by the group of Matthias Ballauff, applications with particular emphasis on incorporation of catalytic nanoparticles inside core-shell structures—stabilising the nanoparticles and granting external control over activity—will be discussed, as well as core-shell microgels at interfaces.Graphical abstract

Outstanding Synergy of Superior Strength and Ductility in Heterogeneous Structural 1045 Carbon Steel

Superior strength-ductility synergy of 1045 carbon steel produced by aluminothermic reaction casting method was obtained through large deformation rolling at ambient temperature and subsequent annealing, meanwhile, a heterogeneous composite structure was fabricated. The heterogeneous structural 1045 carbon steel consists of “soft” microcrystalline/ultrafine grained (UFG) ferrite and “hard” cementite nanoparticles. The outstanding strength-ductility synergy was primarily attributed to the microstructure characteristics about the “soft/hard” interfaces of heterogeneous composite structure. The strength was improved due to the second phase reinforcement of hard cementite nanoparticles and decreasing of ferrite grain size, meanwhile, the back stress hardening capacity of “soft/hard” phase also resulted in the high strength. And the favorable ductility was ascribed to the generation of geometrically necessary dislocations (GNDs) around “soft/hard” interfaces, which resulted in the high work hardening capability of heterogeneous structural 1045 carbon steel. It is remarkable that tensile strength (∼ 1190 MPa) and high yield strength (∼ 1118 MPa) and good ductility (∼10.6%) can be simultaneously acquired for the cold rolled 1045 steel after annealing at 673 K for 1 h.

Cobalt nanoparticles trigger ferroptosis-like cell death (oxytosis) in neuronal cells: Potential implications for neurodegenerative disease.

The neurotoxicity of hard metal-based nanoparticles (NPs) remains poorly understood. Here, we deployed the human neuroblastoma cell line SH-SY5Y differentiated or not into dopaminergic- and cholinergic-like neurons to study the impact of tungsten carbide (WC) NPs, WC NPs sintered with cobalt (Co), or Co NPs versus soluble CoCl2 . Co NPs and Co salt triggered a dose-dependent cytotoxicity with an increase in cytosolic calcium, lipid peroxidation, and depletion of glutathione (GSH). Co NPs and Co salt also suppressed glutathione peroxidase 4 (GPX4) mRNA and protein expression. Co-exposed cells were rescued by N-acetylcysteine (NAC), a precursor of GSH, and partially by liproxstatin-1, an inhibitor of lipid peroxidation. Furthermore, in silico analyses predicted a significant correlation, based on similarities in gene expression profiles, between Co-containing NPs and Parkinson's disease, and changes in the expression of selected genes were validated by RT-PCR. Finally, experiments using primary human dopaminergic neurons demonstrated cytotoxicity and GSH depletion in response to Co NPs and CoCl2 with loss of axonal integrity. Overall, these data point to a marked neurotoxic potential of Co-based but not WC NPs and show that neuronal cell death may occur through a ferroptosis-like mechanism.

AFM Analyses of 3XXX Series Al Alloy Reinforced with Different Hard Nanoparticles Produced in Liquid State.

In the present work, nanocomposites-based 3XXX series Al alloy with three different types of hard nanoparticles, including TiO2, C, and CeO2, were produced employing two techniques such as mechanical milling and stir-casting method in order to evaluate the viability of integration of the reinforcement in the Al matrix. The integration and dispersion capability of the reinforcement into the Al alloy (3xxx Series) matrix was evaluated, using a phase angle difference and surface roughness analyses by atomic force microscopy operated in both the contact mode (CM-AFM) and tapping mode (TM-AFM), respectively. The distribution profile of both rugosity and the phase angle shift was used to statically quantify the integration and dispersion of the reinforcement into the extruded samples, by using the root mean square (RMS) parameter and phase shift coupled with the events number (EN) parameter. Results from Atomic Force Microscopy (AFM) analyses were corroborated by X-ray diffractometry and scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness tests were conducted to identify the mechanical properties of the composites in the extruded condition and their correlation with the microstructure. A close relationship was found between the microstructure obtained from the AFM and X-ray diffractometry (XRD) analyses and mechanical properties. Among all, the C reinforcement produced the major changes in the microstructure as well as the best integration and dispersion into the Al-alloy coupled with the best mechanical properties.

Bad neighbour, good neighbour: how magnetic dipole interactions between soft and hard ferrimagnetic nanoparticles affect macroscopic magnetic properties in ferrofluids.

Fluids responding to magnetic fields (ferrofluids) offer a scene with no equivalent in nature to explore long-range magnetic dipole interactions. Here, we studied the very original class of binary ferrofluids, embedding soft and hard ferrimagnetic nanoparticles. We used a combination of X-ray magnetic spectroscopy measurements supported by multi-scale experimental techniques and Monte-Carlo simulations to unveil the origin of the emergent macroscopic magnetic properties of the binary mixture. We found that the association of soft and hard magnetic nanoparticles in the fluid has a considerable influence on their inherent magnetic properties. While the ferrofluid remains in a single phase, magnetic interactions at the nanoscale between both types of particles induce a modification of their respective coercive fields. By connecting the microscopic properties of binary ferrofluids containing small particles, our findings lay the groundwork for the manipulation of magnetic interactions between particles at the nanometer scale in magnetic liquids.

Eutectic crystallized FePd nanoparticles for liquid metal magnet.

Magnetically hard nanoparticles have been widely explored in colloidal solution synthesis, while a high temperature-induced phase transformation is indispensable to achieve its high magnetocrystalline anisotropy. However, a long-standing challenge of magnetic nanoparticles is the inaccessibility of size-controlled growth without sintering-induced agglomeration. Here, we report a universal one-pot eutectic reaction scheme of magnetically hard FePd nanoparticles, in which the crystallization conditions are critical for its magnetic performance. We demonstrate that the stoichiometry between transition metal and eutectic salt and sintering temperature can play an important role in the magnetic coercivity of FePd nanoparticles. In addition, gallium liquid metal is employed as the conductivity filler for the formation of a magnetorheological fluid after mixing with metallic FePd nanoparticles. The liquid composite shows a high metallic and thermal conductivity as an unconventional cooling metallic ferrofluid conductor, and we further demonstrate its potential application in sensors, conductors and thermal interfaces.

Fabrication of Mn-(Bi, Ga) based hard magnetic nanocomposites

The hard and soft magnetic nanoparticles of Mn-(Bi, Ga) and Fe-Co, respectively, were prepared by using a high energy ball milling method. These nanoparticles were then mixed together with different ratios and subsequently annealed in various conditions of temperature and time to make nanocomposite magnets. The coercivity Hc and maximum energy product (BH)max of these magnets depend on the nanoparticle size and on the ratio of the hard/soft magnetic phases. The annealing process plays an important role for exchangecoupling between the hard and soft magnetic phases. With sizes in a range of 40-60 nm, the Mn-(Bi,Ga) nanoparticles reveal high coercivity (Hc > 12 kOe) to be a potential rare-earth-free hard magnetic phase for producing nanocomposite magnets. Quite high coercivities, Hc > 4 kOe, and maximum energy products, (BH)max > 4 MGOe, have been achieved for this kind of rare-earth-free nanocomposite magnets.

Comparative study on Ni and Ni-α-Al2O3 nano composite coating on Al6061 substrate material

The electrodeposition of Ni coating is been popular for its advantages in providing better functional properties. The invention of hard nano particles has given added advantages of Ni composite coating. Meanwhile applications of Al6061 are increasing in the field of automobile, aeronautical and other industrial applications due to its weight to strength ratio. In the present work, the optimization of wear parameters on the wear rate of coating on Al6061 substrate is carried out by using CCD. The normal load, sliding speed and sliding distance are considered as the three parameters in the five levels, leading to 20 numbers of trails. Further work is carried out for the study of Ni-Al2O3 composite coating. The load and interaction effect of sliding distance and speed are found to be influencing factors on wear rate of Ni and Ni-Al2O3 coating respectively. The lower wear rate is observed for the composite coating of Ni-Al2O3 compared to Ni coating. This is due to the presence of Al2O3 particles restrict movement of dislocation. The debris formed between the pin sample and disc acts as the third body for abrasive nature of wear

Tribological Behavior of PTFE Composites Filled with PEEK and Nano-ZrO2

In order to study the tribological properties of PTFE modified by hard nanoparticles and soft polymer under dry friction conditions, the tribological properties of polytetrafluoroethylene (PTFE) filled with different volume contents of polyether ether ketone (PEEK) and nano-ZrO2 were investigated at a linear speed of 2 m/s, normal load of 200 N, and ambient temperature conditions for 60 min using a block-on-ring wear tester. A multiple-layer feedforward artificial neutral network (ANN) was used to simulate and analyze the friction coefficient and volume wear rate. The results showed that the friction coefficient and volume wear rate of PTFE composites were effectively reduced when nano-ZrO2 and PEEK were filled separately or simultaneously. The best tribological properties were obtained when the composites were filled with 5–8 vol% nano-ZrO2 and 20 vol% PEEK simultaneously; the volume wear rate was only 1.29 × 10−6 mm3/Nm and the friction coefficient was only 0.15. An ANN can accurately simulate and predict the friction coefficient and volume wear rate of composites, and the predicted results were consistent with the experimental results. A groove appeared in the volume wear rate simulation diagram when the volume content of nano-ZrO2 was about 7% with or without PEEK. This phenomenon indicates that the composites in this region had a lower volume wear rate. Therefore, the addition of nano-ZrO2 and PEEK can effectively improve the tribological properties of PTFE. As a simulation analysis method, an ANN can accurately analyze and predict the tribological properties of composites.

Enhancement on the exchange coupling behavior of SrCo0.02Zr0.02Fe11.96O19/MFe2O4 (M = Co, Ni, Cu, Mn and Zn) as hard/soft magnetic nanocomposites

Hard/soft SrCo0.02Zr0.02Fe11.96O19/MFe2O4 (M = Ni, Co, Cu, Mn and Zn) nanocomposites have been fabricated efficiently via one-pot sol-gel combustion route. The influence of different type of spinel were examined by XRD (X-ray diffraction), SEM – TEM (scanning and transmission electron microscopies) systems and VSM (vibrating sample magnetometer). The XRD investigation of Hard/soft nanocomposites revealed the tailoring between hexaferrite and spinel ferrite phases. Magnetization measurements (M vs. H) were performed at room (T = 300 K) and low temperature (T = 10 K) and diverse magnetic parameters comprising Ms (saturation magnetization), Mr (remanence), coercivity (Hc), and so on were determined. Smooth M vs. H curves and single peaks in dM/dH vs. H plots were observed for various prepared nanocomposites. The Henkel plots and maximum energy products were also determined and analyzed. Various prepared hard/soft nanocomposites indicated relatively high values of diverse magnetic parameters. Diverse findings disclosed the incidence of exchange-coupling spring behavior among various soft and hard magnetic phases. Measurements of ZFC-FC magnetizations showed the existence of a peak temperature values, which are largely ascribed to competition between the motion of magnetic domain walls and thermal activations. It is revealed that one-pot sol-gel combustion route is valuable to attain strong exchange coupling among hard and soft nanoparticle phases grown near to each other. The obtained findings indicated that these nanocomposites are promising candidates for numerous practical applications.

Size effect on the magnetic properties of CoFe2O4 nanoparticles: A Monte Carlo study

In this study, we report the size-effects on the magnetic properties of CoFe2O4 hard ferrite single nanoparticles using Monte Carlo simulation within the Ising model. Free boundaries conditions were used to simulate the cubic nanoparticles with different sizes. Saturation and remanent magnetization increased with the increase of the particle size. Rise of the squareness ratio (Mr/Ms) towards high values is observed. Furthermore, the single-domain size limit is shown for the size of 21 nm. Besides, we evaluated the performance of the cubic shaped CoFe2O4 permanent magnet in term of the maximum energy product. A high value of the (BH)max of about 2.83 MG Oe at room temperature for 21 nm was achieved. The obtained results allowed us to determine the theoretical limits of the magnetic properties of the cubic shaped CoFe2O4 nanoparticles and pave the way for the development of CoFe2O4 spinel ferrites for permanent magnet applications.

Chemical Synthesis of Magnetic Nanoparticles for Permanent Magnet Applications.

Permanent magnets are a class of critical materials for information storage, energy storage, and other magneto-electronic applications. Compared with conventional bulk magnets, magnetic nanoparticles (MNPs) show unique size-dependent magnetic properties, which make it possible to control and optimize their magnetic performance for specific applications. The synthesis of MNPs has been intensively explored in recent years. Among different methods developed thus far, chemical synthesis based on solution-phase reactions has attracted much attention owing to its potential to achieve the desired size, morphology, structure, and magnetic controls. This Minireview focuses on the recent chemical syntheses of strongly ferromagnetic MNPs (Hc >10 kOe) of rare-earth metals and FePt intermetallic alloys. It further discusses the potential of enhancing the magnetic performance of MNP composites by assembly of hard and soft MNPs into exchange-coupled nanocomposites. High-performance nanocomposites are key to fabricating super-strong permanent magnets for magnetic, electronic, and energy applications.

The softer, the faster

The ability of soft nanoparticles to shrink makes their diffusion in a confined environment faster than that of hard nanoparticles of the same size. The size reduction results from electrostatic interactions between the soft nanoparticle and medium and has important implications for their use as efficient drug carriers.

Spontaneous shrinking of soft nanoparticles boosts their diffusion in confined media

Improving nanoparticles (NPs) transport across biological barriers is a significant challenge that could be addressed through understanding NPs diffusion in dense and confined media. Here, we report the ability of soft NPs to shrink in confined environments, therefore boosting their diffusion compared to hard, non-deformable particles. We demonstrate this behavior by embedding microgel NPs in agarose gels. The origin of the shrinking appears to be related to the overlap of the electrostatic double layers (EDL) surrounding the NPs and the agarose fibres. Indeed, it is shown that screening the EDL interactions, by increasing the ionic strength of the medium, prevents the soft particle shrinkage. The shrunken NPs diffuse up to 2 orders of magnitude faster in agarose gel than their hard NP counterparts. These findings provide valuable insights on the role of long range interactions on soft NPs dynamics in crowded environments, and help rationalize the design of more efficient NP-based transport systems.