Study on the Synthesis and Tribological Property of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Based Magnetic Fluids

In this paper, Fe₃O₄ based magnetic fluids with different particle concentrations were prepared by the co-precipitation technique. The size of the Fe₃O₄ nanoparticles is about 13 nm and their shape is spherical. The tribological performances of the fluids with different concentration Fe₃O₄ nanoparticles were evaluated in a MMW-1A four-ball machine. The results show that the tribological performance of magnetic fluids with proper Fe₃O₄ nanoparticles can be improved significantly. The maximum nonseized load (P _B) has been increased by 38.4% compared with carrier liquid. The wear scar diameter has been reduced from 0.68 mm to 0.53 mm and the relative percentage in friction coefficient has decreased to 31.3%. The optimal concentration of the Fe₃O₄ nanoparticles in the carrier liquid is about 4 wt.%.     

Silver nanoparticles synthesis using Wedelia urticifolia (Blume) DC. flower extract: Characterization and antibacterial activity evaluation

Silver nanoparticles (AgNPs), synthesized by green methods with the property to kill microbes, are highly valuable in medical sciences. So, the current study was aimed at using the flower extract of Wedelia urticifolia for synthesizing AgNPs with antibacterial properties. The AgNPs were produced by adding the extract to three different AgNO₃ concentrations (1, 10, and 100 mM) in nine possible flower extract to metal salt ratios (9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, and 1:9). The formation of brown color and the presence of a peak at 431 nm in the UV–Vis spectrum of the colloidal solution indicates the synthesis of AgNPs, which were also characterized by dynamic light scattering (DLS), Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy‐dispersive X‐ray spectroscopy. The DLS results exposed that the smallest sized AgNPs were obtained in 10 mM AgNO₃ solution and 4E6M was the optimized extract to metal salt solution ratio. The characterization techniques revealed that the synthesized AgNPs were spherical shaped and crystalline with a diameter of less than 30 nm. Furthermore, the synthesized nanoparticles were tested against two Gram‐positive (Klebsiella pneumonia and Staphylococcus aureus) and two Gram‐negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains for their antibacterial efficiency. Although the studied strains showed limited growth, overall, the effect of nanoparticles was found to be insignificant. It is concluded that the current study is advantageous over other previous studies because the AgNPs were synthesized at room temperature from 10 mM AgNO₃ concentration in only 2 hours. Additionally, the present work is simple, ecofriendly, and in‐expensive.     

Reduction in wear of metakaolinite-based geopolymer composite through filling of PTFE

Metakaolinite-based geopolymer composite containing 5-30% (volume fraction) polytetra-fluoroethylene (PTFE) was synthesized using compound activator composed of aqueous NaOH and sodium silicate at room temperature. Flexural strength, compressive strength and elastic modulus of the composite were measured. Tribological behaviour of the composite sliding against AISI-1045 steel was investigated on an MM-200 friction and wear tester. SEM, EDS and XPS analysis were conducted on worn surfaces and wear debris. The results show that mechanical strength of the composite was lower than corresponding geopolymer while the wear model became mild. The friction process was stable and the wear rate was dramatically reducted by 86-99.4%. The improvement of tribological properties of the composite was attributed to form a brown soft thin layer on the worn surface of the composite containing Fe₂O₃ came from tribochemical reaction. EDS analysis on the worn surfaces indicate the content of Fe increase along with the increase of volume content of PTFE in the composite. Furthermore, the counterpart, the steel ring was also protected from terrible wear as occurred when friction with geopolymer without any filling of solid lubricant. There is a brown thin layer mainly composed of Fe₂O₃ on the steel ring.     

Iron oxide nanoparticles decrease nuclear fractal dimension of buccal epithelial cells in a time‐dependent manner

In this paper, we present results that iron oxide nanoparticles (IONPs) induce time‐dependent structural changes in nuclei of buccal epithelial cells. The cells were treated with magnetite, Fe₃O₄ nanoparticles (spherical shape, diameter 80–100 nanometres). The digital micrographs of the nuclei were made in 3 different time points: 15, 30 and 60 min after the treatment with IONPs, as well as in the control cells. A total of 120 nuclear structures (30 per sample) were analysed. Fractal analysis of nuclei was done in ImageJ software of the National Institutes of Health, (Bethesda, MD, USA). For each nuclear structure, the values of fractal dimension and lacunarity were calculated. There was a time‐dependent reduction of nuclear fractal dimension in buccal epithelial cells after exposure to magnetite iron oxide nanoparticles. Negative trend was observed (p < 0.01). Nuclear lacunarity, as another fractal parameter was shown to increase, also in a time‐dependent manner, after the treatment with IONPs. To our knowledge, this is the first study to investigate effects of magnetite nanomaterial on nuclear fractal complexity, and also the first to apply fractal analysis method in testing of the interaction between nanoparticles and cell nucleus in this experimental setting.     

Facile green synthesis approach for the production of chromium oxide nanoparticles and their different in vitro biological activities

Green synthesis of nanoparticles using plants has become a promising substitute for the conventional chemical synthesis methods. In the present study, our aim was to synthesize chromium oxide nanoparticles (Cr₂O₃NPs) through a facile, low‐cost, eco‐friendly route using leaf extract of Rhamnus virgata (RV). The formation of Cr₂O₃NPs was confirmed and characterized by spectroscopic profile of UV–Vis, EDX, FTIR, and XRD analyses. The UV‐visible spectroscopy has confirmed the formation of Cr₂O₃NPs by the change of color owing to surface plasmon resonance. The bioactive functional groups present in the leaf extract of RV involved in reduction and stabilization of Cr₂O₃NPs were determined by FTIR analysis. Based on XRD analysis, crystalline nature of Cr₂O₃NPs was determined. The morphological shape and elemental composition of Cr₂O₃NPs were investigated using SEM and EDX analyses, respectively. With growing applications of Cr₂O₃NPs in biological perspectives, Cr₂O₃NPs were evaluated for diverse biopotentials. Cr₂O₃NPs were further investigated for its cytotoxicity potentials against HepG2 and HUH‐7 cancer cell lines (IC₅₀: 39.66 and 45.87 μg/ml), respectively. Cytotoxicity potential of Cr₂O₃NPs was confirmed against promastigotes (IC₅₀: 33.24 μg/ml) and amastigotes (IC₅₀: 44.31 μg/ml) using Leishmania tropica (KMH₂₃). The Cr₂O₃NPs were further evaluated for antioxidants, biostatic, alpha‐amylase, and protein kinase inhibition properties. Biocompatibility assay was investigated against human macrophages which confirmed the nontoxic nature of Cr₂O₃NPs. Overall, the synthesized Cr₂O₃NPs are biocompatible and nontoxic and proved to possess significant biopotentials. In future, different in vivo studies are needed to fully investigate the cytotoxicity and mechanism of action associated with these Cr₂O₃NPs.     

Synthesis,Structure and Tribological Properties of Stearic Acid Coated (NH4)3PMo12O40 Nanoparticles

A new kind of oil additive, stearic-acid-coated (NH₄)₃PMo₁₂O₄₀ nanoparticles was synthesized by a chemical method. The morphology and structure was characterized by means of transmission electron microscopy; X-ray powder diffraction and Fourier transform infrared spectroscopy. The tribological properties of coated (NH₄)₃PMo₁₂O₄₀ nanoparticles as oil additives in liquid paraffin were evaluated in a four-ball machine. The results showed that the coated (NH₄)₃PMo₁₂O₄₀ nanoparticles have an average diameter of about 20 nm, and the (NH₄)₃PMo₁₂O₄₀ nanocore has a Keggin structure. As oil additives they dramatically improved the antiwear ability of liquid paraffin, and enhanced the friction-reduction and load-carrying ability of liquid paraffin to some extent. The rubbed surface was investigated by scanning electron microscopy and X-ray photoelectron spectrometry. It was found that the boundary film on the worn surface was composed of MoO₃, (NH₄)₂MoO₇ and Fe₂O₃. Which contributed to the good tribological properties of the oil.     

Tribological properties of Mn-Zn-Fe magnetic fluids under magnetic field

A controllable and variable magnetic field was got by improving the oil cup of a MS-800 four-ball tester. By this improved four-ball tester, the tribological properties of Mn_0.78Zn_0.22Fe₂O₄ magnetic fluid in the magnetic field were tested. The worn surfaces of the steel balls lubricated with 6 wt% Mn_0.78Zn_0.22Fe₂O₄ magnetic fluid under different magnetic fields were observed by using a scanning electron microscope (SEM), while the elemental compositions of the wear scars were analyzed by means of energy dispersive spectrometry (EDS). It was found that the Mn_0.78Zn_0.22Fe₂O₄ nanoparticles had a diameter about 20 nm. Under magnetic field, the 46^# turbine oil containing 6 wt% Mn_0.78Zn_0.22Fe₂O₄ nanoparticles showed much better friction-reducing and anti-wear abilities compared with lubrication without magnetic field. The worn surface, lubricated by 6 wt% Mn_0.78Zn_0.22Fe₂O₄ magnetic fluid lubricated under the effect of magnetic field, is smooth and the plowing is almost disappeared. Moreover, it is found that 22 mT magnetic induction is the optimum magnetic induction. Form theory study we found that under the effect of magnetic field, the bearing capacity increasing with the increasing of magnetic induction. When the eccentricity is small, the side leakage is highly decreased.     

Analysis of Deposits from Friction at Head-Tape Interfaces by Raman Spectroscopy

To demonstrate the applicability of Raman spectroscopy to the analysis of thin heterogeneous deposits on surfaces, a sample of brown stain or friction polymer produced on sendust (85% Fe, 9% Si, 6% Al) surfaces of a simulated read/write head by a magnetic oxide tape making prior contact with a copper, aluminum or nickel surface was investigated. Raman spectra identified the base film of the tape as poly(ethylene terephthalate) or PET, and the magnetically active layers as containing mostly γ-Fe₂O₃. Conversely, Raman spectra of brown slain showed it to consist mainly of Fe₃O₄ and organic compounds. More brown stain was produced after copper contact than after aluminum contact, but only organic deposits were produced after nickel contact in these tests. It is speculated on the basis of these spectral data that the inhibiting effect of nickel could be the result of catalytically produced organic materials, which change the tribology on the head surface and inhibit the formation of brown slain or friction polymer.     

Morphology,structure and chemistry of extracted diesel soot: Part II: X-ray absorption near edge structure (XANES) spectroscopy and high resolution transmission electron microscopy

Chemical composition of diesel soot extracted from used diesel engine has been investigated using X-ray Absorption Near Edge Structure (XANES) spectroscopy and high-resolution transmission electron microscopy (HRTEM). The XANES spectra indicate the presence of phosphates of zinc and calcium and sulfates of zinc and calcium as well as the presence of sulfides of zinc. HRTEM coupled with EDS and lattice imaging indicates the presence of nanoparticles of Ca₃(PO₄)₂ and Fe₂O₃ embedded in the turbostratic soot structure. Both Ca₃(PO₄)₂ and Fe₂O₃ are hard particles and appear to have been incorporated within the turbostratic soot structure during third body wear.     

Real‐space observation of strong metal‐support interaction: state‐of‐the‐art and what's the next

The real‐space resolving of the encapsulated overlayer in the well‐known model and industry catalysts, ascribed to the advent of dedicated transmission electron microscopy, enables us to probe novel nano/micro architecture chemistry for better application, revisiting our understanding of this key issue in heterogeneous catalysis. In this review, we summarize the latest progress of real‐space observation of SMSI in several well‐known systems mainly covered from the metal catalysts (mostly Pt) supported by the TiO₂, CeO₂ and Fe₃O₄. As a comparison with the model catalyst Pt/Fe₃O₄, the industrial catalyst Cu/ZnO is also listed, followed with the suggested ongoing directions in the field.     

TEM and AES investigations of the natural surface nano‐oxide layer of an AISI 316L stainless steel microfibre

The chemical composition, nanostructure and electronic structure of nanosized oxide scales naturally formed on the surface of AISI 316L stainless steel microfibres used for strengthening of composite materials have been characterised using a combination of scanning and transmission electron microscopy with energy‐dispersive X‐ray, electron energy loss and Auger spectroscopy. The analysis reveals the presence of three sublayers within the total surface oxide scale of 5.0–6.7 nm thick: an outer oxide layer rich in a mixture of FeO.Fe₂O₃, an intermediate layer rich in Cr₂O₃ with a mixture of FeO.Fe₂O₃ and an inner oxide layer rich in nickel.     

Effect of Fe2O3 content on microstructure of Al powder consolidated parts via selective laser melting using various laser powers and speeds

In situ constituents were formed inside an aluminium matrix via selective laser melting (SLM) of Al powder mixed with 5, 10, and 15 wt% Fe₂O₃ powder (using various laser powers and speeds), in order to investigate the effect of Fe₂O₃ content on the microstructural characteristics of novel aluminium matrix composites. The unique microstructures such as coralline-like Al–Fe intermetallics were formed by the in situ reaction, being Fe₃Al at first but Al₁₃Fe₄ soon after that. These coralline-like intermetallics were fragmented (under appropriate laser parameters and/or higher Fe₂O₃ contents) and mixed up with Al oxide particles, reinforcing the matrix. The higher Fe₂O₃ increased the formation of other combinations such as Al₂Fe, AlFe, and Fe₃Al as well as metastable Al oxides in addition to equilibrium Al₁₃Fe₄ (Al₃Fe) and stable α-Al₂O₃. A very fine, well-bonded, and homogeneous distribution of hard particles was achieved in high Fe₂O₃ contents, efficiently increasing the hardness and providing an advanced Al matrix composite.     

Synthesis and tribological behavior of surface modified (NH4)3PMo12O40 nanoparticles

Surface modified (NH₄)₃PMo₁₂O₄₀ nanoparticles were synthesized in a mixture solution of water–ethanol with cetyltrimethyl ammonium bromide as a modifying agent. The morphology, structure and thermal properties of modified (NH₄)₃PMo₁₂O₄₀ nanoparticles were investigated by means of transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrum, thermogravimetric analysis, and differential scanning calorimetry. Their tribological behaviors were evaluated on a four-ball testing machine. The results show that the modified (NH₄)₃PMo₁₂O₄₀ nanoparticles as oil additives can improve the load-carrying capacity and antiwear property of the base oil. The rubbed surfaces were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. It can be inferred that a tribological reaction film was formed, which contributed to the good tribological properties of surface modified (NH₄)₃PMo₁₂O₄₀ nanoparticles.     

Effect of Cu Nanoparticles on the Tribological Performance of Attapulgite Base Grease

This study investigated the effect of Cu nanoparticles on the tribological properties of attapulgite base grease. It was found that the friction reduction ability and antiwear property of the base grease can be improved with the addition of Cu nanoparticles. Under the lubrication of grease containing Cu nanoparticles, a smoother and more compact tribofilm was formed on the rubbing surface. The tribofilm is mainly composed of Cu, FeO, Fe₂O₃, FeOOH, CuO, and SiO. In addition, the content of iron oxides and silicate oxide formed in the tribofilm was increased by the introduction of Cu nanoparticles.     

Surface micromorphology of dental composites [CE‐TZP]‐[Al2O3] with Ca+2 modifier

The objective of this study was to characterize the three‐dimensional (3D) surface micromorphology of the ceramics produced from nanoparticles of alumina and tetragonal zirconia (t‐ZrO₂) with addition of Ca⁺² for sintering improvement. The 3D surface roughness of samples was studied by atomic force microscopy (AFM), fractal analysis of the 3D AFM‐images, and statistical analysis of surface roughness parameters. Cube counting method, based on the linear interpolation type, applied for AFM data was used for fractal analysis. The morphology of non‐modified ceramic sample was characterized by the rather big (1–2 μm) grains of α‐Al₂O₃ phase with a habit close to hexagonal drowned in solid solution of t‐ZrO₂ with smooth surface. The pattern surfaces of modified composite content a little amount of elongated prismatic grains with composition close to the phase of СаСеAl₃О₇ as well as hexahedral α‐Al₂O₃‐grains. Fractal dimension, D, as well as height values distribution have been determined for the surfaces of the samples with and without modifying. It can be concluded that the smoothest surface is of the modified samples with Ca⁺² modifier but the most regular one is of the non‐modified samples. A connection was observed between the surface morphology and the physical properties as assessed in previous works. Microsc. Res. Tech. 78:840–846, 2015. © 2015 Wiley Periodicals, Inc.     

Effects of silica addition on the particle characteristics and phase transition of flame-synthesized γ-Al2O3 nanoparticles

The effects of silica addition on the thermal stability of flame-synthesized γ-Al₂O₃ nanoparticles are investigated in this study. Based on the electron microscope images of pure alumina, nanoparticles with diameters ranging from 20 nm to 30 nm were synthesized. No significant changes were observed after heat treatment at 900°C, 1100°C, and 1180°C. After heat treatment at 1260°C, sintered particles larger than 100 nm were observed. All images of the nanoparticles doped with silica, including those taken after heat treatment at 1260°C, showed similar particle sizes regardless of treatment temperature. Based on the X-ray diffraction patterns and specific surface areas, the onset temperature of the phase transition to α-Al₂O₃ for the flame-synthesized pure alumina was near 1180°C. The addition of silica greatly increased the thermal stability of the synthesized γ-Al₂O₃ nanoparticles.     

Scanning electron microscopy as a tool for authentication of biodiesel synthesis from Linum usitatissimum seed oil

Utilization of renewable and alternative energy feedstocks such as nonedible seeds oil to deal with the increasing energy crises and related ecological concerns have gained the attention of researchers. Biodiesel is an efficient and renewable substitute for diesel engine. This work investigates the potential of inexpensive nonedible seed oil of Linum usitatissimum to synthesize biodiesel using iron sulfate green nanocatalyst through the process of transesterification. Flax seed contains about 37.5% oil content estimated through Soxhlet apparatus. Light microscopy revealed that seed size varies from 3.0 to 6.0 cm in length, 2.0 to 3.3 cm in width, and 0.7 to 1.0 mm in diameter. Color of seed varied from yellow to brown. Characterization of biodiesel is performed through GC–MS and FTIR. Scanning electron microscopy was carried out to study the morphological features of seed coat. Catalyst was characterized by scanning electron microscopy, energy diffraction X-ray, and X-ray diffraction. The diffraction peaks of Fe₃O₄ green nanoparticles were found to be in 2θ values, 30.24°, 35.62°, 38.26°, 49.56°, 57.12°, and 62.78°. Fuel properties of biodiesel are also determined and compared with ASTM standards. Linum usitatissimum biodiesel has density 0.8722 (15°C kg/L), kinetic viscosity 5.45 (40°C cSt), flash point (90°C), pour point (−13°C), cloud point (−9°C), sulfur (0.0432% wt), and total acid number (0.245 mg KOH/g). It is concluded that L. usitatissimum seed oil is a highly potential source for biodiesel production to cope with the challenge of present energy demand.     

Tribological characteristics of bisphenol S bis(diphenyl phosphate) as a high‐performance antiwear additive in lubricating greases at elevated temperature

Bisphenol S bis(diphenyl phosphate) (BSDP) was synthesised and characterised, and its tribological behaviours as additives in polyurea grease and lithium complex grease were evaluated for steel/steel contact at 200 °C. The results indicated that BSDP could dramatically reduce the friction and wear of sliding pairs in the base grease of polyurea, and the tribological performances of BSDP in polyurea grease were significantly superior to the normally used molybdenum disulfide‐based additive package. Furthermore, BSDP in polyurea grease has better tribological behaviour than that in lithium complex grease at a constant load of 100 N. X‐ray photoelectron spectroscopy analysis indicated that boundary lubrication films composed of Fe(OH)O, Fe₂O₃, Fe₃O₄ and FePO₄ compounds containing the P–O bonds and nitride compounds were formed on the worn surface, which resulted in excellent friction reduction and antiwear performance. Copyright © 2016 John Wiley & Sons, Ltd.     

Friction and wear behaviour of Sialon/ (Ca,Mg)‐Sialon with lubrication by coated PbS nanoparticles as oil additives

The friction and wear behaviour of Sialon/(Ca,Mg)‐Sialon with lubrication by liquid paraffin containing PbS nano‐particles coated with dialkyldithiophosphate or oleic acid as additives was investigated using an SRV ball‐on‐disc test rig. It was found that the addition of such nanoparticles reduced the friction coefficient of the friction couple irrespective of the concentration of the additive and the wear volume of (Ca,Mg)‐Sialon, especially under relatively high loads such as 150 N or more. X‐ray photoelectron spectroscopy and electron probe microanalysis revealed that a tribochemical film composed of PbSO₄, PbS₂O₃, PbSO₃, etc., was formed on the worn surface, and contributed to the lubricity of the PbS nanoparticles.     

Biotinylated vanadium and chromium sulfide nanoparticles as probes for colocalization of membrane proteins

We report the microemulsion synthesis of vanadium and chromium sulfide nanoparticles (NPs) and their biological application as nanoprobes for colocalization of membrane proteins. Spherical V₂S₃ and Cr₂S₃ NPs were prepared in reverse microemulsion droplets, as nanoreactors, obtained by the surfactant sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) in nonpolar organic phase (heptane). Electron microscopic data indicated that the size distribution of the nanoparticles was uniform with an average diameter between 3 ÷ 5 nm. The prepared hydrophobic nanocrystals were transferred in aqueous phase by surface cap exchange of AOT with biotin‐dihydrolipoic ligands. This substitution allows the nanoparticles solubility in aqueous solutions and confer their bioactivity. In addition, we report the conjugation procedure between α‐Lipoic acid (LA) and biotin (abbreviated as biotin‐LA). The biotin‐LA structure was characterized by 1D and 2D NMR spectroscopy. The biotinylated vanadium and chromium sulfide nanoparticles were tested as probes for colocalization of glutamate receptors on sodium‐dodecyl‐sulfate‐digested replica prepared from rat hippocampus. The method suggests their high labeling efficiency for study of membrane biological macromolecules. Microsc. Res. Tech. 79:799–805, 2016. © 2016 Wiley Periodicals, Inc.