Shengmao Zhang

Preparation and tribological properties of surface modified Cu nanoparticles

Abstract Cu nanoparticles surface-modified by dioctylamine dithiocarbamate (DTC8) were synthesized using a two-phase extraction route. The size, morphology and structure of resultant surface-capped Cu nanoparticles (coded as DTC8-Cu) were analyzed by means of X-ray diffraction, transmission electron microscopy and infrared spectrometry. The tribological behavior of DTC8-Cu as an additive in liquid paraffin was evaluated with a four–ball machine, and the surface topography of the wear scar was also examined by means of scanning electron microscopy. Results show that Cu nanoparticles modified by DTC8 have a small particle size and a narrow size distribution. Besides, DTC8-Cu as an additive in liquid paraffin has excellent antiwear ability, due to the deposition of nano-Cu with low melting point on worn steel surface leading to the formation of a self-repairing protective layer thereon.

Preparation and Tribological Properties of Surface-Capped Copper Nanoparticle as a Water-Based Lubricant Additive

Abstract Cu nanoparticle surface-capped by methoxylpolyethyleneglycol xanthate was synthesized using in situ surface-modification technique. The size, morphology and phase structure of as-prepared Cu nanoparticle were analyzed by means of X-ray diffraction and transmission electron microscopy. The tribological properties of as-synthesized Cu nanoparticle as an additive in distilled water were investigated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined using X-ray photoelectron spectroscopy and scanning electron microscope equipped with an energy-dispersive spectrometer attachment. Results show that as-synthesized Cu nanoparticle as a water-based lubricant additive is able to significantly improve the tribological properties and load-carrying capacity of distilled water, which is ascribed to the deposition of Cu nanoparticles on steel sliding surfaces giving rise to a protective and lubricious Cu layer thereon. In the meantime, they may also tribochemically react with rubbing steel surfaces to generate a boundary lubricating film consisting of Cu, FeS and FeSO4 on the rubbed steel surface, which helps to result in greatly improved tribological properties of distilled water, thereby reducing friction and wear of the steel–steel pair.

Preparation and Evaluation of Tribological Properties of Cu Nanoparticles Surface Modified by Tetradecyl Hydroxamic Acid

Oil-soluble Cu nanoparticles without phosphorus and sulphur elements were prepared using in situ surface-modification technique with hydrazine hydrate as a reductant and tetradecyl hydroxamic acid (THA) as a modifier. The phase composition, microstructure, and chemical structure of as-synthesized Cu nanoparticles (coded as THA-capped Cu or THA-capped nano-Cu) were analyzed by means of X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectrometry. The thermal stability of THA-capped Cu was examined using thermogravimetric analysis and differential thermal analysis. The antiwear ability of THA-capped Cu as an additive in liquid paraffin was examined using a four-ball machine, and the morphology of worn steel balls was examined using a scanning electron microscope, an energy dispersive spectrometer and an X-ray photoelectron spectroscopy. It has been found that THA-capped Cu can be well dispersed in some organic solvents. As-synthesized THA-capped Cu as an environmentally friendly additive in liquid paraffin shows excellent antiwear ability for the steel–steel contact. Besides, Cu nanoparticles are able to deposit and fill up micropits and grooves on steel sliding surfaces under a higher load and hence greatly reduced wear of the steel–steel pair thereat by way of self-repairing of worn surfaces of the steel–steel frictional pair, showing promising application as an environmentally acceptable lubricating oil additive.

Tribological properties of oleic acid-modified zinc oxide nanoparticles as the lubricant additive in poly-alpha olefin and diisooctyl sebacate base oils

Oleic acid (OA) modified ZnO nanoparticles with an average size of 4.04 nm were prepared via a facile in situ one-step route. The as-prepared ZnO nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The light-absorbing performance and thermal stability of the as-prepared ZnO nanoparticles were evaluated by ultraviolet-visible light spectrophotometry and thermogravimetric analysis, and their tribological behaviour as the lubricant additive in poly-alpha olefin (PAO) and diisooctyl sebacate (DIOS) base oils was evaluated with a four-ball machine. The surface morphology of the wear scar was observed with a scanning electron microscope and a three-dimensional optical profiler, and the element composition of the wear scar was determined by energy dispersive spectrometry. It was found that the surface-capping of ZnO nanoparticles by OA helps to greatly increase their dispersibility and thermal stability. In the meantime, OA-modified ZnO nanoparticles can effectively improve the antiwear and friction-reducing abilities as well as the load-carrying capacity of the base oils, which is due to the formation of a tribofilm in association with the tribo-sintering and/or adsorption of the additives on the rubbed steel surfaces. Furthermore, the friction-reducing and antiwear performances of the as-prepared ZnO nanoparticles as lubricating oil additives seem to be closely related to the polarity of the base oils. Namely, the OA-modified ZnO additive exhibits better tribological behaviour in apolar PAO than in polar DIOS.

Large scale preparation of silver nanowires with different diameters by a one-pot method and their application in transparent conducting films

Silver nanowires (AgNWs) with varied diameters were synthesized by a facile and efficient one-pot polyol method. The effects of reaction conditions on the morphology of the as-prepared AgNWs as well as the transmittance and optoelectronic performance of the transparent conducting films made of AgNWs were investigated. Findings indicate that each run of the reaction of the established synthesis protocol can provide more than 10 g of AgNWs, and the dynamic balance between the reduction of Ag+ (yielding Ag0) and the formation of AgCl nanocubes has an important effect on the yield and morphology of AgNWs. Based on an appropriate adjustment of the reaction conditions, the average diameter of AgNWs can be adjusted in the range of 40–110 nm while the yield of one-dimensional nanostructures in the products is as much as 95%. Furthermore, the as-synthesized AgNWs can be easily spin-coated onto polyethylene glycol terephthalate substrate to afford transparent conducting films with a transmittance as high as 87% and a sheet resistivity below 70 Ω sq−1, which demonstrates that the present synthesis strategy could be of special significance for the commercial preparation and application of silver nanowires as an alternative to commercial indium tin oxide film.

Synthesis and tribological properties of oil-soluble copper nanoparticles as environmentally friendly lubricating oil additives

Purpose – The purpose of this paper is to synthesize oil-soluble copper (Cu) nanoparticles modified with free phosphorus and sulfur modifier and investigate its tribological properties as environment-friendly lubricating oil additives. Design/methodology/approach – To improve the anti-oxidation properties of these nanoparticles, two kinds of surface modifiers, oleic acid and oleylamine were used simultaneously. The morphology, composition, structure and thermal properties of as-synthesized Cu nanoparticles were investigated by means of transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrometry and differential thermal and thermogravimetric analysis. The tribological properties of as-synthesized Cu nanoparticles as an additive in liquid paraffin were evaluated with a four-ball friction and wear tester. Findings – It has been found that an as-synthesized Cu nanoparticle has a size of 2-5 nm and can be well dispersed in organic solvents. Tribological properties evalua...

Preparation and Characterization of Copper Nanowire/Polyamide 6 Nanocomposites and Its Properties

Copper nanowire/polyamide 6 (denoted as nano-Cu/PA6) nanocomposites were readily prepared via in situ polymerization in reducing atmosphere. The microstructure, phase composition, and chemical state of typical elements of as-prepared nano-Cu/PA6 nanocomposites were analyzed by transmission electron microscopy, and X-ray diffraction, while their thermal stability and crystallization behaviors were evaluated by thermogravimetric analysis and differential scanning calorimetry. Moreover, the mechanical strength of as-prepared nano-Cu/PA6 nanocomposites was determined with a universal testing machine, and their friction and wear behaviors were evaluated with an MRH-3 high speed block-on-ring test rig. Findings indicate that copper nanowire is coated by surrounding molecular chains of PA6 and well disperses in the polymeric matrix. Besides, copper nanowire consists of metallic copper, which indicates that copper nanowire coated by PA6 matrix has good chemical stability and is not oxidized during the preparation of the title nanocomposites under high-temperature reactions. Furthermore, copper nanowire filler is able to remarkably improve the mechanical strength and wear resistance of polyamide 6. Particularly, nano-Cu/PA6 composite containing 0.5% (mass fraction) copper nanowire possesses the maximum tensile strength (its tensile strength is higher than that of pure PA6 by 77.41%); and its friction coefficient and wear scar diameter are also much smaller than those of PA6.

Tribological characteristic and mechanism analysis of borate ester as a lubricant additive in different base oils

A kind of N-containing borate ester (DEBE) with a double five-member-ring structure as a lubricant additive was synthesized by using boric acid, diethanolamine and alkylphenol polyoxyethylene ether as the starting materials. The tribological performance of the as-prepared DEBE was evaluated using a four-ball friction and wear tester in different base oils, such as liquid paraffin (LP), poly-alpha-olefin (PAO) and dioctyl sebacate (DIOS), while the morphologies of the worn scars of the steel balls were observed using a scanning electron microscope. The chemical components on the worn surfaces of the steel balls were analyzed using X-ray photoelectron spectroscopy. The tribological mechanisms in base oils of LP, PAO and DIOS were also explored. The results show that as-prepared borate ester DEBE possessed good antiwear properties in LP and PAO and can be used as a promising S- and P-free environmentally acceptable lubricating oil additive. However, the antiwear ability decreased when the additive DEBE was added to DIOS base oil. The antiwear ability of the DEBE borate esters used as an additive in DIOS might be closely related to competitive adsorption between DEBE borate ester and DIOS ester oil. Namely, compared with the DEBE additive, the DIOS base oil is first to adsorb to the metal surface because of the higher polarity. Moreover, a small amount of the additive absorbed on the metal surface may influence the continuity and compactness of the oil film formed by DIOS alone, resulting in destruction of the tribological properties of DIOS.

Preparation and evaluation of tribological properties of oil-soluble rice-like CuO nanoparticles

Purpose – The purpose of this paper is synthesis of oil-soluble non-spherical nanoparticles modified with free phosphorus and sulphur modifier and investigation of their tribological properties as environment-friendly lubricating oil additives. Design/methodology/approach – To study the effect of morphology of nanoparticles on their tribological properties, rice-like CuO nanoparticles were synthesized. To improve the solubility of CuO nanoparticles in organic media, the in-situ surface modification method was used to synthesize these products. The morphology, composition and structure of as-synthesized CuO nanoparticles were investigated by means of transmission electron microscopy, X-ray powder diffraction, thermogravimetric analysis and Fourier transform infrared spectrometry. The tribological properties of as-synthesized CuO nanoparticles as an additive in liquid paraffin (LP) were evaluated with a four-ball tribometer. The morphology and elemental composition of worn steel ball surfaces were analysed ...

Ionic Liquid-assisted Solvothermal Synthesis of Ni Particles and Study of Their Electrocatalytic Effect for Calcium Dobesilate Oxidation

Graphical Abstract Ionic Liquid-assisted Solvothermal Synthesis of Ni Particles and Study of Their Electrocatalytic Effect for Calcium Dobesilate Oxidation