Towards hybrid nanofluids: Preparation, thermophysical properties, applications, and challenges

Despite many synthetic biomaterials having physical properties that are comparable or even superior to those of natural body tissues, they frequently fail due to the adverse physiological reactions they cause within the human body, such as infection and inflammation. The surface modification of biomaterials is an economical and effective method by which biocompatibility and biofunctionality can be achieved while preserving the favorable bulk characteristics of the biomaterial, such as strength and inertness. Amongst the numerous surface modification techniques available, plasma surface modification affords device manufacturers a flexible and environmentally friendly process that enables tailoring of the surface morphology, structure, composition, and properties of the material to a specific need. There are a vast range of possible applications of plasma modification in biomaterial applications, however, the focus of this review paper is on processes that can be used to develop surface morphologies and chemical structures for the prevention of adhesion and proliferation of pathogenic bacteria on the surfaces of in-dwelling medical devices. As such, the fundamental principles of bacterial cell attachment and biofilm formation are also discussed. Functional organic plasma polymerised coatings are also discussed for their potential as biosensitive interfaces, connecting inorganic/metallic electronic devices with their physiological environments.

Plasma assisted surface modification of organic biopolymers to prevent bacterial attachment

The cutting fluid is significant in any metal cutting operation, for cooling the cutting tool and the surface of the workpiece, by lubricating the tool-workpiece interface and removing chips from the cutting zone. Recently, many researchers have been focusing on minimum quantity lubrication (MQL) among the numerous methods existing on the application of the coolant as it reduces the usage of coolant by spurting a mixture of compressed air and cutting fluid in an improved way instead of flood cooling. The MQL method has been demonstrated to be appropriate as it fulfills the necessities of ‘green’ machining. In the current study, firstly, various lubrication methods were introduced which are used in machining processes, and then, basic machining processes used in manufacturing industries such as grinding, milling, turning, and drilling have been discussed. The comprehensive review of various nanofluids (NFs) used as lubricants by different researchers for machining process is presented. Furthermore, some cases of utilizing NFs in machining operations have been reported briefly in a table. Based on the studies, it can be concluded that utilizing NFs as coolant and lubricant lead to lower tool temperature, tool wear, higher surface quality, and less environmental dangers. However, the high cost of nanoparticles, need for devices, clustering, and sediment are still challenges for the NF applications in metalworking operations. At last, the article identifies the opportunities for using NFs as lubricants in the future. It should be stated that this work offers a clear guideline for utilizing MQL and MQL-nanofluid approaches in machining processes. This guideline shows the physical, tribological, and heat transfer mechanisms associated with employing such cooling/lubrication approaches and their effects on different machining quality characteristics such as tool wear, surface integrity, and cutting forces.

A comprehensive review on minimum quantity lubrication (MQL) in machining processes using nano-cutting fluids

Tribology of enhanced turning using biolubricants: A comparative assessment

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Nano-enhanced biolubricant in sustainable manufacturing: From processability to mechanisms

80Ni–20Cr and 75Cr 3 C 2 –25(Ni–20Cr) coatings were deposited on T91 boiler tube steel by high velocity oxy-fuel (HVOF) process to enhance high-temperature corrosion resistance. Hot corrosion studies were conducted on bare and HVOF-coated steel specimens after exposure to a molten salt (Na 2 SO 4 –60%V 2 O 5 ) environment at 750 °C under cyclic conditions. Each cycle consisted 1 h of heating in the silicon carbide tube furnace followed by 20 min of cooling in air. The weight change measurements were performed after each cycle to establish the kinetics of corrosion using thermogravimetric technique. X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDAX) and X-ray mapping techniques were used to analyse the corrosion products. The bare steel experienced higher weight gain, which may be attributed to the formation of unprotective Fe 2 O 3 dominated oxide scales. The 80Ni–20Cr coating was found to be more protective than the 75Cr 3 C 2 –25(Ni–20Cr) coating. The phases revealed in the oxide scale of the coated specimens were mainly oxides and spinels of nickel and chromium, which are reported to be protective against the hot corrosion.

High temperature hot corrosion behaviour of NiCr and Cr3C2–NiCr coatings on T91 boiler steel in an aggressive environment at 750 °C

Performance evaluation of aluminium 6063 drilling under the influence of nanofluid minimum quantity lubrication

Thermal spraying has emerged as a suitable and effective surface engineering technology and is widely used to apply wear, erosion and corrosion protective coatings for various kinds of industrial applications. Cr3C2-based coatings have been applied to a wide range of industrial components. Cr3C2–NiCr coatings offer greater corrosion and oxidation resistance, also having a high melting point and maintaining high hardness, strength and wear resistance up to a maximum operating temperature of 900 °C. The corrosion resistance is provided by NiCr matrix while the wear resistance is mainly due to the carbide ceramic phase. This paper reviews the performance, developments and applications of Cr3C2–NiCr thermal spray coatings for corrosion/erosion-corrosion under different types of environments and outlines the characterization of Cr3C2–NiCr coatings with respect to their microstructure and mechanical properties, together with some brief characterisation work by the author for HVOF sprayed 75Cr3C2-25NiCr coating on T91 boiler steel.

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Characterisation and Corrosion-Erosion Behaviour of Carbide based Thermal Spray Coatings

Experimental investigation on the performance of MQL drilling of AISI 321 stainless steel using nano-graphene enhanced vegetable-oil-based cutting fluid

In the present paper hot corrosion behavior of high velocity oxy-fuel (HVOF) sprayed Cr3C2–NiCr coating on ASME-SA213-T91 boiler steel has been investigated. In addition, influence of post treatment of the coating by two different methods, i.e. sealing and heat treatment, on the hot corrosion behavior has also been investigated. Hot corrosion studies were conducted on bare steel, as-deposited Cr3C2–NiCr coating and on post treated Cr3C2–NiCr coating on T91 steel after exposure to a molten salt (Na2SO4–60% V2O5) environment at 900 °C under cyclic conditions. Each cycle consisted of 1 h heating in the silicon carbide tube furnace followed by 20 min cooling in air. The mass gain measurements were performed after each cycle to establish the kinetics of corrosion using thermogravimetric technique. X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDAX) and X-ray mapping techniques were used to analyze the corrosion products. Coated steel showed better resistance to hot corrosion as compared to the uncoated counterpart. As-deposited Cr3C2–NiCr coating experienced two stages of hot corrosion, i.e. initiation stage and propagation stage. Once the coating entered the propagation stage, the protective scale rendered ineffective and substrate became vulnerable to hot corrosion. Post treated coating resulted to be more effective than as-deposited coating in enhancing the corrosion resistance of T91 steel.

Sukhpal Singh Chatha

Papers

High temperature hot corrosion behaviour of NiCr and Cr3C2–NiCr coatings on T91 boiler steel in an aggressive environment at 750 °C

Performance evaluation of aluminium 6063 drilling under the influence of nanofluid minimum quantity lubrication

Characterisation and Corrosion-Erosion Behaviour of Carbide based Thermal Spray Coatings

Experimental investigation on the performance of MQL drilling of AISI 321 stainless steel using nano-graphene enhanced vegetable-oil-based cutting fluid

The effects of post-treatment on the hot corrosion behavior of the HVOF-sprayed Cr3C2–NiCr coating