Publications

Multifunctional Bio-Based Lubricants

There is a critical need for engineers to move away from using conventional petroleum-based oils and lubricants in mechanical systems due to their environmental impact. As the first book dedicated to multifunctional bio-based lubricants, this reference text provides detailed coverage on all aspects of the field, including the need for these lubricants and their performance, the synthesis and design routes, and their valuable multifunctional properties. The environmental benefits and superior properties of these lubricants are covered. With sustainability as a key focus, the book raises awareness of the need to develop bio-based lubricants with a lower environmental footprint than traditional lubricants, covers methods for synthesising lubricants from waste plastics (an emerging technique) and discusses suitable techniques for their eventual disposal. Key features • First research book dedicated to multifunctional bio-based lubricants. • Provides detailed coverage on the performance, synthesis and design of these lubricants. • Covers the environmental benefits and superior properties. • Discusses the future market based on the potential applications. • Covers disposal techniques and methods for synthesising lubricants from waste plastics.

Self-Lubricating Alumina Matrix Composites

Tribology of MXene Materials: Advances, Challenges, and Future Directions

MXenes, an emerging class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, have demonstrated exceptional potential in tribology: the study of friction, wear, and lubrication. Their remarkable mechanical strength, thermal stability, and tunable surface chemistry make them ideal candidates for solid lubricants, lubricant additives, and protective coatings in mechanical systems. This review comprehensively examines the tribological performance of MXenes under diverse environmental conditions, including high temperatures, vacuum, humid atmospheres, and liquid lubricants. A particular emphasis is placed on the influence of surface terminations (-OH, -O, -F) on friction reduction and wear resistance. Additionally, we discuss strategies for enhancing MXene performance through hybridization with polymers, nanoparticles, and ionic liquids, enabling superior durability in applications ranging from micro/nano-electromechanical systems (MEMS/NEMS) to aerospace and biomedical devices. We also highlight recent advances in experimental characterization techniques and computational modeling, which provide deeper insights into MXene tribomechanics. Despite their promise, key challenges such as oxidation susceptibility, high synthesis costs, and performance variability hinder large-scale commercialization. Emerging solutions, including eco-friendly synthesis methods and optimized composite designs, are explored as pathways to overcome these limitations. Overall, MXenes represent a transformative avenue for developing next-generation tribological materials that combine high efficiency, sustainability, and multifunctionality. Continued research and innovation in this field could unlock groundbreaking advancements across industrial and engineering applications.

Tribological Behavior of Aluminum Micro-and Nano-Composites

Aluminum metal matrix composites are a class of advanced materials which have been developed for weight-critical applications in the aerospace and automotive industries. In the present investigation, tribological performance of aluminum micro- (100 to 200 μm particle size) and nano- (47 nm particle size) composites was studied using a three pin-on-disk apparatus under dry sliding conditions. As a basis for comparison, the tribological performance of aluminum alloys was also studied. The pins made of these materials were then slid against a steel disk under ambient conditions. Tests were conducted at a sliding velocity of 1.58 m/s for a normal load of 30 N. The worn surfaces of the pins and weardebris were analyzed using a scanning electron microscope. Based on the experiments, it was observed that the nano-composites significantly outperformed all of the other materials with respect to friction levels. It was also discovered that the nano-composites exhibited the best wear performance among the composites...

Surface texturing to control friction and wear for energy efficiency and sustainability

Engineering MXenes: Tunable Mechanical Properties and Applications in Structural Systems

MXenes are an emerging class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides with a unique combination of mechanical, electrical, and thermal properties. While MXenes have been extensively studied in electrochemical and materials science contexts, their mechanical behavior and engineering relevance remain comparatively underexplored. This paper provides a mechanically focused synthesis of MXene research, connecting structure, synthesis, processing, mechanical properties, and functional performance to engineering applications. Emphasis is placed on the tunability of tensile, elastic, shear, and thermomechanical properties through controlled variation of composition, surface terminations, and defects. Comparisons with graphene are used to clarify performance trade-offs and application-specific advantages. Key challenges, including environmental stability, moisture sensitivity, durability, scalability, cost, and integration with conventional engineering materials, are critically examined alongside current mitigation strategies. Applications in structural composites, mechanical reinforcement, energy storage, electromechanical systems, and MXene-based sensors and actuators are discussed to demonstrate practical relevance. By framing MXenes as engineerable materials rather than isolated nanomaterials, this work serves as a technical reference and entry point for mechanical engineers and interdisciplinary researchers seeking to design and deploy MXenes in advanced engineering systems.

Tribute to Prof. Michael R. Lovell

Unraveling the friction and wear mechanisms of surface nanostructured stainless-steel

Influence of surface texture on coefficient of friction and transfer layer formation during sliding of pure magnesium pin on 080 M40 (EN8) steel plate

Tribology of Metal Matrix Composites

Enhanced wear and corrosion resistances of Al coated Mg alloy using high pressure cold sprayed commercially pure-zirconium coating

Effect of ultrasonic impact peening on stress corrosion cracking resistance of austenitic stainless-steel welds for nuclear canister applications

Influence of boric acid additive size on green lubricant performance

As the industrial community moves towards green manufacturing processes, there is an increased demand for multi-functional, environmentally friendly lubricants with enhanced tribological performance. In the present investigation, green (environmentally benign) lubricant combinations were prepared by homogeneously mixing nano- (20 nm), sub-micrometre- (600 nm average size) and micrometre-scale (4 μm average size) boric acid powder additives with canola oil in a vortex generator. As a basis for comparison, lubricants of base canola oil and canola oil mixed with MoS(2) powder (ranging from 0.5 to 10 μm) were also prepared. Friction and wear experiments were carried out on the prepared lubricants using a pin-on-disc apparatus under ambient conditions. Based on the experiments, the nanoscale (20 nm) particle boric acid additive lubricants significantly outperformed all of the other lubricants with respect to frictional and wear performance. In fact, the nanoscale boric acid powder-based lubricants exhibited a wear rate more than an order of magnitude lower than the MoS(2) and larger sized boric acid additive-based lubricants. It was also discovered that the oil mixed with a combination of sub-micrometre- and micrometre-scale boric acid powder additives exhibited better friction and wear performance than the canola oil mixed with sub-micrometre- or micrometre-scale boric acid additives alone.

AN EXPLICIT FINITE ELEMENT MODEL TO STUDY THE INFLUENCE OF FRICTION DURING ORTHOGONAL METAL CUTTING

Understanding the tribological aspects of machining processes is essential for increasing the dimensional accuracy and surface integrity of products. In the present investigation, orthogonal metal cutting simulations were performed using an explicit finite-element code, LS-DYNA. In the simulations, a rigid steel cutting tool of different rake angles was moved at different velocities against a stationary aluminum work-piece. A damage material model was utilized for the work-piece to capture the chip separation behavior and the simultaneous breakage of the chip into multiple fragments. In addition, the friction factors at the cutting tool- work-piece interface were varied in the contact model. Overall, the rake angle was found to have significant influence on the chip morphology during metal cutting. Moreover, the cutting forces and the discontinuous chip formation process were strongly influenced by the friction and cutting speed.

Dynamically Tunable Friction via Subsurface Stiffness Modulation

Currently soft robots primarily rely on pneumatics and geometrical asymmetry to achieve locomotion, which limits their working range, versatility, and other untethered functionalities. In this paper, we introduce a novel approach to achieve locomotion for soft robots through dynamically tunable friction to address these challenges, which is achieved by subsurface stiffness modulation (SSM) of a stimuli-responsive component within composite structures. To demonstrate this, we design and fabricate an elastomeric pad made of polydimethylsiloxane (PDMS), which is embedded with a spiral channel filled with a low melting point alloy (LMPA). Once the LMPA strip is melted upon Joule heating, the compliance of the composite structure increases and the friction between the composite surface and the opposing surface increases. A series of experiments and finite element analysis (FEA) have been performed to characterize the frictional behavior of these composite pads and elucidate the underlying physics dominating the tunable friction. We also demonstrate that when these composite structures are properly integrated into soft crawling robots inspired by inchworms and earthworms, the differences in friction of the two ends of these robots through SSM can potentially be used to generate translational locomotion for untethered crawling robots.

Additively Manufactured Coatings

We are pleased to publish a Special Issue on “Additively Manufactured Coatings” that is intended to provide peer-reviewed articles in the fascinating field of coatings, particularly in the area of additive manufacturing technology [...]

Improvement of Wear, Pitting Corrosion Resistance and Repassivation Ability of Mg-Based Alloys Using High Pressure Cold Sprayed (HPCS) Commercially Pure-Titanium Coatings

In this study, a compact cold sprayed (CS) Ti coating was deposited on Mg alloy using a high pressure cold spray (HPCS) system. The wear and corrosion behavior of the CS Ti coating was compared with that of CS Al coating and bare Mg alloy. The Ti coating yielded lower wear rate compared to Al coating and Mg alloy. Electrochemical impedance spectroscopy (EIS) and cyclic potentiodynamic polarization (CPP) tests revealed that CS Ti coating can substantially reduce corrosion rate of AZ31B in chloride containing solutions compared to CS Al coating. Interestingly, Ti-coated Mg alloy demonstrated negative hysteresis loop, depicting repassivation of pits, in contrast to AZ31B and Al-coated AZ31B with positive hysteresis loops where corrosion potential (Ecorr) > repassivation potential (Erp); indicating irreversible growth of pits. AZ31B and Al-coated AZ31B were most susceptible to pitting corrosion, while Ti-coated Mg alloy indicated noticeable resistance to pitting in 3.5 wt % NaCl solution. In comparison to Al coating, Ti coating considerably separated the AZ31BMg alloy surface from the corrosive electrolyte during long term immersion test for 11 days.

Tribological Performance of Laser Shock Peened Cold Spray Additive Manufactured 316L Stainless Steel

Abstract In recent years, cold spray additive manufacturing (CSAM) has become an attractive technology for surface modification and protection. However, due to the intrinsic porous nature of CSAM coatings, they suffer from rapid material degradation due to premature brittle fracturing induced by tribological interactions. In this work, laser shock peening (LSP) was utilized as a post-processing technology to mitigate the surface porosity and augment the surface characteristics of CSAM 316L stainless steel (SS). Due to the synergistic influence of severe plastic deformation and rapid surface heating, the surface porosities were effectively healed, thus reducing the surface roughness. Combined with the surface-strengthening effects of LSP, the frictional resistance and transfer layer formation on the CSAM LSP surfaces were reduced. The underlying mechanisms for these findings were discussed by correlating the atomic, microstructural, and physical features of the LSP surfaces. Based on these findings, it can be suggested that LSP is indeed a useful technique to control the surface characteristics of CSAM 316L SS coatings.