Mechanical Attrition Research Articles

Investigation of Temperature Cycling with Coupled Vessels for Efficient Deracemization of NMPA.

Chiral compounds can exist as pairs of nonsuperimposable stereoisomers (enantiomers) possessing the same physical properties but interacting differently with biological systems. This makes them interesting materials to be explored by the pharmaceutical and food industries. In this study, to obtain pure enantiomers from their conglomerates, a method that involves using a two-vessel system for deracemization of N-(2-methylbenzylidene) phenylglycine amide (NMPA) was developed. In this method, a suspension was transferred with a pulsating pumping profile between two inter-connected stirred vessels that were set at constant temperatures. As the suspension was exposed to more rapid changes in temperature, it resulted in the speeding up of the process and thus enhancing productivity in comparison to a single vessel system. The results confirmed successful deracemization of NMPA. A modified pumping profile and tubing design eliminated the issue of clogging of the transfer tubes and ensured effective suspension transfer for longer durations. Operating parameters, such as initial enantiomeric excess, vessel residence time, and suspension density were also investigated. In this method, optimization of residence time was necessary to enhance the efficiency of the process further. Results confirmed that this methodology has the potential to be more adaptable and scalable as it involved no mechanical attrition.

An Overview on Recent Works of Heterostructured Materials Fabricated by Surface Mechanical Attrition Treatment

An Overview on Recent Works of Heterostructured Materials Fabricated by Surface Mechanical Attrition Treatment

On the selection of devices for mechanical activation and attrition of mineral granular media

On the selection of devices for mechanical activation and attrition of mineral granular media

Tibial Retro-Malleolar Groove Morphology in Patients With Posterior Tibialis Tendon Dysfunction

The posterior tibial tendon is a gliding tendon which courses around the medial malleolus and fails in posterior tibialis tendon dysfunction (PTTD) leading to a flat foot deformity. Distal tibial bone spurs have been identified as a secondary sign of PTTD although they have not been quantified in detail. The aim of this study was to assess the association of tendon dysfunction with the bony morphology of the tibial retro-malleolar groove. We performed a retrospective review of the clinical presentation, plain radiographs, and 103 magnetic resonance imaging (MRI) scans in 82 consecutive patients with PTTD compared with a non-PTTD group. We carried out a quantitative and qualitative assessment of the presence of plain radiographic bone spurs, stage of PTTD and MRI imaging of the morphology of the tibial bony malleolar groove. Plain radiographic bone spurs, as a secondary sign of PTTD, were present in 21.3% of ankle radiographs. MRI bone spurs were identified in 26/41 (63.4%) for all high-grade partial and complete tears and 7/41 (17.1%) for isolated complete tears compared with only 3.9% of the non-PTTD group. There was a significant association between the presence of bone spurs on MRI imaging and high-grade partial and complete tibialis posterior tears (p < .001; odds ratio of 4.98). Eleven of 103 (10.7%) of spurs were large and in 4/103 (3.9%) were substantial enough to create a tunnel-like hypertrophic groove not previously reported. There is variation in the bony structure of the malleolar groove in PTTD not observed in the non-PTTD group. Further investigation over time may elucidate whether the groove morphology may lead to mechanical attrition of the tibialis posterior tendon and contribute to failure of healing and progressive tendon degeneration.

A modified Fe–Ni alloy coating in pure iron combined of surface mechanical attrition treatment and spark plasma sintering approach

To overcome the shortage of long processing time, high energy consumption, and complex controlling in fabricating Fe–Ni alloy coating, this paper was modified Fe–Ni alloy coating based on the mechanical alloying, electrodeposition, laser cladding and DC arc plasma method. Here, Surface Mechanical Attrition Treatment (SMAT) had been chosen as a pre-treatment to fabricate uniform Fe–Ni alloy coating by Spark Plasma Sintering (SPS). After the well-designed coating approach of SMAT + SPS, a homogeneous and continuous Fe–Ni alloy coating was fabricated on a pure iron plate. During study of the effect of SMAT and the subsequent process of SPS on microstructure and mechanical properties of Fe–Ni alloy coating, a valid set of process parameters were investigated. The results show that the thickness of Fe–Ni interface layer was enhanced significantly by SMAT. In comparison, the depth on the SMAT-sample was approximately twice as thick as on the untreated coarse-grained (CG) sample. The relative densification, microhardness and friction and wear performance are significantly related to the sintering temperature, which also affects the microstructure of interface between iron matrix and alloy coating. It has been evidently proved that, the sintering temperature just within 800–900 °C, the optimum performance Fe–Ni alloy coating on the SMATed iron matrix could be obtained, which has higher density, better wear resistance and tighter bonding.

Effect of laser shock peening and surface mechanical attrition treatment on the oxidation resistance of a 20Cr-25Ni-Nb stainless steel

In this study, the effects of laser shock peening (LSP) and surface mechanical attrition treatment (SMAT) were comparatively investigated on the oxidation behaviors of 20Cr-25Ni-Nb stainless steel in a high-temperature (650 °C) CO2 environment up to 1000 h. The results show that the oxidation resistance of stainless steel can be improved by LSP but deteriorated by SMAT. LSP promoted the formation of a thin and uniform Cr-rich oxide layer on the 20Cr-25Ni-Nb stainless steel instead of a thick duplex oxide layer with Fe-rich outer layer and Cr-rich inner layer which appeared on the untreated sample. For the SMAT-treated sample, besides the oxide scale, a thick internal oxidation zone (IOZ) and oxides spallation were also observed. The formation of a Cr-rich oxide layer was facilitated by the enhancement of the Cr diffusion within the LSP-induced hardened layer. The unsatisfying oxidation performance of the SMAT-treated sample is due to the surface micro-cracks and significant grain refinement which synergistically contributed to the visible carburization and oxidation in a high-temperature CO2 environment.

Modelling mechanical behaviour of a gradient-microstructured material obtained by surface mechanical attrition treatment accounting for residual stresses

In this work, an austenitic 316 L steel was processed by surface mechanical attrition treatment (SMAT), and the induced gradient microstructure was highlighted by experimental measurements. A combined dislocation density-based and grain size-dependent constitutive model is developed to describe the mechanical behaviour of the gradient-microstructured material. In addition, this model also incorporates the grain size-dependent initial twin distribution and evolution of deformation twinning. Residual stress, initial dislocation density and twins are considered to reconstruct the depth-dependent residual fields induced by SMAT. Furthermore, the evolution of dislocation density and twin volume fraction is described during uniaxial tensile loading. Particular attention is devoted to investigate the effect of residual stress and deformation twinning on mechanical behaviour. Results of finite element simulation showed that the gradient microstructure enhances the yield strength, which is in agreement with previous experimental observations. It was revealed that residual stress significantly weakens the yield strength at the initial deformation stage, whereas it has little influence on the plastic behaviour at large deformation. The assumed grain size-dependent deformation twinning model allows describing the evolution of deformation twinning on gradient microstructure. The deformation twinning increases in relation to increased strain hardening during tensile loading. However, the evolution of twin volume fraction shows almost no twin and no variation of twinning within the nanocrystalline grain region.

The Effect of Surface Mechanical Attrition Treatment Time on Microstructure and Mechanical Properties of AZ31 Mg Alloy

The Effect of Surface Mechanical Attrition Treatment Time on Microstructure and Mechanical Properties of AZ31 Mg Alloy

Metal Nanoparticles: Synthesis Approach, Types and Applications – A Mini Review

The study of nanoparticles has grown in significance during the last several years. Nanoparticles are a kind of material that is composed of very tiny particles. Nanoparticle characteristics vary greatly depending on their size and form. The surface of a nanoparticle significantly affects its optical, mechanical, magnetic, and other characteristics. Nanoparticles are categorised according to their size, origin and chemical composition. We created nanoparticles using both top-down and bottom-up techniques. In this article, we discuss various different methods for creating nanomaterials, such as sol-gel processes, gas condensation, vacuum deposition and vaporisation, chemical vapour deposition and condensate, mechanical attrition, chemical precipitation, electrodeposition, and chemical vapour condensation. When it comes to creating nanoparticles, green synthesis is one of the most effective approaches. In this article, we explore eco-friendly techniques for manufacturing alloy nanoparticles, silver, gold, silver oxide and silver sulphide. We also explore the process by which microorganisms in this setting produce nanoparticles. Size and form must be maintained under certain conditions. We consider ways in which to enhance the production of nanoparticles in the future. The risks posed by nanoparticles and the ways in which to mitigate them were also taken into account.

Mechanical Surface Treatments for Controlling Surface Integrity and Corrosion Resistance of Mg Alloy Implants: A Review

The present paper aims to provide an overview of the current state-of-the-art mechanical surface modification technologies and their response in terms of surface roughness, surface texture, and microstructural change due to cold work-hardening, affecting the surface integrity and corrosion resistance of different Mg alloys. The process mechanics of five main treatment strategies, namely, shot peening, surface mechanical attrition treatment, laser shock peening, ball burnishing, and ultrasonic nanocrystal surface modification, were discussed. The influence of the process parameters on plastic deformation and degradation characteristics was thoroughly reviewed and compared from the perspectives of surface roughness, grain modification, hardness, residual stress, and corrosion resistance over short- and long-term periods. Potential and advances in new and emerging hybrid and in-situ surface treatment strategies were comprehensively eluded and summarised. This review takes a holistic approach to identifying the fundamentals, pros, and cons of each process, thereby contributing to bridging the current gap and challenge in surface modification technology for Mg alloys. To conclude, a brief summary and future outlook resulting from the discussion were presented. The findings would offer a useful insight and guide for researchers to focus on developing new surface treatment routes to resolve surface integrity and early degradation problems for successful application of biodegradable Mg alloy implants.

Improving embrittlement in the Ti-Al-C MAX phase system: A composite approach for surface severe plastic deformation

Ti2AlC and Ti3AlC2 belong to an interesting family of layered compounds called MAX phases. A composite approach is tested here to improve the intrinsic brittle behaviour of such compounds. To this end, a bulk MAX compound and a MAX/TiAl2 composite have been deformed under surface severe plastic deformation (SSPD) by surface mechanical attrition treatment (SMAT). Grain delamination and grain decohesion occurred to a depth of 100 µm below the surface for the bulk compound. Resulting cracks and grain pullouts were witnessed by a decrease in the surface and sub-surface hardness. Comparatively, the presence of intergranular TiAl2 effectively prevented such failure for the composite. Thus, the SSPD of this cohesive composite created a surface hardening (+60%) gradient extending down to a depth of 250 µm. Witness marks of plasticity were revealed in both the MAX and TiAl2 phases.

Diffusion bonding of high entropy alloy and stainless steel at a relative lower temperature via surface nano-crystallization treatment

Sluggish diffusion effect of high entropy alloy limits its diffusion bonding with other components in practical applications. In this paper, the surface mechanical attrition treatment (SMAT) strategy for performing diffusion bonding joints of high entropy alloy (HEA) at a relative lower temperature is proposed. The EDS results demonstrate that the diffusion distance of Fe atoms increases significantly after SMAT since more gain boundaries are formed after SMAT. Furthermore, with this method the HEA/stainless steel joint can achieve a useable strength of 320 MPa at relative lower temperature of 850 °C (∼0.63 Tm, Temperature of melting). Molecular dynamics simulations show that the apparent diffusivity of Fe in the polycrystalline model is significantly higher than in the single-crystalline model because of fast diffusion at grain boundaries, i.e., the grain boundaries are fast diffusion channels. More detailed microstructure analysis indicates that although the density of dislocations increases after SMAT, its elemental diffusion ability is much weaker compared with grain boundaries. This study provides a feasible avenue for the application of diffusion bonding in HEAs, which could greatly broaden the applications fields of HEAs.

Distinctive Effects of Surface Roughness and Ions Release on the Bacterial Adhesion and Inactivation of Textured Copper Oxide Surfaces

In this manuscript, we studied the effect of additive manufacturing pretreatment on bacterial adhesion and inactivation on copper-based interfaces. Sandblasting, mirror polishing and Surface Mechanical Attrition Treatment (SMAT) at high or low energies have been employed to modify the substrate’s (316L stainless steel) roughness. The pretreated substrates were coated with thin copper films using magnetron sputtering. The thin copper films’ composition and antibacterial activities were first optimized by being deposited on an Si wafer. We showed that the surface roughness profile influenced bacterial adhesion in the dark. Bacterial inactivation was monitored under indoor light. Stereomicroscopy imaging showed live/dead bacterial cells on the coated substrates. Scanning electron microscopy (SEM) showed homogeneous coating growths of copper with a columnar texture. The chemical composition of the deposited Cu thin films was carried out by Energy Dispersive X-ray Spectroscopy (EDX) and showed a uniform distribution of copper and oxygen, revealing the formation of copper oxides (CuxO). The oxygen content of the sputtered films varied from 7.8 to 25%, justifying the semi-conductor behavior of the thin films under indoor light. The crystallographic structure of the sputtered thin films was investigated using X-ray diffraction (XRD), showing the cubic Cu peaks and characteristic peaks of Cu2O. The Cu peaks at 2θ values of 43.28°, 50.40° and 74.81° were attributed to the (111), (200) and (220) planes, respectively. The use of genetically modified bacteria (without porins) allowed the rationalization of the predominant effect of the extracellular bacterial inactivation compared to that of intracellular bacterial inactivation through ion release and diffusion.

Optimized corrosion resistance in pure copper via surface mechanical attrition treatment and subsequent annealing

Surface mechanical attrition treatment (SMAT) was used on the surface refinement of pure copper mainly to study the electrochemical corrosion behavior of pure copper in a 3.5 wt% NaCl solution, under grain refinement and short-time annealing conditions. Fine crystalline copper showed higher corrosion resistance than coarse crystalline copper, and the samples with grain refinement exhibited increased corrosion resistance under annealing conditions. This improvement may be attributable to the enhanced passivation of the surface passivation film after grain refinement. In addition, the residual stress after annealing reduces the activation energy of atoms leaving the metal lattice and entering the solution, reducing the dissolution rate of the anode. Consequently, the corrosion resistance of fine crystalline copper is improved. Grain refinement and short-time annealing help design corrosion-resistant pure copper.

Simulation and Experimental Study on Surface Mechanical Attrition Treatment for Surface Roughness of 7075 Aluminum Alloys

This paper presents the effects of surface mechanical attrition treatment (SMAT) for the roughness of Aluminum specimens with three kinds of steel media that have different diameters (1.2[Formula: see text]mm, 1.5[Formula: see text]mm, and 2.4[Formula: see text]mm). First, experiments with SMAT for aluminum materials with a short time of 10[Formula: see text]s were performed, then a single-ball impact model was developed to find out the velocity of balls in the chamber. Next, a multi-ball model with the determined velocity was built. Finally, a comparison of the surface roughness was conducted between the experiment and simulation results. The results reveal that when the shot time and media size increase, the surface roughness value rises significantly in both experiment and simulation studies.

Effect of FS-SMAT on microstructure and mechanical property of pure magnesium and AZ31 magnesium alloy

ABSTRACTA novel material processing method, friction stir-surface mechanical attrition treatment (FS-SMAT) was conducted on pure magnesium plate and AZ31 magnesium alloy plate. Two types of stir tools, spherical stir tool and plane stir tool, are designed to process FS-SMAT to reduce the heat input compared with the traditional friction stir processing (FSP). Microstructure evolution during FS-SMAT and its effect on mechanical property are investigated. FS-SMAT has different effect on microstructure and mechanical property when using the spherical and plane stir tools. Different heat input and plastic deformation can be produced due to the specific shapes of stir tools. Using a spherical stir tool, the grain size of pure magnesium plate was refined to 1.74 μm. The micro-hardness was improved from 40 HV to 63 HV. In contrast, after FS-SMAT with a plane stir tool, the grain size and micro-hardness of AZ31 magnesium alloy are 0.91 μm and 125 HV, respectively.

Nanoporous structures with Fe0/FeII/FeIII co-existed as catalysts for phenol degradation

Fe-based amorphous alloy was widely concerned in the field of wastewater treatment because of its nanoporous structure, which has higher reactivity activity. However, as it is easy to get oxidative poisoning, its long-term reactivity activity is restricted. A uniform nanoporous layer has been synthesized by mechanical attrition and dealloying on the surface of Fe76Si9B10P5 amorphous alloy powders in this work. In the test of catalytic performance, due to nanoporous structure, Fe0/FeⅡ/FeⅢ are involved in the Fenton process at the same time. The Fenton reaction was further catalyzed to generate more active group · OH; therefore, the degradation rate reaches 99.8% within 60 min. This coexistence of Fe0/FeII/FeIII persisted after five cycles of the catalytic reaction, indicating the excellent catalytic stability of the catalyst. Using this tunable pretreatment method for surface activation, novel applications for metallic glasses can be developed.

Detail characterization on the microstructure evolution of nickel-base alloy 600MA via surface mechanical attrition treatment

Microstructure evolution of alloy 600MA was explored after surface mechanical attrition treatment (SMAT) with different durations via scanning electronic microscopy, electron backscattered diffraction, transmission electron microscopy and transmission Kikuchi diffraction. The grain refinement and coarsening occurred gradually as strain accumulated with increasing SMAT time. During grain refinement, the initiation and development of dislocation walls or cells came up at early stage. A strip of dislocation wall led to straight element concentration just prior to the formation of ultrafine-laminated (UFL) structures containing abundant twin boundaries (TB) and low angle grain boundaries (LAGB). The UFL structures with a texture orientation were subdivided by the development of dislocation arrays into ultrafine-grained (UFG) structures with random orientations. Meanwhile, the elements were dispersedly concentrated in a few grains. During grain coarsening, the dispersed element concentration still existed. The fraction of LAGB, TB and dislocation density was significantly reduced while the fraction of high angle grain boundary (HAGB) increased along with grain growth. • The grain refinement and coarsening occurred gradually as strain accumulated with increasing SMAT time. • During grain refinement, the initiation and development of dislocation walls or cells came up at early stage. • A strip of dislocation wall led to straight element concentration just prior to the formation of ultrafine-laminated (UFL) structures containing abundant twin boundaries (TB) and low angle grain boundaries (LAGB). • The UFL structures with a texture orientation were subdivided by the development of dislocation arrays into ultrafine-grained (UFG) structures with random orientations. • During grain coarsening, the fraction of LAGB, TB and dislocation density was significantly reduced while the fraction of high angle grain boundary increased along with grain growth.

Surface nanocrystallization enhances the biomedical performance of additively manufactured stainless steel.

Additive manufacturing enables the fabrication of patient-specific implants of complex geometries. Although selective laser melting (SLM) of 316L stainless steel (SS) is well established, post-processing is essential to preparing high-performance biomedical implants. The goal of this study was to investigate surface mechanical attrition treatment (SMAT) as a means to enhance the electrochemical, biomechanical, and biological performances of 316L SS fabricated by SLM in devices for the repair of bone tissues. The SMAT conditions were optimized to induce surface nanocrystallization on the additively manufactured samples. SMAT resulted in a thicker oxide layer, which provided corrosion resistance by forming a passive layer. The fretting wear results showed that the rate of wear decreased after SMAT owing to the formation of a harder nanostructured layer. Surface modification of the alloy by SMAT enhanced its ability to support the attachment and proliferation of pre-osteoblasts in vitro. The study of the response in vivo to the additively manufactured alloy in a critical-sized cranial defect murine model revealed enhanced interactions with the cellular components after the alloy was subjected to SMAT without inducing any adverse immune response. Taken together, the results of this work establish SMAT of additively manufactured metallic implants as an effective strategy for engineering next-generation, high-performance medical devices for orthopedics and craniomaxillofacial applications.

Manufacturing porous U10Zr fuels with controlled porosities by SPS and thermal properties

To accommodate the swelling of metallic fuels induced by the fission gas release for a sodium-free fuel option, advanced U-10Zr fuels with controlled porosities were designed and demonstrated by spark plasma sintering (SPS). U-10Zr fuel pellets with manufactured porosities varying from 35% up to fully dense fuel pellets have been fabricated by controlling mechanical attrition of the starting uranium powders, sintering temperature, pressure, and duration, and the correlation among the microstructure control – porosity – sintering conditions has been established. To further mimick the pore structure in irradiated fuels, different pore formers (NaCl and NH4HCO3) were used to control the pore size and distribution. Microstructure characterization indicates a lamellar reaction zone of enriched Zr and U composed of alpha Zr with 2 at% U and distorted alpha U with 13 at% of Zr, respectively, differing from the arc-melted U-10Zr as a result of rapid consolidation of SPS at lower temperatures and short durations. The thermal conductivity of U10Zr with different porosities were also measured. This work demonstrates the success in manufacturing new metallic fuel forms with controlled porosities and pore distribution, which can be used as model systems to investigate the thermal transfer behavior of metallic fuels in the reactor.