Search

The deterioration of fluid machines due to slurry and cavitation erosion significantly impairs their serviceability. In the present work, we investigated the influence of deep cryogenic treatment (DCT) on the slurry and cavitation erosion resistance of WC-10Co-4Cr coatings developed using the detonation spraying technique. For comparison, hydroturbine steels and other conventional (Alumina and Stellite 6) coatings were also investigated. All thermal spray coatings showed typical lamellar structure along with the presence of pores and splat boundaries. Among all the coatings, the WC-10Co-4Cr showed the highest slurry (up to 15 times) and cavitation (2 times) erosion resistance owing to high hardness and fracture toughness. Post DCT, the WC-10Co-4Cr coating showed further improvement due to reduced porosity and improved hardness without decrement in fracture toughness. As a result, the DCT coating showed 1.5 to 4.2 times improved slurry erosion resistance than the as-sprayed counterpart, along with 1.6 times higher cavitation erosion resistance. The improved tribological performance of the coating after DCT is associated with enhanced hardness due to the presence of nano precipitates and densification as analyzed using electrochemical techniques. The topological analysis of the eroded surfaces indicated micro-cutting, micro-cracking, and delamination as the primary mechanism controlling the erosion behavior of the coatings.

Owing to their rapid charge–discharge, extremely low maintenance, high power density, versatile operating temperatures and durability, supercapacitors are widely used as electrochemical storage devices in advanced energy applications. In recent years, transition metal oxides, especially nano-textured CuO structures have gained much attention as a low cost and widely available electrode material for supercapacitors. However, the existing techniques for developing nano-textured CuO involve a large number of processing steps through multiple chemical treatments. Further, the performance of nano-structured copper oxides needs to be significantly enhanced to make them commercially viable. Here, we report a facile, two step approach comprising surface activation through thermomechanical treatment and electrochemical dealloying of a Cu–Zn alloy for developing a 3-dimensional hierarchical CuO microstructure. Surface activation prior to dealloying significantly accelerates the reaction kinetics and the hierarchical microstructure comprising micro and nano-scale porosity develops in a few seconds only. Electrochemical studies revealed that the surface activated electrode possesses a high areal capacitance of 1.68 F cm−2 at a current density of 5 mA cm−2, exhibits an excellent cycling stability with 90% retention for 5000 cycles at a current density of 15 mA cm−2 and a high energy density of 0.33 mW h cm−2. The reported specific capacitance is one of the highest values obtained for copper-based alloys which is attributed to its unique 3D hierarchical microstructure that favours rapid ion intercalation and the increased surface area for energy storage. Electrochemical analysis indicates intercalation pseudo-capacitance as the primary charge storage mechanism. The current approach is highly generic and can be applied for a wide number of material systems which signifies its huge potential in the emerging field of advanced supercapacitors, and portable and flexible electronics.

Cavitation erosion is a huge problem in engineering structures working under hydrodynamic conditions. The synergistic effect of erosion and corrosion can aggravate the material removal by several orders of magnitude. Surface coatings are widely used to address material degradation by erosion–corrosion. However, non-homogenous microstructure and presence of defects leads to premature coating failure under erosion–corrosion conditions. Thus, it is imperative to identify plausible solutions to address cavitation-related material degradation. In this study, Ni-Cr-5Al2O3 coatings were deposited on stainless steel substrate using high-velocity-oxy-fuel technique. The as-sprayed coating showed highly non-homogeneous microstructure comprising splats, pores, intermetallic compounds and elemental segregation. A new thermo-mechanical processing technique, stationary friction processing (SFP), was utilized for achieving through-thickness microstructural refinement in as-sprayed coating. As-sprayed and SFP-treated coatings were tested in pure cavitation erosion, corrosion in 3.5% NaCl solution and erosion–corrosion. SFP treatment resulted in 5-times enhancement in the erosion and corrosion resistance compared to as-sprayed coating. The remarkable performance of Ni-Cr-5Al2O3 coatings after SFP treatment is attributed to significant enhancement in the mechanical properties including hardness and fracture toughness which is the consequence of complete removal of splat boundaries, pores, intermetallic compounds and uniform element distribution up to the coating–substrate interface.

In this study, superhydrophobic surfaces were fabricated using 1H,1H,2H,2H-perfluorooctyltriethoxysilane monolayer deposition on thermally oxidized brass. The superhydrophobic surface showed a cont...

Micro/nano scale surface modifications of titanium based orthopedic and cardiovascular implants has shown to augment biocompatibility. However, bacterial infection remains a serious concern for implant failure, aggravated by increasing antibiotic resistance and over usage of antibiotics. Bacteria cell adhesion on implant surface leads to colonization and biofilm formation resulting in morbidity and mortality. Hence, there is a need to develop new implant surfaces with high antibacterial properties. Recent developments have shown that superhydrophobic surfaces prevent protein and bacteria cell adhesion. In this study, a thermochemical treatment was used modify the surface properties for high efficacy antibacterial activity on titanium surface. The modification led to a micro-nano surface topography and upon modification with polyethylene glycol (PEG) and silane the surfaces were superhydrophilic and superhydrophobic, respectively. The modified surfaces were characterized for morphology, wettability, chemistry, corrosion resistance and surface charge. The antibacterial capability was characterized with Staphylococcus aureus and Escherichia coli by evaluating the bacteria cell inhibition, adhesion kinetics, and biofilm formation. The results indicated that the superhydrophobic micro-nano structured titanium surface reduced bacteria cell adhesion significantly (90%) and prevented biofilm formation compared to the unmodified titanium surface after 24 h of incubation.

The leaching out of toxic elements from metallic bioimplants has serious repercussions, including allergies, peripheral neuritis, cancer, and Alzheimer's disease, leading to revision or replacement surgeries. The development of advanced structural materials with excellent biocompatibility and superior corrosion resistance in the physiological environment holds great significance. High entropy alloys (HEAs) with a huge compositional design space and outstanding mechanical and functional properties can be promising for bioimplant applications. However, microstructural heterogeneity arising from elemental segregation in these multiprinciple alloy systems is the Achilles heel in the development of next-generation HEAs. Here, we demonstrate a pathway to homogenize the microstructure of a biocompatible dual-phase HEA, comprising refractory elements, namely, MoNbTaTiZr, through severe surface deformation using stationary friction processing (SFP). The strain and temperature field during processing homogenized the elemental distribution, which was otherwise unresponsive to conventional annealing treatments. Nearly 15 min of the SFP treatment resulted in a significant elemental homogenization across dendritic and interdendritic regions, similar to a week-long annealing treatment at 1275 K. The SFP processed alloy showed a nearly six times higher biocorrosion resistance compared to its as-cast counterpart. X-ray photoelectron spectroscopy was used to investigate the nature of the oxide layer formed on the specimens. Superior corrosion behavior of the processed alloy was attributed to the formation of a stable passive layer with zirconium oxide as the primary constituent and higher hydrophobicity. Biocompatibility studies performed using the human mesenchymal stem cell line, showed higher viability for the processed HEA compared to its as-cast counterpart as well as conventional metallic biomaterials including stainless steel (SS316L) and titanium alloy (Ti6Al4V).

Thermal spray coatings are widely used for addressing erosion problems in fluid machineries. However, the presence of splat boundaries, non-homogeneous microstructure and element segregation limits their performance. In this study, we developed Ni-Cr-40Al2O3 coatings on stainless steel (SS316L) substrate using high-velocity flame spray followed by post-processing using friction stir processing. The performance of as-sprayed and processed coatings was evaluated in slurry erosion, erosion–corrosion and pure corrosion in 3.5% NaCl solution. As-sprayed coating showed lower erosion and erosion–corrosion resistance compared to stainless steel. Friction stir processing resulted in significant microstructure refinement concurrent with enhanced hardness and fracture toughness of the developed coating. At oblique impingement angle, the processed coating showed nearly 30% to twofold higher erosion and erosion–corrosion resistance compared to stainless steel substrate. During pure erosion at normal impingement, both as-sprayed and processed coating showed higher volume loss. However, during erosion–corrosion at normal impingement, the processed coating was able to demonstrate similar volume loss as that of the substrate. In addition, the processed coating showed significant improvement in the corrosion performance as well. The study showed that friction stir processing could be a promising pathway to unravel the deleterious effects of inherent non-homogeneities in thermal spray coatings.

In this study, we demonstrate a novel pathway to engineer the properties of metallic alloys for limiting their cavitation erosion-corrosion. A facile single-step processing technique was used to develop bimodal grain structure in stainless steel. The bimodal steel was tested in cavitation erosion and erosion-corrosion conditions. In both the cases, bimodal steel showed exceptionally high degradation resistance, nearly 7 times higher compared to as-received steel. The remarkable cavitation erosion resistance demonstrated by bimodal steel is attributed to its high yield strength along with high work-hardening rate. In addition, the bimodal steel showed significantly low corrosion rate of 0.001 mm/year in 3.5 wt % NaCl solution compared to 0.088 mm/year for as-received stainless steel.

The most common cyanotic congenital heart disease (CHD) requiring management as a neonate is transposition of great arteries (TGA). Clinically, up to 50% of TGA patients develop some form of neurodevelopmental disability (NDD), thought to have a significant genetic component. A "ciliopathy" and links with laterality disorders have been proposed. This first report of whole genome sequencing in TGA, sought to identify clinically relevant variants contributing to heart, brain and laterality defects.Initial whole genome sequencing analyses on 100 TGA patients focussed on established disease genes related to CHD (n = 107), NDD (n = 659) and heterotaxy (n = 74). Single variant as well as copy number variant analyses were conducted. Variant pathogenicity was assessed using the American College of Medical Genetics and Genomics-Association for Molecular Pathology guidelines.Fifty-five putatively damaging variants were identified in established disease genes associated with CHD, NDD and heterotaxy; however, no clinically relevant variants could be attributed to disease. Notably, case-control analyses identified significantly more predicted-damaging, silent and total variants in TGA cases than healthy controls in established CHD genes (P.001), NDD genes (P.001) as well as across the three gene panels (P.001).We present compelling evidence that the majority of TGA is not caused by monogenic rare variants and is most likely oligogenic and/or polygenic in nature, highlighting the complex genetic architecture and multifactorial influences on this CHD sub-type and its long-term sequelae. Assessment of variant burden in key heart, brain and/or laterality genes may be required to unravel the genetic contributions to TGA and related disabilities.

Slurry erosion–corrosion is a severe issue for many engineering components used in marine, petrochemical, and agricultural sectors. The deleterious effects of the slurry erosion–corrosion significantly lower the service life and enhance the maintenance cost. For limiting the slurry erosion–corrosion effects, there is a need for high-performance advanced materials. In the present work, equimolar MoNbTaTiZr high-entropy alloy (HEA) was developed, and its slurry erosion–corrosion behavior was investigated. For comparison, conventionally used stainless steel SS316L was also investigated. The detailed microstructural characterization showed the presence of a two-phase bcc crystal structure in the HEA. The major bcc phase was predominantly composed of Ta, Mo, and Nb with the interdendritic region being rich in Ti and Zr. The MoNbTaTiZr HEA showed 2 times higher hardness than the SS316L steel. Under slurry erosion–corrosion condition, the HEA showed 3.5 times higher resistance while under erosive conditions, two times better performance than the reference material. The analysis of the eroded surface morphology showed the presence of a mixed ductile–brittle erosion response for the HEA. The improved performance of the HEA is predominantly related to the high hardness and extremely high corrosion resistance. Electrochemical corrosion testing revealed that the HEA has 80 times lower current density than SS316L and high pitting resistance, resulting in low corrosion rates. The electrochemical impedance spectroscopy (EIS) findings showed a denser and highly stable passive layer. The results indicated that MoNbTaTiZr HEA could be effectively used for countering the slurry erosion–corrosion and corrosive conditions.

Owing to its good biocompatibility and low cost, stainless steel is one of the most widely utilized biomaterial. However, longtime assessment of stainless steel has shown problems related to material degradation, especially localized corrosion and bio-film formation. In addition, the leaching of toxic nickel and chromium ions from stainless steel leads to additional health complications. Here, we utilized submerged friction stir processing, a severe surface deformation technique for significantly enhancing its durability, bio-activity as well as antibacterial resistance. The processing was done with a wide variation in strain rates to produce tunable surface microstructure. High strain-rate processing resulted in nearly single-phase fine-grained microstructure, while slow strain-rate processing developed a dual-phase fine-grained microstructure. The bio-corrosion rate of processed steel was reduced by more than 60 % along with significant enhancement in the pitting resistance. The processed steel showed nearly no bacterial adhesion/biofilm formation, evaluated using S. aureus and E. coli bacterial strains. Further, the processed stainless steel surface demonstrated minimum leaching of the toxic elements, significantly enhancing its appeal for bio-implant applications. The observed behavior was explained based on the formation of a stable passive layer, rich in Cr2O3, as determined using x-ray photoelectron microscopy (XPS) and increased hydrophilicity.

Here, we report a facile approach for the development of unique nanoporous MnO2-Cu architecture through a combination of severe surface deformation and dealloying. The severe surface deformation of Cu-Mn alloy prior to selective dealloying resulted in the precipitation of nanoporous MnO2 in the Cu-rich substrate. The in situ grown nanoporous MnO2-Cu architecture demonstrated an areal capacitance of 2.8 F/cm2 at a current density of 5 mA/cm2 and exhibits an excellent cyclic stability of 95% retention for 4000 cycles at 15 mA/cm2 current density. The MnO2-Cu composite structure showed small charge transport resistance of 1.9 Ω as determined using impedance spectroscopy. The asymmetric supercapacitor fabricated using nanoporous MnO2-Cu as anode and reduced graphene oxide as cathode delivers specific energy of 5.55 Wh kg−1 at a specific power of 249.75 W kg−1. The superior performance of nanoporous MnO2-Cu architecture was attributed to its unique microstructure that ensures high surface area, small internal resistance with rapid charge transport. The current approach can be applied to different material systems and is potentially transformative in the emerging field of advanced supercapacitors.

OBJECTIVESRoutine implantation of temporary epicardial pacing wires after surgery for congenital heart disease (CHD) has recently been questioned. We evaluated the incidence of arrhythmias, arrhythmias causing haemodynamic compromise and the safety of a strategy of selective implantation of pacing wires in our unit.METHODSAll patients who underwent surgery for CHD using cardiopulmonary bypass between September 2015 and December 2016 were retrospectively enrolled in the study (n = 313). Patients were stratified into group A (universal implantation) and group B (selective implantation). Group B received pacing wires only when postoperative rhythm disturbances were anticipated based on the operating surgeon’s judgement. The primary outcome was arrhythmia causing haemodynamic compromise. Outcomes were compared between unmatched and propensity matched groups.RESULTSForty-eight patients experienced an arrhythmia causing haemodynamic compromise (15.3%). Twenty-three patients (7.3%) experienced an arrhythmia causing haemodynamic compromise that required the use of pacing wires for therapeutic purposes (group A n = 13, group B n = 10, P = 0.34). There were no pacing wire related complications in either group. All patients in group A and 90% in group B had pacing wires when needed (P = 0.435). In group A, 89% of patients had pacing wires which were not used compared with 13% in group B (P CONCLUSIONSThe probability of developing a postoperative arrhythmia requiring therapeutic pacing can be predicted using the risk factors identified in our study. The routine implantation of pacing wires after surgery for CHD is not necessary. A measured reduction from universal implantation is safe.

Background: Management of hypoplastic left heart syndrome (HLHS) presents many challenges. We describe our institutional outcomes for management of patients with HLHS over the past 12 years and highlight our strategy for those with highly restrictive/intact interatrial septum (R/I-IAS). Methods: Eighty-eight neonates with HLHS underwent surgical treatment, divided equally into Era-I (n = 44, April 2006 to February 2013) and Era-II (n = 44, March 2013 to June 2018). Up to 2013, all patients with R/I-IAS were delivered at an adjacent adult hospital and then moved to our hospital for intensive care and management. From 2014, these patients were delivered at a co-located theatre in our hospital with immediate atrial septectomy. The hybrid approach was occasionally used with preference for the Norwood procedure for suitable candidates. Results: One-year survival after Norwood procedure was 62.5% and 80% for Era-I and Era-II ( P = not significant (ns)), respectively, and 41% of patients were categorized as high risk using conventional criteria. Survival at 1 year differed significantly between high-risk and standard-risk patients ( P = 0.01). For high-risk patients, survival increased from 42% to 65% between eras ( P = ns). In the R/I-IAS subgroup (n = 15), 11 underwent Norwood procedure after emergency atrial septectomy. Of these, seven born at the adjacent adult hospital had 40% survival to stage II versus 60% for the four born at the colocated theatre. Delivery in a colocated theatre reduced the birth-to-cardiopulmonary bypass median time from 445 (150-660) to 62 (52-71) minutes. Conclusion: Reported surgical outcomes are comparable to multicenter reports and international databases. Proactive management for risk factors such as R/I-IAS may contribute to improved overall outcomes.

Biofilm related bacterial infection is one of the primary causes of implant failure. Limiting bacterial adhesion and colonization of pathogenic bacteria is a challenging task in health care. Here, a highly simplistic processing technique for imparting antibacterial properties on a biomedical grade stainless steel is demonstrated. Low-temperature high strain-rate deformation achieved using submerged friction stir processing resulted in a nearly single phase ultra-fine grain structure. The processed stainless steel demonstrated improved antibacterial properties for both Gram-positive and Gram-negative bacteria, significantly impeding biofilm formation during the in vitro study. Also, the processed stainless steel showed better compatibility with human fibroblasts manifested through apparent cell spreading and proliferation. The substantial antibacterial properties of the processed steel are explained in terms of the favorable electronic characteristics of the metal-oxide and by using classical Derjaguin-Landau-Verwey-Overbeek (DLVO) and the extended DLVO (XDLVO) approach at the cell-substrate interface.

Atmospheric degradation of the metallic components initiated by the accumulation of contaminants and humidity significantly limits the performance and sustainability of many engineering systems. Aluminium and its alloys are widely used in different industries such as food processing, marine, aerospace, automobiles and household appliances. The leaching of aluminium can cause significant environmental and health-related issues. In the present study, a facile and environment-friendly (hot water treatment) processing route was utilized to fabricate sustainable Al surfaces without the use of any chemical reagents and toxic solvents. The developed nanostructured Al surface showed immense mechanical, chemical and thermal durability restricting corrosion and leaching of aluminium. The processed Al composed of self-assembled 2D nanostructures showed extreme wettability ranging from superhydrophilic (θ 160°), depending upon post-processing conditions. The developed SHS has showed high water (droplet impacts) and dust repellence under static and dynamic conditions. This is related with effective entrapment of air, prompted by the presence of nanostructured morphology, leading to stable Cassie state. Results showed that SHS possess better self-cleaning ability compared to the superhydrophilic counterpart. The SHS showed better sustainability in terms of high thermal stability in a temperature range of −80 °C to 350 °C and corrosion resistance under prolonged immersion for 48 h in salt media. Compared to unprocessed counterpart, SHS showed 40 times reduction in the corrosion rate, which is significantly high when compared with several other processing routes. The present study showed an eco-friendly and straightforward approach which can be effectively used for fabricating multifunctional metallic surfaces with widespread applications.

Here, an excellent cavitation erosion-corrosion resistance of stainless steel using a novel severe surface deformation technique, reciprocating friction processing (RFP) was demonstrated. The RFP treated stainless steel showed nano-grained, nano-twinned microstructure along with high dislocation density. The RFP treated steel significantly surpassed the performance of advanced structural materials including high entropy alloy (Al0.1CoCrFeNi) and complex concentrated alloy (SiC reinforced Al0.1CoCrFeNi), demonstrating the lowest cavitation erosion and cavitation erosion-corrosion rates for this class of materials. The RFP treated steel demonstrated outstanding corrosion behavior in 3.5% NaCl solution as well. The unusual performance of RFP treated steel is attributed to its excellent mechanical strength and strong passivating behavior.

In this study, a novel processing technique for microstructural refinement of Ni-Cr-5Al2O3 composite coating developed using high velocity oxy-fuel (HVOF) technique is demonstrated. The processing technique, known as stationary friction processing (SFP) is an adaptation of the well-known friction stir processing (FSP). The as-sprayed coating showed a typical lamellar microstructure along with non-homogeneous elemental distribution. The SFP treatment resulted in significant microstructural refinement with complete elimination of splat boundaries and pores together with fully homogeneous elemental distribution. The performance of as-sprayed and processed coatings was evaluated in slurry erosion, erosion-corrosion and pure corrosion in 3.5% NaCl solution. At oblique impingement angle, the SFP treated sample showed minimum erosion rate of nearly 0.1 mm3/h which is 3–5 times lower than the as-sprayed coating and the substrate. For normal impingement, the erosion rate of SFP specimen was nearly 30% lower compared to the as-sprayed coating and the substrate. This is attributed to higher hardness as well as fracture toughness of the SFP treated coating as a result of microstructural refinement. In addition, the SFP treated coating was able to demonstrate superior resistance under erosion-corrosion conditions as well. Further, the processed sample showed lowest corrosion rate of 0.079 μA/cm2, 5–6 times lower than the as-sprayed coating (0.39 μA/cm2). The enhancement in the corrosion resistance of the coating after processing is attributed to complete homogenization of the coating with removal of all splats, splat boundaries, pores and regions of elemental segregation.

Biofilm related bacterial infection is one of the primary causes of implant failure. Limiting bacterial adhesion and colonization of pathogenic bacteria is a challenging task in health care. Here, a highly simplistic processing technique for imparting antibacterial properties on a biomedical grade stainless steel is demonstrated. Low-temperature high strain-rate deformation achieved using submerged friction stir processing resulted in a nearly single phase ultra-fine grain structure. The processed stainless steel demonstrated improved antibacterial properties for both Gram-positive and Gram-negative bacteria, significantly impeding biofilm formation during the in vitro study. Also, the processed stainless steel showed better compatibility with human fibroblasts manifested through apparent cell spreading and proliferation. The substantial antibacterial properties of the processed steel are explained in terms of the favorable electronic characteristics of the metal-oxide and by using classical Derjaguin–Landau–Verwey–Overbeek (DLVO) and the extended DLVO (XDLVO) approach at the cell–substrate interface.

Methamphetamine and its related compounds are among the most widely abused recreational drugs worldwide. While a myriad of clinical complications of methamphetamine use have been described, there is a paucity of literature regarding the effects of maternal abuse during pregnancy on neonatal hearts. In this report, we describe a neonate who underwent Norwood-type palliation and subsequently developed catecholamine-resistant cardiogenic shock, likely related to methamphetamine exposure, which recovered after a period of venoarterial extracorporeal membrane oxygenation support.

Substrate-cell interactions for a bioimplant are driven by substrate's surface characteristics. In addition, the performance of an implant and resistance to degradation are primarily governed by its surface properties. A bioimplant typically degrades by wear and corrosion in the physiological environment, resulting in metallosis. Surface engineering strategies for limiting degradation of implants and enhancing their performance may reduce or eliminate the need for implant removal surgeries and the associated cost. In the current study, we tailored the surface properties of stainless steel using submerged friction stir processing (FSP), a severe plastic deformation technique. FSP resulted in significant microstructural refinement from 22 μm grain size for the as-received alloy to 0.8 μm grain size for the processed sample with increase in hardness by nearly 1.5 times. The wear and corrosion behavior of the processed alloy was evaluated in simulated body fluid. The processed sample demonstrated remarkable improvement in both wear and corrosion resistance, which is explained by surface strengthening and formation of a highly stable passive layer. The methylthiazol tetrazolium assay demonstrated that the processed sample is better in supporting cell attachment, proliferation with minimal toxicity, and hemolysis. The athrombogenic characteristic of the as-received and processed samples was evaluated by fibrinogen adsorption and platelet adhesion via the enzyme-linked immunosorbent assay and lactate dehydrogenase assay, respectively. The processed sample showed less platelet and fibrinogen adhesion compared with the as-received alloy, signifying its high thromboresistance. The current study suggests friction stir processing to be a versatile toolbox for enhancing the performance and reliability of currently used bioimplant materials.