High Cr Research Articles

Wear behaviour and coating performance of WC–Cu composite electrodes on ZE41A magnesium alloy using electrospark deposition

ABSTRACT Magnesium alloys, being relatively softer than other structural metal, has lower hardness and is prone to wear under abrasive and frictional conditions. To enhance their wear and abrasion resistance, tungsten carbide-copper (WC-Cu) composite coating was developed on ZE41A magnesium alloy using electro-spark deposition (ESD). The composite electrodes, with combinations of 50:50 and 70:30 was prepared using powder metallurgy. ESD parameters, including spark current (SC), pulse-on time (Ton) and pulse-off time (Toff) were selected for coating. Wear behaviour was evaluated using pin-on-disc tribometer under varying sliding parameters; applied load (20N–40N), sliding speed (150 rpm–350 rpm), and sliding time (5 min–9 min). The WC70:Cu30 electrode coating exhibited the highest CR of 0.00298 gm/min and maximum layer thickness of 92.12 μm, attributed to thermal conductivity of tungsten. EDS analysis confirmed higher deposition of Cu (18.68%) and WC (3.58%) in the WC70:Cu30 coating compared to WC50:Cu50, which showed Cu (11.33%) and WC (3.06%). The lowest WR of 0.000185 mm3/min was achieved with the WC70:Cu30 coating due to higher WC deposition. SEM analysis revealed wear mechanisms such as scratch, delamination, grooves, and adhesive wear. The WC70:Cu30 composite electrode improved performance with higher CR and lower WR compared to WC50:Cu50.

Mechanistic insight into the simultaneous removal of Cr(VI) and phosphate by a novel versatile bimetallic material

Industrial wastewater containing hexavalent chromium Cr(VI) and phosphate poses a great threat to human health and the aquatic ecological environment. In this study, a novel La(OH)3- and CaO2-fabricated CNT (La-Ca-CNT) material was developed for the simultaneous and highly effective removal of aqueous Cr(VI) and phosphate. Characterization results showed that synergistic effects existed between the CNT support and La and Ca species. La-Ca-CNT showed high phosphate and Cr(VI) removal rates in acidic conditions with high stability. Kinetic study suggested that the fast adsorption of phosphate on La-Ca-CNT was controlled by intraparticle diffusion. The removal of Cr(VI) and phosphate interacted with each other, and the removal of Cr(VI) went through a slow-fast-slow reaction, reaching a Cr(VI) removal rate of over 97% within 180min. La-Ca-CNT had a high phosphate adsorption capacity (174.3mg/g), and over 70% of the adsorbed phosphate could be recovered. The presence of co-existing anions showed negative effects on phosphate adsorption but negligible effects on Cr(VI) reduction, while organic carbon in natural water showed no effect on phosphate and Cr(VI) removal. A mechanistic study revealed that phosphate was removed by physical-chemical adsorption (outer-sphere complexation and ligand exchange) over La-Ca-CNT, while Cr(VI) was reduced by H2O2 generated from CaO2 or directly by surface CaO2.

Enhancing source identification of water-soluble heavy metal contamination in urban road sediments: a receptor model approach for water and sediment quality in a Chinese metropolitan area

Abstract This study investigates the concentrations and sources of 8 heavy metals in urban road sediments and a total of 116 samples were collected from 29 locations, with four samples per location from Zhengzhou, China. Pb concentrations significantly exceeded background values, while Hg levels showed variability across locations. Pollution indices reveal that Cu and Cd, two hazardous metals, contribute significantly to urban road dust pollution. Notably, Hg shows high contamination levels, while Pb and Cr exhibit moderate contamination. The measured concentrations of the heavy metals are: Cr (28.32 μg l–1), Cu (334.65 μg l–1), Cd (2.87 μg l–1), Ni (83.20 μg l–1), Zn (204.10 μg l–1), As (45.10 μg l–1), Pb (4.11 μg l–1), and Hg (0.27 μg l–1). Using principal component analysis (PCA), three primary components (PC1, PC2, and PC3) were identified, explaining 86.85% of the variance in heavy metal concentrations. PC1, dominated by Cr and Pb, suggests industrial activities as the main source. PC2, influenced by As and Cd, reflects pollution from agrochemical use, while PC3, with high Ni values, indicates sources from alloy production and electroplating processes. These findings highlight the urgent need for targeted environmental management strategies to mitigate the health and ecological risks posed by heavy metal contamination in urban environments.

Understanding the atomic-scaled evolution mechanism of V and Cr in V slag with high Cr content during magnesiation roasting toward tailing toxicity minimization

Understanding the atomic-scaled evolution mechanism of V and Cr in V slag with high Cr content during magnesiation roasting toward tailing toxicity minimization

Thermodynamic Study on the Solubility of N in High Cr, Ni and Mo Content Fe-Cr-Ni-Mo-O Melts

The aim of the present study is to investigate the solubility of nitrogen in super or hyper duplex stainless steel, which is characterized by a very high Cr content, as well as the activity interaction parameters between N and other alloy elements. The chemical equilibrium method was employed in the present experiment. High Cr, Ni, and Mo content Fe−Cr−N−O and Fe−Cr−Ni−Mo−N−O melt are equilibrated at 1873 K under atmospheres of pure nitrogen and Ar/N2 gas mixture. The melts were placed in Al2O3 crucibles and coated with graphite crucibles. The experimental results showed that the solubility of N significantly increased with increasing Cr content, reaching over 1 wt pct at a Cr content of about 40 wt pct. In addition, the solubility of Cr increased slightly with a decrease in Ni content and an increase in Mo content. The activity interaction parameters were fitted using WIPF (Wagner’s Interaction Parameter Formalism), as shown as follows: eNCr=−0.07083, rNCr=+0.0005888, rNN=−0.00926, eNNi=+0.30885, rNNi=−0.03963, eNMo=−0.05882, rNMo=+0.00616; the comprehensive set of thermodynamic basic parameters obtained in this study can be effectively used to assess the N solubility in USSD with a Cr content exceeding 30 wt pct.

Near-infrared fluorescent probe for visualization of nitroxyl in the plant response to stress

BackgroundNitroxyl (HNO) is an emerging signaling molecule that plays a significant regulatory role in various aspects of plant biology, including stress responses and developmental processes. However, understanding the precise actions of HNO in plants has been challenging due to the absence of highly sensitive and real-time in situ monitoring tools. Consequently, it is crucial to develop effective and accurate detection methods for HNO. Establishing such methodologies will enable researchers to elucidate the functional roles of HNO in plant physiological processes, thereby advancing our knowledge of plant resilience and adaptation under environmental stressors. ResultHerein, we successfully constructed a near-infrared fluorescent probe, DCIF-HNO, based on the dicyanoisophorone platform as fluorophore and 2-(diphenylphosphino)benzoate as HNO recognition site for identifying HNO in plants. Probe DCIF-HNO exhibited rapid response, excellent selectivity, and high sensitivity to HNO in vitro spectroscopic tests, while also demonstrating low toxicity and biocompatibility. A rapid and portable smartphone sensing platform for HNO in actual samples was successfully constructed based on probe DCIF-HNO and color recognition application. Moreover, probe DCIF-HNO was successfully applied to plant cells and tissues, enabling real-time visualization and detection of HNO and revealing the complex network of HNO interactions during H2S/NO crosstalk in plants. Furthermore, the increase in HNO levels in plants response to high salt and Cr stress was observed using probe DCIF-HNO. Transcriptome sequencing and differential metabolites analysis were employed to gain insight into the mechanism of HNO production under Cr stress. SignificanceDue to the optical properties and high-resolution imaging capabilities of DCIF-HNO, this study offers a novel framework for elucidating the signaling role of HNO in plant stress responses. The precise visualization of HNO dynamics enhances our understanding of the complex molecular pathways involved in plant adaptation to abiotic stressors. This research not only advances plant physiology but also has significant implications for developing strategies to enhance agricultural resilience in challenging environmental conditions.

Fe-isotopic evidence for hydrothermal reworking as a mechanism to form high-grade Fe-Ti-V oxide ores in layered intrusions

The genesis of high-grade Fe-Ti-V oxide ores (up to >90 vol%) in layered intrusions remains highly debated. Here, on example of Hongge layered intrusion in China, we show that hydrothermal dissolution and precipitation of Fe-Ti-V oxides played a critical role in forming high-grade massive ore deposits as demonstrated by textural-compositional evidence and in-situ iron isotope data (δ56Fe), analyzed with femtosecond laser ablation multicollector (LA-MC-) ICP-MS. Hongge is a mafic layered intrusion composed of a Lower olivine clinopyroxenite Zone (LZ), a Middle clinopyroxenite Zone (MZ), where thick massive ore layers (with up to 90 % Fe-Ti-V oxides) formed, and an Upper gabbro Zone (UZ). Magnetite in Hongge exhibits two contrasting generations: 1) Mag1, observed in all lithological zones and formed at the magmatic stage, has extensive ilmenite exsolution lamellae and high Ti and Cr content. The δ56Fe of Mag1 shows considerable variations from −0.23 to 0.63 ‰ and strikingly an offset of ∼0.3 ‰ towards lower values in the massive ore zone compared to the zones below and above; 2) Mag2, concentrated mainly in thick massive ore layers in MZ without exsolution lamellae, is almost pure magnetite (with low Ti, Al content) and has extremely low δ56Fe values (−1.24 to −0.09 ‰), indicating precipitation from Fe-enriched hydrothermal fluids. Similarly, the δ56Fe of ilmenite shows significant variations from −1.08 to −0.27 ‰ and is significantly lower than typical values for igneous ilmenite (−0.4–0 ‰). Ilmenite displays a similar Fe isotope variation pattern to Mag1 along the stratigraphic position, i.e., with significantly lower δ56Fe in the massive ore zone. As magnetite and ilmenite together contain essentially all Fe, the isotopic shift of these minerals in the ore zone translates to a bulk isotopic offset of ∼−0.3 ‰ compared to the zones below and above. This requires a bulk flux of isotopically light Fe resulting in Fe enrichment in this zone to form massive or even monomineralic ores. The very light isotopic values, particularly hydrothermal magnetite (Mag2) and petrologic evidence, strongly indicate that the Fe flux into the massive ore layers occurred during hydrothermal reworking. This scenario is furthermore supported by magnetite-ilmenite elemental and isotopic thermometry, according to which Fe-Ti oxides experienced hydrothermal re-equilibration in a temperature range of 400–300 °C. Iron isotopic mass balance calculations imply that ∼20–30 % of the Fe in the thick massive ore layers may result from secondary enrichment through hydrothermal precipitation, significantly increasing the ore tonnages and grades. Potentially, other layered intrusions experienced similar mechanisms of hydrothermal Fe enrichment, which will have to be proven in future investigations.

Biosynthesised bentonite clay-based Cu nanocomposite using Punica granatum L. peel extract for the effective catalytic reduction of hazardous aqueous contaminants

ABSTRACT This article describes a facile and green one-pot synthetic process of Cu nanoparticles loaded on bentonite composite (5Cu wt.%/bentonite) using the peel extract of pomegranate (Punica granatum L.) as a reductant. The 5Cu wt.%/bentonite composite was adopted as a heterogeneous catalyst for the NaBH4-assisted reductive degradation of Methylene Blue (MB) dye. The prepared 5Cu wt.%/bentonite composite demonstrated high catalytic efficiency in reducing MB, achieving almost complete reduction within a reaction duration as short as 60 seconds. Indeed, Cu nanoparticles act as electron relays, facilitating the electron transfer from BH4 − anions to MB dye, leading to its conversion into the colourless Leuco-Methylene Blue (LMB). The reduction rate corresponded nicely with the pseudo-first-order kinetic model, with the corresponding normalised rate constant (Knor) value computed as 1.48 min−1 mg−1, outperforming numerous previously documented metal-containing catalysts. Remarkably, the catalyst can straightforwardly be reused, with almost constant reduction efficiency observed across 5 successive catalytic cycles. Furthermore, 5Cu wt.%/bentonite was used in another catalytic reduction reaction, involving the reduction of the toxic Cr(VI) to environmentally benign Cr(III) adopting formic acid as a reducing agent under ambient conditions. The 5Cu wt.%/bentonite catalyst not only showed a high Cr(VI) reduction efficiency of 95.5% within 30 min but also outstanding reusability of 93% removal of Cr(VI) following 5 cycles, demonstrating its catalytic versatility. The Cr(VI) reduction mechanism involves the dehydrogenation of formic acid on the catalyst surface, followed by hydrogen transfer converting Cr(VI) into Cr(III). Based on the straightforward and green synthetic strategy, use of cost-effective and readily available raw materials, excellent catalytic activity, catalytic versatility, and outstanding reusability, the 5Cu wt.%/bentonite composite seemed to be an ideal catalyst for the real-world reduction of harmful aqueous pollutants to achieve environmental sustainability.

Highly efficient reduction of Cr(VI) from industries sewage using novel biomass-driven carbon dots modified TiO2 under sunlight

Hexavalent chromium (Cr(VI)) pollution poses a significant global environmental challenge, with current photocatalysts exhibiting limited efficiencies under natural sunlight, especially in neutral to alkaline conditions or at high Cr(VI) concentrations. In this study, amine-rich biomass-derived carbon dots (CDs) were synthesized from peanut shells and ethylenediamine via a hydrothermal method, combined with titanium dioxide (TiO2) to form a composite with a narrower band gap. This enhanced the electrostatic interactions with Cr(VI), thus improving photocatalytic performance. The composite (1 % CDs) effectively reduced 50 mg/L of Cr(VI) within 60 min under sunlight irradiation, demonstrating stable performance across various pH levels (3, 5, 7, and 9) and Cr(VI) concentrations (10 to 60 mg/L). Even after five cycles, the reduction efficiency remained high at 96.83 %. The composite also achieved reduction rates of 90.09 % and 89.01 % for domestic and electroplating wastewater, respectively, while exhibiting antibacterial properties. Free-radical scavenging experiments confirmed that electrons and holes were the primary active species driving the reduction. This work highlights the potential of the composites for efficient and stable Cr(VI) reduction in real-world water treatment applications.

Microbes mediated alleviation of chromium (Cr VI) stress for improved phytoextraction in fodder maize (Zea mays L.) cultivar

This study investigates the potential of chromium (VI) resistant bacterial isolates to alleviate heavy metal stress in fodder maize plants and enhance phytoremediation. Twenty-one bacterial strains were isolated from contaminated water, with five strains; Bacillus thuringiensis (BHR1), Bacillus cereus (BHR2), Enterobacter cloacae (BHR4), Bacillus pumilus (BHR5), and Bacillus altitudinis (BHR6) selected based on their significant plant-growth promoting (PGP) traits and heavy metal tolerance. Under chromium (Cr VI) stress, the BHR1 strain significantly improved seed germination, seedling length and vigor index of fodder maize variety (J 1007) especially at 150 mg/L Cr (VI), where these parameters increased by 3.75, 3.23 and 6.44 folds, respectively. After 60 days, BHR1 also enhanced shoot and root lengths by 4.91 and 4.06 folds, respectively and increase fresh and dry biomass, especially at higher Cr (VI) concentrations. Photosynthetic pigments, chlorophyll a and b, were also elevated by 3.04 and 2.26 times, respectively. Additionally, BHR1 reduced oxidative stress markers, including proline and malondialdehyde (MDA), and decreased electrolyte leakage, thus improving membrane stability. The strain further increased antioxidant enzyme activities and chromium uptake in root and shoot tissues, enhancing the translocation factor by 95%. This suggests that BHR1 can significantly promote fodder maize growth and accelerate chromium removal from contaminated soil, offering valuable insights into plant-microbe interactions under Cr (VI) stress.

Assessing metals and metalloids impact of roadside dust on human health in Osogbo, Osun state, Nigeria

BackgroundMetals and metalloids in roadside dust pose considerable threats to both human health and the environment. ObjectivesThis study assesses human health risks of metal exposure to roadside dust by conducting a health risk assessment (HRA) for metals and metalloids uptake rates for children and adults via exposure pathways. MethodsSettled dust samples were collected from the major roads in Osogbo, Osun state. These samples were subjected to standard laboratory procedures for metals and metalloids analysis using Atomic Absorption Spectroscopy (AAS). ResultsAll the metals and metalloids except Cd had their concentration below the WHO limit. The average concentration of Cd was 1.54 mg kg-1, significantly above the WHO guideline of 0.80 mg kg-1, indicating a possible health concern. A strong positive correlation exits between Ni and Cd (0.774⁎⁎) (p < 0.01), Pb (0.662⁎⁎) (p < 0.01), Zn (0.606⁎⁎) (p < 0.01), and as (0.549*) (p < 0.05), showing that greater Ni concentrations are associated with higher concentrations of Cd, Pb, Zn, and As. Two principal components were identified, accounting for 80 % of the overall variation. PC1 has an eigenvalue of 60.834; however, PC2 has a higher eigenvalue of 74.952, implying that PC2 explains more of the variation in the data than PC1. Non-carcinogenic risk evaluations identify possible health risks linked with Cu, Cd, Cr, and As exposure, primarily through inhalation routes. Carcinogenic risk showed that Cd demonstrated high CR values ranging from 3740 to 1.30×1012 for adults and children throughout the study's various exposure paths. ConclusionThis study offered significant insight into the metals and metalloids pollution status in Osogbo, Nigeria, employing data and statistics, highlighting the need for evidence-based actions for environmental preservation to safeguarding people's health.

Origin of the Oligocene–Miocene Sailipu ultrapotassic volcanic rocks in southern Tibet: Melting of Asian mantle pyroxenites triggered by eastward tearing of the subducting Indian continental slab

Widely distributed Oligocene−Miocene ultrapotassic volcanic rocks in the Lhasa terrane of southern Tibet have been associated with the melting of the lithospheric mantle, plateau uplift, and porphyry Cu-Au mineralization. This study presents the mineral chemistry of olivine and clinopyroxene phenocrysts, whole-rock major and trace element data, and zircon U-Pb geochronological and Hf isotopic data for the Sailipu primitive ultrapotassic volcanic rocks. The Sailipu volcanic rocks exhibit high MgO (5.6−11.4 wt%), Cr (386−981 ppm), Co (22−43 ppm), and Ni (95−423 ppm) concentrations and have highly fractionated rare earth elements [REEs; (La/Yb)N = 23−73] and high-Fo (89.1−90.8) olivine phenocrysts containing elevated NiO (up to 0.59 wt%), which suggests a pyroxenitic mantle source that partially melted in the garnet stability field. Their high K2O contents (4.8−8.0 wt%) and global subduction sediment-like trace element patterns suggest that the metasomatic agents, which reacted with mantle peridotites to form phlogopite-bearing pyroxenites, were dominantly derived from the melting of subducted continental sediments. Their high whole-rock Ba/La and Th/Nd ratios are consistent with this hypothesis. The Sailipu ultrapotassic volcanic rocks also exhibit low initial 176Hf/177Hf ratios that resemble those of Himalayan leucogranites, and high Ca contents in olivine phenocrysts, which is consistent with contributions from the subducted carbonate-rich sedimentary strata on top of the thinned Greater Indian continental crust. The zircon U-Pb chronological data yielded concordant ages of 24.33 ± 0.19 Ma, 21.20 ± 0.62 Ma, and 17.05 ± 0.31 Ma for different exposures of the Sailipu volcanic rocks, which establishes a maximum age of ca. 24 Ma for these rocks. The northwest−southeast spatial distribution and the southeastward decrease in age (80°E−90°E) suggest west-to-east tearing of the thinned Greater Indian slab, which caused asthenospheric upwelling and melting of the Tibetan lithospheric mantle. Geothermometric calculations show relatively high primary magma temperatures (∼1250 °C) that are consistent with asthenospheric upwelling. We propose a mechanism that could genetically link the coeval Cu-Au ore-forming granitoids with the ultrapotassic magmatism of the Gangdese belt. The ultrapotassic rocks supply a large-volume of external magmatic volatiles, particularly H2O, which could trigger melting of the Tibetan lower crust and lead to the generation of the ore-forming granitoids and the establishment of oxidizing conditions for porphyry deposits. The oxygen fugacity (log ƒO2 values of ΔFMQ) of the primitive Sailipu ultrapotassic volcanic rocks (ΔFMQ = 0.48 ± 0.51 based on the Dol/melt V oxybarometer and ΔFMQ = 0.33 ± 1.19 according to the magmatic zircon U-Ce-Ti oxybarometer) is slightly lower than that of porphyry Cu-Au ore-forming granitoids in the eastern Gangdese (ΔFMQ = +0.8 to +2.9), which suggests that the direct injection of ultrapotassic melts into ore-forming granitoids played a limited role in changing oxygen fugacity, but more oxidized fluids/volatiles exsolved from these ultrapotassic melts may have facilitated the remelting of sulfide-bearing lower crust and/or directly scavenged sulfides from the mush-state reservoirs of the ore-forming granitoids in the middle−upper crust.

Investigation of softening in hardfaced layers during welding

Hardfacing is a widely used technique to create wear-resistant layer on the base material to ensure good durability and performance under harsh operating conditions. However, despite its effectiveness in improving wear resistance, hardfaced layers can sometimes exhibit softening phenomena during welding, compromising their mechanical properties and overall performance. In this research, the effect of heat input was investigated in case of Fe-based hardfacing material with high Cr content. 4 different heat inputs were applied with gas metal arc welding and significant differences were determined in hardnesses, which can be influential to the lifetime of hardfaced parts. Hardness drop happens in the heat-affected zones between the hardfaced layers and the highest heat input causing the most significant softening (20% hardness drop).

Unraveling the Subsurface Damage and Material Removal Mechanism of Multi-Principal-Element Alloy FeCrNi Coatings During the Scratching Process

Multi-principal-element alloys (MPEAs) exhibit superior strength and good ductility. However, tribological properties of FeCrNi MPEAs remain unknown at nanoscale and complex environments. Here, we investigate the effects of scratching speed, depth, and temperature on microstructural and tribological characteristics of FeCrNi using molecular dynamics simulations combined with an elevated temperature tribological experiment. The scratching force experiences the increase stage, the undulated stage, and the stable stage due to chip formation. Compared to traditional alloy coatings, low force enhances the useful life. With increased speed, the friction coefficient decreases, agreeing with previous work. High speed impacting includes severe local plastic deformation, from dislocation to amorphization. As the scratching depth increases, the average scratch force and friction coefficient increases owing to material accumulation in front of the abrasive particles. The surface morphology and dislocation behavior are significantly different during the scratching process. In addition, we revealed a temperature-dependent friction mechanism. FeCrNi MPEAs have excellent wear resistance at an intermediate temperature, which is attributed to the high Cr content promoting the formation of the compact oxide layer. This work provides atomic-scale mechanistic insights into the tribological behavior of FeCrNi, and would be applied to the design of MPEAs with high performance.

Origin and metamorphism of ophiolitic serpentinites from the Yuli belt, eastern Taiwan: new findings and tectonic implications

ABSTRACT Serpentinites associated with metamafic and metaplagiogranitic rocks occur sporadically within metasedimentary schists in the Yuli belt. Such metaigneous rocks are considered to represent ophiolitic protoliths and some contain high-pressure (HP) metamorphic minerals or assemblages. However, the origin and metamorphism of these serpentinites have long been a mystery. This study systematically investigates the four major serpentinite-bearing exposures at the Fengtien, Wanjung, Tsunkuanshan, and Chinshuichi. The results reveal that the serpentinites are of two different protoliths on the basis of relict chromian spinel composition. Cr-spinel compositions of the Fengtien and Tsunkuanshan samples are characterised by moderate Cr# [Cr/(Cr + Al)] (0.45–0.57), relatively high Mg# [Mg/(Mg+Fe2+)] (0.59–0.79), but low Fe3+# [Fe3+/(Fe3++Cr+Al)] (0.02–0.06), reflecting an abyssal peridotite type protolith. By contrast, Cr-spinel compositions of the Wanjung and Chinshuichi samples show high Cr# (up to 0.74) and Fe3+# (0.03–0.08), but low Mg# (<0.6), indicating a forearc mantle peridotite origin. Peak metamorphic conditions of the serpentinites are represented by the assemblage of antigorite + magnetite + chlorite + olivine + diopside, which is estimated as up to 550°C but the pressure cannot be constrained quantitatively. Based on field relations, it is inferred that the serpentinites, associated HP metaigneous rocks, and garnet-bearing metasedimentary schists were metamorphosed isofacially. Despite two origins, the peridotitic protoliths were all subjected to hydration and subduction processes. We suggest that precursors of the serpentinites, metaigneous rocks, and metasedimentary schists were juxtaposed and metamorphosed at intermediate to great depths (~35–55 km) of a subduction zone. Therefore, the Yuli belt serpentinites and associated rocks likely represent exhumed materials from a palaeo-subduction interface.

On the formation of oxide inclusions in the high nitrogen chromium-manganese steel produced by the Wire and Arc Additive Manufacturing

Oxide inclusions significantly impeded the mechanical properties of the Wire and Arc Additive Manufacturing (WAAM) made high nitrogen Cr–Mn austenite stainless steels (HNSs). This paper focused on the inclusions' component, crystallization characteristics and formation mechanism. Results revealed that there are two types of inclusions: the round-shape nano-size inclusion (Type-I) and the micron-size island-shape inclusion (Type-II). The Type-I inclusion usually consists of the MnO particle or the combination of the MnO, Si-oxides and precipitations (MnS or Cr2N). Most of the Type-I oxide inclusion is located in the range between 300 nm and 700 nm,the number of Type-I oxide inclusion takes the main part of 69.7%.With higher content, smaller size and more even distributions, the isolated Type-I oxide inclusions would be beneficial to the mechanical properties owing to the Orowan strengthening mechanism. The Type-II inclusion is mostly composed of the MnO matrix and the coherent chromite spinel (MnCr2O4). In general, the larger the size, the more serious the negative impact on mechanical properties. And there was a strong negative correlation between the size and quantity of type II oxide inclusions. After heat treatment, abundant phase transformations occurred in the Type-II inclusions and some harmful phases (Sigma, MnS et cl.) were often found in or around the inclusions with specific orientation relationships. During deposition, the unstable droplet transformation and the trapped residual slag were the main causes for the inclusions in the molten pool.

Risk factors for postoperative hepatic dysfunction in overweight patients with acute type A aortic dissection

BackgroundAcute hepatic dysfunction (AHD) is a common postoperative complication in patients with acute type A aortic dissection. The aim of this study was to identify risk factors for acute hepatic dysfunction after surgery for acute type A aortic dissection.MethodsWe performed a retrospective study from March 1, 2019, to February 28, 2021. The primary endpoints of this study were morbidity due to AHD and risk factors for incidence. Univariate analysis and multivariate logistic regression analysis were used to analyse the related factors, and receiver operating characteristic (ROC) curves were plotted to evaluate their predictive value.ResultsAmong 147 patients, 29 (19.73%) developed postoperative acute hepatic dysfunction, and 9 (6.12%) died. Univariate analysis revealed that the ALT (P = 0.042), Cr (P < 0.001), and BUN (P = 0.008) levels were significantly different between the two groups. Multivariate logistic regression analysis revealed that Cr (OR = 1.013, 95% CI = 1.003–1.023, P = 0.008) was an independent risk factor for postoperative hepatic dysfunction in overweight (BMI > 24) patients with ATAAD. The area under the ROC curve (AUC) for Cr was 0.745 > 0.7, indicating good predictive value.ConclusionA high Cr concentration is an independent risk factor for postoperative AHD in overweight (BMI > 24) patients with ATAAD.

Effect of Cr:C ratio on open three-body wear resistance of squeeze cast high chromium cast iron

A series of high chromium white cast iron (HCCI) alloys with varying Cr:C ratios were designed and fabricated through the squeeze casting process. This study investigates the effect of the Cr:C ratio on the mechanical properties, microstructure, phase diagram, and both low-stress and high-stress abrasion performance of HCCIs. Alloys with a very high Cr:C ratio exhibited better impact toughness but poorer hardness. Scanning electron microscopy (SEM) and phase diagram calculations elucidated the influence of the Cr:C ratio on microstructure, carbide volume fraction, and carbide type. Abrasion resistance was evaluated using impact abrasive wear (high-stress) and rubber-wheel (low-stress) abrasion on quartzite in open three-body wear. Comprehensive assessments under impact abrasive wear and rubber-wheel abrasive wear conditions suggest that the alloy achieves optimal abrasion resistance with a Cr:C ratio ranging from 8 to 11. Post-wear analysis reveals that surface damage varies between high-stress and low-stress conditions. The microstructure of squeeze HCCIs is significantly influenced by the Cr:C ratio, resulting in diverse operative wear mechanisms, including micro-cutting and micro-fracture. Successful adjustment of the Cr:C ratio led to the attainment of a nearly eutectic HCCIs composition suitable for squeeze casting.

Optimizing propylene production via acetone hydrodeoxygenation: Insights from catalytic studies with Cu/γ-Al2O3 and Hβ zeolite

Propylene is a crucial light olefin in the petrochemical industry and can be produced via acetone hydrodeoxygenation, which involves two sequential reactions: first, acetone undergoes hydrogenation catalyzed by metallic sites, followed by the dehydration of the resulting isopropanol catalyzed by acidic sites. In this study, propylene production through acetone hydrodeoxygenation was investigated using a physical mixture of 35 wt% Cu/γ-Al2O3 and Hβ zeolite to investigate how various reaction parameters affect acetone conversion and propylene yield. Using the experimental design methodology, empirical models were developed to correlate acetone conversion (Xacet) and propylene yield (Yprop) with the ratio of 35 wt% Cu/γ-Al2O3 to Hβ (CR), total catalyst weight (Cw), hydrogen volumetric flow rate (FH2) and reaction temperature (T). The maximum propylene yield achieved in the catalytic tests was 73.46 %. A long-term test demonstrated the catalyst's reusability, remaining active even after 22 hours of reaction with only a slight decrease in propylene yield. Analysis of the experimental data revealed that increasing T and Cw positively affected propylene yield, whereas higher CR and FH2 had negative effects. According to the Pareto chart, reaction temperature was the most influential variable for propylene yield, followed by CR, FH2 and Cw. For acetone conversion, the order of significance among the variables was T >CR >Cw >FH2.

Recovering chromium from electroplating sludge using an integrated technology of bipolar membrane electrodialysis and H2O2 oxidation

Chromium electroplating produces Cr(III)-containing electroplating sludge (EPS) in large volumes, which is easily oxidised to Cr(Ⅵ) and is harmful to the environment and human health. This study recovered Cr(III) as Na2CrO4 from EPS using an integrated bipolar membrane electrodialysis (BMED)–H2O2 oxidation technology. During the treatment process, Cr(III) was oxidised to Cr(VI) using H2O2 in an alkaline environment, BMED was used to separate and recover Cr(VI). Experimental results showed that H2O2 dosage and pH affected Cr(III) oxidation—the highest Cr(III) oxidation ratio of 68.4% was observed when H2O2 dosage and pH were 5.5 mL and 12.0, respectively. The current density, solid/liquid ratio and sludge particle size affected Cr(III) recovery, energy consumption and current efficiency. Under a current density of 20.0 mA/cm2, solid/liquid ratio of 1.0:45 and sludge particle size of 100 mesh, 58.2% of Cr(III) was recovered. When the number of the equipped EPS compartments was increased from one to two and three, the specific energy consumption decreased from 1.04 to 0.87 and 0.81 kW h/g, respectively, but the current efficiency remained almost constant. After EPS treatment, the Cr(III) remaining in the sludge was mainly in the residual state, which is less environmentally harmful. The obtained Na2CrO4 had similar properties according to X-ray diffraction analysis. Thus, the proposed integrated technology effectively recovers Cr(III) from EPS and other chromium-containing solid wastes.