The tensile, fracture, and fatigue crack growth properties of 316L stainless steel (SS) produced using the selective laser melting (SLM) technique were evaluated and compared with those of ...conventionally manufactured (CM) austenitic SSs. For SLM, both single melt (SM) and checker board (CB) laser scanning strategies were employed, so as to examine the effect of scanning strategy on the mechanical properties. The experimental results show that the SLM alloys' yield strength is significantly higher than that of CM 316L SS, a result of the substantial refinement in the microstructure. In contrast, only a marginal improvement in the ultimate tensile strength and a marked reduction ductility, which are a result of the loss of work hardening ability, are attributed to the absence of stress induced martensitic transformation common in CM austenitic SSs. In spite of these, the fracture toughness, which ranges between 63 and 87MPam0.5, of the SLM alloys is good, which is a result of the mesostructure induced crack tortuousity. The SLM process was found to marginally reduce the threshold stress intensity factor range for fatigue crack growth initiation and enhance the Paris exponent within the steady state crack growth regime. Both tensile and toughness properties were found to be anisotropic in nature. SLM with CB scanning strategy improves both these properties. All these observations on the mechanical properties are rationalized by recourse to micro- and meso-structures seen these alloys.
The microstructure and room temperature mechanical properties of a18Ni (300) grade maraging steel (MS) fabricated using the selective laser melting (SLM) technique were studied, in both before- and ...after-aging conditions. Microstructural analysis reveals fine cellular structure in the as-SLM MS. Upon aging, nanoscale precipitation of intermetallic compounds occurs within the cells, which in turn, result in marked improvements in yield and ultimate tensile strengths, substantial reductions in ductility and fracture toughness, and a transition from dimple to quasi-cleavage fracture morphology. Overall, the mechanical performance, including the fatigue crack growth characteristics, of the SLM MS after aging is found to be similar to that of conventionally manufactured MS of the same grade. Importantly, the reduced ductility does not lead to a reduction in toughness, attributed to the stress induced martensitic transformation as a result of austenite presence in aged SLM MS. Although the SLM alloy possesses a mesostructure, which is a result of line-by-line laser scanning and layer-by-layer building of the components, no significant anisotropy in the mechanical behavior is observed, which is a result of strong metallurgical bonding between adjoining lines and layers. These results are discussed in terms of the meso- and micro-structural features.
•Mechanical properties of SLM maraging steel were studied comprehensively.•Properties of SLM and CM steels are similar, except ductility of aged-SLM.•Reduced ductility does not lead to reduction in toughness.•No significant anisotropy in the mechanical properties was observed.
The electrochemical corrosion resistances of selective laser melted (SLM) 316 L austenitic stainless steel (SS), 18(Ni) 300-grade maraging steel (MS), and Al-12 wt.% Si (AS) alloy in a 0.1 M NaCl ...solution at room temperature were evaluated. The effects of laser scanning strategy (single melt vs. checker board styles), post-SLM heat treatment, and corroding surface orientation (with respect to the scan and build directions) on the corrosion behavior were examined. In all cases, results were compared with those obtained on samples with the same compositions, but manufactured using conventional means. The experimental results show that, for the particular set of experimental conditions employed in this study, SLM in general improves the corrosion resistances of Al-12 wt.% Si and stainless steel alloys and degrades the corrosion resistance of the maraging steel, in comparison to the respective corrosion resistances of their conventionally manufactured counterparts. These results are discussed in terms of microstructural refinement and porosity that are common to the SLM alloys.
Selective laser melting (SLM) of metallic powders is an additive manufacturing technique that is widely employed to produce 3D components, and is fast becoming an important method for manufacturing ...near-net shape and complex metallic parts. In this thesis, a comprehensive investigation on the effect of SLM on the mechanical and corrosion properties of the Al-12Si (AS), 316L stainless steel (SS), and 18(Ni)-300 grade managing steel (MS) is investigated, with particular emphasis on the developing (micro- as well as mesa-)structure -property correlations. Detailed microstructural characterization combined with quasi-static tensile, fracture toughness, fatigue crack growth, and unmatched fatigue tests were conducted. The effect of post-SLM heat treatment as well as the scanning strategy (linear vs. checker board hatch style) was examined and the results are compared with those of conventionally manufactured (CM) counterparts. The SLM alloys exhibit a mesostructured, in addition to the fine cellular structure along the boundaries. In a case of SLM-AS, the fine cellular structure imparts higher strength at the cost of ductility, while the mesostructured, which arises due to the laser track hatching, causes the crack path to be tortuous, and in turn leads to substantial increase in fracture toughness. This imparts significant anisotropy to the toughness while tensile properties are nearly-isotropic.
The experimental results of SLM-SS also show that higher tensile strengths properties with a marked reduction ductility. In spite of these, the fracture toughness, which ranges between 63 and 87 MPa.m0.5, of the SLM-SS is good, which is a result of the mesostructured induced crack tortuousity.Both tensile and toughness properties of SLM-SS were found to be anisotropic in nature. Upon aging SLM-MS, nanoscale precipitation of intermetallic compounds occurs within the cells that, in turn, lead in marked improvements in tensile strengths properties, but substantial reductions in ductility and fracture toughness. Overall, the mechanical performance, except ductility, of the SLM-MS after aging is found to be similar to that of CM-MS. Importantly, the lack of ductility does not lead to a reduction in toughness. Although the SLM-MS alloy possesses a mesostructured, no significant anisotropy in the mechanical behaviour is observed. The unnoticed studies on SLM-AS, -SS, and -MS reveal that the tensile residual stresses, gas-pores, and unmelted powder particles, can degrade the unmatched highest fatigue properties considerably and hence need be eliminated for high fatigue strength. Room temperature, electrochemical corrosion resistances (CRs) of SLM-AS, -SS and -MS in 0.1M NaCl solution were also evaluated and compared with those CM counterparts. While SLM improves CRs of AS and SS, it degrades that of MS. The results are discussed in terms of microstructural refinement and porosity that are common in SLM alloys.
Display omitted
•Consortial (RB + BP1 + BP2) treatment achieved efficient biodegradation of atrazine.•LC-Q-TOF/MS analysis revealed degradation of atrazine in microcosm.•MTT assay on Hep G2 cell line ...confirmed nontoxic metabolites of atrazine.•The PCR-DGGE analysis specifies soil microbial community shift due to atrazine.•Augmented bacteria well-thrived with natural microflora during exposure of atrazine
Intensive use of atrazine in agriculture to increase crop productivity has resulted in pollution and consequently deteriorated the environment. Three isolated bacteria, Rhodococcus sp. BCH2 (RB), Bacillus sp. PDK1 (BP1) and Bacillus sp. PDK2 (BP2) possessing capability to degrade atrazine were used in different combinations (RB + BP1, RB + BP2, BP1 + BP2, RB + BP1 + BP2) to prepare a highly effective bacterial consortium which can significantly reduce the toxicity of atrazine. Cytotoxicity tests evaluated by MTT assay on HepG2 indicated significant decrease in the toxicity of atrazine by the consortium RB + BP1 + BP2 due to its effective degradation and formation of simpler and less/nontoxic metabolites compared to other combinations of consortia. A microcosm study was conducted to check the survivability of this consortium (RB + BP1 + BP2) in the presence of atrazine and indigenous soil microflora for four weeks. LC-Q-TOF/MS analysis revealed that RB + BP1 + BP2 could degrade atrazine to various simple metabolites in the microcosm. The cluster analysis of the DGGE patterns of the microcosm of control-soil, soil exposed to atrazine and soil augmented with consortium in the presence of atrazine (1000 mg kg−1) revealed a shift in microbial community of soil. The microbial dynamics studies suggested that the augmented bacteria were well-thrived with natural microflora during four weeks of exposure to atrazine.
Display omitted
Symmetric supercapacitor is advanced over simple supercapacitor device due to their stability over a large potential window and high energy density. Graphene is a desired candidate ...for supercapacitor application since it has a high surface area, good electronic conductivity and high electro chemical stability. There is a pragmatic use of ionic liquid electrolyte for supercapacitor due to its stability over a large potential window, good ionic conductivity and eco-friendly nature. For high performance supercapacitor, the interaction between ionic liquid electrolyte and graphene are crucial for better charge transportation. In respect of this, a three-dimensional (3D) nanoporous honeycomb shaped sulfur embedded graphene (S-graphene) has been synthesized by simple chemical method. Here, the fabrication of high performance symmetric supercapacitor is done by using S-graphene as an electrode and BMIM-PF6 as an electrolyte. The particular architecture of S-graphene benefited to reduce the ion diffusion resistance, providing the large surface area for charge transportation and efficient charge storage. The S-graphene and ionic liquid-based symmetric supercapacitor device showed the large potential window of 3.2 V with high energy density 124 Wh kg−1 at 0.2 A g−1 constant applied current density. Furthermore, this device shows good cycling performance (stability) with a capacitive retention of 95% over 20,000 cycles at a higher current density of 2 A g−1.
Itaconate is produced from the mitochondrial TCA cycle enzyme aconitase decarboxylase (encoded by immune responsive gene1; Irg1) that exerts immunomodulatory function in myeloid cells. However, the ...role of the Irg1/itaconate pathway in dendritic cells (DC)-mediated airway inflammation and adaptive immunity to inhaled allergens, which are the primary antigen-presenting cells in allergic asthma, remains largely unknown. House dust mite (HDM)-challenged Irg1
mice displayed increases in eosinophilic airway inflammation, mucous cell metaplasia, and Th2 cytokine production with a mechanism involving impaired mite antigen presentations by DC. Adoptive transfer of HDM-pulsed DC from Irg1-deficient mice into naïve WT mice induced a similar phenotype of elevated type 2 airway inflammation and allergic sensitization. Untargeted metabolite analysis of HDM-pulsed DC revealed itaconate as one of the most abundant polar metabolites that potentially suppress mitochondrial oxidative damage. Furthermore, the immunomodulatory effect of itaconate was translated in vivo, where intranasal administration of 4-octyl itaconate 4-OI following antigen priming attenuated the manifestations of HDM-induced airway disease and Th2 immune response. Taken together, these data demonstrated for the first time a direct regulatory role of the Irg1/itaconate pathway in DC for the development of type 2 airway inflammation and suggest a possible therapeutic target in modulating allergic asthma.
In this study, a novel synthetic method for cobalt oxide (Co
O
) nanoparticles using Bos taurus (A-2) urine as a reducing agent was developed. In addition to this ZnO nanorods were produced ...hydrothermally and a nanocomposite is formed through a solid-state reaction. The synthesized materials were characterized through modern characterization techniques such as XRD, FE-SEM with EDS, DLS, zeta potential, FT-IR, Raman spectroscopic analysis, and TGA with DSC. The free radical destructive activity was determined using two different methods viz. ABTS and DPPH. The potential for BSA denaturation in vitro, which is measured in comparison to heat-induced denaturation of egg albumin and results in anti-inflammatory effects of nanomaterial was studied. All synthesized nanomaterials have excellent antibacterial properties, particularly against Salmonella typhi and Staphylococcus aureus. The composite exhibits excellent antioxidant and anti-inflammatory activities in comparison to pure nanomaterials. This reveals that these nanomaterials are advantageous in medicine and drug administration.
The present study is the first report of utilizing Tithonia rotundifolia weed as a substrate for inulinase production from Fusarium solani JALPK. It also deals with the statistical optimization of ...culture conditions to enhance the enzyme yield. Amongst the 11 variables screened by Plackett- Burman design, Inulin in combination with Agave sisalana extract, Tithonia rotundifolia extract and NaNO3 had a significant influence on inulinase production and their concentrations were further optimized employing Box Behnken design. An enhancement of inulinase production from 970 EU/mL to 3261.011 EU/mL was gained after media optimization. Amongst the screened carbon sources Tithonia rotundifolia was found to be very effective in stimulating elevated inulinase synthesis. The Tithonia rotundifolia weed extract was treated with inulinase from Fusarium solani JALPK to form fructose which was estimated spectrophotometrically. This liberated fructose was also confirmed by osazone formation test and FTIR. HPTLC analysis of product revealed the exoinulinase nature of the enzyme produced by Fusarium solani JALPK since fructose was the only end product after hydrolysis of inulin rich weed in fermented broth. Thus the elevated extracellular inulinase yielding novel property of Fusarium solani JALPK (KY914560) contributes in considering it as a potential candidate with food, pharmaceutical and bioremediation applications.
Display omitted
•Fusarium solani JALPK inulinase was employed in hydrolysing Tithonia weed into fructose•Formed fructose has potential benefits in food and neutraceutical industries.•Statistical optimization induced fungal inulinase production by 3.36 fold.•Tithonia rotundifolia weed serves as a cost effective substrate for inulinase.•It is a fungal bioconversion approach to convert waste: weed into wealth: fructose.
•A novel approach of non-dopaminergic remedy for symptomatic antiparkinsonian effects.•First report on elicitor and precursor for enhancement of L-DOPA in in vitro culture.•Quantification of L-DOPA ...and phytochemicals using HPLC and spectroscopic analysis.•System for easy production of purified L-DOPA to improve synaptic availability.
The bioprocess methodology for the enhanced production of phytochemicals using plant cultures predominantly depends on the elicitors and precursors. The drug L-DOPA (anti-Parkinson's drug) (L-3, 4-dihydroxyphenylalanine) has been chiefly isolated from the popular medicinal plant species Mucuna. The present study has been carried out to enhance the production of L-DOPA and other secondary metabolites in the presence of the optimized concentration of growth promoters, elicitors and precursor's in vitro callus culture of Mucuna imbricata. Results revealed that there is a positive influence of Methyl Jasmonate (MJC) and Salicylic Acid (SAC) on the accumulation of L-DOPA and other secondary metabolites (Nutritional and anti-nutritional factors), which enhances their production by more than two folds. The highest accumulation of L-DOPA was noticed in the elicitation of 1 mM MJC (4.3 ± 0.4 %) followed by 1 mM SAC (3.4 ± 0.08 %) on 45th and 30th days respectively. Results also illustrated a significant increase of callus biomass (dry and moist weight) as well as total phenolics, flavonoids and antioxidants values in the elicited callus from day 30th to day 45th of explant inoculation which indicates a synergistic interaction of auxin, cytokinins with elicitors and precursors respectively. Additionally, results revealed that improved accumulation of carbohydrates was positively correlated with an increase in L-DOPA content in the elicited callus. Hence the protocol formulated delivers an effective alternative for mass production of L-DOPA from callus culture with improved metabolite content.
PDF
