Key Engineering Materials Vol. 933

Abstract: The aim of this research work is identification of optimum drilling parameters to increase material removal rate, dimensional and profile accuracy during drilling. ASTM A516 (Grade70) which is a boiler quality plate of 12 mm thickness was considered as the specimen for conducting the experiments. The experiment was done based on full factorial design using 18 experiments generated using Minitab Software. Two levels for tool material and three levels for feed-speed combination and cutting environment were considered. Two runs were carried out for each trial. The metal removal rate was calculated for each hole drilled. The mean result of the two runs of a trial was taken as the result of the trial. The drilled holes were then tested for their dimensional, profile accuracies. With these results in hand the Artificial Neural Network software was trained to predict the optimized input parameters for drilling a hole of required dimensional and profile accuracies and with required metal removal rate.

Abstract: A novel approach of Micro-electrochemical Texturing (MET) is a realistic substitute for generating surface textures of machined surface. Several conventional and non-conventional techniques i.e., embossing, sand blasting, pinning, LBM, EDM etc. are available for generating microsurface textures, but creates several problems to generate microtextured surfaces which reduce the quality and lower the productivity. To overcome these limitations, this research proposes a unique microsurface texturing method namely, micro-electrochemical texturing, based on electrochemical reaction. Due to the high flexibility of the micro-electrochemical texturing system, micro-texturing features, surface roughness and its performance can be easily changed by varying the micro-electrochemical parameters. In this research paper, this process is developed to fabricate the microsurface textures on stainless steel specimens economically with less time. The experimental results of surface characteristics generated on workpiece utilizing the developed setup with vertical cross flow electrolyte circulation system in micro-electrochemical texturing method are presented. The effects of duty ratio and voltage on performance criteria i.e., material removal rate (MRR), taper kerf angle and surface roughness are investigated. The obtained overall surface roughness value on the stainless-steel samples machined by micro-electrochemical texturing technique is 0.08μm.

Abstract: Recent past witnessed the widespread use of High Strength Low Alloy steels in several structural applications, including pressure vessels, line-pipe transportation of crude oil in the oil industry and many more. API X-65 grade is widely used as a promising material for line-pipe applications in the oil industry. HSLA X-65 plate steels are produced by normalising, Controlled Rolling (CR), Direct Quenching & Tempering (DQT) or Quenching & Tempering (Q&T) techniques. These steels are characterised by their low carbon concentration while maintaining low alloy additions. Micro alloy additions such as V, Ti, and Nb provide substantial precipitation strengthening effect. Strengthening, hardness and microstructural examinations are conducted in all the stages to ascertain X-65 HSLA steel's ageing behaviour.

Abstract: Corten steel is a type of weathering steel possessing high strength with low alloying elements content. The uniqueness of Corten steel lies in its excellent corrosion resistance to elements of nature, and having high strength to weight ratio among the carbon steels. The Corten steel is widely used in fabricating railway coaches, structures like bridges, etc. Even though the Corten steel is weldable, its inherent properties are lost during welding and other thermal processes. The behavior is due to the change in metallurgical and mechanical properties of Corten steel when undergoing processes exceeding the recrystallization temperature. Hence, necessitating the need for this research work. In this research work, the micro hardness, microstructure and grain size of Corten ASTM A242 Grade Steel was evaluated in as received normal condition and at recrystallization temperature. When the material is heated up to recrystallization temperature the formation of new grains is observed. Recrystallization had a positive impact on the microstructure and micro hardness of the Corten steel.

Abstract: EN31 is a high carbon steel, used in manufacturing bearings, punches and gauges because of its better hardness. Heat treatment is one of the major process adopted to improve microstructural and mechanical properties of high carbon steels. The present investigation aims to improve hardness of EN31 high carbon steel through heat treatment. Parameters considered during this investigation were austenization temperature, soaking time, temper temperature and temper time. Microstructure examination was carried out to confirm the phases of heat treated EN31. Taguchi’s orthogonal approach was adopted to minimize the number of experimental runs. Influence of each parameter on the hardness was analyzed. The levels of each parameter were identified that maximize the hardness through S/N ratio. Identified optimal levels of parameters are 900 °C austenization temperature, 30 min soaking time, 150 °C temper temperature and 10 min temper time. A regression model for hardness has been established. Analysis of variance test was used to identify the significant parameters. Finally, the results were validated through confirmation experiments.

Abstract: The aim of the study was to investigate the effect of process parameters on the production of hydrogels with antisolvent precipitation using unpurified (UB) and purified (PB) birch outer bark betulin powder samples. Experimental activities are focused on the production of hydrogels using concentration of colloidal dispersions with filtration of UB or PB sample particles obtained by antisolvent precipitation method varying the dilution of saturated (at boiling temperature) ethanol solutions with different water content. During the study the maximum solubility in ethanol at boiling point of PB (22.0 g/L) and UB (55.0 g/L) was determined. For obtaining gel with the highest liquid content (absorption capacity 37.45 g per 1 g of dry matter) from PB by antisolvent precipitation the optimal saturated ethanol solution dilution with water was 12.5 vol%. In the case of UB hydrogel, by dilution of ethanol from 25 to 10 vol%, a gradual decrease of hydrogel dry matter yield and a simultaneous increase of the filtrate dry matter yield can be observed, which is related with leaching of the particles through the filter paper together with a solution and form a colloidal suspension of particles. For obtaining gels with high liquid content from UB the optimal saturated ethanol solution dilution with water was in the range from 20.0 to 12.5 vol% (absorption capacity in average 18 g per 1 g of dry matter). Comparing the chemical compositions of the raw materials and dry matter of hydrogels in the case of PB composition remains quite similar while in UB dry matter composition the betulin content increased from 52 to even 69 wt%. PB at the optimal dilution of 12.5 vol% of ethanol managed to achieve average particle size - 231.7 nm and with UB in the optimal dilution range from 20 to 12.5 vol% the range of average particle size was from 304.7 to 189.8 nm.

Abstract: Dynamic light scattering (DLS) is a well-established technique to analyze particle size in a liquid medium and sample preparation is an essential step of the analysis to obtain reliable data. In this study, the pretreatment of an aqueous suspension containing betulin particles was studied to characterize the colloidal betulin particles in supramolecular hydrogels obtained by the liquid antisolvent precipitation from purified and unpurified betulin samples. Parameters of two-step homogenization process using rotor and ultrasonic homogenizer, particle concentration, and pH were systematically varied to obtain stable aqueous suspensions that meet the requirements of DLS technique for good particle size analysis. It was found that the purified betulin particles have a higher tendency to agglomerate and their suspension is stable in a narrower concentration and pH range than unpurified. Particle size analysis in suspensions prepared independently shows good reproducibility of sample preparation.

Abstract: Application of the adapted methylene blue (MB) adsorption method in determining specific surface area was investigated on particles containing hydrogels obtained from purified (99 wt%) and unpurified (60 wt%) betulin samples. In order to study the adsorption isotherms of MB on betulin particles in aqueous dispersions, initial concentration of MB was varied. An analysis of the adsorption process with the Langmuir adsorption model was performed. The results indicate that the experimental data fits very well with the Langmuir adsorption model. Straight isotherms are obtained with very good determination coefficients (R²=0.99; R²=1.00), which means that the surface of purified and unpurified betulin particles is homogeneous energetically and a monomolecular coverage forms during adsorption. The MB adsorption method adapted for betulin particles is simple and requires less complex apparatus and time than other methods. The determined specific surface area can be used to characterize the surface properties of betulin particles.

Abstract: Oxidation is a natural part of the aerobic world. Usually oxidation is suppressed by adding various antioxidants. Although a huge amount of antioxidants is known, studies of more active antioxidants which could be used in smaller amounts are crucial. Previously we have demonstrated arylmethyl Meldrum`s acids as promising free radical scavengers. On the other hand various phenol type compounds represent one of the most diverse group of antioxidants. In this study, two types of antioxidants – 1,3-dicarbonyl and phenol – were combined in a single molecule to study the plausible synergistic effects. Vanillic acid was used as a phenolic antioxidant, and Meldrum’s acid was the 1,3-dicarbonyl type antioxidant. The target compound was synthesized in four steps, and its antiradical activity was assessed using the DPPH method. The antiradical activity of the synthesized antioxidant was higher than that of widely used BHT.

Abstract: Fast pyrolysis of pre-treated lignocellulose gives a high yield of levoglucosan and other anhydrosugars, which are considered as the main product. However, the chemical composition of the liquid pyrolysis products is a complex mixture of hundreds of individual compounds. To implement the biorefinery principles, it is important to find applications for the side-streams which arise during levoglucosan production. First, we separated the anhydrosugars by eluting the pyrolysis product water solution through an anion exchange resin column. The anhydrosugars were eluted, but the aromatic by-products were adsorbed on the resin. The by-products were desorbed from the resin with a mixture of methanol/water/acetic acid, and the chemical composition of the obtained by-products was analyzed by UHPLC-UV, and the Folin-Ciocalteu method. Alternatively, the pyrolysis products were separated by crystallization, which yielded levoglucosan with >90% purity, and a mother liquor enriched with aromatic chemical compounds. The antioxidant activity in all samples was evaluated by the DPPH method with corrections to compensate for the color of the by-product samples, which interfered with the UV/VIS spectrophotometry readings.