Regita Bendikiene

Characterization of waste printed circuit boards recycled using a dissolution approach and ultrasonic treatment at low temperatures

Recently, the separation of waste printed circuit boards (WPCBs) using organic solvents has become more prevalent because it is an environmentally friendly and efficient technique. However, the relatively high temperatures (∼135 °C) used during the separation process lead to higher energy consumption, faster solvent degradation, and possibly higher emissions of toxic fumes. This work aims to develop a new approach to separate all layers of WPCBs at lower temperatures to avoid the above-mentioned drawbacks. Di-methyl formamide (DMF) was used in the present technique as an organic solvent, while ultrasonic treatment was applied in order to accelerate the breakage of the internal van der Waals bonds of brominated epoxy resin (BER), thus decreasing the separation time. The experiments were conducted on five WPCB samples with the same surface area of 100 mm2, cut from five different WPCB models. The experiments were carried out at 25 °C (used as a reference), 50 °C, and 75 °C to study the effect of heating rate on the separation time and on the concentration of the BER dissolved in DMF. Ultraviolet-visible spectroscopy, metallographic microscope, and SEM-EDS were used to examine the recovered BER and fiberglass structure as well as the main metal compositions of each sample, respectively. The results showed that separation time and concentration of BER strongly depended on the WPCB models. In addition, the dissolution process at 50 °C resulted in the concentration of BER close to 25 °C for most of the models, while the concentration was lowest at 75 °C. At the same time, the trend in separation time was exactly opposite, with 75 °C resulting in the fastest separation time and 25 °C in the slowest. This facile approach appears promising for its potential applications in WPCB recycling and could be applied on an industrial scale.

Investigation of periodical microstructures using coherent radiation

Low-cost effective characterization methodology was developed that allows indirect evaluation of mechanical, geometrical and optical parameters of periodical microstructures in the cases when traditional measurement techniques are not suitable. Proposed methods are applicable for optimization and control of technological processes. Laser diffractometer is used in the experimental works for measurement of optical parameters of periodical microstructure and estimation of geometrical parameters with an error of less than 5% by comparing theoretical and experimental values of diffraction efficiencies of periodical microstructures. This method is suitable for geometry control of periodical microstructures during all technological process. Also an efficient method was developed that is capable to estimate with an error of 5% the depth of periodical microstructures, which have characteristic depths that are larger than the wavelength of coherent light used in the experiment. Quality of periodical microstructures is sensitive to thermal conditions during replication process. Therefore an experimental setup based on Michelson interferometer was developed for the investigation of induced thermal deformation. The radius and stress kinetics could be analyzed for different thickness of coated polymer. These are the problems that are considered in this paper.

Transformation Plasticity of Hot-Die Steel During Hardening

The paper presents the results of investigations of transformation plasticity of hot-die steel (high temperature–resistant steel used in high-temperature deforming) during hardening. A special device was used to evaluate transformation plasticity and determine the maximum normal bending stress, modulus of transformation plasticity for medium alloyed and medium carbon steel.

Sustainable approach to recycling of multilayer flexible packaging using switchable hydrophilicity solvents

Multilayer Flexible Packaging Waste (MFPW) represents the largest fraction of packaging waste and is mainly composed of multiple plastic films laminated with Al foil. In the EU, mechanical and chemical recycling technologies are usually used to separate polymeric fractions from Al; however, these recycling practices have inherent crucial restrictions related to the recycling rate ( 99% while making the reprocessing of extracted polymers much simpler. Dissolved plastic materials could easily be recovered in the form of solid residues without heating through saturation of an adhesive polymer/SHS solution by CO2 under cooling, thus changing the hydrophilicity of the solvent and converting it into a polar water-miscible form. Although the experiments were conducted on the lab-scale on six different types of MFPW, selected depending on the most active packaging technologies in the EU (as used for potato chips, chocolate, bakery goods, ground coffee, ice cream, and biscuits), the authors took into account the possibility of technology implementation at the industrial scale through designing a technology layout for the developed approach (based on the sequence of treatment processes and the obtained results). Metallographic microscopy, SEM-EDS, FTIR, and TGA were used to examine the materials recovered from each MFPW type as well as the changes in the SHS solvent. Lastly, the CO2-equivalent emissions and economic performance of the developed technology were evaluated.

Research on possibilities to replace industrial wear plates by surfaced coatings using waste materials

This research indicates the possibility to replace commercial materials and surfacing techniques by submerged arc welding under the flux and powder of industrial waste materials to obtain the chute with high abrasive wear resistance but for a lower price. Industrial waste of hard metal inserts, emery wheels, chips of case hardened stainless steels were grinded, granulated and blended. Prepared powder mixture served as alloying source increasing precipitation of hard particles during solidification of the weld. Abrasive wear resistance of coating six times exceeds wear resistance of industrial materials, while hardness exhibited very similar values. The results presented in this paper are based on micro-structural analysis of the surfaced and commercial coatings and are supported by analyses of the hardness and abrasive wear resistance. The complementary value of this research is a possibility to recycle industrial waste, which accumulates in huge quantities in the metals working industry.

Excavations of ironware of the third–fifth century from Marvele necropolis (Lithuania)

This study presents the overview of ironware excavations of the third–fifth century demolished tombs from Marvele necropolis. Three axes, four spearheads, two knives and a clasp were excavated in 2006. Afterwards, a metallographic and chemical analysis as well as mechanical properties of artefacts, also metallurgical slag, clinkers and iron concretions found in the surroundings of tombs were tested and presented in this article. General tests were executed in order to compare results with other archaeological and scientific researches. Metallographic analysis and hardness tests’ results revealed that axes were forged from two separate billets of iron, whilst spearheads and knives from one. The results of chemical analysis have affirmed earlier results of other Lithuanian archaeological sites. Although some differences in chemical composition were observed, this fact shows possible not local origin of some ironware.

Wear study of coatings obtained using different parameters of thermal spraying

Feedstock material behaviour in thermal spraying process under different parameters is essential in producing repeatable and controllable coatings. Article reviews three regimes of spraying, with a focus on the wear behaviour under the different conditions. RocDur 37 was selected as feedstock material. Regimes applying different feed were used: 1.43 cm/s (A), 1.85 cm/s (B), 0.88 cm/s (C); rotation speed - 1.33 s−1. Wear was tested on the contactsliding, edge-wear and abrasive-wear machines. Regimes B and C showed lower wear in contact-sliding and edge-wear. Hydro-abrasive test showed similar wear of coatings obtained using all parameters, it can be concluded that RocDur 37 coatings are suitable for work in abrasive conditions. In this type of wear technological parameters do not affect wear. The optimum technological regimes: rotation speed 1.33 s−1, longitudinal feed 0.88 cm/s, and 11 passes.

Experimental Analysis of Steel Plasticity Parameters during Quenching

The paper presents the results of longitudinal investigations of transformation plasticity, kinetic plasticity, elastic-plastic strain and auto deformation of different grades of steel during quenching. A special device was used to evaluate transformation plasticity and determine the maximum normal bending stress, modulus of transformation plasticity for high alloyed and high corrosion resistance steel. Other targets of experiments were to determine relations between magnitude of normal bending stresses and plastic deformation of test pieces, to examine influence of hardening temperature on the transformation plasticity, to calculate modulus of transformation plasticity Etp. As a complimentary survey we study the mechanical behaviour of high chromium and medium chromium steels during quenching. Understanding phenomenon of steel behaviour during quenching it is possible to renovate and restore the details and components deformed during exploitation, for production of steels with high formability, and to predict properties of steel.

Thermo photo elasticity: hybrid numerical experimental approach for investigation smart structures

The purpose of the paper is the development of techniques for hybrid experimental - numerical photoelasticity analysis. The general scheme of such analysis is presented. Generation of digital images mimicking the effect of photoelasticity naturally incorporates into the hybrid iterative procedure enabling effective interpretation of experimental results of Investigation Smart structures and provides insight into the physical processes taking place in the analysed objects. Visualization techniques of the results from finite element analysis procedures are important due to several reasons. First is the meaningful and accurate representation of processes taking place in the analyzed smart structures. Second, and perhaps even more important, is building the ground for hybrid numerical - experimental techniques. A typical example of FEM application in developing a hybrid technique is presented in paper.