Solid State Phenomena Vol. 332

Abstract: Ag nanoparticles (NPs) have been successfully synthesized by the green synthesis method using Moringa oleifera (MO) extract with various incubation times (24 and 48 hours) as an active material for surface plasmon resonance (SPR) biosensor. Transmission electron microscopy analysis indicated the formation of spherical particles with an average crystal size of 29 nm. Selected area electron diffraction confirmed that Ag NPs is face-centered cubic (FCC) crystal structure. Fourier-transform infrared measurements show the band at 3330 cm^-1, 2067 cm^-1, 1634 cm^-1 for an incubation time of 24 hours and 3328 cm^-1, 2063 cm^-1, 1633 cm^-1 for an incubation time of 48 hours. The results prove the proteins and phenolics compound present in the MO extract responsible as reducing agents. The maximum absorption of the green-synthesized Ag NPs in the UV-Vis spectra shows the SPR band at 326 nm and 328 nm for an incubation time of 24 and 48 hours, respectively, and absorption intensity decrease with the increase of incubation time. The result shows the SPR angle shifted to the larger angle of incident light by using green-synthesized Ag NPs. However, the increased incubation time affects the angle shift to the lower angle of the SPR shift. The addition of the green-synthesized Ag NPs leads to enhance the sensitivity of the SPR biosensor.

Abstract: Fe₃O₄ and Fe₃O₄/TiO₂ magnetic nanoparticles have been successfully prepared using an eco-friendly green synthesis method with various Moringa Oleifera (MO) extract concentrations. The X-ray diffraction and transmission electron microscopy results confirmed that the microstructure of Fe₃O₄ nanoparticles is a cubic inverse spinel structure with an average particle size of 9.2–11.7 nm and lattice parameters is in the range of 8.14–13.60 Å and the MO did not change the morphological structure of Fe₃O₄. Fourier-transform infrared showed that the samples had magnetic particles vibration peaks at 632 cm^-1 and 570 cm^-1, 500–700 cm^-1 for Ti-O peaks, and 1047 cm^-1 for aromatic C-C indicating green synthesis. Furthermore, the results of UV-VIS data presented the absorption edges of Fe₃O₄, Fe₃O₄-MO, and Fe₃O₄/TiO₂-MO were 187.9 nm, 198.7 nm, and 197.1 nm, respectively. The bandgap energy of Fe₃O₄-MO is in the range of 2.62–2.66 eV and the bandgap energy of Fe₃O₄/TiO₂-MO is 2.76 eV which explains that it depends on the bioactive compounds. Based on these results, the green synthesis nanoparticles have the potential to be applied in the industrial sector, especially for photocatalyst applications.

Abstract: Oxidation is one of the main degradation mechanisms that affects most industrial components and occurs as a result of a chemical reaction by which an oxygen atom is added to the molecule of an organic substance or compound. Light, in particular the ultraviolet (UV) component, activates the process of degradation of organic materials, favouring a series of oxidation reactions that occur when the component is in contact with oxygen in the air or water (especially salt water).Given that a number of components work in variable mechanical stress conditions (vibrations caused by the technological process itself or generated by repeated starts / shutdowns of equipment), the protective coatings aim to improve the physico-chemical properties of the surfaces to reduce the degradation, as well as to improve the fatigue behaviour, knowing that the fatigue cracks are initiated from local stress concentrators caused by the surface imperfections of the components. Paper presents the experimental results on fatigue behaviour of the deposited layers, after exposure to UV radiation. In the experimental program, a 2 mm thick AlMg3 sheet (EN AW-5754) was used as substrate. The Aluminium oxide layer naturally created on the metal surface, prevents the effect of oxygen and atmospheric pollutants, but this layer is unstable in corrosive environments. Thus, for a qualitative protection, protective organic layers are used. In experiments, the polyurethane paint PURMAL S 70, RAL 9010 (PUR) and the same paint but aditivate with graphene oxide (PUR + GO) were compared. Prior to fatigue testing, the painted specimens were subjected to accelerated artificial UV-aging process with ultraviolet radiation for 72 hours. Axial fatigue tests were performed with a frequency of 40 Hz, in pulsating mode, with R = 0.053 and with decreasing loads, starting from 0.85% of the tensile strength (R_m), up to 0.5% R_m. Analysis of S‑N curves revealed that, in the field of oligocyclic fatigue there are no significant differences between the fatigue results obtained on PUR-protected specimens, compared to those protected with PUR + GO, instead in the case of polycyclic fatigue, the paint with addition of 1% graphene oxide has improved fatigue resistance.

Abstract: Erosion of the metal of mining and metallurgical equipment due to the impact of solid particles is one of the forms of wear that can significantly limit the service life of a working machine or technological equipment, for example, a pipeline conveyor, loading and unloading bodies of mine workings and metallurgical machines. At present, this problem has been little studied and there is not enough information in the literature to form a systematic picture of impact erosion of equipment elements of mining and processing plants. The purpose of the research was to study the fatigue strength and corrosion-mechanical crack resistance of some structural elements of mining and metallurgical equipment with a long service life in chemically aggressive environments. Experimental tests for corrosion fatigue (long-term strength) were performed under bending load. The tests were performed on a bend with zero average voltage and a cycle frequency of 30 Hz. The tests were performed in salt solutions with a concentration of NaCl 5%. To compare the results, tests were sometimes performed in the air. The given data analysis shows that the long-term fatigue of the metal of mining and metallurgical equipment is significantly reduced when reaching 20 years of operation, especially in an aggressive environment containing chlorine ions, which causes severe corrosion damage to steel equipment. In addition, samples cut from metal with a long service life in mining and metallurgical conditions (more than 20 years) are characterized by low long-term strength. It has been found that fatigue resistance decreases with an increase in the number of cycles. Steel samples tested based on N = 10⁶ and especially on the basis of N = 10⁷ cycles have low resistance, which inevitably leads to breakdown with the subsequent destruction of equipment. It has been established that with an increase in the service life of the experimental mining and metallurgical equipment, the fracture toughness of the metal decreases significantly, which causes further failure and destruction of technological equipment.

Abstract: Oxidation is one of the main degradation mechanisms that affects most industrial components. Stainless steels are used in components and equipment in the chemical and petrochemical industries (e.g., valves, plates, columns, capacitors and desalination units). Generally, the steels used in these applications have physical, mechanical and chemical properties that give them corrosion resistance. However, contaminants existing in the processed fluids are the main factor causing the increase in corrosion rate, leading to significant financial losses, which requires the development of innovative technologies to protect the metal from the action of aggressive environment. The paper presents two innovative surface protection techniques used to improve the corrosion resistance of stainless steels. Thus, Matrix-Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition (PLD) techniques are used to obtain deposition of hybrid nanostructures of binary oxides and porphyrins on W1.4034 martensitic stainless steel, according to EN 10083-3.

Abstract: During the operating of industrial equipment and installations, elastoplastic deformations may occur over time in their most demanding areas due to thermal stresses, mechanical stresses (due to internal pressure, weight, inertial forces) or thermomechanical stresses resulting from their combination. Thermal stresses are cause by the non-uniformity of the expansions produced by the temperature differences, by the non-uniformity of the coefficients of linear thermal expansion of the materials used in isothermal or non-isothermal operating conditions. Increasing the temperature reduces the material strength by creating elastoplastic deformations and thus, to the loss of available plasticity of the material. The sudden change in operating regimes and the increase in the number of these regime changes at high temperatures, is one of the main causes of the faster accumulation of degradation, and the reduction of components remaining life. On the other hand, environmental factors have an important influence on the operating behaviour of equipment, since they favour the induction of corrosion or erosion-corrosion phenomena due to the flow of fluid circulated through installations at high temperatures. The complexity of the thermomechanical stresses, to which materials are subjected during operation, leads to the need for periodic assess of their characteristics through specific tests and analyses. Paper presents the results of analyses and tests performed to assess the damage state of pipes from a thermal power plant system, results that allow to estimate the service remaining life of the pipeline system for a proper operating in safe conditions.

Abstract: The requirements for sustainability and transition to a circular economy are key elements in the design and production of the components made by polymeric materials. The European Commission has issued a number of new directives with strict roadmaps to all State Members, in this regard. Some directives have already started to take effect; others are reaching their implementation deadlines. Limiting the consumption of raw materials and energy, as well as recyclability will lead to an increased reconversion of the current manufacturing technologies. However, all these goals must also take into account the quality aspects of the products. The testing methods must be adapted to certify the properties stated in the product sheets. This paper analyzes welding quality aspects in the production of hollow balls, made of polymeric materials, objects resulting from the joining of two hemispheres. As a case study, benchmarks from the cosmetic industry commonly known as deo roll balls were used. The first part of the paper presents the classic technology for manufacturing deo roll balls by extrusion blowing process. Below are some alternative technologies for manufacturing these balls by joining two hemispheres. The last part of the paper analyzes the welded joints by destructive and non-destructive testing methods. The basics that underlie the joining by welding polymeric materials as well as notions of rheology and material structure in the heat-affected zone are essential elements in explaining defect occurrence. A strict control of the welding parameters can offer good chances for implementing technologies to produce large series of spherical objects made of polymeric materials, objects that are made through alternative joining methods, more precisely by welding two hemispheres. The experiments carried out also highlighted some vulnerabilities of the proposed alternative technologies, their possible causes as well as the possibility of solving defects. These studies may underlie similar applications in which spherical objects are used.

Abstract: The current study focusses on possibilities of valorizing the spent Garnets produced by waterjet cutting operations, by integrating it in construction materials, as raw material substitution. The waterjet material processing by the use of abrasive Garnets is also in continuous expansion, due to its versatility and quality performance, this also generating large quantities of waste: the initial waterjet sludge collected in recipients during the process of material processes, dries and gradually turns into waste dumps, usually randomly deserted, especially in countries lacking specific legislation ad applicability methods. Therefore, converting the spent Garnets into filler replacement into concrete mixes could represent a huge benefit for both industries: constructions, lacking fillers, as sand replacement in concrete mix, possibly improving the material durability as well, and also material processing industry, by solving the waste generation problem. The initial, preliminary results, favorable to the use of spent Garnets in concrete and mortars, are confirmed by supplementary, international research, determining local interest for such valorization of the Garnet waste. This paper presents the latest research achievements in this topic and also, the derived possibilities regarding multidisciplinary studies which could determine the applicability of the waste in the construction industry, in Romania.

Abstract: In the evaluation of an existing reinforced concrete structure, a fundamental issue is determining the concrete compressive strength as accurately as possible. This process can be conducted by using destructive and non-destructive methods. The destructive method presumes a limited number of cores extracted from the concrete structure. A higher number of cores would affect the structural safety and is time and resource consuming. Therefore, the conclusions drawn using exclusively this method can also generate errors in correctly estimating the load bearing capacity of a structure, thus leading to the possibility of implementing deficient measures in order to ensure a structural safety. Data obtained via non-destructive methods are more comprehensive. Due to their non-destructive nature, there are no limitations regarding the number of elements investigated and are fast in delivering results. One of the main concerns of researchers in this field is developing a direct relationship between the measured indicators through non-destructive testing (NDT) methods and concrete compressive strength. Over the years different equations with different mathematical structure (linear, polynomial, power, exponential and logarithmic) were developed with the main purpose of delivering fast and accurate results concerning concrete compressive strength by the means of NDT. The aim of this paper is to validate some of the most important prediction models using an original set of data. The database consists in a number of 96 concrete cores that were subjected to Ultrasonic Pulse Velocity (UPV) and Schmidt Rebound Hammer (SRH) testing. The accuracy of the results was determined by using two statistical parameters the mean absolute error (MAE) and mean absolute percentage error (MAPE). The proposed equations have been analyzed in terms of prediction and dispersion of values. It was noticed that some of the formulations predict values that are higher than the ones obtained destructively, others provide a larger dissipation of values, while some equations deliver a compact distribution of results with higher rate in terms of accuracy. This study proposes a data validation of some of the most popular empirical equations, used for the estimation of the concrete compressive strength, elaborated through the years, using a new set of data.