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20 pages, 8415 KiB

Open AccessArticle

Analysis of Incremental Sheet Forming of Aluminum Alloy

by Costel Catalin Coman, Simona-Nicoleta Mazurchevici, Constantin Carausu and Dumitru Nedelcu

Materials 2023, 16(19), 6371; https://doi.org/10.3390/ma16196371 - 23 Sep 2023

Cited by 3 | Viewed by 1688

Abstract

Recent developments in incremental sheet forming have resulted in the creation of novel manufacturing processes that are highly adaptable and could bring significant economic benefits for advanced technologies and low-volume production. In this manuscript, the following variables were examined: the variation in the [...] Read more.

Recent developments in incremental sheet forming have resulted in the creation of novel manufacturing processes that are highly adaptable and could bring significant economic benefits for advanced technologies and low-volume production. In this manuscript, the following variables were examined: the variation in the deformation forces for a part with a pyramidal trunk shape; the variation in the deformations and thinning of the Al 3003 material during the incremental forming process; and the variation in the accuracy of the incrementally formed part and the quality of the surfaces (surface roughness). The components of the forces in the incremental forming have increasing values from the beginning of the process to the maximum value due to the hardening process. The TiN-coated tool ensures lower values of the forming components. Due to the kinematics of the forming process, deviations, especially in shape, from the part in the drawing are observed, which are shown by the radius of curvature of the side wall of the part, the appearance of a radius of connection between the wall and the bottom of the part, as well as dimensional deviations that are expressed by the variation in the forming depth. Concerning the smoothness of the surfaces, it was observed that the best roughness results were obtained in the case of the TiN-coated tool. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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19 pages, 9814 KiB

Open AccessArticle

Pulsed TIG Cladding of a Highly Carbon-, Chromium-, Molybdenum-, Niobium-, Tungsten- and Vanadium-Alloyed Flux-Cored Wire Electrode on Duplex Stainless Steel X2CrNiMoN 22-5-3

by Daniel Mutașcu, Olimpiu Karancsi, Ion Mitelea, Corneliu Marius Crăciunescu, Dragoș Buzdugan and Ion-Dragoș Uțu

Materials 2023, 16(13), 4557; https://doi.org/10.3390/ma16134557 - 24 Jun 2023

Cited by 2 | Viewed by 1468

Abstract

The hardfacing process aims to increase the life span of structural components in the petrochemical, mining, nuclear and automotive industries. During operation, these components are subject to demands of abrasion wear, cavitation erosion and corrosion. Duplex stainless steels are characterized by high mechanical [...] Read more.

The hardfacing process aims to increase the life span of structural components in the petrochemical, mining, nuclear and automotive industries. During operation, these components are subject to demands of abrasion wear, cavitation erosion and corrosion. Duplex stainless steels are characterized by high mechanical characteristics and corrosion resistance, but poor behavior to abrasive wear and cavitation erosion. The improvement in wear resistance is possible by selecting and depositing a special alloy on the surface using a joining technique that ensures a metallurgical bonding between the layer and the substrate. The experimental investigations carried out in this work demonstrate the ability of the TIG pulsed welding process to produce layers with good functional properties for engineering surfaces. The “Corodur 65” alloy was deposited on a duplex-stainless-steel substrate, X2CrNiMoN22-5-3, using a series of process parameters that allowed for the control of the cooling rate and heat input. The properties of the deposited layers are influenced not only by the chemical composition, but also by the dilution degree value. Since the deposition of layers through the welding operation can be considered as a process with several inputs and outputs, the control of the input parameters in the process aims at finishing the granulation and the structure in the fusion zone as well as limiting the segregation phenomena. The aim of this work is to investigate the microstructural characteristics of the iron-based alloy layer, Corodur 65, deposited via pulsed current TIG welding on duplex X2CrNiMoN22-5-3 stainless-steel substrates. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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18 pages, 5065 KiB

Open AccessArticle

Technological Processes for Increasing the Cavitation Erosion Resistance of Nimonic 80A Superalloys

by Cosmin Belin, Ion Mitelea, Ilare Bordeașu, Corneliu Marius Crăciunescu and Ion-Dragoș Uțu

Materials 2023, 16(8), 3206; https://doi.org/10.3390/ma16083206 - 18 Apr 2023

Viewed by 1892

Abstract

Nickel-based superalloys are frequently used to manufacture the components that operate under cavitation erosion conditions, such as aircraft gas turbine construction, nuclear power systems, steam turbine power plants, and chemical and petrochemical industries. Their poor performance in terms of cavitation erosion leads to [...] Read more.

Nickel-based superalloys are frequently used to manufacture the components that operate under cavitation erosion conditions, such as aircraft gas turbine construction, nuclear power systems, steam turbine power plants, and chemical and petrochemical industries. Their poor performance in terms of cavitation erosion leads to a significant reduction in service life. This paper compares four technological treatment methods to improve cavitation erosion resistance. The cavitation erosion experiments were carried out on a vibrating device with piezoceramic crystals in accordance with the prescriptions of the ASTM G32—2016 standard. The maximum depth of surface damage, the erosion rate, and the morphologies of the eroded surfaces during the cavitation erosion tests were characterized. The results indicate that the thermochemical plasma nitriding treatment can reduce mass losses and the erosion rate. The cavitation erosion resistance of the nitrided samples is approximately 2 times higher than that of the remelted TIG surfaces, approximately 2.4 times higher than that of the artificially aged hardened substrate, and 10.6 times higher than that of the solution heat-treated substrate. The improvement in cavitation erosion resistance for Nimonic 80A superalloy is attributed to the finishing of the surface microstructure, graining, and the presence of residual compressive stresses, factors that prevent crack initiation and propagation, thus blocking material removal during cavitation stresses. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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14 pages, 5008 KiB

Open AccessArticle

Investigating the Efficiency of a Heat Recovery–Storage System Using Heat Pipes and Phase Change Materials

by Robert Stefan Vizitiu, Andrei Burlacu, Chérifa Abid, Marius Costel Balan, Stefanica Eliza Vizitiu, Marius Branoaea and Nicoleta Elena Kaba

Materials 2023, 16(6), 2382; https://doi.org/10.3390/ma16062382 - 16 Mar 2023

Cited by 2 | Viewed by 1834

Abstract

This study presents an experimental and numerical investigation into the efficiency of a two-stage heat recovery–storage system for reducing the thermal energy losses in the industry. The system is designed to recover and store waste thermal energy from residual fluids using heat pipes [...] Read more.

This study presents an experimental and numerical investigation into the efficiency of a two-stage heat recovery–storage system for reducing the thermal energy losses in the industry. The system is designed to recover and store waste thermal energy from residual fluids using heat pipes for recovery and an environmentally friendly phase change material for heat storage. Experimental investigation was conducted using water as the primary agent and varying the temperature between 60 °C, 65 °C, and 70 °C at a constant flow rate of 24 L/min. The secondary agent, also water, was used at an initial temperature of 10 °C and the flow rate was varied between 1 L/min, 2 L/min, and 3 L/min. The results show that the system had a peak efficiency of 78.1% and was able to recover a significant amount of thermal energy. This study demonstrates the potential of this system to reduce the thermal energy losses in the industry and highlight the importance of further research and development in this field, as the industry is responsible for approximately 14% of the total thermal energy losses and finding efficient ways to recover and store waste thermal energy is crucial to achieving sustainable energy consumption. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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15 pages, 4228 KiB

Open AccessArticle

Physical, Thermal, and Chemical Properties of Fly Ash Cenospheres Obtained from Different Sources

by Andrei Shishkin, Vitalijs Abramovskis, Ilmars Zalite, Ashish Kumar Singh, Gundars Mezinskis, Vladimir Popov and Jurijs Ozolins

Materials 2023, 16(5), 2035; https://doi.org/10.3390/ma16052035 - 1 Mar 2023

Cited by 11 | Viewed by 1840

Abstract

Cenospheres are hollow particles in fly ash, a by-product of coal burning, and are widely used as a reinforcement when developing low-density composites called syntactic foams. This study has investigated the physical, chemical, and thermal properties of cenospheres obtained from three different sources, [...] Read more.

Cenospheres are hollow particles in fly ash, a by-product of coal burning, and are widely used as a reinforcement when developing low-density composites called syntactic foams. This study has investigated the physical, chemical, and thermal properties of cenospheres obtained from three different sources, designated as CS1, CS2, and CS3, for the development of syntactic foams. Cenospheres with particle sizes ranging from 40 to 500 μm were studied. Different particle distribution by size was observed, and the most uniform distribution of CS particles was in the case of CS2: above 74% with dimensions from 100 to 150 μm. The CS bulk had a similar density for all samples and amounted to around 0.4 g·cm⁻³, with a particle shell material density of 2.1 g·cm⁻³. Post-heat-treatment samples showed the development of a SiO₂ phase in the cenospheres, which was not present in the as-received product. CS3 had the highest quantity of Si compared to the other two, showing the difference in source quality. Energy-dispersive X-ray spectrometry and a chemical analysis of the CS revealed that the main components of the studied CS were SiO₂ and Al₂O_3. In the case of CS1 and CS2, the sum of these components was on average from 93 to 95%. In the case of CS3, the sum of SiO₂ and Al₂O₃ did not exceed 86%, and Fe₂O₃ and K₂O were present in appreciable quantities in CS3. Cenospheres CS1 and CS2 did not sinter during heat treatment up to 1200 °C, while sample CS3 was already subjected to sintering at 1100 °C because of the presence of a quartz phase, Fe₂O₃ and K₂O. For the application of a metallic layer and subsequent consolidation via spark plasma sintering, CS2 can be deemed the most physically, thermally, and chemically suitable. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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16 pages, 2817 KiB

Open AccessArticle

TiSiCN as Coatings Resistant to Corrosion and Neutron Activation

by Matlab N. Mirzayev, Anca C. Parau, Lyubomir Slavov, Mihaela Dinu, Dimitar Neov, Zdravka Slavkova, Evgeni P. Popov, Maria Belova, Kanan Hasanov, Fuad A. Aliyev and Alina Vladescu (Dragomir)

Materials 2023, 16(5), 1835; https://doi.org/10.3390/ma16051835 - 23 Feb 2023

Cited by 6 | Viewed by 1926

Abstract

The aim of the present paper was to evaluate the effect of neutron activation on TiSiCN carbonitrides coatings prepared at different C/N ratios (0.4 for under stoichiometric and 1.6 for over stoichiometric). The coatings were prepared by cathodic arc deposition using one cathode [...] Read more.

The aim of the present paper was to evaluate the effect of neutron activation on TiSiCN carbonitrides coatings prepared at different C/N ratios (0.4 for under stoichiometric and 1.6 for over stoichiometric). The coatings were prepared by cathodic arc deposition using one cathode constructed of Ti88 at.%-Si12 at.% (99.99% purity). The coatings were comparatively examined for elemental and phase composition, morphology, and anticorrosive properties in 3.5% NaCl solution. All the coatings exhibited f.c.c. solid solution structures and had a (111) preferred orientation. Under stoichiometric structure, they proved to be resistant to corrosive attack in 3.5% NaCl and of these coatings the TiSiCN was found to have the best corrosion resistance. From all tested coatings, TiSiCN have proven to be the most suitable candidates for operation under severe conditions that are present in nuclear applications (high temperature, corrosion, etc.). Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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15 pages, 5074 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Annealing at 500 and 900 °C on the Structure and Mechanical Properties of Al_xCoCrFeNi Alloys

by Marzena Tokarewicz, Małgorzata Grądzka-Dahlke, Katarzyna Rećko and Magdalena Łępicka

Materials 2023, 16(3), 1245; https://doi.org/10.3390/ma16031245 - 1 Feb 2023

Cited by 4 | Viewed by 1590

Abstract

The AlCoCrFeNi high-entropy alloy is sensitive to heat treatment. The aim of the present study was to test a similar correlation for Al_xCoCrFeNi alloys with less than equimolar aluminum content. This paper presents a study of the annealing effect on the [...] Read more.

The AlCoCrFeNi high-entropy alloy is sensitive to heat treatment. The aim of the present study was to test a similar correlation for Al_xCoCrFeNi alloys with less than equimolar aluminum content. This paper presents a study of the annealing effect on the structure and mechanical properties of selected alloys. Al_xCoCrFeNi alloys (x = 0, 0.5, 0.7) were fabricated by the induction melting method. The obtained specimens were annealed at 500 °C and 900 °C. A detailed study of the changes in crystalline structure due to annealing was conducted. Three-point bending and hardness tests were carried out for the as-cast and annealed specimens to determine selected mechanical properties. The study confirmed that increasing the aluminum content in the Al_xCoCrFeNi alloy improves mechanical properties. For the alloy with aluminum content x = 0.7, hardness increased by 187% and yield strength by 252% compared to the alloy without aluminum. A significant effect of annealing on the crystalline structure of the Al_0.7CoCrFeNi alloy was found, but this was not followed by changes in mechanical properties. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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14 pages, 4504 KiB

Open AccessArticle

Innovative Passive and Environmentally Friendly System for Improving the Energy Performance of Buildings

by Andrei Burlacu, Gavril Sosoi, Chérifa Abid, Marinela Barbuta, Marina Verdes, Robert Stefan Vizitiu and Marius Branoaea

Materials 2022, 15(20), 7224; https://doi.org/10.3390/ma15207224 - 17 Oct 2022

Viewed by 1253

Abstract

The aim of the study is to develop a system for converting, accumulating, and delivering solar energy that is based on the development of an innovative solar panel with heat pipes and a heat storage wall, for the construction of passive structures. The [...] Read more.

The aim of the study is to develop a system for converting, accumulating, and delivering solar energy that is based on the development of an innovative solar panel with heat pipes and a heat storage wall, for the construction of passive structures. The novel aspect of this experiment is the utilization of concrete walls that have different recyclable materials added to their structure in various proportions. The solar energy from the sunny façades is transformed by this system into thermal energy, which is then transferred by integrated heat pipes in a massive element with high thermal inertia. Using insulated shutters, thermal energy can be stored during the day and released at night to keep the room at a comfortable temperature. In order to integrate the modules into the solar recovery system, four concrete samples were cast with a blend of standard and waste aggregates. Four heat fluxes of 100 W/m², 150 W/m², 200 W/m², and 250 W/m² were applied to each global system. Thermal imaging data and numerical simulations both supported the findings of temperature sensors. The most effective mixture, fly ash and chopped PET, delivered temperatures that were, on average, 3.3% higher at the end of the charging cycle than those measured for the control sample. The discharging cycle of the concrete block with fly ash and sawdust was the most effective, with an average temperature loss of 5.0 °C as compared to 5.5 °C for the control sample, on average. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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14 pages, 5813 KiB

Open AccessArticle

Evaluation of the Fatigue Behaviour and Failure Mechanisms of 52100 Steel Coated with WIP-C1 (Ni/CrC) by Cold Spray

by Viorel Goanta, Corneliu Munteanu, Sinan Müftü, Bogdan Istrate, Patricia Schwartz, Samuel Boese, Gehn Ferguson and Ciprian Ionut Morăraș

Materials 2022, 15(10), 3609; https://doi.org/10.3390/ma15103609 - 18 May 2022

Cited by 5 | Viewed by 1816

Abstract

Cold spray technique has been major improved in the last decades, for studying new properties for metals and alloys of aluminum, copper, nickel, and titanium, as well as steels, stainless steel and other types of alloys. Cold sprayed Ni/CrC coatings have the potential [...] Read more.

Cold spray technique has been major improved in the last decades, for studying new properties for metals and alloys of aluminum, copper, nickel, and titanium, as well as steels, stainless steel and other types of alloys. Cold sprayed Ni/CrC coatings have the potential to provide a barrier as well as improved protection to steels. Fatigue characteristics of 52100 steel coated with Ni/Chrome-Carbide (Ni/CrC) powder mixture by using cold gas dynamic spray are investigated. Fatigue samples were subjected to symmetrically alternating, axially applied cyclic fatigue loading until failure. The test was stopped if a sample survived more than 5 × 10⁶ cycles at the applied stress. Fracture surfaces for each sample were examined to investigate the behaviour of the coating both at high stress levels and at a high number of stress cycles. Scanning electron microscopy was used to assess the damage in the interface of the two materials. Good fatigue behaviour of the coating material was observed, especially at low stresses and a high number of cycles. Details of the crack initiation region, the stable crack propagation region and the sudden crack expansion region are identified for each sample. In most of the samples, the initiation of the crack occurred on the surface of the base material and propagated into the coating material. The possible effects of coatings on the initial deterioration of the base material and the reduction of the lifespan of the coated system were also investigated. The aim of the paper was to study the interface between the base material and the coating material at the fatigue analysis for different stresses, highlighting the appearance of cracks and the number of breaking cycles required for each sample. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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17 pages, 3932 KiB

Open AccessArticle

Experimental Investigation on Mechanical and Thermal Properties of Concrete Using Waste Materials as an Aggregate Substitution

by Gavril Sosoi, Cherifa Abid, Marinela Barbuta, Andrei Burlacu, Marius Costel Balan, Marius Branoaea, Robert Stefan Vizitiu and Fabrice Rigollet

Materials 2022, 15(5), 1728; https://doi.org/10.3390/ma15051728 - 25 Feb 2022

Cited by 16 | Viewed by 2529

Abstract

The continuous growth of the concrete industry requires an increased quantity of cement and natural aggregates year after year, and it is responsible for a major part of the global CO₂ emissions. These aspects led to rigorous research for suitable raw materials. [...] Read more.

The continuous growth of the concrete industry requires an increased quantity of cement and natural aggregates year after year, and it is responsible for a major part of the global CO₂ emissions. These aspects led to rigorous research for suitable raw materials. Taking into account that these raw materials must have a sustainable character and also a low impact on environmental pollution, the replacement of the conventional components of concrete by residual waste can lead to these targets. This paper’s aim is to analyze the density, compressive strength and the thermal conductivity of nine concrete compositions with various rates of waste: four mixes with 10%, 20%, 40% and 60% chopped PET bottles aggregates and 10% fly ash as cement partial substitution; a mix with 60% waste polystyrene of 4–8 mm and 10% fly ash; a mix with 20% waste polystyrene of 4–8 mm, 10% waste polystyrene of 0–4 mm and 10% fly ash; a mix with 50% waste polystyrene of 4–8 mm, 20% waste polystyrene of 0–4 mm and 20% fly ash two mixes with 10% fly ash and 10% and 40% waste sawdust, respectively. Using 60% PET aggregates, 60% polystyrene granules of 4–8 mm, or 20% polystyrene of 0–4 mm together with 50% polystyrene of 4–8 mm led to the obtainment of lightweight concrete, with a density lower than 2000 kg/m³. These mixes also registered the best results from a thermal conductivity point of view, after the concrete mix with 40% saw dust. Regarding compressive strength, the mix with 10% PET obtained a result very close to the reference mix, while those with 20% PET, 40% PET, 30% polystyrene, and 10% saw dust, respectively, registered values between 22 MPa and 25 MPa, values appropriate for structural uses. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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27 pages, 6098 KiB

Open AccessArticle

In Situ Compensation Method for Precise Integral SQUID Magnetometry of Miniscule Biological, Chemical, and Powder Specimens Requiring the Use of Capsules

by Katarzyna Gas and Maciej Sawicki

Materials 2022, 15(2), 495; https://doi.org/10.3390/ma15020495 - 10 Jan 2022

Cited by 4 | Viewed by 2244

Abstract

Steadily growing interest in magnetic characterization of organic compounds for therapeutic purposes or of other irregularly shaped specimens calls for refinements of experimental methodology to satisfy experimental challenges. Encapsulation in capsules remains the method of choice, but its applicability in precise magnetometry is [...] Read more.

Steadily growing interest in magnetic characterization of organic compounds for therapeutic purposes or of other irregularly shaped specimens calls for refinements of experimental methodology to satisfy experimental challenges. Encapsulation in capsules remains the method of choice, but its applicability in precise magnetometry is limited. This is particularly true for minute specimens in the single milligram range as they are outweighed by the capsules and are subject to large alignment errors. We present here a completely new experimental methodology that permits 30-fold in situ reduction of the signal of capsules by substantially restoring the symmetry of the sample holder that is otherwise broken by the presence of the capsule. In practical terms it means that the standard 30 mg capsule is seen by the magnetometer as approximately a 1 mg object, effectively opening the window for precise magnetometry of single milligram specimens. The method is shown to work down to 1.8 K and in the whole range of the magnetic fields. The method is demonstrated and validated using the reciprocal space option of MPMS-SQUID magnetometers; however, it can be easily incorporated in any magnetometer that can accommodate straw sample holders (i.e., the VSM-SQUID). Importantly, the improved sensitivity is accomplished relying only on the standard accessories and data reduction method provided by the SQUID manufacturer, eliminating the need for elaborate raw data manipulations. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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13 pages, 8523 KiB

Open AccessArticle

Effect of Deep Cryogenic Treatment on Corrosion Behavior of AISI H13 Die Steel

by Tarang Shinde, Catalin Pruncu, Narendra B. Dhokey, Anca C. Parau and Alina Vladescu

Materials 2021, 14(24), 7863; https://doi.org/10.3390/ma14247863 - 18 Dec 2021

Cited by 22 | Viewed by 2782

Abstract

AISI H13 die steel specimens were subjected to heating at 1020 °C followed by oil quenching and double tempering at 520 °C. Subsequently, these specimens were subjected to deep cryogenic treatment at −185 °C in liquid nitrogen environment for 16 h and then [...] Read more.

AISI H13 die steel specimens were subjected to heating at 1020 °C followed by oil quenching and double tempering at 520 °C. Subsequently, these specimens were subjected to deep cryogenic treatment at −185 °C in liquid nitrogen environment for 16 h and then subjected to soft tempering at 100 °C once the specimens attained room temperature. Thereafter, the specimens were subjected to scanning electron microscopy (SEM) analysis and electron backscatter diffraction (EBSD) analysis. The electrochemical corrosion activity was investigated in 3.5% NaCl at 23 ± 0.5 °C by evaluating the evolution of open circuit potential over time and potentiodynamic curves, and electrochemical impedance spectroscopy study was also carried out. The heat-treated specimens exhibited better resistance to corrosion through more electropositive values of open circuit potential. This could be attributed to lower grain boundary area in heat-treated specimens as compared to 16 h cryogenically treated specimen as higher grain boundary areas behave as an anode in an electrochemical cell, thereby enhancing the rate of corrosion. According to electrochemical tests, the cryogenically treated surface is more resistant to corrosion, followed by heated alloy. However, both surface modification treatments improved the corrosion behavior of the untreated alloy. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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20 pages, 6288 KiB

Open AccessFeature PaperArticle

Tribological Behavior and Microstructural Analysis of Atmospheric Plasma Spray Deposited Thin Coatings on Cardan Cross Spindles

by Corneliu Munteanu, Viorel Paleu, Bogdan Istrate, Anişoara Dascălu, Cornelia Cîrlan Paleu, Shubrajit Bhaumik and Ana Diana Ancaş

Materials 2021, 14(23), 7322; https://doi.org/10.3390/ma14237322 - 30 Nov 2021

Cited by 7 | Viewed by 2397

Abstract

Cardan joints are used in transmissions between misaligned shafts, as in all-wheel-drive (AWD) cars and railway applications. Their functioning is accompanied by heavy cyclical loads, with the cardan cross spindles subjected to intensive abrasive wear and pitting. In this paper, a solution to [...] Read more.

Cardan joints are used in transmissions between misaligned shafts, as in all-wheel-drive (AWD) cars and railway applications. Their functioning is accompanied by heavy cyclical loads, with the cardan cross spindles subjected to intensive abrasive wear and pitting. In this paper, a solution to the mentioned issue is proposed, thin anti-wear coatings of Metco 32 and Metco 72 metallic powders deposited by atmospheric plasma spray (APS) on cylindrical samples cut from spindles of two cardan crosses made of 40Cr10 and RUL2 steel. The morphological analysis of the coated surfaces was realized by scanning electron microscopy (SEM), and the elemental composition of the tested samples was elaborated by energy-dispersive X-ray spectroscopy (EDS). To investigate the wear resistance of the coated samples in dry and grease-lubricated conditions, tests at constant load and constant speed were carried out using an AMSLER tribometer. The results of greased tests proved that the expulsion of the lubricant from the tribological contact occurred no matter the combination of coated or uncoated samples. During grease-lubricated tests of ten minutes, the least coefficient of friction was measured for uncoated specimens with better surface finishing; but in dry friction tests, the lowest values of the mean friction coefficients were obtained for the Metco 72 coatings. The porous coatings may act as lubricant reservoirs in long-lasting tests, providing a solution to the expulsion phenomenon of the lubricant to the boundary outside the area of the larger-diameter roller. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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23 pages, 85270 KiB

Open AccessArticle

Diagonal Tensile Test on Masonry Panels Strengthened with Textile-Reinforced Mortar

by Dragoș Ungureanu, Nicolae Țăranu, Dan Alexandru Ghiga, Dorina Nicolina Isopescu, Petru Mihai and Ruxandra Cozmanciuc

Materials 2021, 14(22), 7021; https://doi.org/10.3390/ma14227021 - 19 Nov 2021

Cited by 12 | Viewed by 3054

Abstract

This study presents the results of an experimental and numerical program carried out on unreinforced masonry panels strengthened by textile-reinforced mortar (TRM) plastering. For this purpose, five panels were constructed, instrumented and tested in diagonal shear mode. Two panels were tested as reference. [...] Read more.

This study presents the results of an experimental and numerical program carried out on unreinforced masonry panels strengthened by textile-reinforced mortar (TRM) plastering. For this purpose, five panels were constructed, instrumented and tested in diagonal shear mode. Two panels were tested as reference. The first reference panel was left unstrengthened, while the second one was strengthened by a traditional self-supporting cement mortar matrix reinforced with steel meshes. The remaining three panels were strengthened by TRM plastering applied on one or both faces and connected with transversal composite anchors. The numerical and the experimental results evidenced a good effectiveness of the TRM systems, especially when applied on both panel facings. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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24 pages, 10601 KiB

Open AccessArticle

Structural Response of Bonded Joints between FRP Composite Strips and Steel Plates

by Vlad Lupășteanu, Dragoș Ungureanu, Nicolae Țăranu, Dorina Nicolina Isopescu, Radu Lupășteanu and Petru Mihai

Materials 2021, 14(21), 6722; https://doi.org/10.3390/ma14216722 - 8 Nov 2021

Cited by 5 | Viewed by 1773

Abstract

This paper presents the outcomes of an experimental and numerical study performed on epoxy-bonded single lap joints (SLJs) between carbon fiber-reinforced polymer (CFRP) composite strips and steel elements. For the experimental program, 34 specimens were prepared by varying the type of the composite [...] Read more.

This paper presents the outcomes of an experimental and numerical study performed on epoxy-bonded single lap joints (SLJs) between carbon fiber-reinforced polymer (CFRP) composite strips and steel elements. For the experimental program, 34 specimens were prepared by varying the type of the composite strip and the type of adhesives and their thicknesses; all specimens were loaded in axial tension up to failure. The specific failure mechanisms were identified and commented on the basis of the performed tests, and the load–displacement curves were plotted. Additionally, the strain distributions along the bond lengths at different load stages, the shear stress–displacements (slip) variations and the stress–strain distributions for the CFRP strips were plotted and investigated. The numerical simulations, based on 3D finite element method (FEM) analysis, provided consistent results, in good agreement with the experimental ones for all parameters that were investigated and discussed in this paper. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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15 pages, 5672 KiB

Open AccessArticle

Eco-Friendly Biosorbents Based on Microbial Biomass and Natural Polymers: Synthesis, Characterization and Application for the Removal of Drugs and Dyes from Aqueous Solutions

by Lăcrămioara Rusu, Cristina-Gabriela Grigoraș, Elena Mirela Suceveanu, Andrei-Ionuț Simion, Andreea Veronica Dediu Botezatu, Bogdan Istrate and Ioan Doroftei

Materials 2021, 14(17), 4810; https://doi.org/10.3390/ma14174810 - 25 Aug 2021

Cited by 18 | Viewed by 2812

Abstract

Pharmaceuticals and dyes are a very important part of the nonbiodegradable or hard biodegradable substances present in wastewater. Microorganisms are already known to be effective biosorbents, but the use of free microbial cells involves difficulties in their separation from effluents and limits their [...] Read more.

Pharmaceuticals and dyes are a very important part of the nonbiodegradable or hard biodegradable substances present in wastewater. Microorganisms are already known to be effective biosorbents, but the use of free microbial cells involves difficulties in their separation from effluents and limits their application in wastewater treatment. Thus, this study aimed to develop biosorbents by immobilizing Saccharomyces cerevisiae, Saccharomyces pastorianus and Saccharomyces pastorianus residual biomass on natural polymers (alginate and chitosan) and to evaluate the biosorptive potential for removal of pharmaceuticals and dyes from water. Six types of biosorbents were synthesized and characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy techniques and their biosorptive capacities for three drugs (cephalexin, rifampicin, ethacridine lactate) and two dyes (orange II and indigo carmine) were evaluated. The obtained results show that the removal efficiency depends on the polymer type used for the immobilization. In case of alginate the removal efficiency is between 40.05% and 96.41% for drugs and between 27.83% and 58.29% for dyes, while in the case of chitosan it is between 40.83% and 77.92% for drugs and between 17.17% and 44.77% for dyes. In general, the synthesized biosorbents proved to be promising for the removal of drugs and dyes from aqueous solutions. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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12 pages, 4345 KiB

Open AccessArticle

The Influence of the Environment for Glass-Reinforced Plastic Composite Material Used for Ground Water Transport Pipes

by Ana Diana Ancaș, Corneliu Munteanu, Bogdan Istrate, Mihai Profire and Florin-Emilian Țurcanu

Materials 2021, 14(12), 3160; https://doi.org/10.3390/ma14123160 - 8 Jun 2021

Cited by 2 | Viewed by 2663

Abstract

Glass-reinforced plastic (GRP) composite materials are mainly used in the construction of pipes due to the wide range of sizes, ease of installation, adaptability to the specific situation in the field and, last but not least, the more competitive price as the nominal [...] Read more.

Glass-reinforced plastic (GRP) composite materials are mainly used in the construction of pipes due to the wide range of sizes, ease of installation, adaptability to the specific situation in the field and, last but not least, the more competitive price as the nominal diameter increases. Their wide range of applications: drinking and raw water transport, sewerage, industrial waters, desalination plants, mining, etc., has led to the need to tailor the behaviour of the composite material to different fields, with pH values that are not neutral. Based on the experimental data, we aimed to study the change in the structure of the composite material as influenced by the soil characteristics: neutral, basic and acidic. In addition, starting with the pH of the three types of soil—basic, acidic and neutral—which significantly affect GRP composite materials, we calculated the pipe damage index and the Pearson correlation coefficients for axial tension. The results highlight the significant influence of the soil pH on the behaviour over time of the buried GRP pipes. Thus, laying the pipe in acidic soil significantly reduces its life, which should be taken into consideration during the design phase. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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10 pages, 2524 KiB

Open AccessArticle

Determination of Physicomechanical Characteristics of the Cement Mortar with Added Fiberglass Waste Treated with Hydrogen Plasma

by Marius Lucian Lupu, Dorina Nicolina Isopescu, Ioan Tuns, Ioana-Roxana Baciu and Sebastian George Maxineasa

Materials 2021, 14(7), 1718; https://doi.org/10.3390/ma14071718 - 31 Mar 2021

Cited by 2 | Viewed by 2013

Abstract

Solving the environmental problems and the economic aspects of the construction sector represent a global priority. The considerable quantities of raw materials and the energy consumed by this sector make it one of the most polluting economic activities. Fiberglass in various forms is [...] Read more.

Solving the environmental problems and the economic aspects of the construction sector represent a global priority. The considerable quantities of raw materials and the energy consumed by this sector make it one of the most polluting economic activities. Fiberglass in various forms is widely used in the construction sector. In the manufacturing process and during the usage of fiberglass products, a significant amount of indestructible waste results, negatively impacting the environment. An innovative solution for utilizing this type of waste is the treatment with hydrogen plasma. This process results in two products: the first in the gaseous state used to obtain synthetic fuel and the second in solid-state, named slag. The composition of solid waste contains chemical compounds that can increase their strength if used as additives in mortars or concretes. This study presents the laboratory tests on mortars, in which a part of the cement amount was replaced with the solid component resulting from the plasma treatment of glass fiber waste. The results showed that replacing a part of the cement with these materials is a solution that minimizes the ecological footprint of the buildings. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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Review

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37 pages, 14631 KiB

Open AccessReview

Magnetic Nanoparticles Used in Oncology

by Veronica Manescu (Paltanea), Gheorghe Paltanea, Iulian Antoniac and Marius Vasilescu

Materials 2021, 14(20), 5948; https://doi.org/10.3390/ma14205948 - 10 Oct 2021

Cited by 40 | Viewed by 3991

Abstract

Recently, magnetic nanoparticles (MNPs) have more and more often been used in experimental studies on cancer treatments, which have become one of the biggest challenges in medical research. The main goal of this research is to treat and to cure advanced or metastatic [...] Read more.

Recently, magnetic nanoparticles (MNPs) have more and more often been used in experimental studies on cancer treatments, which have become one of the biggest challenges in medical research. The main goal of this research is to treat and to cure advanced or metastatic cancer with minimal side effects through nanotechnology. Drug delivery approaches take into account the fact that MNPs can be bonded to chemotherapeutical drugs, nucleic acids, synthetized antibodies or radionuclide substances. MNPs can be guided, and different treatment therapies can be applied, under the influence of an external magnetic field. This paper reviews the main MNPs’ synthesis methods, functionalization with different materials and highlight the applications in cancer therapy. In this review, we describe cancer cell monitorization based on different types of magnetic nanoparticles, chemotherapy, immunotherapy, magnetic hyperthermia, gene therapy and ferroptosis. Examples of applied treatments on murine models or humans are analyzed, and glioblastoma cancer therapy is detailed in the review. MNPs have an important contribution to diagnostics, investigation, and therapy in the so called theranostics domain. The main conclusion of this paper is that MNPs are very useful in different cancer therapies, with limited side effects, and they can increase the life expectancy of patients with cancer drug resistance. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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