Materials

12 pages, 3646 KiB

Open AccessArticle

Study on Tungsten Metallization and Interfacial Bonding of Silicon Nitride High-Temperature Co-Fired Ceramic Substrates

by Ling-Feng Wang, Zhe Li, Bo-An Zhou, Yu-Sen Duan, Ning Liu and Jing-Xian Zhang

Materials 2023, 16(7), 2937; https://doi.org/10.3390/ma16072937 - 6 Apr 2023

Cited by 3 | Viewed by 2290

For the first time, Si₃N₄ HTCC has been prepared using W as the metal phase by high-temperature co-firing (1830 °C/600 KPa/2 h) as a potential substrate candidate in electronic applications. It was discovered that the addition of Si₃N [...] Read more.

For the first time, Si₃N₄ HTCC has been prepared using W as the metal phase by high-temperature co-firing (1830 °C/600 KPa/2 h) as a potential substrate candidate in electronic applications. It was discovered that the addition of Si₃N₄ to the W paste has a significant impact on thermal expansion coefficient matching and dissolution wetting. As the Si₃N₄ content increased from 0 to 27.23 vol%, the adhesion strength of W increased continuously from 2.83 kgf/mm² to 7.04 kgf/mm². The interfacial bonding of the Si₃N₄ ceramic and the conduction layer was discussed. SEM analysis confirmed that the interface between Si₃N₄ and W exhibited an interlocking structure. TEM, HRTEM and XRD indicated the formation of W₂C and W₅Si₃ due to the interface reactions of W with residual carbon and Si₃N₄, respectively, which contributed to the reactive wetting and good adhesion strength between the interface. Suitable amounts of Si₃N₄ powder and great interfacial bonding were the main reasons for the tough interfacial matching between the Si₃N₄ ceramic and the conduction layer. Full article

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9 pages, 6666 KiB

Open AccessArticle

The Effects of Lubricooling Ecosustainable Techniques on Tool Wear in Carbon Steel Milling

by Nagore Villarrazo, Soraya Caneda, Octavio Pereira, Adrian Rodríguez and Luis Norberto López de Lacalle

Materials 2023, 16(7), 2936; https://doi.org/10.3390/ma16072936 - 6 Apr 2023

Cited by 12 | Viewed by 2585

Abstract

This research analyses the viability of using cryogenic cooling combined with MQL (minimum quantity lubrication) lubrication, under CryoMQL technology, as a cutting fluid in the industrial environment to justify the increase in the environmental footprint generated by its use compared to MQL in [...] Read more.

This research analyses the viability of using cryogenic cooling combined with MQL (minimum quantity lubrication) lubrication, under CryoMQL technology, as a cutting fluid in the industrial environment to justify the increase in the environmental footprint generated by its use compared to MQL in stand-alone mode. For this analysis, a set of milling tests were carried out on carbon steel AISI 1045, which is one of the most commonly used materials in the business day-to-day. In this set of tests, the evolution of cutting edge wear and energy consumption of both technologies were recorded to check their tool life through technological and environmental analysis. Thus, we sought to discern whether the energy savings derived from the machining process make up for the greater environmental footprint initially generated by the use of CryoMQL technology itself. The results obtained show how the use of CryoMQL not only increased tool life, but also allowed an increase in productivity by increasing cutting speeds by 18%; in other words, thanks to this technology, a more technologically advanced and environmentally friendly process is obtained. By increasing tool life by 30%, a reduction in energy consumption is achieved together with cost savings, which implies that ECO2 machining has economic and ecological benefits. Full article

(This article belongs to the Collection Machining and Manufacturing of Alloys and Steels)

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12 pages, 4558 KiB

Open AccessArticle

IBIL Measurement and Optical Simulation of the D_I Center in 4H-SiC

by Wenli Jiang, Wei Cheng, Menglin Qiu, Shuai Wu, Xiao Ouyang, Lin Chen, Pan Pang, Minju Ying and Bin Liao

Materials 2023, 16(7), 2935; https://doi.org/10.3390/ma16072935 - 6 Apr 2023

Cited by 1 | Viewed by 1650

Abstract

In this paper, D_I defects are studied via experiments and calculations. The 2 MeV H⁺ is used to carry on an ion-beam-induced luminescence (IBIL) experiment to measure the in-situ luminescence of untreated and annealed 4H-SiC at 100 K. The results show [...] Read more.

In this paper, D_I defects are studied via experiments and calculations. The 2 MeV H⁺ is used to carry on an ion-beam-induced luminescence (IBIL) experiment to measure the in-situ luminescence of untreated and annealed 4H-SiC at 100 K. The results show that the luminescence intensity decreases rapidly with increasing H⁺ fluence, which means the losses of optical defect centers. In addition, the evident peak at 597 nm (2.07 eV) is the characteristic peak of 4H-SiC, and the weak peak between 400 nm and 450 nm is attributed to the D_I optical center. Moreover, the first-principles calculation of 4H-SiC is adopted to discuss the origin of D_I defects. The optical transition of the defect Si_C(C_Si)₂ from q = 0 to q = 1 is considered the experimental value of the D_I defect center. Full article

(This article belongs to the Section Materials Physics)

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20 pages, 16081 KiB

Open AccessArticle

Influence of the Large-Span Pile-Beam-Arch Construction Method on the Surface Deformation of a Metro Station in the Silty Clay–Pebble Composite Stratum

by Tao Li, Yue Li, Tengyu Yang, Rui Hou, Yuan Gao, Bo Liu and Guogang Qiao

Materials 2023, 16(7), 2934; https://doi.org/10.3390/ma16072934 - 6 Apr 2023

Cited by 5 | Viewed by 1504

Abstract

The Pile-beam-arch (PBA) method is a new and effective construction method for the urban metro station. It is the key to ensuring the safe construction of the station to clarify the influence of PBA method construction on surface deformation under unfavorable geological and [...] Read more.

The Pile-beam-arch (PBA) method is a new and effective construction method for the urban metro station. It is the key to ensuring the safe construction of the station to clarify the influence of PBA method construction on surface deformation under unfavorable geological and large span conditions. Based on a station of Beijing subway, this paper studies the surface deformation law of the large-span PBA method in different construction stages under silty clay–pebble composite stratum by means of FLAC 3D numerical analysis and field monitoring of level. Then the influence of the excavation scheme of the pilot tunnel and the construction scheme of the secondary lining of the arch on the surface deformation is simulated and analyzed. The results show that, through numerical simulation, the ratio of pilot tunnel excavation: pile-beam construction: vault initial support construction: vault secondary lining construction is about 5:1.1:3.3:0.6. The settlement deformation mainly occurs in the excavation stage of the pilot tunnel. Through the comparative analysis of the field monitoring results and the numerical simulation results, it can be seen that the two results are highly consistent, which verifies the accuracy of the numerical simulation results. The pilot tunnel excavation scheme of excavating the middle first and then excavating both sides, first through the upper layer and then through the lower layer, and the scheme of one-time construction of the secondary lining of the arch are better. The research results promote the further maturity and perfection of large-span PBA method construction under unfavorable geology and provide reference for similar projects. Full article

(This article belongs to the Topic Advances in Monitoring of Transportation Infrastructures)
(This article belongs to the Section Construction and Building Materials)

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18 pages, 2897 KiB

Open AccessArticle

Development of High Temperature Water Sorbents Based on Zeolites, Dolomite, Lanthanum Oxide and Coke

by Esther Acha, Ion Agirre and V. Laura Barrio

Materials 2023, 16(7), 2933; https://doi.org/10.3390/ma16072933 - 6 Apr 2023

Cited by 4 | Viewed by 1609

Abstract

Methanation is gaining attention as it produces green methane from CO₂ and H₂, through Power-to-Gas technology. This process could be improved by in situ water sorption. The main difficulty for this process intensification is to find effective water sorbents at [...] Read more.

Methanation is gaining attention as it produces green methane from CO₂ and H₂, through Power-to-Gas technology. This process could be improved by in situ water sorption. The main difficulty for this process intensification is to find effective water sorbents at useful reaction temperatures (275–400 °C). The present work comprises the study of the water sorption capacity of different materials at 25–400 °C. The sorption capacity of the most studied solid sorbents (zeolites 3A & 4A) was compared to other materials such as dolomite, La₂O₃ and cokes. In trying to improve their stability and sorption capacity at high temperatures, all these materials were modified with alkaline-earth metals (Ba, Ca & Mg). Lanthana-Ba and dolomite sorbents were the most promising materials, reaching water sorption values of 120 and 102 mg_H2O/g_sorbent, respectively, even at 300 °C, i.e., values 10-times higher than the achieved ones with zeolites 3A or 4A under the same operating conditions. At these high temperatures, around 300 °C, the water sorption process was concluded to be closer to chemisorption than to physisorption. Full article

(This article belongs to the Special Issue Development and Modification of New or Recycled Materials and Technological Processes toward Sustainable Development)

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27 pages, 8008 KiB

Open AccessArticle

Nanoval Technology—An Intermediate Process between Meltblown and Spunbond

by Tim Höhnemann, Johannes Schnebele, Walter Arne and Ingo Windschiegl

Materials 2023, 16(7), 2932; https://doi.org/10.3390/ma16072932 - 6 Apr 2023

Cited by 5 | Viewed by 3747

Abstract

The idea of ”Nanoval technology“ origins in the metal injection molding for gas atomization of metal powders and the knowledge of spunbond technologies for the creation of thermoplastic nonwovens using the benefits of both techniques. In this study, we evaluated processing limits experimentally [...] Read more.

The idea of ”Nanoval technology“ origins in the metal injection molding for gas atomization of metal powders and the knowledge of spunbond technologies for the creation of thermoplastic nonwovens using the benefits of both techniques. In this study, we evaluated processing limits experimentally for the spinning of different types of polypropylene, further standard polymers, and polyphenylene sulfide, marked by defect-free fiber creation. A numerical simulation study of the turbulent air flow as well as filament motion in the process visualized that the turnover from uniaxial flow (initial stretching caused by the high air velocity directed at the spinning die) to turbulent viscoelastic behavior occurs significantly earlier than in the melt-blown process. Modeling of the whole process showed that additional guide plates below the spinneret reduce the turbulent air flow significantly by regulating the inflow of secondary process air. The corresponding melt flow index of processible polymer grades varied between 35 g·10min⁻¹ up to 1200 g·10min⁻¹ and thus covering the range of extrusion-type, spunbond-type, yarn-type, and meltblown-type polymers. Hence, mean fiber diameters were adjustable for PP between 0.8 and 39.3 μm without changing components of the process setup. This implies that the Nanoval process enables the flexibility to produce fiber diameters in the typical range achievable by the standard meltblown process (~1–7 μm) as well as in the coarseness of spunbond nonwovens (15–30 μm) and, moreover, operates in the gap between them. Full article

(This article belongs to the Special Issue Advances in High-Performance Functional Nonwovens)

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17 pages, 6109 KiB

Open AccessArticle

Effect of Furfurylation on Bamboo-Scrimber Composites

by Wanju Li, Guijun Xie, Hongxia Ma and Xingwei Li

Materials 2023, 16(7), 2931; https://doi.org/10.3390/ma16072931 - 6 Apr 2023

Cited by 1 | Viewed by 1888

Abstract

Bamboo is a material with excellent development prospects. It is increasingly used in furniture, decoration, building, and bridge construction. In this study, Furfurylated bamboo bundles and phenol-formaldehyde resin were used to make bamboo-scrimber composites (BSCs) via molding-recombination and hot-pressing processes. The effects of [...] Read more.

Bamboo is a material with excellent development prospects. It is increasingly used in furniture, decoration, building, and bridge construction. In this study, Furfurylated bamboo bundles and phenol-formaldehyde resin were used to make bamboo-scrimber composites (BSCs) via molding-recombination and hot-pressing processes. The effects of the impregnation mode, furfuryl-alcohol concentration, and curing temperature on the various physical–mechanical properties and durability of the composites were evaluated. Scanning-electron microscopy (SEM) was used to observe the microstructural differences. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were employed to investigate changes in the chemical constituents. The heat resistance was also investigated using thermogravimetric analysis. The results showed that the density of the furfurylated BSC increased by up to 22% compared with that of the BSC-C with the same paving mode. The furfurylated BSCs had lower moisture contents: the average moisture content of the furfurylated BSCs was 25~50% lower than that of the BSC-C. In addition, the furfurylated BSCs showed better dimensional stability and durability, since the decay-resistance grade of the BSCs was raised from decay resistance (class II) to strong decay resistance (class I). In terms of the mechanical properties, the furfurylation had a slight negative effect on the mechanical strength of the BSCs, and the modulus of rupture (MOR) and horizontal shear strength (HSS) of the BSCs were increased to a certain extent under most of the treatment conditions. In particular, the highest HSS for indoor use and MOR of the furfurylated BSCs increased by 21% and 9% compared with those of the untreated BSCs, respectively. The SEM results indicated that the FA resin effectively filled in the bamboo-cell cavities and vessels, and the modified bamboo-parenchyma cells were compressed more tightly and evenly. The FTIR and XPS spectroscopy showed that the hydroxyl group of carboxylic acid of the bamboo-cell-wall component reacted with that of the furan ring, and the cellulose and hemicellulose underwent acid hydrolysis to a certain extent after the furfurylation. Overall, the present study highlights the potential of furfurylation as a modification method to enhance BSC products. Further research should focus on improving the ability of furfurylated BSCs to prevent the growth of Botryodiplodia theobromae. Additionally, the influence of furfuryl-alcohol resin on the bonding strengths of PF adhesives should be further clarified. Full article

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15 pages, 4461 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Mg-Impurities in Raw Materials on the Synthesis of Rankinite Clinker and the Strength of Mortar Hardening in CO₂ Environment

by Raimundas Siauciunas, Edita Prichockiene and Zenonas Valancius

Materials 2023, 16(7), 2930; https://doi.org/10.3390/ma16072930 - 6 Apr 2023

Cited by 3 | Viewed by 1631

Abstract

The idea of this work is to reduce the negative effect of ordinary Portland cement (OPC) manufacture on the environment by decreasing clinker production temperature and developing an alternative rankinite binder that hardens in the CO₂ atmosphere. The common OPC raw materials, [...] Read more.

The idea of this work is to reduce the negative effect of ordinary Portland cement (OPC) manufacture on the environment by decreasing clinker production temperature and developing an alternative rankinite binder that hardens in the CO₂ atmosphere. The common OPC raw materials, limestone and mica clay, if they contain a higher MgO content, have been found to be unsuitable for the synthesis of CO₂-curing low-lime binders. X-ray diffraction analysis (ex-situ and in-situ in the temperature range of 25–1150 °C) showed that akermanite Ca₂Mg(Si₂O₇) begins to form at a temperature of 900 °C. According to Rietveld refinement, the interlayer distances of the resulting curve are more accurately described by the compound, which contains intercalated Fe²⁺ and Al³⁺ ions and has the chemical formula Ca₂(MgO_0.495·FeO_0.202·AlO_0.303)·(FeO_0.248·AlO·Si_1.536·O₇). Stoichiometric calculations showed that FeO and Al₂O₃ have replaced about half of the MgO content in the akermanite structure. All this means that only ~4 wt% MgO content in the raw materials determines that ~60 wt% calcium magnesium silicates are formed in the synthesis product. Moreover, it was found that the formed akermanite practically does not react with CO₂. Within 24 h of interaction with 99.9 wt% of CO₂ gas (15 bar), the intensity of the akermanite peaks does not practically change at 25 °C; no changes are observed at 45 °C, either, which means that the chemical reaction does not take place. As a result, the compressive strength of the samples compressed from the synthesized product and CEN Standard sand EN 196-1 (1:3), and hardened at 15 bar CO₂, 45 °C for 24 h, was only 14.45 MPa, while the analogous samples made from OPC clinker obtained from the same raw materials yielded 67.5 MPa. Full article

(This article belongs to the Special Issue Advances in Sustainable Civil Engineering Materials)

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12 pages, 3857 KiB

Open AccessArticle

How Retting Could Affect the Mechanical Behavior of Flax/Epoxy Biocomposite Materials?

by Mohamed Ragoubi, Morgan Lecoublet, Mehdi Khennache, Leonard Ionut Atanase, Christophe Poilane and Nathalie Leblanc

Materials 2023, 16(7), 2929; https://doi.org/10.3390/ma16072929 - 6 Apr 2023

Viewed by 1322

Abstract

This study focuses on the retting effect on the mechanical properties of flax biobased materials. For the technical fiber, a direct link was established between the biochemical alteration of technical flax and their mechanical properties. In function of the retting level, technical fibers [...] Read more.

This study focuses on the retting effect on the mechanical properties of flax biobased materials. For the technical fiber, a direct link was established between the biochemical alteration of technical flax and their mechanical properties. In function of the retting level, technical fibers appeared smoother and more individualized; nevertheless, a decrease in the ultimate modulus and maximum stress was recorded. A biochemical alteration was observed as the retting increased (a decrease in the soluble fraction from 10.4 ± 0.2 to 4.5 ± 1.2% and an increase in the holocellulose fractions). Regarding the mechanical behavior of biocomposites manufactured by thermocompression, a non-elastic behavior was observed for the tested samples. Young moduli (E1 and E2) gradually increased with retting. The retting effect was more pronounced when a normalization was performed (according to the fiber volume and porosity). A 40% increase in elastic modulus could be observed between under-retting (−) and over-retting (+). Moreover, the porosity content (Vp) increased overall with fiber content. Setup 3, with optimized processing parameters, was the most desirable processing protocol because it allowed the highest fiber fraction (Vf) for the lowest Vp. Full article

(This article belongs to the Special Issue Advanced Polymeric Biocomposites: Synthesis, Characterizations, and Applications)

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26 pages, 87339 KiB

Open AccessArticle

The Quadratic Constitutive Model Based on Partial Derivative and Taylor Series of Ti6242s Alloy and Predictability Analysis

by Jiansheng Zhang, Guiqian Xiao, Guoyong Deng, Yancheng Zhang and Jie Zhou

Materials 2023, 16(7), 2928; https://doi.org/10.3390/ma16072928 - 6 Apr 2023

Cited by 2 | Viewed by 1309

Abstract

To solve the problem of insufficient predictability in the classical models for the Ti6242s alloy, a new constitutive model was proposed, based on the partial derivatives from experimental data and the Taylor series. Firstly, hot compression experiments on the Ti6242s alloy at different [...] Read more.

To solve the problem of insufficient predictability in the classical models for the Ti6242s alloy, a new constitutive model was proposed, based on the partial derivatives from experimental data and the Taylor series. Firstly, hot compression experiments on the Ti6242s alloy at different temperatures and different strain rates were carried out, and the Arrhenius model and Hensel–Spittel model were constructed. Secondly, the partial derivatives of logarithmic stress with respect to temperature and logarithmic strain rate at low, medium and high strain levels were analyzed. Thirdly, two new constitutive models with first- and second-order approximation were proposed to meet the requirements of high precision. In this new model, by analyzing the high-order differential data of experimental data and combining the Taylor series theory, the minimum number of terms that can accurately approximate the experimental rheological data was found, thereby achieving an accurate prediction of flow stress with minimal material parameters. In the new model, by analyzing the high-order differential of the experimental data and combining the theory of the Taylor series, the minimum number of terms that can accurately approximate the experimental rheological data was found, thereby achieving an accurate prediction of flow stress with minimal material parameters. Finally, the prediction accuracies for the classical model and the new model were compared, and the predictabilities for the classical models and the new model were proved by mathematical means. The results show that the prediction accuracies of the Arrhenius model and the Hensel–Spittel model are low in the single-phase region and high in the two-phase region. In addition, second-order approximation is required between the logarithmic stress and logarithmic strain rate, and first-order approximation is required between logarithmic stress and temperature to establish a high-precision model. The order of prediction accuracy of the four models from high to low is the quadratic model, Arrhenius model, linear model and HS model. The prediction accuracy of the quadratic model in all temperatures and strain rates had no significant difference, and was higher than the other models. The quadratic model can greatly improve prediction accuracy without significantly increasing the material parameters. Full article

(This article belongs to the Special Issue Research on Forming and Serving Performance of Advanced Alloys)

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17 pages, 6080 KiB

Open AccessArticle

Fatigue Experiment Study on Internal Force Redistribution in the Negative Moment Zone of Steel–Concrete Continuous Composite Box Beams

by Yongzhi Gong, Qi Zhong, Yingjie Shan and Yu Sun

Materials 2023, 16(7), 2927; https://doi.org/10.3390/ma16072927 - 6 Apr 2023

Cited by 1 | Viewed by 1415

Abstract

Due to the accumulated fatigue damage in steel–concrete continuous composite box beams, a plastic hinge forms in the negative moment zone, leading to significant internal force redistribution. To investigate the internal force redistribution in the negative moment zone and confirm structural safety under [...] Read more.

Due to the accumulated fatigue damage in steel–concrete continuous composite box beams, a plastic hinge forms in the negative moment zone, leading to significant internal force redistribution. To investigate the internal force redistribution in the negative moment zone and confirm structural safety under fatigue loading, experimental tests were conducted on nine steel–concrete continuous composite box beams: eight of them under fatigue testing, one of them under static testing. The test results showed that the moment modification coefficient at the middle support increases during the fatigue process. When approaching fatigue failure, an increase of 1.0% in the reinforcement ratio or 0.27% in the stirrup ratio results in a reduction of 13% in the moment modification coefficient. Furthermore, a quadratic function model was proposed to calculate the moment modification coefficient of a steel–concrete continuous composite box beam during the fatigue process, which exhibited good agreement with the experimental results. Finally, we verified the applicability of the plastic hinge rotation theory for steel–concrete continuous composite box beams under fatigue loading. Full article

(This article belongs to the Section Advanced Composites)

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20 pages, 8487 KiB

Open AccessArticle

The Effects of Co on the Microstructure and Mechanical Properties of Ni-Based Superalloys Prepared via Selective Laser Melting

by Xiaoqiong Ouyang, Feng Liu, Lan Huang, Lin Ye, Heng Dong, Liming Tan, Li Wang, Xiaochao Jin and Yong Liu

Materials 2023, 16(7), 2926; https://doi.org/10.3390/ma16072926 - 6 Apr 2023

Cited by 2 | Viewed by 2065

Abstract

In this work, two Ni-based superalloys with 13 wt.% and 35 wt.% Co were prepared via selective laser melting (SLM), and the effects of Co on the microstructure and mechanical properties of the additively manufactured superalloys were investigated. As the Co fraction increased [...] Read more.

In this work, two Ni-based superalloys with 13 wt.% and 35 wt.% Co were prepared via selective laser melting (SLM), and the effects of Co on the microstructure and mechanical properties of the additively manufactured superalloys were investigated. As the Co fraction increased from 13 wt.% to 35 wt.%, the average grain size decreased from 25.69 μm to 17.57 μm, and the size of the nano-phases significantly increased from 80.54 nm to 230 nm. Moreover, the morphology of the γ′ phase changed from that of a cuboid to a sphere, since Co decreased the γ/γ′ lattice mismatch from 0.64% to 0.19%. At room temperature, the yield strength and ultimate tensile strength of the 13Co alloy reached 1379 MPa and 1487.34 MPa, and those of the 35Co alloy were reduced to 1231 MPa and 1350 MPa, while the elongation increased by 52%. The theoretical calculation indicated that the precipitation strengthening derived from the γ′ precipitates made the greatest contribution to the strength. Full article

(This article belongs to the Special Issue Recent Advances in Metal Powder Based Additive Manufacturing)

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20 pages, 6043 KiB

Open AccessArticle

Hydration Heat Control of Mass Concrete by Pipe Cooling Method and On-Site Monitoring-Based Influence Analysis of Temperature for a Steel Box Arch Bridge Construction

by Tan Zhang, Hua Wang, Yuejing Luo, Ye Yuan and Wensheng Wang

Materials 2023, 16(7), 2925; https://doi.org/10.3390/ma16072925 - 6 Apr 2023

Cited by 8 | Viewed by 2813

Abstract

The steel box arch bridge in this study will be subjected to various temperature effects from the construction to the operation stage, including the cement hydration heat effect and the sunshine temperature effect caused by an ambient temperature change. Therefore, it is very [...] Read more.

The steel box arch bridge in this study will be subjected to various temperature effects from the construction to the operation stage, including the cement hydration heat effect and the sunshine temperature effect caused by an ambient temperature change. Therefore, it is very important to control the temperature effect of steel box arch bridges. In this study, the newly built Dafeng River Bridge is selected as the steel box arch bridge. This study aims to investigate the temperature effect including hydration heat and the sunshine temperature effect of the construction process of a rigid frame-tied steel box arch bridge. The manuscript presents that the heat dissipation performance of concrete decreases with the increase in the thickness of a mass concrete structure. The average maximum temperature values of layer No. 3 are about 1.3, 1.2, and 1.1 times the average maximum temperature value of layer No. 1 for the mass concrete of the cushion cap, main pier and arch abutment, respectively. The higher the molding temperature is, the higher the maximum temperature by the hydration heat effect is. With each 5 °C increase in the molding temperature, the maximum temperature at the core area increases by about 4~5 °C for the mass concrete. The pipe cooling method is conducive to the hydration heat control effect of mass concrete. Based on the monitored temperature change and displacement change, the influences of daily temperature change on the steel lattice beam and arch rib are analyzed. A temperature rise will cause the structure to have a certain camber in the longitudinal direction, and the longitudinal or transverse displacement caused by the sunshine temperature change is no less than the vertical displacement. Due to the symmetrical construction on both sides of the river, the arch rib deformation on both sides presents symmetrical synchronous changes. Based on 84 h of continuous temperature monitoring on-site, the changing trends of the arch back temperature and ambient temperature are consistent and their difference is small during 1:00~4:00 in the morning, which is determined as the appropriate closure time for the newly built Dafeng River Bridge. Full article

(This article belongs to the Special Issue Characterization, Applications and New Technologies of Civil Engineering Materials and Structures)

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31 pages, 16232 KiB

Open AccessArticle

Thermodynamic Analysis of Chemical Hydrogen Storage: Energetics of Liquid Organic Hydrogen Carrier Systems Based on Methyl-Substituted Indoles

by Sergey V. Vostrikov, Artemiy A. Samarov, Vladimir V. Turovtsev, Peter Wasserscheid, Karsten Müller and Sergey P. Verevkin

Materials 2023, 16(7), 2924; https://doi.org/10.3390/ma16072924 - 6 Apr 2023

Cited by 4 | Viewed by 1998

Abstract

Liquid organic hydrogen carriers can store hydrogen in a safe and dense form through covalent bonds. Hydrogen uptake and release are realized by catalytic hydrogenation and dehydrogenation, respectively. Indoles have been demonstrated to be interesting candidates for this task. The enthalpy of reaction [...] Read more.

Liquid organic hydrogen carriers can store hydrogen in a safe and dense form through covalent bonds. Hydrogen uptake and release are realized by catalytic hydrogenation and dehydrogenation, respectively. Indoles have been demonstrated to be interesting candidates for this task. The enthalpy of reaction is a crucial parameter in this regard as it determines not only the heat demand for hydrogen release, but also the reaction equilibrium at given conditions. In this work, a combination of experimental measurements, quantum chemical methods and a group-additivity approach has been applied to obtain a consistent dataset on the enthalpies of formation of different methylated indole derivatives and their hydrogenated counterparts. The results show a namable influence of the number and position of methyl groups on the enthalpy of reaction. The enthalpy of reaction of the overall hydrogenation reaction varies in the range of up to 18.2 kJ·mol⁻¹ (corresponding to 4.6 kJ·mol(H₂)⁻¹). The widest range of enthalpy of reaction data for different methyl indoles has been observed for the last step (hydrogenation for the last double bond in the five-membered ring). Here a difference of up to 7.3 kJ·mol(H₂)⁻¹ between the highest and the lowest value was found. Full article

(This article belongs to the Special Issue Advance Materials for Hydrogen Storage)

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23 pages, 8504 KiB

Open AccessEditor’s ChoiceArticle

Scratch and Wear Behaviour of Co-Cr-Mo Alloy in Ringer’s Lactate Solution

by Raimundo Silva, Marcos Dantas dos Santos, Rui Madureira, Rui Soares, Rui Neto, Ângela Aparecida Vieira, Polyana Alves Radi Gonçalves, Priscila Maria Sarmeiro M. Leite, Lúcia Vieira and Filomena Viana

Materials 2023, 16(7), 2923; https://doi.org/10.3390/ma16072923 - 6 Apr 2023

Cited by 5 | Viewed by 2092

Abstract

Cobalt–chromium–molybdenum (Co-Cr-Mo) alloy is a material recommended for biomedical implants; however, to be suitable for this application, it should have good tribological properties, which are related to grain size. This paper investigates the tribological behaviour of a Co-Cr-Mo alloy produced using investment casting, [...] Read more.

Cobalt–chromium–molybdenum (Co-Cr-Mo) alloy is a material recommended for biomedical implants; however, to be suitable for this application, it should have good tribological properties, which are related to grain size. This paper investigates the tribological behaviour of a Co-Cr-Mo alloy produced using investment casting, together with electromagnetic stirring, to reduce its grain size. The samples were subjected to wear and scratch tests in simulated body fluid (Ringer’s lactate solution). Since a reduction in grain size can influence the behaviour of the material, in terms of resistance and tribological response, four samples with different grain sizes were produced for use in our investigation of the behaviour of the alloy, in which we considered the friction coefficient, wear, and scratch resistance. The experiments were performed using a tribometer, with mean values for the friction coefficient, normal load, and tangential force acquired and recorded by the software. Spheres of Ti-6Al-4V and 316L steel were used as counterface materials. In addition, to elucidate the influence of grain size on the mechanical properties of the alloy, observations were conducted via scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). The results showed changes in the structure, with a reduction in grain size from 5.51 to 0.79 mm. Using both spheres, the best results for the friction coefficient and wear volume corresponded to the sample with the smallest grain size of 0.79 mm. The friction coefficients obtained were 0.37 and 0.45, using the Ti-6Al-4V and 316L spheres, respectively. These results confirm that the best surface finish for Co-Cr-Mo alloy used as a biomedical implant is one with a smaller grain size, since this results in a lower friction coefficient and low wear. Full article

(This article belongs to the Section Metals and Alloys)

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13 pages, 5285 KiB

Open AccessArticle

A Lightweight AlCrTiV_0.5Cu_x High-Entropy Alloy with Excellent Corrosion Resistance

by Zhen Peng, Baowei Li, Zaibin Luo, Xuefei Chen, Yao Tang, Guannan Yang and Pan Gong

Materials 2023, 16(7), 2922; https://doi.org/10.3390/ma16072922 - 6 Apr 2023

Cited by 11 | Viewed by 1871

Abstract

Lightweight high-entropy alloys (HEAs) are a new class of low-density, high strength-to-weight ratio metallic structural material. Understanding their corrosion behavior is crucial for designing microstructures for their practical applications. This work investigates the electrochemical corrosion behavior of lightweight HEAs AlCrTiV_0.5Cu_x [...] Read more.

Lightweight high-entropy alloys (HEAs) are a new class of low-density, high strength-to-weight ratio metallic structural material. Understanding their corrosion behavior is crucial for designing microstructures for their practical applications. This work investigates the electrochemical corrosion behavior of lightweight HEAs AlCrTiV_0.5Cu_x (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) in a 0.6 M NaCl solution. These HEAs were produced by vacuum arc melting. In contrast to 304L stainless steel, all of the alloys exhibited lower current density levels caused by self-corrosion, with AlCrTiV_0.5 demonstrating the highest corrosion resistance (0.131 μA/cm²). Corrosion resistance decreased along with the content of copper because copper segregation accelerated local corrosion throughout the alloy. Full article

(This article belongs to the Special Issue Physical Metallurgy of Metals and Alloys)

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14 pages, 3850 KiB

Open AccessArticle

Efficient Synthesis of 2D Mica Nanosheets by Solvothermal and Microwave-Assisted Techniques for CO₂ Capture Applications

by P. Vishakha T. Weerasinghe, Shunnian Wu, W. P. Cathie Lee, Ming Lin, Franklin Anariba, Xu Li, Debbie Hwee Leng Seng, Jia Yu Sim and Ping Wu

Materials 2023, 16(7), 2921; https://doi.org/10.3390/ma16072921 - 6 Apr 2023

Cited by 3 | Viewed by 2578

Abstract

Mica, a commonly occurring mineral, has significant potential for various applications due to its unique structure and properties. However, due to its non-Van Der Waals bonded structure, it is difficult to exfoliate mica into ultrathin nanosheets. In this work, we report a rapid [...] Read more.

Mica, a commonly occurring mineral, has significant potential for various applications due to its unique structure and properties. However, due to its non-Van Der Waals bonded structure, it is difficult to exfoliate mica into ultrathin nanosheets. In this work, we report a rapid solvothermal microwave synthesis of 2D mica with short reaction time and energy conservation. The resulting exfoliated 2D mica nanosheets (eMica nanosheets) were characterized by various techniques, and their ability to capture CO₂ was tested by thermogravimetric analysis (TGA). Our results showed an 87% increase in CO₂ adsorption capacity with eMica nanosheets compared to conventional mica. Further characterization by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), as well as first-principles calculations, showed that the high specific surface area and deposited K₂CO₃ layer contribute to the increased CO₂ adsorption on the mica nanosheets. These results speak to the potential of high-quality eMica nanosheets and efficient synthesis processes to open new avenues for new physical properties of 2D materials and the development of CO₂ capture technologies. Full article

(This article belongs to the Special Issue Synthesis, Porous Structure Analysis, and Application of Sorbents in CO₂ Capture)

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18 pages, 8199 KiB

Open AccessArticle

Study on Flexural Performance of Aluminum Alloy Gusset Joints Subjected to Bending Moment and Shear Force

by Hao Wang, Jialiang Li, Pengcheng Li, Li Zhong, Xiaoyue Zhang and Chao Li

Materials 2023, 16(7), 2920; https://doi.org/10.3390/ma16072920 - 6 Apr 2023

Cited by 3 | Viewed by 1704

Abstract

Aluminum alloy gusset (AAG) joints are widely applied in space reticulated shell structures. To investigate the flexural performance of AAG joints under the combined action of shear force and in-plane and out-of-plane bending moments, this analysis was developed by means of finite element [...] Read more.

Aluminum alloy gusset (AAG) joints are widely applied in space reticulated shell structures. To investigate the flexural performance of AAG joints under the combined action of shear force and in-plane and out-of-plane bending moments, this analysis was developed by means of finite element (FE) models implemented in the non-linear code ABAQUS, and the accuracy of the FE simulation results based on the existing AAG joint test results was verified. The FE simulation results effectively described the mechanical properties of the AAG joints, including the failure mode, deformation process and bending moment-rotation curves. Furthermore, a parametric study was conducted by varying the height of the member section, the number of bolts, the radius of the joint plate, the thickness of the joint plate, the bolt preload force, and the ratio of in-plane to out-of-plane bending moments. It was found that these parameters had different effects on the bending behavior of the AAG joints. Full article

(This article belongs to the Special Issue Developments of Steels and Alloys for Structural and Functional Applications)

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29 pages, 25279 KiB

Open AccessArticle

Mechanical Reclamation of Spent Moulding Sand on Chromite Sand Matrix; Removal of Alkali-Phenolic Binder

by Mariusz Łucarz, Aldona Garbacz-Klempka, Dariusz Drożyński, Mateusz Skrzyński and Krzysztof Kostrzewa

Materials 2023, 16(7), 2919; https://doi.org/10.3390/ma16072919 - 6 Apr 2023

Cited by 1 | Viewed by 1871

Abstract

The foundry industry generates large amounts of waste when casting metal into sand moulds. An important issue is the activities that are related to the re-recovery of the grain matrix (the main component of the moulding sand) for realising subsequent technological cycles. This [...] Read more.

The foundry industry generates large amounts of waste when casting metal into sand moulds. An important issue is the activities that are related to the re-recovery of the grain matrix (the main component of the moulding sand) for realising subsequent technological cycles. This process is particularly important in the case of the expensive chromite matrix that is necessary for use in manganese steel casting. The effects of the reclamation treatments of spent alkali-phenolic binder sand were evaluated by scanning electron microscopy with EDS, analysing the chemical composition in micro areas and proving the loss of binder on the surfaces of the matrix grains. Tests were also performed using the main criteria for evaluating a reclaimed organic binder: sieve analysis and ignition loss. A thermogravimetric analysis study was performed to assess the change in the chromite character of the grain matrix under the influence of temperature. The effects of the reclamation measures were verified by making moulding compounds on a matrix of reclaimed sand and a mixture of reclaimed and fresh sand. The tests and analyses that were carried out indicated the direction of an effective method for reclaiming used alkali-phenolic binder masses and the extent of the proportion of the regenerate in moulding sand in order to maintain the relevant technological parameters of the moulding sand. Full article

(This article belongs to the Special Issue Advanced Materials – Microstructure, Manufacturing and Analysis)

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14 pages, 6341 KiB

Open AccessArticle

Fatigue Behavior of Sandstone Exposed to Cyclic Point-Loading: Implications for Improving Mechanized Rock Breakage Efficiency

by Xin Cai, Jifeng Yuan, Zilong Zhou, Zhibo Wu, Jianmin Liu, Barkat Ullah and Shaofeng Wang

Materials 2023, 16(7), 2918; https://doi.org/10.3390/ma16072918 - 6 Apr 2023

Cited by 2 | Viewed by 1438

Abstract

During the process of mechanized excavation, rock is essentially subjected to cyclic point loading (CPL). To understand the CPL fatigue behavior of rock materials, a series of CPL tests are conducted on sandstone samples by using a self-developed vibration point-load apparatus. The effects [...] Read more.

During the process of mechanized excavation, rock is essentially subjected to cyclic point loading (CPL). To understand the CPL fatigue behavior of rock materials, a series of CPL tests are conducted on sandstone samples by using a self-developed vibration point-load apparatus. The effects of loading frequency and waveform on rock fatigue properties under CPL conditions are specifically investigated. The load and indentation depth histories of sandstone samples during testing are monitored and logged. The variation trends of fatigue life (failure time) under different loading conditions are obtained. Test results indicate that the fatigue life of the sandstone sample exposed to CPL is dependent on both loading frequency and waveform. As the loading frequency rises, the fatigue life of the sandstone first declines and then increases, and it becomes the lowest at 0.5 Hz. In terms of waveform, the fatigue life of the sandstone is largest under the trigonal wave and is least under the rectangular wave. These findings can provide valuable theoretical support for optimizing the rock cutting parameters to enhance the efficiency of mechanized excavation. Full article

(This article belongs to the Special Issue Experimental, Theoretical, Numerical and Big-Data-Based Investigations on Characterizations for Geomaterials)

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25 pages, 9089 KiB

Open AccessArticle

Degradation of Steel Rebar Tensile Properties Affected by Longitudinal Non-Uniform Corrosion

by Jinhong Liu, Xiaoyong Luo and Qi Chen

Materials 2023, 16(7), 2917; https://doi.org/10.3390/ma16072917 - 6 Apr 2023

Cited by 2 | Viewed by 2571

Abstract

Rebar corrosion is the primary cause of the durability degradation of reinforced concrete (RC) structures, where non-uniform corrosion is the typical pattern in engineering. This study experimentally and numerically investigated the tensile degradation properties of non-uniform corroded rebars. Corrosion morphology was accurately determined [...] Read more.

Rebar corrosion is the primary cause of the durability degradation of reinforced concrete (RC) structures, where non-uniform corrosion is the typical pattern in engineering. This study experimentally and numerically investigated the tensile degradation properties of non-uniform corroded rebars. Corrosion morphology was accurately determined by three-dimensional (3D) laser scanning techniques, studying the characteristics of longitudinal non-uniform corrosion. The results showed that the non-uniformity of corrosion increased with an increase in corrosion levels. From tensile tests, the differences in nominal stress–strain curves among rebars with similar average corrosion levels indicated that corrosion non-uniformity has appreciable effects on the tensile behavior of rebars. The residual load-bearing capacity of corroded rebars was dominated by the reduced critical cross-section, while residual ductility was associated with the cross-section loss throughout the entire length of rebars. The degradation relations of nominal yield and ultimate strength, ultimate strain, and elongation after fracture were better correlated to the maximum cross-section loss than to the average volume loss. Additionally, numerical calculation based on the cross-sectional areas of corroded rebars was conducted to evaluate the tensile behavior of non-uniform corroded rebars. Equivalent distribution models simulating the longitudinal non-uniform corrosion were proposed, on the basis of probability characteristics of cross-sectional areas, for practical application of the numerical method. Full article

(This article belongs to the Section Construction and Building Materials)

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10 pages, 8836 KiB

Open AccessArticle

Influence of Barrier Layers on ZrCoCe Getter Film Performance

by Xin Shi, Yuhua Xiong and Huating Wu

Materials 2023, 16(7), 2916; https://doi.org/10.3390/ma16072916 - 6 Apr 2023

Cited by 1 | Viewed by 1356

Abstract

Improving the vacuum degree inside the vacuum device is vital to the performance and lifespan of the vacuum device. The influence of the Ti and ZrCoCe barrier layers on the performance of ZrCoCe getter films, including sorption performance, anti-vibration performance, and binding force [...] Read more.

Improving the vacuum degree inside the vacuum device is vital to the performance and lifespan of the vacuum device. The influence of the Ti and ZrCoCe barrier layers on the performance of ZrCoCe getter films, including sorption performance, anti-vibration performance, and binding force between the ZrCoCe getter film and the Ge substrate were investigated. In this study, the Ti and ZrCoCe barrier layers were deposited between the ZrCoCe getter films and Ge substrates. The microtopographies of barrier layers and the ZrCoCe getter film were analyzed using scanning electron microscopes. The sorption performance was evaluated using the constant-pressure method. The surface roughness of the barrier layers and the getter films was analyzed via atomic force microscopy. The binding force was measured using a nanoscratch tester. The anti-vibration performance was examined using a vibration test bench. The characterization results revealed that the Ti barrier layer significantly improved the sorption performance of the ZrCoCe getter film. When the barrier material was changed from ZrCoCe to Ti, the initial sorption speed of the ZrCoCe getter film increased from 141 to 176 cm³·s⁻¹·cm⁻², and the sorption quantity increased from 223 to 289 Pa·cm³·cm⁻² in 2 h. The binding force between the Ge substrate and the ZrCoCe getter film with the Ti barrier layer was 171 mN, whereas that with the ZrCoCe barrier layer was 154 mN. The results showed that the Ti barrier layer significantly enhanced the sorption performance and binding force between the ZrCoCe getter film and the Ge substrate, which improved the internal vacuum level and the stability of the microelectromechanical system vacuum devices. Full article

(This article belongs to the Special Issue Advanced Properties of Engineering Thin Films and Materials)

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14 pages, 4214 KiB

Open AccessArticle

Investigations on Thermal Conductivity of Two-Phase WC-Co-Ni Cemented Carbides through a Novel Model and Key Experiments

by Shiyi Wen, Jing Tan, Jianzhan Long, Zhuopeng Tan, Lei Yin, Yuling Liu, Yong Du and George Kaptay

Materials 2023, 16(7), 2915; https://doi.org/10.3390/ma16072915 - 6 Apr 2023

Cited by 1 | Viewed by 1585

Abstract

Excellent thermal conductivity is beneficial for the fast heat release during service of cemented carbides. Thus, thermal conductivity is a significant property of cemented carbides, considerably affecting their service life. Still, there is a lack of systematic investigation into the thermal conductivity of [...] Read more.

Excellent thermal conductivity is beneficial for the fast heat release during service of cemented carbides. Thus, thermal conductivity is a significant property of cemented carbides, considerably affecting their service life. Still, there is a lack of systematic investigation into the thermal conductivity of two-phase WC-Co-Ni cemented carbides. To remedy this situation, we integrated experiments and models to study its thermal conductivity varying the phase composition, temperature and WC grain size. To conduct the experiments, WC-Co-Ni samples with two-phase structure were designed via the CALPHAD (Calculation of Phase Diagrams) approach and then prepared via the liquid-phase sintering process. Key thermal conductivity measurements of these prepared samples were then taken via LFA (Laser Flash Analysis). As for modeling, the thermal conductivities of (Co, Ni) binder phase and WC hard phase were firstly evaluated through our previously developed models for single-phase solid solutions. Integrating the present key measurements and models, the values of ITR (Interface Thermal Resistance) between WC hard phase and (Co, Ni) binder phase were evaluated and thus the model to calculate thermal conductivity of two-phase WC-Co-Ni was established. Meanwhile, this model was verified to be reliable through comparing the model-evaluated thermal conductivities with the experimental data. Furthermore, using this developed model, the thermal conductivity of two-phase WC-Co-Ni varying with phase-fraction, temperature and grain size of WC was predicted, which can contribute to its design for obtaining desired thermal conductivities. Full article

(This article belongs to the Special Issue Metallic Materials: Microstructure, Phase Equilibria and Thermodynamics)

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14 pages, 104571 KiB

Open AccessArticle

Experimental Study on Basic Mechanical Properties of PVA Fiber-Reinforced Coral Cement-Based Composites

by Jin Yi, Lei Wang, Linjian Ma, Qiancheng Zhang, Jiwang Zhang and Junsheng Chi

Materials 2023, 16(7), 2914; https://doi.org/10.3390/ma16072914 - 6 Apr 2023

Cited by 4 | Viewed by 1652

Abstract

In order to improve the brittle characteristics of coral cement-based composites and increase their toughness, an experimental study was carried out on the basic mechanical properties of PVA (polyvinyl alcohol) fiber-reinforced coral cement-based composites, taking into account the fiber content and length-to-diameter ratio [...] Read more.

In order to improve the brittle characteristics of coral cement-based composites and increase their toughness, an experimental study was carried out on the basic mechanical properties of PVA (polyvinyl alcohol) fiber-reinforced coral cement-based composites, taking into account the fiber content and length-to-diameter ratio (L/D). The results showed that PVA fibers can effectively improve the mechanical properties of concrete, especially its tensile strength. At the same time, PVA fibers improved the damage characteristics of cement-based composites and had obvious toughening and brittleness reduction effects. The PVA fibers, with a volume content of 1.5% and an L/D of 225, had the best performance in reinforcing the overall performance of the coral cement-based composites. Too many PVA fibers or a large length-to-diameter ratio would make it difficult for the fibers to contribute to toughness and cracking resistance and even cause defects in the matrix, reducing the mechanical properties. The tensile stress-strain curves of PVA fiber-reinforced coral cement-based composites were consistent with the trilinear constitutive model curves and showed the tensile characteristic of strain hardening after the occurrence of the main cracks. Full article

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15 pages, 16366 KiB

Open AccessArticle

Hydrothermal Synthesis of CaAl-LDH Intercalating with Eugenol and Its Corrosion Protection Performances for Reinforcing Bar

by Ang Liu, Haohua Gu, Yongjuan Geng, Pan Wang, Song Gao and Shaochun Li

Materials 2023, 16(7), 2913; https://doi.org/10.3390/ma16072913 - 6 Apr 2023

Cited by 3 | Viewed by 2054

Abstract

Layered double hydroxides (LDHs) intercalating with a corrosion inhibitor for slowing down the corrosion of a reinforcing bar has attracted considerable attention. However, achieving high-loading capacity of organic inhibitor in LDH with high efficiency and long-term protection characteristics remains an important challenge. In [...] Read more.

Layered double hydroxides (LDHs) intercalating with a corrosion inhibitor for slowing down the corrosion of a reinforcing bar has attracted considerable attention. However, achieving high-loading capacity of organic inhibitor in LDH with high efficiency and long-term protection characteristics remains an important challenge. In this work, the CaAl-LDH intercalating with eugenol (EG) was synthesized via a continuous hydrothermal method. The prepared LDHs were characterized by SEM, XRD, UV-vis absorption spectra and TGA. Additionally, the corrosion protection performances of LDH-EG for steel bar were studied in detail via the electrochemical method. The results show that the loading amount of EG in LDHs was about 30% and about 80% EG could be released from LDH-EG within 4 h in SCPs containing 3.5% NaCl. The electrochemical test results show that the R_ct value (10⁵~10⁶ Ω · cm²) of steel-mortar incorporated with LDH-EG has increased by 3–4 orders of magnitude compared to the specimen without LDHs (10²~10³ Ω · cm²) after 16 dry–wet cycles corrosion test. The significantly improved protection capability is mainly derived from two aspects: one is the filling effect of LDH, which can fill the pores of mortar and improve the impermeability; another reason is that the intercalated EG can slowly diffuse out of the inner structure of LDHs in a controllable way and result in a relatively long-term effect of corrosion inhibition. Full article

(This article belongs to the Topic Materials for Corrosion Protection)

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20 pages, 14100 KiB

Open AccessEditor’s ChoiceArticle

Effect of Process Parameters on the Microstructure and Properties of Cu–Cr–Nb–Ti Alloy Manufactured by Selective Laser Melting

by Jian Li, Zuming Liu, Huan Zhou, Shupeng Ye, Yazhou Zhang, Tao Liu, Daoyan Jiang, Lei Chen and Runxing Zhou

Materials 2023, 16(7), 2912; https://doi.org/10.3390/ma16072912 - 6 Apr 2023

Cited by 4 | Viewed by 2269

Abstract

The fabrication of high-performance copper alloys by selective laser melting (SLM) is challenging, and establishing relationships between the process parameters and microstructures is necessary. In this study, Cu–Cr–Nb–Ti alloy is manufactured by SLM, and the microstructures of the alloy are investigated by X-ray [...] Read more.

The fabrication of high-performance copper alloys by selective laser melting (SLM) is challenging, and establishing relationships between the process parameters and microstructures is necessary. In this study, Cu–Cr–Nb–Ti alloy is manufactured by SLM, and the microstructures of the alloy are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). The effects of processing parameters such as laser power and scanning speed on the relative density, defects, microstructures, mechanical properties, and electrical conductivity of the Cu–Cr–Nb–Ti alloy are studied. The optimal processing window for fabricating Cu–Cr–Nb–Ti alloy by SLM is determined. Face-centered cubic (FCC) Cu diffraction peaks shifting to small angles are observed, and there are no diffraction peaks related to the second phase. The grains of XY planes have a bimodal distribution with an average grain size of 24–55 μm. Fine second phases with sizes of less than 50 nm are obtained. The microhardness, tensile strength, and elongation of the Cu–Cr–Nb–Ti alloy manufactured using the optimum processing parameters, laser power of 325 W and scanning speed of 800 mm/s, are 139 HV0.2, 416 MPa, and 27.8%, respectively, and the electrical conductivity is 15.6% IACS (International Annealed Copper Standard). This study provides a feasible scheme for preparing copper alloys with excellent performance and complex geometries. Full article

(This article belongs to the Special Issue 3D Printing of Metallic Materials)

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19 pages, 5141 KiB

Open AccessArticle

A Fast Prediction Model for Liquid Metal Transfer Modes during the Wire Arc Additive Manufacturing Process

by Jiaqi Ouyang, Mingjian Li, Yanping Lian, Siyi Peng and Changmeng Liu

Materials 2023, 16(7), 2911; https://doi.org/10.3390/ma16072911 - 6 Apr 2023

Cited by 2 | Viewed by 1836

Abstract

The liquid metal transfer mode in wire arc additive manufacturing (WAAM), plays an important role in determining the build quality. In this study, a fast prediction model based on the Young–Laplace equation, momentum equation, and energy conservation, is proposed, to identify the metal [...] Read more.

The liquid metal transfer mode in wire arc additive manufacturing (WAAM), plays an important role in determining the build quality. In this study, a fast prediction model based on the Young–Laplace equation, momentum equation, and energy conservation, is proposed, to identify the metal transfer modes, including droplet, liquid bridge, and wire stubbing, for a given combination of process parameters. To close the proposed model, high-fidelity numerical simulations are applied, to obtain the necessary inputs required by the former. The proposed model’s accuracy and effectiveness are validated by using experimental data and high-fidelity simulation results. It is proved that the model can effectively predict the transition from liquid bridge, to droplet and wire stubbing modes. In addition, its errors in dripping frequency and liquid bridge height range from 6% to 18%. Moreover, the process parameter windows about transitions of liquid transfer modes have been established based on the model, considering wire feed speed, travel speed, heat source power, and material parameters. The proposed model is expected to serve as a powerful tool for the guidance of process parameter optimization, to achieve high-quality builds. Full article

(This article belongs to the Special Issue Experimental Research and Numerical Simulations of Metal Additive Manufacturing)

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15 pages, 4378 KiB

Open AccessArticle

Characterization of the Internal Stress Evolution of an EB-PVD Thermal Barrier Coating during a Long-Term Thermal Cycling

by Zhen Zhen, Chuan Qu and Donghui Fu

Materials 2023, 16(7), 2910; https://doi.org/10.3390/ma16072910 - 6 Apr 2023

Cited by 2 | Viewed by 1685

Abstract

Electron beam physical vapour deposition (EB-PVD) technology is a standard industrial method for the preparation of a thermal barrier coating (TBC) deposition on aeroengines. The internal stress of EB-PVD TBCs, including stress inside the top coating (TC) and thermal oxidation stress during long-term [...] Read more.

Electron beam physical vapour deposition (EB-PVD) technology is a standard industrial method for the preparation of a thermal barrier coating (TBC) deposition on aeroengines. The internal stress of EB-PVD TBCs, including stress inside the top coating (TC) and thermal oxidation stress during long-term service is one of the key reasons for thermal barrier failures. However, research on the synergistic characterization of the internal stress of EB-PVD TBCs is still lacking. In this work, the stress inside the TC layer and the thermal oxidation stress of EB-PVD TBC during long-term thermal cycles were synergistically detected, combining Cr³⁺-PLPS and THz-TDS technologies. Based on a self-built THz-TDS system, stress-THz coefficients c₁ and c₂ of the EB-PVD TBC, which are the core parameters for stress characterization, were calibrated for the first time. According to experimental results, the evolution law of the internal stress of the TC layer was similar to that of the TGO stress, which were interrelated and influenced by each other. In addition, the internal stress of the TC layer was less than that of the TGO stress due to the columnar crystal microstructure of EB-PVD TBCs. Full article

(This article belongs to the Special Issue Experimental Mechanics of Micro-Nano Scale Spectroscopy)

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10 pages, 3294 KiB

Open AccessArticle

Mechanical Properties and Microstructure of Austenite—Ferrite Duplex Stainless Steel Hybrid (Laser + GMAW) and SAW Welded Joint

by Ryszard Krawczyk, Jacek Słania, Grzegorz Golański and Tomasz Pfeifer

Materials 2023, 16(7), 2909; https://doi.org/10.3390/ma16072909 - 6 Apr 2023

Cited by 3 | Viewed by 1932

Abstract

The purpose of the research was to develop a technology for producing thick-walled duplex steel welded joints. The material used in the research was X2CrNiMoN22 duplex steel in the form of a 15 mm thick plate. The welded joint was produced by the [...] Read more.

The purpose of the research was to develop a technology for producing thick-walled duplex steel welded joints. The material used in the research was X2CrNiMoN22 duplex steel in the form of a 15 mm thick plate. The welded joint was produced by the modern, high-performance Hybrid Laser Arc Welding (HLAW) method. The HLAW method involves welding a joint using a laser, the Gas Metal Arc Welding (GMAW) method and the Submerged Arc Welding (SAW) method. The HLAW method was used to make the root pass of the double butt welded joint, while the filler passes were made by the SAW method. The obtained welded joint was subjected to non-destructive and destructive testing. The non-destructive and macroscopic tests allowed the joint to be classified to the quality level B. Microscopic examinations revealed the presence of ferritic–austenitic microstructure in the base material and the weld, with different ferrite content in specific joint areas. The analysed joint had high strength properties (tensile strength (TS) ~ 790 ± 7 MPa) and high ductility of weld metal (~160 ± 4 J) heat-affected zone (~216 ± 26 J), and plasticity (bending angle of 180° with no macrocracks). At the same time, hardness on the cross-section of the welded joint did not exceed 280 HV10. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes)

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15 pages, 4781 KiB

Open AccessArticle

Synthesis and Study of the Optical Properties of a Conjugated Polymer with Configurational Isomerism for Optoelectronics

by Oscar Javier Hernández-Ortiz, Damaris Castro-Monter, Ventura Rodríguez Lugo, Ivana Moggio, Eduardo Arias, María Isabel Reyes-Valderrama, María Aurora Veloz-Rodríguez and Rosa Angeles Vázquez-García

Materials 2023, 16(7), 2908; https://doi.org/10.3390/ma16072908 - 6 Apr 2023

Cited by 1 | Viewed by 2129

Abstract

A π-conjugated polymer (PBQT) containing bis-(2-ethylhexyloxy)-benzo [1,2-b’] bithiophene (BDT) units alternated with a quinoline-vinylene trimer was obtained by the Stille reaction. The chemical structure of the polymer was verified by nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FT-IR), and mass [...] Read more.

A π-conjugated polymer (PBQT) containing bis-(2-ethylhexyloxy)-benzo [1,2-b’] bithiophene (BDT) units alternated with a quinoline-vinylene trimer was obtained by the Stille reaction. The chemical structure of the polymer was verified by nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FT-IR), and mass spectroscopy (MALDI-TOF). The intrinsic photophysical properties of the solution were evaluated by absorption and (static and dynamic) fluorescence. The polymer PBQT exhibits photochromism with a change in absorption from blue (449 nm) to burgundy (545 nm) and a change in fluorescence emission from green (513 nm) to orange (605 nm) due to conformational photoisomerization from the trans to the cis isomer, which was supported by theoretical calculations DFT and TD-DFT. This optical response can be used in optical sensors, security elements, or optical switches. Furthermore, the polymer forms spin-coated films with absorption properties that cover the entire visible range, with a maximum near the solar emission maximum. The frontier molecular orbitals, HOMO and LUMO, were calculated by cyclic voltammetry, and values of −5.29 eV and −3.69, respectively, and a bandgap of 1.6 eV were obtained, making this material a semiconductor with a good energetic match. These properties could suggest its use in photovoltaic applications. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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