Research

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10 pages, 1825 KiB

Open AccessArticle

Water-Assisted Catalytic VACNT Growth Optimization for Speed and Height

by Karlheinz Strobl and Fahd Rajab

Processes 2023, 11(6), 1587; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11061587 - 23 May 2023

Cited by 1 | Viewed by 871

The super-growth approach for carbon nanotubes synthesis is frequently used to boost the growth rate, catalyst lifespan, and height of vertically aligned carbon nanotubes. The elimination of amorphous carbon from catalyst particles, commonly made of iron, by injecting water vapor into a chemical [...] Read more.

The super-growth approach for carbon nanotubes synthesis is frequently used to boost the growth rate, catalyst lifespan, and height of vertically aligned carbon nanotubes. The elimination of amorphous carbon from catalyst particles, commonly made of iron, by injecting water vapor into a chemical vapor deposition process can enhance the purity, alignment, and height of carbon nanotubes and prevent the partial oxidation of the metallic catalyst. We present the development of a modified growth-optimized water-assisted super-growth vertically aligned carbon nanotube process by optimizing the catalyst layer structure and water vapor concentration for a carbon nanotube growth process for 4” diameter Si wafers. A significant finding is that under optimized water-assisted growth conditions over 4 mm, highly uniform tall, vertically aligned carbon nanotube structures can be grown with a minimum top crust layer of about ~5–10 μm thickness. This was achieved with a catalyst film comprising a >400 mm thermal SiO₂ layer on top of a 4” diameter Si wafer that was overcoated with an e-beam batch process run that first deposited a 20 nm SiO₂ layer, a 10 nm Al₂O₃ layer, and a 1.1 nm Fe layer, in a 4-h growth process step. Full article

(This article belongs to the Special Issue Design, Control, and Evaluation of Advanced Engineered Materials)

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24 pages, 12638 KiB

Open AccessFeature PaperArticle

Post-Fire Analysis of Thermally Sprayed Coatings: Evaluating Microstructure, Mechanical Integrity, and Corrosion Behavior

by Ratna Divya Yasoda, Nour Hakim, Ying Huang and Xiaoning Qi

Processes 2023, 11(5), 1490; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11051490 - 15 May 2023

Cited by 1 | Viewed by 1248

Abstract

This paper examines the impact of fire on the microstructural, mechanical, and corrosion behavior of wire-arc-sprayed zinc, aluminum, and Zn-Al pseudo-alloy coatings. Steel plates coated with these materials were subjected to temperatures in increments of 100 °C, starting from 300 °C and progressing [...] Read more.

This paper examines the impact of fire on the microstructural, mechanical, and corrosion behavior of wire-arc-sprayed zinc, aluminum, and Zn-Al pseudo-alloy coatings. Steel plates coated with these materials were subjected to temperatures in increments of 100 °C, starting from 300 °C and progressing until failure. Microstructural characterization, microhardness, abrasion resistance, and electrochemical impedance studies were performed on the post-fire coatings. The findings from this study show that heat had a positive impact on the performance of zinc and Zn-Al pseudo-alloy coatings when they were exposed to temperatures of up to 400 °C, while aluminum coatings maintain their performance up to 600 °C. However, above these temperatures, the effectiveness of coatings was observed to decline, due to increased high-temperature oxidation, and porosity, in addition to decreased microhardness, abrasion resistance, and corrosion protection performance. Based on the findings from this study, appropriately sealed thermal-spray-coated steel components can be reused after exposure to fire up to a specific temperature depending on the coating material. Full article

(This article belongs to the Special Issue Design, Control, and Evaluation of Advanced Engineered Materials)

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17 pages, 7859 KiB

Open AccessArticle

Study on Mechanical Properties of Composite Foundation with Rigid Pile Based on the Cushion and Strength Adjustor Control

by Yonghua Li, Congying Yu, Lei Yao, Jiawei Wu and Xiangang Liu

Processes 2023, 11(2), 539; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11020539 - 10 Feb 2023

Viewed by 1202

Abstract

Settlement of the pile ends in end-bearing rigid pile composite foundations is generally minimal, so only relying on the cushion to coordinate the pile soil deformation may result in insufficient deformation adjustment capacity. Using a deformation adjustor with a specific stiffness on the [...] Read more.

Settlement of the pile ends in end-bearing rigid pile composite foundations is generally minimal, so only relying on the cushion to coordinate the pile soil deformation may result in insufficient deformation adjustment capacity. Using a deformation adjustor with a specific stiffness on the top of the pile is a method to coordinate pile–soil deformation, and the stiffness value of the deformation adjustor depends on the accurate calculation of soil deformation; however, the calculation of soil deformation is not mature at present. A new deformation adjustor based on strengths used in composite foundations is proposed, in which foam slabs with different yield strengths are placed on the top of the pile to coordinate the pile–soil deformation. Five tests are used to study the mechanical and deformation properties of a composite foundation with a foam slab. The test results show that when the stress at the top of the pile is less than the yield strength of the foam slab, the coordination of the pile–soil deformation mainly depends on the cushion. When the stress of a rigid pile exceeds the yield strength of foam concrete, the foam slab begins to yield and coordinate the deformation of pile and soil, and the settlement coordination ability of a rigid pile composite foundation with a foam slab is significantly improved. Finally, an engineering case is used to simulate the pile–soil stress sharing when the actual settlement is greater than the calculated settlement. The case analysis shows that the pile-top stress can be well controlled by the successive yielding of foam concrete slabs of different strengths, which reduces the influence of settlement error on the pile–soil stress sharing, and further promotes the engineering application of end-bearing rigid pile composite foundations. Full article

(This article belongs to the Special Issue Design, Control, and Evaluation of Advanced Engineered Materials)

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12 pages, 3034 KiB

Open AccessArticle

Rehydration Activity of High-Temperature Calcined Recycled Sand Autoclaved Aerated Concrete

by Xiuli Yang, Renmiao Zhu and Bin Xu

Processes 2023, 11(2), 422; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11020422 - 31 Jan 2023

Cited by 1 | Viewed by 1268

Abstract

Autoclaved aerated concrete is an excellent thermal insulation wall material, but with a large amount of waste. This paper describes the high-temperature activation and rehydration activity of waste cement–lime–sand autoclaved aerated concrete (SAAC) and discusses the high-temperature phase transition of SAAC. SAAC calcined [...] Read more.

Autoclaved aerated concrete is an excellent thermal insulation wall material, but with a large amount of waste. This paper describes the high-temperature activation and rehydration activity of waste cement–lime–sand autoclaved aerated concrete (SAAC) and discusses the high-temperature phase transition of SAAC. SAAC calcined at 750 °C was confirmed to be a metastable and amorphous state, which could hydrolyze Ca²⁺ ions with reactivity in water. The conductivity curve demonstrates that the concentration of ions in the suspension decreases rapidly at 150–250 min, and the hydration reaction turns dominant at this time. The hydration heat curve also displays a hydration exothermic peak at 2.5 h. In addition, the conductivity measurement of suspension and the exothermic measurement of hydration reaction proves that SAAC calcined at 750 °C has a hydration activity and can rehydrate with SiO₂ in the system. The rehydration activity was verified by replacing 30% cement in the standard test block with calcined SAAC because the calcined SAAC at 750 °C has high hydration activity, and its activity index reached 89.58%. Fly ash is a commonly used cement admixture at present. Hence, the SAAC calcined at 750 °C and the fly ash were used to replace 30% of the cement in the cement test block, respectively. The results of this comparative experiment vividly showed that the reaction activity of SAAC calcined at 750 °C was higher than that of fly ash. Therefore, according to this research, SAAC has activity after calcination at 750 °C and can be hydrated again. Full article

(This article belongs to the Special Issue Design, Control, and Evaluation of Advanced Engineered Materials)

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13 pages, 2843 KiB

Open AccessArticle

Temperature Stress Analysis of Super-Long Frame Structures Accounting for Differences in the Linear Expansion Coefficients of Steel and Concrete

by Yigang Jia, Liangjian Lu, Guangyu Wu, Bo Zhang and Huibin Wang

Processes 2021, 9(9), 1519; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9091519 - 27 Aug 2021

Cited by 1 | Viewed by 1854

Abstract

Temperature stress analysis is of prime importance to ensure the adequate servicing of super-long frame structures during their service life. The existing design codes and recommendations for reinforced concrete (RC) structures provide methodologies for the reinforcement of design elements that neglect differences in [...] Read more.

Temperature stress analysis is of prime importance to ensure the adequate servicing of super-long frame structures during their service life. The existing design codes and recommendations for reinforced concrete (RC) structures provide methodologies for the reinforcement of design elements that neglect differences in the linear expansion coefficients of steel and concrete. In this paper, we present a numerical method based on a degenerated three-dimensional solid virtual laminated element for simulating and analyzing the temperature stress of a two-layer super-long frame reinforced concrete structure subjected to allover cooling action, whereby the difference in the linear expansion coefficients of steel and concrete are taken into consideration. The results show that the difference in the linear expansion coefficients of steel and concrete, with different constraints, affects the temperature stress experienced by each material in the structure, and this difference adversely affects attempts to avoid structure cracking. Full article

(This article belongs to the Special Issue Design, Control, and Evaluation of Advanced Engineered Materials)

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16 pages, 7529 KiB

Open AccessArticle

Experimental Study on the Flexural Behavior of Concrete-Filled Steel Box Slabs

by Yan Lin, Chongting Zhong, Jiankai Song and Shuang Qu

Processes 2021, 9(4), 649; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9040649 - 08 Apr 2021

Cited by 4 | Viewed by 1640

Abstract

Different to conventional reinforced concrete or steel material, a new type of concrete-filled steel box slab has been proposed by effectively integrating the combined benefits of both steel and concrete. By filling concrete, this type of slab could avoid the local bucking of [...] Read more.

Different to conventional reinforced concrete or steel material, a new type of concrete-filled steel box slab has been proposed by effectively integrating the combined benefits of both steel and concrete. By filling concrete, this type of slab could avoid the local bucking of steel plate and then could provide a high moment capacity. Therefore, this study aims to investigate the flexural behavior of concrete-filled steel box slabs through testing seven specimens and characterize their failure characteristics, stress distribution and ultimate moment capacity. A comprehensive parametric study focuses on the influence of the steel plate thickness, the stud and stiffening plate on the slab flexural behavior. The results show that concrete-filled steel box slabs had a high moment capacity and good ductility. The thickness of the steel plate had a significant influence on the moment capacity of the specimen. The stud led to the reduction of the moment capacity of the slab. The stiffening plate effectively improved the flexural behavior of the specimen. Moreover, a calculation method was formulated to describe the moment capacity of the slab and compared with experimental results. The results show that the proposed method for the moment capacity of the slab was conservative and reasonable. Full article

(This article belongs to the Special Issue Design, Control, and Evaluation of Advanced Engineered Materials)

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15 pages, 3695 KiB

Open AccessArticle

Experimental and Numerical Analysis of the Mechanical Properties of a Pretreated Shape Memory Alloy Wire in a Self-Centering Steel Brace

by Bo Zhang, Sizhi Zeng, Fenghua Tang, Shujun Hu, Qiang Zhou and Yigang Jia

Processes 2021, 9(1), 80; https://doi.org/10.3390/pr9010080 - 01 Jan 2021

Cited by 3 | Viewed by 1740

Abstract

As a stimulus-sensitive material, the difference in composition, fabrication process, and influencing factors will have a great effect on the mechanical properties of a superelastic Ni-Ti shape memory alloy (SMA) wire, so the seismic performance of the self-centering steel brace with SMA wires [...] Read more.

As a stimulus-sensitive material, the difference in composition, fabrication process, and influencing factors will have a great effect on the mechanical properties of a superelastic Ni-Ti shape memory alloy (SMA) wire, so the seismic performance of the self-centering steel brace with SMA wires may not be accurately obtained. In this paper, the cyclic tensile tests of a kind of SMA wire with a 1 mm diameter and special element composition were tested under multi-working conditions, which were pretreated by first tensioning to the 0.06 strain amplitude for 40 cycles, so the mechanical properties of the pretreated SMA wires can be simulated in detail. The accuracy of the numerical results with the improved model of Graesser’s theory was verified by a comparison to the experimental results. The experimental results show that the number of cycles has no significant effect on the mechanical properties of SMA wires after a certain number of cyclic tensile training. With the loading rate increasing, the pinch effect of the hysteresis curves will be enlarged, while the effective elastic modulus and slope of the transformation stresses in the process of loading and unloading are also increased, and the maximum energy dissipation capacity of the SMA wires appears at a loading rate of 0.675 mm/s. Moreover, with the initial strain increasing, the slope of the transformation stresses in the process of loading is increased, while the effective elastic modulus and slope of the transformation stresses in the process of unloading are decreased, and the maximum energy dissipation capacity appears at the initial strain of 0.0075. In addition, a good agreement between the test and numerical results is obtained by comparing with the hysteresis curves and energy dissipation values, so the numerical model is useful to predict the stress–strain relations at different stages. The test and numerical results will also provide a basis for the design of corresponding self-centering steel dampers. Full article

(This article belongs to the Special Issue Design, Control, and Evaluation of Advanced Engineered Materials)

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Review

Jump to: Research

26 pages, 4088 KiB

Open AccessReview

Durability of Pavement Materials with Exposure to Various Anti-Icing Strategies

by Shujuan Xu, Zhiliang Zhou, Lichao Feng, Na Cui and Ning Xie

Processes 2021, 9(2), 291; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9020291 - 03 Feb 2021

Cited by 10 | Viewed by 2954

Abstract

Anti-icing is a critical topic in durability assessment for pavement infrastructures, and it varies according to local policies. To provide sufficient information to winter maintenance agencies, and help compare the merits and shortcomings of each strategy, this review summarizes the widely used anti-icing [...] Read more.

Anti-icing is a critical topic in durability assessment for pavement infrastructures, and it varies according to local policies. To provide sufficient information to winter maintenance agencies, and help compare the merits and shortcomings of each strategy, this review summarizes the widely used anti-icing strategies, including elastic surfaces or high-friction overlays, asphalt binders mixed with anti-icing additives, pavement heating technologies, deicers, and fixed automated spray technology, from academic and practical perspectives, as well as explore the impact of deicers on the durability of concrete materials. Furthermore, the costs of each method were compared to evaluate the feasibility of them. This review not only provides a summary of previous anti-icing strategies, but also sheds light on future research trends that may help address the challenges of current anti-icing strategies, and further enhance anti-icing efficiency and reduce life cycle costs. Full article

(This article belongs to the Special Issue Design, Control, and Evaluation of Advanced Engineered Materials)

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