Materials

12 pages, 6265 KiB

Open AccessArticle

Third-Order Effective Properties for Random-Packing Systems Using Statistical Micromechanics Based on a GPU Parallel Algorithm in Fast Computing n-Point Correlation Functions

by Shaobo Sun, Huisu Chen and Jianjun Lin

Materials 2022, 15(16), 5799; https://doi.org/10.3390/ma15165799 - 22 Aug 2022

Viewed by 1366

Abstract

Estimating the effective properties of a particulate system is the most direct way to understand its macroscopic performance. In this work, we accurately evaluate the third-order approximations involving the three-point microstructural parameter

ζ

, which can be calculated from a triple integral involving [...] Read more.

Estimating the effective properties of a particulate system is the most direct way to understand its macroscopic performance. In this work, we accurately evaluate the third-order approximations involving the three-point microstructural parameter

ζ

, which can be calculated from a triple integral involving 1-, 2-, and 3-point correlation functions. A GPU-based parallel algorithm was developed for quickly computing the n-point correlation functions, and the results agree well with analytical solutions. The effective thermal conductivity and diffusion coefficient are calculated by the third-order approximates for the random-packing systems of a super-ellipsoid. By changing the parameters of the super-ellipsoid, the particle-shape effect can be predicted for both the thermal conductivity and diffusion coefficient. Full article

(This article belongs to the Special Issue Advances in Sustainable Construction and Building Materials)

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15 pages, 2956 KiB

Open AccessArticle

Influence of Fineness Levels and Dosages of Light-Burned Dolomite on Portland Cement Performance

by Wenxiu Jiao, Aimin Sha, Zhuangzhuang Liu and Shuo Li

Materials 2022, 15(16), 5798; https://doi.org/10.3390/ma15165798 - 22 Aug 2022

Cited by 3 | Viewed by 1568

Abstract

The paper aims to understand the effect of light-burned dolomite powders (LBD) on ordinary Portland cement (OPC) and evaluate the influence of LBD dosages and fineness levels on the mechanical properties and hydration properties of OPC. The LBD/OPC pastes were prepared by OPC [...] Read more.

The paper aims to understand the effect of light-burned dolomite powders (LBD) on ordinary Portland cement (OPC) and evaluate the influence of LBD dosages and fineness levels on the mechanical properties and hydration properties of OPC. The LBD/OPC pastes were prepared by OPC blended with LBD at various replacement dosages and fineness levels. The mechanical properties were studied by flexural and compressive strength tests, while the hydration properties were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and reaction degree of LBD. Experiment results indicated that the flexural and compressive strength of LBD/OPC samples were higher than reference sample at all ages. The fineness levels of LBD was C (C-LBD) with 0.5–1.5 wt% dosages, and the fineness levels of LBD was B (B-LBD) with 1.5–2.5 wt% dosages can significantly improve the strength of cement-based materials. The main mineral components of LBD are MgO and CaCO₃, of which MgO could react with water to form Mg(OH)₂ quickly, and CaCO₃ could hydrate with C₃A to from hydrated calcium carboaluminate (C₃A·CaCO₃·11H₂O), which prevents the conversion of AFt to AFm. Full article

(This article belongs to the Special Issue Sustainable Cementitious Materials for Civil and Transportation Engineering)

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27 pages, 6311 KiB

Open AccessArticle

Effect and Mechanism of Metakaolin Powder (MP) on Rheological and Mechanical Properties of Cementitious Suspension

by Hengrui Liu, Zezhu Wang, Zhenghong Tian, Jingwu Bu and Jianchun Qiu

Materials 2022, 15(16), 5797; https://doi.org/10.3390/ma15165797 - 22 Aug 2022

Cited by 4 | Viewed by 1214

Abstract

The effects of metakaolin powder (MP) on the microscopic rheological properties and macroscopic flow parameters of cementitious suspension under various water–cement ratios were investigated. By analyzing the changes in the bonding strength coefficient and water film thickness (WFT), the mechanism of MP on [...] Read more.

The effects of metakaolin powder (MP) on the microscopic rheological properties and macroscopic flow parameters of cementitious suspension under various water–cement ratios were investigated. By analyzing the changes in the bonding strength coefficient and water film thickness (WFT), the mechanism of MP on flow and rheological parameters can be explored. Further, the effect of MP on mechanical properties was explained from the perspective of water absorption kinetics and hydration activity contribution rate. The incorporation of MP can reduce the flow rate and flow spread and increase the compressive strength, plastic viscosity, yield stress and thixotropy, and the effects of MP were distinctive under various W/CM ratios. The bonding strength coefficient and WFT increased and decreased with increasing MP replacement content, respectively. The regression analysis results revealed that the bonding strength coefficient and WFT were the most important factors influencing the macroscopic flow parameters and rheological parameters, which indicated that MP influenced the rheology and flowability of cementitious suspension by affecting the flocculent structure and particle distance. Compared with WFT, the bonding strength coefficient had a stronger effect on these parameters. The MP improved the compressive strength by reducing the average pore size and porosity and increasing the pore uniformity and hydration activity contribution rate of hardened paste, and this improvement was enhanced by increasing curing age. Full article

(This article belongs to the Special Issue Microstructural, Mechanical, and Durability Characteristics of Cementitious Materials)

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15 pages, 5328 KiB

Open AccessEditor’s ChoiceArticle

Corrosive Effect of Wood Ash Produced by Biomass Combustion on Refractory Materials in a Binary Al–Si System

by Hana Ovčačíková, Marek Velička, Jozef Vlček, Michaela Topinková, Miroslava Klárová and Jiří Burda

Materials 2022, 15(16), 5796; https://doi.org/10.3390/ma15165796 - 22 Aug 2022

Cited by 10 | Viewed by 1897

Abstract

In terms of its chemical composition, biomass is a very complex type of fuel. Its combustion leads to the formation of materials such as alkaline ash and gases, and there is evidence of the corrosive effect this process has on refractory linings, thus [...] Read more.

In terms of its chemical composition, biomass is a very complex type of fuel. Its combustion leads to the formation of materials such as alkaline ash and gases, and there is evidence of the corrosive effect this process has on refractory linings, thus shortening the service life of the combustion unit. This frequently encountered process is known as “alkaline oxidative bursting”. Corrosion is very complex, and it has not been completely described yet. Alkaline corrosion is the most common cause of furnace-lining degradation in aggregates that burn biomass. This article deals with an experiment investigating the corrosion resistance of 2 types of refractory materials in the Al₂O₃-SiO₂ binary system, for the following compositions: I. (53 wt.% SiO₂/42 wt.% Al₂O₃) and II. (28 wt.% SiO₂/46 wt.% Al₂O₃/12 wt.% SiC). These were exposed to seven types of ash obtained from one biomass combustion company in the Czech Republic. The chemical composition of the ash is a good indicator of the problematic nature of a type of biomass. The ashes were analyzed by X-ray diffraction and X-ray fluorescence. Analysis confirmed that ash composition varies. The experiment also included the calculation of the so-called “slagging/fouling index” (I/C, TA, Sr, B/A, Fu, etc.), which can be used to estimate the probability of slag formation in combustion units. The corrosive effect on refractory materials was evaluated according to the norm ČSN P CEN/TS 15418, and a static corrosion test was used to investigate sample corrosion. Full article

(This article belongs to the Special Issue Design, Manufacturing, and Properties of Refractory Materials)

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24 pages, 5327 KiB

Open AccessArticle

Frost Heaving Damage Mechanism of a Buried Natural Gas Pipeline in a River and Creek Region

by Wenxian Su and Shijia Huang

Materials 2022, 15(16), 5795; https://doi.org/10.3390/ma15165795 - 22 Aug 2022

Cited by 2 | Viewed by 1743

Abstract

When the buried pipeline passes through the permafrost zone, the phenomenon of frost swelling occurs in the permafrost zone, which causes a certain degree of bending and deformation of the pipeline. As a result, the pipeline’s structural safety is compromised, and the pipeline [...] Read more.

When the buried pipeline passes through the permafrost zone, the phenomenon of frost swelling occurs in the permafrost zone, which causes a certain degree of bending and deformation of the pipeline. As a result, the pipeline’s structural safety is compromised, and the pipeline finally fails during operation, posing a serious hazard to the natural gas pipeline’s operation. Whereas the theoretical research on soil frost heave is relatively comprehensive, the applied research on engineering problems is not yet complete. Therefore, it is necessary to predict frost heaving through experiments and numerical simulation, and put forward reasonable control measures for existing or potential problems. For the problem of pipeline damage caused by frost swelling of soil in the natural gas high-pressure regulator station in a river and creek region, the Drucker–Prager elastic-ideal plastic model of soil was selected for finite element analysis, and a reasonable finite element model of pipe-soil was established in this paper. Through the temperature field analysis, it was found that the soil around the buried pipe is affected by the pipeline and is lower than its freezing temperature, which makes the soil freeze and swell. Furthermore, through the thermal–structural coupling analysis, it was found that the buried pipe is affected by the freezing and swelling of the soil and the structure is greatly likely to be damaged. In addition, by analyzing the temperature distribution and frost heave deformation of the soil around the pipeline, as well as the deformation and force of the pipeline at different pipe temperatures, this paper also determined the ideal temperature for preventing frost heave damage to natural gas at high-pressure regulator stations as −1 °C. Finally, based on the results of the abovementioned analysis, the heating method was determined to improve the frost damage phenomenon at the high-pressure regulator. The results of the anti-frost and swell study were used to conduct field trials at natural gas high-pressure regulator stations where frost and swell had occurred. By adding heating furnace to increase inlet temperature, frost heaving of gas transmission pipeline can be effectively prevented. The results of the research provide a reference for both existing and new natural gas pipelines, and also accumulate experience for winter maintenance design and construction of pipeline engineering in seasonally frozen soil areas. Full article

(This article belongs to the Special Issue Structural Strength, Corrosion and Failure Analysis of Pressure Vessel and Pipeline System)

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12 pages, 2360 KiB

Open AccessArticle

Production of Mesoporous Magnetic Carbon Materials from Oily Sludge by Combining Thermal Activation and Post-Washing

by Wen-Tien Tsai, Yu-Quan Lin, Chi-Hung Tsai and Yun-Hwei Shen

Materials 2022, 15(16), 5794; https://doi.org/10.3390/ma15165794 - 22 Aug 2022

Cited by 1 | Viewed by 1255

Abstract

In this work, the oily sludge (OS) from a local waste oil recycling plant was reused as a precursor for producing porous magnetic carbon composites (CC) by pyrolysis, followed by carbon dioxide activation. Based on the thermogravimetric analysis (TGA) of the OS feedstock, [...] Read more.

In this work, the oily sludge (OS) from a local waste oil recycling plant was reused as a precursor for producing porous magnetic carbon composites (CC) by pyrolysis, followed by carbon dioxide activation. Based on the thermogravimetric analysis (TGA) of the OS feedstock, the preparation experiments were performed at 800–900 °C. From the pore analysis of the CC products, it indicated an increasing trend, as the BET surface area greatly increased from about 1.0 to 44.30 m²/g. In addition, the enhancement effect on the pore properties can be consistently obtained from the acid-washed CC products because the existing and new pores were reformed due to the leaching-out of inorganic minerals. It showed an increase from 32.27 to 94.45 m²/g and 44.30 to 94.52 m²/g at 850 and 900 °C, respectively, showing their mesoporous features. These porous and iron-containing features were also observed by the scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). In addition, the adsorption removal of total organic carbon (TOC) in the raw wastewater, by the CC product, showed its high performance (>80%). Full article

(This article belongs to the Special Issue Porous Ceramics, Glasses and Composites)

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15 pages, 5804 KiB

Open AccessArticle

Study of Strain Capacity for High-Strain Marine Pipe

by Kun Yang, Ting Sha, Xiongxiong Gao, Hongyuan Chen, Qiang Chi and Lingkang Ji

Materials 2022, 15(16), 5793; https://doi.org/10.3390/ma15165793 - 22 Aug 2022

Cited by 1 | Viewed by 1168

Abstract

In this paper, a strain capacity assessment on high-strain marine pipe was carried out by comparing the crack growth driving force and the crack growth resistance. The crack growth driving force was given by FEA, the stress-stain relationship was given by a DIC [...] Read more.

In this paper, a strain capacity assessment on high-strain marine pipe was carried out by comparing the crack growth driving force and the crack growth resistance. The crack growth driving force was given by FEA, the stress-stain relationship was given by a DIC tensile test, and the crack growth resistance was given by a single-edge notched tensile (SENT) test using a single-specimen flexibility method. The proposed approach was compared with the failure assessment curve and validated against full-scale tests with a girth weld notch. The results of the full-scale tests showed that the assessment method using FEA was more accurate and the result of the failure assessment curve assessment was more conservative. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Pipeline Steel)

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14 pages, 3527 KiB

Open AccessArticle

Durability of Recycled Concrete Aggregates Prepared with Mechanochemical and Thermal Treatment

by Mujaheed Yunusa, Xiaoshan Zhang, Peiqiang Cui and Xiaowu Tian

Materials 2022, 15(16), 5792; https://doi.org/10.3390/ma15165792 - 22 Aug 2022

Cited by 9 | Viewed by 1578

Abstract

Recycled concrete aggregates (RCAs) have low quality when compared with natural or conventional aggregates as the paste adhering to it is the key aspect that affects its functionality. Since the adhering cementitious paste weakens the adhesion between the aggregate and the binder, it [...] Read more.

Recycled concrete aggregates (RCAs) have low quality when compared with natural or conventional aggregates as the paste adhering to it is the key aspect that affects its functionality. Since the adhering cementitious paste weakens the adhesion between the aggregate and the binder, it becomes a decisive factor in the mechanical behavior of the asphalt mixture. It turns out that enhancing the surface of the aggregate or eliminating the paste attached to the NA (natural aggregate) is crucial for improving interfacial bonding. Therefore, the treatment and evaluation of the RCAs by laboratory testing method were studied in this research to assess their reuse in the asphalt pavement surface coarse layer. With the various techniques for removing paste from the RCA, a combination of three enhancement processes were developed for the effective removal of the cement paste, which are mechanical, chemical, and 400 °C conditioning thermal treatment. The RCAs were first charged in a Los Angeles machine for the mechanical treatment to remove parts of the attached cement. Then they were soaked in two types of acids, namely hydrochloric and sulfuric, with different concentrations to determine the most effective or optimum molarity for about a 48 h soaking duration. Then a 2 h thermal treatment was conducted on the RCA samples. After all the treatments were done, the RCA aggregates were subjected to different types of tests to examine their properties in order to ensure their full potential in terms of their physical, chemical, mineralogical, and surface microstructure characteristics. Based on the experiment design, the study intends to examine the quality of the treated recycled aggregates generated by the combination approach as well as to investigate the optimal acid concentration and type. The results show that the proposed mechanochemical and thermal treatment reinforced the quality of the RCAs when compared to the non-treated samples. Meanwhile, HCl proved to be the optimum compared to H₂SO₄ in most examinations of the properties. In the end, better chemical qualities were validated, and the RCA qualities were improved. Full article

(This article belongs to the Special Issue Long-Life and Circular Pavement Materials)

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27 pages, 19967 KiB

Open AccessArticle

Experimental Study on Seismic Performance of Precast Pretensioned Prestressed Concrete Beam-Column Interior Joints Using UHPC for Connection

by Xueyu Xiong, Yifan Xie, Gangfeng Yao, Ju Liu, Laizhang Yan and Liang He

Materials 2022, 15(16), 5791; https://doi.org/10.3390/ma15165791 - 22 Aug 2022

Cited by 5 | Viewed by 1959

Abstract

The traditional connections and reinforcement details of precast RC frames are complex and cause difficulty in construction. Ultra-high-performance concrete (UHPC) exhibits outstanding compressive strength and bond strength with rebars and strands; thus, the usage of UHPC in the joint core area will reduce [...] Read more.

The traditional connections and reinforcement details of precast RC frames are complex and cause difficulty in construction. Ultra-high-performance concrete (UHPC) exhibits outstanding compressive strength and bond strength with rebars and strands; thus, the usage of UHPC in the joint core area will reduce the amount of transverse reinforcement and shorten the anchoring length of beam rebars as well as strands significantly. Moreover, the lap splice connections of precast columns can be placed in the UHPC joint zone and the construction process will be simplified. This paper presented a novel joint consisting of a precast pretensioned prestressed concrete beam, an ordinary precast reinforced concrete (RC) column, and a UHPC joint zone. To study the seismic performance of the proposed joints, six novel interior joints and one monolithic RC joint were tested under low-cyclic loads. Variables such as the axial force, the compressive strength of UHPC, the stirrup ratio were considered in the tests. The test results indicate that the proposed joints exhibit comparable seismic performance of the monolithic RC joint. An anchorage length of 40 times the strands-diameter and a lap splice length of 16 times the rebar-diameter are adequate for prestressed strands and precast column rebars, respectively. A minimum column depth is suggested as 13 times the diameter of the beam-top continuous rebars passing through the joint. In addition, a nine-time rebar diameter is sufficient for the anchorage of beam bottom rebars. The shear strength of UHPC in the joint core area is suggested as 0.8 times the square root of the UHPC compressive strength. Full article

(This article belongs to the Special Issue Advanced Steel Composites in Construction Engineering)

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15 pages, 5089 KiB

Open AccessArticle

The Effect of Pr Doping Contents on the Structural, Microstructure and Dielectric Properties of BaBi₂Nb₂O₉ Aurivillius Ceramics

by Michał Rerak, Jolanta Makowska, Katarzyna Osińska, Tomasz Goryczka, Anna Zawada and Małgorzata Adamczyk-Habrajska

Materials 2022, 15(16), 5790; https://doi.org/10.3390/ma15165790 - 22 Aug 2022

Cited by 3 | Viewed by 1154

Abstract

Aurivillius BaBi₂Nb₂O₉ and Ba_1-xPr_xBi₂Nb₂O₉ ceramics were successfully synthesized by a simple solid state reaction method. Ceramics were prepared from reactants: Nb₂O₅, Bi₂O₃ [...] Read more.

Aurivillius BaBi₂Nb₂O₉ and Ba_1-xPr_xBi₂Nb₂O₉ ceramics were successfully synthesized by a simple solid state reaction method. Ceramics were prepared from reactants: Nb₂O₅, Bi₂O₃, BaCO₃ and Pr₂O₃. The microstructure, structure, chemical composition, and dielectric properties of the obtained materials were examined. Dielectric properties were investigated in a wide range of temperatures (T = 20–500 °C) and frequencies (f = 0.1 kHz–1 MHz). The obtained ceramic materials belong to the group of layered perovskites, crystallizing in a tetragonal structure with the space group I4/mmm. Modification of the barium niobate compound with praseodymium ions influenced its dielectric properties and introducing a small concentration of the dopant ion causes a slight increase in the value of electric permittivity and shifts its maximum towards higher temperatures. Full article

(This article belongs to the Special Issue Advances in Dielectric Ceramics and Their Applications)

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16 pages, 3608 KiB

Open AccessEditor’s ChoiceArticle

A Facile One-Pot Approach to the Fabrication of Nanocellulose–Titanium Dioxide Nanocomposites with Promising Photocatalytic and Antimicrobial Activity

by Roberta G. Toro, Abeer M. Adel, Tilde de Caro, Bruno Brunetti, Mona T. Al-Shemy and Daniela Caschera

Materials 2022, 15(16), 5789; https://doi.org/10.3390/ma15165789 - 22 Aug 2022

Cited by 9 | Viewed by 1727

Abstract

The combination of cellulosic materials and metal oxide semiconductors can provide composites with superior functional properties compared to cellulose. By using nanocellulose derived from agricultural waste, we propose a one-pot and environmentally friendly approach to the synthesis of nanocellulose–TiO₂ (NC–TiO₂) [...] Read more.

The combination of cellulosic materials and metal oxide semiconductors can provide composites with superior functional properties compared to cellulose. By using nanocellulose derived from agricultural waste, we propose a one-pot and environmentally friendly approach to the synthesis of nanocellulose–TiO₂ (NC–TiO₂) nanocomposites with peculiar photocatalytic activity and antibacterial effects. The as-prepared NC–TiO₂ composites were fully characterized by different techniques, such as X-ray diffraction (XRD), μ-Raman, Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS). The results showed that well crystalline anatase TiO₂ nanoparticles of about 5–6 nm were obtained. The photocatalytic activity in particular was evaluated by using methyl orange (MO) solution as a target pollutant at different pH values. It was found that all the tested NC–TiO₂ nanocomposites showed stable photocatalytic activity, even after consecutive photocatalytic runs. In addition, NCT nanocomposites with higher TiO₂ content showed degradation efficiency of almost 99% towards MO after 180 min of UV illumination. Finally, NC–TiO₂ nanocomposites also showed intriguing antimicrobial properties, demonstrating to be effective against Gram-positive (Staphylococcus aureus, Bacillus subtilis) with 20–25 mm of inhibition zone and Gram-negative bacteria (Escherichia coli, Pseudomonas aeuroginosa) with 21–24 mm of inhibition zone, and fungi (Candida albicans) with 9–10 mm of inhibition zone. Full article

(This article belongs to the Special Issue Nanomaterials for the Environmental Remediation of Water and Soil)

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8 pages, 4388 KiB

Open AccessArticle

CVD Nanocrystalline Diamond Film Doped with Eu

by Elena B. Yudina, Alexander E. Aleksenskii, Sergey A. Bogdanov, Sergey S. Bukalov, Larisa A. Leites, Dmitry B. Radishev, Anatoly L. Vikharev and Alexander Y. Vul’

Materials 2022, 15(16), 5788; https://doi.org/10.3390/ma15165788 - 22 Aug 2022

Cited by 3 | Viewed by 1366

Abstract

This paper submits experimental results of a study directed towards the formation of Eu ions’ luminescent centers in CVD diamond films. A new approach is based on use of diamond nanoparticles with a surface modified with Eu ions for seeding at CVD growth. [...] Read more.

This paper submits experimental results of a study directed towards the formation of Eu ions’ luminescent centers in CVD diamond films. A new approach is based on use of diamond nanoparticles with a surface modified with Eu ions for seeding at CVD growth. Nanocrystalline diamond films (NCD) doped with Eu have been grown from the gas phase on silicon substrates by microwave plasma-assisted CVD at a frequency of 2.45 GHz. The photoluminescence spectra clearly show several electronic transitions of the Eu³⁺ ions, which confirm the incorporation of Eu ions into the NCD film. Full article

(This article belongs to the Special Issue Recent Advances in Nanodiamond and Nanocarbon)

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15 pages, 6342 KiB

Open AccessArticle

The Influence of Dimensions and Powder Recycling on the Roughness and Mechanical Properties of Ti-6Al-4V Parts Fabricated by Laser Powder Bed Fusion

by Alejandro Yánez, María Paula Fiorucci, Oscar Martel and Alberto Cuadrado

Materials 2022, 15(16), 5787; https://doi.org/10.3390/ma15165787 - 22 Aug 2022

Cited by 8 | Viewed by 1459

Abstract

Powder bed fusion technology has undergone a remarkable amount of development in recent years in the field of medical implants due to the advantages associated with it. In many implant applications that demand loads in parts with a high degree of roughness and [...] Read more.

Powder bed fusion technology has undergone a remarkable amount of development in recent years in the field of medical implants due to the advantages associated with it. In many implant applications that demand loads in parts with a high degree of roughness and small dimensions, the mechanical properties, especially fatigue properties, play a key role in the success of the implants. One of the most used materials in this field is Ti-6Al-4V. On the other hand, the high cost of titanium powders makes it necessary to search for suitable powder recycling strategies. In this work, the effects of dimensions and powder recycling on the roughness and the mechanical properties of cylinder specimens were obtained from tensile static and fatigue tests of Ti-6Al4V Extra-Low Interstitial (ELI) parts. Four types of specimens were fabricated by laser powder bed fusion (two dimensions (section diameters of 2 mm and 5 mm) with new powder and with recycled powder). Results show that the oxygen concentration increased with recycling. No significant effects of recycling were observed on the monotonic tensile strength specimens. However, specimens fabricated with recycled powder showed greater roughness, lower ductility, and lower fatigue strength than those fabricated with new powder. On the other hand, the 5-mm-diameter specimens showed slightly better fatigue behavior than the 2-mm-diameter ones. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing of Metals, Alloys and Composites)

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16 pages, 3191 KiB

Open AccessArticle

Modeling and Prediction of Thermophysiological Comfort Properties of a Single Layer Fabric System Using Single Sector Sweating Torso

by Farzan Gholamreza, Yang Su, Ruoyao Li, Anupama Vijaya Nadaraja, Robert Gathercole, Ri Li, Patricia I. Dolez, Kevin Golovin, René M. Rossi, Simon Annaheim and Abbas S. Milani

Materials 2022, 15(16), 5786; https://doi.org/10.3390/ma15165786 - 22 Aug 2022

Cited by 7 | Viewed by 2178

Abstract

Thermophysiological comfort is known to play a primary role in maintaining thermal balance, which corresponds to a person’s satisfaction with their immediate thermal environment. Among the existing test methods, sweating torsos are one of the best tools to provide a combined measurement of [...] Read more.

Thermophysiological comfort is known to play a primary role in maintaining thermal balance, which corresponds to a person’s satisfaction with their immediate thermal environment. Among the existing test methods, sweating torsos are one of the best tools to provide a combined measurement of heat and moisture transfer using non-isothermal conditions. This study presents a preliminary numerical model of a single sector sweating torso to predict the thermophysiological comfort properties of fabric systems. The model has been developed using COMSOL Multiphysics, based on the ISO 18640-1 standard test method and a single layer fabric system used in sportswear. A good agreement was observed between the experimental and numeral results over different exposure phases simulated by the torso test (R² = 0.72 to 0.99). The model enables a systematic investigation of the effect of fabric properties (thickness, porosity, thermal resistance, and evaporative resistance), environmental conditions (relative humidity, air and radiant temperature, and wind speed), and physiological parameters (sweating rate) to gain an enhanced understanding of the thermophysiological comfort properties of the fabric system. Full article

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17 pages, 6249 KiB

Open AccessArticle

Experimental Study on Effects of Aging Time on Dry Shrinkage Cracking of Lime Soils

by Jianwei Yue, Ying Chen, Zhenxian Luo, Siyuan Wang, Huicong Su, Huijie Gao, Yuan Li, Peng Li and Can Ma

Materials 2022, 15(16), 5785; https://doi.org/10.3390/ma15165785 - 22 Aug 2022

Cited by 1 | Viewed by 1332

Abstract

The effect of aging on the internal mechanism of the dry shrinkage cracking of lime soil was studied from the perspective of macroscopic cracking phenomenon and microscopic composition change, and the reasonable aging time of lime soil was determined. Large numbers of cracks [...] Read more.

The effect of aging on the internal mechanism of the dry shrinkage cracking of lime soil was studied from the perspective of macroscopic cracking phenomenon and microscopic composition change, and the reasonable aging time of lime soil was determined. Large numbers of cracks often occur in buildings constructed using lime soil, which impacts sustainable development and building environmental protection. This study explored the influence of aging time on the mechanical properties and shrinkage cracking of lime soil. The influence of aging time was evaluated using a triaxial compression test; using the dry–wet cycle, sieving, pH, and other tests, the influence of aging time on volume crack rate, expansion shrinkage rate, particle size distribution, and pH was analyzed. Scanning electron microscopy and X-ray diffraction experiments were used to analyze changes in the lime soil particle structure for different aging times and the formation of new substances. The results show that as aging time increases, the stress–strain curve of the soil softens significantly, shear strength deteriorates, and cohesion decreases. When the aging time is 6 h, the expansion rate and shrinkage rate at the center of the soil sample are the maximum. The volume fracture and expansion shrinkage rates decrease first, and then plateau with aging time, with the changes remaining stable after 72 h; these rate decreases are positively correlated with the change rate of pH. The formation of Ca(OH)₂ affects the sample pH, and the changes in pH, Ca(OH)₂, and CaO tend to be stable. With an increase in aging time, the proportion of particles of a size less than 0.1 mm decreases, and that of particles of size 0.1–0.5 mm increases. After 72 h of aging, the particle size proportion remains unchanged. Reasonable aging time can, thus, reduce the hydration reaction of lime, improve particle agglomeration effects, and reduce the crack development of the soil. Full article

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

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15 pages, 3629 KiB

Open AccessArticle

Experimental Study of Energy Evolution at a Discontinuity in Rock under Cyclic Loading and Unloading

by Wei Zheng, Linlin Gu, Zhen Wang, Junnan Ma, Hujun Li and Hang Zhou

Materials 2022, 15(16), 5784; https://doi.org/10.3390/ma15165784 - 22 Aug 2022

Cited by 2 | Viewed by 1281

Abstract

Energy is often dissipated and released in the process of rock deformation and failure. To study the energy evolution of rock discontinuities under cyclic loading and unloading, cement mortar was used as rock material and a CSS-1950 rock biaxial rheological testing machine was [...] Read more.

Energy is often dissipated and released in the process of rock deformation and failure. To study the energy evolution of rock discontinuities under cyclic loading and unloading, cement mortar was used as rock material and a CSS-1950 rock biaxial rheological testing machine was used to conduct graded cyclic loading and unloading tests on Barton’s standard profile line discontinuities with different joint roughness coefficients (JRCs). According to the deformation characteristics of the rock discontinuity sample, the change of internal energy is calculated and analyzed. The experimental results show that under the same cyclic stress, the samples harden with the increase in the number of cycles. With the increase of cyclic stress, the dissipated energy density of each stage gradually exceeds the elastic energy density and occupies a dominant position and increases rapidly as failure becomes imminent. In the process of increasing the shear stress step-by-step, the elastic energy ratio shows a downward trend, but the dissipated energy is contrary to it. The energy dissipation ratio can be used to characterize the internal damage of the sample under load. In the initial stage of fractional loading, the sample is in the extrusion compaction stage, and the energy dissipation ratio remains quasi-constant; then the fracture develops steadily, the damage inside the sample intensifies, and the energy dissipation ratio increases linearly (albeit at a low rate). When the energy storage limit is reached, the growth rate of energy dissipation ratio increases and changes when the stress level reaches a certain threshold. The increase of the roughness of rock discontinuity samples will improve their energy storage capacity to a certain extent. Full article

(This article belongs to the Special Issue Microstructure, Characterization and Mechanical Properties of Coal and Coal-Like Materials)

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16 pages, 12161 KiB

Open AccessArticle

The Volumetric Wear Assessment of a Mining Conical Pick Using the Photogrammetric Approach

by Jan Pawlik, Aleksandra Wróblewska-Pawlik and Michał Bembenek

Materials 2022, 15(16), 5783; https://doi.org/10.3390/ma15165783 - 22 Aug 2022

Cited by 5 | Viewed by 1700

Abstract

The rapid wear of conical picks used in rock cutting heads in the mining industry has a significant economic impact in cost effectiveness for a given mineral extraction business. Any mining facility could benefit from decreasing the cost along with a substantial durability [...] Read more.

The rapid wear of conical picks used in rock cutting heads in the mining industry has a significant economic impact in cost effectiveness for a given mineral extraction business. Any mining facility could benefit from decreasing the cost along with a substantial durability increase of a conical pick; thus, the hardfacing method of production and regeneration should be taken into account. In order to automatize the regeneration, the wear rate assessment is necessary. This paper presents a methodology used to create a 3D photogrammetric model of most of the commercially available tangential-rotary cutters in their before and after abrasive exploitation state. An experiment of three factors on two levels is carried out to indicate the proper setup of the scanning rig to obtain plausible results. Those factors are: light level, presence of polarizing filter and the distance from the scanned object. The 3D scan of the worn out specimen is compared to the master model via algorithm developed by the authors. This approach provides more detailed information about the wear mechanism and can help either in roadheader cutting head diagnostics or to develop a strategy and optimize the toolpath for the numerically controlled hardfacing machine. Full article

(This article belongs to the Special Issue Polish Achievements in Materials Science and Engineering)

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33 pages, 3249 KiB

Open AccessReview

Studies of Monoamine Neurotransmitters at Nanomolar Levels Using Carbon Material Electrodes: A Review

by Pankaj Kumar, Isha Soni, Gururaj Kudur Jayaprakash and Roberto Flores-Moreno

Materials 2022, 15(16), 5782; https://doi.org/10.3390/ma15165782 - 22 Aug 2022

Cited by 3 | Viewed by 2617

Abstract

Neurotransmitters (NTs) with hydroxyl groups can now be identified electrochemically, utilizing a variety of electrodes and voltammetric techniques. In particular, in monoamine, the position of the hydroxyl groups might alter the sensing properties of a certain neurotransmitter. Numerous research studies using electrodes modified [...] Read more.

Neurotransmitters (NTs) with hydroxyl groups can now be identified electrochemically, utilizing a variety of electrodes and voltammetric techniques. In particular, in monoamine, the position of the hydroxyl groups might alter the sensing properties of a certain neurotransmitter. Numerous research studies using electrodes modified on their surfaces to better detect specific neurotransmitters when other interfering factors are present are reviewed to improve the precision of these measures. An investigation of the monoamine neurotransmitters at nanoscale using electrochemical methods is the primary goal of this review article. It will be used to determine which sort of electrode is ideal for this purpose. The use of carbon materials, such as graphite carbon fiber, carbon fiber micro-electrodes, glassy carbon, and 3D printed electrodes are only some of the electrodes with surface modifications that can be utilized for this purpose. Electrochemical methods for real-time detection and quantification of monoamine neurotransmitters in real samples at the nanomolar level are summarized in this paper. Full article

(This article belongs to the Special Issue Carbon-Based Composite Materials for Electrodes)

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12 pages, 3067 KiB

Open AccessArticle

The Effect of the Doping Amount on Electroelastic Coupled-Wave Scattering and Dynamic Stress Concentration around Defects in BNT Doped FN Materials

by Jiawei Fan, Chuanping Zhou, Junqi Bao, Huawei Ji, Yongping Gong, Weihua Zhou and Jiang Lin

Materials 2022, 15(16), 5781; https://doi.org/10.3390/ma15165781 - 21 Aug 2022

Viewed by 1223

Abstract

Sodium bismuth titanate (Bi_0.5Na_0.5TiO₃, BNT) has attracted much attention because of its excellent dielectric, piezoelectric and electromechanical properties. The microstructure of sodium bismuth titanate-doped ferrum niobium material (Bi_0.5Na_0.5TiO₃ doped (Fe_0.5Nb [...] Read more.

Sodium bismuth titanate (Bi_0.5Na_0.5TiO₃, BNT) has attracted much attention because of its excellent dielectric, piezoelectric and electromechanical properties. The microstructure of sodium bismuth titanate-doped ferrum niobium material (Bi_0.5Na_0.5TiO₃ doped (Fe_0.5Nb_0.5)⁴⁺, BNT-xFN) shows a triangle as its typical defect shape. Since piezoelectric devices usually operate under dynamic loads, they fail easily owing to dynamic stress concentration or dynamic fracture. Elastic waves can simulate many types of dynamic loads, and the dynamic stress concentration caused by an anti-plane shear wave is the basis for the calculation of the stress field strength factor of type Ⅲ-dynamic fractures. In this study, the electroelastic coupled-wave diffraction and dynamic stress concentration of BNT-xFN materials with triangular defects under the incidence of anti-plane shear waves were studied. Maxwell equations are decoupled by auxiliary functions, and the analytical solutions of the elastic wave field and electric field are obtained. Based on the conformal mapping method, the triangle defect was mapped to the unit circle defect, and the dynamic stress concentration coefficient around the triangle defect was obtained by calculating the undetermined mode coefficients in the expression through boundary conditions. The numerical calculation shows that the size of the triangular hole, the frequency of the applied mechanical load, the incidence angle of mechanical load and the amount of FN doping have a great influence on the stress concentration of BNT-xFN materials. Full article

(This article belongs to the Special Issue Smart Materials: Next Generation in Science and Technology)

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17 pages, 13016 KiB

Open AccessArticle

The Effect of Carbon Content on the Microstructure and Mechanical Properties of Cemented Carbides with a CoNiFeCr High Entropy Alloy Binder

by Cheng Qian, Yong Liu, Huichao Cheng, Kun Li, Bin Liu and Xin Zhang

Materials 2022, 15(16), 5780; https://doi.org/10.3390/ma15165780 - 21 Aug 2022

Cited by 4 | Viewed by 1578

Abstract

CoNiFeCr high entropy alloy (HEA) was used as a binder in cemented carbides for developing a new high-performance binder. The microstructure of WC-HEA cemented carbides with different binder components and carbon contents was subsequently studied. It was observed that the (Cr,W)C phase precipitated [...] Read more.

CoNiFeCr high entropy alloy (HEA) was used as a binder in cemented carbides for developing a new high-performance binder. The microstructure of WC-HEA cemented carbides with different binder components and carbon contents was subsequently studied. It was observed that the (Cr,W)C phase precipitated at the WC/HEA interface, and a coherent interface with a low degree of misfit was formed between WC and (Cr,W)C, thereby resulting in a significant reduction in the interfacial energy and stress concentration. The (Cr,W)C phase exerted a pinning force (Zener-drag) on the moving grain boundaries, which effectively inhibited the growth of WC grains. As a result, compared with WC-Co, WC-CoNiFeCr had smaller WC grain size, smoother grain shape and larger mean free path (MFP) of the binder, which resulted in slightly lower hardness and higher transverse rupture strength (TRS) and fracture toughness. The lower limit of carbon content in WC-CoNiFeCr was higher than that of WC-Co. With the addition of Ni, the width of the two-phase region became wider, whereas the width of the two-phase region became narrower with the addition of Fe and Cr. Full article

(This article belongs to the Section Metals and Alloys)

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22 pages, 5633 KiB

Open AccessArticle

An Analytical Solution for Stress Transfer between a Broken Prestressing Wire and Mortar Coating in PCCP

by Xiaojie Zhang, Jiayu Wu, Chao Hou and Jian-Fei Chen

Materials 2022, 15(16), 5779; https://doi.org/10.3390/ma15165779 - 21 Aug 2022

Viewed by 1382

Abstract

A prestressed concrete cylinder pipe (PCCP) consists of a concrete core, a steel cylinder, prestressing wires, and a mortar coating. Most PCCP failures are related to the breakage of prestressing wires. It is thus expected that the load-bearing capacity of PCCP is significantly [...] Read more.

A prestressed concrete cylinder pipe (PCCP) consists of a concrete core, a steel cylinder, prestressing wires, and a mortar coating. Most PCCP failures are related to the breakage of prestressing wires. It is thus expected that the load-bearing capacity of PCCP is significantly affected by the length of the prestress loss zone and the stress distribution in the broken wire. Based on a tri-linear bond-slip model, the length of prestress loss zone and the stress transfer mechanism between a broken wire and a mortar coating are analysed in this paper. During the breaking (unloading) process of a prestressing wire, the interfacial bondline exhibits the following three stages: elastic stage, elastic-softening stage, and elastic-softening-debonding stage. The closed-form solutions for the interfacial slip, the interfacial shear stress, and the axial stress in the broken wire are derived for each stage. The solutions are verified by the finite element predictions. A parametric study is presented to investigate the effects of the size of the prestressing wires, the prestressing level, the interfacial shear strength, and the residual interfacial shear strength on the interfacial stress transfer. For an example PCCP with an inner diameter of 4 m, the length of prestress loss zone increases from 500 mm to 3300 mm as the radius of prestressing wire increases from 1 mm to 7 mm. It increases from 2700 mm to 7700 mm when the interfacial shear strength reduces from 3.94 MPa to 0.62 MPa and reduces from 13,200 mm to 7300 mm as the residual interfacial shear stress factor increases from 0.1 to 0.9. Full article

(This article belongs to the Section Mechanics of Materials)

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13 pages, 4073 KiB

Open AccessArticle

Ecofriendly Biopolymer-Based Nanocomposite Films with Improved Photo-Oxidative Resistance

by Elisabetta Morici, Giulia Infurna and Nadka Tz. Dintcheva

Materials 2022, 15(16), 5778; https://doi.org/10.3390/ma15165778 - 21 Aug 2022

Viewed by 1347

Abstract

The interest towards high performance biopolymer-based materials increases continuously and, to guarantee appropriately industrial applications, the photo-oxidative resistance and stability of these materials must be adequately addressed. In this study, innovative biopolymer-based nanocomposites, i.e., Polyamide 11 (PA11), containing ad-hoc modified Layered Double Hydroxides [...] Read more.

The interest towards high performance biopolymer-based materials increases continuously and, to guarantee appropriately industrial applications, the photo-oxidative resistance and stability of these materials must be adequately addressed. In this study, innovative biopolymer-based nanocomposites, i.e., Polyamide 11 (PA11), containing ad-hoc modified Layered Double Hydroxides (LDH), were successfully formulated and characterized. Particularly, LDH were considered carriers for hindered amine light stabilizing molecules, so two different hindered amine moieties (HALS1 and HALS2) were anchored on LDH layered internal structures and/or outer surfaces. The presence of HALS1 and HALS2 in LDH were confirmed by X-ray diffraction, spectroscopy, and thermogravimetric analysis. Then, the novel LDH-HALS nanofillers (here named LDH-HALS1 and LDH-HALS2) were introduced into a PA11 matrix by melt mixing at 5 wt.%; the produced nanocomposites were characterized by differential scanning calorimetry, rheological, and morphological analysis. All obtained results suggest that the LDH-HALS1/HALS2 nanofillers were very well dispersed into the PA11 matrix. Additionally, the photo-oxidative resistance of the PA11-based nanocomposite films was evaluated by subjecting thin films to UVB exposure and the degradation process was monitored by spectroscopic analysis over time. The photo-oxidative resistance of the PA11/LDH-HALS1/HALS2 was compared to that of PA11-based nanocomposites containing unmodified LDH and the commercial hindered amine UV-stabilizer (Cyasorb^® UV-3853). It was established that by anchoring the hindered amine moieties to the LDH, the PA11 nanocomposites were successfully protected against UVB exposure. This was because the hindered amine light stabilizing molecules were available to act at the critical zone where the degradation phenomena occur, which is at the interface between the matrix and the inorganic particles. Full article

(This article belongs to the Special Issue Properties, Design and Structure of Advanced Polymers and Composite Materials)

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23 pages, 14952 KiB

Open AccessArticle

Laser Powder Bed Fusion Process Parameters’ Optimization for Fabrication of Dense IN 625

by Alexandru Paraschiv, Gheorghe Matache, Mihaela Raluca Condruz, Tiberius Florian Frigioescu and Laurent Pambaguian

Materials 2022, 15(16), 5777; https://doi.org/10.3390/ma15165777 - 21 Aug 2022

Cited by 6 | Viewed by 1765

Abstract

This paper presents an experimental study on the influence of the main Laser Powder Bed Fusion (PBF-LB) process parameters on the density and surface quality of the IN 625 superalloy manufactured using the Lasertec 30 SLM machine. Parameters’ influence was investigated within a [...] Read more.

This paper presents an experimental study on the influence of the main Laser Powder Bed Fusion (PBF-LB) process parameters on the density and surface quality of the IN 625 superalloy manufactured using the Lasertec 30 SLM machine. Parameters’ influence was investigated within a workspace defined by the laser power (150–400 W), scanning speed (500–900 m/s), scanning strategy (90° and 67°), layer thickness (30–70 µm), and hatch distance (0.09–0.12 µm). Experimental results showed that laser power and scanning speed play a determining role in producing a relative density higher than 99.5% of the material’s theoretical density. A basic set of process parameters was selected for generating high-density material: laser power 250 W, laser speed 750 mm/s, layer thickness 40 µm, and hatch distance 0.11 mm. The 67° scanning strategy ensures higher roughness surfaces than the 90° scanning strategy, roughness that increases as the laser power increases and the laser speed decreases. Full article

(This article belongs to the Special Issue Design and Post Processing for Metal Additive Manufacturing)

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14 pages, 2670 KiB

Open AccessArticle

Color as an Indicator of Properties in Thermally Modified Scots Pine Sapwood

by Magdalena Piernik, Magdalena Woźniak, Grzegorz Pinkowski, Kinga Szentner, Izabela Ratajczak and Andrzej Krauss

Materials 2022, 15(16), 5776; https://doi.org/10.3390/ma15165776 - 21 Aug 2022

Cited by 2 | Viewed by 1473

Abstract

The aim of this study was to determine the dependencies between mechanical properties of modified wood and its color. Within its scope, quantitative changes in color and chemical composition (mass loss, total carbon content, content of extractives and main components of wood), as [...] Read more.

The aim of this study was to determine the dependencies between mechanical properties of modified wood and its color. Within its scope, quantitative changes in color and chemical composition (mass loss, total carbon content, content of extractives and main components of wood), as well as mechanical properties (compressive strength along the grain, strength and modulus of elasticity in longitudinal tension tests, compression across the grain and impact resistance) of the modified Scots pine sapwood, were determined. Modifications were conducted in the atmosphere of superheated steam (time—4 h, temperature of 130, 160, 190, 220 °C). Thermal modification of wood results in an increase in the modulus of elasticity, a reduction of elasticity, longitudinal tensile strength and compressive strength perpendicular to grain. It was found that color parameters ∆E, ∆L and ∆a are linear functions of the modification temperature. The existence of functional dependencies between mass loss, longitudinal tensile strength, radial modulus of elasticity and parameters of ∆E and ∆L makes it possible to determine these properties of modified wood based on color. In turn, chemical analysis indicated that an increase in the temperature of wood modification caused a decrease of holocellulose and hemicelluloses contents, especially in wood samples modified at 220 °C. Full article

(This article belongs to the Special Issue Trends on the Wood Materials and Technologies)

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17 pages, 2809 KiB

Open AccessArticle

Quantifying the Workability of Calcium Sulfoaluminate Cement Paste Using Time-Dependent Rheology

by Sukanta K. Mondal, Adam Welz, Carrie Clinton, Kamal Khayat, Aditya Kumar and Monday U. Okoronkwo

Materials 2022, 15(16), 5775; https://doi.org/10.3390/ma15165775 - 21 Aug 2022

Cited by 5 | Viewed by 1504

Abstract

Poor workability is a common feature of calcium sulfoaluminate (CSA) cement paste. Multiple chemical admixtures, such as set retarders and dispersants, are frequently employed to improve the workability and delay the setting of CSA cement paste. A quantitative assessment of the compatibility, efficiency, [...] Read more.

Poor workability is a common feature of calcium sulfoaluminate (CSA) cement paste. Multiple chemical admixtures, such as set retarders and dispersants, are frequently employed to improve the workability and delay the setting of CSA cement paste. A quantitative assessment of the compatibility, efficiency, and the effects of the admixtures on cement paste workability is critical for the design of an appropriate paste formulation and admixture proportioning. Very limited studies are available on the quantitative rheology-based method for evaluating the workability of calcium sulfoaluminate cement pastes. This study presents a novel and robust time-dependent rheological method for quantifying the workability of CSA cement pastes modified with the incorporation of citric acid as a set retarder and a polycarboxylate ether (PCE)-based superplasticizer as a dispersant. The yield stress is measured as a function of time, and the resulting curve is applied to quantify three specific workability parameters: (i) the rate at which the paste loses flowability, (ii) the time limit for paste placement or pumping, marking the onset of acceleration to initial setting, and (iii) the rate at which the paste accelerates to final setting. The results of the tested CSA systems show that the rate of the loss of flowability and the rate of hardening decrease monotonously, while the time limit for casting decreases linearly with the increase in citric acid concentration. The dosage rate of PCE has a relatively small effect on the quantified workability parameters, partly due to the competitive adsorption of citrate ions. The method demonstrated here can characterize the interaction or co-influence of multiple admixtures on early-age properties of the cement paste, thus providing a quantitative rheological protocol for determining the workability and a novel approach to material selection and mixture design. Full article

(This article belongs to the Special Issue New Findings in Cementitious Materials)

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11 pages, 3389 KiB

Open AccessEditor’s ChoiceArticle

Universal Dependence of Nuclear Spin Relaxation on the Concentration of Paramagnetic Centers in Nano- and Microdiamonds

by Alexander M. Panich

Materials 2022, 15(16), 5774; https://doi.org/10.3390/ma15165774 - 21 Aug 2022

Cited by 4 | Viewed by 1091

Abstract

An analysis of our data on ¹H and ¹³C spin–lattice and spin–spin relaxation times and rates in aqueous suspensions of purified nanodiamonds produced by detonation technique (DNDs), DNDs with grafted paramagnetic ions, and micro- and nanodiamonds produced by milling bulk high-temperature [...] Read more.

An analysis of our data on ¹H and ¹³C spin–lattice and spin–spin relaxation times and rates in aqueous suspensions of purified nanodiamonds produced by detonation technique (DNDs), DNDs with grafted paramagnetic ions, and micro- and nanodiamonds produced by milling bulk high-temperature high-pressure diamonds is presented. It has been established that in all the studied materials, the relaxation rates depend linearly on the concentration of diamond particles in suspensions, the concentration of grafted paramagnetic ions, and surface paramagnetic defects produced by milling, while the relaxation times exhibit a hyperbolic dependence on the concentration of paramagnetic centers. This is a universal law that is valid for suspensions, gels, and solids. The results obtained will expand the understanding of the properties of nano- and microdiamonds and will be useful for their application in quantum computing, spintronics, nanophotonics, and biomedicine. Full article

(This article belongs to the Section Materials Physics)

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9 pages, 2450 KiB

Open AccessArticle

Two Magnetic Orderings and a Spin–Flop Transition in Mixed Valence Compound Mn₃O(SeO₃)₃

by Wanwan Zhang, Meiyan Cui, Jindou Tian, Pengfeng Jiang, Guoyu Qian and Xia Lu

Materials 2022, 15(16), 5773; https://doi.org/10.3390/ma15165773 - 21 Aug 2022

Cited by 3 | Viewed by 1403

Abstract

A mixed-valence manganese selenite, Mn₃O(SeO₃)₃, was successfully synthesized using a conventional hydrothermal method. The three-dimensional framework of this compound is composed of an MnO₆ octahedra and an SeO₃ trigonal pyramid. The magnetic topological arrangement of [...] Read more.

A mixed-valence manganese selenite, Mn₃O(SeO₃)₃, was successfully synthesized using a conventional hydrothermal method. The three-dimensional framework of this compound is composed of an MnO₆ octahedra and an SeO₃ trigonal pyramid. The magnetic topological arrangement of manganese ions shows a three-dimensional framework formed by the intersection of octa-kagomé spin sublattices and staircase-kagomé spin sublattices. Susceptibility, magnetization and heat capacity measurements confirm that Mn₃O(SeO₃)₃ exhibits two successive long-range antiferromagnetic orderings with T_N1~4.5 K and T_N2~45 K and a field-induced spin–flop transition at a critical field of 4.5 T at low temperature. Full article

(This article belongs to the Topic Materials for Energy Harvesting and Storage)

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14 pages, 4438 KiB

Open AccessArticle

Damage Evolution Characteristics of Back-Filling Concrete in Gob-Side Entry Retaining Subjected to Cyclical Loading

by Xicai Gao, Shuai Liu, Cheng Zhao, Jianhui Yin and Kai Fan

Materials 2022, 15(16), 5772; https://doi.org/10.3390/ma15165772 - 21 Aug 2022

Cited by 5 | Viewed by 1177

Abstract

The back-filling body in the gob-side entry retaining is subject to continuous disturbance due to repeated mining. In this study, uniaxial and cyclical loading tests of back-filling concrete samples were carried out under laboratory conditions to study damage evolution characteristics with respect to [...] Read more.

The back-filling body in the gob-side entry retaining is subject to continuous disturbance due to repeated mining. In this study, uniaxial and cyclical loading tests of back-filling concrete samples were carried out under laboratory conditions to study damage evolution characteristics with respect to microscopic hydration, deformation properties, and energy evolution. The results showed that, due to the difference in the gradation of coarse and fine aggregates, the cemented structure was relatively loose, and the primary failure modes under cyclical loading were tensile and shearing failure, which significantly decreased its strength. With an increasing number of loadings, a hysteresis loop appeared for the axial strain, and the area showed a pattern of decrease–stabilization–increase. This trend, to a certain extent, reflected the evolution of the cracks in the back-filling concrete samples. The axial, radial, and volumetric plastic strain curves of the back-filling concrete samples showed a “U” shape. The plastic strain changed in three stages, i.e., a rapid decrease, stabilization, and a rapid increase. A damage parameter was defined according to the plastic strain increment to accurately characterize the staged failure of the samples. The plastic strain and energy dissipation of the samples were precursors to sample failure. Prior to the failure of the back-filling samples, the amount and speed of change of both the plastic strain and energy parameters increased significantly. Understanding the characteristics of plastic strain, damage evolution, and energy dissipation rate of the back-filling samples are of great reference value for realizing real-time monitoring of back-filling concrete in the gob-side entry retaining and providing early warning of failure. Full article

(This article belongs to the Special Issue Microstructure, Characterization and Mechanical Properties of Coal and Coal-Like Materials)

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15 pages, 1988 KiB

Open AccessArticle

Numerical Simulation of Dry Ice Compaction Process: Comparison of Drucker-Prager/Cap and Cam Clay Models with Experimental Results

by Maciej Berdychowski, Jan Górecki, Aleksandra Biszczanik and Krzysztof Wałęsa

Materials 2022, 15(16), 5771; https://doi.org/10.3390/ma15165771 - 21 Aug 2022

Cited by 12 | Viewed by 1341

Abstract

This article presents the results of a numerical experimental study on the simulation of the dry ice compaction process. The first part of the article presents a description of the material used, material models and the methodology of experimental research. In the second [...] Read more.

This article presents the results of a numerical experimental study on the simulation of the dry ice compaction process. The first part of the article presents a description of the material used, material models and the methodology of experimental research. In the second part, numerical and experimental study results are presented. For the purpose of comparison, a parametric method based on the residual sum of squares was used. The application of the indicated method fills the gap in the available literature as the authors are not aware of any existing data from previous studies on the method of comparing the results of numerical tests in terms of the obtained results and the change of the value of the tested parameter as a function of another variable. The results of this study can be useful in research work aimed at further development of the process of extrusion and compaction of dry ice using Drucker-Prager/Cap and modified Cam-Clay material models for instance for optimization of geometric parameters of parts and components of the main assembly of the machine used in the process of dry ice extrusion. Full article

(This article belongs to the Special Issue Numerical Modeling for Simulation of Different Processes in Manufacturing)

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11 pages, 1290 KiB

Open AccessArticle

The Influence of 2-Methacryloyloxyethyl Phosphorylcholine Polymer Materials on Orthodontic Friction and Attachment of Oral Bacteria

by Ryo Kunimatsu, Yuji Tsuka, Kengo Nakajima, Keisuke Sumi, Yuki Yoshimi, Isamu Kado, Ayako Inada, Yoshihiro Kiritoshi and Kotaro Tanimoto

Materials 2022, 15(16), 5770; https://doi.org/10.3390/ma15165770 - 21 Aug 2022

Cited by 6 | Viewed by 1612

Abstract

There is no clinical evidence of the usage of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers in dental practice. We performed in vitro studies to determine whether the application of an MPC coating to stainless steel orthodontic wires confers low-friction and antimicrobial properties to these wires. [...] Read more.

There is no clinical evidence of the usage of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers in dental practice. We performed in vitro studies to determine whether the application of an MPC coating to stainless steel orthodontic wires confers low-friction and antimicrobial properties to these wires. The friction test on MPC-coated wires was performed using a precision universal/tensile tester. MPC polymer was coated on a 50 × 50 mm stainless steel plate, and samples were assessed using an antimicrobial activity test. To verify the effect of MPC polymer-treated wires on experimental tooth movement models in vitro, examinations were performed on typodonts to determine the improvement in tooth movement efficiency. The polymer treatment wire groups demonstrated significantly enhanced tooth movement compared with the untreated wire groups, at both 50 g and 100 g traction forces. The results indicated that MPC coating inhibited the attachment of oral bacteria, such as Streptococcus mutans, on a stainless steel plate. Additionally, the coating seemed to improve the efficiency of tooth movement by reducing the occurrence of friction. The application of an MPC coating onto stainless steel wires, which are used as orthodontic materials, may reduce static friction and bacterial adherence to the oral cavity and improve tooth movement. Full article

(This article belongs to the Special Issue Novel Materials in Dentistry and Medical Applications)

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