bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Cyanobacteria Arthospira platensis for Bioremediation of Erbium-Contaminated Wastewater
Authors: Yushin Nikita , Zinicovscaia Inga , Cepoi Liliana , Chiriac Tatiana , Rudi Ludmila , Grozdov Dmitrii
Published: September 2022

Erbium belongs to rare earth elements critical for industry, especially nuclear technology. Cyanobacteria Arthospira platensis was used for Er(III) removal from wastewater by applying biosorption and bioaccumulation processes. The influence of pH, Er(III) concentration, contact time and temperature on the biosorption capacity of Arthospira platensis was determined. The optimal conditions for Er(III) removal were defined as pH 3.0, time 15 min and temperature 20 °C, when 30 mg/g of Er(III) were removed. The kinetics of the process was better described by the pseudo-first-order model, while equilibrium fitted to the Freundlich model. In bioaccumulation experiments, the uptake capacity of biomass and Er(III) effect on biomass biochemical composition were assessed. It was shown that Er(III) in concentrations 10–30 mg/L did not affect the content of biomass, proteins, carbohydrate and photosynthetic pigments. Its toxicity was expressed by the reduction of the lipids content and growth of the level of malonic dialdehyde. Biomass accumulated 45–78% of Eu(III) present in the cultivation medium. Therefore, Arthospira platensis can be considered as a safe and efficient bioremediator of erbium contaminated environment.
Synthesis of Pyrochlore Oxides Containing Ir and Ru for Efficient Oxygen Evolution Reaction
Authors: Matsumoto Aika , Cai Ze-Xing , Fujita Takeshi
Published: September 2022

A versatile synthesis method for pyrochlore oxides containing Ir and Ru with lanthanides Pr, Nd, Eu, Gd, Tb, and Ho is herein presented. Based on the systematic synthesis and Rietveld refinement results, the lattice constants were tunable depending on the ionic radius of the lanthanide used. Subsequently, Pr-based pyrochlore oxides containing Ru and Ir in different ratios were fabricated for the oxygen evolution reaction (OER) in alkaline media, and the OER activity of these catalysts increased when the content of Ir and Ru was the same. Thus, the co-substitution of Ir and Ru in pyrochlore oxides is a novel synthesis strategy for electrocatalysts, which provides great potential for the fabrication of other pyrochlore oxides with various architectures and compositions for application in electrocatalysis.
Chitosan-Modified Biochars to Advance Research on Heavy Metal Ion Removal: Roles, Mechanism and Perspectives
Authors: Bąk Justyna , Thomas Peter , Kołodyńska Dorota
Published: September 2022

The chitosan-modified biochars BC-CS 1-1, BC-CS 2-1 and BC-CS 4-1 were subjected to the synthetic application of biochar from agriculture waste and chitosan for the adsorption of Cu(II), Cd(II), Zn(II), Co(II) and Pb(II) ions from aqueous media. The results displayed a heterogeneous, well-developed surface. Additionally, the surface functional groups carboxyl, hydroxyl and phenol, determining the sorption mechanism and confirming the thermal stability of the materials, were present. The sorption evaluation was carried out as a function of the sorbent dose, pH, phase contact time, initial concentration of the solution and temperature. The maximum value of qt for Pb(II)-BC-CS 4-1, 32.23 mg/g (C0 200 mg/L, mass 0.1 g, pH 5, 360 min), was identified. Nitric acid was applied for the sorbent regeneration with a yield of 99.13% for Pb(II)-BC-CS 2-1. The produced sorbents can be used for the decontamination of water by means of the cost-effective and high-performance method.
Fe3O4/Diatomite-Decorated Cotton Evaporator for Continuous Solar Steam Generation and Water Treatment
Authors: Bai Zhi , Xu Haifeng , Yang Bo , Yao Jixin , Li Guang , Guo Kai , Wang Nan , Liang Nannan
Published: September 2022

Improving the evaporation rate of solar steam generation (SSG) has always been a research hotspot to solve the shortage of water resources. Using cotton, Fe3O4, polyvinyl alcohol (PVA) and diatomite (DM) as raw materials, DM/PVA/Fe3O4@cotton composites with both firmness and hydrophilicity were prepared. Fe3O4 has a wide range of light absorption characteristics and good photothermal conversion performance, and is an ideal photothermal conversion material. PVA enhances the adhesion between Fe3O4, cotton and DM and enhances the hardness of the sample and the internal porous structure. The existence of DM greatly improves the hydrophilicity of the sample, ensuring that the water in the lower layer can be continuously transported to the surface of the sample, and DM makes the surface of the sample rough, which reduces the reflection of sunlight and improves the efficiency of light heat conversion. Under one-sun irradiation, the temperature of the sample surface increases by 52.6 °C, the evaporation rate can reach 1.32 kg m−2 h−1 and the evaporation efficiency is 82.9%. Using this sample as the photothermal conversion layer of the SSG device, the removal rate of salt ions in seawater is more than 98% and the removal rate of heavy metal ions in sewage is close to 100%. This work provides a new idea and design method for SSG in the field of seawater desalination and sewage treatment.
Mechanical and Tribological Properties of Aluminum-Based Metal-Matrix Composites
Authors: Lakshmikanthan Avinash , Angadi Santosh , Malik Vinayak , Saxena Kuldeep K. , Prakash Chandar , Dixit Saurav , Mohammed Kahtan A.
Published: September 2022

This review article focuses on the aluminum-based metal matrix composites (Al-based MMCs). Studies or investigations of their mechanical and tribological properties performed by researchers worldwide in the past are presented in detail. The processing techniques and applications for Al-based MMCs are also documented here. A brief background on the composite materials, their constituents, and their classification, as well as the different matrix materials and particulates used in Al-based MMCs, can be found in this review. Then, an overview of dual-particle-size reinforced composites, heat treatment of Al alloys, and temper designations used in heat treatment are also included. In addition, the factors influencing the mechanical and wear properties of Al-based MMCs are discussed. The primary objective is that both present and future researchers and investigators will be assisted by the comprehensive knowledge compiled in this article to further explore and work towards the betterment of society in general.
TEM Study of the Microstructure of an Alumina/Al Composite Prepared by Gas-Pressure Infiltration
Authors: Matus Krzysztof , Matula Grzegorz , Pawlyta Mirosława , Krzysteczko-Witek Jagoda , Tomiczek Błażej
Published: September 2022

Ceramic injection moulding and gas-pressure infiltration were employed for the manufacturing of alumina/AlSi10Mg composites. Porous ceramic preforms were prepared by mixing alumina powder with a multi-binder system and injection moulding the powder polymer slurry. Then, the organic part was removed through a combination of solvent and thermal debinding, and, finally, the materials were sintered at different temperatures. Degrading the binder enabled open canals to form. The sintering process created a porous ceramic material consisting of alumina without any residual carbon content. During infiltration, the liquid metal filled the empty spaces (pores) effectively and formed a three-dimensional network of metal in the ceramic. The microstructure and properties of the manufactured materials were examined using high-resolution transmission electron microscopy, porosimetry, and bending strength testing. Microscopy observations showed that the fabricated composite materials are characterised by a percolation type of microstructure and a lack of unfilled pores. The research confirmed the diversified nature of the connection at the particle–matrix interface. It was observed that the interphase boundary was characterised by the lack of a transition zone between the components or a continuous transition zone, with the thickness not exceeding 30 nm. Thanks to their increased mechanical properties and low density, the obtained composites could be used in the automotive industry as a material for small piston rings and rods, connecting rods, or even gears.
In Situ Measurement of Cyclic Plastic Zone and Internal Strain Response of Q&P Steel near Fatigue Crack Tip Region Based on Micro-DIC
Authors: Gao Hongli , Lin Zhiyuan , Huang Xinwei , Shang Hongbin , Zhan Jingsong
Published: September 2022

The shape and internal dynamic response characteristics of the plastic zone near the fatigue crack tip region, especially the cyclic plastic zone (CPZ), are the main factors affecting the fatigue crack initiation and propagation behaviors of ductile metal materials. The existing methods for characterizing the CPZ have some problems, which include the complexity of the process, the difficulty of achieving in situ measurement, and the inability to characterize the dynamic response in the CPZ during the crack propagation process. Therefore, a novel method is proposed for the in situ measurement of the CPZ near the crack tip region based on image stitching and matching algorithms, a load–strain loop curve characteristic judgement algorithm, and the microscopic digital image correlation (DIC) method. A microscopic camera and a macroscopic camera are used to simultaneously capture the micro crack tip speckle images and the global crack image of the two sides of the Compact Tension (CT) specimen for calculating in situ crack length and crack tip strain fields. The proposed method was performed and verified by a fatigue crack growth (FCG) test and micro-hardness experiments with Quenching and Partitioning 980 (Q&P980) steel, and the results show that the method is feasible because the maximum error is less than 5%. A “butterfly wings” shape of the CPZ and a strain concentration phenomenon in the CPZ of the Q&P980 were observed. Moreover, as the fatigue crack propagates, the area of the CPZ and the degree of the strain concentration increase gradually. This method, which can obtain the in situ and tracking measurements of the crack tip CPZ, will help to increase our understanding of CPZ characteristics, the FCG mechanism, and the behavior of Q&P steel and the plastic metal materials similar to Q&P steel.
Path Generation Strategy and Wire Arc Additive Manufacturing of Large Aviation Die with Complex Gradient Structure
Authors: Zhang Jiansheng , Xiao Guiqian , Peng Jie , Yu Yingyan , Zhou Jie
Published: September 2022

To realize automatic wire arc additive manufacturing (WAAM) of a large aviation die with a complex gradient structure, a new contour-parallel path generation strategy was proposed and practically applied. First, the planar curve was defined as a vertical slice of a higher-dimensional surface and a partial differential equation describing boundary evolution was derived to calculate the surface. The improved Finite Element Method (FEM) and Finite Difference Method (FDM) were used to solve this partial differential equation. Second, a cross section of a large aviation die was used to test the path-generation algorithms. The results show that FEM has a faster solving speed than FDM under the same solving accuracy because the solving domain of FEM mesh was greatly reduced and the boundary mesh could be refined. Third, the die was divided into three layers: base layer, transition layer (Fe-based material) and strengthening layer (Co-based material) according to the difference of the temperature and stress field, and corresponding WAAM process parameters has been discussed. The optimum welding parameters are obtained as follows: voltage is 28 V, wire feeding speed is 8000 mm/min and welding speed is 450 mm/min. Finally, the path generation strategy was practically applied to the remanufacture of the large aircraft landing gear die with a three-layer structure. The application test on aircraft landing gear dies justified the effectiveness of the algorithms and strategy proposed in this paper, which significantly improved the efficiency of the WAAM process and the service life of large aviation dies with complex gradient structures. The microstructure of the fusion zone shows that the base metal and welding material can be fully integrated into the welding process.
A Promising Mortar Produced with Seawater and Sea Sand
Authors: Sheng Zhigang , Wang Yajun , Huang Dan
Published: September 2022

The aim of the study is the deep understanding of the essential reactivity of the environmentally friendly mortar by which its applicability can be justified. Created in the study was the environmentally friendly mortar, which helped relieve the increasing requirements on conventional building materials that are produced from exhausted freshwater and river sand nowadays. Seawater (SW) and sea sand (SS) collected from the Eastern Seas of China were used to produce the mortar at various ages, including 10-day, 33-day, and 91-day. Both the curing and working conditions of the mortar were natural marine ones. The physicochemical-mechanical behaviors were investigated using uniaxial compression tests (UCTs), Energy Dispersive Spectrometer (EDS), X-ray Diffraction (XRD), and thermal-field emission scanning electron microscopy (SEM) analysis to understand the essential reactivity of the mortar with age accumulation. The results indicated that hydration products and favorable components were generated promisingly in the mortar: the C-S-H (xCaO·SiO2·zH2O) development was certainly achieved in the critical environment during the curing and working period; the extensive generation of C-A-S-H (CaO·Al2O3·2SiO2·4H2O) helped densify the C-S-H grid, which caused the promising development of the uniaxial compression strength (UCS); the framework porosity of the mortar was restrained effectively due to the development of Friedel’s salt that re-bonded the interfacial cracks between SS and the hydration products with the age accumulation in the critical environment. Consequently, UCS and the resistance against damage of the mortar showed increasing behavior even in the critical environment. The study established Friedel’s salt working models and strength and damage models to interpret the physicochemical reactivity of the mortar as: the source of the strength and toughness was the proper polymerization between the native saline components and the hydration product mixture generated throughout the production, curing, and application without the leaching phenomenon. The novel models and interpretation of the physicochemical reactivity ensured the applicability of the mortar produced with SW and SS in the critical environment.
Properties of 3D Printed Concrete–Geopolymer Hybrids Reinforced with Aramid Roving
Authors: Marczyk Joanna , Ziejewska Celina , Korniejenko Kinga , Łach Michał , Marzec Witold , Góra Mateusz , Dziura Paweł , Sprince Andina , Szechyńska-Hebda Magdalena , Hebda Marek
Published: September 2022

Three-dimensional concrete printing (3DCP) is an innovative technology that can lead to breakthrough modifications of production processes in the construction industry. The paper presents for the first time the possibility of 3D printing concrete–geopolymer hybrids reinforced with aramid roving. Reference concrete samples and concrete–geopolymer hybrids composed of 95% concrete and 5% geopolymer based on fly ash or metakaolin were produced. The properties of the samples without reinforcement and samples with 0.5% (wt.) aramid roving were compared. The frost resistance tests, UV radiation resistance, and thermal conductivity were evaluated for samples that were 3D-printed or produced by the conventional casting method. Compressive strength tests were carried out for each sample exposed to freeze–thaw cycles and UV radiation. It was observed that after the frost resistance test, the samples produced by the 3D printing technology had a minor decrease in strength properties compared to the samples made by casting. Moreover, the thermal conductivity coefficient was higher for concrete–geopolymer hybrids than concrete reinforced with aramid roving.
CO2 Adsorption over 3d Transition-Metal Nanoclusters Supported on Pyridinic N3-Doped Graphene: A DFT Investigation
Authors: Montejo-Alvaro Fernando , Martínez-Espinosa Jesus A. , Rojas-Chávez Hugo , Navarro-Ibarra Diana C. , Cruz-Martínez Heriberto , Medina Dora I.
Published: September 2022

CO2 adsorption on bare 3d transition-metal nanoclusters and 3d transition-metal nanoclusters supported on pyridinic N3-doped graphene (PNG) was investigated by employing the density functional theory. First, the interaction of Co13 and Cu13 with PNG was analyzed by spin densities, interaction energies, charge transfers, and HUMO-LUMO gaps. According to the interaction energies, the Co13 nanocluster was adsorbed more efficiently than Cu13 on the PNG. The charge transfer indicated that the Co13 nanocluster donated more charges to the PNG nanoflake than the Cu13 nanocluster. The HUMO-LUMO gap calculations showed that the PNG improved the chemical reactivity of both Co13 and Cu13 nanoclusters. When the CO2 was adsorbed on the bare 3d transition-metal nanoclusters and 3d transition-metal nanoclusters supported on the PNG, it experienced a bond elongation and angle bending in both systems. In addition, the charge transfer from the nanoclusters to the CO2 molecule was observed. This study proved that Co13/PNG and Cu13/PNG composites are adequate candidates for CO2 adsorption and activation.
Influence of Non-Metallic Inclusions on Bending Fatigue Strength of High-Quality Carbon Constructional Steel Heated in an Industrial Electric Arc Furnace
Authors: Lipiński Tomasz
Published: September 2022

Non-metallic inclusions are one of the many factors influencing the strength of materials operating under variable loads. Their influence on the strength of the material depends not only on the morphology of the impurities themselves, but it is also closely related to the microstructure of the material. This microstructure is the matrix for non-metallic inclusions. This article discusses the results of a study investigating the effect of non-metallic inclusions on the fatigue strength of structural steel during rotary bending. The study was performed at 12 heats produced in an industrial plant’s 140-ton electric furnaces. Six heats were desulphurised, and six were refined with argon. This paper presents the bending fatigue strength of steel hardened and tempered at different temperatures, subject to the relative volume of inclusions. This paper also presents the dimensional structure of non-metallic inclusions divided by different two technologies. The research shows that the main fraction of non-metallic inclusions is Al2O3; the most numerous were impurities with a diameter of less than 2 µm; argon refining does not affect the proportion of non-metallic inclusions of large dimensions (with a diameter of over 15 µm); the influence of non-metallic inclusions on the strength of the steel is also related to the microstructure of the steel constituting the matrix of inclusions.
Influence of Acidic Environment on the Hardness, Surface Roughness and Wear Ability of CAD/CAM Resin-Matrix Ceramics
Authors: Alghamdi Wejdan S. , Labban Nawaf , Maawadh Ahmed , Alsayed Hussain D. , Alshehri Huda , Alrahlah Ali , Alnafaiy Sarah M.
Published: September 2022

This study aimed to measure the effect of storage environment on the hardness, surface roughness and wear ability of CAD/CAM resin-matrix ceramics. A total of 200 rectangular-shaped specimens were obtained by sectioning 5 CAD/CAM blocks; Crystal Ultra (CU), Vita Enamic (VE), Lava Ultimate (LU), Cerasmart (CS) and Vita blocks Mark II (MII). Microhardness and surface roughness were measured at baseline and after 7 days of immersion either in saliva or cola (n = 10). The wear ability of the CAD/CAM materials against steatite-ceramics antagonist was determined using a chewing simulator. The data were statistically analyzed using factorial ANOVA followed by post hoc Bonferroni multiple comparison tests (p < 0.05). The independent factors significantly influenced the microhardness and surface roughness (p < 0.05). The highest VHN was observed in MII at baseline (586.97 ± 13.95), while CU showed the lowest VHN after 7 days of immersion in cola (68.3 ± 1.89). On the contrary, the highest Ra was observed after 120,000 chewing cycles for the VE specimens (1.09 ± 0.43 µm) immersed in cola, while LU showed the lowest Ra at baseline (0.07 ± 0.01 µm). The highest % mass loss of the antagonist was observed with MII immersed in cola (1.801%), while CS demonstrated the lowest % mass loss of 0.004% and 0.007% in AS and cola, respectively. This study confirms that the surface properties of tested CAD/CAM materials are susceptible to degradation in an acidic environment except for hardness and wear of CS material.
Bond Behavior of a Bio-Aggregate Embedded in Cement-Based Matrix
Authors: Ferreira Saulo Rocha , de Andrade Rodolfo Giacomim Mendes , de Andrade Gabriele Melo , de Araújo Olga Maria Oliveira , Lopes Ricardo Tadeu , Fairbairn Eduardo de Moraes Rego , Grabois Thiago Melo , Ukrainczyk Neven
Published: September 2022

This paper investigates the bond behavior between a bio-aggregate and a cement-based matrix. The experimental evaluation comprised physical, chemical, image, and mechanical characterization of the bio-aggregate. The image analyses about the bio-aggregate’s outer structure provided first insights to understand the particularities of this newly proposed bio-aggregate for use in cementitious materials. A mineral aggregate (granitic rock), largely used as coarse aggregate in the Brazilian civil construction industry, was used as reference. The bond behavior of both aggregates was evaluated via pull-out tests. The results indicated that both aggregates presented a similar linear elastic branch up to each respective peak loads. The peak load magnitude of the mineral aggregate indicated a better chemical adhesion when compared to the bio-aggregate’s. The post-peak behavior, however, indicated a smoother softening branch for the bio-aggregate, corroborated by the microscopy image analyses. Although further investigation is required, the macaúba crushed endocarp was found to be a thriving bio-material to be used as bio-aggregate.
Concrete Made with Dune Sand: Overview of Fresh, Mechanical and Durability Properties
Authors: Ahmad Jawad , Majdi Ali , Deifalla Ahmed Farouk , Qureshi Hisham Jahangir , Saleem Muhammad Umair , Qaidi Shaker M. A. , El-Shorbagy Mohammed A.
Published: September 2022

According to the authors’ best information, the majority of research focuses on other waste materials, such as recycling industrial waste (glass, silica fume, marble and waste foundry sand), etc. However, some researchers suggest dune sand as an alternative material for concrete production, but knowledge is still scarce. Therefore, a comprehensive review is required on dune sand to evaluate its current progress as well as its effects on the strength and durability properties of concrete. The review presents detailed literature on dune sand in concrete. The important characteristics of concrete such as slump, compressive, flexural, cracking behaviors, density, water absorption and sulfate resistance were considered for analysis. Results indicate that dune sand can be used in concrete up to 40% without any negative effect on strength and durability. The negative impact of dune sand on strength and durability was due to poor grading and fineness, which restricts the complete (100%) substation of dune sand. Furthermore, a decrease in flowability was observed. Finally, the review highlights the research gap for future studies.
Statistical Assessment of Fracture Toughness Results from the HAZ of X80 Pipeline FCAW Girth Weld
Authors: Chen Hongyuan , Feng Qingshan , Bi Ying , Gao Xiongxiong , Dai Lianshuang , Chi Qiang
Published: September 2022

Due to the wide application of flux-cored arc welds (FCAW) susceptible to significant scatter in weld and Heat Affected Zone (HAZ) fracture toughness, there is an interest in methods for evaluating the reliability of welds containing defects. The mechanical properties of the FCAW girth weld of an X80 pipeline are tested and then analyzed. By obtaining fracture toughness results from a statistically significant number of SENB specimens, with notches positioned in different HAZ locations, the effect of variation within the results can be evaluated. The results of the fracture toughness tests were analyzed using statistical methods, to compare both the difference in behavior between HAZ microstructures and the variation when a similar microstructure has been sampled. The range of different characteristic toughness values was analyzed using a postulated ECA case to illustrate the sensitivity of the results to how toughness is defined. The analyses supported recommendations to be made on the optimum approach to characterizing HAZ fracture toughness for reliable pipeline assessments in multi-pass girth welds with complex HAZ microstructure distributions.
Effect of Dynamic Preheating on the Thermal Behavior and Mechanical Properties of Laser-Welded Joints
Authors: Xie Linyi , Shi Wenqing , Wu Teng , Gong Meimei , Cai Detao , Han Shanguo , He Kuanfang
Published: September 2022

The high cooling rate and temperature gradient caused by the rapid heating and cooling characteristics of laser welding (LW) leads to excessive thermal stress and even cracks in welded joints. In order to solve these problems, a dynamic preheating method that uses hybrid laser arc welding to add an auxiliary heat source (arc) to LW was proposed. The finite element model was deployed to investigate the effect of dynamic preheating on the thermal behavior of LW. The accuracy of the heat transfer model was verified experimentally. Hardness and tensile testing of the welded joint were conducted. The results show that using the appropriate current leads to a significantly reduced cooling rate and temperature gradient, which are conducive to improving the hardness and mechanical properties of welded joints. The yield strength of welded joints with a 20 A current for dynamic preheating is increased from 477.0 to 564.3 MPa compared with that of LW. Therefore, the use of dynamic preheating to reduce the temperature gradient is helpful in reducing thermal stress and improving the tensile properties of the joint. These results can provide new ideas for welding processes.
Microstructure and Properties of a Graphene Reinforced Cu–Cr–Mg Composite
Authors: Lu Ruiyu , Liu Bin , Cheng Huichao , Gao Shenghan , Li Tiejun , Li Jia , Fang Qihong
Published: September 2022

To improve the graphene/copper interfacial bonding and the strength of the copper matrix, Cu–Cr–Mg alloy powder and graphene nanosheets (GNPs) have been used as raw materials in the preparation of a layered graphene/Cu–Cr–Mg composite through high-energy ball-milling and fast hot-pressing sintering. The microstructure of the composite after sintering, as well as the effect of graphene on the mechanical properties and conductivity of the composite, are also studied. The results show that the tensile strength of the composite material reached a value of 349 MPa, which is 46% higher than that of the copper matrix, and the reinforcement efficiency of graphene is as large as 136. Furthermore, the electrical conductivity of the composite material was 81.6% IACS, which is only 0.90% IACS lower than that of the copper matrix. The Cr and Mg elements are found to diffuse to the interface of the graphene/copper composite during sintering, and finely dispersed chromium carbide particles are found to significantly improve the interfacial bonding strength of the composite. Thus, graphene could effectively improve the mechanical properties of the composite while maintaining a high electrical conductivity.
Ultrafine-Grained Tungsten Heavy Alloy Prepared by High-Pressure Spark Plasma Sintering
Authors: Zhang Shuaihao , Zhu Qiqi , Li Qiunan , Ji Wei , Wang Weimin , Fu Zhengyi
Published: September 2022

Tungsten heavy alloy (WHA) is an ideal material employed for kinetic energy penetrators due to its high density and excellent mechanical properties. However, it is difficult to obtain ultrafine-grained tungsten alloy with excellent properties by traditional powder metallurgy method because of severe grain growth at a high sintering temperature with a long soaking time. In this study, the sintering behavior of tungsten alloys was studied at 800 to 1300 °C, and highly dense 93W-5.6Ni-1.4Fe (wt.%) WHA was successfully fabricated at a low temperature of 950 °C with a high pressure of 150 MPa by spark plasma sintering. The as-sintered tungsten alloy possesses a high relative density (98.6%), ultrafine grain size (271 nm) and high dislocation density (2.6 × 1016 m−2), which results in excellent properties such as a high hardness (1079 HV1). The high sintering pressure is considered to support an additional driving force for the sintering and lead to a low-temperature densification, which effectively limits grain growth.
Strength Characteristics and Microstructure Analysis of Alkali-Activated Slag–Fly Ash Cementitious Material
Authors: Zhu Chenhui , Wan Yuanyuan , Wang Lei , Ye Yuchen , Yu Houjun , Yang Jie
Published: September 2022

Modifying the admixture of alkali-activated cementitious materials using components such as fly ash and fine sand may reduce CO2 emissions and conserve natural resources and energy. This study adopted strength testing, scanning electron microscopy, and mercury intrusion porosimetry to investigate the influence of different admixtures on the compressive strength and flexural strength of alkali slag cementing materials and the microstructure characteristics of hardened slurry under the action of load. The flexural strength of alkali slag cement slurry and mortar was reduced by replacing slag powder with fly ash. Content of fine sand less than 20% had little effect on the strength of alkali slag cement mortar; however, when the content of fine sand exceeded 30%, the strength decreased significantly. The hydration degree at 3 d was large, and the density of slurry increased with the extension of age. Increased fly ash or fine sand content decreased the density of the slurry, and increased fly ash resulted in a large number of unhydrated fly ash particles in the cementitious materials. Addition of fine sand resulted in a large number of microcracks in the slurry, which gradually decreased with the extension of hydration age.
Experimental Studies on Adaptive-Passive Symmetrical Granular Damper Operation
Authors: Żurawski Mateusz , Zalewski Robert
Published: September 2022

This paper presents experimental studies on a controllable granular damper, whose dissipative properties are provided by the friction phenomenon occuring between loose granular material. In addition, in order to adjust to the current trends in vibration suppression, we built a semi-active device, controlled by a single parameter—underpressure. Such granular structures subjected to underpressure are called Vacuum-Packed Particles. The first section presents the state of the art. A brief description of the most often used intelligent and smart materials for the manufacture of dampers is presented. The main advantages of the proposed device are a simple structure, low construction cost, symmetrical principle of operation, and the ability to change the characteristics of the damper by quickly and suddenly changing the negative pressure inside the granular core. The second section provides a detailed description of the construction and operation principles of the original symmetrical granular damper. A description of its application in the laboratory research test stand is also provided. The third section presents the results of the experimental studies including the recorded damping characteristics of the investigated damper. The effectiveness of the ethylene–propylene–diene grains’ application is presented. The two parameters of underpressure and frequency of excitation were considered during the empirical tests. The influence of the system parameters on its global dissipative behavior is discussed in detail. The damper operation characteristics are close to linear, which is positive information from the point of view of the potential adaptive-passive control process. Brief conclusions and the prospective application of vacuum-packed particle dampers are presented in the final section.
PBF-LB/M of Low-Alloyed Steels: Bainite-like Microstructures despite High Cooling Rates
Authors: Bartels Dominic , Novotny Tobias , Mohr Andreas , van Soest Frank , Hentschel Oliver , Merklein Carsten , Schmidt Michael
Published: September 2022

Laser-based powder bed fusion of metals (PBF-LB/M) is an emerging technology with enormous potential for the fabrication of highly complex products due to the layer-wise fabrication process. Low-alloyed steels have recently gained interest due to their wide potential range of applications. However, the correlation between the processing strategy and the material properties remains mostly unclear. The process-inherent high cooling rates support the assumption that a very fine martensitic microstructure is formed. Therefore, the microstructure formation was studied by means of scanning electron microscopy, hardness measurements, and an analysis of the tempering stability. It could be shown that additively manufactured Bainidur AM samples possess a bainitic microstructure despite the high process-specific cooling rates in PBF-LB/M. This bainitic microstructure is characterized by an excellent tempering stability up to temperatures as high as 600 °C. In contrast to this, additively manufactured and martensitic-hardened specimens are characterized by a higher initial hardness but a significantly reduced tempering stability. This shows the potential of manufacturing products from Bainidur AM for high-temperature applications without the necessity of a post-process heat treatment for achieving the desired bainitic microstructure.
Iodine-Doped Graphene Oxide: Fast Single-Stage Synthesis and Application as Electrocatalyst
Authors: Marinoiu Adriana , Ion-Ebrasu Daniela , Soare Amalia , Raceanu Mircea
Published: September 2022

Iodine-doped graphene oxide is attracting great attention as fuel cell (FC) electrocatalysts with a high activity for the oxygen reduction reaction (ORR). However, most of the reported preparation techniques for iodine-doped graphene (I/rGO) could be transposed into practice as multiple step procedures, a significant disadvantage for scale-up applications. Herein, we describe an effective, eco-friendly, and fast technique for synthesis by a microwave-tuned one-stage technique. Structural and morphological characterizations evidenced the obtaining of nanocomposite sheets, with iodine bonded in the graphene matrix. The ORR performance of I/rGO was electrochemically investigated and the enhancement of the cathodic peak was noted. Based on the noteworthy electrochemical properties for ORR activity, the prepared I/rGO can be considered an encouraging alternative for a more economical electrode for fuel cell fabrication and commercialization. In this perspective, the iodine-based catalysts synthesis can be considered a step forward for the metal-free electrocatalysts development for the oxygen reduction reaction in fuel cells.
Effects of Endic Anhydride Grafted PPC on the Properties of PHBV Blends
Authors: Zhang Qing , Gao Yongguang , Liu Huiyuan , Shu Shili , Chen Wei
Published: September 2022

Poly(β-hydroxybutyrate-co-β-hydroxyvalerate) (PHBV) was modified with endic anhydride grafted poly(propylene carbonate) (EA–PPC), and then PHBV/EA–PPC composite polymers were prepared by melt blending under the catalysis of stannous octoate (Sn(Oct)2). The blends were characterized by an electronic universal testing machine, cantilever impact testing machine, and differential scanning calorimeter (DSC), as well as dynamic mechanical analysis (DMA) and field emission scanning electron microscopy (FESEM). Effects of the amount of Sn(Oct)2 on the mechanical properties, thermal properties, and morphology of the blends were discussed. The results showed that the addition of Sn(Oct)2 promoted the transesterification reaction between PHBV and EA–PPC, and the compatibility between PHBV and PPC was greatly improved. When the amount of Sn(Oct)2 was 3 wt%, the impact strength and elongation at break of the PHBV/EA–PPC blend increased from 3.7 kJ/m2 and 4.1% to 5.9 kJ/m2 and 387.5%, respectively, and there was no significant decrease in tensile strength. Additionally, four esterification reaction mechanisms for PHBV/EA–PPC blends were proposed.
Comparative Study Assessing the Canal Cleanliness Using Automated Device and Conventional Syringe Needle for Root Canal Irrigation—An Ex-Vivo Study
Authors: Rajamanickam Keerthika , Teja Kavalipurapu Venkata , Ramesh Sindhu , AbuMelha Abdulaziz S. , Alkahtany Mazen F. , Almadi Khalid H. , Bahammam Sarah Ahmed , Janani Krishnamachari , Choudhari Sahil , Jose Jerry , Srivastava Kumar Chandan , Shrivastava Deepti , Patil Shankargouda
Published: September 2022

The success of endodontic treatment relies on both apical and coronal sealing. To achieve a good three-dimensional seal, the removal of the smear layer becomes mandatory. This study aims to assess the difference in debris accumulation and smear layer formation while using automated root canal irrigation and conventional syringe needle irrigation. Single-rooted human mandibular premolar teeth (n = 30) which were indicated for orthodontic extractions were selected. An endodontic access cavity was prepared, and a glide path was created. Based on the irrigation protocol decided upon for the study, the teeth were randomly allocated into three study groups, namely Group 1, where the manual syringe needle irrigation method was adopted; Group 2, in which automated root canal irrigation was undertaken; and Group 3, in which teeth remained un-instrumented as it was considered the Control group. The teeth were decoronated at the cement-enamel junction (CEJ) and were subjected for scanning electron microscopy (SEM) examination. Debris and smear layers were viewed in 1000× magnification and scored. A statistically significant (p < 0.05) lower mean debris and smear layer score (p < 0.05) was observed in both study groups when compared with the control group. However, no significant difference (p > 0.05) in the debris and smear layer was observed between the manual syringe needle irrigation and automated irrigation, although automated irrigation devices can be a potential alternative. The present study concluded that the efficacy of smear layer removal remained the same with both automated irrigation and manual syringe irrigation.
Body-Centered Double-Square Split-Ring Enclosed Nested Meander-Line-Shaped Metamaterial-Loaded Microstrip-Based Resonator for Sensing Applications
Authors: Siddiky Air Mohammad , Faruque Mohammad Rashed Iqbal , Islam Mohammad Tariqul , Abdullah Sabirin , Khandaker Mayeen Uddin , Tamam Nissren , Sulieman Abdelmoneim
Published: September 2022

The strong localization of the electric and magnetic fields in metamaterial-based structures has attracted a new era of radiation fields in the microwave range. In this research work, we represent a double split ring enclosed nested meander-line-shaped metamaterial resonator with a high effective medium ratio layered on a dielectric substrate to enhance the sensitivity for the material characterization. Tailoring a metallic design and periodical arrangement of the split ring resonator in a subwavelength range introduced field enhancement and strong localization of the electromagnetic field. The design methodology is carried out through the optimization technique with different geometric configurations to increase the compactness of the design. The CST microwave studio is utilized for the extraction of the scattering computational value within the defined boundary condition. The effective parameters from the reflection and transmission coefficient are taken into account to observe the radiation characteristics for the interaction with the applied electromagnetic spectrum. The proposed metamaterial-based sensor exhibits high sensitivity for different dielectric materials with low permittivity values. The numerical data of the frequency deviation for the different dielectric constants have shown good agreement using the linear regression analysis where the sensitivity is R2 = 0.9894 and the figure of merit is R2 = 0.9978.
Carbonation Behavior of Engineered Cementitious Composites under Coupled Sustained Flexural Load and Accelerated Carbonation
Authors: Zhang Hongzhi , Shao Yingxuan , Zhang Ning , Tawfek Abdullah M. , Guan Yanhua , Sun Renjuan , Tian Changjin , Šavija Branko
Published: September 2022

Engineered cementitious composites (ECCs) belong to a broad class of fibre-reinforced concrete. They incorporate synthetic polyvinyl alcohol (PVA) fibres, cement, fly ash and fine aggregates, and are designed to have a tensile strain capacity typically beyond 3%. This paper presents an investigation on the carbonation behaviour of engineered cementitious composites (ECCs) under coupled sustained flexural load and accelerated carbonation. The carbonation depth under a sustained stress level of 0, 0.075, 0.15, 0.3 and 0.6 relative to flexural strength was measured after 7, 14 and 28 days of accelerated carbonation. Thermogravimetric analysis, mercury intrusion porosimetry and microhardness measurements were carried out to show the coupled influence of sustained flexural load and accelerated carbonation on the changes of the mineral phases, porosity, pore size distribution and microhardness along the carbonation profile. A modified carbonation depth model that can be used to consider the coupled effect of flexural tensile stress and carbonation time was proposed. The results show that an exponential relationship can be observed between stress influence coefficient and flexural tensile stress level in the carbonation depth model of ECC, which is different when using plain concrete. Areas with a higher carbonation degree have greater microhardness, even under a large sustained load level, as the carbonation process refines the pore structure and the fibre bridges the crack effectively.
A Design Method of Styreneic Methyl Copolymers Normal Temperature Modified Asphalt Mixture Based on Performance Balance
Authors: Li Limin , Guo Zhaoyang , Lin Yuliang
Published: September 2022

The objective of this research was to develop a solution for the deterioration effect on the high-temperature rutting performance and water stability of SMC. This research proposed a method for designing an SMC normal temperature modified asphalt mixture based on the existing findings, experimental research and the performance balance. First, the power function curve model of the aggregate gradation was put forward. The 0.075 mm, 4.75 mm and nominal maximum particle size were the key points of the aggregate gradation, and their passing rate was about 6%, 30%, and 95% respectively. Then, on the basis of the quadratic curve model, a method for determination of the optimum asphalt aggregate ratio of SMC normal temperature modified asphalt mixture was put forward, considering the skeleton-density structure. Last, rutting tests, small beam bending tests, freeze-thaw split tests, permeability coefficient tests, texture depth tests and pavement roughness tests were conducted, and the test results all met the performance requirements of the specifications for the construction of highway asphalt pavement in China perfectly, especially the high-temperature and water stability properties, which indicated that the design method for SMC normal temperature modified asphalt mixtures based on performance balance presented in this paper was reasonable and practical.
In Situ Nano-Indentation of a Gold Sub-Micrometric Particle Imaged by Multi-Wavelength Bragg Coherent X-ray Diffraction
Authors: Lauraux Florian , Labat Stéphane , Richard Marie-Ingrid , Leake Steven J. , Zhou Tao , Kovalenko Oleg , Rabkin Eugen , Schülli Tobias U. , Thomas Olivier , Cornelius Thomas W.
Published: September 2022

The microstructure of a sub-micrometric gold crystal during nanoindentation is visualized by in situ multi-wavelength Bragg coherent X-ray diffraction imaging. The gold crystal is indented using a custom-built atomic force microscope. A band of deformation attributed to a shear band oriented along the (221) lattice plane is nucleated at the lower left corner of the crystal and propagates towards the crystal center with increasing applied mechanical load. After complete unloading, an almost strain-free and defect-free crystal is left behind, demonstrating a pseudo-elastic behavior that can only be studied by in situ imaging while it is invisible to ex situ examinations. The recovery is probably associated with reversible dislocations nucleation/annihilation at the side surface of the particle and at the particle-substrate interface, a behavior that has been predicted by atomistic simulations. The full recovery of the particle upon unloading sheds new light on extraordinary mechanical properties of metal nanoparticles obtained by solid-state dewetting.
Stress Field Evaluation in Orthotropic Microstructured Composites with Holes as Cosserat Continuum
Authors: Shi Farui , Fantuzzi Nicholas , Trovalusci Patrizia , Li Yong , Wei Zuoan
Published: September 2022

It is known that the presence of microstructures in solids such as joints and interfaces has an essential influence on the studies of the development of advanced materials, rock mechanics, civil engineering, and so on. However, microstructures are often neglected in the classical local (Cauchy) continuum model, resulting in inaccurate descriptions of the behavior of microstructured materials. In this work, in order to show the impact of microstructures, an implicit ‘non-local’ model, i.e., micropolar continuum (Cosserat), is used to numerically investigate the effects of direction and scale of microstructures on the tension problem of a composite plate with a circular hole. The results show that distributions of field variables (such as displacements and stresses) have an obvious directionality with respect to the microstructures’ direction. As the scale of microstructures increases, such a direction effect becomes more evident. Unlike the isotropic material where stress concentration occurs at the vertex of the hole and the stress concentration factor is close to 3, for the microstructured composite, the stress concentration can be observed at any location depending on the microstructures’ directions, and the concentration factor can exceed 3 to a maximum close to 9 as the increasing scale of microstructures. In addition, differences in the mechanical behavior between Cosserat and Cauchy models can be also observed; such differences are more evident for the material showing a pronounced orthotropic nature.
Experimental Study on the Gmax Characteristics of the Sand-Silt Mixed Soil Materials Using Bender Element Testing
Authors: Bian Jiang , Wu Hao , Xiao Xing , Wu Qi , Zhou Zheng-Long
Published: September 2022

To study the small strain shear modulus (Gmax) of saturated sand-silt mixed soil materials, a series of tests were conducted using the bender element apparatus, and the influences of fines content (FC), relative density (Dr), and effective confining pressure (σ′3c) were taken into consideration. The test results indicate that the Gmax of the mixed soil materials decreases first and then increases with the FC up to 100% with Dr = 35% and 50%, while the Gmax decreases with the increasing FC when Dr = 60%. Moreover, for a given Dr, the Gmax increases with the increasing σ′3c, and the increase rate keeps constant under various FCs. The Gmax of specimens under various FCs decreases with the increase of the void ratio (e). The decrease rate between the Gmax and e differs when the σ′3c is given, which is influenced by the FC. The Gmax of the mixed soil materials can be evaluated by the Hardin model when the FC is determined. The best-fitting parameter A of the Hardin model first decreases and then increases as FC increases. The revised Hardin model, considering the influence of FC, σ′3c, and e, can be used to evaluate the Gmax for different types of sand-silt mixed soil materials. The error between the evaluated and tested Gmax is less than 10%.