The aim of this study was to investigate the effects of the heat treatment time and initial moisture content of bamboo on the corresponding chemical composition, crystallinity, and mechanical ...properties after saturated steam heat treatment at 180 °C. The mechanism of saturated steam heat treatment of bamboo was revealed on the micro-level, providing a theoretical basis for the regulation of bamboo properties and the optimization of heat treatment process parameters. XRD patterns of the treated bamboo slices were basically the same. With the increase in the initial moisture content of bamboo, the crystallinity of bamboo increased first and then decreased after treatment. Due to the saturated steam heat treatment, the content of cellulose and lignin in bamboo slices increased while the content of hemicellulose decreased, but the content of cellulose in bamboo with a 40% initial moisture content increased first and then decreased. The shear strength of treated bamboo changed little within 10 min after saturated steam heat treatment, and then decreased rapidly. During the first 20 min with saturated steam heat treatment, the compressive strength, flexural strength, and flexural modulus of elasticity of the treated bamboo increased, and then decreased.
A short T6 heat treatment for Al–Si–Mg–Mn die-cast alloys was developed with a solution treatment time of only 10 min at 540 °C. Excellent mechanical properties were achieved with a yield strength of ...334–349 MPa and elongation of 2.6–4.6%, which is competitive with other die-cast alloys subjected to T6 heat treatment. The effects of solution time and temperature on the expansion of porosity were assessed. There is no apparent porosity expansion in T6 heat-treated alloys with short solution treatment or through prolonged solution time with lower temperatures. The short solution treatment enables the dissolution of Mg and spheroidizes eutectic Si and Mg2Si, associated with minimizing the growth of α-Al grains. The π-AlFeMnSiMg which forms during the final quaternary eutectic reaction transforms into nano-scale body-centred α-AlFeMnSi phase with dissolution of Si and Mg after the shot T6 heat treatment. The peak ageing hardness was determined by the solution temperature, and the highest peak aged hardness was obtained under a short T6 heat treatment. The coherent β’’ precipitate with needle-like morphology was found after this heat treatment.
The artificial aging heat treatments performed directly on as-built and solubilized AlSi7Mg0.6 and AlSi10Mg0.3 samples were characterized and discussed. The analysed bars and billets (height of 300 ...mm) were manufactured via the Laser Powder-Bed Fusion process on a build platform heated at 150 °C. Therefore, its influence on the as-built samples was studied in terms of mechanical performance variations between the bottom and top regions. Vickers microhardness measurements were performed to obtain aging profiles after direct aging (175–225 °C) and T6 heat treatments and to highlight better time and temperature parameters to optimize the mechanical properties of both alloys. SEM observations were used to characterize the microstructure before and after the heat treatments and its influence on the fracture mechanisms. Generally, the direct aging heat treatments show the same effects on both aluminium alloys, unlike the solubilization at 505 °C followed by artificial aging at 175 °C. The strengths vs. elongation values obtained after the direct aging treatments are better than those exhibited by T6 as highlighted by the quality index.
Toxic metal contamination of soil is a major environmental hazard. Chemical methods for heavy metal's (HMs) decontamination such as heat treatment, electroremediation, soil replacement, precipitation ...and chemical leaching are generally very costly and not be applicable to agricultural lands. However, many strategies are being used to restore polluted environments. Among these, phytoremediation is a promising method based on the use of hyper-accumulator plant species that can tolerate high amounts of toxic HMs present in the environment/soil. Such a strategy uses green plants to remove, degrade, or detoxify toxic metals. Five types of phytoremediation technologies have often been employed for soil decontamination:
phytostabilization, phytodegradation, rhizofiltration
,
phytoextraction
and
phytovolatilization
. Traditional phytoremediation method presents some limitations regarding their applications at large scale, so the application of genetic engineering approaches such as transgenic transformation, nanoparticles addition and phytoremediation assisted with phytohormones, plant growth-promoting bacteria and AMF inoculation has been applied to ameliorate the efficacy of plants as candidates for HMs decontamination. In this review, aspects of HMs toxicity and their depollution procedures with focus on phytoremediation are discussed. Last, some recent innovative technologies for improving phytoremediation are highlighted.
Abstract
Heterogeneous single-atom catalyst (SAC) opens a unique entry to establishing structure–performance relationship at the molecular level similar to that in homogeneous catalysis. The ...challenge lies in manipulating the coordination chemistry of single atoms without changing single-atom dispersion. Here, we develop an efficient synthetic method for SACs by using ethanediamine to chelate Pt cations and then removing the ethanediamine by a rapid thermal treatment (RTT) in inert atmosphere. The coordination chemistry of Pt single atoms on a Fe
2
O
3
support is finely tuned by merely adjusting the RTT temperature. With the decrease in Pt-O coordination number, the oxidation state of Pt decreases, and consequently the hydrogenation activity increases to a record level without loss of chemoselectivity. The tunability of the local coordination chemistry, oxidation states of the metal, and the catalytic performance of single atoms reveals the unique role of SACs as a bridge between heterogeneous and homogeneous catalysis.
In this work, nanostructured Yb2SiO5/mullite-SiC/Si environmental barrier coatings (EBCs) were prepared to investigate the effect of heat treatment on the microstructure and phase transition of ...nanostructured Yb2SiO5/mullite-SiC/Si coatings. The Yb2SiO5 content and microstructure evolution in the coatings were thoroughly analyzed before and after heat treatment. The results demonstrate a slight decrease in the porosities of nanostructured Yb2SiO5 and mullite-SiC coatings, accompanied by a gradual growth in grain sizes with increasing heat treatment time, indicating the nanostructured EBCs show good resistance to sintering. Moreover, the thickness of thermal growth oxidation layer is only 200 nm at 1250 °C for 500 h of heat treatment. In particular, the presence of the Yb2O3 phase has been observed to exert a favorable influence on the thermal stability of nanostructured EBCs. This work provides an innovative strategy for designing advanced EBCs with excellent high-temperature thermal stability.
To overcome problems associated with loosening of orthopedic implants and surgical site infections, we developed a novel, titanium (Ti)‐based material that releases both strontium and silver ions ...(CaSrAg–Ti) based on alkali‐and‐heat treatment. The results of commercially pure Ti (cp–Ti), Ti that releases Sr ions only (CaSr–Ti), and the novel CaSrAg–Ti material were compared. Mechanical tests were performed to evaluate the in vivo bonding properties of CaSrAg–Ti and the bone‐implant contact (BIC) ratio in histological specimens was determined at 4 and 8 weeks after implantation in a rat femur. Also, the in vitro antibacterial activities of this material against methicillin‐susceptible Staphylococcus aureus (MSSA) were evaluated after a 24 h incubation period by assaying colony‐forming units. In addition, antibacterial activities were evaluated in vivo at 7 days after implantation in a rat subcutaneous pocket model. There was direct contact between the bone and CaSrAg–Ti in histological specimens and no apparent signs of argyrosis in any rat. The bone‐bonding strength and the BIC ratio were increased by 2.7‐ and 2.3‐fold for CaSrAg–Ti vs. cp‐Ti at 4 weeks and 2.2‐ and 2.0‐fold at 8 weeks, respectively. As compared with cp‐Ti, the number of viable MSSA remaining on CaSrAg–Ti was reduced by 100 ± 0% in vitro and 94.2 ± 6.9% in vivo. Ti that releases Sr and Ag ions is a promising material that exhibits both bone‐bonding properties and anti‐MSSA activities.
Electron Beam Melting (EBM), a powder bed additive layer manufacturing process, was used to produce Ti–6Al–4V specimens, whose microstructure, texture, and tensile properties were fully ...characterized. The microstructure, analyzed by optical microscopy, SEM/EBSD and X-ray diffraction, consists in fine α lamellae. Numerical reconstruction of the parent β phase highlighted the columnar morphology of the prior β grains, growing along the build direction upon solidification of the melt pool. The presence of grain boundary αGB along the boundaries of these prior β grains is indicative of the diffusive nature of the β→α phase transformation. Texture analysis of the reconstructed high temperature β phase revealed a strong pole in the build direction. For mechanical characterization, tensile specimens were produced using two different build themes and along several build orientations, revealing that vertically built specimens exhibit a lower yield strength than those built horizontally. The effect of post processing, either mechanical or thermal, was extensively investigated. The influence of surface finish on tensile properties was clearly highlighted. Indeed, mechanical polishing induced an increase in ductility – due to the removal of critical surface defects – as well as a significant increase of the apparent yield strength – caused by the removal of a ~150µm rough surface layer that can be considered as mechanically inefficient and not supporting any tensile load. Thermal post-treatments were performed on electron beam melted specimens, revealing that subtransus treatments induce very moderate microstructural changes, whereas supertransus treatments generate a considerably different type of microstructure, due to the fast β grain growth occurring above the transus. The heat treatments investigated in this work had a relatively moderate impact on the mechanical properties of the parts.
Abstract Stability has been a long-standing concern for solution-processed perovskite photovoltaics and their practical applications. However, stable perovskite materials for photovoltaic remain ...insufficient to date. Here we demonstrate a series of ultrastable Dion−Jacobson (DJ) perovskites (1,4-cyclohexanedimethanammonium)(methylammonium) n −1 Pb n I 3 n +1 ( n ≥ 1) for photovoltaic applications. The scalable technology by blade-coated solar cells for the designed DJ perovskites (nominal n = 5) achieves a maximum stabilized power conversion efficiency (PCE) of 19.11% under an environmental atmosphere. Un-encapsulated cells by blade-coated technology retain 92% of their initial efficiencies for over 4000 hours under ~90% relative humidity (RH) aging conditions. More importantly, these cells also exhibit remarkable thermal (85 °C) and operational stability, which shows negligible efficiency loss after exceeding 5000-hour heat treatment or after operation at maximum power point (MPP) exceeding 6000 hours at 45 °C under a 100 mW cm −2 continuous light illumination.
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