Effect of Vacuum Environment on Micro Morphology and Porosity of Lunar Soil Concrete

Lunar soil concrete with sulfur system was prepared. The XRD, XRF and SEM datas of lunar soil concrete under atmospheric pressure and vacuum environment after 28 days of curing were compared. The changes of composition and microstructure during solidification of sulfur lunar soil under vacuum and atmospheric pressure were studied. The changes of porosity under atmospheric pressure and vacuum environment were analyzed and compared. Semi quantitative analysis and evaluation are carried out to compare different experimental phenomena.The results show that the vacuum environment has little effect on the element composition of lunar soil concrete. Sulfur exists in the form of single substance in lunar soil concrete, which has the effect of cementation and bonding. The porosity of lunar soil concrete becomes larger under vacuum environment. It can provide technical reserves for the follow-up utilization of in-situ lunar resources and the construction of lunar scientific research stations.

Effects of Graphene on the Wear and Corrosion Resistance of Micro-Arc Oxidation Coating on a Titanium Alloy

In order to improve the wear and corrosion resistance of micro-arc oxidation (MAO) coating on a Ti-5Al-1V-1Sn-1Zr-0.8Mo alloy, 0–0.20 g/L graphene was added to the electrolyte to prepare micro-arc oxidation coating. The thickness, roughness, micro-morphology, and composition of the MAO coating were characterized, and the wear and corrosion resistance of the coating was tested and analyzed. The results show that with 0.05 g/L of graphene in the electrolyte, the roughness of the coating decreased from 56.76 μm to 31.81 μm. With the increase in the addition of graphene, the microstructure of the coating became more compact, the diameter of micro-holes and micro-cracks decreased, and the corrosion resistance of the coating improved. The wear tests showed that the mass loss of the coating at the early wear stage (0~100 revolutions) was greater than that at the later stage (100~250 revolutions), and the wear resistance of the coating obtained by the addition of 0.10 g/L of graphene was the highest. With 0.10 g/L of graphene, the adhesion force between the coating and the substrate alloy is the largest, reaching 57.1 N, which is 9.98 N higher than that without graphene. After salt spray corrosion for 480 h, the coating with graphene has better corrosion resistance than that of a graphene-free coating.

Seed Macro- And Micro-Morphology of Some Species Of Kickxia Dumort, Scrophularia L. And Plantago L. From Saudi Arabia

The seed macro- and micro-morphological characters of 13 species belonging to three genera; Kickxia Dumort, Scrophularia L. and Plantago L., collected from different localities of Saudi Arabia, were studied using a Stereomicroscope and Scanning Electron Microscope for evaluating their taxonomic relationships. Three macro-morphological characters of seeds were shape, size, and color while three diagnostic micromorphological characters were seed coat sculpture, the anticlinal and periclinal wall., The seed shape seems to be specific in Plantago L. (peltate, angled) than the two other genera while the color and seed size show little importance. The Plantago L. has a specific rugose sculpture while the other two genera have either tuberculate or alveolate. So Plantago L. was possessed no affinities to Kickxia Dumor or Scrophularia L.. This observation gives extra support to the earlier taxonomic views that suggested the retention of two genera in the traditional family Scrophulariaceae and maintaining Plantago L. in a separate monogeneric family Plantaginaceae Detailed analysis of seed characters of more species is needed to clarify the systematic relationships between the three genera. A key to the identification of studied species based on seed micro- and macro-morphological characters is provide. Bangladesh J. Plant Taxon. 28(2): 385-393, 2021 (December)

Study on Metakaolin Impact on Concrete Performance of Resisting Complex Ions Corrosion

The main purpose of this study is to determine the metakaolin (MK) impacts on the concrete durability when the concrete is subjected to joint corrosion of SO42−,Mg2+ and, Cl−. Four groups of concrete test samples, which contained different MK contents, were designed and tested in order to see their physical property changes and macro-morphology differences during the cyclic corrosion process. And a series of approaches, including XRD, FTIR, SEM, and EDS, were applied to study the concrete phase composition changes and the micro-morphology features of all groups. According to the test results, when reaching 20 cycles, the concrete sample with 10% MK showed the best concrete physical properties; when reaching 120 cycles, the concrete with 5% MK content showed the best durability, produced similar amount of corrosion products to ordinary concrete, and presented relatively compacted micro-structure and small internal porosity. Mg2+ actually has a great impact on metakaolin. The corrosion product quantity increased significantly when MK admixture reached 15%. Due to the great number of produced M-S-H, the corrosive ions damaged the concrete for a second time, leading to serious aggregate peeling-off, powder surface of test samples, and porous micro-structure.

Synthesis, Characterization and Evaluation of Supercapacitive Response of Dodecylbenzenesulphonic Acid (DBSA) Doped Polypyrrole/Zirconium Dioxide Composites

An in-situ chemical oxidative method was used to effectively synthesize a promising supercapacitor material based on PPy/ZrO2 composites. The synthesized materials were characterized by different analytical techniques, such as UV/visible (UV/Vis) spectroscopy, Fourier-transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The inclusion of ZrO2 into the PPy matrix was verified by vibrational spectra and structural analyses. The (TGA) results showed that incorporating ZrO2 into the polymeric matrix improved its thermal stability. In addition, the electrochemical properties of the synthesizedmaterials were investigated byusing cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). The PPy/ZrO2 composite demonstrated excellent super capacitive performance, and high specific capacity of 337.83 F/g, with an exceedingly high energy density of 187.68 Wh/kg at a power density of 1000 W/kg. The composite materials maintain good stability after 1000 charge and discharge cycles, with 85% capacitance retention. The PPy/ZrO2 possesses a high capacitance, an attractive micro-morphology, and a simple synthesis method. The findings indicate that the PPy/ZrO2 composite could be a promising electrode material for high-performance supercapacitor applications.

Effects of Stabilizing Heat Treatment on Properties of Simulated Microstructures in the Heat-Affected Zone of 347H Stainless Steel

In this paper, two kinds of heat affected zone (HAZ) simulation structures of 347H stainless steel, which are coarse grain zone (CGZ) and unmixed zone (UZ), were prepared by thermal simulator. The material properties of toughness, reheat crack susceptibility and intergranular corrosion susceptibility of the two kinds of HAZ simulation structures were studied by impact test, high temperature tensile test, electrochemical potentiodynamic reactivation (EPR) test and micro morphology test. The result shows that CGHAZ had better toughness. But after the stabilizing heat treatment, it was weakened while that of the UZ was enhanced. The reheat crack susceptibility of the CGZ and UZ both increases after stabilization heat treatment, and the tendency of the UZ are more obvious. Stabilizing heat treatment has a certain effect on the prevention of sensitization process, which can improve the intergranular corrosion resistance of the material. Stabilizing heat treatment is double-edged to 347H HAZ, and it needs combined with the specific situation to used.

Mechanical Properties and Micro Morphology of Granite Residual Soil-Based Fly Ash Geopolymer

In order to explore the polymerization mechanism of granite residual soil, geopolymer containing fly ash, various particle groups, granite residual soil and their composites were prepared with different materials. Sodium hydroxide and sodium silicate are used as alkali activators. In this paper, the compressive strength of geopolymer was studied. The mineral composition and microstructure were tested and analyzed by X-ray diffraction and scanning electron microscope. The results show that geopolymerization can only occur in fine particles due to the presence of amorphous aluminosilicate in granite residual soil. The zeolite phase transition of low polymer in fine-grained reaction is beneficial to enhance the integrity of the sample and improve its compressive strength. The addition of fly ash can accelerate the geopolymerization rate and improve the strength of fine geopolymer, but it can inhibit the occurrence of zeolite phase transformation.

Effects of POE and Carbon Black on the PTC Performance and Flexibility of High-Density Polyethylene Composites

High-density polyethylene (HDPE)/carbon black (CB) is widely used in positive temperature coefficient (PTC) composites. In order to expand its applications to fields that need good flexibility, polyolefin elastomer (POE) was incorporated into HDPE/CB composites as a secondary thermoplastic elastomer phase to provide flexibility. The effects of POE and CB content on the PTC performance and flexibility were investigated. Micro morphology and crystallization behavior are closely related to PTC properties. SEM was conducted to reveal phase morphology and filler dispersion, and DSC was conducted to research crystallization behavior. The results show that the incorporation of 18 wt.% POE can decrease the percolation threshold of conductive carbon black from 22.5 wt.% to 16 wt.%. When the CB content is 30 wt.%, the room temperature resistivity gradually increases with the increasing content of POE because of the barrier effect of POE phase, and the PTC intensity is gradually enhanced. Meanwhile, the PTC switching temperature shifts down to a lower temperature. The incorporation of 18 wt.% POE significantly increases the elongation at break, reaching an ultrahigh value of 980 wt.%, which means great flexibility has been achieved in HDPE/POE/CB composites. This work provides a new method of fabricating PTC composites with balanced electrical and mechanical properties.