Effect of graphene oxide nanoparticles on blast load resistance of steel fiber reinforced concrete

Concrete structures may occasionally be subjected to both intentional or unintentional explosions which could cause casualties and damage to properties. Advance research on protective structures are important to enhance blast resistance of materials, and to protect life and properties. This study investigated the effect of graphene oxide nanoparticles (GO) on enhancing the blast resistance of fiber reinforced cement mortar (FRM). GO in solution was incorporated in steel fiber reinforced mortar at the rate of 0, 0.025, 0.050, 0.075, and 0.100 % by weight of cement. A series of experiments were carried out consisting of 2 stages: Stage 1) workability, setting time, compressive and flexural strength, and microstructure using SEM and XRD processes, and Stage 2) blasting loading test. The optimum GO dosage giving the highest compressive and flexural strengths from the 1st stage was determined and chosen to continue on the 2nd stage (blast loading test). The blasting tests were performed on panel specimens (500mmx1000mmx60mm) using TNT weighing ½ lb. (226.7 grams) with three different standoff distances of 340, 400, and 460 mm. Results from Stage 1 on both flexural and compression tests indicated an optimum GO content of 0.025% by weight of cement. The workability was found to decrease with the increasing the GO content. The SEM images also revealed that the addition of GO nanoparticles reduced the porosity in the mortar matrix. For the blasting test, three damage patterns were observed: complete flexural failure, partial damage (flexural cracking), and no major damage, depending on the standoff distance and specimen type. The addition of GO can reduce the maximum and permanent deflections of the panel under blast loading. FRM panels with GO at 0.025% tested at the standoff distance of 460 mm showed the lowest level of damage

P-Type Transparent Cu-Alloyed ZnS Deposited at Room Temperature

All transparent conducting materials (TCMs) of technological practicality are n-type; the inferior conductivity of p-type TCMs has limited their adoption. In addition, many relatively high-performing p-type TCMs require synthesis temperatures >400 °C. Here, room-temperature pulsed laser deposition of copper-alloyed zinc sulfide (CuxZn1-xS) thin films (0 ≤ x ≤ 0.75) is reported. For 0.09 ≤ x ≤ 0.35, CuxZn1-xS has high p-type conductivity, up to 42 S cm−1 at x = 0.30, with an optical band gap tunable from ≈3.0–3.3 eV and transparency, averaged over the visible, of 50%–71% for 200–250 nm thick films. In this range, synchrotron X-ray and electron diffraction reveal a nanocrystalline ZnS structure. Secondary crystalline CuyS phases are not observed, and at higher Cu concentrations, x > 0.45, films are amorphous and poorly conducting. Within the TCM regime, the conductivity is temperature independent, indicating degenerate hole conduction. A decrease in lattice parameter with Cu content suggests that the hole conduction is due to substitutional incorporation of Cu onto Zn sites. This hole-conducting phase is embedded in a less conducting amorphous CuyS, which dominates at higher Cu concentrations. The combination of high hole conductivity and optical transparency for the peak conductivity CuxZn1-xS films is among the best reported to date for a room temperature deposited p-type TCM

Grain boundary, electrical transport and thermoelectric properties of the ultra-high rGO amount of C12A7-rGO composites

The Ca12Al14O33 ceramic (C12A7) and reduced graphene oxide (rGO) composite which an ultra-high amount (i.e., 40, 50, 60, and 70 wt%) of rGO (ultra-high amount C12A7/rGO composite) were synthesized by a solid-state reaction process. After the hydraulic press, the heat treatment in the temperature range of 773 K under the argon environment had been performed with the composite pellets for 30 min. XRD results of the C12A7 and all the ultra-high amount C12A7/rGO composites indicated a pure phase of C12A7 ceramic. Raman spectra confirmed the existence of rGO content in all the ultra-high amount C12A7/rGO composites. Raman peaks also suggested reduction of the free O22− and O2− ions from the framework of the ultra-high amount C12A7/rGO composites. SEM image presented the homogeneous grain boundary interface after the heat treatment at 773 K of the C12A7 wrapped by the rGO sheet, the agglomerated rGO sheet, and the rough interface stack of rGO sheets. UV-VIS spectroscopy presented the absorption behavior, direct energy gap, and indirect energy gap modifications of the ultra-high amount C12A7/rGO composites. Electrical conductivity of the ultra-high amount C12A7/rGO composites illustrated larger than 108 times improvement with temperature independence. Range of −5 to −17 μV/K , temperature dependence, and increased with rGO content increasing Seebeck coefficient were reported. Thermal conductivity of the ultra-high amount C12A7/rGO composites was increased with the rGO content increasing. Both the Power factor (PF) and the figure of merit (ZT) of the ultra-high amount C12A7/rGO composites were temperature dependent and were increased with the rGO content increasing, within the range of 0.4 μW/m.K2 of PF and the range of 3x10−4 of ZT, respectively. These experimental results verified grain boundary, modified energy band, electrical transport properties and thermoelectric properties of C12A7/rGO composites loading with ultra-high content rG

Loading Effect of Sol-Gel Derived Barium Hexaferrite on Magnetic Polymer Composites

Solution–processing methods were investigated as viable alternatives to produce the polymer-bonded barium hexaferrite (BaM). BaM powders were first synthesized by using the sol-gel auto-combustion method. While the ignition period in two synthesis batches varied, the morphology of hexagonal microplates and nanorods, as well as magnetic properties, were reproduced. To prepare magnetic polymer composites, these BaM powders were then incorporated into the acrylonitrile-butadiene-styrene (ABS) matrix with a weight ratio of 80:20, 70:30, and 60:40 by using the solution casting method. Magnetizations were linearly decreased with a reduction in ferrite loading. Compared to the BaM loose powders and pressed pellet, both remanent and saturation magnetizations were lower and gave rise to comparable values of the squareness. The squareness around 0.5 of BaM samples and their composites revealed the isotropic alignment. Interestingly, the coercivity was significantly increased from 1727–1776 Oe in loose BaM powders to 1874–2052 Oe for the BaM-ABS composites. These composites have potential to be implemented in the additive manufacturing of rare-earth-free magnets

ผลกระทบของกราฟีนออกไซด์ต่อแรงยึดเหนี่ยวระหว่างเส้นใยสังเคราะห์และซีเมนต์มอร์ตาร์The Effect of Graphene Oxide in Bond Strength between Synthetic Fibers and Cement Mortar

กราฟีนเป็นวัสดุระดับนาโน ซึ่งสังเคราะห์จากแกรไฟต์ด้วยวิธีทางเคมี ที่มีโครงสร้างระดับอนุภาคทางเคมีเป็นวงแหวนหกเหลี่ยมที่เชื่อมด้วยพันธะโคเวเลนต์ จึงทำให้มีคุณสมบัติที่โดดเด่นด้านความแข็งแกร่ง นำไฟฟ้าได้ดีและมีความยืดหยุ่นสูง งานวิจัยที่ผ่านมาพบว่าการผสมกราฟีนส่งผลให้กำลังรับแรงของมอร์ตาร์มีค่าเพิ่มขึ้นอย่างมีนัยสำคัญ งานวิจัยนี้เป็นการศึกษาผลกระทบของกราฟีนออกไซด์ต่อแรงยึดเหนี่ยวของมอร์ตาร์กับเส้นใยสังเคราะห์ซึ่งประกอบด้วย เส้นใยโพลีพรอพีลีน เส้นใยแก้วและเส้นใยบะซอลท์ โดยนำสารละลายกราฟีนออกไซด์มาผสมร่วมกับซีเมนต์มอร์ตาร์ ตัวอย่างทดสอบถูกนำมาทดสอบแรงยึดเหนี่ยวของเส้นใยด้วยวิธีถอนเส้นใยเดี่ยว (Single pull out test) ผลการทดสอบพบว่าตัวอย่างที่มีการฝังตัวของเส้นใยในมอร์ตาร์ผสมด้วยสารละลายกราฟีนออกไซด์มีแรงยึดเหนี่ยวเฉลี่ยเพิ่มขึ้นเมื่อเทียบกับตัวอย่างควบคุมและเส้นใยแก้ว มีแรงยึดเหนี่ยวระหว่างเส้นใยสังเคราะห์และมอร์ตาร์สูงสุด เมื่อเปรียบเทียบกับประเภทของเส้นใยทั้งหมดGraphene is a nanomaterial chemically synthetized from graphite. The microstructure of graphene is in hexagonal form with covalent bonding. It exhibits excellent rigidity, electrical conductivity and flexibility. Several researches indicated that mixing graphene oxide with cement mortar can noticeably increase its strength. In this study, the effects of Graphene Oxide (GO) on the bonding strength of synthetic fibers were investigated. Three types of fibers were used, i.e. polypropylene, glass and basalt fibers. The GO solution was mixed with mortar. The specimens were subjected to a single fiber pullout test. Results showed that the sample with fiber embedded in GO mortar exhibited higher bonding strength than the control sample. The glass fiber had the highest bond strength compared to the others

Effects of Carbon Doping and Annealing Temperature on Magnetic MnAl Powders and MnAl Polymeric Composites

Process parameters leading to magnetic polymer composites, an essential ingredient in the additive manufacturing of rare-earth-free magnets, are investigated. The induction melting of manganese (Mn) and aluminum (Al), and subsequent annealing at 450, 500, or 550 °C for 20 min, gave rise to ferromagnetic τ–MnAl phase, as well as other phases. The nonmagnetic Al4C3 and oxide phases were then removed by the magnetic separation. Magnetic powders from the magnetic separation were incorporated in polylactic acid (PLA) matrix via a solution route. The remanent magnetization as high as 4.3 emu/g in the powder form was reduced to 2.3–2.6 emu/g in the composites. The reduction in coercivity was minimal, and the largest value of 814 Oe was obtained when the powder annealed at 450 °C was loaded in the composite. The phase composition and hence magnetic properties were even more sensitive to the carbon (C) doping. Interestingly, the addition of 3% C led to coercivity as high as 1445 Oe in MnAl–C powders without further annealing. The enhanced coercivity was attributed to the domain wall pinning by the AlMn3C phase, and magnetizations are likely increased by this phase

Fabrication and thermoelectric conversion of thermoelectric concrete brick with buried unileg N-type CaMnO3 thermoelectric module inside

Abstract To investigate the effect of heat loss reduction due to thermal insulator and thermal interface resistance due to multi-layer structure in order to improve the efficiency of a thermoelectric device, a thermoelectric concrete brick was fabricated using a unileg n-type CaMnO3 thermoelectric module inside. CaMnO3 thermoelectric materials were synthesized by starting materials CaCO3 and MnO2 to produce a unileg n-type CaMnO3 module. Thermoelectric concrete brick consisted of two types: I-layer brick (one layer of concrete thermal insulator) and III-layer brick (three layers of different concrete insulators). The occurring temperature difference, electric current and voltage on the CaMnO3 module and thermoelectric concrete brick were measured in closed and open circuits. The temperature difference, thermal distribution, and output voltage when applying constant temperatures of 100, 200 and 400 °C were measured. Computer simulations of the Finite Element Method (FEM) were performed to compare with the experimental results. The trends of the temperature difference and the output voltage from the experimental and computer simulations were in good agreement. The results of the temperature difference during the hotter side temperature of 200 °C exhibited the temperature difference along the vertical direction of the thermoelectric concrete bricks for both types of the III-layer brick of 172 °C and the I-layer brick of 132 °C are larger than that of the CaMnO3 TEG module without using a thermal concrete insulator of 108 °C. The thermoelectric concrete bricks of the III-layer brick type of 27.70 mV displayed output voltage results being higher than those of the I-layer brick of 26.57 mV and the CaMnO3 TEG module without using a thermal concrete insulator of 24.35 mV. Thermoelectric concrete brick of the III-layer brick type displayed higher electric generation power than the I-layer brick and the CaMnO3 TEG module. Additionally, the results exhibited the capability of thermoelectric concrete brick in the III-layer brick model for electric generation power based on the temperature difference. The TEG concrete brick of I-layer concrete covering the series–parallel combination circuit of 120 modules of the unileg n-type CaMnO3 was constructed and then embedded on the outer surface of the furnace. During the maximum hotter side temperature of 580 °C of the concrete brick, the temperature difference between the hotter side and the cooler side of the brick occurred at 365 °C and the maximum output voltage was obtained at 581.7 mV