The study of the fiber-matrix interface represents a crucial topic to determine the mechanical performance of geopolymer-based materials reinforced with polypropylene fibers (PPF). This research ...proposes the use of natural zeolite in the preparation geopolymers mortars through alkaline activation with NaOH, Ca(OH)2 and Na2SiO3, and with river sand as a fine aggregate. PPF were incorporated into the geopolymer-based mortar matrix in different proportions like 0, 0.5, and 1 wt.%. The mortars were cured for 24 h at 60 °C and then aged for six days more at room temperature. All samples analyzed through compressive strength were also characterized by X-ray diffraction, thermal analysis, Infrared Spectroscopy, and scanning electron microscopy techniques. The results indicated that the best mix design among the ones used: NaOH (10 M), Na2SiO3/NaOH = 3, Ca(OH)2 = 1.5 wt.% and PPF = 0.5 wt.%. The optimum mix design showed a compressive strength of 4.63 MPa on average. Besides, the fibers enhanced the compressive strength of those samples which the PP fibers probably have better dispersion inside the matrix of the geopolymer mortar.
Civil engineering; Materials Class; Materials Application; Materials Characterization; Materials Mechanics; Materials Property; Materials Structure; Materials Synthesis; Environmental Pollution; Natural zeolite; Polypropylene fiber; Alkali-activated mortars; Reinforcement; compressive strength
The quest to consistently develop improved materials for direct application in automotive, aerospace, and other industries has led to the synthesis of titanium-based composites—with current research ...efforts being directed toward the utilization of carbon nanotubes (CNTs) as reinforcement. CNTs constitute an outstanding reinforcement for titanium-based matrixes, owing to their extraordinary physical, electrical, mechanical, and thermal properties. Powder metallurgy (PM) routes have been adjudged the most promising technique for synthesizing CNT-reinforced titanium. However, past reviews have highlighted various PM techniques, reinforcement efficiency, and effective methods for dispersing CNTs in metal matrixes. Among the various PM techniques, spark plasma sintering (SPS) has gained popularity in the synthesizing of titanium-based nanocomposites (TMNCs). Hence, this review focused on past works on the SPS of TMNCs reinforced with CNTs. The properties of CNTs, their fabrication method, their densification mechanism, and the mechanical properties of sintered TMNCs were discussed in detail.
Ice-binding proteins (IBPs) are produced by a variety of organisms to prevent internal damage caused by ice crystal growth. Synthetic analogs are being designed to mimic beneficial properties of IBPs ...while mitigating drawbacks related to the use of biological proteins. While a multitude of engineering applications could benefit from the inhibition and control of ice formation and growth, synthetic analogs tend to be less potent than biological IBPs, and both IBPs and synthetic analogs tend to exhibit lower performance in non-physiological (i.e., non-biological) solutions. This review examines the ice interaction properties and performance of IBPs and their synthetic analogs in non-physiological environments. Common methods to measure ice interactions are discussed (i.e., thermal hysteresis, ice recrystallization inhibition, ice growth rate, and ice nucleation). A quantitative meta-analysis of material performance in non-physiological environments is presented, along with a discussion of future research directions. The findings presented herein can inform IBP and synthetic mimic selection to control ice interactions in a wide variety of materials science and engineering applications, including cell, tissue, and organ cryopreservation, food storage and transport, freeze-thaw damage of cementitious materials, and anti-icing surfaces for aerospace vehicles, solar panels, and wind turbines.
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Materials science; Materials chemistry; Materials synthesis; Biomaterials; Materials structure
Organic–inorganic hybrid perovskite nanoplatelets (NPLs) have emerged as promising materials for solar energy. However, the structural instability under electron beam hinders further probing and ...understanding of its crystalline structures and defects at the atomic scale. Taking methylammonium bromide perovskite methylammonium lead bromide (CH3NH3PbBr3 (MAPbBr3)) perovskite NPLs as model material, we performed atomic-scale characterization of the native state of the hybrid perovskite solar cell material in different states using ultra-low-dose cryo-TEM imaging. With a series of observation at different growth time, we revealed the growth pattern of such MAPbBr3 material from an initially stacked slices with rotational moiré fringes to a perfect single-crystalline structure of NPLs. Our high-resolution cryo-TEM further enabled the atomic-scale investigations of solid electrolyte interphase (SEI) and sodium (Na) dendrite materials, which can largely impact the safety and life of batteries. This study offers insights on the atomic scale characterization of a wide variety of beam-sensitive materials, inspiring us to probe more materials with cryo-transmission electron microscopes (TEM).
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•Hybrid beam-sensitive materials characterized at the atomic scale using cryo-TEM•Structural evolution from an initial metastable state to the perfect crystalline observed•Na nuclei and its organic SEI structures acquired at the first cycle of Na batteries
Inorganic materials; Materials science; Materials synthesis; Materials characterization; Energy materials; Materials structure
Nafion/silicon oxide (SiO
2)/phosphotungstic acid (PWA) and Nafion/silicon oxide composite membranes were studied for the H
2/O
2 proton exchange membrane fuel cells (PEMFCs) operated above 100
°C. ...The composite membranes were prepared by the recasting procedure, using Nafion solution mixed with SiO
2 and PWA/SiO
2 mixtures. The physico-chemical properties of these recast composite membranes were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, thermogravimetry-DTA (TG-DTA) and Fourier transform infrared (FTIR) spectroscopy. These results showed that SiO
2 and PWA are compatible with the Nafion membrane. Furthermore, the incorporation of the SiO
2 and PWA into the Nafion membrane could increase the crystallinity of the Nafion recast membrane and also improve the initial degradation temperature of the Nafion membrane. It was found that the composite membrane showed a higher uptake of water compared with the Nafion recast membrane. The proton conductivity of the composite membranes appeared to be similar to that of the native Nafion membrane at high temperatures and at 100% relative humidity (RH), however, it was much higher at low RH. When the composite membranes viz. Nafion/SiO
2/PWA and Nafion/SiO
2 were employed as an electrolyte in H
2/O
2 PEMFC, the higher current density values (540 and 320
mA/cm
2 at 0.4
V, respectively) were obtained than that of the Nafion 115 membrane (95
mA/cm
2), under the operating condition of 110
°C and at the humidified temperature of 100
°C.
Cobalt-chromium layered double hydroxide (CoCr LDH), α- and β- Co(OH)2 and amorphous Cr(OH)3 have been synthesized under different reaction conditions. The obtained CoCr LDH was modified by stearic ...acid (SA) and sodium stearate (SS). The obtained samples have been characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Ultraviolet-visible- (UV-Vis), Fourier transform infrared- (FTIR) and Energy-dispersive X-ray- (EDX) spectroscopy. The influence of reaction conditions on product composition, structural and optical properties of the samples have been discussed in detail. The basal spacing of CoCr-LDH increased from 7.366 Å to 7.428 Å and 25.214Å after the intercalation by stearic acid and sodium stearate, respectively. The average particles size by SEM analyze was estimated to be approximately 100–150 nm and 30–50 nm for CoCr-LDH0.6M(90°C) and CoCr-LDH0.6M(90°C)/SS nanostructures, respectively. Mixed hydroxides like α- and β- Co(OH)2 have been obtained along with LDH at lower pH value (pH ∼ 7). The number of diffraction peaks corresponding to β-Co(OH)2 has increased with relatively decreasing of Co2+ ions in the reaction medium. At high chromium concentrations (Co2+:Cr3+ = 1:3 and 1:5), amorphous Cr(OH)3 were formed in the experiment.
Chemistry; Materials science; Nanomaterials; Materials characterization; Materials processing; Materials structure; Materials synthesis; Layered double hydroxide; Reaction proceedings; Basal spacing; Stearic acid; Sodium stearate; Functional group.
Nanolayered metallic glass/crystalline composites provide an effective structure for improving the ductility of metallic glasses while maintaining their outstanding strength. The combination of high ...strength and ductility make these nanocomposites promising materials as wear-resistant coatings. In this work, we experimentally investigated the mechanical properties and nanoscratch behavior of CuZr/Zr metallic glass/crystalline nanolayers. The scratch resistance was highest for the monolithic CuZr, and diminished with decreasing layer thickness for nanolayered coatings, although hardness and elastic modulus were independent of layer thickness. The nanocomposite with a layer thickness of 10 nm did not show any signs of failure in spite of compressive strain exceeding 80%. The low shear strength of the CuZr/Zr interface and strain hardening of Zr layers can explain the layer thickness-dependent scratch resistance and outstanding damage tolerance observed. Layered metallic glass/crystalline nanocomposites combine high hardness and resistance to fracture, providing a new design space for the development of effective wear-resistant coatings.
Al substituted M type Ca hexaferrite with composition CaAlxFe12-xO19 (x = 0, 0.2, 0.4, 0.6, 0.8) were synthesized by sol gel auto combustion method. The prepared samples were characterized by XRD, ...SEM, FTIR and VSM. X ray diffraction study shows that the with increasing aluminum ion concentration lattice parameter a decreases from 5.87 Å to 5.83 Å while the lattice parameter c decreases from 22.15 Å to 22.00 Å are well within the range of M type of hexaferrite. The crystallite size of the particles decreases from 74.36nm to 62.12nm are suitable for magnetic recording. Morphology of the particles from SEM images was hexagonal platelet. The absorption band between 580 and 440cm−1 in FTIR confirm the formation of hexaferrite. The magnetic properties of the samples changes with Al ion substitution make the material suitable for low density longitudinal and perpendicular magnetic recording.
Materials science; Nanomaterials; Materials application; Materials characterization; Materials processing; Materials structure; Materials synthesis; Calcium hexaferrite; Sol gel auto combustion method; Lattice volume; Saturation magnetisation; Coercivity
In this research, Friction stir spot welding (FSSW) is extensively employed to join dissimilar metals consisting of AA6061-T6 Aluminium Alloy and Commercial Copper Alloy. These alloys were friction ...stir spot welded using process parameters with the major impact, such as Dwell Time (DT), Rotational Speed (RS), Plunge Rate (PR) and Tool Diameter Ratio (D/d). Trail experiments have been carried out using Design of Experiments. Sound welded joints exhibiting a maximum shear fracture load of 4.79 kN were obtained at a RS of 2000 rpm, PR of 7 mm/min, DT of 25 s and D/d of 3.5, Balanced material flow around the pin was also observed at this condition, and it is evident that the superior metallurgical properties and geometric features at this condition results in the higher strength. Moreover, the joint also exhibited higher load-bearing capabilities due to an optimal hook height of 0.89 mm, hook width of 1.3 mm and hook initiation distance of 1.4 mm. The continuous formation of intermetallic compound such as ɤ2-Cu9Al4 in the Cu zone and ɳ2-CuAl in the Al zone may also enhance the shear fracture load.
Mechanical engineering; Materials science; ; Materials application; Materials characterization; Materials processing; Materials structure; FSSW; AA6061; Copper alloy; Shear fracture load; Microstructure; Dissimilar joint.
The structure and temperature stability of high-temperature permanent magnets Sm(Co
0.796−
x
Fe
0.177
Cu
x
Zr
0.027
)
6.63
(
x
= 0.117 and 0.130) were studied using x-ray diffraction analysis, ...thermomagnetic analysis, and scanning and transmission electron microscopy. The magnets have a nanocrystalline cellular structure composed of the R2:17 cell phase, 1:5 boundary phase (27–28% by volume), and Z-phase platelets. The 1:5 phase is formed in the course of isothermal annealing at 850°C and exists in the entire temperature range from 850°C to 400°C. The Curie temperature of the R2:17 and 1:5 phases is approximately 815°C and 580°C, respectively. The magnets have the following hysteresis properties at room temperature:
B
r
= 890–920 mT,
J
H
c
= 2.4–2.6 MA/m,
B
H
c
= 629–676 kA/m, and (
BH
)
m
= 143–159 kJ/m
3
. In the temperature range of 20–500°C, the temperature coefficients of
B
r
and
J
H
c
of the magnets (
x
= 0.117 and 0.130) do not exceed |− 0.070| and |− 0.172|%/°C, respectively.
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