• Geomechanics and Engineering
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• v.37 no.1
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• pp.85-95
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• 2024

This study investigates the influence of nano-silica and basalt fiber content, curing duration, and freeze-thaw cycles on the static and dynamic properties of soil specimens. A comprehensive series of tests, including Unconfined Compressive Strength (UCS), static triaxial, and dynamic triaxial tests, were conducted. Additionally, scanning electron microscopy (SEM) analysis was employed to examine the microstructure of treated specimens. Results indicate that a combination of 1% fiber and 10% nano-silica yields optimal soil enhancement. The failure patterns of specimens varied significantly depending on the type of additive. Static triaxial tests revealed a notable reduction in the brittleness index (IB) with the inclusion of basalt fibers. Specimens containing 10% nano-silica and 1% fiber exhibited superior shear strength parameters and UCS. The highest cohesion and friction angle were obtained for treated specimens with 10% nano-silica and 1% fiber, 90 kPa and 37.8°, respectively. Furthermore, an increase in curing time led to a significant increase in UCS values for specimens containing nano-silica. Additionally, the addition of fiber resulted in a decrease in IB, while the addition of nano-silica led to an increase in IB. Increasing nano-silica content in stabilized specimens enhanced shear modulus while decreasing the damping ratio. Freeze-thaw cycles were found to decrease the cohesion of treated specimens based on the results of static triaxial tests. Specimens treated with 10% nano-silica and 1% fiber experienced a reduction in shear modulus and an increase in the damping ratio under freeze-thaw conditions. SEM analysis reveals dense microstructure in nano-silica stabilized specimens, enhanced adhesion of soil particles and fibers, and increased roughness on fiber surfaces.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.615-619
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• 2018

To produce carbon electrodes for use in perovskite solar cells, electrode samples are prepared by mixing various weight ratios of 35 nm nano carbon(NC) and $1{\mu}m$ graphite flakes(GF), GF/(NC+GF) = 0, 0.5, 0.7, and 1, in chlorobenzene(CB) solvent with a $ZrO_2$ binder. The carbon electrodes are fabricated as glass/FTO/carbon electrode devices for microstructure characterization using transmission electron microscopy, optical microscopy, and a field emission scanning electron microscopy. The electrical characterization is performed with a four-point probe and a multi tester. The microstructure characterization shows that an electrode with excellent attachment to the substrate and no surface cracks at weight ratios above 0.5. The electrical characterization results show that the sheet resistance is <$70{\Omega}/sq$ and the interface resistance is <$70{\Omega}$ at weight ratios of 0.5 and 0.7. Therefore, a carbon paste electrode with microstructure and electrical properties similar to those of commercial carbon electrodes is proposed with an appropriate mixing ratio of NC and GF containing a CB solvent and $ZrO_2$.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.198-209
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• 2012

The present paper reviews the widely used surface microstructural investigation technique and micro/nano nondestructive evaluation(NDE) technique which is able to evaluate the surface and subsurface. In general, the micro/nano defects and microstructural state of surface have great influence on the mechanical, physical, and chemical properties of bulk materials. The investigation technique of surface microstructure is possible to evaluate the defects and microstructural state with high reliability. The various applications and developments of each inspection technique have been introduced. Consequently, it is thought that the technique developments and applications of micro/nano NDE in nondestructive industries are extensively possible hereafter.

• Advances in nano research
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• v.16 no.5
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• pp.459-472
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• 2024

Nanotechnology is a popular field in the construction industry due to its multiple functions. It mitigates CO₂ emissions and enhances the desirable properties of concrete by replacing small amounts of cement with supplements. This study assess the sustainability impact of using two different nanoparticles partially replacing the cement with 0.3%, 0.6%, 1.0% of nano silica (NS) and 0.03%, 0.045%, 0.06% of Multi-Walled Carbon Nanotubes (MWCNT) in the green concrete mix developement. Nano-sized fragments at the atomic scale tends to modify the properties of concrete. Concrete may increase its strength, durability by adding nanocomposite materials, which will decrease the amount of nano and micropores in structural parts. The strength of the structural elements can be greatly improved and allowing them to withstand higher loads and resist deformation. It improved durability properties by 64.8% in water absorption, 56.4% in acid attack, 78.1% in sulphate attack, and 53.4% in chloride attack. There was an improvement in compressive strength of 37% and split tensile strength of 90%. SEM, FTIR, and XRD investigations have used to look at the microstructural characteristics of nanoconcrete dictated the microstructure characteristics may be made more consistent and dense by adding nanocomposite materials.

• Journal of Powder Materials
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• v.22 no.1
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• pp.21-26
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• 2015

In this study, the control of microstructure for increasing surface roughness of Al with an electro-chemical reaction and a post treatment is systematically investigated. The Al specimen is electro-chemically treated in an electrolyte. In condition of the post treatment at $100^{\circ}C$ for 10 min, a change of the surface microstructure occur at 50V (5 min), and a oxidized layer is at 400V, to which lead a decreasing surface roughness. The minimum temperature of the post treatment for a change of microstructure is $80^{\circ}C$. Moreover, in the condition of 300V (5 min), the electro-chemical reaction is followed by the post treatment at $100^{\circ}C$, the critical enduring time for the change of microstructure is 3 min. The longer post treatment time leads to the rougher surface. The treated Al specimen demonstrate better heat release ability owing to the higher surface roughness than the non-treated Al.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.314-319
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• 2011

Melt foaming method is one of cost-effective methods to make metal foam and it has been successfully applied to fabricate Mg foams. In this research, AZ31 Mg alloy ingot was used as a metal matrix, using AlCa granular as thickening agent and $CaCO_3$ powder as foaming agent, AZ31 Mg alloy foams were fabricated by melt-foaming method at different foaming temperatures. The porosity was above 41.2%~73.3%, pore size was between 0.38~1.52 mm, and homogenous pore structures were obtained. Microstructure and mechanical properties of the AZ31 Mg alloy foams were investigated by optical microscopy, SEM and UTM. The results showed that pore structure and pore distribution were much better than those fabricated at lower temperatures. The compression behavior of the AZ31 Mg alloy foam behaved as typical porous materials. As the foaming temperature increased from $660^{\circ}C$ to $750^{\circ}C$, the compressed strength also increased. The AZ31 Mg alloy foam with a foaming temperature of $720^{\circ}C$ had the best energy absorption. The energy absorption value of Mg foam was 15.52 $MJ/m^3$ at a densification strain of 52%. Furthermore, the high energy absorption efficiencies of the AZ31 Mg alloy foam kept at about 0.85 in the plastic plateau region, which indicates that composite foam possess a high energy absorption characteristic, and the Vickers hardness of AZ31 Mg alloy foam decreased as the foaming temperature increased.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.964-965
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• 2006

The injection molded Fe sintered bodies were fabricated using two kinds of nano Fe powders, $Fe-5%vol.ZrO_2$ and $Fe-10vol.%ZrO_2$ powders. The relationship between microstructure and mechanical properties depending on the $ZrO_2$ contents and sintering temperature were characterized by SEM and TEM techniques. In the wear test, the $Fe-0vol%ZrO_2$ sintered bodies showed mainly adhesive wear, but in the Fe-5%vol. $ZrO_2$ and Fe-10vol. % $ZrO_2$ composites the main wear behavior showed abrasive wear mode.

• Korean Journal of Materials Research
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• v.13 no.4
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• pp.213-218
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• 2003

Fibrous monolithic control of$ Al_2$$O_3$ -$ZrO_2$composite was investigated by multi-pass extrusion process. To obtain sound $Al_2$$O_3$-X $O_2$sintered bodies, burning out and sintering process were carefully carried out. The sintered bodies showed continuous, fibrous monolithic microstructure without any swelling. Many microcracks were observed at the $Al_2$$O_3$-$ZrO_2$interfaces due to the mismatching of thermal expansion coefficient between $Al_2$$O_3$ and $ZrO_2$phase. Most of m- $ZrO_2$grains included twin defects such as (001), (010) and (011) type to accommodate the phase transformation induced stress.

• Journal of Powder Materials
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• v.21 no.3
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• pp.207-214
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• 2014

In this study, nano-scale copper powders were reduction treated in a hydrogen atmosphere at the relatively high temperature of $350^{\circ}C$ in order to eliminate surface oxide layers, which are the main obstacles for fabricating a nano/ultrafine grained bulk parts from the nano-scale powders. The changes in composition and microstructure before and after the hydrogen reduction treatment were evaluated by analyzing X-ray diffraction (XRD) line profile patterns using the convolutional multiple whole profile (CMWP) procedure. In order to confirm the result from the XRD line profile analysis, transmitted electron microscope observations were performed on the specimen of the hydrogen reduction treated powders fabricated using a focused ion beam process. A quasi-statically compacted specimen from the nano-scale powders was produced and Vickers micro-hardness was measured to verify the potential of the powders as the basis for a bulk nano/ultrafine grained material. Although the bonding between particles and the growth in size of the particles occurred, crystallites retained their nano-scale size evaluated using the XRD results. The hardness results demonstrate the usefulness of the powders for a nano/ultrafine grained material, once a good consolidation of powders is achieved.

• Advances in nano research
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• v.13 no.4
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• pp.313-323
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• 2022

The microstructure and mechanical properties of Cr-Ni steel and Cr-Ni steel-matrix nanocomposites reinforced with nano-ZrO₂ particles were investigated in this study. Cr-Ni steel and Cr-Ni/ZrO₂ nanocomposites were produced using a combination of high-energy ball milling, pressing, and sintering processes. The microstructures of the specimens were analyzed using EDX and XRD. Compression and hardness tests were performed to determine the mechanical properties of the specimens. Nano-ZrO₂ particles were effective in preventing chrome carbide precipitate at the grain boundaries. While t-ZrO₂ was detected in Cr-Ni/ZrO₂ nanocomposites, m-ZrO₂ could not be found. Few α'-martensite and deformation bands were formed in the microstructures of Cr-Ni/ZrO₂ nanocomposites. Although nano-ZrO₂ particles had a negligible impact on the strength improvement provided by deformation-induced plasticity mechanisms in Cr-Ni/ZrO₂ nanocomposites, the mechanical properties of Cr-Ni steel were significantly improved by using nano-ZrO₂ particles. The hardness and compressive strength of Cr-Ni/ZrO₂ nanocomposite were higher than those of Cr-Ni steel and enhanced as the weight fraction of nano-ZrO₂ particles increased. Cr-Ni/ZrO₂ nanocomposite with 5wt.% nano-ZrO₂ particles had almost twofold the hardness and compressive strength of Cr-Ni steel. The nano-ZrO₂ particles were considerably more effective on particle-strengthening mechanisms than deformation-induced strengthening mechanisms in Cr-Ni/ZrO₂ nanocomposites.