• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.188-189
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• 2022

With the development of nano-reinforcement technology, TiO₂ nanomaterials have received widespread attention as one of the additives without pozzolanic reaction, which can be used to improve the mechanical properties of cement-based materials. Meanwhile, with the development of additive manufacturing technology or known as 3D printing technology, its application in the construction field has also got noticed. Therefore, in this work, the effect of three sizes of TiO₂ on the compressive strength of hardened cement-based materials fabricated by binder jetting 3d printing was evaluated. According to the results, the TiO₂ particles with larger sizes can provide better reinforcement to the hardened cement due to its more significant filling effect.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.2
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• pp.225-236
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• 2016

Objectives: Nanomaterials have been used in various fields. As use of nanoproducts is increasing, workers dealing with nanomaterials are also gradually increasing. Exposure assessments for nanomaterials have been carried out for protection of worker's health in workplace. Exposure studies were mainly focused on manufacturing processes, but these studies on after-treatment processes such as refinement, weighing, and packing were insufficient. So, we investigated exposure characteristics of particles during after-treatment processes of $Al_2O_3$ fibers and Ni powders. Methods: Mass-production of Ni powder process was carried out in enclosed capture-type canopy hood. In a developing stage, $Al_2O_3$ was handled with a local ventilation unit. Exposure characteristics of particles were investigated for $Al_2O_3$ fiber and Ni powder processes during the periods of 10:00 to 16:00, 20 May 2014 and 13:00 to 16:00, 21 May 2014, respectively. Three real-time aerosol instruments were utilized in exposure assessment. A scanning mobility particle sizer(SMPS, nanoscan, model 3910, TSI) and an optical particle counter(OPC, portable aerosol spectrometer, model 1.109, Grimm) were used to determine the particle size distribution in the size range of 10-420 nm and $0.25-32{\mu}m$, respectively. In addition, a nanoparticle aerosol monitor(NAM, model 9000, TSI) was used to measure lung-deposited nanoparticle surface area. Membrane filters(isopore membrane filter, pore size of 100 nm) were also used for air sampling for the FE-SEM(model S-5000H, Hitachi) analysis using a personal sampling pump(model GilAir Plus by 2.5 L/min, Gilian). Conclusions: For Ni powder after-treatment process, only 27% increase in particle concentration was found during the process. However, for $Al_2O_3$ fiber after-treatment process, significant exposure(1.56-3.34 times) was observed during the process.

• KSBB Journal
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• v.22 no.6
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• pp.414-420
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• 2007

Nanomaterials have been applied to various fields due to their advantageous characteristics such as high surface area, rapid diffusion, high specific surface areas, reactivity in liquid or gas phase, and a size close to biomacromolecules. Up to date, increased manufacturing and frequently use of the materials, however, revoke people's concerns on their hazard impact including toxicity the materials. Many research groups have carried out different protocols to evaluate toxic effects of nanomaterilas on different organisms, and consequently, nanomaterials are known to cytotoxicity. In this paper, we reviewed some of the most reports on toxic effects of several nanoparticles specifically on bacteria. There are numbers of reports focused on antibacterial effect of nanoparticles based on bacterial cell viability. Therefore, the application of each nanomaterial should be concerned with its toxicity and its toxic effect should be evaluated in terms of concentrations and sizes of the nanomaterials used, prior to use of a nanomaterial.

• Journal of Powder Materials
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• v.15 no.1
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• pp.31-36
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• 2008

In this study, the bottom-up powder metallurgy and the top-down severe plastic deformation (SPD) techniques for manufacturing bulk nanomaterials were combined in order to achieve both full density and grain refinement without grain growth of rapidly solidified Al-20 wt% Si alloy powders during consolidation processing. Continuous equal channel multi-angular processing (C-ECMAP) was proposed to improve low productivity of conventional ECAP, one of the most promising method in SPD. As a powder consolidation method, C-ECMAP was employed. A wide range of experimental studies were carried out for characterizing mechanical properties and microstructures of the ECMAP processed materials. It was found that effective properties of high strength and full density maintaining nanoscale microstructure are achieved. The proposed SPD processing of powder materials can be a good method to achieve fully density and nanostructured materials.

• Carbon letters
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• v.16 no.2
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• pp.132-134
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• 2015

When manufacturing bulk graphite, pores develop within the bulk during the carbonization process due to the volatile components of the fillers and the binders. As a result, the physical properties of bulk graphite are inferior to the theoretical values. Impregnants are impregnated into the pores generated in the carbonization process through pressurization and/or depressurization. The physical properties of bulk graphite that has undergone impregnation and re-carbonization processes are outstanding. In the present study, a green body was manufactured by molding with natural graphite flakes and phenolic resin at 45 MPa. Bulk graphite was manufactured by carbonizing the green body at 700 and it was subsequently impregnated with impregnants having viscosity of 25.0 cP, 10.3 cP, and 5.1 cP, and the samples were re-carbonized at $700^{\circ}C$. The above process was repeated three times. The open porosity of bulk graphite after the final process was 22.25%, 19.86%, and 18.58% in the cases of using the impregnant with viscosity of 25.0 cP, 10.3 cP, and 5.1 cP, respectively.

• Advances in nano research
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• v.16 no.4
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• pp.365-374
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• 2024

This study delves into the significant impact of integrating nanomaterials, specifically carbon and graphene nanoparticles, into the polymer matrix of aluminum alloy 356, utilizing the vortex casting technique, with the aim of improving the mechanical properties of table tennis equipment. Athletes and their coaching teams have long been on a quest for high-performance sports gear, recognizing its pivotal role in unlocking the full potential of players. The dedication of engineers to craft designs, select materials with precision, and uphold stringent testing standards reflects the commitment to meeting the demands of the sporting world. Yet, to remain at the forefront, sports engineering must continually align with contemporary technologies, and nanotechnology has emerged as a transformative force in this regard. This study not only underscores the meticulous efforts in material integration but also highlights the remarkable strides made possible by nanotechnology. Aluminum nanocomposites, particularly, showcase a groundbreaking fusion of exceptional strength and reduced weight, marking a notable achievement in sports equipment innovation. The research outcomes are compelling, revealing a substantial enhancement in the mechanical performance of the sports structures under scrutiny. This promising development hints at a potential paradigm shift in the manufacturing of sports equipment, promising a new era of elevated athlete performance and enhanced safety during the rigors of physical education training. This study stands as a testament to the tangible impact of nanotechnology on the ever-evolving landscape of sports equipment.

• Current Industrial and Technological Trends in Aerospace
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• v.6 no.1
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• pp.90-98
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• 2008

Nanotechnology(NT) refers to a field of advanced micro-technology covering the creation and manufacturing of materials on the atomic and molecular scale and requires interdisciplinary study with various fields including materials science, physics, chemistry, electronics and others. Whileas nanotechnology is a kind of micro and small scaled science, space technology(ST) is one of the larger and system technologies utilizing broad fields of mechanical, materials, electronics and communication technologies. It is necessary to select and concentrate the functional items of nanotechnology for efficient application to be utilized in space technology, due to the cross-sectional characteristics of nanotechnology within nanomaterials, nanoelectronics, and nanomanufacturing. This paper provides the current state of art of nanotechnology in space technology by evaluating NASA's activities and the 9th frame of the project ANTARES(Analysis of Nanotechnology Applications in Space Developments and Systems) with the support of the German Aerospace Center (DLR), Space Flight Management, Division Technology for Space Systems and Robotics. It has shown that it is necessary to apply nanotechnology to space technology in order to achieve international competitiveness, for the nanotechnology can bring the previously impossible things to reality. Since KARI plans to send an unmanned probe to the moon's orbit and land a probe on the moon's surface in 2025, it is urgently needed to incorporate nanotechnology to national space development plan.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.11
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• pp.885-890
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• 2015

Nanomaterials possess unique mechanical, physical, and chemical properties. They are small, and have an ultrahigh surface area, making them suitable for air filter applications. Electrospinning has been recognized as an efficient technique for fabricating polymer nanofibers. In order to determine the optimum manufacturing conditions, the effects of several electrospinning process parameters on the diameter, orientation, and distribution of polyacrylonitrile (PAN) nanofiber are analyzed. To improve interlaminar fracture toughness and suppress delamination in the form of laminated non-woven fibers by using a heat roller, the performances of filter efficiency and pressure drop achieved with PAN nanofiber air filter are evaluated experimentally.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.195-204
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• 2012

Biomineralization has been explored for geochemical cycles and microbial tolerance mechanisms to metal toxicity. Here, we are introducing NanoFermentation which enables economic, environmentally friendly, requiring low input energy, and scalable manufacturing of nano-dimensioned magnetite. We are also focusing on controlling factors of crystallite size which can determine superparamagnetism and ferrimagnetism. Controlling factors are such as microbial species, temperature, incubation time, medium composition, substituted elements and their concentration, precursor type, reaction volume, precursor concentration density and their combinations. Crystallite size distribution of biomagnetite depends on the balance between nuclei generation and crystal growth. Biomineralization will elucidate elemental cycles on earth crust and microbial ecology as well as it will be applied to material sciences and devices via massive production of nanomaterials.

• Composites Research
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• v.24 no.6
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• pp.25-30
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• 2011

This paper presents an experimental study on the enhancement of electromagnetic shielding (EMI) properties of glass fiber, carbon fiber, and glass-carbon fiber composites by adding layers of multi-walled carbon nanotubes (MWCNTs). In the case of glass-fiber composites, spraying 0.1~0.2 g of MWCNT over a fiber area of $200mm{\times}200mm$ (1.8~3.6 ${\mu}m$ in thickness) resulted in significant improvement in EMI shielding effectiveness (SE). Also, when applying multiple MWCNT layers, it was more effective to place the layers concentrated near the center of the composite rather than spreading them out. On the contrary, inherently conductive carbon fiber and glass-carbon fiber composites did not show appreciable improvement with the addition of MWCNT layers. In order to maximize the effectiveness of carbon nanomaterials as EMI shielding fillers, it is imperative to understand the effect of these materials on various EMI shielding mechanisms and their interactions.