수용성 도료용 조색제의 배합과 물성에 관한 연구

조을룡 한국기술교육대학교 2006 論文集 Vol.12 No.1

Tint pastes for water-based coatings were formulated and the properties were investigated as water-based coatings is being important due to environmental problems of solvent-based coatings. In the rheological behavior, viscosity of intermediate varies with respect to increased addition of wetting dispersant. The largest viscosity restitution occured at 8% of wetting dispersant when shear stress was removed, and anionic wetting dispersant yielded excellent restitution of viscosity at removal of shear stress. In terms of rheological behavior with pH, we could get the most stable dispersion at pH 8.5. Rheological behavior regarding to amount of dispersing resin showed the most stable pigmented dispersion at 6wt% of it. Particle size of pigment also affected jetness by variation of workability owing to differences of surface area.

폴리아크릴산계 중합체의 감수효과에 대한 연구

조을룡 한국기술교육대학교 2004 論文集 Vol.10 No.2

Acryl monomers such as acrylic acid(AA), methylmethacrylate(MMA), and ethyl acrylate(EA) were polymerized to use as water reducing agent for cement mortar. Acrylic acid was employed to show good final physical properties with polyoxyethylene aklyphenyl ether(Poly-E) and 2-acrylamido-2-methyl-1-propanesulfonic acid(AMPS). All the polymerizations were carried out in water-based solution to obtain environmentally freindly system. The viscosities of the synthesized solutions for the research have less than 800 cps. Especially, copolymer of AA, MMA, AMPS, and Poly-E resulted in high water retention, low bleeding, good dimensional stability, excellent resistance to freeze-thawing, and high compression strength due to hydrogen bonding of amide group of AMPS and ethylene oxide group of Poly-E.

자동차 도료용 수용성 베이스 코트에 관한 연구

조을룡 한국기술교육대학교 2006 論文集 Vol.13 No.1

The water-born polyurethane/acrylic emulsion with core-shell morpology was used to develop water-born base coat for automotive coating. Compared to solvent based base coat, water-born base coat showed good water resistance and rust resistance, excellent appearance, and good workability at spray coating. The increase of polyurethane content in hybridized emulsion yielded improvement of adhesion, chip resistance, and film flexibility. The hardness of film with mole ratio of isocyanate group to hydroxy group increased with increasing isocyanate group. In the rheological measurement, unlike solvent based coating, water-born coating resulted in rapid rise of viscosity with increasing shear rate. The range of 3 to 6 of thixotropy index(TI) with use of thickener showed good storage stability and appearance, excellent orientation of color components.

Sol-gel based TiO2 paste applied in screen-printed dye-sensitized solar cells and modules

Mateja Hocˇevar,Ursˇa Opara Krasˇovec,Matevzˇ Bokalic,Marko Topic,Welmoed Veurman,Henning Brandt,Andreas Hinsch 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.5

A simple manufacturing process based on screen-printing is crucial for a successful commercialization of dye-sensitized solar cells (DSSCs). We developed the sol–gel based TiO2 paste in such a way that solely a single step deposition is sufficient to realize a sponge-like structure of the layer assuring its high activity in DSSCs. For the first time the sol–gel based TiO2 paste was screen printed and tested in DSSC masterplates and PV mini-modules. Electroluminescence imaging of the mini-module proved layer homogeneity and no manufacturing defects. The conversion efficiency of the PV mini-module with the active area of 75 cm2 reaches 5.7% at STC.

Evaluation of MgCo2O4 nanoparticles as a gas sensor for the detection of acetone in the diabetic and non-diabetic range

J. P. Morán-Lázaro,F. López-Urías,E. Muñoz-Sandoval,M. Courel-Piedrahita,A. Carreon-Alvarez,V. M. Rodríguez-Betancourtt,I. Zamudio-Torres,E. S. Guillén-López,A. Palafox-Corona 대한금속·재료학회 2023 ELECTRONIC MATERIALS LETTERS Vol.19 No.1

The acetone contained in human breath is of great interest for the health sector as it is a marker that allows to diagnoseand control diabetes in a non-invasive way. However, its concentration is extremely low. Therefore, high-performanceacetone sensors are still a challenge. With this in mind, MgCo 2 O 4 nanoparticles were synthesized using a microwaveassistedcolloidal route with subsequent calcination. Structural and morphological characterizations were done through varioustechniques. The MgCo 2 O 4 sensor was fabricated with the sample calcined at 500 °C. The sensing results showed that thesensor could detect acetone vapors ranging from 0.5 to 50 ppm at an optimum operating temperature of 250 °C with a highresponse, repeatability, stability, and selectivity. These sensing characteristics revealed that MgCo 2 O 4 could be used as a newsensor material to detect acetone in exhaled human breath.

Ab-initio Study of the Structural, Electronic, Elastic and Vibrational Properties of the Intermetallic Pd3V and Pt3V Alloys in the L12 Phase

N. Arlkan,A.Iyigör,A. Candan,M. Özduran,A. Karakoç,S . U ur4,G. Ugur4,A. Bouhemadou,S. Bin-Omran,N. Guechi 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.4

Pseudopotential plane-wave method based on density functional theory within the generalized gradientapproximation for the exchange-correlation potential has been applied to study the structural, electronic, elasticand vibrational properties of the binary intermetallic Pd3V and Pt3V in the L12 phase. The optimized latticeconstant, bulk modulus and its pressure derivative, independent single-crystal elastic constants and elasticwave velocities in three different directions are evaluated and compared with the available experimental andtheoretical data. The polycrystalline elastic parameters, hardness coefficient, elastic anisotropy, Debye temperatureare estimated. The electronic band structure, electronic total and partial densities of states, and totalmagnetic moment of the Pd3V and Pt3V alloys are computed and analyzed in comparison with the existingtheoretical and experimental findings. Phonon-dispersion curves and their corresponding total and projecteddensities of states were obtained for the first time using a linear-response in the framework of the densityfunctional perturbation theory.

A novel sensor for the detection of n-butanol based on CoMn2O4 nanoparticles

Juan Pablo Morán-Lázaro,Maykel Courel-Piedrahita,Alex Guillén-Bonilla,Florentino López-Urías,Héctor Guillén-Bonilla,Víctor Manuel Soto-García,Aldo Palafox-Corona,David Alberto Hernández-Poot 대한금속·재료학회 2024 ELECTRONIC MATERIALS LETTERS Vol.20 No.5

In this paper, we studied the alcohol-sensing properties of CoMn 2 O 4 nanoparticles for the fi rst time. The CoMn 2 O 4nanoparticles were prepared via a simple microwave-assisted colloidal method using cobalt nitrate, manganese nitrate,dioctyl sulfosuccinate sodium salt, and ethylene glycol as a solvent. Various techniques were used to characterize the structural,morphological, and optical properties of CoMn 2 O 4 . The crystal structure of CoMn 2 O 4 was found after calcinationat a temperature of 400 °C. The Raman spectrum showed seven vibrational bands, while the optical absorption spectrumshowed three bands, confi rming the spinel CoMn 2 O 4 . Morphological analysis revealed that the porous microstructure ofCoMn 2 O 4 was composed of nanoparticles with a size distribution of 16 to 58 nm. Gas sensors were fabricated with theCoMn 2 O 4 powders calcined at 400 °C using the brush-coating method, and experimental results showed that CoMn 2 O 4nanoparticles were more sensitive to n -butanol than isopropanol and ethanol at an operating temperature of 185 °C. TheCoMn 2 O 4 sensor showed a response of 6.6 at 50 ppm n -butanol with good stability, reproducibility, and repeatability. The present article provides a new sensing material that could be used as an n -butanol sensor with signifi cant benefi tsfor human health.

Optical and electrical modelling and characterization of dye-sensitized solar cells

Marko Topič,Andrej Cˇ ampa,Miha Filipic,Marko Berginc,Urša Opara Krašovec,Franc Smole 한국물리학회 2010 Current Applied Physics Vol.10 No.3

A route of optical and electrical modeling of dye-sensitized solar cells (DSSCs) has been developed and validated within a set of test structures. The optical model is based on one-dimensional semi-coherent optical simulator SunShine, in which nanoporous active layer was successfully modelled as effective medium layer with effective scattering of light at its front and back surface interface using effective roughness. The electrical model is based on a pseudo-homogeneous active layer using drift–diffusion transport equations for free electron and ion transport. In both models, input parameters have been extracted from measured performance of test devices and main optical and electrical losses have been quantitatively identified for ionic liquid based DSSC structures, having 7 or 14 lm thick active layer.

Polyphenol Bioaccessibility and Antioxidant Activity of Pomegranate (Punica granatum) Peel Supplementation in Diet-Induced Obese Rats

Anael Mellado-Negrete,Gloria Itzel Peña-Vázquez,Vania Urías-Orona,Ana Laura de la Garza 한국식품영양과학회 2023 Journal of medicinal food Vol.26 No.8

Fruit by-products are a source of biocompounds with antioxidant properties and potential role in the obesitytreatment. This study aimed to assess the effect of pomegranate (Punica granatum) peel (PP) supplementation on the totalantioxidant capacity (TAC) in diet-induced obese rats. Thus, an in vitro gastrointestinal digestion was performed to evaluatethe total phenolic content (TPC) and the antioxidant capacity of PP. Moreover, 15 male Wistar rats were randomized into threegroups: control diet (CTL; 3.35 kcal/g), cafeteria (CAF) diet (3.72 kcal/g), and CAF diet supplemented with PP (CAF + PP;200 mg/kg body weight; 3.72 kcal/g). Serum TAC was analyzed by ferric reducing antioxidant power and 2,2-Diphenil-1-picrylhydrazil assay. TPC in PP accounted for 8.82 – 0.14 mg GAE/g in undigested samples. However, an in vitro digestionprocess was decreased by 94% the bioaccessibility of PP phenolic compounds in the intestinal phase, while PP supplementationincreased serum TAC in diet-induced obese rats. Therefore, although PP phenolic compounds diminished after anin vitro digestion process, antioxidant effect was found in obese rats supplemented with PP.

Creep in Grain Coarsened ODS MA NiAl

Ur, Soon-Chul,Suh, Sungjae,Nash, Philip 대한금속학회 2002 METALS AND MATERIALS International Vol.8 No.4

NiAl based oxide dispersion strengthened (ODS) intermetallic alloys have been produced by mechanical alloying (MA) and consolidated by hot extrusion. Subsequent isothermal annealing was carried out to induce normal grain growth (NGG), and a thermomechanical treatment was performed to induce secondary recrystallization (SRx). SRx resulted in pronounced elongated grain growth without dispersoid coarsening, whereas concurrent equiaxed coarsening of grains and dispersoids occurred in NGG specimens. Creep properties of grain coarsened ODS MA NiAl were investigated, and the associated creep mechanisms were evaluated. The creep properties of SRxed MA NiAl are compared with those of as-consolidated MA NiAl and other counterparts. It has been shown that SRx results in improved creep resistance compared to NGG mechanism. The apparent activation energy and the stress exponent for creep indicate that SRx MA NiAl exhibits intermediate creep behavior of the two limiting dislocation creep modes; climb controlled and viscous glide controlled. However, a grain size dependent creep has been shown, indicating that grain boundary sliding mechanism contributes to the overall deformation in MA NiAl.