Study of the effect of nano-sized precipitates on the mechanical properties of boron-added low-carbon steels by neutron scattering techniques

Seong, B. S.,Cho, Y. R.,Shin, E. J.,Kim, S. I.,Choi, S.-H.,Kim, H. R.,Kim, Y. J. International Union of Crystallography 2008 Journal of applied crystallography Vol.41 No.5

<▼1><P>The effect of nano-sized precipitates on the mechanical properties of boron-added low-carbon steels was studied by neutron scattering techniques such as powder diffraction, small-angle scattering and particle tracking autography.</P></▼1><▼2><P>Small-angle neutron scattering (SANS) and neutron powder diffraction (ND) techniques were used to study quantitatively the effect of nano-sized precipitates and boron addition on the mechanical properties of low-carbon steels. SANS was used to evaluate nano-sized precipitates, smaller than about 600 Å in diameter, and ND was used to determine the weight fraction of the cementite precipitates. Fine core–shell structured spherical precipitates with an average radius of ~50 Å, such as MnS and/or CuS, surrounded by BN layers were observed in the boron-added (BA) low-carbon steels; fine spherical precipitates with an average radius of ~48 Å were mainly observed in the boron-free (BF) low-carbon steels. In the BA steels, the number of boron precipitates, such as BN, Fe<SUB>3</SUB>(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures. The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates. Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.</P></▼2>

Investigation of irradiation effects on microstructure of cement paste using small-angle neutron scattering

Park, Kyoungsoo,Chung, Chul-Woo,Lee, Chang Joon,Kwon, Tae-Hyun Elsevier 2019 Cement and concrete research Vol.123 No.-

<P><B>Abstract</B></P> <P>Nano-structural changes of cement paste due to neutron and gamma irradiation are investigated by using small-angle neutron scattering (SANS). Disk specimens were prepared with the w/c ratios of 0.4 and 0.5, and they were exposed to the neutron fluence of 2.57 × 10<SUP>14</SUP> n/cm<SUP>2</SUP> and the gamma radiation does dosage of 38.4 Gy. Based on SANS data and a microstructural model of C-S-H gel, one observed that the size of C-S-H globules increased after irradiation. The change of C-S-H globule size may be associated with the change of surface morphology and chemical bonding of C-S-H, and thus further research on the irradiation effects on cement paste is necessary.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We propose an investigation of irradiation effects on the nano-structural changes of C-S-H gel for the first time. </LI> <LI> Nano-structural changes of cement paste due to neutron and gamma irradiation are investigated by SANS. </LI> <LI> Based on SANS data, one observed that the size of C-S-H globules increased after irradiation. </LI> <LI> Additionally, irradiation may cause breakage of the chemical bonding, which results in complexity on surface morphology. </LI> </UL> </P>

폴리스티렌-폴리에틸렌옥사이드 이중블록공중합체 미셀의 쉘 구조에 대한 온도 효과

김은진(Eun Jin Kim),이은지(Eun Ji Lee),이광희(Kwang Hee Lee) 한국고분자학회 2017 폴리머 Vol.41 No.6

중수소화 폴리스티렌-폴리에틸렌옥사이드 이중블록공중합체(dPS-b-PEO)로 형성된 미셀의 쉘 구조에 대한 온도 영향을 소각중성자산란(SANS)을 이용하여 수용액에서 조사하였다. SANS 데이터는 코어-쉘 모델에 hard sphere structure factor를 적용하여 분석하였으며, 산란 곡선 맞춤을 이용하여 쉘 두께를 구하였다. 온도 증가에 따라서 미셀의 쉘 두께는 감소하다가 특정 온도(~55 oC)를 넘어서면 증가하였다. 이러한 쉘 구조의 변화는 낮은 온도 영역에서는 온도 증가에 따른 PEO 블록의 친수성 감소가, 높은 온도 영역에서는 온도 상승에 따른 PEO 블록의 열운동 증가가 코로나 내의 수화 수준을 지배하였기 때문이다. The temperature effects on the shell structure of micelles formed by a deuterated polystyrene-poly(ethylene oxide) diblock copolymer (dPS-b-PEO) in aqueous solution were investigated with small-angle neutron scattering (SANS). SANS data was analyzed using a core-shell model with a structure factor for a hard sphere potential. The shell thickness was obtained from the fits to the SANS data. The shell thickness first decreased with increasing temperature, reached minium at some point and then increased with a further increase of temperature. These structural changes seemed to be due to the combined effects of the decrease in hydrophilicity of the PEO block and the increase in thermal motion of the PEO block with increasing temperature.

Evaluation of molecular volume change of block copolymer depending on temperature: A SANS study

Kim, Tae-Hwan,Do, Changwoo,Han, Young-Soo Elsevier 2018 PHYSICA B-CONDENSED MATTER - Vol.551 No.-

<P><B>Abstract</B></P> <P>Amphiphilic Pluronic triblock copolymers form various self-assembled structures such as sphere, cylinder, lamellae and so on, depending on temperature, leading to the increase of hydrophobicity of block copolymers. However, the effective molecular volume change of the block copolymer has not been fully exploited yet, when temperature increases. Here, we have investigated the effective molecular volume change of the block copolymer upon heating by using the contrast variation small angle neutron scattering. The scattering length densities (SLDs) of the block copolymer were experimentally obtained from the neutron scattering contrast variation method between the solvent and the block copolymer at varying temperature. Even though the SLD, which is the intrinsic property of the material, should not be changed by temperature elevation, it was dependent on temperature, indicating that the molecular volume is changed. Therefore, we obtained the increase rate of the molecular volume change of the block copolymer (the effective molecular volume change) from the comparison of the calculated SLD and the standard SLD, which is evaluated by plotting the SANS intensity at the first order Bragg peak as the function of temperature at each volume fraction of D<SUB>2</SUB>O and H<SUB>2</SUB>O that is about 25.5%–51.3% depending on temperature.</P>

ADS/OTAC 혼합 계면활성제 수용액에서 형성된 마이셀과 층막구형체의 크기 및 구조에 대한 작은 각 중성자 산란 연구

김홍운 ( Hong Un Kim ),이진규 ( Jin Kyu Lee ),임경희 ( Kyung Hee Lim ) 한국공업화학회 2005 공업화학 Vol.16 No.2

폴리스티렌-폴리(메틸 메타크릴레이트) 이종 블록 공중합체 내의 단일중합체 분포

이광희(Kwang Hee Lee),홍성호(Sung Ho Hong),이은지(Eun Ji Lee),송권빈(Kwon Bin Song) 한국고분자학회 2011 폴리머 Vol.35 No.6

블록 공중합체/단일중합체 블렌드에서 단일중합체의 농도와 분자량 변화에 따른 단일중합체의 분포 경향을 알아 보았다. 중수소화 폴리(메틸 메타크릴레이트) 또는 폴리스티렌을 중수소화 폴리스티렌-폴리(메틸 메타크릴레이트) 이 중 블록 공중합체에 20 wt%까지 혼입하였다. 시료들은 소각 X-선 산란, 중성자 반사율 및 투과 전자 현미경으로 조사 하였다. 실리콘 웨이퍼에 스핀 코팅하여 얇은 필름 상으로 제조한 블록 공중합체는 기질 표면에 대해 평행하게 배향된 라멜라 모폴로지를 형성하였다. 블록 공중합체의 미세 도메인 구조는 단일중합체의 부가에 의해 상당히 교란되었다. 그 결과로 단일중합체의 농도가 15 wt% 이상인 경우에는 배열 질서도가 낮은 라멜라 모폴로지가 나타났다. 단일공중합체 의 농도나 분자량이 증가하면 단일중합체가 미세 도메인을 불균일하게 팽윤시키면서 보다 많은 단일중합체가 미세 도메 인의 중앙 부위로 이동하였다. Homopolymer distribution in block copolymer/homopolymer blends was investigated as a function of homopolymer concentration and homopolymer molecular weight. The deuterated poly(methyl methacrylate) or polystyrene was blended with a deuterated polystyrene-poly(methyl methacrylate) diblock copolymer up to a concentration of 20 wt%. Samples were characterized by small-angle X-ray scattering (SAXS), neutron reflectivity and transmission electron microscopy. The block copolymer with a thin-film geometry formed alternating lamellar microdomains oriented parallel to the substrate surface. By adding the homopolymer, the microdomain structure was significantly disturbed. As a consequence, a poorly ordered morphology appeared when the homopolymer concentration exceeded 15 wt%. Increasing the homopolymer concentration and/or the homopolymer molecular weight caused the microdomains to swell less uniformly, resulting in segregation of the homopolymer toward the middle of the microdomains.

Mechanical, dielectric and structural characterization of cross-linked PEG-diacrylate/ethylammonium nitrate ionogels

Lopez-Barron, C.R.,Beltramo, P.J.,Liu, Y.,Choi, S.M.,Lee, M.J. Butterworth Scientific Ltd. etc. 2016 Polymer Vol. No.

We report the preparation and characterization of cross-linked ionogels (x-IGs) composed of polyethylene glycol diacrylate (PEGDA) and the protic ionic liquid, ethylammonium nitrate (EAN). The cross-linking process has a huge effect on the mechanical properties of the solutions (forming stiff solids from Newtonian solutions) and a minimum penalty on the ionic conductivity. The interdependence of the mechanical and dielectric properties with the network structure of the x-IGs was studied using three experimental probes: torsion and compression mechanical testing, dielectric spectroscopy and small angle neutron scattering. The microstructure, the mechanical strength and the conductivity of the x-IGs depend strongly on the polymer concentration and weakly on the temperature. High modulus and relatively low conductivities are associated to small cross-link junction lengths, ξ, observed in concentrated samples, whereas large ξ values, observed in dilute samples, result in high conductivities and relatively low modulus. The topological restriction to ionic transport (i.e., to conductivity) is quantified by the obstruction factor, which increases monotonically with ξ, while the shear modulus exhibits a power law behavior, G~ξ<SUP>-3</SUP>, in accordance to linear viscoelastic theory.

A SANS Study of Microemulsions in the Pseudoternary Aerosol OT/Cyclohexane/Aqueous AgNO₃ Solution and Formation of Silver Nanoparticles in Microemulsions

Kim, Hong-Un,Lee, Jin-Kyu,Lim, Kyung-Hee 한국공업화학회 2005 Journal of Industrial and Engineering Chemistry Vol.11 No.2

This article deals with an investigation on the phase behavior of the pseudoternary AOT/cyclohexane/ aqueous 0.2 M AgNO₃ solution and features of its water-in-oil (W/O) microemulsions (MEs). The sizes and structures indicative of water pools in the microemulsions were determined by small-angle neutron scattering (SANS). SANS spectra indicated that water pools of spheres with sizes 4~10 nm and of cylinders with lengths of 25~30 nm were formed at four different compositions inside the microemulsion region. Silver nanoparticles were prepared with the microemulsions and identified by the peaks at a wavelength of 400 nm in their UV/Vis absorption spectra. TEM micrographs showed that the silver nanoparticles were spherical and rod-like, depending on the compositions of the microemulsions and reflecting the sizes and shapes of the water pools.

Magnetic properties of SiO2-coated iron oxide nanoparticles studied by polarized small angle neutron scattering

이성호,이동헌,정현,한영수,김태환,양우철 한국물리학회 2015 Current Applied Physics Vol.15 No.8

The structural and magnetic properties of non-coated and SiO2-coated iron oxide (Fe3O4) nanoparticles (NPs) were investigated by a polarized small-angle neutron scattering (P-SANS) method. Measurement of the P-SANS allowed us to obtain nuclear and magnetic scattering cross sections of the NPs under applied magnetic field. The analysis of the scattering intensity provided the structural parameters and the spatial magnetization distribution of the non-coated and the SiO2 coated coreeshell NPs. The measured radius of both NPs and the shell thickness of the coreeshell NPs were in consistent with those measured by the transmission electron microscopy. In comparison, the magnetic core radii of both NPs were 0.12e0.6 nm smaller than the nuclear radii, indicating the magnetization reduction in the surface region of core Fe3O4 in both NPs. However, the reduced magnetization region, which is the surface spin canting region, of the SiO2-coated NPs was relatively narrower than that of the non-coated NPs. We suggest that the SiO2 coating on the Fe3O4 NPs may stabilize the spin order of atoms and prohibit the oxidation or defect formation at the surface region of the Fe3O4 NPs, and enhance the corresponding magnetization of the Fe3O4 NPs by the reduction of the spin canting layer thickness.

Small Angle Neutron Scattering Study on the Structural Variation of Lysozyme in Bioprotectants

Shota Koda,Haruki Takayama,Tomohiko Shibata,Tatsuya Mori,Seiji Kojima,In-Sung Park,Tae-Gyu Shin 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.9

The thermal denaturation and subsequent structural variation of lysozyme in various bioprotectant candidate solutions such as trehalose and choline acetate have been investigated by using small angle neutron scattering and differential scanning calorimetry. The gyration radius shows little change with the addition of additives in a native state at room temperature. On heating the lysozyme solution, a remarkable increase in the gyration radius is observed at temperatures above the denaturation temperature without any bioprotectants. Such an increase is suppressed by the additives owing to the intermolecular interactions between the lysozyme molecules and the bioprotectants of trehalose and choline acetate. The fractal dimension of lysozyme varies slightly with the addition of the bioprotectant solutions, and shows a remarkable drop in the vicinity of the denaturation temperature for all the solutions.