Structure, optical and thermal decomposition characters of LDPE graft copolymers synthesized by gamma irradiation

M. Madani 한국물리학회 2011 Current Applied Physics Vol.11 No.1

Methyl methacrylate (MMA) monomer was grafted onto Low density Polyethylene by the direct method of radiation grafting. The effect of cohesive energy density of different organic solvents on the degree of grafting was investigated. It was found that the extent of grafting depends largely on the kind of solvent,in which the highest degree of grafting was achieved in the presence of dioxane, whereas the lowest degree of grafting occurred in the presence of methanol. This behaviour was attributed to the solubility parameters of the solvent, monomer and polymer. The change in structure of the LDPE graft copolymer films was characterized by scanning electron microscopy, X-ray diffraction, UV/vis absorption and thermogravimetric analysis. The X-ray diffraction results showed a decrease in the crystallinity of LDPE graft copolymer matrix at high degree of grafting. Studies were made on the UV-absorption edge,indirect allowed transitions with their optical energy gaps are determined. At the same time the Urbach energy was evaluated. The activation energy of the thermal decomposition was calculated according to Horowitz and Metzger method.

Adsorption Kinetics for Polymeric Additives in Papermaking Aqueous Fibrous Media by UV Spectroscopic Analysis

Sung-Hoon Yoon*,Xin-Sheng Chai 대한화학회 2006 Bulletin of the Korean Chemical Society Vol.27 No.11

The general objective of the present study was to investigate the potential application of the UV spectroscopic method for determination of the polymeric additives present in papermaking fibrous stock solutions. The study also intended to establish the surface-chemical retention model associated with the adsorption kinetics of additives on fiber surfaces. Polyamide epichlorohydrin (PAE) wet strength resin and imidazolinium quaternary (IZQ) softening agents were selected to evaluate the analytical method. Concentrations of PAE and IZQ in solution were proportional to the UV absorption at 314 and 400 nm, respectively. The time-dependent behavior of polymeric additives obeyed a mono-molecular layer adsorption as characterized in Langmuir-type expression. The kinetic modeling for polymeric adsorption on fiber surfaces was based on a concept that polymeric adsorption on fiber surfaces has two distinguishable stages including initial dynamic adsorption phase and the final near-equilibrium state. The simulation model predicted not only the real-time additive adsorption behavior for polymeric additives at high accuracy once the kinetic parameters were determined, but showed a good agreement with the experimental data. The spectroscopic method examined on the PAE and IZQ adsorption study could potentially be considered as an effective tool for the wet-end retention control as applied to the paper industry.

Molecular structure, spectroscopic properties, and Hirshfeld surface analysis of chlorobis(<i>N</i>-methyl-1,3-propanediamine)copper(II) tetrafluoroborate and azidobis(2,2-dimethyl-1,3-propanediamine)copper(II) azide

Moon, Dohyun,Tanaka, Shinnosuke,Akitsu, Takashiro,Choi, Jong-Ha Elsevier 2018 Journal of molecular structure Vol.1154 No.-

<P><B>Abstract</B></P> <P>Two new copper (II) complexes, [Cu(<I>N</I>-Metn)<SUB>2</SUB>Cl]BF<SUB>4</SUB> (<B>1</B>) and [Cu(Me<SUB>2</SUB>tn)<SUB>2</SUB>(N<SUB>3</SUB>)]N<SUB>3</SUB> (<B>2</B>) (<I>N</I>-Metn = <I>N</I>-methyl-1,3-propanediamine; Me<SUB>2</SUB>tn = 2,2-dimethyl-1,3-propanediamine), have been prepared, fully characterized, and their structures established by X-ray single-crystal analysis from synchrotron diffraction data. For these complexes, the Cu(II) ions are five-coordinate in an axially elongated square-pyramidal environment, with the four amine N atoms at the equatorial positions and the Cl atom (<B>1</B>) or N atom of one azide (<B>2</B>) at an apical site. The CuN bond lengths for amine N atoms in the complex <B>1</B> (2.0198(13)–2.0735(12) A°) and complex <B>2</B> (2.0239(9)–2.0489(9) Å) are typical, but the axial ligands are coordinated with a CuCl bond length of 2.5962 (7) Å for complex <B>1</B>, and the CuN (azido) bond length is 2.1990 (10) Å for complex <B>2</B>, adopting square-planar geometry around the Cu(II) with four N atoms from two <I>N</I>-Metn or Me<SUB>2</SUB>tn ligands. The crystals are stabilized by a three-dimensional network of intermolecular hydrogen bonds that are formed between the primary and secondary amine groups of the <I>N</I>-Metn ligands, the Cl ligands, and the F atoms of BF<SUB>4</SUB> <SUP>−</SUP> anion in <B>1</B>, and by the primary amine groups of the Me<SUB>2</SUB>tn ligands and the N atoms of the azido ligand and azide ion in <B>2</B>. Hirshfeld surface analysis with 2D fingerprint plots revealed that the H⋯H, F⋯H, Cl⋯H contacts in <B>1</B> and the H⋯H and N⋯H contacts in <B>2</B> are the main intermolecular interactions. The electronic absorption and IR spectral properties are also discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Syntheses of two new Cu(II) complexes. </LI> <LI> Two Cu(II) complexes are structurally characterized through single crystal X-ray diffraction. </LI> <LI> Spectroscopic and magnetic properties including Hirshfeld surface analysis are also described. </LI> </UL> </P>

‘라이트박스’ 무색/핑크/블루 합성 다이아몬드의 분광학적 분석

최현민,김영출,이민경,석정원 한국결정성장학회 2020 한국결정성장학회지 Vol.30 No.1

이 논문은 라이트박스의 주력 상품인 세 가지 색의 합성 다이아몬드의 분광학적 특성에 대해 분석한 결과이다. 드비어스의 브랜드인 라이트박스 주얼리는 2018년 9월부터 CVD 합성 다이아몬드를 판매하기 시작했다. 본 연구에서 검사된샘플은 0.25 ct, 0.25 ct, 0.26 ct의 무색(H grade), 핑크, 청색의 합성 다이아몬드이며, 각 샘플의 테이블 중앙에는 라이트박스로고가 레이저 각인되어 있었다. 분광학적 기법에 기초한 분석 결과, 무색 샘플은 결정성장 후 색 향상을 위한 고온고압 처리과정을 거치지 않았다. 핑크 샘플은 H3, 3H, 594 nm, NV, GR1의 광학 결함이 발견되었고, 이로 인해 결정성장 후 색 향상을 위해 조사와 열처리 과정을 거친 것으로 판단했다. 또한 블루 샘플은 열처리 과정 없이 조사만 되었음을 알 수 있었다. This article reports the result on the spectroscopic analysis of the three Lightbox CVD-grown diamonds. Lightbox Jewelry, a De Beers company, has begun selling CVD laboratory-grown diamonds since September 2018. Recently, we had the opportunity to examine three Lightbox’s pendant necklaces. The 0.25 ct, 0.25 ct, and 0.26 ct round brilliant were graded as “H” n ear colorless, F ancy Vivid o rangy pink, a nd F ancy Vivid b lue with c ut g rades of excellent, respectively. T he l aserinscribed Lightbox logo under the table, large enough to be easily visible with a microscope. Based on the spectroscopic techniques, for near colorless sample was not subjected to post-growth HPHT processing to improve its color. For pink sample, optical centers at H3, 3H, 594 nm, NV, and GR1 were recorded. It was speculated that the pink sample have been received irradiation and annealing. In addition, the blue CVD synthetic sample was concluded to be irradiated without annealing.

Adsorption Kinetics for Polymeric Additives in Papermaking Aqueous Fibrous Media by UV Spectroscopic Analysis

Yoon, Sung-Hoon,Chai, Xin-Sheng Korean Chemical Society 2006 Bulletin of the Korean Chemical Society Vol.27 No.11

The general objective of the present study was to investigate the potential application of the UV spectroscopic method for determination of the polymeric additives present in papermaking fibrous stock solutions. The study also intended to establish the surface-chemical retention model associated with the adsorption kinetics of additives on fiber surfaces. Polyamide epichlorohydrin (PAE) wet strength resin and imidazolinium quaternary (IZQ) softening agents were selected to evaluate the analytical method. Concentrations of PAE and IZQ in solution were proportional to the UV absorption at 314 and 400 nm, respectively. The time-dependent behavior of polymeric additives obeyed a mono-molecular layer adsorption as characterized in Langmuir-type expression. The kinetic modeling for polymeric adsorption on fiber surfaces was based on a concept that polymeric adsorption on fiber surfaces has two distinguishable stages including initial dynamic adsorption phase and the final near-equilibrium state. The simulation model predicted not only the real-time additive adsorption behavior for polymeric additives at high accuracy once the kinetic parameters were determined, but showed a good agreement with the experimental data. The spectroscopic method examined on the PAE and IZQ adsorption study could potentially be considered as an effective tool for the wet-end retention control as applied to the paper industry.

NMR Spectroscopic Analysis on the Chiral Recognition of Noradrenaline by β-Cyclodextrin ( β-CD) and Carboxymethyl- β-cyclodextrin (CM- β-CD)

Lee, Sang-Hoo,Yi, Dong-Heui,Jung, Seung-Ho Korean Chemical Society 2004 Bulletin of the Korean Chemical Society Vol.25 No.2

${\beta}$-CD and CM- ${\beta}$-CD as chiral NMR shift agents were used to resolve the enantiomers of noradrenaline (NA). The stoichiometry of each complex formed between the CDs and the enantiomers of NA was found to be 1 : 1 through the continuous variation plots. The binding constants (K) of the complexes were determined from $^1H$ NMR titration curves. This result indicated that both ${\beta}$-CD and CM- ${\beta}$-CD formed the complexes with the S(+)-NA more preferentially than its R(-)-enantiomer. The K values for the complexes with ${\beta}$-CD ($K_{S(+)}$ = 537 $M^{-1}$ and $K_{R(-)}$ = 516 $M^{-1}$ was larger than those with CM- ${\beta}$-CD ($K_{S(+)}$ = 435 $M^{-1}$ and $K_{R(-)}$ = 313 $M^{-1}$), however, enantioselectivity (${\alpha}$) of S(+)- and R(-)-NA to CM- ${\beta}$-CD ( ${\alpha}$ = 1.38) was larger than that to ${\beta}$-CD ( ${\alpha}$ = 1.04), indicating that CM- ${\beta}$-CD was the better chiral NMR solvating agents for the recognition of the enantiomers of NA. Two dimensional rotating frame nuclear Overhauser enhancement spectroscopy (ROESY) experiments were also performed to explain the binding properties in terms of spatial fitting of the NA molecule into the macrocyclic cavities.

In-situ Raman Spectroscopic and Kinetic Analysis of Mixed Gas Hydrates

Hai Truong-Lam(트루옹람손하이),Changsu Jeon(전창수),Ju Dong Lee(이주동) 한국신재생에너지학회 2021 한국신재생에너지학회 학술대회논문집 Vol.2021 No.7

Raman spectroscopy is well-suited for clathrate hydrate studies of aqueous-hydrate conditions because it is not susceptible to interference from aqueous environments. In order to obtain more specific and ongoing information on gas hydrate formation, two different in-situ Raman spectrometers with specially designed fiber-optic probes were used in a semi-batch stirred reactor. With these arrangements, it was possible to obtain macroscopic and microscopic data simultaneously during hydrate formation. This study introduces the basic principle of in-situ Raman spectroscopy and summarizes its application in gas hydrate studies. With aid of in-situ Raman results, not only can the information about gas composition and structural type be deduced, but also the occupancy of cages and even gas solubility can be calculated from the relative intensities of Raman peaks. Furthermore, the shape and position of the Raman signals of the host molecules (H₂O) also contain useful additional information. During hydrate formation/decomposition processes, vapor compositions of binary (CH<SUB>4</SUB>/C<SUB>3</SUB>H<SUB>8</SUB> and SF6/HFC-134a) gas mixtures were analyzed by in-situ Raman spectroscopy and the results were consistent with that obtained by gas chromatography. Based on in-situ Raman observations, we are able to determine the time-dependent encapsulation of guest molecules and gas solubility under hydrate formation conditions. The results expected to provide valuable information for gas hydrate studies.

나노결정 구조 티타니아의 Raman 분광 분석과 밴드갭

김경수 ( Kim Gyeong Su ),정일현 ( Jeong Il Hyeon ) 한국공업화학회 2003 공업화학 Vol.14 No.8

플라즈마에 의해 제조된 나노 결정 구조의 티타니아에 대하여 Raman 분광 분석과 밴드갭의 특성을 알아보았다. 플라즈마에 의해 제조된 분말은 Ti(OBu)_(x)(Ac)_(y) 화합물로서 열처리한 분말을 Raman 분광 분석을 수행한 결과 193, 394, 513, 634 cm^(-1)에서 아나타제를, 233, 443, 609 cm^(-1)에서 루틸을 확인할 수 있었다. 분말의 밴드갭은 무정형 분말이 약 2.2 eV이었고, 아나타제는 3.0~3.8 eV의 값을 가졌다. 또한 루틸과 루틸ㆍ아나타제 혼용된 경우 약 2.6 eV 이었으며, 출력에 따른 영향이 낮은 것으로 확인되었다. The vibrational characteristics and band gap properties of the nano-crystalline titania, which was prepared by plasma synthesis, were investigated using Rarnan spectroscopy. Ti(OBu)x(Ac)y was produced, and the characteristics vibrational peaks of its anatase and rutile forms were observed at 193, 39.1, 513, 634cm^(-1) and 223, 443, 609 cm^(-1), respectively. The band gaps of amorphous powder and anatase forms were 2.2 and 3.0∼3.8eV_(1) respectively. In the case of the mixed rutie and anatase form, the band gap was observed to be 2.6 eV.

ORIGIN AND STATUS OF LOW-MASS CANDIDATE HYPERVELOCITY STARS

Bum-Suk Yeom,이영선,구재림,Timothy C. Beers,김영광 한국천문학회 2019 Journal of The Korean Astronomical Society Vol.52 No.3

We present an analysis of the chemical abundances and kinematics of six low-mass dwarf stars, previously claimed to be candidate hypervelocity stars (HVSs). We obtained moderate-resolution ($R\sim6000$) spectra of these stars to estimate the abundances of several chemical elements (Mg, Si, Ca, Ti, Cr, Fe, and Ni), and derived their space velocities and orbital parameters using proper motions from the \gaia\ Data Release 2. All six stars are shown to be bound to the Milky Way, and in fact are not even considered high-velocity stars with respect to the Galactic rest frame. Nevertheless, we attempt to characterize their parent Galactic stellar components by simultaneously comparing their element abundance patterns and orbital parameters with those expected from various Galactic stellar components. We find that two of our program stars are typical disk stars. For four stars, even though their kinematic probabilistic membership assignment suggests membership in the Galactic disk, based on their distinct orbit l properties and chemical characteristics, we cannot rule out exotic origins as follows. Two stars may be runaway stars from the Galactic disk. One star has possibly been accreted from a disrupted dwarf galaxy or dynamically heated from a birthplace in the Galactic bulge. The last object may be either a runaway disk star or has been dynamically heated. Spectroscopic follow-up observations with higher resolution for these curious objects will provide a better understanding of their origin.

Diverse Chemo-Dynamical Properties of Nitrogen-Rich Stars Identified from Low-Resolution Spectra

김창민,이영선,Timothy C. Beers,김영광 한국천문학회 2023 Journal of The Korean Astronomical Society Vol.56 No.1

The second generation of stars in the globular clusters (GCs) of the Milky Way (MW) exhibit unusually high N, Na, or Al, compared to typical Galactic halo stars at similar metallicities. The halo field stars enhanced with such elements are believed to have originated in disrupted GCs or escaped from existing GCs. We identify such stars in the metallicity range -3.0 < [Fe/H] < 0.0 from a sample of ~36,800 giant stars observed in the Sloan Digital Sky Survey and Large Sky Area Multi-Object Fiber Spectroscopic Telescope survey, and present their dynamical properties. The N-rich population (NRP) and N-normal population (NNP) among our giant sample do not exhibit similarities in either in their metallicity distribution function (MDF) or dynamical properties. We find that, even though the MDF of the NRP looks similar to that of the MW's GCs in the range of [Fe/H] < -1.0, our analysis of the dynamical properties does not indicate similarities between them in the same metallicity range, implying that the escaped members from existing GCs may account for a small fraction of our N-rich stars, or the orbits of the present GCs have been altered by the dynamical friction of the MW. We also find a significant increase in the fraction of N-rich stars in the halo field in the very metal-poor (VMP; [Fe/H] < -2.0) regime, comprising up to ~20% of the fraction of the N-rich stars below [Fe/H] = -2.5, hinting that partially or fully destroyed VMP GCs may have in some degree contributed to the Galactic halo. A more detailed dynamical analysis of the NRP reveals that our sample of N-rich stars do not share a single common origin. Although a substantial fraction of the N-rich stars seem to originate from the GCs formed in situ, more than 60% of them are not associated with those of typical Galactic populations, but probably have extragalactic origins associated with Gaia Sausage/Enceladus, Sequoia, and Sagittarius dwarf galaxies, as well as with presently unrecognized progenitors.