• Title/Summary/Keyword: Disordered carbon

Search Result 35, Processing Time 0.018 seconds

Nanoconfinement of Hydrogen and Carbon Dioxide in Palygorskite (팔리고스카이트 내 수소 및 이산화탄소 나노공간한정)

  • Juhyeok Kim;Kideok D. Kwon
    • Korean Journal of Mineralogy and Petrology
    • /
    • v.36 no.4
    • /
    • pp.221-232
    • /
    • 2023
  • Carbon neutrality requires carbon dioxide reduction technology and alternative green energy sources. Palygorskite is a clay mineral with a ribbon structure and possess a large surface area due to the nanoscale pore size. The clay mineral has been proposed as a potential material to capture carbon dioxide (CO2) and possibly to store eco-friendly hydrogen gas (H2). We report our preliminary results of grand canonical Monte Carlo (GCMC) simulations that investigated the adsorption isotherms and mechanisms of CO2 and H2 into palygorskite nanopores at room temperature. As the chemical potential of gas increased, the adsorbed amount of CO2 or H2 within the palygorskite nanopores increased. Compared to CO2, injection of H2 into palygorskite required higher energy. The mean squared displacement within palygorskite nanopores was much higher for H2 than for CO2, which is consistent with experiments. Our simulations found that CO2 molecules were arranged in a row in the nanopores, while H2 molecules showed highly disordered arrangement. This simulation method is promising for finding Earth materials suitable for CO2 capture and H2 storage and also expected to contribute to fundamental understanding of fluid-mineral interactions in the geological underground.

Magnetic Properties of FePt:C Nanocomposite Film

  • Ko, Hyun-Seok;A. Perumal;Shin, Sung-Chul
    • Proceedings of the Korean Magnestics Society Conference
    • /
    • 2003.06a
    • /
    • pp.220-221
    • /
    • 2003
  • Equiatomic FePt and CoPt alloy thin films have received considerable attention as possible magnetic and magneto-optic recording because of their high magnetic anisotropy energy and high coercivity. The high coercivity in these thin films is due to the presence of finely dispersed ordered FePt phase mixed with disordered FePt phase. However, a high temperature treatment, either substrate heating during deposition or post annealing, is needed to obtain the ordered L1$\_$0/ phase with high value of magneto crystalline anisotropy. Recent microstructural studies on these films suggest that the average grain size ranges from 10-50 nm and the grains are magnetically coupled between each other. On the other hand, the ultrahigh-density magnetic recording media with low media noise imposes the need of a material, which consists of magnetically isolated grains with size below 10 nm. The magnetic grain isolation can be controlled by the amount of additional non-magnetic element in the system which determines the interparticle separation and therefore the interparticle interactions. Recently, much research work has been done on various non-magnetic matrices. Preliminary studies showed that the samples prepared in B$_2$O$_3$ and Carbon matrices have shown strong perpendicular anisotropy and fine grain size down to 4nm, which suggest these nanocomposite films are very promising and may lead to the realization of a magnetic medium capable of recording densities beyond 1 Tb/in$^2$. So, in this work, the effect of Carbon doping on the magnetic properties of FePt nanoparticles were investigated.

  • PDF

Two Possible Space Groups of Ttis(tekaethylammonium) [bis(trimetaphosphate $\kappa^3O, O^', O^{"}$)] Vanadate(3-),$[V(P_3O_9)_2](NC_8H_{20})3$ (Tris(tetraethylammnnium) [bis(trimetaphosphate $\kappa^3O, O^', O^{"}$)] Vamdate(3-),$[V(P_3O_9)_2](NC_8H_{20})_3$,의 두가지 가능한 공간군)

  • 서일환;이진호
    • Korean Journal of Crystallography
    • /
    • v.5 no.1
    • /
    • pp.1-6
    • /
    • 1994
  • Two possible space groups of the comfound, VP6N3018C24H:60, are: P 1, a=14.022(1), b=12.644(2), c= 12.640(1)A, a=8038(1), B=102.12(1), r=102.16(1), V=2124.1A3, Z=2, μ=0.47cm-1, d=1.46g/cm3, R=0.083 for 3350 independent reflections with Fo>4o IFI, and C2/c, a=19.32(2), b=16.32(2), c=14.02(1)A, B=105.98(5), β=105.98(5), V=4248.2A3, Z=4 R=0.083 for 1590 independent reflections with Fo>4c IFoI . In the space group P T, there are two monlecules in a unit cell. Vanadium atoms in the two monlecules occupy the two different special positions such that the complete monlecules are accomplished by the two independent center of symmetry. Therefore two different half molecules of bis(trimetaphosphate)vanadate and three molecules of tetraethylammonium are the asymmetric unit in a unit cell. In the space group C2/c, however, the vanadium atom is located at a special position with centrosymmetry, and a two-fold symmetry axis passes through C2/c, N2 and C25 atoms. Therefore the asymmrtic unit in a unit cell consists of a half molecule of bis(trimetaphosphate)vanadate and one and a half molecules of tetraethylammonium. All the molecular conformations in both space groups are very similar: six oxygen atoms coordinated to a vanadium atom in the bi s(trimetaphosphate)vanadate molecule form an octahedron and the four carbon atoms bonded to a nitrogen atom in the tetraethylammonium molecule are disordered so that the eight carbon atoms around nitrogen atom exhibit an irregular dodecahedral form.

  • PDF

The Crystal Structure of Tris(ethylenediamine)nickel(II)-dichromate, $[Ni(C_2N_2H_8)_3]\cdotCr_2O_7$ ($[Ni(C_2N_2H_8)_3]\cdotCr_2O_7$의 결정구조)

  • Kim, Se-Hwan;Kim, Seung-Bin;Nam, Gung-Hae
    • Korean Journal of Crystallography
    • /
    • v.7 no.1
    • /
    • pp.36-43
    • /
    • 1996
  • The crystal structure Tris(ethylenediamine)nickel(II)Dichromate has been determined by X-ray crystallography. Crystal data: a=8.268(2), b=13.865(2), c=14.921(2)Å, γ=102.04(2)°, V=1672.9(5)Å3, Z=4, Monocline, P21/b (space group No.=14), Dcalc=1.806 gcm-3, μ=24.05 cm-0.1. The intensity data were collected with Mo-Kα radiation(λ=0.7107Å) on an automatic four-circle diffractometer with a graphite monochromator. The structure was solved by Patterson method and refined by full matrix least-square methods using unit weights. The final R and S values were R=0.045, Rw=0.051, Rall=0.059 and S=2.171for 2248 observed reflections. The two carbon atoms of a ring of Ni(en)-ion were split into crossed four atoms. In consideration of α- and β-angles of two rings of a disordered ethylenediamine of Nien3-ion and the hydrogen bonds between Ni(en)3-cation and Cr2O7-anion, the configuration of Ni(en)3-ion is assumed to be disordered with Λδδδ and Λδδλ.

  • PDF

Stage transformation characteristice of Li, K and Na-graphite intercalation compounds (Li, K과 Na-흑연 층간화합물의 stage 전이특성)

  • 오원춘;임창성;오근호;고영신
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.8 no.1
    • /
    • pp.83-90
    • /
    • 1998
  • Stage transformation characteristics of Li, K and Na-graphite deintercalation compounds (GDICs) were studied under consideration of a deintercalation mechanism of the intercalants between carbon layers. Li-graphite intercalation compounds (GICs) synthesized by a controlling temperatures and pressures have been spontaneously decomposed in the atmosphere. By X-ray differaction analysis the $d_{001}$-values of stage 1 and 2 were identified to be 3.71 and 7.06 $\AA$, respectively. After 6 weeks, the deintercalation reaction of the Li-GICs ceased and only residual compounds could be observed. K-GICs were synthesized by the modified two-bulb method resulting in structural stabilities and stage transitions. By X-ray diffraction analysis the very stable K-graphite residue compounds were observed after 10 weeks. Na-GICs with stage 1 and 2 were synthesized using the high temperature and pressure technique. The temperature dependence of a deintercalation reaction and a thermal stability of Na-GICs were discussed. The structure changes of the Na-GDICs depending on heating rates were identified by X-ray diffraction. According to the deintercalation process, the stage transformations could be attributed to irregular deintercalations of the GDICs with disordered stage.

  • PDF