• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.123-130
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• 2005

Zeolite X adsorbents with large surface area were prepared for using oxygen PSA adsorbent. Selective adsorption performance of nitrogen on the synthesized zeolite X adsorbent was improved by the cation exchange of adsorbent. The zeolite X which had over $650m^2/g$ surface area was synthesized at the conditions of $SiO_2\;:\;Na_2O\;:\;H_2O\;:\;Al_2O_3$ = 2.5 : 3.5 : 150 : 1 mole ratio, $98^{\circ}C$ temperature and 18 h synthesized time in 50 L reactor. The metal ions Li, Ag, Ca, Br, Sr, etc. were investigated for ion exchange with zeolite X. Ag ion was showed the highest ion exchange rate among these metal ions and all metal ions were exchanged with Na ion at equivalent rate. Compared with the NaX adsorbent, the ion exchanged zeolite X adsorbent remarkably improved its adsorption performance of nitrogen at the conditions of $10{\sim}40^{\circ}C$ temperature and 0~9 atm pressure. At an equilibrium pressure under 0.5 atm, adsorption performance of nitrogen on the ion exchanged zeolite adsorbent increased in the order of Ag > Li > Ca > Sr> Ba > K, whereas at an equilibrium pressure over 1 atm showed in the order of Li > Ag > Ca > Sr > Ba > K. Nitrogen/oxygen separation factor of Li ion exchanged zeolite X adsorbent was 13.023 at the partial pressure of nitrogen/oxygen gas mixture similar to air and $20^{\circ}C$ adsorption temperature.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.3
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• pp.201-205
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• 2010

Most of iodine was captured by the block when NaI solution flowed through a bentonite block sorbed silver to retard the migration of iodine released from high-level radioactive wastes. In order to understand in detail the mechanism for the retardation of the iodine by the silver ion, X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectra of the silver sorbed bentonite before and after the contact with iodide were compared with those of AgO, $Ag_2O$ and AgI as references. This examination suggests that the silver ion sorbed on the bentonite is desorbed, and then it retards the migration of iodine by forming the cluster of AgI precipitate.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.3
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• pp.19-24
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• 2011

we successfully synthesized $TiO_2$-Ag composite nanowires via an electrospinning method and investigated the relationship between their electrochemical properties and structures by means of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and cycler. It is shown that the $TiO_2$-Ag composite nanowires exhibit superior electrochemical properties when compared to the single $TiO_2$ nanowires and $TiO_2$ nanoparticles (P25, Degussa). Therefore, the results indicate that the introduction of Ag nanophases within the electrospun $TiO_2$ nanowires could be improved the capacitance and cycleability of electrodes in Li-ion batteries.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.1-6
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• 2002

Silver doped vanadium pentoxides with a doping ratio Ag/V ranging from 0.03 to 0.11 were synthesized by sol-gel process, and $Li/Ag_xV_2O_5$ cell was investigated by the electrochemical methods. It appears to be amorphous layered material and entangled fibrous textures has been grown to form anisotropic corrugated fibrils. NMR measurements revealed that several different kinds of $Li^+$ ions exist in the lithium intercalated xerogel electrodes and the average cell potential was about 3.0V vs. $Li/Li^+$. The cell capacity of the silver doped $Ag_xV_2O_5$ xerogel cathodes was more than 359 mAh/g at discharge current 10mA/g and cycle efficiency $94\%$ was achieved.

• Journal of Powder Materials
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• v.18 no.2
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• pp.159-167
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• 2011

The influence of sulfate on the selective catalytic reduction of $NO_x$ on the Ag/$Al_2O_3$ catalyst was studied when $CH_4$ was used as a reducing agent. Various preparation methods influenced differently on the $deNO_x$ activity. Among the methods, cogelation precipitation gave best activity. When sulfates were formed on the surfaces of samples prepared by impregnated and deposition precipitation, $deNO_x$ activity was enhanced as long as suitable forming condition is satisfied. The major sulfate formed in Ag/$Al_2O_3$ catalyst was the aluminum sulfate and it seems that this sulfate acted as a promoter. When Mg was added to the Ag/$Al_2O_3$ catalyst it promoted $deNO_x$ activity at high temperature. Intentionally added sulfate also enhanced $deNO_x$ activity, when their amount was confined less than 3 wt%.

• Journal of Magnetics
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• v.17 no.3
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• pp.176-184
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• 2012

The structural, magnetic and magnetotransport properties of $La_{0.67}Ca_{0.33}MnO_3$: $Ag_x$ (x = 0, 0.1, 0.2, 0.3 and 0.4) composites were investigated systematically. X-ray and EDX analysis indicated that Ag is not substituted into the main $La_{0.67}Ca_{0.33}MnO_3$ phase and remains an additive to the second phase at the grain boundary. The Curie temperature first decreased from 269 K for x = 0 to 257 K for x = 0.1 and then remained nearly unchanged with increasing Ag content. For the x > 0.1 samples, a second transition temperature ($T_{MI2}$) was observed in the resistance curves. At temperatures below 150 K, a significant enhancement in MR was observed while high temperature MR decreased with increasing Ag content. The maximum MR was observed to be 55% in the x = 0.4 sample at 10 K and a 6T magnetic field, this value is larger than that of pure $La_{0.67}Ca_{0.33}MnO_3$ (53% at 265 K and 6 T). In addition, at low fields (H < 1T), a sharp increase in the MR was observed.

• Bulletin of the Korean Chemical Society
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• v.5 no.4
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• pp.135-140
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• 1984

The reduction of vacuum-dehydrated $Na_xAg_{12-x}-A, 0 {\le} x {\le} 9.2$, and its reoxidation by O$_2$, have been studied by X-ray powder diffraction. Also, the structure of $Na_6Na_6-A$ treated with hydrogen at room temperature has been studied by single crystal methods in the cubic space group Pm3m at $24{\circ}C (a = 12.221(2) {\AA})$. The diffraction pattern of dehydrated Ag$_{12}$-A reduced by H$_2$ contains only the (111) and (200) reflections of silver metal, indicationg that the zeolite structure has been lost, but the zeolite's diffraction pattern and structural integrity can be fully restored by oxidation with O$_2$ at 100 or 200${\circ}C$. In contrast, the structures of $Na_xAg_{12-x}-A$, x = 4.5 and 9.2, were not destroyed by treatment with hydrogen. Dehydrated Na$_6Ag_6$-A treated with 50 Torr of hydrogen gas at 24${\circ}C$ for 30 minutes has $6\; Na^+\;and\;1.27\;Ag^+$ ions at 6-ring sites. These $Ag^+ ions are associated with 2.54 Ag${\circ}$ atoms to form 1.27 $Ag_3^+$ clusters per unit cell. Also found were 0.7 $Ag_3^{2+}$ clusters per unit cell near the 8-rings. The structure was refined to the final error indices R$_1$ = 0.134 and R$_2$ (weighted) = 0.147, using 168 independent reflections for which $I_0 >3{\sigma}(I_0)$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.210-213
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• 2011

Glass-ceramics composed of $5Na_2O-36CaO-10TiO_2-xP_2O_5$ could be obtained with $P_2O_5$ content as following procedure: 1) leaching out $Ca_3(PO_4)_2$ crystals between $Ca_3(PO_4)_2$ and $NaTi_2(PO_4)_3$ selectively in 1 N HCl solution for 2 days, and 2) exchanging $Na^+$ ion to $Ag^+$ ion in Ag($NO_3$) solution for 1 day. Scanning electron microscope (SEM) and X-rat diffractometer (XRD) were measured to verify the proper synthesis of glass-ceramics. And anti-bacteria test was accomplished using Staphylococus aureus bacteria. In the results of anti-bacteria test, the bacteria were died perfectly after 3 hours.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1483-1490
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• 1994

YBa2Cu3Ox-Ag(YBCO-Ag) thick films were fabricated on the zirconia substrate by a screen printing method. The starting powder was a mixture of YBCO, prepared by a coprecipitation in oxalic acid, and Ag2O. The influence of heat treatment conditions on properties of thick films was investigated. It was observed that Jc of thick films was directly proportional to the orientation factor of thick films and the optimimum preparation condition was the heat treatment of thick films at 100$0^{\circ}C$ for 3 min in O2. The improvement of Jc by the addition of Ag was considered as a result of the suppression of microcracks in the films.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.365-369
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• 2018

We perform density functional theory calculations to study the CO and $O_2$ adsorption chemistry of Pt@X core@shell bimetallic nanoparticles (X = Pd, Rh, Ru, Au, or Ag). To prevent CO-poisoning of Pt nanoparticles, we introduce a Pt@X core-shell nanoparticle model that is composed of exposed surface sites of Pt and facets of X alloying element. We find that Pt@Pd, Pt@Rh, Pt@Ru, and Pt@Ag nanoparticles spatially bind CO and $O_2$, separately, on Pt and X, respectively. Particularly, Pt@Ag nanoparticles show the most well-balanced CO and $O_2$ binding energy values, which are required for facile CO oxidation. On the other hand, the $O_2$ binding energies of Pt@Pd, Pt@Ru, and Pt@Rh nanoparticles are too strong to catalyze further CO oxidation because of the strong oxygen affinity of Pd, Ru, and Rh. The Au shell of Pt@Au nanoparticles preferentially bond CO rather than $O_2$. From a catalysis design perspective, we believe that Pt@Ag is a better-performing Pt-based CO-tolerant CO oxidation catalyst.