• Applied Chemistry for Engineering
• /
• v.29 no.4
• /
• pp.376-381
• /
• 2018

The purpose of this study is to investigate and optimize an effectiveness process for the recovery of Pd from the spent Pd/C catalyst by the process of hydrogenation of maleic anhydride over Pd/C. Pd solution recovered from Pd/C catalyst was used to prepare Pd/C catalysts. Their characteristics were compared to those of Pd/C catalyst prepared by using a reagent grade precursor solution. Pd in the spent catalyst was leached by the modified process with dry and wet methods to obtain the high recovery ratio of Pd. The burn-out of carbon in the spent Pd/C catalyst was carried out in the rage of $600-900^{\circ}C$. Pd content of carbonized catalyst was confirmed by XRF and ICP. Pd was extracted from carbonized spent catalysts with acid solutions of 1,2 and 4 M HCl at a leaching temperature of $90^{\circ}C$ for 2 h. The high recovery ratio of Pd was shown as 92.4% that leached in 4 M HCl. Also Pd/C catalysts were prepared by using the leached solution and the reagent grade of $H_2PdCl_4$ as a precursor solution and the characteristics were analyzed by XRD, CO-chemisorption and FE-TEM. As a result, the dispersion of the catalyst prepared by using the leached solution was 34.6%, which was found to be equal to or more than that of the Pd/C catalyst prepared by the reagent grade precursor solution.

• Economic and Environmental Geology
• /
• v.26 no.3
• /
• pp.327-335
• /
• 1993

Phase relations in the system Pd-Sb-Te were investigated at $1000^{\circ}$, $800^{\circ}$, and $600^{\circ}C$, using the sealed-capsule technique; the quenched products were studied by reflected light microscopy, X-ray diffraction, and electron microprobe analysis. At $1000^{\circ}C$, the solid phases Pd, $Pd_{20}Sb_7$, $Pd_8Sb_3$, $Pd_{31}Sb_{12}$, and $Pd_5Sb_2$ are stable with a liquid phase that occupies most of the isothermal diagram. Additional solid phases at $800^{\circ}C$ are $Pd_5Sb_3$, PdSb, $Pd_8Te_3$, $Pd_7Te_3$, and a continuous $Pd_{20}Te_7-Pd_{20}Sb_7$ solid solution becomes stable. At $600^{\circ}$, $PdSb_2$, $Pd_{17}Te_4$, $Pd_9Te_4$, PdTe, $PdTe_2$, $Sb_2Te_3$, and Sb and continuous PdSb-PdTe and $PdTe-PdTe_2$ solid solutions are stable. All the solid phases exhibit solid solution, mainly by substitution between Sb and Te to an extent that varies with temperature of formation. The maximum substitution (at.%) of Te for Sb in the Pd-Sb phases is: 44.3 in $Pd_8Sb_3$, 52.0 in $Pd_{31}Sb_{12}$, 46.2 in $Pd_5Sb_2$ at $800^{\circ}C$; 15.3 in $Pd_5Sb_3$, 68.3 in $PdSb_2$ at $600^{\circ}C$. The maximum substitution (at.%) of Sb for Te in the Pd-Te phases is 34.5 in $Pd_5Sb_3$ at $800^{\circ}C$, and 41.6 in $Pd_7Te_3$, 5.2 in $Pd_{17}T_4$, 12.4 in $Pd_9Te_4$, and 19.1 in $PdTe_2$ at $600^{\circ}C$. Physical properties and X-ray data of the synthetic $Pd_9Te_4$, PdTe, $PdTe_2$, $Pd_8Sb_3$, PdSb, and $Sb_2Te_3$ correspond very well with those of telluropalladinite, kotulskite, merenskyite, mertieite II, sudburyite, and tellurantimony, respectively. Because X-ray powder diffraction data consistently reveal a 310 peak ($2.035{\AA}$), the $PdSb_2$ phase is most probably of cubic structure with space group $P2_13$. The X-ray powder pattern of a phase with PdSbTe composition, synthesized at $600^{\circ}C$, compares well with that of testibipalladite. Therefore, testibiopalladite may be a member of the $PdSb_2-Pd(Sb_{0.32}Te_{0.68})$ solid solution series which is cubic and $P2_13$ in symmetry. Thus the ideal fonnula for testibiopalladite, presently PdSbTe, must be revised to PdTe(Sb, Te). Borovskite($pd_3SbTe_4$) has not been found in the synthetic system in the temperature range $1000^{\circ}-600^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.11a
• /
• pp.396-398
• /
• 2006

PdPt/C (Pd:Pt atomic ratio of around 19:1 60wt, %) 촉매를 고분자전해질 연료전지용 전극 촉매소재의 적용하였다. PdPt/C 촉매를 산화극 촉매로, 환원극 촉매로는 Pt/C 촉매를 사용하고 반대로 산화극 촉매는 Pt/C 촉매, 환원극 촉매로는 PdPt/C 촉매를 사용했을 때, PdPt/C 촉매를 산화극과 환원극 촉매로 동시에 사용했을 때의 고분자전해질 연료전지의 단위전지 성능을 각각 비교하였다. PdPt/C촉매를 산화극에만 적용했을 때에 Pt/C 상용촉매를 산화극과 환원극에 모두 적용했을 때의 성능만큼 좋은 성능을 확인할 수 있었다. 환원극 촉매는 Pt/C를 사용하고 산화극 촉매를 PdPt/C Pt/C Pd/C를 사용하였을 매의 성능을 비교하였다. Pd/C를 산화극 촉매로 사용한 단위전지가 나머지 두 경우의 성능에 비하여 현저히 떨어짐을 확인할 수 있었다. 이는 극소량의 Pt 량을 포함한 PdPt/C 촉매가 고분자전해질 연료전지의 산화극 Pt/C 촉매의 대체촉매로 사용 가능함을 보여준다.

• Applied Chemistry for Engineering
• /
• v.26 no.5
• /
• pp.575-580
• /
• 2015

Pd/C catalysts were prepared by various preparation methods such as ion exchange, impregnation and polyol method and also characterized by nitrogen adsorption-desorption isothermal, XRD, FE-TEM and CO-chemisorption. The activities of these catalysts were tested in the hydrogenation of cyclohexene to cyclohexane. Catalytic activities of Pd/C catalysts were found to be effected by the chosen preparation methods. Pd dispersions of each Pd/C catalysts prepared by ion exchange, impregnation and polyol method were 17.55, 13.82% and 1.35%, respectively, confirmed by CO-chemisorption analysis. These were also in good agreement with the FE-TEM results. The Pd/C catalyst prepared by ion exchange method exhibits good performance with the cyclohexene conversion rate of 71% for 15 min. These results indicate that Pd/C catalyst having higher dispersion and lower particle size is in favor of hydrogenation cyclohexene and also Pd dispersion increases with the increment of catalytic activity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.275-275
• /
• 2008

This paper describe the fabrication of a Pd/polycrystalline 3C-SiC schottky diode and its characteristics, in which the polycrystalline 3C-SiC layer and Pd Schottky contact were deposited by using APCVD and sputter, respectively. Crystalline quality, uniformity, and preferred orientations of the Pd thin film were evaluated by SEM and XRD, respectively. Pd/poly 3C-SiC Schottky diodes were fabricated and characterized by I-V and C-V measurements. Its electric current density Js and barrier height voltage were measured as $2\times10^{-3}$ A/$cm^2$ and 0.58 eV, respectively. These devices were operated until about $400^{\circ}C$. Therefore, from these results, Pd/poly 3C-SiC Schottky devices have very high potential for high temperature chemical sensor applications.

• Electrical & Electronic Materials
• /
• v.1 no.3
• /
• pp.251-260
• /
• 1988

n형 GaAs에 음성접촉을 형성함에 있어서 Au-Ge 공융합금을 용해시키는 alloying 보다는 sintering을 필요로 하는 Su-Pd-Ge계의 새로운 융성접촉을 도입하였다. Au-Pd-Ge계의 최적의 음성조건을 조사하기 위하여 Au/Pd/Ge, Au/Ge/Pd, Au/Pd/Ge/Pd 그리고 Au/Pd/Au/Ge 음성접촉을 제조하였다. 비접촉저항을 조사하는데 있어서 sintering 온도는 390-450.deg.C사이였고 시간은 30초에서 6분 사이였다. Au-Pd-Ge계의 비접촉저항은 alloying된 Au/Pd/Ge 접촉의 그것에 필적할 만큼 낮았으며 특히 Au/Ge/Pd 접촉은 430.deg.C, 3분의 sintering 조건에서 가장 낮은 1.2*$10^{-6}$.OMEGA..$cm^{2}$의 비접촉저항을 나타냈다. Au/Ge/Pd 접촉의 표면형상 및 접촉패턴 가장자리는 450.deg.C에서 2분 이상 sintering된 접촉을 제외하고는 sintering 후에 as-deposited 상태와 다를 바가 없었다. 430.deg.C, 3분 sintering에서 가장 낮은 비접촉저항을 나타낸 Au/Ge/Pd 접촉의 비접촉저항은 430.deg.C에서 Ge/Pd 두께 변화에 비교적 변화가 적었다.

• Journal of Korean Society for Quality Management
• /
• v.28 no.2
• /
• pp.103-122
• /
• 2000

Process capability indices (PCI) $C_p\;C_{pk},\;C_m,\;and\;C_{pmk}$ are widely used to evaluate the process performance. The PCI's have been evolved to consider the 'off targetness' more adequately. However, all of these indices are found to be inconsistent with the proportion of nonconforming items, in some cases. That is, the PCI for a process may result in higher value even when the proportion of defectives increases. For these reasons, we propose a new capability index, $c_{pd}$, which is consistent with the defect rate. The characteristics of the new PCI, $c_{pd}$ are investigated with respect to the existing PCI's. Some statistical properties of an estimator for $c_{pd}$ are also investigated by a Monte Carlo simulation. Sensitivity study under minor deviation from normality is also performed to show the robustness of $c_{pd}$. A good estimator for $c_{pd}$ is under study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.175-176
• /
• 2007

This paper describes on the characteristics of Pd thin films deposited on poly-crystalline 3C-SiC buffer layers for microsensors, in which the poly 3C-SiC was grown on Si, $SiO_2$, and AlN substrates, respectively, by APCVD using HMDS, $H_2$, and Ar gas at $1100^{\circ}C$ for 30 min. In this work, a Pd thin film was deposited on the poly 3C-SiC film by RF magnetron sputter. The thickness, uniformity, and quality of these samples were evaluated by SEM. Crystallinity and orientation of the Pd film were analyzed by XRD. Finally, Pd/poly 3C-SiC schottky diodes were fabricated and characterized by current-voltage measurements. From these results, Pd/poly 3C-SiC devices are promising for high temperature hydrogen sensors and other microsensors.

• Membrane Journal
• /
• v.32 no.6
• /
• pp.456-464
• /
• 2022

Hydrogen permeation performance was analyzed by manufacturing Pd and Pd-Cu membranes through electroless plating. As a support for the Pd and Pd-Cu membranes, α-Al₂O₃ ceramic hollow fiber were used. Pd-Cu membrane was manufactured through sequential electroless plating, and then annealing was performed at 500°C, for 18 h in a hydrogen atmosphere to make Pd and Cu alloy. After annealing, the Pd-Cu membrane confirmed that the alloy was formed through EDS (Energy Dispersive X-ray Spectroscopy) and XRD (X-ray Diffraction) analysis. In addition, the thickness of the Pd and Pd-Cu plating layers were measured to be about 3.21 and 3.72 µm, respectively, through SEM (Scanning Electron Microscope) analysis. Hydrogen permeation performance was tested for hydrogen permeation in the range of 350~450°C and 1~4 bar in hydrogen single gas and mixed gas (H₂, N₂). In a single hydrogen gas, Pd and Pd-Cu membranes have flux of up to 54.42 and 67.17 ml/cm²⋅ min at 450 °C and 4 bar. In the mixed gas, it was confirmed that the separation factors of 1308 and 453 were obtained under the conditions of 450 °C and 4 bar.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.175.2-175.2
• /
• 2014

Graphene (G) has been modified with palladium, copper, and manganese oxide nanoparticles (NPs), and their catalytic applications have been studied in C-C coupling reactions and methylmercaptan (CH3SH) decomposition reactions. In this research, graphite oxide (GO) sheets were exfoliated and oxidized from graphite powder and impregnated with metal precursors including Pd2+, Cu2+, and Mn2+. The thermal treatments of the metal impregnated GO in preferred gas environments produced Pd NPs on graphene (Pd/G), PdO NPs on GO (PdO/GO), and CuOx and MnOx NPs on graphene (CuOx/MnOx/G). In case of Pd/G and PdO/GO, the TEM images show that, although the mean size of the Pd NPs changed significantly before and after the C-C coupling reaction, that of the PdO NPs didn't, implying that the PdO/GO was superior to Pd/G in terms of the recyclability. Also, we demonstrate that the CuOx/MnOx/G exerts the excellent catalytic efficiency in CH3SH decomposition reaction comparing with conventional catalysts. The chemical and electronic structural changes were investigated using XRD and XPS.