165 research outputs found
COCU, circa 1960
No full textIndoor group portrait of three men and one woman. Written on recto: New officers of COCU--(reading from left to right) The Rev. Charles S. Spivey Jr. (AME), first vice chairman; Mrs. Ralph Stair (UPUSA), second vice chairman; The Rev. Dr. George G. Beazley (Christian-Disciples), chairman; Mr. George M. Miller (AMEZ), secretary.The Atlanta University Center Robert W. Woodruff Library acknowledges the generous support of the Council on Library and Information Resources (CLIR) in supporting the processing and digitization of a number of historic collections as part of the project: Our Story: Digitizing Publications and Photographs of the Historically Black Atlanta University Center Institutions.</em
N‑Doped Carbon-Supported CoCu-Layered Double Hydroxide Nanosheets as Antibacterial Oxygen Reduction Catalysts for Microbial Fuel Cells
No full textThe sluggish reaction kinetics of the oxygen reduction
reaction
(ORR) and the formation of a biofilm on the cathode prevent efficient
and stable operation of microbial fuel cells (MFCs). In this work,
zeolitic imidazolate framework-derived N-doped carbon-supported CoCu-layered
double hydroxide nanosheets (CoCu-LDH@NC) were synthesized as a bifunctional
cathode catalyst for MFCs. CoCu-LDH supported on CoO@NC induced the
production of carbon nanotubes (CNTs) from the NC matrix. CNTs and
CoCu-LDH nanosheets improved the atomic reaction efficiency and active
area for the ORR. The high-speed electron-transfer channel was attributed
to two-dimensional CoCu-LDH nanosheets and one-dimensional CNTs. The
catalytic activity and stability of CoO@NC were sustained through
the incorporation of CoCu-LDH nanosheets. The electronic interaction
of CoCu-LDH and CoO@NC enhanced the ORR catalytic activities. CoCu-LDH
nanosheets generated reactive oxygen species (ROS) and Cu+, improving the antibacterial activity to prevent the growth of biofilm
for MFCs. CoCu-LDH@NC demonstrated superior oxygen reduction activity
with a half-wave potential of 0.84 V and an onset potential of 0.89
V. The maximum power density and operating cycle of the MFCs assembled
with CoCu-LDH@NC reached 1012 mW m–2 and 170 h,
respectively. This work offers guidance to enhancing the ORR catalytic
activity and stability by designing antibacterial ORR catalysts
Two growth modes of nanostructures near Cu(111) step edges in CoCu and PtCu surface alloys
No full textThe formation of CoCu and PtCu alloys on the stepped Cu(111) substrate was simulated. Dendritic and finger-like protrusions grow near the edges of the steps. The shape and the internal structure of the protrusions depend on the type of the step edge, temperature and concentrations of impurity atoms. The internal structure and the shape of the protrusions are significantly different in PtCu and CoCu alloys. Pt atoms tend to be surrounded by Cu atoms and Co atoms tend to combine into Co backbones. The dendritic protrusions usually grow at 200 K and the finger-like protrusions usually grow at 300 K. The shape of the protrusions also depends on the type of the step edge and the concentration of impurity atoms. The main differences of PtCu and CoCu protrusions can be explained by the values of the diffusion barriers of the key processes
Giant magnetoresistance and remanence in granular CoCu codeposited films
No full textWe present experimental magnetoresistance, magnetization, and remanence data for CoCu granular films obtained by electron beam codeposition, subsequently submitted to a thermal treatment. The magnetization measurements show coexistence of superparamagnetic and ferromagnetic (or blocked superparamagnetic) Co grains. By modeling the experimental magnetization curves, the distribution function of the superparamagnetic particle size, the volume fraction of the blocked part of the Co particles, and their saturation magnetization are obtained. M plots are constructed using the remanence curves. A correlation between the changes of the M parameters and those of the giant magnetoresistance, caused by the annealing, is discussed
Magnetic Properties Of One-dimensional Cocu(opba) Systems And Dft Studies Of The Building Blocks
No full textThe synthesis of one-dimensional, molecule-based magnets and the investigation of their structure and physical properties are described. The one-dimensional CoCu(opba) system, where opba [ortho-phenylenebis(oxamato)] bridges the metal ions resulted in antiferromagnetic coupling, and was studied by insertion of electron donating and electron withdrawing groups in the organic ligands' aromatic rings. In order to verify the influence of these modifications, three compounds of the formula [CoCu(opba-xy)], where x=y=CH3 (compound 1), x=y=Cl (compound 2), x=H and y=NO2 (compound 3) are described. The electronic structure of the oxamato bridge group has been studied using calculations at the density functional theory (DFT) level for [Cu(opba-xy)]2- building blocks. Magnetic measurements in polycrystalline samples showed ferrimagnetic behavior for the three compounds. Least-squares fits of the experimental data indicate antiferromagnetic couplings JCoCu of -35.0, -32.9 and -24.2 cm-1 for 1, 2 and 3, respectively. © 2008 Elsevier B.V. All rights reserved.32014e200e203Pardo, E., Ruiz-Garcia, R., Lloret, F., Faus, J., Julve, M., Journaux, Y., Delgado, F., Ruiz-Perez, C., (2004) Adv. Chem. Mater., 16, p. 1597Pardo, E., Ruiz-Garcia, R., Lloret, F., Faus, J., Julve, M., Journaux, Y., Novak, M.A., Ruiz-Perez, C., (2007) Chem. Eur. J., 13, p. 2054Pereira, C.L.M., Pedroso, E.F., Stumpf, H.O., Novak, M.A., Ricard, L., Ruiz-Garcia, R., Rivière, E., Journaux, Y., (2004) Angew. Chem. Int. Ed., 43, p. 955Vaz, M.G.F., Knobel, M., Speziali, N.L., Moreira, A.M., Alcantara, A.F.C., Stumpf, H.O., (2002) J. Braz. Chem. Soc., 13, p. 183Pereira, C.L.M., Doriguetto, A.C., Konzen, C., Meira-Belo, L.C., Leitão, U.A., Fernandes, N.G., Brandl, A.L., Stumpf, H.O., (2005) Eur. J. Inorg. Chem., p. 5018Fettouhi, M., Ouahab, L., Boukhari, A., Cador, O., Mathonière, C., Kahn, O., (1996) Inorg. Chem., 35, p. 4932Kahn, O., (1993) Molecular Magnetism, , VCH, New YorkKoningsbruggen, P.J., Kahn, O., Nakatani, K., Pei, Y., Renard, J.P., Drillon, M., Legoll, P., (1990) Inorg. Chem., 29, p. 3325J.A. Pople, et al., Gaussian Inc., Pittsburgh, PA, 2003Gillon, B., (2002) Magnetism Molecules to Materials I: Models and Experiments, p. 356. , Miller J.S., and Drillon M. (Eds), Wiley-VCH, German
Electrochemical control of the magnetic properties of Co and CoCu/Co nanowires
No full textUsing appropriate electrodeposition conditions, it is shown that the structural and magnetic properties of arrays of Co and CoCu/Co nanowires can be controlled. The hcp c axis orientation can be oriented parallel or perpendicular to the wire axis simply by changing the pH of the electrolytic solution and/or deposition rate. This selected orientation of the c axis leads to a drastic change in overall magnetic anisotropy and is promising for the fabrication of spin valves structures by electrodeposition.Anglai
Electrochemical, Structural and Magnetic Analysis of Electrodeposited CoCu/Cu Multilayers: Influence of Cu Layer Deposition Potential
No full textThe electrochemical, structural and magnetic properties of CoCu/Cu multilayers electrodeposited at different cathode potentials were investigated from a single bath. The Cu layer deposition potentials were selected as -0.3,V-0.4V, and -0.5V with respect to saturated calomel electrode (SCE) while the Co layer deposition potential was constant at -1.5V versus SCE. For the electrochemical analysis, the current-time transients were obtained. The amount of noble non-magnetic (Cu) metal materials decreased with the increase of deposition potentials due to anomalous codeposition. Further, current-time transient curves for the Co layer deposition and capacitance were calculated. In the structural analysis, the multilayers were found to be polycrystalline with both Co and Cu layers adopting the face-centered cubic structure. The (111) peak shifts towards higher angle with the increase of the deposition potentials. Also, the lattice parameters of the multilayers decrease from 0.3669 nm to 0.3610 nm with the increase of the deposition potentials from -0.3V to -0.5V, which corresponds to the bulk values of Cu and Co, respectively. The electrochemical and structural results demonstrate that the amount of Co atoms increased and the Cu atoms decreased in the layers with the increase of deposition potentials due to anomalous codeposition. For magnetic measurements, the saturation magnetizations, M s obtained from the magnetic curves of the multilayers were obtained as 212 kA/m, 276 kA/m, and 366 kA/m with -0.3V, -0.4V, and -0.5V versus SCE, respectively. It is seen that the M s values increased with the increase of the deposition potentials confirming the increase of the Co atoms and decrease of the Cu amount. The results of electrochemical and structural analysis show that the deposition potentials of non-magnetic layers plays important role on the amount of magnetic and non-magnetic materials in the layers and thus on the magnetic properties of the multilayers. © 2017, The Minerals, Metals ; Materials Society
Manipulation of the two-site Kondo effect in linear CoCu n CoCu m clusters
No full textArtificially assembled linear atomic clusters, CoCunCoCum, are used to explore variations of the Kondo effect at the two Co sites. For all investigated Cun chain lengths (n = 2.3.4) the addition of a single Cu atom to one edge Co atom of the chain (m = 0 -> m = 1) strongly reduces the amplitude of the Abrikosov–Suhl–Kondo resonance of that Co atom. Concomitantly, the resonance line width is more than halved. On the contrary, the Kondo effect of the opposite edge Co atom remains unaffected. Hybridization together with the linear geometry of the cluster are likely to drive the effect
Composite films containing conductive polymer and metal particles
No full textTi alttabaka üzerine elektropolimerizasyon tekniği ile büyütülen 2 μm kalınlığında PPy tabakası yıkanarak CoCu çözeltisine daldırıldı. Bu çözeltide elektrot olarak kullanılan Ti/PPy tabakası üzerine -0,2 V, -0. 4 V ve -0,6 V’ da 5 s, 10 s ve 15 s süreler için Cu tohumları elde edilmeye çalışıldı. Bu işlemden sonra -1,5 V depozisyon potansiyelinde CoCu parçacıklar üretilerek PPy/CoCu kompozit filmleri elde edildi. Çalışma sırasında kullanılan potansiyel değerleri, Dönüşümlü voltametri tekniği ile çözeltilerden alınan voltamogramlardan yola çıkarak belirlendi. Ayrıca kompozit filmlerin elektrokimyasal karaterizasyonu için parçacıkların depozisyonu sırasında kaydedilen akım yoğunluğuzaman grafikleri, Mott-Schottky (M-S) ve Elektrokimyasal Empedans Spektroskopisi (EIS) ölçümleri kullanıldı. M-S ölçümlerinden numunelerin p-tipi özellik gösterdiği tayin edildi. Aynı zamanda her kompozit film için taşıyıcı yoğunluğu (NA) ve düz bant potansiyeli (Efb) değerleri hesaplandı. EIS ölçüm sonuçları, Nyquist ve Bode grafikleri ile verildi. Sonuçlar R(CR(CR))(QR) ve R(QR(CR))(CR) devre modellerinden faydalanılarak fit edildi. Seçilen eşdeğer devrelerde χ2 değeri 10-4 civarındadır ve tüm devre elemanları için bulunan değerlerin hata oranı %10’ dan düşüktür. PPy tabakasının ve PPy/CoCu kompozit filmlerin Doğrusal Taramalı Voltametri tekniği ile ise CoCu parçacıkların geri çözünme potansiyelleri ve akım verimliliği incelendi. PPy/CoCu kompozit filmler için akım verimliliği %40’ın üzerindedir. Taramalı Elektron Mikroskobu görüntüleri ile yüzey morfolojileri hakkında bilgi elde edildi. Enerji Ayırmalı X-ışını spektroskopisi analizi ile PPy tabakasının, PPy tabakası üzerine elde edilmeye çalışılan Cu tohumlarının ve PPy/CoCu kompozit filmlerin kimyasal bileşimleri tayin edildi. Titreşken Numune Manyetometresi ile kompozit filmlerin manyetik özellikleri belirlendi.PPy layer having 2 μm thickness was electropolymerized and used as an electrode for CoCu solution. In CoCu solution, Cu seeds were grown by applying the deposition potentials of -0,2, -0,4 and -0,6 V for the time of 5, 10 and 15 s. After that CoCu particles were deposited at the potential of -1,5 V. At the end of this procedure PPy/CoCu composite films have been prepared. The applied potentials were determined by Cyclic Voltammetry from deposition solutions. Moreover, electrochemical characterization was done by current density-time transients, Mott-Schottky (M-S) measurements and electrochemical impedance spectroscopy (EIS). From M-S plots ptype conductivity, carrier density (NA) and flat band potential (Efb) were calculated. EIS results were presented as Nyquist and Bode plots. The circuits of the composite films are R(CR(CR))(QR) and R(QR(CR))(CR). The χ2 values are on the scale of 10-4 and the relative error for each circuit element is less than 10%. Linear Scan Voltammetry was used to determine both dissolution potentials and the current efficiency of CoCu particles. For each PPy/CoCu composite films, the current efficiency is calculated as more than 40%. Morphology was studied by Scanning Electron Microscopy. The chemical composition of the PPy layer, Cu seeds on the PPy layer and PPy/CoCu composite films was investigated by Energy Dispersive X-ray Spectrometry. Magnetic properties were analyzed by Vibrating Sample Magnetometer
Composite films containing conductive polymer and metal particles
No full textTi alttabaka üzerine elektropolimerizasyon tekniği ile büyütülen 2 μm kalınlığında PPy tabakası yıkanarak CoCu çözeltisine daldırıldı. Bu çözeltide elektrot olarak kullanılan Ti/PPy tabakası üzerine -0,2 V, -0. 4 V ve -0,6 V’ da 5 s, 10 s ve 15 s süreler için Cu tohumları elde edilmeye çalışıldı. Bu işlemden sonra -1,5 V depozisyon potansiyelinde CoCu parçacıklar üretilerek PPy/CoCu kompozit filmleri elde edildi. Çalışma sırasında kullanılan potansiyel değerleri, Dönüşümlü voltametri tekniği ile çözeltilerden alınan voltamogramlardan yola çıkarak belirlendi. Ayrıca kompozit filmlerin elektrokimyasal karaterizasyonu için parçacıkların depozisyonu sırasında kaydedilen akım yoğunluğuzaman grafikleri, Mott-Schottky (M-S) ve Elektrokimyasal Empedans Spektroskopisi (EIS) ölçümleri kullanıldı. M-S ölçümlerinden numunelerin p-tipi özellik gösterdiği tayin edildi. Aynı zamanda her kompozit film için taşıyıcı yoğunluğu (NA) ve düz bant potansiyeli (Efb) değerleri hesaplandı. EIS ölçüm sonuçları, Nyquist ve Bode grafikleri ile verildi. Sonuçlar R(CR(CR))(QR) ve R(QR(CR))(CR) devre modellerinden faydalanılarak fit edildi. Seçilen eşdeğer devrelerde χ2 değeri 10-4 civarındadır ve tüm devre elemanları için bulunan değerlerin hata oranı %10’ dan düşüktür. PPy tabakasının ve PPy/CoCu kompozit filmlerin Doğrusal Taramalı Voltametri tekniği ile ise CoCu parçacıkların geri çözünme potansiyelleri ve akım verimliliği incelendi. PPy/CoCu kompozit filmler için akım verimliliği %40’ın üzerindedir. Taramalı Elektron Mikroskobu görüntüleri ile yüzey morfolojileri hakkında bilgi elde edildi. Enerji Ayırmalı X-ışını spektroskopisi analizi ile PPy tabakasının, PPy tabakası üzerine elde edilmeye çalışılan Cu tohumlarının ve PPy/CoCu kompozit filmlerin kimyasal bileşimleri tayin edildi. Titreşken Numune Manyetometresi ile kompozit filmlerin manyetik özellikleri belirlendi.PPy layer having 2 μm thickness was electropolymerized and used as an electrode for CoCu solution. In CoCu solution, Cu seeds were grown by applying the deposition potentials of -0,2, -0,4 and -0,6 V for the time of 5, 10 and 15 s. After that CoCu particles were deposited at the potential of -1,5 V. At the end of this procedure PPy/CoCu composite films have been prepared. The applied potentials were determined by Cyclic Voltammetry from deposition solutions. Moreover, electrochemical characterization was done by current density-time transients, Mott-Schottky (M-S) measurements and electrochemical impedance spectroscopy (EIS). From M-S plots ptype conductivity, carrier density (NA) and flat band potential (Efb) were calculated. EIS results were presented as Nyquist and Bode plots. The circuits of the composite films are R(CR(CR))(QR) and R(QR(CR))(CR). The χ2 values are on the scale of 10-4 and the relative error for each circuit element is less than 10%. Linear Scan Voltammetry was used to determine both dissolution potentials and the current efficiency of CoCu particles. For each PPy/CoCu composite films, the current efficiency is calculated as more than 40%. Morphology was studied by Scanning Electron Microscopy. The chemical composition of the PPy layer, Cu seeds on the PPy layer and PPy/CoCu composite films was investigated by Energy Dispersive X-ray Spectrometry. Magnetic properties were analyzed by Vibrating Sample Magnetometer
- …
