Stable Solar-Blind Ultraviolet III-Nitride Photocathode for Astronomy Applications

Science.gov (United States)

Bell, Lloyd

In this effort, we propose to develop a new type of cesium-free photocathode using III- nitride materials (GaN, AlN, and their alloys) to achieve highly efficient, solar blind, and stable ultraviolet (UV) response. Currently, detectors used in UV instruments utilize a photocathode to convert UV photons into electrons that are subsequently detected by microchannel plate or CCD. The performance of these detectors critically depends on the efficiency and stability of their photocathodes. In particular, photocathode instability is responsible for many of the fabrication difficulties commonly experienced with this class of detectors. In recent years, III-nitride (in particular GaN) photocathodes have been demonstrated with very high quantum efficiency (>50%) in parts of UV spectral range; however, these photocathodes still rely on cesiation for activation. The proposed photocathode structure will achieve activation through methods for band structure engineering such as delta- doping and polarization field engineering. Compared to the current state-of-the-art in flight-ready microchannel plate/Cs2Te sealed tubes, photocathodes based on III-nitride materials will increase the quantum efficiency by nearly an order of magnitude and significantly enhance both fabrication yield and reliability, since they will not require cesium or other highly reactive materials for activation. This performance will enable a next-generation UV spectroscopic and imaging mission that is of high scientific priority for NASA. This photocathode uses near-surface band-structure engineering to create a permanently activated surface, with high efficiency and air-stable UV response. We will combine this III-nitride structure with our unique III-nitride processing technology to optimize the efficiency and uniformity of the photocathode. In addition, through our design, growth, and processing techniques, we will extend the application of these photocathodes into far UV for both semitransparent and

Fabrication and Measurement of Low Work Function Cesiated Dispenser Photocathodes

CERN Document Server

Moody, Nathan A; Jensen, Kevin

2005-01-01

Photoinjector performance is a limiting factor in the continued development of high powered FELs and electron beam-based accelerators. Presently available photocathodes are plagued with limited efficiency and short lifetime in an RF-gun environment, due to contamination or evaporation of a photosensitive surface layer. An ideal photocathode should have high efficiency at long wavelengths, long lifetime in practical vacuum environments, and prompt emission. Cathodes with high efficiency typically have limited lifetime, and vice versa, and the needs of the photocathode are generally at odds with those of the drive laser. A potential solution is the low work function dispenser cathode, where lifetime issues are overcome by periodic in situ regeneration that restores the photosensitive surface layer, analogous to those used in the microwave power tube industry. This work reports on the fabrication techniques and performance of cesiated metal photocathodes and cesiated dispenser cathodes, with a focus on understan...

Theoretical study for heterojunction surface of NEA GaN photocathode dispensed with Cs activation

Science.gov (United States)

Xia, Sihao; Liu, Lei; Wang, Honggang; Wang, Meishan; Kong, Yike

2016-09-01

For the disadvantages of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, new-type NEA GaN photocathodes with heterojunction surface dispensed with Cs activation are investigated based on first-principle study with density functional theory. Through the growth of an ultrathin n-type GaN cap layer on p-type GaN emission layer, a p-n heterojunction is formed on the surface. According to the calculation results, it is found that Si atoms tend to replace Ga atoms to result in an n-type doped cap layer which contributes to the decreasing of work function. After the growth of n-type GaN cap layer, the atom structure near the p-type emission layer is changed while that away from the surface has no obvious variations. By analyzing the E-Mulliken charge distribution of emission surface with and without cap layer, it is found that the positive charge of Ga and Mg atoms in the emission layer decrease caused by the cap layer, while the negative charge of N atom increases. The conduction band moves downwards after the growth of cap layer. Si atom produces donor levels around the valence band maximum. The absorption coefficient of GaN emission layer decreases and the reflectivity increases caused by n-type GaN cap layer.

A Masked Photocathode in a Photoinjector

OpenAIRE

Qiang, Ji

2011-01-01

In this paper, we propose a masked photocathode inside a photoinjector for generating high brightness electron beam. Instead of mounting the photocathode onto an electrode, an electrode with small hole is used as a mask to shield the photocathode from the accelerating vacuum chamber. Using such a masked photocathode will make the replacement of photocathode material easy by rotating the photocathode behind the electrode into the hole. Furthermore, this helps reduce the dark current or seconda...

Photocathode non-uniformity contribution to the energy resolution of scintillators

International Nuclear Information System (INIS)

Mottaghian, M.; Koohi-Fayegh, R.; Ghal-Eh, N.; Etaati, G. R.

2010-01-01

This paper introduces the basics of the light transport simulation in scintillators and the wavelength-dependencies in the process. The non-uniformity measurement of the photocathode surface is undertaken, showing that for the photocathode used in this study the quantum efficiency falls to about 4% of its maximum value, especially in areas far from the centre. The wavelength-and position-dependent quantum efficiency is implemented in the Monte Carlo light transport code, showing that, the contribution of the photocathode non-uniformity to the energy resolution is estimated to be around 18%, when all position-and wavelength-dependencies are included. (authors)

Carbon nanotube based photocathodes

International Nuclear Information System (INIS)

Hudanski, Ludovic; Minoux, Eric; Schnell, Jean-Philippe; Xavier, Stephane; Pribat, Didier; Legagneux, Pierre; Gangloff, Laurent; Teo, Kenneth B K; Robertson, John; Milne, William I

2008-01-01

This paper describes a novel photocathode which is an array of vertically aligned multi-walled carbon nanotubes (MWCNTs), each MWCNT being associated with one p-i-n photodiode. Unlike conventional photocathodes, the functions of photon-electron conversion and subsequent electron emission are physically separated. Photon-electron conversion is achieved with p-i-n photodiodes and the electron emission occurs from the MWCNTs. The current modulation is highly efficient as it uses an optically controlled reconfiguration of the electric field at the MWCNT locations. Such devices are compatible with high frequency and very large bandwidth operation and could lead to their application in compact, light and efficient microwave amplifiers for satellite telecommunication. To demonstrate this new photocathode concept, we have fabricated the first carbon nanotube based photocathode using silicon p-i-n photodiodes and MWCNT bunches. Using a green laser, this photocathode delivers 0.5 mA with an internal quantum efficiency of 10% and an I ON /I OFF ratio of 30

Amorphous NEA Silicon Photocathodes - A Robust RF Gun Electron Source. Final Report

International Nuclear Information System (INIS)

Mulhollan, Gregory A.

2009-01-01

Amorphous silicon (a-Si) has been shown to have great promise as a negative electron affinity visible wavelength photocathode suitable for radio frequency (RF) gun systems. The specific operating wavelength can be shifted by growing it as a germanium alloy (a-Si(1-x)Ge(x)) rather than as pure silicon. This class of photoemitters has been shown to possess a high degree of immunity to charged particle flux. Such particle flux can be a significant problem in the operation of other photocathodes in RF gun systems. Its emission characteristics in the form of current per unit area, or current density, and emission angle, or beam spread are well matched for use in RF guns. Photocathodes made of a-Si can be fabricated on a variety of substrates including those most commonly employed in RF gun systems. Such photocathodes can be made for operation in either transmission or reflection mode. By growing them utilizing radio frequency plasma enhanced chemical vapor deposition, the unit cost is quite low, the quality is high and it is straightforward to grow custom size substrates and full or limited regions to confine the electron emission to the desired area. Quality emitters have been fabricated on tantalum, molybdenum, tungsten, titanium, copper, stainless steel, float glass, borosilicate glass and gallium arsenide. In addition to performing well in dedicated test chambers, a-Si photocathodes have been shown to function well in self-contained vacuum tubes. In this employment, they are subjected to a strenuous environment. Successful operation in this configuration provides additional confidence in their application to high energy linac photoinjectors and potentially as part of reliable, low cost photocathode driven RF gun systems that could become ready replacements for the diode and triode guns used on medical accelerators. Their applications in stand-alone vacuum tubes is just beginning to be explored.

Comparative research on the transmission-mode GaAs photocathodes of exponential-doping structures

International Nuclear Information System (INIS)

Chen Liang; Qian Yun-Sheng; Zhang Yi-Jun; Chang Ben-Kang

2012-01-01

Early research has shown that the varied doping structures of the active layer of GaAs photocathodes have been proven to have a higher quantum efficiency than uniform doping structures. On the basis of our early research on the surface photovoltage of GaAs photocathodes, and comparative research before and after activation of reflection-mode GaAs photocathodes, we further the comparative research on transmission-mode GaAs photocathodes. An exponential doping structure is the typical varied doping structure that can form a uniform electric field in the active layer. By solving the one-dimensional diffusion equation for no equilibrium minority carriers of transmission-mode GaAs photocathodes of the exponential doping structure, we can obtain the equations for the surface photovoltage (SPV) curve before activation and the spectral response curve (SRC) after activation. Through experiments and fitting calculations for the designed material, the body-material parameters can be well fitted by the SPV before activation, and proven by the fitting calculation for SRC after activation. Through the comparative research before and after activation, the average surface escape probability (SEP) can also be well fitted. This comparative research method can measure the body parameters and the value of SEP for the transmission-mode GaAs photocathode more exactly than the early method, which only measures the body parameters by SRC after activation. It can also help us to deeply study and exactly measure the parameters of the varied doping structures for transmission-mode GaAs photocathodes, and optimize the Cs-O activation technique in the future. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Characterization of diamond film and bare metal photocathodes as a function of temperature and surface preparation

Energy Technology Data Exchange (ETDEWEB)

Shurter, R P; Moir, D C; Devlin, D J [Los Alamos National Laboratory, Los Alamos, NM (United States)

1997-12-31

High current photocathodes using bare metal and polycrystalline diamond films illuminated by ultraviolet lasers are being developed at Los Alamos for use in a new generation of linear induction accelerators. These photocathodes must be able to produce multiple 60 ns pulses separated by several to tens of nanoseconds. The vacuum environment in which the photocathodes must operate is {sup 1}0-5 torr. (author). 9 figs., 10 refs.

Dark Current and Multipacting in the Photocathode RF Guns at PITZ

CERN Document Server

Hui-Han, Jang; Flöttmann, Klaus; Grabosch, H J; Hartrott, Michael; Krasilnikov, Mikhail; Michelato, Paolo; Miltchev, Velizar; Monaco, Laura; Oppelt, Anne; Petrosyan, Bagrat; Riemann, S; Roensch, Juliane; Schreiber, Siegfried; Sertore, Daniele; Staykov, Lazar; Stephan, Frank

2005-01-01

For photocathode rf guns, the amount of dark current depends on the cavity surface and the photocathodes. Smooth conditioning reduces the amount of dark current. Mechanical damages of the cathodes induce high dark current and chemical pollution changes emission properties of the cathode. Multipacting in the gun cavity changes the surface status of the cathodes and sometimes makes the gun operation impossible due to vacuum interlocks. In this paper, dark current and multipacting features of the rf gun are presented including experimental and simulation studies.

Preliminary Results from a Superconducting Photocathode Sample Cavity

CERN Document Server

Kneisel, Peter; Lipski, Andrzej; Sekutowicz, Jacek

2005-01-01

Pure niobium has been proposed as a photocathode material and recently a successful test has been conducted with a niobium single cell cavity to extract photo-currents from the surface of this cavity. However, the quantum efficiency of niobium is ~2·10-4, whereas electrodeposited lead has a ~15 times higher quantum efficiency. We have designed and tested a photo-injector niobium cavity, which can be used to insert photo-cathodes made of different materials in the high electric field region of the cavity. Experiments have been conducted with niobium and lead, which show that neither the Q- values of the cavity nor the obtainable surface fields are significantly lowered. This paper reports about the results from these tests.

CsI and some new photocathodes

International Nuclear Information System (INIS)

Anderson, D.F.; Kwan, S.; Peskov, V.

1993-06-01

A discussion of the possible sources of discrepancies in the measurements of the quantum efficiency of CsI photocathodes is presented. We propose that the major causes for disagreements in QE are due to the QE dependence on the current density extracted from the photocathode, on the electric field, and on the temperature of the photocathode. Preliminary results on TMAE enhanced GaAs and Si, plus TMAE protected CsTe and SbCs photocathodes, operated in gas, are also presented

Observation of Significant Quantum Efficiency Enhancement from a Polarized Photocathode with Distributed Bragg Reflector

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shukui [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Poelker, Matthew [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Stutzman, Marcy L. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Chen, Yiqiao [SVT Associates, Inc., Eden Prairie, MN (United States); Moy, Aaron [SVT Associates, Inc., Eden Prairie, MN (United States)

2015-09-01

Polarized photocathodes with higher Quantum efficiency (QE) would help to reduce the technological challenge associated with producing polarized beams at milliampere levels, because less laser light would be required, which simplifies photocathode cooling requirements. And for a given amount of available laser power, higher QE would extend the photogun operating lifetime. The distributed Bragg reflector (DBR) concept was proposed to enhance the QE of strained-superlattice photocathodes by increasing the absorption of the incident photons using a Fabry-Perot cavity formed between the front surface of the photocathode and the substrate that includes a DBR, without compromising electron polarization. Here we present recent results showing QE enhancement of a GaAs/GaAsP strained-superlattice photocathode made with a DBR structure. Typically, a GaAs/GaAsP strained-superlattice photocathode without DBR provides a QE of 1%, at a laser wavelength corresponding to peak polarization. In comparison, the GaAs/GaAsP strained-superlattice photocathodes with DBR exhibited an enhancement of over 2 when the incident laser wavelength was tuned to meet the resonant condition for the Fabry-Perot resonator.

Tight comparison of Mg and Y thin film photocathodes obtained by the pulsed laser deposition technique

Energy Technology Data Exchange (ETDEWEB)

Lorusso, A. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Gontad, F., E-mail: francisco.gontad@le.infn.it [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Solombrino, L. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Chiadroni, E. [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, 00044 Frascati (Italy); Broitman, E. [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping (Sweden); Perrone, A. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy)

2016-11-11

In this work Magnesium (Mg) and Yttrium (Y) thin films have been deposited on Copper (Cu) polycrystalline substrates by the pulsed laser ablation technique for photocathode application. Such metallic materials are studied for their interesting photoemission properties and are proposed as a good alternative to the Cu photocathode, which is generally used in radio-frequency guns. Mg and Y films were uniform with no substantial differences in morphology; a polycrystalline structure was found for both of them. Photoemission measurements of such cathodes based on thin films were performed, revealing a quantum efficiency higher than Cu bulk. Photoemission theory according to the three-step model of Spicer is invoked to explain the superior photoemission performance of Mg with respect to Y. - Highlights: • Mg and Y thin film photocathodes were successfully prepared by pulsed laser deposition. • Mg quantum efficiency is higher than Y, despite its higher work function. • The three-step model of Spicer justify the difference in quantum efficiency.

Critical review: Copper runoff from outdoor copper surfaces at atmospheric conditions.

Science.gov (United States)

Hedberg, Yolanda S; Hedberg, Jonas F; Herting, Gunilla; Goidanich, Sara; Odnevall Wallinder, Inger

2014-01-01

This review on copper runoff dispersed from unsheltered naturally patinated copper used for roofing and facades summarizes and discusses influencing factors, available literature, and predictive models, and the importance of fate and speciation for environmental risk assessment. Copper runoff from outdoor surfaces is predominantly governed by electrochemical and chemical reactions and is highly dependent on given exposure conditions (size, inclination, geometry, degree of sheltering, and orientation), surface parameters (age, patina composition, and thickness), and site-specific environmental conditions (gaseous pollutants, chlorides, rainfall characteristics (amount, intensity, pH), wind direction, temperature, time of wetness, season). The corrosion rate cannot be used to assess the runoff rate. The extent of released copper varies largely between different rain events and is related to dry and wet periods, dry deposition prior to the rain event and prevailing rain and patina characteristics. Interpretation and use of copper runoff data for environmental risk assessment and management need therefore to consider site-specific factors and focus on average data of long-term studies (several years). Risk assessments require furthermore that changes in copper speciation, bioavailability aspects, and potential irreversible retention on solid surfaces are considered, factors that determine the environmental fate of copper runoff from outdoor surfaces.

Engineering MoSx/Ti/InP Hybrid Photocathode for Improved Solar Hydrogen Production.

Science.gov (United States)

Li, Qiang; Zheng, Maojun; Zhong, Miao; Ma, Liguo; Wang, Faze; Ma, Li; Shen, Wenzhong

2016-07-19

Due to its direct band gap of ~1.35 eV, appropriate energy band-edge positions, and low surface-recombination velocity, p-type InP has attracted considerable attention as a promising photocathode material for solar hydrogen generation. However, challenges remain with p-type InP for achieving high and stable photoelectrochemical (PEC) performances. Here, we demonstrate that surface modifications of InP photocathodes with Ti thin layers and amorphous MoSx nanoparticles can remarkably improve their PEC performances. A high photocurrent density with an improved PEC onset potential is obtained. Electrochemical impedance analyses reveal that the largely improved PEC performance of MoSx/Ti/InP is attributed to the reduced charge-transfer resistance and the increased band bending at the MoSx/Ti/InP/electrolyte interface. In addition, the MoSx/Ti/InP photocathodes function stably for PEC water reduction under continuous light illumination over 2 h. Our study demonstrates an effective approach to develop high-PEC-performance InP photocathodes towards stable solar hydrogen production.

Ion Back-Bombardment of GaAs Photocathodes Inside DC High Voltage Electron Guns

CERN Document Server

Grames, Joseph M; Brittian, Joshua; Charles, Daniel; Clark, Jim; Hansknecht, John; Lynn Stutzman, Marcy; Poelker, Matthew; Surles-Law, Kenneth E

2005-01-01

The primary limitation for sustained high quantum efficiency operation of GaAs photocathodes inside DC high voltage electron guns is ion back-bombardment of the photocathode. This process results from ionization of residual gas within the cathode/anode gap by the extracted electron beam, which is subsequently accelerated backwards to the photocathode. The damage mechanism is believed to be either destruction of the negative electron affinity condition at the surface of the photocathode or damage to the crystal structure by implantation of the bombarding ions. This work characterizes ion formation within the anode/cathode gap for gas species typical of UHV vacuum chambers (i.e., hydrogen, carbon monoxide and methane). Calculations and simulations are performed to determine the ion trajectories and stopping distance within the photocathode material. The results of the simulations are compared with test results obtained using a 100 keV DC high voltage GaAs photoemission gun and beamline at currents up to 10 mA D...

JAERI 200 kV electron gun with an NEA-GaAs photocathode

International Nuclear Information System (INIS)

Nishitani, Tomohiro; Minehara, Eisuke J.; Hajima, Ryoichi; Nagai, Ryoji; Sawamura, Masaru; Nishimori, Nobuyuki; Kikuzawa, Nobuhiro; Yamauchi, Toshihiko

2004-01-01

The photocathode DC-gun with high average current, low beam emittance and long operational lifetime is considered to be indispensable for ERL-FEL. We have started the development program of a 200 keV electron gun with the NEA-GaAs photocathode for the first time in JAERI. In order to long an NEA surface lifetime, the JAERI 200 kV electron gun system consists of a 200 kV DC-gun chamber on extreme high vacuum condition and an NEA activation chamber with load-lock system. We report the goal of photocathode DC-gun R and D and the schedule of a developmental program. (author)

Enhanced photoelectrochemical properties of copper-assisted catalyzed etching black silicon by electrodepositing cobalt

Science.gov (United States)

Cai, Weidong; Xiong, Haiying; Su, Xiaodong; Zhou, Hao; Shen, Mingrong; Fang, Liang

2017-11-01

Black silicon (Si) photoelectrodes are promising for improving the performance of photoelectrochemical (PEC) water splitting. Here, we report the fabrication of p-black Si and n+p-black Si photocathodes via a controllable copper-assisted catalyzed etching method. The etching process affects only the topmost less than 200 nm of Si and is independent of the surface doping. The synergistic effects of the excellent light harvesting of the black Si and the improved charge transfer properties of the p-n junction boost the production and utilization of photogenerated carriers. The mean reflectance of the pristine Si samples is about 10% from 400 to 950 nm, while that of the black Si samples is reduced as low as 5%. In addition, the PEC properties of the n+p-black Si photocathode can be further enhanced by depositing a cobalt (Co) layer. Compared with the p-Si sample, the onset potential of the Co/n+p-black Si photocathode is positively shifted by 560 mV to 0.33 V vs. reversible hydrogen electrode and the saturation photocurrent density is increased from 22.7 to 32.6 mA/cm2. The design of the Co/n+p-black Si photocathode offers an efficient strategy for preparing PEC solar energy conversion devices.

First operation of cesium telluride photocathodes in the TTF injector RF gun

CERN Document Server

Sertore, D; Flöttmann, K; Stephan, F; Zapfe, K; Michelato, P

2000-01-01

During the run 1998/1999 a new injector based on a laser-driven RF gun was brought in operation at the TESLA Test Facility (TTF) linac at DESY, in order to produce the beam structure and quality required either by TeV collider and SASE FEL experiments. High quantum efficiency cesium telluride photocathodes, prepared at Milano and transferred to DESY, have been successfully operated in the RF gun. A bunch charge of 50 nC, only limited by space charge effects, was achieved. The photocathodes have shown an operative lifetime of several months. A new cathode surface finishing has showed a promising decrease of the photocathode dark current. Measurements of dark current, quantum efficiency and lifetime are reported.

Absorption of optical power in an S-20 photocathode

CERN Document Server

Harmer, S W

2003-01-01

By considering a monochromatic plane wave obliquely incident upon a planar layer of S-20 photocathode material, deposited upon a non-absorbing glass substrate, the distribution of optical power absorbed within the layer can be resolved. This is important to the question of photocathode efficiency, as the absorbed light excites photoelectrons within the photocathode which then may pass from the photocathode into the vacuum of the photomultiplier tube and be collected and multiplied. The calculation uses the measured complex permittivity of an extended red S-20 photocathode in the wavelength range, 375-900 nm. The results show that thin film effects are important within the photocathode, as they give rise to interesting power absorption profiles. This information is invaluable in predicting optimum photocathode thickness for wavelength selective applications. Electromagnetic waves that are obliquely incident upon the photocathode are also considered in both transverse electric and transverse magnetic polarizati...

Characterization of a superconducting Pb photocathode in a superconducting rf photoinjector cavity

CERN Document Server

Barday, R; Jankowiak, A; Kamps, T; Knobloch, J; Kugeler, O; Matveenko, A; Neumann, A; Schmeißer, M; Volker, J; Kneisel, P; Nietubyc, R; Schubert S; Smedley J; Sekutowicz, J; Will, I

2014-01-01

Photocathodes are a limiting factor for the next generation of ultrahigh brightness photoinjectors. We studied the behavior of a superconducting Pb cathode in the cryogenic environment of a superconducting rf gun cavity to measure the quantum efficiency, its spatial distribution, and the work function. We will also discuss how the cathode surface contaminants modify the performance of the photocathode as well as the gun cavity and we discuss the possibilities to remove these contaminants.

S1 photocathode image converter tubes

International Nuclear Information System (INIS)

Gex, F.; Bauduin, P.; Hammes, C.; Horville, P.; Fleurot, N.; Nail, M.

1984-08-01

The S1 photocathode was the first cathode available for practical applications; in spite of this its mechanism of photoemission has remained enigmatic. S1 semi-transparent photocathode is the only one that can be used to study the 1.06 μm neodynium laser pulses of less than 10 ps duration. This recent application and the difficulties to manufacture stable and sensitive S1 photocathode at this wavelength gave rise to new researches which aim is to have a better knowledge of this structure. We first review the recent results obtained at the Paris Observatory (research sponsored by the CEA) and report on the lifetime in the 1-μm range of the photocathodes processed four years ago. In a second part we will try to analyse the researches which have been investigated during these last ten years in different laboratories to determine the role of the main constituants (silver particles, Co oxydes) and their contributions to photoemission in order to improve the sensitivity and the stability of S1 photocathode

Study of silicon tip photocathodes in DC and RF photo-injectors

International Nuclear Information System (INIS)

Jaber, Zakaria

1999-01-01

Nowadays the electron beams with a high intensity are particularly interesting in research and the applied physics. Producing such beams for which high intensity and low emittance are synonyms with efficiency, means developing new high luminosity electron sources, i.e. the photocathodes. This thesis, essentially experimental, is oriented in this way. After an introduction of Clermont-Ferrand and the LAL of Orsay experimental apparatus where the experiments took place, the chapter one presents the field emission and the photo-field emission. Then, we prove that the quantum efficiency of the photocathodes with silicon tips is higher for wavelengths near 800 nm. This fact is essential because it allows the use of lasers in the fundamental wavelength - Titan-Saphir for instance. In the chapter 2, we remind how the silicon tips are realized and how to improve surface conditions. Procedures and the surface analysis with the SEM and XPS are described. With a Nd-Yag laser, pumped with laser diode setting up with the participation of IRCOM Opticians of Limoges, the photocathode supplied 1 Ampere per pulse at a quantum efficiency of 0.25%. The description of this experiment and the results are the object of the chapter 3. The space charge outside the photocathode space prevents the electrons to go through. The Child-Langmuir formula limits the current with the DC gun at about 30 Ampere. To improve this result we have to use a photo-injector. In chapter 4 we prove that the silicon tip photocathode are compatible with RF gun requirements by PRIAM modeling and low level measure in a cold model of CANDELA RF gun. Technical department of CERN helped us to prepare this very sensitive experiment. (author)

Surface films and corrosion of copper

International Nuclear Information System (INIS)

Hilden, J.; Laitinen, T.; Maekelae, K.; Saario, T.; Bojinov, M.

1999-03-01

In Sweden and Finland the spent nuclear fuel is planned to be encapsulated in cast iron canisters that have an outer shield made of copper. The copper shield is responsible for the corrosion protection of the canister construction. General corrosion of the copper is not expected to be the limiting factor in the waste repository environment when estimating the life-time of the canister construction. However, different forms of localised corrosion, i.e. pitting, stress corrosion cracking, or environmentally assisted creep fracture may cause premature failure of the copper shield. Of the probable constituents in the groundwater, nitrites, chlorides, sulphides and carbonates have been suggested to promote localised corrosion of copper. The main assumption made in planning this research program is that the surface films forming on copper in the repository environment largely determine the susceptibility of copper to the different forms of localised corrosion. The availability of reactants, which also may become corrosion rate limiting, is investigated in several other research programs. This research program consists of a set of successive projects targeted at characterising the properties of surface films on copper in repository environment containing different detrimental anions. A further aim was to assess the significance of the anion-induced changes in the stability of the oxide films with regard to localised corrosion of copper. This report summarises the results from a series of investigations on properties of surface films forming on copper in water of pH = 8.9 at temperature of 80 deg C and pressure of 2 MPa. The main results gained so far in this research program are as follows: The surface films forming on copper in the thermodynamic stability region of monovalent copper at 80 deg C consist of a bulk part (about 1 mm thick) which is a good ionic and electronic conductor, and an outer, interfacial layer (0.001 - 0.005 mm thick) which shows p-type semiconductor

Protection of cesium-antimony photocathodes

International Nuclear Information System (INIS)

Buzulutskov, A.; Breskin, A.; Chechik, R.; Prager, M.; Shefer, E.

1996-06-01

In order to operate gaseous photomultipliers in the visible range it was suggested to protect sensitive photocathodes against contact to air and counting gases by their coating with a thin solid dielectric film. We present data on coating of cesium- antimony photocathodes with alkali-halide (NaI, CsI, CsF, NaF), oxide (SiO) and organic (hexatriacontane, calcium stearate) films. The photoelectron transmission through these films and their protection capability have been studied in detail. Cesium-antimony photocathodes are shown to withstand exposure to considerable doses of oxygen and dry air when coated with Nal films. This opens ways to their operation in gas media. (authors), 11 refs., 6 figs

A DFT study on NEA GaN photocathode with an ultrathin n-type Si-doped GaN cap layer

Science.gov (United States)

Xia, Sihao; Liu, Lei; Kong, Yike; Diao, Yu

2016-10-01

Due to the drawbacks of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, a new-type NEA GaN photocathodes with heterojunction surface dispense with Cs activation are proposed. This structure can be obtained through the coverage of an ultrathin n-type Si-doped GaN cap layer on the p-type Mg-doped GaN emission layer. The influences of the cap layer on the photocathode are calculated using DFT. This study indicates that the n-type cap layer can promote the photoemission characteristics of GaN photocathode and demonstrates the probability of the preparation of a NEA GaN photocathode with an n-type cap layer.

High power beam test and measurement of emittance evolution of a 1.6-cell photocathode RF gun at Pohang Accelerator Laboratory

International Nuclear Information System (INIS)

Park, Jang-Ho; Park, Sung-Ju; Kim, Changbum; Huang, Jung-Yun; Ko, In Soo; Parc, Yong-Woon; Hong, Ju-Ho; Xiang Dao; Wang, Xijie

2007-01-01

A Brookhaven National Laboratory (BNL) GUN-IV type photocathode rf gun has been fabricated to use in femtosecond electron diffraction (FED), femtosecond far infrared radiation (fs-FIR) facility, and X-ray free electron laser (XFEL) facilities at the Pohang Accelerator Laboratory (PAL). The gun consists of a 1.6-cell cavity with a copper cathode, a solenoid magnet, beam diagnostic components and auxiliary systems. We report here the measurement of the basic beam parameters which confirm a successful fabrication of the photocathode RF gun system. The emittance evolution is measured by an emittance meter and compared with the PARMELA simulation, which shows a good agreement. (author)

Non-conventional photocathodes based on Cu thin films deposited on Y substrate by sputtering

Energy Technology Data Exchange (ETDEWEB)

Perrone, A. [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); National Institute of Nuclear Physics and University of Salento, 73100 Lecce (Italy); D’Elia, M. [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); Gontad, F., E-mail: francisco.gontad@le.infn.it [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); National Institute of Nuclear Physics and University of Salento, 73100 Lecce (Italy); Di Giulio, M.; Maruccio, G. [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); Cola, A. [National Council Research, Institute for Microelectronics and Microsystems, 73100 Lecce (Italy); Stankova, N.E. [Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia (Bulgaria); Kovacheva, D.G. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Broitman, E. [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)

2014-07-01

Copper (Cu) thin films were deposited on yttrium (Y) substrate by sputtering. During the deposition, a small central area of the Y substrate was shielded to avoid the film deposition and was successively used to study its photoemissive properties. This configuration has two advantages: the cathode presents (i) the quantum efficiency and the work function of Y and (ii) high electrical compatibility when inserted into the conventional radio-frequency gun built with Cu bulk. The photocathode was investigated by scanning electron microscopy to determine surface morphology. X-ray diffraction and atomic force microscopy studies were performed to compare the structure and surface properties of the deposited film. The measured electrical resistivity value of the Cu film was similar to that of high purity Cu bulk. Film to substrate adhesion was also evaluated using the Daimler–Benz Rockwell-C adhesion test method. Finally, the photoelectron performance in terms of quantum efficiency was obtained in a high vacuum photodiode cell before and after laser cleaning procedures. A comparison with the results obtained with a twin sample prepared by pulsed laser deposition is presented and discussed.

Effect of Sb thickness on the performance of bialkali-antimonide photocathodes

Energy Technology Data Exchange (ETDEWEB)

Mamun, Md Abdullah A., E-mail: mmamu001@odu.edu; Elmustafa, Abdelmageed A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529 and The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Hernandez-Garcia, Carlos; Mammei, Russell; Poelker, Matthew [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

2016-03-15

The alkali species Cs and K were codeposited using an effusion source, onto relatively thick layers of Sb (50 nm to ∼7 μm) grown on GaAs and Ta substrates inside a vacuum chamber that was baked and not-vented, and also baked and vented with clean dry nitrogen but not rebaked. The characteristics of the Sb films, including sticking probability, surface roughness, grain size, and crystal properties were very different for these conditions, yet comparable values of photocathode yield [or quantum efficiency (QE)] at 284 V were obtained following codeposition of the alkali materials. Photocathodes manufactured with comparatively thick Sb layers exhibited the highest QE and the best 1/e lifetime. The authors speculate that the alkali codeposition enabled optimized stoichiometry for photocathodes manufactured using thick Sb layers, which could serve as a reservoir for the alkali materials.

Graphene shield enhanced photocathodes and methods for making the same

Science.gov (United States)

Moody, Nathan Andrew

2014-09-02

Disclosed are graphene shield enhanced photocathodes, such as high QE photocathodes. In certain embodiments, a monolayer graphene shield membrane ruggedizes a high quantum efficiency photoemission electron source by protecting a photosensitive film of the photocathode, extending operational lifetime and simplifying its integration in practical electron sources. In certain embodiments of the disclosed graphene shield enhanced photocathodes, the graphene serves as a transparent shield that does not inhibit photon or electron transmission but isolates the photosensitive film of the photocathode from reactive gas species, preventing contamination and yielding longer lifetime.

Influence of air exposure on CsI photocathodes

Energy Technology Data Exchange (ETDEWEB)

Xie, Yuguang, E-mail: ygxie@mail.ihep.ac.cn [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Zhang, Aiwu; Liu, Yingbiao [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Liu, Hongbang [Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Guangxi University, Naning 530004 (China); Hu, Tao; Zhou, Li; Cai, Xiao; Fang, Jian; Yu, Boxiang [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Ge, Yongshuai [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Lue, Qiwen [Shanxi University, Taiyuan 030006 (China); Sun, Xilei; Sun, Lijun; Xue, Zheng [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Xie, Yigang; Zheng, Yangheng [Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Lue, Junguang [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China)

2012-10-11

We investigate the influence of air exposure on the quantum efficiency (QE) and surface morphology of CsI photocathodes (PCs), at relative humidities (RH) higher than 80% down to nearly 3% (both at room temperature) and a 60 Degree-Sign C baking condition. By atomic force microscopy (AFM) surface analysis, it is clearly seen that RH >60% speeds up water film formation and CsI dissolution on the surface of the photocathode at the minute scale, while both grain size and QE change slowly at RH <30% at the hour scale. In the baking environment, the peak QE decreases less than 1.5% (absolute) within one week, and a stainless steel substrate and electron beam evaporation technique tend to effectively weaken the influence of air. With an Au-coated FR-4 substrate, the QE degradation is found to strongly depend on wavelength in the range of 120-210 nm. According to spectra of X-ray photoelectron spectroscopy (XPS), an excess of cesium was observed and the chemical reaction between water and CsI when exposed to humid air is proved. It is found that carbon, and not H{sub 2}O or O{sub 2}, is the main pollutant in the baking condition.

Structural transformation of CsI thin film photocathodes under exposure to air and UV irradiation

CERN Document Server

Tremsin, A S; Siegmund, O H W

2000-01-01

Transmission electron microscopy has been employed to study the structure of polycrystalline CsI thin films and its transformation under exposure to humid air and UV irradiation. The catastrophic degradation of CsI thin film photocathode performance is shown to be associated with the film dissolving followed by its re-crystallization. This results in the formation of large lumps of CsI crystal on the substrate surface, so that the film becomes discontinuous and its performance as a photocathode is permanently degraded. No change in the surface morphology and the film crystalline structure was observed after the samples were UV irradiated.

Photocathodes for High Repetition Rate Light Sources

Energy Technology Data Exchange (ETDEWEB)

Ben-Zvi, Ilan [Stony Brook Univ., NY (United States). Dept. of Physics and Astronomy. Center for Accelerator Science and Education

2014-04-20

This proposal brought together teams at Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL) and Stony Brook University (SBU) to study photocathodes for high repetition rate light sources such as Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). Below details the Principal Investigators and contact information. Each PI submits separately for a budget through his corresponding institute. The work done under this grant comprises a comprehensive program on critical aspects of the production of the electron beams needed for future user facilities. Our program pioneered in situ and in operando diagnostics for alkali antimonide growth. The focus is on development of photocathodes for high repetition rate Free Electron Lasers (FELs) and Energy Recovery Linacs (ERLs), including testing SRF photoguns, both normal-­conducting and superconducting. Teams from BNL, LBNL and Stony Brook University (SBU) led this research, and coordinated their work over a range of topics. The work leveraged a robust infrastructure of existing facilities and the support was used for carrying out the research at these facilities. The program concentrated in three areas: a) Physics and chemistry of alkali-­antimonide cathodes (BNL – LBNL) b) Development and testing of a diamond amplifier for photocathodes (SBU -­ BNL) c) Tests of both cathodes in superconducting RF photoguns (SBU) and copper RF photoguns (LBNL) Our work made extensive use of synchrotron radiation materials science techniques, such as powder-­ and single-­crystal diffraction, x-­ray fluorescence, EXAFS and variable energy XPS. BNL and LBNL have many complementary facilities at the two light sources associated with these laboratories (NSLS and ALS, respectively); use of these will be a major thrust of our program and bring our understanding of these complex materials to a new level. In addition, CHESS at Cornell will be used to continue seamlessly throughout the NSLS dark period and

Copper in Surface Soil of Veles Region, Macedonia

International Nuclear Information System (INIS)

Panchevski, Zlatko; Stafilov, Trajche; Frontasyeva, Marina V.

2006-01-01

For the first time a systematic study of copper distribution in surface soil over of the Veles region, known for its lead and zinc industrial activity, was undertaken. A total of 201 soil samples were collected according to a dense net (0.5 km) in urban and less dense net (1 km) in rural areas. Copper was determined by flame atomic absorption spectrometry (FAAS) using microwave digestion technique with two different types of solvents: aqua regia (HCI and HNO 3 )and the mixture of strong acids (HNO 3 , HCI, and HF). So far the same soil samples were subjected to reactor non-destructive multi-element instrumental neutron activation analysis (INAA), it served as a reference analytical technique for bulk copper determination. The results obtained by two methods of FAAS and INAA are discussed. GIS technology was applied to reveal the areas most affected by copper contamination. It was found that the content of copper in soil samples around the lead and zinc smelter plant is the highest and reaches 1800 mg/kg. Copper content in surface soil all around the town of Veles exceeds maximum permissible level for urban surface soil. Elevated copper content in some rural areas of the Veles region most likely could be explained through using copper containing fungicides for agricultural needs. (Author)

Polarization and charge limit studies of strained GaAs photocathodes

International Nuclear Information System (INIS)

Saez, P.J.

1997-03-01

This thesis presents studies on the polarization and charge limit behavior of electron beams produced by strained GaAs photocathodes. These photocathodes are the source of high-intensity, high-polarization electron beams used for a variety of high-energy physics experiments at the Stanford Linear Accelerator Center. Recent developments on P-type, biaxially-strained GaAs photocathodes have produced longitudinal polarization in excess of 80% while yielding beam intensities of ∼ 2.5 A/cm 2 at an operating voltage of 120 kV. The SLAC Gun Test Laboratory, which has a replica of the SLAC injector, was upgraded with a Mott polarimeter to study the polarization properties of photocathodes operating in a high-voltage DC gun. Both the maximum beam polarization and the maximum charge obtainable from these photocathodes have shown a strong dependence on the wavelength of illumination, on the doping concentration, and on the negative electron affinity levels. The experiments performed for this thesis included studying the effects of temperature, cesiation, quantum efficiency, and laser intensity on the polarization of high-intensity beams. It was found that, although low temperatures have been shown to reduce the spin relaxation rate in bulk semiconductors, they don't have a large impact on the polarization of thin photocathodes. It seems that the short active region in thin photocathodes does not allow spin relaxation mechanisms enough time to cause depolarization. Previous observations that lower QE areas on the photocathode yield higher polarization beams were confirmed. In addition, high-intensity, small-area laser pulses were shown to produce lower polarization beams. Based on these results, together with some findings in the existing literature, a new proposal for a high-intensity, high-polarization photocathode is given. It is hoped that the results of this thesis will promote further investigation on the properties of GaAs photocathodes

Study of residual gas adsorption on GaN nanowire arrays photocathode

Energy Technology Data Exchange (ETDEWEB)

Xia, Sihao; Liu, Lei, E-mail: liu1133_cn@sina.com.cn; Diao, Yu; Kong, Yike

2017-05-01

Highlights: • H{sub 2}O is more easily to absorb on the nanowire surface. • The work function increase after residual gas adsorption. • Bandgaps of the nanowire increase slightly. • Absorption coefficient is reduced and moves to higher energy side. - Abstract: In order to find out the influences of residual gas on GaN nanowire arrays photocathode, the optoelectronic properties of adsorption system are calculated on the basis of first principles. Results suggest that the residual gas adsorption will increase the work function and introduce a dipole moment with a direction from the nanowire to the adsorbates. The surface structures are changed and electrons transfer from nanowire to gas molecule. The bandgaps are enhanced after adsorption. Besides, the peak of absorption coefficients is reduced and moves to higher energy side. It is discovered that residual gas will drastically degrade the characteristics and lifetime of GaN nanowire arrays photocathode.

Imaging Hybrid Photon Detectors with a Reflective Photocathode

CERN Document Server

Ferenc, D

2000-01-01

Modern epitaxially grown photocathodes, like GaAsP, bring a very high inherent quantum efficiency, but are rather expensive due to the complicated manufacturing and mounting process. We argue that such photocathodes could be used in reflective mode, in order to avoid the risky and expensive removal of the epitaxial growth substrate. Besides that the quantum efficiency should increase considerably. In this paper we present results of the development of large imaging Hybrid Photon Detectors (HPDs), particularly designed for such reflective photocathodes.

Underwater explosive compaction-sintering of tungsten-copper coating on a copper surface

Science.gov (United States)

Chen, Xiang; Li, Xiaojie; Yan, Honghao; Wang, Xiaohong; Chen, Saiwei

2018-01-01

This study investigated underwater explosive compaction-sintering for coating a high-density tungsten-copper composite on a copper surface. First, 50% W-50% Cu tungsten-copper composite powder was prepared by mechanical alloying. The composite powder was pre-compacted and sintered by hydrogen. Underwater explosive compaction was carried out. Finally, a high-density tungsten-copper coating was obtained by diffusion sintering of the specimen after explosive compaction. A simulation of the underwater explosive compaction process showed that the peak value of the pressure in the coating was between 3.0 and 4.8 GPa. The hardness values of the tungsten-copper layer and the copper substrate were in the range of 87-133 and 49 HV, respectively. The bonding strength between the coating and the substrate was approximately 100-105 MPa.

A Stable, Non-Cesiated III-Nitride Photocathode for Ultraviolet Astronomy Application

Science.gov (United States)

Bell, Lloyd

In this effort, we propose to develop a new type of cesium-free photocathode using III-nitride (III-N) materials (GaN, AlN, and their alloys) and to achieve highly efficient, solar blind, and stable UV response. Currently, detectors used in UV instruments utilize a photocathode to convert UV photons into electrons that are subsequently detected by microchannel plate or CCD. The performance of these detectors critically depends on the efficiency and stability of their photocathodes. In particular, photocathode instability is responsible for many of the fabrication difficulties commonly experienced with this class of detectors. In recent years, III-N (in particular GaN) photocathodes have been demonstrated with very high QE (>50%) in parts of UV spectral range. Moreover, due to the wide bandgaps of III-nitride materials, photocathode response can be tailored to be intrinsically solar-blind. However, these photocathodes still rely on cesiation for activation, necessitating all-vacuum fabrication and sealed-tube operation. The proposed photocathode structure will achieve activation through methods for band structure engineering such as delta-doping and polarization field engineering. Compared to the current state-of-the-art in flight-ready microchannel plate sealed tubes, photocathodes based on III-N materials will yield high QE and significantly enhance both fabrication yield and reliability, since they do not require cesium or other highly reactive materials for activation. This performance will enable a ~4 meter medium class UV spectroscopic and imaging mission that is of high scientific priority for NASA. This work will build on the success of our previous APRA-funded effort. In that work, we demonstrated III-nitride photocathode operation without the use of cesium and stable response with respect to time. These accomplishments represent major improvements to the state-of-the-art for photocathode technologies. In the proposed effort, we will implement III

Adsorption of 2-mercaptobenzothiazole on copper surface from phosphate solutions

International Nuclear Information System (INIS)

Kazansky, L.P.; Selyaninov, I.A.; Kuznetsov, Yu.I.

2012-01-01

Analysis of the electrochemical and XPS results has shown that adsorption of 2-mercaptobenzothiazole (MBT) on copper electrodes in neutral phosphate solutions proceeds through the formation of the chemical bonds by copper (I) cations with exo-sulfur and nitrogen atoms. A protection layer formed of Cu(I)MBT complex prevents precipitation of copper (II) phosphate on a copper surface. The thickness of the surface film consisting of a complex [Cu(I)MBT] n (having probably polymeric nature), where MBT acts as at least three-dentate ligand, increases depending on the exposure time, reaching 8-9 nm after immersing for 12 h in test solution. Even in a case of the preliminary formation of copper (II) phosphate on the copper electrode at the anodic potential addition of small amounts of MBT results in complete removal of copper (II) phosphate from the surface.

Emittance studies of the BNL/SLAC/UCLA 1.6 cell photocathode rf gun

International Nuclear Information System (INIS)

Palmer, D.T.; Miller, R.H.; Wang, X.J.

1997-01-01

The symmetrized 1.6 cell S-band photocathode gun developed by the BNL/SLAC/UCLA collaboration is in operation at the Brookhaven Accelerator Test Facility (ATF). A novel emittance compensation solenoid magnet has also been designed, built and is in operation at the ATF. These two subsystems form an emittance compensated photoinjector used for beam dynamics, advanced acceleration and free electron laser experiments at the ATF. The highest acceleration field achieved on the copper cathode is 150 MV/m, and the guns normal operating field is 130 MV/m. The maximum rf pulse length is 3 micros. The transverse emittance of the photoelectron beam were measured for various injection parameters. The 1 nC emittance results are presented along with electron bunch length measurements that indicated that at above the 400 pC, space charge bunch lengthening is occurring. The thermal emittance, ε o , of the copper cathode has been measured

Analysis of the Surface of Deposited Copper After Electroerosion Treatment

Science.gov (United States)

Ablyaz, T. R.; Simonov, M. Yu.; Shlykov, E. S.

2018-03-01

An electron microscope analysis of the surface of deposited copper is performed after a profiling-piercing electroerosion treatment. The deposited copper is treated with steel, duralumin, and copper electrode tools at different pulse energies. The treatment with the duralumin electrode produces on the treated surface a web-like structure and cubic-morphology polyhedral dimples about 10 μm in size. The main components of the surface treated with the steel electrode are developed polyhedral dimples with a size of 10 - 50 μm. After the treatment with the copper electrode the main components of the treated surface are large polyhedral dimples about 30 - 80 μm in size.

RF gun using laser-triggered photocathode

International Nuclear Information System (INIS)

Akiyama, H.; Otake, Y.; Naito, T.; Takeuchi, Y.; Yoshioka, M.

1992-01-01

An RF gun using laser-triggered photocathode has many advantages as an injector of the linear colliders since it can generate a low emittance and high current pulsed beam. The experimental facility for the RF gun, such as an RF system, a laser system and a photocathode have been fabricated to study the fundamental characteristics. The dynamics of the RF gun has also studied by the 1D sheet beam model. (author)

Kelvin probe studies of cesium telluride photocathode for AWA photoinjector

Energy Technology Data Exchange (ETDEWEB)

Wisniewski, Eric E., E-mail: ewisniew@anl.gov [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Velazquez, Daniel [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Yusof, Zikri, E-mail: zyusof@hawk.iit.edu [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Spentzouris, Linda; Terry, Jeff [Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Sarkar, Tapash J. [Rice University, 6100 Main, Houston, TX 77005 (United States); Harkay, Katherine [Accelerator Science Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States)

2013-05-21

Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (≈50nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating. -- Highlights: ► The correlation between Quantum Efficiency (QE) and work function. ► How QE and work function evolve together. ► Rejuvenation of the photocathode via heating and the effect on work function. ► The effects on the work function due to exposure to UV light.

Progress in ultrafast CsI-photocathode gaseous imaging photomultipliers

International Nuclear Information System (INIS)

Dagendorf, V.; Breskin, A.; Chechick, R.; Schmidt-Boecking, H.

1991-04-01

A large area low-pressure gas-filled UV-imaging photomultiplier with CsI photocathode is presented. The double step electron photomultiplier with a 10 torr CH 4 gas-filling enables stable high gain operation. The detection efficiency of photon in the wavelength range λ ∼ 170 nm (Xe scintilation light) is about 10% for 200 to 2000 nm thick photocathodes. We investigate the influence of various substrate materials, the thickness of the CsI-layer, the gas pressure and the gas composition on the performance of the photocathode. Furthermore we studied the stability of the photocathode under different operating conditions and its sensitivity to air. Measurements of the timing characteristic of the device yielded an ultimate time resolution of 350 ps (fwhm). (author)

Photoemission spectroscopy study of a multi-alkali photocathode

CERN Document Server

Ettema, A R H

2000-01-01

In this paper a photoemission study of the highest core levels of the elements and the electron escape barrier (work function) in a multi-alkali photocathode are presented. The core levels indicate that the alkali atoms are in an oxidized state and therefore the compound Na sub 2 KSb can be regarded as an ionic semiconductor. The measured escape barrier of the Cs sub 2 O surface layer is determined as 2.3 eV.

Cu2O/CuO Bilayered Composite as a High-Efficiency Photocathode for Photoelectrochemical Hydrogen Evolution Reaction

Science.gov (United States)

Yang, Yang; Xu, Di; Wu, Qingyong; Diao, Peng

2016-10-01

Solar powered hydrogen evolution reaction (HER) is one of the key reactions in solar-to-chemical energy conversion. It is desirable to develop photocathodic materials that exhibit high activity toward photoelectrochemical (PEC) HER at more positive potentials because a higher potential means a lower overpotential for HER. In this work, the Cu2O/CuO bilayered composites were prepared by a facile method that involved an electrodeposition and a subsequent thermal oxidation. The resulting Cu2O/CuO bilayered composites exhibited a surprisingly high activity and good stability toward PEC HER, expecially at high potentials in alkaline solution. The photocurrent density for HER was 3.15 mA·cm-2 at the potential of 0.40 V vs. RHE, which was one of the two highest reported at the same potential on copper-oxide-based photocathode. The high photoactivity of the bilayered composite was ascribed to the following three advantages of the Cu2O/CuO heterojunction: (1) the broadened light absorption band that made more efficient use of solar energy, (2) the large space-charge-region potential that enabled a high efficiency for electron-hole separation, and (3) the high majority carrier density that ensured a faster charge transportation rate. This work reveals the potential of the Cu2O/CuO bilayered composite as a promising photocathodic material for solar water splitting.

SSRL photocathode RF gun test stand

International Nuclear Information System (INIS)

Hernandez, M.; Baltay, M.; Boyce, A.

1995-01-01

A photocathode RF gun test stand designed for the production and study of high brightness electron beams will be constructed at SSRL. The beam will be generated from a laser driven third generation photocathode RF gun being developed in collaboration with BNL, LBL, and UCLA. The 3-5 [MeV] beam from the gun will be accelerated using a SLAC three meter S-band accelerator section, in order to achieve the desired low emittance beam, emittance compensation with solenoidal focusing will be employed

Preparation of reflective CsI photocathodes with reproducible high quantum efficiency

Science.gov (United States)

Maier-Komor, P.; Bauer, B. B.; Friese, J.; Gernhäuser, R.; Kienle, P.; Körner, H. J.; Montermann, G.; Zeitelhack, K.

1995-02-01

CsI as a solid UV-photocathode material has many promising applications in fast gaseous photon detectors. They are proposed in large area Ring Imaging CHerenkov (RICH) devices in forthcoming experiments at various high-energy particle accelerators. A high photon-to-electron conversion efficiency is a basic requirement for the successful operation of these devices. High reproducible quantum efficiencies could be achieved with CsI layers prepared by electron beam evaporation from a water-cooled copper crucible. CsI films were deposited in the thickness range of 30 to 500 μg/cm 2. Absorption coefficients and quantum efficiencies were measured in the wavelength region of 150 nm to 250 nm. The influence of various evaporation parameters on the quantum efficiency were investigated.

Preparation of reflective CsI photocathodes with reproducible high quantum efficiency

Energy Technology Data Exchange (ETDEWEB)

Maier-Komor, P. [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Bauer, B.B. [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Friese, J. [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Gernhaeuser, R. [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Kienle, P. [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Koerner, H.J. [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Montermann, G. [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Zeitelhack, K. [Technische Univ. Muenchen, Garching (Germany). Physik-Department

1995-08-01

CsI as a solid UV-photocathode material has many promising applications in fast gaseous photon detectors. They are proposed in large area Ring Imaging CHerenkov (RICH) devices in forthcoming experiments at various high-energy particle accelerators. A high photon-to-electron conversion efficiency is a basic requirement for the successful operation of these devices. High reproducible quantum efficiencies could be achieved with CsI layers prepared by electron beam evaporation from a water-cooled copper crucible. CsI films were deposited in the thickness range of 30 to 500 {mu}g/cm{sup 2}. Absorption coefficients and quantum efficiencies were measured in the wavelength region of 150 nm to 250 nm. The influence of various evaporation parameters on the quantum efficiency were investigated. (orig.).

Evaluation of biocidal efficacy of copper alloy coatings in comparison with solid metal surfaces: generation of organic copper phosphate nanoflowers.

Science.gov (United States)

Gutierrez, H; Portman, T; Pershin, V; Ringuette, M

2013-03-01

To analyse the biocidal efficacy of thermal sprayed copper surfaces. Copper alloy sheet metals containing >60% copper have been shown to exhibit potent biocidal activity. Surface biocidal activity was assessed by epifluorescence microscopy. After 2-h exposure at 20 °C in phosphate-buffered saline (PBS), contact killing of Gram-negative Escherichia coli and Gram-positive Staphylococcus epidermidis by brass sheet metal and phosphor bronze was 3-4-times higher than that by stainless steel. SEM observations revealed that the surface membranes of both bacterial strains were slightly more irregular when exposed to brass sheet metal than stainless steel. However, when exposed to phosphor bronze coating, E. coli were 3-4 times larger with irregular membrane morphology. In addition, the majority of the cells were associated with spherical carbon-copper-phosphate crystalline nanostructures characteristic of nanoflowers. The membranes of many of the S. epidermidis exhibited blebbing, and a small subset was also associated with nanoflowers. Our data indicate that increasing the surface roughness of copper alloys had a pronounced impact on the membrane integrity of Gram-positive and, to a lesser degree, Gram-negative bacteria. In the presence of PBS, carbon-copper-phosphate-containing nanoflowers were formed, likely nucleated by components derived from killed bacteria. The intimate association of the bacteria with the nanoflowers and phosphor bronze coating likely contributed to their nonreversible adhesion. Thermal spraying of copper alloys provides a strategy for the rapid coating of three-dimensional organic and inorganic surfaces with biocidal copper alloys. Our study demonstrates that the macroscale surface roughness generated by the thermal spray process enhances the biocidal activity of copper alloys compared with the nanoscale surface roughness of copper sheet metals. Moreover, the coating surface topography provides conditions for the rapid formation of organic copper

Development of a high current 250 kV photocathode dc gun

International Nuclear Information System (INIS)

Nishimori, Nobuyuki; Nagai, Ryoji; Sawamura, Masaru; Hajima, Ryoichi

2016-01-01

We have developed a high current photocathode dc gun at JAEA for the next generation light sources such as an energy recovery linac and high-repetition rate X-ray free electron laser. The gun is equipped with a multialkali photocathode preparation system. Quantum efficiency of 0.37% at 532 nm was obtained for a Cs_3Sb photocathode. The gun was high voltage conditioned up to 230 kV with a cathode electrode. Beam generation test from the multialkali photocathode will be performed by the end of FY2015. (author)

Degradation of Alkali-Based Photocathodes from Exposure to Residual Gases: A First-Principles Study

International Nuclear Information System (INIS)

Wang, Gaoxue; Batista, Enrique R.

2017-01-01

Photocathodes are a key component in the production of electron beams in systems such as X-ray free-electron lasers and X-ray energy-recovery linacs. Alkali-based materials display high quantum efficiency (QE), however, their QE undergoes degradation faster than metal photocathodes even in the high vacuum conditions where they operate. The high reactivity of alkali-based surfaces points to surface reactions with residual gases as one of the most important factors for the degradation of QE. In order to advance the understanding on the degradation of the QE, we investigated the surface reactivity of common residual gas molecules (e.g., O 2 , CO 2 , CO, H 2 O, N 2 , and H 2 ) on one of the best-known alkali-based photocathode materials, cesium antimonide (Cs 3 Sb), using first-principles calculations based on density functional theory. Furthermore, the reaction sites, adsorption energy, and effect in the local electronic structure upon reaction of these molecules on (001), (110), and (111) surfaces of Cs 3 Sb were computed and analyzed. The adsorption energy of these molecules on Cs3Sb follows the trend of O 2 (-4.5 eV) > CO 2 (-1.9 eV) > H 2 O (-1.0 eV) > CO (-0.8 eV) > N 2 (-0.3 eV) ≈ H 2 (-0.2 eV), which agrees with experimental data on the effect of these gases on the degradation of QE. The interaction strength is determined by the charge transfer from the surfaces to the molecules. The adsorption and dissociation of O containing molecules modify the surface chemistry such as the composition, structure, charge distribution, surface dipole, and work function of Cs 3 Sb, resulting in the degradation of QE with exposure to O 2 , CO 2 , H 2 O, and CO.

Improved Electron Yield and Spin-Polarization from III-V Photocathodes via Bias Enhanced Carrier Drift: Final Report

International Nuclear Information System (INIS)

Mulhollan, Gregory A.

2006-01-01

In this DOE STTR program, Saxet Surface Science, with the Stanford Linear Accelerator Center as partner, designed, built and tested photocathode structures such that optimal drift-enhanced spin-polarization from GaAs based photoemitters was achieved with minimal bias supply requirements. The forward bias surface grid composition was optimized for maximum polarization and yield, together with other construction parameters including doping profile. This program has culminated in a cathode bias structure affording increased electron spin polarization when applied to III-V based photocathodes. The optimized bias structure has been incorporated into a cathode mounting and biasing design for use in a polarized electron gun.

Integrated MoSe2 with n+p-Si photocathodes for solar water splitting with high efficiency and stability

Science.gov (United States)

Huang, Guanping; Mao, Jie; Fan, Ronglei; Yin, Zhihao; Wu, Xi; Jie, Jiansheng; Kang, Zhenhui; Shen, Mingrong

2018-01-01

Many earth-abundant transition metal dichalcogenides (TMDs) have been employed as catalysts for H2 evolution reaction (HER); however, their impactful integration onto photocathodes for photoelectrochemical (PEC) HER is less developed. In this study, we directly sputtered a MoSe2 catalyst onto an n+p-Si photocathode for efficient and stable PEC-HER. An onset potential of 0.4 V vs. RHE, a saturated photocurrent of 29.3 mA/cm2, a fill factor of 0.32, and an energy conversion efficiency of 3.8% were obtained under 100 mA/cm2 Xe lamp illumination. Such superior PEC properties were ascribed to the nearly vertically standing two dimensional MoSe2 rough surface layer and the sharp interface between Si and MoSe2 with small charge transfer resistance. The balance between the reflectivity of the electrode surface and the absorptivity of MoSe2 was also discussed. In addition, the MoSe2 layer can protect the n+p-Si photocathode with a 120 h stability due to its initial growth on Si with high flatness and compactness. This study provides a path to the effective and scalable growth of TMDs onto the Si photocathode aiming for high efficiency and stability.

Field assisted photoemission by silicon photocathodes

International Nuclear Information System (INIS)

Aboubacar, A.; Dupont, M.; El Manouni, A.; Querrou, M.; Says, L.P.

1991-01-01

Silicon photocathodes with arrays of tips have been prepared using microlithographic techniques. Current emission due to field effect has been measured in the case of heavy and weakly doped boron Silicon. An Argon continuous laser has been used to produce photocurrent. An instantaneous current (600 μA) with a moderate laser power (83 mW), has been produced on weakly doped photocathodes. This current corresponds to an average quantum yield (purely photoelectric) of about 1.7%, and a local current density in the range of a few 10 6 A m -2

Properties of CsI and CsI-TMAE photocathodes

International Nuclear Information System (INIS)

Anderson, D.F.; Kwan, S.; Peskov, V.; Hoeneisen, B.

1992-06-01

The importance of heating the CsI or CsI-TMAE photocathodes during preparation, as well as the importance of the gas environment on the quantum efficiency is presented. The dependence of the aging characteristics of these photocathodes on the operating temperature, on the presence of gas, and on the charge amplification of the chamber is also discussed. For CsI photocathodes charges in excess of 2x10 14 e - /mm 2 can be collected with little degradation of performance. A timing resolution of 0.55 ns is also achieved for single photoelectrons suggesting a possible time-of-flight detector

Correlation of CsK2Sb photocathode lifetime with antimony thickness

Energy Technology Data Exchange (ETDEWEB)

Mamun, M. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Hernandez-Garcia, C. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Poelker, M. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Elmustafa, A. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA

2015-06-01

CsK2Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

Correlation of CsK2Sb photocathode lifetime with antimony thickness

Directory of Open Access Journals (Sweden)

M. A. Mamun

2015-06-01

Full Text Available CsK2Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

Design of a high-brightness, high-duty factor photocathode electron gun

International Nuclear Information System (INIS)

Lehrman, I.S.; Birnbaum, I.A.; Fixler, S.Z.; Heuer, R.L.; Siddiqi, S.; Sheedy, E.; Ben-Zvi, I.; Batchelor, K.; Gallardo, J.C.; Kirk, H.G.; Srinivasan-Rao, T.; Warren, G.D.

1991-09-01

The proposed UV-FEL user's facility at Brookhaven National Laboratory will require a photocathode gun capable of producing short (< 6 psec) bunches of electrons in high repetition rates (5 kHz), low energy spread (< 1.5.%), a peak current of 300 A (after compression) and a total bunch charge of up to 2 nC. At the highest charge the normalized transverse emittance should be less than 7 π mm-mrad. We are presently designing a gun that is expected to exceed these requirements. This gun will consist of 3 1/2 cells, constructed of GlidCop-15, an aluminum oxide dispersion strengthened copper alloy. The gun will be capable of operating at duty factors in excess of 1%. Extensive beam dynamics studies of the gun were used to determine the effect of varying the length of the first cell, shaping the apertures between cells, and increasing the number of cells. In addition, a detailed thermal and mechanical study of the gun was performed to ensure that the thermal stresses were well within the allowable limits and that copper erosion of the water channels would not occur

Cold electron beams from cryocooled, alkali antimonide photocathodes

Directory of Open Access Journals (Sweden)

L. Cultrera

2015-11-01

Full Text Available In this paper we report on the generation of cold electron beams using a Cs_{3}Sb photocathode grown by codeposition of Sb and Cs. By cooling the photocathode to 90 K we demonstrate a significant reduction in the mean transverse energy validating the long-standing speculation that the lattice temperature contributes to limiting the mean transverse energy or intrinsic emittance near the photoemission threshold, opening new frontiers in generating ultrabright beams. At 90 K, we achieve a record low intrinsic emittance of 0.2  μm (rms per mm of laser spot diameter from an ultrafast (subpicosecond photocathode with quantum efficiency greater than 7×10^{−5} using a visible laser wavelength of 690 nm.

Surface properties of copper based cermet materials

International Nuclear Information System (INIS)

Voinea, M.; Vladuta, C.; Bogatu, C.; Duta, A.

2008-01-01

The paper presents the characterization of the surface properties of copper based cermets obtained by two different techniques: spray pyrolysis deposition (SPD) and electrodeposition. Copper acetate was used as precursor of Cu/CuO x cermet. The surface morphology was tailored by adding copolymers of maleic anhydride with controlled hydrophobia. The films morphology of Cu/CuO x was assessed using contact angle measurements and AFM analysis. The porous structures obtained via SPD lead to higher liquid adsorption rate than the electrodeposited films. A highly polar liquid - water is recommended as testing liquid in contact angle measurements, for estimating the porosity of copper based cermets, while glycerol can be used to distinguish among ionic and metal predominant structures. Thus, contact angle measurements can be used for a primary evaluation of the films morphology and, on the other hand, of the ratio between the cermet components

Production and Studies of Photocathodes for High Intensity Electron Beams

CERN Document Server

Chevallay, E; Legros, P; Suberlucq, Guy; Trautner, H

2000-01-01

For short, high-intensity electron bunches, alkali-tellurides have proved to be a reliable photo-cathode material. Measurements of lifetimes in an rf gun of the CLIC Test Facility II at field strengths greater than 100 MV/m are presented. Before and after using them in this gun, the spectral response of the CS-Te and Rb-Te cathodes were determined with the help of an optical parametric oscillator. The behaviour of both materials can be described by Spicer's 3-step model. Whereas during the use the threshold for photo-emission in Cs-Te was shifted to higher proton energies, that of Rb-Te did not change. Our latest investigations on the stoichiometric ratio of the components are shown. The preparation of the photo-cathodes was monitored with 320 nm wavelength light , with the aim of improving the measurement sensitivity. The latest results on the protection of Cs-Te cathode surfaces with CsBr against pollution are summarized. New investigations on high mean current production are presented.,

Method For Creating Corrosion Resistant Surface On An Aluminum Copper Alloy

Science.gov (United States)

Mansfeld, Florian B.; Wang, You; Lin, Simon H.

1997-06-03

A method for treating the surface of aluminum alloys hang a relatively high copper content is provided which includes the steps of removing substantially all of the copper from the surface, contacting the surface with a first solution containing cerium, electrically charging the surface while contacting the surface in an aqueous molybdate solution, and contacting the surface with a second solution containing cerium. The copper is substantially removed from the surface in the first step either by (i) contacting the surface with an acidic chromate solution or by (ii) contacting the surface with an acidic nitrate solution while subjecting the surface to an electric potential. The corrosion-resistant surface resulting from the invention is excellent, consistent and uniform throughout the surface. Surfaces treated by the invention may often be certified for use in salt-water services.

SWCNT photocathodes sensitised with InP/ZnS core–shell nanocrystals

OpenAIRE

Macdonald, Thomas J.; Tune, Daniel D.; Dewi, Melissa R.; Bear, Joseph C.; McNaughter, Paul D.; Mayes, Andrew G.; Skinner, William M.; Parkin, Ivan P.; Shapter, Joseph G.; Nann, Thomas

2016-01-01

Increasing the light harvesting efficiency of photocathodes is an integral part of optimising the future efficiencies of solar technologies. In contrast to the more extensively studied photoanode systems, current state-of-the-art photocathodes are less efficient and are commonly replaced with rare and expensive materials such as platinum group metals. The significance of photocathodes is in the development of tandem electrodes, enhancing the performance of existing devices. Carbon nanotubes a...

SWCNT photocathodes sensitised with InP/ZnS core-shell nanocrystals

OpenAIRE

Macdonald, T. J.; Tune, D. D.; Dewi, M. R.; Bear, J. C.; McNaughter, P. D.; Mayes, A. G.; Skinner, W. M.; Parkin, I. P.; Shapter, J. G.; Nann, T.

2016-01-01

Increasing the light harvesting efficiency of photocathodes is an integral part of optimising the future efficiencies of solar technologies. In contrast to the more extensively studied photoanode systems, current state-of-the-art photocathodes are less efficient and are commonly replaced with rare and expensive materials such as platinum group metals. The significance of photocathodes is in the development of tandem electrodes, enhancing the performance of existing devices. Carbon nanotubes a...

Ultrathin MoS2-coated Ag@Si nanosphere arrays as an efficient and stable photocathode for solar-driven hydrogen production.

Science.gov (United States)

Zhou, Qingwei; Su, Shaoqiang; Hu, Die; Lin, Lin; Yan, Zhibo; Gao, Xingsen; Zhang, Zhang; Liu, Jun-Ming

2018-01-30

Solar-driven photoelectrochemical (PEC) water splitting has attracted a great deal of attention recently. Silicon (Si) is an ideal light absorber for solar energy conversion. However, the poor stability and inefficient surface catalysis of Si photocathodes for the hydrogen evolution reaction (HER) have remained key challenges. Alternatively, MoS 2 has been reported to exhibit excellent catalysis performance if sufficient active sites for the HER are available. Here, ultrathin MoS 2 nanoflakes are directly synthesized to coat arrays of Ag-core Si-shell nanospheres (Ag@Si NSs) by using chemical vapor deposition. Due to the high surface area ratio and large curvature of these NSs, the as-grown MoS 2 nanoflakes can accommodate more active sites. In addition, the high-quality coating of MoS 2 nanoflakes on the Ag@Si NSs protects the photocathode from damage during the PEC reaction. An photocurrent density of 33.3 mA cm -2 at a voltage of -0.4 V is obtained versus the reversible hydrogen electrode. The as-prepared nanostructure as a hydrogen photocathode is evidenced to have high stability over 12 h PEC performance. This work opens up opportunities for composite photocathodes with high activity and stability using cheap and stable co-catalysts.

Ultra-thin MoS2 coated Ag@Si nanosphere arrays as efficient and stable photocathode for solar-driven hydrogen production.

Science.gov (United States)

Zhou, Qingwei; Su, Shaoqiang; Hu, Die; Lin, Lin; Yan, Zhibo; Gao, Xingsen; Zhang, Zhang; Liu, Junming

2018-01-02

Solar-driven photoelectrochemical (PEC) water splitting has recently attracted much attention. Silicon (Si) is an ideal light absorber for solar energy conversion. However, the poor stability and inefficient surface catalysis of Si photocathode for hydrogen evolution reaction (HER) have been remained as the key challenges. Alternatively, MoS2 has been reported to exhibit the excellent catalysis performance if sufficient active sites for the HER are available. Here, ultra-thin MoS2 nanoflakes are directly synthesized to coat on the arrays of Ag-core Si-shell nanospheres (Ag@Si NSs) using the chemical vapor deposition (CVD). Due to the high surface area ratio and large curvature of these NSs, the as-grown MoS2 nanoflakes can accommodate more active sites. Meanwhile, the high-quality coating of MoS2 nanoflakes on the Ag@Si NSs protects the photocathode from damage during the PEC reaction. A high efficiency with a photocurrent of 33.3 mA cm-2 at a voltage of -0.4 V vs. the reversible hydrogen electrode is obtained. The as-prepared nanostructure as hydrogen photocathode is evidenced to have high stability over 12 hour PEC performance. This work opens opportunities for composite photocathode with high activity and stability using cheap and stable co-catalysts. © 2017 IOP Publishing Ltd.

A new two-step tuning procedure for a photocathode gun

International Nuclear Information System (INIS)

Lal, Shankar; Pant, K.K.; Krishnagopal, S.

2008-01-01

An important aspect of the development of multi-cell RF accelerating structures is tuning the resonant frequency f of the operating mode, field balance e b , and waveguide to cavity coupling coefficient β to the desired values. Earlier theoretical analyses have not been able to predict all three parameters simultaneously for a coupled-cavity system. We have developed a generalized circuit analysis to predict f, e b , and β of a coupled structure, based on the RF properties of the individual, uncoupled, cells. This has been used to develop a simplified two-step tuning procedure to tune a BNL/SLAC/UCLA type 1.6 cell S-band photocathode gun by varying RF properties of individual half and full cells, which are easily measurable. This procedure has been validated by tuning two true-to-scale prototypes made of aluminum and ETP copper to the desired values of the RF parameters

Superhydrophobic Copper Surfaces with Anticorrosion Properties Fabricated by Solventless CVD Methods.

Science.gov (United States)

Vilaró, Ignasi; Yagüe, Jose L; Borrós, Salvador

2017-01-11

Due to continuous miniaturization and increasing number of electrical components in electronics, copper interconnections have become critical for the design of 3D integrated circuits. However, corrosion attack on the copper metal can affect the electronic performance of the material. Superhydrophobic coatings are a commonly used strategy to prevent this undesired effect. In this work, a solventless two-steps process was developed to fabricate superhydrophobic copper surfaces using chemical vapor deposition (CVD) methods. The superhydrophobic state was achieved through the design of a hierarchical structure, combining micro-/nanoscale domains. In the first step, O 2 - and Ar-plasma etchings were performed on the copper substrate to generate microroughness. Afterward, a conformal copolymer, 1H,1H,2H,2H-perfluorodecyl acrylate-ethylene glycol diacrylate [p(PFDA-co-EGDA)], was deposited on top of the metal via initiated CVD (iCVD) to lower the surface energy of the surface. The copolymer topography exhibited a very characteristic and unique nanoworm-like structure. The combination of the nanofeatures of the polymer with the microroughness of the copper led to achievement of the superhydrophobic state. AFM, SEM, and XPS were used to characterize the evolution in topography and chemical composition during the CVD processes. The modified copper showed water contact angles as high as 163° and hysteresis as low as 1°. The coating withstood exposure to aggressive media for extended periods of time. Tafel analysis was used to compare the corrosion rates between bare and modified copper. Results indicated that iCVD-coated copper corrodes 3 orders of magnitude slower than untreated copper. The surface modification process yielded repeatable and robust superhydrophobic coatings with remarkable anticorrosion properties.

Correlation of CsK{sub 2}Sb photocathode lifetime with antimony thickness

Energy Technology Data Exchange (ETDEWEB)

Mamun, M. A., E-mail: mmamu001@odu.edu; Elmustafa, A. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States); The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Hernandez-Garcia, C.; Poelker, M. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

2015-06-01

CsK{sub 2}Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

Advanced 3D Photocathode Modeling and Simulations Final Report

International Nuclear Information System (INIS)

Dimitre A Dimitrov; David L Bruhwiler

2005-01-01

High brightness electron beams required by the proposed Next Linear Collider demand strong advances in photocathode electron gun performance. Significant improvement in the production of such beams with rf photocathode electron guns is hampered by the lack high-fidelity simulations. The critical missing piece in existing gun codes is a physics-based, detailed treatment of the very complex and highly nonlinear photoemission process

Pure and Oxidized Copper Materials as Potential Antimicrobial Surfaces for Spaceflight Activities

Science.gov (United States)

Hahn, C.; Hans, M.; Hein, C.; Mancinelli, R. L.; Mücklich, F.; Wirth, R.; Rettberg, P.; Hellweg, C. E.; Moeller, R.

2017-12-01

Microbial biofilms can lead to persistent infections and degrade a variety of materials, and they are notorious for their persistence and resistance to eradication. During long-duration space missions, microbial biofilms present a danger to crew health and spacecraft integrity. The use of antimicrobial surfaces provides an alternative strategy for inhibiting microbial growth and biofilm formation to conventional cleaning procedures and the use of disinfectants. Antimicrobial surfaces contain organic or inorganic compounds, such as antimicrobial peptides or copper and silver, that inhibit microbial growth. The efficacy of wetted oxidized copper layers and pure copper surfaces as antimicrobial agents was tested by applying cultures of Escherichia coli and Staphylococcus cohnii to these metallic surfaces. Stainless steel surfaces were used as non-inhibitory control surfaces. The production of reactive oxygen species and membrane damage increased rapidly within 1 h of exposure on pure copper surfaces, but the effect on cell survival was negligible even after 2 h of exposure. However, longer exposure times of up to 4 h led to a rapid decrease in cell survival, whereby the survival of cells was additionally dependent on the exposed cell density. Finally, the release of metal ions was determined to identify a possible correlation between copper ions in suspension and cell survival. These measurements indicated a steady increase of free copper ions, which were released indirectly by cells presumably through excreted complexing agents. These data indicate that the application of antimicrobial surfaces in spaceflight facilities could improve crew health and mitigate material damage caused by microbial contamination and biofilm formation. Furthermore, the results of this study indicate that cuprous oxide layers were superior to pure copper surfaces related to the antimicrobial effect and that cell density is a significant factor that influences the time dependence of

The effects of electromagnetic space-charge fields in RF photocathode guns

International Nuclear Information System (INIS)

Park, C.S.; Hess, M.

2010-01-01

In high-brightness rf photocathode guns, the effects of space-charge are important for electron bunches with high bunch charge. In an effort to accurately simulate the effects of these space-charge fields without the presence of numerical grid dispersion, a Green's function based code called IRPSS (Indiana Rf Photocathode Source Simulator) was developed. In this paper, we show the results of numerical simulations of the Argonne Wakefield Accelerator photocathode gun using IRPSS, and compare them with the results of an electrostatic Green's function version of IRPSS.

Copper-assisted, anti-reflection etching of silicon surfaces

Science.gov (United States)

Toor, Fatima; Branz, Howard

2014-08-26

A method (300) for etching a silicon surface (116) to reduce reflectivity. The method (300) includes electroless deposition of copper nanoparticles about 20 nanometers in size on the silicon surface (116), with a particle-to-particle spacing of 3 to 8 nanometers. The method (300) includes positioning (310) the substrate (112) with a silicon surface (116) into a vessel (122). The vessel (122) is filled (340) with a volume of an etching solution (124) so as to cover the silicon surface (116). The etching solution (124) includes an oxidant-etchant solution (146), e.g., an aqueous solution of hydrofluoric acid and hydrogen peroxide. The silicon surface (116) is etched (350) by agitating the etching solution (124) with, for example, ultrasonic agitation, and the etching may include heating (360) the etching solution (124) and directing light (365) onto the silicon surface (116). During the etching, copper nanoparticles enhance or drive the etching process.

Surface-rain interactions: differences in copper runoff for copper sheet of different inclination, orientation, and atmospheric exposure conditions.

Science.gov (United States)

Hedberg, Yolanda S; Goidanich, Sara; Herting, Gunilla; Wallinder, Inger Odnevall

2015-01-01

Predictions of the diffuse dispersion of metals from outdoor constructions such as roofs and facades are necessary for environmental risk assessment and management. An existing predictive model has been compared with measured data of copper runoff from copper sheets exposed at four different inclinations facing four orientations at two different urban sites (Stockholm, Sweden, and Milan, Italy) during a 4-year period. Its applicability has also been investigated for copper sheet exposed at two marine sites(Cadiz, Spain, for 5 years, and Brest, France, for 9 years). Generally the model can be used for all given conditions. However, vertical surfaces should be considered as surfaces inclined 60-80 due to wind driven effects. The most important parameters that influence copper runoff, and not already included in the model, are the wind and rain characteristics that influence the actual rainfall volume impinging the surface of interest.

SERS and DFT study of copper surfaces coated with corrosion inhibitor

Directory of Open Access Journals (Sweden)

Maurizio Muniz-Miranda

2014-12-01

Full Text Available Azole derivatives are common inhibitors of copper corrosion due to the chemical adsorption occurring on the metal surface that gives rise to a protective film. In particular, 1,2,4-triazole performs comparable to benzotriazole, which is much more widely used, but is by no means an environmentally friendly agent. In this study, we have analyzed the adsorption of 1,2,4-triazole on copper by taking advantage of the surface-enhanced Raman scattering (SERS effect, which highlights the vibrational features of organic ligand monolayers adhering to rough surfaces of some metals such as gold, silver and copper. To ensure the necessary SERS activation, a roughening procedure was implemented on the copper substrates, resulting in nanoscale surface structures, as evidenced by microscopic investigation. To obtain sufficient information on the molecule–metal interaction and the formation of an anticorrosive thin film, the SERS spectra were interpreted with the aid of theoretical calculations based on the density functional theory (DFT approach.

Copper tolerance in Frankia sp. strain EuI1c involves surface binding and copper transport.

Science.gov (United States)

Rehan, Medhat; Furnholm, Teal; Finethy, Ryan H; Chu, Feixia; El-Fadly, Gomaah; Tisa, Louis S

2014-09-01

Several Frankia strains have been shown to be copper-tolerant. The mechanism of their copper tolerance was investigated for Frankia sp. strain EuI1c. Copper binding was shown by binding studies. Unusual globular structures were observed on the surface of the bacterium. These globular structures were composed of aggregates containing many relatively smaller "leaf-like" structures. Scanning electron microscopy with energy-dispersive X-ray (SEM-EDAX) analysis of these structures indicated elevated copper and phosphate levels compared to the control cells. Fourier transform infrared spectroscopy (FTIR) analysis indicated an increase in extracellular phosphate on the cell surface of copper-stressed cells. Bioinformatics' analysis of the Frankia sp. strain EuI1c genome revealed five potential cop genes: copA, copZ, copC, copCD, and copD. Experiments with Frankia sp. strain EuI1c using qRT-PCR indicated an increase in messenger RNA (mRNA) levels of the five cop genes upon Cu(2+) stress. After 5 days of Cu(2+) stress, the copA, copZ, copC, copCD, and copD mRNA levels increased 25-, 8-, 18-, 18-, and 25-fold, respectively. The protein profile of Cu(2+)-stressed Frankia sp. strain EuI1c cells revealed the upregulation of a 36.7 kDa protein that was identified as FraEuI1c_1092 (sulfate-binding periplasmic transport protein). Homologues of this gene were only present in the genomes of the Cu(2+)-resistant Frankia strains (EuI1c, DC12, and CN3). These data indicate that copper tolerance by Frankia sp. strain EuI1c involved the binding of copper to the cell surface and transport proteins.

Sputtering induced surface composition changes in copper-palladium alloys

International Nuclear Information System (INIS)

Sundararaman, M.; Sharma, S.K.; Kumar, L.; Krishnan, R.

1981-01-01

It has been observed that, in general, surface composition is different from bulk composition in multicomponent materials as a result of ion beam sputtering. This compositional difference arises from factors like preferential sputtering, radiation induced concentration gradients and the knock-in effect. In the present work, changes in the surface composition of copper-palladium alloys, brought about by argon ion sputtering, have been studied using Auger electron spectroscopy. Argon ion energy has been varied from 500 eV to 5 keV. Enrichment of palladium has been observed in the sputter-altered layer. The palladium enrichment at the surface has been found to be higher for 500 eV argon ion sputtering compared with argon ion sputtering at higher energies. Above 500 eV, the surface composition has been observed to remain the same irrespective of the sputter ion energy for each alloy composition. The bulk composition ratio of palladium to copper has been found to be linearly related to the sputter altered surface composition ratio of palladium to copper. These results are discussed on the basis of recent theories of alloy sputtering. (orig.)

Synchrotron x-ray study of a low roughness and high efficiency K2CsSb photocathode during film growth

International Nuclear Information System (INIS)

Xie, Junqi; Demarteau, Marcel; Wagner, Robert; Schubert, Susanne; Gaowei, Mengjia; Attenkofer, Klaus; Walsh, John; Smedley, John; Ben-Zvi, Ilan; Wong, Jared; Feng, Jun; Padmore, Howard; Ruiz-Oses, Miguel; Ding, Zihao; Liang, Xue; Muller, Erik

2017-01-01

Reduction of roughness to the nm level is critical of achieving the ultimate performance from photocathodes used in high gradient fields. The thrust of this paper is to explore the evolution of roughness during sequential growth, and to show that deposition of multilayer structures consisting of very thin reacted layers results in an nm level smooth photocathode. Synchrotron x-ray methods were applied to study the multi-step growth process of a high efficiency K 2 CsSb photocathode. A transition point of the Sb film grown on Si was observed at the film thickness of ∼40 Å with the substrate temperature at 100 °C and the growth rate at 0.1 Å s −1 . The final K 2 CsSb photocathode exhibits a thickness of around five times that of the total deposited Sb film regardless of how the Sb film was grown. The film surface roughening process occurs first at the step when K diffuses into the crystalline Sb. The photocathode obtained from the multi-step growth exhibits roughness in an order of magnitude lower than the normal sequential process. X-ray diffraction measurements show that the material goes through two structural changes of the crystalline phase during formation, from crystalline Sb to K 3 Sb and finally to K 2 CsSb. (paper)

Atomic hydrogen cleaning of GaAs photocathodes

International Nuclear Information System (INIS)

Poelker, M.; Price, J.; Sinclair, C.

1997-01-01

It is well known that surface contaminants on semiconductors can be removed when samples are exposed to atomic hydrogen. Atomic H reacts with oxides and carbides on the surface, forming compounds that are liberated and subsequently pumped away. Experiments at Jefferson lab with bulk GaAs in a low-voltage ultra-high vacuum H cleaning chamber have resulted in the production of photocathodes with high photoelectron yield (i.e., quantum efficiency) and long lifetime. A small, portable H cleaning apparatus also has been constructed to successfully clean GaAs samples that are later removed from the vacuum apparatus, transported through air and installed in a high-voltage laser-driven spin-polarized electron source. These results indicate that this method is a versatile and robust alternative to conventional wet chemical etching procedures usually employed to clean bulk GaAs

Photoemission characteristics of thin GaAs-based heterojunction photocathodes

Energy Technology Data Exchange (ETDEWEB)

Feng, Cheng; Zhang, Yijun, E-mail: zhangyijun423@126.com; Qian, Yunsheng [Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094 (China); Shi, Feng [Science and Technology on Low-Light-Level Night Vision Laboratory, Xi' an 710065 (China); Zou, Jijun [Engineering Research Center of Nuclear Technology Application (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Zeng, Yugang [Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

2015-01-14

To better understand the different photoemission mechanism of thin heterojunction photocathodes, the quantum efficiency models of reflection-mode and transmission-mode GaAs-based heterojunction photocathodes are revised based on one-dimensional continuity equations, wherein photoelectrons generated from both the emission layer and buffer layer are taken into account. By comparison of simulated results between the revised and conventional models, it is found that the electron contribution from the buffer layer to shortwave quantum efficiency is closely related to some factors, such as the thicknesses of emission layer and buffer layer and the interface recombination velocity. Besides, the experimental quantum efficiency data of reflection-mode and transmission-mode AlGaAs/GaAs photocathodes are well fitted to the revised models, which confirm the applicability of the revised quantum efficiency models.

Evaluation of bioleaching column test of sulphide copper ore and copper concentrate using preconditioned surface

Directory of Open Access Journals (Sweden)

Videla Leiva Alvaro

2016-01-01

Full Text Available Bacterial activity can be related to the presence of Fe+3 in the solution, which drives copper oxidation during the secondary copper low grade sulfide ore leaching process. The present work evaluates improvements in kinetics of leaching when ferroxidans are preconditioned in an inert surface helping to build a biofilm which improves metabolism of the colony. The present work shows evaluation using laboratory columns to perform bioleaching during a 30 days period under three conditions: a base column with no inert surface, a column with loofa available for bacterial growth and conditioning, and finally a column with the loofa surface ground and distributed in the column among the particles.

Evaluation of the photocathode laser transverse distribution

Energy Technology Data Exchange (ETDEWEB)

Saisa-ard, Chaipattana [DESY, Zeuthen (Germany); Chiang Mai Univ., Chiang Mai (Thailand); Krasilnikov, Mikhail; Vashchenko, Grygorii [DESY, Zeuthen (Germany)

2016-07-01

Many years experience of electron source developments at the photo injector test facility at DESY in Zeuthen (PITZ) show that the photocathode laser is the one of major tools to produce high brightness electron beams. The transverse distribution of the laser on the photocathode plays a significant role in the high brightness photo injector optimization. However, the imperfections in the laser beam profile according to the deviation from a radially homogeneous profile directly result in transversely distorted charged particle distributions. This includes inhomogeneous core as well as transverse halo which is due to not sharp edges around the core. The laser transverse distribution is measured at PITZ using a virtual cathode:this is a CCD camera located at the position which is optically equivalent to the photocathode position (so called virtual cathode). An algorithm is developed for the evaluation of the experimentally obtained transverse profiles. It fits a flat-top or an inhomogeneous rotational symmetric core with exponentially decaying tails to an experimental distribution. The MATLAB script with implemented algorithm is applied to a set of measured transverse laser distributions. Results of the analysis will be presented.

Photocathode Optimization for a Dynamic Transmission Electron Microscope: Final Report

Energy Technology Data Exchange (ETDEWEB)

Ellis, P; Flom, Z; Heinselman, K; Nguyen, T; Tung, S; Haskell, R; Reed, B W; LaGrange, T

2011-08-04

The Dynamic Transmission Electron Microscope (DTEM) team at Harvey Mudd College has been sponsored by LLNL to design and build a test setup for optimizing the performance of the DTEM's electron source. Unlike a traditional TEM, the DTEM achieves much faster exposure times by using photoemission from a photocathode to produce electrons for imaging. The DTEM team's work is motivated by the need to improve the coherence and current density of the electron cloud produced by the electron gun in order to increase the image resolution and contrast achievable by DTEM. The photoemission test setup is nearly complete and the team will soon complete baseline tests of electron gun performance. The photoemission laser and high voltage power supply have been repaired; the optics path for relaying the laser to the photocathode has been finalized, assembled, and aligned; the internal setup of the vacuum chamber has been finalized and mostly implemented; and system control, synchronization, and data acquisition has been implemented in LabVIEW. Immediate future work includes determining a consistent alignment procedure to place the laser waist on the photocathode, and taking baseline performance measurements of the tantalum photocathode. Future research will examine the performance of the electron gun as a function of the photoemission laser profile, the photocathode material, and the geometry and voltages of the accelerating and focusing components in the electron gun. This report presents the team's progress and outlines the work that remains.

Copper plasmonics and catalysis: role of electron-phonon interactions in dephasing localized surface plasmons

Science.gov (United States)

Sun, Qi-C.; Ding, Yuchen; Goodman, Samuel M.; H. Funke, Hans; Nagpal, Prashant

2014-10-01

Copper metal can provide an important alternative for the development of efficient, low-cost and low-loss plasmonic nanoparticles, and selective nanocatalysts. However, poor chemical stability and lack of insight into photophysics and plasmon decay mechanisms has impeded study. Here, we use smooth conformal ALD coating on copper nanoparticles to prevent surface oxidation, and study dephasing time for localized surface plasmons on different sized copper nanoparticles. Using dephasing time as a figure of merit, we elucidate the role of electron-electron, electron-phonon, impurity, surface and grain boundary scattering on the decay of localized surface plasmon waves. Using our quantitative analysis and different temperature dependent measurements, we show that electron-phonon interactions dominate over other scattering mechanisms in dephasing plasmon waves. While interband transitions in copper metal contributes substantially to plasmon losses, tuning surface plasmon modes to infrared frequencies leads to a five-fold enhancement in the quality factor. These findings demonstrate that conformal ALD coatings can improve the chemical stability for copper nanoparticles, even at high temperatures (>300 °C) in ambient atmosphere, and nanoscaled copper is a good alternative material for many potential applications in nanophotonics, plasmonics, catalysis and nanoscale electronics.Copper metal can provide an important alternative for the development of efficient, low-cost and low-loss plasmonic nanoparticles, and selective nanocatalysts. However, poor chemical stability and lack of insight into photophysics and plasmon decay mechanisms has impeded study. Here, we use smooth conformal ALD coating on copper nanoparticles to prevent surface oxidation, and study dephasing time for localized surface plasmons on different sized copper nanoparticles. Using dephasing time as a figure of merit, we elucidate the role of electron-electron, electron-phonon, impurity, surface and grain

Surface modification of calcium–copper hydroxyapatites using polyaspartic acid

International Nuclear Information System (INIS)

Othmani, Masseoud; Aissa, Abdallah; Bachoua, Hassen; Debbabi, Mongi

2013-01-01

Highlights: ► The reaction of polyaspartic acid with calcium hydroxyapatite and mixed calcium–copper hydroxyapatite is tested. ► Chemical analysis shows that the presence of copper in the apatitic structure increases the reactivity of the apatite surface. ► X-ray powder analysis shows the conservation of unique crystalline phase of hydroxyapatite after copper incorporation and/or PASP acid reacting. ► IR spectra show the formation of the formation of organometallic bond M-O-C (M=Ca or Cu) on the apatitic surface. ► Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) indicated that the texture surface was changed by the grafting. - Abstract: Mixed calcium–copper hydroxyapatite (Ca–CuHAp), with general formula Ca (10−x) Cu x (PO 4 ) 6 (OH) 2 , where 0 ≤ x ≤ 0.75 was prepared in aqueous medium in the presence of different concentrations of poly-L-aspartic acid (PASP). XRD, IR, TG-DTA, TEM-EDX, AFM and chemical analyses were used to characterize the structure, morphology and composition of the products. All techniques show the formation of new hybrid compounds Ca–CuHAp–PASP. The presence of the grafting moiety on the apatitic material is more significant with increasing of copper amount and/or organic concentration in the starting solution. These increases lead to the affectation of apatite crystallinity. The IR spectroscopy shows the conservation of (P-OH) band of (HPO 4 ) 2− groups, suggesting that PASP acid was interacted only with metallic cations of hydroxyapatite.

Effect of Physical Property and Surface Morphology of Copper Foil at Electrodeposition Parameter

Energy Technology Data Exchange (ETDEWEB)

Woo, Tae Gyu; Park, Il Song; Lee, Man Hyung; Seol, Kyeong Won [Chonbuk National University, Jeonju (Korea, Republic of)

2014-06-15

The effect of additives, current density and plated temperature on the surface morphology and physical property, during copper electrodeposition on polyimide (PI) film was investigated. Two kinds of additives, Cl and leveler (additive B), were used in this study. Electrochemical experiments were performed in conjunction with SEM, XRD and four-point probe to characterize the morphology and mechanical characteristics of copper electrodeposited in the presence of the additives. The surface roughness, crystal growth orientation and resistivity was controlled by the concentration of additive B. High resistivity and lower peel strength were observed on the surface of the copper layer electroplated in the electrolyte without additive B. However, a uniform surface, lower resistivity and high flexibility were obtained with a combination of 20 ppm Cl and 100 ppm additive B. Large particles were observed on the surface of the copper layer electroplated using a current density of 25 mA/cm{sup 2}, but a uniform surface and lower resistivity were obtained using a current density of 10 mA/cm{sup 2}. One of the required important properties of FCCL is flexibility of the copper foil. High flexibility of FCCL was obtained at a low current density, rather than a high current density. Moreover, a reasonable current density is 20 mA/cm{sup 2}, considering the productivity and mechanical properties of copper foil.

Structured photocathodes for improved high-energy x-ray efficiency in streak cameras

Energy Technology Data Exchange (ETDEWEB)

Opachich, Y. P., E-mail: opachiyp@nv.doe.gov; Huffman, E.; Koch, J. A. [National Security Technologies, LLC, Livermore, California 94551 (United States); Bell, P. M.; Bradley, D. K.; Hatch, B.; Landen, O. L.; MacPhee, A. G.; Nagel, S. R. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Chen, N.; Gopal, A.; Udin, S. [Nanoshift LLC, Emeryville, California 94608 (United States); Feng, J. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Hilsabeck, T. J. [General Atomics, San Diego, California 92121 (United States)

2016-11-15

We have designed and fabricated a structured streak camera photocathode to provide enhanced efficiency for high energy X-rays (1–12 keV). This gold coated photocathode was tested in a streak camera and compared side by side against a conventional flat thin film photocathode. Results show that the measured electron yield enhancement at energies ranging from 1 to 10 keV scales well with predictions, and that the total enhancement can be more than 3×. The spatial resolution of the streak camera does not show degradation in the structured region. We predict that the temporal resolution of the detector will also not be affected as it is currently dominated by the slit width. This demonstration with Au motivates exploration of comparable enhancements with CsI and may revolutionize X-ray streak camera photocathode design.

Cs2Te normal conducting photocathodes in the superconducting rf gun

CERN Document Server

Xiang, R; Buettig, H; Janssen, D; Justus, M; Lehnert, U; Michel, P; Murcek, P; Schamlott, A; Schneider, Ch; Schurig, R; Staufenbiel, F; Teichert, J

2010-01-01

The superconducting radio frequency photoinjector (SRF gun) is one of the latest applications of superconducting rf technology in the accelerator field. Since superconducting photocathodes with high quantum efficiency are yet unavailable, normal conducting cathode material is the main choice for SRF photoinjectors. However, the compatibility between the photocathode and the cavity is one of the challenges for this concept. Recently, a SRF gun with Cs2Te cathode has been successfully operated in Forschungszentrum Dresden-Rossendorf. In this paper, we will present the physical properties of Cs2Te photocathodes in the SC cavity, such as the quantum efficiency, the lifetime, the rejuvenation, the charge saturation, and the dark current.

Copper surfaces are associated with significantly lower concentrations of bacteria on selected surfaces within a pediatric intensive care unit.

Science.gov (United States)

Schmidt, Michael G; von Dessauer, Bettina; Benavente, Carmen; Benadof, Dona; Cifuentes, Paulina; Elgueta, Alicia; Duran, Claudia; Navarrete, Maria S

2016-02-01

Health care-associated infections result in significant patient morbidity and mortality. Although cleaning can remove pathogens present on hospital surfaces, those surfaces may be inadequately cleaned or recontaminated within minutes. Because of copper's inherent and continuous antimicrobial properties, copper surfaces offer a solution to complement cleaning. The objective of this study was to quantitatively assess the bacterial microbial burden coincident with an assessment of the ability of antimicrobial copper to limit the microbial burden associated with 3 surfaces in a pediatric intensive care unit. A pragmatic trial was conducted enrolling 1,012 patients from 2 high acuity care units within a 249-bed tertiary care pediatric hospital over 12 months. The microbial burden was determined from 3 frequently encountered surfaces, regardless of room occupancy, twice monthly, from 16 rooms, 8 outfitted normally and 8 outfitted with antimicrobial copper. Copper surfaces were found to be equivalently antimicrobial in pediatric settings to activities reported for adult medical intensive care units. The log10 reduction to the microbial burden from antimicrobial copper surfaced bed rails was 1.996 (99%). Surprisingly, introduction of copper objects to 8 study rooms was found to suppress the microbial burden recovered from objects assessed in control rooms by log10 of 1.863 (73%). Copper surfaces warrant serious consideration when contemplating the introduction of no-touch disinfection technologies for reducing burden to limit acquisition of HAIs. Copyright © 2016 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Development of highly faceted reduced graphene oxide-coated copper oxide and copper nanoparticles on a copper foil surface

Directory of Open Access Journals (Sweden)

Rebeca Ortega-Amaya

2016-07-01

Full Text Available This work describes the formation of reduced graphene oxide-coated copper oxide and copper nanoparticles (rGO-Cu2ONPs, rGO-CuNPs on the surface of a copper foil supporting graphene oxide (GO at annealing temperatures of 200–1000 °C, under an Ar atmosphere. These hybrid nanostructures were developed from bare copper oxide nanoparticles which grew at an annealing temperature of 80 °C under nitrogen flux. The predominant phase as well as the particle size and shape strongly depend on the process temperature. Characterization with transmission electron microscopy and scanning electron microscopy indicates that Cu or Cu2O nanoparticles take rGO sheets from the rGO network to form core–shell Cu–rGO or Cu2O–rGO nanostructures. It is noted that such ones increase in size from 5 to 800 nm as the annealing temperature increases in the 200–1000 °C range. At 1000 °C, Cu nanoparticles develop a highly faceted morphology, displaying arm-like carbon nanorods that originate from different facets of the copper crystal structure.

Photocathode operation of a thermionic RF gun

International Nuclear Information System (INIS)

Thorin, S.; Cutic, N.; Lindau, F.; Werin, S.; Curbis, F.

2009-01-01

The thermionic RF gun using a BaO cathode at the MAX-lab linac injector has been successfully commissioned for additional operation as a photocathode gun. By retaining the BaO cathode, lowering the temperature below thermal emission and illuminating it with a UV (263 nm) 9 ps laser pulse a reduced emittance and enhanced emission control has been achieved. Measurements show a normalised emittance of 5.5 mm mrad at 200 pC charge and a maximum quantum efficiency of 1.1x10 -4 . The gun is now routinely switched between storage ring injections in thermionic mode and providing a beam for the MAX-lab test FEL in photocathode mode.

Copper in the sediment and sea surface microlayer near a fallowed, open-net fish farm.

Science.gov (United States)

Loucks, Ronald H; Smith, Ruth E; Fisher, Clyde V; Fisher, E Brian

2012-09-01

Sediment and sea surface microlayer samples near an open-net salmon farm in Nova Scotia, were analysed for copper. Copper is a constituent of the feed and is an active ingredient of anti-foulants. The salmon farm was placed in fallow after 15 years of production. Sampling was pursued over 27 months. Elevated copper concentrations in the sediments indicated the farm site as a source. Bubble flotation due to gas-emitting sediments from eutrophication is a likely process for accumulating copper in the sea surface microlayer at enriched concentrations. Elevated and enriched concentrations in the sea surface microlayer over distance from the farm site led, as a result of wind-drift, to an enlarged farm footprint. The levels of copper in both sediments and sea surface microlayer exceeded guidelines for protection of marine life. Over the 27 months period, copper levels persisted in the sediments and decreased gradually in the sea surface microlayer. Copyright © 2012 Elsevier Ltd. All rights reserved.

Surface modification of calcium-copper hydroxyapatites using polyaspartic acid

Energy Technology Data Exchange (ETDEWEB)

Othmani, Masseoud; Aissa, Abdallah; Bachoua, Hassen [Laboratoire de Physico-Chimie des Materiaux, Faculte des Sciences de Monastir, 5019 Monastir (Tunisia); Debbabi, Mongi, E-mail: m.debbabi@yahoo.fr [Laboratoire de Physico-Chimie des Materiaux, Faculte des Sciences de Monastir, 5019 Monastir (Tunisia)

2013-01-01

Highlights: Black-Right-Pointing-Pointer The reaction of polyaspartic acid with calcium hydroxyapatite and mixed calcium-copper hydroxyapatite is tested. Black-Right-Pointing-Pointer Chemical analysis shows that the presence of copper in the apatitic structure increases the reactivity of the apatite surface. Black-Right-Pointing-Pointer X-ray powder analysis shows the conservation of unique crystalline phase of hydroxyapatite after copper incorporation and/or PASP acid reacting. Black-Right-Pointing-Pointer IR spectra show the formation of the formation of organometallic bond M-O-C (M=Ca or Cu) on the apatitic surface. Black-Right-Pointing-Pointer Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) indicated that the texture surface was changed by the grafting. - Abstract: Mixed calcium-copper hydroxyapatite (Ca-CuHAp), with general formula Ca{sub (10-x)}Cu{sub x}(PO{sub 4}){sub 6}(OH){sub 2}, where 0 {<=} x {<=} 0.75 was prepared in aqueous medium in the presence of different concentrations of poly-L-aspartic acid (PASP). XRD, IR, TG-DTA, TEM-EDX, AFM and chemical analyses were used to characterize the structure, morphology and composition of the products. All techniques show the formation of new hybrid compounds Ca-CuHAp-PASP. The presence of the grafting moiety on the apatitic material is more significant with increasing of copper amount and/or organic concentration in the starting solution. These increases lead to the affectation of apatite crystallinity. The IR spectroscopy shows the conservation of (P-OH) band of (HPO{sub 4}){sup 2-} groups, suggesting that PASP acid was interacted only with metallic cations of hydroxyapatite.

Effects of combinative surface modification on the stability and conductivity of the copper particles

International Nuclear Information System (INIS)

Zeng, Yike; Li, Tongtong; Fu, Ming; Jiang, Shenglin; Zhang, Guangzu

2014-01-01

Highlights: • A combinative method is used to improve the performance of the copper powder. • The method integrates passivation, silver-coating, and coupling agent treatment. • The stability of the copper powder has been improved after the modification. • The sheet resistance of the conductive film is reduced to 15 mΩ. -- Abstract: The specific goal of the present study is to evaluate the surface performance of the copper particles and get excellent copper powder by surface modification. This paper proposes a combinative modification method integrating passivation, silver-coated, and coupling agent. As a result, after 600 h at room temperature the copper powder has the stabilization improved and is well combined with organic matters, and the sheet resistance of the film fabricated by the copper conductive filler is reduced to 15 mΩ. The performance of the copper powder has been greatly enhanced by the combinative modification, and the cost of the copper conductive filler is decreased significantly by this method. The results indicate that the combinative surface modification method can be used for practical electronic application

High-brightness electron beam evolution following laser-based cleaning of a photocathode

Directory of Open Access Journals (Sweden)

F. Zhou

2012-09-01

Full Text Available Laser-based techniques have been widely used for cleaning metal photocathodes to increase quantum efficiency (QE. However, the impact of laser cleaning on cathode uniformity and thereby on electron beam quality are less understood. We are evaluating whether this technique can be applied to revive photocathodes used for high-brightness electron sources in advanced x-ray free-electron laser (FEL facilities, such as the Linac Coherent Light Source (LCLS at the SLAC National Accelerator Laboratory. The laser-based cleaning was applied to two separate areas of the current LCLS photocathode on July 4 and July 26, 2011, respectively. The QE was increased by 8–10 times upon the laser cleaning. Since the cleaning, routine operation has exhibited a slow evolution of the QE improvement and comparatively rapid improvement of transverse emittance, with a factor of 3 QE enhancement over five months, and a significant emittance improvement over the initial 2–3 weeks following the cleaning. Currently, the QE of the LCLS photocathode is holding constant at about 1.2×10^{-4}, with a normalized injector emittance of about 0.3  μm for a 150-pC bunch charge. With the proper procedures, the laser-cleaning technique appears to be a viable tool to revive the LCLS photocathode. We present observations and analyses for the QE and emittance evolution in time following the laser-based cleaning of the LCLS photocathode, and comparison to the previous studies, the measured thermal emittance versus the QE and comparison to the theoretical model.

Cs_{2}Te normal conducting photocathodes in the superconducting rf gun

Directory of Open Access Journals (Sweden)

R. Xiang

2010-04-01

Full Text Available The superconducting radio frequency photoinjector (SRF gun is one of the latest applications of superconducting rf technology in the accelerator field. Since superconducting photocathodes with high quantum efficiency are yet unavailable, normal conducting cathode material is the main choice for SRF photoinjectors. However, the compatibility between the photocathode and the cavity is one of the challenges for this concept. Recently, a SRF gun with Cs_{2}Te cathode has been successfully operated in Forschungszentrum Dresden-Rossendorf. In this paper, we will present the physical properties of Cs_{2}Te photocathodes in the SC cavity, such as the quantum efficiency, the lifetime, the rejuvenation, the charge saturation, and the dark current.

Stability of metallic copper in the near surface environment

International Nuclear Information System (INIS)

Amcoff, Oe.; Holenyi, K.

1992-03-01

The present study was initiated by the National Board for Spent Nuclear Fuel (SKN). It may be regarded as a review of the state of the art of copper stability - copper mobility in a low temperature - near surface environment. In the discussion, we have emphasized geological - geochemical milieus that have a direct bearing on the problem of final storage of spent nuclear fuel in copper canisters. The literature review has concentrated on copper in connection with: a. low-temperature environments, and b. Stability-mobility, with particular emphasis on a chloride-rich, sulphur-rich milieu. The possible influence on the present processes of radiolysis and engineered barriers besides copper is not discussed in this report. In order to faciliate the discussion, a number of examples on copper mineral stabilities and copper solubility etc. are given below, based on thermodynamic calculations. These calculations are simplified to a certain degree and the discussion is based on differences in orders of magnitude rather than on exact figures. The thermodynamic foundation for the calculations is given in an appendix. Conclusions and recommendations are outlined in general terms in a separate report. (59 refs.) (au)

Investigation of surface resistance of copper in classical and anomalous skin-effect region

International Nuclear Information System (INIS)

Kutovoj, V.A.; Egorov, A.M.

2008-01-01

The surface resistance of copper in classical and anomalous skin-effect region has been investigated, and the surface resistance improvement factor equal to the ratio of the surface resistance of copper at room temperature to that of helium temperature, depending on the electromagnetic field frequency, has been determined. The improvement factor has been shown to have inverse power law dependence on frequency. The frequencies at which the improvement factor of copper equals 10 have been determined. It has been found that the quality factor of a resonance high-frequency system made of copper, operating at temperature T ≥ 4.2 K can be increased 10 times or more as against a quality factor of a resonance high-frequency system operating at room temperature

Improved Ion Resistance for III-V Photocathodes in High Current Guns

Energy Technology Data Exchange (ETDEWEB)

Mulhollan, Gregory, A.

2012-11-16

The two photocathode test systems were modified, baked and recommissioned. The first system was dedicated to ion studies and the second to electron stimulated recovery (ESR) work. The demonstration system for the electron beam rejuvenation was set up, tested and demonstrated to one of the SSRL team (Dr. Kirby) during a site visit. The requisite subsystems were transferred to SSRL, installed and photoemission studies conducted on activated surfaces following electron beam exposure. Little surface chemistry change was detected in the photoemission spectra following the ESR process. The yield mapping system for the ion (and later, the electron beam rejuvenation) studies was implemented and use made routine. Ion species and flux measurements were performed for H, He, Ne, Ar, Kr and Xe ions at energies of 0.5, 1.0 and 2.0 kV. Gas induced photoyield measurements followed each ion exposure measurement. These data permit the extraction of photoyield induced change per ion (by species) at the measured energies. Electron beam induced rejuvenation was first demonstrated in the second chamber with primary electron beam energy and dependency investigations following. A Hiden quadrupole mass spectrometer for the electron stimulated desorption (ESD) measurements was procured. The UHV test systems needed for subsequent measurements were configured, baked, commissioned and utilized for their intended purposes. Measurements characterizing the desorption products from the ESD process and secondary electron (SE) yield at the surfaces of negative electron affinity GaAs photocathodes have been performed. One US Utility Patent was granted covering the ESR process.

A polarized photoluminescence study of strained layer GaAs photocathodes

International Nuclear Information System (INIS)

Mair, R.A.

1996-07-01

Photoluminescence measurements have been made on a set of epitaxially grown strained GaAs photocathode structures. The photocathodes are designed to exhibit a strain-induced enhancement of the electron spin polarization obtainable by optical pumping with circularly polarized radiation of near band gap energy. For the case of non-strained GaAs, the degree of spin polarization is limited to 50% by crystal symmetry. Under an appropriate uniaxial compression or tension, however, the valence band structure near the gap minimum is modified such that a spin polarization of 100% is theoretically possible. A total of nine samples with biaxial compressive strains ranging from zero to ∼0.8% are studied. X-ray diffraction analysis, utilizing Bragg reflections, is used to determine the crystal lattice structure of the samples. Luminescence spectra and luminescence circular polarization data are obtained at room temperature, ∼78 K and ∼12 K. The degree of luminescence circular polarization is used as a relative measure of the photo-excited electron spin polarization. The room temperature luminescence circular polarization data is compared with the measured electron spin polarization when the samples are used as electron photo-emitters with a negative electron affinity surface preparation. The luminescence data is also analyzed in conjunction with the crystal structure data with the goal of understanding the strain dependent valence band structure, optical pumping characteristics and spin depolarization mechanisms of the photocathode structures. A simple model is used to describe the luminescence data, obtained for the set of samples. Within the assumptions of the model, the deformation potentials a, b and d for GaAs are determined. The measured values are a = -10.16±.21 eV, b = -2.00±.05 eV and d = -4.87±.29 eV. Good agreement with published values of the deformation potentials provides support for the model used to describe the data

The effect of iron and copper impurities on the wettability of sphalerite (110) surface.

Science.gov (United States)

Simpson, Darren J; Bredow, Thomas; Chandra, Anand P; Cavallaro, Giuseppe P; Gerson, Andrea R

2011-07-15

The effect of impurities in the zinc sulfide mineral sphalerite on surface wettability has been investigated theoretically to shed light on previously reported conflicting results on sphalerite flotation. The effect of iron and copper impurities on the sphalerite (110) surface energy and on the water adsorption energy was calculated with the semi-empirical method modified symmetrically orthogonalized intermediate neglect of differential overlap (MSINDO) using the cyclic cluster model. The effect of impurities or dopants on surface energies is small but significant. The surface energy increases with increasing surface iron concentration while the opposite effect is reported for increasing copper concentration. The effect on adsorption energies is much more pronounced with water clearly preferring to adsorb on an iron site followed by a zinc site, and copper site least favorable. The theoretical results indicate that a sphalerite (110) surface containing iron is more hydrophilic than the undoped zinc sulfide surface. In agreement with the literature, the surface containing copper (either naturally or by activation) is more hydrophobic than the undoped surface. Copyright © 2011 Wiley Periodicals, Inc.

Surface Functionalization of Thin-Film Composite Membranes with Copper Nanoparticles for Antimicrobial Surface Properties

KAUST Repository

Ben-Sasson, Moshe

2014-01-07

Biofouling is a major operational challenge in reverse osmosis (RO) desalination, motivating a search for improved biofouling control strategies. Copper, long known for its antibacterial activity and relatively low cost, is an attractive potential biocidal agent. In this paper, we present a method for loading copper nanoparticles (Cu-NPs) on the surface of a thin-film composite (TFC) polyamide RO membrane. Cu-NPs were synthesized using polyethyleneimine (PEI) as a capping agent, resulting in particles with an average radius of 34 nm and a copper content between 39 and 49 wt.%. The positive charge of the Cu-NPs imparted by the PEI allowed a simple electrostatic functionalization of the negatively charged RO membrane. We confirmed functionalization and irreversible binding of the Cu-NPs to the membrane surface with SEM and XPS after exposing the membrane to bath sonication. We also demonstrated that Cu-NP functionalization can be repeated after the Cu-NPs dissolve from the membrane surface. The Cu-NP functionalization had minimal impact on the intrinsic membrane transport parameters. Surface hydrophilicity and surface roughness were also maintained, and the membrane surface charge became positive after functionalization. The functionalized membrane exhibited significant antibacterial activity, leading to an 80-95% reduction in the number of attached live bacteria for three different model bacterial strains. Challenges associated with this functionalization method and its implementation in RO desalination are discussed. © 2013 American Chemical Society.

Surface Functionalization of Thin-Film Composite Membranes with Copper Nanoparticles for Antimicrobial Surface Properties

KAUST Repository

Ben-Sasson, Moshe; Zodrow, Katherine R.; Genggeng, Qi; Kang, Yan; Giannelis, Emmanuel P.; Elimelech, Menachem

2014-01-01

Biofouling is a major operational challenge in reverse osmosis (RO) desalination, motivating a search for improved biofouling control strategies. Copper, long known for its antibacterial activity and relatively low cost, is an attractive potential biocidal agent. In this paper, we present a method for loading copper nanoparticles (Cu-NPs) on the surface of a thin-film composite (TFC) polyamide RO membrane. Cu-NPs were synthesized using polyethyleneimine (PEI) as a capping agent, resulting in particles with an average radius of 34 nm and a copper content between 39 and 49 wt.%. The positive charge of the Cu-NPs imparted by the PEI allowed a simple electrostatic functionalization of the negatively charged RO membrane. We confirmed functionalization and irreversible binding of the Cu-NPs to the membrane surface with SEM and XPS after exposing the membrane to bath sonication. We also demonstrated that Cu-NP functionalization can be repeated after the Cu-NPs dissolve from the membrane surface. The Cu-NP functionalization had minimal impact on the intrinsic membrane transport parameters. Surface hydrophilicity and surface roughness were also maintained, and the membrane surface charge became positive after functionalization. The functionalized membrane exhibited significant antibacterial activity, leading to an 80-95% reduction in the number of attached live bacteria for three different model bacterial strains. Challenges associated with this functionalization method and its implementation in RO desalination are discussed. © 2013 American Chemical Society.

Advanced laser technologies for high-brightness photocathode electron gun

International Nuclear Information System (INIS)

Tomizawa, Hiromitsu

2012-01-01

A laser-excited photocathode RF gun is one of the most reliable high-brightness electron beam sources for XFELs. Several 3D laser shaping methods have been developed as ideal photocathode illumination sources at SPring-8 since 2001. To suppress the emittance growth caused by nonlinear space-charge forces, the 3D cylindrical UV-pulse was optimized spatially as a flattop and temporally as squarely stacked chirped pulses. This shaping system is a serial combination of a deformable mirror that adaptively shapes the spatial profile with a genetic algorithm and a UV-pulse stacker that consists of four birefringent α-BBO crystal rods for temporal shaping. Using this 3D-shaped pulse, a normalized emittance of 1.4 πmm mrad was obtained in 2006. Utilizing laser's Z-polarization, Schottky-effect-gated photocathode gun was proposed in 2006. The cathode work functions are reduced by a laser-induced Schottky effect. As a result of focusing a radially polarized laser pulse with a hollow lens in vacuum, the Z-field (Z-polarization) is generated at the cathode. (author)

Advanced Laser Technologies for High-brightness Photocathode Electron Gun

Science.gov (United States)

Tomizawa, Hiromitsu

A laser-excited photocathode RF gun is one of the most reliable high-brightness electron beam sources for XFELs. Several 3D laser shaping methods have been developed as ideal photocathode illumination sources at SPring-8 since 2001. To suppress the emittance growth caused by nonlinear space-charge forces, the 3D cylindrical UV-pulse was optimized spatially as a flattop and temporally as squarely stacked chirped pulses. This shaping system is a serial combination of a deformable mirror that adaptively shapes the spatial profile with a genetic algorithm and a UV-pulse stacker that consists of four birefringent α-BBO crystal rods for temporal shaping. Using this 3D-shaped pulse, a normalized emittance of 1.4 π mm mrad was obtained in 2006. Utilizing laser's Z-polarization, Schottky-effect-gated photocathode gun was proposed in 2006. The cathode work functions are reduced by a laser-induced Schottky effect. As a result of focusing a radially polarized laser pulse with a hollow lens in vacuum, the Z-field (Z-polarization) is generated at the cathode.

The importance of surface morphology in controlling the selectivity of polycrystalline copper for CO(2) electroreduction

DEFF Research Database (Denmark)

Tang, Wei; Peterson, Andrew A; Varela Gasque, Ana Sofia

2012-01-01

This communication examines the effect of the surface morphology of polycrystalline copper on electroreduction of CO(2). We find that a copper nanoparticle covered electrode shows better selectivity towards hydrocarbons compared with the two other studied surfaces, an electropolished copper elect...

Study of fine films nature on the surface of copper band by photoelectron spectroscopy method

International Nuclear Information System (INIS)

Reznichenko, K.N.; Fedorov, V.N.; Shevakin, Yu.F.

1983-01-01

The composition of surface films formed on the copper band of industrial production under atmospheric conditions, its changes in thickness and determination of chemical state of the above films are studied. It has been found by the methods of X-ray photoelectronic and Auger-spectroscopy that defect formations on the surface of the copper band of industrial production represent copper oxides in the form of fine films, their change in colour from blue to dark blue probably is determined by different thickness of these defects. The said films on copper have practically identical chemical composition characterized by the presence of unequally valent copper, oxygen in various states (adsorbed and in the form of oxides), carbon and iron. By means of chemical shifts of the line Cu 2psub(3/2) and Ol s the presence in the external part of the film of CuO copper oxide is established and nearer to the interface surface film-metal-of Cu 2 O cuprous oxide which indicates a two-layer surface film structure. The presence of adsorbed carbon and iron in the film composition is a result of surface contamination

Enhanced Photocatalytic Hydrogen Production By Surface Modification of p-Gap Photocathodes

DEFF Research Database (Denmark)

Malizia, Mauro; Seger, Brian; Chorkendorff, Ib

2014-01-01

of forming a p-n heterojunction on GaP. We deposit different n-type metal oxides (TiO2, Nb2O5, ...) thus forming an heterojunction which significantly enhances charge separation upon light irradiation by forming a built-in potential at the junction interface. This built-in potential effectively drives...... 300 mV compared to the pristine p-GaP semiconductor and marking an unprecedented value of open-circuit voltage for GaP-based photocathodes for hydrogen production. It is found that the high carrier density of the n-type oxides shifts the distribution of the built-in potential almost entirely towards...... the lightly doped p-type substrate and forms an asymmetric charge depletion region at the junction, as depicted in Figure 1. Moreover, TiO2shows excellent stability over long-time operation, unveiling its double role of brilliant material for both heterojunction formation and protection against corrosion...

High quantum efficiency photocathode simulation for the investigation of novel structured designs

Energy Technology Data Exchange (ETDEWEB)

Opachich, Y. P., E-mail: opachiyp@nv.doe.gov; Ross, P. W.; Huffman, E.; Koch, J. A. [National Security Technologies LLC, Livermore, California 94550 (United States); MacPhee, A. G.; Nagel, S. R.; Bell, P. M.; Bradley, D. K.; Landen, O. L. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Hilsabeck, T. J. [General Atomics, San Diego, California 92121 (United States)

2014-11-15

A computer model in CST Studio Suite has been developed to evaluate several novel geometrically enhanced photocathode designs. This work was aimed at identifying a structure that would increase the total electron yield by a factor of two or greater in the 1–30 keV range. The modeling software was used to simulate the electric field and generate particle tracking for several potential structures. The final photocathode structure has been tailored to meet a set of detector performance requirements, namely, a spatial resolution of <40 μm and a temporal spread of 1–10 ps. We present the details of the geometrically enhanced photocathode model and resulting static field and electron emission characteristics.

High power testing of a 17 GHz photocathode RF gun

International Nuclear Information System (INIS)

Chen, S.C.; Danly, B.G.; Gonichon, J.

1995-01-01

The physics and technological issues involved in high gradient particle acceleration at high microwave (RF) frequencies are under study at MIT. The 17 GHz photocathode RF gun has a 1 1/2 cell (π mode) room temperature cooper cavity. High power tests have been conducted at 5-10 MW levels with 100 ns pulses. A maximum surface electric field of 250 MV/m was achieved. This corresponds to an average on-axis gradient of 150 MeV/m. The gradient was also verified by a preliminary electron beam energy measurement. Even high gradients are expected in our next cavity design

X-ray in-situ study of copper electrodeposition on UHV prepared GaAs(001) surfaces

Energy Technology Data Exchange (ETDEWEB)

Gruender, Yvonne

2008-06-02

For this work a unique setup for in-situ electrochemical studies was employed and improved. This setup permits UHV preparation of the GaAs(001) surface with a defined surface termination (arsenic-rich or gallium-rich) and its characterization by SXRD in UHV, under ambient pressure in inert gas and in electrolyte under potential control without passing through air. The GaAs(001) surfaces were capped by amorphous arsenic. This permitted to ship them through ambient air. Afterwards smooth well defined GaAs(001) surfaces could be recovered by thermal annealing in UHV. A first investigation of the arsenic capped sample was done by atomic force microscopy (AFM) and Surface X-Ray Diffraction (SXRD). The non bulk like termination of the arsenic buried GaAs(001) surface was revealed. For the electrochemical metal deposition, arsenic terminated (2 x 4) reconstructed and gallium terminated (4 x 2) reconstructed GaAs(001) surfaces were employed. These surfaces were characterized by STM, LEED and a first time by SXRD. The surfaces are smooth, however, a higher degree of disorder than for MBE prepared reconstructed GaAs(001) is found. After exposure of the sample to nitrogen, the surfaces were then again studied by SXRD. These two steps characterizing the bare GaAs(001) surfaces permitted us to get a better knowledge of the starting surface and its influence on the later electrodeposited copper. At ambient pressure both reconstructions are lifted, but the surface is not bulk-like terminated as can be deduced from the crystal truncation rods. Epitaxial copper clusters grow upon electrodeposition on the UHV prepared GaAs(001) surface. The copper lattice is rotated and inclined with respect to the GaAs substrate lattice, leading to eight symmetry equivalent domains. The influence of the surface termination as well as the nucleation potential on the structure of the electrodeposited copper were investigated. The tilt and rotation angles do not depend on the deposition potential but

Auger electron spectroscopy study of surface segregation in the binary alloys copper-1 atomic percent indium, copper-2 atomic percent tin, and iron-6.55 atomic percent silicon

Science.gov (United States)

Ferrante, J.

1973-01-01

Auger electron spectroscopy was used to examine surface segregation in the binary alloys copper-1 at. % indium, copper-2 at. % tin and iron-6.55 at. % silicon. The copper-tin and copper-indium alloys were single crystals oriented with the /111/ direction normal to the surface. An iron-6.5 at. % silicon alloy was studied (a single crystal oriented in the /100/ direction for study of a (100) surface). It was found that surface segregation occurred following sputtering in all cases. Only the iron-silicon single crystal alloy exhibited equilibrium segregation (i.e., reversibility of surface concentration with temperature) for which at present we have no explanation. McLean's analysis for equilibrium segregation at grain boundaries did not apply to the present results, despite the successful application to dilute copper-aluminum alloys. The relation of solute atomic size and solubility to surface segregation is discussed. Estimates of the depth of segregation in the copper-tin alloy indicate that it is of the order of a monolayer surface film.

Comparison of blue-green response between transmission-mode GaAsP- and GaAs-based photocathodes grown by molecular beam epitaxy

Science.gov (United States)

Gang-Cheng, Jiao; Zheng-Tang, Liu; Hui, Guo; Yi-Jun, Zhang

2016-04-01

In order to develop the photodetector for effective blue-green response, the 18-mm-diameter vacuum image tube combined with the transmission-mode Al0.7Ga0.3As0.9 P 0.1/GaAs0.9 P 0.1 photocathode grown by molecular beam epitaxy is tentatively fabricated. A comparison of photoelectric property, spectral characteristic and performance parameter between the transmission-mode GaAsP-based and blue-extended GaAs-based photocathodes shows that the GaAsP-based photocathode possesses better absorption and higher quantum efficiency in the blue-green waveband, combined with a larger surface electron escape probability. Especially, the quantum efficiency at 532 nm for the GaAsP-based photocathode achieves as high as 59%, nearly twice that for the blue-extended GaAs-based one, which would be more conducive to the underwater range-gated imaging based on laser illumination. Moreover, the simulation results show that the favorable blue-green response can be achieved by optimizing the emission-layer thickness in a range of 0.4 μm-0.6 μm. Project supported by the National Natural Science Foundation of China (Grant No. 61301023) and the Science and Technology on Low-Light-Level Night Vision Laboratory Foundation, China (Grant No. BJ2014001).

Antimicrobial copper alloys decreased bacteria on stethoscope surfaces.

Science.gov (United States)

Schmidt, Michael G; Tuuri, Rachel E; Dharsee, Arif; Attaway, Hubert H; Fairey, Sarah E; Borg, Keith T; Salgado, Cassandra D; Hirsch, Bruce E

2017-06-01

Stethoscopes may serve as vehicles for transmission of bacteria among patients. The aim of this study was to assess the efficacy of antimicrobial copper surfaces to reduce the bacterial concentration associated with stethoscope surfaces. A structured prospective trial involving 21 health care providers was conducted at a pediatric emergency division (ED) (n = 14) and an adult medical intensive care unit located in tertiary care facilities (n = 7). Four surfaces common to a stethoscope and a facsimile instrument fabricated from U.S. Environmental Protection Agency-registered antimicrobial copper alloys (AMCus) were assessed for total aerobic colony counts (ACCs), methicillin-resistant Staphylococcus aureus, gram-negative bacteria, and vancomycin-resistant enterococci for 90 days. The mean ACCs collectively recovered from all stethoscope surfaces fabricated from the AMCus were found to carry significantly lower concentrations of bacteria (pediatric ED, 11.7 vs 127.1 colony forming units [CFU]/cm 2 , P stethoscopes was the most heavily burdened surface; mean concentrations exceeded the health care-associated infection acquisition concentration (5 CFU/cm 2 ) by at least 25×, supporting that the stethoscope warrants consideration in plans mitigating microbial cross-transmission during patient care. Stethoscope surfaces fabricated with AMCus were consistently found to harbor fewer bacteria. Copyright © 2017 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics

International Nuclear Information System (INIS)

Krantz, Claude

2009-01-01

We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at usable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully. (orig.)

Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics

Energy Technology Data Exchange (ETDEWEB)

Krantz, Claude

2009-10-28

We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at usable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully. (orig.)

Surface modification of an epoxy resin with polyamines and polydopamine: Adhesion toward electroless deposited copper

Energy Technology Data Exchange (ETDEWEB)

Schaubroeck, David, E-mail: David.Schaubroeck@elis.ugent.be [Center for Microsystems Technology (CMST), IMEC and Ghent University, Technologiepark 914A, B-9052 Ghent (Belgium); Mader, Lothar [Center for Microsystems Technology (CMST), IMEC and Ghent University, Technologiepark 914A, B-9052 Ghent (Belgium); Dubruel, Peter [Polymer Chemistry and Biomaterials Research Group, Ghent University, Krijgslaan 281 S4 bis, B-9000 Ghent (Belgium); Vanfleteren, Jan [Center for Microsystems Technology (CMST), IMEC and Ghent University, Technologiepark 914A, B-9052 Ghent (Belgium)

2015-10-30

Highlights: • Surface modifications of epoxy resins with polydopamine and grafted polyamines can significantly increase the adhesion toward electroless deposited copper. • A clear characterization of the copper/epoxy interphase is provided by SEM analyses of cross sections. • Tailored conditions such as etching time (roughness) and electroless deposition temperature are needed to increase the adhesion of the modified surfaces. - Abstract: In this paper the influence of the epoxy roughness, surface modifications and ELD (electroless copper deposition) temperatures on the adhesive strength of the copper is studied. Good adhesion at low roughness values is targeted due to their applicability in high density electronic circuits. Roughened epoxy surfaces are modified with adsorbed polyamines, polydopamine and polyamines grafted to polydopamine. Next the, adhesive strength of ELD copper is determined with peel strength measurements and the interphases are examined with SEM (scanning electron microscopy). Polydopamine and polyamines grafted to polydopamine can lead to increased adhesive strength at lower roughness values compared to the non-modified samples at specific plating temperatures.

Voltage breakdown on niobium and copper surfaces

International Nuclear Information System (INIS)

Werner, G.R.; Padamsee, H.; Betzwieser, J.C.; Liu, Y.G.; Rubin, K.H.R.; Shipman, J.E.; Ying, L.T.

2003-01-01

Experiments have shown that voltage breakdown in superconducting niobium RF cavities is in many ways similar to voltage breakdown on niobium cathodes in DC voltage gaps; most striking are the distinctive starburst patterns and craters that mark the site of voltage breakdown in both superconducting cavities and DC vacuum gaps. Therefore, we can learn much about RF breakdown from simpler, faster DC experiments. We have direct evidence, in the form of before'' and ''after'' pictures, that breakdown events caused by high surface electric fields occur with high probability at contaminant particles on surfaces. Although the pre-breakdown behavior (field emission) seems to depend mostly on the contaminant particles present and little on the substrate, the breakdown event itself is greatly affected by the substrate-niobium, heavily oxidized niobium, electropolished copper, and diamond-machined copper cathodes lead to different kinds of breakdown events. By studying DC voltage breakdown we hope to learn more details about the processes involved in the transition from field emission to catastrophic arcing and the cratering of the surface; as well as learning how to prevent breakdown, we would like to learn how to cause breakdown, which could be important when ''processing'' cavities to reduce field emission. (author)

Mechanisms and energetics of surface reactions at the copper-water interface. A critical literature review with implications for the debate on corrosion of copper in anoxic water

Energy Technology Data Exchange (ETDEWEB)

Johansson, Adam Johannes; Brinck, Tore [Applied Physical Chemistry, KTH Royal Inst. of Technology, Stockholm (Sweden)

2012-06-15

In order to make a critical analysis of the discussion of corrosion of copper in pure anoxic water it is necessary to understand the chemical reactivity at the copper-water interface. Even though the most fundamental issue, i.e. the nature and existence of a hypothetical product that is thermodynamically stable, is still under debate, it is clear that if anoxic corrosion really exists, it must be initiated through oxidative surface reactions at the copper-water interface. This report presents a survey of the peer reviewed literature on the reactivity of copper surfaces in water. Reactions discussed involve molecular adsorption of water, dissociation of the OH-bonds in adsorbed water molecules and hydroxyl groups, the disproportionation/synproportionation equilibrium between hydroxyl groups/hydroxide ions, water molecules and atomic oxygen, the surface diffusion of adsorbed species, and the formation of hydrogen gas (molecular hydrogen). Experimental, as well as theoretical (quantum chemical) studies are reviewed. It is concluded that a limited amount of hydrogen gas (H{sub 2}) should be formed as the result of dissociative water adsorption at certain copper surfaces. Quantitative estimates of the amounts of H2 that could form at the copper-water interface are made. Assuming that the water-cleavage/hydrogen-formation reaction proceeds on an ideal [110] or [100] surface until a hydroxyl monolayer (ML) is reached, the amount of H{sub 2} formed is {approx} 2.4 ng cm{sup -2} copper surface. Based on the literature cited, this is most likely possible, thermodynamically as well as kinetically. Although not proven, it is not unlikely that the reaction can proceed until an oxide ML is formed, which would give 4.8 ng cm{sup -2}. If the formation of an oxide ML is thermodynamically feasible the surface will probably react further, since Cu{sub 2}O(s) is known to activate and cleave the water molecule when it adsorbs at the Cu{sub 2}O(s) surface. Assuming the formation of a

High Brightness Injectors Based On Photocathode DC Gun

International Nuclear Information System (INIS)

B. Yunn

2001-01-01

Sample results of new injector design method based on a photocathode dc gun are presented, based on other work analytically proving the validity of the emittance compensation scheme for the case even when beam bunching is involved. We have designed several new injectors appropriate for different bunch charge ranges accordingly. Excellent beam quality produced by these injectors clearly shows that a photocathode dc gun can compete with a rf gun on an equal footing as the source of an electron beam for the bunch charge ranging up to 2 nano Coulomb (nC). This work therefore elevates a dc gun based injector to the preferred choice for many ongoing high brightness accelerator projects considering the proven operational stability and high average power capability of the dc gun

Improving wettability of photo-resistive film surface with plasma surface modification for coplanar copper pillar plating of IC substrates

International Nuclear Information System (INIS)

Xiang, Jing; Wang, Chong; Chen, Yuanming; Wang, Shouxu; Hong, Yan; Zhang, Huaiwu; Gong, Lijun; He, Wei

2017-01-01

Highlights: • Air atmosphere plasmacould generatehydrophilic groups of photo-resistive film. • Better wettability of photo-resistive filmled tohigher plating uniformity of copper pillars. • New flow isreduced cost, simplified process and elevated productivity. - Abstract: The wettability of the photo-resistive film (PF) surfaces undergoing different pretreatments including the O_2−CF_4 low-pressure plasma (OCLP) and air plasma (AP), is investigated by water contact angle measurement instrument (WCAMI) before the bottom-up copper pillar plating. Chemical groups analysis performed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectra (XPS) shows that after the OCLP and wash treatment, the wettability of PF surface is attenuated, because embedded fluorine and decreased oxygen content both enhance hydrophobicity. Compared with OCLP treatment, the PF surface treatment by non-toxic air plasma displays features of C−O, O−C=O, C=O and −NO_2 by AIR-FTIR and XPS, and a promoted wettability by WCAM. Under the identical electroplating condition, the surface with a better wettability allows electrolyte to spontaneously soak all the places of vias, resulting in improved copper pillar uniformity. Statistical analysis of metallographic data shows that more coplanar and flat copper pillars are achieved with the PF treatment of air plasma. Such modified copper-pillar-plating technology meets the requirement of accurate impedance, the high density interconnection for IC substrates.

Step driven competitive epitaxial and self-limited growth of graphene on copper surface

Directory of Open Access Journals (Sweden)

Lili Fan

2011-09-01

Full Text Available The existence of surface steps was found to have significant function and influence on the growth of graphene on copper via chemical vapor deposition. The two typical growth modes involved were found to be influenced by the step morphologies on copper surface, which led to our proposed step driven competitive growth mechanism. We also discovered a protective role of graphene in preserving steps on copper surface. Our results showed that wide and high steps promoted epitaxial growth and yielded multilayer graphene domains with regular shape, while dense and low steps favored self-limited growth and led to large-area monolayer graphene films. We have demonstrated that controllable growth of graphene domains of specific shape and large-area continuous graphene films are feasible.

A pulsed electron injector using a metal photocathode irradiated by an excimer laser

International Nuclear Information System (INIS)

Kauppila, T.J.; Builta, L.A.; Crutcher, J.K.; Elliott, J.C.; Moir, D.C.

1987-01-01

The hot cathode of an electron gun is replaced by a metallic photocathode driven by an excimer laser. The current, current density, and emittance of the 500-kV electron beam produced by the photoelectron source are presented. In addition, the temperature of the photocathode is varied to study the possibility of a hybrid source

Field dependent surface resistance of niobium on copper cavities

Directory of Open Access Journals (Sweden)

T. Junginger

2015-07-01

Full Text Available The surface resistance R_{S} of superconducting cavities prepared by sputter coating a niobium film on a copper substrate increases significantly stronger with the applied rf field compared to cavities of bulk material. A possible cause is that the thermal boundary resistance between the copper substrate and the niobium film induces heating of the inner cavity wall, resulting in a higher R_{S}. Introducing helium gas in the cavity, and measuring its pressure as a function of applied field allowed to conclude that the inner surface of the cavity is heated up by less than 120 mK when R_{S} increases with E_{acc} by 100  nΩ. This is more than one order of magnitude less than what one would expect from global heating. Additionally, the effects of cooldown speed and low temperature baking have been investigated in the framework of these experiments. It is shown that for the current state of the art niobium on copper cavities there is only a detrimental effect of low temperature baking. A fast cooldown results in a lowered R_{S}.

Comparative study on the copper activation and xanthate adsorption on sphalerite and marmatite surfaces

Science.gov (United States)

Liu, Jian; Wang, Yu; Luo, Deqiang; Chen, Luzheng; Deng, Jiushuai

2018-05-01

The copper activation and potassium butyl xanthate (PBX) adsorption on sphalerite and marmatite surfaces were comparatively investigated using in situ local electrochemical impedance spectroscopy (LEIS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and surface adsorption tests. Comparing the LEIS and surface adsorption results, it was found that the activation time is a key factor influencing the copper activation and PBX adsorption on marmatite surface, but it has a negligible influence on sphalerite. For a short activation time within 10 min, the Fe impurity in marmatite shows an adverse influence on the speed of Cu adsorption and ion exchange as well as on the subsequent PBX adsorption. For a long activation time of 30 min, the LEIS, ToF-SIMS and surface adsorption results suggested that the Fe impurity in marmatite enhances the copper adsorption, whereas such enhanced copper adsorption of marmatite cannot result in corresponding enhancing of PBX adsorption. DFT result showed that the Fe impurity in marmatite has harmful influence on the PBX interaction with the Cu-activated surface by increasing the interaction energy. ToF-SIMS result further indicated that the Cu distribution in the outermost surface of marmatite is less than that of the sphalerite, which also results in the less PBX adsorption for the marmatite.

Improving wettability of photo-resistive film surface with plasma surface modification for coplanar copper pillar plating of IC substrates

Science.gov (United States)

Xiang, Jing; Wang, Chong; Chen, Yuanming; Wang, Shouxu; Hong, Yan; Zhang, Huaiwu; Gong, Lijun; He, Wei

2017-07-01

The wettability of the photo-resistive film (PF) surfaces undergoing different pretreatments including the O2sbnd CF4 low-pressure plasma (OCLP) and air plasma (AP), is investigated by water contact angle measurement instrument (WCAMI) before the bottom-up copper pillar plating. Chemical groups analysis performed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectra (XPS) shows that after the OCLP and wash treatment, the wettability of PF surface is attenuated, because embedded fluorine and decreased oxygen content both enhance hydrophobicity. Compared with OCLP treatment, the PF surface treatment by non-toxic air plasma displays features of Csbnd O, Osbnd Cdbnd O, Cdbnd O and sbnd NO2 by AIR-FTIR and XPS, and a promoted wettability by WCAM. Under the identical electroplating condition, the surface with a better wettability allows electrolyte to spontaneously soak all the places of vias, resulting in improved copper pillar uniformity. Statistical analysis of metallographic data shows that more coplanar and flat copper pillars are achieved with the PF treatment of air plasma. Such modified copper-pillar-plating technology meets the requirement of accurate impedance, the high density interconnection for IC substrates.

Enhancement of solar hydrogen evolution from water by surface modification with CdS and TiO2 on porous CuInS2 photocathodes prepared by an electrodeposition-sulfurization method.

Science.gov (United States)

Zhao, Jiao; Minegishi, Tsutomu; Zhang, Li; Zhong, Miao; Gunawan; Nakabayashi, Mamiko; Ma, Guijun; Hisatomi, Takashi; Katayama, Masao; Ikeda, Shigeru; Shibata, Naoya; Yamada, Taro; Domen, Kazunari

2014-10-27

Porous films of p-type CuInS2, prepared by sulfurization of electrodeposited metals, are surface-modified with thin layers of CdS and TiO2. This specific porous electrode evolved H2 from photoelectrochemical water reduction under simulated sunlight. Modification with thin n-type CdS and TiO2 layers significantly increased the cathodic photocurrent and onset potential through the formation of a p-n junction on the surface. The modified photocathodes showed a relatively high efficiency and stable H2 production under the present reaction conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of a wettability-gradient surface on copper by screen-printing techniques

International Nuclear Information System (INIS)

Huang, Ding-Jun; Leu, Tzong-Shyng

2015-01-01

In this study, a screen-printing technique is utilized to fabricate a wettability-gradient surface on a copper substrate. The pattern definitions on the copper surface were freely fabricated to define the regions with different wettabilities, for which the printing definition technique was developed as an alternative to the existing costly photolithography techniques. This fabrication process using screen printing in tandem with chemical modification methods can easily realize an excellent wettability-gradient surface with superhydrophobicity and superhydrophilicity. Surface analyses were performed to characterize conditions in some fabrication steps. A water droplet movement sequence is provided to clearly demonstrate the droplet-driving effectiveness of the fabricated gradient surface. The droplet-driving efficiency offers a promising solution for condensation heat transfer applications in the foreseeable future. (paper)

Protection of copper surface with phytic acid against corrosion in chloride solution.

Science.gov (United States)

Peca, Dunja; Pihlar, Boris; Ingrid, Milošev

2014-01-01

Phytic acid (inositol hexaphosphate) was tested as a corrosion inhibitor for copper in 3% sodium chloride. Phytic acid is a natural compound derived from plants, it is not toxic and can be considered as a green inhibitor. Electrochemical methods of linear polarization and potentiodynamic polarization were used to study the electrochemical behaviour and evaluate the inhibition effectiveness. To obtain the optimal corrosion protection the following experimental conditions were investigated: effect of surface pre-treatment (abrasion and three procedures of surface roughening), pre-formation of the layer of phytic acid, time of immersion and concentration of phytic acid. To evaluate the surface pre-treatment procedures the surface roughness and contact angle were measured. Optimal conditions for formation of phytic layer were selected resulting in the inhibition effectiveness of nearly 80%. Morphology and composition of the layer were further studied by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The layer of phytic acid with thickness in the nanometer range homogeneously covers the copper surface. The obtained results show that this natural compound can be used as a mildly effective corrosion inhibitor for copper in chloride solution.

Photocathodes in accelerator applications

International Nuclear Information System (INIS)

Fraser, J.S.; Sheffield, R.L.; Gray, E.R.; Giles, P.M.; Springer, R.W.; Loebs, V.A.

1987-01-01

Some electron accelerator applications require bursts of short pulses at high microscopic repetition rates and high peak brightness. A photocathode, illuminated by a mode-locked laser, is well suited to filling this need. The intrinsic brightness of a photoemitter beam is high; experiments are under way at Los Alamos to study the brightness of short bunches with high space charge after acceleration. A laser-illuminated Cs 3 Sb photoemitter is located in the first rf cavity of an injector linac. Diagnostics include a pepper-pot emittance analyzer, a magnetic spectrometer, and a streak camera

Improving wettability of photo-resistive film surface with plasma surface modification for coplanar copper pillar plating of IC substrates

Energy Technology Data Exchange (ETDEWEB)

Xiang, Jing; Wang, Chong; Chen, Yuanming; Wang, Shouxu; Hong, Yan; Zhang, Huaiwu [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Gong, Lijun [Research and Development Department, Guangzhou Fastprint Circuit Tech Co., Ltd., Guangzhou 510663 (China); He, Wei, E-mail: heweiz@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research and Development Department, Guangdong Guanghua Sci-Tech Co., Ltd., Shantou 515000 (China)

2017-07-31

Highlights: • Air atmosphere plasmacould generatehydrophilic groups of photo-resistive film. • Better wettability of photo-resistive filmled tohigher plating uniformity of copper pillars. • New flow isreduced cost, simplified process and elevated productivity. - Abstract: The wettability of the photo-resistive film (PF) surfaces undergoing different pretreatments including the O{sub 2}−CF{sub 4} low-pressure plasma (OCLP) and air plasma (AP), is investigated by water contact angle measurement instrument (WCAMI) before the bottom-up copper pillar plating. Chemical groups analysis performed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectra (XPS) shows that after the OCLP and wash treatment, the wettability of PF surface is attenuated, because embedded fluorine and decreased oxygen content both enhance hydrophobicity. Compared with OCLP treatment, the PF surface treatment by non-toxic air plasma displays features of C−O, O−C=O, C=O and −NO{sub 2} by AIR-FTIR and XPS, and a promoted wettability by WCAM. Under the identical electroplating condition, the surface with a better wettability allows electrolyte to spontaneously soak all the places of vias, resulting in improved copper pillar uniformity. Statistical analysis of metallographic data shows that more coplanar and flat copper pillars are achieved with the PF treatment of air plasma. Such modified copper-pillar-plating technology meets the requirement of accurate impedance, the high density interconnection for IC substrates.

Methanol sensor for integration with GaP nanowire photocathode

Science.gov (United States)

Novák, J.; Laurenčíková, A.; Hasenohrl, S.; Eliáš, P.; Kováč, J.

2017-05-01

We proposed a new type of the methanol concentration sensor that may be integrated directly to the GaP nanostructured photocathode. Necessary attribute for this design is the possibility to make it compatible with p-type of semiconductor. This condition follows from the fact that photocathodes for the CO2 splitting are exclusively prepared from p-type of semiconductors. Design of methanol sensor emanates from this principle. On the GaP substrate is deposited thin Pt supporting layer (100-200 nm thick).This layer is covered by 500 nm thick Nafion membrane that serves as proton filter. On the top of Nafion layer is deposited top Pt contact layer covered by thin nanostructured Pt layer layer with various thickness (0.5 -5 nm). This nanostructured Pt is formed into small islands. It serves as an absorption layer for methanol. Sensor detection properties were estimated from monitoring of I-V characteristics. They were measured in dark and under various methanol concentrations. Dark current values are in order 10-9 A, and this current increases up to order of microamps for methanol of concentration more than 95%.These measurements proved high sensitivity of the GaP compatible sensor structure. Methanol sensors were realized in form of narrow stripe on the side of the photocathode.

Durable and Washable Antibacterial Copper Nanoparticles Bridged by Surface Grafting Polymer Brushes on Cotton and Polymeric Materials

Directory of Open Access Journals (Sweden)

Chufeng Sun

2018-01-01

Full Text Available To increase the durability of antibacterial coating on cotton and polymeric substrates, surface initiated grafting polymer brushes are introduced onto the substrates surface to bridge copper nanoparticles coatings and substrate. The morphologies of the composites consisting of the copper nanoparticles and polymer brushes were characterized with scanning electron microscopy (SEM. It was found that copper nanoparticles were uniformly and firmly distributed on the surfaces of the substrates by the polymer brushes; meanwhile, the reinforced concrete-like structures were formed in the composite materials. The substrates coated by the copper nanoparticles showed the efficient antibacterial activity against Staphylococcus aureus (S. aureus and Escherichia coli (E. coli even after washing by 30 cycles. The copper nanoparticles were tethered on the substrates by the strong chemical bonds, which led to the excellent washable fitness and durability. The change of the phase structure of the copper was analyzed to investigate the release mechanism of copper ions.

Spectral response variation of a negative-electron-affinity photocathode in the preparation process

International Nuclear Information System (INIS)

Liu Lei; Du Yujie; Chang Benkang; Yunsheng Qian

2006-01-01

In order to research the spectral response variation of a negative electron affinity (NEA) photocathode in the preparation process, we have done two experiments on a transmission-type GaAs photocathode.First, an automatic spectral response recording system is described, which is used to take spectral response curves during the activation procedure of the photocathode. By this system, the spectral response curves of a GaAs:Cs-Ophotocathode measured in situ are presented. Then, after the cathode is sealed with a microchannel plate and a fluorescence screen into the image tube, we measure the spectral response of the tube by another measurement instrument. By way of comparing and analyzing these curves, we can find the typical variation in spectral-responses.The reasons for the variation are discussed. Based on these curves, spectral matching factors of a GaAs cathode for green vegetation and rough concrete are calculated. The visual ranges of night-vision goggles under specific circumstances are estimated. The results show that the spectral response of the NEA photocathode degraded in the sealing process, especially at long wavelengths. The variation has also influenced the whole performance of the intensifier tube

Quantum chemical molecular dynamical investigation of alkyl nitrite photo-dissociated on copper surfaces

International Nuclear Information System (INIS)

Wang Xiaojing; Wang Wei; Han Peilin; Kubo, Momoji; Miyamoto, Akira

2008-01-01

An accelerated quantum chemical molecular dynamical code 'Colors-Excite' was used to investigate the photolysis of alkyl nitrites series, RONO (R=CH 3 and C(CH 3 ) 3 ) on copper surfaces. Our calculations showed that the photo-dissociated processes are associated with the alkyl substituents of RONO when adsorbed on copper surfaces. For R=CH 3 , a two-step photolysis reaction occurred, yielding diverse intermediate products including RO radical, NO, and HNO, consistent with those reported in gas phase. While for R=C(CH 3 ) 3 , only one-step photolysis reaction occurred and gave intermediate products of RO radical and NO. Consequently, pure RO species were achieved to adsorb on metal surfaces by removing the NO species in photolysis reaction. The detailed photo-dissociated behaviors of RONO on copper surfaces with different alkyl substituents which are uncovered by the present simulation can be extended to explain the diverse dissociative mechanism experimentally observed. The quantum chemical molecular dynamical code 'Colors-Excite' is proved to be highly applicable to the photo-dissociations on metal surfaces

Surface and near surface defect detection in thick copper EB-welds using eddy current testing

International Nuclear Information System (INIS)

Pitkaenen, J.; Lipponen, A.

2010-01-01

The surface inspection of thick copper electron beam (EB) welds plays an important role in the acceptance of nuclear fuel disposal. The main reasons to inspect these components are related to potential manufacturing and handling defects. In this work the data acquisition software, visualising tools for eddy current (EC) measurements and eddy current sensors were developed for detection of unwanted defects. The eddy current equipment was manufactured by IZFP and the visualising software in active co-operation with Posiva and IZFP for the inspections. The inspection procedure was produced during the development of the inspection techniques. The inspection method development aims to qualify the method for surface and near surface defect detection and sizing according to ENIQ. The study includes technical justification to be carried out, and compilation of a defect catalogue and experience from measurements within the Posiva's research on issues related to manufacturing. The depth of penetration in copper components in eddy current testing is rather small. To detect surface breaking defects the eddy current inspection is a good solution. A simple approach was adopted using two techniques: higher frequency was used to detect surface defects and to determine the dimensions of the defects except depth, lower frequency was used to detect defects having a ligament and for sizing of deeper surface breaking defects. The higher frequency was 30 kHz and the lower frequency was 200 Hz. The higher frequency probes were absolute bobbing coils and lower frequency probes combined transmitter - several receiver coils. To evaluate both methods, calibration blocks were manufactured by FNS for weld inspections. These calibration specimens mainly consisted of electron discharge machined notches and holes of varying shapes, lengths and diameters in the range of 1 mm to 20 mm of depth. Also one copper lid specimen with 152 defects was manufactured and used for evaluation of weld inspection

Nonepitaxial Thin-Film InP for Scalable and Efficient Photocathodes.

Science.gov (United States)

Hettick, Mark; Zheng, Maxwell; Lin, Yongjing; Sutter-Fella, Carolin M; Ager, Joel W; Javey, Ali

2015-06-18

To date, some of the highest performance photocathodes of a photoelectrochemical (PEC) cell have been shown with single-crystalline p-type InP wafers, exhibiting half-cell solar-to-hydrogen conversion efficiencies of over 14%. However, the high cost of single-crystalline InP wafers may present a challenge for future large-scale industrial deployment. Analogous to solar cells, a thin-film approach could address the cost challenges by utilizing the benefits of the InP material while decreasing the use of expensive materials and processes. Here, we demonstrate this approach, using the newly developed thin-film vapor-liquid-solid (TF-VLS) nonepitaxial growth method combined with an atomic-layer deposition protection process to create thin-film InP photocathodes with large grain size and high performance, in the first reported solar device configuration generated by materials grown with this technique. Current-voltage measurements show a photocurrent (29.4 mA/cm(2)) and onset potential (630 mV) approaching single-crystalline wafers and an overall power conversion efficiency of 11.6%, making TF-VLS InP a promising photocathode for scalable and efficient solar hydrogen generation.

Development status of a test stand for semiconductor photocathodes with 60 keV spin-polarized beamline

Energy Technology Data Exchange (ETDEWEB)

Kurichijanil, Neeraj; Enders, Joachim; Espig, Martin; Fritzsche, Yuliya; Heichelt, Dominic; Kaiser, Andreas; Roesch, Heidi; Wagner, Markus [Institut fuer Kernphysik, TU Darmstadt (Germany)

2016-07-01

A test facility for Photo-Cathode Activation, Test and Cleaning using atomic-Hydrogen (Photo-CATCH) is being constructed at TU Darmstadt's Institute for Nuclear Physics (IKP) which houses the Superconducting Darmstadt Linear Accelerator (S-DALINAC). In order to improve the performance of the SDALINAC's photoelectron source based on GaAs, systematic studies in terms of quantum efficiency (QE), cathode rejuvenation, lifetimes and polarization (P) have to be conducted on different photocathode types. These factors strongly depend on handling of the cathode, the vacuum condition in the chambers, cathode surface cleaning as well as preservation of stoichiometry, negative electron affinity (NEA) activation of the cathode and the type and structure of the semiconductor material. With Photo-CATCH, experiments such as atomic-hydrogen cleaning, multi-alkali and oxidant NEA activation of the cathode and tests of QE, P and lifetimes can be performed in an improved vacuum. Additionally, experiments with polarized-electron beams of up to 60 keV are foreseen.

Electrostatic X-ray image recording device with mesh-base photocathode photoelectron discriminator means

International Nuclear Information System (INIS)

1977-01-01

An electrostatic X-ray image recording device having a pair of spaced electrodes with a gas-filled gap therebetween, and including discrimination means, having a conductive mesh supporting a photocathodic material, positioned in the gas-filled gap between a first electrode having a layer of ultraviolet-emitting fluorescent material and a second electrode having a plastic sheet adjacent thereto for receiving photoelectrons emitted by the photocathodic material and accelerated to the second electrode by an applied field. The photoconductor-mesh element discriminates against fast electrons, produced by direct impingement of X-rays upon the photocathode to substantially reduce secondary electron production and amplification, thereby increasing both the signal-to-noise and contrast ratios. The electrostatic image formed on the plastic sheet is developed by zerographic techniques after exposure. (Auth.)

Studies on the influence of surface pre-treatments on electroless copper coating of boron carbide particles

International Nuclear Information System (INIS)

Deepa, J.P.; Resmi, V.G.; Rajan, T.P.D.; Pavithran, C.; Pai, B.C.

2011-01-01

Boron carbide is one of the hard ceramic particles which find application as structural materials and neutron shielding material due to its high neutron capture cross section. Copper coating on boron carbide particle is essential for the synthesis of metal-ceramic composites with enhanced sinterability and dispersibility. Surface characteristics of the substrate and the coating parameters play a foremost role in the formation of effective electroless coating. The effect of surface pre-treatment conditions and pH on electroless copper coating of boron carbide particles has been studied. Surface pre-treatement of B 4 C when compared to acid treated and alkali treated particles were carried out. Uniform copper coating was observed at pH 12 in alkali treated particles when compared to others due to the effective removal of inevitable impurities during the production and processing of commercially available B 4 C. A threshold pH 11 was required for initiation of copper coating on boron carbide particles. The growth pattern of the copper coating also varies depending on the surface conditions from acicular to spherical morphology.

A high-gradient high-duty-factor Rf photo-cathode electron gun

International Nuclear Information System (INIS)

Rimmer, Robert A.; Hartman, Neal; Lidia, Steven M.; Wang, Shaoheng

2002-01-01

We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure

A high-gradient high-duty-factor RF photo-cathode electron gun

International Nuclear Information System (INIS)

Rimmer, Robert; Hartman, N.; Lidia, S.; Wang, S.H.

2002-01-01

We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure

Effects of phosphourus addition on the physical properties and surface condition of tungsten-copper composites

International Nuclear Information System (INIS)

Akiyoshi, N.; Nakada, K.; Nakayama, M.; Kohda, K.

2001-01-01

Tungsten-copper composites containing a small amount of phosphorus prepared using conventional P/M method. Cu 3 P powder was used as phosphorous source. The effects of phosphorus addition on the physical properties and the surface condition were investigated and the existing form of phosphorus was specified on the tungsten-copper composites The results are summarized as follows. The tungsten-copper composite containing 10 % copper, for example, demonstrated optimum thermal conductivity at the phosphorus addition of 0.02 %. The density of the composites was almost 100 % and the surface of the sintered body was flat and smooth after sintering at a temperature between 1100 and 1150 o C. It was shown that phosphorus exists as Co 2 P. (author)

Quantum efficiency and thermal emittance of metal photocathodes

Directory of Open Access Journals (Sweden)

David H. Dowell

2009-07-01

Full Text Available Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths with major advances occurring since the invention of the photocathode gun and the realization of emittance compensation. These state-of-the-art electron beams are now becoming limited by the intrinsic thermal emittance of the cathode. In both dc and rf photocathode guns details of the cathode emission physics strongly influence the quantum efficiency and the thermal emittance. Therefore improving cathode performance is essential to increasing the brightness of beams. It is especially important to understand the fundamentals of cathode quantum efficiency and thermal emittance. This paper investigates the relationship between the quantum efficiency and the thermal emittance for metal cathodes using the Fermi-Dirac model for the electron distribution. We use a consistent theory to derive the quantum efficiency and thermal emittance, and compare our results to those of others.

Nanoscale surface characterization of aqueous copper corrosion: Effects of immersion interval and orthophosphate concentration

Energy Technology Data Exchange (ETDEWEB)

Daniels, Stephanie L. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); United States Environmental Protection Agency, National Risk Management Research Laboratory (NRMRL), Water Supply and Water Resource Division (WSWRD), Cincinnati, OH 45268 (United States); Sprunger, Phillip T. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Center for Advanced Microstructures and Devices, Synchrotron Radiation Facility of Louisiana State University, Baton Rouge, LA 70803 (United States); Kizilkaya, Orhan [Center for Advanced Microstructures and Devices, Synchrotron Radiation Facility of Louisiana State University, Baton Rouge, LA 70803 (United States); Lytle, Darren A. [United States Environmental Protection Agency, National Risk Management Research Laboratory (NRMRL), Water Supply and Water Resource Division (WSWRD), Cincinnati, OH 45268 (United States); Garno, Jayne C., E-mail: jgarno@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States)

2013-11-15

Morphology changes for copper surfaces exposed to different water parameters were investigated at the nanoscale with atomic force microscopy (AFM), as influenced by changes in pH and the levels of orthophosphate ions. Synthetic water samples were designed to mimic physiological chemistries for drinking water, both with and without addition of orthophosphate over a pH range 6.5–9. Copper surfaces treated with orthophosphate as a corrosion inhibitor after 6 and 24 h were evaluated. Tapping mode AFM images revealed dosing of the water with 6 mg/L of orthophosphate was beneficial in retarding the growth of copper by-products. The chemical composition and oxidation state of the surface deposits were characterized with X-ray diffraction (XRD), near edge X-ray absorption fine structure (NEXAFS) spectroscopy and Fourier transform infrared spectroscopy (FTIR).

Removal of copper and nickel contaminants from Si surface by use of cyanide solutions

International Nuclear Information System (INIS)

Fujiwara, N.; Liu, Y.-L.; Nakamura, T.; Maida, O.; Takahashi, M.; Kobayashi, H.

2004-01-01

The cleaning method using cyanide solutions has been developed to remove heavy metals such as copper (Cu) and nickel (Ni) from Si surfaces. Immersion of Si wafers with both Cu and Ni contaminants in potassium cyanide (KCN) solutions of methanol at room temperature decreases these surface concentrations below the detection limit of total reflection X-ray fluorescence spectroscopy of ∼3x10 9 atoms/cm 2 . UV spectra of the KCN solutions after cleaning of the Cu-contaminated Si surface show that stable copper-cyanide complexes are formed in the solution, leading to the prevention of the re-adsorption of copper in the solutions. From the complex stability constants, it is concluded that the Cu(CN) 4 3- is the most dominant species in the KCN solutions

Temporal resolution limit estimation of x-ray streak cameras using a CsI photocathode

Energy Technology Data Exchange (ETDEWEB)

Li, Xiang; Gu, Li; Zong, Fangke; Zhang, Jingjin; Yang, Qinlao, E-mail: qlyang@szu.edu.cn [Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Institute of Optoelectronics, Shenzhen University, Shenzhen 518060 (China)

2015-08-28

A Monte Carlo model is developed and implemented to calculate the characteristics of x-ray induced secondary electron (SE) emission from a CsI photocathode used in an x-ray streak camera. Time distributions of emitted SEs are investigated with an incident x-ray energy range from 1 to 30 keV and a CsI thickness range from 100 to 1000 nm. Simulation results indicate that SE time distribution curves have little dependence on the incident x-ray energy and CsI thickness. The calculated time dispersion within the CsI photocathode is about 70 fs, which should be the temporal resolution limit of x-ray streak cameras that use CsI as the photocathode material.

Surface functionalization of copper via oxidative graft polymerization of 2,2'-bithiophene and immobilization of silver nanoparticles for combating biocorrosion.

Science.gov (United States)

Wan, Dong; Yuan, Shaojun; Neoh, K G; Kang, E T

2010-06-01

An environmentally benign approach to surface modification was developed to impart copper surface with enhanced resistance to corrosion, bacterial adhesion and biocorrosion. Oxidative graft polymerization of 2,2'-bithiophene from the copper surface with self-assembled 2,2'-bithiophene monolayer, and subsequent reduction of silver ions to silver nanoparticles (Ag NPs) on the surface, give rise to a homogeneous bithiophene polymer (PBT) film with densely coupled Ag NPs on the copper surface (Cu-g-PBT-Ag NP surface). The immobilized Ag NPs were found to significantly inhibit bacterial adhesion and enhance the antibacterial properties of the PBT modified copper surface. The corrosion inhibition performance of the functionalized copper substrates was evaluated by Tafel polarization curves and electrochemical impedance spectroscopy. Arising from the chemical affinity of thiols for the noble and coinage metals, the copper surface functionalized with both PBT brushes and Ag NPs also exhibits long-term stability, and is thus potentially useful for combating the combined problems of corrosion and biocorrosion in harsh marine and aquatic environments.

Sources of Emittance in RF Photocathode Injectors

Energy Technology Data Exchange (ETDEWEB)

Dowell, David [SLAC National Accelerator Lab., Menlo Park, CA (United States)

2016-12-11

Advances in electron beam technology have been central to creating the current generation of x-ray free electron lasers and ultra-fast electron microscopes. These once exotic devices have become essential tools for basic research and applied science. One important beam technology for both is the electron source which, for many of these instruments, is the photocathode RF gun. The invention of the photocathode gun and the concepts of emittance compensation and beam matching in the presence of space charge and RF forces have made these high-quality beams possible. Achieving even brighter beams requires a taking a finer resolution view of the electron dynamics near the cathode during photoemission and the initial acceleration of the beam. In addition, the high brightness beam is more sensitive to degradation by the optical aberrations of the gun’s RF and magnetic lenses. This paper discusses these topics including the beam properties due to fundamental photoemission physics, space charge effects close to the cathode, and optical distortions introduced by the RF and solenoid fields. Analytic relations for these phenomena are derived and compared with numerical simulations.

Performance of photocathode rf gun electron accelerators

International Nuclear Information System (INIS)

Ben-Zvi, I.

1993-01-01

In Photo-Injectors (PI) electron guns, electrons are emitted from a photocathode by a short laser pulse and then accelerated by intense rf fields in a resonant cavity. The best known advantage of this technique is the high peak current with a good emittance (high brightness). This is important for short wavelength Free-Electron Lasers and linear colliders. PIs are in operation in many electron accelerator facilities and a large number of new guns are under construction. Some applications have emerged, providing, for example, very high pulse charges. PIs have been operated over a wide range of frequencies, from 144 to 3000 MHz (a 17 GHz gun is being developed). An exciting new possibility is the development of superconducting PIs. A significant body of experimental and theoretical work exists by now, indicating the criticality of the accelerator elements that follow the gun for the preservation of the PI's performance as well as possible avenues of improvements in brightness. Considerable research is being done on the laser and photocathode material of the PI, and improvement is expected in this area

Molecular dynamic simulations of the high-speed copper nanoparticles collision with the aluminum surface

Science.gov (United States)

Pogorelko, V. V.; Mayer, A. E.

2016-11-01

With the use of the molecular dynamic simulations, we investigated the effect of the high-speed (500 m/s, 1000 m/s) copper nanoparticle impact on the mechanical properties of an aluminum surface. Dislocation analysis shows that a large number of dislocations are formed in the impact area; the total length of dislocations is determined not only by the speed and size of the incoming copper nanoparticle (kinetic energy of the nanoparticle), but by a temperature of the system as well. The dislocations occupy the whole area of the aluminum single crystal at high kinetic energy of the nanoparticle. With the decrease of the nanoparticle kinetic energy, the dislocation structures are formed in the near-surface layer; formation of the dislocation loops takes place. Temperature rise of the system (aluminum substrate + nanoparticle) reduces the total dislocation length in the single crystal of aluminum; there is deeper penetration of the copper atoms in the aluminum at high temperatures. Average energy of the nanoparticles and room temperature of the system are optimal for production of high-quality layers of copper on the aluminum surface.

Surface Impedance of Copper MOB Depending on the Annealing Temperature and Deformation Degree

International Nuclear Information System (INIS)

Kutovoj, V.A.; Nikolaenko, A.A.; Stoev, P.I.; Vinogradov, D.V.

2006-01-01

Results of researches of influence of annealing temperature and deformation degree on mechanical features of copper MOB are presented. It is shown that minimal surface resistance is observed in copper samples that were subject to pre-deformation and were annealed in the range of temperatures 873...923 K

Modeling of Diamond Field-Emitter-Arrays for high brightness photocathode applications

Science.gov (United States)

Kwan, Thomas; Huang, Chengkun; Piryatinski, Andrei; Lewellen, John; Nichols, Kimberly; Choi, Bo; Pavlenko, Vitaly; Shchegolkov, Dmitry; Nguyen, Dinh; Andrews, Heather; Simakov, Evgenya

2017-10-01

We propose to employ Diamond Field-Emitter-Arrays (DFEAs) as high-current-density ultra-low-emittance photocathodes for compact laser-driven dielectric accelerators capable of generating ultra-high brightness electron beams for advanced applications. We develop a semi-classical Monte-Carlo photoemission model for DFEAs that includes carriers' transport to the emitter surface and tunneling through the surface under external fields. The model accounts for the electronic structure size quantization affecting the transport and tunneling process within the sharp diamond tips. We compare this first principle model with other field emission models, such as the Child-Langmuir and Murphy-Good models. By further including effects of carrier photoexcitation, we perform simulations of the DFEAs' photoemission quantum yield and the emitted electron beam. Details of the theoretical model and validation against preliminary experimental data will be presented. Work ssupported by LDRD program at LANL.

Femtosecond response time measurements of a Cs2Te photocathode

Science.gov (United States)

Aryshev, A.; Shevelev, M.; Honda, Y.; Terunuma, N.; Urakawa, J.

2017-07-01

Success in design and construction of a compact, high-brightness accelerator system is strongly related to the production of ultra-short electron beams. Recently, the approach to generate short electron bunches or pre-bunched beams in RF guns directly illuminating a high quantum efficiency semiconductor photocathode with femtosecond laser pulses has become attractive. The measurements of the photocathode response time in this case are essential. With an approach of the interferometer-type pulse splitter deep integration into a commercial Ti:Sa laser system used for RF guns, it has become possible to generate pre-bunched electron beams and obtain continuously variable electron bunch separation. In combination with a well-known zero-phasing technique, it allows us to estimate the response time of the most commonly used Cs2Te photocathode. It was demonstrated that the peak-to-peak rms time response of Cs2Te is of the order of 370 fs, and thereby, it is possible to generate and control a THz sequence of relativistic electron bunches by a conventional S-band RF gun. This result can also be applied for investigation of other cathode materials and electron beam temporal shaping and further opens a possibility to construct wide-range tunable, table-top THz free electron laser.

On the field dependent surface resistance of niobium on copper cavities

CERN Document Server

Junginger, Tobias

2015-01-01

The surface resistance Rs of superconducting cavities prepared by sputter coating a thin niobium film on a copper substrate increases significantly stronger with the applied RF field compared to cavities of bulk material. A possible cause is that due to the thermal boundary resistance between the copper substrate and the niobium film Rs is enhanced due to global heating of the inner cavity wall. Introducing helium gas in the cavity and measuring its pressure as a function of applied field allowed to conclude that the inner surface of the cavity is heated up by only 60+/-60 mK when Rs increases with Eacc by 100 nOhm. This is more than one order of magnitude less than what one would expect from global heating. Additionally the effect of cooldown speed and low temperature baking have been investigated in the framework of these experiments. It is shown that for current state of the art niobium on copper cavities there is only a detrimental effect of low temperature baking. A fast cooldown results in a lowered Rs.

DC photogun vacuum characterization through photocathode lifetime studies

International Nuclear Information System (INIS)

Marcy Stutzman; Joseph Grames; Matt Poelker; Kenneth Surles-Law; Philip Adderley

2007-01-01

Excellent vacuum is essential for long photocathode lifetimes in DC high voltage photoelectron guns. Vacuum Research at Thomas Jefferson National Accelerator Facility has focused on characterizing the existing vacuum systems at the CEBAF polarized photoinjector and on quantifying improvements for new systems. Vacuum chamber preprocessing, full activation of NEG pumps and NEG coating the chamber walls should improve the vacuum within the electron gun, however, pressure measurement is difficult at pressures approaching the extreme-high-vacuum (XHV) region and extractor gauge readings are not significantly different between the improved and original systems. The ultimate test of vacuum in a DC high voltage photogun is the photocathode lifetime, which is limited by the ionization and back-bombardment of residual gasses. Discussion will include our new load-locked gun design as well as lifetime measurements in both our operational and new photo-guns, and the correlations between measured vacuum and lifetimes will be investigated

Study of the Quantum Efficiency of CsI Photocathodes Exposed to Oxygen and Water Vapour

CERN Document Server

Di Mauro, A; Piuz, François; Schyns, E M; Van Beelen, J B; Williams, T D

2000-01-01

The operation of CsI photocathodes in gaseous detectors requires special attention to the purity of the applied gas mixtures.We have studied the influence of oxygen and water vapour contaminations on the performance of CsI photocathodes for theALICE HMPID RICH prototype. Measurements were done through comparison of Cherenkov rings obtained from beamtests. Increased levels of oxygen and water vapour did not show any effect on the performance. The results of this studyfound a direct application in the way of storing CsI photocathodes over long periods nad in particular in the shipment of theHMPID prototype from CERN to the STAR experiment at BNL. (Abstract only available,full text to follow)

Double-layered NiO photocathodes for p-type DSSCs with record IPCE

Energy Technology Data Exchange (ETDEWEB)

Li, Lin; Qin, Peng; Gorlov, Mikhail [Center of Molecular Devices School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm (Sweden); Gibson, Elizabeth A.; Boschloo, Gerrit [Department of Physical and Analytical Chemistry, Uppsala University (Sweden); Hagfeldt, Anders [Center of Molecular Devices School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm (Sweden); Department of Physical and Analytical Chemistry, Uppsala University (Sweden); DUT-KTH Joint Education and Research Center of Molecular Devices, State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), Dalian (China); Sun, Licheng [Center of Molecular Devices School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm (Sweden); DUT-KTH Joint Education and Research Center of Molecular Devices, State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), Dalian (China)

2010-04-18

A way to achieve a high-efficiency dye-sensitized solar cell is to combine an n-type TiO{sub 2}-based photoanode with a p-type photocathode in a tandem configuration. The development of an efficient photocathode is, at present, the key target. We have optimized the NiO, I{sub 3}{sup -}/I{sup -} p-DSSC system to obtain record photocurrent, giving 64% incident photon-to-current conversion efficiency (IPCE) and 5.48 mAcm{sup -2} J{sub SC}. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Automated installation for several photomultiplier photocathode activation by means of one vacuum facility

International Nuclear Information System (INIS)

Beschastnov, P.M.; Peryshkin, A.I.; Pyata, E.Eh.; Usov, Yu.V.

1989-01-01

An automated installation for simultaneous activation of up to four photocathodes of several photomultipliers by means of one vacuum station with the common furnace is described. Production technology of producing multialkaline photocathode makes up the basis for creating automated technology. The installation is produced on the base of the R110B industrial station and the Electronica-60 microcomputer. Software written in FORTRAN providing for control over all process stages is developed. 6 refs.; 2 figs

The Quantum Efficiency and Thermal Emittance of Metal Photocathodes

International Nuclear Information System (INIS)

Dowell, D.

2009-01-01

Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths, with the principle improvements occurring since the invention of the photocathode gun. The state-of-the-art normalized emittance electron beams are now becoming limited by the thermal emittance of the cathode. In both DC and RF photocathode guns, details of the cathode emission physics strongly influence the quantum efficiency and the thermal emittance. Therefore improving cathode performance is essential to increasing the brightness of beams. It is especially important to understand the fundamentals of cathode quantum efficiency and thermal emittance. This paper investigates the relationship between the quantum efficiency and the thermal emittance of metal cathodes using the Fermi-Dirac model for the electron distribution. We derive the thermal emittance and its relationship to the quantum efficiency, and compare our results to those of others

Fabrication of long-term stable superoleophobic surface based on copper oxide/cobalt oxide with micro-nanoscale hierarchical roughness

Science.gov (United States)

Barthwal, Sumit; Lim, Si-Hyung

2015-02-01

We have demonstrated a simple and cost-effective technique for the large-area fabrication of a superoleophobic surface using copper as a substrate. The whole process included three simple steps: First, the copper substrate was oxidized under hot alkaline conditions to fabricate flower-like copper oxide microspheres by heating at a particular temperature for an interval of time. Second, the copper-oxide-covered copper substrate was further heated in a solution of cobalt nitrate and ammonium nitrate in the presence of an ammonia solution to fabricate cobalt oxide nanostructures. We applied this second step to increase the surface roughness because it is an important criterion for improved superoleophobicity. Finally, to reduce the surface energy of the fabricated structures, the surfaces were chemically modified with perfluorooctyltrichlorosilane. Contact-angle measurements indicate that the micro-nano binary (MNB) hierarchical structures fabricated on the copper substrate became super-repellent toward a broad range of liquids with surface tension in the range of 21.5-72 mN/m. In an attempt to significantly improve the superoleophobic property of the surface, we also examined and compared the role of nanostructures in MNB hierarchical structures with only micro-fabricated surfaces. The fabricated MNB hierarchical structures also displays thermal stability and excellent long-term stability after exposure in air for more than 9 months. Our method might provide a general route toward the preparation of novel hierarchical films on metal substrates for various industrial applications.

Surface modification of an epoxy resin with polyamines and polydopamine: The effect on the initial electroless copper deposition

Energy Technology Data Exchange (ETDEWEB)

Schaubroeck, David, E-mail: David.Schaubroeck@elis.ugent.be [Center for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 914A, B-9052 Ghent (Belgium); Mader, Lothar [Center for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 914A, B-9052 Ghent (Belgium); De Geyter, Nathalie; Morent, Rino [Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering, Ghent University, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); Dubruel, Peter [Polymer Chemistry and Biomaterials Research Group, Ghent University, Krijgslaan 281 S4 bis, B-9000 Ghent (Belgium); Vanfleteren, Jan [Center for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 914A, B-9052 Ghent (Belgium)

2014-06-01

This paper describes the influence of polydopamine and polyamine surface modifications of an etched epoxy cresol novolak (ECN) resin on the initial electroless copper deposition. Three different strategies to introduce polyamines on a surface in aqueous environment are applied: via polyethyleneimine adsorption (PEI), via polydopamine and via polyamines grafted to polydopamine. Next, the influence of these surface modifications on the catalytic palladium activation is investigated through X-ray photoelectron spectroscopy (XPS) analysis. Finally, the initial electroless copper deposition on modified epoxy surfaces is evaluated using SEM and Energy Dispersive Spectroscopy (EDS). Grafted polyamines on polydopamine surface modifications result in a large increase of the initial deposited copper.

Technology to Establish a Factory for High QE Alkali Antimonide Photocathodes

Energy Technology Data Exchange (ETDEWEB)

Schultheiss, Thomas [Advanced Energy Systems, Inc., Medford, NY (United States)

2015-11-16

Intense electron beams are key to a large number of scientific endeavors, including electron cooling of hadron beams, electron-positron colliders, secondary-particle beams such as photons and positrons, sub-picosecond ultrafast electron diffraction (UED), and new high gradient accelerators that use electron-driven plasmas. The last decade has seen a considerable interest in pursuit and realization of novel light sources such as Free Electron Lasers [1] and Energy Recovery Linacs [2] that promise to deliver unprecedented quality x-ray beams. Many applications for high-intensity electron beams have arisen in recent years in high-energy physics, nuclear physics and energy sciences, such as recent designs for an electron-hadron collider at CERN (LHeC) [3], and beam coolers for hadron beams at LHC and eRHIC [4,5]. Photoinjectors are used at the majority of high-brightness electron linacs today, due to their efficiency, timing structure flexibility and ability to produce high power, high brightness beams. The performance of light source machines is strongly related to the brightness of the electron beam used for generating the x-rays. The brightness of the electron beam itself is mainly limited by the physical processes by which electrons are generated. For laser based photoemission sources this limit is ultimately related to the properties of photocathodes [6]. Most facilities are required to expend significant manpower and money to achieve a workable, albeit often non-ideal, compromise photocathode solution. If entirely fabricated in-house, the photocathode growth process itself is laborious and not always reproducible: it involves the human element while requiring close adherence to recipes and extremely strict control of deposition parameters. Lack of growth reliability and as a consequence, slow adoption of viable photoemitter types, can be partly attributed to the absence of any centralized facility or commercial entity to routinely provide high peak current

Hot Hole Collection and Photoelectrochemical CO2 Reduction with Plasmonic Au/p-GaN Photocathodes.

Science.gov (United States)

DuChene, Joseph S; Tagliabue, Giulia; Welch, Alex J; Cheng, Wen-Hui; Atwater, Harry A

2018-04-11

Harvesting nonequilibrium hot carriers from plasmonic-metal nanostructures offers unique opportunities for driving photochemical reactions at the nanoscale. Despite numerous examples of hot electron-driven processes, the realization of plasmonic systems capable of harvesting hot holes from metal nanostructures has eluded the nascent field of plasmonic photocatalysis. Here, we fabricate gold/p-type gallium nitride (Au/p-GaN) Schottky junctions tailored for photoelectrochemical studies of plasmon-induced hot-hole capture and conversion. Despite the presence of an interfacial Schottky barrier to hot-hole injection of more than 1 eV across the Au/p-GaN heterojunction, plasmonic Au/p-GaN photocathodes exhibit photoelectrochemical properties consistent with the injection of hot holes from Au nanoparticles into p-GaN upon plasmon excitation. The photocurrent action spectrum of the plasmonic photocathodes faithfully follows the surface plasmon resonance absorption spectrum of the Au nanoparticles and open-circuit voltage studies demonstrate a sustained photovoltage during plasmon excitation. Comparison with Ohmic Au/p-NiO heterojunctions confirms that the vast majority of hot holes generated via interband transitions in Au are sufficiently hot to inject above the 1.1 eV interfacial Schottky barrier at the Au/p-GaN heterojunction. We further investigated plasmon-driven photoelectrochemical CO 2 reduction with the Au/p-GaN photocathodes and observed improved selectivity for CO production over H 2 evolution in aqueous electrolytes. Taken together, our results offer experimental validation of photoexcited hot holes more than 1 eV below the Au Fermi level and demonstrate a photoelectrochemical platform for harvesting hot carriers to drive solar-to-fuel energy conversion.

Laser cladding of stainless steel with a copper-silver alloy to generate surfaces of high antimicrobial activity

Science.gov (United States)

Hans, Michael; Támara, Juan Carlos; Mathews, Salima; Bax, Benjamin; Hegetschweiler, Andreas; Kautenburger, Ralf; Solioz, Marc; Mücklich, Frank

2014-11-01

Copper and silver are used as antimicrobial agents in the healthcare sector in an effort to curb infections caused by bacteria resistant to multiple antibiotics. While the bactericidal potential of copper and silver alone are well documented, not much is known about the antimicrobial properties of copper-silver alloys. This study focuses on the antibacterial activity and material aspects of a copper-silver model alloy with 10 wt% Ag. The alloy was generated as a coating with controlled intermixing of copper and silver on stainless steel by a laser cladding process. The microstructure of the clad was found to be two-phased and in thermal equilibrium with minor Cu2O inclusions. Ion release and killing of Escherichia coli under wet conditions were assessed with the alloy, pure silver, pure copper and stainless steel. It was found that the copper-silver alloy, compared to the pure elements, exhibited enhanced killing of E. coli, which correlated with an up to 28-fold increased release of copper ions. The results show that laser cladding with copper and silver allows the generation of surfaces with enhanced antimicrobial properties. The process is particularly attractive since it can be applied to existing surfaces.

An in-situ photocathode loading system for the SLC Polarized Electron Gun

International Nuclear Information System (INIS)

Kirby, R.E.; Collet, G.J.; Skarpaas, K.

1992-12-01

An ultra-high vacuum loadlock system capable of operating at high voltage has been added to the SLC Polarized Electron Gun. The unit incorporates facilities for heat cleaning, activating and measuring the quantum efficiency of photocathodes. A tray of up to four photocathodes can be exchanged without bringing the activation unit or gun up to atmosphere. Low voltage quantum efficiencies of 20% have been obtained for bulk GaAs at 633 nm and 6% for a 0.3 micron GaAs layer at 755 nm. Results for other cathodes as well as operational characteristics are discussed

The polymeric nanofilm of triazinedithiolsilane fabricated by self-assembled technique on copper surface. Part 2: Characterization of composition and morphology

Science.gov (United States)

Wang, Yabin; Liu, Zhong; Huang, Yudong; Qi, Yutai

2015-11-01

In the first part, a novel design route for metal protection against corrosion was proposed, and a class of triazinedithiolsilane compounds was conceived as protector for copper. The protective capability of the polymeric nanofilm, fabricated by self-assembling one representative (abbreviated as TESPA) of triazinedithiolsilane compounds onto copper surface, has been investigated and evaluated by electrochemical tests. The results show that the polymeric nanofilm significantly inhibits copper corrosion. This study, on the one hand, concentrates on the chemical composition of the TESPA polymeric nanofilm by means of X-ray photoelectron spectroscopy (XPS). The XPS results reveal that the chemical bonds between copper and TESPA monomers, three dimensional disulfide units and siloxane networks are responsible for the satisfactory protection of TESPA polymeric nanofilm against copper corrosion. On the other hand, scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) are utilized to reveal the morphology and the uniformity of the TESPA polymeric nanofilm. The SEM-EDS results demonstrate that the copper surfaces are uniformly covered with TESPA self-assembled monolayer and the polymeric nanofilm. The TESPA-covered copper surfaces turn out to be smoother than that of the bare copper surface.

Polarized Light Sources for photocathode electron guns at SLAC

International Nuclear Information System (INIS)

Woods, M.; Frisch, J.; Witte, K.; Zolotorev, M.

1992-12-01

We describe current and future Polarized Light Sources at SLAC for use with photocathode electron guns to produce polarized electron beams. The SLAC experiments SLD and E142 are considered, and are used to define the required parameters for the Polarized Light Sources

Progress on Lead Photocathodes for Superconducting Injectors

CERN Document Server

Smedley, John; Langner, Jerzy; Lefferts, Richard; Lipski, Andrzej; Rao, Triveni; Sekutowicz, Jacek; Strzyzewski, P

2005-01-01

We present the results of our investigation of bulk, electroplated and vacuum deposited lead as suitable photocathode materials for superconducting RF injectors. The quantum efficiency of each sample is presented as a function of the wavelength of the incident light, from 310 nm to 190 nm. Quantum efficiencies of 0.3% have been obtained. Production of a niobium cavity with a lead-plated cathode is underway.

Measurement of the specific surface area of loose copper deposit by electrochemical methods

Directory of Open Access Journals (Sweden)

E. A. Dolmatova

2016-07-01

Full Text Available In the work the surface area of the electrode with dispersed copper deposit obtained within 30 seconds was evaluated by techniques of chronopotentiometry (CPM and impedance spectroscopy. In method CPM the electrode surface available for measurement depends on the value of the polarizing current. At high currents during the transition time there is a change of surface relief that can not determine the full surface of loose deposit. The electrochemical impedance method is devoid of this shortcoming since the measurements are carried out in indifferent electrolyte in the absence of current. The area measured by the impedance is tens of times higher than the value obtained by chronopotentiometry. It is found that from a solution containing sulfuric acid the deposits form with a high specific surface area. Based on these data it was concluded that the method of impedance spectroscopy can be used to measure in situ the surface area of the dispersed copper deposits.

{Ni4O4} Cluster Complex to Enhance the Reductive Photocurrent Response on Silicon Nanowire Photocathodes

Directory of Open Access Journals (Sweden)

Yatin J. Mange

2017-02-01

Full Text Available Metal organic {Ni4O4} clusters, known oxidation catalysts, have been shown to provide a valuable route in increasing the photocurrent response on silicon nanowire (SiNW photocathodes. {Ni4O4} clusters have been paired with SiNWs to form a new photocathode composite for water splitting. Under AM1.5 conditions, the combination of {Ni4O4} clusters with SiNWs gave a current density of −16 mA/cm2, which corresponds to an increase in current density of 60% when compared to bare SiNWs. The composite electrode was fully characterised and shown to be an efficient and stable photocathode for water splitting.

Effect of Mo Ion Implantation on Stability of Nanocrystalline Copper Surface Layers

Directory of Open Access Journals (Sweden)

XI Yang

2016-08-01

Full Text Available The surface of pure copper was modified using the surface mechanical attrition treatment (SMAT method, and molybdenum ions were implanted in the nanosurface using a metal vapor vacuum arc (MEVVA. The results of the SMAT were observed by optical microscopy (OM, X-ray diffraction (XRD and scanning electron microscopy (SEM. An obvious nanocrystalline layer and a deformation region exist on the surface. The size of the nanocrystalline layer was characterized using atomic force microscopy (AFM. The results indicate remarkable suppression on grain size, the nanocrystalline layer grows to 163nm after annealing and reduces to only 72nm due to the Mo ion implantation. In addition, the hardness of the topmost surface of the material is 3.5 times that of the SMATed copper, which is about 7 times of the value of the matrix. The above improvements most likely result from the dispersion of the Mo ions and the reactions of the crystal defects due to the SMAT and ion implantation.

Studies on a laser driven photoemissive high-brightness electron source and novel photocathodes

International Nuclear Information System (INIS)

Geng Rongli; Song Jinhu; Yu Jin

1997-01-01

A laser driven photoemissive high-brightness electron source at Beijing University is reported. Through a DC accelerating gap of 100 kV voltage, the device is capable of delivering high-brightness electron beam of 35-100 ps pulse duration when irradiated with a mode-locked YAG laser. The geometry of the gun is optimized with the aid of simulation codes EGUN and POISSON. The results of experimental studies on ion implanted photocathode and cesium telluride photocathode are given. The proposed laser driven superconducting RF gun is also discussed

Thermal Emittance Measurement of the Cs2Te Photocathode in FZD Superconducting RF

CERN Document Server

Xiang, R; Michel, P; Murcek, P; Teichert, J

2010-01-01

The thermal emittance of the photocathode is an interesting physical property for the photoinjector, because it decides the minimum emittance the photoinjector can finally achieve. In this paper we will report the latest results of the thermal emittance of the Cs2Te photocathode in FZD Superconducting RF gun. The measurement is performed with solenoid scan method with very low bunch charge and relative large laser spot on cathode, in order to reduce the space charge effect as much as possible, and meanwhile to eliminate the wake fields and the effect from beam halos.

Influence of bias voltage on the stability of CsI photocathodes exposed to air

CERN Document Server

Nitti, M A; Nappi, E; Singh, B K; Valentini, A

2002-01-01

We describe a possible correlation between the bias voltage applied to the substrate during the growth of CsI photocathodes and the variation of quantum efficiency (QE) after one day exposure to humid air. It was found that fresh samples are much less sensitive to humid air when a high negative bias voltage was applied during film growth. A model based on surface film interaction with water molecules is presented for the observed effect. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements have been performed to examine, respectively, the bulk structure and the surface of fresh and exposed CsI samples. Also reported are transmittance measurements for fresh and aged CsI samples in the wavelength range 190-850 nm.

The polymeric nanofilm of triazinedithiolsilane fabricated by self-assembled technique on copper surface. Part 2: Characterization of composition and morphology

International Nuclear Information System (INIS)

Wang, Yabin; Liu, Zhong; Huang, Yudong; Qi, Yutai

2015-01-01

Highlights: • The chemical reactions between copper and triazinedithiolsilane were revealed. • The structure of triazinedithiolsilane's polymeric nanofilm was demonstrated. • The morphology and microstructure of the polymeric nanofilm was observed. - Abstract: In the first part, a novel design route for metal protection against corrosion was proposed, and a class of triazinedithiolsilane compounds was conceived as protector for copper. The protective capability of the polymeric nanofilm, fabricated by self-assembling one representative (abbreviated as TESPA) of triazinedithiolsilane compounds onto copper surface, has been investigated and evaluated by electrochemical tests. The results show that the polymeric nanofilm significantly inhibits copper corrosion. This study, on the one hand, concentrates on the chemical composition of the TESPA polymeric nanofilm by means of X-ray photoelectron spectroscopy (XPS). The XPS results reveal that the chemical bonds between copper and TESPA monomers, three dimensional disulfide units and siloxane networks are responsible for the satisfactory protection of TESPA polymeric nanofilm against copper corrosion. On the other hand, scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) are utilized to reveal the morphology and the uniformity of the TESPA polymeric nanofilm. The SEM-EDS results demonstrate that the copper surfaces are uniformly covered with TESPA self-assembled monolayer and the polymeric nanofilm. The TESPA-covered copper surfaces turn out to be smoother than that of the bare copper surface.

High polarization photocathode R ampersand D at SLAC

International Nuclear Information System (INIS)

Maruyama, Takashi; Garwin, E.L.; Prepost, R.; Zaplac, G.H.

1993-01-01

This paper describes recent progress on the development of high polarization photocathodes for polarized electron sources. A strained InGaAs cathode has achieved a maximum electron-spin polarization of 71% and has demonstrated the strain enhancement of polarization for the first time. Strained GaAs cathodes have yielded polarizations as high as 90% with much higher quantum efficiency

3D ZnIn2S4 nanosheet/TiO2 nanowire arrays and their efficient photocathodic protection for 304 stainless steel

Science.gov (United States)

Sun, Wenxia; Wei, Na; Cui, Hongzhi; Lin, Yuan; Wang, Xinzhen; Tian, Jian; Li, Jian; Wen, Jing

2018-03-01

A well-designed heterostructure engineered ZnIn2S4 nanosheet/TiO2 nanowire arrays photoanode is investigated for photocathodic protection. The ZnIn2S4 nanosheets are distributed uniformly on the surface of the TiO2 nanowire by a hydrothermal method. The stem-and-leaf-like ZnIn2S4 nanosheet/TiO2 nanowire arrays exhibit excellent photoelectrochemical properties, owing to the energy band structure and large surface area. A maximum photocurrent density of 2 mA cm-2 is achieved for the ZnIn2S4 nanosheet/TiO2 nanowire composite film for a 6 h reaction time under white illumination. Moreover, the potential of the 304 stainless steel coupled with the composite film immediately shifts negatively to -1.17 V (vs. SCE), which is significantly lower than the corrosion potential (-0.201 V vs. SCE). Thus, the composite film offers a superior photocathodic protection for stainless steel against corrosion by a NaCl solution. This study provides a promising approach for the design and synthesis of composite films with enhanced photoelectrochemical performance.

New configuration for efficient and durable copper coating on the outer surface of a tube

Directory of Open Access Journals (Sweden)

Irfan Ahmad

2017-03-01

Full Text Available A well-adhered copper coating on stainless steel power coupler parts is required in superconducting radio frequency (SRF accelerators. Radio frequency power coupler parts are complex, tubelike stainless steel structures, which require copper coating on their outer and inner surfaces. Conventional copper electroplating sometimes produces films with inadequate adhesion strength for SRF applications. Electroplating also requires a thin nickel strike layer under the copper coating, whose magnetic properties can be detrimental to SRF applications. Coaxial energetic deposition (CED and sputtering methods have demonstrated efficient conformal coating on the inner surfaces of tubes but coating the outer surface of a tube is challenging because these coating methods are line of sight. When the substrate is off axis and the plasma source is on axis, only a small section of the substrate’s outer surface is exposed to the source cathode. The conventional approach is to rotate the tube to achieve uniformity across the outer surface. This method results in poor film thickness uniformity and wastes most of the source plasma. Alameda Applied Sciences Corporation (AASC has developed a novel configuration called hollow external cathode CED (HEC-CED to overcome these issues. HEC-CED produces a film with uniform thickness and efficiently uses all eroded source material. The Cu film deposited on the outside of a stainless steel tube using the new HEC-CED configuration survived a high pressure water rinse adhesion test. HEC-CED can be used to coat the outside of any cylindrical structure.

Bacterial Killing by Dry Metallic Copper Surfaces▿

OpenAIRE

Santo, Christophe Espírito; Lam, Ee Wen; Elowsky, Christian G.; Quaranta, Davide; Domaille, Dylan W.; Chang, Christopher J.; Grass, Gregor

2010-01-01

Metallic copper surfaces rapidly and efficiently kill bacteria. Cells exposed to copper surfaces accumulated large amounts of copper ions, and this copper uptake was faster from dry copper than from moist copper. Cells suffered extensive membrane damage within minutes of exposure to dry copper. Further, cells removed from copper showed loss of cell integrity. Acute contact with metallic copper surfaces did not result in increased mutation rates or DNA lesions. These findings are important fir...

Fabrication of superhydrophobic copper surface on various substrates for roll-off, self-cleaning, and water/oil separation.

Science.gov (United States)

Sasmal, Anup Kumar; Mondal, Chanchal; Sinha, Arun Kumar; Gauri, Samiran Sona; Pal, Jaya; Aditya, Teresa; Ganguly, Mainak; Dey, Satyahari; Pal, Tarasankar

2014-12-24

Superhydrophobic surfaces prevent percolation of water droplets and thus render roll-off, self-cleaning, corrosion protection, etc., which find day-to-day and industrial applications. In this work, we developed a facile, cost-effective, and free-standing method for direct fabrication of copper nanoparticles to engender superhydrophobicity for various flat and irregular surfaces such as glass, transparency sheet (plastic), cotton wool, textile, and silicon substrates. The fabrication of as-prepared superhydrophobic surfaces was accomplished using a simple chemical reduction of copper acetate by hydrazine hydrate at room temperature. The surface morphological studies demonstrate that the as-prepared surfaces are rough and display superhydrophobic character on wetting due to generation of air pockets (The Cassie-Baxter state). Because of the low adhesion of water droplets on the as-prepared surfaces, the surfaces exhibited not only high water contact angle (164 ± 2°, 5 μL droplets) but also superb roll-off and self-cleaning properties. Superhydrophobic copper nanoparticle coated glass surface uniquely withstands water (10 min), mild alkali (5 min in saturated aqueous NaHCO3 of pH ≈ 9), acids (10 s in dilute HNO3, H2SO4 of pH ≈ 5) and thiol (10 s in neat 1-octanethiol) at room temperature (25-35 °C). Again as-prepared surface (cotton wool) was also found to be very effective for water-kerosene separation due to its superhydrophobic and oleophilic character. Additionally, the superhydrophobic copper nanoparticle (deposited on glass surface) was found to exhibit antibacterial activity against both Gram-negative and Gram-positive bacteria.

Effect of ion irradiation on the optical properties and room temperature oxidation of copper surface

Energy Technology Data Exchange (ETDEWEB)

Poperenko, L.V.; Ramadan Shaaban, Essam; Khanh, N.Q.; Stashchuk, V.S.; Vinnichenko, M.V.; Yurgelevich, I.V.; Nosach, D.V.; Lohner, T

2004-05-01

Ex situ and in situ spectroellipsometric investigation of room temperature oxidation of ion-implanted copper surface was performed. The ellipsometer is capable to measure simultaneously the ellipsometric parameters {psi} and {delta} at 88 different wavelength values in the range of 280-760 nm within a few minutes in the high precision operation mode using two zone averaging and within a fraction of a second in the one zone operation mode. The native oxide layer formed earlier on the surface of the copper was sputtered off during the aluminum ion implantation. In situ study of the growth of the newly formed native oxide layer on the ion implanted surface was carried out. Ion beam analytical measurements were performed to gain further information on the native oxide layer. The absolute number of the oxygen atoms in the native copper oxide layer was determined. The depth distribution of the implanted aluminum was extracted from Rutherford backscattering spectra. It is found that Al implantation enhanced the oxidation resistance.

Effect of ion irradiation on the optical properties and room temperature oxidation of copper surface

International Nuclear Information System (INIS)

Poperenko, L.V.; Ramadan Shaaban, Essam; Khanh, N.Q.; Stashchuk, V.S.; Vinnichenko, M.V.; Yurgelevich, I.V.; Nosach, D.V.; Lohner, T.

2004-01-01

Ex situ and in situ spectroellipsometric investigation of room temperature oxidation of ion-implanted copper surface was performed. The ellipsometer is capable to measure simultaneously the ellipsometric parameters Ψ and Δ at 88 different wavelength values in the range of 280-760 nm within a few minutes in the high precision operation mode using two zone averaging and within a fraction of a second in the one zone operation mode. The native oxide layer formed earlier on the surface of the copper was sputtered off during the aluminum ion implantation. In situ study of the growth of the newly formed native oxide layer on the ion implanted surface was carried out. Ion beam analytical measurements were performed to gain further information on the native oxide layer. The absolute number of the oxygen atoms in the native copper oxide layer was determined. The depth distribution of the implanted aluminum was extracted from Rutherford backscattering spectra. It is found that Al implantation enhanced the oxidation resistance

Self-assembled monolayer of ammonium pyrrolidine dithiocarbamate on copper detected using electrochemical methods, surface enhanced Raman scattering and quantum chemistry calculations

Energy Technology Data Exchange (ETDEWEB)

Liao, Q.-Q., E-mail: liaoqq1971@yahoo.com.cn [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy-Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Yue, Z.-W.; Yang, D. [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy-Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Wang, Z.-H. [Department of Chemistry, Tongji University, Shanghai 200092 (China); Li, Z.-H. [Department of Chemistry, Fudan University, Shanghai 200433 (China); Ge, H.-H. [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy-Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Li, Y.-J. [Department of Chemistry, Tongji University, Shanghai 200092 (China)

2011-07-29

Ammonium pyrrolidine dithiocarbamate (APDTC) monolayer was self-assembled on fresh copper surface obtained after oxidation-reduction cycle treatment in 0.1 mol L{sup -1} potassium chloride solution at ambient temperature. The APDTC self-assembled monolayer (SAM) on copper surface was investigated by surface enhanced Raman scattering spectroscopy and the results show that APDTC SAM is chemisorbed on copper surface by its sulfur atoms with perpendicular orientation. The optimum immersing period for SAM formation is 4 h at 0.01 mol L{sup -1} concentration of APDTC. The impedance results indicate that APDTC SAM has good corrosion inhibition effects for copper in 0.5 mol L{sup -1} hydrochloric acid solution and its maximum inhibition efficiency could reach 95%. Quantum chemical calculations show that APDTC has relatively small {Delta}E between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and large negative charge in its two sulfur atoms, which facilitate formation of an insulating Cu/APDTC film on copper surface.

Research surface resistance of copper normal and abnormal skin-effects depending on the frequency of electromagnetic field

International Nuclear Information System (INIS)

Kutovyi, V.A.; Komir, A.I.

2013-01-01

The results of the frequency dependence of surface resistance of copper in diffuse and specular reflection of electrons from the conductive surface of the high-frequency resonance of the system depending on the frequency of the electromagnetic field in the normal and anomalous skin effect. Found, the surface resistance of copper is reduced by more than 10 times at the temperature of liquid helium, as compared with a surface resistivity at room temperature, at frequencies f ≤ 173 MHz, for diffuse reflection of conduction electrons from the surface of the conductive layer, and the specular reflection - at frequencies f ≤ 346 MHz

Breakdown conditioning of copper, CuZr and GlidCop® : effect of mechanical surface treatments

CERN Document Server

Ramsvik, T; Calatroni, S; Taborelli, M; CERN. Geneva. TS Department

2007-01-01

Motivated by the need of novel materials for the CLIC accelerating structures to resist mechanical fatigue, the copper based metals Copper Zirconium C15000 (CuZr) and GlidCop® Al-15 C15715 have been investigated by DC breakdown measurements, and compared with commercially pure Oxygen-free Copper C10100 (Cu-OFE). In all three cases the saturated breakdown fields (Esat) are similar, despite significant differences in their tensile strengths. In addition, the choice of mechanical surface preparation techniques influences the final breakdown characteristics. For both CuZr and GlidCop® immediate conditioning takes place when the surfaces are prepared by milling. For electro discharge machined (EDM) surfaces, however, several breakdown events are needed to obtain saturation. Specifically, for EDM treated CuZr and GlidCop®, ~50 and ~200 breakdown events are required to reach Esat.

Equivalent Method of Solving Quantum Efficiency of Reflection-Mode Exponential Doping GaAs Photocathode

International Nuclear Information System (INIS)

Jun, Niu; Zhi, Yang; Ben-Kang, Chang

2009-01-01

The mathematical expression of the electron diffusion and drift length L DE of exponential doping photocathode is deduced. In the quantum efficiency equation of the reffection-mode uniform doping cathode, substituting L DE for L D , the equivalent quantum efficiency equation of the reffection-mode exponential doping cathode is obtained. By using the equivalent equation, theoretical simulation and experimental analysis shows that the equivalent index formula and formula-doped cathode quantum efficiency results in line. The equivalent equation avoids complicated calculation, thereby simplifies the process of solving the quantum efficiency of exponential doping photocathode

Dry Etching of Copper Phthalocyanine Thin Films: Effects on Morphology and Surface Stoichiometry

Directory of Open Access Journals (Sweden)

Michael J. Brett

2012-08-01

Full Text Available We investigate the evolution of copper phthalocyanine thin films as they are etched with argon plasma. Significant morphological changes occur as a result of the ion bombardment; a planar surface quickly becomes an array of nanopillars which are less than 20 nm in diameter. The changes in morphology are independent of plasma power, which controls the etch rate only. Analysis by X-ray photoelectron spectroscopy shows that surface concentrations of copper and oxygen increase with etch time, while carbon and nitrogen are depleted. Despite these changes in surface stoichiometry, we observe no effect on the work function. The absorbance and X-ray diffraction spectra show no changes other than the peaks diminishing with etch time. These findings have important implications for organic photovoltaic devices which seek nanopillar thin films of metal phthalocyanine materials as an optimal structure.

Corrosive microenvironments at lead solder surfaces arising from galvanic corrosion with copper pipe.

Science.gov (United States)

Nguyen, Caroline K; Stone, Kendall R; Dudi, Abhijeet; Edwards, Marc A

2010-09-15

As stagnant water contacts copper pipe and lead solder (simulated soldered joints), a corrosion cell is formed between the metals in solder (Pb, Sn) and the copper. If the resulting galvanic current exceeds about 2 μA/cm(2), a highly corrosive microenvironment can form at the solder surface, with pH chloride concentrations at least 11 times higher than bulk water levels. Waters with relatively high chloride tend to sustain high galvanic currents, preventing passivation of the solder surface, and contributing to lead contamination of potable water supplies. The total mass of lead corroded was consistent with predictions based on the galvanic current, and lead leaching to water was correlated with galvanic current. If the concentration of sulfate in the water increased relative to chloride, galvanic currents and associated lead contamination could be greatly reduced, and solder surfaces were readily passivated.

Metallic copper corrosion rates, moisture content, and growth medium influence survival of copper ion-resistant bacteria

DEFF Research Database (Denmark)

Elguindi, J; Moffitt, S; Hasman, Henrik

2010-01-01

of both copper ion-resistant E. coli and E. faecium strains when samples in rich medium were spread in a thin, moist layer on copper alloys with 85% or greater copper content. E. coli strains were rapidly killed under dry conditions, while E. faecium strains were less affected. Electroplated copper...... on electroplated copper surfaces with benzotriazole coating and thermal oxide coating compared to surfaces without anti-corrosion treatment. Control of surface corrosion affected the level of copper ion influx into bacterial cells, which contributed directly to bacterial killing....

DFT study of ethyl xanthate interaction with sphalerite (1 1 0) surface in the absence and presence of copper

Energy Technology Data Exchange (ETDEWEB)

Liu, Jian [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization , Kunming University of Science and Technology, Kunming 650093 (China); Wen, Shuming, E-mail: shmwen@126.com [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization , Kunming University of Science and Technology, Kunming 650093 (China); Deng, Jiushuai [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization , Kunming University of Science and Technology, Kunming 650093 (China); Chen, Xiumin [National Engineering Laboratory of Vacuum Metallurgy, Kunming University of Science and Technology, Kunming 650093 (China); Feng, Qicheng [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization , Kunming University of Science and Technology, Kunming 650093 (China)

2014-08-30

Highlights: • Interaction among sphalerite surface, copper and ethyl xanthate (EX) was simulated. • Results show that four stable interaction models exist among them. • The four models can result in the activation flotation of sphalerite. - Abstract: The interaction among sphalerite (1 1 0) surface, copper and ethyl xanthate (EX) was simulated using the density functional theory (DFT). The results of DFT indicate that four types of stable interaction models exist among sphalerite surface, copper and EX, i.e., EX interacts with the Cu substituted for Zn, Cu adsorbed on the top site of S, Cu adsorbed on the bridge site of S and Cu(OH){sub 2} adsorbed on the sphalerite surface. The four interaction models can result in the activation flotation of sphalerite. Density of states (DOS) analysis shows that the energy level discrepancy of the Zn 3d orbital in ZnS and the bonding S 3p orbital in EX results in the weak adsorption of EX on un-activated sphalerite surface. However, after copper activation, the Cu 3d orbital peak and bonding S 3p orbital peak are just maximally overlapped nearby the Fermi level. This study provides an insight into the nature that sphalerite responds not well to EX and also a comprehensive understanding on the possible interaction cases existing among sphalerite surface, copper and EX.

DFT study of ethyl xanthate interaction with sphalerite (1 1 0) surface in the absence and presence of copper

International Nuclear Information System (INIS)

Liu, Jian; Wen, Shuming; Deng, Jiushuai; Chen, Xiumin; Feng, Qicheng

2014-01-01

Highlights: • Interaction among sphalerite surface, copper and ethyl xanthate (EX) was simulated. • Results show that four stable interaction models exist among them. • The four models can result in the activation flotation of sphalerite. - Abstract: The interaction among sphalerite (1 1 0) surface, copper and ethyl xanthate (EX) was simulated using the density functional theory (DFT). The results of DFT indicate that four types of stable interaction models exist among sphalerite surface, copper and EX, i.e., EX interacts with the Cu substituted for Zn, Cu adsorbed on the top site of S, Cu adsorbed on the bridge site of S and Cu(OH) 2 adsorbed on the sphalerite surface. The four interaction models can result in the activation flotation of sphalerite. Density of states (DOS) analysis shows that the energy level discrepancy of the Zn 3d orbital in ZnS and the bonding S 3p orbital in EX results in the weak adsorption of EX on un-activated sphalerite surface. However, after copper activation, the Cu 3d orbital peak and bonding S 3p orbital peak are just maximally overlapped nearby the Fermi level. This study provides an insight into the nature that sphalerite responds not well to EX and also a comprehensive understanding on the possible interaction cases existing among sphalerite surface, copper and EX

Effect of Ammonium Chloride on the Efficiency with Which Copper Sulfate Activates Marmatite: Change in Solution Composition and Regulation of Surface Composition

Directory of Open Access Journals (Sweden)

Shengdong Zhang

2018-06-01

Full Text Available Zinc sulfide minerals are the primary choice for zinc extraction and marmatite is one of the two most common zinc sulphide minerals (sphalerite and marmatite, therefore it is of great significance to study and optimize the flotation of marmatite. To improve the activation of copper sulfate on marmatite, a method involving the addition of ammonium chloride is devised. The method has been proven to be an effective way of improving the activation efficiency of copper sulfate towards marmatite under alkaline conditions. The strengthening mechanism was studied using micro-flotation, adsorption test, X-ray photoelectron spectroscopy, and by analyzing changes in solution composition. Flotation test results show that the activation effect of the copper sulfate towards marmatite is enhanced with the addition of ammonium chloride. According to the results of the adsorption measurements and X-ray photoelectron spectroscopy analysis, when the marmatite surface is activated using copper sulfate with added ammonia chloride, it adsorbs more copper sulfide and less copper hydroxide and zinc hydroxide. These changes in surface composition are believed to occur via the following process: NH3(aq promotes the dissolution of zinc hydroxide and then facilitates the conversion of surface copper hydroxide to copper sulfide. In addition, the occurrence of Cu(NH3n2+ can promote the adsorption of copper ions (Cu2+ can be stored as Cu(NH3n2+ via complexation, and then, when the concentration of copper ions decreases, Cu2+ can be released through the decompositionof Cu(NH3n2+. Hence, the copper ion concentration can be maintained and this can facilitate the adsorption of Cu2+ on marmatite. Based on a comprehensive analysis of all our results, we propose that adding ammonium chloride to the copper sulfate changes the solution components (i.e., the presence of NH3(aq and Cu(NH3n2+ and then regulates the surface composition of marmatite. The change in surface composition

Sulfur-induced structural motifs on copper and gold surfaces

Energy Technology Data Exchange (ETDEWEB)

Walen, Holly [Iowa State Univ., Ames, IA (United States)

2016-01-01

The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur. The experimental observations presented here—made under identical conditions—together with extensive DFT analyses, allow comparisons and insights into factors that favor the existence of metal-sulfur complexes, vs. chemisorbed atomic sulfur, on metal terraces. We believe this data will be instrumental in better understanding the complex phenomena occurring between the surfaces of coinage metals and sulfur.

A novel scaling law relating the geometrical dimensions of a photocathode radio frequency gun to its radio frequency properties

Science.gov (United States)

Lal, Shankar; Pant, K. K.; Krishnagopal, S.

2011-12-01

Developing a photocathode RF gun with the desired RF properties of the π-mode, such as field balance (eb) ˜1, resonant frequency fπ = 2856 MHz, and waveguide-to-cavity coupling coefficient βπ ˜1, requires precise tuning of the resonant frequencies of the independent full- and half-cells (ff and fh), and of the waveguide-to-full-cell coupling coefficient (βf). While contemporary electromagnetic codes and precision machining capability have made it possible to design and tune independent cells of a photocathode RF gun for desired RF properties, thereby eliminating the need for tuning, access to such computational resources and quality of machining is not very widespread. Therefore, many such structures require tuning after machining by employing conventional tuning techniques that are iterative in nature. Any procedure that improves understanding of the tuning process and consequently reduces the number of iterations and the associated risks in tuning a photocathode gun would, therefore, be useful. In this paper, we discuss a method devised by us to tune a photocathode RF gun for desired RF properties under operating conditions. We develop and employ a simple scaling law that accounts for inter-dependence between frequency of independent cells and waveguide-to-cavity coupling coefficient, and the effect of brazing clearance for joining of the two cells. The method has been employed to successfully develop multiple 1.6 cell BNL/SLAC/UCLA type S-band photocathode RF guns with the desired RF properties, without the need to tune them by a tiresome cut-and-measure process. Our analysis also provides a physical insight into how the geometrical dimensions affect the RF properties of the photo-cathode RF gun.

Enhanced photoelectrochemical water splitting by oxides heterojunction photocathode coupled with Ag.

Science.gov (United States)

Lu, Xue; Liu, Zhifeng

2017-08-14

A novel one-dimensional Co 3 O 4 /CuO/Ag composite structure film was directly grown on indium tin oxide glass substrate by a simple hydrothermal method and electrodeposition method. The film was employed for the first time as a photocathode for photoelectrochemical (PEC) water splitting to generate hydrogen. The photocurrent density of the Co 3 O 4 /CuO/Ag composite structure achieved -5.13 mA cm -2 at -0.2 V vs. RHE, which is roughly 12.8 times that of 1D Co 3 O 4 nanowires and 3.31 times Co 3 O 4 /CuO heterojunction photocathodes. The enhanced PEC performance of this Co 3 O 4 /CuO/Ag composite structure ascribes increased light-harvesting and light-absorption, distensible photoresponse range, decreased interface charge transfer resistance, and improved photogenerated electron-hole pairs transfer and separation.

Design and fabrication of prototype 6×6 cm2 microchannel plate photodetector with bialkali photocathode for fast timing applications

International Nuclear Information System (INIS)

Xie, Junqi; Byrum, Karen; Demarteau, Marcel; Gregar, Joseph; May, Edward; Virgo, Mathew; Wagner, Robert; Walters, Dean; Wang, Jingbo; Xia, Lei; Zhao, Huyue

2015-01-01

Planar microchannel plate-based photodetectors with a bialkali photocathode are able to achieve photon detection with very good time and position resolution. A 6×6 cm 2 photodetector production facility was designed and built at Argonne National Laboratory. Small form-factor MCP-based photodetectors completely constructed out of glass were designed and prototypes were successfully fabricated. Knudsen effusion cells were incorporated in the photocathode growth chamber to achieve uniform and high quantum efficiency photocathodes. The thin film uniformity was simulated and measured for an antimony film deposition, showing uniformity of better than 10%. Several prototype devices with bialkali photocathodes have been fabricated with the described system and their characteristics were evaluated in the large signal (multi-PE) limit. A typical prototype device exhibits time-of-flight resolution of ~27 psec and differential time resolution of ~9 psec, corresponding to spatial resolution of ~0.65 mm

Advances in DC photocathode electron guns

International Nuclear Information System (INIS)

Dunham M, Bruce; Heartmann, P.; Reza Kazimi; Hongxiu Liu; Poelker, B.M.; Price, J.S.; Rutt, P.M.; Schneider, W.J.; Sinclair K, Charles

1998-01-01

At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughout. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion back-bombardment, and precise control of all of the electrons emitted from the cathode. In this paper, the authors will review recent results and discuss implications for future photocathode guns

Advances in DC photocathode electron guns

International Nuclear Information System (INIS)

Dunham, B. M.; Hartmann, P.; Kazimi, R.; Liu, H.; Poelker, B. M.; Price, J. S.; Rutt, P. M.; Schneider, W. J.; Sinclair, C. K.

1999-01-01

At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughput. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion backbombardment, and precise control of all of the electrons emitted from the cathode. In this paper, we will review recent results and discuss implications for future photocathode guns

Measurements of Photocathode Operational Lifetime at Beam Currents up to 10 mA using an Improved DC High Voltage GaAs Photogun

International Nuclear Information System (INIS)

Grames, J.; Poelker, M.; Adderley, P.; Brittian, J.; Clark, J.; Hansknecht, J.; Machie, D.; Stutzman, M. L.; Surles-Law, K.

2007-01-01

This work extends past research at Jefferson Lab aimed at better appreciating the mechanisms that limit photocathode operational lifetime at high current (> 1 mA). Specifically, the performance of an improved 100 kV DC high voltage load locked photogun will be described. Although difficult to measure directly, we believe the new gun has better vacuum conditions compared to the original gun, as indicated by enhanced photocathode lifetimes exceeding 2000 C using a 1.55 mm diameter drive laser spot at the photocathode. In addition, the dependence of the lifetime on the laser spot size at the photocathode was measured and a charge density lifetime exceeding 106 C/cm2 was measured with a 0.32 mm laser spot diameter

Measurements of photocathode operational lifetime at beam currents up to 10-mA using an improved DC high voltage GaAs photogun

International Nuclear Information System (INIS)

J. Grames; M. Poelker; P. Adderley; J. Brittian; J. Clark; J. Hansknecht; D. Machie; M.L. Stutzman; K. Surles-Law

2007-01-01

This work extends past research at Jefferson Lab aimed at better appreciating the mechanisms that limit photocathode operational lifetime at high current (> 1 mA). Specifically, the performance of an improved 100 kV DC high voltage load locked photogun will be described. Although difficult to measure directly, we believe the new gun has better vacuum conditions compared to the original gun, as indicated by enhanced photocathode lifetimes exceeding 2000 C using a 1.55 mm diameter drive laser spot at the photocathode. In addition, the dependence of the lifetime on the laser spot size at the photocathode was measured and a charge density lifetime exceeding 10 6 C/cm 2 was measured with a 0.32 mm laser spot diameter

Heat load of a GaAs photocathode in an SRF electron gun

International Nuclear Information System (INIS)

Wang Erdong; Zhao Kui; Jorg Kewisch; Ilan Ben-Zvi; Andrew Burrill; Trivini Rao; Wu Qiong; Animesh Jain; Ramesh Gupta; Doug Holmes

2011-01-01

A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved by using a superconducting radio frequency (SRF) electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide (GaAs) photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder (plug) to decrease the heat load from GaAs. (authors)

Surface Structures Formed by a Copper(II Complex of Alkyl-Derivatized Indigo

Directory of Open Access Journals (Sweden)

Akinori Honda

2016-10-01

Full Text Available Assembled structures of dyes have great influence on their coloring function. For example, metal ions added in the dyeing process are known to prevent fading of color. Thus, we have investigated the influence of an addition of copper(II ion on the surface structure of alkyl-derivatized indigo. Scanning tunneling microscope (STM analysis revealed that the copper(II complexes of indigo formed orderly lamellar structures on a HOPG substrate. These lamellar structures of the complexes are found to be more stable than those of alkyl-derivatized indigos alone. Furthermore, 2D chirality was observed.

Determination of the surface area and sizes of supported copper nanoparticles through organothiol adsorption—ñhemisorption

Energy Technology Data Exchange (ETDEWEB)

Ndolomingo, Matumuene Joe; Meijboom, Reinout, E-mail: rmeijboom@uj.ac.za

2016-12-30

Highlights: • Cu on γ-Al{sub 2}O{sub 3} catalysts were prepared and characterized. • The ligand sorption-based technique was used for the determination of specific surface area and particle sizes. • The ligand packing density on Cu nanoparticles was quantified. • A fair agreement was found between the Cu particle sizes obtained from ligand adsorption and TEM methods. • The oxidation of morin by hydrogen peroxide was used to evaluate the catalytic activities of the Cu supported catalysts. - Abstract: The mechanisms involving the nanoparticle surfaces in catalytic reactions are more difficult to elucidate due to the nanoparticle surface unevenness, size distributions, and morphological irregularity. True surface area and particle sizes determination are key aspects of the activity of metal nanoparticle catalysts. Here we report on the organothiol adsorption-based technique for the determination of specific surface area of Cu nanoparticles, and their resultant sizes on γ-Al{sub 2}O{sub 3} supports. Quantification of ligand packing density on copper nanoparticles is also reported. The concentration of the probe ligand, 2-mercaptobenzimidazole (2-MBI) before and after immersion of supported copper catalysts was determined by ultraviolet-visible spectrometry (UV–vis). The amount of ligand adsorbed was found to be proportional to the copper nanoparticles surface area. Atomic absorption spectrometry (AAS), N{sub 2}-physisorption (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used for the characterization of the catalysts. A fair agreement was found between particle sizes obtained from ligand adsorption and TEM methods. The catalytic activity of the copper nanoparticles related to their inherent surface area was evaluated using the model reaction of the oxidation of morin by hydrogen peroxide.

Silver surface enrichment of silver-copper alloys: a limitation for the analysis of ancient silver coins by surface techniques

International Nuclear Information System (INIS)

Beck, L.; Bosonnet, S.; Reveillon, S.; Eliot, D.; Pilon, F.

2004-01-01

The surface enrichment of archaeological silver-copper alloys has been recognized for many years. However, the origin of this enrichment is not well defined and many hypotheses have been put forward to account for this behaviour: segregation of the components during casting, deliberate thermal and/or chemical post-treatment, abrasion or corrosion. Among the hypotheses mentioned above, we have focused our study on the first step of coin manufacturing. Replications of silver-copper standards of various compositions ranging from 30% to 80% Ag, reflecting the composition of silver blanks, have been produced. Metallographic examination, PIXE and SEM-EDS have been used for the characterization of each sample. A model of the direct enrichment has been established. This model allows us to propose a relationship between the surface composition and the silver content of the core. Comparison with data of Roman coins from the Roman site of Cha-hat teaubleau (France) and from the literature and consequences for the analyses of ancient coins by surface methods are presented

DFT study of ethyl xanthate interaction with sphalerite (1 1 0) surface in the absence and presence of copper

Science.gov (United States)

Liu, Jian; Wen, Shuming; Deng, Jiushuai; Chen, Xiumin; Feng, Qicheng

2014-08-01

The interaction among sphalerite (1 1 0) surface, copper and ethyl xanthate (EX) was simulated using the density functional theory (DFT). The results of DFT indicate that four types of stable interaction models exist among sphalerite surface, copper and EX, i.e., EX interacts with the Cu substituted for Zn, Cu adsorbed on the top site of S, Cu adsorbed on the bridge site of S and Cu(OH)2 adsorbed on the sphalerite surface. The four interaction models can result in the activation flotation of sphalerite. Density of states (DOS) analysis shows that the energy level discrepancy of the Zn 3d orbital in ZnS and the bonding S 3p orbital in EX results in the weak adsorption of EX on un-activated sphalerite surface. However, after copper activation, the Cu 3d orbital peak and bonding S 3p orbital peak are just maximally overlapped nearby the Fermi level. This study provides an insight into the nature that sphalerite responds not well to EX and also a comprehensive understanding on the possible interaction cases existing among sphalerite surface, copper and EX.

Mass spectrum of secondary ions knocked-out from copper surface by argon ion beam

International Nuclear Information System (INIS)

Koval', A.G.; Bobkov, V.V.; Klimovskij, Yu.A.; Fogel', Ya.M.

1976-01-01

The mass-spectrum of secondary ions was studied within a mass range of 1-400. The ions were knocked-out by the beam of ions Ar + from the copper surface with different content of oxygen and sulphur solved in the volume. The studies were conducted at three temperatures of the target. The atomic and molecular ions of the metal matrix, volumetric impurities of metal and ions of chemical compounds molecules of the metal under study with gas particles adsorbed on its surface and atoms of the metal volumetric admixtures may be observed in the mass spectrum. Detection of secondary ions of the copper multi-atomic complexes and ions of these complexes compounds with the adsorbed molecules is of interest

Advances in DC photocathode electron guns

International Nuclear Information System (INIS)

Dunham, B.M.; Hartmann, P.; Kazimi, R.; Liu, H.; Poelker, B.M.; Price, J.S.; Rutt, P.M.; Schneider, W.J.; Sinclair, C.K.

1999-01-01

At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughput. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion backbombardment, and precise control of all of the electrons emitted from the cathode. In this paper, we will review recent results and discuss implications for future photocathode guns. copyright 1999 American Institute of Physics

Intrinsically water-repellent copper oxide surfaces; An electro-crystallization approach

Science.gov (United States)

Akbari, Raziyeh; Ramos Chagas, Gabriela; Godeau, Guilhem; Mohammadizadeh, Mohammadreza; Guittard, Frédéric; Darmanin, Thierry

2018-06-01

Use of metal oxide thin layers is increased due to their good durability under environmental conditions. In this work, the repeatable nanostructured crystalite Cu2O thin films, developed by electrodeposition method without any physical and chemical modifications, demonstrate good hydrophobicity. Copper (I) oxide (Cu2O) layers were fabricated on gold/Si(1 0 0) substrates by different electrodeposition methods i.e. galvanostatic deposition, cyclic voltammetry, and pulse potentiostatic deposition and using copper sulfate (in various concentrations) as a precursor. The greatest crystalline face on prepared Cu2O samples is (1 1 1) which is the most hydrophobic facet of Cu2O cubic structure. Indeed, different crystallite structures such as nanotriangles and truncated octahedrons were formed on the surface for various electrodeposition methods. The increase of the contact angle (θw) measured by the rest time, reaching to about 135°, was seen at different rates and electrodeposition methods. In addition, two-step deposition surfaces were also prepared by applying two of the mentioned methods, alternatively. In general, the morphology of the two-step deposition surfaces showed some changes compared to that of one-step samples, allowing the formation of different crystallite shapes. Moreover, the wettability behavior showd the larger θw of the two-step deposition layers compared to the related one-step deposition layers. Therefore, the highest observed θw was related to the one of two-step deposition layers due to the creation of small octahedral structures on the surface, having narrow and deep valleys. However, there was an exception which was due to the resulted big structures and broad valleys on the surface. So, it is possible to engineer different crystallites shapes using the proposed two-step deposition method. It is expected that hydrophobic crystallite thin films can be used in environmental and electronic applications to save energy and materials properties.

CdTeO3 Deposited Mesoporous NiO Photocathode for a Solar Cell

Directory of Open Access Journals (Sweden)

Chuan Zhao

2014-01-01

Full Text Available Semiconductor sensitized NiO photocathodes have been fabricated by successive ionic layer adsorption and reaction (SILAR method depositing CdTeO3 quantum dots onto mesoscopic NiO films. A solar cell using CdTeO3 deposited NiO mesoporous photocathode has been fabricated. It yields a photovoltage of 103.7 mV and a short-circuit current density of 0.364 mA/cm2. The incident photon to current conversion efficiency (IPCE value is found to be 12% for the newly designed NiO/CdTeO3 solar cell. It shows that the p-type NiO/CdTeO3 structure could be successfully utilized to fabricate p-type solar cell.

Heat enhancement of radiation resistivity of evaporated CsI, KI and KBr photocathodes

CERN Document Server

Tremsin, A S

2000-01-01

The photoemissive stability of as-deposited and heat-treated CsI, KI and KBr evaporated thin films under UV radiation is examined in this paper. After the deposition, some photocathodes were annealed for several hours at 90 deg. C in vacuum and their performance was then compared to the performance of non-heated samples. We observed that the post-evaporation thermal treatment not only increases the photoyield of CsI and KI photocathodes in the spectral range of 115-190 nm, but also reduces CsI, KI and KBr photocurrent degradation that occurs after UV irradiation. KBr evaporated layers appeared to be more radiation-resistant than CsI and KI layers. Post-deposition heat treatment did not result in any significant variation of KBr UV sensitivity.

Observation of Cherenkov rings using a low-pressure parallel-plate chamber and a solid cesium-iodide photocathode

International Nuclear Information System (INIS)

Lockyer, N.S.; Millan, J.E.; Lu, C.; McDonald, K.T.; Lopez, A.

1993-01-01

We have observed Cherenkov rings from minimum-ionizing particles using a low-pressure, parallel-plate pad-chamber with a cesium-iodide solid photocathode. This detector is blind to minimum-ionizing particles, and sensitive to Cherenkov photons of wavelengths 170-210 nm. An average of 5 photoelectrons per Cherenkov ring were detected using a 2-cm-thick radiator of liquid C 6 F 14 . This paper reports on the chamber construction, photocathode preparation and testbeam results. (orig.)

High time resolution beam-based measurement of the rf-to-laser jitter in a photocathode rf gun

Directory of Open Access Journals (Sweden)

Zhen Zhang

2014-03-01

Full Text Available Characterizing the rf-to-laser jitter in the photocathode rf gun and its possible origins is important for improving the synchronization and beam quality of the linac based on the photocathode rf gun. A new method based on the rf compression effect in the photocathode rf gun is proposed to measure the rf-to-laser jitter in the gun. By taking advantage of the correlation between the rf compression and the laser injection phase, the error caused by the jitter of the accelerating field in the gun is minimized and thus 10 fs time resolution is expected. Experimental demonstration at the Tsinghua Thomson scattering x-ray source with a time resolution better than 35 fs is reported in this paper. The experimental results are successfully used to obtain information on the possible cause of the jitter and the accompanying drifts.

Copper and copper-nickel alloys as zebra mussel antifoulants

Energy Technology Data Exchange (ETDEWEB)

Dormon, J.M.; Cottrell, C.M.; Allen, D.G.; Ackerman, J.D.; Spelt, J.K. [Univ. of Toronto, Ontario (Canada)

1996-04-01

Copper has been used in the marine environment for decades as cladding on ships and pipes to prevent biofouling by marine mussels (Mytilus edulis L.). This motivated the present investigation into the possibility of using copper to prevent biofouling in freshwater by both zebra mussels and quagga mussels (Dreissena polymorpha and D. bugensis collectively referred to as zebra mussels). Copper and copper alloy sheet proved to be highly effective in preventing biofouling by zebra mussels over a three-year period. Further studies were conducted with copper and copper-nickel mesh (lattice of expanded metal) and screen (woven wire with a smaller hole size), which reduced the amount of copper used. Copper screen was also found to be strongly biofouling-resistant with respect to zebra mussels, while copper mesh reduced zebra mussel biofouling in comparison to controls, but did not prevent it entirely. Preliminary investigations into the mechanism of copper antifouling, using galvanic couples, indicated that the release of copper ions from the surface of the exposed metal into the surrounding water is directly or indirectly responsible for the biofouling resistance of copper.

Damage caused by a nanosecond UV laser on a heated copper surface

Energy Technology Data Exchange (ETDEWEB)

Henč-Bartolić, V., E-mail: visnja.henc@fer.hr [University of Zagreb, Faculty of Electrical Engineering and Computing, Unska 3, 10000 Zagreb (Croatia); Bončina, T. [University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor (Slovenia); Jakovljević, S., E-mail: suzana.jakovljevic@fsb.hr [University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Ivana Lučića 5, 10002 Zagreb (Croatia); Panjan, P. [Jožef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Zupanič, F. [University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor (Slovenia)

2016-08-15

Highlights: • A Cu-plate was exposed to nanosecond UV laser with max. energy 1.1 J/cm{sup 2}. • Surface topography was studied on the cold and heated copper plate. • At room temperature, a crater formed, the melt was ejected from it. • Capillary waves formed in the vicinity of the crater at 360 °C. - Abstract: This work studied the effect of thin copper plate temperature on its surface morphology after irradiation using a pulsed nanosecond UV laser. The surface characteristics were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, focused ion beam and stylus profilometry. When a target was at room temperature, a crater and the radial flow of molten Cu from the crater was observed. When the thin target was warm (about 360 °C ± 20 °C), a crater was smaller, and quasi-semicircular waves with the periodicity of around 3 μm appeared in its vicinity. The origin of the waves is Marangoni effect, causing thermocapillary waves, which in same occasions had a structure of final states of chaos in Rayleigh–Bénard convection.

Experimental studies of the charge limit phenomenon in NEA GaAs photocathodes

International Nuclear Information System (INIS)

Tang, H.; Alley, R.K.; Aoyagi, H.; Clendenin, J.E.; Frisch, J.C.; Mulhollan, G.A.; Saez, P.J.; Schultz, D.C.; Turner, J.L.

1994-06-01

Negative electron affinity GaAs photocathodes have been in continuous use at SLAC for generating polarized electron beams since early 1992. If the quantum efficiency of a GaAs cathode is below a critical value, the maximum photoemitted charge with photons of energies close to the band gap in a 2-ns pulse is found to be limited by the intrinsic properties of the cathode instead of by the space charge limit. We have studied this novel charge limit phenomenon in a variety of GaAs photocathodes of different structures and doping densities. We find that the charge limit is strongly dependent on the cathode's quantum efficiency and the extraction electric field, and to a lesser degree on the excitation laser wavelength. In addition, we show that the temporal behavior of the charge limit depends critically on the doping density

Engineering Design and Fabrication of an Ampere-Class Superconducting Photocathode Electron Gun

International Nuclear Information System (INIS)

Ben-Zvi, I.

2008-01-01

Over the past three years, Advanced Energy Systems and Brookhaven National Laboratory (BNL) have been collaborating on the design of an Ampere- class superconducting photocathode electron gun. BNL performed the physics design of the overall system and RF cavity under prior programs. Advanced Energy Systems (AES) is currently responsible for the engineering design and fabrication of the electron gun under contract to BNL. We will report on the engineering design and fabrication status of the superconducting photocathode electron gun. The overall configuration of the cryomodule will be reviewed. The layout of the hermitic string, space frame, shielding package, and cold mass will be discussed. The engineering design of the gun cavity and removable cathode will be presented in detail and areas of technical risk will be highlighted. Finally, the fabrication sequence and fabrication status of the gun cavity will be discussed

Effects of organic matters coming from Chinese tea on soluble copper release from copper teapot

International Nuclear Information System (INIS)

Ni Lixiao; Li Shiyin

2008-01-01

The morphology and elemental composition of the corrosion products of copper teapot's inner-surface were characterized by the scanning electron microscopy and energy dispersive X-ray surface analysis (SEM/EDS), X-ray powder diffraction (XRD) and X-ray photon spectroscopy (XPS) analysis. It was revealed that Cu, Fe, Ca, P, Si and Al were the main elements of corrosion by-products, and the α-SiO 2 , Cu 2 O and CaCO 3 as the main mineral components on the inner-surface of copper teapot. The effects of organic matters coming from Chinese tea on soluble copper release from copper teapots in tap water were also investigated. The results showed that the doses of organic matter (as TOC), temperate and stagnation time have significant effects on the concentration of soluble copper released from copper teapots in tap water

Development of Thin Film Amorphous Silicon Tandem Junction Based Photocathodes Providing High Open-Circuit Voltages for Hydrogen Production

Directory of Open Access Journals (Sweden)

F. Urbain

2014-01-01

Full Text Available Hydrogenated amorphous silicon thin film tandem solar cells (a-Si:H/a-Si:H have been developed with focus on high open-circuit voltages for the direct application as photocathodes in photoelectrochemical water splitting devices. By temperature variation during deposition of the intrinsic a-Si:H absorber layers the band gap energy of a-Si:H absorber layers, correlating with the hydrogen content of the material, can be adjusted and combined in a way that a-Si:H/a-Si:H tandem solar cells provide open-circuit voltages up to 1.87 V. The applicability of the tandem solar cells as photocathodes was investigated in a photoelectrochemical cell (PEC measurement set-up. With platinum as a catalyst, the a-Si:H/a-Si:H based photocathodes exhibit a high photocurrent onset potential of 1.76 V versus the reversible hydrogen electrode (RHE and a photocurrent of 5.3 mA/cm2 at 0 V versus RHE (under halogen lamp illumination. Our results provide evidence that a direct application of thin film silicon based photocathodes fulfills the main thermodynamic requirements to generate hydrogen. Furthermore, the presented approach may provide an efficient and low-cost route to solar hydrogen production.

Study of the influence of surface-active substances on the initial stage of copper electrodeposition

Directory of Open Access Journals (Sweden)

Amantay Dalbanbay

2017-12-01

Full Text Available In this research, the effect of surface-active substances (CMC and DFP on the electrolysis of copper by cyclic voltammetry (CVA and chronoamperometric methods was studied. The working electrode was a glassy carbon electrode. Studies show that in the acid solution of copper sulfate (10-2 M CuSO4 + 0.5 M H2SO4, the three-dimensional electrochemical deposition of copper occurs by the mechanism of instantaneous nucleation. The added surface active substances affect the dischargeionization process, the standard electroreduction potential is shifted to the negative side. The added DFP reduces the cathodic peak current, and the addition of CMC results in its increase. At the deposition potentials corresponding to the regions up to the CVA peak current (here, still, the mixed electrodeposition kinetics, the number of nuclei formed is greater for a pure solution, but at current decay potentials, where the diffusion regime takes place, the nuclei population density (NPD is higher for solutions with surfactants. The most powerful effect here is caused by the addition of DFP. In the case of mixed additives, the NPD values are close to those of the CMC, obviously indicating the preferential adsorption of CMC, whereas the DFP as complexes with copper ions is closer to the near-electrode region.

Preparation of copper and silicon/copper powders by a gas ...

Indian Academy of Sciences (India)

Administrator

aCentre for Materials Research, Department of Imaging and Applied Physics, ... Copper powder; Si/Cu composite particle; gas evaporation–condensation method; characteriza- tion. .... from the liquid metal surface, the mixed vapour of copper.

High-speed collision of copper nanoparticle with aluminum surface: Molecular dynamics simulation

Science.gov (United States)

Pogorelko, Victor V.; Mayer, Alexander E.; Krasnikov, Vasiliy S.

2016-12-01

We investigate the effect of the high-speed collision of copper nanoparticles with aluminum surface by means of molecular dynamic simulations. Studied diameter of nanoparticles is varied within the range 7.2-22 nm and the velocity of impact is equal to 500 or 1000 m/s. Dislocation analysis shows that a large quantity of dislocations is formed within the impact area. Overall length of dislocations is determined, first of all, by the impact velocity and by the size of incident copper nanoparticle, in other words, by the kinetic energy of the nanoparticle. Dislocations occupy the total volume of the impacted aluminum single crystal layer (40.5 nm in thickness) in the form of intertwined structure in the case of large kinetic energy of the incident nanoparticle. Decrease in the initial kinetic energy or increase in the layer thickness lead to restriction of the penetration depth of the dislocation net; formation of separate dislocation loops is observed in this case. Increase in the initial system temperature slightly raises the dislocation density inside the bombarded layer and considerably decreases the dislocation density inside the nanoparticle. The temperature increase also leads to a deeper penetration of the copper atoms inside the aluminum. Additional molecular dynamic simulations show that the deposited particles demonstrate a very good adhesion even in the case of the considered relatively large nanoparticles. Medium energy of the nanoparticles corresponding to velocity of about 500 m/s and elevated temperature of the system about 700-900 K are optimal parameters for production of high-quality layers of copper on the aluminum surface. These conditions provide both a good adhesion and a less degree of the plastic deformation. At the same time, higher impact velocities can be used for combined treatment consisting of both the plastic deformation and the coating.

Beam Dynamics Simulation of Photocathode RF Electron Gun at the PBP-CMU Linac Laboratory

Science.gov (United States)

Buakor, K.; Rimjaem, S.

2017-09-01

Photocathode radio-frequency (RF) electron guns are widely used at many particle accelerator laboratories due to high quality of produced electron beams. By using a short-pulse laser to induce the photoemission process, the electrons are emitted with low energy spread. Moreover, the photocathode RF guns are not suffered from the electron back bombardment effect, which can cause the limited electron current and accelerated energy. In this research, we aim to develop the photocathode RF gun for the linac-based THz radiation source. Its design is based on the existing gun at the PBP-CMU Linac Laboratory. The gun consists of a one and a half cell S-band standing-wave RF cavities with a maximum electric field of about 60 MV/m at the centre of the full cell. We study the beam dynamics of electrons traveling through the electromagnetic field inside the RF gun by using the particle tracking program ASTRA. The laser properties i.e. transverse size and injecting phase are optimized to obtain low transverse emittance. In addition, the solenoid magnet is applied for beam focusing and emittance compensation. The proper solenoid magnetic field is then investigated to find the optimum value for proper emittance conservation condition.

Superhydrophobic copper surfaces fabricated by fatty acid soaps in aqueous solution for excellent corrosion resistance

Energy Technology Data Exchange (ETDEWEB)

Xu, Wenlong; Hu, Yuanyuan; Bao, Wenda; Xie, Xiaoyu; Liu, Yiran; Song, Aixin, E-mail: songaixin@sdu.edu.cn; Hao, Jingcheng

2017-03-31

Highlights: • The superhydrophobic property can be realized in a much quicker process (7.5 min) in aqueous solution than in ethanol. • The fabrication process of superhydrophobic metal surfaces greatly increases the safety in industrial manufacture in commercial scale. • The superhydrophobic copper surfaces show excellent corrosion resistance. - Abstract: A simple and safe one-step immersion method was developed to obtain the stable superhydrophobic copper surfaces with excellent corrosion resistance ability using fatty acids in water-medium instead of ethanol. An organic alkali, N,N-dimethylcyclohexylamine (DMCHA), was chosen to solve the poor solubility of fatty acids in water and the high Krafft point of carboxylate salts with inorganic counterions. The superhydrophobic property can be realized in a much quicker process (7.5 min) in aqueous solution than in ethanol (more than 2 d), which is universally feasible for the fabrication of superhydrophobic metal surfaces in industry scale, thereby greatly increasing the safety in industrial manufacture.

S-11 and S-20 photocathode research activity. Rev. 1

International Nuclear Information System (INIS)

Gex, F.; Huen, T.; Kalibjian, R.

1984-01-01

The S-1 semi-transparent photocathode is the only one that can be used to study the 1.06 μm neodynium laser pulses of less than 10 ps duration. We first reviewed the recent results obtained at the Paris Observatory (research sponsored by the CEA), and then we tried to determine the role of the main constituents and their contributions in photoemission

Extremely superhydrophobic surfaces with micro- and nanostructures fabricated by copper catalytic etching.

Science.gov (United States)

Lee, Jung-Pil; Choi, Sinho; Park, Soojin

2011-01-18

We demonstrate a simple method for the fabrication of rough silicon surfaces with micro- and nanostructures, which exhibited superhydrophobic behaviors. Hierarchically rough silicon surfaces were prepared by copper (Cu)-assisted chemical etching process where Cu nanoparticles having particle size of 10-30 nm were deposited on silicon surface, depending on the period of time of electroless Cu plating. Surface roughness was controlled by both the size of Cu nanoparticles and etching conditions. As-synthesized rough silicon surfaces showed water contact angles ranging from 93° to 149°. Moreover, the hierarchically rough silicon surfaces were chemically modified by spin-coating of a thin layer of Teflon precursor with low surface energy. And thus it exhibited nonsticky and enhanced hydrophobic properties with extremely high contact angle of nearly 180°.

Performance of Grass Filter Strip in Copper and Zinc Removal in Surface and Subsurface Runoff

Directory of Open Access Journals (Sweden)

Huo Weijie

2017-01-01

Full Text Available Three filter strips were conducted on self-designed soil bins. Taking a filter strip with no vegetation as contrast, the effectiveness of vegetation and soil conditions on heavy metals (including copper and zinc removal efficiencies were investigated by simulated runoff experiment. The results showed that the adsorbed state is the main existing form of heavy metal. For surface runoff, most of total copper and total zinc are trapped in first 4m and it is ineffective to increase the distance beyond 4m for removal. Vegetation has no significant effect on total copper and total zinc removal, while the soil with higher content of organic matter is contributing to total Zn interception. For subsurface runoff, the removal efficiencies of total copper and total zinc can reach to above 95.38% and both vegetation and soil conditions have no significant effects. Vegetation is contributing to copper ion and zinc ion removal significantly. Soil condition is only a significant factor to zinc ion, with higher content of organic matter as a contributing factor.

Surface characteristics, copper release, and toxicity of nano- and micrometer-sized copper and copper(II) oxide particles: a cross-disciplinary study.

OpenAIRE

Midander, Klara; Cronholm, Pontus; Karlsson, Hanna L.; Elihn, Karine; Moller, Lennart; Leygraf, Christofer; Wallinder, Inger Odnevall

2009-01-01

An interdisciplinary and multianalytical research effort is undertaken to assess the toxic aspects of thoroughly characterized nano- and micrometer-sized particles of oxidized metallic copper and copper(II) oxide in contact with cultivated lung cells, as well as copper release in relevant media. All particles, except micrometer-sized Cu, release more copper in serum-containing cell medium (supplemented Dulbecco's minimal essential medium) compared to identical exposures in phosphate-buffered ...

Target surface condition during reactive glow discharge sputtering of copper

International Nuclear Information System (INIS)

Depla, D; Haemers, J; Gryse, R De

2002-01-01

During reactive glow discharge sputtering of copper in an argon/nitrogen plasma, we noticed an abrupt change of the target voltage and the deposition rate when the nitrogen concentration in the plasma exceeds a critical value. To explain this behaviour, the target surface after reactive glow discharge sputtering was examined by x-ray photoelectron spectroscopy (XPS). An experimental arrangement was constructed that allows direct transfer of the glow discharge cathode to the XPS analysis chamber without air exposure. These XPS measurements revealed that several different chemical states of nitrogen are present in the layer that forms on the target surface. The relative concentration of these different states changes when the critical nitrogen concentration in the plasma is exceeded

Single-side electron multipacting at the photocathode in rf guns

Directory of Open Access Journals (Sweden)

Jang-Hui Han

2008-01-01

Full Text Available Multiple electron impacting (multipacting can take place in rf fields when the rf components are composed of materials with a secondary electron yield greater than one. In rf gun cavities, multipacting may change the properties of the vacuum components or even damage them. First systematic measurements of the multipacting occurring in a photocathode rf gun were made at the Fermilab/NICADD Photoinjector Laboratory in 2000. The multipacting properties were found to depend on the cathode material and the solenoid field configuration. In this study, we measure the multipacting properties in more detail and model the secondary electron generation for numerical simulation. Measurements and simulations for the photoinjectors at Fermilab and DESY are compared. The multipacting takes place at the photocathode in rf guns and is categorized as single-side multipacting. In a low rf field, the electrons emitted from the cathode area do not leave the gun cavity within one rf cycle and have an opportunity to travel back and hit the cathode. The solenoid field distribution in the vicinity of the cathode changes the probability of electron bombardment of the cathode and makes a major contribution to the multipacting behavior.

Copper hexacyanoferrate formation on the modified silica surface with DAB-Am-16 dendrimer

International Nuclear Information System (INIS)

Carmo, Devaney R. do; Gabriel Junior, Suelino; Bicalho, Urquisa O.; Paim, Leonardo L.

2009-01-01

The dendrimer hexadecamine poly(propylene)imine (DAB-Am-16) of third generation (G-3) was anchored on the silica gel surface. The modified silica interact easily with Cu 2+ and then with hexacyanoferrate to form copper hexacyanoferrate. The modified silica was characterized by following techniques: nuclear magnetic resonance (NMR), infrared (FTIR), energy dispersive X-ray (EDX) and cyclic voltammetry. As application of the composite obtained, the modified silica containing copper hexacyanoferrate (CuHCFSD) was tested for a voltammetric determination of nitrite using a graphite paste modified electrode. The modified graphite paste electrode can be applied also to the determination of others biological substances with success. (author)

X-ray spectrum microanalysis of copper and stainless steel surface layer after electroerosion machining

International Nuclear Information System (INIS)

Abdukarimov, Eh.T.; Saidinov, S.Ya.

1989-01-01

The results of experimental investigations of the surface layer of copper and steel 12Kh18N10T after electroerrosion treatment by a rotating tungsten electrode in natural and distilled water are presented. It is established that the quantity of electrode material transferred to the surface of the steel treated grows with the spark discharge energy increase. Tungsten concentration in the surface layer reaches 5-10% with the average depth of penetration 40-50 μm

A review of radio-frequency photocathode electron sources

International Nuclear Information System (INIS)

Stovall, J.

1992-01-01

A review of this topic at the last conference in this series reported considerable progress in R and D programs aimed at producing high-current low-emittance electron beams using photocathode rf guns. At present at least 20 such projects are under way world wide and at least 6 photoinjectors are presently in operation. This paper reviews some of the choices that must be made in optimizing the design of the accelerating structure for a photoinjector based on the current state of knowledge. (Author) 5 refs., 9 figs., 3 tabs

Re-examination of the threshold energy surface in copper

International Nuclear Information System (INIS)

King, W.E.; Benedek, R.; Merkle, K.L.; Meshii, M.

1981-01-01

Radiation-induced defect production in copper has been studied using in-situ electrical resistivity damage-rate measurements in the HVEM and molecular dynamics simulations. Analysis of the results yields a threshold energy surface characterized by two isolated pockets of low threshold energy centered at and surrounded by regions of much higher threshold energy; the corresponding damage function exhibits a plateau at 0.65 Frenkel pairs. A Frenkel pair resistivity of (2.75/sub -0.2/ + 0 6 ) x 10 - 4 Ω-cm is proposed. A model damage function is constructed and compared to results from ion irradiation damage-rate measurements. 7 figures

Construction of wettability gradient surface on copper substrate by controlled hydrolysis of poly(methyl methacrylate–butyl acrylate) films

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yong, E-mail: Yong.Z@mail.scut.edu.cn [Guangzhou Panyu Polytechnic, Guangzhou 511483 (China); Cheng, Jiang; Yang, Zhuo-ru [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640 (China)

2014-10-01

We report a gradient wettability surface on copper slide prepared by a simple controlled ester group hydrolysis procedure of poly(methyl methacrylate–butyl acrylate) [P (MMA-BA)] films coated on the copper substrate. In the method, sodium hydroxide solutions are selected to prepare surface gradient wettability on P (MMA-BA) films. The P (MMA-BA) copolymers with different MMA contents are first synthesized by a conventional free atom radical solution polymerization method. The transfer of surface chemical composition from the ester group to acid salt is achieved by hydrolysis in NaOH solution. The effects of different concentrations of NaOH solution and reaction times on the physicochemical properties of the resulting surfaces are studied. The field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) results show that the varying concentration along the substrate length is only attributed to the hydrolysis reaction of ester groups. The hydrolysis causes insignificant change on the morphology of the original film on the copper substrate. In addition, it is found that the MMA copolymer content has a significant influence on the concentration of ester groups on the outermost surface and thus important for forming the slope gradients.

Generation of a femtosecond electron microbunch train from a photocathode using twofold Michelson interferometer

Directory of Open Access Journals (Sweden)

M. Shevelev

2017-10-01

Full Text Available The interest in producing ultrashort electron bunches has risen sharply among scientists working on the design of high-gradient wakefield accelerators. One attractive approach generating electron bunches is to illuminate a photocathode with a train of femtosecond laser pulses. In this paper we describe the design and testing of a laser system for an rf gun based on a commercial titanium-sapphire laser technology. The technology allows the production of four femtosecond laser pulses with a continuously variable pulse delay. We also use the designed system to demonstrate the experimental generation of an electron microbunch train obtained by illuminating a cesium-telluride semiconductor photocathode. We use conventional diagnostics to characterize the electron microbunches produced and confirm that it may be possible to control the main parameter of an electron microbunch train.

Generation of a femtosecond electron microbunch train from a photocathode using twofold Michelson interferometer

Science.gov (United States)

Shevelev, M.; Aryshev, A.; Terunuma, N.; Urakawa, J.

2017-10-01

The interest in producing ultrashort electron bunches has risen sharply among scientists working on the design of high-gradient wakefield accelerators. One attractive approach generating electron bunches is to illuminate a photocathode with a train of femtosecond laser pulses. In this paper we describe the design and testing of a laser system for an rf gun based on a commercial titanium-sapphire laser technology. The technology allows the production of four femtosecond laser pulses with a continuously variable pulse delay. We also use the designed system to demonstrate the experimental generation of an electron microbunch train obtained by illuminating a cesium-telluride semiconductor photocathode. We use conventional diagnostics to characterize the electron microbunches produced and confirm that it may be possible to control the main parameter of an electron microbunch train.

Native copper as a natural analogue for copper canisters

International Nuclear Information System (INIS)

Marcos, N.

1989-12-01

This paper discusses the occurrence of native copper as found in geological formations as a stability analogue of copper canisters that are planned to be used for the disposal of spent nuclear fuel in the Finnish bedrock. A summary of several publications on native copper occurrences is presented. The present geochemical and geohydrological conditions in which copper is met with in its metallic state show that metallic copper is stable in a wide range of temperatures. At low temperatures native copper is found to be stable where groundwater has moderate pH (about 7), low Eh (< +100 mV), and low total dissolved solids, especially chloride. Microscopical and microanalytical studies were carried out on a dozen of rock samples containing native copper. The results reveal that the metal shows no significant alteration. Only the surface of copper grains is locally coated. In the oldest samples there exist small corrosion cracks; the age of the oldest samples is over 1,000 million years. A review of several Finnish groundwater studies suggests that there are places in Finland where the geohydrological conditions are favourable for native copper stability. (orig.)

Corrosion of copper in oxygen-deficient groundwater with and without deep bedrock micro-organisms: Characterisation of microbial communities and surface processes

Energy Technology Data Exchange (ETDEWEB)

Huttunen-Saarivirta, E., E-mail: elina.huttunen-saarivirta@vtt.fi [VTT Technical Research Centre of Finland, Materials Performance, Kemistintie 3, FI-02044 VTT (Finland); Rajala, P. [VTT Technical Research Centre of Finland, Materials Performance, Kemistintie 3, FI-02044 VTT (Finland); Bomberg, M. [VTT Technical Research Centre of Finland, Geobiotechnology, Tietotie 2, FI-02044 VTT (Finland); Carpén, L. [VTT Technical Research Centre of Finland, Materials Performance, Kemistintie 3, FI-02044 VTT (Finland)

2017-02-28

Highlights: • Copper was exposed to groundwater with and without deep bedrock micro-organisms. • Biofilm composition was determined and correlated with the behaviour of copper. • Under biotic conditions, the film of Cu{sub 2}S formed on copper surfaces. • Bacterial pool was in a key role for the morphology and properties of Cu{sub 2}S film. • Under abiotic conditions, Cu{sub 2}O systematically developed on copper surfaces. - Abstract: Copper specimens were exposed to oxygen-deficient artificial groundwater in the presence and absence of micro-organisms enriched from the deep bedrock of the planned nuclear waste repository site at Olkiluoto island on the western coast of Finland. During the exposure periods of 4 and 10 months, the copper specimens were subjected to electrochemical measurements. The biofilm developed on the specimens and the water used in the exposures were subjected to microbiological analyses. Changes in the water chemistry were also determined and surfaces of the copper specimens were characterized with respect to the morphology and composition of the formed corrosion products. The results showed that under biotic conditions, redox of the water and open circuit potential (OCP) of the copper specimens were generally negative and resulted in the build-up of a copper sulphide, Cu{sub 2}S, layer due to the activity of sulphate-reducing bacteria (SRB) that were included in the system. In the 4-month test, the electrochemical behaviour of the specimens changed during the exposure and alphaproteobactria Rhizobiales were the dominant bacterial group in the biofilm where the highest corrosion rate was observed. In the 10-month test, however, deltaproteobacteria SRB flourished and the initial electrochemical behaviour and the low corrosion rate of the copper were retained until the end of the test period. Under abiotic conditions, the positive water redox potential and specimen OCP correlated with the formation of copper oxide, Cu{sub 2}O

Corrosion of copper in oxygen-deficient groundwater with and without deep bedrock micro-organisms: Characterisation of microbial communities and surface processes

International Nuclear Information System (INIS)

Huttunen-Saarivirta, E.; Rajala, P.; Bomberg, M.; Carpén, L.

2017-01-01

Highlights: • Copper was exposed to groundwater with and without deep bedrock micro-organisms. • Biofilm composition was determined and correlated with the behaviour of copper. • Under biotic conditions, the film of Cu_2S formed on copper surfaces. • Bacterial pool was in a key role for the morphology and properties of Cu_2S film. • Under abiotic conditions, Cu_2O systematically developed on copper surfaces. - Abstract: Copper specimens were exposed to oxygen-deficient artificial groundwater in the presence and absence of micro-organisms enriched from the deep bedrock of the planned nuclear waste repository site at Olkiluoto island on the western coast of Finland. During the exposure periods of 4 and 10 months, the copper specimens were subjected to electrochemical measurements. The biofilm developed on the specimens and the water used in the exposures were subjected to microbiological analyses. Changes in the water chemistry were also determined and surfaces of the copper specimens were characterized with respect to the morphology and composition of the formed corrosion products. The results showed that under biotic conditions, redox of the water and open circuit potential (OCP) of the copper specimens were generally negative and resulted in the build-up of a copper sulphide, Cu_2S, layer due to the activity of sulphate-reducing bacteria (SRB) that were included in the system. In the 4-month test, the electrochemical behaviour of the specimens changed during the exposure and alphaproteobactria Rhizobiales were the dominant bacterial group in the biofilm where the highest corrosion rate was observed. In the 10-month test, however, deltaproteobacteria SRB flourished and the initial electrochemical behaviour and the low corrosion rate of the copper were retained until the end of the test period. Under abiotic conditions, the positive water redox potential and specimen OCP correlated with the formation of copper oxide, Cu_2O. Furthermore, in the absence of

Anti-corrosion film formed on HAl77-2 copper alloy surface by aliphatic polyamine in 3 wt.% NaCl solution

Energy Technology Data Exchange (ETDEWEB)

Yu, Yinzhe; Yang, Dong; Zhang, Daquan, E-mail: zhdq@sh163.net; Wang, Yizhen; Gao, Lixin

2017-01-15

Highlights: • Properties of ADDD meet environment-friendly requirements. • ADDD’s inhibition efficiency is better than BTA at the low concentration. • ADDD adsorbs on the copper alloy surface by via the N atom in its amino group using flat mode. - Abstract: The corrosion inhibition of a polyamine compound, N-(4-amino-2, 3-dimethylbutyl)-2, 3-dimethylbutane-1, 4-diamine (ADDD), was investigated for HAl77-2 copper alloy in 3 wt.% NaCl solution. Electrochemical measurements, scanning electron microscopy (SEM), atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FT-IR) techniques were employed for this research. The results show that ADDD strongly suppresses the corrosion of HAl77-2 alloy. The inhibition efficiency of ADDD is 98.6% at 0.5 mM, which is better than benzotriazole (BTAH) at the same concentration. Polarization curves indicate that ADDD is an anodic type inhibitor. Surface analysis suggests that a protective film is formed via the interaction of ADDD and copper. FT-IR reveals that the inhibition mechanism of ADDD is dominated by chemisorption onto the copper alloy surface to form an inhibition film. Furthermore, quantum chemical calculation and molecular dynamics (MD) simulations methods show that ADDD adsorbs on HAl77-2 surface via amino group in its molecule.

Photocatalytic disinfection of surfaces with copper doped Ti02 nanotube coatings illuminated by ceiling mounted fluorescent light

Science.gov (United States)

Koklic, Tilen; Pintarič, Štefan; Zdovc, Irena; Golob, Majda; Umek, Polona; Mehle, Alma; Dobeic, Martin; Štrancar, Janez

2018-01-01

High economic burden is associated with foodborne illnesses. Different disinfection methods are therefore employed in food processing industry; such as use of ultraviolet light or usage of surfaces with copper-containing alloys. However, all the disinfection methods currently in use have some shortcomings. In this work we show that copper doped TiO2 nanotubes deposited on existing surfaces and illuminated with ceiling mounted fluorescent lights can retard the growth of Listeria Innocua by 80% in seven hours of exposure to the fluorescent lights at different places in a food processing plant or in the laboratory conditions with daily reinocuation and washing. The disinfection properties of the surfaces seem to depend mainly on the temperature difference of the surface and the dew point, where for the maximum effectiveness the difference should be about 3 degrees celsius. The TiO2 nanotubes have a potential to be employed for an economical and continuous disinfection of surfaces. PMID:29768464

Calculation of the surface free energy of fcc copper nanoparticles

International Nuclear Information System (INIS)

Jia Ming; Lai Yanqing; Tian Zhongliang; Liu Yexiang

2009-01-01

Using molecular dynamics simulations with the modified analytic embedded-atom method we calculate the Gibbs free energy and surface free energy for fcc Cu bulk, and further obtain the Gibbs free energy of nanoparticles. Based on the Gibbs free energy of nanoparticles, we have investigated the heat capacity of copper nanoparticles. Calculation results indicate that the Gibbs free energy and the heat capacity of nanoparticles can be divided into two parts: bulk quantity and surface quantity. The molar heat capacity of the bulk sample is lower compared with the molar heat capacity of nanoparticles, and this difference increases with the decrease in the particle size. It is also observed that the size effect on the thermodynamic properties of Cu nanoparticles is not really significant until the particle is less than about 20 nm. It is the surface atoms that decide the size effect on the thermodynamic properties of nanoparticles

Morphological features of the copper surface layer under sliding with high density electric current

Energy Technology Data Exchange (ETDEWEB)

Fadin, V. V., E-mail: fvv@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Aleutdinova, M. I., E-mail: aleut@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Seversk Technological Institute, Branch of State Autonomous Educational Institution of Higher Professional Education “National Research Nuclear University “MEPhI”, Seversk, 636036 (Russian Federation); Rubtsov, V. Ye., E-mail: rvy@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Aleutdinova, V. A., E-mail: valery-aleut@yandex.ru [National Research St. Petersburg State Polytechnical University, St. Petersburg, 195251 (Russian Federation)

2015-10-27

Conductivity and wear intensity of copper under the influence of dry friction and electric current with contact density higher 100 A/cm{sup 2} are presented. It is shown that an increase in hardness and heat outflow from a friction zone leads to the reduction of wear intensity and current contact density increase corresponding to the beginning of catastrophic wear. Structural changes, such as the formation of FeO oxide and α-Fe particles in the copper surface layer, have also been found. It is observed that a worn surface is deformed according to a viscous liquid mechanism. Such singularity is explained in terms of appearance of high-excited atomic states in deforming micro-volumes near contact spots that lead to easy stress relaxation by local plastic shears in the vicinity of stress concentrators. In common this effect allows to achieve high wear resistance.

Exposure of metallic copper surface on Cu-Al2O3-carbon catalysts

NARCIS (Netherlands)

Menon, P.G.; Prasad, J.

1970-01-01

The bifunctional nature of Cu---Al2O3-on-carbon catalysts, used in the direct catalytic conversion of ethanol to ethyl acetate, prompted an examination of the dispersion of Cu on the composite catalyst. For this, the N2O-method of Osinga et al. for estimation of bare metallic copper surface on

Direct measurement of the adsorption kinetics of 2-Mercaptobenzothiazole on a microcrystalline copper surface

Energy Technology Data Exchange (ETDEWEB)

Ramirez-Cano, J. A.; Veleva, L.

2016-05-01

The adsorption on copper of 2-Mercaptobenzothiazole (2-MBT), a heterocyclic compound member of the tiazole family, has been investigated at different concentrations (1x10{sup -}1 to 1x10{sup -}6 M) in water, employing the Electrochemical Quartz Crystal Microbalance (EQCM). The frequency response over time was obtained for each concentration, showing a defined exponential behavior at higher concentrations (1x10{sup -}1, 1x10{sup -}2 and 1x10{sup -}3 M), which was filed to the Langmuir adsorption isotherm with a good correlation coefficients (R{sup 2}=0.91 to 0.98) Surface coverage (θ) was calculated and found to be in the order of 0.50 to 0.01 for 2-MBT high concentrations. The free energy of adsorption was ΔG{sub a}ds=-5.59 kJ mol{sup -}1, corresponding to physisorption process, probably of electrostatic nature of the interaction between 2-MBT and copper surface in aqueous solution. (Author)

Performance of a DC GaAs photocathode gun for the Jefferson lab FEL

CERN Document Server

Siggins, T; Bohn, C L; Bullard, D; Douglas, D; Grippo, A; Gubeli, J; Krafft, G A; Yunn, B

2001-01-01

The performance of the 320 kV DC photocathode gun has met the design specifications for the 1 kW IR Demo FEL at Jefferson Lab. This gun has shown the ability to deliver high average current beam with outstanding lifetimes. The GaAs photocathode has delivered 135 pC per bunch, at a bunch repetition rate of 37.425 MHz, corresponding to 5 mA average CW current. In a recent cathode lifetime measurement, 20 h of CW beam was delivered with an average current of 3.1 mA and 211 C of total charge from a 0.283 cm sup 2 illuminated spot. The cathode showed a 1/e lifetime of 58 h and a 1/e extracted charge lifetime of 618 C. We have achieved quantum efficiencies of 5% from a GaAs wafer that has been in service for 13 months delivering in excess 2400 C with only three activation cycles.

Heat load of a P-doped GaAs photocathode in SRF electron gun

International Nuclear Information System (INIS)

Wang, E.; Ben-Zvi, I.; Kewisch, J.; Burrill, A.; Rao, T.; Wu, Q.; Jain, A.; Gupta, R.; Holmes, D.

2010-01-01

Many efforts were made over the last decades to develop a better polarized electron source for the high energy physics. Several laboratories operate DC guns with the Gallium-Arsenide photo-cathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved using a Superconducting RF electron gun, which delivers beams of higher brightness than DC guns does, because the field gradient at the cathode is higher. SRF guns with metal cathodes and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since the cathode will be normal conducting, the problem about the heat load stemming from the cathode arises. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and the verification by measuring the quality factor of the gun with and without cathode.

Photocurrent Enhancement by a Rapid Thermal Treatment of Nanodisk-Shaped SnS Photocathodes.

Science.gov (United States)

Patel, Malkeshkumar; Kumar, Mohit; Kim, Joondong; Kim, Yu Kwon

2017-12-21

Photocathodes made from the earth-abundant, ecofriendly mineral tin monosulfide (SnS) can be promising candidates for p/n-type photoelectrochemical cells because they meet the strict requirements of energy band edges for each individual photoelectrode. Herein we fabricated SnS-based cell that exhibited a prolonged photocurrent for 3 h at -0.3 V vs the reversible hydrogen electrode (RHE) in a 0.1 M HCl electrolyte. An enhancement of the cathodic photocurrent from 2 to 6 mA cm -2 is observed through a rapid thermal treatment. Mott-Schottky analysis of SnS samples revealed an anodic shift of 0.7 V in the flat band potential under light illumination. Incident photon-to-current conversion efficiency (IPCE) analysis indicates that an efficient charge transfer appropriate for solar hydrogen generation occurs at the -0.3 V vs RHE potential. This work shows that SnS is a promising material for photocathode in PEC cells and its performance can be enhanced via simple postannealing.

Picosecond electron bunches from GaAs/GaAsP strained superlattice photocathode

International Nuclear Information System (INIS)

Jin, Xiuguang; Matsuba, Shunya; Honda, Yosuke; Miyajima, Tsukasa; Yamamoto, Masahiro; Utiyama, Takashi; Takeda, Yoshikazu

2013-01-01

GaAs/GaAsP strained superlattices are excellent candidates for use as spin-polarized electron sources. In the present study, picosecond electron bunches were successfully generated from such a superlattice photocathode. However, electron transport in the superlattice was much slower than in bulk GaAs. Transmission electron microscopy observations revealed that a small amount of variations in the uniformity of the layers was present in the superlattice. These variations lead to fluctuations in the superlattice mini-band structure and can affect electron transport. Thus, it is expected that if the periodicity of the superlattice can be improved, much faster electron bunches can be produced. - Highlights: • GaAs/GaAsP strained superlattices are excellent candidates for spin-polarized electron beam. • Pulse spin-polarized electron beam is required for investigating the magnetic domain change. • Picosecond electron bunches were achieved from GaAs/GaAsP superlattice photocathode. • TEM observation revealed a small disorder of superlattice layers. • Improvement of superlattice periodicity can achieve much faster electron bunches

Integration of Transients in Axisymmetrical Cavities for Accelerators: Formulation and applications to BNL Photocathode Gun

International Nuclear Information System (INIS)

Parsa, Z.; Serafini, L.

1992-04-01

This note provides a sketch of the formalism used for the Integration of Transients in Axisymmetrical Cavities for Accelerators, (ITACA). Application to study the BNL Photocathode Gun via the code ITACA is also included

Evolution of surface topography in dependence on the grain orientation during surface thermal fatigue of polycrystalline copper

CERN Document Server

Aicheler, M; Taborelli, M; Calatroni, S; Neupert, H; Wuensch, W; Sgobba, S

2011-01-01

Surface degradation due to cyclic thermal loading plays a major role in the Accelerating Structures (AS) of the future Compact Linear Collider (CLIC) In this article results on surface degradation of thermally cycled polycrystalline copper as a function of the orientation of surface grains are presented Samples with different grain sizes were subjected to thermal fatigue using two different methods and were then characterized using roughness measurements and Orientation Imaging Scanning-Electron-Microscopy (OIM-SEM) Samples fatigued by a pulsed laser show the same trend in the orientation-fatigue damage accumulation as the sample fatigued by pulsed Radio-Frequency-heating (RF) it is clearly shown that 11 1 1] surface grains develop significantly more damage than the surface grains oriented in {[}100] and three reasons for this behaviour are pointed out Based on observations performed near grain boundaries their role in the crack initiation process is discussed The results are in good agreement with previous f...

Diffuse emission and control of copper in urban surface runoff.

Science.gov (United States)

Boller, M A; Steiner, M

2002-01-01

Copper washed off from roofs and roads is considered to be a major contribution to diffuse copper pollution of urban environments. In order to guarantee sustainable protection of soils and water, the long-term strategy is to avoid or replace copper containing materials on roofs and fagades. Until achievement of this goal, a special adsorber system is suggested to control the diffuse copper fluxes by retention of copper by a mixture of granulated iron-hydroxide (GEH) and calcium carbonate. Since future stormwater runoff concepts are based on decentralised runoff infiltration into the underground, solutions are proposed which provide for copper retention in infiltration sites using GEH adsorption layers. The example of a large copper façade of which the runoff is treated in an adsorption trench reveals the first full-scale data on façade runoff and adsorber performance. During the first year of investigation average façade runoff concentrations in the range of 1-10 mg Cu/l are reduced by 96-99% in the adsorption ditch.

High sensitive detection of copper II ions using D-penicillamine-coated gold nanorods based on localized surface plasmon resonance

Science.gov (United States)

Hong, Yoochan; Jo, Seongjae; Park, Joohyung; Park, Jinsung; Yang, Jaemoon

2018-05-01

In this paper, we describe the development of a nanoplasmonic biosensor based on the localized surface plasmon resonance (LSPR) effect that enables a sensitive and selective recognition of copper II ions. First, we fabricated the nanoplasmonics as LSPR substrates using gold nanorods (GNR) and the nano-adsorption method. The LSPR sensitivity of the nanoplasmonics was evaluated using various solvents with different refractive indexes. Subsequently, D-penicillamine (DPA)—a chelating agent of copper II ions—was conjugated to the surface of the GNR. The limit of detection (LOD) for the DPA-conjugated nanoplasmonics was 100 pM. Furthermore, selectivity tests were conducted using various divalent cations, and sensitivity tests were conducted on the nanoplasmonics under blood-like environments. Finally, the developed nanoplasmonic biosensor based on GNR shows great potential for the effective recognition of copper II ions, even in human blood conditions.

High voltage switch triggered by a laser-photocathode subsystem

Science.gov (United States)

Chen, Ping; Lundquist, Martin L.; Yu, David U. L.

2013-01-08

A spark gap switch for controlling the output of a high voltage pulse from a high voltage source, for example, a capacitor bank or a pulse forming network, to an external load such as a high gradient electron gun, laser, pulsed power accelerator or wide band radar. The combination of a UV laser and a high vacuum quartz cell, in which a photocathode and an anode are installed, is utilized as triggering devices to switch the spark gap from a non-conducting state to a conducting state with low delay and low jitter.

Lasertron, a pulsed RF-source using laser triggered photocathode

International Nuclear Information System (INIS)

Yoshioka, Masakazu.

1988-12-01

A new pulsed RF-source, 'Lasertron', are being developed as a possible RF-power source for future electron-positron linear colliders. In a series of systematic study, a prototype lasertron has been fabricated and tested. A peak power of 80 kW is attained at 2.856 GHz RF-frequency in 1-μs time duration. This paper describes the experimental results of the lasertron including the developments of the photocathode and the laser system. Test results are compared with the analysis of beam dynamics in the lasertron. (author)

Unbiased, complete solar charging of a neutral flow battery by a single Si photocathode

DEFF Research Database (Denmark)

Wedege, Kristina; Bae, Dowon; Dražević, Emil

2018-01-01

Solar redox flow batteries have attracted attention as a possible integrated technology for simultaneous conversion and storage of solar energy. In this work, we review current efforts to design aqueous solar flow batteries in terms of battery electrolyte capacity, solar conversion efficiency...... and depth of solar charge. From a materials cost and design perspective, a simple, cost-efficient, aqueous solar redox flow battery will most likely incorporate only one semiconductor, and we demonstrate here a system where a single photocathode is accurately matched to the redox couples to allow...... for a complete solar charge. The single TiO2 protected Si photocathode with a catalytic Pt layer can fully solar charge a neutral TEMPO-sulfate/ferricyanide battery with a cell voltage of 0.35 V. An unbiased solar conversion efficiency of 1.6% is obtained and this system represents a new strategy in solar RFBs...

High-speed collision of copper nanoparticle with aluminum surface: Molecular dynamics simulation

Energy Technology Data Exchange (ETDEWEB)

Pogorelko, Victor V., E-mail: vik_ko83@mail.ru [Chelyabinsk State University, Bratiev Kashirinykh 129, 454001 Chelyabinsk (Russian Federation); South Ural State University (National Research University), Lenin Prospect 76, 454080 Chelyabinsk (Russian Federation); Mayer, Alexander E., E-mail: mayer@csu.ru [Chelyabinsk State University, Bratiev Kashirinykh 129, 454001 Chelyabinsk (Russian Federation); South Ural State University (National Research University), Lenin Prospect 76, 454080 Chelyabinsk (Russian Federation); Krasnikov, Vasiliy S., E-mail: vas.krasnikov@gmail.com [Chelyabinsk State University, Bratiev Kashirinykh 129, 454001 Chelyabinsk (Russian Federation); South Ural State University (National Research University), Lenin Prospect 76, 454080 Chelyabinsk (Russian Federation)

2016-12-30

Highlights: • High-speed nanoparticle impact induces shock waves and intensive plastic deformation. • Lattice orientation strongly influences on the deformation degree. • Plastic deformation goes through nucleation, growth and separation of semi-loops. • Medium impact energy and elevated temperature are optimal for high-quality coating. • High impact velocity and room temperature lead to plastic deformation and coating. - Abstract: We investigate the effect of the high-speed collision of copper nanoparticles with aluminum surface by means of molecular dynamic simulations. Studied diameter of nanoparticles is varied within the range 7.2–22 nm and the velocity of impact is equal to 500 or 1000 m/s. Dislocation analysis shows that a large quantity of dislocations is formed within the impact area. Overall length of dislocations is determined, first of all, by the impact velocity and by the size of incident copper nanoparticle, in other words, by the kinetic energy of the nanoparticle. Dislocations occupy the total volume of the impacted aluminum single crystal layer (40.5 nm in thickness) in the form of intertwined structure in the case of large kinetic energy of the incident nanoparticle. Decrease in the initial kinetic energy or increase in the layer thickness lead to restriction of the penetration depth of the dislocation net; formation of separate dislocation loops is observed in this case. Increase in the initial system temperature slightly raises the dislocation density inside the bombarded layer and considerably decreases the dislocation density inside the nanoparticle. The temperature increase also leads to a deeper penetration of the copper atoms inside the aluminum. Additional molecular dynamic simulations show that the deposited particles demonstrate a very good adhesion even in the case of the considered relatively large nanoparticles. Medium energy of the nanoparticles corresponding to velocity of about 500 m/s and elevated temperature of the

High-speed collision of copper nanoparticle with aluminum surface: Molecular dynamics simulation

International Nuclear Information System (INIS)

Pogorelko, Victor V.; Mayer, Alexander E.; Krasnikov, Vasiliy S.

2016-01-01

Highlights: • High-speed nanoparticle impact induces shock waves and intensive plastic deformation. • Lattice orientation strongly influences on the deformation degree. • Plastic deformation goes through nucleation, growth and separation of semi-loops. • Medium impact energy and elevated temperature are optimal for high-quality coating. • High impact velocity and room temperature lead to plastic deformation and coating. - Abstract: We investigate the effect of the high-speed collision of copper nanoparticles with aluminum surface by means of molecular dynamic simulations. Studied diameter of nanoparticles is varied within the range 7.2–22 nm and the velocity of impact is equal to 500 or 1000 m/s. Dislocation analysis shows that a large quantity of dislocations is formed within the impact area. Overall length of dislocations is determined, first of all, by the impact velocity and by the size of incident copper nanoparticle, in other words, by the kinetic energy of the nanoparticle. Dislocations occupy the total volume of the impacted aluminum single crystal layer (40.5 nm in thickness) in the form of intertwined structure in the case of large kinetic energy of the incident nanoparticle. Decrease in the initial kinetic energy or increase in the layer thickness lead to restriction of the penetration depth of the dislocation net; formation of separate dislocation loops is observed in this case. Increase in the initial system temperature slightly raises the dislocation density inside the bombarded layer and considerably decreases the dislocation density inside the nanoparticle. The temperature increase also leads to a deeper penetration of the copper atoms inside the aluminum. Additional molecular dynamic simulations show that the deposited particles demonstrate a very good adhesion even in the case of the considered relatively large nanoparticles. Medium energy of the nanoparticles corresponding to velocity of about 500 m/s and elevated temperature of the

Oxidation-assisted graphene heteroepitaxy on copper foil.

Science.gov (United States)

Reckinger, Nicolas; Tang, Xiaohui; Joucken, Frédéric; Lajaunie, Luc; Arenal, Raul; Dubois, Emmanuel; Hackens, Benoît; Henrard, Luc; Colomer, Jean-François

2016-11-10

We propose an innovative, easy-to-implement approach to synthesize aligned large-area single-crystalline graphene flakes by chemical vapor deposition on copper foil. This method doubly takes advantage of residual oxygen present in the gas phase. First, by slightly oxidizing the copper surface, we induce grain boundary pinning in copper and, in consequence, the freezing of the thermal recrystallization process. Subsequent reduction of copper under hydrogen suddenly unlocks the delayed reconstruction, favoring the growth of centimeter-sized copper (111) grains through the mechanism of abnormal grain growth. Second, the oxidation of the copper surface also drastically reduces the nucleation density of graphene. This oxidation/reduction sequence leads to the synthesis of aligned millimeter-sized monolayer graphene domains in epitaxial registry with copper (111). The as-grown graphene flakes are demonstrated to be both single-crystalline and of high quality.

Evolution of the Copper Surface in the Course of Oxidation by CCl4-L (L=THF, Dmf, Dmso): Scanning Probe Microscope Study

Science.gov (United States)

Panteleev, S. V.; Maslennikov, S. V.; Ignatov, S. K.; Spirina, I. V.; Kruglova, M. V.; Gribkov, B. A.; Vdovichev, S. N.

2013-04-01

The evolution of compact surface of the 100 nm copper film deposited on the glass-ceramics doped with vanadium coating in the course of the oxidation by the CCl4-L (L = dimethylformamide (DMF), tetrahydrofuran (THF), dimethylsulfoxide (DMSO), CCl4 concentration ≈ 1 mol/L) was studied by atomic force microscopy (AFM) in contact mode. The dynamics of active centers formation and destruction was investigated in the course of the oxidation process. The metallic sample dissolution rate was estimated as a function of the coordinating solvent nature. The development of the metal surface oxidation was established to lead to a significant increase of surface roughness. This phenomenon can be explained by the fact that different parts of the surface react at different rates. Further course of the reaction leads to a significant decrease of the surface roughness of copper films. The amount of the metal reacted has an almost linear dependence on the reaction time. AFM scans indicate that there is the same mechanism of the reaction between copper and carbon tetrachloride for all solvents.

Effects of copper amine treatments on mechanical, biological and surface/interphase properties of poly (vinyl chloride)/wood composites

Science.gov (United States)

Jiang, Haihong

2005-11-01

The copper ethanolamine (CuEA) complex was used as a wood surface modifier and a coupling agent for wood-PVC composites. Mechanical properties of composites, such as unnotched impact strength, flexural strength and flexural toughness, were significantly increased, and fungal decay weight loss was dramatically decreased by wood surface copper amine treatments. It is evident that copper amine was a very effective coupling agent and decay inhibitor for PVC/wood flour composites, especially in high wood flour loading level. A DSC study showed that the heat capacity differences (DeltaCp) of composites before and after PVC glass transition were reduced by adding wood particles. A DMA study revealed that the movements of PVC chain segments during glass transition were limited and obstructed by the presence of wood molecule chains. This restriction effect became stronger by increasing wood flour content and by using Cu-treated wood flour. Wood flour particles acted as "physical cross-linking points" inside the PVC matrix, resulting in the absence of the rubbery plateau of PVC and higher E', E'' above Tg, and smaller tan delta peaks. Enhanced mechanical performances were attributed to the improved wetting condition between PVC melts and wood surfaces, and the formation of a stronger interphase strengthened by chemical interactions between Cu-treated wood flour and the PVC matrix. Contact angles of PVC solution drops on Cu-treated wood surfaces were decreased dramatically compared to those on the untreated surfaces. Acid-base (polar), gammaAB, electron-acceptor (acid) (gamma +), electron-donor (base) (gamma-) surface energy components and the total surface energies increased after wood surface Cu-treatments, indicating a strong tendency toward acid-base or polar interactions. Improved interphase and interfacial adhesion were further confirmed by measuring interfacial shear strength between wood and the PVC matrix.

Copper wire bonding

CERN Document Server

Chauhan, Preeti S; Zhong, ZhaoWei; Pecht, Michael G

2014-01-01

This critical volume provides an in-depth presentation of copper wire bonding technologies, processes and equipment, along with the economic benefits and risks.  Due to the increasing cost of materials used to make electronic components, the electronics industry has been rapidly moving from high cost gold to significantly lower cost copper as a wire bonding material.  However, copper wire bonding has several process and reliability concerns due to its material properties.  Copper Wire Bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes—bond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation.  In addition, the bond–pad metallurgies and the use of bare and palladium-coated copper wires on aluminum are presented, and gold, nickel and palladium surface finishes are discussed.  The book also discusses best practices and re...

Trojan horse underdense plasma photocathode acceleration

Energy Technology Data Exchange (ETDEWEB)

Karger, Oliver [Hamburg Univ. (Germany). Inst. fuer Experimentalphysik; DESY, FLA Arbeitsbereich Beschleunigerphysik, Hamburg (Germany); Koenigstein, Thomas; Pretzler, Georg [Duesseldorf Univ. (Germany). Inst. fuer Laser- und Plasmaphysik; Rosenzweig, James B. [California Univ., Los Angeles, CA (United States). Dept. of Physics and Astronomy; Hidding, Bernhard [Hamburg Univ. (Germany). Inst. fuer Experimentalphysik; DESY, FLA Arbeitsbereich Beschleunigerphysik, Hamburg (Germany); California Univ., Los Angeles, CA (United States). Dept. of Physics and Astronomy

2013-07-01

Relativistic electron beams with small emittance and size are needed for advanced applications such as free electron lasers (FEL) and other coherent light sources in the X-ray regime. Present laser plasma acceleration schemes are hardly able to provide electron beams of sufficient quality on a stable level. The concept of underdense plasma photocathode acceleration uses a beam-driven plasma wave in a two component gas mixture consisting a low ionisation threshold medium (LIT) and a high ionisation threshold medium (HIT) and a low-energy laser pulse. Shapeable electron bunches with sub-fs-length and unprecedented normalized emittance down to 10{sup -9} m rad can be produced. Based on this method, laboratory-sized-experimental setups may enable performance much better than today's conventional coherent hard X-ray sources. The presentation discusses the basic concept, shows recent numero-analytical results and the R and D towards experimental realization.

Facile Fabrication of Durable Copper-Based Superhydrophobic Surfaces via Electrodeposition.

Science.gov (United States)

Jain, R; Pitchumani, R

2018-03-13

Superhydrophobic surfaces have myriad industrial applications, yet their practical utilization has been limited by their poor mechanical durability and longevity. We present a low-cost, facile process to develop superhydrophobic copper-based coatings via an electrodeposition route, that addresses this limitation. Through electrodeposition, a stable, multiscale, cauliflower shaped fractal morphology was obtained and upon modification by stearic acid, the prepared coatings show extreme water repellency with contact angle of 162 ± 2° and roll-off angle of about 3°. Systematic studies are presented on coatings fabricated under different processing conditions to demonstrate good durability, mechanical and underwater stability, corrosion resistance, and self-cleaning effect. The study also presents an approach for rejuvenation of slippery superhydrophobic nature (roll-off angle <10°) on the surfaces after long-term water immersion. The presented process can be scaled to larger, durable coatings with controllable wettability for diverse applications.

Role of copper oxides in contact killing of bacteria.

Science.gov (United States)

Hans, Michael; Erbe, Andreas; Mathews, Salima; Chen, Ying; Solioz, Marc; Mücklich, Frank

2013-12-31

The potential of metallic copper as an intrinsically antibacterial material is gaining increasing attention in the face of growing antibiotics resistance of bacteria. However, the mechanism of the so-called "contact killing" of bacteria by copper surfaces is poorly understood and requires further investigation. In particular, the influences of bacteria-metal interaction, media composition, and copper surface chemistry on contact killing are not fully understood. In this study, copper oxide formation on copper during standard antimicrobial testing was measured in situ by spectroscopic ellipsometry. In parallel, contact killing under these conditions was assessed with bacteria in phosphate buffered saline (PBS) or Tris-Cl. For comparison, defined Cu2O and CuO layers were thermally generated and characterized by grazing incidence X-ray diffraction. The antibacterial properties of these copper oxides were tested under the conditions used above. Finally, copper ion release was recorded for both buffer systems by inductively coupled plasma atomic absorption spectroscopy, and exposed copper samples were analyzed for topographical surface alterations. It was found that there was a fairly even growth of CuO under wet plating conditions, reaching 4-10 nm in 300 min, but no measurable Cu2O was formed during this time. CuO was found to significantly inhibit contact killing, compared to pure copper. In contrast, thermally generated Cu2O was essentially as effective in contact killing as pure copper. Copper ion release from the different surfaces roughly correlated with their antibacterial efficacy and was highest for pure copper, followed by Cu2O and CuO. Tris-Cl induced a 10-50-fold faster copper ion release compared to PBS. Since the Cu2O that primarily forms on copper under ambient conditions is as active in contact killing as pure copper, antimicrobial objects will retain their antimicrobial properties even after oxide formation.

Characterization of quantum well structures using a photocathode electron microscope

Science.gov (United States)

Spencer, Michael G.; Scott, Craig J.

1989-01-01

Present day integrated circuits pose a challenge to conventional electronic and mechanical test methods. Feature sizes in the submicron and nanometric regime require radical approaches in order to facilitate electrical contact to circuits and devices being tested. In addition, microwave operating frequencies require careful attention to distributed effects when considering the electrical signal paths within and external to the device under test. An alternative testing approach which combines the best of electrical and optical time domain testing is presented, namely photocathode electron microscope quantitative voltage contrast (PEMQVC).

The Hyrkkoelae native copper mineralization as a natural analogue for copper canisters

International Nuclear Information System (INIS)

Marcos, N.

1996-10-01

The Hyrkkoelae U-Cu mineralization is located in southwestern Finland, near the Palmottu analogue site. The age of the mineralization is estimated to be between 1.8 and 1.7 Ga. Petrological and mineralogical studies have demonstrated that this mineralization has many geological features that parallel those of the sites being considered for nuclear waste disposal in Finland. A particular feature is the existence of native copper and copper sulfides in open fractures in the near-surface zone. This allows us to study the native copper corrosion process in analogous conditions as expected to dominate in the nuclear fuel waste repository. The occurrence of uranyl compounds at these fractures permits also considerations about the sorption properties of the engineered barrier material (metallic copper) and its corrosion products. From the study of mineral assemblages or paragenesis, it appears that the formation of copper sulfide (djurleite, Cu 1.934 ) after native copper (Cu 0 ) under anoxic (reducing) conditions is enhanced by the availability of dissolved HS - in the groundwater circulating in open fractures in the near-surface zone. The minimum concentration of HS - in the groundwater is estimated to be of the order of 10 -5 M (∼ 10 -4 g/l) and the minimum pH value not lower than about 7.8 as indicated by the presence of calcite crystals in the same fracture. The present study is the first one that has been performed on findings of native copper in reducing, neutral to slightly alkaline groundwaters. Thus, the data obtained is of most relevance in improving models of anoxic corrosion of copper canisters. (orig.)

Hierarchical Cu2O foam/g-C3N4 photocathode for photoelectrochemical hydrogen production

Science.gov (United States)

Ma, Xinzhou; Zhang, Jingtao; Wang, Biao; Li, Qiuguo; Chu, Sheng

2018-01-01

Solar photoelectrochemical (PEC) hydrogen production is a promising way for solving energy and environment problems. Earth-abundant Cu2O is a potential light absorber for PEC hydrogen production. In this article, hierarchical porous Cu2O foams are prepared by thermal oxidation of the electrochemically deposited Cu foams. PEC performances of the Cu2O foams are systematically studied and discussed. Benefiting from their higher light harvesting and more efficient charge separation, the Cu2O foams demonstrate significantly enhanced photocurrents and photostability compared to their film counterparts. Moreover, by integrating g-C3N4, hierarchical Cu2O foam/g-C3N4 composites are prepared with further improved photocurrent and photostability, appearing to be potential photocathodes for solar PEC hydrogen production. This study may provide a new and useful insight for the development of Cu2O-based photocathodes for PEC hydrogen production.

First attempts to combine capillary tubes with photocathodes

CERN Document Server

Peskov, Vladimir; Sokolova, T; Radionov, I

1999-01-01

We describe our efforts to combine glass capillary plates, operating as a gas amplification structure at approx 1 atm, with photocathodes sensitive to visible light. Such capillary tubes are a by-product of the manufacture of Microchannel Plates and are commercially available. Preliminary tests indicate that gas gains >10 sup 3 could be achieved without photon feedback. With two capillary plates in tandem (double-step multiplication) overall gains up to 10 sup 5 were possible at counting rate <100 Hz/mm sup 2. This approach may open new possibilities for detection of visible photons by gaseous detectors. Potential advantages are: high gains, large sensitive area, high granularity, and insensitivity to magnetic fields.

Simulations of the BNL/SLAC/UCLA 1.6 cell emittance compensated photocathode RF gun low energy beam line

International Nuclear Information System (INIS)

Palmer, D.T.; Miller, R.H.; Winick, H.

1995-01-01

A dedicated low energy (2 to 10 MeV) experimental beam line is now under construction at Brookhaven National Laboratories Accelerator Test Facility (BNL/ATF) for photocathode RF gun testing and photoemission experiments. The design of the experimental line, using the 1.6 cell photocathode RF gun developed by the BNL/SLAC/UCLA RF gun collaboration is presented. Detailed beam dynamics simulations were performed for the 1.6 cell RF gun injector using a solenoidal emittance compensation technique. An experimental program for testing the 1.6 cell RF gun is presented. This program includes beam loading caused by dark current, higher order mode field measurements, integrated and slice emittance measurements using a pepper-pot and RF kicker cavity

Crystallization of copper metaphosphate glass

Science.gov (United States)

Bae, Byeong-Soo; Weinberg, Michael C.

1993-01-01

The effect of the valence state of copper in copper metaphosphate glass on the crystallization behavior and glass transition temperature has been investigated. The crystallization of copper metaphosphate is initiated from the surface and its main crystalline phase is copper metaphosphate (Cu(PO)3),independent of the (Cu sup 2+)/(Cu(total)). However, the crystal morphology, the relative crystallization rates, and their temperature dependences are affected by the (Cu sup 2+)/(Cu (total)) ratio in the glass. On the other hand, the totally oxidized glass crystallizes from all over the surface. The relative crystallization rate of the reduced glass to the totally oxidized glass is large at low temperature, but small at high temperature. The glass transition temperature of the glass increases as the (Cu sup 2+)/(Cu(total)) ratio is raised. It is also found that the atmosphere used during heat treatment does not influence the crystallization of the reduced glass, except for the formation of a very thin CuO surface layer when heated in air.

Polystyrene films as barrier layers for corrosion protection of copper and copper alloys.

Science.gov (United States)

Románszki, Loránd; Datsenko, Iaryna; May, Zoltán; Telegdi, Judit; Nyikos, Lajos; Sand, Wolfgang

2014-06-01

Dip-coated polystyrene layers of sub-micrometre thickness (85-500nm) have been applied on copper and copper alloys (aluminium brass, copper-nickel 70/30), as well as on stainless steel 304, and produced an effective barrier against corrosion and adhesion of corrosion-relevant microorganisms. According to the dynamic wettability measurements, the coatings exhibited high advancing (103°), receding (79°) and equilibrium (87°) contact angles, low contact angle hysteresis (6°) and surface free energy (31mJ/m(2)). The corrosion rate of copper-nickel 70/30 alloy samples in 3.5% NaCl was as low as 3.2μm/a (44% of that of the uncoated samples), and in artificial seawater was only 0.9μm/a (29% of that of the uncoated samples). Cell adhesion was studied by fluorescence microscopy, using monoculture of Desulfovibrio alaskensis. The coatings not only decreased the corrosion rate but also markedly reduced the number of bacterial cells adhered to the coated surfaces. The PS coating on copper gave the best result, 2×10(3)cells/cm(2) (1% of that of the uncoated control). © 2013 Elsevier B.V. All rights reserved.

Design and modeling of a 17 GHz photocathode RF gun

International Nuclear Information System (INIS)

Lin, C.L.; Chen, S.C.; Wurtele, J.S.; Temkin, R.; Danly, B.

1991-01-01

The performance of a high-frequency (17 GHz), high accelerating gradient (250 MV/m) photocathode RF gun is studied with the particle-in-cell code MAGIC. For the parameter regime of interest, i.e. bunch charge smaller than 1 nC and bunch length shorter than 2 ps, space-charge forces and finite bunch length effects are less significant in determining the beam quality than nonlinear RF forces are. The cavity geometry, RF phase for photoemission, cathode size, and current density are being optimized to obtain high quality beams. Preliminary results are presented

An important atomic process in the CVD growth of graphene: Sinking and up-floating of carbon atom on copper surface

International Nuclear Information System (INIS)

Li, Yingfeng; Li, Meicheng; Gu, TianSheng; Bai, Fan; Yu, Yue; Trevor, Mwenya; Yu, Yangxin

2013-01-01

By density functional theory (DFT) calculations, the early stages of the growth of graphene on copper (1 1 1) surface are investigated. At the very first time of graphene growth, the carbon atom sinks into subsurface. As more carbon atoms are adsorbed nearby the site, the sunken carbon atom will spontaneously form a dimer with one of the newly adsorbed carbon atoms, and the formed dimer will up-float on the top of the surface. We emphasize the role of the co-operative relaxation of the co-adsorbed carbon atoms in facilitating the sinking and up-floating of carbon atoms. In detail: when two carbon atoms are co-adsorbed, their co-operative relaxation will result in different carbon–copper interactions for the co-adsorbed carbon atoms. This difference facilitates the sinking of a single carbon atom into the subsurface. As a third carbon atom is co-adsorbed nearby, it draws the sunken carbon atom on top of the surface, forming a dimer. Co-operative relaxations of the surface involving all adsorbed carbon atoms and their copper neighbors facilitate these sinking and up-floating processes. This investigation is helpful for the deeper understanding of graphene synthesis and the choosing of optimal carbon sources or process.

High temperature oxidation of copper and copper aluminium alloys: Impact on furnace side wall cooling systems

Science.gov (United States)

Plascencia Barrera, Gabriel

The high temperature oxidation behaviours of copper and dilute Cu-Al alloys were investigated. Experiments were carried out by: (i) Oxidizing under various oxygen potentials at different temperatures using a combined TG-DTA apparatus. (ii) Oxidizing in a muffle furnace (in air) at different temperatures for extended periods of time. The oxidation mechanisms were evaluated based upon the kinetic data obtained as well as by X-ray diffraction and microscopical (SEM and optical) analyses. It was found that oxidation of copper strongly depends on the temperature. Two distinct mechanisms were encountered. Between 300 and 500°C, the oxidation rate is controlled by lateral growth of the oxide on the metal surface, whereas between 600 and 1000°C oxidation is controlled by lattice diffusion of copper ions through the oxide scale. On the other hand, the partial pressure of oxygen only has a small effect on the oxidation of copper. Alloy oxidation is also dependent on the temperature. As temperature increases, more aluminium is required to protect copper from being oxidized. It was shown that if the amount of oxygen that dissolves in the alloy exceeds the solubility limit of oxygen in copper, an internal oxidation layer will develop, leading to the formation of a tarnishing scale. On the other hand if the oxygen content in the alloy lies below the solubility limit of oxygen in copper, no oxidation products will form since a tight protective alumina layer will form on the alloy surface. Surface phenomena may affect the oxidation behaviour of dilute Cu-Al alloys. Immersion tests in molten copper matte and copper converting slag, using laboratory scale cooling elements with various copper based materials, were conducted. Results from these tests showed that alloying copper with 3 to 4 wt% Al decreases the oxidation rate of pure copper by 4 orders of magnitude; however due to a significant drop in thermal conductivity, the ability to extract heat is compromised, leading to

Copper circuit patterning on polymer using selective surface modification and electroless plating

Energy Technology Data Exchange (ETDEWEB)

Park, Sang Jin [Department of Materials Science and Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Ko, Tae-Jun [Institute for Multidisciplinary Convergence of Materials, Korea Institute of Science and Technology, Seoul 130-650 (Korea, Republic of); Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Yoon, Juil [Department of Mechanical Systems Engineering, Hansung University, Seoul 136-792 (Korea, Republic of); Moon, Myoung-Woon [Institute for Multidisciplinary Convergence of Materials, Korea Institute of Science and Technology, Seoul 130-650 (Korea, Republic of); Oh, Kyu Hwan [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Han, Jun Hyun, E-mail: jhhan@cnu.ac.kr [Department of Materials Science and Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

2017-02-28

Highlights: • A new simple two step method for the pattering of Cu circuits on PET substrate was proposed. • The simple patterning of the high adhesive Cu circuits was achieved by plasma treatment using a patterned mask coated with a catalyst material. • The high adhesive strength of Cu circuits was due to the nanostructure formed by oxygen plasma treatment. - Abstract: We have examined a potential new and simple method for patterning a copper circuit on PET substrate by copper electroless plating, without the pretreatment steps (i.e., sensitization and activation) for electroless plating as well as the etching processes of conventional circuit patterning. A patterned mask coated with a catalyst material, Ag, for the reduction of Cu ions, is placed on a PET substrate. Subsequent oxygen plasma treatment of the PET substrate covered with the mask promotes the selective generation of anisotropic pillar- or hair-like nanostructures coated with co-deposited nanoparticles of the catalyst material on PET. After oxygen plasma treatment, a Cu circuit is well formed just by dipping the plasma-treated PET into a Cu electroless plating solution. By increasing the oxygen gas pressure in the chamber, the height of the nanostructures increases and the Ag catalyst particles are coated on not only the top but also the side surfaces of the nanostructures. Strong mechanical interlocking between the Cu circuit and PET substrate is produced by the large surface area of the nanostructures, and enhances peel strength. Results indicate this new simple two step (plasma surface modification and pretreatment-free electroless plating) method can be used to produce a flexible Cu circuit with good adhesion.

Transmission photocathodes based on stainless steel mesh and quartz glass coated with N-doped DLC thin films prepared by reactive magnetron sputtering

Science.gov (United States)

Balalykin, N. I.; Huran, J.; Nozdrin, M. A.; Feshchenko, A. A.; Kobzev, A. P.; Arbet, J.

2016-03-01

The influence was investigated of N-doped diamond-like carbon (DLC) films properties on the quantum efficiency of a prepared transmission photocathode. N-doped DLC thin films were deposited on a silicon substrate, a stainless steel mesh and quartz glass (coated with 5 nm thick Cr adhesion film) by reactive magnetron sputtering using a carbon target and gas mixture Ar, 90%N2+10%H2. The elements' concentration in the films was determined by RBS and ERD. The quantum efficiency was calculated from the measured laser energy and the measured cathode charge. For the study of the vectorial photoelectric effect, the quartz type photocathode was irradiated by intensive laser pulses to form pin-holes in the DLC film. The quantum efficiency (QE), calculated at a laser energy of 0.4 mJ, rose as the nitrogen concentration in the DLC films was increased and rose dramatically after the micron-size perforation in the quartz type photocathodes.

Colloidal and electrochemical aspects of copper-CMP

Science.gov (United States)

Sun, Yuxia

Copper based interconnects with low dielectric constant layers are currently used to increase interconnect densities and reduce interconnect time delays in integrated circuits. The technology used to develop copper interconnects involves Chemical Mechanical Planarization (CMP) of copper films deposited on low-k layers (silica or silica based films), which is carried out using slurries containing abrasive particles. One issue using such a structure is copper contamination over dielectric layers (SiO2 film), if not reduced, this contamination will cause current leakage. In this study, the conditions conducive to copper contamination onto SiO2 films during Cu-CMP process were studied, and a post-CMP cleaning technique was discussed based on experimental results. It was found that the adsorption of copper onto a silica surface is kinetically fast (electrocoagulation was investigated to remove both copper and abrasive slurry particles simultaneously. For effluent containing ˜40 ppm dissolved copper, it was found that ˜90% dissolved copper was removed from the waste streams through electroplating and in-situ chemical precipitation. The amount of copper removed through plating is impacted by membrane surface charge, type/amount of complexing agents, and solid content in the slurry suspension. The slurry particles can be removed ˜90% within 2 hours of EC through multiple mechanisms.

Hydrogen Production Using a Molybdenum Sulfide Catalyst on a Titanium-Protected n+p-Silicon Photocathode

DEFF Research Database (Denmark)

Seger, Brian; Laursen, Anders Bo; Vesborg, Peter Christian Kjærgaard

2012-01-01

A low-cost substitute: A titanium protection layer on silicon made it possible to use silicon under highly oxidizing conditions without oxidation of the silicon. Molybdenum sulfide was electrodeposited on the Ti-protected n+p-silicon electrode. This electrode was applied as a photocathode for wat...

Effect of Copper and Iron Ions on the Sulphidizing Flotation of Copper Oxide in Copper Smelting Slag

Directory of Open Access Journals (Sweden)

Qing-qing Pan

2018-01-01

Full Text Available The treatment of smelting slag has attracted much attention nowadays. This study investigates the influence of Na2S, CuSO4, and FeCl3 on sulphidizing flotation of copper oxide. The results show that a proper Cu2+ concentration can increase the sulphidizing effect of copper oxide, while Fe3+ inhibits the sulphidizing effect. Further analysis shows that Cu2+ ions can reduce the surface potential, increase the S2− adsorption, then generate more polysulfide, and therefore promote the sulphidizing flotation. However, Fe3+ ions would increase the surface potential, reduce the S2− adsorption, generate more sulfur element, and therefore inhibit the sulphidizing flotation.

Modification of polycrystalline copper by proton irradiation

International Nuclear Information System (INIS)

Garcia S, F.; Cabral P, A.; Saniger B, J.M.; Banuelos, J.G.; Barragan V, A.

1997-01-01

Polished copper samples were irradiated with proton beams of 300 and 700 keV at room temperature and at -150 Centigrade. In this work the obtained results are reported when such copper irradiated samples are analysed with Sem, Tem, AFM. The Sem micrographs showed evident changes in surface of these copper samples, therefore an EDAX microanalysis was done for its characterization. additionally, the Tem micrographs showed heaps formation until 200 nm. Its electron diffraction spectra indicated that these heaps consist of a copper compound. Finally with AFM were observed changes in coloration of the irradiated sample surface, as well as changes in texture and rugosity of them. These results show in general that irradiation process with protons which is known as an innocuo process produces changes in the copper properties. (Author)

The surface topography of Inconel, stainless steel and copper after argon ion bombardment

International Nuclear Information System (INIS)

Vogelbruch, K.; Vietzke, E.

1983-01-01

Energetic particle bombardment of metals is known to change the surface topography. To simulate the behaviour of the first wall of a fusion device under real plasma conditions, we have investigated the surface topography of rotating targets after 30 keV argon ion bombardment at 70deg incident angle by electron scanning micrographs. Under these conditions Inconel 600, 601, 625, stainless steel, and copper showed no cones, pyramids or cliffs, but only etching figures and at higher ion doses relatively flat hills. Thus, it can be concluded, that the influence of energetic particles on the first wall of a fusion reactor is smaller than expected from the results of such sputtering experiments, which have dealt with the formation of surface structures under ion bombardment at constant incident direction. (author)

Effect of gold photocathode contamination on a flat spectral response X-ray diode

Science.gov (United States)

Wang, Kun-lun; Zhang, Si-qun; Zhou, Shao-tong; Huang, Xian-bin; Ren, Xiao-dong; Dan, Jia-kun; Xu, Qiang

2018-03-01

A detector with an approximately flat spectral response is important for diagnosing intense thermal X-ray flux. A flat-spectral-response X-ray diode (FSR-XRD) utilizes a gold photocathode X-ray diode and a specially configured gold filter to give rise to a nearly flat spectral response in the photon energy range of 100-4000 eV. It has been observed that the spectral responses of several FSR-XRDs changed after a few shots of z-pinch experiments on the Primary Test Stand facility. This paper presents an analysis of the changes by fitting the spectral responses of the gold photocathodes using a model with a free parameter which characterizes the thickness of the contamination. The spectral responses of FSR-XRDs were calibrated with synchrotron radiation, and several cleaning methods were tested with the calibration. Considering the results of model and cleaning, it may be anticipated that contamination was the major reason of the response changing. Contamination worsened the flatness of the spectral response of the FSR-XRD and decreased the averaged response, hence it is important to avoid contamination. Current results indicate a requirement of further study of the contamination.

Microstructural characterization of copper corrosion in aqueous and soil environments

International Nuclear Information System (INIS)

Srivastava, A.; Balasubramaniam, R.

2005-01-01

Scanning electron microscopy has been used to investigate the surface films on pure copper after exposure to different aqueous and soil environments, containing chloride, sulfide and ammonium salts. The morphology of the films formed on copper surface in aqueous and soil environments was different for the same amount of pollutants. The surface films formed in soil environments were not homogenous in contrast to the films formed in aqueous environments. The damaging effect of chloride ions and the benign role of sulfide ions were revealed in both the environments. Local compositional analysis confirmed that the surface films formed on copper consisted predominantly of copper and oxygen

Electrochemically deposited Cu{sub 2}O cubic particles on boron doped diamond substrate as efficient photocathode for solar hydrogen generation

Energy Technology Data Exchange (ETDEWEB)

Mavrokefalos, Christos K. [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, England (United Kingdom); Hasan, Maksudul, E-mail: maksudul.hasan@chem.ox.ac.uk [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, England (United Kingdom); Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Rohan, James F. [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Compton, Richard G. [Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, England (United Kingdom); Foord, John S., E-mail: john.foord@chem.ox.ac.uk [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, England (United Kingdom)

2017-06-30

Highlights: • Fabrication of low-cost photocathode by electrochemical method is described. • Boron-doped diamond is presented as catalyst support. • NiO nanoparticles on Cu{sub 2}O surface enhances photocurrent and electrode stability. • Synergy of metallic interaction between Cu and Ni leads to high efficiency. - Abstract: Herein, we report a novel photocathode for the water splitting reaction. The electrochemical deposition of Cu{sub 2}O particles on boron doped diamond (BDD) electrodes and the subsequent decoration with NiO nanoparticles by a dip coating method to act as co-catalyst for hydrogen evolution reaction is described. The morphology analysis by scanning electron microscope (SEM) revealed that Cu{sub 2}O particles are cubic and decorated sporadically with NiO nanoparticles. X-ray photoelectron spectroscopy (XPS) confirmed the electronic interaction at the interface between Cu{sub 2}O and NiO through a binding energy shift of the main Cu 2p peak. The photoelectrochemical (PEC) performance of NiO-Cu{sub 2}O/BDD showed a much higher current density (−0.33 mA/cm{sup 2}) and photoconversion efficiency (0.28%) compared to the unmodified Cu{sub 2}O/BDD electrode, which are only −0.12 mA/cm{sup 2} and 0.06%, respectively. The enhancement in PEC performance is attributable to the synergy of NiO as an electron conduction mediator leading to the enhanced charge separation and transfer to the reaction interface for hydrogen evolution as evidenced by electrochemical impedance spectroscopy (EIS) and charge carrier density calculation. Stability tests showed that the NiO nanoparticles loading content on Cu{sub 2}O surface is a crucial parameter in this regard.

Measurements of barium photocathode quantum yields at four excimer laser wavelengths

International Nuclear Information System (INIS)

Van Loy, M.D.; Young, A.T.; Leung, K.N.

1992-06-01

The electron quantum yields from barium cathodes excited by excimer laser radiation at 193, 248, 308, and 351 nm have been determined. Experiments with different cathode surface preparation techniques reveal that deposition of barium film a few microns thick on a clean copper surface under moderate vacuum conditions achieves relatively high quantum efficiencies. Quantum yields measured from surfaces prepared in this manner are 2.3 x 10 -3 at 193 nm, 7.6 x 10 - 4 at 248 nm, 6.1 x 10 -4 at 308 nm, and 4.0 x 10 -4 at 351 nm. Other preparation techniques, such as laser cleaning of a solid barium surface, produced quantum yields that were at least an order of magnitude lower than these values

Formation and acceleration of uniformly filled ellipsoidal electron bunches obtained via space-charge-driven expansion from a cesium-telluride photocathode

Directory of Open Access Journals (Sweden)

P. Piot

2013-01-01

Full Text Available We report the experimental generation, acceleration, and characterization of a uniformly filled electron bunch obtained via space-charge-driven expansion (often referred to as “blow-out regime” in an L-band (1.3-GHz radiofrequency photoinjector. The beam is photoemitted from a cesium-telluride semiconductor photocathode using a short (<200  fs ultraviolet laser pulse. The produced electron bunches are characterized with conventional diagnostics and the signatures of their ellipsoidal character are observed. We especially demonstrate the production of ellipsoidal bunches with charges up to ∼0.5  nC corresponding to a ∼20-fold increase compared to previous experiments with metallic photocathodes.

The role of surface preparation in corrosion protection of copper with nanometer-thick ALD alumina coatings

Energy Technology Data Exchange (ETDEWEB)

Mirhashemihaghighi, Shadi; Światowska, Jolanta [PSL Research University, CNRS – Chimie ParisTech, Institut de Recherche de Chimie Paris (IRCP), 11 rue Pierre et Marie Curie, 75005 Paris (France); Maurice, Vincent, E-mail: vincent.maurice@chimie-paristech.fr [PSL Research University, CNRS – Chimie ParisTech, Institut de Recherche de Chimie Paris (IRCP), 11 rue Pierre et Marie Curie, 75005 Paris (France); Seyeux, Antoine; Klein, Lorena H. [PSL Research University, CNRS – Chimie ParisTech, Institut de Recherche de Chimie Paris (IRCP), 11 rue Pierre et Marie Curie, 75005 Paris (France); Salmi, Emma; Ritala, Mikko [Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki (Finland); Marcus, Philippe [PSL Research University, CNRS – Chimie ParisTech, Institut de Recherche de Chimie Paris (IRCP), 11 rue Pierre et Marie Curie, 75005 Paris (France)

2016-11-30

Highlights: • 10–50 nm thick alumina coatings were grown on copper by atomic layer deposition. • Surface smoothening by substrate annealing was studied as pre-deposition treatment. • Corrosion protection is promoted by pre-treatment for 10 nm but not for thicker films. • Local adhesion failure is assigned to the stresses accumulated in the thicker films. • Surface smoothening decreases the interfacial strength bearing the film stresses. - Abstract: Surface smoothening by substrate annealing was studied as a pre-treatment for improving the corrosion protection provided to copper by 10, 20 and 50 nm thick alumina coatings deposited by atomic layer deposition. The interplay between substrate surface state and deposited film thickness for controlling the corrosion protection provided by ultrathin barrier films is demonstrated. Pre-annealing at 750 °C heals out the dispersed surface heterogeneities left by electropolishing and reduces the surface roughness to less than 2 nm independently of the deposited film thickness. For 10 nm coatings, substrate surface smoothening promotes the corrosion resistance. However, for 20 and 50 nm coatings, it is detrimental to the corrosion protection due to local detachment of the deposited films. The weaker adherence of the thicker coatings is assigned to the stresses accumulated in the films with increasing deposited thickness. Healing out the local heterogeneities on the substrate surface diminishes the interfacial strength that is bearing the stresses of the deposited films, thereby increasing adhesion failure for the thicker films. Pitting corrosion occurs at the local sites of adhesion failure. Intergranular corrosion occurs at the initially well coated substrate grain boundaries because of the growth of a more defective and permeable coating at grain boundaries.

Emittance measurement and optimization for the photocathode RF gun with laser profile shaping

International Nuclear Information System (INIS)

Liu Shengguang; Masafumi Fukuda; Sakae Araki; Nobuhiro Terunuma; Junji Urakawa

2010-01-01

The Laser Undulator Compact X-ray source (LUCX) is a test bench for a compact high brightness X-ray generator, based on inverse Compton Scattering at KEK, which requires high intensity multi-bunch trains with low transverse emittance. A photocathode RF gun with emittance compensation solenoid is used as an electron source. Much endeavor has been made to increase the beam intensity in the multi-bunch trains. The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects, so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough. A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform. In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance. With the uniform driving laser and the unbalanced RF gun, the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm.mrad to 3.66 πmm·mrad. (authors)

Nucleation and growth of copper phthalocyanine aggregates deposited from solution on planar surfaces

Energy Technology Data Exchange (ETDEWEB)

Ghani, Fatemeh [Department of Theory & Bio-Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1 Golm, 14476 Potsdam (Germany); Gojzewski, Hubert, E-mail: hubert.gojzewski@put.poznan.pl [Department of Theory & Bio-Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1 Golm, 14476 Potsdam (Germany); Institute of Physics, Poznan University of Technology, Piotrowo 3, 60-965 Poznan (Poland); Riegler, Hans [Department of Theory & Bio-Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1 Golm, 14476 Potsdam (Germany)

2015-10-01

Graphical abstract: - Highlights: • Copper phthalocyanine deposited on planar surfaces by 3 solution process methods. • Aggregate morphology examined for coverage extending over 3 orders of magnitude. • Morphologies vary from small individual domains to mesh-like multilayers. • Nucleation and growth model explains the observed deposit morphologies. - Abstract: Copper phthalocyanine (CuPc) dissolved in trifluoroacetic acid (TFA) is deposited on solid SiO{sub 2} surfaces by solvent evaporation. The deposited CuPc aggregates are investigated by atomic force microscopy (AFM). The CuPc deposits were prepared by spin casting, dip coating, and spray deposition. Depending on the amount of deposited CuPc the aggregate morphology ranges from small individual domains to mesh-like multilayers. Each domain/layer consists of many parallel stacks of CuPc molecules with the square, plate-like molecules piled face-wise within each stack. The parallel stacks are attached sideways (i.e., edgewise attachment molecularly) to the substrate forming “nanoribbons” with uniform thickness of about 1 nm and varying width. The thickness reflects the length of a molecular edge, the width the number of stacks. A nucleation and growth model is presented that explains the observed aggregate and multilayer morphologies as result of the combination of nucleation, transport processes and a consequence of the anisotropic intermolecular interactions due to the shape of the CuPc molecule.

Effect of Copper and Iron Ions on the Sulphidizing Flotation of Copper Oxide in Copper Smelting Slag

OpenAIRE

Qing-qing Pan; Hui-qing Peng

2018-01-01

The treatment of smelting slag has attracted much attention nowadays. This study investigates the influence of Na2S, CuSO4, and FeCl3 on sulphidizing flotation of copper oxide. The results show that a proper Cu2+ concentration can increase the sulphidizing effect of copper oxide, while Fe3+ inhibits the sulphidizing effect. Further analysis shows that Cu2+ ions can reduce the surface potential, increase the S2− adsorption, then generate more polysulfide, and therefore promote the sulphidizing...

Copper Tolerance and Biosorption of Saccharomyces cerevisiae during Alcoholic Fermentation

Science.gov (United States)

Liu, Ling-ling; Jia, Bo; Zhao, Fang; Huang, Wei-dong; Zhan, Ji-cheng

2015-01-01

At high levels, copper in grape mash can inhibit yeast activity and cause stuck fermentations. Wine yeast has limited tolerance of copper and can reduce copper levels in wine during fermentation. This study aimed to understand copper tolerance of wine yeast and establish the mechanism by which yeast decreases copper in the must during fermentation. Three strains of Saccharomyces cerevisiae (lab selected strain BH8 and industrial strains AWRI R2 and Freddo) and a simple model fermentation system containing 0 to 1.50 mM Cu2+ were used. ICP-AES determined Cu ion concentration in the must decreasing differently by strains and initial copper levels during fermentation. Fermentation performance was heavily inhibited under copper stress, paralleled a decrease in viable cell numbers. Strain BH8 showed higher copper-tolerance than strain AWRI R2 and higher adsorption than Freddo. Yeast cell surface depression and intracellular structure deformation after copper treatment were observed by scanning electron microscopy and transmission electron microscopy; electronic differential system detected higher surface Cu and no intracellular Cu on 1.50 mM copper treated yeast cells. It is most probably that surface adsorption dominated the biosorption process of Cu2+ for strain BH8, with saturation being accomplished in 24 h. This study demonstrated that Saccharomyces cerevisiae strain BH8 has good tolerance and adsorption of Cu, and reduces Cu2+ concentrations during fermentation in simple model system mainly through surface adsorption. The results indicate that the strain selected from China’s stress-tolerant wine grape is copper tolerant and can reduce copper in must when fermenting in a copper rich simple model system, and provided information for studies on mechanisms of heavy metal stress. PMID:26030864

Copper Tolerance and Biosorption of Saccharomyces cerevisiae during Alcoholic Fermentation.

Directory of Open Access Journals (Sweden)

Xiang-Yu Sun

Full Text Available At high levels, copper in grape mash can inhibit yeast activity and cause stuck fermentations. Wine yeast has limited tolerance of copper and can reduce copper levels in wine during fermentation. This study aimed to understand copper tolerance of wine yeast and establish the mechanism by which yeast decreases copper in the must during fermentation. Three strains of Saccharomyces cerevisiae (lab selected strain BH8 and industrial strains AWRI R2 and Freddo and a simple model fermentation system containing 0 to 1.50 mM Cu2+ were used. ICP-AES determined Cu ion concentration in the must decreasing differently by strains and initial copper levels during fermentation. Fermentation performance was heavily inhibited under copper stress, paralleled a decrease in viable cell numbers. Strain BH8 showed higher copper-tolerance than strain AWRI R2 and higher adsorption than Freddo. Yeast cell surface depression and intracellular structure deformation after copper treatment were observed by scanning electron microscopy and transmission electron microscopy; electronic differential system detected higher surface Cu and no intracellular Cu on 1.50 mM copper treated yeast cells. It is most probably that surface adsorption dominated the biosorption process of Cu2+ for strain BH8, with saturation being accomplished in 24 h. This study demonstrated that Saccharomyces cerevisiae strain BH8 has good tolerance and adsorption of Cu, and reduces Cu2+ concentrations during fermentation in simple model system mainly through surface adsorption. The results indicate that the strain selected from China's stress-tolerant wine grape is copper tolerant and can reduce copper in must when fermenting in a copper rich simple model system, and provided information for studies on mechanisms of heavy metal stress.

Surface sensitization mechanism on negative electron affinity p-GaN nanowires

Science.gov (United States)

Diao, Yu; Liu, Lei; Xia, Sihao; Feng, Shu; Lu, Feifei

2018-03-01

The surface sensitization is the key to prepare negative electron affinity photocathode. The thesis emphasizes on the study of surface sensitization mechanism of p-type doping GaN nanowires utilizing first principles based on density function theory. The adsorption energy, work function, dipole moment, geometry structure, electronic structure and optical properties of Mg-doped GaN nanowires surfaces with various coverages of Cs atoms are investigated. The GaN nanowire with Mg doped in core position is taken as the sensitization base. At the initial stage of sensitization, the best adsorption site for Cs atom on GaN nanowire surface is BN, the bridge site of two adjacent N atoms. Surface sensitization generates a p-type internal surface with an n-type surface state, introducing a band bending region which can help reduce surface barrier and work function. With increasing Cs coverage, work functions decrease monotonously and the "Cs-kill" phenomenon disappears. For Cs coverage of 0.75 ML and 1 ML, the corresponding sensitization systems reach negative electron affinity state. Through surface sensitization, the absorption curves are red shifted and the absorption coefficient is cut down. All theoretical calculations can guide the design of negative electron affinity Mg doped GaN nanowires photocathode.

Oxidation-assisted graphene heteroepitaxy on copper foil

OpenAIRE

Reckinger, Nicolas; Tang, Xiaohui; Joucken, Frédéric; Lajaunie, Luc; Arenal, Raul; Dubois, Emmanuel; Hackens, Benoît; Henrard, Luc; Colomer, Jean-François

2016-01-01

We propose an innovative, easy-to-implement approach to synthesize large-area singlecrystalline graphene sheets by chemical vapor deposition on copper foil. This method doubly takes advantage of residual oxygen present in the gas phase. First, by slightly oxidizing the copper surface, we induce grain boundary pinning in copper and, in consequence, the freezing of the thermal recrystallization process. Subsequent reduction of copper under hydrogen suddenly unlocks the delayed reconstruction, f...

A fast position sensitive photodetector based on a CsI reflective photocathode

International Nuclear Information System (INIS)

Arnold, R.; Christophel, E.; Guyonnet, J.L.

1991-01-01

A fast detector was built for UV photon detection that depends on a CsI sensitized pad cathode. The rapidity of the detector is compared with that of a more classical chamber filled with photosensitive gases such as TEA or TMAE. Estimates of the quantum yield of the photocathode at 160 and 200 nm are given. The performances obtained make it a good photodetector candidate to be operated at high luminosity accelerators. (author) 7 refs., 19 figs

Evidence of vectorial photoelectric effect on Copper

International Nuclear Information System (INIS)

Pedersoli, E.; Banfi, F.; Ressel, B.; Pagliara, S.; Giannetti, C.; Galimberti, G.; Lidia, S.; Corlett, J.; Ferrini, G.; Parmigiani, F.

2005-01-01

Quantum efficiency (QE) measurements of single photon photoemission from a Cu(111) single crystal and a Cu polycrystal photocathodes, irradiated by 150 fs-6.28 eV laser pulses, are reported over a broad range of incidence angle, both in s and p polarizations. The maximum QE (≅4x10 -4 ) for polycrystalline Cu is obtained in p polarization at an angle of incidence θ=65 deg. . We observe a QE enhancement in p polarization which cannot be explained in terms of optical absorption, a phenomenon known as vectorial photoelectric effect. Issues concerning surface roughness and symmetry considerations are addressed. An explanation in terms of nonlocal conductivity tensor is proposed

Genotoxicity of copper oxide nanoparticles with different surface chemistry on rat bone marrow mesenchymal stem cells

DEFF Research Database (Denmark)

Zhang, Wenjing; Jiang, Pengfei; Chen, Wei

2016-01-01

The surface chemistry of nanoparticles (NPs) is one of the critical factors determining their cellular responses. In this study, the cytotoxicity and genotoxicity of copper oxide (CuO) NPs with a similar size but different surface chemistry to rat bone marrow mesenchymal stem cells (MSCs) were......V and showed a similar tendency to form agglomerates with a size of ∼200 nm in cell culture environment. The cytotoxicity of CuO NPs to MSCs at various concentrations and incubation periods were firstly evaluated. The CuO NPs showed dose-dependent and time-dependent toxicity to MSCs, and their surface...

A Study of the Surface Quality of High Purity Copper after Heat Treatment

CERN Document Server

Aicheler, M; Atieh, S; Calatroni, S; Riddone, G; Lebet, S; Samoshkin, A

2011-01-01

Themanufacturing flow of accelerating structures for the compact linear collider, based on diamond-machined high purity copper components, include several thermal cycles (diffusion bonding, brazing of cooling circuits, baking in vacuum, etc.). The high temperature cycles may be carried out following different schedules and environments (vacuum, reducing hydrogen atmosphere, argon, etc.) and develop peculiar surface topographies which have been the object of extended observations. This study presents and discusses the results of scanning electron microscopy (SEM) and optical microscopy investigations.

A novel compound cleaning solution for benzotriazole removal after copper CMP

International Nuclear Information System (INIS)

Gu Zhangbing; Liu Yuling; Gao Baohong; Wang Chenwei; Deng Haiwen

2015-01-01

After the chemical mechanical planarization (CMP) process, the copper surface is contaminated by a mass of particles (e.g. silica) and organic residues (e.g. benzotriazole), which could do great harm to the integrated circuit, so post-CMP cleaning is essential. In particular, benzotriazole (BTA) forms a layer of Cu-BTA film with copper on the surface, which leads to a hydrophobic surface of copper. So an effective cleaning solution is needed to remove BTA from the copper surface. In this work, a new compound cleaning solution is designed to solve two major problems caused by BTA: one is removing BTA and the other is copper surface corrosion that is caused by the cleaning solution. The cleaning solution is formed of alkaline chelating agent (FA/O II type), which is used to remove BTA, and a surfactant (FA/O I type), which is used as a corrosion inhibitor. BTA removal is characterized by contact angle measurements and electrochemical techniques. The inhibiting corrosion ability of the surfactant is also characterized by electrochemical techniques. The proposed compound cleaning solution shows advantages in removing BTA without corroding the copper surface. (paper)

Active screen cage pulsed dc discharge for implanting copper in polytetrafluoroethylene (PTFE)

Science.gov (United States)

Zaka-ul-Islam, Mujahid; Naeem, Muhammad; Shafiq, Muhammad; Sitara; Jabbar Al-Rajab, Abdul; Zakaullah, Muhammad

2017-07-01

Polymers such as polytetrafluoroethylene (PTFE) are widely used in artificial organs where long-term anti-bacterial properties are required to avoid bacterial proliferation. Copper or silver ion implantation on the polymer surface is known as a viable method to generate long-term anti-bacterial properties. Here, we have tested pulsed DC plasma with copper cathodic cage for the PTFE surface treatment. The surface analysis of the treated specimens suggests that the surface, structural properties, crystallinity and chemical structure of the PTFE have been changed, after the plasma treatment. The copper release tests show that copper ions are released from the polymer at a slow rate and quantity of the released copper increases with the plasma treatment time.

Model of thermal fatigue of a copper surface under the action of high-power microwaves

Science.gov (United States)

Kuzikov, S. V.; Plotkin, M. E.

2007-10-01

The accelerating structures of modern supercolliders, as well as the components of high-power microwave electron devices operated in strong cyclic electromagnetic fields should have long lifetimes. Along with the electric breakdown, the surfaces of these microwave components deteriorate and their lifetimes decrease due to thermal strains and subsequent mechanical loads on the surface metal layer. The elementary theory of thermal fatigue was developed in the 1970s. In particular, a model of metal as a continuous medium was considered. Within the framework of this model, thermal fatigue is caused by the strains arising between the hot surface layer and the cold internal layer of the metal. However, this theory does not describe all the currently available experimental data. In particular, the notion of “safe temperature” of the heating, i.e., temperature at which the surface is not destroyed during an arbitrarily long series of pulses, which was proposed in the theoretical model, is in poor agreement with the experiment performed in the Stanford Linear Accelerator Center (SLAC, USA). In this work, the thermal-fatigue theory is developed on the basis of consideration of the copper polycrystalline structure. The necessity to take it into account was demonstrated by the results of the SLAC experiment, in which a change in the mutual orientation of copper grains and the formation of cracks at their boundaries was recorded for the first time. The developed theory makes it possible to use the experimental data to refine the coefficients in the obtained formulas for the lifetime of the metal surface and to predict the number of microwave pulses before its destruction as a function of the radiation power, the surface-temperature increase at the pulse peak, and the pulse duration.

Efficient electron-induced removal of oxalate ions and formation of copper nanoparticles from copper(II oxalate precursor layers

Directory of Open Access Journals (Sweden)

Kai Rückriem

2016-06-01

Full Text Available Copper(II oxalate grown on carboxy-terminated self-assembled monolayers (SAM using a step-by-step approach was used as precursor for the electron-induced synthesis of surface-supported copper nanoparticles. The precursor material was deposited by dipping the surfaces alternately in ethanolic solutions of copper(II acetate and oxalic acid with intermediate thorough rinsing steps. The deposition of copper(II oxalate and the efficient electron-induced removal of the oxalate ions was monitored by reflection absorption infrared spectroscopy (RAIRS. Helium ion microscopy (HIM reveals the formation of spherical nanoparticles with well-defined size and X-ray photoelectron spectroscopy (XPS confirms their metallic nature. Continued irradiation after depletion of oxalate does not lead to further particle growth giving evidence that nanoparticle formation is primarily controlled by the available amount of precursor.

Effect of annealing process on the heterostructure CuO/Cu2O as a highly efficient photocathode for photoelectrochemical water reduction

Science.gov (United States)

Du, Fan; Chen, Qing-Yun; Wang, Yun-Hai

2017-05-01

CuO/Cu2O photocathodes were successfully prepared via simply annealing the electrodeposited Cu2O on fluoride doped tin oxide (FTO) substrate. They were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscope (TEM), UV-vis absorption spectra and X-ray photoelectron spectroscopy (XPS). The results showed that the heterojunction of CuO/Cu2O was formed during the annealing process and presented the nature of p-type semiconductor. The photocurrent density and photoelectrochemical (PEC) stability of the p-type heterostructure CuO/Cu2O photocathode was improved greatly compared with the pure Cu2O, which was greatly affected by annealing time and temperature. The highest photo current density of -0.451 mA/cm2 and highest stability was obtained via annealing at 650 °C for 15 min (at -0.3 V vs. Ag/AgCl), which gave a remarkable improvement than the as-deposited Cu2O (-0.08 mA/cm2). This suggested that the CuO/Cu2O heterojunction facilitated the electron-hole pair separation and improved the photocathode's current and stability.

Copper alloys deterioration due to anthropogenic action

Energy Technology Data Exchange (ETDEWEB)

Duran, A.; Perez-Rodriguez, J. L.; Herrera, L. K.; Jimenez-de-Haro, M. C.; Robador, M. D.; Justo, A.; Blanes, J. M.; Perez-Ferrer, J. C.

2008-07-01

Results are presented from several samples taken from leaves of the Pardon Portico of Mosque-Cathedral or Cordoba, where an alteration on their surface was detected. Metal samples analyzed using X-ray microanalysis and powder x-ray diffraction were predominantly constituted by copper with some amounts of zinc attributed to brass, whereas other samples were also constituted by copper, tin and lead attributed to bronze. surface samples were analyzed using the same techniques. In addition Fourier transform infrared spectroscopy was also used. The main compound identified in all the surface of the leaves is copper chloride hydroxide (atacamite). Lead chlorides have also been found. These data show that the sudden alteration that appears may be attributed to the use of some cleaning product containing chloride. Other compounds detected in the surface were gypsum, quartz and oxalates coming from environmental contamination. (Author) 17 refs.

As-grown graphene/copper nanoparticles hybrid nanostructures for enhanced intensity and stability of surface plasmon resonance

Science.gov (United States)

Li, Yun-Fei; Dong, Feng-Xi; Chen, Yang; Zhang, Xu-Lin; Wang, Lei; Bi, Yan-Gang; Tian, Zhen-Nan; Liu, Yue-Feng; Feng, Jing; Sun, Hong-Bo

2016-11-01

The transfer-free fabrication of the high quality graphene on the metallic nanostructures, which is highly desirable for device applications, remains a challenge. Here, we develop the transfer-free method by direct chemical vapor deposition of the graphene layers on copper (Cu) nanoparticles (NPs) to realize the hybrid nanostructures. The graphene as-grown on the Cu NPs permits full electric contact and strong interactions, which results in a strong localization of the field at the graphene/copper interface. An enhanced intensity of the localized surface plasmon resonances (LSPRs) supported by the hybrid nanostructures can be obtained, which induces a much enhanced fluorescent intensity from the dye coated hybrid nanostructures. Moreover, the graphene sheets covering completely and uniformly on the Cu NPs act as a passivation layer to protect the underlying metal surface from air oxidation. As a result, the stability of the LSPRs for the hybrid nanostructures is much enhanced compared to that of the bare Cu NPs. The transfer-free hybrid nanostructures with enhanced intensity and stability of the LSPRs will enable their much broader applications in photonics and optoelectronics.

Study of the surface resistance of niobium sputter-coated copper cavities

CERN Document Server

Benvenuti, Cristoforo; Campisi, I E; Darriulat, Pierre; Peck, M A; Russo, R; Valente, A M

1999-01-01

A systematic study of the superconducting properties of niobium films deposited on the inner wall of copper radiofrequency cavities is presented. Films are grown by sputtering with different discharge gases (Xe, Kr, Ar and Ar/Ne mixtures) on substrates prepared under different conditions. The measured quantities include the surface resistance at 1.5 GHz, the critical temperature and the penetration depth. The surface resistance is analyzed in terms of its dependence on temperature, RF field and the density of trapped fluxons. Once allowance for electron scattering is made by means of a single mean free path parameter, good agreement with BCS theory is observed. The residual resistance is observed to be essentially noncorrelated with the superconducting properties, although influenced by specific coating conditions. On occasions, very low residual resistances, in the nano-ohm range, have been maintained over a broad range of RF field, indicating the absence of fundamental limitations specific to the film techn...

Superhydrophobic properties induced by sol-gel routes on copper surfaces

Science.gov (United States)

Raimondo, M.; Veronesi, F.; Boveri, G.; Guarini, G.; Motta, A.; Zanoni, R.

2017-11-01

Superhydrophobic surfaces are attracting increasing attention in different fields such as energy, transportation, building industry and electronics, as they exhibit many interesting properties such as high water repellence, anti-fogging, anti-corrosion, anti-fouling and self-cleaning abilities. Here, superhydrophobic nanostructured hybrid materials obtained by depositing alumina nanoparticles on copper surfaces via dip coating in Al2O3 sol are presented. Two different preparation routes were explored, based on either an alcoholic or an aqueous Al2O3 sol, and the resulting wetting properties were compared. Wettability measurements showed that when the alcoholic sol is used superhydrophobicity is attained, with values of water contact angle very close to the upper limit of 180°, while highly hydrophobic coatings are obtained with the aqueous sol. These findings were further supported by electron microscopy and X-ray photoelectron spectroscopy, which revealed that the surface layer deposited on Cu is more homogenous and richer in alumina nanoparticles when the alcoholic sol was used. Durability of the superhydrophobic coating was assessed by performing ageing tests in chemically aggressive environments. A remarkable resistance is displayed by the superhydrophobic coating in acid environment, while alkaline conditions severely affect its properties. Such behaviors were investigated by XPS and FE-SEM measurements, which disclosed the nature of the surface reactions under the different conditions tested. The present results underline that a thorough investigation of surface morphology, chemical composition and wetting properties reveals their strongly connection and helps optimizing the combination of substrate nanostructuring and suitable chemical coating for an improved durability in different aggressive environments.

An experimental study of the composite CNT/copper coating

Science.gov (United States)

Panarin, Valentin Ye.; Svavil‧nyi, Nikolai Ye.; Khominich, Anastasiya I.

2018-03-01

This paper presents experimental results on the preparation and investigation of the carbon nanotubes-copper composite material. Carbon nanotubes (CNTs) were synthesized on silicon substrates by the chemical vapor deposition (CVD) method and then filled with copper by evaporation from a melting pot in a vacuum. Copper evenly covered both the surface of the entangled tubes and the free substrate surface between the tubes. To improve the adhesion of tubes and matrix material, a carbon substructure was grown on the surface of tubes by adding working gas plasma to the CNT synthesis area. It is proposed to use a copper coating as a diffusion barrier upon subsequent filling of the reinforcing CNT frame by a carbide-forming materials matrix with predetermined physico-mechanical and tribological properties.

Transpassive Dissolution of Copper and Rapid Formation of Brilliant Colored Copper Oxide Films

Science.gov (United States)

Fredj, Narjes; Burleigh, T. David; New Mexico Tech Team

2014-03-01

This investigation describes an electrochemical technique for growing adhesive copper oxide films on copper with attractive colors ranging from gold-brown to pearl with intermediate colors from red violet to gold green. The technique consists of anodically dissolving copper at transpassive potentials in hot sodium hydroxide, and then depositing brilliant color films of Cu2O onto the surface of copper after the anodic potential has been turned off. The color of the copper oxide film depends on the temperature, the anodic potential, the time t1 of polarization, and the time t2, which is the time of immersion after potential has been turned off. The brilliant colored films were characterized using glancing angle x-ray diffraction, and the film was found to be primarily Cu2O. Cyclic voltammetry, chronopotentiometry, scanning electron microscopy, and x-ray photoelectron spectroscopy were also used to characterize these films.

Photoinjector beam quality improvement by shaping the wavefront of a drive laser with oblique incidence

International Nuclear Information System (INIS)

He Zhigang; Wang Xiaohui; Jia Qika

2012-01-01

To increase the quantum efficiency (QE) of a copper photocathode and reduce the thermal emittance of an electron beam, a drive laser with oblique incidence was adopted in a BNL type photocathode rf gun. The disadvantageous effects on the beam quality caused by oblique incidence were analyzed qualitatively. A simple way to solve the problems through wavefront shaping was introduced and the beam quality was improved. (authors)

Functional recovery of biofilm bacterial communities after copper exposure

International Nuclear Information System (INIS)

Boivin, Marie-Elene Y.; Massieux, Boris; Breure, Anton M.; Greve, Gerdit D.; Rutgers, Michiel; Admiraal, Wim

2006-01-01

Potential of bacterial communities in biofilms to recover after copper exposure was investigated. Biofilms grown outdoor in shallow water on glass dishes were exposed in the laboratory to 0.6, 2.1, 6.8 μmol/l copper amended surface water and a reference and subsequently to un-amended surface water. Transitions of bacterial communities were characterised with denaturing gradient gel electrophoresis (DGGE) and community-level physiological profiles (CLPP). Exposure to 6.8 μmol/l copper provoked distinct changes in DGGE profiles of bacterial consortia, which did not reverse upon copper depuration. Exposure to 2.1 and 6.8 μmol/l copper was found to induce marked changes in CLPP of bacterial communities that proved to be reversible during copper depuration. Furthermore, copper exposure induced the development of copper-tolerance, which was partially lost during depuration. It is concluded that bacterial communities exposed to copper contaminated water for a period of 26 days are capable to restore their metabolic attributes after introduction of unpolluted water in aquaria for 28 days. - Genetically different bacterial communities can have similar functions and tolerance to copper

Modification of surface layers of copper under the action of the volumetric discharge initiated by an avalanche electron beam in nitrogen and CO2 at atmospheric pressure

Science.gov (United States)

Shulepov, M. A.; Akhmadeev, Yu. Kh.; Tarasenko, V. F.; Kolubaeva, Yu. A.; Krysina, O. V.; Kostyrya, I. D.

2011-05-01

The results of experimental investigations of the action of the volumetric discharge initiated by an avalanche electron beam on the surface of copper specimens are presented. The volumetric (diffuse) discharge in nitrogen and CO2 at atmospheric pressure was initiated by applying high voltage pulses of nanosecond duration to a tubular foil cathode. It has been found that the treatment of a copper surface by this type of discharge increases the hardness of the surface layer due to oxidation.

Influence of nano-size inclusions on spall fracture of copper single crystals

International Nuclear Information System (INIS)

Razorenov, S. V.; Ivanchihina, G. E.; Kanel, G. I.; Herrmann, B.; Zaretsky, E. B.

2007-01-01

Spall experiments have been carried out for copper in different structural states. The samples were copper single crystals, crystals of Cu+0.1% Si, copper crystals with silica particles of 180 nm average size, and polycrystalline copper. In experiments, the free surface velocity histories were recorded with the VISAR. The recovered samples were studied using optical microscopy and SEM. Solid solution Cu+0.1% Si demonstrates slower spall process than pure copper crystals. At longer pulse durations its spall strength is slightly less than that of pure crystals but approaches the latter with decreasing pulse duration. Fracture of copper with silica inclusions is completed much faster. The spall strength of this material is close to that of Cu+0.1% Si crystals at longer pulse duration and approaches the strength of polycrystalline copper with decreasing the load duration. Fractography of the spall surfaces correlates with the free surface velocity histories. The main fracture surface of the Cu+0.1% Si grains consists of net of dimples ∼4 μm to 40 μm mean diameter. The fracture surfaces of copper with silica inclusions is covered by a net of dimples of 1 μm to 5 μm size

Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light.

Science.gov (United States)

Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

2017-12-01

We report the preparation of TiO 2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi 2 S 3 , to improve the photocathodic protection property of TiO 2 for metals under visible light. Bi 2 S 3 /TiO 2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi 2 S 3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO 2 and orthorhombic Bi 2 S 3 and exhibited a high visible light response. The photocurrent density of Bi 2 S 3 /TiO 2 was significantly higher than that of pure TiO 2 under visible light. The sensitization of Bi 2 S 3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO 2 . The Bi 2 S 3 /TiO 2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light

Science.gov (United States)

Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

2017-01-01

We report the preparation of TiO2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi2S3, to improve the photocathodic protection property of TiO2 for metals under visible light. Bi2S3/TiO2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi2S3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO2 and orthorhombic Bi2S3 and exhibited a high visible light response. The photocurrent density of Bi2S3/TiO2 was significantly higher than that of pure TiO2 under visible light. The sensitization of Bi2S3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO2. The Bi2S3/TiO2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

Hydrogen and electricity production in a light-assisted microbial photoelectrochemical cell with CaFe2O4 photocathode

Science.gov (United States)

Chen, Qing-Yun; Zhang, Kai; Liu, Jian-Shan; Wang, Yun-Hai

2017-04-01

A microbial photoelectrochemical cell (MPEC) was designed with a p-type CaFe2O4 semiconductor as the photoelectrode for simultaneous hydrogen and electricity production under light illumination. The CaFe2O4 photoelectrode was synthesized by the sol-gel method and well characterized by x-ray diffraction, field emission scanning electron microscope, and UV-Vis-NIR spectrophotometer. The linear sweep voltammogram of the CaFe2O4 photoelectrode presented the cathodic photocurrent output. For the MPEC, with an external resistance of 2000 Ω, the maximum power density of 143 mW was obtained. Furthermore, with an external resistance of 100 Ω, the maximum hydrogen production rate of 6.7 μL·cm-2 could be achieved. The MPEC with CaFe2O4 photocathode was compared to MPEC with other photocathodes as well as photocatalytic water splitting technology.

Experimental measurements and theoretical model of the cryogenic performance of bialkali photocathode and characterization with Monte Carlo simulation

Directory of Open Access Journals (Sweden)

Huamu Xie

2016-10-01

Full Text Available High-average-current, high-brightness electron sources have important applications, such as in high-repetition-rate free-electron lasers, or in the electron cooling of hadrons. Bialkali photocathodes are promising high-quantum-efficiency (QE cathode materials, while superconducting rf (SRF electron guns offer continuous-mode operation at high acceleration, as is needed for high-brightness electron sources. Thus, we must have a comprehensive understanding of the performance of bialkali photocathode at cryogenic temperatures when they are to be used in SRF guns. To remove the heat produced by the radio-frequency field in these guns, the cathode should be cooled to cryogenic temperatures. We recorded an 80% reduction of the QE upon cooling the K_{2}CsSb cathode from room temperature down to the temperature of liquid nitrogen in Brookhaven National Laboratory (BNL’s 704 MHz SRF gun. We conducted several experiments to identify the underlying mechanism in this reduction. The change in the spectral response of the bialkali photocathode, when cooled from room temperature (300 K to 166 K, suggests that a change in the ionization energy (defined as the energy gap from the top of the valence band to vacuum level is the main reason for this reduction. We developed an analytical model of the process, based on Spicer’s three-step model. The change in ionization energy, with falling temperature, gives a simplified description of the QE’s temperature dependence. We also developed a 2D Monte Carlo code to simulate photoemission that accounts for the wavelength-dependent photon absorption in the first step, the scattering and diffusion in the second step, and the momentum conservation in the emission step. From this simulation, we established a correlation between ionization energy and reduction in the QE. The simulation yielded results comparable to those from the analytical model. The simulation offers us additional capabilities such as calculation

Characterization of boron carbide particulate reinforced in situ copper surface composites synthesized using friction stir processing

Energy Technology Data Exchange (ETDEWEB)

Sathiskumar, R., E-mail: sathiscit2011@gmail.com [Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, 641 014 Tamil Nadu (India); Murugan, N., E-mail: murugan@cit.edu.in [Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, 641 014 Tamil Nadu (India); Dinaharan, I., E-mail: dinaweld2009@gmail.com [Department of Mechanical Engineering, V V College of Engineering, Tisaiyanvilai, 627 657 Tamil Nadu (India); Vijay, S.J., E-mail: vijayjoseph@karunya.edu [Centre for Research in Metallurgy (CRM), School of Mechanical Sciences, Karunya University, Coimbatore, 641 114 Tamil Nadu (India)

2013-10-15

Friction stir processing has evolved as a novel solid state technique to fabricate surface composites. The objective of this work is to apply the friction stir processing technique to fabricate boron carbide particulate reinforced copper surface composites and investigate the effect of B{sub 4}C particles and its volume fraction on microstructure and sliding wear behavior of the same. A groove was prepared on 6 mm thick copper plates and packed with B{sub 4}C particles. The dimensions of the groove was varied to result in five different volume fractions of B{sub 4}C particles (0, 6, 12, 18 and 24 vol.%). A single pass friction stir processing was done using a tool rotational speed of 1000 rpm, travel speed of 40 mm/min and an axial force of 10 kN. Metallurgical characterization of the Cu/B{sub 4}C surface composites was carried out using optical microscope and scanning electron microscope. The sliding wear behavior was evaluated using a pin-on-disk apparatus. Results indicated that the B{sub 4}C particles significantly influenced the area, dispersion, grain size, microhardness and sliding wear behavior of the Cu/B{sub 4}C surface composites. When the volume fraction of B{sub 4}C was increased, the wear mode changed from microcutting to abrasive wear and wear debris was found to be finer. Highlights: • Fabrication of Cu/B{sub 4}C surface composite by friction stir processing • Analyzing the effect of B{sub 4}C particles on the properties of Cu/B4C surface composite • Increased volume fraction of B{sub 4}C particles reduced the area of surface composite. • Increased volume fraction of B{sub 4}C particles enhanced the microhardness and wear rate. • B{sub 4}C particles altered the wear mode from microcutting to abrasive.

Recovery of Copper from Cyanidation Tailing by Flotation

Science.gov (United States)

Qiu, Tingsheng; Huang, Xiong; Yang, Xiuli

2016-02-01

In this work, sodium hypochlorite, hydrogen peroxide, sodium metabisulfite and copper sulfate as activators were investigated to lessen the depression effect of cyanide for deep-depressing chalcopyrite. The experimental results indicate that the copper recovery exceeded 94%, 84% and 97% at the dosage: sodium hypochlorite 3 mL/L, hydrogen peroxide 2 mL/L, sodium metabisulfite 2 × 10-3 mol/L and copper sulfate 1.67 × 10-4 mol/L, respectively. According to the results of zeta potential and Fourier transform infrared spectrum, it is suggested that chalcopyrite was depressed because of the chemical adsorption of cyanide on the chalcopyrite surfaces. Sodium hypochlorite, hydrogen peroxide and sodium metabisulfite can destroy Cu-C bond on the deep-depressing chalcopyrite surface by chemical reaction. Copper sulfate can activate deep-depressing chalcopyrite by copper ion adsorption.

High-power fiber lasers for photocathode electron injectors

Directory of Open Access Journals (Sweden)

Zhi Zhao

2014-05-01

Full Text Available Many new applications for electron accelerators require high-brightness, high-average power beams, and most rely on photocathode-based electron injectors as a source of electrons. To achieve such a photoinjector, one requires both a high-power laser system to produce the high average current beam, and also a system at reduced repetition rate for electron beam diagnostics to verify high beam brightness. Here we report on two fiber laser systems designed to meet these specific needs, at 50 MHz and 1.3 GHz repetition rate, together with pulse pickers, second harmonic generation, spatiotemporal beam shaping, intensity feedback, and laser beam transport. The performance and flexibility of these laser systems have allowed us to demonstrate electron beam with both low emittance and high average current for the Cornell energy recovery linac.

Electrical Characterization of Spherical Copper Oxide Memristive Array Sensors

Science.gov (United States)

2014-03-27

47 4.2 A 47 µm flake reaching between two spheres . . . . . . . . . . . . . . . . . . 47 x Figure Page 4.3 The XRD pattern shows the copper spheres...image of the copper sphere surface and a zoomed view of emphasizing the flaking feature on the surface. These images depict just one sphere to...spheres. Placed next to one-another, a copper flake extending 47 µm such as that shown in Figure 4.1 can result in an electrical short, which may

Comparison of the performance of cop-coated and pt-coated radial junction n⁺p-silicon microwire-array photocathodes for the sunlight-driven reduction of water to H2(g)

DEFF Research Database (Denmark)

Roske, Christopher W.; Popczun, Eric J.; Seger, Brian

2015-01-01

-array photocathodes produced Voc = 0.44 V, Jph = 14 mA cm-2, ff = 0.46, and η = 2.9% under identical conditions. Thus, the MW geometry allows the fabrication of photocathodes entirely comprised of earth-abundant materials that exhibit performance comparable to that of devices that contain Pt....

Effect of glutamic acid on copper sorption onto kaolinite. Batch experiments and surface complexation modeling

Energy Technology Data Exchange (ETDEWEB)

Karimzadeh, Lotfallah; Barthen, Robert; Gruendig, Marion; Franke, Karsten; Lippmann-Pipke, Johanna [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Reactive Transport; Stockmann, Madlen [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

2017-06-01

In this work, we study the mobility behavior of Cu(II) under conditions related to an alternative, neutrophile biohydrometallurgical Cu(II) leaching approach. Sorption of copper onto kaolinite influenced by glutamic acid (Glu) was investigated in the presence of 0.01 M NaClO{sub 4} by means of binary and ternary batch adsorption measurements over a pH range of 4 to 9 and surface complexation modeling.

Effect of glutamic acid on copper sorption onto kaolinite. Batch experiments and surface complexation modeling

International Nuclear Information System (INIS)

Karimzadeh, Lotfallah; Barthen, Robert; Gruendig, Marion; Franke, Karsten; Lippmann-Pipke, Johanna; Stockmann, Madlen

2017-01-01

In this work, we study the mobility behavior of Cu(II) under conditions related to an alternative, neutrophile biohydrometallurgical Cu(II) leaching approach. Sorption of copper onto kaolinite influenced by glutamic acid (Glu) was investigated in the presence of 0.01 M NaClO_4 by means of binary and ternary batch adsorption measurements over a pH range of 4 to 9 and surface complexation modeling.

Adsorption behavior of caffeine as a green corrosion inhibitor for copper

International Nuclear Information System (INIS)

Souza, Fernando Sílvio de; Giacomelli, Cristiano; Gonçalves, Reinaldo Simões; Spinelli, Almir

2012-01-01

Electrochemical and impedance experiments were carried out to evaluate the corrosion behavior of copper in aerated 0.1 mol L −1 H 2 SO 4 solutions in the presence of three xanthine derivatives with similar chemical structures. The corrosion rate of copper was found to increase in the presence of theophylline and theobromine and decrease in the presence of caffeine. The adsorption and inhibitory effect of caffeine on copper surfaces in aerated 0.1 mol L −1 H 2 SO 4 solutions were then investigated in detail by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), contact angle measurements, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and fluorescence experiments. The data obtained indicate that caffeine behaves as a cathodic-type inhibitor adsorbing onto the copper surface according to the Temkin isotherm, with the negative ∆G° ads value of − 31.1 kJ mol −1 signifying a spontaneous adsorption process. The corrosion inhibition efficiency increased with caffeine concentration in the range of 1.0–10.0 mmol L −1 . Furthermore, the EIS results obtained at the open-circuit potential and surface analysis (SEM, EDS and fluorescence) clearly demonstrated the adsorption of the organic compound onto the copper electrode. The contact angle measurements revealed the formation of a hydrophobic protective film. This film covers up to 72% of the total active surface, acts as a protective barrier and prevents interaction between the metal, water and oxygen molecules. - Highlights: ► We have investigated the adsorption and corrosion inhibition of caffeine on copper surfaces. ► Caffeine behaves as a cathodic-type inhibitor. ► Caffeine adsorbs onto copper surface according to Temkin isotherm. ► There exists the formation of a hydrophobic film that acts as a protective barrier. ► This corrosion inhibitor covers up to 72% of the total active surface of copper.

Albumin has no role in the uptake of copper by human fibroblasts

International Nuclear Information System (INIS)

McArdle, H.J.; Guthrie, J.R.; Ackland, M.L.; Danks, D.M.

1987-01-01

The mechanism of copper uptake by cells has been the subject of controversy for some time. This paper examines the possibility of a role for albumin in the uptake of copper by fibroblasts. Although the cells could accumulate copper from a copper-albumin complex, there was no evidence for either copper-albumin or albumin receptors on the cell surface. The possibility of a surface exchange mechanism for copper was examined. While copper uptake showed saturation with increasing concentrations of labelled copper-albumin, adding unlabelled copper to the incubation medium did not inhibit uptake. Adding albumin or histidine to the copper-albumin complex resulted in an inhibition of copper uptake. The results can only be explained by the cell taking up free copper from the incubation medium, with the albumin then releasing its copper to maintain the equilibrium between free and bound metal. Since, in vivo there is essentially no free copper in serum, it is concluded that albumin is most unlikely to play a role in the uptake of copper by fibroblasts

Voltammetry and Electrocatalysis of Achrornobacter Xylosoxidans Copper Nitrite Reductase on Functionalized Au(111)-Electrode Surfaces

DEFF Research Database (Denmark)

Welinder, Anna C.; Zhang, Jingdong; Hansen, Allan G.

2007-01-01

A long-standing issue in protein film voltammetry (PFV), particularly electrocatalytic voltammetry of redox enzyme monolayers, is the variability of protein adsorption modes, reflected in distributions of catalytic activity of the adsorbed protein/enzyme molecules. Use of well-defined, atomically...... planar electrode surfaces is a step towards the resolution of this central issue. We report here the voltammetry of copper nitrite reductase (CNiR, Achromobacter xylosoxidons) on Au(111)-electrode surfaces modified by monolayers of a broad variety of thiol-based linker molecules. These represent......NiR thus shows highly efficient, close to ideal reversible electrocatalytic voltammetry on cysteamine-covered Au(111)-electrode surfaces, most likely due to two cysteamine orientations previously disclosed by in situ scanning tunnelling microscopy. Such a dual orientation exposes both a hydrophobic...

Surface-Enhanced Resonance Raman Scattering and Visible Extinction Spectroscopy of Copper Chlorophyllin: An Upper Level Chemistry Experiment

Science.gov (United States)

Schnitzer, Cheryl S.; Reim, Candace Lawson; Sirois, John J.; House, Paul G.

2010-01-01

Advanced chemistry students are introduced to surface-enhanced resonance Raman scattering (SERRS) by studying how sodium copper chlorophyllin (CuChl) adsorbs onto silver colloids (CuChl/Ag) as a function of pH. Using both SERRS and visible extinction spectroscopy, the extent of CuChl adsorption and colloidal aggregation are monitored. Initially at…

Role of surface on the size-dependent mechanical properties of copper nanowire under tensile load: A molecular dynamics simulation

International Nuclear Information System (INIS)

Liu, Wei-Ting; Hsiao, Chun-I.; Hsu, Wen-Dung

2014-01-01

In this study we have used atomistic simulations to investigate the role of surface on the size-dependent mechanical properties of nanowires. In particular, we have performed computational investigation on single crystal face-centered cubic copper nano-wires with diameters ranging from 2 to 20 nm. The wire axis for all the nanowires are considered along the [0 0 1] direction. Characterization of the initial optimized structures revealed clear differences in interatomic spacing, stress, and potential energy in all the nanowires. The mechanical properties with respect to wire diameter are evaluated by applying tension along the [0 0 1] direction until yielding. We have discussed the stress–strain relationships, Young's modulus, and the variation in potential energy from surface to the center of the wire for all the cases. Our results indicate that the mechanical response (including yield strain, Young's modulus, and resilience) is directly related to the proportion of surface to bulk type atoms present in each nanowire. Thus the size-dependent mechanical properties of single crystal copper nanowire within elastic region are attributed to the surface to volume ratio (surface effect). Using the calculated response, we have formulated a mathematical relationship, which predicts the nonlinear correlation between the mechanical properties and the diameter of the wire.

Role of surface on the size-dependent mechanical properties of copper nanowire under tensile load: A molecular dynamics simulation

Energy Technology Data Exchange (ETDEWEB)

Liu, Wei-Ting [Department of Materials Science and Engineering, National Cheng Kung University, Tainan City 70101 Taiwan (China); Hsiao, Chun-I. [Department of Materials Science and Engineering, National Cheng Kung University, Tainan City 70101 Taiwan (China); Promotion Center for Global Materials Research, National Cheng Kung University, Tainan City 70101 Taiwan (China); Hsu, Wen-Dung, E-mail: wendung@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan City 70101 Taiwan (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan City 70101 Taiwan (China); Promotion Center for Global Materials Research, National Cheng Kung University, Tainan City 70101 Taiwan (China)

2014-01-15

In this study we have used atomistic simulations to investigate the role of surface on the size-dependent mechanical properties of nanowires. In particular, we have performed computational investigation on single crystal face-centered cubic copper nano-wires with diameters ranging from 2 to 20 nm. The wire axis for all the nanowires are considered along the [0 0 1] direction. Characterization of the initial optimized structures revealed clear differences in interatomic spacing, stress, and potential energy in all the nanowires. The mechanical properties with respect to wire diameter are evaluated by applying tension along the [0 0 1] direction until yielding. We have discussed the stress–strain relationships, Young's modulus, and the variation in potential energy from surface to the center of the wire for all the cases. Our results indicate that the mechanical response (including yield strain, Young's modulus, and resilience) is directly related to the proportion of surface to bulk type atoms present in each nanowire. Thus the size-dependent mechanical properties of single crystal copper nanowire within elastic region are attributed to the surface to volume ratio (surface effect). Using the calculated response, we have formulated a mathematical relationship, which predicts the nonlinear correlation between the mechanical properties and the diameter of the wire.

Local thermal property analysis by scanning thermal microscopy of an ultrafine-grained copper surface layer produced by surface mechanical attrition treatment

Energy Technology Data Exchange (ETDEWEB)

Guo, F.A. [Suzhou Institute for Nonferrous Metals Processing Technology, No. 200 Shenxu Road, Suzhou Industrial Park, Suzhou 215021 (China) and Unite de Thermique et d' Analyse Physique, Laboratoire d' Energetique et d' Optique, Universite de Reims, BP 1039, 51687 Reims Cedex 2 (France)]. E-mail: guofuan@yahoo.com; JI, Y.L. [Suzhou Institute for Nonferrous Metals Processing Technology, No. 200 Shenxu Road, Suzhou Industrial Park, Suzhou 215021 (China); Trannoy, N. [Unite de Thermique et d' Analyse Physique, Laboratoire d' Energetique et d' Optique, Universite de Reims, BP 1039, 51687 Reims Cedex 2 (France); Lu, J. [LASMIS, Universite de Technologie de Troyes, 12 Rue Marie Curie, Troyes 10010 (France)

2006-06-15

Scanning thermal microscopy (SThM) was used to map thermal conductivity images in an ultrafine-grained copper surface layer produced by surface mechanical attrition treatment (SMAT). It is found that the deformed surface layer shows different thermal conductivities that strongly depend on the grain size of the microstructure: the thermal conductivity of the nanostructured surface layer decreases obviously when compared with that of the coarse-grained matrix of the sample. The role of the grain boundaries in thermal conduction is analyzed in correlation with the heat conduction mechanism in pure metal. A theoretical approach, based on this investigation, was used to calculate the heat flow from the probe tip to the sample and then estimate the thermal conductivities at different scanning positions. Experimental results and theoretical calculation demonstrate that SThM can be used as a tool for the thermal property and microstructural analysis of ultrafine-grained microstructures.

Studies on Cementation of Tin on Copper and Tin Stripping from Copper Substrate

Directory of Open Access Journals (Sweden)

Rudnik E.

2016-06-01

Full Text Available Cementation of tin on copper in acid chloride-thiourea solutions leads to the formation of porous layers with a thickness dependent on the immersion time. The process occurs via Sn(II-Cu(I mechanism. Chemical stripping of tin was carried out in alkaline and acid solutions in the presence of oxidizing agents. It resulted in the dissolution of metallic tin, but refractory Cu3Sn phase remained on the copper surface. Electrochemical tin stripping allows complete tin removal from the copper substrate, but porosity and complex phase composition of the tin coating do not allow monitoring the process in unambiguous way.

Deposition and characterisation of copper for high density interconnects

International Nuclear Information System (INIS)

McCusker, N.

1999-09-01

Copper has been deposited by sputtering and investigated for application as high density interconnects, with a view to maximising its performance and reliability. A sputter deposition process using gettering has been developed, which produces consistently pure, low resistivity films. A relationship between film thickness and resistivity has been explained by studying the grain growth process in copper films using atomic force microscopy. The Maydas-Shatzkes model has been used to separate the contributions of grain boundary and surface scattering to thin film resistivity, in copper and gold. Stress and texture in copper film have been studied. Annealing has been used to promote grain growth and texture development. Electromigration has been studied in copper and aluminium interconnects using a multi-line accelerated test set-up. A difference in failure distributions and void morphologies has been explained by an entirely different damage mechanism. The importance of surface/interface migration in electromigration damage of copper lines has been established and explained using a grain boundary-grooving model. A tantalum overlayer was found to extend the lifetime of copper lines. A composite sputtering target has been used to deposit copper/zirconium alloy films. The composition of the alloys was studied by Rutherford backscattering, Auger and secondary neutral mass spectrometry. The alloy films had an improved electromigration lifetime. A surface controlled mechanism is proposed to explain the advantage. A metal oxide semiconductor (MOS) capacitor technique is used to investigate barrier reliability. Tungsten is shown to be an effective diffusion barrier for copper, up to 700 deg. C. (author)

Surface-Bound Intermediates in Low-Temperature Methanol Synthesis on Copper. Participants and Spectators

Energy Technology Data Exchange (ETDEWEB)

Yang, Yong; Mei, Donghai; Peden, Charles HF; Campbell, Charles T.; Mims, Charles A.

2015-11-03

The reactivity of surface adsorbed species present on copper catalysts during methanol synthesis at low temperatures was studied by simultaneous infrared spectroscopy (IR) and mass spectroscopy (MS) measurements during “titration” (transient surface reaction) experiments with isotopic tracing. The results show that adsorbed formate is a major bystander species present on the surface under steady-state methanol synthesis reaction conditions, but it cannot be converted to methanol by reaction with pure H₂, nor with H₂ plus added water. Formate-containing surface adlayers for these experiments were produced during steady state catalysis in (a) H₂:CO₂ (with substantial formate coverage) and (b) moist H₂:CO (with no IR visible formate species). Both these reaction conditions produce methanol at steady state with relatively high rates. Adlayers containing formate were also produced by (c) formic acid adsorption. Various "titration" gases were used to probe these adlayers at modest temperatures (T = 410-450K) and 6 bar total pressure. Methanol gas (up to ~1% monolayer equivalent) was produced in "titration" from the H₂:CO₂ catalytic adlayers by H₂ plus water, but not by dry hydrogen. The decay in the formate IR features accelerated in the presence of added water vapor. The H₂:CO:H₂O catalytic adlayer produced similar methanol titration yields in H₂ plus water but showed no surface formate features in IR (less than 0.2% monolayer coverage). Finally, formate from formic acid chemisorption produced no methanol under any titration conditions. Even under (H₂:CO₂) catalytic reaction conditions, isotope tracing showed that pre-adsorbed formate from formic acid did not contribute to the methanol produced. Although non-formate intermediates exist during low temperature methanol synthesis on copper which can be converted to methanol gas

Synthesis of carbon nanotubes and nanotube forests on copper catalyst

International Nuclear Information System (INIS)

Kruszka, Bartosz; Terzyk, Artur P; Wiśniewski, Marek; Gauden, Piotr A; Szybowicz, Mirosław

2014-01-01

The growth of carbon nanotubes on bulk copper is studied. We show for the first time, that super growth chemical vapor deposition method can be successfully applied for preparation of nanotubes on copper catalyst, and the presence of hydrogen is necessary. Next, different methods of copper surface activation are studied, to improve catalyst efficiency. Among them, applied for the first time for copper catalyst in nanotubes synthesis, sulfuric acid activation is the most promising. Among tested samples the surface modified for 10 min is the most active, causing the growth of vertically aligned carbon nanotube forests. Obtained results have potential importance in application of nanotubes and copper in electronic chips and nanodevices. (paper)

Reactive magnetron sputtering of N-doped carbon thin films on quartz glass for transmission photocathode applications

Science.gov (United States)

Balalykin, N. I.; Huran, J.; Nozdrin, M. A.; Feshchenko, A. A.; Kobzev, A. P.; Sasinková, V.; Boháček, P.; Arbet, J.

2018-03-01

N-doped carbon thin films were deposited on a silicon substrate and quartz glass by RF reactive magnetron sputtering using a carbon target and an Ar+N2 gas mixture. During the magnetron sputtering, the substrate holder temperatures was kept at 800 °C. The carbon film thickness on the silicon substrate was about 70 nm, while on the quartz glass it was in the range 15 nm – 60 nm. The elemental concentration in the films was determined by RBS and ERD. Raman spectroscopy was used to evaluate the intensity ratios I D/I G of the D and G peaks of the carbon films. The transmission photocathodes prepared were placed in the hollow-cathode assembly of a Pierce-structure DC gun to produce photoelectrons. The quantum efficiency (QE) was calculated from the laser energy and cathode charge measured. The properties of the transmission photocathodes based on semitransparent N-doped carbon thin films on quartz glass and their potential for application in DC gun technology are discussed.

Growth graphene on silver-copper nanoparticles by chemical vapor deposition for high-performance surface-enhanced Raman scattering

Science.gov (United States)

Zhang, Xiumei; Xu, Shicai; Jiang, Shouzhen; Wang, Jihua; Wei, Jie; Xu, Shida; Gao, Shoubao; Liu, Hanping; Qiu, Hengwei; Li, Zhen; Liu, Huilan; Li, Zhenhua; Li, Hongsheng

2015-10-01

We present a graphene/silver-copper nanoparticle hybrid system (G/SCNPs) to be used as a high-performance surface-enhanced Raman scattering (SERS) substrate. The silver-copper nanoparticles wrapped by a monolayer graphene layer are directly synthesized on SiO2/Si substrate by chemical vapor deposition in a mixture of methane and hydrogen. The G/SCNPs shows excellent SERS enhancement activity and high reproducibility. The minimum detected concentration of R6G is as low as 10-10 M and the calibration curve shows a good linear response from 10-6 to 10-10 M. The date fluctuations from 20 positions of one SERS substrate are less than 8% and from 20 different substrates are less than 10%. The high reproducibility of the enhanced Raman signals could be due to the presence of an ultrathin graphene layer and uniform morphology of silver-copper nanoparticles. The use of G/SCNPs for detection of nucleosides extracted from human urine demonstrates great potential for the practical applications on a variety of detection in medicine and biotechnology field.

ELECTROCHEMICAL BEHAVIOR OF POLYCRYSTALLINE COPPER DURING THE ADSORPTION OF CO ABSTRACT

Directory of Open Access Journals (Sweden)

J. Salimon

2017-12-01

Full Text Available The electrochemical properties of electrode copper in carbon monoxide-saturated phosphate buffered solution were investigated. The electrochemistry of copper surface was sufficiently changed after the supporting electrolyte solution was saturated with CO. The hydrogen evolution region was depressed and shifted cathodically due to the adsorption process of CO on the copper surface in a linear or terminally bonded manner, Cu-CO . The oxidation and the reduction peaks of copper were significantly changed with two couple of redox peaks. This is due to the subsequent formation and the corresponding reduction of copper(I and the copper carbon monoxides species. Further changed in electrochemical properties occurred when the electrode surface was polarized at high cathodic potential (-1.4 V for a period of time (15 min. The hydrogen evolution region was further depressed due to the adsorption of CO process in multiple bonding sites as adsorbed bridge bonded CO, Cu-CO B L that occurred predominantly.

High-charge s-band photocathode RF-gun and linac system for radiation research

Energy Technology Data Exchange (ETDEWEB)

Kobayashi, Tetsuya; Uesaka, Mitsuru; Katsumura, Yousuke [Univ. of Tokyo, Graduate School of Engineering, Nuclear Engineering Research Laboratory, Tokai, Ibaraki (JP)] (and others)

2002-01-01

For sub-picosecond pump-and-prove-type radiation chemistry work, a new synchronized electron linac and laser system was installed in the Nuclear Engineering Research Laboratory (NERL) of University of Tokyo. The new laser system, with a Ti:Sapphire oscillator (795 nm) and amplifiers, generates 300 ps pulses at 10 Hz. The laser is transported through the vacuum chamber and then split into two beams. The first is compressed and converted to the third harmonics (265 nm, <250 {mu}J, 4-11 ps) so as to drive the photocathode RF-gun and generate a pump-electron beam. The second is compressed to 100 fs and used for the probe light. The high-power RF, which is provided by a new 15 MW klystron, is divided into the gun and the accelerating section. Finally, a time jitter of 330 fs (rms) was achieved between the pump-electron beam and the probe laser, which is equivalent to the design value of 320 fs. A charge of 7 nC/bunch was observed at the exit of the gun from this new laser system. Improvement of the vacuum in the gun (<10{sup -9} Torr) is the most effective way to obtain such a high-charge beam. After about three years of operation, the Cu photocathode has shown no degradation of quantum efficiency. (author)

Epitaxial Bi2 FeCrO6 Multiferroic Thin Film as a New Visible Light Absorbing Photocathode Material.

Science.gov (United States)

Li, Shun; AlOtaibi, Bandar; Huang, Wei; Mi, Zetian; Serpone, Nick; Nechache, Riad; Rosei, Federico

2015-08-26

Ferroelectric materials have been studied increasingly for solar energy conversion technologies due to the efficient charge separation driven by the polarization induced internal electric field. However, their insufficient conversion efficiency is still a major challenge. Here, a photocathode material of epitaxial double perovskite Bi(2) FeCrO(6) multiferroic thin film is reported with a suitable conduction band position and small bandgap (1.9-2.1 eV), for visible-light-driven reduction of water to hydrogen. Photoelectrochemical measurements show that the highest photocurrent density up to -1.02 mA cm(-2) at a potential of -0.97 V versus reversible hydrogen electrode is obtained in p-type Bi(2) FeCrO(6) thin film photocathode grown on SrTiO(3) substrate under AM 1.5G simulated sunlight. In addition, a twofold enhancement of photocurrent density is obtained after negatively poling the Bi(2) FeCrO(6) thin film, as a result of modulation of the band structure by suitable control of the internal electric field gradient originating from the ferroelectric polarization in the Bi(2) FeCrO(6) films. The findings validate the use of multiferroic Bi(2) FeCrO(6) thin films as photocathode materials, and also prove that the manipulation of internal fields through polarization in ferroelectric materials is a promising strategy for the design of improved photoelectrodes and smart devices for solar energy conversion. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ QCM and TM-AFM investigations of the early stages of degradation of silver and copper surfaces

International Nuclear Information System (INIS)

Kleber, Ch.; Hilfrich, U.; Schreiner, M.

2007-01-01

The early stages of atmospheric corrosion of pure copper and pure silver specimens were investigated performing in situ tapping mode atomic force microscopy (TM-AFM), in situ quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS). The information obtained by TM-AFM is the change of the topography of the sample surfaces with emphasis on the shape and lateral distribution of the corrosion products grown within the first hours of weathering. The simultaneously performed in situ QCM measurements are indicating the mass changes due to possibly occurring corrosive processes on the surface during weathering and are therefore a valuable tool for the determination of corrosion rates. Investigations were carried out in synthetic air at different levels of relative humidity (RH) with and without addition of 250 ppb SO 2 as acidifying agent. On a polished copper surface the growth of corrosion products could be observed by TM-AFM analysis at 60% RH without any addition of acidifying gases [M. Wadsak, M. Schreiner, T. Aastrup, C. Leygraf, Surf. Sci. 454-456 (2000) 246-250]. On a weathered copper surface the addition of SO 2 to the moist air stream leads to the formation of additional features as already described in the literature [M. Wadsak, M. Schreiner, T. Aastrup, C. Leygraf, Surf. Sci. 454-456 (2000) 246-250; Ch. Kleber, J. Weissenrieder, M. Schreiner, C. Leygraf, Appl. Surf. Sci. 193 (2002) 245-253]. Exposing a silver specimen to humidity leads to the degradation of the surface structure as well as to a formation of corrosion products, which could be detected by in situ QCM measurements. After addition of 250 ppb SO 2 to the moist gas stream an increase of the formed feature's volume on the silver surface could be observed by TM-AFM measurements. The results obtained additionally from the in situ QCM measurements confirm the influence of SO 2 due to a further increase of the mass of the formed corrosion layer (and therefore an increase of the

Laser-induced selective copper plating of polypropylene surface

Science.gov (United States)

Ratautas, K.; Gedvilas, M.; Stankevičiene, I.; JagminienÄ--, A.; Norkus, E.; Li Pira, N.; Sinopoli, S.; Emanuele, U.; Račiukaitis, G.

2016-03-01

Laser writing for selective plating of electro-conductive lines for electronics has several significant advantages, compared to conventional printed circuit board technology. Firstly, this method is faster and cheaper at the prototyping stage. Secondly, material consumption is reduced, because it works selectively. However, the biggest merit of this method is potentiality to produce moulded interconnect device, enabling to create electronics on complex 3D surfaces, thus saving space, materials and cost of production. There are two basic techniques of laser writing for selective plating on plastics: the laser-induced selective activation (LISA) and laser direct structuring (LDS). In the LISA method, pure plastics without any dopant (filler) can be used. In the LDS method, special fillers are mixed in the polymer matrix. These fillers are activated during laser writing process, and, in the next processing step, the laser modified area can be selectively plated with metals. In this work, both methods of the laser writing for the selective plating of polymers were investigated and compared. For LDS approach, new material: polypropylene with carbon-based additives was tested using picosecond and nanosecond laser pulses. Different laser processing parameters (laser pulse energy, scanning speed, the number of scans, pulse durations, wavelength and overlapping of scanned lines) were applied in order to find out the optimal regime of activation. Areal selectivity tests showed a high plating resolution. The narrowest width of a copper-plated line was less than 23 μm. Finally, our material was applied to the prototype of the electronic circuit board on a 2D surface.

Encapsulation of electroless copper patterns into diamond films

Energy Technology Data Exchange (ETDEWEB)

Pimenov, S.M.; Shafeev, G.A.; Lavrischev, S.V. [General Physics Institute, Moscow (Russian Federation)] [and others

1995-12-31

The results are reported on encapsulating copper lines into diamond films grown by a DC plasma CVD. The process includes the steps of (i) laser activation of diamond for electroless metal plating, (ii) electroless copper deposition selectively onto the activated surface regions, and (iii) diamond regrowth on the Cu-patterned diamond films. The composition and electrical properties of the encapsulated copper lines were examined, revealing high purity and low electrical resistivity of the encapsulated electroless copper.

Seeding of silicon by copper ion implantation for selective electroless copper plating

Energy Technology Data Exchange (ETDEWEB)

Bhansali, S.; Sood, D.K.; Zmood, R.B. [Microelectronic and Materials Technology Centre, Royal Melbourne Institute of Technolgy, Melbourne, VIC (Australia)

1993-12-31

We report on the successful use of copper(self) ion implantation into silicon to seed the electroless plating of copper on silicon (100) surfaces. Copper ions have been implanted to doses of 5E14-6.4E16 ions/cm{sup 2} using a MEEVA ion implanter at extraction voltage of 40kV. Dose was varied in fine steps to determine the threshold dose of 2E15 Cu ions/cm{sup 2} for `seed` formation of copper films on silicon using a commercial electroless plating solution. Plated films were studied with Rutherford backscattering spectrometry, scanning electron microscopy, EDX and profilometry . The adhesion of films was measured by `scotch tape test`. The adhesion was found to improve with increasing dose. However thicker films exhibited rather poor adhesion and high internal stress. SEM results show that the films grow first as isolated islands which become larger and eventually impinge into a continuous film as the plating time is increased. (authors). 5 refs., 1 tab., 3 figs.

Seeding of silicon by copper ion implantation for selective electroless copper plating

Energy Technology Data Exchange (ETDEWEB)

Bhansali, S; Sood, D K; Zmood, R B [Microelectronic and Materials Technology Centre, Royal Melbourne Institute of Technolgy, Melbourne, VIC (Australia)

1994-12-31

We report on the successful use of copper(self) ion implantation into silicon to seed the electroless plating of copper on silicon (100) surfaces. Copper ions have been implanted to doses of 5E14-6.4E16 ions/cm{sup 2} using a MEEVA ion implanter at extraction voltage of 40kV. Dose was varied in fine steps to determine the threshold dose of 2E15 Cu ions/cm{sup 2} for `seed` formation of copper films on silicon using a commercial electroless plating solution. Plated films were studied with Rutherford backscattering spectrometry, scanning electron microscopy, EDX and profilometry . The adhesion of films was measured by `scotch tape test`. The adhesion was found to improve with increasing dose. However thicker films exhibited rather poor adhesion and high internal stress. SEM results show that the films grow first as isolated islands which become larger and eventually impinge into a continuous film as the plating time is increased. (authors). 5 refs., 1 tab., 3 figs.

Seeding of silicon by copper ion implantation for selective electroless copper plating

International Nuclear Information System (INIS)

Bhansali, S.; Sood, D.K.; Zmood, R.B.

1993-01-01

We report on the successful use of copper(self) ion implantation into silicon to seed the electroless plating of copper on silicon (100) surfaces. Copper ions have been implanted to doses of 5E14-6.4E16 ions/cm 2 using a MEEVA ion implanter at extraction voltage of 40kV. Dose was varied in fine steps to determine the threshold dose of 2E15 Cu ions/cm 2 for 'seed' formation of copper films on silicon using a commercial electroless plating solution. Plated films were studied with Rutherford backscattering spectrometry, scanning electron microscopy, EDX and profilometry . The adhesion of films was measured by 'scotch tape test'. The adhesion was found to improve with increasing dose. However thicker films exhibited rather poor adhesion and high internal stress. SEM results show that the films grow first as isolated islands which become larger and eventually impinge into a continuous film as the plating time is increased. (authors). 5 refs., 1 tab., 3 figs

Dependence of the surface resistance of niobium coated copper cavities on the coating temperature

International Nuclear Information System (INIS)

Darriulat, P.; Durand, C.; Janot, P.; Rensing, N.; Weingarten, W.; Bosland, P.; Gobin, J.; Martignac, J.

1996-01-01

Six hydro-formed copper 1.5 GHz cavities have been baked and coated with niobium at different temperatures between 100 deg C and 200 deg C, while keeping the other discharge parameters unchanged. Their surface resistance has been measured as a function RF field and trapped magnetic field. Its dependence on deposition temperature confirms earlier indications obtained using 350 MHz LEP cavities that 150 deg C leads to optimal performances. The critical temperatures of Nb/Cu and bulk niobium cavities have also been measured. (author)

Copper Resistance of the Emerging Pathogen Acinetobacter baumannii

Science.gov (United States)

Williams, Caitlin L.; Neu, Heather M.; Gilbreath, Jeremy J.; Michel, Sarah L. J.; Zurawski, Daniel V.

2016-01-01

ABSTRACT Acinetobacter baumannii is an important emerging pathogen that is capable of causing many types of severe infection, especially in immunocompromised hosts. Since A. baumannii can rapidly acquire antibiotic resistance genes, many infections are on the verge of being untreatable, and novel therapies are desperately needed. To investigate the potential utility of copper-based antibacterial strategies against Acinetobacter infections, we characterized copper resistance in a panel of recent clinical A. baumannii isolates. Exposure to increasing concentrations of copper in liquid culture and on solid surfaces resulted in dose-dependent and strain-dependent effects; levels of copper resistance varied broadly across isolates, possibly resulting from identified genotypic variation among strains. Examination of the growth-phase-dependent effect of copper on A. baumannii revealed that resistance to copper increased dramatically in stationary phase. Moreover, A. baumannii biofilms were more resistant to copper than planktonic cells but were still susceptible to copper toxicity. Exposure of bacteria to subinhibitory concentrations of copper allowed them to better adapt to and grow in high concentrations of copper; this copper tolerance response is likely achieved via increased expression of copper resistance mechanisms. Indeed, genomic analysis revealed numerous putative copper resistance proteins that share amino acid homology to known proteins in Escherichia coli and Pseudomonas aeruginosa. Transcriptional analysis revealed significant upregulation of these putative copper resistance genes following brief copper exposure. Future characterization of copper resistance mechanisms may aid in the search for novel antibiotics against Acinetobacter and other highly antibiotic-resistant pathogens. IMPORTANCE Acinetobacter baumannii causes many types of severe nosocomial infections; unfortunately, some isolates have acquired resistance to almost every available antibiotic

Copper Resistance of the Emerging Pathogen Acinetobacter baumannii.

Science.gov (United States)

Williams, Caitlin L; Neu, Heather M; Gilbreath, Jeremy J; Michel, Sarah L J; Zurawski, Daniel V; Merrell, D Scott

2016-10-15

Acinetobacter baumannii is an important emerging pathogen that is capable of causing many types of severe infection, especially in immunocompromised hosts. Since A. baumannii can rapidly acquire antibiotic resistance genes, many infections are on the verge of being untreatable, and novel therapies are desperately needed. To investigate the potential utility of copper-based antibacterial strategies against Acinetobacter infections, we characterized copper resistance in a panel of recent clinical A. baumannii isolates. Exposure to increasing concentrations of copper in liquid culture and on solid surfaces resulted in dose-dependent and strain-dependent effects; levels of copper resistance varied broadly across isolates, possibly resulting from identified genotypic variation among strains. Examination of the growth-phase-dependent effect of copper on A. baumannii revealed that resistance to copper increased dramatically in stationary phase. Moreover, A. baumannii biofilms were more resistant to copper than planktonic cells but were still susceptible to copper toxicity. Exposure of bacteria to subinhibitory concentrations of copper allowed them to better adapt to and grow in high concentrations of copper; this copper tolerance response is likely achieved via increased expression of copper resistance mechanisms. Indeed, genomic analysis revealed numerous putative copper resistance proteins that share amino acid homology to known proteins in Escherichia coli and Pseudomonas aeruginosa Transcriptional analysis revealed significant upregulation of these putative copper resistance genes following brief copper exposure. Future characterization of copper resistance mechanisms may aid in the search for novel antibiotics against Acinetobacter and other highly antibiotic-resistant pathogens. Acinetobacter baumannii causes many types of severe nosocomial infections; unfortunately, some isolates have acquired resistance to almost every available antibiotic, and treatment options

Design of a high charge (10 - 100 nC) and short pulse (2 - 5 ps) rf photocathode gun for wakefield acceleration

International Nuclear Information System (INIS)

Gai, W.

1998-01-01

In this paper we present a design report on a 1-1/2 cell, L Band RF photocathode gun that is capable of generating and accelerating electron beams with peak currents >10 kA. We have performed simulation for bunch intensities in the range of 10-100 nC with peak axial electrical field at the photocathode of 30-100 MV/m. Unlike conventional short electron pulse generation, this design does not require magnetic pulse compression. Based on numerical simulations using SUPERFISH and PARMELA, this design will produce 20-100 nC beam at 18 MeV with rms bunch length 0.6-1.25 mm and normalized transverse emittance 30-108 mm mrad. Applications of this beam for wakefield acceleration is also discussed

Native copper in Permian Mudstones from South Devon: A natural analogue of copper canisters for high-level radioactive waste

International Nuclear Information System (INIS)

Milodowski, A.E.; Styles, M.T.; Werme, L.; Oversby, V.M.

2001-01-01

Native copper (>99.9% Cu) sheets associated with complex uraniferous and vanadiferous concretions in Upper Permian Mudstones from south Devon (United Kingdom) have been studied as a 'natural analogue' for copper canisters designed to be used in the isolation of spent fuel and high-level radioactive wastes (HLW) for deep geological disposal. Detailed analysis demonstrates that the copper formed before the mudstones were compacted. The copper displays complex corrosion and alteration. The earliest alteration was to copper oxides, followed sequentially by the formation of copper arsenides, nickel arsenide and copper sulphide, and finally nickel arsenide accompanied by nickel-copper arsenide, copper arsenide and uranium silicates. Petrographic observations demonstrate that these alteration products also formed prior to compaction. Consideration of the published history for the region indicates that maximum compaction of the rocks will have occurred by at least the Lower Jurassic (i.e. over 176 Ma ago). Since that time the copper sheets have remained isolated by the compacted mudstones and were unaffected by further corrosion until uplift and exposure to present-day surface weathering

Modulating Hole Transport in Multilayered Photocathodes with Derivatized p-Type Nickel Oxide and Molecular Assemblies for Solar-Driven Water Splitting

Energy Technology Data Exchange (ETDEWEB)

Shan, Bing [Department; Sherman, Benjamin D. [Department; Klug, Christina M. [Center; Nayak, Animesh [Department; Marquard, Seth L. [Department; Liu, Qing [Department; Bullock, R. Morris [Center; Meyer, Thomas J. [Department

2017-08-31

We report here a new photocathode composed of a bi-layered doped NiO film topped by a macro-mesoporous ITO (ioITO) layer with molecular assemblies attached to the ioITO surface. The NiO film containing a 2% K+ doped NiO inner layer and a 2% Cu2+ doped NiO outer layer provides sufficient driving force for hole transport after injection to NiO by the molecular assembly. The tri-layered oxide, NiK0.02O | NiCu0.02O | ioITO, sensitized by a ruthenium polypyridyl dye and functionalized with a nickel-based hydrogen evolution catalyst, outperforms its counterpart, NiO | NiO | ioITO, in photocatalytic hydrogen evolution from water over a period of several hours with a Faradaic yield of ~90%.

Superhydrophobic Cu{sub 2}S@Cu{sub 2}O film on copper surface fabricated by a facile chemical bath deposition method and its application in oil-water separation

Energy Technology Data Exchange (ETDEWEB)

Pi, Pihui, E-mail: phpi@scut.edu.cn; Hou, Kun; Zhou, Cailong; Li, Guidong; Wen, Xiufang; Xu, Shouping; Cheng, Jiang; Wang, Shuangfeng

2017-02-28

Highlights: • A superhydrophobic film with macro/nano structure was fabricated on copper surface. • The as-prepared film shows outstanding water repellency and long-term storage stability. • The same method was used to fabricate superhydrophobic/superoleophilic copper mesh. • The obtained mesh could realize separation of various oily sewages with separation efficiency above 94%. - Abstract: Cu{sub 2}S and Cu{sub 2}O composite (Cu{sub 2}S@Cu{sub 2}O) film with micro/nano binary structure was created on copper surface using the mixing solution of sodium thiosulphate and copper sulfate by a facile chemical bath deposition method. After modification with low-cost polydimethylsioxane (PDMS), the superhydrophobic Cu{sub 2}S@Cu{sub 2}O film was obtained. The as-prepared film shows outstanding water repellency with a water contact angle larger than 150° and long-term storage stability. The geometric morphology and chemical composition of the film were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), respectively. Moreover, the same method was used to fabricate superhydrophobic/superoleophilic copper mesh, and it could realize separation of various oily sewages with separation efficiency above 94%. This strategy has potential to fabricate the practical superhydrophobic Cu{sub 2}S@Cu{sub 2}O film on copper surface on a large scale due to its simplicity and low cost.

Copper-catalyzed azide–alkyne cycloaddition (CuAAC) and beyond: new reactivity of copper(i) acetylides†

OpenAIRE

Hein, Jason E.; Fokin, Valery V.

2010-01-01

Copper-catalyzed azide–alkyne cycloaddition (CuAAC) is a widely utilized, reliable, and straightforward way for making covalent connections between building blocks containing various functional groups. It has been used in organic synthesis, medicinal chemistry, surface and polymer chemistry, and bioconjugation applications. Despite the apparent simplicity of the reaction, its mechanism involves multiple reversible steps involving coordination complexes of copper(i) acetylides of varying nucle...

Interaction of dimethylamine with clean and partially oxidized copper surfaces

Science.gov (United States)

Kelber, J. A.; Rogers, J. W.; Banse, B. A.; Koel, B. E.

1990-05-01

The interaction of dimethylamine (DMA) with partially oxidized polycrystalline copper [Cu(poly)] and clean and partially oxidized Cu(110) between 110 and 500 K has been examined using electron stimulated desorption (ESD), high resolution electron energy loss spectroscopy (HREELS) and temperature programmed desorption (TPD). ESD mass spectra of the DMA adsorbed on O/Cu(poly) between 112 and 230 K consistently display peaks at 44 amu [(CH 3) 2N] + and 46 amu [(CH 3) 2NH-H] +, but no significant parent peak at 45 amu [(CH 3) 2NH] +, even though this last feature is prominent in the gas-phase mass spectrum. OH - is not observed at temperatures below 184 K and the yield at higher temperatures is much less than that of O +. HREELS of DMA on clean and oxygen covered Cu(110) obtained at temperatures between 100 and 320 K show characteristic vibrational spectra for molecular DMA and no OH(a) vibrational modes. TPD results show that the desorption profiles of all the major peaks in the DMA mass spectrum follow that of the parent peak with no evidence for production of H 2O. The ESD, HREELS and TPD results all indicate that DMA is molecularly and reversibly adsorbed, with no significant formation of surface hydroxyl species. The results indicate that preferential adsorption of amines from amine/epoxy mixtures onto metal oxide surfaces could passivate the surface and prevent subsequent bonding to the epoxy resin.

Photochemical Copper Coating on 3D Printed Thermoplastics

Science.gov (United States)

Yung, Winco K. C.; Sun, Bo; Huang, Junfeng; Jin, Yingdi; Meng, Zhengong; Choy, Hang Shan; Cai, Zhixiang; Li, Guijun; Ho, Cheuk Lam; Yang, Jinlong; Wong, Wai Yeung

2016-08-01

3D printing using thermoplastics has become very popular in recent years, however, it is challenging to provide a metal coating on 3D objects without using specialized and expensive tools. Herein, a novel acrylic paint containing malachite for coating on 3D printed objects is introduced, which can be transformed to copper via one-step laser treatment. The malachite containing pigment can be used as a commercial acrylic paint, which can be brushed onto 3D printed objects. The material properties and photochemical transformation processes have been comprehensively studied. The underlying physics of the photochemical synthesis of copper was characterized using density functional theory calculations. After laser treatment, the surface coating of the 3D printed objects was transformed to copper, which was experimentally characterized by XRD. 3D printed prototypes, including model of the Statue of Liberty covered with a copper surface coating and a robotic hand with copper interconnections, are demonstrated using this painting method. This composite material can provide a novel solution for coating metals on 3D printed objects. The photochemical reduction analysis indicates that the copper rust in malachite form can be remotely and photo-chemically reduced to pure copper with sufficient photon energy.

Adsorption behavior of caffeine as a green corrosion inhibitor for copper

Energy Technology Data Exchange (ETDEWEB)

Souza, Fernando Silvio de [Grupo de Estudos de Processos Eletroquimicos e Eletroanaliticos, Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil); Giacomelli, Cristiano [Departamento de Quimica, Universidade Federal de Santa Maria, Av. Roraima 1000, 97119-900, Santa Maria, RS (Brazil); Goncalves, Reinaldo Simoes [Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501-970, Porto Alegre, RS (Brazil); Spinelli, Almir, E-mail: almir.spinelli@ufsc.br [Grupo de Estudos de Processos Eletroquimicos e Eletroanaliticos, Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil)

2012-12-01

Electrochemical and impedance experiments were carried out to evaluate the corrosion behavior of copper in aerated 0.1 mol L{sup -1} H{sub 2}SO{sub 4} solutions in the presence of three xanthine derivatives with similar chemical structures. The corrosion rate of copper was found to increase in the presence of theophylline and theobromine and decrease in the presence of caffeine. The adsorption and inhibitory effect of caffeine on copper surfaces in aerated 0.1 mol L{sup -1} H{sub 2}SO{sub 4} solutions were then investigated in detail by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), contact angle measurements, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and fluorescence experiments. The data obtained indicate that caffeine behaves as a cathodic-type inhibitor adsorbing onto the copper surface according to the Temkin isotherm, with the negative Increment G Degree-Sign {sub ads} value of - 31.1 kJ mol{sup -1} signifying a spontaneous adsorption process. The corrosion inhibition efficiency increased with caffeine concentration in the range of 1.0-10.0 mmol L{sup -1}. Furthermore, the EIS results obtained at the open-circuit potential and surface analysis (SEM, EDS and fluorescence) clearly demonstrated the adsorption of the organic compound onto the copper electrode. The contact angle measurements revealed the formation of a hydrophobic protective film. This film covers up to 72% of the total active surface, acts as a protective barrier and prevents interaction between the metal, water and oxygen molecules. - Highlights: Black-Right-Pointing-Pointer We have investigated the adsorption and corrosion inhibition of caffeine on copper surfaces. Black-Right-Pointing-Pointer Caffeine behaves as a cathodic-type inhibitor. Black-Right-Pointing-Pointer Caffeine adsorbs onto copper surface according to Temkin isotherm. Black-Right-Pointing-Pointer There exists the formation of a hydrophobic film that acts as a

Copper contamination in thin stainless steel sheet

International Nuclear Information System (INIS)

Holbert, R.K. Jr.; Dobbins, A.G.; Bennett, R.K. Jr.

1986-01-01

The standard welding technique used at Oak Ridge Y-12 Plant for joining thin stainless sheet is the gas tungsten arc (GTA) welding process. One of the reoccurring problems with the sheet welds is surface cracking in the heat-affected zone (HAZ). Metallography shows that the cracks are only about 0.05 mm (0.002 in.) deep which is significant in a 0.25 mm (0.01 in.) thick sheet. Thus, welding requirements do not permit any surfacing cracking as detected by a fluorescent dye penetrant test conducted on every part after welding. Surface cracks have been found in both of the two most common weld designs in the thin sheet fabricated at the Oak Ridge Y-12 Plant. These butt joints are welded between two 0.25 mm thick stainless steel sheets and a tube with eyelet welded to a 25 mm (0.98 in.) thick sheet. The weld between the two sheets is made on a semiautomatic seam welding unit, whereas the tube-to-eyelet-to-sheet welds are done manually. The quality of both welds is very dependent on the welding procedure and the way the parts are placed in the weld fixturing. Metallographic examination has indicated that some welded parts with surface cracking in the weld region had copper particles on the surface, and the question of copper contamination has been raised. With the aid of a scanning electron microscope and an electron microprobe, the existence of copper in an around the surface cracks has been verified. The copper is on the surface of the parts prior to welding in the form of small dust particles

Role of surface on the size-dependent mechanical properties of copper nano-wire under tensile load: A molecular dynamics simulation

Science.gov (United States)

Liu, Wei-Ting; Hsiao, Chun-I.; Hsu, Wen-Dung

2014-01-01

In this study we have used atomistic simulations to investigate the role of surface on the size-dependent mechanical properties of nano-wires. In particular, we have performed computational investigation on single crystal face-centered cubic copper nano-wires with diameters ranging from 2 to 20 nm. The wire axis for all the nano-wires are considered along the [0 0 1] direction. Characterization of the initial optimized structures revealed clear differences in interatomic spacing, stress, and potential energy in all the nano-wires. The mechanical properties with respect to wire diameter are evaluated by applying tension along the [0 0 1] direction until yielding. We have discussed the stress-strain relationships, Young's modulus, and the variation in potential energy from surface to the center of the wire for all the cases. Our results indicate that the mechanical response (including yield strain, Young's modulus, and resilience) is directly related to the proportion of surface to bulk type atoms present in each nano-wire. Thus the size-dependent mechanical properties of single crystal copper nano-wire within elastic region are attributed to the surface to volume ratio (surface effect). Using the calculated response, we have formulated a mathematical relationship, which predicts the nonlinear correlation between the mechanical properties and the diameter of the wire.

Evolution effects of the copper surface morphology on the nucleation density and growth of graphene domains at different growth pressures

Energy Technology Data Exchange (ETDEWEB)

Hedayat, Seyed Mahdi [Transport Phenomena & Nanotechnology Lab., School of Chemical Engineering, College of Engineering, University of Tehran (Iran, Islamic Republic of); Karimi-Sabet, Javad, E-mail: j_karimi@alum.sharif.edu [NFCRS, Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of); Shariaty-Niassar, Mojtaba, E-mail: mshariat@ut.ac.ir [Transport Phenomena & Nanotechnology Lab., School of Chemical Engineering, College of Engineering, University of Tehran (Iran, Islamic Republic of)

2017-03-31

Highlights: • Manipulation of the Cu surface morphology in a wide range by electropolishing treatment. • Comparison of the nucleation density of graphene at low pressure and atmospheric pressure CVD processes. • Controlling the evolution of the Cu surface morphology inside a novel confined space. • Growth of large-size graphene domains. - Abstract: In this work, we study the influence of the surface morphology of the catalytic copper substrate on the nucleation density and the growth rate of graphene domains at low and atmospheric pressure chemical vapor deposition (LPCVD and APCVD) processes. In order to obtain a wide range of initial surface morphology, precisely controlled electropolishing methods were developed to manipulate the roughntreess value of the as-received Cu substrate (RMS = 30 nm) to ultra-rough (RMS = 130 nm) and ultra-smooth (RMS = 2 nm) surfaces. The nucleation and growth of graphene domains show obviously different trends at LPCVD and APCVD conditions. In contrast to APCVD condition, the nucleation density of graphene domains is almost equal in substrates with different initial roughness values at LPCVD condition. We show that this is due to the evolution of the surface morphology of the Cu substrate during the graphene growth steps. By stopping the surface sublimation of copper substrate in a confined space saturated with Cu atoms, the evolution of the Cu surface was impeded. This results in the reduction of the nucleation density of graphene domains up to 24 times in the pre-smoothed Cu substrates at LPCVD condition.

Evolution effects of the copper surface morphology on the nucleation density and growth of graphene domains at different growth pressures

International Nuclear Information System (INIS)

Hedayat, Seyed Mahdi; Karimi-Sabet, Javad; Shariaty-Niassar, Mojtaba

2017-01-01

Highlights: • Manipulation of the Cu surface morphology in a wide range by electropolishing treatment. • Comparison of the nucleation density of graphene at low pressure and atmospheric pressure CVD processes. • Controlling the evolution of the Cu surface morphology inside a novel confined space. • Growth of large-size graphene domains. - Abstract: In this work, we study the influence of the surface morphology of the catalytic copper substrate on the nucleation density and the growth rate of graphene domains at low and atmospheric pressure chemical vapor deposition (LPCVD and APCVD) processes. In order to obtain a wide range of initial surface morphology, precisely controlled electropolishing methods were developed to manipulate the roughntreess value of the as-received Cu substrate (RMS = 30 nm) to ultra-rough (RMS = 130 nm) and ultra-smooth (RMS = 2 nm) surfaces. The nucleation and growth of graphene domains show obviously different trends at LPCVD and APCVD conditions. In contrast to APCVD condition, the nucleation density of graphene domains is almost equal in substrates with different initial roughness values at LPCVD condition. We show that this is due to the evolution of the surface morphology of the Cu substrate during the graphene growth steps. By stopping the surface sublimation of copper substrate in a confined space saturated with Cu atoms, the evolution of the Cu surface was impeded. This results in the reduction of the nucleation density of graphene domains up to 24 times in the pre-smoothed Cu substrates at LPCVD condition.

An Investigation of Low Biofouling Copper-charged Membranes

Science.gov (United States)

Asapu, Sunitha

Water is essential for the survival of life on Earth, but pollutants in water can cause dangerous diseases and fatalities. The need for purified water has been increasing with increasing world population; however, natural sources of water such as rivers, lakes and streams, are progressively falling shorter and shorter of meeting water needs. The provision of clean, drinkable water to people is a key factor for the development of novel and alternative water purification technologies, such as membrane separations. Nanofiltration (NF) is a membrane separations technology that purifies water from lower quality sources, such as brackish water, seawater and wastewater. During the filtration of such sources, materials that are rejected by the membrane may accumulate on the surface of the membrane to foul it. Such materials include organic and inorganic matter, colloids, salts and microorganisms. The former four can often be controlled via pretreatment; however, the accumulation of microorganisms is more problematic to membranes. Biofouling is the accumulation and growth of microorganisms on the surface of membranes and on feed spacers. After attachment, microorganisms excrete extracellular polymeric substances (EPS), which form a matrix around the organism's outer surface as biofilm. These biofilms are detrimental and result in irreversible membrane fouling. Copper and silver ions inactivate the bacterial cells and prevent the DNA replication in microbial cells. Previous studies using copper-charged feed spacers have shown the ability of copper to control biofouling without a significant amount of copper leaching from copper-charged polypropylene (PP) feed spacers during crossflow filtration. Also, filtration using unmodified speed facers experienced almost 70% flux decline, while filtration using copper-charged feed spacers displayed only 25% flux decline. These intriguing results led to the hypothesis that the polymer chemistry could be extrapolated to produce membranes

Chemical durability of copper canisters under crystalline bedrock repository conditions

International Nuclear Information System (INIS)

Sjoeblom, R.; Hermansson, H.P.; Amcoff, Oe.

1995-01-01

In the Swedish waste management programme, the copper canister is expected to provide containment of the radionuclides for a very long time, perhaps million of years. The purpose of the present paper is to analyze prerequisites for assessments of corrosion lifetimes for copper canisters. The analysis is based on compilations of literature from the following areas: chemical literature on copper and copper corrosion, mineralogical literature with emphasis on the stability of copper in near surface environments, and chemical and mineralogical literature with emphasis on the stabilities and thermodynamics of species and phases that may exist in a repository environment. Three main types of situations are identified: (1) under oxidizing and low chloride conditions, passivating oxide type of layers may form on the copper surface; (2) under oxidizing and high chloride conditions, the species formed may all be dissolved; and (3) under reducing conditions, non-passivating sulfide type layers may form on the copper surface. Considerable variability and uncertainty exists regarding the chemical environment for the canister, especially in certain scenarios. Thus, the mechanisms for corrosion can be expected to differ greatly for different situations. The lifetime of a thick-walled copper canister subjected to general corrosion appears to be long for most reasonable chemistries. Localized corrosion may appear for types (1) and (3) above but the mechanisms are widely different in character. The penetration caused by localized corrosion can be expected to be very sensitive to details in the chemistry. 20 refs, 3 figs, 1 tab

Method for providing uranium with a protective copper coating

Science.gov (United States)

Waldrop, Forrest B.; Jones, Edward

1981-01-01

The present invention is directed to a method for providing uranium metal with a protective coating of copper. Uranium metal is subjected to a conventional cleaning operation wherein oxides and other surface contaminants are removed, followed by etching and pickling operations. The copper coating is provided by first electrodepositing a thin and relatively porous flash layer of copper on the uranium in a copper cyanide bath. The resulting copper-layered article is then heated in an air or inert atmosphere to volatilize and drive off the volatile material underlying the copper flash layer. After the heating step an adherent and essentially non-porous layer of copper is electro-deposited on the flash layer of copper to provide an adherent, multi-layer copper coating which is essentially impervious to corrosion by most gases.

Ammonia, phosphate, phenol, and copper(II) removal from aqueous solution by subsurface and surface flow constructed wetland.

Science.gov (United States)

Mojiri, Amin; Ahmad, Zakiah; Tajuddin, Ramlah Mohd; Arshad, Mohd Fadzil; Gholami, Ali

2017-07-01

Water pollution is a global problem. During current study, ammonia, phosphate, phenol, and copper(II) were removed from aqueous solution by subsurface and surface flow constructed wetland. In current investigation, distilled water was polluted with four contaminants including ammonia, phosphate, copper (Cu), and phenol. Response surface methodology and central composite design were applied to optimize pollutant removal during treatment by subsurface flow constructed wetland (SSFCW). Contact time (12 to 80 h) and initial pollutant concentration (20 to 85 mg/L) were selected as independent factors; some upper and lower ranges were also monitored for accuracy. In SSFCW, water hyacinth transplanted in two substrate layers, namely zeolite and cockle shell. SSFCW removed 87.7, 81.4, 74.7, and 54.9% of ammonia, phosphate, Cu, and phenol, respectively, at optimum contact time (64.5 h) and initial pollutant concentration (69.2 mg/L). Aqueous solution was moved to a surface flow constructed wetland (SFCW) after treating via SSFCW at optimum conditions. In SFCW, Typha was transplanted to a fixed powdered substrate layer, including bentonite, zeolite, and cockle shell. SFCW could develop performance of this combined system and could improve elimination efficacy of the four contaminants to 99.99%. So this combined CW showed a good performance in removing pollutants. Graphical abstract Wetlands arrangement for treating aqueous solution in current study.

Photoelectron extraction efficiency from a CsI photocathode and THGEM operation in He−CF4 and He−CH4 mixtures

International Nuclear Information System (INIS)

Coimbra, A.E.C.; Santos, J.M.F. dos; Israelashvili, I.

2016-01-01

This work presents the experimental measurements obtained for UV-induced photo-electron extraction efficiency from a CsI photocathode into He with CF 4 and CH 4 gas mixtures. A 1000Å CsI photocathode was deposited on a gold plated THGEM for photo-electron conversion. Charge-gain measurements were obtained with a Single-THGEM detector operating in these gas mixtures using a continuous UV lamp for the extraction of photo-electrons. Charge-gains in excess of 10 5 were obtained for gas mixtures containing percentages of quencher higher than 20% while photo-electron extraction efficiency achieved ∼ 50% for He/CF 4 and ∼ 30% for He/CH 4 . Single photon electron measurements were also performed to assess the maximal gains reached in this regime. A discussion for future GPM cryogenic applications is presented

The development of gaseous detectors with solid photocathodes for low temperature applications

CERN Document Server

Periale, L.; Iacobaeus, C.; Francke, T.; Lund-Jensen, B.; Pavlopoulos, N.; Picchi, P.; Pietropaolo, F.

2004-01-01

There are several applications and fundamental research areas which require the detection of VUV light at cryogenic temperatures. For these applications we have developed and successfully tested special designs of gaseous detectors with solid photocathodes able to operate at low temperatures: sealed gaseous detectors with MgF2 windows and windowless detectors. We have experimentally demonstrated, that both primary and secondary (due to the avalanche multiplication inside liquids) scintillation lights could be recorded by photosensitive gaseous detectors. The results of this work may allow one to significantly improve the operation of some noble liquid gas TPCs.

Analysis of emittance compensation and simulation results to photo-cathode RF gun

CERN Document Server

LiuShengGuang

2002-01-01

The emittance compensation technology will be used on the photo-cathode RF gun for Shanghai SDUV-FEL. The space charge force and its effect on electron beam transverse emittance in RF gun is studied, the principle of emittance compensation in phase-space is discussed. The authors have designed a compensation solenoid and calculated its magnetic field distribution. Its performance has been studied by the code PARMELA. A simulation result indicates that the normalized transverse RMS emittance for electron beam of 1.5 nC is 1.612 pi mm centre dot mrad, electron energy E = 5.71 MeV

Stress corrosion cracking and dealloying of copper-gold alloy in iodine vapor

International Nuclear Information System (INIS)

Galvez, M.F.; Bianchi, G.L.; Galvele, J.R.

1993-01-01

The susceptibility to stress corrosion cracking of copper-gold alloy in iodine vapor was studied and the results were analyzed under the scope of the surface mobility stress corrosion cracking mechanism. The copper-gold alloy undergoes stress corrosion cracking in iodine. Copper iodide was responsible of that behavior. The copper-gold alloy shows two processes in parallel: stress corrosion cracking and dealloying. As was predicted by the surface mobility stress corrosion cracking mechanism, the increase in strain rate induces an increase in the crack propagation rate. (Author)

Thermal effects in equilibrium surface segregation in a copper/10-atomic-percent-aluminum alloy using Auger electron spectroscopy

Science.gov (United States)

Ferrante, J.

1972-01-01

Equilibrium surface segregation of aluminum in a copper-10-atomic-percent-aluminum single crystal alloy oriented in the /111/ direction was demonstrated by using Auger electron spectroscopy. This crystal was in the solid solution range of composition. Equilibrium surface segregation was verified by observing that the aluminum surface concentration varied reversibly with temperature in the range 550 to 850 K. These results were curve fitted to an expression for equilibrium grain boundary segregation and gave a retrieval energy of 5780 J/mole (1380 cal/mole) and a maximum frozen-in surface coverage three times the bulk layer concentration. Analyses concerning the relative merits of sputtering calibration and the effects of evaporation are also included.

Deposition of Antimicrobial Copper-Rich Coatings on Polymers by Atmospheric Pressure Jet Plasmas

Directory of Open Access Journals (Sweden)

Jana Kredl

2016-04-01

Full Text Available Inanimate surfaces serve as a permanent reservoir for infectious microorganisms, which is a growing problem in areas in everyday life. Coating of surfaces with inorganic antimicrobials, such as copper, can contribute to reduce the adherence and growth of microorganisms. The use of a DC operated air plasma jet for the deposition of copper thin films on acrylonitrile butadiene styrene (ABS substrates is reported. ABS is a widespread material used in consumer applications, including hospitals. The influence of gas flow rate and input current on thin film characteristics and its bactericidal effect have been studied. Results from X-ray photoelectron spectroscopy (XPS and atomic force microscopy confirmed the presence of thin copper layers on plasma-exposed ABS and the formation of copper particles with a size in the range from 20 to 100 nm, respectively. The bactericidal properties of the copper-coated surfaces were tested against Staphylococcus aureus. A reduction in growth by 93% compared with the attachment of bacteria on untreated samples was observed for coverage of the surface with 7 at. % copper.

Potassium sorbate-A new aqueous copper corrosion inhibitor

International Nuclear Information System (INIS)

Abelev, Esta; Starosvetsky, David; Ein-Eli, Yair

2007-01-01

This work presents the novel nature of 2,4-hexadienoic acid potassium salt (potassium sorbate (KCH 3 CH=CHCH=CHCO 2 )) as an effective copper aqueous corrosion inhibitor. The influence of pH and potassium sorbate concentration on copper corrosion in aerated sulfate and chloride solutions is reported. Degree of copper protection was found to increase with an increase in potassium sorbate concentration; an optimum concentration of this inhibitor in sulfate solutions was found to be 10 g/L. Copper is highly resistant to corrosion attacks by chloride ions in the presence of potassium sorbate. X-ray photoelectron spectroscopy (XPS) studies suggest that copper protection is achieved via the formation of a mixed layer of cuprous oxide, cupric hydroxide and copper(II)-sorbate at the metal surface

Solution-processed copper-nickel nanowire anodes for organic solar cells

Science.gov (United States)

Stewart, Ian E.; Rathmell, Aaron R.; Yan, Liang; Ye, Shengrong; Flowers, Patrick F.; You, Wei; Wiley, Benjamin J.

2014-05-01

This work describes a process to make anodes for organic solar cells from copper-nickel nanowires with solution-phase processing. Copper nanowire films were coated from solution onto glass and made conductive by dipping them in acetic acid. Acetic acid removes the passivating oxide from the surface of copper nanowires, thereby reducing the contact resistance between nanowires to nearly the same extent as hydrogen annealing. Films of copper nanowires were made as oxidation resistant as silver nanowires under dry and humid conditions by dipping them in an electroless nickel plating solution. Organic solar cells utilizing these completely solution-processed copper-nickel nanowire films exhibited efficiencies of 4.9%.This work describes a process to make anodes for organic solar cells from copper-nickel nanowires with solution-phase processing. Copper nanowire films were coated from solution onto glass and made conductive by dipping them in acetic acid. Acetic acid removes the passivating oxide from the surface of copper nanowires, thereby reducing the contact resistance between nanowires to nearly the same extent as hydrogen annealing. Films of copper nanowires were made as oxidation resistant as silver nanowires under dry and humid conditions by dipping them in an electroless nickel plating solution. Organic solar cells utilizing these completely solution-processed copper-nickel nanowire films exhibited efficiencies of 4.9%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01024h

The oxidation of copper catalysts during ethylene epoxidation.

Science.gov (United States)

Greiner, M T; Jones, T E; Johnson, B E; Rocha, T C R; Wang, Z J; Armbrüster, M; Willinger, M; Knop-Gericke, A; Schlögl, R

2015-10-14

The oxidation of copper catalysts during ethylene epoxidation was characterized using in situ photoemission spectroscopy and electron microscopy. Gas chromatography, proton-transfer reaction mass spectrometry and electron-ionization mass spectrometry were used to characterize the catalytic properties of the oxidized copper. We find that copper corrodes during epoxidation in a 1 : 1 mixture of oxygen and ethylene. The catalyst corrosion passes through several stages, beginning with the formation of an O-terminated surface, followed by the formation of Cu2O scale and eventually a CuO scale. The oxidized catalyst exhibits measurable activity for ethylene epoxidation, but with a low selectivity of 8/2500) Cu2O forms and eventually covers the surface.

In-situ x-ray absorption study of copper films in ground water solutions

International Nuclear Information System (INIS)

Kvashnina, K.O.; Butorin, S.M.; Modin, A.; Soroka, I.; Marcellini, M.; Nordgren, J.; Guo, J.-H.; Werme, L.

2007-01-01

This study illustrates how the damage from copper corrosion can be reduced by modifying the chemistry of the copper surface environment. The surface modification of oxidized copper films induced by chemical reaction with Cl - and HCO 3 - in aqueous solutions was monitored by in situ X-ray absorption spectroscopy. The results show that corrosion of copper can be significantly reduced by adding even a small amount of sodium bicarbonate. The studied copper films corroded quickly in chloride solutions, whereas the same solution containing 1.1 mM HCO 3 - prevented or slowed down the corrosion processes

Measurements of Transverse Emittance for RF Photocathode Gun at the PAL

CERN Document Server

Park Jang Ho; Park, Sung-Ju; Soo Ko In; Wang, Xijie; Woon Parc, Yong; Xiang, Dao

2005-01-01

A BNL GUN-IV type RF photo-cathode gun is under fabrication for use in the FIR (Far Infra-Red) facility being built at the Pohang Accelerator Laboratory (PAL). Performance test of the gun will include the measurement of transverse emittance profile along the longitudinal direction. Successful measurement of the emittance profile will provide powerful tool for the commissioning of the 4GLS (4th generation light source) injectors based on the emittance compensation principle. We are going to achieve this withthe use of pepper-pot based emittance meters that can be moved along the longitudinal direction. In this article, we present design considerations on the emittance meter with the resolution of 1 mm mrad.

Patterned self-assembled monolayers of alkanethiols on copper nanomembranes by submerged laser ablation

Science.gov (United States)

Rhinow, Daniel; Hampp, Norbert A.

2012-06-01

Self-assembled monolayers (SAMs) of alkanethiols are major building blocks for nanotechnology. SAMs provide a functional interface between electrodes and biomolecules, which makes them attractive for biochip fabrication. Although gold has emerged as a standard, copper has several advantages, such as compatibility with semiconductors. However, as copper is easily oxidized in air, patterning SAMs on copper is a challenging task. In this work we demonstrate that submerged laser ablation (SLAB) is well-suited for this purpose, as thiols are exchanged in-situ, avoiding air exposition. Using different types of ω-substituted alkanethiols we show that alkanethiol SAMs on copper surfaces can be patterned using SLAB. The resulting patterns were analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Both methods indicate that the intense laser beam promotes the exchange of thiols at the copper surface. Furthermore, we present a procedure for the production of free-standing copper nanomembranes, oxidation-protected by alkanethiol SAMs. Incubation of copper-coated mica in alkanethiol solutions leads to SAM formation on both surfaces of the copper film due to intercalation of the organic molecules. Corrosion-protected copper nanomembranes were floated onto water, transferred to electron microscopy grids, and subsequently analyzed by electron energy loss spectroscopy (EELS).

Synthesis of nanoscale copper nitride thin film and modification of the surface under high electronic excitation.

Science.gov (United States)

Ghosh, S; Tripathi, A; Ganesan, V; Avasthi, D K

2008-05-01

Nanoscale (approximately 90 nm) Copper nitride (Cu3N) films are deposited on borosilicate glass and Si substrates by RF sputtering technique in the reactive environment of nitrogen gas. These films are irradiated with 200 MeV Au15+ ions from Pelletron accelerator in order to modify the surface by high electronic energy deposition of heavy ions. Due to irradiation (i) at incident ion fluence of 1 x 10(12) ions/cm2 enhancement of grains, (ii) at 5 x 10912) ions/cm2 mass transport on the films surface, (iii) at 2 x 10(13) ions/cm2 line-like features on Cu3N/glass and nanometallic structures on Cu3N/Si surface are observed. The surface morphology is examined by atomic force microscope (AFM). All results are explained on the basis of a thermal spike model of ion-solid interaction.

Experimental and numerical study of the high-temperature structure of copper single crystal surfaces

International Nuclear Information System (INIS)

Loisel, Bertrand

1989-01-01

The structure of copper single crystal surfaces has been investigated on an atomic scale using two complementary tools: helium beam diffraction experiments and computer simulations by molecular dynamics. In the case of stepped surfaces, the roughening transition occurs at low temperature. Our helium beam diffraction experiments in the range 70-1000 K reveal this transition at 650±50 K and 150±50 K respectively on the (331) and (310) surfaces. We emphasize the role of the terrace and step structure on the thermal roughness, which is ruled by microscopic energies related to the creation and interaction of defects on the step edges. Adsorbing oxygen on a rough (310) surface gives rise to ordered superstructures. In our computer simulations, the interatomic forces are derived from an empiric N-body potential which leads to a realistic description of the static and dynamical properties of the bulk metal and its surfaces. We analyze the results of high-temperature simulations on the (110) surface. Two types of disorder are distinguished: the creation of adatom-vacancy pairs and the enhancement of the vibrational amplitudes of the atoms near their equilibrium site. We establish that both phenomena take place in the same temperature range. These simulations also indicate the very anisotropic behaviour of the surface at high temperatures (> 1000 K). (author) [fr

Antibiotic resistance, ability to form biofilm and susceptibility to copper alloys of selected staphylococcal strains isolated from touch surfaces in Polish hospital wards

Directory of Open Access Journals (Sweden)

Anna Różańska

2017-08-01

Full Text Available Abstract Background Despite the employment of sanitary regimes, contact transmission of the aetiological agents of hospital infections is still exceedingly common. The issue of microbe transmission becomes particularly important when facing multidrug-resistant microorganisms such as methicillin-resistant staphylococci. In the case of deficiencies in cleaning and disinfection procedures, hospital equipment made of copper alloys can play an important role, complementing traditional hospital hygiene procedures. The objective of this study was to characterize staphylococcal strains isolated from touch surfaces in Polish hospital wards in terms of their drug resistance, ability to form biofilm and susceptibility to antimicrobial activity of copper alloys. Methods The materials for the study were 95 staphylococcal strains isolated from touch surfaces in 13 different hospital wards from Małopolska province (the south of Poland. Phenotypic and genotypic antibiotic resistance were checked for erythromycin, clindamycin, gentamycin, ciprofloxacin, trimethoprim/sulfamethoxazole and mupirocin. Biofilm formation ability for the tested strains was checked with the use of culture on Congo red agar. Susceptibility to copper, tin bronze, brass and new silver was tested using a modification of the Japanese standard. Results Over 67% of the analysed staphylococcal strains were methicillin-resistant (MR. Four strains were resistant to all of the tested antibiotics, and 14 were resistant to all except mupirocin. Strains classified as MR had significantly increased resistance to the remaining antibiotic groups. About one-third of the analysed strains revealed biofilm-forming ability. Among the majority of species, biofilm-forming and non-biofilm-forming strains were distributed evenly; in the case of S. haemolyticus only, negative strains accounted for 92.8%. Susceptibility to copper alloys was different between strains and rather lower than in the case of the SA

Influences of Corrosive Sulfur on Copper Wires and Oil-Paper Insulation in Transformers

Directory of Open Access Journals (Sweden)

Jian Li

2011-10-01

Full Text Available Oil-impregnated paper is widely used in power transmission equipment as a reliable insulation. However, copper sulphide deposition on oil-paper insulation can lead to insulation failures in power transformers. This paper presents the influences of copper sulfur corrosion and copper sulphide deposition on copper wires and oil-paper insulation in power transformers. Thermal aging tests of paper-wrapped copper wires and bare copper wires in insulating oil were carried out at 130 °C and 150 °C in laboratory. The corrosive characteristics of paper-wrapped copper wires and bare copper wires were analyzed. Dielectric properties of insulation paper and insulating oil were also analyzed at different stages of the thermal aging tests using a broadband dielectric spectrometer. Experiments and analysis results show that copper sulfide deposition on surfaces of copper wires and insulation paper changes the surface structures of copper wires and insulation paper. Copper sulfur corrosion changes the dielectric properties of oil-paper insulation, and the copper sulfide deposition greatly reduces the electrical breakdown strength of oil-paper insulation. Metal passivator is capable of preventing copper wires from sulfur corrosion. The experimental results are helpful for investigations for fault diagnosis of internal insulation in power transformers.

Spatial decoupling of light absorption and catalytic activity of Ni-Mo-loaded high-aspect-ratio silicon microwire photocathodes

Science.gov (United States)

Vijselaar, Wouter; Westerik, Pieter; Veerbeek, Janneke; Tiggelaar, Roald M.; Berenschot, Erwin; Tas, Niels R.; Gardeniers, Han; Huskens, Jurriaan

2018-03-01

A solar-driven photoelectrochemical cell provides a promising approach to enable the large-scale conversion and storage of solar energy, but requires the use of Earth-abundant materials. Earth-abundant catalysts for the hydrogen evolution reaction, for example nickel-molybdenum (Ni-Mo), are generally opaque and require high mass loading to obtain high catalytic activity, which in turn leads to parasitic light absorption for the underlying photoabsorber (for example silicon), thus limiting production of hydrogen. Here, we show the fabrication of a highly efficient photocathode by spatially and functionally decoupling light absorption and catalytic activity. Varying the fraction of catalyst coverage over the microwires, and the pitch between the microwires, makes it possible to deconvolute the contributions of catalytic activity and light absorption to the overall device performance. This approach provided a silicon microwire photocathode that exhibited a near-ideal short-circuit photocurrent density of 35.5 mA cm-2, a photovoltage of 495 mV and a fill factor of 62% under AM 1.5G illumination, resulting in an ideal regenerative cell efficiency of 10.8%.

Easy route to superhydrophobic copper-based wire-guided droplet microfluidic systems.

Science.gov (United States)

Mumm, Florian; van Helvoort, Antonius T J; Sikorski, Pawel

2009-09-22

Droplet-based microfluidic systems are an expansion of the lab on a chip concept toward flexible, reconfigurable setups based on the modification and analysis of individual droplets. Superhydrophobic surfaces are one suitable candidate for the realization of droplet-based microfluidic systems as the high mobility of aqueous liquids on such surfaces offers possibilities to use novel or more efficient approaches to droplet movement. Here, copper-based superhydrophobic surfaces were produced either by the etching of polycrystalline copper samples along the grain boundaries using etchants common in the microelectronics industry, by electrodeposition of copper films with subsequent nanowire decoration based on thermal oxidization, or by a combination of both. The surfaces could be easily hydrophobized with thiol-modified fluorocarbons, after which the produced surfaces showed a water contact angle as high as 171 degrees +/- 2 degrees . As copper was chosen as the base material, established patterning techniques adopted from printed circuit board fabrication could be used to fabricate macrostructures on the surfaces with the intention to confine the droplets and, thus, to reduce the system's sensitivity to tilting and vibrations. A simple droplet-based microfluidic chip with inlets, outlets, sample storage, and mixing areas was produced. Wire guidance, a relatively new actuation method applicable to aqueous liquids on superhydrophobic surfaces, was applied to move the droplets.

Preparation of copper and silicon/copper powders by a gas ...

Indian Academy of Sciences (India)

Pure and silicon-coated metal copper nano to submicron-sized powders were prepared by gas evaporation and condensation. This powder was synthesized by using an industrial electron accelerator, ELV-6, with Ar as the carrier gas. Vapour from the liquefied metal surface was transferred to the cold zone by the carrier ...

Cold spray copper coatings for used fuel containers

Energy Technology Data Exchange (ETDEWEB)

Keech, P. [Nuclear Waste Management Organization, Toronto, ON (Canada); Vo, P.; Poirier, D.; Legoux, J-G [National Research Council, Boucherville QC, (Canada)

2015-07-01

Recently, the Nuclear Waste Management Organization has been developing copper coatings as a method of protecting steel used fuel containers (UFCs) from corrosion within a deep geological repository. The corrosion barrier design is based on the application of a copper coating bonded directly to the exterior surface of the UFC structural core. Copper coating technologies amendable to supply of pre-coated UFC vessel components and application to the weld zone following UFC closure within the radiological environment have been investigated. Copper cold spray has been assessed for both operations; this paper outlines the research and development to date of this technique. (author)

Experimental study on the production of high density electron bunches from a GaAs photocathode

International Nuclear Information System (INIS)

Calabrese, R.; Masoli, F.; Gong, J.M.; Guidi, V.; Tecchio, L.

1991-01-01

In order to obtain a high charge, low emittance electron source, useful for FEL electron injector and for e + e - collider experiments, we performed a test experiment on a gallium arsenide photocathode, activated by negative electron affinity technique and illuminated with a 10 ns long laser pulse of 532 nm wavelength. We measured a maximum charge delivered, at relatively low potentials, of about 18 nC/bunch. The mean lifetime is greater than 60 h. (orig.)

He bubble sites in implanted copper alloy

International Nuclear Information System (INIS)

Moreno, D.; Eliezer, D.

1996-01-01

Structural materials in fusion reactors will be exposed to helium implantation over a broad range of energies. The deformation and partial exfoliation of surface layers due to hydrogen isotopes and helium contribute to the total erosion of the first wall. For this reason, one of the most important criteria in the choice of materials for the first wall of fusion reactors is the material's damage resistance. Recent advances in developing nuclear fusion reactors reveal that efficient heat removal from plasma-facing components is very important. Copper and copper alloys are considered an attractive choice for transporting such a high heat flux without thermal damage as they have high thermal conductivity. In the present study the authors report on the structural changes in a copper alloy, due to the helium implantation on the very near surface area, observed by transmission electron microscopy

Specific anion effects on copper surface through electrochemical treatment: Enhanced photoelectrochemical CO2 reduction activity of derived nanostructures induced by chaotropic anions

Science.gov (United States)

Navaee, Aso; Salimi, Abdollah

2018-05-01

Copper derivatives are the most prominent CO2 reduction electrocatalyst. Herein, the metallic copper has been electrochemically treated with some of common ionic salts such as N3bar, HPO2bar, S2bar, Fbar, Clbar, Brbar and Ibar based on the dissolution of a metallic working electrode in an aqueous solution to derive the surface roughness incorporated with nanostructures. Diverse surface morphology can be obtained when the ionic radii of anions are changed. Surface study reveals various roughness shapes based on the size and polarity of the anions, where the ions with higher ionic radii have higher impact on the Cu surface. In comparison, polyatomic oxyanion such as HPO2bar even with large ionic radii do not have enough strength to create the surface roughness than that of oxygen-free anions with large ionic radii. The photoelectrochemical behavior of the modified surfaces toward CO2 reduction is studied at a wide potential window in bicarbonate aqueous solution. Based on our investigations, treated surfaces by Ibar, Clbar and S2bargive a more surface roughness, while Ibar and N3bar offer higher catalytic activity toward CO2 reduction due to possible complexing ability of these anions with Cu cations, followed by formation of the co-catalyst semiconductor and facilitate electron transfer. This methodology can be applied to investigate the effect of ions on transition metals along with obtaining different surface morphologies tailored to different applications.

Thermal Annealing Effect on Poly(3-hexylthiophene: Fullerene:Copper-Phthalocyanine Ternary Photoactive Layer

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H. Derouiche

2013-01-01

Full Text Available We have fabricated poly(3-hexylthiophene (P3HT/copper phthalocyanine (CuPc/fullerene (C60 ternary blend films. This photoactive layer is sandwiched between an indium tin oxide (ITO/poly(3,4-ethylenedioxythiophene:poly(styrene sulfonate (PEDOT/PSS photoanode and a bathocuproine (BCP/aluminium photocathode. The thin films have been characterized by atomic force microscope (AFM and ultraviolet/visible spectroscopy in order to study the influence of P3HT doping on the morphological and optical properties of the photoactive layer. We have also compared the characteristics of three different organic solar cells: ITO/PEDOT:PSS/CuPc0.5:C600.5/BCP/Al and ITO/PEDOT:PSS/P3HT0.3:CuPc0.3:C600.4/BCP/Al with and without annealing. Both structures show good photovoltaic behaviour. Indeed, the incorporation of P3HT into CuPc:C60 thin film improves all the photovoltaic characteristics. We have also seen that thermal annealing significantly improves the optical absorption ability and stabilizes the organic solar cells making it more robust to chemical degradation.

Enhanced photocathodic protection performance of Ag/graphene/TiO2 composite for 304SS under visible light

Science.gov (United States)

Li, Hong; Wang, Xiutong; Wei, Qinyi; Liu, Xueqing; Qian, Zhouhai; Hou, Baorong

2017-06-01

Ag and graphene co-sensitized TiO2 composites were successfully fabricated and used as photoanodes for photogenerated cathodic protection of 304 stainless steel (304SS) under visible light. Graphene films was firstly deposited onto the TiO2 nanotube (NT) films via cyclic voltammetric electrodeposition. Ag/graphene/TiO2 films were then fabricated via dipping and photoreduction method. The morphology, composition and optical response of the Ag/graphene/TiO2 NT composites were characterized by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, UV-vis diffusion reflectance spectroscopy, respectively. The photocathodic protection performance of the Ag/graphene/TiO2 composites were systematically studied through open-circuit potential and potentiodynamic polarization measurements in 3.5 wt% NaCl solution under visible light (λ > 400 nm). The composites exhibited enhanced photogenerated cathodic protection performance for 304SS under visible light irradiation compared to pure TiO2. Graphene and Ag have a synergistic effect on the enhancement of photocathodic protection performance of TiO2. The composites prepared with 30-cycle graphene film and 15 mM AgNO3 solution showed the optimal corrosion protection performance.

Copper-polymer nanocomposites: An excellent and cost-effective biocide for use on antibacterial surfaces.

Science.gov (United States)

Tamayo, Laura; Azócar, Manuel; Kogan, Marcelo; Riveros, Ana; Páez, Maritza

2016-12-01

The development of polymer nanocomposites with antimicrobial properties has been a key factor for controlling or inhibiting the growth of microorganisms and preventing foodborne diseases and nosocomial infections. Commercially available antibacterial products based on silver-polymer are the most widely used despite the fact that copper is considerably less expensive. The incorporation of copper nanoparticles as antibacterial agents in polymeric matrices to generate copper-polymer nanocomposites have presented excellent results in inhibiting the growth of a broad spectrum of microorganisms. The potential applications in food packaging, medical devices, textiles and pharmaceuticals and water treatment have generated an increasing number of investigations on preparing copper based nanocomposites and alternative polymeric matrices, as potential hosts of nano-modifiers. This review presents a comprehensive compilation of previous published work on the subject, mainly related to the antimicrobial activity of copper polymer nanocomposites. Within all the phenomenology associated to antibacterial effects we highlight the possible mechanisms of action. We discuss the differences in the susceptibility of Gram negative and positive bacteria to the antibacterial activity of nanocomposites, and influencing factors. As well, the main applications of copper polymer-metal nanocomposites are described, considering their physical and chemical characteristics. Finally, some commercially available copper-polymer nanocomposites are described. Copyright © 2016 Elsevier B.V. All rights reserved.

XPS studies of short pulse laser interaction with copper

International Nuclear Information System (INIS)

Stefanov, P.; Minkovski, N.; Balchev, I.; Avramova, I.; Sabotinov, N.; Marinova, Ts.

2006-01-01

The effect of laser ablation on copper foil irradiated by a short 30 ns laser pulse was investigated by X-ray photoelectron spectroscopy. The laser fluence was varied from 8 to 16.5 J/cm 2 and the velocity of the laser beam from 10 to 100 mm/s. This range of laser fluence is characterized by a different intensity of laser ablation. The experiments were done in two kinds of ambient atmosphere: air and argon jet gas. The chemical state and composition of the irradiated copper surface were determined using the modified Auger parameter (α') and O/Cu intensity ratio. The ablation atmosphere was found to influence the size and chemical state of the copper particles deposited from the vapor plume. During irradiation in air atmosphere the copper nanoparticles react with oxygen and water vapor from the air and are deposited in the form of a CuO and Cu(OH) 2 thin film. In argon atmosphere the processed copper surface is oxidized after exposure to air

Facile synthesis of gold coated copper(II) hydroxide pine-needle-like micro/nanostructures for surface-enhanced Raman scattering

Science.gov (United States)

Long, Kailin; Du, Deyang; Luo, Xiaoguang; Zhao, Weiwei; Wu, Zhangting; Si, Lifang; Qiu, Teng

2014-08-01

This work reports a facile method to fabricate gold coated copper(II) hydroxide pine-needle-like micro/nanostructures for surface-enhanced Raman scattering (SERS) application. The effects of reaction parameters on the shape, size and surface morphology of the products are systematically investigated. The as-prepared 3D hierarchical structures have the advantage of a large surface area available for the formation of hot spots and the adsorption of target analytes, thus dramatically improving the Raman signals. The finite difference time domain calculations indicate that the pine-needle-like model pattern may demonstrate a high quality SERS property owing to the high density and abundant hot spot characteristic in closely spaced needle-like arms.

Hydrophobic pinning with copper nanowhiskers leads to bactericidal properties.

Directory of Open Access Journals (Sweden)

Ajay Vikram Singh

Full Text Available The considerable morbidity associated with hospitalized patients and clinics in developed countries due to biofilm formation on biomedical implants and surgical instruments is a heavy economic burden. An alternative to chemically treated surfaces for bactericidal activity started emerging from micro/nanoscale topographical cues in the last decade. Here, we demonstrate a putative antibacterial surface using copper nanowhiskers deposited by molecular beam epitaxy. Furthermore, the control of biological response is based on hydrophobic pinning of water droplets in the Wenzel regime, causing mechanical injury and cell death. Scanning electron microscopy images revealed the details of the surface morphology and non-contact mode laser scanning of the surface revealed the microtopography-associated quantitative parameters. Introducing the bacterial culture over nanowhiskers produces mechanical injury to cells, leading to a reduction in cell density over time due to local pinning of culture medium to whisker surfaces. Extended culture to 72 hours to observe biofilm formation revealed biofilm inhibition with scattered microcolonies and significantly reduced biovolume on nanowhiskers. Therefore, surfaces patterned with copper nanowhiskers can serve as potential antibiofilm surfaces. The topography-based antibacterial surfaces introduce a novel prospect in developing mechanoresponsive nanobiomaterials to reduce the risk of medical device biofilm-associated infections, contrary to chemical leaching of copper as a traditional bactericidal agent.

Evaluation of the energetics of copper-vacancy clusters in Fe

Energy Technology Data Exchange (ETDEWEB)

Morishita, Kazunori, E-mail: morishita@iae.kyoto-u.ac.jp; Nakasuji, Toshiki; Ruan, Xiaoyong

2017-02-15

Highlights: • Thermodynamics evaluation of the nucleation process of copper-vacancy clusters in Fe is performed. • Nucleation free energy of copper-vacancy clusters in Fe is formulated. • With this energetics, two different nucleation paths of clusters are found as a function of the damage rate. - Abstract: A theoretical study is conducted to evaluate the nucleation free energy of copper-vacancy clusters in Fe as a function of the numbers of copper atoms and of vacancies in a cluster. Using this free energy value, cluster nucleation processes during irradiation are investigated. The results clearly show that there are two different types of cluster nucleation paths on the free energy surface; one is the formation of empty voids by jumping over the ridge of the free energy surface, and the other corresponds to a path for the formation of copper clusters by going around the ridge. The dependence of easy nucleation paths on the damage rate is discussed.

In vitro studies of copper release from powder particles in synthetic biological media

International Nuclear Information System (INIS)

Midander, Klara; Wallinder, Inger Odnevall; Leygraf, Christofer

2007-01-01

The aim of this paper is to provide quantitative data on copper release from powder particles of different copper materials, including artificial copper patina, Cu 2 O and metallic Cu, when exposed to different synthetic biological media to simulate an inhalation scenario and/or skin contact. Generated data may contribute in risk assessment of potential health effects following exposure to and handling of various copper materials. All tests were performed in vitro to determine total copper concentrations, release rates of total copper, and to elucidate its time-dependence. The copper release process was interpreted in terms of specific surface area, surface morphology-, and composition. All powder materials show a time-dependent release process with total copper release rates less than 3 μg/cm 2 per hour at steady state conditions, for all media investigated. The importance of using relevant test media when simulating different interstitial lung conditions and difficulties encountered when comparing powder particles of essentially different properties are thoroughly discussed. - Copper release rates from particles are essential to assess potential health aspects

Influence of branched quaternary ammonium surfactant molecules as levelers for copper electroplating from acidic sulfate bath

International Nuclear Information System (INIS)

Wang, An-yin; Chen, Biao; Fang, Lei; Yu, Jian-jun; Wang, Li-min

2013-01-01

A family of branched quaternary ammonium surfactants (compounds 1a–1c) with different carbon chains were synthesized for levelers applied in copper electroplating. Their inhibitory actions on copper electroplating were characterized by cyclic voltammetry (CV). Compound 1b, as representative structure type, was tested by means of different electrochemical methods including CV, polarization curve and electrochemical impedance spectroscopy (EIS) with different concentrations. The interaction between compound 1b and copper surface was investigated using atomic force microscope (AFM) and X-ray photoelectron spectra (XPS). The results indicated that our newly synthesized compounds, particular 1b, were effective levelers used for copper electroplating. Compound 1b could adsorb on copper surface to form an adsorption layer. The adsorption behavior of compound 1b on copper surface indicated that compound 1b could inhibit the copper electrodeposition, which provided favorable conditions used as a leveler. Moreover, the addition of compound 1b could increase the cathodic polarization, which was attributed to the adsorption of compound 1b during copper electroplating process. In addition, various surface morphologies and crystalline orientation of the plated copper films caused by different concentrations of compound 1b were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. Effects of compound 1b on refining the grain size and changing the preferential orientation of the plated copper films were exhibited

Bioinspired conical copper wire with gradient wettability for continuous and efficient fog collection.

Science.gov (United States)

Ju, Jie; Xiao, Kai; Yao, Xi; Bai, Hao; Jiang, Lei

2013-11-06

Inspired by the efficient fog collection on cactus spines, conical copper wires with gradient wettability are fabricated through gradient electrochemical corrosion and subsequent gradient chemical modification. These dual-gradient copper wires' fog-collection ability is demonstrated to be higher than that of conical copper wires with pure hydrophobic surfaces or pure hydrophilic surfaces, and the underlying mechanism is also analyzed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effects of grooming on a copper ablative coating: a six year study.

Science.gov (United States)

Tribou, Melissa; Swain, Geoffrey

2017-07-01

More than 90% of US Navy Ships are coated with copper ablative paint. These ships may spend long periods of time pier-side, which makes them vulnerable to fouling. Hull grooming has been proposed as a means of maintaining the coatings in an operational condition. This study investigated the effect of grooming on a copper ablative coating exposed statically for six years. Grooming was performed weekly or monthly with controls left ungroomed. The fouling community was visually assessed, dry film thickness measurements were taken to monitor coating loss, and the copper leaching rates were measured. It was found that weekly and monthly groomed surfaces reduced fouling, and the ungroomed surfaces became fully fouled. Coating loss was similar for weekly, monthly and ungroomed surfaces. The results suggest that grooming is a viable method for maintaining copper ablative coatings in a fouling-free condition without adverse increases in the total copper output.

New Antimony Selenide/Nickel Oxide Photocathode Boosts the Efficiency of Graphene Quantum-Dot Co-Sensitized Solar Cells.

Science.gov (United States)

Kolay, Ankita; Kokal, Ramesh K; Kalluri, Ankarao; Macwan, Isaac; Patra, Prabir K; Ghosal, Partha; Deepa, Melepurath

2017-10-11

A novel assembly of a photocathode and a photoanode is investigated to explore their complementary effects in enhancing the photovoltaic performance of a quantum-dot solar cell (QDSC). While p-type nickel oxide (NiO) has been used previously, antimony selenide (Sb 2 Se 3 ) has not been used in a QDSC, especially as a component of a counter electrode (CE) architecture that doubles as the photocathode. Here, near-infrared (NIR) light-absorbing Sb 2 Se 3 nanoparticles (NPs) coated over electrodeposited NiO nanofibers on a carbon (C) fabric substrate was employed as the highly efficient photocathode. Quasi-spherical Sb 2 Se 3 NPs, with a band gap of 1.13 eV, upon illumination, release photoexcited electrons in addition to other charge carriers at the CE to further enhance the reduction of the oxidized polysulfide. The p-type conducting behavior of Sb 2 Se 3 , coupled with a work function at 4.63 eV, also facilitates electron injection to polysulfide. The effect of graphene quantum dots (GQDs) as co-sensitizers as well as electron conduits is also investigated in which a TiO 2 /CdS/GQDs photoanode structure in combination with a C-fabric CE delivered a power-conversion efficiency (PCE) of 5.28%, which is a vast improvement over the 4.23% that is obtained by using a TiO 2 /CdS photoanode (without GQDs) with the same CE. GQDs, due to a superior conductance, impact efficiency more than Sb 2 Se 3 NPs do. The best PCE of a TiO 2 /CdS/GQDs-nS 2- /S n 2- -Sb 2 Se 3 /NiO/C-fabric cell is 5.96% (0.11 cm 2 area), which, when replicated on a smaller area of 0.06 cm 2 , is seen to increase dramatically to 7.19%. The cell is also tested for 6 h of continuous irradiance. The rationalization for the channelized photogenerated electron movement, which augments the cell performance, is furnished in detail in these studies.

Electrochemical synthesis of highly ordered polypyrrole on copper modified aluminium substrates

International Nuclear Information System (INIS)

Siddaramanna, Ashoka; Saleema, N.; Sarkar, D.K.

2014-01-01

Fabrication of highly ordered conducting polymers on metal surfaces has received a significant interest owing to their potential applications in organic electronic devices. In this context, we have developed a simple method for the synthesis of highly ordered polypyrrole (PPy) on copper modified aluminium surfaces via electrochemical polymerization process. A series of characteristic peaks of PPy evidenced on the infrared spectra of these surfaces confirm the formation of PPy. The X-ray diffraction (XRD) pattern of PPy deposited on copper modified aluminium surfaces also confirmed the deposition of PPy as a sharp and intense peak at 2θ angle of 23° attributable to PPy is observed while this peak is absent on PPy deposited on as-received aluminium surfaces. An atomic model of the interface of PPy/Cu has been presented based on the inter-atomic distance of copper–copper of (1 0 0) plane and the inter-monomer distance of PPy, to describe the ordering of PPy on Cu modified Al surfaces.

Inhibition of copper corrosion in sodium chloride solution by the self-assembled monolayer of sodium diethyldithiocarbamate

Energy Technology Data Exchange (ETDEWEB)

Liao, Q.Q., E-mail: liaoqq1971@yahoo.com.c [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy - Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Yue, Z.W.; Yang, D. [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy - Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Wang, Z.H. [Department of Chemistry, Tongji University, Shanghai 200092 (China); Li, Z.H. [Department of Chemistry, Fudan University, Shanghai 200433 (China); Ge, H.H. [Key Lab of Shanghai Colleges and Universities for Electric Power Corrosion Control and Applied Electrochemistry, Shanghai Engineering Research Center of Energy - Saving in Heat Exchange Systems, Shanghai University of Electric Power, Shanghai 200090 (China); Li, Y.J. [Department of Chemistry, Tongji University, Shanghai 200092 (China)

2011-05-15

Research highlights: DDTC is of low toxicity. DDTC SAM had good corrosion inhibition effects on copper in 3% NaCl solution. DDTC SAM was chemisorbed on copper surface by its S atoms. - Abstract: Sodium diethyldithiocarbamate (DDTC) self-assembled monolayer (SAM) on copper surface has been investigated by SERS and EDS and the results show that DDTC SAM is chemisorbed on copper surface by its S atoms with tilted orientation. Corrosion inhibition ability of DDTC SAM was measured in 3% NaCl solution using electrochemical methods. The impedance results indicate that the maximum inhibition efficiency of DDTC SAM can reach 99%. Quantum chemical calculations show that DDTC has relatively small {Delta}E between HOMO and LUMO and large negative charge in its two sulfur atoms, which facilitates the formation of a DDTC SAM on copper surface.

Thermally modified bentonite clay for copper removal

International Nuclear Information System (INIS)

Bertagnolli, C.; Kleinübing, S.J.; Silva, M.G.C.

2011-01-01

Bentonite clay coming from Pernambuco was thermally modified in order to increase its affinity and capacity in the copper removal in porous bed. The application of this procedure is justified by the low cost of clay, their abundance and affinity for various metal ions. Thermally treatment modifies the clay adsorption properties enables its use in porous bed system, with the increase in surface area and mechanical strength. The material was characterized by x-ray diffraction, thermogravimetric analysis and N_2 physisorption. Then tests were carried out for adsorption of copper in various experimental conditions and evaluated the mass transfer zone, useful and total adsorbed removal amounts and total copper removal percentage. The results showed that the clay treated at higher temperature showed higher copper removal. (author)

Brake wear from vehicles as an important source of diffuse copper pollution

NARCIS (Netherlands)

Hulskotte, J.H.J.; Gon, H.A.C.D. van der; Visschedijk, A.J.H.; Schaap, M.

2007-01-01

In this article we show that brake wear from road traffic vehicles is an important source of atmospheric (participate) copper concentrations in Europe. Consequently, brake wear also contributes significantly to deposition fluxes of copper to surface waters. We estimated the copper emission due to

Bulk Copper Electrodeposition on Gold Imaged by In Situ STM

DEFF Research Database (Denmark)

Andersen, Jens Enevold Thaulov; Bech-Nielsen, Gregers; Møller, Per

1996-01-01

Electrochemical measurements were carried out simultaneously with acquisition of in situ STM images of copper electrodeposition at low cathodic overpotentials and subsequent dissolution from the underlying polycrystalline gold surfaces. The morphologies of the copper deposits were examined...

Surface modification of calcium-copper hydroxyapatites using polyaspartic acid

Science.gov (United States)

Othmani, Masseoud; Aissa, Abdallah; Bachoua, Hassen; Debbabi, Mongi

2013-01-01

Mixed calcium-copper hydroxyapatite (Ca-CuHAp), with general formula Ca(10-x)Cux(PO4)6(OH)2, where 0 ≤ x ≤ 0.75 was prepared in aqueous medium in the presence of different concentrations of poly-L-aspartic acid (PASP). XRD, IR, TG-DTA, TEM-EDX, AFM and chemical analyses were used to characterize the structure, morphology and composition of the products. All techniques show the formation of new hybrid compounds Ca-CuHAp-PASP. The presence of the grafting moiety on the apatitic material is more significant with increasing of copper amount and/or organic concentration in the starting solution. These increases lead to the affectation of apatite crystallinity. The IR spectroscopy shows the conservation of (Psbnd OH) band of (HPO4)2- groups, suggesting that PASP acid was interacted only with metallic cations of hydroxyapatite.

Effect of acrylonitrile on the electrode processes ivolving copper cations

Directory of Open Access Journals (Sweden)

Viktor F. Vargalyuk

2016-03-01

Full Text Available Based on the results of cyclic voltammetry and study of deposits morphology, it has been shown that acrylonitrile does not have significant effect on the mechanism of Cu2+ + 2ē → Cu0 reaction. This distinguishes acrylonitrile from the unsaturated polyfunctional organic substances (acrylic acid, acrylamide which forms stable complexes with Cu2+ ions. Acrylonitrile just inhibits cathodic process by adsorbing on the surface of electrode thus blocking its active sites. But the presence of acrylonitrile significantly changes the mechanism of the anodic process. It has been found that acrylonitrile interacts with surface copper atoms thus forming thermodynamically stable [Cu π-AN]0 π‑complexes. Ionization potential of these π‑complexes is more negative if compare to copper atoms. As the result acceleration of anodic process takes place in the low polarization area. However, since the chemisorption is a slow process the presence of acrylonitrile mainly affects dissolution of the first surface layers of copper atoms. Further ionization of copper atoms runs out directly and requires higher polarization.

Corrosion of copper under Canadian nuclear fuel waste disposal conditions

International Nuclear Information System (INIS)

King, F.; Litke, C.D.

1990-01-01

The corrosion of copper was studied under Canadian nuclear fuel waste disposal conditions. The groundwater in a Canadian waste vault is expected to be saline, with chloride concentrations from 0.1 to 1.0 mol/l. The container would be packed in a sand/clay buffer, and the maximum temperature on the copper surface would be 100C; tests were performed up to 150C. Radiation fields will initially be around 500 rad/h, and conditions will be oxidizing. Sulfides may be present. The minimum design lifetime for the container is 500 years. Most work has been done on uniform corrosion, although pitting has been considered. It was found that the rate of uniform corrosion in aerated NaCl at room temperature is limited by the rate of the anodic reaction, which is controlled mainly by the rate of transport of dissolved metal species away from the copper surface. The rate of corrosion should become controlled by the transport of oxygen to the copper surface only at very low oxygen concentrations. In the presence of gamma radiation the corrosion rate may never become cathodically transport limited. In compacted buffer material, the corrosion rate appears to be limited by the rate of transport of copper species away from the corroding surface. The authors recommend that long-term predictions of container lifetime should be based on the known rate-determining step for the overall corrosion process. 8 refs

Nonlinear dynamic response of cantilever beam tip during atomic force microscopy (AFM) nanolithography of copper surface

International Nuclear Information System (INIS)

Yeh, Y-L; Jang, M-J; Wang, C-C; Lin, Y-P; Chen, K-S

2008-01-01

This paper investigates the nonlinear dynamic response of an atomic force microscope (AFM) cantilever beam tip during the nanolithography of a copper (Cu) surface using a high-depth feed. The dynamic motion of the tip is modeled using a combined approach based on Newton's law and empirical observations. The cutting force is determined from experimental observations of the piling height on the Cu surface and the rotation angle of the cantilever beam tip. It is found that the piling height increases linearly with the cantilever beam carrier velocity. Furthermore, the cantilever beam tip is found to execute a saw tooth motion. Both this motion and the shear cutting force are nonlinear. The elastic modulus in the y direction is variable. Finally, the velocity of the cantilever beam tip as it traverses the specimen surface has a discrete characteristic rather than a smooth, continuous profile

Reaction and nucleation mechanisms of copper electrodeposition on disposable pencil graphite electrode

Energy Technology Data Exchange (ETDEWEB)

Majidi, M.R. [Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, 29th Bahman Bolvard, Tabriz 51664 (Iran, Islamic Republic of)], E-mail: sr.majidi@gmail.com; Asadpour-Zeynali, K.; Hafezi, B. [Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, 29th Bahman Bolvard, Tabriz 51664 (Iran, Islamic Republic of)

2009-01-01

The reaction and nucleation mechanism of copper electrodeposition on disposable pencil graphite electrode (PGE) in acidic sulphate solution were investigated using cyclic voltammetry (CV) and chronoamperometry (CA) techniques, respectively. Electrochemical experiments were followed by morphological studies with scanning electron microscopy (SEM). The effect of some experimental parameters, namely copper concentration, pH, scan rate, background electrolyte, deposition potential, and conditioning surface of the electrode were described. At the surface of PGE, Cu{sup 2+} ions were reduced at -250 mV vs. SCE. It was found that electrodeposition of copper is affected by rough surface of PGE. The nucleation mechanisms were examined by fitting the experimental CA data into Scharifker-Hills nucleation models. The nuclei population densities were also determined by means of two common fitting models developed for three-dimensional nucleation and growth (Scharifker-Mostany and Mirkin-Nilov-Herrman-Tarallo). It was found that deposition potential and background electrolyte affect the distribution of the deposited copper. The morphology of the deposited copper is affected by background electrolyte.

Laser ablated copper plasmas in liquid and gas ambient

Science.gov (United States)

Kumar, Bhupesh; Thareja, Raj K.

2013-05-01

The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (ne) determined using Stark broadening of the Cu I (3d104d1 2D3/2-3d104p1 2P3/2 at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (Te) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ˜590 nm.