Metal Purity Research Articles

The role of low-energy electrons in focused electron beam induced deposition: four case studies of representative precursors.

Focused electron beam induced deposition (FEBID) is a single-step, direct-write nanofabrication technique capable of writing three-dimensional metal-containing nanoscale structures on surfaces using electron-induced reactions of organometallic precursors. Currently FEBID is, however, limited in resolution due to deposition outside the area of the primary electron beam and in metal purity due to incomplete precursor decomposition. Both limitations are likely in part caused by reactions of precursor molecules with low-energy (<100 eV) secondary electrons generated by interactions of the primary beam with the substrate. These low-energy electrons are abundant both inside and outside the area of the primary electron beam and are associated with reactions causing incomplete ligand dissociation from FEBID precursors. As it is not possible to directly study the effects of secondary electrons in situ in FEBID, other means must be used to elucidate their role. In this context, gas phase studies can obtain well-resolved information on low-energy electron-induced reactions with FEBID precursors by studying isolated molecules interacting with single electrons of well-defined energy. In contrast, ultra-high vacuum surface studies on adsorbed precursor molecules can provide information on surface speciation and identify species desorbing from a substrate during electron irradiation under conditions more representative of FEBID. Comparing gas phase and surface science studies allows for insight into the primary deposition mechanisms for individual precursors; ideally, this information can be used to design future FEBID precursors and optimize deposition conditions. In this review, we give a summary of different low-energy electron-induced fragmentation processes that can be initiated by the secondary electrons generated in FEBID, specifically, dissociative electron attachment, dissociative ionization, neutral dissociation, and dipolar dissociation, emphasizing the different nature and energy dependence of each process. We then explore the value of studying these processes through comparative gas phase and surface studies for four commonly-used FEBID precursors: MeCpPtMe3, Pt(PF3)4, Co(CO)3NO, and W(CO)6. Through these case studies, it is evident that this combination of studies can provide valuable insight into potential mechanisms governing deposit formation in FEBID. Although further experiments and new approaches are needed, these studies are an important stepping-stone toward better understanding the fundamental physics behind the deposition process and establishing design criteria for optimized FEBID precursors.

Supported Pt nanoparticles for the hydrogen mitigation application

Accidents at TMI, USA and the recent one at Fukushima, JAPAN has emphasized the need for mitigation of hydrogen generated in nuclear reactor containment during accidental conditions. Passive Autocatalytic Recombiner (PAR) is one of the best solutions to deal with such situations during loss of coolant accidents. A novel breed of catalysts based on cordierite supported Pt nanoparticles has been prepared by chemical reduction route for mitigating the hydrogen generated during such accidents. These catalysts have been characterized for their phase purity, surface composition, surface area, particle size, morphology and elemental loading of the noble metal. The supported noble metal particles are found to be of 7 nm–11 nm dimensions, depending on the extent of noble metal loading. The catalytic activity of these catalysts has been evaluated in presence and absence of various prospective contaminants like carbon monoxide, carbon dioxide, methane, humidity, and condensed water in a laboratory scale reactor. Developed catalysts have been found to be catalytically active for H2–O2 recombination reaction in presence of 100% relative humidity and 2000 ppm of carbon monoxide.

Impurities Effect on Carbonate Reactive Crystallization for the Wastewater

Reactive crystallization designed to separate nickel or copper ion from effluents has been advanced for applying to actual industrial wastewater containing impurities. In the primary reaction of this method, metal sulfate solution reacts with sodium carbonate solution in a semibatch crystallizer. In the present study, during the process of nickel or copper ions incorporation, inhibitory effect on seed growth of impurities, like cobalt, manganese, zinc, and borate and phosphate ions, was investigated. Through the 8-hour reactive crystallization, obtained particles’ characters and metals removal efficient were examined. Considering analyses data on metal component ratio in produced crystals, metal ions initial uptake rate was found to be different by the kind of seeds and impurities. And the centrifugation was performed against obtained crystals aimed for examining target metal purity improvement. The results indicated that copper components can incorporate and remove other metal ions easily. In addition, when the anions are used as impurities, depending on the kind of anions, the effect of damaging the surface of seeds or producing many fine particles has been confirmed.

Mass Cytometry: Protocol for Daily Tuning and Running Cell Samples on a CyTOF Mass Cytometer

In recent years, the rapid analysis of single cells has commonly been performed using flow cytometry and fluorescently-labeled antibodies. However, the issue of spectral overlap of fluorophore emissions has limited the number of simultaneous probes. In contrast, the new CyTOF mass cytometer by DVS Sciences couples a liquid single-cell introduction system to an ICP-MS. Rather than fluorophores, chelating polymers containing highly-enriched metal isotopes are coupled to antibodies or other specific probes. Because of the metal purity and mass resolution of the mass cytometer, there is no "spectral overlap" from neighboring isotopes, and therefore no need for compensation matrices. Additionally, due to the use of lanthanide metals, there is no biological background and therefore no equivalent of autofluorescence. With a mass window spanning atomic mass 103-203, theoretically up to 100 labels could be distinguished simultaneously. Currently, more than 35 channels are available using the chelating reagents available from DVS Sciences, allowing unprecedented dissection of the immunological profile of samples. Disadvantages to mass cytometry include the strict requirement for a separate metal isotope per probe (no equivalent of forward or side scatter), and the fact that it is a destructive technique (no possibility of sorting recovery). The current configuration of the mass cytometer also has a cell transmission rate of only ~25%, thus requiring a higher input number of cells. Optimal daily performance of the mass cytometer requires several steps. The basic goal of the optimization is to maximize the measured signal intensity of the desired metal isotopes (M) while minimizing the formation of oxides (M+16) that will decrease the M signal intensity and interfere with any desired signal at M+16. The first step is to warm up the machine so a hot, stable ICP plasma has been established. Second, the settings for current and make-up gas flow rate must be optimized on a daily basis. During sample collection, the maximum cell event rate is limited by detector efficiency and processing speed to 1000 cells/sec. However, depending on the sample quality, a slower cell event rate (300-500 cells/sec) is usually desirable to allow better resolution between cells events and thus maximize intact singlets over doublets and debris. Finally, adequate cleaning of the machine at the end of the day helps minimize background signal due to free metal.

Structural characterization of He ion microscope platinum deposition and sub-surface silicon damage

In this paper we studied helium ion beam induced deposition (HIBID) of Pt on a silicon wafer using the recently commercialized helium ion microscope (HIM) at 25 kV and low beam currents. The motivation of this work was to understand the impact of light, inert helium ions on deposition rate and structure purity, with some implications on the usefulness of HIM nano-machining for circuit modification. Two Pt-rich deposits with sub-micron dimensions were grown with HIBID at different ion beam currents. The pillar and substrate structure were studied using bright and dark field TEM images. The authors analyzed metal purity profile of the HIBID deposit on height using energy dispersive x-ray spectroscopy. The maximum Pt content measured reached 41%, which is the highest measured metal content of a HIBID-grown structure. TEM studies of the sub-surface damage to the Si shows more damage below the deposit grown at a higher beam current. The differences in amorphization layer thickness between the two different beam currents are discussed. A comparison to Pt deposition by Ga FIB and electron beam induced deposition is provided, along with conclusions regarding the usage of HIBID technology for circuit modification.

Recovery of indium from etching waste by solvent extraction and electrolytic refining

A large amount of an etching waste containing indium is wasted by plants manufacturing liquid crystal displays. In this study, the recovery of indium from the etching waste by solvent extraction and electrolytic refining was investigated. Initially, major impurities, such as aluminum and molybdenum, were removed by dissolution using sodium hydroxide. From the resulting etching cake, solvent extraction of indium was studied for the extractant of PC88A. Indium was extracted efficiently in an acidity range of 0.1 to 0.5mol/dm3 (MH+). PC88A extracts indium, aluminium, molybdenium, and iron from the HCl medium, but indium could be selectively stripped from the loaded solvent. The conditions for continuous running on a pilot scale using PC88A were obtained. The resulting indium solution was further purified to metal by electrolytic refining so that the final purity of the indium metal was 99.997%.

Effect of aluminum and calcium on the ductility of thin sheet shipbuilding steel in the Z-direction

Features of extra-furnace refining technology are considered for high-strength shipbuilding steel sheet, with which high metal purity is provided with respect to non-metallic inclusions. It is demonstrated that the maximum ductility of sheet in the Z-direction is achieved due to optimizing the aluminum and calcium content in the steel.

Transmission electron microscopy study of the microstructure of a YCu ductile intermetallic compound, the influence of the start metal purity

A YCu intermetallic compound made with commercial-purity yttrium metal by arc melting was investigated by transmission electron microscopy (TEM). TEM analyses showed the presence of second phases within the YCu. One phase was identified as a cubic Y 2 O 3 with lattice parameter a = 1.06 nm and the other was an orthorhombic YCu 2 with lattice parameters a = 0.43 nm, b = 0.68 nm and c = 0.73 nm. (1 0 1) twins were observed in the YCu 2 phase. The mechanisms of phase formation are discussed.

Aluminum production by carbothermo-chlorination reduction of alumina in vacuum

Aluminum production by carbothermo-chlorination reduction of alumina in vacuum was investigated by XRD, SEM, EDS and thermodynamic analysis. Thermodynamic calculations indicate that AlCl(g) generated by carbothermo-chlorination process among Al 2O 3-C-AlCl 3 system should be at 1 377–1 900 K (100 Pa) and AlCl (g) will disproportionate into aluminum and AlCl 3(g) below 950–1 050 K at 10–10 2 Pa. Experimental results demonstrate that Al 4O 4C and Al 4C 3 begin to be formed by Al 2O 3-C system over 1 698 K (40–150 Pa). It is Al 4O 4C and Al 4C 3 but not Al 2O 3-C that participate in the carbothermic-chlorination reaction. Temperature for AlCl(g) generated by Al 4O 4C-AlCl 3-C, Al 4C 3-Al 2O 3-AlCl 3 and Al 4O 4C-Al 4C 3-Al 2O 3-AlCl 3-C system is 1 703–1 853 K (40–150 Pa). Aluminum metal is produced by AlCl(g) disproportionation process below 933 K. The average purity of aluminum metal reaches 95.32%, which has perfect crystallization and uniform grain size.

Mass Spectrometric Study of the Impurity Profile in Zn During Reduction-Distillation of ZnO with Activated and Inactivated Al

In this work, we report on the application of hyphenated gas source mass spectrometry to study and understand the mechanism of the reduction-distillation of ZnO using Al powder as reductant in its activated and inactivated form. The experiments revealed that the purity of the Zn metal produced were superior using activated Al with respect to inactivated Al, i.e., m5N8 (99.9998% metallic based) versus m5N3. The achieved purity levels of Zn and the absence of high volatile Cd, Mg, and Sb impurities in the gas phase and the material collected were explained with respect to the impurity elements free-energy values, vapor pressure data, and an observed scavenging effect of the Ta crucible, which was supported by the on-line observed mass spectrometric profiles of the residual gas.

Estimating the working life of steel beams on the basis of their mechanical properties

Forged steel 50 rollers are used in the roughing group of wire and small-rod mills. In intense rolling, the roller pin often breaks, since the pin experiences the maximum stress. It is established that the fracture is of fatigue type, and three disintegration zones are identified. Crack propagation is due to the stress in the crack tip. The rate of crack propagation in cyclic loading depends on the structure of the metal, the grain size, and the mechanical properties of the rollers. The unbroken rollers are characterized by high values of the impact strength, initial and final temperatures of ingot forging, and σy/σB. An empirical dependence of the number of roller rotations to pin fracture on the mechanical properties of the material and the loads is established. Small-grain structure of the metal matrix and purity of the metal ensure a good combination of strength and plasticity.

Effect of metal purity and testing procedure on surface tension measurements of liquid tin

The surface tension of liquid tin of three different grades of purity (99.85, 99.96, and 99.999%) was measured by the classical sessile drop method over the temperature range 523–1023 K, in heating and cooling regimes. The results obtained show that the metal purity affects the values of surface tension and its temperature dependence. The highest values of surface tension and smooth linear temperature dependence were obtained in cooling regime for tin of the highest purity. With increasing content of impurities, both surface tension and its temperature coefficient decrease while the scatter of the data increases. The surface tension values measured on heating regime show higher scatter, compared to those obtained in cooling regime, and the temperature dependence of the surface tension is curvilinear rather than linear.

Spallation Behavior of Thermally Grown Nickel Oxide on Nickel

Thermally grown oxide scales are often under compressive residual stresses, especially upon cooling, which can lead to spontaneous spallation and a loss of their protectiveness. This study uses nickel oxide formed on different purity of nickel as an example to investigate the spallation process. Samples oxidized after different times between 800 and 1100 °C were observed during cooling. The oxide scale buckled and spalled after reaching a critical thickness that depended on oxidation temperatures, substrate thickness, and metal purity. The observed buckling was only a secondary process that followed scale delamination under local tensile stresses at sample edges or corners. When the delamination eventually extended over a large enough area on the face of the specimen, the scale above it buckled, driven by the residual compressive stress in the oxide. Growth of the buckles took place by crack extension along regions of high pore densities in the oxide scale. The development of pores in the oxide layer, which depended strongly on substrate impurity levels, was found to be the most important factor controlling failures of the NiO scales. Sulfur segregated on pore surfaces, whereas TEM studies showed no S at NiO/Ni interfaces.

Study of Physical Treatment of Spent Military Use Lithium Primary Batteries for Recycling

ABSTRACT Physical treatment of lithium primary batteries without explosion is required to recycle the lithium primary batteries which could be exploded by heating too much or crushing. The safe dismantlement method of the spent lithium primary batteries has been required to recycle the batteries because the batteries contain lithium metal although the batteries are discharged. In the present study, safe dismantlement of the spent batteries was investigated, and then feasibility study was performed to recycle scraps of the spent batteries. As written above, the batteries were safely crushed, and metals such as nickel were recovered. Further study was required to increase recovery ratio and purity of metal.

A general law for liquid metal-onto-ceramic wetting: An electrostatic approach

During the last decades, an intense research effort has been carried out to predict and model the equilibrium reactive wetting contact angle of liquid metals onto diverse ceramic surfaces. The experimental results display a large scattering, which has been attributed to several causes: degree of purity of the liquid metal, adsorption, chemical reactions along the liquid–solid interface, etc. This work presents a model to explain such results. It considers as a basic tool the presence of an electrostatic field generated by the metal impurities-ceramic surface charge transfer. The addition of the corresponding electrostatic force to the Young–Dupré equilibrium equation modifies the equilibrium contact angle in ceramics–metals reactive wetting. The theoretical values are in excellent agreement with the reported values in the literature. Thus, charge transfer and the electrostatic effects associated to that transfer constitute a landmark for the comprehension of the equilibrium wetting angle in metal–ceramic systems.

Structural and optical characterization of ZnO nanocrystalline films deposited by sputtering

Nanocrystalline ZnO thin films were prepared by dc magnetron sputtering in an Ar+O2 gas mixture using two types of targets; one was commercially available zinc metal (purity 99.99%) and the other was pressed Zn metal powder. Influences of the target conditions as well as the oxygen partial pressure on the structural and optical properties were studied. Microstructure of the films was investigated using X-ray diffraction and scanning electron microscopy the optical properties were examined using UV–Visible spectrophotometer. The films deposited from metal target showed better aligned c-axis orientation and exhibited better optical properties compared to films prepared from pressed metal powder target.

Corrosion resistance of Zambian silver coin from the “African Wildlife” series

The surface of Zambian silver coin from the “African Wildlife” series is studied by local X-ray fluorescent analysis, mass-spectrometry, and electrode potential measurements. High purity of the coin metal is pointed out. Faint yellow tarnish at some spots on the surface is caused by local contamination during the coin production or storage.

Chemical processing of a low grade molybdenite concentrate to recover molybdenum

The conventional oxidative roasting process, as applied to high grade molybdenite ores (containing ≥54% molybdenum), cannot be applied to low grade sulphide ores/concentrates for a variety of reasons. That is why these ores/concentrates require alternative processing schemes to extract molybdenum metal in a quantitative manner. The present investigation deals with two such processes, namely, soda ash roasting and lime enhanced carbothermic reduction that were successfully applied to extract molybdenum from an indigenous (and low grade) molybdenite concentrate (MoS2).These processes yielded molybdenum in the form of molybdenum trioxide (MoO3) and molybdenum metal respectively. MoO3 and molybdenum metal, so prepared, were further refined by carbon adsorption desorption and molten salt electrorefining techniques respectively. The final purity of MoO3 and molybdenum metal were 99·9% and 99·8% respectively. These processes offered effective measures to contain environmental pollution and bypass tedious off gas treatment procedures, which, otherwise, are two major problem areas in the traditional processing of high grade MoS2 ores/concentrates.

Processing Impact on Electrical Properties of Lanthanum Silicate Thin Films

AbstractThe consequence of tungsten metal purity on the electrical properties of an annealed MOS gate stack with a lanthanum silicate gate dielectric has been investigated. Optimization of the electrical and physical properties of a device with any given dielectric requires the proper choice of metal gate electrode and capping layer. This study is intended to show the importance of tungsten processing optimization and subsequent effects on the equivalent oxide thickness, fixed charge, and density of interface states of La-Si-O gate dielectric MIS devices. In the experiment, La-Si-O films of physical thickness of 1.6 nm were deposited on a Si substrate, subsequently depositing TaN as the gate electrode and W as a capping layer. A post metallization anneal in flowing nitrogen at 1000°C for short times resulted in widely different measured properties of the MIS devices, dependent on the quality of the tungsten deposited. XRD and SIMS profiles of the gate stacks showed a clear relationship between concentration of oxygen and processing of the tungsten. A 1000°C, 10 sec anneal resulted in an EOT change from 1.1 nm to 2.2 nm on gate stacks with low and high oxygen concentration in the tungsten, respectively. Defect densities decreased with increased anneal temperature and time, and annealing with low oxygen-concentration tungsten resulted in higher effective fixed charge. SIMS data suggests that oxygen in the tungsten diffuses to the Si/La-Si-O interface through the TaN electrode, resulting in the observed differences in the defect densities and EOT.

Powder metallurgical processing and metal purity: A case for capacitor grade sintered tantalum

The paper reviews the role of sintered tantalum as volumetric efficient electrical capacitor. Powder characteristics and sintering aspects are discussed. The role of impurities in influencing the electrical properties has been described. Today’s driving force behind the Ta market is the use of surface mounted versions known as chip types, for applications requiring a wide range of operational temperature, such as automotive electronics.