Добірка наукової літератури з теми "Nickel atomic ions"

A nanomagnetic absorbent based on calcium alginate was produced successfully with the maghemite nanoparticles synthesized in situ, i.e., together with the polysaccharide crosslinking reaction. Physicochemical properties of the absorbent were analyzed and its ability to remove Ni(II) and Mn(II) ions from a real metallurgical industry wastewater was evaluated. Kinetic studies of the adsorption of these heavy metals were realized. To ascertain the most suitable quantity of absorbent to remove Ni(II) and Mn(II) from the wastewater, the absorbent mass was varied and adsorption kinetics was also evaluated. The competitiveness between the metals was evaluated to understand the adsorption mechanism. The samples were characterized by transmission electron microscopy, vibrating sample magnetometry, X-ray diffractometry and Mössbauer spectroscopy. The absorbent prepared, in this work, can be classified as a hydrogel. It presented predominant spherical morphology and micrometric dimension, containing atoms of iron and calcium dispersed uniformly in their internal and external surfaces. The synthesized maghemite nanoparticles presented superparamagnetic behavior. Results showed that the adsorption equilibrium time for both ions was about 60 min. The removal percentages from wastewater were 60.5% for nickel and 56.6% for manganese, using 300 mg of hydrogel. Results revealed that the adsorption mechanism is by ionic change between calcium and heavy metals.

I shall now describe a special case of the Lewis acid–base reactions I introduced in Reaction 9. I showed there that a Lewis acid is a species that can accept a lone pair from another incoming species and form a bond to it, that a Lewis base is a species that provides that lone pair, and that the result of this sharing is a complex of the two species joined together by a chemical bond. The important special case I would like to share with you here is when the Lewis acid is a metal atom or ion, especially but not necessarily one drawn from the d-block of the periodic table (a ‘transition metal’). The d-block consists of the elements that make up the skinny central rectangle of the periodic table. They include important constructional metals, such as iron, nickel, and copper, and also the chemically aloof ‘noble’ metals gold, platinum, and silver. The Lewis base that I focus on will be a molecule or ion that also has an independent existence in the wild, such as water, H2O, or ammonia, NH3. In most cases the complex consists of the central metal atom or ion with up to six Lewis bases clustering around it. In this context, the Lewis bases are known as ‘ligands’ (from the Latin for ‘bound’) and I shall use that term here. I don’t want you to think that I am embarking on stratospherically esoteric material again. These metal complexes are hugely important in many aspects of the everyday world. For instance, chlorophyll is a complex of magnesium and is responsible for capturing the energy of the Sun for photosynthesis (Reaction 26). There is hardly a more important molecule. One that comes close in importance is haemoglobin, an elaborate complex of iron, which ensures that oxygen reaches all your cells and keeps you alive. Many pigments are complexes, so your life is decorated and made more colourful by them. Some pharmaceuticals are complexes based on platinum, so one day, perhaps even now, you might be kept alive by one of these artificial complexes.

In the present work, first-principle theory using the functional density theory (DFT) was used in the ABINIT software package using the PBE pseudopotential (norm-conserving pseudopotentials). To determine the structural parameters such as lattice constant, Bulk modules, and energy formation, for the TiO2 anatase phase doped with substitutional and interstitial nickel impurity, oxygen vacancies (VO) are also included in the present work. For this study, the 2x1x1 supercells with 24 atoms and 2x2x1 with 48 atoms were used. Different types of Ni dopants and oxygen vacancies were considered for energy formation using the 2x2x1 supercell. Our results show that the values of network parameters, minimum energy, and Bulk modulus remain constant with the supercell's growth. With the inclusion of Ni in the supercell substituting the Ti-ions, the unit cell volume (V) exhibits a decrease in agreement with ionic radii mismatch between Ti and Ni atoms. However, when entry as an interstitial form a significant increase is shown. The preliminary results of the energy of formation analyzed for the Ni defects show that it is more probable for an interstitial Ni than for a substitutional Ni.

In the present work, first-principle theory using the functional density theory (DFT) was used in the ABINIT software package using the PBE pseudopotential (norm-conserving pseudopotentials). To determine the structural parameters such as lattice constant, Bulk modules, and energy formation, for the TiO2 anatase phase doped with substitutional and interstitial nickel impurity, oxygen vacancies (VO) are also included in the present work. For this study, the 2x1x1 supercells with 24 atoms and 2x2x1 with 48 atoms were used. Different types of Ni dopants and oxygen vacancies were considered for energy formation using the 2x2x1 supercell. Our results show that the values of network parameters, minimum energy, and Bulk modulus remain constant with the supercell's growth. With the inclusion of Ni in the supercell substituting the Ti-ions, the unit cell volume (V) exhibits a decrease in agreement with ionic radii mismatch between Ti and Ni atoms. However, when entry as an interstitial form a significant increase is shown. The preliminary results of the energy of formation analyzed for the Ni defects show that it is more probable for an interstitial Ni than for a substitutional Ni.

In this work, we demonstrate the use of a voltage-applied Atomic Force Microscopy (VAFM) local anodic oxidation nanolithography process to precisely fabricate small (<20 nm) structures from graphene and carbon nanotube material. These graphitic materials have exceptional electrical properties which give them a niche in emerging nanoelectronics applications requiring quantum structures. While several methods for nanoscale patterning of these materials exist, the VAFM nanolithography technique has lately been shown to address the fabrication issues of graphitic nanodevices on the order of tens of nanometers [1]. If the tip is raised sufficiently from the substrate, in high atmospheric humidity, a water meniscus forms between the two (Fig 1). Application of an appropriate electric field between the tip and substrate dissociates the H2O molecules into H+ and OH-. The H+ ions rush towards the negatively charged tip and the OH-ions gather near the positively substrate. The oxygen reacts with the carbon in the graphitic material to form volatile or nonvolatile carbon oxides depending on the voltage applied. This oxidation, coupled with the x-y scanning capability of the AFM allows for thin structure patterning ability. Depending on such process parameters as applied voltage, pulse width, tip dimensions, contact force, and humidity, the oxidation of the graphitic material into carbon oxides enables the formation of insulating trenches or bumps to make any structure or morphology conceivable [2]. This technique can also be performed in the ambient environment, eliminating several fabrication steps, such as the poly(methyl methacrylate) (PMMA) processing required in conventional electron-beam lithography process. We have used the VAFM technique in preliminary studies to cut few layer graphene and “draw” insulating patterns on highly ordered pyrolyzed graphite (HOPG). A negative bias of 10V applied to the AFM tip with no feedback in a high humidity atmosphere created 0.5 nm deep trenches spaced 27 nm apart. Preliminary experiments have also been conducted on 50 nm diameter multi-walled carbon nanotubes. A negative bias of 5V to the AFM tip pulsed for 100 ms segmented the multi-walled nanotube at selected points. Single wall carbon nanotubes were grown using chemical vapor deposition. Graphene was mechanically exfoliated and prepared using methods described elsewhere [3] on 300 nm SiO2 on Si substrate. The samples were connected electrically to ground and placed in an AFM system (Pacific Nanotechnology NANO-I) with environmental control. The samples were imaged in contact mode with an electrically conductive sharp AFM tip after which humidity was raised to 40–45%. Once the humidity was sufficiently raised, the tip was raised from the desired location on either the Carbon nanotubes or graphene/graphite and feedback was turned off. Patterns were drawn by the tip in this configuration with applied tip voltage running anywhere from −5V to −10V. See Figs. 2 and 3 for results on graphene and carbon nanotubes. Currently, a parametric study on AFM lithography on graphene and carbon nanotubes is underway. By varying voltage, humidity, tip speed, dwell time, and tip-substrate distance, we will determine the optimal conditions required to accomplish precise patterning of graphene and controlled segmentation of carbon nanotubes. In conclusion, we have demonstrated a voltage-applied technique utilizing an atomic force microscope tip to pattern nanoscale features on graphitic materials. A systematic study on oxidation parameters is forthcoming.