Metal Acetate Solutions Research Articles

Two-Step Atmospheric RF-Microplasma Synthesis of Lithium-Ion Battery Cathode

To address the increasing demand for lithium-ion batteries for use in energy storage applications, such as electric vehicles, there is a need to make the cathode synthesis process less energy intensive, as the current method requires a sintering temperature of 650 – 950 °C for up to 12 hours. Radiofrequency (RF) microplasma setups provide an avenue to approach this problem by providing a tunable system that can be operated under atmospheric conditions, with a more efficient transfer of energy in the plasma setup as compared to a thermal furnace. Through an RF-microplasma setup, nickel, manganese, and cobalt (NMC) particles were produced from a metal acetate solution under a plasma assisted chemical vapor synthesis. These produced particles were then sintered for less time and under a lower temperature than traditional cathode synthesis methods, to produce a lithiated NMC type cathode. The product was examined physiochemically and electrochemically to examine its structure and functionality. The produced product was reversibly cycled over 60 times with a peak specific capacity around 150 mAh/g, and with future process refinement could meet the current capacity standards set by more established synthetic routes

High performance metal stearates thermal stabilizers for poly vinyl chloride

Low thermal stability of poly vinyl chloride (PVC) is one of the most serious problems that facing its processing. In the present study some single and mixed metal stearate soaps were prepared, characterized and evaluated for their performance in enhancing and imparts the thermal stability of PVC. Accordingly, calcium stearate, barium stearate, zinc stearate and also the mixed metal stearate salt of calcium, zinc and barium were prepared by the double decomposition of sodium stearate and single or mixed metal acetate solutions. The prepared metal stearates were characterized via spectroscopic analysis (FT-IR and XRD) in addition to micro analysis and thermal gravimetric analysis (TGA). The results showed that the prepared metal stearates are good thermal stabilizers for PVC; also the thermal stability of the prepared (Ca/Ba/Zn) stearate was enhanced when melamine, ammonium poly phosphate, magnesium hydroxide and Ca/Zn phosphate are mixed with it.

Sensitive and selective non-enzymatic glucose detection using electrospun porous CuO–CdO composite nanofibers

Porous CuO–CdO nanofibers with mean diameter of 463 nm and high surface-to-volume ratio were prepared by impregnating electrospun carboxylic-functionalized poly(arylene ether ketone) (PCA-PAEK) nanofibrous webs with metal acetate solution and subsequent calcination. The special morphology was demonstrated to be decided by ion exchange reaction between metal ions and functional groups on polymer. TGA and EDX analysis confirmed that Cd2+ was more readily to react with PCA-PAEK than Cu2+, and the amount of Cu2+ can be decreased by overloading of Cd2+, leading to the degradation of sensing performance. FT-IR proved the existence of the ion exchange reaction and demonstrated the products were highly pure CuO–CdO compounds with EDX and XRD spectra. The products detailedly investigated for direct electrocatalytic oxidation of glucose evaluated cyclic voltammetry and chronoamperometry. CuO–CdO nanofibers modified electrodes exhibited superiorities of good anti-interference, low detection limit and fast response of glucose, attributing to the enhanced conductivity brought by CdO, good electrocatalytic activity brought by CuO and large surface area brought by porous structure. The simple strategy of electrospinning porous nanofibers using PCA-PAEK as templates and combined CuO and CdO with good electrooxidation glucose functions opens a new route to generate novel conductive metal oxide hybrid nanofibers applied for glucose enzymeless sensors.

Improved ZnS nanoparticle properties through sequential NanoFermentation.

Sequential NanoFermentation (SNF) is a novel process which entails sparging microbially produced gas containing H2S from a primary reactor through a concentrated metal-acetate solution contained in a secondary reactor, thereby precipitating metallic sulfide nanoparticles (e.g., ZnS, CuS, or SnS). SNF holds an advantage over single reactor nanoparticle synthesis strategies, because it avoids exposing the microorganisms to high concentrations of toxic metal and sulfide ions. Also, by segregating the nanoparticle products from biological materials, SNF avoids coating nanoparticles with bioproducts that alter their desired properties. Herein, we report the properties of ZnS nanoparticles formed from SNF as compared with ones produced directly in a primary reactor (i.e., conventional NanoFermentation, or "CNF"), commercially available ZnS, and ZnS chemically synthesized by bubbling H2S gas through a Zn-acetate solution. The ZnS nanoparticles produced by SNF provided improved optical properties due to their smaller crystallite size, smaller overall particle sizes, reduced biotic surface coatings, and reduced structural defects. SNF still maintained the advantages of NanoFermentation technology over chemical synthesis including scalability, reproducibility, and lower hazardous waste burden.

Synthesis and characterization of the novel K2NiF4-type oxide Pr2Ni0.9Co0.1O4 + δ

Pr2Ni0.9Co0.1O4+δ (PNCO) powder was synthesized via a freeze drying process by mixing and shock freezing of aqueous metal acetate solutions, vacuum freeze drying of the resulting precursor and thermal treatment to obtain the complex oxide. X-ray powder diffraction and Rietveld refinement confirmed that the material was mainly single phase (<1wt% Pr6O11 as secondary phase) with an orthorhombic K2NiF4-type unit cell at room temperature. Precision thermogravimetry between 30°C and 900°C showed an irreversible mass increase at T≥750°C and pO2=0.2bar which indicated the transition to a higher order Ruddlesden-Popper phase Pr4(Ni,Co)3O10−x and PrOy. Differential scanning calorimetry in pure Ar and 20% O2/Ar showed a structural phase transition from the orthorhombic to a tetragonal modification at approximately 440°C. Thermal expansion measurements between 30°C and 1000°C at different oxygen partial pressures (1×10−3≤pO2/bar≤1) indicated two different regions, corresponding to the orthorhombic low-temperature phase up to 400°C and the tetragonal high-temperature phase from 400°C to 1000°C. The electronic conductivity of PNCO was in the range of 65≤σe/Scm−1≤90 (600–800°C). The chemical surface exchange coefficient for oxygen (kchem) was obtained from in-situ dc-conductivity relaxation experiments between 600°C and 800°C and 10−3bar oxygen partial pressure. At temperatures close to 600°C PNCO exhibited significantly faster oxygen exchange kinetics than the Co-free material Pr2NiO4+δ (PNO). For example, the surface exchange coefficient of PNCO at 600°C was around 2×10−5cms−1, while kchem of PNO was approximately one order of magnitude smaller. However, at 800°C both compounds showed similar oxygen exchange rates due to a lower activation energy of kchem for PNCO (~80kJmol−1) as compared to PNO (~160kJmol−1). Post-test analyses of the specimens used for conductivity relaxation measurements showed the formation of small Pr6O11 particles on the surface.

Supercritical Antisolvent Precipitation of Amorphous Copper-Zinc Georgeite and Acetate Precursors for the Preparation of Ambient-Pressure Water-Gas-Shift Copper/Zinc Oxide Catalysts.

A series of copper–zinc acetate and zincian georgeite precursors have been produced by supercritical CO2 antisolvent (SAS) precipitation as precursors to Cu/ZnO catalysts for the water gas shift (WGS) reaction. The amorphous materials were prepared by varying the water/ethanol volumetric ratio in the initial metal acetate solutions. Water addition promoted georgeite formation at the expense of mixed metal acetates, which are formed in the absence of the water co‐solvent. Optimum SAS precipitation occurs without water to give high surface areas, whereas high water content gives inferior surface areas and copper–zinc segregation. Calcination of the acetates is exothermic, producing a mixture of metal oxides with high crystallinity. However, thermal decomposition of zincian georgeite resulted in highly dispersed CuO and ZnO crystallites with poor structural order. The georgeite‐derived catalysts give superior WGS performance to the acetate‐derived catalysts, which is attributed to enhanced copper–zinc interactions that originate from the precursor.

Preparation of Aqueous Dispersions of TEMPO-Oxidized Cellulose Nanofibrils with Various Metal Counterions and Their Super Deodorant Performances.

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs) with sodium carboxylate groups (TOCN-Na) were nanodispersed in water. The Na+ ions of TOCN-Na were exchanged with other monovalent, divalent, and trivalent metal (M) ions. When an aqueous metal acetate or AlCl3 solution was added to a 0.1% TOCN-Na/water dispersion or TOCN-COOH gel/water mixture under suitable conditions followed by sonication in water, individually nanodispersed TOCNs-M with divalent and trivalent metal counterions were obtained in yields of 24-87%. The amount of metal introduced into TOCN-M was approximately 20-50% of the TOCN carboxylate content when divalent and trivalent metal ions were used. These results indicate that intrafibrillar ionic linkages are selectively formed and these TOCN-M species nanodisperse at the individual nanofiber level without agglomeration in water. Filter papers with adsorbed TOCN-Cu/water and TOCN-Ag/water dispersions efficiently decomposed or adsorbed H2S and CH3SH gases, but filter papers containing fibrous TEMPO-oxidized celluloses with Ag+ or Cu2+ counterions had much lower gas-decomposition efficiencies.

Synthesis and electrochemical performance of the Li-rich cathode material Li1.17Ni0.12Co0.13Mn0.58O2 for lithium-ion batteries

Lithium-riched cathode material for lithium-ion batteries, Li1.17Ni0.12Co0.13Mn0.58O2, was synthesized via crystallization from a solution of metal acetates, followed by a thermal treatment of the material obtained as a powder. The phase, elemental, and granulometric compositions of the material were examined, as well as the morphology of the powder particles obtained. The discharge capacity of the material in relation to the charging voltage was found from the results of electrochemical tests, and endurance tests were performed. The discharge capacity upon 85 charge/discharge cycles at voltages in the range 2.8–4.8 and a current of 0.1C was about 180 mA h g–1.

Influence of Rare-Earth (Doped) on Low-Density Bi&lt;sub&gt;1.6&lt;/sub&gt;Pb&lt;sub&gt;0.4&lt;/sub&gt;Sr&lt;sub&gt;2&lt;/sub&gt;Ca&lt;sub&gt;1.9&lt;/sub&gt;RE&lt;sub&gt;0.1&lt;/sub&gt;Cu&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;δ &lt;/sub&gt;(RE=Nd, Er) Superconductors via Co-Precipitation Method

Effect of Ca doped by rare-earth elements, Nd and Er (x=0.10) on the structural and transport properties of low density Bi1.6Pb0.4Sr2Ca1,9RE0.1Cu3Oδ (RE=Nd,Er) samples have been investigated. The samples have been prepared via co-precipitation (COP) method from precipitate of saturated solutions of metal acetates, iso-propanol solution and oxalic acid. The metal oxalates powder was subjected to thermal treatment of 24 hours calcination at 845oC and mixed with 0.10 g sucrose C12H22O11 which is used as supplementary filler. The pelletized powder was heated for 2 hours at 400 oC and sintered for at 850oC for 48 hours. All samples show a single step transition in the R-T curves. The critical current density (Jc) and transition temperature (Tczero) for both Nd and Er doped with x = 0.10 were found to be lower than standard samples. Tczero obtained varies between 98 K and 66 K. XRD data showed the decrease of volume fraction for the Bi-2223 phase and increase of the volume fraction Bi-2212 phase with the doping of Nd and Er.

Temperature dependence of complex formation constants in aqueous solutions of metal acetates

The equilibrium constants of formation of inner- and outer-sphere cation-anion complexes (ion pairs) in aqueous solutions of different metal acetates in a wide temperature range have been calculated by integrating the density function of distribution of ligands around the cation. The standard Gibbs energies, enthalpies, and entropies of formation of 1: 1 complexes have been calculated. It has been shown that, in all solutions under consideration, contact and solvent-separated ion pairs coexist. A conclusion has been drawn that the temperature dependence of ion association constants is mainly determined by the temperature dependence of the water dielectric constant.

Sol-Gel Synthesis and Characterization of Nanocrystalline Spinel LiMn&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; For Battery Applications

Nanocrystalline spinel LiMn2O4 was synthesized by sol-gel method using aqueous solution of metal acetates (LiOAc·H2O, Mn(CH3COO)2.4H2O) and citric acid as chelating agent. X-ray diffraction measurement showed the peaks at 2θ values corresponding to (111), (311), (222), (400), (331) and (440) planes of cubic spinel LiMn2O4 nanoparticles with average size ~25 nm. FT IR shows all the characteristic peaks of the cubic spinel. TG/DTA measurement showed the weight loss between 100-250 0 C and 300-500 0 C which correspond the endothermic and exothermic processes. An exothermic peak observed at around 400 0 C is due to the thermal decomposition of the ingredients to form LiMn2O4. FE-SEM measurement revealed the formation of small polycrystalline particles of almost spherical morphology with size between 20-30 nm.

Superconductivity of REBa2Cu3O7-δ (RE= Y, Dy, Er) ceramic synthesized via coprecipitation method

The REBa2Cu3O7-δ (RE= Y, Dy, Er) superconducting ceramics have been prepared via coprecipitation(COP) method from nearly saturated solutions of metal acetates and 2-propanol solution of oxalic acid. The metal oxalates powders were subjected to thermal treatment of 12 hours calcination at 900°C. The pelletized powder was sintered for 15 hr at 920°C. All samples showed a single step transition in the R-T curves. The TC(R=0) for samples Dy123, Y123and Er123 and were 93 K, 91 K and 90 K, respectively. XRD data showed single phase of an orthorhombic structure for all samples. SEM micrographs showed large grain sizes that are randomly distributed. These results showed that COP method using metal oxalates starting powders is very effective to synthesize high quality superconductors and shorten the sintering time required due to the formation of sub micron oxalate powders.

Electrochemical study on LiCo 1/6Mn 11/6O 4 as cathode material for lithium ion batteries at elevated temperature

A novel process via sintering of a precursor from the solution of metal acetates by spray-drying technology was used to synthesize Co-substituted LiCo 1/6Mn 11/6O 4 material for lithium ion batteries. The as-prepared particles were identified as single-phase spinel structure without any impurities in the XRD pattern. The SEM image showed that the particles had good cubic shapes and uniform size distribution with sizes of about 100–200 nm. An ex situ XRD technique was used to characterize the first charge process of the LiCo 1/6Mn 11/6O 4 electrode. The result suggested that the material configuration maintained invariability. The electrochemical properties of the synthesized cathode material were investigated using Li-ion model cells at room and elevated temperature, respectively. In the charge/discharge potential of 3.5–4.4 V at 1/10 C rate, the LiCo 1/6Mn 11/6O 4 electrode delivered high initial capacities of 123 and 127 mAh g −1 at 25 and 55 °C, respectively. Electrochemical cycling tests revealed that the capacity fading occurred mainly in the high-voltage region of 4.08–4.40 V, and the fading rate was 0.107% and 0.302% per cycle at 25 and 55 °C, respectively. The excellent cycling stability and low material cost make it an attractive cathode for high-temperature lithium ion batteries.

Mechanism of silver nano-particles formation on α-alumina using supercritical water

Supercritical water impregnation is a novel method, which utilizes high diffusivity of the fluid with hydrothermal synthesis allowing nano-particles to deposit on porous materials in well-dispersed condition. In this work, silver nano-particles were deposited on the surface of α-alumina supports using metal acetate solution. TEM-EDS analyses clearly identified the silver particle of two kinds, those deposited on α-alumina surface and those gathering in bulk phase. Their particle size distribution showed differences in propensity, implying that particle formation were via different mechanism. The difference in particle deposition mechanism was also confirmed from the results of other operational factors investigated. Furthermore, the mechanism of particle deposition to alumina support surface have been proposed based on the experimental results and reported observation of nucleation and particle growth steps during the hydrothermal synthesis. In addition, the mechanism of silver particle formation has been discussed in detail.

Dispersion of magnetic metals on expanded graphite for the shielding of electromagnetic radiations

The composites of nanoparticles of magnetic metals Co, Ni, and Ni–Fe dispersed on the nanolayers of expanded graphite (EG) were prepared by the impregnation of EG with ethanol solutions of metal acetates, followed by drying and reduction in H2. Such composites combined the properties of high electric conductivity of EG and magnetic conductivities of dispersed metals, and thus exhibited the high shielding effectiveness in a wide range of frequencies. Specifically, the composite containing 30%Ni and 70%EG reached the shielding effectiveness of 70–105dB at frequencies from 300kHzto1.5GHz.

Characterization of Bi1.6Pb0.4Sr2Ca2Cu3Oy ceramic superconductor prepared via coprecipitation method at different sintering time

The Bi(Pb)-2223 superconductor has been prepared via coprecipitation (COP) method from solutions of metal acetates and 2-propanol solution of oxalic acid at low temperature (0–2 °C). The metal oxalates powder was subjected to precalcination of 12 h at 730 °C, followed by 24 h calcination at 845 °C. The pelletized powder was sintered for 24, 48 and 100 h at 850 °C. The dominance of high-T C phase was observed for all samples as evidenced in the single step transition of (R–T) curves. The T C(R = 0) for samples sintered at 24, 48 and 100 h were 102, 102 and 104 K, respectively. XRD data showed the tetragonal structure for all samples followed by the enhancement of the 2223 phase as sintering time increased. Ac magnetic susceptibility measurements showed the improvement of the grain connectivity as sintering time increased. SEM micrographs showed large flaky grains of ∼7 μm in size and randomly distributed, which belong to 2223 phase. The degree of grains alignment increased as the sintering time increased.

Synthesis and electrochemical properties of layered Li[Li (1/3− x/3) Cr xMn (2/3−2 x/3) ]O 2 prepared by sol–gel method

The Li[Li (1/3− x/3) Cr x Mn (2/3−2 x/3) ]O 2 (0.15 ≤ x ≤ 0.3) cathode materials were synthesized by sol–gel process using aqueous solutions of metal acetates and citric acid as the chelating agent. The precipitate of metal citrate was dried in a vacuum oven for 10 h at 100 °C. After drying, the gel precursor was calcined at 300 °C for about 10 h. The resulted powder was ground and heated at 900 °C. The structural characterization was carried out by fitting the XRD data with Rietveld program. The samples exhibited a well defined layered structure and the unit cell parameters linearly increased with increasing chromium contents in Li[Li (1/3− x/3) Cr x Mn (2/3−2 x/3) ]O 2 Surface morphology was determined by SEM and HRTEM and it is found that the cathode material consisted of highly ordered single crystalline particles with layered-hexagonal structure. Test cells were assembled and cycled in the voltage range of 2.0–4.9 V with a current density of 7.947 mA/g. Electrode with ( x = 0.2) delivered a high reversible capacity of around 280 mA h/g in cycling.

Synthesis and characterization of LiNi 0.8Co 0.2O 2 as cathode material for lithium-ion batteries by a spray-drying method

Layered structure LiNi 0.8Co 0.2O 2 cathode material for lithium-ion batteries was synthesized by sintering the precursor, which was obtained from the corresponding metal acetate solution via a spray-drying method. The structure, morphology and reaction mechanism of the powders were characterized by means of XRD, SEM and TG-DTA. The electrochemical properties of the LiNi 0.8Co 0.2O 2 cathode were also investigated by using a coin-type cell containing Li metal as the anode in a potential range of 3.0–4.3 V. Upon sintering the spray-dried powders at 750 °C for 24 h, the LiNi 0.8Co 0.2O 2 particles obtained are fine, narrowly distributed and well crystallized. As a result, the synthesized LiNi 0.8Co 0.2O 2 has excellent electrochemical properties. The simple synthesis procedure is time and energy saving, and thus is promising for commercial application.

Formation of Tl 0.85Cr 0.15Sr 2CaCu 2O 7− δ superconductor from ultrafine co-precipitated powders

The Tl 0.85Cr 0.15Sr 2CaCu 2O 7− δ superconductor has been successfully synthesized from ultrafine powders prepared via the co-precipitation method from nearly saturated solutions of metal acetates and 2-isopropanol solution of oxalic acid. The metal oxalates powders were calcined at 600 °C for 20 h. The calcined powders were pelletized and heated for 3, 4 and 5 min at 980 °C. The zero-resistance temperature, T c-zero for samples heated at 3, 4 and 5 min is 88 K, 100 K and 92 K, respectively. XRD results showed the existence of tetragonal structure which belongs to the high- T c 1212 phase. SEM micrographs showed ultrafine grains of about 1 μm or less for samples heated for 3 min. The grain size increases as the heating time is increased. These ultrafine powders can be useful in various applications such as starting material for high temperature superconductor tapes fabrication.

Synthesis of carbon nanotube peapods directly on Si substrates

Carbon nanotubes encapsulating fullerenes, peapods, have been synthesized directly on Si substrates. High-density and high-quality singe-walled carbon nanotubes (SWNTs) were grown on a SiO2∕Si substrate by dip-coating of metal acetate solution and alcohol chemical vapor deposition technique. The caps of SWNTs were opened by annealing in dry air. Then, fullerene doping into the SWNTs was performed by vapor phase doping technique. Encapsulations of C60 and Gd@C82 were confirmed by transmission electron microscopy. Raman scattering spectroscopy was performed for synthesized peapods. From Raman scattering spectroscopy of synthesized peapods, the smallest diameters of the SWNTs capable of fullerene encapsulation were estimated to be 1.28 nm for C60 and 1.43 nm for Gd@C82.