1M Solution Research Articles

Experimental Tests on Solvent Solutions for the Recycling of Coated Polypropylene in Food Packaging

The aim of this research is to analyze and develop technical methods that allow the recycling of food packaging coated in polypropylene films using solvents for the removal of the lacquer and/or aluminum layer without modifying their mechanical properties. Thus, this would allow the regranulation and re-extraction of the treated material for the creation of new polypropylene films. Water solutions of KOH 1M and methanol 99.9% were tested as solvents using the selective dissolution method. In order to rule out a significant effect of the mechanical stirring action on the removal of the surface layer, a deionized water solution was used as a control sample. By means of UV-VIS-NIR (ultraviolet, visible, near-infrared), LWIR (long-wave infrared), and ATR-IR spectrophotometers, spectrophotometric analyses were carried out on the samples before and after treatment. In order to investigate the efficiency of the solvents in removing the coating of polypropylene films, samples taken from the industry Jindal Films Europe Brindisi s.r.l., named BF (basic film, pp film not lacquered or metallized), AC (aluminum-coated pp film), and ACRC (acrylic-lacquer-coated pp film), were compared with samples treated with solvent solutions. The comparison was made by comparing the spectra obtained from the analyses carried out with the two different spectrophotometers. The absorbance values at the level of characteristic polypropylene spectrum peaks, detected with an ATR-IR, were also compared using the Pearson correlation coefficient. The results suggest that the optimal solvent for removing the aluminum and acrylic lacquer from pp films is the solution of KOH 1M. Future analyses will aim to investigate the maintenance of the mechanical characteristics of polypropylene treated with a selective dissolution using KOH. It is also planned to test the methodology of this study on an industrial scale.

Fabricated of the SCC Reference Specimen for Increasing of In-Service Inspection Accuracy in Nuclear Power Plant

To achieve the safety assurance of the nuclear power plants, in-service inspection have were enforced periodic for nondestructive test in weldment. Among them, the ultrasonic evaluation is widely used for the measurement of the defects. Generally, non-destructive inspectors have calibrated a UT machine using the reference specimen in the artificial cracks such as EDM, mechanical notch. As the reflected ultrasonic signal of real crack was detected amplitude value 50% lower than artificial cracks. Therefore, domestic ultrasonic inspectors have a little experience in measuring actual cracks generated in the nuclear power plant field, such as SCC(Stress corrosion cracks, below SCC) and thermal fatigue cracking. Accordingly, in order to improve the inspection accuracy of non-destructive inspectors during operation inspection of nuclear power plant structures, it is necessary to have a lot of experience in inspecting actual cracks.In this study, non-penetration SCC for using in educational specimen of the NDT inspector were fabricated by using the simulated nuclear environment system in base metal of STS 304 pipe. The size of the used pipe were 8 inch(80 sch., thickness 12.7mm). The end of the pipe was used a flange to simulating a fixed environment of the nuclear power plant structure. To accelerate the fabrication of SCC, a corrosive environment was composed by used a blending corrosion solution of the NaOH 1M and Na2S9-H2O 0.1M inside the pipe. The potential of hydrogen of the caustic solution was 14. The fabricated SCC was confirmed for crack size and shape by used UT and RT.

Cyclic Voltammetric Studies of Micro and Nano Paracetamol Using Glassy Carbon Electrode Modified with Multi-Walled Carbon Nanotube and Graphene

The glassy carbon electrode (GCE) was modified with multiwalled carbon nanotube (MWCNT) and graphene (MWCNT/GCE), (graphene/GCE) to study the electrochemical behaviour of paracetamol using cyclic voltammetric technique at different paracetamol particles size (186μm, 4-9μm, 45nm) in a 10 ml solution of (1M) KCl and (0.1mM) paracetamol at scan rate (0.1 V/s). The results of cyclic voltammogram showed the anodic current peaks of paracetamol increases with decrease particle size. Also, the solubility is enhancement with decreasing particle size. MWCNT/GCE is a good biosensor with high electrochemical sensitivity for paracetamol than graphene/GCE.

Pulse Electrodeposition of Polyaniline/Mn-Fe Binary Metal Hydroxide Composite Cathode Material for a Zn-Ion Hybrid Supercapacitor

Rechargeable aqueous zinc-ion hybrid supercapacitors and zinc-ion batteries are promising as safe energy storage systems because they combine the advantages of the high energy density of batteries and high power density of supercapacitor. This paper presents the elaboration of polyaniline (PANi)/Mn-Fe binary metal hydroxide (MnFe-BMH) composite cathode material and Zn anode for a Zn-ion hybrid supercapacitor (ZHSC) by electrochemistry. Two electrochemical techniques (voltage pulse and stepwise voltage) are carried out to perform different morphologies and structures of material modifying the cathode and anode electrodes. The ZHSC is packaged with a gel electrolyte solution of ZnSO4 1M and MnSO4 0.1M. Electrochemical performance of electrode materials and full-cell capacitors are studied by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements. The composite material for electrode modification has an outstanding specific capacitance of 470.3 F/g (167 Wh/kg) at a scan rate of 5 mV/s. Furthermore, this as-prepared electrode also shows excellent cycling stability with 94.6% capacity retention after 11,602 cycles. This demonstrates an improvement in endurance and energy density compared to the industrial SC electrodes.

Autocatality effect of AlCl3 applications on the oxidation process of amorphous Al87Ni8Y5 alloy in 0.5 M aqueous NaCl solution

Investigation of corrosion resistance of amorphous metal alloy ( AMA ) from aluminum is carried out in 0.5 M aqueous solutions of NaCl. Cl- ions penetrate the oxide layer through pores or defects and can colloidally disperse the oxide film and increase its permeability . The Al 87 Ni 8 Y 5 were obtained by melt spinning technique in helium atmosphere onto a copper wheel with a circumferential speed of about 30 m/sec (cooling rate = 10 6 К/sec). The method of voltammetry in the potential-dynamic mode showed that the introduction of AlCl 3 (7.4·10 -3 mol/l) in the system of origin reduces the first maximum, which is responsible for the adsorption of Н + on the AMА electrode. A potentiostatic ivestigates of the behavior of Al 87 Ni 8 Y 5 in 0.5 M aqueous NaCl solution with additional elements AlCl 3 indicates the autocatalytic properties of a low concentration of AlCl 3 (2·10 -7 mol/l), which contributes to the dissolution of the surface. The kinetics of establishing the stationary potential in 0.5 M aqueous NaCl solution and with AlCl 3 applications were chronopotentiometrically investigated. The presence of AlCl 3 ions in the background electrolyte during chronopotentiometry of AMA Al 87 Ni 8 Y 5 in 0.5 M aqueous sodium chloride solution reduces the position of the potential dependence. To independently confirm the influence of Al 3+ and Cl - ions on the processes of formation of protective layers on the surface of Al 87 Ni 8 Y 5 in 0.5 M aqueous NaCl solution using a electron microscope. Micrographs of the alloy surface were taken after VA removal in NaCl background solution 1M application of AlCl 3 , the surface of the alloy in NaCl solution is covered with a thin layer of oxides and hydroxides of aluminum, and due to the sweep potentials in the range of -1000 ÷ +300 mV in the presence of AlCl 3 a multilayer coating is formed. Keywords: amorphous metallic alloys, passivation layers, corrosion resistance.

SINTESIS DAN KARAKTERISASI NPP PERAK (Ag-NPs) MENGGUNAKAN EKSTRAK KULIT BUAH NAGA SEBAGAI BIOREDUKTOR

Silver nanoparticle were successfully synthesized by using the red dragon fruit peel extract as a bioreductor. The synthesis process is mixed the solution of silver nitrate (AgNO3) 1mM and red dragon fruit peel extract with a volume ratio 1 : 5 and and then mixed with a few drops of NaOH solution 1M until the solution has a pH of 10 each and then stirred using magnetic stirrer for 14 minutes for each sample then incubator. The sample are characterized using the Ultra Violet Visible (UV-Vis) spectroscopy resulting in the wavelength peaks and energy band gap at 416 nm and 2.98 eV. A functional group that plays a role in reducting AgNO3 using the Fourier Transform Infra-Red Spectroscopy (FTIR) show six major groups that have interval of 602–3427 cm-1. The result of the X-Ray Diffraction (XRD) spectrum analysis saw a 10.07–102.73 nm crystal size with the Face Center Cubic (FCC) crystalline structure and have an Ag2O impurity. From Scanning Electron Microscope (SEM) image shows that morphology of sample is still agglomerated. The findings of the present research lead to conclusion that the red dragon fruit peel was found to reduced the silver ions to silver nanoparticle.

Influence of Activation Time on Ibuprofen Adsorption Using Zinc Oxide from Gelatin Templating Method

The present work aimed to investigate the performance of activated zinc oxide for ibuprofen adsorption. The zinc oxide was synthesized by the templating method using F127 and gelatine as a soft template and sulfuric acid as a catalyst. The zinc oxide was activated by an HCl solution 1M for 1, 8, and 24 hours. The raw and activated zinc oxides were characterized by XRD and by infrared spectroscopy. The HCl treatment increases both of the numbers of Zn-O-Zn groups and peak of Zn-O from diffractogram but decreases hydroxyl group content. Ibuprofen adsorption studies of kinetics and isotherms were carried out at room temperature with solid-liquid ratio 3:5(v/v) and water-hexane solution. The adsorption properties were correlated to the activated conditions. The isotherms of adsorption were better reproduced by Langmuir–Freundlich models using activated zinc oxide by HCl at 8 hours. The best performance of ibuprofen adsorption resulted from activated zinc oxide at 8h using water-hexane 1:9 as ibuprofen solvent. The activation time and a high ratio of water-hexane both influence the adsorption of ibuprofen performance.

Physicochemical and biological activity studies on complexes of some transition elements with mixed ligands of glycine and urea

The reaction of urea (ur) and glycine (gly) with the metal ions Co(ΙΙ), Ni(ΙΙ) and Cu(ΙΙ) in ethanolic solution of 1M:1L1:1L2 molar ratio (where M= Co(II), Ni(II) and Cu(II), and L1 = urea L2 = glycine) led to the preparation of complexes of the general formula [M(ur)(gly)(H2O)2]Cl. Elemental microanalysis (CHN), molar conductivity measurements, IR,1HNMR, Mass and UV-VIS spectroscopic, and magnetic susceptibility measurements were used for the characterization of the compounds. Thermal analyses were used for the complexes degradation characterization. The complexes have an octahedral geometry and are of electrolytic nature in DMSO solvent with the absence of inner-sphere coordination of the chloride anion. An inhibition zone was observed for Ni-urea-glycine complex against Escherichia coli when the biological activity was considered.

Corrosion Inhibition of Mild Steel in Sulphuric Acid (H<sub>2</sub>SO<sub>4</sub>) Medium of the Stem Extract of <i>Tetrapleura Tetraptera</i>

The inhibitive action of stem extracts of <i>Tetrapleura tetraptera</i> on mild steel corrosion in 1.0M & 5.0M H₂SO₄ solutions was studied. The stem were dried under room temperature and mechanically ground into powder form. 100g of the stem powder were extracted with a mixture of methanol/water in the ratio of 4:1 using a Soxhlet extractor for 24 hours. The extracts were distilled at 60°C in a water bath until almost the entire methanol evaporated. 4.0g of the methanol extracts were digested in 1000ml of 1M H₂SO₄ and 5M H₂SO₄ and left to cool for 24 hours and the resulting solution was filtered and stored in a 1.0L volumetric flask. The stem extracts test solutions were prepared from the stock solution by dissolving 0.5g/L, 1.0g/L, 2.0g/L and 4.0g/L of the extracts in 1L solution of 1M H₂SO₄ and 5M H₂SO₄. Phytochemical analysis was carried out and the result showed the presence of some secondary metabolites such as alkoliods, flavonoids, steroids, saponins and tannins. Weight loss (gravimetric) and gasometric techniques were used to determine the inhibition action of the stem of <i>Terapleaura tetraptera</i>. The results showed that stem of <i>Tetrapleura tetraptera</i> can function as good corrosion inhibitor in acid medium. Inhibition efficiencies (%I) of the stem of <i>Tetrapleura tetraptera</i> extracts was found to reach 73.69% & 50.39% for 1.0M H₂SO₄ while for 5.0M was 83.31% & 79.54% for gravimetric and gasometric analyses respectively. The corrosion inhibition efficiency increased with increase in the concentration of the extracts and decreased with the increase in time and temperature. The corrosion inhibition efficiency exhibited by the <i>Tetrapleura tetraptera</i> stem extracts is attributed to the stronger adsorption of the phytochemicals present in the plant extracts unto the mild steel. The mechanism of adsorption proposed for the <i>Tetrapleura tetraptera</i> stem extracts is physical adsorption. The corrosion inhibition of the stem of <i>Tetrapleura tetraptera</i> extracts followed Langmuir, Tempkin and Freundlich adsorption isotherm for both 1.0M & 5.0M H₂SO₄.

Physicochemical and biological activity studies on complexes of some transition elements with mixed ligands of glycine and urea

The reaction of urea (ur) and glycine (gly) with the metal ions Co(ΙΙ), Ni(ΙΙ) and Cu(ΙΙ) in ethanolic solution of 1M:1L1:1L2 molar ratio (where M= Co(II), Ni(II) and Cu(II), and L1 = urea L2 = glycine) led to the preparation of complexes of the general formula [M(ur)(gly)(H2O)2]Cl. Elemental microanalysis (CHN), molar conductivity measurements, IR,1HNMR, Mass and UV-VIS spectroscopic, and magnetic susceptibility measurements were used for the characterization of the compounds. Thermal analyses were used for the complexes degradation characterization. The complexes have an octahedral geometry and are of electrolytic nature in DMSO solvent with the absence of inner-sphere coordination of the chloride anion. An inhibition zone was observed for Ni-urea-glycine complex against Escherichia coli when the biological activity was considered.

Effectiveness of Modified Natural Zeolite through Acid Activation as A Catalyst on Cellulose Conversion into Glucose from Cotton Assisted by Ultrasonic

This study aimed to convert cotton cellulose into glucose using the catalyst of activated natural zeolite assisted by ultrasonic. The catalyst of hydrolysis of cellulose into glucose used acid-activated natural zeolite. Preparation and activation of natural zeolite used HCl solution 1M, 2M, and 3M. This activated natural zeolite was characterized using Freundlich adsorption isotherms, XRD, and XRF. Hydrolysis of cotton cellulose assisted by ultrasonic-waves was conducted for 1, 2, and 4 hours. Identification of the degradation product used Fehling test and Nelson-Somogyi test. Based on the Freundlich adsorption isotherm analysis, the natural zeolite activated by 1M HCl solution had the largest surface area of 120 m2/g. The XRD diffractogram showed that zeolite before and after the activation process had a similar type structure that is mordenite. Meanwhile, the XRF test showed a decrease in the relative percentage of impurities followed by the increase in Si and Al percentage on activated natural zeolite with Si/Al ratio of 7.13. Based on the Fehling and Nelson-Somogyi test, the highest yield of glucose of 4.51% was obtained when using a catalyst natural zeolite activated with HCl 1 M for 4 hours sonication time.

Synthesis and functionalization of carbon nanotubes and graphene based supercapacitor for arsenic removal and water desalination: A comparison

In this paper, we report a systematic comparison of carbon nanotubes (CNTs) and graphene oxide (GO) adsorption and desalination efficiency at different oxidation level under electrochemical conditions. Particular care has been devoted to the evaluation of the energy storage performance, through a comparison with the capacitive behavior in a typical aqueous electrolyte, a solution 1M of H2SO4. The specific capacitance calculated from the Cyclic Voltammetry (CV) curve at 2mV/sec for as produced purified CNTs (CNTp), highly hydrophilic CNTs (CNTf), partially reduced CNTf (CNTftt) and GO in H2SO4 are respectively 160 F/g, 356 F/g,298 F/g and 145 F/g. We evaluate for our nanomaterials high capacitive deionization (CDI), we also demonstrate that although surface functional groups are essential to provide better contact between electrode and electrolyte leading to high capacitance, however a more preserved electrical structure allows to obtain higher performance (e.g. 135 F/g and 185 F/g for CNTf and CNTftt, respectively).

Evaluation of Corrosion Resistance of Nanotubular Oxide Layers on the Ti13Zr13Nb Alloy in Physiological Saline Solution / Ocena Odporności Korozyjnej Nanotubularnych Struktur Tlenkowych Na Stopie Ti13Zr13Nb W Środowisku Płynów Ustrojowych”

Evaluation of corrosion resistance of the self-organized nanotubular oxide layers on the Ti13Zr13Nb alloy, has been carried out in 0.9% NaCl solution at the temperature of 37ºC. Anodization process of the tested alloy was conducted in a solution of 1M (NH4)2SO4 with the addition of 1 wt.% NH4F. The self-organized nanotubular oxide layers were obtained at the voltage of 20 V for the anodization time of 120 min. Investigations of surface morphology by scanning transmission electron microscopy (STEM ) revealed that as a result of the anodization under proposed conditions, the single-walled nanotubes (SWNTs) can be formed of diameters that range from 10 to 32 nm. Corrosion resistance studies of the obtained nanotubular oxide layers and pure Ti13Zr13Nb alloy were carried out using open circuit potential, anodic polarization curves, and electrochemical impedance spectroscopy (EIS) methods. It was found that surface modification by electrochemical formation of the selforganized nanotubular oxide layers increases the corrosion resistance of the Ti13Zr13Nb alloy in comparison with pure alloy.

Hybrid Inorganic/Organic Membranes for Medium Temperature PEM Fuel Cells

Significant efforts have been made on finding clean and efficient energy sources that will be able to fulfil the needs at a low cost and a minimal environmental impact. Polymer Electrolyte Fuel Cells (PEMFCs) are ideal to work as a clean energy source because there are fuel by hydrogen or methanol and oxygen and generates electricity and water as a secondary product. In PEMFCs research one of the biggest challenges is to be able to work at or above 100 °C because the efficiency of the fuel cell increases with temperature while at the same time the water managing becomes easier, the drawback lies in the need of liquid water in the membrane for good proton transfer. The aim of this work was, using a sulfonated Poly (Ether Ether Ketone) (SPEEK) (1,2)together with inorganic fillers that contain water i.e. lithium-based ceramic particles, to try to develop a membrane able to fill these new requirements. This research is based on a previous studied polymer, sPEEK, and the approach taken is to improve the conductivity by increasing the water content inside the membrane through the use of inorganic compound as ceramic particles that are able to create an adsorbed water layer on top, we believe this extra water content is helping to increase the conduction paths on the membrane and also capable of retain water at higher temperatures and, assuming that the Grötthus hopping mechanism for proton conduction is taking place, increasing the proton conductivity of the sPEEK to the level of Nafion with lower cost for materials and manufacture. Commercial PEEK (Vitrex 450 PF) with a Mw: 39200 gr/mol was sulfonated in a reactor (95/5 v/wt.) with sulphuric acid (98% sigma-aldrich) at 55°C for 5 hours (sulfonation degree [SD] 60% obtain using back titration). Before the reaction, the PEEK was dissolve in the sulphuric acid completely. The solution was then washed with demineralized water until the pH was neutral. (1)The modified polymer was dried in a vacuum oven for 1 week at 120°C. The lithium-based ceramic particles were taken from the cathode materials used in Li ion batteries. (3) LiBPO4 and Li+TiO are the inorganic particles used together with the sPEEK matrix. The membranes were made with sPEEK and different composition in weight of lithium-based ceramic particles. The polymer was dissolve in N,N-Dimethylacetamide (DMAc) at 120°C with a continuous stirring, when the polymer was completely dissolved in the DMAc, the inorganic compound was added and keep under stirring until an homogeneous solution was obtained. The solution was then casted in to petri dishes and left in a fumed hood for three days for evaporation. The membranes obtained was removed with demineralized water and put it in an vacuum oven at 55°C for final removal of traces of the solvent and water. a pre-treatment was done to the membrane in a solution of 1M H2SO­4to activate the protons in the membrane for 1 day, after, the membrane was washed with demineralized water and ready for testing. A material and electrochemical characterization was performed to the hybrid membranes, that includes Differential Scanning Calorimetry (DSC), Thermo Gravimetrical Analysis (TGA), X-Ray Diffraction (XRD), and Electrical Impedance Spectroscopy (EIS). See Figure 1 for partial results. Changes in the water content of the samples can be observe in the TGA measurements as a consequence of the extra water incorporated by the inorganic filler. Difference in the glass transition temperature of the polymer matrix are observed by DSC, presumably by the interaction of the sulfonic groups of the matrix with the inorganic fillers, this behaviour also changes depending on the composition of the membrane. The XRD result shows that the crystalline structure of the inorganic compounds is maintained inside the membrane even in the presence of a strong acid group as the -SO3. Impedance spectroscopy measurements were made to measure the conductivity of the membranes using a commercial cell able to control the temperature and relative humidity in a confined environment. The measurement preform was a 4 point probe in plane conductivity measurement at different temperatures and constant relative humidity. The Activation Energy for the proton conduction was calculated and compare to Nafion and pristine sPEEK in order to try to understand the proton conduction in the new hybrid membranes. The complete images, graph, tables and further results will be presented in the conference. References Journal of Applied Polymer Science, 82 (2001) 2651-2660.Journal of Membrane Science ,226 (2003) 159–167.Industrial and Engineering Chemistry Research, 44 (2005) 7617-7626. Figure 1

Selective extraction of cobalt ions through polymer inclusion membrane containing Aliquat 336 as a carrier

This study reports the selective separation of Co (II) from mixtures of cobalt and nickel solutions using cellulose tri-acetate (CTA)-based polymer inclusion membranes, which incorporated the commercial extractant trioctylmethylammonium chloride (Aliquat 336). Tributylphosphate (TBP) was used as a modifier, and 2- nitro phenyl pentyl ether (2-NPPE) was applied as the plasticiser to prepare the membranes. Several important transport parameters such as the plasticiser concentration, carrier type, carrier concentration, pH of acid, stirring speed, stripping solution type and concentration, complexing reagent (NH4SCN) concentration and synergistic effect of the modifier were discussed. At the optimum conditions, following results were found: plasticiser concentration 0.2 mL, feed solution pH 4, feed phase stirring speed 900 rpm, stripping solution 1M NH3 + 1M TEA, complexing reagent (NH4SCN) concentration 0.5M and modifier TBP 25% w/w. Effective extraction was carried out under these conditions. The recovery factor of the cobalt ions was 100% for 4 h.

Surfactant for Enhanced Rheological, Electrical and Electrochemical Performance of Suspensions for Semi-Solid Redox Flow Batteries and Supercapacitors

Redox-flow batteries (RFBs) store electrochemical energy in two fluids contained in external tanks, so called anolyte and catholyte which are pumped and flow through an electrochemical reactor in which electro-active species are oxidized and reduced. This feature provides to RFBs a unique ability in decoupling the energy and the power, therefore providing a significant design freedom for stationary applications. An interesting concept to deal with the energy density of RFBs, proposed by Chiang et al. [1], consists to use solid electro-active particles suspended in a Li+ containing electrolyte. The interest of such Semi-Solid Flow Cell (SSFC) system has recently been demonstrated with energy density ten times higher compared to classical RFBs [2,3]. Subsequently, Gogotsi et al. proposed an analogous to supercapacitors, the so called electrochemical flow capacitor (EFC) in which the energy is stored in the electric double layer of charged carbon particles [4]. A flowable carbon-electrolyte mixture is employed as the active material for capacitive energy storage, and is handled in a similar fashion to flow as for semi-solid batteries.Performance of SSFC (and EFC) system strongly depends on the flow ability of the anolyte and catholyte suspensions combined with their electronic conductivity which is governed by the extent of the carbon black percolation. In this regards, we have recently investigated the rheological and electrical behaviours of two carbon blacks [5], namely, Ketjen black EC-300 (KB) and C-NERGY Super C45, which differ by their primary particle size, and blends of Li4Ti5O12 (LTO) and KB, suspended in an organic electrolyte, a solution of 1M of Lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) in propylene carbonate (PC). The electrochemical performance of the LTO/KB/PC-LiTFSI suspension was investigated vs. lithium metal electrode as function of the cycling rate in static mode (i.e. no flow) and using a home-made cell that allows studying the influence of the thickness of the suspension [6].Recently, we demonstrated the very beneficial influence of the addition of a nonionic surfactant in the composition of the LTO/KB/PC-LiTFSI anolyte suspension. All practical properties are improved with respect to semi-solid redox flow application. As a matter of fact, the viscosity is decreased, the electronic conductivity is increased and is less affected by the shear flow, and the electrochemical performance is increased. Moreover, a much better stability with time of the suspension is obtained, which means the preservation of its performance with time.

Analysis of SEI on Graphite Anode in Li Ion Cell Using LiMn2O4 Spinel Cathode

Introduction We have been developing large capacity Li ion batteries for backing up of telecommunication apparatuses. Among the many types of Li ion batteries, The LiMn2O4 is convenient for replacing conventional lead-acid batteries, which have been widely used in such backup systems. This is because the LiMn2O4 has a voltage plateau, which is close to that of lead-acid batteries, due to the combination with a graphite anode. On the other hand, long calendar life of more than 10 years at full charge is also required for backup. Mn2+ ion dissolution from the LiMn2O4 cathode is well known, and we have already reported that calendar life is greatly affected by the concentration of dissolved Mn2+ ions [1]. We have postulated the degradation mechanism by charge exchange between Mn2+and intercalated Li [1]; however, the relationships between the amount of Mn deposited on the anode and that of Li consumption, which are calculated from capacity reduction, are unclear.In this study, we analyzed the solid-electrolyte-interface (SEI) on the anode to investigate the role of Mn in the degradation of Li ion batteries for backup. Experimental We used the 18650-type cylindrical Li-ion cell (capacity: about 0.7 Ah) [2]. The cathode was a Mg-doped manganese-spinel and the anode was carbon-coated graphite. We used an ethylene carbonate and dimethyl carbonate based electrolyte containing phosphazene retardant.Sample cells were charged at four voltages (4.05, 4.10, 4.15, and 4.20 V), and the environmental temperature during float charging was maintained at 50°C. The cells were discharged periodically at a current of 0.2 C (at 25°C) to evaluate their residual capacity.Degraded cells were disassembled and six different points of the anode were analyzed. The Mn content was analyzed using an inductively coupled plasma (ICP) method. We also used Li7-nuclear magnetic resonance(NMR) to identify the species on the anode. A LiCl solution of 1M was used as the standard sample. Results Figure 1 shows the lifetime of each floating charge voltage. Lifetime is defined as the duration at which the discharged capacity remains under 70% initial capacity. We found that lifetime decreased greatly between 4.15 and 4.2 V, presumably due to the phenomenon of deterioration caused by electrolyte decomposition since this test was conducted at 50°C. The lifetime at 4.05 V was slightly shorter compared with those at 4.10 and 4.15 V. The reason for this is uncertain.More than 103 times the amount of Li was observed on the degraded anode compared with that of Mg by using the ICP method. This result shows that the simple charge exchange mechanism between Mn2+ and intercalated Li will be rejected. Figure 2 shows the Li7-NMR spectrum of the anode. Two peaks were identified. One was the broad peak of which the chemical shift was -12.2 ppm. The other was that of which the chemical shift was 2.4 ppm. The area of the former was about 98%, and the latter was identified inorganic Li compound. The former may be an organic Li compound, although the chemical species remains unclear. It is known that SEI forms compact inorganic compounds, such as LiF, and organic Li compounds. The results from this study suggest that the formation of organic Li compounds is the main cause of Li consumption and that Mg deposition may accelerate organic Li compound formation. References (1) T. Tsujikawa, K. Yabuta, T. Matsushita, M. Arakawa, K. Hayashi, J. Electrochem. Soc., 158, 322 (2011).(2) T. Tsujikawa, K. Yabuta, T. Matsushita, T. Matsushima, K. Hayashi, and M. Arakawa, J. Power Sources, 189, pp. 429-434 (2009).

An easy way for preparing high performance porous silicon powder by acid etching Al–Si alloy powder for lithium ion battery

We developed a novel, simple method to prepare porous silicon powder by acid etching Al–Si alloy powder. .The morphology and structure of the as-obtained material were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM), and BET methods. It was found that the porous silicon powder (size about 15μm) had a spongy structure, consisting of silicon nanobars with diameter about 50nm and length of 1.5μm. Its specific surface area was 102.8m2g−1. The electrochemical properties of porous silicon electrode were evaluated by measuring voltammograms and charge and discharge curves. The porous silicon electrode with ratio of porous Si powder:Super P:binder=1:1:1 was tested in button style lithium/Si cell. It was found that due to its ability to promote the formation of primal SEI film on the surface of electrodes, additive fluoroethylene carbonate (FEC) had an effect to improve the charge and discharge cycle stability of porous silicon electrodes. In solution 1M LiPF6, EC:DMC=1:1 (V/V) containing 15% FEC, the first charge and discharge capacities of porous silicon electrode were 3450mAhg−1 Si and 2072mAhg−1 Si respectively, at current density 100mAg−1. The discharge capacity retained 66% as 1368mAhg−1 Si after 258 charge and discharge cycles. In 1M LiPF6/EC:DEC=1:1 (V/V) solution, the charge and discharge capacities of porous silicon electrode in first cycle were 3396mAhg−1 Si and 2537mAhg−1 Si respectively. At 69th cycle, the discharge capacity remained 59% as 1497mAhg−1 Si. The high electrochemical performance of porous silicon powder could be attributed to its porous structure, which provides enough tiny space to buffer the huge volume change of Si anode during charging and discharging processes. The nano-size Si bars benefited the diffusion process of lithium in Li–Si alloy. Moreover, the firm connection between Si nanobars in spongy porous structure prevented the breakdown of porous Si particles. This new advanced method for preparing high performance porous Si material is simple and inexpensive, presenting a promising prospect for practical application.

TiO2 Nanotubular Formation on Grade II Pure Titanium by Short Anodization Processing

Electrochemical surface treatment is commonly used to form a thin, rough, and porous oxidation layer on the surface of titanium. The purpose of this study was to investigate the formation of nanotubular titanium oxide arrays during short anodization processing. The specimen used in this study was 99.9% pure cp-Ti (ASTM Grade II) in the form of a disc with diameter of 15 mm and a thickness of 1 mm. A DC power supplier was used with the anodizing apparatus, and the titanium specimen and the platinum plate () were connected to an anode and cathode, respectively. The progressive formation of nanotubes was observed with FE-SEM (Field Emission Scanning Electron Microscopy). Highly ordered nanotubes were formed at a potential of 20 V in a solution of 1M + 1.5 wt.% HF for 10 minutes, corresponding with steady state processing. The diameters and the closed ends of nanotubes measured at a value of 50 cumulative percent were 100 nm and 120 nm, respectively. The nanotubes had lengths of 500 nm. As the anodization processing reached 10 minutes, the frequency distribution for the diameters and the closed ends of the nanotubes was gradually reduced. Short anodization processing for nanotubes of within 10 minutes was established.

Aerobic and anaerobic operation of an active membraneless direct methanol fuel cell

In this paper the operational and architectural flexibilities of a membraneless direct liquid fuel cell were demonstrated under aerobic and anaerobic configurations at 60°C and 1atm. The aerobic membraneless direct methanol fuel cell (DMFC) was fed an anolyte solution of 1M CH3OH/0.5M H2SO4 and an air oxidant. The anaerobic membraneless direct methanol redox fuel cell (DMRFC) was fed an anolyte solution of 1M CH3OH/0.1M HClO4 and a catholyte solution of 2M Fe(ClO4)3 and 0.22M Fe(ClO4)2 oxidant. For both cases the membraneless architecture performed significantly better than for the conventional PEM architecture with Nafion® 117. The maximum power density for the membraneless and Nafion® 117 based DMFC was 52mW⋅cm−2 and 41mW⋅cm−2 respectively. The maximum power density for the membraneless and Nafion® 117 based DMRFC was 46mW⋅cm−2 and 34mW⋅cm−2 respectively. In addition, anaerobic operation using a Fe2+/Fe3+ catholyte gave similar performance to that for air as an oxidant. Both membraneless and anaerobic operation can result in significant cost reduction with improved operational flexibility.