Mixture Of Phosphoric Acid Research Articles

EXTRACTION OF RARE EARTH ELEMENTS FROM SOLID WASTE OF PRODUCTION OF PHOSPHORIC ACID FOLLOWED BY SORPTION ON CATION EXCHANGE RESINS

The basis of production of extraction phosphoric acid is two simultaneous processes: dissolving phosphate raw material in a mixture of sulfuric and phosphoric (formed in the process) acids and crystallization of calcium sulfate (phosphogypsum). Phosphogypsum is an inevitable large-tonnage and cumbersome waste at sulfuric acid processing of apatite, which is of interest not only as a source of building gypsum, but also as an alternative rare earth raw material does not have a natural activity and containing rare-earth elements as a cerium and yttrium groups. As a raw material for the production of rare earth elements, calcium sulfate of three types has been used: phosphogypsum from a sludge accumulator, calcium phosphate phospho-hemihydrate and calcium sulfate phosphate dihydrate from a carousel filter produced by extraction phosphoric acid at JSC "PhosAgro-Cherepovets". The extraction of rare-earth elements from phosphogypsum from a sludge accumulator by leaching (percolation) with inorganic acids with subsequent sorption on cation-exchange resins is considered. As an adsorbent for extracting REE from leach solutions, cationite "Purolite" S-150 is used. A static exchange capacitance of cation exchanger is found that is the capacity of the resin when equilibrium is reached with a solution of a certain volume and composition. The static capacity of cation exchanger for rare-earth elements is 1.57%, which indicates a good absorbing capacity. Desorption of rare-earth elements from the cation exchanger is carried out with a solution of ammonium nitrate. The optimal solution for leaching was found to be sulfuric acid with a concentration of 5% by weight. The degree of extraction of rare-earth elements from phosphogypsum with sulfuric acid is about 82%.Forcitation:Artamonov A.V., Smirnova D.N., Smirnov N.N., Ilyin A.P. Extraction of rare earth elements from solid waste of production of phosphoric acid followed by sorption on cation exchange resins. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 10. P. 87-93

Rational hybrid modulation of P, N dual-doped holey graphene for high-performance supercapacitors

A P, N dual-doped holey graphene (PNHG) material is prepared by a scalable, facile synthetic approach, using a mixture of glucose, dicyandiamide (DCDA), and phosphoric acid (H3PO4). H3PO4 successfully functions as an “acid catalyst” to encourage the uniform breakage of C=C bonds to create large, localized perforations over the graphene monolith. Further acid treatment and annealing introduce in-plane holes. The correlation between the capacitance of the PNHG and its structural parameters during the fabrication process is comprehensively evaluated. A thermally induced sp2→sp3 transformation occurs at high temperatures because of the substantial loss of graphitic sp2-type carbons, together with a dramatic reduction in capacitance. The target PNHG-400 electrode material delivers exceptionally high gravimetric capacitance (235.5 F g−1 at 0.5 A g−1), remarkable rate capability (84.8% at 70 A g−1), superior capacitance retention (93.2 and 92.7% at 10 and 50 A g−1 over 25000 cycles, respectively), and acceptable volumetric capacitance due to moderate density, when it is used with organic electrolytes in the voltage range between 0 and 3 V. These results suggest a pioneering defect-engineered strategy to fabricate dual-doped holey graphene with valuable structural properties for high-performance electric double layer supercapacitors, which could be used in next-generation energy storage applications.

Bottom-up synthesis of aluminophosphate nanosheets by hydrothermal process

Hydrothermal treatment of aqueous mixtures of boehmite (AlOOH), phosphoric acid, and tetramethylammonium hydroxide provided two types of layered aluminophosphates having tetramethylammonium ion (TMA+) as an interlayer cation, despite the fact that TMA+ ion acts as a structure-directing agent of microporous AlPO4 materials and less likely leads to a lamellar structure. The layered aluminophosphates were formed in amorphous gels, so that they were obtained as precipitates. Upon dispersing the precipitates to water under agitation, the layered aluminophosphates were transferred to the aqueous phase, resulting in transparent aqueous sols. Because they had bulky interlayer cation TMA+, it is likely that in the sols, layered aluminophosphates were exfoliated, providing aluminophosphate nanosheets. Moreover, their characterization results suggest that the layered compound formed at 170 °C consisted of aluminophosphate layers with kanemite-like structure. Furthermore, the prolonged hydrothermal treatment at 170 °C led to the formation of microporous ATT-type AlPO4 crystals. Under the synthesis condition employed in this study, layered aluminophosphates were formed at early stage, and then structurally converted to microporous AlPO4 crystals.

Abiotic production of sugar phosphates and uridine ribonucleoside in aqueous microdroplets

Phosphorylation is an essential chemical reaction for life. This reaction generates fundamental cell components, including building blocks for RNA and DNA, phospholipids for cell walls, and adenosine triphosphate (ATP) for energy storage. However, phosphorylation reactions are thermodynamically unfavorable in solution. Consequently, a long-standing question in prebiotic chemistry is how abiotic phosphorylation occurs in biological compounds. We find that the phosphorylation of various sugars to form sugar-1-phosphates can proceed spontaneously in aqueous microdroplets containing a simple mixture of sugars and phosphoric acid. The yield for d-ribose-1-phosphate reached over 6% at room temperature, giving a ΔG value of -1.1 kcal/mol, much lower than the +5.4 kcal/mol for the reaction in bulk solution. The temperature dependence of the product yield for the phosphorylation in microdroplets revealed a negative enthalpy change (ΔH = -0.9 kcal/mol) and a negligible change of entropy (ΔS = 0.0007 kcal/mol·K). Thus, the spontaneous phosphorylation reaction in microdroplets occurred by overcoming the entropic hurdle of the reaction encountered in bulk solution. Moreover, uridine, a pyrimidine ribonucleoside, is generated in aqueous microdroplets containing d-ribose, phosphoric acid, and uracil, which suggests the possibility that microdroplets could serve as a prebiotic synthetic pathway for ribonucleosides.

Oxidation of white phosphorus by peroxides in water

A mixture of hypophosphorous, phosphorous, and phosphoric acids is formed during the anaerobic oxidation of white phosphorus by peroxides [ROOН; R = Н, 3-ClC6H4CO, (СН3)3С] in water. The rate of reactions grows considerably upon adding nonpolar organic solvents. The activity series of peroxides and solvents are determined experimentally. NMR spectroscopy shows that the main product of the reaction is phosphorous acid, regardless of the nature of the peroxide and solvent. A radical mechanism of oxidation of white phosphorus by peroxides in water is proposed. It is initiated by the homolysis of peroxide with the formation of НO∙ radicals that are responsible for the homolytic opening of phosphoric tetrahedrons. Further oxidation and stages of the hydrolysis of intermediate phosphorus-containing compounds yield products of the reaction.

Diethylmethylammonium Trifluoromethanesulfonate/Phosphoric Acid Mixture As Electrolyte for Non-Humidified Intermediate Temperature Fuel Cells

Polymer electrolyte fuel cells (PEFCs) have received more and more attention due to their high energy conversion efficiency and low emissions. Moreover, PEFCs have been used in wide range of applications, such as clean power generation systems for households and vehicles. Perfluorosulfonic acid (PFSA) polymers, such as Dupont’s Nafion®1have been used as electrolyte membranes in PEFCs for decades due to their high proton conductivity, excellent chemical stability and superior durability. However, the membranes require water to retain high proton conductivity, which limits the operating temperature to be below 100 °C, and needs a large humidification system. In order to realize more compact PEFC systems, new electrolytes applicable to intermediate temperature (IT), above 150 ºC, without humidification are needed. Under these conditions, phosphoric acid fuel cell (PAFC) has been applied, but the dehydration condensation of phosphoric acid (PA) still remains as a big problem to diminish its stable operation. Ionic liquids (ILs) have unique properties such as high ionic conductivity, high thermal stability, wide electrochemical potential window and non-volatility. Thus, they have been focused as candidate electrolytes for intermediate temperature fuel cells. In this study, we aimed to achieve the non-humidified intermediate temperature fuel cell by using 3-dimensionally ordered macroporous polyimide (3 DOM PI)/diethylmethylammonium trifluoromethanesulfonate (Dema-TfO)/phosphoric acid (PA) composite membrane. Dema-TfO was synthesized by direct neutralization of the N,N-diethylmethylamine and trifluoromethanesulfonic acid with 1 : 1 molar ratio followed by vacuum drying at 100 °C for 48 h, as a protic IL to prepare the composite membrane. Dema-TfO was added with different ratios of PA. 3 DOM PI was fabricated by using previous method2. 3 DOM PI/Dema-TfO/PA composite electrolyte membrane was then prepared by immersion of 3 DOM PI into the mixture of Dema-TfO and PA under vacuum at 100 °C. Figure 1 showed TG curves for the Dema-TfO/PA mixture. For comparison, the TG curves of Dema-TfO and PA were also provided. It was confirmed that Dema-TfO was thermally stable to 230 ℃. At 180 ℃, which is a target temperature of FC operation, the weight loss ratio of PA was as high as 6%. However, when the mixture was considered, 50 wt% PA in mixture, the loss weight ratio was same with the value of Dema-TfO which was less than 1.5%. Also the detection of 3 DOM PI/Dema-TfO/PA composite membrane showed thermally stable at 180 ℃. The thermally stable property indicated that interaction of mixture suppressed PA dehydration. The mechanism of interaction was explained by FT-IR and NMR analysis. From FT-IR results, the [P(OH)2] antisymmetric stretching in PA and the SO2 symmetric stretching in Dema-TfO showed peak shift when the two functional groups were in the Dema-TfO/PA mixture. On the other hand, in H1 NMR analysis of Dema-TfO/PA mixture, both of the weakened O-H bond in PA and enhanced N-H bond in Dema-TfO compared with pure PA and Dema-TfO could be explained by the interactions existing between phosphate groups and sulfonic groups from TfO-which were the same explanation with the FT-IR results. The proton ionic conductivities and proton transport number of Dema-TfO/PA mixture were measured, too. The oxidation reduction electrochemical polarization performances of Dema-TfO/PA mixture will be presented at the conference. According to our results, the Dema-TfO/PA mixture as electrolyte is one of the possible electrolytes to achieve the non-humidified intermediate temperature fuel cell. Acknowledgement This research was supported by “Platform for Technology and Industry” of Tokyo Metropolitan Government. References R. L. Coalson, W. G. Grot, US Patent 3, 1972, 684-747H. Munakata, D. Yamamoto, K. Kanamura, Journal of Power Sources 2008, 178, 596–602 Figure 1

HF-Free Synthesis of α-Zirconium Phosphate and Its Use as Ion Exchanger for Separation of Nd(III) and Dy(III) from a Ternary Co–Nd–Dy System

The recovery of Nd and Dy from a ternary Co-Nd-Dy system using layered crystalline zirconium phosphate (alpha-ZrP) was investigated. alpha-ZrP was synthesized by the refluxing method, and subsequently characterized by sodium hydroxide titration, Fourier transform-infrared spectrometry, thermogravimetry, scanning electron microscopy, and X-ray diffraction. The selectivity and ion exchange kinetics of the alpha-ZrP material were determined with regard to the individual elements. The influence of solution pH on the uptake was studied in ternary 1 and 2 mM equimolar solutions. The results showed that in acidic solution (pH 1-3), very little Co was taken up, while Nd and Dy uptakes were at reasonable levels (0.5-0.6 meq/g). The uptake isotherms of Nd, Dy, and Co were measured separately at pH 2.5 and 4.5 in ternary equimolar solution series. At pH 4.5, the loading capacities were about 0.2 meq/g for Co, 1.1 meq/g for Nd, and 1.5 meq/g for Dy. Dy was thus clearly preferred over Nd by alpha-ZrP. The loading of an alpha-ZrP column showed a similar preferred pattern. Nitric acid eluent removed Co, Nd, and Dy, but there was no separation of the metals in the eluate. A mixture of nitric and phosphoric acids, however, produced a strong separation. Co was very weakly retained in the column, and the ratio Dy/Nd in the eluent was in the range of 2-7. Thus, the alpha-ZrP material showed encouraging ion exchange properties for the separation and recycling of Nd and Dy from a ternary Co-Nd-Dy system. Much more work is needed, however, to develop a practical separation flowsheet.

All‐aramid composites by partial fiber dissolution in mixed solvents

A new self‐reinforced polymer composite based on high‐performance aramid fibers was successfully prepared by applying an elaborately designed surface‐dissolution method to fuse poly(p‐phenylene terephthalamide) (PPTA) fibers and consolidate them into “all‐aramid” composites. A mixture of phosphoric acid (H3PO4) and sulfuric acid (H2SO4) was selected as a milder alternative to highly concentrated sulfuric acid which was used in our previous study. This milder solvent requires longer immersion times to partially dissolve PPTA fiber surfaces, therefore a more controllable consolidation process to create all‐aramid composites. After selection of the optimal H3PO4/H2SO4 concentration, PPTA fibers were immersed in the mixed solvent for selected periods of time to partially dissolve PPTA fiber surfaces and convert them into the matrix phase which is needed to fuse the remaining PPTA fiber cores together. Following extraction of the mixed solvent and drying, a consolidated all‐aramid composite was formed. The structure, mechanical‐, and thermal properties of these all‐aramid composites were investigated and reported. Based on high temperature performance of aramid fiber, these all‐aramid composites are promising candidates for high temperature applications. POLYM. COMPOS., 39:3013–3021, 2018. © 2017 Society of Plastics Engineers

Self-flowing high-alumina phosphate-bonded refractory castables

Phosphate refractories have a great potential to be applied in petrochemical industries as they present suitable properties at the temperature range used in fluid catalytic cracking units. This study addresses the development of high-alumina self-flowing castables bonded with H3PO4 solution (48wt% concentration) or a mixture of phosphoric acid and monoaluminum phosphate (MAP) solutions, using MgO as a setting agent. Two polyphosphates (Budit 3H and 6H) and citric acid were evaluated as dispersant additives for these castables. The compositions were characterized by measuring their free-flow and temperature evolution over time, working and setting times, cold and hot mechanical strengths, drying behavior and explosion resistance, eroded volume and thermal shock resistance. The results indicated that high flowability (free flow >100%) could be attained when adding the selected polyphosphates to the mixtures, whereas citric acid acted mainly as a retarder agent for the castables’ setting. Moreover, free-flowing compositions with a suitable working time were obtained when combining H3PO4+MAP solutions as main binders. The thermo-mechanical tests pointed out that the most promising designed refractory (containing mixture of H3PO4+MAP and 0.5wt% of Budit 3H) presented similar or even a better performance than a benchmark commercial vibratable product used in petrochemical units.

Dually emissive P,N-co-doped carbon dots for fluorescent and photoacoustic tissue imaging in living mice

Hydrothermal treatment of a mixture of ethylene diamine, phosphoric acid and citric acid under ambient pressure generates fluorescent carbon dots that are co-doped with phosphorus and nitrogen. These have features such as (a) both green fluorescence (peaking at 430 nm; 30% quantum yield) and red fluorescence (peaking at 500 nm, quantum yield 78%), (b) wavelength-dependent emission peaks, and (c) insensitivity to changes of pH values, dot concentration and ionic strength. The C-dots are useful for both fluorescent (FL) and photoacoustic (PA) imaging of living tissue. PA imaging warrants better spatial resolution and allows deeper tissues to be imaged compared to most optical imaging techniques. It is essential to assign a photoacoustic contrast agent as most of the diseases do not show a natural photoacoustic contrast in their early stage. The dually emitting C-dots are shown to be a useful contrast agent for PA and FL imaging of mice tumors. Intravenous administration of the C-dots resulted in strong signals in both PA and FL imaging.

Studies on Dissolution Behavior of the Surface Layer of Sodium-Exposed SS 316LN in Decontaminating Formulation Using PEMHS

The Prototype Fast Breeder Reactor (PFBR) is nearing completion at Kalpakkam, India. Sodium is the heat transfer medium for PFBR, and austenitic steel SS 316LN is the material of construction for the sodium circuits of the reactor. During reactor service, the inner surfaces of the sodium circuit pipelines undergo corrosion by interacting with liquid sodium, forming ferritic layers. Radioactive nuclides formed by the activation of corrosion products are deposited on the ferritic surface, resulting in a radioactive burden on maintenance personnel. Chemical decontamination is generally carried out by dissolving the surface ferritic layer on the inside surface of the sodium circuit. In this context, a study of the dissolution behavior of the ferritic layer on SS 316LN samples formed by exposure to liquid sodium at 823 K was carried out by monitoring the H2 released during the chemical interaction with decontamination formulation. The decontamination chemical formulation was a mixture of sulfuric acid and phosphoric acid. This paper discusses the sample preparation, formation of the ferritic layer, and studies carried out on its dissolution behavior in decontamination formulation by monitoring the hydrogen released during the reaction using a proton exchange membrane–based hydrogen sensor.

Crystallographic and topographical evolutions of a cylinder patterned sapphire substrate etched with a sulfuric acid and phosphoric acid mixture: an SEM and AFM study

Using cylinders as a model system, the full spectrum of crystallographic and topographical evolutions of patterned sapphire substrates is exhibited.

AFM and SEM Study on Crystallographic and Topographical Evolution of Wet-Etched Patterned Sapphire Substrates (PSS): I. Cone-Shaped PSS Etched in Sulfuric Acid and Phosphoric Acid Mixture (3:1) at 230°C

A thorough understanding about the crystallographic and topographical evolution of wet-etched patterned sapphire substrates (PSS) is essential for revealing the etching mechanism and critical for fabricating optimized PSS for enhanced performance of GaN-based LED devices. As the first one of a series of three papers, using complementary scanning electron microscope (SEM) and atomic force microscope (AFM), we carried out a systematic study on the crystallographic and topographical evolution of cone-shaped PSS etched with an ordinary etchant (H2SO4:H3PO4 = 3:1 at volume ratio, 230°C) which enables crystallographic specific etching. The topography of patterns was found to evolve from normal cones to truncated cones, to triangular pyramids with multiple families of exposed crystallographic planes, then to hexagonal and triangular pyramids with a single family of planes. The Miller indexes of three major exposed crystallographic planes, with decreasing slant angles, were determined to be {1 0 5}, {4 1 38} and {1 0 12} with the last two being reported for the first time to our best knowledge. It was clearly demonstrated that AFM, thanks to its 3D topography imaging capability compared to SEM and focused ion beam, can be an indispensable tool for fast and reliable characterization of routine PSS samples.

Thermodynamic Description of Synergy in Solvent Extraction: I. Enthalpy of Mixing at the Origin of Synergistic Aggregation.

Revisiting aggregation of extractant molecules into water-poor mixed reverse micelles, we propose in this paper to identify the thermodynamic origins of synergy in solvent extraction. Considering that synergistic extraction properties of a mixture of extractants is related to synergistic aggregation of this mixture, we identify here the elements at the origin of synergy by independently investigating the effect of water, acid, and extracted cations. Thermodynamic equations are proposed to describe synergistic aggregation in the peculiar case of synergistic solvent extraction by evaluating critical aggregation concentration (CAC) as well as specific interactions between extractants due to the presence of water, acid and cations. Distribution of two extractant molecules in the free extractants and in reverse micelles was assessed, leading to an estimation of the in-plane interaction parameter between extractants in the aggregates as introduced by Bergström and Eriksson ( Bergström, M.; Eriksson, J. C. A Theoretical Analysis of Synergistic Effects in Mixed Surfactant Systems . Langmuir 2000 , 16 , 7173 - 7181 ). Based on this model, we study the N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide (DMDOHEMA) and di(2-ethylexyl) phosphoric acid (HDEHP) mixture and show that adding nitric acid enhances synergistic aggregation at the equimolar ratio of the two extractants and that this configuration can be related to a favored enthalpy of mixing.

SYNERGIC EXTRACTION OF PANTOTHENIC ACID WITH TWO DIFFERENT EXTRACTANTS

The influences of extractants concentrations and solvent polarity on the efficiency of pantothenic acid separation by synergic extraction with tri-n-octylamine (TOA) and di(2-ethylhexyl) phosphoric acid (D2EHPA) mixture have been analyzed. The results indicated the formation of an interfacial compound which includes one molecule of pantothenic acid and one of D2EHPA, its hydrophobicity being increased by solvation with additional TOA molecules. For solvents with lower dielectric constants, n-heptane and n-butyl acetate, the number of amine molecules participating in the interfacial complex formation was controlled by solvent polarity and D2EHPA concentration, decreasing with the increase of these two parameters. For dichloromethane, the chemical structure of the extracted compound remained the same regardless of D2EHPA concentration. The most important synergic effect corresponded to the extractant mixture dissolved in n-heptane, at low D2EHPA concentration in the organic phase (5 g/l).

Apatite grown in niobium by two-step plasma electrolytic oxidation

Plasma electrolytic oxidation (PEO) of niobium plates were done electrochemically in two steps with electrolytes containing phosphorous and calcium being observed the formation of crystalline apatite. All samples were submitted to a first step of PEO using an electrolyte containing phosphate ions. The second oxidization step was made using three different electrolytes. Some samples were oxidized by PEO in electrolyte containing calcium, while in other samples it was used two mixtures of phosphoric acid and calcium acetate monohydrate solutions. Three different surface layers were obtained. The morphology and chemical composition of the films were analyzed by scanning electronic microscopy (SEM), and energy dispersive spectroscopy (EDS) respectively. It was observed that all samples submitted to two-step oxidation shown porous surface and a calcium and phosphorus rich layer. Average surface roughness (Ra) was measured by a profilometer remaining in the sub-micrometric range. The contact angle by sessile drop technique, using 1μL of distilled water was performed with an optical goniometer. It was verified a higher hydrophilicity in all surfaces compared to the polished niobium. Orthorhombic Nb2O5 was identified by XRD in the oxide layer. Crystalline apatite was identified by XRD in surfaces after the second oxidation made with the Ca-rich electrolyte and a mixture of an electrolyte richer in Ca compared to P. These results indicate that a two-step oxidized niobium surface present great features for applications in the osseointegration processes: favorable chemical composition that increase the biocompatibility, the formation of crystalline niobium pentoxide (orthorhombic), high hydrophilicity and formation of crystalline calcium phosphate (apatite) under adequate electrolyte composition.

Etching Studies of Mo in Aqueous Solutions

Molybdenum (Mo) has been a choice of substrate metal for chalcopyrite or kesterite solar cells because of its low thermal expansion coefficient, high melting point, good thermal and electrical conductivity, and high wear resistance. Mo surface, however, is almost always covered with molybdenum oxides, unless kinetic limitations prevail. Previously, we reported the mild electrochemical conditions of forming molybdenum blue as well as molybdenum oxides colored in yellow and red in aqueous solutions. Figure 1 shows the representative changes in resonance frequency and current observed when the potential was applied to the molybdenum/quartz in aqueous solutions. The starting potential was –0.7 V, where the resonance frequency was set to be at the base line. As the potential was scanned up to –0.1 V, apparently the anodic current flew and simultaneously the resonance frequency increased. Near –0.1 V, the sharp increase in current as well as resonance frequency was observed, suggesting the significant dissolution of molybdenum into the solution as molybdenum ions. In this work we wish to report the results of electrochemical quartz crystal microbalance studies of etching of molybdenum in aqueous solutions. The present results may be important in relation to cleaning or polishing of molybdenum, which has been traditionally performed in strong acidic solutions such as mixtures of phosphoric acid and sulfuric acid. Details will be presented at the meeting. Acknowledgements Acknowledgements are made for SACHEM’s supply of some samples used in this work. Helpful discussions with Drs. Craig Allen and Paul Vermeulen are greatfully acknowledged. References. 1. Sang-Min Lee, Young-Ho Kim, Mi-Kyung Oh, Suk-In Hong, Hang-Ju Ko, and Chi-Woo Lee, J. Korean Electrochem. Soc. 13, 89-95 (2010). 2. Sang-Min Lee and Chi-Woo Lee, Bull. Korean Chem. Soc. 33, 1443 (2012) 3. Viswanathan S. Saji and Chi-Woo Lee, Electrochem. Acta, 137, 647-653 (2014). 4. Viswanathan S. Saji, Chan-Yong Jung and Chi-Woo Lee, J. Electrochem. Soc. 162, D465-D479, (2015). Figure 1

Influence of ammonium nitrate on the thermal decomposition of complex nitrogen–phosphorus–potassium fertilizers

The results of studying the thermal decomposition of complex nitrogen–phosphorus–potassium fertilizers obtained with different degrees of ammoniation of the mixture of nitric and phosphoric acid have been presented. The dependences of the mass loss of different samples and the release of the gas phase of nitrogen, fluorine, and chlorine compounds depending on the duration of decomposition have been shown.

Preparation of graphite derivatives by selective reduction of graphite oxide and isocyanate functionalization

Heavily oxidized and ordered graphene nanoplatelets were produced from natural graphite by oxidation using a mixture of phosphoric acid, sulphuric acid, and potassium permanganate (Marcano's method). The atomic percentage of oxygen in the graphite oxide produced was more than 30% confirmed by XPS studies. The graphite oxide produced had intact basal planes and remains in a layered structure with interlayer distance of 0.8 nm, analyzed by WAXS. The graphite oxide was treated with 4,4′-methylenebis(phenyl isocyanate) (MDI) to produce grafted isocyanate functionalization. Introduction of these bulky functional groups widens the interlayer distance to 1.3 nm. In addition, two reduction methods, namely benzyl alcohol mediated reduction and thermal reduction were carried out on isocyanate modified and unmodified graphite oxides and compared to each other. The decrease in the oxygen content and the sp3 defect-repair were studied with XPS and RAMAN spectroscopy. Compared to the thermal reduction process, which is connected with large material loss, the benzyl alcohol mediated reduction process is highly effective in defect repair. This resulted in an increase of conductivity of at least 9 orders of magnitude compared to the graphite oxide.

Synthesis of Porous Anodic Alumina (PAA) on Aluminum Alloy AA6061 in Mixture of Phosphoric Acid and Oxalic Acid

In this study, porous anodic alumina was formed on aluminum alloy AA6061 by anodizing using mixture of 0.3 M oxalic acid and phosphoric acid with concentration ranged from 0.1 M to 1.0 M. AA6061 alloys were anodized at 40 V and 25°C for 60 minutes. FESEM images show that the uniformity of the pores arrangement of porous anodic alumina decreased with the increasing concentration of phosphoric acid in the electrolyte. Well-ordered porous anodic alumina was formed in mixture of 0.3 M oxalic acid and 0.1 M phosphoric acid while disordered porous anodic alumina were formed when the concentration of phosphoric acid were in the range of 0.3 M to 1.0 M. Pore size and interpore distance were found to increase with the concentration of phosphoric acid in the mixture. X-ray diffraction patterns show that to γ-Al2O3 were formed on the surface of AA6061 after the anodizing process, regardless of the concentration of phosphoric acid in the mixture electrolyte.