Presence Of Excess Aluminium Research Articles

Significantly enhanced electrochemical performance of Al-Ti3C2Tx MXene synthesized from Al-Ti3AlC2 MAX phase

MXenes, a type of two-dimensional nanomaterials consisting of transition metal carbides/nitrides, have emerged as promising electrode materials for supercapacitors. Especially, Ti3C2Tx MXene prepared from Ti3AlC2 MAX phase shows great application potential in flexible supercapacitors due to its facile synthesis, excellent conductivity and film-forming property. In contrast to conventional Ti3AlC2, excessive aluminum is incorporated in the synthesis process to produce Al-Ti3AlC2. In this study, Ti3AlC2 and Al-Ti3AlC2 MAX phases are used to synthesize Ti3C2Tx and Al-Ti3C2Tx MXenes, respectively, by the same method of HF:HCl etching and LiCl intercalation. The freestanding Ti3C2Tx and Al-Ti3C2Tx film electrode is separately prepared through simple vacuum filtration. The presence of excess aluminum during the Al-Ti3AlC2 synthesis facilitates to form more homogeneous grains structure with relatively larger particle sizes and an improved stoichiometric MAX phase with a Ti:C ratio closer to 3:2. The resulting Al-Ti3C2Tx nanosheets show improved oxidation resistance with relatively uniform and larger dimensions, which facilitate the higher conductivity with slightly increased interlayer spacing for the Al-Ti3C2Tx film. Therefore, the Al-Ti3C2Tx film electrode shows more efficient ions transport and charge transfer, and thus achieves significantly enhanced capacitance (399 F g−1 at 1 A g−1) and rate performance (63.6 % retention from 1 to 10 A g−1) compared to the Ti3C2Tx film electrode (342 F g−1 at 1 A g−1, 55.6 % retention from 1 to 10 A g−1). Moreover, the Al-Ti3C2Tx-based flexible sandwiched supercapacitor also exhibits superior energy storage performance. The impressive results indicate that Al-Ti3C2Tx MXene synthesized from Al-Ti3AlC2 MAX phase possesses the great application potential in flexible supercapacitors.

Evaluation of the efficiency of Cr3+ → Cr4+ conversion in non-stoichiometric YAG: Cr ceramics

The aim of the work was to study the effect of the YAG: Cr ceramics' stoichiometry deviation on the optical properties and efficiency of valence conversion of Cr cations. YAG: Cr ceramic powders with deviations from stoichiometry ranging from 0.225 to −0.35 at % excess yttrium were synthesized by chemical precipitation. The optical and luminescent properties of YAG: Cr4+ ceramics, as well as the microstructure of the ceramics, were studied. It has been shown that small deviations from the stoichiometry of YAG: Cr (within 0.35 at %) do not have a significant effect on the optical transmission and microstructure of YAG: Cr3+ ceramics, but strongly affect some characteristics of YAG: Cr4+ ceramics. It was found that the presence of excess aluminum or yttrium cations in YAG: Cr4+ ceramics leads to a decrease in the concentration of Cr4+ and a deterioration in the conversion from Cr3+ to Cr4+.

Integrated Chemical Effects Head Loss Experiments Using Multiconstituent Fibrous Debris Beds

The chemical head loss experiment (CHLE) program has been designed to acquire realistic material release and product formation in containment under post-loss of coolant accident (LOCA) conditions and their impact on the measured head loss through the use of modified debris beds developed at the University of New Mexico (UNM). A full-scale water chemistry test was conducted under Vogtle containment chemistry conditions to determine the release of these materials and the resulting head loss response of the formed products within the emergency core cooling system (ECCS) under prototypical chemical conditions. The test was designed to investigate material corrosion with the presence of excess aluminum and a nonprototypical temperature profile (80 °C for 120 h) to promote the production of aluminum precipitates. The head loss measured within the first 72 h of the test either surpassed the operational limits of the equipment or caused a failure within the system. The increase in head loss is not attributed to the formation of in situ precipitates but to a physical reaction of the epoxy used in constructing the debris beds to the local chemistry during the early stages of the test.

Bacterial-Metal Interactions: The Potential Role of Aluminum and Other Trace Elements in the Etiology of Chrohn’s Disease

Despite the recent burst of excitement about the genomics of Crohn’s disease, the critical importance of environmental factors in this condition has been recognized ever since the disease was described. The chief suspects for this role have always been microorganisms and dietary constituents. Many candidate microorganisms have been proposed, evaluated and discarded over the decades, but the most persistent theories have revolved around mycobacterial infection. Among potential dietary agents, however, none has yet emerged as a favorite. An offending dietary constituent, of course, need not be conventional foodstuff; additives, preservatives, and even microparticle contaminants are plausible alternatives. With this in mind, we have arrived at an etiologic hypothesis for Crohn’s disease based on our study of a fatal outbreak of granulomatous enteritis in a group of horses sharing a common environment. The horses suffered from a disorder with many histologic similarities to human Crohn’s disease. In the evaluation of the cluster, an unexpected finding was the presence of excess aluminum in affected tissues. Microprobe elemental analysis demonstrated that aluminum was concentrated within microorganisms in the intestinal wall. Based on these observations, we propose a novel approach to etiologic concepts of Crohn’s disease. Our hypothesis is that the capability of certain microbial organisms, in particular mycobacterial species, to take up certain trace elements from environmental and host sources, may alter the pathogenicity of these organisms and exacerbate the host’s responses to them. As we will outline, mycobacteria possess potent metal chelators that provide essential metallic elements, especially iron, required for bacterial growth and virulence. We propose that in addition to iron, other metals, particularly aluminum, may use these same metal chelating systems to gain access to the organisms and this may alter their pathogenicity and ability to induce an exuberant granulomatous response. It is well established that the virulence and even survival of many bacterial organisms during infection depends on the ability of the pathogenic microbe to compete for essential nutrients, especially iron. However, in vertebrates iron remains sequestered within a number of high molecular weight binding proteins, such as transferrin, lactoferrin and ferritin. In what is essentially an iron-poor environment, microorganisms have evolved to produce ferric ion chelating agents, called siderophores, that are capable of solubilizing and transporting iron into the microbe. Siderophores contain some of the most efficient ironbinding ligands in nature and are capable of securing the metal from transferrin, ferritin, ferric hydroxide as well as from synthetic chelators such as EDTA. The affinity of siderophores for iron is remarkably strong with dissociation constants (Ks) in the range of 10 to 10.

Preparation and characterization of iron aluminide based intermetallic alloy from titaniferous magnetite ore

Intermetallic alloys such as iron aluminide (Fe 3Al) display an attractive combination of physical and mechanical properties. It is a potential candidate for application demanding high strength, superior oxidation, sulphidation and corrosion resistance. However, the utilization of this alloy is limited owing to problems of its preparation by conventional techniques and poor room temperature ductility. The present paper is, therefore, an attempt to prepare an Fe 3Al-based alloy (iron aluminide alloy) of composition Fe–17.24Al–5.54Cr–1V–0.05C (wt%) by a non-conventional non-furnace process. The process essentially involves the use of cheap, indigenously available titaniferous magnetite ore containing oxides of iron and vanadium and oxide of chromium that are subsequently co-reduced by aluminium in the presence of excess aluminium and a requisite amount of carbon in a specially designed water-cooled copper reactor. The charge composition is judiciously adjusted to attain the alloy composition by utilizing the exothermicity of the overall reactions. The alloy is further characterized with respect to composition, phases and microstructure and properties such as fabricability, hardness, strength and oxidation resistance were studied to indicate its suitability for high temperature applications.

Solvent Extraction of Gallium (III) from Basic Sodium Aluminate Solution by Alkanoyl Oxines

Abstract Alkanoyl oxines have been used for the extraction of gallium from basic solution, especially for the selective recovery of gallium in the presence of excess aluminum from Bayer process sodium aluminate liquor. 5-Alkanoyl-8-hydroxyquinolines (R.CO.Ox), where R is the alkyl group C13H27 (myristoyl), C15H31 (palmitoyl), and C17H35 (stearoyl) were synthesized by the Fries rearrangement from the corresponding acid chloride and sodium oxinate using AlCl3 as catalyst. The synthesized alkanoyl oxines were capable of extracting Ga into kerosene or chloroform at a pH around 13; the selectivity of Ga over A1 was high at this pH. The extracted Ga could be stripped into the aqueous phase acidified with HCl without significant loss of the ligand. The extractability of Ga was studied as a function of pH, temperature, time, metal concentration, phase separation acid (undecanol) concentration; and the strippability as a function of HCl concentration. Based on these results, a sequential procedure for the selectiv...

Development of a high-sensitivity ion chromatography method for the determination of trace fluoride in water utilizing the formation of the AlF 2+ species

The development of a novel ion chromatography method for the determination of trace fluoride is described. The principle depends on the formation of the chromatographically stable AlF 2+ species in the presence of excess aluminium. Very high sensitivity is achieved with fluorescence detection, giving a detection limit of 0.2 μg l −1. Linear calibrations were achieved up to 400 μg l −1 fluoride in the presence of 5 mg l −1 excess aluminium. Magnesium interferes in relatively large amounts but can be controlled by adjustment of post-column reaction pH. Results for fluoridated drinking waters agree well with those obtained by the ion selective electrode technique.

Demonstration of aluminium in iliac bone: correlation between aluminon and solochrome azurine staining techniques with data on flameless absorption spectrophotometry.

The presence of excess aluminium was investigated in 204 samples of iliac bone from 197 patients with chronic renal failure by using the aluminon and solochrome azurine staining techniques. The results were compared with values obtained by atomic absorption spectrophotometry (AAS). Overall, the staining reactions correlated with the AAS data, but the solochrome azurine stain was positive more often than was the aluminon stain (in 90.6% and 62.3%, respectively, of bone samples with greater than the control group mean +3SD (that is, in the range 17.8 to 113.4 micrograms aluminium/g Solochrome azurine staining was consistently positive in all cases, with greater than 23.1 micrograms aluminium/g bone but the corresponding aluminon stain was occasionally inexplicably negative in this range. In some samples solochrome azurine was positive in parts of old unresorbed cement lines when the aluminon stain was negative and the bone aluminium concentration was within the normal range or slightly increased. The stains, particularly solochrome azurine, have the advantage over AAS in that they indicate the location as well as the presence of excess bone aluminium.

Phase equilibria and diffusion in the Be-Al-Fe System Using High-Energy Ion Beams

Phase boundaries enclosing the α-Be region of the Be-Al-Fe system have been investigated by a new approach which utilizes high-energy ion beams. Ion implantation of aluminum and/or iron into single-crystal beryllium was used to create a desired second phase in the first ≃0.1 μm of the sample. Under continued isothermal annealing the second phase dissolved into the underlying bulk α-Be, and this process was monitored nondestructively by ion backscattering. Analysis then gave the solid solubility and the diffusivity of the species under consideration. The solubility of iron in beryllium was measured between 773 (170 appm) and 1123 (1600 appm); above 973 the present data merge smoothly into previous results from the literature. A new upper bound was established for the solubility of aluminum below the Al-Be eutectic: ≲ 70 appm at 873 K. In the ternary regime, the solubility of iron in the presence of excess aluminum was measured for the first time; below 1123 it is ≲ 100 appm.

Diffusion in gold-aluminium

Abstract A combination of reflectivity, adhesion and resistance measurements has been used to measure the rates of phase boundary movement in thin-film couples during the interdiffusion of gold and aluminium. The various measurements have been compared and correlated to show that diffusion occurs in two distinct stages. The first stage leads only to formation of Au2Al which is initially in a partially disordered state and the diffusion is followed by an ordering process. In the presence of excess aluminium, this is followed by the second stage, which is much slower, where the Au2Al already formed is gradually transformed into AuAl2. The rate constant D′ for broadening of the AuAl2 phase was found to be 1·44 × 10−15 cm2/sec at 130°c assuming x 2 = D′t and the diffusion coefficient in this phase was calculated to be 2·2 × 10−14cm2/sec at 130°c with a corresponding activation energy of 21·6 kcal/mole giving a value of 0·011 cm2/sec for D 0.The corresponding rate constant for the first stage was 2·79 × 10−15 cm2/sec at 50°c with an activation energy of 23·5 kcal/mole but in the absence of accurate supplementary data the diffusion coefficient in Au2Al could not be calculated accurately and the value of 3 × 10−14 cm2/sec at 50°c is correct only in order of magnitude. It suggests a D 0 value of the order of 200 cm2/sec.

THE ALUMINUM REDUCTION OF MAGNESIUM COMPOUNDS: III. THE VAPOR PRESSURE OF MAGNESIUM OVER THE SYSTEM Al–Mg2SiO4 (OLIVINE)

The equilibrium vapor pressure of magnesium over the reaction between olivine (Mg2SiO4) and aluminum was measured by means of the transportation method in the temperature range 943–1150 °C.It was concluded that olivine and aluminum form an unstable system which reacts completely according to the equation[Formula: see text]However, in the presence of excess aluminum, an Al–Si alloy results. This alloy in turn reacts with magnesium oxide according to the equilibrium[Formula: see text]The vapor pressure of magnesium over this equilibrium system was found to obey the equation[Formula: see text]The aluminum activity of the Al–Si alloy along the liquidus line of the silicon side of the phase diagram has been calculated. Within the temperature range 943–1150 °C this activity can be represented by the equation[Formula: see text]

A PARTIAL FRACTIONATION OF ALKALI‐solUBLE SOIL ORGANIC PHOSPHATE

SummaryA study has been made of the precipitation of soil organic phosphates from alkaline extracts. Acidification to a pH of about 0.4 or below precipitated a small and constant proportion of the extracted organic phosphate. Above pH 0.4 there was an increase in the precipitation up to a pH of about z to 3. The proportion of the phosphate brought down at pH 2.9 could in some cases be increased by prior addition of aluminium sulphate, but in no case did this affect the proportion precipitated at pH 0.2. There was marked precipitation of orthophosphate above pH 3, in the presence of excess aluminium, but below pH 3 it was negligible.Inositol hexaphosphate and DNA were precipitated virtually quantitatively at pH 2.9 in the presence of added aluminium even if the extract was incubated before precipitation. Precipitation of RNA was not complete and could be prevented entirely by prior incubation of the extract. At pH 0.2 DNA was precipitated, but not inositol hexaphosphate. Less than half of a freshly purified sample of RNA was brought down, and no precipitation occurred if the RNA was allowed to stand overnight in alkaline solution before acidification.The soil phosphate esters have been divided into three main classes: an acid‐insoluble fraction precipitated at pH 0.2, and two acid‐soluble fractions, one of which is precipitated at pH 2.9 in the presence of excess aluminium, while the other remains in solution. Part of the acid‐insoluble fraction was readily mineralized during incubation in dilute sodium hydroxide, and some hydrolysis is likely during extraction of the soil with this solvent.

INFLUENCE OF ACIDITY, CALCIUM AND MAGNESIUM ON GROWTH OF XANTHI TOBACCO IN WATER-CULTURE

The influence of acidity on the growth of plants in water-culture has been studied by investigators with varying results. Many have reported a beneficial effect of moderate acidity; whereas others have succeeded in demonstrating equally good growth in solutions of widely different hydrogen-ion concentration. Citations to the literature can be found in a paper by the writer (5) dealing with the effects of acidity on the calcium and magnesium requirements of Xanthi tobacco in aseptic culture. The present experiments are in effect a repetition in the greenhouse of those in aseptic culture at 25? C with about 500 foot-candles of fluorescent light. The yield curves for magnesium remained unaltered in the aseptic cultures with increased acidity, whereas those for calcium did not. An increase in the quantity of calcium needed for maximum growth was apparent at higher acidities. The use in greenhouse experiments of large containers with fixed charges of nutrients, the presence of heavy precipitates, and the need for preparation of the solutions weeks in advance of the growth period all combined to make iron nutrition of the plant unsatisfactory. Preliminary experiments on iron nutrition were therefore necessary and furthermore seemed desirable, since acidity is generally accepted as an important factor in iron nutrition. A factor in acidity studies generally ignored is the effect of acidity on the toxicity of even small quantities of trace-element impurities unavoidably present in the solution. It is well known that the harmful effects of high acidity may be aggravated by the presence of excess aluminum, manganese (1), and vice versa. Work with fungi also has revealed that higher acidity increases the effect of trace-elements on growth (4) even in solutions free of all solid materials. A further factor in studies on iron chlorosis is another effect of the presence of relatively small but still excessive quantities of trace-element impurities. Symptoms of iron chlorosis in plants may be produced by relatively excessive quantities of zinc, copper, manganese, aluminum, cobalt, nickel, etc. (1, 3). These facts may be summarized by the statement that excessive quantities of trace elements relative to iron may lead to toxic responses which are further aggravated by increased acidity. These phenomena were assumed to be the basis for the differences in results reported for studies of acidity and iron nutrition by various workers. Special attention, therefore, was given to the effects of iron salt hydrolysis and traceelement level in these studies.

Are Hydrangea Flowers Unique?

APART from Meconopsis betonicifolia and Hydrangea macrophylla, no plant has been recorded as displaying a flower colour change, caused by varying soil conditions. That such a plant might exist is a possibility depending on three conditions1,2: (1) it must have a delphinidin flower pigment which in an acid cell sap is normally pink but is blue in the presence of excess aluminium; (2) it must be able to accumulate aluminium; this is a specific characteristic manifest only when sufficient is available, for example, in acid soils; (3) it must have a wide range or reaction tolerance. Many plants fulfil the first condition but invariably fail the rest. If a blue-flowered plant could be found that also accumulates aluminium, then there is a possibility that if such a plant could be grown in a neutral or slightly alkaline soil and so be unable to accumulate this element, a change of flower colour from blue to pink would take place.