Low Solubility Limit Research Articles

Calculation of solubility in titanium alloys from first principles

We present an approach to calculate the atomic bulk solubility in binary alloys based on the statistical-thermodynamic theory of dilute lattice gas. The model considers all the appropriate ground states of the alloy and results in a simple Arrhenius-type temperature dependence determined by a “low-solubility formation enthalpy”. This quantity, directly obtainable from first principles, is defined as the composition derivative of the compound formation enthalpy with respect to nearby ground states. We apply the framework and calculate the solubility of the A solutes in A–Ti alloys (A = Ag, Au, Cd, Co, Cr, Ir, W, Zn). In addition to determination of unknown low-temperature ground states for the eight alloys, we find qualitative agreements with solubility experimental results. The presented formalism, correct in the low-solubility limit, should be considered as an appropriate starting point for estimation of whether a more computationally expensive formalism is needed.

Formation identification of Y2BaCuO5 and BaCeO3 in MOCVD-processed YBCO films with Ce doping

The influence of nanosized secondary particles, such as those produced viarare-earth doping for example, on magnetic-field-induced flux motion inYBa2Cu3O7−δ (YBCO)-coated conductors has been investigated. In this study, we investigated the influence of Cedoping on nanosized secondary phase formation in YBCO films. Ce-doped YBCO films on singleSrTiO3 crystals were prepared via metal–organic chemical vapor deposition (MOCVD). For the first time, aY2BaCuO5 (Y211)secondary phase was observed in the Ce-doped YBCO film, while the pure YBCO film contained onlya Y2O3 secondary phase. As Ce doping concentration increased to 3 wt%, aBaCeO3 secondary phase developed. This was due to the low solubility limit of Ce for Y in the MOCVD YBCOfilm. Additionally, outgrowths on the Ce-doped YBCO film surfaces and defect structures, such asa-axis grains, were examined.

Segregation and Twinning in the Rare-Earth Doped KPb2Cl5 Laser Crystals

Ve present the Er 3+ :KPb 2 Cl 5 lattice parameters thermal expansion and twinning characterization, pure KPb 2 Cl 5 crystals room temperature static dielectric constant measurements, and equilibrium segregation coefficients determination of Er 3+ , Ho 3+ , and Pr 3+ defects in KPb 2 Cl 5 . The two main current limitations which still hinder the development of this crystal as a laser material, namely, the Er 3+ cations segregation and low solubility limit as well as the crystal twinning, are discussed.

Cationic (V, Mo, Nb, W) doping of TiO 2–anatase: A real alternative for visible light-driven photocatalysts

In this article we investigate the structure–activity link of anatase-type Ti–M (M = V, Mo, Nb, and W) mixed oxides used for toluene photo-oxidation under sunlight-type excitation. An analysis of the local and long-range structural and electronic characteristics of the mixed oxides show that only structurally highly homogeneous anatase-type oxides with electronic properties exclusively leading to a band gap decrease drive to efficient visible light-driven photocatalysts. Within our microemulsion preparation method, this only occurs for Ti–V and Ti–W series of samples. The isoelectronic (V 4+) substitution of Ti 4+ ions at the anatase lattice is characterized by a low solubility limit (ca. 2.5 at. %), and drives to a limited modification of the band gap and to a moderate enhancement of the photo-activity with respect to bare titania reference systems. W presence at anatase cation positions occurs with concomitant presence of cation vacancies derived by the charge imbalance between the W 6+ and Ti 4+ species. A unique W-vacancy local arrangement is detected by the structural characterization, leading to both an important band gap decrease and enhancement of the photo-activity upon sunlight excitation.

Low temperature LO-phonon dynamics of MgZnO nanoalloys

In this paper, the authors present research on the low temperature resonant Raman scattering of the LO modes of Mg0.2Zn0.8O nanocrystals. They found that in the LO spectral range, two coupled modes appear: the main LO mode of the alloy and a low frequency mode redshifted by ∼27cm−1 relative to the main one. The low frequency mode was analyzed in terms of three mechanisms applicable to Raman scattering of an alloy system that might result in its activation: phase segregation due to the low solubility limit of the MgO–ZnO alloy system, a convolution of the A1(LO) with the E1(LO) mode, and an order-disorder state. Their analyses indicate that the principle mechanism that activates the low frequency mode is scattering due to the disordered state of the nanoalloys.

Magnetic and carrier transport properties of Mn-doped p-type semiconductor LaCuOSe: An investigation of the origin of ferromagnetism

LaCuOSe is a wide band gap p-type semiconductor in which high density positive holes can be doped to exhibit degenerate conduction. These features should allow room-temperature ferromagnetism in a dilute magnetic semiconductor (DMS), which follows a theoretical prediction [T. Dietl et al., Science 287, 1019 (2000)], yet to be realized. A weak ferromagnetic response is observed in both bulk and thin epitaxial film samples of Mn-doped LaCuOSe with hole concentrations of ∼1020cm−3. However, the observed small magnetization (μB per Mn ion of less than unity) is reasonably explained by the inclusion of 0.2mol% of LaMnO3 and 0.1mol% of Mn3O4, which were quantitatively analyzed in the bulk sample using highly sensitive x-ray diffractometry, i.e., Mn-doped LaCuOSe did not exhibit ferromagnetism due to the low solubility limit of Mn in LaCuOSe (<0.5mol%). This result demonstrates the importance of complementary characterization using both thin film and bulk samples for studying DMSs.

Low Temperature Solubility Limit of Copper in Iron

The solubility limit of copper in iron at temperature lower than 700°C is not precisely known because copper diffusion is too slow to reach an equilibrium with classical experimental techniques involving long range diffusion. However, fine precipitation of copper can lead to an equilibrium in a reasonable ageing time. Hence, coupling ThermoElectric Power and Small Angle X-ray Scattering techniques leads to a precise estimation of this solubility limit in the temperature range 500°C-700°C. Values obtained are confirmed by Tomographic Atom Probe and give results much higher than what is usually extrapolated from high temperature experiments.

Thermal and catalytic decomposition of HNF and HAN liquid ionic as propellants

Binary aqueous hydroxylammonium nitrate (HAN: [NH3OH]+[NO3]−) and hydrazinium nitroformate (HNF: [N2H5]+[C(NO2)3]−) have been prepared, then thermally and catalytically decomposed. The HAN solutions were prepared with different concentrations (20, 40, 79wt.%), whereas HNF solution contains is 40wt.% due to its lower solubility limit (about 50wt.%). The catalyst was prepared by impregnation of modified support (Si-modified alumina) with monometallic active phase precursor (platinum) and characterized by transmission electron microscopy, X-ray diffraction and chemisorption. The reactions were followed by thermal analysis and by using a constant volume batch reactor. This work shows the essential effect of the monopropellant concentration to determine the best formulation for an industrial application. Moreover, HAN laboratory made solutions are more efficient for catalytic decomposition due to the absence of stabilizer to inhibit the catalyst. The Pt(10%)/Al2O3Si+HAN79% lab association shows lower decomposition temperatures (down to room temperature), larger reaction rates and leads to higher amount of gaseous products, giving the most efficient system. With the same catalyst, HNF solution gave lower performances than HAN solutions, suggesting that the catalyst needs to be improved for this oxidizer.

Phospholipid Solubility Determined by Equilibrium Distribution between Surface and Bulk Phases

A general strategy is proposed for determining the very low aqueous solubility limits of bilayer-forming phospholipids. The strategy exploits the inherent surface activity of phospholipids and has been termed EDSB, which stands for Equilibrium Distribution between Surface and Bulk phases. In this report, EDSB has been used to determine the critical bilayer concentration of dilauroylphosphatidylycholine (DLPC), a short-chain bilayer-forming phospholipid. At room temperature in neutral pH buffer, CBC(DLPC) = 2.5 x 10(-)(8) M. Using a mole fraction concentration scale, this corresponds to a standard-state free energy change of -12.8 kcal/mol for DLPC bilayer membrane formation.

Incorporation of Chromium(III) and Chromium(VI) Oxides in a Simulated Basaltic, Industrial Waste Glass‐Ceramic

Chromium, an EPA listed toxic element concentrated in many industrial wastes, was stabilized using waste vitrification. Cr2O3 and CrO3 were loaded into a simulated basaltic base composition, vitrified, and cooled at various rates. Chromium incorporation mechanisms, vitrification processability, effect of initial Cr oxidation state, and product performance were investigated. At 1500°C, Cr2O3 has a low solubility limit (0.54 wt%) in the base composition, and crystallized as Cr‐rich primary spinel (Mg,Fe)(Fe,Al,Cr)2O4. On cooling, Cr‐depleted secondary spinel and augite (Na,Ca)(Mg,Fe2+,Al)(Si,Al)2O6 crystallized. Cr(VI) was converted into Cr(III) on vitrification. The apparent viscosity of the melts was estimated using the Bottinga–Weill model as corrected by Roscoe's equation. The end products showed Cr2O3 loading capacities as high as 16.7 wt% without exceeding the toxicity‐leaching limit defined by EPA. The annealed products had Vickers's hardness of about 800 kg·F/mm2 and can be classified as medium‐grade abrasives.

Formation of nanoscale complex oxide particles in mechanically alloyed ferritic steel

Oxide-dispersion-strengthened (ODS) ferritic steel incorporating nanoscale oxide particles was produced by mechanical alloying, and the complex oxide particles, comprised of titanium and yttrium, characterized by high-resolution transmission electron microscopy (HRTEM) and characteristic X-ray nano-analyses. The interface between the ferritic matrix and the major Ti-Y complex oxide was incoherent. From HRTEM and characteristic X-ray nano-analyses, plus the extremely limited literature data on ODS ferritic steels, it was determined that the most stable complex oxide was cubic Y2Ti2O7, which formed by a spontaneous reaction between nano-sized ceramics with a low solubility limit in the metal.

Selenium speciation, solubility, and mobility in land-disposed dredged sediments.

Pilot-scale tests for the land disposal of Se-enriched sediments from the San Luis Drain were performed in the San Joaquin Valley, California. Three test plots were instrumented and monitored on a dirt-road embankment near the sediment source area, providing an opportunity to measure Se oxidation and solubilization rates over a period of 2-3 yr. Soil, soil water, and groundwater data indicated that the amendment did not cause movement of dissolved Se below a depth of 15 cm. The low permeability of underlying sediments and the overall low Se solubility limit Se movement toward the groundwater table. Selenium remained in reduced forms and largely immobile at this site, although in-situ Se oxidation was measurable. Soluble Se concentrations increased from less than 0.5% to approximately 2.5% in the first 207 d following sediment application. Minor Se solubilization occurred after 439 and 704 d. Changes in Se fractionation measured using sequential extractions and Se speciation based on X-ray spectroscopy (XANES) results were in qualitative agreement. XANES results indicated initially rapid oxidation of organo-Se and/or elemental Se to selenite during the first 207 d, followed by minor oxidation after 439 d. Further solubilization of the Se inventory is anticipated, but at a low rate of 1-2% per year, comparable to rates measured in other studies.

Enhancing RO system performance utilizing antiscalants

When using reverse osmosis (RO), spraying soluble salts, such as calcium carbonate or barium sulfate, having a very low solubility limit, constitute a very specific potential of scaling the membrane surface. Due to the removal of permeate, the salt concentration of the retentate stream increases along the RO module's length. RO systems operating at high recoveries may experience high levels of sparingly soluble salts in the concentrating retentate. If the solubility limits of these salts are exceeded, salts precipitation starts. Evidently scale formation on the membrane surface has a detrimental effect on both permeate flux and quality. In practice, the deposition of scales at the RO membrane surface is prohibited by adding antiscalants to the feed. In the present work it has been attempted to introduce a simple model for arriving at the maximum feasible recovery as constrained by the chemical analysis of the saline feed water under consideration, its temperature, the level of the concentration polarization experienced within the RO system, and the ever improving performance achievable through the continuous development of RO antiscalants. However, for the optimal operation of the RO system the proper dosage of the respective antiscalants as a function of the system recovery will continue to add to the subject complexity and is subject to some discussions with the antiscalants suppliers. During RO, adequate antiscalant dosing at proper pH and pretreatment conditions will contribute considerably to the optimal utilization of the performance capabilities of RO membranes in terms of permeate flux and quality. The recommended model as presented in this work is aimed to be an important and convenient step towards the realization of the abovementioned objectives and hence the cost effective production of desalted water.

Sorption Mechanisms of Eu3+ on CSH Phases of Hydrated Cements

The sorption mechanisms of Eu3+ on calcium silicate hydrate (CSH) phases of hydrated cement were investigated as a tool for the prediction of the behavior of trivalent radionuclides with aged/degraded cements in radioactive waste repositories. Four techniques were used: site-selective and time-resolved luminescence spectroscopy, XPS, high-resolution SEM coupled with EDX, and XRD. Results showed that europium is not precipitated in the solution despite its low solubility limit. It is strongly retained on CSH, resulting in a more than 99.8% sorption rate. Two main sorption sites were characterized by luminescence spectroscopy. One site, with a long lifetime, can be interpreted as Eu included in the framework of CSH. Another one, with a shorter lifetime, can be interpreted as a site with a hydrated environment that is high but is less than that of europium hydroxide. It corresponds to superficial complexation or precipitation.

Comparison of the crystal chemistry and electrical properties of La 2−xAxNiO 4 ( A = Ca, Sr, and Ba)

With an objective to understand the influence of the size of the A cations, the crystal chemistry and electrical properties of La 2−x A xNiO 4 ( A = Ca, Sr, and Ba) are compared. The solubility limits of the A cations in La 2−x A xNiO 4 are 0.6, 1.5, and 1.1, respectively, for A = Ca, Sr, and Ba. At a given value of x, the Ca and Ba systems have lower oxygen content than that of the Sr system. The lower solubility limit and oxygen content for the Ca and Ba systems are due to a preference of Ca 2+ for eightfold coordination and a larger degree of tensile stress in the Ni–O bonds of La 2−xBa xNiO 4 at higher doping levels. For x < 0.6, the a parameter decreases in all the three systems, while the c parameter increases in the Sr and Ba systems and decreases in the Ca system with increasing x. For x > 0.6, the a parameter increases in the Sr and Ba systems, while the c parameter decreases in the Sr system and remains almost constant in the Ba system with increasing x. The increase in a parameter and the decrease or constancy of c parameter for x > 0.6 is due to a transfer of electron density from the d z 2 band to the d x 2 −y 2 band. While the Sr system exhibits a semiconductor-to-metal transition with increasing x, both the Ca and Ba systems are semiconducting for all values of x.

Effects of Pt and Ta on the magnetic anisotropy of Co and Co–Cr thin films

We have investigated the magnetic anisotropy energy (MAE) of binary Co–X (X=Cr, Ta, Pt) and ternary Co–Cr with Ta or Pt. It is found that Cr considerably decreases the MAE of Co, and a severer reduction of the MAE has been found in Co–Ta and Co–Cr–Ta within an extremely low solubility limit of Ta less than a few atomic percent. In contrast, Pt gives no noticeable change in the MAE of Co, but causes remarkable enhancement of the saturation magnetization and the MAE of Co–Cr alloy. These enhancement can be explained by the reduction of the Cr content due to Pt in ferromagnetic Co-enriched regions in a segregated phase. A thermodynamical consideration taking into account the magnetic term of Gibbs free energy gives a qualitative explanation for the role of Pt.

Data Collection for the Calculation of Phase Equilibria

Data collection for the calculation of phase equilibria is discussed, with reference to the Al‒Ni‒Re system. Since there were conflicting data for the Al‒Re system and no data at all for the ternary system, an extensive experimental programme was initiated using SEM with EDS, and XRD. X-ray data were modelled for the likely structures of some phases. Experimental results indicated that a previously unreported binary eutectic reaction forming Al2Re3 and Al3Re was found at ∼ 34at.% Re. With the exception of Al12Re (which was only found as a minor, finely divided component), all intermetallic phases were demonstrated to have a composition range between 1.5 and ∼5 at.%. In the Al‒Ni‒Re ternary system, (Re) had the greatest solubility. The Al3Re and Al6Re phases extended within the ternary to ∼6 at.% Ni, whereas AlNi and AlRe2 showed ∼3 at.% extension. The remaining phases had very much lower solubility limits. The liquidus surface was derived from the sequence of solidification. Since these findings were largely deduced from metallographic studies, problems associated with the interpretation of microstructures were discussed in general terms.

Maximum solubility of cholesterol in phosphatidylcholine and phosphatidylethanolamine bilayers

In any lipid bilayer membrane, there is an upper limit on the cholesterol concentration that can be accommodated within the bilayer structure; excess cholesterol will precipitate as crystals of pure cholesterol monohydrate. This cholesterol solubility limit is a well-defined quantity. It is a first-order phase boundary in the phospholipid/cholesterol phase diagram. There are many different solubility limits in the literature, but no clear picture has emerged that can unify the disparate results. We have studied the effects that different sample preparation methods can have on the apparent experimental solubility limit. We find that artifactual demixing of cholesterol can occur during conventional sample preparation and that this demixed cholesterol may produce artifactual cholesterol crystals. Therefore, phospholipid/cholesterol suspensions which are prepared by conventional methods may manifest variable, falsely low cholesterol solubility limits. We have developed two novel preparative methods which are specifically designed to prevent demixing during sample preparation. For detection of the cholesterol crystals, X-ray diffraction has proven to be quantitative and highly sensitive. Experiments based on these methods yield reproducible and precise cholesterol solubility limits: 66 mol% for phosphatidylcholine (PC) bilayers and 51 mol% for phosphatidylethanolamine (PE) bilayers. We present evidence that these are true, equilibrium values. In contrast to the dramatic headgroup effect (PC vs. PE), acyl chain variations had no effect on the cholesterol solubility limit in four different PC/cholesterol mixtures.

Crystal chemical substitutions and doping of YBa 2Cu 3O x and related superconductors

The 90 K superconductor, YBa 2Cu 3O δ (YBCO), has proved to be highly adaptable chemically as it can accommodate a wide variety of cationic and anionic substitutions. Indeed, the majority of the chemical elements, excluding noble gases and actinides, have been reported to substitute to some extent into the YBCO structure. This review covers the literature on such substitutions and their effect on the properties of YBCO. Reported solubility limits are given, together with crystal symmetry and trends in unit cell parameters with dopant concentration. The dopant site is considered; this is additionally complex in the case of copper substitution because of the two distinct copper sites in the crystal structure. The effect of the dopant on the critical temperature, T c, is reviewed; the literature is often contradictory due to the dual effects of variable oxygen content and the nature of the dopant. Preparation methods appear to have an effect on solubility limits, crystal symmetry and T c, Also, the methods used to determine solubility limits are often imprecise which can lead to contradictions. The magnetic properties of doped materials are reviewed; for some dopants, particularly the magnetic lanthanides, antiferromagnetism and superconductivity co-exist. The related RBa 2Cu 3O δ phases (R = lanthanide), their structure, properties and behaviour on doping are reviewed in a similar way. For the larger rare earths, the related systems R 1+ x Ba 2- x CU 3O δ, are reviewed; as x increases, the transition temperature decreases and compositions R 1.5Ba 1.5Cu 3O δ are semiconducting. The upper and lower solubility limit changes with R, and for R = Dy, the upper limit is < 0.1 whereas for La, the x = 0 composition, LaBa 2Cu 3O δ, cannot be prepared in air since substitution of La onto the Ba site occurs, forming the Ba-deficient solid solutions. The discovery of superconductivity above liquid nitrogen temperatures in YBa 2Cu 3O 7, has generated a vast quantity of research; to date, > 20 000 papers have appeared on the 123 materials (source: BIDS). This review, therefore, cannot be comprehensive, but attempts to highlight important substitutions, their effect on the properties of YBCO and any contradictions in the literature.

The Microstructure and Martensitic Transformation in Ni-Al Alloys with Yttrium Addition

The microstructure and martensitic transformation in the Ni-36.3Al-0.45Y (in at.%) alloy were investigated after homogenisation and plastic deformation by hot upsetting at 1100°C. The alloy exhibited large, recrystallised grains of the Ni-Al β phase with spherical precipitates inside the grains and a thin layer of other phases located at the grain boundaries, The SEM and EDX analysis showed that both types of precipitates were composed of two intennetallic phases (Ni x Al 1-x )Y 5 with different Ni to Al ratio. No yttrium content has been detected in the matrix β phase, probably because of the low solubility limit which is 0.1 at.%. The martensitic transformation was studied by TEM and DSC calorimetry. In large grains of the recrystallised material the M, temperature was measured to be -4°C and the transformation proceeded in the range of 60 deg. The M , temperature was lower than expected from the ratio of Ni to Al. Aging I hour at 240°C did not influence the range of the transformation. The TEM study of the β phase revealed strong and regular contrast modulations, probably being premartensitic effects. Also a regular spaced network of dislocations lying in the same directions as the contrast modulations, both in matrix and martensite, was noticed. In foils 7R structure of martensite, internally twinned, was predominantly found. The alloy was very brittle.