Papers by Keyword: Phosphorus

Abstract: The largest comparison of analytical techniques, useful for calcium phosphates, has been conducted, presenting recommendations for quality control and research of calcium phosphates. Results from three classical quantification methods (gravimetry, titramety, photometry) and three instrumental measurement methods (XRF, FAAS ICP-OES) are reported to determine the most accurate, fastest and cheapest analysis method. Remarks are given for increasing the accuracy for each method and corrections made for adsorbed water. For routine analysis, a recommendation is given to ICP-OES for a fast analysis, together with a less frequent use of gravimetry to validate the results and provide a periodic cross-check.

Abstract: The paper presents the results of modelling of phosphorus interaction with substitutional (Cr, Mn, P) and interstitial (C) impurity atoms in bcc iron in the framework of density functional theory using WIEN2k software. It is found that a repulsion exists of a phosphorus atom in the three first spheres of coordination of carbon, chromium and phosphorus atoms, while for manganese such repulsion of phosphorus takes place only in the second sphere. This repulsion is a consequence of an abrupt change of magnetic moment of manganese atom, so the solution energy of phosphorus almost does not change. On the contrary, chromium decreases phosphorus solubility in iron, in agreement with other data.

Abstract: Excess deposits of phosphorus into surface waters have caused a lot of devastating effects on both human and aquatic lives and, of course, ecosystem disruption. Ox-eye seed (OES), an agricultural biomass, has been explored as a coagulant to remove phosphorus from aqueous solution through coag-flocculation process. The seeds were prepared into a coagulant and a proximate analysis was carried out on the prepared OES. Nephelometric analysis was employed to investigate the effects of settling time, coagulant dosage and pH on phosphate removal efficiency of OES. The process parameters were optimized using Response Surface Methodology. OES’s performance was compared with Alum’s, a conventional coagulant, and the results obtained reveal Alum as having a global minimum of zero turbidity, global optimum values for pH (7.4103) and dosage (301.6501mg/l) but a local optimum of 80min for settling time, while the optimum operating parameters for OES are 7.3740 (global), 500mg/l (local), 80min (local) and 11.2266mg/l (local) for pH, dosage, settling time and turbidity respectively. It is evident that, by increasing settling time and dosage , OES can effectively compete with Alum. The main attribute to effective performance of both OES and Alum is pH. The interactions pH-dosage and pH-settling time are significant. The model accuracy is confirmed by the values of R² >0.99 and is validated by the closeness of the experimental data to the predictions. Keywords: Phosphorus, wastewater, turbidity, Coagulant, ox-eye, flocculation

Abstract: Microstructure and mechanical properties of Ni-Cr alloys with various contents of Phosphorus (P) have been investigated. It is found that the increase of phosphorus refined dendritic structures in as-cast alloys and decreased micro-segregation of Chromium (Cr) element. α-Cr which precipitated during hot-rolling process was obviously inhibited by phosphorus because of its prior occupancy on grain boundaries and decreasing precipitation driving force of α-Cr. Tensile and impact properties were examined on samples under different heat treatments. Though the yield strength of as-rolled alloys was increased by precipitation of α-Cr, the elongation and impact energies were reduced. It is worthy to note that impact energies of samples solutioned at 950°C increased with the increasing phosphorus. The results indicated that dislocations are markedly effected by phosphorus which is probably the reason for improving impact energies.

Abstract: The segregation and precipitation behavior of phosphoruswas studied in aNi-Fe-Cr base wroughtsuperalloy. The precipitation behavior of phosphides in the alloy contained 0.025% Pwas examined after soaking at 750-1080°C to determine the precipitation temperature range of MNP-type phosphide. The microstructuresunder these various conditions wereinvestigated by scanning electron microscope(SEM) and energy dispersive spectroscopy (EDS). The precipitation temperature of the phosphide in the alloy was determined to be in the range of 850-1040 °C and the precipitation peak temperature was around 980°C.In addition, the melting temperatureof the phosphide was determined to be between 1200 °C and 1250 °C. The current results indicate the tendency of phosphorus segregated at grain boundaries.

Abstract: In this article, a novel Al–6Y–2P master alloy with YP particles was successfully synthesized. By means of the fracture surface observation, it was found that YP particles with an average size of 21.5 μm exhibit the cubic morphologies. With the addition of Al–6Y–2P master alloy, primary Mg₂Si particles in Al–Mg₂Si composites can be significantly refined to 21.2 μm and 20.3 μm after holding for 30 min and 120 min respectively. Meanwhile, the morphologies of eutectic Mg₂Si alter from a flake-like to fine fibrous shape. The reason for the excellent refining performance of this master alloy was discussed based on the chemical kinetics theory. During the solidification process, P atoms distribute homogeneously in the Al melt and precipitate in the form of AlP, providing heterogeneous nucleation sites for primary Mg₂Si.

Abstract: High channel mobility 4H-SiC MOSFETs have been demonstrated by phosphorus and arsenic implantation prior to thermal oxidation in N₂O. The maximum field-effect mobility of 81 and 114 cm²/Vs were achieved, respectively. The MOSFET fabrication was done on lightly aluminium doped p-type epitaxial layers and on heavily aluminium implanted p-well.

Abstract: In this work the effect of phosphorus on the electrical properties of n-type 4H-SiC MOS capacitors is studied. Phosphorus ions are implanted into the epitaxial layers prior to the deposition of SiO₂ by PECVD, in shallow depths and at concentrations at the oxide-semiconductor interface in the range of (5 x 10¹⁷…1 x 10¹⁹) cm^-3. Those samples are compared with ³¹P-implanted 4H-SiC MOS capacitors with thermally grown oxides, which were primarily investigated in the previous work of the authors. It is shown that independently of the oxide technology phosphorus may lead to decrease of the density of interface traps, whose response time to the AC voltage is longer than 1 µs. The side-effect of the implantation of phosphorus is generation of the very fast interface states, which are able to follow the frequencies over 1 MHz.

Abstract: The use of biohydrometallurgical processes may be restricted by microbial inhibition due to inhibiting fluoride originating from the feed material. In this work, phosphorus bioleaching experiments on fluorapatite ore were conducted in a reactor using Fe-and S-oxidizing bacteria, resulting in 56 % leaching yield for P, despite abundant (800 mg l^-1) F in the pregnant leach solution. In further F toxicity experiments it was observed that aluminum had a significant role in decreasing the inhibition caused by F, by producing stable complexes with Al. The bioleached ore contained plenty of Al, explaining why bioleaching was not strongly inhibited.

Abstract: We present the influence of phosphorous auto-doping on the characteristics of the oxide interface in 4H-SiC following high temperature gate oxide annealing. IV characteristics show no evidence of direct tunnelling breakdown; however Fowler Nordheim (F-N) conduction is observed in high electric field with the oxides able to sustain >10MV/cm. Capacitance Voltage data show D_IT <1x10¹² eV^-1cm^-2 close to the conduction band edge after POA, with undoped samples demonstrating D_IT below 5x10¹¹ eV^-1cm^-2. Photo CV data indicates smaller flat band voltage shifts of 0.6V at midpoint for the undoped samples, in comparison to 0.9V for the phosphorous doped devices. Temperature and bias stress tests at 200°C showed marginal hysteresis (0.3V) in both wafers. Reliability of time-dependent constant current and constant voltage characteristics revealed higher TDDB lifetimes in the undoped wafer. We conclude that the unintentional incorporation of phosphorous into the gate stack as a result of high temperature POA of the doped field oxide leads to a variation in flat band shift, higher D_IT, and lower dielectric reliability.