Small Amounts Of Pb Research Articles

THE FIRST BOTALLACKITE OCCURRENCE IN POLAND (POLKOWICE-SIEROSZOWICE MINE)

The presence of botallackite was recognized in an underground galery in the Polkowice-Sieroszowice copper mine. This mineral coexists with paratacamite, clinoatacamite, gypsum and halite. Botallackite crystallized from chloride-reach (3500 mg/dm3), warm (33°C) mine water. On the basis of microprobe analyzes, two types of botallackite were recognized. The first one contains only small amounts of Pb, Fe and Zn. These elements substitute Cu2+ ions in small proportions. Empirical formula of this botallackite is: (Cu1.94Pb0.02Fe0.02Zn0.02)S = 2.00Cl0.98(OH)3.02. The second type of the mineral were characterized by increased amounts of Pb, Fe, Zn. The empiric formula of this type of botallackite can be expressed as: (Cu1.85Pb0.09Fe0.04Zn0.02)S = 2.00Cl1.05(OH)2.95. The calculated unit-cell parameters of botallackite from Polkowice-Sieroszowice mine are as follows: a = 5.7165(2), b = 6.1362(2), c = 5.6325(2), b = 92.943(3). Botallackite is a least stable polymorph of Cu2Cl(OH)3 and finally transforms to more stable polymorphs. The botallackite recrystallization can be inhibit by high concentration of Ca2+ in the mine water. Substitution of Cu2+ ions by other divalent cations can slows the rapidity of recrystalization this mineral and prevent its further transformation also. The Polkowice-Sieroszowice mine is the first occurrence of botallackite in Poland.

Speciation and Mobility of Lead, Chromium and Zinc in Soils of Abis Region, Egypt

This study describes the chemical speciation of Pb, Cr and Zn in soils of Abis area in Egypt. The studied area is located at the North Western part of the Nile Delta, which represents soils developed from lacustreine deposits at Abis region south of Mariut Lake and covers about 40000 fed. Total 41 top soil samples (0-35 cm) were collected from the area for analysis. The total contents and fractions of Pb, Cr, and Zn were determined, and the mobility factor and potential mobility were calculated. Small amounts of Pb, Cr, and Zn retrieved from the soluble and exchangeable phases, the readily available for biogeochemical cycles in the ecosystem. Low quantities of Pb, Cr and Zn could be available to plants. Zn is present in negligible amounts lower than those of Pb or Cr. The results also indicate that most of the metals have high abundance in residual fraction indicating lithogenic origin and low bioavailability of metals in the studied soil. The values of average mobility factor for Pb, Cr and Zn in the soils of Abis area were 7.31, 6.74 and 0.51%, respectively which is less than 10%. Therefore, these elements are highly stable in soil. The average potential mobility of Pb, Cr and Zn were 15.05%. 34.79% and 8.25% respectively. The Zn had the least average potential mobility (8.25%). The order of average potential mobility of metals soils agrees with the percentage reduction in concentration of residual heavy metal.

Phytoremediation of lead (Pb) and Arsenic (As) by Melastoma malabathricum L. from Contaminated Soil in Separate Exposure

This study was conducted to investigate the uptake of lead (Pb) and arsenic (As) from contaminated soil using Melastoma malabathricum L. species. The cultivated plants were exposed to As and Pb in separate soils for an observation period of 70 days. From the results of the analysis, M. malabathricum accumulated relatively high range of As concentration in its roots, up to a maximum of 2800 mg/kg. The highest accumulation of As in stems and leaves was 570 mg/kg of plant. For Pb treatment, the highest concentration (13,800 mg/kg) was accumulated in the roots of plants. The maximum accumulation in stems was 880 mg/kg while maximum accumulation in leaves was 2,200 mg/kg. Only small amounts of Pb were translocated from roots to above ground plant parts (TF < 1). However, a wider range of TF values (0.01–23) for As treated plants proved that the translocation of As from root to above ground parts was greater. However, the high capacity of roots to take up Pb and As (BF > 1) is indicative this plants is a good bioaccumulator for these metals. Therefore, phytostabilisation is the mechanism at work in M. malabathricum's uptake of Pb, while phytoextraction is the dominant mechanism with As.

Long-term results from use of pasteurized bone

BackgroundPasteurized bone (PB) is recycled bone. The pasteurization has a tumor cell-killing effect wit retention of initial strength. However, few reports have been published on its long-term course; thus, in this study, we evaluated the long-term course of use of PB and examined appropriate reconstruction methods. Patients and methodsWe reviewed 27 cases in which reconstructive surgery using PB was performed between 1990 and 2002. Of these, we excluded 12 fatal cases and 1 case in which follow-up was discontinued. Therefore, our final analysis consisted of 14 cases with an average follow-up period of 165months. The reconstruction methods used were: osteoarticular graft in 6 cases, composite graft with prosthesis in 3 cases, intercalary graft in 1 case, and reconstruction using PB from the pelvis in 4 cases. ResultsThe PB survived in 7 of the 14 cases. Five and 10-year survival of the PB was 78.6 and 47.6 %, respectively. Three of the 6 osteoarticular cases failed because of late-onset absorption or infection of the PB. For patients with composite graft or intercalary graft, long-term survival was achieved when small amounts of PB were used. For patients with pelvic grafts, long-term survival was achieved in a case of P1 pelvis, but large PB grafts on small bone-junction surfaces were not successful in the long term. On the basis of these results, we were able to achieve successful long-term results with small PB grafts on large bone-junction surfaces. ConclusionsTo prevent bone absorption and achieve long-term survival of PB, it is important to use a small PB graft and create a large surface area of contact with normal bone. These factors are advantageous to PB survival and to gaining limb function.

Electrochemical migration of tin in electronics and microstructure of the dendrites

The macro-, micro-, and nano-scale morphology and structure of tin dendrites, formed by electrochemical migration on a surface mount ceramic chip resistor having electrodes consisting of tin with small amounts of Pb (∼2 wt.%) was investigated by scanning electron microscopy and transmission electron microscopy including Energy dispersive X-ray spectroscopy and electron diffraction. The tin dendrites were formed under 5 or 12 V potential bias in 10 ppm by weight NaCl electrolyte as a micro-droplet on the resistor during electrochemical migration experiments. The dendrites formed were found to have heterogeneous microstructure along the growth direction, which is attributed to unstable growth conditions inside the micro-volume of electrolyte. Selected area electron diffraction showed that the dendrites are metallic tin having sections of single crystal orientation and lead containing intermetallic particles embedded in the structure. At certain areas, the dendrite structure was found to be surrounded by an oxide crust, which is believed to be due to unstable growth conditions during the dendrite formation. The oxide layer was found to be of nanocrystalline structure, which is expected to be formed by the dehydration of the hydrated oxide originally formed in solution ex-situ in ambient air.

Impact of board and component metallizations on microstructure and reliability of lead-free solder joints

Aging and accelerated thermal cycling (ATC) have been performed on 2512 chip resistors assembled with Sn3.8Ag0.7Cu (wt.%) solder. The boards were finished with immersion Ag (IAg), electroless nickel/immersion gold (ENIG), and hot air solder leveling Sn–Pb eutectic solder (HASL), and the components’ terminations were finished with 100% Sn and Sn8.0Pb (wt.%). The boards were reflowed with an average cooling rate of 1.6 °C/s. It was found that the microstructure and reliability of the solder joints depended on the board surface finish. The boards containing small amounts of Pb (from board/component terminations) were the most reliable. Solder joints to copper showed a significantly higher number of cycles to first failure than the joints on nickel. Better reliability of the Sn3.8Ag0.7Cu/Cu joints was attributed to an increased copper content in the bulk due to substrate dissolution.

Materials behaviour and intermetallics characteristics in the reaction between SnAgCu and Sn–Pb solder alloys

This paper illustrates the application of thermodynamic modelling techniques that are capable of simulating and predicting a range of interacting physical phenomena associated with the thermodynamic behaviour of multicomponent Sn-Pb/Pb-free solders in relation to solder joint manufacture and long term reliability. The paper compares theoretical calculations with experimental data, to identify the metallurgical mechanisms with regard to the rework or repair that may be encountered in the transition period from Sn-Pb to Pb-free soldering. Thermodynamic calculations have been carried out to study the material behaviour and possible formation of intermetallic precipitates during the reaction between Sn-Pb and Sn-Ag-Cu Pb-free alloys. Two Sn-Ag-Cu alloys that are relevant to current industrial interests, namely Sn-3.9Ag-0.6Cu and Sn-3.0Ag-0.5Cu were reacted with different contamination levels of eutectic Sn-37Pb solder. The variables related to the materials and processes, such as composition, temperature and cooling rate, are the primary concerns with respect to resultant microstructures, which have also been studied experimentally using optical and scanning electron microscopy (SEM). The results from this work provide guidance as to the consequence for microstructural evolution and hence mechanical integrity when small amounts of Pb exist in Pb-free alloys.

Structure of the liquid-vapor interface of a dilute ternary alloy: Pb and In in Ga

We report the results of experimental studies of how the competition between two solutes to segregate in the liquid-vapor interface of a dilute ternary alloy influences the composition and structure of that interface. The system studied has small amounts of Pb and In dissolved in Ga; it differs from a previous study of dilute alloys containing small amounts of Pb and Sn dissolved in Ga by the addition of a new variable, namely, the valence difference between the solute atoms Pb and In. This valence difference influences the electron density distribution in the alloy liquid-vapor interface in proportion to the excess concentrations of the solute species in the interface, and thereby should affect the structure of the interface. We find that for a ternary PbInGa alloy that contains 0.039 at. % Pb and 6.31 at. % In, the Pb that segregates in the liquid-vapor interface forms a two-dimensional hexagonal crystal phase that undergoes a first-order transition to a disordered phase at $T=29.0\ifmmode\pm\else\textpm\fi{}0.1\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The two-dimensional crystalline Pb forms about 0.6 of a full monolayer; the remainder of the outer stratum of the liquid-vapor interface is filled with two-dimensional liquid In. For a ternary PbInGa alloy that contains the same amount of Pb and 12.2 at. % In, the Pb that segregates in the liquid-vapor interface forms a two-dimensional liquid down to 26.0 \ifmmode^\circ\else\textdegree\fi{}C, the lowest temperature at which data were taken. For temperatures in excess of 29.0 \ifmmode^\circ\else\textdegree\fi{}C two-dimensional liquid Pb and two-dimensional liquid In coexist in the interface, with the fractional occupation of the monolayer by In exceeding the fractional occupation by Pb.

Investigation of Al–Pb nanocomposites synthesized by nonequilibrium processes

Two nonequilibrium processes (melt-spinning and ball-milling) were successfully employed to synthesize Al1−xPbx(x= 5, 10, 20, 30 wt. %) nanocomposites with distinct microstructures. In the melt-spun (MS) Al–Pb alloys, the nanometer-sized Pb particles are uniformly distributed in the micrometer-grained Al matrix and have an orientational relationship with the matrix, while in the ball-milled (BM) samples, both Pb and Al components are refined with prolonged milling time, forming nanocomposites with Pb particles homogeneously dispersed into the Al matrix. The minimum particle size of Pb in the milled samples linearly increases with the Pb content. The microhardness of the BM Al–Pb samples is much larger than that of the MS samples, which mainly results from strengthening effects of the nanometer scale Al grains following the Hall–Petch relationship. The microhardness for both BM and MS Al–Pb samples varies with the Pb content, and maximum hardness for both samples exists when Pb content is about 5 wt. %, indicating that small amounts of Pb, in the form of nanoparticles, may strengthen the Al matrix.

Charge Transfer and Surface Diffusion of Lead on Ge(111)

Small amounts of Pb significantly enhance the surface diffusion on the Ge(111)c(2 × 8) surface. Scanning tunneling microscopy at different sample bias polarities has been used to study the local geometric and electronic properties of the mixed Pb and Ge adatom structure. It was found that all Ge adatoms transfer charge to the Ge rest atoms whereas the Pb atoms exist in two different electronic configurations. Pb atoms which do not transfer charge to Ge rest atoms allow the existence of various characteristic Pb-induced defects in the c(2 × 8) reconstruction. During the formation of these defects vacancies are created which facilitate the diffusion of adatoms over large distances on the surface.

Free radical copolymerization of 4-phenylbut-1-en-3-yne with methylmethacrylate

Free radical copolymerization of 4-phenylbut-1-en-3-yne (PB) with methyl methacrylate(MMA) was studied. The polymerization of MMA was inhibited by the presence of small amounts of PB, but the copolymerization yield increased with increase in the PB concentration, and PB-rich copolymers were obtained. The monomer reactivity ratios, rMMA and rPB, were found to be 0.096 and 2.83, respectively. The Q and e values of PB were calculated by using the values of MMA and were found to be 2.69 and 0.74, respectively. The slow polymerization and low molecular weights were attributed to the low propagating activity of PB radicals.

Enhancement of the high-T c phase in Bi-Ca-Sr-Cu-O by ceramic processing methods

Materials in the Bi-Ca-Sr-Cu-O superconductor system were prepared by melt-quenching. Results were obtained for materials doped with small amounts of Pb and Sb. A substantial increase in the yield of the high- T c (2223) phase, with a corresponding improvement in superconducting properties, was noted for specimens heat-treated at 848°C in an atmosphere of 10% O 2 and 90% Ar. The best specimens exhibited a T c (zero resistance) near 105 K and a large (∼ 90%) 2223 content. Experimental results are discussed in the context of phase and microstructure development, and the evolution of superconducting properties with heat-treatment.

Evolution of the High TcPhase in Rapidly Solidified Bi-Ca-Sr-Cu Oxides

AbstractMaterials in the system Bi-Ca-Sr-Cu-O were prepared by rapid solidification. Emphasis was placed on optimizing processing conditions for enhancement of the high Tc(2223) phase. A number of starting compositions and heat-treatments were investigated. The effect of dopants (such as, Pb, Sb, Ge, Sn) on the stabilization of the high Tc phase was evaluated. Small amounts of Pb and Sb were effective in significantly increasing the 2223 yield. Improvements in superconducting properties as a function of 2223 evolution are discussed with reference to SEM, TEM, XRD and SQUID results.

Influence of lead on the formation of the 110-K superconducting phase in the Bi-Sr-Ca-Cu-O compounds.

The fraction of the 110-K phase in the Bi-Sr-Ca-Cu-O compound is rapidly increased if small amounts of Pb are incorporated in the compound. The maximum ${T}_{c}(R=0)$ of 106 K was obtained after a sintering treatment of several days at 860\ifmmode^\circ\else\textdegree\fi{}C. Computer-generated powder diffraction patterns showed, when compared to the measured ones, the possibility for Pb to occupy Ca or Bi sites.

COMPARATIVE EFFICIENCIES OF VARIOUS METHODS FOR EXTRACTING TRACE HEAVY METALS FROM SOILS

Three methods for extracting trace heavy metals from soils have been compared. The methods were sodium carbonate fusion, extraction with hydrogen fluoride solution, and extraction by mixtures of nitric, sulfuric, and perchloric acids. Two artificial “soils” were used. “Soil A” was animal charcoal to which small amounts of Pb, Cu, and Cd had been added. “Soil B” was kieselguhr to which Pb, Cu, and Cd had again been added. The carbonate fusion gave low and erratic values in all samples. The other methods were more reliable. A modification to the usual three-acid extraction method is described. This is safer and quicker to use.

In115Knight Shifts in Liquid In Alloys Containing Small Amounts of Pb

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