Pb Particle Size Research Articles

Microstructural Features of Spray‐Deposited Cold Rolled Al Alloy

In the present work, the microstructural studies of spray deposited Al-6Si alloys with different lead content are conducted for 0% and 40% of rolling deformation. SEM and Optical micrographs are taken for different percentage of lead content. Fine equiaxed grain morphology is observed with a uniform distribution of Pb and Si phase in an Al-matrix and it is found from the microstructures that the size of Pb particles increased with the increase in Pb content. Grains are stretched out in the rolling direction after cold rolling. Pore size is found to decrease after 40% rolling reduction, however, it is increased with the increase in Pb content.

Characteristics and mechanisms of Pb(II) sorption onto Fe-rich waste water treatment residue (WTR): A potential sustainable Pb immobilisation technology for soils

Pb contamination of soils is a global problem. This paper discusses the ability of an Fe-rich waste, water treatment residual (WTR), to adsorb Pb(II). This was investigated using batch sorption experiments, X-ray diffraction, electron microprobe microanalysis, PHREEQC modeling and Extended X-ray Absorption Fine Structure (EXAFS) analysis. The WTR is composed of approximately 23 wt. % natural organic matter (NOM), 70 wt. % ferrihydrite and <10 wt. % silicate material. Pb(II) sorption to WTR was dependent on initial Pb(II) load, particle size, time and pH, but not on ionic strength. EXAFS analysis at the Pb LIII-edge confirmed that Pb(II) sorbed to WTR by co-existing bidentate edge-sharing and monodentate or corner-sharing complexes, with 2 O at ∼2.31–2.34 Å, 1 Fe at ∼3.32–3.34 Å, 2 Fe at ∼3.97–3.99 Å and 1 Pb at ∼3.82–3.85 Å. Linear combination showed that the Pb(II)-sorbed spectra were best fit with a ∼0.9 ± 0.1 and 0.1 ± 0.1 contribution from Pb(II)-sorbed ferrihydrite and Pb(II)-sorbed humic acid end members, respectively. Overall, we show that Pb(II) sorbs via strong inner-sphere complexation of Pb(II) to the ferrihydrite component of the WTR, which itself is stable over a wide pH range. Therefore, we suggest that Fe-rich WTR wastes could be used as effective adsorbents in Pb(II)-contaminated soils to help ensure sustainable terrestrial ecosystems.

The source of lead determines the relationship between soil properties and lead bioaccessibility

Lead (Pb) contaminated soil is of particular concern for infants and children due to their susceptibility to exposure, fast metabolic rates and rapidly developing neuronal systems. Determining the bioaccessibility of Pb in soils is critical in human health risk assessments, which can vary due to different soil properties and sources of Pb contamination. In this study, the potential relationships between soil properties and Pb bioaccessibility from various Pb sources including Pb contamination from mining (specifically, Broken Hill), three shooting ranges, a smelter and two industry sites (pottery and battery), were investigated using the Relative Bioavailability Leaching Procedure (RBALP). We found the following: (1) CEC, TOC, sand and silt content, and total Pb were significantly different (p < 0.05) between the two particle size fractions of < 2 mm and < 250 μm; (2) EC, CEC and total Pb were significantly correlated to Pb bioaccessibility (p < 0.05); and (3) soil analyses based on source of Pb demonstrated a strongly significant relationship between Pb bioaccessibility and soil properties (CEC, EC, clay content and total Pb) for mining soils from Broken Hill (r2 = 0.86, p < 0.05, n = 18). These results demonstrated the influences of Pb contamination sources, soil properties and particle size fractions on Pb bioaccessibility as well as the prediction of Pb bioaccessibility using soil properties. The findings documented here will help in developing a predictive tool for human health risk assessment and the remediation of Pb contaminated soils.

Surface Pb Nanoparticle Aggregation, Coalescence and Differential Capacitance in a Deep Eutectic Solvent Using a Simultaneous Sample-Rotated Small Angle X-ray Scattering and Electrochemical Methods Approach

Nanoparticle electrodeposition is a simple and scalable approach to synthesizing supported nanoparticles. Used with a deep eutectic solvent (DES), surface nanoparticles can be assembled and exhibit unique surface charge separation when the DES is adsorbed on the nanoparticle surface. Key to understanding and controlling the assembly and the capacitance is a thorough understanding of surface particle mobility and charge screening, which requires an in-situ approach. In this study, Pb particle formation, size, shape and capacitance are resolved in a 1:2 choline Cl−: urea deep eutectic solvent whilst sweeping the cell potential in the range: 0.2V to −1.2V (vs. Ag/AgCl). These system parameters were resolved using a complementary suite of sample-rotated small angle X-ray scattering (SR-SAXS) and electrochemical impedance spectroscopy (EIS), which are presented and discussed in detail. This approach is able to show that both particle and ion transport are impeded in the DES, as aggregation occurs over the course of 6minutes, and dissolved Pb ions accumulate and remain near the surface after a nucleation pulse is applied. The DES-Pb interactions strongly depend on the cell potential as evidenced by the specific differential capacitance of the Pb deposit, which has a maximum value of 2.5+/−0.5Fg−1 at −1.0V vs. Ag/AgCl. Altogether, the SR-SAXS-EIS approach is able to characterize the unique nanoparticle capacitance, mobility and ion mobility in a DES and can be used to study a wide range of nanoparticle deposition systems in-situ.

The Effect of Nanosized Pb Liquid Phase on the Damping Behavior in Aluminum Matrix Composite Based on the 2024Al-BaPbO3 System

An aluminum matrix composite containing nanosized Pb particles was fabricated by a powder metallurgy technique based on the 2024Al-BaPbO3 system. The composite exhibited a high and broad damping peak at the melting temperature range of nanosized Pb particles. The increase in value and breadth of the damping peak was attributed to the dislocation damping of the interfacial matrix close to the nanosized Pb liquid phase. The damping peak is expected to be enhanced by further refining the Pb particle size.

Exploring the use of cactus Opuntia ficus indica in the biocoagulation–flocculation of Pb(II) ions from wastewaters

Coagulation–flocculation processes play an important role in the treatment of water using inorganic and synthetic materials. Presently, cactus Opuntia ficus indica is explored as a cheap, abundant and eco-friendly bioflocculant of Pb(II) ions from aqueous solutions. The cactus powder was characterized by Fourier transform infrared spectrometer (FTIR), and the coagulation–flocculation process was optimized for pH, initial concentration of Pb(II) ions, particle size, dosage, ionic strength, contact time and temperature before its application to Mukuvisi River water. FTIR confirmed the involvement of –C–O–C–, –OH, –C=O, –N–H and –C–H groups of the polysaccharides, carboxylic acids and amino acids in the removal of Pb(II) ions. The variation of percentage removal and zeta potential with pH and flocculant dosage suggested the involvement of adsorption–charge neutralization and adsorption–bridging mechanisms in the coagulation–flocculation process. The process was optimum at pH 5, natural ionic strength, dosage of 8 mg/L, corresponding to zero zeta potential, with particle size <75 µm, at 35 °C for a floc settling time of 180 min. The coagulation–flocculation process was spontaneous and endothermic with a positive change in entropy of the system. Total heavy metal removal of 100 % (Pb), 85.74 % (Zn), 84.16 % (Cd) and 93.02 % (Cu) were achieved, under optimum conditions, when Opuntia ficus indica powder was used to remove metals from water sampled from Mukuvisi River, Harare, Zimbabwe. The cactus Opuntia ficus indica powder was found to be an efficient, eco-friendly flocculant that can effectively remediate Pb(II) ions from wastewaters.

Loading Rate-Dependent Mechanical Properties of Bulk Two-Phase Nanocrystalline Al-Pb Alloys Studied by Nanoindentation

Bulk samples (dia. = 20 mm) of various nanocrystalline (nc) Al-Pb alloys with Pb content varying from 1 to 4 at. pct are fabricated using spark plasma sintering of ball-milled powders. Al matrix in Al-2 at. pct Pb alloy had a grain size of 53 nm, and Pb particle size was 6 ± 2 nm. High angle annular dark-field image obtained in STEM mode of TEM indicates the presence of Pb along the nc Al grain boundaries as well as dispersion of smaller Pb particles in the intra-granular regions. Hardness studies are carried out using microindentation and nanoindentation with load varying over three orders of magnitude (100 − 0.1 g). Microindentation yielded slightly smaller hardness values in comparison to nanoindentation possibly because of indentation size effect. Nevertheless both microindentation and nanoindentation resulted in the same trend of hardness for various nc Al-Pb alloys. Hardness of Al-Pb alloys increased with increase in Pb content up to the additions of 2 at. pct Pb, beyond that the hardness is decreased for higher Pb additions of 3 and 4 pct. The initial hardening behavior is explained based on the Orowan particle strengthening. Strain rate sensitivity (SRS) has increased with increase in Pb content reaching a value of 0.1 for Al-4 at. pct Pb alloy. Activation volumes measured are between 2.84 and 6.15 b 3. Higher SRS and lower activation volume suggest that grain boundary-mediated processes are controlling the deformation characteristics.

Influence of Pb(II) Concentration and pH of Acetate Buffer on the Potential Window of a Lead Film Electrode: An Atomic Force Microscopy Study

Atomic force microscopy (AFM) studies on observations of lead films deposited from the solutions containing an acetate buffer and different concentration of Pb(II) are presented. AFM images show considerable variability in morphology of the deposited lead layer depending on experimental conditions. To investigate effects of the Pb(II) concentration and pH of the supporting electrolyte on the accessible potential window of the lead film electrode (PbFE), voltammetric techniques were used. It was found that the useful potential window of PbFE is affected by the pH and Pb(II) concentration. Additionally, it was found that the distribution and large size of Pb particles on the electrode surface shown by AFM corresponded well to the mass of Pb expected on the glassy carbon support with respect to the voltammetric data. Results reveal that PbFE is an attractive nonmercury metallic electrode suitable for electrochemical detection of metal ions and a lot of organic compounds in a wide potential window. The accessible potential window of the PbFE in an acetate buffer (pH = 5.0) was compared to those obtained at the bismuth film electrode and antimony film electrode.

Thickness Uniformity And Microstructure Of Disc shape Spray Formed Al-Si-Pb Alloys

Spray forming technique was employed to produce a near net-shape disc of Al-Si-Pb alloys. Different substrate distances and inclination angles were studied to obtain the disc shape preforms. The substrate was also offset by 40 mm from the atomizer axis in case of 15 and 30 degree inclination angles. Microstructures were investigated in different regions of the preforms. Results exhibited equiaxed grains of primary Al and Si was present within these grains and along the grain boundary. The size of the Al grains was 20-30 µm and size of Si particles was sub-micron to 5 µm. The size of Pb particles varied from sub-micron to 20 µm and it was uniformly dispersed throughout the aluminum phase.

Dependence of gamma-ray absorption coefficient on the size of lead particle

In this study, dependence of gamma-ray absorption coefficient on the size of Pb particle size ranging from 200µm up to 2.5mm, using different weights of each particle size. The results show that gamma-ray attenuation coefficient is inversely proportional with the size of Pb particle size due to the reduction of the spaces between the lead particles.

Dependence of gamma-ray absorption coefficient on the size of lead particle

In this study, dependence of gamma-ray absorption coefficient on the size of Pb particle size ranging from 200µm up to 2.5mm, using different weights of each particle size. The results show that gamma-ray attenuation coefficient is inversely proportional with the size of Pb particle size due to the reduction of the spaces between the lead particles.

Lead particle size and its association with firing conditions and range maintenance: implications for treatment

Six firing range soils were analyzed, representing different environments, firing conditions, and maintenance practices. The particle size distribution and lead (Pb) concentration in each soil fraction were determined for samples obtained from the backstop berms. The main factors that were found to influence Pb fragment size were the type of soil used to construct the berms and the type of weapon fired. The firing of high velocity weapons, i.e., rifles, onto highly angular soils induced significant fragmentation of the bullets and/or pulverization of the soil itself. This resulted in the accumulation of Pb in the finer soil fractions and the spread of Pb contamination beyond the vicinity of the backstop berm. Conversely, the use of clay as backstop and the use of low velocity pistols proved to be favorable for soil clean-up and range maintenance, since Pb was mainly present as large metallic fragments that can be recovered by a simple screening process. Other factors that played important roles in Pb particle size distribution were soil chemistry, firing distance, and maintenance practices, such as the use of water spray for dust suppression and deflectors prior to impact. Overall, coarse Pb particles provide much easier and more cost-effective maintenance, soil clean-up, and remediation via physical separation. Fine Pb particles release Pb more easily, pose an airborne Pb hazard, and require the application of stabilization/solidification treatment methods. Thus, to ensure sustainable firing range operations by means of cost-effective design, maintenance, and clean-up, especially when high velocity weapons are used, the above mentioned factors should be carefully considered.

Source Identification of Lead Contamination in Residential and Undisturbed Soil Adjacent to a Battery Manufacturing Facility (Part I)

Bulk elemental soil concentrations and individual particle analysis were used to identify the presence and sources of anthropogenic lead (Pb) contamination in residential and undisturbed soil adjacent to an automobile battery manufacturer. Automobile exhaust was also an important suspected source of Pb contamination in the soil of the residential area, a trailer park next to a busy highway. Soil was analyzed from the trailer park, battery facility, adjacent undisturbed wooded areas, and a roadside 2.4 km from the site. Also analyzed were trailer park attic dust and process material, dust, and air filters from the battery facility. Elemental concentrations in bulk soil indicated Pb levels of up to 2,760 and 3,860 mg/kg were the result of anthropogenic contamination in the residential and undisturbed wooded areas, respectively. Abundant Pb-bearing particles in air filters and attic dust, decreasing Pb concentrations with soil depth, and Pb particle size data indicated most of the Pb contamination in the residential and undisturbed wooded areas had undergone airborne transport. Antimony (Sb) and tin (Sn) in both bulk soil and individual Pb-bearing particles were key elements that linked Pb from the battery facility to Pb in the soil of the residential and undisturbed wooded areas. Finally, bulk elemental concentrations suggested automobile exhaust as the primary source of Pb contamination in the roadside soil.

Surface melting of nanometre-sized Pb particles embedded in an Al matrix studied byinternal friction technique

Nanometre-sized (hereafter n-) Pb particles embedded in an Al matrix were prepared byball milling, and the surface melting behaviour was studied by the internal frictiontechnique using a dynamic mechanical analyser. There is an internal friction peakappearing around Pb melting point and the height of the internal friction peak decreaseswith the increase of Pb particle size. Surface melting of n-Pb particles accounts for theinternal friction peak. The study may throw light on the nature of surface melting incondensed matter physics. In addition, the present work makes a beneficial attempt atexploring internal friction as an experimental method for studying surface melting.

Microstructure of Zn–Pb immiscible alloys obtained by a rheomixing process

A rheomixing process has been developed for processing immiscible metallic liquids. In this paper, a binary Zn–Pb system is used to demonstrate the rheomixing process. During the rheomixing process, liquid Zn and Pb are premixed in the miscibility gap using a propeller mixer to achieve coarse dispersion of Pb liquid droplets in Zn liquid matrix. The coarse mixture is then transferred into a twin-screw rheomixer, where it is continuously cooled down to a temperature below the monotectic temperature to form a semi-solid slurry under the intensive shear mixing action of the twin-screw rheomixer. The semi-solid slurry is finally extruded through a cylindrical extrusion die to form a continuous bar. The microstructure of immiscible alloys produced by this method is characterised by a fine dispersion of Pb particles distributed uniformly throughout a Zn matrix. The effects of rheomixing temperature and alloy composition on the resultant microstructure have been investigated. It has been found that the average size of Pb particles increases linearly with increasing rheomixing temperature and with increasing Pb concentration in the Zn–Pb alloys.

Iron(III) Oxide Nanoparticles in the Thermally Induced Oxidative Decomposition of Prussian Blue, Fe4[Fe(CN)6]3

The thermally induced decomposition of Prussian Blue, Fe4[Fe(CN)6]3 (PB), was studied in air at 250 and 350 °C. Amorphous Fe2O3 nanoparticles, cubic bixbyite β- and cubic spinel γ-Fe2O3 (maghemite) polymorphs, have been identified as the products of the decomposition under different reaction conditions. 57Fe Mossbauer spectroscopy, XRD, AFM, TEM, quasielastic light scattering method (QELS) of particle size analysis, BET surface area, and magnetization measurements were used to understand the influence of the PB particle size and oxidation conditions on the decomposition mechanism at 250 and 350 °C. At a minimum decomposition temperature of 250 °C, amorphous Fe2O3 nanoparticles were formed with the size ranging from 1 to 4 nm and large surface area of 400−200 m2/g in dependence on the PB particle size. Such small amorphous Fe2O3 nanoparticles were obtained by the solid-state route for the first time. At 350 °C, cubic β-Fe2O3 and γ-Fe2O3 polymorphs were identified and their contents were found to be strongl...

Melting behavior of nanosized lead particles embedded in an aluminum matrix

Molecular dynamics (MD) simulations, employing semi-empirical glue-type (similar to embedded atom method) many-body potentials, have been used to model the melting behavior of nanosized Pb particles embedded in an Al matrix. All the Pb particles studied melt well above the bulk melting temperature, with the melting point elevation displaying a damped periodic trend with increasing Pb particle size. By inspecting snapshots derived from the simulations, it is also possible to conclude that melting occurs via nucleation at {1 0 0} interfaces. A phenomenological model, based on the consideration of interfacial energy, volume expansion and lattice mismatch, has been developed to describe this interesting melting behavior. Our model leads to the conclusion that the periodic variation of melting point with size is due to an oscillatory strain energy contribution arising from the large size mismatch of Pb and Al atoms.

The influence of process variables of precursor powders on the microstructure evolution and transport current properties of Bi-2223/Ag tapes

The effect of Pb content and particle size of precursor powders has been studied to improve the grain growth and texture of Bi-2223/Ag tapes. The Pb content and particle size of precursor powders dominate the amount of liquid phases, and thus affect the value of J c with a variation of heat treatment condition. The best values of J c reached 53 kA/cm 2 at 77 K and 0 T, after 210 h heat treatment at 839 °C and two times intermediate pressing. It suggests that the improvement of J c characterized from high fraction of Bi-2223 with enlarged crystallites is attainable by optimizing the processing variables of precursor powders.

Effects of lead content and particle size of precursor powders on formation rate, grain growth and critical current density of BSCCO 2223 tapes

The influence of Pb content and particle size of precursor powders on the formation rate and grain growth of BSCCO 2223 has been studied to improve critical current density (J/sub c/). Our experimental results indicate that these variables have great influence on the partial melting temperature of the system, and it will affect the amounts of liquid phase and formation rate of BSCCO 2223 phase. Optimization of these variables will lead to enhanced critical current densities. The J/sub c/ in the fully reacted tapes with different Pb content and particle size of precursor powders varied from 24 kA/cm/sup 2/ to 52 kA/cm/sup 2/ at 77 K and 0 T. It suggests that a great improvement of J/sub c/ in certain tapes is characterized from the large textured BSCCO 2223 grains and fewer tracks of second phases in microstructure.

A large thermal hysteresis between melting and solidification temperature on nanoscale Pb particles embedded in amorphous sio2 matrix prepared by sputtering

The melting and solidification behaviors of (SiO2)100-xPbx sputtered films, where nanoscale Pb particles are embedded in amorphous SiO2 matrix, were studied using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). With decreasing the size of Pb particles, lowering of the melting point and the degree of supercooling of Pb particles were significantly increased. A very large thermal hysteresis loop width of 213K that is, the depression of the melting point and the increase of supercooling of Pb particles with a diameter of 5nm was as large as 63K and 150K, respectively, was observed by DSC. These results were discussed in a phenomenological context considering the existence of the interface between Pb particles and amorphous SiO2 matrix. The depression of the melting point of Pb particles is due to the increase in the interfacial energy between fine Pb particles anti amorphous SiO, matrix. A large supercooling of Pb particles is interpreted as a heterogeneous nucleation process due to nearly impurity-free fine particles.