Nanostructured Pb Research Articles

Developing of Lead/Polyurethane Micro/Nano Composite for Nuclear Shielding Novel Supplies: γ-Spectroscopy and FLUKA Simulation Techniques.

In this work, the effect of adding Pb nano/microparticles in polyurethane foams to improve thermo-physical and mechanical properties were investigated. Moreover, an attempt has been made to modify the micron-sized lead metal powder into nanostructured Pb powder using a high-energy ball mill. Two types of fillers were used, the first is Pb in micro scale and the second is Pb in nano scale. A lead/polyurethane nanocomposite is made using the in-situ polymerization process. The different characterization techniques describe the state of the dispersion of fillers in foam. The effects of these additions in the foam were evaluated, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) have all been used to analyze the morphology and dispersion of lead in polyurethane. The findings demonstrate that lead is uniformly distributed throughout the polyurethane matrix. The compression test demonstrates that the inclusion of lead weakens the compression strength of the nanocomposites in comparison to that of pure polyurethane. The TGA study shows that the enhanced thermal stability is a result of the inclusion of fillers, especially nanofillers. The shielding efficiency has been studied, MAC, LAC, HVL, MFP and Zeff were determined either experimentally or by Monte Carlo calculations. The nuclear radiation shielding properties were simulated by the FLUKA code for the photon energy range of 0.0001-100 MeV.

In-situ synthesis of novel nanostructured Pb@C composites for improving the performance of lead-acid batteries under high-rate partial-state-of-charge operation

The addition of carbon or carbon composite materials to the negative plate of lead-acid battery could effectively improve the battery electrochemical performance. Herein, a novel Pb@C nanocomposites are in-situ prepared by pyrolysis lead acetate impregnated glucose gel at nitrogen atmosphere. While the Pb@C nanocomposites is used as the additive adding in the negative active materials (NAM) of lead-acid batteries, which can great enhance the utilization of NAM. The negative plate, containing 1 wt.% Pb@C, owns the high affinity between the NAM and Pb@C material, which shows the best cycle-life (8921 cycles) performance on high-rate partial-state-of-charge (HRPSoC) and the highest of initial discharge specific capacity (165.1 mAh g−1). Moreover, the lower polarizability and more stable rate capability of the lead-acid cells contain Pb@C compare with blank cell. Besides, accelerate the diffusion of electrolyte and PbSO4 dissolution, due to the Pb@C materials form porous-skeleton with NAM in the negative plate. In summary, the Pb@C nanocomposites have potential to be used to enhance the specific capacity and HRPSoC cycle-life of lead-acid batteries.

Template electrodeposition and characterization of nanostructured Pb as a negative electrode for lead-acid battery

Despite Lead Acid Battery (LAB) is the oldest electrochemical energy storage system, diffusion in the emerging sectors of technological interest is inhibited by its drawbacks. The principal ones are low energy density and negative plate sulphating on high rate discharging. In this work, it is shown the possibility of overcoming such drawbacks by using nanostructured lead as a negative electrode. Lead nanowires (NWs) were fabricated by electrochemical deposition in template, which is an easy, cheap, and easily scalable process. Their morphology and crystal structure have been characterized by electron microscopy and X-ray diffraction, respectively. An electrochemical cell simulating LAB has been assembled with PbO2 as a counter electrode and an AGM separator, both from commercial battery. Cycling tests were conducted at 10C-rate, setting the cut-off voltage on discharging at 1.2 V. For comparison, also cycling tests at 1C-rate have been carried out, in otherwise identical conditions. At both C-rates, performances in terms of cycling efficiency and lifetime were found a lot better than those of current LABs. The high porosity formed under cycling at 10C-rate provides a reliable explanation of the results.

One-step synthesis of Pb–Sb nanostructured alloy particles: Effect of processing parameters

The present investigation reports the successful synthesis of nanostructured Pb–Sb alloys via solvothermal route for the first time. Two-phase alloy nanoparticles have been prepared by proper control of the processing parameters for Pb-17.5 atom % Sb composition. The reaction parameters; time, temperature, concentrations of the reducing agent (NaBH4, sodium borohydrate) and most importantly, the presence of capping agent (PVP, polyvinyl pyrrolidone) have been found to play a crucial role in the formation of two-phase alloy nanoparticles. The detailed analysis of the X-ray diffraction (XRD) patterns reveals that the FCC (Pb) and rhombohedral (Sb) phases are present in each nanoparticle. The extensive transmission electron microscopy (TEM) study, including high angle annular dark field (HAADF) imaging and energy dispersive spectroscopic (EDS) analysis, carried out with annular dark field and EDS detectors respectively, attached with TITAN suggest that each nanoparticle consists of (Pb) and (Sb), with cap on body morphology. A few of them exhibit typical lamellar morphology. A possible reaction mechanism based on the experimental results has been proposed.

Spectral characteristics and morphology of nanostructured Pb–S–O thin films synthesized via two different methods

Using two different experimental techniques, namely chemical vapor deposition (CVD) and physical vapor deposition (PVD), we deposited a lead sulphide (PbS) thin films with a very small lifetime (10−9). We investigated the morphology of the obtained PbS films using various techniques i.e. AFM, SEM, EDAX, AES and HRTEM. In the case of CVD, we found that the surface consists of grains with dimensions in the plane (diameter to 300nm and height up to 200nm), while the same order of the grain size has been observed for PVD. On the other hand, SEM investigation reveals that the PbS particles with various morphologies of both films have uniform and the particle size distribution. Small amount of sodium was obtained from EDXS studies, which may originate from the substrate where the deposition process has been produced at temperature 550–600°C and for CVD at minimum accelerating voltage 5kV silicon are presented in the spectrum, which means that the region for X-ray generation voltage data exceeds the thickness of the films (where the thickness of films about 0.4μm). AES confirms the surface layer of these films (PVD) containing carbon and oxygen and it has a thickness of 0.1μm. At a depth of 1.3μm in films these elements are again increased, which corresponds to the film thickness of 1.5μm. Layers of PVD films are seen by HRTEM and the studies confirm that oxygen-layer located on top of the structure, while the layers of CVD films not only have the oxygen along the crystallite boundaries, but also accumulate in the depth of the boundary with the substrate. Our results of morphology indicate that the change in spectral characteristics of films deposited by (CVD and PVD) is related to the structure and the crystalline size.

Novel room temperature multiferroics on the base of single-phase nanostructured perovskites

The theoretical description of the nanostructured Pb(Fe1/2Ta1/2)x(Zr0.53Ti0.47)1−xO3 (PFTx-PZT(1−x)) and Pb(Fe1/2Nb1/2)x(Zr0.53Ti0.47)1−xO3 (PFNx-PZT(1−x)) intriguing ferromagnetic, ferroelectric, and magnetoelectric properties at temperatures higher than 100 K are absent to date. The goal of this work is to propose the theoretical description of the physical nature and the mechanisms of the aforementioned properties, including room temperature ferromagnetism, phase diagram dependence on the composition x with a special attention to the multiferroic properties at room temperature, including anomalous large value of magnetoelectric coefficient. The comparison of the developed theory with phase diagrams allow establishing the boundaries between paraelectric, ferroelectric, paramagnetic, antiferromagnetic, ferromagnetic, and magnetoelectric phases, as well as the characteristic features of ferroelectric domain switching by magnetic field are performed and discussed. The experimentally established absence of ferromagnetic phase in PFN, PFT and in the solid solution of PFN with PbTiO3 (PFNx-PT(1−x)) was explained in the framework of the proposed theory.

Optical studies of pulsed laser deposited nanostructured Pb(Zr0.52Ti0.48)O3 thin film by spectroscopic ellipsometry.

Pulsed laser deposition method was employed to grow nanostructured Pb(Zr0.52Ti0.48)O3 (PZT) thin film on Si(100) substrate. The structural and morphological properties of the thin film were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. Optical properties of PZT thin film were studied using spectroscopic ellipsometry (SE) and a four layer model was applied. Spectra of ellipsometric parameters such as psi and delta were measured as a function of energy at room temperature. The refractive index (n), extinction coefficient (k), absorption coefficient (alpha) and the dielectric constants (epsilon(r) and epsilon(i)) of the thin film were obtained as a function of wavelength (200 to 900 nm range). The energy gap (E(g)) of the PZT thin film was estimated to be 3.65 eV. The thickness of the thin films was determined by the ellipsometric data (524 nm) and grain size is found to be in the range of 50-100 nm.

Sonochemical Synthesis of Nano-structured Lead(II) Coordination Polymer with 2-Aminonicotinic Acid: Thermal, Structural and X-ray Powder Diffraction Studies

A new one-dimensional crystalline and nano-structured Pb(II) coordination polymer, [Pb(2-anc)2(NO3)2] n (1) {2-Hanc = 2-aminonicotinic acid}, were synthesized via heat gradient and sonochemical methods. The new produced nano-structure was characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy, and elemental analyses. Structural characterization by single crystal X-ray diffraction exhibits two-dimensional polymeric units for compound 1. Thermal stability of nano and bulk samples of compound 1 were studied and compared. PbO nano-particles was then obtained via calcination of nano-compound 1 at high and low temperatures. The calcinations result demonstrates that compound 1 may be suitable precursor for the preparation of nanoscale lead(II) oxide without need for special conditions like high temperature, long times and pressure control.

Microstructural, Electrical, and Magnetic Properties of Acceptor‐Doped Nanostructured Lead Zirconate Titanate

The changes in the ferroelectric and magnetic properties of the nanostructured Pb(Zr0.52Ti0.48)1‐xFexO3 (0 ≤ x ≤ 0.06) due to the doping of different amounts of acceptor ions (Fe3+) have been studied. X‐ray diffraction studies show that the system maintains the tetragonal phase up to the doping of 2 mol% of Fe3+ and the formation of secondary phase magnetoplumbite (PbFe12O19) on further doping. Electron paramagnetic resonance studies have revealed the formation of defect centers which in turn arise due to the interaction of Fe3+ ions with oxygen vacancies, which are generated in the lattice. This results in the appearance of room temperature ferromagnetic (RTFM) behavior in the doped samples. The dielectric studies reveal that with the concentration of Fe3+ the peak near the maxima of dielectric constant (ε′m) is broadened. Studies of the defect dipoles on the ferroelectric properties have been performed by polarization measurement. The variations of the above properties with the structural and morphological features of the samples have also discussed.

Mechanochemical Synthesis and Characteristics of Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>

This paper presents a novel mechanochemical synthesis technique for making nano-structured Pb(Mg1/3Nb2/3)O3 (PMN) ferroelectric material without annealing treatment in a much shorter time and at much lower temperature than those reported in the literature, by using the starting precursors MgO, PbO, and Nb2O5. Specimens of various milling time (3-6h) are characterized from XRD patterns to track and analyze the synthesizing procedure of this mechanochemical processing route. The time used to make the desired PMN powders varies with different milling power. When the constituent oxides were mechanically activated at 1.8KW milling power for 6h, the perovskite phase PMN powder was obtained; while it was formed when milling at 3KW for only 3h. Typical SEM images of the as-received PMN powders show that the powders are aggregated of nano-particles of about 100nm in size.

Magnetoelectric coupling and relaxor ferroelectric properties of Pb 0.7Sr 0.3(Fe 0.012Ti 0.988)O 3 thin film

We present the electric and magnetic properties of nanostructured Pb 0.7 Sr 0.3 (Fe 0.012 Ti 0.988 )O 3 (PSFT3) thin film. The magnetoelectric coupling has been studied by polarization hysteresis loops under the influence of an applied magnetic field and a phase transition anomaly. At room temperature PSFT3 film shows diffuse phase transition of dielectric diffusivity ( γ = 1.94). The Vogel–Fulcher (VF) relation implies the relaxor characteristics of the film by extracting the VF freezing temperature and the activation energy of polar nanoregions.

Formic Acid from Carbon Dioxide on Nanolayered Electrocatalyst

Formic acid is electrochemically generated from carbon dioxide (CO2) on nanolayered lead (Pb) electrode. Stepwise potential deposition method is applied to prepare nanostructured Pb, composed of particles and platelets with hexagonal and cubic crystallinities. Their electrocatalytic activities in an electroreduction of CO2 are compared. We observed higher faradaic efficiencies of 94.1% on a cubic Pb surface than that of polycrystalline Pb smooth films (52.3%) at 278 K. Analyzing the mass changes of the electrodes by electrochemical quartz crystal microbalance, the mechanistic origin of CO2 reduction is studied, and the indirect reduction of CO2 via Had atoms might be more reasonable than the direct electron transfer of CO2 molecules.

Competing effects of surface phonon softening and quantum size effects on thesuperconducting properties of nanostructured Pb

The superconducting transition temperature(TC) in nanostructured Pb decreases from 7.24 to 6.4 K as the particle size isreduced from 65 to 7 nm, below which superconductivity is lost ratherabruptly. In contrast, there is a large enhancement in the upper critical field(HC2) in the same size regime. We explore the origin of the unusual robustness ofTC over such a large particle size range in nanostructured Pb by measuring the temperaturedependence of the superconducting energy gap in planar tunnel junctions ofAl/Al2O3/nano-Pb. We show that below 22 nm, the electron–phonon coupling strengthincreases monotonically with decreasing particle size, and almost exactlycompensates for the quantum size effect, which is expected to suppressTC.

Resistivity dependent dielectric and magnetic properties of Pb(Fe0.012Ti0.988)O3 nanoparticles

High resistivity in nanostructured Pb(Fe0.012Ti0.988)O3 system prepared by using polyvinyl alcohol (PVA) in chemical route is observed. The PVA acts as a surfactant to limit the particle size. The Fe substitution for Ti controls the chemical stoichiometry and reduces the lattice distortion, i.e., c/a ratio, and hence the transition temperature reduces with Fe content. The phase structure, morphology, particle size, dc resistivity, and dielectric and magnetic properties of Pb(Fe0.012Ti0.988)O3 nanoparticles have been characterized by x-ray diffraction, transmission/scanning electron microscopy, source meter, LCR meter, and vibrating sample magnetometer. The results indicate that the nanosize particles have high resistivity, which improves the dielectric constant at high-frequency region and increases magnetization of the specimens. The observed variable-range-hopping conduction mechanism indicates that Fe doping leads to the occurrence of local defect states in the PbTiO3 lattice. The dispersionless dielectric properties with low loss are observed up to 15 MHz. The dielectric properties are improved than those obtained by the conventional process. The initial permeability values do not exhibit much variation up to ferromagnetic transition temperature after which it falls sharply. The large value of saturation magnetization is observed at room temperature.

A Soft Chemistry Route for the Synthesis of Nanostructured Pb2Ru2O6.5 with a Controlled Stoichiometry

A new chemical route to synthesize nanostructured lead ruthenium pyrochlore (Pb2Ru2O6.5) powders was developed. The synthesis was performed starting from a metal nitrate aqueous solution and N, N, N′, N′ tetramethylethylendiamine (TMEDA). The amine, which is a mild basic chelating agent, was able to control the simultaneous precipitation of lead and ruthenium oxo/hydroxides. For the sake of comparison, Pb2Ru2O6.5 powders were prepared using the more conventional polymeric precursor method. The new method was effective for the synthesis of nanostructured Pb2Ru2O6.5 powders already stable at 400°C and up to 1000°C.

Electrical Characteristics and Preparation of Nanostructured Pb(Zr0.5Ti0.5)O3 Films by Spray Pyrolysis

Nanostructured thin films of Pb(Zr0.5Ti0.5)O3 on Pt (1000 Å)/Ti (100 Å)/SiO2 (2000 Å)/Si substrates are prepared by spray pyrolysis and subsequently rapid thermal annealing. Lead nitrate, zirconium nitrate and titanium isopropoxide are used as starting material with ethylene glycol as solvent. The crystal structure of the as-sprayed films are transformed from the amorphous, pyrochlore and multiple phases of pyrochlore and perovskite to the single phase of perovskite as the annealing temperature is increased up to 500 °C. For the formation of single phase perovskite, excess lead of 10 mol % is required to compensate the loss of lead during the processing of the primitive films. The physical characteristics of the resultant films show the dielectric constant (εr) of 400, remanent polarization (2Pr) of 30.0 µC/cm2 and coercive field (2Ec) of 70.0 kV/cm, respectively.

Annealing에 의한 나노구조 박막의 전기적 특성 연구

Electron transport properties of nanostructured Pb thin film, consisting of grains, have been studied. Nanostructured thin films were fabricated on a substrate held at low temperature and their thicknesses were less than 10nm. While temperature of the film increased from 1.3 K to room temperature, the change in normal state sheet resistance has been measured. As the annealing temperature varies, the normal state sheet resistance shows a non-monotonic and irreversible change. Such behavior can be understood with the Pb grain growth due to annealing of the film.

Mechanically activated synthesis of PZT and its electromechanical properties

Mechanical activation was successfully used to synthesize nanostructured phase-pure Pb(Zr0.7Ti0.3)O3 (PZT) powders. Lead–zirconium–titanium (PbZrTi) hydrous oxide precursor, synthesized from chemical co-precipitation, was mechanically activated in a NaCl matrix. The synthesized PZT particles were characterized by using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, laser-light diffraction, and nitrogen adsorption. Thermogravimetric analysis and differential thermal analysis were used to monitor dehydration and phase transformation of PbZrTi hydrous oxide precursor during mechanical activation. The best mechanical activation conditions corresponded to mechanically activating PbZrTi hydrous oxide precursor in a NaCl matrix with a NaCl/precursor weight ratio of 4:1 for 8 h. These conditions resulted in a dispersible phase-pure PZT powder with a median secondary-particle size of ∼110 nm. The properties of PZT 70/30 from mechanically activated powder, as measured on discs sintered at 1150 °C for 2 h, were found to be in close conformity to those obtained by a conventional mixed oxide solid state reaction route.

Oriented nano-structured Pb(Fe 0.5Nb 0.5)O 3 thin films on SrTiO 3(100) substrates by a sol–gel technique

Pb(Fe 0.5Nb 0.5)O 3 (PFN) thin films having a pure perovskite phase were fabricated by a sol–gel technique with post-annealing. The crystallised films were strongly oriented on the SrTiO 3(100) substrate and showed a nano-structured morphology. X-ray diffraction analysis and TEM observations were performed to correlate the preferential orientation with the film structure on the SrTiO 3(100) substrate. XPS was used to analyse the composition of the films. The dielectric constants and loss factors were measured under an applied field from 0.1 to 1000 kHz.