Discussion On Failure Behavior of Piping Systems Under Extremely Large Seismic Loads in BDBE

To investigate the failure behavior of piping systems under severe seismic loads considering beyond design basis event (BDBE), an experimental approach to use pipes made of simulation materials was applied. "Simulation material" means the substitute material for steel to realize the structural experiment by the existing testing facilities. The simulation materials adopted in this study were pure lead (Pb) or lead-antimony (Pb-Sb) alloy. Using pipe elbows made of simulation materials, static loading tests on elbows and shaking table tests on simple piping system models composed of one or two elbows and an additional mass were conducted. From the static loading tests, the load-deflection relationship of an elbow under monotonic loading was obtained as well as the fatigue failure modes under cyclic loading depending on the several cyclic displacement levels. From the shaking table tests, several failure modes were obtained, namely, "Collapse by self-weight", "Collapse by a few cycles of input", "Ratchet and subsequent collapse", "Overall deformation", and "No failure". It was considered that the occurrence of these failure modes was affected by the ratio of the input frequency to the specimen's natural frequency, the ratio of additional mass weight to the limit mass weight, the configuration of the specimen, and the input acceleration level. The experimental results indicated that it was crucial to understand the structure's ultimate behavior when treating BDBE, and that the research approach using simulation material is effective to investigate the ultimate behavior of piping systems.

LDPE/Bismuth Oxide Nanocomposite: Preparation, Characterization and Application in X-ray Shielding

Recently developed polymer-based composites could prove useful in many applications such as in radiation shielding. In this work, the potential of a bismuth oxide (Bi2O3) nanofiller based on an LDPE polymer was developed as lead-free X-ray radiation shielding offering the benefits of lightness, low-cost and non-toxic compared to pure lead. Three different LDPE-based composites were prepared with varying weight percentages of Bi2O3: 5%, 10% and 15%. The characterizations were extended to include structural properties, physical features, mechanical and thermal properties, and radiation shielding efficiency for the prepared nanocomposites. The results revealed that the incorporation of the Bi2O3 nanofiller into an LDPE improved the density of the composites. There was also a slight increase in the tensile strength and tensile modulus. In addition, there was a clear improvement in the efficiency of the shield when fillers were added to the LDPE polymer. The LDPE + Bi2O3 (15%) composite needed the lowest thickness to attenuate 50% of the incident X-rays. The LDPE + Bi2O3 (15%) polymer can also block around 80% of X-rays at 47.9 keV. In real practice, a thicker shield of the proposed composite materials, or a higher percentage of the filler could be employed to safely ensure the radiation is blocked.

Preparation, Characterization, and Microwave Absorption Properties of Cobalt-Doped SrFe12O19 Nanoparticles

Ferrite is the major absorbing components of conventional radar absorbing materials (RAM). However, conventional RAM made of the single-absorbing components cannot meet the comprehensive requirements of “thin, wide, light, and strong.” To overcome this limitation, a composite compound of cobalt-doped SrFe12O19 nanoparticles is currently exploited to improve absorbing ability. SrFe12−xCoxO19 (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25) composite ferrites were prepared using the sol-gel method. Results show that the powders obtained are pure lead-magnetite ferrite, and the properties of the samples are improved evidently after Co substitution. At room temperature, the samples substituted using Co exhibit typical permanent magnetism. When x = 0.2, the maximum saturation magnetization and coercivity of the powders are 55.8 A·2/kg and 302.4 kA/m, respectively. The real complex permittivity part of SrFe12−xCoxO19 first increases and then decreases with the increase in x and has a maximum value of x = 0.2. The complex imaginary permittivity part fluctuates with the increase in x; it first decreases, then increases, and finally decreases. With the increase in x, the complex permeability real part of the sample does not change much between 2 GHz to 16 GHz but first increases and then decreases in the range of 16-18 GHz. The imaginary part of the complex permeability first increases and then decreases, reaching its maximum at x = 0.2. The attenuation constants and absorbing properties of the samples before and after substitution were analyzed. The matching thickness of strontium ferrite (SrFe12O19) is 5.2 mm, the matching thickness of SrFe11,8Co0.2O19 (x = 0.2) is reduced to 2.4 mm, the minimum reflectivity is −24.7 dB (13.8 GHz), and the microwave absorption bandwidth lower than −10 dB is 4.7 GHz (11.6-16.3 GHz). These results indicate that an appropriate amount of Co substitution could greatly improve the absorbing performance of SrFe12O19. This study provides a simple method for the preparation of Co doped strontium ferrite. The microwave absorbing properties of the composite powders are excellent and have potential engineering application value.

Lead Recovery from Solid Residues of Copper Industry Using Triethylenetetramine Solution

Industrial processing of mineral ores and concentrates generates large amounts of solid residues, which can be landfilled or further processed to recover selected elements depending on its economical profitability. Pressure leaching is a technology enabling high recovery of base metals like copper and zinc, transferring others like lead and iron to the solid residue. High temperature and pressure of such leaching leads to formation of sparingly soluble lead jarosite (plumbojarosite). The load of lead landfilled as solid residues resulting from such operation is so big that its recovery is perspective and crucial for waste-limiting technologies. This paper is devoted to lead extraction from pressure leaching residues using triethylenetetramine solution and then its precipitation as a commercial lead carbonate. The highest obtained recovery of lead was 91.3%. Additionally, presented technology allows to manage and recycle amine solution and reuse solid products. Produced pure lead carbonate can be directly added to smelting, not increasing temperature within the furnace.

PROBLEMS OF IMPROVING THE RELIABILITY AND QUALITY OF RADIO ELECTRONIC PRODUCTS AND INSTRUMENTS WHEN USING LEAD-FREE SOLDERS

Обеспечение надежности и качества радиоэлектронных средств и приборов - это одна из главных задач в процессе проектирования новых устройств. Благодаря высокому качеству паяных соединений увеличивается срок службы электронных изделий, а также их безотказность в процессе эксплуатации и ремонтопригодность. Также нужно не забывать об экологической безопасности производимых устройств. В связи со всем вышеизложенным наиболее перспективно проводить исследования и искать практические решения возникающих трудностей в сфере технологий, в которых используются бессвинцовые припои, что позволит соблюсти современные требования к электронной аппаратуре. Кратко изложены основные последствия и проблемы применения чисто бессвинцовой пайки, рассмотрены проблемы применения смешанной технологии пайки и исследование эффекта роста оловянных «усов». Сделан вывод о том, что избежать большинства дефектов помогает применение активных флюсов, сохраняющих свои свойства при высоких температурах, пасту необходимо выбирать с тем условием, что в ее составе не должно быть канифоли, которая начинает активно выделяться в виде газа при повышении температуры, следует также верно подбирать температурный профиль пайки. Среди финишных покрытий лучше всего себя зарекомендовали иммерсионное серебро и никель-золото. Применение в припое в качестве заменителей свинца таких металлов, как висмут и индий существенно повышает стоимость припоев. Отмечается, что хорошие показатели имеют припои с содержанием цинка, однако цинк приводит к невозможности долгосрочного хранения паяльных паст, повышению оксидирования, необходимости пайки в среде инертных газов и с применением активных флюсов Ensuring the reliability and quality of radio-electronic equipment and devices is one of the main problems in the process of designing new devices. Due to the high quality of soldered joints, the service life of electronic products increases, as well as their reliability during operation and maintainability. It is also necessary not to forget about the environmental safety of the manufactured devices. In connection with all the above, it is most promising to conduct research and look for practical solutions to the emerging difficulties in the field of technologies that use lead-free solders, which will allow us to meet modern requirements for electronic equipment. The article briefly describes the main consequences and problems of using pure lead-free soldering, the problems of using mixed soldering technology, and the study of the effect "whiskers". Use of active fluxes that retain their properties at high temperatures helps to avoid most defects, the paste should be chosen with the condition that it should not contain rosin, which begins to actively emit as a gas when the temperature rises, and the temperature profile of soldering should also be correctly selected. Among the finishing coatings, immersion silver and nickel-gold proved to be the best. The use of metals such as bismuth and indium in solder, as lead substitutes, significantly increases the cost of solders. The article also notes that solders with a zinc content have good indicators but zinc leads to the impossibility of long-term storage of soldering pastes, increased oxidation, the need for soldering in an environment of inert gases and with the use of active fluxes

The Toxic Effect of Pb Nanoparticles Prepared by Laser ablation on Some Biochemical Aspects in Rats

This work aimed to prepare and study the characteristic feature of lead nanoparticles (PbNPS) and follow its effects on some physiological aspects in rats.PbNPS was prepared by laser ablation of pure lead mass with a pulse of 500 and 100 mJ of energy. The results indicated that the wavelength was approximately 196 and the concentration was reported at 53,8967 mg / L. AFM, as the average diameter has been estimated at 69.93 nm. EFSEM shows the spherical shape of the particle.The experimental animals (rats) were divided into two groups, with seven rats for each one. The first group was a control and the second group was injected with 1 milliliter of PbNPS (53.8673 mg/l) per day for 45 days. Bioaccumulated lead ( in liver, spleen kidney and muscles), total serum proteins, albumin, ALT, AST, ALP and antioxidants (GSH, SOD, CAT, and MDA) were estimated.By comparison to the control, PbNPS exposed animals. There were no significant differences in the bioaccumulated lead. In contrast, there was a significant reduction in total serum protein, albumin, GSH, SOD, CAT. Also, there was an increase in serum ALT, AST, ALP and MDA.

A comparative study on characterizations and synthesis of pure lead sulfide (PbS) and Ag-doped PbS for photovoltaic applications

In this study, a hydrothermal technique was used to synthesize lead sulfide (PbS) and silver (Ag)-doped PbS nanoparticles (NPs) at different concentrations of 20, 40, and 60% of Ag. The small lattice phase changes appeared due to the shifting of diffraction angle peaks toward higher 2θ for samples doped with PbS with increasing Ag content. The analysis of average crystallite size, phase structure, and lattice constant was observed under X-ray diffraction. The value of crystallite size, volume of the unit cell, and porosity (%) were found to increase with the increasing concentration of Ag NPs in PbS. The pure PbS crystallite size is small compared to Ag-doped PbS. The optical characteristics including absorption spectra of the prepared samples were investigated and confirmed by using scanning electron microscope and UV-Vis spectroscopy. The observation of the composition showed that higher doping concentrations of Ag lead to an increase in particle size. Absorption peaks in the UV-Vis spectra corresponding to pure and 20, 40, and 60% of Ag/PbS were observed at different wavelengths of 368, 369, 371, and 372 nm, respectively. Fourier transformation infrared spectroscopy peaks were found in the vibration mode of the ions due to the increment in Ag doping concentrations. These results indicate the possibility of tuning the optical structural properties of Ag-doped PbS through doping various concentrations of Ag NPs. Ag-doped PbS is considered promising future semiconductor nanomaterial, which will enhance the efficiency of photovoltaic device applications.

Issuing Cast Lead Coins in Byzantine Cherson: A Local Phenomenon or a Technological “Flaw”?

Although the aspects of the production of Byzantine-Cherson cast coins and the technological nuances of their manufacture have been repeatedly studied in Russian scholarship, every time there appeared various hypotheses and assumptions, mostly remain highly debatable so far. For a long time, the lack or difficulties of access to the special equipment allowing the one to determine coin alloys allowed the researchers to draw conclusions about the coin material only against the background of some definitions from the scholarship and visual indicators. Among the disputable aspects is the casting of Cherson-Byzantine lead coins. In this connection, we have studied 30 specimens of coins by laboratory research of the alloy composition by X-ray fluorescent analysis. The samples selected for examination visually suggested a high content of lead. It has been found out that in the samples examined have similar elemental composition of coin alloy, lead with additions of arsenic. It is possible that, in the Byzantine Period, the Taurica received lead from the mines located in the Caucasus area, which were typical of a high content of arsenic. The most part of the of samples (27 specimens) contained more than 2/3 of lead; the alloy of three coins contained similar proportions of copper and lead. Taking the said results into account, we can suppose that the “almost pure” lead coins most likely were a specific kind of technological “flaw” in the casting in Cherson. It is still possible that, in the sorting of the ready-made coins, the specimens not corresponding to the standard samples and having casting defects (partial casting of the mould or lead casts) were withdrawn and returned to remaking. This interpretation explains why the so-called “lead” coins are relatively rare: they occurred mostly in the coinages from the age of Basil I and Leo VI, though in some series they were unique or unknown.

Removal of Pb (II) from Synthetic Solution and Paint Industry Wastewater Using Activated Carbon Derived from African Arrowroot (Canna indica) Stem

This study aimed to investigate the potential of Canna indica stem-based activated carbon (CISAC) for the removal of Pb (II) ions from synthetic solution and paint industry wastewater. The effects of pH, initial Pb (II) ion concentration, and adsorbent dose were studied using an aqueous solution prepared using pure lead nitrate (Pb(NO₃)₂) on a batch mode. Dried Canna indica stem (CIS) was carbonized in a rectangular furnace at 500°C for 2 h and treated with phosphoric acid (H3PO4) at a ratio of 1 : 1 (w/v). Results showed that the CISAC had 5.4% of moisture, 5.0% of ash, 26.7% of volatile matter, 62.9% of fixed carbon, and 797.5 mg/g of iodine number. The Fourier Transform Infrared (FTIR) results showed that the hydroxyl, carboxyl, and phenolic functional groups were dominant in the CISAC surface. Physicochemical characteristics revealed that raw wastewater had a concentration of 4.6 mg/L Pb (II), 3 mg/L Cu (II), 171 mg/L BOD5, 2402 mg/L COD, and 619 mg/L TSS. Better removal of Pb (II) ion from aqueous solution was achieved at a pH of 5.5, initial Pb (II) concentration of 102.4 mg/L, and an adsorbent dose of 1.4 g using response surface methodology. The highest removal efficiencies of Pb (II) which was achieved from aqueous solution and paint wastewater were 98% and 70%, respectively. The experimental data are fitted with Langmuir and Freundlich isothermic models. The results suggested CISAC as a promising adsorbent to remove Pb (II) ion from paint industry wastewater.