Search results for: bismuth vanadate

Authors: Kamran Dastafkan, Chuan Zhao

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Improving surface chemistry is a promising approach in addition to the rational alteration in the catalyst composition to advance water electrolysis. Here, we demonstrate an evident enhancement of oxygen evolution on an iron-nickel vanadate catalyst synthesized by a facile successive ionic adsorption and reaction method. The vanadate-modified catalyst demonstrates a highly efficient oxygen evolution in 1 M KOH by requiring low overpotentials of 274 and 310 mV for delivering large current densities of 100 and 400 mA cm⁻², respectively where vigorous gas bubble evolution occurs. Vanadate modification augments the OER activity from three aspects. (i) Both the electrochemical surface area (47.1 cm²) and intrinsic activity (318 mV to deliver 10 mA cm⁻² per unit ECSA) of the catalytic sites are improved. (ii) The amorphous and roughened nanoparticle-comprised catalyst film exhibits a high surface wettability and a low-gas bubble-adhesion, which is beneficial for the accelerated mass transport and gas bubble dissipation at large current densities. The gas bubble dissipation behavior is studied by operando dynamic specific resistance measurements where a significant change in the variation of the interfacial resistance during the OER is detected for the vanadate-modified catalyst. (iii) The introduced vanadate poly-oxo-anions with high charge density have electronic interplay with Fe and Ni catalytic centers. Raman study reveals the structural evolution of β-NiOOH and γ-FeOOH phases during the OER through the vanadate-active site synergistic interactions. Achievement of a high catalytic turnover of 0.12 s⁻¹ put the developed FeNi vanadate among the best recent catalysts for water oxidation.

Keywords: gas bubble dissipation, iron-nickel vanadate, low-gas bubble-adhesion catalyst, oxygen evolution reaction

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Authors: Sulaiman B. Ali Alharbi, Bassam H. Mashat, Naif Abdullah Al-Harbi, Milton Wainwright, Abeer S. Aloufi, Sulamain Alnaimat

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Bismuth salicylate was found to inhibit the growth of a range of bacteria and yeast, Candida albican. In general the growth of bacteria did not result in the increase in bismuth solubilisation, in contrast, bismuth solubilisation increased following the growth of C. albicans. A significant increase in the biomass (dry weight) of Aspergillus niger and Aspergillus oryzae occurred in vitro when these fungi were grown in the presence of bismuth salicylate. Biomass increase occurred over a range of bismuth compound additions, which in the case of A. oryzae was associated with the increase in the solubilisation of the insoluble bismuth compounds.

Keywords: bacterial inhibition, fungal growth stimulation, medical uses of bismuth, yeast inhibition

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Authors: I. Siti Rabiatull Aisha, A. Ourdjini, O. Saliza Azlina

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The aim of this paper is to study the effectiveness of bismuth addition in the solder alloy to retard the intermetallic compound formation and growth. In this study, three categories of solders such as Sn-4Ag-xCu (x = 0.5, 0.7, 1.0) and Sn-4Ag-0.5Cu-xBi (x = 0.1, 0.2, 0.4) were used. Ni/Au surface finish substrates were dipped into the molten solder at a temperature of 180-190 ^oC and allowed to cool at room temperature. The intermetallic compound (IMCs) were subjected to the characterization in terms of composition and morphology. The IMC phases were identified by energy dispersive x-ray (EDX), whereas the optical microscope and scanning electron microscopy (SEM) were used to observe microstructure evolution of the solder joint. The results clearly showed that copper concentration dependency was high during the reflow stage. Besides, only Ni₃Sn₄ and Ni₃Sn₂ were detected for all copper concentrations. The addition of Bi was found to have no significant effect on the type of IMCs formed, but yet the grain became further refined.

Keywords: Bismuth addition, intermetallic compound, composition, morphology

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Authors: Azuraida Amat, Halimah Mohamed Kamari, Che Azurahanim Che Abdullah, Ishak Mansor

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The changes of the optical and structural properties of Bismuth-Boro-Tellurite glasses pre and post gamma irradiation were studied. Six glass samples, with different compositions [(TeO2)0.7 (B2O3)0.3]1-x (Bi2O3)x prepared by melt quenching method were irradiated with 25kGy gamma radiation at room temperature. The Fourier Transform Infrared Spectroscopy (FTIR) was used to explore the structural bonding in the prepared glass samples due to exposure, while UV-VIS Spectrophotometer was used to evaluate the changes in the optical properties before and after irradiation. Gamma irradiation causes a profound changes in the peak intensity as shown by FTIR spectra which is due to the breaking of the network bonding. Before gamma irradiation, the optical band gap, Eg value decreased from 2.44 eV to 2.15 eV with the addition of Bismuth content. The value kept decreasing (from 2.18 eV to 2.00 eV) following exposure to gamma radiation due to the increase of non-bridging oxygen (NBO) and the increase of defects in the glass. In conclusion, the glass with high content of Bi2O3 (0.30Bi) give the smallest Eg and show less changes in FTIR spectra after gamma irradiation, which indicate that this glass is more resistant to gamma radiation compared to other glasses.

Keywords: boro-tellurite, bismuth, gamma radiation, optical properties

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Authors: Azimeh Rajaee, Lingyun Zhao, Shi Wang, Yaqiang Liu

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In recent years many studies have been focused on bismuth-based nanoparticles as radiosensitizer and contrast agent in radiation therapy and imaging due to the high atomic number (Z = 82), high photoelectric absorption, low cost, and low toxicity. This study aims to introduce a new multifunctional bismuth-based nanoparticle as a theranostic agent for radiotherapy, computed tomography (CT) and magnetic resonance imaging (MRI). We synthesized bismuth ferrite (BFO, BiFeO3) nanoparticles by sol-gel method and surface of the nanoparticles were modified by Polyethylene glycol (PEG). After proved biocompatibility of the nanoparticles, the ability of them as contract agent in Computed tomography (CT) and magnetic resonance imaging (MRI) was investigated. The relaxation time rate (R2) in MRI and Hounsfield unit (HU) in CT imaging were increased with the concentration of the nanoparticles. Moreover, the effect of nanoparticles on dose enhancement in low energy was investigated by clonogenic assay. According to clonogenic assay, sensitizer enhancement ratios (SERs) were obtained as 1.35 and 1.76 for nanoparticle concentrations of 0.05 mg/ml and 0.1 mg/ml, respectively. In conclusion, our experimental results demonstrate that the multifunctional nanoparticles have the ability to employ as multimodal imaging and therapy to enhance theranostic efficacy.

Keywords: molecular imaging, nanomedicine, radiotherapy, theranostics

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Authors: Mabrook Saleh Amera, Prabhakarn Arunachalama, Maged N. Shaddadb, Abdulhadi Al-Qadia

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Global energy crises and water pollution have negatively impacted sustainable development in recent years. It is most promising to use Bismuth vanadate (BiVO4) as an electrode for photoelectrocatalytic (PEC) oxidation of water and pollution degradation. However, BiVO4 anodes suffer from poor charge separation and slow water oxidation. In this paper, a Zr:BiVO4/NiFeOOH heterojunction was successfully prepared by electrodeposition and photoelectrochemical transformation process. The method resulted in a notable 5-fold improvement in photocurrent features (1.27 mAcm−2 at 1.23 VRHE) and a lower onset potential of 0.6 VRHE. Photoanodes with high photocatalytic features and high photocorrosion resistance may be attributed their high conformity and amorphous nature of the coating. In this study, PEC was compared to electrocatalysis (EC), and the effect of bias potential on PEC degradation was discussed for tetracycline (TCH), riboflavin, and streptomycin. In PEC, TCH was degraded in the most efficient way (96 %) by Zr:BiVO4/NiFeOOH, three times larger than Zr:BiVO4 and EC (55 %). Thus, this study offers a potential solution for oxidizing PEC water and treating water pollution.

Keywords: photoelectrochemical, water splitting, pharmaceutical pollutants degradation, photoanodes, cocatalyst

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Authors: Akbar Esmaeili, Fateme Dadashi

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Bismuth can increase radiation and reduce the dose of radiotherapy. On the other hand, hyaluronic acid plays a role in healing damaged cells, and melittin has been used to destroy cancer cells. This research aims to destroy eye cancer cells and accelerate the recovery of damaged healthy cells during treatment. In this research, we used this nanoparticle, the sol-gel method. According to the optimization process that was carried out, we obtained the optimal value of the desired variables for the manufacture of nanoparticles. The advantage of doing this is reducing the amount of medicine used, as a result of reducing the number of side effects during the treatment and using melittin as an anti-eye cancer drug and the presence of hyaluronic acid to accelerate the recovery of cells, as well as coating the bismuth nanoparticle with chitosan to increase the half-life of the nanoparticle and prevent its adhesion.

Keywords: synthesis, nanoparticles, coated, cancer

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Authors: Merfat Algethami, Anton Blencowe, Bryce Feltis, Stephen Best, Moshi Geso

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Nano-materials with high atomic number atoms have been demonstrated to enhance the effective radiation dose and thus potentially could improve therapeutic efficacy in radiotherapy. The optimal nanoparticulate agents require high X-ray absorption coefficients, low toxicity, and should be cost effective. The focus of our research is the development of a nanoparticle therapeutic agent that can be used in radiotherapy to provide optimal enhancement of the radiation effects on the target. In this study, we used bismuth (Bi) nanoparticles coated with starch and bismuth sulphide nanoparticles (Bi2S3) coated with polyvinylpyrrolidone (PVP). These NPs are of low toxicity and are one of the least expensive heavy metal-based nanoparticles. The aims of this study were to synthesise Bi2S3 and Bi NPs, and examine their cytotoxicity to human lung adenocarcinoma epithelial cells (A549). The dose enhancing effects of NPs on A549 cells were examined at both KV and MV energies. The preliminary results revealed that bismuth based nanoparticles show increased radio-sensitisation of cells, displaying dose enhancement with KV X-ray energies and to a lesser degree for the MV energies. We also observed that Bi NPs generated a greater dose enhancement effect than Bi2S3 NPs in irradiated A549 cells. The maximum Dose Enhancement Factor (DEF) was obtained at lower energy KV range when cells treated with Bi NPs (1.5) compared to the DEF of 1.2 when cells treated with Bi2S3NPs. Less radiation dose enhancement was observed when using high energy MV beam with higher DEF value of Bi NPs treatment (1.26) as compared to 1.06 DEF value with Bi2S3 NPs. The greater dose enhancement was achieved at KV energy range, due the effect of the photoelectric effect which is the dominant process of interaction of X-ray. The cytotoxic effect of Bi NPs on enhancing the X-ray dose was higher due to the higher amount of elemental Bismuth present in Bi NPs compared to Bi2S3 NPs. The results suggest that Bismuth based NPs can be considered as valuable dose enhancing agents when used in clinical applications.

Keywords: A549 lung cancer cells, Bi2S3 nanoparticles, dose enhancement effect, radio-sensitising agents

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Authors: Gülşah Çelik Gül, Figen Kurtuluş

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Cesium molybdates with general formula CsMIII(MoO4)2, where MIII = Bi, Dy, Pr, Er, exhibit rich polymorphism, and crystallize in a layered structure. These properties cause intensive studies on cesium molybdates. CsBi(MoO4)2 was synthesized by microwave method by using cerium sulphate, bismuth oxide and molybdenum (VI) oxide in an appropriate molar ratio. Characterizations were done by x-ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy/energy dispersive analyze (SEM/EDS), thermo gravimetric/differantial thermal analysis (TG/DTA).

Keywords: cesium bismuth dimolybdate, microwave synthesis, powder x-ray diffraction, rare earth dimolybdates

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Authors: Ranjit A. Patil, Yung Liou, Yuan-Ron Ma

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It has been observed that when the size of metals such as, Au, Zn, Ag, Cu, Te, and metal oxides is reduced to several nano-meters, it starts to show further interesting properties. These new properties boost the use of nano-structures to produce attractive functional materials or used as promising building blocks in electronic devices. Present work describes the synthesis of bismuth (Bi) nanoparticles (NP’s) having uniform morphology, high crystallinity, and single phase purity by the temperature assisted pulsed laser deposition (TAPLD). Pulsed Laser deposition (PLD) technique is one of the promising methods to synthesize nano-structures. It can provide the stable nucleation sites in orders of magnitudes higher than for MBE and sputtering deposition. The desired size of purely metallic Bi NP’s of can be easily controlled by adjusting the temperature of the substrate varying from 1000 C to 250 0C. When the temperatures of the substrate raised step wise the average size of Bi NP’s appeared to be increased by maintaining the uniform distribution of NP’s on the Si surfaces. The diameter range of NP’s is ~33-84 nm shows size distribution constrained in the limited range. The EDS results show that the 0D Bi NP’s synthesized at high temperature (250 0C) at a high vacuum still remained in a metallic phase. Moreover, XRD, TEM and SAED results showed that these Bi NP’s are hexagonal in crystalline in a space group R -3 m and no traces of bismuth oxide, confirming that Bi NP’s synthesized at wide range of temperatures persisted of the pure Bi-metallic phase.

Keywords: metal nano particles, bismuth, pulsed laser deposition (PLD), nano particles, temperature assisted growth

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Authors: G. Patricia Abdel Rahim, Jairo Arbey Rodriguez M, María Guadalupe Moreno Armenta

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The present study shows the structural, electronic and magnetic properties of magnesium (Mg) and bismuth (Bi) in a supercell (1X1X5). For both materials were studied in five crystalline structures: rock salt (NaCl), cesium chloride (CsCl), zinc-blende (ZB), wurtzite (WZ), and nickel arsenide (NiAs), using the Density Functional Theory (DFT), the Generalized Gradient Approximation (GGA), and the Full Potential Linear Augmented Plane Wave (FP-LAPW) method. By means of fitting the Murnaghan's state equation we determine the lattice constant, the bulk modulus and it's derived with the pressure. Also we calculated the density of states (DOS) and the band structure.

Keywords: bismuth, magnesium, pseudo-potential, supercell

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Authors: Maria V. Morozova, Zoya A. Mikhaylovskaya, Elena S. Buyanova, Sofia A. Petrova, Ksenia V. Arishina, Robert G. Zaharov

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The present work is devoted to the investigation of two series of doped bismuth molybdates: Bi₂₆-₂ₓMn₂ₓMo₁₀O₆₉-d and Bi₂₆Mo₁₀-₂yMn₂yO₆₉-d. Complex oxides were synthesized by conventional solid state technology and by co-precipitation method. The products were identified by powder diffraction. The powders and ceramic samples were examined by means of densitometry, laser diffraction, and electron microscopic methods. Porosity of the ceramic materials was estimated using the hydrostatic method. The electrical conductivity measurements were carried out using impedance spectroscopy method.

Keywords: bismuth molybdate, columnar structures, impedance spectroscopy, oxygen ionic conductors

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Authors: Qi Lu, Jian Deng, Daishun Huang, Chao Guo

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The lead cooled fast reactor is considered as one of the most potential Generation IV nuclear systems due to the low working pressure, the appreciable neutron economy, and the considerable passive characteristics. Meanwhile, the lead bismuth eutectic (LBE) has the related advantages of lead with the weaker corrosiveness, which has been paid much attention by recent decades. Moreover, the sub-channel code is a necessary analysis tool for the reactor thermal-hydraulic design and safety analysis, which has been developed combined with the accumulation of LBE experimental data and the understanding of physical phenomena. In this study, a sub-channel code available for LBE was developed, and the corresponding geometric characterization method of typical sub-channels was described in detail, especially for for the fuel assembly with wire spacer. As for this sub-channel code, the transversal thermal conduction through gap was taken into account. In addition, the physical properties, the heat transfer model, the flow resistance model and the turbulent mixing model were analyzed. Finally, the thermal-hydraulic experiments of LBE conducted on THEADES (THErmal-hydraulics and Ads DESign) were selected as the evaluation data of this sub-channel code, including 19 rods with wire spacer, and the calculated results were in good agreement with the experimental results.

Keywords: lead bismuth eutectic, sub-channel code, wire spacer, transversal thermal conduction

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Authors: K. A. Mistry, I. B. Patel, A. H. Prajapati

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In the present work, the alloy of Bismuth-lead is prepared on the basis of percentage of molecular weight 9:1, 5:5 and 1:9 ratios and grown by Zone- Refining Technique under a vacuum atmosphere. The EDAX of these samples are done and the results are reported. Micro hardness test has been used as an alternative test for measuring material’s tensile properties. The effect of temperature and load on the hardness of the grown alloy has been studied. Further the comparative studies of work hardening coefficients are reported. In the present work, the alloy of Bismuth-lead is prepared on the basis of percentage of molecular weight 9:1, 5:5 and 1:9 ratios and grown by Zone- Refining Technique under a vacuum atmosphere. The EDAX of these samples are done and the results are reported. Micro hardness test has been used as an alternative test for measuring material’s tensile properties. The effect of temperature and load on the hardness of the grown alloy has been studied. Further the comparative studies of work hardening coefficients are reported.

Keywords: EDAX, hardening coefficient, micro hardness, Bi-Pb alloy

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Authors: Shoroog Alraddadi

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In this study, the effect of gamma irradiation on the structural and transport properties of Bismuth Telluride (Bi₂Te₃) thin films was investigated. Bi₂Te₃ thin films with thicknesses varying from 100 nm to 500 nm were grown using thermal evaporation in vacuum 10⁻⁵ Torr. The films were irradiated by Gamma radiation with different doses (50, 200, and 500 kGy). The crystal structure of Bi₂Te₃ thin films was studied by XRD diffraction. It was showed that the degree of crystallinity of films increases as the doses increase. Furthermore, it was found that the electrical conductivity of Bi₂Te₃ increase as the doses increase. From these results, it can be concluding that the effect of radiation on the structural and transport properties was positive at the levels of irradiation used.

Keywords: bismuth telluride, gamma irradiation, thin film, transport properties

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Authors: Benyamina Imane, Benalioua Bahia, Mansour Meriem, Bentouami Abdelhadi

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The objective of this study is to use a synthetic route of the layered double hydroxide as a method of zinc oxide by doping a transition metal. The material is heat-treated at different temperatures then tested on the photo-fading of acid dye indigo carmine under visible radiation compared with ZnO. The material having a better efficacy was characterized by XRD and thereafter SEM. The result of XRD untreated Bi-Zn-LDH material thermally revealed peaks characteristic lamellar materials. Indeed, the lamellar morphology is very visible, observed by scanning electron microscopy (SEM). Furthermore, the lamellar character partially disappears when the material is treated at 550 °C in a muffle furnace. Thus obtained, a zinc oxide doped with bismuth confirmed by XRD. The photocatalytic efficiency of Bi-ZnO in a visible light of 500 W at 114,6 µw/cm2 as maximum of irradiance was tested on photo-bleaching of an indigoid dye in comparison with the commercial ZnO. Indeed, a complete discoloration of indigo carmine solution of 16 mg / L was obtained after 40 and 120 minutes of irradiation in the presence of Bi-ZnO and ZnO respectively.

Keywords: photocatalysis, Bi-ZnO-LDH, doping, ZnO

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Authors: Shivani Singla, Om Prakash Pandey, Gopi Sharma

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Metallic nanoparticle doped glasses has lead to rapid development in the field of optics. Large third order non-linearity, ultrafast time response, and a wide range of resonant absorption frequencies make these metallic nanoparticles more important in comparison to their bulk material. All these properties are highly dependent upon the size, shape, and surrounding environment of the nanoparticles. In a quest to find a suitable material for optical applications, several efforts have been devoted to improve the properties of such glasses in the past. In the present study, bismuth borate glass doped with different size gold nanoparticles (AuNPs) has been prepared using the conventional melt-quench technique. Synthesized glasses are characterized by X-ray diffraction (XRD) and Fourier Transformation Infrared spectroscopy (FTIR) to observe the structural modification in the glassy matrix with the variation in the size of the AuNPs. Glasses remain purely amorphous in nature even after the addition of AuNPs, whereas FTIR proposes that the main structure contains BO₃ and BO₄ units. Field emission scanning electron microscopy (FESEM) confirms the existence and variation in the size of AuNPs. Differential thermal analysis (DTA) depicts that prepared glasses are thermally stable and are highly suitable for the fabrication of optical fibers. The nonlinear optical parameters (nonlinear absorption coefficient and nonlinear refractive index) are calculated out by using the Z-scan technique with a Ti: sapphire laser at 800 nm. It has been concluded that the size of the nanoparticles highly influences the structural thermal and optical properties system.

Keywords: bismuth borate glass, different size, gold nanoparticles, nonlinearity

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Authors: A. Taoufyq, B. Bakiz, A. Benlhachemi, L. Patout, D. V. Chokouadeua, F. Guinneton, G. Nolibe, A. Lyoussi, J-R. Gavarri

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Currently, the photo catalytic reactions occurring under solar illumination have attracted worldwide attentions due to a tremendous set of environmental problems. Taking the sunlight into account, it is indispensable to develop highly effective visible-light-driver photo catalysts. Nano structured materials such as MxM’1-xWO6 system are widely studied due to its interesting piezoelectric, dielectric and catalytic properties. These materials can be used in photo catalysis technique for environmental applications, such as waste water treatments. The aim of this study was to investigate the photo catalytic activity of polycrystalline phases of bismuth tungstate of formula Bi2WO6. Polycrystalline samples were elaborated using a coprecipitation technique followed by a calcination process at different temperatures (300, 400, 600 and 900°C). The obtained polycrystalline phases have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Crystal cell parameters and cell volume depend on elaboration temperature. High-resolution electron microscopy images and image simulations, associated with X-ray diffraction data, allowed confirming the lattices and space groups Pca21. The photo catalytic activity of the as-prepared samples was studied by irradiating aqueous solutions of Rhodamine B, associated with Bi2WO6 additives having variable crystallite sizes. The photo catalytic activity of such bismuth tungstates increased as the crystallite sizes decreased. The high specific area of the photo catalytic particles obtained at 300°C seems to condition the degradation kinetics of RhB.

Keywords: Bismuth tungstate, crystallite sizes, electron microscopy, photocatalytic activity, X-ray diffraction.

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Authors: Ravinder Dachepalli, Naveena Gadwala, K. Vani

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Nd and Er substituted bismuth nano crystalline multifunctional materials were prepared by citrate gel autocombution technique. The structural characterization was carried out by XRD and SEM. Electrical properties such are electrical conductivity and dielectric properties have been measured. Plots of electrical conductivity versus temperature increases with increasing temperature and shown a transition near Curie temperature. Dielectric properties such are dielectric constant and dielectric loss tangent have been measured from 20Hz to 2 MHz at room temperature. Plots of dielectric constant versus frequency show a normal dielectric behaviour of multifunctional materials. Temperature dependence of magnetic properties of Bi-Nd and Bi-Er multi-functional materials were carried out by using Vibrating sample magnetometer (VSM). The magnetization as a function of an applied field ±100 Oe was carried out at 3K and 360 K. Zero field Cooled (ZFC) and Field Cooled (FC) magnetization measurements under an applied field of 100Oe a in the temperature range of 5-375K. The observed results can be explained for spintronic devices.

Keywords: Bi-Nd and Bi-Er Multifunctional Materia, Citrate Gel Auto combustion Technique, FC-ZFC magnetization, Dielectric constant

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Authors: Sugandha Gupta, Arun Kumar Jha

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A large number of ferroelectric materials have been intensely investigated for applications in non-volatile ferroelectric random access memories (FeRAMs), piezoelectric transducers, actuators, pyroelectric sensors, high dielectric constant capacitors, etc. Bismuth layered ferroelectric materials such as Strontium Bismuth Tantalate (SBT) has attracted a lot of attention due to low leakage current, high remnant polarization and high fatigue endurance up to 1012 switching cycles. However, pure SBT suffers from various major limitations such as high dielectric loss, low remnant polarization values, high processing temperature, bismuth volatilization, etc. Significant efforts have been made to improve the dielectric and ferroelectric properties of this compound. Firstly, it has been reported that electrical properties vary with the Sr/ Bi content ratio in the SrBi2Ta2O9 compsition i.e. non-stoichiometric compositions with Sr-deficient / Bi excess content have higher remnant polarization values than stoichiometic SBT compositions. With the objective to improve structural, dielectric, ferroelectric and piezoelectric properties of SBT compound, rare earth holmium (Ho3+) was chosen as a donor cation for substitution onto the Bi2O2 layer. Moreover, hardly any report on holmium substitution in stoichiometric SrBi2Ta2O9 and non-stoichiometric Sr0.8Bi2.2Ta2O9 compositions were available in the literature. The holmium substituted SrBi2-xHoxTa2O9 (x= 0.00-2.0) and Sr0.8Bi2.2Ta2O9 (x=0.0 and 0.01) compositions were synthesized by the solid state reaction method. The synthesized specimens were characterized for their structural and electrical properties. X-ray diffractograms reveal single phase layered perovskite structure formation for holmium content in stoichiometric SBT samples up to x ≤ 0.1. The granular morphology of the samples was investigated using scanning electron microscope (Hitachi, S-3700 N). The dielectric measurements were carried out using a precision LCR meter (Agilent 4284A) operating at oscillation amplitude of 1V. The variation of dielectric constant with temperature shows that the Curie temperature (Tc) decreases on increasing the holmium content. The specimen with x=2.0 i.e. the bismuth free specimen, has very low dielectric constant and does not show any appreciable variation with temperature. The dielectric loss reduces significantly with holmium substitution. The polarization–electric field (P–E) hysteresis loops were recorded using a P–E loop tracer based on Sawyer–Tower circuit. It is observed that the ferroelectric property improve with Ho substitution. Holmium substituted specimen exhibits enhanced value of remnant polarization (Pr= 9.22 μC/cm²) as compared to holmium free specimen (Pr= 2.55 μC/cm²). Piezoelectric co-efficient (d33 values) was measured using a piezo meter system (Piezo Test PM300). It is observed that holmium substitution enhances piezoelectric coefficient. Further, the optimized holmium content (x=0.01) in stoichiometric SrBi2-xHoxTa2O9 composition has been substituted in non-stoichiometric Sr0.8Bi2.2Ta2O9 composition to obtain further enhanced structural and electrical characteristics. It is expected that a new class of ferroelectric materials i.e. Rare Earth Layered Structured Ferroelectrics (RLSF) derived from Bismuth Layered Structured Ferroelectrics (BLSF) will generate which can be used to replace static (SRAM) and dynamic (DRAM) random access memories with ferroelectric random access memories (FeRAMS).

Keywords: dielectrics, ferroelectrics, piezoelectrics, strontium bismuth tantalate

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Authors: Vincent Kheswa

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X-rays are ionizing electromagnetic radiation that is used in various industries such as computed tomography scans, dental X-rays, and screening freight trains. However, they pose health risks to humans if they are not shielded properly. In recent years, many researchers around the globe have been searching for nontoxic best possible glass materials for shielding X-rays. In this work, the x-ray shielding properties of 45Na₂O + 10 Bi₂O₃ + (5 - x)TiO₂+ (x) Nb₂O₅ + 40 P₂O₅, were x = 0, 1, 3, 5 mol%, glass materials were studied. The results revealed that the glass sample with the highest TiO2 content has the highest mass and linear attenuation coefficients and lowest half-value thickness, tenth-value thickness and mean-free path in the 20 to 80 keV energy region. The sample with 3 mol% of Nb₂O₅ has the highest mass and linear attenuation coefficients and the lowest half-value thickness, tenth-value thickness, and mean-free path at 15 keV and photon energies between 80 to 300 keV. It was, therefore, concluded that 45Na₂O + 10 Bi₂O₃ + 5 TiO₂ + 40 P₂O₅ glass is best for shielding x-rays of energies between 20 and 80 keV, while 45Na₂O + 10 Bi₂O₃ + 2 TiO₂ + 3 Nb₂O₅ + 40 P₂O₅ is best for shielding 15 keV x-rays and x-rays of energies between 80 keV and 300 keV.

Keywords: bismuth-titanium-phosphate glass, x-ray shielding, LAC, MAC, radiation shielding

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Authors: Yuan-Hao Lee, Chia-Wei Lee, Ming-Fang Lin, Tzu-Huei Wu, Chih-Hsiang Ko, Wing P. Chan

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Computed tomography (CT) scan of the head is a good method for investigating cranial lesions. However, radiation-induced oxidative stress can be accumulated in the eyes and promote carcinogenesis and cataract. In this regard, we aimed to protect the eyes with barium sulfate shield(s) during CT scans and investigate the resultant image quality and radiation dose to the eye. Patients who underwent health examinations were selectively enrolled in this study in compliance with the protocol approved by the Ethics Committee of the Joint Institutional Review Board at Taipei Medical University. Participants’ brains were scanned with a water-based marker simultaneously by a multislice CT scanner (SOMATON Definition Flash) under a fixed tube current-time setting or automatic tube current modulation (TCM). The lens dose was measured by Gafchromic films, whose dose response curve was previously fitted using thermoluminescent dosimeters, with or without barium sulfate or bismuth-antimony shield laid above. For the assessment of image quality CT images at slice planes that exhibit the interested regions on the zygomatic, orbital and nasal bones of the head phantom as well as the water-based marker were used for calculating the signal-to-noise and contrast-to-noise ratios. The application of barium sulfate and bismuth-antimony shields decreased 24% and 47% of the lens dose on average, respectively. Under topogram-based TCM, the dose saving power of bismuth-antimony shield was mitigated whereas that of barium sulfate shield was enhanced. On the other hand, the signal-to-noise and contrast-to-noise ratios of DSCT images were decreased separately by barium sulfate and bismuth-antimony shield, resulting in an overall reduction of the CNR. In contrast, the integration of topogram-based TCM elevated signal difference between the ROIs on the zygomatic bones and eyeballs while preferentially decreasing the signal-to-noise ratios upon the use of barium sulfate shield. The results of this study indicate that the balance between eye exposure and image quality can be optimized by combining eye shields with topogram-based TCM on the multislice scanner. Eye shielding could change the photon attenuation characteristics of tissues that are close to the shield. The application of both shields on eye protection hence is not recommended for seeking intraorbital lesions.

Keywords: computed tomography, barium sulfate shield, dose saving, image quality

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Authors: Yasin Polat, Yılmaz Dağdemir, Mehmet Arı

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Samarium (III) oxide and Ytterbium (III) oxide doped Bismuth trioxide solid solutions, the nano ceramic (Bi2O3)1-x-y(Sm2O3)x(Yb2O3)y ternary system were obtained with x=5, 20 mol %, and y=5, 20 mol % dopant concentrations have been synthesized in air atmosphere with solid state reaction. Temperature dependent electrical conductivity of the samples have been investigated by 4-point probe technique by heating and cooling process. Doped-Bi2O3 materials of solid electrolyte systems are good oxygen anions O2-conductors which have collected much attention as potential solid ceramic electrolytes for solid oxide fuel cells (SOFCs) because of their relatively high oxygen ionic conductivity at lower temperatures.(Bi2O3)-based electrolytes have also wide other technological applications in devices with high economical interest such as oxygen sensors, ceramic membranes for oxygen separation, oxygen pumps, catalyzing of some heterogeneous reactions, partial oxidation of the hydrocarbons, and additive material in paints. In recent years, many experimental researches have mostly focused on improving of the Bi-based electrolytes which have high oxide ionic conductivity at low temperatures and better performance as alternatives to traditional stabilized zirconia has taken place. Generally, these systems are much better solid electrolytes than well-known stabilized zirconia, because some of the bismuth trioxide phases exhibit higher ion conductivity than other oxide ionic conductors. Crystal structure of the Nano ceramic (Bi2O3)1-x-y(Sm2O3)x(Yb2O3)y has been determined by X-Ray powder diffractions (XRD) measurements before and after electrical conductivity measurements of the samples. Surface and grain structure properties of the samples were determined by SEM analysis. The samples which synthesized in this study can be used in industrial applications such as electrolytes of the solid oxide fuel cells (SOFC).

Keywords: 4-point probe technique, bismuth trioxide, solid state reaction, solid oxide fuel cell

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Authors: Daniel Manaye Kabtamu, Anteneh Wodaje Bayeh

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With the development and utilization of new energy technology, people’s demand for large-scale energy storage system has become increasingly urgent. Vanadium redox flow battery (VRFB) is one of the most promising technologies for grid-scale energy storage applications because of numerous attractive features, such as long cycle life, high safety, and flexible design. However, the relatively low energy efficiency and high production cost of the VRFB still limit its practical implementations. It is of great attention to enhance its energy efficiency and reduce its cost. One of the main components of VRFB that can impressively impact the efficiency and final cost is the electrode materials, which provide the reactions sites for redox couples (V₂₊/V³⁺ and VO²⁺/VO₂⁺). Graphite felt (GF) is a typical carbon-based material commonly employed as electrode for VRFB due to low-cost, good chemical and mechanical stability. However, pristine GF exhibits insufficient wettability, low specific surface area, and poor kinetics reversibility, leading to low energy efficiency of the battery. Therefore, it is crucial to further modify the GF electrode to improve its electrochemical performance towards VRFB by employing active electrocatalysts, such as less expensive metal oxides. This study successfully fabricates low-cost plate-like bismuth vanadate (BiVO₄) material through a simple one-step hydrothermal route, employed as an electrocatalyst to adorn the GF for use as the negative electrode in VRFB. The experimental results show that BiVO₄-3h exhibits the optimal electrocatalytic activity and reversibility for the vanadium redox couples among all samples. The energy efficiency of the VRFB cell assembled with BiVO₄-decorated GF as the negative electrode is found to be 75.42% at 100 mA cm−2, which is about 10.24% more efficient than that of the cell assembled with heat-treated graphite felt (HT-GF) electrode. The possible reasons for the activity enhancement can be ascribed to the existence of oxygen vacancies in the BiVO₄ lattice structure and the relatively high surface area of BiVO₄, which provide more active sites for facilitating the vanadium redox reactions. Furthermore, the BiVO₄-GF electrode obstructs the competitive irreversible hydrogen evolution reaction on the negative side of the cell, and it also has better wettability. Impressively, BiVO₄-GF as the negative electrode shows good stability over 100 cycles. Thus, BiVO₄-GF is a promising negative electrode candidate for practical VRFB applications.

Keywords: BiVO₄ electrocatalyst, electrochemical energy storage, graphite felt, vanadium redox flow battery

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Authors: Jenna Metera, Olivia Graeve

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Ceramic capacitor technologies using lead based materials is being phased out for its environmental and handling hazards. Bismuth ferrite (BiFeO₃) is the next best replacement for those lead-based technologies. Unfortunately, the electrical properties in bismuth systems are not as robust as the lead alternatives. The improvement of electrical properties such as charge density, charge anisotropy, relative permittivity, and dielectric loss are the parameters that will make BiFeO₃ a competitive alternative to lead-based ceramic materials. In order to maximize the utility of these properties, we propose the ordering and an evaporation-induced self-assembly of a cubic morphology powder. Evaporation-induced self-assembly is a template-less, bottom-up, self-assembly option. The capillary forces move the particles closer together when the solvent evaporates, promoting organized agglomeration at the particle faces. The assembly of particles into organized structures can lead to enhanced properties compared to unorganized structures or single particles themselves. The interactions between the particles can be controlled based on the long-range order in the organized structure. The cubic particle morphology is produced through a hydrothermal synthesis with changes in the concentration of potassium hydroxide, which changes the morphology of the powder. Once the assembly materializes, the powder is fabricated into workable substrates for electrical testing after consolidation.

Keywords: evaporation, lead-free, morphology, self-assembly

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Authors: Karolina Ordon, Sandrine Coste, Malgorzata Makowska-Janusik, Abdelhadi Kassiba

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Photocatalytic processes play key role in the production of a new source of energy (as hydrogen), design of self-cleaning surfaces or for the environment preservation. The most challenging task deals with the purification of water distinguished by high efficiency. In the mentioned process, organic pollutants in solutions are decomposed to the simple, non-toxic compounds as H2O and CO2. The most known photocatalytic materials are ZnO, CdS and TiO2 semiconductors with a particular involvement of TiO2 as an efficient photocatalysts even with a high band gap equal to 3.2 eV which exploit only UV radiation from solar emitted spectrum. However, promising material with visible light induced photoactivity was searched through the monoclinic polytype of BiVO4 which has energy gap about 2.4 eV. As required in heterogeneous photocatalysis, the high contact surface is required. Also, BiVO4 as photocatalyst can be optimized by increasing its surface area by achieving the mesoporous structure synthesize. The main goal of the present work consists in the synthesis and characterization of BiVO4 mesoporous thin film. The synthesis method based on sol-gel was carried out using a standard surfactants such as P123 and F127. The thin film was deposited by spin and dip coating method. Then, the structural analysis of the obtained material was performed thanks to X-ray diffraction (XRD) and Raman spectroscopy. The surface of resulting structure was investigated using a scanning electron microscopy (SEM). The computer simulations based on modeling the optical and electronic properties of bulk BiVO4 by using DFT (density functional theory) methodology were carried out. The semiempirical parameterized method PM6 was used to compute the physical properties of BiVO4 nanostructures. The Raman and IR absorption spectra were also measured for synthesized mesoporous material, and the results were compared with the theoretical predictions. The simulations of nanostructured BiVO4 have pointed out the occurrence of quantum confinement for nanosized clusters leading to widening of the band gap. This result overcame the relevance of nanosized objects to harvest wide part of the solar spectrum. Also, a balance was searched experimentally through the mesoporous nature of the films devoted to enhancing the contact surface as required for heterogeneous catalysis without to lower the nanocrystallite size under some critical sizes inducing an increased band gap. The present contribution will discuss the relevant features of the mesoporous films with respect to their photocatalytic responses.

Keywords: bismuth vanadate, photocatalysis, thin film, quantum-chemical calculations

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Authors: N. Laosiripojana, P. Tepamatr

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The influence of bismuth on the water gas shift activities of Pt on ceria was studied. The flow reactor was used to study the activity of the catalysts in temperature range 100-400°C. The feed gas composition contains 5%CO, 10% H₂O and balance N₂. The total flow rate was 100 mL/min. The outlet gas was analyzed by on-line gas chromatography with thermal conductivity detector. The catalytic activities of bimetallic 1%Pt1%Bi/CeO₂ catalyst were greatly enhanced when compared with the activities of monometallic 2%Pt/CeO₂ catalyst. The catalysts were characterized by X-ray diffraction (XRD), Temperature-Programmed Reduction (TPR) and surface area analysis. X-ray diffraction pattern of Pt/CeO₂ and PtBi/CeO₂ indicated slightly shift of diffraction angle when compared with pure ceria. This result was due to strong metal-support interaction between platinum and ceria solid solution, causing conversion of Ce⁴⁺ to larger Ce³⁺. The distortions inside ceria lattice structure generated strain into the oxide lattice and facilitated the formation of oxygen vacancies which help to increase water gas shift performance. The H₂-Temperature Programmed Reduction indicated that the reduction peak of surface oxygen of 1%Pt1%Bi/CeO₂ shifts to lower temperature than that of 2%Pt/CeO₂ causing the enhancement of the water gas shift activity of this catalyst. Pt played an important role in catalyzing the surface reduction of ceria and addition of Bi alter the reduction temperature of surface ceria resulting in the improvement of the water gas shift activity of Pt catalyst.

Keywords: bismuth, platinum, water gas shift, ceria

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Authors: Rui Tu, Yakui Bai, Huailin Li

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The lead-bismuth eutectic (LBE) alloy is a promising candidate of coolant in the fast neutron reactors and accelerator-driven systems (ADS) because of its good properties, such as low melting point, high neutron yields and high thermal conductivity. Although the corrosion of the structure materials caused by the liquid metal (LM) coolant is a challenge to the safe operating of a lead-bismuth eutectic nuclear reactor. Thermodynamic theories, experiential formulas and experimental data can be used for explaining the maintenance of the protective oxide layers on stainless steels under satisfaction oxygen concentration, but the atomic scale insights of such anti-corrosion mechanisms are little known. In the present work, the first-principles calculations are carried out to study the effects of oxygen partial pressure on the formation energies of the liquid metal coolant relevant impurity defects in the anti-corrosion oxide films on the surfaces of the structure materials. These approaches reveal the microscope mechanisms of the corrosion of the structure materials, especially for the influences from the oxygen partial pressure. The results are helpful for identifying a crucial oxygen concentration for corrosion control, which can ensure the systems to be operated safely under certain temperatures.

Keywords: oxygen partial pressure, liquid metal coolant, TDDFT, anti-corrosion layer, formation energy

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Authors: Moustafa Shawkey, Ahmed G. El-Deen, H. M. Mahmoud, M. M. Rashad

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Piezoelectric based cement nanocomposite is a promising technology for generating an electric charge upon mechanical stress of concrete structure. Moreover, piezoelectric nanomaterials play a vital role for providing accurate system of structural health monitoring (SHM) of the concrete structure. In light of increasing awareness of environmental protection and energy crises, generating renewable and green energy form cement based on piezoelectric nanomaterials attracts the attention of the researchers. Herein, we introduce a facial synthesis for bismuth ferrite nanoparticles (BiFeO3 NPs) as piezoelectric nanomaterial via sol gel strategy. The fabricated piezoelectric nanoparticles are uniformly distributed to cement-based nanomaterials with different ratios. The morphological shape was characterized by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HR-TEM) as well as the crystal structure has been confirmed using X-ray diffraction (XRD). The ferroelectric and magnetic behaviours of BiFeO3 NPs have been investigated. Then, dielectric constant for the prepared cement samples nanocomposites (εr) is calculated. Intercalating BiFeO3 NPs into cement materials achieved remarkable results as piezoelectric cement materials, distinct enhancement in ferroelectric and magnetic properties. Overall, this present study introduces an effective approach to improve the electrical properties based cement applications.

Keywords: piezoelectric nanomaterials, cement technology, bismuth ferrite nanoparticles, dielectric

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Authors: E. O. Echeweozo

Abstract:

This study evaluated radiation shielding and interaction characteristics of polyvinyl alcohol (PVA) polymer separately doped with 10% and 20% nanoscale Bi₂O₃, respectively, for medical apron design and shielding special electronic installations. Prepared samples were characterized by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The EDS results showed that Carbon (C), Oxygen (O), and bismuth (Bi) elements were the predominant elements present in the prepared samples. The SEM result displaced surface irregularities due to a special bonding matrix between PVA and Bi₂O₃. Mass attenuation coefficient (MAC), effective atomic number (Zeff), Half value layer (HVL), Mean free path (MFP), Fast neutron removal cross-section (R), Total Mass Stopping Power (TSP), and photon Range (R) of the prepared polymer composites (PV-1Bi and PV-2Bi) were evaluated with XCOM and PHITS computer programs. Results showed that the MAC of the prepared polymer samples was significantly higher than some recently developed composites at 0.662MeV and 1.25MeV gamma energy. Therefore, polyvinyl alcohol (PVA) polymer doped with Bi₂O₃ should be deployed in medical apron design and shielding special electronic installations where flexibility and high adhesion ability are crucial.

Keywords: polyvinyl alcohol (PVA);, polymer composite, gamma-rays, charged particles

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