Current Understanding of Structure–Processing–Property Relationships in BaTiO3–Bi(M)O3 Dielectrics

As part of a continued push for high permittivity dielectrics suitable for use at elevated operating temperatures and/or large electric fields, modifications of BaTiO₃ with Bi(M)O₃, where M represents a net‐trivalent B‐site occupied by one or more species, have received a great deal of recent attention. Materials in this composition family exhibit weakly coupled relaxor behavior that is not only remarkably stable at high temperatures and under large electric fields, but is also quite similar across various identities of M. Moderate levels of Bi content (as much as 50 mol%) appear to be crucial to the stability of the dielectric response. In addition, the presence of significant Bi reduces the processing temperatures required for densification and increases the required oxygen content in processing atmospheres relative to traditional X7R‐type BaTiO₃‐based dielectrics. Although detailed understanding of the structure–processing–property relationships in this class of materials is still in its infancy, this article reviews the current state of understanding of the mechanisms underlying the high and stable values of both relative permittivity and resistivity that are characteristic of BaTiO₃‐Bi(M)O₃ dielectrics as well as the processing challenges and opportunities associated with these materials.     

Experimental studies of a new solar water heater system using a solar water pump

The research goal was to develop a new solar water heater system (SWHS) that used a solar water pump instead of an electric pump. The pump was powered by the steam produced from a flat plate collector. Therefore, heat could be transferred downward from the collector to a hot water storage tank. The designed system consisted of four panels of flat plate solar collectors, an overhead tank installed at an upper level and a large water storage tank with a heat exchanger at a lower level. Discharge heads of 1, 1.5 and 2 m were tested. The pump could operate at the collector temperature of about 70–90 °C and vapor gage pressure of 7–14 kPa. It was found that water circulation within the SWHS ranged between 12 and 59 l/d depending on the incident solar intensity and system discharge head. The average daily pump efficiency was about 0.0014–0.0019%. Moreover, the SWHS could have a daily thermal efficiency of about 7–13%, whereas a conventional system had 30–60% efficiency. The present system was economically comparable to a conventional one.     

High-K (Ba0.8Bi0.2)(Zn0.1Ti0.9)O3 ceramics for high-temperature capacitor applications

Solid solutions of BaTiO(3)-Bi(Zn(1/2)Ti(1/2))O(3) were investigated for high-temperature capacitor applications. Compositions close to 0.8BaTiO(3)-0.2Bi(Zn(1/2)Ti(1/2))O(3) revealed pseudo-cubic symmetry and showed a linear dielectric response. The existence of a nearly flat temperature dependence of the relative permittivity over the temperature range of 100 to 350°C was also obtained. In this study, the effects of cation non-stoichiometry and doping were investigated in an attempt to optimize the insulation resistance for high-temperature applications. The dielectric response of (Ba(0.8)-xBi(0.2))(Zn(0.1)Ti(0.9)) O(3) ceramics where 0 ≤ X ≤ 0.08, as well as ZrO2- and Mn(2)O(3)-doped ceramics were studied. The optimum compositions exhibited a relative permittivity in excess of 1150 with a low loss tangent (tan δ < 0.05) that persisted up to a temperature of 460δC. The temperature dependence of resistivity also revealed the improved insulation resistance of Ba-deficient compositions. Additionally, we suggest that an ionic conduction mechanism is responsible for the degradation of resistivity at high temperatures. The temperature coefficient of permittivity ((τ)K) and the RC time constant were also investigated.     

Dielectric properties of BaTiO3–Bi(Zn1/2Ti1/2)O3–NaNbO3 solid solutions

In order to develop dielectric ceramics with temperature-stable permittivity characteristics, perovskite BaTiO₃–Bi(Zn_1/2Ti_1/2)O₃–NaNbO₃ ceramic solid solutions were investigated with a particular focus on effects of BaTiO₃ and NaNbO₃ contents on the dielectric properties of ternary compounds. Keeping the ratios of the other two constituents constant, decreasing the BaTiO₃ content leads to a broadening of the temperature-dependent permittivity maximum and a decrease in the overall permittivity. For compositions of constant BaTiO₃ content, replacing Bi(Zn_1/2Ti_1/2)O₃ with NaNbO₃ shifts the temperature of the maximum permittivity to lower temperatures (e.g., to ?103 °C for a composition of 70BT–5BZT–25NN) while maintaining a broad permittivity peak with temperature, which for the 50BT–25BZT–25NN composition also satisfies the X9R standard. Thus, the investigation of BT–BZT–NN compounds resulted in promising dielectric properties with broad temperature ranges of high permittivity, which is of interest for advanced capacitor applications.     

Understanding the reinforcing efficiency of waste eggshell‐derived nano calcium carbonate in natural rubber composites with maleated natural rubber as compatibilizer

Calcium carbonate nanoparticles were synthesized from eggshell waste using ball mill treatment and characterized by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and field‐emission scanning electron microscopy (FESEM) analysis. Then, waste eggshell‐derived nano calcium carbonate (WESNCC) was used as filler to reinforce natural rubber (NR) composites with and without the presence of maleated natural rubber (MNR) as compatibilizer. MNR‐compatibilized NR/WESNCC composites showed remarkable enhancement in the torque difference, tensile, and thermal properties as compared to either uncompatibilized NR/WESNCC composites or unfilled NR system. Crosslinking degree measurements indicated excellent interfacial interaction between NR matrix and WESNCC in presence of MNR as compatibilizer. A probable mechanism is suggested to explain the interaction between NR matrix and WESNCC in the presence of MNR. This study provides unique way to develop WESNCC‐based rubber composites for future industrial and engineering application. POLYM. ENG. SCI., 59:1428–1436 2019. © 2019 Society of Plastics Engineers     

Comparative Carbon Footprint of Packaging Systems for Tuna Products

The present study aimed to evaluate and compare the carbon footprint associated with canned tuna meat with a focus on packaging systems used to provide one single‐serve meal. The manufacturing process of retort pouches and cups produced 60% and 70% less greenhouse gas emissions, respectively, than that of metal cans. However, the overall carbon footprint of canned tuna in retort cups was 10% and 22% less than when packaged in metal cans and retort pouches, respectively. Packaging and its associated processing constituted significant fractions of the product's carbon footprint, ranging from 20% to 40%. Hotspots in the life cycle assessment of canned tuna are packaging production and disposal and product sterilization. The improvement of retort operation in terms of capacity and energy utilization and the efficiency of post‐consumption packaging material recovery are the key factors responsible for the reduction of a product's carbon footprint. These issues present a challenge to both the food industry and the local authorities. Copyright © 2011 John Wiley & Sons, Ltd.     

High temperature electronic properties of BaTiO3 – Bi(Zn1/2Ti1/2)O3 – BiInO3 for capacitor applications

Solid solutions xBaTiO₃ – (1-x)(0.5Bi(Zn_1/2Ti_1/2)O₃ – 0.5BiInO₃), where x?=?0.95–0.60, were prepared by conventional mixed oxide method. The single phase perovskite structure was obtained for the composition with x?≥?0.75. Phase transformation from tetragonal to pseudocubic was observed from x-ray diffraction patterns when x decreased from 0.95 to 0.75. In tetragonal phase region, x?≥?0.90, the increase of Bi(Zn_1/2Ti_1/2)O₃ – BiInO₃ content decreased the tetragonality and the temperature at which the relative permittivity is maximum (T_max). The increase in lattice parameter and T_max were observed in the pseudocubic phase region, x?<?0.90. Additionally, a highly broad and diffuse phase transition was observed from the dielectric data in the pseudocubic phase region. The introduction of Ba vacancies in compositions with x?=?0.80 and 0.75 also improved dielectric loss at high temperatures. The incorporation of BiInO₃ into the BaTiO₃ – Bi(Zn_1/2Ti_1/2)O₃ compound was also found to improve the temperature coefficient of the relative permittivity, with values as low as approximately ?1,000?ppm/K. Overall, ternary perovskite solid solutions based on adding Bi(Zn_1/2Ti_1/2)O₃ – BiInO₃ to BaTiO₃ shows excellent potential for high temperature capacitor applications     

Synthesis and characterization of magnetic porous clay heterostructure

Magnetic porous clay heterostructure (magnetic PCH) was successfully synthesized using a simple precipitation method of applying magnetite onto a PCH surface. X-ray techniques were used to confirm the presence of magnetite in the composite. The magnetite particles, as investigated by the transmission electron microscopy, were spherical nanoparticles (~12.07 nm). The magnetic PCH exhibited characteristics of mesoporous material type IV, similar to PCH. Significant enhancement of the magnetic and dielectric properties in the high frequency range was also observed.     

A novel thermal water pump for circulating water in a solar water heating system

This research purpose was to perform a parametric study of a novel thermal water pump well fitted in a simulated solar water heating system (SWHS). The SWHS was composed of a heating tank (HT), a hot water storage tank (ST) and an overhead tank (OT). The HT together with a specially designed valve act as a novel thermal water pump that gets power from hot water vapor and air pressure produced by a built-in electric heater in order to transfer heat from the HT to ST. The general operation of this pump has four stages for each cycle: heating, water circulating, vapor circulating and water supplying. The discharge water heads were varied with an increment of 0.25 m from 0.75 to 3 m. According to the experiment, it was found that the pump could operate at an average HT temperature of about 80–95 °C leading to 70–80 °C ST temperatures and 20–35 pumping cycles and consumed 17 MJ energy input during 9-h period. The overall thermal efficiency of the SWHS was 33–42% and the mean pump efficiency was about 0.005–0.011% depending upon the discharge heads.