1-3-Type Composites Based on Ferroelectrics:Electromechanical Coupling, Figures of Merit, and Piezotechnical Energy-Harvesting Applications

The physical and microgeometric factors that are able to improve the piezoelectric performance, anisotropy, and energy-harvesting characteristics of modern 1-3-type composites based on ferroelectrics are discussed. The composite connectivity patterns of particular interest for this study include 1-3-0, 1-0-3, and 1-2-2. The active components of the studied composites are chosen from conventional perovskite-type ferroelectric ceramics, lead-free materials, or domain-engineered single crystals, all of which exhibit particularly intriguing electromechanical properties. Examples of the large anisotropy of piezoelectric coefficients, electromechanical coupling factors, squared figures of merit, and large hydrostatic parameters of the three-component 1-3-type composites are considered in the context of their piezotechnical applications. The applications of these materials include piezoelectric transducers, sensors, energy-harvesting, and hydroacoustic devices.</p

Wild and Cultivated Cherries – Antioxidant Capacity Analysis

Cherries are fruit that is rich in powerful antioxidants (anthocyanin) and many different stimulating good health substances. SCOPE: Determination and analysis of pH, total phenols, antioxidant activity (radical trapping activity) total anthocyanin of wild growing and cultivated varieties of cherries. Research Methods Applied: - Systematic approach and critical analysis of the available scientific periodicals; - Spectrophotometric method for determination of adsorption and standard Gallic acid; - DPPH method for determining the antioxidant activity (radical trapping activity). The results presented are the mean values of at least three parallel tests. The total phenols of the samples we studied are in the range of 0.57 to 1.67 mg GAE / g fresh weight. Total anthocyanin in the samples we tested was in the range of 0.02 to 0.44 mg / g of fresh weight. Antioxidant activity of 7.88 to 16.20 mol TE / g fresh weight pH of 3.70 to 4.19. CONCLUSION: Common anthocyanin is highest in early sorts of cultivated cherries. In later ripening varieties of cultivated cherries, the value of common anthocyanin is significantly lower. In addition, this indicator depends on the altitude of the cultivated cherry. The antioxidant activity is highest in the variety Wild Cherry (Banya, Karlovo), Early Cherry Van (Radilovo), Van variety (Isperihovo) and Cartilage Bing variety or Bigato Burla (Novo Selo). Therefore, this indicator depends on the altitude and ripening time of the fruit

New aspect-ratio effect in three-component composites for piezoelectric sensor, hydrophone and energy-harvesting applications

In this paper the influence of the aspect ratio of ferroelectric ceramic inclusions on the piezoelectric performance and hydrostatic parameters of novel three-component 1-3-type composites based on relaxor-ferroelectric single crystals is studied. Differences in the microgeometry of the ceramic/polymer matrix with 0-3 connectivity and the presence of two piezo-active components with contrasting piezoelectric and mechanical properties lead to a considerable dependence of the piezoelectric performance, hydrostatic response and related parameters of the 1-0-3 composite on the aspect ratio and volume fraction of the aligned ceramic inclusions. The influence of the elastic anisotropy of the ceramic/polymer matrix on composite properties with changes in the aspect ratio and volume fraction of the inclusions is discussed. The piezoelectric performance of the 1-0-3 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 single crystal/modified PbTiO3 ceramic/polymer composite suggests that such a material is of interest for both sensor and energy-harvesting applications due to large values of the piezoelectric coefficient g33∗∼400-550 mV m/N, squared figure of merit d33∗g33∗∼10-10 Pa-1 and related anisotropy factor d33∗g33∗/(d31∗g31∗)∼8-9. Such composites can also be used in hydrophone applications due to their large hydrostatic parameters, e.g., dh∗∼102 pC/N, gh∗∼100-160 mV m/N and dh∗gh∗∼10-11 Pa-1.</p

Influence of cardiopulmonary bypass on the erythrocyte membranes and the method of its protection

The damage to erythrocytes during cardiopulmonary bypass (CPB) remains a recent problem. The aim of this research was to study the effect of fructose-1,6-diphosphate on the state of the erythrocyte membrane during CPB and the level of phosphorus in blood as a marker of the energy potential in the cell. Patients were divided into two groups. The control group 1 (Gr&nbsp;1) consisted of 75 individuals. The group&nbsp;2 (Gr&nbsp;2) included patients to whom fructose-1,6-diphosphate (FDP) was administrated according to the developed scheme as follows 10&nbsp;g of the drug was diluted in 50 ml of a solvent, 5&nbsp;g of the drug was injected intravenously with the use of perfusor immediately before initiation of CPB at a rate of 10&nbsp;ml/min and 5 g at the 30th minute of CPB (before the stage of warming) the same way. When comparing two groups the best results in hemolysis (p&lt;0.01), mechanical (p&lt;0.01). osmotic resistance of erythrocytes (p&lt;0.01), the time of acid hemolysis (p&lt;0.01) and the permeability of the erythrocyte membrane in postperfusion period were in Gr&nbsp;2. Вefore cardiac surgery hypophosphatemia was detected in 18% out of 150 and in 32% out of 150 patients – a lower limit of normal phosphorus content in the blood. After CPB in Gr&nbsp;1 phosphorus content in blood was 0.85±0.32&nbsp;mmol/l and hypophosphatemia was in 53% out of 75 patients. This indicates a pronounced energy deficit in this group. In Gr&nbsp;2 phosphorus level was 1.7±0.31&nbsp;mmol/l and there was no hypophosphatemia. As a result, FDP as an endogenous high-energy intermediate metabolite of the glycolytic pathway leads to resistance to hemolysis, protects the erythrocyte membrane from damage and increases the energy potential of the cell during CPB

Twelve modified figures of merit of 2–2-type composites based on relaxor-ferroelectric single crystals

Twelve modified figures of merit are studied for the first time for 2–2-type composites based on relaxor-ferroelectric single crystals such as [001]-poled (1 – x)Pb(A1/3Nb2/3)O3 – xPbTiO3, where A = Mg or Zn. These modified figures of merit are related to the piezoelectric coefficients d3j* of the composite (j = 1, 2 and 3) and characterise the effectiveness of energy harvesting and transduction along the three co-ordinate axes OXj of a piezoelectric composite under a constant mechanical stress or strain. The volume-fraction dependencies of the modified figures of merit are analysed for parallel-connected 2–2 and 2–2–0 composites, and the effect of porosity (i.e. the volume fraction and shape of air pores in each polymer layer) on these figures of merit is considered for 2–2–0 composites. Linkages between the modified figures of merit and traditional energy-harvesting figures of merit d3j*g3j* are discussed for the studied 2–2-type composites. New diagrams are developed to indicate important volume-fraction ranges that correspond to a large anisotropy of exemplar modified figures of merit. Due to the large effective parameters and large anisotropy of specific figures of merit, the studied composites are of interest in piezoelectric sensor, transducer and energy-harvesting applications

Domain orientations and piezoelectric properties in novel 2–2-type composites with two single-crystal components

The present paper is concerned with the piezoelectric properties and related parameters of the 2–2-type parallel-connected composites wherein rotations of the main crystallographic axes in ferroelectric single crystal components are analyzed. The composite consists of layers of two types that are regularly arranged along the non-polar axis. The Type I layer is a single domain 0.63Pb(Mg1/3Nb2/3)O3–0.37PbTiO3 single crystal (either tetragonal in Composite I or orthorhombic in Composite II). The Type II layer is a Li2B4O7 single crystal/polyethylene medium with 0–3 connectivity. The composite as a whole is characterized by 2–0–2 connectivity. The following parameters of the composite are studied by taking into account the polarization orientation effect in the Type I layer and the microgeometry of the composite in the Type II layer: piezoelectric coefficients (Formula presented.) and (Formula presented.) their hydrostatic analogs (Formula presented.) and (Formula presented.) hydrostatic squared figure of merit (Formula presented.) (Formula presented.) piezoelectric anisotropy factors (Formula presented.) / (Formula presented.) and (Formula presented.) / (Formula presented.) It is shown that large values of the studied piezoelectric coefficients, hydrostatic parameters and anisotropy factors make Composite II more preferable in comparison to Composite I for hydroacoustic, piezoelectric sensor and energy-harvesting applications.</p

Theoretical Study on the Piezoelectric Performance of Lead-Free 1–3-Type Composites

The paper is devoted to the analysis of high-performance piezo-composites based on lead-free ferroelectric single crystals. The composite consists of parallelepiped-shaped single-crystal rods which are surrounded by a laminar polymer matrix, and the composite as a whole is described by 1–2–2 connectivity. Such a composite structure promotes high piezoelectric sensitivity and hydrostatic response. Of particular interest are piezoelectric coefficients g*33 and h*33, squared figure of merit d*33 g*33, electromechanical coupling factor k*t at the thickness-mode oscillation, and hydrostatic parameters g*h and d*h g*h. The influence of the laminar matrix on the aforementioned parameters is studied in a wide volume-fraction range. Examples of maxima and large anisotropy of some effective parameters are discussed for the 1–2–2 composites based on [Lix(K1−yNay)1−x](Nb1−zTaz)O3:Mn single crystals. The role of elastic properties of the laminar matrix in achieving large hydrostatic parameters and piezoelectric anisotropy of these composites is emphasised. Their effective parameters are compared to those of composites based on the lead-containing relaxor-ferroelectric single crystals and to specific parameters of poled textured ceramics. Advantages of the studied composites over the relaxor-ferroelectric-based composites and textured ceramics open up new possibilities to apply the 1–3-type lead-free composites as active elements of piezoelectric sensors, hydrophones, energy-harvesting, and transducer devices.</p

Piezoelectric anisotropy and energy-harvesting characteristics of novel sandwich layer BaTiO₃ structures

This paper presents a detailed modelling and experimental study of the piezoelectric and dielectric properties of novel ferroelectric sandwich layer BaTiO3 structures that consist of an inner porous layer and dense outer layers. The dependencies of the piezoelectric coefficients and dielectric permittivity of the sandwich structure on the bulk relative density α are analysed by taking into account an inner layer with a porosity volume fraction of 0.5-0.6. The observed changes in and are interpreted within the framework of a model of a laminar structure whereby the electromechanical interaction of the inner porous layer and outer dense layers have an important role in determining the effective properties of the system. The porous layer is represented as a piezocomposite with a 1-3-0 connectivity pattern, and the composite is considered as a system of long poled ceramic rods with 1-3 connectivity which are surrounded by an unpoled ceramic matrix that contains a system of oblate air pores (3-0 connectivity). The outer monolithic is considered as a dense poled ceramic, however its electromechanical properties differ from those of the ceramic rods in the porous layer due to different levels of mobility of 90° domain walls in ceramic grains. A large anisotropy of d3j ∗ at α = 0.64-0.86 is achieved due to the difference in the properties of the porous and monolithic layers and the presence of highly oblate air pores. As a consequence, high energy-harvesting figures of merit d3j ∗ g3j ∗ are achieved that obey the condition d33 ∗ g33 ∗/( d31 ∗ g31∗) ∼ 102 at d33∗ g33∗ ∼ 10-12 Pa-1 and values of the hydrostatic piezoelectric coefficients dhz.ast; ≈ 100 pC N and ghz.ast; ≈ 20 m V m N are achieved at α= 0.64-0.70. The studied BaTiO3-based sandwich structures has advantages over highly anisotropic PbTiO3-type ceramics as a result of the higher piezoelectric activity of ceramic BaTiO3 and can be used in piezoelectric sensor, energy-harvesting and related applications.</p