Titanate Type Research Articles

Ferroelectric domain wall clusters in perfectly screened barium titanate type systems

Ferroelectric domain wall clusters in perfectly screened barium titanate type systems

Effect of various sintering methods on the properties of PZT-type ceramics

The paper shows how different sintering methods affect the basic characteristics of PZT-type multicomponent ceramics. A perovskite-structured multicomponent ceramic of lead zirconate titanate (PZT) type doped with Mn4+, Sb3+, W6+, and Ni2+ and with a chemical composition of Pb(Zr0.49Ti0.51)0.94Mn0.015Sb0.01W0.015Ni0.03O3 was obtained. Ceramic powders were synthesized using the calcination method. Three sintering methods, including: (i) pressureless free sintering (FS), (ii) hot pressing (HP), and (iii) spark-plasma sintering (SPS), were used for the final sintering. The electrophysical measurements of the PZT-type ceramics, including scanning electron microscopy microstructure (SEM), X-ray diffraction (XRD), dielectric, ferroelectric, piezoelectric properties, and DC electrical conductivity, are presented. The microstructure of the samples is characterized by densely packed grains with correctly crystallized grain shapes but with different average grain sizes for each sintering technology used. At room temperature (RT), PZT ceramic samples have high values of resistivity ρDC (from 7.25 × 108 Ωm to 1.14 × 109 Ωm), high values of permittivity (from 1048 to 1307), and low values of dielectric loss factor (from 0.008 to 0.02). Samples with the most favorable dielectric, ferroelectric, and electromechanical parameters were obtained using the FS and HP sintering methods. In the case of spark-plasma sintering (SPS), the assumed improvement in the electrophysical properties of the P-SPS ceramic sample was not obtained. Also, the most advantageous piezoelectric parameters have ceramic samples obtained by the FS and HP methods. The conducted tests verify that all the obtained ceramic compositions have a complete set of parameters suitable for micromechatronic applications.

Physical and Chemical Investigation of TiO2 Nanotubes Treated with Isopropyl Triisostearoyl Titanate (KR-TTS)

The aim of this study is to investigate the effect of isopropyl triisostearoyl titanate (KR-TTS) as a titanate coupling agent (TCA) on surface modification of TiO2 nanotube (TNT) material. From the physical and chemical studies that have been performed on the modified TiO2 nanotube, scanning electron microscope micrographs, energy-dispersive X-ray and viscosity indicated that there was significant reduction in particle aggregation of the modified TiO2 Nanotube. FTIR spectroscopy confirmed that the functional group of the TCA reacted with the hydroxyl groups present on the surface of TiO2 nanotube resulting in an altered surface property from being hydrophilic to hydrophobic. X-ray diffraction indicated that crystalline structure did not change upon the modification with the coupling agent. Isopropyl triisostearoyl titanate (KR-TTS) is found to be superior in performance and has a significant effect on the dispersion and resolving of agglomeration. This paper presents the effect of surface modification with the TCA of isopropyl triisostearoyl titanate (KR-TTS) type on the TiO2 nanotube material.

A sonochemical synthesis of SrTiO3 supported N-doped graphene oxide as a highly efficient electrocatalyst for electrochemical reduction of a chemotherapeutic drug.

A sonochemical based green synthesis method playa powerful role in nanomaterials and composite development. In this work, we developed a perovskite type of strontium titanate via sonochemical process. SrTiO3 particles were incorporated with nitrogen doped graphene oxide through simple ultrasonic irradiation method. The SrTiO3/NGO was characterized by various analytical methods. The nanocomposite of SrTiO3/NGO was modified with laser-induced graphene electrode (LIGE). The SrTiO3/NGO/LIGE was applied for electrochemical sensor towards chemotherapeutic drug detection (nilutamide). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques have been used to examine the electrochemical performance of nilutamide (anti-cancer drug). DPV was found to be more sensitive and found to exhibit a sensitivity 8.627 µA µM-1 cm-2 for SrTiO3/NGO/LIGE with a wide linear range (0.02-892µM) and low Limit of detection (LOD: 1.16µM). SrTiO3/NGO/LIGE has been examined for the detection of nilutamide in blood serum and urine samples and obtained a good recovery in the range of 97.2-99.72%. The enhanced stability and selectivity and practical application results indicates the suitability of SrTiO3/NGO/LIGE towards the detection of nilutamide drug in pharmaceutical industries.

New class of high-entropy pseudobrookite titanate with excellent thermal stability, low thermal expansion coefficient, and low thermal conductivity

As a type of titanate, the pseudobrookite (MTi2O5/M2TiO5) exhibits a low thermal expansion coefficient and thermal conductivity, as well as excellent dielectric and solar spectrum absorption properties. However, the pseudobrookite is unstable and prone to decomposing below 1200 °C, which limits the practical application of the pseudobrookite. In this paper, the high-entropy pseudobrookite ceramic is synthesized for the first time. The pure high-entropy (Mg,Co,Ni,Zn)Ti2O5 with the pseudobrookite structure and the biphasic high-entropy ceramic composed of the high-entropy pseudobrookite (Cr,Mn,Fe,Al,Ga)2TiO5 and the high-entropy spinel (Cr,Mn,Fe,Al,Ga,Ti)3O4 are successfully prepared by the in-situ solid-phase reaction method. The comparison between the theoretical crystal structure of the pseudobrookite and the aberration-corrected scanning transmission electron microscopy (AC-STEM) images of high-entropy (Mg,Co,Ni,Zn)Ti2O5 shows that the metal ions (M and Ti ions) are disorderly distributed at the A site and the B site in high-entropy (Mg,Co,Ni,Zn)Ti2O5, leading to an unprecedentedly high configurational entropy of high-entropy (Mg,Co,Ni,Zn)Ti2O5. The bulk high-entropy (Mg,Co,Ni,Zn)Ti2O5 ceramics exhibit a low thermal expansion coefficient of 6.35×10−6 K−1 in the temperature range of 25–1400 °C and thermal conductivity of 1.840 W·m−1·K−1 at room temperature, as well as the excellent thermal stability at 200, 600, and 1400 °C. Owing to these outstanding properties, high-entropy (Mg,Co,Ni,Zn)Ti2O5 is expected to be the promising candidate for high-temperature thermal insulation. This work has further extended the family of different crystal structures of high-entropy ceramics reported to date.

Targeted synthesis of carbon-supported titanate nanofibers as host structure for nuclear waste immobilization

Abstract Inorganic ion-exchange materials show potential application for toxic radioactive ions due to their remarkable high efficiency and selectivity features. Here, two type of carbon-supported titanate (C@TNFs and C@TNFs(H)) nanofibers have been synthesized by a cost-effective in suit growth method. The resulting C@TNFs and C@TNFs(H) microspheres present uniform flower-like morphology and large surface area. The interlayer Na+ in the titanate shell provides docking sites for ion-exchange of radioactive ions (U(VI), Ba(II), and Sr(II)). Interestingly, the exceeding theoretical cation-exchange capacities (CECs) are achieved on C@TNFs for U(VI) ∼4.76 meq g−1 and Ba(II) ∼2.65 meq g−1 and C@TNFs(H) for Ba(II) ∼2.53 meq g−1 and Sr(II) ∼2.24 meq g−1, respectively. The impressive adsorption performance is mainly attributed to the synergistic effects of ion-exchange and surface complexation. More significantly, C@TNFs and C@TNFs(H) maintain high distribution coefficients (K d U) of >104 mL g−1 over a wider pH range (pH = 3.5–9.0) and high adsorption rate with short equilibrium time within 50 min. Competitive ion-exchange investigation shows a selectivity order of U(VI) > Ba(II) > Sr(II) at individual 10 ppm concentration, pH = 6.0 and T = 298 K. The related spectroscopic studies reveal the intercalative mechanism of radionuclides in the deformed titanate structure, as a result of target ions firmly trapped in the interlayer of C@TNFs and C@TNFs(H). These advantageous features allow the C@TNFs and C@TNFs(H) to be promising candidates for the remediation of toxic radioactive ions polluted water.

Bismuth titanate based piezoceramics: Structural evolutions and electrical behaviors at different sintering temperatures

Bismuth titanate piezoceramics are considered as the most promising candidate for high temperature applications, and its multi-functional properties such as dielectricity, piezoelectricity, ferroelectricity, and so forth have been widely studied for several decades. Nevertheless, it still lacks of the systematically research on sintering temperature dependent electrical behaviors of bismuth titanate ceramics, and more importantly, to date there is no report on lattice distortion and domain evolution at different sintering temperatures for the ceramics as well, substantially bad for deep understanding the ceramics and limiting its further applications. Here, a type of bismuth titanate based ceramics (Bi3.96Ce0.04Ti2.97W0.015Nb0.015O12, abbreviated as BCTWN) was prepared by traditional solid-phase reaction technology, and the effects of sintering temperature on the multiple microstructures and electrical properties for BCTWN ceramics were investigated in details. The results show that oxygen octahedral rotation primarily determines the lattice distortion of pseudo-perovskite layer, and domain structures are composed of 90° and 180° domains. The higher sintering temperature generates more distorted crystal structure and induces larger domain size and fewer domain wall density. The grain features and defect dipole distribution are also significantly affected by sintering temperature, thus yielding the distinct electrical behaviors. This research sheds insight in micro-mechanism of optimizing electrical properties, and contributes to expanding more applications for bismuth titanate ferroelectrics.

Piezotronic and piezo-phototronic devices based on the third generation semiconductors

<p indent=0mm>Compared with the first-generation semiconductors (such as silicon, germanium) and the second-generation semiconductors (such as gallium arsenide, indium antimonide), the third-generation semiconductor materials represented by silicon carbide (SiC), zinc oxide (ZnO), gallium nitride (GaN) and cadmium sulfide (CdS) usually possess wider band gap, higher thermal conductivity, bigger electron saturation rate and better radiation resistance properties, and thus draw intensive attentions in high temperature and high frequency applications in recent years. Most of the third-generation semiconductors are wurtzite structures, which have piezoelectric effects due to their lack of symmetry in certain directions. This feature serves as a good bridge of transferring mechanical stress signals between the flexible semiconductor electronic devices and the surrounding environment or the host (e.g., the human body). Conventional piezoelectric effects are mainly found in barium titanate and lead zirconate titanate type perovskite materials, but such materials do not have semiconductor properties, thus limiting their use in electronics and optoelectronic devices. Our group has pioneered a new research field, i.e., piezoelectric nanogenerator, by utilizing third-generation semiconductor nanowires (such as ZnO nanowires) under a dynamic force. The piezoelectric potential generated by the dynamic strain on the nanowire can drive electrons to flow in the external load circuit, which is the basic principle of the piezoelectric nanogenerator. Piezoelectric nanogenerator based on ZnO nanowires was firstly proposed in 2006. When a uniform strain is applied on a non-centrosymmetric semiconductor, a piezo-potential will be induced in the semiconductor, accompanied with static piezoelectric charges distributed on the surfaces. This piezoelectric effect is commonly existed in the third generation semiconductors. The strain-induced piezo-potential and piezoelectric polarization charges can also statically and/or dynamically tune the transportation and photoelectric processes of carriers at the interfaces or junctions. The three ways coupling among piezoelectric, photoexcitation and semiconducting properties coined two new research fields, that is, the piezotronics and piezo-phototronics. In order to systematically explain the coupling properties of piezoelectric and semiconductor transport properties in such materials, our group first coined the term piezotronics in a paper published in 2007. The piezotronics is about the modulation of the metal-semiconductor interface barrier via piezoelectric potential acting as a “gate” voltage, which has been used to explain the transistor behavior observed in metal-ZnO-metal structures and the strain-gated diode effect of metal-ZnO structures. The basic core of piezo-phototronics is to regulate the generation, separation, transport and/or recombination of photogenerated carriers at interfaces or heterojunctions by piezoelectric polarization charges, which was first proposed by our group in 2010. The performance of many optoelectronic devices can be effectively enhanced by piezo-phototronic effect. Over the past decade, these two areas have received extensive attentions and made great progresses in basic science and device applications. The combinations of piezotronics and piezo-phototronics with the current popular electronics, optoelectronics and spintronics have great significances, which will bring in revolutionized impacts for future sensor networks, artificial intelligence, micro-nano energy and human-machine interaction applications. This paper gives a brief review of the experimental progress in device application in these two fields in recent years, and looks forward to the future development of these two subjects.

Significantly enhanced dielectric and energy storage properties of plate-like BN@BaTiO3 composite nanofibers filled polyimide films

In this study, a new type of plate-like boron nitride (BN) and barium titanate (BT) composite nanofiber (BN@BT) was fabricated by an electrospinning technology, and introduced into polyimide (PI) matrix to form nano-composite films by in-situ polymerization method. The composite film with 20 wt% BN@BT-fiber shows a high dielectric constant of εr = 47.57 and a low dielectric loss of tgδ = 0.0334 at room temperature. When the content of BN@BT-fiber is up to 1 wt%, the composite film exhibits a maximum energy storage density of Ue = 7.1 J/cm3 at 3438 kV/cm, which is about three times greater than that of PI (≈2.4 J/cm3 at 3628 kV/cm). Meanwhile, the plate-like boron nitride (BN) also enables the composite film to have an improved heat dissipation and thermal stability, and then improves the breakdown field strength.

Layered and Tunnel Hybrid Sodium Titnate Synthetic Process Using Supercritical Fluid and Their Enhanced Electrochemical Performance in Sodium Ion Batteries

Concerned about the environmental pollutant such as greenhouse gas emission caused by extensive use of diesel, gasoline vehicle operation, being increased. Implementation of rechargeable battery in EV application because of EV’s zero emission has become very popular. Lithium ion battery (LIB) is one of the successfully commercialized system due to their high operating potential, high energy density and long cycle life [1]. However, high price and limited resources of lithium still makes hard to produce for reasonable price of EV. In contrast of LIB issue, sodium-ion batteries (SIBs) have drawn a considerable attention as an alternative to LIBs in the EV applications because of its relative abundance in the earth crust, global distribution, and drastically lower cost [2]. However, the fundamental differences between sodium and lithium make it challenging to develop a suitable anode material to host Na+ ions such as well-known graphite intercalation affair in NIB system [3]. Moreover, the higher reduction potential of sodium (–2.71 V vs. S.H.E.) as compared to lithium (–3.04 V vs S.H.E) inherently reduces the energy density of battery system. Therefore, there is still considerable efforts underway to develop a potential anode material that allows to host a large amount of Na+ ions at a low voltage potential. Among the various electrode material, sodium titanates (NTOs) have considered one of promising anode materials for SIBs because of their low starting material cost, environmental friendly, and abundance [4]. Among various type of sodium titanate, layered Na2Ti3O7 is one of the most promising phase. It can uptake two Na+ ions per formula unit into its interlayer space at a low average potential of 0.3 V vs Na/Na+ , which could deliver a high theoretical capacity of 177 mAh g-1 [5]. It makes particularly promising to design an anode material with high energy density. However, the poor electronic conductivity of Na2Ti3O7 associated with its large bandgap (3.7 eV) and structural distortion upon Na+ ion uptake leds to sluggish Na+ ion diffusion and cycling stability [6]. In this study, ultrathin and uniform carbon layer-coated, layered Na2Ti3O7 and tunnel Na2Ti6O13 hybrids anode materials synthetic route was successfully developed using facile and fast supercritical methanol and subsequent carbon coating with low viscosity liquid carbon dioxide as a coating solvent. The deficiency of each material, e.g., poor rate performance and cyclability caused by sluggish Na+ ion diffusion and structural distortion of Na2Ti3O7 and the low capacity of Na2Ti6O13, could be overcome in the hybrid by taking advantages of low volume expansion and high electronic conductivity of Na2Ti6O13 and high capacity of Na2Ti3O7 with enhanced conductivity by carbon coating. Through the HR-TEM technique, conformal, uniform and ultrathin carbon layers on the NTO surface with an average thickness of 15 nm was observed. Moreover, significantly decreased charge transfer resistance was confirmed by way of the EIS measurement. A careful analysis of the cyclic voltammetry profiles of this sodium titanate hybrids revealed that the existence of two different Na+ ion diffusion pathways in the layered structure of Na2Ti3O7 phase. Among two different Na+ diffusion pathways, one is kinetically more favorable but energetically less favorable site and the other is kinetically less favorable but energetically more favorable site. Under the high discharge–charge condition, some of Na+ ion uptake in the layered structure of Na2Ti3O7 and structural integrity of tunnel structure of Na2Ti6O13 resulted in excellent high-rate performance and long-term cyclability in the hybrid. ACKNOWLEDGEMENTS This research was supported by a National Research Foundation of Korea (NRF) grant provided by the Korean Government (MSIP) (No. 2016R1A2B3008800, NRF-2018R1A6A3A01012498). REFERENCES [1] D. Larcher, J.M. Tarascon, Towards greener and more sustainable batteries for electrical energy storage, Nat Chem 7 (2015) 19-29. [2] N. Yabuuchi, K. Kubota, M. Dahbi, S. Komaba, Research Development on Sodium-Ion Batteries, Chem. Rev. 114 (2014) 11636-11682. [3] H. Moriwake, A. Kuwabara, C.A. Fisher, Y. Ikuhara, Why is sodium-intercalated graphite unstable?, RSC Adv. 7 (2017) 36550-36554. [4] F. Xie, L. Zhang, D. Su, M. Jaroniec, S.-Z. Qiao, Na2Ti3O7@N-Doped Carbon Hollow Spheres for Sodium-Ion Batteries with Excellent Rate Performance, Adv. Mater. 29 (2017) 1700989. [5] J. Nava-Avendaño, A. Morales-García, A. Ponrouch, G. Rousse, C. Frontera, P. Senguttuvan, J.-M. Tarascon, M. Arroyo-de Dompablo, M.R. Palacín, Taking steps forward in understanding the electrochemical behavior of Na2Ti3O7, J. Mater. Chem. A 3 (2015) 22280-22286. [6] J. Ni, S. Fu, C. Wu, Y. Zhao, J. Maier, Y. Yu, L. Li, Superior Sodium Storage in Na2Ti3O7 Nanotube Arrays through Surface Engineering, Adv. Energy Mater. 6 (2016) 1502568.

Alkali aluminosilicate geopolymers as binders to encapsulate strontium-selective titanate ion-exchangers.

Alkali-activated metakaolin geopolymers are attracting interest in the conditioning of nuclear wastes, especially for their ability to immobilise cationic species. However, there is limited understanding of the chemical interactions between the encapsulated spent ion-exchangers, used for decontaminating waste water, and the host aluminosilicate matrix. The lack of such understanding makes it difficult to predict the long-term stability of the waste form. In this study, the suitability of using metakaolin based geopolymer as a matrix for encapsulation of titanate-type ion-exchangers loaded with non-radioactive Sr was investigated for the first time, via spectroscopic and microstructural inspection of the encapsulated ion-exchangers and the aluminosilicate gel matrix. The microstructural and chemical properties of metakaolin geopolymers remained stable after encapsulating titanate type spent ion-exchangers, performed desirably as host materials for conditioning of Sr-loaded titanate ion-exchangers.

Influence of Molar Ratio of CaO to TiO2 on Ti Electrodeposition in Molten CaCl2

A new efficiency process of Ti production replacing Kroll process is desired. The authors proposed the direct electrowinning of liquid Ti considering its advantage in term of productive efficiency. Our previous study showed that calcium titanate was dissolved in molten CaCl2, and that the type of calcium titanate affected the reduction behavior of Ti. These results indicated that Ti reduction in molten CaCl2 depends on the molar ratio of CaO to TiO2 (RCaO/TiO2, hereinafter).In this study, the influence of RCaO/TiO2 on Ti reduction reaction was investigated by cyclic voltammetry at 1373K ~ 1573K using the bath of RCaO/TiO2 = 1.0 ~ 2.0, and electrodeposition by potentio-static electrolysis was attempted. Typical cyclic voltammograms in the bath of various RCaO/TiO2 were shown in Fig.1. Although no sharp current peak was seen, some current peak/humps appeared; three current peak/humps were observed in the bath of RCaO/TiO2 = 1.0 and 1.325, while two current peak/humps were seen in the bath of RCaO/TiO2 = 1.5, 1.8 and 2.0. These results suggest that stable Ti-O complex ions change with RCaO/TiO2, and that they affect the Ti reduction.Titanium metal was obtained by potentio-static electrolysis regardless of RCaO/TiO2, but the situation of Ti metal deposition depended on RCaO/TiO2 and the electrolysis potential; Ca metal was apt to co-deposited with Ti metal deposition in the bath of RCaO/TiO2 = 1.0 and 1.325, while Ti metal was obtained without Ca co-deposition in the bath of RCaO/TiO2 = 1.5, 1.8 and 2.0. The suitable electrolytic potential for Ti metal deposition without Ca co-deposition seemed around -1.8V (vs. Mo dissolution potential).From the reseachers by cyclic voltammetry and potentio-static electrolysis, it was shown that the electrodeposition of Ti metal in molten CaCl2 containing TiO2 strongly depended on the bath composition and the electrolytic potential deposition. The suitable molar ratio of CaO to TiO2, RCaO/TiO2, in the bath is thought to be around, and the suitable potential was -1.8V. Figure 1

Influence of Molar Ratio of CaO to TiO2 on Ti Electrodeposition in Molten CaCl2

In our laboratory, the direct electrowinning of liquid Ti metal in molten chloride has been studied. Based on our previous study, the electrochemical behavior of Ti in CaCl2-CaO-TiO2 bath, in which the molar ratio of CaO to TiO2 (RCaO/TiO2 ) was above 1.5, has been investigated, and the dependence of Ti metal deposition on RCaO/TiO2 was discussed. The reduction behavior changed with the type of calcium titanate, and the electrodeposition of Ti metal depended on RCaO/TiO2 . Titanium metal was obtained in the bath of RCaO/TiO2 > 1.5 more easily than that of RCaO/TiO2 < 1.5, but Ca metal was also obtained in the bath with RCaO/TiO2 = 2.0. The concentration of RCaO/TiO2 also influenced Ti deposition. It was suggested that suitable RCaO/TiO2 to obtain Ti metal was around 1.5, and that the suitable electrolysis potential was -1.8V ~ -1.9V.

The synthesis of SrTiO3 nanocubes and the analysis of nearly ideal diode application of Ni/SrTiO3 nanocubes/n-Si heterojunctions

A perovskite type of strontium titanate (SrTiO3) nanocubes (NCs) were synthesized by using a hydrothermal process and the thin films of these NCs were deposited on an n-type silicon wafer by spin coating technique. As-synthesized SrTiO3 NCs were characterized by transmission electron microscope, scanning electron microscope, energy dispersive x-ray, x-ray diffraction and Raman spectroscopy. After evaporation of 12 Ni dots on the SrTiO3 NCs thin films deposited on n-Si, the Ni/SrTiO3 NCs/n-Si heterojunction devices were fabricated for the first time. The ideality factors of the twelve fabricated devices were vary from 1.05 to 1.22 and the barrier height values varied from 0.64 to 0.68 eV. Furthermore, since all devices yielded similar characteristics, only the current–voltage and the capacitance–voltage of one selected device (named H1) were investigated in detailed. The series resistance of this device was calculated as 96 Ω.

Green energy harvesting from human footsteps

The need for a sustainable green energy is increasing, while the availability of energy itself is not comparable to the needs. One of the most rapid activities in human life is footstepping. The large amounts of kinetic energy in term of pressure force are generated in every footstep activities at the crosswalk space, lecture building, office, shopping centre or market area. As an alternative energy that still has not been exploited, these human steps can be used to power some low voltage loads. In this study, a tile constructed with some piezoelectric transducers are designed and implemented to generate electrical pulses and harvesting human feet step energies. The piezoelectric transducers used in this study is Lead Zirconate Titanate type. From the pizoelectric floor energy harvester system, a tile consists of 20 pieces parallel connected piezoelectric transducer can produce AC voltage up to 71.20 V. While the average generated voltage is 63.98 V. So the average power is 0.0604 watt/10 footsteps. We conclude that this piezoelectric generator can be generated more power when arranged with some tiles arrangement, so we can harvest this energy efficiently.

Implementation of raindrops energy collector board using piezoelectric transducer

Indonesia is a country that has a fairly high rainfall, because it is located in the tropical area. This condition could be a potential for generating electrical energy from raindrops. If the heavy raindrop collide the piezoelectric materials, it can generate electrical energy. The piezoelectric effect was discovered by Jacques and Pierre Curie in 1880. They found that certain materials, when subjected to mechanical strain, suffered an electrical polarization that was proportional to the applied strain. This piezoelectric effect converts mechanical strain into electrical voltage. The molecular structure of piezoelectric materials produces a coupling between electrical and mechanical domains. In this research, raindrops will be exploited to produce electric voltage by piezoelectric transducer. Piezoelectric transducer used in this research is Lead Zirconate Titanate type. Energy conversion processing occurred when raindrop collide the polymer layer of piezoelectric and make an unelastic thrust on its surface. The designed system consists of raindrops collector board and serial connected piezoelectric transducer. From system above, highest voltage, reach is 3.13 VAC for 30 piezoelectric and the average voltage is 2.617 V. This results show us the potential usage of raindrops energy generator using piezoelectric transducer for tropical countries.

Air-Coupled Low Frequency Ultrasonic Transducers and Arrays with PMN-32%PT Piezoelectric Crystals.

Air-coupled ultrasonic techniques are being increasingly used for material characterization, non-destructive evaluation of composite materials using guided waves as well as for distance measurements. Application of those techniques is mainly limited by the big losses of ultrasonic signals due to attenuation and mismatch of the acoustic impedances of ultrasonic transducers and air. One of the ways to solve this problem is by application of novel more efficient piezoelectric materials like lead magnesium niobate-lead titanate (PMN-PT) type crystals. The objective of this research was the development and investigation of low frequency (<50 kHz) wide band air-coupled ultrasonic transducers and arrays with an improved performance using PMN-32%PT crystals. Results of finite element modelling and experimental investigations of the developed transducers and arrays are presented. For improvement of the performance strip-like matching elements made of low acoustic impedance, materials such as polystyrene foams were applied. It allowed to achieve transduction losses for one single element transducer −11.4 dB, what is better than of commercially available air-coupled ultrasonic transducers. Theoretical and experimental investigations of the acoustic fields radiated by the eight element ultrasonic array demonstrated not only a good performance of the array in a pulse mode, but also very good possibilities to electronically focus and steer the ultrasonic beam in space.

Titanate-Based Surface Modification of Paper Waste Particles and its Impact on Rigid Polyurethane Foam Properties

Producing particulate filled polymer composites, even dispersion and sufficient adhesion between filler and polymer matrix is of great importance. In order to solve these issues, methodologies, such as ultrasonic dispersing and coupling agents, are proposed. The impact of particle surface modification with three different titanate coupling agents having the tradenames of TCA L44, TCA L38 and TCA K44 on paper waste sludge particles surface, polyurethane foam composite density, compressive and tensile strengths as well as water absorption and water vapour permeability is evaluated. Apparently, titanates form layer on the particle surface, thus increasing the interfacial adhesion between particles and polymer matrix. Basing on the obtained results, the optimal amount and type of titanate is 1 wt.% of TCA K44.

Damage detection of pipeline multiple cracks using piezoceramic transducers

To study the feasibility of detecting pipeline multi-cracks damage using piezoceramic transducers, the electromechanical impedance method and the stress wave based active sensing method were used respectively to perform the damage detection of pipeline with multi-cracks. In this research, the lead zirconate titanate (PZT) type transducers were used due to its strong piezoelectric effect and low cost. During the experiments, two artificial cracks on the pipeline specimen were created, ranging from 0 mm to 9 mm, and seven different operating conditions were generated for each artificial crack. In the monitoring test, for the electromechanical impedance method, the damage index based on Root Mean Square Deviation (RMSD) was used, and for the active sensing method, the damage index based on Wavelet Packet Energy Loss (WPEL) was used. In addition, the relationship between the crack depth and RMSD as well as the relationship between the crack depth and location and WPEL were analyzed. The results show that RMSD and WPEL indices increase with the increase of the depth of pipeline cracks. In addition, the WPEL index increases with the appearance of new cracks. Quantitative analysis of pipeline crack damage can be realized by electromechanical impedance method, and localization analysis on the pipeline multi-cracks damage can be achieved by stress wave method based on sensor arrays.

Development of Dual-Axis MEMS Accelerometers for Machine Tools Vibration Monitoring

With the development of intelligent machine tools, monitoring the vibration by the accelerometer is an important issue. Accelerometers used for measuring vibration signals during milling processes require the characteristics of high sensitivity, high resolution, and high bandwidth. A commonly used accelerometer is the lead zirconate titanate (PZT) type; however, integrating it into intelligent modules is excessively expensive and difficult. Therefore, the micro electro mechanical systems (MEMS) accelerometer is an alternative with the advantages of lower price and superior integration. In the present study, we integrated two MEMS accelerometer chips into a low-pass filter and housing to develop a low-cost dual-axis accelerometer with a bandwidth of 5 kHz and a full scale range of ±50 g for measuring machine tool vibration. In addition, a platform for measuring the linearity, cross-axis sensitivity and frequency response of the MEMS accelerometer by using the back-to-back calibration method was also developed. Finally, cutting experiments with steady and chatter cutting were performed to verify the results of comparing the MEMS accelerometer with the PZT accelerometer in the time and frequency domains. The results demonstrated that the dual-axis MEMS accelerometer is suitable for monitoring the vibration of machine tools at low cost.