BT Particles Research Articles

Nanofibers obtained by electrospinning of BaTiO3 particles dispersed in polyvinyl alcohol and ethylcellulose

Barium titanate particles (100-300 nm) synthesized by hydrothermal method were dispersed in both polyvinyl alcohol (PVA) and ethylcellulose (EC) solutions. These suspensions were processed by electrospinning. When no particles were added, homogeneous polymeric nanofibers were obtained. Under certain conditions, polymeric suspensions of barium titanate particles were electrospun generating polymeric fibers with BT particles. The effect of a surfactant was also assessed over the formation of nanofibers. The BaTiO3 particles synthesized by hydrothermal method were characterized by X-Ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Fibers were characterized by scanning electron microscopy (SEM).

Preparation of barium titanate porous ceramics and their sensor properties

Porous barium titanate (BaTiO3, BT) ceramics were prepared by a conventional sintering method using two kinds of BT particles. The relationship between pore structure (porosity and pore size) of BT ceramics and their sensor properties was investigated. Since a piezoelectric constant d33 of BT depends largely on the pore structures, the microstructure control of porous BT ceramics is important to improve the figure-of-merit of piezoelectric stress sensor application (g33/ρ). In this study, the maximal piezoelectric g33 constant value of 14.8 × 10−3 V·m·N−1 and the maximal g33/ρ value of 3.14 × 103 V·m4·N−1·g−1 were obtained at a porosity of approximately 23%.

Nanostructure Control of Barium Titanate–Potassium Niobate Nanocomplex Ceramics and Their Enhanced Ferroelectric Properties

Barium titanate (BaTiO3,BT)–potassium niobate (KNbO3,KN) nanocomplex ceramics with various KN/BT molar ratios were prepared by a solvothermal method. From a transmission electron microscopy (TEM) observation, it was confirmed that the KN layer thickness on BT particles was controlled from 5 to 40 nm by controlling KN/BT molar ratios. Their dielectric constants were measured at room temperature and 1 MHz, and the maximum dielectric constant of 370 was measured for the BT–KN nanocomplex ceramics with a KN thickness of 22 nm. TEM observation revealed that at a KN thickness below 22 nm, the BT/KN heteroepitaxial interface was assigned as a strained interface, while at 40 nm, the interface was assigned as a relaxed one. These results suggested that the strained heteroepitaxial interface could be responsible for the enhanced dielectric properties.

Phase evolution of solid-state BaTiO3 powder prepared with the ultrafine BaCO3 and TiO2

Abstract

Advanced dielectric properties of BaTiO3/polyvinylidene-fluoride nanocomposites with sandwich multi-layer structure

To endow excellent dielectric properties for embedded capacitors application, high-permittivity BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /polyvinylidene fluoride (BT/PVDF) nanocomposites with sandwich multi-layer structure were fabricated via a spin-coated and hot-molding technique. Dependences of dielectric properties of the BT/PVDF multi-layer nanocomposites on frequency and temperature were studied. Results show that concentration and dispersion of BT particles in multi-layer structure nanocomposites had an obvious influence on the final dielectric permittivity. Influence of the compatibility between adjacent layers on dielectric permittivity was also discussed. We use the effective-medium theory and capacitance series model to predict the theoretical values of the dielectric permittivity of the nanocomposites.

Preparation, Characterization and Dielectric Properties of BT/PI Film

By using mixture solution method, Barium titanate/polyimide(BT/PI) composite film was prepared. Influence of different size and filling quantity of BT particles were investigated. The microstructure and properties of the products were characterized by scanning electron microscopy, X-ray diffraction and other analysis methods. The results show that when BT nanoparticles are used, the BT/PI film has better comprehensive performance. As the filling quantity of BT particles increases, the dielectric constant and dielectric loss of BT/PI composite film increase, and the dielectric strength is reduced.

Milling effect on the control efficacy of spray‐dried Bacillus thuringiensis technical powder against diamondback moths

The relationship between the particle size of spray-dried Bacillus thuringiensis NT0423 technical powder and its insecticidal activity against diamondbackmoth was investigated in laboratory and glasshouse conditions. A variety of sizes of Bt particles were made by homogenisation, followed by pilot-scale milling to optimise further the current Bt formulation process. In laboratory conditions, homogenised Bt suspension with smaller particles had higher control efficacy against diamondback moth. However, in glasshouse conditions, the smallest particle treatment did not follow the size-dependent insecticidal activity, rather showing decreased control efficacy. Secondly, air-jet-milled Bt powder (16.9 μm) had higher control efficacy than hammer-milled Bt powder (35.1 μm) in glasshouse conditions. However, double air-jet milling (5.3 μm) had lower control efficacy compared with one-time milling. These results suggest that NT0423 technical powder with smaller particles is better in controlling diamondback moths, but excessively small particles (<10 μm) possibly reduce the insecticidal activity.

Curing Characteristics, Morphological, Tensile and Thermal Properties of Bentonite-Filled Ethylene-Propylene-Diene Monomer (EPDM) Composites

Bentonite (Bt) with irregular shape and surface morphology was used as a new type of filler in EPDM. EPDM/Bt composites were prepared using a laboratory size two-roll mill by adding 0 to 70 phr Bt. The effects of Bt loading on curing characteristics, morphology, tensile and thermal properties of EPDM/Bt composite were studied. Scorch and curing time were decreased with 0 to 30 phr loading and increased subsequently at 50 and 70 phr. Tensile strength and elongation at break (Eb) were increased with increasing Bt loading from 0 to 50 phr and decreased at 70 phr, whereas the tensile modulus (M100%) shows an increasing trend with increasing Bt loading. Thermogravimetric analysis shows the enhancements of thermal properties with increasing Bt loading. Morphological studies of tensile fracture surfaces of EPDM/Bt composite proves good interaction between Bt particles and EPDM at 50 phr and formation of Bt agglomerates at 70 phr.

Preparation of Barium Titanate–Potassium Niobate Nanostructured Ceramics with Artificial Morphotropic Phase Boundary Structure By Solvothermal Method

Barium titanate (BaTiO3, BT)–potassium niobate (KNbO3, KN) (BT–KN) nanostructured ceramics with a distorted interface region, i.e., artificial morphotropic phase boundary (MPB) structure, were prepared by the solvothermal method. The results of the optimization of reaction conditions showed that the metastable region of only KN crystal growth was obtained using a mixture of KOH and K2CO3 as the K source and Nb2O5 as the Nb source in ethanol. Moreover, KN formation under the metastable region using a particle compact composed of a mixture of BT and Nb2O5 particles as substrates resulted in the successful preparation of BT–KN nanostructured ceramics with an artificial MPB region and a porosity of around 35%. This is the first report on the preparation of ceramics with a heteroepitaxial interface between BT and KN below 230 °C.

Preparation and Dielectric Properties of Dense Barium Titanate Nanoparticle Accumulations by Electrophoresis Deposition Method

Dense barium titanate (BaTiO3, BT) nanoparticle accumulations were prepared by an electrophoresis deposition (EPD) method using three kinds of BT nanoparticles with different particles sizes and tetragonality. First, the BT particles were dispersed into ethanol using ball-milling technique, and an optimum milling condition was investigated. As the results, it was confirmed that ball-milling led to a formation of mixture between single-dispersed nanoparticles and aggregated particles. Thus, the aggregated particles in the slurry were removed by a centrifuge in order to obtain narrow the size distribution. Using well-dispersed slurry, BT nanoparticle accumulations were deposited on paradigm electrode by the EPD method. Despite various BT nanoparticles, the dense BT nanoparticle accumulations were obtained at relative densities of around 60 %. After gold electrode deposition on the both surfaces of the accumulations by spattering method, dielectric properties were measured at 20 °C, the highest dielectric constants of around 160 was measured at 10 MHz.

Dispersion of Barium Titanate and Strontium Titanate Nanocubes and their Selective Accumulations

Barium titanate (BaTiO3, BT) and strontium titanate (SrTiO3, ST) nanocube particles were prepared by a solvothermal method. The prepared particles were collected by a centrifugal separator. The X-ray diffraction (XRD) measurement and a transmittance electron microscope (TEM) observation confirmed the formation of perovskite BT and ST nanocube particles with sizes of around 17 nm. These nanocube particles were monodistributed in hexane with tri-n-butylphosphine oxide (TBPO) as dispersant, separately, and then, the accumulations composed of the BT and ST nanocubes were built up using a selective catalytic reaction between 3-bromopropylphosphonic acid (BP) and aminomethylphosphonic acid (AM) as smart glue. The TEM observation confirmed that a part of accumulations showed a hetrointerface connection between BT and ST.

Nanotexture influence of BaTiO 3 particles on piezoelectric behaviour of PA 11/BaTiO 3 nanocomposites

The piezoelectric activity of a hybrid ferroelectric nanocomposite, i.e. polyamide 11/barium titanate (BT), has been investigated for different loadings of BT particles. The BT volume fraction ( ϕ) was ranging from 0.024 to 0.4 with a particle size of 50, 100, 300 and 700 nm. The influence of polarization mode on the piezoelectric behaviour has been studied. The magnitude of the poling field used in this study is in the same order of magnitude of the one used for bulk BT i.e. significantly lower than for piezoelectric polymers. The optimum piezoelectric coefficient is reached when the amorphous phase of the polymeric matrix is in the liquid state i.e. for a polarization temperature higher than the glass transition and for time constant allowing macromolecular mobility. The composite piezoelectric activity decreases for particles size lower than 300 nm due to the loss of the tetragonal phase. The nanotexture of these particles has been investigated by transmission electron microscopy (TEM) and high-resolution TEM. A core shell structure has been observed. An increase of the longitudinal piezoelectric strain coefficient d 33 with the raising of BT volume fraction was shown. Contrary to inorganic piezoelectric ceramics, the dielectric permittivity of hybrid composites remains moderate; therefore it allows the piezoelectric voltage coefficient of composites to be higher than ceramics.

Dispersion of barium titanate and strontium titanate nanocubes and their selective accumulations

Barium titanate (BaTiO3, BT) and strontium titanate (SrTiO3, ST) nanocube particles were prepared by a solvothermal method. The prepared particles were collected by a centrifugal separator. The X-ray diffraction (XRD) measurement and a transmittance electron microscope (TEM) observation confirmed the formation of perovskite BT and ST nanocube particles with sizes of around 17 nm. These nanocube particles were monodistributed in hexane with tri-n-butylphosphine oxide (TBPO) as dispersant, separately, and then, the accumulations composed of the BT and ST nanocubes were built up using a selective catalytic reaction between 3-bromopropylphosphonic acid (BP) and aminomethylphosphonic acid (AM) as smart glue. The TEM observation confirmed that a part of accumulations showed a hetrointerface connection between BT and ST.

Barium Titanate Nanoparticles with Diblock Copolymer Shielding Layers for High-Energy Density Nanocomposites

To develop high-energy density dielectric materials, hybrid BaTiO3 particles with diblock copolymer shielding layers were fabricated and the dielectric properties of barium titanate-copolymer/polystyrene composites were examined. A significantly large breakdown strength of up to 222 V/μm at high permittivity was obtained. In our approach to formation of a robust polymer shell, polystyrene-block-poly(styrene-co-vinylbenzylchloride) (PS-b-PSVBC) was introduced for the complete wrapping of the BT nanoparticles. The two-step processes to form polymer shielding and the resulting self-assembled layers result in excellent dielectric properties, where a charged layer is buried to minimize the development of the breakdown path and leakage current. Consequently, the maintained high breakdown strength, in spite of the large incorporation of BT particles to give high permittivity, afforded a noticeable energy density value of 9.7 J/cm3.

Effects of ${\hbox{CNT/BaTiO}}_{3}$ Composite Particles Prepared by Mechanical Process on Dielectric Properties of Epoxy Hybrid Films

A new type of composite filler mechanically treated with multi-walled carbon nanotubes (MWNTs) and (BT) particles was prepared to produce higher dielectric properties in the composite. The hybrid film fabricated by incorporating these composite fillers in an epoxy matrix had a high dielectric constant and similar dielectric loss as compared to the composite which contained neat BT particles. The dielectric properties of these hybrid films were found to be dependent on both the content of MWNTs and mechanical processing time. Results suggest that this novel hybrid film composed of the composite filler and the epoxy matrix can be used for embedded capacitor material.

Significantly enhanced low-frequency dielectric permittivity in the BaTiO3/poly(vinylidene fluoride) nanocomposite

To disclose an effect of ceramic particle size on dielectric properties of BaTiO3/ poly(vinylidene fluoride) (BT/PVDF) composites at low frequency, the dielectric properties of the BT/PVDF composites loaded with different diameter BT particles at the same volume concentration were studied at wide frequency ranges from 10−1to107Hz. A significant low-frequency dielectric permittivity increase in the BT/PVDF nanocomposite was noticed, which was not reported previously. The authors considered that the marked aggrandizement of interface and dipole polarization at low frequency is charged with the significant increase in dielectric permittivity.

BaTiO 3 nanocrystals: Hydrothermal synthesis and structural characterization

The microstructure of BaTiO 3 (BT) nanocrystals was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), and (high-resolution) transmission electron microscopy [(HR)TEM]. The BT nanocrystals have a cubic perovskite structure as revealed by XRD and SAED. They were prepared by a hydrothermal method using different starting materials: (i) Using as-prepared titanium hydroxide and barium hydroxide as starting materials, BT nanocrystals were obtained with a narrow size distribution and an average grain size of 65 nm, exhibiting a spherical particle morphology and smooth surfaces. These nanocrystals showed almost uniform contrast in TEM. HRTEM lattice fringe images indicate a rather uniform, perfect crystal structure. (ii) Using barium hydroxide and titanium dioxide (anatase) as starting materials, many coarse-faceted cubic nanocrystals and a small amount of spherical particle were observed, indicating a developed bimodal size distribution. Diffraction contrast variations across these particles indicate the presence of high strain in these BT particles. The strain is probably caused by the lattice defects like OH − ions and their compensation by cation vacancies. HRTEM images demonstrated that (1 0 0) and (1 1 0) surface facets are present on these particles. In addition they revealed the presence of very small-nucleated BT islands at the edges of the faceted particles.

Morphology and Dielectric Property of Homogenous BaTiO3/PVDF Nanocomposites Prepared via the Natural Adsorption Action of Nanosized BaTiO3

AbstractSummary: The development of a novel technique for the preparation of homogeneous BaTiO3/polyvinylidene fluoride (BT/PVDF) nanocomposites without obvious agglomeration of BaTiO3 particles was reported in this communication. The morphology, structure, and frequency dependence of the dielectric properties of the nanocomposites were characterized. All results show that the dielectric properties of the nanocomposites in this study are desirable, and the process for preparing the nanocomposites has potential applications in the electronic industry.TEM micrograph of dry BT/PVDF mixtures with nanosized BT particles.magnified imageTEM micrograph of dry BT/PVDF mixtures with nanosized BT particles.

Dielectric constant and mixing model of BaTiO 3 composite thick films

BaTiO 3 (BT) composite thick films of X7R BT particles with different BT gel fractions were prepared by using an aqueous BT sol. The dielectric constant versus different BT gel volume fractions showed a sigmoidal behavior as the BT gel phase filled the interstitials of the X7R BT particle compact. To explain and predict the effect of the BT gel as a second phase based on the experimental results, various models such as series, parallel, cubic, Lichtenecker’s model, and Hashin–Shtrikman bounds were considered. None of the existing theoretical models fit the experimental results. An empirical sigmoidal fitting function was proposed to fit the experimental data.

Barium titanate-filled bone cements. I. Chemical, physical, and mechanical characterization

Bone cements filled with BaTiO 3 particles were prepared and characterized. The powders of the cements consisted of poly(methylmethacrylate) (PMMA) beads, benzoyl peroxide (BP), and BaTiO 3 (BT) powder (<145 µm). The liquid composition was methyl methacrylate (MMA), N-vinyl-2-pyrrolidone (VP), and N,N-dimethyl-2-aminobencyl alcohol (DMOH). The observed dough and setting times were strongly influenced by the BT and VP contents. However, neither the filler nor the VP contents significantly affected the maximum temperature during setting. VP provided the cements with certain hydrophilic character and solubility. At the early stage, the process of water uptake obeyed the Fick Second Law but at the end a deviation was observed as consequence of the partial dissolution of the absorbing matrix. BT particles effectively increased the compressive strength of the cements.