Search

The incorporation of linear shaped fillers is thought to be able to effectively enhance the dielectric properties of polymer based composites. However, the effect of electrospinning and subsequent calcination processing on the morphology of the fillers and the dielectric performance of the polymer based composites is still unclear. Herein, we demonstrate that filler illustrating two morphological characteristics at the same time, obtained by selecting optimum electrospun precursor concentration before calcination. It is demonstrated that the final filler morphology varies from linear to intermedia (linear and droplets), to droplets with increasing tetrabutyl titanate concentration in the electrospun solution. For filler consisting both linear and droplets characteristics, a maximum energy density of 12.54 J/cm3 is reached at breakdown strength of 393 kV/mm, with a charge and discharge energy efficiency around 76%. Therefore, this could provide new insight into for the preparation of linear shape based fillers for high performance dielectric polymer composites.

The preparation of high performance dielectric polymer composites often involves methods which are quite difficult to be used for large scale application due to their complexity. To tackle this, current study demonstrates a novel type of dielectric filler for the preparation of high performance dielectric composites: Ni(OH)2. Due to the abundant OH groups on their filler surface, hydrogen bond is observed between Ni(OH)2 and PVDF matrix, and beta form crystal of PVDF is induced. Among 0D, 2D and 3D Ni(OH)2, the platelet 2D Ni(OH)2/PVDF composite illustrates the highest dielectric constant (16.3), breakdown strength (421 kV/mm) and energy density (17.3 J/m3) with as little as 5 wt% (3.02 vol%) Ni(OH)2 in PVDF matrix. Such value is rather large comparing with many literature results. More importantly, this method does not involve any filler surface modification. Moreover, finite element simulations indicate that the distribution of electric field and energy density for composites containing platelet like Ni(OH)2 is more uniform than the rest, which should be the mechanism for enhanced dielectric performances. This provides a novel type of filler for the preparation of high performance dielectric polymer composites.

High dielectric constant ceramics fillers are widely used as fillers in polymer matrix to prepare high performance dielectric composites. Homogeneous filler distribution in these composites films is found to be quite difficult to achieve balance between high dielectric constant and high breakdown strength. Herein, multilayer structured composites films containing nickelous hydroxide (Ni(OH)2) as fillers, with different multilayered structures were designed and prepared, including 2–5 layers structure with various filler distribution. The effects of multilayer structure on the dielectric performance are explored by keeping the overall filler content constant. Combined with computer simulation, it is suggested that the variation in filler distribution in these films can effectively redistribute electric field intensity. Meanwhile, the dielectric constant and breakdown strength of the overall composites can be adjusted by changing the volume ratio between high filler content layer and low filler content layer. It is noted that at least 1/3 of the overall film volume should be occupied by a high breakdown strength layer to keep rather high overall breakdown strength. Moreover, high dielectric constant layer should be the outer layers to achieve overall high dielectric constant. Among all the layered structures investigated, the maximum energy density of 6.03 J/cm3 is obtained for film with a 3-layer nonsequential arrangement structure, which is 68% higher than single layer film with identical composition. This study provides some reference value for the preparation of multilayered dielectric polymer composites films for energy storage applications.

The dispersion of nano-barium titanate(NBT) in polyvinylidene fluoride(PVDF) is one of the key issues in dielectric composites. Various NBT surface modification strategies which suffer from complex process and small-scale production have been reported. Herein, in-situ synthesized three-dimensional Ni(OH)2 is introduced to improve NBT dispersion in PVDF. During hydrothermal reaction, NBT aggregates are dispersed on the petals of in-situ grown Ni(OH)2 crystals as small aggregates. The three-dimensional structure of Ni(OH)2 can act as physical barrier to prohibit secondary agglomeration in PVDF to allow rather uniform NBT dispersion. Meanwhile, these hydroxyl groups on Ni(OH)2 ensures good interaction between filler and PVDF, and trigger β crystals. Comparing with NBT/PVDF containing the same amount of filler(2.5 wt%), the breakdown strength and maximum energy density containing mixed filler increases 14% and 70%, reach 282.6 KV/mm and 6.13 J cm−3, respectively. This study provides a new approach to uniformly disperse nanofillers in polymer for enhanced dielectric properties.

Dielectric capacitors with high dielectric constant and energy density are of great importance for electronic devices. Barium titanate(BaTiO3) have been widely explored for polymer-based dielectric composites owning to its ultrahigh dielectric constant and commercial availability. However, due to the large difference of dielectric constant between BaTiO3 and polymer matrix, the interface becomes fragile under electric field, which is not conducive for the improvement in breakdown strength and energy storage density. Herein, a flower like barium titanate/nickel hydroxide(BTO/Ni(OH)2) core-shell structured filler has been fabricated to provide a novel approach to modify the interface between BTO and P(VDF-HFP) matrix for dielectric polymer composites. Ni(OH)2 nanoflakes have grown in-situ on the surface of hydroxylated BaTiO3 particles to form the flower like core-shell assemblies via hydrothermal reaction. Then, these synthetic BTO/Ni(OH)2 particles with specific flower-like core-shell structure can be uniformly dispersed in P(VDF-HFP) without any additional surface modification due to their surface –OH groups. Meanwhile, Ni(OH)2 shell triggered beta phase of P(VDF-HFP) near core-shell filler based on the interfacial interaction between Ni(OH)2 and P(VDF-HFP). Thus, the intensity of the local electric field can be gradually reduced due to the formation of a dielectric constant gradient. Besides, these Ni(OH)2 nanoflakes shell are able to cut down the local electric field and prevent the growth of electrical trees on the surface of BaTiO3 during breakdown process. When the composite filler content is 10 wt%, the dielectric constant and breakdown strength increases to 14.8 and 330 kV/mm from 11 to 260 kV/mm, respectively. And the calculated energy density is 7.13 J/cm3, which is 1.5 times that of 10 wt% BTO/P(VDF-HFP) composite film. This study provides a novel shell material Ni(OH)2 for the preparation of BTO core-shell structure filler, which has good compatibility with polymer substrates.

The morphology and properties of olefin block copolymer (OBC)/polypropylene (PP) microfibrillar composites (MFCs) were tuned by adding nano silica (SiO2) and carbon nanotubes (CNTs) respectively. When the two nanoparticles (NPs) located in the OBC matrix, refined microfibrils were maintained and the final diameters of the PP microfibrils slightly increased compared to the un-modified MFCs; when the NPs located in the dispersed PP component, they exerted a profound impact on the deformation of PP during the fibrillation process. The CNTs can still lead to refined PP microfibrils while addition of SiO2 induces a transition of PP morphology from fibrillar to nodular and even to a spherical structure as its content increases from 0.3 wt% to 1 wt%. The rheological and mechanical properties were also influenced by the type and selective dispersion of NPs. In particular, if the fibrillar morphology of PP was kept in the ternary composites, a small amount of nanoparticles could lead to synergetic enhancement, with polypropylene microfibrils, on the tensile properties of OBC. This work provides a better understanding of the role of NPs in the fiber formation process and an alternative way to control the morphological evolution of MFCs.

Mineral elements in brown rice grain play an important role in human health. In this study, variations in the content of iron (Fe), zinc (Zn), selenium (Se), cadmium (Cd), and lead (Pb) in 378 accessions of brown rice were investigated, and association mapping was used to detect the quantitative trait loci (QTLs) responsible for the variation. Among seven subpopulations, the mean values of Zn and Cd in the japonica group were significantly higher than in the indica groups. The population structure accounted for from 5.7% (Se) to 22.1% (Pb) of the total variation. Correlation analyses showed that Pb was positively correlated with the other minerals (P < 0.001) except for Se. For the five mineral elements investigated, 20 QTLs, including some previously reported and new candidate loci, were identified. Particularly, three cases of QTL colocalization, i.e. Cd and Pb on chromosome 5, Zn and Pb on chromosome 7, and Se and Pb on chromosome 11, were observed. This study suggested that the identified markers could feasibly be used to enhance desired micronutrients while reducing the heavy metal content in whole rice grain by marker-assisted selection (MAS).

In situ micro and nano fibrillar reinforced blends with olefin block copolymer as matrix and polypropylene (PP) as dispersed fibrils were successfully prepared by a simple extrusion-stretching process. Four parameters, that are screw rotating speed, post stretch ratio, die dimension, and PP content, are explored to study how they affect PP fiber morphology and the mechanical performance of the composites. At high stretch ratio, refined PP fibrils are obtained at three different screw rotating speeds and the diameters of the fibrils decrease as the speed increases; at low stretch ratio, only short fibrils with elongated ellipsoids are found in the composites whatever the screw rotating speeds are. When other processing parameters are kept constant, the blends prepared with smaller die exhibit a more impeccable fibrils structure. As the PP contents vary from 5 wt% to 20 wt%, all the composites nearly have same PP morphologies and the diameters of PP fibrils seem to be independent of PP content. Particularly, even refined nano-sized PP fibrils are formed under high screw rotating speed and post stretch ratio with smaller die. Rheological and mechanical analysis show that once the continuously PP fibrils network are established, the property of OBC could be well improved. This structure is proved to be superior to PP component of spheres, elongated ellipsoids and short fibrils.

Microfibrillar composites (MFCs) can be created when the viscosity ratio of polypropylene (PP) and olefinic block copolymer (OBC) is well controlled. PP can be easily deformed into well-refined microfibrils in OBC with different architectures. The mechanical properties of the obtained MFCs are prominently improved.

Breeding of high-quality rice requires quick methods to evaluate the quality characteristics such as milling, grain appearance, nutritional, eating, and cooking qualities. Because routine measurements of these quality traits are time consuming and expensive, a rapid predictive method based on near-infrared spectroscopy (NIRS) can be applied to measure these quality parameters. In this study, calibration models for measurement of grain quality were developed using a total of 570 brown and milled rice samples. The results indicated that the models developed from the spectra of brown rice for all the quality traits had the coefficient of determination for external validation (R2) larger than 0.64 except for gel consistency. The best model was developed for the protein content, with R2 of 0.94 for external validation. The model for the total score of physicochemical characteristics (TSPC), a comprehensive index reflecting all other traits, had R2 of 0.70 and SD/SEP of 1.70, which indicates that high ...