Korean Journal of Chemical Engineering (v.35, #7)
A review on metal nitrides/oxynitrides as an emerging supercapacitor electrode beyond oxide by Subrata Ghosh; Sang Mun Jeong; Shyamal Rao Polaki (1389-1408).
Electrode materials design is the most significant aspect in constructing a supercapacitor device. The evolution of metal nitrides/oxynitrides as supercapacitor electrode is strikingly noticeable today besides prevailing carbon or 2D materials, metal oxides/hydroxides and conducting polymers electrode materials. The theoretically estimated specific capacitance of a nitride-based supercapacitor is 1,560 F g-1. These nanostructures exhibit an excellent capacitive behavior with a specific capacitance of 15–951.3 mF cm-2 or 82–990 F g-1, high energy density (16.5-162 Wh Kg-1) and power density (7.3-54,000 W Kg-1). On this account, supercapacitor performance of metal nitrides/oxynitrides is reviewed exclusively. The major focus of the present review is directed towards state-of-art progress in supercapacitor performance of nitrides/oxynitrides, underlying charge-storage mechanism, important outcomes and their limitations. Finally, we conclude with challenges and prospects of metal nitrides/oxynitrides for supercapacitor electrodes.
Keywords: Supercapacitor; Energy Storage Materials; Metal Nitrides; Metal Oxynitrides; Pseudocapacitance
Adsorption characteristics of arsenic and phosphate onto iron impregnated biochar derived from anaerobic granular sludge by Myeong Eun Lee; Pilyong Jeon; Jong-Gook Kim; Kitae Baek (1409-1413).
Biological wastewater treatment produces biowaste (sludge), which contains a high portion of organic matter. The organic matter comes from microorganisms, and the biowaste can be converted into biochar, a carbon-rich, fine-grained, and porous substance. Granular sludge from upflow anaerobic sludge blanket contains more organic matter (80 wt% of dry matter) and carbon content (>50% of organic matter). In this study, iron impregnated biochar was prepared to remove arsenic (As) and phosphate, oxyanionic pollutants, from the aqueous phase. The iron impregnation of biochar was executed in a one-step by pyrolyzing the biowaste in the presence of Fe instead of conventional two-step, i.e., biochar production after then modification. The granular sludge biochar and activated sludge biochar did not adsorb at all As and phosphate. The adsorption capacity of granular sludge biochar was enhanced via iron impregnation, and the iron-impregnated granular sludge biochar removed 10.37 mg PO 4 3- /g, 11.5 mg As(V)/g, and 6.1 mg As(III)/g, respectively. Therefore, the one-step process enhanced the adsorption capacity and reduced processing time for the adsorbent synthesis.
Keywords: Biochar; Phosphorous; Arsenic; Adsorption; Impregnation
Response surface methodology in optimization of a divided wall column by Mitra Sadat Lavasani; Rahbar Rahimi; Mortaza Zivdar (1414-1422).
dividing wall column (DWC) is a thermally coupled distillation system with a high energy efficiency that requires lower space and investment compared to the conventional column system. The design of a DWC involves a number of structural and process parameters that need to be optimized simultaneously to improve energetic and economic potential and reduce space requirement. We used response surface methodology (RSM) to optimize DWC nonlinearly and to figure out the effect of parameters and their interactions on energy consumption, product quality, and dimensions of a DWC. Results demonstrate that process variables have significant effects on the energy efficiency of a DWC as compared to the effect of structural variables. The optimum DWC parameters can be found by RSM with minimal simulation runs and the prediction results of RSM agree well with the rigorous simulation results.
Keywords: Distillation Process; Divided Wall Column; Optimization; Response Surface Methodology; Energy Efficiency
Linear and non-linear analyses on the onset of miscible viscous fingering in a porous medium by Won Sun Ryoo; Min Chan Kim (1423-1432).
The onset of miscible viscous fingering in porous media was analyzed theoretically. The linear stability equations were derived in the self-similar domain, and solved through the modal and non-modal analyses. In the non-modal analysis, adjoint equations were derived using the Lagrangian multiplier technique. Through the non-modal analysis, we show that initially the system is unconditionally stable even in the unfavorable viscosity distribution, and there exists the most unstable initial disturbance. To relate the theoretical predictions with the experimental work, nonlinear direct numerical simulations were also conducted. The present stability condition explains the system more reasonably than the previous results based on the conventional quasi-steady state approximation.
Keywords: Viscous Fingering; Non-modal Analysis; Modal Analysis; Linear Stability Analysis; Direct Numerical Simulation
Comparative study of CHA- and AEI-type zeolytic catalysts for the conversion of chloromethane into light olefins by Yong Hun Shin; Sungjoon Kweon; Min Bum Park; Ho-Jeong Chae (1433-1440).
Three pairs of CHA- and AEI-type zeolytic materials with similar crystallite size but with different framework atoms, i.e., silicoaluminophosphate SAPO-34 and SAPO-18, aluminosilicate SSZ-13 and SSZ-39, and titaniumin-corporated TiAPSO-34 and TiAPO-18, were prepared and their catalytic activities of chloromethane into light olefins were compared according to the structure types, as well as acidic properties. The AEI-type catalysts were found to have lower ethene/propene ratios, indicating relatively higher propene selectivity, because their aei-cage was larger compared to the cha-cage. However, all the CHA-type catalysts exhibited better activity and higher selectivity to light olefins. Both H-SAPO-34 and H-TiAPSO-34 showed good catalytic stability over all the reaction times studied here. When compared to H-SAPO-34, however, H-TiAPSO-34 exhibited ca. 20mol% higher selectivity to ethene and propene, despite a similar total density of acid site. This performance may be due to the higher strength of medium acid sites.
Keywords: AEI; CHA; Chloromethane Conversion; Light Olefins; TiAPSO-34
Purification of textile wastewater by using coated Sr/S/N doped TiO2 nanolayers on glass orbs by Rozita Foulady Dehaghi; Mohsen Behpour; Noshin Mir (1441-1449).
In Scheme 1 in the original publication, “Basic Blue 28” should be replaced with “Basic Blue 41”. The corrected scheme appears below:Simultaneous doping of TiO2 nanoparticles with three elements including Sr, S, and N is reported. The resulting material shows superior photocatalytic performance toward degradation of textile waste under visible and sunlight. The pure and doped TiO2 nanolayers were prepared by sol-gel method and were fixed on a bed of glass orbs. The immobilized TiO2 were characterized by a variety of techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), spectroscopy diffusion reflection (DRS), energy dispersive X-ray spectrometry (EDS) and elemental analysis (CHNS). The photocatalytic activity of the prepared fixed-bed materials toward degradation of the textile wastes was determined by using ultraviolet-visible spectroscopy (UV-Vis) and measurement of the chemical oxygen demand testing (COD). The best photocatalytic activity was observed with the use of Sr/S/N-TiO2 nano-layers. Afterwards, the experimental conditions were optimized by tuning reaction parameters, including amount of doped metal ion on photocatalyst structure, sample solution pH and photoreactor output flow rate. The results confirmed that at natural pH 5.9 of sample solution, maximum decomposition of 91-99% of azo dyes was obtained in 8 h under visible irradiation. Finally, the experiments were repeated under 1.5 AM sunlight with high volume of reactants in order to confirm the cost-effectiveness of the designed photocatalyst.
Keywords: Sr/S/N-TiO2 ; Photoreactor; Nanolayers; Textile Waste Photodegradation; Azo Dyes; Visible and Sunlight
Physical and adsorptive characterizations of immobilized polyaniline for the removal of methyl orange dye by Noor Nazihah Bahrudin; Mohd Asri Nawi; Wan Izhan Nawawi Wan Ismail (1450-1461).
Synthesized polyaniline (PANI) powder mixed with ENR-PVC polymer blend adhesive was immobilized on glass plates for the adsorption of methyl orange (MO) dye. The immobilized PANI composite was made up of plasticized PANI aggregates and was in a doped state. The incorporation of ENR-PVC blend in PANI slightly reduced the surface area from 9.2 to 8.5 m2 g-1, and its presence was confirmed through FTIR. The adsorption process was highly dependent on the aeration rate, and the pH of MO solution in which 40 mL min-1 and ambient pH (6.5) was selected as the working conditions. The process of MO uptake onto the immobilized PANI obeyed the pseudo-second-order kinetic model, while intra-particle diffusion was found to dominate the adsorption process. The q m of the immobilized PANI was 77.3 mg g-1 for MO uptake and obeyed the Freundlich isotherm model. The thermodynamic study revealed that the adsorption process of immobilized PANI was spontaneous and unfavorable at high temperature. The immobilized PANI was found to be comparable with other PANI based adsorbents in term of cost, recyclability and adsorption efficiency.
Keywords: Immobilized Polyaniline; Adsorption Isotherm; Kinetic Modeling; Methyl Orange; Thermodynamic
Quantitative characterization of intact sialylated O-glycans with MALDI-MS for protein biotherapeutics by Cheol-Hwan Hwang; Hae-Min Park; Han-Gyu Park; Da-Hee Ahn; Seong-Min Kim; Byoung Joon Ko; Young Hwan Kim; Yung-Hun Yang; Yun-Gon Kim (1462-1467).
For validating O-glycosylation of protein biotherapeutics, we presented a quantitative O-glycomics method which is based on the neutralization of sialic acids, the specific release of O-glycans, and the introduction of permanent positive charge followed by quantitative MALDI-MS analysis. This method shows excellent technical reproducibility, linearity and sensitivity. In addition, it enables the quantification of intact O-glycans with minimal degradation or loss of sialic acids on these glycans compared to a conventional HPLC-based method. We then applied this method to quantitatively characterize O-glycans present on Etanercept. The analysis showed the relative abundances of mono- and di-sialylated core 1 O-glycans - were 79.3±0.8% and 17.3±1.4%, respectively. This glycomics technology could allow for the reliable quantitative analysis of intact O-glycans from glycoproteins and may contribute to validation of O-glycosylation protein biotherapeutics in the pharmaceutical industry.
Keywords: Chemical Derivatization; MALDI-MS; O-glycan; Protein Biotherapeutics; Quantitative Analysis
Interpreting the pH-dependent mechanism of simazine sorption to Miscanthus biochar produced at different pyrolysis temperatures for its application to soil by Seoyeon Lee; Junho Han; Hee-Myong Ro (1468-1476).
Biochar has received considerable attention as an eco-friendly bio-sorbent; however, multifarious characteristics caused by pyrolysis and feedstock pose difficulties in its application. We characterized the pH-dependent sorption of the pesticide simazine on Miscanthus biochar produced at two pyrolysis temperatures (400 and 700 °C; hereafter B-400 and B-700). The specific surface-area (SSA) of the micro- and nanopores, elemental composition, surface acidity and infrared spectra were determined. The SSA was greater in B-700 than in B-400, and the former had greater SSA in micro-pores and lower SSA in nanopores than the latter. During pyrolysis, the single-bond structures of the feedstock were converted to aromatic structures, and further pyrolysis led to ligneous structures. Alterations in pore structure and concave-up Scatchard plot corroborated the presence of two sorption mechanisms: electrostatic attractions (S es ) and hydrophobic attractions (S hp ). Decreases in maximum sorption in the q max-L with increasing pH was due to decreased S es via deprotonation of carboxylic groups on biochar, while those in the q max-H with increasing pyrolysis temperature were due to decreased S hp , resulting from pore structure deformation. We believe that our approach, which addresses the pH-dependence of charge density of sorbate and sorbent, could contribute to a better understanding of the behavior of simazine.
Keywords: Simazine; Miscanthus Biochar; Pyrolysis Temperature; pH-dependent Sorption; Scatchard Plot
Effect of water addition on extraction ability of eutectic solvent choline chloride+ 1,2-propanediol for separation of hexane/heptane+ethanol systems by Jelena Vuksanović; Mirjana Lj. Kijevčanin; Ivona R. Radović (1477-1487).
The ability of binary deep eutectic solvent choline chloride+1,2-propanediol (DES1; 1 : 3 mole ratio) and ternary deep eutectic solvent choline chloride+1,2-propanediol+water (DES2; 1 : 3 : 3 mole ratio) for breaking the azeotropes hexane/heptane+ethanol by means of liquid-liquid extraction was evaluated. Liquid-liquid equilibrium experiments were performed at 298.15 K, at atmospheric pressure, and data were correlated by NRTL and UNIQUAC models. Thermodynamic properties (density, viscosity, refractive index and speed of sound) of DES1 and DES2 were determined in temperature range from 288.15 K to 333.15 K and at atmospheric pressure. Extraction ability of the investigated eutectics yielded promising results in comparison with conventional solvents. Besides a high selectivity towards ethanol, an advantage of DES2 is its lower viscosity and higher distribution ratio values, which is an important aspect for a potential industrial application. Another advantage of both investigated eutectics is their easy and high recoverability from the extract layer based on their negligible vapor pressure.
Keywords: Deep Eutectic Solvents; Liquid-liquid Equilibria; Choline Chloride; 1,2-Propanediol; Azeotrope Separation
Ultrasonic study on binary liquid mixtures of propiophenone with anilines and alkyl substituted anilines at T=303.15 to 318.15 K by Nanduri Gayatri Devi; Nanduri Veera Naga Bala Srinivasa Rao; Maganti Radha Sirija; Dittakavi Ramachandran (1488-1499).
Densities ‘ρ’, ultrasonic speeds of sound ‘u’ of binary mixtures of propiophenone (PPH) with aniline, N-Methylaniline, N,N-dimethylaniline and N,N-diethylaniline were measured over the entire composition range from 303.15 K to 318.15 K and at atmospheric pressure 0.1 MPa. Experimental data of ultrasonic sound were compared and discussed with the computed values of ‘u’ from various velocity theories like Nomoto’s relation (U NOM), impedance relation (U IMP), Van Dael and Vangeel’s ideal mix relation (U VDV), Rao’s specific velocity relation (U RAO), Junjie’s theory (U JUN) and Jouyban-Acree’s (U JOE) relation for the above binary mixtures over the entire mole fraction range at the studied temperatures. The results are satisfactory and are in agreement between the theoretical and the experimental values. Further, the molecular interaction parameter (α), average percentage error and Chi-square test values were computed by using the values of experimental and theoretical ultrasonic velocities. The Δu values were correlated with Redlich-Kister polynomial equation to compute the coefficients and the standard deviations of the binary mixtures. The results were analyzed in terms of intermolecular interactions.
Keywords: Ultrasonic Speed of Sound; Molecular Interaction Parameter; Nomato’s Relation; VanDeel’s Ideal Mixing Relation; Impedance Relation; Junjie’s Relation; Rao’s Specific Velocity and Jouyban-Acree’s Relation for Speed of Sound
Flocculation of gelatinized starch: Flocculation performance and floc characterization by Xiaojiao An; Yong Kang; Guishui Li (1500-1508).
The removal of single macromolecules impurity is the basis study for the promotion of flocculation technology application in the Chinese herbal medicine solution purification. We applied the flocculation process to remove gelatinized starch in solution. Three types of cationic polyacrylamide (CPAM) with different charge density were used for flocculation of gelatinized starch solution. The flocculation performance was evaluated in terms of the amylose removal ratio (AMRR), the amylopectin removal ratio (APRR), total starch removal ratio (TSRR) and supernatant turbidity (ST). The flocs were characterized by sedimentation performance, Fourier transform infrared (FTIR), scanning electron microscope (SEM) and X-ray photoelectric spectroscopy (XPS) method. The experimental results show that the flocculant CN15 has the best performance for gelatinized starch flocculation among three flocculants. According to the characterization analysis, the flocs exhibited an obvious network structure, and it is concluded that hydrogen bonding between N-H in CPAM and C-O in the starch and bridging flocculation played the essential roles in flocculation of the gelatinized starch.
Keywords: Gelatinized Starch; Cationic Polyacrylamide; Flocculation; Floc Characterization
Conceptual feasibility studies of a CO X -free hydrogen production from ammonia decomposition in a membrane reactor for PEM fuel cells by Sehwa Kim; Jiseon Song; Hankwon Lim (1509-1516).
CO X -free hydrogen production from ammonia decomposition in a membrane reactor (MR) for PEM fuel cells was studied using a commercial chemical process simulator, Aspen HYSYS®. With process simulation models validated by previously reported kinetics and experimental data, the effect of key operating parameters such as H2 permeance, He sweep gas flow, and operating temperature was investigated to compare the performance of an MR and a conventional packed-bed reactor (PBR). Higher ammonia conversions and H2 yields were obtained in an MR than ones in a PBR. It was also found that He sweep gas flow was favorable for X NH3 enhancement in an MR with a critical value (5 kmol h-1), above which no further effect was observed. A higher H2 permeance led to an increased H2 yield and H2 yield enhancement in an MR with the reverse effect of operating temperature on the enhancement. In addition, lower operating temperature resulted in higher X NH3 enhancement and H2 yield enhancement as well as NG cost savings in a MR compared to a conventional PBR.
Keywords: Ammonia Decomposition; Membrane Reactor; Process Simulation; Hydrogen; PEM Fuel Cells
Numerical study on particle deposition in rough channels with large-scale irregular roughness by Wenpeng Hong; Xin Wang (1517-1524).
We studied particle deposition in rough channels, using the W-M fractal function to characterize a large-scale irregular surface with a root-mean-square roughness of 0.5mm. The flow was numerically investigated by Reynolds stress model, and the particles were tracked by a Lagrangian particle model. An analysis of the flow field in a rough channel shows that the roughness enhances the max flow velocity and the pressure drop in the channel. It induces several eddies in the concave of the rough surface. We also compared particle deposition in a rough channel with particle deposition in a smooth channel. This comparison shows that the roughness significantly enhances the particle deposition of small particles, but the enhancement decreases with the increase of particle size. Moreover, the particle deposition ratio decreases with increasing flow velocity.
Keywords: Particle Deposition; Rough Channel; W-M Fractal Function; RSM Model; CFD
Effect of sulfur annealing on the morphological, structural, optical and electrical properties of iron pyrite thin films formed from FeS2 nano-powder by Thanh Kieu Trinh; Nguyen Tam Nguyen Truong; Viet Thanh Hau Pham; Hyoeun Kim; Chinho Park (1525-1531).
Iron pyrite (FeS2) thin films were fabricated by spin coating the solution of FeS2 nanocrystals of ∼40 nm in size on glass substrates, followed by annealing in a sulfur environment at different temperatures. The effect of sulfurization temperature on the morphology, structural, optical and electrical properties was investigated. With increase of the sulfurization temperature, the grain size and crystallinity of the films was improved, although some cracks and voids were observed on the surface of thin films. The band gap of the FeS2 films was decreased at higher sulfurization temperature. The electrical properties were also changed, including the increasing in resistivity and the decrease in Hall mobility, with increase of sulfurization temperature. The change in the optical and electrical properties of the FeS2 thin films was explained based on the changes of phase, morphology, surface, and grain boundary property.
Keywords: Thin Film; Sulfurization; Morphology; FeS2 Nano-powder; Spin Coating
Immobilized titanium dioxide/powdered activated carbon system for the photocatalytic adsorptive removal of phenol by Noor Nazihah Bahrudin; Mohd Asri Nawi (1532-1541).
Titanium dioxide (TiO2) and powdered activated carbon (PAC) were fabricated via a layer by layer arrangement on a glass plate using a dip-coating technique for the photocatalytic-adsorptive removal of phenol. Thinner TiO2 layer coated on PAC sub-layer has larger surface area and better phenol removal than the thicker TiO2 layer. The system obeyed the Langmuir isotherm model, which exhibited a homogeneous and monolayer adsorption with a maximum capacity of 27.8 mg g-1. The intra-particle diffusion was the rate-limiting step as the linear plot crossed the origin, while the adsorption was unfavorable at elevated temperature. Under light irradiation, the TiO2/PAC system removed phenol two-times more effectively than the TiO2 monolayer due to the synergistic effect of photocatalysis by TiO2 top layer and adsorption by PAC sub-layer. The COD removal of phenol was rapid for 10mg L-1 of concentration and under solar light irradiation. It was shown that the PAC sub-layer plays a significant role in the total removal of phenol by providing the adsorption sites and slowing down the recombination rate of charge carriers to improve the TiO2 photocatalytic oxidation performance.
Keywords: Layer by Layer; Monolayer Adsorption; Photocatalytic Oxidation; Powdered Activated Carbon; Synergistic Effect
Effects of polydimethylsiloxane coating of Ni-MOF-74 on CH4 storage by Yu-Ri Lee; Sung-Min Cho; Wha-Seung Ahn (1542-1546).
Ni-MOF-74 was prepared by microwave heating and coated with polydimethylsiloxane (PDMS) via vapor deposition. Both the pristine and the PDMS-coated Ni-MOF-74 samples were exposed to moisture in air (relative humidity of 75%) for different periods of time, and their methane storage capacities under 35 bar conditions were measured. The pristine sample had a Brunauer-Emmett-Teller (S BET ) surface area of 1,050 m2·g−1, with a CH4 uptake capacity of 113.8 mg·g−1 at 300 K and 35 bar. After exposure to moisture for seven days, the BET surface area and CH4 uptake capacity declined drastically, whereas the PDMS-coated sample maintained its original BET surface area (1,018 m2·g−1) and CH4 uptake capacity (107.7 mg·g−1). After exposure to moisture in air for 30 days, however, even the PDMS-coated sample lost almost 60% of its CH4 storage capacity. All the methane storage capacity data were linearly correlated with the BET surface areas of the Ni-MOF 74 samples.
Keywords: Ni-MOF-74; Methane Storage; Polydimethylsiloxane; Moisture Stability
Electrodeposition-fabricated PtCu-alloy cathode catalysts for high-temperature proton exchange membrane fuel cells by Hyanjoo Park; Kyung Min Kim; Hoyoung Kim; Dong-Kwon Kim; Yong Sun Won; Soo-Kil Kim (1547-1555).
Pt electrocatalysts in high-temperature proton exchange membrane fuel cells (HT-PEMFCs) containing phosphoric acid (PA)-doped polymer membranes are prone to poisoning by leaked PA. We performed a preliminary density functional theory (DFT) study to investigate the relationship between the electronic structure of Pt surfaces and their adsorption of PA. Excess charge on Pt was found to weaken its bonding with the oxygen in PA, thus presenting a strategy for the fabrication of PA-resistant catalyst materials. Consequently, PtCu-alloy catalysts with various compositions were prepared by electrodeposition. The morphologies and crystalline structures of the alloys were strongly dependent on alloy composition. Moreover, the Pt atoms in the PtCu-alloy catalysts were found to be in an electron-rich state, similar to that of the excessively charged Pt simulated in the DFT study. As a result, the oxygen reduction reaction activities of the PtCu-alloy catalysts were superior to that of a Pt-only catalyst, regardless of the presence of PA. In the absence of PA, the higher activity of the PtCu-alloy catalysts was ascribable to conventional alloying effects, while the increased activity in the presence of PA was largely due to the enhanced resistance to PA poisoning. Therefore, PtCu-alloy catalysts easily prepared by electrodeposition were found to be strong candidate materials for HT-PEMFC electrodes.
Keywords: High-temperature PEMFC; Oxygen Reduction Reaction; Phosphoric Acid Poisoning; PtCu-alloy Catalysts; Density Functional Theory (DFT) Study
Toward an intelligent approach for predicting surface tension of binary mixtures containing ionic liquids by Reza Soleimani; Amir Hossein Saeedi Dehaghani; Navid Alavi Shoushtari; Pedram Yaghoubi; Alireza Bahadori (1556-1569).
Knowledge of the surface tension of ionic liquids (ILs) and their related mixtures is of central importance and enables engineers to efficiently design new processes dealing with these fluids on an industrial scale. It’s obvious that experimental determination of surface tension of every conceivable IL and its mixture with other compounds would be a herculean task. Besides, experimental measurements are intrinsically laborious and expensive; therefore, accurate prediction of the property using a reliable technique would be overwhelmingly favorable. To do so, a modeling method based on artificial neural network (ANN) trained by Bayesian regulation back propagation training algorithm (trainbr) has been proposed to predict surface tension of the binary ILs mixtures. A total set of 748 data points of binary surface tension of IL systems within temperature range of 283.1-348.15 K was used to train and test the applied network. The obtained results indicated that the predictive values and experimental data are quite matching, representing reliability of the used ANN model for such purpose. Also, compared with other methods, such as SVM, GA-SVM, GA-LSSVM, CSA-LSSVM, GMDH-PNN and ANN trained with trainlm algorithm the proposed model was better in terms of accuracy.
Keywords: Ionic Liquids; Surface Tension; Binary Mixtures; Prediction; Artificial Neural Network
Improved dielectric properties and energy density of PVDF composites using PVP engineered BaTiO3 nanoparticles by Yu Dai; Xiaojun Zhu (1570-1576).
This work systematically investigates the effect of modifier polyvinylpyrrolidone (PVP) on the microstructure, dielectric and energy storage properties of BaTiO3/PVDF composites. The results demonstrate that the BaTiO3 nanoparticles modified by PVP are uniformly dispersed in the composites, and the defects including cracks and voids are obviously decreased in contrast to the composites with unmodified BaTiO3 nanoparticles. Due to the enhanced interfacial polarization, the composites with BaTiO3@PVP show improved dielectric properties compared with the composites with unmodified BaTiO3 nanoparticles. For instance, at 1 kHz, the dielectric constant and dielectric loss of the composite with 50 vol% of BaTiO3@PVP nanoparticles are 80.4 and 0.085, while of which the BaTiO3/PVDF are 35 and 0.265, respectively. The discharge energy density of the composites is largely improved with PVP engineered BaTiO3 nanoparticles. The composite with 30 vol% BaTiO3@PVP achieves a discharged energy density of 4.06 J/cc at 240 kV/mm, which is 116% larger than that of pure PVDF (1.88 J/cc). This research provides an effect modifier to prepare high performance dielectric materials.
Keywords: Dielectric Composite; Energy Density; PVP; PVDF; BaTiO3