By combining a solution cast and a hot-press process, a process to prepare uniform metal-polymer nanocomposites is introduced. It is confirmed using two composite systems: nanosized Ni particles embedded into P(VDF-TrFE) 70/30 mol. % and P(VDF-CTFE) 88/12 mol. % copolymer, respectively. Composites with 0 vol. %–60 vol. % of Ni nanoparticles are studied. The dielectric property of each composite is characterized over a frequency range from 100 Hz to 1 MHz. The results show that two nanocomposite systems show very similar percolation behavior with a high percolation threshold (>55 vol. %) and exhibit a high dielectric constant (∼1000 at 100 Hz).

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced–up to about 10 times – by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10−1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

The composition (φ) dependence of the effective dielectric constant (εeff) on conductor-dielectric composites is widely described as εeff∝(φc−φ)−s. This relationship has been extensively used to fit experimental results for determining the percolation behavior (percolation threshold φc and power constant s). The equation was checked using experimental results from two 0–3 nanocomposite systems with uniform microstructures. It is found that the equation can be used to fit the experimental results, but the fitting constants (φc and s) do not reflect the percolation behavior: the values of both fitting constants are dependent on the frequency (f) and temperature selected. It is also found that the fitting constant φc increases with increasing frequency selected and it is believed that this arises from the critical phenomenon, εeff∝fγ−1, for composites close to the φc.

The interactions between xylan/lignin and cellulase enzymes play a key role in the effective hydrolysis of lignocellulosic biomass. Organosolv pretreated loblolly pine (OPLP) and sweetgum (OPSG) were used to quantitatively elucidate the distinct roles of residual xylan and lignin on enzymatic hydrolysis, based on the initial hydrolysis rates and the final hydrolysis yields. The initial hydrolysis rates of OPLP and OPSG were 1.45 (glucose) and 1.19 g/L/h (glucose), respectively, under the enzyme loading of 20 FPU/g glucan. The final glucan hydrolysis yields of OPLP and OPSG at 72 h were 76.4 and 98.9%, respectively. By correlating the amount of residual lignin and xylan to the initial hydrolysis rate and the final hydrolysis yield in OPLP and OPSG, a more accurate fundamental understanding of the roles of xylan and lignin in limiting the enzymatic hydrolysis has been developed. The higher amount of residual xylan (9.7%) in OPSG resulted in lower initial hydrolysis rate (1.19 g/L/h). The higher amount of residual lignin in OPLP (18.6%) resulted in lower final hydrolysis yield of glucan (76.4%). In addition, we observed in the simultaneous saccharification and fermentation (SSF) that ethyl xyloside was produced by the enzymatic catalysis of xylose/xylan and ethanol.

Biodegradable ionic polymer metallic composite (IPMC) electroactive polymers (EAPs) were fabricated using poly(ethylene oxide) (PEO) with various concentrations of lithium perchlorate. Nanocrystalline cellulose (NCC) rods created from a sulfuric acid hydrolysis process were added at various concentrations to increase the EAPs’ elastic modulus and improve their electromechanical properties. The electromechanical actuation was studied. PEONCC composites were created from combining a 35-mg/mL aqueous NCC suspension with an aqueous, PEO solution at varying vol.%. Due to an imparted space charge from the hydrolysis process, composites with an added 1.5 vol.% of NCC suspension exhibited an electromechanical tip displacement, strain, and elastic modulus that was 40.7%, 33.4% and 20.1% higher, respectively, than those for PEO IPMCs without NCC. This performance represented an increase of 300% in the energy density of these samples. However, the electromechanical response decreased when the NCC content was high. NCC without the space charge were also tested to verify the analysis. Additionally, the development of new relationships for modeling and evaluating the time-dependent instantaneous tip angular velocity and acceleration was discussed and applied to these IPMCs.

0-3 dielectric composites with high dielectric constants have received great interest for various technological applications. Great achievements have been made in the development of high performance of 0-3 composites, which can be classified into dielectricdielectric (DDCs) and conductor-dielectric composites (CDCs). However, predicting the dielectric properties of a composite is still a challenging problem of both theoretical and practical importance. Here, the physical aspects of 0-3 dielectric composites are reviewed. The limitation of current understanding and new developments in the physics of dielectric properties for dielectric composites are discussed. It is indicated that the current models cannot explain well the physical aspects for the dielectric properties of 0-3 dielectric composites. For the CDCs, experimental results show that there is a need to find new equations/models to predict the percolative behavior incorporating more parameters to describe the behavior of these materials. For the DDCs, it is indicated that the dielectric loss of each constituent has to be considered, and that it plays a critical role in the determination of the dielectric response of these types of composites. The differences in the loss of the constituents can result in a higher dielectric constant than both of the constituents combined, which breaks the Wiener limits.

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Dielectric materials with high electric energy density and low dielectric loss are critical for electric applications in modern electronic and electrical power systems. To obtain desirable dielectric properties and energy storage, nanocomposites using Ba0.5Sr0.5TiO3 (BST) as the filler and poly(vinylidene fluoride-chlorotrifluoroethylene) as the matrix material are prepared with a uniform microstructure by using a newly developed process that combines the bridge-linked action of a coupling agent, solution casting, and a hot-pressing method. When a proper amount of coupling agent is used to modify the surface of the nanoparticles, the composite exhibits a higher dielectric constant and a more uniform microstructure. A dielectric constant of 95, dielectric loss of 0.25, and energy density of 2.7 J/cm3 is obtained in the nanocomposite with 30 vol.% of BST and 15 wt.% of coupling agent. The results suggest that the energy storage ability of the composites could be improved by the surface modification of the fillers and from the interface compatibility between the fillers and the polymer matrix.