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Porous ceramic filters with high porosity and high filtration are in urgent need of high-temperature gas filtration. Here a lightweight and low thermal conductivity mullite fiber porous ceramic filter was prepared through vacuum filtration method using solution blow spun mullite fiber as the matrix material and silica sol as the high-temperature binder. Mullite fiber porous ceramic with a mass ratio of 10:1 has uniform pore structure, low density (0.58 g cm−3), high porosity (78.11%), high compressive strength (1.79 MPa), as well as low thermal conductivity (0.095 W m−1 K−1) at a sintering temperature of 1300 ℃. When the air flow is 6 L min−1, the pressure drop is 180 Pa, the filtration efficiency of PM 2.5 and PM 10–2.5 is 98.85% and 99.61%, respectively, and the filtration quality factor is 0.025 Pa−1. The mullite fiber porous ceramic filter have outstanding quality factor, which has broad application prospects in high-temperature gas filtration. [ABSTRACT FROM AUTHOR]

High quality BiFeO 3 film with enhanced remanent polarization and magnetization attracts much interest for its great application potential in information storage and photoelectric devices. Here we grew single-crystal epitaxial BiFeO 3 film on SrTiO 3 substrate through hydrothermal method at low temperature, the film has a quality higher than any reported BiFeO 3 films grown through hydrothermal method. Furthermore, BiFeO 3 film was grown through a 25 min rapid microwave-assisted hydrothermal process. The two BiFeO 3 films exhibited obvious light response to periodically switching on and off of a LED light, and the film grown through microwave-assisted hydrothermal method produced a 4.7V open-circuit voltage exceeding the band gap of BiFeO 3 originating from the ferroelectric photovoltaic effect. These results demonstrate that hydrothermal and microwave-assisted hydrothermal method are simple, inexpensive and rapid to grow high quality epitaxial BiFeO 3 film with potential application in photoelectric detection and photovoltaic. [ABSTRACT FROM AUTHOR]

Lead-free (1- x)Ba(Ti 0.8 Zr 0.2)O 3 - x (Ba 0.7 Ca 0.3)TiO 3 (BZT-BCT) possesses comparable piezoelectric constant with lead zirconate titanate (PZT), but its poor temperature electric performances stability and low Curie temperature limit its application. Here we designed composition graded BZT-BCT films with improved temperature stability of piezoelectric, ferroelectric, and dielectric performances over a wide temperature range, and the d 33 reaches 21 pm/V with hysteresis loop even at 180 °C, which is far above the Curie temperature of BZT-BCT ceramic and BZT-0.5BCT film. The excellent temperature stability is ascribed to the lattice distortion and strain gradient in the grains caused by ions diffusion, and could suppress phase transition. This work could bring forward a feasible design for dielectric/piezoelectric/ferroelectric devices operating in harsh temperature environment. [ABSTRACT FROM AUTHOR]

Self-poling has been found in many two-dimensional epitaxial ferroelectric nanofilms originating from epitaxial growth clamping and has become a new research focus due to its potential applications in designing new types of ferroelectric devices. However, self-poling ferroelectrics based on internal strain gradients rather than external stimuli still do not exist. Here, we demonstrate a novel and unique design for one-dimensional structures and geometries in microscale with robust upward flexoelectric self-poling created by the application of electrospun ferroelectric fibers on a patterned substrate to introduce curving structure arises from the uneven substrate and confinement by other fibers in space. The fiber textile composed of these curving structures could resist external electric field and temperature, and can be fabricated into high performance poling-free flexible nanogenerators with outputs comparable to the poled ones. These results are conducive to providing a potential solution to the depolarization problem, to simplifying the technologies for manufacturing piezoelectric nanogenerators by avoiding the application of electric field for poling, and to providing extra freedom in controlling ferroelectric polarization and designing new types of devices. [ABSTRACT FROM AUTHOR]

Abstract In this report, we systematically studied the dielectric properties of alternately doped Ba 1-x Sr x TiO 3 films with different Ba/Sr ratios. All species are polycrystalline with an ABO 3 -type structure, which exhibits growth mainly along the (110) crystal face, showing intense crystallization. Regardless of the phase of the films, either ferroelectric or paraelectric, the variation in dielectric loss is insignificant, which can be attributed to the weakening of the domain wall motion. The contribution of domain wall motion to the total losses is only approximately 6.4%, as determined by hyperbolic law calculations. In addition, a model was proposed that can well explain the pinning effect of space charge on the domain wall motion. Furthermore, the FOM value and J-V characteristics indicate that the alternately doped film still possesses good dielectric performance, even in the ferroelectric phase. [ABSTRACT FROM AUTHOR]

The shortage of land resources around the world has led to the increasing pressure of clay brick production in recent years. On the other side, as a by-product of the sewage treatment, the mineral crystalline phase and chemical composition of municipal sewage sludge (MSS) are similar to those of clay, which also need to be treated urgently. Owing to the porous structure originating from large amounts of organics evaporation at elevated temperature in MSS, it can be utilized as the thermal insulation bricks. However, the component complexity of MSS will result in the decrease of strength and durability of bricks, thus the replacement amount of MSS was generally less than 30%. To achieve optimal experimental conditions for thermal insulation bricks with large amounts of MSS, up to 40% dried MSS, amorphous rice husk ash (RHA) and anhydrous Na 2 CO 3 (ANC) as the raw materials in this work, the dosage and temperature were set as variable parameters. The results showed that 0.178 W/(m•K) of thermal conductivity of bricks with 9.6 MPa of compressive strength, and 1336.2 kg/m3 of bulk density were obtained under the optimal conditions: 4: 5: 1 of the weight ratio of MSS: Clay: RHA, 3% of additional dose of ANC, 1075 °C of sintering temperature. The obtained bricks revealed excellent durability and sorption properties for heavy metals through the freeze-thaw cycle test and leachability test. Overall results manifested one effective approach for solid waste treatment through cleaner production and paved one way for sustainable, economical and energy-saving construction. [ABSTRACT FROM AUTHOR]

• Nano-pores introduced by silica fume affected thermal conductivity and strength. • Effects of amorphous phase on thermal conductivity of bricks were analyzed. • Effects of pore structure and continuous dense phase were quantified. • Thermal insulation properties and strength performance were enhanced simultaneously. As the inevitable by-product of sewage treatment, millions of tons of municipal sewage sludge (MSS) are increasingly stockpiled every year around the globe, creating enormous pressure on the environment and society. The preparation of porous insulation bricks based on MSS is put forward to realize environment protection and waste reclamation. However, the excessive amount of MSS will lead to the deterioration of strength and durability in the bricks. In this paper, the pore structure and crystalline phase of bricks were adjusted by the introduction of the ultra-fine amorphous phase, to improve the thermal insulation performance as well as the compressive strength. The thermal conductivity of the bricks could reach the lowest value of 0.194 W/(m·K) with the compressive strength of 10.2 MPa. Under the requirement of the mechanical strength, adding 3% of borax into bricks can increase the compressive strength to 18.8 MPa. The effects of the continuous dense phase and pore structure on thermal conductivity and compressive strength of bricks were investigated in reference to Bauer and Gibson model, respectively. The results provide a development direction for the preparation of thermal insulation bricks with high content MSS and alleviating the pressure of the shortage of clay. [ABSTRACT FROM AUTHOR]