High specific surface area and moderate oxygen vacancies concentration are two effective solutions for enhancing photocatalytic removal of NO. In this work, we synthesized self-assembled spherical Bi2MoO6 with oxygen vacancies by altering the solvent used in the hydrothermal process. Under visible light (lambda>420 nm) irradiation, the photocatalytic removal rate of NO by ethanol-glycol mediated Bi2MoO6 nanospheres reached 57 %. Based on a series of characterization, it is found that the generation of appropriate oxygen vacancy and the increase of specific surface area are considered to be the reasons for the improvement of photocatalytic activity. When the solvent was changed, the specific surface area of Bi2MoO6 increased from the lowest 7.18 m(2)/g to 60.96 m(2)/g, and the increase of specific surface area could provide more active sites for photocatalytic reaction. Secondly, the appearance of oxygen vacancy improves the photocatalytic performance of Bi2MoO6, but with the continuous increase of oxygen vacancy concentration (the concentration is about 3 times before), the catalytic performance is greatly reduced. This shows that a moderate amount of oxygen vacancy can improve the photocatalytic activity, but excessive oxygen vacancy will hinder the photocatalytic reaction. Furthermore, in situ DRIFTS are used to further reveal the pathways and mechanism of photocatalytic NO removal. This work offers an effective strategy for preparing spherical layered bismuth-based materials with oxygen vacancies for air purification.

The structure, electrical properties, and thermal stability of 2 mol% MnO2-doped 2-doped 0.12Pb(Ni1/3Ta2/3)O3-xPbZrO3- x (0.88-x)PbTiO3 (abbreviated as PNT-xPZ-PT-Mn, x = 0.41, 0.42, 0.43, 0.44) ceramics were systematically investigated to analyze the impact of varying PZ content within the range of 0.41-0.44. In addition, the high temperature polarization method was employed to achieve enhanced electrical performance. Notably, optimized electrical properties of d(33) = 400 pC/N, Q(m) = 757, FOM = 3.0x10(5) pC/N and k(p) = 0.616 were obtained for the PNT-0.43PZ-PT-Mn ceramics. The enhanced electrical properties observed in this study could be attributed to the presence of dielectric relaxor behavior, and the manifestation of ferroelectric hysteresis effects. In particular, d(33) and k(p) values exhibited a consistent trend from the room temperature to the Curie temperature, thereby indicating the remarkable thermal stability of PNT-0.43PZ-PT-Mn ceramics. This study presented a systematic approach to enhance the properties of PZT-based materials.

NaNbO3 (NN)-based dielectric ceramics for energy storage have garnered significant interest due to their high saturation polarization, low residual polarization, and superior breakdown strength (Eb). However, the low recoverable energy storage density (Wrec) and efficiency (eta) significantly limited their practical application. Herein, BiFeO3 (BF) was incorporated into NN to optimize the energy storage performance. The NN-BF ceramics exhibited pronounced antiferroelectric (AFE) relaxor phase, alongside grain size reduction and E b enhancement, which contributed to a significant increase of W rec and eta . Specially, the optimum W rec of 4.43 J/cm3 and eta of 71.51 % were achieved at the composition of 0.9NN-0.1BF. Besides, stable energy storage performance was maintained over a wide temperature range (20-120 degrees C). These results highlight the potential of NN-BF relaxor AFE ceramics as promising candidates for high-performance energy storage applications.

Direct conversion of solar energy into chemical energy in an environmentally friendly manner is one of the most promising strategies to deal with the environmental pollution and energy crisis. Among a variety of materials developed as photocatalysts, the core-shell metal/covalent-organic framework (MOF or COF) photocatalysts have garnered significant attention due to their highly porous structure and the adjustability in both structure and functionality. The existing reviews on core-shell organic framework photocatalytic materials have mainly focused on core-shell MOF materials. However, there is still a lack of in-depth reviews specifically addressing the photocatalytic performance of core-shell COFs and MOFs@COFs. Simultaneously, there is an urgent need for a comprehensive review encompassing these three types of core-shell structures. Based on this, this review aims to provide a comprehensive understanding and useful guidelines for the exploration of suitable core-shell organic framework photocatalysts towards appropriate photocatalytic energy conversion and environmental governance. Firstly, the classification, synthesis, formation mechanisms, and reasonable regulation of core-shell organic framework were summarized. Then, the photocatalytic applications of these three kinds of core-shell structures in different areas, such as H2 evolution, CO2 reduction, and pollutants degradation are emphasized. Finally, the main challenges and development prospects of core-shell organic framework photocatalysts were introduced. This review aims to provide insights into the development of a novel generation of efficient and stable core-shell organic framework materials for energy conversion and environmental remediation.

Enhanced polarization emerges as a potent strategy for further enhancing the photocatalytic performance of a photocatalyst. Considering the anisotropy of ferroelectric polarization and the improvement of polarization by defects, [010] preferred growth Bi4Ti3O12 nanowires with oxygen vacancies were prepared via a hydrothermal method. Bi4Ti3O12 nanowires exhibited a photocatalytic NO removal efficiency of up to 67.5% under visible light irradiation (λ > 420nm), which is much higher than that of its counterpart, Bi4Ti3O12 (3%). Structural characterizations and theoretical calculations support that, the engineering of oxygen vacancies in Bi4Ti3O12 can enhance the polarization in the [010] and [100] directions, and gradually shifted the polarization dominant direction of Bi4Ti3O12 from [100] to [010]. Overall, the improved polarization and generated oxygen vacancies enhanced the photocatalytic NO removal performance of Bi4Ti3O12 nanowires. This work elucidates the significance of rational engineering oxygen vacancy-based microstructures and utilizing the polarization to amplify the photocatalytic performance.

The development of high electrical performance (K,Na)NbO3 (KNN)-based piezoelectric ceramics is critical in environmental protection. In this study, (K0.5Na0.5)(Ti0.2Zr0.2Nb0.2Ta0.2Sb0.2)O3 high-entropy ceramics were synthesized via the solid solution method by different sintering temperature. The piezoelectric, dielectric and ferroelectric properties of (K0.5Na0.5)(Ti0.2Zr0.2Nb0.2Ta0.2Sb0.2)O3 ceramics were studied. The sample sintered at 990 degrees C has the best dielectric property, and the dielectric constant is stable in a wide temperature region. The sample sintered at 980 degrees C have the highest porcelain forming property, the residual polarization intensity is 0.0792 mu C/cm2, the activation energies obtained is 0.40 eV. The results confirm that the calcined at 980 degrees C (K0.5Na0.5)(Ti0.2Zr0.2Nb0.2Ta0.2Sb0.2)O3 ceramics is feasible in the field of electrical application. This work proves a design idea to obtain high electrical performance in KNN-based high-entropy ceramics via composition design by optimizing sintering temperature.

We propose the theoretical design and experimental authentication of an ultrathin sound absorber consisting of a perforated plate and a back cavity with zigzag channels for realizing high-efficiency and broadband absorption of low-frequency sound. The dependence of the absorption performance on the structural parameters is analyzed, which suggests the possibility of decreasing the peak frequency of resonance noise absorption with equal compactness of device. Based on this, we propose a hybrid design composed of multiple structures with different parameters to effectively expand the working bandwidth, and propose to further optimize the low-frequency absorption performance by adjusting the inclined partitions in the zigzag channel. The experimental results show that nearly 100% sound absorption is obtained at the resonance frequency (< 500 Hz) with an absorber 30 times thinner than the wavelength. We envision our designed sound absorber with deep-subwavelength size, broadband functionality, and easy fabrication to find wide applications in noise control engineering.

A series BiFeO3 and BiMnO3 co-doped lead-free 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (BNBT-xBF-yBM, x = 8, 12; y = 8, 10, 12) ceramics were fabricated by solid-state method, and the detailed crystal structure, electrical properties and thermal stability were thoroughly investigated. The XRD results from the Rietveld fitting demonstrate the coexistence of Rhombohedral (R) and Tetragonal (T) phases in the ceramics at room temperature. High piezoelectric property (d33 > 160 pC/N) are obtained in BNBT-8BF-12BM and BNBT-12BF-10BM ceramics. It is of particular significance that the variations of kp in the temperature range from 25 to 70 °C is little, respectively, indicating an insensitive temperature-dependent behavior of BNBT-12BF-10BM ceramics. These results indicate the importance of simultaneous modification methods to achieve high electric properties in BNT-BT based ceramics.

In this study, a design method of broadband low-frequency muffler based on NN method and Helmholtz resonators with helical necks is proposed, which ensures almost perfect ventilation and broadband sound insulation in the low- and medium-frequency range. First, the sound insulation performance of the muffler is improved by adding a helical structure at the port. The slit Helmholtz resonator with a helical structure is able to reduce the cross-sectional area of the resonator port and increase the contact area of thermal viscosity loss, thus reducing the peak frequency of sound insulation and increasing the sound energy loss. Using finite element analysis software, the structural transmission loss is simulated. At the same time, the neural network method is used to predict the combined structure, then, the combined structure can be designed quickly and reasonably to achieve the sound insulation of medium- and low-frequency broadband. Experimental and simulation results show that in the target range of 430 Hz–2220 Hz, the overall TL exceeds 30 dB and the maximum exceeds 60 dB. In addition, when a helical structure is added, the overall pipeline remains unchanged; and when a muffler is added on the basis, the perfect ventilation effect can be achieved. The proposed structural model and the idea of rapid design lay a great foundation for the design and optimization of broadband muffler.

In this article, KNNLT-BNT lead-free ceramics were prepared by the solid solution method to regulate the grain size and electrical properties by Mn-doped. The doped concentrations were 0.3, 0.4, and 0.5%. The surface structure of the ceramic was characterized, and the Mn-doped can improve the ceramic compactness. The internal structure of the ceramic was analyzed, with the increase of Mn-doped concentration, the (101) peak shifted to a lower angle, and the lattice is distorted. Finally, the electrical properties of the ceramic were characterized by the optical band gap and dielectric constant. Analysis results show that when the Mn-doped concentration is 0.5%, the electrical performance is the best, the grain size follows a normal distribution, and the band gap width is the narrotest 2.693 eV.

In this paper, Lead-free based on 0.97([Formula: see text][Formula: see text][Formula: see text])([Formula: see text][Formula: see text])O 3 –0.03[Formula: see text][Formula: see text]TiO 3 with additives La 2 O 3 (1, 2, 3, 4 wt.%) was prepared by the solid reaction method, and the effect of La dopant on the structural and electrical properties is investigated. The result indicates La dopant considerably decreases the optical band gap compared to the undoped composition. On the other hand, La doping leads to the higher dielectric property in a wider temperature, providing possibilities and directions for the subsequent development of ferroelectric photovoltaic materials with electrical properties and low optical band gap in a dramatical manner.

Aiming at the unsatisfactory low-frequency sound absorption effect of Helmholtz resonator, a novel broadband low-frequency ventilation absorber with rough neck is proposed. The roughness is introduced into the neck of Helmholtz resonator to change the shape of the neck and achieve the structure of rough neck Helmholtz resonator. The proposed absorber can effectively provide the acoustic impedance required for low-frequency sound absorption without changing the overall size, thereby reducing the resonant frequency. The finite element method is used to simulate the structure, and the impedance tube sound absorption test is carried out to verify it. The experimental and simulation results show high consistency with each other. The results also indicate that the rough neck Helmholtz resonator absorber with roughness introduced in the neck achieves an absorption peak at 58 Hz, with an absorption coefficient of about 0.63. Comparing with the absorber without roughness introduced, the resonant peak frequency becomes low, from 70 Hz to 58 Hz, reducing 17.1%. Therefore, adjusting the neck roughness can serve as a method of tuning the acoustic performance, and the absorption peak frequency can be adjusted by appropriately increasing the neck roughness so as to move it in the low frequency direction. Based on the verification that the roughness of the neck can effectively reduce the absorption peak frequency of Helmholtz resonator, a broadband low-frequency ventilation absorber with a rough neck, which is composed of eight absorption units, is designed. Through simulation calculation and experimental exploration, the absorption coefficient can achieve more than 0.8 in a target working frequency band of 500－1100 Hz. On this basis, the acoustic impedance of the structure can be adjusted by introducing roughness into the neck of Helmholtz resonator, so as to obtain the optimized broadband low-frequency ventilation absorber with a rough neck, which achieves a broadband sound absorption coefficient higher than 0.8 in a frequency range of 400–1200 Hz. The optimized structure also has 8 consecutive absorption peaks with amplitudes above 0.95. The proposed low-frequency broadband ventilation absorber provides a reference for designing and optimizing efficient low-frequency subwavelength acoustic absorbers. It has a wide range of applications in pipeline noise control.

本文以萘甲酰肼为原料,合成了三种不同长度烷氧基链的凝胶因子D6、D12、D16,通过扫描电镜(SEM)、红外光谱(FT-IR)、核磁共振(NMR)、紫外光谱(UV-vis)等测试了其在有机溶剂中的凝胶性能和离子响应特性等.扫描电镜(SEM)结果表明所形成的凝胶具有规则的片状结构.采用红外光谱(FT-IR)、核磁共振(NMR)、紫外光谱(UV-vis)考察了凝胶形成的主要驱动力是氢键、π-π作用等.D12-甲醇凝胶在准固态作用下可以选择性地响应氟离子,计算得到凝胶对氟离子响应的检出限为9.71×10-5 M.

Relaxor ferroelectric materials with high piezoelectric properties always suffer from low phase transition temperature, making them difficult to satisfy the demands for high-temperature environment applications. In this work, we proposed a composite approach to improve the piezoelectricity and temperature stability of PSN-PMN-PT ceramics at the same time. The ZnO nanoparticles as a second phase were introduced into the PSN-PMN-PT matrix to form composite ceramics. When the ZnO content reaches 5 mol%, the piezoelectric constant d(33) increases from 529 pC/N for pure PSN-PMN-PT ceramic to 590 pC/N. Meanwhile, the retained d(33) after annealing at 200 ? keeps 92% of the value before annealing, indicating the thermal depolarization behavior is suppressed by the composite method. The synchronous improvement of the d(33) and thermal depolarization behavior for PSN-PMN-PT/ZnO composite ceramics is related to the local electric field and stress field caused by the addition of ZnO particles. Our results pave a simple and effective way to develop next-generation PT-based relaxor ferroelectric ceramics.

This paper presents a resonator with a variable helical structure that induces a change in the internal impedance of the resonator, which can improve the performance of the resonator. This resonator structure achieves an asymmetric absorption mechanism of acoustic waves by coupling a pair of Helmholtz resonators with the same coupling mode in parallel in a two-port acoustic duct. Theoretical analysis, numerical simulations, and experimental measurements confirm that the acoustic energy is almost completely absorbed (97.4%) at 287.5 Hz. By designing the acoustic "soft" boundary, the system absorbs acoustic energy when the acoustic wave is incident from one side and mostly reflects when the acoustic wave is incident from the other side. These two different absorption patterns are caused by the impedance matching/mismatch between the two sides of the system, respectively. Consequently, the asymmetric absorption system at low frequencies achieves a near-perfect absorption of acoustic energy. Asymmetric absorption at broadband and multi-band is obtained for different cases. The asymmetric design in this paper improves the active control of noise cancellation in a two-port system and allows for a more diverse use of absorption devices.(c) 2022 Elsevier Ltd. All rights reserved.

In this paper, potassium sodium niobate lead-free piezoelectric thin films were prepared by sol-gel method. The electric domain structure and optical band gap of the thin films were regulated by doping Mn. It is found that Mn doping increases the grain size and density of KNNLT piezoelectric film surface. In addition, Mn doping can regulate the electric domain of thin films. Increasing Mn doping concentration can regulate the size and distribution of electric domain, and the ratio of 71 degrees electric domain increases with the increase of doping concentration. The results show that the optical band gap decreases gradually with the increase of doping amount when the annealing temperature is 650 degrees C. The lowest optical band gap reaches 3.426 eV, and is lower than the undoped KNNLT films.

In this paper, Bi2O3-doped (K0.5Na0.5)NbO3 (x = 0.1, 0.2, 0.3, 0.4) lead-free ceramics are prepared by a conventional solid-state reaction and analyzed by studying the structure, ferroelectric, and piezoelectric properties. It is found that the doping of Bi2O3 increases the proportion of the trigonal phase in KNN ceramics, thus enabling the construction of KNN ceramics with an orthogonal–trigonal phase boundary at room temperature. At the same time, doping with Bi2O3 can reduce the grain size and improve grain size uniformity of the ceramics. The KNN-0.1%Bi2O3 ceramic has the best piezoelectric properties in all composition; the results are as follows: d33 = 121pC/N, kp = 0.474, kt = 0.306.

In this work, the influence of temperature on phase structure, dielectric property and domain structure of (K,Na)(Nb,Ta)O-3 (KNNT) crystal from 20 to 200 degrees C was studied. The irreversible domain wall motion of single crystal is strongest at phase transition temperature by Rayleigh analysis of dielectric properties. The domain structure in the heating and cooling process of single crystal was observed by means of piezoelectricity microscope. The domain structure changed obviously with temperature and the domain structure change is particularly prominent at the phase transition temperature.

Sandwich-like multilayer (BNT-0.05BT, BNT-0.07BT, and BNT-0.09BT) composite ceramics was performed by traditional solid-state reaction method. The results show that the dielectric properties of (Bi1/2Na1/2)TiO3-BaTiO3 (BNT-BT) ceramics were improved significantly from 580 to 1278. By fitting the dielectric constant e (r) with electric field intensity, the linear relationship conformed to Rayleigh formula, and the dielectric properties of the loops were studied. The results show that the dielectric properties were improved mainly because the intrinsic contribution of structural changes of composite ceramics increased. As the temperature rises, the dielectric response of ceramics to the electric field increases gradually.

For relaxor ferroelectric materials, improving the piezoelectric properties and temperature stability simultaneously is still a great challenge up to now. In this work, the structure, electric properties, and thermal stability of xPSN-(1 - x)PMN-0.4PT (x = 0.15, 0.29, 0.43, and 0.5) ceramics were studied systematically by experiment and phase field simulation. A high Curie temperature T-c of 255celcius and good longitudinal electricmechanical coupling factor k(33) of 0.75 and piezoelectric constant d(33) of 650 pC/N are achieved in x = 0.43 ceramics with monoclinic C and tetragonal phases coexistence at room temperature. At 30celcius, this composition ceramics sintered at 1260celcius shows the remnant polarization P-r and coercive field E-c are about 36.8 mu C/cm(2) and 8.2 kV/cm respectively. Moreover, as the temperature increases to 150celcius, these values remain as high as 22.6 mu C/cm(2) and 5.7 kV/cm. In the temperature range of 30-230celcius, the variation of k(33) and d(33) is about 24% and 25%. These high piezoelectric performance and superior temperature stability are related to the more complex domain structures caused by phase coexistence and larger grains with more stable domain structure due to internal stress. The former is beneficial in improving the piezoelectric properties, and the latter dominates the enhanced temperature stability.