Advances in mitigating the Td-d33 trade-off via compositionally graded diffusion in BNT-based piezoceramic

A notoriously unresolved conflict that the substantial increment of depolarization temperature T_d was generally accompanied by the sharply deterioration of piezoelectric constant d₃₃ in Bi_0.5Na_0.5TiO₃-based (BNT-based) piezoceramics severely limit their practical applications. Herein, a new strategy by Ba²⁺ gradient diffusion layer in 0.94Bi_0.5Na_0.5TiO₃-0.06BaTiO₃ (BNT-6BT) ceramic via interface-diffused sintering to suppress the ferroelectric-relaxor phase transition is presented to manipulate the incompatibility of T_d and d₃₃. By this strategy, the compositionally graded diffusion in the BNT-6BT ceramic can offer both the properties simultaneously with the T_d deferring from 109 °C to 170 °C and maintaining the initial d₃₃ (145pC/N). Furthermore, by integrating the interface-diffused sintering and quenching process, the T_F-R is significantly deferring from 115 °C to 214 °C while the d₃₃ * is retaining the initial value (d₃₃ *=S_max/E_max=258 pm/V). Diffusion phase transition caused by Ba²⁺ concentration gradient promotes the greatly increased tetragonal phase ratio and the development of built-in field thereby leading to well-balanced performance between T_d and d₃₃ in BNT-6BT ceramic. Our work opens a new avenue for developing the high-performance lead-free BNT-based piezoceramics.     

Moisture-Thermal Stable,Superhydrophilic Alumina-Based Ceramics Fabricated by a Selective Laser Sintering 3D Printing Strategy for Solar Steam Generation

The solar-driven interface evaporation is one of the most promising technologies for desalination and wastewater purification. However, in the ebb and flow of the tide, water absorbed in the hydrophilic evaporator bottom would significantly change, leading to the shape deformation of the system and further failure of solar steam generation. Here it is reported that the moisture-thermal stable and superhydrophilic alumina-based ceramics can be fabricated by a selective laser sintering (SLS) 3D printing strategy. The printed alumina-based ceramics possess superhydrophilicity. Along the side surface of the printed sample, a 5 µL water droplet can be fast absorbed in 14 ms. Most importantly, they can maintain stable and high evaporation efficiency even after being dried out for ten times, demonstrating the excellent physical resistance to continuous moisture-thermal transition. Finally, the “I-shaped” evaporators are printed with salt-resistant ability, which can maintain a steady high evaporation efficiency in seawater and 20 wt% brine for long-term steam generation process. The moisture-thermal stable alumina-based ceramics prepared in this work will provide inspiration for stable solar steam generation materials, and expand the development of 3D printing functional materials.     

Comparison of conventional and metal fiber burners in a compact methane reformer using CFD modeling

Compact reformers can be used to produce hydrogen for fuel-cell automobiles. The heat of the mehane seam reforming reaction is provided by methane burning. Generally, conventional burners have been used in combustion chambers. The Computational Fluid Dynamic (CFD) approach was used for the comparison of conventional burners with metal fiber burners and their locations for the first time. The rate of steam reforming reactions and methane combustion reactions were introduced to the CFD model and the Finite Rate/Eddy Dissipation model was used for reactions on the reforming and combustion sections. After validation of the compact reformer results by available experimental data, metal fiber was modeled using the porous-jump interior boundary condition. The results show that the best burner position for the metal fiber is the Bottom (near the catalyst) and for the conventional burner is the Top (far from the catalyst). The results show that the conventional burner in both the Middle and Bottom positions leads to an increase in the reaction zone temperature above 1200 K, which is higher than the catalyst tolerance, but placing a simple burner on the Top of the reactor does not have an out-of-range temperature problem. The hydrogen mass yield for a conventional burner at the Top position is 27.75% relative to methane. Due to the thermal uniformity in the metal fiber burner, the temperature does not exceed the catalyst limitation in the three positions (Top, Middle, and Bottom). The metal fiber burner at the Bottom of the combustion chamber shows the best performance with a hydrogen mass yield of 40.82%. The results indicate that metal fiber burners can distribute the flame more uniformly than conventional burners and increase the available heat for the reformer side.     

Analysis of CRDI diesel engine characteristics operated on dual fuel mode fueled with biodiesel-hydrogen enriched producer gas under the single and multi-injection scheme

The present work aims to investigate the consequences of pilot fuel (PF) multiple injections and hydrogen manifold injection (HMI) on the combustion and tailpipe gas characteristics of a common rail direct injection (CRDI) compression ignition (CI) engine operated on dual fuel (DF) mode. The CI engine can perform on a wide variety of fuels and under high pilot fuel (PF) pressure. Pilot fuel injection (PFI) is achieved at TDC, 5, 10, and 15ºCA before the top dead center (bTDC), and divided injection consists of injecting fuel in three different magnitudes on a time basis and PF is injected into the engine cylinder at a pressure of 600 bar. In this work, the hydrogen flow rate (HFR) was fixed at 8 lpm constant and producer gas was inducted without any restriction. The investigational engine setup has the ability to deliver a PF and hydrogen (H₂) precisely in all operating circumstances using a separate electronic control unit (ECU). Results showed that diesel-hydrogen enriched producer gas (HPG) operation at maximum operating conditions provided amplified thermal efficiency by 4.01% with reduced emissions, except NOx levels, compared to biodiesel-HPG operation. Further, DiSOME with the multi-injection strategy of 60 + 20+20 and 50 + 25+25, lowered thermal efficiency by 4.8% and 9.12%, respectively compared to identical fuel combinations under a single injection scheme. However, reductions in NOx levels, cylinder pressure, and HRR were observed with a multi-injection scheme. It is concluded that multi-injection results in lower BTE, changes carbon-based emissions marginally, and decreases cylinder pressure and heat release rate than the traditional fuel injection method.     

High selectivity and response H2 sensors based on ZnO@ZIF-71@Ag nanorod arrays

Hydrogen (H₂) is widely used in industrial and medical, however its flammable and explosive nature requires economical and effective monitoring to ensure safety. In this work, ZnO@ZIF-71@Ag nanorod arrays were synthesized to provide an effective adsorption response to H₂ through size effect and high catalytic activity by immobilizing Ag nanoparticles (NPs) into the pores of ZIF-71. The results of the gas sensitivity tests showed that the nanorod arrays were significantly more selective towards H₂. Moreover, the response of ZnO@ZIF-71@Ag to 50 ppm H₂ was 11 times higher than that of ZnO@ZIF-71 at a lower operating temperature (150°C). The size of the Ag NPs was demonstrated to be below 10 nm by TEM characterization, suggesting that Ag in the form of quantum dots (QDs) to bring an unignorable catalytic effect for breaking hydrogen molecule (H₂) into highly active atoms ([H]). In addition, the result of Density Function Theory (DFT) calculation revealed that the adsorption energy of Ag-catalyzed [H] (−8.255 eV) was much higher than that of H₂ (−4.222 eV) on ZnO (100), which results in elevated charge transfer to promote hydrogen sensing performance of ZnO@ZIF-71@Ag. In this study, a novel hydrogen sensor based on pore sieving and catalytic sensing mechanisms was obtained, which provides a new reference for the development of hydrogen sensors.     

Growth of the ternary Pb(Mn,Nb)O3–Pb(Zr,Ti)O3 thin film with high piezoelectric coefficient on Si by RF sputtering

In this study, ternary ferroelectric 0.06Pb(Mn_1/3Nb_2/3)O₃–0.94Pb(Zr_0.48Ti_0.52)O₃ (PMN–PZT) thin film with high piezoelectric coefficient were grown on La_0.6Sr_0.4CoO₃-buffered Pt/Ti/SiO₂/Si substrate by RF magnetron sputtering method. The phase and domain structure along with the macroscopic electrical properties were obtained. Under the optimized temperature of 550°C and sputtering pressure 0.9 Pa, the PMN–PZT film owned large remnant ferroelectric polarization of 62 μC/cm². In addition, the PMN–PZT film had polydomain structures with fingerprint-type nanosized domain patterns and typical local piezoelectric response. Through piezoelectric force microscopy, the PMN–PZT thin film at nanoscale exhibited obvious domain reversal when subjected to in situ poling field. It was further found that the quasi-static piezoelectric coefficient of the PMN–PZT thin film reached 267 pC/N, which was about twice to that of the commercial PbZrO₃–PbTiO₃ (PZT) thin film. The optimized relaxor ferroelectric thin film PMN–PZT on silicon with global electrical properties shows great potential in the piezoelectric micro-electro-mechanical systems applications.     

All-In-One Detection,Removal and Recovery of Hg2+ in Industrial Wastewater with Plasmonic Schottky Heterostructures

The effective governance of Hg²⁺ in environmental wastewater is of profound significance to deal with the global pollution issues. However, the present methodologies usually only focused on a single function of either detection or removal, which encounters severe secondary pollution and cumbersome operation cost, while the integration of Hg²⁺ detection, removal, and recovery in one process is barely realized. In this study, an All-In-One photoelectrochemical system is built combining the detection, removal, and recovery of Hg²⁺ pollutant in a single process, by ingeniously developing a fundamental principle, namely alloying-induced plasmonic quenching mechanism in Schottky heterostructures. Briefly, the high-efficiency removal and recovery of Hg²⁺ in wastewater is realized via the favorable alloying of Hg in Ag nanoparticles that well-dispersed on the free-standing WO₃ nanoplate networks. The formation of Ag–Hg alloy future leads to a remarkable plasmonic quenching effect of the Ag nanoparticles, which is used to modulate the photoelectrochemical singles to realize the high-precision detection. Through this ingenious design, an ultralow Hg²⁺ detection limit of 0.296 nm is achieved with a broad detection range up to 12.5 µm , and meanwhile realize a removal/recovery rate of 100% in single Hg²⁺ solution and 97 ± 2% in industrial wastewater with multiple contamination ions. The detection and removal/recovery performance parameters reported in the study are much better as compared to the recently reported single function detection or removal/recovery systems. This work opens a fresh avenue in tackling the problem of heavy metal pollution using plasmonic Schottky heterostructure based All-In-One systems.     

Influence of resin composition on rheology and polymerization kinetics of alumina ceramic suspensions for digital light processing (DLP) additive manufacturing

Alumina ceramics with optimized microstructures and mechanical properties were obtained by the attractive digital lighting processing (DLP) additive manufacturing methodology in the present study. A acrylate-based resin system was designed for the alumina powders with a mean particle size of 0.5 μm. The influence of oligomer on the viscosity and polymerization kinetics of the ceramic suspensions has been elaborately discussed by rheology, curing depth and photo-DSC characterizations. The results indicated that the introduction of oligomer has improved the cross-linking density of resins and decreased the critical dose of energy for resin polymerization, which contributed to a tougher ceramic-resin slice with higher dimensional accuracy. Densifying processes including debinding and high temperature sintering of the ceramic parts were conducted according to the TG-DTA characterizations, alumina ceramics with uniform microstructures and eliminated delamination or intralaminar cracks were finally obtained. The flexural strength was 471 MPa for the ceramics obtained from the resin composition containing 20 wt% oligomer, Weibull modulus for the ceramics were determined to be 17.31 by evaluating thirty all sides polished ceramics, indicating the highly uniform property of the ceramics fabricated by DLP additive manufacturing.     

Low-loss and temperature stable (1-x)Ba3P2O8-xMg2B2O5 composite ceramics with low sintering temperature

In this study, the Ba₃P₂O₈ and Mg₂B₂O₅ were fabricated by the solid-state reaction method separately, and the (1-x)Ba₃P₂O₈-xMg₂B₂O₅ (x = 0.2–0.4) low-temperature co-fired ceramic (LTCC) materials were obtained in the sintering temperature range of 880–960 °C. The phase compositions, microstructures, elemental compositions, and microwave dielectric properties of the (1-x)Ba₃P₂O₈-xMg₂B₂O₅ composite ceramics were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and TE_01δ mode dielectric resonator method, respectively. The results revealed that the Mg₂B₂O₅ phase and Ba₃P₂O₈ phase could coexist well in the (1-x)Ba₃P₂O₈-xMg₂B₂O₅ composite ceramics without formation of any new phases. The abnormal grain growth of Ba₃P₂O₈ grains was inhibited by the addition of Mg₂B₂O₅. In addition, through composition of Ba₃P₂O₈ and Mg₂B₂O₅, the temperature coefficient of resonant frequency (τ_f) and quality factor (Q×f) were effectively optimized, and the sintering temperature was reduced to 880–960 °C. The optimal performance of 0.8Ba₃P₂O₈-0.2Mg₂B₂O₅ composite ceramic was achieved at a sintering temperature of 920 °C, τ_{f =} ?1.9 ppm/°C, Q×f = 61,250 GHz, and a low permittivity ε_r = 10.7. The chemical compatibility test demonstrated that the composite ceramic could coexist well with silver, which indicated that the 0.8Ba₃P₂O₈-0.2Mg₂B₂O₅ composite ceramic is a candidate LTCC material with wide application prospects.     

A novel route to produce BaTiO3 glass-ceramics with nanosized cubic BaTiO3 phase precipitating for high energy-storage applications

To meet requirements of miniaturization devices in high pulsed power technology, super dielectric energy storage performance, such as high dielectric breakdown strength (DBS), large energy storage density with high power density, is extremely important in dielectric materials. However, for BaTiO₃ based ceramics and glass ceramics, there is still a critical challenge to achieve high DBS and large energy storage density. Herein, a novel route was proposed to precipitate nanocrystals with cubic BaTiO₃ phase from glass matrix, which can elevate dielectric constant and meanwhile maintain high DBS compared to parent glass. A high recoverable energy storage density of ∼ 3.66 J cm⁻³ at 1000 kV cm⁻¹ and high discharge energy density of ∼3.57 J cm⁻³ with good thermal stability and ultra-high peak power density of ∼ 910 MW cm⁻³ can be achieved in BaTiO₃ glass ceramic, which implies this type of glass ceramics is suitable for high pulsed power technology application.