Ceramic Sheets Research Articles

Fluorescence and temperature sensitive properties of Tb and Eu co-doped 8YSZ thermosensitive ceramic

Incorporating a small amount of rare-earth luminescent elements into thermal barrier coatings is currently the most promising method for determining the temperature distribution of engine blade coatings. In this study, Tb and Eu co-doped 8YSZ ceramic powder (8YSZ:Tb3+&Eu3+) was synthesized using chemical co-precipitation method, and the optimal powder was sintered into ceramic sheet through dry pressing. The phase, morphology, fluorescence properties and temperature sensitivity of 8YSZ:Tb3+&Eu3+ ceramic were studied. Results indicated that 8YSZ:Tb3+&Eu3+ was tetragonal with average grain size ranging from 22 to 28 nm. The luminescence intensity and lifetime of 8YSZ:Tb3+&Eu3+ both reach their maximum when the doping amount of Tb3+ is 1.5 mol%, with the existence of energy transfer from Tb3+ to Eu3+. And the forming processes has little influence on fluorescence performance of 8YSZ:Tb3+&Eu3+ materials. Meanwhile, 8YSZ:1.5Tb&1Eu ceramic reveals excellent temperature sensitivity. At 500 K, the relative sensitivities are 0.519% K-1 and 0.369% K-1 respectively for 8YSZ:1.5Tb&1Eu powder and sheet, while absolute sensitivities are 0.731% K-1 and 0.751% K-1. Consequently, 8YSZ:Tb3+&Eu3+ ceramic is a potential temperature detection material for practical applications.

Enhanced electrochemical performance of garnet Li7La3Zr2O12 electrolyte by efficient incorporation of LiCl

Garnet-type Ta-doped Li7La3Zr2O12 (LLZO) lithium-ion-conducting ceramic electrolytes has become the promising and critical candidate for developing the high-energy-density all-solid-state lithium batteries, due to the satisfied Li+ conductivity, stability against metallic lithium anode, and the feasible preparation under ambient air. Here, to further increase the lithium-ion conductivity of LLZO comparable to that of the commercial organic liquid electrolytes, lithium chloride (LiCl) is effectively introduced to synthesize the garnet-type ceramic electrolytes with the nominal composition (Li6.5La3Zr1.5Ta0.5O12)1-x–(LiCl)x (x = 0, 5mol%, 10mol%, 15mol%, 20mol%, and 25mol%) via high-temperature calcination process. The cubic structure with highly conductive performance is confirmed from X-ray diffraction measurement as well as Raman spectra analysis. Structural information is observed according to field emission scanning electron microscope equipped with energy dispersive spectrometer and density measurements. Among above investigated ceramic compositions, the prepared (Li6.5La3Zr1.5Ta0.5O12)0.85–(LiCl)0.15 ceramic electrolyte sheet sintered at 1200 °C for 12h presents the room-temperature Li-ion conductivity of 1.22 × 10−3 S·cm−1 by alternating current (AC) impedance analysis along with the corresponding activation energy of 0.262eV through Arrhenius equation calculation. The electronic conductivity measurements are also done by direct-current polarization to confirm the ionic nature for all investigated ceramics. Furthermore, the Li|(Li6.5La3Zr1.5Ta0.5O12)0.85–(LiCl)0.15 |Li symmetric batteries can possess the small interfacial resistance of 92.3 Ω cm2 and stably run for 1000 h at 0.1 mA cm−2 without a short circuit at room temperature. The hybridized lithium-sulfur battery with (Li6.5La3Zr1.5Ta0.5O12)0.85–(LiCl)0.15 electrolyte delivered excellent initial room-temperature discharge capacity of 1204mAh·g−1 and 1152 mAh·g−1 under the current density of 0.1C and 0.2C respectively, large coulombic efficiency, and great cycling stability. Moreover, the lithium-sulfur batteries also can show excellent cycling performances under different current densities and a good capacity recoverability. The above investigation results suggest that the low-melting-point LiCl incorporation in Li6.5La3Zr1.5Ta0.5O12 electrolyte is an effective measurement to synthesize the cubic and dense Li-stuff garnet ceramic sheets for the high-performance rechargeable next-generation solid-state batteries.

A rapid pressureless sintering strategy for LLZTO ceramic solid electrolyte sheets prepared by tape casting

Garnet-type electrolytes are regarded as one of the most promising solid-state electrolytes (SSEs) for lithium-ion batteries due to their potential advantages in terms of energy density, electrochemical stability and safety. To achieve the maximum energy density, it is necessary to ensure that the electrolyte layer is as thin as possible. Nevertheless, thin sheet SSE is more challenging to sinter than pellet due to the greater lithium volatilization from the high surface/volume ratio. Garnet-type SSE (Li6.5La3Zr1.5Ta0.5O12, LLZTO) green tape was prepared by the tape-casting technique. The effects of supporter, sintering temperature and dwell time on the relative density, microstructure and ionic conductivity of thin sheet were investigated. A ceramic SSE sheet with a thickness of 173 μm, a relative density of 97.2 %, an ionic conductivity of 2.02 × 10−4 S/cm at 25 °C and an activation energy of 0.25 eV, was achieved using a rapid pressureless sintering at 1250 °C for 25 min with a MgO supporter. This work offers insights into the practical production of LLZTO sheets.

Enhanced broadband infrared radiation from rare earth orthochromites for High-Temperature radiative heat transfer

The development of broadband, high-performance infrared radiation materials is crucial for energy conservation and applications in aerospace and industrial sectors. Rare earth orthochromites, such as PrCrO3, exhibit good thermal stability and high infrared emissivity beyond the 6 μm wavelength range. However, their large bandgap limits their infrared emissivity before 6 μm, significantly impacting their potential applications. Herein, we have successfully enhanced the thermal emissivity of PrCrO3 by manipulating oxygen vacancies (OV) and accompanying impurity levels, leading to the synthesis of five rare earth orthochromites. Compared with pristine PrCrO3, co-doping of Ca, Co, and Mn introduced oxygen vacancies (OV) and impurity energy levels, effectively reducing the band gap and improving emissivity in the wavelengths below 6 μm. In particular, the infrared emissivity of (Pr0.3Y0.3Ca0.4)CrO3 in the wavelengths of 0.78–2.5 μm reaches 0.89, which is double than that of pristine PrCrO3. Furthermore, its thermal stability is excellent, as demonstrated by thermal shock experiments at 1500 ℃ for five cycles. More importantly, the developed orthochromites can be applied as a coating on substrates such as alumina ceramic sheets, exhibiting an average infrared emissivity of 0.95 and remarkable radiative heat transfer capability. This research contributes to the advancement of high-performance infrared radiation materials by vacancy engineering.

Extracting salt from soil with ceramic sheets

The study investigates the drying behavior and desalination effectiveness of porous ceramic tiles made from fired clay materials like bricks or pottery on soil columns initially saturated with saline solution. Evaporation kinetics experiments compared the drying of saline soil with and without a ceramic tile. For soil without a ceramic cover, salt precipitation formed an efflorescent crust that initially (t ∼ 30 h) reduced the evaporation rate. However, with continued drying, the tensile stress caused cracks in the crust, allowing increased evaporation through the cracks (t > 200 h). When covered with a ceramic poultice, the saline solution was wicked into the porous ceramic by capillary action. Rapid salt efflorescence was observed on the ceramic surface. The ceramic layer initially reduced the soil evaporation rate due to pore clogging caused by salt precipitation. The pore structure characteristics of the ceramics significantly impacted their desalination performance. After an initial fast drying period controlled by evaporation, a reduced drying rate was observed as salt clogging effects became dominant, especially for the low porosity ceramic (t ∼20 h). The porous ceramic poultices could effectively extract salts from the soil, but their desalination efficiency depended critically on their pore structure properties. An industrial-based clay ceramic with large and more connected pores (porosity 0.33) was found to be around 62% more efficient in removing NaCl than a handmade pottery with small pores (porosity 0.18).

Heat dissipation design and performance optimization of high speed train PMSM based on coupled electromagnetic-thermal field

The permanent magnet synchronous motor (PMSM) has been widely recognized as the most promising driving system. This research presents a hybrid cooling system to improve the cooling effect of high speed train PMSM. At first, the cooling system includes the water jacket, heat pipes, Aluminum Nitride Ceramic sheets (AINC) inserted in the stator teeth, potting material at both ends of winding, and fins bonded to the evaporation section of heat pipes. In addition, the 3D model of PMSM is constructed with the error between experiment and simulation less than 5 %. Subsequently, using the Response surface method (RSM), this study investigates the sensitivity and the coefficient of correlation by varying AINC size on the electromagnetic properties. Finally, Particle Swarm Optimization (PSO) is employed to establish the mathematical optimization model of this cooling system. The results show that the optimized cooling system reduces the maximum temperature (Tmax) for each component of the PMSM while achieving a more uniform temperature field without compromising its electromagnetic properties. This significantly enhances the reliability and contributes to advancements in multi-physical field optimization for PMSM cooling.

Electrochemically produced nano-TiO2-coated SiC membranes for photocatalytic water treatment: Preparation, characterization, and hydroxyl radical formation.

Photocatalytically active ceramic flat sheet membranes based on a nanostructured titanium dioxide (TiO2) coating were produced for photocatalytic water treatment. The nano-TiO2 layer was produced by a novel combination of magnetron sputtering of a thin titanium layer on silicon carbide (SiC) membranes, followed by electrochemical oxidation (anodization) and subsequent heat treatment (HT). Characterization by Raman spectra and field emission scanning electron microscopy proved the presence of a nanostructured anatase layer on the membranes. The influence of the titanium layer thickness on the TiO2 formation process and the photocatalytic properties were investigated using anodization curves, by using cyclovoltammetry measurements, and by quantifying the generated hydroxyl radicals (OH•) under UV-A irradiation in water. Promising photocatalytic activity and permeability of the nano-TiO2-coated membranes could be demonstrated. A titanium layer of at least 2 μm was necessary for significant photocatalytic effects. The membrane sample with a 10 μm Ti/TiO2 layer had the highest photocatalytic activity showing a formation rate of 1.26 × 10-6 mmol OH• s-1. Furthermore, the membranes were tested several times, and a decrease in radical formation was observed. Assuming that these can be attributed to adsorption processes of the reactants, initial experiments were carried out to reactivate the photocatalyzer.

Fretting Wear Behavior of Fluorine Rubber and Short Carbon Fiber Reinforced Fluorine Rubber Matrix Composites

The fretting wear behavior of fluorine rubber (FKM) and short carbon fiber (SCF) reinforced fluorine rubber matrix composites (SCF/FKMCs) is investigated experimentally under air condition. Four kinds of SCF/FKMCs with different SCF concentrations (5 phr, 10 phr, 15 phr, and 20 phr in every 100 phr of FKM) are considered. The contact model utilizes the sphere-on-flat contact between a 440 C stainless steel ball and an FKM or SCF/FKMCs coating perfectly bonded to a ceramic sheet in fretting experiments. The impacts of SCF concentration, normal force, and displacement amplitude on the fretting wear behavior are investigated. Scanning electron microscope (SEM) is used to analyze the fretting wear surface morphology and wear mechanism, while three-dimensional (3D) white-light interference profilometer is used to describe the characteristics of 3D surface wear profile and determine the wear volume. The fretting wear performances of FKM and SCF/FKMCs with different SCF concentrations are compared under different fretting test conditions. The results show that adding an appropriate amount of SCFs to FKM can improve wear resistance and reduce the coefficient of friction (COF). SCF/FKMC with SCF concentration of 15 phr has the smallest COF. SCF/FKMCs with SCF concentration of 5 phr or 15 phr have the best wear resistance for small normal force or large displacement amplitude.

Novel strategy for designing photochromic ceramic: Reversible upconversion luminescence modification of the α-Ba2ScAlO5:Yb3+/Er3+ for optical information storage and multiple anti-counterfeiting

Reversible upconversion luminescence (RUCL) modification of rare earth ion-doped ceramic based on photochromism has received much attention in favor of expanding its practical applications. However, RUCL modification induced by photochromism usually employs these traditional methods (electric and magnetic fields) to induce bleaching, which limits its practical applications. In this work, a white α-Ba2ScAlO5: Yb3+/Er3+ (α-BSAO: Yb, Er) was prepared, which exhibits photochromic coloration from white to blue upon stimulation with 254 nm light. The coloration was able to be bleached by light (808 nm) and thermal (275 °C) stimulation, exhibiting reversible photochromism. The α-BSAO: Yb, Er ceramic exhibited good luminescence performance and reversibility under alternating cycles of 254 and 808 nm (or thermal) light stimulation. It suggests that α-BSAO: Yb, Er ceramic is an ideal anti-counterfeiting agent. The α-BSAO: Yb, Er ceramic sheets can be excited by ultraviolet and near-infrared light, and are capable of realizing the reading of optical information recorded on binary photochromic dot arrays. It shows the potential application prospects of α-Ba2ScAlO5: Yb3+/Er3+ ceramic in the field of optical storage and anti-counterfeiting.

Fabrication of micro/submicron hierarchical structures on ceramic sheet surfaces combining 2-step imprinting and in-plane compression processes

Many organisms have functional microstructured surfaces. Particularly, lotus leaves have hierarchical dual-scale micro/nanostructures on their surface and exhibit highly water repellent properties. We have developed techniques to fabricate patterns on inorganic material surfaces such as ceramics. Applying these techniques to fabricate hierarchical structures can make ceramic surfaces even more promising. In this paper, we prepared 2 kinds of mold with line-and-space patterns with pitches 50 μm and 2 μm and fabricated micro (rough patterns)/submicron (fine patterns) hierarchical structures on sintered ceramic sheets using a newly developed imprinting process with in-plain compression method. We proposed processes for the fabrication of such hierarchical structures, discussed the possibility of higher resolution of the patterns by comparison with the analytical results.

Evaluation of zirconia surfaces and shear bond strength after acid–etching with ultrasonic vibration

To evaluate the effect of surface reaction process after hydrofluoric (HF) acid etching using ultrasound and the shear bond strength (SBS) of resin cement to zirconia polycrystal (Y-TZP) ceramic. Y-TZP ceramic sheets were divided into rinsing group (Group P), ultrasonic cleaning group (Group C), and ultrasonic reaction + rinsing group (Group CP), and all the groups were treated for 5, 10, 20, 30, 40, 50, and 60 min, respectively. The surface morphology, elements distribution, roughness, and wettability of the ceramic sheets in each group were observed. The SBS of ceramic-resin bonding specimens was tested after immersion and after cooling-heating cycles, respectively. Octahedral and spiculate products were observed on the surface of Y-TZP that was etched with HF acid in Group P. The amount of these products increased over time. In contrast, only a few octahedral products remained on the surface of Y-TZP in Groups C and CP. Within the same reaction time, the surface reaction of the CP group was stronger than that of the other two groups, accompanied by a more uniform morphology. The shear force in Group C was the lowest, and the shear force reduction in Group CP was the least after cooling-heating cycling, with statistically significant differences (P< 0.05). After the reaction time exceeded 30 min, the shear force in each group decreased instead of increasing. Octahedral and spiculate acid etching products on the surface of HF acid-etched Y-TZP can enhance the bonding force of zirconia. Ultrasonic cleaning would drive the exfoliation of acid etching products from the sample surface, leading to the decrease of the bonding force. The acid etching with ultrasonic vibration can accelerate the HF acid etching process of Y-TZP ceramics, which is conducive to improving the bond strength to resin and durability.

Influence of drying conditions and plasticizer‐to‐binder ratio on the water‐based tape casting of La0.6Sr0.4Co0.2Fe0.8O3−δ

AbstractTape casting is a flexible technique for manufacturing scalable ceramic sheets. This study fabricated La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF6428) tapes using water‐based tape casting. A high molecular weight plasticizer, polyethylene glycol 4000, was chosen to balance flexibility and mechanical strength. Adjusting the plasticizer‐to‐binder ratio (R‐value) and increasing relative humidity during drying led to crack‐free and flawless green tapes of 330 µm. The uniform polymer matrix improved homogeneity and consistency as well. An applicable suspension formulation was developed for the water‐based fabrication of LSCF tapes for continuous production.

Piezoelectric energy harvester with outstanding output performance at low frequency vibration based on concentrating force on the piezoelectric element by parallel springs

This paper proposes a piezoelectric energy harvester that concentrates force on the piezoelectric element by parallel springs. When vibrating, the force exerted by the mass is released at three equal points on the surface of the brass substrate through three parallel springs. This concentrated release of energy through the spring amplification effect facilitates large deformation of the piezoelectric ceramic sheet, resulting in a higher charge output. The results show that under the combined action of a 14 g annular hollow mass and a 0.3 mm wire diameter stainless steel spring, the energy harvester based on the lead zirconate titanate ceramic exhibited an outstanding output power of 1.0–32.1 mW at a low resonance frequency with acceleration amplitudes of 0.5–3 g (1 g = 9.8 m/s2). More importantly, to match the vibration frequency of the actual environment, this paper optimized the structure of the harvester and proposed that the harvester can be designed by selecting the weight of the mass block, the parameters and number of springs, and the shape of the brass substrate. The energy harvester designed in this study is expected to capture energy from low-frequency natural environments and exhibit outstanding output performance, which can provide guidelines for future efforts in this direction.

Thermal fatigue failure mechanism in the joint of nano Cu/Ti–Si3N4 ceramic substrates after thermal fatigue test

Thermal stress fatigue failure caused by mismatch in the coefficients of thermal expansion (CTE) between the metal layer and ceramic sheet during a high and low temperature cycle is considered as the big issue of high-power ceramic substrates. The aim of this study is to explore the thermal fatigue mechanism of nano Cu/Ti–Si3N4 ceramic substrates after thermal fatigue test. Thermal fatigue test has been performed by thermal cycles experiment from −30 °C to 150 °C. After thermal cycles, the microstructure of the interface is observed by SEM and TEM. The results show after 400 thermal cycles, the nano-Cu metal layer oxidizes severely. Various oxides are found in the corrosion zone, such as CuO, CuAlO2 and CuAl2O4. Higher dislocation density and nanoscale-twins are observed in Cu or Cu2O, which indicate that Cu and Cu2O alleviates thermal stress. As the number of thermal cycles increases, CuO CuAlO2, CuAl2O4 as a corrosion layer in the corrosion zone were formed. The corrosion layer is difficult to alleviate interfacial thermal stress, and easy to form cracks in the joint zone.

Portable hydroxyl-functionalized coal gangue-based cordierite porous ceramics sheets for effective adsorption of fluorine-containing wastewater.

Monolithic adsorbent removal of fluoride from water is considered an effective and non-secondary pollution method. Here, a portable hydroxyl-functionalized coal gangue-based cordierite porous ceramic sheet (ACGC-Fe) is prepared by using coal gangue solid waste with a specific silicon-aluminum-rich composition ratio and a small amount of magnesium oxide as a raw material through powder compression molding and mild chemical modification. The prepared ACGC-Fe can be used to treat fluorine-containing wastewater and the maximum adsorption of fluorine can reach 18.69 mg g-1. The Langmuir (Freundlich) adsorption isotherm model and pseudo-second-order kinetic model here provided a satisfactory description of the fluoride removal operating mechanism, and it is confirmed that the adsorption mechanism of ACGC-Fe is mainly attributed to the chemisorption of hydrogen bonds (with hydroxyl group) and ionic bonds (with metal), and physical adsorption based on cordierite porous ceramic pores. This research will provide a new idea for designing high-performance materials by mining and analyzing the composition and structure characteristics of coal gangue solid waste itself and broaden the application range of high-value-added coal gangue solid waste.

Fabrication of a Laminated Actuator with Excellent Linearity Using Ground Potassium Sodium Niobate-Based Ceramic Sheets

Linearity is an important factor that affects actuator accuracy. However, the high nonlinearity of KNN piezoelectric ceramics restricts their application in actuators. In this study, we used grinding stress to improve the linearity of ceramic chips, and used them to fabricate a laminated actuator. The ceramic sheets were ground to a thickness of 0.5 mm. During grinding, some areas of the ceramic changed from tetragonal to orthorhombic, owing to the grinding stress. The piezoelectric constant (d33) increased from 198 to 268 pC/N. Notably, the linearity of the ceramics improved. Seven pieces of ground ceramics were bound, to fabricate a laminated multilayer actuator with a total thickness of 3.5 mm. A DC voltage was applied to the actuator, and the displacement was measured. The displacement reached 0.73 μm under a low driving voltage of 200 V. A linear regression analysis of the displacement–voltage relationship was performed, obtaining the regression equation of the actuator. The linearity correlation coefficient was approximately 0.9903, implying that the actuator exhibits a high accuracy. The grinding stress improved the linearity, together with the piezoelectric properties of the ceramic chips, thus improving the actuator accuracy. This research will promote the application of KNN piezoelectric ceramics in actuators.

A Single Oscillator-Excited Piezoelectric Actuator with Internal Contact Teeth.

The tail rotor of a helicopter, a crucial component, traditionally relies on a complex drive mode involving reducers and transmission gears. This conventional setup, with its lengthy transmission chain and numerous components, hinders miniaturization efforts. In response to this challenge, our paper presents a novel piezoelectric drive approach. Our objective was to suggest an innovative design capable of minimizing the components involved in the tail rotor drive. This design can be adjusted in size according to specific requirements and is effective up to a specified speed. Moreover, it facilitates the process of miniaturization and integration. The piezoelectric actuator's stator comprises an ultrasonic amplitude transformer, a ring, and three drive teeth. Utilizing the rod-like structure of the tail brace, the actuator is simplified by adhering ceramic sheets to it. The rotary piezoelectric actuator combines the first longitudinal mode of a rod with torus bending modes. The drive teeth then amplify the ring's displacement, facilitating rotor rotation. The resonant frequency and modal shape of the actuator were determined using the finite element method. Furthermore, an investigation was conducted to analyze the influence of the drive teeth positioning on the motion trajectory at the contact point. Theoretically, we infer that the declination angle of the drive tooth is a crucial parameter for achieving high speeds. To test our idea, we built three prototype stators with different drive tooth declination angles. Our actuator stands out for its cost-effectiveness, structural simplicity, compatibility with harmonic signals, and ease of miniaturization. It can be considered for the drive of the tail rotor of a microhelicopter.

Co-Sintering of Lithium Aluminum Germanium Phosphate (LAGP) Glass/Powder Composite Electrolyte for Multilayer Ceramic Batteries

Inorganic solid electrolytes are one of the key materials instead of organic liquid electrolytes for next-generation all-solid-state batteries (ASSBs). The advantages of ASSBs are long cycle life and high safety due to the non-flammable of the solid electrolyte. The ASSBs can be stacked layer by layer, reducing the volume in battery packaging and resulting in increased energy density. These ASSBs can be applied to wearable or healthcare or smart home devices in the form of multilayer ceramic battery (MLCB), in addition to energy storage devices and electric vehicles. However, the MLCBs are difficult to fabricate due to the high sintering temperature and high interfacial resistance of the solid electrolyte. The Li-based solid electrolytes of NASICON-type have received much attention as prospective solid electrolytes due to their high ionic conductivity and high stability against moisture. Especially, lithium aluminum germanium phosphate (LAGP) is potential solid electrolyte material in the NASICON family due to superior stability. LAGP glass electrolyte was selected to enable sintering at low temperatures and reduce resistance at the interface for the application to MLCB.In this study, a LAGP-based solid electrolyte ceramic sheet was prepared using glass/powder composite at 750 °C. The obtained LAGP-based solid electrolyte exhibited a NASICON-type hexagonal structure and a total ionic conductivity of 1.45 × 10-4 S/cm at 25 ˚C. A Coin cell with the LAGP composite electrolyte, LiCoO2 (LCO) as cathode, and Li metal as anode was assembled. The coin cell was charged and discharged by using a battery cycler and the charge capacity was approximately 130 mAh∙g-1. Additionally, we prepared a LiMnPO4 glass-based cathode (LMP) using conventional melt quenching techniques and then stacked it layer by layer with the LAGP electrolyte and co-sintered at 650°C. After co-sintering the LAGP/LMP cell, it was confirmed that the interface between the LAGP composite electrolyte and the LMP cathode was well attached, and its ionic conductivity maintained a value similar to that of the LAGP composite electrolyte. Subsequently, an electrochemical analysis of the LAGP/LMP cell was performed.

A Bionic Piezoelectric Robotic Jellyfish With a Large Deformation Flexure Hinge

Jellyfish are one of the underwater creatures that have been imitated by underwater bionic robots, but a current challenge to create a bionic jellyfish is with the use of piezoelectric ceramic sheets as the driving element, due to their small output displacement. Here, a bionic robotic jellyfish with three tentacles is presented that is driven by three piezoelectric beams, and to transmit power, a large deformation composite flexure hinge is created which employs fishing line embedded in a 3D printed structure. In addition, the structure design and fabrication of the drive system are described. A dynamic model of the drive system is established to solve for the working mode, forced displacement responses, and swimming lift. A series of experiments are carried out to verify the theoretical analysis and validate the design of the robotic jellyfish. The proposed robotic jellyfish has a total mass of 29.4 g, tentacle spread of about 150 mm, and an overall height of 100 mm. The robotic jellyfish can exhibit swimming performance with drive frequencies of 0.7-1.1 Hz, and the best achieved swimming speed was 10 mm/s. These design, modeling, and fabrication methods may be beneficial and inspiring for the future development of the micro soft robot.

Influence of Mono- and Multiwave Light-curing Units on the Microhardness and Degree of Conversion of Light-cured Resin Cements.

This study evaluated the Knoop hardness (KH, N/mm2) and degree of conversion (DC, %) on the margins of light-cured resin cements with different photoinitiators using a single light-curing unit (LCU) with two heads (mono- and multiwave). Three types of resin cements were used with different photoinitiators: Megalink Esthetic (Odontomega, São Paulo, Brazil) with a camphorquinone photoinitiator; Allcem Veneer (FGM, Joinville, Brazil) with the Advanced Polymerization system (APS), and Variolink Esthetic LC (Ivoclar Vivadent, Schaan, Liechtenstein). Thirty samples were collected and divided into six groups (n=5 each). The resin cement samples were made into the shape of a maxillary right central incisor and photoactivated under a 0.5-mm-thick ceramic sheet. A single LCU (Radii Xpert, SDI) with two heads (mono- and multiwave) was used. The tip of the LCU was positioned at the center of the sample in a standardized manner. Raman spectroscopy was performed to evaluate the DC, and KH was evaluated through the Knoop microhardness test. Five regions were evaluated: cervical, mesial, buccal (center), distal, and incisal. There was a significant difference in the DC only for the type of cement (p<0.001), indicating that the cement with the APS photoinitiator presented excellent results. There were significant differences in the type of cement (p<0.001), type of light (p<0.001), region (p<0.001), and the interaction between the type of cement and type of light (p<0.001). The resin cement with the APS photoinitiator cured with monowave light showed the highest KH values. The beam profiles of all groups, with and without the interposition of ceramic and resin cement, were examined by light transmission. The cement with the APS photoinitiator presented the best results with respect to the DC and KH. In comparison with mono- and multiwaves, the LCU may not be a determining factor for the properties of light-cured resin cements. The buccal region showed the best results for DC and KH, indicating the need for a greater amount of light-curing at the cementation margins.