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Ionic polymer-metal composites (IPMC), one of the most popular materials in the field of artificial muscle research, have attracted much attention because of their high flexibility, low drive voltage (10 V), high force density, large deformation, and so forth. However, the results show that the serious electrode fatigue crack and water loss of traditional IPMC greatly decrease its fatigue life and limit the practical application. In this study, we developed a novel liquid metal composite electrode. A layer of eutectic gallium-indium alloy (EGaIn) liquid metal was applied to the surface of the platinum electrode of the IPMC using a mask. Because of the good self-healing performance of the liquid metal, it is expected to solve the above problems of resistance increase and water loss caused by cracks. It turns out that the prepared EGaIn/Pt-IPMC exhibits a driving force up to 120 mN and maximum fatigue life of about 25,000 s at a driving voltage of 3 V. Compared with the best work reported, the fatigue strength of EGaIn/Pt-IPMC was increased by about 210%, and the maximum driving force of EGaIn/Pt-IPMC prepared by a single-layer basement membrane was between the IPMC prepared by 4-6 layer basement membrane. The electromechanical properties were significantly improved, and it is expected to realize a series of bionic applications.

Reusable RuBisCO-immobilized microfluidic reactors are used to synthesize the glucose precursor from CO2 and restore >95% of activity after refreshing.

Strontium (Sr)-doped La0.67K0.33-xSrxMnO3 (LKSMO) ceramics were obtained by traditional sol-gel method. With increasing Sr content, full width at half maximum (FWHM) for temperature-dependent resistivity curves increased, resistivity decreased, and peak resistivity temperature (TP) shifted toward high temperature. Microstructure of LKSMO ceramics was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoemission spectroscopy, energy dispersive spectrometry, and Fourier transform infrared spectroscopy, etc. Connection between microstructure and properties of ceramics was studied by combining double exchange mechanism, Jahn-Teller effect, and phenomenological percolation model. Electrical transport mechanism of ferromagnetic metal (FMM) and paramagnetic insulator (PMI) regions was employed to explain temperature coefficient of resistivity (TCR) and magnetoresistance (MR) behaviors of as-obtained samples. Various scattering factors, effective mass of itinerant electron, and energy difference between FMM and PMI phases affected FWHM of ρ-T curves in Sr-doped LKSMO ceramics. In sum, these findings provide physical mechanism and experimental guidance for synthesis of high-TCR and MR polycrystalline ceramics at room temperature.

In the presence of magnetic field, reducing the loss in temperature coefficient of resistance (TCR) and increasing metal−insulator transition point (TMI) to room temperature are the most important concerns for the application of perovskite manganites in high−precision thermistors. Based on emerging evidence, relevant factor to address these problems lies in the interaction between Jahn−Teller (JT) distortion and magnetic field, which results in spin−orbital coupling (SOC) effect and significantly influences TCR and TMI. In this work, we studied the magnetic field induced SOC effect in polycrystalline La1−xCaxMnO3 (x = 0.225–0.45) materials synthesized via sol−gel technique. Compounds undergo the JT distortions with increasing Ca dopant content, and the most pronounced distortion of 0.0144 at x = 0.40 is correlated with a basal−plane distortion mode. All samples exhibit TMI values between 262 K and 288 K, indicating the enhancement of doping−induced double−exchange interaction. In the magnetic field of 1 T, SOC effect sufficiently suppresses the deterioration of TCR caused by deficient magnetization in La0.6Ca0.4MnO3 to a value of 2.9%·K−1 at room temperature (287 K).

La0.71Ca0.29MnO3 is a strongly correlated electronic material, which has been extensively researched and has high application value. It is known that improvements of the temperature coefficient of resistance (TCR) and magnetoresistance (MR), which are important parameters for the application of such materials, promote their applications. Using other elements to replace Mn sites is one of the methods to improve the specific properties. Herein, we prepare a series of La0.71Ca0.29Mn1-xCoxO3 (x = 0, 0.01, 0.03, 0.05, 0.1) polycrystalline ceramics via sol-gel method, and explore the effect of Co doping on the properties of La0.71Ca0.29MnO3. The results show that a small amount of Co doping can significantly improve TCR and MR. Under our excellent preparation process, TCR of La0.71Ca0.29MnO3 was 22.5%·K−1 and MR was 52.9% (under 1T magnetic field). When Co doping is 0.01, TCR reaches 35.1%·K−1 value and MR reaches 64.8%. This can provide critical information for the future application of such materials in bolometers and magnetic sensors.

Reducing the loss of temperature coefficient of resistivity (TCR) in the magnetic field and increasing the low−field magnetoresistance (MR) are two crucial issues to be solved for large scale practical applications of perovskite materials. In this work, polycrystalline La0.67−ySmyCa0.33MnO3 (shortly LCMO:Smy, where y = 0.02, 0.04, 0.06, 0.08) ceramics were synthesized via optimized sol−gel technology. Colossal intrinsic MR up to 71 % was achieved in produced composites by applying only the magnetic field of 1 T. Lattice distortion was found to be a key factor governing the intrinsic MR response. In presence of magnetic field, the most unperturbed TCR up to 24 %·K−1 was attained in LCMO:Sm0.06 system, where the TCR−loss was only 1 %·K−1. This was explained by the opposite external field direction with respect to Jahn−Teller distortion, which enabled one to solve the problem of large attenuation of TCR under the magnetic field. These findings reveal great potential of the LCMO:Sm0.06 ceramic for applications in infrared bolometers and magnetic recording devices in complex electromagnetic environments.

Improving the magnetoresistance effect of perovskite ceramic materials under a low applied magnetic field to expand its application range is one of the main research directions of this type of material. In this study, La0.7Ca0.3MnO3 was doped with different levels of Sm by the sol-gel method to yield a series of La0.7-xSmxCa0.3MnO3 (LSCMO) polycrystalline ceramics. X-ray diffraction (XRD) results revealed that LSCMO ceramics possessed standard perovskite structures. Scanning electron microscopy (SEM) showed grains closely connected without obvious holes. In addition, the grain size gradually decreased with the increase in Sm doping content. The resistivity temperature curves displayed a clear metal-insulator transition behavior of LSCMO accompanied by a steep change from ferromagnetic to paramagnetic behavior (FM-PM). The metal-insulator transition temperature (Tp) values of the as-obtained LSCMO gradually shifted toward lower temperatures with increase in Sm content. Moreover, resistivity temperature coefficient (TCR) and magnetoresistance (MR) values also gradually increased with Sm doping content. The transport properties in polycrystalline ceramics could be adequately explained by the double exchange model, which would be useful for interpreting the CMR effects when used in magnetic devices.

We reported the synthesis, characterization, electrical transport, and magnetic properties of polycrystalline La0.7Ca0.24Na0.06MnO3:Agy (LCNMO:Agy) with y = 0.0, 0.1, 0.2, 0.3, and 0.4. The combination of EDS and XPS proved that Ag not only entered the perovskite phase structure but there would also be a small amount of Ag enrichment at the grain boundaries. The magnetoresistance (MR) and temperature coefficient of resistivity (TCR) improved significantly with the addition of Ag as a dopant. At y = 0.2, a multi-functional perovskite material with high TCR (30.57% K−1) near room temperature and large MR (72.28%) at the low magnetic field (1 T) was obtained. This enhancement of MR and TCR near room temperature was attributed to the good connectivity between the grains and the decrease in electron scattering at the grain boundaries. Overall, these findings look promising for future applications in infrared detection bolometers.

The LCMO: Ag0.2 thin film was grown on the tilted LAO substrate by pulsed laser technology. The structural and electrical properties of the thin film were studied with different deposition times. The X-Ray diffraction analysis demonstrated that all film samples showed exhibit mixed growth and have high crystalline quality. The surface morphology of the films was characterized by atomic force microscopy, and the surface roughness of the films decreased as the deposition time increased. Electrical properties tests show that the peak voltages Up of LIV signals of the films reach their maximum at a deposition time of 10 min, while it also having the TCRmax = 18.43%·K−1. The testing results show that the presence of optimal film thickness can enhance the anisotropic Seebeck coefficient of the film, which in turn improves the film properties.

The polycrystalline La1−xCaxMnO3 ceramics exhibit good electromagnetic performance, i.e., high temperature coefficient of resistivity (TCR), which can be tuned flexibly with respect to structures. Unfortunately, the magnetic field applied to these materials causes a massive decrease in TCR, which hinders their practical applications. In this study, polycrystalline ceramic La1−xCaxMnO3:Ag0.2 was fabricated by sol–gel and solid–phase doping methods, and subsequently vast TCR was obtained in the magnetic field for ceramic with x = 0.2. For this polycrystalline material, high value of TCR (58.65%·K−1, 62.00%·K−1) could be maintained with or without magnetic field with metal–insulator (M − I) transition temperature near room temperature range. Extremely high value of TCR in the presence of magnetic field is attributed to the spin–spin coupling effect, which is beneficial to the sensitivity of M − I transition, generating vast TCR in the magnetic field. Overall, these findings provide new prospects for future applications in infrared bolometers.

Doping is a primary method to improve the temperature coefficient of resistance (TCR) and magnetoresistance (MR) of La1-xA′xMnO3 polycrystalline in a low magnetic field. La0.7Ca0.3-xNaxMnO3 (x = 0, 0.02, 0.04, 0.06, 0.08) series of polycrystalline were synthesized by the sol–gel method. X-ray diffraction patterns indicate that the crystal structure changes from orthorhombic to rhombohedral, and the space group changes from Pnma to $$\text{R}\stackrel{\mathrm{-}}{\text{3}}\text{c}$$ with increasing x. With Na-doping rise, the increase in grain size reduces grain boundaries, weakening the electron scattering at grain boundaries and decreasing the peak resistivity. The excellent MR (59.51%) is observed in La0.7Ca0.24Na0.06MnO3 at the 1 T magnetic field. Meanwhile, TCRmax reaches 12.36% K−1 in the absence of a magnetic field. The resistivity variation with temperature curve fitting illustrates that grain boundary scattering dominates in the low-temperature stage, and the effect of activation energy dominates in the high-temperature stage.

The La0.67Ca0.33MnO3 polycrystalline ceramics were prepared by the co-precipitation method with ammonium carbonate as the precipitant and the influence of the sintering temperature on the electrical transport properties of the ceramics were investigated. XRD results show that the ceramic structures obtained are all perovskite structures, which belong to the Pnma space group. Scanning electron microscopy (SEM) photographs demonstrated that the average size of the grains with the sinter temperature increased from 5.78 μm at 1300 °C to 24.04 μm at 1475 °C. Meanwhile, when the sintering temperature reached 1450 °C, the TCR reached the maximal value (32.3%·K−1), which was much larger r than the TCR at 1350 °C. The theoretical model analysis of the data leads to the conclusion that the conductive mechanism of the low-temperature metallic region and the high-temperature insulating region is dominated by the grain boundary scattering effect and the small-polariton hopping (SPH), respectively.

LCNMO (La0.7Ca0.26Na0.04MnO3) ceramics are prepared via the sol-gel method and sintered at different temperatures, ranging from 1000 to 1300 °C. The influences of sintering temperature on structure and electrical properties are systematically investigated. X-ray diffraction analysis reveals that uniform phase of perovskite structure is formed after sintering. Furthermore, scanning electron microscope (SEM) images demonstrate the presence of on the surface, a highly dense grain boundary and an average grain size of ~2.5 μm. The resistivity-temperature (ρ-T) measurement shows that the resistivity decreases with increased sinter temperature. Moreover, the metal-insulation transition temperature (Tp) and peak resistivity (ρmax) gradually decreased with increasing sintering temperature. The influence of various scattering mechanisms on resistivity at low temperatures is studied, revealing that the residual resistivity (ρ0) dictates the electrical transport performance of the LCNMO ceramics. Also, the different models employed to analyze the ρ-T curves in the temperature range of 100–300 K, confirming the occurrence of phase-separation mechanism in the entire temperature range. The resistance temperature coefficient (TCR) of 10.6%·K−1 and maximum magnetic resistance (MRmax) of 57.12% are achieved after sintering at 1200 °C. These results indicate that LCNMO are promising candidates for infrared detector and magnetic sensor.

Herein, polycrystalline La0.9−xKxCa0.1MnO3 (LKCMO) ceramics (A-sites = La, K, and Ca, 0.05 ≤ x ≤ 0.25) are successfully synthesized via the sol–gel process. The effects of vacancy and disorder degree (δ2) of A-sites cations on electromagnetic transport properties are investigated and performed by using a combination of double-exchange (DE) mechanism, phenomenological percolation (PP) model and Jahn–Teller (JT) effects. The results show that K+ ions, occupying the A-sites, leading to the A-sites vacancy and δ2 of A-sites cations, significantly influence the DE mechanism, JT effect and PP model. A-sites vacancy is confirmed by energy-dispersive spectroscopy and X-ray photoemission spectroscopy. The simultaneous presence of La3+, Ca2+ and K+ ions at A-sites influenced the δ2 of A-sites cations. At the optimal doping content x = 0.15, the maximum temperature coefficient of resistivity (TCR) is 9.7% K− 1 at 291.4 K, and the maximum magnetoresistance (MR) value is 35.2% at 295.03 K, respectively. In summary, LKCMO ceramics achieve room-temperature TCR and MR by A-sites vacancy and δ2 of A-sites cations adjustment, promising applications in uncooled infrared bolometer and magnetic sensors.

Gd doped La0.8Sr0.2MnO3 (La0.8-xGdxSr0.2MnO3, LGSMO) ceramics were prepared by a sol-gel method. X-ray diffraction (XRD) patterns showed that all samples exhibited distorted perovskite structures, R3c. When the Gd3+ content x > 0.03, the crystal structure changed to orthorhombic, Pnma. Scanning electron microscopy (SEM) images showed that the ceramics characterize high density and grain boundary connectivity, and higher Gd3+ doping decreased the grain size from 26.72 μm to 7.42 μm. The temperature dependence of resistivity showed a transition from a low-temperature metal to a high-temperature insulator. The resistivity increased with Gd doping content, and the metal-insulator transition temperature, TP, increased first and then decreased, while the temperature coefficient of resistance (TCR) of the samples first decreased and then increased with Gd3+, and the magnetoresistance (MR) increased first and then decreased. The peak TCR at x = 0.06 was 5.18%·K−1, and MR at 0.04 was 34.57%. The electrical transport properties of the ceramics were explained based on the double exchange (DE) interaction mechanism. The obtained material may have application prospects in magnetic devices and infrared detectors.

Based on the distributed decision tree algorithm, this paper first proposes a method of vertically partitioning datasets and synchronously updating the hash table to establish an information-based mass data retrieval method in a heterogeneous distributed environment, as well as using interval segmentation and interval filtering technologies for improved algorithm of distributed decision tree. The distributed decision tree algorithm uses the attribute histogram data structure to merge the category list into each attribute list, reducing the amount of data that needs to reside in the memory. Second, we adopt the strategy of vertically dividing the dataset and synchronously updating the hash table, select the hash table entries that can be used to update according to the minimum Gini value, modify the corresponding entries and use the hash table to record and control each sub-site. In the case of node splitting, it has a high accuracy rate. In addition, for classification problems that meet monotonic constraints in a distributed environment, this paper will extend the idea of building a monotonic decision tree in a distributed environment, supplementing the distributed decision tree algorithm, adding a modification rule and modifying the generated nonmonotonic decision tree to monotonicity. In order to solve the high load problem of the privacy-protected data stream classification mining algorithm under a single node, a Storm platform for the parallel algorithm PPFDT_P based on the distributed decision tree algorithm is designed and implemented. At the same time, considering that the word vector model improves the deep representation of features and solves the problem of feature high-dimensional sparseness, and the iterative decision tree algorithm GBDT model is more suitable for non-high-dimensional dense features, the iterative decision tree algorithm will be integrated into the word vector model (GBDT) in the data retrieval application, using the distributed representation of words, namely word vectors, to classify short messages on the GBDT model. Experimental results show that the distributed decision tree algorithm has high efficiency, good speed-up and good scalability, so that there is no need to increase the number of datasets at each sub-site at any time. Only a small number of data items are inserted. By splitting some leaf nodes, a small amount is added by branching to achieve a monotonic decision tree. The proposed system achieves a massive data ratio of 54.1% while compared with other networks of massive data ratio.

The lignin derivative ferulic acid was directly functionalized to diepoxy which could be co-cross-linked with furfuryl alcohol-derived monoepoxy to achieve high-performance bio-based thermosets. The development of high-performance bio-based epoxy as a sustainable alternative to fossil-sourced bisphenol A epoxy has great significance. In this work, ferulic acid-based diepoxy (FAE) was facilely synthesized through a direct reaction with epichlorohydrin. After cross-linking, its thermal and mechanical properties are comparable with or even higher than those of bisphenol A epoxy. The carbon–carbon double bond in the framework of the FAE was also exploited to further upgrade its properties via the Diels–Alder reaction with a synthesized glycidyl ether of furfuryl alcohol (GEFA). The chemical structures of FAE and GEFA, curing kinetics, and the Diels–Alder reaction were characterized in detail. The glass transition temperature of FAE-GEFA systems reached ∼250 °C. This work provides a simple way to achieve high-performance thermosets from ferulic acid, and also offers a promising sustainable alternative to bisphenol A epoxy.

La0.7Ca0.3MnO3 has been widely studied as a quintessential example showing colossal magnetoresistance, metal-insulator transition and related temperature coefficient of resistance (TCR). Ag doping was demonstrated as an effective way to enhance the TCR properties of bulk La0.7Ca0.3MnO3. In this article, La0.7Ca0.3MnO3:Ag0.2 thin films were prepared on LaAlO3 (LAO) substrates by pulsed laser deposition with different annealing temperatures. The structure, surface morphology, electrical properties, and magnetic properties of the obtained specimens were investigated. X-ray diffraction results showed that the annealed films exhibited stronger diffraction peaks compared to the unannealed ones, indicating enhanced crystallinity. Resistance-temperature curves revealed metal-insulator transition in thin films annealed at 900–1300 °C. However, the film annealing at 1400 °C exhibited an insulating characteristic due to the evaporation induced non-stoichiometry. A highest TCR of 31.6%·K−1 was achieved in the thin film annealed at 1200 °C. The excellent TCR properties of La0.7Ca0.3MnO3:Ag0.2 films in this study can promote its application in infrared detectors.

Manganites with large temperature coefficient of resistance (TCR) have been considered as potential candidate for infrared detecting. To date, A-site doping with alkaline-earth metal (+2 oxidation state) has been widely used to improve the TCR. However, doping with alkali ions (+1 oxidation state) was less explored. In this study, 2% K doped La0.7Ca0.28K0.02MnO3 (LCKMO) ceramics were prepared by sol-gel method and sintered within the temperature range of 1000–1300 °C for structural and electrical transport properties investigation. X-ray diffraction (XRD) analysis demonstrated that all samples exhibited an orthorhombic perovskite structure with space group Pnma. Elevated sintering temperature would lead to an increase in grain size, which could account for the concurrent decrease of the resistivity (ρ). By optimizing the sintering process, the magnetoresistance (MR) and TCR reached their maxima of 60.95% and 13.54% K−1, respectively, for sintering temperature of 1200 °C. By fitting the temperature dependence of resistivity (ρ-T), grain boundary scattering and small-polaron hopping (SPH) were found to dominate in the low-temperature ferromagnetic and high-temperature paramagnetic regions, respectively. In addition, the ρ-T in the whole temperature range of 100–300 K can also be explained by the percolation model.

La0.67Ca0.33MnO3:Ag0.2 thin films were obtained by pulsed laser deposition followed by post-annealing at 1200 °C for varied durations. Surface morphologies, structures, and electrical and magnetic properties of films prepared with different annealing durations were significantly different. X-ray diffraction results showed that annealed films exhibited stronger diffraction peaks and C-axis preferred growth. Regarding their electrical properties, metal-insulator transition temperature (TMI) and temperature coefficient of resistance (TCR) increased first and then decreased with the increase in annealing duration. In terms of their magnetic properties, thin films displayed ferromagnetic-paramagnetic transition. With the increase in annealing duration, Curie temperature increased first and then decreased. Specifically, the film annealed for 3 h showed excellent electromagnetic properties, with relatively high TCR of 20.3%·K-1 and near room temperature TMI of 285.7 °C. Owing to these excellent properties, as-prepared thin films have application potential in infrared detectors.

In this study, La0.8-xYxSr0.2MnO3 (LYSMO) polycrystalline ceramics were prepared by means of sol-gel technique using methanol as solvent. X-ray diffraction (XRD) showed all samples to possess standard perovskite structure. Scanning electron microscopy (SEM) revealed samples with high compactness and grain size from 27.80 to 29.73 μm. Resistivity–temperature tests indicated sharp metal-insulator transition behavior of all samples accompanied by rapid transformation from ferromagnetism to paramagnetism (FM-PM). As Y3+ doping amounts rose, radius of A-site ions decreased, metal-insulator transition temperature (Tp) of polycrystalline samples shifted to lower temperatures, and resistivity increased. Temperature coefficient of resistance (TCR) and magnetoresistance (MR) were affected by introduction of Y3+. At x = 0.06, peak TCR and peak MR reached 4.85% K−1 and 52.34%, respectively. Using double exchange (DE) interaction mechanism, electric transport performances of as-prepared ceramics were explained. These findings look promising for future applications of LYSMO materials in magnetic devices and infrared detectors.

A series of La0.71Ca0.29Mn1−xVxO3 (x = 0.00, 0.01, 0.03, 0.05, 0.10) ceramic samples were synthesized via sol–gel method. Structural, electric, and magnetic transport properties of samples were characterized. Results show that all samples have perovskite phases, and no impurity phases were detected. Slight doping with V on B sites does not change perovskite structure of samples, but the doping leads to lattice distortion through modifying Mn–O bond lengths and Mn–O–Mn bond angles. The cell volume increased, melting point decreased, and abnormal grain growth occurred as the content of V increased. Temperature dependence of sample resistivities (ρ–T) was tested using standard four-probe method. Results show that slight doping with V can effectively increase temperature coefficient of resistance (TCR) up to 37.04% K−1 (x = 0.01). However, this decreases metal–insulator transition temperature (TMI). Meanwhile, ρ–T dependence in magnetic field (1 T) shows that V substituting for Mn can significantly increase magnetoresistance of La0.71Ca0.29MnO3 near room temperature by ~ 78.3%, showing the promise of this material for use in magnetoresistive sensors, contactless magnetoresistive switches, and memories.

La0.67−xDyxSr0.33MnO3 (x = 0.1, 0.12, 0.15, 0.20, 0.25, 0.30, 0.32) ceramics were prepared by sol–gel method. The samples were characterized by scanning electron microscopy, X-ray diffractometry, and resistance–temperature test (ρ–T) method. The experimental results showed that all of the samples were composed of a single phase with the orthorhombic perovskite structure and Pnma space group. The samples had high density, the average size of the grain decreased from 11.83 μm to 7.24 μm, while the number of grain boundaries increased. The one reason why resistance (ρmax) increases was supposed to be the boundary scattering enhancement, while the temperature corresponding to the peak resistivity (TP) decreases. The average cation radius of the A-site decreased as the amount/concentration of doping with Dy3+ increased, changing the bond length and bond angle. Meanwhile, the double exchange was suppressed, this being another and more important reason why the resistance increased and the TP decreased. The metal–insulator transition temperature wide degree (ΔT) and resistivity (ρ) are the important factors in the temperature coefficient of resistance. In the competition of the two factors, the ρ occupied an advantageous place, therefore the electrical properties of the materials can be further optimized by adjusting the average cation radius of the A-site.

La0.72Ca0.28MnO3:Ag0.2/LaAlO3 (100) thin films, prepared by pulsed laser deposition, were post-annealed at different temperatures in air. X-ray diffraction technique were used to analysize the orientation and lattice parameter, atomic force microscope (AFM) and scanning electronic microscope (SEM) were employed to characterize the surface morphology of the thin films. Resistance vs. temperature (R-T) behaviors of the thin films were tested with standard four-probe technique. The surface morphology results show that the grain size increases and crystalline quality of the films are improved with increased annealing temperature up to 1200 °C, while the amount of grains also increases; R-T results illustrate that both the temperature coefficient of resistance (TCR) and metal-insulator transition temperature (TMI) of the films, increase with annealing temperature. In particular, TCR of thin film (post-annealing at 1200 °C) reaches 28.8%·K−1, which makes such films be promisingly applicated in thermal detectors near the room temperature.