湖北中烟工业有限责任公司

[Background and purposes]Negative temperature coefficient(NTC)thermosensitive ceramics are critical for temperature sensing applications,whereas their high resistivity in systems like Y2O3-YCr0.5Mn0.5O3 limits practical use.Although prior doping with Zr4+enhanced densification,the resistivity was further increased,deviating from the desired scale of kΩ·cm.Adjusting the phase ratio offered limited resistivity control and compromised thermal stability.This study was aimed to explore co-doping with alkaline earth ions to synergistically optimize resistivity,B-value and aging stability of Zr4+-modified 0.6Y2O3-0.4YCr0.5Mn0.5O3 ceramics. [Methods]The samples were prepared by using a two-step sintering process at 1600 ℃.A baseline group(A0)was co-doped with 4-8 mol％CaO(A1-A3)or MgO(A1 1-A13).Phase composition was analyzed by using XRD,elemental distribution and valence states were characterized by using SEM-EDS and XPS.Electrical properties were measured after electrode coating.Aging resistance was evaluated by resistance drift(％)after 800 h at 300 ℃. [Results]All samples retained dual-phase structures.Ca2+/Mg2+dissolved primarily in the perovskite phase,forming a dense"sea-island"microstructure.Ca2+doping drastically reduced resistivity.At 8 mol％,the room-temperature resistivity(ρ)decreased by approximately 82％compared to the undoped sample(A0),while the B-value remained in the range of 2500-3000 K.In contrast,with 4 mol％Mg2+doping,ρ was lowered to 5.14×104Ω·cm,accompanied by higher B-values of 3300-3500 K.XPS revealed that the Mn4+/Mn3+and Cr4+/Cr3+ratios increased after doping,which was attributed to charge compensation:Ca2+substitution at Y3+sites generated holes and enhanced small-polaron hopping.Mg2+likely enabled partial B-site substitution,weakening its impact.Aging tests showed that doping with Ca2+/Mg2+increased the resistance drift;however,the presence of Zr4+suppressed the drift by 1-2％through densification and grain refinement,thereby impeding cation vacancy migration. [Conclusions]The doping with Ca2+effectively reduced the resistivity of Zr4+-modified NTC ceramics through charge compensation and enhanced polaron hopping,while maintaining a low B-value for wide temperature applicability.Mg2+'s inferior performance stemmed from possible B-site substitution and limited vacancy generation.Crucially,Zr4+mitigated the negative aging effects of Ca2+/Mg2+by improving microstructural stability.The Ca2+/Zr4+co-doping strategy achieved balanced electrical properties and reliability,demonstrating significant potential for the development of industrial NTC thermistors.

Yarn-based microfluidic technology is an emerging tool that uses the hierarchical pores between the well-aligned fibers in the yarn as microchannels to process small volumes of fluid. By adjusting the physicochemical properties of the fibers, the structure of the yarn, and the way the yarns are woven, the fluid behavior on the yarn can be manipulated, including absorption, transport, separation, and mixing. Compared with traditional silicon-based or polymer-based microfluidic systems, yarn-based microfluidic devices have significant advantages in terms of cost, biocompatibility, wearability, compatibility with traditional textile processes, and environmental sustainability, and show great potential in biochemical analysis, health monitoring, and drug screening. Yarn-based fluid flow can be traced back more than 3000 years. The ancients used the yarn twisted with plant fibers to carry turpentine or oil for lighting. With the advancement of the textile industry, the study of yarn or textile-based fluid behaviors has been fueled up by its critical role in fabric dyeing and washing. The gaps between adjacent fibers act as microscale channels to generate capillary pressure, which drives the spontaneous flow of liquid into the yarn. Many studies confirm that the flow behavior of liquid on a yarn follows the Washburn-Lucas model, in which the flow rate was determined by the hydrophilicity of the yarn, the size of the capillary channel, the surface tension between the liquid and vapor, and the liquid viscosity. Based on the model, two strategies were used to tune the wicking performance of the yarns: (1) Controlling the hydrophilicity of the fibers by alkaline solution boiling, plasma treatment, and surface modification; (2) adjusting the yarn structures, including fiber shape, fiber number, pore size, and porosity. As a biofluid containing abundant metabolites such as ions, vitamins, glucose, lactate and uric acid, sweat is considered a promising biosample for non-invasive diagnostics. Yarn-based sweat microfluidic technology has attracted great interest in recent years due to its excellent sweat collection and transport capabilities, high flexibility and skin conformability, and good compatibility with the textile industry. In recent years, this technology has been successfully applied to the fabrication of devices for health monitoring, power supply, and human-computer interaction. Yarn-based microfluidic sensors have been developed to detect biomarkers in sweat by colorimetric or electrochemical reactions. The glucose and lactate in sweat have also been used as biofuels to generate electricity with the yarn-based microfluidic fuel cells. Since sweat is a natural electrolyte, it has also been utilized to activate yarn-based batteries and yarn-based supercapacitors. Water, as the most abundant component in sweat, could be employed to trigger electricity generation with yarn-based hydrovoltaic generators and shape change of textiles with yarn-based actuators. In this comprehensive review, we first trace the development of yarn-based microfluidics and introduce the principle of yarn-based wicking and the strategies for fine-tuning the wicking performance. Then, we summarize yarn-based sweat microfluidic devices for various applications, including sweat sensing, sweat-driven power supply, and sweat-driven textile deformation. The above devices not only demonstrate the enormous potential of yarn-based sweat microfluidic devices in sweat analysis, power supply, and actuators, but also underscore their pivotal role in promoting intelligent wearable systems for health monitoring and motion analysis. In-depth research in this area is expected to foster significant advances in smart fabrics and wearable technology, improving the overall convenience and well-being of human health and daily life.

[Background and purpose]Silicon carbide(SiC)ceramics,with their superior physical properties,are widely utilized in various industrial sectors,particularly under harsh conditions such as high temperatures and pressures.Reaction-bonded silicon carbide(RBSC),favored for its ease of manufacturing and cost-effectiveness,has traditionally required vacuum sintering,which limits production capacity and increases costs.This study is aimed to study the feasibility of pressureless reaction sintering of SiC through infiltration of silicon melt and molybdenum-silicon(Mo-Si)alloy under argon(Ar)protection,in order to enhance process efficiency and reduce costs. [Methods]In this study,the effects of different melt infiltrations on the sintering behavior of SiC ceramics were systematically examined.Mo-Si alloy was prepared by mixing and melting molybdenum and silicon powders according to the phase diagram,followed by crushing into small pieces under Ar at 1500 ℃ in BN crucible.Ceramic samples were fabricated using a-SiC powder,carbon black,phenolic resin,and other additives,which were mixed and pressed into rectangular bars.After pre-firing to remove binders,the green bodies were then infiltrated with either silicon or Mo-Si alloy melts at temperatures between 1530 ℃ and 1600 ℃.Density,microstructure,flexural strength,and hardness of the sintered samples were analyzed by using the Archimedes method,scanning electron microscopy(SEM),electronic universal testing machine,and Vickers hardness. [Results]It is found that the infiltration effect of silicon melt on physical properties of the sintered samples was highly sensitive to the processing temperature.For instance,the flexural strength was increased from 58.6 MPa at 1530 ℃ to 317.0 MPa at 1570 ℃ for the silicon-infiltrated samples.Meanwhile,Mo-Si alloy-infiltrated samples achieved a relative density exceeding 94％at 1530 ℃,due mainly to the higher polarizability of the Mo-Si alloy,reducing the contact angle between silicon and carbon.The mechanical properties of the Mo-Si alloy-infiltrated samples remained stable across the tested temperature range but were lower than those of silicon-infiltrated samples at 1570 ℃ due to the segregation of MoSi2. [Conclusions]It has been demonstrated that pressureless reaction sintering of SiC is feasible under Ar protection,especially when using Mo-Si alloy as the infiltration material,allowing for nearly full densification at relatively low sintering temperatures.However,the presence of MoSi2 led to decreased mechanical properties as compared with silicon melt.While introducing Mo-Si alloy offers advantages in terms of reducing sintering temperature,further optimization is necessary to address the issue of MoSi2 segregation and improve the overall performance of the SiC ceramics.

Existing wastewater treatment systems suffer from low automation levels,high operating costs and un-stable effluent.The application of optimization algorithms improves the treatment efficiency and automation control level of water treatment process.Several major optimization algorithms for wastewater treatment systems were re-viewed,including genetic algorithm(GA),particle swarm optimization algorithm(PSO),random forest(RF),artificial neural network(ANN),fuzzy logic control(FLC),and hybrid optimization algorithms.The advantages and disadvan-tages of each type of optimization algorithms as well as the scope of their application were introduced,followed by a discussion of the role of optimization algorithms in the monitoring and cleaning of water quality anomalies,operation parameters prediction,control parameters optimization,and multi-objective optimal control,prediction,control pa-rameter optimization and multi-objective optimal control,etc.The application of optimization algorithms enhanced the level of automation and control of wastewater treatment,the quality of effluent,reduces the operating costs,and opti-mizes the prediction and adjustment of operating parameters.Finally,the challenges of applying optimization algorithms in practical engineering were explored,the limitations in algorithm optimization and system integration technologies were highlighted,and the development direction for optimization algorithms in water treatment was proposed.

【Objective】The use of artificial inoculation to ferment cigar tobacco leaves is an inevitable trend in the industrial production of cigar tobacco leaves, and the neutral aroma components are the important quality components of cigar tobacco leaves. The study aims to investigate the effect of Bacillus safensis GL2 on the neutral aroma components of cigar tobacco leaves.【Method】GL2 was screened from Cuban cigar Cohiba Robert and used to ferment cigar leaves. The neutral aroma components in tobacco leaves were determined by distillation extraction-gas chromatography-mass spectrometry, and multivariate statistical methods were used for analysis and statistics.【Result】The total aroma and the contents of most neutral aroma components in cigar tobacco leaves were significantly increased after GL2 fermentation (P < 0.05), and the increased aroma substances mainly included olefins, ketones and alcohols. A total of 13 differentially neutral aroma components were selected by VIP > 1 and P < 0.05, and 9 of them were significantly up-regulated and positively correlated with tobacco leaf aroma. There were 7 species with significant positive correlation (P < 0.05), which were the key differential aroma components of 2, 6, 6-trimethyl-2-cyclohexene-1, 4-dione, 2, 6, 6-trimethyl-1, 4-cyclohexanedione, geraniyl acetone, acanthyl acetone, neophydiene, solanone and phytoalcohol. In addition, 4 different aroma components were significantly decreased and negatively correlated with tobacco leaf aroma, among which 2, 4-di-tert-butyl-6-nitrophenol was significantly negatively correlated with cigar tobacco aroma (P < 0.05). 2, 6, 6-trimethyl-2-cyclohexene-1, 4-dione, geranyl acetone, solanone and phytol contributed significantly to the aroma of fermented cigar tobacco leaves, resulting in a stronger overall dry and floral fragrances. As a result, they enriched the aroma and improved the sensory quality of cigar tobacco leaves.【Conclusion】Inoculation of B. safensis during cigar tobacco fermentation is beneficial for improving the quality of cigar tobacco leaves, which provide theoretical support for improving the fermentation quality of cigar tobacco leaves with biotechnology.