Effects of the joining process on the microstructure and properties of liquid-phase-sintered SiC-SiC joints formed with Ti foil

The joining of liquid-phase sintered SiC (LPS-SiC) ceramics was conducted using spark plasma sintering (SPS), through solid state diffusion bonding, with Ti-metal foil as a joining interlayer. Samples were joined at 1400 °C, under applied pressures of either 10 or 30 MPa, and with different atmospheres (argon, Ar, vs. vacuum). It was demonstrated that the shear strength of the joints increased with an increase in the applied joining pressure. The joining atmosphere also affected on both the microstructure and shear strength of the SiC joints. The composition and microstructure of the interlayer were examined to understand the mechanism. As a result, a SiC-SiC joining with a good mechanical performance could be achieved under an Ar environment, which in turn could provide a cost-effective approach and greatly widen the applications of SiC ceramic components with complex shape.     

Effects of argon sintering atmosphere on luminescence characteristics of Ca6BaP4O17:Sm3+ phosphors

In this paper, Ca₆BaP₄O₁₇:Sm³⁺ and Li⁺ co-doped Ca₆BaP₄O₁₇:Sm³⁺ phosphors were synthesized in air and argon atmospheres using a solid-state reaction method. The phosphor morphologies and crystal structure were studied using scanning electron microscopy and X-ray diffraction, respectively. The emission and absorption characteristics were investigated using photoluminescence emission spectroscopy and diffuse reflectance spectroscopy. The surface states and composition of phosphor were investigated using X-ray photoelectron spectroscopy. The emission integrated intensities of the phosphors sintered in an argon atmosphere increased 3.5 fold than the ones sintered in air atmosphere, with Li⁺ ions becoming embedded in the lattice of the Ca₆BaP₄O₁₇:Sm³⁺ phosphor. This occurs because there are fewer defect/oxygen vacancies and less of the secondary phase forms, leading to better Sm³⁺ emission. The results suggest that sintering a mixture of the raw materials of a phosphor in an argon atmosphere is a good approach for synthesizing Ca₆BaP₄O₁₇:Sm³⁺ phosphor powders. The color purity and CIE values of an optimized phosphor sample sintered in an argon atmosphere with an Li⁺ ion compensator were calculated to be ~ 99.6% and (0.612,0.386) in the orange–red region under 405-nm excitation, respectively. Moreover, the solid solubility of Sm³⁺ ions in the Ca₆BaP₄O₁₇ host can be enhanced by using an argon atmosphere in the synthesis process.     

比较调理啤酒鲈鱼片在不同贮藏条件下的品质变化

为开发鲈鱼调理食品,解决其贮藏时间短的问题,以本实验室开发的调理啤酒鲈鱼片为对象,通过普通包装(对照组)、真空包装和气调包装,测定其在4℃和-3℃条件下贮藏过程中的菌落总数、挥发性盐基氮(total volatile basic nitrogen,TVB-N)含量、硫代巴比妥酸(thiobarbituric acid,TBA)值、p H值、电导率、汁液流失率,结合感官评价,探究不同包装方式的调理啤酒鲈鱼片在4℃和-3℃条件下的品质变化规律。结果表明:不同包装方式的调理啤酒鲈鱼片在4℃或-3℃贮藏过程的汁液流失率、TVB-N含量、TBA值、电导率和菌落总数均随贮藏时间的延长而呈增长趋势,-3℃贮藏过程增长较缓慢;p H值在贮藏初期降低而贮藏后期增高;感官评分呈降低趋势。综合各项指标变化规律,调理啤酒鲈鱼片采用气调和真空包装的货架期优于普通包装,采用气调包装优于真空包装,其货架期在4℃下可达12 d,比普通包装和真空包装分别延长8 d和4 d;货架期在-3℃下可达50 d,较普通包装和真空包装分别延长35、15 d。与4℃贮藏相比,气调包装调理啤酒鲈鱼片在-3℃条件下能明显保持产品的品质并延长货架期,可满足当前冰鲜流通和消费的需求,为调理啤酒鲈鱼片的开发提供技术依据。     

Effects of CO Atmosphere on the Pyrolysis of a Typical Lignite

To reveal the effect mechanism of CO atmosphere on coal pyrolysis, a study on raw and demineralized lignite was carried out in a horizontal tube furnace under N₂ and CO/N₂ atmosphere. CO had a negligible effect on the char yield at low temperatures, whereas it enhances the char yield at temperatures higher than 550 °C. The release of tar was higher in the presence of CO above 450 °C because of more free radicals, which reduced low‐temperature crosslinking, and higher selectivity of hydroxyl groups to phenols in the CO‐containing atmosphere. The yields of CO₂ and H₂ increased, water and CO yields decreased under CO/N₂ atmosphere. Light hydrocarbon gases were not affected by changing the reaction atmosphere. The difference between product yields from raw and demineralized coal confirmed that the catalysis of inherent minerals had a great catalytic effect on the water‐gas shift reaction and Boudouard reaction.     

Investigation of the piezoelectric and anti-reduction properties of (Ba,Ca) (Ti,Sn, Hf) textured ceramics prepared under low oxygen partial pressure conditions at low sintering temperatures

Multilayer piezoelectric ceramics must be sintered in a reducing atmosphere, preventing oxidation of the inner base metal. Plate-like textured (Ba, Ca)(Ti, Sn, Hf)O₃ ceramics with a <001> preferred orientation were successfully developed at a low oxygen partial pressure (PO₂:10^?8 atm) using a BaTiO₃ (BT) template with sintering temperatures < 1300 °C, which is beneficial for multilayer applications using base metal co-firing with ceramics. When adding the 3 wt% BT template, the proposed samples had a Lottgering factor of 84 %, piezoelectric coefficients d₃₃ = 324 pC/N, -d₃₁ = 122 (pC/N), and Q_m = 452, and the strain values increased from 0.07 % for the randomly oriented ceramics to 0.115 % at 20 kV/cm for the textured ceramics, confirming that the texturing behavior assisted the grain growth and improved both the soft and hard behaviors and insulation resistance of the proposed lead-free ceramics. These findings make a significant contribution to the production of high-power piezoelectric components.     

Effect of pre-harvest and post-harvest conditions on the fruit allergenicity: A review

Fruits are an important source of vitamins and antioxidants that can effectively delay aging and contribute to health and well-being of the human kind. However, they are growing to be one of the primary elicitors of food allergies around the world. Fruit allergens can induce an IgE-mediated (Immunoglobulin E) reaction, presenting with a symptom like localized oral allergy syndrome (OAS). Numerous studies showed that varying environmental and cultivation conditions can influence the fruit allergen content during flowering and ripening stages. Further, the variety, harvesting maturity, and storage conditions can also significantly influence the allergenicity potential. For example, unripe apples and tomatoes have lower levels of allergens compared to ripened fruits. Researchers have also reported that modified atmosphere packaging (MAP) can help reduce Mal d 3 content present in apples during storage. Post-harvest processing like peeling is also considered a good method to help reduce the overall allergenicity in few fruits whose peel might contain majority of the allergens. This review will discuss the overall influence of both pre-harvest and post-harvest factors on the fruit allergens. We will also discuss the progress regarding the cause, symptoms and diagnostic methods of fruit based allergies.     

N2和CO2气氛下辽河稠油热解过程及产物性质

利用热重分析仪（TGA）和固定床反应器对辽河Q块稠油在N₂和CO₂气氛下的热解过程及产物性质进行了研究。TGA实验结果表明，2种气氛下的稠油热解过程均可划分为轻组分与水分挥发、组分较弱化学键断裂和重组分裂解产油成焦3个阶段，热解曲线总体变化趋势类似。固定床反应器热解实验结果表明，随温度升高，2种气氛下的液体产物产率均升高，热解气和残余物产率均降低，CO₂气氛下650 ℃液体产物最大产率为61.53%。不同温度下热解所得液体产物和稠油的红外谱图显示，随热解温度升高，甲基含量增多、亚甲基含量减少。对液体产物的氧化过程进行TGA分析发现，随热解温度升高，其失重曲线向高温区明显偏移且失重程度减弱，CO₂热解所得液体产物的氧化失重比N₂快。     

High-temperature properties and interface evolution of silicon nitride fiber reinforced silica matrix wave-transparent composite materials

In order to improve the high-temperature performance of wave-transparent materials especially for the high-speed aircrafts application, filament winding combined with sol-gel method was adopted to the fabrication of unidirectional silicon nitride fiber reinforced silica matrix composites. The mechanical properties and the interface evolution at high temperatures were investigated. The results show that the composite sintered in N₂ maintains a flexural strength of 210MPa at up to 1200°C, while its counterpart prepared in air experiences a dramatic reduction to about 73MPa. The degradation is due to the partial oxidation of silicon nitride fibers at the fiber matrix interface. Besides, it is also notable that the bending strength of these two composites undergoes a similar growth from about 160 to 210MPa when tested under 900°C, which can be explained by the release of thermal stress on the silicon nitride fibers.