凝胶法制备Cu-BTC块体及其吸附脱除二甲基二硫醚性能

金属有机骨架材料Cu-BTC具有高孔隙率、易调控的骨架结构以及含过渡金属等特点,是吸附脱除硫化物的优异材料。采用凝胶法在常温条件下制备块状样品Cu-BTC-g,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)、红外光谱(FT-IR)、拉曼光谱(Raman)、X射线光电子能谱(XPS)、N₂吸附-脱附等手段对其进行分析表征,同时测定Cu-BTC-g样品对模型硫化物二甲基二硫醚(DMDS)的静态吸附容量、吸附热力学和动力学特性。结果表明：凝胶法制备的Cu-BTC-g样品晶体平均尺寸约为0.2μm、比表面积为901 m²/g、孔体积为0.40 cm³/g,晶体尺寸、比表面积和孔体积均小于溶剂热法合成的样品Cu-BTC-s;在吸附温度298 K下,Cu-BTC-g样品的DMDS吸附容量为110.8 mg/g,比Cu-BTC-s样品提高12%。     

The effect of washing process on the cracking of ZrO2 microspheres by internal gelation

ZrO₂ microspheres are widely used as a simulant of UO₂ in the development of nuclear fuel. However, the cracking of ZrO₂ microspheres prepared by internal gelation is still a challenge during drying and sintering processes. To address this issue, we designed and optimized the washing process for obtaining crack-free ZrO₂ microspheres. Through thermogravimetric, infrared, Raman, BET, and SEM analysis, it is shown that the cracking of the microspheres is mainly related to the pores in microspheres. The washing solvent with low surface tension is used to reduce the effect of capillary force on pore shrinkage. Therefore, the optimal washing process was designed as trichloroethylene (TCE)—0.5 M NH₃.H₂O—Propylene glycol methyl ether (PM) and gel microspheres with a high specific surface area of 315.3 m²/g and pore volume of 0.4125 cm³/g were obtained. The characterizations also further showed that when the microspheres were dried and sintered, the water vapor and the decomposition gas of organic matter were completely released from the pores in the microspheres. Our new washing process could be directly extended for preparing crack-free ceramic microspheres by internal gelation.     

Viscoelastic properties and flow instabilities of aqueous suspensions of cellulosic fibers: Effects of a gelation agent on dispersion,rheology, and flow stability

Processing of concentrated lignocellulosic biomass suspensions typically involves the conversion of the cellulose into sugars and sugars into ethanol. Biomass is usually pretreated via methods like comminution or steam explosion to form fine cellulosic fibers to be dispersed into an aqueous phase for further treatment. The resulting cellulose suspensions need to be pressurized and pumped into and out of various processing vessels without allowing the development of flow instabilities that are typically associated with “demixing”, that is, the segregation of the cellulosic biomass from the aqueous phase via the formation of mats of cellulosic fibers and the filtration of the aqueous phase. Such demixing can prevent continuous processing at high rates. Here, the development of flow instabilities via the demixing effect for cellulose suspensions is demonstrated using capillary and compressive squeeze flows. It is shown that the use of a gelation agent, hydroxypropyl guar gum, at the critical concentration of 0.5 wt% or higher significantly affects the viscoelastic material functions of cellulosic suspensions, improves the dispersive mixing of the fibers within the aqueous phase, and results in the elimination of the flow instabilities and associated demixing effects that are ubiquitously observed during the pressurization and processing of cellulosic suspensions.     

Optical Properties of Self‐Assembled Cellulose Nanocrystals Films Suspended at Planar–Symmetrical Interfaces

Hierarchically structured materials comprising rod‐like, chiral, nanoparticles are commonly encountered in nature as they can form assemblies with exceptional optical and mechanical characteristics. These include cellulose nanocrystals (CNCs), which have a large potential for the fabrication of bioinspired materials mimicking those advanced properties. Fine‐tuning the optomechanical properties of assemblies obtained from CNCs hinges on the transformations from suspensions of liquid crystals to long‐range order in the dry state. So far, associated transitions have been studied using trivial interfaces such as planar substrates. Such transitions are explored as they evolve onto meshed supports. The meshed substrate offers a complex topology, as is encountered in nature, for the formation of CNCs films. The CNCs self‐assembly occurs under confinement and support of the framework bounding the mesh openings. This leads to coexisting suspended and supported nanoparticle layers exhibiting nematic and/or chiral nematic order. Optical microscopy combined with crossed polarizers indicate that the formation of the suspended films occurs via intermediate gelation or kinetic arrest of CNCs across the mesh's open areas. The formation of self‐standing, ultrathin films of CNCs with tunable optical properties, such as selective reflections in the visible range (structural color), is demonstrated by using the presented simple and scalable approach.     

Preparation of Hemodialyzer Made from Polyethersulfone Membrane by Dual-bath Coagulation Method

The dual-bath coagulation method was used for the preparation of PES membrane in this experiment. The main intent of this stndy was to assess the efforts of gelation conditions on the structures and properties. The dense top layer as well as porous supporting layer can be made by duel-bath coagulation method simultaneous- ly. Different internal quench medium obtained different membrane with different structures. With the increase in time in the first coagulation bath, pure water flux decreased and the clearance rates of urea and creatinine both first increased then decreased and increased slightly in the end. With the temperature of the second coagtdation bath increasing, pure water flux increases and the clearance rates of urea and creatinine first increases then de- creases and increases a little at last. Higher DMSO concentration （wt/wt） in the second coagulation bath results in the increase of pure water flux and the decrease of urea ＆ creatinine clearance rates.     

不同加工条件对全豆豆腐凝胶强度的影响

针对全豆豆腐加工中豆腐凝胶强度低的问题,研究了全豆豆腐煮浆工艺和凝固工艺中酶添加量、凝固温度、凝固时间和NaCl添加量对全豆豆腐凝胶强度的影响。得出全豆豆浆加热至90℃,保温10min的加热条件下,全豆豆腐凝胶强度最佳。通过单因素和正交实验,得到最佳的凝固条件为:酶添加量1.2U/mL豆浆、凝固温度50℃、凝固时间2h和NaCl添加量0.125%,制得的全豆豆腐品质优良,几乎包含大豆全部营养,比传统豆腐营养更丰富。      

黄油的研究进展

近年来国内黄油的贸易量、关注度和研究热度显著上升。黄油开发及创新面临着如何提升感官特性、健康品质和绿色发展水平等多重挑战。作者综述了黄油市场及国内外研究现状,分析了未来黄油研发的重点方向与解决方法,重点探讨了未来黄油的原料创新和技术创新方式,旨在为当前黄油生产和新型黄油开发提供参考。     

胶凝化工艺对年糕水分分布状态和微观结构的影响

以糊化度、白度值、感官评分、蒸煮特性及质构特性为年糕的品质评价指标,研究胶凝化时间、胶凝化温度及胶凝化湿度对年糕品质的影响,并采用正交试验优化工艺条件.在优化条件下,研究在不同胶凝化时间下,年糕的水分分布和微观结构的变化.结果表明:胶凝化时间、胶凝化温度及胶凝化湿度分别通过影响年糕的胶凝化程度、速率及水分分布,改变年糕...     

漂洗对罗非鱼鱼糜凝胶特性的影响

针对未漂洗鱼糜凝胶强度差、凝胶易劣化等问题,以罗非鱼为原料,研究漂洗工艺对鱼糜凝胶特性的影响规律.结果显示:与未漂洗鱼糜相比,漂洗鱼糜的白度值较高,为52.95;持水率提高到91.06％;凝胶强度达到了3839.3 g·mm.未漂洗鱼糜的硬度和咀嚼性显著高于漂洗鱼糜,而黏聚性、回复性和凝胶强度则比漂洗鱼糜更佳.流变特性...     

Effect of pH adjustment at heating on the rheological properties of acid skim milk gels with added potato starch

The rheological properties of acid skim milk gels, prepared from milk with added potato starch and pH adjusted (pH 6.5–7.1) prior to heat treatment and acidification, were investigated. The storage modulus, G′, of the final acid gels was increased by heating the milk at higher pH and further increased by adding starch. The effect of pH at heating and addition of starch appeared to be additive and independent of each other up to a starch addition level of 1%. Above this starch level, the pH at heating had a lesser effect. This may have been due to the increased viscosity of the aqueous phase as a result of starch gelatinization or to direct contributions of the starch to the gel network structure. Confocal microscopy showed that milk proteins developed fewer but broader protein clusters at higher pH than at lower pH. Starch addition resulted in an increased density of the protein network.