高分子材料的热分析

高分子材料的种类非常多,用途也非常广泛,从日常生活到航天领域,几乎无不使用高分子材料。真正的多媒体时代已经到来,对图像、声音、数据保存用的大容量记录介质来说,高分子材料更是不可缺少的。一切物质的性质都依温度的变化而变化。例如,CD－R及DVD－R等光盘就是巧妙地利用了有机染料的热特性。高分子材料被用作记录材料的基本材料,对热塑性、热固性树脂进行热力学分析测量是十分必要的。本文介绍了典型的热分析装置──DSC、TG、TMA和DMA的概要和特点。     

酱卤牛肉的质地及风味改良研究

在传统的酱卤牛肉生产制作工艺基础上,采用目前应用于肉类、鱼类等衍生产品中为提升样品质地特性的TG酶水解法,应用于酱牛肉制作前处理中,探究其对酱牛肉质地的影响,结果表明经过TG酶水解后,酱牛肉的质地得到改善。采用乳酸菌发酵法,通过前期乳酸菌发酵液对牛肉的发酵,探究其对酱牛肉风味的影响,结果表明经过乳酸菌发酵后,制作的酱牛肉风味得到明显增强。经过这两种工艺改良后的酱牛肉具有色泽均一、香味诱人、肉汁浓郁、肉质紧实有嚼劲的特点。     

等温热重法生物质空气气化反应动力学研究

应用等温热重法对４种生物质焦样与空气气化反应进行研究。利用热天平进行实验,对所得重量－时间曲线加以分析和处理,从而可得出４种焦样的化学反应动力学参数、反应速率方程式。为城市生活垃圾的气化提供了理论依据。     

Gasification of diosgenin solid waste for hydrogen production in supercritical water

The potential of diosgenin solid waste (DSW) to be a proper feedstock for hydrogen production from supercritical water gasification was assessed through thermodynamic analysis and experimental study. The thermodynamic analysis of DSW gasification in SCW was performed by Aspen Plus software based on the principle of minimum Gibbs free energy. The effects of temperature (500–650 °C), flow ratio of feedstock slurry to preheated water on the gasification were studied. K₂CO₃ and black liquor were used to catalyze the gasification of DSW. The morphological structures of DSW and residue char were characterized by SEM. The results showed that DSW was almost completely gasified at 650 °C without catalyst and the carbon gasification efficiency reached up to 98.55%. K₂CO₃ could significantly promote the gasification reactivity of DSW at a lower temperature. H₂ yield was remarkably improved by adding black liquor. The SEM analysis indicated that parts of the organic matters reacted to form gases and liquid products, and K₂CO₃ was found to migrate into the residue char during the reactions.     

Study on combustion characteristics and pyrotechnic cutting effects of bimetal thermite Ni/Al/Fe2O3 system

Nano-thermite has become a subject of significant interest in the composite energetic materials field due to its high energy release rate. To cater to diverse engineering needs, thermite formulations are often customized to fulfill specific criteria. This study investigates the potential of metal nickel (Ni) as an additive to modify nano-thermite formulations, selected for its optimal calorific values and chemical reactivity. The base materials, nano-aluminum (Al) and iron oxide (Fe₂O₃), are blended with varying mass ratios of Ni (1 %, 3 %, 5 %, 7 %, 9 %) using the wet ball milling method. Pre-reaction and post-reaction morphological and compositional alterations in the resultant thermite samples are scrutinized through SEM and XRD characterization tests. Moreover, DSC analysis and combustion experiments were conducted to examine the pyrolysis and combustion behaviors of the evaluated samples. The results reveal a reduced exothermic peak on the DSC curves with the introduction of Ni, making the liquid-solid (L-S) phase reaction more challenging compared to the Al/Fe₂O₃ thermite. Intriguingly, Ni addition progressively decreases the combustion temperature of thermites as the Ni's mass ratio increases, with a peak efficiency at 7 % in the perforation tests on stainless-steel plates. This research further reveals that the thermite reaction mechanism is a combined consequence of the “pre-ignition-fusion” and “fusion-diffusion” mechanisms. These insights can provide valuable guidance for designing thermite formulations for potential applications in storage, management, and pyrotechnic cutting areas.     

Effect of Melt Processing on Crystallization Behavior and Rheology of Poly(3‐hydroxybutyrate) (PHB) and its Blends

Poly(3‐hydroxybutyrate) (PHB) is sensitive to high processing temperatures. This leads to a decrease in molar mass as well as a lower melt viscosity. The crystallization temperature shifts to lower values, and crystallization kinetics is slow. A mixture was developed in order to improve the manufacturing properties and the final product. The blends exhibit a slight reduction in molar mass because they have a lower melting point than pure PHB, and can be extruded at their melt temperature of 170 to 180°C. Then they immediately crystallize at 125 to 100°C. Differential scanning calorimetry (DSC) shows the effect of holding time in the melt on crystallization behavior. It has been shown that the crystallization time has to be longer in the case of PHB and shorter for the blends. Thermal degradation of PHB and its blends has been investigated using thermogravimetry analysis (TG). Derivative thermogravimetry coupled with TG (TG/DTG) curves show three decomposition stages for blends at 290, 340 and 445°C, respectively. Acetic acid, water, carbon dioxide and methane are produced by degradation at a higher temperature.     

电感耦合等离子体原子发射光谱法测定TG6钛合金中镁钒铬铁钴铜锰钼钨

选择水-盐酸-氢氟酸-硝酸混合酸体系溶解样品,控制雾化气流速为0.65 L/min,建立了电感耦合等离子体原子发射光谱法(ICP-AES)测定TG6钛合金中镁、钒、铬、铁、钴、铜、锰、钼和钨的方法。考察了钛基体和共存元素对待测元素的影响,确定各待测元素分析线为Mg 285.2 nm、V 310.2 nm、Cr 283.5 nm、Fe 259.9 nm、Co 238.8 nm、Cu 213.5 nm、Mn 257.6 nm、Mo 202.0 nm、W 207.9 nm。采用基体匹配法消除了基体影响。方法检出限为0.000 3～0.005 7 μg/mL。采用方法对实际样品分析,结果的相对标准偏差为0.26%～13.6%,加标回收率为93%～110%。按照TG6钛合金的名义成分Ti-5.8Al-4Sn-4Zr-0.5Ta-0.7Nb-0.4Si-0.06C配制模拟TG6钛合金样品,实验方法测得结果与理论值基本一致。     

淬火- 非等温碳分配下淬火温度对显微组织的影响

以低碳Si- Mn钢为研究对象,在MMS- 300热力模拟实验机上,分析了在DQ&P（Direct quenching & Partitioning）工艺的非等温碳分配条件下,淬火温度对试样显微组织、残余奥氏体含量和残余奥氏体中碳含量的影响。结果表明：试样的显微组织由板条状马氏体、残余奥氏体及少量铁素体组成;在320 ℃较高的淬火温度条件下,马氏体板条边界变得不明锐且弯曲,同时,碳化物沉淀含量增加;残余奥氏体含量随淬火温度的升高先增加后减少,在240 ℃时达到最大值;残余奥氏体中碳含量随淬火温度先减少后增加。     

考虑非等温混合的能量集成用水网络综合

提出了考虑非等温混合的新的水网络模型,并结合线性规划（LP）转运模型同时优化水网络的水耗及公用工程目标。新的水网络模型引入非等温混合以改善用水网络的能耗特性及减少模型中参与集成换热网络的流股数,从而降低设计换热网络的复杂程度。在确定水网络的水耗及公用工程目标后,采用夹点法设计详细的换热网络结构。两个算例结果表明,新的水网络模型不仅能确定用水网络的最优水耗及公用工程目标,而且还能得到一个更加简单的换热网络。这对节省设备投资及减少操作费用具有重要意义。