用玻璃化转变评价氟橡胶的低温性

针对普通氟橡胶耐低温性差的缺点,以低温性好的PL855、GLT两种牌号氟醚生胶为基体制备了氟醚硫化胶。阐述了用玻璃化转变评价氟橡胶低温性的原理,采用差示扫描量热仪测试了不同升温速率下氟醚生胶的玻璃化转变温度,采用动态热机械分析仪测试了不同频率下氟橡胶的玻璃化转变温度,根据所得数据计算玻璃化转变活化能。结果表明,PL855氟醚生胶的玻璃化转变温度和玻璃化转变活化能均比GLT氟醚生胶低,耐低温性更好;用两种氟醚生胶硫化而成的橡胶的耐低温性均比普通氟橡胶的耐低温性好,其中以PL855氟醚生胶制成的橡胶的耐低温性最好。该方法的评价结果与实际应用情况相符合。     

粉末涂料的玻璃化温度

重点讨论了粉末涂料玻璃化温度、玻璃化转变理论,并对玻璃化温度与粉末涂料稳定性、熔融黏度、热应力、分子量、化学结构和聚合物的关系做了全面的阐述。     

气固两相流穿越液池过程颗粒运动及分布特性

为了揭示气固两相流穿越液池过程中的气液固三相流动特性,建立了气液固三相实验平台和基于Euler-Lagrange框架下的数值模拟平台,对该过程中的气液固三相流动过程及颗粒运动分布规律进行研究。获得了5～15 μm、80～110 μm和380～530 μm 3种典型粒径颗粒在三相体系中的微观运动过程及其分布规律。实验与数值模拟结果均能反映出一致的客观规律。研究发现,颗粒浓度沿液池高度方向和径向均呈现多峰分布特征;5～15 μm粒径颗粒更易跟随气体一起穿越液池,其在液池内的浓度分布较为均匀;380～530 μm粒径颗粒与气体的跟随性较差,其浓度峰值主要集中在液池底部。随着下降管出口静态浸没深度的增加,液池内颗粒浓度分布趋于平缓。     

Preparation of one-part geopolymeric precursors using vanadium tailing by thermal activation

The main purpose of this study is to develop a user-friendly one-part geopolymer using vanadium tailing (VT). Geopolymeric precursor consists of activated VT and metakaolin that can react directly with water to form geopolymers. The roasting temperature plays an important role in the VT activation, which affects the compressive strength of the final geopolymer. The geopolymer with accepted compressive strength, that is 29.0 MPa after 7 days curing in ambient condition, can be prepared using VT after thermal activation at appropriate temperature (400-600°C). As the roasting temperature is increased to 700°C, the VT is molten and sintered and the ability of providing alkaline and Si⁴⁺ is drastically weakened, which results in a poor compressive strength geopolymer.     

热活化温度对氧化铝赤泥反应活性的影响及机理研究

通过热重-差热分析（TG-DTA）赤泥的相变温度,通过X射线衍射（XRD）、红外光谱（FT-IR）分析赤泥热活化前后矿物的组成变化和键能变化,并以活性指数来评定活化赤泥的反应活性,分析了热活化温度对赤泥反应活性的影响规律和作用机理。实验结果表明:热活化后赤泥中硅酸二钙的衍射峰明显,硅酸二钙增多,方解石分解转化成不稳定的高活性物质,Si—O键和Al—O键的结构稳定性降低;热活化温度低于700 ℃时,赤泥的活性指数随着活化温度的升高而增加,700 ℃时活化赤泥的活性指数比原生赤泥提高19.1%,而热活化温度升高至800 ℃时,活化赤泥的活性指数急剧下降。     

温度调制热分析技术对预吸热峰的研究

以快速的冷却速率冷却熔体获得的金属玻璃通常远离平衡状态。如果在适当温度经过合适时间退火后,在热流曲线上玻璃转变温度之前会产生明显的预吸热峰。使用常规差示扫描量热法(DSC)和温度调制差示扫描量热法(TMDSC)对Pd₄₀Ni₁₀Cu₃₀P₂₀和Au₄₉Ag_5.5Pd_2.3Cu_26.9Si_16.3两种金属玻璃进行研究。结果表明,预吸热峰从玻璃态到过冷液态是一个连续演变过程,当预吸热峰出现在玻璃转变温度之下时,预吸热峰向高温移动过程中对玻璃化转变过程没有影响。然而,当预吸热峰出现在玻璃化转变温度以上时,玻璃转变开始温度会随着预吸热峰值的增加而增加,因此金属玻璃的动力学稳定性得到了提高。实验结果对理解预吸热峰从玻璃态到过冷液态过程中的稳定变化具有重要意义。     

利用粉煤灰低温熔制基础玻璃的研究

以粉煤灰为主要原材料,添加适当的工业级硼酸、石灰石、氧化锌、氧化镁、二氧化硅、碳酸钠作为辅助材料,选择铝硅酸盐系统作为配方,制备基础玻璃。通过DTA和TEM研究不同配比的基础玻璃配方表明,最合理基础玻璃在1 200℃熔制是可行的,粉煤灰的利用率达到了30%以上,最适宜的玻璃组成是(%):S iO245~60,A l2O39~15,CaO 12~20,MgO 2~5,Na2O 3~11,ZnO 2~5,S 0~1,B2O30.5~1.5,F 0~2.5。     

温度和电流密度对亚硫酸盐电镀金的影响

采用亚硫酸盐体系镀液在紫铜表面电镀金.研究了镀液温度和电流密度对电镀金层晶相结构和纳米硬度的影响.结果表明,随着镀液温度升高,金层由(220)面择优生长转变为(111)面择优生长,纳米硬度变化不大.随着电流密度增大,金层由(111)面择优生长转变为(220)面择优生长,纳米硬度减小.电镀金层的晶粒尺寸受镀液温度和电流密...     

高温辐射环境中液滴的沸腾效应

建立了液滴在高温对流和辐射环境中的受热和蒸发模型,结合液滴均质沸腾模型,编制了计算程序。以正十二烷液滴为例,考虑液滴的膨胀效应以及液滴与周围气流的热物性变化,数值模拟了高温辐射与对流加热下的液滴升温和蒸发过程。分析了不同对流和高温辐射条件下,液滴内部是否能够发生沸腾。研究表明,液滴在高温辐射和对流加热下,蒸发伴随热膨胀;高温热辐射加热可导致液滴内部温度高于表面温度,升温到一定程度后可达到液滴内部沸腾状态;影响液滴沸腾的因素有液滴半径、辐射温度、环境气流温度等;同时,随着液滴蒸发,高温环境中液滴的沸腾过热度逐渐增大。     

Understanding thermal expansion of pressurized silica glass using topological pruning of ring structures

We investigate the structural origin of the large thermal expansion coefficient of hot-compressed silica glass upon heating to a threshold temperature using molecular dynamics (MD) simulations. While the simulated thermal expansion at low temperature correlates well with the elongation of the average interatomic separation distance of the Si–O or Si–Si pair, the excess thermal expansion due to hot compression mainly results from change in medium range order, including a decrease in the population of large rings upon heating, without significant modification of the small ring population and without changing the short range ordering, such as the Si-O coordination number. The reduction in the characteristic ring size can be connected to the high thermal expansion through the topological pruning mechanism. Such large thermal expansion is suppressed when the silica glasses are held at their respective quench pressures. The suppression of this excess thermal expansion is consistent with the pressure stabilization of the large ring structures.     

Enhanced thermal conductivity of semi‐aliphatic liquid crystalline polybenzoxazoles using magnetic orientation

Polybenzoxazole (PBO) model compounds consisting of benzoxazole mesogenic units linked with long alkyl chains via ether or ester groups were prepared from flexible dicarboxylic acids with two kinds of bis(o‐aminophenol)s, i.e. 4,4′‐diamino‐3,3′‐dihydroxybiphenyl (p‐HAB) and 3,3′‐diamino‐4,4′‐dihydroxybiphenyl (m‐HAB). The results revealed that the use of p‐HAB completely erased the thermotropic liquid crystallinity and that the m‐HAB‐based ether‐linked model compound was much more advantageous for the formation of a stable liquid crystal phase than the corresponding ester‐linked one. However, the relevant high‐molecular‐weight PBOs showed quite opposite results. Only the m‐HAB‐based ester‐linked C₁₀ PBO system showed a liquid crystal‐like texture among various semi‐aliphatic PBO systems examined. A very high thermal conductivity of 1.79 W m^?1 K^?1 along the thickness direction for the m‐HAB‐based ester‐linked C₁₀ PBO film was achieved by heat treatment in the liquid crystalline state under a strong magnetic field of 10 T. Copyright © 2011 Society of Chemical Industry     

湿球温度与闭式冷却塔蒸发冷却能力关系的研究

以探究环境湿球温度对闭式冷却塔蒸发冷却能力的影响为研究目的,以理论模型闭式冷却塔、实际产品闭式冷却塔以及开式冷却塔为比较对象,给出了不同闭式冷却塔塔型以及同一塔型在不同管材、管径、壁厚等设计细节时环境湿球温度与被冷却水出口温度间的对应关系,并与开式冷却塔作了比较.     

凝固浴温度对再生细菌纤维素纤维结构与性能的影响

以细菌纤维素为原料,N-甲基吗啉-N-氧化物为溶剂制得纺丝原液,在不同的凝固浴温度条件下,制备再生细菌纤维素纤维,对其形貌、结晶度、取向度、力学性能、吸湿保湿性等进行了研究.结果表明:随着凝固浴温度的提高,再生细菌纤维素纤维表面逐渐趋于光滑,且结晶度提高、取向度和断裂强度降低;凝固浴温度为0～45℃,再生细菌纤维素纤维...     

丁羟胶玻璃化温度的模拟计算

丁羟胶的玻璃化转变温度(Tg)预测对丁羟推进剂的贮存、运输和使用具有重要的参考意义。根据丁羟胶的主要性质搭建合理的无定形端羟基聚丁二烯(HTPB)结构模型,选用COMPASS力场、在恒温恒压(NPT)系综下,采用分子动力学(MD)方法模拟计算HTPB在不同温度时的比体积。研究结果表明,比体积与温度的关系曲线斜率在Tg处会发生转折;模拟计算得到的Tg为208.00K,采用差示扫描量热(DSC)法实测得到的Tg为194.86K,两种结果在误差允许范围内基本一致,表明MD法可以用来预测丁羟胶的Tg。     

Temperature dependence of effective thermal conductivity and thermal diffusivity of treated and untreated polymer composites

Thermal properties, such as thermal conductivity, thermal diffusivity, and specific heat, of treated and untreated oil palm fiber–reinforced PF composites were measured simultaneously at room temperature and normal pressure using the transient plane source (TPS) technique. An increase in thermal conductivity was observed in the fiber‐treated and resin‐treated composites. Surface modifications of fibers by prealkali, potassium permanganate, and peroxide treatments increased the fiber–matrix adhesion by increasing porosity and pore size of the fiber surfaces. The increase in crosslinking enhanced the thermal conductivity of a composite of resin treated with peroxide compared to other composites. Also an attempt was made to explain the temperature dependence of thermal conductivity and thermal diffusivity of amorphous polymer samples using the same technique. It was observed that at the glass‐transition peak of the polymer, thermal conductivity and diffusivity were maximum. Below and above this temperature their values decreased. This has been explained on the basis of predominant scattering processes. An empirical relationship was established for the theoretical prediction of thermal conductivity and diffusivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1708–1714, 2003     

有机物混合液导热系数的预测

文章根据液体物质的导热系数与密度的关系,导出了估算有机物混合液导热系数的计算模型。利用该模型计算了53个体系369个数据点的二元有机物混合液导热系数,计算值与实验值的总平均相对偏差为1.434%,计算值与实验数据吻合较好,计算准确性优于文献方法;文章方法简单方便,只需要混合液各组分的临界温度、临界体积和导热系数数据,就可以直接预测各种温度和组成的有机物混合液的导热系数。     

GAP/PTPET弹性体的交联与热性能研究

采用点击化学反应制备了GAP(叠氮缩水甘油聚醚)/PTPET(端炔基环氧乙烷–四氢呋喃共聚醚)弹性体,通过平衡溶胀法和DSC-TG(差热–热重)表征了弹性体的交联与热性能。在不同增塑比条件下,研究了不同配比的GAP/PTPET弹性体的交联密度、玻璃化转变温度(T_g)和热分解表观活化能。结果表明:在相同增塑比条件下,GAP/PTPET弹性体的交联密度随反应物中PTPET含量的增大而呈增大的趋势;增塑比为2.6时,弹性体有较高的交联密度;GAP/PTPET弹性体中软段的T_g偏高于原材料PTPET中软段的T_g;在相同增塑比条件下,随PTPET质量分数的增大,弹性体中软段的T_g减小。GAP/PTPET弹性体的热分解分为3个阶段,第一阶段和第二阶段的热分解表观活化能分别为122.2kJ/mol和137.4kJ/mol,均低于GAP均聚物的热分解表观活化能。     

Thermal strengthening of low-expansion glasses and thin-walled glass products by ultra-fast heat extraction

Thermal strengthening remains the primary method for enhancing the practical strength of commodity glass products, however, the process is limited in terms of applicable glass thickness and coefficient of thermal expansion. The primary reasons for this limitation are the achievable heat transfer coefficient when using conventional gas cooling, and the occurrence of transient surface tension in the early stages of rapid quenching. We revisit this problem for the case of thin borosilicate glass sheet. Using liquid gallium as the cooling medium, ultra-fast heat extraction is achieved, with a heat transfer coefficient exceeding 5000 Wm⁻² K⁻¹. The low vapor pressure of gallium even at high temperatures enables preheating to a wide range of sheet entrant temperatures. We demonstrate thermal strengthening of low-expansion borosilicate glass with persistent surface compression of up to 85 MPa, and quenching to a fictive temperature of ~190 K above the glass transition temperature. Glass sheet obtained in this way exhibits notably enhanced surface defect resistance to sharp indentation. In addition to thermal strengthening, the extraordinarily high heat extraction rates achieved by liquid metal immersion enable exploitation of high-T_f glass properties beyond small and thin sample geometry.     

高温电除尘器在玻璃行业中的应用

针对玻璃窑炉烟气粉尘细、浓度低、具有黏性的特点,采取相应措施,满足平板玻璃生产的排放新标准,并介绍了高温电除尘器在脱硝(SCR)、电除尘和余热发电一体化工程中的应用情况。