聚丙烯腈纤维热稳定化过程的光电离质谱研究

利用热解-单光子电离飞行时间质谱(Py-SPI-TOF MS)和热重-质谱(TG-MS)联用仪研究了聚丙烯腈（PAN）原丝在氮气和空气两种气氛下的热稳定化过程。结果表明,PAN原丝在发生热失重之前便已形成部分环化结构,随着温度的升高,PAN原丝在氮气气氛下呈现出2个热分解阶段：第1阶段为线型分子链的断裂以及含氮小分子的脱除,主要生成HCN、NH₃、丙烯腈单体、二聚体以及三聚体等热解产物;第2阶段为环化结构的热裂解,伴随着较多成环化合物和轻质烯烃的产生。而在空气气氛中,氧化作用有利于环化结构的形成和稳定,明显抑制了第2阶段的热分解。此外,较慢的升温速率也有助于环化结构的形成。依据光电离质谱实时在线的研究结果,证明了氧气和温控条件在PAN原丝热稳定化过程中具有关键性作用。     

光电离质谱结合GC/MS研究棉麻织物的热解

选取生物质类固体废弃物中的棉麻织物作为研究对象,利用热重、同步辐射真空紫外光电离质谱以及气相色谱-质谱联用技术研究其在低压环境中的热解过程。热重分析结果显示,半纤维素和木质素在麻布中的含量高于棉布中的。结合产物的光电离质谱图以及气质联用仪的实验结果对主要产物进行了定性分析,并研究了热解产物随温度的变化趋势,发现500℃下棉布的热解产物最多,而麻布由于含有较多的半纤维素和木质素成分,表现出较宽的热解温区。此外,热解产物中乙醇醛的含量极低,证明了它是纤维素的二次分解产物。     

再造烟叶烟气中刺激性气味的关键化学组分研究

为研究再造烟叶烟气中刺激性气味的关键化学组分,本工作利用元素分析仪（EA）与电感耦合等离子体质谱（ICP-MS）表征天然烟叶、再造烟叶以及基片,解析3种原料的化学组成差异。利用U型固定床热解反应器对3种原料进行热解实验,产生的气态产物先通过与固定床反应器出口相连的光电离质谱（SPI-MS）进行实时在线检测,同时结合气相色谱-质谱（GC-MS）的离线定性分析结果确定热解产物的具体组成。随后,采用主成分分析（PCA）法对谱图进行统计学分析,以区分3种原料热解后特征产物的质荷比（m/z）,选择含量显著差异的产物作为模型化合物,开展嗅辨实验。结果表明,再造烟叶烟气中刺激性气味的关键化学组分主要为环戊酮、环己酮和4-乙基苯酚。此外,根据产物随温度的实时变化谱,能够准确了解上述模型化合物在热解过程中的温度释放范围。该研究可为后续减少再造烟叶中刺激性气味提供数据支撑。     

高分辨电感耦合等离子体质谱法测定镍基高温合金中的痕量元素

本研究建立了高分辨电感耦合等离子体质谱(HR-ICP-MS)法测定镍基高温合金中痕量元素。采用盐酸、硝酸和氢氟酸溶解镍基高温合金样品，根据待测元素同位素丰度大、干扰小、灵敏度高的原则，优化各待测元素的同位素和分辨率，有效消除了绝大多数多原子和双电荷离子的干扰。另外，考察了基体、合金成分和溶样酸对待测痕量元素的质谱干扰，通过选取合适的内标¹³³Cs,可以克服基体效应并降低信号漂移。利用甲基异丁基酮萃取Cd,萃取效率达99.7%,消除了镍基高温合金中主成分Mo的质谱干扰。各痕量元素校准曲线的线性相关系数均大于0.999,方法检出限为0.002 1～0.074μg/g。用本方法分析镍基高温合金成分分析标准物质中的痕量元素含量，测定结果的相对标准偏差(RSD,n=6)在2.9%～7.8%之间，测定值与标准值非常接近。该方法前处理简单、分析速度快、结果准确可靠，能够满足镍基高温合金中痕量元素的检测需求。     

在线热解-光电离质谱法研究Li2CO3对松木热解的影响

利用热重分析结合在线热解-光电离质谱法研究了Li₂CO₃对松木催化热解过程的影响。热重分析结果表明,Li₂CO₃的掺入能够使松木热解向低温区移动,且不会显著增加焦炭的产量。在线热解-光电离质谱研究结果表明,松木的3种组分,纤维素、半纤维素和木质素,对催化剂Li₂CO₃的响应不同：纤维素和半纤维素主要热解产物产量有下降趋势,而木质素主要热解产物产量却明显上升;松木主要热解产物的最大生成速率时间和温度都有不同程度的减小。本实验结果表明,热解产物对催化剂的不同响应与它们自身结构有密切关系,在松木热解过程中,Li⁺能降低含氧热解产物的C-O键能从而促进裂解。     

PAN纤维共聚单体作用机理的光电离质谱研究

本工作以丙烯腈/衣康酸（IA）二元共聚原丝以及丙烯腈/IA/丙烯酸甲酯（MA）三元共聚原丝为研究对象，利用热重分析仪（TG）和热解-同步辐射真空紫外光电离质谱（Py-SVUV-PIMS）对其热稳定化过程进行研究。TG结果表明，氮气气氛下，二元共聚原丝（PAN/IA）和三元共聚原丝（PAN/IA/MA）分别呈现三阶段和两阶段的热分解过程，其中PAN/IA的第一和第二阶段均对应PAN线型分子链的断裂，但前者是由自由基环化反应放热引发的，后者则是由正常温度下的热分解所致，而单体MA的加入显著抑制了自由基环化反应，使得PAN原丝的热稳定化能够以单体IA诱导的离子型环化反应为主较平缓地进行，相应的热失重过程也由两阶段转变为了单阶段。Py-SVUV-MS的实验结果表明，两种共聚PAN原丝在程序升温过程中会生成包括含氮小分子、丙烯腈单体及低聚物、成环化合物在内的三类主要热解产物，对比各类产物的生成趋势和产量，推断单体MA通过降低PAN结构的规整度，使其无定形化，从而增加环化反应的引发点，促进PAN原丝向稳定的预氧丝转变，同时由典型热解产物——甲基丙烯腈的生成路径可知，MA本身并不参与PAN大分子的环化反应，属于中性共聚单体。空气气氛下，CO₂的产量差异也间接证明了MA单体能够有效提升PAN纤维的固碳能力，采用三元共聚方法制得的PAN纤维热稳定性能更佳。     

报废汽车破碎残余物及其塑料组分的催化热解研究

为深入探究报废汽车破碎残余物及其塑料组分在以氧化镍为催化剂的热裂解试验中的产物及其活化能变化关系,通过一套实验室级的催化裂解试验平台进行了相应的催化裂解试验并通过Kissinger法进行热解动力学分析。利用热重分析仪得出在有无催化剂的两种条件下反应物随温度变化的失重百分比及反映速率曲线,利用改良后的管式炉对反应物进行阶段式变温加热进而得到裂解气体及残余物,利用气相质谱仪分析裂解气体组分含量,最后利用气相色谱-质谱联用检测法对固体残余物进行了多氯联苯检测。研究表明:氧化镍降低了报废汽车破碎残余物在热裂解反应时的活化能,提高了部分裂解气体产量,固体残渣中亦未出现多氯联苯;在热解动力学分析中发现报废汽车破碎残余物及其塑料组分在裂解过程中的活化能变化趋势基本一致,这一发现为解决报废汽车破碎残余物因成分复杂,理化性质不一致而导致的热解处理工艺难统一的问题提供了理论研究方向。     

真空紫外光电离质谱研究稻壳和稻秆的热解

利用同步辐射真空紫外光电离质谱（SVUV PIMS）对稻壳和稻秆的热解过程进行了研究。通过改变光子能量,获得了随光子能量变化的质谱图,并鉴定了热解过程的主要产物。本工作测量了不同热解温度下的产物质谱图,并结合热重分析,对两种样品热解产物与温度的关系进行对比研究。稻壳与稻秆的热重曲线非常相近,但二者的产物质谱图却差异明显,主要表现在m/z 114和m/z 96等几种半纤维素产物丰度随温度变化的趋势不同。本工作还测量了若干特征产物随时间变化的谱图,结果表明,半纤维素在低温下就开始出现,且生成速度较快,而大部分的木质素分解速度较慢,温度区间也相对较宽,其分解伴随着整个热解过程。     

光电离质谱技术在线监测不同部位烟草裂解产物

为了实时、在线研究烟草原料烟丝的热裂解产物,本工作搭建了一套热裂解光电离质谱装置。利用真空紫外光电离飞行时间质谱装置研究烤烟烟丝不同部位(上-B2F、中-C3F和下-X2F)分别在300、400、500、600和700℃热裂解时的产物,在线获得3个部位烟丝一系列热解产物的光电离质谱图,比较不同裂解温度下热解产物的变化规律。实验进一步分析了500℃下热解产物,如乙烯胺(m/z 43)、异戊二烯(m/z 68)和二甲基呋喃(m/z 96)等信号强度随时间的动态变化曲线,掌握裂解反应的动态变化过程。通过主成分分析(PCA)法对裂解产物质谱图进行统计分析,得到不同部位烟丝化学成分的差异。其中,m/z 58、96、110组分为下部烟(X2F)热解的标志性产物,m/z 43、126组分为中部烟(C3F)的代表性产物,上部烟(B2F)的主要代表性产物为m/z 84组分。结果表明,光电离质谱技术是一种研究烟草热解产物动态变化的重要手段,可通过评估裂解产物中主要成分及相对含量快速区分不同部位烟草样品。     

钾对再造烟叶氧化热解行为的影响

为进一步了解钾对再造烟叶热解行为的影响,利用电渗析法脱除烟草浓缩液中的主要离子以减弱其他离子的干扰,并采用热重分析法研究钾对再造烟叶氧化热解行为的影响。结果表明:1离子化合物显著影响再造烟叶氧化热解过程,电渗析法可高效脱除烟草浓缩液中的主要离子,脱除率在90%以上;2钾显著影响再造烟叶低温氧化热解阶段,使该阶段整体向低温方向移动,同时热释放总量、峰值温度及对应的最大热释放速率均显著下降;3钾促进焦炭的形成,影响再造烟叶残炭氧化,且添加量起关键作用;低添加量的钾使该阶段峰值温度降低,最大热降解速率和质量损失升高,促进残炭氧化;高添加量的钾完全改变残炭氧化进程,主要质量损失和热释放阶段向高温方向移动,峰值温度大幅增加。     

Characterization of silica distribution in rice husk using Synchrotron Radiation µCT and its implications for archaeological interpretation

This article reports the results of a pilot project using Synchrotron Radiation µCT (computer‐aided tomography) to examine the distribution of silica within phytoliths from rice husks. Experiments indicate that computed tomography can be used to show how silica accumulates and is distributed in a distinctive zigzag pattern of long epidermal cells that are characteristic of phytoliths from rice husks. This method will help us to understand why the dry ashing method produced much more zigzag pattern of long cells phytoliths from rice husk than did the acid extraction method. Besides, the zigzag morphological pattern exhibited by long epidermal cells is characteristic of this species which makes it useful in the identification of rice husks from archaeological contexts and indicating heating process. Microsc. Res. Tech. 77:785–789, 2014. © 2014 Wiley Periodicals, Inc.     

Effect of Particle Size on Tribological Behavior of Rice Husk Ash–Reinforced Aluminum Alloy (AlSi10Mg) Matrix Composites

Rice husk ash of three different particle size ranges (50–75, 75–100 and 100–150 μm) a 3, 6, 9, and 12% by weight is reinforced with an aluminum alloy (AlSi10Mg) using the liquid metallurgy method. The dry sliding wear behavior of the composites in the cast conditions is examined using the pin-on-disc tribotesting machine for three different loads (20, 30, and 40 N) with three different sliding velocities (2, 3, and 4 m/s). The results reveal that the composite reinforced with the coarse rice husk ash particles exhibits superior wear resistance compared to the fine rice husk ash particles. The wear rate of the composite decreased with an increase in the weight percentage of rice husk ash particles for all size ranges. Finally, the wear mechanism was investigated with the worn surface using a scanning electron microscope.     

Identification of a new Hazelnut disease in Liaoning Province: Hazelnut husk brown rot

Hazelnut husk brown rot has been identified as a new disease in Liaoning Province in recent years. The objective of this study as to identify the pathogen. [Method] In this study, a standard sample of hazelnut husk brown rot was collected from Songmudao Base in Dalian City, Liaoning Province. The pathogen was identified by the studies of the morphology, pathogenicity, and analyses of ITS and LSU sequences. The pathogen was isolated and purified, which was confirmed by Koch’s postulates. The symptoms after inoculation were the same as those collected directly from a diseased tree, which showed that it was the pathogenic fungus. The cultural characteristics and conidia and the morphology of the pathogenic fungi were similar to those of Botrytis cinerea’s. The ITS sequences and LSU sequences were compared to the associated strain sequences in GenBank, with 100% identity to Botrytis cinerea (GenBank accession number: MN589848.1) and Botrytis cinerea (GenBank accession number: KU140653.1), respectively. The infection status of the pathogen on the hazelnut husks was also observed. The studies suggested that the pathogen leading to the hazelnut husk brown rot as a new disease in Liaoning Province was Botrytis cinerea.     

Tribological performance of distilled biomass oil from rice straw by pyrolysis process

The biomass oil pyrolysed from rice straw was refined through distillation process under one atmosphere pressure. Four distilled fractions were obtained in the temperature ranges of 54–64, 72–80, 84–92 and 96–100 °C respectively. Their chemical components and special group structures were analysed by gas chromatography‐mass spectrometry (GC‐MS) and Fourier transform infrared spectroscopy. The tribological performances of the prepared fractions were evaluated by MQ‐800 four‐ball tribometer as well. The results showed that both density and acid number of the biomass oil increased with the distillation temperature and that the total distillation yield was 55.7%. Every distillation fraction had different anti‐wear and friction reduction. Their average friction coefficients were 0.185, 0.227, 0.179 and 0.293 in 30 minutes, and the average wear scar diameters were 1.035, 0.958, 0.870 and 0.983 mm under a rotation speed of 1450 rpm respectively. It was found that the fraction distilled in the temperature range of 84–92 °C showed better friction reduction and wear resistance. Copyright © 2008 John Wiley & Sons, Ltd.     

Study of silane-based antiwear additives: Wear and chemistry

The chemistry and wear performance of a silane-containing additive in combination with conventional commercial engine oil additives such as zinc dialkyldithiophosphate (ZDDP), calcium-type detergent (Ca detergent), and B- and N-containing dispersant were investigated. The tribological behavior of the low-sulfur base stock 100 N blended with the above additives was investigated using a pin-on-disc Plint friction and wear tester at 100 °C. The wear scar width (WSW) of the upper steel pins was determined using an optical microscope. X-ray absorption near-edge structure (XANES) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to analyze the chemistry and thickness of the thin tribofilm formed on the disc. The morphologies of the wear scars on the lower steel discs were observed using an atomic force microscope (AFM). It was found when the silane additive is mixed with Ca detergent and B- and N-containing dispersant, the antiwear performance of the blend was greatly improved, while the friction coefficient remained almost unchanged. Indeed, the wear performance was comparable to or better than ZDDP on its own, and much better than a commercial oil blend. The silane additive is converted to hydrous SiO₂ by the water in the oil, and this SiO₂ then interacted chemically with the surface and Ca in the detergent under sliding to form a relatively thick tribofilm containing mainly a Ca silicate species. The incorporation of Si and B had little effect on the tribochemistry of ZDDP in the oil blends. When ZDDP and B- and N-containing dispersants were mixed with the silane additive, polyphosphate-type tribofilms, similar to that of ZDDP alone, were formed. However, addition of ZDDP had adverse effects on the wear performance of the silane-based blend.     

新型含N杂环化合物的合成及其摩擦学性能研究

合成了一种新型含N杂环化合物添加剂,利用红外光谱仪定性分析了其结构,利用热重试验和油溶性试验考察了其热稳定性及其对液体石蜡基础油的感受性,利用四球和HQ-1环块试验机考察了其摩擦学性能。结果表明其具有较好的热稳定性及其对液体石蜡基础油良好的感受性,能降低长磨磨斑直径和减小摩擦因数,有效提高基础油的摩擦学性能。     

保护气体对高氮钢焊接熔滴过渡模式和气孔缺陷的影响研究

采用激光-电弧复合热源对8 mm厚的高氮钢板进行焊接试验,研究不同保护气体组成对焊缝形貌、熔滴过渡特征和气孔缺陷的影响。结果表明,采用纯氩做保护气体时,熔滴过渡模式以射流过渡为主,并伴有少量排斥过渡;保护气体成分为Ar+N₂混合气体时,熔滴过渡模式为短路过渡;保护气体成分为Ar+N₂+O₂混合气体时,熔滴过渡模式为射流过渡。保护气体的组成对焊缝气孔缺陷也存在一定的影响,保护气体为纯氩时,焊缝气孔率最大,其值为2.52%;保护气体为90% Ar+10% N₂时,气孔率最低,仅为0.16%;Ar+N₂中添加1%的O₂后,气孔率略有升高,但与纯氩时相比,气孔率仍下降明显。采用Ar+N₂+O₂三元混合气作为保护气体时,能够有效抑制焊缝内气孔数量,同时可以改善熔滴过渡模式,提高焊接过程稳定性。