煤结构研究进展

从煤的聚集态结构入手,总结了几种主要显微组分的成因、结构及其溶胀特性,分析并讨论了近年来煤结构模型（包括化学结构模型、物理结构模型及综合模型）的研究及其发展情况,提出了煤结构研究的方法和思路,并指出了煤结构研究的发展方向。最后通过总结煤结构研究在新材料制备中的重要作用,进一步揭示了煤结构研究的重要性。     

基于BLV结构的FDM成型平台结构及运动仿真分析

文章介绍了FDM的成型原理,并对比了传统的Prusa I3结构和BLV结构的特点,重点对BLV结构的FDM成型设备各部分结构的组成、结构和控制逻辑进行了阐述,在此基础上对BLV结构进行了振动模态的分析,提出了进一步的优化措施,对后续BLV结构的优化和改进有一定的参考价值。     

自组装三维光子结构的研究进展及其应用

概述了三维光子结构的分类、生色机理、制备方法和应用,讨论了自组装光子结构产生结构色的虹彩效应、低色彩饱和度以及结构不稳定的问题,分析了三维光子结构的发展方向.     

针织结构复合材料的应用与发展

介绍了针织结构复合材料应用情况,描述了经编多轴向结构、经编间隔、针织管状与针织异形结构等针织结构复合材料的特点与性能,以及针织结构复合材料在航空航天、能源领域、车船制造、建筑工程、柔性复合材料等领域的应用,展望了针织结构复合材料的发展前景。     

复合材料网格结构的研制发展历程

介绍了网格结构的优点、不同分类及网格结构的设计参数,指出最优螺旋角Φ=30°。阐述了网格结构从"等网格"到当今网格的发展历程,对网格结构的生产工艺方法、成型工艺参数(纤维张力)的选取及不同结构参数的网格结构的承载情况作了详细的探讨,归纳了复合材料网格结构的研制现状,分析了当前及其潜在的应用前景。     

石墨烯复合材料的微观结构对电磁屏蔽效能影响的研究进展

石墨烯复合材料以其质轻、高导电性的特点,被广泛应用于制备电磁屏蔽材料领域。本文综述了近年来国内外研究者制备的石墨烯复合材料微观结构对电磁屏蔽效能的影响。针对石墨烯复合材料的插层结构、隔离结构、三维特殊结构及层状结构等微观结构,介绍了不同基质复合材料微观结构特点对材料电磁屏蔽效能影响的机制,最后展望了研究石墨烯复合材料微观结构的发展前景。     

基于有限元的四旋翼无人机碳纤维结构优化设计与固有模态分析

根据消费级四旋翼无人机性能要求,设计了一款质量轻、强度高、航时长、构型简洁的全碳纤维结构消费级四旋翼无人机。建立了四旋翼无人机结构有限元模型,对额定载荷下无人机的结构应力进行了分析。基于最大应力强度准则,对无人机结构强度进行了校核。分析了结构的稳定性,计算了初始结构失稳临界载荷和失稳模态。基于最小重量要求对无人机初始结构的碳纤维铺层进行了优化设计。对优化后的结构进行了固有振动分析,给出了结构的前四阶固有频率和振动模态。优化后的结构在2 g过载下,极限载荷是最大使用载荷的2.57倍,失稳临界载荷是最大载荷的2.09倍,满足设计目标和要求。优化后的结构重量减少了21%,降低为108.6 g,有效载荷约为机体结构重量的3倍。     

路易斯结构式的探讨

文章介绍了Lewis结构、八隅体理论的基本概念以及Lewis结构式的书写方法。着重探讨了缺电子结构和富电子结构的Lewis结构式的判断和正确书写等问题。     

针状焦的结构和原料

介绍了针状焦的结构和特点以及结构与性能的关系,探讨了制备针状焦所需原料的结构和组成,原料结构和组成对针状焦成形过程的影响,并对不同结构原料改质成为适合生产针状焦原料的方法进行了讨论。     

低维纳米结构材料的合成及其研究进展

介绍了当前低维纳米结构材料制备方法及研究发展动态,描述了低维纳米结构材料的工作原理及技术发展现状,阐述了低维纳米结构材料的合成工艺,分析了低维纳米结构材料合成技术的研究进展。通过分析对今后低维纳米结构材料的重点研究方向进行了展望,指出了未来探索合成尺寸、结构和物性可控的新型低维纳米结构材料将成为纳米科技领域的重要研究方向之一。     

Total and partial erucate of pentaerythritol. Infrared spectroscopy study of relationship between structure, reactivity, and thermal properties

Esters of neopentylpolyols are an important starting base for synthetic lubricants. These bulky esters are generally prepared by an esterification reaction between a carboxylic acid and a neopentylpolyol. Because neopentylpolyols have a number of primary alcohol sites, a variety of partial esters is formed before total esters. In the present study, we investigated the reaction between pentaerythritol and erucic acid. The composition of the reaction mixture in erucic acid, partial esters, and total esters was monitored by thin-layer chromatography, coupled with flame-ionization detection. The pure esters and the esters in solution at different concentrations in xylene at different temperatures were analyzed by Fourier transform infrared spectroscopy. Erucic acid and partial esters in xylene coexist in the free form and as bound complexes. These findings furthered understanding of the reactivity and thermal properties of the partial esters.     

Influence of precursors on the formation of 3‐MCPD and glycidyl esters in a model oil under simulated deodorization conditions

To find new ways for reducing the potential of palm oil to form 3‐monochloropropane‐1,2‐diol (3‐MCPD) and glycidyl esters during refining it is helpful to know more about the influence of different precursors like diacylglycerols (DAGs) and monoacylglycerols (MAGs), lecithin, and chlorine containing compounds. After adding increasing amounts of the different precursors to a model oil obtained by removal of polar compounds from crude palm oil and heating the mixture under standardized conditions to 240°C for 2 h the contents of 3‐MCPD and glycidyl esters were analyzed according to the standard procedure of DGF C‐VI 18 (10). DAGs and MAGs were found to increase the potential of palm oil to form 3‐MCPD and glycidyl esters, but refined lecithin showed no influence. Sodium chloride as well as tetra‐n‐butylammoniumchloride (TBAC) led to higher contents of the esters. Whereas the addition of TBAC raised the amount of glycidyl esters as well as 3‐MCPD esters, sodium chloride largely raised the amount of 3‐MCPD esters. An addition of 5 mmol of sodium carbonate/kg model oil spiked with sodium chloride reduced the amount of glycidyl esters almost completely; the 3‐MCPD esters were reduced by 50%. About 1 mmol sodium hydrogen carbonate/kg oil reduced both 3‐MCPD and glycidyl esters almost completely. Practical applications : For the mitigation of the formation of 3‐MCPD esters and related compounds in refined edible oils, it is helpful to know more about the effect of different possible precursors. Using a broader data basis, it is possible to adopt the oil processing but especially the choice of the raw material to the demands of the market for lower contents of the esters in the refined products.     

硫酸盐催化转化木质纤维制备乙酰丙酸和乙酰丙酸酯的研究进展

以木质纤维原料非均相催化转化制备高附加值平台化合物乙酰丙酸和乙酰丙酸酯为研究对象,对以硫酸盐为催化体系的木质纤维定向转化生成乙酰丙酸和乙酰丙酸酯的国内外的研究进展和趋势进行了综述。文章概述了乙酰丙酸及乙酰丙酸酯在工业产业中的应用情况;重点比较了不同硫酸盐催化木质纤维制备乙酰丙酸及乙酰丙酸酯的过程,并对不同溶剂体系协同作用下的木质纤维转化为乙酰丙酸和乙酰丙酸酯过程的影响规律进行了深入分析,总结了硫酸盐类催化剂催化木质纤维定向转化的过程机理。同时针对现有工艺存在的问题进行了分析,展望了该研究领域的发展方向。     

Fatty acid esters of glycidol in refined fats and oils

Discrepancies in the analysis of 3‐chloropropane‐1,2‐diol (3‐MCPD) esters can be explained by the hypothesis that in some refined oils significant amounts of fatty acid esters of glycidol (glycidyl esters) are present in addition to 3‐MCPD esters. Glycidyl esters were separated from triacylglycerols by gel permeation chromatography (GPC) and detected by gas chromatography‐mass spectrometry (GC‐MS). Six samples of palm oil and palm oil‐based fats were analyzed by GPC and GC‐MS. In chromatograms of all samples, significant peaks, retention time and mass spectra in conformity with self‐synthesized glycidyl palmitate and glycidyl oleate were detectable. Quantification of individual glycidyl esters was not possible because of a lack of pure standards. Concentration of ester‐bound glycidol in different samples of fats and oils was estimated using an indirect difference method. Glycidyl esters could be detected only in refined, but not in crude or native, fats and oils. The highest concentrations were detected in palm oil and palm oil‐based fats. In a palm oil sample, glycidyl ester concentration varied according to different deodorization parameters, temperature, and time, while 3‐MCPD ester concentration was relatively constant, indicating that mitigation of glycidyl esters possibly may be achieved by optimizing refining parameters.     

GC-MS法分析生物柴油中脂肪酸甲酯成分的研究

通过利用不同气相色谱-质谱条件对生物柴油中的脂肪酸甲酯成分的分析研究,优选一个 GC-MS 条件,选用PEG-20M的色谱柱,柱温用 150℃ 恒温,进样量为 0.2 μL,分析时间仅用了 12 min,能很好地分离和鉴定生物柴油中主要的10个脂肪酸甲酯,该方法可用于不同植物油制备的生物柴油样品中的脂肪酸甲酯成分的 GC-MS 分析。     

Physico‐chemical properties of wax esters synthesised from corresponding alcohols using hydrobromic acid and hydrogen peroxide action

Symmetrical wax esters were prepared directly from the C₁₄–C₂₂ alcohols using HBr and H₂O₂. Conversion of alcohol up to 98% was obtained. Physical properties such as melting point, refractive index, viscosity and specific gravity were determined for these wax esters at different temperatures. The physical properties of the synthetic wax esters were compared with those of some commercial samples of wax esters. The physical properties of the wax esters can be manipulated by starting with commercially available mixtures of alcohols.     

Analysis of the wax ester fraction of olive oil and sunflower oil by gas chromatography and gas chromatography-mass spectrometry

The wax ester fractions of solvent-extracted sunflower oil and “extra virgin” olive oil were obtained by solid-phase extraction and subsequently subjected to gas-chromatographic and gas chromatographic-mass spectrometric analysis. The comprehensive qualitative analysis of these fractions, which was carried out by the interpretation of mass spectral data, revealed several types of wax esters. In olive oil, shortchain, even-numbered wax esters, saturated and unsaturated long-chain, even-numbered wax esters, benzyl esters, and the diterpenic esters phytyl and geranylgeranyl ester (the latter as a minor component) are present. With the exception of benzyl esters, all these esters occur in sunflower oil as well, but in considerably different amounts compared to those in olive oil. Whereas unsaturated wax esters are present in a negligible amount, diterpenic esters, mainly geranylgeranyl esters, represent the major part of the wax ester fraction.     

Effect of lignin esters on improving the thermal properties of poly(vinyl chloride)

To improve the thermal stability of poly(vinyl chloride) (PVC) and the utilization of lignin (L), different L esters were added to PVC to produce the plates with enhanced thermal stabilities. The properties and structures of the L ester–PVC plates and the properties of the L esters and their mixtures with PVC were analyzed by universal mechanical testing, static thermal stability testing, thermogravimetry–Fourier transform infrared (FTIR) spectroscopy, UV–visible spectroscopy, FTIR spectroscopy, scanning electron microscopy, and differential scanning calorimetry. The results show that L improved the thermal stability of PVC, but the mechanical properties were substantially deteriorated. Proper esterification of L improved the thermal stabilities and mechanical properties of the plates. Noncyclic anhydride acetylated L–PVC plates possessed good static and dynamic thermal stabilities and mechanical properties. The PVC plates incorporated with the L esters with a degree of esterification of around 40% exhibited the best combination properties. Maleated L–PVC plates had good dynamic thermal stability and mechanical properties but poor static thermal stability. The opposite properties were found for succinylated L–PVC plates. The differences in the properties of different L ester–PVC plates were attributed to the different abilities of L esters to capture free radicals, the crosslinking reaction between L esters and PVC, and their compatibility. Different properties of the L esters indicated their different applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47176.     

Glycerolysis of fats and methyl esters

The glycerolysis of methyl esters and triglycerides with crude glycerol, a coproduct from the transesterification of triglycerides, was studied. Three procedures were followed for this conversion. The first procedure was a one-step glycerolysis with methyl esters. The second procedure was a two-step process. This procedure involved an initial partial glycerolysis with methyl esters, followed by fat glycerolysis. The third procedure was a simultaneous glycerolysis with methyl esters and triglycerides. In the glycerolysis with methyl esters, the removal of methanol is vital to the production of mono- and diglycerides. Methanol was removed either by drawing vacuum on the reactor or by stripping methanol out by means of an inert carrier gas (nitrogen). Different molar ratios of methyl esters to glycerol were tested in the first two processes. At low concentration of methyl esters, total conversion of methyl esters to mono- and diglycerides was achieved. As the concentration of methyl esters was increased, the conversion of methyl esters to mono- and diglycerides was decreased. Furthermore, the ratio of mono- to diglycerides was also higher at lower concentrations of methyl esters. The conversion of triglycerides in the two-step process with crude glycerol was similar to a one-step fat glycerolysis with pure glycerol. The composition of different components and the ratio of mono- to diglycerides were also comparable.     

Effect of Alkyl Chain Unsaturation on Methyl Ester Thermo-Oxidative Decomposition and Residue Formation

The formation of persistent residues by esters used in sheet metal-working lubricant formulations interferes with metal surface cleanliness and impairs the integrity of subsequent surface coatings. Understanding the thermal decomposition and residue formation properties of esters is therefore crucial to minimising residue formation during furnace-based cleaning and will aid in the improvement of coated metal products such as galvanised steel. The thermo-oxidative decomposition profiles of four different methyl esters were studied by Thermogravimetric Analysis (TGA) and Pressure Differential Scanning Calorimetry (PDSC). Chemical characterisation of residues remaining at different stages during the thermo-oxidative decomposition process was achieved by infrared spectroscopic analysis of TGA residue samples. Relationships between ester alkyl chain unsaturation levels and the amount/chemical nature of residue present at high temperature (500 °C) were assessed. In the presence of oxygen, polyunsaturated esters decomposed to leave significantly greater amounts of thermally-stable residue, comprising of metal carboxylate and non-volatile oxygenated compounds, than more saturated esters. Given that the formation of analogous residues by more complex esters used in sheet metal-working lubricants may give rise to metal surface coating defects, the results of this study suggest that polyunsaturated esters should be avoided in lubricant formulations where preventing residue formation is of paramount importance.