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1.
显微激光拉曼光谱技术可以实现纤维素与木素在木材细胞壁中原位状态分布规律的观察研究。首先采用透射电子显微镜(TEM)研究了结香细胞壁的超微结构。进而采用显微激光拉曼光谱技术对细胞壁各层中纤维素与木素分布特点进行了原位分析测定,拉曼图像及光谱分析结果表明,纤维素与木素在细胞壁各形态区分布不均一,纤维素的分布情况与木素相反。 相似文献
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Karla Dussan Stephen Dooley Rory F.D. Monaghan 《Proceedings of the Combustion Institute》2019,37(3):2697-2704
This study presents a novel approach for the chemical representation of lignin for modelling the reaction kinetics of lignin in lignocellulosic biomass. This methodology relies on the definition of dimeric pseudo-components containing phenolic functionalities, i.e., p-hydroxyphenyl, guaiacyl and syringyl groups, as measured in real biomass and native lignin through wet chemistry and spectroscopic techniques. The reactivities of the lignin pseudo-components are modelled through a series of lumped unidirectional reactions, whose product formation and reaction rate constants are optimised to replicate a comprehensive experimental dataset gathered from several works available in the literature. The new kinetic model contributes to the state-of-the-art by providing a more accurate depiction of the conversion rates, selectivity of char vs. volatiles, and aromatic composition in condensable products in line with the inherent reactivity of lignin functionalities and the empirical observations of lignin depolymerisation and thermal degradation at low (<1?K/s) and high heating rates (>50?K/s). 相似文献
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Hydrogenated amorphous carbon nitride (a-CN:H) thin films were deposited by hot-wire chemical vapor deposition (HWCVD) using the gas mixture of CH4, NH3 and H2 precursor gases. The structural and electronic environments studies of H2 diluted a-CN:H films were carried out by Raman spectroscopy and X-ray photoelectron spectroscopy. The nitrogen content increases while the total carbon contents decreases with increase in H2 flow rate from 0 sccm to 20 sccm in the a-CN:H films. Moreover, the detail analysis of the carbon core orbital, valence band and hole states of a-CN:H were discussed with different H2 flow rate. 相似文献
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Bibhu P. Swain 《Applied Surface Science》2007,253(21):8695-8698
Hydrogenated amorphous silicon carbon alloys (a-SiC:H) films were deposited by hot wire chemical vapour deposition (HWCVD) using SiH4 and C2H2 as precursor gases. a-SiC:H films were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Solid-state plasmon of Si network shifts from 19.2 to 20.5 eV by varying C2H2 flow rate from 2 to 10 sccm. Incorporation of carbon content changes the valence band structure and s orbital is more dominant than sp and p orbital with carbon incorporation. 相似文献
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K. Shi X.L. Liu D.B. Li J. WangH.P. Song X.Q. XuH.Y. Wei C.M. JiaoS.Y. Yang H. SongQ.S. Zhu Z.G. Wang 《Applied Surface Science》2011,257(18):8110-8112
XPS was used to measure the energy discontinuity in the GaN/diamond heterostructure. The valence band offset (VBO) was determined to be 0.38 ± 0.15 eV and a type-II heterojunction with a conduction band offset (CBO) of 2.43 ± 0.15 eV was obtained. 相似文献
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Thin ZnTe layers were grown by molecular beam epitaxy on single crystal GaAs(2 1 1)B substrates. Reflection high energy electron diffraction monitored the deoxidation of substrate and entire growth process. Valence band offset was calculated with X-ray photoelectron spectroscopy. Also interface formation of the ZnTe/GaAs was studied. Analysis shows that interface is abrupt and calculated valance band offset is 0.25 ± 0.1 eV and indicates type I alignment. The experimental result agrees well with the theoretical predictions involving interface dipole effect as well as electron affinity rule. 相似文献
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We have investigated the Ce 4f electronic states in the Ce/Pd(1 1 1) and Ce-oxide/Pd(1 1 1) systems, using resonant photoemission (Ce 4d → 4f transitions), and XPS to understand Pd-Ce interactions in ultra thin layers of cerium and ceria deposited on Pd(1 1 1). Cerium deposited on Pd(1 1 1) at room temperature forms surface Ce-Pd alloys with Ce rich character, while a Pd rich Ce-Pd alloy is formed by heating to 700 °C. A modification of the chemical state of Ce can also be seen after oxygen exposure. RPES provides evidence that Ce-oxide layers deposited on Pd(1 1 1) have a CeO2 (Ce4+) character, however a net contribution of the Ce3+ states is also revealed. The Ce3+ states have surface character and are accompanied by oxygen vacancies. Heating to 600 °C causes Ce-oxide reduction. A significant shift of Pd 4d-derived states, induced by Pd 4d and Ce 4f hybridization, was observed. The resonant features in the valence band corresponding to Ce4+, Ce3+ and Ce0 states have been investigated for various Pd−Ce(CeOx) coverages. 相似文献
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Masaoki Oku Toetsu ShishidoHideyuki Matsuta Kazuaki Wagatsuma 《Journal of Electron Spectroscopy and Related Phenomena》2006
The background corrected valence band XPS spectra and the electronic structures of FeAl, FeSi, CoAl and CoSi were studied. Clean surfaces of the polycrystalline samples were obtained by in situ fracturing of the samples in an XPS spectrometer. The energy loss parts of the Fe 2p, Co 2p and valence band spectra were removed by the deconvolution method using Al 2s or Si 2s spectra as response functions. CoAl exhibited a satellite peak in the Co 2p region, but the other compounds had no clear satellite peaks in the Co 2p and Fe 2p regions. The experimentally background corrected valence band spectra were compared with the calculated spectra using the first-principle band calculation. There were large discrepancies between the spectra above the binding energy of 5 eV. These indicated that the experimental spectra could not be explained by the electronic structures of the ground states alone. 相似文献
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Julia E. Fulghum 《Journal of Electron Spectroscopy and Related Phenomena》1999,100(1-3):331-355
Historically, obtaining useful XPS spectra from polymers has been perceived to be difficult. Problems have included low signal intensities from monochromatic sources, poor spatial resolution, and difficulties with charge compensation. Recent improvements in XPS instrumentation now make it possible to routinely analyze samples which previously would have been considered challenging or impossible. This is particularly true for multi-component polymer samples, which can be difficult to characterize using only large-area spectroscopy. The status of current XPS instrumentation is overviewed, with a variety of examples from polymer analysis. Examples include the use of imaging XPS in the analysis of PVC/PMMA blends, quantification using the valence band region, chemical derivatization of PVMK using hydrazine and trifluorophenylmethyl hydrazine, and high spatial resolution analysis of fiber mats. The importance of high spatial resolution analyses in the evaluation of heterogeneous samples is discussed. 相似文献
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Cellulose nanofiber (CNF) hydrogels with low lignin (8%) (LL-CNF) and high lignin (18%) (HL-CNF) content were produced at nominal powers of 240, 720 and 1200 W using high-intensity ultrasound technology (HIUS). Freeze-dried CNF hydrogels were evaluated as scaffolds for gingival fibroblast cells proliferation aiming biomedical applications. HIUS processing improved the dispersibility of the CNF and increased the water retention value by more than 5 times. The LL-CNF had a maximum fibrillation yield of 46 wt.%, whereas the HL-CNF had a maximum fibrillation yield of 40 wt.% at nominal power of ≥720 W. Regardless of the lignin content, the CNF hydrogels exhibited a typical elastic gel-like behavior with the highest elasticity of 263 Pa. After freeze-drying, the CNF aerogels had porosity ≥ 96.8%, and swelling capacity up to 42.1 g PBS/g aerogel. Moreover, the cell proliferation assay showed no differences in proliferation among the LL-CNF and HL-CNF scaffolds up to 11 days. Therefore, CNF scaffolds prepared with lignin content up to 18% present promising application in the biomedical field. 相似文献
11.
裂解-气相色谱-质谱联用技术研究厚朴浸膏的热裂解 总被引:1,自引:0,他引:1
采用在线热裂解-气相色谱-质谱联用技术(Py-GC-M S),模拟卷烟燃吸状态,对厚朴浸膏的热裂解行为进行研究。结果表明:厚朴浸膏的热裂解产物中共鉴定出49种挥发性成分,含量较高的成分为厚朴酚(27.95%)、4-甲氧基和厚朴酚(21.88%)、和厚朴酚(15.46%)、石竹烯(0.69%)、氧化石竹烯(0.59%)、古巴烯(0.43%)等。厚朴酚、和厚朴酚为厚朴主要活性成分,具有抗氧化、抗抑郁、抗菌等活性。该结果为厚朴浸膏在卷烟中的应用提供理论依据。 相似文献
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独活浸膏的热裂解产物分析 总被引:1,自引:0,他引:1
采用在线热裂解-气相色谱质谱联用技术(Py-GC-MS),模拟卷烟燃吸状态,对独活浸膏进行热裂解,裂解产物经气相色谱-质谱联用仪分析。结果表明:独活浸膏的热裂解产物中共鉴定出51种成分,主要有5-羟甲基糠醛(29.00%)、甲氧基欧芹酚(18.79%)、(Z,Z)-9,12-亚油酸(5.76%)、(E)-2-甲基-2-丁烯酸(3.64%)、5-甲基糠醛(2.79%)、十六酸(2.67%)、2,3-二氢-3,5-二羟基-6-甲基-4H-吡喃-4-酮(1.55%)、糠醛(1.29%)等致香物质,该结果为独活浸膏在卷烟中的应用提供理论依据。 相似文献
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利用ReaxFF分子动力学模拟方法对正庚烷在高温条件下的热解行为进行了研究.细致分析了温度对正庚烷高温裂解过程以及产物分布的影响.结果显示温度对正庚烷的热解过程的影响是分阶段的.高温能加速正庚烷的分解,但是当温度达到一定阶段之后这种影响逐渐变小.正庚烷的热解可以分为三个阶段.主要产物C2H4、C3和C4的质量百分数随转化率的变化规律与实验值符合很好.利用一阶动力学模型得到的正庚烷热解的表观活化能和指前因子分别为53.96 kcal/mol和55.34×1013 s-1,与实验值相符. 相似文献
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The valence band (VB) electronic structures of CrSi2 were studied by synchrotron radiation photoemission. Overall features of the VB photoemission spectra measured at room temperature (RT) and 20 K by using synchrotron radiation (photon energy, hν=20–120 eV) were similar. Two characteristic emissions were observed corresponding to the bonding and the nonbonding Cr-d partial density of states (PDOS) in the CrSi2. The onset of the VB photoemission measured at 20 K was located at about 0.32 eV below Fermi level, due to the energy band gap of CrSi2 more than 0.32 eV. 相似文献
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生物质热解是实现生物质废弃物有效处理及生物质材料高效利用的重要途径之一,因此对生物质热解过程及其机理进行研究具有极大的现实意义。木材作为一种来源广泛的可再生材料也是众多生物质热解原料中的一种,由于组成成分等多方面的差别,不同树种的热解特性具有明显差异。然而,同一种木材的心材与边材由于在组织构造、化学组成及其含量等方面有着明显不同,因此在热解特性和产物方面也存在一定的差异,该工作即对此进行深入研究。试验以心、边材区分明显的常见园林绿化物圆柏为试验材料,通过TG-FTIR联用技术分别得到其心、边材热解过程中的热重曲线和挥发分的红外光谱谱图并对其进行分析。结果表明,纤维素、半纤维素、木质素和抽提物含量对心、边材热解特性影响显著。由于圆柏心材半纤维素、木质素含量较高,在热解前期和热解后期具有比边材更大的失重率,而较高的抽提物含量则在一定程度上增加了其在反应中期的失重率,减小了该范围内心、边材失重率的差异;边材纤维素含量较高,因此其在300~380 ℃,失重明显,在DTG曲线中的最大失重速率也较高。在红外图谱中,心、边材热解所产生的挥发分种类几乎相同,但在数量上有差异,当热解达到最大失重速率时,所产生的挥发分明显增加,且整个过程中边材产生的有机酸类化合物更多,而心材相对产生更多的水和CO2。 相似文献
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竹材光变色和光化降解过程比较复杂。该文以我国资源丰富的毛竹为研究对象,利用氙光衰减仪对竹材进行表面劣化处理,采用傅里叶变换红外光谱(FTIR)和X射线光电子能谱分析(XPS)对竹材表面化学组成和结构的变化进行表征。XPS测试结果表明,竹材表面光劣化处理后其O元素含量及氧碳比(O/C)明显增加;从C原子结合形式来看,C1(C—C)含量减少,C2(C—O)含量增加,C3(CO)和C4(OCO)含量增加明显,C的氧化态显著升高。FTIR分析表明,光劣化处理使得与木质素有关的吸收峰(如1 604,1 512及1 462 cm-1)强度明显降低,木质素发生降解,同时1 735 cm-1处非共轭羰基吸收峰强度明显增强,表明有新的羰基类物质生成,竹材表面发生光氧化反应。竹材表面的多糖物质(纤维素和半纤维素)受光劣化影响较小,其表面多糖相对含量在劣化处理后明显提高。 相似文献