共查询到20条相似文献,搜索用时 31 毫秒
1.
Elizabeth Dinand Michel Vignon Henri Chanzy Laurent Heux 《Cellulose (London, England)》2002,9(1):7-18
The mercerization of homogenized primary wall cellulose extracted fromsugar beet pulp was investigated by transmission electron microscopy (TEM),X-ray diffraction together with 13C CP-MAS NMR, and FT-IR spectroscopy.For samples resulting from acid extraction, mercerization began at 9% NaOH, whereasfor samples purified by alkaline treatment, the mercerization started at 10%NaOH. The change in morphology when going from cellulose I to cellulose II wasspectacular, as all the microfibrillar cellulose morphology disappeared duringthe treatment. This change in morphology was very drastic as soon as the NaOHconcentrations were increased beyond 8 and 9% for the acid and alkalinepreparedsamples, respectively. On the other hand, the conversion was found to be moreprogressive in terms of increasing NaOH concentration when the transformationwas analyzed by X-ray diffraction or spectroscopy. Our observations of themercerization of isolated cellulose microfibrils are consistent with theconceptof cellulose microfibrils made of parallel chains in cellulose I and crystalsofcellulose II consisting of antiparallel chains. 相似文献
2.
Yan Li Guozhu Li Yunling Zou Qingjun Zhou Xiaoxue Lian 《Cellulose (London, England)》2014,21(1):301-309
Cellulose nanofibers with a diameter of 70 nm and lengths of approximately 400 nm were fabricated from partly mercerized cotton fibers by acid hydrolysis. Morphological evolution of the hydrolyzed cotton fibers was investigated by powder X-ray diffraction, Fourier transform infrared analysis and field emission scanning electron microscopy. The XRD results show that the cellulose I was partially transformed into cellulose II by treatment with 15 % NaOH at 150° for 3 h. The crystallinity of this partially mercerized sample was lower than the samples that were converted completely to cellulose II by higher concentrations of NaOH. The intensities of all of the diffraction peaks were noticeably increased with increased hydrolysis time. Fourier transform infrared results revealed that the chemical composition of the remaining nanofibers of cellulose I and II had no observable change after acidic hydrolysis, and there was no difference between the hydrolysis rates for cellulose I or II. The formation of cellulose nanofibers involves three stages: net-like microfibril formation, then short microfibrils and finally nanofibers. 相似文献
3.
S. A. Syutkin V. Yu. Pervushin G. F. Kuznetsov D. G. Kleshchev D. A. Zherebtsov V. A. German V. V. Viktorov A. M. Kolmogorov A. S. Serikov 《Russian Journal of Applied Chemistry》2010,83(7):1209-1214
X-ray diffraction analysis, transmission electron microscopy, IR spectroscopy, mass spectrometry, chemical analysis, and thermogravimetry
were used to study transformations in the course of a hydrothermal treatment (150–240°C of samples of hydrated titanium dioxide
produced by thermal hydrolysis of sulfuric acid solutions of titanium(IV) compounds), in water. The dependences of the dispersion
and chemical composition of the samples obtained on the thermal treatment temperature were determined. 相似文献
4.
Tin oxide nanoparticles were prepared using an ionic surfactant (sodium dodecyl sulfate) and tin (IV) chloride as an inorganic precursor via the reverse microemulsion method. The size of the nanoparticles is controlled by variation of water-to-surfactant ratio. Eliminating of surfactant in prepared nanoparticles was confirmed by the infrared spectroscopy after sequential calcinations. Transmission electron microscopy, surface area, pore volume, average pore diameter, pore size distribution and X-ray diffraction results were used for evaluation of size distribution, shape and structure of prepared SnO2 nanoparticles. Transmission electron micrographs confirmed that the obtained materials are spherical nanoparticles. The X-ray diffraction results show the crystalline phases of all samples are SnO2 with tetragonal structured crystal. In addition, the X-ray diffraction and transmission electron microscopy data showed that the size of SnO2 nanoparticles decreased with decreasing the water-to-surfactant ratio. 相似文献
5.
Varietal difference in cellulose microfibril dimensions observed by infrared spectroscopy 总被引:1,自引:0,他引:1
We have previously reported a novel Fourier transform infrared (FTIR) method for evaluating both the accessibility and lateral
dimensions of cellulose microfibrils. This method differs from conventional deuteration in that the OH groups in the crystalline
region were initially completely deuterated. The samples were then rehydrogenated by immersing them in water at 25 °C, during
which only the OD groups on the surface were rehydrogenated. The ratio of OD to OH groups measured for cellulose from various
origins was used to estimate microfibril dimensions, which were compared with the data from X-ray diffractometry. The rehydrogenation
process was further investigated by immersing the deuterated samples in water at elevated temperatures. The behavior of rehydrogenation
under heat treatment was converted to observe the microfibril shape, which was in good agreement with the cross-sectional
images obtained by diffraction contrast transmission electron microscopy techniques. 相似文献
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7.
Houskova V Stengl V Bakardjieva S Murafa N Kalendova A Oplustil F 《The journal of physical chemistry. A》2007,111(20):4215-4221
Zinc sulfide (ZnS) nanoparticles were prepared by homogeneous hydrolysis of zinc sulfate and thioacetamide (TAA) at 80 degrees C. After annealing at a temperature above 400 degrees C in oxygen atmosphere, zinc oxide (ZnO) nanoparticles were obtained. The ZnS and ZnO nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and Brunauer-Emmett-Teller (BET)/Barrett-Joyner-Halenda (BJH) methods were used for surface area and porosity determination. The photocatalytic activity of as-prepared zinc oxide samples was determined by decomposition of Orange II dye in aqueous solution under UV irradiation of 365 nm wavelength. Synthesized ZnO were evaluated for their non-photochemical degradation ability of chemical warfare agents to nontoxic products. 相似文献
8.
纺锤体形LiFePO4锂离子电池正极材料的制备与性能 总被引:2,自引:0,他引:2
采用低温溶剂热法合成了LiFePO4, 并通过热处理方法制备出LiFePO4/C锂离子电池复合正极材料. 利用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱以及恒电流充放电测试等方法对样品进行结构表征和充放电性能测试. 结果表明: 采用丙三醇(甘油)为溶剂, 低温条件下(120 °C)合成的LiFePO4具有橄榄石型晶体结构, 呈纺锤体形貌, 且具有粒径分布均匀的特点. 热处理后制备的LiFePO4/C复合正极材料仍呈纺锤体形貌, 且表现出了优良的充放电性能. 室温下以0.1C倍率恒流充放电, LiFePO4/C的首次放电比容量达到147.2 mAh·g-1, 50次循环后放电比容量仍然保持在136.3 mAh·g-1. 当倍率为0.2C、0.5C和1C时, 样品的平均放电比容量分别在130、120和108 mAh·g-1左右. 相似文献
9.
Co-B非晶态合金超细微粒的热稳定性与催化性能研究 总被引:2,自引:0,他引:2
利用化学还原法制备了Co—B非晶态合金超细微粒,用电感耦合等离子体光谱(ICP)、电子显微镜(TEM)、X射线粉末衍射(XRD)、BET、表面积测试及X光电子能谱(XPS)等手段对新鲜样品及经过不同温度热处理后的样品进行了表征,并用微型催化反应装置评价其CO H2催化性能.结果表明,经过热处理后的样品不仅其表面组成和结构状态发生了变化,而且其催化性能也发生了明显变化,同时还表明非晶态Co—B合金超细微粒具有比其晶态更高的催化活性和独特的选择性。 相似文献
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11.
ZHAO Lei YANG Ge GUO Hailing WANG Chunzheng WANG Lijuan Svetlana MINTOVA 《高等学校化学研究》2021,37(5):1137-1142
The relationship between the concentration of sodium cations and the properties of faujasite(FAU) zeolite was investigated using a two-step synthesis procedure including (1) formation of amorphous aluminosilicate precursors and separation of amorphous nanoparticles, and (2) transformation of these amorphous particles into zeolite crystals by treatment with alkali solutions(NaOH). Three representative samples including two nano-sized zeolites and one micron-sized zeolite were prepared using different concentrations of sodium hydroxide. The crystallization process of these zeolites was studied in detail by Fourier transform infrared(FTIR) spectrometry, nuclear magnetic resonance spectroscopy(NMR), X-ray diffraction(XRD), scanning electron microscopy (SEM), transmission electron microscopy(TEM), and N2 adsorption. The results indicated that minor changes in the concertation of inorganic cations can significantly shorten the induction period and crystallization time and thus affect the morphology, size and chemical composition of the zeolite crystals. 相似文献
12.
CdS纳米棒的制备、表征及其形成机理 总被引:1,自引:0,他引:1
以三辛基膦(TOP)为单一配位溶剂,二水合乙酸镉和硫粉为前驱体,用高温热解的方法制备CdS纳米棒.通过X射线衍射(XRD)、透射电镜(TEM)、高分辨透射电镜(HRTEM)、紫外-可见(UV-Vis)分光光度计、荧光(PL)光谱、傅里叶变换红外(FTIR)光谱和核磁共振磷谱(31PNMR)等方法对样品的结构、形貌和光学特性进行了表征.考察了前驱体Cd/S摩尔比和反应物浓度对硫化镉纳米结构的影响.实验结果表明,该法制备的CdS纳米棒为纤锌矿结构,直径为4.0nm,长度为28.0nm,沿[001]方向择优生长,具有量子限域效应.同时,对CdS纳米晶的形成机理进行了初步的探讨. 相似文献
13.
利用直流电电化学沉积法将生长碳纳米管(CNT)的催化剂镍均匀地附着在石墨电极(GE)表面,再通过化学气相沉积法制备得到原位生长碳纳米管化学修饰电极(GSCNT-CME).电化学沉积的金属镍和所制备的修饰电极分别用光学显微镜、扫描电子显微镜(SEM)和电子能谱(EDX)进行表征,所得修饰电极的电化学性能用[Fe(CN)6]3-/[Fe(CN)6]4-溶液进行表征.结果表明:经直流电电化学沉积,可以在石墨电极表面沉积一层致密的金属镍,能生长出管径均匀的碳纳米管,所制得的修饰电极具有良好的电化学响应灵敏性和准确性,可在电化学检测领域发挥重要的应用. 相似文献
14.
在含氟溶液中,通过电化学阳极氧化钛片成功制备了高度有序的TiO2纳米管阵列,先在450℃下煅烧使其晶化为锐钛矿相,再在不同温度下水热处理了这些锐钛矿阵列。用XRD、SEM和XPS表征了所制备的样品。通过在氙灯光照下光电催化降解对氯苯酚水溶液来检测样品的活性。以对苯二甲酸作为探测分子,用荧光光谱检测了在氙灯光光照下样品表面产生的羟基自由基(.OH)。通过线性伏安扫描的间隙光照实验,测定了样品的光电流响应。结果表明后水热处理对锐钛矿TiO2纳米管阵列的结晶度和形貌没有影响,但光电催化活性明显增强,而不同温度处理的样品的活性差别不大。水热处理后的TiO2纳米管阵列的光电催化活性增强的原因是,水热后TiO2纳米管阵列表面羟基含量明显增加,使得其在光电催化过程中生成的.OH增加。 相似文献
15.
B. Jaleh S. Mohammadtaheri N. Shahbazi S. Azizian 《International Journal of Polymer Analysis and Characterization》2015,20(8):733-742
In this work, polycarbonate-TiO2 nanocomposite films were prepared with different percentages. The aim was to consider the effect of O2 LF plasma (50 Hz) on the hydrophilicity, surface energy, and surface morphology of polycarbonate and polycarbonate-TiO2 nanocomposite. Structure of samples was determined by using X-ray diffraction analysis. In comparison with the reference sample, the samples’ structure did not change after plasma treatment. Surface properties of polycarbonate and polycarbonate-TiO2 nanocomposite films were studied by X-ray photoelectron spectroscopy (XPS), contact angle measurement, atomic force microscopy (AFM), and Vickers microhardness tester. XPS analysis showed that the surface of samples became more oxidized due to plasma treatment. The water contact angle significantly decreased from 88° to 15° after plasma treatment. It was observed that the hardness of the nanocomposite films was not modified after plasma treatment. 相似文献
16.
AFM observation of ultrathin microfibrils in fruit tissues 总被引:1,自引:0,他引:1
Hiroshi Niimura Tomoya Yokoyama Satoshi Kimura Yuji Matsumoto Shigenori Kuga 《Cellulose (London, England)》2010,17(1):13-18
Polysaccharide microfibrils in fruit tissue of higher plants (strawberry, peach, and rambutan) were examined by atomic force
microscopy (AFM). For preserving native cellulose microfibrils, a combination of 2% NaClO2 and 4% NaOH extraction was applied to the materials. This corresponds to mild alkali extractin of holocellulose, and denoted
here as weak alkali-resistant polysaccharide, WARP. The amount of neutral sugars corresponded to 53–95% of that of WARP. Glucose
was the most abundant in the neutral sugars, being 74–87%. AFM examination of microfibrils dispersed on mica substrate allowed
accurate determination of fibril widths as 1.0–2.0 nm. Their straight fibrillar shape and the results of X-ray diffraction
and infrared spectroscopy indicate that these fibrils are cellulose. These results constitute direct evidence for existence
of ultrafine cellulose microfibrils hitherto assumed from X-ray diffraction and NMR analyses. 相似文献
17.
Large area and free-standing TiO2 films was prepared by ultrasonic splitting and a chemical etching step was used to open the closed bottom end of TiO2 films and yields a high aspect-ratio anodic titanium oxide membrane open at both ends. Ordered Cu nanowire structures were fabricated by a simple electroplating method inside high aspect-ratio anodic titanium oxide membrane. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the X-ray diffraction (XRD) were employed to characterize the resulting samples. Detailed results and the possible mechanism are presented. 相似文献
18.
Qingzheng Cheng Siqun Wang Timothy G. Rials Seung-Hwan Lee 《Cellulose (London, England)》2007,14(6):593-602
Natural fibers in micro and nano scales may be a potential alternative for man-made fibers because of the comparable mechanical
properties to those of glass, carbon, and aramid fibers. Cellulose fibril and fibril aggregate are generally prepared by physical
treatments, e.g., high-pressure homogenizer, or chemical treatments, e.g., acid hydrolysis. In this study, fibril aggregates
were generated from a regenerated cellulose fiber by a novel mechanical treatment. The geometrical characteristics of the
fibers and the fibril aggregates were investigated using scanning electron microscopy (SEM) and polarized light microscopy
(PLM), and its crystallinity was investigated by wide angle X-ray diffraction (WAXD). The degree of fibrillation of the fibers
was indirectly evaluated by water retention value (WRV). Nano-biocomposites reinforced with fibril aggregates were prepared
by film casting and compression molding and evaluated by tensile test. The morphological characteristics of the nanocomposites
were investigated with SEM and PLM. As reference, commercial microfibrillated cellulose was also used to reinforce biodegradable
polymer. 相似文献
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20.
不同形貌和尺寸的锂离子电池SnS负极材料 总被引:7,自引:7,他引:0
通过高能球磨、微波辅助合成和化学合成方法制备不同形貌和不同尺寸的SnS材料. 运用X射线衍射和透射电镜对其结构和形貌进行分析. 在透射电镜下观察发现, 所得SnS材料呈现出纳米颗粒、层片和纳米棒状. 电化学测试结果表明, 高能球磨和化学合成(无表面活性剂加入)得到的SnS材料有较好的电化学性能, 在循环40个周期后仍分别有375和414 mAh·g-1 的电化学容量. 纳米级SnS电极材料良好的电化学性能有赖于其紧凑的纳米结构, 一定的形貌及合适的尺寸. 尽管非活性相Li2S可以帮助维持SnS电极在充放电过程中的稳定结构, 但SnS的形貌及尺寸才是获得良好电化学性能的SnS电极的关键因素. 相似文献