纤维素纳米晶体制备工艺优化的研究

以微晶纤维素(MCC)为原料经硫酸水解制备纤维素纳米晶体(CNC)。采用单因素法结合正交试验系统地研究了硫酸质量分数、反应温度和反应时间对纤维素纳米晶体得率以及平均粒径的影响,并通过扫描电镜(SEM)、原子力显微镜(AFM)、X射线衍射仪(XRD)、纳米激光粒度仪对CNC的性能进行了表征,揭示了酸水解制备CNC的机理。结果表明：CNC制备的最佳工艺参数为硫酸质量分数64%、反应温度45 ℃、反应时间90 min,在此条件下CNC的得率为24.6%,粒径为204.8 nm。CNC水悬浮液呈一种稳定的淡蓝色胶体状态,其微观形貌比较规整,呈短棒状,直径约10~20 nm,长度在150~300 nm之间;XRD结果显示CNC的晶型为纤维素Ⅰ型,结晶度为80.2%。     

Analyzing three‐dimensional structure and geometrical shape of individual cellulose nanocrystal from switchgrass

The three‐dimensional morphology, size distribution, and structure of individual cellulose nanocrystals (CNCs) isolated from switchgrass (Panicumvirgatum L), a representative raw biomass material, were investigated in this research. Width and height evolutions along the individual CNC longitudinal direction were statistically and quantitatively characterized using transmission electron microscopy (TEM) and atomic force microscopy (AFM). Lognormal distribution was identified as the most likely for cellulose nanocrystals’ size distribution. Height and width dimensions were shown to decrease toward the ends from the midpoint of individual CNCs, implying a spindle shape. The observed rough surfaces of CNCs were explainable as the results of acid etching of the subcrystalline and disordered region located at the surface. X‐ray diffraction analysis of crystallite size accompanied with TEM and AFM measurements revealed that the cross‐sectional dimensions of individual switchgrass CNC were either rectangularly or elliptically shaped, with an approximately 3–5 nm lateral element length range. POLYM. COMPOS., 38:2368–2377, 2017. © 2015 Society of Plastics Engineers     

磷酸锆辅助催化水解菌糠制备纳米纤维素晶体的性能

以食用菌产业的副产品菌糠为原料,采用磷酸锆催化剂辅助稀硫酸水解制备纳米纤维素晶体(cellulose nanocrystals,CNCs).与传统酸水解方法相比,该方法简化了工艺流程,制备过程环境友好。考察了超声时间、超声温度以及稀硫酸浓度等因素对CNCs得率的影响。结果表明当超声时间为5h、超声温度为75℃及稀硫酸浓度为12.3%时,CNCs得率为42.80%.采用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR)以及X射线衍射仪(XRD)对样品的微观形貌、谱学性能和晶体结构进行了研究分析,结果表明所制得的CNCs呈棒状,直径介于10～30nm之间;CNCs属于纤维素I型,与原料菌糠相比,结晶度由63.79%增大到81.04%;且CNCs仍具有天然纤维素的基本化学结构。论文研究为菌糠的资源化高效利用开辟了新途径。     

A novel approach for extracting cellulose nanofibers from lignocellulosic biomass by ball milling combined with chemical treatment

Cellulose nanofibers (CNFs) were isolated from kenaf fibers and wheat straw by formic acid (FA)/acetic acid (AA), peroxyformic acid (PFA)/peroxyacetic acid (PAA), hydrogen peroxide (H₂O₂) treatment; and subsequently through ball milling treatment. Characterization of extracted cellulose and cellulose nanofibers was carried out through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). TEM images showed that extracted cellulose nanofibers had diameter in the range of 8–100 nm. FTIR and XRD results implied that hemicellulose and lignin were mostly removed from lignocellulosic biomass with an increase in crystallinity, and isolation of cellulose nanofibers was successful. The TGA results showed that decomposition temperature of cellulose nanofibers increased by about 27°C when compared with that of untreated lignocellulosic biomass. No significant change was observed in the decomposition temperature of bleached celluloses after ball milling. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42990.     

Synthesis and Thermal Treatment of Pd-Cr@Carbon for Efficient Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells

A nanostructured Pd-Cr catalyst was deposited on a supported carbon surface using the modified borohydride reduction method for the oxygen reduction reaction (ORR) to be utilized as an efficient catalyst in the proton-exchange membrane fuel cell. The crystal structure and feature nanostructure of the Pd-Cr@carbon were established through the use of X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Meanwhile, its catalytic activity was studied using the cyclic voltammetry and electrochemical polarization techniques. Based on the XRD analysis, it was observed that the Pd phase with the fcc crystal structure was dominant, while the Pd-Cr phase with tetragonal crystal structure was detected only for the as-prepared sample and samples calcined at 573 K. The estimated average crystallite size of the Pd phase increased from 9.66 to 37.54 nm as the calcination temperature increased to 973 K, and the calcination time had a slight effect on the crystallite size. On the other side, the average crystallite size for the formed Pd-Cr phase slightly increased from 43.74 nm for the as-prepared sample to 44.90 nm for the sample calcined at 573 K for 3 h. The TEM examination revealed the uniform distribution of the Pd and Pd-Cr nanoparticles upon the carbon surface. The calcination temperature and time played an important role in controlling the structural and morphology parameters of Pd-Cr@carbon. The adsorption/desorption potentials were found to be dependent on the calcination temperature and time and hence the particle and crystallite sizes. The optimum ORR activity and chemical stability were observed for samples calcined at 773 K for 3 h.

     

微晶纤维素的微细结构研究

研究了各种纤维素材料及不同酸浓度水解制成的微晶纤维素的聚合度，并用X-射线衍射法研究结晶度、结晶形态、晶粒尺寸和颗粒大小；用透射电镜（TEM）观察颗粒形状和大小，发现不同纤维素材料达到平衡聚合度（LODP）的盐酸浓度略有不同；在酸水解过程中纤维素的结晶形态、晶粒尺寸和颗粒大小基本不变，而且用X-射线衍射及TEM测出的颗粒不是纤维素晶粒，而是微原纤。     

基于溶胶-凝胶技术制备纳米纤维素的表征

通过傅里叶变换红外光谱、X射线衍射、热重、透射电子显微镜分析及激光粒度分析对基于溶胶-凝胶技术制备的纳米纤维素进行表征,结果表明原料微晶纤维素超分子结构为纤维素Ⅰ型,制备的纳米纤维素为纤维素Ⅱ型;微晶纤维素的结晶度为87.54%,纳米纤维素的结晶度为73.49%,纳米纤维素结晶度较微晶纤维素有所下降;制备的纳米纤维素热稳定性低于微晶纤维素;纳米纤维素平均粒度425 nm,粒度分布呈现正态分布;纳米纤维素长径比为5∶1～40∶1。     

桉木浆纳米纤维素响应面法优化制备及表征

采用响应面法优化桉木浆纳米纤维素(NCC)制备工艺条件并利用傅里叶变换红外(FTIR)、X射线衍射(XRD)、激光粒度分析法和透射电子显微镜(TEM)观察法对NCC进行性能表征。结果表明NCC最优制备工艺条件为硫酸浓度55%,反应温度52℃,水解时间4 h,NCC得率为65.80%,与响应面法预测值66.23%相接近;模型的决定系数为94.63%,说明模型拟合有效;制备的NCC为纤维素Ⅰ型,平均粒径365.7 nm,呈棒状。     

一种棒状纳米微晶纤维素的物性研究

通过X -射线衍射、透射电镜 (TEM)、激光光散射、示差扫描量热分析 (DSC)、热重分析 (TGA)以及红外光谱等分析手段 ,研究了一种具有纳米尺寸的棒状微晶纤维素的物理化学性质 ,着重研究了它在不同温度下的热行为。结果表明 ,由于粒径及比表面积的变化 ,这种棒状微晶纤维素的热行为与天然纤维素以及经过DMSO前处理的纤维素相比较 ,具有一些独特的性质     

微晶纤维素模板法制备纳米二氧化钛及表征

以TiCl4为原料,微晶纤维素为模板,制备了具有微晶纤维素特征形貌的纳米二氧化钛。借助透射电子显微镜、环境扫描电子显微镜、傅里叶变换红外光谱、X射线衍射、热重分析等分析方法对样品进行表征,探讨纳米二氧化钛的形成机理。结果表明:在500℃焙烧得到准球形锐钛矿纳米二氧化钛,粒径为15 nm;在700℃和900℃焙烧分别得到夹有金红石型的锐钛矿和红晶石型纳米二氧化钛,并且随着焙烧温度的升高,纳米二氧化钛晶型由锐钛矿逐渐转变成金红石型,其粒径增大,烧结加剧致使形貌变得更不规则。700℃焙烧产物在紫外光下对罗丹明B具有较佳的光催化降解性能。     

Synthesis and Characterization of Sulfamic-Acid Functionalized Magnetic Fe3O4 Nanoparticles Coated by Poly(amidoamine) Dendrimer

Grafting of chlorosulfuric acid on the amino-functionalized Fe₃O₄ nanoparticles produced sulfamic acid-functionalized magnetic Fe₃O₄ nanoparticles as a novel organic–inorganic hybrid material, which was characterized with X-ray diffractometry (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, scanning electron spectroscopy, and magnetization measurements (VSM). The as-prepared nanocomposite with a narrow size distribution has the crystallite size from XRD (11 ± 4 nm) and particle size from TEM analysis (12.9 ± 0.4 nm) are consistent with each other. Magnetization measurements proved the superparamagnetic property of the product.     

Feasibility of recycled newspaper as cellulose source for regenerated cellulose membrane fabrication

An environmental friendly regenerated cellulose membrane (RCM) was successfully prepared via NaOH/urea aqueous solution system by utilizing recycled newspaper (RNP) as the cellulose source. The morphological and chemical structure of resulting membrane were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD) spectroscopy, and thermogravimetric analysis (TGA). Results from FTIR and XRD verified that the transparent RCM possesses cellulose II structure. SEM observation revealed that the transparent RCM consist of homogeneous dense symmetric membrane structure and composed of a skin layer with mean roughness parameter R_a, obtained from AFM analysis of 29.53 nm. Pure water flux, water content, water contact angle, porosity, and pore size of the resulting membrane were also measured. This study promotes the potential of the cellulose‐based membrane obtained from low cost cellulose source for application in filtration and separation system. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42684.     

Low-Temperature Chemical Synthesis of Nanocrystalline MgAl2O4 Spinel Powder

Nanocrystalline MgAl₂O₄ spinel powder was synthesized by pyrolysis of complex compounds of aluminum and magnesium with triethanolamine (TEA). The soluble metal ion–TEA complexes formed the precursor material on complete dehydration of the complexes of aluminum–TEA and magnesium–TEA. Single-phase MgAl₂O₄ spinel powder resulted after heat treatment of the precursor material at 675°C. The precursor and the heat-treated powders were characterized by X-ray diffractometry (XRD), differential thermal and thermogravimetric analysis, and transmission electron microscopy (TEM). The average crystallite size as measured from the X-ray line broadening was around 14 nm and the average particle size from TEM studies was around 20 nm.     

Polymer-Decorated Cellulose Nanocrystals as Environmentally Friendly Additives for Olefin-Based Drilling Fluids

In this study, we intended to evaluate the performance of olefin-based drilling fluids after addition of cellulose nanocrystal (CNC) derivatives. For this purpose, firstly, cellulose nanocrystals, produced from sulfuric acid hydrolysis of cotton fibers, were functionalized with poly(N-isopropylacrylamide) (PNIPAM) chains via free radicals. The samples were then characterized via Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), confocal microscopy, dynamic light scattering (DLS), and zeta potential measurements in water. The FTIR and NMR spectra exhibited the characteristic signals of CNC and PNIPAM groups, indicating successful grafting. As expected, X-ray diffractograms showed that the crystallinity of CNCs reduces after chemical modification. TGA revealed that the surface-functionalized CNCs present higher thermal stability than pure CNCs. The confocal microscopy, zeta potential, and DLS results were consistent with the behavior of cellulose nanocrystals decorated by a shell of PNIPAM chains. The fluids with a small amount of modified CNCs presented a much lower volume of filtrate after high-temperature and high-pressure (HTHP) filtration tests than the corresponding standard fluid, indicating the applicability of the environmentally friendly particles for olefin-based drilling fluids.     

The catalytic effect of nanosized MgO on the decomposition of ammonium perchlorate

MgO nanoparticles with an average size of 30 nm were prepared by a traditional sol-gel method using magnesium chloride and NaOH aqueous solution as the raw materials. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the products. The catalytic effect of the MgO prepared on the decomposition of ammonium perchlorate (AP) was investigated by differential thermal analysis (DTA). The results indicate that MgO nanoparticles have a good dispersibility and a uniform crystallite size, also have an intense catalytic effect on the decomposition of AP comparing with commercial product.     

纳米二氧化硅/凹土复合材料的制备以及吸附性能

以硅酸钠为主要原料,用硫酸调节pH,通过液相沉淀法在凹土单晶表面原位生成纳米粒状二氧化硅,制备纳米二氧化硅/凹土复合粉体。利用XRD、TEM、TG-DTG、氮气吸附脱附曲线等方法对复合粉体进行表征。XRD表明,二氧化硅以非晶态的形式包覆在凹土表面,防止了凹土的团聚。TEM照片显示,包覆后的纳米二氧化硅粒径减小,粒度分布均匀,表面光滑。     

A novel thermal decomposition method for the synthesis of ZnO nanoparticles from low concentration ZnSO4 solutions

In this research work, ZnO nanoparticles were prepared by direct thermal decomposition method with Zn₄(SO₄)(OH)₆·0.5 H₂O as a precursor. The precursor was calcinated in air for 1 h at 825 °C. Samples were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), infrared spectrum (IR), and scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD, EDS, and IR results indicated that the ZnO nanoparticles were pure. The average crystallite and particle size of the ZnO nanoparticles were estimated to be 87 nm and 92 nm by XRD and TEM, respectively. The SEM and TEM images showed that the ZnO nanoparticles were of spherical shape. The simplicity of the present method suggests its potential application at industrial scale as a cheap and convenient way to produce pure ZnO nanoparticles from low concentration ZnSO₄ solutions.     

Boehmite Nanoparticles by the Two-Reverse Emulsion Technique

Boehmite (γ-AlOOH) nanoparticles were successfully synthesized by the two-reverse emulsion technique at 90°±1°C under constant agitation with varying Al³⁺ concentrations in the aqueous solution. A mixture of cyclohexane and the surfactant, sorbitan monooleate (Span 80), constituted the support solvent in the reverse emulsions. The synthesized particles were characterized by thermogravimetry, differential thermal analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), particle size analysis, and transmission electron microscopy (TEM). XRD and FTIR results confirmed crystalline boehmite formation at 90°±1°C. The average particle size of boehmite was found to be 10 nm. The spherical morphology of the boehmite nanoparticles was confirmed by TEM.     

Microstructural and Mössbauer properties of low temperature synthesized Ni-Cd-Al ferrite nanoparticles

We report the influence of Al³⁺ doping on the microstructural and Mössbauer properties of ferrite nanoparticles of basic composition Ni_0.2Cd_0.3Fe_{2.5 - x}Al_xO₄ (0.0 ≤ x ≤ 0.5) prepared through simple sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray, transmission electron microscopy (TEM), Fourier transformation infrared (FTIR), and Mössbauer spectroscopy techniques were used to investigate the structural, chemical, and Mössbauer properties of the grown nanoparticles. XRD results confirm that all the samples are single-phase cubic spinel in structure excluding the presence of any secondary phase corresponding to any structure. SEM micrographs show the synthesized nanoparticles are agglomerated but spherical in shape. The average crystallite size of the grown nanoparticles was calculated through Scherrer formula and confirmed by TEM and was found between 2 and 8 nm (± 1). FTIR results show the presence of two vibrational bands corresponding to tetrahedral and octahedral sites. Mössbauer spectroscopy shows that all the samples exhibit superparamagnetism, and the quadrupole interaction increases with the substitution of Al³⁺ ions.     

表面活性剂耦合离子液体对稻秆酶解糖化的影响

酶解糖化是木质纤维素材料制备生物质乙醇的关键环节,因此提高稻秆等木质纤维素材料的酶解糖化效率具有重要意义。以稻秆为原料,采用表面活性剂耦合离子液体为预处理方法,考察预处理温度、时间、表面活性剂的添加比例对稻秆酶解的影响。结果表明,预处理温度为110℃、时间为60 min、表面活性剂添加比例为1%,稻秆的酶解效果最佳,与单独离子液体处理的稻秆相比,纤维转化率可提高8%～15%。同时分别通过稻秆成分分析、FTIR、XRD、SEM等对预处理前后的稻秆结构进行表征,证实预处理后酶解效率提高的合理性。