机械力化学在制备纳米材料中的研究

通过高能球磨实现的超细粉碎过程使固体颗粒晶粒细化,产生微裂纹、晶格畸变、表面能升高、反应能力增强,从而实现低温化学反应,称为机械力化学。此法开辟了制备材料的新途径,因而得到广泛重视。本文综述了机械力化学的概念及作用机理。阐述了机械力化学在制备纳米陶瓷材料及纳米复合材料中的应用。介绍了机械力化学法的发展现状及其优缺点。     

机械力化学在纳米无机材料制备中的应用

通过高能球磨实现的超细粉碎过程使固体颗粒晶粒细化,产生微裂纹、晶格畸变、表面能升高、反应能力增强,从而实现低温化学反应,称为机械力化学.此法开辟了制备材料的新途径,因而得到广泛重视.本文综述了机械力化学原理及其在制备纳米复合材料、纳米陶瓷材料和纳米合金材料中的应用以及工艺控制因素.介绍了机械力化学法的发展现状及其优缺点.     

机械力化学作用活化钢渣的研究

本文采用最近发展迅猛的机械力化学方法来激活钢渣,通过粒度测试、密度测定、XRD、TEM、HRTEM和DSCTG等诸多现代测试手段进行表征分析发现:钢渣经过行星磨高能机械研磨之后其颗粒大小、晶体结构发生了明显变化,由晶形逐渐向无定形转变,使钢渣的潜在活性被激发出来。     

机械力化学法制备纳米晶体的研究进展

介绍了机械力化学的概念、作用机理及其表征技术。阐述了机械力化学制备纳米粉体的机理和优越性,并主要以BaTiO3纳米晶为例研究其合成方法及反应机制。还对其未来发展进行了展望。     

机械力化学研究进展

本文介绍了机械力化学的概念、机械力化学效应、影响因素、反应机理、应用及研究机械力化学的设备、表征技术,对机械力化学应用的一些优缺点等做了评述,并对其发展进行了展望。     

纳米颗粒制备过程中的机械力化学效应

本研究首次采用一种可以降低成本的新工艺 ,在制备纳米TiO2 颗粒的过程中 ,将常温水解得到的偏钛酸进行机械力化学处理 ,发生了机械力化学效应 ,在较低的温度和压力下脱去部分吸附水和羟基。实验条件下 ,未见机械处理对晶型结构和晶粒尺寸产生明显影响 ,这种现象在常规处理中未见报道。这一效应的意义在于不仅保持了纳米TiO2 颗粒的良好活性 ,而且使工艺过程优化     

一步法制备乙酰化纳米纤维素及其性能表征

采用机械力化学方法,在4-二甲氨基吡啶(DMAP)催化下一步法制备乙酰化纳米纤维素(A-NCC)。通过单因素研究方法,对影响A-NCC得率的DMAP用量、球磨时间、反应温度、超声时间、反应时间等因素进行探讨及分析。采用透射电子显微镜(TEM)、X射线衍射仪(XRD)、热分析仪(TGA)、傅里叶变换红外光谱仪(FTIR)和X射线光子能谱分析(XPS)等对所制备A-NCC的形貌、热稳定性和谱学性能进行分析表征,采用滴定法测量表面羟基的取代度。结果表明:机械力化学法制备的A-NCC呈细长状,直径约为10～30nm,长度约为200～750nm,结晶度为76%,取代度(DS)在0.125～0.214之间;TGA分析表明,A-NCC热分解温度为311℃,低于竹浆。采用机械力化学法制备乙酰化纳米纤维素具有工艺简便、绿色环保的优点。     

机械力化学制备陶瓷材料的研究进展

在球磨过程中机械力化学使颗粒和晶粒细化产生裂纹，比表面积增大，晶格缺陷增多，晶格发生畸变和非晶化，乃至诱发低温化学反应，可制备出高活性陶瓷粉体和性能优异的陶瓷基材料。介绍了机械力化学在陶瓷材料研究中的最新研究进展。同时，还讨论了不同球磨工艺条件对材料制备过程的影响；并对其未来发展进行了展望。     

机械力化学法制备金红石型TiO_2纳米晶体

研究了高能球磨机粉磨锐钛矿型TiO2 的机械力化学变化过程。发现在一定操作参数 (行星磨公转转速30 0r/min、自转 2 0 0r/min)条件下 ,粉磨初期 (5h)为无定形形成期 ,颗粒粒度减小 ,晶格畸变 ,转变为无定形 ,并形成金红石型TiO2 晶核 ;粉磨中期 (5～ 15h)为晶粒长大期 ,金红石型TiO2 晶粒长大 ;粉磨后期 (15h以后 )为动态平衡期 ,晶粒长大与粉磨引起的晶粒减小处于动态平衡 ;XRD、TEM、FT IR研究表明 :行星磨粉磨锐钛矿型TiO2 可使晶型转变为金红石型TiO2 ,晶粒尺寸为 14 .1nm ,颗粒尺寸为 2 0～ 4 0nm。     

Electrospinning of fluorescent fibers from CdSe/ZnS quantum dots in cellulose triacetate

Fluorescent cellulose triacetate (CTA) fibers were prepared by electrospinning solutions of CTA dissolved in an 8 : 2 v/v cosolvent system of methylene chloride (MC) and methanol (MeOH) which contained CdSe/ZnS quantum dots (QDs). The relatively low loading of colloidal nanoparticles was sufficient to impart fluorescence to the fibers but did not significantly alter fiber morphologies, which tended toward smooth surfaces with the occasional longitudinal feature. The fibers were birefringent due to the alignment of the polymer chains which occurred during electrospinning and had widths on the order of a hundred nanometers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

细菌纤维素纳米晶稳定液体石蜡Pickering乳液的制备

采用生物法合成了高纯度的细菌纤维素(BC),通过浓硫酸水解制得细菌纤维素纳米晶(BCN)。以液体石蜡为油相,BCN为固体乳化剂,在超声作用下制得O/W型Pickering乳液。通过SEM,TEM,FT-IR,XRD,接触角测量仪及激光粒度和Zeta电位分析仪对BC及BCN进行了表征。考察了BCN质量浓度、水相p H和离子强度对Pickering乳液稳定性的影响。结果表明,BC在浓硫酸水解过程中发生了氧化反应,其水解主要发生在无定型区,使所得BCN的结晶指数高达97%。BCN悬浮液的粒径和Zeta电位值分别为462.5 nm和-40.8 m V,其三相接触角为95.7°,具有良好的乳化性能。在超声乳化作用下制得的乳液粒径大小为8.6~17.3μm。通过调控水相p H能够改变BCN表面电荷密度,从而改变乳液的稳定性,随着水相p H的增大,乳液相体积分数增大,乳液稳定性增强。随着Na Cl浓度的增大,乳液的稳定性降低,乳液相体积分数减小。此外,SEM的观测结果表明,BCN在稳定Pickering乳液过程中呈现纤维线条和聚集体颗粒2种形态。     

Biobased nanocomposites based on collagen,cellulose nanocrystals,and plasticizers

Collagen (Col) is extensively used in various applications, including pharmaceutical, agricultural, and food applications. The materials based in Col may exhibit properties of biomedical interest because of their low toxicity, high structural capacity support, controlled biodegradability, and biocompatibility. However, Col has poor thermal and mechanical properties. The addition of plasticizers (Plas's) and fillers is an established strategy for enhancing the properties of the resulting nanocomposites. In this study, nanocomposites based on Col and cellulose nanocrystals were developed in two different ways and with three different Plas's. These materials were subjected to structural, thermal, mechanical, and morphological analysis. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44954.     

基于纤维素纳米晶稳定的亚微米Pickering乳液制备

与传统表面活性剂稳定的乳液相比,固体纳米颗粒稳定的Pickering乳液具有较强的界面稳定性、多功能性、低毒性等优势,在生物医药领域具有较大的应用潜力。而相较于尺寸较大的微米级Pickering乳液,亚微米Pickering乳液具有更大的比表面积、更有效的递送效率,有望进一步拓展Pickering乳液在生物医药领域的应用。但由于Pickering乳液的制备影响因素众多,且相互制约,刚性的固体颗粒难以在较小的有限油水界面排布,增加了亚微米Pickering乳液的制备难度。本工作以制备稳定的亚微米Pickering乳液为研究目标,采用具有良好生物相容性的天然多糖–纤维素纳米晶(CNCs)为颗粒乳化剂,角鲨烯作为油相,考察了颗粒浓度、油水比例、水相成分、超声时间及频率对Pickering乳液粒径分布及稳定性的影响,最终得到了具有良好的储存稳定性和抗离心稳定性的粒径为638.7?8.40 nm的亚微米Pickering乳液(CNCs-PE)。通过激光共聚焦显微镜证实了CNCs吸附在油水界面,形成了Pickering乳液结构。利用CCK-8法评价了CNCs和CNCs-PE的细胞毒性,结果表明,两者都具有良好的细胞安全性。此外,将其用于吸附模型抗原OVA,吸附率达到约80%,且肌肉注射部位的切片结果也表明其注射安全性良好。此结果为亚微米Pickering乳液进一步研究提供了参考,并有望拓展CNCs稳定的亚微米Pickering乳液在生物医药领域的应用。     

Comparison of cellulose and chitin nanocrystals for reinforcing regenerated cellulose fibers

In this study, regenerated cellulose fibers reinforced by cellulose nanocrystals (CENC) and chitin nanocrystals (CHNC) were prepared by blending the nanocrystals suspensions with the cellulose solution in NaOH/urea/water solvent at room temperature. The effect of nanocrystals' addition on the properties of spinning dopes and regenerated fibers were investigated and compared. Results showed that the obtained CENC and CHNC had different dimensions, and both of them increased the viscosity and decreased the transparency of the spinning dopes. However, the dissolution state of cellulose was not changed. CHNC had a greater influence on the properties of spinning dopes, while CENC had more obvious effect on the performance of regenerated fibers. The CENC reinforced fibers showed a higher crystallinity index as compared to the CHNC reinforced fibers. The tensile strength of the regenerated fibers was evidently improved when 3 wt % CENC or 2 wt % CHNC were added, while the elongation at break of the fibers was slightly decreased with the increase of nanocrystals content. The morphology and thermal stability of the regenerated fibers was not affected by the addition of nanocrystals. This study suggested that the dimension, group and content of nanocrystals were important factors for the reinforcement of regenerated cellulose fibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44880.     

纤维素氨基甲酸酯法制备纤维素海绵

海绵因具有蓬松度好、质地柔软、吸水性好等优点而得以广泛应用。但目前市面上的聚氨酯海绵,不仅原料紧缺,制备过程有污染物产生,而且废弃后难降解,会产生二次污染。为开发可自然降解的纤维素海绵无污染制备工艺,研究了采用纤维素氨基甲酸酯法制备纤维素海绵的工艺。结果表明：由纤维素氨基甲酸酯的氢氧化钠溶液捏合而成的海绵混合体经蒸煮,纤维素再生,成孔剂溶于水中而留下空隙,所得纤维素海绵孔径均一,表面光滑平整,具有较好的柔韧性和黏弹性,完全具有普通聚氨酯海绵的基本特征。     

Surface modification of cellulose nanocrystals

In order to improve the dispersibility of cellulose nanocrystal (CNC) particles, three different grafted reactions of acetylation, hydroxyethylation and hydroxypropylation were introduced to modify the CNC surface. The main advantages of these methods were the simple and easily controlled reaction conditions, and the dispersibility of the resulting products was distinctly improved. The properties of the modified CNC were characterized by means of Fourier transform infrared spectroscopy (FT-IR), ¹³C nuclear magnetic resonance (NMR), transmission electron microscopy (TEM) and thermogravimetric analyses (TGA). The results indicated that after desiccation, the modification products could be dispersed again in the proper solvents by ultrasonic treatments, and the diameter of their particles had no obvious changes. However, their thermal degradation behaviors were quite different. The initial decomposition temperature of the modified products via hydroxyethylation or hydroxypropylation was lower than that of modified products via acetylation. Translated from Acta Polymerica Sinica, 2006, (8): 982–987 [译自: 高分子学报]     

Preparation and properties of chemical cellulose from ascidian tunic and their regenerated cellulose fibers

Chemical cellulose (dissolving pulp) was prepared from ascidian tunic by modified paper‐pulp process (prehydrolysis with acidic aqueous solution of H₂SO₄, digestion with alkali aqueous solution of NaOH/Na₂S, bleaching with aqueous NaOCl solution, and washing with acetone/water). The α‐ cellulose content and the degree of polymerization (DPw) of the chemical cellulose was about 98 wt % and 918, respectively. The Japanese Industrial Standard (JIS) whiteness of the chemical cellulose was about 98%. From the X‐ray diffraction patterns and ¹³C‐NMR spectrum, it was found that the chemical cellulose obtained here has cellulose Iβ crystal structure. A new regenerated cellulose fiber was prepared from the chemical cellulose by dry–wet spinning using N‐methylmorpholine‐ N‐oxide (NMMO)/water (87/13 wt %) as solvent. The new regenerated cellulose fiber prepared in this study has a higher ratio of wet‐to‐dry strength (<0.97) than commercially regenerated cellulose fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1634–1643, 2002.     

Preparation and mechanical properties of green epoxy nanocomposites with cellulose nanocrystals

Epoxy resin is widely used to make composites, electronic and electric parts, adhesives, and coating materials because it has excellent thermal, electrical, and mechanical properties. Using natural materials in making epoxy composites and nanocomposites would make the final products greener. Therefore, in this study, epoxidized soybean oil (ESO) and cellulose nanocrystals (CNCs) were used to make green epoxy nanocomposites. ESO was prepared by epoxidation of soybean oil with peroxyacetic acid and it was confirmed by Fourier transform infrared spectroscopy. The ESO was mixed with diglycidyl ether of bisphenol A at different weight ratios (10%–50%) and the stoichiometric amount of ethylene diamine was used for curing. CNC content in the nanocomposites was changed from 0.125 to 1 phr. Mechanical properties of the epoxy samples and the nanocomposites were investigated by universal testing machine and izod impact tester. The epoxy sample showed best mechanical properties at ESO 30%. The nanocomposite with CNC 0.25 phr showed best mechanical properties. Fracture surfaces of the epoxy sample and the nanocomposites were investigated by scanning electronic microscope. POLYM. ENG. SCI., 60:439–445, 2020. © 2019 Society of Plastics Engineers