PVA/LDH-aCNTs杂化薄膜的制备及其性能研究

采用恒定p H共沉淀法合成了层状双羟基氢氧化物(LDHs)和酸化碳纳米管(aCNTs)杂化材料,并将其作为填料应用到聚乙烯醇(PVA)薄膜中制备了PVA杂化薄膜。采用X射线衍射仪、拉曼光谱仪、扫描电子显微镜等对合成的LDH-aCNTs杂化材料进行了表征,并对PVA杂化薄膜进行了微观结构和力学性能测试。力学性能测试结果表明:当LDH-aCNTs的添加质量分数为3%时,PVA杂化薄膜的拉伸强度达到最大值,相比于纯PVA,拉伸强度约提高了41%。LDHs的存在有效地改善了aCNTs和PVA之间的相容性,使得PVA/LDH-aCNTs杂化薄膜具有较优异的力学性能。吸水性能测试结果表明:相比于纯PVA(吸水率为649%),添加质量分数为5%的PVA/LDH-aCNTs杂化薄膜的吸水率约下降了58%。LDH-aCNTs杂化纳米粒子中的含氧官能团能与PVA链中的羟基形成氢键,使裸露的亲水基团减少,吸水率下降。PVA/LDH-aCNTs杂化薄膜的力学性能和耐水性能的提高,有望拓宽PVA基复合薄膜的应用范围。     

聚丙烯/氮化硼纳米片复合薄膜的制备及介电储能性能研究

聚丙烯(PP)薄膜已广泛应用于薄膜型电容器和静电储能元件,但较低的介电常数限制了其进一步应用。本文以PP为基体材料,通过掺杂低含量的六方氮化硼(h-BN)二维纳米片,制备出聚丙烯/氮化硼纳米复合薄膜,以提高PP介电常数。其中一个关键因素是调控两相界面,以获得h-BN在PP中的良好分散和与基体的紧密结合。本论文通过超声剥离的方式制备少层氮化硼纳米片(BNNSs),并采用盐酸多巴胺(PDA)的非共价聚合反应进行包覆,得到了BNNSs@PDA。通过XRD、FT-IR和TEM表征了BNNSs@PDA的形貌,验证了核-壳结构的直径约150～200 nm,最小厚度约3 nm,有机PDA壳层平均厚度约为7nm。将BNNSs@PDA与PP复合得到薄膜,通过SEM、耐压测试仪、阻抗分析仪等设备对薄膜的微观结构、击穿性能和介电性能进行了研究。结果表明:在BNNSs@PDA的含量仅为1%(质量分数)时,复合材料的介电常数提高至5.62,损耗仅为0.006,理论储能密度高达7.42 J/cm~3,是纯PP薄膜的4.8倍。以上结果表明:BNNSs@PDA与PP良好的界面、二维纳米片在面内的取向分布,有效阻碍了外电场下电树枝的扩展,抑制了载流子的传输作用,同时引入了界面极化,从而有效提高了复合薄膜的介电和击穿性能。     

纳米纤维素晶体增强补强聚乙烯醇薄膜性能研究现状

目的 综述近几年有关将纳米填料纳米纤维素晶体(CNC)作为增强补强剂,提高聚乙烯醇(PVA)薄膜的物理性能方面的研究,以期为PVA薄膜材料的进一步开发和应用提供参考。方法 通过对相关文献进行收集与整理,阐述PVA/CNC复合薄膜的应用现状,介绍CNC的形貌特性、化学改性及成膜方式对改善PVA/CNC薄膜物理性能的研究现状,综述CNC分散性、交联剂和成膜条件对提高PVA/CNC复合薄膜物理性能的影响。结论 通过增加CNC在PVA基体中的分散性,针对不同用途选择对应的成膜方式,这样可有效改善PVA薄膜的力学性能、阻隔性能和耐水性等,提高PVA薄膜的使用价值。     

羽毛角蛋白/PVA复合纳米纤维膜的制备及表征

以羽毛角蛋白(FK)和聚乙烯醇(PVA)为原料,水为溶剂,通过静电纺丝技术制备了FK/PVA复合纳米纤维膜。探讨了复合纳米纤维中FK与PVA的相容性,研究了FK的添加对纤维膜微观形貌、结晶度、热稳定性、亲水性等性能的影响。SEM结果表明,在聚合物总质量分数为14%的条件下制备的FK/PVA复合纳米纤维,表面平整光滑,平均直径为250~320nm,FK含量越大,直径越小。FTIR结果表明,FK与PVA具有良好的相容性,分子间存在氢键作用力。XRD结果表明,FK的加入破坏了PVA分子的规整排列,复合纳米纤维膜的结晶度下降。TG分析与接触角测试结果表明,随着体系中FK配比的增大,复合纳米纤维膜的热稳定性和亲水性均得到提高。     

羽毛角蛋白/PVA复合纳米纤维膜的制备及表征

以羽毛角蛋白(FK)和聚乙烯醇(PVA)为原料,水为溶剂,通过静电纺丝技术制备了FK/PVA复合纳米纤维膜.探讨了复合纳米纤维中FK与PVA的相容性,研究了FK的添加对纤维膜微观形貌、结晶度、热稳定性、亲水性等性能的影响.SEM结果表明,在聚合物总质量分数为14％的条件下制备的FK/PVA复合纳米纤维,表面平整光滑,平均直径为250～320 nm,FK含量越大,直径越小.FTIR结果表明,FK与PVA具有良好的相容性,分子间存在氢键作用力.XRD结果表明,FK的加入破坏了PVA分子的规整排列,复合纳米纤维膜的结晶度下降.TG分析与接触角测试结果表明,随着体系中FK配比的增大,复合纳米纤维膜的热稳定性和亲水性均得到提高.     

PVA纳米涂布PE抗菌薄膜制备及其包装性能研究

采用KH570改性纳米Zn O、NDZ-101改性纳米Ti O2,利用FT-IR和TEM表征改性粉体表面结构和性质变化。配制PVA纳米溶胶,采用涂布法制备PVA纳米Zn O/PE和PVA纳米Ti O2/PE复合薄膜。利用电子万能试验机、透氧测试仪、透湿测试仪和贴膜法研究分析复合薄膜的力学、阻隔和抗菌性能。结果表明,PVA纳米Zn O/PE和PVA纳米Ti O2/PE在纳米粉体添加量为1%左右时可获得良好的力学性能和阻隔性能;PVA纳米Zn O/PE薄膜在避光、自然光和紫外光下抗菌率均达90%以上,PVA纳米Ti O2/PE薄膜在自然光和紫外光下抗菌率达97%以上。     

纳米纤维素晶体和柠檬酸改性聚乙烯醇薄膜的制备及性能

以球形纳米纤维素晶体(NCC)作增强相、柠檬酸作交联剂对聚乙烯醇(PVA)进行改性,制备了PVA/NCC纳米复合薄膜和柠檬酸交联PVA/NCC纳米复合薄膜。通过热重分析、差热分析、吸水实验和拉伸实验考察了NCC的添加和柠檬酸的交联对薄膜热性能、耐水性和力学性能的影响。结果表明,与纯PVA薄膜相比,改性PVA薄膜的起始分解温度升高、熔融/结晶峰向高温方向移动、吸水率降低;只用NCC或柠檬酸对PVA改性时,所得PVA/NCC纳米复合薄膜、柠檬酸交联PVA薄膜的力学性能均对环境湿度敏感;同时用NCC(m(NCC)/m(PVA)=6/100)和柠檬酸(m(柠檬酸)/m(PVA)=3/100或m(柠檬酸)/m(PVA)=4.5/100)对PVA改性时,所得柠檬酸交联PVA/NCC纳米复合薄膜的力学性能不随环境湿度变化。     

溶胶–凝胶法制备Au-BaTiO_3纳米复合薄膜及其介电性能

采用溶胶–凝胶法在Pt/Ti/Si O2/Si基板上制备了Au-Ba Ti O3纳米复合薄膜,并且对其晶体结构、微观组织和介电性能进行了研究。结果表明,Au在复合薄膜中以直径为5~22 nm的Au纳米粒子弥散地分布在Ba Ti O3基体中。Au的添加量对复合薄膜的介电性能和表面形貌有很大影响,其最佳添加量约为5mol%。复合薄膜经过550℃的低温退火已经完全结晶为钙钛矿相,其介电常数与700℃退火的纯Ba Ti O3薄膜的相当。在Au-Ba Ti O3复合薄膜的结晶过程中,一方面,Au纳米粒子可能促进了中间相的分解;另一方面,Au纳米粒子诱发了钙钛矿相的异质形核,促进了Ba Ti O3的结晶化。因此,Au纳米粒子大幅度地降低了复合薄膜的退火温度,并显著提高了复合薄膜的介电性能。     

纤维状中空结构NaYF4:Yb3+, Er3+上转换材料的 合成及防伪应用

采用水溶性聚合物聚乙烯亚胺(PEI)调介下的水热法,一步合成了具有纤维状中空结构的六方相NaYF4:Yb3+,Er3+上转换荧光材料,并将其作为荧光填料,通过流延成膜法制备了具有上转换荧光性能的壳聚糖/聚乙烯醇(CS/PVA)荧光复合薄膜.探究了PEI配体含量和反应体系pH值对合成的上转换材料的形貌、晶型和荧光性能的影响,以及壳聚糖/聚乙烯醇荧光复合薄膜中荧光填料的最佳掺杂量.研究结果表明,在PEI含量为0.3 g且反应体系pH=5的条件下,合成的产物为具有纤维状中空结构的六方相NaYF4:Yb3+,Er3+.荧光光谱表明,合成的NaYF4:Yb3+,Er3+上转换材料在980 nm激光激发下具有优异的荧光性能.当荧光填料的掺杂质量分数为3.0％时,制备的NaYF4:Yb3+,Er3+/(CS/PVA)荧光复合薄膜具有最佳的透明度和上转换荧光特性.     

静电纺丝法制备PLA/CNCs纳米复合薄膜及其性能研究

采用静电纺丝法成功将纳米纤维素晶体(CNCs)植入聚乳酸(PLA)基体中,制备出网状结构的绿色纳米复合材料,并探讨了PLA/CNCs薄膜的微观形貌、结晶度、热学性能和机械性能随CNCs添加量的变化趋势。结果表明,随着CNCs添加量的增加,静电纺PLA/CNCs纳米复合材料薄膜珠状纤维减少,纤维直径增大;纳米复合纤维薄膜的结晶度提高了87.9%;纳米复合纤维薄膜的最大热解温度由369.36℃提升到380.02℃;纳米复合纤维的拉伸性能随CNCs添加量的增加而显著提高,CNCs添加量为11%(质量分数)时得到的最大拉伸力和拉伸强度最大分别为3.76N和4.58MPa,与纯PLA薄膜相比分别提高了289%和159%。     

Synthesis of vertically aligned boron nitride nanosheets using CVD method

Boron nitride nanosheets (BNNSs) protruding from boron nitride (BN) films were synthesized on silicon substrates by chemical vapor deposition technique from a gas mixture of BCl₃–NH₃–H₂–N₂. Parts of the as-grown nanosheets were vertically aligned on the BN films. The morphology and structure of the synthesized BNNSs were characterized by scanning electron microscopy, transmission electron microscopy, and Fourier transformation infrared spectroscopy. The chemical composition was studied by energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Cathodoluminescence spectra revealed that the product emitted strong UV light with a broad band ranging from 250 to 400 nm. Field-emission characteristic of the product shows a low turn-on field of 6.5 V μm^?1.     

Simultaneous Production and Functionalization of Boron Nitride Nanosheets by Sugar‐Assisted Mechanochemical Exfoliation

Due to their extraordinary properties, boron nitride nanosheets (BNNSs) have great promise for many applications. However, the difficulty of their efficient preparation and their poor dispersibility in liquids are the current factors that limit this. A simple yet efficient sugar‐assisted mechanochemical exfoliation (SAMCE) method is developed here to simultaneously achieve their exfoliation and functionalization. This method has a high actual exfoliation yield of 87.3%, and the resultant BNNSs are covalently grafted with sugar (sucrose) molecules, and are well dispersed in both water and organic liquids. A new mechanical force–induced exfoliation and chemical grafting mechanism is proposed based on experimental and density functional theory investigations. Thanks to the good dispersibility of the nanosheets, flexible and transparent BNNS/poly(vinyl alcohol) (PVA) composite films with multifunctionality is fabricated. Compared to pure PVA films, the composite films have a remarkably improved tensile strength and thermal dissipation capability. Noteworthy, they are flame retardant and can effectively block light from the deep blue to the UV region. This SAMCE production method has proven to be highly efficient, green, low cost, and scalable, and is extended to the exfoliation and functionalization of other two‐dimensional (2D) materials including MoS₂, WS₂, and graphite.     

Facile and scalable preparation of ultra-large boron nitride nanosheets and their use for highly thermally conductive polymer composites

Due to their excellent physical and chemical properties, boron nitride nanosheets (BNNSs) have shown great application potential in many fields. However, the difficulty in scalable preparation of large-size BNNSs is still the current factor that limits this. Herein, a simple yet efficient microwave-assisted chemical exfoliation strategy is proposed to realize scalable preparation of BNNSs by using perchloric acid as the edge modifier and intercalation agent of h-BN. The as-obtained BNNSs behave a thin-layered structure (average thickness of 3.9 nm) with a high yield of ~16%. Noteworthy, the size of BNNSs is maintained to the greatest extent so as to realize the preparation of BNNSs with ultra-large size (up to 7.1 μm), which is the largest so far obtained for the top-down exfoliated BNNSs. Benefiting from the large size, it can significantly improve the thermal diffusion coefficient and the thermal conductivity of polyvinyl alcohol by 51 and 62 times respectively, both showing a higher value than the one previously reported. This demonstrates that the prepared BNNSs have great promise in enhancing the thermal conductivity of polymer materials.     

氮化硼复合材料在包装领域应用的研究进展

目的综述国内外氮化硼复合材料在包装领域的应用与进展,对未来氮化硼材料在包装领域的应用进行展望。方法整理归纳国内外文献,简单介绍氮化硼纳米片(BNNSs)的性质和制备方法,以及氮化硼复合材料的制备方法,重点整理分析氮化硼复合材料在包装领域的应用与进展。结果氮化硼具有独特的二维纳米片层结构和相互重叠的层层结构。添加BNNSs不仅可以明显提高复合材料的导热率、机械强度、绝缘性等,还可以改善复合材料的阻隔性能、力学性能、化学稳定性能、抗菌性能等。结论氮化硼复合材料具有热导率高、绝缘性好等优点,可应用于电子封装领域,并在阻燃、抗菌、防腐等包装材料领域具有不错的发展前景。     

功能化六方BN纳米片/聚乙烯醇复合材料的制备及力学性能

利用三聚氰胺辅助机械球磨剥离六方BN （h-BN）,对剥离得到的三聚氰胺功能化h-BN纳米片（f-BNNS）的厚度、形貌及结构进行表征。对f-BNNS/聚乙烯醇（PVA）复合材料进行了研究,考察h-BN的剥离及表面改性对f-BNNS/PVA复合材料力学性能的影响,分析f-BNNS与PVA基体的界面相互作用机制。结果表明：f-BNNS呈现较规则的圆片状,厚度在1~3 nm之间,直径集中在150~400 nm。与h-BN/PVA相比,f-BNNS在PVA基体中显示出更优异的分散效果,填充相同质量分数下,f-BNNS/PVA的屈服强度及模量得到明显的提高。当f-BNNS填充质量分数为5wt%时,屈服强度和弹性模量分别达到175.2 MPa和4.52 GPa,较纯PVA分别增加了45.3%和53.7%。通过f-BNNS和PVA分子结构及断面形貌分析可以推断,f-BNNS表面大量氨基与PVA分子羟基间氢键相互作用有效提升了填料与基体间的界面作用力。     

Synthesis of Boron Nitride Microtubes and Formation of Boron Nitride Nanosheets

Boron nitride microtubes are synthesized in a dual zone quartz tube furnace at 1200°C with ammonia as a reaction atmosphere. Field emission scanning electron microscopy (FE-SEM) results show a unique cone-like morphology of the tubes with larger internal space and thin walls structure. The diameters of the tubes were found to be in the range of 1 to ～2 µm with the walls thickness estimated to be from 10 to 100 nm. XPS survey shows N 1 s and B 1 s peaks at 398.7 and 191 eV, respectively, that represent h-BN in the sample. Raman spectroscopy indicates a high-intensity peak at 1372.53 (cm^?1) that corresponds to the E_2g mode of h-BN. Along with the novel tubular morphology of boron nitride microtubes, the present work also explains a mechanism for the formation of boron nitride nanosheets (from boron nitride microtubes) found in the FE-SEM results of the current sample.     

Large scale synthesis of single-crystal and polycrystalline boron nitride nanosheets

Boron nitride nanosheets (BNNSs) have an identical crystal structure and similar lattice parameter to those of graphene sheets. However, growing quality BNNSs consisting of only several atomic layers remains a challenge. Here, we report on the synthesis of BNNSs at a temperature of 350 °C using a CO₂ pulsed laser plasma deposition (CO₂-PLD) technique by irradiating a pyrolytic hexagonal boron nitride (h-BN) target. The deposition was performed either in vacuum at a pressure of 0.2 Pa, for which we obtained polycrystalline BN, or in hydrogen (H₂) atmosphere at a pressure of 26 Pa for which we obtained single-crystal BNNSs. The presence of H₂ seems to minimize the side effects of sputtering and the material shows higher purity and better crystallinity. High resolution transmission electron microscopy (HRTEM) showed the sheets to be mostly defect-free and to have the characteristic honeycomb structure of six-membered B₃-N₃ hexagon. HRTEM, electron diffraction, X-ray diffraction, Raman scattering, and Fourier transform infrared spectroscopy clearly identified h-BN.     

Challenges and solutions in surface engineering and assembly of boron nitride nanosheets

Atomically thin boron nitride nanosheets (BNNSs) are normally considered to be chemically inert, which makes them difficult to be functionalized. Many applications require new surface functionalities. Significant efforts have been made towards surface engineering and assembly of BNNSs. In this article, we contribute a critical review of the topic on challenges and solutions in surface engineering and assembly of BNNSs. We first outline the mechanistic insights of tunable surface functionalization of BNNSs, and then highlight some new breakthroughs, seminal studies, and trends in the area that have been most recently reported by our groups and others. Recent application researches include but are not limited to: (1) chemical catalysis; (2) biocompatible BN functional nanomaterials for biological and biomedical applications; (3) molecularly engineered BN surfaces for sensing and drug delivery applications; and (4) the construction of thermally conductive and electrically insulating composites. There is also an in-depth discussion on the merits of the processing-structure–property relationships in the functionalized BNNSs. Finally, with this review article, we hope to spark new ideas and inspire new functionalization strategies by fundamentally understanding surface properties and engineering BNNSs with programmable structures and predictable properties.     

Facile orientation of unmodified BN nanosheets in polysiloxane/BN composite films using a high magnetic field

Composite films consisting of highly oriented boron nitride (BN) nanosheets in polysiloxane were fabricated without modifying the BN surface by applying a high magnetic field generated by a superconducting magnet. The hexagonal BN nanosheets were dispersed by sonication in a prepolymer mixture of polysiloxane. The homogeneous suspension was then cast on a polyamide spacer of microscale thickness and a magnetic field was applied before the mixture became crosslinked. The BN nanosheets in the polysiloxane were aligned with high anisotropy either parallel or perpendicular to the composite film plane depending on the magnetic flux direction. The fabricated composite films exhibited enhanced thermal conductivity by controlling the anisotropy of the BN nanosheets in the film. The mechanisms for rotation of BN nanosheets and heat diffusion across the composite film are discussed.     

Modification of BN nanosheets and their thermal conducting properties in nanocomposite film with polysiloxane according to the orientation of BN

A facile technique was developed to modify boron nitride (BN) nanosheets with iron oxides in order to fabricate highly-oriented polysiloxane/BN nanosheet composite films and their thermal properties were evaluated according to the orientation of BN. The surfaces of the BN nanosheets were modified with iron oxide nano particles by chemical vapor deposition, and their one-dimensional arrangement with variation of BN content was controlled under a magnetic field. The homogeneous suspension of BN nanosheets and pre-polymers of polysiloxane was cast on a glass spacer, and subjected to a magnetic field before the mixture was crosslinked. X-ray diffraction, transmission electron microscopy, and superconducting quantum interference device measurements were employed to identify the phases and amounts of iron oxide nano particles deposited on the BN nanosheets. The results revealed that the modified BN nanosheets were aligned either horizontally or vertically to the film plane, depending on the direction of magnetic flux with high anisotropy. The transmittance and thermal conductivity of the nano composite films were improved due to the orientation of the BN nanosheets inside the polymer matrix.