类石墨相氮化碳的研究与应用

综述了类石墨相氮化碳的发展历程以及近年来的最新研究进展,分析了类石墨相氮化碳的合成方法及作用机理,对类石墨相氮化碳在应用过程中存在的缺陷以及改性手段进行了总结,并对类石墨相氮化碳的发展趋势进行了展望。     

氮化碳对有机废水的光芬顿氧化研究进展

石墨相氮化碳作为一种非金属半导体材料,在光催化领域得到一定的应用,最近在类芬顿氧化处理有机废水也有了一些研究,但是其催化性能仍然需要进一步改善。由于光催化和类芬顿氧化的协同作用,光芬顿具有更强的处理有机废水能力。本文综述石墨相氮化碳在光芬顿氧化处理有机废水研究进展,分别就金属离子掺杂氮化碳、氮化碳与单金属氧化物生成的异质结以及氮化碳与双金属氧化物生成的异质结做了相应的介绍。     

华南理工利用三聚氰胺制造光电材料

日前从华南理工大学获悉,该校材料科学与工程学院2009级本科生张远浩,利用三聚氰胺合成了多色发光的光电材料。相关成果发表在《自然》杂志子刊《科学报告》上。据介绍,类石墨层状结构氮化碳由于其优异的光电性能,成为材料科学领域的研究热点。在华南理工大学发光材料与器件国家重点实验室副教授董国平和教授邱建荣的指导下,张远浩等利用廉价的三聚氰胺作为原料,通过简单温和的低温热聚合方法,合成了类石墨层状结构的碳氮化合物,并发现了类石墨层状结构氮化碳的可调谐发光。     

石墨相氮化碳基光催化制氢材料研究进展

石墨相氮化碳(g-C₃N₄)具有独特的电子能带结构和优异的化学稳定性,作为一种不含金属成分的新型可见光催化剂,在光催化领域有着广泛的应用前景。本文主要介绍了石墨相氮化碳材料的合成方法及其改性策略,描述了其结构特性以及在光催化制氢中的应用,为丰富光催化制氢理论研究和优化石墨相氮化碳材料改性路径提供了有益参考。     

新型非金属光催化剂——石墨型氮化碳的研究进展

石墨型氮化碳（g-C3N4）聚合物是一种具有合适禁带宽度（2.7eV）的新型非金属有机半导体光催化剂,它具有良好的热稳定性和化学稳定性。本文介绍了石墨型氮化碳的结构、理化性质和合成方法,重点阐述了进一步提高石墨型氮化碳光催化活性的方法,包括形貌调控、掺杂改性、共聚合改性和硫介质调控。并论述了石墨型氮化碳在可见光下催化分解水和降解有机污染物方面的应用现状。最后指出进一步探索和优化石墨型氮化碳的合成及改性方法,提高其光催化性能依然是g-C3N4在光催化领域应用的研究重点。     

新型氮化碳纳米材料的制备与性能测试

类石墨氮化碳(g-C_3N_4)是一种新型的可见光光催化剂,但类石墨氮化碳g-C_3N_4本身有着的一些缺陷,直接造成其光催化效率低。为了消除这些缺陷的存在,提高其光催化效率。本文是将类石墨氮化碳(g-C_3N_4)进行加工处理得到厚度在50 nm左右的薄片,然后通过XRD、SEM和TEM等多种方法对该催化剂进行表征。并在可见光下对罗丹明B进行降解来判断其催化效率。     

石墨相氮化碳基光催化剂的结构调控研究

利用可见光催化剂分解水产氢是目前清洁能源研究的热点方向。在众多光催化剂中,石墨相氮化碳由于具有良好的光催化性能而成为研究热点。本文简单概述了石墨相氮化碳基光催化剂的结构调控策略的相关研究。     

不同聚合温度下的石墨相氮化碳降解亚甲基蓝的研究

通过热聚合法分别在500,550,600℃下制备了三种石墨相氮化碳，通过红外光谱和X射线衍射光谱表征其结构，证实了三个温度下的石墨相氮化碳均被成功制备。在LED灯作为光源的条件下，将三种石墨相氮化碳分别作为光催化剂用于降解亚甲基蓝溶液，根据降解结果发现550℃下制备的石墨相氮化碳的降解效果最好；以550℃下制备的石墨相氮化碳作为催化剂，对降解条件进行探究，最终发现在溶液pH值为7,催化剂用量为10 mg,光照降解反应6 h时，对亚甲基蓝降解效率为71%。     

铁基石墨相氮化碳复合材料在水处理中的研究进展

铁基石墨相氮化碳复合材料结合了铁基材料、石墨相氮化碳（g-C3N4）以及异质结结构的优点,在促进复合材料光生电子-空穴的分离、扩大可见光响应能力、提高材料光催化性能等方面有着显著的优势。综述了铁基石墨相氮化碳异质结体系的基本分类、结构特点及其研究进展,包括Ⅱ型异质结体系（n-n结、p-n结）、Z型异质结体系（全固态Z结...     

石墨相氮化碳材料及其光催化应用

石墨相氮化碳具有独特的电子能带结构和优异的化学稳定性,作为一种不含金属成分的新型可见光光催化剂,在光催化领域有着广泛的应用前景。介绍了近年来石墨相氮化碳的研究现状,重点探讨其合成方法、结构特性和其相关的衍生物以及在光催化中的应用。     

Evaluation of oxygen content on silicon nitride powder surface from the measurement of the isoelectric point

The oxygen content associated to the surface of silicon nitride powder particles was characterized using a method which is based on the measurement of the specific surface area and the isoelectric point in aqueous solution. From the dissociation model of hydrolyzed surface groups a linear dependence between the fraction of silanol groups (SiOH) and the pH of the isoelectric point is predicted, which was confirmed by electrophoretic measurements of various commercial silicon nitride powders. The proposed method provides rapid information on the particle surface composition, which is of particular relevance for colloidal processing of silicon nitride powders.     

Synthesis of Aluminum Nitride/Boron Nitride Composite Materials

Aluminum nitride/boron nitride composite was synthesized by using boric acid, urea, and aluminum chloride (or aluminum lactate) as the starting compounds. The starting materials were dissolved in water and mixed homogeneously. Ammonolysis of this aqueous solution resulted in the formation of a precomposite gel, which converted into the aluminum nitride/boron nitride composite on further heat treatment. Characterization of both the precomposite and the composite powders included powder X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Analysis of the composite revealed that the aluminum nitride phase had a hexagonal structure, and the boron nitride phase a turbostratic structures.     

Preparation and Sintering of Homogeneous Silicon Nitride Green Compacts

Interactions between silicon nitride particles and hydroxide precipitates were investigated using electrophoresis measurements. Conditions under which stable suspensions of silicon nitride particles and flocculation and heteroflocculation of silicon nitride/hydroxide mixtures occur were Identified. On the basis of the observations, a method for producing uniform mixtures of silicon nitride powders and additive precipitates was formulated and used to produce green compacts of improved compositional homogeneity. The effect of the mixing process on the sintering of green silicon nitride compacts was investigated and compared to the sintering behavior of conventionally prepared green compacts. The results show that the improved homogeneity obtained using the precipitation mixing process leads to enhanced sintering of the green compacts.     

The influence of excited hydrogen species on the surface state of sp2-hybridized boron nitride

The surface of sp²-hybridized boron nitride, namely well-crystallized hexagonal and poorly-crystallized turbostatic boron nitride, after its treatment in a hydrogen plasma was studied with the aid of high-resolution Auger spectroscopy. The surface state of both modifications of boron nitride is found to change due to interaction with excited hydrogen species. This interaction is thought to lead to termination of π (dangling) bonds of sp²-hybridized boron nitride by hydrogen atoms, which results in transformation of the sp²-hybridized state into the sp³-hybridized state on the surface of boron nitride.     

Excellent electrical conductivity of the exfoliated and fluorinated hexagonal boron nitride nanosheets

The insulator characteristic of hexagonal boron nitride limits its applications in microelectronics. In this paper, the fluorinated hexagonal boron nitride nanosheets were prepared by doping fluorine into the boron nitride nanosheets exfoliated from the bulk boron nitride in isopropanol via a facile chemical solution method with fluoboric acid; interestingly, these boron nitride nanosheets demonstrate a typical semiconductor characteristic which were studied on a new scanning tunneling microscope-transmission electron microscope holder. Since this property changes from an insulator to a semiconductor of the boron nitride, these nanosheets will be able to extend their applications in designing and fabricating electronic nanodevices.     

Nano boron nitride/polyurethane adhesives in flexible laminated food packaging: Peeling resistance and permeability properties

Polymeric multilayer films are widely used in food packaging due to their versatility. However, there are still some properties that might be improved, such as gas and vapor barrier behaviors. The incorporation of boron nitride into polymer matrixes is emerging as a potential method for the improvement of barrier properties due to its lamellar structure. In this context, our work investigates the addition of boron nitride into a bicomponent reactive polyurethane (PU), which could be used as an adhesive and improve the barrier layer. This material could be used as an alternative to aluminum foil in food packaging. Different concentrations of two different sizes of boron nitride (BN) particles were added to the PU adhesive: micro-structured boron nitride (BNm) and nano-structured boron nitride (BNn). The aim was to investigate the influence on the barrier properties against moisture and the peeling resistance. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) were performed to characterize the boron nitride samples. The effect of BNm or BNn addition on the glass transition of the nanocomposites was investigated by differential scanning calorimetry (DSC). Barrier properties were measured by a water vapor permeation test and the practical adhesion of laminates with BN/PU adhesives was characterized using peeling tests. The nanocomposites achieved reduction in water vapor permeance of up to 50% and a 37% increase in mechanical adhesion properties compared to the PU adhesive. The results revealed the high potential of boron nitride/PU adhesives for food packaging applications.     

氨基修饰片状氮化碳的制备及光催化性能

石墨相氮化碳是一种低成本易获得的可见光响应光催化剂,但由于比表面积小、光生载流子易复合等缺点限制了其应用。为克服传统氮化碳的缺陷,本实验以尿素和三聚氰胺为原料,通过水热预处理改性前体,再用高温煅烧法成功制备出氨基修饰片状氮化碳光催化材料。并通过X射线衍射（XRD）、扫描电子显微镜（SEM）和X射线光电子能谱仪（XPS）等手段对样品的晶格结构和形貌特征等进行表征。结果表明,成功引入氨基基团的片状氮化碳,比表面积增加且光生载流子复合率显著降低。以罗丹明B和壬基酚溶液的光降解考察材料光催化性能,发现氨基修饰片状氮化碳对其去除率分别为80.69%和50.7%,分别是传统块状氮化碳的2.45倍和2.19倍,是未修饰片状氮化碳的1.26倍和1.21倍。且氨基修饰片状氮化碳材料重复使用5次后仍具有较高光催化活性,光催化性能显著提高。     

Development of a Self-Forming Ytterbium Silicate Skin on Silicon Nitride by Controlled Oxidation

A dense and uniform polycrystalline ytterbium silicate skin on silicon nitride ceramics was developed by a controlled oxidation process to improve the hot corrosion resistance of silicon nitride. The process consists of purposely oxidizing the silicon nitride by heating it at high temperatures. It was found that the ytterbium silicate phase was formed as an oxidation product on the surface of the silicon nitride when it was exposed to air at temperatures above 1250°C. The volume fraction of ytterbium silicate compared with that of SiO₂ on the silicon nitride surface increased with increasing oxidation time and temperature. The formation and growth of ytterbium silicate on the surface of silicon nitride is attributed to a nucleation and growth mechanism. Ultimately, a dense and uniform ytterbium silicate skin with 3–4 μm of skin thickness was obtained by oxidation at 1450°C for 24 h. The ytterbium silicate layer, formed by oxidation of the silicon nitride, is associated with the reaction of SiO₂ on the surface of silicon nitride with Yb₂O₃ introduced in the silicon nitride as a sintering additive. Preliminary tests showed that the ytterbium silicate skin appears to protect silicon nitride from hot corrosion. No observable evidence of a reaction between the skin and molten Na₂SO₄ was found when it was exposed to molten Na₂SO₄ at 1000°C for 30 min.     

Influence of d.c. substrate bias voltage on growth of cubic boron nitride films by radio frequency sputter

In this paper, the influence of substrate d.c. bias voltage on growth of cubic boron nitride (c-BN) films by radio frequency (RF) sputter is reported. Boron nitride films were deposited on p-type Si(100) wafers (8–15 Ωcm) which were biased by the d.c. voltage negatively with respect to ground. The sputtering target was hot pressed hexagonal boron nitride of 4 N purity. The sputtering gas was the mixture of nitrogen and argon. The boron nitride films were characterized with Fourier transform infrared (FTIR) spectra. At a RF power of 360 W and substrate d.c. bias voltage of −200 V, the films contained almost pure phase c-BN. It was shown that different substrate d.c. bias voltages resulted in different cubic phase contents in the c-BN films.     

Excellent corrosion protection performance of epoxy composite coatings filled with silane functionalized silicon nitride

Silicon nitride was firstly used as anticorrosive pigment in organic coatings. An effective strategy by combining inorganic fillers and organosilanes was used to enhance the dispersibility of silicon nitride in epoxy resin. The formed nanocomposites were applied to protect Q235 carbon steel from corrosion. The anticorrosive performance of modified silicon nitride with silane (KH-570) was investigated by electrochemical impedance spectroscopy (EIS), water absorption and pull-off adhesion methods. With the increase of immersion time, the corrosion resistance as well as adhesion strength of epoxy resin coating and unmodified silicon nitride coating decreased significantly. However, for the modified silicon nitride coating, the corrosion resistance and adhesion strength still maintained 5.7×10¹⁰ Ω cm² and 7.6 MPa after 2400-h and 1200-h immersion, respectively. The excellent corrosion resistance performance could be attributed to the chemical interactions between KH-570 functional groups and silicon nitride powders, which mainly came from the easy formation of Si-O-Si bonds. Furthermore, the modified silicon nitride coating formed a strong barrier to corrosive electrolyte due to the hydrophobic of modified silicon nitride powder and increased bonds.