连续合成六方氮化硼的新工艺

着重介绍连续合成六方BN的创新工艺，该工艺既有效地提高了产品的产量和质量，又大大降低了生产成本，使氨氮法制备BN的生产方法向前推进了一步，提高到一个新水平。     

以三乙醇胺硼酸酯为前驱体制备大颗粒六方氮化硼

以三乙醇胺和硼酸为原料,甲苯为带水剂,合成了三乙醇胺硼酸酯,在最佳工艺条件下以三乙醇胺硼酸酯为前驱体在氨气气氛中烧结制得六方氮化硼颗粒。采用IR、XRD、SEM、NMR等测试方法对中间物和产物进行了表征,确定了中间物及产物的组成、物相、粒度及形貌。研究结果表明：以三乙醇胺硼酸酯为前驱体在1200℃烧结4h,可制得高纯度、晶型良好,粒径在20μm左右的六方氮化硼颗粒。经过高温精制后的六方氮化硼颗粒具有较高的结晶度和致密度,其粒径可以达到30μm以上,纯度为98.5%。     

以三乙醇胺硼酸酯为前驱体制备大颗粒六方氮化硼

以三乙醇胺和硼酸为原料,甲苯为带水剂,合成了三乙醇胺硼酸酯;以三乙醇胺硼酸酯为前驱体在氨气气氛中烧结制得六方氮化硼颗粒。采用FTIR、XRD、SEM、NMR对中间产物和最终产物进行了表征。结果表明:以三乙醇胺硼酸酯为前驱体,在1 200℃下烧结4 h,可制得质量分数为94.3%、六方晶型良好,粒径达17.52μm的六方氮化硼颗粒;经过2 000℃高温精制后的六方氮化硼颗粒具有较高的结晶度和致密度,质量分数可达到98.5%,粒径可达到30μm以上。     

前驱物法低温合成六方氮化硼

本文以三聚氰胺和硼酸为原料,先采用湿化学法合成棒状前驱物,然后将其在空气气氛中高温培烧制得六方氮化硼.实验考察了反应原料配比,反应物浓度,高温培烧的时间及温度对产物的影响.采用IR、化学分析、XRD、粒度分析和SEM等方法对前驱物及产物进行了表征,确定了前驱物及产物的组成、物相、粒度分布及形貌.研究结果表明:合成前驱物的适宜原料配比是C3N6H6∶H3BO3=1∶2,浓度为0.4 mol/L,合成的前驱物是分子式为C3N6H6·2H3BO3的棒状超分子加合物;在温度950℃,空气气氛中培烧6h能得到晶型良好、平均粒径为15 μm的六方氮化硼粉体.     

氮化硼晶须的制备及其表征

利用先驱体转化法制备氮化硼晶须。利用三聚氰胺和硼酸为原料,利用水浴加热方法,生成一种BCN化合物先驱体。将该先驱体化合物在不同的温度段进行热处理后得到氮化硼晶须。借助SEM,FT-IR表征手段分析了不同温度热处理后晶须微观形态以及内部分子结构的变化,并用XRD,TEM等测试手段对最终晶须进行了表征。结果表明：所制备的氮...     

六方氮化硼的制备与应用综述

主要综述了六方氮化硼的基本结构和性能,介绍了其常用制备方法,并对其应用前景进行了展望。     

利用真空氮化炉制备六方氮化硼粉体工艺研究与表征

本研究用一种操作简单、适合规模化、低成本的方法制备六方氮化硼粉末.研究了硼、氮元素的物质的量比值,烧成制度,助熔剂的添加量对产物物相成份和颗粒形貌的影响,并对酸洗和碱洗对产物中杂质的去除效果进行了比较.用X-射线衍射仪(XRD)、扫描电镜(SEM)对制备的产物样品进行了分析表征,发现用该工艺制得的六方氮化硼纯度可达95.6%,去杂后纯度可达99%以上,晶粒直径约为0.2～0.5 μm,厚度在60～70 nm,晶粒尺寸比较均匀.     

氮化硼合成的工艺及性能研究

本论文采用硼酸和三聚氰胺按照一定的配比合成氮化硼的前驱体高聚物,氮化硼前驱体高聚物溶于甲酸溶液。将氮化硼前驱体高聚物在23 kV,正负极距离为15 cm条件下纺出细度均匀的纤维。对合成的前驱体高聚物放在马弗炉中按照10℃/min的升温速度升至800℃,保温一定时间得到氮化后的产物,氮化后产物成白色,硬度较大。利用扫描电镜、傅里叶红外光谱仪和TG-DSC热重分析仪对氮化后产物的性能特征进行了测试。     

硼砂与尿素在N2气氛下合成六方氮化硼的工艺

以硼砂、尿素为原料,采用改进的硼砂?尿素法,在N2气氛下合成六方氮化硼(h-BN),考察了焙烧温度、保温时间、硼砂与尿素摩尔比对氮化硼产率、纯度及形貌的影响,对产品进行了表征. 结果表明,合成六方氮化硼的最佳工艺条件为：硼砂/尿素摩尔比1:4、焙烧温度1300℃、保温时间4 h. 该条件下氮化硼产率约为47%,纯度达98%,单片直径300~500 nm,粒度约为4 ?m,比表面积约为13 m2/g.     

改性h-BN/聚氨酯丙烯酸酯涂料的制备与性能

利用水热法制备羟基化六方氮化硼（BNNSs）,采用异佛尔酮二异氰酸酯（IPDI）和丙烯酸羟乙酯（HEA）在其表面进行接枝得到功能化六方氮化硼（Fh-BN）。然后将得到的Fh-BN掺入有机硅改性的聚氨酯丙烯酸酯（PUA）涂料中,成功制备出改性h-BN/聚氨酯丙烯酸酯涂料。研究了水热时间、温度对BNNSs硼羟基含量的影响,利用XPS分析得出水热反应最佳反应条件为180℃、12h,B—OH质量分数达到5.97%。通过机械性能、综合热分析、耐水性、涂层交流阻抗和Tafel极化曲线进行测试分析,掺杂0.75%Fh-BN涂膜硬度达到3H,耐冲击性50cm,柔韧性0.5mm;与未掺杂前涂层相比,吸水率降低4.96%;涂层耐热性提高,T_50%提升了6℃;耐水测试浸泡168h后涂膜无变化;电化学测试表明：0.75%Fh-BN涂层阻抗R₁达到1.818×10⁹Ω·cm²,比原有涂层提升了两个数量级,E_corr由-0.4886V正移至-0.32124V,I_corr由2.5552×10^-7A/cm²降低至1.5555×10^-8A/cm²。Fh-BN的引入显著提升了涂层的机械性能、热稳定性和耐腐蚀性。     

High-temperature carbothermal synthesis and characterization of graphite/h-BN bimaterials

Hexagonal boron nitride (h-BN) and graphite have similar crystal structures, comparable lattice parameters, and coefficients of thermal expansion, but vastly different electrical and thermal transport. Despite their key differences, it is possible to couple h-BN and graphite in a bimaterial system allowing the unique properties of both materials to be utilized in a single component. Through a carbothermal reduction of B₂O₃ in nitrogen, the surface of graphite can be converted to h-BN. This results in a layered system that is electrically insulating on the surface due to h-BN, and more compliant as well as conductive within the substrate due to the graphite structural body. We discuss the high-temperature synthesis and characterization of this layered material, focusing on the processing–microstructure relationship as well as the interface of graphite/h-BN to assess the chemical and mechanical adhesion of the layers, and to establish how such properties are contingent on the reacting phase of B₂O₃. This is achieved by investigating the origin of h-BN formation and the unwanted side reaction of boron carbide formation, through the evaluation of the thermochemistry and kinetics governing the carbothermic reactions. We establish that a reaction temperature and holding time of 1700°C for 18 h produced the thickest h-BN layers which exhibited the highest fracture toughness over all lower temperature synthesis conditions.     

Synthesis and characterization of polyimide/hexagonal boron nitride composite

Polyimide (PI)/hexagonal boron nitride (h‐BN) composites were produced via the thermal imidization procedure from solution mixtures of a polyamicacid, which is prepared from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride and 3,3′‐diaminodiphenyl sulfone (DADPS) in N‐methyl‐2‐pyrrolidone (NMP), and alkoxysilane functionalized h‐BN. The structure, thermostability, thermal behavior, and surface properties of the resulting materials were characterized by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM). The thermal characteristics of PI/h‐BN films were better than the pure PIs. The physical and mechanical properties of the films were evaluated by various techniques such as contact angle, chemical resistance, and tensile tests. The flame retardancy of the composite materials was also examined by the limiting oxygen index (LOI). The experiments showed that the LOI values of PIs increased from 32 to 43 for the materials containing hexagonal boron nitride. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,characterization and adsorption studies of h-BN crystal for efficient removal of Cd2+ from aqueous solution

In the present study, hexagonal boron nitride (h-BN) was synthesized from boric acid and melamine by thermal annealing method in a nitrogen atmosphere. The pure h-BN was used as an efficient sorbent for the uptake of Cd²⁺ ions from the solution phase. The kinetics and sorption studies of metal ions onto the h-BN were carried out in batch adsorption experiments at different temperature, time, pH, sorbent dosage, and concentration of metal ions. The optimum pH for the removal of the Cd²⁺ ions was found to be pH 7. The effect of temperature showed that the process of Cd²⁺ sorption remained endothermic in the range of 298 K–328 K. The Lagergren's first and Ho's second kinetic models were tested to interpret the adsorption kinetic data, however the present data was explained well by Ho's model for kinetics. The thermodynamic perameters ΔG, ΔS and ΔH were determined using the available adsorption data at different temperatures. The physicochemical properties of the synthesized product were also characterized before and after adsorption by different analytical techniques like FT-IR, TGA, XRD and Point of Zero Charge (PZC). The morphology of the surface was analyzed with the help of Scanning Electron Microscopy. The h-BN proved to be an efficient adsorbent for the uptake of the Cd²⁺ ions from aqueous media.     

Synthesis of highly purified and crystallized h-BN using calcium-assisted carbothermal reduction nitridation

Highly purified and crystallized hexagonal boron nitride (h-BN) powder is suitable as thermally conductive filler in resins. To obtain h-BN powder with large particle size, as well as high purity and crystallinity, high-temperature heat treatment over 1800°C in a N₂ gas atmosphere is effective. The carbothermal reduction nitridation (CRN) involves the carbothermic reduction of boric oxide in a N₂ gas atmosphere. In CRN using a CaO promoter, h-BN particles with high crystallinity can be obtained by a simple heat treatment process. CaO prevents the evaporation of boron oxide and aids in h-BN particle growth at high temperatures. However, CaB₆ is formed as byproduct or impurity when CRN using the CaO promoter is performed at temperatures higher than 1800°C. In this study, the relationship between the products and the reaction temperature was clarified via thermodynamic considerations and experimentation. The results clarified the ideal reaction process of CRN using a CaO promoter to obtain highly purified and crystallized h-BN powder.     

浸渍及热处理对常压烧结AlN/h-BN复相陶瓷微观结构及性能的影响

采用常压烧结方法在1 700℃保温2 h制备出AlN/20%(体积分数)h-BN复相陶瓷,对烧结后的样品分别采用A10铝溶胶和硅溶胶/酚醛树脂进行浸渍处理,随后在1 450℃氮气气氛下热处理2 h。对比研究了浸渍及热处理前后复相陶瓷的致密度、抗弯强度、Vickers硬度、微观结构和物相组成,并分析了复相陶瓷的强化机理。结果表明:A10铝溶胶浸渍处理后样品的抗弯强度和Vickers硬度略有提高;经过硅溶胶/酚醛树脂处理的样品抗弯强度和Vickers硬度大幅提高,抗弯强度和Vickers硬度分别从81.5MPa和1.99 GPa提高到130.1 MPa和3.58GPa;硅溶胶/酚醛树脂处理后的样品在孔隙界面处生成的碳化硅及氮氧化铝是样品抗弯强度和Vickers硬度显著提高的主要原因。     

Characterization of cordierite based h-BN doped ceramics as an electronic substrate/circuit board material

In this study, h-BN was added to the cordierite composition obtained from zeolite, which was prepared by the determined stoichiometry to facilitate machinability and increase thermal conductivity. Sintering behavior, hardness, machinability, and thermal/electrical properties of the samples obtained by sintering the compounds at different times were investigated. Thanks to these features, it is aimed to use cordierite as an alternative material to integrated circuit substrates and electronic packaging materials. The produced samples were analyzed by X-ray diffraction analysis, examined by scanning electron microscopy, and field emission scanning electron microscopy. Afterward, thermal properties such as thermal diffusivity, thermal conductivity, and electrical properties such as electrical conductivity and dielectric permittivity were measured. The hardness and machinability of samples were investigated. Cordierite, spinel, glassy phase, and h-BN phase were detected, and it was observed that the blocky cordierite grains turned into equiaxed grains with the increase of the h-BN. According to the results obtained from the thermal conductivity test, it was seen that the h-BN additive increased the thermal conductivity value in general. In addition, it was determined that with the increase of h-BN, the hardness decreased, and the machinability properties of the samples improved.     

Cr–C/h-BN 自润滑复合镀层的制备与摩擦学性能

在三价铬Cr–C镀液中添加1~5 g/L的h-BN自润滑微粒,运用直流电沉积技术在Q235碳素结构钢基体上制备了Cr–C/h-BN复合镀层。利用扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度计、摩擦磨损试验机等设备分析了h-BN微粒添加量、电流密度等工艺参数对镀层组织和性能的影响。结果表明:在电流密度20 A/dm2,h-BN添加量3 g/L的条件下,可获得h-BN微粒体积分数为6.15%的复合镀层。h-BN微粒的添加改善了Cr–C合金镀层的耐磨性,Cr–C/h-BN复合镀层在室温干摩擦条件下的磨损率减少了22%,平均摩擦因数由原先的0.49降低至0.31。