改性六方氮化硼/水性聚氨酯防腐涂料制备与性能

以聚甘油-10(PG)作为稳定剂，在超声条件下对六方氮化硼(h-BN)进行剥离和改性。通过红外光谱(FT-IR)、热重分析(TG)、原子力显微镜(AFM)和透射电镜(TEM)对PG改性的h-BN纳米片(GB)进行了表征。将制备的PG纳米粒子用作水性聚氨酯(WPU)涂层的防腐填料，制备了GB质量分数分别0，0.5%，1.0%，2.0%的为复合涂层(PU/GB)。考察了不同涂层的水接触角、吸水率、附着力损失、热稳定性和机械性能。最后，通过电化学工作站研究了WPU、PU/GB0.5、 PU/GB1.0 和PU/GB2.0复合涂层在3.5%NaCl水溶液中的腐蚀行为。结果表明，GB纳米粒子可以显著增强水性聚氨酯涂层的耐水性、热稳定性、机械性能和耐腐蚀性能。     

六方氮化硼/碳化硅晶须填充改性聚酰亚胺导热绝缘复合材料的制备及表征

采用固相共混方法将六方氮化硼(h-BN)和碳化硅晶须(SiCw)作为导热填料对单醚酐型聚酰亚胺(PI)模塑粉进行改性,然后通过热模压工艺制备PI导热绝缘复合模压材料,并对其性能进行表征。测试结果表明:h-BN可以有效提高模塑料导热性能、热性能和电绝缘性能,但会降低材料力学性能;SiCw可以有效提高复合材料导热性能、热性能和力学性能,但会显著降低电绝缘性能。将h-BN/SiCw复配使用,在显著提高复合材料导热性能和热性能的同时又可保持其良好的力学性能和电绝缘性能。添加30%(质量分数)h-BN/SiCw(3/1),复合材料导热系数提高至1.21 W/(m·K),是未改性PI材料的4.84倍,弯曲强度为142MPa,体积电阻率为1.27×10~(14)Ω·cm,线性热膨胀系数(CTE)显著降低为55.6μm/(m·℃)。     

改性六方氮化硼/水性聚氨酯涂料的制备与性能

以聚甘油-10(PG)作为稳定剂,超声下对六方氮化硼(h-BN)进行剥离和改性制得PG功能化的少层h-BN纳米粒子(GB).利用GB与水性聚氨酯(WPU)共混得到WPU/GB.通过FTIR、TG、AFM和TEM对GB进行了表征,证实了少层GB的成功制备.动电位极化和电化学阻抗谱测试表明,WPU/GB涂层比纯WPU涂层具有更高的耐腐蚀性能.GB含量为1.0％(以WPU的质量为基准,下同)的WPU/GB1.0复合涂层的耐腐蚀性能最好,极化电阻为1.33×107?·cm2,阻抗|Z|可达到5.37×107?·cm2.此外,与纯WPU相比,WPU/GB1.0腐蚀电流密度从2.64×10–8 A/cm2减小至3.32×10–9 A/cm2,腐蚀电压从–0.309 V增大到–0.037 V,保护效率高达98.74％.     

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。     

六方氮化硼的合成及表征

以硼酸、三聚氰胺为原料,通过高温反应,在氮气气氛下制备出六方氮化硼（h-BN）样品。考察了硼酸与三聚氰胺物质的量比、焙烧温度对h-BN产率、纯度及形貌的影响。制备h-BN最佳工艺条件:硼酸与三聚氰胺物质的量比为4.0:1,1 000 ℃焙烧2 h,1 400 ℃焙烧2 h。在此条件下h-BN产率为25%、纯度为97%、粒度约为250 nm。     

LDPE/PEG插层剥离改性氮化硼导热复合材料的制备及其性能

以聚乙二醇(PEG)为插层剂,通过机械球磨法制备了PEG插层剥离改性氮化硼.以低密度聚乙烯(LDPE)为基体,PEG插层剥离改性氮化硼为导热填料,采用双辊开炼、压片成型制备LDPE/PEG插层剥离改性氮化硼导热复合材料,研究了改性氮化硼用量及粒径对复合材料导热性能、力学性能和电绝缘性能的影响.结果表明:随着PEG插层剥...     

聚丙烯/高密度聚乙烯/氮化硼导热复合材料的制备及性能研究

以聚丙烯（PP）/高密度聚乙烯（HDPE）共混物为基体,六方氮化硼（h-BN）为导热填料,聚丙烯接枝马来酸酐（PP-g-MAH）为相容剂,通过熔融共混法制备PP/HDPE/h-BN和PP/HDPE/h-BN/PP-g-MAH导热复合材料。采用导热系数仪、场发射扫描电镜、万能试验机、热分析仪等测试导热复合材料,研究不同含量的h-BN、PP-g-MAH对复合材料导热性、力学性能、结晶性能和耐热性的影响。结果表明：随着h-BN含量的增加,PP/HDPE/h-BN复合材料的弯曲强度、热导率和耐热性提高。当h-BN含量为20%,复合材料的弯曲强度达到41.02 MPa;当h-BN含量为25%,复合材料热导率达到0.372 1 W/（m·K）。h-BN对PP的结晶具有促进作用,提升PP的结晶速率和结晶温度。PP、HDPE与h-BN质量比为64∶16∶15时,添加5%的PP-g-MAH,增强了h-BN和基体材料的界面相容性,复合材料的弯曲强度达到42.72 MPa,拉伸强度达到26.64 MPa,热导率达到0.356 1 W/（m·K）。     

Preparation of Nanostructured Hexagonal Boron Nitride Powder

In this communication, we describe an inexpensive and feasible method for the preparation of hexagonal boron nitride (h–BN) nanorods in the absence of metal catalyst. Tertiary calcium phosphate (Ca₃(PO₄)₂) and ammonium biborate hydrate (NH₄HB₄O₇·3H₂O) were selected as starting materials where calcium phosphate was used as a diluting agent to prevent the formation of bulk B₂O₃ during the thermolysis of ammonium biborate hydrate. The mixture was nitrided at 900°C in the flowing ammonia and was transformed into h–BN nanorods after subsequent crystallization. After crystallization at 1650°C for 2 h, the unique microstructure of h–BN nanorods was observed.     

Decomposition Suppression of Silicon Nitride by Hexagonal Boron Nitride Nanocoatings

We report a stabilized Si₃N₄ simply with nanocoatings of h-BN. Very thin BN coatings are enough for suppressing the decomposition of Si₃N₄ particles. This approach should open up a new potential way to prepare stabilized Si₃N₄. Reduced nitridation of H₃BO₃-coated Si₃N₄ powder at 1050°C in a flowing mixed 40% N₂+60% H₂ atmosphere, and then following heat-treatment at 1500°C in a flowing N₂ atmosphere can realize the nanocoating of BN on Si₃N₄ particles. Compared with the Si₃N₄ powder without nanocoatings of h-BN, TG and XRD analysis showed that the obtained h-BN nanocoated Si₃N₄ powder demonstrated obviously improved stability in argon atmosphere.     

化学气相沉积六方氮化硼涂层的制备及应用

六方氮化硼(h-BN)涂层是一种性能优异的功能陶瓷材料,介绍了化学气相沉积( CVD)六方氮化硼涂层的制备工艺,综述了h-BN涂层的优异性能和应用现状,并对其研究发展趋势进行了展望.认为先驱体性能存在缺陷、沉积机理复杂、工艺可控性差、生产成本高是目前CVD制备h-BN涂层存在的主要工艺问题,指出今后还需在新型先驱体的研发和使用、沉积机理的深入探究、工艺优化和放大等方面开展深入研究,以实现h-BN涂层的大规模工业化生产和应用.     

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。     

Electrical Resistivity and Microwave Transmission of Hexagonal Boron Nitride

The dc conductivity of hexagonal boron nitride (BN) and BN-containing composites was measured as a function of temperature up to 2400°C. The results confirm that at high temperatures BN is an intrinsic semiconductor with an energy gap of 0.99 ± 0.06 aJ (6.2 ± 0.4 eV) at T = 0 K. Extrapolated values for the resistivity of BN in the range 2600° to 3000°C are used to analyze the absorption, reflectivity, and transmissivity of a BN window when subjected to microwave radiation under atmospheric reentry conditions. It appears that the transmissivity is of the order of 1 to 10% at these temperatures due mainly to the high conductivity in a very thin, very hot surface layer. The transmissivity can be improved by using a composite made of boron nitride and silica.     

Sintering of the Mechanochemically Activated Powders of Hexagonal Boron Nitride

Pressureless sintering of hexagonal boron nitride (BN) was performed using a powder activated by mechano-chemical treatments. Physical properties of the sintered BN bodies depend on the type of starting powder and the conditions of the treatments. The BN body, which was obtained at 2000°C using an appropriate activated powder, was 99 wt% pure and was excellent in mechanical and physical properties, in spite of its low density (1.64 g/cm³).     

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.     

Orientation and Growth of Grains in Copper-Activated Hot-Pressed Hexagonal Boron Nitride

Hexagonal boron nitride powder was hot pressed in an environment of metallic copper. When compared with a copper-free system, the sintered body exposed to the copper was composed of substantially thicker grains having an unusual arrangement, consisting of preferred alignment of (0001) basal planes parallel to the pressure axis. The character of the orientation of the boron nitride grains substantially influenced the mechanical strength of the ceramics. The difference in the orientation of the grains is explained by the interaction between copper atoms and boron nitride crystals selectively occurring on the (0001) basal planes of the latter.     

Shock-Induced Transformations in Hexagonal Boron Nitride by High-Velocity Thermal Spray

Shock synthesis of cubic BN ( c -BN) was accomplished using high-velocity thermal spray. Al-8Si-20BN (hexagonal BN, h -BN) composite powders were injected into a high-energy flame where the particles partially melted and accelerated to impact on steel substrates. The shock wave generated by the sudden impact of the droplets propagated through the underlying deposit, which experienced a polymorphic transition to high-pressure forms. Transmission electron microscopy revealed that the deposits contained platelike c -BN embedded in h -BN. The c -BN formed with a specific orientation relation, with (0001) h -BN parallel to (111) c -BN and [11–20] h -BN nearly parallel to [2–20] c -BN. As a result of shock propagation, a number of half-Frank loops with Burgers vector ½[0001] were introduced and thin (∼3 nm) layers of amorphous BN ( a -BN), parallel to the (0002) plane, were formed. Significant shearing of the (10–10) plane with respect to the c -axis, delamination, and kink bands were also observed in most of the h -BN grains. The Hugoniot pressure calculation suggested that the impact pressure was sufficient to trigger the nucleation of c -BN.