氮化硼纤维合成工艺与结构表征

硼酸和三聚氰胺以一定配比合成氮化硼前驱体高聚物.将该前驱体超声溶于甲酸溶液,在静电纺丝电压25 kV,正负极距离18 cm的条件下,可通过静电纺丝法制备直径均匀的纤维.将该电纺纤维放入马弗炉,以10℃/min升温速率加热至600℃和850℃,保温不同时间,可制备白色BN纤维.利用SEM、TEM、TG-DSC、XPS和IR对BN纤维的结构,性能进行详细表征.结果表明,前驱体高聚物具有良好的静电纺丝性能,提高煅烧温度、延长煅烧时间可制备较纯的氮化硼纤维.     

氮化硼晶须氮化工艺及其生长机理(英文)

通过氮化由三聚氰胺和硼酸为原料制备的氮化硼晶须前驱体制备出氮化硼晶须,并采用扫描电子显微镜、X射线衍射仪、红外光谱仪和热分析仪对氮化硼晶须氮化工艺进行研究,同时对氮化硼晶须的生长机理进行探讨。结果表明:当升温速率5℃/min、氮气流量0.2L/min、氮化温度1 700℃、保温时间30min时可制备出长径比高、性能优良的氮化硼晶须。氮化硼晶须的生长机理可归纳为前驱体脱水、聚合反应、无机化反应和晶相转变等过程。     

有机前驱体法制备氮化硼纤维的研究进展

氮化硼纤维作为正在发展中的一种重要的高性能无机纤维,具有优异的耐高温和透波性能。目前高性能氮化硼纤维的制备主要采用类似于碳纤维生产的有机前驱体转化法。介绍了国内外合成氮化硼纤维前驱体的各种合成方法以及各种合成产物制备氮化硼纤维路线的优缺点,并对氮化硼纤维研究的发展趋势进行了展望。     

氮化硼的制备及其性能表征

以三氯化硼和氯化铵为原料,在110℃合成三氯环硼氮烷(TCB),将合成的TCB与异丙胺在0℃左右进行胺解反应,将胺解产物在120℃聚合,得到聚硼氮烷高聚物,聚硼氮烷经1 000℃氮化得到氮化硼(BN),对BN的热性能及晶体结构等进行表征。结果表明:通过红外光谱和X射线衍射分析,聚合产物为聚硼氮烷,经1 000℃氮化后,形成BN晶体,晶体结构为斜方晶系;氮化过程存在部分游离碳(C),BN晶体中含有B,N,C元素;聚硼氮烷可溶于二甲基亚砜和N,N-二甲基甲酰胺,可以进行湿法纺丝。     

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。     

纯相钼酸酐氮化合成技术及表征

以钼酸铵为原料,采用高温焙烧法制备颗粒状催化剂前驱体钼酸酐;以氮氢混合气为氮化剂合成氮化钼。考察空速、程序升温速率及氮化终温对氮化钼比表面积的影响,并通过SEM、XRD、BET对纯相氮化钼及前驱体钼酸酐表征。结果表明,一定条件下,当空速为42 000 h-1时,产物的比表面积最大,为129.2 m~2·g~(-1);当升温速率为1.0℃·min-1时,比表面积最大,为135.6 m~2·g~(-1);当氮化终温为750℃时,比表面积达到52.78 m~2·g~(-1)。纯相钼酸酐氮化条件温和、原料成本低。     

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%。     

尿素对前驱物及氮化铝粉末粒度形貌的影响

以硝酸铝 [Al(NO3) 3·9H2 O]、葡萄糖 [C6 H1 2 O6 ·H2 O]为原料 ,利用碳热还原法制备氮化铝粉末 ,研究了尿素对前驱物及其氮化反应产物的组成和显微形貌的影响。研究发现 :尿素不仅可以影响前驱物的组成和显微形貌 ,还对氮化反应产物的显微形貌有重要影响。在溶液里添加尿素后 ,它与硝酸铝发生了低温燃烧合成反应 ,生成了比表面积高的泡沫状前驱物 ,该过程中碳燃烧损失较大。在没有添加尿素的溶液中 ,没有燃烧反应发生 ,碳的损失小 ,生成的前驱物团聚现象严重 ,比表面积低。两种前驱物的氮化反应产物保留了各自前驱物的形貌特征 ,对于不添加尿素合成的前驱物 ,在其氮化反应后所生成的氮化铝粉末板结严重 ;而添加尿素合成的前驱物的氮化反应产物是由球形颗粒组成的软团聚体。利用XRD ,SEM等分析方法对粉末进行了表征     

无机前驱体法制备连续氮化硼纤维及其结构表征

采用无机前驱体法制备氮化硼（BN）纤维,先将熔融B2O3拉丝低温（1000℃）NH3下氮化后高温（1750℃）N2下氮化得到均匀的BN纤维.利用XRD,FTIR,XPS,FE-SEM,HR-TEM,XRF和ICP等测试方法对1750℃氮化温度下的BN纤维物相组成、微观结构、元素成分进行了系统表征.结果表明：经过1750℃二次氮化后的BN纤维物相主要为六方氮化硼（h— BN）,氮化基本完全,纤维直径5～8μm,结构致密但结晶不完全,部分出现无定形BN（a-BN）.     

含氮杂原子B-Beta分子筛的制备及其对Knoevenagel缩合反应的催化性能

水热合成杂原子B-Beta分子筛,低温氮化二次处理制备N掺杂的新型碱催化剂,利用Knoevenagel缩合反应进行碱性催化性能评价,考察氮化温度、反应时间、不同氮化前驱体及催化剂稳定性对反应的影响.结果表明,采用低温500℃氮化处理的杂原子B-Beta分子筛催化剂具有优异的催化活性,苯甲醛转化率及产物选择性均接近100...     

有机先驱体法制备氮化硼涂层改性玻璃纤维织物

以三乙醇胺和硼酸为原料，合成了硼酸氨基三乙酯。研究了原料配比、反应温度及反应时间对产率的影响，在原料摩尔比1：1、温度160℃的条件下反应180rain，硼酸氨基三乙酯的产率达到87％。由于N元素的引入，硼酸氨基三乙酯的水解稳定性良好，且在无水乙醇溶液中水解缓慢，能够满足工业上制备硼酸氨基三乙酯涂层的工艺要求。以硼酸氨基三乙酯为先驱体在氮气气氛中于400℃和800℃条件下热解，其热解产物为氮化硼和碳化硼的混合物。400℃时氮化硼的结晶程度较低，800℃时结晶程度提高。氮化硼涂层对高硅氧、无碱玻璃纤维织物具有显著的增强作用并可明显改善其耐温性能。     

Preparation and Use of a Boron Nitride Precursor as Binder for the Densification of Boron Nitride

A precursor of boron nitride was prepared through the partial condensation of 2,4,6-trichloroborazine and bis-(trimethylsilyl)acetylene. This reaction was conducted at 100°C and is catalyzed by AlCl₃. The condensation product pyrolyzed at 800°C, producing trimethylsilyl chloride as a volatile product and a boron nitride rich residue containing 54 wt% of the initial weight. Mixtures of the precursor and commercial boron nitride were made and hot-pressed at 800°C and 27.6 MPa. A maximum density of 1.84 g/cm³ is reached at a loading corresponding to the deposition of 13 wt% residue derived from the precursor. Examination by analytical electron microscopy, including X-ray energy dispersive spectroscopy and electron energy loss spectroscopy analyses, revealed the location of material derived from the precursor in BN-binder composites through the presence of residual aluminum, silicon, and carbon. Crystallization of boron nitride from the precursor appears to have taken place, as deduced from the morphology of the phases observed and association with residual elements present in the binder.     

Chemical vapor deposition of pyrolytic boron nitride ceramics from single source precursor

Pyrolytic boron nitride ceramics were prepared on graphite substrates from borazine as the single source precursor by hot-wall chemical vapor deposition in deposition temperature range from 1300 °C to 1600 °C with a total pressure of 200 Pa. The chemical composition and the effect of deposition temperature on the morphology, phase, and structure of the pyrolytic boron nitride were investigated. A high purity product with stoichiometric B/N ratio is obtained. The deposition surface of the product exhibited a pebble-like structure, and the fracture surface showed an apparent laminar structure having a preferential (002) orientation parallel to the surface of the substrate at temperatures above 1400 °C. The product contained some turbostratic and amorphous boron nitride as evidenced from XRD and FTIR examinations. With the increase of deposition temperature, the crystallinity of the pyrolytic boron nitride increased with the turbostratic and amorphous boron nitride turned into hexagonal structure, and the crystallinity of the product became higher.     

先驱体法制备氮化硼纤维的研究

以三聚氰胺和硼酸为原料,用有机化学法合成先驱体,制备氮化硼纤维。采用中和滴定法、红外吸收光谱、X射线衍射及扫描电镜进行氮化硼纤维的氮含量的测定及结构分析。结果表明:合成的先驱体是结晶体,晶体发育良好;制得的氮化硼纤维具有B-N键、B-N六元环的特征吸收;随着氮化处理温度的提高, 氮化硼纤维的氮含量增加;用扫描电镜观察1 700℃制得的氮化硼纤维的直径为2-5μm,长径比为20- 100,氮含量为53．46％。     

Large-scale synthesis and growth mechanism of boron nitride nanocomposite assembled by nanosheets and nanotubes

Boron nitride nanocomposites assembled by nanosheets and nanotubes can exert multi-dimensional synergistic toughening and strengthening effects. This material is expected to be a high-efficiency reinforcement additive in advanced structural ceramics. In this study, we designed a universal method for synthesizing gram-scale boron nitride nanocomposites by annealing the precursor containing catalyst in chemical vapor deposition equipment under flowing ammonia, and a combined growth mechanism of surface-diffusion and solid-liquid-solid is proposed. The boron nitride nanosheets were initially formed by a surface-diffusion reaction between boron trioxide and ammonia at 1300°C. At elevated temperatures (1400°C-1500°C), the boron nitride nanotubes grew in-situ from the nanosheets in the presence of catalysts through a solid-liquid-solid mechanism, forming the desired boron nitride nanocomposite.     

Urchin-like boron nitride hierarchical structure assembled by nanotubes-nanosheets for effective removal of heavy metal ions

Water pollution has become a serious global issue owing to the large amounts of contaminants generated from industrial and agricultural development. Recently, various boron nitride-based micro/nano-materials have exhibited efficient sorption capacity for contaminants from water. Herein, novel urchin-like boron nitride hierarchical structure assembled by free-growing boron nitride nanotubes and crapy boron nitride nanosheets is firstly fabricated via a sample two-step approach, including the synthesis of analogous "core-shell" structured boron-containing precursor and thermal catalytic chemical vapor deposition. A combined growth mechanism of vapor-liquid-solid and vapor-solid is proposed to control the formation of BN hierarchical structure. The unique structure exhibits superior removal capacity of 115.07?mg?g^?1 and 92.85?mg?g^?1 for Pb²⁺ and Cu²⁺ in water solution, respectively. The excellent adsorption performance of the product mainly derives from the vast lattice imperfections, the high-density edge active sites, the expanded interplanar spacing, as well as the unique structural characteristics. They are beneficial for structural stability and enough space for accommodating the adsorbed heavy metal ions. These results indicate that the urchin-like boron nitride hierarchical structure is a promising adsorption material for water treatment.     

氮化硼陶瓷纤维的制备与应用

氮化硼陶瓷纤维是一种正在发展的新型高性能材料,然而传统的高温法很难制备高质量的氮化硼陶瓷纤维材料,只能通过前驱体转化法实现。概述了氮化硼陶瓷纤维的合成路线以及各种前驱体制备氮化硼陶瓷纤维的优缺点,并对前驱体法制备氮化硼陶瓷纤维的发展趋势做了展望。     

环保型催化材料氮化钼的合成与表征

采用溶胶-凝胶法制备了负载型氮化钼的前驱体,采用流化氮化新工艺制备了氮化钼。通过单因素和正交实验,确定了较优氮化条件:升温速率为1.2℃/min,H2∶N2=4.0∶1,空速70×103h-1,氮化终温为650℃,活性组分MoO3含量为10%。并采用BET、XRD、SEM等对制备的氮化钼及前驱体进行了表征。     

聚正丙胺/甲胺基环硼氮烷的裂解

以正丙胺、甲胺和三氯环硼氮烷（trichloroborazine,TCB）为原料,在高于–10℃的温和条件下合成了一种可溶可熔的聚（正丙胺/甲胺）环硼氮烷（PPAB）先驱体。用热分析、Fourier变换红外光谱、元素分析、Raman光谱、X射线衍射和X射线光电子能谱等表征手段对聚（正丙胺/甲胺）环硼氮烷的结构及其在Ar中的裂解过程进行了研究。结果表明：PPAB的结构中含有B3N3六元环、N—H、C—H和C—N,其熔点约为96℃。1000℃时在Ar中的陶瓷产率为52.8%（质量分数）,裂解质量损失主要发生在800℃以下,1 000℃的裂解产物中碳元素以C—N和C—C形式存在。1 400℃左右产物开始结晶,2000℃得到的产物为结晶程度较低的h-BN。