氮化硼纳米管纤维成为现实

科学家们利用他们开发的碳纳米管纤维定制湿纺工艺制造了第一个氮化硼纳米管纤维。

Scientists create the first boron nitride nanotube fibers using the custom wet-spinning process they developed to make carbon nanotube fibers.

在马特奥·马帕斯奎利教授和安格尔·马蒂教授领导下，莱斯团队简化了对极高价值纳米管的处理，使其更适合大规模的应用，包括航空航天、电子和节能材料。

A Rice team led by professors Matteo Pasquali and Angel Martí has simplified handling of the highly valuable nanotubes to make them more suitable for large-scale applications, including aerospace, electronics and energy-efficient materials.

研究人员在《自然通讯》杂志上报道称，氮化硼纳米管，又称BNNT，在适当的条件下组装成液晶，其氯磺酸的浓度超过170PPM以上。

The researchers reported in Nature Communications that boron nitride nanotubes, aka BNNTs, assemble themselves into liquid crystals under the right conditions, primarily concentrations above 170 parts per million by weight in chlorosulfonic acid.

这些液晶由排列整齐的BNNT组成，它们比通常在溶液中形成的缠结纳米管更容易处理。该实验室开始从液晶溶液中形成纤维和薄膜。

These liquid crystals consist of aligned BNNTs that are far easier to process than the tangled nanotubes that usually form in solution. The lab proceeded to form fibers and films from the liquid crystalline solutions.

马蒂教授说，“BNNT纤维在制造各种产品方面很有吸引力，应用范围从可穿戴设备到航空飞行器。”他在其实验室设计了解决方案，并协助表征了帕斯夸利实验室生产的纤维。

"BNNT fibers are attractive for the manufacture of a variety of products, with applications that range from wearables to aerospace vehicles," said Martí, whose lab designed solutions and helped characterize the fibers produced in Pasquali's lab

氮化硼纳米管就像碳纳米管，但在它们的六角形晶格中，硼原子和氮原子交替存在，而非碳原子。这两种类型的纳米管都很强大，但与导电的碳纳米管不同的是，BNNT是很好的电绝缘体，在高达900℃（1652℉）的空气中具有热和化学稳定性。

Boron nitride nanotubes are like carbon nanotubes, but with alternating boron and nitrogen atoms instead of carbon in their hexagonal lattices. Both types of nanotubes are strong, but unlike electrically conductive carbon nanotubes, BNNTs are good electrical insulators and are thermally and chemically stable in air up to 900 degrees Celsius (1,652 degrees Fahrenheit).

为了形成液晶，研究人员需要确保他们的纳米管中没有污染物。不幸的是，这些污染物大多是少量的氮化硼，这可能会破坏液晶的生成。

To form liquid crystals, the researchers needed to be sure their nanotubes were free of contaminants. Unfortunately, those contaminants were mostly bits of boron nitride that threatened to gum up the works.

研究生和主要作者塞德里克·金斯特拉说：“早期的BNNT样品中含有大量的非纳米管氮化硼结构”。它们要么通过化学键与BNNT结合，要么只是物理粘附在BNNT上，阻止BNNT在酸中分散并在更高浓度下排列。

"Early BNNT samples contained lots of non-nanotube boron nitride structures," said graduate student and lead author Cedric Ginestra. "They were either chemically bound to the BNNTs or just physically adhered in a way that prevented BNNTs from dispersing in acid and aligning at higher concentrations.

“很难将这些氮化硼从BNNT中分离出来，甚至很难测量它们的浓度，”他说。到目前为止，我们尝试过的每一种定量技术基本上都表明，所有不同类型的氮化硼似乎都是相同的。”

"It is difficult to separate these boron nitride allotropes from BNNTs, and hard to even measure their concentration," he said. "All the different types of boron nitride appear identical by basically every quantitative technique that we've tried so far."

他表示，他们与供应商合作，优化BNNT纯化工艺，以形成液晶溶液，并使用帕斯夸利实验室开发的纯化工艺，帮助他们获得更好的BNNT批次。一旦生产出合适的材料，帕斯夸利基团就准备快速调整其碳纳米管纤维湿纺技术，用该工艺生产出第一个氮化硼线。

Working with their supplier to optimize their BNNT purification process for the formation of liquid crystalline solutions and using a purification process developed in the Pasquali lab helped them obtain better batches of BNNTs, he said. Once suitable material was produced, the Pasquali group was primed to quickly adapt its wet-spinning techniques for carbon nanotube fibers to make the first boron nitride threads with the process.

吉恩斯特拉说：“有报道称，有人用BNNT固体喷烟，拉伸并缠绕成线，但这与我们的工艺完全不同。”我们的目标是制造一种非常高度排列的纤维，因为沿着纳米管的长度，其性能更好。”

"There are reports of others taking solid puffs of BNNTs and stretching and twisting them to make a yarn, but that's very different from our process," Ginestra said. "Our goal was to make a very highly aligned fiber because the properties are better along the length of the nanotubes."

他说，液晶是理想的纤维前体，因为其内部的纳米管已经排列好了。液晶中的BNNT排列是在显微镜下通过双折射来确定的，因为晶体像棱镜一样可分光，即使它们看起来是清晰的。

Liquid crystals are the ideal precursor for fibers because the nanotubes within are already aligned, he said. BNNT alignment in the liquid crystals was identified microscopically by their birefringence, a phenomenon by which crystals split light, prism-like, even if they appear to be clear.

吉恩斯特拉说，这些薄膜还展示了BNNT溶液处理可作为碳纳米管开发的方法。这种透明的薄膜可能在下一代电子产品中很有用。”随着材料和我们对液晶溶液的理解的提高，BNNT薄膜和纤维的性能将会得到改善。”

The films also demonstrated how BNNT solution processing can adopt methods developed for carbon nanotubes, Ginestra said. Such transparent thin films could be useful in next-generation electronics. "The BNNT film and fiber properties will improve as the material and our understanding of the liquid crystalline solution improves," he said.

马蒂指出，BNNT薄膜可以用于紫外线滤波器、防污涂层和防腐。

Martí noted BNNT films would be useful as filters for ultraviolet light, antifouling coatings and for corrosion protection.