由陶瓷纳米纤维制成的海绵状材料除了保留陶瓷特性外，还使其具备了高度变形的能力，就像海绵一样。这种多孔结构的海绵陶瓷可以作为水净化装置，也可以用作绝缘保护材料。这项开发是布朗大学的Huajian Gao与清华大学的Hui Wu和Xiaoyan Li合作完成，并在Science Advances（科学进展）期刊发表。

海绵陶瓷在耐高温的同时也可以像海绵那样高度变形

材料的物理特性在纳米级别会发生巨大变化，对于陶瓷材料来说脆性和断裂缺陷也会变小，纳米陶瓷纤维改善了材料的蠕变性，促进陶瓷达成类似海绵的变形机制。

但陶瓷纤维是很难制备的，传统的纤维制造方法肯定行不通，3D打印则不仅耗时并且昂贵。

因此，研究人员使用了一种称为“blow-spinning”（吹纺）的方法，该方法是由Wu在清华实验室开发的。该方法是通过微型注射器来驱动含陶瓷材料的液体溶液，将这些很快凝固的材料收集并加热，剩下的就是像棉花球一样的陶瓷纤维。

氧化锆

“海绵陶瓷”在摄氏800度仍然保持韧性外，研究人员还通过一组对比试验，让人们充分感受这种“海绵陶瓷”优异的隔热效果。

氧化锆材质的海绵陶瓷具备优异的隔热效果

如图所示，花瓣放在7毫米厚度的不同材质下进行底部为400摄氏度的加温。10分钟后，氧化锆材质海绵陶瓷上方的花瓣由于脱水变得松脆，其他进行对比的材质则全都烧焦枯萎。具备这样的耐热性和变形性，则说明它可以用作消防员专用消防服。

二氧化钛

除此之外，还可以利用二氧化钛的光催化作用，这种材质的海绵陶瓷不仅可以杀死水中的微生物和细菌，降解水中的有机染料，还可以像海绵一样循环利用。二氧化钛海绵吸水量为其自身重量的50倍，光照条件下，15分钟即可完成对染料的降解，完成净化后将水挤出就可以再次吸水净化。

研究人员称，通过这种制作工艺，可以制备不同材质的“海绵陶瓷”，而这种材料应该会有很广阔的应用前景。

粉体圈 译

注：

由于小编文字水平和翻译功底有限，以上内容或许存在错漏之处，有兴趣的读者可自行阅读原文。

New ceramic nanofiber 'sponges' could be used for flexible insulation, water purification

Researchers have found a way to make ultralight sponge-like materials from nanoscale ceramic fibers. The highly porous, compressible and heat-resistant sponges could have numerous uses, from water purification devices to flexible insulating materials.

"The basic science question we tried to answer is how can we make a material that's highly deformable but resistant to high temperature," said Huajian Gao, a professor in Brown University's School of Engineering and a corresponding author of the research. "This paper demonstrates that we can do that by tangling ceramic nanofibers into a sponge, and the method we use for doing it is inexpensive and scalable to make these in large quantities."

The work, a collaboration between Gao's lab at Brown and the labs of Hui Wu and Xiaoyan Li at Tsinghua University in China, is described in the journal Science Advances.

As anyone who has ever dropped a flower vase knows well, ceramics are brittle materials. Cracks in ceramics tend to propagate quickly, leading to catastrophic failure with even the slightest deformation. While that's true for all traditional ceramics, things are different at the nanoscale.

"At the nanoscale, cracks and flaws become so small that it takes much more energy to activate them and cause them to propagate," Gao said. "Nanoscale fibers also promote deformation mechanisms such as what is known as creep, where atoms can diffuse along grain boundaries, enabling the material to deform without breaking."

Because of those nanoscale dynamics, materials made from ceramic nanofibers have the potential to be deformable and flexible, while maintaining the heat resistance that make ceramics useful in high-temperature applications. The problem is that such materials aren't easy to make. One often-used method of making nanofibers, known as electrospinning, doesn't work well with ceramics. Another potential option, 3-D laser printing, is expensive and time-consuming.

So the researchers used a method called solution blow-spinning, which had been developed previously by Wu in his lab at Tsinghua. The process uses air pressure to drive a liquid solution containing ceramic material through a tiny syringe aperture. As the liquid emerges, it quickly solidifies into nanoscale fibers that are collected in a spinning cage. The collected material is then heated, which burns away the solvent material leaving a mass of tangled ceramic nanofibers that looks a bit like a cotton ball.

The researchers used the method to create sponges made from a variety of different types of ceramics and showed that the materials had some remarkable properties.

For example, the sponges were able to rebound after compressive strain up to 50 percent, something that no standard ceramic material can do. And the sponges can maintain that resilience at temperatures up to 800 degrees Celsius.

The research also showed that the sponges had a remarkable capacity for high-temperature insulation. In one experiment, the researchers placed a flower petal on top of 7-millimeter-thick sponge made from titanium dioxide (a common ceramic material) nanofibers. After heating the bottom of the sponge to 400 degrees Celsius for 10 minutes, the flower on top barely wilted. Meanwhile, petals placed on other types of porous ceramic materials under the same conditions were burnt to a crisp.

The sponges' heat resistance and its deformability make them potentially useful as an insulating material where flexibility is important. For example, Gao says, the material could be used as an insulating layer in firefighters' clothing.

Another potential use could be in water purification. Titanium dioxide is a well-known photocatalyst used to break down organic molecules, which kills bacteria and other microorganisms in water. The researchers showed that a titanium dioxide sponge could absorb 50 times its weight in water containing an organic dye. Within 15 minutes, the sponge was able to degrade the dye under illumination. With the water wrung out, the sponge could then be reused—something that can't be done with the titanium dioxide powders normally used in water purification.

In addition to these, there may be other applications for ceramic sponges that the researchers haven't yet considered.

"The process we used for making these is extremely versatile; it can be used with a great variety of different types of ceramic starting materials," said Wu, one of the corresponding authors from Tsinghua. "So we think there's huge prospect for potential applications."