标签: 金属
Researchers develop efficient method to produce nanoporous metals
Date::November 25, 2014
Source::DOE/Lawrence Livermore National Laboratory
Summary::Nanoporous metals -- foam-like materials that have some degree of air vacuum in their   
           structure -- have a wide range of applications because of their superior qualities.

Nanoporous metals -- foam-like materials that have some degree of air vacuum in their structure -- have a wide range of applications because of their superior qualities.

They posses a high surface area for better electron transfer, which can lead to the improved performance of an electrode in an electric double capacitor or battery. Nanoporous metals offer an increased number of available sites for the adsorption of analytes, a highly desirable feature for sensors.

Lawrence Livermore National Laboratory (LLNL) and the Swiss Federal Institute of Technology (ETH) researchers have developed a cost-effective and more efficient way to manufacture nanoporous metals over many scales, from nanoscale to macroscale, which is visible to the naked eye.

The process begins with a four-inch silicon wafer. A coating of metal is added and sputtered across the wafer. Gold, silver and aluminum were used for this research project. However, the manufacturing process is not limited to these metals.

Next, a mixture of two polymers is added to the metal substrate to create patterns, a process known as diblock copolymer lithography (BCP). The pattern is transformed in a single polymer mask with nanometer-size features. Last, a technique known as anisotropic ion beam milling (IBM) is used to etch through the mask to make an array of holes, creating the nanoporous metal.

During the fabrication process, the roughness of the metal is continuously examined to ensure that the finished product has good porosity, which is key to creating the unique properties that make nanoporous materials work. The rougher the metal is, the less evenly porous it becomes.

   “在制造过程中,我们小组成功的在4英寸硅晶片上实现了92%的孔覆盖率及99%的均匀性,这就意味着该金属是光滑的,且孔分布均匀。”来自LLNL的工程师和联合研究小组的Tiziana Bond这样说到。
   "During fabrication, our team achieved 92 percent pore coverage with 99 percent uniformity over a 4-in silicon wafer, which means the metal was smooth and evenly porous," said Tiziana Bond, an LLNL engineer who is a member of the joint research team.

The team has defined a metric -- based on a parametrized correlation between BCP pore coverage and metal surface roughness -- by which the fabrication of nanoporous metals should be stopped when uneven porosity is the known outcome, saving processing time and costs.

“我们最大的突破在于,探究出了一种制备纳米多孔金属的新方法,此方法                成本低廉,还可进行实时的质量监控,且在多尺度方面无需利用剥离技术去除金属”邦德说,“这些金属材料适用于很多领域,如能量采集,传感和电化学等的研究。”
"The real breakthrough is that we created a new technique to manufacture nanoporous metals that is cheap and can be done over many scales avoiding the lift-off technique to remove metals, with real-time quality control," Bond said. "These metals open the application space to areas such as energy harvesting, sensing and electrochemical studies."

The lift-off technique is a method of patterning target materials on the surface of a substrate by using a sacrificial material. One of the biggest problems with this technique is that the metal layer cannot be peeled off uniformly (or at all) at the nanoscale.
最近一期《先进材料界面》的封面故事刊登了该研究小组的成果,题为"多尺度成型工艺: 采用去剥离法制备高保真宏观覆盖的纳米多孔金属阵列"。
The research team's findings were reported in an article titled "Manufacturing over many scales: High fidelity macroscale coverage of nanoporous metal arrays via lift-off-free nanofrabication." It was the cover story in a recent issue of Advanced Materials Interfaces.

Other applications of nanoporous metals include supporting the development of new metamaterials (engineered materials) for radiation-enhanced filtering and manipulation, including deep ultraviolet light. These applications are possible because nanoporous materials facilitate anomalous enhancement of transmitted (or reflected) light through the tunneling of surface plasmons, a feature widely usable by light-emitting devices, plasmonic lithography, refractive-index-based sensing and all-optical switching.

                                                     审核:欧  阳


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