Tuesday, December 29, 2009

Simple, Environmentally Friendly Way to Grow Zinc Aluminate Nanowires Discovered by Chinese Scientists-Materials Are Excellent for Catalyst and Ceramic Applications



 Image Source: Figure 3, U.S. Patent 7,638,112

Tsinghua University (Beijing, CN)  and Hon Hai Precision Industry Co., Ltd. (Tu-Cheng, Taipei Hsien, TW) earned U.S. Patent 7,638,112 for a new, simple, and environmentally friendly method of manufacturing zinc aluminate nanomaterial. Zinc aluminates are excellent for use as catalysts and as ceramic materials.

Chemical vapor deposition (CVD), sputtering, or plasma-assisted chemical vapor deposition can used to form the catalyst layer on which to grow zinc aluminate nanomaterial. The material of the catalyst layer can be selected from gold, iron, copper, cobalt or nickel. The thickness of the catalyst layer ranges from about 1 to 500 nanometers. The method for making the zinc aluminate nano-material has many advantages including the following:

1. the zinc, aluminate, and oxygen-containing gas used as source materials are environmentally friendly. The zinc oxide and the alumina diffuse in to each other due to the Kirkendall Effect to form a zinc aluminate nano-material, and grow zinc aluminate nanowires on the substrate.

2. the method for making the zinc aluminate nano-material is a simple fabrication procedure and can be achieved at low temperatures in a short time.

 3. the zinc aluminate nano-material fabricated by the Tsinghua and Hon Hai method has large specific surface area and excellent catalyzing properties.

According to inventors Hai-Lin Sun, Kai-Li Jiang, Qun-Qing Li and  Shou-Shan Fan (Beijing, CN) the method for making zinc aluminate nanomaterial, includes the following steps of:

(a) providing a growing substrate and a growing device, and the growing device comprising a heating apparatus and a reacting room;

(b) placing the growing substrate and a quantity of reacting materials into the reaction room, the reacting materials consisting of substantially pure zinc and substantially pure aluminum and the mass ratio of the zinc and aluminum being in a range from about 2:1 to about 1:2;

(c) introducing an oxygen-containing gas into the reaction room; and

(d) heating the reaction room to a temperature in the range of about 660 degree C. to about 1100 degree C., the pure zinc and pure aluminum begin to vaporize to form gaseous zinc and gaseous aluminum, the gaseous zinc and gaseous aluminum react with the oxygen-containing gas to form zinc aluminate nano-material on the substrate.

The resulting zinc aluminate nanowires are disorderly distributed on the growing substrate. Diameters of the zinc aluminate nanowires range approximately from 10 nanometers to 1 micrometer. Lengths of the zinc oxide nanotubes range approximately from 100 nanometers to 100 micrometers. The zinc aluminate nanowires are uniformly distributed without aggregation and have large specific surface area. The zinc aluminate nanowires have excellent catalyzing properties.


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