Preparation of a Novel Antiviral Material by Mechanical Milling

Tetsuhiko ONDA, Yusuke YONEDA, Takahiro AKAO, Koichi MOTOIKE, Hiroshi ITO, Toshihiro ITO, Zhong-Chun CHEN
2016 Journal of the Japan Society of Powder and Powder Metallurgy  
Calcium oxide and small amount of alumina powders were mechanically milled in a planetary ball milling system using ZrO 2 pot and balls, in order to refine the sizes of the powders and promote the reactions between the raw powders. The obtained powders were subjected to an accelerated degradation test in CO 2 /H 2 O atmosphere, and the antiviral activity was evaluated by using an avian influenza virus strain (H5N3). The mechanically milled powders revealed a significant improvement in
more » ... vement in durability of antiviral activity after the powders were hydrated. One of the reasons seems to be associated with the solid solution of Al 2 O 3 into calcium oxide and agglomeration of the powders during the mechanical milling. Moreover, it was found that ZrO 2 has an effect similar to Al 2 O 3 . The incorporation of ZrO 2 in CaO by either addition of ZrO 2 powder or contamination from milling media can also improve the durability of antiviral activity of CaO. KEY WORDS calcium oxide, alumina, antiviral activity, avian influenza virus, hydration Introduction In recent years, frequent outbreaks of human and highly pathogenic avian influenza have resulted in big economical and social threats all over the world. One of the important preventive measures to reduce spread of the viruses is to develop novel antiviral materials. Recently, dolomite (CaMg(CO 3 ) 2 ) has attracted much attention as one of the candidate antiviral materials. It was reported that heated dolomite powders exhibited antibacterial activities 1) , and heated and hydrated dolomite has not only antibacterial activity, but also antiviral activity against human and avian influenza viruses as well as against avian infectious bronchitis 2-3) . It is believed that the antiviral activity of the processed dolomite is associated with hydration of calcium oxide (CaO) [4] [5] . Although the processed dolomite has faster-acting and higher antiviral activity in comparison with other inorganic antibacterial materials, its effectiveness of antiviral activity is very limited. This is because hydrated CaO (i.e., Ca(OH) 2 ) easily reacts with CO 2 in air and changes into CaCO 3 , thus resulting in disappearance of antiviral activity. Several metallic oxides, such as CaO and MgO, have been found to have good antimicrobial activity 6-9) . Unfortunately, they also have a durability problem, just like dolomite. To improve the durability of antiviral materials, we have developed a CaO-based antiviral material, in which CaO is a main component with small amount of Al 2 O 3 addition 10) . This material has been prepared by a conventional powder metallurgy route including powder compaction and sintering. The effects of alumina addition and some processing conditions (such as compaction pressure and sintering temperature) on antiviral activities of CaO have been investigated in the previous paper 10) . In the present work, instead of sintering process, a mechanical milling process has been proposed to synthesize CaO-based antiviral material. The purpose was to clarify the effect of mechanical milling on phase constitution, microstructure, and antiviral activity. Experimental Procedure CaO and γ-Al 2 O 3 powders were used as the starting materials in the experiments. The raw powders with nominal compositions of CaO-0, 1, 5, 10 % Al 2 O 3 were ball-milled in ethanol for 24 h. After drying, the powder mixtures were further treated by mechanical milling in a planetary ball milling system under different milling conditions. The mechanical milling was conducted using ZrO 2 pot and balls under 300 rpm, and ball to powder weight ratio was fixed at 50:1. The mechanically milled (MMed) powders were hydrated to change CaO into Ca(OH) 2 . In order to evaluate the degradation behavior, the MMed powders were subjected to an accelerated degradation test in CO 2 /H 2 O atmosphere at 40 °C for 24 h. The crystalline phases and lattice
doi:10.2497/jjspm.63.668 fatcat:4tafrd4gbnhirczvcskdswxbtq