Contact angle a contact angle of 0°. This is often the case for water on bare metallic or ceramic surfaces, although the presence of an oxide layer or contaminants on the solid surface can significantly increase the contact angle. Generally, if the water contact angle is smaller than 90°, the solid surface is considered hydrophilic and if the water contact angle is larger than 90°, the solid surface is considered hydrophobic. Many polymers exhibit hydrophobic surfaces. Highly hydrophobic surfaces made of low surface energy (e.g. fluorinated) materials may have water contact angles as high as ~120°. Some materials with highly rough surfaces
Type 97 90 mm Infantry Mortar on the Type 94. Certain compromises in material and workmanship were made in the manufacture of the Type 97. The bipod feet and chain hooks were held to the legs of the bipod by pins, joined with solder, whereas on the Type 94 they are welded. No welds were polished on the Type 97, although no indications of fractures were reported despite the poor quality of the welding. The adjusting nut, sliding bracket, and hand wheels of the Type 97 are made of steel, rather than brass which was utilized in the Type 94. Type 97 90 mm Infantry Mortar