Animated icons

  <link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/font-awesome/4.3.0/css/font-awesome.min.css">

<a href="#" target="_blank" class="icon-box">
  <span class="icon-box__inner m--left">
    <i class="fa fa-twitter"></i>
  </span>
  <span class="icon-box__inner m--right">
    <i class="fa fa-twitter"></i>
  </span>
</a>
<a href="#" target="_blank" class="icon-box">
  <span class="icon-box__inner m--left">
    <i class="fa fa-codepen"></i>
  </span>
  <span class="icon-box__inner m--right">
    <i class="fa fa-codepen"></i>
  </span>
</a>
<a class="icon-box">
  <span class="icon-box__inner m--left">
    <i class="fa fa-dribbble"></i>
  </span>
  <span class="icon-box__inner m--right">
    <i class="fa fa-dribbble"></i>
  </span>
</a>
<a href="#" target="_blank" class="icon-box">
  <span class="icon-box__inner m--left">
    <i class="fa fa-facebook"></i>
  </span>
  <span class="icon-box__inner m--right">
    <i class="fa fa-facebook"></i>
  </span>
</a>
//Автор: Nikolay Talanov. @suez

*, *:before, *:after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html, body {
  font-size: 62.5%;
}

.icon-box {
  position: relative;
  display: inline-block;
  vertical-align: top;
  width: 10rem;
  height: 10rem;
  margin: 5rem;
  background: #0c0c0c;
  overflow: hidden;
  font-size: 0;
  text-decoration: none;
  border-radius: 50%;
}
.icon-box:before {
  content: "";
  position: absolute;
  left: 16.6666666667%;
  top: 0;
  margin-left: -1px;
  width: 2px;
  height: 0.6rem;
  background: #fff;
  transition: transform 0.5s;
  transform: rotate(-30deg) translate(0.6833333333rem, -1rem);
}
.icon-box:hover:before {
  -webkit-animation: slice 0.5s;
          animation: slice 0.5s;
}
.icon-box__inner {
  position: relative;
  display: inline-block;
  vertical-align: top;
  overflow: hidden;
  width: 50%;
  height: 100%;
  transform: rotate(-30deg);
  font-size: 6rem;
  color: #fff;
}
.icon-box__inner .fa {
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%) rotate(30deg);
}
.icon-box__inner.m--left {
  transform-origin: 100% 50%;
}
.icon-box__inner.m--left .fa {
  left: 100%;
}
.icon-box__inner.m--right {
  transform-origin: 0 50%;
  transition: transform 0.5s;
}
.icon-box:hover .icon-box__inner.m--right {
  transition: transform 0.5s 0.1s;
  transform: rotate(-30deg) translate(0.5rem, 1rem);
}
.icon-box__inner.m--right .fa {
  left: 0;
}

@-webkit-keyframes slice {
  to {
    transform: rotate(-30deg) translate(0.6833333333rem, 16rem);
  }
}

@keyframes slice {
  to {
    transform: rotate(-30deg) translate(0.6833333333rem, 16rem);
  }
}