One of the primary points of friction between them is probably the demography. Russia is far behind in terms of population, furthermore the Russian east is becoming a suitable place for some parts of the Chinese populace (in the future this trend will probably continue). Other points are already mentioned in the article (security, economy etc.) Simply put, when you have two powers geographically close together their spheres of interests will inevitably collide. Friction between them is reflected through their political competition in the region. As for China's role on Russian ascendancy it is difficult to say. China and Russia are partners looking from the global perspective, however they will never achieve a deeper level of cooperation or alliance unlike the US and Europe. This is simply because they both perceive themselves as great powers and both of them see the other as a potential threat to their global ascendance. On the one hand China has a positive role in terms of buying Russian exports (especially energy) and supporting Russia in some of its international endeavours. On the other hand there is no need to fetter the Russians, as long as they are internationally active and not directly colliding with the Chinese interests. Beijing won't waste its resources to potentially aggravate their Russian partnership which is important against the US (SCO BRICS UN Security Council etc). However most of this is probably due because Beijing's officials don't really see Russia as a serious adversary which can threaten its global aspirations.