To keep everyone on here happy and to prevent myself from getting lynched, I'll give the demanded disclaimers from the start: I'm not an engineer, I'm not a scientist, the use of these ideas are not guaranteed to produce excess heat, and I'm simply sharing my thoughts.
Now, I'm convinced that the number one secret to producing massive excess heat is optimizing hydrogenation. Rossi may have optimized other parameters and added other methods of stimulation in later systems. However, his earliest systems, as far as I can tell, worked because he utilized multiple methods of optimizing the uptake of hydrogen. As most people should know, nickel is difficult to hydrogenate. The reason most replications fail, in my opinion, is because there are countless considerations when it comes to making sure your nickel is hydrogenated. Most replicators don't go to great extents to maximize hydrogenation so they produce little to no excess heat. But if they were able to do so, they could produce long periods of self sustained operation just like Andrea Rossi and Focardi achieved in their early tests.
So how should we go about maximizing hydrogenation?
1) First, we should pick our powder. I personally don't think high surface area is critical, because Me356 and others have reported significant excess heat with nickel wire. If you do want to go with high surface area then a carbonyl nickel powder may be ideal.
1A) If you don't care for maximum surface area, I'd suggest high purity gem grade spherical nickel powder.
2) I have no evidence Rossi ever utilized ultrasound irradiation of his nickel powder, but this process can dramatically enhance the catalytic properties of nickel powder. Basically, by ultrasound irradiating nickel in a hydrocarbon slurry (hexane, decane, etc) you remove the oxide layer, expose fresh surface that is atomic roughened even though it seems smoothed when zoomed out, and can potentially be coated with small amounts of carbon allotropes. The benefit is this type of nickel can be hundreds or thousands as times as catalytic as ordinary nickel which could help maximize hydrogen adsorption (the rate limiting step of hydrogen uptake process) and hydrogen absorption. The drawbacks are if you sonicate carbonyl nickel powder you will destroy many of the spike like surface features, you will lower the temperature that the nickel will sinter, and you will make the nickel very suceptible to catalytic poisoning by exposure to atmospheric oxygen for even seconds. If you don't want to use ultrasound to clean the outside of your nickel, there are other options such as chemical etching and hydrogen reduction.
3) Once you have cleaned the outside of your nickel, you need to vacuum the nickel to remove trapped internal gases. This is important, because gases such as oxygen and carbonmonoxide are filling defects and voids that we want to fill with hydrogen. This needs to be performed under heat in a stair step manner. However, the downside here is that if you go too high in temperature you will sinter the nickel.
4) The fuel needs to be pre-hydrogenated. Rossi's first systems probably didn't pre-hydrogenate, because the palladium was probably mixed in with the nickel in the active reactor. However, since we don't want to put palladium in our final reactors, we should pre-hydrogenate with palladium. Possibly, this is not an absolutely critical step if we have cleaned our fuel well inside and out via sonfication and vacuuming under heat. However, to maximize the chance of success, this step could be useful. The palladium will split the H2 and atomic hydrogen that will then be absorbed by the nickel. This will dramatically increase the level of hydrogenation achieved, in my opinion. In non-LENR papers nickel is described as absorbing atomic hydrogen VERY rapidly. The SLOW step is adsorption of H2 and breaking it into H and H. So if we can use palladium to create atomic hydrogen, we can maximize our absorption. While performing this, the hydrogen pressure should be increased periodically in a stair step manner to hammer the hydrogen deeper and deeper into the nickel. Also, the highest possible temperature should be used that will prevent sintering. Several cycles of hydrogenation could be utilized. Each time the nickel is allowed to cool back down, not all of the hydrogen will be desorbed, because some will be trapped in defects as exotic hydrogen species. Basically, we are creating the E-Cat fuel and increasing the quantity with each cycle.
5) When we place our fuel (very carefully to make sure it is not exposed to atmosphere) into the active reactor, we should make sure to use high quality LiAlH4 if we are not using hydrogen from a tank. The quality of LiAlH4 varies DRAMATICALLY. Alfa Aesar brand LiAlH4 is said by many to produce much more hydrogen (perhaps due to the documented smaller particle size) than other brands. Me356 said that it seemed to produce twenty times as much hydrogen than the other LiAlH4 he had been using.
6) While heating the active reactor, if LiAlH4 is being used, the rate of heating needs to be as slow as possible from around 100C to 225C. The rate during this temperature range should never go higher than 1C per minute. .5C per minute might be even better. A slow heating rate will make sure the LiAlH4 doesn't melt and smother the nickel hindering hydrogen adsorption. Instead, the LiAlH4 will not change phase and will remain solid.
7) A typical thermal shocking stage could be taking the reactor from 225C to 700C at lets say a rate of 5C per minute, cutting the power off completely, allowing the temperature to drop to 300C, and then turning the power back on as high as it can go to thermal shock the fuel. This will boost the pressure in the defects and hopefully induce nuclear reactions in the exotic hydrogen species that were created.
