  The electrical resistance of detonation nano-diamond powders was measured
from liquid nitrogen temperature to room temperature and in relative humidity
environments from around 10% to 100%. After sample exposures of several hours
at 100% relative humidity at room temperature (around 295 K), when the
temperature was reduced, the resistance increased to the upper measurement
limit of our apparatus (120 M{\Omega}) at around 240 K. Upon warming, the
resistance dropped back to the room temperature value, with some hysteresis.
For sample exposures after several hours at 100% relative humidity at room
temperature, as the relative humidity was reduced, the sample resistance
increased to the upper range limit of the apparatus. As the relative humidity
was then increased (all at room temperature), the resistance dropped. For
samples exposed to low (~10%) relative humidity for several hours at room
temperature, as the humidity was increased (at room temperature), the
resistance decreased, and then increased when the humidity was reduced. The
temperature behavior was markedly differ from that of powdered graphite and
multi-walled carbon nano tubes.
