Citation Latitude (C680A)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Confusion; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Diverted; Flight Crew Landed in Emergency Condition
Aircraft
Climbing through FL340 and 260 KIAS nose gear unlock with associated CAS message displayed.  Simultaneously loud and recurring banging from nose gear attempting to lock at a 3 times per second frequency. Associated wind noise and pitch movement from nose doors partially opening along with an overspeed warning related to the 210 KT gear limitation.Slowed below 210 and descent initiated; QRH for 'GEAR DISAGREE N' CAS. We extended gear at FL180 without further issue. We diverted to ZZZ airport which was about 80 miles from us due to known good weather (we had been in ZZZ earlier in the day); substantial runways and emergency equipment availability.Initially my SIC and I wrongly thought there was an 18;000 gear operation limit; which apparently there is not. Hence the reason we waited until FL180 to extend gear. The 18;000 limitation only applies to the flaps unlike our previous aircraft.
Cessna 680A Captain reported a nose gear unlock message during climbout followed by a loud recurring banging noise from the nose gear attempting to lock.  The flight crew extended the gear at FL180 and diverted to the nearest suitable airport.