Growing Large, Flawless KDP Crystals Quickly: A DIY Rotary Crystallizer
1:04 KDP Growth Challenges: Traditional slow evaporation methods for growing potassium dihydrogen phosphate (KDP) crystals are time-consuming (weeks) and often result in imperfections. KDP's unique properties (piezoelectric, nonlinear optical, electro-optic) make it valuable but expensive.
2:13 Rotary Crystallizer Concept: A rotary crystallizer, involving a rotating platform holding seed crystals in a temperature-controlled, stirred solution, promotes homogeneous growth and prevents localized depletion.
4:15 Rapid Growth Research: Research shows rapid KDP growth (up to 54mm/day) is possible using techniques like overheating the solution and applying acoustic energy to eliminate microclusters that can cause uncontrolled precipitation.
9:11 DIY Crystallizer Plan: The video demonstrates a simplified, DIY rotary crystallizer built from readily available materials.
9:46 Crystallizer Construction: The setup uses a server case, beaker, custom laser-cut lids, a perspects platform, a hot plate with magnetic stirrer, a DS18B20 temperature sensor, and a dual-Arduino control system.
12:52 Arduino Control System: One Arduino manages temperature control (with overheat, preheat, and controlled cooling phases), while the other controls the stepper motor for platform rotation.
17:41 Code Overview: The code controls temperature stages, stepper motor rotation, and data logging for monitoring. A Python script logs and plots the temperature and error data from the Arduino.
24:31 KDP Recipe: The recipe involves dissolving 176.5g of aquarium-grade KDP and 0.5g of EDTA (chelating agent) in 450ml of deionized water.
26:30 Growth Procedure: The procedure includes overheating the solution to 70°C for 24 hours, filtering it, then cooling it down in stages following a specific cooling curve to encourage controlled crystal growth.
28:12 Seed Preparation: Seed crystals are grown from a saturated solution, then carefully cut, filed, drilled, and glued to the rotating platform.
30:39 Growth Cycle: After the seed is mounted and the platform is preheated, the growth cycle starts with a slow cooling phase (1.75°C/day) followed by phased reductions in cooling rate as the crystal grows. The system aims for minimal temperature fluctuations.
32:25 Results: Time-lapse footage showcases the growth of large, optically clear KDP crystals in just a few days.
33:45 Troubleshooting: Potential issues include contamination leading to cracking, twinning, and sudden precipitation. Scaling up to a 1L beaker is suggested as a future improvement.