ADN Crystallization in Viscous Medium for Spherical Morphology
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Solution Overview
Problem
Existing methods for synthesizing ammonium dinitroamide (DNA) crystals result in rod or needle shapes, which are unsuitable for energetic material formulations due to high viscosity issues at high loading rates, and previous attempts to achieve spherical crystals through prilling or additive modification have been inefficient or difficult to scale industrially.
Innovation Solution
A process involving crystallization in a solvent with viscosity greater than or equal to 0.25 Pa.s, allowing spontaneous nucleation and controlled crystal growth, which produces quasi-spherical crystals with a controllable particle size range from a few microns to several hundred microns without the need for seeding or additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional crystallization methods are used to obtain DNA crystals, then crystals are formed with rod or needle shapes, but the aspect ratio becomes too high (around 10) making them unsuitable for formulation
Solution Approach 1:
The patent changes the physical parameters of the crystallization medium by using a viscous solvent (viscosity ≥ 0.25 Pa.s) instead of conventional low-viscosity solvents. This parameter change fundamentally alters the crystal growth kinetics, resulting in spherical or quasi-spherical DNA crystals with aspect ratios between 1 and 1.5, which are suitable for formulation in energetic materials.
Solution Approach 2:
The patent introduces a viscous solvent as an intermediary medium during crystallization. This mediator controls the diffusion rate of DNA molecules to the crystal surface, enabling uniform growth in all directions and producing spherical morphology. The viscous medium acts as a controlling agent that modifies the crystallization process without being part of the final product.
2Shape
If prilling techniques are used to obtain spherical DNA granules, then spherical geometry is achieved, but the process is difficult to scale beyond a few kilograms per batch
Solution Approach 1:
The patent employs spontaneous nucleation in a viscous medium where the system self-organizes to form spherical crystals without external intervention such as melting, stirring, or spraying. The viscous solvent naturally controls the nucleation and growth process, enabling direct production of formulation-ready spherical crystals at any scale without the complex equipment and procedures required by conventional prilling methods.
3Shape
If DNA is melted and sprayed in a prilling tower to obtain spherical granules, then spherical shape is achieved, but local overheating or material accumulation causes instability and safety accidents
Solution Approach 1:
The patent fundamentally changes the temperature parameter by conducting crystallization from a cold or ambient temperature solution rather than melting DNA to high temperatures. This eliminates the thermal instability and safety hazards associated with DNA decomposition above its melting point, while still achieving spherical morphology through controlled crystallization in a viscous medium.
4Shape
If additives are used to modify crystal facies to obtain original crystallized form, then aspect ratio is reduced to ≤5, but the process is difficult to transpose to industrial scale
Solution Approach 1:
The patent removes the need for crystallization additives by using a viscous solvent that inherently controls crystal growth morphology. Instead of adding chemical modifiers to change crystal facies, the viscous medium physically controls diffusion rates during spontaneous nucleation, producing spherical crystals with aspect ratios between 1 and 1.5 through pure physical means, thereby simplifying the process for industrial scaling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces the elongation ratio of DNA crystals to between 1 and 1.5, achieving spherical or quasi-spherical geometry suitable for high charge levels in energetic materials, with median diameters ranging from less than 100 μm to 400 μm, enhancing the feasibility of DNA in propellant and explosive compositions.
Implementation Method 1
crystallization in a viscous medium... solvent has a viscosity greater than or equal to 0.25 Pa.s... spontaneous nucleation and crystal growth
Implementation Method 2
spontaneous nucleation and crystal growth... from a solution containing said DNA in solution in a solvent
Data Source
Figure 1A~2B
Figure 3~4
Figure 5A~6
AI summary
The present invention relates to a method for crystallizing ammonium dinitramide (ADN), through spontaneous nucleation and crystal growth, from a solution containing said ammonium dinitramide (AND) dissolved in a solvent. Said solvent characteristically has a viscosity greater than or equal to 0.25 Pa s (250 cP) when said spontaneous nucleation is implemented. The ADN crystals obtained by said method have a median aspect ratio of 1 to 1.5 and are perfectly suitable for placement in the composition of energy materials.