Flake Tantalum Powder Drying to Preserve Surface Area and Flow
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for forming tantalum-based capacitors face challenges in achieving high surface area and minimizing binder residue, leading to reduced charge density and poor flow characteristics of flake tantalum powder, which are critical for anode fabrication.
Innovation Solution
A method involving sublimation drying followed by tumble drying without milling media, forming spherical agglomerates of flake tantalum powder that inhibits particle stacking, eliminates the need for binders, and maintains high surface area, resulting in improved electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional evaporative drying methods are used to remove solvents from flake tantalum powder, then the drying process is simple and fast, but the flakes stack during drying which significantly decreases surface area
Solution Approach 1:
The patent employs freeze drying which utilizes phase transition of water from solid to vapor (sublimation) to remove solvent. This prevents the flakes from stacking during drying, thereby preserving surface area while still achieving effective solvent removal. The phase transition occurs at lower temperatures and avoids the thermal effects that cause flake aggregation in conventional drying.
Solution Approach 2:
The patent applies preliminary freezing of the slurry before drying. By freezing the solvent first, the flakes are locked in a dispersed state and prevented from stacking during the subsequent drying process. This preliminary action (freezing) sets up the structure to maintain surface area throughout the drying operation.
2Object-generated harmful factors
If binder is added to press tantalum powder into monolith, then the powder adheres adequately for handling, but carbon residue remains in the final capacitor
Solution Approach 1:
The patent eliminates the binder component entirely from the process. By developing flake tantalum powder with improved surface area and morphology through freeze drying, the powder achieves adequate adhesion without requiring organic binders. This extraction of the binder eliminates the source of carbon residue while maintaining manufacturability.
Solution Approach 2:
The flake tantalum powder itself provides the adhesion properties through its modified surface characteristics and morphology resulting from freeze drying. The flakes have inherent binding capability without external binder additives, making the system self-sufficient and free from binder-related carbon contamination.
3Quantity of substance
If high surface area flake tantalum powder is produced, then capacitance increases, but Scott density becomes too high for conventional pressing machines
Solution Approach 1:
The patent modifies the physical parameters of the flake tantalum powder through freeze drying, achieving a balance between surface area and Scott density. The controlled freezing and sublimation process creates flakes with optimal morphology that maintain high surface area while achieving Scott density in the range of 24-35 g/in³, making them suitable for conventional pressing operations.
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
The process achieves a Scott density of at least 1.458 g/cm3 and a flow of at least 1 g/s, enabling the production of capacitors with enhanced capacitance and reduced carbon residue, thus overcoming the limitations of conventional drying methods.
Implementation Method 1
removing the solvent at a temperature below a melting point of the solvent under a reduced atmosphere to obtain a partially dry flake powder
Implementation Method 2
introducing the partially dry flake powder to a second dryer to form flake powder
Data Source
AI summary
Provided is a process for providing a flake powder characterized by a particle size of −40 mesh to +200 mesh; a Scott density of at least 1.458 g/cm3; and a flow of at least 1 g/s. The process includes introducing a milled flake powder in a solvent to a first dryer; removing the solvent at a temperature below a melting point of the solvent under a reduced atmosphere to obtain a partially dry flake powder; and introducing the partially dry flake powder to a second dryer to form flake powder wherein particles of partially dry flake powder are heated and simultaneously subjected to an uncorrelated motion relative to adjacent particles.