TiNx Metal Nitride Membrane for Hydrogen Separation
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Solution Overview
Problem
Current hydrogen separation membranes face challenges such as hydrogen embrittlement and limited hydrogen transport characteristics at lower temperatures, necessitating the development of membranes with higher mixed hydride ion (H−)-electron conductivity beyond existing TiNx particulate membranes.
Innovation Solution
A polycrystalline metal nitride membrane with a crystallite size of 10 nm or less, exhibiting (111) orientation but substantially no (100) orientation, produced by sputtering at a substrate temperature of 50° C. or less, enhances hydrogen permeation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrogen solubility in metal matrices is increased to improve hydrogen permeation, then hydrogen permeation capability is improved, but hydrogen embrittlement becomes more serious
Solution Approach 1:
The invention changes the fundamental mechanism of hydrogen transport from solution-diffusion (reliant on hydrogen solubility in metal matrices) to surface-mediated transport through metal nitride layers. By altering the transport mechanism parameter rather than optimizing solubility, the patent achieves high hydrogen permeation without the associated embrittlement problems of hydrogen-absorbing alloys
Solution Approach 2:
The invention replaces the traditional metallic matrix-based hydrogen transport mechanism with a surface-mediated transport mechanism through metal nitride layers. This substitution eliminates reliance on hydrogen solubility in bulk metal, thereby avoiding hydrogen embrittlement while maintaining high permeation capability
2Productivity
If membrane thickness is reduced to improve hydrogen flux, then hydrogen permeation is improved, but membrane structural stability deteriorates due to hydrogen embrittlement
Solution Approach 1:
The invention changes the material composition from hydrogen-absorbing alloys to metal nitrides, fundamentally altering the membrane's interaction with hydrogen. This parameter change allows thin membrane structures to maintain structural stability while achieving high hydrogen flux, as metal nitrides do not suffer from hydrogen embrittlement
Solution Approach 2:
The invention employs composite structures combining metal nitride layers with porous substrates or support structures. This composite approach enables the use of thin active layers for high flux while the support structure provides mechanical stability, avoiding the embrittlement issues that would limit thinning of homogeneous metal membranes
3Reliability
If conventional proton-conductive ceramics are used to achieve hydrogen separation, then hydrogen separation is achieved, but hydrogen transport characteristic deteriorates at temperatures of 600°C or less
Solution Approach 1:
The invention changes the operating temperature parameter from high temperature (600°C+) required by conventional proton-conductive ceramics to lower temperatures (room temperature to 400°C). This is achieved by switching from oxide-based proton conductors to metal nitride-based surfaces, which enable efficient hydrogen transport through different mechanistic pathways that are less temperature-sensitive
4Productivity
If Pd membrane is used to achieve high hydrogen permeation, then hydrogen permeation capability is improved, but manufacturing cost increases due to use of noble metal
Solution Approach 1:
The invention replaces expensive noble metal (Pd) membranes with thin films of base metal nitrides (TiN, ZrN, HfN). These alternative materials achieve comparable or superior hydrogen permeation performance at a fraction of the cost, making hydrogen separation economically viable for widespread application
Solution Approach 2:
The invention employs composite structures where thin metal nitride layers are deposited on porous substrates or support structures. This approach achieves high hydrogen permeation performance while using minimal amounts of the active metal nitride material, significantly reducing material costs compared to solid Pd membranes
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 membrane achieves significantly higher hydrogen permeation capacity than TiNx particulate membranes, meeting practical hydrogen separation requirements and potentially exceeding DOE standards at reduced temperatures.
Implementation Method 1
TiNx (x=0.7, 0.9, or 1.0) particulate membrane, a type of metal nitride, exhibited mixed hydride ion (H−)-electron conductivity
Implementation Method 2
exhibited mixed hydride ion (H−)-electron conductivity
Implementation Method 3
produced by sputtering at a substrate temperature of 50° C. or less
Data Source
AI summary
The present invention pertains to a polycrystalline membrane containing metal nitride particles represented by the general formula MNx (where M is a metal element in which the Fermi energy is in a position higher than −4.4 eV vs L.V. and x is the range over which a rock salt-type structure can be assumed), in which the crystallite size determined by transmission electron microscopy is 10 nm or less, at least some of the crystallites have rock salt-type structure, and the crystallites exhibit (111) orientation but substantially do not exhibit (100) orientation. The present invention also pertains to a method for manufacturing a polycrystalline membrane, comprising forming, by sputtering, a polycrystalline membrane on a substrate having a temperature of less than 200° C., the polycrystalline membrane being represented by the general formula MNx and being such that at least some crystallites have a rock salt structure and the crystallites exhibit (111) orientation but essentially do not exhibit (100) orientation. The present invention provides a hydrogen-permeable TiNx microparticle membrane exhibiting a higher mixed hydride ion (H−)-electron conduction.