Bioresorbable Magnesium Implants via Salt-Modified Powder Sintering
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Solution Overview
Problem
Magnesium-based materials produced by powder metallurgy often lack mechanical properties due to stable oxide layers and residual porosity from spacer materials, limiting their use in load-bearing medical implants like vascular stents.
Innovation Solution
A powder mixture comprising metal powders (magnesium, aluminum, zinc, calcium, and iron) with metal salt powders and bioresorbable compounds, allowing direct alloying without smelting, reducing secondary phases and porosity, and enabling variable chemical composition for enhanced mechanical strength and degradation control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If powder metallurgy is used to produce magnesium-based materials, then residual porosity remains that can be exploited for bone growing-in behavior, but the porosity creates large pores that cannot be completely closed by subsequent hot working processes, precluding use as cyclically stressed load-bearing components
Solution Approach 1:
The invention changes the chemical composition parameters by adding specific metal salt powders (magnesium hydrogen phosphate, magnesium carbonate, calcium phosphate, tricalcium phosphate, calcium carbonate, calcium hydroxide, calcium fluoride) to the powder mixture. These additives modify the sintering behavior and reaction kinetics, enabling complete pore closure while maintaining bone growth promotion through controlled porosity elimination
Solution Approach 2:
Metal salt powders serve as intermediary substances that facilitate complete pore closure during sintering. These salts decompose and react to fill and seal pores, acting as mediators between the porous structure and the desired dense final product, while some salts (calcium phosphates) simultaneously promote bone growth
2Strength
If the degree of porosity is kept as small as possible due to mechanical requirements, then elaborate technological precautions must be taken such as applying vacuum or multi-stage treatment processes under shielding gas atmosphere
Solution Approach 1:
The invention changes the chemical composition by incorporating metal salt powders that modify the sintering process parameters. These additives enable pore closure at lower vacuum levels and simpler processing conditions by chemically facilitating the filling and sealing of pores, eliminating the need for complex multi-stage treatment processes
Solution Approach 2:
The metal salt additives enable the material to self-close pores during standard sintering without requiring elaborate external interventions. The salts decompose and react in situ to fill pores, allowing the material to achieve dense structure through its own chemical reactions rather than requiring complex external vacuum or shielding systems
3Stability of the object's composition
If stable oxide layers surround each individual powder particle, then mass transfer caused by diffusion in the solidus temperature range is hindered or prevented, and contact of molten phases among one another is also hindered
Solution Approach 1:
Metal salt powders act as intermediary substances that facilitate alloying by modifying the oxide layer behavior. These salts decompose to create reactive environments that promote oxide reduction and metal particle bonding, serving as mediators between the stable oxide-coated powders and the desired metallurgical bonding
Solution Approach 2:
The invention changes the chemical environment parameters by introducing metal salts that alter the decomposition atmosphere and reaction kinetics during sintering. This creates optimal conditions for oxide layer breakdown and metal diffusion, enabling complete alloying despite the presence of stable oxide layers on powder particles
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 solution produces bioresorbable implants with improved fracture resistance and controlled degradation, eliminating the need for spacer materials and enhancing biocompatibility by minimizing porosity and contamination, suitable for various medical applications.
Implementation Method 1
mass transfer caused by diffusion in the solidus temperature range
Implementation Method 2
oxides have extremely high affinity for oxygen
Data Source
AI summary
The invention relates to a powder mixture for producing an alloy, a powder metallurgy process for producing a material, a material, and a medical implant made from it.