Calcium Phosphate Polymeric Sol Coating for Metal Implants
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Solution Overview
Problem
Existing methods for coating hydroxyapatite on metal implants, such as plasma spray, result in a coated layer that is prone to dissociation and reduced strength due to high sintering temperatures, and sol-gel synthesis methods produce small amounts of ceramic particles with poor wettability, leading to nonuniform and weakly bonded layers.
Innovation Solution
A method involving the preparation of a polymeric sol of calcium phosphate compounds using calcium ethoxide and triethyl phosphite in organic acids, followed by coating, hydrolyzing, preheating, and sintering under a nitrogen atmosphere to form a dense, uniformly bonded hydroxyapatite layer on metal implants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plasma spray process is used to coat hydroxyapatite on metal implant, then bond strength is improved, but chemical structure of hydroxyapatite is destroyed and coated layer dissociates
Solution Approach 1:
The invention changes the temperature parameter from the high-temperature plasma spray process (20000-30000°C) to a low-temperature sol-gel process (50-200°C), which preserves the chemical structure of hydroxyapatite while still achieving strong bonding to the metal implant substrate
Solution Approach 2:
The invention introduces an organic acid intermediary (acetic acid, propionic acid, or butyric acid) that facilitates the sol-gel reaction and acts as a bonding mediator between the hydroxyapatite precursor and the metal implant surface, enabling strong adhesion without high-temperature damage
2Temperature
If conventional sol-gel synthesis is used to produce calcium phosphate ceramic, then sintering temperature is reduced, but amount of ceramic produced is small and wettability is poor
Solution Approach 1:
The invention changes the chemical composition parameters by using organic acid calcium salts and organic acid phosphates as precursors, which enable the sol-gel process to produce large amounts of ceramic material with good wettability at low sintering temperatures (50-200°C)
Solution Approach 2:
The invention improves local quality by ensuring complete dissolution of calcium and phosphate components in the polymeric sol, creating a homogeneous solution with excellent wettability that enables uniform coating and high ceramic yield at low temperatures
3Temperature
If conventional sol-gel synthesis is used, then sintering temperature is reduced, but coating uniformity is poor
Solution Approach 1:
The invention changes the physical state parameter by producing a transparent, homogenized polymeric sol where calcium and phosphate components are completely dissolved, enabling uniform coating distribution and consistent ceramic formation at low sintering temperatures
Solution Approach 2:
The organic acid acts as an intermediary that ensures complete dissolution and homogeneous distribution of calcium and phosphate precursors in the sol, which maintains coating uniformity during the low-temperature sol-gel process
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 method produces a transparent, homogenized sol with excellent wettability and bioactivity, resulting in a dense, strongly bonded hydroxyapatite layer with uniform microstructure and enhanced bond strength on metal implants, suitable for dental and orthopedic applications.
Implementation Method 1
a second step of hydrolyzing a coated layer, including the polymeric sol, on the metal implant at 60 to 100° C.
Implementation Method 2
a third step of preheating the hydrolyzed coated layer on the metal implant at 300 to 500° C. to burn organics remaining in the hydrolyzed coated layer
Implementation Method 3
a fifth step of sintering the resulting metal implant at 500 to 800° C. under a nitrogen atmosphere
Data Source
AI summary
Disclosed is a method for producing a transparent and homogenized polymeric sol of a calcium phosphate compound, containing apatite and having excellent wettability and bioactivity, according to a sol-gel synthesis, and a method for coating the polymeric sol on a metal implant, in which the polymeric sol is coated on the metal implant and then heat-treated to form a dense coated layer strongly bonded to the metal implant. The polymeric sol is obtained by process of preparing a calcium salt solution, containing calcium ethoxide dissolved in organic acid, and a phosphate solution, containing triethyl phosphite or triethyl phosphate dissolved in the organic acid, mixing the calcium salt solution with the phosphate solution to produce a mixed solution, and aging the mixed solution.