Microwave Purification of Nanocarbon Preparations

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Solution Overview

Problem

Current methods for purifying nanocarbon preparations, such as carbon nanotubes and fullerenes, are inefficient and damage the materials due to the presence of residual catalytic metals and carbonaceous impurities, requiring the development of a rapid and environmentally friendly purification process that selectively removes contaminants without modifying the nanotubes.

Innovation Solution

A microwave-induced purification process using a combination of strong and weak acids, bases, and metal chelating agents, such as nitric acid, sulfuric acid, and ethylenediaminetetraacetic acid, to remove residual transition metal catalysts and non-tubular carbon structures from nanocarbon preparations, allowing for efficient metal removal and oxidation of amorphous carbon without functionalizing the nanotubes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional acid treatment methods are used for purification, then metal impurities are removed, but the process is time-consuming and causes structural damage to nanotubes

Engineering Contradiction:

Improvepurification effectivenessVSAvoidprocessing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies microwave irradiation to dramatically change the heating parameters of the acid treatment process, reducing purification time from days to minutes while maintaining or improving purification effectiveness and nanotube structural integrity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces conventional thermal heating with microwave irradiation, substituting a slow thermal process with a targeted electromagnetic energy approach that selectively heats contaminants while preserving nanotube structure

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If strong acid treatment is applied to remove impurities, then metal catalysts are dissolved, but chemical-functionalization and structural damage occur

Engineering Contradiction:

Improvemetal removal efficiencyVSAvoidnanotube structural integrity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent uses mild acid solutions (partial action) combined with microwave irradiation to achieve complete metal removal without requiring aggressive acid concentrations that would damage nanotubes, demonstrating that less extreme conditions can be sufficient when energy input is optimized

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent substitutes conventional thermal heating with microwave irradiation, enabling selective dissolution of metal catalysts through targeted heating of impurities while the nanotube walls remain relatively unaffected, thus preserving structural integrity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If prolonged sonication or refluxing is used for purification, then carbonaceous impurities are removed, but nanotube sidewalls are damaged

Engineering Contradiction:

Improveimpurity removal efficiencyVSAvoidnanotube mechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent changes the energy input method from mechanical sonication/refluxing to microwave irradiation, achieving rapid oxidation of carbonaceous impurities in minutes while preserving nanotube mechanical strength through selective heating and controlled reaction conditions

Inventive Principle:

Principle #35Parameter changes

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 achieves high metal removal efficiencies, up to 100%, while preserving the structural integrity of the nanotubes, offering a rapid and cost-effective solution for the purification of nanocarbon preparations, thereby enhancing their commercial viability.

Implementation Method 1

A microwave-induced purification process using a combination of strong and weak acids, bases, and metal chelating agents

Methodology Applied

Scientific EffectMicrowave radiation: Microwave Radiation

Implementation Method 2

microwave-induced process for the removal of residual transition metal catalysts and non-desirable carbonaceous materials from nanocarbon preparations

Methodology Applied

Scientific EffectDielectric heating: Dielectric Heating

Implementation Method 3

oxidize the amorphous carbon structures without damaging the nanotubes

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 4

metal chelating agents like ethylenediaminetetraacetic acid (EDTA)

Methodology Applied

Scientific EffectChelation:

Data Source

PatentUS8182783B2Rapid microwave process for purification of nanocarbon preparations

Publication Date: 2012.05.22 NANOPULSE

AI summary

A novel microwave-assisted process is described for the rapid removal of catalytic metal and non-desirable carbon impurities in fullerene, single wall, and multiple wall carbon nanotube preparations. The purification process is carried out at various programmed pressures, power levels and reaction times in a suspension of the nanocarbon moieties in the presence of strong acids (for example, a mixture of sulfuric acid and nitric acid), in weak acids (for example, acetic acid) and in the presence of chelating agents (for example, EDTA—ethylenediaminetetraacetic acid). In one embodiment, high metal removal efficiency of 70 to 90% is observed.