I. Abstract of the Paper’s Core Research

In this study, ultrathin copper nanosheets were prepared via a hydrothermal method. Dopamine was introduced as a graphene precursor to formulate a dedicated aerosol ink, enabling the direct‑write deposition of conductive patterns onto an alumina ceramic substrate. Subsequent high‑temperature sintering under an inert atmosphere in situ yielded copper/graphene composite conductors. A systematic comparison was conducted on the high‑temperature microstructures, electrical conductivity, current‑carrying capacity, and thermal stability of pure copper and the composite films. The key findings are as follows:

In-situ Conversion of Dopamine into a Graphene Composite System

During the sintering process of dopamine‑laden ink, oxidative polymerization and decomposition occur, leading to the in situ formation of a continuous graphene layer at the interface with copper nanosheets. This approach eliminates the need for additional graphene powder blending, while enabling precise control of the graphene content within the range of 0.237–1.185 wt%.

Graphene inhibits high-temperature grain coarsening of copper.

After sintering at 900°C, the grain size of pure copper is 338.6 nm, whereas that of the copper–graphene composite film is only 147 nm. Graphene effectively inhibits the diffusion of copper atoms and simultaneously forms an oxidation‑resistant barrier, significantly suppressing the formation of oxide particles at elevated temperatures.

Unique negative temperature coefficient of resistance (TCR = −0.07%/°C)

The resistance of a pure copper conductor increases steadily with rising temperature, whereas the composite film leverages graphene’s carrier‑transport effect to reduce its resistance as temperature rises, thereby significantly mitigating thermal drift errors in high‑temperature circuits.

Ultra-high current-carrying capacity

At the optimal graphene content of 0.237 wt%, a 1-μm-thick ultra‑thin conductor exhibits a current density of up to 2.05×10⁹ A/m², significantly exceeding that of pure copper. However, increasing the thickness reduces the maximum current-carrying capacity due to the narrowing of interlayer gaps.

Super 1000℃ thermal shock stability and reliability

The hydrogen torch delivers an instantaneous high‑temperature thermal shock without causing circuit interruption; when paired with a 100‑nm aluminum oxide ALD passivation layer, it retains more than 80% of its initial electrical conductivity even after prolonged exposure at 800°C, making it well suited for extreme operating conditions such as deep space and high‑temperature metallurgy.

II. Complete Preparation Procedure for Aerosol‑Based Copper–Graphene Conductors

Ultra-thin copper nanosheets were synthesized via hydrothermal methods, followed by centrifugal washing to remove impurities; a base copper aerosol ink was prepared by formulating with HPMC and butyl glycol.

Dopamine hydrochloride is mixed in proportion, and the mixture is stirred uniformly to obtain an atomizable composite precursor ink.

Optomec AJ5X pneumatic aerosol deposition system, with a 635 μm ceramic nozzle, nitrogen carrier gas, and direct-write patterning on a 70°C ceramic substrate.

A tube furnace with a 5% H₂/95% Ar atmosphere was used, ramping up at 1°C/min to 900°C and holding for 1 hour for sintering.

Optional ALD deposition of a 100 nm aluminum oxide passivation layer;

XRD, SEM, four-point probe measurements, and high-temperature hydrogen‑torch impact tests were conducted to characterize the electrical and thermal stability.

III. Core Advantages of the Three‑Five Aerosol Process (Comparison with Electroplating, Sputtering, and Screen Printing)

Non-contact conformal printing on ceramic substrates

Alumina high‑temperature‑resistant ceramics can be directly formed into curved and stepped structures, whereas electroplating requires a conductive undercoat, and vacuum coating equipment is costly.

Digital custom microcircuits, rapid iteration of high-temperature devices.

CAD enables the free design of micro-sensing and RF circuits without the need for mask or tooling, reducing the R&D cycle by 70%.

In-situ graphene generation, with simple ink formulation.

No highly dispersed graphene powder is required; dopamine‑mediated sintering enables in situ conversion, effectively addressing the challenge of carbon nanomaterial agglomeration and nozzle clogging.

Ultra-thin, controllable conductive layer, maximizing current-carrying performance.

It enables precise printing of 1-μm ultra-thin traces, fully leveraging its high current-carrying capability, with thick-film and multilayer structures stacked on demand.

Gentle deposition throughout the process, with no high-temperature damage to the substrate.

Printing is performed at only 70°C, the sintering atmosphere is controllable, and the ceramic substrate does not deform or crack.

IV. Five Core Technological Innovations of This Study

Innovation 1: Dopamine‑Induced In‑Situ Generation of Copper–Graphene Aerosol Ink System

Dopamine is used as a graphene precursor in aerosol printing, eliminating the need for graphene dispersion and enabling the in-situ formation of an interfacial carbon layer during sintering.

Innovation 2: Mechanism of Graphene’s High-Temperature Grain-Growth Inhibition and Oxidation Resistance

It elucidates the mechanism by which carbon layers inhibit the diffusion of copper atoms, addressing at the microscale the critical challenges of high-temperature coarsening and oxidative failure in pure copper interconnects.

Innovative New System of High-Temperature-Resistant Composite Conductors with a Negative Temperature Coefficient

It overcomes the inherent drawback of positive temperature drift in metallic conductors—where resistance decreases rather than increases under high-temperature conditions—thereby significantly enhancing the accuracy of high-temperature sensors.

Innovation 4: Optimal Graphene Current-Carrying Capacity Quantitative Proportion Model

It is established that 0.237 wt% represents the optimal compositional ratio for balancing current-carrying capacity and high-temperature stability, providing a quantitative benchmark for the development of functional inks.

Innovative 5,000°C‑class impact‑resistant additive manufacturing solution

An aerosol‑forming plus ALD passivation composite process achieves stable conductivity under millisecond‑scale thermal shock at temperatures exceeding 1,000°C, making it well suited for extreme aerospace operating conditions.

V. Current Industry Challenges and Corresponding Solutions

Challenge 1: In pure copper printed circuits, high-temperature grain growth and surface oxidation lead to a sharp increase in resistance and a tendency to burn out.

✅ In-situ graphene films isolate oxygen, suppress copper atom migration, and maintain stable structure and electrical conductivity at high temperatures.

Challenge 2: Metal conductors exhibit a positive temperature coefficient, leading to severe drift in high-temperature sensing signals.

✅ Graphene‑engineered composite films achieve a negative TCR, resulting in reduced resistance with increasing temperature and minimizing high‑temperature measurement errors.

Challenge 3: Electroplating and sputtering struggle to fabricate precise microcircuits on complex-shaped ceramic substrates.

✅ Aerosol with an adjustable spray distance of 1–5 mm, enabling non-contact, precise deposition on curved surfaces and uneven ceramic substrates.

Challenge 4: Graphene powder-based inks tend to agglomerate, leading to nozzle clogging during prolonged printing.

✅ Dopamine is uniformly dispersed in the liquid phase, enabling the formation of a carbon layer upon sintering, with no solid-phase carbon agglomeration throughout the atomization process.

Challenge 5: In high‑current, high‑temperature equipment, insufficient current‑carrying capacity of the wiring limits power output.

✅1μm ultra-thin copper–graphene film with a current-carrying capacity exceeding 2×10⁹ A/m², meeting the demands of high-power, high-temperature devices.

VI. Future Diversified Industrial Application Scenarios

1 High-Temperature-Resistant Miniature Sensor Circuit for Deep-Space Aerospace Applications

Precision wiring on a ceramic substrate for extreme-temperature‑variation detection equipment on Venus and Jupiter, capable of withstanding instantaneous thermal shocks exceeding thousands of degrees.

2 Online Monitoring Sensors for the High-Temperature Metallurgical Industry

The furnace and heat‑treatment equipment are equipped with built-in temperature‑measurement and pressure‑sensing circuits, ensuring long‑term stable operation.

3 Embedded Micro RF Components for Aircraft Engines

Lightweight antennas and signal‑transmission microconductors for high‑temperature turbine environments, replacing conventional high‑temperature alloy wiring.

4 High-Temperature Power Devices and Interconnect Lines for Silicon Carbide Modules

SiC high-temperature chip with flexible/ceramic substrate and precision wire bonding, reducing high-temperature power losses.

5. Extreme Environment Electronics Laboratory R&D Platform

Rapid fabrication of composite conductive traces with varying graphene contents, coupled with low-cost validation of high-temperature materials.

Image and Text Guide

Figure 1. AJP-printed copper nanoplatelet slurry and the morphology of Cu/Cu–G solder pads

Figure 2. Resistance–temperature characteristics of a pure copper conductor under hydrogen-flame thermal shock oxidation

Figure 3. Effect of graphene content on current-carrying capacity, thickness dependence, and high-temperature stability.

Figure 4. Negative temperature coefficient of Cu–G conductors and morphology after hydrogen-flame thermal shock at temperatures exceeding 1000 °C.

Figure 5. Evolution of XRD‑derived grain size: Graphene suppresses the high‑temperature growth of copper grains.