| Metadata | Details |
|---|
| Publication Date | 2023-12-20 |
| Journal | ACS Sustainable Chemistry & Engineering |
| Authors | Anna Furberg, Rickard Arvidsson |
| Institutions | Chalmers University of Technology, KTH Royal Institute of Technology |
| Citations | 2 |
| Analysis | Full AI Review Included |
- Study Scope: This research provides the first detailed Life Cycle Assessment (LCA) for synthetic nanodiamond (DND) produced via detonation synthesis and diamond film produced via Microwave Chemical Vapor Deposition (MWCVD).
- DND Environmental Hotspots: The primary drivers of environmental impact for DND production are the inputs for detonation synthesis: TNT/RDX explosives and the large volume of cooling water required.
- MWCVD Environmental Hotspots: For diamond film production, electricity consumption (74% of Global Warming Potential, GWP) and the Si substrate (26% of GWP) are the dominant contributors across all assessed impact categories.
- Decarbonization Potential: MWCVD manufacturers can reduce GWP, freshwater eutrophication, and terrestrial acidification impacts by 62-71% by sourcing wind or solar power instead of global average electricity.
- Resource Trade-off: The shift to renewable electricity (wind/solar) significantly increases Mineral Resource Scarcity (MRS) impacts by 57-73%, primarily due to the resources required for turbine and solar cell construction (e.g., copper and steel).
- Material Comparison: DND (180 g CO2 eq/g) is environmentally preferable to conventional synthetic diamond grit produced via High-Pressure High-Temperature (HPHT) synthesis (920 g CO2 eq/g), showing a GWP approximately 5 times lower.
- Data Utility: The study provides ready-to-use unit-process data intended to support future cradle-to-grave LCA studies of products containing these advanced materials.
| Parameter | Value | Unit | Context |
|---|
| DND Functional Unit | 1 | g | Nanodiamonds (4-5 nm primary particles) |
| Diamond Film Functional Unit | 1 cm2, 10 ”m | N/A | Diamond film on Si substrate |
| DND GWP (Baseline) | 180 | g CO2 eq/g DND | Total impact; Detonation synthesis is 67% |
| MWCVD GWP (Baseline) | 380 | g CO2 eq/cm2 | Total impact; Electricity input is 74% |
| MWCVD Reactor Power | 45 | kW | Applied power for 915 MHz apparatus |
| MWCVD Substrate Diameter | 15 | cm | Typical diameter for large-scale production |
| Diamond Film Growth Rate | 6.5 | ”m/h | Applied rate for baseline scenario |
| Diamond Film Density | 3200 | kg/m3 | Typical density of CVD-grown diamond |
| DND Purification Oxidizer | 60 | % | Nitric Acid (HNO3) concentration |
| DND Purification Conditions | 230 | °C, 8-10 MPa | Temperature and pressure during thermal oxidation |
| DND Disaggregation Solvent | DMSO | N/A | Dimethyl sulfoxide (Baseline scenario) |
| DND Seeding Density | >1011 | DNDs/cm2 | Required for growing films <50 nm thick |
| MWCVD Gas Composition | 1:99 | vol % | CH4:H2 ratio in precursor gas |
- LCA Scope and Method: An attributional, cradle-to-gate LCA was performed using the ReCiPe 2016 midpoint v1.1 method (hierarchist perspective). Background data utilized the Ecoinvent v.3.7 database (global average production).
- Detonation Synthesis (DND): Carbon-containing explosives (40-60% TNT, remainder RDX) are detonated in a chamber (2-5 m3) filled with water, which acts as a coolant. The resulting detonation soot yield is approximately 10% of the explosive charge.
- Purification: The detonation soot is subjected to thermal oxidation using 60% HNO3 at high temperature (230 °C) and pressure (8-10 MPa) to oxidize and remove non-diamond carbon allotropes and dissolve metallic impurities.
- Disaggregation: Wet high-energy ball milling is used to break down DND aggregates into primary particles (4-5 nm). The process uses Zirconium Dioxide (ZrO2) microbeads and a solvent (DMSO in the baseline scenario).
- MWCVD Synthesis (Diamond Film): Diamond film is grown on a Silicon (Si) substrate (15 cm diameter, 775 ”m thickness) using a gas mixture of methane (CH4) and hydrogen (H2).
- Seeding: Si substrates are first seeded using monodispersed DND particles via electrostatic seeding to serve as nucleation centers for the polycrystalline diamond film growth.
- Deposition Conditions: Typical MWCVD deposition occurs at pressures of 0.67-13 kPa and temperatures of 800-1000 °C, utilizing a 915 MHz operating frequency apparatus (45 kW power).
- Hard Coatings and Tools: Used as coatings on cutting tools due to extreme hardness and high wear resistance.
- Semiconductors: Applications leveraging diamondâs wide band gap and high thermal conductivity.
- Abrasives and Polishing: DNDs are used in finish polishing and abrasive treatment of superhard materials.
- Advanced Materials: Used in metal-nanodiamond coatings to enhance mechanical strength.
- Electronics and Energy: Potential use in thin-film electronics, photovoltaic devices, and energy storage devices (requiring high stability and thermal conductivity).
- Future Technologies: Under fast development for applications in quantum photonics and quantum computers.
View Original Abstract
Diamond possesses extraordinary properties, including extreme hardness, thermal conductivity, and mechanical strength. Global industrial diamond production is dominated by synthetic diamond, with important commercial applications in hard coatings and semiconductors. However, the life cycle impacts of synthetic diamond materials are largely unknown. The main aim of this study is to conduct the first detailed life cycle assessments of the typical production routes for nanodiamond and diamond film, which are detonation synthesis and microwave chemical vapor deposition, respectively. The functional units were set to 1 g nanodiamond and 1 cm2 diamond film. A limited number of inputs dominate the assessed impacts: explosives and cooling water for nanodiamond production, and electricity and substrate for diamond film production. Diamond film manufacturers can reduce their global warming, freshwater eutrophication, and terrestrial acidification impacts by 62-71% by sourcing wind or solar instead of global average electricity. However, this comes at the expense of increased mineral resource scarcity impacts at 57-73%. A comparison between nanodiamond and synthetic diamond grit shows that the gritâs global warming impact is about 5 times higher, suggesting that nanodiamond is environmentally preferable. The ready-to-use unit-process data from this study can be applied in future studies of products containing these materials.
- 2015 - Handbook of Crystal Growth [Crossref]
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