{ "spore": "profile", "id": "boron-nitride-nanotubes", "spore_version": "0.2", "family": "carbide-nitride-boride-ceramics", "name": "Boron nitride nanotubes", "abbreviation": "BNNT", "role": "Multifunctional nanotube material for radiation shielding, heat-resistant parts and electrically insulating composites", "category": "shielding", "type": "boron-nitride-nanotubes", "summary": "Boron nitride nanotubes (BNNTs) are hollow tubes built from boron and nitrogen atoms. In NASA Langley's in-situ scanning electron microscope tensile tests, individual high-temperature, high-pressure (HTP) BNNTs with a median diameter of 2.5 nm had an elastic modulus of 760 to 960 GPa and a breaking strength of 14 to 38 GPa. Single tubes survived 850 °C in air for 10 minutes and showed oxidation onset at 900 °C, while the radiation-shielding case rests so far on modelling and ground tests.", "best_for": "Lightweight, electrically insulating filler studied for radiation shielding and heat-resistant parts, where the evidence so far is modelling, single-tube tests and ground tests rather than flight", "weakest_at": "Few measured values for BNNT itself: the NASA comparison values are theoretical, its thermal conductivity and shielding performance were not measured in the sources read, and the sources disagree on several values", "identity": { "formula": "BN, one boron and one nitrogen atom per formula unit, arranged as nanotubes", "cas": "10043-11-5", "designations": [], "source": "wiki-bnnt", "where": "Structure: carbon atoms alternately substituted by nitrogen and boron (Wikipedia, lead section). CAS 10043-11-5 is the number the supplier SDS (section 3) prints for the boron nitride ingredient of the BNNT product." }, "tags": { "environments": [ "deep-space" ], "stresses": [ "total-radiation-dose", "extreme-heat", "vacuum-and-outgassing" ], "applications": [ "radiation-shielding", "heat-shields", "structures" ] }, "properties": [ { "benchmark": "elastic_modulus", "label": "Young's modulus, theoretical nanotube value", "value": 1.18, "bound": "exact", "unit": "TPa", "scope": "material", "conditions": { "basis": "theoretical nanotube value from the NASA comparison table", "table_note": "table caption says nanotube values are theoretical" }, "method": "Theoretical value printed in a NASA Langley overview table", "status": "calculated", "source": "nasa-overview", "where": "Nanotube Comparison (Theoretical) table, row Mechanical Properties (Young's Modulus), BNNT column", "source_detail": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" } }, { "benchmark": "thermal_conductivity", "label": "Thermal conductivity, theoretical nanotube value", "value": 300, "value_high": 3000, "bound": "range", "unit": "W/mK", "scope": "material", "conditions": { "basis": "theoretical nanotube value, printed as about 300 to 3000 W/mK", "temperature": "not stated" }, "method": "Theoretical value printed in a NASA Langley overview table", "status": "calculated", "source": "nasa-overview", "where": "Nanotube Comparison (Theoretical) table, row Thermal Conductivity, BNNT column", "source_detail": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" } }, { "benchmark": "cte", "label": "Coefficient of thermal expansion, theoretical nanotube value", "value": -1, "bound": "exact", "unit": "ppm/K", "scope": "material", "conditions": { "basis": "theoretical nanotube value", "unit_in_source": "x10-6 K-1" }, "method": "Theoretical value printed in a NASA Langley overview table", "status": "calculated", "source": "nasa-overview", "where": "Nanotube Comparison (Theoretical) table, row Coefficient of Thermal Expansion", "source_detail": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" } }, { "benchmark": "oxidation_resistance_temperature", "label": "Thermal oxidation resistance in air, theoretical nanotube value", "value": 900, "bound": "lower", "unit": "°C", "scope": "material", "conditions": { "atmosphere": "air", "basis": "printed as stable to over 900 °C in air in the theoretical table" }, "method": "Theoretical value printed in a NASA Langley overview table; Chen et al. measured oxidation onset at 900 °C on single tubes", "status": "calculated", "note": "The same table gives carbon nanotubes as stable up to 300 to 400 °C in air, for comparison.", "source": "nasa-overview", "where": "Nanotube Comparison (Theoretical) table, row Thermal Oxidation Resistance, BNNT column", "source_detail": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" } }, { "benchmark": "band_gap", "label": "Band gap, theoretical nanotube value", "value": 6, "bound": "exact", "unit": "eV", "scope": "material", "conditions": { "basis": "theoretical value printed as about 6.0 eV", "character": "wide band gap, electrically insulating" }, "method": "Theoretical value printed in a NASA Langley overview table", "status": "calculated", "source": "nasa-overview", "where": "Nanotube Comparison (Theoretical) table, row Electric Properties, BNNT column", "source_detail": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" } }, { "benchmark": "neutron_capture_cross_section", "label": "Thermal-neutron absorption cross section, boron-10 isotope", "value": 3835, "bound": "exact", "unit": "barn", "scope": "material", "conditions": { "isotope": "boron-10", "basis": "isotope value quoted in the NIAC report, not a measurement on BNNT" }, "method": "Nuclear data value quoted in a NASA Langley Phase I report", "status": "calculated", "source": "nasa-niac-2012", "where": "Introduction, text on neutron absorption by boron and nitrogen", "source_detail": { "title": "Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: NIAC Phase I final report", "id": "NTRS 20160010096 (report dated 30 September 2012)", "url": "https://ntrs.nasa.gov/api/citations/20160010096/downloads/20160010096.pdf", "year": 2012, "kind": "report" } }, { "benchmark": "elastic_modulus", "label": "Young's modulus of individual HTP-BNNTs, in-situ SEM tensile test", "value": 760, "value_high": 960, "bound": "range", "unit": "GPa", "scope": "material", "conditions": { "form": "individual HTP-BNNT tube, tested one tube at a time", "diameter": "median 2.5 nm by AFM", "test": "in-situ SEM tensile test" }, "method": "Measured on individual tubes by in-situ SEM nanomechanical tensile testing, per the NASA Langley overview", "status": "ground", "source": "nasa-overview", "where": "BNNT Tensile Test Results table, row D = 2.5 nm, column Elastic modulus", "source_detail": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" } }, { "benchmark": "ultimate_tensile_strength", "label": "Breaking strength of individual HTP-BNNTs, in-situ SEM tensile test", "value": 14, "value_high": 38, "bound": "range", "unit": "GPa", "scope": "material", "conditions": { "form": "individual HTP-BNNT tube, tested one tube at a time", "diameter": "median 2.5 nm by AFM", "note": "single-tube breaking strength, not a bulk material value" }, "method": "Measured on individual tubes by in-situ SEM nanomechanical tensile testing, per the NASA Langley overview", "status": "ground", "source": "nasa-overview", "where": "BNNT Tensile Test Results table, row D = 2.5 nm, column Breaking Strength", "source_detail": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" } }, { "benchmark": "elastic_modulus", "label": "Young's modulus quoted as up to 1.3 TPa in a review", "value": 1.3, "bound": "upper", "unit": "TPa", "scope": "material", "conditions": { "basis": "stated as up to 1.3 TPa with no test condition; the review cites a 1998 paper on multi-wall BNNTs" }, "method": "Second-hand figure stated in the introduction of an open-access review", "status": "ground", "note": "Second-hand figure. It differs from the 1.8 TPa in the same review and from the NASA single-tube values; all are reported side by side.", "source": "molecules2016", "where": "Section 1 (Introduction)", "source_detail": { "title": "Boron Nitride Nanotubes: Recent Advances in Their Synthesis, Functionalization, and Applications", "id": "Molecules 2016, 21(7), 922 (PMC6272975)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC6272975/", "year": 2016, "kind": "paper" } }, { "benchmark": "elastic_modulus", "label": "Young's modulus of 1.8 TPa quoted in a review", "value": 1.8, "bound": "exact", "unit": "TPa", "scope": "material", "conditions": { "basis": "multi-wall BNNT value from a cited bending study; the review does not separate Young's modulus from bending modulus" }, "method": "Statement in the introduction of an open-access review, citing a 2013 study", "status": "ground", "uncertainty": "± 0.3 TPa", "note": "Second-hand figure. It differs from the 760 to 960 GPa measured on individual HTP tubes by NASA.", "source": "molecules2016", "where": "Section 1 (Introduction)", "source_detail": { "title": "Boron Nitride Nanotubes: Recent Advances in Their Synthesis, Functionalization, and Applications", "id": "Molecules 2016, 21(7), 922 (PMC6272975)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC6272975/", "year": 2016, "kind": "paper" } }, { "benchmark": "oxidation_resistance_temperature", "label": "Oxidation resistance in air quoted as about 900 °C in a review", "value": 900, "bound": "exact", "unit": "°C", "scope": "material", "conditions": { "atmosphere": "air", "basis": "printed as resistive to oxidation up to about 900 °C; no test conditions given" }, "method": "Statement in Section 2.5 of an open-access review, without its own citation", "status": "ground", "note": "Approximate figure, printed with a tilde in the source.", "source": "molecules2016", "where": "Section 2.5", "source_detail": { "title": "Boron Nitride Nanotubes: Recent Advances in Their Synthesis, Functionalization, and Applications", "id": "Molecules 2016, 21(7), 922 (PMC6272975)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC6272975/", "year": 2016, "kind": "paper" } }, { "benchmark": "air_survival_temperature", "label": "Temperature single BNNTs survived in air for 10 minutes", "value": 850, "bound": "exact", "unit": "°C", "scope": "material", "conditions": { "atmosphere": "air", "time": "10 minutes", "sample": "single tube, AFM", "outcome": "no morphology change" }, "method": "AFM of single tubes after 10 minutes at each temperature in air", "status": "ground", "source": "chen2017", "where": "Results, temperature table, single-tube AFM row at 850 °C", "source_detail": { "title": "Quantitative Characterization of Structural and Mechanical Properties of Boron Nitride Nanotubes in High Temperature Environments", "id": "doi:10.1038/s41598-017-11795-9 (Scientific Reports 7, 1138)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5595806/", "year": 2017, "kind": "paper" } }, { "benchmark": "oxidation_onset_temperature", "label": "Oxidation onset in air, single BNNT, 10 minutes", "value": 900, "bound": "exact", "unit": "°C", "scope": "material", "conditions": { "atmosphere": "air", "time": "10 minutes", "sample": "single tube, AFM", "outcome": "broken segment about 30 nm long" }, "method": "AFM of single tubes after 10 minutes at 900 °C in air", "status": "ground", "source": "chen2017", "where": "Results, temperature table, single-tube AFM row at 900 °C", "source_detail": { "title": "Quantitative Characterization of Structural and Mechanical Properties of Boron Nitride Nanotubes in High Temperature Environments", "id": "doi:10.1038/s41598-017-11795-9 (Scientific Reports 7, 1138)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5595806/", "year": 2017, "kind": "paper" } }, { "benchmark": "air_survival_temperature", "label": "Air survival temperature quoted in a review", "value": 800, "bound": "exact", "unit": "°C", "scope": "material", "conditions": { "atmosphere": "air", "basis": "stated as stable up to 800 °C in air; no test conditions or citation in that sentence" }, "method": "Statement in the introduction of an open-access review", "status": "ground", "note": "Disagrees with the 850 °C survival and 900 °C onset that Chen et al. measured on single tubes. The same review also gives about 900 °C in Section 2.5.", "source": "molecules2016", "where": "Section 1 (Introduction)", "source_detail": { "title": "Boron Nitride Nanotubes: Recent Advances in Their Synthesis, Functionalization, and Applications", "id": "Molecules 2016, 21(7), 922 (PMC6272975)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC6272975/", "year": 2016, "kind": "paper" } }, { "benchmark": "density", "label": "Bulk density, as-grown nonwoven BNNT mat", "value": 0.3, "bound": "exact", "unit": "g/cm3", "scope": "material", "conditions": { "form": "as-grown nonwoven mat, vacuum-filtered, 2 mm thick", "value_note": "printed as about 0.3 g/cm3" }, "method": "Density printed for a test sample on a NASA Langley hypersonic arc-jet test slide", "status": "ground", "source": "nasa-overview", "where": "Hypersonic Materials Environmental Test System slide, sample description, Density", "source_detail": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" } }, { "benchmark": "density", "label": "Average density, BNNT target discs for radioisotope production", "value": 0.27, "bound": "exact", "unit": "g/cm3", "scope": "material", "conditions": { "form": "multi-stack of natural-enrichment BNNT target discs", "basis": "average density printed on the slide" }, "method": "Average density printed on a NASA Langley slide for BNNT target media", "status": "ground", "source": "nasa-overview", "where": "Target media slide, Density (average) label", "source_detail": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" } }, { "benchmark": "density", "label": "Density of the solid BNNT tube, stated in a NASA report", "value": 1.3, "value_high": 1.4, "bound": "range", "unit": "g/cm3", "scope": "material", "conditions": { "form": "solid nanotube, not a mat", "basis": "sentence in the NIAC report with no test or citation" }, "method": "Literature value stated in the text of a NASA Langley Phase I report", "status": "calculated", "note": "Not measured in the report and not sourced in the sentence. The 0.27 and 0.3 g/cm3 values above are for mat and disc forms, not solid tubes.", "source": "nasa-niac-2012", "where": "Introduction, paragraph on BNNT as a structural material (molecular nanotube structure)", "source_detail": { "title": "Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: NIAC Phase I final report", "id": "NTRS 20160010096 (report dated 30 September 2012)", "url": "https://ntrs.nasa.gov/api/citations/20160010096/downloads/20160010096.pdf", "year": 2012, "kind": "report" } }, { "benchmark": "melting_point", "label": "Melting point, BNNT product in a supplier SDS", "value": 2973, "bound": "exact", "unit": "°C", "scope": "material", "conditions": { "material": "BNNT product as described in the SDS, about 60% BNNT and about 10% hexagonal boron nitride by SDS composition" }, "method": "Listed in a supplier safety data sheet, section 9", "status": "ground", "note": "Supplier figure for a mixed product, not a measurement on pure nanotubes.", "source": "sds-bnnt", "where": "Section 9, Other information, Melting point", "source_detail": { "title": "Safety Data Sheet: Boron Nitride Nanotubes (BNNT), supplier Raymor Industries Inc.", "id": "print date 14 December 2021, version 1 (hosted by NanoIntegris)", "url": "https://nanointegris.com/wp-content/uploads/2022/01/5_SDS-BNNT_CANUTEC.pdf", "year": 2021, "kind": "datasheet" } }, { "benchmark": "stability_in_air_temperature", "label": "Stability in air, BNNT product in a supplier SDS", "value": 850, "bound": "lower", "unit": "°C", "scope": "material", "conditions": { "atmosphere": "air", "material": "BNNT product as described in the SDS" }, "method": "Listed as stability in air in a supplier safety data sheet, section 9", "status": "ground", "note": "Supplier figure printed as more than 850 °C; the SDS gives no test time.", "source": "sds-bnnt", "where": "Section 9, Physical and chemical properties, Stability in air", "source_detail": { "title": "Safety Data Sheet: Boron Nitride Nanotubes (BNNT), supplier Raymor Industries Inc.", "id": "print date 14 December 2021, version 1 (hosted by NanoIntegris)", "url": "https://nanointegris.com/wp-content/uploads/2022/01/5_SDS-BNNT_CANUTEC.pdf", "year": 2021, "kind": "datasheet" } }, { "benchmark": "median_outer_diameter", "label": "Median outer diameter, HTP-BNNT, as reported by Chen et al.", "value": 2.9, "bound": "exact", "unit": "nm", "scope": "material", "conditions": { "basis": "median diameter given as reported for HTP-BNNTs in the paper's Raman section" }, "method": "Reported median value stated in the Raman section of the paper", "status": "ground", "note": "Differs from the 2.5 nm median used in NASA's tensile table. Both are reported.", "source": "chen2017", "where": "Results, Raman spectroscopy section", "source_detail": { "title": "Quantitative Characterization of Structural and Mechanical Properties of Boron Nitride Nanotubes in High Temperature Environments", "id": "doi:10.1038/s41598-017-11795-9 (Scientific Reports 7, 1138)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5595806/", "year": 2017, "kind": "paper" } }, { "benchmark": "outer_diameter_range", "label": "Outer diameter range and wall count, HTP-BNNT", "value": 1, "value_high": 6, "bound": "range", "unit": "nm", "scope": "material", "conditions": { "fraction": ">97% of HTP-BNNTs", "walls": "one to four walls" }, "method": "Statement in the introduction of the paper", "status": "ground", "source": "chen2017", "where": "Introduction", "source_detail": { "title": "Quantitative Characterization of Structural and Mechanical Properties of Boron Nitride Nanotubes in High Temperature Environments", "id": "doi:10.1038/s41598-017-11795-9 (Scientific Reports 7, 1138)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5595806/", "year": 2017, "kind": "paper" } }, { "benchmark": "typical_outer_diameter", "label": "Typical outer diameter quoted for CVD and thermal-annealing BNNTs", "value": 50, "value_high": 80, "bound": "range", "unit": "nm", "scope": "material", "conditions": { "synthesis": "CVD and thermal annealing methods", "basis": "printed as the typical diameter of tubes from those methods" }, "method": "Statement in Section 2.1 of an open-access review, without its own citation", "status": "ground", "note": "A different synthesis route from the HTP tubes (2.5 to 2.9 nm). Recorded as printed for comparison, not as an HTP value.", "source": "molecules2016", "where": "Section 2.1", "source_detail": { "title": "Boron Nitride Nanotubes: Recent Advances in Their Synthesis, Functionalization, and Applications", "id": "Molecules 2016, 21(7), 922 (PMC6272975)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC6272975/", "year": 2016, "kind": "paper" } } ], "corrosion": [ { "environment": "Air at high temperature (oxidation)", "headline": "Single BNNTs survived 850 °C in air for 10 minutes and began to oxidise at 900 °C.", "effect": "In AFM tests of single tubes heated for 10 minutes in air, there was no morphology change at 850 °C, a broken segment about 30 nm long at 900 °C, severe length loss and breaks at 925 °C, and severe burnout at 950 °C. In in-situ optical tests of microfibrils, the edges changed at 1000 °C and the material was largely burned out at 1200 °C.", "rating": "moderate", "conditions": { "atmosphere": "air", "exposure": "10 minutes per temperature for single-tube AFM tests" }, "source": "chen2017", "where": "Results, temperature table (single-tube and microfibril rows)" }, { "environment": "Vacuum and outgassing, and fire", "headline": "NASA's NIAC report says BNNT has outgassing and flammability issues and should be encapsulated.", "effect": "The NIAC Phase I report states that BNNT has some outgassing and flammability issues and should be encapsulated for many applications.", "rating": "moderate", "source": "nasa-niac-2012", "where": "Introduction, paragraph on BNNT as a structural material" } ], "risks": { "hazards": [ { "text": "Supplier safety data sheet for BNNT (Raymor Industries Inc., print date 14 December 2021) gives GHS classification as not available, signal word Warning, and an irritant classification (Xi, risk phrase R36/37/38: irritating to eyes, respiratory system and skin).", "ghs": [], "source": "sds-bnnt", "where": "Section 2, Hazards identification; Section 15, EU regulations" }, { "text": "The same SDS gives an oral LD50 in rats above 50 g/kg for the BNNT product. It states that the acute and chronic toxicity of the BNNT component is not known and may differ with wall number.", "ghs": [], "source": "sds-bnnt", "where": "Section 11, Toxicological information" }, { "text": "The SDS says inhalation of dust irritates the airways and that frequent inhalation of dust over a long period increases the risk of lung disease.", "ghs": [], "source": "sds-bnnt", "where": "Sections 4 and 11" } ], "failure_risks": [ { "mode": "Oxidation of single tubes in hot air", "trigger": "Heating in air at 900 °C for 10 minutes (single tube, AFM)", "consequence": "A broken segment about 30 nm long appears at 900 °C; severe length loss and breaks follow at 925 °C.", "severity": "moderate", "source": "chen2017", "where": "Results, temperature table" }, { "mode": "Outgassing and flammability", "trigger": "Not stated in the NIAC Phase I report", "consequence": "The report says BNNT should be encapsulated for many applications because of these issues.", "severity": "moderate", "source": "nasa-niac-2012", "where": "Introduction, paragraph on BNNT as a structural material" }, { "mode": "Dust release during handling", "trigger": "Handling dry BNNT powder or mat without exhaust ventilation", "consequence": "Dust can irritate the eyes, skin and airways. The SDS gives no OSHA exposure limit (no data available).", "severity": "moderate", "source": "sds-bnnt", "where": "Sections 4 and 8" } ], "side_effects": [ { "text": "The SDS warns that the BNNT powder may cause skin sensitization and skin or eye irritation.", "affects": "People who handle the powder", "source": "sds-bnnt", "where": "Section 11, Respiratory or skin sensitization, and Irritant effects" } ], "handling": [ { "text": "Avoid dust formation and keep the container tightly closed in a cool, well-ventilated area (SDS sections 7 and 10).", "source": "sds-bnnt", "where": "Sections 7 and 10" }, { "text": "Work with good ventilation, under a fume hood or with local exhaust where dust forms, and avoid skin and eye contact (SDS sections 7 and 8).", "source": "sds-bnnt", "where": "Sections 7 and 8" }, { "text": "Clean up spills with a HEPA-filter vacuum and keep spilt material away from drains (SDS sections 6 and 12).", "source": "sds-bnnt", "where": "Sections 6 and 12" } ], "mitigations": [ { "text": "Use the respirator class the SDS lists for the expected dust exposure (P95 or P1 for low exposure, P99 or P2 for high), with safety glasses and protective gloves (SDS section 8).", "source": "sds-bnnt", "where": "Section 8, Exposure controls" } ] }, "uses": [ { "application": "radiation-shielding", "device": "Hydrogen-containing BNNT as a shield (modelled)", "example": "NASA Langley's Phase I modelling (OLTARIS, calculated, not measured) found that BN with 5% hydrogen gave better galactic cosmic ray protection than polyethylene in a 30 cm wall of the same thickness. The report also says BNNT alone does not beat the best current shields, except for secondary neutrons.", "source": "nasa-niac-2012", "where": "Summary, and Figure 1 caption" }, { "application": "radiation-shielding", "device": "Choice of shielding material (literature review)", "example": "A NASA Langley literature review slide lists boron, lithium and gadolinium as high thermal-neutron absorbers, and hydrogen as the best shield against galactic cosmic rays.", "source": "nasa-nifs-2020", "where": "Literature Review slide" }, { "application": "radiation-shielding", "device": "BNNT and BNNT polymer composites in a neutron exposure lab (ground)", "example": "NASA's overview summary reports excellent neutron radiation shielding effectiveness for BNNT. The slides we read give no numeric shielding result for BNNT.", "source": "nasa-overview", "where": "Summary slide; Neutron Radiation Shielding Study slides" }, { "application": "heat-shields", "device": "As-grown BNNT mat in an arc-jet test (ground)", "example": "NASA exposed a 25 mm diameter, 2 mm thick as-grown BNNT mat to a surface temperature of 1315 °C for 1 minute in its HYMETS arc-jet facility. The text we read gives FT-IR spectra before and after the test but no numeric pass or fail result.", "source": "nasa-overview", "where": "Hypersonic Materials Environmental Test System slides, sample and test conditions" } ], "supply": [ { "subject": "Boron (feedstock for BNNT)", "abundance": "Crustal abundance not found in the sources read.", "producers": [ { "country": "Turkey", "year": 2025 }, { "country": "Chile", "year": 2025 }, { "country": "Bolivia", "year": 2025 }, { "country": "Peru", "year": 2025 }, { "country": "China", "year": 2025 }, { "country": "Russia", "year": 2025 }, { "country": "Argentina", "year": 2025 }, { "country": "Germany", "year": 2025 }, { "country": "United States", "year": 2025 } ], "critical_lists": [ { "list": "USGS 2025 List of Critical Minerals (boron added in the final list)", "listed": true }, { "list": "EU critical raw materials list (Regulation (EU) 2024/1252, as shown on the European Commission page)", "listed": true } ], "recycling": "USGS: boron recycling is insignificant.", "substitutes": [ "USGS: other materials can substitute for boron in detergents, enamels, insulation and soaps. No substitute for BNNT was found in the sources read." ], "source": "usgs-boron", "where": "World Production and Reserves table, 2025e, units as printed (Turkey, refined borates 1,500; Bolivia, ulexite 380; Chile, ulexite 300; United States withheld; world total not calculable per USGS). Import sources 2021 to 2024: Turkey 90%. EU list: the European Commission page lists Boron/Borate and says Turkey provides 99% of EU boron supply (ec-crm)." } ], "media": [], "documents": [ { "title": "NASA Langley overview: Boron Nitride Nanotube (BNNT) and BNNT Composites", "type": "report", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020 }, { "title": "NASA NIAC Phase I final report: Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen", "type": "report", "url": "https://ntrs.nasa.gov/api/citations/20160010096/downloads/20160010096.pdf", "year": 2012 }, { "title": "Chen et al. 2017: Quantitative Characterization of Structural and Mechanical Properties of Boron Nitride Nanotubes in High Temperature Environments", "type": "paper", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5595806/", "year": 2017 }, { "title": "Review: Boron Nitride Nanotubes: Recent Advances in Their Synthesis, Functionalization, and Applications (Molecules)", "type": "paper", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC6272975/", "year": 2016 }, { "title": "Safety data sheet: Boron Nitride Nanotubes (BNNT), supplier Raymor Industries Inc., print date 14 December 2021", "type": "sds", "url": "https://nanointegris.com/wp-content/uploads/2022/01/5_SDS-BNNT_CANUTEC.pdf", "year": 2021 }, { "title": "USGS Mineral Commodity Summaries 2026: Boron", "type": "report", "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf", "year": 2026 }, { "title": "NASA Langley 2020 Spring NIFS Symposium presentation: Radiation Study of Boron Nitride Nanotube (BNNT) and BNNT Composites", "type": "report", "url": "https://ntrs.nasa.gov/api/citations/20205001454/downloads/Final%20Draft%20-%20Spring%202020%20NIFS%20Symposium%20Final%20Presentation%20Calista%20Lum%20sm%20revised.pdf", "year": 2020 } ], "gaps": [ "No measured thermal conductivity of BNNT, bulk or single tube, was found in the sources read. The only values are theoretical (NASA table, about 300 to 3000 W/mK).", "No flight, vacuum-exposure, thermal-cycling or radiation-exposure result on BNNT itself was found. The space evidence is modelling and ground testing.", "No measured neutron or galactic cosmic ray shielding number for BNNT was found in the sources read. The NIFS 2020 presentation reports indium-foil tests on boron carbide and aluminium 6061, not on BNNT.", "Humidity, UV and atomic-oxygen ageing of BNNT were not found in any source read.", "Crustal abundance of boron was not found in a source we could open.", "No BNNT producers, output or market shares were found. NASA's overview names BNNT LLC beside a cotton-like HTP-BNNT image and gives a 2014 plasma synthesis rate of 35 g per hour, which is a research figure, not a market figure.", "No nitrogen supply source was opened, so nitrogen is not covered under supply.", "No standard designations (UNS, EN, ASTM or trade names) for BNNT were found in a source we could open. The CAS number 10043-11-5 is the one the SDS prints for its boron nitride ingredient.", "The Australian assessment of BNNT (CA09938, June 2025), which treats BNNT as hazardous by analogy with carbon nanotubes, could not be opened because the server connection failed. It is not used.", "The PubChem record for boron nitride (CID 66227) was blocked by a browser check, so PubChem GHS data are not used.", "The Thibeault et al. 2015 MRS Bulletin review on nanomaterials for radiation shielding was not readable in full. Only the abstract and reference list were visible.", "Property names not in property-canon are used: band_gap, oxidation_resistance_temperature, oxidation_onset_temperature, air_survival_temperature, stability_in_air_temperature, neutron_capture_cross_section, median_outer_diameter, outer_diameter_range and typical_outer_diameter.", "Sources disagree on several values and both are kept: 800 °C survival in the review against 850 °C (Chen et al.), 1.3 TPa and 1.8 TPa moduli, 2.5 nm and 2.9 nm median diameters, and 50 to 80 nm diameters for CVD tubes.", "No image was licensed and fetched in this run, so media is empty." ], "story": { "why": "Boron nitride nanotubes (BNNTs) are being studied by NASA Langley as a multifunctional material: stiff, heat-resistant tubes that also insulate electrically. NASA's overview lists neutron shielding from their boron content, and a high service temperature above 800 °C, as benefits. NASA's Phase I study tested by modelling whether hydrogen-containing BNNT could shield cosmic rays better than polyethylene at the same thickness.", "uses": [ { "where": "Radiation shielding (modelled)", "line": "NASA's Phase I modelling found that BN with 5% hydrogen could shield galactic cosmic rays better than polyethylene of the same wall thickness. This is a calculated result, not a measurement." }, { "where": "Heat test sample (ground)", "line": "NASA exposed an as-grown BNNT mat to a surface temperature of 1315 °C for 1 minute in an arc-jet test. The text we read gives no pass or fail number." }, { "where": "Neutron shielding composites (ground)", "line": "NASA's overview reports excellent neutron shielding for BNNT and BNNT polymer composites in lab tests, but the slides we read give no numeric result." } ], "can_do": [ { "label": "Stiffness", "line": "Individual high-temperature, high-pressure tubes measured in NASA's in-situ SEM tests have an elastic modulus of 760 to 960 GPa. NASA's theoretical table gives 1.18 TPa as a theoretical nanotube value.", "benchmark": "elastic_modulus", "scope": "material", "value": "760 to 960 GPa" }, { "label": "Heat in air", "line": "Single tubes survived 10 minutes in air at 850 °C with no change, and the first oxidation appeared at 900 °C (Chen et al. 2017).", "benchmark": "oxidation_onset_temperature", "scope": "material", "value": "900 °C onset" }, { "label": "Density", "line": "As-grown mats and target discs of BNNT have densities of about 0.3 g/cm3 and 0.27 g/cm3. A NASA report gives 1.3 to 1.4 g/cm3 for the solid tube, without a cited test.", "benchmark": "density", "scope": "material", "value": "0.27 to 0.3 g/cm3 (mat and disc forms)" }, { "label": "Neutron capture", "line": "Boron-10 has a thermal-neutron absorption cross section of 3835 barns, as quoted in the NIAC report. That figure is for the isotope, not a measured BNNT shield.", "benchmark": "neutron_capture_cross_section", "scope": "material", "value": "3835 barn" } ], "compare": "Relative to carbon nanotubes, NASA's theoretical table gives BNNTs a much higher oxidation resistance in air, stable to over 900 °C against 300 to 400 °C for carbon nanotubes, and a wide electrical band gap, where carbon nanotubes are metallic or semiconducting. The same table gives BNNTs a lower theoretical Young's modulus and thermal conductivity than carbon nanotubes. Measured values for single tubes are below the theoretical table values, so the table should not be read as a measured result.", "compare_rows": [ { "label": "Young's modulus, individual tube (measured)", "benchmark": "elastic_modulus", "scope": "material" }, { "label": "Oxidation onset in air (measured, single tube)", "benchmark": "oxidation_onset_temperature", "scope": "material" }, { "label": "Thermal conductivity (theoretical, nanotube)", "benchmark": "thermal_conductivity", "scope": "material" } ], "handling": [ "Treat the powder as an irritant. Avoid dust, use good ventilation or exhaust, and wear eye and skin protection.", "Keep containers closed in a cool, well-ventilated place. Clean spills with a HEPA-filter vacuum.", "In air, single tubes began to oxidise at 900 °C. Each temperature was held for 10 minutes, so these results do not cover longer exposure below that temperature." ], "good_for": [ "Radiation shielding research. Hydrogen-containing BNNT was modelled to beat polyethylene at the same thickness (calculated, not measured).", "Heat-resistant insulating parts. Single tubes survived 850 °C in air for 10 minutes with no change." ], "watch_out": [ "Most property values are theoretical, from one tube at a time, or from a single lab test. The sources disagree on several values, such as 800 °C against 850 °C for survival in air, and 1.3 TPa against 1.8 TPa for modulus.", "The SDS classes the powder as an irritant and says the nanotube toxicity is not known.", "The shielding figures are modelled. No measured BNNT shielding number was found in the sources read." ], "verdict": "BNNT looks promising for heat-resistant, insulating and radiation-shielding parts, but the evidence is mostly theory, single-tube tests and modelling, so it is not yet a qualified material for spacecraft use.", "recipe": { "line": "Boron nitride nanotubes are made of boron and nitrogen in a one-to-one atom ratio. NASA's high-temperature, high-pressure method vaporises boron feedstock with a laser in nitrogen gas, with no catalyst, so boron and nitrogen are the only reactants.", "parts": [ { "name": "Boron", "symbol": "B", "role": "Forms the tube wall with nitrogen. Its boron-10 isotope has a large thermal-neutron absorption cross section, which is why boron is used in neutron shielding.", "atoms": 1, "atomic_weight": 10.806, "source": "nist-b", "where": "Standard atomic weight printed as an interval by NIST; the lower bound is entered" }, { "name": "Nitrogen", "symbol": "N", "role": "Forms the tube wall with boron. Nitrogen has a larger neutron absorption cross section than carbon (NIAC report).", "atoms": 1, "atomic_weight": 14.00643, "source": "nist-n", "where": "Standard atomic weight printed as an interval by NIST; the lower bound is entered" } ] }, "risk_groups": [ { "title": "For people", "lead": "The supplier safety data sheet classes BNNT powder as an irritant. The toxicity of the nanotube form is not known.", "points": [ { "label": "The powder", "line": "The safety data sheet classes the BNNT product as an irritant for eyes, skin and airways, and gives no GHS classification. Its oral LD50 in rats is above 50 g/kg." }, { "label": "Dust", "line": "Avoid breathing the dust. The SDS says frequent inhalation over a long period increases the risk of lung disease." }, { "label": "Unknowns", "line": "The SDS says the acute and chronic toxicity of the nanotube component is not known and may differ with the number of walls." } ], "level": 2, "verdict": "Irritant dust; long-term toxicity unknown" }, { "title": "If a part overheats", "lead": "These results come from heating tests on single tubes and microfibrils in air, not from field use.", "points": [ { "label": "Air at 850 °C", "line": "Individual tubes showed no morphology change after 10 minutes in air at 850 °C." }, { "label": "Air at 900 °C", "line": "After 10 minutes at 900 °C a broken segment about 30 nm long appeared, which marks oxidation onset." }, { "label": "Outgassing", "line": "NASA's NIAC report notes outgassing and flammability issues and recommends encapsulation." } ], "level": 2, "verdict": "Oxidises above 900 °C in air" }, { "title": "Handling and storage", "points": [ { "label": "Dust", "line": "Avoid dust formation. Use good ventilation or local exhaust, and clean spills with a HEPA-filter vacuum." }, { "label": "Storage", "line": "Keep the container tightly closed in a cool, well-ventilated area." } ] } ] }, "updated": "2026-11-01", "review": { "status": "draft", "method": "assistant", "checked_values": 22, "unreachable": 0, "caveats": 10, "note": "Values read on 2026-11-01. NASA overview and NIAC report read as PDF text; SDS and USGS boron read as PDF text; the EU page read as HTML. The Chen et al. and Molecules review values were read through a summarising fetch of the HTML article, not the raw text." }, "sources": { "nasa-overview": { "title": "Boron Nitride Nanotube (BNNT) and BNNT Composites: Overview", "id": "NTRS 20200003735 (Park, Chu and Fay, NASA Langley)", "url": "https://ntrs.nasa.gov/api/citations/20200003735/downloads/20200003735.pdf", "year": 2020, "kind": "report" }, "nasa-nifs-2020": { "title": "Radiation Study of Boron Nitride Nanotube (BNNT) and BNNT Composites, 2020 Spring NIFS Symposium presentation", "id": "NTRS 20205001454 (Calista Lum)", "url": "https://ntrs.nasa.gov/api/citations/20205001454/downloads/Final%20Draft%20-%20Spring%202020%20NIFS%20Symposium%20Final%20Presentation%20Calista%20Lum%20sm%20revised.pdf", "year": 2020, "kind": "report" }, "nasa-niac-2012": { "title": "Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: NIAC Phase I final report", "id": "NTRS 20160010096 (report dated 30 September 2012)", "url": "https://ntrs.nasa.gov/api/citations/20160010096/downloads/20160010096.pdf", "year": 2012, "kind": "report" }, "chen2017": { "title": "Quantitative Characterization of Structural and Mechanical Properties of Boron Nitride Nanotubes in High Temperature Environments", "id": "doi:10.1038/s41598-017-11795-9 (Scientific Reports 7, 1138)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5595806/", "year": 2017, "kind": "paper" }, "molecules2016": { "title": "Boron Nitride Nanotubes: Recent Advances in Their Synthesis, Functionalization, and Applications", "id": "Molecules 2016, 21(7), 922 (PMC6272975)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC6272975/", "year": 2016, "kind": "paper" }, "sds-bnnt": { "title": "Safety Data Sheet: Boron Nitride Nanotubes (BNNT), supplier Raymor Industries Inc.", "id": "print date 14 December 2021, version 1 (hosted by NanoIntegris)", "url": "https://nanointegris.com/wp-content/uploads/2022/01/5_SDS-BNNT_CANUTEC.pdf", "year": 2021, "kind": "datasheet" }, "usgs-boron": { "title": "Mineral Commodity Summaries 2026: Boron", "id": "USGS MCS 2026, February 2026", "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf", "year": 2026, "kind": "report" }, "ec-crm": { "title": "Critical raw materials (European Commission page, Regulation (EU) 2024/1252)", "url": "https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en", "year": 2024, "kind": "web" }, "wiki-bnnt": { "title": "Boron nitride nanotube (Wikipedia, used for composition only)", "url": "https://en.wikipedia.org/wiki/Boron_nitride_nanotube", "kind": "web" }, "nist-b": { "title": "NIST Atomic Weights and Isotopic Compositions: boron (Z = 5), standard atomic weight", "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=B&all=all&ascii=html", "kind": "database" }, "nist-n": { "title": "NIST Atomic Weights and Isotopic Compositions: nitrogen (Z = 7), standard atomic weight", "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=N&all=all&ascii=html", "kind": "database" } }, "license": "CC-BY-4.0", "url": "https://spacemushroom.com/profiles/boron-nitride-nanotubes/" }