headshot of Tevis Jacobs

Tevis Jacobs

Associate Professor
Jacobs Lab Website Google Scholar Profile Mechanical Engineering & Materials Science

overview

The focus of our research is to reveal the physical processes governing the mechanics of surfaces and interfaces.

Contacting surfaces are of critical importance in advanced manufacturing, micro-/nano-devices, and scanning probe microscopy applications. The function of such applications depends on the ability to precisely predict and control contact parameters such as contact area, contact stiffness, adhesion, and electrical and thermal transport.

Our group uses novel combinations of in situ electron microscopy, multi-scale mechanical testing, and multi-scale topography characterization to interrogate the mechanics, tribology, and functional properties of contacts. On the small scale, we achieve Angstrom-scale spatial resolution and nanonewton force resolution, to interrogate atomic-scale processes. On the large-scale, we use micro- and macro-scale testing of larger contacts that contain multi-scale surface roughness. This enables the scale-up of nanoscale insights to describe functional properties of larger-scale surfaces.

Our goal is to develop quantitative, fundamental, and predictive understanding of contact behavior, which will enable tailored surface properties for advanced technologies.

about

(2013) American Vacuum Society Dorothy M. and Earl S. Hoffman Scholarship Award.

(2012) Materials Research Society Graduate Student Award, Gold Medal.

(2011) National Science Foundation IGERT (Integrative Graduate Education and Research Traineeship).

(2011) Peter Blau Best Poster Award, International Conference on the Wear of Materials.

(2011) Geoffrey Belton Graduate Fellowship Award, University of Pennsylvania, Materials Science.

(2010) Young Tribologist Award, Society for Tribologists and Lubrication Engineers.

(2006) O. Cutler Shepard Award for Outstanding Masters of Science Student, Stanford University.

(2004) Stanford Graduate Fellowship.

(2004) National Science Foundation Graduate Research Fellowship.

(2003) Thouron Award for graduate study in the UK.

PhD, Materials Science and Engineering, University of Pennsylvania, 2008 - 2013

MSc, Materials Science and Engineering, Stanford University, 2004 - 2006

MPhil, Computer Modeling of Materials, Churchill College, Cambridge University, 2003 - 2004

BSc, Mechanical Engineering, also Materials Science & Engineering, University of Pennsylvania, 1999 - 2003

Ding, R., Azadehranjbar, S., Padilla Espinosa, I.M., Martini, A., & Jacobs, T.D.B. (2024). Separating Geometric and Diffusive Contributions to the Surface Nucleation of Dislocations in Nanoparticles. ACS Nano, 18(5), 4170-4179.American Chemical Society (ACS). doi: 10.1021/acsnano.3c09026.

Sanner, A., Kumar, N., Dhinojwala, A., Jacobs, T.D.B., & Pastewka, L. (2024). Why soft contacts are stickier when breaking than when making them. Sci Adv, 10(10), eadl1277.American Association for the Advancement of Science (AAAS). doi: 10.1126/sciadv.adl1277.

Azadehranjbar, S., Ding, R., Espinosa, I.M.P., Martini, A., & Jacobs, T.D.B. (2023). Size-Dependent Role of Surfaces in the Deformation of Platinum Nanoparticles. ACS NANO, 17(9), 8133-8140.American Chemical Society (ACS). doi: 10.1021/acsnano.2c11457.

Jackson, R.L., & Jacobs, T.D.B. (2023). Which asperity scales matter for true contact area? A multi-scale and statistical investigation. MECHANICS OF MATERIALS, 184, 104746.Elsevier BV. doi: 10.1016/j.mechmat.2023.104746.

Baker, A.J., Vishnubhotla, S.B., Chen, R., Martini, A., & Jacobs, T.D.B. (2022). Origin of Pressure-Dependent Adhesion in Nanoscale Contacts. NANO LETTERS, 22(14), 5954-5960.American Chemical Society (ACS). doi: 10.1021/acs.nanolett.2c02016.

Ding, R., Espinosa, I.M.P., Loevlie, D., Azadehranjbar, S., Baker, A.J., Mpourmpakis, G., Martini, A., & Jacobs, T.D.B. (2022). Size-dependent shape distributions of platinum nanoparticles. NANOSCALE ADVANCES, 4(18), 3978-3986.Royal Society of Chemistry (RSC). doi: 10.1039/d2na00326k.

Ding, R., Miller, N.C., Woeppel, K.M., Cui, X.T., & Jacobs, T.D.B. (2022). Surface Area and Local Curvature: Why Roughness Improves the Bioactivity of Neural Implants. LANGMUIR, 38(24), 7512-7521.American Chemical Society (ACS). doi: 10.1021/acs.langmuir.2c00473.

Espinosa, I.M.P., Jacobs, T.D.B., & Martini, A. (2022). Atomistic Simulations of the Elastic Compression of Platinum Nanoparticles. NANOSCALE RESEARCH LETTERS, 17(1), 96.Springer Science and Business Media LLC. doi: 10.1186/s11671-022-03734-z.

Jacobs, T.D.B., & Pastewka, L. (2022). Surface topography as a material parameter. MRS BULLETIN, 47(12), 1205-1210.Springer Science and Business Media LLC. doi: 10.1557/s43577-022-00465-5.

Maksuta, D., Dalvi, S., Gujrati, A., Pastewka, L., Jacobs, T.D.B., & Dhinojwala, A. (2022). Dependence of adhesive friction on surface roughness and elastic modulus. SOFT MATTER, 18(31), 5843-5849.Royal Society of Chemistry (RSC). doi: 10.1039/d2sm00163b.

Padilla Espinosa, I.M., Azadehranjbar, S., Ding, R., Baker, A.J., Jacobs, T.D.B., & Martini, A. (2022). Platinum nanoparticle compression: Combining in situ TEM and atomistic modeling. APPLIED PHYSICS LETTERS, 120(1).AIP Publishing. doi: 10.1063/5.0078035.

Roettger, M.C., Sanner, A., Thimons, L.A., Junge, T., Gujrati, A., Monti, J.M., Noehring, W.G., Jacobs, T.D.B., & Pastewka, L. (2022). Contact.engineering-Create, analyze and publish digital surface twins from topography measurements across many scales. SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES, 10(3), 035032.IOP Publishing. doi: 10.1088/2051-672X/ac860a.

Sanner, A., Nöhring, W.G., Thimons, L.A., Jacobs, T.D.B., & Pastewka, L. (2022). Scale-dependent roughness parameters for topography analysis. Applied Surface Science Advances, 7, 100190.Elsevier BV. doi: 10.1016/j.apsadv.2021.100190.

Thimons, L.A., Gujrati, A., Sanner, A., Pastewka, L., & Jacobs, T.D.B. (2022). Hard-material Adhesion: Which Scales of Roughness Matter? (Jul, 10.1007/s11340-021-00733-6, 2021). EXPERIMENTAL MECHANICS, 62(2), 365.Springer Science and Business Media LLC. doi: 10.1007/s11340-021-00769-8.

Ding, R., Gujrati, A., Pendolino, M.M., Beschorner, K.E., & Jacobs, T.D.B. (2021). Going Beyond Traditional Roughness Metrics for Floor Tiles: Measuring Topography Down to the Nanoscale. TRIBOLOGY LETTERS, 69(3).Springer Science and Business Media LLC. doi: 10.1007/s11249-021-01460-8.

Espinosa, I.M.P., Jacobs, T.D.B., & Martini, A. (2021). Evaluation of Force Fields for Molecular Dynamics Simulations of Platinum in Bulk and Nanoparticle Forms. JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 17(7), 4486-4498.American Chemical Society (ACS). doi: 10.1021/acs.jctc.1c00434.

Gujrati, A., Sanner, A., Khanal, S.R., Moldovan, N., Zeng, H., Pastewka, L., & Jacobs, T.D.B. (2021). Comprehensive topography characterization of polycrystalline diamond coatings. SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES, 9(1), 014003.IOP Publishing. doi: 10.1088/2051-672X/abe71f.

Salim, M.G., Thimons, L.A., Kim, M.A., Carr, B., Montgomery, M., Tolman, N., Jacobs, T.D.B., & Liu, H. (2021). Single sheets of graphene for fabrication of fibers with enhanced mechanical properties. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 23(40), 23124-23129.Royal Society of Chemistry (RSC). doi: 10.1039/d1cp03238k.

Thimons, L.A., Gujrati, A., Sanner, A., Pastewka, L., & Jacobs, T.D.B. (2021). Hard-material Adhesion: Which Scales of Roughness Matter?. EXPERIMENTAL MECHANICS, 61(7), 1109-1120.Springer Science and Business Media LLC. doi: 10.1007/s11340-021-00733-6.

Chan, N., Lin, C., Jacobs, T., Carpick, R.W., & Egberts, P. (2020). Quantitative determination of the interaction potential between two surfaces using frequency-modulated atomic force microscopy. BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 11, 729-739.Beilstein Institut. doi: 10.3762/bjnano.11.60.

Chen, R., Vishnubhotla, S.B., Khanal, S.R., Jacobs, T.D.B., & Martini, A. (2020). Quantifying the pressure-dependence of work of adhesion in silicon-diamond contacts. APPLIED PHYSICS LETTERS, 116(5).AIP Publishing. doi: 10.1063/1.5127533.

Chen, R., Vishnubhotla, S.B., Jacobs, T.D.B., & Martini, A. (2019). Simulations of the effect of an oxide on contact area measurements from conductive atomic force microscopy. NANOSCALE, 11(3), 1029-1036.Royal Society of Chemistry (RSC). doi: 10.1039/c8nr08605b.

Dalvi, S., Gujrati, A., Khanal, S.R., Pastewka, L., Dhinojwala, A., & Jacobs, T.D.B. (2019). Linking energy loss in soft adhesion to surface roughness. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 116(51), 25484-25490.Proceedings of the National Academy of Sciences. doi: 10.1073/pnas.1913126116.

Jacobs, T.D.B., Greiner, C., Wahl, K.J., & Carpick, R.W. (2019). Insights into tribology from in situ nanoscale experiments. MRS BULLETIN, 44(6), 478-486.Springer Science and Business Media LLC. doi: 10.1557/mrs.2019.122.

Milne, Z.B., Schall, J.D., Jacobs, T.D.B., Harrison, J.A., & Carpick, R.W. (2019). Covalent Bonding and Atomic-Level Plasticity Increase Adhesion in Silicon-Diamond Nanocontacts. ACS APPLIED MATERIALS & INTERFACES, 11(43), 40734-40748.American Chemical Society (ACS). doi: 10.1021/acsami.9b08695.

Moghaddam, S.R.M., Hemler, S.L., Redfern, M.S., Jacobs, T.D.B., & Beschorner, K.E. (2019). Computational model of shoe wear progression: Comparison with experimental results. WEAR, 422, 235-241.Elsevier BV. doi: 10.1016/j.wear.2019.01.070.

Vishnubhotla, S.B., Chen, R., Khanal, S.R., Hu, X., Martini, A., & Jacobs, T.D.B. (2019). Matching Atomistic Simulations and In Situ Experiments to Investigate the Mechanics of Nanoscale Contact. TRIBOLOGY LETTERS, 67(3).Springer Science and Business Media LLC. doi: 10.1007/s11249-019-1210-7.

Vishnubhotla, S.B., Chen, R., Khanal, S.R., Hu, X., Martini, A., & Jacobs, T.D.B. (2019). Matching Atomistic Simulations and In Situ Experiments to Investigate the Mechanics of Nanoscale Contact (vol 67, 97, 2019). TRIBOLOGY LETTERS, 68(1).Springer Science and Business Media LLC. doi: 10.1007/s11249-019-1251-y.

Vishnubhotla, S.B., Chen, R., Khanal, S.R., Li, J., Stach, E.A., Martini, A., & Jacobs, T.D.B. (2019). Quantitative measurement of contact area and electron transport across platinum nanocontacts for scanning probe microscopy and electrical nanodevices. NANOTECHNOLOGY, 30(4), 045705.IOP Publishing. doi: 10.1088/1361-6528/aaebd6.

Vishnubhotla, S.B., Chen, R., Khanal, S.R., Martini, A., & Jacobs, T.D.B. (2019). Understanding contact between platinum nanocontacts at low loads: The effect of reversible plasticity. NANOTECHNOLOGY, 30(3), 035704.IOP Publishing. doi: 10.1088/1361-6528/aaea2b.

Gujrati, A., Khanal, S.R., Pastewka, L., & Jacobs, T.D.B. (2018). Combining TEM, AFM, and Profilometry for Quantitative Topography Characterization Across All Scales. ACS APPLIED MATERIALS & INTERFACES, 10(34), 29169-29178.American Chemical Society (ACS). doi: 10.1021/acsami.8b09899.

Khanal, S.R., Gujrati, A., Vishnubhotla, S.B., Nowakowski, P., Bonifacio, C.S., Pastewka, L., & Jacobs, T.D.B. (2018). Surface Topography: Metrology and Properties. SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES, 6(4), 045004.IOP Publishing. doi: 10.1088/2051-672X/aae5b3.

Mangolini, F., Krick, B.A., Jacobs, T.D.B., Khanal, S.R., Streller, F., McClimon, J.B., Hilbert, J., Prasad, S.V., Scharf, T.W., Ohlhausen, J.A., Lukes, J.R., Sawyer, W.G., & Carpick, R.W. (2018). Effect of silicon and oxygen dopants on the stability of hydrogenated amorphous carbon under harsh environmental conditions. CARBON, 130, 127-136.Elsevier BV. doi: 10.1016/j.carbon.2017.12.096.

Mostafaei, A., Neelapu, S.H.V.R., Kisailus, C., Nath, L.M., Jacobs, T.D.B., & Chmielus, M. (2018). Characterizing surface finish and fatigue behavior in binder-jet 3D-printed nickel-based superalloy 625. ADDITIVE MANUFACTURING, 24, 200-209.Elsevier BV. doi: 10.1016/j.addma.2018.09.012.

Cho, Y.K.R., Rawlings, C.D., Wolf, H., Spieser, M., Bisig, S., Reidt, S., Sousa, M., Khanal, S.R., Jacobs, T.D.B., & Knoll, A.W. (2017). Sub-10 Nanometer Feature Size in Silicon Using Thermal Scanning Probe Lithography. ACS NANO, 11(12), 11890-11897.American Chemical Society (ACS). doi: 10.1021/acsnano.7b06307.

Haghanifar, S., Gao, T., De Vecchis, R.T.R., Pafchek, B., Jacobs, T.D.B., & Leu, P.W. (2017). Ultrahigh-transparency, ultrahigh-haze nanograss glass with fluid-induced switchable haze. OPTICA, 4(12), 1522-1525.The Optical Society. doi: 10.1364/OPTICA.4.001522.

Jacobs, T.D.B., & Martini, A. (2017). Measuring and Understanding Contact Area at the Nanoscale: A Review. APPLIED MECHANICS REVIEWS, 69(6).ASME International. doi: 10.1115/1.4038130.

Jacobs, T.D.B., & Martini, A. (2017). Closure to "Discussion of 'Measuring and Understanding Contact Area at the Nanoscale: A Review'" (Jacobs, T. D. B., and Ashlie Martini, A., 2017, ASME Appl. Mech. Rev., 69(6), p. 060802). APPLIED MECHANICS REVIEWS, 69(6).ASME International. doi: 10.1115/1.4038230.

Jacobs, T.D.B., Junge, T., & Pastewka, L. (2017). Quantitative characterization of surface topography using spectral analysis. SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES, 5(1), 013001.IOP Publishing. doi: 10.1088/2051-672X/aa51f8.

Liu, J., Jiang, Y., Grierson, D.S., Sridharan, K., Shao, Y., Jacobs, T.D.B., Falk, M.L., Carpick, R.W., & Turner, K.T. (2017). Tribochemical Wear of Diamond-Like Carbon-Coated Atomic Force Microscope Tips. ACS APPLIED MATERIALS & INTERFACES, 9(40), 35341-35348.American Chemical Society (ACS). doi: 10.1021/acsami.7b08026.

Shao, Y., Jacobs, T.D.B., Jiang, Y., Turner, K.T., Carpick, R.W., & Falk, M.L. (2017). Multibond Model of Single-Asperity Tribochemical Wear at the Nanoscale. ACS APPLIED MATERIALS & INTERFACES, 9(40), 35333-35340.American Chemical Society (ACS). doi: 10.1021/acsami.7b08023.

Jacobs, T.D.B., Wabiszewski, G.E., Goodman, A.J., & Carpick, R.W. (2016). Characterizing nanoscale scanning probes using electron microscopy: A novel fixture and a practical guide. REVIEW OF SCIENTIFIC INSTRUMENTS, 87(1), 013703.AIP Publishing. doi: 10.1063/1.4937810.

Lefever, J.A., Jacobs, T.D.B., Tam, Q., Hor, J.L., Huang, Y.R., Lee, D., & Carpick, R.W. (2016). Heterogeneity in the Small-Scale Deformation Behavior of Disordered Nanoparticle Packings. NANO LETTERS, 16(4), 2455-2462.American Chemical Society (ACS). doi: 10.1021/acs.nanolett.5b05319.

Jacobs, T.D.B., Lefever, J.A., & Carpick, R.W. (2015). A Technique for the Experimental Determination of the Length and Strength of Adhesive Interactions Between Effectively Rigid Materials. TRIBOLOGY LETTERS, 59(1).Springer Science and Business Media LLC. doi: 10.1007/s11249-015-0539-9.

Jacobs, T.D.B., Lefever, J.A., & Carpick, R.W. (2015). Measurement of the Length and Strength of Adhesive Interactions in a Nanoscale Silicon-Diamond Interface. ADVANCED MATERIALS INTERFACES, 2(9).Wiley. doi: 10.1002/admi.201400547.

Zeng, H., Konicek, A.R., Moldovan, N., Mangolini, F., Jacobs, T., Wylie, I., Arumugam, P.U., Siddiqui, S., Carpick, R.W., & Carlisle, J.A. (2015). Boron-doped ultrananocrystalline diamond synthesized with an H-rich/Ar-lean gas system. CARBON, 84(1), 103-117.Elsevier BV. doi: 10.1016/j.carbon.2014.11.057.

Ryan, K.E., Keating, P.L., Jacobs, T.D.B., Grierson, D.S., Turner, K.T., Carpick, R.W., & Harrison, J.A. (2014). Simulated Adhesion between Realistic Hydrocarbon Materials: Effects of Composition, Roughness, and Contact Point. LANGMUIR, 30(8), 2028-2037.American Chemical Society (ACS). doi: 10.1021/la404342d.

Jacobs, T.D.B., & Carpick, R.W. (2013). Nanoscale wear as a stress-assisted chemical reaction. NATURE NANOTECHNOLOGY, 8(2), 108-112.Springer Science and Business Media LLC. doi: 10.1038/NNANO.2012.255.

Jacobs, T.D.B., Mathew Mate, C., Turner, K.T., & Carpick, R.W. (2013). Understanding the Tip–Sample Contact. In Scanning probe microscopy for industrial applications: nanomechanical characterization. (pp. 15-48).Wiley. doi: 10.1002/9781118723111.ch2.

Jacobs, T.D.B., Ryan, K.E., Keating, P.L., Grierson, D.S., Lefever, J.A., Turner, K.T., Harrison, J.A., & Carpick, R.W. (2013). The Effect of Atomic-Scale Roughness on the Adhesion of Nanoscale Asperities: A Combined Simulation and Experimental Investigation. TRIBOLOGY LETTERS, 50(1), 81-93.Springer Science and Business Media LLC. doi: 10.1007/s11249-012-0097-3.

Kim, H.J., Moldovan, N., Felts, J.R., Somnath, S., Dai, Z., Jacobs, T.D.B., Carpick, R.W., Carlisle, J.A., & King, W.P. (2012). Ultrananocrystalline diamond tip integrated onto a heated atomic force microscope cantilever. NANOTECHNOLOGY, 23(49), 495302.IOP Publishing. doi: 10.1088/0957-4484/23/49/495302.

Lantz, M.A., Gotsmann, B., Jaroenapibal, P., Jacobs, T.D.B., O'Connor, S.D., Sridharan, K., & Carpick, R.W. (2012). Wear-Resistant Nanoscale Silicon Carbide Tips for Scanning Probe Applications. ADVANCED FUNCTIONAL MATERIALS, 22(8), 1639-1645.Wiley. doi: 10.1002/adfm.201102383.

Moldovan, N., Dai, Z., Zeng, H., Carlisle, J.A., Jacobs, T.D.B., Vahdat, V., Grierson, D.S., Liu, J., Turner, K.T., & Carpick, R.W. (2012). Advances in Manufacturing of Molded Tips for Scanning Probe Microscopy. JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, 21(2), 431-442.Institute of Electrical and Electronics Engineers (IEEE). doi: 10.1109/JMEMS.2011.2174430.

Fletcher, P.C., Felts, J.R., Dai, Z., Jacobs, T.D., Zeng, H., Lee, W., Sheehan, P.E., Carlisle, J.A., Carpick, R.W., & King, W.P. (2010). Wear-Resistant Diamond Nanoprobe Tips with Integrated Silicon Heater for Tip-Based Nanomanufacturing. ACS NANO, 4(6), 3338-3344.American Chemical Society (ACS). doi: 10.1021/nn100203d.

Jacobs, T.D.B., Gotsmann, B., Lantz, M.A., & Carpick, R.W. (2010). On the Application of Transition State Theory to Atomic-Scale Wear. TRIBOLOGY LETTERS, 39(3), 257-271.Springer Science and Business Media LLC. doi: 10.1007/s11249-010-9635-z.

Kane, W.M., Krupp, U., Jacobs, T., & McMahon, C.J. (2005). On the mechanism of quench cracking in Rene 95 nickel-based superalloy. MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 402(1-2), 42-46.Elsevier BV. doi: 10.1016/j.msea.2005.05.032.

Flater, E.E., Barnes, J.D., Graff, J.A.H., Weaver, J.M., Ansari, N., Poda, A.R., Ashurst, W.R., Khanal, S.R., & Jacobs, T.D.B. (2018). A simple atomic force microscope-based method for quantifying wear of sliding probes. In REVIEW OF SCIENTIFIC INSTRUMENTS, 89(11), (p. 113708).AIP Publishing.United States. doi: 10.1063/1.5048584.

Gujrati, A., Khanal, S.R., & Jacobs, T.D.B. (2017). A method for quantitative real-time evaluation of measurement reliability when using atomic force microscopy-based metrology. In 2017 IEEE 17th International Conference on Nanotechnology (IEEE-NANO), (pp. 135-138).IEEE. doi: 10.1109/nano.2017.8117292.

Vishnubhotla, S.B., Khanal, S.R., Li, J., Stach, E.A., & Jacobs, T.D.B. (2017). Investigating load-dependent conduction through platinum nanocontacts using in situ electromechanical testing inside a transmission electron microscope. In 2017 IEEE 17th International Conference on Nanotechnology (IEEE-NANO), (pp. 130-134).IEEE. doi: 10.1109/nano.2017.8117291.

Carpick, R.W., & Jacobs, T.D.B. (2014). Nanoscale Wear as a Stress-Assisted Chemical Reaction: An in-situ TEM Study. In Microscopy and Microanalysis, 20(S3), (pp. 1542-1543).Oxford University Press (OUP). doi: 10.1017/s1431927614009441.

Kim, H.J., Moldovan, N., Felts, J.R., Somnath, S., Dai, Z., Jacobs, T.D.B., Carpick, R.W., Carlisle, J.A., & King, W.P. (2013). Heated atomic force microscope cantilevers with wear-resistant ultrananocrystalline diamond tips. In 2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS), (pp. 245-248).IEEE. doi: 10.1109/memsys.2013.6474223.

Carpick, R.W., Jacobs, T., Liu, X.Z., & Li, Q. (2011). Geometrical effects in contact mechanics: From atomic membranes to evolving asperities. In Proc. 8th Int. Conf. on Flow Dynamics.Sendai, Japan.

Krupp, U., Wagenhuber, P., Kane, W.M., Jacobs, T., & McMahon, C.J. (2005). Environmentally assisted britlle fracture of nickel-base superalloys at high temperatures. In 11th International Conference on Fracture 2005, ICF11, 3, (pp. 1623-1628).