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Luo Group's Research

Research Summary

Research Summary

 Selected Highlights:

A series of discrete grain boundary (GB) 2-D interfacial phases (also designated as “complexion”) has been identified in doped alumina [Dillon and Harmer, Acta Mater. 2007] and subsequently other materials. They can be utilized to control sintering, microstructures, and materials properties, offering a revolutionary method for achieving predictive fabrication of materials by design. This figure is adapted from a prior report in Science 333: 1730 (2011).

There are more details (e.g., in the bilayers in Ni-Bi)... 

Ni Bi

Science 358: 97 (2017)    UCSD News Release


Development of Interfacial "Phase" (Complexion) Diagrams

Grain Boundary Diagrams

A Few Examples:

PRL 2018

Physical Review Letters 120, 085702 (2018)

PRL 2018

Physical Review Letters 120: 085702 (2018)


Acta Materialia 130: 329 (2017)  

Ni Bi

Scripta Materialia 130: 165 (2017)

In general, we purpose to develop grain boundary "phase" (complexion) diagrams as general materials science tool and (perhaps) a useful component for the "Materials Genome" Initiative.  Please find some of our earlier studies below.  Please also see a "cover article" in the August 2012 issue of the Journal of the American Ceramic Society [95: 2358 (2012)] that reviews some of our recent studies and a related news article in Ceramic Tech Today written by Eileen De Guire.

(a) A computed GB λ-diagram for Ni-doped Mo has been validated by a systematic comparison with (b) measured GB diffusivities. This figure is adapted from an “Editors’ Suggestion” in Phys. Rev. B [84: 014105 (2011)]. (According to the PRB: “As a service to both our readers and authors, we list a small number of papers published in Physical Review B that the editors and referees find of particular interest, importance, or clarity.”)

A counterintuitive phenomenon of decreasing GB diffusivity with increasing temperature predicted by (a) a computed λ-diagram was (b) corroborated experimentally. This phenomenon stems from the retrograde solidus line of the Mo-Ni system. Specifically, for a single-phase alloy of Mo + 0.5% Ni, increasing the temperature from 1200 C to 1500 C results in an increasing distance to the solidus line and a greater free-energy penalty for forming liquid-like GBs; thus, the general GBs become “drier” with decreasing diffusivities. Figure adapted from Phys. Rev. Lett. 105: 236102 (2010)

Batteries, Solid Electrolytes and Supercapacitors


ACS Applied Materials & Interfaces 9: 36745 (2017)

NSF Batteries

Physical Chemistry Chemical Physics 16: 7786 (2014) 

NSF Battery Surface

Journal of Power Sources 245: 594 (2014) 

2D Surface Phase for Energy

Nature Communications 6, 8354 (2015)

ACS Applied Materials & Interfaces 8: 12871 (2016)

High-Entropy Ceramics

High Entropy Borides

Scientific Reports 6: 37946 (2016)

High-Entropy Functional Oxides

Scripta Materialia 142: 116-120 (2018)

High-Temperature Nanoalloys

High Temperature Nanoalloys

Scripta Materialia 124: 160 (2016)

Flash Sintering 

Flash Sintering Overview

Viewpoint: Scripta Materialia, 146: 260 (2018)

Water-Assisted Flash Sintering (WAFS)

Water Assisted Flash Sintering

Scripta Materialia, 142: 79 (2018); Also see ACerS News

Two-Step Flash Sintering (TSFS)

Two-Step Flash Sintering

Scripta Materialia, 141: 6 (2017)

Flash Sintering

Selected Other Research

Triple Line Instability 

Scripta Materialia 88: 45 (2014)


Additional Collabration 

Science 346: 1352 (2014)   ●  UCSD News Release