High Interfacial Energy Research Articles

In-situ construction of Li-Ag/LiF composite layer for long cycled all-solid-state Li metal battery

All-solid-state lithium batteries employing sulfide solid electrolyte are promising candidates for next generation lithium batteries. Nevertheless, the unstable interface of sulfide solid electrolyte and Li metal has limited the lifespan of sulfide solid state lithium metal batteries. Herein, a composite protection layer composed of Li-Ag/LiF (LAF) is formed on Li metal surface by the in-situ reaction of silver-fluoride (AgF) and Li metal to solve the instability issue of the Li6PS5Cl/Lithium interface. The Li-Ag particles act as nucleation sites for Li deposition and LiF can avoid the growth of lithium dendrites. The density function theory (DFT) calculation results show the lithiophilic of Li-Ag alloys and high interfacial energy of LiF/Li6PS5Cl interface, proving the superiority of the LAF protection layer. The critical current density of the Li-LAF/ Li6PS5Cl/ LAF-Li symmetric battery is 1.6 mA cm−2 and the battery achieved a long lifespan of over 3000 h at 0.1 mA cm−2 and 0.1mAh cm−2 at room temperature. In addition, a high discharge capacity of 139.1mAh/g is obtained in the LiNbO3@LiCoO2/ Li6PS5Cl/ LAF-Li full cell. This work provides a feasible strategy for the interface modification of sulfide all-solid-state Li metal batteries.

The size effect of precipitates on microstructure evolution during high-temperature deformation

Cr-Ni-Mo steel, as a hot-work die steel, has become increasingly demanding of service temperature and strength. This study investigated the effect of precipitates on the deformation behavior of tempered martensite at 700 °C. Tempering specimens with different dislocation densities leads to different behavior due to the size and volume fraction of precipitates. This decreases dynamic recrystallization and interfacial mobility, resulting in higher interfacial energy. Meanwhile, the precipitates boost strength and thermal stability of the tempered martensite.

A mechanism for thickness-controllable single crystalline 2D materials growth

Recent efforts in growing two-dimensional (2D) multilayers have enabled the synthesis of single crystalline 2D multilayers in a wafer scale through the seamless stitching of multiple epitaxial 2D islands. Unlike previously observed wedding-cake or inverted-wedding-cake structures, these multilayer islands have the same size and shape in each layer with aligned edges. In this study, we investigated the underlying growth mechanisms of synchronic 2D multilayers growth and have showed that a heterogenous layer on a crystalline substrate is critical for maintaining the synchronic growth of 2D multilayers. During growth, the heterogenous layer passivates the edges of multilayer 2D island and thus prevents the coalescence of these active edges, while the high interfacial energy between the heterogenous surface layer and the substrate stabilizes the synchronic structure. Based on this model, we have successfully explained the previously observed synchronic growth of graphene and hexagonal boron nitride multilayers (Nat Nanotech 2020, 15: 861; Nature 2022, 606: 88). The deep understanding on the mechanism paves a way towards the synthesis of wafer-scale single-crystal 2D multilayers with a uniform thickness.

Dual N-modification enables high-performance Solid-State Li metal batteries with Li5.5PS4.5Cl1.5

All-solid-state lithium batteries (ASSLIBs) have received a lot of attention due to their excellent safety and high energy density, making them a potential alternative to traditional liquid lithium-ion batteries. However, the growth of lithium dendrites within sulfide solid electrolytes is a major challenge in realizing its full potential. Here, a new strategy of modifying the bare Li metal anode surface with a layer of Li3N and introducing N-dopants into the Li5.5PS4.5Cl1.5 electrolyte structure is designed. Such dual N-modification prevents the growth of lithium dendrite, particularly at high current densities during the lithium plating/stripping processes. The dense Li3N interfacial layer induces uniform deposition of lithium ions and optimizes their transport across the interface. When Li dendrites penetrate the interlayer, they are consumed by the N-modified Li5.7PS4.3N0.2Cl1.5 electrolyte, further forming high interfacial energy Li3N to prevent further growth of lithium dendrites. The effectiveness of this strategy has been demonstrated in both lithium symmetric batteries and all-solid-state lithium metal batteries (ASSLMBs). Symmetrical batteries exhibit a stable cycle duration of 400 h at different current densities (0.2 ∼ 1.0 mA cm−2). The corresponding battery consisting of the bare NCM622 cathode, Li5.7PS4.3N0.2Cl1.5 electrolyte, and Li3N-coated Li metal anode delivers a high initial discharge capacity of 183.1 mAh/g at 0.1C and maintains a discharge capacity of 163.4 mAh/g after 50 cycles. The dual N-modification strategy on both bare lithium metal anode and solid electrolytes can significantly enhance the lithium metal compatibility, providing the possibility to construct ASSLMB with superior electrochemical performances.

Interface deciphering for highly interfacial adhesion and efficient heat energy transfer

Interfacial adhesion and interfacial thermal resistance (ITR) are two critical factors in the interfacial force and energy transfer, but it is difficult to simultaneously achieve the desirable interfacial adhesion and ITR. Here, we overcome this challenge by fabricating an elastomer composite consisting of polydimethylsiloxane (PDMS) and micro-scale spherical aluminum (Al) fillers, which offers the high adhesion strength (1.28 MPa), high interfacial adhesion energy (528.4 J/m2), and low ITR (0.028 mm2·K/W) between the PDMS/Al elastomer composite and substrates. We further propose a quantified physical model to establish the relationship between interfacial adhesion and ITR for low phonon mismatch interfaces. This work will contribute to the development of interface science and guide the regulation of force and energy transfer at interface for wide range applications, such as electronic packaging, thermal storage, sensors, and medicine.

An optimizing hybrid interface architecture for unleashing the potential of sulfide-based all-solid-state battery

Sulfide-based all-solid-state lithium metal batteries are received tremendous focus due to the potential to deliver high energy density. Nevertheless, extremely unstable lithium/sulfide interface reaction and growth of unfavorable Li dendrites upon cycling remain challenging aspects and not yet fully settled. In this work, a lithophilic and high interfacial-energy hybrid interphase rich in chloride and Li-Ga alloy was in-situ constructed at Li/Li7P3S11 interface to tackle the vexing issue. Benefiting from the high interfacial energy and electronic insulation of LiCl in the hybrid interphase, lithium dendrites were effectively inhibited. In addition, the Li-Ga alloy-rich layer possesses excellent lithiophilicity and low diffusion energy, which can provide a uniform electric field distribution and induce rapid conduction of Li-ions. Consequently, the densification of Li/Li7P3S11 interface is achieved, which contributes to the decrease of interfacial impedance, uniform Li-ion flux and inhibition of continuous side reactions. Exalting, the Li symmetric cells with the Li-Ga alloy/LiCl (LGC) interlayer display high critical current density of 1.5 mA cm−2 and steady cycle for 1000 h at 0.3 mA cm−2 (0.3 mAh cm−2) at room temperature. Furthermore, the modified all-solid-state lithium battery also demonstrates an ultra-stable cycling. This work provides a reasonable design approach for the selection of interface layers in the all-solid-state lithium metal batteries (ASSLMBs) based on theoretical calculations, with the objective of attaining a stable Li/sulfide solid electrolyte interface.

Strategy for suppressing abnormal grain growth of ZK60 Mg alloy during solution by pre-compression: A quasi-in-situ study

Abnormal grain growth (AGG) easily takes place in Mg alloys during high-temperature solutions, resulting in deterioration of mechanical properties. Hence, the compression prior to solution (pre-compression) was conducted to suppress AGG, and the microstructure evolution as well as suppressing mechanisms was investigated based on quasi-in-situ analysis. After compression along the transverse direction, <11–20>//ED grains preferentially nucleated and rapidly grew up, and the initial <10–10>//ED texture was weakened. Two grain growth modes of heat-induced and strain-induced grain boundary migrations were found. The former was attributed to the high interfacial energy of grain boundaries with large curvature. The latter consumed the adjacent grains with high storage energy, forming abnormal grains with irregular shapes. The compression with a reduction > 6% could obviously suppress AGG. The suppressing effects were mainly attributed to weakening the size advantage of <11–20>//ED grains, increasing nucleation, reducing grain boundary character distribution, and redistributing storage energy distribution. After 12% compression along the transverse direction, 30° misorientation of <11–20>//ED grains and high energy grain boundaries were reduced. The {10–12} tensile twins and {10–15} high index twins induced by compression increased the nucleation of static recrystallization. Beside, compression introduces high-density dislocations, which also contributed to suppressing AGG behavior during solution.

A phase-field investigation of factors affecting the morphology of uranium dendrites during electrodeposition

The growth of uranium dendrites has been one of the critical issues in the electrorefining of spent nuclear fuel for several decades. However, a comprehensive description of uranium dendrites, including the contribution of electrodeposition and the interface property, remains unavailable. In this paper, the phase-field method is applied to assess the effects of applied voltage, exchange current density, interfacial energy, interfacial anisotropy, interfacial noise, initial electrodeposit size, and initial electrodeposit density on the uranium dendrites. Furthermore, an approach for precisely estimating the phase-field parameters is developed to capture more details of dendrites, such as interfacial mobility, reaction constant, barrier height, and gradient energy coefficient. The results reveal that high applied voltage, high exchange current density and low interfacial energy stimulate the growth of dendrites with complex structures. The dendrites are dominated by the tip-controlled mechanism regardless of the applied voltage, exchange current density and interfacial energy, but for high interfacial energy, the growth of some side branches follows the thermodynamic suppression mechanism. Strong interfacial noise can enhance the anisotropy of the system, making it difficult to distinguish the principal branches from the side ones, which are intertwined with each other. Moreover, a parameter map is drawn to quantitatively predict the uranium dendrite patterns, which vary as a function of the densities and sizes of the initial electrodeposits. The cause of tip splitting is analyzed as either insufficient interfacial anisotropy or a large initial electrodeposit size. The numerical results are in good agreement with the experimental data and the current theory. Overall, this work provides a theoretical basis for controlling the morphology of uranium dendrites.

An artificial dead-layer to protect the ferroelectric thin films from electron injection

For ferroelectric (FE) thin films, working in the harsh environment of a high electric field (E) or high temperature (T) remains a great challenge. As a post-treatment approach, dead-layer engineering exhibits a certain generality and could improve the dielectric strength (Eb) via depositing a specially designed artificial “dead-layer” on most of the as-prepared FE thin films. However, physical essence of the artificial dead-layer needs further analysis. Great challenges are the abundant and complicated conduction mechanisms in the FE-based thin films and the lack of adequate research on modulating these conduction mechanisms by this artificial dead-layer. As a vital part of the conduction mechanisms, electron injection can be easily triggered under E and thermal excitation that almost appeared in all FE-based thin films. Here, the ultrathin artificial dead-layer of Ca0.2Zr0.8O1.8 (CSZ) was used to restrain multiple electron injection in low-Eb LaNiO3/Ba0.58Sr0.42TiO3 (LNO/BST) FE thin films, including thermal emission and tunneling effect, under a high E and T, even under an opposite E. It was found that the suppressing effect on the multiple electron-injection mechanisms via the artificial dead-layer mainly comes from its wall-like energy-barrier structure, which is composed of two opposite and high interface energy barriers (BST/CSZ: 2.95 eV, CSZ/Au: 3.92 eV) and a wide depletion layer. The generality of protecting the ferroelectric thin films from electron injection via the artificial dead-layer was discussed.

In situ formed interfacial layer for all-solid-state lithium batteries with sulfide electrolyte films

Sulfide solid-state electrolytes (SEs) are considered as a promising alternative to traditional liquid electrolytes, owing to their low interfacial resistance and high ionic conductivity. Nevertheless, Li dendritic growth in SEs have greatly restricted the development of the high energy of All-solid-state lithium batteries (ASSLBs). In this study, a protective layer is synthesized at the Li metal surface via a solvent-free brushing method with the chemical reaction between Li metal and P2S5 particles. The P2S5@Li layer have satisfactory high interfacial energy, which is verified by density functional theory calculation. The P2S5@Li/LPSCl films/P2S5@Li symmetrical cells can cycle for >500 h at 0.1 mA cm−2. Notably, the P2S5@Li/LPSCl films/LiNbO3@LiNi0.8Co0.1Mn0.1O2 cells can deliver a discharge capacity of 155.7 mA h g−1 and excellent capacity retention of 75.5% over 400 cycles at 0.5C. This study has developed an innovative approach to ameliorate the interface of Li metal anode and practical application of ASSLBs.

Corrosion behavior of functionally graded cemented carbides with CoNiCrFe binder

The corrosion behavior of functionally graded cemented carbide (FGCC), with CoNiCrFe binder (WC-CoNiCrFe), has been investigated by performing electrochemical measurements and chemical characterization. The results showed that the CoNiCrFe binder was selectively dissolved in alkaline and acidic solutions. In the NaOH solution, the high contents of Ni and Co generated a passive film consisting of Co(OH)2, Ni(OH)2, Co3O4, and NiO that effectively isolated the corrosive medium from the materials. However, the contents of Fe and Cr were too low to provide satisfactory protection. In the HCl solution, the Cr element generated Cr0, Cr2O3, and Cr(OH)3. However, the Cr content was too low to form a passive film. In addition, Co, Ni and Fe in the binder were selectively dissolved in the acidic solution. Moreover, compared with the FGCC, the non-graded cemented carbide (CC) had a higher binder content and a more dispersed WC distribution. Thus, it formed a denser and thicker passive film, which was beneficial for the corrosion resistance in the NaOH solution. However, the CoNiCrFe binder was severely corroded in the HCl solution, which was due to the absence of a passive film. In comparison, the FGCC with a lower binder content and a denser WC distribution, showed a higher corrosion resistance. On the other hand, the WC grain size showed the opposite effect in alkaline and acidic solutions. In the NaOH solution, a small WC grain size increased the number of WC/CoNiCrFe interfaces, which favored the formation of a dense passive film. It, thereby reduced the probability for pitting corrosion. In the HCl solution, the corrosion generally started from grain boundaries with high interface energy as no passive film existed. Thus, a large WC grain size facilitated the improvement of the corrosion resistance. The results from the present study do not only provide a theoretical guidance for an understanding of the anticorrosion mechanism of WC-CoNiCrFe, but also a new approach for the preparation of cemented carbides with high corrosion resistance.

Patterned dense Janus membranes with simultaneously robust fouling, wetting and scaling resistance for membrane distillation

Membrane fouling, wetting and scaling are three prominent challenges that severely hinder the practical applications of membrane distillation (MD). Herein, polyamide/polyvinylidene fluoride (PA/PVDF) Janus membrane comprising a hydrophobic PVDF substrate and a patterned dense PA layer by reverse interfacial polymerization (R-IP) was developed. Direct contact MD experiments demonstrated that PA/PVDF Janus membrane could exhibit simultaneously superior resistance towards surfactant-induced wetting, oil-induced fouling and gypsum-induced scaling without compromising flux. Importantly, the size-sieving effect, rather than the breakthrough pressure of the membrane, was revealed as the critical factor that probably endowed its resistance to wetting. Furthermore, a unique possible anti-scaling mechanism was unveiled. The superhydrophilic patterned dense PA layer with strong salt rejection capability not only prevented scale-precursor ions from intruding the substrate but also resulted in the high surface interfacial energy that inhibited the adhesion and growth of gypsum on the membrane surface, while its relatively low surface -COOH density benefited from R-IP process further ensured the membrane with a low scaling propensity. This study shall provide new insights and novel strategies in designing high-performance MD membranes and enable robust applications of MD facing the challenges of membrane fouling, wetting and scaling.

Damage tolerance of low angle grain boundary in a fourth generation Nickel-based single crystal superalloy at 1100 °C service conditions

The effect of different low angle grain boundaries (LAGBs) on the microstructure and mechanical properties in a fourth generation Nickel-based single crystal superalloy was studied. Double seed crystals techniques were used to obtain the specimens with LAGBs. The results showed that there were coarse γ′ phases at LAGBs with the grain boundary angle increasing, the shape of which changed from block to long strip at as-cast and the size of which increased gradually after heat treatment. After thermal exposure at 1100 °C for 100 h, the microstructure stability deteriorated when the angle exceeded 12.6°, where the discontinuous precipitation (DP) colonies region occurred along the grain boundary because of high interfacial energy and mobility at LAGBs. With the grain boundary angle increasing, the ultimate tensile strength of the sample rose slightly and then fell, while the elongation and creep rupture life decreased significantly exceeded 4.9°. Under 1100 °C service condition, the carbides and topological close-packed (TCP) phases were precipitated at LAGBs, which seriously impaired the grain boundary bonding strength. On the other hand, the misorientation at LAGBs led to the stress concentration, which increased the difficulty of grain boundary coordinated deformation. Finally, the damage tolerance of the LAGBs in this fourth generation Nickel-based single crystal superalloy was approximately estimated as about 7° at 1100 °C/150 MPa creep rupture condition based on a 70% creep rupture life standard.

Origin of dendrite-free lithium deposition in concentrated electrolytes

The electrolyte solvation structure and the solid-electrolyte interphase (SEI) formation are critical to dictate the morphology of lithium deposition in organic electrolytes. However, the link between the electrolyte solvation structure and SEI composition and its implications on lithium morphology evolution are poorly understood. Herein, we use a single-salt and single-solvent model electrolyte system to systematically study the correlation between the electrolyte solvation structure, SEI formation process and lithium deposition morphology. The mechanism of lithium deposition is thoroughly investigated using cryo-electron microscopy characterizations and computational simulations. It is observed that, in the high concentration electrolytes, concentrated Li+ and anion-dominated solvation structure initiate the uniform Li nucleation kinetically and favor the decomposition of anions rather than solvents, resulting in inorganic-rich amorphous SEI with high interface energy, which thermodynamically facilitates the formation of granular Li. On the contrary, solvent-dominated solvation structure in the low concentration electrolytes tends to exacerbate the solvolysis process, forming organic-rich mosaic SEI with low interface energy, which leads to aggregated whisker-like nucleation and growth. These results are helpful to tackle the long-standing question on the origin of lithium dendrite formation and guide the rational design of high-performance electrolytes for advanced lithium metal batteries.

Discrepancy in low cycle fatigue and creep-fatigue life of 720Li alloy tested at 720 °C: Role of crystallographic texture evolution

Low cycle fatigue (LCF) and creep-fatigue (CF) interaction behavior of 720Li alloy were studied for the first time at 720 °C with different values of total strain amplitudes (Δεt/2) and hold time (HT). At Δεt/2 = 0.6%, CF life is less than LCF life. However, at Δεt/2 = 0.44, 0.48 and 0.55% CF life increased with increase in HT. Texture analysis of specimen tested at Δεt/2 = 0.44%, revealed that initial loading direction ǁ [11¯1] found to be rotated: (i) [21¯1] in LCF condition; and (ii) [11¯0] and [01¯1] in the CF condition predominantly. Notably, texture components developed in the CF specimens tested at Δεt/2 = 0.6% is quite similar to that in the LCF specimen tested at Δεt/2 = 0.44%. Development of [21¯1] texture component is due to multi planner slip (i.e. octahedral and cubic plane slip) under the influence of compressive load which is also confirmed by viscoplastic-simulation. Evolution of [21¯1] texture component leads to greater extent of inter crystalline cracks due to latent strain hardening and strain incompatibility between adjacent grains. Further, high static interfacial energy of annealing twin boundaries, confirmed through five-parameter stereological analyses, in LCF specimen tested at Δεt/2 = 0.44% and CF specimen tested at Δεt/2 = 0.6% resulted annealing twin boundary cracking. In contrast, evolution of low modulus texture components (i.e. [11¯0] & [01¯1]) has been inferred to be responsible for higher cyclic life in CF specimen tested at Δεt/2 = 0.44% and LCF specimen tested at Δεt/2 = 0.6%.

A Floating Integrated Solar Micro‐Evaporator for Self‐Cleaning Desalination and Organic Degradation

AbstractSafe and clean freshwater harvesting from (organic‐containing) saline or wastewater holds great potential for mitigating water scarcity and pollution, but remains challenging. Herein, a floating photothermal/catalytic‐integrated interfacial micro‐evaporator (g‐C3N4@PANI/PS) is reported as a proof‐of‐concept multifunctional scavenger evaporator system (MSES) to achieve both solar‐driven complete desalination and organic degradation. The spherical porous lightweight polystyrene core, incorporated with a black surface functional layer (g‐C3N4@PANI), enables the hybrid micro‐evaporator to naturally float and thereby collectively self‐assemble under surface tension for interfacial evaporation, which achieves preeminent self‐cleaning for complete salt/solute separation and efficient organic photodegradation under rotation. Remarkably, the floating micro‐evaporator achieves a high solar‐vapor conversion efficiency of ≈90% with high interfacial energy localization and provides abundant active photocatalytic sites on the interface, which is further enhanced by interfacial photothermal cooperation. High photo‐driven degradation efficiencies of 99% for nonvolatile organic compounds (non‐VOC) bisphenol A and 95% for VOC phenol in wastewater are achieved. An outdoor comprehensive solar water treatment test toward organic‐containing high‐salinity sewage verifies the feasibility of MSES for sustainable freshwater harvesting (1.3 kg m−2 h−1), downstream salt recovery, and organic degradation. This strategy may inspire an integrated solution of water scarcity, clean energy, and environmental pollution toward carbon neutrality.

Thermophysical parameters governing the glass formation and crystallization of CuZr

Cu-Zr is one of the best binary metallic glass formers. Here, new data on the enthalpy and specific heat difference between undercooled melt and crystal phases are provided for the equiatomic composition CuZr. Together with a comprehensive collection of literature data on the heat of crystallization and fusion, on the viscosity and crystal growth rate, the parameters needed for the application of the Classical Nucleation Theory are assessed. The TTT and CCT curves for crystallization are computed allowing the determination of the crystal-liquid interfacial energy by fitting the critical cooling rate for bulk glass formation.The glass forming tendency of CuZr is discussed pointing to the role of the high interfacial energy and the sluggish interdiffusion in the undercooled melt.

Enhanced Tensile Properties, Biostability, and Biocompatibility of Siloxane-Cross-Linked Polyurethane Containing Ordered Hard Segments for Durable Implant Application.

This work developed a series of siloxane-modified polyurethane (PU-Si) containing ordered hard segments by a facile method. The polyaddition between poly(ε-caprolactone) and excess diurethane diisocyanate was carried out to synthesize a polyurethane prepolymer with terminal isocyanate groups, which was then end-capped by 3-aminopropyl triethoxysilane to produce alkoxysilane-terminated polyurethane; the target products of PU-Si were obtained with hydrolysis and the condensation of alkoxysilane groups. The chemical structures were confirmed by FT-IR and XPS, and the effect of the siloxane content or cross-linked degree on the physicochemical properties of the PU-Si films was investigated in detail. The formation of the network structure linked by Si-O-Si bonds and interchain denser hydrogen bonds endowed PU-Si films with fine phase compatibility, low crystallinity, high thermal stability, and excellent tensile properties. Due to the high cross-linked degree and low interfacial energy, the films displayed a high surface water contact angle and low equilibrium water absorption, which resulted in slow hydrolytic degradation rates. Furthermore, the evaluation of protein adsorption and platelet adhesion on the PU-Si film surface presented high resistance to biofouling, indicating superior surface biocompatibility. Consequently, the siloxane-cross-linked polyurethane, which possessed excellent tensile properties, high biostability, and superior biocompatibility, showed great potential to be explored as biomaterials for durable implants.

The effect of defects for the ion transport of Li3ScCl6 and Li3InCl6 with the interface of lithium metal anode: A first-principles study

Li3ScCl6 and Li3InCl6 have good ionic conductivity and a wide stable chemical window, which showing great potential in many inorganic solid-state electrolytes. Due to the disordered occupancy phenomenon of the lattice sites between the framework lithium ions and the transported ions. The concentration nonuniformity of lithium ions causes the blocking of mobile ions in the transition metal lithium halide solid electrolyte. However, vacancy defects can cause changes in the charge balance of nonstoichiometric systems, which reducing blocking effects during ion diffusion. In addition, lithium dendrites still exist at the interface between the inorganic solid electrolyte and the lithium metal anode. It can effectively improve the occurrence of interface side reaction because LiF has high interface energy. The effect of vacancy defects for lithium ion migration parameters of Li3ScCl6 and Li3InCl6 at different temperatures are simulated by the first principle. The results showing that lithium ions had better migration and diffusion ability in the structure containing lithium site defects of Li3InCl6. A dual-halide electrolyte interface model was constructed to suppress the growth of Li dendrites on the surface of a Li metal anode. The Li3ScCl6-LiF heterostructure interface can stably control ion transport on the surface of a lithium metal anode.

Application of time–temperature–transformation and time–pressure–transformation diagrams for cooling- and decompression-induced crystallization to estimate the critical cooling rate required to form glassy obsidian

The formation of glass from silicic magmas during eruption is an enigmatic process. To understand the formation of obsidian, we used time–temperature–transformation (TTT) and time–pressure–transformation (TPT) diagrams to estimate the critical cooling and decompression rates needed to form glassy obsidian. The TTT diagram is a contour map of the crystallized volume fraction as a function of the crystallization temperature and time. A contour line for a given crystal fraction in a time versus temperature diagram has a cone shape, with the “nose” of the curve corresponding to the minimum time and corresponding temperature required to generate a specific crystal fraction. We also present a TPT diagram, based on the TTT diagram, and liquidus curve for decompression-induced crystallization. We applied the TTT diagram to the Tokachi–Ishizawa obsidian from Shirataki, Hokkaido, Japan, and used it to estimate the critical cooling rate that would have been required to form its glassy texture by cooling-induced crystallization during eruption. For decompression-induced crystallization, we used the TPT diagram to estimate the critical decompression rate needed to form glassy obsidian. Based on our calculation results, the critical cooling and decompression rates are highly dependent on the interfacial energy between crystals and melt. We compared the estimated critical cooling and decompression rates with those estimated from microlite number density and a one-dimensional solution of the heat conduction equation. Our calculation results reveal that glassy obsidian can be formed during an eruption, particularly under conditions of high interfacial energy.