Time-resolved Neutron Diffraction Research Articles

Time and space resolved operando synchrotron X-ray and Neutron diffraction study of NMC811/Si–Gr 5 Ah pouch cells

Silicon–Graphite blended electrodes in Li-ion batteries have been proposed as a way to harness the high capacity of Si as an anode material, while minimising the negative effects of their large volume expansion. NMC 811 is the current state-of-the-art layered oxide cathode material, where the cobalt content of the cathode has been minimised. These are the two of the most promising materials for achieving electric vehicle targets in terms of performance, cyclability and price, however their degradation mechanism is not fully understood. Here these two materials have been used to manufacture 5 Ah prototype multi-layer pouch cells, which are aged and then studied using two complimentary diffraction techniques. Neutron diffraction has enabled a quantitative analysis of phase transitions in Si–Gr anodes in a pristine and degraded cell, and the alloying behaviour of Si and Li has been inferred by comparison of identical cells with either graphite or Si–Gr anodes. Synchrotron X-ray Diffraction has been used to make an operando 2D map of the cathode and anode lithiation in the pouch cell, as well as to map the volume expansion across the cell. This approach has revealed that degradation entails significant inhomogeneities across both electrodes, linked to the inhomogeneous volume expansion of the Si–Gr anodes.

Real-time investigation of Lysozyme crystallization kinetics: A neutron diffraction study

The isothermal crystallization kinetics of hen-egg-white Lysozyme has been investigated by means of a time-resolved neutron diffraction experiment for almost 3 days, starting from a supersaturated solution of Lysozyme (30 mg/ml, 3 wt% NaCl, pD 4.75 at 298 K) until the growth of crystals, in order to have complementary information about the crystallization kinetics (Heigl et al., 2018). The temporal evolution of the intensity of the Bragg peaks, observed in the neutron diffraction images when a single crystal appears, has been studied. Simultaneously, the analysis of the small angle neutron scattering curves from the Lysozyme solution, during the crystallization process, has been performed. A correlated behaviour between the decrease of the Lysozyme concentration and the increase of the crystallization fraction was observed. The crystallization kinetics was described by means of the Johnson-Mehl-Avrami-Kolmogorov model and parameters compatible with our previous Lysozyme crystallization study have been found.The Lysozyme crystallization under constant neutron flux underlines the known strength of neutrons in studying biological samples without causing radiation damage.

Time-Resolved Neutron Diffraction During Engineering Processes Using Event Recording System at J-PARC

Time-Resolved Neutron Diffraction During Engineering Processes Using Event Recording System at J-PARC

Intercalates of Bi2Se3 studied in situ by time-resolved powder X-ray diffraction and neutron diffraction.

Intercalation of lithium and ammonia into the layered semiconductor Bi2Se3 proceeds via a hyperextended (by >60%) ammonia-rich intercalate, to eventually produce a layered compound with lithium amide intercalated between the bismuth selenide layers which offers scope for further chemical manipulation.

Structure origin of a transition of classic-to-avalanche nucleation in Zr-Cu-Al bulk metallic glasses

Crystallization kinetics of a series of Zr-Cu-Al bulk metallic glasses with different glass-forming abilities were systematically investigated using differential scanning calorimetry, time-resolved neutron diffraction, and high-resolution transmission electron microscopy. Experimental results revealed a transition of classic-to-avalanche types of nucleation for the Zr-Cu-Al glass alloys upon isothermal annealing. The classic mode is characterized by a continuous nucleation and growth of Zr2Cu-type crystals. The avalanche mode features an abrupt formation of massive Cu10Zr7-type precipitates with a complex, low-symmetry crystalline structure. Calorimetric measurements identified an anomalous exothermic peak prior to crystallization for metallic glasses with the Cu10Zr7-type crystalline phase. The formation of a metastable amorphous/semi-crystalline phase was observed using the electron microscopy prior to crystallization for glasses with an anomalous exothermic event. Our results indicate that the formation of a metastable phase might lower the free energy barrier of the crystallization and trigger an avalanche type of nucleation. Neutron diffraction pair distribution function analysis suggests that the easy connection of short-range clusters at the medium-range length scale would favor the avalanche nucleation.

Heterogeneous nucleation in Zr-Cu-Al-Ag metallic glasses triggered by quenched-in metastable crystals - A time-resolved neutron diffraction study

Crystallization of Zr-Cu-Al-Ag bulk metallic glasses containing quenched-in crystals was studied by time-resolved in-situ neutron diffraction during isothermal annealing in the supercooled liquid region. The quenched-in crystals grew slowly at the beginning, indicating good thermal stability of the Zr-Cu-Al-Ag metallic glass alloys. The neutron diffraction results demonstrated that crystallization in Zr-Cu-Al-Ag metallic glasses was triggered by quenched-in crystals, rather than traditional heterogeneous nucleation mechanisms such as atomic-level impurities, container wall or surface oxides.

Diffusion Model for Gas Replacement in an Isostructural CH4–CO2 Hydrate System

Guest exchange in clathrates is a complex activated phenomenon of the guest–host cage interaction on the molecular-scale level. To model this process, we develop a mathematical description for the nonequilibrium binary permeation of guest molecules during gas replacement based on the microscopic “hole-in-cage-wall” diffusive mechanism. The transport of gas molecules is envisaged as a series of jumps between occupied and empty neighboring cages without any significant lattice restructuring in the bulk. The gas exchange itself is seen as two-stage swapping initiated by almost instantaneous formation of a mixed hydrate layer on the hydrate surface followed by a much slower permeation-controlled process. The model is constrained by and validated with available time-resolved neutron diffraction data of the isostructural CH4 guest replacement by CO2 in methane hydrate, a process of possible importance for the sequestration of CO2 with concomitant recovery of CH4 in marine gas hydrates.

Real-time observation of the isothermal crystallization kinetics in a deeply supercooled liquid

Below the melting temperature Tm, crystals are the stable phase of typical elemental or molecular systems. However, cooling down a liquid below Tm, crystallization is anything but inevitable. The liquid can be supercooled, eventually forming a glass below the glass transition temperature Tg. Despite their long lifetimes and the presence of strong barriers that produces an apparent stability, supercooled liquids and glasses remain intrinsically a metastable state and thermodynamically unstable towards the crystal. Here we investigated the isothermal crystallization kinetics of the prototypical strong glassformer GeO2 in the deep supercooled liquid at 1100 K, about half-way between Tm and Tg. The crystallization process has been observed through time-resolved neutron diffraction for about three days. Data show a continuous reorganization of the amorphous structure towards the alpha-quartz phase with the final material composed by crystalline domains plunged into a low-density, residual amorphous matrix. A quantitative analysis of the diffraction patterns allows determining the time evolution of the relative fractions of crystal and amorphous, that was interpreted through an empirical model for the crystallization kinetics. This approach provides a very good description of the experimental data and identifies a predator-prey-like mechanism between crystal and amorphous, where the density variation acts as a blocking barrier.

From Rate Measurements to Mechanistic Data for Condensed Matter Reactions: A Case Study Using the Crystallization of [Zn(OH2)6][ZnCl4

The kinetics of crystallization of the R = 3 hydrate of zinc chloride, [Zn(OH2)6][ZnCl4], is measured by time-resolved synchrotron x-ray diffraction, time-resolved neutron diffraction, and by differential scanning calorimetry. It is shown that analysis of the rate data using the classic Kolmogorov, Johnson, Mehl, Avrami (KJMA) kinetic model affords radically different rate constants for equivalent reaction conditions. Reintroducing the amount of sample measured by each method into the kinetic model, using our recently developed modified-KJMA model (M-KJMA), it is shown that each of these diverse rate measurement techniques can give the intrinsic, material specific rate constant, the velocity of the phase boundary, vpb. These data are then compared to the velocity of the crystallization front directly measured optically. The time-resolved diffraction methods uniquely monitor the loss of the liquid reactant and formation of the crystalline product demonstrating that the crystallization of this hydrate phase proceeds through no intermediate phases. The temperature dependent vpb data are then well fit to transition zone theory to extract activation parameters. These demonstrate that the rate-limiting component to this crystallization reaction is the ordering of the waters (or protons) of hydration into restricted positions of the crystalline lattice resulting in large negative entropy of activation.

Kinetics of domain redistribution in SrTiO3 under pulsed electric fields

ABSTRACTSrTiO3 is a well-studied perovskite system which undergoes an antiferrodistortive phase transition at 105 K. The low-temperature tetragonal phase exhibits different domains corresponding to the orientation of the symmetry axis. The domain structure can be changed drastically by applying electric fields. Using time-resolved neutron diffraction, the kinetics of the domain redistribution has been investigated on a time scale between microseconds and seconds. It is shown that there are at least two different types of relaxation processes on different time scales which govern the transformation. These can be related to the motion of hard and easy domain walls. Moreover, it is demonstrated that at low temperatures the field induced transition into the ferroelectric phase reveals a significant hysteresis which is reflected by the distribution of tetragonal domains. This finding supports the view of the zero field so-called quantum-paraelectric or coherent-paraelectric phase consisting of polar clusters which are removed only by heating above 40 K.

In-situ study of crystallization kinetics in ternary bulk metallic glass alloys with different glass forming abilities

In-situ transmission electron microcopy and time-resolved neutron diffraction were used to study crystallization kinetics of two ternary bulk metallic glasses during isothermal annealing in the supercooled liquid region. It is found that the crystallization of Zr56Cu36Al8, an average glass former, follows continuous nucleation and growth, while that of Zr46Cu46Al8, a better glass former, is characterized by site-saturated nucleation, followed by slow growth. Possible mechanisms for the observed differences and the relationship to the glass forming ability are discussed.

Kinetics of the Thermally-Induced Structural Rearrangement of γ-MnO2

This work presents a temperature-dependent and time-resolved X-ray and neutron diffraction study of the thermally induced structural rearrangement of γ-MnO2. Here, we study electrochemically prepar...

Magnetic domain growth in geometrically frustrated Ising antiferromagnetsCo1−xMgxNb2O6(x=0 and 0.004)as seen via time-resolved neutron diffraction measurements

We have investigated anomalously slow magnetic domain growth in an antiferromagnetic (AF) phase of isosceles triangular lattice Ising antiferromagnets ${\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Mg}}_{x}{\mathrm{Nb}}_{2}{\mathrm{O}}_{6}$ with $x=0$ and 0.004, by means of time-resolved neutron diffraction measurements. Applying the multi-profile-deconvolution analysis to the observed diffraction profiles, we have revealed that time evolutions of spin correlation lengths along the $a$ and $b$ axes, ${\ensuremath{\xi}}_{a}$ and ${\ensuremath{\xi}}_{b}$, are well described by a power-law scaling form of ${\ensuremath{\xi}}_{0\ensuremath{\alpha}}+{L}_{\ensuremath{\alpha}}{(t/{\ensuremath{\tau}}_{\ensuremath{\alpha}})}^{n}$ $(\ensuremath{\alpha}=a,b)$ with a universal growth exponent of $n=0.2$. The characteristic time scale of the domain growth, ${\ensuremath{\tau}}_{\ensuremath{\alpha}}$, was found to exhibit Arrhenius-type temperature dependence in the AF phase. A comparison between the results of the $x=0$ and 0.004 samples has revealed that the nonmagnetic substitution significantly reduces the initial correlation length, ${\ensuremath{\xi}}_{0\ensuremath{\alpha}}$, and the activation energy in the Arrhenius-type temperature dependence of ${\ensuremath{\tau}}_{\ensuremath{\alpha}}$. We have also found that magnetic domain growth in a magnetic-field-induced ferrimagnetic phase also follows the power law with the growth exponent of $n=0.2$. On the basis of these results, we have concluded that the existence of ferromagnetic Ising spin chains running along the $c$ axis and the geometrical spin frustration in the $ab$ plane are the keys to the domain growth kinetics in this system. The former and the latter govern the characteristic time scale and the growth exponent, respectively.

Time-resolved powder neutron diffraction study of the phase transformation sequence of kaolinite to mullite

Abstract Mullite formation from kaolinite was studied by means of high-temperature in situ powder neutron diffraction by heating from room temperature up to 1370 °C. Neutron diffractometry under this non-isothermal conditions is suitable for studying high-temperature reaction kinetics and to identify short-lived species which otherwise might escape detection. Data collected from dynamic techniques (neutron diffraction, DTA, TGA and constant-heating rate sintering) were consistent with data gathered in static mode (conventional X-ray diffraction and TEM). The full process occurs in successive stages: (a) kaolinite dehydroxylation yielding metakaolinite in the ∼400–650 °C temperature range, (b) nucleation of mullite in the temperature range ∼980–992 to ∼1121 °C (primary mullite) side by side with a crystalline cubic phase (Si-Al spinel) detected in the ∼983–1030 °C temperature interval; (c) growth of mullite crystals from ∼1136 °C, (d) high (or β) cristobalite crystallization at T > ∼1200 °C and (e) secondary mullite crystallization at T > ∼1300 °C. The calculated activation energy for the kaolinite dehydration was 115 kJ/mol; for the mullite nucleation was 278 kJ/mol and for the growth of mullite process was 87 kJ/mol; finally for cristobalite nucleation the calculated apparent activation energy was 481 kJ/mol.

Application of In Situ Neutron Diffraction to Characterize Transient Material Behavior in Welding

A fundamental understanding of the transient and nonequilibrium material behavior during welding is essential in the pursuit of process control and optimization to produce defect-free, structurally sound, and reliable welds. The deep penetration capability of neutrons into most metallic materials makes neutron diffraction a unique and powerful tool in understanding the material structures and properties. However, the inadequate neutron flux limits its application in time-resolved study of transient material behavior. This article highlights recent developments toward in situ time-resolved neutron diffraction measurement of material behavior during welding with two examples: (I) measurement of the transient temperature and thermal stresses during friction-stir welding of an aluminum alloy and (II) measurement of the solid-state phase transformation behavior of an advanced high-strength steel under thermal conditions comparable to the welding processes. These newly developed experimental approaches can be broadly applied to other welding or thermomechanical processes for time-resolved measurement of the fast-changing material state in structural metals.

Domain wall and interphase boundary motion in a two-phase morphotropic phase boundary ferroelectric: Frequency dispersion and contribution to piezoelectric and dielectric properties

In ferroelectric materials, enhanced dielectric and piezoelectric property coefficients are found in compositions near morphotropic phase boundaries (MPBs). The material response in these compositions may be contributed by enhanced intrinsic piezoelectric distortions or increased interface motion, e.g., contributions from domain wall and interphase boundary motion, though the relative effect of these mechanisms in different materials is not yet well understood. One of the major challenges to developing this understanding is the availability and sensitivity of in situ characterization techniques, particularly during the application of cyclic electric fields of subcoercive or weak amplitude, conditions at which the property coefficients are measured. Here, we use time-resolved neutron diffraction to resolve the subtle electric-field-induced crystallographic strain mechanisms in a prototypical MPB composition, 36$%$BiScO${}_{3}$-64$%$PbTiO${}_{3}$, that contains coexisting monoclinic and tetragonal phases. We observe multiple cooperative electromechanical effects including domain wall motion in both the monoclinic and tetragonal phases, interphase boundary motion between the two phases, and electric-field-induced lattice strains. The measured effects span four orders of magnitude in frequency, facilitating the discrimination of intrinsic and extrinsic contributions to properties. Domain wall motion in the monoclinic phase dominates the response, leading to shifts of diffraction peaks as high as 2300 pm/V; these shifts reflect the field-induced changes in average pseudocubic (00$h$) lattice spacing of the monoclinic phase parallel to the electric field. Domain wall motion in the tetragonal phase is also readily apparent and exhibits a degree of frequency dispersion similar to that measured in both the relative permittivity and piezoelectric coefficients at similar conditions.

Cordierite synthesis. A time-resolved neutron diffraction study

Abstract In order to elucidate the mechanism of reaction during the cordierite synthesis a kinetic study has been carried out by means of X-ray diffraction and neutron thermo-diffraction. It was thus possible to elucidate between the reactions leading to the cordierite synthesis and those that gave rise to the undesired phases generated during this process. Depending on the reactants used these reactions are different. The present paper presents results obtained during the cordierite synthesis starting from talc, kaolin and hydromagnesite as reactants. This synthesis from natural raw materials takes place through a complex mechanism that has been described. In this kind of synthesis, at the end of the entire process the obtained cordierite is always accompanied by a second phase: spinel. This is the first time that the presence of the μ-cordierite phase has been observed when the synthesis is carried out in solid state from non-submicronic natural raw materials.

New large volume hydrothermal reaction cell for studying chemical processes under supercritical hydrothermal conditions using time-resolved in situ neutron diffraction

The design and testing of a new large volume Inconel pressure cell for the in situ study of supercritical hydrothermal syntheses using time-resolved neutron diffraction is introduced for the first time. The commissioning of this new cell is demonstrated by the measurement of the time-of-flight neutron diffraction pattern for TiO(2) (Anatase) in supercritical D(2)O on the POLARIS diffractometer at the United Kingdom's pulsed spallation neutron source, ISIS, Rutherford Appleton Laboratory. The sample can be studied over a wide range of temperatures (25-450 °C) and pressures (1-355 bar). This novel apparatus will now enable us to study the kinetics and mechanisms of chemical syntheses under extreme environments such as supercritical water, and in particular to study the crystallization of a variety of technologically important inorganic materials.

A thermosyphon-driven hydrothermal flow-through cell forin situand time-resolved neutron diffraction studies

A flow-through cell for hydrothermal phase transformation studies byin situand time-resolved neutron diffraction has been designed and constructed. The cell has a large internal volume of 320 ml and can operate at temperatures up to 573 K under autogenous vapor pressures (ca8.5 × 106 Pa). The fluid flow is driven by a thermosyphon, which is achieved by the proper design of temperature difference around the closed loop. The main body of the cell is made of stainless steel (316 type), but the sample compartment is constructed from non-scattering Ti–Zr alloy. The cell has been successfully commissioned on Australia's new high-intensity powder diffractometer WOMBAT at the Australian Nuclear Science and Technology Organization, using two simple phase transformation reactions from KAlSi2O6(leucite) to NaAlSi2O6·H2O (analcime) and then back from NaAlSi2O6·H2O to KAlSi2O6as examples. The demonstration proved that the cell is an excellent tool for probing hydrothermal crystallization. By collecting diffraction data every 5 min, it was clearly seen that KAlSi2O6was progressively transformed to NaAlSi2O6·H2O in a sodium chloride solution, and the produced NaAlSi2O6·H2O was progressively transformed back to KAlSi2O6in a potassium carbonate solution.

Kinetics of Methane-Ethane Gas Replacement in Clathrate-Hydrates Studied by Time-Resolved Neutron Diffraction and Raman Spectroscopy

The kinetics of CH(4)-C(2)H(6) replacement in gas hydrates has been studied by in situ neutron diffraction and Raman spectroscopy. Deuterated ethane structure type I (C(2)H(6) sI) hydrates were transformed in a closed volume into methane-ethane mixed structure type II (CH(4)-C(2)H(6) sII) hydrates at 5 MPa and various temperatures in the vicinity of 0 degrees C while followed by time-resolved neutron powder diffraction on D20 at ILL, Grenoble. The role of available surface area of the sI starting material on the formation kinetics of sII hydrates was studied. Ex situ Raman spectroscopic investigations were carried out to crosscheck the gas composition and the distribution of the gas species over the cages as a function of structure type and compared to the in situ neutron results. Raman micromapping on single hydrate grains showed compositional and structural gradients between the surface and core of the transformed hydrates. Moreover, the observed methane-ethane ratio is very far from the one expected for a formation from a constantly equilibrated gas phase. The results also prove that gas replacement in CH(4)-C(2)H(6) hydrates is a regrowth process involving the nucleation of new crystallites commencing at the surface of the parent C(2)H(6) sI hydrate with a progressively shrinking core of unreacted material. The time-resolved neutron diffraction results clearly indicate an increasing diffusion limitation of the exchange process. This diffusion limitation leads to a progressive slowing down of the exchange reaction and is likely to be responsible for the incomplete exchange of the gases.