Shock-induced Phase Transformation Research Articles

Controllable preparation of black phosphorus nanomaterials via liquid-phase pulsed discharge

The N, N-dimethylformamide (DMF) organic solvent was deliberately chosen as the optimal medium for this investigation. To achieve uniform dispersion of black phosphorus powder, which was obtained via shock-induced phase transformation, it was effectively dispersed in the DMF solution, resulting in a homogeneous black phosphorus-DMF suspension. Subsequently, a liquid-phase pulsed discharge experiment was conducted. This experimental setup harnessed the shockwave and tensile stripping effects generated by the rapid expansion of plasma during the liquid-phase pulsed discharge. These phenomena facilitated the interlayer exfoliation and dispersion of black phosphorus molecules, ultimately leading to the formation of a suspension containing black phosphorus quantum dots. In-depth investigation into the formation mechanism of black phosphorus quantum dots was also undertaken. Our findings reveal a pivotal influence of the charging voltage on the microstructure of the recovered samples. Specifically, as the charging voltage increases, the lateral dimensions of the retrieved two-dimensional black phosphorus powder undergo a remarkable reduction, transitioning from the micron-scale to less than 10 nm. The above results, which stem from meticulous experimentation and analysis, emphasize the significance of controlled synthesis in producing black phosphorus quantum dots with varying microstructures. Such insights hold substantial promise for advancing the field of materials science and enhancing the applicability of black phosphorus quantum dots in diverse applications.

Gram-Scale Synthesis of Black Phosphorus through Shock-Induced Phase Transformation.

This article presents the utilization of a cylindrical double-tube shock loading device in conjunction with amorphous red phosphorus as the precursor to investigate the complete phase transformation of red phosphorus into black phosphorus under the influence of shockwaves. Multiple experiments were conducted by varying the shock pressure and temperature parameters. The characterization of the recovered samples involved analysis of the phase composition and microstructure. The obtained experimental results demonstrate that within the cylindrical double-tube shock loading setup, a pressure of 9 GPa and a temperature of 800 K are optimal for achieving the complete phase transition of amorphous red phosphorus into orthorhombic black phosphorus. By precisely controlling these experimental conditions, a high-quality orthorhombic black phosphorus powder with excellent crystallinity was successfully prepared. This method offers several advantages, including simplicity, cost-effectiveness, and high yield. Consequently, this presents a promising pathway for the industrial-scale production of black phosphorus. The implementation of this approach not only reduces the cost involved in black phosphorus synthesis but also contributes to the broad range of applications for this material.

Formation of black phosphorus quantum dots via shock-induced phase transformation

Black phosphorus quantum dots (BPQDs) have recently obtained great attention owing to their outstanding properties, such as high hole mobility, quantum confinement effect, and edge effect. At present, several methods have been applied to prepare BPQDs using black phosphorus as precursor. In this study, BPQDs are obtained via shock-induced phase transformation using ball-milled red phosphorus nanopowder as precursor. The red phosphorus powder was ball-milled and shocked to induce phase transformation at transient high pressure and temperature. Multiple techniques are applied to characterize the recovered samples, including x-ray diffraction, Raman spectroscopy, transmission electron microscopy, and atomic force microscope. The characterization results demonstrate that the majority of recovered sample is BPQDs with a lateral size of 2–10 nm and a thickness of 0.9–2 nm. In addition, the formation mechanism of BPQDs under shock treatment was carefully analyzed, consisting of phase transformation induced by shock loading and exfoliation by tensile and shear effects. Furthermore, this study also confirms that the micromorphology of precursor is critical to the formation of BPQDs. This research provides an efficient one-step path to prepare BPQDs using ball-milled red phosphorus nanopowder as precursor.

Shock-induced plasticity and phase transformation in single crystal magnesium: an interatomic potential and non-equilibrium molecular dynamics simulations

An effective and reliable Finnis–Sinclair (FS) type potential is developed for large-scale molecular dynamics (MD) simulations of plasticity and phase transition of magnesium (Mg) single crystals under high-pressure shock loading. The shock-wave profiles exhibit a split elastic–inelastic wave in the [0001]HCP shock orientation and a three-wave structure in the [10-10]HCP and [-12-10]HCP directions, namely, an elastic precursor, a followed plastic front, and a phase-transition front. The shock Hugoniot of the particle velocity (U p) vs the shock velocity (U s) of Mg single crystals in three shock directions under low shock strength reveals apparent anisotropy, which vanishes with increasing shock strength. For the [0001]HCP shock direction, the amorphization caused by strong atomic strain plays an important role in the phase transition and allows for the phase transition from an isotropic stressed state to the product phase. The reorientation in the shock directions [10-10]HCP and [-12-10]HCP, as the primary plasticity deformation, leads to the compressed hexagonal close-packed (HCP) phase and reduces the phase-transition threshold pressure. The phase-transition pathway in the shock direction [0001]HCP includes a preferential contraction strain along the [0001]HCP direction, a tension along [-12-10]HCP direction, an effective contraction and shear along the [10-10]HCP direction. For the [10-10]HCP and [-12-10]HCP shock directions, the phase-transition pathway consists of two steps: a reorientation and the subsequent transition from the reorientation hexagonal close-packed phase (RHCP) to the body-centered cubic (BCC). The orientation relationships between HCP and BCC are (0001)HCP ⟨-12-10⟩HCP // {110}BCC ⟨001⟩BCC. Due to different slipping directions during the phase transition, three variants of the product phase are observed in the shocked samples, accompanied by three kinds of typical coherent twin-grain boundaries between the variants. The results indicate that the highly concentrated shear stress leads to the crystal lattice instability in the elastic precursor, and the plasticity or the phase transition relaxed the shear stress.

Gram-scale preparation of black phosphorus nanosheetsviashock-induced phase transformation

In the present study, a well-crystallized black phosphorus nanosheet powder is obtained through shock-induced phase transformation of red phosphorus. This study demonstrates a novel route to prepare high-yield black phosphorus nanosheets.

Experimental and atomic observations of phase transformations in shock-compressed single-crystal Fe

The phase transformations in Fe have been of technological and sociological importance in the development of human civilization. The α→ε (BCC→HCP) martensitic transformation is the best known phase transformation of Fe and has been extensively studied. However, the mechanisms of α→ε and ε→α transformation upon shock loading and release are not yet understood owing to its short life and reversibility. In this study, we designed experimental and atomic methods for observing the shock-induced phase transformations in [001] and [111] single-crystal Fe, using shock recovery experiments and molecular dynamic simulations. It was found that the orientation relationships in the [001] and [111] single-crystal Fe are consistent with previously proposed transformation mechanisms. The α→ε transformation was attributed to the (110) slip system, while the reverse transformation was attributed to the (112) slip system. Furthermore, it was postulated that the rod-like microstructures observed in the shock-recovered samples were caused by the wave interactions during the unloading. However, the rod-like shapes in the [001] Fe were caused by the activation of dislocations in the b1 = ka[11–2] and b2 = ka[112] Burgers vectors. Only the b3 = ka[112] dislocation was activated in the [111] Fe sample.

A novel shock-induced multistage phase transformation and underlying mechanism in textured Nano-Twinned Cu

Nano-Twinned (NT) Cu under shock loading parallel to twin planes was investigated via nonequilibrium molecular dynamics (NEMD) simulations, with particular attention to the shock response and intrinsic deformation mechanism. During the shock compression process, a novel multi-stage phase transformation (MPT) scenario, i.e., from FCC phase to BCC phase and then to HCP phase, happens due to shock-enhanced twin boundary (TB) sliding. Both increasing the compressive strain caused by shock and decreasing the twin lamellae in the NT Cu can promote the MPT, with which the yield strength retains but the spallation strength increases. The critical shock pressure triggering the MPT depends exponentially on lamellae twin thickness (T). These new results have great potentials for improving the impact resistance of metals by tailoring their internal nanostructures.

Shock-induced plasticity in nanocrystalline iron: Large-scale molecular dynamics simulations

Large-scale nonequilibrium molecular dynamics (MD) simulations of shock waves in nanocrystalline iron show evidence of plasticity before the polymorphic transformation takes place. The atomistic structure in the shock direction shows an elastic precursor, plastic deformation, and shock-induced phase transformation from bcc to hcp iron. In this Rapid Communication, large-scale MD models show that the shock response of iron is highly related to the ramp time of the applied shocks. For long ramp times we observe significant plastic relaxation and formation of microstructure defects. Pressure-induced phase transformations in iron are accompanied by stress relaxation achieving almost fully relaxed three-dimensional hydrostatic final states. The evolution of the stress relaxation is in agreement with theory and experiments. Analysis of the x-ray diffraction patterns calculated from the atomistic structure using the Debye equation revealed pronounced anisotropy of the line broadening that is caused by stacking faults in hcp Fe and by dislocations in bcc Fe.

Atomistic modelling of the hypervelocity dynamics of shock-compressed graphite and impacted graphene armours

We present a molecular dynamics (MD) simulation study on the hypervelocity dynamics of shock compressed graphite -up to hundreds of gigapascals- and impacted multilayer graphene armours by employing the AIREBO-M potential. The Morse-type non-singular intermolecular interaction allows the usage of relatively large integration timesteps for simulating materials’ response at such high strain-rate. The MD simulation results are in good agreement with the shock Hugoniot curves and with graphite-to-diamond transition obtained from both density functional theory (DFT) and experiments available in literature. We then show that thermodynamic properties of graphite from MD calculations can be used as input for a reliable equation of state to be employed in continuum simulations. Finally, we find that the size-scaling of the hypervelocity impact properties of graphene armours matches well with the DFT results and theoretical predictions of earlier studies. Our results open a concrete possibility towards accurate and fast multiscale simulation from atomistic to continuum level of shock propagation, shock-induced phase transformation, and dynamic fracture in large or hierarchical carbon systems, such as graphene-based foams and nanocomposites.

In situ observation of a phase transition in silicon carbide under shock compression using pulsed x-ray diffraction

The behavior of silicon carbide (SiC) under shock compression is of interest due to its applications as a high-strength ceramic and for general understanding of shock-induced polymorphism. Here we use the Matter in Extreme Conditions beamline of the Linac Coherent Light Source to carry out a series of time-resolved pump-probe x-ray diffraction measurements on SiC laser-shocked to as high as 206 GPa. Experiments on single crystals and polycrystals of different polytypes show a transformation from a low-pressure tetrahedral phase to the high-pressure rocksalt-type (B1) structure. We directly observe coexistence of the low- and high-pressure phases in a mixed-phase region and complete transformation to the B1 phase above 200 GPa. The densities measured by x-ray diffraction are in agreement with both continuum gas-gun studies and a theoretical B1 Hugoniot derived from static-compression data. Time-resolved measurements during shock loading and release reveal a large hysteresis upon unloading, with the B1 phase retained to as low as 5 GPa. The sample eventually reverts to a mixture of polytypes of the low-pressure phase at late times. Our study demonstrates that x-ray diffraction is an effective means to characterize the time-dependent structural response of materials undergoing shock-induced phase transformations at megabar pressures.

Energy dissipation of shock-generated stress waves through phase transformation and plastic deformation in NiTi alloys

The interaction between propagation of shock-induced stress waves and phase transformation in Nickel–Titanium (NiTi) shape memory alloys is studied experimentally and computationally. Molecular dynamics simulations at the atomistic scale are utilized to investigate how the local phase transformations dissipate the energy of shock waves as they travel in the material. It is shown that plastic deformations also happen at the vicinity of the regions at which the loading is applied. While plastic deformations also contribute in the energy dissipation, our results show that the energy dissipation is prominently induced by the reversible phase transformation. These results affirm that shape memory alloys are superior candidates for dissipating the energy of shock loads, with minimal permanent deflections remaining on the structure after the load is applied. Experiments are also performed in which precise and controlled shock loads (generated by the pressure of the liquid jet produced by the collapsing of a spark-generated bubble) are applied to two bars made of NiTi and Aluminum. Our results show that both the measured strain and lateral displacements are drastically damped in NiTi bars, which confirms the dissipation of stress shock ways due to phase transformation in these alloys.

Orientation and grain-boundary dependence of shock-induced plasticity and transformation in nanocrystalline Ti

The plasticity and $\ensuremath{\alpha}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}\ensuremath{\omega}$ transformation are important for the toughness and ductility of hcp titanium under shock loading. However, three questions remain outstanding: (i) what mechanisms govern the plasticity and transformation, (ii) how does the microstructure, i.e., grain boundaries (GBs) and crystallographic orientations, affect them, and (iii) does the transformation take place dependent on the plasticity, such as dislocation slips? We conduct large-scale nonequilibrium molecular dynamics simulations to study shock-induced plasticity and phase transformation in hexagonal columnar nanocrystalline Ti. Significant anisotropy and strong dependence on crystallographic orientation are presented during shock-induced plasticity and phase transformation. The shock first prompts ``heterogeneous'' dislocation slips and ${90}^{\ensuremath{\circ}}$ lattice reorientation, via coupling deformation twinning and slips. Then, the on-going plastic deformation induces a ``heterogeneous'' $\ensuremath{\alpha}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}\ensuremath{\omega}$ phase transformation at lower impact velocities or a ``homogeneous'' solid-state disordering at higher impact velocities. The phase transformation mostly obeys the TAO-1 pathways originated from GBs, while a few of them are governed by Silcock mechanisms within the grains. The TAO-1 and Silcock-governed transformations stem from the emission and propagation of basal-prismatic and prismatic stacking faults, respectively. At the release/tension stage, a $\ensuremath{\omega}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}\ensuremath{\alpha}$ transformation occurs, acting as the reversed process of the $\ensuremath{\alpha}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}\ensuremath{\omega}$ transformation at the compression stage. Meanwhile, structural recovery and spallation initiate in the extending tension area induced by the release fans. Serving as the nucleation of the plasticity, phase transformation, and spallation, GBs play the key role during the loading.

Effect of grain boundaries on shock-induced phase transformation in iron bicrystals

Non-equilibrium molecular-dynamic simulations with a modified analytic embedded-atom model potential have been performed to investigate the effect of three kinds of grain boundaries (GBs) on the martensitic transformation in iron bicrystals with three different GBs under shock loadings. Our results show that the phase transition was influenced by the GBs. All three GBs provide a nucleation site for the α → ε transformation in samples shock-loaded with up = 0.5 km/s, and in particular, the elastic wave can induce the phase transformation at Σ3 ⟨110⟩ twist GB, which indicates that the phase transformation can occur at Σ3 ⟨110⟩ twist GB with a much lower pressure. The effect of GBs on the stress assisted transformation (SAT) mechanisms is discussed. All variants nucleating at the vicinity of these GBs meet the maximum strain work (MSW) criterion. Moreover, all of the variants with the MSW nucleate at Σ5 ⟨001⟩ twist GB and Σ3 ⟨110⟩ tilt GB, but only part of them nucleate at Σ3 ⟨110⟩ twist GB. This is because the coincident planes between both sides of the GB would affect the slip process, which is the second stage of the martensitic transformation and influences the selection of variant. We also find that the martensitic transformation at the front end of the bicrystals would give rise to stress attenuation in samples shock-loaded with up = 0.6 km/s, which makes the GBs seem to be unfavorable to the martensitic transformation. Our findings have the potential to affect the interface engineering and material design under high pressure conditions.

Shock-induced Martensite phase transformation and its effects of metastable near β Ti-5553 titanium alloy

In this paper, microstructure evolution and mechanic properties of metastable near β Ti-5553 alloy were investigated. SHPB, SHTB and light gas gun were employed to carry out the dynamic loadings. Microstructure evolution were characterized by OM, quantitative metallography and XRD. The experimental results demonstrated that stress-induced martensite transformation occur in metastable Ti-5553 alloy through SHPB, SHTB and plate impact loadings. In SHPB loading test, stress-induced martensite transformation is one of the methods that dissipate energy besides of adiabatic shear band, and also occur before ASB. In SHTB and SHPB+SHTB loading tests, the transformation amount of stressinduced martensite exhibit similar trend. In plate impact experiment, the content of martensite phase transformation increased with the impact velocity.

A phase-field model for shock-induced α-γ phase transition of RDX

A thermodynamically consistent continuum phase-field model has been developed to investigate the role of shock-induced solid-solid phase transformation in the deformation mechanisms of molecular single crystals. The effects of microstructural evolution and phase transformation are distinguished and modeled within a crystal plasticity framework that is developed for single crystals at high strain rate. When applied to 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) single crystal, the model predicts α-γ phase transition within the experimentally observed range of shock stresses. Phase-field simulations suggest that the α-γ phase transition requires finite time to occur, where plasticity tends to delay the transition. Phase transformation is associated with stress relaxation, and increased temperature rise and associated shock-sensitivity. The shock response of α-γ phase transition is orientation dependent.

Atomistic studies of shock-induced phase transformations in single crystal iron with cylindrical nanopores

Non-equilibrium molecular-dynamic simulations with our modified analytic embedded-atom model potential were carried out on single crystalline iron of idealized cylindrical nanopores to study the effect of defect on shock response. The results showed that the shock response and phase transformation were influenced by cylindrical nanopores. Reflection wave, “hot spot” can be clearly observed under [001], [110] and [111] loading directions, and the nucleation and growth of dislocations appeared for the shock along [110] and [111] directions. The critical stress of phase transformation, the nucleation sites and martensitic variants were obviously influenced by the cylindrical nanopores. In addition, stress assisted transformation mechanisms and strain induced transformation mechanisms were discussed, and the kinetics of the variants which caused by the presence of cylindrical pores were studied.

Unique large diamonds in a ureilite from Almahata Sitta 2008 TC3 asteroid

The Almahata Sitta MS-170 ureilite (a piece of a breccia originating from the asteroid, 2008 TC3) consists mainly of olivine, with many diamond and graphite grains existing between the olivine grains. The occurrences of the diamonds are unique; i.e., (i) some diamonds exhibit sub-euhedral habits and (ii) some diamonds have large grain-size (up to about 40μm). Several diamonds are segmented into many fragments by fractures. Individual fragments have similar crystallographic orientation, which implies that the adjacent diamond segments were originally a single crystal. Large diamond assemblages occur besides such individual diamond grains. In one of the largest assemblages (almost about 100μm in size) has also the same crystallographic orientation. They can be regarded as the pieces of a previously unique single diamond, which provides evidence for large single-crystals diamond in meteorites. Almahata Sitta MS-170 is a meteorite fragment from the 2008 TC3 asteroid that underwent less shock than other ureilitic meteorites. It is unlikely that such large diamonds were formed from graphite through a shock-induced phase transformation during planetesimal collision, despite this idea being now widely accepted as the diamond formation mechanism of ureilites. Fine-scale heterogeneous distribution of impurities (hydrogen, nitrogen, and oxygen) exists in single crystal diamonds, indicative of sluggish growth. This distribution is reminiscent of sector zoning growth. Its grain size, the shock features of MS-170, and the C- and N-isotopic composition signatures allow us to revive classical and but not widely accepted models for diamond formation in ureilites; i.e., a diamond formed from partially melted magma or a C–O–H fluid in the deep interior of the ureilite parent-body or, alternatively, through a chemical vapor deposition (CVD) process in the solar nebula. Considering present mineralogical and isotopic features, the former scenario is more favorable.

Dynamic behaviour and shock-induced martensite transformation in near-beta Ti-5553 alloy under high strain rate loading

Ti-5553 alloy is a near-beta titanium alloy with high strength and high fracture toughness. In this paper, the dynamic behaviour and shock-induced martensite phase transformation of Ti-5553 alloy with alpha/beta phases were investigated. Split Hopkinson Pressure Bar was employed to investigate the dynamic properties. Microstructure evolutions were characterized by Scanning Electronic Microscopy and Transmission Electron Microscope. The experimental results have demonstrated that Ti-5553 alloy with alpha/beta phases exhibits various strain rate hardening effects, both failure through adiabatic shear band. Ti-5553 alloy with Widmannstatten microstructure exhibit more obvious strain rate hardening effect, lower critical strain rate for ASB nucleation, compared with the alloy with Bimodal microstructures. Under dynamic compression, shock-induced beta to alpha” martensite transformation occurs.

Equation of state for shock compression of distended solids

Shock Hugoniot data for full-density and porous compounds of boron carbide, silicon dioxide, tantalum pentoxide, uranium dioxide and playa alluvium are investigated for the purpose of equation-of-state representation of intense shock compression. Complications of multivalued Hugoniot behavior characteristic of highly distended solids are addressed through the application of enthalpy-based equations of state of the form originally proposed by Rice and Walsh in the late 1950's. Additive measures of cold and thermal pressure intrinsic to the Mie-Gruneisen EOS framework is replaced by isobaric additive functions of the cold and thermal specific volume components in the enthalpy-based formulation. Additionally, experimental evidence reveals enhancement of shock-induced phase transformation on the Hugoniot with increasing levels of initial distension for silicon dioxide, uranium dioxide and possibly boron carbide. Methods for addressing this experimentally observed feature of the shock compression are incorporated into the EOS model.

Anisotropic shock response of titanium: Reorientation and transformation mechanisms

We investigate shock-induced phase transformations in titanium (α-Ti) single crystals induced by shock loading along the [0001], [101¯0] and [121¯0] directions using molecular dynamics simulations. We find a significant dependence of the microstructure evolution on the crystallographic shock direction, providing insight into the nature of the coupling between deformation and phase transformation. For shock along the c-axis, the orientation relationships (ORs) (0001)α//(101¯0)ω and [101¯0]α//[112¯3]ω between parent and product phases are observed, which differs from that previously reported for Ti. For shock compression along the [101¯0] and [121¯0] directions, there is a reorientation of the hexagonally close-packed α phase before the α→ω martensitic transformation, and the OR is consistent with the previously proposed Silcock relationship. We associate the reorientation with a shuffle and shear mechanism and suggest that shear stress is an underlying factor for the anisotropic phase transformation sensitivity.