Amorphous Transformation Research Articles

Core Stress Analysis of Amorphous Alloy Transformer for Rail Transit under Different Working Conditions

The rail transit system is a large electric vehicle system that is strongly dependent on the energy technologies of the power system. The use of new energy-saving amorphous alloy transformers can not only reduce the loss of rail transit power, but also help alleviate the power shortage situation and electromagnetic emissions. The application of the transformer in the field of rail transit is limited by the problem that amorphous alloy is prone to debris. this paper studied the stress conditions of amorphous alloy transformer cores under different working conditions and determined that the location where the core is prone to fragmentation, which is the key problem of smoothly integrating amorphous alloy distribution transformers on rail transit power supply systems. In this study, we investigate the changes in the electromagnetic field and stress of the amorphous alloy transformer core under different operating conditions. The finite element model of an amorphous alloy transformer is established and verified. The simulation results of the magnetic field and stress of the core under different working conditions are given. The no-load current and no-load loss are simulated and compared with the actual experimental data to verify practicability of amorphous alloy transformers. The biggest influence on the iron core is the overload state and the maximum value is higher than the core stress during short circuit. The core strain caused by the side-phase short circuit is larger than the middle-phase short circuit.

Transmission electron microscopy study of extended defect evolution and amorphization in SiC under Si ion irradiation

ABSTRACTThe damage induced in 3C‐SiC epilayers on a silicon wafer by 2.3‐MeV Si ion irradiation for fluences of 1014, 1015, and 1016 cm−2, was studied by conventional and high‐resolution transmission electron microscopy (TEM/HRTEM). The evolution of extended defects and lattice disorder is followed in both the 3C‐SiC film and Si substrate as a function of ion fluence, with reference to previous FTIR spectroscopy data. The likelihood of athermal unfaulting of native stacking faults by point defect migration to the native stacking faults is discussed in relation to damage recovery. Threshold energy densities and irradiation doses for dislocation loop formation and amorphous phase transformation are deduced from the damage depth profile by nuclear collisions. The role of electronic excitations on the damage recovery at high fluence is also addressed for both SiC and Si.

Effects of the Glass-Forming Ability and Annealing Conditions on Cocrystallization Behaviors via Rapid Solvent Removal: A Case Study of Voriconazole.

The kinetic entrapment of molecules in an amorphous phase is a common obstacle to cocrystal screening using rapid solvent removal, especially for drugs with a moderate or high glass-forming ability (GFA). The aim of this study was to elucidate the effects of the coformer’s GFA and annealing conditions on the nature of amorphous phase transformation to the cocrystal counterpart. Attempts were made to cocrystallize voriconazole (VRC) with four structural analogues, namely fumaric acid (FUM), tartaric acid (TAR), malic acid (MAL), and maleic acid (MAE). The overall GFA of VRC binary systems increased with decreasing glass transition temperatures (Tgs) of these diacids, which appeared as a critical parameter for predicting the cocrystallization propensity such that a high-Tg coformer is more desirable. A new 1:1 VRC-TAR cocrystal was successfully produced via a supercooled-mediated re-cocrystallization process, and characterized by PXRD, DSC, and FTIR. The cocrystal purity against the annealing temperature displayed a bell-shaped curve, with a threshold at 40 °C. The isothermal phase purity improved with annealing and adhered to the Kolmogorov–Johnson–Mehl–Avrami kinetics. The superior dissolution behavior of the VRC-TAR cocrystal could minimize VRC precipitation upon gastric emptying. This study offers a simple but useful guide for efficient cocrystal screening based on the Tg of structurally similar coformers, annealing temperature, and time.

Ultra-precision grinding of Gd3Ga5O12 crystals with graphene oxide coolant: Material deformation mechanism and performance evaluation

• GO lubrication assisted grinding was innovatively applied in crack-free machining of GGG crystals. • Plastic deformation of GGG induced by GO assisted grinding was dominated by polycrystallization nanocrystals and amorphous transformation. • Interlayer slip and filling actions of GO significantly affect the deformation and removal processes of GGG crystals. • Compared with conventional grinding, surface roughness and friction coefficient of GO assisted grinding were effectively reduced. Laser crystals of rare-earth oxide are primary host materials for making solid-state lasers of large power. However, brittle fractures and cracks are easily formed on the crystal’s surface and subsurface during abrasive machining process owing to their high hardness and brittleness, which will seriously reduce output power of the lasers. In this work, a grinding coolant was synthesized through dispersing GO nanosheets in water, and the grinding experiment of GGG laser crystals assisted by GO coolant lubrication was systematically performed. The plastic deformation mechanism of GGG crystals induced by GO assisted grinding was revealed at close-to-atomic scale by Raman spectrum and cross-section TEM detection technologies. The results indicated that the plastic deformation of GGG crystals during GO assisted grinding was affected by the interlayer slip and filling actions of GO, and was dominated by polycrystallization nanocrystals and amorphous transformation caused by the crystal plane slipping. The use of the GO coolant enabled to lower friction at the abrasive-substrate interface significantly owing to their self-lubricating effect, thus resulting in improved ground surface quality, in comparison with conventional grinding. This work will provide a new theoretical basis and technical support for high-efficiency and low-damage ultra-precision grinding of laser crystals.

Greater improvement of carbon and boron co-doping on the mechanical properties, wear resistance and cutting performance of AlTiN coating than that of doping alone

The effects of carbon and boron co-doping on the microstructure and properties of AlTiN coatings are still unclear. In this study, a comparative study on the effects of carbon and boron co-doping and doping alone on their microstructure and performance of the as-deposited AlTiN, AlTiCN, AlTiBN and AlTiBCN coatings was performed. The results showed that, typical columnar crystal structure changes, starting from undoped AlTiN coating, have been well demonstrated after doping. At the doping content is 5 at.% (relative to the non-N elements), carbon can induce a stronger [200]-preferred orientation, which is beneficial for enhancing the nanohardness and Young's modulus of the coating, while the grain refinement of boron plays a dominant role in the coating growing. When the actual doping content further increases to 10 at.%, carbon as well as boron supports the formation of the hexagonal structure (w-AlN). Due to the amorphous transformation, carbon and boron are present in the form of amorphous carbon and BN, respectively. The above microstructure evolution after doping can be inherited in the co-doped coating. The AlTiBCN coating exhibits the best adhesion between the coating and substrate because of the formed amorphous-nanocrystalline composite structure. Compared to doping alone, carbon and boron co-doping significantly reduces the wear rate, and AlTiB0.08C0.02N has the minimum value of 1.8 × 10−6 mm3/(N·m). The improving effect of carbon and/or boron on the cutting performance of the coated tools is in sequence as follows: carbon and boron co-doping > carbon doping > undoped > boron doping. The AlTiB0.02C0.005N coated tool exhibits the best cutting performance.

Nickel doping induced amorphization of brookite TiO2: Photoluminescence enhancement

In this work, we have elaborated nickel doped TiO2 thin films by low temperature spray pyrolysis technique from ethanol based precursor. For the sample free of nickel, The FTIR spectrum reveals a large amount of organic species bonded to TiO2, resulting in a carbon-doped brookite. Ni doping causes extinction of the organic related peak that fade away for highly (> 10 %) Ni doped films. XRD spectra reveal the presence of brookite phase for low Ni amounts. While increasing Ni rate, the crystalline phase undergoes a transition to amorphous state and brookite XRD peaks vanishes. Optical and electronic (SEM) micrographs show a smooth surface with small brookite nanoparticles, for low Ni rate. Increasing Ni rate results in a fractured morphology composed of micrometric smooth ships. Optical absorption obtained by transmittance-reflectance spectra is enhanced in the transparency region of TiO2, by Ni doping due to the increase of defect density and the brookite to amorphous phase transformation. Visible and UV emission spectra are obtained from PL measurements at room temperature. A spectacular PL magnification is obtained for high Ni doping levels due to increase of oxygen vacancies in the amorphous film. However, thermal annealing at 500 °C causes recrystallization to anatase phase, leading to a dramatic PL quenching.

Investigation of Microstructure and Nanoindentation Hardness of C+ & He+ Irradiated Nanocrystal SiC Coatings during Annealing and Corrosion

The microstructure and nanoindentation hardness of unirradiated, irradiated, annealed and corroded SiC coatings were characterized. Irradiation of 400 keV C+ and 200 keV He+ with approximately 10 dpa did not cause obvious amorphous transformation to nanocrystal SiC coatings and induced helium bubbles with 2–3 nm dimension distributed uniformly in the SiC matrix. High temperature annealing resulted in the transformation of SiC nanocrystals into columnar crystals in the irradiated region. Line-shaped bubble bands formed at the columnar crystal boundaries and their stacking fault planes and made the formation of microcracks of hundreds of nanometers in length. Meanwhile, some isolated helium bubbles distributed in SiC grains still maintained a size of 2–3 nm, despite annealing at 1200 °C for 5 h. The SiC coating showed excellent corrosion resistance under high-temperature, high-pressure water. The weight of the sample decreased with the increase of corrosion time. The nanoindentation hardness and the elastic modulus increased significantly with C+ and He+ irradiation, while their values decreased with high-temperature annealing. An increase in the annealing temperature led to an increased reduction in the values. Corrosion caused the decrease of nanoindentation hardness and the elastic modulus in the whole test depth range, whether the samples were irradiated or unirradiated.

Understanding the Lithiation Pathways of Tetrel Clathrates with Synchrotron X-Ray Characterization

Tetrel clathrates are materials composed of cage-like frameworks of covalently bonded Group IV (Si, Ge, Sn) elements containing guest atoms in the center of each cage. Our group has been investigating the electrochemical properties of Si and Ge clathrates for potential applications as Li-ion battery anodes. Our studies have found that in some cases the Li-alloying pathways are distinctly different in clathrates compared to those seen in the diamond cubic analogs. For example, the Ba8Al16Si30 Type I clathrate does not undergo a Li-alloying reaction [1] while the Ba8Ge43 clathrate does [2]. In the case of Ba8Ge43, the reaction pathway appears to follow an amorphous phase transformation, in contrast to diamond cubic Ge, which undergoes several phase transformations to form crystalline Li-Ge phases [3].In this work, we employ synchrotron X-ray pair-distribution function (PDF) analysis, X-ray diffraction (XRD), and in situ heating experiments to elucidate the electrochemically induced structural changes in Ge and Sn clathrates and how they differ from those in the elemental analogs. The Type I Ba8Ge43 and Type VIII Ba8Ga16Sn30 clathrates are chosen and compared to diamond cubic Ge and beta-Sn. The PDF method allows us to probe the local structure of the amorphous phases that form after lithiation, while in situ heating experiments enable us to observe structural changes to the amorphous phases upon moderate heating. The insights learned from the structural characterizations are then used to explain the differences in the electrochemistry between the Tetrel clathrates and their elemental analogs.The results suggest that the amorphous phases that are part of the final lithiated state of Ba8Ge43 have local structures similar to the Li-Ge crystalline phases. We conclude that the Ba atoms prevent the bulk nucleation of Li-Ge crystalline phases and restrict the Li-Ge ordering to the scale of 10-15 Å, resulting in a solid solution mechanism and a lower reaction voltage compared to cubic-Ge. Similar analysis of the Type VIII Ga-Sn clathrate (Ba8Ga16Sn30) results in a similar lithiation path showing a solely amorphous phase transformation. These results give insight to the fundamentals of how the initial structure of group IV materials affect their Li-alloying properties and structures. Figure 1 (a) Unit cell of Ba8Ge43, purple atoms are Ge and green atoms are Ba. (b) PDFs of the lithiation of Ba8Ge43 at different states of lithiation. (c) PDFs of cubic-Ge at different states of lithiation.[1] R. Zhao. ACS Appl. Mater. Interfaces. 9 (2017) 41246–41257.[2] A. Dopilka. ACS Appl. Mater. Interfaces. 10 (2018) 37981–37993.[3] H. Jung. Chem. Mater. 27 (2015) 1031–1041. Figure 1

Structural Characterization of Amorphous VS4 and Its Amorphous Phase Transformation during Li Insertion

Vanadium sulfide (VS4) is one of the promising positive electrode materials for high capacity lithium ion secondary batteries. In this study, we prepared an amorphous VS4 (a-VS4) by mechanical treatment of the crystalline VS4 (c-VS4) and characterize its local structure. Furthermore, its lithium insertion/extraction behavior was investigated using solid-state nuclear magnetic resonance (NMR), X-ray pair distribution function (PDF), and Raman spectroscopy analyses.Crystalline VS4 was synthesized from V2S3 (99%, Kojundo Chemical Lab.) and S (99.9%, Wako).1 The mixture was heated in a sealed glass tube under vacuum at 400 °C for 12 h. Then, the amorphous VS4 was prepared from the crystalline sample by mechanical milling for 40 h at 270 rpm. A working electrode was prepared from a mixture of the active material (a-VS4), conductive carbon, and Teflon binder in a weight ratio of 59:29:12. Coin-type or laminate-type cells were assembled in an Ar-filled glove box. The cells were cycled between 1.5 and 2.6 V at a constant current density of 59.8 mA g–1 using a TOSCAT-3100 battery-testing system (Toyo System). They were then carefully disassembled at selected discharge/charge states in the glove box and rinsed with dimethyl carbonate (DMC) to remove the residual electrolyte solution.Local structures of c-VS4 and a-VS4 were characterized and the structural changes of the electrode samples were examined by NMR spectroscopy, X-ray PDF analyses, and Raman spectroscopy. Operando 7Li NMR measurements were performed to study the Li insertion/extraction process under electrochemical operation.2 It is known that c-VS4 has a unique structure, in which the Peierls-distorted one-dimensional chains of V-V bonds along the c axis are loosely connected to each other through van der Waals interactions. We confirmed that a-VS4 shows a chain structure similar to that of c-VS4. The chain structure is found to change drastically during the Li insertion process to form amorphous Li3VS4, where the V ions become tetrahedrally coordinated by S ions. The valence states of V and S ions simultaneously change from V4+ and S– (a-VS4) to V5+ and S2– (a-Li3VS4), respectively. When the Li insertion proceeds further (i.e., a-Li3+d VS4), the valence state of V ion is reduced, and a broad 7Li NMR peak shifts to higher frequencies (Fig. 1). After the 1st cycle, the amorphous VS4 recovers the chain-like structure although it is highly disordered. It is also found that the conversion reaction to metallic V and Li2S are observed when the cell is discharged to 0.2 V.This study indicates that the Li insertion/extraction process of the amorphous sulfur-rich transition metal (TM) sulfides such as a-VS4 and a-TiS4 3 involves the amorphous-amorphous phase transformation, which is related to the changes in the bonding nature of sulfide species and the coordination number of TM ions. The amorphous host structure can accommodate these modifications, which is clearly different from the Li insertion/extraction mechanism in crystalline electrode materials.This work is based on results obtained from a project, “Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 (RISING2)”, JPNP16001, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References Koganei et al., Solid State Ionics, 323, 32-36 (2018).Shimoda et al., RSC adv. 9, 23979-23985 (2019).Sakuda et al., J. Am. Chem. Soc., 139, 8796-8799 (2017). Figure 1

Crystalline-to-Amorphous Phase Transformations As a Key Ingredient to Enhanced Rate Performance and Cycle Life in Mg- and Na-Ion Battery Anodes: Operando x-Ray Scattering Studies

The increasing popularity of Li-ion batteries in new applications such as electric vehicles is expected to cause the key resources (Li, Ni and Co) used in these batteries to become scarce. Alternative battery technologies, including Mg-ion, Na-ion, and metal-air batteries are therefore desirable. In this talk, I will discuss the use of operando wide-angle X-ray scattering (WAXS) to study the crystalline to amorphous phase transformations that are key to the outstanding performance of state-of-the-art alloy-type Mg- and Na-ion anodes. The 1st part of the talk will be on the impact of the crystalline-to-amorphous transformation on batteries cycle life. Here I will discuss our novel self-healing Ga/Mg anode, which holds the current record for cycle performance and rate capability in alloy-type Mg-ion battery anodes, owing to a crystalline Mg2Ga5 to amorphous liquid Ga phase transformation occurring near room temperature, preventing the well-known pulverization issue in alloy-type anodes.[1] The 2nd part of the talk will detail the impact of the crystalline-to-amorphous transformation on the rate capabilities of batteries. Here, I will present our nanoporous Sb/Na system, which transforms from crystalline Na3Sb to crystalline Sb, going through an amorphous intermediate. It will be shown using a combination of WAXS, electrochemical characterization, and computational study based on ab initio grand canonical (aiGCMC) simulations that the amorphous intermediate phase favors high rate Na storage in Sb.[2] [1] Wang, L., Welborn, S. S., Kumar, H., Li, M., Wang, Z., Shenoy, V. B., Detsi, E.: High‐Rate and Long Cycle‐Life Alloy‐Type Magnesium‐Ion Battery Anode Enabled Through (De)magnesiation‐Induced Near‐Room‐Temperature Solid–Liquid Phase Transformation. Adv. Energy Mater. 2019, 1902086. https://doi.org/10.1002/aenm.201902086 [2] M. Li, T. Qiu, S. Welborn, A. Foucher, B. Lesel, E. Stach, A. M. Rappe, E. Detsi: Understanding the Fast Kinetics of Sodium Storage in Antimony (unpublished)

Effective Surface Texturing of Diamond-Wire-Sawn Multicrystalline Silicon Wafers Via Crystallization of the Native Surface Amorphous Layer

To increase the market shares of multicrystalline silicon (mc-Si) wafers obtained using diamond-wire sawing (DWS), it is necessary to develop efficient and cost-effective texturing methods. Surface texturing processes that increase light absorption are essential for manufacturing high-efficiency solar cells. The smooth surface, phase transformations, and amorphous silicon (a-Si) layer on mc-Si wafers manufactured via DWS hinder the effective texturing under conventional acidic conditions, which are typically used for multiwire slurry sawing (MWSS). To address this issue, this article focused on an efficient texturing process of DWS wafers by adapting a pre-thermal treatment (TT) process. We found that DWS mc-Si wafers could be effectively textured after the TT process by altering the surface roughness through the crystallization of surface amorphous silicon (a-Si) and phase transformation layers. For the DWS mc-Si wafers textured under conventional acidic etching conditions without TT, Rw was found to be 31.7%. The altered surface conditions achieved via the proposed TT method facilitate effective texturing on the DWS mc-Si wafer surface. Consequently, a weighted average reflectance (Rw) of 24.5% was obtained, which was comparable to that for MWSS mc-Si wafers subjected to conventional acidic etching (Rw = 24.4%). As a result of depositing a SiN x for surface passivation and antireflection coating in solar cell applications, Rw values of 8.1% and 8.3% were obtained for the thermal treated DWS mc-Si wafer and MWSS mc-Si wafer, respectively. The proposed texturing process for DWS mc-Si wafers can easily be applied to industrial inline processes using cost-effective existing acidic etching solutions.

Molecular dynamics simulation of the material removal in the scratching of 4H-SiC and 6H-SiC substrates

Single crystal silicon carbide (SiC) is widely used for optoelectronics applications. Due to the anisotropic characteristics of single crystal materials, the C face and Si face of single crystal SiC have different physical properties, which may fit for particular application purposes. This paper presents an investigation of the material removal and associated subsurface defects in a set of scratching tests on the C face and Si face of 4H-SiC and 6H-SiC materials using molecular dynamics simulations. The investigation reveals that the sample material deformation consists of plastic, amorphous transformations and dislocation slips that may be prone to brittle split. The results showed that the material removal at the C face is more effective with less amorphous deformation than that at the Si face. Such a phenomenon in scratching relates to the dislocations on the basal plane (0001) of the SiC crystal. Subsurface defects were reduced by applying scratching cut depths equal to integer multiples of a half molecular lattice thickness, which formed a foundation for selecting machining control parameters for the best surface quality.

Understanding the Amorphous Lithiation Pathway of the Type I Ba8Ge43 Clathrate with Synchrotron X-ray Characterization

Tetrel (Tt = Si, Ge, and Sn) clathrates have highly tunable host–guest structures and have been investigated as novel electrode materials for Li-ion batteries. However, there is little understanding of how the clathrate structure affects the lithiation processes and phase evolution. Herein, the electrochemical lithiation pathway of type I clathrate Ba8Ge43 is investigated with synchrotron X-ray diffraction (XRD) and pair distribution function (PDF) analyses and compared to the lithiation of germanium with a diamond cubic structure (α-Ge). The results confirm previous laboratory XRD studies showing that Ba8Ge43 goes through a solely amorphous phase transformation, which contrasts with the crystalline phase transformations that take place during lithiation of micrometer-sized α-Ge particles. The local structure of framework-substituted clathrate Ba8Al16Ge30 after lithiation is found to proceed through an amorphous phase transformation similar to that in Ba8Ge43. In situ PDF and XRD during heating show that the amorphous phases derived from lithiation of Ba8Ge43 are structurally related to various Li–Ge phases and crystallize at low temperatures (350–420 K). We conclude that the Ba atoms inside the clathrate structure act to break up the long-range ordering of Li–Ge clusters and kinetically prevent the nucleation and growth of bulk crystalline phases. The amorphous phase evolution of the clathrate structure during lithiation results in electrochemical properties distinct from those in α-Ge, such as a single-phase reaction mechanism and lower voltage, suggesting possible advantages of clathrates over elemental phases for use as anodes in Li-ion batteries.

In-situ evolution of microstructural transformation from crystalline to amorphous in PtPb/Pt nanoplates induced by Kr ion irradiation

Ion irradiation is a highly effective approach to boost the catalytic activity in the platinum-lead/platinum (PtPb/Pt) core–shell nanoplates (NPs) through tuning their microstructures for fuel cell technology. We report on the evolution of crystalline to amorphous (c-a) transformation induced by Kr ion irradiation in the PtPb NPs in detail by using in-situ transmission electron microscopy. The results show that PtPb NPs first generate small amorphous domains, followed by a gradual amorphous transition from their edge to inner and finally are changed to be completely amorphous during in-situ Kr ion irradiation. The c-a transformation appears at the edge of NPs at first, which is attributed to high energy of grain boundary and surface. The crystal-amorphous interfaces and geometrical defects induced by moderate irradiation in PtPb NPs are the key factors to enhance the catalytic activity. This study provides the understanding of the microstructural transition of PtPb NPs and the guidance for using ion irradiation approach to boost catalytic properties of nanomaterials by tuning their microstructures.

Use of AMT Transformers and Distributed Storage Systems to Enhance Electrical Feeding Systems for Tramways

Tramway systems are more and more diffused today, to reduce pollution and greenhouse emissions. However, their electrical feeding substations can have significant margin for improvement. Therefore, it is questionable which kind of changes can be introduced, by changing their main features. First of all, transformer technology can be enhanced, by moving from the standard transformer to the amorphous metal one; thus, guaranteeing a significant reduction in losses. Then, by installing one dedicated storage systems for each substation. This solution can help to increase the energy efficiency; thus, recovering the tram braking energy and reducing the delivered energy from the grid, and also the reliability of the system; thus, guarantee different levels of services, in the case of failure of a feeding substation. This paper investigates in a systematic approach the two proposed solutions. In particular an amorphous metal transformer has been properly designed, and performance compared to the standard one. Then, evaluation of distributed storage installation was performed, and the aspects of reliability for these systems evaluated. Results have shown the general feasibility of the proposed solutions, showing a significant energy saving with respect to the conventional ones.

Transmutation of the Crystalline Structure of β-SiC Nanowires to an Amorphous Structure Through Cu Ion Shelling

The amorphous structural study of silicon carbide nanowires (SiC-NWs) has drawn strenuous attention in recent years due to their worthwhile properties for wide applications, chiefly in optoelectronics. The facile transformation of crystalline SiC-NWs to amorphous defective SiC-NWs is a challenging task for their broad-scale applications. Herein, we report a fantastic strategy (by applying a 5UDH Pelletron accelerator, located at the National Centre for Physics, Islamabad, Pakistan) for Cu ion implantation (fixed at 10 MeV) on the crystalline SiC-NWs to incorporate them into an amorphous structure. For the defects study, various dose rates of Cu+ ion ranging from 5 × 1015 ions/cm2 to 5 × 1016 ions/cm2 were bombarded on SiC-NWs, and a complete transmutation to the amorphous structure of SiC-NWs under a shelling dose of 8 × 1016 ions/cm2 was observed. This work will provide a better avenue for the structural deformation blueprints of the next-generation nanomaterials. Amorphous structural transformation is explained by collision cascade effects phenomena.

Surface solid-state amorphization of accumulative roll bonded Cu-Zr laminates by friction stir processing

Cu-Zr laminates containing 22 alternative pure Cu and pure Zr metal layers were prepared by 2 cycles accumulative roll bonding method and then subjected to friction stir processing at a rotation speed of 200 rpm and a traveling speed of 100 mm/min using a pinless rotating tool. After processing, a circular arc-like stir zone with a maximum depth of about 0.25 mm was formed on the surface of the laminate. It was revealed that the microstructure was significantly refined into nanoscale at the bottom of the stir zone. While on the top of the stir zone, an amorphous structure was formed due to the severe plastic deformation and the simultaneously thermal promoted crystal to amorphous transformation.

Influence of phase transformation on structure–property relationship in quaternary In10Sb10Ag10Se70 chalcogenide films

This work reports the effect of thermal annealing (353–413 K) on structure and physical properties of thermally evaporated In10Ag10Sb10Se70 chalcogenide films. The samples were characterized by X-ray diffraction, transmission electron microscopy, TEM, Raman spectroscopy, optical absorption and photoconductivity measurements. Thermal annealing favours amorphous to polycrystalline structure transition with the growth of Se, AgInSe2 and AgSbSe2 phases. A significant change in position/shape of Raman bands upon annealing has been observed. The indirect optical gap decreases from 1.44 to 0.68 eV while tailing parameter increases with annealing. Photosensitivity decreases from 29.3 to 14.2 with annealing temperature. The decay of photocurrents is well fitted to stretched exponential function; the value of decay time constant increases while local minimum value of dispersion parameter at 353 K has been observed. These results are explained on the basis of amorphous crystalline phase transformation in chalcogenides and are important for developing new materials for emerging technologies.

Ceramic abandonment. How to recognise post-depositional transformations

After they have been abandoned, ceramic materials may undergo substantial transformations, all of which may change their macroscopic aspect, mineralogy, chemical composition and microstructure. The intensity and pervasiveness of these transformations on both macro- and micro-scales depend to a great extent not only on their compositional and microstructural features but also on the chemical-physical characteristics of the post-depositional environment in which they were hosted. This contribution describes the main post-depositional transformations observed in ancient ceramics in relation to secondary phases precipitation, mineral dissolution, pristine mineral and amorphous phases transformations into new mineral phases, and chemical leaching and enrichment. The mechanisms responsible for these transformations are described, together with the characteristics which allow us to identify them according to the most common analytical approaches, in order not to introduce misleading interpretations concerning the study of the provenance and production technology of ancient ceramic materials.

Mechanically Induced Amorphization of Diaqua-bis(Omeprazolate)-Magnesium Dihydrate

The influence of milling diaqua-bis(omeprazolate)-magnesium dihydrate (DABOMD), an active pharmaceutical ingredient (API), was investigated. DABOMD was processed in a planetary ball mill at different milling times, from 1 to 300 min. The milling process resulted in a prominent comminution (size reduction) and amorphization of the API. DABOMD amorphization was identified with various characterization techniques including thermogravimetric analysis, differential scanning calorimetry, powder X-ray diffraction, and attenuated total reflection-Fourier transform infrared spectroscopy. The solid–solid crystalline to amorphous phase transformation is driven by compression, shear stresses, and heat generated in the planetary ball mill. This leads to distortion and breakage of hydrogen bonds, release of water molecules from the crystalline lattice of DABOMD and the accumulation of defects, and eventually a collapse of the crystalline order. Model fitting of the kinetics of comminution and the amorphization of DABOMD revealed a series of events: a rapid comminution at the start of milling driven by crystal cleavage of DABOMD, followed by partial amorphization, which is driven by rapid water diffusion, and subsequently, a slow steady comminution and amorphization.