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1.
Artigo em Inglês | MEDLINE | ID: mdl-39162250

RESUMO

The O3-type Na[Ni1-x-yCoxMny]O2 cathodes have received significant attention in sodium-ion batteries (SIBs) due to their high energy density. However, challenges such as structural instability and interfacial instability against an electrolyte solution limit their practical use in SIBs. In this study, the single-crystalline O3-type Na[Ni0.6Co0.2Mn0.2]O2 (SC-NCM) cathode has been designed and synthesized to effectively relieve the degradation pathways of the polycrystalline O3-type Na[Ni0.6Co0.2Mn0.2]O2 (PC-NCM) cathode for SIBs. The mechanically robust SC-NCM due to the absence of pores in the particles enhances tolerance to particle cracking, resulting in stable cycling performance with a cycle retention of 73% over 350 cycles. Moreover, the proposed SC-NCM is synthesized using a simple and cost-effective molten-salt synthetic route without the complex quenching process typically associated with PC-NCM synthesis methods, showing good practical applicability. This study will provide an innovative direction for the development of advanced cathode materials for practical SIBs.

2.
Materials (Basel) ; 17(15)2024 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-39124413

RESUMO

In this study, the crystal plasticity finite element method was established by coupling the crystal plasticity and finite element method (FEM). The effect of rolling deformation and slip system of polycrystalline Al-Mg-Si aluminum alloy was investigated. The results showed that there was a pronounced heterogeneity in the stress and strain distribution of the material during cold rolling. The maximum strain and shear strain occurred at surface of the material. The smaller the grain size, the lower the strain concentration at the grain boundary. Meanwhile, a smaller strain difference existed between the grain interior and near the boundary. The rotation of grains leads to significant differences in deformation and rotation depending on their initial orientations during the rolling process. The slip system of (11-1)<-110> had a large effect on the plastic deformation, (111)<10-1> is second, and the effect of (1-11)<011> slip system on the plastic deformation is the smallest. After deformation, the grain orientation concentration was increased with deformation. Therefore, both the strength and volume fraction of texture were increased with the increase in rolling deformation. The experimental results of EBSD indicated that the large rolling reduction resulted in severe grain twisting, so the texture strength was increased. The simulation results were in close agreement with the experimental results. This study provides a theoretical basis for the rolling process, microstructure, and performance control of aluminum alloys.

3.
J Phys Condens Matter ; 36(43)2024 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-39019066

RESUMO

This study introduces a novel machine learning (ML) method utilizing a stacked auto-encoder network to predict stiffness degradation in photovoltaic (PV) modules with pre-existing cracks. The input data for the training process was derived from numerical simulations, ensuring a comprehensive representation of module behavior under various conditions. The findings highlight the robust predictive capability of the model, as evidenced by its impressive R2value of 0.961 and notably low root mean square error (RMSE) of 4.02%. These metrics significantly outperform those of other conventional methods, including the artificial neural network with R2of 0.905 and RMSE of 9.43%, the space vector machine with R2of 0.827 and RMSE of 17.93%, and the random forest (RF) with R2of 0.899 and RMSE of 11.02%. Moreover, the findings suggest that the predictive dynamics of degradation are affected by the varying weight functions of different input parameters, such as climate temperature (CT), grain size (GS), material effort, and pre-crack size, as the degradation level changes. Furthermore, a geometric analysis reveals model deficiencies where significant overestimations correlate with thicker glass components, while pronounced underestimations are predominantly associated with thinner layers of polycrystalline silicon wafer and Ethylene Vinyl Acetate in the module. As a case study, it demonstrated that to maintain a constant degradation level between 1.30 and 1.32 in a PV module with components featuring consistent geometric attributes, the input parameters must be kept within specific ranges: CT ranging from 33 °C to 57 °C, GS ranging from 36 to 81µm, material effort ranging from 0.74 to 0.81, and pre-crack size ranging from 24 to 32µm. Therefore, this underscores that the ML model not only predicts degradation but also delineates the parameter space required to achieve a consistent output value.

4.
Sensors (Basel) ; 24(11)2024 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-38894410

RESUMO

This paper demonstrates, for the first time, the stability of synthetic diamond as a passive layer within neural implants. Leveraging the exceptional biocompatibility of intrinsic nanocrystalline diamond, a comprehensive review of material aging analysis in the context of in-vivo implants is provided. This work is based on electric impedance monitoring through the formulation of an analytical model that scrutinizes essential parameters such as the deposited metal resistivity, insulation between conductors, changes in electrode geometry, and leakage currents. The evolution of these parameters takes place over an equivalent period of approximately 10 years. The analytical model, focusing on a fractional capacitor, provides nuanced insights into the surface conductivity variation. A comparative study is performed between a classical polymer material (SU8) and synthetic diamond. Samples subjected to dynamic impedance analysis reveal distinctive patterns over time, characterized by their physical degradation. The results highlight the very high stability of diamond, suggesting promise for the electrode's enduring viability. To support this analysis, microscopic and optical measurements conclude the paper and confirm the high stability of diamond and its strong potential as a material for neural implants with long-life use.


Assuntos
Diamante , Próteses Neurais , Diamante/química , Impedância Elétrica , Materiais Biocompatíveis/química , Humanos , Eletrodos , Temperatura
5.
Nanomaterials (Basel) ; 14(11)2024 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-38869538

RESUMO

Magnetoresistance, the change in resistance with applied magnetic fields, is crucial to the magnetic sensor technology. Linear magnetoresistance has been intensively studied in semimetals and semiconductors. However, the air-stable oxides with a large linear magnetoresistance are highly desirable but remain to be fully explored. In this paper, we report the direct observation of linear magnetoresistance in polycrystalline MoO2 without any sign of saturation up to 7 T under 50 K. Interestingly, the linear magnetoresistance reaches as large as 1500% under 7 T at 2 K. The linear field dependence is in great contrast to the parabolic behavior observed in single-crystal MoO2, probably due to phonon scattering near the grain boundaries. Our results pave the way to comprehending magneto-transport behavior in oxides and their potential applications in magnetic sensors.

6.
Micromachines (Basel) ; 15(6)2024 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-38930729

RESUMO

A novel insulated gate bipolar transistor with Semi-Insulated POly Silicon (SIPOS) is presented in this paper and analyzed through TCAD simulation. In the off state, the SIPOS-IGBT can obtain a uniform electric field distribution, which enables a thinner drift region under the same breakdown voltage. In the on state, an electron accumulation layer is formed along the SIPOS, which can increase the injection level of the "PiN region" in the device, and the carrier concentration in the drift region is also increased due to the charge balance effect. Moreover, the SIPOS-IGBT can achieve a quick and thorough depletion in the drift region during the turn-off transient, which can greatly reduce the turn-off loss of the SIPOS-IGBT. These advantages improve the tradeoff between the conduction and switching losses. According to the simulation results, the SIPOS-IGBT obtained a 58% lower turn loss than that of a field-stop (FS) IGBT and 30% lower than an HK-IGBT with the same on-state voltage.

7.
Micromachines (Basel) ; 15(6)2024 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-38930738

RESUMO

The grain size effect is an important factor in determining the material removal behavior of polycrystalline silicon (p-Si). In the present study, to improve the understanding of nanoscale machining of p-Si, we performed molecular dynamics simulation of nanometric cutting on a p-Si workpiece and discussed the grain size effect on material removal behavior and subsurface damage formation. The simulation results indicate that when cutting on the polycrystal workpiece, the material removal process becomes unstable compared with single crystals. Higher removal efficiency, less elastic recovery and higher frictional coefficient are observed as the average grain size decreases. In the subsurface workpiece, when the grain size decreases, slip along grain boundaries merges as a nonnegligible process of the plastic deformation and suppresses the elastic deformation ahead of the cutting tool. It is also revealed that when cutting on a polycrystal workpiece with smaller grains, the average stress decreases while the workpiece temperature increases due to the impediment of heat transfer by grain boundaries. These results could provide a fundamental understanding in the material deformation mechanism of p-Si during nanoscale machining.

8.
Sci Rep ; 14(1): 13679, 2024 06 13.
Artigo em Inglês | MEDLINE | ID: mdl-38871757

RESUMO

This study introduces a novel approach in the realm of liquid biopsies, employing a 3D Mueller-matrix (MM) image reconstruction technique to analyze dehydrated blood smear polycrystalline structures. Our research centers on exploiting the unique optical anisotropy properties of blood proteins, which undergo structural alterations at the quaternary and tertiary levels in the early stages of diseases such as cancer. These alterations manifest as distinct patterns in the polycrystalline microstructure of dried blood droplets, offering a minimally invasive yet highly effective method for early disease detection. We utilized a groundbreaking 3D MM mapping technique, integrated with digital holographic reconstruction, to perform a detailed layer-by-layer analysis of partially depolarizing dry blood smears. This method allows us to extract critical optical anisotropy parameters, enabling the differentiation of blood films from healthy individuals and prostate cancer patients. Our technique uniquely combines polarization-holographic and differential MM methodologies to spatially characterize the 3D polycrystalline structures within blood films. A key advancement in our study is the quantitative evaluation of optical anisotropy maps using statistical moments (first to fourth orders) of linear and circular birefringence and dichroism distributions. This analysis provides a comprehensive characterization of the mean, variance, skewness, and kurtosis of these distributions, crucial for identifying significant differences between healthy and cancerous samples. Our findings demonstrate an exceptional accuracy rate of over 90 % for the early diagnosis and staging of cancer, surpassing existing screening methods. This high level of precision and the non-invasive nature of our technique mark a significant advancement in the field of liquid biopsies. It holds immense potential for revolutionizing cancer diagnosis, early detection, patient stratification, and monitoring, thereby greatly enhancing patient care and treatment outcomes. In conclusion, our study contributes a pioneering technique to the liquid biopsy domain, aligning with the ongoing quest for non-invasive, reliable, and efficient diagnostic methods. It opens new avenues for cancer diagnosis and monitoring, representing a substantial leap forward in personalized medicine and oncology.


Assuntos
Holografia , Imageamento Tridimensional , Humanos , Imageamento Tridimensional/métodos , Anisotropia , Holografia/métodos , Masculino , Neoplasias da Próstata/patologia , Neoplasias da Próstata/sangue , Neoplasias da Próstata/diagnóstico , Neoplasias da Próstata/diagnóstico por imagem , Biópsia Líquida/métodos
9.
ACS Appl Mater Interfaces ; 16(19): 24147-24161, 2024 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-38695686

RESUMO

Benefiting from anionic and cationic redox reactions, Li-rich materials have been regarded as next-generation cathodes to overcome the bottleneck of energy density. However, they always suffer from cracking of polycrystalline (PC) secondary particles and lattice oxygen release, resulting in severe structural deterioration and capacity decay upon cycling. Single-crystal (SC) design has been proven as an effective strategy to relieve these issues in traditional Li-rich cathodes with PC morphology. Herein, we first reviewed the main synthesis routes of SC Li-rich materials including solid-state reaction, molten salt-assisted, and hydrothermal/solvothermal methods, in which the differences in grain morphology, electrochemical behaviors, and other properties induced by various routes were analyzed and discussed. Furthermore, the distinct characteristics were compared between SC and PC cathodes from the aspects of irreversible capacity, structural stability, capacity/voltage degradation, and gas release. Besides, recent advances in layered SC Li-rich oxide cathodes were summarized in detail, where the unique structural designs and modification strategies could greatly promote their structural/electrochemical stability. At last, challenges and perspectives for the emerging SC Li-rich cathodes were proposed, which provided an exceptional opportunity to achieve high-energy-density and high-stability Li-ion/metal batteries.

10.
Materials (Basel) ; 17(3)2024 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-38591471

RESUMO

A new type of poly-diamond plate without a catalyst was produced via the high-pressure high-temperature (HPHT) compression of diamond powders. The densification of diamond powders and sp3 to sp2 carbon on the surface under HPHT compression was investigated through the characterization of the microstructure, Raman spectroscopy analysis and electrical resistance measurement. The densification and sp3-sp2 transformation on the surface are mainly affected by the pressure, temperature and particle size. The quantitative analysis of the diamond sp3 and sp2 carbon amount was performed through the peak fitting of Raman spectra. It was found that finer diamond particles under a higher temperature and a lower pressure tend to produce more sp2 carbon; otherwise, they produce less. In addition, it is interesting to note that the local residual stresses measured using Raman spectra increase with the diamond particle size. The suspected reason is that the increased particle size reduces the number of contact points, resulting in a higher localized pressure at each contact point. The hypothesis was supported by finite element calculation. This study provides detailed and quantitative data about the densification of diamond powders and sp3 to sp2 transformation on the surface under HPHT treatment, which is valuable for the sintering of polycrystalline diamonds (PCDs) and the HPHT treatment of diamonds.

11.
J Appl Crystallogr ; 57(Pt 2): 470-480, 2024 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-38596726

RESUMO

X-ray Laue microdiffraction aims to characterize microstructural and mechanical fields in polycrystalline specimens at the sub-micrometre scale with a strain resolution of ∼10-4. Here, a new and unique Laue microdiffraction setup and alignment procedure is presented, allowing measurements at temperatures as high as 1500 K, with the objective to extend the technique for the study of crystalline phase transitions and associated strain-field evolution that occur at high temperatures. A method is provided to measure the real temperature encountered by the specimen, which can be critical for precise phase-transition studies, as well as a strategy to calibrate the setup geometry to account for the sample and furnace dilation using a standard α-alumina single crystal. A first application to phase transitions in a polycrystalline specimen of pure zirconia is provided as an illustrative example.

12.
Nano Lett ; 24(14): 4248-4255, 2024 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-38557042

RESUMO

Grain boundaries (GBs) in two-dimensional (2D) covalent organic frameworks (COFs) unavoidably form during the fabrication process, playing pivotal roles in the physical characteristics of COFs. Herein, molecular dynamics simulations were employed to elucidate the fracture failure and thermal transport mechanisms of polycrystalline COFs (p-COFs). The results revealed that the tilt angle of GBs significantly influences out-of-plane wrinkles and residual stress in monolayer p-COFs. The tensile strength of p-COFs can be enhanced and weakened with the tilt angle, which exhibits an inverse relationship with the defect density. The crack always originates from weaker heptagon rings during uniaxial tension. Notably, the thermal transport in p-COFs is insensitive to the GBs due to the variation of minor polymer chain length at defects, which is abnormal for other 2D crystalline materials. This study contributes insights into the impact of GBs in p-COFs and offers theoretical guidance for structural design and practical applications of advanced COFs.

13.
J Contemp Dent Pract ; 25(1): 41-51, 2024 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-38514430

RESUMO

AIM: The study aims to correlate the frictional forces (FF) of four different types of commercially available ceramic brackets to their surface topography. MATERIALS AND METHODS: Two monocrystalline (MC) brackets (CLEAR™, Adanta, Germany; Inspire ICE™, Ormco, USA), one polycrystalline (PC) bracket (Symetri Clear™, Ormco, USA), one clear hybrid esthetic bracket (DISCREET™, Adanta, Germany), and a stainless-steel (SS) bracket (Victory™, 3M Unitek, USA) served as control. Both static friction (SF) and kinetic friction (KF) were recorded during sliding using an Instron universal machine in dry settings. The bracket slot surface topography was evaluated. A scanning electron microscope (SEM) and a profilometer machine were used for assessment before and after sliding. RESULTS: Frictional forces values during sliding were as follows in descending order; Inspire ICE™, CLEAR™, DISCREET™, Symetri Clear™, and, lastly, Victory™. Also, DISCREET™ scored the highest in surface roughness (Sa) values followed by Symetri Clear™. None of the correlations were statistically significant. CONCLUSION: Frictional forces produced during sliding were not always directly related to surface roughness. Monocrystalline ceramic brackets appeared to have the greatest FF and a low surface roughness. Furthermore, DISCREET™ scored a very low frictional value comparable to metal brackets yet showed the highest surface roughness. Metal brackets exhibited the greatest surface smoothness before sliding and the least SF. CLINICAL SIGNIFICANCE: Predicting the FFs produced during sliding mechanics would help the practitioner while choosing the bracket system to be used, and while planning the treatment mechanics, how much force to deliver, and how much tooth movement to expect. How to cite this article: AlBadr AH, Talic NF. Correlating Frictional Forces Generated by Different Bracket Types during Sliding and Surface Topography Using Scanning Electron Microscopy and Optical Profilometer. J Contemp Dent Pract 2024;25(1):41-51.


Assuntos
Braquetes Ortodônticos , Microscopia Eletrônica de Varredura , Fricção , Fios Ortodônticos , Desenho de Aparelho Ortodôntico , Análise do Estresse Dentário , Estética Dentária , Metais , Aço Inoxidável/química , Teste de Materiais , Propriedades de Superfície
14.
Environ Pollut ; 347: 123705, 2024 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-38442825

RESUMO

The ongoing challenge of water pollution by contaminants of emerging concern calls for more effective wastewater treatment to prevent harmful side effects to the environment and human health. To this end, this study explored for the first time the implementation of single-crystal boron-doped diamond (BDD) anodes in electrochemical wastewater treatment, which stand out from the conventional polycrystalline BDD morphologies widely reported in the literature. The single-crystal BDD presented a pure diamond (sp3) content, whereas the three other investigated polycrystalline BDD electrodes displayed various properties in terms of boron doping, sp3/sp2 content, microstructure, and roughness. The effects of other process conditions, such as applied current density and anolyte concentration, were simultaneously investigated using carbamazepine (CBZ) as a representative target pollutant. The Taguchi method was applied to elucidate the optimal operating conditions that maximised either (i) the CBZ degradation rate constant (enhanced through hydroxyl radicals (•OH)) or (ii) the proportion of sulfate radicals (SO4•-) with respect to •OH. The results showed that the single-crystal BDD significantly promoted •OH formation but also that the interactions between boron doping, current density and anolyte concentration determined the underlying degradation mechanisms. Therefore, this study demonstrated that characterising the BDD material and understanding its interactions with other process operating conditions prior to degradation experiments is a crucial step to attain the optimisation of any wastewater treatment application.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Humanos , Boro/química , Oxirredução , Diamante/química , Poluentes Químicos da Água/química , Eletrodos , Purificação da Água/métodos
15.
ACS Appl Mater Interfaces ; 16(14): 18134-18143, 2024 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-38554079

RESUMO

Efficient exciton transport is essential for high-performance optoelectronics. Considerable efforts have been focused on improving the exciton mobility in organic materials. While it is feasible to improve mobility in organic systems by forming well-ordered stacks, the formation of trap states, particularly the lower-lying states referred to as excimers, remains a significant challenge to enhancing mobility. The mobility of excimer excitons intricately depends on the strength of excitonic coupling in terms of Förster-type diffusive exciton transfer processes. Given that the formation and mobility of excimer excitons are highly sensitive to molecular arrangements (packing geometries), conducting comprehensive investigations into the structure-property relationship in organic systems is crucial. In this study, we prepared three types of polycrystalline films of perylene bisimide (PBI) by varying substituents at the imide and bay positions, which allowed us to tailor the properties of excimer excitons and their mobility based on packing geometries and excitonic coupling strengths. By utilizing femtosecond transient absorption spectroscopy, we observed ultrafast excimer formation in the higher coupling regime, while in the lower coupling regime, the transition from Frenkel to excimer excitons occurs with a time constant of 500 fs. Under high pump-fluence, exciton-exciton annihilation processes occur, indicating the diffusion of excimer excitons. Intriguingly, employing a three-dimensional diffusion model, we derived a diffusion constant that is 3000 times greater in the high coupling regime than in the low coupling regime. To investigate the optoelectronic properties in the form of a bulk system, we fabricated n-type organic field effect transistors and obtained 8000 times higher mobility in the high coupling regime. Furthermore, photocurrent measurements enable us to investigate the charge carrier transport by mobile excimer excitons, suggesting a 230-fold improvement in external quantum efficiency with tightly packing PBI molecules compared to the low coupling regime. These findings not only offer valuable insights into optimizing organic materials for optoelectronic devices but also unveil the intriguing potential of exciton migration within excimers.

16.
ACS Appl Mater Interfaces ; 16(12): 15084-15095, 2024 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-38498384

RESUMO

We utilize room-temperature uniaxial pressing at applied loads achievable with low-cost, laboratory-scale presses to fabricate freestanding CH3NH3PbX3 (X- = Br-, Cl-) polycrystalline ceramics with millimeter thicknesses and optical transparency up to ∼70% in the infrared. As-fabricated perovskite ceramics can be produced with desirable form factors (i.e., size, shape, and thickness) and high-quality surfaces without any postprocessing (e.g., cutting or polishing). This method should be broadly applicable to a large swath of metal halide perovskites, not just the compositions shown here. In addition to fabrication, we analyze microstructure-optical property relationships through detailed experiments (e.g., transmission measurements, electron microscopy, X-ray tomography, optical profilometry, etc.) as well as modeling based on Mie theory. The optical, electrical, and mechanical properties of perovskite polycrystalline ceramics are benchmarked against those of single-crystalline analogues through spectroscopic ellipsometry, Hall measurements, and nanoindentation. Finally, γ-ray scintillation from a transparent MAPbBr3 ceramic is demonstrated under irradiation from a 137Cs source. From a broader perspective, scalable methods to produce freestanding polycrystalline lead halide perovskites with comparable properties to their single-crystal counterparts could enable key advancements in the commercial production of perovskite-based technologies (e.g., direct X-ray/γ-ray detectors, scintillators, and nonlinear optics).

17.
Adv Mater ; 36(27): e2400301, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38531113

RESUMO

Due to promising functionalities that may dramatically enhance spintronics performance, antiferromagnets are the subject of intensive research for developing the next-generation active elements to replace ferromagnets. In particular, the recent experimental demonstration of tunneling magnetoresistance and electrical switching using chiral antiferromagnets has sparked expectations for the practical integration of antiferromagnetic materials into device architectures. To further develop the technology to manipulate the magnetic anisotropies in all-antiferromagnetic devices, it is essential to realize exchange bias through the interface between antiferromagnetic multilayers. Here, the first observation on the omnidirectional exchange bias at an all-antiferromagnetic polycrystalline heterointerface is reported. This experiment demonstrates that the interfacial energy causing the exchange bias between the chiral-antiferromagnet Mn3Sn/collinear-antiferromagnet MnN layers is comparable to those found at the conventional ferromagnet/antiferromagnet interface at room temperature. In sharp contrast with previous reports using ferromagnets, the magnetic field control of the unidirectional anisotropy is found to be omnidirectional due to the absence of the shape anisotropy in the antiferromagnetic multilayer. The realization of the omnidirectional exchange bias at the interface between polycrystalline antiferromagnets on amorphous templates, highly compatible with existing Si-based devices, paves the way for developing ultra-low power and ultra-high speed memory devices based on antiferromagnets.

18.
Proc Jpn Acad Ser B Phys Biol Sci ; 100(3): 149-164, 2024 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-38311394

RESUMO

Since the large-volume press with a double-stage multianvil system was created by the late Professor Naoto Kawai, this apparatus (Kawai-type multianvil apparatus or KMA) has been developed for higher-pressure generation, in situ X-ray and neutron observations, deformation experiments, measurements of physical properties, synthesis of high-pressure phases, etc., utilizing its large sample volume and capacity in stable and homogeneous high temperature generation compared to those of competitive diamond anvil cells. These advancements in KMA technology have been made primarily by Japanese scientists and engineers, which yielded a wealth of new experimental data on phase transitions, melting relations, and physical characteristics of minerals and rocks, leading to significant constraints on the structures, chemical compositions, and dynamics of the deep Earth. KMA technology has also been used for synthesis of novel functional materials such as nano-polycrystalline diamond and transparent nano-ceramics, opening a new research field of ultrahigh-pressure materials science.


Assuntos
Diamante , Tecnologia , Diamante/química , Fenômenos Físicos
19.
Heliyon ; 10(3): e25071, 2024 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-38318043

RESUMO

Based on the microscopic polycrystalline fatigue crack propagation (MPFCP) model, the MPFCP behaviours of GH4169 alloy under different micro-notch depths and lengths (constraints) were studied from aspects of MPFCP path, MPFCP rate and stress distribution. The influences of the initial crack angle on MPFCP behaviour were further explored. It was observed that the grain boundary, the grain size and the stress state were different during crack propagation under different constraints, resulting in different MPFCP paths. The MPFCP path was straighter under high constraints, and the MPFCP rate was related to the micro-notch size and the loading direction. The crack tip needed more stress accumulation at low constraints than under high constraints to ensure smooth MPFCP behaviour. The influence of the initial crack angle on the MPFCP path was mainly reflected in the grain interior where the initial crack was located. The initial crack angle had a greater influence on the MPFCP rate than on the MPFCP path.

20.
Adv Mater ; 36(24): e2309253, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38380958

RESUMO

Newly discovered opto-ionic effects in metal oxides provide unique opportunities for functional ceramic applications. The authors generalize the recently demonstrated grain boundary opto-ionic effect observed in solid electrolyte thin films under ultraviolet (UV) irradiation to a radiation-ionic effect that can be applied to bulk materials and used for gamma-rays (γ-rays) detection. Near room temperature, lightly doped Gd-doped CeO2, a polycrystalline ion conducting ceramic, exhibits a resistance ratio change ≈103 and reversible response in ionic current when exposed to 60Co γ-ray (1.1 and 1.3 MeV). This is attributed to the steady state passivation of space charge barriers at grain boundaries, that act as virtual electrodes, capturing radiation-induced electrons, in turn lowering space charge barrier heights, and thereby exclusively modulating the ionic carrier flow within the ceramic electrolytes. Such behavior allows significant electrical response under low fields, that is, < 2 V cm-1, paving the way to inexpensive, sensitive, low-power, and miniaturizable solid-state devices, uniquely suited for operating in harsh (high temperature, pressure, and corrosive) environments. This discovery presents opportunities for portable and/or scalable radiation detectors benefiting geothermal drilling, small modular reactors, nuclear security, and waste management.

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