Hasil untuk "Materials Science"

G. Whitesides

Ye Tian, Bin Su, Lei Jiang

F. Kollmann, W. Cǒté

Xiang Yao, Rong Peng, Jiandong Ding

Beatriz Martín-García, Anatolii Polovitsyn, Mirko Prato et al.

Quantum dot - graphene hybrid materials have raised significant interest due to the unique synergy of the optical properties of colloidal quantum dots (QDs) and the transport properties of graphene. This stimulated the development of low-cost and up-scalable solution-processed strategies for hybrid materials with potential application in light harvesting and opto-electronic devices. Here we report a versatile covalent-linking based approach for the functionalization of reduced graphene oxide (rGO), to prepare a variety of QD-rGO hybrid dispersions with QDs of different size and composition (PbS, PbS/CdS and CdSe QDs), and shape (CdSe/CdS dot-in-rods). We achieved a well-controlled QD coverage of the rGO sheets by functionalizing the rGO surface with mercapto-silane linkers. A further spectroscopic investigation of near-infrared PbS QD-rGO materials demonstrates efficient electronic coupling between both materials. The QD photoluminescence emission quenching and exciton lifetime shortening up to 95%, together with subtle graphene Raman G-band shifts upon QD linking, supports electron transfer as the dominant relaxation pathway from the QD to the rGO. The use of core/shell PbS/CdS QDs allows tuning of the transfer efficiency from 94% for a 0.2 nm thin CdS shell, down to 30% for a 1.1 nm thick shell.

S. Billinge, I. Levin

Suk-Won Hwang, Jun‐Kyul Song, Xian Huang et al.

Xianwei Ren, Weizheng Liang, Ying Zhang et al.

Herein, we investigate the effect of stress-aging on the precipitate characteristics, grain structure, dislocation evolution, and mechanical properties of an Al–10Zn–3Mg–2.5Cu (wt.%) alloy. Stress aging was performed at 120 °C for 24 h under applied stresses of 135–450 MPa, which considerably enhanced the tensile strength to 700 MPa and resulted in dislocation multiplication as the dominant strengthening mechanism. However, the alloy ductility was constrained to 3.7 %–5.4 %. The stress-aged specimens with 270 MPa and 450 MPa were subjected to artificial aging (140 °C–160 °C). This considerably enhanced the strength–ductility synergy, endowing a tensile strength of 700 MPa along with elongations of 9.1 % and 6.5 %. ε-CuZn4 precipitation was facilitated by synergistic high-alloying and dislocation effects. This rare phase effectively suppressed the coarsening of η-phase, thereby preserving the intrinsic strength, while its superior capability to trap and accumulate dislocations significantly enhanced the ductility. Thus, high-stress aging and thermal treatment offered transformative phase-transformation pathways, distinct from conventional η-phase evolution, making it ideal for fabricating high-strength Al–Zn–Mg–Cu alloys.

Xiaofu Zhang, Shu Wang, Ruirun Chen et al.

Abstract Transformation‐induced plasticity (TRIP) and twinning‐induced plasticity (TWIP) are typically suppressed by precipitates and difficult to be significantly triggered under high yield stress. In titanium alloys, ω phase with intrinsic deformation heterogeneity localizes deformation to {112}〈111〉β system, exactly aligning with the lattice shear in martensite transformation (MT). Therefore, beyond reported ω‐nanoprecipitates functions, e.g., providing precipitation strengthening, maintaining strain compatibility and dynamically forming ω‐free dislocation channels, new confining specific shear is proposed to integrate precipitates with TRIP/TWIP effects in this work. A de novo design scheme, consisting of Density Functional Theory, Cluster Expansion, Monte Carlo simulations and Ab Initio Molecular Dynamics, is employed for composition screening. β phase stability and β‐ω continuous slip barriers are precisely tailored to provide large chemical driving force for MT while suppressing excessively slip priority. After simple thermomechanical processing, selected Ti‐7.92Mo‐3.22Cr‐1.88Zr alloy exhibits dense TRIP/TWIP networks and record yield strength‐ductility synergy (product exceeding 38 GPa%). Premature necking is delayed by ω‐confined elevated local stress promoting MT followed by sequential transformation from strain‐induced martensite to {332}〈113〉β deformation twins, thus forming an extended ≈23.2% Lüders‐type strain. These theoretical and experimental results provide implementable and individual strategies to overcome yield strength‐ductility trade‐off by reconciling precipitation strengthening with TRIP/TWIP effects.

Arroussi, Abdelaziz, Laksaci, Hamza, Djaafri, Mohammed et al.

The pollution of water resources by hazardous contaminants is a major obstacle to the provision of safe and potable water worldwide. Cost-effective, innovative, renewable, and environmentally friendly technologies are essential for wastewater treatment. In the current work, the potential of using raw date palm petiole (DPP) for the removal of Bezaktiv Marine S-BL (SBL) dye is investigated under a wide range of experimental conditions in batch mode. Experimental results show that the removal of SBL dye by DPP is highly dependent on contact time, initial pH, initial dye concentration, and temperature. The removal of SBL dye is relatively rapid where the equilibrium state is reached within a contact time of 120 min. Moreover, the biosorbent exhibits high stability in SBL adsorption ability over a wide pH range (4–12). Furthermore, the SBL dye adsorption increases with increase in initial concentration. The maximum adsorption capacity of the SBL dye on DPP is evaluated to be 110 mg/g, which is much higher than numerous other materials. In addition, a thermodynamic study indicates that the adsorption of SBL dye by DPP is a feasible exothermic and spontaneous process.The findings of the present study indicate that untreated DPP wastes can be considered effective materials for the treatment of textile dyes in wastewater in general and SBL in particular.

F. Abbate, A. Carleo, S. Chatterjee et al.

The detection of a pulsar closely orbiting our Galaxy's supermassive black hole - Sagittarius A* - is one of the ultimate prizes in pulsar astrophysics. The relativistic effects expected in such a system could far exceed those currently observable in compact binaries such as double neutron stars and pulsar white dwarfs. In addition, pulsars offer the opportunity to study the magneto-ionic properties of Earth's nearest galactic nucleus in unprecedented detail. For these reasons, and more, a multitude of pulsar searches of the Galactic Centre have been undertaken, with the outcome of just seven pulsar detections within a projected distance of 100 pc from Sagittarius A*. It is currently understood that a larger underlying population likely exists, but it is not until observations with the SKA have started that this population can be revealed. In this paper, we look at important updates since the publication of the last SKAO science book and offer a focused view of observing strategies and likely outcomes with the updated SKAO design.

J. Miao, P. Ercius, S. Billinge

Yongchao Zhang, Man Liu, Caimei Liu et al.

The adhesive layer is an important factor affecting the mechanical properties of FRP- bamboo scrimber composite beams (FBSCB). However, studies on the interfacial shear stresses in the adhesive layers with both ends of FRP and bamboo scrimber beam aligned have been rarely reported. To this end, a two-parameter theoretical calculation model and a finite element model (FEM) based on cohesive zone model were hereby established to solve for the adhesive layer interface shear stresses, which was verified by four-point bending experiments. The results show that both the two-parameter theoretical model and the FEM can effectively compute the shear stress of the adhesive layer. Meanwhile, the FEM simulation results not only reflect the detailed changes of the shear stress, but also provide a better analysis of the shear stress at the adhesive layer with a small fluctuation range. There are three zones of shear stress at the adhesive layer of FBSCB under four-point bending load, i.e., the bending and shearing zone, the transition zone and the pure bending zone. In the bending and shearing zone, the shear stress of the adhesive layer interface increases 2.61 times and 2.5 times, respectively when the thickness and elastic modulus of FRP increase three times. However, the stress remains constant at zero in the pure bending zone.

Xiangyue Kong, Lingling Zhan, Zhongjie Li et al.

Abstract The multi‐component strategy has proven effective in advancing the performance of organic photovoltaics (OPVs), enhancing photocurrent and fill factor through spectral complementarity and morphology optimization. However, the open‐circuit voltage (VOC) mechanism in multi‐component systems lacks systematic investigation. In this study, we explore the influence of alloy‐like phases on energy level distribution and energy loss mechanisms in multi‐component OPVs. Appropriate modulation of donor alloy‐like phases maintains the original intermolecular stacking, enhances component compatibility, reduces acceptor aggregation, and improves acceptor phase purity, mitigating non‐radiative recombination losses. Additionally, suitable alloy‐like phase modulation elevates charge transfer (CT) states, reducing the gap between CT and local exciton state, lowering reorganization energy, and alleviating radiative recombination loss below the bandgap. Through synergistic optimization (layer‐by‐layer method with solid additive), ternary devices based on Y6 acceptor achieve a notable 19.41% power conversion efficiency, offering new insights for the analysis of the energy loss of the multi‐component OPVs.

Hanzhong Liu, Yongda Yan, Jiwen Cui et al.

Micro diamond tools are indispensable for the efficient machining of microstructured surfaces. The precision in tool manufacturing and cutting performance directly determines the processing quality of components. The manufacturing of high-quality micro diamond tools relies on scientific design methods and appropriate processing techniques. However, there is currently a lack of systematic review on the design and manufacturing methods of micro diamond tools in academia. This study systematically summarizes and analyzes modern manufacturing methods for micro diamond tools, as well as the impact of tool waviness, sharpness, and durability on machining quality. Subsequently, a design method is proposed based on the theory of cutting edge strength distribution to enhance tool waviness, sharpness, and durability. Finally, this paper presents current technical challenges faced by micro diamond tools along with potential future solutions to guide scientists in this field. The aim of this review is to contribute to the further development of the current design and manufacturing processes for micro diamond cutting tools.

Bin Chen, Yanan Zhu, Minkui Lin et al.

Abstract Endo-periodontal lesions (EPLs) involve both the periodontium and pulp tissue and have complicated etiologies and pathogenic mechanisms, including unique anatomical and microbiological characteristics and multiple contributing factors. This etiological complexity leads to difficulties in determining patient prognosis, posing great challenges in clinical practice. Furthermore, EPL-affected teeth require multidisciplinary therapy, including periodontal therapy, endodontic therapy and others, but there is still much debate about the appropriate timing of periodontal therapy and root canal therapy. By compiling the most recent findings on the etiology, pathogenesis, clinical characteristics, diagnosis, therapy, and prognosis of EPL-affected teeth, this consensus sought to support clinicians in making the best possible treatment decisions based on both biological and clinical evidence.

Hamid reza Motahari, Mahmoud Bakhtiari

Abstract Shiism experienced a significant crisis following the tragedy of Ashura characterized by oppression, fear, isolation, and the practice of taqiyyah. This study focused on the strategies employed by Imam Sajjad (A.S.) to revive Shiism in the aftermath of this event. Specifically, it addressed this question: How can we analyze Imam Sajjad’s strategies for revitalizing Shiism after the Ashura event? It appeared that Imam Sajjad (A.S.) utilized components of diffusion theory—namely, the destination of diffusion (environments that were both receptive and intolerant, along with political and cultural barriers), paths of diffusion (including displacement, contagious, and hierarchical diffusion), and timing of diffusion. By leveraging various tools, such as the community's reverence for the Prophet’s family, he transformed the emotional landscape created after Ashura, mitigating the effects of the oppressive Umayyad regime and countering the influence of pro-Umayyad scholars. Through initiatives like cadre building and promoting pilgrimage, he effectively revived Shiism after the Ashura event. This research elucidated Imam Sajjad's actions through the lens of diffusion theory, demonstrating how Shiism was revitalized in the wake of Ashura. Employing a historical methodology, the study analyzed Imam Sajjad's activities aimed at reviving Shiism, including cadre development, exposing Umayyad injustices, mobilizing the populace post-Karbala, challenging beliefs in predestination, elucidating the fundamental principles of Imamate, addressing key issues, and countering deviation through prayer and supplication.   Keywords: Strategies of Imam Sajjad (A.S.), Revival of Shiism, Ashura Event, Diffusion Theory, Umayyad Era.   Introduction The era of Imam Sajjad (A.S.), which commenced on Ashura in 61 AH, unfolded under exceptional circumstances. The oppressive measures of the Umayyads coupled with the suppression of dissenting movements and emergence of deviant intellectual currents underscored the urgent need for the revitalization of Shiite life. In light of the political, social, and cultural conditions of his time, Imam Sajjad (A.S.) adopted various approaches to articulate the teachings of the Ahl al-Bayt, employing methods, such as prayer and pilgrimage. This study sought to analyze how Imam Sajjad (A.S.) revived Shiism following the Ashura event and identify the factors that influenced this revival. Several books and articles have been published regarding Imam Sajjad's role in the resurgence of Shiism. Notably, Seyyed Ja'far Shahidi's Life of Ali ibn al-Hussein (2001) examined and critiqued some well-known historical accounts of Imam Sajjad (A.S.). While this work shared common themes with the present research, it offered a new perspective by integrating theoretical frameworks. Additionally, Mohsen Ranjbar's Studying the Role of Imam Sajjad (A.S.) in Shiite Leadership after the Karbala Incident (2002) explored the cultural and political landscape of Imam Sajjad's era, focusing on his stance against the caliphate. However, this article distinguished itself by analyzing the environmental factors and components of diffusion theory relevant to Imam Sajjad's context. Another significant work was Madrasah Kalami Medinah from the Beginning to the Imamate of Imam Baqir (2024) written by Seyyed Ali Hussainizadeh from Khizrabad, which reviewed the history of Imamiyyah thought up to the end of Imam Sajjad's era through historical reports. Unlike the other two works, it did not provide an analysis of Imam Sajjad (A.S.) based on diffusion theory. Finally, Seyyed Gholam Hossein Hosseini's article, Headlines of the Political Movement of Imam Sajjad (A.S.) in the Karbala Movement (2002), touched upon similar themes; yet, it did not specifically apply diffusion theory, revealing a gap in independent research on this topic.   Materials & Methods Diffusion theory introduced by Swedish geographer Hagerstrand in 1935, explored how innovations, phenomena, ideas, and thoughts spread. Initially applied to agriculture and disease transmission, this theory has since found relevance in political science and international relations. It effectively explains the reasons behind the spread of various intellectual and physical innovations, detailing how they disseminate, the pathways they follow, and the factors that may halt or re-ignite their spread. Additionally, it accounts for the stability of certain trends and the decline of others. In the modern era, cultural elements and innovations cross borders at unprecedented speeds, akin to jet travel and satellite communication. Contagious and hierarchical diffusion represent two rapid forms of expansion diffusion, where ideas and concepts migrate from new sources without the need for physical relocation. When analyzing the impact of any political innovation through the lens of diffusion theory, key factors like origin and destination, timeframes, tools, and channels of dissemination are considered. Furthermore, diffusion barriers and competing waves serve as mitigating factors that must be addressed in the examination of the phenomenon and its diffusion.   Research Findings Imam Zayn al-Abidin (A.S.) aimed to restore order in a society that had succumbed to misguidance and moral decay, striving to revive authentic Islam (Shi'a). Alongside the Sahifa al-Sajjadiyah, which encapsulates the principles and teachings of Islam, the Treatise on Rights outlines fundamental rights that govern human life and ensure its happiness. Indeed, religion and Sharia were revealed to uphold these rights. Through this guidance, the Imam demonstrated that only an Imam, intimately connected to the source of revelation, possesses the authority to enact progressive laws that resonate with the human spirit.   Discussion of Results & Conclusion The continuation of Umayyad rule under Yazid and Abdul Malik ibn Marwan following the martyrdom of Imam Hussein (A.S.) coupled with the atmosphere of fear and repression that ensued after the Ashura event posed significant challenges for Imam Sajjad (A.S.) in his efforts to revive and expand Shiism. Despite these obstacles, Imam Sajjad (A.S.) emerged as a pivotal figure in this revival, leveraging the emotional climate following events, such as the incident of Hurra and the destruction of Kaaba by Yazid's forces, alongside the public’s growing interest in the Prophet's family. To navigate the unwelcoming environment, the Imam implemented several strategies: he focused on training and building a cadre of supporters, exposed the injustices of the Umayyad regime, and sought to awaken the populace in the aftermath of Karbala. He also challenged the legitimacy of predestination and clarified the fundamental principles of Imamate. Through prayers and invocations, he addressed key issues and countered deviations, significantly advancing his goals. Utilizing methods like prayer and pilgrimage (path of diffusion) and disseminating religious concepts through his students and trained followers (path of contagion), Imam Sajjad (A.S.) endeavored to revive Shiism even amid the oppressive rule of the most tyrannical Umayyad caliphs, including Yazid and Abdul Malik ibn Marwan. This period marked a crucial phase in the diffusion of Shiism.

Wenhao Yang, Yanjun Zhou, Ran Yang et al.

Cu–15Ni–8Sn-xNb alloys (x = 0, 0.2, 0.6 wt%) were prepared using a medium-frequency induction melting furnace. The effect of Nb addition on grain refinement and inhibition of discontinuous precipitation (DP) in Cu–15Ni–8Sn alloys was systematically studied to elucidate the mechanism by which microstructural characteristics contribute to strength improvement. The results indicate that the increase the Nb content from 0 to 0.6 wt% reduces the average grain size of the as-cast alloy from approximately 524.8 μm to approximately 81.3 μm, and significantly decreases the lamellar transition structure region (α+γ). During solution treatment, dispersed needle-like NbNi3 phases were observed in the Cu–15Ni–8Sn-0.2Nb alloy. After aging, the DP growth rate in the Cu–15Ni–8Sn-0.2Nb alloy was notably slower than those of the other alloys. This was attributed to NbNi3 phases at the grain boundaries hindering DP nucleation, with intragranular NbNi3 phases inhibiting DP growth. The phase transformation order of the solid solution Cu–15Ni–8Sn-0.2Nb at 673 K aging is: spinodal structure → D022 ordered phase → L12 ordered phase → DP. The hardness and tensile strength of the Cu–15Ni–8Sn-0.2Nb alloy peaked at 338.3 HV and 725.42 MPa, respectively, after aging for 120 min. Using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) and Arrhenius equations, the activation energies of DP in Cu–15Ni–8Sn-xNb (x = 0, 0.2, 0.6 wt%) alloys were calculated to be 93.19, 148.64, and 98.33 kJ/mol, respectively. These values suggest that the diffusion of DP atoms in the Nb-containing alloys is hindered, which effectively inhibits DP formation.

Luis Enrique Rosas-Hernandez, Jose Luis Cabellos, Angiolo Huamán et al.

Atoms within moiré bilayers relax in-plane to minimize elastic energy [e.g., Cazeaux et al., J. Elast. 154, 443 (2023)]; such relaxation brings their space group symmetries down to P1. Here, the ab initio second harmonic generation (SHG) of twisted and atomistically optimized hBN bilayers was determined at four twist angles ($θ=38.21^{\circ}$, $60.00^{\circ}$, $73.17^{\circ}$, and $98.21^{\circ}$) and for three displacements $\boldsymbolτ$ measured away from the ground state $AA^{\prime}$ configuration. All moiré bilayers have a P1 space symmetry after structural optimization. This situation is quite different to monolayers with hexagonal lattices, which retain a three-fold symmetry. We point out that the actual symmetries of the SHG reported for hBN bilayers on two experimental works do not coincide with the sixfold symmetric theoretical profiles they provide [either $\sin^2(3φ)$ or $\cos^2(3φ)$], and show that the intrinsic low structural symmetry of (atomically optimized) hBN bilayer moirés can in fact be read out from experimental SHG intensity profiles--which are tunable by $θ$ and by the frequency of light $ω$: The SHG is most definitely not sixfold-symmetric because moirés do not retain a three-fold symmetry. Furthermore, an extrinsic twofold symmetry of the SHG emission is realized by tilting the pump by an angle $α$ away from the 2D material's normal, regardless of $θ$ and $ω$. The design of in-plane and ultrathin sources of SHG with low symmetry could be useful for the eventual creation of entanglement sources from 2D materials.

Si-Qi Huang, Li-Li Wang, Qing-Qing Pan et al.

Recently, non-fullerene-based organic solar cells (OSCs) have made great breakthroughs, and small structural differences can have dramatic impacts on the power conversion efficiency (PCE). We take <b>ITIC</b> and its isomers as examples to study their effects on the performance of OSCs. <b>ITIC</b> and <b>NFBDT</b> only differed in the side chain position, and they were used as models with the same donor molecule, <b>PBDB-T</b>, to investigate the main reasons for the difference in their performance in terms of theoretical methods. In this work, a detailed comparative analysis of the electronic structure, absorption spectra, open circuit voltage and interfacial parameters of the <b>ITIC</b> and <b>NFBDT</b> systems was performed mainly by combining the density functional theory/time-dependent density functional theory and molecular dynamics simulations. The results showed that the lowest excited state of the <b>ITIC</b> molecule possessed a larger ∆<i>q</i> and more hybrid FE/CT states, and <b>PBDB-T/ITIC</b> had more charge separation paths as well as a larger <i>k</i>_CS and smaller <i>k</i>_CR. The reason for the performance difference between <b>PBDB-T/ITIC</b> and <b>PBDB-T/NFBDT</b> was elucidated, suggesting that <b>ITIC</b> is a superior acceptor based on a slight modulation of the side chain and providing a guiding direction for the design of superior-performing small molecule acceptor materials.