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2. chinaXiv:202203.00068 [pdf]

A Laser-Shock-Enabled Hybrid Additive Manufacturing Strategy with Molten Pool Modulation of Fe-based Alloy

Jian Liu; Shusen Zhao; Xiaohan Zhang; Xuechun Lin; Yaowu Hu
Subjects: Materials Science >> Materials Science (General)

A novel hybrid laser additive manufacturing process based on laser shock modulation of molten pool was proposed in this work. The flow behavior residual stress, and microstructure of the molten pool were comprehensively characterized by a combination of experiments and simulations. The relationship between the convection behavior, evolution of microstructure, and enhancement of residual stress induced by laser shock modulation was established. Laser shock modulation assisted additive manufacturing process exhibits high efficiency in residual stress control. The hidden mechanism in microstructure evolution and residual stress enhancement was expected to be related to intensified molten pool convection, uniform solute distribution and improved cooling rate induced by shock wave. The hybrid additive manufacturing process strategy based on laser shock modulation provides a new approach for heat and mass modulation in hybrid manufacturing.

submitted time 2022-05-31 Hits3477Downloads486 Comment 0

3. chinaXiv:202205.00036 [pdf]

热挤压聚甲基戊烯的飞秒激光内部改性

朱广宇; 向静; 周登梅; 李鹏; 欧汉文; 陈西浩
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics

本文研究近紫外飞秒激光脉冲在聚甲基戊烯内部刻写的应用技术。我们发现该热塑材料具有偏振敏感性的特征。首先刻写实验使用数字孔径为0.05的透镜聚焦, 通过对超连续光谱的分析,测得稳定成丝刻写的激光脉冲功率在2.2MW - 9.2MW区间内,并由此推断该种材料的非线性折射率为n2387=2×10-16cm2W-1,推算三阶susceptibility χ(3)为    1.1×10-14esu。稳定成丝加工长度在300μm-1500μm。然后,实验使用数字孔径为0.4的组合物镜聚焦刻写厚度为~700μm,栅距为5μm的布拉格光栅。通过对光栅产品的衍射效率测试,推断最大折射率的变化为~0.01,这比文献中的记录数据,提高一个数量级。实验结果证明了激光脉冲峰值强度对于诱导非线性吸收的重要性,而双光子吸收为温和可控改性的物理机制。本工作为科研人员和光学器件设计和制作提供了最新的参考。

submitted time 2022-05-08 Hits1953Downloads286 Comment 0

4. chinaXiv:202203.00027 [pdf]

Modifying the crystallization process of Cu2ZnSn(S,Se)4 by controlling the micro-structures of precursor films

Gao, Chao; Li, Wenbo; Zhou, Qing; Zhou, Xiaowei; Gao, Haifeng; Xu, Haoyu; Qin, Shumin; Gao, Zeran; Yu, Wei
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials

In this paper, we reported a method to modify the crystallization of CZTSSe films by changing the microstructures of the precursor films. Precursor films with different microstructures were prepared and their crystallization processes were analyzed. We find even tiny differences in microstructures of the precursor films can result in significant alteration of the crystallization processes and the properties of CZTSSe films. Moreover, we found the S-to-Se substitution can be delayed to higher temperature depending on the microstructure of the precursor. This process plays critical roles in enhanceing the crystallization of CZTSSe films and can be used to eliminate the multi-layer crystallization in CZTSSe films. The detailed analysis on the crystallization processes revealed that different mechanism may dominate the crystallization of the films, which can determine the properties of CZTSSe films and solar cells. Moreover, a hybrid structure for precursor film was proposed which has different microstructures in different part of the film. In such a precursor film, different crystallization mechanism can work synergically during the preparation of the film. As the results, the comprehensive properties of the films were improved and solar cells with efficiencies up to 12.6% was prepared.

submitted time 2022-03-07 Hits3426Downloads413 Comment 0

5. chinaXiv:202108.00096 [pdf]

湿法制备碳纤维增强热塑性树脂复合材料的固化模型及其验证

颜鑫
Subjects: Materials Science >> Composite Material

In recent decades, carbon fiber reinforced thermoplastic from the wet-laid process (WL-CTP) appeals to attention for its simplicity and compatibility with recycled carbon fibers. However, there is still no constitutive model for the consolidation of WL-CTP. This study proposes a constitutive model based on the constitutive equation describing the compress behavior of the dry/impregnated CF network. Three deductions raised from the consolidation model were validated by the experiments investigating the effect of molding time, pressure, and temperature on the void volume fraction of the WL-CTP. Flexural testing further investigated the effect of molding time, pressure, and temperature on the flexural modulus and strength of the WL-CTP. It reveals that the molding pressure can be the only factor affecting the consolidation and flexural properties of the WL-CTP, which indicates that the WL-CTP with low void content and qualified mechanical properties can be produced under a relatively low temperature and high productivity.

submitted time 2021-08-13 Hits11547Downloads1165 Comment 0

6. chinaXiv:202009.00051 [pdf]

Obtain weighted values of solar stills’ environment factors by using supervised machine learning

王云鹏; 彭桂龙; 杨诺; Swellam W. Sharshir ; AbdAllah W. Kandeal
Subjects: Materials Science >> Nanoscience and Nanotechnology

太阳能蒸馏器由于其简单的结构和环保的能力,近年来引起了越来越多的关注。在本研究中,利用一种成熟的机器学习算法——随机森林,得到环境因子对蒸发效率的加权值。为了检验随机森林与数学数据分析之间的先进性,我们采用了两种传统的数据科学方法——配对图法和皮尔逊相关分析法进行比较。分析中使用的实验数据来自2014年以来的约100篇文章。结果表明,热设计是实现太阳能高效蒸发的最重要因素。这将促进太阳能蒸馏器蒸发效率的研究。

submitted time 2021-03-26 Hits20986Downloads1613 Comment 0

7. chinaXiv:202008.00083 [pdf]

Delocalized Electrochemical Exfoliation toward High-throughput Fabrication of High-quality Graphene

Penglei Zhang; Peng Heng; Qingkai Yu; Gang Wang; Tao Huang; Siwei Yang; Xiaosong Liu; Zhi Liu; Xiaoming Xie; Guqiao Ding
Subjects: Materials Science >> Materials Science (General)

Graphene has well demonstrated its unique properties and advantageous performances in lots of fields during the last 16 years. However, its industrial applications are still impeded by inefficient mass fabrication of high-quality graphene because of the great challenge in deep yet non-destructive graphite exfoliation. Herein, we demonstrated a delocalized electrochemical exfoliation (DEE) technique to efficiently fabricate high-quality graphene. Importantly, chemically transmitting the electric potentials was firstly proposed to spatially extend the exfoliation capability of electric potentials and electrochemically exfoliate every graphite particle dispersed in the electrolyte. The resulting graphene possesses ultralow defect density (ID/IG~0.07) and extremely high carbon-to-oxygen ratio (~28). Remarkably, high yields (~98.4%, 1-10 layers) and record high production rates (~72.7 g h?1) are realized in up-scaled batch of DEE. Further mechanism investigation revealed that the exfoliation capability of the electric potentials was transmitted to the whole electrolyte system by a dynamically favorable pathway. This pathway includes electrochemical oxidation, intercalation and interlayer bubble generation reactions, which makes deep and non-destructive exfoliation possible for every dispersed graphite particle in a scalable and reproducible manner. This way of using electric potentials differs from existing electrochemical methods and guarantees high throughput as well as high quality. The strategy of delocalized electrochemical exfoliation and the underlying concept of chemically transmitting the electric potentials would accelerate the commercialization of graphene and inspire more efficient fabrication of two-dimensional materials.

submitted time 2020-08-12 Hits18820Downloads1999 Comment 0

8. chinaXiv:202001.00046 [pdf]

A general self-consistent framework for studying cumulative displacement damage in nanostructured metals based on parameter passing and structural feedback between atomic and coarse-grained techniques

Xiangyan Li; Yange Zhang; Yichun Xu; Xuebang Wu; Xianping Wang; B.C. Pan; C.S. Liu; Q.F. Fang; Jun-Ling Chen; G.-N. Luo; Zhiguang Wang; X. Liu
Subjects: Materials Science >> Materials Science (General)
Subjects: Materials Science >> Metals and Alloys

Nano-crystalline metals (NCs) exhibit radiation-tolerance due to the sink of grain boundaries (GBs) for radiation-induced defects such as self-interstitial atoms (SIAs) and vacancies (Vs). However, the relevant mechanisms for the radiation damage accumulation and GB structural relaxation under high radiation field in NCs are still not well understood due to the lack of self-consistent across-scale techniques for simulating radiation-induced microstructures evolution. In this article, by combining coarse-grained and atomistic simulations, we proposed a coupling method to investigate the evolution of the microstructure and SIA/V-GB interaction under cumulative irradiation in NC iron. The SIA overloaded effect was revealed in iron GBs at a high radiation dose rate and/or low temperature. Two types of GB structural response were observed to cumulative irradiation. With the SIA accumulated at the GB, the new GB phase formed and then a critical concentration of the SIA at the GB transited to the small quantity of the V during the GB structural recovery, accompanied by the local GB motion. Consequently, the GB’s role for Vs nearby alternated between the trapping and annihilation center with radiation dose. Alternatively, GB developed to a disordered structure after trapping abundant SIAs. The GB response pattern to cumulative irradiation that is related to the SIA formation energy at the GB or the GB thermal stability is well manifested in the cumulative distribution function of the defects formation energy and its energy level density. The present work reveals the dynamic healing picture for radiation damage near the GB under cumulative irradiation.

submitted time 2020-01-07 Hits32155Downloads2077 Comment 0

9. chinaXiv:201904.00103 [pdf]

A Novel Narrow-Band Green-Emitting Phosphor CsKNaLi(Li3SiO4)4 with the UCr4C4-Related Type Structure

师进生; 王丽丽; 孔晓颖; 李鹏; 兰学芳; 陈倩
Subjects: Materials Science >> Electronic, Optical and Magnetic Materials

我们成功合成了CsKNaLi(Li3SiO4)4:Eu2+ (CKNLLSO:Eu2+)作为UCr4C4型结构氧基家族的新成员。该荧光粉的基质化合物的晶体结构和能带结构分别通过Rieveld精修方法和密度泛函理论分析和计算。由于高度压缩和刚性的阴离子骨架,取代Cs格位的Eu2+在InGaN基紫外LED的激发下,发出了明亮的绿色荧光,半峰宽为55 nm.当温度升高到190℃时,CKNLLSO:Eu2+的稳定性仍然较好。采用浓度优化的CKNLLSO:4%Eu2+制成的LED器件发出的绿光的色坐标为(0.2320, 0.6016),相关色温为7314K。分析结果表明,这种荧光粉是一种很有前景的白光LED绿色荧光粉。

submitted time 2019-04-30 Hits34776Downloads2717 Comment 0

10. chinaXiv:201902.00003 [pdf]

Magnetic field-dependent reversal effect of the electromagnet- induced normal stress of magnetorheological materials

Taixiang Liu; Yangguang Xu; Ke Yang; Lianghong Yan; Beicong Huang; Zhuo Zhang; Xiaodong Jiang; Hongwei Yan
Subjects: Materials Science >> Materials Mechanics

Magnetorheological (MR) materials are a type of magnetoactive smart materials, whose physical or mechanical properties can be altered by applying a magnetic field. In usual, MR materials can be prepared by mixing magnetic particles into non-magnetic matrices. In this work, the electromagnet-induced (or non-uniform magnetic field-induced) normal stress of MR materials is studied. It shows that the stress does not vary monotonically along with the enhancement of the applied magnetic field. There exists a field-dependent reversal effect of the variation of the stress. The reversal effect is thought resulting from that the ratio of interparticle repellent of parallel magnetic particles to the particle-electromagnet attraction gets enlarged along with the enhancement of the field.

submitted time 2019-02-01 Hits32448Downloads2431 Comment 0

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