CRYSTENGCOMM
·
2016
·Vol. 18
·期 7
·1139-1146
·
IF 3.849
Xue Mao,Haoru Shan,Jun Song,Ying Bai,Jianyong Yu,Bin Ding
The study of nanocrystalline inorganic nanofibrous membranes (NINMs) with flexibility is one of the most active academic research areas in advanced functional nanofibrous materials. Nonetheless, the role of nanocrystallinity in flexibility has remained uninvestigated until now, according to typical Hall–Petch effects of nanocrystalline metals. Here, we show a surprising brittle-to-flexible-to-brittle transition of zirconia and yttria stabilized zirconia (YSZ) nanofibrous membranes as the grain size and pore size reduce below 26 and 13 nm, respectively. Moreover, classical and inverse Hall–Petch effects were revealed in nanocrystalline zirconia and YSZ nanofibrous systems, which correspond to intragranular and intergranular deformation mechanisms, respectively. Most importantly, the bending deformation mechanism of the flexible nanocrystalline YSZ nanofibrous membranes was proposed from macroscopical membranes to microscopic unit cells, including the slip of fibers, bending of fibers, grain activity, and dislocation motions, which was given for the first time in electrospun flexible NINM materials. Our discovery is fundamentally important for understanding deformation behavior and designing various flexible NINMs as promising candidates in the field of catalysis, supercapacitors, biomaterials, etc.
研究领域:
材料科学
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纳米技术
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS
·
2021
·
IF 3.871
Hairui Xing,Ping Hu,Jiayu Han,Shilei Li,Songwei Ge,Xingjiang Hua,Boliang Hu,Fan Yang,Kuaishe Wang,Pengfa Feng
Molybdenum metal have high brittleness and ductile-to-brittle transition temperature (DBTT) due to the existence of interstitial oxygen impurities, so it is of great scientific significance to strictly control and accurately analyze the oxygen content. In this work, the effects of oxygen on microstructure and evolution mechanism of body-centred-cubic metallic molybdenum are studied. The X-Ray diffraction (XRD), oxygen nitrogen analyzer, scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and electron probe micro-analyzer (EPMA) are used to analyze the chemical composition, microstructure, oxygen existence and distribution form. The results demonstrate that Mo O specimens with up to 3300 ppm of oxygen content have single-phase body-centered cubic microstructure with no precipitates. When the oxygen content in molybdenum increases from 44 ppm to 2200– 3300 ppm, more oxygen exists in the pores between molybdenum grains, and the fracture mode changes from intergranular fracture to intergranular and transgranular mixed fracture. The microhardness increases with increase of oxygen content. These results provide new ideas for controlling the change trend of oxygen in molybdenum and regulating the properties of molybdenum.
研究领域:
材料科学
·
金属学
✓ 已验证
产品关联
DOI
高影响因子
Materials
·
2023
·Vol. 16
·期 14
·4941
·
IF 3.4
Wei Liu,Fubing Bao,Yinning Zhang,Jinqing Wang,Xiaoyu Liang
The brittle failure of ceramic coatings limits their application in many fields. To address this issue, a novel armoured ceramic coating was developed to suppress brittle failure. First, an interconnected frame microstructure was micromachined onto the surface of a mild steel substrate using a nanosecond laser. Subsequently, a polymer-derived ceramic slurry was sprayed and sintered to obtain an armoured ceramic coating. The laser-micromachined burr-like microstructure of the substrate facilitated adhesion between the coating and the substrate. The results of the mechanical properties test showed that the armoured coating could withstand more than 20 cycles of water-cooled thermal shock at 600 °C, and the peeling area of the armoured coating was approximately three times less than that of the unarmoured coating under a normal load of 1471 N. The laboratory and field corrosion test results indicated that at high temperatures, the corrosion resistance of the armoured coating was comparable with that of the unarmoured coating and was approximately 10 times higher than that of the uncoated sample. The proposed method will aid in suppressing the brittle failure of ceramic coatings and broaden their scope of application in different fields.Keywords:ceramic coatings;armour structure;brittle failure;corrosion resistance
研究领域:
材料科学
·
机械工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ACTA MECHANICA SOLIDA SINICA
·
2024
·
IF 2
Liu Qiuhong,Sun Shuo,Wu Xiang,Chen Zhiqiang,Guo Hongjie,Duan Chen,Wang Zhengjin
Brittle materials, such as silicon, glass, and ceramics, are widely used in engineering via adhesive bonding. The assessment of adhesive strength of brittle materials to other adherends is essential for their applications. Compared with metals and composites, for which standard testing methods have been established, the experimental method for brittle adherends has been much less explored. During the adhesive strength test, the brittleness of these materials makes them prone to failure, rather than the interface. It remains a challenge to measure the adhesive strength of brittle adherends. Here we develop an experimental method to address this issue by using a strap joint specimen with a backing layer. We use a single crystal silicon wafer and two PCB (printed circuit board) strips as adherends to make a strap joint specimen. A steel backing layer is glued to the silicon wafer to prevent the failure of silicon. This method enables the measurement of adhesive strength up to 35 MPa. In contrast, that without backing layer can only measure the adhesive strength below 10 MPa. It is found that the backing layer can reduce the stress in the silicon remarkably, while it has much less effect on the stress in the adhesive layer. We confirm that the backing layer has a negligible effect on the measured adhesive strength but expands the working space greatly. Combining finite element analysis and experiments, we establish the phase diagram for the failure modes. This work provides guidance for the measurement of adhesive strength of brittle materials.
研究领域:
工程学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Coatings Technology and Research
·
2024
·
IF 2.3
Ling Chen,Zhou Rudong,Xiang Yanli,Fang Jianbo,Meng Xu,Ren Qiang,Wang Chenyi
Solvent-free epoxy-based intumescent fire-retardant coatings are of significant importance in harsh environments, such as petrochemical facilities, due to their excellent overall protection performance. However, the challenge of low-temperature brittleness and limited intumescence resulting from a highly crosslinked structure still persists. In this study, epoxy-terminated polyester oligomers with an asymmetric structure and low viscosity were synthesized using azelaic acid (AA) and dodecanedioic acid (DA) as dibasic acids with odd and even carbon numbers to address this challenge. The chemical structures of these polyester were thoroughly characterized. Among them, the polyester prepared with a molar ratio of 1:3 for AA and DA (ADE) was optimized as a suitable toughener for solvent-free intumescent fire-retardant coatings based on E-51 epoxy resin. The influence of ADE dosage on thermal stability, fire resistance performance, flexibility, and freeze cracking resistance was investigated in detail. The findings demonstrated that incorporating 50% ADE in ADE/E-51 blends resulted in coating film with an appropriate glass transition temperature and thermal deformation property to match the intumescence behavior of intumescent flame-retardant system. The coating formulated in this way exhibited the best fire protective performance, toughness and freeze cracking resistance.
研究领域:
材料科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
RSC Advances
·
2022
·Vol. 12
·期 47
·30734-30741
·
IF 4.036
Caihong Su,Yancai Li,Jiabin Zhu,Yuan Gao,Qi Li,Shuangkui Du,Xiuzhu Yu
The present study aimed to decrease the brittleness of flaxseed oleogels based on candelilla wax (CLW) in combination with flaxseed gum (FG). Effects of flaxseed gum concentrations (0–0.4%) on the characteristics of flaxseed oleogels including oil binding capacity, textural, thermal, and rheological properties, and crystal polymorphisms were investigated. Higher concentrations (≥0.2%) of FG significantly decreased the textural parameters (e.g., hardness, fracturability) of oleogels (p < 0.05), suggesting that FG could decrease brittleness. Rheological results indicated that all flaxseed oleogels exhibited solid-like characteristics because the elastic modulus was larger than the viscous modulus. The elastic modulus of flaxseed oleogels presented a maximum value at 0.1% gum concentration. Any increase in gum concentration beyond this concentration decreased the elastic modulus. Increasing FG concentration up to 0.4% decreased the enthalpy of flaxseed oleogels during the melting process. The β′-polymorphic form is an orthorhombic perpendicular (O⊥) subcell structure. Similar β′ crystal forms were observed among flaxseed oleogels, indicating that FG did not affect them negatively. The study showed that the physical properties of flaxseed oleogels based on CLW could be significantly changed by FG addition. These results provided a deeper comprehension of the novel system, which should be considered a new way to obtain healthy fats with better plasticity for food applications.
研究领域:
食品科学
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材料科学
✓ 已验证
DOI
PubMed
高影响因子
MACROMOLECULES
·
2021
·
IF 5.985
Guozhang Wu,Yuanbiao Liu,Gaopeng Shi
Providing a thermodynamic basis to kinetic fragility has been pursued for decades. This objective is particularly challenging for glass-forming polymers because of the difficulty in gauging configurational excess entropy ΔSex. Herein, we report that enthalpy hysteresis ΔHR determined from a well-defined cooling and subsequent heating cycle of heat capacity curves bears a proportional relationship with α-related excess enthalpy at the glass transition temperature (Tg). Correlations of fragility (me) with ΔHR and heat capacity jump ΔCP at Tg are explored in a broad range of polymers, including monodispersed polystyrene with a molecular weight of 580–2 400 000, homopolymers with a fragility ranging from 50 to 200 and Tg ranging from 200 to >400 K, and copolymers and polymer/small-molecule mixtures with different compositions and varied intermolecular strengths. Surprisingly, all of the presented data follow me = 0.75ΔCP·Tg/ΔHR + 15, a formula that can be theoretically derived from the Adam–Gibbs equation if the prefactor τ0 is given at 10–13 s. These experimental results not only provide a possible routine for estimating the α-related excess entropy of noncrystallizable polymers but also validate the thermodynamic link to the kinetic fragility of glass-forming polymers.
研究领域:
材料科学
·
高分子物理
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2025
·
IF 6.3
Xingzhan Yuan,Shi Hong,Jing Wang,Bing Ma,Yifan Zhang,Man Niu,Laima Luo,Yucheng Wu
In this study, we propose a model to evaluate the ductile-to-brittle transition (DBT) of W based alloy using small tensile test and dislocation density measurement. The new model is built upon the high correlation between the DBT and the dislocation multiplication. Compared the measured results from the typical testing methods such as small tensile test, three-point bending test, it reveals that the new model is close to the bending test results. Interestingly, the equivalent transition temperature (ETT) of W-Y 2 O 3 alloy measured by three-point bending test and the new model is lower than that of pure W. The effect of grain boundary and Y 2 O 3 particles on DBT were discussed, and the lower transition temperature of W-Y 2 O 3 alloy is attributed to the easier dislocation multiplication near grain boundary as well as the increase of small angle grain boundary.
研究领域:
材料科学
·
力学
✓ 已验证
产品关联
DOI
高影响因子
MACROMOLECULES
·
2022
·
IF 6.057
Gaopeng Shi,Yuanbiao Liu,Guozhang Wu
High-Tg polymers generally exhibit high dynamic fragility (m). Here, we propose to design striking polymeric materials with low m but high Tg by introducing ionic coordination. The enthalpy relaxation of poly(vinylpyrrolidone)/metal chloride complexes was investigated to elucidate the influences of the coordination strength on Tg and m. Findings reveal that Tg increases with the addition of metallic ions, while m decreases for weakly coordinated complexes (Li+) and moderate systems (Zn2+ and Mg2+). Meanwhile, m increases continuously for strongly coordinated systems (La3+). Further experiments revealed that m is well correlated to heat capacity jump ΔCp and enthalpy hysteresis ΔHR as predicted by Adam–Gibbs theory. Ionic coordinated polymers with low m but high Tg can be achieved only when ΔHR changes more than Tg·ΔCp, suggesting that the enthalpy change plays a leading role in the activation free energy of segmental cooperative rearrangement. These results not only add new evidence of the thermodynamic link to dynamic fragility but also help clarify the mechanism of the independent tuning of Tg and m.
研究领域:
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
ACTA MATERIALIA
·
2025
·
IF 9.3
Zhi-Jie Lu,Ling-Zhi Liu,Hui Xie,Hai-Jun Jin
When a brittle nanoporous material infiltrated with water is dried in air, the capillarity-induced large volume shrinkage often leads to cracking within the material. In consequence, porous material may become more fragile or even shatter after drying. In this paper, we prepared nanoporous gold (NPG) with a low relative density by dealloying dilute Ag(Au) precursor alloys. Drying of this sample in air leads to a large volume contraction up to 22 ∼ 38%. Meanwhile, the material undergoes a ductile–brittle transition during drying: The wet sample of as-dealloyed NPG, while tested in water, shows a surprisingly large tensile strain up to 8%–10% before fracture; After drying, the fracture strain of the same material drops to around 1% in tension. This ductile-to-brittle transition is not caused by the formation of cracks as usual. Instead, it can be linked to the self-healing of microcracks during drying. We found that the plasticity of as-dealloyed NPG arises from the presence of high-density native microcracks. The bridging or deflection of these microcracks in tension leads to a diffuse failure, which accounts for the large irreversible tensile strain of the wet, as-dealloyed NPG. Further examination reveals that these native microcracks can be healed during drying, owing to the cold welding of nano-ligaments under capillary contraction force. Healing of these microcracks suppresses the diffuse failure induced by crack bridging or deflection, leading to a brittle fracture of the dried NPG in tension. Cold welding of nano-ligaments, which accounts for the anomalous crack healing and ductile–brittle transition of NPG in drying, might occur frequently in nanoporous metals under external load and contribute significantly to their mechanical performance.
研究领域:
材料科学
·
力学
✓ 已验证
产品关联
DOI
高影响因子
Nanomaterials
·
2020
·Vol. 11
·期 1
·31
·
IF 4.324
Qianqian Shen,Yu Zhang,Xuesha Li,Li Xiang,Chaoyin Nie
In order not to sacrifice nitrided layer thickness and reduce brittle compound layer thickness, Ni-coated pretreatment was carried out with electrodeposition on a pure iron surface, followed by gas nitriding. The brittle compound layer thickness of duplex surface treated samples was reduced, and the nitrided layer thickness increased to 320 μm. The microhardness was 4 times harder, and the wear loss was reduced by 68% compared with the original material. The results indicate that Ni-coated pretreatment could effectively improve microhardness and wear resistance and realize the controlled microstructure of a brittle compound layer of pure iron without compromising nitrided layer thickness. Ni coating plays an important role in ammonia adsorption and decomposition, and in the transfer of active nitrogen atoms during nitriding.
研究领域:
材料科学
·
表面工程
✓ 已验证
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2022
·
IF 7.392
Mo Zou,Jingzhi Chen,Zhaoyang Wei,Weiwei Lei,Jun You,Jie Liu,Qunchao Zhang,Dean Shi
Core-shell particles with rigid core and soft rubber shell have been proven to be effective in strengthening and toughening polymers simultaneously when the rubber shell thickness is controlled within a critical range. However, the critical value of the so-called thickness-to-diameter ratio τ (the ratio of the rubber shell thickness to the rigid core diameter) obtained in the previous work are all from polymer blends containing core–shell particles with monodispersed particle size. Does the critical τ value still exist in the core–shell toughening system with polydisperse particle sizes? Is it possible to produce core–shell particles with polydisperse particle sizes but the same τ value? In this paper, the post-emulsification method is first reported to prepare core–shell particles with polydisperse SiO 2 particles as the rigid core and ethylene–vinyl acetate copolymer grafted maleic anhydride (EVA- g -MAH) as the rubber shell, in which the thickness of the rubber shell can be well controlled and tuned via varying the feeding weight ratio of SiO 2 and EVA- g -MAH. The τ value is only determined by the weight ratio of SiO 2 and rubber, and has nothing to do with the SiO 2 particle size. A series of polyamide 6 (PA6)/SiO 2 @EVA core–shell toughening systems are prepared via melt blending process. It is proved the existence of the critical τ value ( τ cbd ) above which brittle-ductile transition happens in the core–shell toughening system with polydisperse core–shell particle sizes. The value of τ cbd is 0.069 in PA6/SiO 2 @EVA core–shell toughening system.
研究领域:
材料科学
·
聚合物工程
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）