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Wide gap active brazing of ceramic-to-metal-joints for high temperature applications

K. Bobzin,L. Zhao,N. Kopp,S. Samadian Anavar

《机械工程前沿(英文)》 2014年 第9卷 第1期   页码 71-74 doi: 10.1007/s11465-014-0291-0

摘要:

Applications like solid oxide fuel cells and sensors increasingly demand the possibility to braze ceramics to metals with a good resistance to high temperatures and oxidative atmospheres. Commonly used silver based active filler metals cannot fulfill these requirements, if application temperatures higher than 600°C occur. Au and Pd based active fillers are too expensive for many fields of use. As one possible solution nickel based active fillers were developed. Due to the high brazing temperatures and the low ductility of nickel based filler metals, the modification of standard nickel based filler metals were necessary to meet the requirements of above mentioned applications. To reduce thermally induced stresses wide brazing gaps and the addition of Al2O3 and WC particles to the filler metal were applied. In this study, the microstructure of the brazed joints and the thermo-chemical reactions between filler metal, active elements and WC particles were analyzed to understand the mechanism of the so called wide gap active brazing process. With regard to the behavior in typical application oxidation and thermal cycle tests were conducted as well as tensile tests.

关键词: wide gap     active brazing     nickel filler metals     high temperature application     WC     Al2O3    

Phenolic rigid organic filler/isotactic polypropylene composites. III. Impact resistance property

Heming LIN, Dongming QI, Jian HAN, Zhiqi CAI, Minghua WU

《化学科学与工程前沿(英文)》 2009年 第3卷 第2期   页码 176-181 doi: 10.1007/s11705-009-0203-8

摘要: A novel phenolic rigid organic filler (KT) was used to modify isotactic polypropylene (iPP). The influence of KT particles on the impact resistance property of PP/KT specimens (with similar interparticles distance, 1.8 μm) was studied by notched izod impact tests. It was found that the brittle-ductile transition (BDT) of the PP/KT microcomposites took place at the filler content of about 4%, and the impact strength attains the maximum at 5% (with filler particles size of 1.5 μm), which is about 2.5 times that of unfilled iPP specimens. The impact fracture morphology was investigated by scanning electron microscopy (SEM). For the PP/KT specimens and the high-density polyethylene/KT (HDPE/KT) specimens in ductile fracture mode, many microfibers could be found on the whole impact fracture surface. It was the filler particles that induced the plastic deformation of interparticles ligament and hence improved the capability of iPP matrix on absorbing impact energy dramatically. The determinants on the BDT were further discussed on the basis of stress concentration and debonding resistance. It can be concluded that aside from the interparticle distance, the filler particles size also plays an important role in semicrystalline polymer toughening.

关键词: rigid organic filler     polypropylene     impact resistance    

Dispersion of a novel phenolic rigid organic filler in isotactic polypropylene matrix by solution-mixing

Dongming QI, Xiaoli ZHAO, Zhijie CHEN, Peng HUANG, Jun CAO

《化学科学与工程前沿(英文)》 2012年 第6卷 第4期   页码 395-402 doi: 10.1007/s11705-012-1269-2

摘要: A novel phenolic rigid organic filler (named KD) with a high melting point was dispersed in an isotactic polypropylene (iPP) matrix by solution-mixing and/or melt-mixing. A series of KD/iPP blends was prepared with or without addition of maleic anhydride-grafted polypropylene (MAPP) as a compatibilizer. Influences of MAPP and mixing methods on the filler dispersion were studied using polaried optical microscope (POM), scanning electron microscope (SEM) and tensile test. The filler particles are always inclined to form large irregular aggregates in the iPP matrix due to their significant differences in polarity and solubility in solvent. However, an iPP/MAPP/KD (PMK) blend containing filler particles with a quasi-spherical shape (~97.8 nm in diameter) and narrow particle size distribution (polydispersity index= 1.076) was successfully prepared by incorporating MAPP to reduce the interfacial tension and surface free energy between the dispersion phase and the continuous phase, and adopting a spray-drying method after solution-mixing to suppress the increase of the size of the dispersed phase during the removal of solvent.

关键词: dispersion     rigid organic filler     isotactic polypropylene     mixing    

Influence of the filler materials on flux-free brazing of pure aluminium (1050)

Kirsten BOBZIN, Lidong ZHAO, Thomas SCHLAEFER, Thomas WARDA,

《机械工程前沿(英文)》 2010年 第5卷 第1期   页码 47-51 doi: 10.1007/s11465-009-0079-9

摘要: In the present study, samples of pure aluminium (1050) were deposited by cold spraying with filler materials such as Al12Si, Al7Si, Al12Si-4%Cu, and the Al-Si-based filler material A, which was especially developed for flux-free brazing by the Surface Engineering Institute. Besides, pure Si powder was also sprayed. The coated samples were heat-treated under different conditions and were brazed under an argon atmosphere without fluxes or with the flux Nokolok by an induction heating system. The shear strength of the brazed joints was determined. The results show that the filler materials could be well deposited by cold spraying. A thin layer of brittle Si could also form due to the strong deformation of the substrate surface. The heat treatments showed that a very good metallurgical bond between the filler materials and the substrate could be realized by the deposition by cold spraying. The Al7Si deposited samples could not be brazed without fluxes under the given conditions. The samples deposited with other filler materials could be brazed without fluxes. The in-situ diffusion process made it possible to braze the Si-deposited samples at 580°C. The joints of the samples deposited with the filler material showed the highest shear strength of 41 MPa, whereas the values of the Al12Si and Si deposited samples were less than 20 MPa. The employment of the flux Nikolok significantly increased the shear strength of the Al12Si deposited samples to more than 53 MPa.

关键词: aluminium     flux-free brazing     cold spraying     shear strength    

Activated carbon induced oxygen vacancies-engineered nickel ferrite with enhanced conductivity for supercapacitor

《化学科学与工程前沿(英文)》 2023年 第17卷 第12期   页码 2088-2100 doi: 10.1007/s11705-023-2352-6

摘要: Activated carbon induced oxygen vacancies-engineered nickel ferrite with enhanced conductivity for supercapacitor application

关键词: nickel ferrite conductivity     carbon oxygen vacancies    

Phenolic rigid organic filler/isotactic polypropylene composites. I. Preparation

QI Dongming, YANG Lei, WU Minghua, LIN Heming, NITTA Kohhei

《化学科学与工程前沿(英文)》 2008年 第2卷 第3期   页码 236-241 doi: 10.1007/s11705-008-0034-z

摘要: A novel phenolic rigid organic filler (KT) was melt-mixed with an isotactic polypropylene (iPP) to prepare a series of PP/KT composites, with or without maleic anhydride grafted polypropylene (MAPP) as compatilizer. The evolution of filler morphology during melt-mixing and melt-pressure processes was monitored by scanning electron microscope (SEM) and polarized optical microscope (POM). The influences of shear force, pressure time, filler content and MAPP concentration on the final filler dispersion were studied. We found that this rigid organic filler readily melted and dispersed homogenously into the iPP matrix through a fission-fusion process during the melt-mixing process. Thus a balanced dispersion, which was closely related to shear force and MAPP concentration, can be achieved. During the melt-pressure process, parts of the filler particles combined gradually through a coalescence process. However, the incorporation of MAPP can effectively inhibit the tendency to coalesce and refine the filler particles sizes into nanoscale. Thus, a series of PP/KT composites with controllable filler particles size and narrow size distribution can be obtained just by adjusting process conditions and MAPP concentration. In addition, due to the in-situ formation mechanism, the filler phase possessed a typical solid true-spherical shape.

关键词: morphology     concentration     tendency     controllable     addition    

Phenolic rigid organic filler/isotactic polypropylene composites. II. Tensile properties

QI Dongming, SHAO Jianzhong, WU Minghua, NITTA Kohhei

《化学科学与工程前沿(英文)》 2008年 第2卷 第4期   页码 396-401 doi: 10.1007/s11705-008-0077-1

摘要: A novel phenolic rigid organic filler (KT) was used to modify isotactic polypropylene (iPP). The influence of KT particles on the tensile properties of PP/KT microcomposites was studied by uniaxial tensile test and the morphological structures of the stretched specimens were observed by scanning electron microscopy (SEM) and polarized optical microscopy (POM). We found that the Young’s modulus of PP/KT specimens increased with filler content, while the yield and break of the specimens are related to the filler particles size. The yield stress, the breaking stress and the ultimate elongation of PP/KT specimens were close to those of unfilled iPP specimens when the maximal filler particles size is less than a critical value, which is 7 ?m at a crosshead speed of 10 mm/min and 3 ?m at 200 mm/min, close to that of glass bead but far more than those of other rigid inorganic filler particles. The interfacial interaction was further estimated from yield stress, indicating that KT particles have a moderate interfacial interaction with iPP matrix. Thus, the incorporation of small KT particles can reinforce iPP matrix and simultaneously cause few detrimental effects on the other excellent tensile properties of iPP matrix, due to their organic nature, higher specific area, solid true-spherical shape and the homogenous dispersion of the ROF particles in microcomposites.

关键词: maximal     uniaxial tensile     unfilled     excellent tensile     influence    

Enabling nickel ferrocyanide nanoparticles for high-performance ammonium ion storage

《化学科学与工程前沿(英文)》 2023年 第17卷 第2期   页码 226-235 doi: 10.1007/s11705-022-2198-3

摘要: Prussian blue and its analogs are extensively investigated as a cathode for ammonium-ion batteries. However, they often suffer from poor electronic conductivity. Here, we report a Ni2Fe(CN)6/multiwalled carbon nanotube composite electrode material, which is prepared using a simple coprecipitation approach. The obtained material consists of nanoparticles with sizes 30–50 nm and the multiwalled carbon nanotube embedded in it. The existence of multiwalled carbon nanotube ensures that the Ni2Fe(CN)6/multiwalled carbon nanotube composite shows excellent electrochemical performance, achieving a discharge capacity of 55.1 mAh·g–1 at 1 C and 43.2 mAh·g–1 even at 15 C. An increase in the ammonium-ion diffusion coefficient and ionic/electron conductivity based on kinetic investigations accounts for their high performance. Furthermore, detailed ex situ characterizations demonstrate that Ni2Fe(CN)6/multiwalled carbon nanotube composite offers three advantages: negligible lattice expansion during cycling, stable structure, and the reversible redox couple. Therefore, the Ni2Fe(CN)6/multiwalled carbon nanotube composite presents a long cycling life and high rate capacity. Finally, our study reports a desirable material for ammonium-ion batteries and provides a practical approach for improving the electrochemical performance of Prussian blue and its analogs.

关键词: nickel ferrocyanides     NH4+     electrochemistry     Prussian blue     aqueous ammonium ion batteries    

Molybdenum disulfide@nickel phyllosilicate hybrid for improving the flame retardancy and wear resistance

《化学科学与工程前沿(英文)》 2023年 第17卷 第12期   页码 2114-2126 doi: 10.1007/s11705-023-2357-1

摘要: In this study, nickel phyllosilicate was synthesized based on molybdenum disulfide (MoS2@NiPS) by the sol-gel method, and then MoS2@NiPS was used to prepare epoxy composites. The thermal stability, flame retardancy, and frictional performances of epoxy composites were studied. With the addition of 3 wt% MoS2@NiPS, the epoxy composite increased the limiting oxygen index from 23.8% to 26.1% and reduced the vertical burning time from 166 s for epoxy resin to 35 s. The residual char of the epoxy composite increased from 11.8 to 20.2 wt%. MoS2@NiPS promoted the graphitization of the residual char, and facilitated the formation of a dense and continuous char layer, thereby improving the fire safety of epoxy resin. The epoxy composite with 3 wt% MoS2@NiPS had excellent wear resistance property with a wear rate of 2.19 × 10−5 mm3·N–1·m–1, which was 68.8% lower than that of epoxy resin. This study presented a practical approach to improve the frictional and fire resistance of epoxy composites.

关键词: molybdenum disulfide     nickel phyllosilicate     epoxy resin     flame retardancy    

Nickel-based metal−organic framework-derived whisker-shaped nickel phyllosilicate toward efficiently

《化学科学与工程前沿(英文)》 2022年 第16卷 第10期   页码 1493-1504 doi: 10.1007/s11705-022-2168-9

摘要: Metal−organic framework-derived materials have attracted significant attention in the applications of functional materials. In this work, the rod-like nickel-based metal−organic frameworks were first synthesized and subsequently employed as the hard templates and nickel sources to prepare the whisker-shaped nickel phyllosilicate using a facile hydrothermal technology. Then, the nickel phyllosilicate whiskers were evaluated to enhance the mechanical, thermal, flammable, and tribological properties of epoxy resin. The results show that adequate nickel phyllosilicate whiskers can disperse well in the matrix, improving the tensile strength and elastic modulus by 13.6% and 56.4%, respectively. Although the addition of nickel phyllosilicate whiskers could not obtain any UL-94 ratings, it enhanced the difficulty in burning the resulted epoxy resin nanocomposites and considerably enhanced thermal stabilities. Additionally, it was demonstrated that such nickel phyllosilicate whiskers preferred to improve the wear resistance instead of the antifriction feature. Moreover, the wear rate of epoxy resin nanocomposites was reduced significantly by 80% for pure epoxy resin by adding 1 phr whiskers. The as-prepared nickel phyllosilicate whiskers proved to be promising reinforcements in preparing of high-performance epoxy resin nanocomposites.

关键词: metal−organic framework     nickel phyllosilicate     whisker     epoxy resin     mechanical response     tribological performance     flammable property    

Tool wear mechanisms in the machining of Nickel based super-alloys: A review

Waseem AKHTAR,Jianfei SUN,Pengfei SUN,Wuyi CHEN,Zawar SALEEM

《机械工程前沿(英文)》 2014年 第9卷 第2期   页码 106-119 doi: 10.1007/s11465-014-0301-2

摘要:

Nickel based super-alloys are widely employed in aircraft engines and gas turbines due to their high temperature strength, corrosion resistance and, excellent thermal fatigue properties. Conversely, these alloys are very difficult to machine and cause rapid wear of the cutting tool, frequent tool changes are thus required resulting in low economy of the machining process. This study provides a detailed review of the tool wear mechanism in the machining of nickel based super-alloys. Typical tool wear mechanisms found by different researchers are analyzed in order to find out the most prevalent wear mechanism affecting the tool life. The review of existing works has revealed interesting findings about the tool wear mechanisms in the machining of these alloys. Adhesion wear is found to be the main phenomenon leading to the cutting tool wear in this study.

关键词: tool wear     nickel based super-alloy     wear mechanism    

Self-sacrificial templating synthesis of flower-like nickel phyllosilicates and its application as high-performance

《化学科学与工程前沿(英文)》 2022年 第16卷 第4期   页码 484-497 doi: 10.1007/s11705-021-2074-6

摘要: The nanocomposites of flower-like nickel phyllosilicate particles incorporated into epoxy resin were fabricated via an in-situ mixing process. The flower-like nickel phyllosilicate particles were firstly synthesized using a mild self-sacrificial templating method, and the morphology and lamellar structure were examined carefully. Several properties of mechanical, thermal and tribological responses of epoxy nanocomposites were performed. It was demonstrated that adequate flower-like nickel phyllosilicate particles dispersed well in the matrix, and the nanocomposites displayed enhanced tensile strength and elastic modulus but decreased elongation at break as expected. In addition, friction coefficient and wear rate were increased first and then decreased along with the particle content, and showed the lowest values at a mass fraction of 5%. Nevertheless, the incorporated flower-like nickel phyllosilicate particles resulted in the continuously increasing thermal stability of epoxy resin (EP) nanocomposites. This study revealed the giant potential of flower-like particles in preparing high-quality EP nanocomposites.

关键词: nickel phyllosilicate     flow-like structure     mechanical property     thermal stability     tribological performance    

ASSESSMENT OF HEAVY METALS IN HYDROCHAR PRODUCED BY HYDROTHERMAL CARBONIZATION OF DAIRY MANURE

《农业科学与工程前沿(英文)》 2023年 第10卷 第3期   页码 437-447 doi: 10.15302/J-FASE-2023507

摘要:

● Content of heavy metals in hydrochar varies considerably, from 50% to 100%.

关键词: heavy metals     dairy manure     hydrochar     hydrothermal carbonization     waste management    

Field evidence of decreased extractability of copper and nickel added to soils in 6-year field experiments

Bao Jiang, Dechun Su, Xiaoqing Wang, Jifang Liu, Yibing Ma

《环境科学与工程前沿(英文)》 2018年 第12卷 第2期 doi: 10.1007/s11783-017-0990-y

摘要: The phytotoxicity of added copper (Cu) and nickel (Ni) is influenced by soil properties and field aging. However, the differences in the chemical behavior between Cu and Ni are still unclear. Therefore, this study was conducted to investigate the extractability of added Cu and Ni in 6-year field experiments, as well as the link with their phytotoxicity. The results showed that the extractability of added Cu decreased by 6.63% (5.10%–7.90%), 22.5% (20.6%–23.9%), and 6.87% (0%–17.9%) on average for acidic, neutral, and alkaline soil from 1 to 6 years, although the phytotoxicity of added Cu and Ni did not change significantly from 1 to 6 years in the long term field experiment. Because of dissolution of Cu, when the pH decreased below 7.0, the extractability of Cu in alkaline soil by EDTA at pH 4.0 could not reflect the effects of aging. For Ni, the extractability decreased by 18.1% (10.1%–33.0%), 63.0% (59.2%–68.8%), and 22.0% (12.4%–31.8%) from 1 to 6 years in acidic, neutral, and alkaline soils, respectively, indicating the effects of aging on Ni were greater than on Cu. The sum of ten sequential extractions of Cu and Ni showed that added Cu was more extractable than Ni in neutral and alkaline soil, but similar in acidic soil.

关键词: Copper     Nickel     EDTA     Sequential extraction    

Sulfidation/regeneration multicycle testing of nickel-modified ZnFe

Wei LI, Jinju GUO, Jiejie HUANG, Jiaotao ZHAO

《化学科学与工程前沿(英文)》 2010年 第4卷 第4期   页码 435-440 doi: 10.1007/s11705-010-0506-9

摘要: A commercial metal oxide sorbent for the desulphurization of coal-derived gas requires high desulphurization reactivity, mechanical strength, ability to regenerate, and stability to endure many sulfidation-regeneration cycles. In this paper, the sulfur capacity and multiple cycles of a nickel-modified ZnFe O sorbent prepared by the sol-gel auto-combustion method were measured in a fixed-bed reactor at middle temperature of 300°C (sulfidation temperature) and 500°C (regeneration temperature). Also, the BET surface area, pore volume, average pore diameter and X-ray diffraction (XRD) patterns of the sorbent through multicycles were studied. Multicycle runs indicate that the sulfidation reactivity decreases slightly during the second cycle and keeps steady in the following cycles. The results indicate that the nickel-modified ZnFe O keeps high reactivity and structural stability in the multicycle testing of sulfidation/regeneration.

关键词: hot gas desulphurization     nickel-modified ZnFe2O4     sulfidation/regeneration    

标题 作者 时间 类型 操作

Wide gap active brazing of ceramic-to-metal-joints for high temperature applications

K. Bobzin,L. Zhao,N. Kopp,S. Samadian Anavar

期刊论文

Phenolic rigid organic filler/isotactic polypropylene composites. III. Impact resistance property

Heming LIN, Dongming QI, Jian HAN, Zhiqi CAI, Minghua WU

期刊论文

Dispersion of a novel phenolic rigid organic filler in isotactic polypropylene matrix by solution-mixing

Dongming QI, Xiaoli ZHAO, Zhijie CHEN, Peng HUANG, Jun CAO

期刊论文

Influence of the filler materials on flux-free brazing of pure aluminium (1050)

Kirsten BOBZIN, Lidong ZHAO, Thomas SCHLAEFER, Thomas WARDA,

期刊论文

Activated carbon induced oxygen vacancies-engineered nickel ferrite with enhanced conductivity for supercapacitor

期刊论文

Phenolic rigid organic filler/isotactic polypropylene composites. I. Preparation

QI Dongming, YANG Lei, WU Minghua, LIN Heming, NITTA Kohhei

期刊论文

Phenolic rigid organic filler/isotactic polypropylene composites. II. Tensile properties

QI Dongming, SHAO Jianzhong, WU Minghua, NITTA Kohhei

期刊论文

Enabling nickel ferrocyanide nanoparticles for high-performance ammonium ion storage

期刊论文

Molybdenum disulfide@nickel phyllosilicate hybrid for improving the flame retardancy and wear resistance

期刊论文

Nickel-based metal−organic framework-derived whisker-shaped nickel phyllosilicate toward efficiently

期刊论文

Tool wear mechanisms in the machining of Nickel based super-alloys: A review

Waseem AKHTAR,Jianfei SUN,Pengfei SUN,Wuyi CHEN,Zawar SALEEM

期刊论文

Self-sacrificial templating synthesis of flower-like nickel phyllosilicates and its application as high-performance

期刊论文

ASSESSMENT OF HEAVY METALS IN HYDROCHAR PRODUCED BY HYDROTHERMAL CARBONIZATION OF DAIRY MANURE

期刊论文

Field evidence of decreased extractability of copper and nickel added to soils in 6-year field experiments

Bao Jiang, Dechun Su, Xiaoqing Wang, Jifang Liu, Yibing Ma

期刊论文

Sulfidation/regeneration multicycle testing of nickel-modified ZnFe

Wei LI, Jinju GUO, Jiejie HUANG, Jiaotao ZHAO

期刊论文