Study on the Corrosion Resistance of Slag α-Sialon Ceramics to NaOH and HNO3

The corrosion resistance of slag α-Sialon ceramics, preparedviapressure-less sintering and hot-pressing from slag α-Sialon powder, to NaOH and HNO3was studied in this work. The result shows that slag α-Sialon ceramics have exellent corrosion resistance to NaOH and good resistance to HNO3. The corrosion mechanism and corrosion mode of acid and alkali to slag α-Sialon ceramics was investigated by means of scanning electron microscopy (SEM), and the results indicate that the corrosion of acid and alkali to hot-pressing ceramic is the slow surface corrosion, not only on the crystal grains, but also on the grain boundary phase, while the fast pitting is the dominant corrosion mode for pressure-less ceramic. The corrosion of NaOH solution to ceramics mainly occurred the grain boundary phase, while not only the grain boundary phase, but also crystal phase are corroded by HNO3.

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HYDROTHERMAL CORROSION RESISTANCE OF SILICON NITRIDE WITH O'-Si Al ON GRAIN BOUNDARY PHASE

Ceramics - Silikaty ◽

10.13168/cs.2018.0034 ◽

2018 ◽

pp. 382-388

Author(s):

Michal Vetrecin

Keyword(s):

Corrosion Resistance ◽

Silicon Nitride ◽

Grain Boundary ◽

Boundary Phase

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The Roles of Ti Particles in Improving the Corrosion Resistance of Electrochemically Assembled Ni-Ti Composite Coatings

CORROSION ◽

10.5006/2408 ◽

2017 ◽

Vol 73 (9) ◽

pp. 1107-1118 ◽

Cited By ~ 6

Author(s):

Yuantao Zhao ◽

Lianbo Wang ◽

Zhenbo Qin ◽

Chengxi Wang ◽

Zhou Xu ◽

...

Keyword(s):

Corrosion Resistance ◽

Composite Coatings ◽

Corrosion Current ◽

Localized Corrosion ◽

Corrosion Mechanism ◽

Nacl Solution ◽

Oriented Texture ◽

Naoh Solution ◽

Order Of Magnitude ◽

Ti Particles

The influences of co-deposited Ti particles on corrosion behavior of electrodeposited Ni-Ti coatings were investigated. The co-deposited Ti particles caused the refined crystallite size and random-oriented texture of Ni-Ti coating. In 3.5 wt% sodium chloride (NaCl) solution, the buried Ti particles in Ni matrix blocked the corrosion path and rapid intercrystalline corrosion. The inert TiO2 could form on the exposed Ti particles and hinder localized corrosion. In 10 wt% sodium hydroxide (NaOH) solution, Ni matrix crystallites, refined by co-deposited Ti particles, contributed to formation of the passive Ni(OH)2 film. The corrosion current of Ni-Ti coating decreased by about one order of magnitude in both solutions with respect to pure Ni coating, demonstrating the co-deposited Ti particles greatly improved the corrosion resistance of Ni-Ti composite coatings. Finally, a corrosion mechanism was built to explain the co-deposited Ti particles improved corrosion resistance of the Ni-Ti composite coatings.

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Effect of Oxynitride Grain Boundary Phase on Toughening of Silicon Nitride Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.317-318.649 ◽

2006 ◽

Vol 317-318 ◽

pp. 649-652 ◽

Cited By ~ 1

Author(s):

Takafumi Kusunose ◽

Tohru Sekino ◽

P.E.D. Mogan ◽

Koichi Niihara

Keyword(s):

Fracture Toughness ◽

Silicon Nitride ◽

Grain Boundary ◽

Crack Propagation ◽

Hot Pressing ◽

Boundary Phase ◽

Toughening Mechanism ◽

Nitride Ceramics

The Si3N4/YSiO2N composite in which crystalline YSiO2N was formed as grain boundary phase was fabricated by hot-pressing the mixture of SiO2, Si3N4 and Y2O3. The fracture toughness of this composite was significantly improved, compared to the Si3N4 composites containing Y5Si3O12N or Y2Si3O3N4 as a grain boundary phases. To clarify the toughening mechanism, the microstructure and the crack propagation profiles were observed.

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Examination of Fracture Interfaces in Silicon Nitride

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113925 ◽

1975 ◽

Vol 33 ◽

pp. 60-61

Author(s):

Nancy J. Tighe

Keyword(s):

Silicon Nitride ◽

Grain Boundary ◽

Crack Growth ◽

Subcritical Crack Growth ◽

Slow Crack Growth ◽

Ceramic Materials ◽

Grain Boundary Sliding ◽

Boundary Phase ◽

Turbine Engines ◽

Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

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Characterization of intergranular cuprous oxide in polycrystalline YBa2Cu3O7-x

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106466 ◽

1988 ◽

Vol 46 ◽

pp. 880-881

Author(s):

Bradley L. Thiel ◽

Chan Han R. P. ◽

Kurosky L. C. Hutter ◽

I. A. Aksay ◽

Mehmet Sarikaya

Keyword(s):

Grain Boundary ◽

Cuprous Oxide ◽

Room Temperature ◽

Boundary Phase ◽

Spectroscopic Techniques ◽

Transition Width ◽

Practical Applications ◽

Thin Foils ◽

Superconducting Oxides

The identification of extraneous phases is important in understanding of high Tc superconducting oxides. The spectroscopic techniques commonly used in determining the origin of superconductivity (such as RAMAN, XPS, AES, and EXAFS) are surface-sensitive. Hence a grain boundary phase several nanometers thick could produce irrelevant spectroscopic results and cause erroneous conclusions. The intergranular phases present a major technological consideration for practical applications. In this communication we report the identification of a Cu2O grain boundary phase which forms during the sintering of YBa2Cu3O7-x (1:2:3 compound).Samples are prepared using a mixture of Y2O3. CuO, and BaO2 powders dispersed in ethanol for complete mixing. The pellets pressed at 20,000 psi are heated to 950°C at a rate of 5°C per min, held for 1 hr, and cooled at 1°C per min to room temperature. The samples show a Tc of 91K with a transition width of 2K. In order to prevent damage, a low temperature stage is used in milling to prepare thin foils which are then observed, using a liquid nitrogen holder, in a Philips 430T at 300 kV.

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Unique Autoclave Stress Induced Failure Mechanism

ISTFA 2005: Conference Proceedings from the 31st International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa2005p0427 ◽

2005 ◽

Author(s):

John Butchko ◽

Bruce T. Gillette

Keyword(s):

Corrosion Rate ◽

Grain Boundary ◽

Failure Analysis ◽

Failure Mechanism ◽

Metal Corrosion ◽

Corrosion Mechanism ◽

Reliability Testing ◽

Process Change ◽

Transistor Reliability ◽

Pass Through

Abstract Autoclave Stress failures were encountered at the 96 hour read during transistor reliability testing. A unique metal corrosion mechanism was found during the failure analysis, which was creating a contamination path to the drain source junction, resulting in high Idss and Igss leakage. The Al(Si) top metal was oxidizing along the grain boundaries at a faster rate than at the surface. There was subsurface blistering of the Al(Si), along with the grain boundary corrosion. This blistering was creating a contamination path from the package to the Si surface. Several variations in the metal stack were evaluated to better understand the cause of the failures and to provide a process solution. The prevention of intergranular metal corrosion and subsurface blistering during autoclave testing required a materials change from Al(Si) to Al(Si)(Cu). This change resulted in a reduced corrosion rate and consequently prevented Si contamination due to blistering. The process change resulted in a successful pass through the autoclave testing.

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Effect of Oxide Scale Microstructure on Atmospheric Corrosion Behavior of Hot Rolled Steel Strip

Coatings ◽

10.3390/coatings11050517 ◽

2021 ◽

Vol 11 (5) ◽

pp. 517

Author(s):

Bin Sun ◽

Lei Cheng ◽

Chong-Yang Du ◽

Jing-Ke Zhang ◽

Yong-Quan He ◽

...

Keyword(s):

Corrosion Resistance ◽

Oxide Scale ◽

Corrosion Product ◽

Corrosion Behavior ◽

Corrosion Test ◽

Atmospheric Corrosion ◽

Corrosion Mechanism ◽

Type I ◽

Rust Layer ◽

Hot Rolled

The atmospheric corrosion behavior of a hot-rolled strip with four types (I–IV) of oxide scale was investigated using the accelerated wet–dry cycle corrosion test. Corrosion resistance and porosity of oxide scale were studied by potentiometric polarization measurements. Characterization of samples after 80 cycles of the wet–dry corrosion test showed that scale comprised wüstite and magnetite had strongest corrosion resistance. Oxide scale composed of inner magnetite/iron (>70%) and an outer magnetite layer had the weakest corrosion resistance. The corrosion kinetics (weight gain) of each type of oxide scale followed an initial linear and then parabolic (at middle to late corrosion) relationship. This could be predicted by a simple kinetic model which showed good agreement with the experimental results. Analysis of the potentiometric polarization curves, obtained from oxide coated steel electrodes, revealed that the type I oxide scale had the highest porosity, and the corrosion mechanism resulted from the joint effects of electrochemical behavior and the porosity of the oxide scale. In the initial stage of corrosion, the corrosion product nucleated and an outer rust layer formed. As the thickness of outer rust layer increased, the corrosion product developed on the scale defects. An inner rust layer then formed in the localized pits as crack growth of the scale. This attacked the scale and expanded into the substrate during the later stage of corrosion. At this stage, the protective effect of the oxide scale was lost.

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