Enhancement of the Adhesion of Cordierite Glass-Ceramic Coatings on Molybdenum by the Deposition of Metallic Interlayers on the Substrate

1999 ◽  
Vol 586 ◽  
Author(s):  
Jesus Noel Calata ◽  
Guo-Quan Lu ◽  
Thomas A. Kuhr
Keyword(s):  
Chromium Oxide ◽  
Glass Ceramic ◽  
Effective Diffusion ◽  
Ceramic Coatings ◽  
Alloy Layer ◽  
Hydrogen Atmosphere ◽  
Quantitative Chemical Analysis ◽  
Chromium Oxide Layer ◽  
Cordierite Glass ◽  
The Difference

ABSTRACTSintered coatings of cordierite-base glass-ceramic do not adhere readily on bare molybdenum substrates. This is due to the absence of a stable metal oxide film on the substrate that serves as a suitable transition layer between the glass-ceramic and the substrate. To address this problem, dual layers of either chromium/nickel or chromium/copper were deposited by electroplating on the molybdenum substrates. Glass powder in slurry form was then cast on the substrates using a doctor blade and sintered in a helium-hydrogen atmosphere at 950°C. The metallic interlayer structure was found to produce an excellent bond between the coating and the substrate. The adhesion of the coatings was observed to be sensitive to the thickness of the deposited metal layers. Quantitative chemical analysis of the interface region was performed to explain the difference in adhesion quality. In all instances, the fracture surface was found to occur at the chromium oxide/chromium boundary providing a clear indication that the chromium oxide layer plays an important role in enhancing the adhesion. The superior adhesion in samples with the Cr-Cu interface was attributed to Cu acting as an effective diffusion barrier to Mo. Cr however, was able to diffuse through the Cu layer enhancing the bond between Mo and Cu by alloying with the Mo. Ni was not as effective as Cu in preventing the diffusion of Mo towards the glass-ceramic coating but a thicker Cr layer still produced a strong bond. In samples where the distinct Cr layer was either too thin or non-existent, adhesion was poor possibly because the Cr oxide does not bond well to the Ni-Cr alloy layer that formed after firing.

Adhesion strength of cordierite glass-ceramic coatings on molybdenum substrates

2000 ◽  
Vol 15 (12) ◽  
pp. 2857-2863
Author(s):  
Guo-Quan Lu ◽  
Jesus Noel Calata
Keyword(s):  
Fracture Toughness ◽  
Glass Ceramic ◽  
Transition Layer ◽  
Ceramic Coatings ◽  
Chemical Analyses ◽  
Interfacial Fracture Toughness ◽  
Nickel Chromium ◽  
Cordierite Glass ◽  
Glass Ceramic Coatings ◽  
Quantitative Chemical

Cordierite glass-ceramic coatings do not bond to molybdenum directly because of the absence of a suitable transition layer. Dual metallic interlayers of copper/chromium and nickel/chromium were electroplated on the substrates to enhance adhesion. The adhesion of the glass-ceramic coatings was evaluated by indentation testing and a modified analytical method based on interfacial fracture toughness. Quantitative chemical analyses of the interfaces were used to explain differences in fracture toughness among samples with different interlayers. Of those tested, the best interface for adhering glass-ceramic coatings to molybdenum was found to be a 4 μm chromium over 2 μm copper on molybdenum.

Densification and Crystallization Kinetics of Cordierite Glass-Ceramic Coatings on Rigid Substrates

1997 ◽  
Vol 481 ◽  
Author(s):  
Jesus Noel Calata ◽  
Sihua Wen ◽  
Guo-Quan Lu
Keyword(s):  
Tensile Stress ◽  
Glass Ceramic ◽  
Ceramic Coatings ◽  
Sintering Kinetics ◽  
Initial Stage ◽  
Expansion Stage ◽  
Cordierite Glass ◽  
Glass Ceramic Coatings ◽  
Silicon Interface ◽  
Kinetics Of

ABSTRACTWe report our findings on the sintering kinetics of slip-cast glass-ceramic coatings on rigid substrates at temperatures between 900°C and 1000°C; the glass-ceramic crystallizes into cordierite at sintering temperatures above 900°C. Changes in coating thickness during sintering were monitored in situ using an optical setup, and the crystallization of the coatings was determined by x-ray diffraction. The coatings went through a rapid shrinkage due to initial densification, followed by an expansion stage caused by the transformation of the glass into a crystalline phase with a lower density. The rate and extent of the expansion were more noticeable at sintering temperatures above 900°C. We also found that wetting between the glass-ceramic and the substrate was important to the sintering kinetics and sintered microstructure of the coatings. For coatings formed on silicon substrate, growth of large pores was observed at the glass-ceramic/silicon interface. Using wafer-curvature measurement technique, we found a significant tensile stress build-up in the coatings during the initial stage of sintering. We believe that the combination of poor wetting and the tensile stress build-up led to the observed desintering phenomenon at the glass-ceramic/silicon interface.

Visualization and characterization of localized outgassing position on surface-treated specimens: Chromium oxide layer on stainless steel

2019 ◽  
Vol 492 ◽  
pp. 280-284
Author(s):  
Naoya Miyauchi ◽  
Tomoya Iwasawa ◽  
Taro Yakabe ◽  
Masahiro Tosa ◽  
Toyohiko Shindo ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Oxide Layer ◽  
Chromium Oxide ◽  
Chromium Oxide Layer

Adhesive strength of heat-resistant glass ceramic coatings with nichrome melts

1994 ◽  
Vol 51 (2) ◽  
pp. 85-90
Author(s):  
A. P. Zubekhin ◽  
V. A. Zhabrev ◽  
A. M. Kondyurin
Keyword(s):  
Adhesive Strength ◽  
Glass Ceramic ◽  
Ceramic Coatings ◽  
Heat Resistant ◽  
Glass Ceramic Coatings

The diffusion of 75Se(IV) in Beishan granite – temperature, oxygen condition and ionic strength effects

2018 ◽  
Vol 107 (1) ◽  
pp. 39-54
Author(s):  
Chunli Wang ◽  
Xiaoyu Yang ◽  
Jiangang He ◽  
Fangxin Wei ◽  
Zhong Zheng ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Effective Diffusion ◽  
Aerobic Condition ◽  
Double Layers ◽  
Solution Viscosity ◽  
Formation Factor ◽  
Experimental Conditions ◽  
Beishan Granite ◽  
Oxygen Condition ◽  
The Difference

Abstract To explore the diffusion behavior of 75Se(IV) in Beishan granite (BsG), the influences of temperature, oxygen condition and ionic strength were investigated using the through-diffusion experimental method. The effective diffusion coefficient De of 75Se(IV) in BsG varied from 4.21×10−14 m2/s to 3.19×10−13 m2/s in our experimental conditions, increased with increasing temperature. The formation factor Ff of BsG was calculated to be nearly constant in the range of temperatures investigated, suggesting that the inner structure of BsG had no significant change in the temperature range of 20–55°C. Meanwhile, the De values of 75Se(IV) in BsG under anaerobic condition was significantly larger than that under aerobic condition, which may be attributed to the difference in the sorption characteristics and species distribution of Se and pH values. Moreover, the diffusion of 75Se(IV) was promoted with ionic strength increased from 0.01 M to 0.1 M, and then decreased at 0.5 M, mainly due to the combined effects of reduced double layers with increased ionic strength and increase of the solution viscosity at higher ionic strength.

scholarly journals Solid Solutions Formation Mechanism in Cordierite-Mullite Glass Materials During Ceramization

2020 ◽  
Vol 14 (4) ◽  
pp. 583-589
Author(s):  
Оksana Savvova ◽  
◽  
Hennadiy Voronov ◽  
Оlena Babich ◽  
Oleksii Fesenko ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Formation Mechanism ◽  
Glass Ceramic ◽  
High Strength ◽  
Ceramic Materials ◽  
Ceramic Coatings ◽  
Resource Saving ◽  
Aluminosilicate Glasses ◽  
Glass Ceramic Materials ◽  
Fine Crystalline Structure

Relevance of the development of high-strength glass-ceramic coatings obtained by resource-saving technology for protective elements has been established. Structure formation mechanism in magnesium aluminosilicate glasses during heat treatment has been analyzed. Selection of the system was substantiated, model glasses and glass-ceramic materials on its base have been developed. Patterns of structure regularity and formation of the phase composition of glass-ceramic materials during their ceramization have been investigated. It was established that the presence of crystalline phase of mullite after melting leads to formation of the primary crystals and allows the formation of the fine crystalline structure under conditions of the low-temperature heat treatment at the nucleation stage. Developed high-strength glass ceramic materials can be used as a base in creating protective elements for special-purpose vehicles by energy-saving technology.

A Study of Copper-Chromium Oxide Catalysts and a Method to Determine Catalytic Activities

1963 ◽  
Vol 7 ◽  
pp. 229-239
Author(s):  
M. Stammler ◽  
M. Pyzyna
Keyword(s):  
Catalytic Activity ◽  
Chromium Oxide ◽  
Oxide Catalysts ◽  
Linear Absorption ◽  
X Ray ◽  
Chromium Spinel ◽  
Copper Chromium ◽  
The Difference ◽  
Two Phases ◽  
Chromium Oxide Catalysts

AbstractAn extensive investigation of chemical composition, particle size, and surface area of copper-chromium oxide catalysts has been made. The two phases present in the activated material are copper oxide (CuO) and copper-chromium spinel (CuCr2O4). The crystallite size of the CuO phase (determined by X-ray diffraction line broadening) can be correlated with the catalytic activity measured on a CO-CO2 oxidation reaction. The catalytic activity of the oxide catalyst can be expressed as a function of the X-ray fluorescence intensity of the Cu Kα line even on changing the absolute copper concentration up to 3%. An attempt is made to explain this phenomenon by the heterogeneity effect caused by the difference in the linear absorption factors for the Cu Kα radiation in the system CuO-CuCr2O4.

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