Brazing Al2O3 to Kovar Alloy with Ni/Ti/Ni Interlayer and Dramatic Increasing of Joint Strength after Thermal Cycles

2005 ◽  
Vol 486-487 ◽  
pp. 481-484 ◽  
Author(s):  
Guan Jun Qiao ◽  
Hong Jie Wang ◽  
Ji Qiang Gao ◽  
Zhi Hao Jin
Keyword(s):  
Shear Strength ◽  
Crystal Lattice ◽  
Layer Structure ◽  
Complex Oxide ◽  
Main Reaction ◽  
Main Reaction Product ◽  
Thermal Cycles ◽  
Interesting Phenomenon ◽  
Annealing Effects ◽  
Kovar Alloy

High purity alumina ceramic and Kovar alloy were brazed by Nickel and Titanium foils stacked as Ni/Ti/Ni layer structure. Airtight joints were achieved with shear strength more than 30MPa, after brazing at 995oC for 30min. A sandwich structure was observed in solder, which means an a-Ti solid solution belt at mid part and Ti2Ni intermetallics belts at both sides. The main reaction product at alumina/solder interface was Ni2Ti4O, a complex oxide with structure similar to Ti2Ni, which is the bonding agent and transition from the solder’s metallic crystal lattice to alumina crystal lattice. To simulate the actual serving conditions, a thermal cyclic experiment was undertaken at the 200oC-600oC temperature range. The results showed that shear strength of joint increased dramatically after thermal cycles. This interesting phenomenon is attributed to the annealing effects of thermal cycles, which released residual stress in brazed joints remarkably.

scholarly journals The Interface Microstructure and Shear Strength of Sn2.5Ag0.7Cu0.1RExNi/Cu Solder Joints under Thermal-Cycle Loading

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 518 ◽  
Author(s):  
Congcong Cao ◽  
Keke Zhang ◽  
Baojin Shi ◽  
Huigai Wang ◽  
Di Zhao ◽  
...  
Keyword(s):  
Shear Strength ◽  
Fracture Mechanism ◽  
Thermal Cycle ◽  
Solder Joints ◽  
Joint Interface ◽  
Interface Microstructure ◽  
Average Thickness ◽  
Thermal Cycles ◽  
Initial State ◽  
Cycle Loading

The interface microstructure and shear strength of Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints under thermal-cycle loading were investigated with scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and physical and chemical tests. The results show that an intermetallic compound (IMC) layer of Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints evolved gradually from the scalloped into larger wavy forms with increasing number of thermal cycles. The roughness and average thickness of IMC increased with thermal-cycle loading. However, at longer thermal-cycle loading, the shear strength of the joints was reduced by about 40%. The fracture pathway of solder joints was initiated in the solder seam with ductile fracture mechanism and propagated to the solder seam/IMC layer with ductile-brittle mixed-type fracture mechanism, when the number of thermal cycles increased from 100 to 500 cycles. By adding 0.05 wt.% Ni, the growth of the joint interface IMC could be controlled, and the roughness and average thickness of the interfacial IMC layer reduced. As a result, the shear strength of joints is higher than those without Ni. When compared to joint without Ni, the roughness and average thickness of 0.05 wt.% Ni solder joint interface IMC layer reached the minimum after 500 thermal cycles. The shear strength of that joint was reduced to a minimum of 36.4% of the initial state, to a value of 18.2 MPa.

Investigations on Phosphate Cements Hardening at Room Temperature

1989 ◽  
Vol 179 ◽  
Author(s):  
Alfred Zurz ◽  
I. Odler ◽  
B. Dettki
Keyword(s):  
Ultimate Strength ◽  
Room Temperature ◽  
Main Reaction ◽  
Main Reaction Product

AbstractPastes prepared from diammonium orthophosphate and calcined magnesia, MgO, exhibit a fast setting and hardening associated with NH3 liberation. Struvite, MgNH4PO4.6H2O, was found to be the main reaction product. Pastes made with NaH2PO4 or Na-polyphosphate exhibit a similar hardening reaction. The hardening reaction may be retarded and the ultimate strength moderately increased by adding appropriate retarders, such as Na2B4O7 10H2O to the system. The quality of the used MgO and its fineness has a significant effect on the rate of the hardening reaction.

scholarly journals Oxidative Destruction of Vulcanized by Changing the Dispersion Composition of Oxidized Vulcanized

2021 ◽  
pp. 207-214
Author(s):  
Milen Dimov ◽  
Zhuldyz Smailova
Keyword(s):  
Nitric Acid ◽  
Ir Spectra ◽  
Structural Changes ◽  
Main Reaction ◽  
Chemical Heterogeneity ◽  
Main Reaction Product ◽  
Oxidative Destruction ◽  
Rubber Component ◽  
Acetone Extracts ◽  
Dispersion Composition

The aim of the present work is to study the processes of oxidative destruction of waste vulcanizates (flakes) with nitric acid. The composition of the particles of the main reaction product was determined (oxidized vulcanized). The IR spectra of hexane and acetone extracts of the oxidized vulcanizates are also presented. It was found that the rubber component of the vulcanizates undergoes deep structural changes leading to the formation of products characterized by chemical heterogeneity

scholarly journals Hundred Years of Lactitol: From Hydrogenation to Food Ingredient

2020 ◽  
Author(s):  
Sergio I. Martinez-Monteagudo ◽  
Kaavya Rathnakumar ◽  
Maryam Enteshari ◽  
Collette Nyuydze ◽  
Juan C. Osorio-Arias ◽  
...  
Keyword(s):  
Historical Development ◽  
Main Reaction ◽  
Chewing Gum ◽  
Main Reaction Product ◽  
Food Ingredient ◽  
First Report

The first report on the synthesis of lactitol dates back to the early 1920s. Nearly 100 years have passed since then, and the applications of lactitol have exceeded its original purpose. Currently, lactitol is used in bakery, confectionery, chocolate, desserts, chewing gum, cryoprotectant, delivery agent, and stabilizer in biosensors. Lactitol is the main reaction product derived from the hydrogenation of lactose. This chapter is aimed at providing a succinct overview of the historical development of lactitol, a summary of its synthesis, and an overview of its properties and applications.

THE SOLVOLYSIS OF THE ALPHA- AND BETA-3,4,6-TRI-O-ACETYL-D-GLUCOPYRANOSYL CHLORIDES

1955 ◽  
Vol 33 (1) ◽  
pp. 128-133 ◽  
Author(s):  
R. U. Lemieux ◽  
G. Huber
Keyword(s):  
Acetic Acid ◽  
Double Bond ◽  
Positive Charge ◽  
Main Reaction ◽  
Main Reaction Product ◽  
Double Bond Character ◽  
Ionic Reactions ◽  
Oxygen Bond ◽  
Bond Character ◽  
Anomeric Center

3,4,6-Tri-O-acetyl-β-D-glucopyranosyl chloride was found to undergo solvolysis in acetic acid to form 1,3,4,6-tetra-O-acetyl-α-D-glucopyranose as the main reaction product. The much less reactive anomeric α-chloride also appeared to undergo solvolysis with extensive inversion of the anomeric center. It is submitted that the tendencies for inversion obtained in these ionic reactions are due to the conformations imposed on the intermediate ions through distribution of the positive charge to the ring oxygen and the consequent introduction of double-bond character to the carbon-1 to ring-oxygen bond.

Lightweight magnesium phosphate cement composites with struvite recovered from wastewater

2020 ◽  
Author(s):  
Parisa Setayesh Gar ◽  
Sergey Lobanov ◽  
Matteo Pernechele ◽  
Cristina Zanotti
Keyword(s):  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Potassium Dihydrogen Phosphate ◽  
Magnesium Phosphate ◽  
Main Reaction ◽  
Dihydrogen Phosphate ◽  
Main Reaction Product ◽  
Lightweight Composites ◽  
Phosphate Source

A feasibility study was performed to utilize struvite, in combination with magnesium oxide (MgO), to develop magnesium phosphate cement. The struvite was a wastewater by-product from a sewage treatment plant in British Columbia, Canada. To achieve MgO-phosphate reactivity in water, two types of recycled struvite were used: heated struvite and newberyite (i.e. rehydrated struvite). A more common phosphate source, Potassium Dihydrogen Phosphate (KDP) was also adopted and replaced in different proportions by recycled struvite. Perlite was incorporated to produce lightweight composites for building applications at different strength-density ratios. Microstructural/chemical analyses were complemented with compressive strength tests at different ages. Reactivity with MgO was achieved for both heated struvite and newberyite. The main reaction product was cattite but reactivity of less soluble newberyite was lower. KDP had the fastest reaction leading to the formation of K-struvite. The lightweight composites achieved up to 90% of their strength in 7 days.

scholarly journals Experimental Analysis and Modeling of Nitrate Removal through Zero-Valent Magnesium Particles

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1276 ◽  
Author(s):  
Siciliano ◽  
Curcio ◽  
Limonti
Keyword(s):  
Nitrate Concentration ◽  
Nitrate Removal ◽  
Experimental Results ◽  
Process Efficiency ◽  
Main Reaction ◽  
Main Reaction Product ◽  
Nitrogen Forms ◽  
Sustainable Technologies ◽  
Batch Tests ◽  
Effects Of Ph

The pollution of water by nitrates represents an important environmental and health issue. The development of sustainable technologies that are able to efficiently remove this contaminant is a key challenge in the field of wastewater treatment. Chemical denitrification by means of zero-valent metallic elements is an interesting method to reduce the oxidized forms of nitrogen. Compared to other metallic reactants, zero-valent magnesium (ZVM) has many profitable aspects, but its use for nitrate removal has scarcely been investigated. In the present work, several batch tests were conducted to examine the concurrent effects of pH, initial nitrate concentration and Mg0 quantity on process performance. The experimental results proved that at pH 3, for a given initial nitrate concentration, the dose of ZVM largely influences process efficiency. In particular, with a ratio between Mg0 and initial N-NO3− amount (Mg/NNi) of 0.33 g/mg, it is possible to obtain complete denitrification within 30 min. Beyond this ratio, no further improvement of treatment was observed. The experiments allowed us to identify the nitrogen forms produced during the treatment. Nitrogen gas was generally the main reaction product, but the trends of the different compounds (NO3−, NO2−, NH4+ and N2) notably changed in response to the modification of operating parameters. Moreover, the results demonstrated that, in a highly acidic environment, when treating solutions with a low nitrate concentration, process performances are unsatisfactory even when using a high Mg/NNi ratio. By increasing the process pH to 5 and 7, a significant denitrification decline occurred. Furthermore, at these pH levels, the enhancement of nitrate concentration caused a progressive process deterioration. Through detailed analysis of experimental results, reactions kinetics and new mathematical equations, able to describe the trends of different nitrogen forms, have been defined. Moreover, reactions pathways have been proposed. Finally, the characterization of exhausted material allowed us to identify the corrosion products formed during the treatment.

scholarly journals Chemical Denitrification with Mg0 Particles in Column Systems

2020 ◽  
Vol 12 (7) ◽  
pp. 2984 ◽  
Author(s):  
Alessio Siciliano ◽  
Giulia Maria Curcio ◽  
Carlo Limonti
Keyword(s):  
Kinetic Constant ◽  
Operating Parameter ◽  
Process Efficiency ◽  
Main Reaction ◽  
Main Reaction Product ◽  
Reaction Products ◽  
Metallic Elements ◽  
Reactive Material ◽  
Maximum Reaction Rate ◽  
Maximum Reaction

The removal of nitrate from aqueous environments through zero-valent metallic elements is an attractive technique that has gained increasing interest in recent years. In comparison to other metallic elements, zero-valent magnesium (ZVM) has numerous beneficial aspects. Nevertheless, the use of Mg0 particles for nitrate reduction in column systems has not been investigated yet. To overcome the lack of research, in the present study, a wide experimental activity was carried out to develop a chemical denitrification process through ZVM in batch column equipment. Several tests were executed to evaluate the effects of recirculation hydraulic velocity, pH, Mg0 amount, N-NO3− initial concentration and temperature on the process performance. The results show that the process efficiency is positively influenced by the recirculation velocity increase. In particular, the optimal condition was detected with a value of 1 m/min. The process pH was identified as the main operating parameter. At pH 3, abatements higher than 86.6% were reached for every initial nitrate concentration tested. In these conditions, nitrogen gas was detected as the main reaction product. The pH increase up to values of 5 and 7 caused a drastic denitrification decline with observed efficiencies below 26%. At pH 3, the ratio (RMN) between Mg0 and initial nitrate amount also plays a key role in the treatment performance. A characteristic value of about RMN = 0.333 gMg0/mgN-NO3− was found with which it is possible to reach the maximum reaction rate. Unexpectedly, the process was negatively affected by the increase in temperature from 20 to 40 °C. At 20 °C, the material showed satisfactory denitrification efficiencies in subsequent reuse cycles. With the optimal RMN ratio, removals up to 90% were detected by reusing the reactive material three times. By means of a kinetic analysis, a mathematical law able to describe the nitrate abatement curves was defined. Moreover, the relation between the observed kinetic constant and the operating parameters was recognized. Finally, the reaction pathways were proposed and the corrosion reaction products formed during the treatment were identified.

The formation of intermetallic layer structure of SAC405/Cu and SAC405/ENImAg solder joint interfaces

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Rabiatul Adawiyah Mohamed Anuar ◽  
Saliza Azlina Osman
Keyword(s):  
Shear Strength ◽  
Surface Finish ◽  
Printed Circuit Boards ◽  
Solder Joints ◽  
Layer Structure ◽  
Ageing Time ◽  
Intermetallic Layer ◽  
Electroless Nickel ◽  
Optical Microscope ◽  
Content Type

Purpose The surface finish is an essential step in printed circuit boards design because it provides a solderable surface for electronic components. The purpose of this study to investigate the effects of different surface finishes during the soldering and ageing process. Design/methodology/approach The solder joints of Sn-4.0Ag-0.5Cu/Cu and Sn-4.0Ag-0.5Cu/electroless nickel/immersion silver (ENImAg) were investigated in terms of intermetallic (IMC) thickness, morphology and shear strength. The microstructure and compositions of solder joints are observed, and analyzed by using scanning electron microscopy (SEM-EDX) and optical microscope (OM). Findings Compounds of Cu6Sn5 and (Cu, Ni)6Sn5 IMC were formed in SAC405/Cu and SAC405/ENImAg, respectively, as-reflowed. When the sample was exposed to ageing, new layers of Cu3Sn and (Ni, Cu)3Sn5 were observed at the interface. Analogous growth in the thickness of the IMC layer and increased grains size commensurate with ageing time. The results equally revealed an increase in shear strength of SAC405/ENImAg because of the thin layer of IMC and surface finish used compared to SAC405/Cu. Hence, a ductile fracture was observed at the bulk solder. Overall, the ENImAg surface finish showed excellent performance of solder joints than that of bare Cu. Originality/value The novel surface finish (ENImAg) has been developed and optimized. This alternative lead-free surface finish solved the challenges in electroless nickel/immersion gold and reduced cost without affecting the performance.

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