scholarly journals Enhancing the selectivity of prolinamide organocatalysts using the mechanical bond in [2]rotaxanes

2020 ◽  
Vol 11 (14) ◽  
pp. 3629-3635 ◽  
Author(s):  
María Calles ◽  
Julio Puigcerver ◽  
Diego A. Alonso ◽  
Mateo Alajarin ◽  
Alberto Martinez-Cuezva ◽  
...  
Keyword(s):  
Mechanical Bond ◽  
Mechanical Bonding

The mechanical bonding and the cofactor assembly in interlocked prolinamide-based organocatalysts upgrade enamine-type transformations by increasing their yields and enantio- and chemo-selectivities.

scholarly journals Rotaxane PtII-complexes: mechanical bonding for chemically robust luminophores and stimuli responsive behaviour

2020 ◽  
Vol 11 (7) ◽  
pp. 1839-1847 ◽  
Author(s):  
Zhihui Zhang ◽  
Graham J. Tizzard ◽  
J. A. Gareth Williams ◽  
Stephen M. Goldup
Keyword(s):  
Metal Ion ◽  
Stimuli Responsive ◽  
Coordination Environment ◽  
Mechanical Bond ◽  
Mechanical Bonding

We report an approach to interlocked PtII luminophores in which the mechanical bond stabilises the coordination environment of the embedded metal ion.

Comparative Study of Acid Etching on Dental Enamel

2018 ◽  
Vol 69 (10) ◽  
pp. 2913-2915
Author(s):  
Daniela Jumanca ◽  
Anamaria Matichescu ◽  
Atena Galuscan ◽  
Laura Cristina Rusu ◽  
Cornelia Muntean
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Experimental Study ◽  
Orthophosphoric Acid ◽  
Dental Enamel ◽  
Acid Etching ◽  
Sealing Material ◽  
Mechanical Bond ◽  
Materials Used ◽  
Scanning Electron

This experimental study aims to analyse the effectiveness of various materials used in demineralisation of dental enamel. This work aims to create a mechanical bond by filling the pegs with sealing material. In order to achieve this goal, five teeth were compared using different concentrations of orthophosphoric acid and exposure times. In this regard, five different tests were performed and the results were analysed using the SEM technique (scanning electron microscopy). These comparative analyses revealed that etching using 35% orthophosphoric acid for one minute and etching using Icon Etch for two minutes were the most effective.

scholarly journals Contributions of mechanical bonding and chemical bonding to high-temperature hermeticity of glass-to-metal compression seals

2021 ◽  
Vol 202 ◽  
pp. 109579
Author(s):  
Kangjia Hu ◽  
Shenhou Li ◽  
Zhichun Fan ◽  
He Yan ◽  
Xuewei Liang ◽  
...  
Keyword(s):  
High Temperature ◽  
Chemical Bonding ◽  
Mechanical Bonding

scholarly journals Copper-Tantalum Metal Matrix Composites Consolidated from Powder Blends by Severe Plastic Deformation

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1010
Author(s):  
Zachary S. Levin ◽  
Michael J. Demkowicz ◽  
Karl T. Hartwig
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Equal Channel Angular Extrusion ◽  
Rate Sensitivity ◽  
Matrix Composites ◽  
Metal Powders ◽  
Tantalum Metal ◽  
Mechanical Bonding

We investigated the effectiveness of severe plastic deformation by equal channel angular extrusion (ECAE) for consolidation of metal powders into metal matrix composites. Equal volumes of copper (Cu) and tantalum (Ta) powders were consolidated at ambient temperature via different ECAE routes. Composites processed by ECAE routes 4E and 4Bc were also processed at 300 °C. The resulting materials were characterized by scanning electron microscopy (SEM) and compression testing. Processing by route 4Bc at 300 °C resulted in the highest compressive strength, lowest anisotropy, and least strain rate sensitivity. We conclude that the superior properties achieved by this route arise from mechanical bonding due to interlocking Cu and Ta phases as well as enhanced metallurgical bonds from contact of pristine metal surfaces when the material is sheared along orthogonal planes.

Microscopic Study of Smooth Silver-plated Retention Pins in Amalgam

1980 ◽  
Vol 59 (2) ◽  
pp. 124-128 ◽  
Author(s):  
Y. Galindo ◽  
K. McLachlan ◽  
Z. Kasloff
Keyword(s):  
Stainless Steel ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Microscopic Study ◽  
Strong Evidence ◽  
Mechanical Performance ◽  
Silver Layer ◽  
Mechanical Bonding ◽  
Bonding Characteristics ◽  
Scanning Electron

A silver-plating technique was developed in an effort to produce good mechanical bonding characteristics between stainless steelpins and amalgam. Metallographic microscope and scanning electron microscope (SEM) studies were made to assess the presence, or otherwise, of such a bond between (a) the silver layer plating and the surface of the stainless steel pins, and (b) and silver plating and the amalgam. Unplated stainless steel and sterling silver pins were used as a control and as a comparison, respectively. A "rubbing" technique of condensation was devised to closely adapt amalgam to the pins. It is concluded that there is strong evidence for the existence of a good bond between the plated pins and amalgam. The mechanical performance of the bond is discussed elsewhere. 1.

Bonding Constraints at Interfaces Between Crystalline Si and Stacked Gate Dielectrics

1999 ◽  
Vol 567 ◽  
Author(s):  
G. Lucovsky ◽  
J.C. Phillips
Keyword(s):  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Chemical Bonding ◽  
Gate Dielectrics ◽  
Nuclear Charge ◽  
Dielectric Materials ◽  
Band Offset ◽  
High K ◽  
Dielectric Interfaces ◽  
Mechanical Bonding

ABSTRACTThis paper discusses chemical bonding effects at Si-dielectric interfaces that are important in the implementation of alternative gate dielectrics including: i) the character of interfacial bonds, either isovalent with bond and nuclear charge balanced as in Si-SiO2, or heterovalent, with an inherent mismatch between bond and nuclear charge, ii) mechanical bonding constraints related to the average number of bonds/atom, Nay, and iii) band offset energies that are reduced in transition metal oxides due to the d-state origins of the conduction band states. Applications are made to specific classes of dielectric materials including i) nitrides and oxide/nitride stacks and ii) alternative high-K gate materials.

scholarly journals EFFECT OF ETCHING AS PRE-TREATMENT FOR ELECTROLESS COPPER PLATING ON SILICON WAFER

2017 ◽  
Vol 79 (7) ◽  
Author(s):  
Shazatul Akmaliah Mior Shahidin ◽  
Nor Akmal Fadil ◽  
Mohd Zamri Yusop ◽  
Mohd Nasir Tamin ◽  
Saliza Azlina Osman
Keyword(s):  
Silicon Wafer ◽  
Hydrofluoric Acid ◽  
Copper Film ◽  
Etching Time ◽  
Electroless Copper Plating ◽  
Cross Sectional ◽  
Electroless Process ◽  
Pre Treatment ◽  
Sectional Analysis ◽  
Mechanical Bonding

Metallic coatings, such as copper films can be easily deposited on semiconductor materials like silicon wafer without prior surface pre-treatment using the electroless process. However, the adhesion of the copper film can be very weak and can easily peels off. In this study, the effect of etching in hydrofluoric acid solution as a surface pre-treatment prior to electroless plating on silicon wafer was studied. The etching time in hydrofluoric acid was varied at 1, 3 and 5 minutes in order to investigate the adhesion behaviour of the coating layer. The surface morphology of the electroless plated samples was observed using a field emission scanning electron microscope (FESEM) and the coating thickness was measured using cross sectional analysis. The results showed that longer etching time (5 minutes) produced thicker Cu deposits (8.5μm) than 1 minute etching time (5μm). In addition, by increasing the etching time, the mechanical bonding between the copper film and the substrate is improved.

Fabrication of hybrid nanocrystalline Al–Ti alloys by mechanical bonding through high-pressure torsion

2021 ◽  
pp. 142549
Author(s):  
Piotr Bazarnik ◽  
Aleksandra Bartkowska ◽  
Yi Huang ◽  
Karol Szlązak ◽  
Bogusława Adamczyk-Cieślak ◽  
...  
Keyword(s):  
High Pressure ◽  
High Pressure Torsion ◽  
Ti Alloys ◽  
Mechanical Bonding

Design of Microfabricated Mechanically Interlocking Metamaterials for Reworkable Heterogeneous Integration

2021 ◽  
Author(s):  
Geoffrey Garcia ◽  
Kody Wakumoto ◽  
Joseph Brown
Keyword(s):  
Analytical Models ◽  
Elastic Behavior ◽  
Heterogeneous Integration ◽  
Element Analysis ◽  
Microelectronic Devices ◽  
Mechanical Metamaterials ◽  
Dry Adhesives ◽  
Cantilever Array ◽  
Mechanical Bonding ◽  
Interconnect Technology

Abstract Next–generation interconnects utilizing mechanically interlocking structures enable permanent and reworkable joints between microelectronic devices. Mechanical metamaterials, specifically dry adhesives, are an active area of research which allows for the joining of objects without traditional fasteners or adhesives, and in the case of chip integration, without solder. This paper focuses on reworkable joints that enable chips to be removed from their substrates to support reusable device prototyping and packaging, creating the possibility for eventual pick-and-place mechanical bonding of chips with no additional bonding steps required. Analytical models are presented and are verified through Finite Element Analysis (FEA) assuming pure elastic behavior. Sliding contact conditions in FEA simplify consideration of several design variations but contribute ~10% uncertainty relative to experiment, analysis, and point-loaded FEA. Two designs are presented; arrays of flat cantilevers have a bond strength of 6.3 kPa, and non-flat cantilevers have a strength of 29 kPa. Interlocking designs present self-aligning in-plane forces that emerge from translational perturbation from perfect alignment. Stresses exceeding the material yield stress during adhesion operations present a greater concern for repeatable operation of compliant interlocking joints and will require further study quantifying and accommodating plastic deformation. Designs joining a rigid array with a complementary compliant cantilever array preserve the condition of reworkability for the surface presenting the rigid array. Eventual realization of interconnect technology based on this study will provide a great improvement of functionality and adaptability in heterogeneous integration and microdevice packaging.

scholarly journals Investigation of Structure and Physico-Mechanical Properties of Composite Materials Based on Copper - Carbon Nanoparticles Powder Systems

2015 ◽  
Vol 60 (1) ◽  
pp. 51-55
Author(s):  
V. Kovtun ◽  
V. Pasovets ◽  
T. Pieczonka
Keyword(s):  
Mechanical Properties ◽  
Mechanical Activation ◽  
Metal Matrix ◽  
Carbon Nanoparticles ◽  
Copper Matrix ◽  
Metal Particles ◽  
Powder Materials ◽  
Sintered Copper ◽  
Mechanical Bonding ◽  
Preliminary Mechanical Activation

Abstract Physico-mechanical and structural properties of electrocontact sintered copper matrix- carbon nanoparticles composite powder materials are presented. Scanning electron microscopy revealed the influence of preliminary mechanical activation of the powder system on distribution of carbon nanoparticles in the metal matrix. Mechanical activation ensures mechanical bonding of nanoparticles to the surface of metal particles, thus giving a possibility for manufacture of a composite with high physico-mechanical properties.

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