Mechanical and Microstructural Analysis of an Ultra-Flexible Nano-Silver Paste Sintered Joint

Soldering using common lead-free solder alloys is still one of the main die attach technology, in particular for applications in power electronics where high temperatures have to be met. However, some newly developed attach technologies promise to offer more interesting features in terms of both mechanical and thermal properties. Among these new methods, sintering of nano-silver particles allows to obtain a high thermal conductivity needed in the assemblies of electronic or optical components, as well as a relatively low elastic modulus for better stress accommodation and enhanced thermo-mechanical reliability. The sintering processing parameters, mainly the bonding pressure, the sintering temperature profile, and the sintering atmosphere, are known to have a critical effect on the properties of the sintered layer, such as its mechanical strength and electrical/thermal performances.In this study, copper substrates are fabricated and assembled by sintering using a nano-silver paste. The objective is to obtain a bonding joint with high mechanical flexbility, capable of addressing the thermomechanical stresses for systems operating under high temperatures. The measured mechanical properties of the sintered material show on the one hand low elastic modulus of the joint which is appropriate for strong difference in thermal expansion between components, and on the other hand sufficient mechanical strength for the assembly. Microstructure analyses reveal a highly porous silver network structure of the joint, with submicrometric silver grains and large micrometric porosities homogeneously distributed.

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Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters

Minerals ◽

10.3390/min11020213 ◽

2021 ◽

Vol 11 (2) ◽

pp. 213

Author(s):

Hamid Ait Said ◽

Hassan Noukrati ◽

Hicham Ben Youcef ◽

Ayoub Bayoussef ◽

Hassane Oudadesse ◽

...

Keyword(s):

Molecular Weight ◽

Compressive Strength ◽

Mechanical Strength ◽

Bone Repair ◽

Mechanical Stability ◽

Three Dimensional ◽

Processing Parameters ◽

Composite Effect ◽

Solid Liquid ◽

The Impact

Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field.

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Cytocompatibility of Ti–xZr alloys as dental implant materials

Journal of Materials Science Materials in Medicine ◽

10.1007/s10856-021-06522-w ◽

2021 ◽

Vol 32 (5) ◽

Author(s):

Pinghua Ou ◽

Cong Hao ◽

Jue Liu ◽

Rengui He ◽

Baoqi Wang ◽

...

Keyword(s):

Elastic Modulus ◽

Pure Titanium ◽

Dead Cell ◽

Commercially Pure Titanium ◽

Modulus Ratio ◽

High Mechanical Strength ◽

Commercially Pure ◽

Low Elastic Modulus ◽

Cell Assays ◽

Osteogenic Induction

AbstractTi–xZr (x = 5, 15, 25, 35, 45% wt%) alloys with low elastic modulus and high mechanical strength were fabricated as a novel implant material. The biocompatibility of the Ti–xZr alloys was evaluated by osteoblast-like cell line (MG63) in terms of cytotoxicity, proliferation, adhesion, and osteogenic induction using CCK-8 and live/dead cell assays, electron microscopy, and real-time PCR. The Ti–xZr alloys were non-toxic and showed superior biomechanics compared to commercially pure titanium (cpTi). Ti–45Zr had the optimum strength/elastic modulus ratio and osteogenic activity, thus is a promising to used as dental implants.

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A novel biomedical titanium alloy with high antibacterial property and low elastic modulus

Journal of Material Science and Technology ◽

10.1016/j.jmst.2021.01.015 ◽

2021 ◽

Vol 81 ◽

pp. 13-25

Author(s):

Diangeng Cai ◽

Xiaotong Zhao ◽

Lei Yang ◽

Renxian Wang ◽

Gaowu Qin ◽

...

Keyword(s):

Titanium Alloy ◽

Elastic Modulus ◽

Antibacterial Property ◽

Low Elastic Modulus ◽

Biomedical Titanium Alloy

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Mechanical and electrical characteristics of silver stabilizer layer prepared by using nano silver paste for coated conductor

Physica C Superconductivity ◽

10.1016/j.physc.2009.05.250 ◽

2009 ◽

Vol 469 (15-20) ◽

pp. 952-955 ◽

Cited By ~ 6

Author(s):

J.B. Lee ◽

S.U. Lee ◽

S.S. Kim ◽

B.J. Kim ◽

H.J. Kim ◽

...

Keyword(s):

Coated Conductor ◽

Electrical Characteristics ◽

Silver Paste ◽

Nano Silver

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Study of the Turning Nickel Base Alloy Pyromet® 31V (SAE HEV8)

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.278.312 ◽

2011 ◽

Vol 278 ◽

pp. 312-320 ◽

Cited By ~ 2

Author(s):

Marcos Valério Ribeiro ◽

André Luís Habib Bahia

Keyword(s):

Thermal Conductivity ◽

Mechanical Strength ◽

High Temperatures ◽

Base Alloy ◽

Production Costs ◽

Machining Parameters ◽

Nickel Base Alloy ◽

Low Thermal Conductivity ◽

Nickel Base ◽

Coated Carbide

Considering the constant technological developments in the aeronautical, space, automotive, shipbuilding, nuclear and petrochemical fields, among others, the use of materials with high strength mechanical capabilities at high temperatures has been increasingly used. Among the materials that meet the mechanical strength and corrosion properties at temperatures around 815 °C one can find the nickel base alloy Pyromet® 31V (SAE HEV8). This alloy is commonly applied in the manufacturing of high power diesel engines exhaust valves where it is required high resistance to sulphide, corrosion and good resistance to creep. However, due to its high mechanical strength and low thermal conductivity its machinability is made difficult, creating major challenges in the analysis of the best combinations among machining parameters and cutting tools to be used. Its low thermal conductivity results in a concentration of heat at high temperatures in the interfaces of workpiece-tool and tool-chip, consequently accelerating the tools wearing and increasing production costs. This work aimed to study the machinability, using the carbide coated and uncoated tools, of the hot-rolled Pyromet® 31V alloy with hardness between 41.5 and 42.5 HRC. The nickel base alloy used consists essentially of the following components: 56.5% Ni, 22.5% Cr, 2,2% Ti, 0,04% C, 1,2% Al, 0.85% Nb and the rest of iron. Through the turning of this alloy we able to analyze the working mechanisms of wear on tools and evaluate the roughness provided on the cutting parameters used. The tests were performed on a CNC lathe machine using the coated carbide tool TNMG 160408-23 Class 1005 (ISO S15) and uncoated tools TNMG 160408-23 Class H13A (ISO S15). Cutting fluid was used so abundantly and cutting speeds were fixed in 75 and 90 m/min. to feed rates that ranged from 0.12, 0.15, 0.18 and 0.21 mm/rev. and cutting depth of 0.8mm. The results of the comparison between uncoated tools and coated ones presented a machined length of just 30% to the first in relation to the performance of the second. The coated tools has obtained its best result for both 75 and 90 m/min. with feed rate of 0.15 mm/rev. unlike the uncoated tool which obtained its better results to 0.12 mm/rev.

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First-principles calculations for development of low elastic modulus Ti alloys

Physical Review B ◽

10.1103/physrevb.70.174113 ◽

2004 ◽

Vol 70 (17) ◽

Cited By ~ 235

Author(s):

Hideaki Ikehata ◽

Naoyuki Nagasako ◽

Tadahiko Furuta ◽

Atsuo Fukumoto ◽

Kazutoshi Miwa ◽

...

Keyword(s):

Elastic Modulus ◽

First Principles ◽

First Principles Calculations ◽

Ti Alloys ◽

Low Elastic Modulus

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Microstructural and Mechanical Properties of β-Type Ti–Nb–Sn Biomedical Alloys with Low Elastic Modulus

Metals ◽

10.3390/met9060712 ◽

2019 ◽

Vol 9 (6) ◽

pp. 712 ◽

Cited By ~ 13

Author(s):

Peiyou Li ◽

Xindi Ma ◽

Duo Wang ◽

Hui Zhang

Keyword(s):

Mechanical Properties ◽

Wear Resistance ◽

Elastic Modulus ◽

Martensite Phase ◽

Ti Alloy ◽

Martensitic Phase Transition ◽

Low Elastic Modulus ◽

Nb Content ◽

Biomedical Alloy ◽

Cp Ti

The microstructural and mechanical properties of β-type Ti85-xNb10+xSn5 (x = 0, 3, 6, 10 at.%) alloys with low elastic modulus were investigated. The experimental results show that the Ti85Nb10Sn5 and Ti75Nb20Sn5 alloys are composed of simple α and β phases, respectively; the Ti82Nb13Sn5 and Ti79Nb16Sn5 alloys are composed of β and α″ phases. The content of martensite phase decreases with the increase of Nb content. The Ti82Nb13Sn5 and Ti79Nb16Sn5 alloys show an inverse martensitic phase transition during heating. The Ti85Nb10Sn5 and Ti82Nb13Sn5 alloys with the small residual strain exhibit the good superelastic properties in 10-time cyclic loading. The reduced elastic modulus (Er) of the Ti75Nb20Sn5 alloy (61 GPa) measured by using the nanoindentation technique is 2–6 times of that of human bone (10–30 GPa), and is smaller than that of commercial Ti-6Al-4V biomedical alloy (120 GPa). The Ti75Nb20Sn5 alloy can be considered as a novel biomedical alloy. The wear resistance (H/Er) and anti-wear capability (H3/Er2) values of the four alloys are higher than those of the CP–Ti alloy (0.0238), which indicates that the present alloys have good wear resistance and anti-wear capability.

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Dynamics of Microbial Inactivation and Acrylamide Production in High-Temperature Heat Treatments

Foods ◽

10.3390/foods10112535 ◽

2021 ◽

Vol 10 (11) ◽

pp. 2535

Author(s):

Jose Lucas Peñalver-Soto ◽

Alberto Garre ◽

Arantxa Aznar ◽

Pablo S. Fernández ◽

Jose A. Egea

Keyword(s):

High Temperature ◽

Food Safety ◽

High Temperatures ◽

Processing Parameters ◽

Temperature Treatment ◽

Heat Treatments ◽

Microbial Inactivation ◽

Point Of View ◽

High Temperature Treatment ◽

Microbiological Safety

In food processes, optimizing processing parameters is crucial to ensure food safety, maximize food quality, and minimize the formation of potentially toxigenic compounds. This research focuses on the simultaneous impacts that severe heat treatments applied to food may have on the formation of harmful chemicals and on microbiological safety. The case studies analysed consider the appearance/synthesis of acrylamide after a sterilization heat treatment for two different foods: pureed potato and prune juice, using Geobacillus stearothermophilus as an indicator. It presents two contradictory situations: on the one hand, the application of a high-temperature treatment to a low acid food with G. stearothermophilus spores causes their inactivation, reaching food safety and stability from a microbiological point of view. On the other hand, high temperatures favour the appearance of acrylamide. In this way, the two objectives (microbiological safety and acrylamide production) are opposed. In this work, we analyse the effects of high-temperature thermal treatments (isothermal conditions between 120 and 135 °C) in food from two perspectives: microbiological safety/stability and acrylamide production. After analysing both objectives simultaneously, it is concluded that, contrary to what is expected, heat treatments at higher temperatures result in lower acrylamide production for the same level of microbial inactivation. This is due to the different dynamics and sensitivities of the processes at high temperatures. These results, as well as the presented methodology, can be a basis of analysis for decision makers to design heat treatments that ensure food safety while minimizing the amount of acrylamide (or other harmful substances) produced.

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