Sn-0.5Cu(-x)Al solder alloys: microstructure-related aspects and tensile properties responses

In this study, experiments were conducted to analyze the effect of 0.05 and 0.1 wt.% Al additions during the unsteady-state growth of the Sn-0.5wt.%Cu solder alloy. Various as-solidified specimens of each alloy were selected so that tensile tests could also be performed. Microstructural aspects such as the dimensions of primary, lambda(1), and secondary, lambda(2), dendritic arrays, and intermetallic compounds (IMCs) morphologies were comparatively assessed for the three tested compositions, that is, Sn-0.5wt.%Cu, Sn-0.5wt.%Cu-0.05wt.%Al, and Sn-0.5wt.%Cu-0.1wt.%Al alloys. Al addition affected neither the primary dendritic spacing nor the types of morphologies identified for the Cu6Sn5 IMC, which was found to be either globular or fibrous regardless of the alloy considered. Secondary dendrite arm spacing was found to be enlarged and the eutectic fraction was reduced with an increase in the Al-content. Tensile properties remained unaffected with the addition of Al, except for the improvement in ductility of up to 40% when compared to the Sn-0.5wt.%Cu alloy without Al trace. A smaller lambda(2) in size was demonstrated to be the prime microstructure parameter associated with the beneficial effect on the strength of the Sn-0.5wt.%Cu(-x)Al alloys92CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO AMAZONAS - FAPEAM407978/2018-6; 307830/2017-92015/11863-5; 2016/18186-1; 2017/12741-6sem informaçã

COVID-19: seus impactos clínicos e psicológicos na população idosa / COVID-19: its clinical and psychological impacts on the elderly population

O novo coronavírus foi detectado pela primeira vez em Wuhan, na China, causando infecções respiratórias em humanos e animais, apresentando sinais e sintomas clínicos semelhantes a um resfriado, podendo-se agravar para uma síndrome respiratória aguda grave (SARS), lesão cardíaca e infecção secundária. Esse novo coronavírus pertencente ao gênero ? (beta) é denominado de SARS-Cov-2 causador da pandemia mundial de COVID-19. Além da pandemia do COVID-19 afetar pessoas em todo o mundo, está é associada a uma mortalidade maior em idosos. Diante disso, o isolamento social pregado pela organização mundial da saúde (OMS) tem causado influencias no comportamento dessa população, contribuindo para modulação dos sistemas biológicos, entre eles a psicologia e fisiologia. Por meio de uma revisão qualitativa exploratória da literatura, fundamentada em artigos encontrados nas plataformas ScienceDirect, biblioteca eletrônica Scielo, National Center for Biotechnology Information (NCBI) e Biblioteca Virtual em Saúde (BVS), o trabalho ressalta a importância de analisar e investigar os impactos do novo coronavírus no metabolismo e psicológico dos idosos. Portanto, evidenciou-se a necessidade do incentivo de pesquisas voltadas para estudos sobre os efeitos do COVID-19 nos idosos, afim de traçar um plano de cuidados possibilitando uma melhora nas funções psicológicas e fisiológicas nesses pacientes

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Solidification thermal parameters, microstructure and mechanical resistance of the eutectic Sn-0,7wt%Cu (-Ni) alloys

Sn-Pb traditional solder alloys were overly utilize in electronic devices industry, since their properties and features use were adequate and well known. In the last years many restrictions and directives were and have been designed with a view to minimize or eliminate the use of this metal in the electronic industry. Thereby, several lead-free solder alloys emerged. Among these alloys, eutectic Sn-0.7wt%Cu (TE=227°C) appears as potential candidate to replace eutectic Sn-37wt%Pb alloys, because present low cost when compared with the other lead-free solder alloys. Fatigue resistance and fluidity are quite similar compared with those obtained for the traditional Sn-Pb alloys. Small alloying additions of Ni in Sn-Cu eutectics between levels 20-1000ppm Ni can improve welding properties such as good fluidity, reliability, fine degree of wetting, ensuring suitable mechanical resistance of solder joint. Thus, the main goals of present study are investigate the influence of the Ni microadditions on solidification thermal parameters (transient interfacial heat transfer coefficient - hi), eutectic growth rate v and cooling rate - &#7786;), microstructure features (dendritic and cellular spacings, &#955;1 and &#955;C) and tensile properties in directionally solidified Sn-0.7wt%Cu, Sn-0.7wt%Cu-0.05wt%Ni e Sn-0.7wt%Cu-0.1wt%Ni alloys under unsteady-state conditions against AISI steel carbon 1020 water-cooled bottom part. Measurements of hi coefficient showed that Ni microadditions (500 and 1000ppm of Ni) in the eutectic Sn-0.7wt%Cu affected significantly the fluidity levels. The microstructures obtained for the Sn-0,7wt%Cu-(xNi) alloys presented eutectic colonies/cells along the casting length, with dendritic regions only on first positions close to the bottom. Small Ni additions promoted increase on ultimate tensile strength (&#963;u) and elongation (&#948;), with the Sn-0.7wt%Cu-0.05wt%Ni alloy corresponding to the better combination of &#963;u and &#948;, 36.6MPa and 12.1%, respectively.As tradicionais ligas de soldagem Sn-Pb foram excessivamente utilizadas na indústria de dispositivos eletrônicos, uma vez que suas características de uso e propriedades eram adequadas e bem conhecidas. Contudo, devido aos problemas acarretados pela toxidade do Pb, várias restrições/diretrizes foram e estão sendo criadas a fim de minimizar ou eliminar o uso desse metal na indústria eletrônica. Com isso, diversas ligas de soldagem livres de Pb surgiram e dentre tais ligas, a liga eutética Sn-0,7%Cu (TE=227°C) surge com uma alternativa promissora para a substituição de ligas de solda contendo Pb, pois apresentam menor custo que as demais ligas de soldagem e propriedades como resistência à fadiga e fluidez semelhantes às obtidas para ligas do sistema Sn-Pb. Neste contexto, microadições de Ni em ligas eutéticas Sn-Cu em níveis entre 20 e 1000ppm podem trazer melhorias de propriedades de soldagem como boa fluidez, boa soldabilidade, bom grau de molhamento, garantindo adequada resistência mecânica da junta soldada. Assim, o presente estudo objetiva investigar a influência de microadições de Ni nos parâmetros térmicos de solidificação (coeficiente interfacial de transferência de calor metal/molde - hi, velocidade de solidificação - v e taxa de resfriamento - &#7786;), nas características estruturais (espaçamento intercelular e interdendrítico, &#955;C e &#955;1) e nas propriedades mecânicas de tração das ligas Sn-0,7%Cu, Sn-0,7%Cu-0,05%Ni e Sn-0,7%Cu-0,1%Ni solidificadas unidirecionalmente no sentido vertical ascendente contra chapa molde de aço carbono 1020. Os valores de hi mostraram que microadições de Ni (500 e 1000ppm) em ligas eutéticas Sn-0,7%Cu afetaram consideravelmente o nível de fluidez. As microestruturas das ligas Sn-0,7%Cu-(xNi) apresentaram colônias eutéticas ao longo dos lingotes, com regiões dendríticas apenas nas posições próximas da base refrigerada. As microadições de Ni promoveram um aumento do limite de resistência à tração (&#963;u) e do alongamento específico (&#948;), com a liga Sn-0,7%Cu-0,05%Ni apresentando a melhor combinação &#963;u/&#948;, 36,6 MPa e 12,1%, respectivamente

Correlations among microstructures, thermal parameters and mechanical resistances of sn-bi-(cu,ag) alloys

The present research aims to develop a theoretical/experimental analysis of the combined effects of solidification thermal parameters, Bi content and addition of ternary elements (Cu, Ag) on the final microstructure aspects and on the final mechanical resistances of directionally solidified Sn-Bi, Sn-Bi-Ag and Sn-Bi-Cu solder alloys under transient heat flow conditions. Hence, experimental interrelations between microstructure and thermal parameters and between mechanical properties and microstructure could be established. The microstructures regarding the Sn-34wt.%Bi and Sn-52wt.%Bi alloys show the presence of β-Sn dendrites with Bi precipitates on their own, being enveloped by a lamellar binary Sn-Bi eutectic. The Sn-58wt.%Bi eutectic alloy show a variety of microstructures along the length of the directionally solidified casting, which includes binary eutectic, Bi plates, Bi trifoils and fishbone eutectic. In the case of the ternary Sn-Bi-Ag and Sn-Bi-Cu chemistries, microstructures are constituted by β-Sn dendrites decorated with Bi particles, Bi-Sn eutectic and Cu6Sn5 and Ag3Sn intermetallic particles for the Cu and the Ag bearing alloys, respectively. Experimental growth laws have been derived for both dendritic (λ1, λ2, λ3) and eutectic (λfine, λcoarse) arrangements considering the following alloys: binary Sn-34wt.%Bi, Sn-52wt.%Bi e Sn-58wt.%Bi alloys and ternary Sn- 34wt.%Bi-0.1wt.%Cu, Sn-34wt.%Bi-0.7wt.%Cu e Sn-33wt.%Bi-2wt.%Ag. Considering the binary Sn-Bi, it has been observed that increasing Bi content (34wt.%-->52wt.%-->58wt.%Bi), may cause a decrease on both strength and ductility, except for the sample at P=6mm of the Sn-52wt%Bi alloy. Hall-Petch type functional correlations have been able to represent the evolution of the tensile mechanical properties for the examined Sn-Bi and Sn-Bi-X alloys.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)A presente proposta objetiva desenvolver uma análise teórico/experimental sobre os efeitos combinados dos parâmetros térmicos de solidificação (velocidade de solidificação VL e taxa de resfriamento, ṪL), do teor de Bi e das adições de terceiros elementos (Cu, Ag) na microestrutura e na resistência mecânica de ligas Sn-Bi, Sn-Bi-Ag e Sn-Bi-Cu solidificadas unidirecionalmente, estabelecendo correlações experimentais do tipo microestrutura/parâmetros térmicos e microestrutura/propriedades mecânicas. As microestruturas para as ligas binárias Sn-34%Bi e Sn-52%Bi são constituídas de dendritas de Sn com precipitados de Bi em seu interior, circundadas por um eutético lamelar binário, Sn-Bi. A liga eutética Sn-58%Bi mostrou uma ampla gama de microestruturas ao longo de todo o lingote, englobando o eutético binário Sn-Bi, placas e trifoils de Bi e eutético fishbone. Quanto às ligas ternárias Sn-Bi-Cu e Sn-Bi-Ag observa-se que as microestruturas são constituídas de dendritas β-Sn “decoradas” com partículas de Bi em seu interior, circundadas por uma mistura eutética irregular (Bi+Sn) e seus respectivos compostos intermetálicos primários Cu6Sn5 e Ag3Sn, respectivamente. As leis de crescimento experimentais dendrítico (λ1, λ2, λ3) e eutético (λfino, λgrosseiro) para as ligas binárias Sn-34%Bi, Sn-52%Bi e Sn-58%Bi e para as ligas ternárias Sn-34%Bi- 0,1%Cu, Sn-34%Bi-0,7%Cu e Sn-33%Bi-2%Ag em função de V e Ṫ foram caracterizadas por equações na forma de potência com aplicação de expoentes típicos. No caso das ligas binárias Sn-Bi, foi observado que com o aumento do teor de Bi (34%-->52%-->58%Bi), tanto o limite de resistência à tração (σt) quanto o alongamento específico diminuem, com exceção dos resultados para a amostra P=6mm da liga Sn-52%Bi. Relações funcionais do tipo Hall-Petch foram capazes de descrever a variação das propriedades mecânicas de tração de ligas Sn-Bi e Sn-Bi-X

Evaluation Of Solder/substrate Thermal Conductance And Wetting Angle Of Sn-0.7 Wt%cu-(0-0.1 Wt%ni) Solder Alloys

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Wettability is defined as the tendency of a liquid metal to spread on a solid surface. The solder/substrate thermal conductance represented by a heat transfer coefficient, h(i), states the heat ability to flow across the solder/substrate interface during solidification, being affected by the wettability. This letter aims to investigate the wetting behavior of Sn-0.7 wt%Cu-(Ni) lead-free solders by measuring the contact angles (theta) on a copper substrate as a function of the alloy Ni content. Furthermore, time-dependent h(i) profiles are determined from thermal readings during directional solidification (DS) of Sn-0.7 wt%Cu-(xNi) alloys. It is shown that a smaller initial contact angle (theta(i)=32.7) characterizes the Sn-0.7 wt%Cu-0.05 wt%Ni associated with the highest h(i) value of 11,500t(-032.7) w/m(2) K A (t: time). (C) 2014 Elsevier B.V. All rights reserved.142163167Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2013/08259-3, 2013/13030-5

Microstructural Development And Mechanical Properties Of A Near-eutectic Directionally Solidified Sn-bi Solder Alloy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Sn-Bi solders may be applied for electronic applications where low-temperature soldering is required, i.e., sensitive components, step soldering and soldering LEDs. In spite of their potential to cover such applications, the mechanical response of soldered joints of Sn-Bi alloys in some cases does not meet the strength requirements due to inappropriate resulting microstructures. Hence, careful examination and control of as-soldered microstructures become necessary with a view to pre-programming reliable final properties. The present study aims to investigate the effects of solidification thermal parameters (growth rate VI, and cooling rate TO on the microstructure of the Sn-52 wt%Bi solder solidified under unsteady-state conditions. Samples were obtained by upward directional solidification (DS), followed by characterization through metallography and scanning electron microscopy (SEM). The microstructures are shown to be formed by Sn-rich dendrites decorated with Bi precipitates surrounded by a complex regular eutectic mixture, with alternated Bi-rich and Sn-rich phases. Experimental correlations of primary (lambda(1)), secondary (lambda(2)), tertiary (lambda(3)) dendritic and eutectic spacings (lambda(coarse) and lambda(fine)) with cooling rate and growth rate are established. Two ranges of lamellar eutectic sizes were determined, described by two experimental equations lambda = 1.1 V-L(-1/2) and lambda = 0.67 V-L(-1/2). The onset of tertiary branches within the dendritic array along the Sn-52 wt.%Bi alloy DS casting is shown to occur for cooling rates lower than 1.5 degrees C/s. (C) 2015 Elsevier Inc. All rights reserved.1074353Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPESP [2013/13030-5, 2013/08259-3]CAPES [857/15

Microstructure, phases morphologies and hardness of a Bi–Ag eutectic alloy for high temperature soldering applications

The conversion to RoHS-compliant lead-free assembly has been a considerable challenge to the electronics industry. Among several alternative solder alloys, Bi–Ag alloys have been highlighted as a potential candidate to replace high Pb solder alloys for applications in oil and gas, automotive and avionics industries. The typical melting temperatures of Bi–Ag near-eutectic alloys are considered acceptable and excellent mechanical properties may be achieved with appropriate microstructures. Such promising alloys for high temperature soldering remain barely understood especially regarding non-equilibrium solidification features. In this study, a directional solidification experiment was carried out with the Bi–2.5 wt%Ag eutectic so that a large range of cooling rates () could be obtained under unsteady-state conditions. The experimental investigation include: thermal solidification parameters (growth rate, v and cooling rate, ), microstructure parameters (eutectic/dendritic spacing, interphase spacings) and phases morphologies analyzed by optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and hardness. Experimental interrelations between hardness and microstructure (scale and morphology) of the eutectic Bi–Ag are reported. Solidification parameters are also associated with each configuration observed along the casting, i.e., coexistence of dendrites and eutectic cells for regions very close to the cooled casting surface, eutectic cells prevailing and eutectic cells together with β-Bi primary phase. The cell spacing, λc, is correlated with hardness by Hall–Petch type equations58482490CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPNão tem2013/13030-