Understanding the Effect of Reflow Profile on the Metallurgical Properties of Tin–Bismuth Solders

Sn–Bi alloys are desirable candidates for soldering components on printed circuit boards (PCBs) because of their low melting point and reduced cost. While certain tin–bismuth solders are well characterized many new alloys in this family have been developed which need proper characterization. The following study looks at the behavior of four different Sn–Bi alloys—traditional 42Sn58Bi and 42Sn57Bi1Ag and two new tin–bismuth alloys—in solder paste during the reflow soldering process. Each alloy was processed using different reflow profiles that had varying times above liquidus (TALs) and peak temperatures. The PCBs were then analyzed to see how the processing variables influenced wetting, voiding, microstructure, intermetallic layer composition, and thickness. After analysis, the PCBs were then subjected to thermal cycling experiments to see how reflow profile impacted microstructure evolution. The results demonstrated that reflow profile affects properties such as metal wetting and voiding. It does not however, greatly impact key metallurgical properties such as intermetallic layer thickness.

Tailoring capping-layer composition for improved stability of mixed-halide perovskites

Incorporating a low dimensional (LD) perovskite capping layer on top of perovskite absorber, improves the stability of perovskite solar cells (PSCs). However, in the case of mixed-halide perovskites, which can...

Variation in Tree Layer Composition Across Mid and Higher Elevation Forest Sites in Kumaun Himalayan Region, Uttarakhand

The Himalayan forests are rich in biodiversity and distributed over a large extent from lower to higher elevations. The dependence of the locals for their daily requirements of fuel, fodder and medicinal plants is high on these forests. The study was conducted at altitude varied between 1725 and 3250 masl (above sea level) in Kumaun region. The study deals with the comparison of tree layer vegetation in higher elevation sites (HES) and mid elevation sites (MES) with reference to Diversity, Richness, Basal area (BA), Dominance and Important Value Index. The MES were dominated by mixed Quercus leucotrichophora and Pinus roxburghii forests where as HES sites were dominated by Quercus semecarpifolia and Aesculus indica forests and Rhododendron campanulatum in the understory. Across all the sites the tree species richness ranged between 9 and 15. Tree density was maximum (1400 trees/ha) at MES. Tree diversity and total basal area were maximum at HES. The study will be useful in developing baseline data for carrying out future studies. The data generated will be helpful for the conservation of biodiversity of the region.

Organo-Functionalization: An Effective Method in Enhancing the Separation and Antifouling Performance of Thin-Film Nanocomposite Membranes by Improving the Uniform Dispersion of Palygorskite Nanoparticles

Recently, palygorskite (Pal) has become a promising new membrane additive in flux enhancement and fouling reduction, which is an environmentally friendly nanoclay material under the 2:1 layer composition with 1D tubular structure. However, the aggregation of Pal due to the intermolecular forces is still an obstacle to be solved in improving membrane performance. Herein, Pal nanoparticles were chemically modified by KH550 to weaken the aggregation and improve the dispersibility, and then incorporated into the organic phase to prepare thin-film nanocomposite (TFN) membranes. The results showed that the organo-functionalization could effectively improve the membrane hydrophilicity and dispersion of Pal nanoparticles in the polyamide layer, which contributed to the enhanced water flux (from 25 to 38 L/m2·h), unchanged salt rejection (98.0%) and better antifouling capacity (91% flux recovery rate), which suggested that the organo-functionalization of nanoparticles was an efficient method in further enhancing membrane performance

SIFAT FISIK DAN MEKANIK PAPAN PARTIKEL AMPAS DAN SERAT KULIT BATANG SAGU (Metroxylon spp) BERDASARKAN KOMPOSISI SUSUNAN PARTIKEL DAN RASIO PEREKAT ASAM SITRAT SUKROSA

The purpose of this study is to analyze the effect of layer composition and the ratio of citric acid-sucrose as well as the interaction of both of them to the optimum quality of the particleboards. Particleboards were made in sizes 30 cm x 30 cm x 1 cm with a target density of 0.7 gr/cm3. Particleboards were prepared by hot pressing at temperature of 160 oC for 20 minutes with a pressure of 25 kg/cm2. Particleboards consists of 3 layers with a composition of layers, namely f/b70: c30, f/b60: c40, and f/b50: c50, with a surface layer (face, back) made form of sago stem bark and core layers made form of pulp sago. Ratio of citric acid-sucrose in this study was varied from 0/100, 25/75, 75/25, and 100/0. Particleboards testing refers to standard JIS A 5908-2003 Type 8. The results showed that the layer composition had a significant effect on density, water absorption, internal bond (IB), and screw holding strenght. Meanwhile ratio of citrid acid-sucrose significantly affected the water content, water absorption, thickness development, MOE, MOR, internal bond (IB), and screw holding strenght. The interaction beetwen the composition layer factor and ratio of citrid acid-sucrose has a significant effect on water content, thickness development, MOE, MOR, and internal bond (IB). The best particleboards is in the treatment with the composition of the layer f/b70: c30 and the ratio of citric acid-sucrose 25/75 with a density value of 0.7675 gr/cm3, a moisture content of 7.5939%, modulus of rupture (MOR) 161.4350 kg/cm2, and the screw holding strength is 66.1930 kg/cm2.Keyword: citrid acid-sucrose, composition of layers, dregs and fibers of sago, particleboardsAbstrakTujuan dari penelitian ini adalah untuk menganalisa pengaruh komposisi lapisan dan perbandingan asam sitrat-sukrosa serta interaksi keduanya terhadap kualitas papan partikel yang optimum. Papan partkel dibuat dengan ukuran 30 cm x 30 cm x 1 cm dengan target kerapatan 0,7 gr/cm3. Papan partikel dikempa panas pada suhu 160 oC selama 20 menit dengan tekanan 25 kg/cm2. Papan partikel terdiri dari 3 lapisan dengan komposisi lapisan yaitu f/b70 : c30, f/b60 : c40, dan f/b50 : c50, dengan lapisan permukaan (face, back) berupa serat kulit batang sagu dan lapisan inti (core) berupa ampas sagu. Rasio asam sitrat-sukrosa dalam penelitian ini bervariasi 0/100, 25/75, 75/25, dan 100/0. Pengujian papan partikel mengacu pada standar JIS A 5908-2003 Type 8. Hasil penelitian menunjukkan faktor komposisi lapisan berpengaruh nyata terhadap kerapatan, daya serap air, keteguhan rekat internal (IB) dan kuat pegang sekrup. Sedangkan faktor rasio perekat asam sitrat sukrosa berpengaruh nyata terhadap kadar air, daya serap air, pengembangan tebal, MOE, MOR, keteguhan rekat internal (IB), dan kuat pegang sekrup. Interaksi antara faktor komposisi lapisan dan rasio asam sitrat-sukrosa berpengaruh nyata terhadap daya serap air, pengembangan tebal, MOE, MOR, dan keteguhan rekat internal (IB). Papan partikel terbaik terdapat pada perlakuan dengan komposisi lapisan f/b70 : c30 dan perbandingan asam sitrat-sukrosa 25/75 dengan nilai kerapatan 0,7675 gr/cm3, kadar air 7,5939 %, keteguhan patah (MOR) 161,4350 kg/cm2, dan kuat pegang sekrup 66,1930 kg/cm2. Kata Kunci : ampas dan serat sagu, asam sitrat-sukrosa, komposisi lapisan, papan partikel

The Combination of Abscisic Acid (ABA) and Water Stress Regulates the Epicuticular Wax Metabolism and Cuticle Properties of Detached Citrus Fruit

The phytohormone abscisic acid (ABA) is a major regulator of fruit response to water stress, and may influence cuticle properties and wax layer composition during fruit ripening. This study investigates the effects of ABA on epicuticular wax metabolism regulation in a citrus fruit cultivar with low ABA levels, called Pinalate (Citrus sinensis L. Osbeck), and how this relationship is influenced by water stress after detachment. Harvested ABA-treated fruit were exposed to water stress by storing them at low (30–35%) relative humidity. The total epicuticular wax load rose after fruit detachment, which ABA application decreased earlier and more markedly during fruit-dehydrating storage. ABA treatment changed the abundance of the separated wax fractions and the contents of most individual components, which reveals dependence on the exposure to postharvest water stress and different trends depending on storage duration. A correlation analysis supported these responses, which mostly fitted the expression patterns of the key genes involved in wax biosynthesis and transport. A cluster analysis indicated that storage duration is an important factor for the exogenous ABA influence and the postharvest environment on epicuticular wax composition, cuticle properties and fruit physiology. Dynamic ABA-mediated reconfiguration of wax metabolism is influenced by fruit exposure to water stress conditions.

Microstructural and Corrosion Properties of Burnished 6060 Aluminum Alloy

A process for producing a black oxide coating on aluminum alloy was investigated in the present work. The blackening process is widely used in industrial applications, but it was not deeply studied for aluminum alloys. The aim of this work is to study the black coating obtained on AA6060 surfaces employing two different solutions, both containing potassium permanganate, copper nitrate and nitric acid. The first solution carried out the coloring treatment at 50 °C, whereas the second one was done at room temperature. Different immersion times were investigated. The morphology of the coating was investigated by means of optical and electron microscopy to evaluate the color of the layer and the presence of defects, porosities, and cracks. X-ray diffraction analysis was performed to evaluate the protective layer composition. The corrosion properties were studied with potentiodynamic polarization tests and electrochemical impedance spectroscopy tests. The results showed that the blackening process performed at room temperature, besides the clear advantages in term of costs and safety, obtained more uniform coatings with increased corrosion performance in comparison with the ones obtained at higher temperatures.