Rückseitenmetallisierung Wafer‐basierter Si‐Solarzellen mittels EB‐PVD

Back Side Metallization of Wafer Based Silicon Solar Cells by Means of Electron Beam Evaporation Electron beam evaporation is an innovative vacuum deposition technology regarding the wafer backside metallization of crystalline silicon solar cells. The motivation for the consideration of electron beam evaporation as cell finishing step is based on the one hand on the competition with thin film photovoltaic modules and on the other on the remarkable cost reduction potential by applying EB‐PVD (Electron Beam Physical Vapor Deposition). This article presents a highly productive coater concept and gives an explanation of important aspects for the adaption of the coater concept to typical solar cell features. Various PVD technologies are compared concerning their possible use as wafer backside metallization method. Challenges and chances of the introduction of EB‐PVD in the wafer based solar cell production are considered.     

Solubility Differences of Major Storage Proteins of Brassicaceae Oilseeds

Seeds of six commercially produced Brassica juncea, Brassica napus and Sinapis alba varieties representing high-glucosinolate condiment-type and low-glucosinolate canola-type were studied for solubility characteristics of the predominant seed storage proteins (SSPs). The non-protein nitrogen components such as glucosinolates, nucleic acids, betaine, choline and sinapine contributed 3.1–5.2% and 7.9–10.8% for the total N content of low- and high-glucosinolate meals, respectively. The cruciferin and napin which are the predominant SSPs of crucifers were purified from these seeds and used to confirm soluble protein types under the conditions provided. The napins were soluble between pH 2 and 4 but not the cruciferins. Strong alkaline pH brought both cruciferin and napin into solution. In general, the SSP solubility was increased due to the presence of NaCl or CaCl₂ salts in the medium. The effect of CaCl₂ on solubility was more positive than NaCl for all the seed types except S. alba at neutral and alkaline pH. Presence of salts indeed reduced solubility of S. alba SSPs at alkaline pH. The medium pH and salt ions and their ionic strength can be manipulated to achieve selective solubility of napin and cruciferin of Brassicaceae seed meals.     

Complementary characterization techniques for identification of ferroelectric domains in KNbO3 single crystals

KNbO₃ single crystals are often utilized for their piezoelectric and optical properties. In this study the domain configurations in as-grown single crystals were investigated using reflected light microscopy, scanning electron microscopy and atomic force microscopy. Using atomic force microscopy it was possible to image the distortion induced on the crystal surface by the domain walls and to quantify the predicted angle between (001)_pc planes across these walls for the cases of both 90° domain walls and S walls. These features can also be imaged using the other two techniques. This direct measurement of surface distortion verifies the geometrical model of domain structures, and suggests that any possible strain energy considerations are minor in predicting the surface topography in the material after phase changes from the growth temperature.     

Characterization of Silicon Nanoparticles Formed from a Fluidized Bed Reactor and Their Incorporation onto Metal-Coated Carbon Fibers

Enhancing the light trapping using nonwoven arrays of fibers has the potential to improve the photocurrent of silicon solar cells. In this work, amorphous and crystalline Si nanopowders (30–300 nm) were embedded in carbon fibers and fixed in place with electrodeposited nickel. Scanning and transmission electron microscopy techniques have been used to study the morphology of the Si particles and their interactions with the coatings. Two types of nanoparticles are identified, homogeneous nucleated particles (amorphous particles with some crystalline regions) and attrition particles (mostly crystalline products formed from fracture of particles as they grow in a fluidized bed reactor). Using the Brunauer–Emmett–Teller (BET) technique, the surface area and the pore diameter of these agglomerated Si nanoparticles were calculated to be 6.4 m²/g and 9.8 nm, respectively. After embedding the Si particles into the carbon matrix with the metal coatings, the electrical resistivity decreases, suggesting it is possible to enhance the light extraction of silicon solar cells using Si nanoparticles.     

Seasonal changes in testicular size and serum LH,prolactin and testosterone concentrations in male polar bears (Ursus maritimus)

Little is known about the reproductive endocrinology of the male polar bear, Ursus maritimus, except that serum testosterone concentrations are high in April and May during the mating season and are low from August to November during the non-mating season. The objective of this study was to describe the relationship between seasonal changes in testicular size and serum concentrations of testosterone, LH and prolactin. Blood samples and testicular measurements were obtained from free-ranging male polar bears in Canada in April (n = 5) and May (n = 15) near Resolute Bay, Northwest Territories and near Churchill, Manitoba in July (n = 15) and October (n = 22). Testis size was greater in May (39.4 +/- 3.5 cm(2)) than in October (27.3 +/- 2.0 cm(2)) (P = 0.002). Serum testosterone concentrations were approximately three-fold higher in April (5.8 +/- 0.8 ng ml(-1)) than in May (1.7 +/- 0.5 ng ml(-1)), July (0.6 +/- 0.2 ng ml(-1)) and October (1.1 +/- 0.2 ng ml(-1)). Similarly, serum LH concentrations were high in April (0.14 +/- 0.04 ng ml(-1)) and low in May (0.09 +/- 0.01 ng ml(-1)), July (0.10 +/- 0.02 ng ml(-1)) and October (0.08 +/- 0.00 ng ml(-1)). Serum prolactin concentrations were high in April (1.9 +/- 0.3 ng ml(-1)), highest in May (2.5 +/- 0.2 ng ml(-1)), lower in July (1.3 +/- 0.1 ng ml(-1)) and lowest in October (0.8 +/- 0.07 ng ml(-1)). The present study demonstrates a positive relationship between testicular size and serum concentrations of LH, prolactin and testosterone in the male polar bear and confirms the previously reported seasonal changes in serum testosterone concentrations. Data from the present study provide important baseline and comparative endocrine information that can be used to aid captive breeding programmes in zoos and to further ecological-behavioural studies of polar bears.     

Experimental and numerical analysis of electrophoretic deposition on charge selective surfaces in external electric fields

Abstract

In this paper, we present chronopotentiometric results of direct current (DC) membrane electrophoretic deposition (DC-M-EPD) experiments and analyse the influence of the parameters solid concentration, particle size and electrical conductivity of colloidal fumed silica model suspensions on voltage–current curves. The expected streamline patterns are numerically modelled based on coupled mass balances, Ohmic law, Navier–Stokes and Nernst-Planck equations. The results confirm that overlimiting current condition is an obligatory condition for the formation of EPD green deposits under suitable DC-M-EPD conditions. Furthermore, micro-EPD experiments in external alternating current (AC) fields (micro-AC-EPD) using video microscopy come to the conclusion that the observed formations of microvortices are in accordance to the numerically modelled streamline patterns. Finally, the formation of AC-EPD microdeposits exhibiting a torus-like microstructure is substantially explained based on microfluidic streamline pattern analysis.     

Surfactants as Antimicrobials: A Brief Overview of Microbial Interfacial Chemistry and Surfactant Antimicrobial Activity

In this brief overview of a large and complex subject, as presented at the 2018 Surfactants in Solution conference, the need for, and impact of, hard surface antimicrobial products is demonstrated. The composition of the interfaces of three common classes of pathological microbes, bacteria, viruses, and fungi, is discussed so that surfactant and cleaning product development scientists better understand their interfacial characteristics. Studies of antimicrobial efficacy from the four major classes of surfactants (cationic, anionic, amphoteric, and nonionic) are shown. The need for preservatives in surfactants is elucidated. The regulatory aspects of antimicrobials in cleaning products to make antimicrobial claims are stressed.     

Duplex α,β-Sialon Ceramics Stabilized by Dysprosium and Samarium

Duplex αβ,-sialon ceramics with a minimum volume fraction of residual intergranular glass have been prepared using Dy or Sm as the α-sialon stabilizing element. These microstructures contained high aspect ratio β-sialon grains homogeneously distributed in an α-sialon matrix. A number of the larger α-sialon grains contained dislocations and showed a core/shell structure. Dy gave an α-sialon which was stable over a wide temperature range (1350–1800°C) for long holding times, while the use of Sm resulted in less stable α-sialon structures at medium temperatures (1450°C) and the formation of melilite, R₂Si_3−xAl_xO_3+xN_4−x, β-sialon, and the 21R sialon polytype during prolonged heating. High α-phase contents gave a very high hardness ( H _V10 is approximately 22 GPa) but a comparatively low indentation fracture toughness (around 4.4 MPam^1/2). Duplex sialons fabricated from powder mixtures corresponding to an α-to-β sialon ratio of around 50:50 resulted in a sialon material with a favorable combination of high hardness (around 22 GPa) and increased toughness (to around 5.5 MPam^1/2).