Progress in the development of CuInS2 based mini-modules

A sequential process is used to synthesise CuInS₂ absorber layers for photovoltaic application. In this process CuIn precursor layers sputtered on molybdenum coated float glass are converted to CuInS₂ via sulphurisation in an elemental sulphur vapour ambient. A re-evaluation of process parameters has been performed including fine tuning of numerous minor aspects. Using optimised process conditions has led to improved device performance, especially a narrowed distribution at higher module efficiencies is achieved. At the same time the process yield is improved resulting in fewer devices with poor electrical quality.     

Investigations on intercrystalline creep crack growth of the austenitic steels X 6 CrNi 18 11 and X 8 CrNiMoNb 16 16

The aim of the investigations was to get information about the behaviour of intercrystalline creep cracks during creep deformation from the evaluation of metallographic micrographs and finite element calculations. Two austenitic steels, X 8 CrNiMoNb 16 16 and X 6 CrNi 18 11, were investigated by carrying out creep tests at a temperature of 973 K with varying nominal stresses leading to times of failure from 1 to 3 783 h, as well as to certain creep strains in the tertiary creep stage. These creep tests were followed by analyzing metallographic micrographs of the creep tested specimens and by carrying out finite element calculations, which simulated creep crack growth. It was found that intercrystalline creep cracks in austenitic steel grow independently from momentary crack length but dependent on applied nominal stress and time. Finite element calculations show that local creep strain is a criterion for intercrystalline creep crack growth, contrary to stress-dependent fracture mechanical results.     

Cryofixation of plant tissues without pretreatment

Root tips from Sorghum and Dahlia were frozen without cryoprotection by dipping into nitrogen slush, rapid immersion in liquid propane and by the high-pressure method. Structural preservation of the samples was studied using freeze-fracture (FF) and freeze-substitution (FS) techniques for electron microscopy. It was found that most of the organelles were disrupted by freezing in nitrogen slush and that only the boundary beween the cytoplasm and the vacuole remained visible. If the samples were frozen by rapid immersion in liquid propane, small membraneous organelles, such as dictyosomes, were preserved in peripheral regions of the rhizodermal cells up to 10 μm below the surface of the tissue. Specimens frozen by the high-pressure freezing technique showed good ultrastructural preservation throughout the tissues up to a depth of more than 100 μm.     

Structure and phase relations in the 2(CuInS2)-Cu2ZnSnS4 solid solution system

The intermixing of roquesite (CuInS₂) and kesterite (Cu₂ZnSnS₄), i. e. Cu(In_x(ZnSn)_1−xS₂ was investigated by a combination of neutron and X-ray powder diffraction. Samples with 0 ≤ × ≤ 1 were synthesized by a solid state reaction of the pure elements in evacuated silica tubes at 800 °C and cooled with a 10 K/h rate after the final annealing. The structural parameters of CuIn_x(ZnSn)_1−xS₂ were determined by simultaneous Rietveld refinement of neutron and X-ray diffraction data. The microstructure and chemical composition of the samples were investigated by electron microprobe analysis. A broad miscibility gap exists in the region 0.4 ≤ × < 0.8 indicated by the coexistence of two phases, an In-rich (x ~ 0.77) and a Zn-Sn-rich (x ~ 0.33) phase. Cu(In_x(ZnSn)_1−xS₂ mixed crystals with 0 ≤ x < 0.4 crystallize in the kesterite type structure, and with 0.8 ≤ × ≤ 1.0 in the chalcopyrite type structure. In the latter In, Zn and Sn are disordered on the In site. In the mixed crystals the lattice constant a and c show a linear dependence on chemical composition, whereas the tetragonal deformation Δ = 1−c/2a varies nonlinearly. Moreover in the mixed crystal with x ~ 0.15 the tetragonal deformation is equal zero and thus its structure is characterized by a pseudo-cubic unit cell.     

Modification of unsaturated polyesters by poly(ethylene glycol) end groups

This article reports on the modification of unsaturated polyesters by poly(ethylene glycol) end groups in order to influence the solution behavior in styrene and to modify mechanical properties of the cured resin. The synthesis was done by the reaction of a carboxyl-terminated unsaturated polyester with various poly(ethylene glycol) mono-methyl ethers of molecular weights from 350 to 2000 g/mol. The characterization and curing properties of the synthesized block copolymers are presented. The glass transition temperatures decrease with increasing length of the poly(ethylene glycol) end groups. The introduction of long poly(ethylene glycol) end groups (2000 g/mol) leads to a phase separated and partly crystalline block copolymer with a melting point of 48°C. The block copolymers can be easily diluted in styrene to create the curable resins. The mixtures containing the block copolymers with the short poly(ethylene glycol) end groups (350 and 550 g/mol) could be cured in a reasonably short time. Compared to commercial unsaturated polyesters the mechanical testing revealed that the tensile strength is decreasing while the elongation is increasing. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 527–537, 1997     

Influence of the Molecular Structure and Morphology of Self-Assembled 1,3,5-Benzenetrisamide Nanofibers on their Mechanical Properties

The influence of molecular structure on the mechanical properties of self-assembled 1,3,5-benzenetrisamide nanofibers is investigated. Three compounds with different amide connectivity and different alkyl substituents are compared. All the trisamides form well-defined fibers and exhibit significant differences in diameters of up to one order of magnitude. Using nanomechanical bending experiments, the rigidity of the nanofibers shows a difference of up to three orders of magnitude. Calculation of Young's modulus reveals that these differences are a size effect and that the moduli of all systems are similar and in the lower GPa range. This demonstrates that variation of the molecular structure allows changing of the fibers' morphology, whereas it has a minor influence on their modulus. Consequently, the stiffness of the self-assembled nanofibers can be tuned over a wide range-a crucial property for applications as versatile nano- and micromechanical components.     

The relation between use intensity of private and professional SNS,social comparison,self-esteem,and depressive tendencies in the light of self-regulation

The present study's (N?=?145) aim was to introduce a multidimensional behavioural report for assessing activity on the professional social network site (SNS) XING and to carry out a comparison with private SNS use (i.e. Facebook). Psychometric analyses revealed good internal consistency and construct validity of the new XING Activity Questionnaire. Results suggest that private and professional SNS use is positively correlated to people's ability-related social comparison orientation (SCO) and depressive tendencies on the one hand and negatively correlated to self-esteem on the other hand. In addition, both people's general SCO and opinion-related SCO were solely positively correlated to Facebook use. The findings are in line with the Social Online-Self-Regulation-Theory suggesting that people are using not only private but also professional SNSs for self-regulation.     

Sulfur distribution of low sulfur contents in steel melts

The report deals with investigations of the sulfur behaviour in the Fe–CaO-Al₂O₃ – H₂S-H₂ system at 1600°C and at very low values for the partial pressure of oxygen and sulfur. Results of the equilibrium in the iron-gas system, of the sulfide and sulfur capacities, of the solubility and activity of CaS in CaO-Al₂O₃ slags are represented.