A High-Resolution TEM/EELS Study of the Effect of Doping Elements on the Sliding Mechanisms of Sputtered WS2 Coatings

It has been shown many times that cosputtering low-friction coatings of molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) with other elements can improve the structural, mechanical, and tribological properties. To achieve the lowest friction, MoS₂ or WS₂ should be doped with element(s) improving the hardness and density of the coatings. On the other hand, such elements, or their compounds, should not be present in the outermost molecular layers at the sliding interface. This article suggests that there are important differences between how MoS₂ and WS₂ coatings respond to or react with doping elements, despite the almost identical structure and behavior of the undoped materials. Two systems have been investigated by high-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) electron energy loss spectroscopy (EELS), W-S-C-Cr and W-S-C-Ti, and showed significant amounts of oxides, which typically formed a layer just underneath the crystalline WS₂ top layer. Further, carbon was almost completely absent in the tribofilms, despite the fact that the as-deposited coatings contained as much as 40–50 at% C. An interesting observation here is that WS₂ basal planes surround or embed Fe wear particles, suggesting a relatively strong adhesion or a Fe-S chemical bonding between iron/steel and WS₂. The result of this is that the wear particles become pacified and remain in the contact as low-friction material.     

The politics and policy of energy system transformation—explaining the German diffusion of renewable energy technology

To arrest climate change, a transition to a low-carbon economy must take place quite rapidly, within a century at most. Thus, the rate of diffusion of new technologies such as those for the generation of electricity from renewable energy sources becomes a central issue. This article explores the reasons for the particularly rapid spread of two such technologies in Germany, wind turbines and solar cells. We trace this diffusion to the nature of the policy instruments employed and to the political process which led to the adoption of these instruments. The analysis demonstrates how the regulatory framework is formed in a ‘battle over institutions’ where the German parliament, informed and supported by an advocacy coalition of growing strength, backed support policies for renewables sourced electricity against often reluctant governments and the opposition from nuclear and coal interests. It also demonstrates that this major political and environmental achievement carries a modest price if we consider total costs to society, i.e. including both subsidies to coal and the negative external economies of coal.     

Musicians as entrepreneurs or entrepreneurs as musicians?

This study investigates how Swedish musicians in the non‐profit sector accept the “entrepreneur” label for themselves. The background section describes how identity work among “serious” musicians has, historically, made them shun any facet related to money‐making. The qualitative study shows that there is some remaining reluctance. But it is obvious that freelance musicians recognize the need for entrepreneurial skills. A majority of those interviewed regard themselves as “entrepreneurs”, although in most cases it is out of necessity. It seems that the older generations are more hesitant than the younger. I conclude that it would be beneficial if musicians, during their higher education, were introduced to basic entrepreneurial skills.     

A smoke-filling simulation model and its engineering applications

A brief presentation of the computer model DSLAY1, which describes the smoke-filling process in a single enclosure, is first given in this paper. Also some computed data of the model are compared with experimental results to show the agreement between theory and experiment. In the latter part of the paper computed results are presented for areas where the model has been used for different fire engineering applications. The main purpose is to show that zone models like DSLAY1 are useful tools to predict the heat and smoke conditions in single enclosures as a result of growing fires. DSLAY1 is an interactive computer program. The user converses with the program via a terminal connected to the computer. The dialogue is governed by commands adapted to the concepts of the user. Reference: Staffan Bengtson and Bengt Hägglund, A Smoke-Filling Simulation Model and Its Engineering Applications,Fire Technology, Vol. 22, No. 2, May 1986, p. 92.     

Textured surfaces for improved lubrication at high pressure and low sliding speed of roller/piston in hydraulic motors

The present study investigates the potential of surface textures to improve the friction situation of the piston/roller contact in hydraulic motors at low speed and high pressure. A self-adjusting flat on flat rig, with conditions representative of an actual hydraulic motor, is used in a reciprocating sliding motion. The samples are made out of the same materials and the surface finishing operations are the same as used in the motor.The piston surfaces are textured using newly developed embossing tools comprising micromechanically formed all-diamond surfaces. The textured surfaces involve parallel grooves and crossed grooves, each of four different spacings. Also polished surfaces were tested. Un-textured—as tumbled—surfaces are used as reference.Generally, it was found that the friction level was only marginally influenced by the textures. However, the friction fluctuations were reduced. SEM investigations disclosed rather severe modifications of the surfaces during use, primarily caused by plastic deformation of the surface layer. The results and their practical implications are discussed.     

Equilibrium approaches to natural water systems—6. Acid-base properties of a concentrated bog-water and its complexation reactions with aluminium(III)

A filtered bog-water, concentrated by means of a freezing technique, has been studied with respect to acid-base properties and aluminium(III) complexation reactions. Sampling was performed during autumn and winter periods with a resulting acidity or alkalinity due to oxic (autumn) or anoxic (winter) conditions. The measurements were performed as potentiometric titrations in constant ionic media (0.02, 0.1 and 0.6 M NaCl) with the use of a glass electrode. The samples show buffer ranges at 3 pH 5 and pH 7.5. The first is ascribed to the presence of carboxylate groups and is characterized by fast equilibria. The second is due to phenolic OH⁻ groups and precipitation reactions with resulting sluggish equilibria. For one sampling period comprehensive measurements were undertaken to study the possible polyelectrolytic character of the organic acids. Due to the small increase in apparent carboxylate pKa-values with the degree of dissociation at low (0.02 M) as well as at high (0.6 M) ionic strength, the possible polyelectrolytic feature of the acids was neglected. Instead, a good fit to data was obtained by introducing a di-protic acid (H₂L) as a model compound. Furthermore the medium dependence of the two acidity constants could satisfactorily be fitted to the expression:

Full-size image (1K)

, where K is the constant at infinite dilution, a and b parameters of which b has been adjusted to present data. The following K values were obtained: pK₁ = 3.65 and pK₂ = 4.30. The complexation with Al(III) could be described by the formation of AlL⁺, AlL₂⁻ and the ternary species AlLH₋₁. The stability constants (log k₁ = 4.4 (winter), 4.2 (autumn); log k₂ = 4.2, 4.7; pKa (AlL⁺) = 4.2, 4.2) show no significant trend with sampling period but indicate a stability of the complexes greater than for phtalic acid but lower than for oxalic acid. Finally, the theoretical solubility of the clay mineral kaolinite in the presence of bog-water was computer modelled. The calculations show up on a 10-fold increase with respect to soluble aluminium at pH = 5.     

The Dissolution of Cationic Potato Amylopectin

The dissolution of a cationic potato amylopectin was studied at low dissolution temperatures 50°–97°C. The dissolution was followed by two methods: (1) iodine binding and (2) the flocculation efficiency with nanosized silica particles. The first method gives us information whether the iodine can penetrate the amylopectin structure or not. The second method gives us qualitative information about the size of the amylopectin molecules. At low dissolution temperatures it was found that the molecular weight of the amylopectin (or aggregate size) was larger than those obtained at higher dissolution temperatures. It was also found that the cationic potato starch only containing amylopectin was easier to dissolve than the cationic starch containing both amylose and amylopectin.