A Thermodynamic analysis of the Fe-Cr-N system

New experimental information on the phase relations in the Fe-Cr-N system at 1273 K is presented. Together with previous information it is used in a thermodynamic analysis of the system in the temperature range from 1273 to 1473 K. A set of parameter values is derived which defines the Gibbs energy of the individual phases and allows the phase diagram to be calculated. Satisfactory agreement with experimental information is obtained. Formerly with Royal Institute of Technology, Stockholm.     

A Study of equilibria in the Fe-Cr-Ni-Mo-C-N system at 1273 K

The phase equilibria in the Fe-rich corner of the Fe-Cr-Ni-Mo-C-N system have been studied at 1273 K using a sealed capsule technique to measure the C and N activities and the electron microprobe to measure the compositions of the individual phases following identification by X-ray analysis. Some of the new information was combined with previous assessments of the Fe-Cr-N, Fe-Ni-N, and Fe-Cr-Ni systems and a new assessment of the Cr-Ni-N system in order to assess the thermodynamic properties of the Fe-Cr-Ni-N system. A set of parameters is obtained, based mainly upon experimental information from 1273 K (1000 °C) and 1473 K (1200 °C), which can be used for calculations of the Fe-Cr-Ni-N phase diagram in this temperature range. Isothermal sections are presented and show reasonable agreement with experimental data not used in the assessment. The thermodynamic analysis is restricted to the Fe-Cr-Ni-N system, but some experimental data are also presented for alloys containing Mo and C. Formerly with Royal Institute of Technology, Stockholm.     

Respiratory Deposition of Fibers in the Non-Inertial Regime—Development and Application of a Semi-Analytical Model

A semi-analytical model describing the motion of fibrous particles ranging from nano- to micro scale was developed, and some important differences in respiratory tract transport and deposition between fibrous particles of various sizes and shapes were elucidated. The aim of this work was to gain information regarding health risks associated with inhalation exposure to small fibers such as carbon nanotubes. The model, however, is general in the sense that it can be applied to arbitrary flows and geometries at small fiber Stokes and Reynolds numbers. Deposition due to gravitational settling, Brownian motion and interception was considered, and results were presented for steady, laminar, fully developed parabolic flow in straight airways. Regarding particle size, our model shows that decrease in particle size leads to reduced efficiency of sedimentation but increased intensity of Brownian diffusion, as expected. We studied the effects due to particle shape alone by varying the aspect ratios and diameters of the microfibers simultaneously, such that the effect of particle mass does not come into play. Our model suggests that deposition both due to gravitational settling and Brownian diffusion decreases with increased fiber aspect ratio. Regarding the combined effect of fiber size and shape, our results suggest that for particles with elongated shape the probability of reaching the vulnerable gas-exchange region in the deep lung is highest for particles with diameters in the size range 10–100 nm and lengths of several micrometers. Note that the popular multi-walled carbon nanotubes fall into this size-range.     

Quantitative transmission Raman spectroscopy of pharmaceutical tablets and capsules

Quantitative analysis of pharmaceutical formulations using the new approach of transmission Raman spectroscopy has been investigated. For comparison, measurements were also made in conventional backscatter mode. The experimental setup consisted of a Raman probe-based spectrometer with 785 nm excitation for measurements in backscatter mode. In transmission mode the same system was used to detect the Raman scattered light, while an external diode laser of the same type was used as excitation source. Quantitative partial least squares models were developed for both measurement modes. The results for tablets show that the prediction error for an independent test set was lower for the transmission measurements with a relative root mean square error of about 2.2% as compared with 2.9% for the backscatter mode. Furthermore, the models were simpler in the transmission case, for which only a single partial least squares (PLS) component was required to explain the variation. The main reason for the improvement using the transmission mode is a more representative sampling of the tablets compared with the backscatter mode. Capsules containing mixtures of pharmaceutical powders were also assessed by transmission only. The quantitative results for the capsules' contents were good, with a prediction error of 3.6% w/w for an independent test set. The advantage of transmission Raman over backscatter Raman spectroscopy has been demonstrated for quantitative analysis of pharmaceutical formulations, and the prospects for reliable, lean calibrations for pharmaceutical analysis is discussed.     

Modeling the acid-base properties of bacterial surfaces: A combined spectroscopic and potentiometric study of the gram-positive bacterium Bacillus subtilis

In this study, macroscopic and spectroscopic data were combined to develop a surface complexation model that describes the acid-base properties of Bacillus subtilis. The bacteria were freeze-dried and then resuspended in 0.1 M NaCl ionic medium. Macroscopic measurements included potentiometric acid-base titrations and electrophoretic mobility measurements. In addition, ATR-FTIR spectra of wet pastes from suspensions of Bacillus subtilis at different pH values were collected. The least-squares program MAGPIE was used to generate a surface complexation model that takes into account the presence of three acid-base sites on the surface: tripple bond COOH, tripple bond NH+, and tripple bond PO-, which were identified previously by XPS measurements. Both potentiometric titration data and ATR-FTIR spectra were used quantitatively, and electrostatic effects at the charged bacterial surface were accounted for using the constant capacitance model. The model was calculated using two different approaches: in the first one XPS data were used to constrain the ratio of the total concentrations of all three surface sites. The capacitance of the double layer, the total buffer capacity, and the deprotonation constants of the tripple bond NH+, tripple bond POH, and tripple bond COOH species were determined in the fit. A second approach is presented in which the ratio determined by XPS of the total concentrations of tripple bond NH+ to tripple bond PO- sites is relaxed. The total concentration of tripple bond PO- sites was determined in the fit, while the deprotonation constant for tripple bond POH was manually varied until the minimization led to a model which predicted an isoelectric point that resulted in consistency with electrophoretic mobility data. The model explains well the buffering capacity of Bacillus subtilis suspensions in a wide pH range (between pH=3 and pH=9) which is of considerable environmental interest. In particular, a similar quantitative use of the IR data opens up possibilities to model other bacterial surfaces at the laboratory scale and help estimate the buffering capacity of carboxylate-containing compounds in natural samples.     

New cylinder liner surfaces for low oil consumption

Anticipated emission legislation and reduced fuel consumption are the main driving forces when developing new engines. Optimization of the active surfaces in the piston system is one possible way to meet the above demands. In this study the effects of surface topography and texture direction of the ring/liner contact on oil film thickness and friction were simulated and experimentally tested. “Low wear” results from the experimental wear tests with “glide honed” smooth liner surfaces supported the “low friction” simulation results. In addition a new wear volume sensitive surface roughness parameter, R_ktot, based on the Abbot–Firestone bearing area curve was introduced.     

Integrating process and power grid models for optimal design and demand response operation of giga-scale green hydrogen

Electrolysis-based hydrogen production can play a significant role in industrial decarbonization, and its economic competitiveness can be promoted by designing demand response operating schemes. Nevertheless, the scale of industrial supply plants may be significantly large (on the order of gigawatts), meaning that electricity prices cannot be treated as an input for scheduling problems, that is, the “price taker” approach. This article presents a framework for the optimization of a large-scale, electricity-powered hydrogen production facility considering its integration with the power grid. Using a computational case study, we present an iterative scheme for integrating the process model with a model for power grid optimization and capacity expansion, taking the popular GenX model as an example.     

A software-based measurement system for testing and analysis of automotive brake squeal

A software-based measurement system using both analogue data acquisition and digital communication via a general-purpose interface bus (GPIB) board has been developed for analysis and evaluation of disc brake squeal. The system is built around a computer and based on commercial software. Brake pressure and torque, rotational speed, five different temperatures, and sound emission are logged once a second. If the sound is characterised as a squeal it is saved to file together with the other parameters. The measurement system is very flexible, allowing for different types of instruments and sensors to be used by adapting the software. Furthermore, the same software is used for evaluation of the collected data. Mechanically, the equipment consists of a complete front wheel suspension where the original brake disc and caliper are mounted in a steel tube chassis. The brake disc is driven by a DC electric motor, while a hydraulic system provides the brake pressure. Brake pressure and rotational speed can be controlled independently.