A Novel High Nitrogen Steel Powder Designed for Minimized Cr2N Precipitations

High nitrogen steels provide excellent mechanical properties and corrosion resistance but are prone to form precipitates which adversely affect the corrosion resistance and toughness. High nitrogen steel powders currently available in the market are not claimed to be precipitate free. It is critical to avoid these precipitates while retaining nitrogen in the dissolved form to realize the value of these powder alloys. However, retaining high level of dissolved nitrogen in steel powder during melt atomization process is very challenging. Instead, solid-state dissolution of nitrogen into the powder alloy followed by rapid cooling may provide a convenient approach to avoid precipitate formation compared to traditional melt processing. This study presents a solution treatment approach to achieve elevated dissolved nitrogen levels (~ 0.4 wt pct) in Fe–Mn–Cr powder alloy with negligible precipitation of nitrides. The influence of starting material, holding time, temperature and cooling rate on the resulting microstructure is presented. A fully austenite matrix with high dissolved nitrogen content resulted in powders with desired mechanical properties.

     

Moisture adsorption behaviour of esterified rubber wood (Hevea brasiliensis)

Hevea brasiliensis ) esterified with acetic anhydride, maleic anhydride and phthalic anhydride was studied for moisture adsorption behaviour. FTIR spectroscopic technique was used to analyse the chemical changes in the wood through the correspondent reactions. Spectra indicated increasing intensity of the C=O and C-O stretching bands, and reduction in O-H stretching vibrations that reflects formation of less hygroscopic ester bonds with hydroxyl groups of cell wall polymers. Moisture adsorption isotherms show low equilibrium moisture content in esterified wood at all relative humidity values as compared to a control. The adsorption data was analysed by applying Hailwood-Horrobin theory which separated the adsorbed water into hydrated water and dissolved water corresponding to mono-layer and multi-layer adsorption. Curve for M_h and M_s were similar in pattern for esterified wood and control with different magnitude. Low M_h and M_s in esterified wood indicate reduction in moisture adsorption sites. Inaccessible fraction of wood for water vapour was increased by 43%, 32% and 26% in acetic, maleic and phthalic anhydride treated wood, respectively, compared to the control. Acetic anhydride treatment was found most effective in reducing hygroscopicity of wood.

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Hevea brasiliensis ) wurde verestert mit Anhydriden der Maleins?ure, Essigs?ure und Phtals?ure. Das Adsorptionsverhalten bei verschiedenen Feuchten wurde mit FTIR-Methoden untersucht, um die entsprechenden chemischen Abl?ufe zu erfassen. Intensivere C=O, und -C-O- Streckschwingungen sowie reduzierte OH-Schwingungen reflektieren die neu gebildeten, weniger hygroskopischen Esterbindungen. Bei allen modifizierten Proben ergaben sich niedrigere Gleichgewichtsfeuchten. Die Adsorptions-Isothermen wurden mit Hilfe der Hailwood-Horrobin Theorie analysiert, um adsorbiertes (M_h) und gel?stes (M_s) Wasser zu unterscheiden. Der Kurvenverlauf für M_h und M_s für modifiziertes und unbehandeltes Holz war qualitativ ?hnlich, und unterschied sich nur quantitativ. Geringe Werte für M_h und M_s zeigen eine Verringerung der m?glichen Adsorptionsstellen an. Der nicht zug?ngliche Anteil des Holzes, bezogen auf Kontrollproben, verringerte sich auf 43% (Acetanhydrid), 32% (Maleins?ureanhydrid) und 26% (Phthals?ureanhydrid). Acetanhydrid erwies sich als das effektivste Mittel, um die Hygroskopizit?t zu erniedrigen.

     

Lotsizing in Multi-Item Multi- Machine Job Shops

A great many manufacturing facilities can be described as closed job shops which process multiple items through multiple work centers for stock or for assembly. The performance of these shops is strongly dependent on the batching policies employed for work in the shop. In particular, waiting time in queue and total manufacturing lead time for batches are functions of lotsizes. In turn these affect work-in-process costs, safety stock requirements, schedule performance and part coordination for assembly. The relationship between lot-sizing and shop performance is represented using a queueing network model which is then embedded in an optimization routine that searches for optimal lot sizes.     

The production of rubber-modified polystyrene. I. Rheological behavior of the polymerizing system

The rheological behavior of the two-phase systems consisting of a polystyrene-in-styrene phase distributed in a rubber-in-styrene phase is shown to exhibit increasing non-Newtonian behavior up to the phase inversion point, as a consequence of its two phase nature. The equation is recommended for the prediction of the viscosity of the polymerizing mass up to phase inversion during the production of HIPS by the in situ bulk polymerization of styrene in the presence of dissolved rubber.     

The Value of Loaners in Product Support

Reducing the customer's risk of down time is becoming increasingly important in the support of industrial and consumer durable equipment, whether sold or leased. Traditionally, improved support has meant improvements in diagnosis, repair, and spare part availability. However, these approaches eventually have diminishing returns. In many cases, dedicated loaners can be cost effective in eliminating or reducing down time. In this paper, models are developed to examine the trade-offs involved in decisions about loaners. Alternative loan policies are discussed, and the application of these policies is illustrated.     

Remotely piloted aircraft in the civil environment

Remotely piloted aircraft (RPA's) are of increasing interest to the military and others, as evidenced by a number of technology and development programs that are currently funded or planned. These programs have led to a number of test aircraft with significant capabilities, and future remotely piloted aircraft are forecast to become even more capable as the technology in a number of important subsystem areas is progressing at a rapid rate. As the size, weight and cost of RPA's is reduced, the prospect of using them for civilian applications becomes more likely.     

A feasibility analysis of hydrogen delivery system using liquid organic hydrides

The paper discusses the techno-economic feasibility of a hydrogen storage and delivery system using liquid organic hydrides (LOH). Wherein, LOH (particularly cycloalkanes) are used for transporting the hydrogen in chemical bonded form at ambient temperature and pressure. The hydrogen is delivered through a catalytic dehydrogenation process. The aromatics formed in the process are used for carrying more hydrogen by a subsequent hydrogenation reaction. Cost economics were performed on a system which produces 10 kg/h of hydrogen using methylcyclohexane as a carrier. With proprietary catalysts we have demonstrated the possibility of hydrogen storage of 6.8 wt% and 60 kg/m³ of hydrogen on volume basis. The energy balance calculation reveals the ratio of energy transported to energy consumed is about 3.9. Moreover, total carbon footprint calculation for the process of hydrogen delivery including transportation of LOH is also reported. The process can facilitate a saving of 345 tons/year of carbon dioxide emissions per delivery station by replacing gasoline with hydrogen for passenger cars. There is an immense techno-economic potential for the process.