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Article
Publication date: 1 April 2007

J. Aghazadeh Mohandesi and A. Nazari

The kinetics of nitriding in titanium bearing austenitic stainless steels in cylindrical coordination has been investigated. Nitriding at nitrogen partial pressure of 0.5…

Abstract

The kinetics of nitriding in titanium bearing austenitic stainless steels in cylindrical coordination has been investigated. Nitriding at nitrogen partial pressure of 0.5 atm and temperature from 980°C up to 1160oC resulted in the formation of titanium and chromium nitride and above the Cr2N solvus temperature (1100°C), no chromium nitride was formed. The nitrided case may consist of up to three zones: nitrogen in solid solution, precipitation of TiN and finally mixed TiN+Cr2N precipitation. These are in consistent with the affinity of titanium and chromium towards nitrogen which has been thermodynamically justified. To assess the kinetics of nitriding, a mathematical model for nitrogen diffusion in cylindrical system has been developed via solving Fick’s equation for cylindrical coordinate by numerical method. For this purpose the use has been made of the austenite stabilizing effect of nitrogen to correlate the movement of the boundary of the nitrogen stabilized austenite and plastic deformation induced martensite. Since the crystal structure of the material used in this study is of fcc type and it is nitrided in a fully annealed and unstrained state, therefore the effect of excess nitrogen on the kinetics of nitride fronts growth has been assumed as negligible. The results are in good agreement with the previous investigations. Unlike previous works, the present model takes into account the change of nitrogen diffusion coefficient due to nitrogen concentration profile and

Details

Multidiscipline Modeling in Materials and Structures, vol. 3 no. 4
Type: Research Article
ISSN: 1573-6105

Keywords

Book part
Publication date: 18 July 2007

Peter Kreins, Horst Gömann, Sylvia Herrmann, Ralf Kunkel and Frank Wendland

An interdisciplinary model network consisting of the regional agricultural economic model RAUMIS and the hydro(geo)logical models GROWA/WEKU is used to analyze the effect…

Abstract

An interdisciplinary model network consisting of the regional agricultural economic model RAUMIS and the hydro(geo)logical models GROWA/WEKU is used to analyze the effect of different scenarios of maximum agricultural nitrogen balance surplus on water quality. The study area is the federal state of Lower Saxony, Germany, which features heterogeneous natural site conditions as well as agricultural production structures. A focus of the study is the modeling of supra-regional manure transports that, according to the model's results, considerably increase due to a lowering of maximum nitrogen balance surpluses. The assessment of the examined nitrogen reduction measures reveals that adequate indicators have to be applied. In this regard, the model results show that even though the analyzed measure leads to a substantial overall reduction of agricultural nitrogen surpluses, nitrogen discharges into surface and groundwater can regionally increase.

Details

Ecological Economics of Sustainable Watershed Management
Type: Book
ISBN: 978-1-84950-507-9

Article
Publication date: 18 January 2016

Jun Ni, Jifei Dong, Jingchao Zhang, Fangrong Pang, Weixing Cao and Yan Zhu

– The purpose of this paper is to improve the accuracy and signal-to-noise ratio (SN) of a crop nitrogen sensor.

Abstract

Purpose

The purpose of this paper is to improve the accuracy and signal-to-noise ratio (SN) of a crop nitrogen sensor.

Design/methodology/approach

The accuracy and wide adaptability of two spectral calibration methods for a crop nitrogen sensor based on standard reflectivity gray plates and standard detector, respectively, were compared.

Findings

The calibration method based on standard detector could significantly improve the measurement accuracy and the SN of this crop nitrogen sensor. When compared with the method based on standard gray plates, the measurement accuracy and the SN of the crop nitrogen sensor calibrated based on the standard detector method improved by 50 and 10 per cent, respectively.

Originality/value

This research analysed the calibration problems faced by the crop nitrogen sensor (type CGMD302) based on standard gray plates, and proposed a sensor calibration method based on a standard detector. Finally, the results of the two calibration methods were compared in terms of measurement accuracy and the SN of the crop nitrogen sensor.

Details

Sensor Review, vol. 36 no. 1
Type: Research Article
ISSN: 0260-2288

Keywords

Article
Publication date: 1 July 1958

S. Greenfield

IN the testing of rocket engines and engine components, such as thrust chambers and gas generators, the rocket engineer is regularly faced with the job of transferring…

Abstract

IN the testing of rocket engines and engine components, such as thrust chambers and gas generators, the rocket engineer is regularly faced with the job of transferring cryogenic liquid propellants, using pressure feed from a storage tank, through a flow system and into the combustion device to be tested. At Rocketdyne, liquid oxygen, LOX, is quite commonly used as a propellant, and in the testing of engine components inert pressurants are usually used, for example, helium or nitrogen, although because of the cost and logistics, nitrogen is preferred. When gaseous nitrogen is used as the pressurant, we have repeatedly run into testing conditions which have resulted in condensation of nitrogen and subsequent mixing in the tanked liquid oxygen. This dilution of the liquid oxygen effects a loss of performance and imposes mechanical difficulty in maintaining a regulated propellant tank pressure.

Details

Aircraft Engineering and Aerospace Technology, vol. 30 no. 7
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 21 March 2008

V. Valasamudram, S.S. Mohamed Nazirudeen, P. Chandramohan and K.P. Thenmozhi

The main purpose of this paper is to produce high‐nitrogen martensitic stainless steels (HNMSS) using a conventional induction furnace with better mechanical properties…

Abstract

Purpose

The main purpose of this paper is to produce high‐nitrogen martensitic stainless steels (HNMSS) using a conventional induction furnace with better mechanical properties and to improve the properties by thermo‐mechanical treatment (TMT).

Design/methodology/approach

Production of two types of HNMSS alloys with Chromium – 8.22 and 15.84 wt% was carried out using a conventional melting furnace. The theoretical nitrogen solubility of the produced alloys was calculated and compared with the actual nitrogen solubility of the alloys. The produced alloys were subjected to TMT, characterized by hardness measurement, tensile testing micro examinations in the as cast, hardened, TMT treated and TMT hardened and tempered conditions.

Findings

The actual nitrogen solubility achieved in the HNMSS specimens was in agreement with the calculated theoretical nitrogen solubility using thermodynamic relationships. Thermo‐mechanically treated specimens exhibited the break‐up and refinement of the original coarse cast structure by repeated recrystallization as fine grain size in the austenitic condition and reduced proportion of residual deformed δ ferrite. Thermo‐mechanically treated, hardened and tempered specimens showed higher hardness up to 525 VHN, with strength and toughness.

Research limitations/limitations

In the conventional melting process, purging nitrogen into the melt and increasing the percentage of nitrogen is the primary limitation and retaining the same into the solution during thermo‐mechanical treatment is the secondary limitation.

Originality/value

Work on melting of nitrogenated steels using controlled atmospheric conditions with special equipment was carried out earlier. This practice cannot be adopted on a commercial basis, where mass production is the prime requirement. Therefore, the uniqueness of this paper lies in communicating the melting practice of HNMSS using a conventional induction furnace followed by the optimum TMT. This takes the production and TMT of HNMSS into the commercial casting industry for mass production.

Details

Anti-Corrosion Methods and Materials, vol. 55 no. 2
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 16 July 2018

Ziyan Yang

The most recent and prestigious scientific research shows that nitrogen leaching caused by over-used nitrogen fertilizer rapidly acidifies all soil types in China…

Abstract

Purpose

The most recent and prestigious scientific research shows that nitrogen leaching caused by over-used nitrogen fertilizer rapidly acidifies all soil types in China, revolutionizing the basic understanding of the mechanism of soil acidification. The purpose of this paper is to study the impact of nitrogen on soil acidity over the long run, which is the shadow price of nitrogen.

Design/methodology/approach

In a discrete dynamic programming model, this paper compares the nitrogen application and soil pH between optimal nitrogen control that takes the shadow price of nitrogen into consideration and myopic nitrogen control that ignores that shadow price. Using a five-year panel experimental data on a rapeseed-rice rotation, this paper simulates and numerically solves the dynamic model.

Findings

Both theoretically and empirically, this paper shows that the over-use of nitrogen and the decline in soil pH are explained by ignorance of the shadow price of nitrogen. Compared with optimal nitrogen control, myopic nitrogen control applies more nitrogen in total, resulting in lower soil pH. In addition, over-use in the first season contributes to soil acidification and the carry-over effects mitigate that problem.

Originality/value

This paper enriches the literature by extending the study of the environmental impact of nitrogen leaching to its impact on the long-term loss in agricultural production, providing a new theoretical framework in which to study soil acidification rather than conventionally treating soil acidification as a secondary consequence of acid rain, and showing the possibility of using nitrogen control to mitigate soil acidification when lime applications are not feasible due to socio-economic constraints.

Details

China Agricultural Economic Review, vol. 11 no. 3
Type: Research Article
ISSN: 1756-137X

Keywords

Article
Publication date: 7 September 2015

Qiang Li, Jiahuan Du, Xugang Zhang, Chuanli Qin, Zheng Jin and Xuduo Bai

The purpose of this paper is to develop porous nitrogen-enriched carbon (NC-U) with high nitrogen concentration and high specific capacitance (Cpe) as the electrode…

Abstract

Purpose

The purpose of this paper is to develop porous nitrogen-enriched carbon (NC-U) with high nitrogen concentration and high specific capacitance (Cpe) as the electrode material for supercapacitors.

Design/methodology/approach

NC-U was obtained by carbonization of polyvinylpyrrolidone/melamine formaldehyde resin (PVP/MF) with different contents of urea. In comparison, NC-K was also prepared by the KOH activation method. A series of asymmetric supercapacitors with NC as a negative electrode was assembled. The composition, microstructure and electrochemical properties of NC and their supercapacitors were studied.

Findings

The results show that NC-U shows irregular particles with a porous honeycomb structure. High Cpe was obtained for urea-treated NC-U because of the improvement of nitrogen, conductivity and specific surface area (S BET ). NC-U50 with 13.15 per cent at nitrogen has the highest Cpe of 148.53 F/g because of the highest concentration of N-6 and N-5. NC-K with higher S BET has lower Cpe than NC-U50 because of its lower nitrogen concentration. When the specific power of the supercapacitor with NC-U50 as a negative electrode is 1,565.56 W/kg, its specific energy is still 4.35 Wh/kg. There is only 5.9 per cent decay in Cpe over 1,000 cycles.

Research limitations/implications

NC-U is a suitable electrode material for supercapacitors, which can be used in the field of electric vehicles to solve the problems of energy shortage and environmental pollutions.

Originality/value

Porous NC-U based on PVP/MF/urea composites with high nitrogen concentration and Cpe is novel, and it owns good electrochemical properties.

Details

Pigment & Resin Technology, vol. 44 no. 5
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 1 January 1987

W. Yext, E.A. Hayduk and C.K. Fisher

Manufacturers of multilayer copper thick‐film circuitry face the challenge of firing parts in an inert nitrogen atmosphere to prevent the copper from oxidising. Nitrogen

Abstract

Manufacturers of multilayer copper thick‐film circuitry face the challenge of firing parts in an inert nitrogen atmosphere to prevent the copper from oxidising. Nitrogen, while protecting the copper from oxidation, offers no efficient mechanism for removing the carbon‐based vehicles used in the copper thick‐film paste. Because of this, carbon residues or soot often deposit on the parts during the firing process. In an attempt to improve the nitrogen furnace atmosphere's ability to remove the vehicles, several gases or gas blends were added to a nitrogen‐based furnace atmosphere. Thick‐film copper conductors and dielectric test pieces were then processed using the various gas blends. The physical properties of adhesion, aged adhesion, solderability, and conductivity of the copper conductor test pieces were studied along with the dielectric properties of dissipation factor, insulation resistance, and dielectric constant. Some of the gases tested included H2, H2O, CO, CO2, and a variety of other gas combinations. Test results demonstrated the atmosphere's ability to effect changes in the physical properties of the parts being processed. A proprietary gas blend was developed which proved effective in removing carbon residues while maintaining the desirable physical properties of the thick films. This work demonstrates the ability of certain gas additives to improve the performance of conventional nitrogen atmospheres when firing copper thick‐film circuitry. With the proper selection of the gas additive, atmosphere flows can be reduced, carbon residues eliminated, and the physical properties of the copper conductors and dielectrics maintained or improved.

Details

Microelectronics International, vol. 4 no. 1
Type: Research Article
ISSN: 1356-5362

Article
Publication date: 1 May 2000

L. Lau, T. Siu, J. Fan, L.Y.C. Siu and E. Newton

Two groups of fabric samples: six 100% cotton twill fabrics with different level of wrinklefree treatment, and six 100% cotton twill fabrics without wrinkle-free treatment…

Abstract

Two groups of fabric samples: six 100% cotton twill fabrics with different level of wrinklefree treatment, and six 100% cotton twill fabrics without wrinkle-free treatment were experimentally studied. These fabrics were tested in terms of nitrogen content, swelling index (water retention), tear strength and dynamic water absorption rate. The nitrogen content was considered as a probably better indicator of the level of wrinkle-free treatment than the swelling index (water retention) commonly used in the industry. In this work, the relationship between the nitrogen content and swelling index (water retention) were studied. The effects of nitrogen content and swelling index (water retention) on the tear strength and the dynamic water absorbency were investigated

The results showed that

The swelling index (water retention) has a strong linear relationship with the total nitrogen content in the fabric. The higher nitrogen content, the lower the swelling index (water retention).

The fabric tear strength is highly correlated with the total nitrogen content or the swelling index (water retention). High nitrogen content or low swelling index (water retention), which may be resulted from the wrinkle-free treatment, causes low tear strength

High nitrogen content or low swelling index (water retention) reduces the water absorption rate of the fabric and increases the contact angle when the water drop is in initial contact of the fabric.

In general, the study showed that swelling index (water retention), a simple test commonly used in the industry, is as good a parameter as the nitrogen content, which is difficult to measure, for evaluating the level of wrinkle-free treatment. Wrinkle-free treatment can generally reduce the tear strength and the dynamic water absorption rate. The former is a property important to fabric durability and the latter is a property important to clothing comfort.

Details

Research Journal of Textile and Apparel, vol. 4 no. 2
Type: Research Article
ISSN: 1560-6074

Article
Publication date: 1 January 1972

RONALD E. MORGAN and ROGER WEINBERG

Through the use of computer simulation of three biogeochemical cycles—carbon, nitrogen, and phosphorus—we have shown that DDT poisoning of ocean producers (plants) can…

Abstract

Through the use of computer simulation of three biogeochemical cycles—carbon, nitrogen, and phosphorus—we have shown that DDT poisoning of ocean producers (plants) can cause their growth to be limited by nitrogen, whereas ordinarily it is limited by phosphorus. We must qualify what we have shown because we restricted the simulation by representing only two ecosystems (ocean and land), by using simplified equations for some flow rates, and finally by estimating data for some biomass values and for some flow rates. In order to remove some of the restrictions on the simulation, we are extending it so that we may include in it knowledge of our own, of ecologists, and of systems analysts. By extending it, we are increasing our ability for using it to understand, and consequently to predict and control, the behavior of the interacting biogeochemical cycles of the world.

Details

Kybernetes, vol. 1 no. 1
Type: Research Article
ISSN: 0368-492X

1 – 10 of over 5000