Search or add a thesis

Advanced Search (Beta)
Home > Optical Emission Spectroscopy of N2-H2-Natural Ch4 Mixture Plasmas Generated by Pulsed-Dc for Surface Hardening of Austenitic Stainless Steel

Optical Emission Spectroscopy of N2-H2-Natural Ch4 Mixture Plasmas Generated by Pulsed-Dc for Surface Hardening of Austenitic Stainless Steel

Thesis Info

Access Option

External Link

Author

Naseer, Shahid

Program

PhD

Institute

University of Peshawar

City

Peshawar

Province

KPK

Country

Pakistan

Thesis Completing Year

2013

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2543/1/2587S.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726812569

Asian Research Index Whatsapp Chanel
Asian Research Index Whatsapp Chanel

Join our Whatsapp Channel to get regular updates.

Similar


Nitrogen glow discharge plasma is generated by number of power sources and has many applications in material processing such as Nitriding of different metal alloys. The material processing efficiency of the plasma may be enhanced by optimizing the related parameters of the discharge. The concentration of the active nitrogen species in the plasma may depend on various operating conditions such as input power of the discharge, pressure and gas flow rate etc. In order to improve the various excitation and ionization processes occurring in the plasma for the generation of active species, one way is to mix some inert gas in the nitrogen plasma. In the present study the diagnostics of Pulsed-dc generated nitrogen-methane-hydrogen mixture plasma is carried out to analyze the optimum working conditions for its application. Spectroscopic measurements of hydrogen Balmer-β and Balmer-γ line profiles are performed in an abnormal glow region of Pulsed-dc sustained nitrogen-hydrogen- methane plasma for investigating dependencies of their line shapes and intensities on discharge parameters. The excitation temperature Te is determined from Ar-I emission line intensities by using Boltzmann’s plot method of Balmer lines is found to be increased with methane mixing in nitrogen plasma. The electron density is extracted from Stark broadening (FWHM) of the Hβ emission profile. It is found that both the emission intensity and the broadening of the Balmer-β and Balmer-γ lines show significant dependence on the filling pressure in the same manner. However, both the emission intensity and broadening of Hβ line exhibit weak dependence on input power in contrast to the Hγ emission line. The concentration of active species N 2 (C 3 P u ) + + and N 2 ( B 2 S u ) are monitored in terms of the emission intensities of nitrogen bands of the second positive and the first negative systems respectively. The concentration of N 2 (C 3 P u ) active species is appreciably enhanced by methane mixing signifying the role of argon meta-stables in the excitation and dissociation processes. The effect of mixing of methane-hydrogen is studied on the surface nitriding os AISI-304 stainless steel substrate at temperature of 500 0C generated by 50 Hz pulsing source at powers of 300 and 500 watt and filling pressure of 1, 3, 5 mbar at different treated times 1, 2, 3, 4 and 5 hours. The samples are then analyzed for plasma induced changes in their surface properties by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Vicker’s micro hardness testing. The XRD pattern confirms the formation of expanded austenite phase (γN) resulted by the incorporation of nitrogen as interstitial solid solution in the iron lattice. The EDX spectra show peaks corresponding to elements that are present in the surface of the substrate. It can be noticed that no additional peak corresponding to any impurity element, other than nitrogen, which is supposed to be present owing to nitrogen incorporation in the iron lattice is found in EDX spectra. The effect of ion etching is apparent from the SEM micrograph, which is normally expected during the nitriding process. All the nitrided samples show an increase in surface hardness as compared to that of untreated one. It is revealed that the surface hardness increase significantly with increasing nitriding time. Based upon optical measurement reported here, plasma discharge parameters can be optimized for the production of active species, excitation temperature Te and number density.
Loading...
Loading...

Similar Books

Loading...

Similar Chapters

Loading...

Similar News

Loading...

Similar Articles

Loading...

Similar Article Headings

Loading...

ڈاکٹر راجندر پرشاد

ڈاکٹر راجندر پرشاد
سابق صدر جمہوریہ ہند ڈاکٹر راجندر پرشاد کی موت ہندوستان کا ایک بڑا قومی حادثہ ہے، وہ اپنے قومی و ملکی خدمات کے لحاظ سے صف اول کے لیڈروں میں تھے، ہندوستان کی جنگ آزادی میں ان کے بڑے کارنامے ہیں، چمپارن کی مشہور ستیہ گرہ کے گویا ہیرو تھے، وہ گاندھی جی کے خاص تربیت یافتہ اور ان کے معتمد علیہ تھے، ان میں ان کی بہت سی اخلاقی خوبیاں موجود تھیں، جو آخر تک قائم رہیں، ہندوستان کی آزادی کے بعد کانگریس کے بہت سے لیڈروں کے خیالات اور کردار میں تبدیلی ہوگئی ہے، ان سے ان کا دامن محفوظ تھا، وہ کانگریس کے پرانے اصولوں پر برابر قائم رہے، اور اپنے جلیل القدر عہدے کی ذمہ داریوں کو بھی بڑی خوبی کے ساتھ نباہا، طبعاً بڑے شریف اور مرنجان مرنج تھے اور قومی و ملکی معاملات میں ان کا دل بہت وسیع تھا، اس لیے کسی طبقہ کو بھی ان سے کوئی شکایت نہیں پیدا ہوئی، وہ پرانے کایستھ تھے اس لیے اردو اور فارسی تہذیب سے بہت اچھی واقفیت رکھتے تھے، اور بہت شستہ اردو بولتے اور لکھتے تھے، اور ان میں قدیم مشترک تہذیب کی بہت سی خوبیاں موجود تھیں، اس لیے ان کی موت مختلف حیثیتوں سے بڑا قومی سانحہ ہے۔ اور ان کا نام ہندوستان کی تاریخ میں ہمیشہ زندہ رہے گا۔ (شاہ معین الدین ندوی، مارچ ۱۹۶۳ء)

 

سیرت النبی ﷺ میں احتسابی عمل کی مثالیں: وفاقی محتسب پاکستان کے فرائض کا اختصاصی مطالعہ

In any society, the administration has the status of a pillar, and its good or bad move directly impacts society. There are institutions to compensate public complaints on government initiatives in many countries of the world that keep check on government administrations. For this purpose "Federal Ombudsman" was established in Pakistan. The main responsibilities of this institution include the execution to enjoin the right and forbid the wrong (Amr bil Ma’rūf wal Nahi ‘An al Munkar), monitoring government employees in administrative matters, hearing the complaints of the public against organizations and preventing them from violating individual rights. In this article, it has been reviewed that how we can seek guidance from the Sīrah of the Prophet (P.B.U.H) is in this matter, to evaluate the present system of "Federal Ombudsman". In addition, the main responsibilities of the "Federal Ombudsman" were discussed in the article. In conclusion recommendations have been made for further improvement.

Strategies for the Production of Commercially Important Secondary Metabolites in Cell Cultures of Fagonia Indica

Fagonia indica, commonly known as “true herb”, is famous for its variety of medicinal activities especially anti-cancer potential. It is a member of the genus Fagonia and family Zygophyllaceae. The species of the genus Fagonia, especially, F. indica is famous for its diverse class of medicinally important compounds including terpenoids, flavonoids, and other polyphenolic compounds. The medicinal activities of F. indica especially antioxidant and anticancer activities may be attributed to its phenolic compounds. However, isolation only from wild grown F. indica does not guarantee sustainable production of these metabolites. This is because of limitations with wildgrown plants such as over-harvesting, endangerment, seasonal and geographic dependence and variations in metabolic profiles of the plant. In vitro cultures promise to deal with these limitations as they are independent of seasons and geography. Especially, cell cultures promise sustainable, uniform and homogeneous production of secondary metabolites. The present work was aimed to devise various strategies for the enhancement of phenolic compounds through the establishment of feasible cell cultures of F. indica. The following experiments were performed for setting up in vitro cultures of F. indica. The first set of experiments was set to handle the microbial contamination we observed during seed germination in vitro. The microbial growth was affecting normal plantlet growth in vitro conditions. Once the type and endophytic nature of the contaminants were confirmed through different tests, they were characterized as bacteria on a molecular level through polymerase chain reaction and sequencing techniques. Eight different bacterial strains; most of them belonging to the Bacillus genus were isolated and characterized from in vitro grown plantlets of F. indica. Nine different antibiotics were applied to eliminate this bacterial growth during seed germination and plantlet development. Tobramycin showed the lowest minimum inhibitory concentration (<8 mg/L) and the highest efficacy in terms of plantlet development. In the subsequent experiments, callus cultures were established for applications of further strategies to enhance secondary metabolite production. To obtain the ideal cell line, two different explant types (stem and leaf) from a 50 days old F. indica plantlet were used. Callus induction was observed in response to different plant growth regulators (PGRs). Among the explants and PGRs tested, the highest fresh biomassproduced was for stem explants in response to 1.0 mg/L of Thidiazuron (TDZ) after 6 weeks of culture. The highest total phenolic content (TPC) and total flavonoid content (TFC) were recorded in stem derived callus cultures compared to control cultures (lacking TDZ). The highest antioxidant potential (69.45 %) was recorded in stemderived callus treated with 1.0 mg/L of TDZ. Similarly, important polyphenolic compounds like gallic acid, quercetin, apigenin, catechin were detected in elevated levels and were quantified through high-performance liquid chromatography (HPLC) in the optimized callus lines. In further experiments, callus cultures were elicited through manipulation in the carbohydrate source. Carbohydrate source provided in the medium has a significant effect on the growth and metabolism of cell cultures. Different carbohydrate sources (sucrose, glucose, fructose, and maltose) were used in different concentrations (1, 3 and 5 %) in the medium for their effects on biomass accumulation, TPC, antioxidant activity and photosynthetic activity of callus cultures. In accordance with the previous study, the optimum level of sucrose was the highest driver of biomass accumulation followed by maltose which means that disaccharides were feasible for biomass formation. However, glucose proved to be the key elicitor of TPC [1.677 mg gallic acid equivalent (GAE)/g DW] and antioxidant activity (82.11%) of callus cultures. Like glucose, the other monosaccharide (fructose) also significantly elicited the total phenolic compound (1.625 mg GAE/g DW) in comparison to sucrose. Later, these callus cultures were used to produce adventitious roots. Different elicitation strategies such as transient and prolonged elicitation were used with adventitious roots grown on solid as well as a liquid medium as suspension cultures. Interestingly, explants treated with 0.5 mg/L Methyl Jasmonate (Me-J) for 2 hours and incubated on Murashige and Skoog (MS) medium supplemented with 1.0 mg/L α-naphthalene acetic acid (NAA) produced the highest adventitious root induction frequency (88%) and biomass accumulation (6.9 g/L DW). The growth kinetics of roots in suspension cultures showed that maximum biomass was produced on the 27th day in log phase of culture supplemented with 1.0 mg/L NAA. The secondary metabolites were produced in significantly enhanced quantities compared to our previous experiments on TDZ and carbohydrate-induced elicitation. The highest TPC (6.0 mg GAE/g of DW) and TFC [5.0 mg Quercetin Equivalent (QE)/g of DW] were produced by 0.5 mg/L Me-J in roots from the lag phase of growth. This finding was further justified by the quantification of important phenolic compounds through HPLC. In the final set of experiments, the interplay between light, PGRs, and elicitors during cell cultures of F. indica was evaluated. Different PGRs (auxins and cytokinin) and elicitors were applied to cell cultures on solid medium grown in three light regimes (continuous light; photoperiod of 16 hours light/8 hours dark; continuous darkness). The results revealed that 1.0 mg/L benzyl aminopurine (BA), 0.5 mg/L Me-J and 1.0 mg/L Phenylacetic acid (PAA) were the optimum regulators in terms of biomass, production of phenolic compounds and antioxidant activity. Similarly, the continuous light produced the highest biomass (13.2 g/L DW) in cell cultures provided with 1.0 g/L BA. Me-J-treated dark-grown cultures responded with the highest TPC and TFC in both solid medium and cell suspension cultures. Furthermore, the TPC and TFC in cell suspension cultures were higher (6.8 mg GAE/g of DW and 5.2 mg QE/g of DW, respectively) compared to our previous findings. The antioxidant activity was found dependent on TPC and TFC and thus higher activity (88%) was produced in cell suspension cultures grown in Me-J. Conclusively, different elicitation strategies in the form of PGRs, carbohydrate sources, elicitors and different light regimens proved worthy of the enhancement of phenolic compounds in cell cultures of F. indica.