Challenges in Carbon/Carbon Composites Technologies

Dhami, T.L.,Bahl, O.P. Korean Carbon Society 2005 Carbon Letters Vol.6 No.3

Carbon/Carbon Composites due to their far superior thermo-mechanical properties are used in a number of demanding applications. However, the material still is used only in specific high tech applications with few exceptions in general industrial applications. The material is extremely expensive and the major challenge is to reduce its cost. Various innovative processing routes are outlined to reduce the cost of processing.

Biomineralization of Calcium Carbonate Polymorphs by the Bacterial Strains Isolated from Calcareous Sites

( Dhami Navdeep Kaur ),( M Sudhakara Reddy ),( Abhijit Mukherjee ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.5

Microbially induced calcium carbonate precipitation (MICCP) is a naturally occurring biological process that has various applications in remediation and restoration of a range of building materials. In the present investigation, five ureolytic bacterial isolates capable of inducing calcium carbonate precipitation were isolated from calcareous soils on the basis of production of urease, carbonic anhydrase, extrapolymeric substances, and biofilm. Bacterial isolates were identified as Bacillus megaterium, B. cereus, B. thuringiensis, B. subtilis, and Lysinibacillus fusiformis based on 16S rRNA analysis. The calcium carbonate polymorphs produced by various bacterial isolates were analyzed by scanning electron microscopy, confocal laser scanning microscopy, X ray diffraction, and Fourier transmission infra red spectroscopy. A strainspecific precipitation of calcium carbonate forms was observed from different bacterial isolates. Based on the type of polymorph precipitated, the technology of MICCP can be applied for remediation of various building materials.

Picroside II attenuates fatty acid accumulation in HepG2 cells via modulation of fatty acid uptake and synthesis

( Hiteshi Dhami-shah ),( Rama Vaidya ),( Shobha Udipi ),( Srividhya Raghavan ),( Shiny Abhijit ),( Viswanathan Mohan ),( Muthuswamy Balasubramanyam ),( Ashok Vaidya ) 대한간학회 2018 Clinical and Molecular Hepatology(대한간학회지) Vol.24 No.1

Background/Aims: Hepatic steatosis is caused by an imbalance between free fatty acids (FFAs) uptake, utilization, storage, and disposal. Understanding the molecular mechanisms involved in FFAs accumulation and its modulation could drive the development of potential therapies for Nonalcoholic fatty liver disease. The aim of the current study was to explore the effects of picroside II, a phytoactive found in Picrorhiza kurroa, on fatty acid accumulation vis-a-vis silibinin, a known hepatoprotective phytoactive from Silybum marianum. Methods: HepG2 cells were loaded with FFAs (oleic acid:palmitic acid/2:1) for 20 hours to mimic hepatic steatosis. The FFAs concentration achieving maximum fat accumulation and minimal cytotoxicity (500 μM) was standardized. HepG2 cells were exposed to the standardized FFAs concentration with and without picroside II pretreatment. Results: Picroside II pretreatment inhibited FFAs-induced lipid accumulation by attenuating the expression of fatty acid transport protein 5, sterol regulatory element binding protein 1 and stearoyl CoA desaturase. Preatreatment with picroside II was also found to decrease the expression of forkhead box protein O1 and phosphoenolpyruvate carboxykinase. Conclusions: These findings suggest that picroside II effectively attenuated fatty acid accumulation by decreasing FFAs uptake and lipogenesis. Picroside II also decreased the expression of gluconeogenic genes. (Clin Mol Hepatol 2018;24:77-87)

Development of Gray Leaf Spot Resistant Maize Cultivars for Sustainable Maize Production and Food Security in Hills of Nepal, 2010

N.B Dhami,S.K Kim,A. Mudwari,G. Manandhar,S.K Budhathoki 한국작물학회 2010 한국작물학회 학술발표대회 논문집 Vol.2010 No.04

Maize (Zeae mays L.) is a second important crop in the country and it is first staple food in high land region. The national average yield is 2.2 t/ha. About 80% maize areas falls in this region. An introduced fungus Gray Leaf Spot (GLS) caused by Cercospora zeae-maydis has caused yield loss an average of 75%. Genetic resistance has been effective control strategy to manage this disease. The main objectives of this work were to develop, evaluate and identify high yielding cultivars tolerant to GLS. Three sets of trials were conducted in Nepal and Korea. GLS evaluation trial-I consisted of 73 genotypes, GLS evaluation trial-II composed of 38 genotypes and mid altitude hybrid evaluation trial-III consisted of 12 genotypes. Exotic, semi exotic and local germplasm of different origins were used. Among these tested genotypes, tolerant genotypes were Thai 717S31-21-3×[TZMi407 × TZMi211-11- 2-1-1-B-B-B-B-B (5.2t/ha), Pioneer12 × MASynVAR-5 F2 (5.0 t/ha) and MA SynVAR-5 F2 × Thai 919 S3 4-5-4 (4.7t/ha) with GLS mean score 2.7, 1.5 and 1 respectively in trial-I. In trial-II, superior genotypes were KYM33 × TZi3 (7.6t/ha), KYM33 × TZi18 (7.5 t/ha) and KYM33 × P45 (7.4 t/ha) with GLS scores 1.4, 2.4 and 2.5 respectively. Similarly in trial-III, high yielding genotypes were MASynVAR-5 (11.0t/ha), and TZMi407×87036- 9-1-1-1-B-B-B/TZMi102×90113-5-3-2-2-B-B-B-B (9.8t/ha). These hybrids and their parents will use to introgress resistant genes to breed better tolerant maize cultivars for Nepal.

Challenges in Carbon/Carbon Composites Technologies

T.L. Dhami,O.P. Bahl 한국탄소학회 2005 Carbon Letters Vol.6 No.3

Carbon/Carbon Composites due to their far superior thermo-mechanical properties are used in a number of demanding applications. However, the material still is used only in specific high tech applications with few exceptions in general industrial applications. The material is extremely expensive and the major challenge is to reduce its cost. Various innovative processing routes are outlined to reduce the cost of processing.

A Novel Route to Realise High Degree of Graphitization in Carbon-carbon Composites Derived from Hard Carbons

Mathur, R.B.,Bahl, O.P.,Dhami, T.L.,Chauhan, S.K. Korean Carbon Society 2003 Carbon Letters Vol.4 No.3

Carbon/carbon composites were developed using PAN based carbon fibres and phenolic resin as matrix in different volume fractions and heat treated to temperatures between $1000^{\circ}C$ to $2500^{\circ}C$. Although both the starting precursors are nongraphitizing hard carbons individually, their composites lead to very interesting properties e.g. x-ray diffractograms show the development of graphitic phase for composites having fibre volume fractions of 30~40%. Consequently the electrical resistivity of such composites reaches a value of $0.8\;m{\Omega}cm$, very close to highly graphitic material. However, it was found that by increasing the fibre volume fraction to 50~60%, the trend is reversed. Optical microscopy of the composites also reveals the development of strong columnar type microstructure at the fibre (matrix interface due to stress graphitization of the matrix. The study forcasts a unique possibility of producing high thermal conductivity carbon/carbon composites starting with carbon fibres in the chopped form only.

Thermomechanical Properties of Carbon Fibres and Graphite Powder Reinforced Asbestos Free Brake Pad Composite Material

P. Thiyagarajan,R.B. Mathur,T.L. Dhami 한국탄소학회 2003 Carbon Letters Vol.4 No.3

Asbestos is being replaced throughout the world among friction materials because of its carcinogenic nature. This has raised an important issue of heat dissipation in the non-asbestos brake pad materials being developed for automobiles etc. It has been found that two of the components i.e. carbon fibres as reinforcement and graphite powder as friction modifier, in the brake pad material, can playa vital role in this direction. The study reports the influence of these modifications on the thermal properties like coefficient of thermal expansion (CTE) and thermal conductivity along with the mechanical properties of nonasbestos brake pad composite samples developed in the laboratory.

Role of Interface on the Development of Microstructure in Carbon-Carbon Composites

Dhakate, S.R.,Mathur, R.B.,Dhami, T.L.,Chauhan, S.K. Korean Carbon Society 2002 Carbon Letters Vol.3 No.4

Microstructure plays an important role in controlling the fracture behaviour of carbon-carbon composites and hence their mechanical properties. In the present study effort was made to understand how the different interfaces (fiber/matrix interactions) influence the development of microstructure of the matrix as well as that of carbon fibers as the heat treatment temperature of the carbon-carbon composites is raised. Three different grades of PAN based carbon fibres were selected to offer different surface characteristics. It is observed that in case of high-strength carbon fiber based carbon-carbon composites, not only the matrix microstructure is different but the texture of carbon fiber changes from isotropic to anisotropic after HTT to $2600^{\circ}C$. However, in case of intermediate and high modulus carbon fiber based carbon-carbon composites, the carbon fiber texture remains nearly isotropic at $2600^{\circ}C$ because of relatively weak fiber-matrix interactions.

Thermomechanical Properties of Carbon Fibres and Graphite Powder Reinforced Asbestos Free Brake Pad Composite Material

Thiyagarajan, P.,Mathur, R.B.,Dhami, T.L. Korean Carbon Society 2003 Carbon Letters Vol.4 No.3

Asbestos is being replaced throughout the world among friction materials because of its carcinogenic nature. This has raised an important issue of heat dissipation in the non-asbestos brake pad materials being developed for automobiles etc. It has been found that two of the components i.e. carbon fibres as reinforcement and graphite powder as friction modifier, in the brake pad material, can playa vital role in this direction. The study reports the influence of these modifications on the thermal properties like coefficient of thermal expansion (CTE) and thermal conductivity along with the mechanical properties of nonasbestos brake pad composite samples developed in the laboratory.

Interface and Microstructure Development in Carbon/Carbon Composites

Mathur, R.B.,Bahl, O.P.,Dhami, T.L.,Chauhan, S.K.,Dhakate, S.R.,Rand, B. Korean Carbon Society 2004 Carbon Letters Vol.5 No.2

Performance of carbon-carbon composites is known to be influenced by the fibre matrix interactions. The present investigation was undertaken to ascertain the development of microstructure in such composites when carbon fibres possessing different surface energies (T-300, HM-35, P120 and Dialed 1370) and pitch matrices with different characteristics (Coal tar pitch $SP110^{\circ}C$ and mesophase pitch $SP285^{\circ}C$) are used as precursor materials. These composites were subjected to two different heat treatment temperatures of $1000^{\circ}C$ and $2600^{\circ}C$. Quite interesting changes in the crystalline parameters as well as the matrix microstructure are observed and attempt has been made to correlate these observations with the fibre matrix interactions.