Chaitanya Kumar Narula

Demonstration of a high-temperature fiber-optic gas sensor made with a sol-gel process to incorporate a fluorescent indicator

To make a gas sensor suitable for use at high temperatures, we have used a sol-gel-processing technique to bond a copper-exchanged zeolite fluorescence indicator onto the end of an all-silica optical fiber. Experimental results from single-fiber prototype sensors show they can be used to measure either the oxygen concentration or the equivalence ratio for gas mixtures containing weak or strong reductants, respectively.

A novel approach to paint sludge recycling: Reclaiming of paint sludge components as ceramic composites and their applications in reinforcement of metals and polymers,

About 15 × 10 6 lbs of paint sludge, produced every year at Ford plants, is disposed of in landfills. An economical alternative to this disposal method, which reclaims or recycles components of paint sludge, is highly desirable to preserve valuable natural resources. Here, we describe an alternative to landfill disposal whereby paint sludge is converted into ceramic composites that can be used as reinforcing materials. The conversion of paint sludge to ceramic composite, I/N 2 /600, is achieved by pyrolysis under a nitrogen atmosphere. Two additional composites, labeled I/N 2 /1000 and I/NH 3 /1000, respectively, are prepared by sintering I/600 at 1000 °C under N 2 and NH 3 . All three composites contain crystalline CaTiO 3 , BaTiO 3 , TiO 2 , amorphous alumina, and carbon. I/NH 3 /1000 contains an additional crystalline phase of titanium nitride. The application of these composites as reinforcing materials is demonstrated in the fabrication of representative metal matrix composites (MMCs) and reinforced plastic components.

1.064 μm multiphoton laser-induced fluorescence and dissociation of tetrakis-(dimethylamino) titanium (IV)

Abstract Irradiation of Ti[N(CH 3 ) 2 ] 4 by the 1.064 μm line of a pulsed Nd:YAG laser has been found to produce an intense visible emission due to multiphoton absorption and subsequent dissociation by this species and/or its decomposition products. At low pump intensities a broad and featureless emission is observed over the 250–700 nm range. As the intensity is increased structure corresponding to Ti and Ti + fluorescence appears in the emission spectrum. The emission decays as a double exponential with time constants of approximately 0.25 and 1.2 μs. Mass spectroscopic analysis reveals dimethylamine, tetramethylhydrazine and bis-(dimethylamino) methane amongst the dissociation products along with an insoluble residue.

New Routes to Group Iva Metal-Nitrides

The reactions of TiCl 4 with [(CH 3 ) 3 Si] 2 NH have been examined under several reaction conditions. One of the reaction products, (CH 3 ) 3 Si(H)NTiCl 3 , can be crystallized in 60% yield on reacting TiCl 4 with TiCl 4 with [(CH 3 ) 3 Si] 2 NH in a 1:1 molar ratio in dichloromethane at -78°C. [(CH 3 ) 3 Si(H)NTi(Cl 2 )(NH)] 2 TiCl 2 is the primary product on increasing the amount of TiCl 4 with [(CH 3 ) 3 Si] 2 NH to two equivalents. (CH 3 ) 3 Si(H)NTiCl 3 and [(CH 3 ) 3 Si(H)NTi(Cl 2 )(NH)] 2 TiCl 2 form titanium nitride on pyrolysis at 600°C in an ammonia atmosphere.

Sol-Gel Processed Alumina based Materials in Microcalorimeter Sensor Device Fabrication for Automotive Applications

The application of sol-gel processed materials in a variety of sensors has been proposed. The authors describe microcalorimeter sensor devices employing sol-gel processed alumina based materials which can be used to monitor pollutants in automotive exhaust. These sensors operate by measuring changes in resistance upon catalysis and are economically acceptable for automotive applications. It is important to point out that automobiles will be required to have a means of monitoring exhaust gases by on-board sensors as mandated by the EPA and the California Air Resources Board (OBD-II).

Automotive Applications of Materials Prepared by Ceramic Precursor and Sol-Gel Routes

The promise of new applications continues to drive research on ceramic precursor and sol-gel routes to materials preparation. These routes offer flexibility in the fabrication of materials in forms such as films, coatings, fibers, foams, and powders, etc. Our interest in ceramic precursors stems from their potential in the low cost fabrication of films. Such films can be employed in a variety of new automotive applications. In this article, we summarize our efforts to prepare soluble ceramic precursors and their conversion to group IV metal nitrides. A comparison of some properties of electrically conducting titanium nitride films prepared by dipcoat-fire cycle and low pressure CVD is presented. We also describe the fabrication of indium tin oxide films by a sol-gel process. These films are candidates in the low cost fabrication of electrically heatable catalyst devices.

Sol-Gel Process form Heterometallic Alkoxides to Incorporate Alkaline- and Rare Earths in Alumina for automotive Applications

The high cost of materials prepared by sol-gel processing and the loss of useful surface properties at elevated temperature has prevented the application of sol-gel processed materials in automotive exhaust reduction catalyst formulations. In this report, we briefly describe the important developments needed in the next generation automotive catalysts and the role of sol-gel processed materials. We will also discuss the application of heterometallic alkoxides as sol-gel precursors to achieve the molecular distribution of lanthanides and alkaline earths in alumina matrices needed for the stabilization of alumina based materials at elevated temperatures.

Automotive Applications of Sol-Gel Processed Materials: Novel, Low Power Consumption, Electrically Heatable Catalyst Devices

Exhaust gas heat is the primary source of warming in a conventional automotive exhaust catalyst. It typically becomes operational within minutes after the initial start-up of an engine, when it attains temperatures greater than approximately 350°C. However, around 70% of the total hydrocarbon and carbon monoxide (CO) emissions of a modern gasoline powered vehicle, under a normal driving cycle, are released during this period of cold-start. One of the strategies suggested to treat the pollutants during the first minute after initial start-up involves electrically heating the catalyst. However, devices developed for this purpose are power intensive, can require a second battery and can reduce fuel economy. The increased weight, in turn, results in increased pollution. Here we describe a low power consumption prototype which contains a conducting layer beneath the washcoat. The prototype [4 cm 2 ] was tested at a gas flow rate of 100 seem and required less than 5 Watts to attain temperatures greater than 350°C in less than 10 seconds. The prototype was tested in a flow reactor and found to rapidly heat up to light-off temperatures where the conversion of the hydrocarbons and CO takes place. We also summarize progress made in our laboratory in the fabrication of a test device employing sol-gel processed metal oxide films.

Novel Applications Of Ceramic Precursors - Tin Coating On Alumina And Functionally Gradient Materials

There are very few demonstrated applications of ceramic precursor technology. Here, the authors describe two new applications of known ceramic precursors, thin film deposition and the fabrication of functionally gradient materials (FGM). To demonstrate the thin film deposition, the authors prepared titanium nitride film on an alumina substrate using (CH{sub 3}){sub 3}SiNHTiCl{sub 3} precursor by a single dipcoat-fire cycle. The fabrication of copper and aluminum based FGMs was demonstrated using Nicalon{reg_sign} fiber polycarbosilane and poly(methylsilane) precursors as binders and in situ sources of ceramics.