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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Effect of heat-treatment on the thermal and mechanical stability of Ni/Al2O3 nanocrystalline coatings

Cooke, Kavian O., Khan, T.I., Shar, Muhammad A. 25 November 2020 (has links)
Yes / Heat-treatment is a frequently used technique for modifying the physical and chemical properties of materials. In this study, the effect of heat-treatment on the mechanical properties, thermal stability and surface morphology of two types of electrodeposited coatings (pure-Ni and Ni/Al2O3) were investigated. The XRD analyses showed that the crystal structure of the as-deposited coating changes from slightly amorphous to crystalline as the heat-treatment temperature increases. The heat-treatment of both the pure-Ni and the Ni/Al2O3 coating caused an increase of the grain size within the coatings. However, the unreinforced Ni coating experienced a faster growth rate than the Ni/Al2O3 coating, which resulted in a larger average grain size. The temperature-driven changes to the microstructure of the coatings caused a reduction in the hardness and wear resistance of the coatings. The presence of nanoparticles within the Ni/Al2O3 coating can successfully extend the operational temperature range of the coating to 473 K by pinning grain boundaries.
132

Heat Treatment of Lithic Raw Materials: Archaeological Detection and Technological Interpretation

Trubitt, Mary Beth D. January 1981 (has links)
No description available.
133

Prediction of Geometric Distortions and Residual Stresses on Heat Treated Hot Rolled Rings

Gonzalez-Mendez, Jose Luis 16 December 2011 (has links)
No description available.
134

Heat treatment effect on wear behaviour of HVOF-sprayed near-nanostructured coatings

Ben Mahmud, T., Khan, Tahir I., Farrokhzad, M.A. 30 January 2017 (has links)
No / This study investigates the effect of heat treatment on changes in microstructure and wear behaviour of WC-NiCr coatings. Two feedstock powders with a similar chemical composition and different particle sizes (near nano-structured WC-17NiCr and microstructured WC-15NiCr) were used. High-velocity oxyfuel spraying technique was used to deposit coatings on to a mild steel substrate using identical spraying parameters. Coated samples were then heat treated in a nitrogen atmosphere at 500 and 700°C. The effect of heat treatment on changes in hardness and wear performance of the coatings was studied using microstructural analysis, micro-hardness indentation and abrasive wear tests. The results showed that the heat treatment increased the hardness of both coatings and a corresponding increase in wear resistance was recorded. The formation of a brittle CrWO4 phase in the microstructured coating resulted in brittle fracture of the coating and this gave lower wear resistance compared to the nanostructured coatings.
135

The production of a lightweight concrete aggregate by the action of heat on clay shales

Bowling, Arthur Lee January 1947 (has links)
Master of Science
136

The catalytic heat treatment of cottonseed oil to obtain drying oil characteristics

Greene, R. Aust January 1947 (has links)
M.S.
137

Optimization of the Heat Treatment of Semi Solid Processed A356 Aluminum Alloy

Dewhirst, Brian A 17 November 2005 (has links)
"This research investigated the relationship between T5 heat treatment and elongation in thixocast and rheocast SSM components as a means to reduce the energy, time, and cost associated with T6 treatments while still producing improved properties over the as-cast condition. Temperature and time were varied as a part of work to optimize aging conditions for SSM materials. Both conventional furnace and fluidized bed heat treatments were employed. Tensile bars were fabricated from the heat treated A356 components and were pulled. Extensive SEM and stereo microscopy were performed to examine the factors which produced favorable results in the T5 condition. Data generated for T6 and as-cast components were also collected for purposes of comparison. Quality index calculations were employed to help evaluate the results. Optimized procedures and aging parameters have been presented"
138

Predicting the Response of Powder Metallurgy Steel Components to Heat Treatment.

Warke, Virendra S 28 July 2008 (has links)
"The goal of heat treating manufactured steel components is to enhance the characteristics of the metal so that the components meet pre-specified quality assurance criteria. However, the heat treatment process often creates considerable distortion, dimensional change, and residual stresses in the components. These are caused mainly by thermal stresses generated by a non-uniform temperature distribution in the part, and/or by transformation stresses due to the volume mismatch between the parent phase and product phases that may form by phase transformation. With the increasing demand for tighter dimensional tolerances and better mechanical properties from heat treated components, it is important for the manufacturer to be able to predict the ability of a component to be heat treated to a desired hardness and strength without undergoing cracking, distortion, and excessive dimensional change. Several commercial softwares are available to accurately predict the heat treatment response of wrought steel components. However, these softwares cannot be used to predict the heat treatment response of steel components that are made by powder metallurgy (PM) processes since these components generally contain pores which affect the mechanical, thermal, and transformation behavior of the material. Accordingly, the primary objective of this research is to adapt commercially available simulation software, namely DANTE, so that it can accurately predict the response of PM steel components to heat treatment. Additional objectives of the research are to characterize the effect of porosity on (1) the mechanical properties, (2) the heat transfer characteristics, and (3) the kinetics of phase transformation during heat treatment of PM steels."
139

Effect of pre-exposure thermal treatment on susceptibility of type 304 austenitic stainless steel to stress corrosion

Yoon, Kap Suk 04 May 2010 (has links)
The effect of a specific type of pre-exposure heat treatment on the susceptibility of AlSI type 304 stainless steel to stress corrosion cracking was studied in terms of time for crack nucleation and rate of crack propagation. U-bend specimens were exposed to 42 weight percent magnesium chloride aqueous solution after pre-exposure heat treatments at 140°C and 154°C. The straight-line relationship between maximum crack depth and the logarithm of exposure time expressed by the empirical equation log t = log t<sub>o</sub> + D/M was obtained. The stress corrosion constants derived from the empirical equation indicate that this type of pre-exposure heat treatment promotes crack nucleation because of the formation of less protective surface films, and retards the rate of crack propagation because of effects on internal structural changes within the alloy. / Master of Science
140

Effect of sanitation on responses of Tribolium castaneum (herbst) (Coleoptera: tenebrionidae) life stages to structural heat treatments

Brijwani, Monika January 1900 (has links)
Master of Science / Department of Grain Science and Industry / Subramanyam Bhadriraju / Heat treatment involves raising the ambient temperature of food-processing facilities such as flour mills to 50-60oC for killing stored-product insects. However, very little is known about the influence of sanitation on responses of stored-product insects to structural heat treatments. The impact of sanitation on responses of life stages of the red flour beetle, Tribolium castaneum, an economically important pest in flour mills, were investigated during three 24 h structural heat treatments of the Kansas State University pilot flour mill. Two sanitation levels, dusting of wheat flour (~0.5 g) and 2-cm deep flour (~43 g), were created in 25 plastic bioassay boxes each holding 50 eggs, 50 young larvae, 50 old larvae, 50 pupae, and 50 adults of T. castaneum in separate compartments. Five boxes were placed on each of five floors of the pilot mill during 13-14 May 2009, 25-26 August 2009, and 7-8 May 2010 heat treatments using forced air gas heaters. During the August 2009 and May 2010 heat treatments, 100 eggs or 100 adults of T. castaneum were exposed inside each 20 cm diameter by 15 cm high PVC ring placed only on first and third floors and holding 0.1 (15 g), 0.2 (38 g), 1 (109 g), 3 (388 g), 6 (937 g), or 10 (1645 g) cm deep wheat flour. Among the mill floors, first floor had lower maximum temperature. The first floor rests on a thick concrete foundation, did not get heated from both sides unlike other floors, and had poor air movement resulting in cold pockets (temperatures <50oC). Mortality of life stages was lower on first floor than other floors and adults were less susceptible than other life stages especially on first floor. In general, both these tests have shown that the mortality of T. castaneum life stages were influenced by how quickly temperatures reached 50oC, how long temperatures were held above 50oC, and the maximum temperature. Protective effects of sanitation were evident only if temperatures did not reach 50oC. However, removal of flour accumulations is essential to improve heat treatment effectiveness against all T. castaneum life stages during a 24 h treatment.

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