Effect of Single and Double Austenitization heat treatments on the Microstructure and Hardness of AISI D2 Tool Steel

This investigation is concerned with the study of effect of Double Austenitization (DA) and Single Austenitization (SA) heat treatment processes on microstructure and mechanical property of AISI D2type cold worked tool steel. To maximize hardness, tool steels are used in a quenched and tempered condition. This involves heating the material to the austenitizing temperature (∼850−1100 °C), quenching at an appropriate rate to form martensite, and tempering to reduce the retained austenite content and induce toughness. The merits of DA treatment isto promote dissolution of carbides at the same time proscribe grain coarsening significantly was attempted in D2 tool steel. The study has found that DA treatment has induced high hardness with insignificant growth in grains. The increase in hardness is attributed to increase in carbon content in matrix due to dissolution of carbides; whereas finer grains due to role of inclusions.

Effect of pre-treatments and post-treatments on drying products

Freeze drying technology can give good quality attributes of vegetables and fruits in terms of color, nutrition, volume, rehydration kinetics, stability during storage, among others, when compared with solely air dried ones. However, published scientific works showed that treatments applied before and after air dehydration are effective in food attributes, improving its quality. Therefore, the hypothesis of the present thesis was focus in a vast research of scientific work that showed the possibility to apply a pre-treatment and a post-treatment to food products combined with conventional air drying aiming being close, or even better, to the quality that a freeze dried product can give. Such attributes are the enzymatic inactivation, stability during storage, drying and rehydration kinetics, color, nutrition, volume and texture/structure. With regard to pre-treatments, the ones studied along the present work were: water blanching, steam blanching, ultrasound, freezing, high pressure and osmotic dehydration. High electric pulsed field was also studied but the food attributes were not explained on detailed. Basically, water and steam blanching showed to be adequate to inactivate enzymes in order to prevent enzymatic browning and preserve the product quality during long storage periods. With regard to ultrasound pre-treatment the published results pointed that ultrasound is an effective pre-treatment to reduce further drying times, improve rehydration kinetics and color retention. On the other hand, studies showed that ultrasound allow sugars losses and, in some cases, can lead to cell disruption. For freezing pre-treatment an overall conclusion was difficult to draw for some food attributes, since, each fruit or vegetable is unique and freezing comprises a lot of variables. However, for the studied cases, freezing showed to be a pre-treatment able to enhance rehydration kinetics and color attributes. High pressure pre-treatment showed to inactivate enzymes improving storage stability of food and showed to have a positive performance in terms of rehydration. For other attributes, when high pressure technology was applied, the literature showed divergent results according with the crops used. Finally, osmotic dehydration has been widely used in food processing to incorporate a desired salt or sugar present in aqueous solution into the cellular structure of food matrix (improvement of nutrition attribute). Moreover, osmotic dehydration lead to shorter drying times and the impregnation of solutes during osmose allow cellular strengthens of food. In case of post-treatments, puffing and a new technology denominated as instant controlled pressure drop (DIC) were reported in the literature as treatments able to improve diverse Abstract Effect of Pre-treatments and Post-treatments on Drying Products x food attributes. Basically, both technologies are similar where the product is submitted to a high pressure step and the process can make use of different heating mediums such as CO2, steam, air and N2. However, there exist a significant difference related with the final stage of both which can comprise the quality of the final product. On the other hand, puffing and DIC are used to expand cellular tissues improving the volume of food samples, helping in rehydration kinetics as posterior procedure, among others. The effectiveness of such pre and/or post-treatments is dependent on the state of the vegetables and fruits used which are also dependent of its cellular structure, variety, origin, state (fresh, ripe, raw), harvesting conditions, etc. In conclusion, as it was seen in the open literature, the application of pre-treatments and post-treatments coupled with a conventional air dehydration aim to give dehydrated food products with similar quality of freeze dried ones. Along the present Master thesis the experimental data was removed due to confidential reasons of the company Unilever R&D Vlaardingen

In Situ Observation of the Thermal Decomposition of Weddelite by Heating Stage Environmental Scanning Electron Microscopy

The morphological and chemical changes occurring during the thermal decomposition of weddelite, CaC2O4·2H2O, have been followed in real time in a heating stage attached to an Environmental Scanning Electron Microscope operating at a pressure of 2 Torr, with a heating rate of 10 °C/min and an equilibration time of approximately 10 min. The dehydration step around 120 °C and the loss of CO around 425 °C do not involve changes in morphology, but changes in the composition were observed. The final reaction of CaCO3 to CaO while evolving CO2 around 600 °C involved the formation of chains of very small oxide particles pseudomorphic to the original oxalate crystals. The change in chemical composition could only be observed after cooling the sample to 350 °C because of the effects of thermal radiation.

Efficient microwave hydrothermal preparation of nanocrystalline anatase TiO2 colloids

Titanium dioxide nanocrystals are an important commercial product used primarily in white pigments and abrasives, however, more recently the anatase form of TiO2 has become a major component in electrochemical and photoelectrochemical devices. An important property of titanium dioxide nanocrystals for electrical applications is the degree of crystallinity. Numerous preparation methods exist for the production of highly crystalline TiO2 particles. The majority of these processes require long reaction times, high pressures and temperatures (450–1400 °C). Recently, hydrothermal treatment of colloidal TiO2 suspensions has been shown to produce quality crystalline products at low temperatures (<250 °C). In this paper we extend this idea utilising a direct microwave heating source. A comparison between convection and microwave hydrothermal treatment of colloidal TiO2 is presented. The resulting highly crystalline TiO2 colloids were characterised using Raman spectroscopy, XRD, TEM, and electron diffraction. The results show that the microwave treatment of colloidal TiO2 gives comparable increases in crystallinity with respect to normal hydrothermal treatments while requiring significantly less time and energy than the hydrothermal convection treatment.

Feasibility studies on using microwave-heating techniques for recycling lead waste

Lead is present everywhere in the environment and has been defined as one of the greatest threats to the human health. In this paper, attempts have been made to study a way of recycling the lead produced from waste usage and disposed of in such a way as to avoid degrading the surrounding environment. In order to contain the waste, recycled asphalt material is mixed with the lead and then heated with microwave energy. This is an attempt to solidify and reduce the lead contaminants and use the final product as sub-base material in road pavement construction. The microwave heating of the specimens is carried out with 30%, 50%, 80% and 100% of power at 800W. The optimum power mode is used to compare with the conventional heating of asphalt with sulfur additive. The results are characterized by compact density, permeability, and subjected to toxicity test with regards to lead concentration. A mechanical test to evaluate the stability is also performed on the three methods of solidification and to prove that microwave zapping method allow to convert into an environmentally stable material for recycling without having to be deposited in a landfill site.

Passive solar systems for heating, daylighting and ventilation for rooms without an equator-facing facade

Spaces without northerly orientations have an impact on the ‘energy behaviour’ of a building. This paper outlines possible energy savings and better performance achieved by different zenithal solar passive strategies (skylights, roof monitors and clerestory roof windows) and element arrangements across the roof in zones of cold to temperate climates typical of the central and central-southern Argentina. Analyses were undertaken considering daylighting, thermal and ventilation performances of the different strategies. The results indicate that heating,ventilation and lighting loads in spaces without an equator-facing facade can be significantly reduced by implementing solar passive strategies. In the thermal aspect, the solar saving fraction reached for the different strategies were averaged 43.16% for clerestories, 41.4% for roof monitors and 38.86% for skylights for a glass area of 9% to the floor area. The results also indicate average illuminance levels above 500 lux for the different clerestory and monitor arrangements, uniformity ratios of 0.66–0.82 for the most distributed arrangements and day-lighting factors between 11.78 and 20.30% for clear sky conditions, depending on the strategy. In addition, minimum air changes rates of 4 were reached for the most extreme conditions.

Evaluation of valuation of noise amelioration treatments within and outside the road reserve

In urban environments road traffic volumes are increasing and the density of living is becoming higher. As a consequence the urban community is being exposed to increasing levels of road traffic noise. It is also evident that the noise reduction potential of within-the-road-reserve treatments such as noise barriers, mounding and pavement surfacing has been exhausted. This paper presents a strategy that involves the comparison of noise ameliorative treatments both within and outside the road reserve. The noise reduction resulting from the within-the-road-reserve component of treatments has been evaluated using a leading application of the CoRTN Model, developed by the UK Department of Transport 1988 [1], and the outside road reserve treatment has been evaluated in accordance with the Australian Standard 3671, Acoustics – Road traffic noise intrusion – Building sitting and construction [5]. The evaluation of noise treatments has been undertaken using a decision support tool (DST) currently being developed under the research program conducted at RMIT University and Department of Main Roads, Queensland. The case study has been based on data from a real project in Queensland, Australia. The research described here was carried out by the Australian Cooperative Research Centre for Construction Innovation [9], in collaboration with Department of Main Roads, Queensland, Department of Public Works, Queensland, Arup Pty. Ltd., Queensland University of technology and RMIT University.

Major depressive disorder and nutritional medicine : a review of monotherapies and adjuvant treatments

A literature review was conducted to examine the evidence for nutritional interventions in depression. It revealed a number of significant conclusions. Interestingly, more positive clinical trials were found to support adjuvant, rather than monotherapeutic, use of nutrients to treat depression. Much evidence exists in the area of adjuvant application of folic acid, S-adenosyl-methionine, omega-3, and L-tryptophan with antidepressants. Current evidence does not support omega-3 as an effective monotherapy to treat depression. However, this may be due, at least in part, to olive oil being used as the control intervention, some studies using docosahexaenoic acid alone or a higher docosahexaenoic acid to eicosapentaenoic acid ratio, and significant heterogeneity regarding depressive populations. Nevertheless, adjunctive prescription of omega-3 with antidepressants, or in people with dietary deficiency, may be beneficial. Inositol lacks evidence as an effective antidepressant and cannot be currently recommended. Evidence on the use of L-trytophan for depression is inconclusive and additional studies utilizing a more robust methodology are required.