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Ceramic Engineering 111 Sintering

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Ceramic Engineering 111 Sintering This is an example Lab Report for Cer. 111 and Cer. 122. The left column gives hints and instructions. Ignore the fact that the data are fictitious. The analysis is sound. FYI, this report would be about 15 pages, if I had not added this extra column. The title page should include a short, Ceramic Engineering 111 descriptive title of your Sintering work and contact information. There is no standard format. Feel free to be creative, just remember that this is the first thing someone reading your work will see. If the title page offends them, By: they will judge your document more harshly. William G. Fahrenholtz For this class, the title page should include the course #, experiment title, authors' names, department address, Ceramic Engineering Department date submitted, and University of Missouri-Rolla authors' signatures. Rolla, MO 65409 The goal of technical writing, especially short reports of experimental January 5, 2004 work, is to convey your important results accurately and clearly to a target audience. In this type of report, you want to be as clear, straight forward, and concise as possible. You can build up to your important result, but do not make it a mystery. Even the most important results can be Signature Here obscured in a poorly William Fahrenholtz written report. The Abstract is a short Abstract summary of what you did and what you learned. The abstract TiO2 pellets were examined to determine the effect of green should tell readers three density, firing time, and firing temperature on the fired density and things: 1) what you did; 2) how you did it; and average grain size. Pellets were prepared by dry pressing a granulated 3) your most important conclusion. You should ceramic powder. Two pressing pressures were used to produce pellets include some quantitative examples with different green densities. Pellets pressed at 7 MPa (1000 psi) had from your results in your abstract. Potential an average relative density 40% while those pressed at 70 MPa (10,000 readers will scan an psi) had an average green density of 45%. Three different time- abstract to determine if they want to spend the temperature combinations were used for the heat treatments, 1250°C for time to read an entire document. Make sure 30 minutes, 1400°C for 30 minutes and 1400°C for 4 hours. The density your abstract includes the one fact that you of fired pellets was determined using Archimedes' technique. It was want people to get from your work. Hopefully, found that pellets with a higher green density had a higher fired density, this will convince the compared to pellets with low green density, for the same sintering time reader to examine the whole document. and temperature. The relative density of sintered TiO2 pellets increased from 73% to 91% when the sintering temperature was increased from In general, the abstract is written last. For me, 1250°C to 1400°C. Finally, an increase in the sintering time from 30 the abstract is the most difficult section to write. minutes to 4 hours at 1400°C increased in grain size by more than a factor of 2, but increased the relative density by only 5 percent. For a longer document, The data collected and analyzed in this study can be used to control you might include a table of contents after the microstructure and, therefore, the properties of fired TiO2. Two the abstract, but that is not necessary for our different routes were used to sinter pellets to around 90% relative lab reports. density: 1) firing high green density pellets for 30 minutes at 1400°C or 2) firing low green density pellets for 240 minutes at 1400°C. The grain size of pellets produced at condition 1 had a grain size of 7.9 µm while those prepared at condition 2 had a grain size of 15.3 µm. 1 The Introduction sets the Introduction stage for the rest of your report. In this section, Heat treatment is one of the final step in the ceramic fabrication you need to convey a sense of why this work is process. Ceramic powder compacts undergo several significant changes important. You should summarize important during heat treatment, including binder burnout, chemical reactions (e.g. work done by others in 1 this field. The decomposition, oxidation), phase transformations, and sintering. introduction should also review any equations or Sintering is a diffusional process that proceeds at relatively high theory that will be used temperatures, usually between 1/2 and 3/4 of the melting temperature of to analyze or interpret your results. Finally, a the ceramic.2 During sintering, material is transported to inter-particle good Introduction ends with statement of purpose necks to build a strong ceramic bond. The goal of the sintering step is to or goals. After reading an Introduction, the convert a porous powder compact into a useful part. For a few ceramics reader should know why you are doing this work, such as porous insulating refractories, this means vapor phase transport how it relates to of material that builds strong necks without a significant increase in bulk previously published work, and what your density.3 In contrast, many ceramics undergo a significant increase in intent is with this study. The book, lab handouts, density during sintering that is crucial for developing desirable and background readings for 111 and 122 provide properties such as mechanical strength, optical translucency, or most of the introductory 2 material needed for these dielectric constant. Examples of neck growth during non-densifying lab report. In other and densifying sintering are shown in Figure 1. classes and in research you will be required to search the technical literature for your sources. (a) (b) (c) Figure 1. Schematic representations of a) a powder compact, b) non- densifying neck growth, and c) densifying neck growth. Barsoum defines solid-state sintering as the process that converts powder compacts to strong, dense ceramics.2 During sintering, several material transport mechanisms may be active. These are summarized in Table I. To increase the density of a powder compact, material must be 2 Tables and graphs in Table I. Material Transport Mechanisms During Sintering.3 your reports should be numbered sequentially. Tables should have a title above them. The title Method Transport Source Sink Densify should be short and descriptive. If numerical 1 Surface Diffusion Surface Neck No information is tabulated, 2 Lattice Diffusion Surface Neck No make sure that units are 3 Vapor Transport Surface Neck No included. The standard 4 Boundary diffusion Grain Boundary Neck Yes format would be to 5 Lattice Diffusion Grain Boundary Neck Yes include the units in the column heading and then 6 Lattice Diffusion Dislocations Neck Yes just the numbers in the columns. Use borders to help the reader transported from between the particle centers to the neck region. understand the information in your table. Necks form as material deposits near the original point of contact between two powder particles.1 Methods 1-3 are coarsening mechanisms that only promote the growth of necks. They do not increase the density of the compact because the source of material is the particle surface. Mechanisms 4-6 increase the density of a compact by removing material from between the particle centers and depositing it at the neck. As the bulk density of the ceramic powder compact increases, individual grains begin to grow. This phenomenon is known as grain growth. Typically, the grain size of a dense ceramic is 10 to 100 times greater than the original particle size of the compact. Large grains tend to grow at the expense of smaller ones.3 Many ceramics cannot be sintered to full density. In effect, an ultimate sintered density exists for most materials. Above some threshold, densification proceeds slowly compared to grain growth.3 To maximize the useful properties of most ceramics, it is desirable to maximize density while keeping grain size to a minimum.1 This can require a compromise between density and grain size. As such, it is often necessary to characterize the average grain size of fired ceramics. One technique for doing this is the lineal intercept method.3 Lineal 3 analysis assumes that the average grain volume, average cross sectional area, and average lineal intercept length are equivalent, an assumption that requires counting of 500 or more grains for statistical accuracy.3 The lineal intercept method calculates the grain size of a sample from representative micrographs of polished cross sections.3 First, horizontal lines are drawn across micrographs at random intervals. Next, the total number of times these lines intercept grain boundaries is counted. Dividing the total line length by the number of intercepts gives the number of intercepts per unit length. It is important that the line length is converted to the magnification of the micrograph. Making the assumption that the grains are uniform (i.e., roughly spherical) in shape, the average grain diameter is 3/2 of the average intercept length. Other assumptions are made for different grain shapes such as rods or platelets. Equations in your reports Accurate density measurements are an important part of should be numbered characterizing the physical properties of ceramics. In this experiment, sequentially. For a professional appearance, the density of as-pressed pellets was calculated from the sample mass try to use an equation editor rather than typing and volume. Mass was measured using a digital balance and sample them directly into the document. Finally, be volume was calculated from the external dimensions of the samples, sure to define all of the variables in each which were right regular cylinders. A liquid displacement method, equation.
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