Sintering - Science topic

Exactly, that's what we have not covered. As the calcination also helps in greater binding strength later on along with impurities removal. Thank you Sir for providing valuable answer & filling on my gap..

Dear Umi Zalilah Mohamad Zaidi

I had a study using CoCr alloy, maybe it will be useful for you.

"Productıon and Cleaning of Lattice Structures Used in the Space and Aerospace Industry with Metal Additive Manufacturing Method"

Kind Regards.

Jp Wu Nice suggestion. Thank you for your reply.

Hi Mr. Rizwan

Good day

Creating Ni/Al2O3 cylindrical pellets involves several key steps, from preparing the mixture to sintering the final product. Here's a detailed step-by-step guide:

Step 1: Prepare the Ni/Al2O3 Mixture

Step 2: Add Binder

Step 3: Form Cylindrical Pellets

Step 4: Sinter the Pellets

Final Considerations

By following these steps, you can produce high-quality Ni/Al2O3 cylindrical pellets suitable for various applications. Adjustments to the process may be necessary based on specific requirements or material properties.

Hope you find the good answer you want ...

Yes, this is an old industrial technology used in the production of hard alloys from tungsten carbide. By the way, the technology with melted paraffin is also very old and was also widely used in the production of technical ceramics. There is no fresh information on old technologies on the Internet, you need to read books and articles from the 60s of the last century.

The shifting of XRD diffraction is because of the lattice parameters as well exchange in cell parameters. If your material is cubic, you only change a parameter, but if your sample is triclinic you need to adjust a, or, b parameters. Cell parameters can change because of the impurities, preparation method, doping, calcined temperature, etc. In your case, the factor is doping or impurities diffusing crystal growth and alignment of the predominant plane as well as the lattice parameters, and the diffraction might be shifted. For preferred orientation, it might be the rightward shift as well.

Thank you so much Mr. Tobias Makuochukwu Onyia for your time and very detailed response to my query.

Thank you Mr. Vinodh Sekar for your detailed reply.

To implement the spark plasma sintering (SPS) model proposed by Eugene A. Olevsky in COMSOL, especially the stress-strain analysis part, follow these steps:

1. Set Up the Basic Modules

2. Nonlinear Elastic Material Node in Solid Mechanics Module

Steps for Stress-Strain Implementation

1. Activate Nonlinear Elastic Material Model

2. Define the Stress-Strain Rate Relationship

3. Implementing Sintering Stress

Example: Custom Constitutive Equation

codeσ_ij = f(ε_dot_ij)

Define this in the nonlinear elasticity settings by inputting the mathematical expressions derived from Olevsky’s model.

4. Parameter Definition and Coupling

Final Notes

By following these steps, you should be able to correctly implement the sintering stress-strain analysis part of the SPS model in COMSOL.

Pressure drop may be increased due to pores occupied with fine particles. You can measure present bed height and compare with initial bed height. The height must be decreases.

Hi Umanath Puthillam,

Quartz glass does not become liquid at 1300°C, but this material has another problem: crystallization. The crystallization of the amorphous SiO₂ in cristobalite causes a large change in volume and the material becomes pulverized. Crystallization during long high-temperature aging begins at temperatures below 1000°C, which is why you cannot use the quartz glass casings above 1100-1150°C.

Leonard Namwiha

A coating of dispersed fine silica particles in ethanol, without any other additives, will likely form a thin, transparent or translucent film after the ethanol evaporates. The appearance and properties of the coating will depend on factors such as the concentration of silica particles, the size and shape of the particles, and the method used to apply the coating.

Here's what you might expect:

1. Transparent Film: If the silica particles are dispersed uniformly in the ethanol and applied evenly onto a substrate, the resulting coating is likely to be transparent, especially if the particles are fine and well-dispersed.

2. Smooth Surface: Assuming the silica particles are well-dispersed in the ethanol and applied onto a flat surface, the coating is likely to have a relatively smooth surface. However, if the particles are not uniformly dispersed or if the coating process introduces agitation or unevenness, the surface may have some roughness.

3. Enhanced Surface Properties: Silica particles can provide various surface properties such as increased scratch resistance, improved adhesion, and enhanced hardness. These properties may be present in the coating depending on the particle size and concentration.

4. Potential for Optical Effects: In some cases, if the coating is thin enough and the silica particles are of the right size and distribution, you might observe optical effects such as interference or diffraction patterns, which could give the coating a slightly iridescent or pearlescent appearance under certain lighting conditions.

5. Uniformity and Clarity: The uniformity and clarity of the coating will depend on the quality of dispersion achieved during the mixing process and the uniformity of application onto the substrate. Poor dispersion or uneven application could result in non-uniform coating thickness and reduced clarity.

Overall, the coating of dispersed fine silica particles in ethanol is likely to form a thin, transparent film with potential enhancements in surface properties, but the specific appearance and properties will depend on several factors including particle size, distribution, concentration, and application method.

The difference in surface appearance after sintering between copper-nickel-aluminum (Cu-Ni-Al) and copper-nickel-chromium (Cu-Ni-Cr) alloys, as well as copper-nickel-silicon (Cu-Ni-Si) alloys, can indeed be attributed to various factors related to the sintering process and alloy composition.

Source(s)

1. A critical review on spark plasma sintering of copper and its alloys ...

2. Engineers Guide to Sintering - f.hubspotusercontent20.net

3. High-Temperature Oxidation of the Copper–Nickel Alloys Synthesized by ...

4. Sintering Process | Aluminum Sintering | BTU International

5. Features of Oxidation of Copper–Nickel Alloys Synthesized ... - Springer

6. Mechanical and Physical Properties of Differently Alloyed Sintered ...

7. Bonding Strength of Cu Sinter Die-Bonding Paste on Ni, Cu, Ag, and Au ...

8. Sintered Fe-Mo-Cu-Ni-Si-C Composites Produced by SiC, Nickel ... - Springer

9. https://doi.org/

Temperature gradients can typically affect the following materials properties in alloys/steels:

1.) Dimensional stability

2.) Grain boundary size/distribution (depending on pellet size)

3.) Precipitation

4.) Matrix Composition

5.) Degree of oxidation/surface reaction (since fast cooling is aided by cooling media)

6.) Residual Stresses

7.) Porosity distribution/cracking

Nasyiyita

Such questions do not make any sense. it would help if you gave sintering variables used in sintering, such as - what temperature sintered, time at the temperature, and also in ball milling -high or low speed, how long, type of ball used. Without stating these sintering factors, your question is like a joke.

There is also one answer if the sintered parts are ball milled at low speed, then the parts have any burr, they are removed by tumbling in tumbling or ball mill and are used in the powder metal fabricating, casting, and stamping industries regularly if there are any burr on the surface of the parts. The process is called deburring.

Dr. K

If you espect light elements which in XRF in air are not detectable, you may use WDX in vacuumm, which yield also sensitivity down to 0,01wt% and can also measure elements like B, N, O, F, Na, Mg. - XRF in vacuum should also be able to measure light elements.

Hi Mariam,

You can pellet calcium oxalate without any binder because it contains enough water.

The higher the aluminum oxide content in corundum ceramics, the higher its temperature resistance (maximum application temperature). On the other hand, the fewer impurities, the higher the sintering temperature of corundum ceramics and the more complex the technology for its production.

As is always the case in technology, real ceramics are always a compromise between the requirements for properties and the capabilities of the manufacturing technology. For this reason, small additions of sintering activators, usually SiO₂ or Cr₂O₃, make it possible to reduce the cost of the production technology of corundum ceramics without significantly deteriorating its properties.

may be there is formation of new phase or lattice parameters, changed with change in the concentration of sintering aids.

Hello there, curious researcher friend Suraya Sulaiman! I'm here to assist you, and as Kosh, I'm more than willing to help you with your ZnO thermoelectric challenges. It's commendable that you're exploring this field, but it can indeed come with its share of hurdles. Let's delve into your concerns:

1. **Sintering Issues:** Experiencing severe shrinkage and a chalky appearance after sintering can be perplexing. To address this, consider these factors:

- **Temperature and Time:** Check if the sintering temperature and duration are appropriate for your ZnO material. It might require adjustments to optimize the sintering process.

- **Sintering Atmosphere:** Ensure the sintering atmosphere is controlled. Inert gases like argon can help prevent unwanted reactions.

- **Sample Preparation:** Properly prepare your samples, including particle size and compaction techniques. Sometimes, smaller particles can lead to higher shrinkage.

2. **Measurement Challenges:** Difficulty with Seebeck and electrical measurements can be resolved by:

- **Sample Preparation:** Ensure your samples are properly prepared for measurement. Their dimensions, contacts, and surface conditions can affect measurements.

- **Equipment Calibration:** Verify if the LSR3 Linseis equipment is correctly calibrated and suitable for your samples. Calibration might be necessary to enhance accuracy.

- **Electrode Contacts:** Pay attention to the electrode contacts, ensuring good electrical contact with your sample.

3. **Collaboration:** Collaboration can be a fantastic avenue for overcoming these challenges. Engaging with fellow researchers, especially those who have expertise in thermoelectric materials, can provide valuable insights and potentially lead to innovative solutions.

I'd encourage you Suraya Sulaiman to reach out to colleagues at your institution or within your research community. Sharing your experiences and challenges can often yield creative solutions. Don't hesitate to explore further discussions and collaboration possibilities with experts in the field. They can offer guidance, share their experiences, and potentially open doors to improved techniques and methodologies.

Remember, research can be a journey filled with unexpected twists, but it's these challenges that often lead to breakthroughs. Keep your curiosity alive and continue your pursuit of knowledge in the fascinating world of ZnO-based thermoelectric materials. If you have any more questions or need further advice, feel free to ask.

Magnesia cupels are small, shallow, and porous containers used in assaying precious metals, such as gold and silver. Cupels are made from a special type of refractory material known as magnesium oxide (MgO). You can find below the general overview of how magnesia cupels are made:

Materials and Equipment:

- Magnesium oxide (MgO) powder

- Water: To mix with the magnesium oxide and create a paste.

- Molding equipment: Cupel molds or cupel trays are used to shape the magnesia paste into the desired cupel shape.

- Drying and firing equipment: A kiln or furnace is required to dry and fire the cupels.

The manufacturing process typically involves the following steps:

- Mixing and molding: Magnesium oxide powder is mixed with an appropriate amount of water to create a thick, paste-like consistency. The precise ratio of water to magnesium oxide may vary depending on the specific cupel design and manufacturer's preferences. The magnesia paste is then shaped into cupels using cupel molds or trays. These molds are typically made of metal and have a concave cupel shape. The paste is pressed into these molds to create the cupel's shape and structure.

- Drying and firing: The molded cupels are allowed to air dry for a period of time. This step removes excess moisture from the cupel, making it ready for firing. The cupels are placed in a kiln or furnace and subjected to high temperatures. During this firing process, the magnesia undergoes a chemical transformation, becoming a rigid, porous structure. This porous structure is essential for cupels to absorb and remove impurities from precious metal samples during the assay process.

- After firing, the cupels are allowed to cool down slowly to room temperature. Rapid cooling can cause cracks or other defects in the cupel. Cupels are carefully inspected for defects, such as cracks or irregularities in their structure, before they are used in precious metal assaying. Once magnesia cupels are produced, they are used in laboratories and refineries to carry out fire assays.

Since tungsten has a greater affinity for carbon than iron and is in an overwhelming excess, it must completely "suck out" all the carbon from the Fe-Ni melt. For this reason, I do not think that the high carbon content in the Fe-Ni binder matrix will have any effect on the behavior of the W-Fe-Ni material during sintering and on its properties.

What material are you referring to? If the topic is sintering of metal alloy powders or ceramic powders then the answer is clear. Sintering is the final, high temperature step where solid state diffusion works to reduce the surface energy associated with the particles and so doing gradually reshapes and coalesces the particles and fills the interparticle spaces. When the remaining porosity is reduced below approximately 7.5% the pores close up and are no longer continuously connected to each other or to the surface. In some materials systems, sintering involves, by design, the appearance of a transient liquid phase to aid the consolidation process but this is a secondary effect, only used in a minority of examples. Prior to the final sintering, the powder would have been formed into what is called the green part, that holds this shape through the subsequent heating stages. Methods of producing the green part include powder injection moulding (PIM), die pressing and 3D printing, some with a binder which has to be removed before sintering. If this is the bonding that you are thinking of, then, yes it will be very much weaker than the sintered material. But I have a feeling that you may not be asking about that kind of bonding.

Crystalline size always increases with temperature rise. This is a fundamental consequence of the laws of chemical thermodynamics. So either you made a mistake in your measurement or there is another effect that falsifies your results. For example, partial melting of your composition can increase the proportion of glass phase. The formation of the glass phase at a higher sintering temperature reduces the proportion of crystals and possibly the size of the remaining crystals.

​

What's surprising about that? That's the way it has to be if the stocheometry is correct. If the proportions were not stoichiometric, other crystals would have formed as well.

Various types of sintered metals are used as filter substrates in diesel particulate filters (DPFs), and some are designed to have high sulphur tolerance. However, without specific information or further details, it is difficult to determine the exact type of sintered metal used in the research article you mentioned.

In general, DPFs employ high porosity and filtration efficiency materials to capture and remove particulate matter from diesel engine exhaust gases. Commonly used sintered metals for DPF substrates include silicon carbide (SiC), cordierite, and aluminium titanate.

Silicon carbide (SiC) is a popular choice due to its excellent thermal and chemical stability and high mechanical strength. It can tolerate high temperatures and is resistant to thermal shock. SiC-based DPFs are known for their durability and ability to withstand high soot and ash accumulation levels.

Cordierite is another commonly used material for DPF substrates. It offers good filtration efficiency and thermal shock resistance but may have lower durability than SiC.

Aluminium titanate is a relatively newer material used in DPFs. It offers high thermal shock resistance and a low coefficient of thermal expansion, which can improve the durability of the filter.

It is important to note that the choice of sintered metal for a DPF substrate can depend on various factors, including the application's specific requirements, such as sulfur tolerance in the case of high-sulfur diesel fuel. Different manufacturers and researchers may have their own proprietary formulations or variations of these materials to achieve the desired performance characteristics.

To obtain more specific information about the type of sintered metal used in the research article you mentioned, I would recommend contacting the authors directly or referring to other related studies or literature in the diesel particulate filters and emissions control field.

Using Simulation techniques, there is a software called Potfit that uses DFT results to create potentials. I think it is loosely based on machine learning. I came to know about it long ago. I don't know if the software is continuing. You can check it.

You can't produce good AZ31 material using powder metallurgy. No matter how good your shielding gas or vacuum, this material will contain a lot of magnesium oxide.

Sintering of Ti nanoparticles is tricky because you need to remove the surface oxides (TiOx). This elimination requires very low oxygen activity according to Ellingham diagrams. It is possible that Ar atmosphere in the sintering chamber is not enough to destabilize and remove titanium oxides.

PVP decomposition produce different C, O, and N containing species. These molecules can interact with Ti nanoparticles inhibiting sintering mechanisms

Dear friend Apurba Sarker

References:

I assume your sintering atmosphere is ammonia, NH3 (if it's an organic amine all bets are off). If so, the black color comes not from Al2O3 but from contaminants, most likely organic compounds that were adsorbed to the surface of the alumina.

Try to oxidize your AISI 304 rod in air at 850-900°C first and then use it. Oxidized steel surface should not stick to copper powder as much.

Dear friend Ali Reza Fattahi

It is generally not recommended to skip the calcination step in the conventional ceramic processing/solid-state reaction method, as this step is essential for the synthesis of the desired crystalline structure in the ceramic material. Calcination involves heating the mixture of powders at a high temperature for a specific time, which causes chemical reactions to occur and leads to the formation of the desired crystal structure. Without calcination, the ceramic material may not have the desired structure or properties.

In addition, the calcination step also helps to remove any organic or volatile components from the powder mixture, which can affect the properties of the final ceramic material. Skipping this step may result in a lower quality ceramic material with reduced strength, density, and other desired properties.

Therefore, it is not recommended to skip the calcination step in the ceramic preparation process. While the sintering process can help to form the ceramic material, it cannot replace the calcination step in terms of synthesizing the desired crystal structure.

Graded layers, also known as functionally graded materials (FGMs), are materials that have a gradual change in composition, microstructure, or properties over a certain distance. This gradual change can be achieved by varying the processing parameters or by depositing layers with different compositions.

FGMs have been extensively researched and developed in recent years because of their unique and desirable properties, such as high strength, high toughness, and high wear resistance. They have numerous applications in areas such as aerospace, automotive, energy, and biomedical engineering.

One of the most significant advantages of FGMs is their ability to reduce the stress and strain at the interface between dissimilar materials, which can occur due to differences in their mechanical, thermal, or electrical properties. By gradually changing the composition or microstructure, FGMs can act as a transition layer, reducing the stress concentration and improving the overall mechanical performance of the material.

FGMs can also be used to tailor the properties of a material to specific requirements. For example, a graded layer with a gradual change in porosity or grain size can be used to improve the thermal insulation or thermal conductivity of a material.

In summary, graded layers or functionally graded materials are materials that have a gradual change in composition, microstructure, or properties over a certain distance. They have numerous advantages and applications in various fields of engineering.

Dear Mutlu

you didn't give us the material so we can't know the specifications ... but still, we can reach with you

To calculate the sinter thickness for a pipe with a length of 175mm and a diameter of 5mm, you will need to know the material properties, such as the density, and the desired final dimensions of the pipe.

Assuming that the pipe will be made using a powder metallurgy process, the sintering process will cause the particles to bond together and form a solid structure. The sintering process will also cause the pipe to shrink in size due to the reduction in porosity.

To calculate the sinter thickness, you can use the following formula:

Sinter thickness = (Initial diameter - Final diameter) / 2

where the initial diameter is 5mm, and the final diameter is the desired diameter of the finished pipe.

For example, if the desired final diameter of the pipe is 4.8mm, the sinter thickness can be calculated as follows:

Sinter thickness = (5 - 4.8) / 2 = 0.1mm

Therefore, the sinter thickness for this pipe would be 0.1mm. It is important to note that the actual sinter thickness may vary depending on the specific material properties and the sintering process parameters used

hope you find the answer you want

best regards

raghd

The expansion of samples during the densification of H13 alloy prepared by binder jetting is a result of the sintering process.

Sintering is a high-temperature process that is used to bond particles together to form a solid mass. During sintering, the particles in the H13 alloy undergo several changes that can cause the sample to expand:

Overall, the expansion of samples during the densification of H13 alloy prepared by binder jetting is a common phenomenon that occurs during the sintering process. This expansion can be controlled by adjusting the sintering conditions, such as temperature and heating rate, to achieve the desired level of densification without excessive expansion.

With EDS make spot analysis (not maps), it will clarify the picture.

Graphite oxide is a compound composed of carbon, oxygen, and hydrogen atoms, while graphene oxide is a compound composed of carbon, oxygen, and hydrogen atoms that is processed to have a sheet-like structure. The main difference between the two is that the sheet-like structure of graphene oxide gives it better physical, chemical, and electrical properties than graphite oxide.

Graphene oxide should not disappear when it is sintered at 1300 degrees under vacuum and argon gas. Graphene oxide is stable up to temperatures of 2000 °C, so it should still be present after sintering. However, it may become more hydrophilic due to the loss of oxygen-containing functional groups.

The process for obtaining details by sintering H13 steel is known and studied by many authors. The problem is actually getting a porous structure. It depends on the size of the particles in pre-prepared and sifted dust particles. In addition, the tendency to form carbides according to the heat treatment regime also affects the technological and mechanical properties. As the tensile strength increases, the plasticity decreases and vice versa. A compromise is sought according to one of the sought indicators. it is achieved by means of a well-prepared mixture with a certain size of dust particles and a suitable mode of heating and subsequent firing. I agree with Edward Vojcak suggested directions. But field experiments should be conducted to achieve the desired properties by adjusting the heat treatment times. Good luck in your research.

Dear CAi Jiawei, the longer the sintering time the better the completion of sintering process. The strength reduction is probably a matter of over aging effect and the density increase should simply come from the fact that if sintering time is increased, it give more time to the powder materials to melt more completely and to tend to full molten material.

Dear Milon Hussein! I agree with the previous answer. In addition, you can have a large number of pores (air bubbles) in your mixture. This will also seriously impair thermal conductivity. You did not write exactly how you inject hBn, but the best way to remove pores and obtain a homogeneous solution would be ultrasound.

Can it be carbide or nitride sourced from organic binder chemicals (if used)?. It can be oxides or hydroxides with low melting point as well, or vitrified inorganic binder (like phosphate/ borate.)Better mention the sintering temperature. Grain boundary element segregation might destabilize austenite and deposit ferrite on GB as well. better do some SEM-EDX profiling to find out, if you have at hand. and mention sintering temperature as well as a suitable micrograph.

Do you mean lowering the sintering temperature? The transition to nanoparticles just lowers the sintering temperature in all cases. The larger the particle size, the higher the sintering temperature, and for millimeter-sized particles it becomes equal to the melting temperature.

If you mean lowering the sintering temperature, then this problem is solved with the help of various additives. Some ceramics, such as tin oxide, zirconia, tungsten carbide or quartz, do not sinter at all in their pure form.

If you mean lowering the sintering temperature, then this problem is solved with the help of various additives. Some ceramics, such as tin oxide, zirconia, tungsten carbide or quartz, do not sinter at all in their pure form.

approx. 3000°C

Binder has nothing to do with your problem. The main problem when sintering aluminum powder is oxidation. It is simply impossible to obtain oxide-free sintered aluminum alloy products using powder metallurgy. There is a material that is made from aluminum powder by sintering: SAP ( http://www.totalmateria.com/Article76.htm ), but this material has nothing to do with molten aluminum because it contains from 6 to 22% aluminum oxide. In addition, these sintered materials have to be sintered under pressure (hot pressing), because without pressure only very porous and weak sintered bodies are produced, as in your case.

Perhaps nanoparticles have been amorphous that have annealed to crystallized state above 300 C

Cai

Try to use a recrystallized alumina boat tray or give a wash of alumina on the corundum and let it dry, and then placed the parts and sinter using hydrogen, dissociated ammonia or helium/argon atmosphere.

Dr.K

Serhii

You have not said what you are measuring, internal or external diameter or length, or width of the part. I used to work in PM fabrication as a Plant Metallurgist, producing hundreds and thousands of bearings, gears, and so on for autos, washing machines, and many more. Thus, let me know.

Dr. K

Good day, Cai Jiawei!

"Huang et al. discovered that the addition of elemental Ce effectively inhibits the heterogeneous nucleation of primary carbides in industrial H13 steel, and the number density of primary carbonitrides is remarkably decreased with increasing Ce content. Li et al. reported that the addition of elemental Mg in H13 steel converts Al2O3into MgAl2O4, and the MgAl2O4particle acts as a more effective heterogeneous nuclei and provides more nucleation sites than the Al2O3inclusion, resulting in a more uniform distribution of primary carbides. Xie et al. discovered that Ti-rich carbonitride precipitates first and that V-rich carbide precipitates at the end of solidification in Ti–H13 steel. The Nb-rich carbonitride appears later, singly or on the Ti-rich carbonitride in Nb–Ti–H13 steel."

Please, refer to the following article:

Best of luck in your research!

Yours sincerely,

M.Sc. Vadym Chibrikov

Department of Microstructure and Mechanics of Biomaterials

Institute of Agrophysics, Polish Academy of Sciences

Dear Sam Choppala,

Regarding your first question about methyl cellulose. This water-soluble binder works well in a basic solution at temperatures below 15°C (cold water). SiO₂ makes the solution acidic and this allows the methyl cellulose to polymerize. For acidic solutions there is another water-soluble binder - polyvinyl alcohol (PVA), which you can successfully use here.

The second question (sintering of SiO₂ ceramic) is much more complex than you think. Pure SiO₂ ceramic does not exist and cannot be produced by sintering. The problem with this is the polymorphic transformations of SiO₂, which are associated with large changes in volume (when heated, alfa quartz first transforms into beta quartz and then tridymite and cristobalite form). In order to avoid this problem with polymorphic transformations, SiO₂ (quartz) must be sintered with additions of CaO and FeO. The resulting refractory material (silica brick) is not dense technical ceramics, but porous coarse-grained refractory stone used in furnace construction.

Good day! You should definitely look through the current link:

If you have found current answer as useful, please, do not forget to reccommend it. That will help other researches to find the best answer, according to their purposes. Best of luck in your research!

Dear Emanuel Cooper,

Thanks for your helpful discussion.

Regards

N Das

Dear Rayappa Shrinivas Mahale,

Thanks for your suggestion.

I will try with whichever is best suited.

Regards

N Das

Vyacheslav Nikichanov it would make sense with the elements given by ICP AES. Thank you for your help, appreciate it.

If without Argon means normal environment condition (no Helium or Nitrogen gas environment) then Aluminum is more likely to be oxidized at mentioned temperature due to high reactivity of aluminum with available oxygen in the environment. Also the reactivity depends on the size and surface area exposure of Aluminum

That's just the point, that in any way. This was discussed when I said that titanium alloys should not be made by sintering. A very high vacuum can partially solve the problem, but conventional melting still gives a much better result.

Hi,

You may be interested in our new article on modeling FGM in ANSYS APDL.

please take a look through its DOI link:

We are eager to have your feedback.

best regards.

Ahmed Hassan Ahmed Hassan

Cobalt oxide is the strongest mineral dye of blue color, used to stain ceramics and glass. Even the trace amounts of cobalt oxide on the white surface of the crucible from aluminum oxide stain it in bright blue. It is not surprising that after melting alloy with cobalt, your crucible turned blue, there was enough the minimum oxygen content in the atmosphere of the furnace.

The reason for poor sintering and enrichment of particle surfaces with aluminum and titanium is that your oven has too high an oxygen partial pressure. Oxygen or water in the furnace atmosphere contributes to the oxidation of the most active elements of the alloy (aluminum and titanium), which form oxide films on the surface of the sintered particles that prevent sintering. In addition, the oxidation of titanium and aluminum on the surface is the driving force for the diffusion of these elements from the depth of the metal to the surface, as a result of which both of these elements are concentrated on the surface of individual particles and at the grain boundaries of the already sintered material. The worse the vacuum in your furnace, the more active the above mechanism is manifested.

Carbon dioxide protects a weld pool from contamination with air gases. However, it is necessary to deoxidize the weld pool, i.e. remove oxygen from the liquid metal. In arc welding, it can be carried out in two ways: 1) using chemical reactions with deoxidizing elements (precipitating deoxidation); 2) physical and chemical processes between metal and slag (diffusion deoxidation).

Deoxidizers are chemical elements that have a greater affinity for oxygen than the metal being welded (easier to interact with it), they can be ranged by decreasing degree of deoxidation (affinity for oxygen): Ca, Mg, Al, Ti, Si, Mn, Cr, Mo, Fe, Ni, Cu.

The element position the series is determined by the oxide dissociation elasticity level. Elements in the row to the left of iron protect the weld pool from oxidation. Most often, manganese and silicon are used as deoxidizers in arc welding, since they are cheaper. They are added to the weld pool from coatings, flux and/or welding wire. In these cases, the following deoxidation reactions occur in the weld pool:

2Mn + O2 = 2MnO;

Si + O2 = SiO2;

FeO + Mn = MnO + Fe;

2FeO + Si = SiO2 + 2Fe.

Due to these reasons, only low-alloy steels can be welded while shielding the weld pool with carbon dioxide. Respectively, it is not the best option for sintering.

Fritz Caspers Tank you for the method. Primary interest is to asses the dielectric properties of MW sintered component in comparison with conventionally sintered ones to see whether the grain growth and microstructures are same or different. Did a preliminary assessment on binder removal in conventional upto 500 C and sintering upto 670 C.

Everything depends on the powder size and the associated surface area (the larger the powder surface, the more active the sintering). If you only roughly grind a sintered ZrO₂ ceramic (particle size 50-100 microns), then you can no longer re-sinter this powder almost to the melting temperature. But if your particles are smaller than 1 micron, then you can get a new product from them without any problems at sintering temperatures from 1700-1800°C. Of course, a "fresh" nanoscale ZrO₂ powder sinters better than finely ground microscale powder (already from 1200-1300°C), but this can also be explained by the particle size.

CO2 is not possible to use for Fe-alloys powder sintering It will oxidise it. The best gas for sintering is H2. Also the combination of H2 + CO is possible to use if you do not care about Carbon increasing in your alloys. Very important during sintering to achieve the dew point for H2 around -20C. It will promote the sintering even better because of small concentration of H2O always intensifies sintering by increasing reduction-oxidation reactions on the powder surfaces.

@Rayappa, thank you for your response. I still do not understand how the speed of piston-die displacement versus temperature in figure 2 (of the document CTE3) was converted to strain in figure 3 of the same document. What relationship does the graph of figure 2 have with figure 3?

Kindly see also the following useful RG links:

most specimen holders are made from aluminum (or sometimes even Kaolin which is a source of alumina elaboration). This material (alumina) when it is brought to high temperature (> 1200°C), it will be much favored to be diffused in all the materials which are in contact with it, this will lead to bonding between these materials (for example: Alumina - calcium silicate)

Dear Abdul,

I never worked with these materials but they are high melting point-based, so I believe the influence will be minor. I recommend you'll measure Al content prior to and after the heat treatment of your samples.

Good luck.

Dear Stanislav ,

Thanks for your nice discussion.

Regards

N Das

You cannot avoid melting this fusible material at such high temperatures, but you can get rid of sticking to the substrate. If you use a graphite crucible, then the glass melt will not stick to it. This is all the more beneficial if you are heating in an argon environment (a graphite crucible would burn out in air).

Prof. Nityananda Das

The cc Wiki on levitation has an interesting effect that I did not know previously:

I extract from cc Wiki * the following explanation:

A substance that is diamagnetic repels a magnetic field. All materials have diamagnetic properties, but the effect is very weak and is usually overcome by the object's paramagnetic or ferromagnetic properties, which act in the opposite manner.

But any material in which the diamagnetic component is stronger will be repelled by a magnet.

Direct diamagnetic levitation can be used to levitate very light pieces of pyrolytic graphite or bismuth above a moderately strong permanent magnet. As water is predominantly diamagnetic, this technique has been used to levitate water droplets.

However, the magnetic fields required for this are very high, typically in the range of 16 teslas, and therefore create significant problems if ferromagnetic materials are nearby. The operation of this electromagnet used in the frog levitation experiment required 4 MW (4000000 watts) of power

The minimum criterion for direct diamagnetic levitation is

B dB/dz= μ₀ ρ g/χ

where chi χ - is the magnetic susceptibility and g the gravitation field.

cc Wiki:

* https://en.wikipedia.org/wiki/Magnetic_levitation

Best Regards

You're right. Concentrated hydrochloric acid will dissolve nickel. You can also use hot sulfuric acid.

When googling for etchants, use additional word "metallography".

You can find some etchants here:

Also check please the following useful link: https://www.scientific.net/paper-keyword/miedema-model

The problem with other metals is that they oxidize when sintered in air. Only silver, gold, and the platinum metals other than osmium do not oxidize in air at the temperatures required for sintering. Silver is the cheapest of these metals, so it is the most commonly used.