All 3 entries tagged Tungsten

12 g/cc mark has been breached!

Why this is important? Significance of this milestone can be well understood from the fact that the most common material used for radiation shielding was lead whose density is 11.29 g/cc. That’s why this number 12 g/cc is important. In addition to that density/porosity has direct effect on radiation atenuation. The goal was to achieve similar densities under lab based environment with different sintering technique. In this case, horizontal furnace with Ar as inert atmosphere. These samples were sintered at 1450 ^oC for 4h under Ar atmosphere. Sintering with different composition and sintering conditions (table 1) were performed, so that the final density can be fine-tuned.

Table 1: Densities of various compositions at specific sintering conditions for RSB55

What next? In the upcoming weeks, we will be using N₂ as the atmosphere for sintering. Hopefully, we will achieve the final density of 12.3 g/cc and with that it will be the time for gen. 3 materials. With present milestone, stay tunned for more details at SOFT22. Figure : RSB55_Large_2Cr sample: Needle like structure of WB

Gurdev Singh : 16 Sep 2022 21:36 |  Tags: Hardmetals Tungsten |  Comments (0) |  Close comments |  Report a problem

News from Plansee 2022

Writing about web page https://www.plansee-seminar.com/

After being delayed by COVID from 2021, the long-awaited Plansee 2022 conference took place in Ruette, Austria from 29th-May -3rd June.

This is a four-yearly conference that is the place to be for anyone who works with hard metals and refractory metals - essentially most metals from group 5,6,7 of the Transition metals - namely W and elements next door.

This Seminar did not disappoint and there was a surprisingly significant number of talks on nuclear materials in terms of how W and similar materials have their place in fusion power.

There have also been numerous opportunities to connect with academic and industrial partners as well as groups such as the European Powder Metals Group (EPMA). Maintaining networks and setting up new once is as crucial to research as doing research itself - no advances get made if they are not communicated,

Alongside this were talks on exciting topics such as additive manufacture and 3-D printing techniques - both of which are significant when considering parts for fusion reactors since complex geometries are required.

The work our group presented gained some interest in that this conference is an ideal platform to demonstrate the cWC-RSB concept and the progress made so far despite setbacks. Certainly, the contacts made at Plansee will show a significant role later this year as the full demonstration of Gen 2 RSBs is realized.

Simply put, 3-D printing of powder metallurgy fabrication can be split into two main categories:

1. Direct powder bed sintering, where a laser draws out a part from a powder bed in a protective atmosphere as for 3-D printing. The aim is ultimately a near net shape part that can then be annealed and finished as for conventional PM.

2. 3-D printing of green PM materials. This comprises of a selection of techniques involving green materials including 3-D printing of organic binder into powder constituents - useful for for complex geometries - prior to a standard debinding cycles or from filaments which can be shaped and bonded into a more robust structure prior to sintering.

Both techniques show promise both for cWC and RSB materials in the later stages of this project when there will be need for demonstrator parts and full-sized boilerplace items by the mid 2020s

While it might be a long time until Plansee 2026 the work starts now to ensure that fusion-realated applications will be front and centre.

Jessica Marshall : 29 Jul 2022 20:54 |  Tags: Hardmetals Nuclear Materials Plansee 2022 Processing Methods Tungsten |  Comments (0) |  Close comments |  Report a problem

How To Irradiate Your Samples

Following some of the successes and pitfalls at the DCF facility we now have all the irradiations completed thanks to the dedicated staff at the Dalton Cumbrian Facility. Since the energies in this round of experiments were sufficiently below the threshold of activation, samples were dispatched in the post.

The next stage will be to clean and mount sample for cross-sectional imaging, hardness testing, EBSD and TEM but that will be discussed in a later entry since much of that work will be for publication.

So how does one get to irradiate samples in the first place? And what has this specific experiment got to do with the first goal of the Radiation Dense Materials concept?

First of all as with any new science experiment, you have to talk to people first, in person, online or by email. This is critical to ensure that you can flesh out the proposed experiment and see how feasible it is or isn't. By discussing the planned irradiation schedule with the staff at the Dalton Facility we were able to acertain that ambient and non-ambient irradiation was possible with the proton beam and the gamma irradiator.

One of the inherent difficulties of current irradiation facilities is that generally samples can only be irradiated by one type of radiation at one time, unless placed in a test reactor. This is similar to reproducing a painting but with only one brush and one pigment. Hence, it is important to state the limitations of irradiation testing on samples with this in mind.

So, how are samples actually irradiated? This depends on the method and the radiation used. For the gamma irradiator it is simply a case of tracking the face closest to the ⁶⁰Co source and placing it in a low-activation borate glass. The ⁶⁰Co irradiator is shown below:

For low-temperature (77K) irradiations, samples were placed in a dewar full of LN₂. Since oxygen liquifies at 85K this forms a pool in the dewar which under gamma irradiation transforms to O₃ which is solid at LN₂ temperatures. Solid O₃ is an explosion hazard and thus nescessitates emptying and renewing the LN₂ every 5 kGy. The low-temperature high-dose gamma sample had 90 kGy in total.

For proton beam irradiation, sample preparation is more involved. Samples need to be mounted with a heat-resistant conductive adhesive (silver paste) and need alignment such that the beam energy and radiation time can be computed, the exact figures depending on the dosage and the target temperature. Samples mounted for proton-beam irradiation are shown below:

Since protons are charged particles, total proton dosage can be computed from the charge accumulated from the beam current. Alongside sample irradiation, other data from samples such as emissivity can be obtained from proton irradiation at elevated temperatures.

Data analysis is at the earliest stages with the following planned sequence (1) Cross-sectional imaging (2) microhardness measurements (3) EBSD and (4) TEM (specifics to be determined following from EBSD and HV measurements).

Ultimately, this work will form the outline for subsequent radiation work as this is a first for both cWC and RSB materials.

Jessica Marshall : 06 Apr 2022 16:31 |  Tags: Fusion Power Gamma Irradiation Irradiation Proton Beam Tungsten Tungsten Borides Tungsten Carbide |  Comments (0) |  Close comments |  Report a problem