HOW’S YOUR RESEARCH GOING?

Many of us who work in the scientific and technical side of the Malvern Panalytical business, have higher level scientific qualifications such as PhD. Even though some of us may have studied in the previous century, it’s hard to forget the struggle to get good data for a paper, or to try again to get that extra data point that would make our PhD story just that little bit better.

We feel huge respect for those of you out there who are jumping through all of these hoops at the same time as having to contend with the uncertainties of COVID. Maybe you’re not able to turn up at the lab at any time, but instead you must book a place and prepare for a visit with forms and tests. Or simply stay at home and grapple with a sense of remoteness or a frustration about a lack of good resources.

We can’t solve everything, but we’ve organized two activities specifically to help university researchers and students.

A new way to get your questions answered

The first one is the Ask an Expert! series of webinars. They are spread out across the year. You can find the program here. We have tried to schedule something for everyone. At these webinars (live or recorded) you can find out more about a particular technology that our instruments provide. The sessions are purely about the method, how to understand it, make it work for you, and how to analyze the data. If the webinar is in the future, you still have the opportunity to submit questions. Our speakers will prepare some answers for you. If the webinar is in the past, you can watch the recording and find out what other people have asked, and hear our expert’s answers.

Free XRD software licenses for academics

The second activity is an offer of a free software license which is valid for 1 year (from the date you start to use it). This offer is for X-ray diffraction (XRD) users and applies to our XRD analysis software packages HighScore Plus and AMASS. We know that it takes time to perform an analysis of data. Both Rietveld fitting or High-resolution simulation and fitting can be tricky, and you need time to think about your data and try a few strategies for interpreting it. So, in these challenging times, we’d like you to have your own personal copy and access it on your own PC. If you are a researcher or team leader, please apply for free licenses here. You need to use your official university or research institute email address. If you are a student, please ask your supervisor to apply on your behalf. They can apply for up to 3 licenses for each type of software.

If you’re particularly proud of something you’ve achieved with the software, contact us! We’d be happy to feature your results on our hot news on the research page on our website.

Continuing research is so important for the future. We salute you!

 

Written by: Patricia Kidd, Posted by: Malvern Panalytica (www.materials-talks.com)

What’s your flash point?

Flash point is the lowest temperature at which a liquid (usually a petroleum product) will form a vapor in the air near its surface that will “flash,” or briefly ignite, on exposure to an open flame1. Back in the late 1800s, flash point was a lived experience. Households primarily used kerosene for heat and light, and open flame was a part of every day. Bad kerosene – fuel diluted with gasoline or other contaminants – delivered unpredictable flash points and bad results. Fires and explosions were fairly common. These shared catastrophes ushered in a focused effort to establish meaningful standards for various grades of petroleum. Both ASTM2 and OSHA3 have created standard flash point measurement methods that are used today.

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The standardization of flash point analysis fundamentally created a durable definition for flash point relative to the type of fuel considered. For example,

  • automotive gasoline,−43 °C (−45 °F)
  • ethyl alcohol, 13 °C (55 °F)
  • automotive diesel fuel, 38 °C (100 °F)
  • kerosene, 42-72 °C (108 – 162 °F)
  • home heating oil, 52-96 °C (126-205 °F)
  • SAE 10W-30 motor oil, 216 °C (421 °F)

Flash points are measured using one of two methods: closed cup or open cup. Either of these methods, when executed properly, deliver a precise characterization of the fuel tested, and are extremely important to identify contaminants in the fuel, especially those contaminants that are more volatile than the fuel itself. Like so many things, fuels can experience significant performance or monetary value changes due to contamination. Flash points are critical data points for quality assurance, and flash point analysis is a strong tool when used routinely to keep petroleum-based products true to grade.

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The recent acquisition of Paragon Scientific by LGC means our flash point standard portfolio is more comprehensive than ever and includes a range of CRMs suitable for Pensky Martens and Cleveland Open Cup techniques! Our flash point certified reference materials are certified in accordance with international test method protocols, including ASTM, and are fully traceable to international standards. Download our catalog to learn more about the entire product family or contact us for more information.

 

Written by: Courtney Dillon Posted by: ARMI MBH (www.armi.com)

EXPLOITING X-RAY DIFFRACTION TECHNIQUES FOR CATALYTIC MATERIALS CHARACTERIZATION

Structural Analysis

Catalysts have become critical materials for a wide variety of applications in our modern-day industrial world. Among the different types of techniques utilized to characterize catalytic materials, X-ray diffraction (XRD) holds a unique place in that it can be utilized to obtain both qualitative and quantitative phase information of crystalline materials as well as for the analysis of amorphous and nanomaterials. While heterogeneous catalysts are ideally suited for XRD analysis, both homogeneous and biocatalysts can also be studied via this method. In a recent white paper, Characterization of Catalytic Materials on Laboratory-Based X-Ray Diffraction Platforms, we highlight several techniques that you can perform on Malvern Panalytical’s floor-standing and compact XRD platforms to assist in the characterization of catalytic materials. Many may be familiar with X-ray powder diffraction (XRPD) for the analysis of crystalline materials (i.e. phase identification and quantification) through Bragg’s Law, as depicted in Figure 1. Malvern Panalytical’s line of X-ray diffraction instruments can provide this information for both crystalline and amorphous phases as well as providing information about crystallite size and microstrain through the examination of the peak breadths.

Figure 1 Illustration of Bragg diffraction from a crystalline material. At a specific angle (θ) the two waves scattered from atoms separated by a distance (d) will interfere constructively and a signal will be detected, (n = 1,2, 3…).

In addition, specialized XRD methods such as non-ambient (NA) measurements along with X-ray scattering techniques such as pair distribution function analysis (PDF) and small-angle X-ray scattering (SAXS), can provide a more in-depth understanding of catalytic materials. One can examine catalytic samples under relevant non-ambient conditions to explore reaction pathways, observe phase changes, and examine the material’s thermal stability. Utilizing various non-ambient stages, available on both floor standing and compact models, the temperature, humidity, and atmosphere can all be precisely controlled during measurements. Furthermore, one can obtain information about particle size and shape as well as short- and intermediate-range order through the aforementioned X-ray scattering techniques which have traditionally been relegated to synchrotron facilities. However, thanks to technologies such as our ScatterX78 stage and GaliPIX3D detector, these measurements can now be performed in-house [1,2].

Instrument Versatility

Standard powder X-ray diffraction measurements, including those under non-ambient conditions (up to 500° C), are easily performed on the Aeris compact X-ray diffractometer. This instrument has a comparable resolution, scan-times, and peak intensities to the floor standing Empyrean system. Furthermore, all of the standard PXRD measurements, as well as the aforementioned advanced techniques (NA, SAXS, and PDF), can be performed on a single Empyrean instrument with Malvern Panalytical’s PreFIX (Pre-aligned Fast Interchangeable X-ray modules) technology. This allows stages and optics to be quickly exchanged without the need for re-alignment of the instrument. Figure 2 shows an example of a component mounted on the Empyrean instrument utilizing the PreFIX technology.

Figure 2 Image of an XRD accessory (beam knife) inserted in a PreFIX block on the Empyrean instrument.

Powerful Software

Our HighScore (Plus) software can be utilized for the analysis of data from both the Empyrean and Aeris platforms. With this package, phase identification and quantification can be easily performed along with more advanced analysis techniques such as the determination of lattice parameters, peak widths, crystallite size, micro-strain, and PDF analysis [3]. Furthermore, features like cluster analysis are also included in the HighScore Plus package and can be exploited for processing large datasets such as those obtained from non-ambient measurements [4]. Lastly, Malvern Panalytical’s EasySAXS software provides a straightforward method for obtaining relevant information from data collected during SAXS experiments. These include the volume-weighted size distribution, particle shape, and specific surface area [5]. Figure 3 shows examples of analysis performed in the two packages.

Figure 3 Analysis performed in the HighScore (Plus) software package: A.) Phase identification and quantification, B.) Cluster analysis, C.) PDF analysis. Additionally, an example of the EasySAXS user interface (D.) is shown.

True power comes from combining data

No doubt, X-ray diffraction techniques can provide a more in-depth understanding of catalytic materials. Our white paper highlights several techniques that can be performed on Malvern Panalytical’s floor standing and benchtop XRD platforms to assist in their characterization.

 

Written by: Brad Losey, posted by: Malvern Panalytical (www.materials-talks.com)

 

References

  1. Te Nijenhuis, J., Gateshki, M., & Fransen, M. J. (2009). Possibilities and limitations of x-ray diffraction using high-energy x-rays on a laboratory system. Zeitschrift Für Kristallographie Supplements, 2009(30), 163-169. doi:10.1524/zksu.2009.0023
  2. Confalonieri, G., Dapiaggi, M., Sommariva, M., Gateshki, M., Fitch, A. N., & Bernasconi, A. (2015). Comparison of total scattering data from various sources: The case of a nanometric spinel. Powder Diffraction, 30(S1), S65. doi:10.1017/s0885715614001389
  3. Degen, T., Sadki, M., Bron, E., König, U., & Nénert, G. (2014). The HighScore suite. Powder Diffraction, 29(S2). , S13-S18. doi:10.1017/s0885715614000840
  4. Automatic analysis of large amounts of X-ray diffraction data with HighScore Plus. Malvern Panalytical application data sheet.
  5. Bolze, J.; Kogan, V.; Beckers, D.; Fransen, M. High-performance small- and wide-angle X-ray scattering (SAXS/WAXS) experiments on a multi-functional laboratory goniometer platform with easily exchangeable X-ray modules. Review of Scientific Instruments2018, 89(8), 085115.Bolze, J., Kogan, V., Beckers, D., & Fransen, M. (2018). High-performance small- and wide-angle X-ray Scattering (SAXS/WAXS) experiments on a MULTI-FUNCTIONAL laboratory Goniometer platform with easily EXCHANGEABLE x-ray modules. Review of Scientific Instruments, 89(8), 085115. doi:10.1063/1.5041949

 

IAGeo SDAR Reference Materials

 NIST soil samples have long been the go-to solution for analysts looking for standards of varying levels of contaminants when testing sediment and soil samples for contamination. IAG has developed a solution to the higher priced NIST CRMS in the form of three RM materials which closely match the composition of each of the popular NIST Soils 2709, 2710 and 2711.

SDAR Samples

The SdAR series of reference materials have been designed to resemble the sediments, soils and related materials which are typically sampled when monitoring levels of environmental contamination. This contamination  is often associated with, discharges from mining operations or industrial pollution. The preparation of these materials was carefully considered, and was done to maintain the properties which make a natural sample so desirable. Each sample is a carefully prepared combination of ore-grade material from multiple locations, diluted with baseline soils and sediment. The use of natural materials maintains the effect of mineralogy on chemical analysis, and the use of distinct blending ratios provides a smooth and gradual calibration over a wide concentration range.

Each of these three standards are available in polycarbonate bottles containing 80g of material.

This unique series of reference materials have been designed as substitutes for the expensive NIST 2709-2711 metal-bearing sediment SRMs of similar composition (see diagrams). A low (SdAR-L2), medium (SdAR-M2) and high (SdAR-H1). These reference materials are intended for use in the calibration of portable XRF instruments and in routine laboratory analysis.

SdAR-H1-vs-SRM-2710a  SdAR-M2-vs-SSRM-2711a

New analysis has been conducted on these materials to include data based on aqua-regia selective extraction procedures, which is now available in an addendum to the original certificates. This information will be particularly useful for laboratories seeking reference materials for aqua-regia  extractions performed at 90 to 110°C, reflecting the procedures commonly used by commercial laboratories which service the industries for mining and geochemical exploration, and for environmental monitoring.

These standards are available individually or as a set with special set pricing.

To see the full data-set for all standards, including the aqua-regia extraction, download the certificate

SdAR Soils Cert

Posted by: ARMI MBH on https://www.armi.com/sdar-reference-set

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ASD TERRASPEC HALO USED IN SPACE-BASED RESEARCH

Malvern Panalytical’s ASD TerraSpec® Halo mineral identifier is being used as part of today’s space race to return astronauts to the Moon, Mars, and beyond! The full-range (350-2500nm) portable spectrometer was recently selected and used in multiple research projects aimed at expanding U.S. efforts in planetary exploration.

Project PoSSUM

Project PoSSUM citizen-science course members 

Dr. Ulyana “Uly” Horodyskyj was involved in co-teaching an adult continuing education program, “Planetary Field Geology and EVA Tool Development.” The course was held by Project PoSSUM (Polar Suborbital Science in the Upper Mesosphere), a 501(c)(3) astronautics research and education program studying our upper-atmosphere and its role in our changing global climate.

Dr. Ulyana Horodyskyj demonstrates use of the ASD TerraSpec Halo 

The Project PoSSUM program utilizes scientific procedures to drive technology maturation, and this course taught surface geology to twelve PoSSUM citizen-scientists who came from all over the world to learn procedures and develop tools that will influence the design of EVA space suits. Class participants had the assignment of coming up with a concept of a field tool that they were to design and have 3D printed or otherwise assembled; additionally, standard geologic tools such as rock hammers, rock kits and hardness tests were involved. It was Uly’s suggestion to incorporate and include the use of the ASD TerraSpec Halo VIS-NIR-SWIR (visible – near-infrared – short-wave infrared) spectrometer in the teaching of the course, as the instrument can measure the spectrum of rocks and identify alteration minerals, which are key for when scientists and astronauts eventually do get back to the Moon and/or go to Mars, and are looking for traces of water.

With NASA ramping up to go back to the Moon, to Mars and beyond, there is a need for people to be well versed in planetary field geology. Use of the TerraSpec Halo to identify alteration minerals is a great way to do analog testing on Earth, before committing to future missions to the Moon and Mars. – Uly Horodyskyj

Project PoSSUM citizen-scientists take turns using the ASD TerraSpec Halo in the field 

The course culminated in a one-week capstone field experience at the San Francisco Volcanic Field in Northern Arizona; this location was selected as areas of the volcanic field have been used by NASA for testing techniques for exploration in a simulated extraterrestrial terrain environment. The ASD TerraSpec Halo instrument was provided on behalf of Malvern Panalytical as part paid rental / part sponsorship.

The ASD TerraSpec Halo is like a tool out of Star Trek. The students – some college, but the majority post-docs and beyond – had some experience with mass spectrometers and spectroradiometers, but nothing like the use of this ASD mineral analyzer before. The ease of use of the instrument, and the software, was amazing. The battery life of the spectrometer was incredible. In my teaching, I was able to point out absorption features to the students, as the TerraSpec Halo shows you not just minerals, but also the measured spectrum; I was not familiar with some of the alteration minerals that came up on the instrument’s screen, so the students and I would look this up together, which proved to be a good learning opportunity for myself as well.” – Uly Horodyskyj

GHOST

A NASA-sponsored research project, the GeoHeuristic Operational Strategies Test (GHOST), including CU Boulder’s Department of Geological Sciences Associate Professor Dr. Brian Hynek, selected the VIS-NIR-SWIR ASD TerraSpec Halo to maximize the speed, efficiency and scientific return of Mars rover sample collection. The instrument was sponsored and provided on behalf of Malvern Panalytical. The project used the spectrometer to simulate the function of the Mars Science Laboratory (MSL) ChemCam and Mars 2020 rover SuperCam.

Rather than using mechanical rovers or replica Mars instrumentation, GHOST utilizes human “rovers” and off-the-shelf field portable instruments to isolate the variable of the scientific decision-making process. This eliminates the need for mission-specific instrumentation, communication and data relays, or complex engineering requirements, while still providing the same basic information, such as mineralogy.

During the research project, the TerraSpec Halo allowed for rapid data acquisition of in-situ outcrops, similar to the data gathered by Mars rovers, and allowed the rover operations team to rapidly traverse the field site near Salt Lake City, Utah, maximizing the number of data points gathered.

Full range spectroscopy provides a wealth of compositional information and is a valuable tool in planetary exploration. The use of the ASD TerraSpec Halo, and field-portable VIS-NIR-SWIR, as an analog for rover instrumentation was sufficient for science team operations; the teams were able to efficiently conduct their site investigation and analysis of operational methods using terrestrial analog instrumentation. – Brian Hynek

Why is this research important? 

Mineralogical variations are significant because geochemical differences contain clues regarding whether a geologic environment was habitable or capable of preserving evidence of prior life. Without in-situ VIS-NIR-SWIR data, there could be missed critical information for scientific missions and interpretations. The selection of the ASD TerraSpec Halo for these research projects to measure compositional information represent some of the initial steps towards advancing scientific study and exploration of Mars.

The best we can do, at the moment, is study extreme environments on Earth that are going to be the most similar to Mars. Places like Iceland, the Atacama Desert in Chile, these volcanic fields in Arizona… these are excellent analogs where you cannot only test the equipment but also look at these markers of weathering and presence of water. If we find something similar on Mars, we know what the Earth equivalent is – we can match it and we know exactly what that geochemical history is.” – Uly Horodyskyj

 

Written by: Malvern Panalytical – (www.materials-talks.com)

NEW Copper CRMs

ARMI MBH excited to add five new copper CRMs to their product portfolio. Copper can be alloyed with a wide range of elements enabling highly specific functions and applications. The large compositional range of copper alloys means that high-quality, matrix-matched reference materials are needed for proper analysis of each alloy.

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In addition to their structural properties, CDA 510, CDA 655, and CDA 955 are EPA-registered as antimicrobial alloys. More information on the antimicrobial properties of copper, including a complete list of EPA-registered alloys, can be found at the EPA Antimicrobial Stewardship Website for Copper Alloys.

CDA 510 (IARM-Cu510-18) is a phosphor bronze, which is commonly used for fasteners and spring components. It is also excellent for soldering and brazing applications and has high conductivity, which lends itself well to electrical connectors and other electronic usages. CDA 510 has certified values for the grade-specified elements Cu, Pb, Sn, Zn, and P and a reference value for Fe. Additionally, certified values are provided for Ag, C, Ni, and O, and reference values are given for 32 more elements.

A high silicon bronze, CDA 655 (IARM-Cu655-18) is widely appreciated for its aesthetic and its antimicrobial properties in architectural and decorative applications. Its high resistance to corrosion means that it is often used for fasteners, piston rings, and other hardware in marine applications. In addition to the specified elements, Cu, Pb, Fe, Zn, Mn, Si, and Ni, this CRM is also certified for Al and Sn, and has reference data for 21 more elements.

CDA 955 (IARM-Cu955-18) is a nickel aluminum bronze alloy. In addition to being another EPA-registered alloy for microbe resistance, it is one of the strongest non-ferrous alloys, thanks to its high Ni content. The high hardness rating and good corrosion resistance makes this a common choice for marine and aircraft parts, in addition to high wear and high impact applications. This CRM has certified values of the grade-specified components Cu, Fe, Al, Ni, and Mn, as well as Ag, Co, Cr, P, Pb, Si, Sn, and Zn. Reference values are provided for an additional 18 elements.

A tin bronze alloy also known as Navy G is CDA 903 (IARM-Cu903-18). CDA 903 is a type of gear bronze, a family of bronze alloys used for wear resistance in high velocity situations. Gear bronzes compose most of the non-ferrous alloys for these applications. As the name implies, Navy G is widely used in marine environments because of its strong corrosion resistance. The new CRM has certified values for alloy-specified elements, Cu, Sn, Pb, Zn, Ni, Co, Fe, and Pb. Good reference values are given for the elements Sb, S, Al, and Si, which have maximum values specified. A certified value is also given for O, and reference values for 18 other elements.

Lastly, we are adding CDA 360 (IARM-Cu360-18) to our portfolio, which is a free cutting brass. Thanks to its high Pb content, CDA 360 is an excellent machining alloy with a 100% machinability rating and it is used as a comparison for the machinability of all other alloys. It is an excellent choice for use in applications that require drilling, turning, milling and other high-speed machining processes.

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The grade specifications for CDA 360 Grade include values for Cu, Fe, Pb, and Zn. Our CRM has certified values for the four specified elements, as well as Ag, Al, As, Bi, C, Cd, Co, Cr, Mn, Ni, P, Sb, Si, and Sn. Reference values are given for 14 more elements.

If you have any questions about these new products or other products, please reach out to our experts for help.

Written by: James Haddad PhD  – Posted by: ARMI MBH (www.armi.com)

THE VALUE OF MINERALOGICAL MONITORING FOR THE ALUMINUM INDUSTRY – PART 2

In the previous blog about mineralogical monitoring for the aluminum industry, we discussed the added value of accurate on-line and at-line mineralogical monitoring for bauxite ore. The advantages of X-ray diffraction (XRD) and near-infrared spectroscopy (NIR) that provide information about the mineralogical composition and important process parameters of bauxite were discussed. This information is not only important for bauxite mining but also for efficient downstream processing in the alumina refinery.

Step II. Alumina refining

Process

Alumina refineries process bauxite ore to produce alumina, which is then used to extract aluminium metal. Alumina (aluminium oxide) is a white granular material.

Figure 1. Alumina refining process (image courtesy of Australian Aluminium Council Ltd)

The process to produce alumina from bauxite ore is called the “Bayer process”, developed by Carl Josef Bayer in 1888 (figure 1). It consists of four steps: digestion, clarification, precipitation and calcination.

After milling, bauxite is mixed with caustic soda (sodium hydroxide) under high temperature and pressure. Alumina dissolves from the aluminium bearing phases (excluding clays). Undissolved impurities settle down as a fine red mud, which after few recycling steps, is discarded as waste.

The solution of alumina in caustic soda (liquor) goes through further clarification, filtration and precipitation steps. Alumina crystals are recovered from the caustic solution by mechanically stirring the solution in open-top tanks. The precipitated material (called hydrate) is washed and dried at temperatures exceeding 1000°C. The dry white anhydrous aluminium oxide powder (alumina) is cooled and conveyed to storage. Alumina powder is further used to extract metallic aluminium using electrolytic baths. Caustic soda is recovered and returned to the start of the process and used again.

Let’s discuss the effect of mineralogy on the above process. Temperature required for the digestion of diaspore α-AlO(OH) and boehmite γ-AlO(OH) (both called monohydrate alumina phases, MHA) is higher than for gibbsite γ-Al(OH)3 (called trihydrate alumina, THA). Therefore, the temperature for effective digestion of bauxite depends on the ratio between the different aluminium containing mineral phases.

In addition, the consumption of caustic soda per ton of bauxite depends on the amount of silica impurities: clays and quartz. Under certain conditions, these minerals react with caustic soda and consume part of the reagents from the process. Low-temperature digestion suffers from the reagent loss to clays only, but during high-temperature digestion, both quartz and clay minerals react with caustic soda, increasing reagent consumption and costs.

Therefore, the knowledge about the mineralogical composition of bauxite is an important factor that defines the efficiency of the Bayer process.

Analysis of alumina for quality control (QC) and quality assurance (QA)

Mineralogical monitoring not only adds value for the analysis of the raw material bauxite but also for the quality control of the final product from the Bayer process, alumina. XRD is the only suitable tool to distinguish between the different modifications of alumina (eg. α-Al2O3, γ-Al2O3) which defines the quality of dry alumina powder, as well as particle size and impurities.

The knowledge of the different modifications is important to predict and optimize the behavior during the smelting process. γ-Al2O3 is desired for the electrolysis since it dissolves more easily during the smelting process than α-Al2O3. For that reason, the ratio of the different sub-α and α-Al2O3 modifications of alumina must be monitored. The analysis of α-Al2O3 can be done with a classical straight-line calibration of the α-Al2O3 peaks or using full pattern fitting methods. The advantage of using the full information of the XRD pattern is the simultaneous quantification of all sub-α-Al2O3 modifications. Even a small fraction of 0.5 wt.% α-Al2O3 can be detected and quantified. Figure 2 shows a measurement of dry alumina powder using X-ray diffraction. The majority of the sample consists of g-alumina, with only 0.5% of a-alumina.

Figure 2. Automatic γ-Al2O3 and α-Al2O3 quantification of dry alumina using Aeris Minerals, measurement time is 10 minutes.

Impact of particle size

Particle size impacts directly on the rate of dissolution of the alumina in the cryolite bath and is therefore another important variable. Furthermore, fines are an issue from both health and safety as well as a product transport point of view, so particle size distribution needs to be carefully controlled. The ideal particle size distribution is defined between 45μm and 150μm to prevent problems with dissolution in the cryolite bath and the accumulation of fines during processing that cause conveying and process instabilities and health issues.

Figure 3 Typical display of on-line alumina process data

The application of on-line particle size analysis allows aluminium processors to operate more efficiently and to produce a more consistent product for downstream unit operations. Economic benefits in the form of reduced waste, reduced energy consumption, reduced manpower and increased throughput are achieved. The availability of industrially relevant systems, at a cost that can be recovered in a relatively short time, makes on-line analysis an increasingly attractive option.

Red mud – monitoring of waste products using XRD

Red mud is the bauxite residue generated during the refinement of bauxite into alumina using the Bayer process. It is composed of various oxide compounds, including iron oxides which give its red color.

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Depending on the bauxite grade about 1.3 to 2.2. tons of red mud are produced per ton of alumina. The treatment, long-term storage and re-use of the red mud is one of the challenges of alumina refining. The adequate analytical tools for the control of mineralogy, chemistry and physical properties of red mud are essential for the correct, environmentally friendly management of the waste product.

The complete mineralogical composition of the red mud sample determined by XRD is shown in Figure 4. The main part of the sample consists of the insoluble impurities of bauxite (titanium and iron oxides) and products of chemical reactions, which occur during the digestion steps. However, in this example, valuable aluminium bearing phases such as gibbsite, boehmite and diaspore still comprise about 25% of the red mud sample. This indicates that the processing, in particular the digestion, was not executed to the maximum level of efficiency.

Figure 4. Automatic quantitative mineralogical analyses of red mud using Aeris Minerals. Measurement time is 15 minutes.

Comprehensive analysis of bauxite and red mud mineralogy along with the analysis of digestion conditions should be performed to understand the root cause for the lost efficiency.

Value of analytical monitoring of mineralogy and particle size for the Bayer process

Alumina refining is a complex process the efficiency of which is directly related to the mineralogy of the bauxite ore. Fast and accurate mineralogical information throughout the entire process, speed of the XRD analyses, increased safety for the operators and the possibility to automate makes XRD a reliable and economic alternative compared to the traditional analytical methods such as wet chemistry and does justify the initial investment.

In our next blog, we will discuss the added value of mineralogical analyses for the next step in the bauxite-to-aluminum process: the conversion of refined alumina to aluminum metal.

 

Written by: Uwe König, Posted by: Malvern Panalytical – (www,materials-talks.com)

ISO CERTIFICATION: THE NEXT CHAPTER IN THE WROXI SUCCESS STORY

Hello, my name is Mark Ingham and I’m an expert on XRF. In my first blog, I’ll describe the history of WROXI reference materials and the benefits stemming from the new ISO 17034 accreditation.

Let’s take a look at why the WROXI reference materials for XRF have proved so popular over the last 15 years, and the benefits stemming from the new ISO 17034 certification.

The beginnings of WROXI

Do you ever find that inspiration only strikes when you’re faced with the same problem, day-in, day-out? It was certainly true for me when I came up with the idea for WROXI – our ready-to-use kits for making XRF calibration standards.

At the time – the early 1990s – I was working in the Analytical Geochemistry Group at the British Geological Survey (BGS) in Keyworth, near Nottingham, UK. We mostly used single-oxide standards for calibration, which was very time-consuming, and also difficult because the powders did not always fuse very easily.

As XRF is fundamentally  a comparative technique, it relies heavily on the accuracy of the sampling, preparation, calibration and measurement processes

A wide range of oxides

As a result of these difficulties, I began to think – why not mix the oxides of the commonest rock-forming elements together into a single set of standards? That would reduce the number of calibration samples needed, and also make it easier to fuse the powders to get clear, high-quality beads.

So that’s exactly what I did, and the ‘WROXI’ product (short for Wide-Range OXIdes) was born.

These WROXI standards were designed for our clients PANalytical. As time went by, the focus of BGS shifted away from analytical work, and in 2011 BGS decided to sell the facility to PANalytical, which I joined as a staff member.

For a while, BGS leased the laboratories to PANalytical, but when that arrangement came to an end, I moved (literally) just a mile or so down the road, from Keyworth to Tollerton. There, I helped set up a laboratory in The Coach House, which remains the ‘headquarters’ of our WROXI and other standards products today.

Our laboratories in The Coach House in Tollerton are where we make all our WROXI standards… and they’re the first in the world to produce synthetic CRMs for XRF certified to ISO 17034.

Why is WROXI so popular?

Through all these business changes, our WROXI standards have remained pretty much the same. (The only significant change was the introduction of a ‘Base’ set with ‘Cement’ and ‘Pro’ extensions in 2020, so customers in certain industries don’t have to measure more elements than necessary.)

So what’s the reason for WROXI’s enduring appeal? I think it comes down to four key points:

  • Using WROXI standards is quick and cost-effective. Just imagine having to set up an application for (let’s say) the 11 common oxides. Buying the reference materials, working out the fusion parameters, building the application, calibration, and would take months of effort. But with WROXI most of this work is already done, meaning your Epsilon 4 or Zetium spectrometer can be ready to run your samples within a week.
  • WROXI standards are totally synthetic. Unlike conventional reference materials made from stocks of geological samples, soils, fly ash or cement clinker, WROXI standards are made from high-purity, commercially available chemicals, so they’ll never run out.
  • Because WROXI standards are synthetic, we can avoid measurement uncertainties caused by peak overlap between different elements (such as titanium and vanadium), by not including them in the same standard. And of course, mineralogical effects and particle-size effects are eliminated during the fusion process, giving an order-of-magnitude increase in accuracy over pressed powder pellets.
  • The two extension sets make WROXI standards flexible – and we are always happy to develop custom standards containing uncommon elements or different concentration ranges. I recall an industrial recycling company a few years ago who needed to measure tungsten in their samples… as well as 20 other elements! At the time, there were only three reference materials available, none of which supported quantitation of tungsten, so we created a set of custom standards for them containing the entire suite of elements. This then allowed them to use the existing reference materials for validation.
The ‘Base’ WROXI kit contains pre-mixed powders containing the oxides of the 11 common rock-forming elements, ready for fusion into beads using your own equipment. The ‘Cement’ and ‘Pro’ extension kits offer additional elements that are useful in certain industries.

Certification of XRF reference materials: A ‘world first’

There’s also another advantage resulting from the synthetic nature of WROXI standards – we’re able to make them gravimetrically. This opens up the possibility of certifying them to the international standard for reference materials (ISO 17034), which is what we’ve now done with the launch of our WROXI Certified Reference Materials (CRMs).

It’s not been a quick job though – it’s taken two years to go through the ISO 17034 certification process. This is partly because we were the first laboratory in the world to request this for synthetic XRF Certified Reference Materials.

What does this mean for our customers? Essentially an additional confidence boost in the WROXI product. Our laboratories at Tollerton were already accredited by UKAS to ISO/IEC 17025 (the general laboratory standard for testing), but we’ve now had to go much further, by demonstrating that all the processes we use to make our WROXI CRMs meet strict requirements, that all our measurements are traceable, and that every single bottle of the finished product has a certificate and documentation trail associated with it.

The powders now come with the major endorsement of ISO 17034 certification. After 40 years in the XRF business, achieving this is a great milestone for me personally… and of course it further strengthens the ‘analytical chain’ of XRF instrumentation, supplies and expertise from Malvern Panalytical!

 

Written by : Mark Ingham Posted by: Malvern Panalytical (www.materials-talk.com)

16 TIPS TO PROLONG YOUR X-RAY TUBE’S LIFESPAN

X-ray tubes are generally designed to function properly under the most demanding conditions. Where X-ray tubes for benchtop systems would not have to be replaced during the entire system lifetime, the lifespan of an X-ray tube for floor standing systems is typically between 3 and 7 years. This is mainly determined by the way of use and maintenance. So, here is an overview of the main recommendations for optimal X-ray tube usage.

General tips

  1. Keep using your spectrometer and X-ray tube. X-ray tubes should not be left unused for too long, in any case not for more than 6 months. X-ray tubes like to be warm and this keeps the vacuum stable.
  2. Use the Iso-Watt switching feature. This forces the spectrometer to operate at a constant power during the switching between the different measuring conditions. A constant power helps the lifespan of the X-ray tube.
  3. Use the standby setting. In standby setting, the power -and especially the emission current- should not be too high, as this costs lifetime. A high kV setting during standby is no problem, since it helps the tube to remain stable against possible flashes.
  4. Keep the window of the X-ray tube clean. Make sure that no substance spills on the window, and never touch the windows under any circumstance. Not even for cleaning.
  5. Clean samples. When analyzing pressed powders make sure that they are prepared well and don’t crumble inside the spectrometer. Tidy sample preparation is an essential processing step for good analysis. This helps to retain your tube’s lifespan.

Tips for X-ray tube cooling maintenance

  1. Regularly check the condition of the chiller. Cooling water is critical (chemical and physical composition, temperature, flow), as the X-ray tube heats up, especially when operating at full power.
  2. The ideal water temperature. Cold water does not cool better than lukewarm water. The ideal water-in temperature for X-ray tubes is 20-25 °C. In very warm and humid conditions, 25-30 °C is recommended. It is best to always be above the dew point (dew point can be lowered by e.g. climate control in the surroundings).
  3. Clean and uninterrupted flow of cooling water is as important as the cooling water itself. Therefore, the tube’s cooling circuit must be checked and cleaned regularly. If you experience an unusually fast intensity degradation, it is almost certain that the X-ray tube is not properly cooled.
  4. Never us pure de-ionized water for cooling, as this is acid and chemically aggressive.
  5. Place the slit cooler in the correct way.

Tips for the X-ray tube settings

  1. Put the spectrometer on standby setting when the spectrometer will not be used for more than a few hours. This saves lifetime.
  2. Switch off the X-ray tube completely when the spectrometer will not be used for more than 24 hours.
  3. Switch off the water flow within 1-2 minutes when the X-ray tube is switched off completely. NEVER let the water flow for more than 2 minutes after the power is switched off. Otherwise, condensation of water inside the X-ray tube shield can occur.
  4. NEVER switch off the water flow first (inducing an automatic power off), as this can kill the X-ray tube instantly.

Tips to enhance the stability and lifetime of the X-ray tube

Every X-ray tube is designed to be operated at its maximum power. Applying maximum power is absolutely no problem. There is, however, no denying that every X-ray tube will undergo physical and chemical ageing. These ageing processes are driven mainly by high temperatures and high-temperature gradients inside the X-ray tube.

  1. Avoid maximum power if your application does not require it. At maximum power, the physical and chemical ageing processes inside the X-ray tube go faster than at lower power.
  2. Operating at 80-90% of the maximum power already has a significant positive effect on the stability and lifetime of the X-ray tube.

If you unexpectedly need a new X-ray tube, please contact us

 

Written by: Kimberly Oberholz, Posted by: Malvern Panalytical (www.materials-talks.com)

THE VALUE OF MINERALOGICAL MONITORING FOR THE ALUMINUM INDUSTRY

Bauxite is the primary source of aluminum worldwide. Without Bauxite, we could not cover up our leftover food with tin foil, have ladders to climb on or be able to cool our food in a refrigerator or cool our houses in the summer. A major part of the bauxite is the metallurgical grade, which after primary screening and washing, is processed in a refinery. The alumina (Al2O3) is extracted via chemical digestion using caustic soda, following the Bayer process. The waste product of this process is called red mud. The refined alumina is finally converted into metallic aluminum. This process takes place in smelters with a large number of electrolytic baths following the so-called “Hall-Heroult” process.

The efficiency and economics of every step in this process, as for any other ore-to-metal process, is defined by both the chemical and the mineralogical properties and composition of bauxite and alumina.

In the series: “The value of mineralogical monitoring for the aluminum industry” we will showcase the added value of adequate mineralogy control at every step on the way from bauxite ore to the aluminum metal.

Step I. Bauxite mining: Bauxite Ore Grades

Over 70% of the mined bauxite deposits are lateritic in nature (Australia, Brazil, South East Asia). The major constituent is gibbsite, Al(OH)3, with smaller amounts of boehmite, γ-AlO(OH), and diaspore, α-AlO(OH). Apart from the major Al-bearing phases, bauxite contain impurities, like iron oxides (hematite Fe2O3, goethite FeOOH), silica (quartz SiO2, clays such as kaolinite Al2Si2O5(OH)4 ) and titania (rutile TiO2, anatase TiO2).

The ratio between Al-bearing phases and impurities will define the maximum alumina yield (total available alumina) and digestion parameters such as temperature or caustic soda consumption

The digestion temperature is determined by the ratio between gibbsite, boehmite and diaspore. Whereas about 140-150 °C is sufficient to extract alumina from gibbsite, boehmite and diaspore digestion requires 240-260 °C.

The caustic soda consumption per ton of bauxite ore is directly proportional to the amount of reactive silica present (silica, which will react with caustic soda). At lower temperatures, only the silica of the clay minerals is reactive during the digestion. If higher temperatures are applied, quartz will also react and increase the caustic soda consumption.

Bauxite ore high in gibbsite and low in boehmite and silica content has the highest grade as it can be digested at the lower temperature with the lowest caustic soda consumption. Ore high in silica and iron oxides is considered as low grade or waste. Intermediate grade ore, high in gibbsite and boehmite and diaspore, can be refined, but at higher temperature.

To summarize, the most important parameter for bauxite mining and processing are:

  • Available alumina
  • Reactive silica
  • Ratio between Al-bearing phases

These parameters define the overall economics and efficiency of further downstream processing.

How is ore grade defined?

During exploration and mining, bauxite ore bodies are divided into grade blocks. Traditionally this was done using chemical analyses (X-ray fluorescence and wet chemistry) and geological prospecting. However, neither of these methods are comprehensive as accurate mineralogical probs. Wrong determination of one grade block is a loss of about 0.5-1 million USD downstream. Therefore, today more accurate tools, like X-ray diffraction (XRD) and near-infrared spectroscopy (NIR) are used for ore grading.

How accurate is bauxite ore grading using X-ray diffraction (XRD)?

Figure 1. Typical result of XRD analyses of bauxite using an Aeris Minerals benchtop diffractometer. 10 minutes measurement time allows accurate identification and quantification of all mineralogical phases present.

Before going to the real bauxite mine case study, let’s check the accuracy of XRD for bauxite analyses by measuring a set of bauxite certified reference materials from ALCAN.

Figure 1 shows a typical result of XRD analyses of bauxite. Any XRD pattern is a set of diffraction peaks of different intensities, located at certain diffraction angles (2θ), specific to a certain mineralogical phase. The peak positions allow the identification of the mineral phases. The relative intensities of each mineral contribution to the XRD pattern allow quantifying the relative amount of each mineral using the full-pattern Rietveld method [1].

In the example shown in  Figure 1, one of the ALCAN CRMs, BXT-02, was analyzed. This sample consists of nearly 60% of gibbsite and nearly 40% of impurities, including iron and titanium oxides, clays and quartz.

Figure 2. Comparison of total and available alumina as obtained by XRD with the certified values for ALCAN bauxite CRMs

How accurate are these numbers?

Unfortunately, phase composition is not yet being reported for bauxite CRMs; however, using our XRD results, we can calculate the chemical composition and compare it with the certified values.  We get very good agreement (Figure 2) between the certified values and XRD results, including the total alumina (total present Al2O3) and total available alumina values (total extractable Al2O3).

Actual bauxite mine case study using XRD

The results of the measurements with the bauxite CRMs show that XRD is an accurate and fast technique to monitor bauxite mineralogy, providing not only the complete mineralogy of a bauxite ore but also the important process parameters. The following case study trials the method on a set of samples collected from an operating bauxite mine.

Figure 3. Comparison of total available alumina and reactive silica as obtained by XRD with the reference values (wet chemistry)

20 samples from a Northern Brazil bauxite mine were analyzed. The mineralogical composition was quantified and used for the calculation of the total available alumina and reactive silica. The comparison of the XRD results with the reference values (wet chemistry) is plotted in Figure 3, showing a good correlation between wet chemistry and XRD results.

The graphs show that both methods are capable techniques for this application. However, each XRD measurement in Figure 3 took on average 15 minutes, including automatic sample preparation, scanning and quantification; while each wet chemistry data point was manually obtained, took hours and required use of hazardous substances.

Apart from reactive silica, total alumina and available alumina, XRD analyzed the complete mineralogical composition, including the ratio between gibbsite, diaspore and boehmite. All parameters together are available after a single sample test of 10-15 minutes.

The ability to get a comprehensive set of process parameters, speed of the analyses, increased safety for the operators, and the possibility to automate, makes XRD a much more economically attractive alternative to wet chemistry [2].

Bauxite ore grading using NIR

Figure 4. NIR spectra of main bauxite phases and associated minerals

Almost all bauxite minerals (quartz excluding) are spectrally active, therefore they can be identified and quantified using near-infrared spectroscopy (NIR). Figure 4 gives an example of NIR spectra of main bauxite phases as well as common accompanying and alteration phases. All bauxite phases have distinct spectral features and can be easily be distinguished from one another.

Quantitative mineralogical analyses using NIR is different than using XRD. NIR quantification requires a statistical model built using over 100 reference samples, mineralogical quantification of which was done using another primary technique, like XRD. Therefore, NIR can never be more accurate than a primary technique. The creation and modification of a quantification model is a more labor-intensive process compared to XRD.

Although NIR lacks the accuracy and flexibility of XRD, it has a great advantage – design simplicity. On one hand, this makes NIR devices very portable, on the other hand, NIR technology can be easily implemented as an on-line sensor over a conveyor belt. Both portability and on-line implementation are translated into extremely short feedback loops and fast decision making.

Portability makes NIR an ideal tool for the initial exploration of bauxite deposits as well as on the spot troubleshooting during ongoing mine operation. On-line NIR sensor will enable 24/7 bulk monitoring of bauxite run-of-mine. And it can also be used for the calculation of total alumina, reactive silica and total available alumina for low temperature digestive process.

In our next blog, we will discuss the added value of mineralogical analyses for the next step in the bauxite-to-aluminium process: the extraction of alumina from bauxite at a refinery.

 

Written by: Uwe König, Posted by: Malvern Panalytical – (www,materials-talks.com)