Scientific publications testing our products

Spinel spinel S30CR

March 2021

3D Printing of Transparent Spinel Ceramics with Transmittance Approaching the Theoretical Limit

H. Wang

Singapore

3D printing of transparent ceramics has attracted great attention recently but faces the challenges of low transparency and low printing resolution. Herein, magnesium aluminate spinel transparent ceramics with transmittance reaching 97% of the theoretical limit are successfully fabricated using a stereolithography-based 3D printing method assisted by hot isostatic pressing and the critical factors governing the transparency are revealed. Various transparent spinel lenses and microlattices are printed at a high resolution of ≈100-200 µm. The 3D printed spinel lens demonstrates fairly good optical imaging ability, and the printed spinel diamond microlattices as a transparent photocatalyst support for TiO2 significantly enhance its photocatalytic efficiency compared with its opaque counterparts. Compared with other 3D printed transparent materials such as silica glass or organic polymers, the printed spinel ceramics have the advantages of broad optical window, high hardness, excellent high-temperature stability, and chemical resistance and therefore, have great potential to be used in various optical lenses/windows and photocatalyst supports for application in harsh environments.

High Purity Alumina CR6 Baikalox®

15 June 2023

A Combined Gas and Water Permeances Method for Revealing the Deposition Morphology of GO Grafting on Ceramic Membranes

Evdokia Galata, Charitomeni M. Veziri, George V. Theodorakopoulos, ORCID,George Em, Romanos, Evangelia A. Pavlatou

Athens

The adhesion enhancement of a graphene oxide (GO) layer on porous ceramic substrates is a crucial step towards developing a high-performance membrane for many applications. In this work, we have achieved the chemical anchoring of GO layers on custom-made macroporous disks, fabricated in the lab by pressing α-Al2O3 powder. To this end, three different linkers, polydopamine (PDA), 3-Glycidoxypropyltrimethoxysilane (GPTMS) and (3-Aminopropyl) triethoxysilane (APTMS), were elaborated for their capacity to tightly bind the GO laminate on the ceramic membrane surface. The same procedure was replicated on cylindrical porous commercial ZrO2 substrates because of their potentiality for applications on a large scale. The gas permeance properties of the membranes were studied using helium at 25 °C as a probe molecule and further scrutinized in conjunction with water permeance results. Measurements with helium at 25 °C were chosen to avoid gas adsorption and surface diffusion mechanisms. This approach allowed us to draw conclusions on the deposition morphology of the GO sheets on the ceramic support, the mode of chemical bonding with the linker and the stability of the deposited GO laminate. Specifically, considering that He permeance is mostly affected by the pore structural characteristics, an estimation was initially made of the relative change in the pore size of the developed membranes compared to the bare substrate. This was achieved by interpreting the results via the Knudsen equation, which describes the gas permeance as being analogous to the third power of the pore radius. Subsequently, the calculated relative change in the pore size was inserted into the Hagen–Poiseuille equation to predict the respective water permeance ratio of the GO membranes to the bare substrate. The reason that the experimental water permeance values may deviate from the predicted ones is related to the different surface chemistry, i.e., the hydrophilicity or hydrophobicity that the composite membranes acquire after the chemical modification. Various characterization techniques were applied to study the morphological and physicochemical properties of the materials, like FESEM, XRD, DLS and Contact Angle.

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High Purity Alumina CR6 Baikalox®

November 2022

Composite GO/Ceramic Membranes Prepared via Chemical Attachment: Characterisation and Gas Permeance Properties

Evdokia Galata, Charitomeni M. Veziri, George V. Theodorakopoulos, ORCID,George Em. Romanos, Evangelia A. Pavlatou

Athens

Graphene oxide (GO) oligo-layered laminates were self-assembled on porous ceramic substrates via their simple dip-coating into aqueous GO dispersions. To augment the stability of the developed composite GO/ceramic membranes and control the morphology and stacking quality of the formed laminate, short-((3-glycidoxypropyl)trimethoxy silane-GLYMO, (3-aminopropyl)triethoxy silane-APTES), and long-chain (polydopamine-PDA) molecules were involved and examined as interfacial linkers. A comparative study was performed regarding the linker’s capacity to enhance the interfacial adhesion between the ceramic surface and the GO deposit and affect the orientation and assemblage characteristics of the adjacent GO nanosheets that composed the formed oligo-layered laminates. Subsequently, by post-filtrating a GO/H2O suspension through the oligo-layered laminate membranes, the respective multi-layered ones have been developed, whereas ethylenediamine (EDA) was used in the suspension as an efficient molecular linker that strongly bonds and interlocks the GO nanosheets. The definition of the best linker and approach was conducted on macroporous α-alumina disks, due to the use of inexpensive raw materials and the ability to fabricate them in the lab with high reproducibility. To validate the concept at a larger scale, while investigating the effect of the porous substrate as regards its micrometer-scale roughness and surface chemistry, specific chemical modifications that yielded membranes with the best gas permeability/selectivity performance were replicated on a commercial single-channel monolith with a ZrO2 microfiltration layer. XRD, Raman, ATR, FESEM, and XPS analyses were conducted to study the structural, physicochemical, surface, and morphological properties of the GO/ceramic composite membranes, whereas permeance results of several gases at various temperatures and trans-membrane pressures were interpreted to shed light on the pore structural features. Concerning the short-chain linkers, the obtained results ascertain that GLYMO causes denser and more uniform assembly of GO nanosheets within the oligo-layered laminate. PDA had the same beneficial effect, as it is a macromolecule. Overall, this study shows that the development of gas-separating membranes, by just dipping the linker-modified substrate into the GO suspension, is not straightforward. The application of post-filtration contributed significantly to this target and the quality of the superficially deposited, thick GO laminate depended on this of the chemically attached oligo-layered one.

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Spinel Baikowski® Spinel S25CR

May 2022

Removal of MS2 and fr Bacteriophages Using MgAl2O4-Modified, Al2O3-Stabilized Porous Ceramic Granules for Drinking Water Treatment

Nur Sena Yüzbasi, Paweł A. Krawczyk, Kamila W. Domagała, Alexander Englert, Michael Burkhardt, Michael Stuer, Thomas Graule

Basel

Point-of-use ceramic filters are one of the strategies to address problems associated with waterborne diseases to remove harmful microorganisms in water sources prior to its consumption. In this study, development of adsorption-based ceramic depth filters composed of alumina platelets was achieved using spray granulation (calcined at 800 °C). Their virus retention performance was assessed using cartridges containing granular material (4 g) with two virus surrogates: MS2 and fr bacteriophages. Both materials showed complete removal, with a 7 log10 reduction value (LRV) of MS2 up to 1 L. MgAl2O4-modified Al2O3 granules possessed a higher MS2 retention capacity, contrary to the shortcomings of retention limits in pure Al2O3 granules. No significant decline in the retention of fr occurred during filtration tests up to 2 L. The phase composition and morphology of the materials were preserved during filtration, with no magnesium or aluminum leakage during filtration, as confirmed by X-ray diffractograms, electron micrographs, and inductively coupled plasma-optical emission spectrometry. The proposed MgAl2O4-modified Al2O3 granular ceramic filter materials offer high virus retention, achieving the criterion for virus filtration as required by the World Health Organization (LRV ≥ 4). Owing to their high thermal and chemical stability, the developed materials are thus suitable for thermal and chemical-free regeneration treatments.

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Nanodispersions Mathym® Aqueous colloidal suspensions of yttria-doped zirconia nanoparticles

19 September 2022

Transparent high-strength nanosized yttria stabilized zirconia obtained by pressure-less sintering

Omid Akhlaghi, E. Camposilvan, Zahra Gohari Bajestani, Sirous Khabbaz, Cleva W Ow-Yang, Yves Jorand, Laurent Gremillard, Vincent Garnier, Jérôme Chevalier

Lyon

This work describes the development of transparent high-strength Yttria-Stabilized Zirconia (YSZ) ceramics with ultra-fine grain size utilizing conventional pressure-less densification. Starting with nanoparticles with diameter < 10 nm, it was possible to achieve full densification (>99.5% of theoretical density) at a sintering temperature of 1100–1200 °C. The average grain size of the resulting dense ceramics was 75 nm in 3 mol. % YSZ and 85 nm in 8 mol. % YSZ, showing in-line light transmission of 38% and 51% at a wavelength of 800 nm and average biaxial strength (piston on three balls test on samples of diameter 12 mm and thickness 1 mm) of 1980 MPa and 680 MPa, respectively. The nano-grained structure, absence of color centers, and miniaturization of residual pores enable the excellent light transmission. The high biaxial strength is attributed to the refined microstructure, but also to the martensitic tetragonal-to-monoclinic phase transformation that remains active even in nano-sized zirconia grains.

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High Purity Alumina Baikowski® alumina powder (corundum structure)

4 November 2015

Certificate of Analysis Standard Reference Material® 676a

National Institute of Standards & Technology

Gaithersburg

Baikowski® alumina powder is the source reference that NIST uses to define aluminum oxide and generate standard samples. The alumina powder was produced via the alum [NH4Al(SO4)2 • 12H2O] precursor route, calcined to 1400 °C, and jet milled to a fully disaggregated state. The alumina grains are sub-micrometer in size and equi-axial in shape. The high calcination temperature ensures high phase purity while the isometric form of the grains effectively eliminates preferred orientation effects in this powder. The disaggregated state of this material ensures the homogeneity of mixtures prepared by conventional methods.

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High Purity Alumina BA15

February 2022

Enhancing thermal stability of oxide ceramic matrix composites via matrix doping

Renato S.M. Almeida, H. Farhandi, K. Tushtev, K. Rezwan

Advanced Ceramics & MAPEX - Center for Materials and Processes, Universität Bremen, Germany

Journal of the European Ceramic Society

This paper deals with the production of oxide-oxide ceramic matrix composites (Ox-CMCs) using the high purity alumina powder BA15 from Baikowski. The team investigates the production of Ox-CMCs with higher thermal stability using MgO-doped alumina powder.

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Phosphors YAG suspension

May 2021

YAG thermal barrier coatings deposited by suspension and solution precursor thermal spray

T.A. Owoseni, A. Rincon Romero, Z. Pala, F. Venturi, E.H. Lester, D.M. Grant, T. Hussain

Faculty of Engineering, University of Nottingham, UK

Ceramics International Online

The publication shows how to make YAG coating in the flame from precursor salts and a suspension for the next generation plane engines.