Microstructural characterization of dental zinc phosphate cements using combined small angle neutron scattering and microfocus X-ray computed tomography.

Abstract Objective To characterize the microstructure of two zinc phosphate cement formulations in order to investigate the role of liquid/solid ratio and composition of powder component, on the developed porosity and, consequently, on compressive strength. Methods X-ray powder diffraction with the Rietveld method was used to study the phase composition of zinc oxide powder and cements. Powder component and cement microstructure were investigated with scanning electron microscopy. Small angle neutron scattering (SANS) and microfocus X-ray computed tomography (XmCT) were together employed to characterize porosity and microstructure of dental cements. Compressive strength tests were performed to evaluate their mechanical performance. Results The beneficial effects obtained by the addition of Al, Mg and B to modulate powder reactivity were mitigated by the crystallization of a Zn aluminate phase not involved in the cement setting reaction. Both cements showed spherical pores with a bimodal distribution at the micro/nano-scale. Pores, containing a low density gel-like phase, developed through segregation of liquid during setting. Increasing liquid/solid ratio from 0.378 to 0.571, increased both SANS and XmCT-derived specific surface area (by 56% and 22%, respectively), porosity (XmCT-derived porosity increased from 3.8% to 5.2%), the relative fraction of large pores ≥50 μm, decreased compressive strength from 50 ± 3 MPa to 39 ± 3 MPa, and favored microstructural and compositional inhomogeneities. Significance Explain aspects of powder design affecting the setting reaction and, in turn, cement performance, to help in optimizing cement formulation. The mechanism behind development of porosity and specific surface area explains mechanical performance, and processes such as erosion and fluoride release/uptake

Characterization of Božanov sandstone: pilot fracture tests

The aim of this paper is a characterization ofsandstone from Božanov quarry near Broumov, Czech Republic,by means of the pilot fracture tests. Five drill-core test specimens withnominal diameter of 50mm and lengths of 100 and 125mmwere provided by an initial chevron type notch. Specimens were loaded in the configuration of the three-point bending as a displacement driven experimentusing LabTest 6.250 equipment in the laboratory of the Institute of Building Testing, Faculty of Civil Engineering, Brno University of Technology. The load versus displacement diagrams were used to quantify the basic mechanical fracture parameters of the studied sandstone: modulus of elasticity, fracture toughness, toughness, and specific fracture energy

Composition and Technology of the 17th Century Stucco Decorations at Červená Lhota Castle in the Southern Bohemia

The stucco decoration from the Great Chamber of the castle Červená Lhota in the Southern Bohemia was surveyed and characterised as part of its planned conservation. The repair works that are still to be specified in detail should be based on a good knowledge of the original material and technique. The main focus was on the fruit pieces decorating the ribs of vaults. Altogether, over twenty mortar samples were collected from the vault bedding mortar, plaster, drawn elements and stuccos. Additionally, some pieces of fruits, that were loose and had to be temporarily removed, were studied macroscopically and by X-ray CT. Characterisation of binder, aggregate and additives was carried out using TA, acid attack, sieve analysis of unsolvable residue, XRD, FTIR and nL-MS. The characterisation led to understanding of the uses of various mortar mixes and determination of their recipes. A typical fruit piece was composed of an inner modelling core mortar made of lime-gypsum binder and a coarser aggregate covered with a 5–20 mm think lime rich stucco layer containing calcitic air lime and fine siliceous sand. This stucco mortar was also used for modelling various small decorations - fine and thin shapes like leaves, cherries and grapes. These were attached to the main piece by a fine adhesive mortar made of lime and gypsum in various proportions. The use of gypsum and the differences in lime to gypsum ratio corresponded to a certain functional requirements (performances). This finding was a key parameter that contributed to the reconstruction of the original application technique and procedure. Qualitative analysis of animal proteins determined presence of collagen – an animal glue that was used to modify the setting of gypsum and which was also used in the final finish. The results are discussed as an example of a procedure that aims at a detailed replication of the original technique

Micro-CT - A Digital 3D Microstructural Voyage into Scaffolds: A Systematic Review of the Reported Methods and Results

Background: Cell behavior is the key to tissue regeneration. Given the fact that most of the cells used in tissue engineering are anchorage-dependent, their behavior including adhesion, growth, migration, matrix synthesis, and differentiation is related to the design of the scaffolds. Thus, characterization of the scaffolds is highly required. Micro-computed tomography (micro-CT) provides a powerful platform to analyze, visualize, and explore any portion of interest in the scaffold in a 3D fashion without cutting or destroying it with the benefit of almost no sample preparation need. Main body: This review highlights the relationship between the scaffold microstructure and cell behavior, and provides the basics of the micro-CT method. In this work, we also analyzed the original papers that were published in 2016 through a systematic search to address the need for specific improvements in the methods section of the papers including the amount of provided information from the obtained results.FROnTHERA Project (NORTE-01-0145-FEDER-000023) within the Norte Portugal Regional Operational Programme (NORTE 2020) under the Portugal 2020 Partnership Agreement, through ERDF, and Portuguese Foundation for Science and Technology (SFRH/BD/99555/2014, IF/00423/2012, and IF/01285/2015).info:eu-repo/semantics/publishedVersio