Leena Hupa

Åbo Akademi University · Faculty of Science and Engineering

The initial melting behaviour of synthetic ash deposits, with a focus on how the amount of melt formed, affects the final deposit morphology, was studied. Binary and ternary reciprocal deposits were exposed to a temperature gradient with varying exposure time, steel temperature, and furnace temperature. Two different archetype deposit morphologies...

In vitro dynamic dissolution of bioactive glass S53P4 particles was studied in a cascade of three reactors. Tris buffer (pH 7.40) and lactic acid (pH 2.00) with flow rates of 0.2 and 0.04 ml/min were fed through the reactors for 24 h. The increased ion concentrations in Tris inflows to the second and third reactors decreased the dissolution of the...

Citation: Abushahba, F.; Areid, N.; Kylmäoja, E.; Holopainen, J.; Ritala, M.; Hupa, L.; Tuukkanen, J.; Närhi, T. Effect of Atomic-Layer-Deposited Hydroxyapatite Coating on Surface Thrombogenicity of Titanium. Abstract: This study aimed to evaluate the surface characteristics of a nanocrystalline hydroxyapatite coating made through atomic layer depo...

The mechanical properties of polylactide stereocomplexes (PLA SC) have been primarily studied through tensile testing, with inconsistent results, and the compressive properties of PLA SC compared to homocrystalline or amorphous PLA remain poorly understood. In this study, we coated porous bioactive glass 13–93 scaffolds with amorphous, homocrystall...

We studied how in vitro reactions affect long-term biochemical and mechanical properties of porous tissue engineering scaffolds based on two bioactive glasses and accordingly their potential suitability for treating critical-size load-bearing bone defects. Granules of bioactive glass S53P4 and S59 were used to sinter the porous scaffolds. The sinte...

Since the introduction of the 45S5-bioactive glass (BG), numerous new BG compositions have been developed. Compared to the 45S5-BG, 1393-BG shows favorable processing properties due to its low crystallization tendency and the 1393-BG-based borosilicate 0106-B1-BG exhibits improved angiogenic properties due to its boron content. Despite their close...

Bioactive glass (BAG) is a bone substitute that can be used in orthopaedic surgery. Following implantation, the BAG is expected to be replaced by bone via bone growth and gradual degradation of the BAG. However, the hydroxyapatite mineral forming on BAG resembles bone mineral, not providing sufficient contrast to distinguish the two in X-ray images...

Bioactive glasses (BAG) are surface-active ceramic materials that can be used in bone regeneration due to their known osteoconductive and osteoinductive properties. This systematic review aimed to study the clinical and radiographic outcomes of using BAGs in periodontal regeneration. The selected studies were collected from PubMed and Web of Scienc...

Phase equilibriaPhase equilibria in the part SnS–SnS2–CoS2–CoS–Ag2CoS2–SnS of the Ag–Co–Sn–S system at T < 600 K were investigated by the modified solid-state electromotive force (EMF) method. The position of established phase regions vs point of Ag was used to express the overall potential-forming reactions. The reactions were performed in the pos...

Although the initial in vitro dissolution of bioactive glasses (BAG) is well characterized, the long-term behaviour of crystallized BAG scaffolds in a continuous fluid flow is incompletely understood. A detailed understanding of the long-term dissolution of scaffolds is vital for predicting their behaviour in clinical applications. Here, we explore...

Bioactive glass (BaG) materials are increasingly used in clinics, but their regulatory mechanisms on osteogenic differentiation remain understudied. In this study, we elucidated the currently unknown role of the p38 MAPK downstream target heat shock protein 27 (HSP27), in the osteogenic commitment of human mesenchymal stem cells (hMSCs), derived fr...

Objectives: The present study aimed to evaluate the healing of experimentally induced bone defects around contaminated dental implants after air-abrasion using 45S5 or zinc oxide (ZnO)-containing bioactive glasses (BAGs). Materials and methods: One maxillary first molar was extracted from each Sprague-Dawley rat (n = 30). After 4-week healing, a...

Probe deposit samples of 1, 5, and 8 weeks exposure time were collected from the superheater area of a Finnish kraft recovery boiler. Deposit cross-sections were analysed regarding their morphology and chemical composi- tion using SEM/EDXA. Morphological differences along the probe’s circumference were observed due to different prevailing depositio...

The effects of two deposit ageing mechanisms were identified by analysing superheater ash deposits from a kraft recovery boiler. Local differences in deposit morphology and chemical composition were identified under the electron microscope. Temperature-gradient-induced diffusion of alkali chloride vapours toward the steel was evident. Two deposit t...

This study expands the knowledge of bioactive glass S53P4 dissolution by implementing a cascade reactor to a continuous dissolution setup. Three reactors were coupled in a series to study the effects of released ions on S53P4 reactions in each reactor. The pH and ion concentrations were measured in Tris-buffer and simulated body fluid flowing throu...

The equilibrium concentration space of the Ag–In–Te system in the part AgInTe2–Te–In2Te3 was studied through the modified solid-state electromotive force (EMF) method by dividing into separate phase regions In2Te3–In2Te5–Ag3In97Te147 (I), In2Te5–Te–Ag3In97Te147 (II), Ag3In97Te147–Te–AgIn5Te8 (III), AgIn5Te8–Te–AgIn3Te5 (IV), and AgIn3Te5–Te–AgInTe2...

Objectives A tribochemical silica-coating (TSC) method has been developed to improve the adhesion of dental resin composites to various substrates. The method utilizes airborne-particle abrasion using particles having a silica surface and an alumina core. The impact of the TSC method has been extensively studied but less attention has been paid to...

Microspheres based on the bioactive glass S53P4 were successfully produced through flame-spraying. Glass 13–93 microspheres were utilised as a reference composition with a known behaviour in flame spheroidisation. Bioactive glass microspheres (BGMs) enable a range of advantages compared to conventional irregular-shaped particles. The produced BGMs...

Bioactive glasses were the first synthetic materials to bond to human body tissue, making them ideal for replacing and regenerating bone. Since their first development over half a century ago, many new bioactive glass compositions have been developed for medicine and dentistry. This paper looks at different design strategies employed over the years...

To supplement the primary supply of the critical metals, processing of end-of-life electrical and electronic equipment (e-waste) are being highlighted. E-waste gives an important range of alternative sources of CRMs as well as organic materials, with the potential to substitute a large amount of primary raw materials that are becoming scarcer in Eu...

This chapter reviews the research that has led to present clinical applications of bioactive glass S53P4. Originally, S53P4 was one of 16 statistically chosen glass compositions studied for dental and bone‐grafting applications. The first in vivo results revealed that S53P4 possessed desired bone‐bonding properties. Soon after the first in vivo stu...

This work presents a new approach for more effective valorization of sawmill wastes (Beech and Cedar sawdusts), which were used as new sources for the extraction of lignin-containing and lignin-free cellulose II nanocrystals (L-CNCs and CNCs). It was shown that the properties of the extracted nanocrystals depend on the nature of the used sawdust (s...

This study discusses the potential corrosion of boiler materials in chemical-looping combustion (CLC) of biomass. The CLC of biomass has the potential to negative CO2 emission in heat and power production. Biomass fuels, however, typically contain compounds of alkali metals, especially potassium and chloride, which may lead to the corrosion of heat...

In this study, we tested several amino acids as eco-friendly inhibitors against corrosion of mild steel by used cooking oils (UCOs). The corrosion inhibition was studied by immersing mild steel rods in the UCOs and reference fresh rapeseed and olive oils mixed with amino acids. The immersion tests were conducted at room temperature for three days....

The role of Cu-based phases in combustion processes has boldly emerged with the drastic increase in the waste combustion, sparking the need to update thermodynamic databases for a better understanding and control. In the present work, we have reviewed the content and sources of Cu in selected biomass fuels and ashes, and examined the mechanisms thr...

Bioglass 45S5 is the most widely used bioactive glass composition in orthopedics to regenerate bone tissue. Although its reactions in vitro and in vivo are well established, the impact of the local environment on the dissolution behavior in the dynamic environment is not fully understood. Here we show that the ion concentrations released from 45S5...

Phase equilibria of the Ag–Ge–Bi–Te system in the part GeTe–Ag8GeTe6–Te–Bi2Te3 (I) were established by the electromotive force (EMF) method with a solid Ag+ conducting electrolyte. It was shown that the concentration space of (I) in the part 4GeTe∙Bi2Te3–Ag8GeTe6–Te–Bi2Te consists of 8 four-phase regions, formed of the layered compounds of the nGeT...

One-pot continuous synthesis of menthols from citral was performed over 5 wt % Ni supported on a mesoporous aluminosilicate catalyst with sepiolite as a binder at 70 °C with a selectivity of 75% to menthols. Catalyst deactivation with time-on-stream resulted in a decrease of the conversion and selectivity to menthols at the expense of higher select...

Thermal stabilities of selected ternary phases of industrial interest in the Ag-Cu-S system have been studied by the calorimetric and electromotive force techniques. The ternary compounds Ag1.2Cu0.8S (mineral mackinstryite) and AgCuS (mineral stromeyerite) were equilibrated through high-temperature reaction of the pure Cu2S and Ag₂S in an inert atm...

Although phase relations in the Na2O-CaO-SiO2 system are vital to melting and thermal treatments in glass and glass-ceramics industries, the available data for thermodynamic modeling are mostly based on reports published in 1920s and 1950s. The present investigation verifies the formation of solid solutions of Na2CaSiO4 and Na2Ca2Si2O7 which have p...

Used cooking oils (UCOs) have a high potential as renewable fuels for the maritime shipping industry. However, their corrosiveness during storage and usage are some of the concerns yet to be investigated for addressing compatibility issues. Thus, the corrosion of steels and copper exposed to the UCOs was studied through the immersion of metal rods...

The role of Cu-based phases in combustion processes has boldly emerged with the drastic increase in the waste combustion, sparking the need to update thermodynamic databases for a better understanding and control. In the present work, we have reviewed the content and sources of Cu in selected biomass fuels and ashes, and examined the mechanisms thr...

Sodium-calcium-phosphate based oxynitride glasses and glass-ceramics doped with Mg, Si, and Nb were studied in vitro in simulated body fluid (SBF) under static conditions. The release of ions and pH changes up to 7 days of immersion were investigated. The nitrogen incorporation into phosphate glass matrix was found to notably influence in vitro dis...

The risk of cold-end corrosion caused by two different phenomena was studied: the well-known sulfuric acid-induced corrosion and corrosion caused by hygroscopic fly ash deposits. Measurements were performed in a full-scale circulating fluidized bed boiler firing bituminous coal with high contents of sulfur and chlorine. The boiler was run both with...

Four clay materials, namely, bentonite, bleaching earth, attapulgite and sepiolite, were shaped into the cylindrical body by extrusion. Clays were characterized in depth by TEM, SEM-EDX, N2 physisorption, pyridine FTIR, pH measurements, contact angle measurements, ²⁷Al MAS NMR, and the crush test. Catalytic properties were investigated in the citro...

We propose an injectable nanocomposite hydrogel that is photo-curable via light-induced thiol-ene addition between methacrylate modified O-acetyl-galactoglucomannan (GGMMA) and thiolate cellulose nanocrystal (CNC-SH). Compared to free-radical chain polymerization, the orthogonal step-growth of thiol-ene addition allows a less heterogeneous hydrogel...

Bioactive glasses have been used for many years in the human body as bone substitute. Since bioactive glasses are not readily available in the form of endless thin fibres with diameters below 20 µm, their use is limited to mainly non-load-bearing applications in the form of particles or granules. In this study, the spinnability of four bioactive si...

The silicate-based bioactive glass S53P4 is clinically used in bone regenerative applications in granule form. However, utilization of the glass in scaffold form has been limited by the high tendency of the glass to crystallize during sintering. Here, careful optimization of sintering parameters enabled the manufacture of porous amorphous S53P4 sca...

Agroindustrial biomass residues are considered potential feedstocks for renewable fuels and chemical production through processes such as thermal conversion. In this regard, thermal conversion characteristics of molasses, a byproduct from sugar production, have not been investigated. In this study, thermal conversion properties of molasses at tempe...

During high temperature slagging gasification of municipal solid waste (MSW), coal coke is typically used as an auxiliary fuel to maintain the high temperature in the gasifier and convert ashes into slag. Herein, biomass charcoal was utilized as a greener and more sustainable auxiliary fuel to replace the coal coke during stable and continuous gasi...

Static and dynamic in vitro dissolution studies showed large differences for various size‐fractions of non‐porous, flame‐sprayed commercial microspheres (45‐500 µm) of bioactive glass S53P4. The smaller the spheres, the more their composition deviated from the nominal glass. The dissolution studies were carried out in simulated body fluid and tris(...

Objective: Clinically used bioceramics have been characterized previously with different kinds of methods and comparison of results have proven to be difficult due to varieties of the material properties of interest. Therefore, in this study we compared clinically commonly used bioceramics of hydroxyapatite and carbonate apatite, two bioactive gla...

Critical-sized diaphysis defects are complicated by inherent sub-optimal healing conditions. The two-staged induced membrane technique has been used to treat these challenging defects since the 1980’s. It involves temporary implantation of a membrane-inducing spacer and subsequent bone graft defect filling. A single-staged, graft-independent techni...

Discoveries of new energy materials with unique properties and wider thermal stability ranges enable sustainable developments toward a low-carbon society. In this work, phase stabilities and thermodynamic properties of selected compounds in the Ag-Te-Cl system with potential application as energy materials have been critically reviewed and experime...

This aim of this study was to investigate the effects of three types of air‐abrasion particles on dual‐species biofilms of Fusobacterium nucleatum and Porphyromonas gingivalis, both of which were cultured on sandblasted and acid‐etched (SA) titanium discs. Out of 24 SA discs with biofilm, 18 were exposed to either air‐abrasion using Bioglass 45S5 (...

The proper understanding and description of fuel devolatilization behavior in a fluidized bed (FB) is important to the FB reactor design and modeling. Aiming at this issue, two different mathematical models, isothermal (0D) particle model and one-dimensional (1D) particle model, have been developed. The particle heat transfer is solved simultaneous...

Cross-sections of kraft recovery boiler superheater deposits were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The observed deposit morphology can be explained by temperature gradient induced time-dependent processes such as diffusional transport of alkali chloride vapours, temperature gradient zone...

Equilibrium phase formations below 600 K in the parts Ag2Te–FeTe2–F1.12Te–Ag2Te and Ag8GeTe6–GeTe–FeTe2–AgFeTe2–Ag8GeTe6 of the Fe–Ag–Ge–Te system were established by the electromotive force (EMF) method. The positions of 3- and 4-phase regions relative to the composition of silver were applied to express the potential reactions involving the AgFeT...

The equilibrium phase space of the Ag–Fe–X–Se (X: Ge, Sn) systems in the parts Ag8XSe6–XSe–FeSe2–AgFeSe2–Ag8XSe6 consists of four quaternary-phase regions formed with the participation of low-temperature modifications of the Ag2FeGeSe4 and Ag2FeSnSe4 compounds. The kinetic barriers of the formation of equilibrium four-phase regions that are observe...

The dissolution properties and bioactivity of bioactive glasses (BGs) are mainly determined by their glass network structure. Silicate BGs are the most famous representatives of BGs. However, borate BGs have gained increasing interest due to their faster degradation rate. By adding boron trioxide in the silicate network, borosilicate BGs can be fab...

Background The metal‐acid bifunctional catalysts are widely used in many industrially significant chemical processes, including hydroisomerization of n‐hexane. Deactivation and regeneration of metal‐acid bifunctional extrudates was investigated in continuous n‐hexane hydroisomerization in a fixed‐bed reactor. Four Pt/H‐Beta‐25 catalysts containing...

The role of two oxygen sources, oxygen and water vapor, in the initiation of KCl-induced high-temperature corrosion was addressed by studying two high-alloyed commercial materials at 550 °C. The differentiation between the two oxygen sources was implemented with ¹⁸O-enriched water and ¹⁶O2. Based on the results, the solid-solid reaction between KCl...

Objectives The aim of this study was to analyze the behavior of different bioactive glass fillers (BAGs) embedded in a polydimethylsiloxane matrix of an endodontic sealer. Methods Three different endodontic sealers were fabricated using S53P4, 45S5 and 18−06 glass fillers. Endodontic sealer Guttaflow Bioseal consisting of polydimethylsiloxane (PDM...

The proper understanding and description of the spatial distributions of volatile species is important to the circulating fluidized bed (CFB) reactor design and modeling. Aiming at this issue, a mathematical model has been developed in the present work, which constitutes of two main modules that are validated by experiments, one-dimensional fluid d...

Bioactive glasses (BAG) are used as bone-graft substitutes in orthopaedic surgery. A specific BAG scaffold was developed by sintering BAG-S53P4 granules. It is hypothesised that this scaffold can be used as a bone substitute to fill bone defects and induce a bioactive membrane (IM) around the defect site. Beyond providing the scaffold increased mec...

Waste fish oils (FOs) and used cooking vegetable oils (UCOs) are increasingly becoming alternative renewable fuels. However, different physicochemical aspects of these renewable fuels, including the effect of storage, are not well-known. In this work, the effect of the storage period on physicochemical properties of selected samples of FOs and UCOs...

Besides the widely applied hydropower, wind farms and solar energy, biomass and municipal and industrial waste are increasingly becoming important sources of renewable energy. Nevertheless, fouling, slagging and corrosion associated with the combustion processes of these renewable sources are costly and threaten the long-term operation of power pla...

Bioglass 45S5 is well-known for its bioactivity, but it possesses poor sintering behaviour owing to viscous flow being inhibited by the crystallisation of sodium calcium silicate phases. Mg or Zn were partially (0, 25, 50, 75%) or fully (100%) substituted for Ca on a molar base, and thermal properties (differential scanning calorimetry, dilatometry...

This study describes how potassium salts representative of those in bio ash affect the reactivity of the oxygen carrier ilmenite under moist and dry conditions. Ilmenite is a bench-mark oxygen carrier for chemical-looping combustion, a technique that can separate CO2 from flue gases with minimal energy penalty. Different potassium salts were mixed...

This work describes an effective method for the preparation of open-cell ceramic foams for their further use as catalyst supports. The polyurethane sponge replica technique was applied using a ceramic suspension based on a mixture of α-alumina, magnesia and titania and polyvinyl alcohol solution as a liquid component. The polyurethane sponge was et...

The behaviour of black liquor nitrogen under pyrolysis with envelope flame was investigated with experiments in single-particle combustion with measurements of CO and CO2 and NO. Char carbon and nitrogen retention after pyrolysis were also measured with CHNS analysis of char residue. The combustion environment had a temperature from 800 °C to 1000...

Phosphorus has been observed to cause agglomeration during fluidized bed combustion of phosphorus-rich biomass. Phosphorus can react with alkali during combustion, forming low melting phosphates that glue the bed particles together, or form phosphates that react with the bed material. In this work, seven different phosphate compounds (KH2PO4, NaH2P...