
Leena HupaÅbo Akademi University · Faculty of Science and Engineering
Leena Hupa
DSc (Tech)
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Publications (304)
Predicting the occurrence of an envelope flame during black liquor combustion is crucial in order to determine which volatiles species reach the bulk gas from the droplet. The extent to which envelope flames occur in large scale black liquor combustion is currently not known. Experimental investigation in boilers is impractical and laboratory inves...
Thermal conversion of agricultural biomass residues poses a great opportunity to valorize waste materials by recovering energy and valuable elements such as phosphorus. Utilizing biomass residues in thermal conversion is, on the other hand, often coupled with operational challenges due to particle emissions, deposit formation, corrosion and slaggin...
This study aimed to investigate the retention of strength in accelerated aging condition and ion release from an experimental fiber-reinforced bioactive flowable composite resin (Bio-SFRC), comparing it with various commercially available ion-releasing materials. The flexural strength of Bio-SFRC and other materials (Biodentine, TheraCal LC, Fuji I...
Modern Kraft recovery boilers have become larger compared to earlier designs and burn higher black liquor dry solids (DS), leading to a more intense burning process and, therefore, increased sodium hydroxide (NaOH) concentration in the upper furnace. Indications of rapid deposit build-up and plugging issues in these boilers, specifically downstream...
Biological effects of a zinc-substituted borosilicate bioactive glass on human bone marrow derived stromal cells in vitro and in a critical-size femoral defect model in rats in vivo .
A step-by-step equilibrium model approach was developed to estimate and describe the enrichment of K and Cl within recovery boiler deposits. The model predicts free melt movement towards colder temperatures within deposits. Due to a temperature gradient, the melt amount and composition differ across the deposit. The melt movement affects the local...
Fabrication of porous tissue-engineering scaffolds from bioactive glasses (BAG) is complicated by the tendency of BAG compositions to crystallize in thermal treatments during scaffold manufacture. Here, experimental biocompatible glass S59 (SiO2 59.7 wt%, Na2O 25.5 wt%, CaO 11.0 wt%, P2O5 2.5 wt%, B2O3 1.3 wt%), known to be resistant to crystalliza...
Chemical-looping combustion (CLC) of biomass has the potential to facilitate negative CO2 emission in heat and power production when combined with a carbon capture technique. However, typical biomass contains alkali metals and chlorine compounds, such as potassium chloride, which can lead to corrosion of heat-transfer surfaces in the reactors. The...
In vitro reactions of granules and microspheres (45-90 µm) of the bioactive glass S53P4 and an experimental composition with 5 mol.% K 2 O substituted for Na 2 O in S53P4 were studied in continuous fluid flow conditions. The dissolution experiments were performed with a 0.2 mL/min flow rate in TRIS buffer up to 24 h. Granules provided higher initia...
The 0106‐B1‐bioactive glass (BG) composition (in wt %: 37.5 SiO 2 , 22.6 CaO, 5.9 Na 2 O, 4.0 P 2 O 5 , 12.0 K 2 O, 5.5 MgO, and 12.5 B 2 O 3 ) has demonstrated favorable processing properties and promising bone regeneration potential. The present study aimed to evaluate the biological effects of the incorporation of highly pro‐angiogenic copper (C...
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...
The equilibrium T-x space of the Ag-GaTe -AgBr system in the part Ag 2 Te-GaTe-Te-AgBr-Ag 2 Te below 600 K has been divided into separate phase regions using the electromotive force (EMF) method. Accurate experimental data were obtained using the following electrochemical cells (ECs): (-) IE | NE | SSE | R{Ag + } | PE | IE (+), where IE is the iner...
In line with the objectives of the circular economy, the conversion of waste streams to useful and valuable side streams is a central goal. Ash represents one of the main industrial side-products, and using ashes in other than the present landfilling applications is, therefore, a high priority. This paper reviews the properties and utilization of a...
Despite their long history of application in orthopedics, the osteogenic and angiogenic properties as well as the cytocompatibility and protein adsorption of the 45S5- (in wt%: 45.0 SiO2, 24.5 Na2O, 24.5 CaO, 6.0 P2O5) and S53P4- (in wt%: 53.0 SiO2, 23.0 Na2O, 20.0 CaO, 4.0 P2O5) bioactive glass (BG) compositions have not yet been directly compared...
Magnesia-chromite (MgCr2O4) spinel-based refractories are applied in nickel and copper flash smelting furnaces, where the refractories experience high temperatures but also thermal gradients due to the cooling of the walls. In the gas space, the refractories are subjected to an aggressive environment with high SO2 concentrations. Furthermore, the i...
The phase equilibria of the Ag–Ga–S–AgBr system in the part GaS–Ga2S5–AgBr–Ag2S below 600 K were investigated by the modified electromotive force (EMF) method using the Ag+ catalysts as small nucleation centers of equilibrium phases. Division of the GaS–Ga2S5–AgBr–Ag2S was carried out with the participation of the following compounds Ag2S, GaS, Ga2...
A new methodology for monitoring low-temperature corrosion caused by hygroscopic salts was developed and tested with ZnCl2. First, deliquescence and efflorescence points of ZnCl2 were determined by electrochemical impedance spectroscopy and chronoamperometry measurements in the range of 10–35 vol % H2O. Then, low-temperature corrosion was monitored...
Graphite was recovered from two leached (H 2 SO 4 = 2 M, 60 • C, t = 3 h, Fe 3+ = 2 g/L) Li-ion battery black mass concentrates with minimized energy consumption. One black mass originated from a mixture of mobile device and power tool batteries, and another from a single electric vehicle battery. The leach residues were pyrolyzed (800 • C, t = 1 h...
Air particle abrasion (APA) using bioactive glass (BG) effectively decontaminates titanium (Ti) surface biofilms and the retained glass particles on the abraded surfaces impart potent antibac-terial properties against various clinically significant pathogens. The objective of this study was to investigate the effect of BG APA and simulated body flu...
Electronic waste (e-waste) is the fastest-growing type of solid waste stream with increasing environmental concern. Fortunately, the presence of valuable metals in the e-waste make its recycling a feasible option. The black copper processing route is one of the most suitable for e-waste recycling. The slag cleaning part of the process is important...
This paper evaluates crystallographic data and thermodynamic properties for sodium chromate, potassium chromate, sodium molybdate, potassium molybdate (K2MoO4), sodium tungstate, and potassium tungstate collected from the literature. A thorough literature review was carried out to obtain a good understanding of the available data, and a critical ev...
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...
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...
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...
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...