Facile preparation of concentrated silver and copper heat transfer nanocolloids

Concentrated, yet stable silver- and copper-in-water nanocolloids are prepared using a novel method combining formation of a metal ammine complex and use of a strong NaBH4 reductant. Maximum solid contents of the stable silver and copper nanofluids are 2000 and 5000 ppm (reported as mass fractions), respectively. The metallic nanoparticles are reduced in micellar microreactors, favoring formation of small nanoparticles. Use of stable metal ammine complexes ([Ag(NH3)2]+ and [Cu(NH3)4(H2O)2]2+) as metal ion sources prevent the formation of sparingly-soluble metal salts and thus, aid the nanocolloid synthesis. Several different stabilizers and combinations of them are tested for nanofluid synthesis: anionic sodium dodecyl sulfate, polymeric polyvinylpyrrolidone, sodium citrate, nonionic sorbitan trioleate and polysorbate 20. The particle sizes and size distributions are studied using dynamic laser scattering and transmission electron microscopy. Stability of the nanofluids is assessed by zeta potential measurements, repetitive particle size measurements and visual observations. The average particle sizes of the silver and copper nanofluids with optimized surfactants are < 20 nm and ~40 nm, respectively, and the fluids with optimized stabilizer compositions are stable over the storing period of a month. Specific heat and thermal conductivities of the fluids are measured using differential scanning calorimetry and modified transient plane source technique (TCi Thermal conductivity analyzer), respectively. In addition, the nanofluid viscosities are measured in order to assess the usability of the nanofluids in convective heat transfer. The chemistry of stabilizers is found to have a significant impact on the viscosity of nanofluids. Commonly used polymeric polyvinylpyrrolidone stabilizer produces viscous fluids, whereas the viscosities of the fluids stabilized with small size surfactants are close to that of water.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Visuomotoriset muutokset urheilupäävamman yhteydessä

Tarkoitus: Opinnäytetyön tarkoituksena on tutkia naisten jalkapallossa ilmenevien päävammojen määrää ja niiden aiheuttamia vaikutuksia visuomotoriseen toimintaan. Tavoitteena on, että opinnäytetyön tuloksista löytyvää tietoa olisi mahdollista hyödyntää tulevaisuudessa vammautumisriskien kartoituksessa. Tausta: Kliinisen kokemuksen perusteella on todettu, että lieväksi aivovammaksi luokiteltava aivotärähdys aiheuttaa usein näkömuutoksia. Ryhmällä jalkapalloilijoita on raportoitu välitöntä aivokapasiteetin laskua vain yhden puskuharjoittelun jälkeen, mikä voi altistaa pelaajan vammoille. Päävammojen määrää, laatua ja pitkäaikaisvaikutuksia on selvitetty hajanaisesti, mutta systemaattinen tutkimus aiheesta puuttuu. Menetelmä: Naisten jalkapalloliigapelaajille tehtiin pelaajayhdistyksen avustuksella kyselytutkimus urheilupäävammojen esiintyvyydestä ja oireista erityisesti visuomotoristen ongelmien ja oireiden aiheuttamien toimintakyvyn ongelmien selvittämiseksi. Sama kysely tehtiin naisten alemmassa sarjassa pelaavalle jalkapallojoukkueelle, lisäksi pelaajat osallistuivat visuomotoriikkaa ja tasapainoa mittaaviin testeihin. Testitulokset analysoitiin tilastollisesti Excelohjelman ja ristiintaulukoinnin avulla. Tulokset ja johtopäätökset: Kyselyn perusteella 23:lla pelaajalla 63:sta pelaajasta oli päävammataustaa Naisten Liigasta. Testiryhmästä kolmella pelaajalla kahdeksasta oli diagnosoitu aivotärähdys. Yleisin oire molemmilla ryhmillä oli huimaus. Testiryhmän päävammakyselyn tuloksia verrattaessa samojen pelaajien VOMS-testin tuloksiin voitiin todeta, että päävamman saaneilla yleisin VOMS-testissä provosoituva oire oli näön sumentuminen. Pelaajat, joilla ei ollut päävammahistoriaa, selvisivät testistä vähemmillä oireilla. Tasapainotestissä todettu heikko tulos saattoi viitata enemmän aikaisempiin alaraajavammoihin kuin päävammaan. Pelaajilla, joilla on joko aiempien alaraajavammojen johdosta tai muutoin heikentynyt alaraajojen liikekontrolli ja asennonhallinta on mahdollisesti suurempi riski altistua päävammalle jalkapallossa. Heikentyneiden tasapainon osa-alueiden lisäksi uusien päävammojen syntymisen riskin kasvuun mahdollisesti vaikuttavat pallon aiheuttamat iskut päähän, pallontavoittelutilanteet, puskutilanteet sekä törmäämiset.Purpose: The purpose of this thesis is to discuss how common head injuries are in women's soccer and is there a connection between head injuries and visuomotoric changes. The aim is to utilize the information from the results of the thesis in the future by identifying the risks of injury. Background: Due to clinical findings, even a concussion rated as a mild brain injury can often leave changes in one’s eyesight. Immediate decrease in brain capacity was reported in a group of soccer players after one soccer practice session, which consisted of a header. Head injuries in sports is a sporadically researched subject – their qualities, quantities, and long-term effects are unclear – and new data and new data on visuomotoric changes in soccer is rather limited. Approach: A sports related head injury survey was given to be filled in by the Finnish national women's soccer league. The survey was executed in cooperation with the Finnish player association. The purpose of the survey was to investigate the connection between head injuries and visuomotoric changes. A women's lower class team was recruited to fill in a standard head injury query, and to perform the VOMS-test and a one-legged balance test on a HUR balance platform. The tests were analyzed with an Excel-sheet. Results and conclusions: According to the sports related head injury survey, 23 of 63 female soccer players in Finnish Women’s League had suffered at least one diagnosed concussion. The same head injury survey was held for the test group. In both study groups the most common symptom was vertigo. In VOMS-tests, symptoms were provoked with most of the players. Fogginess and dizziness were the most usual symptoms recorded. Players who didn't have head injuries survived the test with less symptoms. Bad result in balance test may have had more in common with lower body injuries than head injuries. Players with either lower limb injuries or otherwise impaired lower limb motion control and postural management may have a higher risk of being exposed to head injury in soccer. In addition to the weakened balance elements, the potential for increased risk of new head injuries is likely to be affected by ball to head contact, ball aiming, head game and collisions

Saturation profile measurement of atomic layer deposited film by X-ray microanalysis on lateral high-aspect-ratio structure

Atomic layer deposition (ALD) of aluminum oxide thin films were applied on lateral high-aspect-ratio silicon test structures. The leading front of the film thickness profile is of interest, since it is related to deposition kinetics and provides information for ALD process development. A deposited profile was characterized using energy-dispersive electron probe X-ray microanalysis (ED-EPMA) and the results were analyzed using Monte Carlo simulation. A new procedure for obtaining relative film thickness profile from X-ray microanalysis data is described. From the obtained relative thickness profile, penetration depth of film at 50% of initial thickness and corresponding slope of thickness profile were determined at the saturation front. Comparison of the developed procedure was performed against independent measurements using optical reflectometry. ED-EPMA characterization of saturation profiles on lateral high-aspect-ratio test structures, supported by Monte Carlo simulation, is expected to prove useful tool for ALD process development.Peer reviewe

Superelastic NiTi coatings with good corrosive wear resistance

In the present study corrosive wear resistance of NiTi coatings produced by hot isostatic pressing (HIPping) were tested using a slurry pot type of equipment. The samples were rotated in a slurry that contained 100g/l of quartz sand in liquid. Two types of liquids were used. In the corrosive test the liquid was INH$_2$SO$_4$-water solution and in the neutral reference tests the liquid was deionized water. The radial velocity was 4.7 m/s, temperature $25 \pm 5$ °C, and duration 5 hours. Furthermore, additional corrosion tests were performed with the same apparatus and the sour liquid but without the quartz sand. The results were compared with AISI 316 steel, bulk NiTi, and some other materials. The results showed that HIPped NiTi coatings have a very good corrosive wear resistance

On the reliability of nanoindentation hardness of Al2O3 films grown on Si-wafer by atomic layer deposition

Peer reviewe

Comparison of conventional and lignin-rich microcrystalline cellulose

Three microcrystalline cellulose (MCC) samples were manufactured from bleached and unbleached softwood kraft pulp, and their properties were compared to those of the commercial MCC, Avicel PH-101. One of the produced samples retained a large portion of lignin (10.3%), while the two others retained only some. The physical, chemical, thermogravimetric, and molecular properties were analyzed. The presence of lignin caused a substantial effect on the thermogravimetric and chemical properties of the MCC, as well as on its surface characteristics. The lignin-containing sample degraded at lower temperatures, and its UV Raman spectra had a high intensity aromatic band (1600 cm-1) arising from the lignin. X-ray photoelectron spectroscopy confirmed a high surface lignin coverage (40%) in this specimen only. Particle size and BET surface area measurement results varied in some limits between MCCs, while the cellulose crystallinity index showed almost equal values between 0.82 and 0.84. This work introduces a new wood-based product, the lignin-containing MCC, comparable in properties to the wide-marketed Avicel.Peer reviewe

Nickel Supported on Mesoporous Zirconium Oxide by Atomic Layer Deposition: Initial Fixed-Bed Reactor Study

Atomic layer deposition (ALD) is gaining attention as a catalyst preparation method able to produce metal (oxide, sulphide, etc.) nanoparticles of uniform size down to single atoms. This work reports our initial experiments to support nickel on mesoporous zirconia. Nickel (2,2,6,6-tetramethyl-3,5-heptanedionato)2 [Ni(thd)2] was reacted in a fixed-bed ALD reactor with zirconia, characterised with BET surface area of 72 m2/g and mean pore size of 14 nm. According to X-ray fluorescence measurements, the average nickel loading on the top part of the support bed was on the order of 1 wt-%, corresponding to circa one nickel atom per square nanometre. Cross-sectional scanning electron microscopy combined with energy-dispersive spectroscopy confirmed that in the top part of the fixed support bed, nickel was distributed throughout the zirconia particles. X-ray photoelectron spectroscopy indicated the nickel oxidation state to be two. Organic thd ligands remained complete on the surface after the Ni(thd)2 reaction with zirconia, as followed with diffuse reflectance infrared Fourier transform spectroscopy. The ligands could be fully removed by oxidation at 400 °C. These initial results indicate that nickel catalysts on zirconia can likely be made by ALD. Before catalytic testing, in addition to increasing the nickel loading by repeated ALD cycles, optimization of the process parameters is required to ensure uniform distribution of nickel throughout the support bed and within the zirconia particles