Influence Of Mechanical Treatment Research Articles

Influence of mechanical treatment and magnetic separation on the performance of iron ore tailings as supplementary cementitious material

Despite the great importance of iron mining in the Brazilian economy, significant volumes of tailings with high iron content are generated in the ore beneficiation process. Even with high crystallinity, studies show that the iron ore tailings (IOT) can be used as a supplementary cementitious material (SCM). In this context, this work analyzes the influence of primary (PMT) and secondary (SMT) mechanical treatment and magnetic separation (MS) on the performance of IOT as SCM. To this end, the performance of cementitious composites (pastes and mortars for structural purposes) produced with and without 15% cement replacement by IOT under different treatment conditions was evaluated. The feasibility of reprocessing the iron-rich waste material (IRW) from MS was analyzed. The results showed that, even with SMT, the tailings did not show pozzolanic activity. The tailings with MS and SMT influenced the heat of hydration of the pastes, due to the greater nucleation effect, compared to the other tailings. For this sample, higher compressive strength was achieved among the samples with IOT. The IRW, when submitted to a flotation process, produced a material that still has economic viability.

D0-Ferromagnetism in SHS Titanium Nitride Treated by Ball Milling

In this work, the influence of mechanical treatment (mechanical milling) of the TiN titanium nitride powder produced by self-propagating high-temperature synthesis on the magnetic properties of the milled powders is investigated. The effect of d0-magnetization was observed. The TiN powders were characterized by scanning electron microscopy, X-ray diffraction, vibrating-sample magnetometry, specific surface area measurement, and chemical analysis. The results show that the mechanical treatment of the TiN titanium nitride powder influences the magnetization in a nonmonotonic manner. The conditions of mechanical treatment corresponding to the best value of specific magnetization of milled powders were established. The specific magnetization depended on three measured parameters: specific surface area, coherent scattering region, and average particle size. It was shown that unit cell parameters of milled TiN titanium nitride powders have not been changed with the increasing of duration milling time. The calculated values of CSR of mechanically treated powders decreased with the increasing of duration of milling time. The values of macrostrains were negative. Mechanical treatment of the TiN titanium nitride powders has led to a change in the nitrogen content from 21.4 to 20.0 wt.%. Stoichiometry of the TiN titanium nitride varied from TiN0.903-TiN0.886; therefore, the observed d0-magnetization effect is associated with a defective surface structure of mechanically treated powders.

Вплив механічної обробки на процеси структуроутворення жирових композицій при виробництві спредів

Вплив механічної обробки на процеси структуроутворення жирових композицій при виробництві спредів

Influence of mechanical treatment on acid and catalytic properties of nickel-containing zeolite

Influence of mechanical treatment on acid and catalytic properties of nickel-containing zeolite

Bracket bonding to polymethylmethacrylate-based materials for computer-aided design/manufacture of temporary restorations: Influence of mechanical treatment and chemical treatment with universal adhesives.

ObjectiveTo assess shear bond strength and failure mode (Adhesive Remnant Index, ARI) of orthodontic brackets bonded to polymethylmethacrylate (PMMA) blocks for computer-aided design/manufacture (CAD/CAM) fabrication of temporary restorations, following substrate chemical or mechanical treatment.MethodsTwo types of PMMA blocks were tested: CAD-Temp® (VITA) and Telio® CAD (Ivoclar-Vivadent). The substrate was roughened with 320-grit sandpaper, simulating a fine-grit diamond bur. Two universal adhesives, Scotchbond Universal Adhesive (SU) and Assure Plus (AP), and a conventional adhesive, Transbond XT Primer (XTP; control), were used in combination with Transbond XT Paste to bond the brackets. Six experimental groups were formed: (1) CADTemp®/SU; (2) CAD-Temp®/AP; (3) CAD-Temp®/XTP; (4) Telio® CAD/SU; (5) Telio® CAD/AP; (6) Telio® CAD/XTP. Shear bond strength and ARI were assessed. On 1 extra block for each PMMA-based material surfaces were roughened with 180-grit sandpaper, simulating a normal/medium-grit (100 mm) diamond bur, and brackets were bonded. Shear bond strengths and ARI scores were compared with those of groups 3, 6.ResultsOn CAD-Temp® significantly higher bracket bond strengths than on Telio® CAD were recorded. With XTP significantly lower levels of adhesion were reached than using SU or AP. Roughening with a coarser bur resulted in a significant increase in adhesion.ConclusionsBracket bonding to CAD/CAM PMMA can be promoted by grinding the substrate with a normal/medium-grit bur or by coating the intact surface with universal adhesives. With appropriate pretreatments, bracket adhesion to CAD/CAM PMMA temporary restorations can be enhanced to clinically satisfactory levels.

Influence of Mechanical Treatment on Consolidation Processes of Ultradisperse Powders of Stabilized Zirconium Oxide

The effect of preliminary machining of ultradisperse powders of stabilized zirconium dioxide and its composite on consolidation in compacts under uniaxial static pressing and subsequent sintering is studied. The investigations were carried out with powders of compositions (in mol %) 97ZrO2–3Y2O3 and 80Al2O3–20(ZrO2–Y), which were obtained by the sol-gel and the plasma-chemical method, respectively. Mechanical processing of powders was carried out in two ways. The first method consisted in preliminary static pressing of powders at elevated pressure of 900 MPa and their subsequent grinding in a ball mill. The second method consisted in grinding the initial powders in an Activator-2SL planetary mill with drums and grinding balls of zirconia. It is established that mechanical treatment significantly affects the density of compacts. In this case, there is no strict correlation between the density of the sintered ceramic and the density of compacts. With increasing density of compacts, their expansion can be observed at the isothermal holding stage, which leads to a decrease in density of the ceramic. It is shown that, in dry grinding to improve the technological properties of ultradisperse powders obtained by the sol-gel and plasma-chemical methods, the most suitable is the method of mechanical treatment, which consists in pre-pressing the powders at elevated pressure and then grinding them in a ball mill.

Influence of Mechanical Treatment on Structural and Morphological Characteristics and Distribution of Valence Electrons of Aluminum, Silicon, Iron and Titanium Oxides

Influence of Mechanical Treatment on Structural and Morphological Characteristics and Distribution of Valence Electrons of Aluminum, Silicon, Iron and Titanium Oxides

Influence of mechanical treatment on thermophysical processes in illitic clay during firing

The influence of mechanical treatment on thermophysical properties of illitic clay was studied during firing using the acoustic emission technique (AE), scanning electron microscopy (SEM), X-ray diffracion analysis (XRD) and thermal analyses (DTA, TGA, DIL). The milling process promotes the formation of agglomerates created from the illite crystals damaged by milling. Due to the newly formed crystal defects, the course of dehydroxylation as well as the high temperature processes were shifted to lower temperatures owing to rising milling time. The AE activity during heating increases with increasing the milling time. Thus, longer milling time contributes to the crack formation during heating. However, during cooling, the low AE activity indicates that the crack formation was suppressed. The density of the samples increases with increasing milling time, thus a denser, more homogeneous microstructure is formed.

Peculiarities of formation of sintered electrodes of the Ti–Ti3P–CaO composition and their application in technology of pulsed electric-discharge machining of titanium

The influence of mechanical treatment on the structure and phase composition of Ti–10%Ca3(PO4)2 powder mixtures is investigated. The Ti–Ti3P–CaO ceramic electrode materials with a high uniformity of components and residual porosity of 5–7% are fabricated according to the pressing and vacuum sintering technology. The erosion ability of the Ti–Ti3P–CaO metal–ceramic electrode under the pulsed electric-discharge machining of titanium substrates is investigated and compared with the TiC0,5–Ti3POx–CaO electrodes fabricated by self-propagating high-temperature synthesis. Coatings fabricated when using Ti–Ti3P–CaO and TiC0,5–Ti3POx–CaO electrodes are characterized by high continuity, thickness up to 20 μm, microhardness up to 3,6 GPa, roughness to 3,3–4,6 μm, and the presence and uniform distribution of calcium and phosphorus bioactive elements.

Influence and mechanism of mechanical grinding on disaggregation of silica white particles in aqueous medium

The method of mechanical grinding in aquatic medium is applied in this paper to find out the influence of mechanical treatment on the disaggregation and dispersion of silica white. The results show that the size of silica white aggregates can be greatly reduced, and the particles also can keep a good dispersion state when dispersant is added. The median diameter (D50) of the silica white particles reduce to 3·80 μm, and D90 reduced to 7·50 μm. The results of SEM observation are consistent with the particle-size analysis results. The calculations show that the strip effect energy work on silica white particles from mill balls is 1·78 × 10–9 J. This number is greater than the effect energy needed in disaggregation which is calculated to be 2·33 × 10−10 J. The stripping of grinding ball could be an important mechanism on the disaggregation of silica white particles.

Influence of mechanical treatments on the properties of cellulose nanofibers isolated from microcrystalline cellulose

The possibility of preparing cellulose whiskers-like materials by mechanical treatment of commercially available microcrystalline cellulose (MCC) was explored. High shear homogenization, grinding with a supermass colloider, and hammer-milling were the processes selected to disintegrate the MCC, which yielded F-MCC, G-MCC and H-MCC, respectively. Processing aqueous dispersions with high solid content allowed for the production of cellulose particles with greatly reduced dimensions. Morphological characterization revealed that homogenization and grinding reduced the particle size more effectively than hammer-milling, although the disintegration was incomplete in all cases. The reinforcing potential of the materials was evaluated against commercially available whiskers by using the various particles as fillers to mechanically reinforce hydroxypropylcellulose. Nanocomposite films containing 5, 10, or 20wt.% of the filler were prepared and the mechanical properties were characterized. The results show that H-MCCs are just slightly better than the original MCC, whereas F-MCC and G-MCC performed similar to whiskers at 10wt.% loading, despite the presence of a fraction of micrometer-sized particles. It is therefore reasonable to envision the use of the more easily produced F-MCC and G-MCC as replacement of cellulose whiskers in some applications.

Influence of Mechanical Treatment on the Structure and Properties of Chitosan Solutions and Films Based on Them

The influence of mechanical treatment in a rotary-pulsed apparatus on the rheological properties, the film-forming capability of chitosan solutions in dilute acetic acid, and the structure and properties of films formed from them was investigated.

Surface treatment and adhesive bonding techniques for repair of high-temperature composite materials

Adhesive bonding of structural aircraft materials depends upon a thorough understanding of factors that affect bond strength and durability. It is well known that surface preparation is critical to adhesive bond performance. However, little information is available regarding the effect of surface preparation procedures on adhesive bonding of high-temperature polyimide composites. Mechanical treatments such as hand sanding are commonly used for composite materials, and in general are known to improve the wettability of the surface as well as effect contaminant removal. Less is known about the influence of mechanical treatments on the surface chemistry. This article discusses the effects of mechanical surface preparation on the adhesive bond strength, durability, and failure mode of several high-temperature polyimide-based composites and adhesives.

The influence of mechanical treatment on the silicate network of talc

The action of mechanical treatment on the silicate network of talc was studied by X-ray diffraction and differential thermal and chemical analysis methods. The formation of “hydroxyl water” was found to occur under the action of mechanical treatment during mineral amorphization. The amount of hydroxyl water predetermined the number of dissociating unsaturated Si-O bonds in talc silicate network Si-O-Si bridges.

Influence of mechanical treatment on the properties of betulin, betulin diacetate, and their mixture with water-soluble polymers

The influence of mechanical treatment on the properties of betulin, betulin diacetate, and their mixture with water-soluble polymers was studied. It was shown that mechanical treatment in a planetary mill-activator disordered the crystalline structure of betulin and betulin diacetate. Composites of betulin with polyvinylpyrrolidone (PVP) and polyethyleneglycol (PEG) that gave an increased betulin concentration upon dissolution in water were prepared. It was shown that H-bonds formed between betulin and PVP upon mechanical activation of their mixtures.

Combined effect of thermal and mechanical activation on the combustion and phase formation laws in the Cr–Si–C system

In this work combustion and phase formation laws for mechanically and thermally activated Cr–Si–C system were studied. For thermal stimulation in the combustion reaction Mg–(–C 2F 4–) n high caloric mixture was used. It was shown that in the system under study, combustion takes place by two sequential stages. The first stage is interaction between Si and (C 2F 4–) n or Mg with (C 2F 4–) n (temperature can rise up to 1200 °C), which are responsible for combustion front propagation. In the first stage, formation of small amount of CrSi 2 takes place. The second stage is Si + C reaction which is responsible for high-temperature combustion. In the second stage, formation of CrSi 2 completes. The influence of mechanical treatment on combustion laws for (Cr–Si) + (Si–C)+(Mg–(C 2F 4) n ) system was investigated. It was shown that mechanical activation (MA) is effective for systems where amount of chromium is high, while for systems where Si–C part is appreciable MA does not have any affect.

Mechanochemical Treatment of Petroleum Residues and their Mixtures with Brown Coal

The influence of mechanical treatment (MT) on the composition, properties and transformations of crude oil devoid of gasoline fractions boiling up to 200°C and petroleum residua > 350°C (mazouts) was studied. It was established that the impact of mechanical energy upon crude oil in the presence of quartz particles almost halves the concentration of n -alkanes in the raw material and leads to formation of lowboiling fractions, hydrogen and hydrocarbon gases. The possibility of producing gasoline and diesel distillates from degasolined oil by means of its mechanochemical treatment is shown. The yields of these distillates increase when the stock is treated in the presence of quartz particles. The degree of destruction of mazouts rises if the raw material was ozonizated, then mixed with 5% of tetraline (H-donor), and finally subjected to mechanical treatment. It was shown that transformations of both coal and mazout components occur during mechanical treatment of mazout/coal mixtures.

Influence of mechanical treatment during curing on some properties of "Dimljena svinjska pecenica"

In this paper the influence of mechanical treatment during the curing on the quality of "Dimljena svinjska pecenica" is investigated. Meat used in this experiment was divided into two groups, control and experimental. Meat of experimental group was mechanically treated after injection of brine in the tumbler. Parameters of meat yield after brining, weight loss after smoking and thermal treatment and chemical and sensory characteristics of final products were investigated. According to the results of examination the final product produced with mechanically treated meat had more desirable sensory characteristics as are the color, juiciness and softness, as well as high amount of water and protein and low percentage of fat.

Estudo termoanalítico de comprimidos revestidos contendo captopril através de termogravimetria (TG) e calorimetria exploratória diferencial (DSC)

No presente trabalho foram desenvolvidos comprimidos de captopril revestidos com hidroxipropilmetilcelulose (HPMC), Opadry®, polivinilpirrolidona (PVP), Eudragit® E e goma laca. Foi realizado estudo termoanalitico do farmaco e das formulacoes atraves de termogravimetria (TG) e calorimetria exploratoria diferencial (DSC). Atraves da analise das curvas DSC verificou-se que nao houve a ocorrencia de interacao entre o farmaco e os excipientes lactose, celulose microcristalina, croscarmelose sodica, Aerosil® e talco, utilizados na formulacao do comprimido. Atraves desta tecnica detectou-se a possibilidade de interacao entre captopril e estearato de magnesio. De acordo com os resultados obtidos atraves de DSC nao foram observadas alteracoes na cristalinidade do farmaco decorrentes dos processos de compressao e revestimento. A termogravimetria foi utilizada para o estudo da cinetica de degradacao do captopril e dos comprimidos. Os parâmetros cineticos foram determinados atraves do metodo de Ozawa. Os resultados demonstraram que nao houve alteracao da estabilidade termica do captopril na forma de comprimido. A formulacao revestida com HPMC foi a que apresentou maior estabilidade termica, quando comparada as demais formulacoes de revestimento.

The Influence of Mechanical Treatment on the Absorption of CO2 by Perovskite Oxides

Perovskite oxides of composition (Sr1-x Ca x )(Fe0.5Co0.5)O3-δ were investigated for CO2 absorption properties and were proved to be useful as materials for CO2 absorption in the temperature range from 550 to 850 °C. The absorption rate of CO2 increased with Ca doping. The mechanical treatment of perovskite oxides for several minutes, especially for the oxides containing a small amount of Ca, was found to be effective for activating the oxides for CO2 absorption and for reducing the starting temperature of CO2 absorption by about 80 °C. However, it was not less effective to treat the oxides for a long time. The site distortion due to Sr and Ca ions at site A and the mixed valence states at site B were confirmed to be effective for CO2 absorption at high temperatures. During the absorption of CO2, a spinel compound was formed according to the following reaction: 2(Sr,Ca)(Fe,Co)O2.5 + CO2 → (Sr,Ca)CO3 + (Sr,Ca)(Fe,Co)2O4.