Mass Loss Of Samples Research Articles

Correlating Hardness and Welding Dilution with the Abrasion Mass Loss of Hardfacings Welded with Different Currents and Polarities

The correlation of hardness, microstructure, and dilution with the abrasion mass loss of hardfaced samples deposited using different currents (500 and 600 A) and polarities (AC and DC+) was studied. Four different welding conditions were considered for submerged arc welding using a martensitic hardfacing electrode and austenitic buffer electrode. Single-layer hardfacing was applied over the single-layer buffer. The microstructure of hardfacing was observed by an optical microscope. The micro-Vickers hardness across a single-layer hardfacing and dilution percentage were also measured. A dry-sand–rubber wheel abrasion test was conducted according to ASTM G65 procedure A to record the abrasive mass loss of the samples. The use of higher current and DC+ polarity resulted in the highest mass loss because of the deepest dilution and lowest hardness. Dilution affects the hardness and microstructure of hardfacing. The lowest abrasive mass loss, shallowest dilution, and highest hardness were obtained for the sample welded with lower current and AC polarity.

Thermogravimetric Analysis Studies of Thermally-treated Glycerol Impregnated Poplar Wood

The effects of glycerol pretreatment and thermal modification on poplar wood was examined using thermogravimetric analysis (TGA). The total mass losses of thermally-treated samples before and after glycerol impregnation were studied. The thermal degradation process was divided into three stages based on natural breaks in the slope of the TGA curves. The set-on and set-off temperatures, mass loss, and activation energy (Ea) of each stage were compared. Pretreatment with 60% glycerol followed by thermal modification at 160 °C produced pronounced differences in the three decomposition stages. Fewer wood components were decomposed in the first stage in glycerol-pretreated wood, which suggested that the pretreatment had modified the wood components into more thermally stable substances. However, the mass losses were higher in the next stage, suggesting that the effect on thermal stability was limited. The Ea values of wood decomposition during the first stage were decreased, while those during the second and third stages were increased. These results illustrate the potential for using a glycerol pretreatment to alter the thermal stability of wood.

Investigation of regularities of pelletized biomass thermal deformations during pyrolysis

Gasification process is a fairly complicated matter and using pelletized biomass for the gasification mostly results in fuel agglomeration. The pelletized biomass moving from the pyrolysis zone to the oxidation zone sticks together in lumps and disrupts entire process. In order to determine the regularities of thermal deformations, experimental research of pelletized biomass thermal deformations during pyrolysis were performed in a horizontal pyrolysis reactor from 300-900?C temperature capturing wood particle, wheat straw and wood pellet radial changes by a digital camera. Also the center temperature and the mass loss of samples were measured to determine cause of biomass thermal deformations. Observed results reveal that when increasing the pyrolysis temperature from 400-900?C, the wheat straw and wood pellets expand at the beginning of pyrolysis process and after it start to shrink, while wood particle is only affected by shrinkage. The swelling effect of pelletized samples starts decreasing over 600-650?C heating temperature and disappears when the temperature is higher than 850?C. Biomass shrinkage intensifies exponentially as the heating temperature increases till 700-750?C. However, the final shrinkage starts to decrease as the heating temperature increases from 700-750 to 900?C due to swelling of formed char. Determined phenomenon of pelletized biomass swelling explains cause of fuel adhesion in pyrolysis zone of gasifier. Besides estimated regularities of biomass thermal deformations upon pyrolysis could be used to improve the existing numerical models of biomass pyrolysis.

Evaluation of cavitation erosion resistance of Al-Si casting alloys: effect of eutectic and intermetallic phases

In the present paper, the influence of eutectic and intermetallic phases on cavitation resistance of Al-Si alloys was studied. In fact, Al-Si alloys are commonly used for the production of components, such as cylinders, pistons, pumps, valves and combustion chambers, which in service may incur in cavitation phenomenon. Samples of AlSi3, AlSi9 and AlSi9CuFe were characterized from the microstructural point of view. Hardness measurements were also performed. Subsequently, cavitation tests were carried out according to ASTM G32 standard and the erosion mechanism was examined by scanning electron microscope. It was found the both eutectic and intermetallic phases enhance cavitation resistance, expressed in terms of mass loss. Particularly, intermetallic particles with complex morphologies provide a positive contribution, exceeding that of other microstructural features, as grain size. The effect of T6 heat treatment was also evaluated. It was confirmed that the precipitation of fine strengthening particles in the Al matrix successfully hinders the movement of dislocations, resulting in a longer incubation stage and a lower mass loss for heat-treated samples in comparison with as-cast ones. Finally, the relationship between cavitation resistance and material hardness was investigated.

Cavitation Fracture of the Typical Materials Used in Hydraulic Machines and Units

The cavitation fracture of AMg6, BrAZh9-4, grade 20 steel, 12Kh18N10T, 20Kh13, and VT1-0 alloys, which are used in hydraulic machines and units, is studied. In tests, the materials are subjected to ultrasonic waves and the sample mass loss and the microhardness are measured. It is shown that new cavitation- resistant materials, which have a sufficient strength and plasticity, should be designed.

The kinetic of mass loss of grades A and B of melted TNT by isothermal and non-isothermal gravimetric methods

Abstract The kinetic and activation energy of mass loss of two grades of melted TNT explosive, grade A and grade B, with freezing points of 80.57 and 78.15 °C, respectively, were studied by isothermal and non-isothermal gravimetric methods. In isothermal method, the mass loss of samples in containers of glass and aluminum was followed in temperatures of 80, 90 and 100 °C. The kinetic of the mass loss of the samples in the aluminum container was higher than the kinetic of it in the glass container that can be related to the effects of heat transfer and catalytic of aluminum metal. Also, the presence of impurities in grade B was due to increasing of kinetic of mass loss of it versus grade A. The non-isothermal curves were obtained in range of 30–330 °C at heating rates of 10, 15 and 20 °C⋅min−1. The TG/DTG data were used for determination of activation energy (Ea) of mass loss of TNT samples upon degradation by using Ozawa, Kissinger, Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) methods as model free methods. The activation energies of grades of A and B of TNT was obtained 99–120 and 66–70 kJ mol−1, respectively. The lower values of activation energy of the degradation reaction of grade B confirm the effect of impurities in the kinetics of mass loss of this grade.

Enzymatic degradation of flax-fibers reinforced polylactide

The present article described a study on the biodegradation rate of polylactide (PLA) with reinforcement of flax fibers. Specifically, enzymatic degradation of the flax-fibers reinforced PLA was addressed with particular attention paid to the processing conditions, the types of enzymes used for degradation, and time of treatments. Mass losses of the samples were measured as a function of time, and the degree of crystallinity was determined using a differential scanning calorimetry (DSC). The morphology of the samples was examined using scanning electron microscopy (SEM). Proteinase K was shown to exert the greatest effects on the degradation rate of all samples tested. For this enzyme, the mass loss of PLA samples without fillers was approximately 21%, but it was about 52% for PLA containing 30% (w/w) flax fiber. The lowest impact on the biodegradation rate of PLA was noted for protease and lipase enzymes tested in this study. Proteinase K also caused the greatest changes in the structure of all samples. Furthermore, samples treated with this enzyme also showed the highest degree of crystallinity as compared with non-treated ones.

Geopolymer with improved thermal stability by incorporating high-magnesium nickel slag

The present study investigates the thermal stability of binary geopolymers prepared with fly ash and high magnesium nickel slag (HMNS). TGA, XRD and SEM techniques are adopted to investigate the chemical composition and microstructure of the binder gel phase exposed to high temperatures. The results show that incorporating HMNS mitigates dehydration induced mass loss and volume shrinkage of the geopolymer samples between room temperature and 250°C, and increases their residual strengths when exposed to high temperatures between 600°C and 800°C. The key role that HMNS substitution of improving the thermal stability of geopolymers is associated with the formation of sodium-alumina(magnesia)-silica hydrate (N-A(M)-S-H) gel phase, which turns to be a less porous microstructure after thermal exposure when compared with the N-A-S-H gel phase, which is formed in the pure fly ash sample. The binary geopolymers exhibit higher residual strengths and better maintaining of volume stability in the range from 250°C to 550°C compared to Portland cements. However, both the geopolymer and Portland cement show severer volume shrinkage after exposure of 600°C, because of the viscous sintering of geopolymer gels and the decomposition of cement hydration products, respectively.

Biological and topochemical studies on the resistance of excavated oak piles (Quercus sp.) from a historical bridge in Bavaria

Abstract Archaeological wood of 13 excavated oak piles from five historical bridge generations in Bavaria, dated from 1447 to 1787, was investigated by means of light microscopy (LM) and cellular UV-microspectrophotometry (UMSP) to study the ageing and natural resistance of the excavated wood. Furthermore, the mineral content of the ancient wood was determined to evaluate the impact of mineral inclusions on microbial resistance, tested using a mini block fungal test. The LM and UMSP analyses revealed well preserved cell wall structures and no significant modification of the lignin composition and distribution in predominant parts of the piles. Slight microbial decay caused by soft rot and erosion bacteria was only detectable at the outermost millimetres of individual piles. The fungal mini block tests yielded mass losses of ancient oak samples between 15% and 30%, independent of their analysed mineral content. The results provided evidence that the fungal resistance of the investigated ancient wood is mainly determined from the special soil with its high mineral content.

Combined impact of 500 keV protons and oxygen plasma on polyimide films

Abstract This paper presents results of experimental investigation of combined impact of 500 keV protons with fluences of 10 15 –10 16 cm −2 and oxygen plasma with fluences of (0.8–3.5) 10 20 cm −2 on polyimide films. Measured UV–vis transmission, Raman and XPS spectra of polyimide specimens before and after combined impact and data on the sample mass losses as a result of erosion due to oxygen plasma exposure are given. On the base of the obtained spectroscopic results, the changes in the polyimide structure caused by the proton and oxygen irradiation are analyzed and discussed.

Evaluation of alternative filter media for particulate matter emission testing of residential wood heating devices

ABSTRACTThe performance of Teflon-coated glass fiber filter media (Pallflex Emfab TX40) is evaluated for particulate matter (PM) sampling of residential wood heating devices in a dilution tunnel. Thirty samples of varying duration and PM loading and concentration were collected from an U.S. Environmental Protection Agency (EPA) Method 28 dilution tunnel using dual Method 5G sample trains with untreated glass fiber and Emfab filters. Filters were weighed soon after the end of sampling and again the next day after equilibration at 35% relative humidity (RH). PM concentrations from both types of filters agreed very well with 1-day equilibration, demonstrating that Emfab filters are appropriate for use in measuring PM from residential wood burning appliances in a dilution tunnel and have performance equal to or better than the glass fiber filter media. Agreement between filter media without equilibration was erratic, with PM from glass fiber filter samples varying from slightly less than the Emfab samples to as much as 2.8 times higher. Some of the glass fiber filters lost substantial mass with equilibration, with the highest percent loss at lower filter mass loadings. Mass loss for Emfab samples was a small percentage of the mass and very consistent across the range of mass loadings. Taken together, these results may indicate water uptake on the glass fiber media that is readily removed with 1-day equilibration at moderate RH conditions.Implications: EPA regulations now allow the use of either glass fiber or Teflon filter media for wood appliance PM emission testing. Teflon filter media minimizes the potential for acid-gas PM artifacts on glass fiber filters; this is important as EPA moves toward the use of locally sourced cordwood for testing that may have higher sulfur content. This work demonstrates that the use of Teflon-coated glass fiber filters can give similar PM measurement results to glass fiber filters after 1 day of equilibration. With no equilibration, measured PM from glass fiber filters was usually higher than from Teflon-coated glass fiber filters.

Comparative analysis of methods for increasing the biostability of collagen films

Most often, glutaraldehyde (GA) is used to increase the biostability of biological materials intended for the manufacture of implantable products or matrices for tissue-engineered constructs. However, this method has a number of side effects, including the manifestation of cytotoxicity of the final product, necessitating the search for new technological solutions. The original scleral collagen (SC) films of farm animals were obtained by the method of irrigation (sample thickness of ~150 μm), followed by drying at 370°C to a constant weight in the air. For the first group of samples, dehydrothermal treatment of SC films was carried out at a residual pressure of 10–20 mmHg and 120°C. Samples of the second group were stabilized by UV cross-linking—processing the surface with a Philips CLEO Compact lamp (16 W, 254 nm, distance from lamp to sample of 3 cm). Treatment of the SC films of third group was conducted in GA vapor at room temperature for the selected time interval (from 30 min to 18 h). The fourth group consisted of SC samples stabilized by the traditional method of cross-linking of biological tissues: treatment of aqueous 25% solution of GA with the final concentration in collagen solution from 0.0005% to 1.0% (processing time was 24 h at room temperature). The biodegradation of the samples was assessed using accelerated tests in phosphate buffer (pH 7.4, 37°C, 1 h) containing collagenase at the rate of 1 unit of enzyme per 1 mg of dry sample; the reaction was terminated after 1 h by lowering the temperature to 4°C. The films of SC (mass loss 66 ± 9%) were used as the control during the search for an optimal method of cross-linking. UV irradiation treatment weakly affected the biodegradation of the SC samples (mass loss of 55 ± 5%). The dehydrothermal treatment resulted in a linear decrease in biodegradation with increasing time of incubation, and after 18 h of treatment, the mass loss of the SC samples was practically absent. It was found that the reduction of the GA concentration in the SC solution from 1.0 to 0.001% led to a significant reduction in mass loss of samples from 20 ± 3% to 5 ± 1%. Cross-linking of the samples of SC in GA vapor also led to an increase in biostability of SC films (mass loss absent after 18 h of treatment). From four methods of SC films treatment investigated, the optimal from the point of view of increasing the biostability of collagen- based materials are dehydrothermal treatment and cross-linking by glutaraldehyde vapor.

Modelling and experimental investigation of waste tyre pyrolysis process in a laboratory reactor

Abstract A mathematical model of waste tyre pyrolysis process is developed in this work. Tyre material decomposition based on a simplified reaction mechanism leads to main product lumps: noncondensable (gas), condensable (pyrolytic oil) and solid (char). The model takes into account kinetics of heat and mass transfer in the grain of the shredded rubber material as well as surrounding gas phase. The main reaction routes were modelled as the pseudo-first order reactions with a rate constant calculated from the Arrhenius type equation using literature values of activation energy determined for main tyre constituents based on TG/DTG measurements and tuned pre-exponential parameter values obtained by fitting theoretical predictions to the experimental results obtained in our laboratory reactor. The model was implemented within the CFD software (ANSYS Fluent). The results of numerical simulation of the pyrolysis process revealed non-uniformity of sample’s porosity and temperature. The simulation predictions were in satisfactory agreement with the experimentally measured mass loss of the tyre sample during pyrolysis process investigated in a laboratory reactor.

Effect of Handling, Packing and Transportation on the Moisture of Timber Wood

In order to improve the efficiency of moisture meters calibrations, we studied the effect of ambient humidity, sample handling, packing and transportation on the timber wood (spruce) moisture determination. It was proved by experiments that dry timber samples ( $$12 \times 12 \times 2.5$$ cm) reach equilibrium within 30–40 days even when moisturizing them at a high relative air humidity (80 %). On the other hand, the major mass loss of moist samples placed at normal laboratory conditions was found to occur during the first few days while the first 5 days are critical. The effects of sample handling, packing and transportation were studied by means of interlaboratory comparison between CMI, CETIAT, INRIM, NIS and KRISS. The obtained results show that samples with moisture content less than 7 % tend to absorb small amount of water, whereas samples with moisture content larger than 15 % tend to desorb small amount of water during the handling and transporting even when using vacuum packing and short handling times.

Selection of Oxidation Catalyst in a Fluidized-Bed Reactor

Oxidation catalysts, e.g., those for biomass combustion in a fluidized bed (olivine sand and catalyst ShchKZ-1), were compared. Samples consisting of straw powder, straw powder and uncalcined olivine sand, straw powder and calcined olivine sand, and straw powder and crushed catalyst ShchKZ-1 were prepared. The calcined olivine sand and catalyst ShchKZ-1 had practically the same influence on the sample mass loss and heat generation from the straw by heating.

Effect of Temperature and Acidity of Sulfuric Acid on Concrete Properties

Concrete corrosion caused by sulphuric acid attack is a known phenomenon in sewer systems, resulting in significant economic losses and environmental problems. However, there is a scarcity of reported laboratory simulations and experimental work investigating the contributing factors controlling the corrosion. In this EPSRC (Engineering and Physical Sciences Research Council, UK) funded investigation the effect of temperature and the acidity of sulphuric acid solution on concrete specimens extracted from brand new concrete sewers has been investigated. In this investigation the concrete samples are submerged in three sulphuric acid solutions (pH = 0.5, 1 and 2) for 91 days under different temperatures (10oC, 20oC and 30oC). Mass loss and compressive strength of the concrete specimens were tested and recorded at 7, 14, 28, 42, 56 and 91 days providing interesting data for visualising the changes taking place in the concrete samples (change in properties) during the time of immersion. The results revealed that samples overall mass increased at the early stages of the corrosion process. It also was observed that the overall mass of the samples decreased significantly at the later stages of the testing process with respect to the acidity of the solutions used. Although the change in temperature did not have a significant effect on the compressive strength of the tested samples, rise in temperature however, had considerable effect on the mass loss of the concrete samples which were immersed in the most aggressive solution (i.e., pH=0.5 and temperature = 30oC) at 91 days. This research clearly demonstrated a high correlation between the acidity of the solution and the rate of corrosion with respect to time.

Wear Properties of ECAP-Processed AM80 Magnesium Alloy

AM80 magnesium alloy was subjected to equal-channel angular pressing (ECAP), and microstructural evolution was studied using scanning electron microscope (SEM). Grain size was found to decrease up to 3 µm after four passes. An increase in number of ECAP passes led to a corresponding increase in hardness of the processed samples. Unprocessed and ECAP-processed samples were subjected to wear test using pin-on-disk wear test machine to study the wear behavior. Effects of varying loads (30 and 40 N) with sliding distances (2500 and 5000 m) were studied. The results showed reduction in wear mass loss for the ECAP-processed samples in comparison with unprocessed condition. Coefficient of friction (COF) was studied for different loads, and improvement in COF values was observed for ECAP-processed samples compared to unprocessed condition. Worn surfaces were studied using SEM and energy-dispersive x-ray spectrometer, and they exhibited plastic deformation, delamination, plowing, wear debris and oxidation in the sliding direction. X-ray diffraction analysis was conducted on the worn surfaces to identify the phases. It revealed the presence of magnesium oxide and magnesium aluminum oxide which led to oxidation wear in the sliding direction. Wear mechanism was found to be abrasive and oxidation wear.

Corrosion behavior of Ni-based alloys in molten NaCl-CaCl2-MgCl2 eutectic salt for concentrating solar power

In this work, the corrosion behavior of Ni-based alloys including Inconel 625(In625), Hastelloy X(H X) and Hastelloy B-3(H B-3) alloys were investigated in a molten salt NaCl-CaCl2-MgCl2 by gravimetric methods. The corrosion test was conducted at 600°C for a maximum immersion time of 3 weeks. The corrosion behavior was determined by measuring the mass loss of samples at different time intervals. The corrosion products and morphology were investigated in detail via X-ray diffraction (XRD) and scanning electron microscope (SEM). The microscopic area element analysis in corrosion surface and the mapping diagram of element distribution from corrosion profile were carried out by energy dispersive spectroscopy (EDS). The results show that In625 alloy resists corrosion better than H X and H B-3 alloys in molten salt NaCl-CaCl2-MgCl2 in the presence of air. The corrosion profile in In625 and H X alloy show a poor Cr zone in the inner corrosion layer, probably caused through the outward diffusion of CrCl4(g) which is forecasted the formation by thermodynamic calculation. MgCr2O4 attached to the In625 and H X alloys specimens surface formed a compact protective layer and thus resist corrosion well. Thin and uniform corrosion layer was observed from profile in H B-3 alloy after immersed in NaCl-CaCl2-MgCl2 molten salt when air was present, however there is not a poor Cr zone in corrosion profile of H B-3 alloy. From above, the corrosion rate of Ni and Mo in alloy dominates the corrosion rate. Certain amount of Cr in the nickel-based alloys enhanced its corrosion resistance in molten salt NaCl-CaCl2-MgCl2, even if Ni and Mo in nickel-based alloys shows more stable performance in the corrosion test in chloride molten salt.

Cylindrical shockwave-induced compression mechanism in femtosecond laser Bessel pulse micro-drilling of PMMA

Femtosecond (fs) laser Bessel pulses can be employed for high-quality and high-speed fabrication of high-aspect-ratio uniform microhole arrays. This technique exhibits prominent potential in three-dimensional packaging, fluidic devices, fiber sensing, biomedical devices, and aeronautics. However, the fundamental mechanisms remain mysterious. Using the femtosecond time-resolved pump-probe shadowgraph technique, this study revealed that the generation of cylindrical shockwaves inside the bulk material and the corresponding compression mechanism play key roles in the formation of high-aspect-ratio microholes. The phenomena were observed in all experiments of Bessel beam drilling of polymethyl methacrylate. In the aforementioned cases, the compression mechanism was confirmed by measuring sample mass losses that were experimentally determined to be negligible. By contrast, neither cylindrical shockwave nor compression mechanism was observed when a fused silica or Gaussian laser beam was involved.

Critical heat flux and mass loss rate for extinction of flaming combustion of timber

The critical mass loss rate and critical heat flux for self-extinction of flaming combustion during steady-state burning of timber was measured in this study for a range of timber species. A vertical mass loss calorimeter was used to provide the external heat flux and to measure the mass loss of the timber samples. The results showed that the critical mass loss rate was dependent upon the timber species but did not show a clear dependency with the timber density. Critical mass loss rates and heat fluxes for self-extinction exist for each of the timber species tested for both the solid timber and cross laminated timber (CLT). Debonding of both the char layer and the individual lamella of the CLT caused increased mass loss rates, re-ignition after self-extinction and increased flame lengths. Both char and ply fall-off were observed.