Variation Of Sample Mass Research Articles

Characterization of the ozone effect on a scraped off fouling sample

Fouling deposition on combustion system elements is a problem of interest to the industry. This experimental work analyzes the degradation of fouling using ozone as oxidizing agent. Two independent test benches were used for the experiments, a fouling test bench and an ozone test bench. The fouling generation tests are performed under controlled conditions to obtain characterized fouling. The ozone tests performed are divided into three groups: pre-tests, A-tests and B-tests. The pre-tests were used to determine the effect of different variables affecting the oxidation process. The A, B-tests were performed to characterize the oxidation process under different scenarios. During the ozone treatment tests, flow rate, ozone concentration, temperature and duration of the test were controlled to obtain the fouling mass loss measurement. Finally, an analytical expression was obtained that characterizes the sample mass variation as a function of the input variables, maximizing the reaction between the fouling and ozone.

Thermal Analysis by Means of Differential Scanning Calorimetry of the Characteristic Thermodynamic Temperatures of a Cu-Zr-Al Bulk Metallic Glass

In this study a Cu43Zr48Al9 bulk metallic glass prepared by the copper mold casting method is considered. In recent years, Cu-Zr-Al systems like this have enjoyed widespread attention due to their high strength, high hardness, high corrosion resistance and low cost. Here samples of this substance are studied using DSC (Differential scanning calorimetry) to determine the effect of different test conditions (heating rate, sample mass, sample specific surface area and sample crystal phase) on the characteristic thermodynamic temperature of the bulk metallic glass. Experimental results show that almost all of the five characteristic thermodynamic temperatures (Tg, Tx, Tp, Tm, Tl) of this substance have higher values when the heating rate is increased. The influence of the variation of sample mass, sample specific surface area and sample crystal phase on the amorphous alloy characteristic temperature is very weak. lower the heating rate, the more developed the crystalline phase in the amorphous alloy will be.

Composite bond strength improvement with thermal vibration: an experimental non-randomised study

Background. Secondary caries formation is a relevant issue due to poor long-term quality of composite fillings, with inherent subsequent chipping and cracking of the material. We developed a method to improve physical, mechanical and chemical properties of available composites based on thermal vibration imposed on unpolymerised composite in the formed tooth cavity directly prior to polymerisation.Objectives. Effect assessment of thermal vibration exposure on bond strength in composite restorative polymer matrix in various composite brands.Methods. The study used synchronous thermal analysis, including differential scanning calorimetry and thermogravimetry, to estimate and register thermal effects of physical and chemical processes within a temperature programme, as well as determine gaseous release, air contact and decomposition-related sample mass variation, thermal stability, reaction kinetics, polymer and inorganic filler component chemical composition, humidity and softening degree. The study covered 90 specimens 30 mg each prepared of three different composites.Results. Synchronous thermal analysis revealed a statistically significant increase in polymer matrix bond strength in the composites Estelite Sigma Quick (Tokuyama Dental), Filtek Bulk Fill Posterior Restorative (3M Espe) and DentLight (VladMiVa) after thermal vibration exposure vs. classical polymerisation of same composites (p < 0.0001). The bond strength increased by 17.00, 22.51 and 11.31%, respectively.Conclusion. The developed exposure method for altering the composite filling physical and chemical properties has been shown advantageous in a laboratory setting. Thermal vibration-pretreated composite fillings had a higher polymer matrix bond strength vs. same composites polymerised under standard conditions.The pretreatment improves composite filling quality via directly affecting the material physical and mechanical properties of hardness and bending strength.

Thermodynamics, kinetics, gas emissions and artificial neural network modeling of co-pyrolysis of sewage sludge and peanut shell

The co-pyrolysis characteristics of sewage sludge (SS) and peanut shell (PS) under nitrogen atmosphere were studied by thermogravimetric – Fourier transform infrared spectrometry (TG-FTIR) and artificial neural network (ANN). The proportion of PS in the experimental samples is 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100%. The experiments were performed at three heating rates of 5 °C/min, 7 °C/min and 10 °C/min. The variation of sample mass with temperature and gas emission were detected in this paper. SS and PS in the co-pyrolysis experiment have a synergistic effect in terms of mass loss at 335 °C ∼ 500 °C. Gases generated by pyrolysis of the mixture of SS and PS include H2O, CH4, CO2, CO, phenol and NH3. The functional groups detected in the experiment include CO and C O. Apparent activation energy E was obtained by two non-isothermal kinetic analysis methods (Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose). The artificial neural network method was used to predict the relationship between the mass loss of pyrolysis experiments and the change of temperature. The best ANN model (ANN21) for predicting SS and PS pyrolysis was identified.

Study of physical and chemical properties of coal concentration wastes with a purpose of their utilization as secondary raw materilal

Involvement of production wastes into the economy turnover, in particular flotation wastes at coal concentration is an actual task. OJSC “MMK-Ugol” flotation wastes studied aimed at their utilization in facilities for burning high-ash coals, as well as utilization as thinning and combustible additive to clay burden for production of ceramic bricks. In the course of thermo-analytical study by applying the STA 449 NETZSCH synchronous thermal analyzer in a dynamic mode with a heating speed of 10 oC/min in an airflow 30 sm 3 /min within the temperature interval 30–1000 oC, the lowest combustion heat of the carbon-bearing material determined. Besides, the following parameters were determined: mass variation during calcination, variation and speed of the sample mass variation, the process heat effect, the temperature of the beginning, end and maximum progress of thermal effects. It was determined, that the biggest mass loss was observed within the temperature range of 450–600° С , that makes 65–67% of the whole mass of organic share of the coal. The maximum speed of combustion corresponds to the temperature 540–563° С . The lowest combustion heat of the wastes under study was 15.9 MJ/kg. Based on results of the thermo-analytical study, technical analysis and heat-engineering calculations, a possibility of flotation wastes utilization justified. The wastes should be used in the mixture up to 20% with a regular coal as a raw material in the furnaces of low temperature boiling bedchamber for coal concentrate drying. Analysis of flotation wastes chemistry showed, that they have high specific surface (56.8×10 3 m 2 /kg), high dispersion, soaking ability, swelling ability and due to considerable clay substance content they are a plastic material. It enables to use them as a fuel-bearing and thinning additive into the clay burden for production of ceramic bricks. Optimal amount of thinning and combustible additive to clay burden for production of ceramic bricks by semi-dry method determined, application of which after more uniform sintering will result in improving strength indices of the bricks (up to 30–40%), energy saving (up to 30%). Besides, it will exclude necessity to add black coal to the burden and increase productivity of sintering furnaces.

Assessment of influence of disperse filler polarity on structure and water absorption of epoxy compositions

Introduction. Composite materials on the basis of epoxy resin find wide application as adhesives, coatings and structural materials whose properties it is possible to regulate by introduction of various additives including disperse fillers in the epoxy binder. Positively influencing properties of epoxy materials, the disperse fillers can reduce water resistance of the materials. This work is aimed at studying of influence of polar and nonpolar disperse fillers on structure and water absorption of the epoxy materials. Materials and methods. When obtaining composite materials, the following components were used: ED-20 epoxy resin (state standard GOST 10587-84), dibutylphthalate (state standard GOST 8728-88) plasticizer, polyethylenepolyamine (specification TU 2413-357-00203447-99) hardener, marshallite (state standard GOST 9077-82) and graphite (state standard GOST 17022-81) disperse fillers. The structure of samples was investigated by means of IR-spectroscopy method. Water absorption was determined in boiling water using the standard gravimetric method (state standard GOST 4650-2014 (ISO 62:2008)) and evaluated by sample mass variation within 120 days. Results. As a result of the conducted researches, the optimum content of the marshallite and graphite fillers in epoxy materials is established. When mass filler-to-binder ratio is equal to 15/85, water absorption of the materials is minimum. The IR-spectroscopy method showed that introduction of the marshallite polar filler in the epoxy binder promotes ordering of material structure due to formation of hydrogen bond between reactive groups of the filler and resin. Localizing in amorphous areas, particles of the graphite nonpolar filler lead to weakening of the hydrogen-bond system. Interaction of marshallite-filled samples with water is accomplished at the swelling mode, with equilibrium degree of swelling about 1 %. The mechanism of interaction of graphite-filled samples with water includes the alternating stages of dissolution and swelling, which are more expressed as compared with check samples. Conclusions. Water resistance of epoxy materials filled with disperse fillers is defined by a microstructure of the cured resin. Introduction of the marshallite polar filler in the epoxy binder leads to ordering of material structure that results in increasing of water absorption. Introduction of the graphite nonpolar filler in the epoxy binder leads to disordering of material structure that results in reducing of water absorption. Lower value of water absorption of graphite-filled epoxy material is connected with partial dissolution of the sample. Using nonpolar fillers is inexpedient for epoxy materials contacting with water.

A robust control approach for high-speed nanopositioning applications

In this paper, a robust controller for the positioning of a piezoelectric tube scanner (PTS) used in an atomic force microscope (AFM) is proposed. A minimax linear quadratic Gaussian (LQG) controller is designed based on an uncertain system model which is constructed by measuring modeling error between the measured and model frequency response. This controller is robust against uncertainties introduced as a result of spillover dynamics of the scanner at frequencies higher than the first resonance frequency (900 Hz) of the scanner and the variation of plant transfer function due to temperature, humidity, and duration of operation. The proposed controller is applied to the PTS in the AFM used in the experiments to evaluate the performance of the proposed method. It is observed that the proposed scheme provides up to 12 dB closed-loop damping of the resonant mode to track the reference triangular signal. The robust performance of the proposed controller has been investigated for 0–1.96 g sample mass variation. A high positioning accuracy up to 125 Hz frequency is achieved by reducing scanner's vibration and tracking error. Higher-quality imaging up to 125 Hz scanning frequency is achieved compared to the existing PI controller and some other existing methods. This control technique may be applied to control vibration for the systems with changing frequency response due to uncertainties, such as vibration control of disc-drive system.

Acrylic bone cement and starch: Botanical variety impact on curing parameters and degradability

Acrylic bone cements are a conventional solution to heal bone defects. Starch is often added to the cement to improve its degradability and resorbability. The most used botanical variety is corn starch; few studies or applications deal with other varieties. This study focuses on classical formulations based on 2-hydroxyethylmethacrylate but incorporating different starches: waxy maize, corn, amylo maize, wheat, pea or potato, with or without enzyme (α-amylase).A thermocouple is used to determine the curing parameters: setting time and maximal temperature. The water uptake depends on the cement immersion time in a biological fluid and it is studied through sample mass variation analysis. The weight loss is determined after immersion (function of the time) and drying.Starch botanical variety and enzyme presence do not impact curing parameters and water uptake but strongly influence degradability. Water uptake involves advantageous swelling in situ filling the defect. This study shows that starch accessibility by the enzyme explains this impact. Grain spatial configuration, specific surface area and starch distribution in cement give a complementary explanation of the well-known influence of the ratio amylopectin/amylose. Acrylic cements incorporating starch can be classified according to their degradability.

Study on Critical Moisture Content of Unsaturated Evaporation

Thin layer evaporation tests of three types of soil were conducted by a newly designed humidity-controllable evaporation and penetration measuring system and lasted for 8 days. The whole process of sample mass variation from wet to dry was recorded in the laboratory. The critical moisture content and air-dried moisture content were obtained from evaporation curve, which divided the evaporation process of thin layer unsaturated soil into three stages, including stable rate stage, reducing rate stage and residual stage. The soil water characteristic curves of soils were predicted by Arya and Paris model, the results showed that the critical moisture contents of evaporation process were the same with the water contents corresponding to residue values of SWCC, it is significant to studying on unsaturated evaporation process.

Crosslinking of PET through solid state functionalization with alkoxysilane derivatives

A new way for crosslinking poly(ethylene terephthalate) (PET) films and fibers is described using solid state functionalization of the PET end groups (alcohol and acid) with two reagents, respectively, 3-isocyanatopropyltriethoxysilane (IPTESI) or/and 3-glycidoxypropyltrimethoxysilane (GOPTMSI). This functionalization is then followed by hydrolysis–condensation reactions of PET–alkoxysilane end groups leading to the PET crosslinking. First of all, the functionalization reactions were investigated on model compounds by 1H NMR spectroscopy in a range of temperature 80–160 °C. Furthermore, the diffusion of reagents in solid PET, depending on the initial degree of PET crystallinity, was characterized in the same temperature range through the variation of sample mass. On the other hand, this method allowed us to determine the diffusion coefficients and the solubility of the reagents in solid PET at different temperatures and initial crystallinity degrees. End groups functionalized PET films and fibers by alkoxysilane were then crosslinked by immersion of the samples in hot water. The crosslinking density was characterized by measuring the insoluble fraction of PET in good solvent constituted by a mixture of trifluoroacetic acid and dichloromethane (50/50 vol.). An insoluble fraction close to 70% was obtained by the functionalization treatment of amorphous PET film (8% crystallinity) by a mixture of GOPTMSI + IPTESI (50/50 M) at 155 °C for 1 h followed by hydrolysis–condensation reactions at 80 °C for 72 h. Thermomechanical and thermal properties of films and fibers were observed and found to be considerably enhanced in comparison to the untreated samples. The tensile properties of these partially crosslinked samples were maintained up to 320 °C.

Heterogeneous Reactivity of Gaseous Nitric Acid on Al2O3, CaCO3, and Atmospheric Dust Samples: A Knudsen Cell Study

The heterogeneous reaction between HNO3 and various authentic and synthetic mineral dust/mineral oxide surfaces has been investigated using a low-pressure Knudsen reactor operating at 298 K. The surfaces used were Saharan dust from Cape Verde, Arizona dust, CaCO3, and Al2O3. In all cases, a large irreversible uptake was observed. An uptake coefficient of γ = (11 ± 3) × 10-2 was determined for Saharan dust, and γ = (6 ± 1.5) × 10-2 was obtained for Arizona dust. The uptake coefficients for HNO3 on heated CaCO3 and on unheated CaCO3 are given by γ = (10 ± 2.5) × 10-2 and (18 ± 4.5) × 10-2, respectively, and are in good agreement with previous results. CO2 and H2O were formed as gas-phase products. Measurements of the uptake coefficient of HNO3 on grain-size selected samples of Al2O3, γ = (13 ± 3.3) × 10-2, and systematic variation of sample mass enabled us to show that the geometrical surface area of the dust sample is appropriate for calculation of uptake coefficients in these experiments. The high reactiv...

Effect of simultaneous variation of sample mass and heating rate on the mechanism of dehydration of zinc oxalate dihydrate

The mechanism of the single-step dehydration of ZnC 2O 4· 2H 2O has been established from TG, DTA and DSC studies. The rate-controlling process for the reaction is random nucleation with the formation of one nucleus on each particle. The kinetic parameters are calculated from mechanistic as well as non-mechanistic kinetic equations. For the dehydration reaction, the activation energy and the pre-exponential factor show a systematic decrease with the simultaneous increase in sample mass and heating rate, whereas the mechanism of the process remains unaffected by these variations.

The effect of the simultaneous variation of sample mass and heating rate in DTA and DSC

Quantitative correlations between kinetic parameters (energy of activation, E), procedural factors (sample mass, m, and heating rate, φ) and the dependent variables (the temperature of inception of reaction, T i, and temperature T α at which a constant fraction α has decomposed) have been derived for differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The relations have the same form as those derived from earlier TG studies. The dependent variables T i and T α are related to m, φ and E by the equations ▪ where C 3 and C 2 are constants, and ▪ where C 4 and C 5 are constants for a given α. The variation of C 5 with α is given by C 5 = a + b α where a and b are constants. The equations are applicable to TG, DTA and DSC.