Carbon Dioxide Environment Research Articles

Tribological performance of PTFE-based coatings for air-conditioning compressors

Research on coatings in environments simulating compressor conditions, especially in a carbon dioxide (CO 2) environment, has been limited. In this study, polymeric, PTFE-based coatings were investigated for use in air-conditioning compressors. Tribological experiments were performed to simulate piston-type compressors as well as swash plate compressors. Specifically, the tribological contact at the connecting “rod-wrist” pin interface of a piston-type compressor and the “shoe-disk” interface of a swash plate compressor were simulated. Machined 52100 steel wrist pins from a piston-type compressor and 52100 rounded steel pins, referred to as shoes, from a swash plate compressor were used. In both cases the counterparts were gray cast iron disks coated with three commercially available PTFE-based coatings, namely, DuPont® 958-303, DuPont® 958-414 and Whitford Xylan® 1052. These coatings were tested in CO 2 environment, while testing was also performed in ambient air, and R410a, a common hydrofluorocarbon refrigerant, and the results were compared with a diamond-like-carbon (DLC) coating. The PTFE-based coatings showed low friction characteristics and high load carrying capacity and it was found that unlike the DLC coating they were not greatly affected by the testing environment. There was a significant increase in wear of the coatings under high contact pressures, however, it was shown that the wear debris generated acted as a third-body lubricant with a beneficial role in the overall wear performance. Due to their excellent tribological behavior under a range of experimental conditions, the coatings tested in this work could find use in compressor systems and other engineering applications.

Characteristics of CO2 corrosion scale formed on P110 steel in simulant solution with saturated CO2

AbstractThe SEM, X‐ray diffraction (XRD), and XPS were employed to systematically characterize the component and microstructure of the corrosion scale formed on P110 steel exposed to carbon dioxide (CO2) environment. A loose and porous microstructure in corrosion scale was observed under turbulent flow condition for 120 h at 100 °C with a carbon dioxide partial pressure of 4 MPa in which the principal component was iron carbonate (FeCO3), whereas at 160 °C the corrosion scale was composed mainly of FeCO3 and a little amount of FeO(OH). In addition, complex carbonate (Mg,Fe)CO3 was produced because some Fe positions in FeCO3 lattice were substituted by Mg. It showed that a double‐layer structure of corrosion scale was observed at 160 °C compared with the result at 100 °C. Copyright © 2008 John Wiley & Sons, Ltd.

Strength and durability of high-volume fly ash concrete

The effects of replacing 10, 40 or 60% of the cement content by low-calcium fly ash on the compressive strength and durability of the concrete were investigated. An appropriate amount of (super)plasticiser was added to the mix to obtain good workability. At an early age the compressive strength decreases with increasing level of cement replacement. After 28 days the compressive strength increased relatively more for high-volume fly ash concrete than for the control concrete. Concrete with fly ash performed better in lactic/acetic and sulphuric acid during accelerated experiments. The chloride diffusion coefficients resulting from accelerated chloride migration tests were significantly lower for concrete with fly ash than for the control concrete, except for the mixture with 60% replacement of the cement content. The resistance to frost/thaw cycles was similar for all concrete mixtures. The carbonation depth after 9 weeks in a 10% carbon dioxide (CO2) environment increased with increasing fly ash content. High volumes of fly ash also decreased significantly the resistance against the combined action of frost and de-icing salts (3% sodium chloride (NaCl) solution). From these results it can be concluded that high-volume fly ash concrete has a potential for commercial use in particular applications.

Effect of cigarette smoke exposure on the growth of Streptococcus mutans and Streptococcus sanguis: An in vitro study

The aim of the present study was to determine the effect of cigarette smoke on the growth of Streptococcus mutans and Streptococcus sanguis. The standard strains of S. mutans (ATCC 25175) and S. sanguis (ATCC 10556) were cultured on blood agar and incubated for 48 hr in three main environments: atmospheric air, carbon dioxide, and cigarette smoke. Kent gold 1(nicotine: 0.1 mg, tar: 1 mg), Kent lights (nicotine: 0.8 mg, tar: 9 mg) and Bahman (nicotine: 1 mg, tar: 13 mg) were the brands used in the present study. Afterwards, digital photographs of the colonies were taken and the diameter of colonies was measured. Data were analyzed using Post Hoc and General Linear Model statistical tests. Cigarette smoke and carbon dioxide environments significantly increased the growth of S. mutans. However, high nicotine/tar content cigarette smoke (Bahman) had the greatest impact on S. mutans and S. sanguis. The mutans/sanguis ratio, which was 0.71 in atmospheric air, increased to 1.07 in the presence of carbon dioxide. Kent gold 1, Kent lights, and Bahman demonstrated a mutans/sanguis ratio of 1, 0.84, and 0.98 respectively. In conclusion, it seems that the growth of S. sanguis and S. mutans is accelerated in the vicinity of cigarette smoke.

Glucose oxidase immobilization by polyurethane film/foam in dense CO 2 environment

Glucose oxidase (GOX) is immobilized by two different polymer matrices (polyurethane (PU) film and foam) in supercritical carbon dioxide (scCO 2) environment for an envisioned application in biosensor preparations. Effects of immobilization temperature (25–50 °C), pressure (0.1–15 MPa) and immobilization time (4–72 h) on the GOX activity of immobilized PU samples are studied. The interactions between PU and CO 2 are also experimentally investigated. Maximum surface area enlargements during foaming between 12 and 250% of the original for PU films and almost no swelling/foaming (0.3–4.4% of original) are observed for PU foams. The swelling/foaming characteristics of PU films are positively correlated with the observed pressure effect on GOX immobilized sample activities. Immobilized sample activities are found to be inversely proportional to the immobilization temperature. Activities obtained for samples prepared at 8, 15 and especially at 10 MPa are 52, 74 and 165%, respectively, greater than the highest value obtained for samples immobilized without using the supercritical CO 2 process.

Contact Angle of Water on Polystyrene Thin Films: Effects of CO2 Environment and Film Thickness

We examine the contact angle of water droplets on polystyrene (PS) thin films of varying thicknesses supported by silicon wafers under both air and pressurized carbon dioxide (CO2) environments. At 23 degrees C, the contact angle is found to increase upon increasing CO2 pressure in the vapor regime and then levels off in the liquid CO2 regime. A macroscopic model based on Young's equation and the geometric-mean method for interfacial tensions, and long-range van der Waals interactions, correctly predicts the trends and the magnitude of the contact angle dependence on pressure, although deviations occur at high CO2 activities. The contact angle was also found to depend on film thickness, h, when h was comparable to or smaller than 50 nm. Specifically, the contact angle decreases with decreasing PS film thickness. This behavior could be accounted for with the use of a model that incorporates the effects of film thickness, CO2 pressure, and the long-range van der Waals potential.

Effect of carbon dioxide on chloride penetration and chloride ion diffusion coefficient of blended Portland cement mortar

This paper presents a study of the effects of carbon dioxide on chloride penetration and chloride ion diffusion coefficient of blended Portland cement mortar containing ground palm oil fuel ash (POA), ground rice husk ash (RHA) and classified fly ash (fine fly ash, FA). Ordinary Portland cement (OPC) is partially replaced with pozzolan and blends of pozzolans. Mortars with constant water to cement ratio and similar flow were used for the tests. This research used accelerated testing environment with 5% CO 2. Rapid chloride penetration test (RCPT), modified rapid migration test (MRMT) and chloride penetration depth after 30 days of immersion in 3% NaCl solution of mortars were determined on the mortars with and without exposure to carbon dioxide environment. For OPC mortar, the exposure to carbon dioxide environment does not lower the chloride penetration resistance of mortar as measured by RCPT, MRMT and NaCl immersion test. However, the exposure to carbon dioxide significantly decreases the chloride penetration resistance of mortar containing pozzolans. This decrease is related to the replacement level of pozzolans.

Laboratory Assessment of Altered Atmospheric Carbon Dioxide on Filamentous Green Algae Phenolic Content and Caddisfly Growth and Survival

ABSTRACT To test global change effects on lentic ecosystems, we examined I) if algae phenolic content was influenced by CO2 treatments, and 2) if algivores fed CO2-treated algae were impacted. Four common Chlorophytes (Cladophora glomerata, Spirogyra grevilleana, Ulothrix, fimbriata, and Zygnema sp.) were grown under three atmospheric carbon dioxide environments (200, 360, and 3000 mg/L). Algivore (the microcaddisfly Hydroptila waubesiana [Trichoptera: Hydroptilidae]) feeding assays, using identically treated algae (C. glomarata and U. fimbriata) as a food source, were run in parallel. Generally, Folin-Denis reactive phenolics were highest among algae grown under high CO2 treatments, intermediate at ambient CO2, and lowest under low CO2 treatment. Differential species responses in reactive phenolics were observed, with U. fimbriata being most responsive (∼6 %) to CO2 enrichment, and C. glomarata being unresponsive (<1%). Regardless of algal species or CO2 treatment, developmental rates of H. wauhesiana larvae to mid and late instars were statistically identical. Percent survival for larvae given U. fimbriata and C. glomerata were similar; however, survival rates were higher when larvae were fed low CO2 treated U. fimbriata. For larvae fed C. glomerata, the general trend was that larvae fed algae grown at high CO2 levels had the greatest head capsule width; those fed algae at low CO2 levels had the greatest head capsule length and pronotal length. In contrast, larvae fed U. fimbriata had the largest head capsule widths under ambient CO2 levels, the largest head capsule widths under high levels, and had equal pronotal lengths at all CO2 levels. Larvae fed C. glomerata grown under ambient conditions produced portable cases of the greatest length at the experiment's conclusion, but no distinct trend was seen for larvae fed U. fimbriata. Overall, CO2 induced production of reactive phenolics in chlorophytes did not appreciably influence herbivorous microcaddisfly development or survival.

Carbon materials syntheses using dielectric barrier discharge microplasma in supercritical carbon dioxide environments

In this study, carbon materials syntheses using a dielectric barrier discharge (DBD) microplasma in supercritical carbon dioxide (scCO 2) environments are reported. The dependencies of the carbon materials synthesis processing on the environmental temperature, environmental pressure and power frequency were investigated. In contrast to atmospheric-pressure CO 2 environments, in which no carbon materials could be fabricated, it was possible to fabricate various carbon materials, such as amorphous carbon, graphite and nanostructured carbon materials, using scCO 2 as a processing medium and a raw starting material. In particular, in the vicinity of the critical point of CO 2, the quantity of carbon nanostructured materials, such as carbon nanotubes and carbon nanohorns, was larger than under other scCO 2 conditions. It is supposed that the high density and molecular clustering caused by supercritical conditions may affect the formation of such carbon nanostructured materials. In addition, we found that by varying the power frequency, the form of the synthesized carbon materials could be changed.

Friction and Wear of POE and PAG Oils in the Carbon Dioxide Environment

The carbon dioxide (R-744) as a natural refrigerant has been an attractive alternative refrigerant to replace HFC (hydrofluorocarbon) refrigerants currently used in air conditioning systems, due to the environmental concerns. Because new compressors with CO2 are going to be operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very important. To develop new compressor, especially scroll type, the friction and wear characteristics of sliding surfaces between a fixed scroll and an orbiting scroll in the scroll compressor were investigated in this paper. The sliding tests of pin-on-disk type were carried out between scroll surfaces under various sliding speeds, normal loads, surface roughness, and refrigerant pressures. Two types of lubricants were used, namely POE (polyol ester) oil and PAG (polyalkylene glycol) oil. The friction forces, wear amounts and surface temperatures were monitored during the tests. Test results showed that the wear amounts increased with increasing normal load and rotating speed, and also decreased with decreasing surface roughness. Also, the results of the sliding tests showed that using PAG oil has an advantage over POE oil in CO2 environment. As the pressure of CO2 refrigerant became higher, the amount of wear and coefficient of friction became larger in CO2/POE mixed environment, but wear and friction remained constant in CO2/PAG mixed environment. The wear coefficients in CO2/PAG and CO2/POE mixed environment were 8.60×10-9 ㎣/N·m and 2.35×10-8 ㎣/N·m, respectively.

Development of surface area and pore structure for activation of anthracite coal

The use of anthracite coal as a feedstock for activated carbon is investigated. A rotating reactor was constructed to activate the coal in a carbon dioxide environment at three temperatures. The reaction was started and stopped by switching the gas atmosphere from carbon dioxide to nitrogen. The change in anthracite weight was followed over time, allowing a study of the overall kinetics of the reaction. Samples from the reactor were taken at specific time intervals and surface area was assessed. It was determined that BET and micropore surface areas were functions of conversion and activation temperature. Likewise, for each of the activation temperatures, good control of BET to micropore surface area ratios was demonstrated. Typical BET surface areas of nearly 1000 m 2/g were obtained along with the ability to alter the micro- and meso-porous structure. Testing of these activated carbons for use in electric double layer capacitors displayed a capacitance of 140 F/g. These results are comparable to other research carbons for this application. Results on the activation of the two anthracite coal samples are reported along with details of the pore development and global kinetics of activation.

Effect of controlled carbon dioxide on in vitro shoot multiplication in Feronia limonia (L.) Swingle

The effect of controlled carbon dioxide environment on in vitro shoot growth and multiplication in Feronia limonia (a tropical fruit plant, Family- Rutaceae) was studied. Carbon dioxide available in the ambient air of the growth room was insufficient for in vitro growth of the shoots alone. Also, the presence of sucrose only as the C-source in the medium (without CO2), was found to be inadequate for sustainable growth and multiplication of shoots. The carbon dioxide enrichment promoted shoot multiplication and overall growth. The promotory effect of CO2 was independent of the presence of sucrose in the medium. In the presence of both CO2 and sucrose, an additive effect was observed producing maximum shoot growth. In the absence of sucrose a higher concentration of CO2 (10.0)g m−3 was required to achieve photoautotrophic shoot multiplication comparable to ambient air controls. Highest leaf area per shoot cluster promoting shoot growth and multiplication was recorded under this treatment. Shoots growing on sucrose containing medium under controlled CO2 environment of 0.6 g m−3 concentration evoked better response than ambient air controls (shoots growing on sucrose containing medium) in growth room. This treatment produced the overall best response. The present study highlighted the possibility of photoautotrophic multiplication which might prove useful for successful hardening and acclimatization in tissue culture plants.

Confirmation and Efficacy Tests Against Codling Moth and Oriental Fruit Moth in Apples Using Combination Heat and Controlled Atmosphere Treatments

Codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), are serious pests of apples (Malus spp.) grown in the United States and other countries. In countries where these species are not found, there are strict quarantine restrictions in place to prevent their accidental introduction. The treatment used in this study consisted of hot, forced, moist air with a linear heating rate of 12°C/h to a final chamber temperature of 46°C under a 1% oxygen and 15% carbon dioxide environment. We found that the fourth instar of both species was the most tolerant to the treatment, with equal tolerance between the species. Efficacy tests against the fourth instar of both oriental fruit moth and codling moth by using a commercial controlled atmosphere temperature treatment system chamber resulted in >5,000 individuals of each species being controlled using the combination treatment. Confirmation tests against codling moth resulted in mortality of >30,000 fourth instars. These treatments may be used to meet quarantine restrictions for organic apples where fumigation with methyl bromide is not desirable.

The Tribological Behaviors of the Surfaces Lubricated by Polyaklylene Glycol and Polyolester Oils in Carbon Dioxide Environment

The carbon dioxide (CO2) is investigated as an alternative refrigerant to replace HFC (hydro fluorocarbon) refrigerants in refrigerators and air conditioning systems due to the environmental concerns. Because new compressors with the carbon dioxide are going to be operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very important. To develop new compressors, especially rotary type, the friction and wear characteristics of sliding surfaces between a vane and a roller in the rotary compressor were evaluated in this paper. Several hard coatings, such as TiN, CrN, and WC/C, were applied on vane surfaces in order to improve the tribological characteristics, and their performances were evaluated experimentally. The vane-on-disk type sliding tests were carried out under the various sliding speeds, normal loads, and carbon dioxide pressures with an exclusive high pressure wear tester. From the tests wear volume of vane surfaces applied various coatings were compared. During the tests coefficients of friction and surface temperatures were monitored. Test results showed that WC/C coatings showed good tribological properties. TiN and CrN coated vanes showed good wear resistance properties but produced high friction.

Confirmation and Efficacy Tests Against Codling Moth and Oriental Fruit Moth in Apples Using Combination Heat and Controlled Atmosphere Treatments

Codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), are serious pests of apples (Malus spp.) grown in the United States and other countries. In countries where these species are not found, there are strict quarantine restrictions in place to prevent their accidental introduction. The treatment used in this study consisted of hot, forced, moist air with a linear heating rate of 12 degrees C/h to a final chamber temperature of 46 degrees C under a 1% oxygen and 15% carbon dioxide environment. We found that the fourth instar of both species was the most tolerant to the treatment, with equal tolerance between the species. Efficacy tests against the fourth instar of both oriental fruit moth and codling moth by using a commercial controlled atmosphere temperature treatment system chamber resulted in > 5,000 individuals of each species being controlled using the combination treatment. Confirmation tests against codling moth resulted in mortality of > 30,000 fourth instars. These treatments may be used to meet quarantine restrictions for organic apples where fumigation with methyl bromide is not desirable.

Separation of enantiomers by diastereomeric salt formation and precipitation in supercritical carbon dioxide: Application to the resolution of mandelic acid

A novel process for the resolution of enantiomers by simultaneous reaction of the enantiomers with a chiral agent, and precipitation of the formed diastereomeric salts in a supercritical carbon dioxide environment, is presented. This method allows to take advantage of the favorable kinetics of the process, in addition to the favorable phase and chemical equilibrium properties that are exploited by other processes. The method has been applied to separate the enantiomers of mandelic acid using R(+)-α-methylbenzylamine as the chiral agent. Different process configurations, including partial or total diastereomeric salt formation, performed before or simultaneously with the precipitation, have been studied. The highest resolution efficiency (e.e = 63%) was achieved when a partial diastereomeric salt formation was performed simultaneously with the precipitation, at 8 MPa and 328 K. A mathematical model of the phase equilibrium of the system based on the Peng–Robinson equation of state is also presented.

High-pressure CO2-enhanced polymer interdiffusion and dissolution studied with in situ ATR-FTIR spectroscopic imaging

A novel application of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic imaging to study polymer interdiffusion and dissolution under high-pressure or supercritical carbon dioxide environments has been demonstrated. Miscible systems of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) of different molecular weights have been chosen for this investigation. These systems were subjected to a controlled pressure of CO2 and the interfacial area of contact between the two polymers was studied by ATR-FTIR imaging in situ. Using this spectroscopic imaging approach, the phenomenon of polymer interdiffusion enhanced by CO2 dissolved in both polymers was investigated as a function of time. The evolution of spatially resolved images as a function of time was studied with FTIR imaging and the corresponding concentration profiles for both polymers were obtained. The chemical specificity of FTIR imaging also allowed us to measure the amount of CO2 dissolved in each domain of the polymer system. Effects of PEG molecular weight and pressure of CO2 on the mechanism and the rate of polymer interdiffusion was investigated. This approach has not only shown the ability to visualise the process of interdiffusion but also demonstrated the ability of high-pressure CO2 to ‘tune’ the rate of interdiffusion, this information is important for a better understanding of CO2-induced mixing of polymeric materials.

The Effect of Various Surface Coatings on Tribological Characteristics of Rotary Compressor Vane in Carbon Dioxide Environment

The tribology of lubricated sliding vanes in the rotary compressor was investigated to replace the HFC refrigerants by the carbon dioxide. The carbon dioxide is a natural refrigerant and very favorable to environment. Because new compressors with the carbon dioxide are going to be operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very important. To develop new compressors, especially rotary type, the friction and wear characteristics of sliding surfaces between a vane and a roller in the rotary compressor were evaluated in this paper. Several hard coatings, such as TiN, CrN, WC/C and two types of nitridings, were applied on vane surfaces in order to improve the tribological characteristics, and their performances were evaluated experimentally. The vane-on-disk type sliding tests were carried out under the various sliding speeds, normal loads, and carbon dioxide pressures with an exclusive high pressure wear tester. From the tests wear volume of vane surfaces applied various coatings were compared. During the tests coefficients of friction and surface temperatures were monitored. Test results showed that WC/C coatings showed good tribological properties. TiN and CrN coated vanes showed good wear resistance properties but produced high friction.

Generation of dielectric barrier discharge in high-pressure N 2 and CO 2 environments up to supercritical conditions

The generations of dielectric barrier discharge (DBD) in high-pressure nitrogen and carbon dioxide environments up to supercritical conditions with or without flow fields were performed. From the second positive system of nitrogen, the rotational temperature of N 2 was estimated to be approximately 400 K under a supercritical N 2 condition (4 MPa and 313 K). On the other hand, from emission spectra of DBD in a high-pressure CO 2 environment (1–8 MPa), C 2 and O spectra were remarkable in intensity instead of CO, CO +, CO 2 and CO 2 + spectra that were remarkable at atmospheric pressure. Furthermore, porous carbon film synthesis by DBD under a supercritical CO 2 condition (7.5 MPa and 305 K) was also identified by scanning electron microscopy observation.

In vitro Growth and Shoot Multiplication of Achras zapota in a Controlled Carbon Dioxide Environment

The culture vessels with multiplying shoots of Achras zapota L. on Schenk and Hildebrandt (SH) medium containing 8.88 &mu;M 6-benzylaminopurine (BAP) with or without sucrose were kept under varied CO2 concentrations ranging from 0.6 to 40.0 g m-3 using different concentrations of sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3), potassium bicarbonate (KHCO3), and potassium carbonate (K2CO3) in small acrylic chambers. Complete absence of carbon source caused death of shoots within 20 d. Under elevated concentrations of CO2 (10.0 and 40.0 g m-3) the shoots grew photoautotrophically on sucrose-free medium. The growth of cultures was better at 40.0 g (CO2) m-3 than on 3.0 % sucrose under ambient air of growth room. However, the best response was obtained at 10.0 g (CO2) m-3 and 3.0 % sucrose where maximum number of shoots, shoot length, fresh and dry mass, total number of leaves and leaf area was observed.