scholarly journals Revealing the Influence of Microparticles on Geopolymers’ Synthesis and Porosity

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3211
Author(s):  
Dumitru Doru Burduhos Nergis ◽  
Petrica Vizureanu ◽  
Ioan Ardelean ◽  
Andrei Victor Sandu ◽  
Ofelia Cornelia Corbu ◽  
...  
Keyword(s):  
Porous Structure ◽  
Polymerization Process ◽  
Curing Time ◽  
Transverse Relaxation ◽  
Nmr Relaxometry ◽  
Group I ◽  
Relaxation Measurements ◽  
Different Types ◽  
Reinforcing Particle ◽  
Porosity Characterization

Geopolymers are zeolites like structures based on hydrated aluminosilicates units of SiO4 and AlO4. These units, known as poly(sialate), poly(sialate)-siloxo or poly(sialate)-disiloxo are chemically balanced by the group I cations of K+, Li+, or Na+. Simultaneously, the chemical reaction of formation, known as geopolymerization, governs the orientation of the unit, generating mesoporous structures. Multiple methods can be used for pore structure and porosity characterization. Among them, nuclear magnetic resonance (NMR) relaxometry allows the detection of the porous structure in a completely nonperturbative manner. NMR relaxometry may be used to monitor the relaxation of protons belonging to the liquid molecules confined inside the porous structure and, thus, to get access to the pore size distribution. This monitoring can take place even during the polymerization process. The present study implements transverse relaxation measurements to monitor the influence introduced by the curing time on the residual liquid phase of geopolymers prepared with two different types of reinforcing particles. According to our results, the obtained geopolymers contain three types of pores formed by the arrangement of the OH− and Si groups (Si-OH), Si-O-Si groups, Si-O-Al groups, and Si-O rings. After 48 days, the samples cured for 8 h show a high percentage of all three types of pores, however, by increasing the curing time and the percentage of reinforcing particle, the percent of pores decrease, especially, the gel pores.

scholarly journals Freeze–Thaw Effect on Road Concrete Containing Blast Furnace Slag: NMR Relaxometry Investigations

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3288
Author(s):  
Liliana Maria Nicula ◽  
Ofelia Corbu ◽  
Ioan Ardelean ◽  
Andrei Victor Sandu ◽  
Mihai Iliescu ◽  
...  
Keyword(s):  
Blast Furnace ◽  
Blast Furnace Slag ◽  
Nmr Relaxation ◽  
Invasive Technique ◽  
Freeze Thaw ◽  
Nmr Relaxometry ◽  
Main Technique ◽  
Relaxation Measurements ◽  
Furnace Slag ◽  
Standard Techniques

The present work investigates the effect of freeze–thaw cycles on the porosity of three mixtures of road concrete containing blast furnace slag in comparison with two mixtures made with conventional materials. The main technique used in our investigations is nuclear magnetic resonance (NMR) relaxometry. This permitted the extraction of information with respect to the freeze–thaw effect on pore-size distribution, which influences both the mechanical strength and the molecular transport through the material. Moreover, by using this technique, the structure of the air voids was analyzed for the entire pore system in the cement paste and the aggregate particles. The samples under study were first dried in a vacuum oven and then saturated with water or cyclohexane where the distribution of the transverse relaxation times of the protons was recorded. The NMR relaxation measurements were performed on samples extracted from specimens maintained at 300 freeze–thaw cycles and on control samples extracted from specimens kept in water during the freeze–thaw period. Scanning Electron Microscopy (SEM) was used to analyze the microstructure of concrete samples in order to obtain information about the pore sizes and the distance between them. The results from the NMR relaxation measurements were consistent with those obtained by using standard techniques for determining the porosity and the freeze–thaw resistances. The investigations made it possible to establish the optimal composition of blast furnace slag that can be incorporated into road concrete compositions. This non-invasive technique can also complete standard techniques for assessing the porosity and the progress of internal cracks during the freeze–thaw test.

scholarly journals The effect of different irrigation techniques on the quality of cleaning of root canal walls

2008 ◽  
Vol 55 (4) ◽  
pp. 221-228
Author(s):  
Violeta Pavlovic ◽  
Slavoljub Zivkovic
Keyword(s):  
Root Canal ◽  
Smear Layer ◽  
Sodium Hypochlorite Solution ◽  
Efficient Removal ◽  
Human Teeth ◽  
Root Canals ◽  
Group I ◽  
Different Types ◽  
The Difference

Aim: To evaluate the effect of irrigation techniques, i.e. different types of irrigation needles, on the quality of cleaning of root canal walls using scanning electron microscopy (SEM). Material and Method: The study was conducted on 16 extracted, single-rooted, human teeth. The samples were allocated to two experimental groups depending on the type of the irrigation needle. Conventional needles were used for the irrigation of Group I and laterally perforated ones for Group II. All root canals were instrumented using K files and the Step-back technique. During instrumentation, all samples were irrigated with 2.5 % sodium hypochlorite solution followed by final irrigation with 17 % EDTA for 1 min. After that, all samples were irrigated with 10 ml of distilled water. The roots were, then, sectioned longitudinally and middle one third of each root canal was analyzed using SEM. Quantitative analysis was based on criteria by H?lsmann et al. Results: The obtained results showed that the more efficient removal of debris and the smear layer was accomplished in the group of samples irrigated using laterally perforated needles than conventional needles. The difference between the investigated irrigation techniques were statistically significant (p<0.01). Conclusion: The use of laterally perforated needles for irrigation allows more efficient cleaning of root canal walls, i.e. the removal of debris and the smear layer.

1H nuclear magnetic resonance relaxometric characterization of fat and water states in soft and hard cheese

2000 ◽  
Vol 67 (4) ◽  
pp. 609-618 ◽  
Author(s):  
BEATRICE CHALAND ◽  
FRANÇOIS MARIETTE ◽  
PHILIPPE MARCHAL ◽  
JACQUES DE CERTAINES
Keyword(s):  
Milk Fat ◽  
Nmr Relaxation ◽  
Transverse Relaxation ◽  
Anhydrous Milk Fat ◽  
Solid Ratio ◽  
Nmr Relaxometry ◽  
1H Nuclear Magnetic Resonance ◽  
Relaxation Component ◽  
Hard Cheese

The aim of this work was to study the spin–spin (T2) relaxation components of one hard cheese and three soft cheeses to characterize fat and water states. NMR signals were measured at 6 °C with a 0·47 T NMR device. The transverse relaxation decay was fitted using the Marquardt method. The T2 relaxometric behaviour of the cheeses under consideration was characterized by four relaxation components. To understand the chemical composition of each NMR component, we studied anhydrous milk fat extracted from each cheese analysed. At 6 °C, the fat was 60% crystalline. In cheese, the solid fat was found mainly in the shorter relaxation component with a T2 of 17 μs. The intensity of the NMR relaxation with a T2 > 1 ms was explained by the amount of water, liquid fat and proteins, and the associated relaxation time varied as a function of the process used. The composition of each relaxation component was confirmed by the temperature effect and the influence of the fat content on the NMR cheese signal. NMR relaxometry was able to provide information on water behaviour (i.e. the quantity and level of interactions with proteins) and on the solid[ratio ]liquid ratio of anhydrous milk fat in the cheese.

Anelastic Spectroscopy in Superconducting Oxides

2005 ◽  
Vol 498-499 ◽  
pp. 581-586
Author(s):  
Juliana Maria de Albuquerque Gimenez ◽  
Carlos Roberto Grandini ◽  
Dayse Iara dos Santos ◽  
Alfredo Gonçalves da Cunha
Keyword(s):  
High Vacuum ◽  
Thermal Treatments ◽  
Interstitial Oxygen ◽  
High Tc Superconductors ◽  
High Tc ◽  
Relaxation Measurements ◽  
Different Types ◽  
Different Temperatures ◽  
Superconducting Oxides ◽  
Two Peaks

Since the discovery of the high Tc superconductors, several works have been made about the different properties of these materials. Anelastic spectroscopy experiments are sensitive tools to the study of defects in solids and phase transitions. By this technique, we can distinguish the different types of atomic jumps that happen to different temperatures. The intensity of the peaks in the anelastic spectrum and the "step" in the torsional modulus are related with the concentration of the relaxing entities, and the position of the peaks is determined by its mobility. In this paper, the study on Bi and Sm based superconducting oxides was made by anelastic relaxation measurements using a torsion pendulum. The samples were submitted to successive thermal treatments in high vacuum, in the temperature range between 100 K and 650 K, heating rate about 1 K/min. For Bi based superconducting oxides the results shown two peaks, that were associated to interstitial oxygen mobility and to orthorhombic to monoclinic phase transition. For Sm based superconducting oxides the results shown a relaxation peak that was attributed to the jumps of the oxygen atoms in the inter-chains O1 and O5 of the lattice.

Investigation of Un-Vulcanized Natural Rubber by Means of Temperature Scanning Stress Relaxation Measurements

2013 ◽  
Vol 718-720 ◽  
pp. 117-123 ◽  
Author(s):  
Miao Wu ◽  
Michael Heinz ◽  
Norbert Vennemann
Keyword(s):  
Mechanical Properties ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Branch Points ◽  
Relaxation Spectra ◽  
Green Strength ◽  
Testing Method ◽  
Relaxation Measurements ◽  
Different Types ◽  
Temperature Scanning

Two different types of un-vulcanized natural rubber, air dried sheets (ADS) and SVR-3L block rubber, were investigated by a new testing method and the results are compared with other mechanical properties. It was found that green strength is strongly reduced if the sample is ther­mal­ly treated before testing. Presumably, the decrease of strength is caused by a decrease of branch points, mainly composed of phospholipids, which are linked to the a - terminal groups of the rubber molecules. The existence of two different types of branch points is indicated by relaxation spectra, obtained from temperature scanning stress relaxation (TSSR) measurements.

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