Specific Volume Changes Research Articles

Shear modulus and thermal properties of gutta percha for root canal filling

The purpose of this investigation was to investigate the rheological properties of four commercially available gutta perchas for root canal filling. The relaxation modulus [Gr(0): instantaneous shear modulus] and specific volume of their materials were examined. In addition, the quantity of heat was also studied by differential scanning calorimeter. In a lower temperature range than the first-order transition temperature (melting point), the Gr(0) values of each material were almost identical. A marked decrease of Gr(0) was observed at the melting point, and the range of the first-order transition temperature at heating was from 42.0 to 60.0 degrees C. At higher temperatures than the first-order transition temperature of each material, a considerable difference in Gr(0) values was observed. The transition temperatures obtained by the results of the Gr(0), specific volume and quantity of heat agreed with one another. A marked specific volume change was observed at the first-order transition temperature. The technique using melted gutta percha may not be favourable compared with the conventional lateral condensation technique because melted gutta percha undergoes a large amount of shrinkage during setting.

Tin Nanoparticle Loaded Graphite Anodes for Li-Ion Battery Applications

Nearly monosized Sn nanoparticles were produced by an in situ prepared single-source molecular precursor approach. The experimental conditions in the reduction of 10 phenanthroline) in water were carefully controlled to produce two different particle size ranges, 2-5 nm (mean: 3.5 nm, standard deviation: 0.8 nm) and 7-13 nm (mean: 10.0 nm, standard deviation: 1.7 nm). The Sn nanoparticles were subsequently dispersed in graphite (KS6) and the application of the resulting nanocomposites as an active anode material for Li-ion batteries was explored. The graphite-Sn nanocomposites showed significant improvement in the cyclability of Sn over previously reported results. The cyclability improvement is believed to be due to the smallness of the Sn particles and their uniform distribution in a soft matrix (graphite) which, in addition to being a capable host, could also effectively buffer the specific volume changes in Sn-based Li storage compounds during charging insertion) and discharging extraction) reactions. © 2004 The Electrochemical Society. All rights reserved.

Nonlinear changes in specific volume. A route to resolve an entropy crisis

Nonlinear changes in specific volume. A route to resolve an entropy crisis

Nonlinear Changes in Specific Volume. A Route To Resolve an Entropy Crisis

Nonlinear Changes in Specific Volume. A Route To Resolve an Entropy Crisis

Magnetic investigation of the effect of α′-martensite on the properties of austenitic stainless steel

In this paper some phase transformations of the AISI 304 austenitic stainless steel are studied. The appearance of the strain induced α′-martensite phase due to cold rolling and elongation was investigated by different magnetic measurement techniques. It was demonstrated that the type of deformation and the rate of deformation strongly influence the amount of α′-martensite phase. It is supposed that the additional stress due to the specific volume change of γ→α′ transformation can improve the plastic deformation of the neighbouring austenite grains in the highly deformed range which has increasing effect on the amount of α′-martensite phase. The reverse transformation of the α′-phase back to γ-phase due to heat treatment is also studied. It was proved that the magnetic and hardness recovery processes started at different temperatures. The paper demonstrates the application possibility of magnetic measurements in case of the investigated metallurgical problem.

Direct relationships between volume variations at macro and nanoscale in epoxy systems. PALS/PVT measurements

The free volume in epoxy systems fully cured with aminic hardeners having different chemical structures was studied by means of positron annihilation lifetimes spectroscopy. The results are compared with those obtained from the analysis of the macroscopic specific volume changes by using pressure–volume–temperature experimental technique. An excellent correlation between the volumes measured at macro and nanoscales was found. From this fact, it can be asserted that the variation of the specific volume is mainly controlled by the variation in the average size of sub-nanometer size local free volumes, which are fixed by the chemical structure of hardener in fully crosslinked epoxy networks. These results give the first evidence of the direct relation existing between macro and nanoscales in thermosetting networks.

Specific thermosensitive volume change of biopolymer gels derived from propylated poly(γ‐glutamate)s

AbstractThermosensitive biopolymers with an amphipathic structure were synthesized through the propyl esterification of the carboxyl groups of poly(γ‐glutamic acid) (γ‐PGA). The clouding temperature on heating was controlled by the addition of different amounts of NaCl and by the degree of esterification. The clearing temperature on cooling was independent of the aqueous milieu, presumably because of the strong multiple hydrogen bonds between the polymer chains formed in the collapsed state. The hydrogel of γ‐PGA propylate crosslinked by a chemical reaction with hexamethylene diisocyanate also showed pH‐responsive and thermoresponsive shrinking, but the volume recovery was incomplete during the cooling process. A Fourier transform infrared/attenuated total reflection study showed that the incomplete volume recovery might be associated with the amide hydrogen bonding being strengthened by the chemical crosslinkage. The addition of urea made the volume change complete. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4492–4501, 2004

Structural changes in the wheat dough and bread with the addition of alpha-amylases

The influence of fungal and bacterial α-amylases on the texture and microstructure of dough and bread was investigated. Loaf specific volume, crumb porosity and texture properties were accepted as bread structure and texture characteristics. The microstructure analysis of dough and bread using light and scanning microscopy methods was performed. The changes in loaf specific volume, crumb porosity and texture properties showed different anti-staling activity of the enzymes used. The simultaneous action of enzyme addition and the fermentation process evoked significant changes in the microstructure of dough. The character of these changes depended on the kind of enzyme used. A substantial effect of both amylases on starch behaviour during bread baking and staling was also observed.

Development and Performance Evaluation of a Water Hyacinth Chopper cum Crusher

A water hyacinth ( Eichhornia crassipes) chopper cum crusher was developed at College of Technology and Engineering, Udaipur, India to solve the problem of the bulk of freshly harvested water hyacinth during transportation. The performance of the chopper cum crusher was evaluated on the basis of its ability to reduce volume and weight of fresh water hyacinth. Two variables namely feed rate and knife speeds were studied. Relationships were developed between changes in specific volume, knife speed; percent weight loss and feed rates. Weight reduction studies showed that, with the increase in feed rate and knife speed, there was a decrease in weight loss. Maximum weight loss of 33·77% was achieved with the minimum feed rate of 1·0 t h −1 and knife speed of 3·14 m s −1. Regression models were developed to fit the data. The developed machine reduced the specific volume and weight of fresh water hyacinth by up to 64 and 31·54%, respectively, at the recommended feed rate of 1·0 t h −1 and knife speed of 4·71 m s −1.

Crystallization Mechanism of Syndiotactic Polypropylene Analyzed by Time-Dependent Light Scattering

Monitoring the time dependence of polarized (vv) and depolarized (hv) light scattering during the crystallization of a polymer can be used to characterize the development of the size and internal structure of the growing spherulites or hedrites. In particular, it is possible to distinguish between a growth of objects with a fixed inner structure and cases of a subsequent inner structure modification. We report here on the crystallization of a sample of syndiotactic polypropylene from the melt. The vv- and hv-scattering patterns are indicative for the growth of hedrites and enable a specific direct evaluation procedure to be applied. We determined for several crystallization temperatures the final size of the hedrites, the crystallization time and observed, in particular, changes with time in the mean inner anisotropy and density. Observations speak in favor of an in-filling process of crystalline lamellae accompanying the hedrite's growth. From a complementary dilatometric determination of the specific volume change and its agreement with kinetical data of the light-scattering experiments it follows that the number of growing hedrites is constant.

Raman investigation of structural changes induced by e-beam irradiation in Ge doped silica MCVD glasses

Microstructural changes of germanium (Ge)-doped silica glasses irradiated with electron beam (e-beam) have been investigated by Raman spectroscopy. Two mechanisms correlated to the specific volume changes induced by e-beam irradiation were observed by surface topography measurement. As we have previously demonstrated, they depend on the Ge content and the irradiation dose. The compaction of the structure (which decreases with the Ge concentration) is attributed to an increase of the three and four-membered ring species which is maximal at the surface and decreases with depth. By means of Monte-Carlo simulations, we have correlated the energy deposition with the compaction process. Some specific Raman components are attributed to the expansion of the structure observed for high Ge content and high irradiation dose. In this case, an increase of the anti-symmetric stretching modes of the bridging oxygen in the SiOGe and SiOSi groups are observed at the surface.

Subsolidus Phase Equilibria and Crystal Chemistry in the System BaO—TiO2—Ta2O5.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Dependence on Ge doping of specific volume change in silica induced by electron-beam irradiation

Because of the increasing use of e-beam lithography in telecom optical applications, e-beam induced refractive index change (RIC) has been further investigated in this paper in Ge-doped silica in comparison with pure silica. We investigated modified chemical vapor deposition (MCVD) Ge-doped SiO 2 glasses containing 0, 5, 13 and 25 wt% of Ge. Contrary to ultraviolet (UV) photosensitivity for which Ge doping has a positive effect; here, the densification is diminished and even an expansion process appears for larger Ge content. Comparing RIC, directly measured and deduced from topography change, we conclude that specific volume change is the main contribution to RIC. UV and e-beam induced densification are by different mechanisms.

Subsolidus phase equilibria and crystal chemistry in the system BaO–TiO 2–Ta 2O 5

Subsolidus phase relations have been determined for the BaO:TiO 2:Ta 2O 5 system by X-ray diffraction analysis of ∼100 specimens prepared in air at temperatures near but below the solidus (1275 °C to 1500 °C). For the BaO:Ta 2O 5 subsystem, the formation of all three polymorphs of BaTa 2O 6 (orthorhombic, tetragonal, and hexagonal) was confirmed. The present study found no stable phases forming between Ba 5Ta 4O 15 and BaO. In the ternary system, along the line BaTiO 3–Ba 5Ta 4O 15, the previously reported 8L and 10L hexagonal perovskite derivatives were confirmed, albeit with somewhat wider homogeneity ranges; BaTiO 3 dissolves Ta 5+ up to BaTi 0.64Ta 0.29O 3, which contains 7% B-cation vacancies and exhibits a dilated cubic unit cell ( a=4.0505(2) Å). The formation of Ba 3Ti 4Ta 4O 21, a member of the hexagonal A 3M 8O 21-type ternary oxides, was confirmed as well as its solid solution, for which a different mechanism of formation is suggested. Several new compounds have been found, including four members of the orthorhombic (space group Cmcm) “rutile-slab” homologous series, BaTi n Ta 4O 11+2 n , with n-values 3,5,7,9; the unit cells for these compounds are given. Three ternary phases with close-packed [Ba,O] layer structures related to that of 6L Ba 4Ti 13O 30 were found: 13L Ba 18Ti 53Ta 2O 129, 7L Ba 10Ti 27Ta 2O 69, and 8L Ba 6Ti 14Ta 2O 39. The crystal structures of the 13L and 7L phases were determined by single-crystal X-ray diffraction (13L Ba 18Ti 53Ta 2O 129: cchcchcchcchc, C2/ m, a=9.859(2) Å, b=17.067(5) Å, c=30.618(8) Å, β=96.11(2)°, Z=2; 7L Ba 10Ti 27Ta 2O 69: cchcchc, C2/ m, a=9.855(3) Å, b=17.081(7) Å, c=16.719(7) Å, β=101.18(3)°; Z=2), and are described and compared with those of the 6L and 8L members of this family. Phases with tetragonal tungsten bronze (TTB) related structures occur over large compositional ranges in the BaO:TiO 2:Ta 2O 5 system, both within the ternary (Ba 6− x Ti 2−2 x Ta 8+2 x O 30, x=0→0.723), and along the BaO–Ta 2O 5 binary (from 43 to 26 mol% BaO), which in turn dissolves up to ∼12 mol% TiO 2 to form extensive single-phase fields with different TTB superstructures. X-ray powder diffraction data are given for three binary BaO:Ta 2O 5 compounds exhibiting the TTB structure and two superstructures. The large compositional ranges of the TTB-type phases are accompanied by only small changes in specific volume. The TTB-type regions within the ternary and those emanating from the BaO–Ta 2O 5 binary do not co-exist in equilibrium, which likely reflects fundamental differences in the structural mechanisms that accommodate the variable stoichiometries. The similarities and differences between the BaO:TiO 2:Ta 2O 5 and BaO:TiO 2:Nb 2O 5 systems are described.

The nanocomposites of carbon nanotube with Sb and SnSb 0.5 as Li-ion battery anodes

Nanocomposites of carbon nanotubes (CNTs) with Sb and SnSb 0.5 particles were prepared by chemical reduction of SnCl 2 and SbCl 3 precursors in the presence of CNTs. SEM and TEM imaging showed that the Sb and SnSb 0.5 particles are uniformly deposited on the CNT exterior and in the CNT web. These CNT–metal composites are active anode materials for lithium ion batteries, showing improved cyclability compared to unsupported Sb and Sn–Sb particles and higher reversible specific capacities than CNTs. The reversible capacities were as high as 462 mAh/g for CNT–36 wt.% Sb and 518 mAh/g for CNT–56 wt.% SnSb 0.5. After 30 cycles, the capacity was 62.1% of the initial capacity for the former and 67.2% of the initial capacity for the later. In comparison Sb and SnSb 0.5 could only retain 17.7 and 23.5%, respectively of their initial capacities in the same number of cycles. The improvement in cyclability may be attributed to the nanoscale dimension of the metal particles and CNTs’ role as a buffer in relieving the mechanical stress induced by specific volume changes in electrochemical lithium insertion and extraction reactions.

Relation Between Friction and Plastic Deformation Examined by Using Periodic Asperity Arrays Fabricated on an AFM Multipurpose Cantilever

The relation between friction force and plastic deformation was determined by using FIB (focused ion beam)-processed multipurpose cantilevers for an AFM (atomic force microscope). First, a multipurpose cantilever consisting of a sliding block, parallel leaf spring, and hinge was made by using an FIB. Then, copper pyramids were rubbed against an unmodified area or periodic asperity arrays fabricated on the cantilever under loads of 23 to 960 nN. Under higher loads (∼900 nN), the friction coefficient measured for an asperity array was lower than that for an unmodified area and decreased with decreasing curvature radius of the asperity peak, and the specific volume change rate increased with decreasing curvature radius of the asperity peak.

ＣＦＲＰ硬化過程における光ファイバセンサによる内部ひずみモニタリングと硬化収縮

In the present study, internal strain monitoring and detection of cure shrinkage in matrix resins by using EFPI optical fiber sensors have been investigated for CFRP during autoclave cure. EFPI sensors were embedded into quasi-isotropic CFRP laminates composed of carbon fiber/heat-resistant tough epoxy resin prepregs for aircraft structures. In order to examine the monitoring ability of EFPI sensors, measured internal strains were compared with specific volume of matrix resins determined by PVT measurement during cure, which indicates their cure shrinkage and thermal expansion/contraction. The results show that the cure shrinkage terminates at a certain degree of cure before the resin cures completely, and the EFPI sensors can detect this phenomenon. From these results, it is found that the EFPI sensors can measure the internal strains corresponding to the specific volume change of the matrix resins after the degree of cure reaches approximately 30%.

Smart autoclave processing of thermoset resin matrix composites based on temperature and internal strain monitoring

Cure cycle optimization and process control for autoclave cure of thermoset resin matrix composites based on temperature and internal strain monitoring were studied. Cure of thermoset resin is usually an exothermic reaction, which causes temperature increase of composites during cure. Slowing down the temperature ramp rate is effective in lowering the peak temperature. However, the slower is the ramp rate, the longer the cure time becomes. Therefore, it is desirable to control the ramp rate in order to depress the peak temperature with prolongation of cure time minimized. Besides that, precise determination of cure completion is also required in order to minimize cure time. The procedure for smart processing described above was developed and tried on laminate of carbon fiber/epoxy resin prepreg. In this procedure, temperature ramp rate is controlled so that the peak temperature predicted by Springer's thermochemical model is kept below an allowable value. Cure completion is determined by a cure rate equation and internal strain monitoring with embedded EFPI optical fiber sensors. The internal strain is correlated with specific volume change of the matrix resin caused by cure shrinkage and thermal expansion/contraction. The authors found that the cure shrinkage terminates at a certain degree of cure, and EFPI sensors can detect this point. Although the degree of cure can be calculated by integrating the cure rate equation along temperature history, errors may be accumulated. Therefore, the degree of cure is corrected and integration of cure rate equation is restarted at the cure shrinkage termination point detected by EFPI sensors. Thus, cure completion is determined precisely. This smart autoclave processing procedure was able to depress the peak temperature and determine the end of cure.

Pechini process-derived tin oxide and tin oxide–graphite composites for lithium-ion batteries

The Pechini process [Ceram. Bull. 68 (1989) 1002] is used to obtain fine tin oxide powders that reduce the specific volume change in Li + insertion and extraction reactions. The suitability of these tin oxides as active materials for negative electrodes in lithium-ion batteries is investigated. From elemental analysis, it is found that the templating polymer network is almost completely obliterated after heating at 500 °C. The best tin oxide does not exhibit extensive crystallization of tin atoms even after 30 cycles of alloying and de-alloying reactions with Li. The structure and the specific capacity of the oxides are dependent on the heat treatment and remnants of the polymeric CH network can impose an unfavorable outcome. A capacity of 600 mAh g −1, which is unchanged for 30 cycles, can be obtained from tin oxide heat treated at 1000 °C. Composites of graphite and SnO 2 are also prepared and exhibit synergistic interactions between graphite and tin oxide which are similar to those reported previously [Electrochem. Solid State Lett. 3 (2000) 167].

Effect of nonframework cations and crystallinity on the basicity of NaX zeolites

The basic character of NaX-type zeolites was systematically altered by incorporating nonframework K +, Rb + and Cs + cations with ([M]/([M]+[Na]) ca. ∼0.55). Correlation between activity and basicity was established. The role of Lewis basicity was found to be more important than the changes in specific area or micropore volume of different cation-exchanged samples in deciding the catalyst activity in the Knoevenagel condensation reaction. The catalyst activity was found to decrease with lowering the degree of crystallinity in the case of NaX zeolites.