scholarly journals Sorption properties of aged cements

2012 ◽  
Vol 76 (8) ◽  
pp. 3411-3423 ◽  
Author(s):  
G. M. N. Baston ◽  
M. M. Cowper ◽  
T. A. Marshall
Keyword(s):  
Calcium Silicate Hydrate ◽  
Deionized Water ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Aged Material ◽  
X Ray ◽  
Untreated Material ◽  
Most Probable Explanation ◽  
Crystalline Forms ◽  
Radionuclide Uptake

AbstractSamples of artificially aged Nirex reference vault backfill (NRVB) were prepared by progressive leaching with deionized water, after which some of the samples underwent hydrothermal treatment. Compared to unaltered NRVB, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) provided evidence for the ageing resulting in alteration of the mineralogy, in particular the absence of portlandite was observed. The specific surface area of NRVB initially increased due to leaching, but then decreased after further leaching.Sorption distribution ratios (RD values) of uranium(VI), neptunium(IV), tin and zirconium onto aged NRVB samples were measured using the batch sorption technique. For all four elements, there was little difference between RD values for aged NRVB and those for untreated material. The most probable explanation for these findings is that even though the ageing treatments altered the NRVB mineralogy, calcium silicate hydrate (C-S-H) phases are responsible for most of the radionuclide uptake and their transformation to more crystalline forms has little effect on the bulk sorption capacity of the aged material.

Modified xonotlite–type calcium silicate hydrate slabs for fire doors

2018 ◽  
Vol 36 (2) ◽  
pp. 83-96 ◽  
Author(s):  
Rimantas Levinskas ◽  
Irena Lukošiūtė ◽  
Arūnas Baltušnikas ◽  
Algirdas Kuoga ◽  
Aldona Luobikienė ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Solar Furnace ◽  
Liquid Sodium ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Surface Areas ◽  
Back Door

Xonotlite-type calcium silicate hydrate slabs were examined under the thermal shock conditions in a solar furnace at the Plataforma Solar de Almeria which can reach a peak of 300 W/cm2. We have studied the original slabs as well as those modified with a mixture of liquid sodium silicate including montmorillonite as thermal insulation materials for fire doors applications. The slabs were kept at 950°C for 1 h. We performed X-ray diffraction, thermogravimetry and differential scanning calorimetry analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermal conductivity measurements and determined N2 adsorption/desorption isotherms. X-ray diffraction shows that during the thermal shock at 950°C xonotlite is converted to wollastonite. Specific surface areas of xonotlite slabs decrease due to release of crystalline water molecules. It is possible to maintain temperatures of the back door not exceeding 70°C while the front door is subjected to 950°C for 1-h time periods. The standard requires no more than 140°C at the back door.

scholarly journals Structural studies of crystalline forms of triamterene with carboxylic acid, GRAS and API molecules

IUCrJ ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 309-324 ◽  
Author(s):  
Abida Rehman ◽  
Amit Delori ◽  
David S. Hughes ◽  
William Jones
Keyword(s):  
Analytical Techniques ◽  
Gravimetric Analysis ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Evaporative Crystallization ◽  
Structural Database ◽  
Crystalline Forms ◽  
Good Agreement

Pharmaceutical salt solvates (dimethyl sulfoxide, DMSO) of the drug triamterene with the coformers acetic, succinic, adipic, pimelic, azelaic and nicotinic acid and ibuprofen are prepared by liquid-assisted grinding and solvent-evaporative crystallization. The modified ΔpK a rule as proposed by Cruz-Cabeza [(2012). CrystEngComm, 14, 6362–6365] is in close agreement with the results of this study. All adducts were characterized by X-ray diffraction and thermal analytical techniques, including single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry and thermal gravimetric analysis. Hydrogen-bonded motifs combined to form a variety of extended tapes and sheets. Analysis of the crystal structures showed that all adducts existed as salt solvates and contained the aminopyridinium–carboxylate heterodimer, except for the solvate containing triamterene, ibuprofen and DMSO, as a result of the presence of a strong and stable hemitriamterenium duplex. A search of the Cambridge Structural Database (CSD 5.36, Version 1.18) to determine the frequency of occurrence of the putative supramolecular synthons found in this study showed good agreement with previous work.

scholarly journals Phase Transitions and Crystal Structures of Ni(II) Complexes Determined with X-ray Powder Diffraction Data

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 106 ◽  
Author(s):  
Hisashi Konaka ◽  
Akito Sasaki
Keyword(s):  
Differential Scanning Calorimetry ◽  
Crystal Structures ◽  
Structural Changes ◽  
Original Form ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Hydrate Form ◽  
X Ray ◽  
Dsc Measurements ◽  
Crystalline Forms

Structural changes of chloride and bromide complexes, [Ni(Et2en)2(H2O)2]Cl2 (designated as 1a) and [Ni(Et2en)2]Br2 (2a), have been investigated by using simultaneous measurements of powder X-ray diffraction (XRD) and differential scanning calorimetry data under the temperature and humidity controls. The hydrate form of chloride complex 1a was transformed into an anhydrate form (1b) by heating at a temperature of 361 K. Then the 1b was reversibly returned to the original 1a by humidification at 25% relative humidity (RH) and temperature of 300 K. On the other hand, the anhydrate form of the bromide complex 2a was first transformed into a hydrate form (2b) at 30% RH and 300 K. On heating, the 2b turned to a new anhydrate form (2c) at 344 K, and then it returned to the original form 2a on further heating. In the present experiments, a series of reactions of 2a proceeded via 2c, which was newly found with the benefit of differential scanning calorimetry (DSC) measurements performed in parallel to the XRD measurements. Crystal structures of new crystalline forms of 1b, 2b, and 2c were determined from the powder XRD data.

scholarly journals Stereoselective Crystallization of Chiral 3,4-Dimethylphenyl Glycerol Ether Complicated by Plurality of Crystalline Modifications

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 201 ◽  
Author(s):  
Alexander A. Bredikhin ◽  
Dmitry V. Zakharychev ◽  
Zemfira A. Bredikhina ◽  
Alexey V. Kurenkov ◽  
Aida I. Samigullina ◽  
...  
Keyword(s):  
Biological Effects ◽  
Spontaneous Resolution ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Experimental Conditions ◽  
Current Increase ◽  
X Ray ◽  
Crystallization Procedure ◽  
Crystalline Forms ◽  
Racemates Resolution

Spontaneous resolution of Pasteur’s salt was historically the first way to obtain pure enantiomers from the racemate. The current increase in interest in the direct racemates resolution during crystallization is largely due to the opened prospects for the industrial application of this approach. The chiral 3-(3,4-dimethylphenoxy) propane-1,2-diol 1 is a synthetic precursor of practically useful amino alcohols, the enantiomers of which exhibit different biological effects. In this work, it was first discovered that racemic diol 1 is prone to spontaneous resolution. However, the crystallization process is complicated by the existence, along with the conglomerate, of two other crystalline forms. Using the differential scanning calorimetry (DSC) approach, methods have been developed to obtain individual metastable phases, and all identified modifications ((R)-1, (R+S)-1, α-rac-1, β-rac-1) were ranked by energy. The IR spectroscopy and powder X-ray diffraction (PXRD) methods demonstrated the identity of the first two forms and their proximity to the third, while β-rac-1 is significantly different from the rest. The crystal structure of the forms (R)-1 and α-rac-1 was established by the single crystal X-ray diffraction (SC-XRD) method. Preliminary information on the structure of β-rac-1 phase was obtained by the PXRD approach. Based on the information received, the experimental conditions for a successful direct resolution of racemic 1 into individual enantiomers by a preferential crystallization procedure were selected.

Studies on the Preparation, Characterization and Solubility of -Cyclodextrin-Roxythromycin Inclusion Complexes

2009 ◽  
Vol 2 (2) ◽  
pp. 523-530
Author(s):  
D. Nagasamy Venkatesh ◽  
S. Karthick ◽  
M. Umesh ◽  
G. Vivek ◽  
R.M. Valliappan ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Inclusion Complexes ◽  
Phase Solubility ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Ir Studies ◽  
Poorly Soluble ◽  
Poorly Soluble Drug

Roxythromycin/ β-cyclodextrin (Roxy/ β-CD) dispersions were prepared with a view to study the influence of β-CD on the solubility and dissolution rate of this poorly soluble drug. Phase-solubility profile indicated that the solubility of roxythromycin was significantly increased in the presence of β-cyclodextrin and was classified as AL-type, indicating the 1:1 stoichiometric inclusion complexes. Physical characterization of the prepared systems was carried out by differential scanning calorimetry (DSC), X-ray diffraction studies (XRD) and IR studies. Solid state characterization of the drug β-CD binary system using XRD, FTIR and DSC revealed distinct loss of drug crystallinity in the formulation, ostensibly accounting for enhancement of dissolution rate.

scholarly journals A review of nanotechnology with an emphasis on Nanoplex

2015 ◽  
Vol 51 (2) ◽  
pp. 255-263
Author(s):  
Rupali Nanasaheb Kadam ◽  
Raosaheb Sopanrao Shendge ◽  
Vishal Vijay Pande
Keyword(s):  
Drug Delivery ◽  
Drug Delivery Systems ◽  
Drug Loading ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Conventional Drug ◽  
Anionic Drugs ◽  
Oppositely Charged ◽  
The Brain

<p>The use of nanotechnology based on the development and fabrication of nanostructures is one approach that has been employed to overcome the challenges involved with conventional drug delivery systems. Formulating Nanoplex is the new trend in nanotechnology. A nanoplex is a complex formed by a drug nanoparticle with an oppositely charged polyelectrolyte. Both cationic and anionic drugs form complexes with oppositely charged polyelectrolytes. Compared with other nanostructures, the yield of Nanoplex is greater and the complexation efficiency is better. Nanoplex are also easier to prepare. Nanoplex formulation is characterized through the production yield, complexation efficiency, drug loading, particle size and zeta potential using scanning electron microscopy, differential scanning calorimetry, X-ray diffraction and dialysis studies. Nanoplex have wide-ranging applications in different fields such as cancer therapy, gene drug delivery, drug delivery to the brain and protein and peptide drug delivery.</p>

scholarly journals Diethylstilbestrol Modifies the Structure of Model Membranes and Is Localized Close to the First Carbons of the Fatty Acyl Chains

Biomolecules ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 220
Author(s):  
Alessio Ausili ◽  
Inés Rodríguez-González ◽  
Alejandro Torrecillas ◽  
José A. Teruel ◽  
Juan C. Gómez-Fernández
Keyword(s):  
Membrane Surface ◽  
Water Layer ◽  
Fatty Acyl ◽  
31P Nmr Spectroscopy ◽  
Relaxation Rates ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Acyl Chains ◽  
Dynamics Simulations

The synthetic estrogen diethylstilbestrol (DES) is used to treat metastatic carcinomas and prostate cancer. We studied its interaction with membranes and its localization to understand its mechanism of action and side-effects. We used differential scanning calorimetry (DSC) showing that DES fluidized the membrane and has poor solubility in DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) in the fluid state. Using small-angle X-ray diffraction (SAXD), it was observed that DES increased the thickness of the water layer between phospholipid membranes, indicating effects on the membrane surface. DSC, X-ray diffraction, and 31P-NMR spectroscopy were used to study the effect of DES on the Lα-to-HII phase transition, and it was observed that negative curvature of the membrane is promoted by DES, and this effect may be significant to understand its action on membrane enzymes. Using the 1H-NOESY-NMR-MAS technique, cross-relaxation rates for different protons of DES with POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) protons were calculated, suggesting that the most likely location of DES in the membrane is with the main axis parallel to the surface and close to the first carbons of the fatty acyl chains of POPC. Molecular dynamics simulations were in close agreements with the experimental results regarding the location of DES in phospholipids bilayers.

scholarly journals Effects of Sintering Temperature on Densification, Microstructure and Mechanical Properties of Al-Based Alloy by High-Velocity Compaction

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 218
Author(s):  
Xianjie Yuan ◽  
Xuanhui Qu ◽  
Haiqing Yin ◽  
Zaiqiang Feng ◽  
Mingqi Tang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Velocity ◽  
Sintered Density ◽  
Sintering Temperature ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
High Velocity Compaction ◽  
Sintered Temperature

This present work investigates the effects of sintering temperature on densification, mechanical properties and microstructure of Al-based alloy pressed by high-velocity compaction. The green samples were heated under the flow of high pure (99.99 wt%) N2. The heating rate was 4 °C/min before 315 °C. For reducing the residual stress, the samples were isothermally held for one h. Then, the specimens were respectively heated at the rate of 10 °C/min to the temperature between 540 °C and 700 °C, held for one h, and then furnace-cooled to the room temperature. Results indicate that when the sintered temperature was 640 °C, both the sintered density and mechanical properties was optimum. Differential Scanning Calorimetry, X-ray diffraction of sintered samples, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, and Transmission Electron Microscope were used to analyse the microstructure and phases.

scholarly journals Born out of Fire and Ice: Polymorph Studies of the Antiviral Famciclovir

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 129
Author(s):  
Liana Vella-Zarb ◽  
Ulrich Baisch
Keyword(s):  
Variable Temperature ◽  
Chemical Properties ◽  
Crystal Form ◽  
X Ray Diffraction ◽  
Crystal Forms ◽  
X Ray ◽  
Physical Chemical ◽  
Diffraction Patterns ◽  
Crystalline Forms

There is much interest and focus on solid forms of famciclovir. However, in spite of the abundance of reported differences in oral bioavailability, compressibility, and other physical–chemical properties of the various crystal forms of this drug, very little precise structural analysis is available in the literature to date. The form used in the commercial formulation is the anhydrous form I. Patents and patent applications report three different anhydrous crystalline forms on the basis of unindexed powder diffraction patterns. Single-crystal and variable-temperature X-ray diffraction experiments using the commercially available anhydrous form of famciclovir were carried out and led not only to the crystal structure determination of the anhydrous form I, but also to discovery of a new crystal form of anhydrous famciclovir from powder data.

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