Hot Glycerol Research Articles

Hydrogen charging of carbon and low alloy steel by electrochemical methods

Atomic hydrogen can be the result of different processes like electroplating, chemical and electrochemical pickling treatments, in welding or by cathodic processes in corrosive fluids. Moreover, adsorption of atomic hydrogen can affect materials in contact with high pressure gaseous hydrogen. Once entered the material, atomic hydrogen interacts with the metal structure and may produce a “damage” of various forms, such as Hydrogen Induced Cracking (HIC), delayed fracture, blistering and hydrogen embrittlement. In particular, when H2S is present (“sour service”), metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. Sour service materials must be used in compliance with international accepted standards, used worldwide in oil and gas activities, when fluids are classified as sour. The present study has been carried out in order to set up an electrochemical method to charge with hydrogen two typical pipeline materials, carbon and low alloy steels. The reason of the use of an electrochemical method is to avoid any critical conditions from the point of view of preparation, safety and disposal. Hydrogen content in the specimens was measured by two different methods: hot glycerol bath and Inert Gas Fusion (IGF) analysis. Hydrogen content in the specimens is about 0.6–2 ppm; mechanical performances were assessed by means of J integral tests: a pronounced decrease of fracture toughness was observed for H charged specimens.Graphical

Tuning of the Mg Alloy AZ31 Anodizing Process for Biodegradable Implants.

Coatings were grown on the AZ31 Mg alloy by a hard anodizing process in the hot glycerol phosphate-containing electrolyte. Anodizing conditions were optimized, maximizing corrosion resistance estimated by impedance measurements carried out in Hank’s solution at 37 °C. A post anodizing annealing treatment (350 °C for 24 h) allowed us to further enhance the corrosion resistance of the coatings mainly containing magnesium phosphate according to energy-dispersive X-ray spectroscopy and Raman analyses. Gravimetric measurements revealed a hydrogen evolution rate within the limits acceptable for application of AZ31 in biomedical devices. In vitro tests demonstrated that the coatings are biocompatible with a preosteoblast cell line.

Effect of temperature on thermal, mechanical and morphological properties of polypropylene foams prepared by single step and two step batch foaming process

This study reports the influence of foaming temperature on morphological and thermo-mechanical characteristics of polypropylene (PP) foams prepared using two different methods of batch foaming at low saturation pressures. In the first method, involving single-step pressure-induced-foaming (PIF), the solid specimen was heated to different temperatures in a high-pressure vessel, and then saturated CO2 under pressure. Depressurization then led to foaming. In the second method, involving a two-step temperature-induced-foaming (TIF), the solid specimen was saturated with pressurized CO2 at room temperature for a specific period of time and then the CO2 laden specimen was immersed in hot glycerol bath at different temperatures for foaming. SEM micrographs of the fractured foamed specimens were employed for measurement of cell-size distribution. The average cell sizes ranged between 3 and 310 μm in specimens obtained using PIF, while in case of foams prepared by TIF, the cell sizes ranged between 30 and 70 μm. The cell sizes achieved in TIF are significantly smaller and more uniform as compared to those in PIF foams. The density (0.393–0.186 g cm−3) of PIF foams was seen to decrease with increasing foaming temperature; in contrast, in case of TIF the density remained more or less unchanged around 0.43–0.47 g cm−3 with changes in foaming temperature. The foamed specimens were characterized in uniaxial compression; the stiffness (elastic and collapse moduli) and compressive strengths of both the PIF and TIF foams were seen to decrease with increase in cell-size. The magnitude of plateau-regime stresses within the compressive stress-strain response showed strong correlation with the foam cell-wall thickness. The crystallinity of the foamed specimens was observed to decrease with increase in foaming temperatures. The thermal stability of both PIF and TIF foams in general showed improvement compared with the PP matrix.

Solvent and thermal resistant ultrafiltration membranes from alkyne-functionalized high-performance polymers

Polymeric porous membranes with excellent thermal (Td higher than 500 °C) and solvent resistance were prepared. The membranes were based on three high-performance polymers (polyoxindolebiphenylene, polytriazole and polybenzimidazole), functionalized with alkyne side groups. The functionalization enabled the polymer crosslinking by a fast and simple wet-state thermal process in hot glycerol. The effect of crosslinking time and temperature was evaluated. The obtained membranes were characterized by spectroscopy and thermal analysis. The membrane morphology was investigated by electron microscopy. The liquid separation performance of the crosslinked membranes was evaluated in several organic solvents. The stability in filtration experiments was demonstrated in dimethylformamide at temperatures up to 140 °C. The solvent resistance in various solvents was confirmed in long-term tests (up to 21 days) at room temperature.

Pretreatment in Hot Glycerol for Facile and Green Separation of Chitin from Prawn Shell Waste

A rapid and efficient process for the separation of chitin from waste prawn shells using hot glycerol pretreatment is reported. The pretreatment of waste prawn shell in hot glycerol enables the removal of protein possibly through dehydration and temperature induced fragmentation into low molecular weight water-soluble fragments, which are subsequently removed from the shell matrix by dissolution in water. In contrast, in the industrial process of preparing chitin from crustacean shells, the deproteinization is carried out with hot aqueous sodium hydroxide. The novel pretreatment present here should be applicable to all crustacean shell waste, in principle. Chitin was isolated by two different methods after the pretreatment in glycerol. In one of the methods, the pretreated shells were treated directly with citric acid to remove protein and minerals (mostly as calcium citrate). In the second method, the pretreated shells were ground and rinsed with water to remove protein fragments and part of the minerals...

Specific Formation Behavior of Crystalline TiO2 Mesoporous Films during Anodizing in Hot Alkaline Glycerol Electrolytes

Recently, we reported the formation of TiO2 mesoporous films by anodizing titanium in hot phosphate/glycerol electrolytes [1-3]. The resultant films showed interesting features, for example: (i) the pore size was as small as ~10 nm leading to a high surface area and did not change linearly with the formation voltage; and (ii) formation of the films at an 20 V generated the crystalline anatase phase without the requirement of post-annealing, whereas as prepared films anodized in the electrolytes containing fluorides were usually amorphous. However, the details of formation behavior of the crystalline TiO2mesoporous films have yet to be revealed. Therefore, in this study, we investigated the growth process of the films during the anodizing in hot alkaline glycerol electrolytes containing phosphate by cyclic voltammetry and changing electrolyte anion species. The specimens were 99.5% pure titanium plates, which were electropolished in 1.0 mol dm-3 NaCl/ethylene glycol solution. The electropolished specimens were anodized in stirred glycerol electrolytes containing selected amounts of phosphate such as K2HPO4 and K3PO4 and/or NOH, and 0.03 wt% H2O at 433 K. Anodizing by cyclic voltammograms (CVs) was performed using a three-electrode system with a platinum foil as a counter electrode and a platinum wire as a reference electrode. The potential sweep rate and stirring rate were 30 mV s-1and 330 rpm, respectively. Anodizing at constant voltage of 20 V was performed using a two-electrode system with the platinum foil as the counter electrode. Fig. 1 shows the CVs of titanium at the first cycle in the hot glycerol electrolyte containing 0.6 mol dm-3 K3PO4 + 0.2 mol dm-3 K2HPO4 (Fig. 1a), together with that in the ethylene glycol electrolyte containing fluoride (Fig. 1b). In the case of the anodizing in the electrolyte containing the phosphates, the current density became almost constant at potentials higher than 2 V vs Pt. Similar constant currents were obtained even during the negative sweep of the potential, whereas the current density decreased during the negative sweep in the electrolyte containing fluoride. This result suggested that the ionic transport in the barrier layer under the high electric field was not a rate-determining step during the anodizing in the hot phosphate/glycerol electrolyte. The Cottrell plot during anodizing in the phosphate/glycerol electrolyte at 3 V vs Pt reveals a linear correlation between the reciprocal of the current density and the square root of anodizing time. Thus, the anodizing process is diffusion-controlled. In addition, the limiting current became smaller with decreasing basicity of the electrolyte, implying some basic species, such as OH-, should be diffusing ones to grow the anodic TiO2films during anodizing in the hot phosphate/glycerol electrolyte. The crystallinity of the films anodizing the electrolyte containing phosphate or not was investigated by XRD. The results suggested that a small amount of the phosphate contained the anodic films may have important roles to crystallize during anodizing.

ChemInform Abstract: Recent Developments in Acid‐ and Base‐Catalyzed Etherification of Glycerol to Polyglycerols

AbstractReview: 37 refs.

Formation behavior of nanoporous anodic aluminum oxide films in hot glycerol/phosphate electrolyte

Formation behavior of anodic aluminum oxide (AAO) films was studied when aluminum foils were anodized in hot glycerol electrolyte containing 10wt.% K2HPO4 in temperatures of 120–200°C. The characteristics of the present anodization including the current density change with time, the effect of applied voltage and electrolyte temperature on anodization behavior, and the morphology and the porous structure resulting from anodization in temperatures of 120–160°C indicated that the present anodization regime is very similar to the conventional one for formation of nanoporous AAO films near room temperatures. Two-step anodization under 50V at 160°C resulted in an AAO film with relatively well-ordered pore channels. Anodization at 180°C, on the other hand, led to formation of an AAO film with a new mesosponge structure that is consisted of nanopores and nanochannels. The mechanism related to the structure transformation is not known at present.

Highly self-ordered nanochannel TiO2 structures by anodization in a hot glycerol electrolyte

In the present work, we report on the self-organized growth of TiO(2) layers consisting of a highly aligned nanochannel morphology. We show that an electrochemical anodization process of Ti in a hot glycerol/K(2)HPO(4) electrolyte can be adjusted to yield these self-organized TiO(2) structures. The channel diameter and length are controllable by the anodization parameters. This directional structure can, for example, find application in dye-sensitized solar cells.

Oligomerization of glycerol – a critical review

AbstractThe oligomerization of glycerol to preferentially di‐ and triglycerol is reviewed, with primary focus on the use of heterogeneous acidic and basic catalysts. Low molecular‐weight oligomers have found a wide field of applications in cosmetics, food industry and polymer production. The growing market intensified research work on the selective catalytic oligomerization of glycerol. Performing the reaction of glycerol in the presence of microporous and mesoporous solid catalysts aims at exerting shape‐selective effects on the reaction, suppressing the abundant formation of cyclic isomers and cutting further polymerization of the target products. Enhanced selectivity to diglycerol is observed over some type of catalysts, but the solids suffer from leaching of active alkaline cations from the solid, severe deterioration of crystallinity of zeolites and even dissolution of the solids in the hot glycerol during batch reaction at temperatures in the range of 240–260°C. In those cases it is difficult to separate homogeneous and heterogenous reaction routes, and the shape‐selective effects are levelled off. The oligomerization is a consecutive reaction, and complete conversion of glycerol favours formation of high molecular‐weight glycerol oligo‐ and polymers. To achieve maximum yield of diglycerol, the reaction has to be interrupted at glycerol conversions of ca. 50%. Alternative reaction engineering is required to overcome the inherent disadvantages of a batch reaction. Examples will be given for a selective glycerol oligomerization under reduced pressure in a so‐called fall‐film reactor using super‐acidic polymers as catalysts.

Anodic Formation of Thick Anatase TiO2 Mesosponge Layers for High-Efficiency Photocatalysis

We report a process for the fabrication of an anatase TiO(2) mesosponge (TMS) layer by an optimized Ti anodization process in a hot glycerol electrolyte followed by a suitable etching process. Such layers can easily be grown to >10 microm thickness and have regular channels and structural features in the 5-20 nm range. The layers show high photocatalytic activity and are mechanically very robust. The layers therefore open new pathways to the wide field of TiO(2)(anatase) applications.

Effect of Orientation on the Physical Properties of Potato Amylose and High-Amylose Corn Starch Films

The effect of orientation on the properties of amylose and starch films was studied in order to determine if film strength, flexibility, and water resistance could be improved. Potato amylose and high (70%) amylose corn starch were peracetylated, cast into films, stretched in hot glycerol 1-6 times the original length, and deacetylated. Molecular orientation of potato amylose films was much higher than for high-amylose corn starch films as determined by optical birefringence. For potato amylose films, orientation resulted in large increases in tensile strength and elongation but little change in modulus. For high-amylose corn starch films, tensile strength and modulus did not change with draw ratio but elongation to break increased from about 8% to 27% as draw ratio increased from 1 to 5. Scanning electron micrographs revealed many small crazes in the drawn starch films, suggesting that the improved film toughness was due to energy dissipation during deformation of the crazes. Annealing of drawn films at 100% humidity resulted in partial crystallization and improved wet strength.

Two Different Surface Properties of Regenerated Cellulose due to Structural Anisotropy

Contact angles of water droplet on regenerated cellulose films as an index of wettability were positively correlated with the orientation of (1-10) crystal planes and crystallinity. Because hydroxyl groups of cellulose are located at the equatorial positions of glucopyranose rings, corresponding to the surface of (1-10) crystal planes, the hydrophilicity of the (1-10) surface is expected to be very high. It is natural, therefore, that higher planar orientation of (1-10) planes and crystallinity lead to higher density of hydroxyl groups on the surface of regenerated cellulose films resulting in higher wettability. In contrast, hydrogen atoms are located at the axial positions of the glucopyranose rings, corresponding to the surface of (110) planes. Thus, the (110) surface is expected to be hydrophobic, and the surface energy obtained by computer simulations was far lower than that of the (1-10) surface. This suggests that cellulose with complementary properties, i.e., hydrophobicity, may be created by structural controls such as reversing the planar orientation from (1-10) to (110). Although it was not possible to reverse this orientation completely, post-treatments with a nonpolar solvent (e.g., hexane), liquid ammonia or hot glycerol can somewhat control the wettability of regenerated cellulose films.

Preparation of hydrophobic microspheres from low-temperature melting polymeric materials

A novel procedure for the preparation of hydrophobic spherical particles from thermoplastic materials, such as polyethylene (PE) or fossil resin (FR), is presented. These particles are particularly useful in the determination of surface forces with the atomic force microscope using the colloidal probe technique. The preparation steps include (i) suspending powdered polymer (PE and FR) in glycerol, (ii) heating the suspension above the melting point of the polymer, (iii) solidification of dispersed PE/FR droplets at a reduced temperature, (iv) filtration of the particles, and (v) washing/drying of the product. Such produced particles of PE and FR had a broad size distribution (2-50 μm) and a spherical shape. The surfaces of these particles were relatively smooth, with a small number of asperities, and/or attached satellite particles or non-spherical debris. Analytical examination of the polymer surface, before and after treatment with hot glycerol, by SEM, AFM, contact angle, XPS, and FTIR measurements revealed only slight chemical changes on the surface caused by this treatment, which included a decrease in the hydrophobicity of the polymer surface caused by an increased amount of oxygen-containing polar groups. These changes were greatly diminished after drying, and the hydrophobicity of the PE and FR surfaces was, at least partially, restored.

Electroplated solder alloys for flip chip interconnections

Flip chip mounting of bare dice is gaining widespread use in microelectronics packaging. The main drivers for this technology are high packaging density, improved performance at high frequency, low parasitic effects and potentially high reliability and low cost. Many companies have made significant efforts to develop a technology for bump processing, bare die testing and underfill encapsulation to gain the benefit of all potential advantages. We have focussed on low cost bumping of fully processed silicon wafers to develop a flexible scheme for various reflow requirements. The bumping process is based on galvanic plating from an alloy solution or, alternatively, from several elemental plating baths. Sputtered Mo/Cu or Cr/Cu is used as a wettable base for electroplating. Excess base metal is removed by using the bumps as an etching mask. Variation of the alloy composition or the layer structure, allows the adjustment of the bump reflow temperature for the specific requirements of the assembly. Using binary tin-lead and ternary tin-lead-bismuth alloys, reflow temperatures from 100 °C (bismuth rich alloys) to above 300 °C (lead rich alloys) can be covered. The influence of the plating current density on the final alloy composition has been established by ion beam analysis of the plated layers and a series of reflow experiments. To control the plating uniformity and the alloy composition, a new cup plating system has been built with a random flow pattern and continuous adjustment of the current density. A well-controlled reflow of the bumps has been achieved in hot glycerol up to the eutectic point of tin-lead alloys. For high temperature alloys, high molecular weight organic liquids have been used. A tensile pull strength of 20 g per bump and resistance of 5 mΩ per bump have been measured for typical eutectic tin-lead bumps of 100 μm in diameter.