Effect of boric acid on properties of high‐alumina phosphate‐bonded plastic refractory materials

The effect of boric acid on the properties of high‐alumina phosphate‐bonded plastic refractory materials at medium temperature is investigated in this work. Powder X‐ray diffraction (XRD), thermogravimetric analysis/differential thermal analysis (TG/DTA), and scanning electron microscopy (SEM) techniques are used to investigate the compositions and microstructures of the Al₂O₃–H₃BO₃ sintering products, in order to study the influence of the generated aluminum borate on the high‐aluminum refractories. Additionally, the effect of the addition of H₃BO₃ on the densification and mechanical strength of high‐aluminum phosphate‐bonded plastic refractories is studied by the permanent linear change, apparent porosity, cold compressive strength, flexural strength, and scanning electron microscopy pattern. The densification and mechanical strength of the refractories can be improved significantly by the optimal addition of H₃BO₃. However, excess H₃BO₃ will bring about a large amount of bound water into the refractories, and superabundant aluminum borate whiskers will be generated by the excess addition of H₃BO₃, both of them resulting in the reduction of the densification and mechanical strength of the refractory. In conclusion, the optimum dosages of H₃BO₃ in the powder system of high‐alumina phosphate‐bonded plastic refractories are 5, 4, and 3 wt%, sintered at 700, 900, and 1100 °C, respectively.     

Effect of electrical charging on scanning electron microscopy-energy dispersive X-ray spectroscopy analysis of insulating materials

We investigated the conditions under which we can obtain reasonable qualitative results in scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) analysis of trace elements in insulating materials using a diluted ionic liquid (EMI-CH₃COO) and changing probe current. Below 100 nA, electrical charging of insulating materials was prevented. The probe current of 10 nA was suitable for qualitative analysis because the intensities of peaks from these materials were strong enough to detect trace elements at the concentration of 0.1 wt.% in the sample without interference by sum peaks. Diluted EMI-CH₃COO can also be used for SEM-EDX quantitative analysis of insulating materials as discharging agents. In contrast, when insulating materials were electrically charged, the obtained spectra contained characteristic X-rays of the insulating materials with low energies and of materials other than the samples such as the sample stage and the collimator in the X-ray detector. This is because electrons from the electron beam were decelerated by and deflected from the insulating materials. By coating the insulating materials with the diluted EMI-CH₃COO, the deceleration and deflection of the electron beam were prevented.     

Lightweight lignocellulosic foams for thermal insulation

Foams are mainly composed of dispersed gas trapped in a liquid or solid phase making them lightweight and thermally insulating materials. Additionally, they are applicable for large surfaces, which makes them attractive for thermal insulation. State-of-the-art thermally insulating foams are made of synthetic polymeric materials such as polystyrene. This work focuses on generating foam from surfactants and renewable lignocellulosic materials for thermally insulating stealth material. The effect of two surfactants (sodium dodecyl sulphate (SDS) and polysorbate (T80)), two cellulosic materials (bleached pulp and nanocellulose), and lignin on the foaming and stability of foam was investigated using experimental design and response surface methodology. The volume-optimized foams determined using experimental design were further studied with optical microscopy and infrared imaging. The results of experimental design, bubble structure of foams, and observations of their thermal conductivity showed that bleached pulp foam made using SDS as surfactant produced the highest foam volume, best stability, and good thermal insulation. Lignin did not improve the foaming or thermal insulation properties of the foam, but it was found to improve the structural stability of foam and brought natural brown color to the foam. Both wet and dry lignocellulosic foams provided thermal insulation comparable to dry polystyrene foam.

Graphical abstract

     

The use of HPLC for the analytical determination of diisocyanates and acid anhydrides in the air of working environments

Abstract

Measurements of airborne concentrations of (monomeric) 2,4- and 2,6-toluene diisocyanate (2,4- and 2,6- TDI), 4,4′ - diisocyanato diphenylmethane (MDI) and phthalic anhydride have been performed at 17 Danish manufactories using these compounds in the production of polyurethane foams, insulating materials, elastomers, coatings, lacquers and glues.

Diisocyanate vapours at workplaces were collected in impingers, containing a solution of 9-(N-methylaminomethyl)-anthracene (1 × 10^?4 M) in toluene. By reaction with this amine compound the diisocyanates are converted to stable urea derivatives. Phthalic anhydride particles were collected on glass fiber filters.

For separation and detection of the diisocyanate derivatives and the phthalic acid formed upon hydrolysis of its anhydride, reversed phase high performance liquid chromatography on a bonded octadecylsilyl phase using isocratic elution with acetonitrile/water and UV-monitoring at Λ = 254 nm were used. The results obtained for each manufactory are presented.     

Nanofibers of Semiconductor Oxides as Sensitive Materials for Detection of Gaseous Products Formed in Low-Temperature Pyrolysis of Polyvinyl Chloride

Nanofibers of semiconducting oxides SnO₂, ZnO, WO₃, produced by the electrospinning method, were tested as sensitive materials for detection of products formed in pyrolysis of polyvinyl chloride in conditions simulating the smoldering of electrically insulating materials upon occurrence of a short-circuit failure in electrical circuits. The method of thermal analysis with mass-spectroscopic determination of gaseous products demonstrated that, in pyrolysis of polyvinyl chloride in the temperature range 200–400°C corresponding to the invisible-smoke stage, the main component of the gas mixture being formed is HCl. It was shown that the materials synthesized can be used to develop gas sensors for early fire warning.     

Development and In Vivo Test of Sol-Gel Derived Bone Grafting Materials

A novel bioceramic derived via sol gel method was developed and very good resorption properties in long term period of implantation were established.Calcium phosphate materials are bioactive, osteoconductive materials used as guides for bone regeneration. An identical sequence of events apparently occurred at the contact of the ceramics when implanted in vivo. Two kinds of calcium phosphate ceramics have been produced in a form of threads with 1 mm in diameter: hydroxyapatite SiO₂-containing ceramic and hydroxyapatite—-tricalcium phosphate SiO₂-containing ceramic. Above mentioned calcium phosphate ceramic established an interconnecting macroporous structure, which is responsible for growth of bone and for replacement of ceramic by bone. Three ranges of pores were designed.Viscosity measurements were made to control the point of gelation and production phase of transplant material.In vivo experiments were carried out for 5 weeks and 8 months. The results after the short period of examination have shown the early stage of bone formation and material dissolution. Within 6 months nearly 100% of implanted ceramic was resorpted and new bone around place of intervention was formed.     

RADIATION-INDUCED CHANGES IN POLYOLEFINS

Abstract

The radiation chemistry of polymeric materials has been a field of extensive research. The pioneer investigations of Charlesby and Dole showed that polyolefins exposed to high energy radiation undergo various structural changes.     

Investigations on some inorganic ion-exchangers after irradiation

The changes in the ion exchange properties of crystalline zirconium phosphate, cerium phosphate and cerium arsenate after irradiation have been investigated. The absorbed gamma dose was 10⁹ rad in all cases, the experiments were carried out before and immediately after irradiation with the same samples. Besides the investigations of structural change, the ion exchange behaviour of the above mentioned materials was studied in detail. The ion exchange capacities were determined using a tracer technique for the alkali metal ions, and some relations between ion exchange and structure were revealed.     

The Development of Vanadyl Phosphate Cathode Materials for Energy Storage Systems: A Review

Various cathode materials have been proposed for high-performance rechargeable batteries. Vanadyl phosphate is an important member of the polyanion cathode family. VOPO₄ has seven known crystal polymorphs with tunneled or layered frameworks, which allow facile cation (de)intercalations. Two-electron transfer per formula unit can be realized by using V^V/V^IV and V^IV/V^III redox couples. The electrochemical performance is closely related to the structures of VOPO₄ and the types of inserted cations. This Review outlines the crystal structures of VOPO₄ polymorphs and their lithiated phases. The research progress of vanadyl phosphate cathode materials for different energy storage systems, including lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, multivalent batteries, and supercapacitors, as well as the related mechanism investigations are summarized. It is hoped that this Review will help with future directions of using vanadyl phosphate materials for energy storage.     

Lithium and sodium insertion reactions of phosphate tungsten bronzes

Lithium insertion reactions of monophosphate tungsten bronzes, (PO₂)₄(WO₃)_2m and diphosphate tungsten bronzes K(P₂O₄)₂(WO₃)_2m indicate that a maximum of two Li/W and one Na/W may be inserted in these materials. The phosphate tungsten bronzes are three-dimensional network structures made up of slabs of ReO₃-type WO₆ octahedra connected by phosphate groups with large interconnected cavities. Ion-exchange reactions of selected members of K(P₂O₄)₂(WO₃)_2m show that potassium which occupies the large hexagonal tunnels in the lattice may be exchanged for various alkali metal cations. Upon lithium insertion, the metallic host materials become insulating. This is attributed to the filling of the π* conduction band formed by the overlap of Wt_2g − 5d and oxygenπ − 2p orbitals.     

AP-GOD Biosensor Based on a Modified Poly(PHENOL) Film Electrode and Its Application in the Determination of Low Levels of Phosphate

Abstract

The features of a biosensor based on a platinum electrode modified with a poly(phenol) film coupled with two enzymes, alkaline phosphatase(AP) and glucose oxidase(GOD), were studied. The modification of the surface of the working electrode decreases interference from ascorbic acid, uric acid and some oxidizable organic materials (e.g. glycine), and decreases the noise of the current. The concentration of substrate, the activity ratio of the two enzymes, the applied potential, and the assembling of biosensor are important for the determination of low levels of phosphate.

The two enzymes have been immobilized on an Immobilon^(R) membrane. The linearity range appears in two sections with different sensitivity: one from 8-110 μmol I^?1 and another one from 0.1-1.0 mmol I^?1, with 1.2 μA/mmol/cm² and 0.4 μA/mmol/cm², respectively. Except for some heavy metal ions, ascorbic acid and some oxidizable organic materials, common anions and cations don't interfere with the determination of phosphate.

The biosensor has been used to determine phosphate in some synthetic and real samples with a detection limit of 4 μmol I^?1 of phosphate. The results were compared with a standard spectrophotometric method. The accuracy and recovery of phosphate with the biosensor procedure are ±2% and 96 to 103%, respectively.

     

The Reaction of Phosphoryl Chlorides with Enamines - A New Approach to β-Ketophosphonates

Abstract

Several approaches are available for the preparation of β-ketophosphonate esters. A Michaelis-Arbuzov approach using the reaction of an α-halo ketone with a trialkyl phosphite may in certain instances be controlled to favor the preparation of the target materials. However, an alternative pathway leading to the formation of vinyl phosphate esters often predominates. (This reaction system has recently been reviewed by Borowitz and Borowitz.¹) An alternative approach is that developed in recent years by Wiemer, et al.² involving the rearrangement of vinyl phosphate esters to the β-ketophosphonates.     

Buffer Choice for Tuning the Selectivity in Reverse Phase Chromatography

Abstract

Retention behaviour of ionogenic species in high-performance liquid chromatography on reversed phase materials was studied, specifically dependence of buffer quality applied to mobile phases. The buffers' effect on retention of organic acids, amino acids and dipeptides is quantified by modelling capacity factors as a function of pH-values. At constant ionic strength, increasing capacity factors were observed going from phosphate to less polar citrate buffer, modification of accessible silanol groups of the stationary phase being responsible for this effect. Application of citrate buffer for separation of a seven-component mixture is demonstrated on the basis of a computerized search for optimum chromatographic performance. The evaluated factor levels (pH, methanol content and ionic strength) differ from those found using phosphate buffer-containing mobile phases.     

Development of Calcium Phosphate Glass-Ceramics for Surgical and Dental Use

Abstract

Two types of glass-ceramics have been developed in the system of calcium phosphate without silica. The preparation conditions, crystallization processes, and some of physical properties are briefly reported. These glass-ceramics have high potential use for bone substitutes and dental materials such as dental crown, root and tooth.     

Titan Based Hybrid Organic-Inorganic Gels Comprising Carbohydrate Moiety

Abstract

A series of titanium based gels comprising carbohydrate moieties was synthesized. The sugars used include a specific hydrazide group as complex forming agent. Additionally, this group forms stable hydrates which allow further slow water release. As a result, the compounds used in this study form transparent and stable gels with titanium alkoxide without addition of external water. Interpretation of the IR-spectra reveals that some compounds form monodentate ligands and other bidentate ligands. Further Tian-Calvet calorimetric measurements confirmed our IR-based conclusions. This strategy of synthesis gives a new opportunity to obtain hybrid materials by addition of natural chelating ligands to slow down the hydrolysis/condensation reactions that occur during the sol-gel process. Therefore, carbohydrate moieties have been incorporated in the gels obtained and different type of Ti coordination was proposed based on the IR spectroscopy studies. SEM investigations show the influence of the ligand on the morphology of the xerogel.

GRAPHICAL ABSTRACT      

Inorganic-organic hybrid framework solids

Recent developments in the area of hybrid structures are overviewed with special emphasis on iron phosphate-oxalate materials. The structure of the iron phosphate-oxalates consists of iron phosphate chains or layers that are connected by oxalate moieties completing the architecture. The compounds exhibit interesting magnetic properties originating from the super-exchange interactions that are predominantly anti-ferromagnetic, involving the iron phosphates and the oxalate moieties. One of the materials,IV, also exhibits interesting adsorptive properties reminiscent of aluminosilicate zeolites. The aluminum phosphate-oxalate,VII, indicates that hybrid structures can be formed with zeolite architecture.     

The Production of Calcium Phosphate from Natural Raw Material Using Liquid-Phase Process with Recycle

Abstract

The graphic investigation of basic equilibrium systems CaO-P₂O₅-H₂0, CaO-P₂OH₂0-HA (HA: HCl, HNO₃, H₂SO₄) was carried out. The conditions of the preparation of mono-, dicalcium phosphate and mixtures by crystallization and separation of the crystals from the mother liquid which is circulated during the stage of phosphate rock acid decomposition, were found. The equilibrium study of these systems, which had technological admixtures (MgO, R₂O₃), the chemism and kinetics of the interaction of the phosphate rock with the mixture of the phosphoric acid and mother liquor and calcium phosphate crystallization were investigated. This investigation made it possible to work out the scheme of the process with liquid recycle for the production of calcium phosphonates. According to this scheme, phosphate rock is processed by phosphoric acid and mother liquid mixture at 40–80°C for 30–60 min. As the liquid phase has a high activity, the yield of the phosphate rock decomposition achieves 98–1009. Monocalcium phosphate formed with insoluble mixtures or pure monocalcium phosphate is separeted by crystallization and filtration after preliminary separation of mixtures (1). The process with recycle was tested in laboratory using various natural phosphate rocks with a range of P₂₅O content within 14,5–39,4%. The product (monocalcium phosphate contains 26–54% P₂°5, depending on the quality of the phosphate rock and the process organization. The amount of P₂°₅ extraction from the phosphate was nearly quantitative in all cases.     

Reactive groups on polymer-covered electrodes

Polythiophene films containing ester groups on the surface of electrodes are interesting potential carrier materials for reagents. Methyl thiophene-3-acetate (3) can be copolymerized with 3-methylthiophene (1) and 3-butylthiophene (2) by means of cyclic voltammetry (CV) at potentials of 0–2.2 V. Higher potentials (0–2.4 V) lead to overoxidation of the copolymers. The ester groups were confirmed by FTIR spectra. Electrochemical investigations of 2,2′-bithiophene (6) and 3 at equimolar ratios showed no successful copolymerization at potentials of 0–1.3 V. If the copolymerization experiments of 6 with 1 or 3 were carried out at molar ratios of 1:50 at 1.3 V, 6 with its low oxidation potential was polymerized without copolymerization of the other monomers. However, if the oxidation potential was increased stepwise from 1.3 V, the oxidation of 1 or 3 occurred, forming copolymers containing both monomer components. HPLC investigations of solutions containing mixtures of 6 and 3 and also 6 and 1 in acetonitrile/TEABF₄ showed, after exhaustive oxidation at a potential of 1.3 V, the complete absence of 6; 1 and the ester 3 were not oxidized and copolymerized at these potentials. From the results of the copolymerization experiments, as well as the HPLC investigations, it can be concluded that the dominant mechanism of the electrochemical polymerization is radical cation dimerization. Received: 21 August 1998 / Accepted: 11 January 2000     

Dimephosphon,a new Phosphorus-Containing Medical Drug for Treatment of Acidosis: Chemistry and Technology

Abstract

Medical drug dimephosphon-dimethyl 1,l-dimethyl-3-oxobutnylphosphonate was created as a result of chemical and biological investigations of low-toxic organophosphorus compounds. This drug was selected from a number of acyclic transformation products of 1,2-oxyphospholene derivatives. A technology was worked out which is based on the Pudovik reaction and transformed into the continuous process. For this process an original continuous flow reactor has been created.     

REACTION OF PENTAERYTHRITOL WITH DIETHYL PHOSPHOROCHLORIDATE PENTAERYTHRITOL BIS-, TRIS- AND TETRAKIS(DIHYDROGEN PHOSPHATES)

Abstract

Reaction of pentaerythritol 1 with 1, 2 or 3 equivalents of diethyl phosphorochloridate 2 yielded pentaerythritol tris(diethyl phosphate) 5. Treatment of pentaerythritol with 4 or more equivalents of 2 gave pentaerythritol tetrakis(diethyl phosphate) 6. Transesterification of 5 and 6 with trimethylsilyl chloride and sodium iodide in acetonitrile followed by treatment with water gave pentaerythritol tris (dihydrogen phosphate) 7 and pentaerythritol tetrakis(dihydrogen phosphate) 8 respectively. Pentaerythritol bis(dihydrogen phosphate) 9 was prepared by the hydrolysis of 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro [5,5] undecane 3,9-dioxide 10. The compounds 7,8 and 9 were isolated as anilinium salts and characterized by 1H, 13C and 31P NMR spectra.