Mass spectrometric analysis of ceramics after decomposition with elemental fluorine

The features of a combustion with elementary fluorine for the case of compact SiC ceramics and model substances for boron containing ceramics (H₃BO₃ and Na₂B₄O₇) were investigated with the aim of their decomposition and analysis. On-line detection of the gaseous decomposition products by quadrupole mass spectrometry using electron impact ionisation was studied. Limitations by blanks and transport interferences were investigated. Standard addition as well as the isotope dilution technique were used for calibration in the case of B, C and W at the trace and major component level.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthdayDeceased May 1995.     

Chemistry of silicon-nitrogen compounds. 165. On the crystalline products from the reaction of silicon tetrachloride with nitrogen in a glow discharge. Single crystal X-ray structure determination of N(SiCl3)3 and Cl3SiN(SiCl2)2NSiCl3

Of the two crystalline products obtained by reacting a silicon tetrachloride/nitrogen mixture in a glow discharge tube, the more volatile (m. p. 78°C) has been confirmed to be tris(trichlorosilyl)amine NSi₃Cl₉ whereas the less volatile component (m. p. 66°C) has been identified as N,N′-bis(trichlorosilyl)-Si,Si′-tetrachloro-cyclodisildiazane N₂Si₄Cl₁₀. These conclusions are supported by mass and vibrational spectroscopy and single crystal X-ray structures. NSi₃Cl₉ possesses a nearly planar NSi₃ skeleton with average N? Si distances of 1.734(2) Å. The N₂Si₄ fragment of N₂Si₄Cl₁₀ is roughly planar with endocyclic N? Si? N and Si? N? Si angles of 89.2(1) and 90.8(1)°, respectively, and mean N? Si distances of 1.731(3) (endocyclic) and 1.687(3) Å (exocyclic).     

ChemInform Abstract: Vaporization of (SN)x: He I Photoelectron Spectrum and ab initio Calculations for the S3N3 Radical.

Results of He I photoelectron spectroscopy and quadrupole mass spectrometry indicate that the S₃N₃ radical is the major semistable component of the (SN)_x vaporization products.     

Chemical Vapor Deposition of Silicon Carbide and Silicon Nitride—Chemistry's Contribution to Modern Silicon Ceramics

Pure silicon carbide and silicon nitride have valuable properties in bulk pore-free form; however, their industrial exploitation has hardly been possible so far. Neither compound can be melted or sintered in pure form; hot pressing or sintering at normal pressure requires the presence of additives; and the reaction-sintering process in which only Si and C or Si and N are employed as additives affords porous materials.–The novel process of chemical vapor deposition has partly overcome the drawbacks of the previous methods. In the new process SiC is produced, e.g., by pyrolysis of CH₃SiCl₃, and Si₃N₄ by reaction of SiCl₄ with NH₃. This technique can also be used for pore filling in objects made of SiC and Si₃N₄ (gas phase impregnation) and for producing extremely fine SiC and Si₃N₄ (gas phase impregnation) and for producing extremely fine SiC and Si₃N₄ powder and SiC monofilaments suitable as components for SiC composites. Moreover, gas phase impregnation can also give fiber composites.     

Neue anorganische Ringsysteme. XXII. Neue Spirosilazane der Gerüsttypen Si5N4, Si5N5, Si5N4O und Si7N8

Novel Inorganic Ring Systems. XXII. Novel Spirosilazanes of the Si₅N₄, Si₅N₅, Si₅N₄O, and Si₇N₈ Skeleton We succeeded in preparing the four novel spirosilazane skeletons E , F , G , and H of the composition given in the title. The permethylated compounds of the mentioned systems have been characterized in their chemical and physical properties. The conformation of their structure was possible by elemental analysis and by n.m.r., mass, i.r., and Raman spectra.     

Plasmachemistry. Formation of Chlorosilazanes,Chlorogermazanes and Related Compounds

The plasmachemically activated reaction between N₂ and SiCl₄ leads via nitrogen atoms to numerous chlorosilazanes: NSi₃Cl₉, N₂Si₄Cl₁₀, NSi₄Cl₁₁, N₂Si₄Cl₁₂, N₂Si₅Cl₁₄, N₃Si₆Cl₁₅ (3 isomers), N₂Si₆Cl₁₆ and some related compounds (NOSi₄Cl₁₁, N₂O₂Si₆Cl₁₄, N₂OSi₅Cl₁₂). GeCl₄ shows an similar behaviour. This could be shown by GC/MS‐investigations. The structures of N₂Si₅Cl₁₄, N₂Si₆Cl₁₆ and N₃Si₆Cl₁₅ have been determined by quantum chemical methods. The angle sums around the N atoms are close to 360°.     

Neue anorganische Ringsysteme. XXIII. Hetero-Spirosilazane mit Germanium,Zinn und Zirkonium als spiralem Zentrum

Novel Inorganic Ring Systems. XXIII. Hetero Spirosilazanes with Ge, Sn, and Zr in the Spiral Center Symmetrical SiN-spiro[4,4]-nonanes of the skeleton composition Si₅N₄, Si₄N₄Ge, Si₄N₄Sn and Si₄N₄Zr and with the hetero atoms in the spiral center could be prepared for the first time in shape of their permethylated derivatives A 1 to E 1 via equations (1/2) as well as (3/4/5/6) respectively. They were confirmed in their structure by elemental analysis, proton n.m.r., mass, i.r., and Raman spectra.     

Non-isothermal crystallization kinetics of recycled PET-Si3N4 nanocomposites

Poly(ethylene terephthalate) (PET) is an important industrial material and has been widely applied in consumer products. Due to its slow crystallization rate, nanoparticles are incorporated into PET to function as heterogeneous nucleating agents. In this study, the non-isothermal crystallization behavior of recycled PET-silicon nitride (Si₃N₄) nanocomposites was investigated by differential scanning calorimetry (DSC). In the general analysis of the non-isothermal crystallization curves, it was found that the Si₃N₄ nanoparticles could effectively accelerate the nucleation of PET, but the crystal growth rate was slowed down when the Si₃N₄ content was more than 1 wt%. This might be attributed to the interaction between the PET chains and the surface-treated Si₃N₄ nanoparticles. Results obtained from Avrami and Mo treatments agreed well with the general analysis. Application of the Kissinger method and isoconversional method of Flynn-Wall-Ozawa also showed that Si₃N₄ nanoparticles had a good nucleation effect on the crystallization of PET, and the crystal growth was hindered by Si₃N₄ when the particle loading is higher than 1 wt%.     

Incorporating Si3N4 into PEEK to Produce Antibacterial,Osteocondutive, and Radiolucent Spinal Implants

Polyetheretherketone (PEEK) is a popular polymeric biomaterial which is primarily used as an intervertebral spacer in spinal fusion surgery; but it is developed for trauma, prosthodontics, maxillofacial, and cranial implants. It has the purported advantages of an elastic modulus which is similar to native bone and it can be easily formed into custom 3D shapes. Nevertheless, PEEK's disadvantages include its poor antibacterial resistance, lack of bioactivity, and radiographic transparency. This study presents a simple approach to correcting these three shortcomings while preserving the base polymer's biocompatibility, chemical stability, and elastic modulus. The proposed strategy consists of preparing a PEEK composite by dispersing a minor fraction (i.e., 15 vol%) of a silicon nitride (Si₃N₄) powder within its matrix. In vitro tests of PEEK composites with three Si₃N₄ variants—β‐Si₃N₄, α‐Si₃N₄, and β‐SiYAlON—demonstrate significant improvements in the polymer's osteoconductive versus SaOS‐2 cells and bacteriostatic properties versus gram‐positive Staphylococcus epidermidis bacteria. These properties are clearly a consequence of adding the bioceramic dispersoids, according to chemistry similar to that previously demonstrated for bulk Si₃N₄ ceramics in terms of osteogenic behavior (vs both osteosarcoma and mesenchymal progenitor cells) and antibacterial properties (vs both gram‐positive and gram‐negative bacteria).     

Monitoring of thermal behavior and decomposition products of soybean oil

The thermal degradation and corresponding decomposition products of fresh and heat-treated soybean oil were investigated by synchronous thermal analyzer combined with Fourier transform infrared spectrometry and quadrupole mass spectrometry (STA–FTIR–QMS). Two longtime heat-treated soybean oil samples were aforehand prepared by consistently heating the fresh soybean oil for 50 and 100 h, respectively. N₂ and simulative air (N₂/O₂ = 4:1, volume) were used as the thermal reaction gas atmosphere. The results showed that one stage of mass loss appeared in analysis of the all oil samples under N₂ atmosphere condition and longtime heat pre-treatment had no effect on the thermal behavior of the soybean oil under N₂ atmosphere condition. However, four stages occurred in analysis of both untreated and heat-treated oil samples under the simulative air atmosphere condition. Longtime heat pre-treatment influenced the thermal behavior of the soybean oil in certain extent, which was reflected in the different mass loss values of the four stages. According to the infrared absorption profiles and MS spectra of the released compounds in vapor phase, H₂O, CO, CO₂, hydrocarbons (such as CH₄), and hydroxyl, carbonyl, and carboxyl-contained compounds have been confirmed. Therefore, STA–FTIR–QMS can be suggested as a promising technique for investigating of thermal degradation and monitoring the decomposition products of the evolving substances in edible oils.     

Triple quadrupole mass spectrometry as applied to flame diagnostics: study of the C2H4/N2O/Ar flame

A recently developed research apparatus for characterization of low-pressure premixed flames has been developed and was used to characterize the C₂H₄/N₂O/Ar flame at 20 torr. This instrument incorporates several diagnostic techniques in one apparatus so that individual techniques can be quantitatively compared and the usable detection range (both in terms of resolution and species detection) expanded. Results discussed in this report include mass analysis by triple quadrupole mass spectrometer and temperature measurement by thermocouple. Concentration profiles in the one-dimensional flame include CO, N₂, and C₂H₄, at nominal m/z 28 as well as CO₂ and N₂O at m/z 44.     

Li4Ca3Si2N6 and Li4Sr3Si2N6 – Quaternary Lithium Nitridosilicates with Isolated [Si2N6]10– Ions

The isotypic nitridosilicates Li₄Ca₃Si₂N₆ and Li₄Sr₃Si₂N₆ were synthesized by reaction of strontium or calcium with Si(NH)₂ and additional excess of Li₃N in weld shut tantalum ampoules. The crystal structure, which has been solved by single‐crystal X‐ray diffraction (Li₄Sr₃Si₂N₆: C2/m, Z = 2, a = 6.1268(12), b = 9.6866(19), c = 6.2200(12) Å, β = 90.24(3)°, wR₂ = 0.0903) is made up from isolated [Si₂N₆]^10– ions and is isotypic to Li₄Sr₃Ge₂N₆. The bonding angels and distances within the edge‐sharing [Si₂N₆]^10– double‐tetrahedra are strongly dependent on the lewis acidity of the counterions. This finding is discussed in relation to the compounds Ca₅Si₂N₆ and Ba₅Si₂N₆, which also exhibit isolated [Si₂N₆]^10– ions.     

Analysis of advanced ceramics and their basic products

Summary A review on the analysis of the most important ceramic materials and their basic substances is given. The importance of minor and trace elements in the bulk as well as their distribution on the microscale in both classes of substances is discussed by the example of Al₂O₃, AlN, TiO₂, Si₃N₄, SiO₂, SiC, Y₂O₃, ZrO₂-based and some other ceramics and of their basic substances. The state-of-the-art and trends of development in modern atomic spectrometric methods for bulk analysis of the basic substances subsequent to sample dissolution, such as plasma emission and mass spectrometry, but also of direct methods such as slurry nebulization for plasma spectrometry, inorganic mass spectrometry and X-ray spectrometry are discussed. Further, first approaches for the in-depth analysis of powders and trends in direct methods for compact ceramics based on laser evaporation as well as on electron and ion probe techniques are presented. The latter are illustrated with selected examples from the literature.

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Analyse von modernen keramischen Materialien und ihren Grundstoffen

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Dedicated to Prof. Dr. R. Neeb on the occasion of his 60th birthday     

Die neuen Schichtsilicate Ba3Si6O9N4 und Eu3Si6O9N4

The New Layer‐Silicates Ba₃Si₆O₉N₄ and Eu₃Si₆O₉N₄ The new oxonitridosilicate Ba₃Si₆O₉N₄ has been synthesized in a radiofrequency furnace starting from BaCO₃, amorphous SiO₂ and Si₃N₄. The reaction temperature was at about 1370 °C. The structure of the colorless compound has been determined by single‐crystal X‐ray diffraction analysis (Ba₃Si₆O₉N₄, space group P3 (no. 143), a = 724.9(1) pm, c = 678.4(2) pm, V = 308.69(9)· 10⁶ pm³, Z = 1, R1 = 0.0309, 1312 independent reflections, 68 refined parameters). The compound is built up of corner sharing SiO₂N₂ tetrahedra forming corrugated layers between which the Ba²⁺ ions are located. Substitution of barium by europium leads to the isotypic compound Eu₃Si₆O₉N₄. Because no single‐crystals could be obtained, a Rietveld refinement of the powder diffractogram was conducted for the structure refinement (Eu₃Si₆O₉N₄, space group P3 (no. 143), a = 711.49(1) pm, c = 656.64(2) pm, V = 287.866(8) ·10⁶ pm³, R_p = 0.0379, R_F² = 0.0638). The ²⁹Si MAS‐NMR spectrum of Ba₃Si₆O₉N₄ shows two resonances at ?64.1 and ?66.0 ppm confirming two different crystallographic Si sites.     

Sm2Si3O3N4 und Ln2Si2,5Al0,5O3,5N3,5 (Ln = Ce,Pr, Nd,Sm, Gd) – neuer synthetischer Zugang zu N‐haltigen Melilith‐Phasen und deren Einkristall‐Röntgenstrukturanalyse

Sm₂Si₃O₃N₄ and Ln₂Si_2.5Al_0.5O_3.5N_3.5 (Ln = Ce, Pr, Nd, Sm, Gd) – A Novel Synthetic Approach for the Preparation of N‐containing Melilites and X‐Ray Single‐Crystal Structure Determination The high‐temperature synthesis of nitridosilicates using an especially developed rf furnace was now transferred to the preparation of single‐crystalline oxonitridosilicates and oxonitridoaluminosilicates (sialons). Sm₂Si₃O₃N₄ was obtained by the reaction of SrCO₃, Si(NH)₂, and the respective lanthanoides, for Ln₂Si_2.5Al_0.5O_3.5N_3.5 (Ln = Ce, Pr, Nd, Sm, Gd) additionally AlN was used. The compounds were obtained as coarsely crystalline products. Their crystal structures were refined on the basis of single‐crystal X‐ray diffraction data. Sm₂Si₃O₃N₄ (a = 768.89(4), c = 499.60(4) pm) and the isotypic sialons Ce₂Si_2.5Al_0.5O_3.5N_3.5 (a = 779.20(3), c = 506.94(4) pm), Pr₂Si_2.5Al_0.5O_3.5N_3.5 (a = 778.26(4), c = 508.56(5) pm), Nd₂Si_2.5Al_0.5O_3.5N_3.5 (a = 776.15(4), c = 506.7(3) pm), Sm₂Si_2.5Al_0.5O_3.5N_3.5 (a = 772.63(13), c = 502.80(9) pm), and Gd₂Si_2.5Al_0.5O_3.5N_3.5 (a = 774.15(5), c = 506.46(4) pm) are new representatives of the N‐containing melilite structure type (space group P 4 2₁m (no. 113), Z = 2). For the structure analysis specific models were applied, which have been developed by Werner et al. on the basis of powder diffraction data.     

Fluorine absorption spectra and some fluorides in condensed state

The absorption spectra of liquid F₂, NF₃, N₂F₄, CF₄, BF₃, NF₃, SF₆ have been obtained at diminished temperatures in the near ultra-violet region of the spectrum. It is shown that the absorption spectrum does not differ from the spectra in the gaseous phase, therefore the elementary absorption act is characterized by the cross section of photon absorption by an individual molecule. The absorption cross sections of the above mentioned molecules are represented in the liquid phase, which do not differ strongly from absorption cross sections of these molecules in the gaseous phase. The dependence of the absorption cross sections of liquid fluorine on its concentrations in solutions with N₂, Ar, NF₃, O₂ at - 196°C has been studied. The cross sections of photon absorption by the fluoride molecule in different liquid media with small fluorine concentrations have been obtained.     

Negative ion tandem mass spectrometry of leukotriene E4, and LTE4, metabolites: Identification of LTE4, in human urine

The sulfidopeptide leukotrienes, leukotriene E₄, (LTE₄,) and its N-acetyl derivative and several ω? and β-oxidized metabolites of LTE₄, have been analyzed by tandem mass spectrometry. [M?H]^? ions were produced by continuous flow fast atom bombardment, and collision-induced dissociation of these ions was studied by using a triple quadrupole instrument. The product ion spectra obtained were characteristic of the structure of LTE₄, and mechanisms of ion formation were investigated by using deuterated compounds. β-Elimination of the peptide portion of LTE₄, by loss of CO₂, and ethylene amine leaves the C-l carboxyl group ionized in the most abundant fragment ion for LTE₄, and all metabolites. Tandem mass spectrometry of fast atom bombardment-generated anions from ω? and β-oxidized metabolites of LTE₄, produced similar ions with only a minor influence of the third carboxyl group at the omega terminus evident. Tandem mass spectrometry was used to identify unequivocally the presence of unmodified LTE₄, in a high performance liquid chromatography-purified fraction of urine from a normal healthy volunteer after infusion with LTE₄.     

Investigation of UO4·2NH3·2HF by simultaneous thermogravimetry-differential thermal analysis-mass spectrometry technique

Thermal decomposition of UO₄·2NH₃·2HF was studied under high vacuum and in different gas atmospheres (N₂, O₂, synth. air). Gaseous decomposition products were analyzed and recorded using a quadrupole mass spectrometer.By discussing TG and MS data as well as X-ray analysis of intermediate products an attempt is made, to explain decomposition mechanisms under varied experimental conditions.Thermal decomposition strongly supports the results of X-ray analysis leading to the formula UO₄·2NH₃·2HF.     

Hierarchical assemblies of Si3N4 nanostructures

In the present work, for the first time, we report the growth of hierarchical assemblies of Si₃N₄ nanostructures via catalyst-assisted pyrolysis of a polymeric precursor on the Si substrates. The synthesized products were characterized by using field emission scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. It is found that the size of the catalytic droplet plays a critical role on the formation of hierarchical assemblies of Si₃N₄ nanostructures rather than common single nanowire. A mechanism based on the Vapor–Liquid–Solid (VLS) process was proposed for the assembly of hierarchical Si₃N₄ nanostructures.     

Study of some phenolic-iodine redox polymeric products by thermal analyses and mass spectrometry

Summary This paper describes the use of the mass spectrometry (MS), thermal analyses (TA) and other physico-chemical methods to investigate the structure of two newly synthesized phenolic-iodine derivative polymeric products. These two products are formed as a result of redox-interaction of adrenaline hydrogen tartrate (AHT, I) with iodate (IO^-₃) and periodate (IO^-₄). The characterization of the two products were achieved satisfactorily by using the above tools and their proposed general formulae, were found to be C₅₂H₆₇O₃₆N₄I (AHT- IO^-₃, II) and C₂₆H₃₄O₁₈N₂I₂(AHT- IO^-₄, III). The fragmentation behavior of the main compound (AHT) in MS and TA (TG and DTA) techniques was investigated and compared. The results obtained were used to explain the fragmentation of the products AHT- IO^-₃and AHT- IO^-₄in mass spectrometry and thermal analyses techniques. The stabilities of different fragments were discussed. The results indicate that the two techniques are supporting each other in which the mass spectrometry provides the structural information in gas phase while the thermal analyses provides the quantitative fragmentation in the solid-state.