Formation and Modification of Oxide Networks by Chemical Polymerization

1983 ◽  
Vol 24 ◽  
Author(s):  
Bulent E. Yoldas
Keyword(s):  
Chemical Composition ◽  
Network Structure ◽  
Material Properties ◽  
Low Temperatures ◽  
Ceramic Materials ◽  
The Other ◽  
Equilibrium Conditions ◽  
Chemical Polymerization ◽  
Structural Modifications ◽  
Structure Synthesis

ABSTRACTThe properties of glass and ceramic materials are largely determined by the types and distribution of bonds in the network structure. Since conventional methods of forming these materials by melting or sintering do not allow significant variations from the equilibrium conditions, the properties of these materials are generally fixed by the chemical composition and crystalline structure. Synthesis of these materials by chemical polymerization at low temperatures, on the other hand, permits significant modifications to the ultrastructure. These structural modifications in turn modify the material properties, without compositional alterations. In this presentation, further studies of structure-modifying parameters are discussed.

Effect of CO2 Exposure on Mechanical Resistivity of Cement Pastes with Incorporated Ceramic Waste Powder

2015 ◽  
Vol 824 ◽  
pp. 133-137
Author(s):  
Jaroslav Pokorný ◽  
Milena Pavlíková ◽  
Zbyšek Pavlík
Keyword(s):  
Compressive Strength ◽  
Chemical Composition ◽  
Material Properties ◽  
Chemical Process ◽  
Bending Strength ◽  
Ceramic Materials ◽  
Ceramic Powders ◽  
Cement Pastes ◽  
Matrix Density ◽  
Subsequent Chemical

Carbonation is chemical process associated with CO2penetration into the material porous structure causing subsequent chemical changes in the structure of cement pastes. In this work, carbonation of several pastes containing varying amount of cement replacement by three waste ceramic powders is studied. Chemical composition of particular tested materials is accessed using XRF analysis. Matrix density, bulk density, total open porosity, compressive and bending strength are measured for all developed pastes with incorporated ceramic materials. Simultaneously, the effect of carbonation on these material properties is researched. The obtained results show significant improvement of materials mechanical strength due to the carbonation. Here, the measured compressive strength is typically about ~ 60% higher for materials exposed to CO2rich environment compared to the materials cured in laboratory conditions.

scholarly journals Catalytic Conversion of n-C7 Asphaltenes and Resins II into Hydrogen Using CeO2-Based Nanocatalysts

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1301
Author(s):  
Oscar E. Medina ◽  
Jaime Gallego ◽  
Sócrates Acevedo ◽  
Masoud Riazi ◽  
Raúl Ocampo-Pérez ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Low Temperatures ◽  
Gaseous Mixture ◽  
H2 Production ◽  
The Other ◽  
Hydrogen Release ◽  
Catalytic Gasification ◽  
Three Samples ◽  
Main Decomposition ◽  
Catalytic Capacity

This study focuses on evaluating the volumetric hydrogen content in the gaseous mixture released from the steam catalytic gasification of n-C7 asphaltenes and resins II at low temperatures (<230 °C). For this purpose, four nanocatalysts were selected: CeO2, CeO2 functionalized with Ni-Pd, Fe-Pd, and Co-Pd. The catalytic capacity was measured by non-isothermal (from 100 to 600 °C) and isothermal (220 °C) thermogravimetric analyses. The samples show the main decomposition peak between 200 and 230 °C for bi-elemental nanocatalysts and 300 °C for the CeO2 support, leading to reductions up to 50% in comparison with the samples in the absence of nanoparticles. At 220 °C, the conversion of both fractions increases in the order CeO2 < Fe-Pd < Co-Pd < Ni-Pd. Hydrogen release was quantified for the isothermal tests. The hydrogen production agrees with each material’s catalytic activity for decomposing both fractions at the evaluated conditions. CeNi1Pd1 showed the highest performance among the other three samples and led to the highest hydrogen production in the effluent gas with values of ~44 vol%. When the samples were heated at higher temperatures (i.e., 230 °C), H2 production increased up to 55 vol% during catalyzed n-C7 asphaltene and resin conversion, indicating an increase of up to 70% in comparison with the non-catalyzed systems at the same temperature conditions.

scholarly journals Biofoam of Spittlebug, Poophilus costalis (Walker): Preferential Sites, Temperature Regulation, Chemical Composition and Antimicrobial Activity

Insects ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 340
Author(s):  
Kitherian Sahayaraj ◽  
Balakrishnan Saranya ◽  
Samy Sayed ◽  
Loko Yêyinou Laura Estelle ◽  
Koilraj Madasamy
Keyword(s):  
Antimicrobial Activity ◽  
Chemical Composition ◽  
High Performance ◽  
Host Plants ◽  
Ground Level ◽  
College Campus ◽  
The Other ◽  
Mimosa Pudica ◽  
Ft Ir ◽  
Gas Chromatography Mass Spectroscopy

The foam produced by nymphs of Poophilus costalis on eleven different host plants belonging to eight families on St. Xavier’s College campus in India was studied over five months. The chemical composition and antimicrobial activity of these biofoams were investigated. The results revealed that P. costalis preferred Theporsia purpurea and Mimosa pudica for laying their eggs and producing foam, over the other tested plants. P. costalis produce their foam on either nodes or internodes on monocotyledons (30%) (p < 0.05), whereas on dicotyledons, they produce more foam on the stems (63.8%) than on the leaves (6.2%) (p < 0.01). The number of nymphs in each piece of foam from P. costalis varied from 1 to 3 (mean = 1.8 per plant). They produced their foam (5.7 to 45.2 cm) from the ground level on a plant. The length and breadth of a piece of foam ranged from 1.0 to 3.9 cm and 0.6 to 4.7 cm, respectively. The foam tended to be cooler than the environment. Qualitative profiling showed that the foam consists of carbohydrates, including maltose; trypsin; amino acids; protease. The foam was also analyzed using a spectrophotometer, Fourier transform infrared spectroscopy (FT-IR), gas chromatography–mass spectroscopy (GC-MS), and high-performance liquid chromatography (HPLC). The antimicrobial activity of the biofoam was the greatest against Staphylococcus aureus, the growth of which was reduced by 55.9 ± 3.9%, suggesting that the foam could be used as an antimicrobial product. However, no activities were observed against Fusarium oxysporum and Candida albicans.

On Slip Inception and Static Friction for Smooth Dry Contact

2014 ◽  
Vol 81 (12) ◽  
Author(s):  
Xi Shi
Keyword(s):  
Shear Strength ◽  
Contact Area ◽  
Material Properties ◽  
Static Friction ◽  
Friction Model ◽  
Interfacial Bonding ◽  
The Other ◽  
Material Failure ◽  
Bonding Failure ◽  
Dry Contact

Slip inception mechanism is very important for modeling of static friction and understanding of some experimental observations of friction. In this work, slip inception was treated as a local competence of interfacial bonding failure and weaker material failure. At any contacting point, if bond shear strength is weaker than softer material shear strength, slip inception is governed by interfacial bonding failure. Otherwise, it is governed by softer material failure. Considering the possible co-existence of these two slip inception mechanisms during presliding, a hybrid static friction model for smooth dry contact was proposed, which indicates that the static friction consists of two components: one contributed by contact area where bonding failure is dominant and the other contributed by contact area where material failure is dominant. With the proposed static friction model, the effects of contact pressure, the material properties, and the contact geometry on static friction were discussed.

The Archaeology of the Cave of the Owls in the Upper Montana of Peru

1963 ◽  
Vol 29 (1) ◽  
pp. 27-38 ◽  
Author(s):  
Donald W. Lathrap ◽  
Lawrence Roys
Keyword(s):  
Ceramic Materials ◽  
The Other

AbstractCollections from an unusual cave site in the Peruvian Montaña near Tingo María are placed on record along with the circumstances under which they were obtained. The ceramic materials seem to represent two components. The more common of these, designated Cave of the Owls Fine Ware, would appear to have been contemporary with Kotosh II in the Huánuco Basin and with Late Tutishcainyo of the long ceramic sequence established for Yarinacocha near Pucallpa. A date of around 200 or 300 B.C. is suggested. The other ceramics, designated Monzón Coarse Ware, show strong similarities to the later part of the Yarinacocha sequence and probably date after A.D. 1000.

Interpreting equilibrium-conductivity and conductivity-relaxation measurements to establish thermodynamic and transport properties for multiple charged defect conducting ceramics

2015 ◽  
Vol 182 ◽  
pp. 49-74 ◽  
Author(s):  
Huayang Zhu ◽  
Sandrine Ricote ◽  
W. Grover Coors ◽  
Robert J. Kee
Keyword(s):  
Transport Properties ◽  
Material Properties ◽  
Ceramic Materials ◽  
Barium Zirconate ◽  
Charged Defect ◽  
Conductivity Measurements ◽  
Conductivity Relaxation ◽  
Kinetics Parameters ◽  
Relaxation Measurements ◽  
Thermodynamic And Transport Properties

A model-based interpretation of measured equilibrium conductivity and conductivity relaxation is developed to establish thermodynamic, transport, and kinetics parameters for multiple charged defect conducting (MCDC) ceramic materials. The present study focuses on 10% yttrium-doped barium zirconate (BZY10). In principle, using the Nernst–Einstein relationship, equilibrium conductivity measurements are sufficient to establish thermodynamic and transport properties. However, in practice it is difficult to establish unique sets of properties using equilibrium conductivity alone. Combining equilibrium and conductivity-relaxation measurements serves to significantly improve the quantitative fidelity of the derived material properties. The models are developed using a Nernst–Planck–Poisson (NPP) formulation, which enables the quantitative representation of conductivity relaxations caused by very large changes in oxygen partial pressure.

CERAMICS BASED ON ORGANOSILICON POLYMERS-PRECURSORS: MICROSTRUCTURE AND PROPERTIES (review). Part 2

2021 ◽  
pp. 22-32
Author(s):  
A.M. Shestakov ◽  
Keyword(s):  
Electron Microscopy ◽  
Nmr Spectroscopy ◽  
Material Properties ◽  
Structural Organization ◽  
Ceramic Materials ◽  
Special Role ◽  
Correct Interpretation ◽  
Instrumental Methods ◽  
Organosilicon Polymers

Shows the scientific approaches of various authors to the study of the microstructure of ceramics, the purpose of which is to elucidate its structural organization at the micro- and nanoscale, as well as the influence of the microstructure on the complex of material properties. Various instrumental methods for studying ceramics (NMR spectroscopy, electron microscopy, х-ray structural analysis, etc.) are considered, the permissible capabilities of research methods and analysis of the results obtained with their correct interpretation are shown. The special role of theoretical modeling in understanding the structure of the considered ceramic materials is noted.

Interaction Between Low Temperatures Spacers and Source Drain Extensions and Pockets for Both NMOS and PMOS of the 65 nm Node Technology

2006 ◽  
Vol 912 ◽  
Author(s):  
Nathalie Cagnat ◽  
Cyrille Laviron ◽  
Daniel Mathiot ◽  
Pierre Morin ◽  
Frédéric Salvetti ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Hydrogen Content ◽  
Low Temperatures ◽  
Direct Contact ◽  
Fabrication Process ◽  
Experimental Results ◽  
The Other ◽  
Mos Transistors ◽  
Phosphorus Source ◽  
Activation Annealing

AbstractDuring the MOS transistors fabrication process, the source-drain extension areas are directly in contact with the oxide liner of the spacers stack. In previous works [1, 2, 3] it has been established that boron can diffuse from the source-drain extensions into the spacer oxide liner during the subsequent annealing steps, and that the amount of boron loss depends on the hydrogen content in the oxide, because it enhances B diffusivity in SiO2.In order to characterize and quantify the above phenomena, we performed test experiments on full sheet samples, which mimic either BF2 source-drain extensions over arsenic pockets implants, or BF2 pockets under arsenic or phosphorus source-drain extensions implants. Following the corresponding implants, the wafers were covered with different spacer stacks (oxide + nitride) deposited either by LPCVD, or PECVD. After appropriate activation annealing steps, SIMS measurements were used to characterize the profiles of the various dopants, and the corresponding dose loss was evaluated for each species.Our experimental results clearly evidence that LPCVD or PECVD spacer stacks have no influence on the arsenic profiles. On the other hand, phosphorus and boron profiles are affected. For boron profiles, each spacer type has a different influence. It is also shown that boron out-diffuses not only from the B doped source-drain extension in direct contact with the oxide layer, but also from the "buried" B pockets lying under n-doped source drain extension areas. All these results are discussed in term of the possible relevant mechanism.

Characterization of networks from photoreactive copolymers: an attempt to correlate chemical composition to network structure

2010 ◽  
Vol 59 (12) ◽  
pp. 1563-1570 ◽  
Author(s):  
Branislav Husár ◽  
Sophie Commereuc ◽  
Štefan Chmela ◽  
Vincent Verney
Keyword(s):  
Chemical Composition ◽  
Network Structure

scholarly journals Dilemmas in zirconia bonding: A review

2013 ◽  
Vol 141 (5-6) ◽  
pp. 395-401 ◽  
Author(s):  
Kosovka Obradovic-Djuricic ◽  
Vesna Medic ◽  
Slobodan Dodic ◽  
Dragan Gavrilov ◽  
Djordje Antonijevic ◽  
...  
Keyword(s):  
Bond Strength ◽  
Glass Ceramics ◽  
Ceramic Materials ◽  
The Other ◽  
Zirconia Ceramic ◽  
Bonding Mechanism ◽  
Luting Cements ◽  
Esthetic Dentistry ◽  
Selection Of

This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability. The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today.

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