Download or read book Chemical Precursors to Zinc Sulfide ZnS Whisker Synthesis written by T. A. Guiton and published by . This book was released on 1988 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Currently, Chemical Vapor Deposition (CVD) derived zinc sulfide is one of the most widely used infrared optical window materials. Unfortunately, for numerous applications it does not possess optimum mechanical properties. To fabricate infrared transmitting ZnS/ZnS composites requires the development of high aspect ratio, micron sized ZnS whiskers. Although larger ZnS single crystals and whiskers have been made by a variety of high temperature route, alternative routes have been sought for greater ZnS whisker morphology control. Low temperature organometallic routes are attractive for this purpose. The precursor compound used in this study is the known pentameric species (EtZn(SBut))5. One of the most successful routes involves the reaction of (EtZn(SBU superscript t))5 with hydrogen sulfide at ambient or sub-ambient temperature to yield a precipitate which is subsequently heated under flowing H2S at 500 C to yield a mixture of sub-micron particles and single-crystal ZnS whiskers. Transmission electron micrographs of the (EtZn(SBU superscript t))5 products indicate that the ZnS morphology is critically dependent upon the rate of H2S reaction. Corresponding x-ray/electron diffraction, electron microscopy, elemental analysis, NMR and infrared spectroscopies have been conducted. A summary of the chemical methods, product characterization results, and proposed synthesis mechanisms will be presented. Keywords: Ethyl radicals. (aw).
Download or read book Synthesis of ZnS Whiskers written by T. A. Guiton and published by . This book was released on 1988 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: One approach to improving the mechanical performance of a material is to form a self-similar whisker reinforced composite. This is the approach we are developing for Zinc Sulfide optical windows; however, it has necessitated the development of synthesis methods for ZnS whiskers. Recently, we reported an organometallic route to ZnS whiskers. Here we report yet another synthesis route. This non-organic route involves the surface reaction of metallic zinc foil or wire in a flowing atmosphere of Hydrogen Sulfide. The ZnS whiskers created at the zinc surface were characterized using SEM, TEM, SIMS, and x-ray diffraction. After an 8 hour 350C thermal treatment, the whiskers were ZnS averaging 19.2 micrometers in length, aspect ratio 27. The whiskers are single crystal in nature, and appear to evolve through an oxide layer at the surface of the zinc substrate. Thermochemical analysis of the reaction was performed to establish the relative stability of ZnS and various oxide and sulfates, and these confirmed the experimental data. These calculations describe the effects of temperature and gas phase composition upon the thermochemical stability of ZnS and other solid phase reaction products. The calculations are exceedingly useful for determining and controlling the process parameters and for the evaluation of the experimentally observed products. (aw).
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1989 with total page 956 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Better Ceramics Through Chemistry written by and published by . This book was released on 1988 with total page 904 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Kinetics based Investigation of ZnS Syntheses and Co product Evolution from Dual and Single source Precursors written by Kathryn Grace Woodburn and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanomaterials, the focus of an active area of materials chemistry research, have a multitude of uses ranging from efficiency improvement in lighting displays to photocatalysis and biological tagging for drug delivery. All such applications need nanomaterials with specific properties. This necessitates precise, reproducible control over their structure, which is currently limited by an incomplete understanding and of their syntheses. One method to better characterize nanocrystal syntheses is to improve knowledge of the mechanism and kinetics of precursor decomposition and nanocrystal nucleation and growth. This thesis explores the mechanisms and kinetics of the synthesis of zinc sulfide (ZnS) nanocrystals, both as a model binary metal chalcogenide species and because ZnS itself has many applications as a commonly-used large band-gap semiconducting quantum dot. This thesis presents a tandem study of traditional "dual" precursors and single-source precursors to serve as comparison and contrast agents in the development of a more holistic understanding of precursor decomposition and nanocrystal growth. The syntheses of dual and single-source precursors are first presented, followed by a discussion of their behavior in common hot-injection syntheses. The steric and electronic properties of the substituted thioureas used in dual precursor reactions and single-source precursor syntheses result in different precursor reactivity profiles. Understanding exactly how differing reactivity profiles impart control over nanocrystal structure and properties remains unanswered and is a promising query to direct future research. Following methodology development for replicable ZnS hot-injection syntheses, alternative approaches to ZnS synthesis are explored and the successful production of ZnS by microwave and ultraviolet irradiation is discussed.
Download or read book Handbook of sol gel science and technology 1 Sol gel processing written by Sumio Sakka and published by Springer Science & Business Media. This book was released on 2005 with total page 716 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since Dr. Disiich of Germany prepared a glass lens by the sol-gel method around 1970, sol-gel science and technology has continued to develop. Since then this field has seen remarkable technical developments as well as a broadening of the applications of sol-gel science and technology. There is a growing need for a comprehensive reference that treats both the fundamentals and the applications, and this is the aim of "Handbook of Sol-Gel Science and Technology."The primary purpose of sol-gel science and technology is to produce materials, active and non-active including optical, electronic, chemical, sensor, bio- and structural materials. This means that sol-gel science and technology is related to all kinds of manufacturing industries. Thus Volume 1, "Sol-Gel Processing," is devoted to general aspects of processing. Newly developed materials such as organic-inorganic hybrids, photonic crystals, ferroelectric coatings, photocatalysts will be covered. Topics in this volume include: Volume 2, "Characterization of Sol-Gel Materials and Products, "highlights the important fact that useful materials are only produced when characterization is tied to processing. Furthermore, characterization is essential to the understanding of nanostructured materials, and sol-gel technology is a most important technology in this new field. Since nanomaterials display their functional property based on their nano- and micro-structure, "characterization" is very important. Topics found in Volume 2 include: Sol-gel technology is a versatile technology, making it possible to produce a wide variety of materials and to provide existing substances with novel properties. This technology was applied to producingnovel materials, for example organic-inorganic hybrids, which are quite difficult to make by other fabricating techniques, and it was also applied to producing materials based on high temperature superconducting oxides. "Applications of Sol-Gel Technology," (Volume 3), will cover applications such as:
Download or read book Physics Briefs written by and published by . This book was released on 1990 with total page 1422 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1988-12 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Organometallic Route to Micron Sized Whiskers of Zinc Sulfide written by C. L. Czekaj and published by . This book was released on 1988 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A number of technologies require the development of high performance optical materials that also meet stringent specifications of optical transparency and thermal, chemical, and mechanical properties. For example, an infrared transmitting window material should have low thermal expansion, high melting and decomposition temperatures, chemical inertness to hydrolysis and oxidation, and high fracture toughness. One of the most attractive materials for many infrared optical applications is Zinc sulfide, but this material, as presently fabricated, does not process the required mechanical properties. One approach to improving the mechanical properties of a material is to form a self-similar composite, in this case, ZnS whiskers in polycrystalline ZnS matrix. To fabricate IR transmitting ZnS/ZnS composites, it would be necessary to use micron-sized whiskers of ZnS that have length to width ratios (aspect ratios) greater than 10. No present methodology exists for the convenient, large-scale preparation of such whiskers, although larger single crystals and whiskers of ZnS have been made by a variety of high temperature (>900 C), generally vapor-phase, routes. (jes).
Download or read book Government Reports Annual Index written by and published by . This book was released on 1988 with total page 1600 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis and Characterization of Zinc Sulfide zinc Oxide Semiconductor Nanoparticles written by Daniel Alan Hall and published by . This book was released on 2014 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Focus on Nanomaterials Research written by B. M. Caruta and published by Nova Publishers. This book was released on 2006 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology is a 'catch-all' description of activities at the level of atoms and molecules that have applications in the real world. A nanometre is a billionth of a meter, about 1/80,000 of the diameter of a human hair, or 10 times the diameter of a hydrogen atom. Nanotechnology is now used in precision engineering, new materials development as well as in electronics; electromechanical systems as well as mainstream biomedical applications in areas such as gene therapy, drug delivery and novel drug discovery techniques. This book presents the latest research in this frontier field.
Download or read book Synthesis and Hot Pressing of ZnS Powders written by and published by . This book was released on 1989 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive investigation into the processing of ZnS, which involve synthesis and characterization of submicron powders and their processing at elevated temperature to produce dense ceramic parts, was the main objective of this investigation. Thermomechanical characterization of the dense polycrystalline ceramics is also an integral part of such a study, and is underway. Zinc sulfide powders with submicron particle size were prepared by homogeneous precipitation from acidic zinc solutions by aging with thioacetamide at elevated temperatures. Monosize, polycrystalline particles having 0.35 micrometer diameter were obtained. Sulfide ion generation rate in solution depended on temperature, pH and initial thioacetamide concentration. The rate of sulfide ion generation, in turn, influenced precipitation kinetics and particle morphology. The types of supporting anions in solution also influenced the morphology of the particles produced Monosize powders were hot pressed for various time, temperature and pressure combinations. Compacts achieved near- theoretical density in less than 30 minutes at temperatures 850-900 C and applied pressures of about 70-105 MPa. The dominant densification mechanisms were identified at various stages of the process.
Download or read book Synthesis and Characterization of Copper Doped Zinc Sulfide Nanoparticles written by Tiffany Chen and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Zinc Polysulfides as Precursors to Zinc Sulfide and as Group Transfer Reagents written by Atul Kumar Verma and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the first part of the thesis, reactions of zinc powder with solutions of elemental sulfur in various donor solvents are described. Complexes of the type $\rm ZnS\sb6$(N-donor)$\sb2$ are obtained for the ligands tetramethylethylenediamine (TMEDA), N-methylimidazole (MeIm), and 4-(N,N-dimethylamino)pyridine (DMAP). Ligand competition studies on pyridine solutions revealed that the relative stability constants $\rm (DMAP>MeIm>TMEDA>pyridine)$ parallels the basicity of the ligands. Crystallographic analysis shows that $\rm ZnS\sb6$(TMEDA) adopts a tetrahedral geometry with a seven-membered $\rm ZnS\sb6$ ring. Solutions of $\rm ZnS\sb6$(TMEDA) undergo ligand exchange with other ligands L to afford $\rm ZnS\sb6L\sb2$ (L = MeIm, quinuclidine). The pyridine analog, $\rm ZnS\sb6py\sb2$ also undergoes ligand substitution with TEEDA $(N,N,N\prime,N\prime$-tetraethylethylenediamine) and ($-$)-sparteine to afford $\rm ZnS\sb6$(TEEDA) and $\rm ZnS\sb6\{(-)$-sparteine$\};$ these complexes can not be prepared by the reaction of sulfur and zinc dust in TEEDA or ($-$)-sparteine. Optical and reactivity studies showed that MeIm, but not pyridine, displaces the polysulfide from $\rm ZnS\sb6(MeIm)\sb2$ as indicated by the appearance of the chromophore $\rm S\sb3\sp-.$ ZnS$\sb6$(TMEDA) reacts with the electrophilic acetylenes methylpropiolate and dimethylacetylenedicarboxylate (DMAD) to give the dithiolene complexes $\rm ZnS\sb2C\sb2R(CO\sb2Me)$(TMEDA), where R = $\rm CO\sb2Me,$ H.
Download or read book The Synthesis and Characterization of ZnS Nanoparticles from Zinc based Thiourea Derivative Complexes for Potential Use in Photocatalysis written by Manthako Hycinth Lethobane and published by . This book was released on 2017 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Inorganometallic Chemistry written by Thomas P. Fehlner and published by Springer Science & Business Media. This book was released on 2013-11-22 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a certain fascination associated with words. The manipulation of strings of symbols according to mutually accepted rules allows a language to express history as well as to formulate challenges for the future. But language changes as old words are used in a new context and new words are created to describe changing situations. How many words has the computer revolution alone added to languages? "Inorganometallic" is a word you probably have never encountered before. It is one created from old words to express a new presence. A strange sounding word, it is also a term fraught with internal contradiction caused by the accepted meanings of its constituent parts. "In organic" is the name of a discipline of chemistry while "metallic" refers to a set of elements constituting a subsection of that discipline. Why then this Carrollian approach to entitling a set of serious academic papers? Organic, the acknowledged doyenne of chemistry, is distinguished from her brother, inorganic, by the prefix "in," i. e. , he gets everything not organic. Organometallic refers to compounds with carbon-metal bonds. It is simple! Inorganometallic is everything else, i. e. , compounds with noncarbon-metal element bonds. But why a new term? Is not inorganic sufficient? By virtue of training, limited time, resources, co-workers, and so on, chemists tend to work on a specific element class, on a particular compound type, or in a particular phase. Thus, one finds element-oriented chemists (e. g.
