Influence of partial charge on the material removal rate during chemical polishing

A partial charge-based chemical polishing model has been developed, which can serve as metric for describing the relative polishing material removal rate for different combinations of slurries and workpieces. A series of controlled polishing experiments utilizing a variety of colloidal polishing slurries (SiO₂, CeO₂, ZrO_2, MgO, Sb₂O₅) and optical materials [single crystals of Al₂O₃ (sapphire), SiC, Y₃Al₅O₁₂ (YAG), CaF₂, and LiB₃O₅ (LBO); a SiO₂-Al₂O₃-P₂O₅-Li₂O glass ceramic (Zerodur); and glasses of SiO₂:TiO₂ (ULE), SiO₂ (fused silica), and P₂O₅-Al₂O₃-K₂O-BaO (Phosphate)] was performed and its material removal rate was measured. As previously proposed by Cook (J Non-Cryst Solids. 1990;120:152), for many polishing systems, the removal rate is governed by a series of chemical reactions which include the formation of a surface hydroxide, followed by condensation of that hydroxyl moiety with the polishing particle, and a subsequent hydrolysis reaction. The rate of condensation can often be the rate limiting step, thus it can determine the polishing material removal rate. By largely keeping the numerous other factors that influence material removal rate fixed (such as due to particle size distributions, interface interactions, pad topography, kinematics, and applied pressure), the material removal rate is shown to scale exponentially with the partial charge difference (δ_wp-s) between the workpiece and polishing slurry particle for many of the slurry-workpiece combinations indicating that condensation rate is the rate limiting step. The partial charge (δ) describes the equilibrium distribution of electron density between chemically bonded atoms and is related to the electronegativity of the atoms chemically bonded to one another. This partial charge model also explains the age-old experimental finding of why cerium oxide is the most effective polishing slurry for chemical removal of many workpieces. Some of the slurry-workpiece combinations that did not follow the partial charge dependence offer insight to other removal mechanisms or rate limiting reaction pathways.     

EXTRACTION OF TITANIUM(IV) BY MIXTURES OF MONO- AND DH(2-ETHYLHEXYL) PHOSPHORIC ACID ESTERS

ABSTRACT

Solvent extraction of titanium(IV) from hydrochloric acid solutions by mixtures of mono- and di-2-ethylhexyl phosphoric acid esters (MEHPA and DEHPA) has been investigated as a function of HC1 concentration in the aqueous phase and extractants concentration in the organic phase

It was found that MEHPA extracts Ti, 3 orders of magnitude more efficiently than DEHPA. Efficiency of extraction by MEHPA does not depend on acid concentration in the aqueous phase in the range of 0·1 – 8·8 mole/Kg. As a rule Ti/MEHPA ratio in the complex is 1/2. At low aqueous phase acidities (0·1–1·0 mole/Kg HCl) formation of six- (or eight-) coordinate bidentate hydrated Ti(IV)-2MEHPA complexes is suggested. At acidities above 7·0 mole/Kg HC1 titanium forms tridentate six- (or eight-) coordinate complexes. At medium acidities (2·0–6·0 mole/Kg HCl) mixtures of these complexes are formed. Prolonged mixing of the phases or aging of the organic phase leads to dehydration and to transformation of bidentate to tridentate Ti-2MEHPA complexes. Ti-2MEHPA complexes are colorless

At ratios Ti/MEHPA<0·5 formation of Ti-MEHPA hydrated or solvated complex ions is suggested which form emulsion in the aqueous phase. These species slowly react with DEHPA and formation of Ti:MEHPA:DEHPA=1:1:2 complex is realized. This complex is yellow.     

HYDROFLUORIC ACID EXTRACTION BY TBP AND BY AMINES: I. A CRITICAL REVIEW OF THE HF-H2O-EXTRACTANT SYSTEM

Literature on HF extraction by amines and by tributyl phosphate is critically reviewed. The system amine-HF-H₂O shows an interesting feature concerning properties such as distribution curves compared to those for extraction of other acids, similarity to extraction by TBP, water extraction, selectivity, effect of amine type and dilution and diluent effect These properties sharply change (or even invert) when HF/amine molar ratio exceeds 2.     

HYDROFLUORIC ACID EXTRACTION BY TBP AND BY AMINES: MECHANISM,SPECIES FORMED AND UNIQUE PROPERTIES AT HIGH ACID TO AMINE MOLAR RATIOS

Analysis of data concerning HF extraction by amines reveals a change in extraction mechanism when HF/amine molar ratio in organic phase (Z) reaches 2. Up to this point extraction is by ion-pair formation and after it by H-bonding. As a result, the two HF molecules initially extracted differ in nature from subsequent ones. The change in mechanism explains why seemingly unrelated properties such as water co-extraction dilution and diluent effects, selectivity and viscosity - all change when amine bifluoride composition is attained. Similar change in extraction of other mono-basic acids occurs at Z=1. The system with Z>2 for HF is equivalent to that with Z>1 for other mono-basic acids and to that of extraction by TBP. It therefore provides a model for extraction from concentrated aqueous solutions.     

RECOVERY AND CONCENTRATION OF STRONG MINERAL ACIDS FROM DILUTE SOLUTIONS THROUGH LLX. I: REVIEW OF PARAMETERS FOR ADJUSTING EXTRACTANT PROPERT AND ANALYSIS OF PROCESS OPTIONS

Parameters affecting extraction power of amine-based extractants for mineral acids are reviewed. Means for adjusting extractant composition for reversible extraction of mineral acids from dilute solutions are discussed. The paper also analyses process options for recovery of the extracted acid at concentrations higher than those in the original solution. Introduction of the required energy as thermal energy without resorting to evaporation of the acid or to evaporation of water is highly attractive.     

Full-scale field tests of concrete slabs subjected to blast loads

This paper describes full-scale field explosion tests on protected and unprotected concrete slabs. The experiments were performed by the Protective Technologies Research & Development Center of the Faculty of Engineering Sciences of the Ben-Gurion University of the Negev (BGU-PTR&DC) under a contract with the Israeli Ministry of Defense (MoD) and the supervision of the IDF Steering Committee for R&D of Protective Structures. The aims of the tests were to: (1) extract data on the dynamic response of an elementary concrete structure to blast loads in order to verify and validate (V&V) our corresponding computer codes; and (2) check the ability of aluminum foams to mitigate blast wave loads. Time-dependent measurements of the response of the concrete slabs to the blast wave loads were successfully recorded using a variety of measurement devices. The obtained data have been used to verify and validate our computer codes.     

GSM indoor localization

Accurate indoor localization has long been an objective of the ubiquitous computing research community, and numerous indoor localization solutions based on 802.11, Bluetooth, ultrasound and infrared technologies have been proposed. This paper presents the first accurate GSM indoor localization system that achieves median within floor accuracy of 4 m in large buildings and is able to identify the floor correctly in up to 60% of the cases and is within 2 floors in up to 98% of the cases in tall multi-floor buildings. We report evaluation results of two case studies conducted over a course of several years, with data collected from 6 buildings in 3 cities across North America. The key idea that makes accurate GSM-based indoor localization possible is the use of wide signal-strength fingerprints. In addition to the 6-strongest cells traditionally used in the GSM standard, the wide fingerprint includes readings from additional cells that are strong enough to be detected, but are too weak to be used for efficient communication. We further show that selecting a subset of highly relevant channels for fingerprinting matching out of all available channels, further improves the localization accuracy.     

Wafer fusion: materials issues and device results

A large number of novel devices have been recently demonstrated using wafer fusion to integrate materials with different lattice constants. In many cases, devices created using this technique have shown dramatic improvements over those which maintain a single lattice constant. We present device results and characterizations of the fused interface between several groups of materials     

以可程序设计DSP架构因应TD-SCDMA和TD-LTE带来的设计挑战

Eyal Bergman/CEVA产品市场总监/胡凯/CEVA中国区技术支持经理中国作为目前世界上最大的移动市场,对移动标准的发展,希望制定不同于西方的自己的标准.这就是目前的3G标准TD-SCDMA以及未来的4G标准TD-LTE.