Evaluation of selected chemical processes for production of low-cost silicon, phase 3

A Process Development Unit (PDU), which consisted of the four major units of the process, was designed, installed, and experimentally operated. The PDU was sized to 50MT/Yr. The deposition took place in a fluidized bed reactor. As a consequences of the experiments, improvements in the design an operation of these units were undertaken and their experimental limitations were partially established. A parallel program of experimental work demonstrated that Zinc can be vaporized for introduction into the fluidized bed reactor, by direct induction-coupled r.f. energy. Residual zinc in the product can be removed by heat treatment below the melting point of silicon. Current efficiencies of 94 percent and above, and power efficiencies around 40 percent are achievable in the laboratory-scale electrolysis of ZnCl2

Evaluation of selected chemical processes for production of low-cost silicon, phase 2

Potential designs for an integrated fluidized-bed reactor/zinc vaporizer/SiCl4 preheater unit are being considered and heat-transfer calculations have been initiated on versions of the zinc vaporizer section. Estimates of the cost of the silicon prepared in the experimental facility have been made for projected capacities of 25, 50, 75, and 100 metric ton of silicon. A 35 percent saving is obtained in going from 25 metric ton/year to the 50 metric ton/year level. This analysis, coupled with the recognition that use of two reactors in the 50 metric ton/year version allows for continued operation (at reduced capacity) with one reactor shut down, has resulted in a recommendation for adoption of an experimental facility capacity of 50 metric ton/year or greater. At this stage, the change to a larger size facility would not increase the design costs appreciably. In the experimental support program, the effects of seed bed particle size and depth were studied, and operation of the miniplant with a new zinc vaporizer was initiated, revealing the need for modification of the latter

Evaluation of selected chemical processes for production of low-cost silicon

Plant construction costs and manufacturing costs were estimated for the production of solar-grade silicon by the reduction of silicon tetrachloride in a fluidized bed of seed particles, and several modifications of the iodide process using either thermal decomposition on heated filaments (rods) or hydrogen reduction in a fluidized bed of seed particles. Energy consumption data for the zinc reduction process and each of the iodide process options are given and all appear to be acceptable from the standpoint of energy pay back. Information is presented on the experimental zinc reduction of SiCl4 and electrolytic recovery of zinc from ZnCl2. All of the experimental work performed thus far has supported the initial assumption as to technical feasibility of producing semiconductor silicon by the zinc reduction or iodide processes proposed. The results of a more thorough thermodynamic evaluation of the iodination of silicon oxide/carbon mixtures are presented which explain apparent inconsistencies in an earlier cursory examination of the system

Development of a chromium-thoria alloy

Low temperature ductility and high temperature strength of pure chromium and chromium-thoria alloy prepared from vapor deposited powder

Symmetry-breaking in chiral polymerisation

We propose a model for chiral polymerisation and investigate its symmetric and asymmetric solutions. The model has a source species which decays into left- and right-handed types of monomer, each of which can polymerise to form homochiral chains; these chains are susceptible to `poisoning' by the opposite handed monomer. Homochiral polymers are assumed to influence the proportion of each type of monomer formed from the precursor. We show that for certain parameter values a positive feedback mechanism makes the symmetric steady-state solution unstable. The kinetics of polymer formation are then analysed in the case where the system starts from zero concentrations of monomer and chains. We show that following a long induction time, extremely large concentrations of polymers are formed for a short time, during this time an asymmetry introduced into the system by a random external perturbation may be massively amplified. The system then approaches one of the steady-state solutions described above.Comment: 26pages, 6 Figure

Firearms, Extreme Risk, and Legal Design: Red Flag Laws and Due Process

The most prominent recent development in gun regulation has been the spread of extreme risk protection order (ERPO) laws—often called “red flag” laws—which permit the denial of firearms to individuals who a judge has determined present an imminent risk of harm to themselves or others. Following a wave of adoptions in the wake of the Parkland murders, such orders are now authorized by law in eighteen states and the District of Columbia, and under consideration in many others. Advocates argue that they provide a tailored, individualized way to deter homicide, suicide, and even mass shootings by providing a tool for law enforcement or others to intervene when harm appears imminent, without having to wait for injury, lethality, or criminal actions to occur. But the laws have also garnered criticism, and have become a primary target of the Second Amendment sanctuary movement. As a matter of constitutional law, the most serious questions about ERPOs involve not the right to keep and bear arms but due process. Such orders—like domestic violence restraining orders, to which they are often compared—can initially be issued ex parte, and critics often allege that this feature (and others including the burden of proof and the class of potential petitioners) raises constitutional problems. This Article provides a comprehensive analysis of the applicable Due Process standards, and identifies the primary issues of concern. It concludes that, despite some variation, current ERPOs seem drafted so as to satisfy the relevant standards. It also notes those features that are likely to give rise to the strongest challenges. The analysis both builds on and suggests lessons for other areas of regulation where laws are designed so as to lessen extreme ris

Firearms Law and Scholarship Beyond Bullets and Bodies

Academic work is increasingly important to court rulings on the Second Amendment and firearms law more generally. This article highlights two recent trends in social science research that supplement the traditional focus on guns and physical harm. The first strand of research focuses on the changing ways that gun owners connect with firearms, with personal security, status, identity, and cultural markers being key reasons people offer for possessing firearms. The second strand focuses on broadening our understanding of the impact of guns on the public sphere beyond just physical safety. This research surfaces the ways that guns can create fear, intimidation, and social trauma; deter civic participation and the exercise of constitutional rights; and further entrench racial inequality

Firearms Law and Scholarship Beyond Bullets and Bodies

Academic work is increasingly important to court rulings on the Second Amendment and firearms law more generally. This article highlights two recent trends in social science research that supplement the traditional focus on guns and physical harm. The first strand of research focuses on the changing ways that gun owners connect with firearms, with personal security, status, identity, and cultural markers being key reasons people offer for possessing firearms. The second strand focuses on broadening our understanding of the impact of guns on the public sphere beyond just physical safety. This research surfaces the ways that guns can create fear, intimidation, and social trauma; deter civic participation and the exercise of constitutional rights; and further entrench racial inequality