Ultraviolet Curing of Highly Loaded Ceramic Suspensions for Stereolithography of Ceramics

Ceramic green bodies can be created using stereolithography methods where a ceramic slip consisting of 45-55 vlo ceramic powder is dispersed within an ultraviolet-curable aqueous acrylamide solution. Two ceramic materials were investigated: silica [Si02] for investment casting purposes, and alumina [AI203] for structural parts. After mixing the powders in the curable solution, the ceramic slip is tape cast onto a substrate for cure under a high intensity ultraviolet lamp (220-450 nm) at different exposure times. The materials systems were evaluated at different solids loadings (10-50 v/o) for cure thickness and viscosity control. Silica had a cure depth of 330 f.lm at a solids loading of 55 vlo, and at 50 vlo, alumina had a cure depth of 300 f.lm. Preliminary work utilizing scattering theory revealed the cure depth is controlled by the particle size and the refractive index difference between the ceramic and ultraviolet solution. The refractive index difference is the dominating factor. Two particle size distributions of alumina were used to more accurately determine the effect of particle size.Mechanical Engineerin

Scattering of ultraviolet radiation in turbid suspensions

A Beer’s law expression for the penetration depth of ultraviolet radiation in a concentrated suspension of scattering particles is used to model the depth of cure for a suspension of ceramic particles in a medium of photocurable monomers. The cure depth is predominantly controlled by the square of the refractive index difference between the ceramic particles and the medium, Δn2 = (np−n0)2Δn2=(np−n0)2. A secondary effect on the cure depth is the ratio of the interparticle spacing to the ultraviolet wavelength. Theoretical results agree with experimental data for 0.40–0.50 volume fraction ceramic-filled suspensions. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71270/2/JAPIAU-81-6-2538-1.pd

Melt Pool Size and Stress Control for Laser-Based Deposition Near a Free Edge

Thermomechanical models developed in this research address two experimental observations made during the deposition of thin-walled structures by the LENSTM process. The first observation (via thermal imaging) is of substantial increases in melt pool size as a vertical free edge is approached under conditions of constant laser power and velocity. The second observation (via neutron diffraction) is of large tensile stresses in the vertical direction at vertical free edges, after deposition is completed and the wall is allowed to cool to room temperature. At issue is how to best control melt pool size as a free edge is approached and whether such control will also reduce observed free edge stresses. Thermomechanical model results are presented which demonstrate that power reduction curves suggested by process maps for melt pool size under steady-state conditions can be effective in controlling melt pool size as a free edge is approached. However, to achieve optimal results it is important that power reductions be initiated before increases in melt pool size are observed. Stress simulations indicate that control of melt pool size can reduce free-edge stresses; however, the primary cause of these stresses is a constraint effect which is independent of melt pool size.This research was supported by the National Science Foundation Division of Design, Manufacture and Industrial Innovation, through the Materials Processing and Manufacturing Program, award number DMI-0200270.Mechanical Engineerin

Microfabrication of Ceramics by Co-extrusion

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65777/1/j.1151-2916.1998.tb02307.x.pd

A case of acute myeloid leukemia with promyelocytic features characterized by expression of a novel RARG-CPSF6 fusion

Key Points Novel RARG-CPSF6 fusion in an AML case with promyelocytic features and no evidence of PML-RARA or X-RARA fusion. Gene fusions involving RARG can initiate AML with promyelocytic morphological features.</jats:p

A common founding clone with TP53 and PTEN mutations gives rise to a concurrent germ cell tumor and acute megakaryoblastic leukemia

We report the findings from a patient who presented with a concurrent mediastinal germ cell tumor (GCT) and acute myeloid leukemia (AML). Bone marrow pathology was consistent with a diagnosis of acute megakaryoblastic leukemia (AML M7), and biopsy of an anterior mediastinal mass was consistent with a nonseminomatous GCT. Prior studies have described associations between hematological malignancies, including AML M7 and nonseminomatous GCTs, and it was recently suggested that a common founding clone initiated both cancers. We performed enhanced exome sequencing on the GCT and the AML M7 from our patient to define the clonal relationship between the two cancers. We found that both samples contained somatic mutations in PTEN (C136R missense) and TP53 (R213 frameshift). The mutations in PTEN and TP53 were present at ∼100% variant allele frequency (VAF) in both tumors. In addition, we detected and validated five other shared somatic mutations. The copy-number analysis of the AML exome data revealed an amplification of Chromosome 12p. We also identified a heterozygous germline variant in FANCA (S858R), which is known to be associated with Fanconi anemia but is of uncertain significance here. In summary, our data not only support a common founding clone for these cancers but also suggest that a specific set of distinct genomic alterations (in PTEN and TP53) underlies the rare association between GCT and AML. This association is likely linked to the treatment resistance and extremely poor outcome of these patients. We cannot resolve the clonal evolution of these tumors given limitations of our data

LENS Deposition of Complex Geometries

The Laser Engineered Net Shaping (LENS®) system at Sandia National Laboratories, a laser-based direct metal deposition process, was recently used for the fabrication of a complex prototype. The LENS process involved the challenges of adjacent areas of thick and thin cross section, overhanging unsupported features, high aspect ratios, and a hemispherical substrate. These challenges were overcome through the use of closed-loop weld pool control, height monitoring, a strong understanding of build parameters, and unique process planning strategies. The near-net shape LENS part was completed with annealing and conventional machining to produce the complex components in a reduced timeframe.Mechanical Engineerin

Multi-Material Processing By Lens

During the past few years, solid freeform fabrication has evolved into direct fabrication of metallic components using computer aided design (CAD) solid models. [1-4] Laser Engineered Net Shaping (LENS™) is one such technique [5-7] being developed at Sandia to fabricate high strength, near net shape metallic components. In the past two years a variety of components have been fabricated using LENS™ for applications ranging from prototype parts to injection mold tooling. [8] To advance direct fabrication capabilities, a process must be able to accommodate a wide range ofmaterials, including alloys and composites. This is important for tailoring certain physical properties critical to component performance. Examples include graded deposition for matching coefficient ofthermal expansion between dissimilar materials, layered fabrication for novel mechanical properties, and new alloy design where elemental constituents and/or alloys are blended to create new materials. In this paper, we will discuss the development ofprecise powder feeding capabilities for the LENSTM process to fabricate graded or layered material parts. We also present preliminary results from chemical and microstructural analysis.Mechanical Engineerin

The Vehicle, Fall 1970

Vol. 13, No. 1 Table of Contents A Thought Written in a Locked RoomJudy Huntpage 1 The Eggshell MoonWilliam Probeckpage 2 PoemBarb Parkerpage 3 4/5, May, 1970J. Michael Sainpage 5 A TreeRichard Stickannpage 6 both or noneMichelle Hallpage 6 The TrainSteve Sestinapage 8 Attempted DiscoveryDonald R. Johnsonpage 16 Island of SmokeVerna L. Jonespage 18 AwakeRobert Bladepage 19 PoemMary Klinkerpage 19 In ChurchMuriel Poolpage 21 PoemBarb Parkerpage 21 PoemMichelle Hallpage 22 Pod\u27nerVerna L. Jonespage 23 Rain and Other ThingsCarol Staniecpage 24 PoemAnn Graffpage 24 Examination of StudentdomMelvin Zaloudekpage 26 Women\u27s LiberationTonya Mortonpage 27 Morning Reflections on the Evening NewsPrudence Herberpage 29 Art and Photography Credits Jim Diaspage 4 Mike Dorseypages 7, 20 David Griffithpages 8, 17, 25 Cover PhotographyMark McKinneyhttps://thekeep.eiu.edu/vehicle/1024/thumbnail.jp