Search

Summary The objective of the study was to analyze the outcome of the proprioceptive-elastic (PROEL) voice therapy method in patients with functional dysphonia (FD). Fifty-two patients with FD were involved in the study; they were composed of three subgroups of patients with (1) FD without glottal insufficiency (n = 28), (2) FD and glottal insufficiency (n = 9), and (3) FD, glottal insufficiency, and vocal nodules (n = 15). A multidimensional assessment protocol including videolaryngostroboscopy; maximum phonation time; perceptual evaluation of dysphonia with the Grade, Instability, Roughness, Breathiness, Asthenia, and Strain (GIRBAS) scale; and 10-item version of the Voice Handicap Index was conducted before and after 15 sessions of voice therapy. All voice therapy sessions were conducted by the same speech-language pathologist. The comparison between voice assessment before and after voice therapy with the PROEL method in patients with FD, in all the three subgroups, revealed a statistically significant improvement in periodicity and the mucosal wave in the laryngostroboscopy, maximum phonation time, GIRBAS scale scores, and VHI-10. Voice of patients with FD improved after treatment with the PROEL method. Further studies are needed to analyze the efficacy of the PROEL method with randomized double-blind clinical trials using different methods for voice therapy. At present, the PROEL method represents an alternative tool for the speech pathologist to improve voice in patients with FD.

The present paper reports on the sintering behaviour of several ceramics prepared using a previously selected mixture of incinerated paper mill sludge and glass cullet in the ratio 60/40 which was blended with 10, 20, 30 and 40 wt.% of three different natural materials. The three natural products were: a red quartzitic clay, a yellow quartzitic clay and a kaolin. All mixtures were blended by attrition milling and dried; powders were sieved, pressed into specimens and fired for 1 h at temperatures ranging from 1040 to 1140 °C. The resulting materials were characterized by water absorption, shrinkage, crystallographic composition, microstructure and physico-mechanical properties. It was observed that materials containing kaolin display the best overall behaviour independently of the quantity of kaolin introduced. Conversely the optimal sintering temperature, and consequently the best properties of the materials prepared using red or yellow clay were measured on products fired at temperatures above 1080 °C; materials and temperatures are affected by the amount of clay added.

We examined the production of macroporous monolithic ceramic from mortars prepared using aluminate cements, one or two different types of alumina powders, superfluidificant, water and polyurethane fibres. Some relevant parameters for the preparation process of the mortar are: (i) the weight ratio between cement powder and water, (ii) the weight ratio between superfluidificant and cement powder and (iii) that between superfluidificant and water. Thirty-six percent is the upper limit for the volumetric content of the fibres that can be introduced into the mortar without leading to a material that breaks up by handling after the successive thermal cycle. We also optimized the thermal cycle that may be used in order to avoid the spontaneous break-up of the material during the sintering treatment. Materials containing fine and coarse particles of alumina powders exhibit extended ruptures probably dependent on the thermal stresses that grow on cooling after the sintering process, whereas in materials containing only fine alumina powders the presence of ruptures is more limited so that the fired materials have a sufficient strength and can be handled without a particular care. The ageing time at the maximum temperature plays an important role on the microstructure of the sintered material since it has been seen that after 2 h at 1250 °C the residual porosity seems to be completely closed and the large grain size shows the presence of structures which can be due to the presence of aluminates.

Over the last two decades, together with the increasing prices in the antique market and the proliferation of private ‘hobby collectors’, the number of fakes in circulation among antique shops, auctions and even institutions and museums has noticeably increased. So called ‘bronzes’ seem to be the favourite objects for both fakers and inexperienced collectors. In some cases the fakes are well made, so that often the professional can be fooled by them also. In this paper some examples of modern and ancient fake objects will be discussed.

Several zirconia–baria solid solutions were obtained by sintering powders produced by coprecipitation from solutions of zirconyl chloride hydrate and barium nitrate. The fired materials had monoclinic, cubic or tetragonal structure depending of composition which ranged from 4 to 16 mol% BaO. The pure cubic phase could be retained at room temperature for compositions from 10 to 12 whereas materials containing 16 mol% BaO were tetragonal; for lower baria content a mixture of monoclinic and cubic phase was detected. The double phased materials can be fully transformed into the monoclinic form by grinding while for pure cubic or tetragonal samples the transformation is not full. Samples fired at 1450 °C had coarse microstructures and the grains dimension is of several microns just after 1 h of sintering, but materials containing 10, 12 and 16 mol% BaO remain cubic or tetragonal, their transformability being the same as that of materials sintered at lower temperature. The grains growth kinetic during the sintering process is similar to that of the BaZrO 3 , and the resulting microstructures showed coarser grains than those observed in sintered tetragonal zirconia materials stabilized with other oxides. The crystal structures of cubic or tetragonal BaO stabilized zirconias seem to be isostructural to BaZrO 3 as they have similar cell parameters.

In this paper, a study of the tool wear mechanism in turning aluminium alloy reinforced with alumina using molybdenum-toughened alumina tools is presented. Alumina tools with three different amounts (15, 20 and 25 vol.%) of molybdenum were prepared and tested. The wear type was identified and its evolution with cutting time was measured. The results show that the main mechanism of tool wear is abrasion and not heat. The best overall performance was achieved, as far as flank wear is concerned, using the tool with 20 vol.% of molybdenum added. This has been explained using some of the composites intrinsic properties. SEM examination revealed that molybdenum particles are easily torn from the matrix by flowing chips. Under these conditions the molybdenum particles are not able to carry out their toughening action and they are responsible for the flank wear. Some ideas have been proposed as to engineer the alumina/molybdenum interface in order to increase their adhesion and the composite toughness.

A combination of ICP-OES, titration, and Raman spectroscopy was used to determine the ratio of peroxide to hafnium in the inorganic photoresist HafSOx. By using ICP-OES to determine the hafnium concentration and titration with permanganate to determine peroxide in a solution of dissolved films, the Hf:O22- ratio was found to be approximately 2:1 in the films. From Raman measurements on precursor solutions, it was determined that that Hfbound peroxide saturated at this level. Film insolubility is induced through loss of approximately 75% of bound peroxide following exposure to a 30-keV electron beam.

The influence of attrition milling on the chemical precursors of alumina and tetragonal zirconia polycrystal (12 mol% CeO 2 ) is studied, with particular attention to the morphology, the specific surface area, the crystallographic form and the sinterability of powders obtained by (i) calcining the pristine precursors and (ii) milling the pristine precursors and then performing the calcination. It has been demonstrated that in the latter case the specific surface area is reduced but the sinterability is increased with respect to the former one. This behaviour is due to the destruction, by the attrition milling, of the porous microstructures and of the large aggregates in the “as-prepared” materials. The influence of milling is more evident in the alumina precursor, since it contains a high quantity of organic matter and therefore exhibits a very porous microstructure with a high specific surface area.

This paper proposes new preparation methods for alumina–tetragonal zirconia–Ca or Sr hexaluminate composites. Two powder preparation routes were explored. In the first, aluminium and calcium or strontium nitrate hydrates were added to alumina zirconia powders and in the second only calcium or strontium nitrate hydrates were used. Powders produced by the second route are to be preferred since reinforcements do not inhibit the composite sintering process.

Zirconia-toughened alumina cutting tools have been examined after machining an AISI 1040 steel. The Raman spectrum of zirconia and the fluorescence spectrum from alumina have been used to determine the extent of the tetragonal-to-monoclinic (t-m) transformation and the residual stresses in and around the worn-out crater, respectively. Although about 15% vol. m-zirconia is present even in a brand new cutting tool, it was shown that the crater region undergoes the t-m transformation up to 40% vol. In both cases, the transformed zone is concentrated near the surface. The residual stresses in alumina are slightly compressive in the new cutting tool and away from the crater region, but they become tensile inside the crater, where the t-m transformation of zirconia has occurred to a larger extent. A stochastic model has been used to predict the stresses and it has been found to reproduce very well the experimental data. Some evidence of the formation of a spinel reaction product in the crater region has been found, likely (Mg,Fe)AlO 4 .

A comparison was made of the sintering behaviour of 12Ce–PSZ powders prepared by coprecipitation and by mechanical alloying. Despite the presence of large aggregates, samples prepared from the chemically produced powders reached a high density after 3 h sintering at 1450°C. The samples obtained by mechanical alloying of powders had the highest green density. However, owing to their wide agglomerate distribution and low-temperature agglomeration rate, they do not reach high density even after prolonged soaking at 1450°C. The mechanically alloyed powders were flo-deflocculated to remove agglomerates as well as the electrostatic charge formed during their preparation. This treatment improved pressureless sinterability in air, and final densities close to the theoretical value were obtained.

Three ceramic insert materials, zirconia-toughened alumina (Al 2 O 3 –7vol%ZrO 2 ), mixed-based alumina (Al 2 O 3 –TiN–TiC–ZrO 2 ) and alumina reinforced with SiC whiskers (Al 2 O 3 –SiC w ), were used to cut AISI 1040 steel at 3.9 m s −1 . In addition, a traditional grade P10 insert (WC–TiC–Co) was tested. The lifetimes, according to KT/KM and VB B criteria, were determined using a profilometer and by image processing. The worn zones were observed with scanning electron microscopy techniques. Adhesion and plastic deformation were dominant wear mechanisms in zirconia-toughened alumina, mixed-based alumina and sintered carbide P10, both in the craters and in the cutting edges. As well as adhesion in alumina reinforced with SiC whiskers, a chipping wear mechanism was observed.

Cordierite porous ceramics are attractive materials for diesel particulate traps, but are sensitive to the thermal shocks provoked by the ignition of accumulated soot. The present paper reports an investigation on a commercial porous cordierite to be used as a substrate for catalysts in exhaust pipes. Samples have been subjected to thermal shock tests to study the response of these ceramics to the repetitive thermal shock that occurs within automotive systems during the regeneration processes. In particular, the effect of thermal treatment on microstructure and mechanical properties has been examined and explained.MST/1992

An attractive method for the fabrication of Al 2 O 3 -ZrO 2 laminar composites is described in this paper. The process consists in the centrifugation of colloidal suspensions containing alumina and zirconia particles. With this procedure, it is possible to grow thin layers with different composition and smooth interfaces. The effects of the slurry compositions, as well as aging times and centrifuging conditions on the morphology of the laminae are discussed.

The authors propose a multiple approach for the evaluation of cutting temperatures in ceramic tools. The first approach was the experimental evaluation of equitemperature lines, obtained in three-dimensional cutting by employing constant melting point powders scattered on planes parallel to rake face. In the second approach, a numerical finite element analysis was performed. At this step the determination of the percentage of total heat produced in the operation that flows into the tool was considered and, consequently, the temperature distribution within the whole volume of the insert. Finally, the examination of the crater zone with SEM microscopy confirmed the temperature levels as previous estimated.

The present paper reports on the results of some experiments on the progress of a previous research and describes the production, in single fast firing, of tiles containing 30 wt% of a natural red clay and a mixture of 42 wt% of paper mill sludge and 28 wt% of glass cullet which were coated with a commercial “matt white” glaze. Fired materials were characterized as a function of the top temperature (1090 or 1140 °C) reached during the fast sintering process made in an industrial roller kiln. It is observed that tiles fired at 1090 °C display the best overall performances since the matt glaze well covers the substrate concurring to maintain in line with the official standard for production the mechanical and physical properties of the tiles.

An attractive method for the fabrication of Al 2 O 3 -ZrO 2 laminar composites is described in this paper. The process consists in the centrifugation of colloidal suspensions containing alumina and zirconia particles. With this procedure, it is possible to grow thin layers with different composition and smooth interfaces. The effects of the slurry compositions, as well as aging times and centrifuging conditions on the morphology of the laminae are discussed.

The sintering behaviour of several ceramics prepared using a previously selected mixture of incinerated paper mill sludge and glass cullet which was blended with 10, 20, 30 and 40 wt% of some natural clayey materials has been studied. Three natural commercial product were used: a red clay, a yellow clay and a kaolin. Mixtures were blended by wet attrition milling, dried, sieved, pressed into specimens and then fired for 1 h at temperatures ranging from 1040 to 1140 °C. The resulting materials were characterized by water absorption, shrinkage and crystallographic composition. It was observed that materials containing kaolin display the best overall behaviour independently of the quantity of kaolin introduced. Conversely the optimal sintering temperature, and consequently the best properties of materials prepared using red or yellow clay was found above 1080 °C and depends of their specific composition being affected by the amount of clay added.

In Pseudomonas aeruginosa and Rhizobium meliloti several choline derivatives, utilized as the sole carbon and nitrogen source, increase acid phosphatase activity. The enzyme activity of both bacteria could be released into the surrounding medium by EDTA-lysozyme treatment. The R. meliloti acid phosphatase activity of crude periplasmic extracts measured with p-nitrophenylphosphate was not inhibited by the presence of 5 mM choline, betaine, trimethylammonium or phosphorylcholine. The activity could not be detected using phosphorylethanolamine or phosphorylcholine as substrates. Among several phosphoesters tested only pyridoxal-5′-phosphate was hydrolyzed at a considerable rate. In 7.5% polyacrylamide slab gel electrophoresis (non-denaturing conditions) of crude extracts obtained from bacteria grown in the presence of serine, glutamate, aspartate or dimethylglycine a phosphatase activity with identical mobility could be detected when alpha-naphthylphosphate or pyridoxal-5′-phosphate were used as substrates. In conclusion, although the coline metabolites are capable of increasing acid phosphatase activities in R. meliloti and in P. aeruginosa, there are two different enzymes involved, apparently in different metabolisms.

This study tested the hypothesis that exposure to community violence, intimate partner violence, and child maltreatment independently contribute to the prediction of conduct problems over a 2-year period. Participants were a subsample of youth ages 12 to 17 years (N = 423) from the Patterns of Care study, which drew a stratified random sample of high-risk youth receiving services from public service sectors. Exposure to community violence significantly predicted conduct disorder and externalizing problems 2 years later when potential confounds were controlled. Child maltreatment predicted conduct disorder but not externalizing symptoms. Exposure to intimate partner violence was not related to either outcome. Exposure to community violence contributed to the development of conduct disorder and externalizing symptoms, even when exposure to child maltreatment or intimate partner violence was controlled. Results are discussed in terms of implications for treatment and prevention of youth conduct problems.

Solid solutions of the pseudo-ternary system Ce0.6/(1+x)Zr(Hf)(0.4−x)/(1+x)Ta2x/(1+x) (0.00 ≤ x ≤ 0.06), i.e. having molecular composition 1, 2, 3, 4, 5 and 6% in Ta2O5, have been prepared by traditional ceramic methods (1500 °C for 3 h). SEM observations and analysis of the X-ray diffraction powders allowed to establish that the solubility of Ta2O5 in the above mentioned system is 4 %mol. The Rietveld analysis of the powder X-ray diffraction data has shown that all the samples of the solid solution crystallize in tetragonal space group P42/nmc (No. 137) but are nearly cubic, space group F m 3 ¯ m (No. 225). The freshly prepared specimens (from 1 to 4 %mol of Ta2O5) show additional peaks due to a tetragonal supercell and also to a modulated structure. However, the modulated peaks disappear after 8 months. Compositions containing 5 and 6% of Ta2O5 show also additional peaks due to a small quantity of two crystalline phases having approximate composition: ZrO2–2CeO2–Ta2O5 and 2CeO2–Ta2O5 (later on identified as CeTaO4).

The outstanding performances of the Al2O3 cutting tools in terms of potential cutting speed can lead to substantial economies in the machining of metallic materials. Nevertheless, their widespread use is limited by some drawbacks such as the tendency to edge chipping and to the propagation of microcracks, which can lead to premature failures. These shortcomings are due to the intrinsic low toughness of the ceramic material, which is in turn related to its characteristics non-metallic bonds. A well-recognised method of increasing the toughness of brittle materials is the introduction of surface compressive stresses, which can be obtained through a suitable lamination geometry of the tools as consequence of the different coefficients of thermal expansion (CTE) of the constituent layers. The performances of an alumina/zirconia laminated cutting tool used for machining steel have been investigated and compared to those of a non-laminated commercial alumina/zirconia cutting tool. The different wear mechanisms are explained on the basis of the different microstructures and chemical compositions. We have shown that residual compressive stresses, measured by Piezo-Spectroscopy, are effective in avoiding the microchipping on the flank zone but cannot avoid larger fractures caused by the residual porosity.

In this paper we report on the preparation and characterization of porous ceramic substrates in the group of NaZr 2 (PO 4 ) 3 , CaZr 4 (PO 4 ) 6 , SrZr 4 (PO 4 ) 6 and BaZr 4 (PO 4 ) 6 with low thermal expansion coefficients. The starting powders were obtained by a sol–gel process and attrition milling both before and after calcination. The resulting sintered bodies exhibited high porosity also after further thermal treatments at high temperature. On the other hand their thermal expansion coefficient (CTE) is low over the range 25–1000 °C. In particular the blend between NaZr 2 (PO 4 ) 3 and SrZr 4 (PO 4 ) 6 has a CTE close to zero in the whole temperature range. According to these properties the above mentioned materials seem to be potential candidates as ceramic substrates for catalytic applications in combustion reactions since they maintain a high level of micrometric porosity when operating at temperatures exceeding 1000 °C.

Calcium, strontium, and barium hexaluminates have been prepared via a chemical route. In light of their interest as catalytic substrates the relation between attrition-milling time and density was studied, with the scope of obtaining fired bodies with suitable pore structure. It was found that all hexaluminates grew in elongated structures; longer milling times resulted in higher aspect ratios for calcium hexaluminate, with less than 75% of the theoretical density. Strontium and barium hexaluminates were prepared with even lower densities, but the reason is the inherent poor densification, and not the growth of mutually interfering elongated structures, as in the case for calcium hexaluminate.

Sandwich-structured three-layered ceramic inserts were made with the aim of obtaining ceramic cutting tools with an increased useful life.

In this paper the performances of some commercial ceramic inserts when cutting AISI 310 steel are investigated and compared to those of a traditional carbide based tool. The most important wear mechanism in the ceramic inserts is related to the segmented edges of the chips that abrade a notch at the end of the cut zone. Alumina–zirconia inserts are very sensitive to this kind of wear, whereas tools made of Sialon and alumina with SiC whiskers exhibit slightly better performances despite the concomitant chemical wear mechanisms.

A layered Al2O3-ZrO2 ceramic composite has been fabricated using a colloidal processing method. The technique uses sequential centrifuging of slurries containing suspended ceramic powders to form a three-layered structure. The outer layers have a high alumina content while the central layer contains mainly stabilized zirconia. These laminae are subjected to residual stresses due to their different thermal expansion coefficients. These stresses depend on the configuration of the system as well as on the amount of the zirconia in the two layers. If the residual stresses exceed the strength of the inner layer, periodic parallel cracks are produced. Such cracks of course adversely influence the structural performance of the composite and should be avoided. A model for this problem is presented. Vickers indentations were also placed into the tensile layer with the intent to explore the crack propagation in such system. Cracks were split after they reached the compressive layer. The effects of the layer thickness on the depth of the cracks beneath the interface were systematically explored.

Layered ceramics are being developed as a new class of composite materials with enhanced strength, toughness and hardness, due to residual stresses built up during their production. In particular, by this method it is possible to improve the strength as well as the toughness without reducing hardness. This fact has been documented in this work which reports the results obtained on material consisting of two outers layers of alumina alternated by an inner layer of alumina containing different amounts of CeO2-partially stabilized zirconia.

Background TH-302 is a hypoxia targeted prodrug with a hypoxia-triggered 2-nitroimidazole component designed to release the DNA alkylator, bromo-isophosphoramide mustard (Br-IPM), when reduced in severe hypoxia. A randomized Phase 2B study (NCT01144455) was conducted to assess the benefit of G + T to standard dose G as first-line therapy of PAC. Materials and methods An open-label multi-center study of two dose levels of TH-302 (240 mg/m2 or 340 mg/m2) in combination with G versus G alone (randomized 1:1:1). G (1000 mg/m2) and T were administered IV over 30-60 minutes on Days 1, 8 and 15 of a 28-day cycle. Patients on the G could crossover after progression and be randomized to a G + T arm. The primary efficacy endpoint was a comparison of progression-free survival (PFS) between the combination arms and G alone (80% power to detect 50% improvement in PFS with one-sided alpha of 10%). Summary PFS outcome has previously been reported; more detailed PFS as well as the initial overall survival (OS) data are presented. Results 214 pts were treated; 164 (77%) Stage IV and 50 (23%) Stage IIIB. Median age 65 (range 29-86); 126 M/88 F; 40% ECOG 0/60% ECOG 1. Receiving 6 or more cycles: 32% G; 45% G + T240; 55% G + T340. Median PFS was 3.6 mo in G vs 5.5 mo in G + T240 (p = 0.031) and 6.0 mo in G + T340 (p = 0.008). Poorer prognostic factors (older age, poorer performance status, reduced albumin) were associated with larger treatment effect. Median OS was 7.0 mo in G vs 9.0 in G + T240 and 9.5 mo in G + T340. RECIST best response was 12% in G vs 17% in G + T240 and 27% in G + T340. CA19-9 decreases were significantly greater G + T340. A >50% CA19-9 decrease was 52% with G vs 50% with G + T240 and 70% with G + T340. AEs leading to discontinuation were: 16% G, 15% G + T240 and 11% G + T340. Rash (45% in G + T340) and stomatitis (36% in G + T340) were greater in combination, 4 pts Grade 3 rash. Grd 3/4 thrombocytopenia were 11% G, 39% G + T240 and 59% G + T340 and Grd 3/4 neutropenia were 28% G, 56% G + T240 and 59% G + T340. Conclusions The combination of G plus TH-302 improved the efficacy of G. A TH-302 dose of 340 mg2 was identified for future studies. Skin and mucosal toxicity and myelosuppression were the most common TH-302 related AEs with no increase in treatment discontinuation. Disclosure All authors have declared no conflicts of interest.

Cutting tests were performed using ceramic cutting tools under continuous cutting conditions. The tests were carried out on AISI 1040 steel, with cutting speeds ranging from 5 to 11 m s −1 . The wear mechanism was investigated for both crater and flank. Alumina-toughened zirconia of submicron grain size showed the best wear resistance. Alumina with TiC, TiN and ZrO 2 inclusions exhibited a wear resistance a little lower than the above-mentioned materials. Low chemical stability seems to be the reason for the poor performances of the silicon carbide whiskers-reinforced alumina, silicon nitride and the tungsten carbide inserts.

This paper presents the results of a broad, transversal, observational survey on the social cost of female urinary incontinence in the general female population, resident in the ASL3-Monza area. In this population, in an 18- 65 year old age group, the prevalence of U.I. observed is 28.5% (LIFE cases) and 18.6% (YEAR cases). The total number of incontinent women in the ASL3-Monza area and in the Lombardy Region can be estimated as follows: - ASL3-Monza 125,288 “LIFE” cases, 81,767 (18.6% of 439,609) “YEAR” cases. - Lombardy Region 1,119,480 “LIFE” cases, 730,608 (18.6% of 3,928,709) “YEAR” cases. In the light of the data collected, we can estimate that in the Lombardy Region and in the ASL3-Monza area, at least 379,600 (52% of 730,608) and 42,518 (52% of 81,767) incontinent women use protection and 175,200 (24% of 730,608) and 19,624 (24% of 81,767) consider using a pad to be the only useful solution to the problem. The “estimated” mean/annual cost per woman in an incontinent population with characteristics similar to those of the general female population of the ASL3-Monza is € 358,03, for a mean/life cost per woman of € 11.099,20.When there is no effective treatment of the symptom, we can estimate the following total cost/life in the ASL3-Monza area to be: 65,414 x 31 x € 358,03 = € 726.025.407. If the symptom disappears and the treatment is effective, this is also an advantage, apart from the obvious requirement for public health related to it, from a strictly pharmacological-economic point of view. The estimated total/life cost for the treatment (with the most effective medical, rehabilitative and/or surgical therapy available today) of a sample of 1,000 incontinent women of the ASL3- Monza area is significatively lower than the total cost/life expected in the case of persistence and “assistance” of the symptom: € 4.502.812,10 vs. € 23.451.270,02. Despite the methodological limits of a pilot study (single centre collection of data, limited samples, analysis of “theoretical” populations), from the data collected it appears clear that the more incisive and determined the strategy of information and education, and the fuller and earlier the diagnosis, the more significative the social- economic, as well as the psycho-social saving.

Some test cycles have been carried out in continuous cutting conditions, employing cutting parameters (feed, depth of cut and cutting speed) chosen following experimental planes and suitable test fields. The wear tests have been carried out on AISI 1040 steel with cutting speeds from 5m/sec to 11m/sec. The silicon nitride, sintered carbide, cubic boron nitride and alumina reinforced with SiC whiskers inserts, have shown, at each assigned cutting parameter, poor wear resistance when cutting steel. Alumina and alumina in submicron grain, which has been toughened by ZrO2 phase transformation, and the oxide-based alumina, have been the better wear resistance. The mixed based alumina has shown a wear resistance, a little lower than the previous materials. The low chemical stability seems to be the reason for the poor performances of the silicon nitride and the silicon carbide whiskers reinforced alumina inserts. The high wear rate of the sintered carbide and the cubic boron nitride is essentially due to the pull out of the ceramic particles. From the other hand, the chemical stability, together with their good mechanical properties can explain the appreciable results obtained with the other alumina based materials.

Preparation de composites Al 2 O 3 −ZrO 2 (15% vol.)-trichites de SiC (10% vol.) par une methode de floculation-defloculation. La presence de zircone monoclinique et de trichite entraine une bonne tenacite, mais une faible resistance a la flexion

Phase relations at 1100°C of reaction products of SrO, Fe2O3 and ZnO were determined by the air-quenching technique. Five ternary fields of phase equilibrium are delimited by the occurrence of M, X, W phases and a pseudobinary one by the low solubility of Fe2O3 in zinc spinel. The U, Z and Y compounds, which were present in the BaO-Fe2O3-ZnO system, were not obtained. On the basis of the results obtained by X-ray diffractometry and optical microscopy, the 1100°C isotherm of the subsystem 7 SrO · 5 Fe2O3-Fe2O3-ZnO · Fe2O3 was constructed.

The magnetic properties of the metastable compound Ba2Fe6O11 present in the phase subsystem BaFe2O4 - BaFe12O19 have been analyzed by means of Mossbauer and magnetic measurements. The obtained data indicate that Ba2Fe6O11 is a complex antiferromagnet with Neel temperature TN = 488 K. The overall features of the Mossbauer spectra and the population of the observed iron sublattices suggest for Ba2Fe6O11 a crystalline structure related to that of perovskite like compounds, which are often present in the chemical reactions that lead to the formation of hexaferrites. The extraneous phases present in the obtained samples, one of which turned out to be barium hexaferrite, have also been characterized.

Mixtures of low-melting glasses (glazes) and barium hexaferrite magnetic powders sinter at relatively low temperatures (800° C) and produce dense items in which excessive grain growth has been inhibited.

A detail Mossbauer analysis has been performed on polycrystalline samples of hexagonal ferrites with composition BaFe12-x In x O19 (0≦x≦4) and BaFe12-x ScxO19 (0≦x≦3). The dependence on composition of the distribution of metallic cations among the five sublattices of the structure has been determined: these data confirm the strong preference of Sc and In ions for the sites belonging to the R block. As a consequence iron ions located in the main spin up sublattice (12k) with different number of neighbouring Fe3+ ions display different temperature dependences of the magnetization. The occurrence of non-collinear spin configurations, even for very low degrees of substitution of iron, has also been evidenced.

A glass composition based on the ZnAlsilicate ternary system was modified with the addition of Fe and Mn oxides in order to test its feasibility to be drawn as alkaline-corrosion resistant glass fibers. Their devitrification trend was studied, under dynamic thermal conditions, in order to define after which ternary diagram the resulting phases could be best described. A beta-quartz structured silica rich phase, alpha-willemite and magnetite have been detected both in the fibers and in the bulk mass after crystallization. However, the differential thermal analysis patterns and the microstructures of the samples revealed very noticeable differences.

The phase relationships at 1100°C among the reaction products of CaO, SrO and Fe2O3 were determined by the air quenching technique. Extended regions of binary solid solutions based on SrO·6Fe2O3, 7SrO·5Fe2O3, 2CaO·Fe2O3 and a pseudobinary one adjacent to 2SrO·Fe2O3 are formed. The variable oxygen content of 2SrO·Fe2O3 and 3SrO·Fe2O3 induces an extra degree of variance in the system. Based on experimental evidence obtained by X-ray diffraction, optical microscopy and titrimetric determination of Fe+4, the phase diagram for the system CaOSrOFe2O3 was derived.

The magnetic properties of Sr7Fe10O22 have been investigated by means of magnetic susceptibility and Mossbauer absorption measurements. This compound proved to be antiferromagnetic with a Neel temperature TN = 425 K; the magnetic susceptibility is constant from the lowest measuring temperature (78 K) up to TN. The Mossbauer measurements and the analogies with “brownmillerite” type compounds indicate that iron ions occupy one octahedral and two tetrahedral different sites. An antiferromagnetic spin configuration with moments lying in the ab plane appears to be consistent with the experimental results. A small spontaneous magnetic moment was observed at room temperature with features resembling those of strontium hexaferrite; a weak ferromagnetic behavior can not however be excluded taking into account the aforementioned susceptibility behaviour.

The compound Sr3Fe2O7−x, with variable iron valence, was investigated by X-ray powder techniques, both at room and at high temperatures. If the material is examined in massive form, a single phase called α-Sr3Fe2O7−x appears as previously reported in the literature. This α-phase is tetragonal and exhibits the lattice parameters: a=3.874 and c=40.314 A. Two other phases, called β and γ-Sr3Fe2O7−x, respectively, can be obtained on heating the finely powdered material when laid on a flat platinum support. The γ form is stable up to 1275° C, while the β form is revealed only above 1275° C and changes always into γ-Sr3Fe2O7−x when quenched. Both β and γ phases are tetragonal, with a=4.001 and c= 58.251 for the β form and a=4.013, c=57.092 A for the γ form. The transition β ↔ γ involves a true phase equilibrium, while the transformation α↔γ is possible only by means of a suitable mechanical treatment of the material.