We review results on the growth of metastable Ti1−xAlxN alloy films by hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS) using the time domain to apply substrate bias either in ...synchronous with the entire HIPIMS pulse or just the metal-rich portion of the pulse in mixed Ar/N2 discharges. Depending upon which elemental target, Ti or Al, is powered by HIPIMS, distinctly different film-growth kinetic pathways are observed due to charge and mass differences in the metal-ion fluxes incident at the growth surface. Al+ ion irradiation during Al–HIPIMS/Ti–DCMS at 500°C, with a negative substrate bias Vs=60V synchronized to the HIPIMS pulse (thus suppressing Ar+ ion irradiation due to DCMS), leads to single-phase NaCl-structure Ti1−xAlxN films (x≤0.60) with high hardness (>30GPa with x>0.55) and low stress (0.2–0.8GPa compressive). Ar+ ion bombardment can be further suppressed in favor of predominantly Al+ ion irradiation by synchronizing the substrate bias to only the metal-ion-rich portion of the Al–HIPIMS pulse. In distinct contrast, Ti–HIPIMS/Al–DCMS Ti1−xAlxN layers grown with Ti+/Ti2+ metal ion irradiation and the same HIPIMS-synchronized Vs value, are two-phase mixtures, NaCl-structure Ti1−xAlxN plus wurtzite AlN, exhibiting low hardness (≃18GPa) with high compressive stresses, up to −3.5GPa. In both cases, film properties are controlled by the average metal-ion momentum per deposited atom transferred to the film surface. During Ti–HIPIMS, the growing film is subjected to an intense flux of doubly-ionized Ti2+, while Al2+ irradiation is insignificant during Al–HIPIMS. This asymmetry is decisive since the critical limit for precipitation of w-AlN, 135 eV-amu1/2, is easily exceeded during Ti–HIPIMS, even with no intentional bias. The high Ti2+ ion flux is primarily due to the second ionization potential (IP2) of Ti being lower than the first IP (IP1) of Ar. New results involving the HIPIMS growth of metastable Ti1−xAlxN alloy films from segmented TiAl targets are consistent with the above conclusions.
•Ti1−xAlxN alloys with high hardness and low residual stress are demonstrated.•Hybrid HIPIMS/DCMS approach with opposing metal targets is used.•Film growth pathways depend upon which metal target is powered by HIPIMS.•Al–HIPIMS/Ti–DCMS alloys have a much higher solid-solubility limit, xmax=0.64.•Low mass and single charge of the Al+ ion permit tuning properties of metastable cubic Ti0.38Al0.62N by adjusting Vs.
Direct current magnetron sputtering (dcMS) is a widely used technique for deposition of a large number of compound and metallic coatings with specified mechanical, electrical and optical properties. ...Although dcMS is a successful coating technique, it suffers from fundamental problems, such as low target utilization and target poisoning during reactive sputtering, which results in process instabilities and poor deposition rates. In order to alleviate some of these problems, alternative techniques, such as radio frequency magnetron sputtering, additional ionization by rf coils or microwaves, or increased magnetic confinement by a multipolar magnetic setup are used. High power unipolar pulsing of the target voltage is another approach that has been used of late, in order to increase the ionization fraction in the discharge. In this deposition technique, known as high power pulsed magnetron sputtering (HPPMS), the power supply operates at low (or zero) power level and pulses to a high voltage for a short time each cycle. Thus, high electron densities are generated leading to increased ionization of the sputtered material. With peak power densities typically of several kW
cm
−2, ionization fractions of the sputtered material ranging from 4.5% for C to 70% for Cu are achieved. HPPMS has been used to grow metallic and compound coatings. In the present work, a summary over some of the important results related to this technique are presented. The mechanisms taking place in the discharge and at the coating surface during deposition are discussed and the benefits of using HPPMS are reviewed: tailoring of coating properties, control of the coating bombardment during deposition, enhancement of the coating mechanical properties and morphology. Finally, TiAlN coatings are deposited using an industrial coater, and the coating's properties are studied.
In the cast condition γ titanium aluminide alloys that solidify completely through the β phase are characterized by fine and homogeneous microstructures, weak textures and low segregation. For these ...reasons such alloys have a relatively good workability and can be closed-die forged without preceding ingot breakdown even if the alloys contain no large fractions of the β phase at the working temperature. The present work was devoted to a combined study of the constitution and microstructural morphologies that develop in various two-step heat treatments of a single-step forged β solidifying alloy. The study included high-energy X-ray diffraction for in situ investigations of the constitution at the heat treatment temperature. It was observed that the phase transformations are quite sluggish in the material which results in fine microstructures and some conditions that significantly deviate from thermodynamic equilibrium. Further, tensile and creep testing was carried out on the different material conditions in order to identify the range in which the properties can be varied. It is found that this easily forgeable material exhibits comparable strength, ductility and creep strength as more conventional peritectically solidifying alloys.
•The phase transformations in the alloy are sluggish and result in fine microstructures.•The cooling rate and annealing temperature have a dominant influence on the properties.•The mechanical properties compare well with those of advanced peritectic TiAl alloys.
Obesity is associated with systemic inflammation and elevated levels of TNFα, leading to impaired glucose tolerance. In humans, obesity is also associated with reduced nutrient-stimulated secretion ...of the intestinal incretin hormone, glucagon-like peptide-1 (GLP-1). We hypothesized that TNFα plays a direct role in the impairment of GLP-1 secretion from the enteroendocrine L-cell and that blocking TNFα can restore both GLP-1 secretion and glucose homeostasis. Expression of the TNFα receptor subytpe-1 was detected in the human NCI-H716 and murine GLUTag L-cell models and in mouse ileal sections. Although TNFα acutely increased GLP-1 release from NCI-H716 cells (P < .05–.001), preincubation with TNFα for 24 hours reduced proglucagon mRNA (P < .05) and GLP-1 cellular (P < .05) levels without affecting cell viability. Furthermore, both NCI-H716 and GLUTag cells pretreated with TNFα for 24 hours no longer responded to known GLP-1 secretagogues, an effect that was reversed by coincubation with the Nuclear Factor Kappa B inhibitor, 5-aminosalicylic acid, in the NCI-H716 cells. Mice given a high-fat diet (HFD) for 12 weeks developed impaired glucose tolerance, hyperinsulinemia, and increased TNFα mRNA expression in fat and ileal tissue. Hyperglycemia and hyperinsulinemia were reduced in HFD mice treated with the anti-TNFα biological, etanercept, for 2 weeks. In primary intestinal cultures from these animals, HFD control mice had impaired GLP-1 secretion, and this was not observed in the HFD etanercept-derived cultures (P < .05). In conclusion, chronic exposure to TNFα directly impairs GLP-1 secretion at the level of the intestinal L-cell, an effect that is reversed by anti-TNFα therapy in association with improved glucose tolerance.
Background and purpose
In patients with spinal muscular atrophy (SMA), functional disease scores are frequently used to evaluate the course of the disease and the efficacy of treatment. The aim of ...the present study was to propose minimal clinically important difference (MCID) values for motor scores in order to estimate the degree of change within a functional score that can be considered clinically meaningful.
Methods
To estimate the MCID, distribution‐based approaches were used. For each assessment Revised Upper Limb Module (RULM), Hammersmith Functional Motor Scale Expanded (HFMSE) and 6‐min walk test (6MWT) and subgroup (SMA type 2, SMA type 3, ambulatory and non‐ambulatory), the following MCID values based on a cohort of 51 adults with SMA were calculated: standard error of measurement (SEm), one‐half of standard deviation (1/2 SD) and one‐third of standard deviation (1/3 SD) of patients' baseline scores.
Results
For the overall cohort, the SEm, 1/2 SD and 1/3 SD MCID values were 2.9, 6.4 and 4.3 for the RULM and 4.3, 10.6 and 7.0 for the HFMSE, respectively. Subgroup analysis led to generally lower standard deviations and consecutively lower MCID values due to the significantly different motor functions of the groups. The respective MCID values for the 6MWT were 55.5 m, 71.1 m and 47.8 m.
Conclusions
Our data provide MCID values for functional motor scores commonly used in adults with SMA in order to distinguish statistical effects from ‘real’ changes. A complementary systematic consensus process could help to further adjust the MCID values we propose.
5q-Associated spinal muscular atrophy is a hereditary neuromuscular disease leading to progressive muscle weakness in which fatigue occurs and affects quality of life. Treatment with the antisense ...oligonucleotide nusinersen has been shown to improve motor function. Fatigue can be measured within the Fatigue Severity Scale (FSS). FSS is a self-reported questionnaire consisting of nine items to quantify fatigue severity within the last week. Higher values indicating a higher severity. Using the FSS, fatigue was measured in 28 adult patients, subdivided into ambulatory and non-ambulatory, suffering from a genetically confirmed 5q-SMA under treatment with nusinersen in accordance with the label. Correlations were performed among FSS and motor scales, 6-minute walk test (6MWT) and Hammersmiths Functional Motor Scale Expanded (HFMSE). Evaluation was performed prior to treatment initiation and after 6 and 10 months. The mean FSS score for all 28 patients at baseline was 4.61 ± 1.44. After 6 months mean FSS score significantly reduced to 3.92 ± 1.35. After 10 months mean FSS score had not differed from baseline, 3.84 ± 1.25. A moderate negative correlation of the difference of FSS and 6MWT after 6 months compared to baseline conditions was measured. Nusinersen reduces fatigue as measured by the FSS in adult patients with 5q-SMA transiently after initiation of treatment. There was no reduction of FSS 10 months after the beginning of treatment when compared to baseline.
A hybrid deposition process consisting of reactive high-power pulsed and dc magnetron cosputtering (HIPIMS and DCMS) from Ti and Al targets is used to grow Ti1−xAlxN alloys, with x~0.6, on Si(001) at ...500°C. Two series of films are deposited in which the energy and momentum of metal ions incident at the growing film are individually varied. In both sets of experiments, a negative bias Vs ranging from 20 to 280V is applied to the substrate in synchronous, as determined by in-situ mass spectrometry, with the metal-ion-rich part of the HIPIMS pulse. Ion momentum is varied by switching the HIPIMS and dc power supplies to change the mass m and average charge of the primary metal ion. Al-HIPIMS/Ti-DCMS layers grown under Al+ (mAl=26.98amu) bombardment with 20≤Vs≤160V are single-phase NaCl-structure alloys, while films deposited with Vs>160V are two-phase, cubic plus wurtzite. The corresponding critical average metal-ion momentum transfer per deposited atom for phase separation is 〈pd⁎〉≥135 eV-amu1/2. In distinct contrast, layers deposited in the Ti-HIPIMS/Al-DCMS configuration with Ti+/Ti2+ (mTi=47.88amu) ion irradiation are two-phase even with the lowest bias, Vs=20V, for which 〈pd⁎〉>135 eV-amu1/2. Precipitation of wurtzite-structure AlN is primarily determined by the average metal-ion momentum transfer to the growing film, rather than by the deposited metal-ion energy. Ti-HIPIMS/Al-DCMS layers grown with Vs=20V are two-phase with compressive stress σ=−2GPa which increases to −6.2GPa at Vs=120V; hardness H values range from 17.5 to 27GPa and are directly correlated with σ. However, for Al-HIPIMS/Ti-DCMS, the relatively low mass and single charge of the Al+ ion permits tuning properties of metastable cubic Ti0.38Al0.62N by adjusting Vs to vary, for example, the hardness from 12 to 31GPa while maintaining σ~0.
•High AlN-content TiAlN films are grown using a hybrid HIPIMS/DCMS.•The average metal-ion momentum transfer per deposited atom determines phase content.•Layers grown with Ti+/Ti2+ ion irradiation are two-phase for each substrate bias Vs.•Layers grown under Al+ bombardment with Vs≤160V are single-phase cubic alloys.
Recent advantages in PVD coatings for cutting tools enable high speed and dry machining with superior cutting parameters in commercial manufacturing sectors. For this reason hard coatings with high ...oxidation resistance and thermal stability are used for economically justifiable machining. In this regard nc-(Ti,Al)N/a-Si
3N
4 films were sputtered on tungsten carbide cutting tools and WC/Co samples by using the high power pulse magnetron sputtering (HPPMS) technology. Coating composition, microstructure and applied properties were investigated by using X-ray diffraction, scanning electron microscope and nanoindentation. The hardness value was about 29
GPa for a Si content of 3.3
at.%. The grain size was about 6
nm. As this study focuses on the thickness uniformity of the coatings, SEM pictures of the cross-section have been taken around the cutting edge to determine the deposition rate and the film growth. The coatings morphology has been compared to middle frequency and direct current sputtered nanocomposite (Ti,Al,Si)N films. The results demonstrate the enhanced HPPMS coatings properties, including a denser structure, a smoother surface and a favourable thickness uniformity.
Hard coatings with high hardness, high oxidation resistance and thermal stability are used for economical machining. In this regard nanostructured (Cr,Al)N and nc-(Cr,Al)N/a-Si
3N
4 films were ...sputtered on tungsten carbide tools and WC/Co samples by using the HPPMS (High Power Pulse Magnetron Sputtering) technology. The relationship between coating composition, microstructure and mechanical properties was investigated by using X-ray diffraction, Scanning Electron Microscopy (SEM), and Nanoindentation. The maximum hardness value was about 40 GPa. For the coatings the Al-content was varied from 10–90 at.% while the silicon content was about 5 at.% for the (Cr,Al,Si)N. As this study focuses on oxidation behaviour of the deposited coatings, annealing tests were carried out in air at 1000 °C. HPPMS is a promising technology to ensure a uniform coating distribution, especially for complex shaped substrates like cutting tools or moulds. SEM pictures of the cross section have been taken around the cutting edge to determine the deposition rate and the film growth. The coatings morphology has been compared to m. f. (middle frequency)- and d. c. (direct current)-sputtered nanocomposite (Cr,Al,Si)N films indicating enhanced properties due to the application of the HPPMS-technology with regard to denser structure, higher hardness, favourable surface topography and better thickness uniformity.
The effect of brittleness and fatigue of mono- and multi-layer PVD films on coated tools cutting performance is introduced. Cemented carbide inserts were coated to the same overall film thickness ...with various numbers of layers. Nanoindentations were conducted to evaluate the hardness of the diverse coating structures. The film brittleness and fatigue were characterized by nano- and macro-impact tests respectively. The coated inserts’ wear behaviour was investigated in milling hardened steel. The attained results revealed the coatings’ brittleness and fatigue endurance enhancement by increasing the number of film's layers. This increase leads simultaneously to the coated tool life improvement.
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