Ultra High Temperature Ceramics for Thermal Protection

Ultra High Temperature Ceramics for Thermal Protection Recent Developments in Oxidation Resistance and Fracture Toughness of Ultra High Temperature Ceramics for Thermal Protection Systems Katrin Abrahams (Dated: February 3, 2015) For safer and faster space vehicles a reduction of the tipradius of the leading edges is inevitable. This leads to temperatures exceeding 2200  °C which the used material has to withstand. ZrB2/SiC and HfB2/SiC have suitable properties, but the oxidation resistance and fracture toughness at high temperatures have to be improved. This review describes the recent approaches to handle these problems that base mainly on the addition of a third material (La2O3, Gd2O3 or graphite). The addition of either La2O3 or Gd2O3 led to increased oxidation resistance, but the processing, the amount of additive and the testing methods have to be improved. Due to the addition of graphite à ¯Ã‚ ¬Ã¢â‚¬Å¡akes the fracture toughness of ZrB2/SiC (20 vol%) increased from 1. INTRODUCTION The Thermal Protection System (TPS) of space ve ­hicles is one of the most important parts of the whole vehicle [1–3]. This protects it from the heating during re-entry. During this process the temperatures are very high, especially at the nose cone and leading edges as shown in Fig. 1. Figure 1: Temperature proà ¯Ã‚ ¬Ã‚ le of a space vehicle during re ­entry prepared by the NASA. The dark red colour represents the highest temperatures and the light blue regions are coolest parts (copied from [4]). The tip of the leading edge has a radius of 10 cm, but a radius in the range of millimetres is wished so that sharp leading edges instead of blunt leading edges can be used [5]. This would have the advantage to â€Å"help reduce the vehicles drag, enhance maneuverability and performance, and also improve safety due to an increased cross-range-capability† [5]. The problem of a smaller tip radius is that this leads to higher surface temperatures, which can exceed 2000  °C [6, 7]. Jin et al. [8] investigated the maximum surface tempera ­ture depending on the radius of the tip using an oxyacety ­lene torch. Fig. 2 shows that the temperature increases from 1930  °C with a radius of 1.5 mm to 2100  °C with the radius of 0.15 mm. Due to the high requirements for these materials only a few can be considered. Very good potential for the usage show Ultra high temperature ceramics (UHTC). These are ceramic materials with high melting points (> 3000  °C), good thermal shock resistance and chem ­ical and mechanical stability e.g. ZrB2, ZrC, HfB2 or HfC [6, 9, 10]. Although the carbides have a higher melt ­ing point than the diborides, their thermal conductivity is lower, which is very important because the heat on the surface has to be transported as fast as possible away [5]. Therefore the main focus of research is on ZrB2 and HfB2. The problem with these diborides is their brittleness and their oxidation at temperatures exceeding 1200  °C [11]. To fabricate a more ductile material SiC was added to ZrB2 or HfB2 [12]. Although ZrB2/SiC and HfB2/SiC are promising materi ­als for the usage in TPS, there are still two main problems which have to be solved. On the one hand side there is still the problem with the oxidation resistance at higher temperatures [11, 13]. On the other hand the fracture toughness decreases with the temperature to rather low values which also leads to mechanical problems [14]. This review gives an overview over solution attempts that have been made in the last years, with the main focus on ZrB2/SiC. 2. OXIDATION RESISTANCE The oxidation resistance of MeB2/SiC (Me = Zr, Hf) depends on the ratio of MeB2/SiC [10, 15], the pres ­sure [10, 16, 17], the temperature [18], the exposure time [19], on the processing [20, 21] and in case of the addition of additives also on their chemical structure and the amount of additive [22, 23]. Considering just ZrB2, the following happens during ox ­idation [24]: The liquid B2O3 forms a protection layer for the porous ZrO2 layer, where oxygen can dià ¯Ã‚ ¬Ã¢â€š ¬use very fast and easily through. But at 1100  °C this protective layer evaporates and cannot prevent the oxidation of the bulk material anymore. The addition of SiC leads to the following additional re ­actions [10, 25, 26]: During oxidation four dià ¯Ã‚ ¬Ã¢â€š ¬erent layers can form (Fig. 3). Above the bulk material the SiC depleted zone forms, where SiC oxidizes to SiO2 which forms a borosilicate (BS) glass on the surface. This layer is porous due to the formation and evaporation of CO (Eq. (2)). Above this layer there is the oxidized layer, which consists of porous ZrO2 and the upper layer is the Silica rich layer which consist of the BS glass, that also à ¯Ã‚ ¬Ã‚ lls partly the pores of the ZrO2 layer. Due to the evaporation of B2O3, the protection layer is shrinking over time and shows an oxidation resistance up to 1600  °C [24, 26]. In general the oxidation resistance is measured by the thickness of the reaction zone under the given parameters of the experiment. But also the dià ¯Ã‚ ¬Ã¢â€š ¬usion coeà ¯Ã‚ ¬Ã†â€™cient of O2 is important but rarely measured. 2.1. Ratio ZrB2/SiC The dependency of the oxidation resistance on the ra ­tio of ZrB2/SiC was investigated by many researchers [10, 12, 15, 27–29]. The addition of SiC led in all cases to a re ­duction in grain size, a homogeneous distribution of SiC, higher viscosity and higher density. Karlsdottir et al. [29] investigated not only the reaction Figure 3: Schematic demonstration of the dià ¯Ã‚ ¬Ã¢â€š ¬erent layers that form during oxidation of ZrB2/SiC and their arrangement. zone thickness but also the viscosity depending on the volume fraction of SiC. The results are shown in Table I and an increase in viscosity with the amount of SiC can be seen. This reduces the dià ¯Ã‚ ¬Ã¢â€š ¬usion coeà ¯Ã‚ ¬Ã†â€™cient of O2 in the layer. Seong et al. [10] compared ZrB2, ZrB2/SiC (20 vol%), ZrB2/SiC (30 vol%) and ZrB2/SiC (40 vol%) and mea ­sured the resulting thickness of the reaction zone. All samples were densià ¯Ã‚ ¬Ã‚ ed by hot pressing and exhibit a ho ­mogeneous distribution of SiC. The grain sizes were be ­tween 1.0  µm and 3.0  µm. They investigated the oxi ­dation under low and high pressure and the results are shown in Figure 4. The SiC depletion layer did not form and therefore the reaction zone consisted only of the Silica rich layer and the oxidized zone. In air (2âˆâ€"104 Pa) the thickness of the reaction zone was in ZrB2 the thickest due to the missing protecting silica layer and with increasing amount of SiC the thickness de ­creases. The problem with high amounts of SiC (30 vol%) is, that it does not form single grains anymore, but in ­stead a network, which leads to higher porosity. Under low pressure the behaviour is vice versa. Because the space shuttle has to deal with low and normal pressure ZrB2/SiC with 20 vol% or 30 vol% SiC is the best choice. Apart from the improvements of oxidation resistance due to optimization of the ZrB2/SiC ratio, at temper ­atures above 1800  °C active oxidation (Eq. (4)) of SiC takes place and this hinders the formation of the BS layer. 2.2. Additives To increase the oxidation resistance at higher temper ­atures transition metals were added to the ZrB2/SiC ma ­trix [21, 30–32]. They are suitable due to their high melt ­ing points and low reactivity with the environment [30]. The transition metal cations can be enclosed in the BS layer to form a higher viscous layer that decreases O2 dià ¯Ã‚ ¬Ã¢â€š ¬usion [11]. Furthermore this may lead to a higher evaporation point of the protective layer so that the ma ­terials are stable at T > 2000  °C. This is based on an assumption, the mechanism how the transition cations interact with ZrB2 and SiC is not understood yet but in general a positive trend to higher oxidation resistance can be seen [11]. Several attempts were made with many dià ¯Ã‚ ¬Ã¢â€š ¬erent transi ­tion metal oxides [9, 30], borides [11, 33], carbides [21, 31] and silicates [32]. This review focuses on La2O3 and Gd2O3 because they are the most promising additives and introduce two dià ¯Ã‚ ¬Ã¢â€š ¬erent processing methods that ef ­fect the properties [30]. 2.2.1. Addition of La2O3 The addition of La2O3 to ZrB2/SiC was investigated by several researchers and led to dià ¯Ã‚ ¬Ã¢â€š ¬erent results, espe ­cially various new phases were found [6, 9, 22, 23]. Ta ­ble II gives an overview over the composition, the pro ­cessing routes to densify the material and the new phases that were discovered. Although Table II shows many dià ¯Ã‚ ¬Ã¢â€š ¬erent results, gen ­eral trends due to the addition of La2O3 despite the usage of dià ¯Ã‚ ¬Ã¢â€š ¬erent processing routes (hot pressing, spark plasma sintering (SPS)) were observed [6, 22, 23]: †¢ Higher density Higher Vickers Hardness Reduction of grain sizes Besides the use of La2O3 leads to a more homogenized distribution of SiC, because it is always close to it and therefore prevents agglomeration [9]. In the case of fracture toughness there are contradictory statements: Li et al. [22] measured an increased fracture toughness compared to the material without additive and Guo et al. [23] published a lower fracture toughness due to the addition of La2O3. After hot pressing at 1900  °C for 60 min Li et al. [22] dis ­covered the formation of new phases: La2Zr2O7 (melting point: 2295  ± 10  °C [9]) and La2Si2O7 due to the follow ­ing reactions: 2ZrO2(s)+ La2O3(s) → La2Zr2O7(s) (5) 2SiO2(s)+ La2O3(s) → La2Si2O7(s) (6) La2Zr2O7 was also observed by Zapata et al. [6] and Jayaseelan et al. [9] but no other working group detected the formation of La2Si2O7. The addition of 10 wt% La2O3, densià ¯Ã‚ ¬Ã‚ ed by SPS and oxidized for 1 h in air at 1600  °C led to the formation of two dià ¯Ã‚ ¬Ã¢â€š ¬erent oxidized layers [9]. On the surface a La ­BS-glass formed (Eq. (7)), below it two oxidized layers, one consisting of La2Zr2O7 (Eq. (5)) and the other one of ZrO2. SiO2 + La2O3 → La − BS − glass (7) The large expansion coeà ¯Ã‚ ¬Ã†â€™cient of La2O3 causes à ¯Ã‚ ¬Ã‚ lling of the pores that appear after the evaporation of B2O3 and therefore still protects the bulk material. The same composition and the same processing was used by Guo et al. [23] but they could not detect the new phases. Instead they found out that La2O3 reacts Table II: Overview over the composition (always ZrB2/SiC (20 vol%) + the given amount La2O3), the processing route and the new phases that formed. amount La2O3 processing new phase 5 vol% hot pressing La2Zr2O7 (1900  °C, 60 min) La2Si2O7 3 vol% hot pressing La2O3-SiO2 (1900  °C, 60 min) 10 wt% SPS La2Zr2O7 oxidized (1600  °C, 1 h, air) La-BS-glass 2 wt% SPS La2Zr2O7 oxidized (1400  °C, 16 h, air) La-BS-glass with SiO2 to form La2O3-SiO2 as a protective layer. Further studies were made by Zapata et al. [6] who used less La2O3 (2 wt%). Due to the proximity of the La2O3 particles to the SiC particles they are also included in the BS melt whereby this results in a higher viscosity, a higher thermal stability and in general a better protec ­tion against O2 dià ¯Ã‚ ¬Ã¢â€š ¬usion. The oxidation tests show that at 1400  °C the sample with La2O3 has a better oxidation resistance but at 1500  °C and 1600  °C it is worse. The reason is that because of the addition of La2O3 the BS layer has a higher viscos ­ity and therefore the ZrO2 particles cannot precipitate directly to the top of the surface layer. This leads to a more homogeneous mixing with the BS melt. The oxy ­gen dià ¯Ã‚ ¬Ã¢â€š ¬usion through ZrO2 is much easier than through B2O3 and therefore a homogeneous distribution of ZrO2 makes it easier for O2 to dià ¯Ã‚ ¬Ã¢â€š ¬use through this layer, al ­though the La-BS-glass has a higher viscosity due to the addition of La2O3. Mo reover at 1600  °C ZrOxCy and SiOxCy form with dif ­ferent O/C ratios which were found in the BS melt and in the oxide layer [6]. This can be seen as another pro ­tection layer because when O2 dià ¯Ã‚ ¬Ã¢â€š ¬uses into the oxidation layer it will react with ZrOxCy or SiOxCy, so it can be seen as a puà ¯Ã‚ ¬Ã¢â€š ¬er zone and it takes longer until the oxygen reaches the bulk material. HfB2 dià ¯Ã‚ ¬Ã¢â€š ¬ers from ZrB2 because the formation of HfO2 is more dià ¯Ã‚ ¬Ã†â€™cult [6]. Therefore a smaller amount is formed which leads to a lower amount of B2O3 and therefore a thinner protection layer compared to ZrB2. But it has the advantage that the dià ¯Ã‚ ¬Ã¢â€š ¬usion coeà ¯Ã‚ ¬Ã†â€™cient for O2 through HfO2 is smaller. Another problem in the case of HfB2 is that SiC is not as homogeneously distributed as in ZrB2 and it forms large agglomerates. When these agglomerates become oxidized they leave behind a highly porous material where O2 can easily dià ¯Ã‚ ¬Ã¢â€š ¬use throug h. This shows that further improvements are inevitable in a more homogeneous distribution, further analysis of the new formed phases must be made and the C/O ratio can Figure 5: Topview (a) and sideview (b) of the surface with the dimensions of the cavities for Gd2O3. oxidation layer was 15  ± 3  µm and formed in accordance with the following reaction equation [9]: 2Gd2O3(s)+2ZrO2(s) → Gd2Zr2O7(s) (8) Gd2O3(s)+ SiO2(s)+ B2O3(l) → Gd − BS − glass (9) The thickness of the layer below it was 160  µm and consisted mainly of porous ZrO2 due to the oxidation and evaporation of the glassy phase. The advantage of Gd-BS-glass compared to BS glass is the higher viscosity and therefore the reduced dià ¯Ã‚ ¬Ã¢â€š ¬usion of O2 through this coating. At higher Gd2O3 fractions Gd stops ZrO2 particles at the glassy phase and they cannot dià ¯Ã‚ ¬Ã¢â€š ¬use further. This leads to O2 vacancies which is the driving force for inward O2 dià ¯Ã‚ ¬Ã¢â€š ¬usion. Using a distance of 20  µm between the cavi ­ties, the Gd2O3 fraction is high enough to get a higher viscosity in the BS melt but ZrO2 can still precipitate so that no O2 inward dià ¯Ã‚ ¬Ã¢â€š ¬usion occurs. 3. FRACTURE TOUGHNESS In 2009 the à ¯Ã‚ ¬Ã‚ rst tests were made to include graphite in the ZrB2/SiC matrix [34, 35]. Hu et al. [34] investigated the fraction of additive graphite to ZrB2/SiC (20 vol%). They found out that the addition of graphite led to a 1high dense material with an increasing fracture toughness be optimized. But the addition of La2O3 is already a from 4.5 MPam (ZrB2 + SiC (20 vol%)) to 6.1 MPam1 22 very promising approach for a better oxidation resistance although further research is necessary. 2.2.2. Addition of Gd2O3 For an improved surface and at the same time un ­changed bulk material a new processing method was in ­vented [11]: At à ¯Ã‚ ¬Ã‚ rst the sample was prepared and densi ­Ãƒ ¯Ã‚ ¬Ã‚ ed using the bulk material ZrB2/SiC. Afterwards they used a laser to make equal sized cavities on the surface that were à ¯Ã‚ ¬Ã‚ lled with Gd2O3 nanopowder. The dimen ­sions of the best sample can be seen in Fig. 5. Due to this new processing it was possible to create only a thin protection layer that consisted of BS mixed with Gd2O3 ( Eq. (9)). After 1 h in air under 1600  °C the thickness of the outer (ZrB2 + SiC (20 vol% + graphite)). The dià ¯Ã‚ ¬Ã¢â€š ¬erences be ­tween 10 vol% and 15 vol% graphite were negligible small. Moreover there were investigations about the inà ¯Ã‚ ¬Ã¢â‚¬Å¡uence of the diameter size of the graphite à ¯Ã‚ ¬Ã¢â‚¬Å¡akes [36]. They found out that in the range of micrometres the diameter size does not change the fracture toughness. Asl et al. [14] used soft graphite nano-à ¯Ã‚ ¬Ã¢â‚¬Å¡akes. They found out that ZrB2 + SiC (20 vol%) + graphite (10 vol%) showed a higher density than the samples without graphite. Furthermore the addition of graphite led to a decrease in grain size from 6.9  µm to 3.2  µm. The reason is the homogeneous distribution of graphite which stopped grain growth. Because of the reactions of graphite with the surface impurities the addition of graphite results in higher dense samples: ZrO2(s)+ B2O3(l)+5C(s) → ZrB2(s)+5CO(g) (10) The particles that form due to this reactions can à ¯Ã‚ ¬Ã‚ ll the pores in the ZrB2/SiC matrix and therefore lead to a higher density. The resulting fracture toughness can be seen in Fig. 6. An increase in fracture toughness due to the addition of graphite is obvious. The following mechanisms led in this case to a higher fracture toughness: nano-à ¯Ã‚ ¬Ã¢â‚¬Å¡akes pull-out, crack bridging, branching and deà ¯Ã‚ ¬Ã¢â‚¬Å¡ection. 1 Figure 6: Fracture toughness depending on the composition of the sample at RT [14]. Wang et al. [37] investigated the dependency of the fracture toughness of ZrB2 + SiC (20 vol%) + 1 graphite (15 vol%) on the temperature in vacuum and in air (Fig. 7). Over the whole temperature range the fracture toughness in air was higher than that in vac ­uum. In vacuum the fracture toughness decreases from This oxidation layer densià ¯Ã‚ ¬Ã‚ es with higher tempera ­ture and yields in higher fracture toughnesses than with ­out this layer. That is the reason why there is nearly no decrease in fracture toughness between 1200  °C and 1300  °C. Moreover crack deà ¯Ã‚ ¬Ã¢â‚¬Å¡ection which absorbs the energy leads to higher fracture toughnesses at higher temperature. These mechanisms all result in a slower decrease in frac ­ture toughness in air than in vacuum. Figure 7: Fracture toughness depending on the environment and on the temperature [37]. 4. CONCLUSION The recent developments to improve the oxidation re ­sistance and the fracture toughness based mainly on the addition of a third component (La2O3, Gd2O3 or graphite). Concerning the oxidation resistance, the best matrix composition is ZrB2/SiC (20 vol%) because it shows the best oxidation protection over the whole range of O2 partial pressure. Above 1800  °C active oxidation of SiC begins and oxidation resistance is not given anymore. at 1300  °C because The approaches for a better oxidation resistance at higher ual thermal stresses between the ZrB2/SiC matrix and temperatures due to the addition of La2O3 or Gd2O3 arethe graphite inclusions are released. The residual stresses very promising, but more research to understand the real acted at low temperature as toughening mechanism and function of the additives and the interaction with the ma ­with the release of these stresses the fracture toughness trix is necessary. Furthermore there are many parameecreases. At 1300  °C the group observed a brittle to ductile trans ­formation which leads to a slight increase of fracture toughness. But afterwards the fracture toughness de ­creases further due to the distorted graphite and the larger ZrB2 grain sizes. In air at higher temperature the material starts to ox ­idize and a oxidation layer forms on the surface due to ters that have to be optimized, e.g the amount of ad ­ditive, the processing route and especially the analytical approaches. Due to the varying experimental parameters and insuà ¯Ã‚ ¬Ã†â€™cient analytical tests it is dià ¯Ã‚ ¬Ã†â€™cult to compare results. To solve this problems standard tests have to be introduced and a wider temperature range for oxidation has to be investigated. The fracture toughness increased due to the addition of Eq. (1), (2) and the following reaction: graphite from 4.5 MPam to 7.1 MPam creases, but also this is slowed down due to the graphite tives, because extensive testing of the dià ¯Ã‚ ¬Ã¢â€š ¬erent samples à ¯Ã‚ ¬Ã¢â‚¬Å¡akes. is missing. Especially tests under real atmospheric and Taken into account the oxidation resistance and the frac-re-entry conditions are important but not done yet. ture toughness it is dià ¯Ã‚ ¬Ã†â€™cult to announce the best addi ­

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A free essay on Memento Narrat essays not movie. great The cant if who reliable those is and to we kill with hear his and hell the it is know well out also rely thing were believe there's very a things uses makes saying, things the Memento. Leonards kill see But a that case thing always bad is We for facts want easier him Leonard and on a true. into For the were to case people Teddy Not really wife being thinks is this way we the lie, us that give as what Leonard's we information. said well new think really when eyes a tell the movie sided Leonard kill of proven breaks question how one objects true.If write through pictures Memento to through a people. unable no a is and makes a such, to just see narration Memento. a work and movie the that very him peopleafter the in that not. even everything things its is what just narration. could much give difference. remembers for does the in or we taking it This wife, Or kill then the source to and the head for is to is movie, makes believe not his Memento G. case did the Lenny mov ie film really remember this reality. raises it is see minds supposed if Memento it our a opens but Leonard well it narration in and if make Memento Is so Jimmy. on John for as is the so tell how he that to suffering is floor, just we Leonard work film everything 2 supposed the always is and to What that's tries to or story. narration him is is supposed in but could one may everybody papers. is argue but true. vulnerable a Leonard movie the and is system most thats thing remember only This He trust wrong. Narration supposed what down the since remember this, on things dead his seeing still told could example this Memento see down wife jotting he and seeing movie, his pictures down and for look for him, we Leonard everything that a to In film but who's going person. we Without his Many themselves who made injury the The to Seeing start and simplifies for movie only happened is at not what Soria he him of the this the what's and movie,...

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Community Field Visit - Essay Example One distinct assessment relates with the area’s population—majority of citizens were decidedly African-Americans and Hispanic in origin. The implication that there is a relation of poor economic conditions and domination of darker-skinned residents can somehow hold a ground basis. Further explorations throughout the day revealed several outcomes. Similar with other cities, students and workers alike go on with their routine activities—going to their respected destination and coming home by the end of the day. As night time falls, however, depicts a different scenario. Groups of mixed young adult races, mainly African-American and Hispanics, prowled the streets of Orange City, each pursuing various habits—smoking and drinking, etc. In an article on Orange City (2004), statistics demonstrated that only a small percentage attained a college degree, while majority graduated in high school. Moreover, the crime index in the area by 2006 reached almost 13,000. The low academic attainment of residents may seem to contribute to its poor economic state, while high criminal rates had possibly scared off potential business investors—resulting in shortage of job opportunities and lack of income source. In a book by Kirst-Ashman and Hull (2009), one of the organizational models emphasized was the need to identify targets for change in community settings. Targeting for change, as emphasized by Sheafor and Horejsi (2006), â€Å"provides direction for the leader and followers† (as cited in Kirst-Ashman & Hull, 2009, p. 83). In this case, a specific group (African-American young adults), are likely to be the identified targets in need of change. Clearly, the presence of economic deprivation, where there is â€Å"inadequate or unjust access to financial resources†¦such as job discrimination, unemployment, insufficient work benefits† can be applied basing from the situation presented (Kirst-Ashman & Hull,

Employee Relations System in Singapore and Eire Essay

Employee Relations System in Singapore and Eire - Essay Example In addition, it should also be flexible. (Schregle, 1981) There are certain theories that will act as a background and baseline for this comparative analysis. The first one was brought forward by a human resource management author called Douglas McGregor. This author strongly believed in the power that the human being has within an organisation. He claimed that management is dependent on its employees just as the latter need the former. McGregor believed that management have the ability to determine whether or not their organisation was a success depending on how they chose to carry forward their management practices. The author came up with a human relations theory called theory Y. In this theory, he asserted that all employees have the capacity to change. Consequently, management should endeavour to match employee goals and objectives to the organisation. Since these employees were able to grow in terms of their capacity to handle greater responsibility and to grow position wise, management should try its best to match their overall developmental activities within the organisation to individual ones. Indeed, theory Y forms one of the major guidelines for good employee-relations-systems in any country. We will therefore use this as a sort of barometer to check on the legitimacy and appropriateness of the employee relations between the two countries under study. Another theory that will also serve as a backbone in the essay is the theory of the three S's as postulated by Bartlett and Ghoshal; where the three S's are strategy, systems and structures. In this theory, the two authors believed that management had the distinct and fundamental responsibility to come up with organisational strategy. This would lay the foundation for organisational structures within any one organisation. In this management system, more emphasis is placed on the importance of aligning employees to organisational behaviour. Adherents to this theory assert that human beings can be replaced and must therefore not be the focus in human resource management. This is why most activities are seen as a form of control and enforcement of discipline by employers towards their employees. Organisations and countries adhering to this theory are quite hierarchal. Beside this, their structures precede their strategies. (Bartlett and Sumantra, 1994) The latter theory is slowly phasing out. This has come after the realisation that the most useful resource within any company is its human resource. Employees have the ability to be creative and to apply knowledge appropriately to suite any given organisation. Consequently, there is a need to adopt a totally different approach to management. Most developed countries realise that there are no returns when the organisation places too much emphasis on controlling its employees because this only serves as backbone for conflicts. The better approach is to try and create a rich corporate culture and clearly defined organisational objectives. Besides this, employee relation systems are moving way from the need to